On the electrification of CO2-based methanol synthesis via a reverse water–gas shift : a comparative techno-economic assessment of thermo-catalytic and plasma-assisted routes

A thorough cost analysis based on the conceptual process design of a two-step CO2-to-methanol synthesis route is performed, comprising CO2 hydrogenation in an electrified reverse water-gas shift (RWGS) reactor, followed by a conventional methanol synthesis reactor. In the former step, both thermal and nonthermal plasma reactors are considered, i.e., direct current (DC) arc and microwave (MW) plasma, respectively, and benchmarked against the conventional thermo-catalytic counterpart. It is found that employment of any type of plasma promotes higher CO2 conversions in the RWGS step than the conventional thermo-catalytic reactors (82-90 vs 61%), thereby higher single-pass methanol yields (24-27 vs 17%). This comes at the expense of higher electricity demand, which minorly affects the process economics since green H-2 utilized in RWGS and methanol synthesis is the cost driver. The economic analysis shows that the current green H-2 prices (2022 scenario) render the two-step CO2-to-methanol process economically unviable, regardless of the reactor technology used, attaining approximately a 4-fold higher levelized cost of methanol (LCOM), 1875-1900 ton(-1), compared to the state-of-the-art route, i.e., syngas production through steam methane reforming (SMR) and coal gasification, followed by WGS and methanol synthesis reactors. However, the two-step CO2-to-methanol route could be viable for a long term (2050 scenario), driven by lower costs of electricity (10 MW h(-1)) and green H-2 (1.0 kg(-1)) along with the avoided emission credits. This originates from the lower greenhouse gas (GHG) emissions that the two-step CO2-to-methanol route attains compared with the state-of-the-art. In the 2050 frame, plasma technologies are anticipated to be at least 45% more profitable than thermo-catalytic reactors, while the profitability of nonthermal plasmas will significantly improve if vacuum operation is avoided, mitigating the excessive compression energy demand and subsequently decreasing the operating cost.