Lanthanide-promoted rhodium catalysts and process for producing synthesis gas

Abstract

Lanthanide-promoted rhodium-containing supported catalysts that are active for catalyzing the net partial oxidation of methane to CO and H 2 are disclosed, along with their manner of making and high efficiency processes for producing synthesis gas employing the new catalysts. A preferred catalyst comprises highly dispersed, high surface area rhodium on a granular zirconia support with an intermediate coating of a lanthanide metal and/or oxide thereof and is thermally conditioned during catalyst preparation. In a preferred syngas production process a stream of methane-containing gas and O 2 is passed over a thermally conditioned, high surface area Rh/Sm/zirconia granular catalyst in a short contact time reactor to produce a mixture of carbon monoxide and hydrogen.

1 . A method of partially oxidizing a reactant gas mixture comprising a light hydrocarbon and oxygen to form a product mixture containing carbon monoxide and hydrogen, the method comprising: 
 in a reactor, passing said reactant gas mixture over a highly dispersed, high surface area rhodium based catalyst structure such that the reactant gas mixture is exposed to a significant portion of the rhodium, said catalyst structure characterized by having a metal surface area of at least 1.25 square meters of metal per gram of catalyst structure, such that a product mixture containing carbon monoxide and hydrogen is formed.    
     
     
         2 . The method of  claim 1  wherein said catalyst structure is characterized by having a metal surface area of at least 1.5 square meters of metal per gram of catalyst structure.  
     
     
         3 . The method of  claim 1  wherein said catalyst structure is characterized by having a metal surface area of at least 2.0 square meters of metal per gram of catalyst structure.  
     
     
         4 . The method of  claim 1  wherein the rhodium surface area of said catalyst is at least 1.25 square meters of rhodium per gram of catalyst structure.  
     
     
         5 . A catalyst structure having catalytic activity in a partial oxidation reaction process, wherein the catalyst structure comprises: 
 a refractory support; and    highly dispersed, high surface area rhodium disposed on said refractory support, said catalyst structure characterized in that the catalyst structure has a metal surface area of at least about 1.25 square meters of metal per gram of catalyst structure.    
     
     
         6 . The catalyst structure according to  claim 5 , wherein the metal surface area is at least about 1.5 square meters of metal per gram of catalyst structure.  
     
     
         7 . The catalyst structure according to  claim 6 , wherein the metal surface area is at least about two square meters of metal per gram of catalyst structure.  
     
     
         8 . The catalyst structure according to  claim 5  further including a lanthanide or lanthanide oxide disposed between said rhodium and said refractory support.  
     
     
         9 . The catalyst structure according to  claim 5  wherein the rhodium and lanthanide are present on the catalyst support in a ratio of rhodium to lanthanide in the range of about 0.5 to about 2.  
     
     
         10 . The catalyst structure of  claim 9  wherein the rhodium and lanthanide are present on the catalyst support in a ratio of rhodium metal to lanthanide metal in the range of about 0.5 to about 2 and the rhodium comprises a majority of the metal surface area.  
     
     
         11 . The catalyst structure according to  claim 5  wherein the lanthanide is one of praseodymium, samarium, and ytterbium.  
     
     
         12 . The catalyst structure of  claim 10  wherein the lanthanide is samarium.  
     
     
         13 . The catalyst structure of  claim 5 , wherein the refractory support comprises a metal oxide wherein the metal has an atomic number less than 58.  
     
     
         14 . A method of making a high metal surface area catalyst structure having catalytic activity in a partial oxidation reaction process, the method comprises: 
 selecting a refractory support;    applying rhodium and a lanthanide on said refractory support in such manner as to form a catalyst structure having a metal surface area of at least about 1.25 square meters of metal per gram of catalyst structure.    
     
     
         15 . The method of  claim 14 , wherein said step of applying rhodium and lanthanide comprises: 
 making a solution comprising a decomposable rhodium precursor compound and a separate solution comprising a decomposable lanthanide precursor compound,    applying said solutions in separate steps to a refractory support, and    stabilizing at least the first applied said lanthanide or rhodium on the refractory support prior to application of the second solution.    
     
     
         16 . The method of  claim 15 , wherein the step of stabilizing the first applied said lanthanide or rhodium comprises thermally conditioning the refractory support with the first rhodium or lanthanide compound thereon, and wherein the method further comprises a calcining step after the second solution has been applied to the refractory support.  
     
     
         17 . The method of  claim 15 , wherein the lanthanide is chosen from the group consisting of praseodymium, samarium, and ytterbium, and the lanthanide solution is applied to the support prior to the application of the rhodium solution.  
     
     
         18 . The method of  claim 14 , wherein the step of selecting the refractory support comprises selecting a refractory support containing a metal oxide, the metal of which having an atomic number less than 58 and wherein the lanthanide is praseodymium, samarium or ytterbium.  
     
     
         19 . The method of  claim 14 , wherein the metal surface area is at least about 1.5 square meters of metal per gram of the catalyst structure.  
     
     
         20 . The method of  claim 14 , wherein the metal surface area is at least about two square meters of metal per gram of the catalyst structure.  
     
     
         21 . The method of  claim 14 , wherein the step of applying rhodium and lanthanide further comprises applying the rhodium and lanthanide so as to form a catalyst structure having a ratio of rhodium to lanthanide of between about 0.5 and about 2.