Sulfur exchange on CoMo/Al 2O 3 hydrodesulfurization catalyst using 35S radioisotope tracer

Abstract

A commercial CoMo/Al 2O 3 catalyst was labeled with the radioisotope 35S in hydrodesulfurization (HDS) of 35S-labeled dibenzothiophene ( 35S-DBT) in a high-pressure flow reactor at 50 kg/cm 2. Then, HDS of 4-methyldibenzothiophene (4-MDBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) or sulfur exchange of H 2S were carried out on the labeled catalyst at 50 kg/cm 2 and 260–360°C. The amounts of labile sulfur participating in the reaction were determined from the radioactivity of 35SH 2S released from the 35S-labeled catalyst. In the HDS reactions, the amount of labile sulfur participating in the reaction decreased in the order: DBT > 4-MDBT > 4,6-DMDBT. In the sulfur exchange reaction with H 2S, the adsorption of H 2S on the catalyst reached saturation above a H 2S partial pressure of 0.36 kg/cm 2. It was suggested that the release of H 2S from the labile sulfur may be the rate determining step of the HDS reaction.