MAXWELL-STEFAN ANALYSIS OF MULTICOMPONENT TRANSIENT DIFFUSION IN A CAPILLARY AND ADSORPTION OF HYDROCARBONS IN ACTIVATED CARBON PARTICLE

This paper reports the results of detailed studies of the combined eff ect of the viscous flow and diffusive flow in the transient diffusion of a mixture containing N species in a capillary, and in the transient adsorption of a mixture of hydrocarbons in an activated carbon partic le. The Maxwell-Stefan approach is applied to describe the interaction of diffusing species in the large pore network, where the viscous flo w mechanism operates in conjunction with the other diffusion mechanism s. In the pure diffusion systems, the viscous flow affects significant ly the overall diffusion flux when the molecular weights of the diffus ing species are significantly different or when the pore size is small . In the adsorption systems, the viscous flow can enhance the adsorpti on process as the loss of mass from the gas phase may render the visco us flow significant. We test the theory with the adsorption of nitroge n/ethane/propane onto activated carbon, and it is shown that the theor y describes well the adsorption kinetics of this mixture. (C) 1998 Els evier Science Ltd. All rights reserved.