HYDROTREATING CATALYTIC FUNCTIONALITIES OF SBA-16 SUPPORTED Mo, CoMo, AND NiMo CATALYSTS

摘要

High surface area SBA-16 was used as a support for Mo, CoMo, and NiMo formulation. The supports and catalysts were characterized by BET surface area, XRD, Temperature Programmed Reduction and Low Temperature Oxygen Chemisorption. Surface area and XRD analysis indicate that the dispersion remains more or less constant up to 8wt% Mo and beyond this loading larger MoO3 crystallites are observed. The oxygen chemisorption studies indicated that the anion vacancy concentration increases upto 8wt%Mo and then start decreasing. The TPR studies on oxide precursors indicated a two-peak pattern at lower loading and one peak pattern at higher loading due to presence of two types of reducible species. At lower loading metal to support interaction is very high and gives octahedral and tetrahedral species. At higher Mo loadings octahedral species are formed due to optimum metal support interaction. Promoters Co/or Ni seem to facilitate the reduction of molybdenum species at lower temperature. Finally, a comparison of activities of Co (Ni) Mo catalysts supported over SBA-16 and γ-Al2O3 indicate the superior activity of the former catalyst for both HDS and HYD reactions due to high dispersion of metal species as shown by O2 uptake. This higher activity is attributable to cubic mesopore connectivity resulting in better catalyst dispersion, higher reducibility of Mo, and faster diffusion of reactants and products in case of SBA-16 supported catalysts.