Multicomponent adsorption of H2, CH4, CO and CO2 in zeolites NaX, CaX and MgX. Evaluation of performance in PSA cycles for hydrogen purification

Abstract

Abstract In PSA processes for hydrogen purification, adsorbents play an extremely important role. In this work, the impact of using different zeolites 13X, obtained through ion exchange, on the performance of a PSA process has been studied. Zeolite 13X (NaX) exchanged with Ca2+ (CaX) and with Mg2+ (MgX) were synthesized. The adsorption isotherms of H2, CH4, CO and CO2, as well as their diffusion constants in micropores in the three materials have been obtained. Then, multicomponent breakthrough curve experiments of a mixture of H2/CH4/CO/CO2 with a composition 75.89/4.01/3.03/17.07% vol. (analogous to the feed stream of an industrial PSA cycle of hydrogen production from steam methane reforming) were simulated using a mathematical model. Finally, the influence of the different cations in zeolite 13X on the performance of a hydrogen purification PSA unit with a multilayer bed (activated carbon/zeolite) has been studied by simulation, considering in each simulation a layer of zeolite NaX, CaX or MgX. Results have shown that zeolite CaX yields better PSA performance parameters in terms of hydrogen recuperation and productivity compared to the parental NaX zeolite and MgX zeolite.