THE EFFECTS OF PYRIDINE AND COKE POISONING ON BENZOTHIOPHENE HYDRODESULFURIZATION OVER CoMo/AI2O3 CATALYST†

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Abstract
The kinetics of benzothiophene hydrodesulphurizaiion (HDS) and hexene hydrogenation over a sulfided CoMo/Al2O3 catalyst were studied in a stirred flow microbalance reactor at atmospheric pressure. The effects of pyridine poisoning and coking on catalyst deactivation and kinetics were also determined. Benzothiophene HDS kinetics on the lined-out catalyst were best correlated with a Langmuir-Hinshel-wood equation of the form where r is the rate, kT the rate constant, p are partial pressures, K's are adsorption constants, and subscripts T, H and S stand for benzothiophene. H2 and H2S, respectively. This rate equation was the same for pyridine poisoned or coked catalyst, KT being lower, but KT and Ks being the same within experimental error. The rate of hexene hydrogenation was first order in hexene and hydrogen, and inhibited by hexene and hydrogen; but an explicit best equation could not be obtained. Pyridine deactivation of HDS was more selective than coke. At least two HDS sites exist, one being poisoned and the other unaffected by pyridine. Hydrogenation was more strongly affected by pyridine than HDS. Some cracking of hexene was also observed. The three reactions of HDS, hydrogenation and cracking appear to take place on different sites.