Carbon Isotope Fractionation during Shale Gas Transport through Organic and Inorganic Nanopores from Molecular Simulations

Wang, Gang; Ma, Yiwei; Zhao, Yaozhong; Chen, Wei

doi:10.1021/acs.energyfuels.1c01448

Cited by 12 publications

(6 citation statements)

References 77 publications

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“…In an actual PEMFC system, a pressure difference is generated due to the different stoichiometric ratios of hydrogen and air. As for EF-NEMD simulations, the effect of a transmembrane pressure difference can be mimicked by applying a constant force in the x direction (Figure 4) on each small molecule [31,50]. Water molecules and hydronium ions transfer through the Nafion membrane under the driving force.…”

Section: Methodsmentioning

confidence: 99%

Molecular Study of Nonequilibrium Transport Mechanism for Proton and Water in Porous Proton Exchange Membranes

Wang

Liu

et al. 2023

International Journal of Energy Research

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The transport process of proton and water through a porous proton exchange membrane (PEM) under pressure difference is significant to fuel cell performance. Nonequilibrium molecular dynamics simulations were conducted to investigate the diffusion mechanisms of hydronium ions and water molecules under pressure differences. Here, different driving forces (0.15 kcal/(mol·Å)–0.45 kcal/(mol·Å)) were applied to hydronium ions and water molecules as they transported through Nafion 117 membrane at temperatures between 300 K and 350 K. Results indicated that the transport diffusion coefficient of water molecules was larger than that of hydronium ions under different pressure drops due to the lower molecular weight and diffusion activation energy of water molecules (20.25 kJ/mol). Hydronium ions formed stronger hydrogen bonds with sulfonic acid groups than water molecules, which resulted in a higher diffusion activation energy for hydronium ions (21.15 kJ/mol). The proton conductivity rose with the increase in pressure difference. Moreover, the transport diffusion coefficient of water molecules and hydronium ions were positively correlated with temperature. This is because the kinetic energy of molecules increased and the pore size of the Nafion membrane enlarged at high temperatures. In addition, the dynamics of the hydrogen bond between hydronium ions and sulfonic acid groups/water molecules were accelerated at elevated temperatures, which further promoted proton transfer.

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Section: Methodsmentioning

confidence: 99%

Molecular Study of Nonequilibrium Transport Mechanism for Proton and Water in Porous Proton Exchange Membranes

Wang

Liu

et al. 2023

International Journal of Energy Research

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“…This method has been used in many previous studies to simulate nanoconfined flow. [56][57][58][59] The motion equation was integrated using the velocity Verlet algorithm with a time step of 1 fs. [60] The NEMD simulation was conducted for 10 ns to obtain a steady flow.…”

Section: Methodsmentioning

confidence: 99%

Molecular Dynamic Simulations of Proton and Water Transport Mechanism in a Nafion Pore

2023

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Herein, nonequilibrium molecular dynamics simulations are conducted to study the hydraulic permeation and vehicle transport of protons in proton exchange membranes (PEMs) with different structures. The results indicate that water molecules and hydronium ions are transported in porous PEMs in the form of clusters. Water molecules are more concentrated in the bulk areas of pores, whereas hydronium ions had a high‐density profile near the pore surface areas since sulfonate ions of the side chain exhibit a stronger adsorption effect on hydronium ions. Due to the confined pore size, the slip flow of water molecules and hydronium ions occurs near the pore surfaces and it becomes more significant as side chain separation or pore size increases. As pore size decreases, the reduction of movement region and the deep attractive potential near the pore wall lower the specific enthalpy due to enhanced molecule‐wall collisions. In addition, the transport diffusivity coefficients of positively charged hydronium ions are smaller than that of water molecules due to the stronger Coulomb interactions and hydrogen bonding with negatively charged side chains. Transport diffusivity coefficients of water molecules and hydronium ions increase as pore size and side chain separation increase.

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“…Recent studies have found significant carbon isotope fractionation when monitoring the isotopic composition of released gas during canister degassing − and transport simulation − experiments. Further investigation revealed that the fractionation characteristics (duration and amplitude) during methane transport are correlated with the material composition, , pore structure, ,, GIP content, , and AGR, ,,,,, providing a novel approach to assess the gas-bearing parameters using isotopic fractionation. Li et al proposed a carbon isotope fractionation (CIF) model that can effectively characterize the entire shale gas degassing process based on experimental findings and mechanism analysis.…”

Section: Introductionmentioning

confidence: 99%

Comparison and Verification of Gas-Bearing Parameter Evaluation Methods for Deep Shale Based on the Pressure Coring Technique

Zhao

Wu³

et al. 2023

Energy Fuels

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Gas-bearing properties, such as gas-in-place (GIP) content and adsorbed gas ratio (AGR), have drawn considerable attention because they are essential for shale gas resource evaluation and sweet spot forecasting. The above-mentioned metrics have been determined using a variety of approaches, but they lack systematic comparison and accuracy verification, particularly for deep shale gas, where conventional methods frequently fall short. A total of 30 shales were taken for the investigation utilizing pressure and conventional coring methods from Wufeng and Longmaxi Formations in the Sichuan Basin, China. For pressure coring samples, we developed the experimental protocols and a GIP content classification scheme that categorizes the GIP content into four categories: lost gas (estimated using the temperature-corrected pressure-holding ratio), extracted gas from depressurization, degassed gas, and residual gas. The four pressure coring samples from well Y206 with measured GIP content range from 2.84 to 5.58 m 3 /tonne, with an average of 4.72 m 3 /tonne. In contrast to the calculated GIP content of the pressure coring samples, the validity of the current GIP content evaluation methodologies has been confirmed. The comparison results demonstrate that the GIP content assessed using the United States Bureau of Mines (USBM) method is frequently underestimated for samples from conventional coring and notably overstated for samples from pressure coring. The polynomial fitting method dramatically overestimated the GIP content. With its accurate time-dependent boundary conditions and strict theoretical foundation, the simplified carbon isotope fractionation (s-CIF) model exhibits the highest level of accuracy in determining GIP content. Additionally, the s-CIF model can find yet another crucial parameter of AGR. Shale samples from well Y206 had an average AGR of 20.4% but a range from 12.2 to 33.2%. The examination of the influencing factors demonstrates that the lost gas ratio, AGR, and diffusion coefficient are responsible for controlling the calculation error of the USBM method. The lost gas ratio prior to core retrieval increases with decreasing AGR (or increasing diffusion coefficient), which increases the computation error of the USBM method.

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Carbon Isotope Fractionation during Shale Gas Transport through Organic and Inorganic Nanopores from Molecular Simulations

Cited by 12 publications

References 77 publications

Molecular Study of Nonequilibrium Transport Mechanism for Proton and Water in Porous Proton Exchange Membranes

Molecular Study of Nonequilibrium Transport Mechanism for Proton and Water in Porous Proton Exchange Membranes

Molecular Dynamic Simulations of Proton and Water Transport Mechanism in a Nafion Pore

Comparison and Verification of Gas-Bearing Parameter Evaluation Methods for Deep Shale Based on the Pressure Coring Technique

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