Purification catalyst for exhaust gas, production method therefor, and purification catalyst equipment for exhaust gas

Abstract

A purification catalyst for exhaust gas which exhibits satisfactory performance even at a low temperature operation of starting or idling of engine (not more than 400° C.), and a production method therefor are provided. The catalyst comprises an aluminum oxide supporting Pd, and the aluminum oxide is LnAlO 3 (Ln: rare-earth metal).

1 . A purification catalyst for exhaust gas comprising an Al oxide supporting Pd and PdO, where the Al oxide is (Ln: rare-earth metal) generated as a single phase and trigonal or rhombohedral. 
   
   
       2 . A purification catalyst for exhaust gas according to  claim 1  wherein the catalyst is produced by adding at least one kind of compound selected from the group of compounds of carboxylic acid having a hydroxyl group or a mercapto group and having a carbon number of 2 to 20, dicarboxylic acid having a carbon number of 2 or 3, and monocarboxylic acid having a carbon number of 1 to 20 to aqueous nitrate solution including Ln and Al. 
   
   
       3 . The purification catalyst for exhaust gas according to  claim 2 , wherein the catalyst is produced by evaporating the aqueous nitrate solution completely, to produce a carboxylic acid complex polymer and heating the carboxylic acid complex polymer. 
   
   
       4 . The purification catalyst for exhaust gas according to  claim 3 , wherein Pd is supported on LnAlO 3  in which Ln is a rare-earth metal, and an oxidation state of Pd in a surface supporting Pd is a state of Pd 2+ . 
   
   
       5 . A Purification catalyst equipment for exhaust gas, comprising the purification catalyst for exhaust gas according to  claim 1  or  2 . 
   
   
       6 . The purification catalyst for exhaust gas according to  claim 1 , wherein the purification catalyst is a powder having a surface-to-weight ratio of 8 m 2  or more. 
   
   
       7 . The purification catalyst for exhaust gas according to  claim 3 , wherein the carboxylic acid is malic acid.