Understanding catalytic CO2 and CO conversion into methanol using computational fluid dynamics

The kinetics of methanol synthesis from a mixture of CO2/CO/H2, using a Cu/Zn/Al2O3 catalyst, have been widely studied in the literature. Yet the role of direct CO hydrogenation is still unclear. In our paper, a computational fluid dynamics (CFD) model was developed to compare two of the newest kinetic models for methanol synthesis available in the literature, one which includes CO hydrogenation (Park’s kinetic model) and one which does not (Nestler’s kinetic model). From the comparison, it could be identified that including a mechanism for direct CO hydrogenation in the kinetic model can better identify potential inhibitions caused by the presence of H2O. In addition, while the two available kinetic models produced accurate results at the outlet of the reactor, the predicted flow profiles varied significantly. This is due to the relative importance of the CO hydrogenation mechanism between the two kinetic models. The produced CFD model offered a unique insight and visualisation of the internal spatial species concentration, temperature variations, and reaction rates equilibrium. Furthermore, it was able to identify potential inconsistencies in the applied kinetic models, which would otherwise might not have been observed using a more simplified modelling approach. As such, when applied as a kinetic investigation method, it can guide future experimental efforts to better understand the role of CO hydrogenation in the methanol synthesis process.