ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Fabrication of Si-CHA/SSZ-13 bilayer membrane for CO₂/CH₄ separation in wet conditions

Azam Aydani and Hafez Maghsoudi

Chemical Engineering Faculty, Sahand University of Technology, Tabriz, Iran

E-mail: hmaghsoudi@sut.ac.ir

Received: 7 November 2021  Accepted: 26 March 2022

Abstract:

One of the most challenging issues in the SSZ-13 membranes is the negative impact of moisture on gas permeance and separation properties. Increasing the surface hydrophobicity of the membranes layer with a layer which has a high Si/Al ratio and can reduce the moisture effect on gas permeation. Therefore, in this paper, Si-CHA/SSZ-13 bilayer membrane was synthesized and evaluated for CO₂/CH₄ separation in wet conditions. Also, the existence of ion exchange property of the bilayer membrane was evaluated due to the cations in the SSZ-13 structure. Characterizations including FESEM, XRD, and EDX revealed that the Si-CHA layer has been successfully grown on the SSZ-13 layer, while there was no damage in crystal structure. The results showed that in the wet condition, CO₂ permeance reduced about 89% in the SSZ-13 membrane, while this amount was 70% in the bilayer membrane at 100 kPa pressure difference and 30 °C, indicating that the bilayer membrane is more resistant in wet conditions. Also, the ideal selectivity of CO₂/CH₄ raised from 43 to 54 in wet gas conditions after adding the Si-CHA layer on the SSZ-13 membrane. Moreover, ion exchanging of the membranes demonstrated that CO₂/CH₄ selectivity increased almost five times in bilayer membranes, while that of the Si-CHA membrane slightly changed. Si-CHA layer made a hydrophobic surface on SSZ-13 layer and reduced the negative effect of the humidity on gases separation with maintaining the ion-exchanging capability of the membrane, simultaneously. These results confirm the advantages of ion-exchange property of the bilayer membrane over the Si-CHA membrane.

Keywords: Bilayer zeolite membranes; Si-CHA/SSZ-13 bilayer membrane; Hydrophobic zeolite membranes; CO2/CH4 separation process

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-022-02202-3

Chemical Papers 76 (8) 4669–4678 (2022)