INFLUENCE OF ZIRCONIA PREPARATION ON THE SELECTIVITY FOR OXIDATIVE COUPLING OF METHANE

The oxidative coupling of methane has been studied on various zirconia. ZrO2 prepared from ZrCl4, ZrOCl2 · 8H2O, or ZrO(NO3)2 · 2H2O by the addition of ammonium hydroxide showed low selectivity to C2 compounds (≈9%), whereas ZrO2 prepared from ammonium hydroxide and potassium hydroxide produced relatively high selectivities (up to 47%) together with an approximately similar conversion as that found with the ammonia-treated ZrO2 (ca. 10% of methane conversion) at 775°C. When LiOH or NaOH was employed in place of KOH, the selectivity was as low as 8%. The high selectivity to C2 compounds on ZrO2 may be attributed to two factors: a small quantity of surface potassium and the presence of surface hydroxyl groups. © 1993 Academic Press, Inc.