Gaseous Alkanes Research Articles

Arylation of Gaseous Alkanes in Flow

Arylation of Gaseous Alkanes in Flow

Differences in the Genesis and Sources of Hydrocarbon Gas Fluid from the Eastern and Western Kuqa Depression

The Kuqa Depression is rich in oil and gas resources and serves as a key production area in the Tarim Basin. However, controversy persists over the genesis of oil and gas in the various structural zones of the Kuqa Depression. This study employs natural gas composition analysis, gas carbon isotope analysis and gold pipe thermal simulation experiments, to comprehensively analyze the differences in the genesis and sources of hydrocarbon gas fluid from the eastern and western Kuqa Depression. The results show that the Kuqa Depression is dominated by alkane gas, with an average gas drying coefficient of 95.6, with nitrogen and carbon dioxide as the primary non-hydrocarbon gases. The average of δ13C1, δ13C2 and δ13C3 values in natural gas are −27.70‰, −20.43‰ and −21.75‰, respectively. Based on comprehensive natural gas geochemical maps, the CO2 in the natural gas from the Tudong and Dabei areas, as well as the KT-1 well of the Kuqa Depression, is thought to be of organic origin. Additionally, natural gas formation in the Tudong area is relatively simple, consisting entirely of thermally generated coal gas derived from the initial cracking of kerogen. The natural gas in the KT-1 well and the Dabei area are mixed gasses, formed by the initial cracking of kerogen from highly evolved lacustrine and coal-bearing source rocks, exhibiting characteristics resembling those of crude oil cracking gas. The methane (CH4) content of natural gas in the Dabei area is high and the carbon isotopes are unusually heavy. Considering the regional geological background, potential source rock characteristics and geochemical features may be related to the large-scale invasion of dry gas contributed by CH4 from highly evolved, underlying coal-bearing source rocks. Consequently, the CH4 content in the mixed gas is generally high (Ln (C1/C2) can reach up to 5.38), while the relative content of heavy components is low, though remains relatively unchanged. Thus, the map of the relative content of heavy components still reflects the characteristics of the original gas genesis (initial cracking of kerogen). Mixed-source gas was analyzed using thermal simulation experiments and natural gas composition ratio diagrams. The contributions of natural gas from deep, highly evolved coal-bearing source rocks in the KT-1 well and the Dabei area accounted for more than 90% and approximately 60%, respectively. This analysis provides theoretical guidance for natural gas exploration in the research area.

Deeper insights into the devolatilization mechanism of biomass fixed-bed gasification under various atmospheres

In recent years, biomass oxy-fuel gasification has prompted increased interest for its ability to produce a gas with low tar content and to assist in carbon reduction. It is noteworthy that the type of atmosphere is a crucial factor influencing the devolatilization process in biomass gasification and the specific mechanisms by which an oxy-fuel atmosphere influences the devolatilization process remain inadequately explored. This work aimed to investigate the effect of various reaction atmospheres on devolatilization behavior, reaction kinetics, intermediate product formation, and biochar functional groups (BFGs) evolution. In comparison to an inert atmosphere, the oxy-fuel atmosphere facilitated the release of volatiles, and enhanced energy self-sustainability within the devolatilization system. The presence of O2 and CO2 promoted the generation of potential anhydrosugars while suppressing the formation of phenolic compounds. The synergistic effect present in the oxy-fuel atmosphere augments the exothermic effect and promotes the release of volatile and alkane gases during the devolatilization process. Furthermore, as oxygen concentrations increased in the reaction atmosphere, the sequential response of BFGs primarily followed the order: C-O → aromatic ring → C-OH/C–H/COO– → C=O. Moreover, advanced characterization analyses revealed that the oxy-fuel environment was more effective in promoting the aromatization and pore structure of biochar than an inert atmosphere. Collectively, these findings have substantial implications for reaction modeling in biomass fixed-bed gasification under real gas atmospheres and guide future research on tar control strategies.

Genetic mechanism and exploration progress of global deep alkane gases and small molecule gases (H2, He)

From the perspective of global oil and gas exploration trends, deep to ultra-deep gas exploration has emerged as a focal point in the past decade, shaping the future landscape of fossil energy exploration. Specifically, China has undertaken oil and gas exploration ventures reaching depths of 10,000 m, drawing significant attention to the genesis of gas accumulation at such extreme depths. An analysis of crucial geological factors including basin formation, hydrocarbon generation, storage and accumulation reveals that kerogen cracking gas, crude oil cracking gas, and coal cracking gas served as vital gas sources for ultra-deep paraffin gas in highly over-mature oil-bearing basins, establishing a model for the formation, evolution, and accumulation of natural gas. With the continuous expansion of hydrocarbon genesis theory and the increasing global demand for clean energy, hydrogen, as an important link between inorganic and organic hydrocarbon generation theory, and as a promising clean energy, has gradually aroused extensive attention in the academic community. The genetic types of natural hydrogen are mainly generated from inorganic genetic mechanisms, including earth degassing, water-rock interaction, and water radiolysis. The lithology of the reservoir and the sealing property of the cap layer control the accumulation of natural hydrogen, with the salt-rock cap layer beneficial to the large-scale preservation of natural hydrogen reservoir. Helium, as a constituent resource of natural gas, represents the primary target for exploration among deep small molecule gases. Helium within natural gas reservoirs can be categorized into atmospheric, crust-source and mantle-source varieties based on their origins. Helium source rocks exhibit significant disparities in helium generation capacity attributed to variations in rock types, mineral compositions, and ages, resulting in a relatively complex mechanism governing helium reservoir release, migration and accumulation. Typically, helium-rich gas reservoirs lack optimal cap sealing performance, as excessive sealing inhibits the formation of pressure relief conduits, thereby impeding the supply of helium-rich fluid to the reservoir. Through an analysis of genetic types, formation and evolution models, and reservoir preservation mechanisms pertinent to deep alkane gases and small molecule gases, it is revealed that the large-scale pool-forming geologic units and giant hydrocarbon enrichment zones in ultra-deep strata are key and promising prospects for delivering successive discoveries, and the energy significance and development trend of natural hydrogen and helium in the future were pointed out, in order to provide references for promoting the transition from high carbon to low carbon and carbon-free energy in the energy field.

Surface geochemistry as a key to understanding the petroleum system in regions of complex geology - Polish Outer Carpathians

The goal of the study is to investigate the relationships between soil gas composition and geological structures in a structurally complex area of the Carpathian fold and thrust belt. Surface geochemical surveys, aimed at determining the molecular and isotopic composition of soil gas samples, were carried out in the central part of the Polish Outer Carpathians in two major tectonic units, the Magura Unit and the Fore-Magura Group of units, which outcrop at the front of the former and within it as a tectonic window (the so-called Mszana Dolna Tectonic Window, MDTW). The tectonic structure of the area has numerous deformations, such as folds, thrusts, and strike-slip faults, that are accompanied by broad zones of mélange. In all 572 soil gas samples, the concentrations of light alkanes, gaseous alkenes as well as non-hydrocarbon (e.g. hydrogen) components were determined, and part of the samples were analysed to test the carbon isotope composition of methane and carbon dioxide.The results of the surface geochemical survey showed significant differences in the recorded microconcentrations of hydrocarbons within the tectonic units of the Outer Carpathians. Significantly higher concentrations of total alkanes C2-C5 were mainly recorded in the MDTW, although the distribution of total alkane values within the Window shows strong connections with the arrangement of strata and the strike of faults and thrusts. Generally, the sealing is insufficient within the MDTW to support the existence of conventional economically viable hydrocarbon accumulations. Our data confirms the sealing role of the Magura Unit in the Carpathian oil system. Therefore, hydrocarbon sources (i.e. potential hydrocarbon accumulations) may be expected within the Fore-Magura Group beneath the cover of the Magura Unit.Our results are also of key importance for the interpretation of surface geochemistry data in other oil and gas provinces with a complex geological structure.

Cross-Coupling of Gaseous Alkanes with (Hetero)Aryl Bromides via Dual Nickel/Photoredox Catalysis.

Gaseous alkanes represent the most abundant carbon-based chemical feedstocks in our planet. However, the intrinsic inertness of their C-H bonds has rendered the use of these alkanes very difficult for purposes beyond aerobic combustion and energy intensive processes. Thus, clean and energy-efficient transformations for their use in synthetic organic chemistry are still rare. Here we report a catalytic methodology for the direct cross-coupling of gaseous alkanes with (hetero)aryl bromides through the combination of metallaphotoredox-mediated hydrogen atom transfer and nickel catalysis. This protocol provides an efficient platform for the addition of short alkyl groups into diverse (hetero) aromatic rings, providing a wide range of high-value alkyl(hetero)arenes, and bypassing the longstanding need of using preactivated alkylating agents in C(sp2)-C(sp3) cross-couplings. The method features high chemoselectivity, regioselectivity and a remarkable functional group tolerance, operates under mild conditions, and exhibits operational simplicity.

Cross‐Coupling of Gaseous Alkanes with (Hetero)Aryl Bromides via Dual Nickel/Photoredox Catalysis

Gaseous alkanes represent the most abundant carbon‐based chemical feedstocks in our planet. However, the intrinsic inertness of their C‐H bonds has rendered the use of these alkanes very difficult for purposes beyond aerobic combustion and energy intensive processes. Thus, clean and energy‐efficient transformations for their use in synthetic organic chemistry are still rare. Here we report a catalytic methodology for the direct cross‐coupling of gaseous alkanes with (hetero)aryl bromides through the combination of metallaphotoredox‐mediated hydrogen atom transfer and nickel catalysis. This protocol provides an efficient platform for the addition of short alkyl groups into diverse (hetero) aromatic rings, providing a wide range of high‐value alkyl(hetero)arenes, and bypassing the longstanding need of using preactivated alkylating agents in C(sp2)‐C(sp3) cross‐couplings. The method features high chemoselectivity, regioselectivity and a remarkable functional group tolerance, operates under mild conditions, and exhibits operational simplicity

Main-group compounds selectively activate natural gas alkanes under room temperature and atmospheric pressure

Most C–H bond activations of natural gas alkanes rely on transition metal complexes. Activations by using main-group systems have been reported but required heating or photo-irradiation under high atmospheric pressure with rather low regioselectivity. Here we report that Lewis acid-carbene adducts facilely undergo oxidative additions to C–H bonds of ethane, propane and n-butane with high selectivity under room temperature and atmospheric pressure. The Lewis acids can be moved by the addition of a base and the carbene-derived products can be easily converted into aldehydes. This work offers a route for main-group element compounds to selectively functionalise C–H bonds of natural gas alkanes and other small molecules.

Nucleation mechanism of methane heterogeneous condensation under different driving forces

Clarifying alkane gas condensation characteristics is crucial to designing and optimizing liquefaction heat exchangers, which imposes higher demands on the microscopic understanding of alkane heterogeneous condensation. Thus, in this study, the condensation process of methane nucleation under different driving forces is investigated by molecular dynamics (MD) simulations. The dynamics characteristics of nucleation in methane heterogeneous condensation are analyzed by varying initial gas-phase pressure, cold wall temperature, and ethane content. The results showed that increasing the initial gas-phase pressure enhances intermolecular interactions, which alter the cluster formation path and significantly increase the methane gas nucleation rate from 1.997 × 1033/(m3·s) to 1.068 × 1034/(m3·s). While lowering the cold wall temperature promotes condensation by weakening the thermal motion of the gas molecules. Once condensation nuclei form in the system, the lower temperature conditions from lowering the cold wall temperature result in a higher growth rate of the clusters. Additionally, the addition of easily condensable component ethane can improve the condensation nucleation characteristics of low-saturated methane gas, facilitating the liquefaction of methane. This study aims to provide a microscopic understanding of the advancement of gas liquefaction technology by investigating the heterogeneous nucleation of alkane under different conditions from a microscopic perspective.

C1-4 Alkylation of Aryl Bromides with Light Alkanes enabled by Metallaphotocatalysis in Flow.

The homologous series of gaseous C1-4 alkanes represents one of the most abundant sources of short alkyl fragments. However, their application in synthetic organic chemistry is exceedingly rare due to the challenging C-H bond cleavage, which typically demands high temperatures and pressures, thereby limiting their utility in the construction of complex organic molecules. In particular, the formation of C(sp2)-C(sp3) bonds is crucial for constructing biologically active molecules, including pharmaceuticals and agrochemicals. In this study, we present the previously elusive coupling between gaseous alkanes and (hetero)aryl bromides, achieved through a combination of Hydrogen Atom Transfer (HAT) photocatalysis and nickel-catalyzed cross coupling at room temperature. Utilizing flow technology allowed us to conduct this novel coupling reaction with reduced reaction times and in a scalable fashion, rendering it practical for widespread adoption in both academia and industry. Density Functional Theory (DFT) calculations unveiled that the oxidative addition constitutes the rate-determining step, with the activation energy barrier increasing with smaller alkyl radicals. Furthermore, radical isomerization observed in propane and butane analogues could be attributed to the electronic properties of the bromoarene coupling partner, highlighting the crucial role of oxidative addition in the observed selectivity of this transformation.

C1‐4 Alkylation of Aryl Bromides with Light Alkanes enabled by Metallaphotocatalysis in Flow

The homologous series of gaseous C1‐4 alkanes represents one of the most abundant sources of short alkyl fragments. However, their application in synthetic organic chemistry is exceedingly rare due to the challenging C–H bond cleavage, which typically demands high temperatures and pressures, thereby limiting their utility in the construction of complex organic molecules. In particular, the formation of C(sp2)–C(sp3) bonds is crucial for constructing biologically active molecules, including pharmaceuticals and agrochemicals. In this study, we present the previously elusive coupling between gaseous alkanes and (hetero)aryl bromides, achieved through a combination of Hydrogen Atom Transfer (HAT) photocatalysis and nickel‐catalyzed cross coupling at room temperature. Utilizing flow technology allowed us to conduct this novel coupling reaction with reduced reaction times and in a scalable fashion, rendering it practical for widespread adoption in both academia and industry. Density Functional Theory (DFT) calculations unveiled that the oxidative addition constitutes the rate‐determining step, with the activation energy barrier increasing with smaller alkyl radicals. Furthermore, radical isomerization observed in propane and butane analogues could be attributed to the electronic properties of the bromoarene coupling partner, highlighting the crucial role of oxidative addition in the observed selectivity of this transformation.

Enhancing extinguishing efficiency for lithium-ion battery fire: Investigating the extinguishing mechanism and surface/interfacial activity of F-500 microcapsule extinguishing agent

Due to the high flammability and combustion enthalpy, electrolyte solvents such as dimethyl carbonate (DMC) are regarded as the main fuel in combustion reactions for lithium-ion batteries (LIBs). Herein, to understand the combustion reaction kinetics of LIB fires and explore the efficient extinguishing agent, the chemical oxidation kinetics of DMC at 740–1160 K are studied through a jet-stirred reactor system coupled to the synchrotron vacuum ultraviolet photoionization mass spectrometry and GC. The major consumption path of DMC is the H-abstraction reaction of OH∙ and H∙ radicals. CH3∙ radicals produce to CH4, C2H4 and other common alkane gases in LIB fires through H-abstraction reactions and compound reaction. On this basis, the extinguishing mechanism of F-500 extinguishing agent for LIB fires is studied. The hydrophilic (-[CH2-CH2-O]5) and oleophilic ([C16H33]-) groups give F-500 molecules the amphiphilic characteristics of adsorbing on the solution surface and associating inside the solution to form micelles. Based on the results of dynamic light scattering and cryo-electron microscopy, the size and number of micelles continue to increase and the structure of micelles gradually changes from spherical to rod-shaped, which enhance the solubilization effect. F-500 can strengthen the extinguishing effectiveness of water mist by capturing and encapsulating the DMC inside the water to form “DMC-F-500-Water” microcapsule. DMC is dispersed in the water, which leads to the heat loss and the reduction of concentration and flammability. Moreover, the adsorption of F-500 molecules along the solid-liquid-gas three-phase contact line can reduce the interfacial tension of water and promote wetting process, which leads to the larger spreading area and speed of evaporation. During the application of the extinguishing agent, F-500 agent can improve the cooling efficiency of water. This work provides a reference for the design and development of novel extinguishing agent for LIB fires.

Recovering high-quality glass fibers from end-of-life wind turbine blades through swelling-assisted low-temperature pyrolysis

The recycling of end-of-life wind turbine blades has become a global environmental challenge driven by the rapid growth of wind power. Pyrolysis is a promising method for recovering glass fibers from these discarded blades, but traditional pyrolysis is often operated at high temperatures, which degrades the mechanical properties of recovered fibers. To address this issue, a swelling-assisted pyrolysis method was proposed to recover high-quality glass fibers from end-of-life wind turbine blades at low temperatures. The results confirmed that the decomposition of the resin matrix within the blade was significantly promoted at low temperatures in the swelling-assisted pyrolysis process, achieving a resin decomposition ratio of 76.8 % at 350 °C. This improvement was attributed to enhanced heat transfer and co-pyrolysis with acetic acid. Swelling could physically disrupt the cross-linked structure of the blade, creating a more porous and layered structure, thereby enhancing heat transfer during the pyrolysis process. Simultaneously, the co-pyrolysis with acetic acid could generate hydrogen radicals, which promoted the cracking of macromolecular oligomers into lighter products or gaseous alkanes. Consequently, the formation of pyrolysis char within the solid pyrolysis product was reduced, shortening the oxidation duration to 30 min. In comparison to traditional pyrolysis, the swelling-assisted pyrolysis process effectively suppressed the diffusion of surface defects over the recovered fibers, leading to promising improvements in their flexibility, elasticity, and mechanical properties, with tensile strength notably increased by 27.5 %. These findings provided valuable insights into recovering high-quality glass fibers from end-of-life wind turbine blades.

Coupling noble gas and alkane gas isotopes to constrain normally pressured shale gas expulsion in SE Sichuan Basin, China

Coupling noble gas and alkane gas isotopes to constrain normally pressured shale gas expulsion in SE Sichuan Basin, China

Coupling Nitrate-Dependent Anaerobic Ethane Degradation with Anaerobic Ammonium Oxidation.

The microbial oxidation of short-chain gaseous alkanes (SCGAs, consisting of ethane, propane, and butane) serves as an efficient sink to mitigate these gases' emission to the atmosphere, thus reducing their negative impacts on air quality and climate. "Candidatus Alkanivorans nitratireducens" are recently found to mediate nitrate-dependent anaerobic ethane oxidation (n-DAEO). In natural ecosystems, anaerobic ammonium-oxidizing (anammox) bacteria may consume nitrite generated from nitrate reduction by "Ca. A. nitratireducens", thereby alleviating the inhibition caused by nitrite accumulation on the metabolism of "Ca. A. nitratireducens". Here, we demonstrate the coupling of n-DAEO with anammox in a laboratory-scale model system to prevent nitrite accumulation. Our results suggest that a high concentration of ethane (6.9-7.9%) has acute inhibition on anammox activities, thus making the coupling process a significant challenge. By maintaining ethane concentrations within the range of 1.7-5.5%, stable ethane and ammonium oxidation, nitrate reduction, and dinitrogen gas generation without nitrite accumulation were finally achieved. After the accomplished coupling of n-DAEO with anammox, nitrate reduction rates increased by 8.1 times compared to the rate observed with n-DAEO alone. Microbial community profiling via 16S rRNA gene amplicon sequencing showed "Ca. A. nitratireducens" (6.6-12.9%) and anammox bacteria "Candidatus Kuenenia" (3.4-5.6%) were both dominant in the system, indicating they potentially form a syntrophic partnership to jointly contribute to nitrogen removal. Our findings offer insights into the cross-feeding interaction between "Ca. A. nitratireducens" and anammox bacteria in anoxic environments.

C(sp3)–H sulfinylation of light hydrocarbons with sulfur dioxide via hydrogen atom transfer photocatalysis in flow

Sulfur-containing scaffolds originating from small alkyl fragments play a crucial role in various pharmaceuticals, agrochemicals, and materials. Nonetheless, their synthesis using conventional methods presents significant challenges. In this study, we introduce a practical and efficient approach that harnesses hydrogen atom transfer photocatalysis to activate volatile alkanes, such as isobutane, butane, propane, ethane, and methane. Subsequently, these nucleophilic radicals react with SO2 to yield the corresponding sulfinates. These sulfinates then serve as versatile building blocks for the synthesis of diverse sulfur-containing organic compounds, including sulfones, sulfonamides, and sulfonate esters. Our use of flow technology offers a robust, safe and scalable platform for effectively activating these challenging gaseous alkanes, facilitating their transformation into valuable sulfinates.

Generation of abnormal distributions of inter- and intramolecular δ13C compositions in hydrocarbons from gold tube pyrolysis of an Australian torbanite

Abnormal stable carbon isotopic (δ13C) compositions, deviating from the conventional order of δ13C1 < δ13C2 < δ13C3, are frequently observed in natural gas reservoirs. For thermogenic gas, these anomalies, such as δ13C1 < δ13C3 < δ13C2 or δ13C1 > δ13C2 > δ13C3, have multiple formation mechanisms including gas mixing in conventional systems and desorption processes of gaseous hydrocarbons in unconventional shale gas systems due to their inconsistency with Rayleigh fractionation processes. Considering distinct reaction pathways (e.g., C1 polymerized to C2), these aberrant δ13C signatures are often construed as intrinsic hallmarks of extensively evolved natural gas. However, on the basis of gas generation simulation, not all findings exhibit abnormal δ13C values, hinting at multifaceted and intricate mechanisms governing the isotopic fractionation of alkane gas components. This study conducted gold tube pyrolysis of an Australian torbanite, revealing four distinct types of δ13C anomalies in hydrocarbon classes. Polycyclic aromatic hydrocarbons (PAHs) exhibited δ13C values more negative than co-occurring n-alkanes. δ13C3 displayed a negative trend shift from EasyRo = 3.5 %, resulting in a partially δ13C-reversed gas (δ13C1 < δ13C3 < δ13C2) formed at EasyRo ≈ 4.1 %. Moreover, intramolecular δ13C3 (both terminal and central carbons, termed δ13Ca and δ13Cb, respectively) reversed alongside the overall δ13C3 trend. Additionally, the evolution of site preference in δ13C3 (termed ‰SP = δ13Ca – δ13Cb) transitioned from progressively negative to positive. The results of this study demonstrate that the potential conversion between saturated hydrocarbons, aromatic hydrocarbons, and alkane gases is at least partially responsible for δ13C anomalies, but also that gaseous hydrocarbons formed from other fractions at high maturity cannot be ruled out, such as kerogen and pyrobitumen.

A series of triphenylamine-derived fluorophores attached to a Cu-based MOF for gaseous CO optical sensing: synthesis, performance, and mechanism.

A series of triphenylamine-derived fluorescent dyes were attached to a Cu2+-containing MOF (metal-organic framework), denoted as Pm@CuMOF. The molecular structures of these dyes were discussed by the single crystal structures. Their major absorption bands peaked at 410-450 nm, showing emission bands ranging from 556 to 586 nm with emission quantum yields ranging from 8.0 to 15.1%. It was found that the [-N(C2H5)2] group generally improved sensing performance, and the -OH group in the dyes helped the Cu2+ quenching effect. Pm@CuMOF was observed by SEM as nanorods with a width of ~100 nm and a length of 300 nm. Their XRD patterns and N2 adsorption/desorption isotherms were recorded to confirm their porous structure. A low probe loading level of ~4% was determined by TGA result. The CO sensing mechanism was revealed as a Cu2+/Cu+-involved sensing mechanism based on the result of NMR titration, IR, XPS, and EPR. The fluorescence of these triphenylamine-derived dyes was firstly quenched by CuMOF. In contact with CO, Cu2+ was reduced to Cu+, accompanied by the release and fluorescence recovery of the fluorescent dyes, showing emission turn-on effect towards CO gas. Pm@CuMOF showed increased emission intensity at CO level of 0.005% (versus N2), with response times ranging from 123 s to 280 s (depending on various temperatures). Good selectivity was observed over competing alkane gases, with stable emission for at least 5 days, but no linear calibration plots were observed.

Alkene Cross-Metathesis with 2,5-Dimethyl-2,4-Hexadiene Enables Isobutylenyl/Prenyl Functionalizations and Rubber Valorization.

2,5-Dimethyl-2,4-hexadiene is a readily available and easily managable compound, whose symmetric and polymethylated dienic structure should be prone to engage in cross-metathesis reactions with other alkenes, but this has not been apparently exploited so far. Here we show that this reactant enables the easy synthesis of tri- and tetra-susbtituted alkenes (i. e. isobutylenyl and prenyl groups) from simple alkenes under mild reaction conditions, not only with the conventional 2nd generation Grubbs catalyst but also with other Grela-type catalyts such as StickyCat,TM AquaMetTM and GreenCatTM. The use of liquid and low volatile 2,5-dimethyl-2,4-hexadiene avoids the use of gaseous alkene reactants and, besides, showcases the reactivity of polyisoprene (rubber), thus allowing to optimize the reaction conditions for rubber upcycling, after metathesis reaction of the pristine or used polymer with simple alkenes. These results bring low volatile isoprene-type compounds as privileged poly-substituted reactants for alkene cross-metathesis reactions.

Characteristics of carbon isotopic composition of alkane gas in large gas fields in China

Exploration and development of large gas fields is an important way for a country to rapidly develop its natural gas industry. From 1991 to 2020, China discovered 68 new large gas fields, boosting its annual gas output to 1 925×108 m3 in 2020, making it the fourth largest gas-producing country in the world. Based on 1696 molecular components and carbon isotopic composition data of alkane gas in 70 large gas fields in China, the characteristics of carbon isotopic composition of alkane gas in large gas fields in China were obtained. The lightest and average values of δ13C1, δ13C2, δ13C3 and δ13C4 become heavier with increasing carbon number, while the heaviest values of δ13C1, δ13C2, δ13C3 and δ13C4 become lighter with increasing carbon number. The δ13C1 values of large gas fields in China range from −71.2‰ to −11.4‰ (specifically, from −71.2‰ to −56.4‰ for bacterial gas, from −54.4‰ to −21.6‰ for oil-related gas, from −49.3‰ to −18.9‰ for coal-derived gas, and from −35.6‰ to −11.4‰ for abiogenic gas). Based on these data, the δ13C1 chart of large gas fields in China was plotted. Moreover, the δ13C1 values of natural gas in China range from −107.1‰ to −8.9‰, specifically, from −107.1‰ to −55.1‰ for bacterial gas, from −54.4‰ to −21.6‰ for oil-related gas, from −49.3‰ to −13.3‰ for coal-derived gas, and from −36.2‰ to −8.9‰ for abiogenic gas. Based on these data, the δ13C1 chart of natural gas in China was plotted.