Isothermal Li4SiO4-based integrated carbon capture and utilization driven by green hydrogen for efficient methanol production

Conventional methanol production relies predominantly on fossil-derived syngas and is associated with high energy consumption and carbon emissions, while variable renewable-electricity supply challenges stable green-hydrogen utilization. Here, a methanol production system integrating Li 4 SiO 4 -based mid-temperature CO 2 capture, alkaline water electrolysis, and in-situ hydrogen-assisted conversion is proposed. Industrial flue gas is used as the CO 2 source, and the absorption and desorption reactors operate at the same nominal temperature of 600 °C, avoiding repeated heating and cooling of the circulating sorbent. Green hydrogen serves as both a sweep gas for sorbent regeneration and a reactant for partial reverse water–gas shift and methanol synthesis. Temperature-dependent fractional conversions derived from thermogravimetric CO 2 -uptake data were implemented in RStoic blocks. The system consumes 1.40 t CO 2 and 0.19 t H 2 per tonne of methanol and achieves energy and exergy efficiencies of 65.26% and 74.02%, respectively, 5.30 and 5.67 percentage points higher than those of the steam-methane-reforming–CaO reference system. Energy-utilization-diagram analysis shows that near-isothermal operation and cascade heat recovery reduce energy-level mismatch and exergy destruction. Under the adopted Xinjiang regional green-power scenario, the levelized cost of methanol is 338.10 $/t, 13.6% lower than that of the reference system. These results demonstrate the thermodynamic and economic potential of Li 4 SiO 4 -based integrated carbon capture and utilization, while long-term sorbent stability, solid circulation, and pilot-scale integration require further investigation.