Search

In this study, a novel cellulose nanocrystal/metal-organic framework composite (MC) was developed as a stabilizer for alkenyl succinic anhydride (ASA) Pickering emulsions, demonstrating remarkable sizing performance and antimicrobial properties for advanced food packaging applications. The MCs exhibited superior emulsion stabilization capabilities compared to pure metal-organic frameworks, with the optimum MC concentration identified as 1.0 wt% CNC. The hydrophobicity of the sizing paper was found to be enhanced with increasing CNC content. The MC-ASA sized paper demonstrated commendable storage stability, robust gas adsorption, and resistance to water vapor or water droplets. The MCs-ASA sized paper showed excellent food preservation efficacy, maintaining the freshness of strawberries for up to seven days, compared to ASA-sized paper without MCs. The antimicrobial assays targeting Escherichia coli and Staphylococcus aureus highlighted the intrinsic antimicrobial properties of the MCs, contributing to the extended freshness of the encased strawberries. The water vapor barrier efficacy and water retention capabilities of MCs-ASA sized paper were found to be superior to those of the paper without MCs, emphasizing the potential of the developed composite as an innovative and effective food packaging solution. This study offers valuable insights into the synthesis and implementation of CNC/MOF composite particles for versatile applications in food packaging, water-resistant materials, and environmental protection. [Display omitted] • CNC/MOF composites boost ASA Pickering emulsions' sizing performance. • MCs elevate hydrophobicity, gas adsorption, and sizing paper stability. • MCs-ASA paper extends strawberry freshness to 7 days in food packaging. • Research paves way for sustainable, eco-friendly advanced packaging solutions. [ABSTRACT FROM AUTHOR]

In this work, we examine two modifications of fine-ground calcium carbonate material (GCC) in order to enhanced sorption of NO2 and subsequent reaction properties toward NO2−/NO3− formation by firstly exposing the GCC to supercritical (sc) CO2 in order to increase particle surface area, a choice specifically made to avoid altering the surface chemistry, and secondly considering the potential advantage of using a surface coupling agent toward NO2. The modification by the coupling agent amino silane (AMEO silane) was applied in a supercritical CO2–ethanol mixture. The samples were characterised before and after modification by field emission scanning electron microscopy (FESEM), specific surface area determination (BET nitrogen adsorption), ATR-FTIR spectroscopy and ion chromatography to reveal the effects of the surface modification(s) on the morphology, surface textural properties and sorption versus reaction properties with NO2. The performance of the treated sorbents for NO2 capture was evaluated at room temperature. Results show that reactivity of NO2 with GCC was observed to increase as a function of increased surface area resulting from scCO2 exposure, but that the presence of AMEO silane on the surface, while enhancing initial adsorption of NO2 was seen subsequently to act to block reactivity. Thus, judicious use of coupling agent can provide desired rapid initial adsorption of the gas, but the goal of long-term CaCO3-consuming reactivity, so as to prolong the uptake of NO2 beyond surface saturation alone, is achieved by increasing surface area while retaining chemical-free exposed CaCO3 surface. [ABSTRACT FROM AUTHOR]

This paper evaluates the effect of different synthesis conditions on the structural properties of the porous metal–organic frameworks MIL-53(Al) produced by the microwave method at different reaction temperatures (120, 150, and 180 °C) and times (30, 180 min). The morphologies, chemical contents and crystal structures of the synthesized samples were determined by the SEM-EDS and XRD methods, respectively. The structural properties of MIL-53(Al)s were analysed according to isotherm data obtained from nitrogen gas adsorption by applying the Brunauer–Emmett–Teller (BET), Langmuir, Dubinin–Radushkevich (DR), t-plot, Barrett–Joyner–Halenda (BJH) and quenched solid density functional theory (QSDFT) methods, as well as the new numerical clustering-based adsorption analysis (LBET) method, which is a unique numerical method that provides advanced assessment for porous structures. The LBET analysis showed that the MIL-53(Al) sample at a reaction temperature of 180 °C for 30 min has the best adsorption properties, with the highest volume of the first adsorbed layer and the highest value of the energy parameter for higher layers. Due the LBET method, it was possible to evaluate the porous structure of the MIL-53(Al) samples with high precision and reliability, and thus to determine the precise influence of the conditions of their preparation on the formation of their structure. In turn, based on the shapes of the pore size distributions (PSD), the materials analysed have very similar PSD, with only the MIL-35(AL)S1 sample having a significantly lower PSD height. In conclusion, attention was paid to the necessity of complex evaluation of adsorbent properties, taking into account not only their adsorption properties but also their mechanical and functional properties, as well as production costs and the impact of adsorbent production and utilization on the environment. [ABSTRACT FROM AUTHOR]

The contribution of Eunice Foote (1819-1888) to early understanding of the relationship between atmospheric gases and climate change has become a focus of interest in the scholarly community and more widely on social media. In this article we offer a detailed interpretation of both of her known published papers, focusing particularly on her first and most significant paper of 1856, in which she related changes in the types and amounts of atmospheric gases, including carbon dioxide, to warming and changes in climate. We trace the derivation of her ideas and explore how she constructed, carried out, and interpreted her experiments. [ABSTRACT FROM AUTHOR]

Titanium zirconium vanadium (TiZrV) is a widely used non-evaporable getter (NEG) material with the characteristics of a low activation temperature and a large gas absorption capacity. At present, the research on TiZrV getters mainly focuses on the thin-film state, with little research on the bulk state. In this paper, a TiZrV getter was optimized by adding Al, and the phase structure, activation properties, and gettering performance were studied. With the addition of Al, the α-Zr phase and Ti2Zr phase changed into the Ti-Zr phase and Al-Zr, Al-Ti phase. The newly generated phase promoted the diffusion of hydrogen and oxygen atoms. The activation temperature decreased significantly, as shown in the in situ XPS results. The H2 and CO gettering performance of TiZrVAl samples was promoted to 2073 cm3·s−1 and 1912.8 cm3·s−1, increased by 40.7% and 40.3%. This paper provides valuable ideas for optimizing the properties of bulk TiZrV getters. [ABSTRACT FROM AUTHOR]

This article introduces PyRTlib, a new standalone Python package for non-scattering line-by-line microwave radiative transfer simulations. PyRTlib is a flexible and user-friendly tool for computing down- and upwelling brightness temperatures and related quantities (e.g., atmospheric absorption, optical depth, opacity, mean radiating temperature) written in Python, a language commonly used nowadays for scientific software development, especially by students and early-career scientists. PyRTlib allows for simulating observations from ground-based, airborne, and satellite microwave sensors in clear-sky and in cloudy conditions (under non-scattering Rayleigh approximation). The intention for PyRTlib is not to be a competitor to state-of-the-art atmospheric radiative transfer codes that excel in speed and/or versatility (e.g., ARTS, Atmospheric Radiative Transfer Simulator; RTTOV, Radiative Transfer for TOVS (Television Infrared Observation Satellite (TIROS) Operational Vertical Sounder)). The intention is to provide an educational tool, completely written in Python, to readily simulate atmospheric microwave radiative transfer from a variety of input profiles, including predefined climatologies, global radiosonde archives, and model reanalysis. The paper presents quick examples for the built-in modules to access popular open data archives. The paper also presents examples for computing the simulated brightness temperature for different platforms (ground-based, airborne, and satellite), using various input profiles, showing how to easily modify other relevant parameters, such as the observing angle (zenith, nadir, slant), surface emissivity, and gas absorption model. PyRTlib can be easily embedded in other Python codes needing atmospheric microwave radiative transfer (e.g., surface emissivity models and retrievals). Despite its simplicity, PyRTlib can be readily used to produce present-day scientific results, as demonstrated by two examples showing (i) an absorption model comparison and validation with ground-based radiometric observations and (ii) uncertainty propagation of spectroscopic parameters through the radiative transfer calculations following a rigorous approach. To our knowledge, the uncertainty estimate is not provided by any other currently available microwave radiative transfer code, making PyRTlib unique for this aspect in the atmospheric microwave radiative transfer code scenario. [ABSTRACT FROM AUTHOR]

The gas sweetening process is essential for removing harmful acid gases, such as hydrogen sulfide (H2S) and carbon dioxide (CO2), from natural gas before delivery to end-users. Consequently, chemical absorption-based acid gas removal units (AGRUs) are widely implemented due to their high efficiency and reliability. The most common solvent used in AGRU is monodiethanolamine (MDEA), often mixed with piperazine (PZ) as an additive to accelerate acid gas capture. The absorption performance, however, is significantly influenced by the solvent mixture composition. Despite this, solvent composition is often determined through trial and error in experiments or simulations, with limited studies focusing on predictive methods for optimizing solvent mixtures. Therefore, this paper aims to develop a predictive technique for determining optimal solvent compositions under varying sour gas conditions. An ensemble algorithm, Extreme Gradient Boosting (XGBoost), is selected to develop two predictive models. The first model predicts H2S and CO2 concentrations, while the second model predicts the MDEA and PZ compositions. The results demonstrate that XGBoost outperforms other algorithms in both models. It achieves R2 values above 0.99 in most scenarios, and the lowest RMSE and MAE values of less than 1, indicating robust and consistent predictions. The predicted acid gas concentrations and solvent compositions were further analyzed to study the effects of solvent composition on acid gas absorption across different scenarios. The proposed models offer valuable insights for optimizing solvent compositions to enhance AGRU performance in industrial applications. [ABSTRACT FROM AUTHOR]

It is imperative to conduct experimental studies on the seepage behavior of gas-bearing coal under cyclic dynamic loading conditions. This paper focuses on the evolution of coal permeability under the combined effects of dynamic loading, static loading, and gas adsorption. The principal conclusions are as follows: (1) As the frequency and amplitude of dynamic loading increase, the development of pore and fissure structures within the coal body becomes increasingly pronounced during dynamic loading cycles, resulting in a gradual rise in permeability. Notably, as the coal approaches its yielding stage, the permeability can increase by up to 47%. (2) The permeability curve is divided into four regions: the compaction reduction zone, the oscillation zone, the gradual recovery zone, and the abrupt failure increase zone. Ultimately, in the failure phase, the permeability surges dramatically, potentially reaching four to five times the initial permeability. (3) When the static loading stage and dynamic load are constant, the rate of change in coal permeability decreases with increasing adsorption amounts. When the adsorption amount is constant, the rate of change in permeability of the coal under dynamic loading increases with the increase in the static loading stress stage, with the maximum increase reaching 75.2%. It can be concluded from the rate of change in permeability and the dynamic loading sensitivity coefficient that the permeability of coal is highly sensitive to cyclic dynamic loading, with increased sensitivity associated with larger static loading stages and decreased sensitivity with greater adsorption amounts. [ABSTRACT FROM AUTHOR]

Nowadays, some fracking fluids can enable resourceful extraction of coalbed methane and reduce greenhouse gas emissions. However, their toxicity or corrosiveness will cause harm to downhole workers and pollute groundwater resources. Thus, five kinds of clean composite fracturing fluids were developed in this paper by using starch solution as the matrix and adding various preparations. The change rule of methane adsorption capacity by microstructure changes of coal samples was investigated systematically, and the optimal composite fracturing fluid was determined. The results showed that the new fracturing fluid increased the degree of aromatic ring condensation by 43.3% and the average pore size by 52.1%. Also, the adsorption constants of a value decreased by 11.6% and b value decreased by 23.9%, which can remarkably reduce the methane adsorption. The experimental results provide theoretical support for the clean production of coalbed methane. [ABSTRACT FROM AUTHOR]

Accurately predicting the adsorbed gas content in coal reservoirs is crucial for evaluating the gas content in deep coal seams. However, due to the significant variations in temperature and pressure conditions across different coal reservoirs, accurately assessing the adsorbed gas quantity presents challenges. Based on the adsorption potential theory, this paper proposes a prediction model of adsorbed gas that is applicable under various temperature and pressure conditions. The results indicate that the adsorbed gas content in deep coal reservoirs is influenced by a combination of temperature, pressure, and coal rank. The increase in pressure and coal rank enhances the inhibitory effect of temperature on methane adsorption. Meanwhile, there are significant differences in the results obtained from various virtual saturated vapor pressure models. Among them, the Amankwah model theoretically satisfies the uniqueness of the adsorption characteristic curve, with the optimal k values for different coal rank samples ranging between 2 and 9. In terms of predicting the adsorption gas, the performance of the models is ranked as follows: Amankwah model > Antonie model > Astakhov model > Dubinin model > Reid model. The Amankwah model exhibits the smallest average relative error and root mean square error. In addition, as burial depth increases, the influence of the pressure on methane adsorption decreases, while the significance of temperature increases, with the critical depth located around 1600 m. At depths shallower than the critical depth, adsorbed gas tends to preferentially accumulate and form reservoirs, which generally have lower commercial value. At depths deeper than the critical depth, free gas has the potential to form reservoirs. At this stage, gas reservoirs dominated by adsorbed gas start transitioning to those containing free gas. These findings are expected to deepen the understanding of deep coalbed methane and provide a scientific basis for exploration and development in the study area. [ABSTRACT FROM AUTHOR]

It is of great significance for coal mining and utilization to study the adsorption process of mixed gas in coal. In this paper, the Monte Carlo method (MC) is employed to study the competitive saturation adsorption of oxygen and water vapor inside coal particles, and then the convection, diffusion and adsorption inside and between particles are studied by lattice Boltzmann method (LBM). In addition, this study examines the impacts of porosity, average particle size, and gas concentration on the process of adsorption in coal porous media. The research results show that oxygen and water vapor present in the mixed gas experience increased permeability, diffusion rate, and saturated adsorption capacity as the porosity and average particle size of the coal porous medium increase. However, the time required to achieve saturated adsorption decreases. Under the condition of maintaining the proportion of gas components and altering the initial gas concentrations from 4.087 to 53.131 mol/m3, saturated adsorption capacity of both gases remains nearly unchanged. Yet, the effective diffusivity of gases declines with increasing initial concentration. Additionally, it is also found that water vapor diffuses more quickly than oxygen in the mixed gas and achieves adsorption saturation faster. [ABSTRACT FROM AUTHOR]

Taking the Longmaxi deep-marine shale gas reservoir in Zigong region as the research target, this paper aimed to characterize the nano-scale pore structure and investigate the reservoirs' heterogeneity based on fractal theory. By conducting a series of experimental studies, mainly including TOC, XRD, gas adsorption (N2 and CH4), we were able to clarify the main controlling factors for the heterogeneity of deep shale pore structure. Our results indicated that the deep marine shale possessed a significant amount of organic matter, as the average TOC value is 3.68%. The XRD analysis results show that quartz and clay were the main mineral types, and the total content of these two minerals averaged 77.5%. Positive correlations were observed between TOC and quartz, while TOC decreases as the clay mineral increases, this discovery indicating that quartz is biogenic. Based on FHH (Frenkele-Halseye-Hill) method, by using the LTNA adsorption isotherms, we took relative pressure P/P0 = 0.5 as the boundary, then two separate fractal dimension were deduced, D1 and D2 represent the fractal characteristics of small and large pores, respectively. Our study revealed that both D1 and D2 demonstrated positive correlations with N2 adsorption pore volume and adsorption specific surface area, while negatively correlated with the adsorption average pore diameter. Moreover, the two fractal dimensions showed positive associations with TOC and quartz and negative associations with clay. Additionally, D1 and D2 also demonstrated a positive correlation with Langmuir volume. The presence of micropores was found to significantly influence the formation of an irregular pore structure in shale. As the pore size decreased, the adsorption specific surface area increased, resulting in a more intricate pore structure, and the fractal dimension of the pores elevated, ultimately. This intricate structure is beneficial for the accumulation of shale gas. These research findings offer valuable insights for the comprehensive assessment of deep shale gas, and enrich our knowledge of enrichment mechanisms in deep shale gas reservoirs. [ABSTRACT FROM AUTHOR]

The pore-throat structure is a critical factor in the study of unconventional oil and gas reservoirs, drawing particular attention from petroleum geologists, and it is of paramount significance to analyze to enhance oil and gas production. In tight sandstone, which serves as a significant hydrocarbon reservoir, the internal pore-throat structure plays a decisive role in the storage and migration of fluids such as water, gases, and hydrocarbons. This paper employs casting thin section (CTS), field emission scanning electron microscope (FE-SEM), high-pressure mercury injection (HPMI), and low-temperature nitrogen gas adsorption (LT−N2−GA) experimental tests to qualitatively and quantitatively analyze the characteristics of the pore-throat structure in tight sandstone. The results indicate that the pore types in tight sandstone include intergranular residual pores, dissolution pores, intercrystalline pores, and microfractures, while the throat types encompass sheet-shaped, curved-sheet-shaped, and tubular throats. Analysis of the physical and structural parameters from 13 HPMI and 5 LT−N2−GA samples reveals a bimodal distribution of pore-throat radii. The complexity of the pore-throat structure is identified as a primary controlling factor for reservoir permeability. The fractal dimension (D) exhibits an average value of 2.45, displaying a negative correlation with porosity (R2 = 0.22), permeability (R2 = 0.65), the pore-throat diameter (R2 = 0.58), and maximum mercury saturation (R2 = 0.86) and a positive correlation with threshold pressure (R2 = 0.56), median saturation pressure (R2 = 0.49), BET specific surface area (R2 = 0.51), and BJH total pore volume (R2 = 0.14). As D increases, reservoir pores tend to decrease in size, leading to reduced flow and deteriorated physical properties, indicative of a more complex pore-throat structure. [ABSTRACT FROM AUTHOR]

Oil-immersed power transformers generate characteristic gases after failure,Therefore, it is necessary to analyse and monitor the soluble gases in transformer oil samples. In this study, the DFT calculation method was used to study the adsorption properties of H2, CO, C2H2, and C2H4 gases in oil on both intrinsic MoTe2 and Rh-doped MoTe2 films. In order to analyse the adsorption characteristics, this paper first obtains the most stable Rh-doped MoTe2 monolayer model through the modelling and computational analysis of different doping sites, then, the adsorption of these gases on the material surface is studied by analysing adsorption energy, charge transfer, total state density, parting density, energy band structure, differential charge density map, molecular front orbital and desorption time, and finally concludes that Rh-MoTe2 monolayer film is the ideal material for hydrogen sensing elements, due to the extremely long desorption time of CO gas, indicating that CO gas is hard to desorption on the surface of adsorbent,which shows that this process has played a certain role in promoting CO removal. Highlights Study focused on gas adsorption using DFT: Rh-MoTe2 ideal for hydrogen sensing and effective for CO removal, intrinsic MoTe2 ineffective and required metal doping. Rh doping enhanced conductivity and gas adsorption capacity in MoTe2. Rh-MoTe2 was suitable for detecting H2, C2H2, and C2H4 gases. Desorption times vary with temperature, with CO removal particularly effective at higher temperatures. Findings suggest potential applications for Rh-MoTe2 in gas sensing and removal. [ABSTRACT FROM AUTHOR]

The two-dimensional distribution method based on the laser spectrum is widely used in the reconstruction of two-dimensional temperature fields or concentration fields. However, the existing methods are all based on small-scale measurements. In large-scale spatial detection of farmland, the detection accuracy cannot reach the expected result due to the long optical path and the noise of various frequencies brought by environmental factors such as vibration, temperature, and other interfering gases. Aiming at the above-mentioned problems, this paper proposes a method to reduce open optical path noise interference in two-dimensional gas detection of farmland to improve detection accuracy. The signal denoising approach combines variational modal decomposition with the SG filtering algorithm to decompose, smooth out, and rebuild the detection signal. In addition, we built a two-dimensional detection system based on an open optical path. Throughout experimental validation, the proposed method outperformed the traditional method by 24% and 19%, respectively, in terms of the fitting degree and fitting effect of the gas absorption curve. [ABSTRACT FROM AUTHOR]

SO2F2 and SOF2 are the main components from the decomposition of insulation gas SF6. Photoacoustic spectroscopy (PAS) has been acknowledged as an accurate sensing technique. Polar material adsorption for SO2F2 and SOF2 in the photoacoustic gas cell of PAS may affect detection efficiency. In this paper, the optical gas-cell dynamic adsorptions of four different materials and the detection effects on SO2F2 and SOF2 are theoretically analyzed and experimentally demonstrated. The materials, including grade 304 stainless steel (SUS304), grade 6061 aluminum alloy (Al6061), polyvinylidene difluoride (PVDC), and polytetrafluoroethylene (PTFE), were applied inside the optical gas cell. The results show that, compared with metallic SUS304 and Al6061, plastic PVDC and PTFE would reduce the gas adsorption of SO2F2 and SOF2 by 10 to 20% and shorten the response time during gas exchange. The complete gas defusing period in the experiment was about 30 s. The maximum variations of the 90% rising time between the different adsorption materials were approximately 3 s for SO2F2 and 6 s for SOF2, while the generated photoacoustic magnitudes were identical. This paper explored the material selection for PAS-based gas sensing in practical applications. [ABSTRACT FROM AUTHOR]

Infrared multispectral imaging technology can achieve the long-distance, wide-ranging and fast detection of target gas, and has been widely used in the fields of dangerous-gas detection and environmental monitoring. However, due to the difficulty in acquiring background radiation as well as atmospheric disturbance and noise interference in the detection process, the quantitative detection of gas concentration has become a difficult problem to solve. Therefore, this paper proposes an inversion method for gas column concentration based on infrared multispectral imaging technology. Firstly, infrared background radiation images of the non-target gas absorption spectrum band were collected and converted into background radiation images of the target gas absorption spectrum band according to the dual-channel mapping relationship. Then, combined with the gas radiation images of the target gas absorption spectrum band, the column concentration distribution of the gas was obtained by using the measured calibration relationship between absorbance and column concentration. Experiments of gas detection in different environments were carried out, and the column concentration distribution of the target gas was inverted using this method; the results showed that the average relative error of the inversion of the gas column concentration was 4.84%, which enables the quantitative detection of gas column concentration in a complex environment. [ABSTRACT FROM AUTHOR]

Context: To lessen the impact of the dangerous metal Cr, this paper applies the first principles to investigate the adsorption behavior and photoelectric properties of GaS on Cr. The effects of doped GaS on Cr adsorption behavior are investigated with four GaS systems, which are pure, boron (B)-doped, nitrogen (N)-doped, and oxygen (O)-doped, in order to maximize the characteristics of GaS for use in novel sectors, to obtain understanding of the impact of doping on the electronic structure and optical properties of GaS adsorption of Cr, as well as to promote the development of the material. Four GaS adsorbed Cr systems, pure, B-doped, N-doped, and O-doped, are optimized, and the optimized results show that the stable adsorption position of Cr on both pure and doped GaS is the top position of Ga atoms, whereas doped elements B, N, and O can promote the adsorption of Cr on GaS, and the order of the strength of this promotion is B > N > O. Method: In this paper, molecular simulation calculations and analyses using the CASTEP module in the software Materials Studio are performed to simulate the structure optimization of GaS-adsorbed Cr materials doped with B, N, and O atoms by using the generalized gradient approximation (GGA) plane-wave pseudopotential approach [1] and the Perdew-Burke-Ernzerhof (PBE) generalized function [2]. From the convergence test, it is reasonable to set the K-point network to 4 × 4 × 1 and the truncation energy to 500 eV [3]. In this paper, a 3 × 3 × 1 supercell structure with 18 S atoms and 18 Ga atoms is selected. The convergence value of the iterative accuracy is 1.0e − 5 eV/atom, and all the atomic forces are less than 0.02 eV/Å. A vacuum layer of 16 Å is also set in the C direction to avoid interlayer interactions of GaS. First, we optimize the geometry of the model and then analyze the nature of the adsorption energy and electronic structure corresponding to the model. [ABSTRACT FROM AUTHOR]

CO and HCHO are the main pyrolysis gases in long-term running dry-type reactors, and thus the diagnosis of thermal insulation faults inside such devices can be realized by sensing these gases. In this paper, a single Au atom-decorated WS2 (Au-WS2) monolayer is proposed as an original sensing material for CO or HCHO detection to evaluate the operation status of dry-type reactors. It was found that the Au atom prefers to be adsorbed at the top of the S atom of the pristine WS2 monolayer, wherein the binding force is calculated as −3.12 eV. The Au-WS2 monolayer behaves by chemisorption upon the introduction of CO and HCHO molecules, with the adsorption energies of −0.82 and −1.01 eV, respectively. The charge density difference was used to analyze the charge-transfer and bonding behaviors in the gas adsorptions, and the analysis of density of state as well as band structure indicate gas-sensing mechanisms. As calculated, the sensing responses of the Au-WS2 monolayer upon CO and HCHO molecule introduction were 58.7% and −74.4%, with recovery times of 0.01 s and 11.86 s, respectively. These findings reveal the favorable potential of the Au-WS2 monolayer to be a reusable and room-temperature sensing candidate for CO and HCHO detections. Moreover, the work function of the Au-WS2 monolayer was decreased by 13.0% after the adsorption of CO molecules, while it increased by 1.2% after the adsorption of HCHO molecules, which implies its possibility to be a work-function-based gas sensor for CO detection. This theoretical report paves the way for further investigations into WS2-based gas sensors in some other fields, and it is our hope that our findings can stimulate more reports on novel gas-sensing materials for application in evaluating the operation conditions of dry-type reactors. [ABSTRACT FROM AUTHOR]

Zeolite LTA, with high porosity and uniform pore distribution, has been widely used in the gas adsorption field. In this paper, a 1.38 nm thick two-dimensional zeolite LTA was synthesized from kaolin, changing the cubic morphology of the traditional zeolite LTA. SEM and TEM images showed that the zeolite LTA exhibited a lamellar structure. In a comparative experiment with CO2 adsorption at different temperatures, the 2D zeolite LTA with a large specific surface area could capture more CO2 than the conventional 3D zeolite LTA. In addition, the CO2/CH4 selectivity of the 2D Zeolite LTA was 76.78 at 298 K. [ABSTRACT FROM AUTHOR]

Dispersive Fourier transform (DFT) has emerged as a powerful technique, enabling the transformation of spectral information from an optical pulse into a temporal waveform. This advancement facilitates the implementation of absorption spectroscopy using a single-pixel photodetector and a pulsed laser, particularly effective when operating on wavelengths near the absorption lines of the gas under study. This paper introduces a DFT-spectrometer employing a mode-locked tunable fiber laser with the central wavelength of 1531.6 nm. We demonstrate fast acquisition NH 3 absorption spectroscopy with a 0.2 nm spectral resolution, achieved through the utilization of the HITRAN database for estimating ammonia concentrations. Alongside the successful demonstration of NH 3 absorption spectroscopy, we explore practical limiting factors influencing the system's performance. Furthermore, we discuss potential avenues for enhancing sensitivity and spectral resolution, aiming to enable more robust and accurate gas sensing applications. [ABSTRACT FROM AUTHOR]

In this paper, the evolution of nanoscale pores, covering inter-particle pores and inter-layer pores, in illite-dominant clay during consolidation is monitored using small angle X-ray scattering (SAXS) and nitrogen gas adsorption (N2GA) techniques. No obvious change observed in the characteristic peaks of SAXS intensity curves during consolidation suggests that the intra-particle structure of the clay, including interlayer spacings, is not affected by mechanical loading, at least up to 4 MPa. The N2GA test results show that the volume of inter-particle pores inside the aggregates does decrease gradually as the compression proceeds, which is accompanied by a gradual reduction in specific surface area, probably due to the rearrangement of the particles composing the aggregates. The inter-particle pores are compressed as a whole during consolidation instead of the progressive collapse in an ordered manner, from the larger to the smaller. By comparing the pore-size distributions of illite-dominant clay obtained by MIP (mercury intrusion porosimetry) and N2GA techniques, it is found that the shapes of the two distributions in the common measurement range are obviously not matched, essentially due to the sequential nature of the drying and wetting processes. While filling the research gap in the evolution of intra-aggregate pores during consolidation, this study also shows that the N2GA technique and SAXS measurement used in conjunction with each other appear as a powerful approach for clay nano-pores identification. [ABSTRACT FROM AUTHOR]

Microporous organic polymers (MOPs) are a new type of porous materials, which have advantages of synthetic diversity, chemical and physical stability, microporous size controllability, etc. MOPs indicate broad applications in various fields such as heterogeneous catalysis, gas adsorption, separation, and storage. In recent years, MOPs have attracted an enormous attention in greenhouse gas capture due to their great potential in physisorptive gas storage. Carbazole and its derivatives have been studied extensively as Metal-Organic Polyhedra (MOPs) building blocks due to their unique structural features and versatile functionalization possibilities. This paper systematically reviews the synthesis, characterization and application of carbazole-based polymers, and relationship of structures and properties of these polymers. The application of the polymers in carbon dioxide (CO2) capture field is analysed taking advantage of their adjustable microporous structure and electron rich properties. This review also provides novel insights regarding functional polymer materials that have high ability of greenhouse gas capture and absorbing selectivity will be obtained by reasonable molecular design and efficient synthesis. [ABSTRACT FROM AUTHOR]

This paper reviews the 40-year evolution and application of the magnetic suspension balance (MSB) and discusses some challenging issues of the technique. An MSB, as defined herein, is a magnetic suspension coupling (MSC) connected to an analytical balance. With an MSC, an object can be weighed in a different environment than the balance itself, making it possible for contactless weighing. Over the past 40 years, the MSB has been commonly used in research areas requiring accurate object weighings, notably gas density measurements by MSB-based densimeters and gas adsorption measurements by MSB-based sorption analyzers. More than 15 MSB-based densimeters have been built to date; these are generally called two-sinker densimeter and single-sinker densimeter. They have produced highly accurate density data of many pure fluids and fluid mixtures. These data serve as the basis for the development of reference equations of state, which play an essential role in various industrial and scientific areas. Moreover, such systems are central to the metrology program of many countries. The MSB technique is also very successful in adsorption science: more than 85 MSB-based sorption analyzers have been set up in over 20 countries. The number of new MSB-based sorption analyzers, and peer-reviewed publications resulting from them, are both increasing exponentially since 2004. They have produced highly reliable gas adsorption data at high pressures for many applications, mainly in the energy and environmental sectors. Although further development of innovative instruments based on the MSB is threatened by the proprietary nature of MSB technology, the development will continue, e.g., toward cryogenic measurements and a more compact design. [ABSTRACT FROM AUTHOR]

The paper demonstrates the prospects of using an approach for calculating adsorption isotherms of gases on micropore industrial zeolites based on the example of H2, CO2, CO, CH4, N2 adsorption on 13X and 5A zeolites using the Dubinin–Radushkevich–Astakhov (DRA) equation. Experimental adsorption isotherms of H2, CO2, CO, CH4, N2 gases on 13X and 5A zeolites of various manufacturers have been obtained, as well as ranges of the limiting adsorption volume and characteristic adsorption energy have been established. It made it possible to correctly calculate isotherms using the DRA equation in the temperature range 293–323 K and pressure range 0–30 atm. The paper proposes and solves the optimization problem of determining affinity coefficients, which allows the calculation of gas adsorption isotherms on zeolites using only one experimental isotherm of standard gas N2. The mismatch between the experimental isotherms and those calculated by the DRA equation is 14.69% for H2 (maximum) and 1.81% for CO2 (minimum). This approach makes it possible to significantly reduce the number of necessary expensive experiments in comparison with the traditional approach (using the Langmuir equations or equations derived from it), at the same time providing acceptable accuracy for practice. [ABSTRACT FROM AUTHOR]

Fourier transform infrared spectroscopy (FTIR) is widely used in gas detection of SF6 decomposition components. A gas cell is an important element in the detection system, which can directly affect the accuracy and sensitivity of detection. During the long-term use of the gas cell, SF6 decomposition components may be adsorbed on the inner wall of the gas cell, which affects the detection results and the life of the gas cell. Therefore, the study on the adsorption between the gas cell material and the SF6 decomposition component is of great significance for improving the accuracy of detection. In this paper, based on the density functional theory, the adsorption process and adsorption degree of SF6 decomposition components (SOF2, SO2F2, CO, SO2, and H2S) with three typical main gas cell materials (Al, Cu, and Fe) and two gas cell coating materials (Teflon and Au) were simulated. It was found that the adsorption of Teflon and Au with gas was weak in the five materials and that of Teflon was the weakest. The adsorption energy of the three main gas cell materials was 2.65–6.31 times that of Teflon. The simulation results were also verified by FTIR and the GC-Materials Studio (MS) method. FTIR results showed that Teflon and Au had the weakest influence on the infrared spectral absorption peak and the effect of the two materials on SOF2 and SO2F2 gas absorption peaks is only less than 0.1. The results of gas chromatograph-mass spectrometer (GC-MS) showed that the effects of Teflon materials and Au on gas concentration were 2%–9.41% and the effects of Cu, Fe, and Al on gas concentration were 4.48%–65.43%. Therefore, Au and Teflon are suitable as coating materials for gas cells, which can reduce the adsorption of gas and improve the accuracy of infrared spectroscopy measurement. The results of this paper provide a reference for the development of application of optical gas detection technology in SF6 decomposition component detection. [ABSTRACT FROM AUTHOR]

LaNi 5 -based alloy is capable of storing and purifying hydrogen, however, it is susceptible to poisoning by impurities like O 2 and CO, ultimately diminishing its hydrogen storage performance. In this paper, a comprehensive study on the effect of oxygen on the gas adsorption properties of LaNi 4.25 M 0.75 (M = Co, Mn) and the effect of different oxygen concentrations and temperatures on LaNi 4. 25 Mn 0.75 was conducted. The results reveal that the gas adsorption capacity of LaNi 4.25 M 0.75 (M = Co, Mn) alloys increased from 150.73 ml/g and 136.51 ml/g to 186.37 ml/g and 165.04 ml/g, respectively, after introducing 1000 ppm oxygen during the initial exposure cycle. This augmentation is primarily attributed to the reaction between H 2 and O 2 , leading to the formation of H 2 O. As the number of poisoning cycles increases, the gas adsorption capacity of the alloys tends to decrease. Under varying oxygen concentrations, a higher oxygen content exerted more pronounced effects on LaNi 4. 25 Mn 0.75 , potentially linked to the accelerated rate of oxidation layer coverage with increasing oxygen levels. Regarding temperature variations, the LaNi 4. 25 Mn 0.75 alloy exhibited superior resistance to O 2 at higher temperatures compared to low temperatures. This is explained by the fact that impurity gases are more easily desorbed at elevated temperatures, thereby enhancing the likelihood of H 2 adsorption on the alloy surface. • Comprehensive O 2 on the hydrogenation/dehydrogenation performance of LaNi 4.25 M 0.75 (M = Co, Mn) alloys is systematically investigated. • The gas adsorption capacity of LaNi 4.25 M 0.75 (M = Co, Mn) alloys increased from 150.73 ml/g and 136.51 ml/g to 186.37 ml/g and 165.04 ml/g, respectively, after introducing 1000 ppm oxygen during the initial exposure cycle. • Under varying oxygen concentrations, a higher oxygen content exerted more pronounced effects on LaNi 4. 25 Mn 0.75. • The LaNi 4. 25 Mn 0.75 alloy exhibited superior resistance to O 2 at higher temperatures compared to low temperatures. [ABSTRACT FROM AUTHOR]

Three new three-dimensional (3D) metal–organic frameworks [M2(ttdc)2(dabco)] (M = Zn(II), 1-Zn; Cu(II), 1-Cu; and Zn/Cu, 1-ZnCu) based on thieno[3,2-b]thiophene-2,5-dicarboxylate (ttdc2−) were synthesized and characterized by a combination of physicochemical methods (single crystal X-ray diffraction, powder X-ray diffraction, chemical and thermogravimetric analyses and IR spectroscopy). 1-Cu demonstrated permanent porosity (Vpore = 0.790 cm3 g−1 and SBET = 1725 m2 g−1) and significant CO2, CH4, C2H2, C2H4 and C2H6 gas uptakes under ambient conditions. The adsorption selectivities for gas mixtures, calculated by IAST, were 10.8 (10.7), 14.6 (9.4), 1.7 (1.6) and 1.5 (1.6) for the equimolar gas mixture compositions CO2/N2, C2H6/CH4, C2H6/C2H4 and C2H6/C2H2 at 1 bar and 273 K (298 K), respectively. The mixed-metal compound 1-ZnCu was prepared by a crystal-to-crystal ion exchange metathesis reaction from 1-Zn with a 52% degree of ion substitution, confirmed by energy-dispersive X-ray spectroscopy, optical microscopy and single crystal X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]

Holmium based metal–organic frameworks (MOFs) are attractive due to their potential biomedical and radiotherapeutic applications. Two new three-dimensional MOFs consisting of holmium(III) and 3,3′,5,5′-azobenzenetetracarboxylate (H4abtc) were prepared. The microporous Ho(III) binuclear MOF (Ho2-abtc) with the chemical formula of [Ho2(abtc)1.5(DMF)4]·DMF exhibited a three-dimensional framework. A hexacluster (RE6X8) based three-dimensional MOF with the chemical formula ([Ho6(abtc)3(μ3-X)8]·DMA; X = OH−/F−, DMA = dimethyl ammonium) exhibited Ho6 clusters bridged by OH−/F− ions. The presence of hexaclusters in the holmium MOFs opens up the design of new MOFs for the holmium delivery with high holmium content. The crystal structures of the MOFs were solved. These MOFs are characterized by single-crystal X-ray diffraction (SC-XRD), powder XRD, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), 19F nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), gas adsorption analysis, and X-ray photoelectron spectroscopy (XPS). [ABSTRACT FROM AUTHOR]

Context: The adsorptions of gas (CO, CO2, NH3) by metal (Au, Ag, Cu)-doped single layer WS2 are studied by density functional theory. The doping of metal atoms makes WS2 behave as n-type semiconductors. The final adsorption sites for CO, CO2, and NH3 are close to the atomic sites of the doped metal. The adsorptions of CO and NH3 gases on Cu/WS2, Ag/WS2, and Au/WS2 are dominated by chemisorption. The doped metal atoms enhance the hybridization of the substrate with the gas molecular orbitals, which contributes to the charge transfer and enhances the adsorption of the gas with the material surface. The adsorptions of CO and NH3 on Cu/WS2 and Ag/WS2 allow favorable desorption in a short time after heating. The single-layer Cu/WS2 is proved to have the potential to be used as a reliable recyclable sensor for CO. This work provides a theoretical basis for developing high-performance WS2-based gas sensors. Methods: In this paper, the adsorption energy, electronic structure, charge transfer, and recovery time of CO, CO2, and NH3 in the doped system have been investigated based on the CASTEP code of density functional theory. The exchange correlation function used is the Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA). The TS (Tkatchenko-Scheffler) dispersion correction method was used to involve the effects of van der Waals interaction on the adsorption energies for all adsorption system. The ultrasoft pseudopotentials are chosen and the plane-wave cut-off energies are set to 500 eV. The k-point mesh generated by the Monkhorst package scheme is used to perform the numerical integration of the Brillouin zone and 5 × 5 × 1 k-point grid is used. The tolerances of total energy convergence, maximum ionic force, ionic displacement, and stress component are 1.0 × 10−5 eV/atom, 0.03 eV/Å, 0.001 Å, and 0.05 GPa, respectively. [ABSTRACT FROM AUTHOR]

Context: The adsorptions of gas (CO, CO2, NH3) by metal (Au, Ag, Cu)-doped single layer WS2 are studied by density functional theory. The doping of metal atoms makes WS2 behave as n-type semiconductors. The final adsorption sites for CO, CO2, and NH3 are close to the atomic sites of the doped metal. The adsorptions of CO and NH3 gases on Cu/WS2, Ag/WS2, and Au/WS2 are dominated by chemisorption. The doped metal atoms enhance the hybridization of the substrate with the gas molecular orbitals, which contributes to the charge transfer and enhances the adsorption of the gas with the material surface. The adsorptions of CO and NH3 on Cu/WS2 and Ag/WS2 allow favorable desorption in a short time after heating. The single-layer Cu/WS2 is proved to have the potential to be used as a reliable recyclable sensor for CO. This work provides a theoretical basis for developing high-performance WS2-based gas sensors. Methods: In this paper, the adsorption energy, electronic structure, charge transfer, and recovery time of CO, CO2, and NH3 in the doped system have been investigated based on the CASTEP code of density functional theory. The exchange correlation function used is the Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA). The TS (Tkatchenko-Scheffler) dispersion correction method was used to involve the effects of van der Waals interaction on the adsorption energies for all adsorption system. The ultrasoft pseudopotentials are chosen and the plane-wave cut-off energies are set to 500 eV. The k-point mesh generated by the Monkhorst package scheme is used to perform the numerical integration of the Brillouin zone and 5 × 5 × 1 k-point grid is used. The tolerances of total energy convergence, maximum ionic force, ionic displacement, and stress component are 1.0 × 10−5 eV/atom, 0.03 eV/Å, 0.001 Å, and 0.05 GPa, respectively. [ABSTRACT FROM AUTHOR]

Based on crystal engineering, three Zn/Cd-based metal--organic frameworks (MOFs) (FUM-153(Zn--H), FUM-167(Cd--H), and FUM-176(Cd--NH2)) were successfully prepared from rigid O-donor/flexible N-donor linkers (H2bdc (terephthalic acid) (L(O) H) or NH2-H2bdc (2-aminoterephthalic acid) (L(O) NH2) and bpfb (N,N'- 1,4-(phenylene) diisonicotinamide) (L(N))) with Zn/Cd ions. Structurally, the major difference among the FUMs is the various behaviors of the DMF solvent in the lattice or the coordination environment of the structures. This study investigated the effect of hydrogen bonding of NH2 substitution in 2-D layer linkers and its effect on the layer architecture. The results showed that hydrogen bonding indirectly affects the coordination of DMF solvent to the metal center and the porosity. To investigate the effect of the NH2 substitution in the presence or absence of the DMF solvent in the FUMs, the Cambridge Structural Database (CSD) was surveyed for similar structures with the L(O) H and L(O) NH2 linkers. Remarkably, the obtained data suggested that the existence of NH2 substitution may reduce the probability of the coordination of DMF to the metal centers. Theoretical studies were carried out to explore the gas adsorption performance of the title FUMs. A better CH4 adsorption compared to CO2 for all FUMs was observed. It is worth noting that CH4 and CO2 gas adsorption in FUM-176(Cd--NH2) is higher than that in FUM-153(Zn--H) and FUM-167(Cd--H). It can be deduced that the NH2 substitution in 2-D layer linkers prevented the entering of DMF molecules into the framework (lattice or coordinated solvent). Consequently, more accessible pores are provided for gas molecules. The work demonstrates the role of linker functionality in the crystal structure, pore size, and gas adsorption properties. [ABSTRACT FROM AUTHOR]

To elucidate the relationship between internal nanopore structure parameters and pulverized size during coal pulverization, in this paper, we investigated the nanopore structure evolution law, fractal characteristics, different types of pore contribution rates, and related mechanisms of anthracite samples during pulverization by cryogenic N2 adsorption experiments. The results showed more pore volume (PV) and pore surface area (PSA) will be gradually exposed during coal pulverization, thus enhancing the adsorption performance. The sample size was negatively correlated with microporous PV proportion, and the contribution rate of micropores to total PV gradually increased with decreasing sample size, whereas the contribution rate of transition pores and mesopores gradually decreased. The sample size shows a similar law to the PSA proportion of corresponding pores. As sample sizes continue to be refined, D1 and D2 basically showed an increasing trend. In addition, it was confirmed that there is a risk of inaccuracy when a single fractal dimension (FD) metric is used to characterize changes in sample PSA. The increase of sample PV/PSA during pulverization is related to the gradual evolution of isolated closed pores and the increase of inter-particle pores. The research results can help researchers deeply understand the law and mechanism of mine gas outburst. [ABSTRACT FROM AUTHOR]

In this paper, the bimetallic metal–organic frameworks (MOFs) of FeNi-BDC and FeNi-BDC-NH2 (BDC, 1,4-benzenedicarboxylate) with similar Fe/Ni molar ratio, crystal structure, porosity and thermal stability were synthesized by a solvothermal method. The results of adsorption experiments at ambient conditions showed that the adsorptive uptake of NO, CO2, O2 and N2 on FeNi-BDC were all very small under different adsorption partial pressures, with FeNi-BDC displaying a weak adsorption property because of its lack of unsaturated adsorption sites. On the contrary, at 100 kPa, the adsorption of NO by FeNi-BDC-NH2 was considerably higher than that by FeNi-BDC, indicating that the incorporation of NH2 on the ligand could effectively enhance the adsorption of NO. The adsorption capacity of FeNi-BDC-NH2 for NO reached 142.17 cm3 g−1, which was considerably higher than its capacity for CO2, O2 and N2 under the same conditions. Ideal Adsorption Solution Theory simulations calculated the adsorption selectivity for NO/CO2 and NO/O2 under a mixed atmosphere to reach 1325 and 13,346 respectively, demonstrating high adsorption selectivity. Through in situ infrared experiments and calculations of the enthalpy of adsorption, it was demonstrated that FeNi-BDC-NH2 adsorbed NO because NO can combine with NH2 in the material to form a NONOate structure. A preliminarily exploration of the mechanism of NO adsorption and the influence of NH2 functional groups on the adsorption and separation of NO revealed that the selectivity of adsorption was closely related to the variability of the enthalpy of adsorption. This also provided a new strategy for the adsorption and separation of NO in the flue gas environment. The bimetallic metal–organic frameworks of FeNi-BDC and FeNi-BDC-NH2 (BDC, 1,4-benzenedicarboxylate) with similar Fe/Ni molar ratio, crystal structure, porosity and thermal stability were synthesized by a solvothermal method. FeNi-BDC-NH2 demonstrated superior NO adsorption performance and high adsorption selectivity, indicating that the introduction of NH2 on the ligand can improve the adsorption capacity and selectivity of the material for NO, which also provides a new strategy for adsorption and separation of NO in a flue gas environment. (Image credit: Li Hao.) [ABSTRACT FROM AUTHOR]

This paper investigates a hybrid coupled plasmonic gas sensor with stacked gold-SiO2 layers for air-quality monitoring. The gas absorption characteristics of hybrid-stacked layers sensors are studied and compared with single-layer sensors. Gases with different refractive indexes changing from 1 to 1.4 are studied. The total absorption radar cross section (ACS) has increased from 1.681 × 105 nm2 for single-layer sensors to 5.021 × 105 nm2 for hybrid stacked layers sensors. A graphene monolayer is used to enhance the total gas absorption. It acts as an insulator to the dipole sensor. The lumped-element equivalent circuit is developed using a particle swarm optimization technique (PSO). The sensitivity is 788 nm/RIU for the single-layer sensor and 910 nm/RIU for the hybrid-stacked layers sensor with a graphene monolayer placed as a cover for the plasmonic dipole. A polarization-insensitive sensor concerning the direction of the electric field (single layer/hybrid-stacked layers) is constructed from 45° quad-rotated dipole arms of sensors. The total ACS is enhanced to 2.31 × 105 nm2 for the polarization-insensitive single-layer sensor and 6.76 × 105 nm2 for the polarization-insensitive hybrid-stacked layers sensor. Planar arrays of 3 × 3, 4 × 4, and 5 × 5 elements of the last sensor are investigated for absorption and sensitivity enhancement. Ethanol, acetone, nitrogen dioxide, and toluene gases are tested with a total ACS peak value of 8.7 × 106 nm2. The sensitivity is 895.5 nm/RIU for 4 × 4 array elements. [ABSTRACT FROM AUTHOR]

The employment of graphene for multifunctional uses has been a cornerstone in sensing technology. Due to its excellent electrochemical properties, graphene has been used in its pure and composite forms to detect target molecules over a wide range of surfaces. The adsorption process on the graphene-based sensors has been studied in terms of the change in resistance and capacitance values for various industrial and environmental applications. This paper highlights the performance of graphene-based sensors for detecting different kinds of domestic and industrial gases. These graphene-based gas sensors have achieved enhanced output in terms of sensitivity and working range due to specific experimental parameters, such as elevated temperature, presence of particular gas-specific layers and integration with specific nanomaterials that assist with the adsorption of gases. The presented research work has been classified based on the physical nature of graphene used in conjugation with other processed materials. The detection of five different types of gases, including carbon dioxide (CO2), ammonia (NH3), hydrogen sulphide (H2S), nitrogen dioxide (NO2) and ethanol (C2H5OH) has been shown in the paper. The challenges of the current graphene-based gas sensors and their possible remedies have also been showcased in the paper. [ABSTRACT FROM AUTHOR]

In this paper, we conducted comprehensive analysis of the selective adsorption of CO2 by carbon and silicon prismanes along with metal ions. The results of calculations from B3LYP/6-31G(d,p) and M06-2X/6-31G(d,p) levels of theory show that Be 2 + , Mg 2 + , Ca 2 + and Li + , Na + , K + ions are bounded strongly enough to prismanes. The Be 2 + ion binds more strongly to the C8 H8 cubane with binding energy 9.66 eV compared to Li + , Na + , K + , Mg 2 + and Ca 2 + ions having binding energies 1.26, 0.63, 0.51, 4.60 and 3.36 eV, respectively. Similar results were obtained for larger prismanes C 1 0 H 1 0 and C 1 2 H 1 2 . Instead of binding energy, we determine the adsorption of gases on metal-ion prismane complex along with effect of temperature on different gas adsorption shows that C8H8_Mg 2 + and C8H8_Be 2 + are active adsorbents at temperatures above room temperature. It is also observed that in comparison to N2 and CH4, CO2 interacts more strongly with all prismanes decorated with metal ions. These non-covalent interaction plots are used to study the prismane and metal-ion interaction. Comparable study of silicon prismanes with M06 2X/6-31G (d, p) basis set, in terms of binding energy, adsorption of gases on prismane along with temperature effect, also possesses similar selectivity to CO2 molecule with even higher adsorption energies. Thus, beryllium-decorated prismanes can be considered as promising adsorbents of carbon dioxide with good selectivity and high adsorption energy. [ABSTRACT FROM AUTHOR]

We demonstrate the successful implementation of an artificial neural network (ANN) to eliminate detrimental spectral shifts imposed in the measurement of laser absorption spectrometers (LASs). Since LASs rely on the analysis of the spectral characteristics of biological and chemical molecules, their accuracy and precision is especially prone to the presence of unwanted spectral shift in the measured molecular absorption spectrum over the reference spectrum. In this paper, an ANN was applied to a scanning grating-based mid-infrared trace gas sensing system, which suffers from temperature-induced spectral shifts. Using the HITRAN database, we generated synthetic gas absorbance spectra with random spectral shifts for training and validation. The ANN was trained with these synthetic spectra to identify the occurrence of spectral shifts. Our experimental verification unambiguously proves that such an ANN can be an excellent tool to accurately retrieve the gas concentration from imprecise or distorted spectra of gas absorption. Due to the global shift of the measured gas absorption spectrum, the accuracy of the retrieved gas concentration using a typical least-mean-squares fitting algorithm was considerably degraded by 40.3%. However, when the gas concentration of the same measurement dataset was predicted by the proposed multilayer perceptron network, the sensing accuracy significantly improved by reducing the error to less than ±1% while preserving the sensing sensitivity. [ABSTRACT FROM AUTHOR]

This article introduces PyRTlib, a new standalone Python package for non-scattering line-by-line microwave Radiative Transfer simulations. PyRTlib is a flexible and user-friendly tool for computing down and up-welling brightness temperatures and related quantities (e.g., atmospheric absorption, optical depth, opacity, mean radiating temperature) written in Python, a language commonly used nowadays for scientific software development especially by students and early career scientists. PyRTlib allows simulating observations from ground-based, airborne, and satellite microwave sensors in clear sky and in cloudy conditions (under non-scattering Rayleigh approximation). The intention for PyRTlib is not to be a competitor for state-of-the-art atmospheric radiative transfer codes that excel for speed and/or versatility (e.g., ARTS, RTTOV). The intention is to provide an educational tool, completely written in Python, to readily simulate atmospheric microwave radiative transfer from a variety of input profiles, including predefined climatologies, global radiosonde archives, and model reanalysis. The paper presents quick examples for the built in modules to access popular open data archives. The paper also presents examples for computing simulated brightness temperature for different platforms (ground-based, airborne, and satellite), using various input profiles, showing how to easily modify other relevant parameters, such as observing angle (zenith, nadir, slant), surface emissivity, and gas absorption model. PyRTlib can be easily embedded in other Python codes needing atmospheric microwave radiative transfer (e.g., surface emissivity models and retrievals). Despite its simplicity, PyRTlib can be readily used to produce present-day scientific results, as demonstrated by two examples showing (i) absorption model comparison and validation with ground-based radiometric observations and (ii) uncertainty propagation of spectroscopic parameters through the radiative transfer calculations following a rigorous approach. To our knowledge, the uncertainty estimate is not provided by any other currently available microwave radiative transfer code, making PyRTlib unique for this aspect in the atmospheric microwave radiative transfer code scenario. [ABSTRACT FROM AUTHOR]

Improving the adsorption performance of activated carbon can effectively reduce the emission of volatile organic compounds (VOCs). In this paper, the influences of pore size, functional groups, and water molecular content on the adsorption for four gasoline evaporation VOCs (n‐butane, n‐hexane, p‐xylene, and ethanol) were investigated in terms of equilibrium adsorption capacity and threshold pressure by molecular simulation. The simulation results show that capillary condensation can increase the equilibrium adsorption capacity of gas, while functional groups and water molecules will reduce the effective adsorption volume of activated carbon. On the other hand, the threshold pressure depends primarily on the interaction energy and the number of adsorption sites. The superposition effect of the adsorption force field makes the lowest threshold pressure of four VOCs. The threshold pressure of n‐butane, n‐hexane, and p‐xylene is increased by the presence of functional groups and water molecules, while functional group modification and a certain amount of water molecules can improve the adsorption capacity of ethanol at low pressure. The results of the study can provide a reference for the selection of activated carbon in vehicle carbon canisters and the development of high‐performance activated carbon. [ABSTRACT FROM AUTHOR]

This paper aims to describe methane adsorption in coal under the conditions of high temperature and high pressure, as well as quantitatively decipher the change rule of energy in the isothermal adsorption process. The isothermal adsorption test was carried out with four groups of middle-rank coals from the Linxing area with different degrees of metamorphism. The impacts of the degree of deterioration of coal, temperature, and pressure on adsorption were analyzed with regard to the adsorption amount, adsorption potential, and adsorption space. Additionally, the energy change during the adsorption of methane by the coal was considered. The results show that the coal adsorption capacity hinges on the degree of deterioration of the coal, as well as the pressure and temperature. Additionally, the impact of temperature upon coal methane adsorption under depth conditions is highlighted. Like the adsorption space, the adsorption potential is an important parameter used to quantitatively characterize the adsorption ease and adsorption capacity; furthermore, the adsorption potential of millipores exceeds that of mesopores, as they are capable of offering a larger specific surface area for adsorption. The total decrease in the surface free energy during adsorption increases as the pressure increases; simultaneously, the increase rate is fast and then slow. The total decrease in the above-described free energy diminishes as the temperature escalates. Under the same pressure, the total decrease in the aforementioned free energy increases as the reflectance of the specular body of the coal increases. The decrease in the aforementioned free energy at each point of pressure lessens as the pressure grows; notably, when the pressure is comparatively low, the reduction is very fast. As the pressure escalates continuously, the decrease speed is slow. Regarding the effect of pressure and temperature upon adsorption, the adsorption gas volume of coal exists in a conversion depth from 1200 m to 1500 m; at the same time, the impact of pressure upon adsorption is dominant up to this depth. Additionally, beyond this depth, temperature gradually comes to have the greatest impact on adsorption. [ABSTRACT FROM AUTHOR]

The thermophoresis of nanoparticles suspended in gas is investigated in the transition regime by molecular dynamics simulations. It is found that there exists significant discrepancy between the simulation results and the theoretical predictions for the thermophoretic force, which is attributed to the adsorption of gas molecules on nanoparticles and the gas–particle non-rigid body collisions. By using the effective particle radius, the simulation results and Talbot et al.'s equation could agree with each other in the transition regime. In addition, the effect of the finite system size of the molecular dynamics simulations is non-negligible, and the simulation results modified by effective particle radius can coincide with Phillips' equation quite well. Therefore, for particles of a few nanometers, the non-rigid body collision effect and the adsorption of gas molecules and the effective radius of the nanoparticle under strong gas–particle coupling should be taken into account in the theoretical model. The investigation presented in this paper provides guidance for the application of nanoparticles in aerosol science. [ABSTRACT FROM AUTHOR]

Cobalt molybdenum nitrides are one of the most promising ammonia-synthesis catalysts of the future. However, the selection of the optimal promoter composition is a challenging task. In this paper, the structure–property relationship of ternary cobalt molybdenum nitrides as ammonia synthesis catalysts promoted with potassium was studied. A series of catalysts containing 0.2–3.5 wt% potassium was analyzed by means of X-ray diffraction, volumetric gas adsorption, and activity tests in ammonia synthesis. The catalysts were subjected to thermal aging in the same catalytical reactor. The influence of the potassium promoter on the thermostability was determined. The observed loss of activity in catalysts with a high potassium content was related to the concentration of Co2Mo3N and Co3Mo3N phases, the mean crystallite sizes, the specific surface area, and the pore size distribution. [ABSTRACT FROM AUTHOR]

Among other porous materials, porous organic polymers have already been proven to be a valuable alternative for the selective adsorption of CO2 over N2. In a rational design of new porous organic systems, computational methods can help us to better understand structural features responsible for efficient and selective adsorption of gases. In this paper, a comprehensive approach relying on complementary computational chemistry methods including calculation of binding energies, visualization of electrostatic potential maps and using GCMC simulations to obtain adsorption isotherms and density plots is suggested for a detailed analysis of nitrogen--nitrogen linked porous organic systems. Three different linkages (azo, azoxy and azodioxy) and two different connectors (trisubstituted benzene and triazine) were computationally investigated referring to similar hexagonal porous organic structures. Considering the reversibility in azodioxy bond formation, azodioxy-based 2D layered structures, along with azoxy systems, seem to be new promising candidates for future development of porous organic materials capable of selective binding of CO2 over N22. [ABSTRACT FROM AUTHOR]

This review discusses the most commonly employed methods for determining pore size and pore size distribution in bioaerogels. Aerogels are materials with high porosity and large surface areas. Most of their pores are in the range of mesopores, between 2 and 50 nm. They often have smaller or larger pores, which presents a significant challenge in determining the exact mean pore size and pore size distribution in such materials. The precision and actual value of the pore size are of considerable importance since pore size and pore size distribution are among the main properties of aerogels and are often directly connected with the final application of those materials. However, many recently published papers discuss or present pore size as one of the essential achievements despite the misinterpretation or the wrong assignments of pore size determination. This review will help future research and publications evaluate the pore size of aerogels more precisely and discuss it correctly. The study covers methods such as gas adsorption, from which BJH and DFT models are often used, SEM, mercury porosimetry, and thermoporometry. The methods are described, and the results obtained are discussed. The following paper shows that there is still no precise method for determining pore size distribution or mean pore size in aerogels until now. Knowing that, it is expected that this field will evolve in the future. [ABSTRACT FROM AUTHOR]

The idea of fluidised bed application allows a significantly increased heat transfer coefficient between adsorption bed and the surface of a heat exchanger, improving the performance of adsorption cooling and desalination systems [[11]]. The results confirmed the effect of the duration of adsorption and desorption on the COP and SCP of the adsorption chiller. The paper [[9]] presents experimental results of the metal-based and carbon nanotube additives influence on sorption kinetics of a silica-gel-based adsorption bed in an adsorption chiller. The authors in [[8]] conducted energy and exergy analyses of an adsorption chiller to investigate the effect of recooling-water temperatures on the cooling capacity and COP with variable cycle modes. [Extracted from the article]

A large and growing number of theoretical papers report the possible role of defects and heteroatoms on the chemical properties of single-layer graphene. Indeed, they are expected to modify the electronic structure of the graphene film, allow for chemisorption of different species, and enable more effective functionalisation. Therefore, from theoretical studies, we get the suggestion that single and double vacancies, Stone–Wales defects and heteroatoms are suitable candidates to turn nearly chemically inert graphene into an active player in chemistry, catalysis, and sensoristics. Despite these encouraging premises, experimental proofs of an enhanced reactivity of defected/doped graphene are limited because experimental studies addressing adsorption on well-defined defects and heteroatoms in graphene layers are much less abundant than theoretical ones. In this paper, we review the state of the art of experimental findings on adsorption on graphene defects and heteroatoms, covering different topics such as the role of vacancies on adsorption of oxygen and carbon monoxide, the effect of the presence of N heteroatoms on adsorption and intercalation underneath graphene monolayers, and the role of defects in covalent functionalisation and defect-induced gas adsorption on graphene transistors. [ABSTRACT FROM AUTHOR]

The fractal theory has been widely applied to the analysis of gas adsorption isotherms, which are used for the pore structure characterization in unconventional reservoirs. Fractal dimension is a key parameter that can indicate the complexity of the pore structures. So far, most fractal models for gas adsorption are for N2 adsorption, while fractal models for CO2 adsorption are rarely reported. In this paper, we built a fractal model for CO2 adsorption by combining a thermodynamic model and the Dubinin–Astakhov model. We then applied the new model to three CO2 adsorption isotherms measured on shale samples. The results show that the fractal dimension from the new model lies between 2 and 3, which agrees with the fractal geometry. The new model presented in this paper can be used for the CO2 adsorption analysis, which allows characterizing micropore structures in shales. [ABSTRACT FROM AUTHOR]

The surface states of gas sensing materials based on oxide semiconductors are closely related to their sensing dynamics. In this work, using surface engineering, p-type ZnCo2O4 architectures are prepared through a feasible hydrothermal strategy followed by subsequent annealing treatment and are applied for the detection of inert xylene gas. The as-prepared ZnCo2O4 architecture (ZCO-300) exhibits a higher response and selectivity toward xylene gas at a working temperature of 170 °C. Moreover, the ZCO-300 sensor also presents superior stability/reliability, good moisture resistance and a low detection limit of 0.1 ppm. The larger number of oxygen vacancy defects and higher specific surface area in ZCO-300 not only promote the catalytic oxidation of xylene gas by p-type semiconductor ZnCo2O4, but also provide more gas adsorption sites and surface reaction sites on sensing material surfaces, thereby endowing ZCO-300 with superior xylene gas sensing properties. [ABSTRACT FROM AUTHOR]

Detection of SF 6 decomposition gases is crucial in power equipment maintenance. This paper investigates the adsorption behavior of SO 2 and H 2 S on the intrinsic and Fe-modified net-Y surfaces using density functional theory. The adsorption parameters and electronic attributes of diverse configurations have been scrutinized. Calculations indicate that net-Y exhibits limited adsorption capacity for both gases. The doped substrate exhibits a localized magnetic moment around the Fe atom, indicating the possible occurrence of the Kondo effect in the system. The substrate chemisorbs with the target gas through the Fe 3d orbitals. Additionally, after the adsorption of gases, the system undergoes a transition from metallic to semiconductor properties, accompanied by a near-complete disappearance of magnetism. Specifically, in two adsorption configurations, the systems manifest the characteristics of half-semiconductor and half-metal, respectively. Our study provides evidence that the incorporation of Fe-modified net-Y shows potential as a disposable device for detecting and purifying the decomposition products of SF 6 , presenting a prospective application for net-Y in spintronic devices. [ABSTRACT FROM AUTHOR]