Adsorption equilibrium studies of CO2, CH4 and N2 on various modified zeolites at high pressures up to 200 bars

Abstract

Power generation industries are mostly built on integrated gasification combine cycle (IGCC) which uses high pressure system to turn fossil fuels into pressurized gas i.e. synthesis gas (syngas) which in turn produce energy in the form of H2. Unlike post combustion process, this system requires separation of H2 and CO2 after water-gas shift at slightly higher pressure and higher temperature. Thus porous and strong solid sorbents having the capability of selectively separating and storing CO2 under harsh condition of pressure and temperatures are highly recommended for this technology to be economical viable. Thus various solid sorbents such as silicates, activated carbon, porous polymers network, zeolites and metal organic framework have been investigated for CO2 capture at high pressure. In this article we have experimentally tested six different zeolites including ZSM-5 (3 different silica-to alumina ratio, Si/Al), Mordenite, zeolite Y and zeolite for high pressure CO2, CH4 and N2 adsorption. All commercially available materials were subjected to pressure as high as 200 bars using state of the art equipment magnetic suspension balance (MSB) at three different temperatures 308 K, 323 K and 338 K. Results revealed that zeolite has the largest capacity and can capture up to the maximum of 72 mmol/g of CO2 but possess comparatively lower selectivity for CO2:CH4:N2. ZSM-5 (CBV-2314) has shown the lowest performance by adsorbing around 19 mmol/g with lower selectivity under similar condition. The capturing capacity of three ZSM-5 materials was found to be strongly dependent on the pore volume and Si/Al ratio while the capturing capacity of the rest of materials was independent of the physical parameters. Adsorption rate (mass transfer coefficient) and isosteric heat of adsorption was calculated only for zeolite-due to its relatively better performance.