Progress in application of molten salt mixer adsorption materials for high temperature carbon dioxide capture and thermochemical energy storage

Recently, the research team of  Shanghai Institute of Applied Physics (SINAP), Chinese Academy of Sciences (CAS) has made progress in the application of molten salt doped sodium orthosilicate (Na4SiO4) adsorption materials for high temperature carbon dioxide capture and thermochemical energy storage. The article entitled "Performance improvement of Na4SiO4 doped with Li2CO3-K2CO3 for high-temperature CO2 capture and thermochemical energy storage" has been published in the journal of Chemical Engineering Journal. Associate Prof. Changjian Ling is the first author, and Prof. Zhongfeng Tang is the corresponding author.

Molten salt has the advantages of wide operating temperature range, low working pressure, strong heat transfer and storage and good chemical stability. As an ideal heat transfer and storage working medium, molten salt plays an important role in the fields of nuclear energy, energy storage, solar energy and high temperature catalysis. Under the background of "two-carbon strategy", the research on high temperature carbon dioxide capture and thermochemical heat storage by using the advantages of molten salt has become a hot spot. In this work, molten salt adsorption materials doped with Li2CO3-K2CO3 (LiKCO3) eutectic salt were prepared by molten salt doping method, and the dynamic, isothermal, and cyclic CO2 capture performances and the TCES performances of adsorption materials based on the CO2/Na4SiO4 reaction system were systematically investigated. The results indicated that the maximum CO2 sorption capacity of molten salt adsorption material reached 20.64 wt% at 725 °C, the maximum conversion efficiency and thermochemical energy storage density reached high levels of 95.7% and 788 kJ/kg, respectively, and the cyclic sorption capacity was about 50% higher than that of un-doped adsorption material. The CO2 chemisorption mechanisms on the molten salt adsorption materials co-adsorption surfaces were studied via density functional theory (DFT) calculations. The results demonstrated that molten salt doping could enhance CO2 adsorption energy and C–OS covalent interaction on the sorbent surface and reduce the energy levels of the system. These changes were beneficial to CO2 chemisorption and agreed well with the experimental values, which provided a new strategy for the design of high temperature CO2 capture and thermochemical energy storage materials.

This study has received support from the National Natural Science Foundation of China and the Foundation from Qinghai Science and Technology Department.