Adsorption of butane isomers and SF6 on Kureha activated carbon:: 2.: Kinetics

The desorption kinetics of n-butane and isobutane in Kureha carbon has been investigated by means of the TEOM technique. The model used to describe the desorption profiles is based on the nonlinear Toth type adsorption isotherm and the overall rate of desorption controlled by both mass transfer across the gas film surrounding each particle and micropore diffusion. The strong concentration-dependent micropore diffusion in Kureha carbon could be well described by the structural approach proposed by Do (Chem. Eng. Sci. 1996,51, 4145-4158), in which the diffusivity at zero coverage appeared to be independent of loading. The concentration dependence of micropore diffusivities in the structural approach is stronger than the so-called Darken correction; for n-butane it is stronger than that for isobutane. Under similar conditions, the diffusivities of n-butane in Kureha carbon are slightly larger than those of isobutane. The diffusivity activation energy at zero loading for n-butane is larger than that for isobutane because of the penetration of n-butane molecules in the smaller micropores of Kureha carbon, in which there are stronger interactions between adsorptive and adsorbent.