Mesoporous molecular sieve MCM-41 supported Co-Mo catalyst for hydrodesulfurization of dibenzothiophene in distillate fuels

A mesoporous aluminosilicate molecular sieve with MCM-41 type structure was synthesized using aluminum isopropoxide as the Al source. Supported Co-Mo/MCM-41 catalysts were prepared by co-impregnation of Co(NO₃)₂·6H₂O and (NH₄)₆Mo₇O₂₄ followed by calcination and sulfidation. For comparison, conventional Al₂O₃-supported sulfided Co-Mo catalysts were also prepared using the same procedure. These two types of catalysts were examined at two different metal loading levels in hydrodesulfurization of a model fuel containing 3.5 wt% sulfur as dibenzothiophene in n-tridecane. At 350-375°C under higher H₂ pressure (6.9 MPa), sulfided Co-Mo/MCM-41 catalysts show higher hydrogenation and hydrocracking activities at both normal and high metal loading levels, whereas Co-Mo/Al₂O₃ catalysts show higher selectivity to desulfurization. Co-Mo/MCM-41 catalyst at high metal loading level is substantially more active than the Co-Mo/Al₂O₃ catalysts.