Modelling sorption and diffusion in activated carbon: a novel low pressurepulse-response technique

A novel low pressure pulse-response technique, referred to as Multitrack, w as applied for the simultaneous determination of the adsorption and diffusi on parameters of gases in porous materials in a packed bed. Measurements we re performed on two different carbons, Kureha and Sorbonorit B3, in the tem perature range between 473 and 700 K. The modelling procedure of the pulse responses consisted of two parts. The transport parameters through the pack ed bed were determined from the pulse responses of non-adsorbing argon. Ads orption and diffusion parameters were determined for the adsorbing gases n- butane and hexafluoropropylene. As a general rule it is concluded that micr oporous materials must be described with a basic three-parameter model, whi le macroporous materials must be described with a simplified two-parameter model. The heats of adsorption, determined from the adsorption equilibrium constant, agree well with the values determined independently from uptake e xperiments. With Multitrack a single value for the diffusivity is obtained at a given temperature, valid for the low pressure limit, whereas with upta ke a range of diffusivities is found, covering a wide concentration range. The values were of the same order of magnitude. Multitrack is a promising m ethod for the simultaneous determination of adsorption and diffusion parame ters. (C) 2001 Elsevier Science Ltd. All rights reserved.