Oxidative coupling of methane over calcium chloride-promoted calcium chlorophosphate Original Research Article

CaCl2-promoted calcium chlorophosphate catalysts exhibited high catalytic performance for oxidative coupling of methane (OCM), while unpromoted calcium chlorapatite and calcium chlorophosphate exhibited poor catalytic performance. The presence of CaCl2 also yielded high ethene selectivity. Partial substitution of the calcium with transition metals, such as zinc, lead and nickel further enhanced the catalytic performance at 973 K; the optimum extent of substitution was about 4%. At 1023 K, however, the effect of substitution appeared to be little. Too excessive substitution gave rise to a decrease of the activity. At 1023 K, the highest C2 yield of around 22% was obtained with the C2 selectivity of 56–59%. The C2H4 selectivity was also high, around 50%. Production of a significant amount of H2 was observed over the CaCl2-promoted calcium chlorophosphate catalysts. We propose that the major pathways for the production of H2 are the steam reforming and partial oxidation of ethane and ethene which accompany simultaneous production of CO.