Effect of reduction temperature on the activity of Pt-Sn/Al2O3 catalysts for propane dehydrogenation

Abstract

Due to the growing attention toward the propane dehydrogenation (PDH) process, the understanding of Pt-containing bimetallic catalysts, especially Pt-Sn systems that are widely applied in PDH, is essential for improving the efficiency of PDH. While the reduction of PtSn catalysts for PDH process is crucial, it has yet to be thoroughly investigated. In this study, we prepared Pt-Sn/Al2O3 catalysts with 3 wt. % Pt and 4.5 wt. % Sn loadings and reduced these catalysts at different temperature of 100–600 ℃. The prepared catalysts were characterized via H2-temperature programmed reduction (TPR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), CO-diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), Raman spectroscopy, and transmission electron microscopy (TEM). Their catalytic activity for PDH was also evaluated. As the reduction temperature increased, the catalytic activity also increased. The catalyst reduced at 300 ℃ exhibited the highest conversion of propane. However, beyond the reduction temperature of 300 ℃, propane conversion decreased. Based on XRD results, as the reduction temperature increased, Pt particles of the calcined catalyst were transformed to Pt3Sn alloys and then to PtSn alloys, which were sintered at higher reduction temperatures. Based on characterization studies, the decrease in catalytic activity at higher reduction temperatures could be attributed to the formation and sintering of PtSn as well as the blocking of Pt-Sn particles by Sn species. TPR and CO-DRIFTS results suggested that the moderate interaction between Pt and Sn was more suitable for PDH reaction. The optimized reduction temperature of 300 ℃ obtained in this study that was lower than the commercially adopted reaction conditions could trigger the optimal reduction process design for PDH.