The hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT) over two catalysts: commercial CoMo/Al2O3 and synthesized nanosized MoS2 catalyst was investigated in a batch reactor.  The HDS reactions advanced through two parallel-consecutive reaction pathways: direct desulfurization (DDS) and hydrogenation (HYD), in which two main intermediates 3,3'-dimethylbiphenyl and partially hydrogenated-4,6-DMDBT were involved.  Kinetic models were developed to account for the partial contributions of these intermediates in the overall reaction network as well as for their selectivities.  The models allow a precise estimation of the apparent rate constants of all steps being involved in the reaction network.  In the HDS reactions of 4,6-DMDBT, the HYD pathway was more pronounced than the DDS route over the nanosized MoS2 catalyst .  Different selectivities in terms of yield fraction (percentage ratio of HYD/DDS) were observed from the HDS reaction over these catalysts.  The kinetic results according to these models show that the partially hydrogenated-4,6-DMDBT intermediate transformed mainly to 3,3'-dimethylcyclohexylbenzene.  The model predicts the preferable mechanism a catalyst may use in such parallel-consecutive reactions and may set a reliable standard on evaluating catalyst performances according to their activities and selectivities.

Kinetic models for assessment of the reaction network in hydrodesulfurization of polyaromatic sulfur-containing compounds

246th National Meeting (2013)

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