Kinetic models for complex parallel-consecutive reactions assessment of reaction network and product selectivity

Kinetic models were developed to account for the partial contributions of intermediates in complex parallel-consecutive reactions. The models allow precise estimation of the apparent rate constants of all steps in such a reaction network. The hydrodesulfurization (HDS) of dibenzothiophene (DBT) over CoMo-based alumina and carbon catalysts, and over an unsupported molybdenum sulfide catalyst, were investigated in a batch reactor and used to represent this type of reaction. The HDS reactions proceeded through two parallel-consecutive reaction pathways, i.e., direct desulfurization (DDS) and hydrogenation (HYD), in which two main intermediates, namely biphenyl and partially hydrogenated DBT, were involved. Different selectivities in terms of yield fraction (percentage ratio of HYD/DDS) were observed for these catalysts. The results are discussed in the context of proposed HDS reaction networks. Use of these models enables more accurate assessment of differences among the performances of different catalysts.