JPS6345621B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves mixing an aluminum 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 method for catalyst catalysis, 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 the highly dispersed silica-supported metal catalyst Even if catalytic metals are formed, only a small amount of the catalytic metals appear on the silica surface, and therefore it cannot be said that the catalytic metals are 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. This is 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 such as adducts with ethylene glycol. This is because they cannot be mixed uniformly (exactly the same phenomenon is seen with propanedione 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, aluminum alkoxide,
Aluminum 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 aluminum 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 alumina as a carrier, which is characterized by scattering bonded 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.
The aluminum alkoxide and the catalytic metal salt must be dissolved in a polar compound having polydentate or bridging coordination ability, and the polar compound and preparation temperature must be selected so as to form 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-ditanediol, 2,5-dimethyl-2,5-hexanediol, 2,3-butadiol, 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 preparation temperature is set to prevent the reduction and precipitation of the catalyst metal salt by alcohols and precipitation due to the formation of insoluble complexes, as well as 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 Al) formation, it is important to avoid excessive heating, and it is best to heat the material between 20°C and 75°C for hydrolysis.

Due to etherification or esterification of hydroxyl groups, polar compounds containing hydroxyl or carboxyl groups significantly reduce the immobilization 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 loss of alcohol and organic acid due to unavoidable etherification and esterification, and to exert a fixed bonding function between the support metal and the catalyst metal or between the support metals, the amount of the polar compound is not necessarily specified, but the support alumina It is desirable to use 1 mol or more of the polar compound per 1 atom of aluminum, that is, per mol of aluminum alkoxide. However, if a polar compound with polydentate and crosslinking coordination ability is present in large excess with respect to aluminum 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 from 1 mol to 1 mol of aluminum alkoxide.
A range of 15 moles is desirable.

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, lanthanide, 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 aluminum alkoxides, hydrolysis is generally rapid, so acid or alkali is not necessarily required as a hydrolysis accelerator; however, when diketone complexes of aluminum are used, hydrolysis may be slow, and in such cases, In some cases, it is better to use an acid or an alkali as a hydrolysis accelerator, and the present invention does not exclude the combined use of an acid or an alkali when preparing a 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, oxalic acid,
tartaric acid, malonic acid, succinic acid, ethanolamine,
These include propanolamine.

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 alumina-supported catalyst is completed by heat treatment to scatter the polar compound, and the temperature and atmosphere of the heat treatment may be set according to 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, the surface area varies depending on the polar compound used, but it is much larger than that of catalysts made by general impregnation methods or coprecipitation methods, from 300 to 900 m ² /g. The pulse adsorption method using the method revealed that the catalyst prepared by this method had many pores of 4 to 6.5 Å, which was different from ordinary alumina-supported catalysts.

In addition, such porous alumina-supported catalysts have high catalytic activity because the catalytic metal or catalytic metal oxide is uniformly distributed, and can be effectively used as a catalyst for hydrogenation, catalytic oxidation, isomerization, or hydration reactions. It is possible.

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

Example 1 15 ml of ethanol is placed in a 300 ml beaker, and 0.91 g of nickel chloride hexahydrate is dissolved therein at 25°C. Add 50 g of pinacol to this solution and warm it for 30 minutes while dissolving at 65°C to make a completely homogeneous solution.
Next, 92.9 g of aluminum sec-butoxide was added, and the mixture was stirred for 2 hours while warming at the same temperature. Add 100ml of ethanol solution containing 5.5g of water to this solution.
After heating and stirring at the same temperature for an additional 2 hours, 50 ml of an ethanol solution containing 5.5 g of water is added and the mixture solidifies into agar-like form. Leave the gel at the same temperature for 30 minutes, and then leave it at 25°C overnight. Crush the gel into a suitable size, place it in a 200 ml eggplant-shaped flask, and dry it at 100°C under reduced pressure using a rotary evaporator for 24 hours. Yield after drying: 44.0 g (approximately 2.3 times the calculated amount of Al ₂ O ₃ ). The dried gel was pulverized, spread in a quartz tube, and heat treated at 400℃ for 8 hours in a hydrogen stream.
19.8 _g of 2wt% Ni- _Al2O3 catalyst was obtained. The surface area of the catalyst was 680 m ² /g.

Example 2 Put 10ml of ethanol in a 300ml beaker,
Dissolve 0.652g of cupric chloride dihydrate at 25°C, add 50g of pinacol, and warm at 45°C to make a completely homogeneous solution. 52.6g in this solution
of aluminum butoxide and 33.9 g of aluminum isopropoxide were dissolved and stirred while heating at 60°C for 3 hours. Next, 30 ml of an ethanol solution containing 6 g of water was added, and after stirring while heating at the same temperature for 1 hour, 16 ml of an ethanol solution containing 6 g of water was added dropwise again to solidify. The operations after solidification were carried out in the same manner as in Example 1, except that the final heat treatment was carried out at 500° C. for 4 hours. The surface area of the catalyst was 360 m ² /g.

Example 3 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. 50.1g of hexylene glycol was added to this solution, and after warming at 55°C for 30 minutes with stirring, 93.8g of aluminum sec-butoxide was added.
Warm and stir at 60℃ for 3 hours. Next, 30 ml of an ethanol solution containing 6 g of water was added dropwise over about 30 minutes, stirred at the same temperature for 1 hour, and then 20 ml of an ethanol solution containing 6 g of water was added to solidify. The following procedure was carried out in the same manner as in Example 2. Surface area
823m ² /g.

Example 4 Put 20ml of ethanol in a 300ml beaker,
1.54 g of ferric nitrate nonahydrate is dissolved in this at 25°C. Add 3-hydroxy-3-methyl-
After adding 51 g of 2-butanone and heating at 65°C for 30 minutes, 93.4 g of aluminum sec-butoxide was added and stirred for 3 hours while warming at 65°C. Next, 25 ml of an ethanol solution containing 11 g of water was added, and 30 minutes later, 10 ml of a 50% ethanol aqueous solution was added to solidify. The subsequent operations were carried out in the same manner as in Example 1. The surface area of the obtained catalyst is 330m ² /
It was hot at g.

Example 5 Put 25 ml of tert-butanol in a 300 ml beaker, dissolve 1.52 g of chromium nitrate nonahydrate, and add 50.2 g of diacetone alcohol (4-hydroxy-4-methyl-2-pentanone). Add, warm at 70℃ for 30 minutes, and stir. in this solution
Add 93.4 g of aluminum sec-butoxide;
After warming and stirring at the same temperature for 3 hours, 100 ml of a tert-butanol solution containing 11 g of water was added, and while stirring while warming at the same temperature, the mixture solidified. The subsequent operations were carried out in the same manner as in Example 2. The surface area of the catalyst obtained was 605 m ² /g.

Example 6 Put 20ml of tert-butanol in a 300ml beaker, dissolve 1g of hexachloroplatinic acid hexahydrate, add 70g of hexylene glycol,
Warm and stir at ℃ for 30 minutes. 114g in this solution
Add disec-butoxyacetoacetate aminium and stir at the same temperature for 3 hours while warming. Next, a tert-butanol solution containing 11 g of water
Add 100ml and solidify while stirring while warming at 55℃. The subsequent operations were carried out in the same manner as in Example 1. The surface area of the obtained catalyst was 710 m ² /g.

Claims (1)

[Claims] 1. Using an aluminum 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 at a molar ratio of aluminum alkoxide to the polar compound of 1: 1-15
A homogeneous solution consisting of an aluminum alkoxide, a catalytic 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 alumina 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 aluminum alkoxide is one or a mixture of two or more aluminum alkoxides having an alkoxy carbon number of 1 to 5. 6 Aluminum alkoxide is one of aluminum methoxide, aluminum ethoxide, aluminum n-propoxide, aluminum iso-propoxide, aluminum n-butoxide, aluminum iso-butoxide, aluminum sec-butoxide, aluminum dibutoxyacetoacetate, or The method according to claim 1, which is a mixture of two or more types. 7 Solution formation temperature and hydrolysis temperature from 20℃
The method of claim 1, wherein the temperature is 75°C.