WO2013022009A1

WO2013022009A1 - Noble metal- supporting material and its use in hydrogen peroxide production and propylene oxide production

Info

Publication number: WO2013022009A1
Application number: PCT/JP2012/070129
Authority: WO
Inventors: Tomonori Kawabata; Tetsuro Yonemoto; Mitsuaki Kumazawa
Original assignee: Sumitomo Chemical Company, Limited
Priority date: 2011-08-09
Filing date: 2012-08-01
Publication date: 2013-02-14
Also published as: BE1020386A3; JP2013034948A

Abstract

The invention provides a noble metal-supporting material comprising a noble metal and a carrier as constituent components, the ratio of a desorbed amount of hydrogen to an adsorbed amount of being in the range of 0.01 to 0.40, wherein the desorbed amount of hydrogen is the value calculated from the sum of the areas of the peaks of the desorbed component with a maximum in the range of 50°C to 350°C, as observed in accordance with a temperature-programmed desorption method with a programming rate of 10°C/min, with a pre-treated sample, and the adsorbed amount of carbon monoxide is the value obtained from metal surface area measurement based on the carbon monoxide pulse method, with a pretreated sample.

Description

DESCRIPTION

Title of Invention

NOBLE METAL- SUPPORTING MATERIAL AND ITS USE IN HYDROGEN PEROXIDE PRODUCTION AND PROPYLENE OXIDE PRODUCTION

Technical Field

[0001] The present invention relates to a noble metal-supporting material, and to its use.

Background Art

[0002] Alkylene oxides such as propylene oxide are commonly produced by using a noble metal-supporting material as a first catalyst to obtain hydrogen peroxide from hydrogen and oxygen, and then using a titanosilicate as a second catalyst in the same reactor for reaction of the obtained hydrogen peroxide with an olefin such as propylene. The term "titanosilicate" refers to a compound in which some of the silicon atoms in a silicon dioxide skeleton are replaced by titanium atoms.

[0003] Patent Literature 1 discloses supporting palladium tetramine chloride on active carbon, as a noble metal-supporting material that can serve as the first catalyst. It further discloses a method for producing propylene oxide from oxygen, hydrogen and propylene using a titanosilicate as the second catalyst.

Citation List

Patent Literature

[0004] [Patent Literature 1 ] JP 2008-201776 A

Summary of Invention

Technical Problem

[0005] It is an object of this invention to provide a novel catalyst that produces a high alkylene oxide yield when used in combination with a titanosilicate-containing catalyst in a reaction for production of an alkylene oxide from oxygen, hydrogen and an olefin.

Solution to Problem

[0006] The invention is the result of much diligent research by the present inventors on the production method described above.

Specifically, the present invention relates to the following.

1. A noble metal-supporting material comprising a noble metal and a carrier as constituent components, the ratio of a desorbed amount of hydrogen to an adsorbed amount of carbon monoxide being in the range of 0.01 to 0.40 (this will also referred to hereunder as "the present noble metal-supporting material").

Here, the " desorbed amount of hydrogen " is a value calculated from the sum of the areas of the peaks of the desorbed component having a maximum value in the range of 50°C to 350°C, as observed in accordance with a temperature-programmed desorption method with a programming rate of 10°C/min, with regard to a sample left in a vacuum at 50°C for 8 hours or more, under a normal pressure helium gas stream at 50°C for 1 hour, then under a normal pressure hydrogen gas stream at 50°C for 2 hours, and further left under a normal pressure helium gas stream at 50°C for 1 hour and thereby obtained, while the " adsorbed amount of carbon monoxide " is the value obtained by metal surface area measurement based on the carbon monoxide pulse method, of a sample left in a vacuum at 50°C for 8 hours or more, then under a normal pressure helium gas stream at 50°C for 1 hour, under a normal pressure hydrogen gas stream at 50°C for 2 hours, and further left under a normal pressure helium gas stream at 50°C for 1 hour and thereby obtained.

2. The noble metal-supporting material as described in 1., wherein the peaks of the desorbed component with a maximum value in the range of 50°C to 350°C as observed in temperature-programmed desorption method with a programming rate of 10°C/min does not have a maximum value between 50°C and 210°C, and have one or more maximum values in the range of 210°C to 350°C.

3. A noble metal-supporting material as described in 1. or 2., which is obtained by contacting a carrier with a noble metal dispersion comprising noble metal particles, such that a 0.5 % by weight aqueous dispersion of noble metal particles has a streaming potential in the range of 10 μeq/g to 50 μeq/g.

4. The noble metal-supporting material as described in 3., wherein the noble metal particles are obtained by mixing an acid-containing solution with either (a) a noble metal particle precursor such that a 0.5 % by weight aqueous dispersion has a streaming potential in the range of 50 μeq/g to 300 μeq/g, or (b) a mixture of the noble metal particle precursor with a solvent.

5. The noble metal-supporting material as described in 4., wherein the acid is hydrochloric acid.

6. The noble metal-supporting material as described in 3., wherein the noble metal particles are obtained by using an oxidizing agent for partial oxidation of either (a) a noble metal particle precursor such that a 0.5 % by weight aqueous dispersion has a streaming potential in the range of 50 μeq/g to 300 μeq/g, or (b) a mixture of the noble metal particle precursor with a solvent. 7. The noble metal-supporting material as described in 6., wherein the oxidizing agent is oxygen and/or sodium nitrite.

8. The noble metal-supporting material as described in any one of 1. to 7., wherein the noble metal is palladium.

9. The noble metal-supporting material as described in any one of 1. to

8., wherein the carrier comprises at least one species selected from a group consisting of active carbon, aluminum oxide, titanium oxide and zirconium oxide.

10. A method for producing hydrogen peroxide, which comprises a step of reacting oxygen with hydrogen in the presence of a noble metal-supporting material as described in any one of 1. to 9. (this will also be referred to hereunder as "the present method for producing hydrogen peroxide").

11. A method for producing alkylene oxide, which comprises a step of reacting oxygen, hydrogen and an olefin in the presence of a noble metal-supporting material as described in any one of 1. to 9. and a titanosilicate-containing catalyst (this will also be referred to hereunder as "the present method for producing alkylene oxide").

12. The method as described in 11., wherein the olefin is propylene. 13. The method as described in 11. or 12., wherein the titanosilicate-containing catalyst comprises titanosilicate particles having an X-ray diff action pattern with peaks at the positions indicated by lattice spacings d/A of 12.4 ±0.8, 10.8 ±0.5, 9.0 ±0.3, 6.0 ±0.3, 3.9 ±0.3 and 3.4 ±0.1.

14. The method as described in any one of 11. to 13., wherein the step is a step of reacting oxygen, hydrogen and an olefin in the presence of a solvent.

15. The method as described in 14., wherein the solvent is an organic solvent.

16. The method as described in 14., wherein the solvent is a mixed solvent comprising an organic solvent and water.

17. The method as described in 15. or 16., wherein the organic solvent is acetonitrile.

Advantageous Effects of Invention

[0007] The present invention can provide a novel catalyst capable of producing a high alkylene oxide yield when used in combination with a titanosilicate-containing catalyst in a reaction for production of an alkylene oxide from oxygen, hydrogen and an olefin.

Brief Description of Drawings

[0008] Fig. 1 is a graph showing the hydrogen desorption spectrum of the present noble metal-supporting material (A), and a method for calculating a desorbed amount of hydrogen.

Fig. 2 is a graph showing the hydrogen desorption spectrum of the reference noble metal-supporting material (1), and a method for calculating a desorbed amount of hydrogen.

Description of Embodiments

[0009] The present noble metal-supporting material comprises a noble metal and a carrier as constituent components, the ratio (MH₂/MCO) of a desorbed amount of hydrogen (MH₂) to an adsorbed amount of carbon monoxide(MCO) being in the range of 0.01 to 0.40.

[0010] The "desorbed amount of hydrogen (MH₂)" is the value calculated from the sum of the areas of the peaks of the desorbed component having a maximum value in the range of 50°C to 350°C, as observed in accordance with a temperature-programmed desorption method with a programming rate of 10°C/min, with regard to a sample left in a vacuum at 50°C for 8 hours or more, under a normal pressure helium gas stream at 50°C for 1 hour, then under a normal pressure hydrogen gas stream at 50°C for 2 hours, and further left under a normal pressure helium gas stream at 50°C for 1 hour and thereby obtained.

[0011] The " desorbed amount of hydrogen (MH₂)" can be calculated from the hydrogen desorption spectrum obtained by temperature-programmed desorption method with the following equipment and measuring conditions.

• Detector: TPD-l-ATw, Fully automatic thermal desorption spectrometer by Bel Japan, Inc.

• Gas flow rate: 50 mL/min

· Sample weight: approximately 0.15 g

Pretreatment: Vacuum treatment at 50°C for 8 hours, followed by treatment under a normal pressure helium gas stream at 50°C for 1 hour, a normal pressure hydrogen gas stream at 50°C for 2 hours and a normal pressure helium gas stream at 50°C for 1 hour, in that order.

· Measurement Conditions: Hydrogen desorption spectrum by temperature-programmed desorption method under a normal pressure helium gas stream, with a programming rate of 10°C/min.

• Detection: Quadrupole MS

• Detected fragment: m/z = 2

· Calculation of MH₂: The sum of the areas under the peaks for the desorbed component with a maximum in the range of 50°C to 350°C was calculated.

[0012] The upper limit of MH₂ may be for example 0.10 cm /g or less, and preferably 0.08 cm /g or less, while the lower limit of MH₂ may be for example 0.01 cm /g or more, and preferably 0.03 cm /g or more.

[0013] The "adsorbed amount of carbon monoxide (MCO)" is a value as measured by metal surface area measurement based on the carbon monoxide pulse method, of a sample left in a vacuum at 50°C for 8 hours or more, under a normal pressure helium gas stream at 50°C for 1 hour, then under a normal pressure hydrogen gas stream at 50°C for 2 hours, and further left under a normal pressure helium gas stream at

50°C for 1 hour and thereby obtained.

[0014] The "adsorbed amount of carbon monoxide (MCO)" can be calculated after measurement with the following equipment and measuring conditions.

· Detector: BEL-METAL-3SP metal dispersion rate measuring apparatus by Bel Japan, Inc.

• Gas flow rate: 50 mL/min

• Sample weight: approximately 0.15 g

• Pretreatment: Vacuum treatment at 50°C for 8 hours, followed by treatment under a normal pressure helium gas stream at 50°C for 1 hour, a normal pressure hydrogen gas stream at 50°C for 2 hours and a normal pressure helium gas stream at 50°C for 1 hour, in that order.

• Conditions: Carbon monoxide pulse injection under normal pressure helium gas stream, measurement of carbon monoxide adsorption.

[0015] The upper limit of MCO may be for example 1.00 cm /g or less, and preferably 0.50 cm /g or less, while the lower limit of MCO may be for example 0.10 cm /g or more, and preferably 0.20 cm /g or more.

[0016] The noble metal-supporting material of the present embodiment may have MH₂/MCO in the range of 0.01 to 0.40, but preferably the peaks of the desorbed component having a maximum value in the range of 50°C to 350°C as observed in the temperature-programmed desorption method with the programming rate of 10°C/min does not have a maximum value between 50°C and 210°C, and have one or more maximum values in the range of 210°C to 350°C.

[0017] Examples of the carrier include oxides such as silicon oxide, aluminum oxide, titanium oxide, zirconium oxide and niobium oxide, hydroxides such as niobic acid, zirconic acid, tungstic acid and titanic acid, carbon, and mixtures of the foregoing. Active carbon, aluminum oxide, titanium oxide and zirconium oxide are preferred examples.

[0018] The noble metal content may be, for example, 0.00001 part by weight or more to 100 parts by weight of the present noble metal-supporting material, with 0.01 part by weight or more being preferred, 0.1 part by weight or more being more preferred, a range of 0.01 part by weight to 20 parts by weight being yet more preferred, and a range of 0.1 part by weight to 5 parts by weight being especially preferred.

[0019] The noble metal-supporting material can be obtained, for example, by contacting a carrier with a noble metal dispersion that contains noble metal particles.

As a general range, the noble metal particles have a mean particle size in the range of 1 nm to 200 nm, and preferably they contain an iron component in the range of 0.1 % by weight to 3 % by weight with respect to the total. More preferably, the streaming potential of the noble metal particles as a 0.5 % by weight aqueous dispersion is in the range of 10 μeq/g to 50

Noble metal particles that satisfy this condition have a shorter pot life, but exhibit superior catalytic activity. Their streaming potential is measured using a streaming potential meter (PCD-03-PH by Mutec, Germany being a specific example).

[0020] In another mode of the noble metal particles, portions of the surfaces of the noble metal particles may form oxides and/or hydroxides, and it is preferred for at least about 25% of the surfaces of the noble metal particles to be covered by oxides and/or hydroxides.

[0021] The "noble metal dispersion" used in production of the noble metal-supporting material may be obtained, for example, by treating (a) a noble metal particle precursor, or (b) a mixture of a noble metal particle precursor and a solvent, by either of the following method A or

B.

Method A: Mixture of component (a) or (b) with an acid-containing solution.

Method B: Partial oxidation of component (a) or (b) with an oxidizing agent to cover the particle surfaces with an oxide and/or hydroxide.

[0022] The "noble metal particle precursor" can be obtained by reducing a noble metal salt (preferably both a noble metal salt and an iron salt) in water, an organic solvent or a mixture of the two, in the presence of a reducing agent.

[0023] A preferred "noble metal particle precursor" has a streaming potential in the range of 50 to 300 μeq/g as a 0.5 % by weight aqueous dispersion, because a noble metal particle precursor satisfying this condition will exhibit a longer pot life and superior manageability.

[0024] The "noble metal salt" may be, for example, a chloride, nitrate, sulfate, acetate or organic acid salt of palladium, platinum, ruthenium, rhodium, iridium, osmium or gold, or a combination of the foregoing.

Specific examples include gold chloride, palladium chloride, palladium nitrate, palladium acetate and ruthenium chloride, as well as their combinations.

[0025] Examples of "iron salts" include organic acid salts of iron such as iron acetate, inorganic acid salts of iron such as iron chloride, iron nitrate and iron sulfate, and combinations of the foregoing.

[0026] Examples of "organic solvent" include alcohols such as 4-hydroxy-4-methyl-2-pentanone and tetrahydroforfuryl alcohol, ethers such as propyleneglycol monomethyl ether and diethyleneglycol monoethyl ether, and combinations of the foregoing.

[0027] Examples for the "reducing agent" include ferrous sulfate, ferrous ammonium sulfate, ferrous oxalate, trisodium citrate, tartaric acid, L(+)-ascorbic acid, sodium borohydride and sodium hypophosphite. Preferred examples include ferrous sulfate and ferrous ammonium sulfate.

[0028] The following is a detailed explanation of a method wherein either a noble metal particle precursor or a mixture of the noble metal particle precursor with a solvent, prepared in the manner described above, (a) is mixed with an acid-containing solution (also referred to hereunder as "method A") or (b) is partially oxidized with an oxidizing agent (also referred to hereunder as "method B"). [0029] In method A, the acid may be, for example, an inorganic acid such as nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, perchloric acid, boric acid or fluorosulfonic acid, an organic acid such as formic acid, acetic acid, propionic acid or tartaric acid, or any combination of the foregoing. Preferred examples are hydrochloric acid, phosphoric acid, and organic acids.

The acid will usually be used in the form of a solution prepared by dissolution in a solvent, where "solvent" refers to water, or an alcohol, ether, ester or ketone, or any mixture of the foregoing, with water being preferred.

The concentration of the acid in the solution may be between 0.01 % by weight and 99 % by weight, with a preferred range of between 0.1 % by weight and 50 % by weight.

[0030] Either the noble metal particle precursor or the mixture of the noble metal particle precursor and the solvent is mixed with the acid-containing solution at a temperature in the range of, for example, 0°C to 100°C, and preferably 20°C to 80°C. The duration for mixture of either the noble metal particle precursor or the mixture of the noble metal particle precursor and the solvent with the acid-containing solution may be in the range of 0.1 hours to 240 hours, and is preferably between 0.5 hours and 24 hours.

[0031] For method B, the "oxidizing agent" may be, for example, oxygen, hydrogen peroxide, ozone, a permanganate, an alkali metal or alkaline earth metal nitrate or nitrite, or any combination of these. It is preferably a combination of oxygen and an alkali metal or alkaline earth metal nitrite. It is more preferably a combination of oxygen and sodium nitrite.

[0032] The oxidizing agent will be added in varying amounts depending on its type, but it is preferably an amount that allows some portions of the noble metal particle surfaces (at least about 25% being most desirable) to be converted to metal oxides and/or hydroxides.

More specifically, the oxidizing agent may be added in the range of 0.01 mol to 0.2 mol and preferably in the range of 0.02 mol to 0.15 mol, to 1 mol of the total metals. The oxidizing conditions are not especially restricted, and may include heating and stirring, as necessary.

[0033] The method for producing a noble metal-supporting material may be, for example, an ordinary wet loading method by impregnation, dipping, wet adsorption, ion-exchange or solvent evaporation, or any combination of the foregoing.

[0034] The solvents used for such wet loading methods may be, for example, aqueous solvents, nonaqueous solvents, or mixtures thereof.

Such solvents preferably ones that can maintain stability as uniform colloid solutions.

[0035] Examples of such solvents include water solvents such as purified water, ion-exchanged water, tap water and industrial water; alcohols such as methanol, ethanol, isopropanol, hexanol and octanol; hydrocarbon solvents such as pentane, petroleum ether, hexane, cyclohexane, benzene, toluene and xylene; ketones such as acetone, ethyl methyl ketone, cyclohexanone and acetophenone; halogenated hydrocarbon-based solvents such as methyl chloride, methylene chloride, chloroform, carbon tetrachloride, dichloroethane, tetrachloroethane, propyl chloride, chlorobenzene, dichlorobenzene and methyl fluoride; esters such as methyl acetate, ethyl acetate and propyl acetate; ethers such as diethyl ether, dipropyl ether, tetrahydrofuran and dioxane; nitriles such as acetonitrile and propionitrile; organic acids such as acetic acid and propionic acid; amines such as dimethylamine, trimethylamine, triethylamine, propylamine and aniline; and amides such as dimethylformamide, diethylformamide and dimethylacetamide, with water being preferred. These solvents may be used alone or in any desired combinations.

There are no special restrictions on the amount of solvent that is used, but it is preferably an amount sufficient for thorough contact with the entire carrier. A very excessive amount of solvent will require a long time for drying, but conversely, too little solvent will not easily allow uniform dispersion on the carrier.

[0036] The system employed for loading by a wet loading method may be based on stationing, stirring, solution circulation, solvent reflux or the like, or any combination thereof.

[0037] The noble metal-supporting material can be obtained in the manner described above. When an excess of solvent or noble metal-containing solution is present with the obtained noble metal-supporting material, it will usually be desirable to separate and remove the excess portion, or to evaporate off the excess solvent or noble metal-containing solution and recover the present noble metal-supporting material.

The method for accomplishing this may be a common solid-liquid separation process involving steps such as filtration, centrifugal separation and decantation. Evaporation of the excess solvent or noble metal-containing solution can be accomplished, for example, by natural evaporation, reduced pressure evaporation, ventilating evaporation or bubble evaporation by air circulation.

[0038] The noble metal-supporting material obtained as described above may be used as is, or if necessary, it may be subjected to ordinary heat treatment in an oven or the like, or heated with an inert gas, reduced with a reducing gas such as hydrogen, carbon monoxide, methane, ethane, propane, butane, ethylene, propylene, butene or butadiene, oxidized with an agent such as air, or treated by any combination of the above as appropriate pretreatment or activating treatment, before use as a catalyst for reaction.

[0039] The noble metal-supporting material catalyst can be used as a catalyst for production of hydrogen peroxide from oxygen and hydrogen. It can also be used as a catalyst for production of an alkylene oxide from hydrogen, oxygen and an olefin. The noble metal-supporting material catalyst may be used together with a titanosilicate-containing catalyst (either in integrated form or separately), to obtain a high yield of an alkylene oxide from oxygen, hydrogen and an olefin.

The noble metal-supporting material catalyst also has high selectivity for alkylene oxides and low selectivity for alkanes, based on hydrogen (that is, the product has a low content of by-products such as propane).

[0040] A method for producing hydrogen peroxide according to this embodiment will now be described. The method for production of hydrogen peroxide comprises a step of reacting oxygen with hydrogen in the presence of the present noble metal-supporting material.

[0041] Oxygen and hydrogen are required for this step, and they may be obtained from any sources. For oxygen, high-purity oxygen gas produced by cryogenic separation, oxygen gas produced by an economical pressure swing process, or air, may be used.

The molar ratio of hydrogen and oxygen used in the step (1¾:θ2) may be in the range of 1:50 to 50:1, for example, with 1 :10 to 10:1 being a preferred range, and 1:5 to 5:1 being a more preferred range.

[0042] An inert gas may also be used in the step with the oxygen and hydrogen, for dilution. Examples of suitable inert gases include helium, argon, nitrogen, methane, ethane, propane and carbon dioxide, with nitrogen being preferred. Using an inert gas in the reactor will allow the oxygen and hydrogen levels in the reaction mixture to be advantageously maintained within the explosion limit.

[0043] The process may also be carried out in the presence of a solvent.

The solvent may be water, an organic solvent or a mixture of the two. Examples of organic solvents include alcohol solvents with 1 to 12 carbon atoms such as methanol, ethanol, isopropyl alcohol and glycerin, ketone solvents with 3 to 12 carbon atoms such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone and cyclohexenone, nitrile solvents with 2 to 12 carbon atoms such as acetonitrile, propionitrile, isobutyronitrile, butyronitrile and benzonitrile, ether solvents such as diethyl ether, tetrahydrofuran and propyleneglycol dimethyl ether, aliphatic hydrocarbon solvents with 5 to 12 carbon atoms such as pentane, cyclopentane, hexane, cyclohexane, ethylene dichloride and chloroform, aromatic hydrocarbon solvents with 6 to 12 carbon atoms such as benzene, toluene, xylene and chlorobenzene, ester solvents such as ethyl acetate, butyl acetate and propyleneglycol diacetate, and any mixtures of the foregoing. It is preferred to use a nitrile solvent or alcohol solvent alone, or a mixture of a nitrile solvent or alcohol solvent with water. A more preferred example is a mixture of acetonitrile or methanol with water.

When a mixture of water and an organic solvent is used, the water/organic solvent ratio (weight ratio) may be in the range of 90:10 to 0.01 :99.99, for example, with the preferred range being 50:50 to 0.1 :99.9.

[0044] The method for production of hydrogen peroxide may be conducted in any desired mode, such as continuous-flow, semi-batch or batch mode, although continuous flow mode is preferred. The present noble metal-supporting material may also be used in a slurry or fixed bed.

[0045] The reaction temperature for production of hydrogen peroxide may be in the range of 0°C to 100°C, for example, with the preferred range being 20°C to 60°C. The lower limit for the reaction pressure for production of hydrogen peroxide may be at least 0.1 MPa, and preferably 1 MPa, while the upper limit may be 20 MPa, and preferably

10 MPa.

[0046] It will often be advantageous to carry out the method for producing hydrogen peroxide in the presence of an acid.

An acid used in the present method for producing hydrogen peroxide may be an inorganic acid such as nitric acid, sulfuric acid, phosphoric acid, hydrochloric acid or hydrobromic acid, or an organic acid such as pyrophosphoric acid or acetic acid.

The amount of acid used may be in the range of 0.1 ppm to 1000 ppm to 1 part by weight of the reaction mixture, with a preferred range being between 0.1 ppm and 100 ppm, and a more preferred range being between 1 ppm and 10 ppm.

[0047] A method for producing an alkylene oxide according to this embodiment will now be described. Specifically, the method comprises a step of reacting oxygen, hydrogen and an olefin in the presence of a noble metal-supporting material and a titanosilicate-containing catalyst.

[0048] Examples of titanosilicate-containing catalysts include catalysts referred to as titanosilicate particles. The titanosilicate particles essentially have a structure with a tetracoordinated Ti atom, the ultraviolet and visible absorption spectrum in the wavelength range of 200 nm to 400 nm having an absorption peak maximum in the wavelength range of 210 nm to 230 nm (see Chemical Communications 1026-1027(2002) Fig. 2(d), (e), for example). The ultraviolet and visible absorption spectrum can be measured by the diffuse reflection method, using an ultraviolet and visible spectrophotometer equipped with a diffuse reflection sensor.

[0049] When the titanosilicate particles are to be used, for example, as a catalyst in a method for producing hydrogen peroxide by reaction of oxygen and hydrogen in the presence of the present noble metal-supporting material (that is, in the present method for producing hydrogen peroxide), titanosilicate particles that have been pre-contacted with hydrogen peroxide may be used. The hydrogen peroxide to be provided for contact may be at a concentration in the range of 0.0001 % by weight to 50 % by weight, for example.

[0050] Examples of titanosilicate particles include the following titanosilicates listed as 1 to 7.

[0051] 1. Crystalline titanosilicates with pores formed by 10-membered oxygen rings:

TS-1 having an MFI structure (for example, US 4,410,501 B), TS-2 having an MEL structure (for example, Journal of Catalysis 130, 440-446, (1991)), Ti-ZSM-48 having an MRE structure (for example, Zeolites 15, 164-170, (1995)) and Ti-FER having an FER structure (for example, Journal of Materials Chemistry 8, 1685-1686 (1998)), based on the IZA (International Zeolite Association) structure code.

[0052] 2. Crystalline titanosilicates with pores formed by 12-membered oxygen rings:

Ti-Beta having a BEA structure (for example, Journal of Catalysis

199,41-47,(2001)), Ti-ZSM-12 having an MTW structure (for example, Zeolites 15, 236-242, (1995)), Ti-MOR having an MOR structure (for example, The Journal of Physical Chemistry B 102, 9297-9303, (1998)), Ti-ITQ-7 having an ISV structure (for example, Chemical Communications 761-762,(2000)), Ti-MCM-68 having an MSE structure (for example, Chemical Communications 6224-6226, (2008)), and Ti-MWW having an MWW structure (for example, Chemistry Letters 774-775, (2000)).

[0053] 3. Crystalline titanosilicates with pores formed by 14-membered oxygen rings:

Ti-UTD-1 having a DON structure (for example, Studies in Surface Science and Catalysis 15, 519-525, (1995)).

[0054] 4. Layered titanosilicates with pores formed by 10-membered oxygen rings:

Ti-ITQ-6 (for example, Angewandte Chemie International Edition 39, 1499-1501, (2000)).

[0055] 5. Layered titanosilicates with pores formed by 12-membered oxygen rings:

Ti-MWW precursors (for example, EP 1731515 Al), Ti-YNU-1 (for example, Angewandte Chemie International Edition 43, 236-240(2004)), Ti-MCM-36 (for example, Catalysis Letters 113,

160-164(2007)), Ti-MCM-56 (for example, Microporous and Mesoporous Materials 113, 435-444(2008)).

[0056] 6. Mesoporous titanosilicates:

Ti-MCM-41 (for example, Microporous Materials 10, 259-271, (1997)), Ti-MCM-48 (for example, Chemical Communications 145-146,

(1996)), Ti-SBA-15 (for example, Chemistry of Materials 14, 1657-1664, (2002)).

[0057] 7. Silylated titanosilicates:

Compounds that are silylated forms of the titanosilicates listed above, such as silylated Ti-MWW.

[0058] As used herein, "pore" refers to an opening formed by Si-O bonds or Ti-O bonds. The pores may be, for example, half-cup pores known as "side pockets" (that is, it is not essential that they penetrate the primary particles of the titanosilicate).

The phrase "not smaller than an X-membered oxygen ring" (X being an integer) will be used hereunder to signify that at least X oxygen atoms constitute the ring structure either (a) at a cross-section at the narrowest part of the pore or (b) at the entrance of the pore. Generally, it can be confirmed that titanosilicate particles have pores not smaller than an X-membered oxygen ring by analysis of the X-ray diffraction pattern, and if the structure is known, this can be easily confirmed by comparison with the X-ray diffraction pattern.

[0059] "Layered titanosilicate" is a term that includes all titanosilicates with a layered structure, such as layered precursors of crystalline titanosilicates or titanosilicates that result from expansion between layers of crystalline titanosilicates. A layered structure can be confirmed with an electron microscope or by analysis of the X-ray diffraction pattern. "Layered precursor" is a titanosilicate that forms a crystalline titanosilicate by treatment such as dehydrating condensation. That the layered titanosilicate has pores not smaller than a 12-membered oxygen ring can be easily confirmed by analyzing the structure of the corresponding crystalline titanosilicate.

[0060] "Mesoporous titanosilicate" is a term including all titanosilicates having regular mesopores. "Regular mesopores" denotes a structure with a regularly repeating arrangement of mesopores. A mesopore is a pore having a pore size of 2 nm to 10 nm.

[0061] The term "silylated titanosilicate" refers to a compound obtained by treatment of any of the titanosilicates listed as 1. to 4. above, using a silylating agent. Examples of silylating agents include 1,1,1,3,3,3-hexamethyldisilazane and trimethylchlorosilane (as described in EP 1488853A1, for example). The silylated titanosilicate may also be mixed with a hydrogen peroxide solution (this may be referred to hereunder as "hydrogen peroxide treatment"). The concentration of the hydrogen peroxide solution used for such hydrogen peroxide treatment may be in the range of 0.0001 % by weight to 50 % by weight, for example. The solvent of the hydrogen peroxide solution may be, for example, water, or the same solvent used in the present method for producing alkylene oxide. The temperature for hydrogen peroxide treatment may be in the range of 0°C to 100°C, for example, with a preferred range of 0°C to 60°C. The mixing time will depend on the hydrogen peroxide concentration but will generally be in the range of 10 minutes to 10 hours, the preferred range being 1 hour to 3 hours.

[0062] The preferred type of titanosilicate particles consist of titanosilicate having pores not smaller than a 12-membered oxygen ring. The titanosilicate may be either crystalline or layered titanosilicate. Titanosilicate having pores not smaller than a 12-membered oxygen ring include, specifically, Ti-MWW and Ti-MWW precursors.

[0063] The titanosilicate particles having pores not smaller than a 12-membered oxygen ring most desirably exhibit an X-ray diffraction pattern with peaks at the following positions, as lattice spacings.

<Positions of peaks in X-ray diffraction pattern as lattice spacings

(lattice spacing d/angstrom)>

12.4 ±0.8, 10.8 ±0.5, 9.0 ±0.3, 6.0 ±0.3, 3.9 ±0.3, 3.4 ±0.1

[0064] The X-ray diffraction pattern can be measured in the following manner.

[0065] A common commercially available X-ray diffraction apparatus with copper K-alpha radiation as the line source may be used. For example, the titanosilicate particle sample may be analyzed using an RINT2500V X-ray diffraction apparatus by Rigaku Corp.

(Measuring conditions)

• Output: 40 kV-300 mA

· Scanning zone: 2Θ = 0.75-20°

• Scanning rate: 1 min

[0066] Specific examples of titanosilicate particles that exhibit such an X-ray diffraction pattern (having peaks at the aforementioned positions represented as lattice spacings) include Ti-MWW precursors (for example, those mentioned in JP 2005-262164 A), Ti-YNU-1 (for example, those mentioned in (Angewandte Chemie International Edition) 43, 236-240(2004)), Ti-MWW compounds which are crystalline titanosilicates with an MWW structure based on the IZA (International Zeolite Association) structure code (for example, those mentioned in JP 2003-327425 A), and Ti-MCM-68 compounds which are crystalline titanosilicates with an MSE structure based on the IZA structure code (for example, those mentioned in JP 2008-50186 A).

[0067] A Ti-MWW precursor is a titanosilicate that has a layered structure and forms Ti-MWW by dehydrating condensation. The dehydrating condensation will usually be carried out by heating the

Ti-MWW precursor at a temperature of higher than 200°C and no higher than 1000°C, and preferably between 300°C and 650°C. During the production method, the Ti-MWW precursor may also be treated with a structural control agent, as described hereunder. The resulting Ti-MWW precursor may then be subjected to repeat treatment with a structural control agent. Ti-MWW precursors obtained in this manner are also included within the term "Ti-MWW precursor" for the purpose of the invention.

[0068] Such a Ti-MWW precursor can be used as a catalyst for various forms of oxidation reaction. The molar ratio of silicon and nitrogen (Si/N ratio) in the Ti-MWW precursor may be in the range of 5 to 100, for example, with 10 to 20 as the preferred range.

[0069] The following are specific methods for producing Ti-MWW precursors.

[0070] (1) First method: A method comprising a step of heating a mixture containing a structural control agent, a compound that contains an element of Group 13 of the Periodic Table (hereunder referred to as "Group 13 element-containing compound"), a silicon-containing compound, a titanium-containing compound and water (hereunder referred to as "step (1-1)"), and a step of mixing the layered compound obtained in step ( 1 - 1 ) with an acid.

[0071] (2) Second method: A method comprising a step of heating a mixture containing a structural control agent, a Group 13 element-containing compound, a silicon-containing compound and water (hereunder referred to as "step (2-1)"), and a step of mixing the layered compound obtained in step (2-1) with a titanium-containing compound and an acid.

[0072] (3) Third method: A method comprising a step of heating a mixture containing a structural control agent, a Group 13 element-containing compound, a silicon-containing compound, a titanium-containing compound and water (hereunder referred to as "step

(3-1)"), and a step of mixing the layered compound obtained in step (3-1) with a titanium-containing compound and an acid.

[0073] (4) Fourth method: A method comprising a step of first obtaining a layered borosilicate by heating a mixture comprising a structural control agent, a Group 13 element-containing compound, a silicon-containing compound and water (preferably after removing the structural control agent by contact with an acid or the like), firing it to obtain B-MWW, subsequently deboronating the B-MWW with an acid or the like and then combining this with a structural control agent, a titanium-containing compound and water, heating the obtained mixture to obtain a layered compound, and subsequently contacting this compound with approximately 6 M nitric acid (see Chemical Communication 1026-1027(2002), for example).

[0074] Ti-MWW precursors obtained by any of the first to fourth methods are preferably subjected to additional treatment with a structural control agent to adjust the molar ratio of silicon and nitrogen

(Si/N ratio) to the prescribed values (for example, values within the range of 10 to 20).

[0075] For example, the titanosilicate-containing catalyst may be mixed with the structural control agent and water in an airtight pressure-resistant container such as an autoclave, the container sealed and the contents allowed to stand or stirred, under heat and pressure, to obtain a liquid mixture from which the solid product is separated by filtration, centrifugal separation or the like. Alternatively, the components may be mixed in a glass flask under atmospheric pressure, with or without stirring, and the solid product separated out from the resulting liquid mixture by filtration, centrifugal separation or the like. [0076] The titanosilicate-containing catalyst can also be rinsed with water, for example. The rinsing may be carried out with appropriate adjustment of the amount of washing solution, or while monitoring the pH of the rinsing filtrate, as necessary. The rinsed product may then be dried by blow drying, reduced pressure drying, vacuum freeze-drying or the like in a temperature range of 0°C to 200°C, for example, until no further weight reduction occurs.

[0077] The temperature for the mixing procedure may be in the range of 0°C to 250°C, for example, with a preferred range of between 20°C and 200°C and a more preferred range of between 50°C and 180°C.

[0078] The duration of the mixing procedure may be in a range of between 1 hour and 720 hours, for example, with 2 hours to 720 hours being preferred, 4 hours to 720 hours being more preferred, and 8 hours to 720 hours being especially preferred. The pressure during the mixing procedure is not particularly restricted, and may be a gauge pressure of 0 MPa to 10 MPa, for example.

[0079] The amount of titanium-containing compound used in the methods described above may be in the range of 0.001 to 1 part by weight, for example, as the weight of titanium atoms in the titanium-containing compound with respect to 1 part by weight of the layered compound that is obtained, with a range of 0.01 to 0.5 part by weight being preferred.

[0080] The acid used in the aforementioned methods may be, for example, an inorganic acid such as nitric acid, hydrochloric acid, sulfuric acid, perchloric acid, boric acid or fluorosulfonic acid, an organic acid such as formic acid, acetic acid, propionic acid or tartaric acid, or any combination of the foregoing. Preferably, the acid includes at least one inorganic acid with a higher oxidation-reduction potential than tetravalent titanium. The "inorganic acid with a higher oxidation-reduction potential than tetravalent titanium" may be nitric acid, perchloric acid, fluorosulfonic acid, a combination of nitric acid and sulfuric acid or a combination of nitric acid and boric acid, for example.

[0081] The acid will usually be used in the form of a solution prepared by dissolution in a solvent. Here, "solvent" refers to, for example, water, or an alcohol, ether, ester or ketone solvent, or any mixture of the foregoing, with water being preferred. The concentration of the acid in the solution may be between 0.01 mol/1 and 20 mol/1, for example. When an inorganic acid is used, its concentration is preferably in the range of 1 mol/1 to 5 mol/1.

[0082] The "element of Group 13 of the Periodic Table", which is to be used in the method for producing a Ti-MWW precursor, may be present in a boron-containing compound, aluminum-containing compound or gallium-containing compound, for example, among which boron-containing compounds are preferred.

Examples of boron-containing compounds include boric acid, boric acid salts, boron oxide, boron halides, and trialkylboron compounds having alkyl groups with 1 to 4 carbon atoms, among which boric acid is preferred. Sodium aluminate is an example of an aluminum-containing compound. Gallium oxide is an example of a gallium-containing compound.

[0083] The amount of Group 13 element-containing compound used in the method for producing a Ti-MWW precursor may be in the range of 0.01 mol to 10 mol to 1 mol of silicon in the silicon-containing compound, with a preferred range of 0.1 mol to 5 mol.

[0084] Examples for the "silicon-containing compound" to be used in the method for producing a Ti-MWW precursor include silicic acid, silicates, silicon oxide, silicon halides, tetraalkylorthosilicates and colloidal silica, with preferred examples including orthosilicic acid, metasilicic acid, meta-disilicic acid. Examples of silicates include alkali metal silicates such as sodium silicate and potassium silicate, and alkaline earth metal silicates such as calcium silicate and magnesium silicate.

[0085] Examples of silicon oxides include crystalline silicas such as quartz, and amorphous silicas such as fumed silica, among which fumed silica is a preferred example. The "fumed silica" may be any commercially available product with a BET specific surface area of 50 m /g to 380 m /g. Manageability will be facilitated if the BET specific surface area is 50 m /g to 200 m /g, while solubility in aqueous solutions will be improved if the BET specific surface area is 100 mVg to 380 m²/g.

[0086] Examples of silicon halides include silicon tetrachloride and silicon tetrafluoride.

[0087] Examples of tetraalkylorthosilicates include tetramethyl orthosilicate and tetraethyl orthosilicate.

[0088] Examples for the "titanium-containing compound" to be used in the method for producing a Ti-MWW precursor include titanium alkoxides, titanates, titanium oxides, titanium halides, inorganic acid salts of titanium and organic acid salts of titanium.

Examples of titanium alkoxides include titanium alkoxides having alkoxy groups with 1 to 4 carbon atoms, such as tetramethyl orthotitanate, tetraethyl orthotitanate, tetraisopropyl orthotitanate and tetra-n-butyl orthotitanate, among which titanium alkoxides are preferred examples, and tetra-n-butyl orthotitanate is an especially preferred example.

[0089] Titanium acetate is an example of an organic acid salt of titanium, while examples of inorganic acid salts of titanium include titanium nitrate, titanium sulfate, titanium phosphate and titanium perchlorate.

[0090] Titanium tetrachloride is an example of a titanium halide, and titanium dioxide is an example of a titanium oxide.

[0091] The "water" to be used in the method for producing a Ti-MWW precursor may be purified water, such as distilled water or ion-exchanged water. The amount of water used may be in the range of 5 mol to 20 mol to 1 mol of silicon in the silicon-containing compound, the preferred range being 10 mol to 50 mol.

[0092] Examples of structural control agents to be used in the method for producing a Ti-MWW precursor (that is, structural control agents capable of forming zeolite with an MWW structure) include piperidine, hexamethyleneimine, N,N,N-trimethyl-l-adamantane ammonium salts (for example, N,N,N-trimethyl-l-adamantane ammonium hydroxide, N,N,N-trimethyl-l-adamantane ammonium iodide and the like) and octyltrimethylammonium salts (for example, octyltrimethylammonium hydroxide, octyltrimethylammonium bromide and the like) (see Chemistry Letters 916-917 (2007), for example). Preferred examples include piperidine and hexamethyleneimine. Any of these compounds may be used alone, or two or more thereof may be used in admixture in any desired proportion.

[0093] The amount of structural control agent used may be in the range of 0.1 mol to 5 mol to 1 mol of silicon in the silicon-containing compound, with a preferred range of 0.5 mol to 3 mol.

[0094] The amount of structural control agent used for structural control agent treatment of the Ti-MWW precursor may be, for example, in the range of 0.001 to 100 parts by weight to 1 part by weight of the titanosilicate, the preferred range being 0.1 to 10 parts by weight.

[0095] The amount of the present noble metal-supporting material used for reaction in the present method for producing alk lene oxide will differ depending on its type and on the reaction conditions, but it is preferably in the range of 0.01 to 20 parts by weight to 100 parts by weight of the entire mixture comprising the acetonitrile-containing solvent, the present noble metal-supporting material, the titanosilicate-containing catalyst and the starting materials, that is used in the reactor. A more preferred range is between 0.1 and 10 parts by weight, and an even more preferred range is between 0.5 and 8 parts by weight.

[0096] An "acetonitrile-containing solvent" is a solvent that contains acetonitrile, but it may include solvents other than acetonitrile. Examples of solvents other than acetonitrile include organic solvents other than acetonitrile, and water. The acetonitrile is preferably present in a weight ratio of 50% or more in the acetonitrile-containing solvent, with a preferred range of between 60% and 100%.

[0097] The "olefin", as one of the starting materials for the reaction in the present method for producing alkylene oxide, may be an optionally substituted hydrocarbyl compound, or a compound in which hydrogen is bonded to a carbon atom forming part of an olefin double bond.

[0098] Examples of substituents for the "hydrocarbyl group" include hydroxyl groups, halogen atoms, carbonyl groups, alkoxycarbonyl groups, cyano groups and nitro groups. Examples of hydrocarbyl groups include saturated hydrocarbyl groups such as alkyl groups.

[0099] Specific examples of olefins include alkenes with 2 to 10 carbon atoms and cycloalkenes with 4 to 10 carbon atoms.

[0100] Examples of "alkenes with 2 to 10 carbon atoms " include ethylene, propylene, butene, pentene, hexene, heptene, octene, nonene, decene, 2-butene, isobutene, 2-pentene, 3 -pentene, 2-hexene, 3 -hexene, 4-methyl-l -pentene, 2-heptene, 3 -heptene, 2-octene, 3 -octene,

2-nonene, 3-nonene, 2-decene and 3-decene. Examples of "C4-10 cycloalkenes" include cyclobutene, cyclopentene, cyclohexene, cycloheptene, cyclooctene, cyclononene and cyclodecene.

[0101] Examples of preferred olefins include alkenes with 2 to 10 carbon atoms, which are more preferably alkenes with 2 to 5carbon atoms, with propylene being especially preferred.

[0102] When the olefin is propylene, it may be produced by, for example, thermal decomposition, heavy oil catalytic cracking or methanol catalytic reforming.

[0103] The propylene may be purified propylene, or crude propylene obtained without a purification process. The propylene preferably has a purity of at least 90 % by volume, and more preferably at least 95 % by volume.

[0104] Propylene may contain impurities such as propane, cyclopropane, methylacetylene, propadiene, butadiene, butanes, butenes, ethylene, ethane, methane and hydrogen.

[0105] The propylene may be in the form of a gas or liquid. In this case, the "liquid" may be (i) liquid propylene alone, or (ii) a mixture of propylene dissolved in an organic solvent or a mixture of an organic solvent and water. A "gas" may be (i) gaseous propylene alone, or (ii) a mixture of gaseous propylene with nitrogen gas, hydrogen gas or another gas component.

[0106] The amount of propylene or other olefin will depend on its type and on the reaction conditions, but as an example, it may be 0.01 part by weight or more to 100 parts by weight of the mixture comprising the acetonitrile-containing solvent, titanosilicate-containing catalyst and starting materials in the reaction system, and this is more preferably 0.1 part by weight or more.

[0107] The titanium atom content in the titanosilicate of the titanosilicate-containing catalyst to be used for the present method for producing alkylene oxide may be in the range of 0.001 to 0.1 mol to 1 mol of silicon atoms, with a preferred range of 0.005 to 0.05 mol. The weight ratio of the noble metal with respect to titanosilicate (noble metal weight/titanosilicate weight) may be in the range of 0.01 % by weight to 100 % by weight and is preferably between 0.1 % by weight and 20 % by weight.

[0108] The solvent for the present method for producing alkylene oxide may be the same type of solvent used in the present method for producing hydrogen peroxide. It is preferably a nitrile solvent alone or a mixture of a nitrile solvent with water, and it is more preferably a mixture of acetonitrile and water.

[0109] When a mixture of water and an organic solvent is used, the water/organic solvent ratio (weight ratio) may be in the range of 90:10 to 0.01:99.99, for example, with a preferred range of between 50:50 and 0.1:99.9.

[0110] It will often be advantageous to carry out the present method for producing alkylene oxide in the presence of a buffering agent. Here,

"buffering agent" refers to a compound comprising an anion and cation that exhibit pH buffer action. The buffering agent is preferably dissolved in the reaction mixture, but the buffering agent may also be included in the present noble metal-supporting material. The buffering agent may be used in an amount in the range of 0.001 mmol/kg to 100 mmol/kg, with respect to 1 kg of the solvent.

[0111] The reaction temperature for the present method for producing alkylene oxide may be in the range of 0°C to 200°C, for example, with the preferred range being 40°C to 150°C. The reaction pressure (gauge pressure) may be 0.1 MPa or more, for example, with pressurization at 1 MPa or more being preferred, pressurization at 10 MPa or more being more preferred, and pressurization at 20 MPa or more being even more preferred.

[0112] An ammonium salt, alkylammonium salt, alkylarylammonium salt or the like may be added to the reaction system for the present method for producing alkylene oxide. [0113] Adding a buffering agent to the reaction system can prevent reduction in catalytic activity and further increase the catalytic activity, and will tend to improve the oxygen and hydrogen utilization efficiency. Here, "buffering agent" refers to a salt or other compound that has buffering action on the hydrogen ion concentration of the solution. Such buffering agents may be included in amounts up to solubility in the mixture that comprises the acetonitrile-containing solvent, the present noble metal-supporting material and the starting materials in the reaction system. A preferred range is between 0.001 mmol and 100 mmol, to 1 kg of the mixture.

[0114] The buffering agent may be one that comprises (1) an anion selected from a group consisting of sulfate ion, hydrogensulfate ion, carbonate ion, hydrogencarbonate ion, phosphorate ion, hydrogenphosphate ion, dihydrogenphosphate ion, hydrogenpyrophosphate ion, pyrophosphorate ion, halide ion, nitrate ion, hydroxide ion and carboxylate ions with 1 to 10 carbon atoms, and (2) a cation selected from among ammonium ion, alkylammonium ions with 1 to 20 carbon atoms, alkylarylammonium ions with 7 to 20 carbon atoms, alkali metals and alkaline earth metals.

[0115] Examples of carboxylate ions with 1 to 10 carbon atoms include acetate ion, formate ion, acetate ion, propionate ion, butyrate ion, valerate ion, caproate ion, caprylate ion, caprate ion and benzoate ion.

[0116] Examples of alkylammonium ions with 1 to 20 carbon atoms include tetramethylammonium, tetraethylammonium, tetra-n-propylammonium, tetra-n-butylammonium and cetyltrimethylammonium. [0117] Examples of cations selected from a group consisting of alkali metals and alkaline earth metals include lithium cation, sodium cation, potassium cation, rubidium cation, cesium cation, magnesium cation, calcium cation, strontium cation and barium cation.

[0118] Preferred examples of buffering agents include ammonium salts of carboxylic acids with 1 to 10 carbon atoms, such as ammonium sulfate, ammonium hydrogensulfate, ammonium carbonate, ammonium hydrogencarbonate, diammonium hydrogenphosphate, ammonium dihydrogenphosphate, ammonium phosphate, ammonium hydrogenpyrophosphate, ammonium pyrophosphate, ammonium benzoate and ammonium acetate, ammonium salts of inorganic acids such as ammonium chloride and ammonium nitrate, and ammonium salts of carboxylic acid such as ammonium acetate, the preferred ammonium salts being ammonium benzoate, ammonium dihydrogenphosphate and diammonium hydrogenphosphate.

[0119] The reaction in the method for producing alkylene oxide is preferably conducted in a continuous manner. For example, the starting materials may be continuously supplied to an epoxidated reaction tank holding an acetonitrile-containing solvent and a catalyst, and the reaction allowed to proceed inside the epoxidated reaction tank for production of alkylene oxide.

[0120] When hydrogen peroxide is to be produced from oxygen and hydrogen in the reaction in the method for producing alkylene oxide, the partial pressure ratio of oxygen and hydrogen in the oxygen/hydrogen mixed gas supplied to the reactor may be in the range of oxygen:hydrogen = 1:50 to 50:1, with the preferred range being oxygemhydrogen = 1:10 to 10:1. An oxygen partial pressure higher than oxygen:hydrogen = 1 :50 is preferred because it will tend to increase the alkylene oxide production rate, while an oxygen partial pressure of lower than oxygen:hydrogen = 50:1 is preferred because it will tend to reduce production of by-products resulting when the carbon/carbon double bonds of the olefin are reduced by hydrogen, and can thus increase the selectivity for the alkylene oxide.

[0121] The mixture of oxygen and hydrogen gas is preferably handled in the copresence of a diluent gas. The "diluent gas" may be nitrogen, argon, carbon dioxide, methane, ethane, propane, or the like, with nitrogen and propane being preferred, and nitrogen being especially preferred.

[0122] When the oxygen, hydrogen, olefin and diluent gas are to be treated as a mixture, the blending ratio (assuming nitrogen gas as the diluent gas) is preferably a total of 4.9 % by volume or less for the hydrogen and olefin, 9 % by volume or less for oxygen, and nitrogen gas as the remainder, or a total of 50 % by volume or more for the hydrogen and olefin, 50 % by volume or less for oxygen, and nitrogen gas as the remainder.

[0123] The oxygen used may be oxygen gas or air, which contains oxygen. The oxygen gas may be the product of an inexpensive pressure swing process, or if necessary it may be high purity oxygen gas produced by cryogenic separation. The oxygen supply may be in the range of 0.005 to 10 mol to 1 mol of the olefin, the preferred range being 0.05 to 5 mol.

[0124] The hydrogen may be obtained by steam reforming of a hydrocarbon. The hydrogen may be of a purity level of 80 % by volume or more, and preferably 90 % by volume or more. The hydrogen supply may be in the range of between 0.05 mol and 10 mol to 1 mol of the olefin, with the preferred range being 0.05 mol to 5 mol.

[0125] A quinoid compound is preferably added to the reaction system for production of hydrogen peroxide from oxygen and hydrogen by the present method for producing alkylene oxide, as this will further increase the selectivity for the alkylene oxide.

[0126] Examples of quinoid compounds include compounds represented by formula (1):

Y

wherein R¹, R², R³ and R⁴ each independently represent a hydrogen atom, or R¹ and R² or R³ and R⁴ may be bonded to each other to form a benzene ring that may have a substituent or a naphthalene ring that may have a substituent, together with carbon atoms to which R , R , R and R⁴ each are bonded, and X and Y each independently represent an oxygen atom or NH group.

[0127] Examples of compounds of formula (1) include:

1) quinone compounds (1A) of formula (1) wherein R¹, R², R³ and R⁴ are hydrogen and X and Y are both oxygen atoms,

2) quinoneimine compounds (IB) of formula (1) wherein R , R , R and R⁴ are hydrogen atoms, X is an oxygen atom and Y is an NH group, and 3) quinonediimine compounds (1C) of formula (1) wherein R¹, R², R³ and R⁴ are hydrogen atoms and X and Y are NH groups.

[0128] Examples of other compounds represented by formula (1) include anthraquinone compounds represented by formula (2):

Y

wherein X and Y have the same definitions as for formula (1), and R⁵,

R 6 , R 7 and R 8 each i ·ndependently represent hydrogen, hydroxyl group or alkyl group (for example, a alkyl group with 1 to 5 carbon atoms such as methyl group, ethyl group, propyl group, butyl group or pentyl group).

[0129] In formula (1), X and Y are preferably an oxygen atom.

Examples of compounds represented by formula (1) include quinone compounds such as benzoquinone and naphthoquinone; anthraquinones; 2-alkylanthraquinone compounds such as 2-ethylanthraquinone, 2-t-butylanthraquinone, 2-amylanthraquinone, 2-methylanthraquinone, 2-butylanthraquinone, 2-t-amylanthraquinone, 2-isopropylanthraquinone, 2-s-butylanthraquinone and

2-s-amylanthraquinone; polyalkylanthraquinone compounds such as

1.3- diethylanthraquinone, 2,3-dimethylanthraquinone,

1.4- dimethylanthraquinone and 2,7-dimethylanthraquinone; polyhydroxyantiiraquinone compounds such as

2,6-dihydroxyanthraquinone; p-quinoid compounds such as naphthoquinone, 1 ,4-phenanthraquinone; and o-quinoid compounds such as 1,2-phenanthraquinone, 3,4-phenanthraquinone and 9,10-phenanthraquinone. Preferred compounds include anthraquinone and 2-alkylanthraquinone compounds (compounds of formula (2) wherein X and Y are an oxygen atom, R⁵ is an alkyl group, R⁶ is a hydrogen atom and R and R are a hydrogen atom).

[0130] The amount of such quinoid compounds used in the reaction of the present method for producing alkylene oxide may be in the range of 0.001 to 500 mmol, for example, for 1 kg of solvent, with a preferred range of 0.01 mmol to 50 mmol.

[0131] The quinoid compound can be prepared by oxidation of the dihydro form of the quinoid compound in the reactor using oxygen. For example, a quinoid compound such as 9,10-anthracenediol or a hydrogenated compound such as hydroquinone may be added to the liquid phase and oxidized by oxygen in the reactor to generate a quinoid compound.

Examples of dihydro forms of quinoid compounds include compounds represented by formula (3):

(wherein R¹, R², R³, R⁴, X and Y have the same meanings as above), which are dihydro forms of compounds represented by formula (1), and compounds represented by formula (4):

YH

(wherein X, Y, R , R , R and R have the same meanings as above), which are dihydro forms of compounds represented by formula (2).

[0132] Preferred compounds among those represented by formula (3) and formula (4) include dihydro forms corresponding to the aforementioned preferred quinoid compounds. Also, X and Y in the compounds represented by formula (3) and formula (4) are preferably oxygen atoms.

Examples

[0133] The invention will now be explained in greater detail by the following examples.

[0134] <Analyzers used in the examples>

(Elemental analysis)

The Pd (palladium), Ti (titanium), Si (silicon) and B (boron) contents of the present noble metal-supporting materials, the noble metal particles and the noble metal particle precursors were measured by a method based on alkali fusion-nitric acid solution-ICP luminescence analysis. Specifically, a 20 mg sample was measured out into a platinum crucible and covered with sodium carbonate, and then fused with a gas burner. After fusion, the contents of the platinum crucible were heated to melting with purified water and nitric acid, and after restoring a constant volume with purified water, the elements in the measuring solution were quantified with an ICP emission analyzer

(ICPS-8000 by Shimadzu Corp.).

N (nitrogen) content for a sample weighed out to 10-20 mg was measured with an oxygen circulating combustion/TCD detection system employing a SUMIGRAPH (product of Sumitomo Chemical Analysis Center) (reaction temperature: 850°C, reduction temperature: 600°C).

The separating column used was a porous polymer bead-filled column, with acetoanilide as the reference sample.

[0135] (X-ray diffraction (XRD))

The X-ray diffraction patterns for the present noble metal-supporting material, noble metal particles and noble metal particle precursor were measured with the following apparatus and measuring conditions.

• Apparatus: RINT2500V by Rigaku Corp.

• Line source: Cu K-alpha radiation

· Output: 40 kV-300 mA

• Scanning zone: 2Θ = 0.75-20°

• Scanning rate: l°/min

[0136] (Ultraviolet and visible absorption spectrum (UV-Vis))

The present noble metal-supporting material, the noble metal particles and the noble metal particle precursor were thoroughly ground with an agate mortar and pelletized (7 mmcp) to prepare a measuring sample. The ultraviolet and visible absorption spectrum of the sample was measured with the following apparatus and measuring conditions.

• Apparatus: Diffuse reflection sensor (Praying Mantis, by HARRICK)

• Accessory: Ultraviolet and visible spectrophotometer (V-7100 by JASCO Corp.)

• Pressure: Atmospheric pressure

• Measured value: Reflectance

• Data acquisition time: 0.1 second

• Band width: 2 nm

· Measuring wavelength: 200-900 nm

• Slit height: Semi-open

• Data acquisition interval: 1 nm

• Baseline compensation (reference): BaS0₄ pellets (7 rnmcp)

[0137] (Measurement of streaming potential of noble metal particle aqueous dispersion)

The "streaming potential" of the noble metal particles was measured by titration with the following apparatus and measuring conditions, using a noble metal particle aqueous dispersion obtained by dispersing noble metal particles in water in an amount for a final concentration of 0.5 % by weight.

• Apparatus: Streaming potential meter (PCD-03-PH by Mutec)

• Titrant: 0.00 IN Poly-Dadmac solution by Metron

[0138] (Mean particle size measurement)

The mean particle sizes of the noble metal particles and noble metal particle precursor were measured with the following apparatus.

• Apparatus: MICROTRAC particle size distribution meter (Nikkiso Co., Ltd.)

[0139] (Hydrogen desorption spectrum measurement for noble metal-supporting material)

The desorbed amount of hydrogen (M¾) of the present noble metal-supporting material was calculated based on the hydrogen desorption spectrum, measured by temperature-programmed desorption using the following apparatus and measuring conditions.

• Apparatus: TPD-l-ATw, Fully automatic thermal desorption spectrometer by Bel Japan, Inc.

· Gas flow rate: 50 mL/min (for pretreatment, measurement and calibration curve plotting)

• Sample weight: approximately 0.15 g

• Measurement Conditions: Hydrogen desorption spectrum by temperature-programmed desorption under a normal pressure helium gas stream, with temperature increase of 10°C/min.

· Detection: Quadrupole MS

• Detected fragment: m/z = 2

• Calculation of MH₂: The sum of the area under the peaks for the desorbed component with a maximum in the range of 50°C to 350°C was calculated.

Calibration curve plotting conditions: Circulation (30 minutes) of normal pressure hydrogen gas diluted to 5% with helium. [0140] Fig. 1 shows an example of a hydrogen desorption spectrum for the present noble metal-supporting material (A), and Fig. 2 shows a hydrogen desorption spectrum for a different noble metal-supporting material (1) as reference. The abscissa of the spectrum represents sample temperature. The results show that the noble metal-supporting material A of the invention has no maximum between 50°C and 210°C, and one maximum between 210°C and 350°C. Also shown is that noble metal-supporting material 1 has one maximum between 50°C and 210°C and one maximum between 210°C and 350°C.

[0141] MH₂ was calculated using waveform analysis software by Bel Japan, Inc. In each graph, the line connecting the origin of the first peak in the hydrogen desorption spectrum and the minimum between 210°C and 350°C, plotted with measuring time as the abscissa (graph inserts), was used as background to calculate the area value (a) from the baseline-compensated spectrum. The background was then subtracted from the spectrum calibration curve conditions, and the area value (b) was calculated for approximately 5 minutes of circulation of normal pressure hydrogen gas diluted to 5% with helium. MH₂ per 1 g of catalyst was calculated by the following formula, based on the total hydrogen flow during the time period ((c), units: seconds). The area value (b) was a count of 5,355,802,000 and the time (c) was 213 seconds.

[0142] MH₂ = [area value (a) *50 xtime (c) x 5]/[area value (b) x 60 x 100 sample weight (g)]

[0143] The calculated MH₂ was 0.038 cm³/g-cat for the present noble metal-supporting material (A), and 0.132 cm /g-cat for the reference noble metal-supporting material (1).

[0144] Measurement of adsorbed amount of carbon monoxide (MCO)

MCO of the present noble metal-supporting material was calculated after measuring the metal surface area by the carbon monoxide pulse method, with the following equipment and measuring conditions.

• Detector: BEL-METAL-3SP metal dispersion rate measuring apparatus by Bel Japan, Inc.

• Gas flow rate: 50 mL/min

· Sample weight: approximately 0.15 g

· Measurement Conditions: Carbon monoxide pulse injection several times at 0.45 cm each under normal pressure helium gas stream at 50°C, adsorption measurement. Measurement was performed 2 times and the average value was calculated.

[0145] Example 1: Preparation of noble metal particle aqueous monodispersion (P-l)

A mixed metal salt solution was prepared by adding 9.6 g of palladium nitrate dihydrate and 0.1 g of aqueous iron citrate to 100 g of purified water. After then adding 200 g of aqueous trisodium citrate as a stabilizer to the mixed metal salt solution, 81.2 g of aqueous ferrous sulfate at 25 % by weight concentration was added as a reducing agent, and the resulting mixture was stirred for 20 hours under a nitrogen atmosphere to prepare a liquid noble metal mixture. The palladium particles were separated and collected from the noble metal mixture using a centrifugal separator. The palladium particles were rinsed with 1 % by weight aqueous hydrochloric acid and then dispersed in purified water.

The dispersion was subjected to wet grinding using a nanomizer system (LA-33-S by Nanomizer, Inc.) to prepare an aqueous monodispersion (P-l) of the noble metal particles. The palladium concentration of the aqueous monodispersion (P-l) was 3.1 % by weight as palladium metal (ICP luminescence analysis), and the Fe content was 0.42 % by weight with respect to Pd (ICP luminescence analysis). The streaming potential of an aqueous dispersion of the noble metal particles at 0.5 % by weight concentration was 156 eq/g, and the mean particle size was 10 nm.

[0146] Example 2: Pretreatment of support

After rinsing 20 g of active carbon with a pore volume of 1.22 cc/g (Active Carbon by Wako Pure Chemical Industries, Ltd., powder form) using 10 L of hot water at 100°C, it was dried at 150°C for 6 hours under a nitrogen stream to prepare "rinsed active carbon". The pore volume of the active carbon was calculated from the nitrogen gas adsorption near a relative pressure of 0.99, in an absorption isotherm obtained by adsorption of nitrogen gas at liquid nitrogen temperature onto the sample, previously dried in a vacuum at 150°C for 4 hours, using AUTOSORB 6 by Quanta Chrome Corp.

[0147] Example 3: Preparation of noble metal dispersion (A)

A noble metal dispersion (A) was prepared by mixing 2.164 g of the noble metal particle aqueous monodispersion (P-l) obtained in Example 1, 40 g of distilled water and 0.004 g of hydrochloric acid (Wako Pure Chemical Industries, Ltd.), stirring for 30 minutes in air at 20°C, and then rinsing using an ultrafilter membrane. The palladium concentration of the noble metal dispersion (A) was 2.5 % by weight as palladium metal (ICP luminescence analysis), and the Fe content was 0.42 % by weight with respect to Pd (ICP luminescence analysis). The streaming potential of an aqueous dispersion of the noble metal particles at 0.5 % by weight concentration was 29 ^eq/g, and the mean particle size was 10 nm.

[0148] Example 4: Preparation of present noble metal-supporting material (A)

After adding 20 g of the rinsed active carbon obtained in Example 2 and 300 mL of water into a 1 L volumetric flask, the mixture was stirred in air at 20°C. A 100 mL aqueous solution comprising 7.78 g of the noble metal dispersion (A) obtained in Example 3 was slowly added dropwise to the carrier suspension in air at room temperature. Upon completion of the dropwise addition, the suspension was stirred at room temperature for 8 hours in air. After stirring, the moisture in the suspension was removed with a rotary evaporator and the residue was vacuum dried at 80°C for 6 hours to obtain present noble metal-supporting material (A), comprising palladium supported on active carbon. The palladium concentration of the present noble metal-supporting material (A) was 1.1 % by weight as palladium metal (ICP luminescence analysis).

Only one hydrogen desorption peak (at 235°C) was observed in the range of 50°C to 350°C in temperature-programmed desorption with a 10°C/min programming rate. M¾ was 0.038 cm /g and MCO was 0.20 cmVg, and therefore MH₂/MCO was 0.19.

[0149] Example 5: Preparation of noble metal dispersion (B)

After mixing 2.164 g of the noble metal particle aqueous monodispersion (P-1) obtained in Example 1 with 40 g of distilled water and 0.008 g of sodium nitrite (Wako Pure Chemical Industries, Ltd.), the mixture was stirred for 1 hour by air bubbling at 20°C with a flow rate of 0.2 mL/min, and then rinsed with an ultrafilter membrane to prepare noble metal dispersion (B). The palladium concentration of the noble metal dispersion (B) was 2.1 % by weight as palladium metal (ICP luminescence analysis), and the Fe content was 0.52 % by weight with respect to Pd (ICP luminescence analysis). The streaming potential of an aqueous dispersion of the noble metal particles at 0.5 % by weight concentration was 38 μeq/g, and the mean particle size was 10 nm.

[0150] Example 6: Preparation of present noble metal-supporting material (B)

After adding 6 g of the rinsed active carbon obtained in Example 2 and 300 mL of water into a 1 L volumetric flask, the mixture was stirred in air at 20°C. A 100 mL aqueous solution comprising 2.91 g of the noble metal dispersion (B) obtained in Example 5 was slowly added dropwise to the carrier suspension in air at room temperature. Upon completion of the dropwise addition, the suspension was stirred at room temperature for 8 hours in air. After stirring, the moisture in the suspension was removed with a rotary evaporator and the residue was vacuum dried at 80°C for 6 hours to obtain present noble metal-supporting material (B), comprising palladium supported on active carbon. The palladium concentration of the present noble metal-supporting material (B) was 0.95 % by weight as palladium metal (ICP luminescence analysis).

Only one hydrogen desorption peak (at 253 °C) was observed in the range of 50°C to 350°C in temperature-programmed desorption with a 10°C/min programming rate. MH₂ was 0.043 cm³/g and MCO was 0.21 cm³/g, and therefore MH₂ MCO was 0.21.

[0151] Example 7: Preparation of present noble metal-supporting material (C)

After adding 6 g of zirconium oxide (RSC-100, by Daiichi Kigenso Kagaku Kogyo Co., Ltd.) and 300 mL of water into a 1 L volumetric flask, the mixture was stirred in air at 20°C. A 100 mL aqueous solution comprising 2.91 g of the noble metal dispersion (B) obtained in Example 5 was slowly added dropwise to the carrier suspension in air at room temperature. Upon completion of the dropwise addition, the suspension was stirred at room temperature for 8 hours in air. After stirring, the moisture in the suspension was removed with a rotary evaporator and the residue was vacuum dried at 80°C for 6 hours to obtain present noble metal-supporting material (C), comprising palladium supported on zirconium oxide. The palladium concentration of the present noble metal-supporting material (C) was 1.05 % by weight as palladium metal (ICP luminescence analysis).

[0152] Example 8: Preparation of noble metal dispersion (C)

A mixture of 2.164 g of the noble metal particle aqueous monodispersion (P-l) obtained in Example 1 with 40 g of distilled water and 0.5 g of acetic acid (Wako Pure Chemical Industries, Ltd.) was mixed in an approximately 50 cc volume glass vessel. The mixture was stirred for 30 minutes in air at 20°C to prepare noble metal dispersion (C).

[0153] Example 9: Preparation of present noble metal-supporting material (D)

After adding 6 g of active carbon with a pore volume of 1.22 cc/g (Active Carbon by Wako Pure Chemical Industries, Ltd., powder form) and 300 mL of water into a 1 L volumetric flask, the contents were stirred in air at 20°C. The total amount of the noble metal dispersion (C) obtained in Example 8 was slowly added dropwise to the carrier suspension in air at room temperature. Upon completion of the dropwise addition, the suspension was stirred at room temperature for 8 hours in air. After stirring, the filtrate was separated from the suspension by filtration to obtain a residue. The residue was rinsed with 3 L of hot water and then vacuum dried for 6 hours to obtain present noble metal-supporting material (D), comprising palladium supported on active carbon.

The palladium concentration of the present noble metal-supporting material (D) was 0.94 % by weight as palladium metal (ICP luminescence analysis). Only one hydrogen desorption peak (at 276°C) was observed in the range of 50°C to 350°C in temperature-programmed desorption with a 10°C/min programming rate. MH₂ was 0.025 cm /g and MCO was 0.16 cm /g, and therefore MH₂/MCO was 0.16.

[0154] Example 10: Preparation of noble metal dispersion (D) A mixture of 2.164 g of the noble metal particle aqueous monodispersion (P-1) obtained in Example 1 with 40 g of distilled water and 0.5 g of phosphoric acid (Kanto Kagaku Co., Ltd.) was mixed in an approximately 50 cc volume glass vessel. The mixture was stirred for 30 minutes in air at 20°C to prepare noble metal dispersion (D).

[0155] Example 11: Preparation of present noble metal-supporting material (E)

After adding 6 g of active carbon with a pore volume of 1.22 cc/g (Active Carbon by Wako Pure Chemical Industries, Ltd., powder form) and 300 mL of water into a 1 L volumetric flask, the contents were stirred in air at 20°C. The total amount of the noble metal dispersion (D) obtained in Example 11 was slowly added dropwise to the carrier suspension in air at room temperature. Upon completion of the dropwise addition, the suspension was stirred at room temperature for 8 hours in air. After stirring, the filtrate was separated from the suspension by filtration to obtain a residue. The residue was rinsed with 3 L of hot water and then vacuum dried for 6 hours to obtain present noble metal-supporting material (E), comprising palladium supported on active carbon.

The palladium concentration of the present noble metal-supporting material (E) was 1.02 % by weight as palladium metal (ICP luminescence analysis). Only one hydrogen desorption peak (at 262°C) was observed in the range of 50°C to 350°C in temperature-programmed desorption with a 10°C/min programming rate. MH₂ was 0.022 cmVg and MCO was 0.19 cm³/g, and therefore

MH₂/MCO was 0.12. [0156] Reference Example 1 : Production of reference noble metal-supporting material (1)

After adding 18 g of the rinsed active carbon obtained in Example 2 and 300 mL of water into a 1 L volumetric flask, the mixture was stirred in air at 20°C. A 100 mL aqueous solution comprising 5.88 g of the noble metal particle aqueous monodispersion (P-l) obtained in Example 1 was slowly added dropwise to the carrier suspension in air at room temperature. Upon completion of the dropwise addition, the suspension was stirred at room temperature for 8 hours in air. After stirring, the moisture in the suspension was removed with a rotary evaporator and the residue was vacuum dried at 80°C for 6 hours to obtain a reference noble metal-supporting material (1), comprising palladium supported on active carbon. The palladium concentration of the reference noble metal-supporting material (1) was 1.09 % by weight as palladium metal (ICP luminescence analysis). Two hydrogen desorption peaks (at 113°C and 230°C) were observed in the range of 50°C to 350°C in temperature-programmed desorption with a 10°C/min programming rate. MH₂ was 0.132 cm³/g and MCO was 0.28 cm³/g, and therefore MH₂/MCO was 0.47.

[0157] Reference Example 2: Production of reference noble metal-supporting material (2)

A mixture of 3 g of the active carbon described in Example 2 (non-rinsed) and 225 mL of acetonitrile (Nacalai Tesque, Inc.) was added into a 1 L volumetric flask and the mixture was stirred in air at 20°C. To this carrier suspension there was slowly added dropwise 35 mL of acetonitrile comprising 0.0647 g of palladium acetate (Aldrich Co.), in air at room temperature. Upon completion of the dropwise addition, the suspension was stirred at room temperature for 8 hours in air. After stirring, the moisture in the suspension was removed with a rotary evaporator and the residue was vacuum dried at 80°C for 6 hours to obtain a reference noble metal-supporting material (2), comprising palladium supported on active carbon. The palladium concentration of the reference noble metal-supporting material (2) was 1.07 % by weight as palladium metal (ICP luminescence analysis). Two hydrogen desorption peaks (at 167°C and 261°C) were observed in the range of 50°C to 350°C in temperature-programmed desorption with a 10°C/min programming rate. MH₂ was 0.17 cm /g and MCO was 0.23 cm /g, and therefore MH₂/MCO was 0.74.

[0158] Comparative Example 1 : Production of comparison noble metal-supporting material (1)

A comparison noble metal-supporting material (1) was prepared following the method described in Example 1 of JP 2008-201776 A.

Specifically, 6 g of active carbon with a pore volume of 1.22 cc/g (Active Carbon by Wako Pure Chemical Industries, Ltd., powder form) and 425 mL of water were added into a 1 L volumetric flask, and the contents were stirred in air at 20°C. To this carrier suspension there was slowly added dropwise 75 mL of an aqueous solution comprising 0.60 mmol palladium tetramine chloride, in air at 20°C. Upon completion of the dropwise addition, the suspension was stirred in air at 20°C for 6 hours. After stirring, the moisture in the suspension was removed with a rotary evaporator and the residue was vacuum dried at 80°C for 6 hours to obtain a noble metal-supporting material (1) for comparison (comparison noble metal-supporting material (1)), comprising palladium supported on active carbon. The palladium concentration of the comparison noble metal-supporting material (1) was 1.14 % by weight as palladium metal (ICP luminescence analysis). Two hydrogen desorption peaks (at 185°C and 258°C) were observed in the range of 50°C to 350°C in temperature-programmed desorption with a 10°C/min programming rate. MH₂ was 0.125 cm Ig and MCO was 0.19 cm³/g, and therefore MH₂/MCO was 0.66.

[0159] Example 12: Production of titanosilicate-containing catalyst

A combination of 899 g of piperidine and 2402 g of ion-exchanged water mixed under an air atmosphere at room temperature (22°C) was stirred. To this mixture, 46 g of TBOT (tetra-n-butyl orthotitanate) was added dropwise and dissolved while stirring. After dissolution of the TBOT was complete, 565 g of boric acid was added and dissolved while stirring. Next, 410 g of fumed silica (Cab-o-sil M7D by Cabot) was added and dissolved under an air atmosphere while stirring, and the mixture was further aged for 1.5 hours. After transferring the aged solution into a 5 L autoclave equipped with two anchor-type stirrers, the autoclave was sealed. An airtightness test was conducted at 1.5 MPa (gauge pressure) using argon gas, and then the pressure was released and the autoclave was resealed. The contents of the autoclave were heated to 150°C over a period of 8 hours while rotating the anchor-type stirrers. After holding the reaction product in the autoclave at the same temperature for 120 hours, it was cooled to obtain a suspension. The obtained suspension was filtered, and then the filtered solid was rinsed with ion-exchanged water until the rinsed filtrate pH reached about 10. The rinsed solid was then dried until no further weight reduction was observed (drying temperature: 50°C). The dried product was rinsed with ion-exchanged water and then dried to obtain approximately 520 g of a layered compound. This procedure was repeated 6 times to obtain a total of

3120 g of the layered compound.

[0160] In a glass-lined metal container (200 L, equipped with jacket and reflux tube) there were charged 3 kg of the layered compound, 158 kg of 2 M aqueous nitric acid and 0.38 kg of TBOT under an air atmosphere, at an outdoor air temperature of 20°C to 30°C. The jacket temperature of the container was raised to 115°C, this temperature was maintained for 9 hours and subsequently raised to 124°C, and the mixture was then refluxed for 7 hours at the same temperature. Following reflux, the jacket heating was suspended and the contents were allowed to cool to room temperature. The contents were filtered, and the filtered solid was rinsed with ion-exchanged water until the rinsed filtrate pH reached about 5.

The rinsed solid was dried until no further weight reduction was observed (drying temperature: 80°C), to obtain a white solid which was further pulverized to obtain a white powder. A portion of white powder was packed into a glass tube and heated from room temperature to 530°C over a period of 2 hours under a nitrogen stream provided at 6 L (0°C, 1 atm)/hr, and after holding it at the same temperature for 2 hours, the nitrogen stream was replaced by an air stream at 6 L (0°C, 1 atm)/hr, and the powder was held at 530°C for 4 hours.

[0161] In a 1.5 L autoclave there were charged 150 g of the white powder fired in the above manner, 300 g of piperidine and 600 g of ion-exchanged water, under an air atmosphere at room temperature. The charged contents were dissolved in the same atmosphere while stirring at the same temperature, and further aged for 1.5 hours. After transferring the aged solution into a 1.5 L autoclave equipped with a single anchor-type stirrer, the autoclave was sealed. An airtightness test was conducted at 1.0 MPa (gauge pressure) using argon gas, and then the pressure was released and the autoclave was resealed.

[0162] The contents of the autoclave were heated to 150°C over a period of 4 hours while rotating the anchor-type stirrer. They were then held at a temperature in a range of 150°C to 170°C aimed at 160°C, for 1 day of heating. After heating, the contents of the autoclave were cooled to obtain a suspension. After filtering the suspension, the filtered solid was rinsed with ion-exchanged water that had been heated to about 100°C, until the rinsed filtrate pH reached about 9, to obtain a white solid.

[0163] The white solid was thoroughly dried at 150°C using a vacuum drier, and then pulverized to obtain a white powder. Elemental analysis showed that the white powder had a Ti content of 2.0 % by mass and a Si content of 36 % by mass. The results of XRD and ultraviolet and visible absorption spectrum analysis confirmed that the white powder was a titanosilicate (Ti-MWW precursor).

[0164] Example 13: Present method for producing hydrogen peroxide (Hydrogen peroxide production (A))

After charging 0.06 g of the present noble metal-supporting material (A) into a 0.5 L autoclave, it was supplied with a source gas with a nitrogen/hydrogen/oxygen volume ratio of 90.9/4.7/4.4 at a rate of 18 L/h and with a solvent (water/acetonitrile = 20/80 (weight ratio)) at a rate of 171 g/h, and the reaction mixture was extracted from the autoclave through a filter in a continuous reaction. The reaction was conducted with a temperature of 40°C, a gauge pressure of 0.8 MPa and a residence time of 45 minutes.

Gas chromatography analysis of the liquid phase and gas phase extracted 4.5 hours after start of the reaction showed a hydrogen peroxide yield of 0.59 mmol hr (weight concentration: 0.023%).

[0165] Reference Example 3: Reference method for production of hydrogen peroxide (Reference hydrogen peroxide production (1))

Hydrogen peroxide was produced by the same method as Example 12, except for using the reference noble metal-supporting material (1) obtained in Reference Example 1 instead of the present noble metal-supporting material (A).

Gas chromatography analysis of the liquid phase and gas phase extracted 4.5 hours after start of the reaction showed a hydrogen peroxide yield of 0.46 mmol/hr (weight concentration: 0.018%).

[0166] Example 14: Present method for producing alkylene oxide (Propylene oxide production (A))

After charging 1.14 g of the titanosilicate-containing catalyst obtained in Example 12, 0.53 g of the present noble metal-supporting material (A) obtained in Example 4 and 117 g of a water/acetonitrile = 30/70 (weight ratio) solution into a 0.5 L autoclave, the autoclave was sealed. To the autoclave there were then supplied a source gas with an oxygen/hydrogen/nitrogen propylene volume ratio of 3.8/3.1/93.0/86.9/6.3, at a rate of 107 L/h, and a solution of water/acetonitrile = 30/70 (weight ratio) containing 0.7 mmol/kg anthraquinone and 3.0 mmol/kg diammonium hydrogenphosphate at a rate of 117 g/h, and the reaction mixture was extracted from the autoclave through a filter in a continuous reaction. The reaction was conducted with a temperature of 60°C, a gauge pressure of 0.8 MPa and a residence time of 60 minutes. Sampling was at 2 hours and 5 hours after start of the reaction, with analysis of the sampled liquid phase and gas phase by gas chromatography, and the results showed a propylene oxide yield of 60.0 mmol/g (noble metal-supporting material)/h, and a hydrogen-based propylene oxide selectivity (propylene oxide yield/hydrogen consumption 100) of 84% (average of values at 2 hours and 5 hours).

[0167] Example 15: Present method for producing alkylene oxide (Propylene oxide production (B))

Propylene oxide was produced by the same method as Example 14, except for using the present noble metal-supporting material (B) obtained in Example 6 instead of the present noble metal-supporting material (A). Sampling was at 2 hours and 5 hours after start of the reaction, with analysis of the sampled liquid phase and gas phase by gas chromatography, and the results showed a propylene oxide yield of 55.5 mmol/g (noble metal-supporting material)/h, and a hydrogen-based propylene oxide selectivity (propylene oxide yield/hydrogen consumption x 100) of 84% (average of values at 2 hours and 5 hours).

[0168] Example 16: Present method for producing alkylene oxide (Propylene oxide production (C)) Propylene oxide was produced by the same method as Example 14, except for using the present noble metal-supporting material (C) obtained in Example 7 instead of the present noble metal-supporting material (A). Sampling was at 2 hours and 5 hours after start of the reaction, with analysis of the sampled liquid phase and gas phase by gas chromatography, and the results showed a propylene oxide yield of 78.5 mmol/g (noble metal-supporting material)/h, and a hydrogen-based propylene oxide selectivity (propylene oxide yield/hydrogen consumption 100) of 86% (average of values at 2 hours and 5 hours).

[0169] Example 17: Present method for producing alkylene oxide

(Propylene oxide production (D))

Propylene oxide was produced by the same method as Example 14, except for using the present noble metal-supporting material (D) obtained in Example 9 instead of the present noble metal-supporting material (A). Sampling was at 2 hours and 5 hours after start of the reaction, with analysis of the sampled liquid phase and gas phase by gas chromatography, and the results showed a propylene oxide yield of 42.1 mmol/g (noble metal-supporting material)/h, and a hydrogen-based propylene oxide selectivity (propylene oxide yield/hydrogen consumption x 100) of 89% (average of values at 2 hours and 5 hours).

[0170] Example 18: Present method for producing alkylene oxide (Propylene oxide production (E))

Propylene oxide was produced by the same method as Example 14, except for using the present noble metal-supporting material (E) obtained in Example 11 instead of the present noble metal-supporting material (A). Sampling was at 2 hours and 5 hours after start of the reaction, with analysis of the sampled liquid phase and gas phase by gas chromatography, and the results showed a propylene oxide yield of 32.3 mmol/g (noble metal-supporting material)/h, and a hydrogen-based propylene oxide selectivity (propylene oxide yield/hydrogen consumption x 100) of 81% (average of values at 2 hours and 5 hours).

[0171] Reference Example 4: Reference method for production of alkylene oxide (Reference propylene oxide production (1))

Propylene oxide was produced by the same method as Example 15, except for using the reference noble metal-supporting material (1) obtained in Reference Example 1 instead of the present noble metal-supporting material (A). Sampling was at 2 hours and 5 hours after start of the reaction, with analysis of the sampled liquid phase and gas phase by gas chromatography, and the results showed a propylene oxide yield of 70.2 mmol/g (noble metal-supporting material)/h, and a hydrogen-based propylene oxide selectivity (propylene oxide yield/hydrogen consumption x 100) of 72% (average of values at 2 hours and 5 hours).

[0172] Reference Example 5: Reference method for production of alkylene oxide (Reference propylene oxide production (2))

Propylene oxide was produced by the same method as Example

15, except for using the reference noble metal-supporting material (2) obtained in Reference Example 2 instead of the present noble metal-supporting material (A). Sampling was at 2 hours and 5 hours after start of the reaction, with analysis of the sampled liquid phase and gas phase by gas chromatography, and the results showed a propylene oxide yield of 56.8 mmol/g (noble metal-supporting material)/h, and a hydrogen-based propylene oxide selectivity (propylene oxide yield/hydrogen consumption x 100) of 65% (average of values at 2 hours and 5 hours).

[0173] Comparative Example 2: Alkylene oxide comparison production (1)

Propylene oxide was produced by the same method as Example 15, except for using the comparison noble metal-supporting material (1) obtained in Comparative Example 1 instead of the present noble metal-supporting material (A). Sampling was at 2 hours and 5 hours after start of the reaction, with analysis of the sampled liquid phase and gas phase by gas chromatography, and the results showed a propylene oxide yield of 30.0 mmol/g (noble metal-supporting material)/h, and a hydrogen-based propylene oxide selectivity (propylene oxide yield/hydrogen consumption x 100) of 59% (average of values at 2 hours and 5 hours).

[0174] The experimental results for production of propylene oxide are summarized in Table 1. As seen in the table, combined use of the present noble metal-supporting material with a titanosilicate-containing catalyst increased the yield of propylene oxide from oxygen, hydrogen and propylene. The noble metal-supporting material catalyst of the present invention was also demonstrated to have high hydrogen-based alkylene oxide selectivity.

[0175] [Table 1] Noble metal-supporting PO

PO yield*¹

material selectivity*²

Present noble metal- Propylene oxide

Example 14 60.0 84

supporting material (A) production (A)

Present noble metal- Propylene oxide

Example 15 55.5 84

supporting material (B) production (B)

Present noble metal- Propylene oxide

Example 16 78.5 86

supporting material (C) production (C)

Present noble metal- Propylene oxide

Example 17 42.1 89

supporting material (D) production (D)

Present noble metal- Propylene oxide

Example 18 32.3 81

supporting material (E) production (E)

Ref. Reference noble metal- Propylene oxide

70.2 72

Example 4 supporting material (1 ) reference production (1 )

Ref. Reference noble metal- Propylene oxide

56.8 65

Example 5 supporting material (2) reference production (2)

Comp. Comparison noble metal- Propylene oxide

30.0 59

Example 2 supporting material (1) comparison production (1 )

* 1 : [mmol (propylene oxide)/g (noble metal-supporting material)/h]

*2: [%] mmol (propylene oxide)/mmol (supplied hydrogen) χ 100

[0176] Example 19: Present method for producing alkylene oxide

(Propylene oxide production (A 1))

After charging 2.28 g of the titanosilicate-containing catalyst obtained in Example 12, 0.63 g of the present noble metal-supporting material (A) obtained in Example 4, 3.0 g of PTFE zeolite (Teflon

Boiling Stone) and 90.5 g of a water/acetonitrile = 30/70 (weight ratio) solution into a 0.3 L autoclave, the autoclave was sealed.

There were then supplied a source gas with an oxygen/hydrogen/nitrogen volume ratio of 3.2/3.8/93.0, at a rate of 284

L/h, a solution of water/acetonitrile = 30/70 (weight ratio) containing

0.7 mmol/kg anthraquinone and 3.0 mmol/kg diammonium hydrogenphosphate at a rate of 135 g/h, and propylene at a rate of 54 g/hr, with the reaction mixture being extracted from the autoclave through a filter in a continuous reaction. The reaction was conducted with a temperature of 50°C, a gauge pressure of 6.0 MPa and a residence time of 40 minutes.

Sampling was at 2, 3 and 4 hours after start of the reaction, with analysis of the sampled liquid phase and gas phase by gas chromatography, and the results showed a propylene oxide yield of

306.5 mmol/g (noble metal-supporting material)/h, a hydrogen-based propylene oxide selectivity (propylene oxide yield/hydrogen consumption x 100) of 85%, and a propane selectivity (propane yield/(total propylene oxide, propylene glycol and propane yield) x 100) of 6.3% (average of values at 2, 3 and 4 hours).

[0177] Example 20: Present method for producing alkylene oxide (Propylene oxide production (B 1 ))

Propylene oxide was produced by the same method as Example 19, except for using the present noble metal-supporting material (B) obtained in Example 6 instead of the present noble metal-supporting material (A). Sampling was at 2, 3 and 4 hours after start of the reaction, with analysis of the sampled liquid phase and gas phase by gas chromatography, and the results showed a propylene oxide yield of

356.6 mmol/g (noble metal-supporting material)/h, a hydrogen-based propylene oxide selectivity (propylene oxide yield/hydrogen consumption x 100) of 68%, and a propane selectivity (propane yield/(total propylene oxide, propylene glycol and propane yield) x 100) of 3.5% (average of values at 2, 3 and 4 hours).

[0178] Reference Example 5: Reference method for production of alkylene oxide (Reference propylene oxide production (3))

Propylene oxide was produced by the same method as Example 19, except for using the reference noble metal-supporting material (1) obtained in Reference Example 1 instead of the present noble metal-supporting material (A). Sampling was at 2, 3 and 4 hours after start of the reaction, with analysis of the sampled liquid phase and gas phase by gas chromatography, and the results showed a propylene oxide yield of 281.4 mmol/g (noble metal-supporting material)/h, a hydrogen-based propylene oxide selectivity (propylene oxide yield/hydrogen consumption x 100) of 74%, and a propane selectivity (propane yield/(total propylene oxide, propylene glycol and propane yield) 100) of 7.5% (average of values at 2, 3 and 4 hours).

[0179] The experimental results for production of propylene oxide are summarized in Table 2. As seen in the table, combined use of the present noble metal-supporting material with a titanosilicate-containing catalyst increased the yield of propylene oxide from oxygen, hydrogen and propylene. The noble metal-supporting material catalyst of the invention was also shown to have high hydrogen-based alkylene oxide selectivity, and low hydrogen-based alkane selectivity (that is, producing a low content of by-products such as propane).

[0180] [Table 2]

1 : [mmol (propylene oxide)/g (noble metal-supporting material)/h] 2: [%] mmol (propylene oxide)/mmol (supplied hydrogen) x 100 *3: [%] mmol (propane)/mmol (total propylene oxide, propylene glycol and propane) x 100

[0181] Example 21: Present method for producing alkylene oxide (Propylene oxide production (A2))

After charging 2.28 g of the titanosilicate-containing catalyst obtained in Example 12, 1.06 g of the present noble metal-supporting material (A) obtained in Example 4, 3.0 g of PTFE zeolite (Teflon Boiling Stone) and 90 g of a water/acetonitrile = 30/70 (weight ratio) solution into a 0.3 L autoclave, the autoclave was sealed.

There were then supplied a source gas with an oxygen/hydrogen/nitrogen volume ratio of 3.2/3.8/93.0, at a rate of 284 L/h, a solution of water/acetonitrile = 30/70 (weight ratio) containing 0.7 mmol/kg anthraquinone and 3.0 mmol/kg diammonium hydrogenphosphate at a rate of 90 g/h, and propylene at a rate of 36 g/hr, extracting the reaction mixture from the autoclave through a filter in a continuous reaction. The reaction was conducted with a temperature of 50°C, a gauge pressure of 4.0 MPa and a residence time of 60 minutes.

Sampling was at 3, 4.5 and 6 hours after start of the reaction, with analysis of the sampled liquid phase and gas phase by gas chromatography, and the results showed a propylene oxide yield of 339.0 mmol/g (noble metal-supporting material)/h, a hydrogen-based propylene oxide selectivity (propylene oxide yield/hydrogen consumption x 100) of 75%, and a propane selectivity (propane yield/(total propylene oxide, propylene glycol and propane yield) x 100) of 2.1% (average of values at 3, 4.5 and 6 hours). [0182] Reference Example 6: Reference method for production of alkylene oxide (Reference propylene oxide production (5))

Propylene oxide was produced by the same method as Example 21, except for using the reference noble metal-supporting material (1) obtained in Reference Example 1 instead of the present noble metal-supporting material (A). Sampling was at 3, 4.5 and 6 hours after start of the reaction, with analysis of the sampled liquid phase and gas phase by gas chromatography, and the results showed a propylene oxide yield of 166.4 mmol/g (noble metal-supporting material)/h, a hydrogen-based propylene oxide selectivity (propylene oxide yield/hydrogen consumption x 100) of 66%, and a propane selectivity (propane yield/(total propylene oxide, propylene glycol and propane yield) x 100) of 4.4% (average of values at 3, 4.5 and 6 hours).

[0183] Reference Example 7: Reference method for production of alkylene oxide (Reference propylene oxide production (6))

Propylene oxide was produced by the same method as Example 21, except for using the reference noble metal-supporting material (2) obtained in Reference Example 2 instead of the present noble metal-supporting material (A). Sampling was at 3, 4.5 and 6 hours after start of the reaction, with analysis of the sampled liquid phase and gas phase by gas chromatography, and the results showed a propylene oxide yield of 161.7 mmol/g (noble metal-supporting material)/h, a hydrogen-based propylene oxide selectivity (propylene oxide yield/hydrogen consumption x 100) of 62%, and a propane selectivity (propane yield/(total propylene oxide, propylene glycol and propane yield) x 100) of 8.3% (average of values at 3, 4.5 and 6 hours). [0184] Comparative Example 3: Comparison method for production of alkylene oxide (Propylene oxide comparison production (2))

Propylene oxide was produced by the same method as Example 21, except for using the comparison noble metal-supporting material (1) obtained in Comparative Example 1 instead of the present noble metal-supporting material (A). Sampling was at 3, 4.5 and 6 hours after start of the reaction, with analysis of the sampled liquid phase and gas phase by gas chromatography, and the results showed a propylene oxide yield of 118.7 mmol/g (noble metal-supporting material)/h, a hydrogen-based propylene oxide selectivity (propylene oxide yield/hydrogen consumption x 100) of 55%, and a propane selectivity (propane yield/(total propylene oxide, propylene glycol and propane yield) x 100) of 12.6% (average of values at 3, 4.5 and 6 hours).

[0185] The experimental results for production of propylene oxide are summarized in Table 3. As seen in the table, combined use of the present noble metal-supporting material with a titanosilicate-containing catalyst increased the yield of propylene oxide from oxygen, hydrogen and propylene. The noble metal-supporting material catalyst was also shown to have high hydrogen-based alkylene oxide selectivity, and low hydrogen-based alkane selectivity (that is, producing a low content of by-products such as propane).

[0186] [Table 3] Noble metal- PO Propane

PO yield*¹

supporting material selectivity*² selectivity"³

Present noble

Example Propylene oxide metal-supporting 339.0 75 2.1

21 production (A2) material (A)

Reference noble

ef. Propylene oxide metal-supporting 166.4 66 4.4

Example 6 reference production (5) material (1)

Reference noble

Ref. Propylene oxide metal-supporting 161.7 62 8.3

Example 7 reference production (6) material (2)

Comparison noble

Comp. Propylene oxide metal-supporting 118.7 55 12.6

Example 3 comparison production (2) material (1 )

* 1 : [mmol (propylene oxide)/g (noble metal-supporting material)/h]

*2: [%] mmol (propylene oxide)/mmol (supplied hydrogen) χ 100

*3: [%] mmol (propane)/mmol (total propylene oxide, propylene glycol and propane) x 100

Industrial Applicability

[0187] The invention can provide a novel catalyst capable of producing a high alkylene oxide yield when used in combination with a titanosilicate-containing catalyst, in a reaction for production of an alkylene oxide from oxygen, hydrogen and an olefin.

Claims

1. A noble metal-supporting material comprising a noble metal and a carrier as constituent components, the ratio of a desorbed amount of hydrogen to an adsorbed amount of carbon monoxide being in the range of 0.01 to 0.40; wherein

the "desorbed amount of hydrogen" is the value calculated from the sum of the areas of the peaks of the desorbed component having a maximum value in the range of 50°C to 350°C, as observed in accordance with a temperature-programmed desorption with a programming rate of 10°C/min, with regard to a sample left in a vacuum at 50°C for 8 hours or more, under a normal pressure helium gas stream at 50°C for 1 hour, then under a normal pressure hydrogen gas stream at 50°C for 2 hours, and further left under a normal pressure helium gas stream at 50°C for 1 hour and thereby obtained, while the "adsorbed amount of carbon monoxide" is the value as measured by metal surface area measurement based on the carbon monoxide pulse method, of a sample left in a vacuum at 50°C for 8 hours or more, under a normal pressure helium gas stream at 50°C for 1 hour, then under a normal pressure hydrogen gas stream at 50°C for 2 hours, and further left under a normal pressure helium gas stream at 50°C for 1 hour and thereby obtained.

2. The noble metal-supporting material according to claim 1, wherein the peaks of the desorbed component with a maximum value in the range of 50°C to 350°C as observed in the temperature-programmed desorption method with a programming rate of 10°C/min does not have a maximum value between 50°C and 210°C, and have one or more maximum values in the range of 210°C to 350°C.

3. The noble metal-supporting material according to claim 1 or 2, obtained by contacting a carrier with a noble metal dispersion containing noble metal particles, such that a 0.5 % by weight aqueous dispersion of noble metal particles has a streaming potential in the range of 10 μeq/g to 50 μeq/g.

4. The noble metal-supporting material according to claim 3, wherein the noble metal particles are obtained by mixing an acid-containing solution with either (a) a noble metal particle precursor such that a 0.5 % by weight aqueous dispersion has a streaming potential in the range of 50 μeq/g to 300 μeq/g, or (b) a mixture of the noble metal particle precursor with a solvent.

5. The noble metal-supporting material according to claim 4, wherein the acid is hydrochloric acid.

6. The noble metal-supporting material according to claim 3, wherein the noble metal particles are obtained by using an oxidizing agent for partial oxidation of either (a) a noble metal particle precursor such that a 0.5 % by weight aqueous dispersion has a streaming potential in the range of 50 μeq/g to 300 μeq/g, or (b) a mixture of the noble metal particle precursor with a solvent.

7. The noble metal-supporting material according to claim 6, wherein the oxidizing agent is oxygen and/or sodium nitrite.

8. The noble metal-supporting material according to any one of claims 1 to 7, wherein the noble metal is palladium.

9. The noble metal-supporting material according to any one of claims 1 to 8, wherein the carrier comprises at least one species selected from a group consisting of active carbon, aluminum oxide, titanium oxide and zirconium oxide.

10. A method for producing hydrogen peroxide comprising:

a step of reacting oxygen with hydrogen in the presence of the noble metal-supporting material according to any one of claims 1 to 9.

11. A method for producing an alkylene oxide, comprising:

a step of reacting oxygen, hydrogen and an olefin in the presence of the noble metal-supporting material according to any one of claims 1 to 9, and a titanosilicate-containing catalyst.

12. The method according to claim 11, wherein the olefin is propylene.

13. The method according to claim 11 or 12, wherein the titanosilicate-containing catalyst comprises titanosilicate particles having an X-ray diffraction pattern with peaks at the positions indicated by lattice spacings d/A of 12.4 ±0.8, 10.8 ±0.5, 9.0 ±0.3, 6.0 ±0.3, 3.9 ±0.3 and 3.4 ±0.1.

14. The method according to any one of claims 11 to 13, wherein the step is a step of reacting oxygen, hydrogen and an olefin in the presence of a solvent.

15. The method according to claim 14, wherein the solvent is an organic solvent.

16. The method according to claim 14, wherein the solvent is a mixed solvent comprising an organic solvent and water.

17. The method according to claim 15 or 16, wherein the organic solvent is acetonitrile.