CO2 capture in humid gas using ZnO/activated carbon and ZnO reactivity with CO2

Abstract

Carbon dioxide capture with ZnO/activated carbon adsorbates and reactivity of ZnO particle with CO2 are discussed for the effective CO2 capture in humid exhaust gas. Coarse ZnO particles (d = 670 nm), and small diameters, d < 20 nm, of zinc oxide particles on activated carbon supports were prepared. The amounts of CO2 adsorbed on ZnO particles and activated carbon supports were measured and calculated. The calculated value and thermal gravimetric analysis results indicate that only the surface layer (<0.5 nm) of ZnO particles reacts with CO2 and H2O for all sizes of ZnO particles. These results lead to the conclusion that ZnO reactivity with CO2 is still independent of the particle size even in the small diameters in this study. The results quantitatively present the gas-phase carbonation rate of ZnO and its independency on the particle diameter for the first time. This research sheds light on the difficulty in using ZnO as CO2 adsorbent. Some possible solutions for the difficulty are also discussed in view of enhancing of its reactivity.