Oxidative coupling of methane over Na+-ZrO2-Cl-/Al2O3 catalysts

Oxidative coupling of methane (OCM) was carried out over Na+-ZrO2-Cl/Al2O3 catalysts in a temperature range from 1023 to 1123 K. The catalysts were prepared by impregnating the alpha- or gamma-Al2O3 supports with sodium carbonate and/or zirconyl chloride. The OCM activity was examined using the catalysts prepared by three different preparation procedures. The best catalyst was the one prepared by subsequent impregnation of sodium carbonate-preimpregnated gamma-Al2O3 with a mixed solution of sodium carbonate and zirconyl chloride. It was found that preimpregnated sodium played an important role in reducing the combustion activity of the gamma-Al2O3,. The catalyst with an optimal composition showed the highest C-2-selectivity and yield of 40.8% and 15.1%, respectively. From the X-ray diffraction analysis it was found that tetragonal ZrO2 was formed and that NaCl existed in the catalysts with relatively high sodium contents.