Partial oxidation of methane to synthesis gas using carbon dioxide

INCREASING concern about world dependence on petroleum oil has generated interest in the more efficient use of natural gas1–4. The conversion of methane to the common feedstock synthesis gas (carbon monoxide and hydrogen) by steam reforming is already well established5, and we have shown recently that yields of syn-thesis gas in excess of 90% can be obtained at moderate tem-peratures and ambient pressure by partial oxidation, with air or oxygen, over supported transition-metal catalysts6,7. The use of carbon dioxide as an oxidant for conversion of natural gas to synthesis gas is well established in steam reforming5, and is also known in CO2 reforming (for example, the Calcor process8,9), in which the use of excess CO2 yields mainly CO. In the present work, we describe an alternative catalytic strategy for CO2 reform-ing which gives excellent yields (90%) from a stoichiometric (1:1) feed of CO2 and CH4. Carbon deposition ('coking'), which is a hazard of CO2-reforming routes, is suppressed here by the use of catalysts based on platinum-group metals. We show that the exothermic partial oxidation of CH2 and the endothermic CO2-reforming reaction can be carried out simultaneously, thus introducing the possibility of tuning the thermodynamics of the process.