Preparation and desulfurization kinetics of activated carbons from semi-coke of coal liquefaction residual

Microporous activated carbons were prepared from the semi-coke of coal liquefaction residual by KOH activation. The gas evolution during the activation process was analyzed by thermogravimetry-mass spectrometry. The SO2 adsorption equilibrium and desulfurization kinetics at low temperatures were also investigated. The results of this study indicate that three reactions are mainly responsible for the formation of pore structure in the activated carbons. The physical adsorption dominates the adsorption of SO2 (250-1250 ppm SO2, N-2 as balance gas) at lower temperature for activated carbons. The Boltzmann model was found to be suitable for describing the desulfurization behavior of selected activated carbon at low temperatures under non-oxygen atmosphere instead of the linear driving force model. The apparent sorption rate constant of activated carbon ranges from 0.0027 to 0.0038 s(-1). The temperature-programmed desorption study of the adsorption-saturated (393 K, 5% O-2 + 1250 ppm SO2 + N-2 balance) activated carbon suggests the presence of two types of adsorbed SO2 with the bond energy of 45.17 and 52.00 kJ mol(-1), respectively.