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Liquid-vapor interfacial properties of alkane mixtures present a challenge for experimental determination, especially under conditions relevant to the energy industry processes. Molecular dynamics (MD) simulations can accurately predict interfacial tensions (IFTs) for complex alkane mixtures under virtually any conditions, thereby alleviating the need for difficult and costly experiments. MD simulations with the CHARMM force field and empirical corrections for the IFT and pressure were used to obtain the IFT for three binary mixtures of ethane (with n -pentane, n -hexane, and n -nonane) and a ternary system (ethane/ n -butane/ n -decane) under a variety of conditions. The results were thoroughly validated against experimental data from the literature, and new original IFT data were collected using the pendant drop method. The simulations are able to reproduce the experimental IFT to better than 0.5 mN/m or 5% on average and within 1 mN/m or 10% in the worst case. IFTs for the studied three binary and ternary alkane mixtures were predicted for wide ranges of conditions with no known experimental data. Finally, using the MD simulation data, the reliability of the widely used empirical parachor model for predicting IFT was reaffirmed, and the significance of the empirical parameters examined to establish an optimal balance between the accuracy and broad applicability of the model.

Acetic acid (AA), a vital compound in chemical production and materials manufacturing, is conventionally synthesized by starting with coal or methane through multiple steps including high‐temperature transformations. Here we present a new synthesis of AA from ethane through photocatalytic selective oxidation of ethane by H2O2 at 0–25 °C. The catalyst designed for this process comprises g‐C3N4 with anchored Pd1 single‐atom sites. In situ studies and computational simulation suggest the immobilized Pd1 atom becomes positively charged under photocatalytic condition. Under photoirradiation, the holes on the Pd1 single‐atom of OH−Pd1⊕ ${{}^{\oplus }}$ /g‐C3N4 serves as a catalytic site for activating a C−H instead of C−C of C2H6 with a low activation barrier of 0.14 eV, through a concerted mechanism. Remarkably, the selectivity for synthesizing AA reaches 98.7 %, achieved under atmospheric pressure of ethane at 0 °C. By integrating photocatalysis with thermal catalysis, we introduce a highly selective, environmentally friendly, energy‐efficient synthetic route for AA, starting from ethane, presenting a promising alternative for AA synthesis. This integration of photocatalysis in low‐temperature oxidation demonstrates a new route of selective oxidation of light alkanes. [ABSTRACT FROM AUTHOR]

The Well Mitan-1 has achieved a major breakthrough in the exploration of Ordovician subsalt natural gas in the mid-eastern Ordos Basin, demonstrating a high-yield industrial gas flow in fourth member of the Majiagou Formation of Ordovician (O1m4). Despite this success, there are ongoing disputes regarding the origin of the natural gas found in Well Mitan-1. Measured results show that the natural gas in Well Mitan-1 is mainly composed of alkane gas (95.18 %). The gas drying coefficient (C1/C1-5) is measured at 0.947, and the H2S content is 3.49 %, with a small amount of N2 and CO2 in the non-hydrocarbon gas. The carbon isotopic compositions of methane, ethane, and propane in the natural gas are -45.5‰, -26.4‰, and -24.3‰, respectively. Based on the regional geological background, the characteristics of potential source rocks and the geochemical characteristics of natural gas, it is considered that the natural gas in Well Mitan-1 is self-generated and self-accumulated oilassociated gas in Ordovician subsalt carbonate rocks. However, certain geochemical anomalies, such as the lighter methane carbon isotope value (d13C1) and coal-type gas characteristics in ethane carbon isotope (d13C2), raise questions. Further insights from thermal simulation experiments on hydrocarbon generation and the analysis of residual gas in rocks suggest a close relationship between the special geochemical characteristics of Well Mitan-1 and the presence of gypsum rocks. The ubiquitous gypsum rock serves a dual purpose: acting as an effective caprock, facilitating the retention of early-generated natural gas, and promoting the generation of heavy hydrocarbon gases (C2+) and H2S. The relatively low H2S content (less than 5 %) and higher C2+ content indicate that thermochemical sulfate reduction (TSR), if present, is not strong enough to significantly impact methane. The d13C2 is identified as a potentially sensitive parameter for identifying TSR. [ABSTRACT FROM AUTHOR]

The thermal pyrolysis of ethane and propane at a pressure of 1–3 atm was experimentally studied in a through-flow reactor. Kinetic modeling of the process under these conditions showed good agreement with experimental data in terms of both the conversion of alkanes and the yield of pyrolysis products, which allowed us to expand the modeling range of pressure. The results obtained show that the pressure change in the range of 1–15 atm has no noticeable effect on the pyrolysis of light alkanes. On this basis, we concluded that the previously established effect of pressure on the oxidative cracking of ethane was associated with its effect on the oxidative stages of the process. [ABSTRACT FROM AUTHOR]

The Energy, Environment, Science and Technology (EES&T) Directorate of the Idaho National Laboratory (INL) launched an advanced manufacturing platform in 2015, which has evolved into a national laboratory initiative across all INL directorates as of 2018. Thus, all three INL Directorates, including nuclear and cyber security, are engaged in a unified advanced manufacturing strategy. The ultimate goal of this initiative is to increase the economic competitiveness of energy-generation systems, security systems, structural components, and industrial chemical processes by advancing the knowledge that supports improved fabrication and manufacturing technologies. To move this innovation forward, INL is designing, building and testing what is not possible with traditional manufacturing techniques. The development of advanced manufacturing technologies has the potential to significantly expand the design options of the solutions to manufacturing problems that have been challenging the industrial sector for years. • This article will describe the focus areas that INL has decided to address in the industrial chemical processes thrust. In this regards, high energy-consuming and low energy-efficient processes are of our top concerns. The manufacturing of olefins from natural gas components namely methane and ethane presents these challenges and give us the opportunity to address it as a first priority in the INL's recently established advanced manufacturing initiative. • One may envision the conversion of alkanes to alkenes as the first step of functionalization, i.e. creating unsaturation sites that convert low reactive alkanes into more reactive building units. • This new vision of Lego-like chemical manufacturing is a paradigm shift from the historical chemical manufacturing approach of starting from heavy crude and cracking down to smaller hydrocarbon building blocks. INL's new chemical manufacturing approach leads to significant energy saving and reduction of waste products. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

• Mo-V-Te-Nb-O mixed oxides have been prepared successfully by reflux method by optimizing the synthesis parameters. • These catalysts present high activity and selectivity for partial oxidation of propane to acrylic acid. • These Mo-V-Te-Nb-O catalysts are active and selective for the ethane oxidative dehydrogenation. • The catalytic behavior is strongly related to the presence of orthorhombic M1 phase. The investigation here presented studies the effect of the synthesis temperature (from 80 to 110 °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 °C/N 2), of the structure type (TeO) 2 M 20 O 56 (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 °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. [ABSTRACT FROM AUTHOR]

Cometabolic biodegradation of 1,4-dioxane (dioxane) in the presence of primary substrates is a promising strategy for treating dioxane at environmentally relevant concentrations. Seven aqueous amendments (i.e., tetrahydrofuran (THF), butanone, acetone, 1-butanol, 2-butanol, phenol and acetate) and five gaseous amendments (i.e., C1–C4 alkanes and ethylene) were evaluated as the primary substrates for dioxane degradation by mixed microbial consortia. The aqueous amendments were tested in microcosm bottles and the gaseous amendments were tested in a continuous-flow membrane biofilm reactor with hollow fibers pressurized by the gaseous amendments. Ethane was found to be the most effective gaseous substrate and THF was the only aqueous substrate that promoted dioxane degradation. A diverse microbial community consisting of several putative dioxane degraders—Mycobacterium, Flavobacterium and Bradyrhizobiaceae—were enriched in the presence of ethane. This is the first study showing that ethane was the most effective substrate among the short-chain alkanes and it promoted dioxane degradation by enriching dioxane-degraders that did not harbor the well-known dioxane/tetrahydrofuran monooxygenase. [ABSTRACT FROM AUTHOR]

A new type of high‐pressure reactor based on liquid‐flow pressurisation using a HPLC pump has been developed. This high‐pressure reactor allows the easy and safe performance of reactions with gaseous alkanes under high‐pressures up to 10 MPa (100 atm), without the need for high‐pressure gas cylinders. The amount of substrate gas required for a single reaction is very small compared with reactions using a conventional autoclave, which, when using expensive substrate gasses, such as 13C‐labelled ethane, becomes critical. Employing this high‐pressure reactor in conjunction with cytochrome P450BM3 and the assistance of decoy molecules, the direct hydroxylation of gaseous alkanes was drastically improved. At 5 MPa the TOF of propane hydroxylation increased 10‐fold, reaching 2200 min−1. Hydroxylation of ethane was also substantially accelerated at 5 MPa, reaching a TOF of 28 min−1. [ABSTRACT FROM AUTHOR]

Emissions of C2‐C5 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 C2‐C5 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 (C2H6) and propane (C3H8), and emissions of these species are largest in the central United States. Observed mixing ratios of C2‐C5 alkanes show enhancements over the central United States below 2 km. A nested GEOS‐Chem simulation underpredicts observed C3H8 mixing ratios in the boundary layer over several U.S. regions, and the relative underprediction is not consistent, suggesting C3H8 emissions should receive more attention moving forward. Our decision to consider only C4‐C5 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 C2‐C5 alkanes. We suggest additional monitoring of C2‐C5 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. Key Points: Oil and gas development is the largest source of ethane and propane in the United States; this sector is the third largest source of C4‐C5 alkanesPropane is underpredicted over several U.S. regionsBoundary layer enhancements of C2‐C5 alkanes mixing ratios are largest over the central United States [ABSTRACT FROM AUTHOR]

Abstract The compositional and bulk isotopic signatures of hydrocarbon compounds are routinely characterized to constrain the origin of oils and natural gases in sedimentary basins. Recent developments in clumped isotope geochemistry have given rise to a suite of measurements that provide new information on the thermal history of low molecular weight hydrocarbon gases. However, to date no study has linked these compositional, bulk and clumped isotope constraints to any mechanistic understanding of how these signatures develop and evolve. In this study, we developed a kinetic Monte Carlo method to predict consistent and simultaneous molecular distributions, bulk isotopic content, and detailed (multiply substituted and site-specific) isotopic structures of hydrocarbons from a cracking model. The detailed isotopic structure of the source (initially modeled as long alkanes), the intermediates, and the product molecules is followed as a function of the level of conversion due to cracking reactions. The bulk 13C content of gaseous alkane products generated via the model is shown to follow the linear natural gas plot at low conversion, but to deviate at high conversions. As examples of the information generated, the populations of center vs. terminal 13C-substituted propane are reported as a function of the starting alkane chain length and conversion and the population of doubly-13C-substituted ethane is described as a function of conversion and for different 13C substitution patterns in the source. The results are compared to experiment where possible and highlight the possibility of constraining hydrocarbon source isotopic structure and the nature of the generation processes leading to the formation of natural hydrocarbon deposits. [ABSTRACT FROM AUTHOR]

We present a comprehensive computational simulation and theoretical analysis of the pressure-vs-temperature explosion limits of oxygen with hydrogen (H 2), methane (CH 4), ethane (C 2 H 6) or propane (C 3 H 8), as well as the binary fuels of H 2 –CH 4 , H 2 –C 2 H 6 and H 2 –C 3 H 8. Results show that the C 1 –C 3 explosion limit curves all confluence around a single, pivot, state corresponding to the upper turning point of the hydrogen explosion limit Z-curve. Furthermore, while hydrogen has the widest range of explosion temperature for pressures below the pivot state as compared to those of the alkanes, the response is reversed for pressures above the pivot state. Studies on the kinetic effects of hydrogen in the binary fuels show the dominance of the alkanes in that progressively larger amount of hydrogen addition is needed, from methane to propane, in order to impart the hydrogen explosion characteristics to the binary fuels. The reaction mechanisms responsible for the observed behavior are identified through sensitivity and reaction pathway analyses. A comprehensive explosion regime diagram of the observed behavior is proposed for H 2 and C 1 to C 3 alkanes in an extensive pressure-temperature range. Practical implications of the understanding gained herein are suggested. [ABSTRACT FROM AUTHOR]

Sooting behavior of premixed C 1 –C 4 n -alkanes/air mixtures at maximum temperatures lower than 1400 K is studied experimentally using a micro flow reactor with a controlled temperature profile. Flame and soot responses to equivalence ratio (1.5–4.0) are observed for all mixtures. Critical sooting equivalence ratio observed for methane, propane and n-butane is 1.8, whereas, for ethane it is 1.9. Sooting behavior at similar critical equivalence is further interpreted qualitatively by observing relative axial locations of upstream edges of sooting region, where relative downstream location indicates delayed soot formation. The order of axial location of upstream edge of soot at equivalence ratio 1.8 is: propane < n -butane < methane; and, the order at equivalence ratio 1.9 is: propane ∼ n -butane ∼ ethane < methane. Sooting region shifts upstream for ethane, propane and n -butane with increasing equivalence ratio. However, it does not change for methane with increasing equivalence ratio above 2.0. One dimensional computations with detailed chemistry are performed to study observed flame and soot responses. Ethane is found to be most reactive fuel due to coupling of H abstraction from fuel and H production in the flame. Computed flame positions vary widely among mechanisms for methane. Most exothermic reaction at flame is CH 3 + CH 3 = C 2 H 6 for all mechanisms and for all the fuels. Computations using KAUST mechanism are performed for all the fuels at various equivalence ratios in the range 1.35–4.0 to discuss overall sooting behavior. Maximum computed pyrene mole fractions are used to study relative sooting behavior qualitatively as they correlate well with soot. The trends of maximum computed pyrene mole fractions qualitatively explain observed trends of critical sooting equivalence ratios and overall sooting behavior of fuels in the current experiments. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mesoporous NIIC-20 is a superior material for separation of light alkanes. • The best combination of adsorption uptakes and selectivities for CH 4 /C 2 H 6 /C 3 H 8. • Efficient breakthrough separation of gas mixtures with remarkable productivity. • An influence of the alkyl substituent on the MOF adsorption properties was explored. Adsorption and separation of light saturated hydrocarbons (methane, ethane and propane) as main components of natural gas on a series of isoreticular mesoporous metal–organic frameworks NIIC-20-G (G = ethyleneglycol, 1,2-propyleneglycol, 1,2-butyleneglycol, 1,2-pentylenglycol, glycerol) has been thoroughly investigated. An impact of the size and nature of the glycol moiety on fundamental parameters of the adsorption (gas uptakes, adsorption constants, enthalpy and entropy, adsorption selectivity factors) was revealed and rationalized. The highest gas uptakes at 1 bar and 298 K are 13.2 ml(STP)·g−1 for CH 4 , 55.0 ml(STP)·g−1 for C 2 H 6 and 125.4 ml(STP)·g−1 for C 3 H 8. The IAST adsorption selectivities at ambient conditions (298 K, 1:1 gas mixture) reach 24.2 for C 2 H 6 /CH 4 , 29.0 for C 3 H 8 /C 2 H 6 and as high as 1110 for C 3 H 8 /CH 4. A rare combination of high adsorption uptakes and superb adsorption selectivity values achieved for NIIC-20-G put those MOFs ahead of the most other materials for light saturated hydrocarbon adsorption and separation. Dynamic breakthrough gas separation experiments on NIIC-20-Pr fully confirm effective separation of lighter alkanes from the corresponding binary or ternary mixtures. The obtained methane productivities are 1182 ml(STP)·g−1 (52.8 mol·kg−1) for C 2 H 6 /CH 4 , and 4193 ml(STP)·g−1 (187.3 mol·kg−1) for C 3 H 8 /CH 4 equimolar gas mixtures, which greatly surpass earlier published data. The ethane productivity for an equimolar C 3 H 8 /C 2 H 6 gas mixture is 3009 ml(STP)·g−1 (134.4 mol·kg−1). The breakthrough separation experiments validate a remarkable performance of the studied MOFs in the practical separation of natural gas or other relevant mixtures of light alkanes to valuable individual components. [ABSTRACT FROM AUTHOR]

It is shown that the steam reforming of C-C alkanes over nickel-aluminum catalysts in a temperature range of 300-600 °C is accompanied by the formation of methane, leading to a lower yield of hydrogen. By the addition of oxygen to the gaseous reaction mixture it is possible to increase the conversion of alkanes, to reduce the methane content, and to lessen the carbonization of the catalyst. Modification of the Ni-AlO catalyst with lanthanum oxide increases its stability in an oxygen environment, and modification with cerium oxide leads to increased selectivity for CO by reducing the contribution from the water gas shift reaction. [ABSTRACT FROM AUTHOR]