In hydrotreating of light cycle oil, poly-aromatic compounds are also hydrogenated as well as the removal of sulfur and nitrogen compounds when conventional hydrotreating catalysts are used, resulting in the consumption of much hydrogen and rare formation of one ring aromatic compounds with high value. In the present study, a series of CoMo catalysts supported on titanium-substituted SBA-15 (Ti-SBA-15) supports synthesized by microwave-assisted method were prepared to investigate the relationship between active slabs structure and catalytic activity as to develop a new catalyst with high hydrodesulfurization (HDS) and controlled hydrodearomatization (HDA) activity that only convert three- or two-ring aromatic compounds to one ring aromatic compounds. The Ti-SBA-15 supports with different ratio of Ti/Si (0 to 40) were synthesized by an original microwave-assisted hydrothermal method that shortened the synthesis time from 24 h to 1 h. Silicon source TEOS, titanium source Ti(OCH2CH3)4 and directing agent P-123 were used. CoMo supported catalysts were prepared using impregnated method and characterized by means of XRD, FT-IR, XPS and TEM. The activity tests of catalysts were carried out by using a pressurized fixed-bed flow reactor at 260-340 oC, under H2 pressure of 5 MPa, with WHSV of 39 h-1. 4,6-Dimethyldibenzothiophene (4,6-DMDBT), and o-xylene, 1-methylnaphthalene, and phenanthrene were used as compounds in HDS, and HDA, respectively. Regarding XRD results, no titanium oxide peaks were observed, and three characteristic SBA-15 peaks were confirmed for all Ti-SBA-15 samples. A band at around 958 cm-1 indicating the formation of Ti-O-Si bond in IR spectra was only observed for Ti-SBA-15 samples. Thus, titanium was successfully inserted into SBA-15 structure, and the SBA-15 zeolite structure was maintained by substitution of titanium for silicon. CoMo/Ti-SBA-15 catalyst showed higher HDS activity and lower HDA activity than CoMo/SBA-15 catalyst. The XPS results reveal that the reduction of molybdenum from Mo6+ to Mo4+ readily occurred with insertion of titanium, resulting in an increase in Mo4+ species and CoMoS phase on sulfided catalysts. Moreover, the presence of Ti3+ for CoMo/Ti-SBA-15 suggested that Ti-Mo-S phase-a new active phase was formed and played a role as new activity sites in hydrotreating. TEM micrographs indicated that CoMo/Ti-SBA-15 has smaller and high stacking layer of CoMoS activity slabs in compared with CoMo/SBA-15 catalyst.

Synthesis of Ti-SBA-15 by use of microwave-assisted method and its application in hydrotreating

254th National Meeting (2017)

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