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Adsorption (2008) 14: 687–693 DOI 10.1007/s10450-008-9126-9 Optimization of synthesis procedures for structured PSA adsorbents Alessandra Mosca · Jonas Hedlund · Firas N. Ridha · Paul Webley Received: 30 April 2007 / Revised: 22 January 2008 / Accepted: 18 April 2008 / Published online: 30 April 2008 © Springer Science+Business Media, LLC 2008 Abstract Structured adsorbents in the form of supported thin zeolite films may represent a competitive alternative to traditional zeolite adsorbents in form of beads or pellets used in PSA processes, due to the reduction of mass- and heat-transfer limitations typical of packed beds. Thin NaX films were grown by hydrothermal treatment using a clear solution on cordierite monoliths. Films grown by a multi- ple synthesis procedure were dense and uniform with a very small amount of sediments adjacent to the film, which may be an advantage in PSA applications. The CO2 adsorption capacity and the pressure drop for the supported films were compared to those of a packed NaX bed. Although the ad- sorption capacity of the column filled with the structured adsorbents was 67 times lower than when the column was filled with zeolite beads, the pressure drop was 100 times lower for the structured adsorbent. The adsorption capac- ity can be increased by increasing the film thickness or the cell density of the monoliths without increasing the pres- sure drop significantly, indicating the potential advantage of structured adsorbents in PSA processes. Further investiga- tions are needed in order to prove this hypothesis. Keywords Zeolite NaX · Traditional adsorbents · Structured adsorbents · PSA · Adsorption · Pressure drop A. Mosca () · J. Hedlund Div. of Chemical Technology, Luleå University of Technology, Luleå 971 87, Sweden e-mail: Alessandra.Mosca@ltu.se F.N. Ridha · P. Webley Dept. of Chemical Engineering, Monash University, Clayton, VIC 3800, Australia 1 Introduction Zeolites represent a broad class of crystalline aluminosili- cate materials used in adsorption processes, catalysis, mem- brane, and sensor technology. Gas separation via adsorp- tion can occur in the porous framework because of the in- teractions between the dipole moments of the gas mole- cules with the electrical field inside the pores of the ad- sorbent (equilibrium separation), size or steric exclusion of certain components (molecular sieving), or because of the ability of some components to enter the pores faster than others (kinetic selectivity). The vast majority of indus- trial gas separation processes by zeolite occurs via equi- librium. NaX zeolite is a widely used adsorbent for CO2 recovery due to its high working capacity, equilibrium se- lectivity and low purge requirement (Chue et al. 1995; Chou and Chen 2004). High purity carbon dioxide can be obtained on zeolite X, where it adsorbs for equilibrium affin- ity between the quadrupole moment of the carbon dioxide molecules and the electrical field generated by the cations inside the zeolite pores. Pressure swing adsorption is a widely used technique for carbon dioxide capture from flue gas (Gomes and Yee 2002; Chou and Chen 2004; Reynolds et al. 2006) or oxygen enrichment from air (Li et al. 1998a, 1998b). Adsorption columns with randomly packed zeolite beads, pellets and ex- trudates are generally used in PSA processes for oxygen pro- duction and carbon dioxide separation because of the high productivity and low cost of the adsorbent material. How- ever, PSA processes which use adsorbing materials in this form have high pressure drop and heat—and mass—transfer limitations as main drawbacks. A high pressure drop in the packed bed might gen- erate high capital and operating costs for the pressuriza- tion/depressurization steps in a PSA process (Jain et al.PDF Image | Structured Zeolite Adsorbents for PSA Applications
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