Gaseous Research Articles

In Situ Helium Isotope Microimaging of Meteorites.

Isotope imaging is commonly used to investigate the localization of trace elements and their isotopes. In situ noble gas analysis of meteorites revealed the distribution of primordial noble gases that were trapped in the building blocks of asteroids and planets during the early stage of the solar system evolution. Solar wind noble gases are among the primordial gases present in meteorites and were trapped through exposure to solar wind. Micrometer-resolution in situ noble gas analysis has not been achieved due to the lack of sensitivity and spatial resolution. The microscale imaging technique is crucial for identifying the carrier phase of the solar wind noble gases. We have developed 4He isotope imaging utilizing secondary neutral mass spectrometry with strong field postionization. This technique achieved a lateral resolution of 2 μm and a 4He detection limit of 2 × 1017 cm-3. This development allows for the study of a solar wind gas-rich meteorite, Northwest Africa 801 carbonaceous chondrite, with micrometer resolution. The solar wind 4He carriers are fine-grained particles and are sparsely scattered in the matrix region.

Investigation and analysis of acute poisoning of organic fluorine mixed gas in a fluorine polymerization plant

In January 2021, an acute chemical poisoning incident occurred at a fluorine polymerization plant. Through the analysis of the occupational health situation of the enterprise, combined with the clinical manifestations of the poisoned patients and the laboratory examination results, it was determined that the incident was an acute poisoning incident caused by the inhalation of organic fluorine mixed gas in the fluorine polymerization plant. Subsequently, it was clarified that the accident was caused by the illegal operation of the employees of the fluorine polymerization plant, which caused the discharge of the organic fluorine mixed gas containing high concentration of octafluoroisobutene, resulting in the poisoning of the on-site construction personnel. In order to avoid the occurrence of similar incidents, enterprises should implement the main responsibility of safety production, regularly organize supervision and inspection, eliminate illegal operations, conduct safety education and training for the staff of the unit and outsourced staff, and improve the emergency rescue ability of sudden poisoning incidents.

High efficiency triethylamine gas sensor based on SmVO4 nano octahedron granules

Triethylamine (TEA) is typical hazardous volatile organic gas (VOCs), it is particularly important for us to effectively detect triethylamine in complex places. In this work, high efficiency triethylamine gas sensor based on SmVO4 was successfully obtained by means of hydrothermal reaction and assisted calcination. Characterization of analytical materials, SmVO4 octahedral nanoparticles formed clusters similar to pomegranate fruits. There is a trace +4 valence state of vanadium in the material, which contributes to the oxidation-reduction reaction between the target gas and the surface of the material. Gas sensitive test results found that the SmVO4 sensor still has a 2.45 response to the target gas (triethylamine) at low concentrations (1 ppm). SmVO4 shows excellent selectivity for triethylamine, with a response value more than three times that of other gases. In 25 days, it shows excellent stability and fast response recovery time (15 s/40 s). In addition, the gas sensing mechanism is analyzed.

High-Performance Room Temperature Ammonia Sensors Based on Pure Organic Molecules Featuring B-N Covalent Bond.

Exploring organic semiconductor gas sensors with high sensitivity and selectivity is crucial for the development of sensor technology. Herein, for the first time, a promising chemiresistive organic polymer P-BNT based on a novel π-conjugated triarylboron building block is reported, showcasing an excellent responsivity over 30000 (Ra/Rg) against 40ppm of NH3, which is ≈3300 times higher than that of its B-N organic small molecule BN-H. More importantly, a molecular induction strategy to weaken the bond dissociation energy between polymer and NH3 caused by strong acid-base interaction is further executed to optimize the response and recovery time. As a result, the BN-H/P-BNT system with rapid response and recovery times can still exhibit a high responsivity of 718, which is among the highest reported NH3 chemiresistive sensors. Supported by in situ FTIR spectroscopy and theoretical calculations, it is revealed that the N-H fractions in BN-H small molecule promoted the charge distribution on phenyl groups, which increases charge delocalization and is more conducive to gas adsorption in such molecular systems. Notably, these distinctive small molecules also promoted charge transfer and enhanced electron concentration of the P-BNT sensing polymer, thus achieving superior B-N-containing organic molecules with excellent sensing performance.

Organic nanowire sensor with seeing, smelling and heat sensation capabilities

Ultra-long high aspect ratio one dimensional (1D) organic semiconductor nanowire is extremely valuable but very challenging to prepare. Based on diacetylene-bridged perylene mono-imide small molecule, scalable 1D nanowire is prepared by simple method, lengths of wires are more than 3 mm and aspect ratios are higher up to ∼9000. Organic flexible conductive wires made devices exhibit good multi-functional sensibilities to light, organic gases and heat. Single wire photodetector shows 80 mA/W responsivity and 3.05×1012 Jones detectivity at 532 nm. Mass-wire sensors demonstrate excellent sensibility, (tetrahydrofuran 0.0166 Ω/ppm; acetone 0.0139 Ω/ppm; ethanol 0.0164 Ω/ppm), low detection limitation and good repeatability to various volatile compounds and sensitive temperature variation response (0.394 mA K−1). The nanowires provide flexible media of sensors for the next generation miniature devices.

Near-infrared dual-band sensing of trace volatile organic compound gases via metal-organic framework patch array integrated on metal film

Near-infrared dual-band sensing of trace volatile organic compound gases via metal-organic framework patch array integrated on metal film

Gas-sensing properties of p-type of nitrogen-doped ZnO nanorods prepared by deep cryogenic treatment

This study developed p-type nitrogen-doped zinc oxide nanorods (NZO NRs) using a chemical bath deposition and deep cryogenic treatment. These NRs were employed to create the device structure of metal-oxide-metal (MSM) and p-n junction for a volatile organic compound gas sensor. Deep cryogenic treatment is the process of immersing ZnO NRs in liquid nitrogen to achieve NZO NRs. SEM results show that the morphology of NZO changes from hexagonal to nib shapes. XRD and TEM results demonstrate that the peak of (002) shifts, and lattice dislocation was observed in NZO specimen. XPS and EDS analysis proved that the N atoms were successfully doped into ZnO. Optical analysis showed the lower band gap and a broader absorption region of NZO NRs. The doping mechanism of NZO is deduced as polar molecules distributed on the high-surface area of ZnO NRs, with iron playing a catalytic role. The MSM structure of the p-type NZO gas sensor, exhibiting high response, lifetime and selectivity, was verified at room temperature. The gas sensor with a p-n junction structure exhibits a faster response time to ethanol.

Preserving non-negative porosity values in a bi-phase elasto-plastic material under Terzaghi’s effective stress principle

Poromechanics is a well-established field of continuum mechanics which seeks to model materials with multiple phases, usually a stiff solid phase and fluid phases of liquids or gases. Applications are widespread particularly in geomechanics where Terzaghi’s effective stress is widely used to solve engineering soil mechanics problems. This approach assumes that the solid phase is incompressible, an assumption that leads to many advantages and simplifications without major loss of fidelity to the real world. Under the assumption of finite (as opposed to infinitesimal) strains, the poromechanics of two- or bi-phase materials gains complexity and while the compressible solid phase case has received attention from researchers, the incompressible case has received less. For the finite strain - incompressible solid phase case there is a fundamental issue with standard material models, in that for some loadings solid skeleton mass conservation is violated and negative Eulerian porosities are predicted. While, to the authors’ best knowledge, acknowledgement of this essential problem has been disregarded in the literature, an elegant solution is presented here, where the constraint on Eulerian porosity can be incorporated into the free energy function for a material. The formulation is explained in detail, soundly grounded in the laws of thermodynamics and validated on a number of illustrative examples.

Volatile acetic acid selective adsorption by biomass-derived activated carbon with humidity-resistance: Tunable implanting and activation approach of activator

The selective adsorption and capture of polar organic acid gas by activated carbon (AC) absorbent could solve the challenge of irritant volatile organic compound discharge. However, volatile acid gas selective adsorption by traditional activated carbon with humidity resistance remains challenged. In this study, we developed an innovative one-step chemical synthesis method using discarded banana peels as a carbon source to create porous carbon materials. The selection of activators including sodamide and potassium hydroxide along with tunable implanting means of activator under different activated temperatures were modulated to optimize the fabrication of activated carbon. The results reveal that the low dosage of NaNH2 activator (NaNH2/carbon precursor = 1) implanted into carbon precursor through one-step ball-milling could contribute an excellent structural properties, and higher activated temperature makes the mesoporous behavior of activated carbon more obvious. Based on various optimization conditions, the optimal sample, BAC900, displays remarkable structural features (SBET = 2302 m2/g, Vtotal = 1.968 cm3 g−1, V>2nm = 1.474 cm3 g−1), achieving exceptional acetic acid adsorption efficiency (24.105 mmol g−1). Comparative analysis under various synthetic conditions revealed a close linear relationship between the structural characteristics (total pore volume) of adsorbent and acetic acid adsorption efficiency. We further explored the role of mesopores in facilitating acetic acid adsorption at relatively high pressures and their contribution to enhancing the hydrophobicity of the adsorbent. Additionally, we employed the Differential Isothermal Heat (DIH) technique to predict adsorption selectivity at varying relative humidity, revealing the higher adsorption heat (57 kJ mol−1) of acetic acid compared to water vapor (36 kJ mol−1). This comprehensive study emphasizes the outstanding adsorption selectivity of adsorbent for acetic acid, even in humid environments. Furthermore, the low adsorption heat of the BAC900 indicates good reversibility and reusability, paving the way for the practical application of biomass-derived functional biochar adsorbents in the environmental management of threatening acid VOCs pollutants.

Secondary Organic Aerosol Formation Potential from Vehicular Non-tailpipe Emissions under Real-World Driving Conditions.

Traffic emissions are a dominant source of secondary organic aerosol (SOA) in urban environments. Though tailpipe exhaust has drawn extensive attention, the impact of non-tailpipe emissions on atmospheric SOA has not been well studied. Here, a closure study was performed combining urban tunnel experiments and dynamometer tests using an oxidation flow reactor in situ photo-oxidation. Results show a significant gap between field and laboratory research; the average SOA formation potential from real-world fleet is 639 ± 156 mg kg fuel-1, higher than the reconstructed result (188 mg kg fuel-1) based on dynamometer tests coupled with fleet composition inside the tunnel. Considering the minimal variation of SOA/CO in emission standards, we also reconstruct CO and find the critical role of high-emitting events in the real-world SOA burden. Different profiles of organic gases are detected inside the tunnel than tailpipe exhaust, such as more abundant C6-C9 aromatics, C11-C16 species, and benzothiazoles, denoting contributions from non-tailpipe emissions to SOA formation. Using these surrogate chemical compounds, we roughly estimate that high-emitting, evaporative emission, and asphalt-related and tire sublimation share 14, 20, and 10% of the SOA budget, respectively, partially explaining the gap between field and laboratory research. These experimental results highlight the importance of non-tailpipe emissions to atmospheric SOA.

Migration and transformation mechanisms of Pb/Cd with HCl in organic solid waste incineration flue gas on the composite-modified kaolinite surface

Cadmium/lead (Cd/Pb) pollutants from organic solid wastes (OSW) incineration are of global concern due to high volatility and biotoxicity. The strong interaction between modified kaolinite and Cd/Pb species inspires its utilization for the elimination of heavy metals. However, the specific mechanism of the migration and transformation of Cd/Pb species is yet unclear. Consequently, the migration and transformation mechanisms of Cd/Pb species on the modified kaolinite (001) surface are examined by density functional theory (DFT), considering the effect of HCl. The outcomes show that the HCl significantly alters the characteristics of the kaolinite, which enhances the surface activity of kaolinite and promotes the adsorption and transformation of Cd/Pb species. Furthermore, the chlorination routes of Cd0/Pb0 are fully elucidated in both 2-step and 1-step routes. The first step of the 2-step route obeys the Langmuir-Hinshelwood mechanism and the second step obeys the Eley-Rideal mechanism, while the 1-step chlorination route obeys the Eley-Rideal mechanism. In addition, the oxidation route of Cd0/Pb0 follows the Mars-van Krevelen mechanism. The comparison of the energy barriers shows that the 1-step Cd0/Pb0 chlorination route has the lowest energy barrier. The kaolinite surface is found to have elevated activity for the adsorptive trapping of Cd/Pb species in the presence of HCl, which offers a preliminary theoretical framework for pollutant control on the modified kaolinite surface.

Phase equilibria calculations of a hydrocarbon system consisting water and asphaltene using association equation of state: A generalized auto-tune procedure

A generalized algorithm is proposed for four-phase flash calculations in hydrocarbon-water systems in which asphaltene has tendency to be precipitated. The systems which are going to be studied in this paper can be either single phase, two-phase, three-phase or four-phase of gas, oil-rich, asphaltene-rich and aqueous phases. The properties of vapor and oil-rich (liquid) phases can be predicted using any EOS while Henry's law is performed for calculating the properties of water-rich (aqueous) phase. In addition, an association equation of state (AEOS) has been used to predict the amount of the precipitated asphaltenes at different conditions. Using the proposed algorithm, one can predict the number and types of phases and also the properties of each phase, as accurate as possible. As tuning of EOS models is tedious and time consuming, a generalized and auto-tune method based on sensitivity and optimization algorithms is also applied in this study so that the best model could be found easily, quickly and automatically. The proposed approach proved to be efficient, and very good agreement between the results of the presented method and experimental data was found for different test problems. This new procedure can be very useful in compositional reservoir simulation of certain enhanced oil recovery methods and in surface facility process simulation.

Modeling Novel Aqueous Particle and Cloud Chemistry Processes of Biomass Burning Phenols and Their Potential to Form Secondary Organic Aerosols.

Phenols emitted from biomass burning contribute significantly to secondary organic aerosol (SOA) formation through the partitioning of semivolatile products formed from gas-phase chemistry and multiphase chemistry in aerosol liquid water and clouds. The aqueous-phase SOA (aqSOA) formed via hydroxyl radical (•OH), singlet molecular oxygen (1O2*), and triplet excited states of organic compounds (3C*), which oxidize dissolved phenols in the aqueous phase, might play a significant role in the evolution of organic aerosol (OA). However, a quantitative and predictive understanding of aqSOA has been challenging. Here, we develop a stand-alone box model to investigate the formation of SOA from gas-phase •OH chemistry and aqSOA formed by the dissolution of phenols followed by their aqueous-phase reactions with •OH, 1O2*, and 3C* in cloud droplets and aerosol liquid water. We investigate four phenolic compounds, i.e., phenol, guaiacol, syringol, and guaiacyl acetone (GA), which represent some of the key potential sources of aqSOA from biomass burning in clouds. For the same initial precursor organic gas that dissolves in aerosol/cloud liquid water and subsequently reacts with aqueous phase oxidants, we predict that the aqSOA formation potential (defined as aqSOA formed per unit dissolved organic gas concentration) of these phenols is higher than that of isoprene-epoxydiol (IEPOX), a well-known aqSOA precursor. Cloud droplets can dissolve a broader range of soluble phenols compared to aqueous aerosols, since the liquid water contents of aerosols are orders of magnitude smaller than cloud droplets. Our simulations suggest that highly soluble and reactive multifunctional phenols like GA would predominantly undergo cloud chemistry within cloud layers, while gas-phase chemistry is likely to be more important for less soluble phenols. But in the absence of clouds, the condensation of low-volatility products from gas-phase oxidation followed by their reversible partitioning to organic aerosols dominates SOA formation, while the SOA formed through aqueous aerosol chemistry increases with relative humidity (RH), approaching 40% of the sum of gas and aqueous aerosol chemistry at 95% RH for GA. Our model developments of biomass-burning phenols and their aqueous chemistry can be readily implemented in regional and global atmospheric chemistry models to investigate the aqueous aerosol and cloud chemistry of biomass-burning organic gases in the atmosphere.

Life cycle environmental impact assessment of natural gas distributed energy system

Natural gas distributed energy is recognized as a pivotal means to enhance energy efficiency and mitigate carbon dioxide emissions through localized energy cascading. Positioned as a key option for advancing the Sustainable Development Goals, this system optimizes energy utilization near end-users. While maximizing energy efficiency, it is imperative to address potential environmental challenges. A thorough, comprehensive environmental assessment, facilitated by the life cycle assessment method, proves instrumental in meeting this standard. Employing this method enables an intuitive grasp of the environmental strengths and weaknesses inherent in natural gas distributed energy within the power structure. This insight serves as a foundation for informed project decision-making, fostering the growth of the industry. We selected six environmental impact assessment categories based on the CML 2001 method, and conducted the life cycle analysis across four stages. China's inaugural natural gas distributed energy demonstration project was chosen as a model case, and an environmental impact assessment inventory was established, utilizing survey data and literature for comprehensive data collection and analysis. Results from case testing yield environmental impact assessment outcomes, with a specific sensitivity analysis for stages with notable environmental impact factors. The study underscores that the operation phase has the highest environmental impact, comprising 78.37% of the total combined environmental impact, followed by the fuel production phase. Comparative analyses with coal-fired and conventional natural gas power generation, based on dimensionless literature data, reveal that abiotic resources depletion potential is the primary contributor to the environmental impact of 1 kWh of electricity product, constituting 52.76% of the total impact value, followed by global warming potential. Concrete strategies have been outlined for decision-making in both the operational and planning phases of natural gas distributed energy projects. The strengthening of policies is pinpointed towards grid connection and scale expansion.

Effect of Ordered Vacancy Compounds on the Carrier Collection in Wide‐Gap (Ag,Cu)(In,Ga)Se2 Solar Cells

This contribution studies the effect of ordered vacancy compounds (OVCs) on the minority carrier collection in wide‐gap (Ag,Cu)(In,Ga)Se2 (ACIGS) solar cells. For this purpose, three samples with different ([Ag]+[Cu])/([In]+[Ga]) (I/III) values were processed: 1) a very off‐stoichiometric absorber (I/III = 0.31), consisting of isolated chalcopyrite patches embedded in a major OVC bulk phase, 2) a moderately off‐stoichiometric absorber (I/III = 0.77) with OVC patches at the front and back interfaces and 3) a close‐stoichiometric absorber (I/III = 0.94) with only very few, isolated OVC patches. For each of these samples, synchrotron‐based X‐ray fluorescence (XRF) was measured on a nanoscale (55 nm resolution), while simultaneously recording the X‐ray beam induced current (XBIC). The results, complemented by transmission electron microscopy and electron‐beam induced current analyses, clearly indicate that the presence of the OVC phase reduces the carrier collection and thus the short‐circuit current density of off‐stoichiometric wide‐gap ACIGS solar cells.

Parameterizations of US wildfire and prescribed fire emission ratios and emission factors based on FIREX-AQ aircraft measurements

Abstract. Extensive airborne measurements of non-methane organic gases (NMOGs), methane, nitrogen oxides, reduced nitrogen species, and aerosol emissions from US wild and prescribed fires were conducted during the 2019 NOAA/NASA Fire Influence on Regional to Global Environments and Air Quality campaign (FIREX-AQ). Here, we report the atmospheric enhancement ratios (ERs) and inferred emission factors (EFs) for compounds measured on board the NASA DC-8 research aircraft for nine wildfires and one prescribed fire, which encompass a range of vegetation types. We use photochemical proxies to identify young smoke and reduce the effects of chemical degradation on our emissions calculations. ERs and EFs calculated from FIREX-AQ observations agree within a factor of 2, with values reported from previous laboratory and field studies for more than 80 % of the carbon- and nitrogen-containing species. Wildfire emissions are parameterized based on correlations of the sum of NMOGs with reactive nitrogen oxides (NOy) to modified combustion efficiency (MCE) as well as other chemical signatures indicative of flaming/smoldering combustion, including carbon monoxide (CO), nitrogen dioxide (NO2), and black carbon aerosol. The sum of primary NMOG EFs correlates to MCE with an R2 of 0.68 and a slope of −296 ± 51 g kg−1, consistent with previous studies. The sum of the NMOG mixing ratios correlates well with CO with an R2 of 0.98 and a slope of 137 ± 4 ppbv of NMOGs per parts per million by volume (ppmv) of CO, demonstrating that primary NMOG emissions can be estimated from CO. Individual nitrogen-containing species correlate better with NO2, NOy, and black carbon than with CO. More than half of the NOy in fresh plumes is NO2 with an R2 of 0.95 and a ratio of NO2 to NOy of 0.55 ± 0.05 ppbv ppbv−1, highlighting that fast photochemistry had already occurred in the sampled fire plumes. The ratio of NOy to the sum of NMOGs follows trends observed in laboratory experiments and increases exponentially with MCE, due to increased emission of key nitrogen species and reduced emission of NMOGs at higher MCE during flaming combustion. These parameterizations will provide more accurate boundary conditions for modeling and satellite studies of fire plume chemistry and evolution to predict the downwind formation of secondary pollutants, including ozone and secondary organic aerosol.

Adsorption behaviors of organic molecules on Nb/Zr–modified bismuthene: A first–principles study

In this work, the geometric and electronic properties of the adsorption of volatile organic molecules (VOCs) such as CH2O, C2H4O, C2H6O on bismuthene monolayer with transition metal (TM = Nb, Zr) atoms adsorbed are investigated by using first–principles methods, aiming to explore the potential applications of TM–modified bismuthene monolayer in the field of organic molecular gas sensors. In contrast to the adsorption of organic molecules on Zr–bismuthene, Nb–bismuthene appears the chemisorption with multiple organic molecules, and it can be found that Nb–bismuthene could stably adsorb target molecules and exhibit outstanding charge transfer. The longer desorption time of organic molecules on Nb–bismuthene and the higher organic molecular adsorption capacity of the substrate at most temperatures, which suggests that Nb–bismuthene is suitable as a disposable sorbent for organic molecules, providing a viable direction for the application of Nb–bismuthene monolayer as a sensitive material for the removal of organic molecules.

Materials Enabling Methane and Toluene Gas Treatment.

This paper summarizes the latest research results on materials for the treatment of methane, an important greenhouse gas, and toluene, a volatile organic compound gas, as well as the utilization of these resources over the past two years. These materials include adsorption materials, catalytic oxidation materials, hydrogen-reforming catalytic materials and non-oxidative coupling catalytic materials for methane, and adsorption materials, catalytic oxidation materials, chemical cycle reforming catalytic materials, and degradation catalytic materials for toluene. This paper provides a comprehensive review of these research results from a general point of view and provides an outlook on the treatment of these two gases and materials for resource utilization.

Effects of explosion suppressants on the dust explosion and pyrolysis characteristics of the fungicide fenaminstrobin

In this study, the explosion and pyrolysis characteristics of fungicide fenaminstrobin dust were studied, and the inhibitory effects of three explosion suppressants, namely, NH4H2PO4, KH2PO4, and KCl, on dust explosion were compared. A combined thermogravimetric (TG)–Fourier transform infrared (FTIR)–mass spectrometry (MS) technique was adopted to analyze the inhibition mechanism. The results showed that the minimum ignition energy (MIE) was 5 mJ, the explosion index (Kst) was 305.7 bar m/s, and the dust explosion hazard was severe. We found that all three compounds (NH4H2PO4, KH2PO4, and KCl) could be used as explosion suppressants. When the addition dose of NH4H2PO4 was 35%, the Kst value dropped by 40.7%, and MIE exceeded 1000 mJ. When the addition of KH2PO4 was 50%, the Kst value dropped by 37.3%, and the MIE increased to 300 mJ. In comparison, NH4H2PO4 showed the best inhibitory effect, while KCl demonstrated the worst inhibitory effect. The pyrolysis of fenaminstrobin produced organic gases, including quinoline, benzonitrile, and methyl isocyanate, and generated large quantities of free radicals. The explosion suppressants could inhibit the explosion through physical pathways (endothermic, coating, and oxygen-diluting processes) and chemical pathways (free-radical capture).

Machine learning - based shale wettability prediction: Implications for H2, CH4 and CO2 geo-storage

Shale wettability determines shale gas productivities and gas (H2, CH4 and CO2) geo-storage efficiencies. However, shale wettability is a complex parameter which depends on multiple influencing factors, thus very time-consuming and costly to measure experimentally. Herein, we combined the eXtreme gradient boosting (XGBoost) and Shapley additive explanation (SHAP) machine learning methods to accurately predict brine advancing (θA) and receding (θR) contact angles and estimate shale wettability. The XGBoost model demonstrated much higher prediction accuracies than the commonly-used multiple linear regression and partial least squares regression models, e.g., R2 was 0.946–0.999, 0.794–0.821, and 0.635–0.674, respectively for these three models. The SHAP sensitivity analyses showed that total organic carbon content and gas molecular weight (MG) were the two most significant factors influencing shale wettability. In addition, shale hydrophobicity positively correlated with MG, calcite content, pressure and brine ionic strength, while negatively correlated with temperature and quartz content. This work provides an efficient approach for shale wettability estimation, thus aiding in the implementation of improved gas recovery and gas geo-storage processes, to further guarantee energy security and mitigate climate change.