JPS5851909B2 - Manufacturing method for titanium oxide molded products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a titanium oxide molded article.

More specifically, the present invention relates, for example, to a method for producing a molded article containing titanium oxide as a main component, which has a suitable surface area and porosity as a catalyst carrier, and has sufficient strength for practical use.

In general, solid catalysts are used in the form of a catalyst component supported on a carrier with an appropriate shape and particle size, or in the form of a catalyst component itself molded into an appropriate shape and particle size. The following methods are widely used, but in either case, a certain level of strength is required for use on an industrial scale.

If the strength is not sufficient, it may collapse during filling into the reaction tower, or it may become clogged due to powdering or destruction due to wind pressure, thermal shock, etc. during the reaction, and cannot withstand actual use.

Titanium oxide has excellent properties as a catalyst carrier or as a catalyst itself, but it is difficult to obtain molded products that maintain excellent mechanical strength.

For example, in order to mold titanium dioxide into a molded product for use as a catalyst carrier, the usual method is to mix fine powdered titanium dioxide with water, extrude it in an extruder, cut it into appropriate lengths, and then sinter it. However, in this case, strong agglomeration is difficult to occur and it is difficult to obtain a molded product with high strength.

On the other hand, by sintering titanium dioxide at a high temperature of 1000°C or higher, it can be made extremely hard and resistant to thermal shock, but the resulting sintered body becomes extremely dense and has a small surface area. It is small and not suitable as a catalyst carrier.

The present invention was developed as a result of various studies aimed at obtaining a molded product containing titanium oxide as a main component, which has a particularly suitable surface area and porosity as a catalyst carrier, and has sufficient strength for practical use. proposed a method in which titanium oxide is mixed with an aqueous medium containing an inorganic acid or a lower aliphatic carboxylic acid and then fired.

According to this method, a titanium oxide molded product with excellent strength can be obtained, but it cannot be said that the surface area and porosity as a catalyst carrier are necessarily satisfactory.

In view of the above circumstances, the inventors of the present invention made further studies and obtained a titanium oxide molded product that has a high surface area, high porosity, and is practically satisfactory in terms of strength by adding a certain type of shaping additive. The present invention was achieved by discovering that this can be done.

That is, the gist of the present invention is to combine titanium oxide or a mixture of titanium oxide and alumina with a water-soluble cellulose compound,
At least one selected from polyacrylamide, starch, polyethylene glycol, polyvinyl acetate, higher aliphatic carboxylic acids, polyethylene, urea, and activated carbon is mixed with an aqueous medium in the presence of an inorganic acid or lower aliphatic carboxylic acid. , a method for producing a titanium oxide molded product, characterized in that it is molded and then fired.

The present invention will be explained in more detail below.

The titanium oxide used in the present invention can be obtained, for example, by hydrolyzing titanium salts such as titanium tetrachloride and titanium sulfate, and neutralizing and washing as necessary. Leave the wet cake as it is,
Alternatively, it is used in partially dehydrated or dried powder form.

Further, after drying, it can be further used by firing at a relatively low temperature of less than about 800°C.

Titanium oxide can be used alone, or may be used in combination with alumina.

Examples of alumina used to obtain a molded product from titanium oxide and alumina include γ-alumina, θ-alumina, θ-alumina, and boehmite produced by thermal decomposition of alumina hydrate using conventional method 1. An alumina hydrate is used, as well as an alumina sol or an aluminum salt such as aluminum nitrate, which is converted to alumina by calcination.

The amount of alumina added is usually 0.1 to 50% by weight based on the total amount.

Auxiliary agents used in molding titanium oxide or a mixture of titanium oxide and alumina include crystalline cellulose,
Water-soluble cellulose such as methylcellulose, carboxymethylcellulose and its salts: polyacrylamide;
Starch; Polyethylene glycol: Polyvinyl acetate;
Examples include at least one selected from higher aliphatic carboxylic acids such as stearic acid and palmitic acid; polyethylene; urea and activated carbon.

Since these are burnt off as carbon dioxide gas and water during firing, they do not impair the original properties of the titanium dioxide support and can increase the surface area and porosity of the molded product after molding and firing. Preferred are cellulose compounds and polyacrylamide.

Their effective addition amount is usually 0.1 to 20% by weight, preferably 1 to 10% by weight of the titanium oxide or the mixture of titanium oxide and alumina.

On the other hand, examples of acids added with the above-mentioned additives include sulfuric acid, nitric acid, hydrochloric acid, etc., and examples of lower aliphatic carboxylic acids include formic acid, acetic acid, propionic acid, oxalic acid, butyric acid,
Examples include maleic acid and chloroacetic acid, but nitric acid or acetic acid is particularly effective.

The amount of these additives is selected from the range of 0.01 to 50 parts per 100 parts of titanium oxide or a mixture of titanium oxide and alumina, but it is usually effective to add about 0.1 to 10 parts. , used as an aqueous solution.

Titanium oxide or a mixture of titanium oxide and alumina, the above-mentioned molding aid, and an inorganic acid or lower aliphatic carboxylic acid are mixed as uniformly as possible with water and then molded.

For example, it is extruded using an extrusion molding machine and cut into appropriate dimensions.

The molded product thus molded is dried and then fired.

Firing is usually carried out in an air atmosphere at a temperature below 1000°C, preferably in the range from 500°C to 900°C.

When the heating temperature exceeds 1000°C, the strength increases, but strong sintering occurs, the material becomes dense, and both the surface area and porosity decrease significantly.

Although the firing time also affects the physical properties and strength of the carrier, it is usually suitably 1 hour to 10 hours.

The molded product thus obtained has sufficient mechanical strength to withstand industrial use, and maintains sufficient physical properties such as surface area and porosity as a catalyst carrier.
It is particularly suitable as a catalyst for gas phase catalytic reactions or a carrier for the catalyst.

For example, a catalyst obtained by supporting a catalytic metal such as vanadium oxide on a molded product obtained by the present invention maintains a high level of catalytic activity for a long time when used as a catalyst for ammonia reduction and decomposition of nitrogen oxides. Moreover, there is no risk of crushing, pulverization, etc. due to long-term use.

The present invention will be explained below using examples.

The compressive strength in the Examples and Comparative Examples was determined by measuring the compressive strength as the linear compressive strength in the longitudinal direction of the molded product using a Honya type hardness tester, and the surface area was measured by N2 gas adsorption using the BET method.

Example 1 A wet cake of titanium hydroxide obtained by hydrolyzing, neutralizing and washing titanium sulfate was dried and then calcined at 500° C. for 3 hours to obtain titanium dioxide powder.

Microcrystalline cellulose (
6 g (3% by weight) of Avicel TG-101 (product of Asahi Kakai Kogyo Co., Ltd.) and 116 rILl of a 5% acetic acid solution were added and kneaded well.

This mixture was extruded using an extrusion molding machine (EXKPELLETTER EXKF-1 manufactured by Fuji Paudal ■), and a cutter was used to make 5 mm φxi.
After drying, it was baked in an air stream for 700803 hours.

The compressive strength of the fired molded product is 8.6 kg, and the surface area is 4.
6, 11 m/g, and the water absorption rate was 46%.

Example 2 Titanium sulfate was hydrolyzed, a wet cake of titanium hydroxide that had been neutralized and washed was dried, and then calcined at 600° C. for 6 hours to obtain titanium dioxide powder.

Add 10 g of γ-alumina and 6 g of Azehil to 190 g of this titanium dioxide powder, and add 1287 Vl of 1% acetic acid solution.
! was added and kneaded.

Subsequently, extrusion molding was performed in the same manner as in Example 1, and after drying, the product was baked at 800° C. for 3 hours under air circulation.

The compressive strength of the obtained molded product is s, i kll,
It has sufficient strength to be used as a catalyst carrier, and has a surface area of 3
7.96 ml/g, water absorption rate was 53%.

Example 3 200 g of the same titanium dioxide powder as in Example 4 was taken, and 1 g of polyacrylamide and 128 g of a 5% acetic acid solution were added thereto for crosstalk.

Subsequently, extrusion molding was performed in the same manner as in Example 1, and after drying, the product was baked at 700° C. for 3 hours under air circulation.

The compressive strength of the molded product obtained was 10.1 kg, and the surface area was 4.
3.15m7g, water absorption rate was 42%.

Example 4 20 (l) of the same titanium dioxide powder as in Example 1 and 11 stearic acid were taken, 110M of 1% acetic acid solution was added thereto, mixed, and then extrusion molded in the same manner as in Example 1. After drying, the mixture was molded in an air stream. It was fired at 800°C for 3 hours.

The compressive strength of the obtained molded product was 10.9 kg, and the surface area was 3
The water absorption rate was 3.11 m/g and 37%.

Example 5 190.9% of the same titanium dioxide powder as in Example 1 was taken, and 11% of activated carbon (Shirasagi A manufactured by Narita Pharmaceutical Co., Ltd.) was added thereto.
Further, 137mA'77p of 5% acetic acid solution was added, kneaded, and extrusion molded in the same manner as in Example 1.

After drying, it was calcined for 3 hours at SOO° C. in a stream of air.

The compressive strength of the molded product obtained was 9.7 kg, and the surface area was 3
0.51 rrt/9, water absorption rate was 38%.

Claims (1)

[Claims] 1. Titanium oxide or a mixture of titanium oxide and alumina is mixed with at least one selected from water-soluble cellulose compounds, polyacrylamide, starch, polyethylene glycol, polyvinyl acetate, higher aliphatic carboxylic acids, polyethylene, urea, and activated carbon and an inorganic acid. Alternatively, a method for producing a titanium oxide molded product, which comprises mixing it with an aqueous medium in the presence of a lower aliphatic carboxylic acid, molding it, and then firing it.