Kinetic models discrimination for the high pressure WGS reaction over a commercial CoMo catalyst

A mechanistic kinetic model has been study to describe the bench scale water-gas shift reaction over a commercial presulfided CoMo catalyst using an industrial coal-derived gas feed. A rigorous kinetic network has been considered on the basis of formate, associative and direct oxidation mechanisms. Kinetic models were derived by using LHHW formalism and steady-state approximation for reaction intermediates. Kinetic parameters were estimated by nonlinear regression of the experimental data using the Marquardt–Levenberg algorithm. The WGS kinetic data were measured by experiments over a wide range of reaction conditions and comparisons for various rate equations were also established. A preliminary discrimination resulted in the necessity of rewrite models as a unique parameter models. The model based on direct oxidation mechanism successfully predicted the CO2 formation within the range of experimental conditions (high pressure and temperature). WGS rate expressions based on the regenerative process (oxidation-reduction) with the assumption that CO2 desorption reaction can be regarded as the rate determining step were found to be the best.

► A mechanistic kinetic model to describe the high pressure bench scale water-gas shift reaction. ► A commercial sulfur-resistant CoMo catalyst and an industrial coal-derived gas feed. ► A rigorous kinetic network on the basis of formate, associative and direct oxidation mechanisms. ► Kinetic parameters estimated by nonlinear regression using the Marquardt–Levenberg algorithm. ► Direct oxidation mechanism successfully predicted the CO2 formation with the assumption that CO2 desorption reaction can be regarded as the rate determining step.