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Topics in Current Chemistry (Cham) May 2020During the last decade, organometallic, coordination, and catalytic chemistry of the three-dimensional metals such as copper (Cu) has been greatly affected by the... (Review)
Review
During the last decade, organometallic, coordination, and catalytic chemistry of the three-dimensional metals such as copper (Cu) has been greatly affected by the emergence of nitrogen heterocyclic carbene (NHC) complexes. The NHCs, and in particular the mononuclear Cu-based ones, have been proven vastly useful in several applications such as in biosynthesis, catalysis, photochemistry, etc. This review tries to thoroughly describe a series of mononuclear Cu NHC complexes and their subcategories such as heteroleptics, and bidentate and tridentate heteroatom complexes, and give some detailed insights on their development, emergence, and applications. A brief outlook is also disclosed to enable other researchers to further develop a platform for future advances and studies in the field of Cu-based NHCs.
Topics: Coordination Complexes; Copper; Heterocyclic Compounds; Methane; Molecular Structure; Nitrogen
PubMed: 32367181
DOI: 10.1007/s41061-020-00304-8 -
Molecules (Basel, Switzerland) Oct 2022Switchgrass earned its place globally as a significant energy crop by possessing essential properties such as being able to control erosion, low cost of production,...
Switchgrass earned its place globally as a significant energy crop by possessing essential properties such as being able to control erosion, low cost of production, biomass richness, and appeal for biofuel production. In this study, the impact of a Ca(OH)-assisted thermal pretreatment process on the switchgrass variety Shawnee for methane fuel production was investigated. The Ca(OH)-assisted thermal pretreatment process was optimized to enhance the methane production potential of switchgrass. Solid loading (3-7%), Ca(OH) concentration (0-2%), reaction temperature (50-100 °C), and reaction time (6-16 h) were selected as independent variables for the optimization. Methane production was obtained as 248.7 mL CH gVS under the optimized pretreatment conditions. Specifically, a reaction temperature of 100 °C, a reaction time of 6 h, 0% Ca(OH), and 3% solid loading. Compared to raw switchgrass, methane production was enhanced by 14.5%. Additionally, the changes in surface properties and bond structure, along with the kinetic parameters from first order, cone, reaction curve, and modified Gompertz modeling revealed the importance of optimization.
Topics: Methane; Biofuels; Anaerobiosis; Biomass; Panicum; Crops, Agricultural
PubMed: 36296483
DOI: 10.3390/molecules27206891 -
The Science of the Total Environment Jan 2022The intensifying globalization contributes to the anthropogenic methane (CH) emissions outsourcing, a strong greenhouse gas and harmful air pollutant, through the...
The intensifying globalization contributes to the anthropogenic methane (CH) emissions outsourcing, a strong greenhouse gas and harmful air pollutant, through the increasingly complex global trade network. However, the CH flow patterns embodied in global traded goods and services have not been interpreted from the perspective of a complex network. In this paper, we integrate global CH emission inventory from the EDGAR (the Emission Database for Global Atmospheric Research) databases, global multi-regional input-output model from the GTAP database, and complex network analysis to reveal the structural characteristics of the global CH flow network (GCFN). In the GCFN, more than one quarter of the global anthropogenic CH emissions in 2014 are associated with international trade. The top 20 economies contribute to about 70% of the total embodied CH emission flows. The GCFNs mainly consist of tripartite patterns centered on China, the USA and Russia. Some emerging countries, such as Thailand and Brazil, also exhibit dominated positions in different kinds of GCFNs. Moreover, the core-periphery structure of the GCFN confirms the existence of a few hub economies associated with a large amount of CH emissions. The results emphasize the multinational cooperation on global CH emission mitigation, and well-focused mitigation policies should be implemented on some key economies.
Topics: Commerce; Greenhouse Gases; Internationality; Methane; Outsourced Services
PubMed: 34482130
DOI: 10.1016/j.scitotenv.2021.150008 -
Environmental Science & Technology Jan 2021In this study, a ground-based mobile measurement system was developed to provide rapid and cost-effective emission surveillance of both methane (CH) and volatile organic...
In this study, a ground-based mobile measurement system was developed to provide rapid and cost-effective emission surveillance of both methane (CH) and volatile organic compounds (VOCs) from oil and gas (O&G) production sites. After testing in several controlled release experiments, the system was deployed in a field campaign in the Eagle Ford basin, TX. We found fat-tail distributions for both methane and total VOC (C4-C12) emissions (e.g., the top 20% sites ranked according to methane and total VOC (C4-C12) emissions were responsible for ∼60 and ∼80% of total emissions, respectively) and a good correlation between them (Spearman's = 0.74). This result suggests that emission controls targeting relatively large emitters may help significantly reduce both methane and VOCs in oil and wet gas basins, such as the Eagle Ford. A strong correlation (Spearman's = 0.84) was found between total VOC (C4-C12) emissions estimated using SUMMA canisters and data reported from a local ambient air monitoring station. This finding suggests that this system has the potential for rapid emission surveillance targeting relatively large emitters, which can help achieve emission reductions for both greenhouse gas (GHG) and air toxics from O&G production well pads in a cost-effective way.
Topics: Air Pollutants; Cost-Benefit Analysis; Environmental Monitoring; Methane; Volatile Organic Compounds
PubMed: 33314919
DOI: 10.1021/acs.est.0c06545 -
Environmental Science & Technology Aug 2023Government policies and corporate strategies aimed at reducing methane emissions from the oil and gas sector increasingly rely on measurement-informed, site-level...
Government policies and corporate strategies aimed at reducing methane emissions from the oil and gas sector increasingly rely on measurement-informed, site-level emission inventories, as conventional bottom-up inventories poorly capture temporal variability and the heavy-tailed nature of methane emissions. This work is based on an 11-month methane measurement campaign at oil and gas production sites. We find that operator-level top-down methane measurements are lower during the end-of-project phase than during the baseline phase. However, gaps persist between end-of-project top-down measurements and bottom-up site-level inventories, which we reconcile with high-frequency data from continuous monitoring systems (CMS). Specifically, we use CMS to (i) validate specific snapshot measurements and determine how they relate to the temporal emission profile of a given site and (ii) create a measurement-informed, site-level inventory that can be validated with top-down measurements to update conventional bottom-up inventories. This work presents a real-world demonstration of how to reconcile CMS rate estimates and top-down snapshot measurements jointly with bottom-up inventories at the site level. More broadly, it demonstrates the importance of multiscale measurements when creating measurement-informed, site-level emission inventories, which is a critical aspect of recent regulatory requirements in the Inflation Reduction Act, voluntary methane initiatives such as the Oil and Gas Methane Partnership 2.0, and corporate strategies.
Topics: Methane; Natural Gas; Air Pollutants
PubMed: 37506319
DOI: 10.1021/acs.est.3c01121 -
Chemical Reviews Feb 2022Direct conversion of methane to C compounds by oxidative and nonoxidative coupling reactions has been intensively studied in the past four decades; however, because... (Review)
Review
Direct conversion of methane to C compounds by oxidative and nonoxidative coupling reactions has been intensively studied in the past four decades; however, because these reactions have intrinsic severe thermodynamic constraints, they have not become viable industrially. Recently, with the increasing availability of inexpensive "green electrons" coming from renewable sources, electrochemical technologies are gaining momentum for reactions that have been challenging for more conventional catalysis. Using solid-state membranes to control the reacting species and separate products in a single step is a crucial advantage. Devices using ionic or mixed ionic-electronic conductors can be explored for methane coupling reactions with great potential to increase selectivity. Although these technologies are still in the early scaling stages, they offer a sustainable path for the utilization of methane and benefit from the advances in both solid oxide fuel cells and electrolyzers. This review identifies promising developments for solid-state methane conversion reactors by assessing multifunctional layers with microstructural control; combining solid electrolytes (proton and oxygen ion conductors) with active and selective electrodes/catalysts; applying more efficient reactor designs; understanding the reaction/degradation mechanisms; defining standards for performance evaluation; and carrying techno-economic analysis.
Topics: Electrodes; Hydrocarbons; Methane; Oxides; Temperature
PubMed: 34962796
DOI: 10.1021/acs.chemrev.1c00447 -
Bioengineered Dec 2019The rise in intermittent renewable electricity production presents a global requirement for energy storage. Biological hydrogen methanation (BHM) facilitates wind and... (Review)
Review
The rise in intermittent renewable electricity production presents a global requirement for energy storage. Biological hydrogen methanation (BHM) facilitates wind and solar energy through the storage of otherwise curtailed or constrained electricity in the form of the gaseous energy vector biomethane. Biological methanation in the circular economy involves the reaction of hydrogen - produced during electrolysis - with carbon dioxide in biogas to produce methane (4H + CO = CH + 2H), typically increasing the methane output of the biogas system by 70%. In this paper, several BHM systems were researched and a compilation of such systems was synthesized, facilitating comparison of key parameters such as methane evolution rate (MER) and retention time. Increased retention times were suggested to be related to less efficient systems with long travel paths for gases through reactors. A significant lack of information on gas-liquid transfer co-efficient was identified.
Topics: Biofuels; Bioreactors; Biotechnology; Carbon Dioxide; Hydrogen; Methane; Renewable Energy
PubMed: 31679461
DOI: 10.1080/21655979.2019.1684607 -
Water Research Jun 2022Coastal wetlands are an important source of methane emissions, and understanding the mechanisms that control methane emissions from coastal wetlands is of great...
Coastal wetlands are an important source of methane emissions, and understanding the mechanisms that control methane emissions from coastal wetlands is of great significance to global warming. Anaerobic oxidation of methane driven by sulfate is an important process to prevent methane emissions from coastal wetlands. The effects of environmental changes on this process and the function of the sulfate-methane transition zone (SMTZ) are poorly understood. In this study, spatiotemporal variations in pore-water geochemistry (concentrations of SO, CH and DIC as well as δC-DIC and δC-CH) in the Beidagang wetland, Tianjin, China, were investigated to unravel factors controlling the role of anaerobic oxidation of methane in coastal wetlands. Results show that the geochemical profile of pore-water is characterized by significant spatial and temporal variability, which may be related to changes in sulfate concentration, temperature and dissolved oxygen. The carbon isotope fractionation factors (ε) during methane oxidation range from 8.9‰ to 12.5‰, indicating that the sulfate-driven anaerobic oxidation of methane (S-AOM) dominates the methane oxidation in the Beidagang coastal wetland in both winter and summer, in both high and low salinity wetlands, and in both open water and littoral areas. However, sulfate concentration has a strong influence on the sulfate reduction pathways and methane consumption. The consumption of methane and sulfate by S-AOM is more significant in coastal wetlands with high sulfate concentrations, with S-AOM consuming nearly all of the upward-diffusing methane (96%) and downward-diffusing sulfate (96%). In addition, the dissolved inorganic carbon (DIC) produced in the pore-water mainly comes from methanogenesis, accounting for more than 80% of the total DIC pool, but in the areas with high sulfate concentrations in water column, the contribution of S-AOM to the DIC pool is greater, although only a small fraction of the total DIC pool (9%). The depth and width of the SMTZ show a clear spatial and temporal pattern, with active methanogenesis activity and upward high methane flux shoaling the SMTZ and increasing the risk of high methane emissions from coastal wetlands with low sulfate concentrations. Our findings highlight the importance of sulfate-driven anaerobic oxidation of methane in coastal wetlands and the effect of sulfate concentration on it. It contributes to our understanding of the mechanism of methane production and emissions from the coastal wetland system, particularly in light of the increased demand for coastal wetland restoration under global warming.
Topics: Methane; Sulfates; Sulfur Oxides; Water; Wetlands
PubMed: 35430469
DOI: 10.1016/j.watres.2022.118441 -
The Science of the Total Environment Nov 2019The effects of divergent phenotypic classification in crossbreed Holstein × Gyr dairy heifers for methane emissions in relation to performance, digestibility, energy...
The effects of divergent phenotypic classification in crossbreed Holstein × Gyr dairy heifers for methane emissions in relation to performance, digestibility, energy and nitrogen partition, blood metabolites and temperature of body surface were evaluated. Thirty-five heifers were classified as high and low emission for CH production (g/day), yield (g/kg dry matter intake) and intensity (g/kg average daily gain). Digestibility was evaluated by total collection of feces and urine. Gas exchanges were obtained in open-circuit respiratory chambers. A completely randomized design was used and divergent groups were compared by Fisher's test. No differences were found in intake traits between groups of CH production and intensity. The low yield group had higher intake. For digestibility and temperature at different body sites were no differences between variables. High production group had higher energy losses as methane and heat production. Low intensity group had higher digestible energy, energy balance and ratio between metabolizable and digestible energy. Urinary nitrogen was 14.3% lower for low production group. There was a difference between methane yield divergent groups for nitrogen intake, digestible and retained. Energy and nitrogen partitioning traits are correlated to the animals divergent for methane production and yield. The low production group presented lower blood insulin concentration. It was not possible to identify divergent animals for CH emission using the infrared thermography technique.
Topics: Animals; Cattle; Energy Metabolism; Feces; Female; Methane
PubMed: 31466153
DOI: 10.1016/j.scitotenv.2019.06.489 -
Chemical Society Reviews Mar 2022Methyl-coenzyme M reductase (MCR) containing a nickel hydrocorphinoid cofactor, F430, is an essential enzyme that catalyzes anaerobic methane generation and oxidation.... (Review)
Review
Methyl-coenzyme M reductase (MCR) containing a nickel hydrocorphinoid cofactor, F430, is an essential enzyme that catalyzes anaerobic methane generation and oxidation. The active Ni(I) species in MCR converts methyl-coenzyme M (CHS-CoM) and coenzyme B (HS-CoB) to methane and heterodisulfide (CoM-S-S-CoB). Extensive experimental and theoretical studies focusing on the substrate-binding cavity including the F430 cofactor in MCR have suggested two principally different reaction mechanisms involving an organonickel CH-Ni(III) species or a transient methyl radical species. In parallel with research on native MCR itself, the functionality of MCR has been investigated in the context of model complexes of F430 and recent protein-based functional models, which include a nickel complex. In the latter case, hemoproteins reconstituted with tetradehydro- and didehydrocorrinoid nickel complexes have been found to represent useful model systems that are responsible for methane generation. These efforts support the proposed mechanism of the enzymatic reaction and provide important insight into replicating the MCR-like methane-generation process. Furthermore, the modeling of MCR described here is expected to lead to understanding of protein-supported nickel porphyrinoid chemistry as well as the creation of MCR-inspired catalysis.
Topics: Catalysis; Methane; Nickel; Oxidation-Reduction; Oxidoreductases
PubMed: 35148362
DOI: 10.1039/d1cs00840d