Computational Identification of Descriptors for Selectivity in Syngas Reactions on a Mo₂C Catalyst

A microkinetic model containing 53 elementary steps based on extensive Density Functional Theory calculations is developed to describe syngas reactions on a Mo2C catalyst under high temperature and pressure conditions, with the aim of determining the elementary steps that control reaction selectivity. The effects of adsorbate–adsorbate interactions are found to be strong, so these interactions are described using the quasi-chemical approximation. Agreement with experimental observations of selectivity for syngas reactions at P = 30 bar and T = 573 K was found to be good without parametrizing the model in any way to the experimental reaction data. The activation energies of the elementary steps in the model were estimated using a Bronsted–Evans–Polanyi relation, and sensitivity analysis is used to examine the impact of uncertainties in this relation on the selectivity-determining steps of the reaction network. Our results are a useful example of identification of key elementary steps in a complex reaction network for the reactions available with syngas over a heterogeneous catalysis.