In order to increase the typically low equilibrium CO₂ conversion to methanol using commercially proven technology, the addition of two intermediate condensation units between reaction steps is evaluated in this work. Detailed process simulations with heat integration and techno-economic analyses of methanol synthesis from green H₂ and captured CO₂ are presented here, comparing the proposed process with condensation steps with the conventional approach. In the new process, a CO₂ single-pass conversion of 53.9% was achieved, which is significantly higher than the conversion of the conventional process (28.5%) and its equilibrium conversion (30.4%). Consequently, the total recycle stream flow was halved, which reduced reactant losses in the purge stream and the compression work of the recycle streams, lowering operating costs by 4.8% (61.2 M€·a⁻¹). In spite of the additional number of heat exchangers and flash drums related to the intermediate condensation units, the fixed investment costs of the improved process decreased by 22.7% (94.5 M€). This was a consequence of the increased reaction rates and lower recycle flows, reducing the required size of the main equipment. Therefore, intermediate condensation steps are beneficial for methanol synthesis from H₂/CO₂, significantly boosting CO₂ single-pass conversion, which consequently reduces both the investment and operating costs.

A three-site mean-field extended microkinetic model was developed based on ab initio DFT calculations from the literature, in order to simulate the conversion of syngas (H₂/CO/CO₂) to methanol on Cu (211) and Cu/Zn (211). The reaction network consists of 25 reversible reactions, including CO and CO₂ hydrogenation to methanol and the water-gas shift reaction. Catalyst structural changes are also considered in the model. Experiments were performed in a plug flow reactor on Cu/ZnO/Al₂O₃ at various gas hourly space velocities (24–40 L h⁻¹ g_cat ⁻¹), temperatures (210–260 °C), pressures (40–60 bar), hydrogen feed concentrations (35–60% v/v), CO feed concentrations (3–30% v/v), and CO₂ feed concentrations (0–20% v/v). These experiments, together with experimental data from the literature, were used for a broad validation of the model (a total of 690 points), which adequately reproduced the measurements. A degree of rate control analysis showed that the hydrogenation of formic acid is the major rate controlling step, and formate is the most sensitive surface species. The developed model contributes to the understanding of the reaction kinetics, and should be applicable for industrial processes (e.g. scale-up and optimization).

Speeding up microkinetic modeling by a surrogate artificial neural network.