JPS6345620B2 - - Google Patents

Description

Detailed Description of the Invention The present invention involves mixing an alkoxysilane and a supported metal salt in a solvent containing a polar compound having polydentate or crosslinking coordination ability to form a homogeneous solution, and then converting the homogeneous sol into agar or jelly by hydrolysis. The present invention relates to a method for preparing a metal-supported catalyst, which is characterized by carrying out a gelation step in which the catalyst solidifies into a solid state, and utilizing the cross-linking coordination ability of a polar compound to uniformly and highly disperse the supported metal and to make the catalyst porous.

For metal catalysts, metal-supported catalysts in which catalytically active components are supported on a carrier are usually used for the purpose of increasing the thermal stability and efficiency of the catalyst and preventing deterioration due to melting, but the reaction proceeds on the surface of the metal particles. Therefore, increasing the surface area of the catalytic metal particles will increase the catalytic activity. In order to increase the surface area, it is sufficient to make a catalyst that supports fine metal particles with a smaller particle size, that is, a catalyst with a high degree of dispersion. Such catalysts have high activity per unit metal weight and are resource-saving, and are extremely economical, especially for noble metal catalysts.

The most commonly used methods for preparing supported catalysts are impregnation and coprecipitation. The impregnation method is a method of preparing a supported catalyst by immersing a carrier in a solution in which a supported metal salt is dissolved, adsorbing the dissolved metal salt, and then drying the carrier. Although this is a simple method, concentration distribution tends to occur during adsorption and drying depending on the amount supported, so it is not necessarily recommended as a method for preparing a homogeneous and highly dispersed supported catalyst. The coprecipitation method is a method for preparing a catalyst by simultaneously precipitating a carrier and a supported metal salt. Although this method is said to be easier to obtain a homogeneous catalyst than the impregnation method, it has the disadvantage that the salts used to generate the precipitate are incorporated as impurities during precipitation. Furthermore, since precipitation of precipitates often occurs with extremely small precipitates as nuclei, the concentration distribution of the supported metal salt tends to occur during the growth of the precipitate, making it difficult to obtain a satisfactory homogeneous and highly dispersed supported metal catalyst. Furthermore, in both the impregnation method and the coprecipitation method, it is difficult to make the catalyst porous during catalyst preparation.

In recent years, a new catalyst preparation method, which is different from both the impregnation method and the coprecipitation method, has been discovered. In other words, the method of dissolving and mixing a carrier metal alkoxide and a carrier metal salt in ethylene glycol, and hydrolyzing the mixture after heating is called catalyst volume 24, volume 58.
(1982) and Vol. 25, p. 311 (1983). It is said that relatively uniform silica-supported nickel, cobalt and rhodium catalysts and titania-supported nickel catalysts can be obtained by this method, but due to the high temperature during preparation, there are various drawbacks and differences from the present invention as shown below. There is a point. That is, in this method, ethylene glycol turns into dialkyl cellosolve (Catalyst, Vol. 25, p. 311) and loses its polydentate and bridging coordination ability, making it impossible to bind the silicon support to the supported metal, or to bind silicon to each other. Therefore, during firing, the supported metal becomes easy to move, large metal particles are generated, and the degree of dispersion becomes poor.At the same time, since there is little ethylene glycol remaining until heat treatment, less ethylene glycol is scattered during heat treatment, making it difficult to form porosity. In addition, in this method, the supported metal M is immobilized by M-O-Si bonds and incorporated into the silica network structure (Catalyst Vol. 24, p. 58), resulting in a highly dispersed silica-supported metal catalyst. However, only a small amount of the catalytic metal appears on the silica surface, and therefore it cannot be said that the catalytic metal is used effectively. Furthermore, because the preparation temperature is high in this method, insoluble materials are formed and precipitates occur depending on the supported metal species, and it is often impossible to obtain a homogeneous and highly dispersed catalyst.In addition, since the amount of ethylene glycol is too large relative to the alkoxysilane, the entire solution becomes agar-like. It may not gel into a gelatinous or jelly-like state.

The present inventors conducted various studies to improve these points, and as a result, they arrived at the present invention. The present invention uses an alkoxysilane, a catalytic metal salt, and a polar compound having multidentate coordination ability or crosslinking coordination ability under the conditions of a temperature of 10 to 75°C and a molar ratio of alkoxysilane and polar compound of 1:1 to 10. After hydrolyzing the polar compound solution containing the alkoxysilane and catalytic metal salt formed below to form a gel, and drying under conditions in which the bound polar compound contained in the gel does not substantially volatilize, The present invention provides a method for preparing a porous highly dispersed metal catalyst, which is characterized by subjecting the gel to a high temperature heat treatment to scatter bound polar compounds remaining in the gel to form pores.

In other words, the first step in preparing a homogeneous and highly dispersed catalyst is to create a homogeneous solution.
A low temperature of 75°C or lower, preferably 20°C to 70°C, at which the alkoxysilane, catalytic metal salt, and polar compound are uniformly mixed and the catalytic metal salt does not precipitate.
It is best to warm it up. In the case of polar compounds with hydroxyl groups, it is important to avoid excessive heating in order to prevent their etherification and to prevent the formation of catalytic metal siloxane (M-O-Si) bonds. It is appropriate to heat it between 20℃ and 70℃.

Etherification of the hydroxyl group causes an extreme decrease in the coordination ability of the diol, and significantly reduces the ability of the diol to immobilize catalytic metals and crosslink, so it is necessary to avoid etherification as much as possible, and to reduce the amount of diol due to etherification. It is important to take this into account when determining the amount of diol when preparing the catalyst. If the amount of diol used is too large relative to the alkoxysilane, the entire sol will not solidify during hydrolysis, resulting in a state where jelly or agar-like substances are floating in the diol solution. In such cases, most of the catalyst metal salt has been dissolved in the diol, so even if the gel and diol solution are separated, it is essentially the same as the impregnation method, and a homogeneous and highly dispersed catalyst cannot be obtained. do not have. The amount of polar compounds and alkoxysilane used is
Generally, 1 to 10 mol, preferably 1.5 to 5 mol of the polar compound is suitable per 1 mol of alkoxysilane. As a polar compound, the boiling point at normal pressure is
It is common to use a temperature of 100℃ or higher.

Diols with low alkyl substituents often form insoluble complexes with certain catalytic metal salts resulting in precipitation. For example, when ethoxysilane and rhodium chloride are mixed under heating in ethylene glycol in order to prepare a silica-supported rhodium catalyst, fine precipitates occur and the solution becomes opaque, that is, becomes non-uniform. In such cases, diols that do not cause precipitation, generally highly branched diols such as pinacol or 2-methyl-2,4-
Pentanediol (hexylene glycol) is used, but keto alcohols, amino alcohols, oxycarboxylic acids, ketocarboxylic acids, dicarboxylic acids,
In special cases, a homogeneous and porous highly dispersed silica-supported metal catalyst (supported metal particle size 20 Å Below, surface area 150-1000m ² /g, pore volume 0.01-0.4
cm ³ /g). Therefore, it is necessary to change the polar compound or use a mixture of two or more kinds depending on the situation of the supported metal.

Catalytic metal salts used in the present invention include titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, arsenic, selenium, niobium, molybdenum, technetium, rhodium, palladium, silver, cadmium, Indium, tin, antimony, tellurium, lanthanide, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum,
Examples include salts of gold, mercury, thallium, lead, bismuth, polonium, astatine, or actinides. These materials may be used alone or in a mixture. The amount of the catalyst metal supported in the product is generally about 0.1 to 10% by weight, preferably about 0.5 to 5% by weight.

When preparing at a low temperature to prevent precipitation during the mixing process, or when hydrolysis does not proceed quickly due to the nature of the alkoxide and requires a long period of time, a hydrolysis accelerator such as acid or alkali may be used. When used, hydrolysis can be carried out smoothly. The hydrolysis accelerator may be any of ordinary inorganic salts, organic acids, inorganic alkalis, and organic bases. acids, oxycarboxylic acids, etc.)
Alternatively, organic bases (amines, amino alcohols, etc.) such as formic acid, oxalic acid, tartaric acid, malonic acid, succinic acid, ethanolamine, propanolamine, etc. are suitable.

The jelly-like or agar-like gel produced by hydrolysis is pulverized to an appropriate size, and the gel is crushed under conditions in which the bound polar compounds contained in the gel are not substantially volatilized, for example, at a temperature of 80°C to 110°C and under reduced pressure. 10 hours to 30
Dry for an hour. This drying process removes volatile water and polar compounds contained in the gel, but
The polar compound bonded to the silicon carrier and the catalyst metal remains in the gel without being substantially volatilized. Next, a heat treatment is performed to scatter the polar compound to complete a porous highly dispersed silica-supported catalyst, and the temperature and atmosphere of the heat treatment may be set according to the intended use of the catalyst. In this case, all usual heat treatment methods can be employed, and it is also possible to combine several heat treatment methods. For example, heat treatment can be carried out only in a hydrogen atmosphere, heat treatment can be carried out in oxygen or air, or heat treatment can be carried out in oxygen, air or inert gas followed by further heat treatment in a hydrogen stream.

The catalyst prepared by the method described above does not show clear diffraction lines in powder X-ray diffraction, and electron microscopy confirms that the supported metal particle size is less than 20 Å and is highly dispersed. The surface area was 150 to 1000 m ² /g, the pore diameter was 40 Å or less, and the pore volume was 0.01 to 0.4 cm ³ /g, although it varied depending on the polar compound used during preparation. It is generally extremely difficult to prepare catalysts with such high dispersion and small pore volume using impregnation methods or coprecipitation methods. In addition, the porous silica-supported catalyst obtained in this way has high catalytic activity because the catalytic metal or catalytic metal oxide is uniformly distributed, and is effective as a catalyst for hydrogenation, catalytic oxidation, isomerization, or hydration reactions. It can be used for

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 1 g of osmium trichloride in a 200 ml beaker and
Add 50g of ethylene glycol and warm at 65°C for 30 minutes to completely dissolve. Next, 109g of tetraethoxysilane was added and heated at the same temperature for 3 hours, and 19g of water was added to the resulting homogeneous solution.
While stirring at the same temperature, the sol gradually becomes viscous, and within 1 to 2 hours after adding water, the entire solution solidifies into an agar-like gel. The gel was left at the same temperature for 1 hour, and then left at room temperature overnight. Next, the gel is crushed into appropriate sizes, placed in a 300 ml eggplant-shaped flask, and dried in a rotary evaporator at 100°C under reduced pressure for 24 hours. Yield: 57.3 g (approximately 1.8 times the weight calculated as _SiO2 ). Heat treatment was performed at 400° C. for 8 hours to obtain 32.5 g of 2 wt% Os-SiO ₂ catalyst. Surface area
794 m ² /g, pore volume 0.10 cm ² /g.

Example 2 Put 10ml of ethanol into a 200ml beaker,
To this, 0.0652g of cupric chloride dihydrate and 0.912g
Dissolve 50g of cobalt chloride hexahydrate at 25℃
Add ethylene glycol and heat at 65℃ for 30 minutes. Add 63.3 g of tetraethoxysilane to this solution and stir at the same temperature for 3 hours. Next, an aqueous solution of 1.0 g of tartaric acid dissolved in 11.5 g of water was added and stirred at the same temperature for 50 minutes.
When adding g of aqueous solution and stirring at the same temperature, approx.
It solidifies after 10 minutes. Yield: 29.2g. When heat treated under the same conditions as Example 1, 0.1wt% of the surface area of 712m ² /g
18.8g of Cu-1wt%Co- _SiO2 catalyst was obtained.

Example 3 Place 10 ml of ethanol in a 200 ml beaker and dissolve 0.75 g of nickel chloride hexahydrate at 30°C. After adding 50 g of 2,3-butanediol to this solution and warming it at 60°C for 1 hour, 63.4 g of tetraethoxysilane was added, and the mixture was stirred while heating at the same temperature for 3 hours. Next, 22 g of water is added to this solution, and while stirring while warming at the same temperature, it becomes a gel in about 2 hours after the addition of water. Yield after drying 32.4
g. When heat treatment was carried out in the same manner as in Example 1, 19 g of 1 wt% Ni-SiO ₂ catalyst with a surface area of 537 m ² /g was obtained.

Example 4 50 g of ethanolamine is placed in a 300 ml beaker, and 0.5 g of rhodium trichloride is dissolved therein at 60°C. Add 73.8 g of tetraethoxysilane to this solution and stir while heating at 60°C for 2 hours. Next, 14 g of water was added to this solution, which solidified into agar-like form. Drying and heat treatment were performed in the same manner as in Example 1, and a Rh-SiO ₂ catalyst with a surface area of 382 m ² /g was used.
21.5g was obtained.

Example 5 Put 10ml of ethanol in a 300ml beaker,
Dissolve 1.5g of hexachloroplatinic acid and add 100g of
g of 1,4-butanediol was added and heated at 55° C. for 30 minutes, then 63.3 g of tetraethoxysilane was added and stirred while heating at the same temperature for 4 hours.
Next, 22 g of water is added to this solution and stirred while warming at the same temperature, resulting in gelation within 2 to 3 hours after water addition. When drying and heat treatment were performed in the same manner as in Example 1, the surface area was 959 m ² /g and the pore volume was 0.2.
19 g of 3wt% Pt-SiO ₂ catalyst of cm ³ /g was obtained.

Claims (1)

[Claims] 1. Using an alkoxysilane, a catalytic metal salt, and a polar compound having multidentate coordination ability or bridging coordination ability, at a temperature of 10 to 75°C and a molar ratio of alkoxysilane to polar compound of 1:1. A polar compound solution containing an alkoxysilane and a catalytic metal salt formed under the conditions of ~10 is hydrolyzed to form a gel, and then dried under conditions that do not substantially volatilize the bound polar compound contained in the gel. 1. A method for preparing a porous highly dispersed metal catalyst, the method comprising: followed by high-temperature heat treatment to scatter bound polar compounds remaining in the gel to form pores. 2 The catalyst metal salt is titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, arsenic, selenium, niobium, molybdenum, technetium, rhodium, palladium, silver, cadmium, indium, tin,
antimony, tellurium, lanthanoids, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, mercury, thallium,
The method of claim 1, wherein the salt is a lead, bismuth, polonium, astatine, or actinide salt. 3. Claim No. 3 in which the polar compound is one or a mixture of two or more of monohydric alcohol, dihydric alcohol, amino alcohol, keto alcohol, diketone, monocarboxylic acid, ketocarboxylic acid, oxycarboxylic acid, and dicarboxylic acid. Method in section 1. 4. The method according to claim 3, wherein the dihydric alcohol is one or a mixture of two or more diols having 14 or less carbon atoms. 5 The dihydric alcohol is ethylene glycol,
1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 2,3-butanediol, 1,3-butanediol, 1,4-
butanediol, 1,2-pentanediol,
1,4-pentanediol, 2,4-pentanediol, 1,2-hexanediol, 1,5-hexanediol, 1,6-hexanediol,
2,5-hexanediol, 2-methyl-2,4
-pentanediol, 3-methyl-1,3-butanediol, 2,5-dimethyl-2,5-hexanediol, pinacol, 1,2-cyclohexanediol, 1,3-cyclohexanediol and 1,4-cyclohexanediol The method according to claim 4, which is one type or a mixture of two or more types. 6 Alkoxysilane has alkoxy group carbon number of 1
The method of claim 1, wherein the alkoxysilane is one or a mixture of two or more of the following alkoxysilanes. 7. Claim No. 7, wherein the alkoxysilane is one or a mixture of two or more of methoxysilane, ethoxysilane, n-propoxysilane, iso-propoxysilane, n-butoxysilane, iso-butoxysilane, and sec-butoxysilane. Method in section 1. 8 Solution formation temperature and hydrolysis temperature from 20℃
The method of claim 1, wherein the temperature is 70°C. 9. The method according to claim 1, wherein the molar ratio of alkoxysilane to polar compound is 1:1.5 to 5.