Preparation and characterization of NiW supported on Al-modified MCM-48 catalyst and its high hydrodenitrogenation activity and stability

摘要

Al-containing MCM-48 with different Si/Al ratios and aluminum free MCM-48 materials were successfully prepared with hexadecyl trimethyl ammonium bromide (CTAB) and poly(ethylene oxide) poly(propylene oxide)-poly(ethylene oxide) triblock copolymer (P123) as a co-template. A series of characterizations show that both the supports and the NiW supported catalysts are highly ordered. The acid strength of the supports is enhanced when Al is introduced and when its content is increased. The acid amount and strength is further improved by supporting the NiW species. The oxide precursors show a high degree of sulfidation under mild sulfidation conditions. The activity of the Al-modified catalysts for quinoline hydrodenitrogenation (HDN) is much higher than that of aluminum free NiW/MCM-48 and NiW/gamma-Al2O3 catalysts. The addition of CS2 to the feed could boost the conversion of quinoline HDN and change the product distribution due to modification of the active site distribution of hydrogenation and C-N bond cleavage. Moreover, the stability of the resulting catalysts was also investigated, and no dramatic decrease in HDN conversion was observed in 960 h, which suggests that they could be candidates for industrial HDN catalysts.