The chemistry of resorcinol carboxylation and its possible application to the CO2 removal from exhaust gases

Abstract The carbon dioxide uptake by resorcinol solutions has been investigated under different operational procedures and experimental conditions. Batch experiments have been carried out in aqueous and glycerol–water solutions of KOH, KHCO 3 or K 2 CO 3 , and the yield of resorcinol carbonatation has been investigated as a function of the CO 2 partial pressure as well as reaction temperature and time. The β-resorcylic acid (2,4-dihydroxy benzoic acid) has been isolated in the solid state and identified on the basis of its IR spectrum. The 13 C NMR analysis has been applied to identify and quantify the carbonated species in solution upon CO 2 uptake and after thermal resorcinol regeneration. The maximum yield of resorcinol conversion into β-resorcylic acid was 60% with 1.0 bar of CO 2 and 120 min reaction time at 110 °C. A 34% yield of resorcinol conversion was also obtained with the resorcinol/K 2 CO 3 solution in the absence of CO 2 . A relationship between the CO 2 absorption capacity and the possible mechanism of CO 2 capture has been proposed. The CO 2 absorption efficiency from a simulated flue gases (15% CO 2 in air) has been measured in continuous cycles of CO 2 absorption–desorption carried out in packed columns and with a glycerol–water solution of resorcinol/KOH/KHCO 3 . The maximum absorption efficiency was 82% at absorption-desorption temperatures of 70 °C and, respectively, 170 °C. Oxidative conditions and the presence of H 2 S did not affect the yield of β-resorcylic acid and the resorcinol capacity of CO 2 capture. Finally, a simple method for the selective separation of H 2 S from CO 2 has been reported.