Cerium oxide-zirconium oxide-based mixed oxide and method for producing the same

Abstract

The present invention provides a cerium oxide-zirconium oxide-based mixed oxide having superior platinum dispersibility and a suitable OSC, and a simple production process thereof. The cerium oxide-zirconium oxide-based mixed oxide comprises cerium oxide and zirconium oxide, wherein (1) the weight ratio of CeO 2 : ZrO 2 is 60:40 to 90:10, and (2) the cerium oxide and the zirconium oxide are present as a mixture, the zirconium oxide being composed of a solid solution in which tetragonal or cubic zirconium oxide contains cerium.

1 . A cerium oxide-zirconium oxide-based mixed oxide comprising cerium oxide and zirconium oxide, wherein (1) the weight ratio of CeO 2 :ZrO 2  is 60:40 to 90:10, and (2) the cerium oxide and the zirconium oxide are present as a mixture, the zirconium oxide being composed of a solid solution in which tetragonal or cubic zirconium oxide contains cerium.  
   
   
       2 . The cerium oxide-zirconium oxide-based mixed oxide according to  claim 1 , wherein the ratio of the cerium oxide as calculated from the X-ray diffraction peak intensity after heat treatment for 3 hours at 1000° C. in air is 50% by volume or more.  
   
   
       3 . The cerium oxide-zirconium oxide-based mixed oxide according to  claim 1  or  2 , wherein the mixed oxide contains 1 to 20 wt % of one type or two or more types of oxides selected from rare earth elements excluding cerium, transition metal elements, aluminum and silicon.  
   
   
       4 . A method for producing a cerium oxide-zirconium oxide-based mixed oxide comprising: a first step of adding a sulfating agent to a cerous salt to obtain a slurry containing a cerous sulfate-alkali metal mixed salt; a second step of adding a cerium salt and a zirconium salt to the slurry; a third step of adding an alkali to the mixture obtained in the second step to obtain a mixed hydroxide containing cerium hydroxide and zirconium hydroxide; and a fourth step of heat-treating the mixed hydroxide to obtain a mixed oxide containing cerium oxide and zirconium oxide.  
   
   
       5 . The method for producing a cerium oxide-zirconium oxide-based mixed oxide according to  claim 4 , wherein one type or two or more types of metal salt selected from rare earth elements excluding cerium, transition metal elements, aluminum and silicon is added in the second step.