Abstract
Two series of WP/Al 2O 3 catalyst precursors with WP mass loading in the range 18.5%–37.1% were prepared using the impregnation method and mixing method, respectively, and the catalysts were then obtained by temperature-programmed reduction of supported tungsten phosphate (precursor of WP/Al 2O 3 catatlysts) in H 2 at 650°C for 4h. The catalysts were characterized by XRD, BET, TG/DTA, XPS and 31P MAS-NMR. The activities of these catalysts were tested in the hydrodenitrogenation (HDN) of pyridine and hydrodesulfurization (HDS) of thiophene at 340°C and 3.0MPa. The results showed that owing to the stronger interaction of the support with the active species, the precursor of WP/Al2O 3 catalyst was more difficultly phosphided and a greater amount of W species was in a high valence state W 6+ on the surface of the catalyst prepared by the impregnation method than that by the mixing method. 31P MAS-NMR results indicated that 31P shift from 85% H 3PO 4 of 2.55 × 10 −4 for WP and 2.57 × 10 −4 for WP/γ-Al 2O 3 catalysts prepared by mixing method. Such WP/Al 2O 3 catalysts showed higher HDN activities and lower HDS activities than those prepared by the impregnation method under the same loading of WP. WP/γ-Al 2O 3 catalysts with weak interaction between support and active species were favorable for HDN reaction while the WP/γ-Al 2O 3 catalysts with strong interaction were favorable for HDS reaction.
Published Version
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