Critical assessment of steady-state kinetic models for the synthesis of methanol over an industrial Cu/ZnO/Al2O3 catalyst

Abstract

In this paper a thorough comparison is made between steady state kinetic models for methanol synthesis from Graaf et al. (1988), Vanden Bussche and Froment (1996), Seidel et al. (2018), Ma et al. (2009) and Villa et al. (1985). A new experimental dataset using an industrial Cu/ZnO/Al2O3 catalyst is presented and used together with the dataset of Seidel et al. (2018) for refitting the kinetic models. The models are refitted using the statistical cross-validation (CV) method to test for predictive capabilities and model variance. A new kinetic model is proposed with the aim to reduce parameter identifiability problems. The model is derived based on physical observations from literature. This physically consistent model has ten parameters, however more experiments are needed, because the current dataset is not discriminating enough for regression of adsorption isotherms. The proposed model is further reduced to only six parameters. This model is predicting the dataset equally well or better than current higher parameter models. It is shown that the model is a good predicting model for experiments outside the training set. The model is valid for pressures from 20 to 70 bara and temperatures from 450 to 530 K with a high probability of predicting well outside these boundaries.