Excess Sorption Research Articles

Water sorption behavior of poly(norbornene)-based anion exchange polyelectrolytes: Experiments and simulation

Poly(norbornene)s (PNBs) are great potential candidates for anion exchange polyelectrolytes (AEPs), however, PNBs-based AEPs usually suffer from excessive water sorption. Herein, the underlying mechanism behind high water sorption was proposed by using the quaternized PNBs as a model AEP. With a moderate ionic content of 2.15 mmol/g, the hydrogenated AEP has a high water uptake of 253 % at 25 °C, which is caused by heterogeneous quaternization and weak interchain interactions. When the brominated AEP was immersed in trimethylamine aqueous (TMA/H2O) solution, TMA penetrates tightly packed polymer chains, seriously destroying vdW interchain interactions. Subsequently, the quaternized cationic groups induce spontaneous water sorption. Although ionic moieties possess strong interchain electrostatic interactions, the solid AEPs restrict polymer chains to form highly cohesive domains for resisting water sorption. Additionally, carbon–carbon double bonds in the PNBs preferentially interact with TMA/H2O, further increasing water uptake. This work provides theoretical guidance for preparing high-performance AEPs based on all-hydrocarbon aliphatic backbones.

Bituminous Coal Sorption Characteristics and Its Modeling of the Main Coal Seam Gas Component in the Huaibei Coalfield, China

Knowledge of the gas sorption and permeability characteristics of a coal provides an essential basis for the evaluation of coalbed methane reserves and their recoverability. Thus, the gas excess sorption capacities of the main gas component of coal seam gas (CSG) in bituminous coal samples derived from the Xutuan Coal Mine in the Huaibei Coalfield, in the Anhui Province of China, were measured using a volumetric method. The results showed that under the same equilibrium pressure, the order of excess sorption capacity was CO2 > CH4 > N2. Furthermore, the sorption capacity ratios of coal from the Xutuan Mine for CO2, CH4, and N2 were approximately 6.0:2.3:1. It was also demonstrated that the sorption capacity during depressurization was always larger than that of the adsorption process, which is indicative of desorption hysteresis. The behaviors of three adsorption models, Langmuir, BET, and D-R, all of which include two parameters, are considered in this paper. The different gas sorption measurement data were fitted by the three models. For the bituminous coal samples, the fits of the D-R equation of all three different gases are higher than 0.99, the fits of the Langmuir equation are higher than 0.985, while the fits of the BET equation for CH4 and N2 absorption are higher than 0.95. However, the fits of the BET equation for CO2 absorption are only about 0.5. Coal sorption has an apparent influence on coal permeability; the permeability of the same coal sample to N2, CH4, and CO2 gases was tested and analyzed. The result shows that the permeability of CO2 was found to be lower than that of other coal seam gas constituents, CH4 and N2, due to their different adsorption abilities.

High-Pressure Adsorption of CO2 and CH4 on Biochar-A Cost-Effective Sorbent for In Situ Applications.

The search for an effective, cost-efficient, and selective sorbent for CO2 capture technologies has been a focus of research in recent years. Many technologies allow efficient separation of CO2 from industrial gases; however, most of them (particularly amine absorption) are very energy-intensive processes not only from the point of view of operation but also solvent production. The aim of this study was to determine CO2 and CH4 sorption capacity of pyrolyzed spruce wood under a wide range of pressures for application as an effective adsorbent for gas separation technology such as Pressure Swing Adsorption (PSA) or Temperature Swing Adsorption (TSA). The idea behind this study was to reduce the carbon footprint related to the transport and manufacturing of sorbent for the separation unit by replacing it with a material that is the direct product of pyrolysis. The results show that pyrolyzed spruce wood has a considerable sorption capacity and selectivity towards CO2 and CH4. Excess sorption capacity reached 1.4 mmol·g-1 for methane and 2.4 mmol·g-1 for carbon dioxide. The calculated absolute sorption capacity was 1.75 mmol·g-1 at 12.6 MPa for methane and 2.7 mmol·g-1 at 4.7 MPa for carbon dioxide. The isotherms follow I type isotherm which is typical for microporous adsorbents.

Experimental and modelling studies of carbon dioxide capture onto pristine, nitrogen-doped, and activated ordered mesoporous carbons.

The search for suitable materials for carbon dioxide capture and storage has attracted the attention of the scientific community in view of the increased global CO2 levels and its after-effects. Among the different materials under research, porous carbons and their doped analogues are extensively debated for their ability to store carbon dioxide at high pressures. The present paper examined high-pressure carbon dioxide storage studies of 1-D hexagonal and 3-D cubic ordered mesoporous pristine and N-doped carbons prepared using the nano-casting method. Excess carbon dioxide sorption isotherms were obtained using the volumetric technique and were fitted using the Toth model. Various parameters that influence CO2 storage on metal-free ordered mesoporous carbons, such as the effect of pore size, pore dimension, pyrolysis temperature, the impact of nitrogen substitution, and the effect of ammonia activation are discussed. It was observed that the carbon dioxide storage capacity has an inverse relation to the total nitrogen doped, the amount of pyridinic nitrogen functionality, and the pyrolysis temperature, whereas the pore size seems to have a linear relationship. On the other hand, the presence of oxygen has a positive effect on the sorption capacity. Among the prepared ordered mesoporous carbons, the ammonia-treated one has shown the highest adsorption capacity of 37.8 mmol g-1 at 34 bar and 0 °C.

Impact of Supercritical CO2 on Shale Reservoirs and Its Implication for CO2 Sequestration

Hydraulic fracturing has transformed the international energy landscape by becoming the go-to method for the exploitation of natural gas from unconventional shale reservoirs. However, in the recent years, the search for an alternative method of shale-gas exploration has intensified, because of various problems (e.g., contamination of ground and surface water, overexploitation of precious water resources, air pollution, etc.) associated with the usage of water-based fracturing techniques. The use of CO2 for shale gas exploitation has emerged as a better alternative to aqueous-based gas exploration techniques. CO2 when injected into deep shale reservoirs, transitions into supercritical CO2 (SC-CO2) when temperature and pressure condition exceeds the critical point, i.e., 31.1 °C and 7.38 MPa. In this paper, we comprehensively review the impact of SC-CO2 on shale gas reservoirs during the different stages of shale-gas exploration, i.e., (i) drilling, which involves the superiority of SC-CO2 over water-based drilling fluids, in terms of achieving under-balanced well condition, higher rates of penetration, and resistance to formation damage; (ii) fracturing, which involves factors affecting the tortuosity of fractures created by SC-CO2 fracturing, breakdown pressure, and proppant-carrying capacity; and (iii) injection, which involves the twin-headed benefit of enhanced recovery due to CO2/CH4 competitive adsorption and geological sequestration, CO2 vs CH4 excess sorption as a function of pressure, etc. Several research works have indicated discrepancies on how SC-CO2 impacts different shale properties. Some studies show low-pressure N2-gas-adsorption-derived surface area and total pore volume to be increasing with SC-CO2 imbibition, while others show a decreasing trend for the same. Similarly, for some shales, the quartz content, along with the clay mineral contents, decreased as the exposure to SC-CO2 increased, while in some other studies, with similar long-term exposure to SC-CO2, the quartz content was observed to increase along with the decrease in clay content and vice versa. Essentially, the increased exposure to SC-CO2 results in the dissolution of primary porous structures and fractures, and reformation of newer porous structure and conduits in shales. Nonetheless, these changes in the mineralogy weaken the microstructure of the rock bringing significant changes in the mechanical properties of the shales with implications on the wellbore stability and fracturing efficiency. The mechanical properties such as uniaxial compressive strength (UCS), Young’s modulus, and tensile strength decrease as the SC-CO2 saturation period increases. However, some studies have shown factors like bedding angle and phase-state of CO2 having varying effect on the strength behavior of the shales. Moreover, changes in the structure of shales caused by the creation of fractures and the reduction of their strength can also pose major risks, because of potential leakage of CO2 through these created pathways. How these processes would interact at field scale would control the sealing capacity, especially at field-scale for addressing long-term seepage of CO2.

Highly efficient CO2 hydrogenation to methanol via in-situ condensation and sorption in a novel multi-stage circulating fast fluidized bed reactor

The theme of this study is to explore the enhancement of carbon conversion to methanol by introducing the concept of circulating fast fluidization coupled with in-situ condensation (IC) and in-situ sorption. According to the best of our knowledge, this is the first time a novel multi-stage circulating fast fluidized bed reactor (CFFBR) is implemented in methanol synthesis. The validity of the reactor and thermodynamic models was verified by industrial and experimental data and good agreement is found. It has been found that the combination of IC and in-situ sorption with the short reactor bed policy achieves remarkable improvement in carbon conversion to MeOH (99.20%). The simulation results indicate that considerable improvement in conversion to MeOH (88.02%) can be achieved by the single bed CFFBR configuration with the in-situ sorption. For the same reactor condition, the IC achieves 59.95% conversion to MeOH. It is apparent that sorption is more pronounced than that of IC. Also, it is found that a large multi-stage configuration with IC can greatly improve the carbon conversion to MeOH (98.24%). It has been observed that excessive sorption inhibits the WGS and increases the accumulation of CO, leads to a considerable drop in carbon conversion to MeOH. Two critical points were identified and used to determine the instantaneous equilibrium of the WGS and the beginning of the total carbon conversion to methanol. The results of this study reveal that fascinating phenomena appear when the in-situ sorption with highly selective water adsorbent of zeolite-4A particles is implemented in the single bed CFFBR.

The use of sorption and excess sorption isotherm in the mathematical modeling of the unsteady-state heat and humidity regime of the building envelope

In the given article the development of the moisture transfer equation based on the theory of moisture potential is considered. The task of combined heat and moisture transfer is one of the most complicated tasks in the building thermal physics field. The classical equations of moisture transfer by K.F. Fokin representing the transfer of moisture under the action of partial transfer potentials - the gradient of the partial pressure of water vapor and the gradient of humidity F - are listed. The possibility of uniform accounting of the combined water vapor transfer on the basis of the moisture potential F is described. The sorption isotherm for aerated concrete is constructed in accordance with the experiment carried out in a desiccator with an aqueous solution of sulfuric acid. A new equation of moisture transfer which takes into account moistening with vaporous moisture in the sorption zone of moisture and liquid moisture in the excess sorption zone of moisture is derived. In order to simplify the work with the obtained equation a new value of the relative potential capacity is introduced. A graph construction of sorption and excess sorption isotherms which are obtained using an analytical expression for the relative potential capacity is proposed. In the sorption zone of humidification the sorption and excess sorption isotherms coincide with the classical sorption isotherm. Meanwhile, in the excess sorption zone of humidification the sorption and excess sorption isotherms depend on temperature.

Sorption of Neuropsychopharmaca in Microfluidic Materials for In Vitro Studies.

Sorption (i.e., adsorption and absorption) of small-molecule compounds to polydimethylsiloxane (PDMS) is a widely acknowledged phenomenon. However, studies to date have largely been conducted under atypical conditions for microfluidic applications (lack of perfusion, lack of biological fluids, etc.), especially considering biological studies such as organs-on-chips where small-molecule sorption poses the largest concern. Here, we present an in-depth study of small-molecule sorption under relevant conditions for microphysiological systems, focusing on a standard geometry for biological barrier studies that find application in pharmacokinetics. We specifically assess the sorption of a broad compound panel including 15 neuropsychopharmaca at in vivo concentration levels. We consider devices constructed from PDMS as well as two material alternatives (off-stoichiometry thiol–ene–epoxy, or tape/polycarbonate laminates). Moreover, we study the much neglected impact of peristaltic pump tubing, an essential component of the recirculating systems required to achieve in vivo-like perfusion shear stresses. We find that the choice of the device material does not have a significant impact on the sorption behavior in our barrier-on-chip-type system. Our PDMS observations in particular suggest that excessive compound sorption observed in prior studies is not sufficiently described by compound hydrophobicity or other suggested predictors. Critically, we show that sorption by peristaltic tubing, including the commonly utilized PharMed BPT, dominates over device sorption even on an area-normalized basis, let alone at the typically much larger tubing surface areas. Our findings highlight the importance of validating compound dosages in organ-on-chip studies, as well as the need for considering tubing materials with equal or higher care than device materials.

Characterization of shale using Helium and Argon at high pressures

In order to estimate the shale gas in place and the eventual recovery during shale gas operations, one of the key requirements is to accurately characterize the shale's petrophysical and transport properties such as porosity, permeability, diffusivity, and storage capacity. Despite the many efforts reported in the technical literature aiming to provide an improved understanding of the complex pore structures and the associated fluid flow in gas shales, a complete characterization of organic-rich shale samples still poses a big challenge. In this work, we have characterized mass transfer and sorption in shale at different length scales using Helium (He) and Argon (Ar) as probe gases. Thermogravimetric analysis (TGA) with a shale cube of ~1 cm3 in size and gas expansion experiments with a full-diameter core (3.5” in diameter) were used to measure sorption kinetics/isotherms and mass transfer, respectively. Both samples are from the same depth/location in the Marcellus shale formation. The TGA steady-state technique was initially used to generate excess sorption isotherms for Ar, while dynamic TGA experiments were used to study its sorption kinetics. The TGA experiments demonstrate that Ar, which has a similar sorption potential as Methane, but is generally assumed to be inert, adsorbs onto the surfaces of the mesoporous and microporous regions of the shale samples according to a Langmuir-type behavior. Helium expansion experiments, on the full-diameter core, were used to measure the overall porosity, on the basis that He is a non-sorbing and inert gas as compared to Ar. The He expansion experiments, furthermore, allow us to delineate the mass transfer of gas across the inherent hierarchy of pore sizes, including macropores (macro- and micro-cracks), mesopores and micropores. Similar expansion experiments were also performed with Ar to study the combined impact of mass transfer and sorption. A triple-porosity model (TPM) was utilized to interpret the He expansion experiments with the shale core and to extract (estimate) relevant transport parameters. We report and compare here the diffusivities and permeabilities of the whole core for both He and Ar, as calculated from the modeling and fitting of the experimental data. On the premise that the shale cube is representative of the matrix region of the core, the Ar sorption kinetics from the cube experiments were subsequently combined with the transport parameters extracted from the He experiments to predict the behavior of the Ar expansion test with the full-diameter core. An excellent agreement is observed between the model predictions and the experimental data. The experimental observations and their interpretation indicate that one must be cautious when using Ar to estimate the true porosity and permeability of shales. In addition, we demonstrate that He and Ar probe gases, when used in tandem, can be employed effectively as a tool to characterize shales in terms of mass transfer and sorption dynamics across scales.

Ultrahigh Hydrogen Uptake in an Interpenetrated Zn 4 O-Based Metal–Organic Framework

As a highly promising candidate for hydrogen storage, crucial to vehicles powered by fuel cells, metal–organic frameworks (MOFs) have attracted the attention of chemists in recent decades. H2 uptak...

Effect of 2-MeIM/Zn Molar Ratio on CO2 Permeability of Pebax/ZIF-8 Mixed Matrix Membranes

The impact of controlling molar ratio of ZIF-8 precursors on Pebax 1657 and Pebax 2533 based Mixed Matrix Membranes (MMMs) on the CO2 permeability and CO2 /N2 ideal selectivity was investigated. Three types of ZIF-8 were synthesized by controlling molar ratio of 2-methylimidazole and zinc nitrate hexahydrate as 2/1, 8/1, and 32/1. The SEM images and XRD patterns of ZIF-8 showed that particle sizes and crystallinity peaks were decreased as molar ratio of ZIF-8 increased. The CO2 permeability of Pebax MMM was improved by filling with the ZIF-8 particles compared to the pure Pebax. At equivalent temperatures, the highest CO2 permeability was shown in Pebax 1657/ZIF-8 with the ZIF8 precursors’ molar ratio of 32/1 and Pebax 2533/ZIF-8 with the molar ratio of 2/1. As molar ratio of ZIF-8 precursors increases, CO2 permeability of Pebax 1657 was increased by excessive sorption of CO2 by imidazolium ions in ZIF-8, whereas CO2 permeability of Pebax 2533 was decreased by decreasing pore size and particle size of ZIF-8. The CO2 permeability was higher in Pebax 2533/ZIF-8 compared to Pebax 1657/ZIF-8, because Pebax 2533 has more concentrations of polar groups in the polymer matrix than Pebax 1657. However, the CO2 /N2 ideal selectivity was higher in Pebax 1657/ZIF-8 compared to Pebax 2533/ZIF-8 because diffusivity of Pebax 1657 compared to Pebax 2533 is lower for nonpolar gases, such as N2 , and the solubility is higher for polarizable gases like CO2 . As increasing temperature, Pebax/ZIF-8 MMMs showed enhancement of CO2 and N2 permeability but decreased in CO2 /N2 ideal selectivity.

High-Pressure Sorption of Methane, Ethane, and Their Mixtures on Shales from Sichuan Basin, China

High-pressure sorption isotherms of CH4, C2H6, and their mixtures on shales from Sichuan Basin, China, were measured by a volumetric method. The sorption measurements for pure components were conducted at 40, 60, and 80 °C, with the pressure up to ∼20 MPa. The binary sorption measurements were performed to ∼11 MPa at 40 °C and ∼16 MPa at 80 °C, and two feed gas compositions of C2H6 (10 and 20%) were studied. The excess sorption isotherms of pure components were fitted by the three-parameter Langmuir model, and the extended Langmuir (EL) model was used to predict the absolute sorption isotherms of binary mixtures. The sorption discrepancies of CH4/C2H6 were discussed, and the preferential sorption of C2H6 was quantitatively analyzed. As the temperature decreases, the excess sorption isotherm of C2H6 presents a more sharp increase and then a more rapid decrease. The excess sorption isotherms of C2H6 at 40 °C show significant differences with other CH4/C2H6 isotherms. In comparison to gas composition, the temperature has a more notable effect on binary excess sorption isotherms. C2H6 shows a stronger affinity than CH4, and its stronger affinity is less significant in the mixtures compared to the single component. The sorption selectivity presents a first increasing and later decreasing trend with the pressure. The presence of C2H6 mainly reduces the excess sorption of CH4 at a high pressure, and its effect at a low pressure is negligible.

How much carbon can be added to soil by sorption?

Quantifying the upper limit of stable soil carbon storage is essential for guiding policies to increase soil carbon storage. One pool of carbon considered particularly stable across climate zones and soil types is formed when dissolved organic carbon sorbs to minerals. We quantified, for the first time, the potential of mineral soils to sorb additional dissolved organic carbon (DOC) for six soil orders. We compiled 402 laboratory sorption experiments to estimate the additional DOC sorption potential, that is the potential of excess DOC sorption in addition to the existing background level already sorbed in each soil sample. We estimated this potential using gridded climate and soil geochemical variables within a machine learning model. We find that mid- and low-latitude soils and subsoils have a greater capacity to store DOC by sorption compared to high-latitude soils and topsoils. The global additional DOC sorption potential for six soil orders is estimated to be 107 pm 13 Pg C to 1 m depth. If this potential was realized, it would represent a 7% increase in the existing total carbon stock.

Experimental determination of porosity and methane sorption capacity of organic-rich shales as a function of effective stress: Implications for gas storage capacity

Gas storage capacity estimates of shales are routinely assessed using laboratory data from unconfined methane sorption and porosity measurements. In this study, the stress dependence of the methane excess sorption capacity and specific pore volume are investigated simultaneously. Experiments were performed on dry core plugs (Cambrian–Ordovician Alum, Jurassic Bossier, Late Cretaceous Eagle Ford, and Jurassic Kimmeridge shales) at 30°C under controlled confining stress up to 40 MPa and gas pressures up to 20 MPa. Increasing overburden stress results in a significant decrease of both specific pore volume and excess sorption capacity. The stress sensitivity of the specific pore volume was most prominent for the total organic carbon (TOC)–rich Kimmeridge sample (45% TOC) and further decreased in the order of Bossier, Eagle Ford, and Alum. Stress dependence of the methane excess sorption capacity, expressed as percentage reduction at 40-MPa overburden as compared to unconfined conditions, decreases in the order Eagle Ford (∼56%), Bossier (∼30%), Kimmeridge (∼14%), and Alum (∼5%). Although the decrease of specific pore volume is definitely caused by poroelastic compression, the mechanism(s) leading to the reduction of excess sorption capacity with stress require further investigation. Gas storage calculations show that routine methods based on unconfined data may grossly overestimate the total storage capacity. In this scenario, at 2500-m depth, the total gas storage capacity will be overestimated by 5% for the Alum, 28% for the Bossier, 18% for the Eagle Ford, and 28% for the Kimmeridge if the stress dependent reduction of volume and sorptive storage capacity is not considered.

Synthetic Approach to Hydrocarbon Proton Exchange Membranes Using Anion Exchange Membrane Precursors

Proton exchange membranes (PEMs) are a crucial component to many electrochemical energy conversion devices, including low temperature hydrogen fuel cells and water electrolyzers. Perfluorosulfonic acid-based PEMs have overwhelmingly been the material of choice for these applications however, they are not ideal due to high cost, low glass transition temperature, and lack of synthetic diversity leading to unoptimized material performance. Hydrocarbon PEMs on the other hand have been explored as alternatives to perfluorosulfonic acid materials, although in general have lower proton conductivity, excessive water sorption and poor oxidative stability. Despite a large body of works focusing on hydrocarbon PEMs, most are based on aryl ether containing polymers such as poly(aryl ether sulfone). Recently, the PEM research community has shown that wholly aromatic polymer systems exhibit improved oxidative stability and restrict water uptake, allowing for higher ion exchange capacities. The synthetic routes of these polymer systems, however, are limited to sulfonation of aromatic unit through hash sulfonating conditions leading to ill-defined polymers or through complicated multistep synthetics routes, often requiring transition metal catalysts. Herein, we report widely applicable synthetic methods and exceptional properties of hydrocarbon based PEMs without any aryl ether linkages. To achieve this PEMs were synthesized from materials bearing a haloalkyl side chains. Since, anion exchange membranes (AEM) are commonly synthesized from haloalkyl bearing polymers and the polymer property requirements of PEMs and AEMs are similar, (i.e. no aryl ether linkages, high IEC, dimensional stability, ect.) this ushers in a new generation of stable hydrocarbon PEM materials from the vast library of stable AEMs. Furthermore, the synthetic procedures are based on simple SN2 and oxidation chemistry requiring no metal catalysts or harsh reaction condition. The resulting polymers show excellent conductivity and restricted water uptake at higher temperatures due to improved phase separation stemming from the attaching sulfonate group to a tethered side chain of polymer. Additionally, in highly oxidative Fenton’s reagent test, no discernable changes to the polymer performance of structure was observed.

Physicochemical Properties of Experimental Resin-Based Materials Containing Fluoridated Calcium Phosphates

The aim of this study was to evaluate the physicochemical properties of experimental adhesives containing tailored fluoridated calcium phosphate fillers. Five experimental resins were formulated, one contained no calcium phosphate filler (Control) and the other four resins contained 40wt% of calcium phosphate fillers doped with increasing concentration of fluoride: adhesives CaP (no fluoride), CaP-2F (2wt% F), CaP-4F (4wt% F) and CaP-8F (8wt% F). Resin specimens were prepared for three-point bending test to evaluate the elastic modulus (E) and flexural strength (FS) at 24h and after 2 months of water storage. Disk-shaped specimens were prepared to analyze the water sorption (Ws) according to ISO 4049. The degree of conversion (DC) of the tested resins was also assessed through FTIR. Statistical analysis was performed with ANOVA and Tukey’s test (p 0.05) compared to the filler-free resin. However, these same experimental resins showed the highest E after water storage. All resins had a significant reduction of the FS after water storage (p<0.001), but at lower percentage rate for those experimental resins containing fluoride-free CaP or fluoride-doped CaP-2F.. These latter experimental resins achieved similar Ws to control filler-free resin. Conversely, those resins containing 4wt% or and 8wt% fluoride-doped CaP promoted had a significant Ws increase (p<0.05). In conclusion, the incorporation of calcium phosphate particles without fluoride and or with 2wt% fluoride may represent be a promising strategy to generate adhesive resins with specific physicochemical properties. Fluoride incorporation in CaP fillers for dental resin adhesive should be performed at low concentrations in order to avoid excessive water sorption and decrease of polymerization.

Isotherms and kinetics of deformation of coal during carbon dioxide sequestration and their relationship to sorption

An in-depth understanding of the carbon dioxide (CO2) sorption behavior on coal is critical for CO2 sequestration in coal seams and enhanced coalbed methane recovery. However, CO2 induces the deformation of coal through physical and/or chemical reactions during the CO2 injection process, which has a significant effect on the gas flow and stability of the coal seams. This study investigates the isotherms and kinetics of CO2 sorption and hence deformation of a bituminous coal sample during isotherm tests at three different temperatures. The isotherms and kinetics curves of sorption and deformation can be described by the Langmuir and the pseudo-second-order (PSO) models, respectively. The experiment results and PSO model parameters indicate that a pore-filling effect at low pressure results in an overestimated amount of excess sorption, leading to a mismatched phenomenon between the sorption and swelling, that is the maximum amount of sorption fails to induce corresponding maximum swelling. The CO2-induced deformation is anisotropic and heterogeneous during the whole sorption process, which can be attributed to the bedding structure of coal and heterogeneous maceral distribution in coal. Because of the difference in the sorption characteristic between different macerals, the clay + inertinite-rich regions first rapidly swell and then suffer from compression through the later swelling of the vitrinite + liptinite -rich regions in coal, showing an “overshoot” behavior. The dissolution of CO2 induces a structural rearrangement of coal, leading to strains in different directions maintain changes without further CO2 intake. This phenomenon is observed in the first few sorption steps until the structure of coal reaches a stable state. The kinetic relationships between sorption and deformation in individual pressure steps are nearly linear or are linear up to a certain point but slopes of these curves are different, resulting in a simple quadratic polynomial relationship between sorption and deformation isothermals during the whole sorption process.

Effect of shale properties on CH4 and CO2 sorption capacity in Czech Silurian shales

The study involved an experimental assessment of the CO2 and CH4 sorption capacity of seven dark Silurian shale samples from three formations in the Barrandian Basin (Czech Republic). The shale samples had dominant inorganic matter consisting mainly of clay minerals, quartz, calcite and plagioclase, and very low organic matter. Most of the organic particles were the remains of zooclasts, especially graptolites and bitumens. The graptolite reflectance (Rr) reflecting the degree of thermal maturation of the shales ranges between 0.56% in the Kopanina Formation and 1.09% in the Litohlavy Formation, with the exception of the probably thermally altered part of the Motol Formation, which has reflectance higher than 1.70%. The total organic carbon (TOC) content was found to be in the range of 0.34–2.37 wt%. The porosity values were from 4.6% to 18.8%. In all shale samples, the high pressure excess sorption isotherms of CO2 and CH4 were measured at a temperature of 45 °C for both gases at pressures up to 8 MPa for CO2 and up to 15 MPa for CH4 on dry samples, using a manometric sorption apparatus. The Gibbs equation was used for evaluation of the maximum excess sorption (nmax,CO2 and nmax,CH4). The nmax,CO2 values ranged from 0.118 mmol/g to 0.244 mmol/g, while the nmax,CH4 values were more than twice lower (0.050 mmol/g - 0.088 mmol/g). The xCO2/CH4 ratio ranged from 1.47 to 2.98, with a median value of 2.54, calculated without the sample from the Kopanina Formation (4.36). The influence of the shale parameters on the CO2 and CH4 sorption capacity was determined. No relation has been proven between the value of Rr and the TOC-normalized CO2 and CH4 sorption capacities. The CO2 sorption capacity showed a negative correlation with TOC and with clay minerals but a positive correlation with quartz, while the behaviour of CH4 was opposite in these cases. A strong positive correlation was found between the volume of micropores and the CO2 excess sorption capacity, and negative dependence was found for CH4. The CO2 sorption capacities always depend on the micropores content, and the CH4 capacities depend on the shale components.

Investigation and Comparison of 5 % Diphenyl – 95 % Dimethyl Polysiloxane Capillary Columns

In gas chromatography, for the analysis, the most important thing is the well-chosen column. After having decided about which stationary phase is the best for our measurement and we know the length, the inner diameter and film thickness, we can buy the column from a lot of manufacturers. The products of these manufacturers’ look similar to each other, but they are different, because of the different manufacturing technologies. These differences could have significant influence on the separation. It is so important to compare the „same” columns, despite the manufacturers’ efforts to produce the best quality columns.5 % diphenyl – 95 % dimethyl polysiloxane stationary phase is widely used. Its slight polarity makes it able to determine very different compounds from the alkanes, through volatiles, drugs, fatty acid methyl esters, amines or phenols.In our work, we tested 5 % diphenyl – 95 % dimethyl polysiloxane stationary phase columns with an 8-component mixture. These columns were from different manufacturers. During isothermal conditions, we determined the height equivalent of theoretical plates on 8 linear velocity level. We represented these parameters as the function of linear velocity. With a constant linear velocity, we measured the excess sorption enthalpy and entropy. From the chromatograms we spotted differences in the retention and in resolution, which is important if we use the column for volatiles or for complex samples. With these parameters we can show many differences between the columns. These parameters have significant influence when we want to use our column for a given task.

Experimental Investigation of the Dependence of Accessible Porosity and Methane Sorption Capacity of Carbonaceous Shales on Particle Size

Crushing and grinding of carbonaceous shale samples is likely to enhance the accessibility of pores and embedded organic matter as compared to the intact rock. This may lead to an overestimation of the total (volume and sorptive) gas storage capacity. In order to investigate the importance of these effects we have measured unconfined apparent grain densities (helium pycnometry) and methane sorption capacities (high-pressure methane excess sorption) of four carbonaceous shales (Cambro-Ordovician Alum Shale, Jurassic Kimmeridge Clay, Jurassic/Cretaceous Bazhenov Shale, and Late Cretaceous Eagle Ford Shale) as a function of particle size. Measurements were first conducted on 38 mm diameter core plugs, which then were crushed and milled to successively smaller particle sizes (&lt;10 mm, &lt;2 mm, &lt;64 μm, and &lt;1 μm). Apparent grain densities of the smallest particle fractions of the Alum, Bazhenov and Kimmeridge samples were consistently higher by 0.5 to 1% than apparent grain densities of the original sample plugs. Methane excess sorption capacity increased significantly for particle sizes &lt;64 μm for the Alum and &lt;1 μm for the Bazhenov and Kimmeridge samples while no significant changes upon grinding were observed for the Eagle Ford Shale. For the Bazhenov Shale, the apparent grain density increased slightly from 2.446 g/cm3 to 2.450 g/cm3 upon particle size reduction from &lt;64 μm to &lt;1 μm while the maximum sorption capacity (“Langmuir volume”) increased substantially from 0.11 mmol/g to 0.19 mmol/g. Similarly, for the Kimmeridge Clay and Alum Shale, a slight increase of the apparent grain density from 1.546 g/cm3 to 1.552 g/cm3 and from 2.362 g/cm3 to 2.385 g/cm3, respectively, was accompanied by increases in sorption capacity from 0.37 mmol/g to 0.45 mmol/g and from 0.14 mmol/g to 0.185 mmol/g, respectively. The increase in sorption capacity indicates an opening of a considerable amount of micropores with large internal surface area upon physical disruption of the rock fabric and/or removal of included fluids. It may also be due to increased swelling abilities of clay minerals and organic matter upon destruction of the stabilizing rock fabric with decreasing particle size. Grain density and sorption isotherms measured on small particle sizes are likely to overestimate the gas storage capacities and the amounts of producible gas-in-place since under field conditions (largely undisrupted rock fabric), significant portions of this storage capacity are essentially inaccessible. Poor interconnectivity of the pore system and slow, diffusion-controlled transport will massively retard gas production. Based on these findings, particle sizes &gt;64 μm should be used for porosity and sorption measurements because they are more likely to retain the properties of the rock fabric in terms of accessible pore volume and sorptive storage capacity.