The decomposition of light paraffins was investigated using a Ni/Ca/carbon-based catalyst and an Ag-Pd membrane-type reactor (PMR). The use of this combined system resulted in the formation of smaller amounts of methane (< 10% yield) than in fixed-bed reactor systems (10-50% yield). The initial activity of CH4 decomposition seems to be little affected by these impurities such as NO, SO2, CO2, and H2O. The activity in the presence of SO2, however, was found to be completely lost after 250 min.