Exhaust gas purifying catalyst and method for producing the same

Abstract

Provided is an exhaust gas purifying catalyst with an excellent effect of suppressing deterioration due to aggregation of a noble metal catalyst that would occur during endurance at a high temperature. The exhaust gas purifying catalyst includes a porous support and a noble metal catalyst carried on the porous support. The porous support contains particles of an alumina-ceria-zirconia composite oxide, and the porous support has the following physical property values after subjected to baking at 900° C. for 5 hours: a pore diameter of the particles in the range of 2 to 20 nm, a specific surface area of the particles in the range of 75 to 115 m2 / g, a crystallite size of a ceria-zirconia composite oxide that is contained in the particles in the range of 4 to 6 nm, and a bulk density of the particles in the range of 0.5 to 0.9 cm3 / g.

Description

CLAIM OF PRIORITY[0001]The present application claims priority from Japanese patent application JP 2015-098296 filed on May 13, 2015, JP 2016-024929 filed on Feb. 12, 2016, the content of which is hereby incorporated by reference into this application.BACKGROUND[0002]1. Technical Field[0003]The present invention relates to an exhaust gas purifying catalyst and a method for producing the same.[0004]2. Background Art[0005]In a variety of industries, a variety of attempts has been made worldwide to reduce environmental impacts and burdens. In particular, in the automobile industry, development for promoting the spread of not only fuel-efficient gasoline engine vehicles, but also so-called eco-friendly vehicles, such as hybrid vehicles and electric vehicles, as well as for further improving the performance of such vehicles has been advanced day by day. In addition to the development of such eco-friendly vehicles, research about an exhaust gas purifying catalyst for purifying exhaust gas...

AI Technical Summary

Benefits of technology

The present invention provides an exhaust gas purifying catalyst that can effectively suppress the aggregation of noble metal catalysts during endurance at high temperatures. The catalyst contains a composite oxide support with a specific pore size, and a specific surface area, and a combination of these properties results in high durability and efficient purification of exhaust gas. The method for producing the catalyst allows for the production of composite oxide with a fine pore size, ensuring optimal performance. Overall, the invention provides an improved exhaust gas purifying catalyst with improved performance and durability.

Problems solved by technology

The engine may sometimes discharge environmentally harmful substances, such as CO, NOx, and unburned HC and VOC.

By the way, exhaust gas purifying catalysts have a problem in that they have deteriorated catalyst performance when exposed to a high temperature.

However, when a number of relatively large pores are formed within powder of a porous support, the effect of suppressing sintering (aggregation) of a noble metal catalyst would decrease, and further, when the volume of the powder of the porous support is increased, another problem may occur such that the amount of the catalyst that can be applied to a monolith is limited.

Meanwhile, when the number of pores is reduced, the specific surface area of the porous support will decrease, and it becomes difficult for the porous support to carry a noble metal catalyst.

Thus, it is quite difficult to adjust the number of pores from the perspective of both carrying a noble metal catalyst and suppressing the aggregation of the noble metal catalyst after endurance.

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