Unary Adsorption Equilibria of Hydrogen, Nitrogen, and Carbon Dioxide on Y-Type Zeolites at Temperatures from 298 to 393 K and at Pressures up to 3 MPa

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This article references 66 other publications.

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   Zanco, S. E.; Pérez-Calvo, J.-F.; Gasós, A.; Cordiano, B.; Becattini, V.; Mazzotti, M. Postcombustion CO₂ Capture: A Comparative Techno-Economic Assessment of Three Technologies Using a Solvent, an Adsorbent, and a Membrane. ACS Eng. Au 2021, 1, 50– 72,  DOI: 10.1021/acsengineeringau.1c00002

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   Postcombustion CO2 Capture: A Comparative Techno-Economic Assessment of Three Technologies Using a Solvent, an Adsorbent, and a Membrane

   Zanco, Stefano E.; Perez-Calvo, Jose-Francisco; Gasos, Antonio; Cordiano, Beatrice; Becattini, Viola; Mazzotti, Marco

   ACS Engineering Au (2021), 1 (1), 50-72CODEN: AEACB3; ISSN:2694-2488. (American Chemical Society)

   This work compares three postcombustion CO2 capture processes based on mature technologies for CO2 sepn., namely, (i) absorption using an aq. piperazine soln., (ii) adsorption using Zeolite 13X in conventional fixed beds (either vacuum swing adsorption or temp. swing adsorption), and (iii) multistage membrane sepn. using a polymeric material (with CO2/N2 selectivity of 50 and permeability for CO2 of 1700 GPU). All three capture plants are assumed to be retrofitted to a generic industrial CO2-emitting source with 12% CO2 vol./vol. (with 95% relative humidity at the inlet temp. and pressure of 30°C and 1.3 bar, resp.) to deliver CO2 at 96% purity. In the cases of adsorption and membranes, the flue gas is dried before feeding it to the CO2 capture unit. In a first step, the capture processes (i.e., components and design parameters) are optimized based on their tech. performance, defined through process exergy requirement and plant productivity; exergy-productivity Pareto fronts are computed for varying CO2 recovery rates. Second, the economic performance of the processes is assessed through a cost anal. Ests. of CO2 capture costs are provided for each process as a function of the plant size and CO2 recovery rate. The comparative assessment shows that, although the adsorption- and membrane-based processes analyzed may become cost competitive at the small scale (i.e., below sizes of 100 tons of flue gas processed per day) and low recovery rates (i.e., below ca. 40%), the absorption-based process considered is the most cost-effective option at most plant sizes and recovery rates.
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   Chao, C.; Deng, Y.; Dewil, R.; Baeyens, J.; Fan, X. Post-combustion carbon capture. Renew. Sustain. Energy Rev. 2021, 138, 110490,  DOI: 10.1016/j.rser.2020.110490

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   Streb, A.; Mazzotti, M. Novel Adsorption Process for Co-Production of Hydrogen and CO₂ from a Multicomponent Stream─Part 2: Application to Steam Methane Reforming and Autothermal Reforming Gases. Ind. Eng. Chem. Res. 2020, 59, 10093– 10109,  DOI: 10.1021/acs.iecr.9b06953

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   Novel Adsorption Process for Co-Production of Hydrogen and CO2 from a Multicomponent Stream-Part 2: Application to Steam Methane Reforming and Autothermal Reforming Gases

   Streb, Anne; Mazzotti, Marco

   Industrial & Engineering Chemistry Research (2020), 59 (21), 10093-10109CODEN: IECRED; ISSN:0888-5885. (American Chemical Society)

   In this paper, we assess the performance of vacuum pressure swing adsorption (VPSA) for co-purifn. of H2 and CO2 through modeling and process optimization. VPSA allows for the integration of two sepn. tasks, which can simplify the coupling of H2 prodn. with carbon capture and storage (CCS). We assess the performance of five different VPSA cycles, four different feeds typical for steam methane reforming (SMR) and autothermal reforming (ATR) of natural gas or biomethane, and two different H2 purity levels, i.e., 99.9 and 99.97%. Three out of the five cycles can achieve the co-purifn. reaching CCS specifications for CO2 and even the higher H2 purity level at a recovery above 90%. For ATR, argon as a trace impurity is difficult to sep., thereby limiting the attainable purity to 99.9%, but an argon-adjusted purity of over 99.97% can still be reached. The min. electricity required for the sepn. is in the range of 300-500 kJ/kg CO2, with lower values for configurations with a low temp. water-gas shift reactor and for the lower H2 purity level. This is well within the range of the exergy requirement of absorption-based pre-combustion CO2 capture processes, while reaching up to more than twice their productivity and integrating two sepn. units, i.e., CO2 capture unit and H2 purifn. unit, within a single one.
6. 6

   Ward, A.; Pini, R. Efficient Bayesian Optimization of Industrial-Scale Pressure-Vacuum Swing Adsorption Processes for CO₂ Capture. Ind. Eng. Chem. Res. 2022, 61, 13650– 13668,  DOI: 10.1021/acs.iecr.2c02313

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   Efficient Bayesian optimization of industrial-scale pressure-vacuum swing adsorption processes for CO2 capture

   Ward, Adam; Pini, Ronny

   Industrial & Engineering Chemistry Research (2022), 61 (36), 13650-13668CODEN: IECRED; ISSN:0888-5885. (American Chemical Society)

   The design of adsorption systems for sepn. of CO2/N2 in carbon capture applications is notoriously challenging because it requires constrained multiobjective optimization to det. appropriate combinations of a moderately large no. of system operating parameters. The status quo in the literature is to use the nondominated sorting genetic algorithm II (NSGA-II) to solve the design problem. This approach requires 1000s of time-consuming process simulations to find the Pareto front of the problem, meaning it can take days of computational time to obtain a soln. As an alternative approach, we have employed a Bayesian optimization algorithm, the Thompson sampling efficient multiobjective optimization (TSEMO). For constrained productivity/energy usage optimization, we find that the TSEMO algorithm is able to find an essentially identical soln. to the design problem as that found using NSGA-II, while requiring 14 times less computational time. We have used the TSEMO algorithm to design a postcombustion carbon capture system for a 1000 MW coal fired power plant using two adsorbent materials, zeolite 13X and ZIF-36-FRL. Although ZIF-36-FRL showed promising process-scale performance in previous studies, we find that the industrial-scale performance is inferior to the benchmark zeolite 13X, requiring a 21% greater cost per tonne of CO2 captured. Finally, we have also tested the performance of the Bayesian design framework when coupled with a data-driven machine learning process modeling framework. In this instance, we find that the incumbent NSGA-II offers better computational performance than the Bayesian approach by a factor of 3.
7. 7

   Ward, A.; Li, K.; Pini, R. Assessment of dual-adsorbent beds for CO₂ capture by equilibrium-based process design. Sep. Purif. Technol. 2023, 319, 123990,  DOI: 10.1016/j.seppur.2023.123990

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   Assessment of dual-adsorbent beds for CO2 capture by equilibrium-based process design

   Ward, Adam; Li, Ke; Pini, Ronny

   Separation and Purification Technology (2023), 319 (), 123990CODEN: SPUTFP; ISSN:1383-5866. (Elsevier B.V.)

   We have carried out a model-based assessment of dual-adsorbent beds for post-combustion CO2 capture, whereby we consider systems in which two distinct adsorbent materials are homogeneously mixed to form a fixed bed adsorber. We have employed an equil.-based process model (D-BAAM) to simulate and optimize the process performance of a four-step vacuum swing adsorption cycle for CO2 capture with a dual-adsorbent bed. We have used the developed framework to screen the performance of 2,850 binary combinations of adsorbents from a database of 76 promising materials for post-combustion capture, which includes zeolites, activated carbons, metal org. frameworks (MOFs) and zeolitic imidazolate frameworks (ZIFs). Through unconstrained purity/recovery process optimization, we det. that only one pure material in a material pair needs to itself satisfy regulatory constraints on CO2 purity/recovery for post-combustion capture to yield a dual-adsorbent process which satisfies the constraints. For these dual-adsorbent combinations, we have assessed the optimal process performance in the constrained working capacity/energy usage Pareto plane and have identified nine distinct categories of process behavior. Five of these categories have the potential to allow for a redn. in the energy penalty of the sepn., as compared to the constituent single-adsorbent processes. We have obsd. redns. in the energy penalty of the sepn. of approx. 20%. We contend that such processes may be economically optimal depending on a process specific balance of capital, operating and material costs, and should be investigated in more detail using dynamic process modeling and an assocd. techno-economic assessment.
8. 8

   Haghpanah, R.; Majumder, A.; Nilam, R.; Rajendran, A.; Farooq, S.; Karimi, I. A.; Amanullah, M. Multiobjective optimization of a four-step adsorption process for postcombustion CO₂ capture via finite volume simulation. Ind. Eng. Chem. Res. 2013, 52, 4249– 4265,  DOI: 10.1021/ie302658y

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   Multiobjective Optimization of a Four-Step Adsorption Process for Postcombustion CO2 Capture Via Finite Volume Simulation

   Haghpanah, Reza; Majumder, Aniruddha; Nilam, Ricky; Rajendran, Arvind; Farooq, Shamsuzzaman; Karimi, Iftekhar A.; Amanullah, Mohammad

   Industrial & Engineering Chemistry Research (2013), 52 (11), 4249-4265CODEN: IECRED; ISSN:0888-5885. (American Chemical Society)

   This work reports development of a robust, efficient, finite vol.-based adsorption process simulator, essential for rigorous optimization of a transient cyclic operation without resorting to any model redn. It also presents a detailed algorithm for common boundary conditions encountered in non-isothermal and non-isobaric adsorption process simulations. A comprehensive comparison of high-resoln., total variation-diminishing schemes, i.e., van Leer and Superbee, with the weighted essentially non-oscillatory finite vol. scheme was done, and trade-off plots are presented to identify the numerical scheme most suitable to simultaneously attain speed and accuracy. The simulator was then used to perform rigorous optimization of a 4-step process for post-combustion CO2 capture from dry flue gas on zeolite 13X. The aim was to identify operating conditions at which purity and recovery demands are met and to calc. corresponding energy consumption and process productivity. Purity/recovery and energy/productivity Paretos were generated by multi-objective optimization. Results showed that, for a strict vacuum swing adsorption process, an evacuation pressure of 0.02 bar is required to satisfy the regulatory demands to attain a CO2 purity and recovery of 90%. It was also quant. shown that pressurizing the flue gas is detrimental to process energy consumption, although it improves productivity.
9. 9

   García, S.; Pis, J. J.; Rubiera, F.; Pevida, C. Predicting Mixed-Gas Adsorption Equilibria on Activated Carbon for Precombustion CO₂ Capture. Langmuir 2013, 29, 6042– 6052,  DOI: 10.1021/la4004998

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   Predicting Mixed-Gas Adsorption Equilibria on Activated Carbon for Precombustion CO2 Capture

   Garcia, S.; Pis, J. J.; Rubiera, F.; Pevida, C.

   Langmuir (2013), 29 (20), 6042-6052CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)

   Exptl. measured adsorption isotherms are presented of CO2, H2, and N2 on a phenol-formaldehyde resin-based activated carbon, which had been previously synthesized for the sepn. of CO2 in a precombustion capture process. The single component adsorption isotherms were measured in a magnetic suspension balance at three different temps. (298, 318, and 338 K) and over a large range of pressures (from 0 to 3000-4000 kPa). These values cover the temp. and pressure conditions likely to be found in a precombustion capture scenario, where CO2 needs to be sepd. from a CO2/H2/N2 gas stream at high pressure (∼1000-1500 kPa) and with a high CO2 concn. (∼20-40 vol. %). Data on the pure component isotherms were correlated using the Langmuir, Sips, and dual-site Langmuir (DSL) models, i.e., a two-, three-, and four-parameter model, resp. By using the pure component isotherm fitting parameters, adsorption equil. was then predicted for multicomponent gas mixts. by the extended models. The DSL model was formulated considering the energetic site-matching concept, recently addressed in the literature. Exptl. gas-mixt. adsorption equil. data were calcd. from breakthrough expts. conducted in a lab.-scale fixed-bed reactor and compared with the predictions from the models. Breakthrough expts. were carried out at a temp. of 318 K and five different pressures (300, 500, 1000, 1500, and 2000 kPa) where two different CO2/H2/N2 gas mixts. were used as the feed gas in the adsorption step. The DSL model was found to be the one that most accurately predicted the CO2 adsorption equil. in the multicomponent mixt. The results presented in this work highlight the importance of performing exptl. measurements of mixt. adsorption equil., as they are of utmost importance to discriminate between models and to correctly select the one that most closely reflects the actual process.
10. 10

    Hefti, M.; Marx, D.; Joss, L.; Mazzotti, M. Adsorption equilibrium of binary mixtures of carbon dioxide and nitrogen on zeolites ZSM-5 and 13X. Microporous Mesoporous Mater. 2015, 215, 215– 226,  DOI: 10.1016/j.micromeso.2015.05.044

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    Adsorption equilibrium of binary mixtures of carbon dioxide and nitrogen on zeolites ZSM-5 and 13X

    Hefti, Max; Marx, Dorian; Joss, Lisa; Mazzotti, Marco

    Microporous and Mesoporous Materials (2015), 215 (), 215-228CODEN: MIMMFJ; ISSN:1387-1811. (Elsevier Inc.)

    An investigation of the adsorption equil. of carbon dioxide (CO2) and nitrogen (N2) and their mixts. on zeolites ZSM-5 and 13X is presented. Pure component isotherms are measured at five different temps. in the range of 25 °C and pressures up to 10 bar, and the resulting data are described with an appropriate isotherm equation. Adsorption equil. of CO2/N2 mixts. was measured at two temps. (25 °C and 45 °C) and three pressure levels (1.2 bar, 3 bar and 10 bar) using three feed gas compns. on both materials tested. The isotherms obtained from the pure component measurements are used to predict the binary data using two approaches: An empirical extension of the Sips isotherm and the application of ideal adsorbed soln. theory (IAST). In the context of the binary CO2/N2 adsorption, it was found that for ZSM-5 the system behaves close to ideal over the whole range of pressure and temp. investigated here and thus is well described by the IAST prediction. On the other hand, our results demonstrate non-ideal behavior in the adsorbed phase with increasing pressure for zeolite 13X, thus motivating the use of real adsorbed soln. theory (RAST) to accurately describe the binary adsorption data.
11. 11

    Ritter, J. A.; Bhadra, S. J.; Ebner, A. D. On the Use of the Dual-Process Langmuir Model for Correlating Unary Equilibria and Predicting Mixed-Gas Adsorption Equilibria. Langmuir 2011, 27, 4700– 4712,  DOI: 10.1021/la104965w

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    On the use of the dual-process Langmuir model for correlating unary equilibria and predicting mixed-gas adsorption equilibria

    Ritter, James A.; Bhadra, Shubhra J.; Ebner, Armin D.

    Langmuir (2011), 27 (8), 4700-4712CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)

    A new model was developed for predicting mixed-gas adsorption equil. from multicomponent gas mixts. based on the dual-process Langmuir (DPL) formulation. It predicts ideal, nonideal, and azeotropic adsorbed soln. behavior from a knowledge of only single-component adsorption isotherms and the assertion that each binary pair in the gas mixt. correlates in either a perfect pos. (PP) or perfect neg. (PN) fashion on each of the two Langmuir sites. The strictly PP and strictly PN formulations thus provide a simple means for detg. distinct and abs. bounds of the behavior of each binary pair, and the PP or PN behavior can be confirmed by comparing predictions to binary exptl. adsorption equil. or from intuitive knowledge of binary pairwise adsorbate-adsorbent interactions. The extension to ternary and higher-order systems is straightforward on the basis of the pairwise additivity of the binary adsorbent-adsorbate interactions and two rules that logically restrict the combinations of PP and PN behaviors between binary pairs in a multicomponent system. Many ideal and nonideal binary systems and 2 ternary systems were tested against the DPL model. Each binary adsorbate-adsorbent pair exhibited either PP or PN behavior but nothing in between. This binary information was used successfully to predict ternary adsorption equil. based on binary pairwise additivity. Overall, predictions from the DPL model were comparable to or significantly better than those from other models in the literature, revealing that its correlative and predictive powers are universally applicable. Because it is loading-explicit, simple to use, and also accurate, the DPL model may be one of the best equil. models to use in gas-phase adsorption process simulation.
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    Myers, A. L. Activity coefficients of mixtures adsorbed on heterogeneous surfaces. AIChE J. 1983, 29, 691– 693,  DOI: 10.1002/aic.690290428

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    Activity coefficients of mixtures adsorbed on heterogeneous surfaces

    Myers, A. L.

    AIChE Journal (1983), 29 (4), 691-3CODEN: AICEAC; ISSN:0001-1541.

    The nonideal behavior of mol. interaction between the unlike components of adsorbed mixts. on a heterogeneous surface (e.g. activated C) is responsible for deviation of the calcd. values of the activity coeff. of the adsorbed mixt. component from exptl. value. The application of a new more satisfactory model for a realistic continuous energy distribution gives results comparable to those obtained by using the simplistic 2-site model.
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    Ruthven, D. M. Principles of Adsorption and Adsorption Processes; John Wiley and Sons: New York, 1984.

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    Boer, D. G.; Langerak, J.; Pescarmona, P. P. Zeolites as Selective Adsorbents for CO₂ Separation. ACS Appl. Energy Mater. 2023, 6, 2634– 2656,  DOI: 10.1021/acsaem.2c03605

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    Zeolites as Selective Adsorbents for CO2 Separation

    Boer, Dina G.; Langerak, Jort; Pescarmona, Paolo P.

    ACS Applied Energy Materials (2023), 6 (5), 2634-2656CODEN: AAEMCQ; ISSN:2574-0962. (American Chemical Society)

    A review. Zeolites are a very versatile class of materials that can display selective CO2 adsorption behavior and thus find applications in carbon capture, storage and utilization (CCSU). In this contribution, the properties of zeolites as CO2 adsorbents are reviewed, by critically presenting and discussing their assets and limitations. For this purpose, we first provide an overview of the CO2 adsorption mechanisms on different types of zeolites. Then, we systematically discuss the relationship between the physicochem. properties of zeolites (framework type, Si/Al ratio, and extra-framework cations) and their performance as CO2 adsorbents for the sepn. of CO2/CH4 (biogas) and CO2/N2 (flue gas) mixts. Based on the trends and properties identified, we provide a comparison of the different zeolites and highlight their advantages and drawbacks for applicability in CO2 adsorption. Finally, we present the state of the art in the shaping of zeolites in macroscopic format, which is a key step toward their industrial utilization as adsorbents.
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    Barrer, R.; Davies, J.; Rees, L. Thermodynamics and thermochemistry of cation exchange in zeolite Y. J. Inorg. Nucl. Chem. 1968, 30, 3333– 3349,  DOI: 10.1016/0022-1902(68)80130-7

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    Thermodynamics and thermochemistry of cation exchange in zeolite Y

    Barrer, Richard M.; Davies, John Alwyn; Rees, Lovat V. C.

    Journal of Inorganic and Nuclear Chemistry (1968), 30 (12), 3333-49CODEN: JINCAO; ISSN:0022-1902.

    A thermodynamic and thermochem. study has been made of the exchanges Na+ → Li+, Na+ → K+, Na+ → Rb+, Na+ → Cs+, Na+ → Ag+, Na+ → Tl+, 2Na+ → Ca2+, 2Na+ → Sr2+, and 2Na+ → Ba2+ in the near-faujasite Linde Sieve Y. Of these ions only Li+, K+, and Ag+ replaced all Na+ at 25°; the remainder replaced ∼70% of the Na+. An attempt was made to correlate this limit with known cation positions of the Na+ ions. From the exchange equil., thermodynamic affinity sequences have been obtained for the ions that give complete or partial exchange with Na+. For the former group Ag+ > K+ > Na+ > Li+; and for the latter Tl+ > Cs+ > Rb+ > Ba2+ > Na+ > Sr2+ > Ca2+. The thermodynamic equil. consts. were calcd. from exchange capacities corresponding to the max. observed extents of exchange. From exchange heats obtained by direct calorimetry, standard heats of partial and complete exchange have been evaluated. Exchanges of Na+ by Li+, Ca2+, and Sr2+ were endothermic, the remainder exothermic. Exchange of Na+ by K+ in solns. of MeOH showed that the solvent had little effect upon this equil. but greatly influenced the rate of exchange. Standard entropy changes for the replacement of Na+ have been evaluated where possible. These were neg. for uni-univalent exchanges except for Na+ → Ag+ and Na+ → Tl+. Pos. entropy changes were observed for exchanges of Na+ by divalent ions. The thermodynamic functions for the formation of the mixed exchangers showed that the end members formed nonideal solid solns. with each other. This behavior was also reflected in the activity coeffs. of the exchange ions in the mixed exchangers.
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    Shiralkar, V.; Kulkarni, S. Sorption of carbon dioxide in cation exchanged Y type zeolites: Chemical affinities, isosteric heats and entropies. Zeolites 1985, 5, 37– 41,  DOI: 10.1016/0144-2449(85)90009-0

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    Sorption of carbon dioxide in cation exchanged Y type zeolites: chemical affinities, isosteric heats and entropies

    Shiralkar, V. P.; Kulkarni, S. B.

    Zeolites (1985), 5 (1), 37-41CODEN: ZEOLD3; ISSN:0144-2449.

    Sorption affinities, isosteric heats, and entropies of CO2 sorbed at 273-423 K in zeolite type Y cation exchanged with La3+, Ca2+, and H+ were detd. Highest sorption affinity was exhibited by the parent zeolite Na-Y, while at higher temp. by Ca(85)-Y. Zeolite Na-Y provided the most homogeneous surface as compared to cation exchanged zeolites. Isosteric heat for CO2 sorption extrapolated to 0 coverage was highest (≃100 kJ mol-1) for Ca(85)-Y. The differential molar entropies (‾S1) for CO2 sorption in zeolites did not show a definite trend with the amt. sorbed. The integral entropies (‾S1), however, increase with the coverage, except for Na-Y. Most of the ‾S1 curves and the entire ‾S1 curves for all the zeolites lie between entropies of liq. CO2 and pseudo-solid CO2. The freedom of zeolitic CO2 is reduced considerably. The characteristic curves in accordance with the modified Polyanyi potential theory represent the sorption equil. satisfactorily in energetically heterogeneous sorbents along with the energetically homogeneous sorbents.
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    Walton, K. S.; Abney, M. B.; LeVan, M. D. CO₂ adsorption in Y and X zeolites modified by alkali metal cation exchange. Microporous Mesoporous Mater. 2006, 91, 78– 84,  DOI: 10.1016/j.micromeso.2005.11.023

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    CO2 adsorption in Y and X zeolites modified by alkali metal cation exchange

    Walton, Krista S.; Abney, Morgan B.; LeVan, M. Douglas

    Microporous and Mesoporous Materials (2006), 91 (1-3), 78-84CODEN: MIMMFJ; ISSN:1387-1811. (Elsevier B.V.)

    Ion exchange was performed on NaY and NaX zeolites with alkali metal cations Li+, K+, Rb+, and Cs+ and studied by adsorption of CO2. This is the 1st study to examine adsorption equil. isotherms and capacities of CO2 on the alkali metal series for both Y and X zeolites under mild conditions. CO2 capacity increased as Cs < Rb ≈ K < Li ≈ Na for Y zeolites. For X zeolites, the capacity for CO2 increased in the order Cs < Rb < K < Na < Li (the order of decreasing ionic radii). For both zeolites the larger cation forms (Cs, Rb, K) exhibited strongly nonlinear concave downward isotherms, which is indicative of strong interactions between CO2 and the zeolite. This is consistent with an increased basicity of the framework compared to the smaller cation forms, given that CO2 is a weakly acidic gas. This is also reflected by the Henry's law slopes obtained from the Toth isotherm equation. Measurements show that, in general, CO2 capacities are greatest for the Li forms, in which the ion-quadrupole interaction is dominant. Adsorption equil. measurements of CO2 on each ion-exchanged material reveal behaviors and trends based on cation size and acid-base surface properties that can have an important impact on tuning adsorptive properties of zeolites by ion exchange.
18. 18

    Feng, L.; Shen, Y.; Wu, T.; Liu, B.; Zhang, D.; Tang, Z. Adsorption equilibrium isotherms and thermodynamic analysis of CH₄, CO₂, CO, N₂ and H₂ on NaY Zeolite. Adsorption 2020, 26, 1101– 1111,  DOI: 10.1007/s10450-020-00205-8

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    Adsorption equilibrium isotherms and thermodynamic analysis of CH4, CO2, CO, N2 and H2 on NaY Zeolite

    Feng, Li; Shen, Yuanhui; Wu, Tongbo; Liu, Bing; Zhang, Donghui; Tang, Zhongli

    Adsorption (2020), 26 (7), 1101-1111CODEN: ADSOFO; ISSN:0929-5607. (Springer)

    Adsorption capacities of CH4, CO2, CO, N2 and H2 on NaY zeolite were measured at 298 K, 318 K, 338 K and 358 K with pressure ranged from 0 to 10 bar. The order of adsorption capacity was CO2 >> CH4 > CO > N2 >> H2. The expt. data were fitted by the Langmuir, Toth and Sips equations. The fitting relativity of above models were also compared. Moreover, the isosteric heat of adsorption were calcd. by the Clausius-Clapeyron equation, the results showed that the adsorption heat of CO2 is the largest (41.89764 kJ/mol with adsorption loading of 5.8 mmol/g) and that of H2 is the smallest. Finally, the selectivity of binary mixt. was predicted according to the IAS theory.
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    Gang, L.; May, E. F.; Webley, P. A.; Huang, S. H.-W.; Chan, K. I. Method for Gas Separation. Patent Application US 2017/0348670 A1, 2017.

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    Wu, Y.; Yuan, D.; Zeng, S.; Yang, L.; Dong, X.; Zhang, Q.; Xu, Y.; Liu, Z. Significant enhancement in CH₄/N₂ separation with amine-modified zeolite Y. Fuel 2021, 301, 121077,  DOI: 10.1016/j.fuel.2021.121077

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    Significant enhancement in CH4/N2 separation with amine-modified zeolite Y

    Wu, Yaqi; Yuan, Danhua; Zeng, Shu; Yang, Liping; Dong, Xingzong; Zhang, Quan; Xu, Yunpeng; Liu, Zhongmin

    Fuel (2021), 301 (), 121077CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)

    Adsorption based process for CH4/N2 sepn. is promising and attractive while it remains a challenge endeavor due to the lack of efficient adsorbents. In this work, amine ion-exchanged Y zeolites were developed for CH4/N2 sepn. By simple ion-exchanged with tetramethylammonium cation (TMA+) and choline cation (Ch+), CH4 adsorption amts. of the resulting adsorbents were obviously increased while their N2 adsorption amts. were significantly decreased. Consequently, CH4/N2 sepn. performances of resulted samples were greatly improved compared to pristine NaY. CH4/N2 selectivities of resulting sample TMAY and ChY were up to 6.32 and 6.50, resp., at 25°C and 100 kPa. Monte Carlo calcns. were used to study the interaction affinity for CH4 and N2 on the adsorbents. Breakthrough expts. were further confirmed the excellent sepn. performances of TMAY and ChY. The excellent sepn. performances of the resulting adsorbents verified the efficiency of the simple ion-exchange strategy and the application potential of the adsorbents.
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    Sadeghi Pouya, E.; Farmahini, A.; Sadeghi, P.; Peikert, K.; Peikert, K.; Sarkisov, L.; May, E. F.; Arami-Niya, A. Enhanced CH₄-N₂ Separation Selectivity of Zeolite Y via Cation Exchange with Ammonium Salts. SSRN Electron. J. 2023, 1– 4,  DOI: 10.2139/ssrn.4457433

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    Simple theoretical adsorption isotherm for zeolites

    Ruthven, D. M.

    Nature (London), Physical Science (1971), 232 (29), 70-1CODEN: NPSCA6; ISSN:0300-8746.

    A theoretical adsorption isotherm for zeolites is derived by using the principles of statistical thermodynamics and is obsd. to be a good fit to the exptl. data for the sorption of propane in Linde 5A zeolite at 85°. The theoretical and exptl. isotherms agree well for 0-65% satn., and equally good agreement was obsd. at other temps. with other hydrocarbon sorbates.
24. 24

    Hwang, J.; Azzan, H.; Pini, R.; Petit, C. H₂, N₂, CO₂, and CH₄ Unary Adsorption Isotherm Measurements at Low and High Pressures on Zeolitic Imidazolate Framework ZIF-8. J. Chem. Eng. Data 2022, 67, 1674– 1686,  DOI: 10.1021/acs.jced.1c00900

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    24

    H2, N2, CO2, and CH4 Unary Adsorption Isotherm Measurements at Low and High Pressures on Zeolitic Imidazolate Framework ZIF-8

    Hwang, Junyoung; Azzan, Hassan; Pini, Ronny; Petit, Camille

    Journal of Chemical & Engineering Data (2022), 67 (7), 1674-1686CODEN: JCEAAX; ISSN:0021-9568. (American Chemical Society)

    Excess adsorption of CO2, CH4, N2, and H2 on ZIF-8 was measured in the pressure range ranging from vacuum to 30 MPa at 298.15 K, 313.15 K, 333.15 K, 353.15 and 394.15 K gravimetrically using a magnetic suspension balance. The textural properties of the adsorbent material - i.e. skeletal d., surface area, pore vol., and pore-size distribution - were estd. by helium gravimetry and N2 (77 K) physisorption. The adsorption isotherms were fitted with the Sips isotherm model and the virial equation, and the values of isosteric heat of adsorption and Henry consts. for the gases were detd. using the latter.
25. 25

    Rouquerol, J.; Llewellyn, P.; Rouquerol, F. In Characterization of Porous Solids VII; Llewellyn, P., Rodriquez-Reinoso, F., Rouqerol, J., Seaton, N., Eds.; Studies in Surface Science and Catalysis; Elsevier, 2007; Vol. 160, pp 49– 56.

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26. 26

    Osterrieth, J. W. M.; Rampersad, J.; Madden, D.; Rampal, N.; Skoric, L.; Connolly, B.; Allendorf, M. D.; Stavila, V.; Snider, J. L.; Ameloot, R.; Marreiros, J.; Ania, C.; Azevedo, D.; Vilarrasa-Garcia, E.; Santos, B. F.; Bu, X.-H.; Chang, Z.; Bunzen, H.; Champness, N. R.; Griffin, S. L.; Chen, B.; Lin, R.-B.; Coasne, B.; Cohen, S.; Moreton, J. C.; Colón, Y. J.; Chen, L.; Clowes, R.; Coudert, F.-X.; Cui, Y.; Hou, B.; D’Alessandro, D. M.; Doheny, P. W.; Dincă, M.; Sun, C.; Doonan, C.; Huxley, M. T.; Evans, J. D.; Falcaro, P.; Ricco, R.; Farha, O.; Idrees, K. B.; Islamoglu, T.; Feng, P.; Yang, H.; Forgan, R. S.; Bara, D.; Furukawa, S.; Sanchez, E.; Gascon, J.; Telalović, S.; Ghosh, S. K.; Mukherjee, S.; Hill, M. R.; Sadiq, M. M.; Horcajada, P.; Salcedo-Abraira, P.; Kaneko, K.; Kukobat, R.; Kenvin, J.; Keskin, S.; Kitagawa, S.; Otake, K.-i.; Lively, R. P.; DeWitt, S. J. A.; Llewellyn, P.; Lotsch, B. V.; Emmerling, S. T.; Pütz, A. M.; Martí-Gastaldo, C.; Padial, N. M.; García-Martínez, J.; Linares, N.; Maspoch, D.; Suárez del Pino, J. A.; Moghadam, P.; Oktavian, R.; Morris, R. E.; Wheatley, P. S.; Navarro, J.; Petit, C.; Danaci, D.; Rosseinsky, M. J.; Katsoulidis, A. P.; Schröder, M.; Han, X.; Yang, S.; Serre, C.; Mouchaham, G.; Sholl, D. S.; Thyagarajan, R.; Siderius, D.; Snurr, R. Q.; Goncalves, R. B.; Telfer, S.; Lee, S. J.; Ting, V. P.; Rowlandson, J. L.; Uemura, T.; Iiyuka, T.; van der Veen, M. A.; Rega, D.; Van Speybroeck, V.; Rogge, S. M. J.; Lamaire, A.; Walton, K. S.; Bingel, L. W.; Wuttke, S.; Andreo, J.; Yaghi, O.; Zhang, B.; Yavuz, C. T.; Nguyen, T. S.; Zamora, F.; Montoro, C.; Zhou, H.; Kirchon, A.; Fairen-Jimenez, D. How Reproducible are Surface Areas Calculated from the BET Equation?. Adv. Mater. 2022, 34, 2201502,  DOI: 10.1002/adma.202270205

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    How Reproducible are Surface Areas Calculated from the BET Equation?

    Osterrieth, Johannes W. M.; Rampersad, James; Madden, David; Rampal, Nakul; Skoric, Luka; Connolly, Bethany; Allendorf, Mark D.; Stavila, Vitalie; Snider, Jonathan L.; Ameloot, Rob; Marreiros, Joao; Ania, Conchi; Azevedo, Diana; Vilarrasa-Garcia, Enrique; Santos, Bianca F.; Bu, Xian-He; Chang, Ze; Bunzen, Hana; Champness, Neil R.; Griffin, Sarah L.; Chen, Banglin; Lin, Rui-Biao; Coasne, Benoit; Cohen, Seth; Moreton, Jessica C.; Colon, Yamil J.; Chen, Linjiang; Clowes, Rob; Coudert, Francois-Xavier; Cui, Yong; Hou, Bang; D'Alessandro, Deanna M.; Doheny, Patrick W.; Dinca, Mircea; Sun, Chenyue; Doonan, Christian; Huxley, Michael Thomas; Evans, Jack D.; Falcaro, Paolo; Ricco, Raffaele; Farha, Omar; Idrees, Karam B.; Islamoglu, Timur; Feng, Pingyun; Yang, Huajun; Forgan, Ross S.; Bara, Dominic; Furukawa, Shuhei; Sanchez, Eli; Gascon, Jorge; Telalovic, Selvedin; Ghosh, Sujit K.; Mukherjee, Soumya; Hill, Matthew R.; Sadiq, Muhammed Munir; Horcajada, Patricia; Salcedo-Abraira, Pablo; Kaneko, Katsumi; Kukobat, Radovan; Kenvin, Jeff; Keskin, Seda; Kitagawa, Susumu; Otake, Ken-ichi; Lively, Ryan P.; DeWitt, Stephen J. A.; Llewellyn, Phillip; Lotsch, Bettina V.; Emmerling, Sebastian T.; Puetz, Alexander M.; Marti-Gastaldo, Carlos; Padial, Natalia M.; Garcia-Martinez, Javier; Linares, Noemi; Maspoch, Daniel; Suarez del Pino, Jose A.; Moghadam, Peyman; Oktavian, Rama; Morris, Russel E.; Wheatley, Paul S.; Navarro, Jorge; Petit, Camille; Danaci, David; Rosseinsky, Matthew J.; Katsoulidis, Alexandros P.; Schroder, Martin; Han, Xue; Yang, Sihai; Serre, Christian; Mouchaham, Georges; Sholl, David S.; Thyagarajan, Raghuram; Siderius, Daniel; Snurr, Randall Q.; Goncalves, Rebecca B.; Telfer, Shane; Lee, Seok J.; Ting, Valeska P.; Rowlandson, Jemma L.; Uemura, Takashi; Iiyuka, Tomoya; van der Veen, Monique A.; Rega, Davide; Van Speybroeck, Veronique; Rogge, Sven M. J.; Lamaire, Aran; Walton, Krista S.; Bingel, Lukas W.; Wuttke, Stefan; Andreo, Jacopo; Yaghi, Omar; Zhang, Bing; Yavuz, Cafer T.; Nguyen, Thien S.; Zamora, Felix; Montoro, Carmen; Zhou, Hongcai; Kirchon, Angelo; Fairen-Jimenez, David

    Advanced Materials (Weinheim, Germany) (2022), 34 (27), 2201502CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)

    Porosity and surface area anal. play a prominent role in modern materials science. At the heart of this sits the Brunauer-Emmett-Teller (BET) theory, which has been a remarkably successful contribution to the field of materials science. The BET method was developed in the 1930s for open surfaces but is now the most widely used metric for the estn. of surface areas of micro- and mesoporous materials. Despite its widespread use, the calcn. of BET surface areas causes a spread in reported areas, resulting in reproducibility problems in both academia and industry. To prove this, for this anal., 18 already-measured raw adsorption isotherms were provided to sixty-one labs, who were asked to calc. the corresponding BET areas. This round-robin exercise resulted in a wide range of values. Here, the reproducibility of BET area detn. from identical isotherms is demonstrated to be a largely ignored issue, raising crit. concerns over the reliability of reported BET areas. To solve this major issue, a new computational approach to accurately and systematically det. the BET area of nanoporous materials is developed. The software, called "BET surface identification" (BETSI), expands on the well-known Rouquerol criteria and makes an unambiguous BET area assignment possible.
27. 27

    Hwang, J.; Joss, L.; Pini, R. Measuring and modelling supercritical adsorption of CO₂ and CH₄ on montmorillonite source clay. Microporous Mesoporous Mater. 2019, 273, 107– 121,  DOI: 10.1016/j.micromeso.2018.06.050

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    27

    Measuring and modeling supercritical adsorption of CO2 and CH4 on montmorillonite source clay

    Hwang, J.; Joss, L.; Pini, R.

    Microporous and Mesoporous Materials (2019), 273 (), 107-121CODEN: MIMMFJ; ISSN:1387-1811. (Elsevier B.V.)

    Clay mineral porosity is dominated by nanoscale pores which provide a large surface area for phys. and chem. interactions with surrounding fluids, including gas adsorption. Measuring gas adsorption at subsurface conditions is difficult because elevated pressure is required and interactions between the supercrit. gas and clay are relatively weak. Measured CO2 and CH4 adsorption isotherms on the source clay, Na-montmorillonite (SWy-2), at different temps. (25-115°) over a wide pressure range (0.02-25 MPa) are reported. Exptl. observations were analyzed considering net and excess adsorbed amts., and by extg. adsorption metrics (e.g., Henry's consts., adsorption enthalpy). Results consistently indicated SWy-2 favors CO2 adsorption over CH4 with selectivity, S ≈ 5.5. Exptl. data were successfully described using a lattice d. functional theory (LDFT) model. Model estd. adsorption energetics compared well with exptl. obtained adsorption enthalpies. Even at the highest pressure, clay pore space was only partially filled and the degree of satn. increased upon approaching the gas crit. temp. The LDFT model ability to reveal pore-dependent adsorption behavior demonstrated its potential vs. empirical models (e.g., Langmuir equation) which fail to capture the complexities of supercrit. gas adsorption at subsurface conditions.
28. 28

    Lemmon, E. W.; Bell, I. H.; Huber, M. L.; McLinden, M. O. NIST Standard Reference Database 23: Reference Fluid Thermodynamic and Transport Properties - REFPROP; NIST, 2018; https://www.nist.gov/srd/refprop.

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    Leachman, J. W.; Jacobsen, R. T.; Penoncello, S. G.; Lemmon, E. W. Fundamental Equations of State for Parahydrogen, Normal Hydrogen, and Orthohydrogen. J. Phys. Chem. Ref. Data 2009, 38, 721– 748,  DOI: 10.1063/1.3160306

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    29

    Fundamental Equations of State for Parahydrogen, Normal Hydrogen, and Orthohydrogen

    Leachman, J. W.; Jacobsen, R. T.; Penoncello, S. G.; Lemmon, E. W.

    Journal of Physical and Chemical Reference Data (2009), 38 (3), 721-748CODEN: JPCRBU; ISSN:0047-2689. (American Institute of Physics)

    If the potential for a boom in the global hydrogen economy is realized, there will be an increase in the need for accurate hydrogen thermodn. property stds. Based on current and anticipated needs, new fundamental equations of state for parahydrogen, normal hydrogen, and orthohydrogen were developed to replace the existing property models. To accurately predict thermophys. properties near the crit. region and in liq. states, the quantum law of corresponding states was applied to improve the normal hydrogen and orthohydrogen formulations in the absence of available exptl. data. All three equations of state have the same max. pressure of 2000 MPa and upper temp. limit of 1000 K. Uncertainty ests. in this paper can be considered to be ests. of a combined expanded uncertainty with a coverage factor of 2 for primary data sets. The uncertainty in d. is 0.04% in the region between 250 and 450 K and at pressures up to 300 MPa. The uncertainties of vapor pressures and satd. liq. densities vary from 0.1% to 0.2%. Heat capacities are generally estd. to be accurate to within 1%, while speed-of-sound values are accurate to within 0.5% below 100 MPa. (c) 2009 American Institute of Physics.
30. 30

    Pini, R.; Ansari, H.; Hwang, J. Measurement and interpretation of unary supercritical gas adsorption isotherms in micro-mesoporous solids. Adsorption 2021, 1– 13

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    Nguyen, H. G. T.; Horn, J. C.; Thommes, M.; Van Zee, R. D.; Espinal, L. Experimental aspects of buoyancy correction in measuring reliable high-pressure excess adsorption isotherms using the gravimetric method. Meas. Sci. Technol. 2017, 28, 125802,  DOI: 10.1088/1361-6501/aa8f83

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    Experimental aspects of buoyancy correction in measuring reliable highpressure excess adsorption isotherms using the gravimetric method

    Nguyen, Huong Giang T.; Horn, Jarod C.; Thommes, Matthias; van Zee, Roger D.; Espinal, Laura

    Measurement Science and Technology (2017), 28 (12), 125802/1-125802/11CODEN: MSTCEP; ISSN:0957-0233. (IOP Publishing Ltd.)

    Addressing reproducibility issues in adsorption measurements is crit. to accelerating the path to discovery of new industrial adsorbents and to understanding adsorption processes. A National Institute of Stds. and Technol. Ref. Material, RM 8852 (ammonium ZSM-5 zeolite), and two gravimetric instruments with asym. two-beam balances were used to measure high-pressure adsorption isotherms. This work demonstrates how common approaches to buoyancy correction, a key factor in obtaining the mass change due to surface excess gas uptake from the apparent mass change, can impact the adsorption isotherm data. Three different approaches to buoyancy correction were investigated and applied to the subcrit. CO2 and supercrit. N2 adsorption isotherms at 293 K. It was obsd. that measuring a collective vol. for all balance components for the buoyancy correction (helium method) introduces an inherent bias in temp. partition when there is a temp. gradient (i.e. anal. temp. is not equal to instrument air bath temp.). We demonstrate that a blank subtraction is effective in mitigating the biases assocd. with temp. partitioning, instrument calibration, and the detd. vols. of the balance components. In general, the manual and subtraction methods allow for better treatment of the temp. gradient during buoyancy correction. From the study, best practices specific to asym. two-beam balances and more general recommendations for measuring isotherms far from crit. temps. using gravimetric instruments are offered.
32. 32

    Nguyen, H. G. T.; Sims, C. M.; Toman, B.; Horn, J.; van Zee, R. D.; Thommes, M.; Ahmad, R.; Denayer, J. F. M.; Baron, G. V.; Napolitano, E.; Bielewski, M.; Mangano, E.; Brandani, S.; Broom, D. P.; Benham, M. J.; Dailly, A.; Dreisbach, F.; Edubilli, S.; Gumma, S.; Möllmer, J.; Lange, M.; Tian, M.; Mays, T. J.; Shigeoka, T.; Yamakita, S.; Hakuman, M.; Nakada, Y.; Nakai, K.; Hwang, J.; Pini, R.; Jiang, H.; Ebner, A. D.; Nicholson, M. A.; Ritter, J. A.; Farrando-Pérez, J.; Cuadrado-Collados, C.; Silvestre-Albero, J.; Tampaxis, C.; Steriotis, T.; Řimnáčová, D.; Švábová, M.; Vorokhta, M.; Wang, H.; Bovens, E.; Heymans, N.; De Weireld, G. A reference high-pressure CH₄ adsorption isotherm for zeolite Y: results of an interlaboratory study. Adsorption 2020, 26, 1253– 1266,  DOI: 10.1007/s10450-020-00253-0

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    A reference high-pressure CH4 adsorption isotherm for zeolite Y: results of an interlaboratory study

    Nguyen, H. G. T.; Sims, C. M.; Toman, B.; Horn, J.; van Zee, R. D.; Thommes, M.; Ahmad, R.; Denayer, J. F. M.; Baron, G. V.; Napolitano, E.; Bielewski, M.; Mangano, E.; Brandani, S.; Broom, D. P.; Benham, M. J.; Dailly, A.; Dreisbach, F.; Edubilli, S.; Gumma, S.; Mollmer, J.; Lange, M.; Tian, M.; Mays, T. J.; Shigeoka, T.; Yamakita, S.; Hakuman, M.; Nakada, Y.; Nakai, K.; Hwang, J.; Pini, R.; Jiang, H.; Ebner, A. D.; Nicholson, M. A.; Ritter, J. A.; Farrando-Perez, J.; Cuadrado-Collados, C.; Silvestre-Albero, J.; Tampaxis, C.; Steriotis, T.; Rimnacova, D.; Svabova, M.; Vorokhta, M.; Wang, H.; Bovens, E.; Heymans, N.; De Weireld, G.

    Adsorption (2020), 26 (8), 1253-1266CODEN: ADSOFO; ISSN:0929-5607. (Springer)

    This paper reports the results of an international interlab. study led by the National Institute of Stds. and Technol. (NIST) on the measurement of high-pressure surface excess methane adsorption isotherms on NIST Ref. Material RM 8850 (Zeolite Y), at 25°C up to 7.5 MPa. Twenty labs. participated in the study and contributed over one-hundred adsorption isotherms of methane on Zeolite Y. From these data, an empirical ref. equation was detd., along with a 95% uncertainty interval (Uk = 2). By requiring participants to replicate a high-pressure ref. isotherm for carbon dioxide adsorption on NIST Ref. Material RM 8852 (ZSM-5), this interlab. study also demonstrated the usefulness of ref. isotherms in evaluating the performance of high-pressure adsorption expts.
33. 33

    Lowell, S.; Shields, J.; Thomas, M.; Thommes, M. Characterization of Porous Solids and Powders: Surface Area, Pore Size and Density; Particle Technology Series; Springer: Netherlands, 2012.

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    Nguyen, H. G. T.; Espinal, L.; van Zee, R. D.; Thommes, M.; Toman, B.; Hudson, M. S. L.; Mangano, E.; Brandani, S.; Broom, D. P.; Benham, M. J.; Cychosz, K. A.; Bertier, P.; Yang, F.; Krooss, B. M.; Siegelman, R. L.; Hakuman, M.; Nakai, K.; Ebner, A. D.; Erden, L.; Ritter, J. A.; Moran, A.; Talu, O.; Huang, Y.; Walton, K. S.; Billemont, P.; De Weireld, G. A reference high-pressure CO₂ adsorption isotherm for ammonium ZSM-5 zeolite: results of an interlaboratory study. Adsorption 2018, 24, 531– 539,  DOI: 10.1007/s10450-018-9958-x

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    A reference high-pressure CO2 adsorption isotherm for ammonium ZSM-5 zeolite: results of an interlaboratory study

    Nguyen, H. G. T.; Espinal, L.; van Zee, R. D.; Thommes, M.; Toman, B.; Hudson, M. S. L.; Mangano, E.; Brandani, S.; Broom, D. P.; Benham, M. J.; Cychosz, K.; Bertier, P.; Yang, F.; Krooss, B. M.; Siegelman, R. L.; Hakuman, M.; Nakai, K.; Ebner, A. D.; Erden, L.; Ritter, J. A.; Moran, A.; Talu, O.; Huang, Y.; Walton, K. S.; Billemont, P.; De Weireld, G.

    Adsorption (2018), 24 (6), 531-539CODEN: ADSOFO; ISSN:0929-5607. (Springer)

    This paper reports the results of an international interlab. study led by the National Institute of Stds. and Technol. (NIST) on the measurement of high-pressure surface excess carbon dioxide adsorption isotherms on NIST Ref. Material RM 8852 (ammonium ZSM-5 zeolite), at 293.15 K (20°C) from 1 kPa up to 4.5 MPa. Eleven labs. participated in this exercise and, for the first time, high-pressure adsorption ref. data are reported using a ref. material. An empirical ref. equation nex = (d/(1+exp[( - ln(P) + a)/b])c), [nex-surface excess uptake (mmol/g), P-equil. pressure (MPa), a = -6.22, b = 1.97, c = 4.73, and d = 3.87] along with the 95% uncertainty interval (Uk=2 = 0.075 mmol/g) were detd. for the ref. isotherm using a Bayesian, Markov Chain Monte Carlo method. Together, this zeolitic ref. material and the assocd. adsorption data provide a means for labs. to test and validate high-pressure adsorption equipment and measurements. Recommendations are provided for measuring reliable high-pressure adsorption isotherms using this material, including activation procedures, data processing methods to det. surface excess uptake, and the appropriate equation of state to be used.
35. 35

    Quirke, N.; Tennison, S. The interpretation of pore size distributions of microporous carbons. Carbon N. Y. 1996, 34, 1281– 1286,  DOI: 10.1016/0008-6223(96)00099-1

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    Pini, R. Interpretation of net and excess adsorption isotherms in microporous adsorbents. Microporous Mesoporous Mater. 2014, 187, 40– 52,  DOI: 10.1016/j.micromeso.2013.12.005

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    Interpretation of net and excess adsorption isotherms in microporous adsorbents

    Pini, Ronny

    Microporous and Mesoporous Materials (2014), 187 (), 40-52CODEN: MIMMFJ; ISSN:1387-1811. (Elsevier Inc.)

    Adsorption data are routinely reported as net or excess amts. adsorbed; although measuring techniques are nowadays well established, the interpretation and further use of these two measures is limited by the uncertainty on the estd. internal pore vol. of the material and, accordingly, the vol. (or d.) of the adsorbed fluid. In this study, adsorption data are presented that have been measured with CO2 on 13X zeolite in both crystal and pellet forms at 50 °C and in the pressure range 0.02-14 MPa by using a magnetic suspension balance. The adsorbents' structural parameters have been obtained through a combination of independent measuring techniques, including low-pressure adsorption and mercury intrusion porosimetry, and a methodol. is presented where both net and excess adsorption isotherms are simultaneously evaluated through a graphical method. While providing addnl. insights on the meaning of these two different frameworks, the application of such an integrated approach allows for a more consistent interpretation of the obtained adsorption data. It is shown that for both materials the adsorption process is entirely controlled by the filling of the micropores and that the adsorbent's vol. is overestimated when helium is used as a probing gas. The statistical adsorption isotherm model proposed by Ruthven is applied to describe the measured adsorption isotherms and provides a much better fit than the Langmuir model. For both crystals and pellets, and over the whole pressure range, CO2 adsorbs as a dense liq. with d. values starting from the crit. d. of the fluid and reaching ∼ 27 mol/L (i.e. 15 mols./cage) at the highest pressure of the expt.
37. 37

    Findenegg, G. H. In Fundamentals of Adsorption; Myers, A., Belfort, G., Eds.; Engineering Foundation: New York, 1984; p 207.

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    Murata, K.; El-Merraoui, M.; Kaneko, K. A new determination method of absolute adsorption isotherm of supercritical gases under high pressure with a special relevance to density-functional theory study. J. Chem. Phys. 2001, 114, 4196– 4205,  DOI: 10.1063/1.1344926

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    A new determination method of absolute adsorption isotherm of supercritical gases under high pressure with a special relevance to density-functional theory study

    Murata, Katsuyuki; El-Merraoui, Mustapha; Kaneko, Katsumi

    Journal of Chemical Physics (2001), 114 (9), 4196-4205CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)

    A new detn. method of an abs. adsorbed amt. nab from the surface excess mass nex for high-pressure adsorption isotherms of a supercrit. gas was proposed. The effectiveness of new method was examd. by using the d.-functional theory (DFT). The DFT study showed that this anal. can provide reasonable results; both of the abs. adsorbed amt. detd. from the proposed method and the DFT agreed within 5% at 90 MPa and only 1[percent] below 5 MPa. Furthermore, we applied this new method to the exptl. surface excess isotherm in the literature, which has a max. The analyzed abs. adsorption isotherm from the surface excess adsorption isotherm having a max. were of IUPAC type I or type II. This method gave the thickness of the interfacial layer of the adsorbed phase.
39. 39

    Ruthven, D. M. Sorption of oxygen, nitrogen, carbon monoxide, methane, and binary mixtures of these gases in 5A molecular sieve. AIChE J. 1976, 22, 753– 759,  DOI: 10.1002/aic.690220419

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    Sorption of oxygen, nitrogen, carbon monoxide, methane, and binary mixtures of these gases in 5A molecular sieve

    Ruthven, Douglas M.

    AIChE Journal (1976), 22 (4), 753-9CODEN: AICEAC; ISSN:0001-1541.

    Equil. data for the sorption of O, N, CO, and CH4 in 5A mol. sieve are analyzed in terms of a simple theor. model isotherm. The model provides an excellent correlation of the single-component isotherms over the entire concn. range. Equil. data for sorption of binary mixts. of these gases are correctly predicted by the model using the parameters (Henry consts. and mol. vols.) derived from anal. of the single-component isotherms. The model predicts that mixts. of 2 sorbates with equal mol. vols. should show approx. ideal soln. behavior in the adsorbed phase. The exptl. data of P.B. Lederman (1961) for the sorption of N-CH4 mixts. show the expected behavior over a wide range of pressures.
40. 40

    Ruthven, D. M. A simple theoretical isotherm for zeolites: further comments. Zeolites 1982, 2, 242– 243,  DOI: 10.1016/S0144-2449(82)80062-6

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    A simple theoretical isotherm for zeolites: further comments

    Ruthven, Douglas M.

    Zeolites (1982), 2 (4), 242-3CODEN: ZEOLD3; ISSN:0144-2449.

    A simplified statistical model adsorption isotherm, appropriate to zeolitic systems in which the cages of the zeolite can be considered as distinct non-interacting sub-systems, is proposed. When the ratio of cage vol. to effective mol. vol. of sorbate is small, the isotherm reduces to Langmuir's equation while for large values of this ratio it approaches the Volmer form. The model is shown to provide a good representation of exptl. isotherms for C6H6 on 13-X zeolite.
41. 41

    Langmi, H.; Walton, A.; Al-Mamouri, M.; Johnson, S.; Book, D.; Speight, J.; Edwards, P.; Gameson, I.; Anderson, P.; Harris, I. Hydrogen adsorption in zeolites A, X, Y and RHO. J. Alloys Compd. 2003, 356–357, 710– 715,  DOI: 10.1016/S0925-8388(03)00368-2

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    Hydrogen adsorption in zeolites A, X, Y and RHO

    Langmi, H. W.; Walton, A.; Al-Mamouri, M. M.; Johnson, S. R.; Book, D.; Speight, J. D.; Edwards, P. P.; Gameson, I.; Anderson, P. A.; Harris, I. R.

    Journal of Alloys and Compounds (2003), 356-357 (), 710-715CODEN: JALCEU; ISSN:0925-8388. (Elsevier Science B.V.)

    We have investigated the use of zeolites as potential hydrogen storage materials. The zeolites A, X, Y and rho, which encompass a range of different pore geometries and compns., were synthesized by hydrothermal methods, and different cation-exchanged forms were prepd. by ion-exchange from aq. metal nitrate solns. The phase compn. and crystallinity of samples were investigated by powder x-ray diffraction. SEM revealed cubic crystals of zeolites both before and after ion-exchange. Hydrogen adsorption capacities were measured using a const. pressure thermogravimetric analyzer; data were obtained over a range of pressures from 0 to 15 bar and isothermally at temps. from -196 to 300°. The results showed that hydrogen uptake in zeolites is strongly dependent upon temp., and also on framework and cation type. Surface area measurements were also carried out on these materials and the results were used to interpret the hydrogen adsorption data.
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    Breck, D. W.; Grose, R. W. A Correlation of the Calculated Intracrystalline Void Volumes and Limiting Adsorption Volumes in Zeolites. Advances in Chemistry 1973, 121, 319– 329,  DOI: 10.1021/ba-1973-0121.ch029

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    Correlation of the calculated intracrystalline void volumes and limiting adsorption volumes in zeolites

    Breck, D. W.; Grose, R. W.

    Advances in Chemistry Series (1973), 121 (Mol. Sieves, Int. Conf., 3rd), 319-29CODEN: ADCSAJ; ISSN:0065-2393.

    The limiting adsorption vols. for various adsorbates (H2O, N, O, neopentane) in the zeolites A, X, L, mordenite, omega, and synthetic offretite were detd. from isotherms. These were compared with the void vols. calcd. from the known crystal structures. For most adsorbates, the measured and calcd. void vols. agree. However, He and N exhibit anomalous behavior. A void vol.-framework d. relation for zeolites is given.
43. 43

    Langmuir, I. The Adsorption of Gases on Plane Surfaces of Glass, Mica and Platinum. J. Am. Chem. Soc. 1918, 40, 1361– 1403,  DOI: 10.1021/ja02242a004

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    The adsorption of gases on plane surfaces of glass, mica and platinum

    Langmuir, I.

    Journal of the American Chemical Society (1918), 40 (), 1361-1402CODEN: JACSAT; ISSN:0002-7863.

    According to L.'s hypothesis, gaseous mols. impinging on a liquid or solid surface do not in general rebound from it elastically, but are held or adsorbed on the surface by forces similar to those holding the atoms or group mols. of solid bodies. The adsorbed film should not exceed one mol. in thickness. Adsorption of permanent gases involves only secondary valence forces. In metals particularly, adsorption may be governed by primary valence forces. It is suggested that stoichiometric relations should govern the adsorption on a surface unless interfering effects caused by steric hindrance are involved. At room temp. the absorption by glass and mica was negligible, not over 1 % of the surface being covered by a single layer of mols. At lower temps. much larger quantities of gas were taken up. With Pt no absorption was observed at - 183° unless the Pt were first activated by proper heating. The adsorption of O2 was irreversible and corresponded to a monomolecular layer. CO likewise showed the same behavior. In the presence of one or the other gas adsorbed on the Pt the adsorbed and unadsorbed gases reacted immediately to form CO2.
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    Bard, Y. Nonlinear Parameter Estimation; Academic Press: New York, 1973.

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    Kresnawahjuesa, O.; Olson, D.; Gorte, R.; Kühl, G. Removal of tetramethylammonium cations from zeolites. Microporous Mesoporous Mater. 2002, 51, 175– 188,  DOI: 10.1016/S1387-1811(01)00467-X

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    Removal of tetramethylammonium cations from zeolites

    Kresnawahjuesa, O.; Olson, D. H.; Gorte, R. J.; Kuhl, G. H.

    Microporous and Mesoporous Materials (2002), 51 (3), 175-188CODEN: MIMMFJ; ISSN:1387-1811. (Elsevier Science B.V.)

    Zeolite α (high-silica LTA), a potential shape-selective catalyst, is synthesized in the presence of tetramethylammonium (TMA) ions. Since TMA+ ions are incapable of forming olefins at low temp., temps. in excess of 500 °C are required to thermally decomp. them and burn off the carbonaceous deposits, frequently causing damage to the structure. In this paper, the thermal decompn. of zeolitic TMA+ ions is investigated. This work led to a less severe method for removing TMA+ ions by stepwise reaction with ammonia at low temps. TMA+ ions located in the supercage can easily be removed at a temp. as low as 250 °C, generating mono- and dimethylamine. Sodalite cage TMA+ ions require a temp. of not more than 400 °C to be degraded. Although this treatment raises the Si/Al ratio somewhat, damage to the structure is minimal. Since the size of the zeolitic pores defines the type of mols. capable of escaping from the zeolite cavities, decompn. of TMA+ ions in NaTMA-Y and NaTMA-high-silica sodalite have been included for comparison.
46. 46

    Barrer, R. M.; Davies, J. A.; Rees, L. V. Comparison of the ion exchange properties of zeolites X and Y. J. Inorg. Nucl. Chem. 1969, 31, 2599– 2609,  DOI: 10.1016/0022-1902(69)80593-2

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    Comparison of the ion exchange properties of zeolites x and y

    Barrer, Richard Maling; Davies, John Alwyn; Rees, Lovat V. C.

    Journal of Inorganic and Nuclear Chemistry (1969), 31 (8), 2599-609CODEN: JINCAO; ISSN:0022-1902.

    Thermodynamic and thermochem. aspects have been compared for exchanges of the monovalent cations Li+, Na+, K+, Rb,+ and Cs+, and the divalent ions Ca2+, Sr2+, and Ba2+ in zeolite Na-X contg. initially 87 Na+ ions per unit cell and in zeolite Na-Y contg. initially 52 Na+ and 5 H+ per unit cell. These 2 zeolites both have the aluminosilicate framework of faujasite, so that the comparison has served to show effects of changing the cation ds. upon heats, standard free energies, standard entropies, and selectivities of the exchange reaction. Explanations were possible for most of the observed differences.
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    Baur, W. H. On the cation and water positions in faujasite. Am. Mineral. 1964, 49, 697– 704

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    On the cation and water positions in faujasite

    Baur, Werner H.

    American Mineralogist (1964), 49 (), 697-704CODEN: AMMIAY; ISSN:0003-004X.

    The structure of faujasite was refined from the data of Bergerhoff, et al. (CA 53, 19717f). Faujasite has the most open silicate framework known. Approx. 40% of exchangeable cations occupy a position (occupancy 0.54) within the cubeoctahedral aluminosilicate cage, whereas 16% of the H2O mols. occupy one position within and one outside the cage. The remaining cations and H2O mols. are randomly distributed through the aluminosilicate framework.
48. 48

    Rima, D.; Djamal, D.; Fatiha, D. Synthesis of high silica zeolites using a combination of pyrrolidine and tetramethylammonium as template. Mater. Res. Express 2019, 6, 035017,  DOI: 10.1088/2053-1591/aaf497

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    Synthesis of high silica zeolites using a combination of pyrrolidine and tetramethylammonium as template

    Rima, Djari; Djamal, Dari; Fatiha, Djafri

    Materials Research Express (2019), 6 (3), 035017/1-035017/7CODEN: MREAC3; ISSN:2053-1591. (IOP Publishing Ltd.)

    High silica ZSM-39 (MTN structure), ZSM-35 (FER structure) and ZSM-5(MFI structure) zeolites were successfully synthesized using pyrrolidine and tetramethylammonium as structure directing agents (SDAs), in absence of alk. cation and fluoride medium. The effect of the relative amt. of tetramethylammonium and pyrrolidine, and Si/Al molar ratio on the cryst. phases was investigated. All structures could be synthesized using pyrrolidine as solely SDA. On the other hand, when a mixed template system being used, the crystn. was accelerated by a factor of 2 times, TMA+ would then play a generally beneficial but structurally non-specific role in the crystn. spicily for FER and MFI zeolites. The obtained products were characterized by XRD, 13C solid-state CP MAS NMR, TGA and SEM techniques. The XRD patterns confirmed the formation of pure zeolites with high crystallinity. 13C CP MAS NMR spectroscopy confirmed the incorporation of pyrrolidine and tetramethylammonium in the structure of Al-ZSM-5 and Al-ZSM-35 zeolites. These two kinds of SDAs played a cooperative role in the crystn. of these zeolites. The role of pyrrolidine was to provide the initial nucleation and tetramethylammonium to provide both space-filling and basicity capacities.
49. 49

    Zafar, M. S.; Zahid, M.; Athanassiou, A.; Fragouli, D. Biowaste-Derived Carbonized Bone for Solar Steam Generation and Seawater Desalination. Adv. Sustain. Syst 2021, 5, 2100031  DOI: 10.1002/adsu.202100031

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    Nguyen, H. G. T.; Tao, R.; Zee, R. D. V. Porosity, Powder X-Ray Diffraction Patterns, Skeletal Density, and Thermal Stability of NIST Zeolitic Reference Materials RM 8850, RM 8851, and RM 8852. J. Res. Natl. Inst. Stand. Technol. 2021, 126, 1– 10,  DOI: 10.6028/jres.126.047

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    Verboekend, D.; Vilé, G.; Pérez-Ramírez, J. Mesopore Formation in USY and Beta Zeolites by Base Leaching: Selection Criteria and Optimization of Pore-Directing Agents. Cryst. Growth Des. 2012, 12, 3123– 3132,  DOI: 10.1021/cg3003228

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    Mesopore Formation in USY and Beta Zeolites by Base Leaching: Selection Criteria and Optimization of Pore-Directing Agents

    Verboekend, Danny; Vile, Gianvito; Perez-Ramirez, Javier

    Crystal Growth & Design (2012), 12 (6), 3123-3132CODEN: CGDEFU; ISSN:1528-7483. (American Chemical Society)

    Mol. criteria for the selection of org. pore-directing agents (PDAs) in NaOH leaching, i.e., desilication, were investigated on USY and beta zeolites of distinct aluminum contents (Si/Al = 15-385). PDAs prove particularly useful for FAU and BEA topologies since they serve a dual purpose: tailoring the mesopore structure while preventing realumination and amorphization of the crystals. An efficient PDA is pos. charged and contains ca. 10-20 carbon atoms, for example, TPA+ or CTA+. Compositional, textural, morphol., structural, and acidity studies performed on selected hierarchical zeolites confirmed the presence of extensive secondary porosity coupled to well-preserved zeolitic properties. Inclusion of TPA+ in the alk. soln. led to the largest preservation of the intrinsic zeolite properties, whereas CTA+ facilitates the reassembly of dissolved species during alk. treatment. Finally, we report the prepn. of mesoporous zeolites in a continuous-mode using a tubular reactor and a high-shear reactor, attaining productivities up to 100 times higher than in conventional batch prepn.
52. 52

    Do, D. D.; Do, H. D. Appropriate volumes for adsorption isotherm studies: The absolute void volume, accessible pore volume and enclosing particle volume. J. Colloid Interface Sci. 2007, 316, 317– 330,  DOI: 10.1016/j.jcis.2007.08.020

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    Appropriate volumes for adsorption isotherm studies: The absolute void volume, accessible pore volume and enclosing particle volume

    Do, D. D.; Do, H. D.

    Journal of Colloid and Interface Science (2007), 316 (2), 317-330CODEN: JCISA5; ISSN:0021-9797. (Elsevier)

    In adsorption studies the choice of an appropriate void vol. in the calcn. of the adsorption isotherm is very crucial. It is often taken to be the apparent vol. as detd. by the He expansion expts. Unfortunately this method has difficulties esp. when dealing with microporous solids, in which adsorption of He might become significant at ambient temps. The amt. adsorbed is traditionally obtained as the excess amt. and the term excess refers to the excess over the amt. occupying the apparent vol. that has the same d. as the bulk gas d. This could give rise to the max. in the plot of excess amt. vs. pressure under supercrit. conditions, and in some cases giving neg. excess. Such behavior is difficult to analyze because the excess amt. is not amenable to any classical thermodn. treatments. The authors will present a method to det. the abs. void vol., and in that sense this vol. is independent of temp. and adsorbate. The vol. that is accessible to the centers of gas mols. is also studied, and it is called the accessible vol. This vol. depends on the choice of adsorbate, and it is appropriate to use this vol. to calc. the pore d. because the authors can assess how dense the adsorbed phase is. In the quest to det. the abs. adsorption isotherm so that a thermodn. anal. can be applied, it is necessary to introduce the concept of enclosing vol., which is essentially the vol. that encloses all solid particles, including all void spaces in them. The amt. adsorbed is defined by the no. of mols. residing in this vol. Having these vols., the authors can derive the geometrical accessible void vol. inside the particle and the solid vol., from which the particle and solid densities can be calcd.
53. 53

    Do, D. D.; Do, H. D.; Fan, C.; Nicholson, D. On the Existence of Negative Excess Isotherms for Argon Adsorption on Graphite Surfaces and in Graphitic Pores under Supercritical Conditions at Pressures up to 10,000 atm. Langmuir 2010, 26, 4796– 4806,  DOI: 10.1021/la903549f

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    On the Existence of Negative Excess Isotherms for Argon Adsorption on Graphite Surfaces and in Graphitic Pores under Supercritical Conditions at Pressures up to 10,000 atm

    Do, D. D.; Do, H. D.; Fan, Chunyan; Nicholson, D.

    Langmuir (2010), 26 (7), 4796-4806CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)

    In this paper, we consider in detail the computer simulation of argon adsorption on a graphite surface and inside graphitic slit pores under supercrit. conditions. Exptl. results in the literature for graphitic adsorbents show that excess isotherms pass through a max. and then become neg. at high pressures (even for adsorption on open surfaces) when a helium void vol. is used in the calcn. of the excess amt. Here we show that, by using the appropriate accessible vol. (which is smaller than the helium void vol.), the excess isotherms still have a max. but are always pos. The existence and the magnitude of this max. is because the rate of change of the adsorbed d. is equal to that of the bulk gas, which has a large change in bulk gas d. for a small variation in pressure for temps. not far above the crit. point. However for temps. far above Tc, this change in the bulk gas d. is no longer significant and the max. in the surface excess d. becomes less pronounced and even disappears at high enough temps. The positivity of the adsorption excess persists for all pressures up to 10 000 atm for adsorption on surfaces and in slit pores of all sizes. For adsorption on a surface, the surface excess d. eventually reaches a plateau at high pressures as expected, because the change in the adsorbed phase is comparable to that of the bulk gas. Pos. excess lends support to our phys. argument that the adsorbed phase is denser than the bulk gas, and this is logical as the forces exerted by the pore walls should aid to the compression of the adsorbed phase.
54. 54

    Brandani, S.; Mangano, E.; Sarkisov, L. Net, excess and absolute adsorption and adsorption of helium. Adsorption 2016, 22, 261– 276,  DOI: 10.1007/s10450-016-9766-0

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    Net, excess and absolute adsorption and adsorption of helium

    Brandani, Stefano; Mangano, Enzo; Sarkisov, Lev

    Adsorption (2016), 22 (2), 261-276CODEN: ADSOFO; ISSN:0929-5607. (Springer)

    The definitions of abs., excess and net adsorption in microporous materials are used to identify the correct limits at zero and infinite pressure. Abs. adsorption is shown to be the fundamental thermodn. property and methods to det. the solid d. that includes the micropore vol. are discussed. A simple means to define when it is necessary to distinguish between the three definitions at low pressure is presented. To highlight the practical implications of the anal. the case of adsorption of helium is considered in detail and a combination of expts. and mol. simulations is used to clarify how to interpret adsorption measurements for weakly adsorbed components.
55. 55

    Nguyen, H. G. T.; Horn, J. C.; Bleakney, M.; Siderius, D. W.; Espinal, L. Understanding Material Characteristics through Signature Traits from Helium Pycnometry. Langmuir 2019, 35, 2115– 2122,  DOI: 10.1021/acs.langmuir.8b03731

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    Understanding Material Characteristics through Signature Traits from Helium Pycnometry

    Nguyen, Huong Giang T.; Horn, Jarod C.; Bleakney, Matthew; Siderius, Daniel W.; Espinal, Laura

    Langmuir (2019), 35 (6), 2115-2122CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)

    Although helium pycnometry is generally the method of choice for skeletal d. measurements of porous materials, few studies provided a wide range of case studies that demonstrate how to best interpret raw data and perform measurements using it. By examg. several different classes of materials, signature traits from helium pycnometry data are highlighted. Exptl. parameters important in obtaining the most precise and accurate value of skeletal d. from the helium pycnometer are as high as possible percent fill vol. and good thermostability. The degree of sample activation is demonstrated to affect the measured skeletal d. of porous zeolitic, carbon, and hybrid inorg.-org. materials. In the presence of a significant amt. of physisorbed contaminants (water vapor, atm. gases, residual solvents, etc.), which was the case for ZSM-5, MIL-53, and F400, but not ZIF-8, the skeletal d. tended to be overestimated in the low percent vol. region. The kinetic data (i.e., skeletal d. vs. measurement cycle) reveals distinctive traits for a properly activated vs. a nonactivated sample for all examd. samples: activated samples with a significant amt. of mass loss show a curved down plot that eventually reaches the equil. value, whereas nonactivated, nonporous, or extremely hydrophobic samples exhibit a flat line. This work illustrates how helium pycnometry can provide information about the structure of a material, and that, conversely, by knowing the structure of the material and its percent mass loss after activation (amt. of physisorbed contaminants), the behavior of activated and nonactivated samples in terms of skeletal d., percent fill vol., and measurement cycle can be predicted.
56. 56

    Malbrunot, P.; Vidal, D.; Vermesse, J.; Chahine, R.; Bose, T. K. Adsorbent Helium Density Measurement and Its Effect on Adsorption Isotherms at High Pressure. Langmuir 1997, 13, 539– 544,  DOI: 10.1021/la950969e

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    Adsorbent Helium Density Measurement and its Effect on Adsorption Isotherms at High Pressure

    Malbrunot, P.; Vidal, D.; Vermesse, J.; Chahine, R.; Bose, T. K.

    Langmuir (1997), 13 (3), 539-544CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)

    On the basis of exptl. study over a large temp. range, the authors conclude that "helium densities" of adsorbents measured at room temp. can be erroneous due to a non-negligible effect of He adsorption. The authors propose that the d. obtained with He at high temp. (e.g., at the regeneration temp. of the adsorbent) be considered as the adsorbent d. By using the cor. densities of 3A, 4A, 5A, and 13X zeolites and of activated and graphitized carbons and of silica gel, the authors exptl. detd. the adsorption of He on these adsorbents at room temp. and over a large pressure range ≤ 500 MPa. The shape of the adsorption isotherm reveals no satn. at high pressure. These exptl. data are in agreement with Monte Carlo simulations of adsorption of a Lennard-Jones gas by a rigid plane as well as by a microporous rigid solid interface. The authors also examd. implications of the new He d. of activated carbon for the previous measurements of adsorption at high pressure. The result is the disappearance of the inexplicable neg. part of the isotherms and even a renewed increase in the curves at high pressure. Moreover, a comparison with Monte Carlo simulations of Ar adsorption on microporous graphite is in good agreement with the shape of the adsorption curve at high pressure. Finally, the role of the microporous structure of adsorbents and of the gas-adsorbent interaction in adsorption at high pressure is discussed.
57. 57

    Thommes, M.; Kaneko, K.; Neimark, A. V.; Olivier, J. P.; Rodriguez-Reinoso, F.; Rouquerol, J.; Sing, K. S. W. Physisorption of gases, with special reference to the evaluation of surface area and pore size distribution (IUPAC Technical Report). Pure Appl. Chem. 2015, 87, 1051– 1069,  DOI: 10.1515/pac-2014-1117

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    Physisorption of gases, with special reference to the evaluation of surface area and pore size distribution (IUPAC Technical Report)

    Thommes, Matthias; Kaneko, Katsumi; Neimark, Alexander V.; Olivier, James P.; Rodriguez-Reinoso, Francisco; Rouquerol, Jean; Sing, Kenneth S. W.

    Pure and Applied Chemistry (2015), 87 (9-10), 1051-1069CODEN: PACHAS; ISSN:0033-4545. (Walter de Gruyter, Inc.)

    Gas adsorption is an important tool for the characterization of porous solids and fine powders. Major advances in recent years have made it necessary to update the 1985 IUPAC manual on Reporting Physisorption Data for Gas/Solid Systems. The aims of the present document are to clarify and standardise the presentation, nomenclature and methodol. assocd. with the application of physisorption for surface area assessment and pore size anal. and to draw attention to remaining problems in the interpretation of physisorption data.
58. 58

    Janssen, A. H.; Koster, A. J.; de Jong, K. P. Three-Dimensional Transmission Electron Microscopic Observations of Mesopores in Dealuminated Zeolite Y. Angew. Chemie Int. Ed. 2001, 40, 1102– 1104,  DOI: 10.1002/1521-3773(20010316)40:6<1102::AID-ANIE11020>3.0.CO;2-6

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    Three-dimensional transmission electron microscopic observations of mesopores in dealuminated zeolite Y

    Janssen, Andries H.; Koster, Abraham J.; De Jong, Krijn P.

    Angewandte Chemie, International Edition (2001), 40 (6), 1102-1104CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH)

    Three dimensional TEM results of the size, shape and connectivity of mesopores in a series of steamed and acid leaches Y zeolites are given. A quant. comparison between the 3D-TEM images and nitrogen physisorption is made.
59. 59

    Zeolite Y; Zeolyst International, 2014; https://www.zeolyst.com/our-products/standard-zeolite-powders/zeolite-y.html.

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    Mignon, P.; Geerlings, P.; Schoonheydt, R. Understanding the concept of basicity in zeolites. A DFT study of the methylation of Al-O-Si bridging oxygen atoms. J. Phys. Chem. B 2006, 110, 24947– 24954,  DOI: 10.1021/jp064762d

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    Understanding the concept of basicity in zeolites. A DFT study of the methylation of Al-O-Si bridging oxygen atoms

    Mignon, Pierre; Geerlings, Paul; Schoonheydt, Robert

    Journal of Physical Chemistry B (2006), 110 (49), 24947-24954CODEN: JPCBFK; ISSN:1520-6106. (American Chemical Society)

    DFT calcns. on a 4-ring cluster and on ONIOM models of faujasite were carried out to assess the concept of basicity in zeolites, exchanged with alkali cations. The considered reaction is the methylation of the Si-O-Al bridging oxygen by methanol and Me iodide. The reaction involves both the dissocn. of the H3C-OH or H3C-I bonds and the formation of the C-O-zeolite bond. The former involves the hardness of the alk. cation. The latter reflects the charge d. of the basic oxygen, well described by the "hard" descriptor: the mol. electrostatic potential. The harder is the alkali metal, the easier is the H3C-OH or H3C-I bond dissocn., and the lower is the basicity of the bridging oxygen, and thus the more difficult is the C-O-zeolite bond formation. The fact that these two processes compete has been established by comparing the energy profiles for the methylation with Me iodide and methanol. For methanol the role of the alk. metal on the bond dissocn. prevails because of the larger hardness of the OH group as compared to that of the iodine atom. For Me iodide the oxygen basicity prevails over the interaction of I with metal. This study clearly shows that in both exptl. and theor. studies the role of the Lewis acidity or hardness of the alkali metal ion and the role of the basicity of the framework oxygen have to be sepd. from each other for a good interpretation of zeolite basicity. Also, the hardness of the probe mol. is particularly important when considering the interaction with the alkali metal ion.
61. 61

    Subramanian Balashankar, V.; Rajagopalan, A. K.; de Pauw, R.; Avila, A. M.; Rajendran, A. Analysis of a Batch Adsorber Analogue for Rapid Screening of Adsorbents for Postcombustion CO₂ Capture. Ind. Eng. Chem. Res. 2019, 58, 3314– 3328,  DOI: 10.1021/acs.iecr.8b05420

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    Analysis of a Batch Adsorber Analogue for Rapid Screening of Adsorbents for Postcombustion CO2 Capture

    Subramanian Balashankar, Vishal; Rajagopalan, Ashwin Kumar; de Pauw, Ruben; Avila, Adolfo M.; Rajendran, Arvind

    Industrial & Engineering Chemistry Research (2019), 58 (8), 3314-3328CODEN: IECRED; ISSN:0888-5885. (American Chemical Society)

    A simplified proxy model based on a well-mixed batch adsorber for vacuum swing adsorption (VSA)-based CO2 capture from dry post-combustion flue gas is discussed. A graphic representation of model output allowed for the rationalization of broad process performance trends. Simplified model results were compared with a detailed VSA model which accounted for mass and heat transfer, column pressure drop, and column switching, to understand its potential and limitations. A new classification metric to identify whether an adsorbent can produce CO2 purity and recovery values which meet current US Department of Energy targets for post-combustion CO2 capture and to calc. corresponding parasitic, was developed. The model, which is evaluated within a few seconds, showed a classification Matthew correlation coeff. of 0.76 vs. 0.39, the best offered by any traditional metric. The model could also predict energy consumption within 15% accuracy of the detailed model for 83% of studied adsorbents. The developed metric and correlation were then used to screen the National Institute of Stds. and Technol./ARPA-E database to identify promising adsorbents for CO2 capture applications.
62. 62

    Azzan, H.; Rajagopalan, A. K.; L’Hermitte, A.; Pini, R.; Petit, C. Simultaneous Estimation of Gas Adsorption Equilibria and Kinetics of Individual Shaped Adsorbents. Chem. Mater. 2022, 34, 6671– 6686,  DOI: 10.1021/acs.chemmater.2c01567

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    Simultaneous estimation of gas adsorption equilibria and kinetics of individual shaped adsorbents

    Azzan, Hassan; Rajagopalan, Ashwin Kumar; L'Hermitte, Anouk; Pini, Ronny; Petit, Camille

    Chemistry of Materials (2022), 34 (15), 6671-6686CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)

    Shaped adsorbents (e.g., pellets, extrudates) are typically employed in several gas sepn. and sensing applications. The performance of these adsorbents is dictated by two key factors, their adsorption equil. capacity and kinetics. Often, adsorption equil. and textural properties are reported for materials. Adsorption kinetics are seldom presented due to the challenges assocd. with measuring them. The overarching goal of this work is to develop an approach to characterize the adsorption properties of individual shaped adsorbents with less than 100 mg of material. To this aim, we have developed an exptl. dynamic sorption setup and complemented it with math. models, to describe the mass transport in the system. We embed these models into a deriv.-free optimizer to predict model parameters for adsorption equil. and kinetics. We evaluate and independently validate the performance of our approach on three adsorbents that exhibit differences in their chem., synthesis, formulation, and textural properties. Further, we test the robustness of our math. framework using a digital twin. We show that the framework can rapidly (i.e., in a few hours) and quant. characterize adsorption properties at a milligram scale, making it suitable for the screening of novel porous materials.
63. 63

    Kim, M.; Cho, I.; Park, J.; Choi, S.; Lee, I. Influence of Surface Energetic Heterogeneity of Microporous Adsorbents on Adsorptive Separation of CO₂, CO, N₂, and H₂ from a Controlled-Combustion of Solid Wastes. Proceedings of the European Combustion Meeting 2015 2015, 1– 4

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    Pham, T. D.; Hudson, M. R.; Brown, C. M.; Lobo, R. F. Molecular basis for the high CO₂ adsorption capacity of chabazite zeolites. ChemSusChem 2014, 7, 3031– 3038,  DOI: 10.1002/cssc.201402555

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    Molecular Basis for the High CO2 Adsorption Capacity of Chabazite Zeolites

    Pham, Trong D.; Hudson, Matthew R.; Brown, Craig M.; Lobo, Raul F.

    ChemSusChem (2014), 7 (11), 3031-3038CODEN: CHEMIZ; ISSN:1864-5631. (Wiley-VCH Verlag GmbH & Co. KGaA)

    CO2 adsorption in Li-, Na-, K-CHA (Si/Al = 6, = 12), and silica chabazite zeolites was investigated by powder diffraction. Two CO2 adsorption sites were found in all chabazites with CO2 locating in the 8-membered ring (8MR) pore opening being the dominant site. Elec. quadrupole-elec. field gradient and dispersion interactions drive CO2 adsorption at the middle of the 8 MRs, while CO2 polarization due to interaction with cation sites controls the secondary CO2 site. In Si-CHA, adsorption is dominated by dispersion interactions with CO2 obsd. on the pore walls and in 8 MRs. CO2 adsorption complexes on dual cation sites were obsd. on K-CHA, important for K-CHA-6 samples due to a higher probability of two K+ cations bridging CO2. Trends in isosteric heats of CO2 adsorption based on cation type and concn. can be correlated with adsorption sites and CO2 quantity. A decrease in the hardness of metal cations results in a decrease in the direct interaction of these cations with CO2.
65. 65

    Wong-Ng, W.; Kaduk, J.; Huang, Q.; Espinal, L.; Li, L.; Burress, J. Investigation of NaY Zeolite with adsorbed CO₂ by neutron powder diffraction. Microporous Mesoporous Mater. 2013, 172, 95– 104,  DOI: 10.1016/j.micromeso.2013.01.024

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    Investigation of NaY Zeolite with adsorbed CO2 by neutron powder diffraction

    Wong-Ng, W.; Kaduk, J. A.; Huang, Q.; Espinal, L.; Li, L.; Burress, J. W.

    Microporous and Mesoporous Materials (2013), 172 (), 95-104CODEN: MIMMFJ; ISSN:1387-1811. (Elsevier Inc.)

    The crystal structure of dehydrated NaY zeolite (Na-FAU structure type) with and without adsorbed CO2 has been detd. at 4 K and at room temp. (RT) using neutron powder diffraction techniques. The CO2-contg. sample was prepd. at 195 K and 0.1 MPa pCO2 (dry ice sublimation conditions). Neutron diffraction data provides direct evidence that adsorption of CO2 results in significant migration of the extra-framework Na cations in the zeolite structure. At 4 K, 45 of the apparent 76 CO2/cell were located in two crystallog. independent sites bonding to the Na cations (Na10) in the supercage site II. While the CO2 mol. in the first site has a linear configuration interacting with Na10 via one terminal oxygen, the CO2 mol. in the second site appears to have a bent O-C-O configuration (148.3(3)°), with both oxygen atoms coordinating to two symmetry-related Na10. Using DFT total energy calcns., the authors found that the Na-CO2 interaction slightly facilitates the bending motion for CO2 by decreasing the energy cost for the 148.3(3)° bond angle by ≈0.2 eV/CO2. However, this Na-CO2 interaction is not enough to cause a 32° bond angle distortion in CO2 (the energy cost of ≈0.66 eV/CO2). The authors propose that rotational disorder plays a significant role in the appearance of the bent CO2, while a small bending is possible. These studies will help to provide a basis for interpreting CO2 adsorption phenomena in NaY and related zeolites.
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    Hu, G.; Zhao, Q.; Manning, M.; Chen, L.; Yu, L.; May, E. F.; Li, K. G. Pilot scale assessment of methane capture from low concentration sources to town gas specification by pressure vacuum swing adsorption (PVSA). Chem. Eng. J. 2022, 427, 130810,  DOI: 10.1016/j.cej.2021.130810

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    Pilot scale assessment of methane capture from low concentration sources to town gas specification by pressure vacuum swing adsorption (PVSA)

    Hu, Guoping; Zhao, Qinghu; Manning, Mitch; Chen, Li; Yu, Lanjin; May, Eric F.; Li, Kevin Gang

    Chemical Engineering Journal (Amsterdam, Netherlands) (2022), 427 (), 130810CODEN: CMEJAJ; ISSN:1385-8947. (Elsevier B.V.)

    Methane (CH4) is the second largest contributor to anthropogenic greenhouse gas (GHG) emissions. The sepn. of CH4 from nitrogen (N2) is crucial for the capture of CH4 from low concn. sources, such as coal seam gas, to reduce GHG emissions. Pressure vacuum swing adsorption (PVSA) provides a flexible and scalable method for CH4/N2 sepn. In this work, a novel adsorbent (ILZ) was used in a 112 kg scale PVSA pilot facility to test the feasibility of sepg. CH4 from low concn. sources (4.7-44.5%). A product purity of 44.5% CH4 and a methane recovery of 81% were achieved from a feed gas contg. just 4.7% CH4 via a 3-stage PVSA process. Such a product gas can then be transported using pipelines and used for either power generation or 4T town gases in China. The total energy consumption was 133 kJ per mol CH4 captured, which is 85% lower than its heating value (∼880 kJ/mol). This study demonstrates that the capture of CH4 from large but low concn. sources incentivises GHG emissions redn.