Method and catalyst composite for production of vinyl acetate monomer

Abstract

Provided are catalyst composites useful for the production of vinyl acetate monomer, as well as methods of making using same. The catalyst composites may comprise a support comprising silica and about 1 to about 3 wt % alumina, wherein the support has a surface area of about 175 to about 300 m 2 /g; and an eggshell layer on the support comprising Pd and Au.

What is claimed is: 
     
         1 . A catalyst composite comprising an inner region and an outer region:
 the outer region comprising Pd and Au;   the inner region comprises a spherical support comprising silica and about 1 to about 3 wt % alumina and the inner region being free of Pd and Au;   wherein:   the outer region has a depth from the surface of the catalyst composite to about 500μm;   the catalyst composite has a surface area of about 175 m 2 /g to about 300 m 2 /g; and   the catalyst composite has a diameter of about 3 mm to about 7 mm;   
     
     
         2 . The catalyst composite of  claim 1 , wherein the inner region comprises about 2 wt % alumina. 
     
     
         3 . The catalyst composite of  claim 1 , wherein the catalyst composite has a surface area of about 200 m 2 /g to about 250 m 2 /g. 
     
     
         4 . The catalyst composite of  claim 3 , wherein the catalyst composite has a surface area of about 225 m 2 /g. 
     
     
         5 . The catalyst composite of  claim 1 , wherein the Au is present in the outer region in an amount of about 0.9 g per liter to about 5 g per liter of catalyst composition and palladium in an amount of about 3 g per liter to about 10 g per liter of catalyst composition. 
     
     
         6 . The catalyst composite of  claim 5 , wherein the outer region further comprises potassium acetate in an amount of about 25 g per liter to about 60 g per liter of catalyst composition. 
     
     
         7 . A method of producing vinyl acetate monomer, the method comprising
 contacting a gas comprising ethylene, acetic acid and oxygen with particles of a catalyst composite;   wherein:
 individual particles of the catalyst composite comprise an inner region and an outer region: 
 the outer region comprising Pd and Au; 
 the inner region comprises a spherical support comprising silica and about 1 to about 3 wt % alumina and the inner region being free of Pd and Au; 
 the outer region has a depth from the surface of the catalyst composite to about 500 μm; 
   the catalyst composite has a surface area of about 175 m 2 /g to about 300 m 2 /g; and   the particles having a diameter of about 3 mm to about 7 mm.   
     
     
         8 . The method of  claim 7 , wherein the inner region comprises about 2 wt % alumina. 
     
     
         9 . The method of  claim 7 , wherein the catalyst composite has a surface area of about 200 m 2 /g to about 250 m 2 /g. 
     
     
         10 . The method of  claim 9 , wherein the catalyst composite has a surface area of about 225 m 2 /g. 
     
     
         11 . The method of  claim 7 , wherein the Au is present in the outer region in an amount of about 0.9 g per liter to about 5 g per liter of catalyst composition and palladium in an amount of about 3 g per liter to about 10 g per liter of catalyst composition. 
     
     
         12 . The method of  claim 11 , wherein the outer region further comprises potassium acetate in an amount of about 25 g per liter to about 60 g per liter of catalyst composition.