Layered composition and processes for preparing and using the composition

Abstract

A layered composition which can be used in various processes has been developed. The composition comprises an inner core such as a cordierite core and an outer layer comprising a refractory inorganic oxide, a fibrous component and an inorganic binder. The refractory inorganic oxide layer can be alumina, zirconia, titania, etc. while the fibrous component can be titania fibers, silica fibers, carbon fibers, etc. The inorganic oxide binder can be alumina, silica, zirconia, etc. The layer can also contain catalytic metals such as gold and platinum plus other modifiers. The layered composition is prepared by coating the inner core with a slurry comprising the refractory inorganic oxide, fibrous component, an inorganic binder precursor and an organic binding agent such as polyvinyl alcohol. The composition can be used in various hydrocarbon conversion processes including production of vinyl acetate.

1 . A method for preparing a catalyst for alkenyl alkanoate production, comprising:
 coating an inner core with a slurry comprising an outer refractory inorganic oxide, an inorganic binder precursor, a fibrous component, an organic bonding agent and a solvent to give a coated core with an outer layer; and   calcining the coated core at a temperature of at least 200° C. for a time sufficient to bond the outer layer to the inner core to provide a layered composition;   where the layered composition comprises at least palladium and gold dispersed on the outer layer.   
     
     
         2 . The method of  claim 1  further comprising impregnating the outer layer with one or more solutions comprising palladium, gold or combinations thereof. 
     
     
         3 . The method of  claim 2  where the impregnating step comprises co-impregnation of palladium and gold. 
     
     
         4 . The method of  claim 2  where the impregnating step comprises sequential impregnation of palladium and gold. 
     
     
         5 . The method of  claim 1  wherein the slurry comprises palladium, gold or combinations thereof. 
     
     
         6 . The method of  claim 1  wherein the refractory inorganic oxide has previously been contacted with palladium, gold or combinations thereof. 
     
     
         7 . The method of  claim 1  where the fibrous component comprises inorganic fibers, organic fibers or combinations thereof. 
     
     
         8 . The method of  claim 7  where the inorganic fibers comprise mullite, titania, potassium titanate, alumina, zirconia, silica, silicon carbide, cordierite, glass or combinations thereof. 
     
     
         9 . The method of  claim 1  where the inner core comprises alpha alumina, theta alumina, silicon carbide, metals, montmorillonite, cordierite, gamma alumina or combinations thereof. 
     
     
         10 . The method of  claim 1  where the outer refractory inorganic oxide comprises gamma alumina, delta alumina, eta alumina, theta alumina, silica/alumina, zeolites, nonzeolitic molecular sieves, titania, zirconia, niobia or combinations thereof. 
     
     
         11 . The method of  claim 1  where the inorganic binder comprises alumina, silica, zirconia, titania, aluminum phosphate or combinations thereof. 
     
     
         12 . The method of  claim 1  further comprising impregnating the outer layer with one or more solutions comprising a promoter. 
     
     
         13 . The method of  claim 1  where the outer layer has deposited thereon from one to about five additional layers and where adjacent layers comprise different inorganic oxides. 
     
     
         14 . The method of  claim 1  where the inner core has a lower capacity for catalytic components relative to the outer layer. 
     
     
         15 . The method of  claim 18  where the catalyst comprises between about 1 to about 10 grams of palladium, and about 0.5 to about 10 grams of gold per liter of catalyst, with the amount of gold being from about 10 to about 125 wt % based on the weight of palladium. 
     
     
         16 . The method of  claim 19  where the catalyst further comprises a potassium containing promoter component dispersed on the outer layer in an amount between about 10 and about 70 grams per liter of catalyst. 
     
     
         17 . The method of  claim 1  where the inner core comprises cordierite. 
     
     
         18 . The method of  claim 17  where the outer layer comprises zirconia. 
     
     
         19 . The method of  claim 18  wherein the inorganic fiber comprise titania. 
     
     
         20 . The method of  claim 1  wherein the fibrous component is dispersed throughout the outer layer.