CaO dispersed on carbon as an SO 2 sorbent

Abstract

Calcium-containing carbons were tested as low-temperature sorbents for SO 2. CaO particles dispersed on carbon were prepared by thermal decomposition of calcium acetate. Samples with calcium contents ranging from 1.5 to 8.0 wt% were analysed. CO 2 chemisorption was used to characterize the area of the CaO particles available to interact with and retain SO 2. CaO surface areas confirm that CaO dispersed on a high-surface-area carbon has a much larger available surface than unsupported CaO obtained by decomposition of a large variety of limestones. Isothermal reaction experiments on SO 2 retention at 50–400°C were performed in a thermobalance. SO 2 molar conversion at 300°C reached values from 0.3 to 0.89. SEM-EDX analysis, TPD and TPR experiments and conversion values at different temperatures showed that the SO 2-CaO interaction is not restricted to the surface of the CaO, as was found with limestone-derived CaO. Of interest for practical application is the observation that bulk CaSO 3 formation occurs to a significant extent in comparison with the behaviour found with unsupported CaO. The degree of regeneration of the sorbents by thermal treatment was found to depend on calcium content and dispersion.