High-temperature molten salt capture and electrolysis technology of CO2 for the effective preparation of elemental carbon materials are considered to be an exceedinglyare gaining traction as promising carbon capture utilization and storage technology.The reason is their excellent selectivity and ease of operation,making them suitable for the effective preparation of elemental carbon materials from CO2.Nonetheless,the current research on the kinetic mechanism of CO2 capture in high-temperature molten salt systems is inadequate.Furthermore,the energy consumption and production costs associated with the process of preparing elemental carbon materials through CO2 molten salt electrolysis are relatively high.Therefore,achieving efficient CO2 capture in high-temperature molten salts and low-energy consumption electrolysis is very crucial.This paper delves into the thermodynamics of CO2 capture by various alkali metals/alkaline earth metal oxides.It also compares the theoretical decomposition voltage and energy consumption of various alkali metals/alkaline earth metal carbonates.The capture behavior of CO2 in typical binary chloride molten salts is also examined.The study further explores the thermodynamics of CO2 capture in molten salts to carbonates and calculates the theoretical voltage and power consumption during carbonate electrolysis in a high-temperature molten salt system.The kinetics of CO2 capture in typical CaCl2-based molten salts are examined by advanced technologies such as online gas mass spectrometry,carbon-sulfur analyzer,X-ray diffraction,and energy spectroscopy.The effects of temperature and voltage on the electrolysis process,electrolytic energy consumption,and product structure of elemental carbon materials prepared by CO2 electrolysis are investigated in typical ternary Na2CO3-K2CO3-Li2CO3 molten salts and ternary CaCl2-NaCl-CaO molten salts using scanning electron microscopy(SEM),Raman spectroscopy,and constant voltage electrolysis.The results indicate that CaO outperforms alkali metal oxide as a CO2 capture agent,and CaCO3 obtained by energy and conversion exhibits the lowest theoretical decomposition voltage and electrolytic energy consumption.In a typical CaCl2-3.0%CaO(mass fraction)molten salt,the CO2 capture capacity is 0.016 gCO2·g-1.Compared with the Na2CO3-K2CO3-Li2CO3 molten salt,the CaCl2-NaCl-CaO molten salt has a lower electrolysis voltage and energy consumption.Moreover,the current efficiency of the electrolytic elemental carbon material reaches up to 95.3%,with the minimum electrolytic energy consumption being only 14.1 kW·h·kg-1 under the optimal conditions of 750℃and 1.5 V.Therefore,this study provides a foundation for exploring CO2 molten salt capture materials that combine excellent performance,low cost,and environmental friendliness.It also offers theoretical and data support for optimizing the process and reducing the cost of the actual electrolysis.
关键词
二氧化碳捕集/电解/高温熔盐/单质碳/电耗
Key words
CO2 capture/electrolysis/high-temperature molten salt/carbon/energy consumption
万方数据