JP5022697B2 - Method for producing denitration catalyst - Google Patents

Description

  The present invention relates to a denitration catalyst used for denitration treatment of exhaust gas from a power generation gas turbine, coal-fired boiler, various chemical plants, incinerators, and the like, and more specifically, corrugated ceramic fiber sheets and flat ceramic fibers The present invention relates to a method for producing a denitration catalyst carrier using a honeycomb structure formed by alternately laminating sheets and a denitration catalyst using the same.

  Conventionally, in order to produce a denitration catalyst, in order to increase the strength of the honeycomb structure, the honeycomb structure is cured with silica gel, and then titania as a carrier is supported thereon. However, this method has a large number of processes, which causes high costs.

  In titania loading, titania sol is used as a medium for supporting titania fine particles, but titania fine particles exhibit higher catalytic activity than titania derived from titania sol. Can be considered. However, in this case, since the supporting ratio of titania sol-derived titania and titania fine particles is substantially the same as the ratio of the former and the latter in the liquid, the latter cannot be effectively supported on the carrier.

  In addition, in the denitration catalyst, the amount of titania fine particles supported affects the catalyst performance. In the liquid obtained by adding titania fine particles to titania sol, titania in the titania sol is present in addition to the titania fine particles, and the latter causes gas inside the catalyst Diffusion resistance increases, which adversely affects catalyst performance.

  Furthermore, after that, a catalytic metal such as vanadium is supported on titania. However, since the catalytic metal is also supported on titania in titania sol in addition to the titania fine particles, the amount of expensive catalytic metal used is increased, resulting in high costs. It was.

As a prior art based on the present invention, there is Patent Document 1 by the present applicant.
Example of Japanese Patent Application No. 2006-255914

  An object of the present invention is to provide a method for producing a denitration catalyst carrier capable of solving the above-described problems of the conventional catalyst carrier and a denitration catalyst using the same.

  As a result of repeated studies to solve the above-mentioned problems, the present inventors changed the titania sol, which has been conventionally used as a supporting medium for titania fine particles, to the silica sol used for the curing treatment, and the curing treatment. The titania supporting treatment can be performed simultaneously, the number of manufacturing steps can be reduced, and since only titania fine particles are supported, this can be effectively supported on the surface of the support, and the gas diffusibility inside the catalyst is improved. It has been found that this can reduce the amount of expensive catalytic metal used.

That is, the method for producing a denitration catalyst carrier according to the present invention is based on silica sol in the production of a denitration catalyst carrier having a honeycomb structure in which corrugated ceramic fiber sheets and flat ceramic fiber sheets are alternately laminated. The honeycomb structure is immersed in a slurry in which titania fine particles are suspended, dried and fired, and titania and silica are simultaneously supported on the honeycomb structure. The solid content concentration of the slurry is 45 wt%, and the silica in the slurry the ratio of the titania is characterized 20:80 der Rukoto.

The present invention, Ri Na carrying vanadium oxide and / or tungsten oxide on the catalyst carrier prepared by the process according to the invention, the pore diameter of the catalyst is that are distributed in the region of 20 to 100 Å centered on 50 Å denitration A catalyst is provided.

  According to the present invention, since the honeycomb structure is immersed in a slurry in which titania fine particles are suspended in silica sol, the titania supporting treatment and the curing treatment with silica can be simultaneously performed on the honeycomb structure, thereby reducing the number of manufacturing steps. Thus, manufacturing cost savings can be achieved. Since only the titania fine particles are supported, they can be effectively supported on the surface of the carrier, maintaining the voids inside the catalyst and improving the gas diffusivity, thereby reducing the amount of expensive catalyst metal used. can do.

  Next, in order to specifically explain the present invention, examples of the present invention and comparative examples for showing comparison with the examples will be given.

Example 1 (see FIG. 1)
1) A honeycomb structure was formed by alternately laminating corrugated ceramic fiber sheets and flat ceramic fiber sheets.

  2) The honeycomb structure was immersed in a slurry (solid content ratio: 45% by weight, ratio of silica and titania; 20:80) in which titania fine particles were suspended in silica sol, and taken out from the slurry. Dried and fired at 500 ° C. Thus, titania was held in the voids of the ceramic fiber sheet constituting the honeycomb structure.

  3) The honeycomb structure holding titania was immersed in an aqueous ammonium metavanadate solution, taken out from the aqueous solution, and then dried at 220 ° C. In this way, vanadium was adsorbed and supported on the titania of the honeycomb structure.

  4) The vanadium-supporting honeycomb structure was immersed in an aqueous ammonium metatungstate solution, taken out from the aqueous solution, and then fired at 400 ° C. In this way, a denitration catalyst having a honeycomb structure in which vanadium and tungsten were supported on titania was obtained.

Comparative example (see FIG. 2)
1) A honeycomb structure was formed by alternately laminating corrugated ceramic fiber sheets and flat ceramic fiber sheets.

  2) The honeycomb structure was immersed in silica sol, taken out from the sol, and fired at 500 ° C. In this way, silica as a curing component was held in the voids of the ceramic fiber sheet constituting the honeycomb structure.

  3) The honeycomb structure was immersed in a slurry in which titania fine particles were suspended in titania sol, taken out from the slurry, dried at 170 ° C., and fired at 500 ° C. Thus, titania was held in the voids of the ceramic fiber sheet constituting the honeycomb structure.

  4) The honeycomb structure holding titania was immersed in an aqueous ammonium metavanadate solution, taken out from the aqueous solution, and then dried at 220 ° C. In this way, vanadium was adsorbed and supported on the titania of the honeycomb structure.

  5) The vanadium-supporting honeycomb structure was immersed in an aqueous solution of ammonium metatungstate, taken out from the aqueous solution, and then fired at 400 ° C. In this way, a denitration catalyst having a honeycomb structure in which vanadium and tungsten were supported on titania was obtained.

Performance Test The denitration performance of the catalysts produced in the examples and comparative examples was measured using the apparatus shown in FIG. 3 under the conditions shown in Table 1 (MFC in FIG. 3 is an abbreviation for Mass Flow Controller).

When the obtained denitration performance is represented by a reaction rate constant ratio,
Reaction rate constant of the catalyst of Example 1 relative to the reaction rate constant of the catalyst of Comparative Example 1: 1.3
It becomes.

  The reaction rate constant is expressed by the following equation.

Reaction rate constant = −ln (1−x / 100) × AV
(X: Denitration rate, AV: Area velocity)

The pore size distribution of both catalysts was measured by a nitrogen adsorption method using [ASAP2000] manufactured by Micromeritics. The result is shown in FIG.

The water absorption rate of both catalysts was measured from the weight increase by immersing the catalyst in water and then measuring its weight. The results are shown in Table 2.

  As can be seen from the reaction rate constant ratio, the catalyst of Example 1 is about 30% higher in catalytic activity than the catalyst of the comparative example (conventional catalyst). The following two points can be considered as the cause.

(1) As can be seen from the pore size distribution graph shown in FIG. 4, in the catalyst of Example 1, the pore size is distributed in the region of 20 to 100 angstrom centering on 50 angstrom. On the other hand, in the catalyst of Comparative Example 1, the pore diameter has a distribution centered at 150 angstroms in addition to the region of 20 to 100 angstroms centered on 50 angstroms. Fewer. This indicates that titania fine particles functioning as a catalyst have a pore size distribution centered on 50 Å, and titania derived from the titania sol used as a support medium has a pore size distribution centered on 150 Å. . That is, since the catalyst of Example 1 has a high content of titania fine particles that function as a catalytically active component, it exhibits high catalytic activity.

(2) From the results of the water absorption shown in Table 2, it can be seen that the catalyst of Example 1 shows a higher water absorption than the catalyst of Comparative Example 1. A high water absorption means that there are many voids inside the catalyst, and if the voids inside the catalyst become large, the amount of gas diffusion into the catalyst increases, thus improving the catalytic activity.

It is a flow sheet which shows this invention method. It is a flow sheet which shows the conventional method. It is a flow sheet which shows a performance test device. It is a graph which shows the pore diameter distribution of a catalyst.

Claims (2)

  In the manufacture of a denitration catalyst carrier based on a honeycomb structure obtained by alternately laminating corrugated ceramic fiber sheets and flat ceramic fiber sheets, the honeycomb structure is in a slurry in which titania fine particles are suspended in silica sol. The honeycomb structure is loaded with titania and silica simultaneously, the slurry has a solid content concentration of 45 wt%, and the ratio of silica to titania in the slurry is 20:80. A method for producing a denitration catalyst carrier. Wherein Rukoto claim 1 Ri Na carrying vanadium oxide and / or tungsten oxide on the catalyst carrier prepared in the method described, the pore diameter of the catalyst is not distributed in the region of 20 to 100 Å centered on 50 Å DeNOx catalyst.

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