Hydrogenation of carbon monoxide over the mixed catalysts composed of cobalt-nickel/manganese oxide-zirconium oxide and zeolite catalysts

Mechanical mixtures of Co-Ni/MnO-ZrO₂ and zeolite were used as catalysts for the selective synthesis of gasoline by carbon monoxide hydrogenation. Formation of branched alkanes was promoted, but that of hydrocarbons higher than a carbon number of 10 was suppressed by a combination with zeolite. The reactivity of zeolite for higher hydrocarbons has the decisive role in the product distribution on these mixed catalysts, and thus the product distribution strongly depended on the type of zeolite. Since the hydrogenolysis of higher hydrocarbons proceeds on the strong acid sites, the formation of branched alkanes was promoted by increasing the aluminium content in the zeolite. Ammonia temperature-programmed desorption suggests that increasing the aluminium content in the zeolite increases the number of strong acid sites, but weakens the average strength of the acid sites. Pentasil zeolite with an aluminium content of 1.32 mmol g^-1 is effective for enhancing the yield of gasoline as well as its octane number.