A novel approach for kinetic measurements in exothermic fixed bed reactors: advancements in non-isothermal bed conditions demonstrated for methanol synthesis

Abstract

Kinetic modelling of methanol synthesis remains one key challenge for the implementation of power-to-methanol technologies based on CO₂-rich gas streams and sustainably produced H₂. Within this work, a novel approach for kinetic model validation and parameter estimation using an experimental miniplant setup with polytropic bed conditions is presented. The miniplant setup features a highly resolved fibre optic temperature measurement combined with FTIR product composition analysis. Comparison of the experimental temperature and concentration data to a simulation model applying literature kinetic models, confirmed the necessity of axial experimental data to deliver an appropriate kinetic description of the methanol synthesis reaction network. A refitting of the literature kinetic models was performed in order to enhance their capability to account for the catalytic behaviour of a modern commercial catalyst. Besides the traditional measurement of the outlet concentration, it was shown that the temperature profile as a direct consequence of exothermic reactions in polytropic miniplant setups can be used to derive an improved kinetic description if appropriate models for heat transfer and diffusion are provided. Finally, the behaviour of the proposed new kinetic model is discussed on the industrial scale by means of a sensitivity analysis emphasizing the applicability of the presented novel approach for the scale-up from miniplant to industrial scale.