Molten salt-mediated carbon capture and conversion

Abstract

The post-combustion capture is a promising technology to reduce industrial CO2 emission. This review articles concluded the recent advances in molten salt strategies for CO2 capture and conversion. In terms of CO2 capture, MgO-based sorbents can efficiently capture CO2 through a reversible carbonation/calcination reaction at intermediate temperatures (300–500 °C). The addition of alkali metal molten salt to MgO-based sorbents can greatly promote the CO2 uptake, which are promising candidates applied in the post combustion CO2 capture technology. Besides, molten salts such as ZnCl2/NaCl can be served as both activating agents and templates for synthesis of porous carbons from biomass and plastics. Particularly, N-doped porous carbons with highly microporous structures are more suitable for CO2 capture under ambient conditions. In terms of CO2 conversion, the electrochemical reduction in molten salts has been widely developed for producing carbon materials and fuels. Additionally, molten salts (normally single and mixed alkali metal carbonates) acting as both catalysts and heat transfer mediums can enhance the CO2 gasification of carbon feedstocks to produce CO-rich syngas. A significant challenge in the CO2 gasification of biomass/coal and their chars in molten alkali metal carbonates is the potential agglomeration between alkali metal species and minerals in the ash under high temperatures. To achieve sorbents regeneration and CO2 utilization, it is strongly recommended that more further researches should be performed on the integrated CO2 capture and in-situ electro-/thermo-chemical conversion processes for selectively production of high-value chemicals and fuels, which can alleviate the crisis of fossil fuels shortage and reduce the greenhouse gas emission.