Absorption of carbon dioxide by hydrogen donor under atmospheric pressure

Commonly, carbon dioxide (CO2) capture and resource utilization (CCRU) covers a broad area of research with different technical challenges. Thus, more exploratory technological investigations are needed to discover new applications and reactions. In this paper, an innovative method for CO2 absorption by sodium borohydride (NaBH4) from coal-fired flue gas was developed under atmospheric pressure and moderate temperature. The effects of influencing factors, such as volume ratio of ethanol to water, NaBH4 concentration, reaction temperature, solution pH, and concentrations of sulfur dioxide, nitric oxide and oxygen on CO2 absorption were investigated. The average absorption efficiency of CO2 was 54.06% under optimal experimental conditions, in which volume ratio of ethanol to water was 80%, NaBH4 concentration was 0.439molL−1, reaction temperature was 318K and solution pH was 9.0. The coexisting gases of sulfur dioxide, nitric oxide and oxygen in flue gas had no significant competition or inhibition effect on CO2 absorption. Ion Chromatography and Fourier Transform Infrared Spectroscopy analyses of products proved that the main reaction product was formate with 41.52% of the selectivity. Combined with the analysis of the electrode potentials, the mechanism of CO2 reaction with NaBH4 was proposed. Meanwhile, a comparative research of CO2 resource utilization can provide a useful reference for developing new CCRU technologies.