JPH10182505A - Dehydrogenation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for suppressing the precipitation of carbon on a catalyst and alleviating the deterioration of the catalyst in producing an alkene by dehydrogenation of an alkane in the presence of a dehydrogenation catalyst. SOLUTION: A raw material alkane and hydrogen are supplied by using a catalyst obtained by supporting platinum and tin on a complex carrier which is prepared by supporting zinc oxide on γ-alumina carrier having >=150m<2> /g surface area, >=0.55cm<3> /g pore volume, 90-200 angstrom pore diameter and comprising >=60% based on the total pore volume of pore volume having 90-200 angstrom pore diameter as a dehydrogenation catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for dehydrogenation,
More specifically, the present invention relates to a method for producing an alkene by a dehydrogenation reaction of an alkane in the presence of a dehydrogenation catalyst.

[0002]

2. Description of the Related Art In recent years, demand for alkenes represented by propylene and isobutylene has been increasing. This is because the demand for polypropylene using propylene as a raw material is increasing as a resin for packaging materials and automobile parts, and the addition of methyl-t-butyl ether (MTBE), a high octane fuel additive for gasoline produced from isobutylene as a raw material. This is because demand is increasing. These propylene and isobutylene are obtained by fluidized bed catalytic cracking (FCC) for gasoline production or as a by-product of pyrolysis for ethylene production, but the amount obtained by such a method is limited. Therefore, establishment of another manufacturing method is desired. Under these circumstances, alkane such as C ₃ and C ₄ , which is used only as a fuel, is used as a raw material to produce propylene, isobutylene, or n-
Various attempts have been made to produce alkenes such as butenes. As a method for producing an alkene using an alkane as a raw material, a method based on a catalytic dehydrogenation reaction in the presence of a catalyst has been conventionally known as an effective method (see, for example, JP-A-3-288548). As a dehydrogenation catalyst for this purpose, a catalyst in which an active substance such as a metal or a metal oxide is supported on a carrier such as silica, alumina, zeolite, or activated carbon is conventionally used. In particular, a chromium oxide / alumina catalyst is often used. (See, for example, US Pat. No. 4,581,339).

[0003]

However, since the dehydrogenation reaction is an endothermic reaction, the reaction is generally carried out at a high temperature, and therefore, catalyst deterioration due to coke formation (carbon deposition on the catalyst) is often observed. In such a case, it is necessary to frequently perform regeneration in order to maintain the activity of the catalyst, resulting in a decrease in process efficiency. Therefore, prevention of catalyst deterioration due to coke generation is strongly desired. That is, the present invention provides a method for producing an alkene by dehydrogenation of an alkane in the presence of a dehydrogenation catalyst, wherein carbon deposition on the catalyst is suppressed and deterioration of the catalyst is alleviated.

[0004]

SUMMARY OF THE INVENTION The present invention provides a method for producing at least one alkene by dehydrogenating at least one alkane containing from 2 to 5 carbon atoms per molecule in the presence of a dehydrogenation catalyst. In the method, the surface area of the dehydrogenation catalyst is 150 m ² / g or more, and the pore volume is 0.55 cm ³ / g.
g or more, a composite carrier comprising zinc oxide on a γ-alumina carrier having an average pore diameter of 90 to 200 angstroms and pores having a pore diameter of 90 to 200 angstroms occupying 60% or more of the total pore volume, The object is achieved by providing a method characterized by using a catalyst carrying platinum and tin and supplying hydrogen together with a raw alkane.

[0005]

DETAILED DESCRIPTION OF THE INVENTION Since the dehydrogenation of alkanes using a solid catalyst is essentially a gas-solid contact operation, it is important to increase the surface area of the catalyst together with the selection of the active metal in order to increase the activity. is there. In order to increase selectivity and suppress activity deterioration, it is necessary to suppress the isomerization reaction or decomposition reaction and to form the target compound preferentially, and to provide surface characteristics that suppress coke deposition. is important. Therefore, in order to prevent a decrease in activity and selectivity, it is important that changes in the surface area and surface characteristics are small. In the present invention, a catalyst having a large surface area and favorable surface properties is obtained by supporting platinum and tin on a composite carrier comprising a specific amount of zinc oxide supported on a specific γ-alumina carrier, and such a catalyst is obtained. By supplying hydrogen together with the raw material alkane to the reaction region containing, the large surface area and the preferable surface characteristics are maintained for a long period of time.

The specific porous γ-alumina support has a surface area of 150 m ² / g or more and a pore volume of 0.55 cm ³ / g.
As described above, the average pore diameter is 90 to 200 angstroms, and the pores having a pore diameter of 90 to 200 angstroms occupy 60% or more of the total pore volume. If the average pore diameter is smaller than 90 angstroms, diffusion of alkane molecules and alkene molecules in the pores is rate-determining, and the entire catalyst surface area cannot be used effectively. On the other hand, if the average pore diameter is larger than 200 angstroms, the surface area cannot be increased. A γ-alumina support satisfying the above conditions is:
The slurry of aluminum hydroxide produced by the neutralization of the aluminum salt was filtered and washed, and dehydrated and dried.
It is obtained by baking at 00 to 800 ° C. for about 1 to 6 hours.

The above specific porous γ-alumina carrier includes:
Zinc oxide [ZnO] is preferably supported at 5 to 50% by weight. It is believed that this zinc oxide forms a complex with alumina on the alumina surface and plays a role in providing favorable surface properties. If the loading amount is less than 5% by weight, the surface of the γ-alumina carrier cannot be uniformly covered with the composite of alumina and zinc oxide, so that a sufficient effect cannot be obtained.
If the content exceeds 0% by weight, the surface characteristics of the composite of alumina and zinc oxide will change, and the surface area will decrease significantly. In order to carry zinc oxide on the γ-alumina carrier, the carrier may be impregnated with an aqueous solution of a zinc compound such as zinc nitrate, dried and fired.

[0008] Platinum, preferably 0.0
5 to 1.5% by weight is supported. Examples of the platinum compound used herein include chloroplatinic acid, ammonium platinate, platinum bromide, platinum dichloride, platinum tetrachloride hydrate, carbonyl platinum dichloride dichloride, dinitrodiamine platinum salt, and the like. . For supporting platinum, a step of impregnating the composite carrier with an aqueous solution of a platinum compound such as chloroplatinic acid, followed by calcining and then reducing at a high temperature in hydrogen gas is usually used. Other reduction methods may be used instead of reduction.

[0009] Tin is supported together with platinum on the composite carrier. The supported amount of tin is preferably 0.5 to 10% by weight. The tin compound used here is preferably a water-soluble compound and / or a compound soluble in an organic solvent such as acetone. Examples of such tin compounds include stannous bromide, tin acetate, stannous chloride, stannic chloride, and hydrates thereof, stannic chloride acetylacetonate complex, tetramethyltin, tetraethyltin , Tetrabutyltin,
And tetraphenyltin. The supporting of tin is usually carried out by impregnating the carrier after the above-mentioned reduction step with an aqueous solution of a tin compound and / or an organic solvent solution to dry and remove water or an organic solvent, and then reducing at high temperature in hydrogen gas. However, in the present invention, other reduction methods may be used instead of hydrogen reduction.

[0010] On the composite carrier, at least one alkaline metal selected from the group consisting of Group 1A and Group 2A of the periodic table can be supported together with platinum and tin. This is more effective for preventing the deterioration of the catalyst. The loading amount of the alkaline metal is preferably from 0.01 to 10% by weight. "Alkaline metal" refers to a metal element of Groups 1A and 2A of the periodic table, including lithium, sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium and barium. As the alkaline metal compound used for supporting the catalyst on a catalyst, a water-soluble compound or a compound soluble in an organic solvent such as acetone is preferable. As such compounds, chlorides, bromides, iodides, nitrates, sulfates, acetates, propionates and the like of the above-mentioned alkaline metals can be suitably used. The loading of the alkaline metal is
After the reduction step, a method of impregnating the carrier with an aqueous solution of an alkaline metal compound or an organic solvent solution to dry and remove the water or the organic solvent, and then subjecting the carrier to a high temperature treatment is usually used.

[0011] The catalyst composition obtained as described above,
Finally, when high-temperature reduction treatment is performed in the presence of a reducing gas, deterioration at high temperatures is further alleviated. As the reducing gas used here, hydrogen or a mixed gas containing hydrogen is preferable, and it is more preferable to use hydrogen gas alone. Usually, the high-temperature reduction treatment is 500 to 700 ° C, preferably 550 to 650 ° C.
At a temperature of about 1 to 20 hours. The high-temperature reduction treatment does not necessarily need to be performed before the catalyst is charged into the reaction tube, and after the catalyst is charged into the reaction tube, hydrogen gas is introduced before the raw material alkane is introduced and the dehydrogenation reaction is performed. What is necessary is just to circulate through a reaction tube.

The production of an alkene by dehydrogenation of an alkane is usually carried out by feeding a raw alkane into a tubular reactor filled with a dehydrogenation catalyst and reacting the alkane under a condition heated to 450 to 650 ° C. The space velocity of the raw material alkane is in the range of 100~10000hr ^-1, preferably preferably in the 100~2000hr ^-1. At this time, in the present invention, hydrogen is supplied to the reactor inlet together with the raw alkane. The supply amount of hydrogen is about 1:
A range from 1 to about 1:20 is preferred. Hydrogen supply is 1:
If it exceeds 1, the effect of equilibrium hindering the progress of the reaction becomes strong, and if the supply amount of hydrogen is less than 1:20, the effect of suppressing the precipitation of carbon becomes insufficient. In the case of a tubular reactor, the problem of catalyst deterioration due to the deposition of carbon has been a problem near the inlet of the reactor. This is because hydrogen is released as the dehydrogenation reaction proceeds, so the hydrogen increases in the atmosphere as the distance from the reactor inlet side increases,
This is thought to be because carbon deposition is suppressed. In the present invention, since hydrogen is supplied together with the raw material alkane, hydrogen is present in the atmosphere throughout the reactor, and carbon deposition is prevented. The method of the present invention has a remarkable effect particularly when a piston flow type reactor such as a tubular reactor is used, but also when a quasi-perfect mixing type reactor such as a fluidized bed type is used. Effectively prevents carbon deposition.

The raw material alkane is generally a compound having 2 to 5 carbon atoms.
Use one. Preferred examples are propane, n-
Butane, isobutane, n-pentane, 2-methylbutane (isopentane) and the like. Then, these are dehydrogenated by the method of the present invention to obtain propene (propylene), butene-1, butene-2, isobutene (isobutylene), pentene-1, pentene-2, 2-methylbutene-1, 2-methylbutene. -2 and the like are obtained.

[0014]

In the following, examples are shown in which a dehydrogenation reaction test was carried out using the dehydrogenation method of the present invention and a conventional method without adding hydrogen. In the following, all values of% are% by weight. (1) Production of γ-alumina support A γ-alumina support was produced as described in Example 1 in JP-B-6-72005. In brief, this method was used to obtain a suspension of an aluminum hydroxide slurry (pH 10) by instantly adding an aqueous sodium aluminate solution while stirring vigorously in hot dilute sulfuric acid. Is repeated by alternately adding hot dilute sulfuric acid and aqueous sodium aluminate solution for a certain period of time to obtain a filter washing cake, extruding and drying it, and then baking it at 500 ° C. for 3 hours. . The properties of γ-alumina thus obtained are typically as shown in Table 1 below.

[Table 1]

(2) Production of a catalyst carrying platinum / tin (/ alkali) 27.5 g of the above-mentioned γ-alumina carrier was taken, and ZnO was added thereto.
30% zinc nitrate [Zn (NO ₃ ) ₂ ] aqueous solution so that the / Al ₂ O ₃ ratio becomes 30/70.
The composite support was prepared by firing at 00 ° C. for 3 hours. The composite carrier is impregnated with 2.0% aqueous solution of chloroplatinic acid [H ₂ PtCl ₆ ] so that the amount of Pt carried is 0.3%, and after impregnation, the carrier is dried.
It was calcined at 0 ° C. for 3 hours, and further reduced at 400 ° C. for 3 hours in a hydrogen stream. Next, the platinum-supported composite carrier after the reduction was impregnated with a 3% aqueous solution of stannous chloride [SnCl ₂ ] so that the amount of supported Sn became 3.5%. After drying, hydrogen reduction was performed at 400 ° C. for 30 minutes. A platinum / tin supported catalyst was obtained.
Further, the amount of K supported on the platinum / tin supported catalyst is 0.5
%, And impregnated with an aqueous solution of potassium nitrate [KNO ₃ ], and air-dried to prepare a platinum / tin / potassium supported catalyst.

(3) Dehydrogenation reaction test The platinum / tin supported catalyst obtained above was filled in a quartz reaction tube having a diameter of 18 mm, and isobutane was used as a raw material at a temperature of 5%.
A dehydrogenation reaction test was performed at 60 ° C. and a space velocity of GHSV of 500 hr ⁻¹ for 20 hours, and the gas at the outlet of the reactor was analyzed by gas chromatography. Further, the catalyst after the completion of the reaction was extracted, and the carbon deposition amount was measured. Next, hydrogen was added at a molar ratio of 0.05 to 0.40 (1:20 to 1: 2.5) with respect to isobutane (GHSV: 25 to 200 hr ^-1 ), and a dehydrogenation reaction test was performed in the same manner. . The results are shown in Table 2 below.

[Table 2]

Next, the platinum / tin-supported catalyst obtained above was filled in a quartz reaction tube having a diameter of 18 mm, treated at 600 ° C. for 3 hours under a hydrogen flow, and then purged sufficiently with nitrogen. went. Thereafter, isobutane is used as a raw material at a temperature of 5 ° C.
A dehydrogenation reaction test was performed at 60 ° C. and a space velocity of GHSV of 500 hr ⁻¹ for 20 hours, and the gas at the outlet of the reactor was analyzed by gas chromatography. Further, the catalyst after the completion of the reaction was extracted, and the carbon deposition amount was measured. Next, hydrogen was added at a molar ratio of 0.05 to 0.20 (1:20 to 1: 5) with respect to isobutane (GHSV: 25 to 100 hr ^-1 ), and a dehydrogenation reaction test was performed in the same manner. The results are shown in Table 3 below.

[Table 3]

Next, the platinum / tin / potassium supported catalyst obtained above was filled in a quartz reaction tube having a diameter of 18 mm, and isobutane was used as a raw material at a temperature of 560 ° C. and a space velocity of GHS.
A dehydrogenation reaction test was performed at V500 hr ^-1 for 20 hours, and the gas at the reactor outlet was analyzed by gas chromatography. Further, the catalyst after the completion of the reaction was extracted, and the carbon deposition amount was measured. Then, 0.05 to 0.20 relative to isobutane
Hydrogen was added at a molar ratio of (1:20 to 1: 5) (GH
SV 25 to 100 hr ^-1 ), and a dehydrogenation reaction test was performed in the same manner. The results are shown in Table 4 below.

[Table 4]

As is clear from Tables 2 to 4, when hydrogen was supplied together with the raw material isobutane to carry out the dehydrogenation reaction, the amount of carbon deposited on the catalyst was significantly reduced, and the catalyst activity was also significantly lowered. Was relaxed.

[0020]

As described above, according to the method of the present invention, the surface area is 150 m ² / g or more, the pore volume is 0.55 cm ³ / g or more, the average pore diameter is 90 to 200 Å,
And a catalyst in which platinum and tin are supported on a composite carrier in which zinc oxide is supported on a γ-alumina carrier in which pores having a pore size of 90 to 200 angstroms occupy 60% or more of the total pore volume, and If hydrogen is supplied together with the raw material alkane, carbon deposition on the catalyst is suppressed, and catalyst deterioration is remarkably reduced.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI C07B 61/00 300 C07B 61/00 300 C07C 5/333 C07C 5/333 (72) Inventor Susumu Yamamoto Tsurumi, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture Chuo 2-chome No. 1 Chiyoda Kako Construction Co., Ltd. (72) Inventor Sachio Asaoka 2-1-1 Tsurumi Chuo 2-chome, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture Chichida Kako Construction Co., Ltd.

Claims (13)

[Claims] 1. The method according to claim 1, wherein the presence of a dehydrogenation catalyst is limited to 2 to 2 per molecule.
A method for producing at least one alkene by dehydrogenating at least one alkane containing 5 carbon atoms, wherein the dehydrogenation catalyst has a surface area of 150 m ² / g or more and a pore volume of 0.55 cm ³ / g or more, average pore diameter 90 to
200 Å and a pore size of 90 to 20
Using a catalyst in which platinum and tin are supported on a composite carrier in which zinc oxide is supported on a γ-alumina carrier in which 0 angstrom pores occupy 60% or more of the total pore volume, and hydrogen together with the raw material alkane is used. A method characterized by providing. 2. The method according to claim 1, wherein the loading amount of zinc oxide on the composite carrier is 5 to 50% by weight. 3. The amount of platinum supported on the composite carrier is 0.0
3. The method according to claim 1, wherein the amount is 5 to 1.5% by weight. 4. The amount of tin carried on the composite carrier is 0.5
The method according to claim 1, wherein the amount is from 10 to 10% by weight. 5. The composite carrier further comprises 1A of the periodic table
At least one selected from the group consisting of group A and group 2A
5. The method according to claim 1, wherein two alkaline metals are supported. 6. The method according to claim 5, wherein the amount of the alkali metal carried on the composite carrier is 0.01 to 10% by weight. 7. Hydrogen is added in a ratio of 1: 1 to hydrogen to the raw alkane.
7. The method according to claim 1, wherein the molar ratio is 1:20. 8. The method according to claim 1, wherein the dehydrogenation is performed at a reaction temperature of 450 ° C. to 650 ° C. 9. The method according to claim 9, wherein the at least one alkane is propane, n-butane, isobutane, n-pentane or 2
9. The method according to claim 1, which is -methylbutane. 10. The at least one alkene is propylene, butene-1, butene-2, isobutene, pentene-1, pentene-2, 2-methylbutene-1 or 2-methylbutene-2. 10. The method according to any one of items 9 to 9. 11. The method according to claim 1, wherein the dehydrogenation catalyst is subjected to a high-temperature reduction treatment in the presence of a reducing gas. 12. The high-temperature reduction treatment is performed at 500 to 700 ° C.
The method according to claim 11, which is performed at a temperature of: 13. The method according to claim 1, wherein the reducing gas is hydrogen.
13. The method according to 1 or 12.