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.