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This project investigated passive adsorbent sampling of light (C2-C5) hydrocarbons which are the sensitive tracers of fugitive emissions from oil and natural gas (ON under the worst case relative humidity level of 95% RH, VOCs uptake rates dropped to 27-39% of those in dry air. This effect potentially causes results to be biased low when cartridges are deployed at high RH, including overnight when RH is often elevated over daytime levels. Nonetheless, representative sampling results were obtained under ambient conditions during three field studies where cartridges were evaluated alongside whole air sample collection in canisters. Agreement varied by compound: Ethane and alkenes correlated poorly and could not be analyzed with satisfactory results; results for C3-C5 alkanes were much better: i-butane correlated with R2 > 0.5, and propane, n-butane, i-pentane, and n-pentane with R2 > 0.75, which demonstrates the feasibility of the passive sampling of these latter O&NG tracers.

The preparation, characterization and application of hydroxyapatite silica propyl bis aminoethoxy ethane cuprous complex (HASPBAEECC) as a novel hybrid nano-catalyst for synthesis of new benzimidazole-1,2,3-triazole hybrid analogues as promising antifungal agents have been described. HASPBAEECC is fully characterized by different microscopic, spectroscopic and physical techniques, including scanning electron microscopy (SEM), transmission, X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TGA) and FT-IR. The 'Click̕ Huisgen cycloaddition reaction of N-propargyl benzimidazole with diverse azidoalkyls in a THF-water media at ambient temperature provides the products in good-to-excellent yields using HASPBAEECC. HASPBAEECC is proved to be a stable, low cost, reusable and environmentally benign nanohybrid catalyst. The target compounds were screened against some pathogenic fungal comprising Candida albicans, Candida krusei, Candida parapsilosis, Aspergillus fumigatus and Aspergillus flavus in which it was determined that compounds 11f and 11 h have displayed promising antifungal activity similar to fluconazole as a reference drug. HASPBAEECC is a novel hybrid nano-catalyst for highly efficient synthesis of new benzimidazole-1,2,3- triazole hybrid analogues as antifungal agents.

Previous studies demonstrated that methane can be used as an electron donor to microbially remove various oxidized contaminants in groundwater. Natural gas, which is more widely available and less expensive than purified methane, is potentially an alternative source of methane. However, natural gas commonly contains a considerable amount of ethane (C2H6) and propane (C3H8), in addition to methane. It is important that these gaseous alkanes are also utilized along with methane to avoid emissions. Here, we demonstrate that perchlorate (ClO4-), a frequently reported contaminant in groundwater, can be microbially reduced to chloride (Cl-) driven by C2H6 or C3H8 under oxygen-limiting conditions. Two independent membrane biofilm reactors (MBfRs) supplied with C2H6 and C3H8, respectively, were operated in parallel to biologically reduce ClO4-. The continuous ClO4- removal during long-term MBfR operation combined with the concurrent C2H6/C3H8 consumption and ClO4- reduction in batch tests confirms that ClO4- reduction was associated with C2H6 or C3H8 oxidation. Polyhydroxyalkanoates (PHAs) were synthesized in the presence of C2H6 or C3H8 and were subsequently utilized for supporting ClO4- bio-reduction in the absence of gaseous alkanes. Analysis by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) showed that transcript abundance of bmoX (encoding alpha hydroxylase subunit of C2H6/C3H8 monooxygenase) was positively correlated to the consumption rates of C2H6/C3H8, while pcrA (encoding a catalytic subunit of perchlorate reductase) was positively correlated to the consumption of ClO4-. High-throughput sequencing targeting 16S rRNA, bmoX, and pcrA indicated that Mycobacterium was the dominant microorganism oxidizing C2H6/C3H8, while Dechloromonas may be the major perchlorate-reducing bacterium in the biofilms. These findings shed light on microbial ClO4- reduction driven by C2H6 and C3H8, facilitating the development of cost-effective strategies for ex situ groundwater remediation.

Abiotic transformation of trichloroethene (TCE) in fractured porous rock such as sandstone is challenging to characterize and quantify. The objective of this study was to estimate the pseudo first-order abiotic reaction rate coefficients in diffusion-dominated intact core microcosms. The microcosms imitated clean flow through a fracture next to a contaminated rock matrix by exchanging uncontaminated groundwater, unamended or lactate-amended, in a chamber above a TCE-infused sandstone core. Rate coefficients were assessed using a numerical model of the microcosms that were calibrated to monitoring data. Average initial rate coefficients for complete dechlorination of TCE to acetylene, ethene, and ethane were estimated as 0.019 y-1 in unamended microcosms and 0.024 y-1 in lactate-amended microcosms. Moderately higher values (0.026 y-1 for unamended and 0.035 y-1 for lactate-amended) were obtained based on 13C enrichment data. Abiotic transformation rate coefficients based on gas formation were decreased in unamended microcosms after ∼25 days, to an average of 0.0008 y-1. This was presumably due to depletion of reductive capacity (average values of 0.12 ± 0.10 μeeq/g iron and 18 ± 15 μeeq/g extractable iron). Model-derived rate coefficients and reductive capacities for the intact core microcosms aligned well with results from a previous microcosm study using crushed sandstone from the same site.

[EN] A comparative study of the catalytic properties for the oxidation of C2-C3 alkanes and olefins has been carried out over unpromoted and M-promoted NiO catalysts (Me¿=¿K, La, Ce, al, Zr, Sn, Nb). The catalysts have been characterized by several physico-chemical techniques (UV Raman, Visible Raman, FTIR of adsorbed CO and XPS). The characteristics of promoter elements are of paramount importance, since they are able to modify both the nature of the active nickel and the concentration of electrophilic O2¿/O¿ oxygen species. Thus, a relatively high acidity and valence of the promoter oxide (with oxidation state higher than¿+¿3) are necessary to achieve high selectivity to olefins during the oxidative dehydrogenation (ODH) of C2¿C3 alkanes. In addition, an inverse correlation between the selectivity to the corresponding olefin and the concentration of electrophilic oxygen species has been observed, although the selectivity to propene during propane ODH is lower than the selectivity to ethylene achieved during ethane ODH. On the other hand, a very low influence of alkane conversion on the selectivity to the corresponding olefins is observed. This behaviour can be explained by considering that the reaction rate for olefin combustion is lower than the reaction rate for alkane oxidation. However, the comparative study of the oxidation of alkanes and olefins suggest that the differences observed between the ODH of propane and ethane are not related to the reactivity of olefins, but to the different number and reactivity of C¿H bonds in both alkanes. A discussion on the importance of the concentration of active sites and the characteristics of the alkanes fed on the selectivity to olefin during the alkane ODH is also presented., The authors would like to acknowledge the Ministerio de Ciencia, Innovacion y Universidades of Spain (RTl2018-099668-B-C21 and MAT2017-84118-C2-1-R projects) and FEDER. Authors from ITQ also thank Project SEV-2016-0683 for supporting this research. D.D. thanks MINECO and Severo Ochoa Excellence Program for his fellowship (SVP-2014-068669).

A comprehensive experimental and kinetic modeling study of the ignition delay time (IDT) characteristics of some binary blends of C1–C2 gaseous hydrocarbons such as methane/ethylene, methane/ethane, and ethane/ethylene was performed over a wide range of composition (90/10, 70/30, 50/50%), temperature (∼800–2000 K), pressure (∼1–40 bar), equivalence ratio (∼0.5–2.0), and dilution (∼75–90%). An extensive literature review was conducted, and available data were extracted to create a comprehensive database for our simulations. Based on the existing literature data, an experimental matrix was designed using the Taguchi approach (L9) in order to identify and complete the experimental matrix required to generate a comprehensive experimental IDT set necessary for the validation of a chemical kinetic model. The required high- and low-temperature IDTs were collected using low-/high-pressure shock tubes and rapid compression machines, respectively. The predictions of NUIGMech1.0 are examined versus all of the available experimental data, including those taken in the current study using the IDT simulations and a correlation technique. Moreover, the individual effect of the studied parameters, including mixture composition, pressure, equivalence ratio, and dilution on IDT, is investigated over the studied temperature range. Correlations that were developed based on NUIGMech1.0 are presented for each specific blended fuel over the conditions studied. These correlations show an acceptable performance versus the experimental data. The authors would like to express their gratitude to Shell Research Ltd. and Science Foundation Ireland (SFI) for funding via project numbers 15/IA/3177 and 16/SP/3829. The authors from PCFC, RWTH Aachen University, would like to recognize the funding support from the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG) through the project number – 322460823 (HE7599/2-1). peer-reviewed 2021-06-03

Shipboard measurements of offshore oil and gas facilities were conducted in the Gulf of Mexico in February 2018. Species measured at 1 s include methane, ethane, carbon-13 (13C) and deuterium (D) i...

Combustion and flame 234, 111626 (2021). doi:10.1016/j.combustflame.2021.111626, Published by Elsevier Science, Amsterdam [u.a.]

9 figures, 2 tables., In the present work, a simple soft chemistry method was employed to prepare cobalt mixed oxide (Co3O4) materials, which have shown remarkably high activity in the heterogeneously catalyzed total oxidation of low reactive VOCs such as the light alkanes propane, ethane, and methane. The optimal heat-treatment temperature of the catalysts was shown to depend on the reactivity of the alkane studied. The catalytic activity of the Co3O4 catalysts was found to be as high as that of the most effective catalysts based on noble metals. The physicochemical properties, from either the bulk (using XRD, TPR, TPD-O2, and TEM) or the surface (using XPS), of the catalysts were investigated to correlate the properties with the catalytic performance in the total oxidation of VOCs. The presence of S1 low-coordinated oxygen species at the near surface of the Co3O4-based catalysts appeared to be linked with the higher reducibility of the catalysts and, consequently, with the higher catalytic activity, not only per mass of catalyst but also per surface area (enhanced areal rate). The co-presence of propane and methane in the feed at low reaction temperatures did not negatively affect the propane reactivity. However, the co-presence of propane and methane in the feed at higher reaction temperatures negatively affected the methane reactivity., This research was funded by MINECO-Spain, grant number PRE2018-085211. This work was also funded by the MAT2017-84118-C2-1-R MCIN/AEI/10.13039/501100011033/ project and FEDER Una manera de hacer Europa. Comunidad de Madrid, grant number 2017-T1/IND-6025, within the program “Atracción y Retención de Talento Investigador” of the V PRICIT.

Adsorption of fluids in nanoporous materials is important for several applications including gas storage and catalysis. The pore network in natural, as well as engineered, materials can exhibit different degrees of connectivity between pores. While this might have important implications for the sorption of fluids, the effects of pore connectivity are seldom addressed in the studies of fluid sorption. We have carried out Monte Carlo simulations of the sorption of ethane and CO2 in silicalite, a nanoporous material characterized by sub-nanometer pores of different geometries (straight and zigzag channel like pores), with varied degrees of pore connectivity. The variation in pore connectivity is achieved by selectively blocking some pores by loading them with methane molecules that are treated as a part of the rigid nanoporous matrix in the simulations. Normalized to the pore space available for adsorption, the magnitude of sorption increases with a decrease in pore connectivity. The increased adsorption in the systems where pore connections are removed by blocking them is because of additional, albeit weaker, adsorption sites provided by the blocker molecules. By selectively blocking all straight or zigzag channels, we find differences in the absorption behavior of guest molecules in these channels.

International audience; In this paper, we report the first grand canonical Monte Carlo simulation study aiming at characterizing the competitive trapping of CH4 and C2H6 molecules into clathrate hydrates under temperature conditions typical of those encountered at the surface of Titan. Various compositions of the fluid in contact with the clathrate phase have been considered in the simulations, including pure methane, pure ethane, and mixed fluids made of various methane/ethane ratios. The trapping isotherms obtained from the simulations clearly show that ethane molecules can be enclathrated at lower pressures than methane molecules. In addition, they provide evidence that the methane molecules can occupy both small and large cages of the clathrate lattice, whereas the ethane molecules have a strong preference for the large cages, in accordance with experimental conclusions. However, increasing the pressure may also lead to the trapping of ethane in the small cages of the clathrates, leading to a possible competition between methane and ethane molecules for these small cages at high pressure, if both molecules are concomitantly present in the fluid phase. The abovementioned features could strongly influence the composition of a mixed methane/ethane fluid phase in contact with the clathrate phase, which might thus be first impoverished in ethane before methane starts getting trapped into the clathrate. However, this conclusion strongly depends on the clathrate structure considered in the simulations.

International audience; Production of coal and natural gas is responsible for one third of anthropogenic methane (CH4) emissions in the United States. Here we examine CH4 emissions from coal and natural gas production in southwestern Pennsylvania. Using a top-down methodology combining measurements of CH4 and ethane, we conclude that while Environmental Protection Agency inventories appear to report emissions from coal accurately, emissions from unconventional natural gas are underreported in the region by a factor of 5 (±3). However, production-scaled CH4 emissions from unconventional gas production in the Marcellus remain small compared to other basins due to its large production per well. After normalizing emissions by energy produced, total greenhouse gas emissions from Pennsylvania unconventional natural gas production produce half the carbon footprint compared to regionally produced coal, with carbon dioxide emissions from combustion being the dominant source of greenhouse gas emissions for both sources.

Spatially resolved emission inventories were used with an atmospheric dispersion model to predict ambient concentrations of methane, ethane, and propane in the Eagle Ford oil and gas production region in south central Texas; predicted concentrations were compared to ground level observations. Using a base case inventory, predicted median propane/ethane concentration ratios were 106% higher (95% CI: 83% higher-226% higher) than observations, while median ethane/methane concentration ratios were 112% higher (95% CI: 17% higher-228% higher) than observations. Predicted median propane and ethane concentrations were factors of 6.9 (95% CI: 3-15.2) and 3.4 (95% CI: 1.4-9) larger than observations, respectively. Predicted median methane concentrations were 7% higher (95% CI: 39% lower-37% higher) than observations. These comparisons indicate that sources of emissions with high propane/ethane ratios (condensate tank flashing) were likely overestimated in the inventories. Because sources of propane and ethane emissions are also sources of methane emissions, the results also suggest that sources of emissions with low ethane/methane ratios (midstream sources) were underestimated. This analysis demonstrates the value of using multiple light alkanes in attributing sources of methane emissions and evaluating the performance of methane emission inventories for oil and natural gas production regions.

Hydrocarbon detection in the gas phase represents a powerful tool to guide oil exploration and production operations for the oil & gas industry. This application requires highly sensitive, selective and robust spectroscopic techniques. In this work, a quartz-enhanced photoacoustic sensor system designed to detect methane (C1), ethane (C2) and propane (C3), employing a single interband cascade laser emitting in the spectral range 3.342–3.349 μm, is reported. Detection levels in the part-per billion concentration range for C1 and C2 and a few parts per million for C3 were achieved. Measurements at both low and atmospheric pressures were carried out for mixtures simulating typical downhole hydrocarbon concentrations.

Termination process of Si(100)-2 × 1 as well as Ge(100)-2 × 1 reconstructed surfaces have been explored comprehensively through the dehydrogenation of ethane and ammonia-borane and their several analogues by employing density functional theory (DFT). From our study, it is evident that the termination of Si-surface via the dehydrogenation of aforementioned ethane and NH3BH3 derivatives is more feasible compared to Ge-surface. For ethane, the investigation shows that the substitution of non-participating hydrogens with +I group (electron donating) causes an enhancement in the kinetic and thermodynamic feasibility of the termination process, whereas the implementation of -I substituent (electron withdrawing) makes an adverse effect. While exploring the termination of Si- as well as Ge-surfaces through the dehydrogenation of NH3BH3 and its derivatives, it is noticed that from both the kinetic as well as thermodynamic perspectives, the termination processes are more feasible than that of ethane and its derivatives. We have further examined the detailed mechanism of each termination process by analyzing the geometrical parameters and NPA charges. From bonding evaluation, it is evident that the hydrogen abstraction from ethane by both the surfaces is symmetric in nature, where both the hydrogens show slightly positive charge. But for NH3BH3 the hydrogen abstraction process becomes asymmetric, where the boron associated hydrogen is abstracted as hydride by the electrophilic surface Si (Ge) and the hydrogen bonded with the N-centre is abstracted as proton by the nucleophilic surface Si (Ge). Overall, the present theoretical work reveals one of the efficient chemical processes for terminating Si as well as Ge(100)-2 × 1 reconstructed surfaces through the formation of non-polar Si H bonds.

This study compares the aerobic and anaerobic transformation of ethanol using FeVO4 and V2O5 catalysts. Despite their different structure, the two oxides showed very similar catalytic performances and their main product was acetaldehyde. However, in the absence of oxygen, the catalysts produced an equimolar amount of ethane and acetaldehyde, and this aspect has been little studied in the literature. In-situ XPS and DRIFT spectroscopy studies showed that the active species for the disproportionation of the alcohol into ethane and aldehyde was the reduced V3+ ion; nevertheless, the Fe in the FeVO4 catalysts was responsible for directing the reduction of metals toward the formation of a Fe-V-O spinel phase which was homogeneous and more stable than V2O5. Moreover, an in-situ DRIFT spectroscopy study showed that ethanol adsorbs in different ways on the surface of the catalysts during the reduction of samples (anaerobic reaction), forming H-bonded and dissociated ethoxy species, and giving rise to new surface OH groups that participate in the aldehyde/alkane formation. To conclude, a new mechanism of hydrogen transfer for the anaerobic ethanol disproportionation into ethane and acetaldehyde is proposed. This research completes the picture about ethanol oxidation to acetaldehyde on V-based catalysts, demonstrating that the catalytic behavior is mainly affected by the oxidation degree of the vanadium species which, in turn, depends on the reaction environment, and not on the structure itself.

Chromium oxide supported on mesoporous organo-silica (MOS) was synthesized with different Cr loading by an incipient method. The catalytic performance of a Cr(x)/MOS catalyst for CO2-based ethane dehydrogenation was investigated. The synthesized catalysts were characterized by XRD, BET, TEM, SEM, XPS, FTIR, and UV–Vis DR measurements. The textural properties of the prepared samples showed that the mesoporous nature of MOS sample was not disturbed by chromium impregnation. Among the prepared samples, Cr(8)/MOS catalyst exhibited good distribution of chromium species along with superior concentration of Cr6+ and the highest recorded Cr6+/Cr3+ ratio. The results revealed that the superior catalytic performance was reached at Cr(8)/MOS, with 50.4% and 90.1% of ethane conversion and ethylene selectivity, respectively. The catalytic activity decreased slowly over reaction time, it declined approximately 22% after 10 h of stream operation. The roles of CO2-based ethane dehydrogenation were also studied, where carbon dioxide can be a source of lattice oxygen and as a hydrogen consumer in reverse water–gas shift (RWGS) reaction. The effect of various catalytic factors, such as catalytic temperature, reaction time, space gas velocity, and CO2 partial pressure on the conversion of ethane, yield, and selectivity to ethylene, were investigated as well.

International audience; Hydrocarbons such as methane and ethane are present in many solar system objects, including comets, moons and planets. The interaction of these hydrocarbons with water ice at low temperatures could lead to the formation of inclusion compounds, such as clathrate hydrates (water based host cages trapping hydrocarbons guest molecules), modifying their retention, stability and therefore evolution. The occurrence of =clathrate hydrates on solar system surfaces could be established by remote sensing of their spectroscopic signatures. In this study, we measure and analyse ethane clathrate hydrate spectra recorded in the temperature range from 5.3 to 160K, covering most of the temperature range of interest for solar system objects. Specific infrared band signatures are identified for the ethane encaged guest. We provide evidence that ethane clathrate hydrate outcrops can be detected by remote sensing on the surface of planetary bodies.

Combustion and flame 228, 401-414 (2021). doi:10.1016/j.combustflame.2021.02.009, Published by Elsevier Science, Amsterdam [u.a.]

An unprecedented amount of fungal and fungal-like infections has recently brought about some of the most severe die-offs and extinctions due to fungal drug resistance. Aimed to alleviate the situation, new effort was made to develop novel purinylthiazolylethanone derivatives, which were expected to combat the fungal drug resistance. Some prepared purinylthiazolylethanone derivatives possessed satisfactory inhibitory action towards the tested fungi, among which compound 8c gave a MIC value of 1 μg/mL against C. albicans. The active molecule 8c was able to kill C. albicans with undetectable resistance as well as low hematotoxicity and cytotoxicity. Furthermore, it could hinder the growth of C. albicans biofilm, thus avoiding the occurrence of drug resistance. Mechanism research manifested that purinylthiazolylethanone derivative 8c led to damage of cell wall and membrane disruption, so protein leakage and the cytoplasmic membrane depolarization were observed. On this account, the activity of fungal lactate dehydrogenase was reduced and metabolism was impeded. Meanwhile, the increased levels of reactive oxygen species (ROS) and reactive nitrogen species (RNS) disordered redox equilibrium, giving rise to oxidative damage to fungal cells and fungicidal effect.

Atmospheric emissions from oil and gas production operations are composed of multiple hydrocarbons and can have large variations in composition. Accurate estimates of emission compositions are needed to estimate the fate and impacts of emissions and to attribute emissions to sources. This work presents a database, constructed with empirical data and thermodynamic models, that can be queried to estimate hydrocarbon compositions from emission sources present at oil and gas production sites. The database can be searched for matches using between two and seven well parameters as query inputs (gas-to-oil ratio, API gravity, separator pressure, separator temperature, methane molar fraction in produced gas, ethane molar fraction of produced gas, and propane molar fraction in produced gas). Database query performance was characterized by comparing returns from database queries to a test data set. Application of the database to well parameters for tens of thousands of wells in the Barnett, Eagle Ford, and Fayetteville production regions demonstrates variations in emission compositions. Ethane to methane ratio varies by more than an order of magnitude from well to well and source to source. VOC to methane ratios are comparable in variability to ethane to methane ratios for most emission sources, but have a higher variability for emissions from flashing of liquid hydrocarbon tanks.

C2/C1 hydrocarbon separation is an important industrial process that relies on energy-intensive cryogenic distillation methods. The use of porous adsorbents to selectively separate these gases is a viable alternative. Highly stable covalent triazine frameworks (urea-CTFs) have been synthesized using 1,3-bis(4-cyanophenyl)urea. Urea-CTFs exhibited gas uptakes of C2H2 (3.86 mmol/g) and C2H4 (2.92 mmol/g) at 273 K and 1 bar and is selective over CH4. Breakthrough simulations show the potential of urea-CTFs for C2/C1 separation.

The direct, one-pot oxidation of ethane to acetic acid was, for the first time, performed using a C-scorpionate complex anchored onto a magnetic core-shell support, the Fe3O4/TiO2/[FeCl2{&kappa, 3-HC(pz)3}] composite. This catalytic system, where the magnetic catalyst is easily recovered and reused, is highly selective to the acetic acid synthesis. The performed green metrics calculations highlight the &ldquo, greeness&rdquo, of the new ethane oxidation procedure.

We report on a fiber-coupled, quartz-enhanced photoacoustic spectroscopy (QEPAS) near-IR sensor for sequential detection of methane (CH4 or C1) and ethane (C2H6 or C2) in air. With the aim of developing a lightweight, compact, low-power-consumption sensor suitable for unmanned aerial vehicles (UAVs)-empowered environmental monitoring, an all-fiber configuration was designed and realized. Two laser diodes emitting at 1653.7 nm and 1684 nm for CH4 and C2H6 detection, respectively, were fiber-combined and fiber-coupled to the collimator port of the acoustic detection module. No cross talk between methane and ethane QEPAS signal was observed, and the related peak signals were well resolved. The QEPAS sensor was calibrated using gas samples generated from certified concentrations of 1% CH4 in N2 and 1% C2H6 in N2. At a lock-in integration time of 100 ms, minimum detection limits of 0.76 ppm and 34 ppm for methane and ethane were achieved, respectively. The relaxation rate of CH4 in standard air has been investigated considering the effects of H2O, N2 and O2 molecules. No influence on the CH4 QEPAS signal is expected when the water vapor concentration level present in air varies in the range 0.6&ndash, 3%.

Author(s): Nicewonger, MR; Aydin, M; Prather, MJ; Saltzman, ES | Abstract: Biomass burning is an important component of the Earth system in terms of global biogeochemistry, atmospheric composition, climate, terrestrial ecology, and land use. This study examines published ice core trace gas measurements of acetylene, ethane, and methane, which have been used as proxies for paleofire emissions. We investigate the consistency of these records for the past 1,000nyears in terms of (1) temporal trends in global fire emissions and (2) quantitative estimates for changes in global burning (dry matter burned per year). Three-dimensional transport and box models were used to construct emissions scenarios for the trace gases consistent with each ice core record. Burning histories were inferred from trace gas emissions by accounting for biome-specific emission factors for each trace gas. The temporal trends in fire inferred from the trace gases are in reasonable agreement, with a large decline in biomass burning emissions from the Medieval Period (MP: 1000–1500nCE) to the Little Ice Age (LIA: 1650–1750nCE). However, the three trace gas ice core records do not yield a consistent fire history, even assuming dramatic (and unrealistic) changes in the spatial distribution of fire and biomes. Substantial changes in other factors such as meteorological transport or atmospheric photochemical lifetimes appear to be required to reconcile the trace gas records.

We reported the characteristics of hydrate-bound hydrocarbons in lake-bottom sediments at the Kedr mud volcano in Lake Baikal. Twenty hydrate-bearing sediment cores were retrieved, and methane-stable isotopes of hydrate-bound gases (δ13C and δ2H of − 47.8‰ to − 44.0‰ V-PDB and − 280.5‰ to − 272.8‰ V-SMOW, respectively) indicated their thermogenic origin accompanied with secondary microbial methane. Powder X-ray diffraction patterns of the crystals and molecular composition of the hydrate-bound gases suggested that structure II crystals showed a high concentration of ethane (around 14% of hydrate-bound hydrocarbons), whereas structure I crystals showed a relatively low concentration of ethane (2–5% of hydrate-bound hydrocarbons). These different crystallographic structures comprised complicated layers in the sub-lacustrine sediment, suggesting that the gas hydrates partly dissociate, concentrate ethane and form structure II crystals. We concluded that a high concentration of thermogenic ethane primarily controls the crystallographic structure of gas hydrates and that propane, iso-butane (2-methylpropane) and neopentane (2,2-dimethylpropane) are encaged into crystals in the re-crystallisation process.

Understanding the mechanisms controlling the redox transformation of organic contaminants mediated by biochar is of great significance for application of biochar in remediation of contaminated soils and sediments. Here we investigated the mediation effect of a pine wood-derived biochar (P-char) in comparison with multiwalled carbon nanotubes (MCNTs) and graphite on the reductive dechlorination of hexachloroethane by sulfide. Upon normalization of the mediator's surface area, the reduction rate of hexachloroethane follows an order of P-char < MCNTs < graphite. Aqueous polysulfides and polysulfide free radicals were readily produced by reacting sulfide only with P-char, and the supernatant separated from the reaction system could account for 83.4% of the pseudo-kinetic rate constant of hexachloroethane mediated by P-char. In contrast, MCNTs and graphite had weak abilities to produce reactive sulfur species, and the supernatant exhibited very low reduction capability (

Emissions of C 2 -C 5 alkanes from the U.S. oil and gas sector have changed rapidly over the last decade. We use a nested GEOS-Chem simulation driven by updated 2011NEI emissions with aircraft, surface, and column observations to (1) examine spatial patterns in the emissions and observed atmospheric abundances of C 2 -C 5 alkanes over the United States and (2) estimate the contribution of emissions from the U.S. oil and gas industry to these patterns. The oil and gas sector in the updated 2011NEI contributes over 80% of the total U.S. emissions of ethane (C 2 H 6 ) and propane (C 3 H 8 ), and emissions of these species are largest in the central United States. Observed mixing ratios of C 2 -C 5 alkanes show enhancements over the central United States below 2 km. A nested GEOS-Chem simulation underpredicts observed C 3 H 8 mixing ratios in the boundary layer over several U.S. regions, and the relative underprediction is not consistent, suggesting C 3 H 8 emissions should receive more attention moving forward. Our decision to consider only C 4 -C 5 alkane emissions as a single lumped species produces a geographic distribution similar to observations. Due to the increasing importance of oil and gas emissions in the United States, we recommend continued support of existing long-term measurements of C 2 -C 5 alkanes. We suggest additional monitoring of C 2 -C 5 alkanes downwind of northeastern Colorado, Wyoming, and western North Dakota to capture changes in these regions. The atmospheric chemistry modeling community should also evaluate whether chemical mechanisms that lump larger alkanes are sufficient to understand air quality issues in regions with large emissions of these species., SCOPUS: ar.j, info:eu-repo/semantics/published

We reported experimental measurements of the diffusion coefficient of methane at effectively infinite dilution in methylbenzene and in heptane at temperatures ranging from (323 to 398) K and at pressures up to 65 MPa. The Taylor dispersion method was used and the overall combined standard relative uncertainty was 2.3%. The experimental diffusion coefficients were correlated with a simple empirical model as well as the Stokes–Einstein model with the effective hydrodynamic radius of methane depending linearly upon the solvent density. The new data address key gaps in the literature and may facilitate the development of an improved predictive model for the diffusion coefficients of dilute gaseous solutes in hydrocarbon liquids.

A comprehensive experimental and modeling study of the ignition delay time (IDT) characteristics of some single prominent C1–C2 hydrocarbons including methane, ethane, and ethylene has been performed over a wide range of temperatures (∼800–2000 K), pressures (∼1–80 bar), equivalence ratios (∼0.5–2.0), and dilutions (∼75–90%). An extensive literature review was conducted, and available data were extracted to create a comprehensive database used in our simulations. Based on existing literature data, an experimental matrix was designed using the Taguchi approach (L9) in order to identify and complete the experimental matrix required to generate a comprehensive validation set necessary for validation of a chemical kinetic model. The required IDTs were recorded using a high-pressure shock tube for shorter IDTs and a rapid compression machine for longer times, which encompass high- and low-temperature ranges, respectively. The predictions of a C3-NUIG mechanism have been compared with all of the available experimental data including those from the current study using the IDT simulations and the correlation technique. Moreover, individual and total effects of the studied parameters including pressure, equivalence ratio, and dilutions on IDT have been studied over a wide temperature range. Moreover, correlations which were developed based on the NUIG mechanism are presented for each specific fuel over the conditions studied. These correlations show acceptable performance versus the experimental Taguchi matrix data. The authors would like to express their gratitude to Shell Research Ltd and Science Foundation Ireland (SFI) via their Research Centre Program through project number 16/SP/3829. The authors from PCFC, RWTH Aachen University would like to recognize the funding support from the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG) through the Project Number 322460823 (HE7599/2-1). peer-reviewed 2021-02-03

Olefins are among the most important structural building blocks for a plethora of chemical reaction products, including petrochemicals, biomaterials and pharmaceuticals. An ever-increasing economic demand has urged scientists, engineers and industry to develop novel technical methods for the dehydrogenation of parent alkane molecules. In particular, the catalysis over precious metal or metal oxide catalysts has been put forward as an alternative way route to thermal-, steam- and fluid catalytic cracking (FCC). Multiscale system modeling as a tool to theoretically understand processes has in the past decade period evolved from a rudimentary measurement-complementing approach to a useful engineering environment. Not only can it predict various experimentally obtained parameters, such as conversion, activity, and selectivity, but it can help us to simulate trends, when changing applicative operating conditions, such as surface gas temperature or pressure, or even support us in the search for the type of materials, their geometrical properties and phases for a better functional performance. An overview of the current set state of the art for saturated organic short chain hydrocarbons (ethane, propane and butane) is presented. Studies that combine at least two different dimensional scales, ranging from atomistic-, bridging across mechanistic mesoscale kinetics, towards reactor- or macroscale, are focused on. Insights considering reactivity are compared.

Volcanic areas emit a number of gases including methane and other short chain alkanes, that may serve as energy source for the prevailing microorganisms. The verrucomicrobial methanotroph Methylacidiphilum fumariolicum SolV was isolated from a volcanic mud pot, and is able to grow under thermoacidophilic conditions on different gaseous substrates. Its genome contains three operons encoding a particulate methane monooxygenase (pMMO), the enzyme that converts methane to methanol. The expression of two of these pmo operons is subjected to oxygen-dependent regulation, whereas the expression of the third copy (pmoCAB3) has, so far, never been reported. In this study we investigated the ability of strain SolV to utilize short-chain alkanes and monitored the expression of the pmo operons under different conditions. In batch cultures and in carbon-limited continuous cultures, strain SolV was able to oxidize and grow on C1–C3 compounds. Oxidation of ethane did occur simultaneously with methane, while propane consumption only started once methane and ethane became limited. Butane oxidation was not observed. Transcriptome data showed that pmoCAB1 and pmoCAB3 were induced in the absence of methane and the expression of pmoCAB3 increased upon propane addition. Together the results of our study unprecedently show that a pMMO-containing methanotroph is able to co-metabolize other gaseous hydrocarbons, beside methane. Moreover, it expands the substrate spectrum of verrucomicrobial methanotrophs, supporting their high metabolic flexibility and adaptation to the harsh and dynamic conditions in volcanic ecosystems.

Quartz-enhanced photoacoustic spectroscopy represents a valuable candidate for natural gas analysis in the oil & gas field. The core element of this spectroscopy technique is a quartz tuning forks, employed as high quality-factor optoacoustic transducers, capable of operating in a wide range of temperatures and pressures. The robustness and compactness of these sensors, together with the possibility to avoid the use of optical detectors, open the way to the development of a new generation of small-sized gas spectrometers to be potentially employed downhole for source rock characterization and estimation of oil & gas properties. We report here on the realization of a shoe-box sized quartz-enhanced photoacoustic spectroscopy system capable of: i) selective detection of methane and ethane in the parts-per-billion range, and propane in the parts-per-million range, by employing a single interband cascade laser emitting at 3.345 µm; ii) selective detection of 12CH4 and 13CH4 isotopes at the parts-per-billion sensitivity level by employing a quantum cascade laser operating around 7.73 µm.

Lipase stability in organic solvent is crucial for its application in many biotechnological processes as biocatalyst. One way to improve lipase’s activity and stability in unusual reaction medium is its immobilization on inert supports. Here, lipases from different sources and immobilized through weak chemical interactions on hydrophobic and ionic supports had their transesterification ability dramatically dependent on the support and also on the solvent that had been used. The ethanolysis of sardine oil was carried out at the presence of cyclohexane and tert-amyl alcohol, in which Duolite A568-Thermomyces lanuginosa lipase derivative achieved 49% of ethyl esters production after 24 h in cyclohexane. The selectivity of immobilized lipases was also studied and, after 3 h of synthesis, the reaction with Duolite A568-Thermomyces lanuginosa derivative in cyclohexane produced 24% ethyl ester of eicosapentaenoic acid and 1.2% ethyl ester of docosahexaenoic acid, displaying a selectivity index of 20 times the ethyl ester of eicosapentaenoic acid. Different derivatives of Candida antarctica lipases fraction B (CALB) and phospholipase Lecitase® Ultra (Lecitase) were also investigated. Along these lines, a combination between these factors may be applied to improve the activity and selectivity of immobilized lipases, decreasing the total cost of the process., The authors thank the financial support from the São Paulo Research Foundation (FAPESP – grants 2012/09054-3 and 2013/00530-0), and the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior—Brasil (CAPES – grant number 3894/13-4).

[EN] The investigation here presented studies the effect of the synthesis temperature (from 80 to 110 degrees C) and the time (from 1 to 4 days) employed to precipitate catalyst precursors by reflux method, on the physic-chemical and the catalytic properties of the resulting Mo-V-Te-Nb mixed oxide catalysts for both propane partial oxidation into acrylic acid and ethane oxidative dehydrogenation (ODH) to ethylene. The insight obtained has allowed an important optimization of the not commonly used reflux method to prepare Mo-V-Te-Nb oxide materials with competitive catalytic performance. The yields achieved overcome those from optimized catalysts prepared by conventional hydrothermal method, and approach those reached with catalysts prepared using the "slurry method". The optimum rise for the synthesis temperature is found as a key factor for the reflux method. It allows access to an increased vanadium content into the reflux precipitate, which favors the formation of a pseudo-amorphous Mo-V-Te-Nb oxometallate. This precipitate behaves as a precursor for the crystallization, during the solid-state activation step at high-temperature (600 degrees C/N-2), of the structure type (TeO)(2)M20O56 (M = Mo, V, Nb), key for the selective conversion of propane or ethane. On the other hand, for the optimum temperature of synthesis, i.e. 110 degrees C, higher synthesis time of the precursor leads to smaller crystal sizes in the final catalyst (higher specific surface areas) and lowers the average oxidation state of vanadium from V+5 to V+4, which significantly enhances the catalytic behavior., Authors gratefully acknowledge the funds from DGICYT (Spain) by the project RTI2018-099668-B-C21, as well as the funds from Comunidad de Madrid by the project 2017-T1/IND-6025 within the program "Atraccion y Retencion de Talento Investigador" of the V PRICIT.

Biomass burning drives changes in greenhouse gases, climate-forcing aerosols, and global atmospheric chemistry. There is controversy about the magnitude and timing of changes in biomass burning emissions on millennial time scales from preindustrial to present and about the relative importance of climate change and human activities as the underlying cause. Biomass burning is one of two notable sources of ethane in the preindustrial atmosphere. Here, we present ice core ethane measurements from Antarctica and Greenland that contain information about changes in biomass burning emissions since 1000 CE (Common Era). The biomass burning emissions of ethane during the Medieval Period (1000-1500 CE) were higher than present day and declined sharply to a minimum during the cooler Little Ice Age (1600-1800 CE). Assuming that preindustrial atmospheric reactivity and transport were the same as in the modern atmosphere, we estimate that biomass burning emissions decreased by 30 to 45% from the Medieval Period to the Little Ice Age. The timing and magnitude of this decline in biomass burning emissions is consistent with that inferred from ice core methane stable carbon isotope ratios but inconsistent with histories based on sedimentary charcoal and ice core carbon monoxide measurements. This study demonstrates that biomass burning emissions have exceeded modern levels in the past and may be highly sensitive to changes in climate.

1,2-Dibromoethane (ethylene dibromide; EDB) is a probable human carcinogen that was historically added to leaded gasoline as a scavenger to prevent the build-up of lead oxide deposits in engines. Studies indicate that EDB is present at thousands of past fuel spill sites above its stringent EPA Maximum Contaminant Level (MCL) of 0.05 μg/L. There are currently no proven in situ options to enhance EDB degradation in groundwater to meet this requirement. Based on successful laboratory studies showing that ethane can be used as a primary substrate to stimulate the aerobic, cometabolic biodegradation of EDB to0.015 μg/L (Hatzinger et al., 2015), a groundwater recirculation system was installed at the FS-12 EDB plume on Joint Base Cape Cod (JBCC), MA to facilitate in situ treatment. Groundwater was taken from an existing extraction well, amended with ethane, oxygen, and inorganic nutrients and then recharged into the aquifer upgradient of the extraction well creating an in situ reactive zone. The concentrations of EDB, ethane, oxygen, and anions in groundwater were measured with time in a series of nested monitoring wells installed between the extraction and injection well. EDB concentrations in the six monitoring wells that were hydraulically well-connected to the pumping system declined from ~ 0.3 μg/L (the average concentration in the recirculation cell after 3 months of operation without amendment addition) to0.02 μg/L during the 4-month amendment period, meeting both the federal MCL and the more stringent Massachusetts MCL (0.02 μg/L). The data indicate that cometabolic treatment is a promising in situ technology for EDB, and that low regulatory levels can be achieved with this biological approach.

Nitroalkane oxidase (NAO) and nitronate monooxygenase (NMO) are two different types of nitroalkane oxidizing flavoenzymes identified in nature. A previous study suggested that the hypothetical protein PA4202 from Pseudomonas aeruginosa PAO1 is NMO and utilizes only anionic nitronates. However, the structural similarity between the PA4202 protein and Streptomyces ansochromogenes NAO has motivated investigation for what features of the two enzymes differentiate between the NAO and NMO activities. Herein, we report the crystal structure of PA4202 in a ternary complex with a neutral nitroethane (NE) and flavin mononucleotide (FMN) cofactor to elucidate the substrate recognition mechanism using a site-directed mutagenesis. The ternary complex structure indicates that the NE is bound with an orientation, which is poised for the proton transfer to H183 (which is the essential first catalytic step with nitroalkanes), and subsequent reactions with FMN. Moreover, a kinetic study reveals that the catalytic reactions of the wild type and H183 mutants PA4202s with nitroalkane substrates may yield the products of hydrogen peroxide and nitrite that are specified to NAO, although they show a low catalytic efficiency. Our results provide the first structure-based molecular insight into the substrate binding property of the hypothetical protein PA4202, including the interactions with neutral nitroalkanes as the substrate.

Sodium persulfate has become the most popular oxidant source for the in situ chemical oxidation (ISCO) treatment of organic contaminants in the subsurface. The most common persulfate activators, iron chelates and base, are often ineffective in initiating the generation of reactive oxygen species in field applications. In this study, glucose was investigated as a persulfate activator in systems containing varying concentrations of sodium hydroxide using nitrobenzene as a hydroxyl radical probe and hexachloroethane as a reductant + nucleophile probe. Glucose activation of persulfate increased as a function of sodium hydroxide addition, but was still effective at circumneutral pH regimes. Use of central composite rotatable experimental designs showed that hydroxyl radical and reductant + nucleophile generation rates increased as a function of persulfate at near-neutral pH regimes. Glucose activation of persulfate has the advantages over other activation pathways of more options and flexibility for effective process chemistry and of minimizing or eliminating the mass of sodium hydroxide added to the subsurface. The results of this research can be applied in the field by first evaluating glucose activation compared to base and iron chelate activation of persulfate in laboratory treatability studies.

We use molecular simulations to study the adsorption of ethane and ethylene in zeolitic imidazolate frameworks. The separation of these two compounds is a crucial step in many industrial processes, most of them related to production of ethylene. Separation methods such as fractional cryogenic distillation require large energy consumption that increases the costs of ethylene production. Here, we analyze the suitability of zeolitic imidazolate frameworks for the separation of these gases on the basis of structural and chemical features. We pay special attention to the effect exerted by other gases on the adsorption and diffusion of ethane and ethylene in the structures. We found that nitrogen has an important role in the separation process and depending on the structure, it can enhance or hinder the adsorption selectivity for ethane. The presence of gases other than nitrogen also causes an effect on the ethane/ethylene separation. A mixture containing hydrogen, oxygen, methane, carbon monoxide, carbon dioxide, ethane, and ethylene in zeolitic imidazolate frameworks is also investigated. Our results identify ZIFs with rho, crg, and lta topologies as good candidates for the separation of ethane and ethylene.

The partial oxidation of ethane to ethylene and acetic acid on supported MoVNbPd/TiO2 (P25 of Degussa) has been investigated. Pd was added in a nano-metallic form. The catalyst composition was also different from similar studied catalysts. This results in a better selectivity towards acetic acid formation. The reaction was carried out in a tubular reactor at temperature range 225–275 °C, total pressure range 0–200 psig and oxygen percentage in the feed gas of 10–40%. The feed gas contains ethane and oxygen. In this work, we develop a kinetic model for the reaction for the developed catalyst. In this model, we assume that oxidation reactions take place on different sites; ethane oxidation takes place on one site, ethylene oxidation on another site, and CO is oxidized to CO2 on a third site. The model exhibits good agreement with the experimental data.

Non-methane hydrocarbons (NMHCs) are vital to people's health and plants' growth, especially inside a controlled ecological life support system (CELSS) built for long-term space explorations. In this study, we measured 54 kinds of NMHCs to study their changing trends in concentration levels during a 4-person-180-day integrated experiment inside a CELSS with four cabins for plants growing and other two cabins for human daily activities and resources management. During the experiment, the total mixing ratio of measured NMHCs was 423 ± 283 ppbv at the first day and it approached 2961 ± 323 ppbv ultimately. Ethane and propane were the most abundant alkanes and their mixing ratios kept growing from 27.5 ± 19.4 and 31.0 ± 33.6 ppbv to 2423 ± 449 ppbv and 290 ± 10 ppbv in the end. For alkenes, ethylene and isoprene presented continuously fluctuating states during the experimental period with average mixing ratios of 30.4 ± 19.3 ppbv, 7.4 ± 5.8 ppbv. For aromatic hydrocarbons, the total mixing ratios of benzene, toluene, ethylbenzene and xylenes declined from 48.0 ± 44 ppbv initially to 3.8 ± 1.1 ppbv ultimately. Biomass burning, sewage treatment, construction materials and plants all contributed to NMHCs inside CELSS. In conclusion, the results demonstrate the changing trends of NMHCs in a long-term closed ecological environment's atmosphere which provides valuable information for both the atmosphere management of CELSS and the exploration of interactions between humans and the total environment.

Acetofenate (AF) is a chiral organochlorine pesticide used for controlling hygiene pests. In this study, the metabolism of AF in rabbits in vivo and in vitro was investigated and the primary chiral metabolite acetofenate-alcohol (AF-A) was analyzed. The cytotoxicity of AF and AF-A was also determined. AF in rabbits in vivo was eliminated so rapidly that AF could not be detected within 10min after intravenous administration at 20mg/kg (body weight), and AF-A was quickly formed. In vitro metabolism assay, using plasma and liver microsomes, showed that AF was also quickly metabolized to AF-A and the metabolic process was significantly enantioselective with preferential degradation of (-)-AF and formation of (-)-AF-A. The cytotoxicity of AF and AF-A were investigated by assessing cell proliferation, apoptosis and generation of reactive oxygen species. The results showed that AF and AF-A induce enantioselective cytotoxicity. This study will be helpful for improving knowledge about the metabolism and toxicity of AF on an enantiomeric level and providing evidence to understand the potential environmental risk.

Chemical vapor deposition has emerged as a promising approach for high-quality graphene synthesis. Graphene quality, including the defect density, the size of monocrystal domains, and the number of layers, depend on the growth conditions. The main experimental parameters include temperature, metal catalyst composition, growth atmosphere, and gaseous dynamics in the reaction chamber. Here we show, that even for the same growth conditions, simply changing carbon source from methane to ethane or acetylene yields drastically different growth mode that allows the production of single-crystal-like graphene on a polycrystalline metal foil substrate. This new single crystal growth mechanism does not require local supply of carbon precursors or special single crystal catalytic substrate that were introduced earlier. We assign the observed differences in the growth mechanism to formation of stable and mobile dimeric C2Hx intermediate species from ethane and acetylene, in contrast to less mobile CHx and C3Hx species formed from methane and propane.

[EN] The discovery of new materials for separating ethylene from ethane by adsorption, instead of using cryogenic distillation, is a key milestone for molecular separations because of the multiple and widely extended uses of these molecules in industry. This technique has the potential to provide tremendous energy savings when compared with the currently used cryogenic distillation process for ethylene produced through steam cracking. Here we describe the synthesis and structural determination of a flexible pure silica zeolite (ITQ-55). This material can kinetically separate ethylene from ethane with an unprecedented selectivity of ~100, owing to its distinctive pore topology with large heart-shaped cages and framework flexibility. Control of such properties extends the boundaries for applicability of zeolites to challenging separations., We gratefully acknowledge financial support from ExxonMobil Research and Engineering Company, Instituto de Tecnologia Quimica researchers also thank the European Research Council (grant ERC-2014-AdG-671093 "MATching zeolite SYNthiesis with CATalytic activity") and the Spanish government (grants MAT2015-71842-P MINECO/FEDER and Severe Ochea SEV-2012-0267 and SEV-2016-0683) for economic support

Unmodified and sulfate-modified SBA-15-supported Cr2O3 catalysts were prepared by impregnation method. The physico-chemical properties of the supports and catalysts were determined by nitrogen adsorption/desorption, powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), laser-Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), UV–Vis diffuse reflectance spectroscopy (UV-DRS), inductively coupled plasma optical emission spectroscopy (ICP-OES), transmission electron microscopy (TEM) and temperature-programmed reduction (TPR) techniques. Oxidative dehydrogenation of ethane to ethylene (ODE) with CO2 as oxidant was carried out on these catalysts in a fixed-bed reactor at temperatures in the range of 600–700 °C and at atmospheric pressure. The changes in structural and textural properties because of sulfate modification were identified. Sulfate modification affected the nature of interaction of CrO x species with the SBA-15 support. During the evaluation, it was observed that sulfate modification enhances ethane conversion and ethylene selectivity of the catalyst. Better dispersion of CrO x and the increase in Cr6+/Cr3+ ratio seem to be the reasons for the higher performance of the sulfate-modified catalysts compared to that of the unmodified catalyst.

The laminar flame speed plays an important role in spark-ignition engines, as well as in many other combustion applications, such as in designing burners and predicting explosions. For this reason, it has been object of extensive research. Analytical correlations that allow it to be calculated have been developed and are used in engine simulations. They are usually preferred to detailed chemical kinetic models for saving computational time. Therefore, an accurate as possible formulation for such expressions is needed for successful simulations. However, many previous empirical correlations have been based on a limited set of experimental measurements, which have been often carried out over a limited range of operating conditions. Thus, it can result in low accuracy and usability. In this study, measurements of laminar flame speeds obtained by several workers are collected, compared and critically analyzed with the aim to develop more accurate empirical correlations for laminar flame speeds as a function of equivalence ratio and unburned mixture temperature and pressure over a wide range of operating conditions, namely [Formula: see text], [Formula: see text] and [Formula: see text]. The purpose is to provide simple and workable expressions for modeling the laminar flame speed of practical fuels used in spark-ignition engines. Pure compounds, such as methane and propane and binary mixtures of methane/ethane and methane/propane, as well as more complex fuels including natural gas and gasoline, are considered. A comparison with available empirical correlations in the literature is also provided.

Polybrominated dibenzo-p-dioxins (PBDDs) and hydroxylated polybrominated diphenyl ethers (OH-PBDEs) can be formed from bromophenols (BPs) by thermal degradation, biosynthesis or phototransformation. However, it is unknown whether PBDDs and OH-PBDEs can be formed during the chemical production processes that utilize BPs as raw materials. 2,4,6-tribromophenol (2,4,6-TBP) is an important raw material for the synthesis of 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), a novel brominated flame retardant. In this study, PBDDs, polybrominated dibenzofurans (PBDFs) and OH-PBDEs have been identified and quantified in commercially available BTBPE and 2,4,6-TBP. Furthermore, their formation as unintentional by-products during the laboratory synthesis of BTBPE from 2,4,6-TBP and 1,2-dibromoethane in the presence of sodium carbonate has also been investigated. 2,3,7,8-substituted PBDDs and PBDFs (2,3,7,8-PBDD/Fs) were undetectable in commercial samples of BTBPE and present in low levels (nanogram per gram) in 2,4,6-TBP. Two tetrabrominated dibenzo-p-dioxins (TeBDDs), namely 1,3,6,8- and 1,3,7,9-TeBDD, and three hydroxylated pentabrominated diphenyl ethers (OH-pentaBDEs), namely 4'-OH-BDE121, 2'-OH-BDE121, and 6'-OH-BDE100, were identified or tentatively identified, and quantitatively estimated to be at concentrations in the range of undetectable to several thousands of nanograms per gram in commercial BTBPE and 2,4,6-TBP. TeBDDs and OH-pentaBDEs were formed as by-products from 2,4,6-TBP during BTBPE synthesis. Further studies need to be conducted in order to determine whether PBDD/Fs and OH-PBDEs are also formed during the industrial synthesis of other chemical compounds that utilize BPs as raw materials or intermediates.

Recently, we have developed ultralow-temperature high-performance liquid chromatography (HPLC) at -196°C using liquid nitrogen-based mobile phases. In this study, a retention model for ultralow-temperature HPLC, in which adsorption exchange and "pseudo partition" modes are combined, is proposed to describe the effect of the mobile phase composition on the retention of analytes. The experimental results agreed well with the equation of the proposed model. It was revealed that, in the low and high additive concentration regions, adsorption exchange and pseudo partition retention, respectively, dominate the analyte retention. The difference in the retention behavior between bare-silica and octadecylsilyl-modified silica (ODS) columns was also studied. Retention of alkanes in the ODS column was greater than that in the bare-silica one. Addition of both ethane and ethylene to the mobile phase in the ODS column afforded the elution of propylene, which was not eluted with the bare-silica column at -196°C.

Incomplete combustion during flaring can lead to production of black carbon (BC) and loss of methane and other pollutants to the atmosphere, impacting climate and air quality. However, few studies have measured flare efficiency in a real-world setting. We use airborne data of plume samples from 37 unique flares in the Bakken region of North Dakota in May 2014 to calculate emission factors for BC, methane, ethane, and combustion efficiency for methane and ethane. We find no clear relationship between emission factors and aircraft-level wind speed or between methane and BC emission factors. Observed median combustion efficiencies for methane and ethane are close to expected values for typical flares according to the US EPA (98%). However, we find that the efficiency distribution is skewed, exhibiting log-normal behavior. This suggests incomplete combustion from flares contributes almost 1/5 of the total field emissions of methane and ethane measured in the Bakken shale, more than double the expected value if 98% efficiency was representative. BC emission factors also have a skewed distribution, but we find lower emission values than previous studies. The direct observation for the first time of a heavy-tail emissions distribution from flares suggests the need to consider skewed distributions when assessing flare impacts globally.