Microporous structure and gas adsorption model of fusain in lignite

Fuel ◽  
2022 ◽  
Vol 309 ◽  
pp. 122186
Author(s):  
Geng Li ◽  
Yong Qin ◽  
Miao Zhang ◽  
Boyang Wang ◽  
Jiuqing Li
Keyword(s):  
Gas Adsorption ◽  
Microporous Structure ◽  
Adsorption Model

scholarly journals Statistical Mechanical Model of Gas Adsorption in a Metal-Organic Framework Harboring a Rotaxane Molecular Shuttle

2020 ◽  
Author(s):  
Jonathan Carney ◽  
David Roundy ◽  
Cory M. Simon
Keyword(s):  
Mechanical Model ◽  
Gas Adsorption ◽  
Adsorption Properties ◽  
Temperature Sensitive ◽  
Adsorption Model ◽  
Adsorption Sites ◽  
Statistical Mechanical Model ◽  
Metal Organic ◽  
Statistical Mechanical ◽  
Molecular Shuttle

Metal-organic frameworks (MOFs) are modular and tunable nano-porous materials with applications in gas storage, separations, and sensing. Flexible/dynamic components that respond to adsorbed gas can give MOFs unique or enhanced adsorption properties. Here, we explore the adsorption properties that could be imparted to a MOF by a rotaxane molecular shuttle (RMS) in its pores. In the unit cell of an RMS-MOF, a macrocyclic wheel is mechanically interlocked with a strut of the MOF scaffold. The wheel shuttles between stations on the strut that are also gas adsorption sites. At a level of abstraction similar to the seminal Langmuir adsorption model, we pose and analyze a simple statistical mechanical model of gas adsorption in an RMS-MOF that accounts for (i) wheel/gas competition for sites on the strut and (ii) gas-induced changes in the configurational entropy of the shuttling wheel. We determine how the amount of gas adsorbed, position of the wheel, and differential energy of adsorption depend on temperature, pressure, and the interactions of the gas/wheel with the stations. Our model reveals that, compared to a rigid, Langmuir material, the chemistry of the RMS-MOF can be tuned to render gas adsorption more or less temperature-sensitive and to release more or less heat upon adsorption. The model also uncovers a non-monotonic relationship between the temperature and the position of the wheel if gas out-competes the wheel for its preferable station.

scholarly journals Statistical Mechanical Model of Gas Adsorption in a Metal-Organic Framework Harboring a Rotaxane Molecular Shuttle

2020 ◽  
Author(s):  
Jonathan Carney ◽  
David Roundy ◽  
Cory M. Simon
Keyword(s):  
Mechanical Model ◽  
Gas Adsorption ◽  
Adsorption Properties ◽  
Temperature Sensitive ◽  
Adsorption Model ◽  
Adsorption Sites ◽  
Statistical Mechanical Model ◽  
Metal Organic ◽  
Statistical Mechanical ◽  
Molecular Shuttle

Metal-organic frameworks (MOFs) are modular and tunable nano-porous materials with applications in gas storage, separations, and sensing. Flexible/dynamic components that respond to adsorbed gas can give MOFs unique or enhanced adsorption properties. Here, we explore the adsorption properties that could be imparted to a MOF by a rotaxane molecular shuttle (RMS) in its pores. In the unit cell of an RMS-MOF, a macrocyclic wheel is mechanically interlocked with a strut of the MOF scaffold. The wheel shuttles between stations on the strut that are also gas adsorption sites. At a level of abstraction similar to the seminal Langmuir adsorption model, we pose and analyze a simple statistical mechanical model of gas adsorption in an RMS-MOF that accounts for (i) wheel/gas competition for sites on the strut and (ii) gas-induced changes in the configurational entropy of the shuttling wheel. We determine how the amount of gas adsorbed, position of the wheel, and differential energy of adsorption depend on temperature, pressure, and the interactions of the gas/wheel with the stations. Our model reveals that, compared to a rigid, Langmuir material, the chemistry of the RMS-MOF can be tuned to render gas adsorption more or less temperature-sensitive and to release more or less heat upon adsorption. The model also uncovers a non-monotonic relationship between the temperature and the position of the wheel if gas out-competes the wheel for its preferable station.

scholarly journals Comparative Experiment Study on Nitrogen Injection and Free Desorption of Methane-Rich Bituminous Coal Under Triaxial Loading

2017 ◽  
Vol 62 (4) ◽  
pp. 911-928 ◽  
Author(s):  
Lei Zhang ◽  
Zhiwei Ye ◽  
Jun Tang ◽  
Dingyi Hao ◽  
Cun Zhang
Keyword(s):  
Coal Seam ◽  
Coalbed Methane ◽  
Gas Adsorption ◽  
Injection Pressure ◽  
Rapid Decline ◽  
Time Interval ◽  
Adsorption Model ◽  
Adsorption Phenomenon ◽  
Nitrogen Injection ◽  
Displacement Ratio

Abstract As a kind of associated geological gas, coalbed methane (CBM) is mainly adsorbed in the coal seam. The coal-methane adsorption phenomenon can be described by Langmuir monolayer adsorptio n model, BET multilayer adsorption model and the Theory of Volume Filling of Micropore (TVFM), whereas the binary gas adsorption phenomenon can be described by the extended Langmuir Model. For the CBM in the low permeability coal seam, the amount of gas released by direct drainage is relatively limited, which cannot eliminate the gas explosion and outburst hazards. Gas injection is an effective method to promote methane drainage. In this paper, the free desorption and nitrogen injection displacement experiments are comparatively analyzed, which allows verifying the effectiveness of nitrogen injection’s enhancement to gas drainage. The experiment of injecting nitrogen gas into the coal body shows that the coal fracture can be maintained or expanded by the injected gas pressure so that more methane can be released. The nitrogen injection has a higher time efficiency than that of free desorption as well. The displacement ratio of N2/CH4 is in the range of 1-3. Both the injection pressure and confining pressure affect the displacement ratio. The analysis of the desorbed gas components shows that the relationship between the methane component and gas flooding time is an “inverted S” shape curve, and the appropriate time for the methane collection can be inferred by the time interval of the rapid decline of the curve.

scholarly journals Gas adsorption and desorption effects on cylinders and their importance for long-term gas records

2015 ◽  
Vol 8 (12) ◽  
pp. 5289-5299 ◽  
Author(s):  
M. C. Leuenberger ◽  
M. F. Schibig ◽  
P. Nyfeler
Keyword(s):  
Mole Fraction ◽  
Pressure Dependence ◽  
Gas Adsorption ◽  
Binding Energies ◽  
Adsorption Model ◽  
Climate Chamber ◽  
Temperature Coefficients ◽  
Monolayer Adsorption ◽  
Pressure Changes ◽  
Adsorption Desorption

Abstract. It is well known that gases adsorb on many surfaces, in particular metal surfaces. There are two main forms responsible for these effects (i) physisorption and (ii) chemisorption. Physisorption is associated with lower binding energies in the order of 1–10 kJ mol−1, compared to chemisorption which ranges from 100 to 1000 kJ mol−1. Furthermore, chemisorption only forms monolayers, contrasting physisorption that can form multilayer adsorption. The reverse process is called desorption and follows similar mathematical laws; however, it can be influenced by hysteresis effects. In the present experiment, we investigated the adsorption/desorption phenomena on three steel and three aluminium cylinders containing compressed air in our laboratory and under controlled conditions in a climate chamber, respectively. Our observations from completely decanting one steel and two aluminium cylinders are in agreement with the pressure dependence of physisorption for CO2, CH4, and H2O. The CO2 results for both cylinder types are in excellent agreement with the pressure dependence of a monolayer adsorption model. However, mole fraction changes due to adsorption on aluminium (< 0.05 and 0 ppm for CO2 and H2O) were significantly lower than on steel (< 0.41 ppm and about < 2.5 ppm, respectively). The CO2 amount adsorbed (5.8 × 1019 CO2 molecules) corresponds to about the fivefold monolayer adsorption, indicating that the effective surface exposed for adsorption is significantly larger than the geometric surface area. Adsorption/desorption effects were minimal for CH4 and for CO but require further attention since they were only studied on one aluminium cylinder with a very low mole fraction. In the climate chamber, the cylinders were exposed to temperatures between −10 and +50 °C to determine the corresponding temperature coefficients of adsorption. Again, we found distinctly different values for CO2, ranging from 0.0014 to 0.0184 ppm °C−1 for steel cylinders and −0.0002 to −0.0003 ppm °C−1 for aluminium cylinders. The reversed temperature dependence for aluminium cylinders points to significantly lower desorption energies than for steel cylinders and due to the small values, they might at least partly be influenced by temperature, permeation from/to sealing materials, and gas-consumption-induced pressure changes. Temperature coefficients for CH4, CO, and H2O adsorption were, within their error bands, insignificant. These results do indicate the need for careful selection and usage of gas cylinders for high-precision calibration purposes such as requested in trace gas applications.

Chemical activation of biochar for energy and environmental applications: a comprehensive review

2019 ◽  
Vol 35 (7) ◽  
pp. 777-815 ◽  
Author(s):  
Baharak Sajjadi ◽  
Tetiana Zubatiuk ◽  
Danuta Leszczynska ◽  
Jerzy Leszczynski ◽  
Wei Yin Chen
Keyword(s):  
Functional Groups ◽  
Gas Adsorption ◽  
Chemical Activation ◽  
Chemical Processes ◽  
Microporous Structure ◽  
Key Factors ◽  
Comprehensive Overview ◽  
Current Review ◽  
Mineral Structure ◽  
Post Modification

Abstract Biochar (BC) generated from thermal and hydrothermal cracking of biomass is a carbon-rich product with the microporous structure. The graphene-like structure of BC contains different chemical functional groups (e.g. phenolic, carboxylic, carbonylic, etc.), making it a very attractive tool for wastewater treatment, CO2 capture, toxic gas adsorption, soil amendment, supercapacitors, catalytic applications, etc. However, the carbonaceous and mineral structure of BC has a potential to accept more favorable functional groups and discard undesirable groups through different chemical processes. The current review aims at providing a comprehensive overview on different chemical modification mechanisms and exploring their effects on BC physicochemical properties, functionalities, and applications. To reach these objectives, the processes of oxidation (using either acidic or alkaline oxidizing agents), amination, sulfonation, metal oxide impregnation, and magnetization are investigated and compared. The nature of precursor materials, modification preparatory/conditions, and post-modification processes as the key factors which influence the final product properties are considered in detail; however, the focus is dedicated to the most common methods and those with technological importance.

Comparative DFT dual gas adsorption model of ZnO and Ag/ZnO with experimental applications as gas detection at ppb level

2021 ◽  
Author(s):  
Utkarsh Kumar ◽  
Shih-Ming Huang ◽  
Zen-In Deng ◽  
Cheng-Xin Yang ◽  
Wen-Min Huang ◽  
...  
Keyword(s):  
Density Functional ◽  
Reaction Rate ◽  
Gas Adsorption ◽  
Gas Detection ◽  
Adsorption Model ◽  
Ag Nps ◽  
Functional Theory ◽  
Peak Intensity ◽  
Homo Lumo ◽  
Good Agreement

Abstract By experimental and density functional theory (DFT) calculations, the toxic gases (O3 and NO2) sensing capability and mechanism of ZnO NRs and Ag/ZnO NRs have been comparatively studied in this work. The arrays of Ag NPs were employed as a templet for the growth of ZnO NRs. The experimental results show the response and adsorption rate towards the gases obviously change after adding Ag NPs in ZnO. From the TDOS plot, it has been observed that the HOMO-LUMO gap changes after interaction with different oxidizing gases similarly the peak intensity also decreases which confirms the electron has been transferred from ZnO to NO2 and O3. The response towards the gases decreases and the adsorption reaction rate has been calculated by the Eyring-Polanyi equation and found to be increased after adding Ag in the ZnO NRs which is very similar to our experimental data. We also find that the absorption coefficient is different for O3 and NO2. The mechanism of the gas sensor was explored. Finally, the findings of the response experiment and theoretical calculation were compared and found to be in good agreement.

Moisture Damage Evaluation of Asphalt Mixtures by Considering Both Moisture Diffusion and Repeated-Load Conditions

2003 ◽  
Vol 1832 (1) ◽  
pp. 42-49 ◽  
Author(s):  
DingXin Cheng ◽  
Dallas N. Little ◽  
Robert L. Lytton ◽  
James C. Holste
Keyword(s):  
Surface Energy ◽  
Diffusion Model ◽  
Gas Adsorption ◽  
Moisture Diffusion ◽  
Moisture Damage ◽  
Asphalt Mixtures ◽  
Asphalt Binders ◽  
Adsorption Model ◽  
Damage Models ◽  
Adhesion Failure

Two moisture damage models based on major moisture failure mechanisms are proposed. The adhesion failure model was developed to analyze the adhesive fracture between asphalt and aggregate in the presence of water. Cohesive and adhesive fractures in an asphalt-aggregate system are directly related to the surface energy characteristics of asphalt and aggregate. The surface energy of adhesion with or without the presence of water can be calculated from the surface energies of asphalt and aggregate. A moisture diffusion model was developed based on the one-dimensional consolidation of soil and a gas adsorption model. The moisture diffusion model was used to obtain the moisture diffusion characteristics of asphalt binders, including the amount of moisture that can permeate a binder and the diffusivity of the binder. The amount of moisture that permeates a binder is identified as a key factor in the moisture damage. Finally, mechanics-based experiments conducted on asphalt mixtures validated the results from the adhesion failure and diffusion models.

scholarly journals Gas adsorption and desorption effects on cylinders and their importance for long-term gas records

2014 ◽  
Vol 14 (13) ◽  
pp. 19293-19314 ◽  
Author(s):  
M. C. Leuenberger ◽  
M. F. Schibig ◽  
P. Nyfeler
Keyword(s):  
Gas Adsorption ◽  
Binding Energies ◽  
Adsorption Model ◽  
Climate Chamber ◽  
Temperature Coefficients ◽  
Monolayer Adsorption ◽  
Gas Consumption ◽  
Pressure Changes ◽  
Adsorption Desorption

Abstract. It is well known that gases adsorb on many surfaces, in particular metal surfaces. There are two main forms responsible for these effects (i) physisorption and (ii) chemisorption. Physisorption is associated with lower binding energies in the order of 1–10 kJ mol−1 compared to chemisorption ranging from 100 to 1000 kJ mol−1. Furthermore, chemisorption forms only monolayers, contrasting physisorption that can form multilayer adsorption. The reverse process is called desorption and follows similar mathematical laws, however, it can be influenced by hysteresis effects. In the present experiment we investigated the adsorption/desorption phenomena on three steel and three aluminium cylinders containing compressed air in our laboratory and under controlled conditions in a climate chamber, respectively. We proved the pressure effect on physisorption for CO2, CH4 and H2O by decanting a steel and an aluminium cylinder completely. The results are in excellent agreement with a monolayer adsorption model for both cylinders. However, adsorption on aluminium (0.3 ppm and 0 ppm for CO2 and H2O) was about 20 times less than on steel (6 ppm and 30 ppm, respectively). In the climate chamber the cylinders were exposed to temperatures between −10 to +50 °C to determine the corresponding temperature coefficients of adsorption. Again, we found distinctly different values for CO2 ranging from 0.0011 to 0.0133 ppm °C−1 for steel cylinders and −0.0003 to −0.0005 ppm °C−1 for aluminium cylinders. The reversed temperature dependence for aluminium cylinders is most probably due to temperature and gas consumption induced pressure changes. After correction, aluminium cylinders showed no temperature independence. Temperature coefficients for CH4, CO and H2O adsorption were, within their error bands, insignificant. These results do indicate the need for careful selection and usage of gas cylinders for high precision calibration purposes such as requested in trace gas applications.

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