JPS6345622B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves mixing a titanium 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 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 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, titanium alkoxide;
Titanium 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 titanium alkoxide to polar compound of 1:1 to 15. After hydrolyzing and gelling a homogeneous solution consisting of an alkoxide, a catalytic metal salt, and a polar compound,
A titania characterized in that the gel is dried under conditions in which the bound polar compounds contained in the gel are not substantially volatilized, and then subjected to high temperature heat treatment to scatter the bound polar compounds remaining in the gel to form pores. A method for preparing a porous highly dispersed metal catalyst using a carrier as a carrier is provided.

In other words, the first step in preparing a homogeneous and highly dispersed catalyst is to create a homogeneous solution.
Titanium 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 is preferable. 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 the formation of Ti), 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 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 bonding 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 titania It is desirable to use 1 mol or more of the polar compound per 1 atom of titanium, that is, per mol of titanium alkoxide. However, if a polar compound with polydentate and crosslinking coordination ability is present in large excess with respect to titanium 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 even in the unfixed 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 mol of titanium alkoxide.

Catalytic metal salts used in the present invention include vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, arsenic,
Selenium, niobium, molybdenum, technetium, rhodium, palladium, silver, cadmium, indium, tin, antimony, tellurium, lanthanoids,
Salts of 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 catalyst metal supported in the product is
Generally, it is about 0.1 to 10% by weight, preferably about 0.5 to 5% by weight.

In the case of titanium alkoxide, hydrolysis is generally rapid, so acids and alkalis are not necessarily required as hydrolysis accelerators. However, in rare cases, hydrolysis may be slow, and in such cases, acids or alkalis are used as hydrolysis accelerators. Since there are cases where it is better to use an alkali, 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.).
Specific examples of these include, for example, formic acid, cilic acid, tartaric acid, malonic acid, succinic acid, ethanolamine, and 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. Although volatile water and polar compounds contained in the gel are removed by this drying process, polar compounds bonded to the carrier metal and catalyst metal remain in the gel without being practically volatilized. After drying, a porous highly dispersed titania-supported catalyst is completed by heat treatment to scatter the polar compound, but 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. It was done. In addition, the surface area is 5 to 100 m ² /g, and the surface area of the rutile type, brookite type, and anatase type of general titania catalysts is 4 to 15
m ² /g (Elemental Catalyst Handbook, page 225, Jijinshokan).

In addition, in this porous titania-supported catalyst, the catalytic metal or catalytic metal oxide is uniformly distributed, so the catalytic activity is high, and it 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 2.0 g of ruthenium trichloride is dissolved therein at 25°C.
Add 60g of hexylene glycol to this solution,
After warming at 65℃ for 1 hour with stirring, 88.9
g of titanium iso-propoxide was added for 3 hours.
Stir while warming at the same temperature. Next, 5.7g
Add 60 ml of ethanol solution containing water and incubate for 30 minutes.
After stirring while warming at the same temperature, add 5.7
30 ml of an ethanol solution containing 10 g of water was added and stirred at the same temperature. After 30 minutes, add 50% ethanol aqueous solution again.
Add 22ml and continue stirring at the same temperature until it becomes an agar-like gel. Leave the gel at the same temperature for 30 minutes and then at room temperature overnight. Crush the gel into a suitable size, put it into a 300 ml eggplant-shaped flask, and dry it at 100°C under reduced pressure using a rotary evaporator for 24 hours. Yield after drying 44.9 g (1.8 times the calculated value as _TiO2 ). The dried gel was pulverized, spread in a quartz tube, and heat treated at 300℃ for 8 hours in a hydrogen stream.
Obtain 3wt% Ru- _TiO2 catalyst. The surface area of the catalyst obtained was 50.2 m ² /g.

Example 2 Put 20ml of ethanol in a 300ml beaker,
To this, 0.91g of nickel chloride hexahydrate and 0.0652g
of cupric chloride dihydrate at 25°C, and then add 50g of cupric chloride dihydrate.
Add pinacol and dissolve. Add 55g of titanium ethoxide to this solution and stir at 60°C for 3 hours. Next, 30 ml of an ethanol solution containing 5 g of water was added and heated and stirred at 60°C for 1 hour.
When 16 ml of an ethanol solution containing 4 g of water is added again and stirred at the same temperature, the mixture turns into an agar-like gel. The operations after gelation were carried out in the same manner as in Example 1, except that the final heat treatment was carried out at 400° C. for 4 hours.
The surface area of the catalyst obtained was 23 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 room temperature. 50.1 g of hexylene glycol is added to this solution, and the mixture is heated at 55°C for 30 minutes with stirring, and then 75.3 g of titanium iso-propoxide tetramer is added, and the mixture is heated and stirred at 60°C for 3 hours. Next, 30 ml of ethanol solution containing 4 g of water was added dropwise over about 30 minutes, and after stirring at the same temperature for 1 hour,
Further, 20 ml of an ethanol solution containing 5 g of water is added to solidify. After drying the gel in air at 300℃
After calcination for 10 hours, reduction was carried out at 300°C for 8 hours in a hydrogen stream to prepare a Co-TiO ₂ catalyst. The surface area of the catalyst obtained was 75 m ² /g.

Example 4 Put 20ml of ethanol in a 300ml beaker,
1.54 g of ferric nitrate nonahydrate is dissolved in this at room temperature. Add 3-hydroxy-3-methyl-
After adding 51 g of 2-butanone and warming at 65°C for 30 minutes, 68.5 g of titanium iso-propoxide was added and stirred for 3 hours while warming at 65°C. Next, 25 ml of an ethanol solution containing 4 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 35 m ² /g
It was hot.

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). addition
Warm and stir at 70℃ for 30 minutes. 54.4 to this solution
g of titanium ethoxide was added, and after warming and stirring at the same temperature for 3 hours, a tert-oxide containing 9 g of water was added.
Add 100ml of butanol solution and solidify while stirring at the same temperature. The subsequent operations were carried out in the same manner as in Example 2. The surface area of the catalyst obtained was 9 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 titanium iso-propoxide tetramer and stir at the same temperature for 3 hours while heating. Next 13g
Add 100 ml of tert-butanol solution containing water,
It solidifies while stirring while heating at 55℃.
The subsequent operations were carried out in the same manner as in Example 1. The surface area of the catalyst obtained was 6 m ² /g.

Claims (1)

[Claims] 1. Using a titanium 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 titanium alkoxide to the polar compound of 1: After a homogeneous solution consisting of a titanium alkoxide, a catalyst metal salt, and a polar compound is hydrolyzed and gelled under conditions 1 to 15, conditions in which the bound polar compound contained in the gel does not substantially volatilize. 1. A method for preparing a porous highly dispersed metal catalyst using titania as a carrier, which comprises drying the catalyst at a high temperature, followed by high-temperature heat treatment to scatter bound 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, comprising one or a mixture of two or more titanium alkoxides having an alkoxy carbon number of 1 to 5. 6 Titanium alkoxide is titanium methoxide, titanium ethoxide, titanium n-
propoxide, titanium iso-propoxide,
The method according to claim 1, comprising one or a mixture of two or more of titanium n-butoxide, titanium iso-butoxide, titanium sec-butoxide, and titanium butoxide tetramer. 7 Solution formation temperature and hydrolysis temperature from 20℃
The method of claim 1, wherein the temperature is 75°C.