Theoretical Analysis of Mixed Gas Adsorption Behaviour of
(CH4+CO2) on Metal Organic Framework (MOF)

Abstract

Any realistic process development in a chemical industry requires estimation and/or prediction of mixed gas adsorption behavior. Invariably, any industrial process involves mixture of gases to be separated. The practical demonstration of such a process at laboratory scale is an extremely cumbersome exercise and there is a scarcity on mixed gas experimental data in literature and more specifically on MOFs. It is pragmatic to gauge the efficiency of a particular adsorbent towards specific separation at the lab scale before being implemented at industrial level in a pressure swing adsorption (PSA) column. This work is aimed at predicting the mixed gas adsorption behavior on MOFs. Pure gas adsorption data of CH4 and CO2 on various MOFs that has been reported over the years was taken from literature. Based on the Heat of Adsorption and the loading data collected CO2 uptake capacity of all the MOFs has been found to be much more than that of CH4. Plausible explanation has been given with data to support it. The retrieved experimental data for Cr-BDC and Cu-BTC has been model fit using Dual Site Langmuir and Virial Langmuir respectively selected from a pool of standard isotherm models viz. Langmuir, Freundlich, Freundlich-Langmuir, and Virial models. The corresponding various model parameters have been found out and the binary or mixed gas behavior of (CO2 + CH4) mixture using IAST (Ideal Adsorbed Solution Theory) has been predicted. The separation factor has been found out and the possible use of Cu-BTC as a potential adsorbent in PSA column applications has been predicted.