CO2 Isotherms Research Articles

Multicomponent adsorption of H2, CH4, CO and CO2 in zeolites NaX, CaX and MgX. Evaluation of performance in PSA cycles for hydrogen purification

Abstract In PSA processes for hydrogen purification, adsorbents play an extremely important role. In this work, the impact of using different zeolites 13X, obtained through ion exchange, on the performance of a PSA process has been studied. Zeolite 13X (NaX) exchanged with Ca2+ (CaX) and with Mg2+ (MgX) were synthesized. The adsorption isotherms of H2, CH4, CO and CO2, as well as their diffusion constants in micropores in the three materials have been obtained. Then, multicomponent breakthrough curve experiments of a mixture of H2/CH4/CO/CO2 with a composition 75.89/4.01/3.03/17.07% vol. (analogous to the feed stream of an industrial PSA cycle of hydrogen production from steam methane reforming) were simulated using a mathematical model. Finally, the influence of the different cations in zeolite 13X on the performance of a hydrogen purification PSA unit with a multilayer bed (activated carbon/zeolite) has been studied by simulation, considering in each simulation a layer of zeolite NaX, CaX or MgX. Results have shown that zeolite CaX yields better PSA performance parameters in terms of hydrogen recuperation and productivity compared to the parental NaX zeolite and MgX zeolite.

Experimental validation of multi-objective optimization techniques for design of vacuum swing adsorption processes

The efficacy of multi-objective optimization techniques for designing adsorption-based gas separation processes is validated experimentally for the concentration of CO2 from a mixture of 15% CO2 + 85% N2 using two different vacuum swing adsorption (VSA) cycles. The isotherms of CO2 and N2 on Zeolite 13X pellets were measured using volumetry and their competition was characterized by dynamic column breakthrough experiments. A mathematical model that uses inputs from these experiments was combined with genetic algorithm to obtain the Pareto curves for the multi-objective optimization problem that aims to maximize CO2 purity and recovery. The decision variables corresponding to selected points on the Pareto curve were translated into experiments on a lab-scale two-column VSA rig containing 162 g of adsorbent in each column. The experimental performance indicators, viz., CO2 purity and recovery, and the transients of temperatures, outlet flow and composition showed very good match with the experiments thereby establishing multi-objective optimization approaches as a reliable way to design VSA separations.

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.

The carbon dioxide, methane and nitrogen high-pressure sorption properties of South African bituminous coals

In this paper, we report the CO2, CH4 and N2 sorption isotherms of four dry South African bituminous coals at pressures up to 16 MPa at 55 °C. The sorption capacities of the samples with respect to the adsorbate gases decreased in the order: CO2 > CH4 ≈ N2 by weight, and CO2 > CH4 > N2 by volume. A new model, based on a hybrid Dubinin-Radushkevich and Henry law approach (DR-HH) provided substantially better fits to the sorption isotherm data than the previously used modified DR (M-DR) model. Obtained uncertainty metrics show that the DR-HH model generally returned lower error sum of squares (ESS) and root mean square (RMS) residuals, and higher quality of fit (QOF) compared to the M-DR model. The net heat of sorption, βEs, of the samples for the three adsorbate gases were generally low (8.5–12.8 kJ/mol), but comparable to previous determinations of other coals, indicating that physisorption was the dominating sorption mechanism. The sorption capacities of the samples were found to be rank-dependent as they decreased with increasing vitrinite reflectance and elemental carbon content. The micropore properties of the samples as measured by both CO2 low-pressure gas adsorption (LPGA) and small angle X-ray scattering (SAXS), impacted the sorption properties of the sample more than both the mesopore and macropore properties determined from N2 LPGA, SAXS, and mercury intrusion porosimetry. The sorption capacities of the samples were found to increase with increasing lithotypes abundance, suggesting that lithotype bandings enhances either the fluid transport processes or the micropore properties of the coal matrix. In addition, it has been demonstrated that critical properties of the adsorbate gases influenced their sorption properties.

Adsorption of hydrogen sulfide, carbon dioxide, methane, and their mixtures on activated carbon

H2S and CO2 are acid contaminants of natural gas and biogas, which removal have been studied using adsorption data for monocomponent and binary mixtures. However, equilibrium adsorption data for H2S + CO2 + CH4 mixture has not been investigated yet. In this work, H2S and CO2 partition coefficients (K) and activated carbon (AC) selectivity (S) for H2S + CO2 + CH4 mixture separation at high-pressure and different temperatures were determined. To reach this goal, monocomponent isotherms for H2S, CO2 and CH4 on Brazilian babassu coconut hush AC were experimentally determined at different temperatures and pressures. Then, obtained data were correlated by Langmuir and Tóth models, and multicomponent adsorption was predicted using Extended Langmuir, Extended Tóth and Ideal Adsorption Solution Theory (IAST) methods. Results indicate AC captures approximately 26 wt% of H2S or CO2. K values for CO2 and H2S reached more than 3 and 26, respectively, depending on the predictive model utilized and were higher for diluted mixtures (high CH4 content in gas phase). S values for CO2 and H2S can reach values greater than 25 for Tóth + IAST. Furthermore, selectivity toward H2S is approximately 5.6 times greater than CO2. The effect of temperature on multicomponent results indicate K and S values decrease as temperature increases. Therefore, results obtained herein show that is possible to separate H2S and CO2 from mixture containing CH4 using this AC as adsorbent and better separation performance was observed for low H2S and CO2 concentrations and lower temperatures.

Electrical swing adsorption on functionalized hollow fibers

Temperature swing adsorption (TSA) is a favorable adsorption technique when applied for capturing CO2 but limited by long cycle times and low concentrations of the recovered adsorbate. Direct heating of the adsorbent can mitigate these drawbacks. Combined with the beneficial mass transfer of a hollow fiber geometry it offers a powerful sorption process. In this study, we combine the advantages of direct heating and the benefits of the hollow fiber geometry in electrically conducting hybrid hollow fibers. Two different solid sorbents are manufactured and characterized: polyethylenimine-impregnated silicon carbide fibers (SiC-PEI) and fibers consisting of a carbon nanotube matrix with dispersed zeolite particles (CNT-zeolite). Both fibers exhibit Joule heating properties and high adsorption capacities. The CO2 uptake, CO2 isotherms, and the kinetic behavior are examined. The maximum CO2 uptakes at 30 °C and 15 vol% CO2 are 8.3 mg/gfiber for SiC-PEI and 102.2 mg/gfiber for CNT-zeolite. A lab-scale module is designed and used to determine the CO2 capacity of a fiber bundle. The energy requirement to heat such a fiber bundle from ambient temperature to 80 °C is 3.1 J/gFiberK (SiC-PEI) and 15.8 J/gFiberK (CNT-zeolite). To investigate the suitability of the fibers for real process applicability, a mathematical model is established and simulation results are presented and discussed. The two different approaches prove to be viable options for CO2 separation. They are not limited to CO2 capture but can be expanded to other gas separation tasks.

Spherical activated carbons for the adsorption of a real multicomponent VOC mixture

The objective of this work is to study the adsorption of a multicomponent gaseous mixture (acetaldehyde, formaldehyde, 2-propenal, 1,3-butadiene and benzene) in which the components are present at different concentration on spherical activated carbons (SACs). Attention is paid to the influence of the carbons’ properties on such adsorption, especially their porosities and distributions. For this purpose, a series of spherical activated carbons were prepared by physical activation with CO2 of a commercial spherical carbon. Their physico-chemical properties were characterized by N2 and CO2 isotherms, temperature programmed desorption and scanning electron microscopy. Measurements of the adsorption of the volatile organic compounds (VOC) mixture on SACs were performed in a flow-typed fixed bed system at room temperature under atmospheric pressure. Regarding porosity, our results show that, for this particular mixture, SACs with narrow micropore size distribution and moderate porous texture development (surface area in the range of 1000 m2/g or even lower) exhibit higher multicomponent adsorption capacities than others with much larger porosities. This can be explained considering that the VOC present in larger concentration in the mixture, aldehydes, present low adsorption affinities and their adsorption is enhanced in adsorbents with narrow micropore size distribution.

Adsorption microcalorimetry as a tool in the characterization of amine-grafted mesoporous silicas for CO2 capture

In this work, amine-grafted mesoporous silica were investigated using a adsorption microcalorimetry and supplementary techniques in order to study the influence of increasing the density of grafted amine on the CO2 binding mechanisms. A Tian–Calvet microcalorimeter coupled to a manometric setup was used to evaluate the energetic heterogeneity of adsorption sites and to calculate the thermokinetic parameter from the differential enthalpy curves. With such device, equilibrium adsorption isotherms of CO2 were simultaneously measured at 25 °C for all samples up to 1 bar. The adsorption microcalorimetric study suggests a change in active sites distribution as the density of grafted amines increases. The maximum thermokinetic parameter of 471 s for the pure silica support at 30.7 kJ mol−1 suggests that physisorption is the dominant binding mechanism. A different behavior occurs with the grafted samples: they have considerably higher enthalpy values corresponding to the formation of reacted species on the surface (chemisorbed CO2), which depend on grafted amine density and available free surface silanols. Kinetics of formation of chemisorption products, together with hindered CO2 diffusion, seriously impair the approach to equilibrium, which leads to a decrease in uptake upon isothermal pressure-swing cycles at low temperatures (25 °C). CO2 could be successfully desorbed at 120 °C from the sample with highest uptake (MSG60), which showed a constant uptake for three adsorption–desorption cycles using only vacuum at 50 °C.

Comparison of SO2 with CO2 for recovering shale resources using low-field nuclear magnetic resonance

Adsorption isotherms of pure CH4, C2H6, CO2, and SO2 are measured on one typical shale sample using the static volumetric method. The adsorption capacity of the above four gases is then compared to elucidate the affinity of each gas species on shale. Nuclear magnetic resonance (NMR) technique is then used to investigate how SO2 and CO2 exert the influence on the adsorbed CH4 and C2H6 on the organic shale. Based on the measured adsorption isotherms, SO2 presents the strongest adsorption capacity among the four gases, and is followed by C2H6, CO2, and CH4. It suggests that SO2 can be served as a potential agent for recovering the heavier hydrocarbon species, i.e., C2H6, from organic shale, while CO2 may be only suitable for the shale CH4 recovery. After introducing CO2 or SO2, based on the variation of T2 spectrum of the “CH4 or C2H6-saturated” shale sample, we infer that the adsorbed CH4 can be readily replaced by CO2 and SO2 from shale surface. However, the adsorbed C2H6 molecules are less probably replaced by CO2 compared to SO2. In addition, the amount of desorbed CH4 and C2H6 resulted from CO2 is much smaller than that of SO2, suggesting the superiority of SO2 for shale resource recovery. We expect this strategy will inspire new perspectives for the recovery of shale resources using the method of flue-gas treatment.

Development of the adsorption capability of MCM-41 particles synthesized at room temperature using 8-hydroxyquinoline-5-sulfonic acid for removal of Co(II) and Cr(VI) in binary systems

A novel MCM-41 material containing 8-hyrdoxyquinoline-5-sulfonic acid (HQS/MCM-41) synthesized by in-situ coprecipitation of 8-HQS into MCM-41 was developed in this study. The performance of HQS/MCM-41 as a dual-function material for simultaneous adsorption of Co(II) cations and Cr(VI) anions was evaluated. The results showed that 8-HQS-free MCM-41 has the ability to adsorb Cr(VI) anions while failed in case of Co(II) cations. By using HQS/MCM-41, almost complete removals are achieved for both Co(II) and Cr(VI) in binary systems in pH ranges 3.5–8.5 and 3–4.3, respectively, which reflected the importance of the developing agent 8-HQS. Both Lagergren’s pseudo-first-order and Ho’s pseudo-second-order kinetic models succeeded to describe the kinetic data of Cr(VI) anions while those of Co(II) cations are better fitted by Lagergren’s model. Equilibrium isotherms of Co(II) and Cr(VI) ions are better described by Temkin and Freundlich isotherm models, respectively. Adsorption capacities of Co(II) and Cr(VI) using HQS/MCM-41 are compared with those reported in literature using other materials. The radiation and thermal stability of the synthesized material were further evaluated. Desorption of Co(II) and Cr(VI) loaded onto HQS/MCM-41 was tested using different inorganic and organic desorbing agents. Eventually, the adsorption mechanism of Co(II) and Cr(VI) ions onto HQS/MCM-41 was suggested.

H2S separation from biogas by adsorption on functionalized MIL-47-X (X = −OH and − OCH3): A simulation study

Monte Carlo molecular simulations in grand canonical ensemble were performed to study the H2S, CO2 and CH4 adsorption and separation on the MIL-47 and the functionalized MIL-47-X (X = -OH and -OCH3). The preferred situation for the adsorption of gas molecules on the studied MOFs was also investigated. The calculated adsorption isotherms of CO2 on the MIL-47 agreed well with the experimental uptakes. Furthermore, the simulated adsorption selectivities of three MOFs for the CO2/CH4, H2S/CH4 and H2S/CO2 mixtures were in the order H2S/CH4 > H2S/CO2 > CO2/CH4. These MOFs had higher selectivity for H2S over CH4 indicating that they can be good adsorbents for the H2S separation. The probability distribution of the adsorbed molecules showed that the guest molecules were more localized near the metal centers and functional groups.

Enhanced N-doped Porous Carbon Derived from KOH-Activated Waste Wool: A Promising Material for Selective Adsorption of CO₂/CH₄ and CH₄/N₂.

Separation of impurities (CO2 and N2) from CH4 is an important issue for natural gas alternatives (such as coalbed gas, biogas, and landfill gas) upgrading. It is notably challenging to synthesize high N-doped porous carbon with an appropriate porous structure. In this work, high N content (14.48 wt %) porous carbon with micropore size of 0.52 and 1.2 nm and specific surface area of 862 m2 g−1 has been synthesized from potassium hydroxide (KOH) activated waste wool upon the urea modification. Pure component adsorption isotherms of CO2, CH4, and N2 are systematically measured on this enhanced N-doped porous carbon at 0 and 25 °C, up to 1 bar, to evaluate the gases adsorption capability, and correlated with the Langmuir model. These data are used to estimate the separation selectivities for binary mixtures of CO2/CH4 and CH4/N2 at different mixing ratios according to the ideal adsorbed solution theory (IAST) model. At an ambient condition of 25 °C and 1 bar, the predicted selectivities for equimolar CO2/CH4 and CH4/N2 are 3.19 and 7.62, respectively, and the adsorption capacities for CO2, CH4, and N2 are 2.91, 1.01, and 0.13 mmol g−1, respectively. This report introduces a simple pathway to obtain enhanced N-doped porous carbon with large adsorption capacities for gas separation of CO2/CH4 and CH4/N2.

A new approach to the upgrading of the traditional propylene carbonate washing process with significantly higher CO2 absorption capacity and selectivity

Although a series of advanced technologies and materials, like ionic liquids and metal organic frameworks, is being developed for carbon capture, traditional techniques, like propylene carbonate (PC) washing, are still widely applied in industry because of their low material costs and ease of operation. Considering the low CO2 solubility and selectivity in PC, we have tried to improve the PC washing process by adding 2-methylimidazole (mIm) to PC in the presence of ethylene glycol (EG) as cosolvent. A series of EG-mIm-PC complex solvents was prepared and their viscosities measured at different temperatures. The absorption isotherms of CO2 in these complex absorbents, as well as in pure PC, were measured at 293.15, 303.15, and 313.15 K at 0.1–0.8 MPa. The heats of CO2 absorption in these solvent mixtures were calculated using the Clausius-Clapeyron equation. For evaluating the effect of mIm on the selectivity of CO2 over other gas species, the absorption isotherms of CH4, N2, and H2 in pure PC and in 24%-mIm complex solvent with highest CO2 solubility were also measured. The results showed that the viscosities of these complex absorbents, as well as the solubility and heats of absorption of CO2 in all of them, moderately or slowly increased with an increase in mIm mass fraction, when the mIm content was lower than 20 wt%, and rapidly increased when it surpassed 20 wt%. The CO2 solubility could be more than doubled when the mIm content reached 24 wt% while viscosity and absorption heat still remains at low levels, that is, lower than 14 mPa·s and 26 kJ/mol, respectively. More importantly, the solubilities of CH4, N2, and H2 drastically decreased in the presence of mIm; using the 24 wt%-mIm complex absorbent instead of pure PC, the selectivity of CO2 over those other gas species increased by: 0.7–2.8 times for CH4, 3.9–6.3 times for N2, and 3.5–7.7 times for H2, with more significant improvements at lower pressure ranges. This work presents a very promising approach to PC washing technology upgrading.

Synthesis of a modified HF-free MIL-101(Cr) nanoadsorbent with enhanced H2S/CH4, CO2/CH4, and CO2/N2 selectivity

Despite worldwide attention toward MIL-101(Cr) as a superior adsorbent during past decade, it is still failed to be commercialized. The main barrier can be addressed to the poisonous and expensive synthesis procedure of MIL-101(Cr). In this study, nitric acid (HNO3) was introduced as a premier, inexpensive and non-poisonous substitute for typical hydrofluoric acid (HF) in the hydrothermal synthesis of MIL-101(Cr). A series of MIL-101-HNO3 nanoadsorbents, with different amounts of HNO3, were synthesized and characterized by different techniques. For the first time, the H2S, CO2, CH4, and N2 isotherms on the MIL-101-HNO3 samples were measured in a wide pressure region (1–35 bar) and different temperatures (273, 283, and 293 K) using an in-house made volumetric setup. The results indicated that the MIL-101-HNO3-1 possessed the maximum surface area (3841 m2/g), pore volume (1.72 cm3/g), and as a consequence, the highest H2S (8.80 mmol/g at 1 bar and 27.16 mmol/g at 35 bar) and CO2 uptake (5.86 mmol/g at 1 bar and 21.98 mmol/g at 35 bar) among all synthesized samples. More importantly, ideal adsorbed solution theory (IAST) indicated that H2S/CH4, CO2/CH4, and CO2/N2 adsorption selectivity elevated up to 166.9%, 21.8%, and 13.6% at 1 bar compared to the conventional MIL-101-HF-1. These advantageous were all ascribed to the additional open Cr3+ metal sites and more electrostatic adsorptive behavior of MIL-101-HNO3-1. The impressive preferential gas adsorption, along with excellent cyclic performance, thermal and water stability, made the MIL-101-HNO3-1 a promising replacement for hazardous MIL-101-HF-1 and other commercial adsorbents.

Sorption and permeation of gases in hyper-cross-linked hybrid poly(POSS-imide) networks: An in silico study

Networked hybrid materials containing various types of organic imides covalently bonded with polyhedral oligomeric silsesquioxanes (POSS) have recently been developed. One of their possible applications is for gas-separation under extreme conditions of pressure and/or temperature. Experimental results indicate that their permeation properties depend on the specific organic dianhydride precursor used in the synthesis. In this work, atomistic models of 6FDA-based and PMDA-based poly(POSS-imide) crosslinked networks have been used to investigate the sorption, desorption, relaxation and permeation properties of such materials at the molecular level and their dependence on the nature of the imide linker. Results have been compared to available experimental data.A highly-efficient parallelised version of the excluded volume map sampling test particle insertion (EVMS-TPI) method was used to obtain the infinite dilution solubilities of a number of small penetrants (N2, O2, CH4 and CO2) in these model networks. Analyses of the Boltzmann-weighted probability densities for the distribution of the insertion energies showed that very reliable estimates of solubilities could be obtained.Extensive molecular dynamics simulations were then performed to obtain the complete model sorption isotherms for CO2 and CH4 at 35 °C up to pressures of over 60 bar using an iterative technique which matches the chemical potential of the penetrant in the poly(POSS-imide) phase to that in the corresponding gas phase. The sorption-induced changes in volume, the significant space available to penetrants, the mean insertion energies and their distributions were characterized. Comparisons were not only made between both types of poly(POSS-imide) to characterize the effect of the linker, but also with (hypothetical) uncrosslinked mixtures of the POSS and dianhydride molecules in order to elucidate the effects of crosslinking. Given the known conditioning properties of CO2, desorption isotherms were also obtained for this penetrant. These showed significant hysteresis. Prolonged exposure to high concentrations of CO2 was also found to lead to slow relaxations that have significant effects on the solubility.Permeabilities were obtained for methane and carbon dioxide at 100 °C, 200 °C and 300 °C at a pressure of ~ 2 bar. Differences in permeabilities were largely diffusion dependent.

WITHDRAWN: Adsorbent screening for CO2/CO separation for applications in syngas production

Abstract Single gas carbon dioxide (CO2) and carbon monoxide (CO) adsorption behaviour is investigated in detail with different adsorbents for the potential separation of syngas. In this study, 20 zeolites, 2 activated aluminas, 3 activated carbons, and 2 silica gels were investigated by determining pure gas isotherms of CO2 and CO at 30 °C. The results were compared to literature to determine which adsorbents would be the most promising for CO2 separation from syngas at this temperature. Since CO2 concentrations vary in syngas based on the method of production, different adsorbents were selected for purification and bulk separation of CO2 from a syngas mixture. The individual adsorption capacities of CO2 and CO were analysed separately using a gravimetric system, modelled, and then compared for all of the adsorbents studied. CO2 is shown to be more favourably adsorbed compared to CO, with CO2 having higher adsorption capacities and heats of adsorption for all adsorbent samples studied. High-density silica gel and H-Y type zeolites were found to be promising adsorbents for the bulk separation of CO2 from syngas due to the shape of their isotherms, large CO2 adsorption capacities, their favourable adsorption capacity ratios for CO2 over CO. For the purification of syngas, Na+ exchanged FAU structured zeolites with their high CO2 adsorption capacity at low pressures, and favourable CO2 over CO adsorption capacity ratios was found to be the most promising adsorbent.

Gas and water vapor sorption and diffusion in a triptycene-based polybenzoxazole: effect of temperature and pressure and predicting of mixed gas sorption

Fundamental gas transport properties of a novel thermally rearranged polymer (TPBO) prepared from a co-polyimide precursor with controlled triptycene molar content are discussed. He, N2, CH4, CO2 and C2H6 sorption isotherms were experimentally measured in the range 5–50 °C and up to 32 atm and analyzed with the dual mode model. Water vapor sorption and diffusion at 35 °C was also investigated. TPBO exhibits larger gas and vapor sorption capacity relative to previously reported thermally rearranged polymers. The dual mode parameters retrieved from the analysis of single gas sorption isotherms were used to estimate a priori the sorption behavior in mixed gas conditions. The predicted mixed gas solubility-selectivity is significantly higher than ideal solubility-selectivity and it is comparable to that exhibited by other glassy polymers. Gas and vapor diffusion coefficients in TPBO were estimated from the solution-diffusion model and from sorption kinetics, respectively, and are larger than in previously reported thermally rearranged polymers. The dual sorption-mobility model indicates that the polymer rigidity significantly affects gas diffusion coefficients. CO2/CH4 diffusivity-selectivity was larger than in other glassy polymers, pointing out the superior size-sieving ability provided by triptycene units. Water vapor sorption experiments revealed that TPBO is more hydrophilic relative to previously reported thermally rearranged polymers: theoretical models were exploited to speculate water vapor distribution in the polymer matrix.

Enhanced resolution of ultra micropore size determination of biochars and activated carbons by dual gas analysis using N2 and CO2 with 2D-NLDFT adsorption models

In this study, biochars obtained by either direct carbonization or hydrothermal treatment of corn stems were used as precursors of two series of activated carbons (ACs). The pore size distributions (PSDs) of biochars and ACs were evaluated from N2 and CO2 adsorption isotherms using models based on the two-dimensional version of the non-local density functional theory (2D-NLDFT). We showed that more detailed carbon PSDs might be obtained from simultaneous (dual) gas analysis of both N2 and CO2 isotherms than from single isotherms. The dual gas method showed a peak at about 0.4 nm which was not detected by the single N2 analysis. This fact is related to the restricted diffusion of N2 into very narrow micropores at low temperatures and pressures. By modifying the lower pore width limit wmin in the nitrogen model, we obtained an excellent fit of the dual model to both isotherms for all studied samples, which demonstrates the reliability and robustness of this refined method. Finally, we demonstrated that this approach would allow measuring N2 isotherms at relative pressures starting at about 0.001 rather than at 10−6, which would save time without losing resolution of the calculated PSD.

Construction of high-pressure adsorption isotherm: A tool for predicting coalbed methane recovery from Jharia coalfield, India

Adsorption isotherm relates the gas storage capacity as a function of pressure at constant temperature. In this paper, adsorption isotherm of two dry borehole samples was constructed in the laboratory using the manometric method. Isotherm was measured for two gases, i.e., CH4 and CO2 to pressure up to 8.4 MPa. Before the construction of sorption isotherm, coal was characterized by proximate, ultimate and petrographic analysis. Coalbed gas content of these two samples was found 2.29 m3/t and 2.75 m3/t. SEM images were obtained for the pore size distribution of coal using pore image analysis. Prediction of coalbed methane recovery from CH4 adsorption isotherm showed that these coalbeds are under saturated. CO2 isotherm was constructed to estimate enhanced coalbed methane (ECBM) recovery. Volume wise CO2/CH4 sorption ratio was found 2.09 times to 2.75 times respectively. This paper presents the interpretation of isotherm data to find the recovery factor of methane production from Jharia coalfield.

CO2 Sorption Properties over Ordered Mesoporous Carbon CMK-3 in the Presence of MDEA Solution

By using the hard template method, CMK-3 can be synthesized. The large Brunauer–Emmett–Teller surface area and total pore volume of CMK-3 were 1134 m2/g and 1.128 cm3/g, respectively. The sorption isotherms of CO2 on CMK-3 in the presence of MDEA solutions were measured. It was shown that the CO2 sorption capacity at low pressure was enhanced by chemical absorption and was higher than that of CMK-3 in the presence of water. However, the formation of the CO2 hydrate was inhibited. When the concentration of the MDEA solution exceeded 1.4 mol/L, no hydrate was formed, and the sorption capacity was only 13 mmol/g at approximately 3.5 MPa, which was significantly lower than that of the water under the same pressure. The inhibitory effect of MDEA on hydrate formation was reduced at a low solution concentration. When the concentration of the MDEA solution was 0.52 mol/L, the gas hydrate was formed at approximately 1.88 MPa; the sorption capacity was approximately 28.7 mmol/g at 3.58 MPa, which was close to the h...