Permeation of wet and dry gas mixtures through zeolite membranes

Gas permeation through zeolite membranes (i.e., NaY, SAPO-34 and 4A) was investigated for several mixtures (e.g., simulating biogas, biohydrogen etc.). Mass transport through zeolite pores was well described considering the competition between surface and gas translation diffusion [1, 2]. The CO2:H2 and CO2:CH4 dry equimolecular mixtures through NaY and SAPO-34 membranes, respectively, were used for model validation. A CO2/H2 mixture selectivity of 28 was estimated in NaY membrane at 303 K [1], which coincides with the experimental value of Kusakabe et al. 308 K [3]. The experimental permeances of CO2 and CH4 through SAPO-34 membrane measured by Li et al. [4] were well described in the temperature and feed pressure ranges of 270- 400 K and 100 - 600 kPa. A CO2/CH4 selectivity of about 40 was estimated at room temperature. Mixtures containing water vapor in addition to other permanent gases were analyzed through a 4A membrane [2] and the experimental permeances of CH4, CO and H2 [5], which are reduced by the presence of water vapor, were accurately predicted. The water adsorption hinders adsorption and, hence, the permeation of the other gases. Therefore, selectivities towards H2O are very high especially at low temperatures. Thus, zeolite membranes are good candidates for separating different gas mixtures. The competition between surface and gas translation diffusion allows a successfully prediction of the permeation of both dry and wet mixtures. [1] Zito P.F.; Caravella A.; Brunetti A.; Drioli E.; Barbieri G. Discrimination among gas translation, surface and Knudsen diffusion in permeation through zeolite membranes, J. Membr. Sci. 564 (2018) 166-173. [2] Zito P.F.; Brunetti A.; Caravella A.; Drioli E.; Barbieri G. Water vapor permeation and its influence on gases through a zeolite-4A membrane, J. Membr. Sci. 2018, submitted. [3] Kusakabe K.; Kuroda T.; Uchino K.; Hasegawa Y.; Morooka S. Gas permeation properties of ion-exchanged faujasite-type zeolite membranes, AIChE J. 45 (1999) 1120-1226. [4] Li S.; Falconer J.L.; Noble R.D.; SAPO-34 membranes for CO2/CH4 separation, J. Membr. Sci. 241 (2004) 121-135. [5] Zhu W.; Gora L.; van den Berg A.W.C.; Kapteijn F.; Jansen J.C.; Moulijn J.A. Water vapour separation from permanent gases by a zeolite-4A membrane, J. Membr. Sci. 253 (2005) 57-66.