Gas Adsorption Characteristics Research Articles

Petrographical and Thermo-chemical Investigation of some North East Indian High Sulphur Coals

Abstract: The Tertiary North East Indian coals, classified as sub-bituminous rank, have found less industrial application owing to their physico-chemical attributes. These coals are characterized by low ash (<15%), high volatile matter (>35%) and high sulphur (2.9-4.46%). Majority of the sulphur occurs in organic form affixed to the coal matrix owing to marine influence, is difficult to remove. The coal maceral analysis shows the dominance of vitrinite (>75%) with lesser amounts of liptinite and inertinite. Reflectance measurements (Rmax) of these sub-bituminous coals fall in the range of 0.57 to 0.65. In this study, the petrographical (maceral), thermal and other physico-chemical analyses of some low rank Tertiary sub-bituminous coals from north-east India were carried out to assess their potential for combustion, liquefaction and coal bed methane formation. The petrofactor, conversion (%) and oil yield (%), combustion efficiency of the coal samples were determined. The respective linear correlations of conversion (%) of the coals with their vitrinite contents, petrofactor and oil yield values have been discussed. The relative combustion efficiency of the coals was measured from the thermo gravimetric analysis (TGA) of coals. The influence of maceral composition upon gas adsorption characteristics of these high volatile coals showed the increase in methane adsorption with vitrinite enrichment. Both the maceral and mineral matter contents were observed to have important influence on the gas adsorption characteristics.

Investigation of a Correlation Between Structures of Mesoporous Carbon an Gas Adsorption Characteristics

Introduction PEFCs are paid much more attention since the commercialization of FCVs and are deeply related to carbon materials, which are components of PEFCs themselves and also related systems. In our group, we have been studying mesoporous carbon (MC), which has meso-channel structures with about 10 nm diameter, as a catalyst support and have successfully improved durability of PEFCs, so far. In order to further improve performance and durability of PEFCs and related systems, it is important to understand the fundamentals of adsorption properties of fuels involving hydrogen gas, oxygen gas, and water vapor. In this research, a correlation between structures of mesoporous carbon and gas adsorption characteristics is investigated. Experimental General MC was synthesized by mixing Pluronic® F127, resorcinol, formaldehyde, and trimethyl orthacetate and heated under nitrogen atmosphere. Other MC materials1 were also made by slightly different conditions as shown in Table 1. Then, gas adsorption properties of each sample were evaluated after the ball milling and heat treating at 900 oC. Results & discussion Hydrogen adsorption dependence on the pore size of MC is discussed here. If MC#1 and MC#2 in Table 1are compared, MC#2 has larger pores based on the pore distribution obtained from nitrogen adsorption measurements. The values of BET specific surface area of the MC#1 and the MC#2 results in not very much different, 615 m2/g and 650 m2/g, respectively. The maximum hydrogen absorption content (wt%) at 7 MPa has resulted in 0.6 % for MC#1 and 0.35 % for MC#2. Considering Chahine rule2 for carbon materials, revealing that linear relationship between the hydrogen absorption content and the specific surface area, our results are against that rule. Therefore, hydrogen adsorption properties can be explained by other than the specific surface area in our materials. The possible mechanism of hydrogen adsorption is further discussed through the analyses of several MC materials. (1) Y. Sonoda, A. Hayashi, Y. Minamida, E. Akiba, Chemistry Letters, 44, 503-505 (2015). (2) R. Chahine, T.K. Bose, 11th WHEC, 1996; Pergamon Press: Oxford, U.K., 1259 (1996). Figure 1

Remarkable Improvement in the Mechanical Properties and CO2 Uptake of MOFs Brought About by Covalent Linking to Graphene.

Metal-organic frameworks (MOFs) are exceptional as gas adsorbents but their mechanical properties are poor. We present a successful strategy to improve the mechanical properties along with gas adsorption characteristics, wherein graphene (Gr) is covalently bonded with M/DOBDC (M=Mg(2+) , Ni(2+) , or Co(2+) , DOBDC=2,5-dioxido-1,4-benzene dicarboxylate) MOFs. The surface area of the graphene-MOF composites increases up to 200-300 m(2) g(-1) whereas the CO2 uptake increases by ca. 3-5 wt % at 0.15 atm and by 6-10 wt % at 1 atm. What is significant is that the composites exhibit improved mechanical properties. In the case of Mg/DOBDC, a three-fold increase in both the elastic modulus and hardness with 5 wt % graphene reinforcement is observed. Improvement in both the mechanical properties and gas adsorption characteristics of porous MOFs on linking them to graphene is a novel observation and suggests a new avenue for the design and synthesis of porous materials.

Remarkable Improvement in the Mechanical Properties and CO2 Uptake of MOFs Brought About by Covalent Linking to Graphene

AbstractMetal–organic frameworks (MOFs) are exceptional as gas adsorbents but their mechanical properties are poor. We present a successful strategy to improve the mechanical properties along with gas adsorption characteristics, wherein graphene (Gr) is covalently bonded with M/DOBDC (M=Mg2+, Ni2+, or Co2+, DOBDC=2,5‐dioxido‐1,4‐benzene dicarboxylate) MOFs. The surface area of the graphene–MOF composites increases up to 200–300 m2 g−1 whereas the CO2 uptake increases by ca. 3–5 wt % at 0.15 atm and by 6–10 wt % at 1 atm. What is significant is that the composites exhibit improved mechanical properties. In the case of Mg/DOBDC, a three‐fold increase in both the elastic modulus and hardness with 5 wt % graphene reinforcement is observed. Improvement in both the mechanical properties and gas adsorption characteristics of porous MOFs on linking them to graphene is a novel observation and suggests a new avenue for the design and synthesis of porous materials.

Impacts of long-term water inrush on characteristics of coal gas adsorption and seepage

Frequent coal mine flooding is bound to impact not only the stope stress effects of working face, but also the absorption and seepage characteristics of coal mass. In this paper, we examined the effects of long-term water inrush on coal pore structure as well as gas adsorption and seepage characteristics using water-flooded Taoyuan Coal Mine, Anhui Province, China, as an example. Results showed that: 1) after water inrush, the volume, area, and porosity of coal samples, as well as the proportion of micro-pores decreased significantly with the distance from the water inrush site increasing; 2) the amount of gas adsorption of coal samples near the water inrush site was higher than that away from the site; 3) within 13 m from the site, the seepage capacity of coal gas increased; 4) the water seeped into the coal dissolves a mass of inorganic minerals and organic matter and carries them away. [Received: December 26, 2014; Accepted: June 13, 2015]

Impacts of long-term water inrush on characteristics of coal gas adsorption and seepage

Frequent coal mine flooding is bound to impact not only the stope stress effects of working face, but also the absorption and seepage characteristics of coal mass. In this paper, we examined the effects of long-term water inrush on coal pore structure as well as gas adsorption and seepage characteristics using water-flooded Taoyuan Coal Mine, Anhui Province, China, as an example. Results showed that: 1) after water inrush, the volume, area, and porosity of coal samples, as well as the proportion of micro-pores decreased significantly with the distance from the water inrush site increasing; 2) the amount of gas adsorption of coal samples near the water inrush site was higher than that away from the site; 3) within 13 m from the site, the seepage capacity of coal gas increased; 4) the water seeped into the coal dissolves a mass of inorganic minerals and organic matter and carries them away. [Received: December 26, 2014; Accepted: June 13, 2015]

Modeling the adsorption of mixed gases based on pure gas adsorption properties

Sorption-based Joule-Thomson (JT) cryocoolers usually operate with pure gases. A sorption-based compressor has many benefits; however, it is limited by the pressure ratios it can provide. Using a mixed-refrigerant (MR) instead of a pure refrigerant in JT cryocoolers allows working at much lower pressure ratios. Therefore, it is attractive using MRs in sorption- based cryocoolers in order to reduce one of its main limitations. The adsorption of mixed gases is usually investigated under steady-state conditions, mainly for storage and separation processes. However, the process in a sorption compressor goes through various temperatures, pressures and adsorption concentrations; therefore, it differs from the common mixed gases adsorption applications. In order to simulate the sorption process in a compressor a numerical analysis for mixed gases is developed, based on pure gas adsorption characteristics. The pure gas adsorption properties have been measured for four gases (nitrogen, methane, ethane, and propane) with Norit-RB2 activated carbon. A single adsorption model is desired to describe the adsorption of all four gases. This model is further developed to a mixed-gas adsorption model. In future work more adsorbents will be tested using these four gases and the adsorption model will be verified against experimental results of mixed-gas adsorption measurements.

A new method for accurate and rapid measurement of underground coal seam gas content

Coal seam gas content is one of the basic parameters for gas disaster prevention and gas utilization in underground coal mines. It is also an important index for coal seam outburst danger evaluation and gas extraction effect investigation, which require a lot of measuring work and must be tested in large areas in underground coal mines. Due to the calculated error of the lost gas in the direct method and difficulties in accurately measuring the gas pressure used to calculate the gas content in the indirect method, the accurate determination of gas content remains a difficult problem. In this paper, the main component of gas content and current measurement methods used in China were discussed, and a new method of coal seam gas content measurement based on the small gap of gas adsorption and desorption characteristics of coal seams in the same geologic unit was proposed. In this new method, we first established a reasonable calculation model for the lost and residual gas contents based on laboratory measurements of desorption characteristics; an accurate and rapid determination of the underground gas content could then be directly obtained. This method requires a small workload and a short measuring time and is particularly applicable to a single underground coal seam with a demand for large quantity measurement. From an engineering perspective, this method not only can rapidly determine coal seam gas content but also can reflect the real gas pressure, satisfying the large area multi-point measurement of coal seam gas content with higher reliability and safety.

Shale Gas Productivity Predicting Model and Analysis of Influence Factors

In order to find the dynamic characteristics of shale gas reservoirs and improve shale gas well production, it is very important to research on shale gas seepage mechanism and production evaluation. Based on the shale gas seepage mechanism, adsorption and desorption characteristics, the diffusion mechanism and mass conservation theory in shale gas development, the dual pore medium shale gas reservoir mathematical model is set up. The mathematical model is built by the finite difference method based on start-up pressure gradient, slippage effect and the isothermal adsorption principle, and then programmed to solve it. Finally, this paper analyzed the impact of Langmuir volume, Langmuir pressure, start-up pressure gradient and slippage coefficient and other factors on shale gas wells production.

Thermodynamics of gases adsorption on microporous adsorbents under supercritical temperatures

Methods of description of isotherms and thermodynamic characteristics of gas adsorption on active carbons and zeolites were considered in a wide range of temperatures below and higher than critical values.

Synthesis, Characterization, Stability, and Gas Adsorption Characteristics of a Highly Stable Zirconium Mesaconate Framework Material

AbstractA new ZrIV mesaconate framework material was synthesized by heating a mixture of ZrCl4, mesaconic acid, and acetic acid in a molar ratio of 1:1:30 in DMF at 150 °C for 24 h. The influence of the molar ratio of ZrCl4/acetic acid on the crystallinity of the compound was examined. The as‐synthesized compound was Soxhlet‐extracted with ethanol and subsequently heated under vacuum to remove guest solvent molecules from the pores. Both the as‐synthesized sample and the thermally activated sample of this new material were characterized by X‐ray powder diffraction (XRPD), FTIR spectroscopy, thermogravimetry, and elemental analysis. The compound is thermally stable up to 320 °C under air. XRPD experiments indicate that the compound maintains its crystallinity upon exposure to water, acetic acid, and 1 M HCl. According to the N2 sorption analyses, the compound possesses a BET surface area of 662 m2 g–1. Thus, the material is a promising candidate for gas storage and separation owing to its high physiochemical stability and considerable porosity.

Effect of an electrostatic field on gas adsorption and diffusion in tectonic coal

The characteristics of adsorption, desorption, and diffusion of gas in tectonic coal are important for the prediction of coal and gas outbursts. Three types of coal samples, of which both metamorphic grade and degree of damage is different, were selected from Tongchun, Qilin, and Pingdingshan mines. Using a series of experiments in an electrostatic field, we analyzed the characteristics of gas adsorption and diffusion in tectonic coal. We found that gas adsorption in coal conforms to the Langmuir equation in an electrostatic field. Both the depth of the adsorption potential well and the coal molecular electronegativity increases under the action of an electrostatic field. A Joule heating effect was caused by changing the coal–gas system conductivity in an electrostatic field. The quantity of gas adsorbed and ΔP result from competition between the depth of the adsorption potential well, the coal molecular electronegativity, and the Joule heating effect. ΔP peaks when the three factors control behavior equally. Compared with anthracite, the impact of the electrostatic field on the gas diffusion capacity of middle and high rank coals is greater. Compared with the original coal, the gas adsorption quantity, ΔP, and the gas diffusion capacity of tectonic coal are greater in an electrostatic field. In addition, the smaller the particle size of tectonic coal, the larger the ΔP.

Laboratory measurements of methane desorption on coal during acoustic stimulation

An apparatus considering the impacts of acoustic waves (mechanical vibration effect, thermal effect, and the cavitation effect) was designed to study the characteristics of gas adsorption and desorption on coals. Experiments of methane desorption on coals were performed under the effects of different acoustic frequencies and different acoustic intensities. The results showed that acoustic wave has promoted desorption of methane on coals. It was found that the initial desorption rate is relatively high, and then desorption rate decreases slowly with time, and finally achieves equilibrium. The desorption amount of methane on coals under the effect of acoustic waves is higher than that obtained without acoustic waves, and we found that desorption amount of methane on coals increases as acoustic intensities increase. It was also found that desorption rate of methane on coals is promoted under the effect of acoustic waves. Since the existing desorption models cannot describe the desorption characteristics of methane on coals under the effect of the acoustic intensity, a correction term was introduced into the existing models in this study, and thus a new model that is able to describe methane desorption under the effect of acoustic waves was established. The promotion mechanism of methane desorption on coals by the acoustic waves was also studied, it was found that the thermal effect of acoustic waves on methane desorption can be clearly seen.

Research of Coal Pores and Integrity Evaluation Method Based on Fractal Theory

Coal is a natural porous media, its porosity and structural integrity influenced the gas adsorption and desorption characteristics greatly, as well as physical and mechanical properties of coal. Scanning electron microscopy (SEM) is applied to acquire SEM image of four kinds of coal samples at different zoom levels, and the box dimension can be worked out based on the pore preprocessing of SEM images. Then, the numerical value of box dimension is used to describe the development degree of the four kinds of coal sample and four development degrees’ sequence. At last, the intrinsic relevance between fractal dimension and other parameters is analyzed through mathematic method. The results show as follows: coal sample has self-similarity characteristic; the fractal dimension is related to both the total number of pores and porosity degree; the data of the coal pore, analyzed through fractal dimension, are consistent with that through traditional method; what’s more, fractal dimension has more advantages in describing accuracy and simplicity.

Separation of CO2/CH4 and CH4/N2 mixtures by M/DOBDC: A detailed dynamic comparison with MIL-100(Cr) and activated carbon

In this report we studied the gas adsorption and breakthrough characteristics of M/DOBDC (M=Mg, Co, or Ni) metal–organic frameworks, with honeycomb-like structures and high concentrations of coordinatively unsaturated sites. We studied these characteristics by using M/DOBDC to separate CO2/CH4 and CH4/N2 mixtures and compared those results to separation using MIL-100(Cr) and activated carbon, particularly focusing on the adsorption capacities and equilibrium times. We show that the presence of coordinatively unsaturated sites greatly influences gas adsorption, separation, and regeneration. Mg/DOBDC displayed excellent separation efficiency for CO2/CH4 and simple regeneration under dynamic conditions, while Ni/DOBDC had superior CH4/N2 adsorption selectivity and CH4/N2 separation and exhibited strong interactions between CH4 molecules and its coordinatively unsaturated Ni atoms. Overall, the M/DOBDC frameworks demonstrated extremely high capacity, high selectivity, and easy regeneration for CO2 and CH4 separation under dynamic conditions, making them suitable for gas separation.

2-2-4 ガス分離プロセス構築に向けたセミクラスレートハイドレートのガス吸着および拡散特性(Session 2-2 ハイドレート 1)

2-2-4 ガス分離プロセス構築に向けたセミクラスレートハイドレートのガス吸着および拡散特性(Session 2-2 ハイドレート 1)

Adsorption Characteristics of Metal–Organic Frameworks Containing Coordinatively Unsaturated Metal Sites: Effect of Metal Cations and Adsorbate Properties

Metal–organic frameworks in the M/DOBDC series are known to contain a large number of coordinatively unsaturated metal (M) sites. In this work, we study the influence of various metal cations (M = Mg, Mn, Co, and Ni) in the framework on its gas adsorption characteristics. The probe gases (viz. CO2, CO, CH4, C2H6, N2, and Ar) were carefully chosen to cover a wider range of polarity and polarizability. While a significant impact of metal atom in the framework is observed on adsorption of polar gases such as CO2 and CO, it has a negligible effect on adsorption of other relatively nonpolar gases. On one hand, Henry’s constant of CO2 for Mg/DOBDC is about 4–10 times higher than that for other frameworks; on the other, Henry’s constant for CO on Ni/DOBDC is about 100 times larger than that on Mn/DOBDC. The pore volume of the framework governs adsorption capacity at higher pressures. Each of the frameworks exhibits widely different adsorption enthalpies for polar gases such as CO2 and CO. At pressures below 15 b...

Growth of 2D sheets of a MOF on graphene surfaces to yield composites with novel gas adsorption characteristics

Homogeneous graphene-MOF composites based on a 2D pillared-bilayer MOF (Cd-PBM), {[Cd4(azpy)2(pyrdc)4(H2O)2]·9H2O}n (azpy = 4,4'-azopyridine, pyrdc = pyridine-2,3-dicarboxylate), have been synthesized, using both graphene oxide (GO) and benzoic acid functionalized graphene (BFG). The composites GO@Cd-PBM and BFG@Cd-PBM demonstrate growth of the 2D nano-sheets of MOF on the graphene surface. While the pristine MOF, Cd-PBM shows selective CO2 uptake with a single-step type-I adsorption profile, the composites show stepwise CO2 uptake with a large hysteresis. With H2O and MeOH, on the other hand, the composites show a single-step adsorption unlike the parent MOF.

Simulation of the interaction of methane, carbon dioxide and coal

Gas adsorption has an important influence on gas flow in a coal body. Research on the characteristics of coal and gas adsorption is the theoretical basis for studying gas flow in coal. In this paper, the interaction between methane, carbon dioxide and surface molecules of anthracite was simulated using the quantum chemistry method. Adsorption energy and adsorption configurations of different quantities of gas molecules absorbed on the coal surface were calculated. The results show that adsorption between coal and the two kinds of gas molecules is a physical adsorption process and there is an optimal configuration. Gas molecules are more easily adsorbed in the hydroxyl-containing side chain, while it is difficult for them to be adsorbed at the position of the benzene ring. Besides, carbon dioxide molecules are more readily adsorbed on the coal surface than methane molecules. The findings have an important significance in revealing the nature of gas adsorption in coal.

Simplified De Bore Model of Coal Adsorption Gas

With respect to the problems existed in the description of the adsorption characteristics of super-low rank and super-high rank coals using the conventional Langmuir adsorption model, in this paper, We first introduces the De Bore adsorption model into the coal seam gas adsorption, and utilizes the results of the ab initio calculation of quantum chemistry result and the isothermal adsorption test statistical results, simplifies the De Bore model equation. The new adsorption model is more suitable for describing the gas adsorption characteristics of the whole coal ranks. This new model has the stronger function and wider suitable scope than the Langmuir adsorption model.