METHANE COUPLING REACTION ON OXIDE SOLID-SOLUTION CATALYSTS

The methane coupling reaction to form C2 hydrocarbons has been studied over perovskite-type oxides La1-xSrxB1-yMyO3-δ(B = Co, Cr, Fe, Mn, Y; M Nb, Ti), K2NiF4-type superconducting oxides A2-xBxCuO4-δ(A = La, Nd; B = Sr, Ce), and the solid solution La0.9Sr0.1O1.45. The reaction was performed in a fixed bed flow reactor with a feed containing 30% methane, 5% oxygen, and balance helium at 795°C. The results indicated that the superconducting oxides and the perovskites with high p-type electronic conductivity were not active for the methane conversion to C2 hydrocarbons. The compounds with n-type conductivity, electrolytes, and insulators were all found to proceed with selective oxidation to C2 compounds. A combination of an insulator or electrolyte associated with increased oxygen vacancy concentration appears to increase the C2 yield. Electrical conductivity, oxygen diffusion coefficient, and oxygen vacancy concentrations of the materials were considered to explain the observed variations in the methane coupling reactivity. © 1993 by Academic Press, Inc.