Isobutane Dehydrogenation over InPtSn/ZnAl2O4 Catalysts: Effect of Indium Promoter

Dehydrogenation of saturated isobutane provides an alternative process to produce isobutene from nonpetroleum resources. InPtSn/ZnAl2O4 catalysts with various In contents were prepared by sequential impregnation for the isobutane dehydrogenation. The catalysts were investigated by several characterizations such as X-ray diffraction, N-2 adsorption, H-2 chemisorption, NH3 temperature programmed desorption, pyridine-adsorbed Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, and temperature-programmed oxidation. We reveal that with the suitable addition of In component in the PtSn/ZnAl2O4 catalysts, the Pt dispersion increases, and the surface acidity decreases. The presence of In improves the stability of the reaction greatly because it is beneficial to stabilize the oxidation states of SnOx. The excessive addition of In will lead to decrease of the Pt dispersion and increase of the surface acidity, which cause the decline in the catalytic activity. The addition of 0.4 wt % In on PtSn/ZnAl2O4 catalyst shows the optimized catalytic performance. The isobutane conversion decreases from 54.7 to 40.5% within 8 h, and the isobutene selectivity is above 95% even after 20 reaction-regeneration cycles.