Single-component Adsorption Isotherms Research Articles

Influence of Carbon Uniformity on Its Characteristics and Adsorption Capacities of CO2 and CH4 Gases

Activated carbons of resorcinol-formaldehyde aerogels (AC-RFA) were prepared and mixed with multiwall carbon nanotubes (MWCNTs) with various ratios. Samples were characterized by different techniques. The novelty of the study is in evaluating the effect of uniformity of carbon nanocomposites on their performance for the adsorption of CH4 and CO2 gases as well predicting the separation of their mixtures. The results indicated that, by increasing the percentage of MWCNTs into the sample, its structural uniformity and order ascend. The capacities of CH4 and CO2 by adsorption were measured at various temperatures, and were correlated with the extended dual site Langmuir (DSL) model. Overall, results showed that the adsorption capacity of MWCNTs towards gases is relatively very low compared to that of activated carbons. The DSL model was utilized to forecast the separation of the binary CO2/CH4 mixed gas based on knowledge of single component adsorption isotherm parameters. Adsorption equilibrium data of the CO2/CH4 binary gas mixture was forecasted at different temperatures by DSL model in accordance with the perfect-negative (PN) or perfect-positive (PP) behaviors on the heterogeneous surface of the adsorbent.

Kinetic separation of C4 olefins using Y-fum-fcu-MOF with ultra-fine-tuned aperture size

The separation of C4 olefin mixtures into pure components is one of the most challenging processes in chemical industries. Adsorption-based separation, using ultra-microporous materials, is considered as a viable alternative to reduce the operating cost of the currently employed but energy intensive distillation technique. The understanding of structural properties-relationships for C4 olefins separation using solid state materials is still lacking particularly for microporous materials with purely cage-based structures. Herein, the adsorptive separation of C4 olefins (butene isomers and 1,3-butadiene) by the microporous MOF, Y-fum-fcu-MOF, containing octahedral and tetrahedral cages with triangular pore aperture size (≈4.7 Å), is studied. The adsorption capacities of the MOF for C4 olefins were assessed by measuring the single component adsorption isotherms at 30 °C which led to very similar equilibrium adsorption uptakes at saturation for the components (excluding isobutylene). However, adsorption breakthrough curves collected at 25 °C and Pulse Gas Chromatography experiments, conducted to define the guest–host affinity at very low concentration (Henry’s region), evidenced kinetically driven separation of C4 olefins by Y-fum-fcu-MOF. In fact, a strong relation between pores window size, kinetic diameter of the components and their adsorption behavior was observed. The breakthrough capacity decreases at increasing molecular size, allowing the separation of cis- and trans-2-butene despite the quite similar adsorption enthalpies for these components (42.0 and 37.7 kJ/mol, respectively).

CO2 capture on natural zeolite clinoptilolite: Effect of temperature and role of the adsorption sites

In this study, the adsorption capacity of the low-cost zeolite clinoptilolite was investigated for capturing carbon dioxide (CO2) emitted from industrial processes at moderate temperature. The CO2 adsorption capacity of clinoptilolite (a commercial natural zeolite) and ion-exchanged (with Na+ and Ca2+) clinoptilolite were tested under both dynamic (using a fixed-bed reactor operating with 10% vol. CO2 in N2) and equilibrium conditions (measuring single component adsorption isotherms). The dynamic CO2 adsorption capacity of bare clinoptilolite and ion-exchanged clinoptilolite were evaluated in the temperature range from 293 K to 338 K and the obtained breakthrough curves were compared with those of the commercial zeolite 13X (Z13X). Although the adsorption capacity of Z13X exceeded those of bare clinoptilolite and ion-exchanged clinoptilolite at 293 K, the clinoptilolite exhibited the highest CO2 uptake at a moderate temperature of 338 K (i.e. 25 % higher than Z13X). This feature appears in agreement with the lower isosteric heat of CO2 adsorption on clinoptilolite compared to the other samples. The surface species affecting the qiso and adsorption capacity were investigated through the FTIR spectroscopy using CO2 as probe molecule. As a whole, it has been observed that CO2 forms linear adducts onto K+ and Mg2+ cations of the bare clinoptilolite, and carbonate-like species onto its basic sites. With the Na-exchanged clinoptilolite, Na+ ions led to a decrease in surface basicity and to the formation of both single (Na+···OCO) and dual (Na+···OCO⋯Na+) cationic sites available for the formation of linear adducts.As a result of the remarkable adsorption capacity of clinoptilolite at 338 K, this material appears to be a promising adsorbent for the direct CO2 removal from different flue gases sources operating at such temperatures.

Modification of the pore environment in UiO-type metal-organic framework toward boosting the separation of propane/propylene

The separation of propane (C3H8) from propylene (C3H6) to obtain high purity C3H6 as a petrochemical raw material is an important, but challenging process. In the traditional industrial process, the separation mainly relies on energy-intensive cryogenic distillation. One alternative process that is currently becoming more attractive in the separation of C3H6 is adsorptive separation technology. Using porous materials, especially C3H8 selective adsorbents, high purity C3H6 can be directly obtained and thus, significantly simplifies the process. Herein, a series of functionalized ligands were introduced into UiO-type materials to finely regulate the C3H8 separation performance. Single-component adsorption isotherms reveal that BUT-10 has a distinct binding affinity for C3H8 over C3H6 over a wide range of temperature from 298 to 338 K and thus, achieved by far the highest C3H8 capture capacity (105 cm3 g−1 at 0.1 bar and 298 K) reported among the C3H8-selective materials reported to date. A combination of Grand Canonical Monte Carlo and density-function theory simulations demonstrate that the favorable pore environment provided by the multiple host-guest interactions toward C3H8 result in the higher C3H8 binding affinity observed in the separation process. Breakthrough experiments indicate that BUT-10 can selectively separate C3H8 from C3H8/C3H6 (1/1 and 1/15, v/v) mixtures and thus, directly produces high purity C3H6 (>99.99%) under ambient conditions.

Electrically heated catalyst device

The performance of the MIL-101(Cr) loaded with cuprous oxide (Cu2O) nanoparticles was evaluated in both equilibrium and kinetic conditions for adsorption of propane and propylene via volumetric method. The single-component adsorption isotherms were measured at temperatures of 303, 323, 343 and 363 K and pressures up to 400 kPa. To correlate the experimental isotherm data points, temperature-dependent Sips model was applied, which exhibited high accuracy of prediction. The synthesized samples were characterized by XRD, BET, FE-SEM, EDS mapping and TEM techniques. The binary mixture adsorption behavior and selectivity of propane/propylene were calculated by using the ideal adsorbed solution theory (IAST). Obtained results showed that by increasing the loading of Cu2O nanoparticles up to 15 wt%, the propylene selectivity of MIL-101(Cr) was enhanced from 1.5 to 12.2 at 100 kPa and 303 K. Moreover, the optimum performance in terms of both adsorption capacity and selectivity was achieved using 12%[email protected](Cr) sample. Fast diffusion of the adsorbates, obtained by accurate fitting of the isothermal micropore model to the uptake curves data, along with reusability suggest the 12%[email protected](Cr) as a promising adsorbent for effective separation of propane/propylene mixture.

Adsorptive Separation of Geometric Isomers of 2-Butene on Gallate-Based Metal-Organic Frameworks.

The separation of mixed C4 olefins is a highly energy-intensive operation in the chemical industry due to the close boiling points of the unsaturated C4 isomers. In particular, the separation of trans/cis-2-butene is among the most challenging separation processes for geometric isomers and is of prime importance to increase the added value of C4 olefins. In this work, we report a series of isostructural gallate-based metal-organic frameworks (MOFs), namely, M-gallate (M = Ni, Mg, Co), featuring oval-shaped pores, that are ideally suitable for shape-selective separation of trans/cis-2-butene through their differentiation in minimum molecular cross-section size. Significantly, Mg-gallate displays a record high trans/cis-2-butene uptake selectivity of 3.19 at 298 K, 1.0 bar in single-component adsorption isotherms. These gallate-based MOFs not only exhibit the highest selectivity for trans/cis-2-butene separation but also accomplish a highly efficient separation of 1,3-butadiene, 1-butene, and iso-butene. DFT-D study shows that Mg-gallate interacts strongly with trans-2-butene and 1,3-butadiene along with short distances of C···H-O cooperative supramolecular interaction of 2.57-2.83 and 2.45-2.79 Å, respectively. In breakthrough experiments, Mg-gallate not only displays prominent separation performance for trans/cis-2-butene but also realizes the clean separation of a ternary mixture of 1,3-butadiene/1-butene/iso-butene and a binary mixture of 1-butene/iso-butene. This work indicates that M-gallate are industrially promising materials for adsorption separation of geometric isomers of C4 hydrocarbons.

Separation of propane/propylene mixture using MIL-101(Cr) loaded with cuprous oxide nanoparticles: Adsorption equilibria and kinetics study

The performance of the MIL-101(Cr) loaded with cuprous oxide (Cu2O) nanoparticles was evaluated in both equilibrium and kinetic conditions for adsorption of propane and propylene via volumetric method. The single-component adsorption isotherms were measured at temperatures of 303, 323, 343 and 363 K and pressures up to 400 kPa. To correlate the experimental isotherm data points, temperature-dependent Sips model was applied, which exhibited high accuracy of prediction. The synthesized samples were characterized by XRD, BET, FE-SEM, EDS mapping and TEM techniques. The binary mixture adsorption behavior and selectivity of propane/propylene were calculated by using the ideal adsorbed solution theory (IAST). Obtained results showed that by increasing the loading of Cu2O nanoparticles up to 15 wt%, the propylene selectivity of MIL-101(Cr) was enhanced from 1.5 to 12.2 at 100 kPa and 303 K. Moreover, the optimum performance in terms of both adsorption capacity and selectivity was achieved using 12%Cu@MIL-101(Cr) sample. Fast diffusion of the adsorbates, obtained by accurate fitting of the isothermal micropore model to the uptake curves data, along with reusability suggest the 12%Cu@MIL-101(Cr) as a promising adsorbent for effective separation of propane/propylene mixture.

Ultrahigh-CO2 Adsorption Capacity and CO2/N2 Selectivity by Nitrogen-Doped Porous Activated Carbon Monolith

Abstract Among microporous adsorbents, N-doped activated carbon monolith has been developed to achieve functionalized nanoporous carbon via cross-linked polymer precursors, which are used in Friedel-Craft alkylation and pyrolysis. Nitrogen-doping is establish an efficient method for boosting the CO2 adsorption capacity of carbon-based adsorbents, and research in this area is still full of challenges to reach a fit doping level of nitrogen (N) and intrinsic microporosity. Herein is an easy method that enables the preparation of microporous nitrogen-doped porous carbon monolith with proportion of 4.6 wt% N, which employs poly (H-BINAM) as primary material. By virtue of chemical activation, high microporosity is generated and gives a monolithic structured porous nitrogen-doped activated carbon (MPC-700). The resulting material showed a remarkable CO2 adsorption capacity (6.74 mmol g−1 at 273 K and 5.18 mmol g−1 at 298 K under 1 bar), and an excellent CO2 over N2 selectivity (153), which is measured from single-component adsorption isotherms according to Henry’s Law. This value exceeds the CO2 over N2 selectivity of reported carbon-based adsorbents including diverse nitrogen doped examples, the features of which are largely associated with remarkably high N-content and furthermore partial graphitic framework.

Adsorption of Light Alkanes and Alkenes on Activated Carbon and Zeolite 13X at Low Temperatures

The separation of short-chained alkanes and alkenes is challenging because of their chemical similarity and thus being costly in energy. The implementation of a cryogenic adsorption process may overcome this problem, but systematic studies on light hydrocarbon adsorption at low temperatures are virtually lacking. Therefore, as a first step, in this paper, we present single-component adsorption isotherms of ethane, ethylene, propane, and propylene on activated carbon (AC) and zeolite 13X for temperatures of −80 to +20 °C and partial pressures of 5–1250 Pa. Based on these experimental data, the interactions of the adsorptives with the chemically different surfaces and their temperature dependence are discussed. Results show a strong increase in capacity with decreasing temperature for both AC and zeolite 13X. Cryogenic adsorption increases the overall (calculated) selectivity of alkane–alkene separation, especially for the zeolite 13X.

Grand Canonical Monte Carlo Modeling of Anesthetic Xe Separation from Exhale Gas Mixtures Using Metal Organic Frameworks

Xe has been shown to be a promising candidate for anesthetic applications. However, its high price prevents its usage in clinical industry. An alternative approach is to recover Xe from anesthetic exhale gas mixture and recycle it to the inhale gas stream. Although, many membranes and/or adsorbents have been proposed for recovering anesthetic Xe, using metal organic frameworks (MOFs) for adsorption based separation of anesthetic Xe exhale gas mixtures has been newly studied. MOFs have tunable pore sizes, large surface areas, and high porosities which make them potential candidates for gas separation applications. Currently, very little is known about anesthetic Xe recovery performances of MOFs. We theoretically investigate adsorption based separation of single component and binary mixtures of CO2, Xe, and N2 in three MOFs, namely CECYOY, SUDBOI, and ZUQPOQ. Single component and binary adsorption isotherms and adsorption selectivities are calculated using Grand Canonical Monte Carlo simulations for each MOF in order to characterize their performances as adsorbents. Results suggest that while MOFs prefer adsorption of CO2 for CO2/Xe mixture, Xe adsorption is favorable in the case of Xe/N2 mixture. While SUDBOI shows significantly large CO2 adsorption selectivity for CO2/Xe mixture, ZUQPOQ has the largest adsorption selectivity for Xe/N2 mixture.

Effect of Si/Al Ratio on the Catalytic Activity of Two‐Dimensional MFI Nanosheets in Aromatic Alkylation and Alcohol Etherification

AbstractZeolite catalysts with pronounced two‐dimensional (2D) morphologies, specifically 2D MFI nanosheets composed of multilamellar stacks of MFI nanosheets, are hypothesized to offer accessibility advantages in catalytic reactions involving large, bulky molecules. The Si/Al ratio of zeolite catalysts is an important parameter determining their performance. However, the effect of Si/Al ratio on catalytic reactivity is not well understood in 2D zeolite catalysts. To provide further insight into this issue, the catalytic performance of 2D MFI nanosheet materials with different Si/Al ratios is compared using the liquid phase Friedel‐Crafts alkylation of mesitylene with benzyl alcohol & the self‐etherification of benzyl alcohol that occurs in parallel, both of which are catalyzed by Brønsted acid sites. The turnover frequency (TOF) of the catalysts is found to decrease with decreasing Si/Al ratio, with the etherification reaction being the main contributor to this trend. When the same reaction is carried out in the presence of a bulky poison, 2,6 di‐tert‐butylpyridine (DTBP), to selectively deactivate the external acid sites, only the etherification reaction of benzyl alcohol takes place in the micropores of the 2D MFI catalyst and the effectiveness factor is found to decrease with decreasing Si/Al ratio. The single component adsorption isotherms of benzyl alcohol show that the uptake normalized per acid site decreases with decreasing Si/Al ratio. Thus, increasing the density of acid sites in the micropores by decreasing the Si/Al ratio makes it more difficult for the reactant molecules to access them, as demonstrated by the decrease in TOF and the effectiveness factor. While the micropore reactions (benzene alkylation, alcohol etherification) showed a clear trend with Si/Al ratio, the reaction catalyzed on the external surface (mesitylene alkylation) did not, showing distinct differences in reactivity.

Highly selective adsorption of CO over N2 on CuCl-loaded SAPO-34 adsorbent

Abstract Carbon monoxide (CO)/N2 separation is of importance for current chemical industry. However, CO/N2 separation remains a challenge due to the similar molecular size and the small variance of volatility of CO and N2. In this work, molecular sieve SAPO-34 was loaded with CuCl by monolayer dispersion method for the preparation of Cu(I) containing adsorbents. The resulted adsorbents were characterized via nitrogen adsorption/desorption at 77 K, X-ray fluorescence (XRF) and X-ray diffraction (XRD). The results indicated that CuCl was successful loaded into the molecular sieve and well-dispersed. CO and N2 single component adsorption isotherms were recorded under 298 K, 308 K and 318 K by using volumetric method. One of the CuCl-loaded SAPO-34 adsorbent exhibited a very high CO adsorption capacity of 1.84 mmol/g at 100 kPa, 298 K and high CO/N2 selectivity.

Adsorption Performance Indicator for Power Plant CO2 Capture on Graphene Oxide/TiO2 Nanocomposite

This study presents the adsorption performance indicator for the evaluation of thermal power plant CO2 capture on mesoporous graphene oxide/TiO2 nanocomposite. To begin, this adsorbent was synthesized and characterized using N2 adsorption-desorption measurements (BET and BJH methods), X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM) and FT-IR spectroscopy. Subsequently, the pure single-component adsorption isotherms measured at 298 K and the Ideal Adsorbed Solution Theory (IAST) solved with direct search minimisation were applied to estimate the selectivity of the synthesized mesoporous graphene oxide/TiO2 nanocomposite for CO2 over N2 and predict CO2 adsorption capacity in the CO2:N2 binary gas mixtures, including the molar ratio of 5:95, 10:90 and 15:85. Finally, the results validated by the breakthrough experiments at a fixed-bed column were applied to estimate the Adsorption Performance Indicator (API) for the evaluation of CO2 separation from N2 in the Pressure Swing Adsorption (PSA) process with respect to different types of thermal power plants.

Modeling the competitive adsorption of sample solvent and solute in supercritical fluid chromatography

Uncommon retention behavior of a series of n-alkylbenzene homologues as well as the effect of different sample solvents on chromatographic efficiency were studied in supercritical fluid chromatography. After testing various columns, an alkylamide stationary phase was selected for detailed studies. The results showed that even a small amount of methanol originating only from the sample, overloaded the column and competitive adsorption was induced between the analytes and the sample solvent for adsorption on the stationary phase. This was indicated by the changes in column efficiency, retention and peak widths. The concentration of the analytes in the sample was negligible compared to the amount of methanol – but their adsorption was influenced by the solvent – while the adsorption of methanol remained unaffected by the n-alkylbenzenes. First, the competition was described by determining the single-component adsorption isotherms for both the analytes and their solvent, then competitive isotherms were calculated. Based on the peak profiles, bi-Langmuir and competitive bi-Langmuir isotherms were assumed. The solvent effect was modeled by a numerical method created in-house where the differential mass balance equation given by the equilibrium–dispersive (ED) model was integrated using the Rouchon algorithm. The experimental observations were confirmed by in silico experiments and additional cases involving two hypothetical analytes were studied as well.

Stable fluorinated 3D isoreticular nanotubular triazole MOFs: synthesis, characterization and CO2 separation

Much of the efficient efforts have been largely devoted to enhancing the CO2 binding affinity in MOFs. In this paper, three isoreticular triazolate frameworks with the formula LIFM-1(TAZ).solvents, LIFM-1(MTAZ).solvents and LIFM-1(AmTAZ).solvents (TAZ = 1,2,4-triazole; MTAZ = 3-methyl-1H-1,2,4-triazole; AmTAZ = 3-amino-1H-1,2,4-triazole) have been prepared by using divalent zinc ions with the ligands of TAZ and its amino and methyl substituted derivatives for comparison of their sorption properties. High thermal stability and phase purity of the three MOFs were verified by thermogravimetric analysis and powder X-ray diffraction, respectively. Single component adsorption isotherms of N2, CO2 and H2 were also measured experimentally. Virial method shows that the porous frameworks of LIFM-1(AmTAZ) display high selectivity of CO2 over N2.

Utilization of zeolite as a potential multi-functional proppant for CO2 enhanced shale gas recovery and CO2 sequestration: A molecular simulation study on the competitive adsorption of CH4 and CO2 in zeolite and organic matter

It is well known that CO2 is one of the most effective enhanced hydrocarbon recovery agents due to its thermodynamic characteristics, and extensive research and pilot studies have been conducted in recent years on how to utilize CO2 for enhanced gas recovery in shales. The common delivery method involves injecting CO2 in its liquid or supercritial form into a shale formation. In this paper, we propose a novel approach to shale gas recovery that uses zeolite as a multi-functional proppant and carrier of adsorbed CO2 to enhance shale gas recovery as well as CO2 sequestration and storage. This process involves complex thermodynamic and transport processes, among which the competitive adsorption behaviors of CO2 and CH4 into organic matter and zeolite is the most critical to the success of the proposed approach.In this paper, we carry out a systematic molecular simulation study to investigate the adsorption behaviors of methane and CO2 into organic matter (kerogen) and silica zeolite (silicalite-1). We use grand canonical Monte Carlo simulations to measure single-component adsorption isotherms and calculate the isosteric heat of adsorption at surface temperature and at elevated temperatures of up to 425 K. Moreover, we simulate the competitive adsorption of binary mixtures of CH4 and CO2 with various compositions and investigate the competition between the two gas components in kerogen and silicalite-1. Both silicalite and kerogen show a stronger affinity for CO2 than for CH4. While the adsorption capacity of kerogen is about two times that of silicalite, the isosteric heat of adsorption demonstrates that the kerogen/CO2 interaction is the strongest among all four single-component adsorption systems. These findings demonstrate the great potential of using zeolite as a proppant and CO2 carrier to displace CH4 in shale organic matter under subsurface conditions. This observation is also validated via a competitive adsorption study, in which kerogen preferentially adsorbs CO2 over CH4 under all conditions and silicalite exhibits weaker CO2/CH4 selectivity, especially when the CO2 fraction is very low in the bulk phase.These results suggest the potential applicability of using zeolite as a proppant and CO2 carrier to enhance shale gas recovery. In reservoir conditions, the CO2 desorbed from zeolite can be favorably adsorbed by kerogen due to the increase in temperature and decrease in pressure; in the meantime, it can displace the adsorbed CH4 to enhance gas production.

Inverse Adsorption Separation of CO2/C2H2 Mixture in Cyclodextrin-Based Metal-Organic Frameworks.

The demand for CO2/C2H2 separation, especially the removal of CO2 impurity, continues to grow because of the high-purity C2H2 required for various industrial applications. The adsorption separation of C2H2 and CO2 via porous materials is gaining a considerable attention as it is more energy-efficient compared with cryogenic distillation. The ideal porous materials are those that preferentially adsorb CO2 over C2H2; however, very few adsorbents meet such requirement. Herein, two isostructural cyclodextrin-based CD-MOFs (CD-MOF-1 and CD-MOF-2) were demonstrated to have an inverse ability to selectively capture CO2 from C2H2 by single-component adsorption isotherms and dynamic breakthrough experiments. These two MOFs showed excellent adsorption capacity and benchmark selectivity (118.7) for CO2/C2H2 mixture at room temperature, enabling the pure C2H2 to be obtained in only one step. This work revealed that these materials were promising adsorbents for obtaining high-purity C2H2 via selectively capturing CO2 from C2H2.

Competitive adsorption of heavy metals in aqueous solution onto biochar derived from anaerobically digested sludge

Heavy metals often coexist in contaminated wastewater systems and their competitive behavior could affect the adsorption capacity of biochar. Till now, the competitive adsorption of heavy metals by biochar derived from anaerobically digested sludge has never been reported. In this work, biochar from anaerobically digested sludge was synthesized and characterized to explore the competitive behavior of widely co-existed Pb(II) and Cd(II). The mutual effects and inner mechanisms of their adsorption on studied biochar were systematically investigated via single-metal and binary-metals systems. In single-metal system, the biochar exhibited much higher adsorption capacity for Pb(II) compared to that for Cd(II). The maximum adsorption capacities of Pb(II) and Cd(II) based on single-component adsorption isotherm were 0.75 and 0.55 mmoL/g, respectively, which were much higher than those reported biochars from different materials. In binary-metals system, the Cd(II) adsorption on biochar was severely inhibited, while the uptake of Pb(II) was not affected significantly. The results of binary-components adsorption isotherm clearly demonstrated the competitive adsorption between two metals occurred as well as the preference of biochar for Pb(II) compared to Cd(II). FTIR and metal characteristics analysis results revealed that Pb(II) had exactly the same adsorption sites with Cd(II), but Pb(II) has a greater affinity than Cd(II), thereby exhibiting a competitive advantage in the coexisting system.

Competitive adsorption equilibrium modeling of volatile organic compound (VOC) and water vapor onto activated carbon

In this study, the Potential theory-based Manes method was used to describe competitive multicomponent adsorption of VOC and water vapor onto activated carbon. The thermodynamically consistent method was extended to water-miscible VOCs using a Raoult’s law-like relation. The method uses as input the pure single-component adsorption isotherms, which were obtained from the modified Dubinin-Radushkevich (MDR) model for VOCs and the Qi-Hay-Rood (QHR) model for water vapor. The MDR model was applicable for the studied VOCs (2-propanol, acetone, n-butanol, toluene, 1,2,4-trimethylbenzene) with an overall r2 value of 0.998. The QHR isotherm provided a good description for water vapor adsorption on activated carbon with 0.999 r2 value. Experimental validation tests revealed that the multicomponent adsorption isotherm model predicted the VOC adsorption capacity during competitive adsorption with water vapor with an overall mean relative absolute error (MRAE) of 1.9% for non-polar VOCs and 5.2% for polar VOCs. These results are encouraging, as they indicate a good agreement between modeled and experimental results. Hence, the model can potentially be integrated with dynamic adsorption models to optimize adsorber design and operation or model adsorption kinetics.

An indium-based ethane-trapping MOF for efficient selective separation of C2H6/C2H4 mixture

The purification of ethylene (C2H4) from the cracking gas ethane/ethylene mixture (1:15, v/v) is a typical energy-intensive process in the chemical industry. As an alternative, adsorptive separation with much lower energy consumption and operational cost has attracted escalating attention. In this work, we reported an interesting C2H6-trapping adsorbent, In-soc-MOF-1, an indium-based metal-organic framework exhibiting the preferential adsorption of C2H6 over C2H4. Single-component adsorption isotherms showed that the C2H6 adsorption capacities were higher than those of C2H4 under measured temperatures (288, 298 and 308 K). For example, the uptakes of C2H6 and C2H4 were 4.04 and 3.72 mmol/g at 298 K and 100 kPa, respectively. The calculated IAST selectivity of C2H6/C2H4 (1:15) on In-soc-MOF-1 was in the range of 1.4–4.8. Moreover, the dynamic separation performance of In-soc-MOF-1 toward the C2H6/C2H4 binary mixture was evaluated by the breakthrough experiments, the result of which suggests that In-soc-MOF-1 could achieve efficient separation by trapping the impurity C2H6 molecules out of the C2H6/C2H4 binary mixture. Notably, In-soc-MOF-1 not only showed good water and moisture stability but also exhibited excellent recyclability, where negligible decrease in C2H6 adsorption capacity was observed during five cycles of adsorption-desorption tests. These properties suggest that In-soc-MOF-1, as a C2H6-trapping adsorbent, could be considered as a potential candidate in the practical application of separating the cracking gas mixture.