JPS6345623B2 - - Google Patents

Description

Detailed Description of the Invention The present invention involves mixing a zirconium alkoxide and a catalytic metal salt in a solution of a polar compound having polydentate or bridging 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 crosslinking coordination ability of a polar compound to uniformly and highly disperse the catalytic metal and to make the catalyst porous.

Supported metal catalysts, in which catalytically active components are supported on a carrier, are usually used for reactions in order to increase the thermal stability and efficiency of the catalyst and to prevent deterioration due to melting, but reactions occur on the surface of metal particles. Therefore, if the surface area of the catalytic metal particles is increased, the catalytic activity will be increased. In order to increase the surface area, a catalyst supporting fine metal particles with a smaller particle size, that is, a catalyst with a high degree of dispersion, may be produced. 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 containing a supported metal salt, adsorbing the dissolved metal salt, and then drying the carrier. Although this is a simple method, concentration distribution tends to occur during adsorption or drying depending on the amount supported, and 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. Compared to the impregnation method, this method
Although it is said that it is easy to obtain a homogeneous catalyst, there is a drawback that the salts used to generate the precipitate are incorporated as impurities during precipitation. In addition, when forming a precipitate, very small precipitates are often used as the core, so the concentration distribution of the catalytic 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. Hard to get caught. Furthermore, in both the impregnation method and the coprecipitation method, it is difficult to make the catalyst porous or fine when preparing the catalyst.

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 the carrier metal alkoxide and the catalyst metal salt in ethylene glycol and hydrolyzing it after heating is the catalyst volume 24.
Reported on page 58 (1982) and volume 25, page 311 (1983). Although this method is said to yield relatively uniform silica-supported nickel, cobalt and rhodium catalysts and titania-supported nickel catalysts, it has various drawbacks as shown below. In other words, in this method, perhaps due to the high temperature during preparation, ethylene glycol turns into dialkyl cellosolve (Catalysts Vol. 25, p. 311), and loses its multidentate and crosslinking coordination ability, which makes it difficult to bond the silicon support and the catalyst metal. , it becomes impossible to bond silicon comrades together. Therefore, during firing, the supported metal moves easily, large metal particles are generated, and the degree of dispersion deteriorates.At the same time, there is little ethylene glycol remaining until heat treatment, so less ethylene glycol is scattered during heat treatment, making it difficult to form porosity. In addition, in this method, the catalyst metal M is immobilized by M-O-Si bonds and incorporated into the silica network structure (Catalysts, Vol. 24, p. 58), so a highly dispersed silica-supported metal catalyst is formed. Even if it were possible, only a small amount of the catalytic metal appears on the silica surface, so it cannot be said that the catalytic metal is used effectively. Furthermore, since the preparation temperature is high in this method, metal ions may be reduced and precipitated during preparation depending on the catalyst metal species, or insoluble matter may form and precipitate, making it impossible to produce a homogeneous and highly dispersed catalyst. There are also many. Although several drawbacks have been mentioned above, the biggest drawback of this method is that it can only be applied to the preparation of silica-supported catalysts. because,
When this method is applied to alumina, titania, or zirconia supported catalysts, various alkoxides such as aluminum alkoxide, titanium alkoxide, and zirconium alkoxide form insoluble complexes like adducts with ethylene glycol. This is because they cannot be mixed (exactly the same phenomenon is seen with propanediol and glycerin). If uniform mixing is not possible, it is of course impossible to obtain a homogeneous gel or to prepare a homogeneous and highly dispersed supported metal catalyst.

The present inventors conducted various studies to improve these points, and as a result, they arrived at the present invention.

According to the invention, zirconium alkoxide,
Zirconium formed using a catalytic metal salt and a polar compound having multidentate coordination ability or bridging coordination ability at a temperature of 10 to 80°C and a molar ratio of zirconium alkoxide to polar compound of 1:1 to 15. After a homogeneous solution consisting of an alkoxide, a catalytic metal salt, and a polar compound is hydrolyzed to form a gel, it is dried under conditions in which the bound polar compound contained in the gel does not substantially volatilize, and then subjected to high-temperature heat treatment. There is also provided a method for preparing a porous highly dispersed metal catalyst using zirconia as a carrier, which is characterized by scattering the bonded polar compound 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.
Zirconium alkoxides and catalytic metal salts are dissolved in polar compounds with polydentate or bridging coordination ability,
Polar compounds and preparation temperatures must be selected to obtain a homogeneous solution. For this purpose, it is best to choose amino alcohols or highly branched oxygen-containing compounds (diols, keto alcohols, carboxylic acids) as polar compounds, such as ethanolamine, propanolamine, pinacol, hexylene glycol, 3-methyl -1,3-butanediol, 2,5-dimethyl-2,5-hexanediol, 2,3-butanediol, 2,4-pentanediol, 1,2-cyclohexanediol,
1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,5-pentanediol, 1,6-hexanediol, 2,5-hexanediol, diacetone alcohol and 3-hydroxy-3-methyl-2-butanone etc. are good. The adjustment temperature is set to prevent the catalyst metal salt from being reduced and precipitated by alcohols and precipitation due to the formation of insoluble complexes, and also to prevent the etherification of alcohol hydroxyl groups and esterification of carboxylic acids such as in alkyl cellosolve. bond (M-O-
In order to prevent the formation of Zr) bonds, it is important to avoid excessive heating, and it is best to perform hydrolysis by heating between 20°C and 75°C.

Due to etherification or esterification of hydroxyl groups, polar compounds containing hydroxyl or carboxyl groups will significantly reduce the immobilization ability and crosslinking ability of the catalyst metal salt, so the preparation of this catalyst is carried out at low temperatures where etherification and esterification do not occur. Must. In addition, in order to compensate for the decrease in alcohol and organic acid due to unavoidable etherification and esterification, and to exert a fixed connection function between the support metal and the catalyst metal or between support metals, the amount of polar compound is not necessarily specified, but the support zirconia Zirconium 1
It is desirable to use at least 1 mole of polar compound per atom, ie per mole of zirconium alkoxide. However, if the polar compound with polydentate and crosslinking coordination ability is present in large excess relative to the zirconium alkoxide, the entire sol will not solidify during hydrolysis, resulting in a state where jelly or agar is floating in the polar compound solution. Become. In such a case, the catalytic metal salt dissolves considerably in the unsolidified solution, so the method is essentially the same as the impregnation method, and a homogeneous and highly dispersed catalyst that takes advantage of the characteristics of this method cannot be obtained. Therefore, the amount of polar compound used is preferably in the range of 1 mol to 15 mol per 1 mol of zirconium alkoxide.

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, Salts of indium, tin, antimony, tellurium, lanthanides, hafnium, tantalum, tungsten, rhenium, ruthenium, osmium, iridium, platinum, gold, mercury, thallium, lead, bismuth, polonium, astatine, or actinides may be mentioned. 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.

In the case of zirconium alkoxide, hydrolysis is generally quick, so acids or alkalis are not necessarily required as hydrolysis accelerators. However, in some cases, hydrolysis may be slow, and in such cases, It is better to use an acid or an alkali, and the present invention does not exclude the combined use of an acid or an alkali when preparing the catalyst. The hydrolysis accelerator may be any of ordinary inorganic acids, organic acids, inorganic bases, and organic bases, but the most important ones are organic acids (carboxylic acids, ketocarboxylic acids, , oxycarboxylic acids, etc.) or organic bases (amines, amino alcohols, etc.), and specific examples of these include formic acid, silicic acid, tartaric acid, malonic acid, succinic acid, ethanolamine, propanolamine, etc. be.

The jelly-like or agar-like gel produced by hydrolysis is crushed into appropriate sizes, 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 under reduced pressure. From 6 hours
Dry for 30 hours. This drying process removes volatile water and polar compounds contained in the gel, but the polar compounds bonded to the carrier metal and catalyst metal remain in the gel without being substantially volatilized. After drying, a porous highly dispersed zirconia supported catalyst is completed by heat treatment to scatter the polar compound, and the temperature and atmosphere of the heat treatment may be set depending on the intended use of the catalyst. In this case, all the usual heat treatment methods can be used and
It is also possible to combine several heat treatment methods. For example, heat treatment can be carried out only in a hydrogen atmosphere, or heat treatment can be carried out in oxygen, air, or inert gas, and then further heat treatment in a hydrogen stream.

The catalyst prepared by the method described above did not show clear diffraction lines in powder X-ray diffraction, and electron microscopy confirmed that the supported metal particle size was 20 Å or less and highly dispersed. Ta.

In addition, in such porous zirconia-supported catalysts, the catalytic metal or catalytic metal oxide is uniformly distributed, and the surface area is 2 to 10 times larger than that of ordinary zirconia, resulting in high catalytic activity and hydrogen absorption. It can be effectively used as a catalyst for oxidation, catalytic oxidation, isomerization, or hydration reactions.

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

Example 1 10 ml of ethanol is placed in a 300 ml beaker, and 0.0652 g of cupric chloride dihydrate and 1 g of ruthenium trichloride are dissolved therein at 30°C. 50.1 to this solution
g of pinacol was added, and after heating at 70°C for 30 minutes, 50.7g of zirconium n-propoxide was added, and the mixture was stirred while warming at 65°C for 3 hours. Next, 60 ml of an ethanol solution containing 5.5 g of water is added, and while stirring at the same temperature, it solidifies into agar-like form within a few minutes. Leave the gel at the same temperature for 30 minutes, and then leave it at room temperature overnight. Crush the gel into appropriate sizes,
Place in a 300ml eggplant-shaped flask and dry under reduced pressure at 100°C for 24 hours using a rotary evaporator.
Yield after drying: 27g (approximately 1.4 of the calculated amount as _ZrO2 )
times). The dried gel was pulverized, spread in a quartz tube, and heat-treated at 350°C for 6 hours in a hydrogen stream, resulting in a concentration of 2wt%.
Ru−0.2wt%Cu−ZrO ₂ catalyst (surface area 12m ² /g)
get.

Example 2 15 ml of ethanol is placed in a 300 ml beaker, and 0.91 g of nickel chloride hexahydrate is dissolved therein at 30°C. 42.1 g of hexylene glycol was added to this solution and heated at 70° C. for 30 minutes, then 50.4 g of zirconium n-propoxide was added and stirred for 3 hours while warming at the same temperature.

Next, 50 ml of an ethanol solution containing 6 g of water is added, and as the mixture is stirred and heated at the same temperature, it gels into agar-like form. The following operations were carried out in Example 1, except that heat treatment was performed at 400°C for 8 hours in a hydrogen stream.
It is similar to The catalyst surface area was 2.2 m ² /g.

Example 3 Put 60.1g hexylene glycol in a 300ml beaker, dissolve 2.0g rhodium trichloride in it,
Stir while warming at 65°C for 40 minutes. Add 55.1g of zirconium ethoxide to this solution, stir for 3 hours while warming at the same temperature, add 70ml of an ethanol solution containing 8g of water, and stir while warming at the same temperature to form an agar-like gel. . After drying the gel, it was baked at 300℃ in air for 12 hours.
The mixture was then treated in a hydrogen stream at 300°C for 12 hours. The catalyst surface area was 30.2 m ² /g.

Example 4 Put 20 ml of tert-butanol in a 300 ml beaker, dissolve 1 g of hexachloroplatinic acid hexahydrate, add 55 g of diacetone alcohol, and add 55 g of diacetone alcohol.
Stir while warming at ℃ for 30 minutes. in this solution
Add 59.2 g of zirconium n-butoxide and stir while heating at the same temperature for 3 hours. Next, 6g
Add 65 ml of tert-butanol solution containing 55
It solidifies when stirred while warming at °C. The subsequent operations were carried out in the same manner as in Example 1. The catalyst surface area was 2.3 m ² /g.

Example 5 10 ml of ethanol is placed in a 300 ml beaker, and 0.91 g of cobalt chloride hexahydrate is dissolved therein at 25°C. Add 60 g of 3-hydroxy-3-methyl-2-butanone to this solution, warm it at 55°C for 30 minutes with stirring, and then add 50.5 g of zirconium n
- Add propoxide, warm and stir at the same temperature for 3 hours. Next, this solution is hydrolyzed by blowing nitrogen gas bubbling through the water for one week while stirring at 25°C, and the solution becomes a gel.
The subsequent operations were carried out in the same manner as in Example 3. The surface area of the catalyst was 18 m ² /g.

Example 6 Put 60g of propanolamine in a 300ml beaker, add 1g of ruthenium trichloride and 0.091g of propanolamine.
After dissolving cobalt chloride hexahydrate at 25°C and stirring for 1 hour, 50.6 g of zirconium n-propoxide was added and the mixture was stirred at 25°C for 5 hours.

Next, while stirring this solution at room temperature, nitrogen gas bubbling in water is sprayed on the solution for 10 days to gel it. The subsequent operations were the same as in Example 2, except that prior to the heat treatment in a hydrogen stream, calcination was performed at 450° C. for 5 hours in an oxygen stream. Surface area 1.2m ² /g.

Claims (1)

[Claims] 1. Using a zirconium alkoxide, a catalytic metal salt, and a polar compound having multidentate coordination ability or bridging coordination ability, at a temperature of 10 to 80°C and a molar ratio of zirconium alkoxide to the polar compound of 1: 1-15
A homogeneous solution consisting of a zirconium alkoxide, a catalyst metal salt, and a polar compound is prepared under the following conditions, and then hydrolyzed and gelled under the same conditions. A method for preparing a porous highly dispersed metal catalyst using zirconia as a carrier, which comprises drying under conditions that do not volatilize the gel, followed by high-temperature heat treatment to scatter bonded polar compounds remaining in the gel to form pores. . 2. 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. 3. The method according to claim 2, wherein the dihydric alcohol is one or a mixture of two or more diols having 14 or less carbon atoms. 4 The dihydric alcohol is pinacol, 2-methyl-2,4-pentanediol, 3-methyl-
1,3-butanediol, 2,5-dimethyl-
2,5-hexanediol, 2,3-butadiol, 2,4-pentanediol, 1,5-pentanediol, 1,6-hexanediol, 2,5
- One or two of hexanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol and 1,4-cyclohexanediol
The method of claim 2, which is a mixture of more than one species. 5. The method according to claim 1, wherein the zirconium alkoxide has one to five alkoxy carbon atoms or a mixture of two or more zirconium alkoxides. 6. The zirconium alkoxide consists of one or a mixture of two or more of zirconium methoxide, zirconium ethoxide, zirconium n-propoxide, zirconium iso-propoxide, zirconium n-butoxide, zirconium iso-butoxide, and zirconium sec-butoxide. The method according to claim 1. 7 Solution formation temperature and hydrolysis temperature from 20℃
The method of claim 1, wherein the temperature is 75°C.