CaO dispersed on carbon as an SO2 sorbent

Calcium-containing carbons were tested as low-temperature sorbents for SO2. 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. CO2 chemisorption was used to characterize the area of the CaO particles available to interact with and retain SO2. 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 SO2 retention at 50-400 degrees C were performed in a thermobalance. SO2 molar conversion at 300 degrees 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 SO2-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 CaSO3 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. (C) 1997 Elsevier Science Ltd.