2016 Volume 59 Issue 2 Pages 46-58
The relationships between the morphologies and dispersion of supported Mo sulfide catalysts and their catalytic functions evaluated by model test reactions are reviewed. The catalyst support had large effects on the morphologies through the electronic interaction and geometrical relationship between the catalyst and the support surface. High hydrogenation activities were obtained for Al2O3 supported catalysts due to high dispersion, whereas high hydrogenolysis activities were obtained for TiO2-supported catalysts due to the electronic interaction. Relatively large single-layered MoS2 structures were formed on the {110} γ-Al2O3 surface, whereas microclusters and multi-layered MoS2 structures were more favorably formed on the {111} and {100} γ-Al2O3 surfaces. Multi-layered MoS2 structures had the edge-bonding orientation on anatase-TiO2 with an epitaxial relationship by sulfidation in H2S/N2. Single-layered MoS2 catalysts exhibited relatively hydrogenation-oriented function, whereas multi-layered MoS2 catalysts had relatively hydrogenolysis-oriented function. Steric hindrance affected the catalytic functions, particularly in hydrogenation that required η6 adsorption of aromatic rings. Long-term uses in hydrotreating caused growth of the MoS2 structures in the lateral direction, which decreased the number of active sites. Simultaneously, the aging caused deep sulfiding of the catalysts, which weakened the interaction with the support and increased the intrinsic activities of the catalysts.
