JP2000037627A - Dehydrogenation catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dehydrogenation catalyst applicable to the production of alkenes by dehydrogenating alkanes which maintains high catalytic activity and selectivity over a long period even under high temperature reaction conditions. SOLUTION: A catalyst is prepared by a method in which at least one alkaline metal selected from the group consisting of platinum, tin, the group IA elements, and the group IIA elements of the periodic table is supported on a composite carrier in which zinc oxide is supported on γ-alumina carrier at least 150 m2/g in surface area, at least 0.55 cm3/g in pore volume, and 90-200 angstrom in average pore diameter in which the volume of pores 90-200 angstrom in pore diameter occupies at least 60% of the total pore volume, and the support of the alkaline metal is performed prior to that of tin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a dehydrogenation catalyst,
More specifically, it relates to a dehydrogenation catalyst used for producing an alkene by a dehydrogenation reaction of an alkane.

[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 therefor, 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 (for example, U.S. Pat. No. 4,581,339
), A catalyst using zinc oxide-platinum-chromium together with alumina (for example, see JP-A-7-206718), a platinum / alumina catalyst (for example, Japanese Patent Publication No. 7-4223).
No. 7) has been used for a long time.

[0003] Since the dehydrogenation reaction is an endothermic reaction, the reaction is generally carried out at a high temperature, so that 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. In view of these points, JP-A-9-70535 and JP-A-9-70544 disclose a method in which platinum and tin are supported on a composite carrier in which a specific amount of zinc oxide is supported on a specific γ-alumina carrier. The resulting catalyst is disclosed as having high activity, high selectivity and a lower rate of degradation than conventional catalysts. Furthermore, Japanese Patent Application No. 8-34331
No. 54 is a composite carrier obtained by supporting a specific amount of zinc oxide on a specific γ-alumina carrier, together with platinum and tin,
Disclosed is a catalyst obtained by supporting at least one alkaline metal selected from the group consisting of Group 1A and Group 2A of the periodic table, in which carbon deposition is suppressed and the deterioration rate is further improved.

[0004]

However, the suppression of catalyst activity and selectivity and deterioration of catalyst activity under high temperature reaction conditions cannot be said to be sufficient, and dehydrogenation having a longer catalyst life and excellent stability. A catalyst is desired. That is, the present invention provides a dehydrogenation catalyst used for production of an alkene by dehydrogenation of an alkane, wherein the dehydrogenation catalyst maintains high catalytic activity and selectivity for a long time even under high-temperature reaction conditions. is there.

[0005]

SUMMARY OF THE INVENTION The present invention is directed to a method for fabricating a surface having a surface area of 150.
m ² / g or more, pore volume 0.55 cm ³ / g or more, average pore diameter 90 to 200 Å, and pore diameter 9
The pores of 0 to 200 angstroms have a total pore volume of 60
%, At least one alkaline metal selected from the group consisting of platinum, tin and Group 1A and Group 2A of the periodic table is supported on a composite carrier comprising zinc oxide supported on a γ-alumina carrier occupying at least The above object is achieved by providing a dehydrogenation catalyst characterized in that the loading of the alkaline metal is performed before the loading of the tin.

[0006]

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. It is. 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 specific support is used in which a specific amount of zinc oxide is supported on a specific γ-alumina support, and at least one selected from the group consisting of platinum, tin, and groups 1A and 2A of the periodic table. By supporting one alkaline metal and then supporting the alkaline metal before tin, the acid properties on the composite carrier are neutralized and coated with the alkaline metal, thereby effectively depositing coke on the carrier. The present invention provides a dehydrogenation catalyst which is prevented from being damaged and has a large surface area and favorable surface properties maintained over a long period of time.

The specific porous γ-alumina carrier 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:
For example, it is disclosed in Japanese Patent Publication No. 6-72005,
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 such as zinc nitrate, dried and fired.

[0009] 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 method in which the composite carrier is impregnated with an aqueous solution of a platinum compound such as chloroplatinic acid and then calcined, and then reduced at a high temperature in hydrogen gas is usually used. Other reduction methods may be used instead of reduction.

On the composite carrier, platinum and at least one alkaline metal selected from the group consisting of Group 1A and Group 2A of the periodic table are supported together with platinum. In that case, the alkaline metal is supported before tin. The loading amount of the alkaline metal is preferably from 0.01 to 10% by weight. As used herein, "alkaline metal"
A metal element of Group 1A and Group 2A of the periodic table including lithium, sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium and barium. As a compound of an alkaline metal used for carrying, a water-soluble compound and / or a compound soluble in an organic solvent such as acetone are preferable. Examples of such compounds include potassium chloride, potassium bromide, potassium iodide, potassium nitrate, potassium sulfate, potassium acetate, potassium propionate, rubidium chloride,
Rubidium bromide, rubidium iodide, rubidium nitrate,
Rubidium sulfate, rubidium acetate, rubidium propionate, lithium chloride, lithium bromide, lithium iodide,
Lithium nitrate, lithium sulfate, lithium acetate, lithium propionate, cesium chloride, cesium bromide, cesium iodide, cesium nitrate, cesium sulfate, cesium acetate,
Cesium propionate, magnesium chloride, magnesium bromide, magnesium iodide, magnesium nitrate, magnesium sulfate, magnesium acetate, magnesium propionate, calcium chloride, calcium bromide, calcium iodide, calcium nitrate, calcium sulfate, calcium acetate, propionic acid There is calcium and the like. For supporting the alkaline metal, a method of impregnating the composite carrier with an aqueous solution of an alkaline metal compound and / or an organic solvent solution to dry and remove water or an organic solvent, and then performing a high temperature treatment is usually used.

After supporting the alkaline metal, tin is supported on the composite carrier. Tin carrying amount is 0.5-1
0% by weight is preferred. The tin compound used here is preferably a water-soluble compound and / or a compound soluble in an organic solvent such as acetone. Such tin compounds include:
Stannous bromide, tin acetate, stannous chloride, stannic chloride and their hydrates, stannic chloride acetylacetonate complex, tetramethyltin, tetraethyltin, tetrabutyltin, tetraphenyltin, etc. No. The supporting of tin is carried out by adding an aqueous solution of a tin compound and / or
Or, after drying and removing water or organic solvent by impregnating with an organic solvent solution or the like, a method of reducing at a high temperature in hydrogen gas is usually used, but in the present invention, not necessarily a method of hydrogen reduction but using another reduction method. Is also good.

The catalyst composition obtained as described above comprises:
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 distribute | circulate and process through a reaction tube.

[0013]

In the following, a dehydrogenation reaction test was carried out using a dehydrogenation catalyst A of the present invention in which an alkali metal was supported prior to tin loading and a dehydrogenation catalyst B in which an alkali metal was loaded after tin loading. Here is an example of performing the above. In the following, all values of% are% by weight.

(1) Production of γ-alumina carrier A γ-alumina carrier 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 dehydrogenation catalyst A 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 35/65.
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 solution is dried.
Baking at 0 ° C. for 3 hours. Then, a 1.5% aqueous solution of potassium nitrate [KNO ₃ ] was impregnated so that the amount of supported K became 1.0%, and the mixture was air-dried and then reduced in a hydrogen stream at 400 ° C. for 3 hours. Then, the reduced potassium-platinum-supported composite carrier is impregnated with 0.4% stannous chloride [SnCl ₂ ] methanol solution so that the amount of Sn supported becomes 0.7%, and after drying, it is heated at 400 ° C. for 30 minutes. By carrying out hydrogen reduction, a platinum / potassium / tin supported catalyst A was obtained.

(3) Production of dehydrogenation catalyst B 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 35/65.
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 solution is dried.
It was calcined at 0 ° C. for 3 hours, and further reduced at 400 ° C. for 3 hours in a hydrogen stream. Then, the reduced platinum-supported composite carrier is impregnated with a 2% methanol solution of stannous chloride [SnCl ₂ ] so that the amount of Sn supported is 2.0%.
Hydrogen reduction was performed at 00 ° C. for 30 minutes. Next, 1% potassium nitrate [KNO ₃ ] was added so that the amount of K carried was 0.5%.
An aqueous solution was impregnated and air-dried to obtain a platinum / tin / potassium supported catalyst B.

(4) Dehydrogenation reaction test The catalysts A and B obtained above were 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 sufficiently treated with nitrogen. Was purged. Then, using isobutane as a raw material, at a temperature of 560 ° C. and a space velocity of GHS
A dehydrogenation reaction test was carried out at V 500 hr ^-1 for 20 hours, and the gas at the outlet of the reactor was analyzed by gas chromatography. The results are shown in Table 2 below.

[Table 2]

As is clear from Table 2, when the dehydrogenation reaction was carried out using a catalyst supporting potassium as an alkaline metal prior to supporting tin, the activity of the dehydrogenation catalyst was reduced while maintaining the selectivity. It was possible to remarkably improve and to reduce the amount of tin used.

[0019]

As described above, the dehydrogenation catalyst of the present invention comprises:
When an alkene is produced by an alkane dehydrogenation reaction, the dehydrogenation catalytic activity is significantly improved while maintaining a high level of selectivity.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C07C 5/333 C07C 5/333 11/09 11/09 // C07B 61/00 300 C07B 61/00 300 ( 72) Inventor Susumu Yamamoto 2-1-1, Tsurumichuo, Tsurumi-ku, Yokohama-shi, Kanagawa F-term in Chiyoda Kako Construction Co., Ltd. BC22B BC35A BC35B BC75A BC75B BD01B BD02B BD06B BD12B BE01B BE06B CB07 DA06 EC03X EC04X EC05X EC07X EC08X EC14X EC15X EC28 FA02 FA05 FA06 FA08 FB05 FB14 FB29 FB30 FB44 FB57 FB67 BA12 BA12 BA12 BA12 BA06 BA07 BA06 BA06 BA06 BA07 BA06 CC10

Claims (8)

[Claims] 1. A surface area of 150 m ² / g or more and a pore volume of 0.1 m ² / g.
Composite comprising zinc oxide supported on a γ-alumina carrier having a pore size of at least 55 cm ³ / g, an average pore size of 90 to 200 Å, and pores having a pore size of 90 to 200 Å occupying 60% or more of the total pore volume. At least one alkali metal selected from the group consisting of platinum, tin and Group 1A and Group 2A of the periodic table is supported on the carrier, and the supporting of the alkaline metal is performed prior to the supporting of the tin. A dehydrogenation catalyst, comprising: 2. The catalyst according to claim 1, wherein the amount of zinc oxide carried 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 catalyst according to claim 1, wherein the amount of the catalyst is 5 to 1.5% by weight. 4. The amount of tin carried on the composite carrier is 0.5
The catalyst according to any one of claims 1 to 3, which is 10 to 10% by weight. 5. The catalyst according to claim 1, wherein the amount of the alkaline metal supported on the composite carrier is 0.01 to 10% by weight. 6. The catalyst according to claim 1, wherein the alkaline metal is potassium. 7. A catalyst obtained by subjecting the catalyst according to claim 1 to a high-temperature reduction treatment in the presence of a reducing gas. 8. The catalyst according to claim 7, wherein the high-temperature reduction treatment is performed at a temperature of 500 to 700 ° C.