JP2018008179A - Catalyst for dehydrogenation reaction - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a catalyst for dehydrogenation reaction high in catalyst activity in a dehydrogenation reaction by suppressing side reactions of the dehydrogenation reaction.SOLUTION: There is provided a catalyst for dehydrogenation reaction containing alumina, an alumina carrier containing silica adhered to the alumina and platinum carried on the alumina carrier, where the adhered amount of the silica based on the weight of the alumina is 3.0×10to 1.0×10mol/g. The adhered amount of the silica based on weight of the alumina is preferably 4.0×10to 5.0×10mol/g, the number of acid points of the catalyst for dehydrogenation reaction is preferably 250 μmol or less, and carrying ratio of platinum based on the weight of the catalyst for dehydrogenation reaction is preferably 0.1 to 5.0 wt.%.SELECTED DRAWING: None

Description

  The present invention relates to a catalyst for dehydrogenation reaction.

  Conventionally, a catalyst in which platinum fine particles are supported on an alumina carrier has been used as a dehydrogenation reaction catalyst. However, alumina has acid sites and base sites that act as a catalyst, and there is a problem that side reactions other than dehydrogenation occur due to the acid sites. Therefore, several catalysts for dehydrogenation reaction in which the occurrence of side reaction of dehydrogenation reaction is suppressed by reducing the activity of acid sites have been proposed.

  Patent Document 1 discloses a composite carrier obtained by coating porous alumina having mesosize pores of 2 to 50 nm on the surface of a non-porous high-density ceramic oxide such as alumina containing magnesium. There has been proposed a catalyst for a hydrocarbon conversion process, which carries a binary metal of platinum and co-catalyst tin. Patent Document 2 proposes a catalyst carrier in which the acid sites of porous oxides such as alumina, titania and zirconia are neutralized with at least one selected from alkali metals, alkaline earth metals and rare earth elements. . However, in these methods, since the activity of the acid sites of the catalyst carrier cannot be sufficiently lowered, there is a limit in suppressing the occurrence of side reactions in the dehydrogenation reaction.

JP 2006-198616 A JP 2004-337724 A

  An object of the present invention is to provide a catalyst for a dehydrogenation reaction that can suppress the occurrence of a side reaction of the dehydrogenation reaction and has a high catalytic activity in the dehydrogenation reaction.

As a result of intensive studies on the catalyst for dehydrogenation reaction, the present inventor has found that the use of alumina to which silica is attached as a carrier suppresses the occurrence of side reaction of the dehydrogenation reaction, leading to the present invention. . That is, the present invention
An alumina support containing alumina and silica adhered to the alumina;
A catalyst for dehydrogenation reaction comprising platinum supported on the alumina support,
The amount of the silica deposited based on the weight of the alumina support is a catalyst for dehydrogenation reaction of 3.0 × 10 ^{−5 to} 1.0 × 10 ⁻³ mol / g.

  The catalyst for dehydrogenation reaction of the present invention can suppress the occurrence of side reaction of dehydrogenation reaction and has high catalytic activity in the dehydrogenation reaction.

  Hereinafter, although embodiment of this invention is described, the following description is not the meaning which limits this invention to specific embodiment.

  The catalyst for dehydrogenation reaction of the present invention includes an alumina carrier containing alumina and silica adhering to the alumina (hereinafter sometimes simply referred to as “alumina carrier”), and platinum supported on the alumina carrier. .

  There is no restriction | limiting in particular as the kind of alumina which comprises an alumina support | carrier, For example, alpha-alumina, gamma-alumina etc. are mentioned. The shape of the alumina is not particularly limited, and may be an irregular shape obtained by crushing or a spherical shape obtained by granulation.

  Silica attached to alumina is not particularly limited, but those obtained from alkoxysilane, which is a precursor of silica, are preferable from the viewpoint of easy attachment to alumina. Examples of alkoxysilane include tetramethoxysilane, tetraethoxysilane, and tetraisopropoxysilane. Alkoxysilane is hydrolyzed and polycondensed by a so-called sol-gel method. Silicon hydroxide is produced by hydrolysis of alkoxysilane, and then silica is produced by condensation polymerization of silicon hydroxide.

  Hydrolysis and polycondensation of alkoxysilane is preferably performed in a solution containing alumina in order to make silica easily adhere to alumina. Solvents contained in the solution containing alumina include methanol, ethanol, n-propyl alcohol, isopropyl alcohol, acetone, acetonitrile, dimethyl sulfoxide, dimethylformamide, dimethylimidazolidinone, ethylene glycol, tetraethylene glycol, dimethylacetamide, N -Methyl-2-pyrrolidone, tetrahydrofuran, dioxane, methyl ethyl ketone, cyclohexanone, cyclopentanone, 2-methoxyethanol (methyl cellosolve), 2-ethoxyethanol (ethyl cellosolve), ethyl acetate and the like.

  After hydrolysis of the alkoxysilane, the solvent is removed, and then heat treatment is performed so that silica adheres to the alumina and an alumina support is obtained. The heat treatment temperature is preferably 200 to 600 ° C. The heat treatment time is preferably 30 minutes or longer.

In the alumina to which silica is adhered, silica covers at least a part of the alumina surface. Further, silica may adhere to the pores of alumina. The adhesion amount of silica based on the weight of alumina is 3.0 × 10 ^{−5 to} 1.0 × 10 ⁻³ mol / g, preferably 3.0 × 10 ^{−5 to} 7.0 × 10 ⁻⁴ mol. / G, more preferably 4.0 × 10 ^{−5 to} 5.0 × 10 ⁻⁴ mol / g, particularly preferably 4.0 × 10 ^{−5 to} 2.0 × 10 ⁻⁴ mol / g. If it is said range, the effect which suppresses generation | occurrence | production of the side reaction of a dehydrogenation reaction will increase. The amount of silica adhered based on the weight of alumina can be calculated from the number of moles of silica obtained from the alkoxysilane used and the amount of alumina used.

  The distribution of platinum supported on the alumina support is not particularly limited and may be any of uniform support, outer layer support, inner layer support, and center support, but the outer layer support is preferable from the viewpoint of catalytic activity.

  The method for supporting platinum on the alumina carrier is not particularly limited. For example, after adding a reducing agent to a platinum compound solution to obtain a platinum colloid solution, the platinum colloid solution is impregnated with the alumina carrier, and the solvent in the platinum colloid solution is obtained. And a method for removing the.

  Platinum compounds include chloroplatinic acid, ammonium platinate, bromoplatinic acid, platinum dichloride, platinum tetrachloride hydrate, carbonyl platinum dichloride, dinitrodiamine platinate, platinum oxide, platinum black, etc. Is mentioned. A platinum compound may be used independently and may use 2 or more types together. Examples of the solvent contained in the platinum compound solution include water, acetone, and ethanol.

  Examples of the reducing agent include alcohol, carboxylic acid, ketone, ether, aldehyde, ester and the like. A reducing agent may be used independently and may use 2 or more types together. Examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, ethylene glycol, glycerin, and pyrogallol. Examples of the carboxylic acid include formic acid, acetic acid, fumaric acid, malic acid, citric acid, succinic acid, aspartic acid, tannic acid, gallic acid, and alkali metal (lithium, sodium, potassium) salts thereof. Examples of the ketone include acetone and methyl ethyl ketone. Examples of ethers include diethyl ether. Examples of the aldehyde include formaldehyde and acetaldehyde. Examples of the ester include methyl formate, methyl acetate, and ethyl acetate.

The concentration of the platinum compound in the platinum compound solution is preferably 1 × 10 ⁻⁶ to 15 × 10 ⁻⁴ mol / L. The amount of the reducing agent used is preferably 1 to 40 equivalents relative to the number of moles of the platinum compound. After adding the reducing agent to the platinum compound solution, the solvent is refluxed for about 30 minutes to 5 hours, and the reaction is quenched by quenching to room temperature. Subsequently, a platinum colloid solution is obtained by removing an unreacted platinum compound and a reducing agent using an ion exchange resin.

  There is no restriction | limiting in particular as a method of removing the solvent in a platinum colloid solution, For example, the method of removing using an evaporator etc. are mentioned.

  The platinum loading based on the weight of the catalyst for dehydrogenation reaction is preferably 0.1 to 5.0% by weight, more preferably 0.3 to 2.0% by weight. If it is said range, the catalytic activity of the catalyst for dehydrogenation will become high.

  The number of acid sites in the dehydrogenation reaction catalyst is preferably 250 μmol / g or less. Here, the acid point of the catalyst for dehydrogenation reaction is a structural unit exhibiting the acid property of the catalyst for dehydrogenation reaction, and the number can be measured by the following method.

<Method for measuring the number of acid sites on the catalyst for dehydrogenation reaction>
After putting 0.05 g of a catalyst for dehydrogenation reaction in a cell provided in a fully automatic thermal desorption spectrum apparatus “TPD-ATw” [manufactured by Nippon Bell Co., Ltd.], heat-treating at 400 ° C. for 60 minutes in a helium atmosphere Then, ammonia was adsorbed at 100 ° C., and excess ammonia was removed at 100 ° C. in a helium atmosphere, and then the amount of ammonia desorbed was measured while raising the temperature at 10 ° C./min in a helium atmosphere. From the amount of ammonia desorbed, the number of moles of ammonia adsorbed on 1 g of the dehydrogenation reaction catalyst was calculated, and this was used as the number of acid sites of the dehydrogenation reaction catalyst.

  The examples illustrate the invention in detail. However, the following examples show examples of the present invention, and the present invention is not limited to the following examples.

<Example 1>
[Production of alumina support]
Ethanol is added to tetraethoxysilane [manufactured by Shin-Etsu Chemical Co., Ltd.] 100 μL (0.451 mmol) so that the total liquid volume becomes 11 mL, and alumina “GB-13” [average particle size: 2 mm, specific surface area] : 180 m ² / g, pore volume: 0.5 cm ³ / g, average pore diameter: 11.1 nm, manufactured by Mizusawa Chemical Industry Co., Ltd.] 10 g was added and left at room temperature for 24 hours. Next, the ethanol was removed by leaving it in a dryer at 80 ° C. for 1 hour, and then heat treated at 400 ° C. for 3 hours to obtain an alumina carrier.

[Preparation of colloidal platinum solution]
184.22 mL of ultrapure water was placed in a 200 mL round bottom flask equipped with a reflux apparatus, and ultrapure water was refluxed for 30 minutes using a mantle heater. Next, 5.31 mL of 4 wt% chloroplatinic acid [Oura Precious Metal Industry Co., Ltd.] was added, and the mixture was further refluxed for 40 minutes. Next, 2.05 mL of 1M potassium carbonate aqueous solution as a pH adjusting agent and 8.42 mL of 15 wt% tannic acid aqueous solution were added and refluxed for 30 minutes, and chloroplatinic acid was reduced to obtain a platinum colloid solution. Subsequently, it cooled to normal temperature, the impurity in a platinum colloid solution was removed using 32g of ion exchange resin "Amberlite MB-1" [made by Organo Corporation], and the platinum colloid solution (platinum concentration: 250 ppm) was obtained.

[Supporting platinum]
5 g of an alumina carrier and 120 mL of a platinum colloid solution were placed in a 500 mL eggplant flask, and platinum was supported while dehydrating using an evaporator, to obtain a catalyst E-1 for dehydrogenation reaction.

<Example 2>
A catalyst E-2 for dehydrogenation reaction was obtained in the same manner as in Example 1 except that the amount of tetraethoxysilane was 200 μL (0.902 mmol).

<Example 3>
A dehydrogenation reaction catalyst E-3 was obtained in the same manner as in Example 1 except that the amount of tetraethoxysilane was 400 μL (1.80 mmol).

<Example 4>
A catalyst E-4 for dehydrogenation reaction was obtained in the same manner as in Example 1 except that the amount of tetraethoxysilane was 2 mL (9.02 mmol).

<Example 5>
Alumina is added to “GB-45” [average particle size: 4 mm, specific surface area: 180 m ² / g, pore volume: 0.5 cm ³ / g, average pore size: 11.1 nm, manufactured by Mizusawa Chemical Co., Ltd.] Except having changed, it carried out similarly to Example 1, and obtained the catalyst E-5 for dehydrogenation.

<Comparative Example 1>
A catalyst for dehydrogenation reaction C-1 was obtained in the same manner as in Example 1 except that tetraethoxysilane was not added.

<Comparative example 2>
A catalyst for dehydrogenation C-2 was obtained in the same manner as in Example 1 except that the amount of tetraethoxysilane was 20 μL (0.0902 mmol).

<Comparative Example 3>
A dehydrogenation catalyst C-3 was obtained in the same manner as in Example 1 except that the amount of tetraethoxysilane was 40 μL (0.180 mmol).

<Comparative Example 4>
A catalyst for dehydrogenation C-4 was obtained in the same manner as in Example 1 except that the amount of tetraethoxysilane was 4 mL (18.0 mmol).

<Comparative Example 5>
A dehydrogenation catalyst C-5 was obtained in the same manner as in Example 1 except that the amount of tetraethoxysilane was 6 mL (27.1 mmol).

<Comparative Example 6>
A catalyst C-6 for dehydrogenation was obtained in the same manner as in Example 1 except that the amount of tetraethoxysilane was 10 mL (45.1 mmol).

<Comparative Example 7>
A catalyst C-7 for dehydrogenation reaction was obtained in the same manner as in Example 1 except that tetraethoxysilane was not added and alumina was changed to “GB-45” [manufactured by Mizusawa Chemical Industry Co., Ltd.]. .

<Comparative Example 8>
No tetraethoxysilane was added, and alumina was silica “Q-30” [average particle size: 1.7 mm, specific surface area: 100 m ² / g, pore volume: 1.0 cm ³ / g, average pore size: 30 nm The catalyst for dehydrogenation C-8 was obtained in the same manner as in Example 1 except that the product was changed to “Fuji Silysia Chemical Co., Ltd.”.

<Amount of silica attached to alumina>
In the catalysts for dehydrogenation prepared in Examples 1 to 5 and Comparative Examples 1 to 8, the amount of silica attached based on the weight of alumina is the number of moles of silica obtained from the tetraethoxysilane used and the amount of alumina used. Calculated from

<Method for measuring the number of acid sites on the catalyst for dehydrogenation reaction>
The number of acid sites of the dehydrogenation reaction catalysts prepared in Examples 1 to 5 and Comparative Examples 1 to 8 was measured by the same method as the above measurement method.

<Measurement of platinum loading on catalyst for dehydrogenation reaction>
Examples 1-5, 50 mg of the catalyst for dehydrogenation prepared in Comparative Examples 1-8 were placed in a 50 mL Teflon reaction vessel together with 5 mL of aqua regia, and the Teflon reaction vessel was placed in a SUS vessel and sealed. Heat treatment was performed at 170 ° C. for 6 hours. Next, the mixture was cooled to room temperature, and the mixed solution of dehydrogenation catalyst and aqua regia was diluted 100 times with ultrapure water. The platinum concentration in the diluted solution was measured by ICP-MS, and the platinum loading was measured. The results are shown in Table 1.

<Measurement of hydrogen production in dehydrogenation reaction>
The catalyst for dehydrogenation prepared in Examples 1 to 5 and Comparative Examples 1 to 8 was filled in a fixed bed flow type reactor at 3.5 cm ³ and heated to 300 ° C. 200 μL of methylcyclohexane was put into a carrier gas supply device and heated to be vaporized. The carrier gas [nitrogen: air = 3: 1 (volume ratio)] at 170 ° C. was poured there at a flow rate of 240 mL / min, so that methylcyclohexane was fed into the fixed bed flow reactor filled with the catalyst for dehydrogenation reaction. It is. The amount of hydrogen produced by the dehydrogenation reaction of methylcyclohexane was measured for 7.5 minutes. The results are shown in Table 1.

  The dehydrogenation reaction catalysts of Examples 1 to 5 produced more hydrogen than the dehydrogenation reaction catalysts of Comparative Examples 1 to 7. That is, by supporting platinum on an alumina carrier containing alumina with silica adhered thereto, the catalytic activity as a catalyst for the dehydrogenation reaction was increased, and the occurrence of a side reaction of the dehydrogenation reaction could be suppressed. Further, when alumina was not used as a carrier and silica itself was used as a carrier (Comparative Example 8), the amount of hydrogen produced was small compared to the dehydrogenation reaction catalysts of Examples 1-5. This is because the dehydrogenation reaction is an endothermic reaction, and in order to proceed with the reaction, it is necessary to rapidly supply heat to the reaction field, but alumina has better thermal conductivity than silica. It is considered that the catalytic activity of the catalyst for dehydrogenation reaction is increased by the silica adhering to the alumina within a range not inhibiting the thermal conductivity of the alumina (the acid sites of the alumina are covered with the silica film).

  The catalyst for dehydrogenation reaction of the present invention can suppress the occurrence of side reactions of the dehydrogenation reaction and has high catalytic activity in the dehydrogenation reaction. For example, various saturated hydrocarbons, particularly cyclohexane, methylcyclohexane, It can be suitably used as a catalyst for producing hydrogen and cyclic unsaturated hydrocarbons from cyclic saturated hydrocarbons such as decalin.

Claims (3)

An alumina support containing alumina and silica adhered to the alumina;
A catalyst for dehydrogenation reaction comprising platinum supported on the alumina support,
The amount of the silica adhered based on the weight of the alumina is 3.0 × 10 ^{−5 to} 1.0 × 10 ⁻³ mol / g. 2. The catalyst for dehydrogenation reaction according to claim 1, wherein an amount of the silica adhered based on a weight of the alumina is 4.0 × 10 ^{−5 to} 5.0 × 10 ⁻⁴ mol / g.   The catalyst for dehydrogenation reaction according to claim 1 or 2, wherein the platinum loading based on the weight of the catalyst for dehydrogenation reaction is 0.1 to 5.0 wt%.