Experimental and modeling study of adsorption and diffusion of gases in Cu-BTC

Abstract

In this study, several samples of Cu-BTC, a member of the MOF adsorbent family, were synthesized following synthesis routes that represent some modifications of published recipes. The sample that gave stable adsorption capacity after several adsorption-desorption cycles was chosen for further study. The equilibrium and kinetic measurements of natural gas and bio gas components, CO 2, CH 4 and N 2, were performed on this screened sample. Single component isotherm measurements of the aforementioned gases were conducted over a wide range of pressures and temperatures using a constant volume apparatus, designed to minimize the required amount of adsorbent. The experimental adsorption equilibrium data of all three gases were well captured by the Langmuir isotherm model. The equilibrium data for the three gases were also compared with those on a commercial Cu-BTC sample, produced by BASF and marketed as Basolite ® C300. In addition, extensive dynamic column breakthrough experiments were conducted with the synthesized sample to establish the gas transport mechanism. Detailed analyses of the breakthrough responses, carried out using a non-isothermal, axially dispersed plug flow model with independently estimated axial dispersion coefficient, linear driving force (LDF) representation of the inter-phase mass transfer and Langmuir isotherm parameters obtained from measured equilibrium data, reveal that in Cu-BTC particles transport of the three gases studied was controlled by a combination of molecular diffusion in the macropores and external gas film resistance. Correction of the measured column dynamics for the extra-column dead volume is also discussed in details. © 2012 Elsevier Ltd.