Influence of the Composition and Morphology of the Active Phase of Quaternary P–Ni–Mo–W/Al2O3 Catalysts with Different P2O5 Contents in the Modified Support on Their Catalytic Activity

Abstract

A series of Ni–P–Mo–W catalysts with different P2O5 contents in the support (0, 0.5, 1.0, 2.0, and 5.0 wt % P2O5, Mo : W = 1 : 1) were synthesized. Heteropoly acids H3PMo12O40·nH2O and H3PW12O40·nH2O, as well as nickel citrate, served as the active phase precursors. The sulfide phase morphology and surface were examined by the HRTEM and XPS methods. The catalytic properties of the samples in the dibenzothiophene hydrodesulfurization and naphthalene hydrogenation reactions were determined. The XPS examination showed that the ratios of different Mo species (Mo6+, MoSxOy, MoS2) for samples modified with 0.5 and 1.0 wt % P2O5 deviated significantly from those for the rest of the samples. Specifically, with an increase in the phosphorus content the proportion of the Mo6+ species decreased, while that of the MoSxOy species, increased, and for the W species, a linear increase in the WS2 proportion (from 15.3 to 35.0%) was revealed in parallel with the corresponding decrease in the W6+ species proportion (from 78.8 to 57.1%). The catalytic activity of the samples in the dibenzothiophene hydrogenolysis and naphthalene hydrogenation reactions exhibited an extremal dependence on the P2O5 content with a maximum observed at 0.5–1.0 wt % P2O5.