Preparation of highly dispersed Pt–Sn/Al2O3 catalysts via supercritical fluid deposition and their catalytic performance

Naphtha catalytic reforming is an important process due to the production of BTX (benzene, toluene, and xylene) using platinum-based catalysts, in which tin can be used as a second metal to improve the catalytic performance. In this work, the influence of different Sn salts and precursor salts with different Sn/Pt ratios on the structure–activity relationship of Pt–Sn/Al2O3 prepared by supercritical fluid deposition is studied systematically. Results showed that when Na2PtCl6 and SnCl2 are used as precursor salts, the metal particle size of Pt–Sn/Al2O3 is the smallest at 0.7 nm; bimetals exist in the form of PtSn alloy and its catalytic reforming activity is also the best. An increase in the Sn/Pt ratio will further reduce the particle size of Pt and increase its dispersion. When the Sn/Pt ratio is 1.5, it shows the best catalytic activity. The metal particle size of the catalyst has a great influence on the dehydrogenation process of methylcyclopentane (MCP), showing an obvious size effect. The dehydrogenation performance of the Pt–Sn/Al2O3 prepared by the SFD method is significantly higher than that of the catalyst prepared by the impregnation method. By increasing temperature, pressure and liquid space velocity, the conversion of MCP, the selectivity of benzene and the production capacity of benzene are further improved.