Heat Of Adsorption Values Research Articles

Experimental evaluation of Adsorption Heat for Water vapour/Silica gel pair for chiller application

Isosteric adsorption heat is crucial in assessing adsorption cycle performance. Typically, adsorption heat is indirectly estimated from the isotherm equation fitted to the experimental uptake data. This indirect method is susceptible to the accuracy and choice of isotherm equation. Consistency of this indirect method with actual adsorption heat measurements is rarely examined. Present work addresses this research gap by simultaneously measuring adsorption uptake and heat. This is achieved by incorporating heat flux sensors within an existing constant volume variable pressure (CVVP) setup. The measurements are carried out for water vapour/RD-silica gel pair with temperature and pressure ranging from 298 to 363 K and 0.15 kPa to 6.3 kPa respectively. Two popular isotherms viz. Dubinin–Astakhov (D–A) and Tóth isotherm equation are used to estimate the indirect adsorption heat. Both isotherm equations show a good fit with the experimental uptake (< 5% deviation). Interestingly, indirect adsorption heat estimated using Tóth isotherm fails to predict (∼15% deviation) the uptake dependent adsorption heat trend shown by calorimetric data, whereas D–A isotherm agrees well (<5% deviation). Therefore, the present work forms fundamental basis for identifying suitable isotherm equation, which is consistent with experimental adsorption uptake as well as heat data. Subsequently, a comparison of theoretical coefficient of performance (COP) for water vapour/RD-silica gel adsorption chiller is undertaken, based on indirect adsorption heat values available in the literature. The comparison reveals that COP prediction is sensitive to adsorption heat. This further emphasizes the necessity for experimentally measuring adsorption heat.

The dual role of acetate additives among carbon materials functionalized and CH4/N2 separation

Carbon materials with superior advantages have attracted much attention in the field of CH4/N2 separation, and selecting suitable carbon precursors and activated ways can be crucial to driving the further development of this domain. Through it, we proposed a feasible method to prepare composite carbon materials (Ni@C-n and Co@C-n) based on cellulose acetates (CA) with acetate activation. Such additives played a dual role, which means the produced thermal decomposition of anions to optimize the porous structure and they induce cations transforming into metal species to enhance the adsorbed potential towards CH4. Consequently, the N2 adsorption-desorption isotherm showed that the excellent Ni@C-M adsorbent was rich in micropores and mesopores, with a BET surface area of 610.2 cm2/g and microporous area of 358.8 cm2/g. The Ni@C-M adsorbent reached 18.2 cm3/g at 298 K and 0.1 MPa, increasing by 43.3% compared to C support, and exhibited the highest CH4/N2 selectivity of 7.5 (5/95, v/v) among various series adsorbents, which was superior to most carbon materials reported so far. The values of adsorption heat (Qst) ranged between 14.63–19.23 kJ/mol and 22.69–24.87 kJ/mol for C support and Ni@C-M adsorbents respectively, confirming Ni@C-M with the stronger adsorption potential energy towards CH4. This research provides promising adsorbents for the purification of low-concentration coal gas and offers new clues for functionalizing carbon materials via utilizing metal salts.

A Comparative Investigation of the Adsorption Characteristics of CO2, O2 and N2 in Different Ranks of Coal

The adsorption mechanism of carbon dioxide, oxygen and nitrogen in coal is important for preventing and controlling coal spontaneous combustion and for understanding the technology of CO2 storage in goaf. Adsorption amount and adsorption heat are key adsorption parameters that are required to understand the material and energy conversions during adsorption in coal. In this study, we studied the factors that influence the adsorption amounts and adsorption heat values of carbon dioxide, oxygen and nitrogen in coal by testing four different coal samples using conventional coal quality analysis, low-pressure nitrogen and carbon dioxide adsorption, Fourier transform infrared spectroscopy and three gas adsorption experiments at different temperatures. Then, we analyzed the relationships between the structural parameters of the coal samples and the adsorption amounts and the adsorption heat values of carbon dioxide, oxygen and nitrogen. The results show that the adsorption isotherms of carbon dioxide conform to the Langmuir equation, and the adsorption isotherms of oxygen and nitrogen conform to Henry’s law between 0 and 110 kPa. The adsorption amounts of carbon dioxide, oxygen and nitrogen decreased with an increase in temperature, and the change in the rate of the adsorption amount with temperature was determined by the adsorption heat. The results of the pore structure show that the pores of the coal samples are composed of mesopores and micropores; the micropores contribute to the main specific surface area. The micropore and mesopore structures are the main determinants of the adsorption amounts of carbon dioxide, oxygen and nitrogen in coal. The gas adsorption heat is affected by the pore structure and the chemical composition of coal. The adsorption heat of nitrogen correlates positively with the pore structure of the coal. The adsorption heat of oxygen correlates positively with the ash, elemental nitrogen, elemental sulfur and mineral contents of the coal. The adsorption heat of carbon dioxide correlates positively with the elemental sulfur content of the coal.

Effective removal of cationic dyes from aqueous solutions by using black cumin (Nigella sativa) seed pulp and biochar

Black cumin seed pulp (C), as well as biochar (CC) produced via pyrolysis of black cumin seed pulp were used to remove methylene violet 2B (MV) and basic yellow 28 (BY28) from aqueous solution. Adsorption isotherms and kinetics were applied at 10, 25, and 35 °C. The adsorption of methylene violet 2B and basic yellow 28 on the black cumin seed pulp and biochar surface was exothermic; the heat of adsorption values were lower than 0. The adsorption capacities of BY28-C, BY28-CC, MV-C, and MV-CC were 212.8, 625, 164, and 909 mg g-1 at 25 °C, respectively. The adsorption of black cumin seed pulp and biochar data were examined with the Freundlich, Langmuir, Temkin, Dubinin-Radushkevich (D-R), and Flory-Huggins (F-H) isotherm models. The kinetics of the adsorption were fitted to the pseudo first-order and pseudo second order equations. The pseudo second order equation gave a better fit than the pseudo first-order equation.

Role of nitrogen doping and pore volume for CO2 capture in metal-organic framework derived ultramicroporous carbon material

We report the synthesis of four MOF-derived nitrogen and oxygen co-doped ultramicroporous/microporous carbon (MNOUCs) at different carbonization temperatures and their applications as adsorbents for efficient CO2 capture. MNOUC-900, carbonized at 900 ℃ having the highest surface area of 1320 m2/g and highest ultramicropore volume of 0.205 cm3 g−1 showed the maximum CO2 uptake of 4.65 mmol g−1 at 0 ℃ and 1 bar. Contrary to this, MNOUC-600, which was synthesized at 600 ℃ showed the highest CO2/N2 selectivity of 31. This study revealed that CO2 uptake had been found to be correlated with ultramicropore volume while selectivity (CO2 vs N2) improves with increasing basic nitrogen functionalities such as pyridinic and pyrollic. The heat of adsorption values was found to be 25–40 kJ mol−1 suggesting the physisorption nature of the interaction. Dynamic CO2 uptake experiment was performed for MNOUC-900, which revealed its good efficiency to be used as a CO2 adsorbent.

Computational Characterization of Zr-Oxide MOFs for Adsorption Applications.

Zr-oxide secondary building units construct metal-organic framework (MOF) materials with excellent gas adsorption properties and high mechanical, thermal, and chemical stability. These attributes have led Zr-oxide MOFs to be well-recognized for a wide range of applications, including gas storage and separation, catalysis, as well as healthcare domain. Here, we report structure search methods within the Cambridge Structural Database (CSD) to create a curated subset of 102 Zr-oxide MOFs synthesized to date, bringing a unique record for all researchers working in this area. For the identified structures, we manually corrected the proton topology of hydroxyl and water molecules on the Zr-oxide nodes and characterized their textural properties, Brunauer-Emmett-Teller (BET) area, and topology. Importantly, we performed systematic periodic density functional theory (DFT) calculations comparing 25 different combinations of basis sets and functionals to calculate framework partial atomic charges for use in gas adsorption simulations. Through experimental verification of CO2 adsorption in selected Zr-oxide MOFs, we demonstrate the sensitivity of CO2 adsorption predictions at the Henry's regime to the choice of the DFT method for partial charge calculations. We characterized Zr-MOFs for their CO2 adsorption performance via high-throughput grand canonical Monte Carlo (GCMC) simulations and revealed how the chemistry of the Zr-oxide node could have a significant impact on CO2 uptake predictions. We found that the maximum CO2 uptake is obtained for structures with the heat of adsorption values >25 kJ/mol and the largest cavity diameters of ca. 6-7 Å. Finally, we introduced augmented reality (AR) visualizations as a means to bring adsorption phenomena alive in porous adsorbents and to dynamically explore gas adsorption sites in MOFs.

Comparison of Adsorption Coefficients of Argon, Krypton, and Xenon on Various Activated Charcoal Grades in Static Conditions

Coefficients of adsorption (Henry’s constants) of noble gases (argon, krypton, xenon) on activated charcoal grades AG-3, VSK-5, SKT-3, NWC 12x40 in the temperature range of 15 °C to 80 °C were determined. Temperature dependence parameters of Henry’s constants were determined with a calculation of isosteric adsorption heat values. The experimental data were used to calculate stationary operating conditions of a radiochromatographic column in NPP’s noble gas delay system. Out of all the studied charcoals, the results show that coconut charcoals VSK-5 and NWC 12x40 have the highest decontamination factor to airflow purification from radioactive noble gases. They far outweigh sulfur–potassium activated peat charcoal SKT-3 used presently at most Russian nuclear power plants. Activated charcoal AG-3 does not ensure the decontamination level required. The results also show that the overall decontamination factor depends heavily on temperature. Precooling gas flow at the adsorber’s input can considerably increase air decontamination factor from radioactive noble gases.

Facile fabrication of copper oxide modified activated carbon composite for efficient CO2 adsorption

Copper oxide modified activated carbon (CuO/AC) composites for the CO2 capture were synthesized via a facile assembly strategy associated with a direct solid-state heat dispersion process by introducing CuO into AC using Cu(NO3)2 as the copper source. The synthesized CuO/AC composites with various CuO contents were characterized by powder X-ray diffraction, scanning electron microscopy and nitrogen adsorption-desorption measurement, and the CO2 adsorption performance was investigated. The characterization results indicate that the Cu(NO3)2 species was well dispersed into the AC pore channels and then converted to a highly dispersed CuO after the activation process. The adsorption results reveal that the CO2 adsorption performance can be significantly improved by introducing CuO onto the AC surfaces, and the CuO(0.6)/AC composite with a CuO loading of 0.6 mmol/g AC shows a high CO2 adsorption capacity and adsorption selectivity and displays an excellent reversibility. Additionally, the calculated adsorption heat values of CO2 on the CuO(0.6)/AC composite are in the range of 27.3 to 33.9 kJ/mol.

Adsorption separation of CF4, O2, CO2, and COF2 from an excimer gas mixture

The use of adsorbents is explored as an option for the removal of trace impurities of CO2, CF4, COF2, and O2 from F2, Kr, and Ne for applications in excimer lasers. Due to the incompatibility of many adsorbents to F2 and HF, aluminas and polymeric adsorbents were selected as potentially compatible materials. To determine the adsorption potential of these adsorbents in the low concentration region, the concentration pulse chromatographic technique was chosen to determine the Henry’s Law constants of CO2, CF4, and O2 gases with three polymeric adsorbents (HayeSep Q, HayeSep B, and Fluorinated DVB) and two aluminas (AA-300, and Alumina A). The results were plotted and compared on van’t Hoff plots (the natural logarithm of Henry’s Law constants as a function of inverse absolute temperature) with the heat of adsorption values being calculated from the lines of best fit for all gases and adsorbents tested in this study. Due to the large energies required to operate the excimer lasers, a cryo-cooler was determined to be feasible to precool the feed stream before separation, which increases the adsorption capacity and the compatibility of the adsorbents to F2 and HF. The van’t Hoff plots were extrapolated to colder temperatures to determine the Henry’s Law constants to analyze the potential of using the cryo-cooler. From this study, it was determined that HayeSep Q was the best polymeric adsorbent with significant adsorption of CO2 at temperatures below −50 °C while being the best performing CF4 adsorbent. AA-300 was the best performing alumina in this study while having significant adsorption of CF4 at temperatures below −135 °C. However, from a compatibility standpoint, both of these materials need to be tested to determine their robustness in the presence of F2 and HF at room and reduced temperatures.

Thermodynamic characteristics of CH4 adsorption by continental shale: A case study of the Upper Triassic Yanchang shale in the Yanchang Gasfield, Ordos Basin

In order to improve the calculation method of the isosteric adsorption heat, clarify thermodynamic characteristics of CH4 adsorption by continental shale and reveal the adsorption mechanism, this paper selected shale samples from the seventh Member of Yanchang Formation of Upper Triassic in the Yanchang Gasfield of the Ordos Basin as the research object. The isothermal adsorption experiment was carried out on the CH4 adsorption by continental shale and the excess adsorption curves were plotted. Then, the characteristics of the isosteric adsorption heat of the shale with different types of adsorption capacity were illustrated by analyzing and comparing the difference between excess and absolute adsorption capacity. And the following research results were obtained. First, under the same temperature and pressure, absolute adsorption capacity is higher than the excess values. The difference between them is higher under low temperature and high pressure and it is in the relationship of exponential function with the equilibrium pressure. If excess adsorption capacity is used to evaluate the adsorptive property of shale reservoirs, the evaluation result will be underestimated. Second, for CH4 adsorption by Yanchang Formation shale, the absolute and excess isosteric adsorption heat values have a linear positive correlation with absolute and excess adsorption capacity respectively, and the intermolecular force of adsorbate has a dominant effect on isosteric adsorption heat values. Third, absolute isosteric adsorption heat value is less than the excess heat. The relative error is in the range of 18.18–49.79%, and it is higher in the stage with low adsorption capacity. If excess adsorption capacity is taken as the basic data to calculate initial isosteric adsorption heat values, the calculation result will be overvalued, and consequently, the evaluation of the intermolecular force of adsorbent and adsorbate is overestimated.

Adsorption behavior of oil-displacing surfactant at oil/water interface: Molecular simulation and experimental

In alkaline-surfactant-polymer flooding processes, the adsorption of residual surfactants in the oil/water interface significantly affected the emulsification and stabilization of produced water. In order to thoroughly investigate the effect of that on oil-water separation efficiencies, the adsorption behaviors of a surfactant, sodium dodecylbenzene sulfonate (SDBS) were carried out by using both molecular simulation and experimental approaches. The effects of temperature on the stability of monolayer SDBS films, and the interfacial film thicknesses and interface formation energies of SDBS at n-dodecane/water interface, were obtained and then compared with the tested values of adsorption heat of the surfactant within the simulated produced water samples and with experimentally-determined interfacial tensions of the samples. The experimental and computational results are consistent in the variation of adsorption heat.

Performance of Synthesized Acetone Based Inhibitor on Low Carbon Steel Corrosion in 1 M HCl Solution

1-[(5-Phenyl-1,3, 4-oxadiazol-2-yl)thio] acetone (POTA) was synthesized and tested as a new corrosion inhibitor for low carbon steel in 1 M hydrochloric acid. The diagnosis of POTA was carried out by FTIR and NMR analysis. Inhibitor performance was investigated using mass loss technique. POTA was acted as a moderate corrosion inhibitor for low carbon steel in 1 M hydrochloric acidic solution with efficiency more than 70%. The inhibitor performance was attributed to the formation of an adsorption layer on the low carbon steel surface. The mechanism of inhibitor adsorption on the low carbon steel surface was according to the Langmuir adsorption isotherm. The value of adsorption heat was within the range of chemical adsorption. Quantum chemical studies were adopted as a theoretical tool to clarify the mechanism of inhibition and to support the experimental part.

Ag Nanoparticles Supported on a Resorcinol-Phenylenediamine-Based Covalent Organic Framework for Chemical Fixation of CO2.

Covalent organic frameworks are a new class of crystalline organic polymers possessing a high surface area and ordered pores. Judicious selection of building blocks leads to strategic heteroatom inclusion into the COF structure. Owing to their high surface area, exceptional stability and molecular tunability, COFs are adopted for various potential applications. The heteroatoms lining in the pores of COF favor synergistic host-guest interaction to enhance a targeted property. In this report, we have synthesized a resorcinol-phenylenediamine-based COF which selectively adsorbs CO2 into its micropores (12 Å). The heat of adsorption value (32 kJ mol-1 ) obtained from the virial model at zero-loading of CO2 indicates its favorable interaction with the framework. Furthermore, we have anchored small-sized Ag nanoparticles (≈4-5 nm) on the COF and used the composite for chemical fixation of CO2 to alkylidene cyclic carbonates by reacting with propargyl alcohols under ambient conditions. Ag@COF catalyzes the reaction selectively with an excellent yield of 90 %. Recyclability of the catalyst has been demonstrated up to five consecutive cycles. The post-catalysis characterizations reveal the integrity of the catalyst even after five reaction cycles. This study emphasizes the ability of COF for simultaneous adsorption and chemical fixation of CO2 into corresponding cyclic carbonates.

Investigation on energy consumption of desiccant coated heat exchanger based heat pump: Limitation of adsorption heat of desiccant

DCHE (Desiccant coated heat exchanger) based heat pump systems can handle sensible and latent loads simultaneously and separately within one single component via flowing refrigerant and coated desiccant. Their characteristics have a crucial impact on the performance of the whole system. To ensure energy efficiency of DCHE based systems, the restriction between refrigerant and desiccant is discussed based on energy consumption analysis. Results show that energy consumption of the DCHE based heat pump is intimately related with its coefficient of performance and adsorption heat of coated desiccant. R410A and R32 are found to be promising refrigerants for DCHE systems. Maximum allowable values of adsorption heat under different ambient air conditions and sensible heat ratios are obtained. Desiccant materials with adsorption heat of 2300–3000 kJ/kg such as various silica gels, all-silica zeolites and salt supported composites are within maximum allowable values of adsorption heat for most conditions. When applying the majority of zeolite type desiccants that possess adsorption heat more than 4000 kJ/kg, great attention should be paid to the determination of supply-air temperature difference. This paper provides the underlying insights needed to guide a fast and proper selection of refrigerants and desiccants for DCHE based systems.

Analytical model and experimental investigation of the adsorption thermodynamics of coalbed methane

The study on adsorption thermodynamics is conducive to a deep understanding of the heat and mass transfer mechanism of coalbed methane in a coal seam. In this work, the analytical expressions of the isosteric heat for six adsorption models taking into account the temperature variations are directly derived according to Clausius–Clapeyron equation. Meanwhile, the adsorption content and adsorption heat at different pressures and temperatures are measured by the volumetric method of adsorption with a microcalorimetry system. It is found that the the adsorption heats obtained by different adsorption models exhibit different trends. The fitting quality of the experimental isotherms for different adsorption models affects the adsorption heat result. However, even if the models well fit the experimental isotherms, the theoretical adsorption heat values may be inconsistent. Furthermore, the calorimetric heats for all coal samples decreases with the increase in adsorption content in relation to the micropore distribution of coal. For all coal samples, the modified Dubinin–Astakhov (D–A) model can well fit the experimental isotherms and agree well with the results of calorimetric heats. By comparing the theoretical heat for different k values and the measured heat, the pseudo-saturation vapor pressure of the modified D–A model can be determined. Finally, by virtue of the isosteric heat of adsorption in a small temperature range, the adsorption isotherms at other adjacent temperatures are predicted successfully.

Adsorption of xylene isomers using Ba-faujasite type zeolite: Equilibrium and kinetics study

In the present study, liquid phase isotherm adsorption of single component of para xylene, meta xylene, ortho xylene, and ethylbenzene onto a commercial molecular sieve adsorbent (SPX3000-fine) at three different temperatures of 25, 50 and 75°C had been investigated. It was found that para xylene was the most adsorbed component followed by ethylbenzene, meta xylene and ortho xylene, showing the strong adsorption of para xylene by the understudy adsorbent. All kinds of used xylene isomers brought out decreased adsorption loading on SPX3000-fine zeolite with increasing the temperature in the range of 25–75°C. Aims to study the description of equilibrium adsorption data, Langmuir, Freundlich, and Tempkin isotherms were applied, which superiority of Langmuir model to describing equilibrium isotherm data with the highest R2 values was obtained. The kinetic study was performed by applying three kinetic models of pseudo-first-order, pseudo-second-order and intraparticle diffusion. According to the obtained results, the pseudo-second-order model is the best representative model to describe the kinetic adsorption data. Also, thermodynamic study revealed that due to the negative values of adsorption heat and Gibbs free energy changes, the adsorption of para xylene in the binary system proceeded an exothermic spontaneous process.

Cation exchange modification of clinoptilolite –thermodynamic effects on adsorption separations of carbon dioxide, methane, and nitrogen

Abstract This study details an experimental analysis of the thermodynamics of adsorption equilibrium behaviour of pure CO2, CH4, and N2 gases on raw, Fe3+, Ca2+, and Cs+ cation exchanged clinoptilolite. Equilibrium adsorption isotherms were experimentally determined for CO2, CH4, and N2 at three different temperatures ranging from 303 K up to 363 K, at pressures up to 8.0atm using the microgravimetric technique. Kinetic adsorption uptake data was measured at different temperatures for CH4 and N2 gases, and the results were compared for raw and Ca2+ clinoptilolite. Heat of adsorption values were calculated for all three gases on the studied clinoptilolite samples using the chromatographic method. These results were compared to the isosteric adsorption enthalpies determined from the adsorption isotherms at different temperatures. The isosteric heat of adsorption was the highest for CO2 followed by CH4, and N2. Temperature dependent Sips, Toth, and Dual-Site Langmuir isotherm models were fitted with experimental data and selectivity factor values were calculated for CO2/CH4 and CH4/N2 gas separations using the regressed isotherm models. Ca2+ clinoptilolite shows the best potential for CO2/CH4 separations due to its high selectivity. However, higher temperatures are needed in order to compensate for the slow kinetic behaviour. For CH4/N2 separations, Fe3+ clinoptilolite selectivity displays both high values and less variability compared to Cs+ clinoptilolite over a broader range of temperatures and pressures.

Sustainable packaging waste-derived activated carbon for carbon dioxide capture

Global greenhouse gases emissions have increased tremendously since 1950’s due to excessive burning of fossil fuel. The objective of this work is to develop and investigate packaging waste-derived activated carbon for carbon capture. Activated carbon was synthesized by carbonization of peanut-shaped packaging waste followed by chemical activation using KOH at a ratio of one to four. The activated carbon was characterized for it is textural properties using N2 adsorption at 77 K, and carbon dioxide adsorption isotherms at 273, 298 and 323 K. Non-Linear Density Functional Theory (NDLFT) was applied to carbon dioxide isotherm at 273 K to characterize narrow micropores and microporous structure of activated carbon. Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) were used to investigate morphology and microstructure. TEM micrographs confirmed the existence of random micropores. We have also noticed that the textural properties were highly dependent on the concentration of the activating agent. Carbon dioxide adsorption on activated carbon materials has shown dependency on the volume of narrow micropores (less than 0.8 nm). The activated carbon materials have narrow micropore volume in a range of 0.155–0.292 cm3, and BET surface area of 761–1383 m2/g. Carbon activated with KOH ratio of three (WDC-03) has shown excellent CO2 uptake of 5.33 and 4.24 mmol/g at 273 and 298 K respectively. Moreover, it has also shown a high value for the isosteric heat of adsorption (29.8–14.3 KJ/mol) and selectivity of ∼16 over nitrogen.

Optimizing Carbon Dioxide Uptake and Carbon Dioxide‐Methane Selectivity of Oxygen‐Doped Porous Carbon Prepared from Oxygen Containing Polymer Precursors

AbstractThe reproducible synthesis is reported for oxygen containing porous carbons (OPC) by the KOH activation at 500–800 °C of two oxygen containing precursor polymers: polyfurfuryl alcohol (PFFA) and polyanisyl alcohol (PAA) yielding FFA‐OPC and AA‐OPC, respectively. Both OPCs exhibits good thermal stability and reproducible gas uptake properties over multiple cycles. The surface area and pore volumes of the OPC are independent of the precursor identity, but controlled by the activation temperature. Similarly, the uptake of CO2 is determined by the physical properties of the OPC: activation at 750 °C results in uptake that equals or out‐performs existing PCs for high pressure uptake (30 bar) at 24.0 °C (FFA‐OPC750: 117 wt%; AA‐OPC750: 115 wt%). The high uptake is related to a high relative percentage of pores &lt;2 nm. The uptake of CH4 for both OPCs is greatest for samples activation at 750 °C, FFA‐OPC750 shows enhanced uptake compared to AA‐OPC750, 15.5 wt% versus 13.7 wt%, respectively. Uptake for CH4 appears to relate to a high relative percentage of pores 1–2 nm, which is observed for AA‐OPC750. As a consequence, AA‐OPC750 demonstrates superior selectivity for CO2 capture over CH4 uptake (AA‐OPC750: Vmass(CO2/CH4)=8.37 at 30 bar) as compared to reported PCs. A higher value for the isosteric heat of adsorption of CO2 (33 kJ mol−1) versus CH4 (11 kJ mol−1) suggests a new temperature dependent strategy for removing CO2 from natural gas via selective adsorption and desorption cycles.

Adsorption characteristics of clay minerals in shale

ABSTRACTBased on the adsorption potential theory, this paper describes the adsorption characteristics of four kinds of clay minerals, i.e. Montmorillonite, Kaolinite, Chlorite, and Illite, in clay shales, meanwhile adding quartzite as control sample. We focus on adsorption amount a, differential adsorption work A, characteristic energy E, characteristic coefficient n in adsorption potential analysis. The results show that the differential adsorption work decreases as the adsorption energy increases, which can generally represent the change features during each stage; the optimum value of n is around 1.5 for five kinds of inorganic minerals; E slightly decreases as the temperature increases. For clay minerals, the absolute values of adsorption heat and the result of maximum adsorption can meet that Montmorillonite> Kaolinite> Chlorite> Illite.