Metal-supported crystalline silica aluminophosphate catalyst and process for producing the same

Abstract

Disclosed is a metal-supported catalyst produced by (a) preparing a dispersion of crystalline silicoaluminophosphate particles; (b) mixing an aqueous active ingredient metal compound solution into the dispersion; (c) spray-drying the mixture; (d) washing the spray-dried product and (e) heat-treating (calcining) the washed product at 400 to 900° C.Also disclosed is an aluminum phosphate-modified metal-supported crystalline silicoaluminophosphate catalyst having a content of aluminum phosphate in the catalyst of 0.1 to 40% by weight in terms of Al2O3+P2O5 based on the metal-supported crystalline silicoaluminophosphate particles.

Description

TECHNICAL FIELD[0001]The present invention relates to a metal-supported catalyst suitable for use in exhaust gas treatment in internal combustion engines with an enhanced exhaust gas treatment efficiency and a process for producing the same.BACKGROUND ART[0002]Contaminants such as HC (hydrocarbons), CO (carbon monoxide), NOx (nitrogen oxide), and PM (particulate matter) are contained in exhaust gases discharged from diesel engines. Among these contaminants, NOx cannot be purified by three-way catalysts, which have been put to practical use in oxidation catalysts and gasoline automobiles, without difficulties, and, thus, selective reduction-type NOx catalysts (hereinafter referred, to as “SCR catalysts”) are under development as promising NOx-purifying catalysts.[0003]Catalysts that have a honeycomb structure and comprise an active ingredient such as V (vanadium), Cr (chromium), Mo (molybdenum), Mn (manganese), Fe (iron), Ni (nickel), Cu (copper), Ag (silver), Au (gold), Pd (palladiu...

AI Technical Summary

Benefits of technology

[0014]An object of the present invention is to provide a process for producing a metal-supported catalyst, which has high hydrothermal stability and can maintain high activity for a long period of time, and to provide a metal-supported catalyst.

[0015]Another object of the present invention is to provide an aluminum phosphate-modified metal-supported crystalline silicoaluminophosphate catalyst, which particularly has high low-temperature activity, and to provide a process for producing the same.

[0056]The present invention can provide a metal-supported crystalline silicoaluminophosphate catalyst and a NOx reducing catalyst for exhaust gas treatment that have high hydrothermal stability at ultrahigh temperatures of approximately 700° C. or above. The metal-supported crystalline silicoaluminophosphate catalyst and the NOx reducing catalyst for exhaust gas treatment can maintain high activity for a long period of time.

[0057]The aluminum phosphate-modified metal-supported crystalline silicoaluminophosphate catalyst has high low-temperature activity.

[0058]The process for producing a metal-supported crystalline silicoaluminophosphate catalyst according to the present invention is simple in steps and has excellent cost effectiveness.

Problems solved by technology

Conventional crystalline porous material catalysts such as the above-described zeolites, when used at 700° C. or above in a reaction that produces water, cause lowered crystallinity and specific surface area that in turn results in lowered activity.

The following facts, however, have been found: (1) a method in which ion-exchange is carried out in an aqueous metal salt solution is disadvantageous in that a metal in an amount large enough to provide satisfactory activity cannot be supported, (2) a method in which a crystalline silicoaluminophosphate is dispersed in an aqueous metal salt solution to hydrolyze the metal salt and to precipitate a metal hydroxide is disadvantageous in that the crystallinity of the crystalline silicoaluminophosphate is sacrificed, and (3) a method in which a crystalline silicoaluminophosphate is impregnated with a metal salt is disadvantageous in that satisfactory activity cannot be provided probably due to ununiformly distributed metal on the surface of pores of the crystalline silicoaluminophosphate.