Power-to-methanol process: A review of electrolysis, methanol catalysts, kinetics, reactor designs and modelling, process integration, optimisation, and techno-economics

In this paper, the power-to-methanol chain is reviewed from a process system engineering perspective with detailed assessments of major technologies. The evaluation encompasses electrolysis technologies and catalyst developments, kinetics, reactor technology options for methanol synthesis, as well as their design principles, modelling techniques, and research and optimisation gaps. The review extends to discuss process synthesis considering water-based and co-electrolysis-based power-to-methanol routes with reference to process integration, optimisation, modelling techniques, industrial applications and the associated techno-economics. Key gaps and opportunities for improvements are identified. The novelty of the paper lies in the holistic evaluation of technology design, performance and modelling. Foremost among the findings, advanced and detailed models of the electrolysis units, methanol reaction kinetics (e.g. considering identifiability and sensitivity) and methanol reactor with improved predictive capabilities under varying conditions are required. Additionally, the overall design, flexibility and reliability requirements concerning variable power-to-methanol deserve further detailed investigation. On the other hand, studies on the model-based process synthesis of power-to-methanol are limited, especially those considering dynamic modelling, multi-objective, process configuration and scheduling optimisations, and techno-economic and environmental analyses under uncertainty conditions. The few model-based studies available are mostly based on deterministic approaches and sequential pinch-analysis. Furthermore, limited studies evaluate power-to-methanol in the context of CO2/energy/H2 utilisation industrial hubs and repurposing/retrofitting of existing infrastructures (with part of the capital cost already offset) taking advantages of synergies and application-specific analysis of methanol, which may give additional attractive business cases. Lastly, incentives and dynamics in renewable electricity, electrolysis, CO2 utilisation and the methanol market hold a strong position to make power-to-methanol feasible and must be investigated further to support policy decisions.