Conversion of CO_2 to CO with CH_4 over Ni/SiO_2 Catalyst:Photoacoustic Measurements of Reaction Rate

摘要

The catalyzed reaction of carbon dioxide with methane to produce hydrogen and carbon monoxide,CO_2+CH_4->2CO+2H_2 (DELTAHdeg=59.1 kcal/mol),has received increasing attention from both an environmental and an industrial perspective.The reaction is attractive because the greenhouse gases (CO_2 and CH_4 can be converted into a synthesis gas with a low H_2/CO ratio,which is suitable for the syntheses of valuable oxygenated chemicals such as aldehydes,methyl alcohol,acetic acid,and dimethyl ether.Ni,Pt,and Ru based catalysts are known to be effective for the CO_2-CH_4 reaction.One of the major problems is the deactivation of catalysts due to the formation of coke on the catalysts during the reaction.The noble metal based catalysts are less sensitive to coking compared to nickel based catalysts.Nevertheless,it is still worthwhile to develop the nickel-based catalysts resistant to the formation of coke because the noble metals are expensive and of limited availability.The reforming of methane with carbon dioxide over nickel based catalysts has been studied by many investigators.However,there are few reports about fundamental kinetic parameters at present and there are some disagreements on the reaction mechanism including the reaction orders and the activation energy.