Journal of Membrane Science 349 (2010) 83–89 Contents lists available at ScienceDirect Journal of Membrane Science journal homepage: www.elsevier.com/locate/memsci Influence of NO x adsorbed species on component permeation through ZSM-5 membranes Indra Perdana a,b , Derek Creaser b,∗ , Jonas Lindmark c , Jonas Hedlund c a Department of Chemical Engineering, Gadjah Mada University, Indonesia b Chemical Reaction Engineering, Dept. of Chemical and Biological Engineering, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden c Division of Chemical Engineering, Luleå University of Technology, SE-971 87 Luleå, Sweden article info Article history: Received 31 August 2009 Received in revised form 13 November 2009 Accepted 14 November 2009 Available online 23 December 2009 Keywords: ZSM-5 membrane Zeolite membrane Permeation Transport properties NOx abstract A thin ZSM-5 film was grown on an -alumina support, resulting in a composite membrane. The mem- branes were characterized by SEM and adsorption branch n-hexane/helium permporometry. In addition, the permeation of gas mixtures containing NO 2 , NO, N 2 and argon was evaluated. The effect of tem- perature and gas mixture composition on the component permeation and selectivity was investigated. It was found that NO x permeation through the ZSM-5 membrane was partially surface concentration dependent and was thermally activated. However, transport by gas translational diffusion seemed to dominate at the conditions studied. The presence of various NO x adsorbed species appeared to influence diffusion of NO 2 in ZSM-5 and reduced transport of other inert and weakly adsorbed components over a wide temperature range (20–400 ◦ C). Strongly adsorbed surface nitrate species formed in the presence of gas phase NO x should be responsible for the reduced transport of these components at the elevated temperature. The findings are of interest for possible applications of ZSM-5 membranes for component separation at high temperature. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Zeolites are porous crystalline aluminosilicates of natural or synthetic origin with a three-dimensional framework of silicon–aluminum–oxygen tetrahedra. In addition to their supe- rior thermal stability, the zeolite framework is built of pores and channels in the molecular dimension range. A negative charge results due to substitution of Al 3+ for Si 4+ in the framework. Non- framework cations are required for charge compensation and the cations are exchangeable. These properties make zeolites interest- ing for catalysis and separation applications [1–4]. Among various potential uses, zeolites have been studied and used as catalysts for NO x removal in exhaust gas treatment sys- tems. Several types of zeolites such as ZSM-5, ferrierite (FER) and mordenite (MOR) modified with transition metal ions have been found to be active catalysts for hydrocarbon and ammonia selec- tive catalytic NO x reduction [5–7]. Also, the zeolite structure with pores of molecular dimension offers a unique shape selectivity effect. A physical mixture of zeolites of different pore systems has been studied as a new generation of catalysts for NO x selective cat- alytic reduction in a so-called dual-pore zeolite system [8–10]. Mass ∗ Corresponding author. Tel.: +46 7723023. E-mail address: creaser@chalmers.se (D. Creaser). transport of NO x molecules in zeolites is believed to considerably affect the activity of zeolite based catalysts [10]. In general, since the pore size in zeolites is in the molecu- lar dimension range, transport of components through the zeolite framework is determined by both adsorption and mobility of the diffusing molecules [11]. The transport is frequently called con- figurational or intra-crystalline diffusion and the transport rates strongly depend on temperature. Zeolites can also be synthe- sized in the form of continuous thin films on support materials. When the support material is also porous, the zeolite film and porous support form a composite membrane. However, large pores and defects might also be present in zeolite films through which bulk/molecular diffusion and Knudsen diffusion can contribute to the transport. The adsorption properties and mobility of diffusing components can determine the separation selectivity of zeolite membranes. The strongly adsorbing molecules hinder the diffusion of other weakly adsorbing molecules in the membrane. However, at elevated tem- perature adsorption becomes weaker and mobility of the diffusing components will determine the separation selectivity. Therefore, low temperature is required to achieve highly selective separations with zeolite membranes based on differing adsorption properties of components. This understanding of the influence of adsorption of species transported by surface diffusion on selective permeation principally applies to physisorbed species. However, little is known 0376-7388/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.memsci.2009.11.030