JPH04331768A - Production of titanium oxide formed article - Google Patents

Abstract

PURPOSE:To provide a producing method of formed article having excellent mechanical strength and containing titanium oxide as a main component without changing pore volume, specific surface area and catalyst activity. CONSTITUTION:A titanium oxide raw material is mixed with additives capable of generating nascent oxygen and the mixture is formed and then fired.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for manufacturing a molded product containing titanium oxide as a main component, and more specifically, the present invention relates to a method for manufacturing a molded product containing titanium oxide as a main component, and more specifically, to improve the compressive strength, abrasion strength, etc. of a titanium oxide carrier or a catalyst composed of titanium oxide and other components. This invention relates to a method for manufacturing a molded product with high mechanical strength.

0002

[Prior Art] Supports or catalysts currently used industrially are molded products in shapes such as cylinders, rods, pipes, rings, spheres, and honeycombs, and are used in fixed and moving bed reactors. However, for practical purposes, a certain level of strength is required. If the strength is weak, it will collapse when it is filled into the reactor, and during the reaction it will collapse or powder due to its own weight and dust contained in the process gas, causing blockage in the reactor and increasing pressure loss. , a decline in catalyst function, and other adverse effects on downstream equipment. Titanium oxide has excellent properties as a catalyst carrier or as a catalyst itself, and can be used as a catalyst for the synthesis of maleic anhydride, acetonitrile, phthalic anhydride, etc., as a catalyst for the Claus reaction, and as a catalyst for the Claus reaction.
Alternatively, it is used as a carrier. Further, most catalysts for ammonia reduction and decomposition of nitrogen oxides (NOx) in exhaust gas are catalysts containing titanium oxide as a main component. One way to improve the mechanical strength of a molded product whose main component is titanium oxide is to increase the strength by increasing the bonding strength between the particles that make up the molded product by firing the molded product at a high temperature. However, this method has the disadvantage that the specific surface area, pore volume, etc. required for the carrier and catalyst are small. Furthermore, as a method to increase the mechanical strength of titanium oxide molded products, there is a method of mixing titanium oxide with acid, alumina sol or aluminum salt, molding, drying, and firing (
(Japanese Patent Publication No. 56-33350), a method of mixing titanium oxide with titanium oxalate or its salt, molding and firing (Japanese Patent Publication No. 60-33350)
-42185), a method in which a titanium compound is mixed with a boron compound, molded, and then heat treated (JP-A-53-2430
6), C that generates CaO by heating the titanium oxide raw material
A method of mixing a compound, molding, drying and firing (Japanese Patent Publication No. 57-26819) is disclosed. but,
Molded products obtained by these conventional methods did not necessarily have sufficient mechanical strength. In particular, in the case of a honeycomb-shaped molded product of a catalyst for ammonia reduction and decomposition of NOx whose main component is titanium oxide, a method of increasing the mechanical strength without impairing the activity has been desired.

0003

[Object of the invention] The object of the present invention is to provide a method for manufacturing a molded product mainly composed of titanium oxide, which has excellent mechanical strength, which is an important requirement for an industrial catalyst. The object of the present invention is to provide a method for producing a molded product having excellent mechanical strength without changing the pore volume, specific surface area, or catalytic activity.

0004

SUMMARY OF THE INVENTION The present invention relates to a method for manufacturing a molded product containing titanium oxide as a main component, which comprises mixing a titanium oxide raw material with an additive that can generate nascent oxygen, molding the mixture, and then firing the mixture. .

[0005]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, a molded product containing titanium oxide as a main component refers to one in which the proportion of titanium oxide in the carrier or catalyst is 50 wt% or more, and the titanium oxide raw material contains titanium oxide. Not only titanium oxide hydrates such as titanium, metatitanic acid, orthotitanic acid, but also mixtures or composite oxides of titanium oxide or titanium oxide hydrates with other oxides or their precursors, such as TiO2-WO3,
TiO2-M0O3, TiO2-SiO2, TiO2-
Also included are Al2O3 and the like. In the present invention, the titanium oxide raw material is mixed with an additive that can generate nascent oxygen, and the additives that can generate nascent oxygen include hydrogen peroxide, chloric acid, peroxide, etc. Compounds that release nascent oxygen with strong oxidizing power upon decomposition, such as chloric acid and their salts, are included. Hydrogen peroxide is particularly preferred because it does not remain in the molded product. The amount of the additive to be mixed into the titanium oxide raw material is 0.005 mol or more, preferably 0.01 to 0.5 mol, more preferably 0.02 to 0.1 mol, per 21 mol of TiO. desirable. If the amount of the additive is less than 0.005 mol, the improvement in the mechanical strength of the resulting molded product will be small, and even if the amount is more than 0.5 mol, the rate of improvement in mechanical strength will not change, making it economical. Not on point. In one embodiment of the present invention, a titanium oxide raw material, for example, titanium oxide powder, is mixed with water and an additive that can generate nascent oxygen in a kneader, and if necessary, the mixture is heated,
After kneading to obtain a kneaded product having plasticity, the product is molded into a desired shape by means such as extrusion molding, dried, and fired to prepare a molded product. Usually, during extrusion molding, organic molding aids such as carboxymethyl cellulose, polyvinyl alcohol, and methylcellulose are used to improve moldability, but if a large amount of organic molding aids is used, the mechanical strength of the resulting molded product will decrease. It tends to become weaker. In the present invention, since an additive capable of generating nascent oxygen is used, moldability is improved and the use of an organic molding aid is unnecessary, or the amount of organic molding aid used may be small. For this reason, during firing, the resulting molded product is less likely to experience a local temperature rise on the surface of the molded product due to the combustion of organic matter, or to remove the oxygen necessary for the combustion of organic matter from the active metal species present near the organic matter. Changes in the oxidation state of metal species, etc. are reduced, making it easier to manufacture catalyst molded products with stable activity, and increasing mechanical strength. The shape of the molded product in the present invention is
It can be arbitrarily selected to have a cylindrical, pipe-like, spherical, or honeycomb shape, and the drying and calcination conditions for drying and calcination of a normal carrier or catalyst are adopted. Firing is usually performed at 300°C to 1000°C under an inert gas atmosphere or air atmosphere.
It is desirable to carry out the treatment for 0.5 to 10 hours within the range of 0.5 to 10 hours. In another embodiment of the present invention, titanium oxide powder is mixed with water and an additive that can generate nascent oxygen, and the moisture-adjusted powder is molded into a spherical shape using a granulator, and then dried and fired. A molded product containing titanium oxide as a main component can be prepared by using this method. The molded product obtained by the present invention has sufficient mechanical strength to withstand industrial use and maintains various physical properties such as large pore volume and specific surface area, so it can be used as a support or catalyst. suitable. In particular, the honeycomb-shaped denitrification catalyst molded product, which is mainly composed of titanium oxide and contains vanadium, tungsten, etc., obtained by the present invention has strong mechanical strength and does not have a decrease in activity compared to conventional denitrification catalysts, so it is suitable for industrial use. Suitable as a catalyst.

[0006]

[Examples] The present invention will be explained below with reference to Examples. Example 1 2k of 35wt% hydrogen peroxide in 20kg of titanium oxide powder
g was added and kneaded using a kneader. Next, 12 liters of water and 1 kg of vanadium pentoxide were added and kneaded. After kneading, the moisture content was adjusted while heating, and the resulting kneaded product was extruded into a honeycomb shape. The molded product was dried at 70°C for 3 days and then calcined at 500°C for 3 hours to obtain catalyst A. Example 2 5 kg of 6.0 wt% ammonium perchlorate (NH4ClO4) was added to 20 kg of titanium oxide powder and kneaded in a kneader. Next, 9 liters of water and 1 kg of vanadium pentoxide were added and kneaded. Further, 100 g of carboxymethylcellulose was added and kneaded, and the moisture content was adjusted while heating, and the obtained kneaded product was molded into a honeycomb shape. After drying the molded product at 70°C for 3 days, it was calcined at 500°C for 3 hours to obtain catalyst B. Examples 3 to 5 In Example 1, the concentration of hydrogen peroxide was 25 and 25, respectively.
Catalyst C
, D, and E were prepared. Example 6 6 kg of a 5.0 wt % hypochlorous acid aqueous solution (HClO) was added to 20 kg of titanium oxide powder and kneaded in a kneader. Next, 7 liters of water and 1.2 kg of metavanazine ammonium were added and kneaded. Further, 100 g of carboxymethyl cellulose was added and kneaded, and the resulting kneaded product was adjusted in moisture while being heated and extruded into a honeycomb shape. After drying the molded product at 70°C for 3 days, it was dried at 500°C.
The catalyst was calcined for 3 hours to obtain catalyst F. Comparative Example 1 6 kg of 5.0 wt% hydrochloric acid was added to 20 kg of titanium oxide powder and kneaded in a kneader. Next, 7 liters of water and 1 kg of vanadium pentoxide were added and kneaded. Further, 100 g of carboxymethylcellulose was added and kneaded, and the resulting kneaded product was adjusted in moisture while heating and extruded into a honeycomb shape. After drying the molded product at 70°C for 3 days, it was calcined at 500°C for 3 hours to obtain catalyst G. Comparative Example 2 13 liters of water and 100 g of carboxymethyl cellulose were added to 10 kg of titanium oxide powder and kneaded in a kneader. Next, 500 g of badium pentoxide was added to this and further kneaded. After adjusting the moisture content while heating this kneaded material,
Extruded into a honeycomb shape. After drying the molded product at 70°C for 3 days, it was calcined at 500°C for 3 hours to obtain catalyst H. Comparative Example 3 13 liters of water and 100 g of carboxymethyl cellulose were added to 10 kg of titanium oxide powder and kneaded in a kneader. Next, 7 liters of water and 1.2 kg of ammonium metavanadate were added and kneaded. Further, 100 g of carboxymethylcellulose was added and kneaded, and the resulting kneaded product was extruded into a honeycomb shape by adjusting the moisture content. After drying the molded product at 70°C for 3 days, it was calcined at 620°C for 3 hours to obtain Catalyst I. Example 7 <Evaluation Test> Compressive strength, pore volume, and specific surface area were measured for catalysts A to F obtained in Examples 1 to 6 and catalysts G to I obtained in Comparative Examples 1 to 3. Compressive strength and abrasion strength were measured as follows. <Compressive strength> A cubic honeycomb catalyst with a side of 50 mm is cut out, and a load is applied to the test piece at a constant speed using a compression testing machine (manufactured by Tokyo Test Instruments Manufacturing Co., Ltd.), and the maximum load is determined when the test piece is completely destroyed. Read. Its maximum load is 25c
The value divided by m2 is taken as the compressive strength. <Abrasion strength> A sample of 70□ x 100Lmm was cut out, and a gas containing sand was bombarded with the sample under the following conditions.
Evaluate based on weight loss rate. Gas flow rate 20m/s Sand concentration 40g/m3 Average sand size 250μm Sand passing time
The results are shown in Table 1 for 6 hours. Furthermore, denitrification activity was measured using these catalysts. The results are shown in Table 1. In addition, the activity measurement conditions are as follows. Amount of catalyst used: 150mlSV
15,000h-1N
Ox 200ppmNH3
240ppmO2
4vol%H2O 10
vol%N2 balance
e Gas temperature: 350° C. The NOx concentration at the inlet and outlet of the reactor was measured using a chemiluminescent NOx analyzer manufactured by Yanagimoto, and was calculated using the following formula.

[Table 1]

[0007]

[Effect] The titanium oxide molded product obtained by the method of the present invention is
Compared to conventional methods, this method has superior compressive strength and abrasion strength, and there is no decrease in pore volume or specific surface area, so it is suitable as a carrier or a catalyst. In particular, the denitrification catalyst prepared by the method of the present invention is preferred because it has high strength and does not reduce denitrification activity.

Claims (1)

[Claims] 1. A method for producing a molded article containing titanium oxide as a main component, which comprises mixing a titanium oxide raw material with an additive capable of generating nascent oxygen, molding the mixture, and then firing the mixture.