Distribution Of CO Research Articles

Research on CO2 sequestration in saline aquifers with different relative permeability considering CO2 phase conditions

Saline aquifers are the most feasible potential site for the storage of CO2. The behavior of CO2 in different phase states may significantly affect the flow properties and sequestration efficiency. It is important to understand and predict the effects of different CO2 phases. This study conducted relative permeability tests under two experimental conditions with CO2 in different phases. Incorporating experimental data into reservoir-scale simulations to analyze the effects of different phases of CO2 on structural, solubility, and residual sequestration mechanisms, and to predict CO2 behavior in saline aquifers. The results show that the CO2 relative permeability and residual CO2 saturation are high under supercritical conditions. It is more favorable to consider the relative permeability and hysteresis effects on the supercritical CO2 results, with a more dispersed distribution of CO2 at the bottom of the reservoir. There was a significant difference in residual sequestration, with the gaseous group showing a 14.16 % reduction in residual sequestration and a 4.27 % reduction in total sequestration compared to the supercritical group. The ratio of structural sequestration, solubility sequestration, and residual sequestration in the total sequestration in this study is about 50 %:30 %:20 %.

Mathematical model of permeability evolution of liquid CO2 pressurized coal

To examine the permeability alterations in coal seams induced by liquid CO2 injection, we employed COMSOL simulations to recreate the flow, force, and temperature fields, along with the corresponding physical parameters of the geological formation. We established a mathematical model to track the evolution of the coal body’s permeability, enabling us to capture the phase distribution of CO2, the dynamics of fluid transportation, and the coal body’s mechanical responses during the liquid CO2 injection process. Our findings revealed that the coal seam undergoes significant changes due to low-temperature freezing and shrinkage, gas-liquid phase transitions, and expansion impacts from solid-liquid phase changes. These factors collectively modify the pore structure, subsequently influencing the coal seam’s permeability. Notably, the coal body’s permeability, influenced by the pore structure and the Klinkenberg effect, increases logarithmically with rising injection pressure and falling temperatures. The structural changes in the coal body are markedly impacted by seepage and phase change pressures, with the permeability enhancement from secondary phase changes being 2.28 times greater than that from primary phase changes, and five times greater than in scenarios without phase change.

Pressure Distributions and Flow Regimes: An Integrated Approach For CO2 Sequestration Project Design and Evaluation in Hydraulically Fractured Shale Reservoirs

This paper introduces an integrated approach for estimating the key parameters of CO2 storage projects in depleted hydraulically fractured shale reservoirs. The approach focuses deep insights into evaluating these projects based on the pressure distribution and flow regimes. The objective is reducing the uncertainties in the design and evaluation criteria of CO2 storage by better understanding the flow mechanisms in the porous media. This understanding helps in perfectly modeling CO2 distribution and characterizing the expected flow regimes.Several analytical models are developed for the pressure behavior of CO2 multi-size scale flow mechanisms. Diffusion flow, slip flow, adsorption flow, and Darcy and non-Darcy flow are all considered. The flow in the nano-size organic particles, the micro-size kerogen particles, and the macro-size matrix is analytically described. The flow inside natural fractures in the stimulated and unstimulated reservoir volume as well as the flow of CO2 in the hydraulic fractures are modeled. Several rectangular reservoir configurations, hydraulic fracture characteristics, and petrophysical properties of the matrix, kerogen, and organic matter are examined. An estimation model for the total volume of CO2 that could be stored in the depleted fractured reservoirs is presented. The contribution of the unstimulated and stimulated porous media as well as the hydraulic fractures to the total volume is determined by characterizing the flow regimes. Different models are proposed for the time at which CO2 reaches the hydraulic fracture tips, the borders between stimulated and unstimulated porous media, and the reservoir boundary. Profound explanations are introduced for the impact of the constrained pressure on the total capacity of the reservoirs for CO2 storage.The study has reached several conclusions. The characteristics of the organic matter, kerogen, and the micro-size scale matrix do not significantly impact the pressure distribution and flow regimes. Conversely, the pressure distribution and flow regimes are significantly impacted by the characteristics of the hydraulic and natural fractures. The hydraulic fractures may offer a reasonable capacity for CO2 storage, meanwhile, the capacity of stimulated and unstimulated reservoir volume is controlled by reservoir configuration and fracture spacing. The constrained pressure may strictly reduce the total capacity of CO2 storage in the reservoir. The total volume of the injected CO2 can be determined from the pressure point when the injection pulse has reached to reservoir boundary. Beyond this point, it is not recommended to inject CO2 as it could increase reservoir pressure more than initial pressure. The pressure of the depleted reservoir before injection is a key parameter in the design and evaluation of the CO2 storage in shale reservoirs.This study introduces a novel approach for the design and evaluation criteria of CO2 storage in depleted shale reservoirs. The approach uses the pressure distribution and flow regimes that could be observed in the multi-size scale components of the reservoirs. The study proposes several models for estimating CO2 geosequestration capacity in the hydraulic fractures, stimulated and unstimulated reservoir volume as well as the total storage capacity of the reservoirs. The approach confidently addresses the concerns regarding the applicability of unconventional resources for CO2 storage and the total capacity offered by these reservoirs for this purpose.

Distribution and air-sea fluxes of CO2 in coral reefs in the Greater Bay Area, China

From May to June 2021, the sea surface partial pressure of CO2 (pCO2) and air-sea CO2 fluxes around six coral reefs in the Great Bay Area (contain Pearl River Estuary (PRE) and Daya Bay) were investigated respectively. The distribution of seawater pCO2 around different coral reefs were quite different. The seawater pCO2 of the coral reef region of Daya Bay is relatively high, ranging from 268 to 496 µatm. In contrast, the pCO2 levels in the coral reef area of the PRE are significantly lower, with measurements ranging from 84 to 374 µatm. Further analysis showed that the distribution of seawater pCO2 around the coral reefs of the PRE were mainly affected by biological metabolism and seawater mixing, while those in Daya Bay were mainly controlled by temperature and seawater mixing. During the survey, the three coral reefs in the PRE were affected by algal blooms showing strong sinks of atmospheric CO2 ranging from −12.3 to −19.2 mmol CO2 m−2 d−1. However, the difference between the seawater pCO2 and atmospheric pCO2 in the three coral reefs of Daya Bay were all very small, and they were weak sources or sinks of atmospheric CO2, respectively.

A Review of Satellite-Based CO2 Data Reconstruction Studies: Methodologies, Challenges, and Advances

Carbon dioxide is one of the most influential greenhouse gases affecting human life. CO2 data can be obtained through three methods: ground-based, airborne, and satellite-based observations. However, ground-based monitoring is typically composed of sparsely distributed stations, while airborne monitoring has limited coverage and spatial resolution; they cannot fully reflect the spatiotemporal distribution of CO2. Satellite remote sensing plays a crucial role in monitoring the global distribution of atmospheric CO2, offering high observation accuracy and wide coverage. However, satellite remote sensing still faces spatiotemporal constraints, such as interference from clouds (or aerosols) and limitations from satellite orbits, which can lead to significant data loss. Therefore, the reconstruction of satellite-based CO2 data becomes particularly important. This article summarizes methods for the reconstruction of satellite-based CO2 data, including interpolation, data fusion, and super-resolution reconstruction techniques, and their advantages and disadvantages, it also provides a comprehensive overview of the classification and applications of super-resolution reconstruction techniques. Finally, the article offers future perspectives, suggesting that ideas like image super-resolution reconstruction represent the future trend in the field of satellite-based CO2 data reconstruction.

The effects of formation inclination on the operational performance of compressed carbon dioxide energy storage in aquifers

Compressed CO2 energy storage in aquifers (CAESA) is a net-zero energy storage technology. Due to the widespread existence of inclined aquifers in nature, it is of practical significance to study the influence of inclined reservoirs on CO2 migration, safety and energy efficiency of the storage system. We build 3D numerical models with different dips (0°–16°), analyze the hydrodynamic and thermodynamic behavior of the system, and discuss the effects of injection schemes (temperature and pressure) on wellbore pressure, temperature, and energy efficiency. The results show that formation dip affects the energy storage characteristics of the system mainly by affecting the migration and distribution of CO2 in the aquifer. The greater the formation dip, the greater the difference in CO2 distribution, and the farther the CO2 diffuses upward along the dip direction. The farthest migration distances in the low- and high-pressure aquifers, occurring in the case of 16° formation dip, increase by 100 and 53 m, respectively, compared with those of the flat formation. The average daily energy storage efficiency decreases with the increase in formation dip angle. The dip angle of aquifer which is selected for compressed CO2 energy storage should not exceed 8°.

Software for CO2 Storage in Natural Gas Reservoirs

The paper presents a simulation-based approach for optimizing CO2 injection into depleted gas reservoirs, with the goal of enhancing underground CO2 storage. The research employs a two-dimensional dynamic reservoir model, developed using Darcy’s law, to describe gas flow in a pressure-homogeneous porous medium, along with real gas equations. The model integrates the Du Fort–Frenkel and finite-difference methods to accurately simulate the behavior of CO2 during injection and storage. Real data from an operational gas storage facility were used to calibrate the model. CO2sim v1 software, specifically developed for this purpose, simulates CO2 injection cycles and quiescence phases, enabling the optimization of storage capacity and energy efficiency. The reservoir model, based on the engineering of the geological structure, is discretized into approximately 16,000 cells and solved using the finite-difference method, allowing for rapid simulation of CO2 injection and quiescence processes. The average computation time for a 150-day cycle is approximately 5 min. Simulation results indicate that increasing the number of injection wells and carefully controlling the injection rates significantly improves the distribution of CO2 within the reservoir, thereby enhancing storage efficiency. Additionally, appropriate well placement and prolonged quiescence periods lead to better CO2 dispersion, increasing the storage potential while reducing energy costs. The study concludes that further development of the software, along with comprehensive technical and economic assessments, is required to fully optimize CO2 storage on a commercial scale.

A physics-constraint neural network for CO2 storage in deep saline aquifers during injection and post-injection periods

CO2 capture and storage is a viable solution in the effort to mitigate global climate change. Deep saline aquifers, in particular, have emerged as promising storage options, owing to their vast capacity and widespread distribution. However, the task of proficiently monitoring and simulating CO2 behavior within these formations poses significant challenges. To address this, we introduce the physics-constraint neural network for CO2 storage (CO2PCNet), a model specifically designed for simulating and monitoring CO2 storage in deep saline aquifers during injection and post-injection periods. Recognizing the significant challenges in accurately modeling the distribution and movement of CO2 under varying permeability conditions, the CO2PCNet integrates the principles of physics with the robustness of deep learning, serving as a powerful surrogate model. The architecture of CO2PCNet starts with an encoder that adeptly processes spatial features from overall mole fraction (zCO2) and pressure fields (Pl), capturing the complex dynamics of a CO2 trajectory. By incorporating permeability information through a conditioning step, the network ensures a faithful representation of the influences on CO2 behavior in subsurface conditions. A ConvLSTM module subsequently discerns temporal evolutions, reflecting the real-world progression of CO2 plumes within the reservoir. Lastly, the decoder precisely reconstructs the predictive spatial profile of CO2 distribution. CO2PCNet, with its integration of convolutional layers, recurrent mechanisms, and physics-informed constraints, offers a refined approach to CO2 storage simulation. This model offers the potential of utilizing advanced computational methods in advancing CCS practices.

Nanoconfinement effect on the miscible behaviors of CO2/shale oil/surfactant systems in nanopores: Implications for CO2 sequestration and enhanced oil recovery

Currently, CO2 flooding is the most promising carbon capture, utilization, and storage (CCUS) technology in the energy industry. Understanding the nanoconfinement effect on the CO2-oil miscible process is crucial for accurately determining the minimum miscibility pressure (MMP) of CO2/oil in shale reservoirs. In this study, we conducted molecular dynamics (MD) simulations to investigate the effects of pore size, surfactants, and pore type on the MMP of nanoconfined CO2/shale oil/surfactant systems. Validations against experimental data show a deviation of 2.98 % in the CO2 MMP. The MMPs under nanoconfinement are found to be significantly lower than those in bulk phase conditions (up to 22.94 %). The simulation results reveal that decreasing pore size can enhance the miscibility of CO2 and oil by increasing the CO2 adsorption ratio, improving CO2-surfactant interactions, and inhibiting the tendency of CO2 molecules to self-aggregate. The enhancement of CO2-oil miscibility caused by surfactants is ranked by CFP > SF > SDS according to the mixing degrees (Dmix) and the spatial distribution of CO2 around surfactant molecules. In addition, pore type exhibits various abilities in influencing the MMP, owing to their different mineral surface properties and ability to influence CO2-surfactant interactions. Nanopores with stronger hydrophobicity and a denser CO2 distribution around surfactant molecules have lower MMPs. The results show that the order of MMP in terms of pore types is Quartz < Kaolinite < I/M clay. This study elaborates the micro-mechanisms of surfactant-assisted CO2-oil miscibility under nanoconfinement, offering valuable insights for effectively designing CO2 miscible flooding in shale oil reservoir development.

Distribution and control mechanism of pCO2 and water-air CO2 efflux in the Pearl River Estuary.

Estuaries are generally considered to be important sources of atmospheric CO2. However, the differences between estuaries, and inadequate observations of partial pressure of CO2 in estuarine water (pCO2water) hamper global estuarine CO2 budgeting. In this study, the longitudinal distribution of CO2 in the waters of Modaomen (MSE) and Lingdingyang (LSE), two sub-estuaries of the Pearl River Estuary (PRE), and its influencing mechanism are studied. The change in the distribution of pCO2water along the distance from the upstream estuary to the ocean between LSE and MSE was significantly different. pCO2water at the LSE ranges from 238 to 7267 µatm, whereas the MSE ranges from 406 to 3078 µatm. Stronger microbial respiration and relatively long water retention times were the main influences that led to higher pCO2water at LSE than at MSE. Seasonally, the increase of soil CO2 into the water in the upstream basin caused by precipitation is the potential influencing factor that the water pCO2water in the flood season is higher than in the dry season. PRE was a net source of atmospheric CO2 with an average annual water-air flux of 41.2 ± 33.3mmolm-2day-1. Our results suggest that the differences in longitudinal gradients of pCO2water between estuaries in the same region and the effects of different gas transport velocity models on CO2 emission estimates need to be considered in estuarine CO2 emission budgeting.

Tertiary amine based-biphasic solvent using ionic liquids as an activator to advance the energy-efficient CO2 capture

The newly developed tertiary amine-based biphasic solvents have low reaction heat, and good desorption performance, but no CO2 reactivity under low CO2 pressure. A novel tertiary amine-based biphasic solvent (DMEA/[DETAH]Lys/n-BuOH/H2O, abbreviated as D-DL-B-H) using ionic liquids (ILs) as the activator was proposed. With the assistance of [DETAH]Lys, the CO2-rich phase exhibited enhanced CO2 loading (from 3.69 to 4.09 mol/L) and CO2 distribution (from 88.5 % to 96.8 %). In addition, at 5 kPa, D-DL-B-H achieved an absorption capacity up to 1.58 mol/L, which was 79 times that of the DMEA/n-BuOH/H2O, suggesting the D-DL-B-H had good CO2 capture property at low CO2 pressure. At 393.15 K, the desorption efficiency of D-DL-B-H was as high as 80.9 %. In addition, the Qreg of D-DL-B-H was reduced to 1.78 GJ/t CO2, accounting for 44.61 % of the 30 wt% MEA. At 323.15 K, the viscosity of the CO2-rich phase was only 4.63 mPa·s, and the corrosion rate was 46.88 % of 30 wt% MEA. The reaction mechanism obtained from 13C NMR and DFT analysis indicated that [DETAH]Lys was more inclined to react with CO2 than DMEA. The main reason for the occurrence of phase splitting was the formation of hydrogen bonds between the CO2 product and the water.

Trends in Emissions from Road Traffic in Rapidly Urbanizing Areas

The process of urbanization has facilitated the exponential growth in demand for road traffic, consequently leading to substantial emissions of CO2 and pollutants. However, with the development of urbanization and the expansion of the road network, the distribution and emission characteristics of CO2 and pollutant emissions are still unclear. In this study, a bottom-up approach was initially employed to develop high-resolution emission inventories for CO2 and pollutant emissions (NOx, CO, and HC) from primary, secondary, trunk, and tertiary roads in rapidly urbanizing regions of China based on localized emission factor data. Subsequently, the standard road length method was utilized to analyze the spatiotemporal distribution of CO2 emissions and pollutant emissions across different road networks while exploring their spatiotemporal heterogeneity. Finally, the influence of elevation and surface vegetation cover on traffic-related CO2 and pollutant emissions was taken into consideration. The results indicated that CO2, CO, HC, and NOx emissions increased significantly in 2020 compared to those in 2017 on trunk roads, and the distribution of CO2 and pollutant emissions in Fuzhou was uneven; in 2017, areas of high emissions were predominantly concentrated in the central regions with low vegetation coverage levels and low topography but expanded significantly in 2020. This study enhances our comprehension of the spatiotemporal variations in carbon and pollutant emissions resulting from regional road network expansion, offering valuable insights and case studies for regions worldwide undergoing similar infrastructure development.

In-situ construction of g-C3N4/LaPO4 S-scheme heterostructure with nitrogen vacancy for boosting photocatalytic reduction of CO2

It is a realizable way to enhance the performance of photocatalytic reduction of carbon dioxide by constructing S-scheme heterojunctions due to its unique interfacial structures. In this article, g-C3N4/LaPO4 heterojunctions with surface nitrogen vacancies were prepared by in-situ one-pot hydrothermal method. The experimental results show that the generation rate of carbon monoxide produced via the best g-C3N4/LaPO4 heterojunction is 145.8μmol g−1 h−1, which is 4.0 times and 11.2 times as large as pure g-C3N4 and LaPO4, respectively. The heterojunction structure is characterized by UPS, in situ XPS and DFT calculation. The construction of S-scheme heterojunction can efficiently promote the separation of photogenerated electron holes and improve the redox capacity to boost photocatalytic activity. Furthermore, nitrogen vacancy in g-C3N4/LaPO4 heterojunction could provide more reaction active sites, which is conductive to the absorption, distribution and activation of CO2 and H2O molecules. In summary, this advancement opens up a promising avenue for the development of more potent photocatalysts, offering potential solutions for environmental and energy-related applications.

Study on Geological Deformation of Supercritical CO2 Sequestration in Oil Shale after In Situ Pyrolysis

After the completion of in situ pyrolysis, oil shale can be used as a natural place for CO2 sequestration. However, the effects of chemical action and formation stress-state changes on the deformation of oil shale should be considered when CO2 is injected into oil shale after pyrolysis. In this study, combined with statistical damage mechanics, a transverse isotropic model of oil shale with coupled damage mechanisms was established by considering the decreased mechanical properties and the chemical damage caused by CO2 injection. The process of injecting supercritical CO2 into oil shale after pyrolysis was simulated by COMSOL6.0. The volume distribution of CO2 and the stress evolution in oil shale were analyzed. It is found that CO2 injection into oil shale after pyrolysis will not produce new force damage, and the force damage caused by the decrease in the mechanical properties of oil shale after pyrolysis can offset the ground uplift caused by CO2 injection to a certain extent. Under the combined action of chemical damage and mechanical damage, the uplift of a formation with a thickness of 200 m is only 10 cm. The injection of supercritical CO2 is beneficial for maintaining the stability of oil shale after in situ pyrolysis.

Molecular simulation study on the adsorption and storage behavior of CO2 in different matrix components of shale

ABSTRACT This study investigates the adsorption and storage behaviour of CO2 in the different matrix components of shale based on a molecular simulation method. First, based on the Grand Canonical Monte Carlo (GCMC) method, we successfully established five pore models three fluid models to study the effects of temperature, pressure, pore diameter, water content, and CH4 on the adsorption of CO2. Then, based on the actual data from the shale of the Longmaxi Formation in Sichuan Basin, China, the storage capacity of CO2 in the shale is determined by calculating the density distribution of CO2 and the proportion of excess adsorbed gas. The results demonstrate that both high temperatures and water content are unfavourable for the adsorption of CO2 in the shale pores. The adsorption of CO2 increases with rising pressure while it decreases with increasing pore size. The magnitude and stability of CO2 adsorption in the pores of various matrix components is as follows: organic matter > montmorillonite > illite > kaolinite > quartz. Compared to the scenarios neglecting the adsorption of CO2, the storage capacity of CO2 decreases by 7.87%. The main finding of this study is expected to provide theoretical guidelines for CO2 adsorption storage in shale.

Assessment of airborne viral transmission risks in a large-scale building using onsite measurements and CFD method

Screening patients for potential respiratory infections through nucleic acid sampling was a critical non-pharmacologic intervention during a respiratory infectious disease pandemic. Evaluating the cross-infection risk of crowded activities conducted indoors is necessary. We conducted a field study of this event in a large-scale stadium and measured the variation in CO2 concentrations. We conducted simulations on the stadium's flow field, CO2 and N2O concentration distribution using the CFD method, which was validated by the on-site measured data. We simulated the diffusion of virus aerosols exhaled by the sampled individuals under an all-fresh and primary return air system, respectively. It was found that space morphology and airflow pattern are the main factors influencing the concentration distribution of human exhaled contaminants. Primary return air systems can reduce the infection risk for sampled individuals by the filtration system and improve the airflow pattern. With the ratio of fresh air to return air of 1.2, the primary return air systems with 70 %, 85 %, and 95 % filtration levels can reduce the infection risk by an average of 54.5 %, 58.3 %, and 62.1 %, respectively, compared to all-fresh air system. It is necessary to optimize the processes and queue setups for nucleic acid sampling activities in the room based on the room airflow characteristics and the return air system using an efficient filtration system.

The Direct Radiative Effect of CO2 Increase on Summer Precipitation in North America

AbstractPrecipitation changes in full response to CO2 increase are widely studied but confidence in future projections remains low. Mechanistic understanding of the direct radiative effect of CO2 on precipitation changes, independent from CO2‐induced SST changes, is therefore necessary. Utilizing global atmospheric models, we identify robust summer precipitation decreases across North America in response to direct CO2 forcing. We find that spatial distribution of CO2 forcing at land surface is likely shaped by climatological distribution of water vapor and clouds. This, coupled with local feedback processes, changes in convection, and moisture supply resulting from CO2‐induced circulation changes, could determine North American hydroclimate changes. In central North America, increasing CO2 may decrease summertime precipitation by warming the surface and inducing dry advection into the region to reduce moisture supply. Meanwhile, for the southwest and the east, CO2‐induced shift of subtropical highs generates wet advection, which might mitigate the drying effect from warming.

Exploring how the heterogeneous urban landscape influences CO2 concentrations: The case study of the Metropolitan Area of Barcelona

Monitoring CO2 concentrations in urban areas is crucial for determining the efficacy of climate change mitigation policies. However, highly heterogeneous land use, local geography, and local convection patterns, which vary throughout the urban landscape, complicate this task. To establish continuous monitoring programs, it is important to first determine the heterogeneity of urban landscapes on the ground. To understand the role these factors play in the distribution of CO2 over an urban area, we conducted a CO2 measurement campaign over the Metropolitan Area of Barcelona (AMB) over four urban land uses: impervious, green, forest, and agricultural. There is a clear tendency for CO2 mixing ratios to decrease as the degree of urban vegetation increases, even in the midst of a developed boundary layer. For example, CO2 concentrations were 429 and 427 ppm at forest and agricultural sites, respectively, while 485 ppm was reported at urban sites. A decrease in atmospheric CO2 was observed from 458 to 428 ppm in the gradient from urban to suburban areas, in which the biosphere component increased. The biosphere component of the CO2 signal was significant and was observed in the gradient from urban to suburban areas, which averaged a reduction from 458 to 428 ppm. Our findings show that the large spatial variability in CO2 concentrations (ranging from 410 to 495 ppm) is best explained by anthropogenic activity. We propose increasing the spatiotemporal resolution of CO2 monitoring in the AMB to determine these trends more precisely over longer periods of time.

Thermal effects of organic porous media on absorption and desorption behaviors of carbon dioxide

As a result of global warming, people are increasingly concerned about greenhouse gas emissions, particularly carbon dioxide (CO2). Many countries have been promoting carbon capture, storage (CCS) projects in order to alleviate climate degradation and achieve net zero carbon emissions. To study the thermal effects of organic porous media on CO2 absorption and desorption, molecular dynamics coupled with Monte Carlo (MDMC) were used in this study. A part of the CO2 molecules will be trapped within kerogen matrix due to its complex porous structure. The affinity of kerogen to CO2 facilitates CO2′s adsorption within the kerogen porous media, resulting in a heterogeneous distribution of CO2. The kerogen forms high potential energy peaks and low potential energy wells in the matrix, which provide preferred adsorption sites for CO2 in the porous space. The low stress state of CO2 also indicates that it prefers adsorption in the matrix as CO2 performs a lower potential energy state in the kerogen matrix than in the bulk phase. This study examines different thermal effects of kerogen, and results indicate that increasing CO2 thermal motion facilitates its absorption, while a high temperature matrix promotes CO2 desorption. Adsorbed layer provides resistance for CO2′s diffusion behaviors. The free energy of CO2′s diffusion is analyzed in relation to its mechanism, revealing that irregular thermal motion causes uncertainty in the adsorption capacity.

Electrostatically driven kinetic inverse CO2/C2H2 separation in LTA-type zeolites

The identical molecular size and similar physical properties of carbon dioxide (CO2) and acetylene (C2H2) make their adsorptive separation extremely challenging to achieve with most adsorbents. Reports on the separation of CO2 and C2H2 mixtures by zeolites are even rarer with the mechanism of adsorptive separation requiring further exploration. In this paper, we report that ion modulation of zeolite 5A promotes the difference in kinetic diffusion of CO2 and C2H2, realizing the inverse separation of zeolite from selective adsorption of C2H2 to selective adsorption of CO2. Creating a compact pore space restricting the orientation of gas molecules enables charge recognition. The positive electrostatic potential at the pore openings was utilized to hinder the diffusion of C2H2 between the cages while ensuring the transfer of CO2, increasing their diffusion differences in pore channels and leading to the CO2/C2H2 kinetic selectivity of 31.97. Grand canonical Monte Carlo (GCMC) simulation demonstrates that the CO2 distribution in K-5A-β is significantly higher than that of C2H2. Dynamic breakthrough experiments verify the excellent performance of material in practical CO2/C2H2 separation, for CO2/C2H2 (50/50 and 1/99, V/V) mixtures can be separated in one step, thus directly generating high purity C2H2 (> 99.95%), which provides a promising thought for the zeolite-based separation of CO2 and C2H2.