Catalysis Letters, Vol.39, No.1-2, 43-47, 1996
Nonoxidative Methane Coupling over Co-Pt/NaY Bimetallic Catalysts
Methane activation and coupling of the CHx species formed from methane into higher hydrocarbons over NaY, Pt/NaY, Co/NaY, Co-Pt/NaY and Co-Pt/Al2O3 have been compared. Co-Pt/NaY and C0-Pt/Al2O3 showed exceptionally high yields (100%) referred to the adsorbed CHx species and high selectivity in the formation of C-2+ hydrocarbons (83.6 and 92.6%, respectively) in the two-step reaction using 523 K for chemisorption and 523 K for hydrogenation. However, the amount of CHx is four-fold higher on Co-Pt/NaY than Co-Pt/Al2O3. The synergistic effect can be interpreted by insertion of Co into Pt inside the zeolite cages which causes a preferential coupling of CHx species vs. its hydrogenation into methane. Separate experiments carried out on the removal of CHx species with deuterium show that deep dissociation of methane does not occur on bimetallic catalyst and the weakly bonded CHx species can easily participate in chain building reaction on the surface.
Keywords:TRANSITION-METALS;REACTION SEQUENCE;NAY-ZEOLITE;HYDROGENATION;CONVERSION;PLATINUM;HOMOLOGATION;MECHANISM;STABILITY;SURFACE