NEW FEATURES OF SOL GEL PREPARED RUTHENIUM CATALYSTS IN CO HYDROGENATION AND CH4 COUPLING/

CO hydrogenation and the low temperature non-oxidative methane couplin g to form higher hydrocarbons over Ru/SiO2 and Ru/Al2O3 prepared by in cipient wetness method and Ru/Al2O3 prepared by sol/gel method (denote d by catalysts I, II and III, respectively) have been compared. Cataly sts II and III possess selectivity for the formation of C5+ hydrocarbo ns higher than sample I and the energy of activation is 85.7 kJ/mol on the catalyst III, which is about 29-33 kJ/mol less than those measure d for catalysts I and II, The striking feature of the Anderson-Schulz- Flory distribution (ASF) points to the existence of an umbilical cord mechanism and at lower temperature the reinsertion of alpha-olefins in concurrence with hydrogenolysis results in a sigmoid distribution. Wi th increase in temperature insertion becomes more and more prevalent p rocess and the sigmoid curve is transformed into two straight lines wi th different slopes, Similar behavior is valid for the ''two-step reac tion'' in the methane coupling carried out over different ruthenium ca talysts, of which sample III has the highest selectivity for C2+ hydro carbons. (C) 1997 Elsevier Science B.V.