Composition Based On Oxides Of Zirconium, Praseodymium, Lanthanum Or Neodymium, Method For The Preparation And Use Thereof In A Catalytic System

Abstract

The composition is based on zirconium oxide and at least one additive selected from zirconium oxide and at least one additive chosen from praseodymium, lanthanum or neodymium oxides, has a specific surface of at least 29 m 2/g after calcination at 1000° C. during a period of 10 hoursand is is obtained by a method wherein a mixture of zirconium compounds and additive is precipitated with a base; the medium thus obtained, containing a precipitate, is heated and a compound chosen from anionic surfactants, non-ionic surfactants, polyethylene glycols, carboxylic acids and the salts thereof and surfactants such as the ethoxylates of caroboxymethyl fatty alcohols is added to the compound and the precipitate is calcinated; the composition can be used as a catalyst.

1 - 19 . (canceled) 
   
   
       20 . A composition based on zirconium oxide, comprising at least one additive being an oxide of praseodymium, lanthanum or neodymium, sand having a specific surface area of at least 29 m 2 /g after calcination for 10 hours at 1000° C. 
   
   
       21 . The composition as claimed in  claim 20 , wherein the specific surface area is of at least 35 m 2 /g, optionally of at least 40 m 2 /g, after calcination for 10 hours at 1000° C. 
   
   
       22 . The composition as claimed in  claim 21 , wherein the specific surface area is of at least 50 m 2 /g after calcination for 10 hours at 1000° C. 
   
   
       23 . The composition as claimed in  claim 20 , having a specific surface area of at least 10 m 2 /g after calcination for 4 hours at 1100° C. 
   
   
       24 . The composition as claimed in  claim 23 , wherein the specific surface area is of at least 15 m 2 /g after calcination for 4 hours at 1100° C. 
   
   
       25 . The composition as claimed in  claim 21 , having a specific surface area of at least 2 m 2 /g, optionally of at least 3 m 2 /g, after calcination for 10 hours at 1200° C. 
   
   
       26 . The composition as claimed in  claim 20 , having a specific surface area of at least 45 m 2 /g after calcination for 4 hours at 900° C. 
   
   
       27 . The composition as claimed in  claim 26 , wherein thespecific surface area of at least 50 m 2 /g, optionally of at least 55 m 2 /g, after calcination for 4 hours at 900° C. 
   
   
       28 . The composition as claimed in  claim 20 , having an additive content which does not exceed 50% by weight of additive oxide with respect to the weight of the composition. 
   
   
       29 . The composition as claimed in  claim 28 , wherein the additive content is between 10% and 40%. 
   
   
       30 . The composition as claimed in  claim 29 , wherein the additive content is between 10% and 30%. 
   
   
       31 . The composition as claimed in  claim 20 , further having mesopores between 10 nm and 500 nm in size. 
   
   
       32 . The composition as claimed in  claim 20 , wherein it further comprises aluminum oxide or silica. 
   
   
       33 . A method for preparing a composition as defined in  claim 20 , comprising the following steps:
 (a) forming a mixture comprising compounds of zirconium, of additive and, optionally, of aluminum or silicon;   (b) contacting the mixture obtained in step a) with a basic compound whereby a precipitate is obtained;   (c) heating the precipitate obtained in step b) in a liquid medium;   (d) adding a compound to the precipitate obtained in step c), said compound being an anionic surfactant, nonionic surfactant, polyethyleneglycol, carboxylic acid, a salt thereof, or a carboxymethylated fatty alcohol ethoxylate; and   (e) calcining the precipitate thereby obtained in step d).   
   
   
       34 . The method as claimed in  claim 33 , wherein the compounds of zirconium, of additive and of aluminum compounds are nitrates, acetates or chlorides. 
   
   
       35 . The method as claimed in  claim 33 , wherein in step c) the heating of the precipitate is carried out at a temperature of at least 100° C. 
   
   
       36 . A catalytic system, wherein comprising a composition as defined in  claim 20 . 
   
   
       37 . The catalytic system as claimed in  claim 36 , further comprising a transition metal or a precious metal, supported by the composition. 
   
   
       38 . A method for treating exhaust gases of internal combustion engines, comprising the step of treating said gases in the presence of the catalyst system as defined in  claim 37 .