Effect of Different Loadings on the Performance of Ni2P/Al2O3 Catalysts for Low-Temperature Thioethering and Selective Hydrogenation of Diolefins in Liquefied Petroleum Gas
Xiao Han, Sun Jinru, Song Guoliang, Xie Xianna, Ke Ming, Tong Yanbing, Zhao Zhiping, Wang Zijian, Li Jiahan
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In this study, different loadings of x%Ni2P/γ-Al2O3 (x = 6%, 9%, 12%, 15%, 18%) catalysts with aluminum oxide (Al2O3) as the carrier, nickel chloride (NiCl2) as the nickel (Ni) source, and ammonium hypophosphite (NH4H2PO2) as the phosphorus (P) source were prepared by the equal volume impregnation method to investigate the effects of different loadings on the performance of the selective hydrogenation of diolefins and thiol etherification in LPG. The physicochemical properties of the catalysts were characterized by XRD, BET, SEM, TEM, H2-TPR, and XPS, and the catalytic activity of the catalysts was evaluated in a fixed-bed microreactor. The results showed that a change in the loading affected the catalyst crystalline phase structure and size, specific surface area, P coverage, active phase dispersion, and catalytic activity. At 6%, 9%, and 12% loadings the catalysts had an Ni phase but there was no obvious Ni2P phase in the nickel phosphide; at 15% loading a single Ni2P phase was obtained, and at 18% loading both Ni2P and Ni12P5 phases appeared. There was a P enrichment on the catalyst surface, and the higher the loading the more P species were enriched on the surface, but some of the P was lost during the catalyst reduction process due to the production of phosphine (PH3) gas. The 15%Ni2P/γ-Al2O3 catalyst had the largest Ni/Al ratio and the best dispersion. The Ni2P active phase size was small at about 4.25 nm and Ni2P was uniformly dispersed on the catalyst surface without agglomeration. The 15%Ni2P/γ-Al2O3 catalyst had the best catalytic activity at a pressure of 2.0 MPa, a liquid hourly space velocity (LHSV) of 3.0 h-1, and a hydrogen to hydrocarbon ratio of 12. The 1,3-butadiene conversion was 97.45% and the methanethiol removal was 100% at a temperature of 140°C.