Catalyst material and a process for its preparation

Abstract

A powdered catalyst material based on aluminum oxide, which contains at least one basic metal oxide and at least one noble metal from the platinum group of the Periodic System of Elements in addition to aluminum oxide. The catalyst material is obtainable by loading a support material already stabilized by basic oxides by renewed impregnation with further basic oxides. After drying and calcining this post-impregnated material at temperatures below 800° C., the catalytically active noble metals are also incorporated into the support material by impregnation.

We claim:  
     
         1 . A powdered catalyst material of aluminum oxide, at least one basic metal oxide, and at least one catalytically active noble metal, wherein aluminum oxide and the at least one basic metal oxide form a support material for the at least one catalytically active component, the powdered catalyst material obtained by a process comprising: 
 a) providing as a support material a powdered aluminum oxide stabilized with at least one basic oxide, and having a specific surface area greater than 80 m 2 /g;    b) impregnating the support material with a solution of at least one precursor compound of a member selected from the group consisting of at least one alkaline earth metal and at least one rare earth metal;    c) drying the resulting impregnated support material; and    d) calcining the resulting dried impregnated support material at a temperature below 800° C.;    e) repeating process steps b) through d) until a desired loading with basic oxides is achieved; and    f) impregnating the resulting calcined impregnated support material with a solution of at least one precursor compound of at least one catalytically active noble metal;    g) drying the resulting further impregnated support material; and    h) calcining the resulting dried impregnated support material to obtain the powdered catalyst material product.    
     
     
         2 . The catalyst material according to  claim 1 , wherein the powdered aluminum oxide support material provided has a concentration of basic oxides in step a) of from 0.5 to 20 wt %, with respect to the total weight of support material.  
     
     
         3 . The catalyst material according to  claim 2 , wherein the concentration of the member selected from the group consisting of at least one alkaline earth metal and at least one rare earth metal incorporated into the support material by impregnation in step b) is from 0.5 to 15 wt. %, with respect to the total weight of support material.  
     
     
         4 . The catalyst material according to  claim 1 , wherein the at least one basic oxide of step a) is selected from the group consisting of alkaline earth oxides and rare earth oxides.  
     
     
         5 . The catalyst material according to  claim 4 , wherein the at least one basic oxide is at least one member selected from the group consisting of lanthanum oxide and cerium oxide.  
     
     
         6 . The catalyst material according to  claim 1 , wherein the at least one catalytically active noble metal is at least one member selected from the group consisting of platinum, palladium, rhodium, iridium, and mixtures thereof, which are present in a concentration of from 0.01 to 5 wt. %, with respect to the total weight of catalyst material.  
     
     
         7 . A powdered catalyst material comprising aluminum oxide, at least one basic metal oxide, and at least one catalytically active noble metal, 
 wherein the aluminum oxide and the at least one basic metal oxide form a composite support material for catalytically active components,    wherein the catalyst material has a specific surface area of more than 80 m 2 /g,    wherein a ratio of SIMS intensities of the basic metal oxides to SIMS intensities of the aluminum, at the surface of the powder particles, is at least 20% greater than that at a depth of more than 100 atomic layers from the surface of the particles.    
     
     
         8 . The catalyst material according to  claim 7 , wherein the at least one basic metal oxide is at least one member selected from the group consisting of alkaline earth oxides and rare earth oxides.  
     
     
         9 . The catalyst material according to  claim 8 , wherein the at least one basic metal oxide is at least one member selected from the group consisting of lanthanum oxide and cerium oxide.  
     
     
         10 . The catalyst material according to  claim 9 , wherein the at least one basic metal oxide is present in a concentration, with respect to the total weight of the catalyst material, of between 1 and 35 wt. %.  
     
     
         11 . The catalyst material according to  claim 10 , wherein the at least one noble metal is at least one member selected from the group consisting of platinum, palladium, rhodium, iridium, and mixtures thereof and is present in a concentration of 0 01 to 5 wt %, with respect to the total weight of the catalyst material.  
     
     
         12 . A process for preparing a powdered catalyst material, comprising: 
 a) providing as support material a powdered aluminum oxide stabilized with at least one basic oxide, and having a specific surface area greater than 80 m 2 /g;    b) impregnating the support material with a solution of at least one precursor compound of at least one member selected from the group consisting of an alkaline earth metal and a rare earth metal;    c) drying the resulting impregnated support material, and,    d) calcining the dried support material at a temperature below 800° C.;    e) repeating steps b) through d) until a desired loading with the at least one basic oxide is achieved; and    f) impregnation of the loaded support material with a solution of at least one precursor compound of the at least one catalytically active noble metal; and,    g) final drying and calcining to obtain the powdered catalyst material product.    
     
     
         13 . The process according to  claim 12 , wherein the stabilized aluminum oxide provided as support material in step a) has a concentration of 1 to 20 wt. % of the at least one basic oxide.  
     
     
         14 . A process according to  claim 13 , wherein the at least one member selected from the group consisting of an alkaline earth metal and a rare earth metal additionally incorporated into the support material in step b) amounts to 0.5 to 15 wt. %, with respect to the total weight of support material.  
     
     
         15 . A powdered support material of aluminum oxide, at least one basic metal oxide, and at least one noble metal, obtained by a process comprising: 
 a) providing as support material a powdered aluminum oxide stabilized with at least one basic oxide, and having a a specific surface area of more than 80 m 2 /g;    b) impregnating the support material with a solution of at least one precursor compound of at least one member selected from the group consisting of an alkaline earth metal and a rare earth metal;    c) drying the impregnated support material; and    d) calcining the dried support material at a temperature below 800° C.; and,    e) repeating process steps b) through d) until a desired loading with the at least one basic oxide is achieved.