In this work, we examine the thermochemistry of methanol synthesis intermediates using density functional theory (DFT) and analyze the methanol synthesis reaction network using a steady-state micro-kinetic model. The energetics for methanol synthesis over Zn-terminated ZnO (0001) are obtained from DFT calculations using the RPBE and BEEF-vdW functionals. The energies obtained from the two functionals are compared and it is determined that the BEEF-vdW functional is more appropriate for the reaction. The BEEF-vdW energetics are used to construct surface phase diagrams as a function of CO, H2O, and H2 chemical potentials. The computed binding energies along with activation barriers from literature are used as inputs for a mean-field micro-kinetic model for methanol synthesis including the CO and CO2 hydrogenation routes and the water–gas shift reaction. The kinetic model is used to investigate the methanol synthesis rate as a function of temperature and pressure. The results show qualitative agreement with experiment and yield information on the optimal working conditions of ZnO catalysts.
- Zinc oxide
- Phase diagram
Medford, A. J., Sehested, J., Rossmeisl, J., Chorkendorff, I., Studt, F., Nørskov, J. K., & Moses, P. G. (2014). Thermochemistry and micro-kinetic analysis of methanol synthesis on ZnO (0001). Journal of Catalysis, 309, 397-407. https://doi.org/10.1016/j.jcat.2013.10.015