Synergistic effect of low valence manganese ions in manganese-based catalysts for non-oxidative dehydrogenation of isobutane

A series of manganese-based catalysts supported on γ-Al2O3 with low loading amount of manganese from 0.5% to 2.0% were prepared by incipient impregnating method. All catalysts were tested on non-oxidative dehydrogenation of isobutane at 600 °C. In order to explore physicochemical properties of all catalysts, various characterizations including XRD, H2-TPR, XPS, UV-vis, NH3-TPD and TG were carried out on manganese-based catalysts. The experimental results indicated that MnOx species were highly dispersed on γ-Al2O3 support, and both Mn2+ and Mn3+ ions are main active species for isobutane dehydrogenation. The reduced catalyst 1.5%Mn/γ-Al2O3 exhibited the most optimal dehydrogenation performance among all catalysts, reaching at isobutane conversion of 36% and isobutene selectivity of 79%. The main reasons for the excellent activity and selectivity of 1.5%Mn/γ-Al2O3 were related to the high proportion of low valence manganese ions including Mn2+ and Mn3+ as well as the high concentration of medium strong acid sites and weak strong acid strength.