Biogas reforming for syngas production: The effect of methyl chloride

Biogas is a mixture of primarily methane and carbon dioxide produced from the anaerobic microbial digestion of biomass. A 4% Rh/Al2O3 catalyst was investigated for its ability to reform biogas in the presence of a chloride impurity, specifically CH3Cl that is often found in biogas systems. The conditions tested included temperatures between 350 degrees C and 700 degrees C with CH3Cl concentrations between 0 and 200 ppm at atmospheric pressure and 1050 h(-1) WHSV. It was determined that in the dry reforming reaction CH3Cl reacts with the alumina support to produce surface chloride which increases the surface acidity and reversibly poisons the reverse water-gas shift reaction. For example, with the addition of 50 ppm CH3Cl the H-2/CO ratio increased by 40% at 350 degrees C and by 2% at 700 degrees C. All changes were reversible upon removal of CH3Cl from the feed. Furthermore, less surface chloride was observed using XPS at 700 degrees C compared to 400 degrees C, and the effect on selectivity decreased with CH3Cl concentrations less than 50 ppm. Therefore the degree of chloride poisoning is directly proportional to CH3Cl concentration and inversely proportional to temperature. (C) 2013 Elsevier B.V. All rights reserved.