Effects of non-ideal adsorption equilibria of gas mixtures on column dynamics

Yun, Je Moon; Choi, Dae Ki; Kim, Sung Hyun; Moon, Hee

doi:10.1007/bf02707054

Cited by 5 publications

(6 citation statements)

References 10 publications

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“…Azeotropic behavior in binary vapor–liquid equilibria (VLE) and adsorption azeotropic behavior in gas–solid adsorption equilibria − are very similar with both being quite common, as noted recently by Jiang et al An adsorption azeotrope occurs when the gas ( y i ) and adsorbed ( x i ) phase mole fractions in a binary gas mixture are equal at a given temperature ( T ) and pressure ( P ), i.e., when they intersect the 45° diagonal on an x–y diagram at constant T and P . Just like in VLE, this means that the selectivity S 12 = ( x 1 / y 1 )/( x 2 / y 2 ) = 1.0 at this point.…”

Section: Introductionmentioning

confidence: 71%

“…2,3,8,9,12,14,15,33,35−37 Numerous articles are also reported in the literature on the development of models or correlations t h a t p r e d i c t a d s o r p t i o n a z e o t r o p e b e h a vior. [4][5][6][7][8][9][10][11][12][13][14]17,18,[20][21][22][23][24][25][26][29][30][31][32][34][35][36]38,39 The most recent work by Jiang et al 39 theoretically assessed the necessary and sufficient conditions for the formation of an adsorption azeotrope in a binary gas mixture when this mixture exhibits either intersecting or nonintersecting single-gas isotherms. However, none of these articles have ever clearly answered the question of whether adsorption azeotropes can form in a binary gas mixture below the intersection P of the corresponding singlegas isotherms.…”

Section: ■ Introductionmentioning

confidence: 99%

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Theoretical Analysis of the Pressure Regions Where Adsorption Azeotropes Exist in Binary Gas Mixtures

2022

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This work confirmed theoretically whether adsorption azeotropes can form in a binary gas mixture at a pressure P below the intersection pressure of the corresponding single-gas isotherms. The thermodynamically consistent dual-process Langmuir (DPL) model with equal component i saturation capacities q i, j s on site j and the general DPL model with nonequal q i, j s on site j were used for this purpose. Relationships derived from both DPL models, in terms of the single-gas isotherm DPL model parameters, were used to answer this question. When the P range where adsorption azeotropes always exist is infinite beyond the onset P of adsorption azeotropic formation, both DPL models and experimental data showed that it is possible to form adsorption azeotropes in the corresponding binary gas mixture at pressures not only above but even below the single-gas isotherm intersection P. When the P range where adsorption azeotropes always exist is finite beyond the onset P of adsorption azeotropic formation, only the general DPL model predicts the onset P of this finite P range can be below the intersection P of the corresponding single-gas isotherms. Without theoretical proof, the thermodynamically consistent DPL model seemingly restricts this P range to be equal to or greater than the intersection P of the corresponding single-gas isotherms. For a finite P region where adsorption azeotropes always exist in a binary gas mixture, the binary selectivity inverts when traversing from below the lower onset P to the higher cessation P. Both models also showed, counterintuitively, that perfect positive energetic site matching can result in the formation of adsorption azeotropes in binary gas mixtures, not just perfect negative energetic site matching. Overall, this work provides some confirmation that it is indeed possible to form adsorption azeotropes in a binary gas mixture at pressures below the intersection P of the corresponding single-gas isotherms based on two physically sound formulations of the DPL model.

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Section: Introductionmentioning

confidence: 71%

Section: ■ Introductionmentioning

confidence: 99%

Theoretical Analysis of the Pressure Regions Where Adsorption Azeotropes Exist in Binary Gas Mixtures

2022

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“…2,4−16 Other studies have developed models or correlations that predict adsorption azeotropic behavior. [5][6][7][8]11,[13][14][15][17][18][19][20][21][22][23][24][25][26][27][28][29]32,33,36 The contention has been that a necessary condition for the formation of an adsorption azeotrope in a binary gas mixture is that the corresponding single gas isotherms must intersect each other. 24,37,38 However, several studies have shown that an adsorption azeotrope can form in a binary gas mixture even when the corresponding single gas isotherms do not intersect.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Just like in VLE, this means the selectivity S 12 = ( x 1 / y 1 )/( x 2 / y 2 ) = 1.0 at this point. Although less known and less understood than VLE azeotropic behavior, adsorption azeotropic behavior appears to be a common phenomenon in gas–solid adsorption equilibria. − …”

Section: Introductionmentioning

confidence: 99%

“…Perhaps the first report on the formation of an adsorption azeotrope in a binary gas mixture was published by Damkohler in 1933 as mentioned by Brunauer in 1943 . Since that time, numerous articles have appeared in the literature reporting on the experimental formation of adsorption azeotropes in binary gas mixtures for a variety of adsorbate–adsorbent systems. ,− Other studies have developed models or correlations that predict adsorption azeotropic behavior. − ,,− ,− ,,, The contention has been that a necessary condition for the formation of an adsorption azeotrope in a binary gas mixture is that the corresponding single gas isotherms must intersect each other. ,, However, several studies have shown that an adsorption azeotrope can form in a binary gas mixture even when the corresponding single gas isotherms do not intersect. ,,,,, …”

Section: Introductionmentioning

confidence: 99%

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Theoretical Analysis of the Necessary and Sufficient Conditions for the Formation of Adsorption Azeotropes in Binary Gas Mixtures

2021

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This work theoretically assessed the necessary and sufficient conditions for the formation of an adsorption azeotrope in a binary gas mixture when this mixture exhibits either intersecting or nonintersecting single gas isotherms. The thermodynamically consistent dual process Langmuir (DPL) model with equal component i saturation capacities q i,j s on site j and the general DPL model with nonequal q i,j s on site j were used for this purpose. Analytical expressions derived for both DPL models, in terms of the single gas isotherm DPL model parameters, were used to find examples or to determine theoretically when an adsorption azeotrope forms in a binary gas mixture for both intersecting and nonintersecting single gas isotherms. For the general DPL model, it was determined that neither necessary nor sufficient conditions exist for the formation of an adsorption azeotrope in a binary gas mixture. This means that an adsorption azeotrope can form irrespective of whether the corresponding single gas isotherms intersect or not. For the thermodynamically consistent DPL model, it was determined that the intersection of the single gas isotherms is a sufficient condition for the formation of an adsorption azeotrope in a binary gas mixture, but it is not a necessary condition. This means that intersecting single gas isotherms guarantee the formation of an adsorption azeotrope in the corresponding binary gas mixture, while nonintersecting single gas isotherms can also result in the formation of an adsorption azeotrope in the corresponding binary gas mixture. Overall, this analysis provides a well-posed resolution to the question of necessity and sufficiency for the formation of adsorption azeotropes in binary gas mixtures and the intersection of their corresponding single gas isotherms based on two physically sound formulations of the very popular DPL model.

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