CO2 Adsorption Isotherms Research Articles

Organic Mesopore and Micropore Structures and Their Effects on Methane Adsorption in Marine Organic-Rich Shales

Organic pores in organic-rich shale reservoirs can provide major pore space for adsorbed and free gas storage. In this study, the organic micropore and mesopore structures in organic-rich shale reservoirs and their influence on gas adsorption are investigated by comparing CO2, N2, and methane adsorption isotherms for organic matter-combusted and non-combusted organic-rich shale samples taken from the Wufeng–Longmaxi Formation in the Sichuan Basin. Experimental results show that organic pores in organic-rich shales from the Wufeng–Longmaxi Formation in Sichuan Basin are mainly smaller than 15 nm in diameters. Volumes of organic micropores and mesopores are mainly distributed in the diameter size ranges of 0.3–0.9 and 2–8 nm, respectively. Specific surface areas of organic micropores and mesopores are mainly distributed in the diameter size ranges of 0.3–0.7 and 2–4 nm, respectively. Organic pores dominate in the organic-rich shales from the Wufeng–Longmaxi Formation, contributing 49–77% and 50–84% of the entire micropore and mesopore volumes and specific surface areas, respectively. Organic micropores contribute 42–84% and 44–85% of the entire micropore volume and specific surface area, respectively, and organic mesopores contribute 48–84% and 59–89% of the entire mesopore volume and specific surface area, respectively. Organic pores are dominant pore spaces for adsorbed methane in organic-rich shale reservoirs and contribute 75–87% of the total amount of adsorbed methane in shales from the Wufeng–Longmaxi Formation. Outcomes of this study demonstrate that organic matter combustion is a useful method for evaluating organic pores in organic-rich shales mainly according to following lines of evidence: (1) after combustion, samples have low volumes and specific surface areas for micropores and mesopores as well as extremely low contents of adsorbed methane. This suggests that combustion does not result in the generation of <15 nm inorganic micropores and mesopores in clay minerals to provide pore space for adsorbed methane. (2) The total organic carbon content (TOC) positively correlates with the organic pore volume and specific areas as well as the absolute amount of methane adsorption, suggesting that organic pores determined in this study are mainly controlled by TOC values and combustion caused the removal of organic micropores and mesopores.

Study of pore structure of shale formation for CO2 storage

Carbon Geosequestration is considered a trending research area as it helps in mitigating the greenhouse gas effects on the environment by controlling global temperature. Recently, geo sequestration is considered one of the alternative ways to store CO2 for long periods. The shale is considered as the most suitable geological formation for CO2 storage due to its high adsorption capacity, microfractures, etc. Adsorption capacity in shale formation is highly influenced by pore structure, mineral composition, geomechanical properties, pressure, depth, etc. The shale pore structure is mainly dominated by mesopores (2–50 nm) and micropores (less than 2 nm). Storage of CO2 in the pores matrix is generally studied by using low-pressure N2 and CO2 adsorption isotherms, FE-SEM, etc. These techniques help in identifying types of pores, and their sizes, morphology, etc. Evaluation of pore microstructures helps to estimate the CO2 storage capacity in the formations. The present article discusses the importance of pore size, pore diameter, and pore volume distribution in shale formation for CO2 storage. A detailed review is carried out to analyze the methods of CO2 storage.

CRAFTED: An exploratory database of simulated adsorption isotherms of metal-organic frameworks

Grand Canonical Monte Carlo is an important method for performing molecular-level simulations and assisting the study and development of nanoporous materials for gas capture applications. These simulations are based on the use of force fields and partial charges to model the interaction between the adsorbent molecules and the solid framework. The choice of the force field parameters and partial charges can significantly impact the results obtained, however, there are very few databases available to support a comprehensive impact evaluation. Here, we present a database of simulations of CO2 and N2 adsorption isotherms on 690 metal-organic frameworks taken from the CoRE MOF 2014 database. We performed simulations with two force fields (UFF and DREIDING), six partial charge schemes (no charges, Qeq, EQeq, MPNN, PACMOF, and DDEC), and three temperatures (273, 298, 323 K). The resulting isotherms compose the Charge-dependent, Reproducible, Accessible, Forcefield-dependent, and Temperature-dependent Exploratory Database (CRAFTED) of adsorption isotherms.

Preparation of activated carbon from pine (Pinus radiata) sawdust by chemical activation with zinc chloride for wood dye adsorption

Wastewater containing dyes are released into water bodies generating serious problems in human health and marine life. To contribute to the solution of this problem, a novel activated carbon was prepared from untreated pine (Pinus radiata) sawdust by dry chemical activation with ZnCl2 and was used for wood dye adsorption. The carbon was characterized by point of zero charge, N2 and CO2 adsorption isotherms, SEM-EDX, and FTIR. N2 and CO2 surface areas were 471.4 and 319.5 m2 g−1, respectively, with 91% of micropores. Wood dye adsorption was studied in function of pH (2–12), adsorbent dose (0.1–4 g L−1), time (up to 48 h for blue and red and 12 h for black), and initial concentration (5–500 mg L−1). The equilibrium data for the blue and black dyes were satisfactorily fitted to the Freundlich model while those for the red dye to the Langmuir model. Kinetic data were explained by the pseudo-second order (chemisorption process) and intraparticle diffusion models. At 5 mg L−1, a 100% removal efficiency was achieved at all pH for the blue dye, whereas for the red and black, natural pH (5.1) and pH = 2, respectively, led to the best removal efficiencies, 96 and 56%. Increasing concentration above 25 mg L−1 significantly reduced adsorption efficiency for blue and red dyes. For the black dye increasing the dose to 1 g L−1, the adsorption efficiency reached 82% at 25 mg L−1. High removal efficiencies were achieved for all dyes at 25 mg L−1 and 4 g L−1.

Ideal Adsorbed Solution Theory (IAST) of Carbon Dioxide and Methane Adsorption Using Magnesium Gallate Metal-Organic Framework (Mg-gallate)

Ideal Adsorbed Solution Theory (IAST) is a predictive model that does not require any mixture data. In gas purification and separation processes, IAST is used to predict multicomponent adsorption equilibrium and selectivity based solely on experimental single-component adsorption isotherms. In this work, the mixed gas adsorption isotherms were predicted using IAST calculations with the Python package (pyIAST). The experimental CO2 and CH4 single-component adsorption isotherms of Mg-gallate were first fitted to isotherm models in which the experimental data best fit the Langmuir model. The presence of CH4 in the gas mixture contributed to a lower predicted amount of adsorbed CO2 due to the competitive adsorption among the different components. Nevertheless, CO2 adsorption was more favorable and resulted in a higher predicted adsorbed amount than CH4. Mg-gallate showed a stronger affinity for CO2 molecules and hence contributed to a higher CO2 adsorption capacity even with the coexistence of a CO2/CH4 mixture. Very high IAST selectivity values for CO2/CH4 were obtained which increased as the gas phase mole fraction of CO2 approached unity. Therefore, IAST calculations suggest that Mg-gallate can act as a potential adsorbent for the separation of CO2/CH4 mixed gas.

Development of mesoporous activated carbons derived from brewed coffee waste for CO2 adsorption

The primary cause of rising CO2 concentrations in the atmosphere is the use of fossil fuels in motor vehicles and factory activities in industry. CO2 levels in the atmosphere can be controlled and reduced by using low-carbon energy and capturing and storing CO2. One widely used way for CO2 capture and storage is adsorption method. This method necessitates the use of an adsorbent, one of which is activated carbon. In this study, brewed coffee waste was converted into activated carbons, characterized, and tested for carbon dioxide adsorption. Brewed coffee waste was dehydrated at 105 ºC for an hour before being carbonized at 550 °C and activated at 670, 700, and 730 °C, with a 200-ml/min nitrogen injection during activation. Activated carbons with activation temperatures of 670, 700, and 730 °C were denoted as AC-670, AC-700, and AC-730, respectively. A series of TGA, SEM, and adsorption isotherm tests were used to determine the proximate components, surface morphology, and surface structure of the activated carbons produced. To assess the adsorption capacities of activated carbon on CO2, the gravimetric CO2 adsorption isotherm method was used. According to the findings of the study, increasing activation temperatures cause variable properties in activated carbon. When using an activation temperature of 700 °C, the most appropriate properties of activated carbon can be obtained. It has 425.843 m2/g specific surface area, 0.345 cm3/g pore volume, 3.423 nm pore diameter, 235.628 cm3/g nitrogen adsorption capacity, and 4.183 mmol/g CO2 adsorption performance. This study provided a simple way converting brewed coffee waste into activated carbon with excellent performance for CO2 adsorption

Comparative studies on adsorption isotherm and kinetic for CO2 capture using iron oxide impregnated activated carbon

Activated carbon AC was treated with Kmn04 and the treated AC was used to be impregnated with iron oxide. The ratio of 0.1 M KMnO4 treatment on AC to the 0.1 M iron sulfate precursor (0.1KMnO4:0.1Fe) showed the most efficient adsorbent with an adsorption capacity of 108.60 mg/g. The CO2 adsorption isotherm at 25 °C was assessed with the adsorption isotherm model found that the Freundlich model to be the best fit which implies the multilayer adsorption onto heterogeneity surface. The adsorbent was used to perform CO2 adsorption at 30, 40, 50 and 70 °C in which the optimum adsorption temperature was at 30 °C. The decrease in adsorption capacity with increasing temperature indicates that a physisorption process takes place. The kinetic data for CO2 adsorption at different temperatures were well fitted to the pseudo-second-order kinetic. The adsorption was near to the chemisorption process based on the activation energy of 39.8 kJ/mol. It might be due to the weak interaction between CO2 and AC and strong bonding between CO2 and iron oxide. The adsorption capacity insignificantly reduced by 3.5% after four cycles showed practically efficient in CO2 capture.

MIL-160(Al) as a Candidate for Biogas Upgrading and CO2 Capture by Adsorption Processes

The microporous bioderived Al dicarboxylate MIL-160(Al) MOF in its shaped form has been evaluated as a candidate for biogas upgrading (BU) and/or carbon capture and storage (CCS) by studying adsorption isotherms of CO2, CH4, and N2 at 313, 343, and 373 K until 8 bar. The isotherms disclosed the following loading capacities: 4.2 (CO2), 2.07 (CH4), and 0.69 (N2) mol/kg at 5.8 bar and 313 K, which fitted with the dual-site Langmuir model. The linear-driving-force coefficients (LDFs) for CO2 and CH4 calculated from uptake rate experiments are in the order of 0.021–0.096 and 0.041–0.165 s–1 at 313 K between 0.11 and 2.76 bar, respectively. The Response Surface Methodology (RSM) was also applied to maximize the selectivity for mixtures CO2/CH4 and CO2/N2 with interest for BU or CCS. Breakthrough curve experiments with mixtures CO2/CH4 and CO2/N2 at the optimum selectivity conditions were developed and simulated using ASPEN Adsorption. This work clearly demonstrates the potential of MIL-160(Al) to be used in BU- and/or CCS-related applications.

Improving performance of mesoporous MOF AlTp impregnated with ionic liquids for CO2 adsorption

In this work, the CO2 adsorption performance of metal–organic frameworks (MOFs) impregnated with ionic liquids (ILs) was studied using quartz crystal microbalance (QCM) at the temperature of 298.15 K and pressures up to 5 bar. The hybrid composites consist of aluminum terephthalate metal–organic framework (AlTp) impregnated of 1-butyl-4-methyl pyridinium and 1-butyl-3-methylimidazolium–based ionic liquids (ILs) with different anions, viz. tetrafluoroborate ([BF4]−), thiocyanate ([SCN]−), chloride ([Cl]−), and bromide ([Br]−). ILs-impregnated AlTp synthesized was characterized using scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), the thermogravimetry analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. CO2 adsorption isotherms of the IL/AlTp composites and AlTp were measured to evaluate the ILs effect on the CO2 adsorption of the AlTp. Comparison of CO2 adsorption in ILs/AlTp with different anion ([Cl]−, [Br]−, [SCN]−, [BF4]−) reveals that CO2 adsorption in ILs/AlTp was increased in the order as: [BF4]− < [SCN]− < [Br]− < [Cl]−. The results show that [BMPyr][Cl]/AlTp the highest CO2 adsorption capacity, 2.6 times higher than that of AlTp at 5 bar and 298.15 K which helps to guide the logical design of new mixtures for gas separation applications. Also, adsorption/desorption test show that regeneration performance of [BMPyr][Cl]/AlTp is 96.53% after five consecutive cycles adsorption/desorption.

Fe-MOF with U-Shaped Channels for C2H2/CO2 and C2H2/C2H4 Separation.

The development of high-performance adsorbents is critical for the low-energy separation of acetylene. Herein, we synthesized an Fe-MOF (MOF, metal-organic framework) with U-shaped channels. The adsorption isotherms of C2H2, C2H4, and CO2 show that the adsorption capacity of acetylene is significantly larger than that of the other two gases. Meanwhile, the actual separation performance was verified by breakthrough experiments, indicating the potential to separate C2H2/CO2 and C2H2/C2H4 mixtures at normal temperatures. Grand Canonical Monte Carlo (GCMC) simulation demonstrates that the framework with U-shaped channels interacts more strongly with C2H2 than with C2H4 and CO2. The high C2H2 uptake and low adsorption enthalpy highlight Fe-MOF as a promising candidate for C2H2/CO2 separation with a low regeneration energy.

Triethylenetetramine-impregnated ZIF-8 nanoparticles for CO2 adsorption

One way to enhance the CO2 adsorption capacity of adsorbents is the incorporation of amines into the structure of the adsorbent. In this study, the impact of impregnation of zeolitic imidazolate framework (ZIF-8) with triethylenetetramine (TETA) over CO2 adsorption was surveyed. ZIF-8 and two TETA-impregnated ZIF-8 samples containing 10 wt% and 15 wt% of TETA were prepared and carefully characterized by Fourier-transform infrared (FTIR), X-ray diffraction (XRD), Thermogravimetric analysis (TGA), N2 adsorption-desorption, and Field emission scanning electron microscope (FESEM) techniques. The CO2 adsorption capacity of prepared adsorbents was examined at various temperatures and pressures using the static volumetric method. Outcomes indicated that at lower pressures than 2.5 bars, the CO2 adsorption capacity of TETA-impregnated ZIF-8 samples was slightly higher than ZIF-8, but by increasing the pressure the ZIF-8 sample showed a higher CO2 adsorption capacity in comparison with TETA-impregnated ZIF-8 samples. Also, CO2 adsorption isotherms of prepared adsorbents were investigated using the Monte Carlo method. Theoretical CO2 adsorption isotherms were similar to experimental ones. Additionally, the CO2 diffusion coefficient in prepared adsorbents was surveyed using molecular dynamics simulation. Results indicated that with the incorporation of TETA molecules in the ZIF-8 structure the diffusion coefficient of CO2 was decreased.

Breakthrough analysis for parameter estimation of CO2 adsorption on pelletized flexible metal–organic framework

Pellets of elastic layer-structured metal–organic framework-11 (ELM-11), one of the flexible metal–organic frameworks (MOFs), were prepared by mixing ELM-11 powder with a cellulose binder, and the CO2 adsorption behavior of ELM-11 pellets in a fixed-bed adsorber was analyzed to estimate equilibrium and kinetic parameters. Adsorption breakthrough tests were performed under various conditions for the simulated flue gas (20 % CO2–80 % N2) of a blast furnace gas in addition to CO2 isotherm measurements. Experimental CO2 adsorption isotherms on ELM-11 followed a weighted dual-site Langmuir equilibrium model well. The breakthrough analysis results by numerical calculation using the equilibrium model suggested that the gate-opening pressure of ELM-11 shifted to a lower pressure through repeated breakthrough tests. The CO2 adsorption kinetics on ELM-11 pellets agreed well with the linear-driving-force model. Furthermore, CO2 adsorption behavior under various conditions was described well by a mathematical model using a constant value of the mass transfer coefficient under the condition of this study, which was validated against additional experimental data. In addition, it was found that the mass transfer becomes slow under certain conditions that the driving force of the phase transition of ELM-11 is smaller than a threshold, where the amount of CO2 adsorbed on the breakthrough tests did not reach the equilibrium capacity of CO2, which may because the rate-limiting step may be dependent on the CO2 partial pressure and temperature.

Porous Polymer Supported Amino Functionalized Ionic Liquid for Effective CO2 Capture

A decrease in CO2 emissions is urgently required in the present situation due to the fast growth of carbon dioxide (CO2) in the atmosphere, which has caused a series of global climate issues. This study used an impregnation-evaporation method to immobilize an amino functionalized ionic liquid [C2OHmim][Lys] on a chromatographic column filler GDX-103 and create a novel supported ionic liquid. The results showed that the supported ionic liquid with 60 wt % ionic liquid content had the best adsorption performance at 40 °C, and the CO2 adsorption isotherm showed that the adsorption capacity at 0.1 MPa was 1.29 mmol CO2/g sorbent, which was 6 times greater than the adsorption capacity of the pure carrier. The sample with 60% ionic liquid content has an adsorption capacity of 1.02 mmol CO2/g sorbent under the condition of CO2/N2 mixed gas with 10% CO2 content. This is 43 times greater than the adsorption capacity of the pure carrier, and its adsorption performance is stable after three adsorption and desorption cycles. Through the rich porous structure of GDX-103, the ionic liquid is effectively supported and dispersed, which expands the contact area between CO2 and ionic liquid and enhances the mass transfer of CO2. At the same time, CO2 can be chemically bound to the groups on the anion of ionic liquid and be immobilized, so it has a high selective adsorption capacity of CO2, which makes it a great alternative to traditional CO2 adsorbents.

Adsorption Isotherm and Surface Analysis for the Carbonate Formation on Nano Coral Shaped Iron(III) Oxide

The α-Fe2O3 was synthesized using the hydrolysis method to obtain the nano coral-shaped morphology. The adsorption isotherm and surface analysis upon CO2 adsorption were identified. The adsorption capacity for nano coral-shaped α-Fe2O3 was measured at 8.66 cm3/g (17.00 mg/g). Experimental data from CO2 adsorption isotherm at 25 ℃ best fits with the Freundlich isotherm model which implies the adsorption process is favorable and the multilayer adsorption on the heterogeneous surface. A decrease in the α-Fe2O3 crystallite peaks in the X-ray diffractogram after the CO2adsorption was associated with the carbonate complexes species formation. IR spectra indicate higher intensities over the CO2 exposure time of 4, 12 and 24 h, especially at absorption bands 1041 and 1627 cm-1 that corresponded to C-O and asymmetry O-C-O stretches, respectively, for carbonate. The morphology of the carbonate formation on nano coral-shaped α-Fe2O3 over the CO2 exposure time was analyzed using FESEM-EDX. Although the carbonate formation was not distinct, the increment in the C element also confirmed the capability of the α-Fe2O3 in adsorbing CO2 for a long adsorption time of 24 h.

Aromatic Amine-Functionalized Covalent Organic Frameworks (COFs) for CO2/N2 Separation.

CO2 is a prominent example for an exhaust gas, and it is known for its high impact on global warming. Therefore, carbon capture from CO2 emissions of industrial processes is increasingly important to halt and prevent the disruptive consequences of global warming. Covalent organic frameworks (COFs) as porous nanomaterials have been shown to selectively adsorb CO2 in high quantities and with high CO2/N2 selectivity. Interactions with amines are recognized to selectively adsorb CO2 and help capture it from exhaust emissions. Herein, a novel COF (Me3TFB-(NH2)2BD), which was not accessible via a direct condensation reaction, was synthetized by dynamic linker exchange starting with Me3TFB-BD. Despite the linker exchange, the porosity of the COF was largely maintained, resulting in a high BET surface area of 1624 ± 89 m2/g. The CO2 and N2 adsorption isotherms at 273 and 295 K were studied to determine the performance in carbon capture at flue gas conditions. Me3TFB-(NH2)2BD adsorbs 1.12 ± 0.26 and 0.72 ± 0.07 mmol/g of CO2 at 1 bar and 273 and 295 K, respectively. The COF shows a high CO2/N2 IAST selectivity under flue gas conditions (273 K:83 ± 11, 295 K: 47 ± 11). The interaction of the aromatic amine groups with CO2 is based on physisorption, which is expected to make the regeneration of the material energy efficient.

Estimation of CO2 Separation Performances through CHA-Type Zeolite Membranes Using Molecular Simulation.

Chabazite (CHA)-type zeolite membranes are a potential material for CO2 separations because of their small pore aperture, large pore volume, and low aluminum content. In this study, the permeation and separation properties were evaluated using a molecular simulation technique with a focus on improving the CO2 separation performance. The adsorption isotherms of CO2 and CH4 on CHA-type zeolite with Si/Al = 18.2 were predicted by grand canonical Monte Carlo, and the diffusivities in zeolite micropores were simulated by molecular dynamics. The CO2 separation performance of the CHA-type zeolite membrane was estimated by a Maxwell-Stefan equation, accounting for mass transfer through the support tube. The results indicated that the permeances of CO2 and CH4 were influenced mainly by the porosity of the support, with the CO2 permeance reduced due to preferential adsorption with increasing pressure drop. In contrast, it was important for estimation of the CH4 permeance to predict the amounts of adsorbed CH4. Using molecular simulation and the Maxwell-Stefan equation is shown to be a useful technique for estimating the permeation properties of zeolite membranes, although some problems such as predicting accurate adsorption terms remain.

A 2D flexible cobalt-MOF: reversible solid-state structural transformation, two-step and gate-opening adsorption behaviours, and selective adsorption of C2H2 over CO2 and CH4.

A new 2D flexible cobalt(II) framework (Co-MOF) exhibits a reversible solid-state structural transformation upon guest molecule removal/uptake. After activation, Co-MOF-α with 1D porous channels transformed into Co-MOF-β (0D voids) accompanied by a shift in metal and carboxylate coordination modes, the rotation of organic linkers and the contraction of interstitial spaces. Gas adsorption experiments reveal that Co-MOF-β exhibits a two-step CO2 adsorption isotherm and close-to-open (type F-IV) isotherms for C2H2, C2H4 and C2H6 at 195 K. Moreover, it shows typical type I adsorption isotherms for the above gases and the selective uptake of C2H2 over CH4 and CO2 at room temperature.

Rapid synthesis of MCM-41 and SBA-15 by microwave irradiation: promising adsorbents for CO2 adsorption

It is known that the world scenario is one of constant search for sustainable technologies that can reduce the emission of carbon dioxide (CO2) in the atmosphere. This is because CO2 is seen as the main responsible for the increase in the generation of greenhouse gases, which leads to global warming and climate change. The development of efficient adsorbents for CO2 capture is a current challenge. MCM-41 and SBA-15 were synthesized in a microwave reactor and used as adsorbents in this work. Microwave irradiation presents itself as an easy synthesis strategy with less preparation time and energy requirement. The silica synthesis period was extremely reduced (1 h) at a temperature of 60 and 80 °C in the microwave reactor, obtaining silica with good textural and chemical properties. The CO2 adsorption isotherms were performed at 0, 25, and 40 °C at 1 bar. The MCM-41 and SBA-15 present favorable results for CO2 capture processes, showing that pure silica synthesized by microwave already obtains promising results, reaching a maximum adsorption capacity of 2.16 mmol g−1 (1 bar—0 °C) and a good fit for the Langmuir, DsL and Toth models. Furthermore, to increase CO2 adsorption, the mesoporous silica was also modified via impregnation with branched polyethylene diamine (PEI) or tetraethylenepentamine (TEPA). It is worth mentioning that microwave irradiation reduced the synthesis steps and improved the properties and adsorption capacity of the silica. This work opens new opportunities in the efficient preparation of materials that require optimizing the adsorbent synthesis process.Graphical CO2 adsorption capacity of MCM-41 and SBA-15 prepared by rapid synthesis using microwave irradiation and amino functionalized.

A Green, Economic Method for Bench-Scale Activation of a MIL-101(Cr) Nanoadsorbent

Research teams have been showing an increasing interest in using MIL-101(Cr) in a variety of applications, in recent years. Furthermore, the removal of unreacted terephthalic acid (ur-H2BDC) during post-synthesis purification is also among the greatest challenges in the synthesis of MIL-101(Cr), which if dealt with through simple, environmentally-friendly, and inexpensive methods can constitute a stride in the path to the commercial production and application of MIL-101(Cr). This research is focused on the development of a method based on the application of aqueous solutions of sodium bicarbonate (NaHCO3) with various concentrations, as well as applying various reaction times to remove ur-H2BDC to evaluate the efficiency of the method. The obtained results were compared to those of conventional activation methods, indicating the high efficiency of using a 0.06 M NaHCO3 solution for 24 h, which led to an acceptable BET surface area of 3271 m2·g–1 without any damages to the framework as indicated by X-ray diffraction (XRD) analysis. The study also provides a novel approach to quantifying ur-H2BDC residuals (trapped inside of framework pores) using back-titration (1.67% residual ur-H2BDC in 1 g of the nanoadsorbent). CO2, CH4, and N2 adsorption isotherms on the activated MILs were acquired using a volumetric laboratory facility at pressures ranging from 1 to 35 bar and 298 K. Data of the adsorption of CO2 on activated MIL-101(Cr)-NaHCO3 revealed great gas separation ability (23.1 mmol/g at 35 bar). According to the adsorbed ideal solution theory (IAST), the selectivity values of CO2/CH4 and CO2 /N2 were around 11.60 at 1 bar and 5.85 at 35 bar and 135.44 at 1 bar and 48.96 at 35 bar, respectively. Furthermore, the procedure was associated with bench-scale MIL-101(Cr) activation with satisfactory results.

Adsorption of CO2 and N2 on bimetallic Mg-Al hydrotalcites and Z-13X zeolites under high pressure and moderate temperatures

The adsorption of carbon dioxide on a commercial hydrotalcite (HT) was investigated using gravimetric analysis at 473 K, 573 K and 673 K and pressures up to 10 bar. The CO2 adsorption performance of HT was correlated with a wide range of physicochemical characterisation techniques. For further understanding and comparative purposes, the same adsorption and characterisation measurements are reported for a commercial zeolite 13X (Z-13X). The HT exhibited higher adsorption capacities per unit mass of sorbent at relatively low pressures and per unit surface area over the whole range of pressures analysed, compared to zeolite 13X. However, HT showed adsorption-desorption isotherms with a hysteresis loop indicating a stronger binding energy. The HT also presented deactivation upon cycling (up to ∼ 10%, depending on conditions) suggesting the need for future studies focused on improvement of its regenerability. The same performance regarding hysteresis and deactivation was observed in the presence of N2. The CO2 adsorption isotherms of HT were successfully fitted to the Freundlich model. The values of heat of adsorption calculated -56 and -84 kJ mol−1 for the 1st and 5th cycle, are indicative of a chemisorption process. The data of this work provide information regarding fundamentals of CO2 adsorption of the materials that is useful in the design of realistic adsorption units in conventional and novel H2Carbon Dioxide Capture processes, especially in the sorption-enhanced H2 reaction process.