Mesoporous molecular sieve MCM-41 supported Co-Mo catalyst for hydrodesulfurization of petroleum resids

In this work, we explored the potential of mesoporous zeolite-supported Co-Mo catalyst for hydrodesulfurization of petroleum resids, atmospheric and vacuum resids at 350-450°C under 6.9 MPa of H₂ pressure. A mesoporous molecular sieve of MCM-41 type was synthesized; which has SiC₂/Al₂O₃ ratio of about 41. MCM-41 supported Co-Mo catalyst was prepared by co-impregnation of Co(NO₃)₂·6H₂O and (NH₄)₆Mo₇O₂₄ followed by calcination and sulfidation. Commercial Al₂O₃ supported Co-Mo (criterion 344TL) and dispersed ammonium tetrathiomolybdate (ATTM) were also tested for comparison purposes. The results indicated that Co-Mo/MCM-41(H) is active for HDS, but is not as good as commercial Co-Mo/Al₂O₃ for desulfurization of petroleum resids. It appears that the pore size of the synthesized MCM-41 (28 Å) is not large enough to convert large-sized molecules such as asphaltene present in the petroleum resids. Removing asphaltene from the resid prior to HDS has been found to improve the catalytic activity of Co-Mo/MCM-41(H). The use of ATTM is not as effective as that of Co-Mo catalysts, but is better for conversions of >540°C fraction as compared to noncatalytic runs at 400-450°C.