Partial oxidation of methane to synthesis gas using carbon dioxide

Abstract

INCREASING concern about world dependence on petroleum oil has generated interest in the more efficient use of natural gas^1–4. 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 catalysts^6,7. 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 process^8,9), 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.