Methane Ethane Research Articles

Ice Formation, Exsolution, and Multiphase Equilibria in the Methane–Ethane–Nitrogen System at Titan Surface Conditions

Titan is unique among the icy satellites in that it has a thick atmosphere, stable surficial bodies of liquid, and a precipitation system that promotes interactions between the two. Although Titan’s surface conditions are typically assumed to be above the freezing point temperatures of the major constituent species of the climate system (methane, ethane, and nitrogen), conditions may be sufficiently cool across parts of Titan to allow for ice formation alongside known liquid-vapor phases. In this study, we used Raman spectroscopy, visual inspection, and the CRYOCHEM 2.0 equation of state to map the appearance of first ice and to quantify the amount of nitrogen dissolution into liquid in the methane–ethane–nitrogen system along a 1.5 bar isobaric cooling path in the temperature range 80–95 K. This was with the intent of (1) determining the effects nitrogen has on the phase behaviors of the methane–ethane binary system, and (2) establishing the temperatures and ternary mixing ratios needed for ice formation on Titan’s surface. We found that ethane-rich mixtures enter a three-phase solid–liquid–vapor equilibrium and are characterized by nitrogen-rich exsolution upon freezing and ice that form at the bottom of the sample. With sufficient methane content, the mixtures cross a univariant four-phase solid–liquid–liquid–vapor boundary, which contributes to a distinct isothermal freezing point profile and ice that forms starting at the liquid–liquid interface. Our results generally agree with findings from previous studies of the methane–ethane–nitrogen system and are intended to add to our current understanding of Titan’s geochemical processes.

Determination of the Binary Diffusion Coefficients and Interaction Viscosities of the Systems Carbon Dioxide–Nitrogen and Ethane–Methane in the Dilute Gas Phase from Accurate Experimental Viscosity Data Using the Kinetic Theory of Gases

The results of viscosity measurements at moderate densities on the two gaseous mixtures carbon dioxide–nitrogen and ethane–methane including the pure gases between 253.15 K and 473.15 K, originally performed by Humberg et al. at Ruhr University Bochum, Germany, using a rotating-cylinder viscometer between 0.1 MPa and 2.0 MPa, were employed to determine the interaction viscosity, eta _{12}^{(0)}, and the product of molar density and diffusion coefficient, (rho D_{12})^{(0)}, each in the limit of zero density. The isothermal viscosity data were evaluated by those authors with density series restricted to the second order at most to derive the zero-density viscosities and initial density viscosity coefficients, eta _textrm{mix}^{(0)} and eta _textrm{mix}^{(1)}, for the mixtures, as well as, eta _i^{(0)} and eta _i^{(1)} (i=1,2), respectively, for the pure gases. Humberg et al. have already compared their eta _textrm{mix}^{(0)} and eta _i^{(0)} data for carbon dioxide–nitrogen and ethane–methane with corresponding viscosity values theoretically computed for the nonspherical potentials of the intermolecular interaction. Now we employed eta _textrm{mix}^{(0)} and eta _textrm{mix}^{(1)} as well as eta _i^{(0)} and eta _i^{(1)} in two procedures to derive eta _{12}^{(0)} values. For this, we needed A_{12}^* values (ratio between effective cross-sections of viscosity and diffusion). But the second procedure applying the initial density viscosity coefficients eta _textrm{mix}^{(1)} and eta _i^{(1)} failed to yield reasonable eta _{12}^{(0)} values. The first procedure should provide the best results when it is possible to use A_{12}^* values computed for the nonspherical potential. The effect is comparatively small if eta _{12}^{(0)} is determined. But if (rho D_{12})^{(0)} is calculated from eta _{12}^{(0)} using A_{12}^* values for the nonspherical potential, the impact is several percent. Moreover, the experimentally based eta _{12}^{(0)} and (rho D_{12})^{(0)} data agree with theoretically calculated values for the nonspherical potentials.

Natural Gas Pyrolysis in a Liquid Metal Bubble Column Reaction System—Part II: Pyrolysis Experiments and Discussion

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.

Synthesis of Satellite and Surface Measurements, Model Results, and FRAPPÉ Study Findings to Assess the Impacts of Oil and Gas Emissions Reductions on Maximum Ozone in the Denver Metro and Northern Front Range Region in Colorado

AbstractThe Denver Metro/Northern Front Range area has been designated a severe nonattainment area (NAA) for O3. Previous research associated with the 2014 Front Range Air Pollution and Photochemistry Éxperiment field campaign and a 2017 O3 source apportionment modeling analysis point to north‐south gradients in oil and gas (O&G) impacts on O3, with greater contributions to the north and a dominance of mobile sources to the south. Recent analysis of Atmospheric Infrared Sounder satellite methane enhancement and ethane trends in the area show ∼50% and ∼70% reductions in methane and ethane, respectively, from 2013 to 2020. These are consistent with reductions in O&G volatile organic compound (VOC) emissions estimated in the most recent O3 State Implementation Plan but inconsistent with a timeline of top‐down methane flux estimates for limited periods from 2012 to 2021. Reductions in annual fourth maximum eight‐hour O3 concentrations from 2012 to 2019 are 5 ppb greater at Fort Collins West (FTCW) to the north than at Chatfield Reservoir to the south. Bayesian correlation analyses and partial correlations between FTCW O3 and ethane conditioned for tropospheric NO2 from the Aura satellite Ozone Monitoring Instrument suggest that most of the 9‐ppb reduction here is due to declines in O&G emissions, and 9 ppb is comparable to estimated O&G VOC contributions on high‐concentration days in the northern portion of the study area. The gradient in trends suggests that significant O&G emissions reductions have benefited locations in the central and northern portions of the NAA.

Steam Conversion of Ethane and Methane–Ethane Mixtures in a Membrane Reactor with a Foil Made of a Pd–Ru Alloy

Steam Conversion of Ethane and Methane–Ethane Mixtures in a Membrane Reactor with a Foil Made of a Pd–Ru Alloy

Steam Conversion of Ethane and Methane–Ethane Mixtures in Membrane Reactor with a Foil from Pd–Ru Alloy

The features of steam conversion of ethane and methane-ethane mixtures containing 5, 10 and 15% ethane in a membrane reactor with a 30 μm thick Pd–Ru foil at temperatures of 1800 and 3600 h–1 and steam/feed rations of 3 and 5 have been investigated. Comparative experiments with “non-membrane” reaction have shown that in the membrane reactor the feedstock conversion to form H2 and CO2 increases and ethane hydrocracking decreases. Increasing the rate of H2 recovery through the membrane by permeate evacuation leads to an increase in the yield of H2 and CO2. With a decrease in the steam/feed ratio from 5 to 3, the ethane hydrocracking and the rate of carbon deposits formation increases. Optimal conditions for steam conversion of ethane and methane-ethane mixtures are T = 773 K, feed space velocity of 1800 h–1 and steam/feed ratio of 5. The established regularities are similar to those obtained earlier for other types of raw materials (mixtures of methane with propane, propane, n-butane, a mixture simulating the average composition of associated petroleum gas) in this membrane reactor.

New ruthenium(II) complexes with cyclic thio- and semicarbazone: evaluation of cytotoxicity and effects on cell migration and apoptosis of lung cancer cells.

We describe the synthesis, physicochemical characterization, and in vitro antitumor assays of four novel analogous ruthenium(II) complexes with general formula cis-[RuII(N-L)(P-P)2]PF6, where P-P = bis(diphenylphosphine)methane (dppm, in complexes 1 and 2) or bis(diphenylphosphine)ethane (dppe, in complexes 3 and 4) and N-L = 5,6-diphenyl-4,5-dihydro-2H-[1,2,4]triazine-3-thione (Btsc, in complexes 1 and 3) or 5,6-diphenyltriazine-3-one (Bsc, in complexes 2 and 4). The data were consistent with cis arrangement of the biphosphine ligands. For the Btsc and Bsc ligands, the data pointed to monoanionic bidentate coordination to ruthenium(II) through N,S and N,O, respectively. Single-crystal X-ray diffraction showed that complex 1 crystallized in the monoclinic system, space group P21/c. Determination of the cytotoxicity profiles of complexes 1-4 gave SI values ranging from 1.19 to 3.50 against the human lung adenocarcinoma cell line A549 and the non-tumor lung cell line MRC-5. Although the molecular docking studies suggested that the interaction between DNA and complex 4 was energetically favorable, the experimental results showed that they interacted weakly. Overall, our results demonstrated that these novel ruthenium(II) complexes have interesting in vitro antitumor potential and this study may contribute to further studies in medicinal inorganic chemistry.

New insight into abiotic or biotic gas in deep reservoirs of the CL-I gas field in Songliao Basin (China) by light hydrocarbons associated with natural gas

Abiotic synthesis through carbon dioxide (CO2) reduction may provide the prebiotic organic compounds needed for the emergence of life, whereas petroleum geologists pay more attention to whether abiotic gas generated by purely chemical reactions plays a prominent role in the formation of industrial gas pools like biotic gas. The Cretaceous reservoir associated with volcanic rocks of the Songliao Basin in northeastern China is suspected of possessing abiotic gas due to some abnormal geochemical characteristics, such as abundant 13C-enriched CO2, 13C-enriched CH4, 13C-depleted C2H6, and an isotopic trend of decreasing 13C content with growing carbon number. To understand further the genesis of deep natural gas, we examined the molecular and isotopic compositions of C1–C4 alkanes, CO2, and light hydrocarbons (LHs) of equal number (four) of gas samples collected from the Yingcheng (K1yc) volcanic and Denglouku (K1d) clastic reservoirs in the Changling (CL-I) gas field. Compared with the products of abiotic polymerization composed of 13C-depleted straight-chain alkanes, various 13C-enriched LH isomers that are highly compatible with the molecular and isotopic compositions of coal-derived thermogenic gas are confirmed in our samples, such as 2-methylhexane (2-MH), 2,3-dimethylpentane (2,3-DMP), cyclohexane (CH), methylcyclohexane (MCH), and other branched-chain alkanes or cycloalkanes. The striking invariable K1 ratio and resemblance of isotopic curves of LHs further indicate that the natural gas in different reservoirs is derived from underlying homologous source rocks, regardless of the variation of CO2 content (K1yc > 15% and K1d < 1%). Combining geological conditions, we propose that C1–C4 and LHs that have no inherent correlation with the concentration of CO2, which is predominantly derived from mantle degassing, are generated from the thermal decomposition of 13C-enriched type III organic matter during burial and diagenesis rather than sourced from mantle degassing, abiotic polymerization, or mixing of thermogenic gas. In addition, we also suggest that the geochemical anomalies consisting of 13C-enriched methane and 13C-depleted ethane are the products of the chemical mechanisms controlled by high temperature, and mantle-derived non-hydrocarbon gas (e.g., CO2 and He) are simply added to thermogenic gas.

Natural Gas Storage Filled with Peat-Derived Carbon Adsorbent: Influence of Nonisothermal Effects and Ethane Impurities on the Storage Cycle.

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.

Wetting Properties of Clathrate Hydrates in the Presence of Polycyclic Aromatic Compounds: Evidence of Ion-Specific Effects

Polycyclic aromatic hydrocarbons (PAHs) have attracted remarkable multidisciplinary attention due to their intriguing π–π stacking configurations, showing enormous opportunity for their use in a variety of advanced applications. To secure progress, detailed knowledge on PAHs’ interfacial properties is required. Employing molecular dynamics, we probe the wetting properties of brine droplets (KCl, NaCl, and CaCl2) on sII methane–ethane hydrate surfaces immersed in various oil solvents. Our simulations show synergistic effects due to the presence of PAHs compounded by ion-specific effects. Our analysis reveals phenomenological correlations between the wetting properties and a combination of the binding free-energy difference and entropy changes upon oil solvation for PAHs at oil/brine and oil/hydrate interfaces. The detailed thermodynamic analysis conducted upon the interactions between PAHs and various interfaces identifies molecular-level mechanisms responsible for wettability alterations, which could be applicable for advancing applications in optics, microfluidics, biotechnology, medicine, as well as hydrate management.

Diffusion of fluids confined in carbonate minerals: A molecular dynamics simulation study for carbon dioxide and methane–ethane mixture within calcite

The ability to calculate how different compounds diffuse within mesoporous structures is paramount for a number of applications in the oil & gas sector, from oil exploration to separation, and even for the design of Carbon Capture, Utilization, and Storage (CCUS) processes. Molecular Dynamics simulations entail an excellent alternative to cases for which an experimental determination is unfeasible or extremely difficult, as it happens for fluids in mesopores. Nonetheless, being confined within a mineral mesopore makes the fluid spatial distribution inhomogeneous, requiring appropriate methods to compute the diffusion coefficients. Recently, some of us presented a new method for this purpose (Franco et al. 2016). In this work, we present a detailed study on how to apply such a method exploring fluids confined within calcite walls, which is a mineral representative of carbonate rocks found in several geological formations. From our results, we were able to map the evolution of the self-diffusion tensor components throughout the pore, showing the anisotropy among the components at different directions. We also show the influence of confinement and observe a significant effect at the center of the pore for small mesopores (< 7.5 nm), where the density distribution is constant. This is an unexpected result that shows how the confinement effect is manifested even at the so-called “bulk-like” region at the center of the pore.

Quantifying fossil fuel methane emissions using observations of atmospheric ethane and an uncertain emission ratio

Abstract. We present a method for estimating fossil fuel methane emissions using observations of methane and ethane, accounting for uncertainty in their emission ratio. The ethane:methane emission ratio is incorporated as a spatially and temporally variable parameter in a Bayesian model, with its own prior distribution and uncertainty. We find that using an emission ratio distribution mitigates bias from using a fixed, potentially incorrect emission ratio and that uncertainty in this ratio is propagated into posterior estimates of emissions. A synthetic data test is used to show the impact of assuming an incorrect ethane:methane emission ratio and demonstrate how our variable parameter model can better quantify overall uncertainty. We also use this method to estimate UK methane emissions from high-frequency observations of methane and ethane from the UK Deriving Emissions linked to Climate Change (DECC) network. Using the joint methane–ethane inverse model, we estimate annual mean UK methane emissions of approximately 0.27 (95 % uncertainty interval 0.26–0.29) Tg yr−1 from fossil fuel sources and 2.06 (1.99–2.15) Tg yr−1 from non-fossil fuel sources, during the period 2015–2019. Uncertainties in UK fossil fuel emissions estimates are reduced on average by 15 % and up to 35 % when incorporating ethane into the inverse model, in comparison to results from the methane-only inversion.

Numerical investigation on flow and heat transfer characteristics of supercritical methane–ethane mixture in a straight channel

Printed Circuit Heat Exchanger (PCHE) is considered as a promising heat exchanger for offshore Liquefied Natural Gas (LNG) production due to its compactness and high efficiency. To reveal the flow and heat transfer performance of real component nature gas mixture in PCHE, numerical study was conducted to obtain flow and heat transfer characteristics of supercritical methane–ethane mixture in a straight channel of PCHE. The influence of operating parameters including inlet temperature, mass flux and outlet pressure are investigated. The simulation results show that heat transfer coefficient and pressure drop increase with the increase of inlet temperature and mass flux, and decrease with the increase of outlet pressure. The overall variation tendency of heat transfer coefficient and pressure drop in supercritical methane–ethane mixture flow was similar to those in supercritical methane flow, but there still exists some difference due to their different physical properties. For the value of heat transfer coefficient, supercritical methane flow is about 7% larger than that of supercritical methane–ethane mixture flow. And for frictional pressure drop, supercritical methane flow is much larger by about 12%. Finally, new correlations were proposed for supercritical methane–ethane mixture flow, which are helpful for a more accurate flow and heat transfer calculation in PCHE designing for natural gas.

A novel anti‐freezing methane propellant subcooling approach and its performance analysis

AbstractUsing subcooled propellant could improve the overall performance of spacecraft. In cryogenic propellant subcooling process, liquid nitrogen is the most common cold source. For methane propellant, ice blockage may occur in the propellant subcooling operation since the saturation temperature of liquid nitrogen is lower than the freezing temperature of liquid methane. In this paper, a novel anti‐freezing subcooling approach for methane propellant is proposed. By mixing light alkane such as ethane or propane into methane, a methane mixture propellant with lower freezing temperature could be prepared. To guide the propellant preparation, the working principle of the subcooling scheme is introduced, and the thermodynamic performance of the mixed propellant is analyzed. The results show that for the methane–ethane system, the lowest freezing temperature is 72.9 K when the methane mole fraction is about 0.71. Icing‐free subcooling can be achieved in a liquid nitrogen heat exchanger subcooled approach when the methane fraction is controlled within 0.54 to 0.80. For the methane–propane system, the minimum freezing temperature of 72.0 K occurs at the methane fraction of 0.68, and the non‐icing range is about 0.42–0.79. For the methane–ethane–propane ternary system, the lowest solidification temperature even reaches 63.1 K. Moreover, apparent propellant densification could be yielded by the proposed subcooling scheme. In general, the present subcooling scheme can effectively avoid the freezing risk in the methane subcooling process and also prepare a densified methane propellant, and the new scheme is beneficial for fully exploiting the potential performance of the subcooled methane propellant.

Understanding the Effect of Pore Size on the Separation Efficiency of Methane–Ethane Mixtures Using Kinetic Monte Carlo Simulation

Understanding the Effect of Pore Size on the Separation Efficiency of Methane–Ethane Mixtures Using Kinetic Monte Carlo Simulation

Direct conversion of methane into methanol and ethanol via spherical Au@Cs2[closo-B12H12]and Pd@Cs2[closo-B12H12] nanoparticles

In this present study, novel aqueous-phase catalytic systems, namely spherical Au and Pd nanoparticles (NPs) capped with Cs2 [closo-B12H12], were used to produce ethanol and methanol via direct oxidation of methane in the presence of H2O2 and O2 under mild conditions. The ethanol selectivity surpassed 52.96% and 86.33% at 50 °C, and the productivity reached 8.86 and 25.18 mol·kgcat–1·h–1, respectively. Plausible methane–ethane–ethanol pathway involving free radial •OH radicals was proposed based on the electron paramagnetic resonance (EPR) result. According to the theoretical calculations, the surfaces of {111} plane of Au NPs and {100} plane of Pd NPs were capped with Cs2 [closo-B12H12], and Au–B and Pd–B bonds were consequently formed, respectively. Moreover, the binding energies of Au NPs and Pd NPs capped with Cs2 [closo-B12H12] were calculated to be −128.9 and −230.1 kcal mol−1, respectively. Based on the theoretical calculations, higher binding energy indicates a larger amount of charge on the surfaces of the planes of NPs. A lower peak intensity can lead to the formation of a more stable catalyst with enhanced catalytic activity. Thus, the ethanol selectivity of the as-prepared catalyst was considerably higher than that for methanol.

Phase Diagram for the Methane–Ethane System and Its Implications for Titan’s Lakes

Abstract On Titan, methane (CH4) and ethane (C2H6) are the dominant species found in the lakes and seas. In this study, we have combined laboratory work and modeling to refine the methane–ethane binary phase diagram at low temperatures and probe how the molecules interact at these conditions. We used visual inspection for the liquidus and Raman spectroscopy for the solidus. Through these methods, we determined a eutectic point of 71.15 ± 0.5 K at a composition of 0.644 ± 0.018 methane–0.356 ± 0.018 ethane mole fraction from the liquidus data. Using the solidus data, we found a eutectic isotherm temperature of 72.2 K with a standard deviation of 0.4 K. In addition to mapping the binary system, we looked at the solid–solid transitions of pure ethane and found that, when cooling, the transition of solid I–III occurred at 89.45 ± 0.2 K. The warming sequence showed transitions of solid III–II occurring at 89.85 ± 0.2 K and solid II–I at 89.65 ± 0.2 K. Ideal predictions were compared with molecular dynamics simulations to reveal that the methane–ethane system behaves almost ideally, and the largest deviations occur as the mixing ratio approaches the eutectic composition.

Experimental Measurement of Multiple Hydrate Structure Formation in Binary and Ternary Natural Gas Analogue Systems by Isochoric Equilibrium Methods

Traditionally, it is commonly assumed that a single gas hydrate (or clathrate hydrate) structure/phase is formed in natural gas systems—e.g., “s-II natural gas (NG) hydrates” or “s-I methane hydrates”—based on that which is understood to be the most thermodynamically stable at incipient phase boundary conditions. This applies with respect to both studies of hydrates in natural sediments, and in the case of hydrocarbon production operations, including the testing of low-dosage hydrate inhibitors (LDHIs). Here, we present the results of experimental studies of simple propane (C₃), binary methane–propane (C₁–C₃), and ternary methane–ethane–propane (C₁–C₂–C₃) hydrate systems, aimed at investigating phase behavior at higher subcoolings where significant water conversions to clathrates—and associated gas fractionation—might be expected to result in the formation of more than one hydrate structure. Measurements were made by means of established, reliable, isochoric equilibrium step-heating/cooling approaches. In the single guest propane system, pressure–temperature (PT) conditions follow the gas hydrate phase boundary, in agreement with the univariant hydrate + gas + water (H + G + W) equilibrium. By contrast, binary and ternary mixes clearly show PT behavior consistent with the growth of at least two and four hydrate phases, respectively, with these forming sequentially on cooling, and dissociating in the corresponding reverse order upon heating. In-house hydrate model (HydraFLASH) predictions support experimental observations, pointing to processes being gas fractionation driven; the mixed C₃–C₁ or C₃–C₂–C₁ s-II type hydrates formed first close to the phase boundary preferentially incorporating the most strongly clathrate cage (5¹²6⁴) stabilizing propane, making the remaining gas leaner. Once C₃ is largely consumed, trends agree with less stable C₂–C₁ structures (s-II followed by s-I) then growing (where ethane is present), with this, like C₃ uptake, making remaining free gas increasingly of almost pure C₁. This ultimately drives systems toward the final simple, single guest C₁ s-I clathrate formation as the well-established univariant phase boundary for this structure is reached. As observed phase behavior arises because of gas fractionation, it can be expected to occur during hydrate formation in all mixed gas systems of relatively fixed composition (at constant volume or pressure). The findings highlight that care should be taken in the application of isochoric methods to multicomponent gas systems, given the potential for numerous (rather than just one) clear changes in heating curve slopes as different hydrate structures form/dissociate. In addition, results show that extending equilibrium steps well into the hydrate region can reveal important information on clathrate phase behavior with potentially significant implications for issues such as gas production from hydrates in sediments, hydrate technologies for gas capture/separation/storage in the energy industry, and flow assurance in hydrocarbon production operations.

Trichloroethylene dechlorination rates, pathways, and efficiencies of ZVMg/C in aqueous solution

The removal mechanism from the reductive dechlorination of trichloroethylene (TCE) by zero valent magnesium (ZVMg) in aqueous solution is systematically studied. Following the preparation and characterization of ball-milled micro ZVMg with graphite (ZVMg/C) particles, this paper evaluated the TCE reaction rates, pathways, utilization rates and aging effects of ZVMg/C particles in aqueous solution under uncontrolled pH conditions. Overall, 38 μM of TCE was transformed by 10 g/L of ZVMg/C to methane (62.51%) and n-hexane (11.86%) and ethane (7.40%) and other alkene and alkyne products through the catalytic hydrogenation pathway. The measured surface area normalized pseudo-first order rate constants (KSA) were up to 9.31 × 10−2 L/m2/h and the utilization rate of Mg0 accounted for around 60%. The KSA were decreased to 1.90 × 10−2 L/m2/h in case of ZVMg/C being exposed in the atmosphere for 6 days due to 7.3% reduction in the utilization rate of Mg0 from the initial 85.2%, and 5.11 × 10−2 L/m2 h in case of ZVMg/C aged in water for one day. The removal efficiencies of approximately 56%, 58% and 87% by 10 g/L of ZVMg/C were achieved in the contaminated groundwater comprising 38 μM of TCE, 43 μM of 1,2-dichlorobenzene and 8.12 μM of trichlormethane. Therefore, it is concluded that ZVMg/C is viewed as a potential and effective remediation reagent for the groundwater remediation.

Non-oxidative Coupling of Methane: N-type Doping of Niobium Single Atoms in TiO2 -SiO2 Induces Electron Localization.

Photodriven nonoxidative coupling of CH4 (NOCM) is an attractive potential way to use abundant methane resources. Herein, an n-type doped photocatalyst for NOCM is created by doping single-atom Nb into hierarchical porous TiO2 -SiO2 (TS) microarray, which exhibits a high conversion rate of 3.57 μmol g-1 h-1 with good recyclability. The Nb dopant replaces the 6-coordinated titanium on the (1 0 1) plane and forms shallow electron-trapped surface polarons along [0 1 0] direction and the comparison of different models proves that the electron localization caused by the n-type doping is beneficial to both methane activation and ethane desorption. The positive effect of n-type dopant on CH4 conversion is further verified on Mo-, W- and Ta-doped composites. In contrast, the doping of p-type dopant (Ga, Cu, Fe) shows a less active influence.