Oxidation catalyst for a diesel engine exhaust

Abstract

An oxidation catalyst is described for treating an exhaust gas produced by a diesel engine comprising a catalytic region and a substrate, wherein the catalytic region comprises a catalytic material comprising: bismuth (Bi), antimony (Sb) or an oxide thereof; a platinum group metal (PGM) selected from the group consisting of (i) platinum (Pt), (ii) palladium (Pd) and (iii) platinum (Pt) and palladium (Pd); and a support material, which is a refractory oxide; wherein the platinum group metal (PGM) is supported on the support material; and wherein the bismuth (Bi), antimony (Sb) or an oxide thereof is supported on the support material and/or the refractory oxide comprises the bismuth, antimony or an oxide thereof.

1 . An oxidation catalyst for treating an exhaust gas produced by a diesel engine comprising a catalytic region and a substrate, wherein the catalytic region comprises a catalytic material comprising:
 bismuth (Bi), antimony (Sb) or an oxide thereof;   a platinum group metal (PGM) selected from the group consisting of (i) platinum (Pt), (ii) palladium (Pd) and (iii) platinum (Pt) and palladium (Pd); and   a support material, which is a refractory oxide;   wherein the platinum group metal (PGM) is supported on the support material; and   wherein the bismuth (Bi), antimony (Sb) or an oxide thereof is supported on the support material.   
     
     
         2 . An oxidation catalyst according to  claim 1 , wherein the refractory oxide is a particulate refractory oxide, and the bismuth, antimony or an oxide thereof is dispersed over a surface of the particulate refractory oxide. 
     
     
         3 . An oxidation catalyst according to  claim 1 , wherein the catalytic material comprises bismuth (Bi) or an oxide thereof. 
     
     
         4 . An oxidation catalyst according to  claim 3 , wherein the refractory oxide is a particulate refractory oxide having a bulk particulate structure, and the bismuth or an oxide thereof is contained within the bulk particulate structure of the refractory oxide. 
     
     
         5 . An oxidation catalyst according to  claim 3 , wherein refractory oxide is impregnated with bismuth or an oxide thereof. 
     
     
         6 . An oxidation catalyst according to  claim 1 , wherein the catalytic region has a total loading of bismuth or antimony of 1 to 200 g ft −3 . 
     
     
         7 . An oxidation catalyst according to  claim 3 , wherein the refractory oxide further comprises tin (Sn) or an oxide thereof. 
     
     
         8 . An oxidation catalyst according to  claim 1 , wherein the catalytic material comprises bismuth or antimony in an amount of 0.1 to 15.0% by weight. 
     
     
         9 . An oxidation catalyst according to  claim 1 , wherein the catalytic region comprises bismuth or antimony in an amount of 1.0 to 2.5% by weight. 
     
     
         10 . An oxidation catalyst according to  claim 1 , wherein the refractory oxide comprises alumina, silica or a mixed or composite oxide of silica and alumina. 
     
     
         11 . An oxidation catalyst according to  claim 1 , wherein the refractory oxide comprises alumina doped with silica. 
     
     
         12 . An oxidation catalyst according to  claim 1 , wherein the platinum group metal (PGM) is platinum (Pt). 
     
     
         13 . An oxidation catalyst according to  claim 1 , wherein the platinum group metal (PGM) is palladium (Pd). 
     
     
         14 . An oxidation catalyst according to  claim 1 , wherein the platinum group metal (PGM) is platinum (Pt) and palladium (Pd). 
     
     
         15 . An oxidation catalyst according to  claim 1 , wherein the catalytic material comprises a ratio by weight of the platinum group metal (PGM) to bismuth (Bi) or antimony (Sb) of 10:1 to 1:10. 
     
     
         16 . An oxidation catalyst according to  claim 1 , wherein the substrate is a flow-through monolith or a filtering monolith. 
     
     
         17 . An exhaust system for treating an exhaust gas produced by a diesel engine, wherein the exhaust system comprises the oxidation catalyst of  claim 1  and optionally an emissions control device. 
     
     
         18 . A vehicle comprising a diesel engine and an exhaust system according to  claim 17 .