On the Reaction Mechanism of CO2 Reforming of Methane Over a Bed of Coal Char

CO2 reforming of methane was studied over a bed of coal char in a fixed bed reactor at temperatures between 1073 and 1223 K and atmospheric pressure with a feed composition of CH4/CO2/N-2 in the ratio of 1:1:8. Experimental results showed that the char was an effective catalyst for the production of syngas with a maximum H-2/CO ratio of one. It was also found that high H-2/CO ratios were favoured by low pressures and moderate to high temperatures. These results are supported by thermodynamic calculations. A mechanism of seven overall reactions was studied and three catalytic reactions of CH4 decomposition, char gasification and the Boudouard reaction was identified as being of major importance. The first reaction produces carbon and H-2, the second consumes carbon, and the third (the Boudouard reaction) converts CO2 to CO while consuming carbon. Equilibrium calculations and experimental results showed that any water present reacts to form H-2 and carbon oxides in the range of temperatures and pressures studied. Carbon deposition over the char bed is the major cause of deactivation. The rate of carbon formation depends on the kinetic balance between the Surface reaction of the adsorbed hydrocarbons with oxygen containing species and the further dissociation of the hydrocarbon. (c) 2006 The Combustion Institute. Published by Elsevier Inc. All rights reserved.