JPS5935028A - Preparation of calcined titanium oxide and catalyst - Google Patents

Abstract

PURPOSE:To obtain the titled calcined material, having a large surface area and improved strength and heat resistance, and suitable for a catalyst or catalytic carrier, by calcining metatitanic acid in the form of a sol containing one or more compounds selected from a tungsten compound and a molybdenum compound and fine particulate silicic acid. CONSTITUTION:Metatitanic acid in the form of a sol containing (A) fine particulate silicic acid and (B) a tungsten compound and/or a molybdenum compound is calcined to prepare a calcined titanium oxide. The calcined titanium oxide remains in the form of ungrown anatase type crystal by the action of the respective compounds contained in the titanium oxide in the calcination. The resultant calcined material has a large surface area, and the mechanical strength and the heat resistance are remarkably improved. The resultant calcined material as a carrier is used to support metallic oxides having the catalytic activity of removing nitrogen oxide. Thus, an excellent catalyst having the activity of removing the nitrogen oxide for a long term by the synergistic action of the metallic oxides, anatase type titanium oxide and the fine prticulate silicic acid and a very low oxidation ratio of SO2 into SO3 is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a fired titanium oxide product and a catalyst.
In detail, the main component is titanium oxide, which has a large surface area.
Furthermore, a method for producing a fired titanium oxide product that has excellent strength and heat resistance and can therefore be suitably used as a catalyst carrier or a catalyst as it is, and a method for producing a catalyst for removing nitrogen oxides using this fired titanium oxide product as a carrier. Regarding.

It is already known that fired titanium oxide products are used as carriers or catalysts, but surface area, crystal form, mechanical strength, heat resistance, etc., which have important effects on carrier or catalyst functions, depend on the manufacturing method and the presence or absence of additives. , differs depending on the type, amount, etc., and various manufacturing methods have been proposed in the past.

For example, if additives such as silica are added to titanium oxide and fired, the resulting fired product will generally have a larger surface area and improved heat resistance. According to the method, titanium oxide is formed by adding additives to titanium salts such as titanium tetrachloride or titanium sulfate, neutralizing and hydrolyzing the titanium salts, and calcining the titanium hydroxide thus formed. Titanium hydroxide becomes orthotitanic acid, so if this is fired,
There is a problem that titanium oxide tends to become tU-type titanium oxide or rutile-type titanium oxide, which is unsuitable as a catalyst.

On the other hand, if metatitanic acid is fired, there are other factors as well.
- It is already known that anatase-type titanium oxide, which is a crystalline form that is generally preferred as a carrier or a catalyst, can be obtained. However, according to the method of adding additives such as silica to metatitanic acid and firing, it is difficult to obtain a mixture with a uniform composition. Since it is gel-like, the additive cannot be uniformly dispersed in metatitanic acid, and therefore, a high-performance support or catalyst cannot be obtained.

As a result of intensive research in order to solve the various problems described above, the present inventors found that they used a tungsten compound and/or a molybdenum compound as well as particulate silicic acid as additives, and made them exist in sol-formed metatitanic acid. By firing the metatitanic acid, the crystal growth of titanium oxide is suppressed and the ungrown anatase crystals remain, thereby obtaining a fired product with a large surface area and improved mechanical strength and heat resistance. Furthermore, by using this as a carrier to support certain metal oxides, the synergistic effect of each oxide on the carrier and these metal oxides led to an unprecedented improvement in nitrogen oxidation. The present invention was based on the discovery that a catalyst for removing substances can be obtained.

The method for producing a fired product according to the present invention is characterized by firing a sol-formed metatitanic acid containing (81) fine-particle silicic acid and (b) at least one compound selected from a tungsten compound and a molybdenum compound.

The fine particle silicic acid used in the present invention is also known as white carbon, and one of its characteristics is that it has a very large specific surface area. These fine particles of silicic acid may be produced by either the individual method or the dry method (
In the present invention, commercially available energized products can be used. Commercial products of fine particle silicic acid that can be suitably used in the present invention include, for example, Fine Seal, Hycle, Vulcasil, Carplex, Nip Seal, Toku Seal, Vita Seal, Siloid, and Aerosil. In particular, the average particle size is 1O ~
Those having a specific surface area of 50 mμ and a specific surface area of 200 to 300 rrr/g are preferably used.

Further, the tungsten compound used in the present invention is tungsten oxide and a precursor that forms tungsten oxide by firing, and examples of this precursor include ammonium metatungstate.

Similarly, the molybdenum compound used in the present invention is molybdenum oxide and a precursor that gives molybdenum oxide by calcination, and examples of the precursor include ammonium molybdate.

In the present invention, the amount of fine particle silicic acid, tungsten compound, and molybdenum compound added is 5 to 50% by weight based on titanium oxide, and when it is less than 5% by weight, the addition amount is 5% to 50% by weight based on titanium oxide. Sometimes, the effect of suppressing the crystal growth is poor, and the effect of improving the carrier or catalyst performance by adding these additives in the fired product is small.
On the other hand, if the weight exceeds 50 weight, the mixture with sol-formed metatitanic acid will gel, making it difficult to mix uniformly, and the resulting fired product will have a relatively low content of titanium oxide. 1. When this is used as a carrier or as a catalyst as it is, it is not preferable because the performance of the carrier and catalyst based on titanium oxide deteriorates.

In the present invention, preferably, metatitanic acid is made into a sol, and particulate silicic acid and at least one compound selected from the above-mentioned tungsten compound and molybdenum are added thereto, mixed, and then fired. Further, after adding fine particle silicic acid and at least lfi of compounds selected from the above tungsten compound and molybdenum to metatitanic acid,
Metatitanic acid may be solized and mixed. In any case, it is necessary to have particulate silicic acid and the above compound present in the metatitanic acid that has been partially or completely solified, so that these additives can be uniformly mixed with the metatitanic acid. .

The method of solization is not particularly limited, and for example, metatitanic acid is washed with water to remove most of the sulfuric acid groups, and then hydrochloric acid or nitric acid is added to partially or completely solize it.

Alternatively, if sulfate roots are not removed by washing with water, add alkaline earth metal chlorides such as barium chloride, strontium chloride, and calcium chloride to metatitanic acid, or alkaline earth metal chlorides such as barium nitrate, strontium nitrate, and calcium nitrate. A nitrate is added to fix the sulfate group as a water-insoluble barium salt (")"), and a part or all of the reaction mixture is made into a sol. The amount of these gelling agents added is appropriately selected depending on the degree to which the reaction mixture is to be made into a sol.

Note that metabutanoic acid sol gels at a pH of 1 to 2 or more, so it may be gelled if necessary, as long as the tungsten and/or molybdenum compound is sufficiently uniformly mixed therein.

The mixture of metatitanic acid, particulate silicic acid, and the tungsten and/or molybdenum compound thus obtained is dried, and then calcined at a temperature of 800°C or less, preferably 700 to 200°C, When crushed, a powdered baked product is obtained. In this case, according to the present invention, metatitanic acid is used, resulting in anatase-type titanium oxide, which is preferable as a carrier or catalyst in calcination. In addition, when the fired product is used as a carrier or catalyst in a predetermined shape such as a honeycomb shape, the dried product obtained by drying the mixture mentioned above can be processed by any conventionally known method such as extrusion molding, It may be molded by a method such as rolling granulation and then fired. Further, the powdered fired product described above can be molded into a desired shape and then fired again. In this case, after forming into the desired shape, it may be fired again at a temperature of 800°C or lower, preferably 700 to 200°C. In this way, according to the present invention, a fired titanium oxide product can be obtained in the form of a powder or a molded product.

In addition, in the present invention, in any of the above cases, ζ is also
By adding metatitanic acid sol or gel to a powdered dried or fired product, molding it into the desired shape, and firing it, various physical properties such as mechanical strength, porosity, specific surface area, and pore distribution can be improved. The shrinkage rate during firing can be suppressed. When darning, the amount of metatitanic acid sol or gel added is 5 to 5% of the weight of the molded product in terms of titanium oxide.
It is 0 weight percent weight. In addition, it is of course possible to use conventionally known molding aids such as Avicel and methyl cellulose during molding.

In the present invention, the firing atmosphere is not limited at all, and may be air, combustion gas, inert gas, or the like.

As described above, the fired titanium oxide product obtained according to the present invention is not limited in any way by theory, but due to the presence of fine particles of silicic acid, a tungsten compound, and/or a molybdenum compound, metatitanic acid is oxidized during firing. Since the crystal growth of titanium is suppressed and remains as an ungrown anatase crystal, the resulting fired product has a large surface area and has excellent mechanical strength and heat resistance, and can be used as a catalyst carrier or as it is. It can be suitably used as a catalyst.

The fact that the fired product obtained by the present invention contains ungrown anatase is confirmed by its X-ray spectrum showing low and broad peaks, as shown in Figure 1; In the case of anatase-type titanium oxide, its X-ray spectrum is shown in Figure 2, as the crystals grow extremely well and the peak is high and sharp.

The fired titanium oxide product according to the present invention is suitable for use as a carrier, and is also suitable for use in reaction 1! Cheek Niyo°ζ can be used as a catalyst as it is. For example, the above-mentioned fired product has a catalytic reduction activity of nitrogen oxides using ammonia as a reducing agent and can be put to practical use as it is. However, according to the present invention, the calcined titanium oxide product obtained as described above is used as a carrier, and an oxide conventionally known to have catalytic activity for removing nitrogen oxides is supported on this carrier. For example, due to an unexpected synergistic effect with the oxides constituting the fired product, it is possible to obtain a nitrogen oxide removal catalyst with excellent selective catalytic reduction activity of nitrogen oxides using ammonia as a reducing agent.

Immediately, the nitrogen oxide removal catalyst according to the present invention is produced by calcining sol-formed metatitanic acid containing +ai fine particle silicic acid and tb) at least one compound selected from tungsten compounds and molybdenum compounds. at least one selected from vanadium, tungsten, molybdenum, copper, iron, chromium, manganese and cerium.
It is characterized by supporting oxides of certain elements. In this method, the production of the fired product is as described above.

The method for supporting the above-mentioned oxide on the titanium oxide fired product according to the present invention can be any method conventionally used for preparing catalysts. For example, the above-mentioned oxide or its After impregnating or coating with a solution or dispersion containing an RF precursor, it may be fired to a predetermined temperature as necessary. Of course, the powdered fired product and the melt 11η may be kneaded with a dispersion liquid, molded into a desired shape, and then fired to a predetermined temperature as necessary to form the nitrogen oxide of the present invention. A removal catalyst can be obtained.

In order to remove nitrogen oxides from a mixed gas containing nitrogen oxides using the catalyst of the present invention, ammonia is added in an amount of 0.5 to 5 times the mole of nitrogen oxides contained in the mixed gas, preferably 1 to 2 times the mole of nitrogen oxides contained in the mixed gas. is added and passed through a reaction bed filled with a catalyst. Any of a moving bed, a fluidized bed, a fixed bed, etc. can be used as the reaction bed.

Since the catalyst of the present invention contains particulate silicic acid and has excellent heat resistance, the reaction temperature may range from 200 to 600°C, but preferably from 300 to 500°C. In addition, the space velocity of gas is 1000 to 100000 hr.
, preferably in the range of 3,000 to 3,000,001+r.

The catalyst according to the invention can be used to treat any gas containing nitrogen oxides, but in particular boiler exhaust gas, i.e. 100 to 1000 ppm of nitrogen oxides, mainly nitrogen monoxide, as well as 200 to 2000 ppm of nitrogen oxides. It removes nitrogen oxides from exhaust gas that contains ppm of sulfur oxides, mainly sulfur dioxide, 1 to 10% by volume of oxygen, 5 to 20% by volume of carbon dioxide, and 5 to 20% by volume of water vapor. It can be suitably used for.

As described above, in the method of the present invention, since fine particle silicic acid and at least one selected from Kunges-Then compounds and molybdenum compounds are present in the sol-formed metatitanic acid, these compounds are uniformly dispersed in the resulting mixture. Moreover, when this is fired, the titanium oxide remains in the ungrown anatase crystal form due to the action of the above compounds, so the fired product obtained has a large surface area.
Moreover, its mechanical strength and heat resistance are significantly improved. Therefore, in the nitrogen oxide removal catalyst of the present invention obtained by using such a calcined product as a carrier and supporting metal oxides having catalytic activity for removing nitrogen oxides, it is possible to obtain Due to its synergistic effect with anatase-type titanium oxide and particulate silicic acid, it maintains high nitrogen oxide removal activity over a long period of time even under severe usage conditions, and the rate of oxidation of sulfur dioxide to sulfur dioxide is extremely low. Therefore, it is outstanding as a practical and industrial catalyst for removing nitrogen oxides.

Although the present invention will be explained with reference to examples, the present invention is not limited to these examples in any way.

Example 1 A titanium sulfate solution obtained from a titanium oxide production process using a sulfuric acid method was thermally hydrolyzed to obtain metatitanic acid, 1 kg of this was taken as titanium oxide, and 80 g of barium chloride (trihydrate) was added to this. The mixture was made into a sol and thoroughly stirred and mixed. Next, 250 ml of 10% methylamine solution containing 200 g of fine silicic acid fine seal (Tokuyama Soda side layer) and 110 g of ammonium paratungstate was added.
After stirring and mixing thoroughly, heat at 100°C for 12 hours.
It was dried for an hour and then fired at a temperature of 500°C for 3 hours.

This fired product was pulverized using a temple mill to adjust the particle size. After adding an appropriate amount of water and kneading, the mixture is extruded into a lattice-shaped molded product using an extruder, heated from room temperature to 100°C to dry, and then fired at 500'C for 3 hours to produce a fired product. Obtained. This calcined product was used as it was as a catalyst for removing nitrogen oxides.

The X-ray spectrum of the fired product obtained in this way is
As shown in the figure. Since the peak is low and wide, it is
It is clear that the type crystal remains ungrown.

In addition, the X-ray spectrum was obtained using an X-ray diffractometer RΔD manufactured by Rigaku Denki Koku.
- Measured using HA, and the surveying conditions are as follows.

Scanning speed 1°/4 min full scale 1000 cpS time constant
1 second dart speed: 10 m1/min Target: Copper tube voltage: 30 KV Tube current: 10 mA For comparison, the X-ray spectrum of the commercially available pigment anatase titanium oxide is shown in FIG. The measurement conditions are the same as above except that the full scale is 4000 cps.

Example 2 A fired product was obtained in exactly the same manner as in Example 1, except that 300 ml of a methylamine solution containing 120 g of ammonium molybdate was used instead of ammonium paratungstate.

This was used as it was as a catalyst for removing nitrogen oxides.

Example 3 110 g of ammonium paratungstate and 1 gram of ammonium metavanadate were added to the powdered baked product obtained in Example 1.
After adding 250ml of 10% methylamine solution containing 0g and kneading, extrusion molding into a lattice-shaped molded product using an extruder, heating from the product temperature to 100°C to dry, and then
The catalyst was calcined at 00°C for 3 hours to obtain a -U catalyst for removing nitrogen oxides on which tungsten oxide and vanadium oxide were supported.

Example 4 The powdered calcined product obtained in Example 2 was treated in the same manner as in Example 3 to prepare a catalyst for removing nitrogen oxides on which tungsten oxide and vanadium oxide were supported.

Comparative Example 1 A fired product was obtained in exactly the same manner as in Example 1, except that metatitanic acid was not sol-formed using barium chloride. This was used as it was as a nitrogen oxide removal catalyst.

Comparative Example 2 In Example 1, metatitanic acid was not sol-formed with barium chloride, and the odor of Example 1 (instead of ammonium burn tungstate, 300 ml of a mediylamine solution containing 120 g of ammonium molybdate was used).
A baked product was obtained in exactly the same manner as in Example 1 except that Example 1 was used. This was used as it was as a catalyst for removing nitrogen oxides.

Comparative Example 3 An aqueous solution containing log ammonium metavanadate and 25 g of Shuwi was added to the fired product obtained in Comparative Example 1, thoroughly kneaded, extruded, dried at 100°C for 2 hours, and then heated at 500°C for 3 hours. A nitrogen oxide removal catalyst was obtained by firing for a period of time.

Comparative Example 4 To the fired product obtained in Comparative Example 2, an aqueous solution containing 10 g of ammonium metavanadate and 825 g of Shikou was added, thoroughly kneaded, extruded, dried at 100°C for 2 hours, and then heated at 500°C for 3 hours. The mixture was fired to obtain a nitrogen oxide removal catalyst.

Comparative Example 5 The same metatitanic acid as in Example 1 was used as titanium oxide.
g was taken out, 80 g of barium chloride (dihydrate) was added, the mixture was thoroughly stirred and mixed, and then heated at 100°C for 12 hours.
It was dried for an hour and then fired at 500°C for 3 hours. This was crushed and the particle size was adjusted. To this, 200 g of fine particle silicic acid Fine Seal (manufactured by Tokuyama Soda 01) and 250 ml of a 10% methylamine solution containing 110 g of ammonium paratungstate were added, and after stirring and mixing thoroughly, an appropriate amount of water was added and kneaded. , extrusion molded into a lattice-shaped molded product using an extruder, heated from product temperature to 100°C to dry, then,
The mixture was calcined at 500''C for 3 hours to obtain a catalyst for removing nitrogen oxides.

Comparative Example 6 Comparative Example 3 except that the fired product obtained in Comparative Example 5 was used.
A nitrogen oxide removal catalyst was obtained in exactly the same manner as above.

Each of the nitrogen oxide removal catalysts obtained in the above Examples and Comparative Examples contained 200 ppm of nitrogen oxides, 200 ppm of ammonia, 10% of water vapor, 12% of carbon dioxide, and 80% of sulfur dioxide.
A mixed gas with a composition of 0 ppm and the balance nitrogen was heated to a temperature of 38
The nitrogen oxide (NOx) removal rate and the sulfur dioxide (502) oxidation rate were measured by contacting at 0°C and a space velocity of 50,001°C. The results are shown in Table 2. Note that the nitrogen oxide removal rate (%) and the sulfur dioxide oxidation rate (%) were determined by the following formulas.

Nitrogen oxide removal rate (%) = (Catalyst waste input NOxa degree - catalyst layer outlet NOx concentration) / (catalyst layer inlet NOx 71!i
degree) X100 Sulfur dioxide oxidation rate (%) = (Catalyst waste S02 concentration -
Catalyst layer outlet S02 concentration)/(catalyst layer inlet (S02
3) Concentration) Disadvantages due to the formation of sulfur dioxide can be eliminated.

[Brief explanation of the drawing]

FIG. 1 shows an X-ray spectrum of a fired titanium oxide product obtained by the method of the present invention, and FIG. 2 shows an X-ray spectrum of a titanium oxide pigment for comparison. Patent applicant: Mitsubishi Heavy Industries, Ltd. Figure 1 2d 2 1
z6 z(,27
Figure 2 z3 24 237 i
6 17 Mitsubishi Heavy Industries, Ltd. Nagasaki Shipyard & Machinery Works, 1-1 Akunoura-cho, Nagasaki City 0 Inventor: Toru Seto, 4-6-22 Kannon Shinmachi, Hiroshima-ku, Mitsubishi Heavy Industries, Ltd. Hiroshima Research Center 0 Inventor: Junsuke Miyake, Tokyo Inventor: 2-5 Marunouchi, Chiyoda-ku Inventor: Toshikatsu Baba, Sakai Chemical Industry Co., Ltd. Central Research Laboratory, 5-1 Ebisujima-cho, Sakai-shi, Abe-Mitsu 5-1 Sakai Chemical Industry Co., Ltd. Central Research Laboratory 0 Inventors: Toshiaki Matsuda 5-1 Ebisujima-cho, Sakai City Sakai Chemical Industry Co., Ltd. Central Laboratory

Claims (1)

[Claims] +11 (8l fine particle silicic acid, (bl
A method for producing a fired titanium oxide product, which comprises firing a sol-formed metatitanic acid containing a seed compound. +21 (al ff1l [Solized metatitanic acid containing particle silicic acid and at least one compound selected from Tbl tungsten compounds and molybdenum compounds is fired, and the fired product thus obtained contains vanadium, tungsten, molybdenum, copper, A method for producing a catalyst for removing nitrogen oxides, which comprises supporting an oxide of at least one element selected from iron, chromium, manganese, and cerium.