Mechanism Discrimination for Bimolecular Reactions: Revisited with a Practical Hydrogenation Case Study

Abstract

The governing mechanism of surface reactions is a fundamental concern in heterogeneous catalysis. The Langmuir–Hinshelwood (LH) mechanism is widely accepted to control the surface reactions in many catalytic systems. This contribution derives and compares several important surface rate equations to evaluate their quality of fitting to the experimental data collected for a vapor-phase hydrogenation case study to produce furfuryl alcohol over supported copper catalysts. Meanwhile, a few essential but less addressed issues in determining the surface reaction mechanism were underlined. It is established that the Eley–Rideal mechanism would be equally (if not more) viable compared to the LH rate model all with coefficients of multiple determination larger than 97%, a conclusion in some contradiction with the common assumption of the previous publications for this case study. This investigation further highlighted that a good fit to any rate expression should not be taken as a proof of the assumed mechanism unless the opponent cases are tested within adequately wide ranges of concentrations.