Search

Renewable cracking feedstocks from plastic waste and the need for novel reactor designs related to electrification of steam crackers drives the development of accurate and fundamental kinetic models for this process, despite its large scale implementation for more than half a century. Pressure dependent kinetics have mostly been omitted in fundamental steam cracking models, while they are crucial in combustion models. Therefore, we have assessed the importance of pressure dependent kinetics for steam cracking via in-depth modelling and experimental studies. In particular we have studied the influence of considering fall-off on the product yields for ethane and propane steam cracking. A high-pressure limit fundamental kinetic model is generated, based on quantum chemical data and group additive values, and supplemented with literature values for pressure dependent kinetic parameters for β-scission reactions and homolytic bond scissions of C 2 and C 3 species. Model simulations with high-pressure limit rate coefficients and pressure dependent kinetics are compared to new experimental measurements. Steam cracking experiments for pure ethane and propane feeds are performed on a tubular bench-scale reactor at 0.17 MPa and temperatures ranging from 1058 to 1178 K. All important product species are identified using a comprehensive GC × GC-FID/q-MS. For homolytic bond scissions, the inclusion of pressure dependent kinetics has a significant effect on the conversion profile for ethane steam cracking. On the other hand, pressure dependence of C 2 β-scissions significantly influences conversion and product species profiles for both ethane and propane steam cracking. The C 3 β-scissions pressure dependence has a negligible effect in ethane steam cracking, while for propane steam cracking the effect is non-negligible on the product species profiles.

Selenate (Se(VI)) contamination in groundwater is one of major concerns for human health, in particular in shale gas extraction sites. Microbial selenate reduction coupled to methane (CH 4 ) oxidation has been demonstrated very recently. Little is known whether ethane (C 2 H 6 ) and butane (C 3 H 8 ) are able to drive selenate reduction, although they are also important components in shale gas. In this study, we demonstrated Se(VI) bio-reduction could be achieved using C 2 H 6 and C 3 H 8 as electron donors and carbon sources. Scanning electron microscopy coupled to energy dispersive X-ray spectroscopy (SEM-EDX) confirmed elemental Se (Se 0 ) was the major final product formed from Se(VI) bio-reduction. Polyhydroxyalkanoates (PHAs) were generated in the biofilms as the internal electron-storage materials, which were consumed for sustaining Se(VI) bio-reduction in absence of C 2 H 6 and C 3 H 8 . Microbial community analysis showed that two genera capable of oxidizing gaseous alkanes dominated in the biofilms, including Mycobacterium (in both C 2 H 6 and C 3 H 8 -fed biofilms) and Rhodococcus (in C 3 H 8 -fed biofilm). In addition, several potential Se(VI) reducers (e.g., Variovorax) were detected in the biofilms. Investigation of Communities by Reconstruction of Unobserved States analysis supported that predictive genes associated with alkanes oxidation, denitrification and PHAs cycle were enriched in the biofilms. These findings offer insights into the process of selenate reduction driven by C 2 H 6 and C 3 H 8 , which ultimately may help to develop a solution to use shale gas for groundwater remediation, especially near shale gas exploitation sites., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

1,2-Dibromoethane (ethylene dibromide; EDB) is a probable human carcinogen that was previously used as both a soil fumigant and a scavenger in leaded gasoline. EDB has been observed to persist in soils and groundwater, particularly under oxic conditions. The objective of this study was to evaluate options to enhance the aerobic degradation of EDB in groundwater, with a particular focus on possible in situ remediation strategies. Propane gas and ethane gas were observed to significantly stimulate the biodegradation of EDB in microcosms constructed with aquifer solids and groundwater from the FS-12 EDB plume at Joint Base Cape Cod (Cape Cod, MA), but only after inorganic nutrients were added. Ethene gas was also effective, but rates were appreciably slower than for ethane and propane. EDB was reduced to <0.02 μg/L, the Massachusetts state Maximum Contaminant Level (MCL), in microcosms that received ethane gas and inorganic nutrients. An enrichment culture (BE-3R) that grew on ethane or propane gas but not EDB was obtained from the site materials. The degradation of EDB by this culture was inhibited by acetylene gas, suggesting that degradation is catalyzed by a monooxygenase enzyme. The BE-3R culture was also observed to biodegrade 1,2-dichloroethane (DCA), a compound commonly used in conjunction with EDB as a lead scavenger in gasoline. The data suggest that addition of ethane or propane gas with inorganic nutrients may be a viable option to enhance degradation of EDB in groundwater aquifers to below current state or federal MCL values., (Copyright © 2014 Elsevier B.V. All rights reserved.)

We studied the effect of pressure up to 300 bar on the catalytic efficiency of subtilisin Carlsberg suspended in compressed propane, near-critical ethane, near-critical carbon dioxide and tert-amyl alcohol, at constant temperature and fixed enzyme hydration. Increasing pressure lowered the catalytic efficiency of the enzyme in all the solvents, resulting in positive activation volumes, delta V#. The delta V# values in compressed propane and in tert-amyl alcohol were similar and larger in magnitude than the value reported in the literature for the same reaction in an aqueous buffer, although within the range of typical delta V# values in aqueous media. In the near-critical fluids, the delta V# were much larger, e.g., an increase in pressure of only 200 bar causing a sixfold decrease in the catalytic efficiency of subtilisin in carbon dioxide. These data should reflect the proximity of ethane and carbon dioxide to the critical point, and the resulting condensation of solvent molecules about the solutes, yielding negative solute partial molar volumes.

Rapid freezing is the most important step in sample preparation for freeze-fracture and other cryotechniques for electron microscopy. A simple heat transfer model is experimentally validated to show that convection from the cryogen to the specimen is the limiting step in rapid freezing of small samples [Biot modulus, (hd/k) less than 1] by measuring cooling rates in a variety of samples, materials, and cryogens. In comparison to the commonly accepted conduction-limited model, the convection-limited model predicts, and our experiments show, that cooling rates are proportional to the surface area to volume ratio, independent of the sample thermal conductivity, and inversely proportional to the product of sample density and heat capacity. We show that almost any material can be frozen at similar rates if the sample thickness, the cryogen, and the method and velocity of contact with cryogen are similar. Liquid ethane or propane cooled to liquid nitrogen temperature are shown to give the best results.

Specimens sandwiched between copper planchettes were plunged up to a depth of 430 mm into coolants used for cryofixation. Hydrated gelatin containing a miniature thermocouple was used to mimic the behaviour of tissue during freezing. Gelatin and red blood cells were used for ice-crystal analysis. Ethane produced the fastest cooling rates and the smallest ice-crystal profiles, and Freon 22 produced the slowest cooling rates and the largest crystal profiles. Smaller crystal profiles were often seen in the centre of the specimens than in subsurface zones. The results show that ethane, rather than propane, should be used for freezing metal-sandwiched freeze-fracture specimens by the plunging method, and probably also in the jet-cooling method. They further suggest that good cryofixation could occur at the centre of thin specimens rather than only at their surfaces. Comparison between theoretical and experimental ice-crystal sizes was satisfactory, indicating that where the experimental parameters can be defined then realistic predictions can be made regarding cryofixation results.

Liquid propane and similar coolants are used in the rapid freezing of biological specimens. These coolants form explosive gas mixtures with air, with a 14,000-fold increase in volume over that of the liquid. The liquefied gases have high vapour pressures and, unless they are maintained below their flashpoint, the vapour above them will reach ignitable concentrations. The flashpoint of liquid propane is -104 degrees C. Ethane has a higher vapour pressure, and vapour mixed with air above liquid ethane can be ignited at a coolant temperature of -130 degrees C. The danger is minimized if the coolant is maintained near its freezing point and under a nitrogen atmosphere, in a fume cupboard. Liquid nitrogen evaporates to a 690-fold increase in volume at room temperature. It is important to ventilate the working area, especially when cryo-sectioning in a small room, otherwise there is a possibility of asphyxiation.

Copyright of China Synthetic Fiber Industry is the property of Sinopec Baling Petrochemical Company and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We use global airborne observations of propane (C3H8) and ethane (C2H6) from the Atmospheric Tomography (ATom) and HIAPER Pole-to-Pole Observations (HIPPO), as well as U.S.-based aircraft and tower observations by NOAA and from the NCAR FRAPPE campaign as tracers for emissions from oil and gas operations. To simulate global mole fraction fields for these gases, we update the default emissions' configuration of C3H8 used by the global chemical transport model, GEOS-Chem v13.0.0, using a scaled C2H6 spatial proxy. With the updated emissions, simulations of both C3H8 and C2H6 using GEOS-Chem are in reasonable agreement with ATom and HIPPO observations, though the updated emission fields underestimate C3H8 accumulation in the arctic wintertime, pointing to additional sources of this gas in the high latitudes (e.g., Europe). Using a Bayesian hierarchical model, we estimate global emissions of C2H6 and C3H8 from fossil fuel production in 2016-2018 to be 13.3 ± 0.7 (95% CI) and 14.7 ± 0.8 (95% CI) Tg/year, respectively. We calculate bottom-up hydrocarbon emission ratios using basin composition measurements weighted by gas production and find their magnitude is higher than expected and is similar to ratios informed by our revised alkane emissions. This suggests that emissions are dominated by pre-processing activities in oil-producing basins.

Aim: The purpose of this article is to present the most important information and conclusions about gas-powered motor vehicles and the associated risks during fires and local emergencies. An additional area of consideration for the article’s authors is the challenges that emergency services may encounter during rescue and firefighting operations involving such vehicles. Introduction: Technological advances in propulsion systems used in vehicles and machinery pose a variety of challenges for fire protection. It results in the evolution of known threats and the emergence of new ones. Among other things, these developments have a significant impact on the technologies of rescue operations during fires and traffic accidents involving vehicles with different propulsion systems (increasingly using gaseous fuels). Equally important is ensuring fire safety when operating such vehicles. Methodology: On the basis of a review and analysis of the literature on the subject, as well as available research results, conclusions have been formu- lated regarding the fire safety of gas-powered vehicles. Aspects relevant to conducting rescue and firefighting operations involving such vehicles were taken into account. Conclusions: Necessary measures to improve fire protection, including the conduct of effective rescue and firefighting operations during incidents involving alternatively powered vehicles include: 1. Keeping as accurate a record as possible of fires and local emergencies involving the vehicles in question. 2. Urgently developed and updated educational materials that allow training, both for the rescuers and commanders of KSRG units, in blended learning mode, and systematically conducted such training. An example of this is the educational platform prepared by CNBOP-PIB in 2009 for OSP rescuers (rescue operations) and rural residents (handling emergency situations). The platform is still in place today, and although it needs updating, it has been used successfully for many years for training and professional development of a wide range of the rescuers. 3. A rescue database of vehicles involved in incidents urgently prepared and made available to the rescuers of firefighting units that are part of the KSRG. Such a base should be established immediately or be available on terms convenient to the rescue units (such as CRS or ERG). Keywords: alternative propulsion, CNG, LNG, methane, LPG, ethane, propane, methanol, fuel cells, emergency cards, fire safety

In this work, the explosion limits of three different natural gas mixtures (with various proportions of methane (CH 4), ethane (C 2 H 6), and propane (C 3 H 8)) have been investigated numerically based on detailed chemical kinetics. Furthermore, a comprehensive investigation of the effects of hydrogen (H 2) and inert gas (N 2 , CO 2) addition on the explosive properties of natural gas has been carried out. The results indicate that the C 3 H 8 components have a dominant effect on the explosion limits of natural gas. The addition of high-hydrocarbons in natural gas can significantly reduce the auto-ignition temperature, shorten the ignition delay time, and enhance the explosion risk of the mixture. Furthermore, the negative temperature coefficient (NTC) response of natural gas in the second explosion limit gradually disappears, and changes to the Z-curve response with the addition of H 2. However, the explosion tendency of the mixture is reduced with the addition of H 2 under normal to high-pressure conditions. In addition, with the increase of inert gas (N 2 , CO 2), the explosion limits of the mixtures shift upwards to a higher-pressure region, which significantly reduces the explosion tendency. Nevertheless, the explosion propensity of the mixture increases significantly under low-pressure conditions when the mixture contains hydrogen. To elucidate the critical control reactions and determine their synergistic effects, sensitivity analyses under different conditions are performed. Finally, the interaction of different fuels in natural gas mixtures is further summarized by analyzing the explosion limits of single-component, binary-component, and multi-component mixtures of hydrogen to propane. This paper provides an important guidance for the development of natural gas with high safety, low risk, and low pollution. [ABSTRACT FROM AUTHOR]

This article is devoted to the study of natural gas production by such methods as hydraulic fracturing, drilling, and underwater extraction. The authors analyzed the dynamics of gas production in Russia from old and new wells, as well as recovered from inactive wells, during the period from 2012 to 2021. Mathematical models have been selected to accurately represent the changes in the parameters under study. A forecast for natural gas production in 2025 has also been made, indicating an increase in natural gas production through hydraulic fracturing, drilling, and underwater extraction methods. [ABSTRACT FROM AUTHOR]

Aim: The aim of the article is to review information about motor vehicles that use alternative propulsion systems (in this case, electric propulsion) and the risks associated with their use. The discussion of these issues is crucial for undertaking rescue and firefighting operations during incidents (fires, local emergencies) involving alternatively powered vehicles and the effectiveness of these operations. Knowledge in the areas of: hazard identification, improvement of rescue technologies, necessary devices and equipment for effective rescue and firefighting operations during traffic incidents, including fires, with the involvement of vehicles with alternative propulsion systems can be gained from both theoretical and empirical studies. Introduction: Technical and technological advances in the area of drives used in vehicles and machinery pose new challenges for fire protection. They concern, among other things, the technology of rescue operations during fires and traffic accidents involving such vehicles, as well as ensuring fire safety when operating and storing them in buildings, garages and parking areas, and during charging. Methodology: The article was prepared based on national and foreign sources, literature on the subject, research results and the authors’ diverse experiences. It describes the current state of knowledge in terms of hazards and how to deal with them during rescue and firefighting operations against incidents involving alternatively powered vehicles. Conclusions: The number of motor vehicles in Poland and other countries continues to grow, and together with it also the number of vehicles equipped with alternative drives to internal combustion engines (gasoline, diesel). An analysis of the literature on the subject, available research results, as well as individual incidents, lead to the reasonable conclusion that the risks during rescue and firefighting operations associated with the incidents involving electric and hybrid vehicles are no greater than for conventionally powered vehicles. They are different to some extent, which is due in particular to the used power system, which is based on energy storage devices – batteries. Keywords: alternative propulsion, CNG, LNG, methane, LPG, ethane, propane, hybrid propulsion, electric vehicles, fuel cell, rescue, rescue and firefighting operations

Hydrate–liquid–vapour (HLV) equilibrium of aqueous clathrates formed from gas mixtures can be complex compared to hydrates formed with single guests. Typically, pressure and temperature are controlled to obtain these data, but for multicomponent systems, it is necessary to control/report more intensive variables, namely, composition. Metastability, manifested as impractically long experimental times, has been reported to be a challenge with some multicomponent systems. We present HLV equilibrium conditions of two ternary gas mixtures: methane + ethane + propane (90:7:3 molar ratio) and methane + propane + carbon dioxide (55:5:40 molar ratio). Conditions varied in the temperature range of 275–285 K and the pressure range of 1.24–4.75 MPa. Experimental standard uncertainties were on average 0.10 K and 0.005 MPa for methane + ethane + propane and 0.19 K and 0.005 MPa for methane + propane + carbon dioxide. Our technique allowed us to bypass the limitations reported in the literature and provided fast, reproducible HLV equilibria for gas‐dominated systems. [ABSTRACT FROM AUTHOR]

Copyright of Safety & Fire Technology (2657-8808) is the property of Centrum Naukowo-Badawcze Ochrony Przeciwpozarowej and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

[Display omitted] • C 2 H 6 + C 3 H 8 mixtures were investigated as a potential 'gas-phase modulator'. • Improved thermodynamic stability was observed by using C 2 H 6 + C 3 H 8 mixtures. • The maximum composition of H 2 in the C 2 H 6 + C 3 H 8 + H 2 hydrate was 44.37%. • Enhanced gas uptake and H 2 split fraction was observed as injected H 2 increased. As the global climate crisis intensifies with rising carbon dioxide (CO 2) concentrations, blue hydrogen (H 2) produced through the integration of CO 2 capture technologies is emerging as a promising alternative energy source and is challenging traditional fossil fuels in the de-fossilization paradigm. Gas hydrate could be one of the feasible storage medium for energy-efficient H 2 storage, due to its potential for eco-friendly features and high H 2 storage capacity. However, extreme thermodynamic formation conditions for pure H 2 hydrate need to be mitigated for practical application. Here, we demonstrate a novel approach by blending a 'gas-phase modulator' with H 2 , specifically a C 2 H 6 (70%) + C 3 H 8 (30%), to enable hydrate-based H 2 storage under moderate thermodynamic formation conditions. In this study, we systematically examined thermodynamic stability, crystallographic structure, guest occupation behavior, and the formation kinetics of the C 2 H 6 + C 3 H 8 + H 2 hydrates by varying the H 2 composition. The results revealed that the C 2 H 6 + C 3 H 8 mixture played a notable role in promoting thermodynamic formation condition of H 2 hydrates. The mixed C 2 H 6 + C 3 H 8 + H 2 hydrates were predominantly comprised of sII hydrate, with small amount of sI hydrate. Considering the small to large cage ratio of sI and sII hydrate, this observation indicates a significant advantage for H 2 storage due to primarily occupation behavior of H 2 into the small cages. In addition, as the H 2 composition in the feed gas increased, we confirmed that not only that H 2 storage in the hydrate was enhanced but also that the degree of the H 2 enclathration ratio into the hydrate was elevated. Moreover, the maximum composition of H 2 in the C 2 H 6 (14%) + C 3 H 8 (6%) + H 2 (80%) hydrate was 44.37%. Hence, we believe that our findings can contribute valuable insights into the potential application of gas-phase modulators for hydrate-based H 2 storage, we emphasize that C 2 H 6 + C 3 H 8 can act as a potential gas-phase modulator for energy-efficient H 2 storage. [ABSTRACT FROM AUTHOR]

Research in ultra-low temperature refrigeration applications has intensified in recent years after the appearance of vaccines in response to the COVID-19 pandemic. There are few current technologies for this low-temperature range, with reduced energy performance and high global warming potential refrigerants. This work analyses the introduction of the ejector in two-stage cascade cycles for ultra-low temperature refrigeration. The proposal includes the assessment of the behaviour of the ejector while implementing it in a single stage or simultaneously in both stages. The study is carried out with refrigerants R-290 in the high-temperature stage and R-170 in the low-temperature stage since these are natural refrigerants with very low global warming potential. The results show that the ejector is a component that causes improvements in the cycle when placed in the high-temperature and low-temperature stages. On the other hand, changing evaporation and condensation temperatures, the evaporation temperature is more critical regarding cycle energy performance. With the results obtained, a cascade cycle with an ejector in both stages is proposed, obtaining a 21% higher coefficient of performance than the standard cascade cycle. Also, the cycle with the ejector in both stages causes an improvement of 13.6% compared to the previous generation's refrigerants (R-23 and R-507A) in the same cycle. The carbon footprint analysis shows that this cycle emits less than half of the equivalent CO2 than actual cycles for ultra-low temperatures, also with a new refrigerant like R-472A.

Objective The co-cracking technology of ethane and propane is optimized. Methods The BSPA ethylene cracking evaluation test equipment of KBR company is used to optimize the separate cracking of ethane and propane and the blending cracking technology according to different ratios in the laboratory. Results When the blend proportion of ethane is 20 %- 90 %, t he yields of ethylene, diene and triene are increased. When the blend proportion of ethane is 80%-90%, the highest yields of ethylene, diene and triene are 55. 28 %, 56. 05 % and 58. 01 %, respectively. Conclusion T he optimized result is applied in industrial ethylene cracking plant, the total ethylene yield and the diene yield don't decrease when the proportion of light cracking feedst0ck in t he whole cracking feedstock reduced more than 10%, and the remarkable industrial application effect has been obtained. [ABSTRACT FROM AUTHOR]

Copyright of Safety & Fire Technology (2657-8808) is the property of Centrum Naukowo-Badawcze Ochrony Przeciwpozarowej and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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 vanadium (V)-nitrogenase of Azotobacter vinelandii catalyses the in vitro conversion of carbon monoxide (CO) to hydrocarbons. Here we show that an A. vinelandii strain expressing the V-nitrogenase is capable of in vivo reduction of CO to ethylene (C2H4), ethane (C2H6) and propane (C3H8). Moreover, we demonstrate that CO is not used as a carbon source for cell growth, being instead reduced to hydrocarbons in a secondary metabolic pathway. These findings suggest a possible role of the ancient nitrogenase as an evolutionary link between the carbon and nitrogen cycles on Earth and establish a solid foundation for biotechnological adaptation of a whole-cell approach to recycling carbon wastes into hydrocarbon products. Thus, this study has several repercussions for evolution-, environment- and energy-related areas.

Membrane technologies are widely used in various modern technological processes. In the chemical industry, membranes are used to solve several problems from increasing the efficiency of targeted processes to ensuring strict environmental legislation. A special synergistic effect is expected in the field of membrane catalysis when it becomes possible not only to accelerate the main reaction using a catalyst affecting the kinetics of the process but also shift the reaction equilibrium toward the products due to the membrane separation of one or more products from the main reaction volume. This advantage of membrane catalytic technologies is especially in demand for endothermic processes. This mini review is devoted to the dehydrogenation of hydrocarbons exemplified by the production of the high demand monomers ethylene, propylene, and styrene and the dehydrogenation of alcohols exemplified by methanol as a key compound of the C1 chemistry. [ABSTRACT FROM AUTHOR]

• A propane low-temperature package refrigeration unit has been retrofitted to operate with ethane at ultra-low temperature. • The retrofitted system has been experimentally tested between -80 °C and -65 °C of evaporating temperature. • The systems showed a COP between 0.6 and 1.6 in the experimented range. • The reliability of the system has been assessed by evaluation of the power consumption and the discharge temperature. While the global refrigeration capacity installed in ultra-low temperature applications is considerably lower than in standard refrigeration, the interest in such systems has risen during the last months due to their emerging demand for the preservation of mRNA vaccines. Several theoretical studies can be found in the literature for ultra-low temperature applications. However, there is still a lack of reliable experimental data that may be used for the models validation and, thereby, to perform more rigorous investigations. In light of this, the present manuscript proposes an ultra-low temperature refrigeration unit based on an indirect cascade system, developed by retrofitting a standard low-temperature R290 packaged unit. In this investigation, firstly, the suitability of the original components is assessed and, then, the unit is experimentally tested within a wide range of operating conditions. Thereby, the system's reliability is evaluated by assessing different parameters, such as discharge, condensing and evaporating temperatures and performance ratios. The main results showed a successful behaviour at the operating conditions tested, exhibiting a COP that ranged from 0.6 to 1.6 for cold room temperatures between -80 °C and -65 °C, respectively. [ABSTRACT FROM AUTHOR]

A growing dependence on natural gas for energy may exacerbate emissions of the greenhouse gas methane (CH4). Identifying fingerprints of these emissions is critical to our understanding of potential impacts. Here, we compare stable isotopic and alkane ratio tracers of natural gas, agricultural, and urban CH4 sources in the Barnett Shale hydraulic fracturing region near Fort Worth, Texas. Thermogenic and biogenic sources were compositionally distinct, and emissions from oil wells were enriched in alkanes and isotopically depleted relative to natural gas wells. Emissions from natural gas production varied in δ(13)C and alkane ratio composition, with δD-CH4 representing the most consistent tracer of natural gas sources. We integrated our data into a bottom-up inventory of CH4 for the region, resulting in an inventory of ethane (C2H6) sources for comparison to top-down estimates of CH4 and C2H6 emissions. Methane emissions in the Barnett are a complex mixture of urban, agricultural, and fossil fuel sources, which makes source apportionment challenging. For example, spatial heterogeneity in gas composition and high C2H6/CH4 ratios in emissions from conventional oil production add uncertainty to top-down models of source apportionment. Future top-down studies may benefit from the addition of δD-CH4 to distinguish thermogenic and biogenic sources.

An effect of hydrogen additions to the initial mixture on the parameters of the oxidative cracking of propane at atmospheric pressure, temperatures of 500–750°C, reaction time of 2 s, and С3H8/О2 initial ratio ~2 was experimentally investigated. It was shown that small amounts of hydrogen promote the process due to the formation of additional active radicals OH• and H•. Performance of the oxidative cracking of propane in a large excess of hydrogen results in an increase in the yield of methane and ethane, while the yield of ethylene, the target product of the process, decreases. [ABSTRACT FROM AUTHOR]

• New experiemental IDTs for binary bleneded C 2 –C 3 alkanes/alkene are presented. • Newly developed NUIGMech1.1 is evaluated versus the newly taken IDTs. • NUIGMech1.1 predicts the IDTs accurately over the wide range of studied conditions. • Some correlations were derived based on NUIGMech1.1. • The correlations satisfactorily anticipated IDTs data within the studied range. In this work, the ignition delay time characteristics of C 2 – C 3 binary blends of gaseous hydrocarbons including ethylene/propane and ethane/propane are studied over a wide range of temperatures (750 – 2000 K), pressures (1 – 135 bar), equivalence ratios (φ = 0.5 – 2.0) and dilutions (75 – 90%). A matrix of experimental conditions is generated using the Taguchi (L 9) approach to cover the range of conditions for the validation of a chemical kinetic model. The experimental ignition delay time data are recorded using low- and high-pressure shock tubes and two rapid compression machines (RCM) to include all of the designed conditions. These novel experiments provide a direct validation of the chemical kinetic model, NUIGMech1.1, and its performance is characterized via statistical analysis, with the agreement between experiments and model being within ~ 26.4% over all of the conditions studied, which is comparable with a general absolute uncertainty of the applied facilities (~ 20%). Sensitivity and flux analyses allow for the key reactions controlling the ignition behavior of the blends to be identified. Subsequent analyses are performed to identify those reactions which are important for the pure fuel components and for the blended fuels, and synergistic/antagonistic blending effects are therefore identified over the wide range of conditions. The overall performance of NUIGMech1.1 and the correlations generated are in good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

• Experimental speeds of sound for carbon monoxide and ethane or propane mixtures are reported in the gas region. • An accurate spherical resonator was used for the measurements. • Experimental data were fitted to a virial-type equation. • Isobaric heat capacities as perfect gas were derived from the speeds of sound. • The results were compared with reference EoS such as GERG-2008 and AGA8-DC92. Speed of sound data are reported for (carbon monoxide + ethane) and (carbon monoxide + propane) mixtures in the gas region at mole fractions of carbon monoxide of 0.25, 0.5 and 0.75 in the temperature range from 273.15 K to 350 K for mixtures containing ethane, and compositions x CO = 0.5 and 0.75 at T = (260 to 350) K for mixtures with propane. Measurements are performed by means of a spherical acoustic resonator with an expanded relative uncertainty (k = 2) better than 250 parts in 106. Experimental data are fitted to a virial type equation, obtaining standard deviations within the uncertainty of the measurements, and the adiabatic coefficient as perfect gas is derived from this fitting. Finally, all these data are compared to GERG-2008 and AGA92-DC equations of state, which are used as reference in the gas industry. [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.

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]

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. [ABSTRACT FROM AUTHOR]

In this study, two novel integrated single mixed refrigerant (SMR) processes are proposed to coproduce liquefied natural gas (LNG) and high-purity liquid ethane, which are suitable for improving the economic benefits of high ethane-containing natural gas. In Process 1, cryogenic distillation and conventional SMR process are integrated to separate ethane while producing LNG. Since the distillation pressure is below the critical pressure of methane, heat transfer temperature difference in the low temperature section may be relatively large. Therefore, in Process 2, the pressure of natural gas is increased by adding a compressor after the distillation column. Aspen HYSYS is used to simulate the proposed processes, and the key parameters of the refrigeration cycles are optimized by genetic algorithms. Based on the comprehensive consideration of initial investment and operating cost, Process 2 is recommended for large-scale plant, while Process 1 for small-scale plant and situations with requirement of simple system, for example floating LNG production (FLNG). Furthermore, a simplified Process 1, with propane eliminated from the mixed refrigerant, is presented for better adaption to FLNG conditions. [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]

The combined use of experimental viscosity ratios together with ab initio calculations for helium has driven significant improvements in the description of dilute gas transport properties. Here, we first use improvements made to ab initio helium calculations to update viscosity ratios measured for H2, Ar, CH4, and Xe by May et al. [Int. J. Thermophys. 28, 1085 (2007)] over the temperature range of 200–400 K, reducing the uncertainties of the data to 0.055%, 0.038%, 0.067%, and 0.084%, respectively. Separately, we extend the technique of combining viscosity ratios with ab initio calculations to develop new reference correlations for the dilute gas viscosity of 10 gases: helium, neon, argon, krypton, xenon, hydrogen, nitrogen, methane, ethane, and propane. This is achieved by combining the ratios of viscosities calculated ab initio at the target temperature and at 298.15 K with experimentally based reference viscosity values for each gas at 298.15 K. The new reference dilute gas viscosity correlations span temperature ranges from at least 150 K to 1200 K with relative uncertainties between 30% (krypton) and 85% (methane) lower than the original ab initio results. For the noble gases, ab initio calculations for the Prandtl number are used to develop reference correlations for thermal conductivity ranging from at least 100 K to 5000 K, with relative uncertainties ranging from 0.04% (argon) to 0.20% (xenon). The new reference correlations are compared with available experimental data at dilute gas conditions. In general, the data agree with the new correlations within the claimed experimental uncertainty. [ABSTRACT FROM AUTHOR]

It is shown that the method of synthesis and source of bismuth greatly affect the physicochemical properties of modified MoVTeNbO catalysts. Adding an organic bismuth compound with a neutral pH at the stage of mixing the solutions of the initial components is accompanied by precipitation and the formation of inactive phases when the required M1 phase is missing. Regardless of the nature of the initial bismuth compound, introducing it into a dry MoVTeNb precursor leads to considerable destruction of it, resulting in a lower content of the M1 phase and the formation of binary V–Mo and Te–Мo oxides. It has been established that the ethylene yield attains a maximum (76.5 %) in the oxidative ethane dehydrogenation (OED)reaction, when the calcined MoVTeNb oxide catalyst is impregnated with a bismuth organic compound solution. The yield of acrylic acid is ≈48% over the same catalyst in the reaction of propane oxidation. Introducing bismuth nitrate into a solution of the initial components is nevertheless a more technologically advanced way of preparing bismuth-containing catalysts. The maximum ethylene yield is ≈76% in the OED reaction over the catalyst obtained using bismuth nitrate. [ABSTRACT FROM AUTHOR]