Using transient breakthrough experiments for screening of adsorbents for separation of C2H4/CO2 mixtures

Zandvoort, Ilona van; Ras, Erik‐Jan; Graaf, Robbert de; Krishna, Rajamani

doi:10.1016/j.seppur.2020.116706

Cited by 24 publications

(22 citation statements)

References 21 publications

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“…In addition, CO 2 as an impurity frequently exists in C 2 hydrocarbons. For example, CO 2 is inevitably generated in the transformation of CH 4 to C 2 H 2 and C 2 H 4 via oxidative coupling. − Therefore, removal of CO 2 from C 2 hydrocarbons is in great demand. For the mixtures mentioned above, adsorptive separation is considered as an energy/cost-saving technique.…”

Section: Introductionmentioning

confidence: 99%

Lanthanide–Organic Frameworks Featuring Three-Dimensional Inorganic Connectivity for Multipurpose Hydrocarbon Separation

et al. 2021

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Implementation of lanthanide−organic frameworks (LOFs) as solid adsorbents has been frequently handicapped by their permanent porosity being difficult to establish owing to the remarkable flexibility and diversity of lanthanide ions in terms of coordination number and geometry. Construction of robust LOFs with permanent porosity for industrially important hydrocarbon separation will greatly expand their application potential. In this work, by distributing N and O donors into an m-terphenyl skeleton, we rationally synthesized a heterofunctional linker, and constructed a pair of isostructural LOFs. Due to the inclusion of a rarely observed three-dimensional metal−carboxylate backbone serving as a highly connected inorganic secondary building unit, their permanent porosities were successfully established by diverse gas isotherms. They can be applied as separating media not only for natural gas purification and removal of carbon dioxide from C 2 hydrocarbons but also more importantly for single-step ethylene (C 2 H 4 ) purification from a three-component C 2 H n mixture during the adsorption process. The latter separation is very challenging and has been less reported in the literature. This work provides a unique example of LOFs featuring three-dimensional inorganic connectivity applied to multipurpose hydrocarbon separations.

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Section: Introductionmentioning

confidence: 99%

Lanthanide–Organic Frameworks Featuring Three-Dimensional Inorganic Connectivity for Multipurpose Hydrocarbon Separation

et al. 2021

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“…When P i 0 are used as the upper limits in the definite integrals in eq , these result in the same value of the adsorption potential π A / RT , which serves as a practical proxy for the spreading pressure π. The adsorbed phase mole fractions x i are then determined from A number of experimental investigations ,− for adsorption of CO 2 -containing binary mixtures in cation-exchanged zeolites demonstrate that the IAST does not provide quantitatively accurate estimates of component loadings and adsorption selectivities, S ads , defined by As an illustration, Figure a presents the experimental data of Wilkins and Rajendran for component loadings, q i , of CO 2 and N 2 for adsorption of CO 2 /N 2 mixtures in 13X zeolite at 296 K and total pressure p t = 97 kPa as a function of the mole fraction of CO 2 in the bulk gas phase, y 1 . The dashed lines are the IAST estimations using the experimental data on the unary isotherms.…”

Section: Introductionmentioning

confidence: 99%

Using Molecular Simulations for Elucidation of Thermodynamic Nonidealities in Adsorption of CO₂-Containing Mixtures in NaX Zeolite

Krishna

Baten

2020

ACS Omega

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Cation-exchanged zeolites are of potential use in pressure swing adsorption (PSA) technologies for CO 2 capture applications. Published experimental data for CO 2 /CH 4 , CO 2 /N 2 , and CO 2 /C 3 H 8 mixture adsorption in NaX zeolite, also commonly referred to by its trade name 13X, have demonstrated that the ideal adsorbed solution theory (IAST) fails to provide adequately accurate estimates of mixture adsorption equilibrium. In particular, the IAST estimates of CO 2 /CH 4 and CO 2 /N 2 selectivities are significantly higher than those realized in experiments. For CO 2 /C 3 H 8 mixtures, the IAST fails to anticipate the selectivity reversal phenomena observed in experiments. In this article, configurational-bias Monte Carlo (CBMC) simulations are employed to provide confirmation of the observed thermodynamic nonidealities in adsorption of CO 2 /CH 4 , CO 2 /N 2 , and CO 2 /C 3 H 8 mixtures in NaX zeolite. The CBMC simulations provide valuable insights into the root cause of the failure of the IAST, whose applicability mandates a homogeneous distribution of adsorbates within the pore landscape. By sampling 10 5 equilibrated spatial locations of individual guest molecules within the cages of NaX zeolite, the radial distribution functions (RDFs) of each of the pairs of guest molecules are determined. Examination of the RDFs clearly reveals congregation effects, wherein the CO 2 guests occupy positions in close proximity to the Na + cations. The positioning of the partner molecules (CH 4 , N 2 , or C 3 H 8 ) is further removed from the CO 2 guest molecules; consequently, the competition in mixture adsorption faced by the partner molecules is less severe than that anticipated by the IAST. The important message to emerge from this article is the need for quantification of thermodynamic nonideality effects in mixture adsorption.

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“…Despite the widespread usage of the IAST, a limited number of investigations have found that IAST estimates of component loadings for mixture adsorption are not in quantitative agreement with experimental data. These studies include the adsorption of CO 2 /N 2 , CO 2 /CH 4 , − CO 2 /C 3 H 8 , − CO 2 /C 2 H 4 , − CO 2 /H 2 S, and H 2 S/C 3 H 8 mixtures in cation-exchanged zeolites such as NaX (commonly known by its trade name 13X), LTA-5A, ZSM-5, and H-MOR.…”

Section: Introductionmentioning

confidence: 99%

How Reliable Is the Ideal Adsorbed Solution Theory for the Estimation of Mixture Separation Selectivities in Microporous Crystalline Adsorbents?

Krishna

Baten

2021

ACS Omega

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Microporous crystalline adsorbents such as zeolites and metal–organic frameworks (MOFs) have potential use in a wide variety of separation applications. The adsorption selectivity S ads is a key metric that quantifies the efficacy of any microporous adsorbent in mixture separations. The Ideal Adsorbed Solution Theory (IAST) is commonly used for estimating the value of S ads , with unary isotherms of the constituent guests as data inputs. There are two basic tenets underlying the development of the IAST. The first tenet mandates a homogeneous distribution of adsorbates within the pore landscape. The second tenet requires the surface area occupied by a guest molecule in the mixture to be the same as that for the corresponding pure component. Configurational-bias Monte Carlo (CBMC) simulations are employed in this article to highlight several scenarios in which the IAST fails to provide a quantitatively correct description of mixture adsorption equilibrium due to a failure to conform to either of the two tenets underpinning the IAST. For CO 2 capture with cation-exchanged zeolites and MOFs with open metal sites, there is congregation of CO 2 around the cations and unsaturated metal atoms, resulting in failure of the IAST due to an inhomogeneous distribution of adsorbates in the pore space. Thermodynamic non-idealities also arise due to the preferential location of CO 2 molecules at the window regions of 8-ring zeolites such as DDR and CHA or within pockets of MOR and AFX zeolites. Thermodynamic non-idealities are evidenced for water/alcohol mixtures due to molecular clustering engendered by hydrogen bonding. It is also demonstrated that thermodynamic non-idealities can be strong enough to cause selectivity reversals, which are not anticipated by the IAST.

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Using transient breakthrough experiments for screening of adsorbents for separation of C2H4/CO2 mixtures

Cited by 24 publications

References 21 publications

Lanthanide–Organic Frameworks Featuring Three-Dimensional Inorganic Connectivity for Multipurpose Hydrocarbon Separation

Lanthanide–Organic Frameworks Featuring Three-Dimensional Inorganic Connectivity for Multipurpose Hydrocarbon Separation

Using Molecular Simulations for Elucidation of Thermodynamic Nonidealities in Adsorption of CO₂-Containing Mixtures in NaX Zeolite

How Reliable Is the Ideal Adsorbed Solution Theory for the Estimation of Mixture Separation Selectivities in Microporous Crystalline Adsorbents?

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Using transient breakthrough experiments for screening of adsorbents for separation of C2H4/CO2 mixtures

Cited by 24 publications

References 21 publications

Lanthanide–Organic Frameworks Featuring Three-Dimensional Inorganic Connectivity for Multipurpose Hydrocarbon Separation

Lanthanide–Organic Frameworks Featuring Three-Dimensional Inorganic Connectivity for Multipurpose Hydrocarbon Separation

Using Molecular Simulations for Elucidation of Thermodynamic Nonidealities in Adsorption of CO2-Containing Mixtures in NaX Zeolite

How Reliable Is the Ideal Adsorbed Solution Theory for the Estimation of Mixture Separation Selectivities in Microporous Crystalline Adsorbents?

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Using Molecular Simulations for Elucidation of Thermodynamic Nonidealities in Adsorption of CO₂-Containing Mixtures in NaX Zeolite