(144e) Thermodynamic Conditions for Adsorption Azeotropes

Adsorption azeotropy is a common phenomenon in mixed-gas adsorption equilibria. Since the first literature report of binary adsorption azeotrope in 1933,¹ numerous studies investigated the thermodynamic conditions for adsorption azeotrope formation but failed to reach definitive conclusions.^2-7 This study presents the necessary and sufficient thermodynamic condition for adsorption azeotropes as derived from the generalized Langmuir (gL) ^{8, 9} isotherm model for multicomponent adsorption equilibria. The thermodynamic condition for azeotrope formation has been validated against many azeotrope-forming adsorption systems. Furthermore, the effects of pressure, temperature, and adsorbed phase non-ideality on adsorption azeotropes have been investigated.

(1) Damkohler, G. Adsorption of mixtures of nitrogen and argon. Z. Phys. Chem. B 1933, 23, 69-88.

(2) Cook, W.; Basmadjian, D. The prediction of binary adsorption equilibria from pure component isotherms. The Canadian Journal of Chemical Engineering 1965, 43 (2), 78-83.

(3) Dunne, J.; Myers, A. L. Adsorption of gas mixtures in micropores: effect of difference in size of adsorbate molecules. Chemical Engineering Science 1994, 49 (17), 2941-2951. DOI: 10.1016/0009-2509(94)e0112-4.

(4) Do, D. D.; Do, H. D. On the Azeotropic Behaviour of Adsorption Systems. Adsorption 1999, 5 (4), 319-329. DOI: 10.1023/a:1008944329330.

(5) Nguyen, C.; Do, D. Multicomponent supercritical adsorption in microporous activated carbon materials. Langmuir 2001, 17 (5), 1552-1557.

(6) Jiang, H.; Ebner, A. D.; Ritter, J. A. Theoretical Analysis of the Necessary and Sufficient Conditions for the Formation of Adsorption Azeotropes in Binary Gas Mixtures. Langmuir 2021, 37 (46), 13584-13594. DOI: 10.1021/acs.langmuir.1c01933.

(7) Jiang, H.; Ebner, A. D.; Ritter, J. A. Theoretical Analysis of the Pressure Regions Where Adsorption Azeotropes Exist in Binary Gas Mixtures. ACS Omega 2022. DOI: 10.1021/acsomega.2c05947.

(8) Hamid, U.; Vyawahare, P.; Tun, H.; Chen, C.-C. Generalization of thermodynamic Langmuir isotherm for mixed‐gas adsorption equilibria. AIChE Journal 2022, 68 (6), e17663. DOI: 10.1002/aic.17663.

(9) Hamid, U.; Vyawahare, P.; Chen, C.-C. Estimation of isosteric heat of adsorption from generalized Langmuir isotherm. Adsorption 2023, 29 (1), 45-64. DOI: 10.1007/s10450-023-00379-x.