Abstract
We have investigated the catalytic activity of NiMo sulfide catalysts supported on TiO
2-coated Al
2O
3 carriers during the HDS of dibenzothiophene, 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene at 603
K and 3
MPa. TiO
2-Al
2O
3 supports were prepared by chemical vapor deposition of TiCl
4 on the surface of γ-Al
2O
3 (240
m
2
g
−1, 0.84
cm
3
g
−1). Using XPS, we showed that TiO
2 is highly dispersed on the surface of Al
2O
3 for TiO
2 loadings up to ca. 14
wt%. Moreover, TiO
2-Al
2O
3 (14
wt% TiO
2) support showed textural properties very similar to those of the parent alumina support. The composite support with TiO
2 loading around 14
wt% was used as support for NiMo sulfide catalysts. The sulfidation degree of Mo, as determined by XPS, was higher for NiMo/TiO
2-Al
2O
3 than for NiMo/Al
2O
3. This can be attributed to the lower interaction of molybdenum species with the TiO
2-Al
2O
3 composite support. The hydrodesulfurization (HDS) tests conducted here showed that NiMo/TiO
2-Al
2O
3 catalysts are more active than NiMo/Al
2O
3 ones for the HDS of dibenzothiophene, 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene. Comparison of product selectivity of cyclohexylbiphenyl (CHB)/biphenyl (BP) values showed that NiMo/TiO
2-Al
2O
3 catalysts exhibit higher hydrogenation activity than NiMo/Al
2O
3.