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Hydrogen is not only an important industrial chemical but also an energy carrier with increasing demand. However, the current production techniques are based on technologies that result in massive CO2 emissions. In contrast, the pyrolysis of alkanes in a liquid metal bubble column reactor does not lead to direct CO2 emissions. In order to transfer this technology from lab-scale to industrial applications, it has to be scaled up and the influences of the most common constituent of natural gas on the pyrolysis process have to be determined. For this study, the liquid metal bubble column technology developed at the KIT was scaled up by a factor of 3.75, referred to as the reactor volume. In this article, the experimental setup containing the reactor is described in detail. In addition, new methods for the evaluation of experimental data will be presented. The reactor, as well as the experimental results from pure methane pyrolysis (PM), will be compared to the previous generation of reactors in terms of methane conversion. It could be proven that scaling up the reactor volume did not result in a decrease in methane conversion. For part II of this publication, methane-ethane (MEM) gas mixtures and high calorific natural gas (nGH) were pyrolyzed, and the results were discussed on the basis of the present part I.

Although polyethylene (PE) and polypropylene (PP) are by far the world's largest volume plastics, only a tiny fraction of these energy-rich polyolefins are currently recycled. Depolymerization of PE to its constituent monomer, ethylene, is highly endothermic and conventionally accessible only through unselective, high-temperature pyrolysis. Here, we provide experimental demonstrations of our recently proposed tandem catalysis strategy, which uses ethylene to convert PE to propylene, the commodity monomer used to make PP. The approach combines rapid olefin metathesis with rate-limiting isomerization. Monounsaturated PE is progressively disassembled at modest temperatures via many consecutive ethenolysis events, resulting selectively in propylene. Fully saturated PE can be converted to unsaturated PE starting with a single transfer dehydrogenation to ethylene, which produces a small amount of ethane (1 equiv per dehydrogenation event). These principles are demonstrated using both homogeneous and heterogeneous catalysts. While selectivity under batch conditions is limited at high conversion by the formation of an equilibrium mixture of olefins, high selectivity to propylene (≥94%) is achieved in a semicontinuous process due to the continuous removal of propylene from the reaction mixture.

In the recent study, the dehydrogenation of isobutane to isobutene was accomplished using a NiO/γ-Al2O3 catalyst, and significant improvement in the time-on-stream yield of isobutene was accomplished. During the normal catalytic dehydrogenation of alkanes, the catalyst is covered by the carbon deposition that is generated during the reaction, which drastically reduces activity with time-on-stream. Therefore, no examples of the catalytic dehydrogenation of isobutane have yet been reported. This study used either ethane or propane as a source of isobutane to examine whether the activity was improved with time-on-stream. As a result, in the dehydrogenations of both ethane and propane on a NiO/γ-Al2O3 catalyst, the catalytic activity decreased with time-on-stream when the supporting amounts of NiO was small. By contrast, when the supporting amount of NiO was large, the catalytic activity improved with time-on-stream. The results using a NiO/γ-Al2O3 catalyst with small and large NiO loadings were similar to those of isobutane dehydrogenation and it was confirmed that the dehydrogenation activity was improved with time-on-stream in the catalytic dehydrogenations of ethane, propane, and isobutane using large NiO loadings. Intermediate behavior using a moderate amount of NiO loading, which was not detected in the dehydrogenation of isobutane, was also observed, which resulted in a maximum yield of either ethylene or propylene at 2.0 or 3.25 h on-stream, respectively. We concluded that the reason the catalytic activity did not improve with time-on-stream when using a NiO/γ-Al2O3 catalyst was because the supporting amount of NiO was too small. These results show that activity with time-on-stream could also be improved in the dehydrogenations of other alkanes.

Co/TiO2 catalysts with different cobalt loadings (3.8, 7.5 and 15 wt%) were prepared by impregnation method of Co(NO3)2 6H2O over titania. Samples containing Co(NO3)2·6H2O and TiO2 in stoichiometric proportions in order to obtain CoTiO3 and Co2 TiO4 phases were also synthesized. The effect of the calcination treatment at two different temperatures, 550 and 1150 °C, was investigated. Characterizations by several techniques, such as XRD, UV–vis–NIR, DRS, Raman and XPS, were carried out. XRD showed the coexistence of three phases: CoTiO3; Co2TiO4 and Co3O4 after calcination at 550 °C, while calcination at high temperature (1150 °C) led to single-phase systems (CoTiO3 or Co2TiO4). Diffuse reflection and XPS spectroscopy showed that divalent cobalt occupies octahedral sites in the ilmenite phase, and both tetrahedral and octahedral sites in the spinel phase. The catalytic performances of the prepared catalysts were evaluated in the oxidative dehydrogenation reaction (ODH) of ethane to ethylene, as a function of the Co content for Co/TiO2 catalysts and as a function of the calcination temperatures for the CoTiO3 and Co2TiO4 phases. Co(7.5)/TiO2 was the most active, although the conversion of ethane decreased in the first 150 min of the reaction, reaching values comparable to those of Co2TiO4 and CoTiO3; however, Co(7.5)/TiO2 was confirmed as having the best selectivity to ethylene in comparison with the bulk phases, CoTiO3 and Co2TiO4. The influence of the reaction mixture composition, specifically the presence of water, at different percentages, was investigated. There is a decrease in the overall ethane conversion and an increase in the ethylene selectivity when the percentage of water increases. This behavior can likely be attributed to an increase in the surface concentration of hydroxyl species (OH), resulting in heightened surface acidity.

This contribution presents the results of continued investigations on the production of hydrogen by means of pyrolysis in a liquid metal bubble column reactor, as developed at the Karlsruhe Institute of Technology in recent years. Part I of this contribution described the motivation and the methodology of this study, as well as a significant scale-up, and discussed its results for pure methane pyrolysis. Here in part II, two additional experimental campaigns with methane–ethane mixtures (MEMs) and high-calorific natural gas (nGH) will be presented and discussed for the first time, using the up-scaled liquid metal bubble column reactor. It could be proven that an MEM as the feed gas led to an increase in methane conversion at low temperatures, which is consistent with the literature data. The nGH pyrolysis confirms this trend and also results in a significant rise in methane conversion compared to pure methane pyrolysis. Furthermore, the nGH pyrolysis leads to an increased methane conversion even at higher temperatures compared to MEM pyrolysis. Additionally, both MEM and nGH pyrolysis also showed a shift in the formation of by-products toward lower temperatures.

Numerical computations comprising of Grand Canonical-Monte Carlo (GCMC) and Canonical Statistical Ensemble (NVT) Molecular Dynamics (MD) simulations were used to study the diffusion and sorption characteristics primarily for methane, ethane, and ethene molecules and for their ternary mixtures at different temperatures in ZIF-8 porous material. Methane as pure component or in mixture proved to be the sorbed hydrocarbon with the higher molecular mobility at the temperature range of 273-373 K among alkanes and alkenes. In addtion, alkenes were the hydrocarbons with the higher self-diffusion coefficients compared to the respective alkanes. In the ternary mixtures ethane was preferentially sorbed in ZIF-8 at all temperatures studied. Direct comparisons of the self-diffusivity data obtained from the NVT-MD simulations with recently reported Magic Angle Spinning Pulsed Field Gradient Nuclear Magnetic Resonance (MAS PFG NMR) measurements showed reasonable agreement. Furthermore, the NVT-MD self-diffusivity coefficients in conjunction with the aforementioned MAS PFG NMR experimental measurements, and sorption thermodynamic data obtained from the present GCMC simulations were utilized for the development of individual Artificial Neural Networks (ANNs) predictive modeling procedures in order to provide additional quantitative and qualitative information regarding the diffusion and sorption of small alkanes, alkenes in ZIF-8. The ANNs predictions were in good agreement with the experimental measurements and with the molecular simulation data. The modeling and analysis capabilities of ANNs along with their fast computations using moderate computer resources can significantly assist the irreplaceable molecular simulation and experimental approaches to cope with complicated problems at the molecular level.

The photocatalytic reduction of carbon dioxide (CO

Glycerin, a low-valued waste from biodiesel production, and dopamine were used as precursors for adsorbent materials. The study is centered on the preparation and application of microporous activated carbon as adsorbent materials in the separation of ethane/ethylene and of gases that are natural gas or landfill gas components (ethane/methane and carbon dioxide/methane). The activated carbons were produced by the following sequence reactions: facile carbonization of a glycerin/dopamine mixture and chemical activation. Dopamine allowed the introduction of nitrogenated groups that improved the selectivity of the separations. The activating agent was KOH, but its mass ratio was kept lower than one to improve the sustainability of the final materials. The solids were characterized by N2 adsorption/desorption isotherms, SEM, FTIR spectroscopy, elemental analysis, and point of zero charges (pHPZC). The order for adsorption of the different adsorbates (in mmolg−1) on the most well performing material—Gdop0.75—is methane (2.5) < carbon dioxide (5.0) < ethylene (8.6) < ethane (8.9).

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.

As a novel reaction mode of oxidative dehydrogenation of ethane to ethylene, the chemical looping oxidative dehydrogenation (CL-ODH) of ethane to ethylene has attracted much attention. Instead of using gaseous oxygen, CL-ODH uses lattice oxygen in an oxygen carrier or redox catalyst to facilitate the ODH reaction. In this paper, a perovskite type redox catalyst LaMnO3+δ was used as a substrate, Ce3+ with different proportions was introduced into its A site, and its CL-ODH reaction performance for ethane was studied. The results showed that the ratio of Mn4+/Mn3+ on the surface of Ce-modified samples decreased significantly, and the lattice oxygen species in the bulk phase increased; these were the main reasons for improving ethylene selectivity. La0.7Ce0.3MnO3 showed the best performance during the ODH reaction and showed good stability in twenty redox cycle tests.

Atmospheric methane plays a significant role in warming the climate. Characterizing its sources and sinks is important for future climate and air quality impacts. Global methane background trends suggest a sustained increase in emissions since 2007. There is no debate that reducing anthropogenic (human-driven) emissions can lead to short-term decreases in atmospheric methane, posing an attractive avenue towards mitigating climate change. Yet, effective policy to limit emissions from energy-related activities relies on accurate emission estimates, and historically, it has been challenging to diagnose both the magnitude and origin of methane leaks from a wide range of facilities and components across production, transmission, storage, and distribution systems. We present a novel Bayesian hierarchical model to improve methane emission estimates on global and regional scales from oil and gas processes. We also present methods to optimize time and cost of model simulations of certain trace gases, including several of which have important climate implications. Finally, we present our efforts in characterizing fossil methane from burgeoning oil production in Oklahoma and Texas using long term ground-based remote-sensing observations combined with Stochastic Time-Inverted Larangian Transport modeling.

This thesis discusses the binding of alkanes (saturated hydrocarbons) to transition metal complexes. The thesis describes: (i) the first direct Nuclear Magnetic Resonance (NMR) spectroscopic observation of alkane coordination to group 8 transition metal centres; (ii) the only complete group of analogous transition metal alkane σ-complexes (Fe, Ru and Os); and (iii) the first set of methane σ-complexes, formed from molecular methane, that are sufficiently stable to analyse using NMR spectroscopy. Chapter 1 is a general introduction for the non-specialist, introducing the concepts of coordination chemistry and in particular the formation of σ-complexes including complexes of molecular hydrogen and alkanes. Chapter 2 contains an introduction to methane in organometallic chemistry and describes results from low temperature NMR spectroscopic and computational investigations into the methane σ-complexes [η5-CpM(CO)2(CH4)][Al(OC(CF3)3)4] (M = Os (5), Ru (13), Fe (17)) that were produced using an improved in situ NMR sample photolysis apparatus. The bound methane fragments in 5, 13 and 17 have 1H resonances at δ −2.16, δ −2.10 and δ −4.27; 13C resonances at δ −56.3, δ −48.8, and δ −53.0; and 1J C-H couplings of 127 Hz, 126 Hz, and 126 Hz respectively. Of these three species, 13 is the least stable and 5 is the most stable. DFT and ab initio calculations provide further insight into the structures of the [η5-CpM(CO)2(CH4)]+ (M = Os (5), Ru (13) and Fe (17)) complexes and find that the binding free energies of 5, 13 and 17 are -13.6 kcal mol- 1, -10.5 kcal mol-1 and -11.7 kcal mol-1 respectively. Chapter 3 describes results from the low temperature NMR spectroscopic and computational investigations into the ethane σ-complex [η5-CpOs(CO)2(C2H6)][Al(OC(CF3)3)4] (19). The proton resonances, at δ −2.39 (for the osmium-bound CH3) and δ 1.32 (for and the non-bound CH3) were correlated to 13C resonances at δ −30.7 and δ 11.1 respectively. DFT calculations support the observation that there is no exchange observed between the bound and non-bound methyl groups at temperatures as high as -75 ℃, with calculations predicting the barrier to exchange to be a relatively high value of 13.7 kcal mol-1. NMR data show that 19 is more stable than the methane analogue 5, discussed in Chapter 2, consistent with the free energy of binding being calculated to be higher in the case of the ethane complex (-16.6 kcal mol-1). Chapter 4 describes results from the low temperature NMR spectroscopic investigations into the cyclopentane σ-complexes [η5-CpM(CO)2(c-C5H10)][Al(OC(CF3)3)4] (M = Os (20), Ru (22), Fe (23)). The cyclopentane σ-complexes show the same trend in stability as was reported for the methane complexes (20 > 23 > 22). The osmium centred cyclopentane σ-complex (20) is the most stable of the cyclopentane σ-complexes studied here and is sufficiently stable to be observed in solution for a short period (t1/2 = 7.8 mins) at temperatures as high as -50 ℃, making it one of the most stable alkane σ-complexes to be studied in the solution state. Chapter 5 describes preliminary results from the low temperature NMR spectroscopic investigation into the n -pentane σ- complexes [η5-CpM(CO)2(n -C5H12)][Al(OC(CF3)3)4] (M = Os (24) and Ru (25)). NMR data show that the osmium complex preferentially binds methyl groups during UV irradiation, but in the dark the methyl-bound species isomerises to preferentially bind the methylene groups. The ruthenium complex (25) shows a preference to bind via methylene groups under all conditions examined. Chapter 6 draws some overarching conclusions from the investigations presented in this thesis and gives some suggestions to direct future studies in this field. Chapter 7 describes the design and production of an improved experimental apparatus for conducting in situ photolysis of NMR samples with added gaseous reagents and describes the experimental procedures and synthesis of precursor compounds.

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.

The absolute coverage of CO has been a missing piece in the mechanistic puzzle of the CO reduction reaction (CORR) on Cu. For the first time, we revealed the upper bound of the CO coverage under electrocatalytic conditions to be 0.05 monolayer at atmospheric pressure and the saturation CO coverage to be ∼0.25 monolayer by conducting surface enhanced infrared spectroscopy at CO pressures up to 60 barg in a custom-designed spectroelectrochemical cell. CORR activities on Cu were also determined in the same pressure range. Calculated reaction orders of C

Adsorbed natural gas (ANG) is a promising solution for improving the safety and storage capacity of low-pressure gas storage systems. The structural–energetic and adsorption properties of active carbon ACPK, synthesized from cheap peat raw materials, are presented. Calculations of the methane–ethane mixture adsorption on ACPK were performed using the experimental adsorption isotherms of pure components. It is shown that the accumulation of ethane can significantly increase the energy capacity of the ANG storage. Numerical molecular modeling of the methane–ethane mixture adsorption in slit-like model micropores has been carried out. The molecular effects associated with the displacement of ethane by methane molecules and the formation of a molecule layered structure are shown. The integral molecular adsorption isotherm of the mixture according to the molecular modeling adequately corresponds to the ideal adsorbed solution theory (IAST). The cyclic processes of gas charging and discharging from the ANG storage based on the ACPK are simulated in three modes: adiabatic, isothermal, and thermocontrolled. The adiabatic mode leads to a loss of 27–33% of energy capacity at 3.5 MPa compared to the isothermal mode, which has a 9.4–19.5% lower energy capacity compared to the thermocontrolled mode, with more efficient desorption of both methane and ethane.

At a time of unpredictable challenges for health, one trend is certain: there is an exceedingly high demand for functional implants, particularly bone grafts. This has encouraged the emergence of bone tissue engineering substitutes as an alternative method to conventional bone grafts. However, the current approaches in the field face several limitations that have prevented the ultimate translation into clinical settings. As a result, many attempts have been made to fabricate synthetic bone implants that can offer suitable biological and mechanical properties.Light curable methacrylate-based polymers have ideal properties for bone repair. These materials are also suitable for 3D printing which can be applicable for restoration of both function and aesthetics. The main objective of this research was to investigate the role of calcium phosphate (CaP) incorporation in a mechanically stable, biologically functional and 3D printable polymer for the reconstruction of complex craniofacial defects. The experimental work initially involved the synthesis of (((((((((((3R,3aR,6S,6aR)- hexahydrofuro[3,2-b]furan-3,6-diyl)bis(oxy))bis(ethane-2,1- 48 diyl))bis(oxy))bis(carbonyl))bis(azanediyl))bis(3,3,5-trimethylcyclohexane-5,1- 49 diyl))bis(azanediyl))bis(carbonyl))bis(oxy))bis(ethane-2,1-diyl) bis(2-methylacrylate) referred to as CSMA and fabrication of composite discs via a Digital Light Printing (DLP) method. The flow behaviour of the polymer as a function of CaP addition, surface remineralisation potential, in vitro cell culture, using MC3T3 and Adipose-Derived Mesenchymal Stem Cells (ADSCs) and ex ovo angiogenic response was assessed. Finally, in vivo studies were carried out to investigate neo-bone formation at 4- and 8-weeks post-implantation. Quantitative micro-CT and histological evaluation did not show a higher rate of bone formation in CaP filled CSMA composites compared to CSMA itself. Therefore, such polymeric systems hold promising features by allowing more flexibility in designing a 3D printed scaffold targeted at the reconstruction of maxillofacial defects.

Five- and six-coordinate cationic bis(phosphine) cobalt(III) metallacycle complexes were synthesized with the general structures, [(depe)Co(cycloneophyl)(L)(L′)][BArF4] (depe = 1,2-bis(diethylphosphino)ethane; cycloneophyl = [κ-C:C-(CH2C(Me)2)C6H4]; L/L′ = pyridine, pivalonitrile, or the vacant site, BAr4F = B[(3,5-(CF3)2)C6H3]4). Each of these compounds promoted facile directed C(sp2)–H activation with exclusive selectivity for ortho-alkylated products, consistent with the selectivity of reported cobalt-catalyzed arene-alkene-alkyne coupling reactions. The direct observation of C–H activation by cobalt(III) metallacycles provided experimental support for the intermediacy of these compounds in this class of catalytic C–H functionalization reaction. Deuterium labeling and kinetic studies provided insight into the nature of C–H bond cleavage and C–C bond reductive elimination from isolable cobalt(III) precursors.

Diastereo- and enantioselective kinetic resolution of racemic planar-chiral 1-iR/i-2-vinylferrocenes (irac/i-b1/b) was attained by the molybdenum-catalyzed asymmetric metathesis dimerization (AMD). Two sequential AMD reactions ofirac/i-b1a/b(R = Br) provided (iE/i)-(iS/i,iS/i)-1,2-di(2-bromoferrocenyl)ethylene ingt;99% ee, which was converted to (iS/i,iS/i)-1,2-bis[(2-diphenylphosphino)ferrocenyl]ethane (iS/i,iS/i)-b5/b. Planar-chiral bisphosphine (iS/i,iS/i)-b5/bcoordinated to a dichloropalladium(II) fragment in aitrans/i-chelating fashion, which was applied as a chiral ligand in the palladium-catalyzed asymmetric allylic alkylation showing enantioselectivity of up to 90% ee.

[ES] Resumen del trabajo: El objetivo del trabajo es diseñar un ultracongelador capaz de almacenar unos (150-200) litros de vacunas Pzizer a una temperatura en el rango de los (-85,-80) grados celcius utilizando un ciclo de refrigeración en cascada con refrigerantes naturales( etano para la primera etapa y propano para la segunda etapa), para ello, se realizaran los siguientes pasos: 1- Dimensionar las paredes interiores del congelador teniendo en cuenta las dimensiones de las cajas de vacunación. 2-Dimensionar las paredes exteriores mediante el cálculo del grosor de las diferentes capas utilizadas para aislar termicamente el congelador. 3-sketch en 3D del ultracongelador ya con las dimensiones calculadas. 4-Definir los parametros de trabajo y con ellos la capacidad de enfriamento necesaria del ciclo, teniendo en cuenta las pérdidas de calor y el uso diario del congelador( que se abra la puerta dos veces al dia durante 20 segundos). 5- Diseño del ciclo de refrigeración en cascada y selección de componentes en el mercado para cumplir los parámetros de trabajo. 6- Diseño del condensador de la segunda etapa,el cual incluiria un ventilador., [EN] Due to the rapidly increasing demand by pharmaceutical companies to transport and store COVID-19 vaccines to combat the pandemic that is currently affecting us all, the demand for ultra-low temperature freezers has increased significantly in the past years, therefore the objective of this diploma thesis is the design of an ultra-low temperature freezer for vaccine or other medical uses. To achieve extremely low temperatures (-70 °C to -85 °C) a, it has to be noticed that safety precautions would need to be taken into consideration in the use of the HC pair due to their flammability hazard. Nowadays, Low-temperature circuit cascade refrigeration systems usually use ozone-depleting or global warming (CFC and HCFC) refrigerants, therefore there is an increasing interest in the investigation and development of natural refrigerants in this type of system. Carbon dioxide is a nonflammable, easily obtained refrigerant that does not damage the ozone layer and has a very low global warming potential, however it works at higher temperatures and pressures than HFCs and other natural refrigerants[1]. For low-temperature applications, ethane has the best refrigerant effect and performance, as shown in [2] where theoretical analysis with nitrous oxide, ethane, and ethylene as the LT fluids in a cascaded system was made. Propane is going to be our HT refrigerant as it has a low price, a low GWP (3), and excellent thermodynamic properties, which lead to high energy efficiency, for example, the latent heat of vaporization of propane is almost two times higher than that of the most common HFC refrigerants[3]. All this information will be later discussed when designing the CRS system which will lead us to highly recommend the use of the HC pair (R290/R170) both in the transportation and storage of COVID-19 vaccines. The design of the Ultra-low freezer will follow a logical process of steps trying to emulate the approach a real cold-storage company would take.

Aromatization of light hydrocarbons can contribute to a secure supply of aromatics for the chemical industry. In this work, we investigate the influence of modification of zeolite ZSM-5 with Ga and Mo on the reaction mechanism underlying the activation and aromatization of ethane. Well-defined Mo/ZSM-5 and Ga/ZSM-5 zeolites efficiently promote ethane aromatization to benzene-toluene-xylene mixtures. Both catalysts suffer from coke formation, which leads to rapid deactivation. From catalytic tests, temperature-programmed surface reaction and pulsed reaction experiments, we infer that ethane conversion on Ga/ZSM-5 follows a conventional sequential dehydrogenation-oligomerization-aromatization mechanism, while the reaction over Mo/ZSM-5 involves reactive surface carbon (hydrocarbon pool) species.

The novel binuclear η

This paper describes an experimental system for simultaneous permeation of a pressurized test gas through different gas permeable membranes and provides a proof of concept for a novel approach for gas identification/fingerprinting for potential construction of electronic noses. The design, construction, and use of a six-channel system which allows simultaneous gas permeation from a single pressurized gas compartment through six different parallel membranes are presented. The permeated gas is accumulated in confined spaces behind the respective membranes. The rate of gas pressure accumulation behind each membrane is recorded and used as a measure of the gas permeation rate through the membrane. The utilized gas permeable membranes include Teflon AF, silicone rubber, track-etch hydrophilic polycarbonate, track-etch hydrophobic polycarbonate, track-etch polyimide, nanoporous anodic aluminum oxide, zeolite ZSM-5, and zeolite NaY. An analogy between the rate of pressure accumulation of the permeating gas behind the membrane and the charging of an electric capacitor in a single series RC circuit is proposed and thoroughly validated. The simultaneous permeation rates through different membranes demonstrated a very promising potential as characteristic fingerprints for 10 test gases, that is, helium, neon, argon, hydrogen, nitrogen, carbon dioxide, methane, ethane, propane, and ethylene, which are selected as representative examples of mono-, di-, tri-, and polyatomic gases and to include some homologous series as well as to allow testing the potential of the proposed system to discriminate between closely related gases such as ethane and ethylene or carbon dioxide and propane which have almost identical molecular masses. Finally, a preliminary investigation of the possibility of applying the developed gas permeation system for semiquantitative analysis of the CO

Anaerobic ammonium oxidation (anammox) and nitrification, two common biological ammonium oxidation pathways, are critical for the microbial nitrogen cycle. Short chain alkanes (C

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.

For bottom-up proteomics, peptide separation with high peak capacity under MS-compatible conditions is of vital significance to increase proteome coverage. Herein, a surface-charged ethane-bridged hybrid monolithic column was prepared based on the efficient ring-opening reaction of

Scatter plot analyses for 14,169 phenylethanes of the substructure C

Author(s): Liu, J; He, N; Zhang, Z; Yang, J; Jiang, X; Zhang, Z; Su, J; Shu, M; Si, R; Xiong, G; Xie, HB; Vile, G | Abstract: We report herein the preparation, characterization, and catalytic performance of a series of heterogeneous catalysts featuring highly dispersed zinc sites on zeolitic SSZ-13 and ZSM-5 frameworks. The materials are evaluated in the CO2-assisted oxidative ethane dehydrogenation, a very important reaction for the synthesis of platform chemicals. In particular, we find that Zn2.92/SSZ-13 exhibits high reactivity in the conversion of C2H6 and CO2 and high ethene selectivity. In line with the experimental results, we show that the selective character of the catalyst is due to the characteristic compositional structure of the support and its topology that can effectively confine CO2 molecules. An in-depth molecular analysis via operando studies and DFT calculations shows that the rate-limiting step of the reaction with CO2 is the second C-H bond dissociation to give C2H4. The addition of CO2 effectively reduces the energy barrier of this step, favoring desorption of C2H4 while limiting byproduct formation. Overall, this work demonstrates the breakthrough potential of catalysts made of highly dispersed zinc species on zeolites in relevant transformations.

The methane emission intensity (methane emitted/gas produced or methane emitted/methane produced) of individual unconventional oil and gas production sites in the United States has a characteristic temporal behavior, exhibiting a brief period of decrease followed by a steady increase, with intensities after 10 years of production reaching levels that are 2-10 times the 10 year production-weighted average. Temporal patterns for methane emission intensity for entire production regions are more complex. Historical production data and facility data were used with a detailed basin-wide methane emission model to simulate the collective behavior of tens of thousands of wells and associated midstream facilities. For production regions with few to no new wells being brought to production, and existing wells having reached a mature stage, as in the Barnett Shale production region in north central Texas, the methane emission intensity gradually increases, as natural gas production decreases faster than emissions decrease, following the general pattern exhibited by individual wells. In production regions that are rapidly evolving, either with large numbers of new wells being put into production or with the introduction of source-specific regulations, the behavior is more complex. In the Eagle Ford Shale, which has had both a large number of new wells and the introduction of source-specific regulations, the methane emission intensity stays within relatively narrow bounds but the distribution of sources varies. As source distributions vary, basin-wide propane-to-methane and ethane-to-methane emission ratios vary, impacting methods used in source attribution.

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.

Based on Materials Studio and Aspen Plus, the reaction mechanism of producing benzene and styrene from ethane steam heat lysis was investigated through the addition reaction of free radicals + alkenes or free radicals + alkynes to form large free radicals and then through the cyclization and dehydrogenation of large free radicals to form aromatic hydrocarbons. It was found the thermal cracking of ethane had 2 paths to form benzene and 1 path to form styrene. The 1st path to form benzene is that the product ethylene form C2H3• through a chain transfer, then C2H3• and ethylene additively react to form 1-C4H7•-4, which then reacts with ethylene to form C6H11•, and finally, benzene is produced by dehydrogenation and transfer of C6H11•. The 2nd path to form benzene is that acetylene is produced by dehydrogenation of C2H3•, and then acetylene reacts via two sub-paths to form 1,3-C4H5•-4, which is cyclized to form C6H9•, and finally, benzene is formed through dehydrogenation and transfer. The path to form styrene is that 1,3-C4H5•-4 and 1,3-butadiene are cyclized to form C8H11•, and styrene is finally formed through dehydrogenation and chain transfer. Comparative analysis with industrial data showed there were 3 cycles in the ethane thermal cracking reaction network. The simulation data were well consistent with the industrial production data.

Porous solids with channel sizes that are not much above the size of small hydrocarbons can yield extremely large adsorption selectivity. Our Grand Canonical Monte-Carlo simulations indicate exceptionally high selectivity for the separation of methane, ethane and propane from natural gas. At 250 K the C

A series of the layered double oxides supported molybdenum oxide catalysts were synthesized and evaluated in the oxidative dehydrogenation of ethane with CO2 (CO2-ODHE). The 22.3 wt% Mo/LDO catalyst delivered a 92.3%selectivity to ethylene and a 7.9% ethane conversion at relatively low temperatures. The molybdenum oxide catalysts were fully characterized by XRD, BET, SEM, TEM, UV–vis, Raman TG, and XPS. Isolated [MoO4]2− dominated on the surface of the fresh 12.5 wt% Mo/LDO catalyst. With the increase of the Mo content, the Mo species transformed from [MoO4]2− to [Mo7O24]6− and [Mo8O26]4− on the 22.3 wt% and 30.1 wt% Mo/LDO catalysts, respectively. The redox mechanism was proposed and three Mo species including [MoO4]2−, [Mo7O24]6−, and [Mo8O26]4− showed quite different functions in the CO2-ODHE reaction: [MoO4]2−, with tetrahedral structure, preferred the non-selective pathway; [Mo7O24]6−, with an octahedral construction, promoted the selective pathway; and the existence of [Mo8O26]4− reduced the ability to activate ethane. This work provides detailed insights to further understand the relationship between structure–activity and the role of surface Mo species as well as their aggregation state in CO2-ODHE.

Distinguishing biotic compounds from abiotic ones is important in resource geology, biogeochemistry, and the search for life in the universe. Stable isotopes have traditionally been used to discriminate the origins of organic materials, with particular focus on hydrocarbons. However, despite extensive efforts, unequivocal distinction of abiotic hydrocarbons remains challenging. Recent development of clumped-isotope analysis provides more robust information because it is independent of the stable isotopic composition of the starting material. Here, we report data from a

Top-down proteomics is challenged by the high complexity of biological samples. The coelution of intact proteins results in overlapped mass spectra, and hence, an increased peak capacity for protein separation is needed. Herein, ethane-bridged hybrid monoliths with well-defined large mesopores were successfully prepared based on the sol-gel condensation of 1,2-bis(trimethoxysilyl)ethane and tetramethoxysilane, followed by two-step base etching of the Si-O-Si domain while maintaining the Si-C-C-Si domain in the structure. Relatively homogeneous macropores of 1.1 μm and large mesopores of 24 nm were obtained, permitting fast mass transfer of large molecules and efficient diffusion without obstruction. The use of less hydrophobic C1 ligand further sharpened the peak shape and improved peak capacity. A 120 cm-long capillary column was used for top-down proteomic analysis of

Anaerobic microorganisms are thought to play a critical role in regulating the flux of short-chain gaseous alkanes (SCGAs; including ethane, propane and butane) from terrestrial and aquatic ecosystems to the atmosphere. Sulfate has been confirmed to act as electron acceptor supporting microbial anaerobic oxidation of SCGAs, yet several other energetically more favourable acceptors co-exist with these gases in anaerobic environments. Here, we show that a bioreactor seeded with biomass from a wastewater treatment facility can perform anaerobic propane oxidation coupled to nitrate reduction to dinitrogen gas and ammonium. The bioreactor was operated for more than 1000 days, and we used 13C- and 15N-labelling experiments, metagenomic, metatranscriptomic, metaproteomic and metabolite analyses to characterize the microbial community and the metabolic processes. The data collectively suggest that a species representing a novel order within the bacterial class Symbiobacteriia is responsible for the observed nitrate-dependent propane oxidation. The closed genome of this organism, which we designate as ‘Candidatus Alkanivorans nitratireducens’, encodes pathways for oxidation of propane to CO2 via fumarate addition, and for nitrate reduction, with all the key genes expressed during nitrate-dependent propane oxidation. Our results suggest that nitrate is a relevant electron sink for SCGA oxidation in anaerobic environments, constituting a new microbially-mediated link between the carbon and nitrogen cycles.

The accessibility of bromonitromethane has declined in recent years, limiting its viability as a reagent for chemical synthesis. The reinvestigation and optimization of a variety of preparations, and the development of safe operating principles, are described. The reproducible protocol described here leverages the effectiveness of hydroxide for nitromethane bromination while respecting its incompatibility with the product it forms. This careful balance was achieved at scales up to 56 g, resulting in a reproducible procedure that provides straightforward, sustainable, and affordable access to this critical reagent.

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

Multi-elemental C-Br-Cl compound-specific isotope analysis was applied for characterizing abiotic and biotic degradation of the environmental pollutant 1-bromo-2-chloroethane (BCE). Isotope effects were determined in the model processes following hydrolytic dehalogenation and dihaloelimination pathways as well as in a microcosm experiment by the microbial culture from the contaminated site. Hydrolytic dehalogenation of BCE under alkaline conditions and by DhaA enzyme resulted in similar dual isotope slopes (ɅC/Br 21.9 ± 4.7 and 19.4 ± 1.8, respectively, and ɅC/Cl ~ ∞). BCE transformation by cyanocobalamin (B12) and by Sulfurospirillum multivorans followed dihaloelimination and was accompanied by identical, within the uncertainty range, dual isotope slopes (ɅC/Br 8.4 ± 1.7 and 7.9 ± 4.2, respectively, and ɅC/Cl 2.4 ± 0.3 and 1.5 ± 0.6, respectively). Changes over time in the isotope composition of BCE from the contaminated groundwater showed only a slight variation in δ13C values and were not sufficient for the elucidation of the BCE degradation pathway in situ. However, an anaerobic microcosm experiment with the enrichment cultures from the contaminated groundwater presented dual isotope slopes similar to the hydrolytic pathway, suggesting that the potential for BCE degradation in situ by the hydrolytic dehalogenation pathway exists in the contaminated site.

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...

Here, we report the kinetic energy distributions (KEDs) of the fragment ions produced from multiply ionized ethane (C₂H₆) molecules in single electron capture collisions with 1.2 MeV C²⁺. To systematically investigate the fragmentation dynamics, the KEDs were obtained as functions of the charge state of the intermediate C₂H₆r⁺* ions r transiently generated prior to fragmentation. r was determined from coincidence measurement of the fragment ions and the number of emitted electrons. The KEDs are drastically different depending on the number of broken C–H bonds. The underlying causes are explained by the variation of the relative contributions of the multiply ionized states and preferential fragmentation pathways. For instance, CHn⁺ fragment ions with smaller n exhibit lower KEs because they are likely to be correlated with H⁺ emission, which carries away a large portion of the KE release. In addition, we report the KEDs of H₃⁺ produced from doubly and triply charged states., Special Issue: Proceedings of the 19th International Conference on the Physics of Highly Charged Ions (HCI 2018), Caparica, Lisboa, Portugal, 3‐7 September 2018

A quartz enhanced photoacoustic spectroscopy (QEPAS) sensor capable to detect high concentrations of methane (C1) and ethane (C2) is here reported. The hydrocarbons fingerprint region around 3 µm was exploited using an interband cascade laser (ICL). A standard quartz tuning fork (QTF) coupled with two resonator tubes was used to detect the photoacoustic signal generated by the target molecules. Employing dedicated electronic boards to both control the laser source and collect the QTF signal, a shoe-box sized QEPAS sensor was realized. All the generated mixtures were downstream humidified to remove the influence of water vapor on the target gases. Several natural gas-like samples were generated and subsequently diluted 1:10 in N

The aim is to produce aliphatic liquid hydrocarbons using heterogeneous ethylene oligomerization. Thiscould potentially produce renewable synthetic fuels. Heterogeneous catalysis has some advantages overhomogeneous catalysis regarding some sustainability aspects. To achieve this, a setup was built using a heatedfixed bed reactor with an in-situ has chromatography to study conversion and gaseous products, and ex-situGC as well as NMR for analyzing liquid products. Ethylene was oligomerized on a commercial ZSM-5 zeoliteunder varying temperature conditions and feed gas dilution with hydrogen or helium. The gas and liquidproducts were analyzed and evaluated. Additionally, the ZSM-5 was studied at different silica to alumina ratios. The thesis discusses how conversion, liquid yield and selectivity of gas products using GC together withanalysis of liquid products using H-NMR can be used as a simple and quick evaluation. The liquid product isevaluated by the distribution of olefinic and aromatic hydrocarbon species using the hydrogen signal area inthe characteristic chemical shifts of olefinic and aromatic hydrogen. At 250-400oC, 6 bar of ethylene, with andwithout feed dilution, and WHSV of 204 h-1, conversion was consistently above 95% for the diluted 400oCruns. Though the liquid yield fell to around 6%, compared to the best yield at 18% for the pure 300oC run.Diluting the feed had a positive effect on increasing olefinic hydrogen signal while decreasing aromatichydrogen signal. The difference between diluting with H2 or helium had a surprisingly small effect. Decreasingthe Si/Al ratio had no significant effect on performance, while increasing the Si/Al ratio made the zeolite loseits catalytic ability. With a pure ethylene feed the lowest aromatic hydrogen signal was found at 350oC, whilethe olefinic signal did not vary too much with temperature. With diluted feed the higher temperature did leadto a lower olefinic hydrogen signal and higher aromatic hydrogen signal.