Partial Oxidation and Steam Reforming of Methane over Ce_(0.9)Gd_(0.1)O_(2-x)

摘要

The reaction of Ce_(0.9)Gd_(0.1)O_(2-x) (CGO) with methane and its activity as a steam reforming catalyst have been investigated using micro-reactor techniques. Temperature programmed reaction (TPRx) and isothermal reaction at 900°C were carried out in 5 % methane in argon and at steam to methane ratios from 0 to 5.5. CGO was found to have useful methane steam reforming activity at high temperatures producing H_2, CO and some CO_2 with an intrinsic rate that is lower than a conventional Ni-based catalyst or SOFC anode. The steam reforming reaction rate is proportional to the methane partial pressure and independent of the steam partial pressure. The turnover frequency (approximately 1 site~(-1) min~(-1) at 900°C) and activation energy (153 kJ mol~(-1)) for steam reforming are approximately equal to those for reaction between CGO and dry methane. This suggests a reaction mechanism which is controlled by the slow reaction of adsorbed methane with oxygen in CGO and a facile reaction between steam and CGO to replenish the oxygen. CGO is extremely resistant to carbon deposition in both dry methane and in steam reforming conditions.