Basic exchange for enhanced redox os materials for emission control applications

Abstract

An Oxygen Ion Conductor (OIC)/Oxygen Storage (OS) material is disclosed, more particularly an OIC/OS having a stable cubic crystal structure, related to a method for the promotion of the catalytic properties of OIC/OS by the post-synthetic introduction of non-precious metals via a basic (alkaline) exchange process and the application of said materials to control of vehicle exhaust emissions.

We claim: 
     
         1 . A method for the production of catalytic materials containing highly dispersed metal atoms or metal ion based upon the contacting of metal oxide support material with precursor solution of dissolved cation under conditions of high pH/low Hydronium Ion (H 3 O + )/low proton (H + ) content, followed by drying and calcination of cation solution to remove any solvent and to convert cations into highly dispersed metallic or metal oxide ensembles or clusters. 
     
     
         2 . The method of  claim 1  wherein the cation solution employed contains an ammoniacal complex of the metal cations. 
     
     
         3 . The method of  claim 1  wherein the cation solution contains an organic amine complex of the metal cations. 
     
     
         4 . The method of  claim 1  wherein the cation solution contains a hydroxide compound of the metal cations. 
     
     
         5 . The method of  claim 1  wherein the cation solution is a cation complex in solution which is a base/common metal selected from the group consisting of a transition metal, an alkali metal, an alkaline earth metal and group Mb metal. 
     
     
         6 . The method of  claim 1  wherein the material is calcined at temperatures in excess of 350° C. to convert metal precursor into final dispersed metal/metal oxide state. 
     
     
         7 . The method of  claim 1  wherein the concentration of metal species thus introduced is about 0.01 weight % to about 10 weight %. 
     
     
         8 . A material obtained by the method of  claim 1  wherein the concentration of metal species thus introduced is 0.1 weight % to about 2.5 weight %. 
     
     
         9 . The material of  claim 8  wherein the resultant product contains metal at high levels of dispersion such that phase analysis by conventional X-Ray diffraction method reveals a substantially phase pure Cubic Fluorite phase (>95%), with bulk metal oxide dopant phase being recorded at <5% and dopant metal oxide particle size, as determined by line-broadening/Scherrer equation determination, is about 30 Å to about 100 Å. 
     
     
         10 . The material of  claim 8  wherein the resultant product contains metal at high levels of dispersion such that phase analysis by XRD reveals the promoted material maintains at least 95% Cubic Fluorite phase after hydrothermal oxidising aging at 1100° C. 
     
     
         11 . The method of  claim 1  wherein the oxide support is a refractory oxide. 
     
     
         12 . The method of  claim 1  wherein the oxide support contains Cerium oxide. 
     
     
         13 . The method of  claim 1  wherein the Cerium oxide is a solid solution of Cerium and Zirconium Oxide (Ce—Zr Oxide). 
     
     
         14 . The method of  claim 1  wherein the Ce—Zr oxide is substantially phase pure solid solution with oxygen ion conducting properties and comprises
 a. Up to about 95% Zirconium 
 b. Up to about 95% Cerium 
 c. Up to about 20% of a stabiliser selected from the group consisting of rare earths, yttrium and combinations comprising at least one of the stabilisers. 
 
     
     
         15 . A material produced by the method of  claim 1  wherein the support of contains metal at high levels of dispersion such that phase analysis by XRD reveals promoted material maintaining at least 95% Cubic Fluroite phase after hydrothermal oxidizing aging at 1100° C. and which displays enhanced Oxygen Ion Conductivity at low temperature, as determined by conventional Temperature Programmed Reduction (TPR), when compared to the undoped support, the extent of promotion is related to the type and concentration of metal promoter but shall decrease the TPR maximum from about 50° C. to about 500° C., compared to the parent material. 
     
     
         16 . A material produced by the method of  claim 1  wherein the support contains metal at high levels of dispersion such that phase analysis by XRD reveals promoted material maintaining at least 95% Cubic Flurote phase after gydrothermal oxidizing aging at 1100° C., and, wherein the promotion of redox, as determined by TPR, is substantially retained after hydrothermal oxidising aging at 1100° C.