The importance of finite adsorption kinetics in the sorption of hydrocarbon gases onto a nutshell-derived activated carbon

An activated carbon sample was synthesized from nutshells using a sequential step of carbonization and CO2 physical activation. Sorption equilibria and kinetics of hydrocarbon gases were measured on this sample at various temperatures and concentrations. The structural heterogeneity of the carbon is characterized by its micropore distribution, which is derived from the analysis of isotherms. The finite kinetics (FK) model [Do, D.D., Wang, K., 1998b. Predictions of adsorption equilibria of non-polar hydrocarbons onto activated carbon. Langmuir 14, 7271-7277; Do, D.D., Wang, K., 1998a. Dual diffusion and finite mass exchange model for adsorption kinetics in activated carbon. A.I.Ch.E. Journal 44, 68.] was employed to describe the sorption kinetics of pure gases and to predict those of binary gas mixtures. The performance of the FK model is compared to that of the HMSD model which assumes the same surface heterogeneity but infinite rates of interchange between the bulk and adsorbed phases. It is demonstrated that the finite kinetics play an important role in the simulation/prediction of desorption kinetics and sorption kinetics of binary gas mixtures.