Search

The water medium explosion container is an experimental device that simulates explosion in different water depth environments by loading different hydrostatic pressures and different doses of explosive. To ensure its safety during service, it is necessary to study the dynamic response of water medium explosion container. Because the dynamic response is complicated and the correlation between the response and the load of the container is nonlinear, it is difficult to calculate the dynamic response by analytical and numerical methods. In this paper, a model is built based on convolutional neural network (CNN) to predict the dynamic response of water medium explosion container. The accuracy and usability of the CNN prediction model are verified by comparison with the prediction results of the BP neural network model. The results show that CNN can be effectively used to predict the strain response of the dynamic response of water medium explosion container. and this method will play an important role in the later study of the overall feature analysis of the dynamic response of the water medium explosion vessel. [ABSTRACT FROM AUTHOR]

[Display omitted] Constructing donor–acceptor structures in polymeric carbon nitride (CN) provides an attractive pathway for facilitating charge carrier separation in photocatalytic reactions. However, achieving the implantation of donor or acceptor moieties at molecule level precision remains challenging. Here we develop a three-dimensional (3D) porous thiophene implanted carbon nitride (TCN) with donor–acceptor structure via a supramolecular assembly strategy. The specific-designed triazine derivatives with similar hydrogen bonding sites allow for the uniform introduction of thiophene groups at molecule level precision during the supramolecular assemble stage. The electron-donating thiophene groups in TCN can continuously tune electronic band structure, expand visible light absorption range, and promote charge carriers' separation. The optimized properties enable TCN-3 an outstanding H 2 evolution rate of 5620 μmol h−1 g−1, greatly exceeding bulk CN (95 μmol h−1 g−1). Briefly, our work may offer opportunities to prepare highly active photocatalysts with molecule level precise donor–acceptor structure. [ABSTRACT FROM AUTHOR]

[Display omitted] • The MOFs ligand is replaced by OH– along with electrooxidation of Ni ions in OER. • The ultrathin MOFs promote the transformation as β-NiOOH due to sufficient OH–. • The γ-NiOOH is generated on the thicken Ni-MOFs with insufficient OH– in OER. • The β-NiOOH displays the lower energy than γ-NiOOH for formation of O. In-situ generated hydroxides and oxyhydroxides have been gradually recognized as the real active sites of metal organic frameworks (MOFs) towards the oxygen evolution reaction (OER). Nevertheless, the fine phase evolution process is still less of concern and elusive. Herein, we successfully construct serious of Ni-MOFs with differing thickness ranging from 1 nm to 270 nm through a competitive coordination strategy. Utilizing the operando resonance spectroscopy, an accurate phase inversion behavior of the Ni-MOFs has been witnessed during the OER, and demonstrated as a thickness-dependent process. Ultrathin architecture is identified as a positive factor to promote the exchange between MOFs ligands and applied electrolyte during the electrochemical test. Hence, after removing most of the internal ligands, 2D MOFs favor to be transformed as β-NiOOH, which is more active than the generated γ-NiOOH in bulky system. The density function theory (DFT) calculation alongside with the in-situ electrochemistry tests further affirm the β/γ-NiOOH transformation behavior. This work offers a new understanding of the electrocatalytic mechanism from the view point of phase evolution in 2D MOFs. [ABSTRACT FROM AUTHOR]

The granular dispersion for different wall thicknesses of the inner channel in a dense gas–solid coaxial jet is investigated by morphology. In the wave dispersion, the Kelvin–Helmholtz instability has a strong influence on the granular stream. However, increasing the wall thickness damps the K–H instability, namely weakens the wave dispersion. Consequently, the non-dimensional wavelength increases and the non-dimensional amplitude decreases as the wall thickness increases for the same annular gas velocity. The instability analysis combining with the modification of the vorticity thickness of the annular gas stream indicates that the non-dimensional wavelength increases linearly with the non-dimensional modified vorticity thickness. The relation between the amplitude of the granular dispersion and the non-dimensional modified vorticity thickness is reliable for the wave dispersion as well. In addition, the granular dispersion angle is proportional to the annular gas velocity, which slightly depends on the wall thickness. [ABSTRACT FROM AUTHOR]

On the basis of the results of simulation experiments, now we better understand the contribution of high carbon number hydrocarbons to diamondoid generation during thermal pyrolysis of crude oil and its sub-fractions (saturated, aromatic, resin, and asphalene fractions). However, little is known about the effect of volatile components in oil on diamondoid generation and diamondoid indices due to the lack of attention to these components in experiments. In this study, the effect of volatile components in oil on diamondoid generation and maturity indices was investigated by the pyrolysis simulation experiments on a normal crude oil from the HD23 well of the Tarim Basin and its residual oil after artificial volatilization, combined with quantitative analysis of diamondoids. The results indicate that the volatile components (≤ nC) in oil have an obvious contribution to the generation of adamantanes, which occurs mainly in the early stage of oil cracking (Easy R<1.0%), and influences the variations in maturity indices of adamantanes; but they have no obvious effect on the generation and maturity indices of diamantanes. Therefore, some secondary alterations e.g., migration, gas washing, and biodegradation, which may result in the loss of light hydrocarbons in oil under actual geological conditions, could affect the identification of adamantanes generated during the late-stage cracking of crude oil, and further influence the practical application of adamantane indices. [ABSTRACT FROM AUTHOR]

The particle entrainment behaviors at the outlet of a nozzle in the gas–particle coaxial jets are experimentally investigated by morphology. The particles in the surface of the granular stream discharging from an inner channel are entrained into the recirculation region due to the drag force of the gas backflow. Hence, the gas backflow is the most essential and crucial factor in the entrainment phenomena. Moreover, the experimental results demonstrate that the particle mass flow rate, the inner duct thickness and the particle size have influences on the formation as well as the characteristics of the entrainment phenomena. The particle entrainment critical annular gas velocity increases linearly with the initial particle velocity and is responsible for the inner duct thickness and the particle size. The entrainment length of the particles and the reverse dispersion angle are employed to analyze qualitatively and quantitatively the motions of the particles. Finally, two empirical correlations on the entrainment length of the particles and the reverse dispersion angle are achieved. [ABSTRACT FROM AUTHOR]

Thermal maturation-related variations in the abundance and distribution of diamondoids in source rocks were investigated by thermal simulation experiments on extracts and kerogen obtained from a same marine shale, and by quantitative analysis of diamondoids within pyrolysates using highly sensitive and selective gas chromatography–triple quadrupole mass spectrometry (GC–MS–MS). The results indicate that diamondoids within the marine shale are generated mainly during 0.8%–1.7% EasyRo, generally deriving from extractable organic matter within source rocks, and are destroyed after 1.7% EasyRo to be entirely removed by ca. 3.0% EasyRo. Ternary plots of the relative distribution of diamondoids and bivariate diagrams for diamondoid parameters (e.g., DMA/MD vs. DMAI-1, and DMA/MD vs. TMAI-1) show systematic changes in diamondoids with increasing thermal maturity (expressed as EasyRo). [ABSTRACT FROM AUTHOR]

Abstract: This study investigates the origin and evolution of adamantanes and diamantanes in petroleum, based on the results of pyrolysis experiments on different group components of crude oil and quantitative analyses of diamondoids in the pyrolysates. Results show that the formation and evolution of lower diamondoids in petroleum occurs in three main stages: (1) early generation during the formation of oil (< ca. 0.8–1.0% EasyRo), (2) generation during the cracking of oil (>1.0% EasyRo), and (3) destruction during the late period of oil cracking. The lower diamondoids that formed during the early generation stage include free diamondoids present in the original oil and diamondoids released or transformed from group fractions of oil at relatively low levels of maturity (< ca. 0.8–1.0% EasyRo). During the process of oil cracking, all four group fractions (saturated, aromatic, resin, and asphaltene fractions) can produce adamantanes and diamantanes. Overall, adamantanes are generated primarily within the maturity range 1.0–2.3% EasyRo, and diamantanes within the maturity range 1.6–2.7% EasyRo. Group composition of the oil is probably a major factor controlling the yield and distribution of diamondoids in the main generation stage. The yield ratios of diamondoids can be used as maturity indices to assess the thermal maturity of oil, while the isomerization ratios of diamondoids are potential source facies indices for the generation stage of diamondoids. The destruction of diamondoids is observed at thermal maturity ranges >2.3% EasyRo in adamantanes and >2.7% EasyRo in diamantanes. The thermal stability of diamondoid compounds becomes a critical factor influencing the isomerization index of diamondoids during the destruction stage. The isomerization ratios of some diamondoids (e.g., MAI, DMAI-1, DMAI-2, TMAI-1, TMAI-2, and EAI) are well correlated with maturity within certain maturity ranges, indicating that isomerization indices provide good estimates of the thermal maturity of highly cracked oils. Bivariate diagrams of concentration versus isomerization indices of diamondoids are introduced to assess the maturity of oils; these diagrams provide more refined maturity assessments over a wider range of maturities than are available from single diamondoid parameters only. [Copyright &y& Elsevier]

Diamondoid compounds are widely used to reflect thermal maturation of high mature source rocks or oils and oil cracking extents. However, diamondoids and thiadiamondoids were demonstrated to have newly been generated and decomposed in our hydrothermal pyrolysis of crude oil and TSR experiments. Our results show that adamantanes and diamantanes are generated primarily within the maturity range 0.48–2.1% and 1.2–3.0% EasyRo, respectively. Their formation is enhanced and the decomposition of diamantanes obviously lags at elevated temperatures compared with anhydrous experiments. MDI, EAI, DMAI-1, DMDI-2 may serve as reliable maturity proxies at > ca.1.0% EasyRo, and other isomerization indices (TMAI-1, TMAI-2 and DMAI-2) are effective for the highly mature organic matter at EasyRo > 2.0%. The extent of oil cracking (EOC) calculated from the broadly used (3- + 4-) MD method (Dahl et al. in Nature 399:54–56, 1999) is proven to overestimate, especially for highly cracked samples due to the new generation of (3- + 4-) MD. Still, it can be corrected using a new formula at < 3.0% EasyRo. Other diamondoid-related indices (e.g., EAI, DMDI-2, As/Ds, MAs/MDs, DMAs/DMDs, and DMAs/MDs) can also be used to estimate EOC. However, these indices cannot be applied to TSR-altered petroleum. TSR is experimentally confirmed to generate diamantanes and thiaadmantanes at 1.81% EasyRo likely via direct reactions of reduced S species with hydrocarbons and accelerate the decomposition of diamantanes at > 2.62% EasyRo compared with thermal chemical alteration (TCA). More studies are needed to assess specific mechanisms for the formation of thiadiamondoids under natural conditions. [ABSTRACT FROM AUTHOR]

Abstract: In this study, changes in the abundance and distribution of diamondoids in petroleum with thermal maturity were investigated by a simulation oil cracking experiment. Highly sensitive and selective gas chromatography–triple quadrupole mass spectrometry (GC–MS–MS) was employed to quantify diamondoids at ppm and sub-ppm levels. The results indicate that diamondoids were generated primarily within the maturity range 1.0–2.1% EasyRo and destroyed at high thermal maturity (>2.1% EasyRo). Hence, the occurrence of high concentrations of diamondoids probably corresponds to the maturity range from the wet gas to the early dry gas stage (i.e., 1.5–2.5% EasyRo). Good correlations were observed between a few ratios of diamondoids (i.e., EAI, DMAI-1, DMDI-1 and TMAI-1) and EasyRo. This finding indicates that these parameters may be useful maturity indices for organic matter from the late oil window to the dry gas window. [Copyright &y& Elsevier]

Abstract: In this study, headspace single-drop microextraction (HS-SDME) coupled with gas chromatography-flame ionization detection (GC-FID) was tested to determine C6–C12 light hydrocarbons (LHs) in petroleum and aqueous samples. Several significant experimental parameters, such as drop solvent type, drop volume, sample solution ionic strength, agitation speed and extraction time were optimized. Under optimum extraction conditions, specifically, a 1.5μl microdrop of n-hexadecane, 30min extraction of a 5ml aqueous sample placed in a 10ml vial, and stirring at 1000rpm at room temperature, the reproducibility and accuracy of this method were found to be satisfactory. Two examples using this method indicated that HS-SDME is a simple, efficient and promising technique for the determination of volatile C6–C12 LHs in complex matrices. [Copyright &y& Elsevier]

Diamondoid compounds are widely used to reflect thermal maturation of high mature source rocks or oils and oil cracking extents. However, diamondoids and thiadiamondoids were demonstrated to have newly been generated and decomposed in our hydrothermal pyrolysis of crude oil and TSR experiments. Our results show that adamantanes and diamantanes are generated primarily within the maturity range 0.48–2.1% and 1.2–3.0% EasyRo, respectively. Their formation is enhanced and the decomposition of diamantanes obviously lags at elevated temperatures compared with anhydrous experiments. MDI, EAI, DMAI-1, DMDI-2 may serve as reliable maturity proxies at > ca.1.0% EasyRo, and other isomerization indices (TMAI-1, TMAI-2 and DMAI-2) are effective for the highly mature organic matter at EasyRo > 2.0%. The extent of oil cracking (EOC) calculated from the broadly used (3- + 4-) MD method (Dahl et al. in Nature 399:54–56, 1999) is proven to overestimate, especially for highly cracked samples due to the new generation of (3- + 4-) MD. Still, it can be corrected using a new formula at < 3.0% EasyRo. Other diamondoid-related indices (e.g., EAI, DMDI-2, As/Ds, MAs/MDs, DMAs/DMDs, and DMAs/MDs) can also be used to estimate EOC. However, these indices cannot be applied to TSR-altered petroleum. TSR is experimentally confirmed to generate diamantanes and thiaadmantanes at 1.81% EasyRo likely via direct reactions of reduced S species with hydrocarbons and accelerate the decomposition of diamantanes at > 2.62% EasyRo compared with thermal chemical alteration (TCA). More studies are needed to assess specific mechanisms for the formation of thiadiamondoids under natural conditions. [ABSTRACT FROM AUTHOR]

The well-defined lanthanide co-doped upconversion nanoparticles(UCNPs) had been synthesized using a simple solvothermal route at 150 °C, which was lower than previous reports. The shuttle-like and spherical UCNPs co-doped by Yb 3+ /Tm 3+ had been prepared, respectively. The morphology, crystal phase and size distribution of various UCNPs could be easily controlled. The growth mechanism and morphology transition of UCNPs had been deduced by schematic diagram. UC luminescence could be tuned by employing different host lattices (GdF 3 , YF 3 , NaGdF 4 and NaYF 4 ). NaGdF 4 :Yb 3+ /Tm 3+ displayed the strongest UC luminescence at 475 nm among four kinds of UCNPs, and its emission intensity was almost 10 times higher than that of NaYF 4 :Yb 3+ /Tm 3+ . UC mechanism had been determined by energy level diagrams. It’s revealed that the accumulation and energy transfer of Gd 3+ could be demonstrated in polycrystalline structure. The work provided a simple method for preparation of UCNPs with tunable UC luminescence. [ABSTRACT FROM AUTHOR]

We attempted to differentiate the effects of thermal chemical alteration (TCA) from thermochemical sulfate reduction (TSR) on formation and isomeric distribution of thiadiamondoids and diamondoids in oils and condensate from deeply buried Cambrian and Ordovician carbonate reservoirs in the Tarim Basin, China. Diamondoids and thiadiamondoids with 1–3 cages were detected in all the oils analyzed. Total thiadiamondoid concentrations reflect extent of TSR. Diamondoid concentrations and most of the diamondoid-based maturity proxies and the source rock lithology proxy increase with increasing extent of TSR, indicating that they are controlled by the extent of the TSR process (or reaction with H 2 S) to a greater degree than by TCA. TSR may have oxidized hydrocarbons to oxygenated species and finally to CO 2 and newly generated and concentrated diamondoids and organic sulfur compounds. The most extensive TSR-altered ZS1C condensate contains 3.2 wt% total dibenzothiophenes, 0.4 wt% thiadiamondoids and 5.9 wt% diamondoids together with higher polymantanes including tetramantanes and pentamantanes in association with polythiadiamondoids, including dithiaadamantanes, trithiaadamantanes and tetrathiaadamantanes. These polythiadiamondoids have been detected only from heavily TSR-altered petroleum in this study and North American samples and may be derived from the sulfurization of hydrocarbons, including diamondoids, under high temperature and highly reducing conditions during advanced stages of TSR. The polymantanes may have been generated from alkylation of lower-cage diamondoids and subsequent homologation, or from free radical reactions. This study indicates that TSR may have led to the generation and isomerization of thiadiamondoids and diamondoids, and thus diamondoid-based maturity and lithology proxies cannot be used to reflect maturity and lithology in the TSR active areas, and that the occurrence of polythiadiamondoids can be used to indicate heavy TSR alteration. [ABSTRACT FROM AUTHOR]

An interstitial vacancy on molybdenum nitride has been determined as a negative factor towards the alkaline hydrogen evolution reaction (HER) by reason of upraising the d orbitals of Mo. Nevertheless, investigations aiming to eliminate the vacancies are rarely reported. Here, an interstitial reconfiguration method for the design of stoichiometric molybdenum carbonitride (Mo2CN) is proposed, in which the vacancies are fulfilled by lattice carbon. Multiple fine structural analyses alongside with the theoretical calculations indicate that beyond lower the d orbitals of Mo by the hybridization of additive p‐d orbitals, lattice carbon also behaves as the extra active center with exceptional H adsorption/desorption energy. Mo2CN reveals an adorable overpotential of −84 mV at a current density of 10 mA cm−2 with a long‐term electrochemical stability by accompanying the nitrogen‐doped carbon substrate. It is anticipated that the vacancy‐eliminating concept will provide a constructive entry point for the rational design of electro‐catalysts and beyond. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pyrolysis experiments on four organic matter types simulate diamondoid evolution. • Principal component analysis explains the main factors affecting diamondoid indices. • PCA-Fisher discriminant analysis model objectively identifies oil source types. • PCA-regression analysis model quantitatively predicts oil thermal maturity. Assessing the origins and thermal maturity of oils is an important issue in applied petroleum geochemistry. In this study, we extracted information regarding the sources and thermal maturity of oils from diamondoid data using multivariate statistical analysis based on four series of thermal simulation experiments conducted on Type I, II, and III kerogens and a crude oil. Using principal component analysis (PCA) and discriminant analysis (DA), we established the relationship between diamondoid indices and kerogen type, which was then used to identify the source of oils in some oil fields in China. PCA and regression analysis (RA) were used to determine the quantitative relationship between diamondoid indices and thermal maturity, which was then used to estimate the thermal maturity of the studied oils. Our results indicate that this approach is effective for determining the source and maturity of oils, particularly for condensates. [ABSTRACT FROM AUTHOR]

With the increasing number of shale gas wells being hydraulically fractured with recycled flowback and produced water to reduce the consumption of fresh water, geochemical indicators of hydraulic fracturing flowback fluids (HFFFs) from such wells need to be found to evaluate the potential pollutants caused by shale gas development. To fill this knowledge gap, we analysed 64 HFFF samples from 3 Changning wells (fracked with recycled wastewater) to form a time series and compared them to HFFF samples from 3 Weiyuan wells (fracked with fresh water). We also made comparisons of HFFFs from two types of wells in the Appalachian Basin with reported data. The results indicated that regardless of the fracturing fluid being used, the water‒rock reaction caused by the hydraulic fracturing process resulted in the release of exchangeable phase elements, such as lithium, boron, with relatively depleted δ7Li and δ 11B, and strontium with relatively enriched 87Sr/86Sr values on the shale surface, into the HFFFs. The composition of the injected fracturing fluid affected the strength of the water‒rock reaction, but the effect is negligible, as the fracturing process can still form the unique Sr, Li, and B isotope ratios of the HFFF. Thus, the elemental signatures (B/Cl and Sr/Cl) and isotopic fingerprints (δ 11B, δ7Li, and 87Sr/86Sr) derived from HFFFs can be used to distinguish between HFFFs from wells hydraulically fractured by either fresh water or recycled wastewater and flowback water from conventional oil and gas wells. The results are important for the environmental evaluation of the large number of wells being fracked with recycled wastewater each year. [Display omitted] • δ 11B and 87Sr/86Sr can be used as indicator for HFFF in Changning field. • Hydraulic fracturing caused the release of minerals enriched in 10B, 6Li, and 87Sr. • Shale formation water composition determined the ratio between Na, Ca, Cl, and Br. • Fracturing fluid composition impact the major elements of HFFFs in the first dozens of days. [ABSTRACT FROM AUTHOR]

Abstract: In this study, a simple solvent dilution followed by highly selective and sensitive gas chromatography–triple quadrupole mass spectrometry (GC–MS–MS) detection was employed to quantify diamondoids in crude oils. Runtime parameters, i.e., parent and daughter ions, collision energy (CE) and scan time, were optimized to obtain maximum selectivity and sensitivity for target analytes. Under optimum conditions, the reproducibility and accuracy of the method were tested and found to be satisfactory. Comparison of GC–MS–MS and GC–MS methods for the determination of diamondoids indicates that GC–MS–MS yields higher sensitivity (method quantitation limits of 0.08–0.37μg/goil) and better selectivity than GC–MS (method quantitation limits of 0.78–8.44μg/goil) due to the elimination of matrix ion interferences using the selected reaction monitoring (SRM) mode. In addition, quantitative data confirm that group separation has a considerable effect on the quantification of diamondoids and the effect appears to depend on multiple factors. Two crude oils (TZ261 and TD2) from the Tarim Basin, China were used to evaluate the GC–MS–MS method. The results prove that the GC–MS–MS method is a promising tool for quantitative analysis of diamondoids in crude oils, especially for oil samples with low diamondoid concentrations. [Copyright &y& Elsevier]

Abstract: In this study, headspace single-drop microextraction (HS-SDME) coupled with gas chromatography–isotope ratio mass spectrometry (GC–IRMS), was employed to determine compound specific carbon isotopic values (δ13C) of gasoline range hydrocarbons. The reproducibility of the method was found to be satisfactory. By comparison with the δ13C values of the twelve target compounds determined using direct injection of their n-C16 solution, no obvious isotopic fractionation was observed during the HS-SDME procedures. Some parameters that could affect the carbon isotopic fractionation, such as ionic strength of working solutions and inlet split ratio, were examined. The results also suggest that these factors had no significant effect on the carbon isotopic determination of gasoline range hydrocarbons. The application of HS-SDME to a crude oil sample proved that this method could be a promising tool for the determination of carbon isotopic values of gasoline range hydrocarbons in oils or aqueous samples. [Copyright &y& Elsevier]

By 2013, more than 20 gas fields related to Late Paleozoic coal measures have been discovered in China, primarily distributed in the Bohai Bay, Ordos, Sichuan, and Junggar Basins. The total proven reserve in these gas fields is more than 3200 × 10 9  m 3 , accounting for 30.1% of the proven gas reserves in China. After analyzing the molecular compositions, stable carbon isotopes, and helium isotopes of 375 gas samples, genetic types and origins of the natural gas, as well as the secondary alterations it experienced, are discussed in this study. Most of the natural gas related to the Late Paleozoic coal measures are coal-type gas, with some of the gases from the Sichuan Basin and the Jingbian gas field in the Ordos Basin being oil-type gases generated from marine mudstones in the Permian Longtan Formation and marine carbonates in the Ordovician Majiagou Formation, respectively. The equivalent vitrinite reflectance values based on stable carbon isotopes of natural gases vary from 0.8% to 2.5%, indicating the mature to over mature stage. Positive carbon isotope series (δ 13 C-CH 4  < δ 13 C-C 2 H 6  < δ 13 C-C 3 H 8 ) are observed in most gas samples, and carbon isotope reversals occur in the forms of δ 13 C-CH 4  > δ 13 C-C 2 H 6 and δ 13 C-CH 4  < δ 13 C-C 2 H 6  > δ 13 C-C 3 H 8 . The form of δ 13 C-CH 4  > δ 13 C-C 2 H 6 is primarily resulted from the mixing of oil-type gases of different maturities, while the form of δ 13 C-CH 4  < δ 13 C-C 2 H 6  > δ 13 C-C 3 H 8 is primarily resulted from the mixing of coal-type gases of different maturities. High concentrations of hydrogen sulfide in natural gas from the Sichuan Basin and the Chenghai gas field in the Bohai Bay Basin are resulted from thermochemical sulfate reduction (TSR), which causes, to some extent, the fractionation of carbon isotopes. By contrast, the fractionation of methane carbon isotopes resulting from the TSR effect is not clear. Carbon dioxide from the Bohai Bay and Junggar Basins is primarily biogenic, generated via the thermal decomposition of organic matter, while that from the Ordos Basin, Sichuan Basin, and Chenghai gas field is generated via the thermal decomposition of carbonates. Carbon dioxide related to the TSR effect has also contributed to the Sichuan Basin and Chenghai gas field. [ABSTRACT FROM AUTHOR]

According to the compositional and isotopic analyses of He, CO 2 and CH 4 of 95 gas samples from the Ordos Basin and 76 gas samples from the Bohaibay Basin in China, this study carried out a detailed investigation on the geochemical characteristics of helium and CO 2 from the cratonic and rift basins, especially the cratonic Ordos Basin and rift Bohaibai Basin in China. Compared to the rift Bohaibay Basin, the cratonic Ordos Basin has lower level of helium and CO 2 , lower R/Ra ratio and lower δ 13 C CO2 maximum value. When the content of CO 2 is < 10%, both cratonic and rift basins have organic CO 2 associated with the hydrocarbon generation process and inorganic CO 2 from the thermal decomposition of carbonates or dissolution of organic acid. Rift basin can also have CO 2 > 20% and δ 13 C CO2 of − 6 ± 2‰ or − 4‰ –− 9‰, which is of volcanic-magmatic or mantle-derived origin, while cratonic basin has no such type of CO 2 . The cratonic basins (Ordos, Sichuan) have CO 2 < 5% and relatively smaller variation range of δ 13 C CO2 , i.e., 25.6‰ (− 0.8‰ –− 26.4‰). The rift basins have higher level of CO 2 , R/Ra ratios and δ 13 C CO2 values. The content of CO 2 can reach 100%, the R/Ra ratio can be up to 6.45 and the variation range of δ 13 C CO2 is 34‰ (7‰ –− 27‰). Bigger variation range of δ 13 C CO2 implies stronger tectonic activities, which is not favorable for the gas accumulation. While smaller variation range means more stable structure, which is favorable for the discovery of large gas fields. Sample in the cratonic basin in China generally has CH 4 / 3 He of 10 9 – 10 12 and R/Ra < 0.1 and in the rift basin it has CH 4 / 3 He of 10 5 – 10 13 and R/Ra of 0.1– 6.45. It is concluded that methane with CH 4 / 3 He ≤ 10 8 is of inorganic origin and methane with CH 4 / 3 He ≥ 10 11 is of organic origin. The regression equation for the CH 4 / 3 He-R/Ra in the cratonic basin is: y = 3E + 11e − 46.28x and it is: y = 4E + 10e − 1.791x in the rift basin. Both Ordos and Bohaibay basins found gas wells with He > 0.05%, which has significant commercial values and provides a clue for the exploration of helium-rich gas fields. Traps with R/Ra > 2 is a favorable clue for the discovery of CO 2 gas fields. Seven CO 2 gas fields have been found in the Bohaibay Basin, but no systematic development has been carried out and only some liquid CO 2 has been injected for tight oil from the Huagou CO 2 gas field. [ABSTRACT FROM AUTHOR]

This work discussed the origins, alteration and accumulation processes of the oil and gas in the Kekeya gas condensate field based on molecular compositions, stable carbon isotopes, light hydrocarbons, diamondoid hydrocarbons and biomarker fingerprints. A comparison study is also made between the geochemical characteristics of the Kekeya hydrocarbons and typical marine and terrigenous hydrocarbons of the Tarim Basin. Natural gas from the Kekeya gas condensate field is derived from Middle-Lower Jurassic coal measures while the condensates are derived from Carboniferous-Permian marine source rocks with a higher maturity. In the study area, both natural gas and condensates have experienced severe water washing. A large amount of methane was dissolved into the water, resulting in a decrease in the dryness coefficient. Water washing also makes the carbon isotopic compositions of the natural gas more negative and partially reverse. Considering that the gas maturities are higher than once expected, gas generation intensity in the study area should be much stronger and the gas related to the Jurassic coal measures could promise a greater prospecting potential. As a result of evaporative fractionation, the Kekeya condensates are enriched in saturates and lack aromatics. Evaporative fractionation disguises the original terrigenous characteristics of the light hydrocarbons associated with the natural gas, making it appear marine-sourced. Thus, alteration processes should be fully taken into consideration when gas-source correlations are carried out based on light hydrocarbons. With the condensates discovered in the study area all being 'migration phase', the pre-salt Cretaceous and Jurassic reservoirs may promise great exploration potential for the 'residual phase' hydrocarbons. This research not only is of significance for oil and gas exploration in the southwest Tarim Basin, but also sheds light on the oil/ gas-source correlations in general. [ABSTRACT FROM AUTHOR]

Although the annual production of shale gas in China was 13 × 10 8 m 3 in 2014, a systematic study on geochemical and isotopic characteristics of these unconventional gases has not been well addressed. In the present study, almost all shale gas samples available in China, including marine shale gas from the Wufeng-Longmaxi Formation in the Sichuan Basin (O 3 w–S 1 l) and terrestrial shale gas from Chang 7 Member (T 3 y 7 ) in the Ordos Basin, were collected and analyzed for their geochemical and isotopic compositions. The shale gas from the Wufeng-Longmaxi Shale is dry gas with an average methane content of 98.38% and records a highest content of CH 4 in the world (99.59%), which is consistent with the very high thermal maturity levels of the gas shales that have equivalent vitrinite reflectance (EqVRo) values between 2.4 and 3.6%. The δ 13 C 1 values are correspondingly heavy and record a heaviest δ 13 C 1 values (−26.7‰) for the shale gases found in the world as well. The average values of δ 13 C 1 , δ 13 C 2 and δ 13 C 3 for the Wufeng-Longmaxi shale gas are −31.3‰, −35.6‰, and −47.2‰, respectively, displaying a complete carbon isotopic reversal (i.e., δ 13 C 1 > δ 13 C 2 > δ 13 C 3 ). δ 2 H CH4 and δ 2 H C2H6 has an average value of −148‰ and −173‰, respectively, also yielding a hydrogen isotopic reversal (i.e., δ 2 H CH4 > δ 2 H C2H6 ). The Chang 7 shale has an average TOC content of 13.81% with vitrinite reflectance (VRo) values between 0.7 and 1.2%. The Chang 7 shale gas is wet gas with an average methane content of 84.90% and is rich in heavy gaseous hydrocarbons (C 2 –C 5 ). The respective values of δ 13 C 1 , δ 13 C 2 and δ 13 C 3 are −48.7‰, −36.4‰ and −31.3‰, displaying a positive carbon isotopic distribution pattern (i.e., δ 13 C 1 < δ 13 C 2 < δ 13 C 3 ). The average δ 2 H CH4 , δ 2 H C2H6 and δ 2 H C3H8 values are −256‰, −244‰ and −188‰, respectively, and are characterized by a positive distribution pattern (i.e., δ 2 H CH4 < δ 2 H C2H6 < δ 2 H C3H8 ). The differences in gas wetness and carbon and hydrogen isotopic distribution patterns between the shale gases from the Wufeng-Longmaxi and Chang 7 shale are attributed to variations in thermal maturity levels. CO 2 is present in low content in both the Wufeng-Longmaxi and Chang 7 shale gases, mostly less than 1%. δ 13 C values for the CO 2 in the Wufeng-Longmaxi Formation are between 8.9 and −9.2‰, indicating an inorganic origin from the cracking of carbonate mineral in the shales under high temperatures. In contrast, δ 13 C values of the CO 2 in the Chang 7 shale gas range from −8.2 to −22.7‰, indicating an organic origin from the thermal degradation of organic matter. Helium in both the Wufeng-Longmaxi and Chang 7 shale gases is dominantly of curst origin in terms of their R/Ra ratios that vary from 0.01 to 0.08. Positive carbon isotopic distribution pattern is typical of primitive thermogenic gas. However, it can be converted into complete or partial carbon isotopic reversal patterns due to secondary alteration. The causes that yield carbon isotopic reversal include (1) mixing of gases with the same source but different thermal maturity levels; (2) secondary cracking of oil or wet gas; (3) formation water-involved reactions; (4) gas diffusion; and (5) carbon isotope exchange between alkane gases at high temperature. Among them, carbon isotopic exchange between alkane gases at high temperature is a key factor. Nine plots have been drawn based on the shale gases from China, USA and Canada. Among them, the plot of δ 13 C 2 versus wetness demonstrates a “lying-S” shape with two inflection points on the gas wetness axis. The wetness value of 1.4% represents a critical point from pyrolytic gas (primary cracking gas) to cracking gas (secondary cracking gas) and whereas the wetness value of 6% marks the end of oil generation. On the diagram of wetness versus δ 13 C, shale gases with wetness values greater than 1.6% are characterized by positive carbon isotopic distribution pattern, whereas a complete or partial carbon isotopic reversals are observed for shale gases with wetness values less than 1.6%. [ABSTRACT FROM AUTHOR]

[Display omitted] • A loofah-like carbon nitride sponge(LCN) is successfully synthesized. • The LCN features 3D hierarchical porous structure and ultrathin thickness. • Oxygen doping and nitrogen vacancies engineering are simultaneously constructed. • The LCN shows excellent photocatalytic activity and stability. • The mechanism of transfer hydrogenation with water as hydrogen source is revealed. The vigorous development of photocatalytic water splitting technology has laid the foundation for the photocatalytic transfer hydrogenation of organic substrates to produce the high value-added chemicals using water as hydrogen source. Nevertheless, the high dissociation energy of the O–H bond impedes its academic progress and the practical applications. Herein, we synthesize a 3D hierarchical porous loofah-like carbon nitride sponge (LCN) with ultrathin thickness via the supramolecular pre-organization coupling with the oxidation etching process, in which the heterogeneous oxygen atoms and the nitrogen vacancies are in-situ engineered. On top of the adorable photocatalytic H 2 evolution (4812 μmol h−1 g−1), LCN associated with Pt cocatalyst reveals a conversion rate of 96.5 % towards the hydrogenation of 4-nitrophenol, substantially superior to the reference experiment (8.3 %). Further based on the isotope-labeling tests and the density functional theory calculations, the photo-generated H0 from water is clarified to be the direct reducing agent, tactfully skipping the hydrogen extraction step in the traditional path. This work provides a green and sustainable methodology to transfer the solar energy to the valuable fine chemicals, as well as highlights the importance of the 3D hierarchical porous structure to the catalytic activity. [ABSTRACT FROM AUTHOR]

The Zizhou gas field is a large, tight sandstone gas field in the Ordos Basin, China. Based on the analysis of the geological background, gas components, light hydrocarbon composition, carbon and hydrogen isotope values of alkane gases, and the geochemical correlation between gases of the Zizhou gas field and analogs from other fields in the basin, we conclude that : (a) most natural gases in the Zizhou gas field are dry with a small content of wet gas; (b) the gases have similar carbon isotopic and light hydrocarbon compositions to the analogs from other fields, as well as much more positive δ 13 C values and high contents of C 5–7 i -alkanes and methylcyclohexanes, indicating typical coal-derived gas; (c) carbon isotopic reversal in some gas samples is due to mixing of coal-derived gases of different maturities; (d) the gases are sourced from mature to high-mature Carboniferous–Permian coal-measures; and (e) the gas reservoirs represent continuous accumulations. [ABSTRACT FROM AUTHOR]

• A series of 2D coordination polymers based on our firstly reported poly (triazine imide) ligand is fabricated via a bottom-up strategy. • As-prepared Ni/Fe coordination polymers shows an ultrathin thickness of ∼5 nm and a desirable catalytic activity towards the OER. • Mechanism investigations elaborate that the poly (triazine imide) ligand not only help to realize the 2D morphological generation, but also afford additive catalytic centers through creating the Lewis base sites, thus accelerating the oxygen species absorption and the reaction rate. 2D metal coordination polymers have emerged as a new serious of efficient electrocatalysts in OER for their abundant unsaturated coordination centers and high charge-carrier mobility. However, the synthetic routes are mostly depending on the top-down exfoliation with unavoidable structural fragmentation and the annoying sheets' re-stacking. Here, an electrocatalytic poly (triazine imide) ligand is firstly synthesized and successfully applied to construct the 2D Ni/Fe coordination polymers nanosheets (Ni/Fe-CPNs) through a bottom-up strategy. Average thickness of the nanosheets is around 5 nm, enabling the highly exposed reactive centers. Further benefiting from the ligand promotion effect, absorption of the oxygen species during the OER is effectively accelerated, thus improving the reaction kinetics. Accordingly, the Ni/Fe-CPNs reveals an adorable overpotential of 244 mV at the current density of 10 mA cm−2, and the Tafel value of 65.8 mv dec−1. Both values are much better than that of commercial RuO 2 , and competitive to most of the reported catalysts. The ex-situ techniques, including Raman, FT-IR and XPS analysis alongside with applied potential, are also applied to elaborate the catalytic mechanism. This work offers a new point of view to improve the catalysts' activity. [Display omitted] [ABSTRACT FROM AUTHOR]

Highlights: [•] An improved sample pre-treatment method for the analysis of SCFAs in RICO products. [•] Combine the HS-SDME with derivatization method for quantitative analysis of SCFAs in complex matrices. [•] This method allows detection of the studied analytes at low concentrations in aqueous phases. [ABSTRACT FROM AUTHOR]

Abstract: In this study, headspace single-drop microextraction (HS-SDME) coupled with gas chromatography-flame ionization detection (GC-FID), was employed to determine short-chain fatty acids (SCFAs) in ruthenium tetroxide (RuO4) oxidation products of asphaltenes. Several significant parameters, such as drop solvent type, drop volume, sample solution ionic strength, agitation speed, extraction time, and ratio of headspace volume to sample volume were optimized. Under optimum extraction conditions (i.e., a 3-μL drop of 1-butanol, 20min exposure to the headspace of a 6mL aqueous sample placed in a 10mL vial, stirring at 1000rpm at room temperature, and 30% (w/v) NaCl content), the reproducibility and accuracy of the method have been tested and found to be satisfactory. The analysis of a real asphaltene sample using this method proved that HS-SDME can be a promising tool for the determination of volatile SCFAs in complex matrices. [Copyright &y& Elsevier]