Conclusion
Serial Al and Ti modified supports are successfully prepared by a stepwise and post-synthetic method. It is found that the intact structure of SBA-16 material can be maintained after modification of Al and Ti species, whose existent forms in Al-Ti-SBA-16 composite should be co-existed in the framework and external framework. Meanwhile, the incorporation of Al and Ti atoms into SBA-16 material can increase the proportions of Mo(Td) and Mo(Oh) species on NiMo loading catalysts, respectively. The DBT HDS evaluation reveals that the HDS efficiency can be significantly improved by incorporation Al and Ti atoms into NiMo catalysts through enhancing acidity and properties of active metals. NiMo/AT-7.5 catalyst presents the highest HDS efficiency should be ascribed to the factors including high pore volume and pore size of AT-7.5 support, appropriate acidity for NiMo/AT-7.5 catalyst, highest proportion of MoS2 phase and concentration of S-edge sites with high efficiency. Interestingly, the B acid site can facilitate the formation of S-edge sites. The HYD/DDS ratios can be well related with the concentration ratios of S-edge and Mo-edge. The reason why NiMo/Al-Ti-SBA-16 catalyst shows high HDS performance should be assigned to the synergistic effect with high efficiency. Finally, the kinetic and thermodynamic analyses disclosed that there are correlations existing between amount of B acid sites and kDS, the dispersion degree of MoS2 and HDS efficiency, the total concentration of S-edge and Mo-edge and HDS efficiency, the S-edge/Mo-edge ratio and kDDS/kHYD.