Do the Differential Enthalpies of Adsorption Vary Between 77 K and 302 K? An Experimental Case Study of Argon and Nitrogen on Two Faujasite Type Zeolites

Llewellyn, Philip L.; Maurin, Guillaume; Poyet, Thomas; Dufau, Nathalie; Denoyel, Renaud; Rouquérol, F.

doi:10.1007/s10450-005-5901-z

Cited by 9 publications

(6 citation statements)

References 19 publications

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“…17 The sample was activated by heating to 150 °C under secondary vacuum (<1 Â 10 À3 mbar). The apparent BrunauerÀEmmettÀTeller (BET) surface area was determined by adsorption of N 2 at 77 K in the relative pressure range of P/P 0 = 0.0002À0.01, following the guidelines proposed by Rouquerol et al 30 The sample was found to have a surface area of 1628 m 2 /g and a pore volume of 0.64 cm 3 /g. These values are among the highest reported in the literature and are very close to the values reported by Chang et al 17 for CuBTC prepared by microwave synthesis (1656 m 2 /g).…”

Section: ' Materials and Methodsmentioning

confidence: 99%

Understanding CO₂ Adsorption in CuBTC MOF: Comparing Combined DFT–ab Initio Calculations with Microcalorimetry Experiments

et al. 2011

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Section: ' Materials and Methodsmentioning

confidence: 99%

Understanding CO₂ Adsorption in CuBTC MOF: Comparing Combined DFT–ab Initio Calculations with Microcalorimetry Experiments

et al. 2011

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“…Although it is not implicit in the thermodynamic definition of the isosteric heat of adsorption, it is often assumed that this quantity is at least approximately independent of temperature. Numerous experimental studies, performed mostly on conventional heterogeneous adsorbents such as silicas, zeolites, and carbons, confirmed that the isosteres of adsorption are linear in a wide range of temperatures, and therefore the isosteric heats of adsorption can be assumed to be temperature-independent. ,,, Only a few papers discuss the temperature dependence of the isosteric heats of adsorption. ,,,,− Barrer and Stuart were perhaps the first to note considerable temperature dependence for heats of N 2 adsorption on Faujasite zeolites . Huang presented the T -dependence of Q st for N 2 in zeolites LiX, NaX, KX, and amorphous silica-alumina .…”

Section: Introductionmentioning

confidence: 99%

“…In determining the isosteric heat of adsorption from experimental data, eq is typically applied to several isotherms measured at different temperatures. − In certain cases, calculations from a single experimental isotherm is possible, if an accurate model is available to predict isotherms at other temperatures . Calorimetry is used for direct measurements. ,− When a molecular model is available for an adsorbent, the isosteric heat of adsorption can be computed directly from molecular simulations. − The isosteric heat of adsorption is important in detailed design of adsorption beds, as variations in bed temperature lead to changes in adsorption equilibrium. − The isosteric heat of adsorption is also a useful proxy for adsorption selectivity in considering a range of materials for a separation of interest. ,, …”

Section: Introductionmentioning

confidence: 99%

Significant Temperature Dependence of the Isosteric Heats of Adsorption of Gases in Zeolites Demonstrated by Experiments and Molecular Simulations

et al. 2019

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Heat of adsorption is an important factor in determining the utility of a porous material for gas separation and storage applications. Although theoretically the heat of adsorption can depend on temperature, it is common practice to assume that this dependence is so weak that it can be ignored. In this paper, we challenge this common wisdom. We simulated the adsorption isotherms and heats of adsorption of small molecules (CO 2 , CH 4 , and N 2 ) in reference siliceous (LTA, CHA, MFI) and cation-exchanged (LTA-4A, Na-LTA Si/Al = 2,5) zeolites and found very significant temperature dependence of the isosteric heat of adsorption for CO 2 at low loadings for some systems. In cation-exchanged LTA zeolites, we found more than a 15 kJ/mol decrease over a 300 K range (∼30% variation). We also found remarkable temperature dependence for CO 2 in some siliceous zeolites with eight-membered-ring windows (e.g., ITQ-29). A weak temperature dependence was observed for CO 2 on silica MFI and for CH 4 and N 2 adsorption in all materials. Concurrent adsorption microcalorimetry measurements on cationic 4A and siliceous ITQ-29 (LTA) zeolites fully support the theoretical predictions. Our results demonstrate how the temperature dependence of the isosteric heat is related on the microscopic level to the redistribution of adsorption sites with changes in temperature. A wider implication of our findings is that many porous materials exhibit distinct populations of adsorption sites that can lead to significant temperature dependence of the isosteric heats of adsorption. Therefore, care should be exercised when reporting isosteric heats of adsorption on such materials. For some systems, the significant temperature dependence of the isosteric heats of adsorption may need to be accounted for in process design.

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“…26 The sample was activated by heating to 150 °C under secondary vacuum (<1.10−3 mbar). Apparent BET surface area was determined by adsorption of N 2 at 77 K in the relative pressure range P/P 0 = 0.0002−0.01, following the guidelines proposed by Rouquerol et al 27 The sample was found to have a surface area of 1628 m 2 /g and a pore volume of 0.64 cm 3 /g. These values are among the highest reported in the literature and are very close to the values reported by Chang et al 26 for CuBTC prepared by microwave synthesis (1656 m 2 /g).…”

Section: ■ Introductionmentioning

confidence: 99%

Adsorption of Propane and Propylene on CuBTC Metal–Organic Framework: Combined Theoretical and Experimental Investigation

et al. 2013

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A combined experimental and theoretical investigation of propane and propylene adsorption in the metal− organic framework CuBTC is presented. The dependence of adsorption enthalpies on the adsorbed amount was determined by microcalorimetry up to 8 mmol g −1 coverage (roughly C 3 H n /Cu 2+ ratio of 1.5). Trends observed experimentally were interpreted on the basis of accurate calculations carried out at the hybrid DFT−ab initio level. Three types of adsorption sites were identified; however, qualitatively different results were obtained for propane and propylene. Propane preferentially adsorbs at the cage center sites (−ΔH°= 43 kJ mol −1 ), followed by adsorption at the cage window sites (31 kJ mol −1 ), while the interaction with the coordinatively unsaturated sites (CUS) is relatively weak (24 kJ mol −1 ). On the contrary, propylene preferentially interacts with the CUS (56 kJ mol −1 ), while the adsorption at the cage center and cage window sites was found to be only 45 and 34 kJ mol −1 , respectively. Due to the topology of CuBTC, lateral interactions are significantly more important among the adsorbates located at the cage center and cage window sites (populated in the case of propane) than among adsorbates at the CUS and cage center sites (populated in the case of propylene). Therefore, adsorption energies obtained for coverages above 6 mmol g −1 of adsorbed amount were larger for propane than for propylene. Consequently, the presence of small cages makes the CuBTC MOF less suitable for propane/propylene separation than MOFs having the Cu 2+ CUS but without small cages (e.g., CPO-27).

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Do the Differential Enthalpies of Adsorption Vary Between 77 K and 302 K? An Experimental Case Study of Argon and Nitrogen on Two Faujasite Type Zeolites

Cited by 9 publications

References 19 publications

Understanding CO₂ Adsorption in CuBTC MOF: Comparing Combined DFT–ab Initio Calculations with Microcalorimetry Experiments

Understanding CO₂ Adsorption in CuBTC MOF: Comparing Combined DFT–ab Initio Calculations with Microcalorimetry Experiments

Significant Temperature Dependence of the Isosteric Heats of Adsorption of Gases in Zeolites Demonstrated by Experiments and Molecular Simulations

Adsorption of Propane and Propylene on CuBTC Metal–Organic Framework: Combined Theoretical and Experimental Investigation

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Do the Differential Enthalpies of Adsorption Vary Between 77 K and 302 K? An Experimental Case Study of Argon and Nitrogen on Two Faujasite Type Zeolites

Cited by 9 publications

References 19 publications

Understanding CO2 Adsorption in CuBTC MOF: Comparing Combined DFT–ab Initio Calculations with Microcalorimetry Experiments

Understanding CO2 Adsorption in CuBTC MOF: Comparing Combined DFT–ab Initio Calculations with Microcalorimetry Experiments

Significant Temperature Dependence of the Isosteric Heats of Adsorption of Gases in Zeolites Demonstrated by Experiments and Molecular Simulations

Adsorption of Propane and Propylene on CuBTC Metal–Organic Framework: Combined Theoretical and Experimental Investigation

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Understanding CO₂ Adsorption in CuBTC MOF: Comparing Combined DFT–ab Initio Calculations with Microcalorimetry Experiments

Understanding CO₂ Adsorption in CuBTC MOF: Comparing Combined DFT–ab Initio Calculations with Microcalorimetry Experiments