Basic studies on deactivation of hydrotreating catalysts by vanadium
In order to evaluate catalyst deactivation by vanadium, two series of vanadium-containing catalysts were prepared from a sulfided NiMo/alumina catalyst by impregnation with a vanadium salt (IMP) and by reaction with vanadyl tetraphenylporphyrin (TPP). In addition, catalysts coked with a heavy resid feed were subsequently treated with vanadyl tetraphenylporphyrin, resulting in low coke catalysts (LCTP) or high coke catalysts (HCTP). After resulfiding, the vanadium-containing catalysts were tested for catalytic activities for hydrodesulfurization (HDS), hydrogenation (HYD) and hydrodenitrogenation (HDN), using a mixture of model compounds (dibenzothiophene, naphthalene, and indole). The IMP catalysts were more deactivated than the TPP catalysts at the same level of vanadium. The extent of deactivation with vanadium content was different for these reactions. The HCTP catalysts showed the greatest deactivation, indicating that both coke and vanadium contributed to catalyst deactivation. However, deactivation of LCTP catalysts was not appreciably different from that of the TPP catalysts, showing that the low levels of coke had no effect on the poisoning deactivation of the vanadyl tetraphenylporphyrin. Comparison with catalysts deactivated in bench-scale testing with an actual feed, showed that the HCTP catalysts gave more deactivation at the same vanadium and coke levels. For the TPP and LCTP catalysts, activation energies for HDS, HYD and hydrogenolysis of the first carbon-nitrogen (CNH) were almost constant, suggesting that the nature of active sites was not altered. The activation energies were 22.5 for HDS and 29.5 kcal/mol for HYD and CNH, respectively. For all catalysts, ethylcyclohexane selectivity in HDN was controlled by the HYD functionality.
- Research Organization:
- Utah Univ., Salt Lake City, UT (United States)
- OSTI ID:
- 39324
- Country of Publication:
- United States
- Language:
- English
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