Conversion of methane and n-pentane over Pt-Sn/γ-Al2O3 systems under non-oxidative conditions

Abstract

Monometallic catalysts Pt/Al2O3 and Sn/Al2O3 and bimetallic systems Pt—Sn/Al2O3 with the platinum and tin contents ∼0.51 and 0.13–0.38 wt.%, respectively, were synthesized. The introduction of tin into the Pt/Al2O3 catalyst decreases the electron deficiency and dispersion of platinum but exerts almost no effect on the concentration of the Lewis acid sites on the support surface. The degree of dehydrogenation of the activated forms of methane (CHx fragments) on the catalysts with tin additives is lower than that on the surface of the monometallic Pt/Al2O3 catalyst. The reactivity of the CHx species formed on the surface of the Pt—Sn/Al2O3 samples was studied in the co-conversion of the activated forms of CH4 with n-pentane to benzene and toluene under the non-oxidative conditions. The introduction of tin into the Pt/Al2O3 decreases the electron deficiency of platinum but does not decrease the yield of aromatic hydrocarbons. The modifying effect of tin appears as a decrease in the degree of dehydrogenation of the activated forms of methane, which results in an increase in the reactivity of activated methane during co-conversion with n-pentane.