CN103183356B - Method for modifying titanium silicalite molecular sieve by precious metal source - Google Patents

Abstract

A method for modifying a titanium silicalite molecular sieve by a precious metal source is characterized in that a mixture of modification liquid and a titanium silicalite molecular sieve is treated in a closed reaction vessel at 120-200 DEG C for at least 2 hours, and then the product is dried and roasted, wherein the water contained in the reaction vessel can form saturated water steam under the reaction condition, and has a weight ratio to the titanium silicalite molecular sieve being less than 1.2; the modification liquid comprises a silicone source, a titanium source, water, organic base, a precious metal source, and a reducing agent; the weight ratio of the titanium silicalite molecular sieve to the modification liquid is 100:(1-150); and the treating capacity of the titanium silicalite molecular sieve is at least 10 g per liter of the reaction vessel volume. The method needs no mother liquor separation, omits procedures of filtration or washing, greatly reduces environment pollution, improves volume utilization efficiency of high pressure equipment, increases productivity, reduces preparation cost, and improves the environmental protection and economic benefits of the synthesis.

Description

A method for modifying titanium-silicon molecular sieve with precious metal source

technical field

The invention relates to a method for modifying titanium-silicon molecular sieves with precious metals under water vapor.

Background technique

Titanium-silicon molecular sieve is a new type of heteroatom molecular sieve developed in the early 1980s. At present, TS-1 with MFI structure, TS-2 with MEL structure, MCM-22 with MWW structure and TS-48 with larger pore structure have been synthesized. Titanium-silicon molecular sieves are used as catalysts, and non-polluting low-concentration hydrogen peroxide can be used as oxidants, which can catalyze various types of organic oxidation reactions, such as epoxidation of alkenes, partial oxidation of alkanes, oxidation of alcohols, and oxidation of phenols. Hydroxylation, ammoxidation of cyclic ketones, etc., avoid the problems of complex oxidation process and environmental pollution, and have the incomparable advantages of energy saving, economy and environmental friendliness of traditional oxidation systems, and have good reaction selectivity.

Although hydrogen peroxide (H ₂ O ₂ ) is recognized as a green oxidant, its oxidation by-product is only water. However, because H ₂ O ₂ is extremely unstable, rough surfaces, heavy metals and other impurities will decompose when exposed to heat and light, and it is corrosive, so special safety measures must be taken during packaging, storage and transportation. Therefore, the application of _H2O2 on site, or the _combination of _H2O2 production process _and downstream process using _H2O2 , can make more efficient use _of this chemical product. Using H ₂ and O ₂ can directly synthesize H ₂ O ₂ , and the atomic utilization rate is 100%, and then people want to use H ₂ and O ₂ to synthesize H ₂ O ₂ in situ and then oxidize organic raw materials to solve the problem of direct utilization of H ₂ O ₂ cost and safety issues. Since Pt, Pd, Au, etc. are effective components for the synthesis of H ₂ O ₂ from H ₂ and O ₂ , there are many literature and patent reports that they can be supported on titanium-silicon materials to generate H ₂ O ₂ in situ for the selective oxidation of organic matter. Research. For example, Meiers R. et al. (J.Catal., 1998, 176:376～386) used Pt-Pd/TS-1 as a catalyst to study the gas-phase epoxidation of propylene; US 6867312B1 and US 6884898B1 etc. have also carried out research in this area. Although the method of loading noble metals on titanium-silicon materials to generate H ₂ O ₂ in situ for selective oxidation of organic matter has mild conditions and good selectivity (up to 95%), the catalytic activity of titanium-silicon materials loaded with noble metals is low. Poor stability.

Contents of the invention

The purpose of the present invention is to provide a method for modifying titanium-silicon molecular sieves with precious metals on the basis of the prior art.

The method for modifying titanium-silicon molecular sieves with noble metals provided by the present invention includes placing a mixture of a modified liquid and titanium-silicon molecular sieves in a closed reaction vessel and treating them at 120-200°C for at least 2 hours, and then drying and roasting the product to obtain the product. Wherein, the reaction kettle contains water that forms saturated water vapor under reaction conditions and has a weight ratio of less than 1.2 to the titanium-silicon molecular sieve. In the molar composition of the modified liquid, silicon source: titanium source: organic base: water: precious metal source : reducing agent = 1: (0～0.1): (0.05～5): (15～100): (0.001～0.1): (0.001～0.5), silicon is calculated as _SiO2 , titanium is calculated as _TiO2 , noble metal source The weight ratio of the titanium-silicon molecular sieve to the modifying liquid is 100: (1-150) based on the precious metal element, and the processing capacity of the titanium-silicon molecular sieve is at least 10 g/L of the reactor volume.

The method of noble metal modified titanium silicon molecular sieve provided by the present invention has the following advantages:

1. The consumption of organic bases and precious metals in the treatment process is low, there is no filtration and separation of mother liquor, and there is no discharge of washing wastewater, and the environmental protection efficiency of the production process is significantly improved.

2. The volume utilization rate of high-voltage equipment is improved, the production capacity is expanded, the production efficiency is improved, and the production cost is reduced.

Detailed ways

The method provided by the invention is applicable to various types of titanium-silicon molecular sieves. Common titanium-silicon molecular sieves include TS-1, TS-2, Ti-Beta, Ti-MWW, Ti-MCM-41 molecular sieves, etc. The oxidation activity of the titanium-silicon molecular sieve obtained by the method can be effectively improved, and the TS-1 molecular sieve is preferred.

In the method provided by the present invention, in the molar composition of the modified liquid, silicon source: titanium source: organic base: water: precious metal source: reducing agent=1: (0.01～0.05): (0.3～3.0): ( 20-50): (0.005-0.1): (0.001-0.2).

In the method provided by the present invention, the silicon source includes silicon oxide, silica gel, silica sol and organosilicate, and the preferred silicon source is organosilicate; the general formula of the organosilicate is R ¹ ₄ SiO ₄ , wherein R ¹ is preferably an alkyl group having 1-4 carbon atoms, and the preferred alkyl group is ethyl.

In the method provided by the present invention, the titanium source includes inorganic titanium salt or organic titanate, and the preferred titanium source is organic titanate; the inorganic titanium salt can be TiCl ₄ , Ti(SO ₄ ) ₂ or TiOCl ₂ ; the general formula of the organic titanate is Ti(OR ² ) ₄ , wherein R ² is preferably an alkyl group with 1-6 carbon atoms, and the preferred alkyl group is ethyl, propyl or butyl.

In the method provided by the present invention, the organic base may be selected from organic base compounds such as quaternary ammonium base compounds, fatty amine compounds and alcohol amine compounds. Described quaternary ammonium alkali compound can be selected from tetrapropyl ammonium bromide, tetrapropyl ammonium hydroxide, tetraethyl ammonium hydroxide, tetramethyl ammonium hydroxide, tetrabutyl ammonium hydroxide etc., described fatty amine The alcohol amine compound can be ethylamine, n-propylamine, n-butylamine, di-n-propylamine, butanediamine or hexamethylenediamine, etc., and the alcohol amine compound can be monoethanolamine, diethanolamine or triethanolamine. The organic base can also be selected from tetrapropylammonium hydroxide, tetraethylammonium hydroxide, tetramethylammonium hydroxide, tetrabutylammonium hydroxide, ethylamine, n-propylamine, n-butylamine, di-n-propylamine, butylated One or more of diamine, hexamethylenediamine, monoethanolamine, diethanolamine, triethanolamine, for example, a mixture of tetraethylammonium hydroxide and n-butylamine, a mixture of tetraethylammonium hydroxide and n-butylamine, ethyl Mixture of diamine and tetrapropylammonium hydroxide, mixture of di-n-propylamine and tetrapropylammonium hydroxide, mixture of tetraethylammonium hydroxide and tetrapropylammonium hydroxide, hexamethylenediamine and tetrapropylammonium hydroxide All mixtures of ammonium can be used in the present invention, and there is no special requirement for the above mixing ratio, as long as the present invention can be realized.

In the method provided by the present invention, the weight ratio of the titanium-silicon molecular sieve to the modifying liquid is 100:(10-150), preferably the weight ratio of the titanium-silicon molecular sieve to the modifying liquid is 100:(30-120).

The noble metal source is selected from one or more of elemental Ru, Rh, Pd, Re, Os, Ir, Pt, Ag and Au, or selected from , Ag and Au, or a compound of one or more of them, or a mixture of several of the above noble metal simple substances or compounds. Organic or inorganic substances, preferably palladium, platinum, gold, silver, can be oxides, halides, carbonates, nitrates, ammonium nitrate salts, ammonium chloride salts, hydroxides or other complexes of noble metals, etc. . In a preferred embodiment of the present invention, the noble metal source is noble metal halide, ammonium chloride salt. Taking palladium as an example, the palladium source can be an inorganic palladium source and/or an organic palladium source. Wherein the inorganic palladium source can be palladium oxide, palladium carbonate, palladium chloride, palladium nitrate, ammonium palladium nitrate, ammonia palladium chloride, palladium hydroxide or other complexes of palladium, etc., and the organic palladium source can be palladium acetate, acetylacetone palladium etc. The inventors of the present invention have found that, surprisingly, when using noble metal halides as the source of the noble metal, compared with titanium-silicon molecular sieves obtained by modification using other sources of noble metals, the conversion of propylene and the selectivity of the target product propylene oxide (PO) All have better effect, therefore, the noble metal source described in the present invention is preferably the halide of noble metal, such as the chloride of noble metal or ammonium chloride salt, is for example palladium chloride or ammonium chloride palladium with palladium.

In the method provided by the invention, the reducing agent can be selected from but not limited to one or a mixture of hydroxylamine, formaldehyde, hydrazine, borohydride and sodium citrate, wherein hydrazine can be hydrazine hydrate, hydrazine hydrochloride , hydrazine sulfate, etc., borohydride can be sodium borohydride, potassium borohydride, etc.

In the method provided by the present invention, the reaction kettle preferably contains water that forms saturated water vapor under reaction conditions and has a weight ratio of less than 1.0 to the titanium-silicon molecular sieve, and the water quantity that forms saturated water vapor can be provided by the reactant material in the reaction kettle , can also be achieved by adding external water vapor.

In the method provided by the present invention, the reaction mixture is treated in a closed reactor at a temperature of 120-200°C, preferably 140-180°C, and a treatment time of 2-72 hours, preferably 6-72 hours.

In the method provided by the present invention, after the temperature and pressure in the reactor return to close to normal temperature and pressure, the product in the reactor can be recovered through the drying process and roasting process without filtering and washing steps. The drying process can be carried out at room temperature to 200°C, and the roasting can be carried out at 300°C to 800°C in an air atmosphere for 2 to 12 hours. These processes are familiar to those skilled in the art, and there is no special requirement here. .

The present invention will be further described below by embodiment, but content of the present invention is not limited thereby.

In the examples, all reagents used are commercially available chemically pure reagents. The titanium-silicon molecular sieve used in the comparative examples and examples is a TS-1 molecular sieve sample synthesized according to the method described in the prior art Zeolites, 1992, Vol.12 pages 943-950.

Comparative example 1

This comparative example illustrates the process of conventionally synthesizing supported palladium/titanium silicate molecular sieve catalysts.

Add 20g of titanium-silicon molecular sieve TS-1 and 20mL of ammonium palladium nitrate solution with a concentration of 0.01g/mL (calculated as palladium atoms) into 20mL of deionized water, stir evenly, seal properly, and soak at 40°C for 24h. Then it was dried naturally, and subjected to reduction activation at 300° C. for 5 hours in a hydrogen atmosphere to obtain the traditional supported palladium/titanium silicate molecular sieve catalyst DB.

Example 1

Mix the metered tetraethyl orthosilicate, palladium chloride, sodium citrate and tetraethylammonium hydroxide, add an appropriate amount of distilled water, mix well, stir at room temperature for 1.0h, and then stir at 75°C for 3h to obtain modification Liquid, its molar composition is silicon: titanium: organic base: water: precious metal source: reducing agent = 1:0:0.85:20:0.05:0.05 (where silicon and titanium are calculated as _SiO2 and _TiO2 , and precious metals are calculated as simple substances) . Take 12 g of TS-1 molecular sieves and mix with 10 g of the modified solution obtained above. The above mixture was filled into a 50 mL polytetrafluoroethylene liner and placed in a 100 mL polytetrafluoroethylene liner, and then reacted in a sealed autoclave at 175° C. for 12 h. The obtained product was dried at 150° C. for 120 minutes, and then calcined at 580° C. for 5 hours to obtain noble metal modified TS-1 molecular sieve A.

Example 2

Mix the measured amount of amorphous silica gel, palladium acetate, hydrazine hydrate and tetrapropylammonium hydroxide, and add an appropriate amount of distilled water. After mixing evenly, stir at room temperature for 1.5h, then add n-butyl titanate and stir for 0.5h, then at 70°C Down stirring 3h obtains modified solution, and its molar composition is silicon: titanium: organic base: water: precious metal source: reducing agent=1: 0.02: 0.75: 25: 0.025: 0.15 (wherein silicon and titanium are SiO ₂ and TiO ₂ , precious metals are calculated as elemental substances). Take 10g of TS-1 molecular sieve and mix with 8.5g of the modified solution obtained above. The mixture was filled into 50 mL polytetrafluoroethylene liner, and then placed in 100 mL polytetrafluoroethylene liner, and then reacted at 180° C. for 24 h in a sealed autoclave. The obtained product was dried at 150° C. for 120 minutes, and then calcined at 650° C. for 2 hours to obtain noble metal modified TS-1 molecular sieve B.

Example 3

Mix the measured tetraethyl orthosilicate, tetraethyl titanate, palladium carbonate, formaldehyde and tetrapropylammonium hydroxide, and add an appropriate amount of distilled water, mix well, stir at room temperature for 1.0h, and then stir at 80°C for 3h Obtain modified liquid, its molar composition is silicon: titanium: organic base: water: precious metal source: reducing agent=1: 0.02: 0.75: 35: 0.02: 0.025 (wherein silicon and titanium are in SiO ₂ and TiO ₂ meter, precious metal in elemental meter). Take 15g of TS-1 molecular sieve and mix evenly with 13g of the modified solution obtained above. The mixture was charged into a 50 mL polytetrafluoroethylene liner and placed in a 100 mL polytetrafluoroethylene liner, and then reacted at 160° C. for 62 h in a sealed autoclave. The obtained product was dried at 135° C. for 240 minutes, and then calcined at 560° C. for 3 hours to obtain noble metal modified TS-1 molecular sieve C.

Example 4

Mix the measured tetraethyl orthosilicate, tetrabutyl titanate, platinum nitrate, sodium borohydride, triethanolamine and tetrapropylammonium bromide, and add an appropriate amount of distilled water, mix well, stir at room temperature for 1.0h, and then Stir at 75° C. for 3 h to obtain a modified solution, the molar composition of which is silicon: titanium: triethanolamine: tetrapropylammonium bromide: water: precious metal source: reducing agent = 1: 0.015: 0.35: 0.3: 20: 0.01: 0.2 ( Among them, silicon and titanium are counted as SiO ₂ and TiO ₂ , and precious metals are counted as simple substances). Take 12g of TS-1 molecular sieve and mix evenly with 9.5g of the modified solution obtained above. The mixture was filled into 50mL polytetrafluoroethylene liner, and then placed on the support of 100mL polytetrafluoroethylene liner, and then reacted in a sealed autoclave at 165°C for 48h. The obtained product was dried at 100°C for 360 minutes, and then calcined at 540°C for 6 hours to obtain noble metal modified TS-1 molecular sieve D.

Example 5

Mix measured amounts of white carbon black silica, chloroauric acid, hydrazine hydrochloride, tetrapropylammonium bromide and n-butylamine, add appropriate amount of distilled water, stir at room temperature for 2.0h, then add n-butyl titanate and stir for 0.5h , followed by stirring at 75° C. for 3 h to obtain a modified solution, the molar composition of which is silicon: titanium: tetrapropylammonium bromide: n-butylamine: water: precious metal source: reducing agent = 1: 0.025: 0.85: 1: 25: 0.1:0.12 (where silicon and titanium are calculated as SiO ₂ and TiO ₂ , and precious metals are calculated as simple substances). Take 12g of TS-1 molecular sieve and mix with 5g of the modified solution obtained above. The mixture was filled into 50 mL polytetrafluoroethylene liner and placed on the support of 100 mL polytetrafluoroethylene liner, and 5 mL of water was added under it, and then reacted in a sealed autoclave at 155 ° C for 36 h. The obtained product was dried at 175° C. for 180 minutes, and then calcined at 500° C. for 5 hours to obtain noble metal modified TS-1 molecular sieve E.

Example 6

Mix measured amounts of silica sol, silver nitrate, hydrazine hydrate, di-n-propylamine and tetrapropylammonium hydroxide, add an appropriate amount of distilled water, mix well, stir at room temperature for 1.5h, then add tetraethyl titanate and stir for 0.5h, then Stir at 65° C. for 5 h to obtain a modified liquid, the molar composition of which is silicon: titanium: di-n-propylamine: tetrapropylammonium hydroxide: water: precious metal source: reducing agent = 1: 0.02: 0.35: 1.2: 30: 0.03: 0.1 (where silicon and titanium are calculated as SiO ₂ and TiO ₂ , and precious metals are calculated as simple substances). Take 10g of TS-1 molecular sieve and mix evenly with 5g of the modified solution obtained above. The mixture was charged into a 100 mL polytetrafluoroethylene liner, and then treated in a sealed autoclave at 150 °C for 65 h. The obtained product was dried at 160° C. for 120 minutes, and then calcined at 700° C. for 3 hours to obtain noble metal modified TS-1 molecular sieve F.

Example 7

Mix measured Z-type silica gel, ammonium palladium nitrate, hydroxylamine, n-butylamine, and tetrapropylammonium bromide, add appropriate amount of distilled water, stir at room temperature for 1.5h, then add tetraethyl titanate, and then stir at 75°C 3h obtains modified solution, and its molar composition is silicon: titanium: n-butylamine: tetrapropyl ammonium bromide: water: noble metal source: reducing agent=1: 0.02: 0.95: 0.8: 45: 0.06: 0.18 (wherein silicon and Titanium is calculated as SiO ₂ and TiO ₂ , and precious metals are calculated as simple substances). Take 12g of TS-1 molecular sieve and mix evenly with 6g of the modified solution obtained above. The above mixture was filled into a 50 mL polytetrafluoroethylene liner and placed on a support provided by a 100 mL polytetrafluoroethylene liner, and then reacted in a sealed autoclave at 180° C. for 18 h. The obtained product was dried at 130° C. for 270 minutes, and then calcined at 550° C. for 3 hours to obtain noble metal modified TS-1 molecular sieve G.

Example 8

This example is used to illustrate the method for modifying titanium-silicon molecular sieves with noble metals according to the present invention.

The titanium-silicon molecular sieve was modified with noble metals by the same method as in Example 1, except that palladium acetate was used instead of palladium chloride to obtain noble metal-modified titanium-silicon molecular sieve H when preparing the catalyst.

Example 9

This example is used to illustrate the method for modifying titanium-silicon molecular sieves with noble metals according to the present invention.

The titanium-silicon molecular sieve was modified with noble metals in the same manner as in Example 2, except that palladium chloride was used instead of palladium acetate to obtain noble metal-modified titanium-silicon molecular sieve I when preparing the catalyst.

Example 10

This example is used to illustrate the method for modifying titanium-silicon molecular sieves with noble metals according to the present invention.

The titanium-silicon molecular sieve was modified with noble metals by the same method as in Example 3, except that when preparing the catalyst, palladium ammonium chloride was used instead of palladium carbonate to obtain noble metal-modified titanium-silicon molecular sieve J.

test case

This test example illustrates the effect of the example sample provided by the present invention and the sample synthesized in the comparative example for the synthesis of propylene oxide by gas-phase epoxidation of propylene in the presence of hydrogen.

Take 0.5 g of the samples of the above-mentioned Examples 1-10 and Comparative Example 1 respectively and add them to an epoxidation reaction vessel containing 50 mL of methanol, and feed propylene, oxygen, hydrogen and nitrogen to form a mixed atmosphere of propylene-oxygen-hydrogen-nitrogen (Molar ratio is 1:1:1:7), under the conditions of temperature 60°C, pressure 1.0MPa, propylene space velocity 10h-1, the reaction of epoxidation to generate propylene oxide (PO) is carried out.

Table 1 shows the data of propylene conversion and PO selectivity for reaction 2h.

Wherein the calculating formula of propylene conversion rate and PO selectivity is as follows:

It can be seen from the data in Table 1 that the catalytic performance of the molecular sieve obtained by the treatment method of the present invention is superior to that of the molecular sieve DB obtained by the comparative example. It shows that compared with the ordinary load modification method, the method of the present invention not only maintains the advantages in performance, but also reduces production costs and reduces environmental pollution.

Table 1

source of samples Sample serial number Propylene conversion % PO selectivity % Example 1 A 5.8 93 Example 2 B 5.1 92 Example 3 C 5.3 94 Example 4 D 5.6 93 Example 5 E 5.2 91 Example 6 F 4.9 90 Example 7 G 4.7 93 Example 8 h 5.2 91 Example 9 I 5.9 95 Example 10 J 5.6 96 Comparative example 1 DB 2.6 89

It can also be seen from the data in Table 1 that when palladium halides are used as the noble metal source, compared with other noble metal source modified titanium silicon molecular sieves (embodiments 2, 3, 8 and embodiments 1, 9, 10) , its propylene conversion and PO selectivity have better effects.

Claims (10)

1. the method with noble metal source modifying titanium-silicon molecular sieve, it is characterized in that the mixture of a kind of modification liquid and HTS to be placed in closed reactor to process at least 2h at 120 ~ 200 DEG C, then product drying and roasting, wherein, modification liquid is by silicon source, titanium source, water, organic bases, noble metal source and reductive agent composition, its molar ratio is silicon source: titanium source: organic bases: water: noble metal source: reductive agent=1: (0 ~ 0.1): (0.05 ~ 5): (15 ~ 100): (0.001 ~ 0.1): (0.001 ~ 0.5), silicon source is with SiO ₂meter, titanium source is with TiO ₂meter, noble metal source is in precious metal simple substance, containing forming saturated steam at reaction conditions and the water yield being less than 1.2 with the weight ratio of HTS in said reactor, the part by weight of HTS and modification liquid is 100: (1 ~ 150), and the treatment capacity of HTS is at least 10g/L reactor volume.

2., according to the process of claim 1 wherein, described HTS is TS-1, TS-2, Ti-Beta, Ti-MWW, Ti-MCM-41 molecular sieve.

3. according to the method for claim 1, wherein, in mole composition of described modification liquid, silicon source: titanium source: organic bases: water: noble metal source: reductive agent=1: (0.01 ~ 0.05): (0.3 ~ 3.0): (20 ~ 50): (0.005 ~ 0.1): (0.001 ~ 0.2).

4., according to the process of claim 1 wherein, described HTS and the part by weight of modification liquid are 100: (30 ~ 120).

5., according to the process of claim 1 wherein, it is R that described silicon source is selected from silicon oxide, silica gel, silicon sol or general formula ¹ ₄siO ₄organosilicon acid esters, R ¹be selected from the alkyl of 1 ~ 4 carbon atom.

6., according to the process of claim 1 wherein, described titanium source is selected from TiCl ₄, Ti (SO ₄) ₂or TiOCl ₂, or general formula is Ti (OR ²) ₄organic titanate, R ²be selected from the alkyl of 2 ~ 4 carbon atoms.

7. according to the process of claim 1 wherein, described organic bases be selected from quaternary ammonium hydroxide compound, amine compound or alcohol amine compound one or more.

8. according to the method for claim 1, wherein, described organic bases be selected from TPAOH, tetraethyl ammonium hydroxide, Tetramethylammonium hydroxide, TBAH, ethamine, Tri N-Propyl Amine, n-Butyl Amine 99, di-n-propylamine, butanediamine, hexanediamine, monoethanolamine, diethanolamine and trolamine one or more.

9. according to the method for claim 1, wherein, described noble metal source is selected from one or more in simple substance Ru, Rh, Pd, Re, Os, Ir, Pt, Ag and Au, or the compound be selected from containing one or more in Ru, Rh, Pd, Re, Os, Ir, Pt, Ag and Au, or be selected from several mixture in above-mentioned precious metal simple substance or compound.

10., according to the process of claim 1 wherein, described reductive agent is selected from the mixture of one or more in azanol, formaldehyde, hydrazine, hydroborate and Trisodium Citrate.