EFFECT OF PROMOTION WITH SN ON SUPPORTED PT CATALYSTS FOR CO2 REFORMING OF CH4

The reforming of CH4 with CO2 (dry reforming:) was studied at 800 degr ees C over SiO2 and ZrO2 supported Pt-Sn catalysts. Several preparatio n methods were investigated. It was found that the Pt/ZrO2 catalyst ha d much higher activity and stability than the Pt/SiO2 catalyst due to the ability of the ZrO2 to promote CO2 dissociation. On this catalyst, the decomposition of CH4 and the dissociation of CO2 occur via two in dependent pathways. The longterm activity of the catalyst is dependent upon the balance between the rate of CH4 decomposition and the rate o f cleaning of carbonaceous deposits. The co-impregnation of Sn and Pt on the ZrO2 results in lower activity and stability than the monometal lic catalysts. Depending on the reaction conditions, disruption of the Pt-Sn alloys may occur, causing deposition of tin oxide that inhibits the role of the ZrO2. Special preparation methods can result in the c ontrolled placement of Sn on the Pt particle, minimizing the promoter- support interaction. These catalysts exhibit higher activity and stabi lity than the monometallic catalyst under severely deactivating condit ions, 800 degrees C, and a 3:1 ratio of CH4:CO2. It is possible to dep osit Sn onto Pt/ZrO2 catalysts in a manner which reduces carbon deposi tion without inhibiting the beneficial role of the support. (C) 1998 A cademic Press.