Effects of nitrogen fertilizer,soil moisture and temperature on methane oxidation in paddy soil were investigated under laboratory conditions. Addition of 0.05 g N kg-1 soil as NH4Cl strongly inhibited methane oxidati...Effects of nitrogen fertilizer,soil moisture and temperature on methane oxidation in paddy soil were investigated under laboratory conditions. Addition of 0.05 g N kg-1 soil as NH4Cl strongly inhibited methane oxidation and addition of the same rate of KCl also inhibited the oxidation but with more slight effect,suggesting that the inhibitory effect was partly caused by increase in osmotic potential in microorganism cell.Not only NH but also NO greatly affected methane oxidation.Urea did not affect methane oxidation in paddy soil in the first two days of incubation,but strong inhibitory effect was observed afterwards.Methane was oxidized in the treated soil with an optimum moisture of 280 g kg-1, and air-drying inhibited methane oxidation entirely.The optimum temperature of methane oxidation was about 30℃in paddy soil,while no methane oxidation was observed at 5℃or 50℃展开更多
The denitrifying anaerobic methane oxidation is an ecologically important process for reducing the potential methane emission into the atmosphere.The responsible bacterium for this process was Candidatus Methylomirabi...The denitrifying anaerobic methane oxidation is an ecologically important process for reducing the potential methane emission into the atmosphere.The responsible bacterium for this process was Candidatus Methylomirabilis oxyfera belonging to the bacterial phylum of NC10.In this study,a new pair of primers targeting all the five groups of NC10 bacteria was designed to amplify NC10 bacteria from different environmental niches.The results showed that the group A was the dominant NC10 phylum bacteria from the sludges and food waste digestate while in paddy soil samples,group A and group B had nearly the same proportion.Our results also indicated that NC10 bacteria could exist in a high p H environment（pH 9.24）from the food waste treatment facility.The Pearson relationship analysis showed that the p H had a significant positive relationship with the NC10 bacterial diversity（p0.05）.The redundancy analysis further revealed that the p H,volatile solid and nitrite nitrogen were the most important factors in shaping the NC10 bacterial structure（p=0.01）based on the variation inflation factors selection and Monte Carlo test（999 times）.Results of this study extended the existing molecular tools for studying the NC10 bacterial community structures and provided new information on the ecological distributions of NC10 bacteria.展开更多
Methane oxidation by paddy soils in a closed system could be simulsted by the equation where xo and x are the CH4 concentrations at time zero and t, respectively; k1 and k2 are constants related to the constant of fir...Methane oxidation by paddy soils in a closed system could be simulsted by the equation where xo and x are the CH4 concentrations at time zero and t, respectively; k1 and k2 are constants related to the constant of first-order-kinetics. According to the equation the change of soil ability to oxidize CH4 could be estimated by the equstion The results showed that the soil ability to oxidize CH4 varied, depending on the initial CH4 concentration.High initial CH4 concentration stimulated soil ability to consume CH4, while low concentration depressed the ability. This characteristic of paddy soil seemed to be of considerable significance to self-adjusting CH4 emission from flooded rice fields if there exist oxic microsites in the soil.展开更多
In this study,a top cover system is investigated as a control for emissions during the aftercare of new landfills and for old landfills where biogas energy production might not be profitable.Different materials were s...In this study,a top cover system is investigated as a control for emissions during the aftercare of new landfills and for old landfills where biogas energy production might not be profitable.Different materials were studied as landfill cover system in lab-scale columns：mechanical–biological pretreated municipal solid waste（MBP）;mechanical–biological pretreated biowaste（PB）;fine（PBSf）and coarse（PBSc）mechanical–biological pretreated mixtures of biowaste and sewage sludge,and natural soil（NS）.The effectiveness of these materials in removing methane and sulphur compounds from a gas stream was tested,even coupled with activated carbon membranes.Concentrations of CO2,CH4,O2,N2,H2S and mercaptans were analysed at different depths along the columns.Methane degradation was assessed using mass balance and the results were expressed in terms of methane oxidation rate（MOR）.The highest maximum and mean MOR were observed for MBP（17.2 g CH4/m^2/hr and 10.3 g CH4/m^2/hr,respectively）.Similar values were obtained with PB and PBSc.The lowest values of MOR were obtained for NS（6.7 g CH4/m^2/hr）and PBSf（3.6 g CH4/m^2/hr）,which may be due to their low organic content and void index,respectively.Activated membranes with high load capacity did not seem to have an influence on the methane oxidation process：MBP coupled with 220 g/m^2and 360 g/m^2membranes gave maximum MOR of 16.5 g CH4/m^2/hr and 17.4 g CH4/m^2/hr,respectively.Activated carbon membranes proved to be very effective on H2S adsorption.Furthermore,carbonyl sulphide,ethyl mercaptan and isopropyl mercaptan seemed to be easily absorbed by the filling materials.展开更多
In a series of laboratory incubations using soils of two contrasting sitesfrom a temperate marsh on the Qinghai-Tibet Plateau, potential methane (CH_4) oxidation rates weremeasured to study the effects of inorganic N ...In a series of laboratory incubations using soils of two contrasting sitesfrom a temperate marsh on the Qinghai-Tibet Plateau, potential methane (CH_4) oxidation rates weremeasured to study the effects of inorganic N inputs on CH_4 oxidation. For adrained site, subsurfacepeat (5--15 cm) at an initial 20 mu L CH_4 L^(-1) showed a significantly different (P < 0.05) CH_4oxidation rate compared to other soil depths, with a maximal rate of 20.9 ng CH_4 gDW (dryweight)^(-1) h^(-1); the underlying mineral soil layers (15--30 and 30--50 cm) also had a strongCH_4 oxidation capacity at about an initial 2 000 mu L CH_4 L^(-1). With a waterlogged site, theCH_4 oxidation rate in an aerobic incubation was significantly greater (P < 0 05) in the surfacesoil layer (0--5 cm) compared to the 15--30 and 30--50 cm depths. There was generally no or a veryweak effect from addition of NO_3^- on CH_4 oxidation. In marked contrast, NH_4^+ salts, such as(NH_4)_2SO_4, NH_4Cl and NH_4NO_3, exhibited strong inhibitions, which varied as a function of theadded salts and the initial CH_4 level Increasing NH_4^+ usually resulted in greater inhibition andincreasing initial CH_4 concentrations resulted in less NH_4^+ inhibition on CH4 oxidation innatural high-altitude, low-latitude wetlands could be as important as has been reported foragricultural and forest soils. The NH_4^+ effects on the CH_4 oxidation rate need to be furtherinvestigated in a wide range of natural wetland soil types.展开更多
Large amounts of gas hydrate are distributed in the northern slope of the South China Sea,which is a potential threat of methane leakage.Aerobic methane oxidation by methanotrophs,significant methane biotransformation...Large amounts of gas hydrate are distributed in the northern slope of the South China Sea,which is a potential threat of methane leakage.Aerobic methane oxidation by methanotrophs,significant methane biotransformation that occurs in sediment surface and water column,can effectively reduce atmospheric emission of hydrate-decomposed methane.To identify active aerobic methanotrophs and their methane oxidation potential in sediments from the Shenhu Area in the South China Sea,multi-day enrichment incubations were conducted in this study.The results show that the methane oxidation rates in the studied sediments were 2.03‒2.36μmol/gdw/d,which were higher than those obtained by sediment incubations from other areas in marine ecosystems.Thus the authors suspect that the methane oxidation potential of methanotrophs was relatively higher in sediments from the Shenhu Area.After the incubations family Methylococcaea(type I methanotrophs)mainly consisted of genus Methylobacter and Methylococcaea_Other were predominant with an increased proportion of 70.3%,whereas Methylocaldum decreased simultaneously in the incubated sediments.Collectively,this study may help to gain a better understanding of the methane biotransformation in the Shenhu Area.展开更多
Palladium based catalysts are the most active for methane oxidation. The tuning of their composition, structure and morphology at macro and nanoscale can alter significantly their catalytic behavior and robustness wit...Palladium based catalysts are the most active for methane oxidation. The tuning of their composition, structure and morphology at macro and nanoscale can alter significantly their catalytic behavior and robustness with a strong impact on their overall performances. Among the several combinations of supports and promoters that have been utilized, Pd/CeO2 has attracted a great attention due to its activity and durability coupled with the unusually high degree of interaction between Pd/Pd O and the support. This allows the creation of specific structural arrangements which profoundly impact on methane activation characteristics. Here we want to review the latest findings in this area, and particularly to envisage how the control(when possible) of Pd-CeO2 interaction at nanoscale can help in designing more robust methane oxidation catalysts.展开更多
To reduce greenhouse gas emission from oil and gas production,it is essential to better convert methane to useful chemicals(rather) than to flare it.Conversion of methane to liquid oxygenates(mainly methanol) has attr...To reduce greenhouse gas emission from oil and gas production,it is essential to better convert methane to useful chemicals(rather) than to flare it.Conversion of methane to liquid oxygenates(mainly methanol) has attracted extensive attention and countless efforts have been made;however,running this reaction in a green,efficient,and practical way has remained elusive.The novel catalyst and oxidants play a critical role in activating methane and converting it to oxygenates(methanol).In this review,the work of commonly used oxidants for methane partial oxidation have been summarized,in which,earth abundant oxidants,O;and H;O are promising.Moreover,H;or CO can activate O;to produce H;O;that catalyzes methane partial oxidation more efficiently and selectively than O;or H;O.Therefore,the work of using reducing agent,such as CO and H;have been reviewed,focusing on rational catalyst design that features multifunction(H;O;production and CH;activation).The novel catalyst design has advanced this reaction towards practicality with green oxidants and H;using zeolites-based catalyst.Environmentally friendly zeolite preparation methods and novel two-dimensional(2 D) zeolites that can reduce waste,improve synthesis and catalytical performance substantially are also reviewed in this work to provide insights for a more comprehensive approach to meet the environment protection needs.展开更多
Nitrite-dependent anaerobic methane oxidation (n-damo), performed by the bacteria associated with Candidatus Methylomirabilis oxyfera, acts as a novel methane sink in coastal wetlands. Conversion of coastal wetlands i...Nitrite-dependent anaerobic methane oxidation (n-damo), performed by the bacteria associated with Candidatus Methylomirabilis oxyfera, acts as a novel methane sink in coastal wetlands. Conversion of coastal wetlands into paddy fields is a common land-use change that has profound effects on methane emissions, but its impact on n-damo process is nearly unknown. Our study adopted a space-for-time substitution method to compare n-damo activity and community of Methylomirabilis-like bacteria between natural vegetation covered by Phragmites australis, Kandelia candek, or Bruguiera sexangula and adjacent converted paddy fields in six China’s coastal wetlands. Generalized linear mixed model indicated that the activity of n-damo significantly increased by 43.6% and 165.8% after conversion of K. candek and B. sexangula wetlands into rice paddies, respectively, while the activity exhibited no significant change after conversion of P. australis wetlands. Furthermore, the abundance of Methylomirabilis-like bacteria significantly increased by 90.2%, 210.0%, and 110.1% following the conversion in wetlands covered by K. candek, B. sexangula, and P. australis, respectively. Principal co-ordinates analysis revealed significant changes in community structure of Methylomirabilis-like bacteria among vegetation types, with K. candek and B. sexangula showing a greater divergence than P. australis when compared to respective paddy fields. Path analysis indicated that land conversion resulted in changes in soil moisture content, organic carbon content, bulk density, and salinity and further affected the abundance of Methylomirabilis-like bacteria and ultimately n-damo activity. Overall, this is the first study to reveal the impact of conversion of coastal wetlands into paddy fields on n-damo activity and Methylomirabilis-like bacteria, and the impact was closely associated with the original native plant types. The results can enhance our understanding of the microbial-driven mechanisms of the impact of land conversion on methane emissions.展开更多
Anaerobic oxidation of methane(AOM)can contribute to reducing methane emissions in landfills;however,the AOM rates vary depending on the inoculum source.This study addressed the capacity of AOM of a fermentative micro...Anaerobic oxidation of methane(AOM)can contribute to reducing methane emissions in landfills;however,the AOM rates vary depending on the inoculum source.This study addressed the capacity of AOM of a fermentative microbial community derived from a reactor treatingmunicipal solidwastes.First,the inoculum’s autotrophic capacitywas verified using a gasmixture of 75% CO_(2) and 25% H_(2).Results demonstrated that the fermentative microbial community reached amaximum CO_(2) consumption rate of 22.5±1.2 g CO_(2)/(m^(3)·h),obtaining acetate as the main product.Then,the inoculum was grown on a gas mixture of 50%CH_(4),35%CO_(2),and 15%N_(2),using iron(Fe^(3+))as the electron acceptor.The AOM rates increased over time and peaked at 3.1±0.9 g CH_(4)/(m^(3)·h)by 456 h with the simultaneous consumption of CO_(2).Acetate was the main product,with amaximum concentration of 180±9mg/L.By 408 h,a bacterial cluster of indicator species correlated with the AOM rates,including to Rhodobactereceae(r=0.80),Oceanicola(r=0.80),Propionicicella(r=0.77),Christensenellaceae(r=0.58),Oscillospiraceae(r=0.53),Mobilitalea(r=0.66),Hungateiclostridiaceae(r=0.46),and Izemoplasmatales(r=0.77).Methanosarcina,Methanobacterium,and Methanoculleus correlated with the AOM and CO_(2) consumption rates.A co-occurrence network analysis showed that Methanosarcina positively interacted with syntrophic bacteria like Christensenellaceae and Acinetobacter and diverse heterotrophic bacteria.This study demonstrated the feasibility of obtaining a CH_(4)-oxidizing microbial community in 16 days,exhibiting AOM rates higher than those reported for soils.展开更多
The direct activation of methane under mild condition to achieve highly selective of oxygenates is a challenging project.In this study,a well dispersed silver supported ZnTiO_(3) catalyst was prepared to achieve selec...The direct activation of methane under mild condition to achieve highly selective of oxygenates is a challenging project.In this study,a well dispersed silver supported ZnTiO_(3) catalyst was prepared to achieve selective preparation of methanol from methane and water under mild condition.X-ray diffraction,transmission electron microscopy and X-ray photoelectron spectroscopy characterizations demonstrate that silver species are uniformly dispersed on ZnTiO_(3) surface in the form of metallic silver nanoparticles.The photoelectric characterizations reveal that the addition of silver species enhances light absorption and promotes charge separation of the catalysts.Under the reaction conditions of 50℃and 3 MPa,the methanol is obtained as the only liquid product over the designed Ag/ZnTiO_(3) catalyst under light irradiation.In this photocatalytic process,the holes generated by ZnTiO_(3) activate water to produce intermediate·OH,which further reacts with methane to synthesize methanol.The silver species as co-catalysts extend the light absorption range of ZnTiO_(3) as well as promote charge separation.展开更多
Selective photocatalytic aerobic oxidation of methane to value-added chemicals offers a promising pathway for sustainable chemical industry,yet remains a huge challenge owing to the consecutive overoxidation of primar...Selective photocatalytic aerobic oxidation of methane to value-added chemicals offers a promising pathway for sustainable chemical industry,yet remains a huge challenge owing to the consecutive overoxidation of primary products.Here,a type II heterojunction were constructed in Ag-AgBr/ZnO to reduce the oxidation potential of stimulated holes and prevent the undesirable CH_(4) overoxidation side reactions.For photocatalytic oxidation of methane under ambient temperature,the products yield of 1499.6μmol gcat^(-1) h^(-1) with a primary products selectivity of 77.9%was achieved over Ag-AgBr/ZnO,which demonstrate remarkable improvement compared to Ag/ZnO(1089.9μmol gcat^(-1) h^(-1) ,40.1%).The superior activity and selectivity result from the promoted charge separation and the redox potential matching with methane activation after introducing AgBr species.Mechanism investigation elucidated that the photo-generated holes transferred from the valence band of ZnO to that of AgBr,which prevent H_(2)O oxidation and enhance the selective generation of•OOH radical.展开更多
Methane(CH_(4))has a higher heat capacity(104.9 kcal/mol)than carbon dioxide(CO_(2)),and this has inspired research aimed at reducing methane levels to retard global warming.Hydroxylation under ambient conditions thro...Methane(CH_(4))has a higher heat capacity(104.9 kcal/mol)than carbon dioxide(CO_(2)),and this has inspired research aimed at reducing methane levels to retard global warming.Hydroxylation under ambient conditions through methanotrophs can provide crucial information for understanding the harsh C-H activation of methane.Soluble methane monooxygenase(sMMO)belongs to the bacterial multi-component monooxygenase superfamily and requires hydroxylase(MMOH),regulatory(MMOB),and reductase(MMOR)components.Recent structural and biophysical studies have demonstrated that these components accelerate and retard methane hydroxylation in MMOH through protein-protein interactions.Complex structures of sMMO,including MMOH-MMOB and MMOH-MMOD,illustrate how these regulatory and inhibitory components orchestrate the di-iron active sites located within the four-helix bundles of MMOH,specifically at the docking surface known as the canyon region.In addition,recent biophysical studies have demonstrated the role of MmoR,aσ54-dependent transcriptional regulator,in regulating sMMO expression.This perspective article introduces remarkable discoveries in recent reports on sMMO components that are crucial for understanding sMMO expression and activities.Our findings provide insight into how sMMO components interact with MMOH to control methane hydroxylation,shedding light on the mechanisms governing sMMO expression and the interactions between activating enzymes and promoters.展开更多
Methane chemistry is one of the“Holy Grails of catalysis”.It is highly desirable but challenge to transform methane into value-added chemicals,because of its high C-H bonding energy(435 kJ/mol),lack ofπbonding or u...Methane chemistry is one of the“Holy Grails of catalysis”.It is highly desirable but challenge to transform methane into value-added chemicals,because of its high C-H bonding energy(435 kJ/mol),lack ofπbonding or unpaired electrons.Currently,commercial methane conversion is usually carried out in harsh conditions with enormous energy input.Photocatalytic partial oxidation of methane to liquid oxygenates(PPOMO)is a future-oriented technology towards realizing high efficiency and high selectivity under mild conditions.The selection of oxidant is crucial to the PPOMO performance.Hence,attentions are paid to the research progress of PPOMO with various oxidants(O_(2),H_(2)O,H_(2)O_(2)and other oxidants).Moreover,the activation of the selected oxidants is also highly emphasized.Meanwhile,we summarized the methane activation mechanisms focusing on the C-H bond that was broken mainly by·OH radical,O-specie or photogenerated hole(h+).Finally,the challenges and prospects in this subject are briefly discussed.展开更多
Oxidative coupling of methane (OCM) is one of the most promising approaches to produce ethylene and ethane (C_(2)-hydrocarbons) in the post-oil era.The MnO_(x)-Na_(2)WO_(4)/SiO_(2) system shows promising OCM performan...Oxidative coupling of methane (OCM) is one of the most promising approaches to produce ethylene and ethane (C_(2)-hydrocarbons) in the post-oil era.The MnO_(x)-Na_(2)WO_(4)/SiO_(2) system shows promising OCM performance,which can be further enhanced by cofed steam.However,the positive effect of steam on C_(2)-hydrocarbons selectivity practically disappears above 800℃.In the present study,we demonstrate that the use of SiC as a support for MnO_(x)-Na_(2)WO_(4) is beneficial for achieving high selectivity up to 850℃.Our sophisticated kinetic tests using feeds without and with steam revealed that the steam-mediated improvement in selectivity to C_(2)-hydrocarbons is due to the inhibition of the direct CH_(4) oxidation to carbon oxides because of the different enhancing effects of steam on the rates of CH_(4) conversion to C_(2)H_(6) and CO/CO_(2).Other descriptors of the selectivity improvement are MnO_(x) dispersion and the catalyst specific surface area.The knowledge gained herein may be useful for optimizing OCM performance through catalyst design and reactor operation.展开更多
Aged refuse from waste landfills closed for eight years was examined and found to contain rich methanotrophs capable of biooxidation for methane. Specially, community structure and methane oxidation capability of meth...Aged refuse from waste landfills closed for eight years was examined and found to contain rich methanotrophs capable of biooxidation for methane. Specially, community structure and methane oxidation capability of methanotrophs in the aged refuse were studied. The amount of methanotrophs ranged 61.97×10^3-632.91×10^3 cells/g （in dry basis） in aged refuse from Shanghai Laogang Landfill. Type I and II methanotrophs were found in the aged refuse in the presence of sterilized sewage sludge and only Type I methanotrophs were detected in the presence of nitrate minimal salt medium （NMS）. The clone sequences of the pmoA gene obtained from the aged refuse were similar to the pmoA gene of Methylobacter, Methylocaldum, and Methylocystis, and two clones were distinct with known genera of Type I methanotrophs according to phylogenetic analysis. Aged refuse enriched with NMS was used for methane biological oxidation and over 93% conversions were obtained.展开更多
A 1% Fe-30% Hf over yttria-stabilized zirconia catalyst in combination with novel plasma-assisted activation techniques for a direct partial oxidation of methane to methanol was tested using dielectric barrier dischar...A 1% Fe-30% Hf over yttria-stabilized zirconia catalyst in combination with novel plasma-assisted activation techniques for a direct partial oxidation of methane to methanol was tested using dielectric barrier discharge plasma at ambient temperature and atmospheric pressure. However, instead of methanol, the reaction products were dominated by HE, CO, CO2, C2, and H2O. A catalytically activated plasma process increased the production of methanol compared with a noncatalytic plasma process. The maximum selectivity of methanol production was achieved using a catalyst that was treated at higher applied power.展开更多
Ba0.5Sr0.5Co0.8Fe0.2O3-delta and Ba0.5Sr0.5Co0.8Ti0.2O3-delta oxides were synthesized by a combined EDTA-citrate complexing method. The catalytic behavior of these two oxides with the perovskite structure was studied ...Ba0.5Sr0.5Co0.8Fe0.2O3-delta and Ba0.5Sr0.5Co0.8Ti0.2O3-delta oxides were synthesized by a combined EDTA-citrate complexing method. The catalytic behavior of these two oxides with the perovskite structure was studied during the reaction of methane oxidation. The pre-treatment with methane has different effect on the catalytic activities of both the oxides. The methane pre-treatment has not resulted in the change of the catalytic activity of BSCFO owing to its excellent reversibility of the perovskite structure resulting from the excellent synergistic interaction between Co and Fe in the oxide. However, the substitution with Ti on Fe-site in the lattice makes the methane pre-treatment have an obvious influence on the activity of the formed BSCTO oxide.展开更多
A series of Ce1-xFexO2 （x=0, 0.2, 0.4, 0.6, 0.8, 1） complex oxide catalysts were prepared using the coprecipitation method. The catalysts were characterized by means of XRD and H2-TPR. The reactions between methane ...A series of Ce1-xFexO2 （x=0, 0.2, 0.4, 0.6, 0.8, 1） complex oxide catalysts were prepared using the coprecipitation method. The catalysts were characterized by means of XRD and H2-TPR. The reactions between methane and lattice oxygen from the complex oxides were investigated. The characteristic results revealed that the combination of Ce and Fe oxide in the catalysts could lower the temperature necessary to reduce the cerium oxide. The catalytic activity for selective CH4 oxidation was strongly influenced by dropped Fe species. Adding the appropriate amount of Fe2O3 to CeO2 could promote the action between CH4 and CeO2. Dispersed Fe2O3 first returned to the original state and would then virtually form the Fe species on the catalyst, which could be considered as the active site for selective CH4 oxidation. The appearance of carbon formation was significant and the oxidation of carbon appeared to be the rate-determining step; the amounts of surface reducible oxygen species in CeO2 were also relevant to the activity. Among all the catalysts, Ce0.6Fe0.402 exhibited the best activity, which converted 94.52% of CH4 at 900 ℃.展开更多
Nano-sized γ-alumina （γ-Al2O3） was first prepared by a precipitation method. Then, active component of cobalt and a series of alkaline- earth metal promoters or nickel （Ni） with different contents were loaded on...Nano-sized γ-alumina （γ-Al2O3） was first prepared by a precipitation method. Then, active component of cobalt and a series of alkaline- earth metal promoters or nickel （Ni） with different contents were loaded on the γ-Al2O3 support. The catalysts were characterized by N2 adsorption-desorption, X-ray diffraction （XRD） and thermogravimetry analysis （TGA）. The activity and selectivity of the catalysts in catalytic partial oxidation （CPO） of methane have been compared with Co/γ-Al2O3, and it is found that the catalytic activity, selectivity, and stability are enhanced by the addition of alkaline-earth metals and nickel. The optimal loadings of strontium （Sr） and Ni were 6 and 4 wt%, respectively. This finding will be helpful in designing the trimetallic Co-Ni-Sr/γ-Al2O3 catalysts with high performance in CPO of methane展开更多
文摘Effects of nitrogen fertilizer,soil moisture and temperature on methane oxidation in paddy soil were investigated under laboratory conditions. Addition of 0.05 g N kg-1 soil as NH4Cl strongly inhibited methane oxidation and addition of the same rate of KCl also inhibited the oxidation but with more slight effect,suggesting that the inhibitory effect was partly caused by increase in osmotic potential in microorganism cell.Not only NH but also NO greatly affected methane oxidation.Urea did not affect methane oxidation in paddy soil in the first two days of incubation,but strong inhibitory effect was observed afterwards.Methane was oxidized in the treated soil with an optimum moisture of 280 g kg-1, and air-drying inhibited methane oxidation entirely.The optimum temperature of methane oxidation was about 30℃in paddy soil,while no methane oxidation was observed at 5℃or 50℃
基金supported by the Special Fund of Environmental Protection Research for Public Welfare, Ministry of Environmental Protection of China (No. 201209022)the China Scholarship Council (CSC) for scholarship support
文摘The denitrifying anaerobic methane oxidation is an ecologically important process for reducing the potential methane emission into the atmosphere.The responsible bacterium for this process was Candidatus Methylomirabilis oxyfera belonging to the bacterial phylum of NC10.In this study,a new pair of primers targeting all the five groups of NC10 bacteria was designed to amplify NC10 bacteria from different environmental niches.The results showed that the group A was the dominant NC10 phylum bacteria from the sludges and food waste digestate while in paddy soil samples,group A and group B had nearly the same proportion.Our results also indicated that NC10 bacteria could exist in a high p H environment（pH 9.24）from the food waste treatment facility.The Pearson relationship analysis showed that the p H had a significant positive relationship with the NC10 bacterial diversity（p0.05）.The redundancy analysis further revealed that the p H,volatile solid and nitrite nitrogen were the most important factors in shaping the NC10 bacterial structure（p=0.01）based on the variation inflation factors selection and Monte Carlo test（999 times）.Results of this study extended the existing molecular tools for studying the NC10 bacterial community structures and provided new information on the ecological distributions of NC10 bacteria.
文摘Methane oxidation by paddy soils in a closed system could be simulsted by the equation where xo and x are the CH4 concentrations at time zero and t, respectively; k1 and k2 are constants related to the constant of first-order-kinetics. According to the equation the change of soil ability to oxidize CH4 could be estimated by the equstion The results showed that the soil ability to oxidize CH4 varied, depending on the initial CH4 concentration.High initial CH4 concentration stimulated soil ability to consume CH4, while low concentration depressed the ability. This characteristic of paddy soil seemed to be of considerable significance to self-adjusting CH4 emission from flooded rice fields if there exist oxic microsites in the soil.
文摘In this study,a top cover system is investigated as a control for emissions during the aftercare of new landfills and for old landfills where biogas energy production might not be profitable.Different materials were studied as landfill cover system in lab-scale columns：mechanical–biological pretreated municipal solid waste（MBP）;mechanical–biological pretreated biowaste（PB）;fine（PBSf）and coarse（PBSc）mechanical–biological pretreated mixtures of biowaste and sewage sludge,and natural soil（NS）.The effectiveness of these materials in removing methane and sulphur compounds from a gas stream was tested,even coupled with activated carbon membranes.Concentrations of CO2,CH4,O2,N2,H2S and mercaptans were analysed at different depths along the columns.Methane degradation was assessed using mass balance and the results were expressed in terms of methane oxidation rate（MOR）.The highest maximum and mean MOR were observed for MBP（17.2 g CH4/m^2/hr and 10.3 g CH4/m^2/hr,respectively）.Similar values were obtained with PB and PBSc.The lowest values of MOR were obtained for NS（6.7 g CH4/m^2/hr）and PBSf（3.6 g CH4/m^2/hr）,which may be due to their low organic content and void index,respectively.Activated membranes with high load capacity did not seem to have an influence on the methane oxidation process：MBP coupled with 220 g/m^2and 360 g/m^2membranes gave maximum MOR of 16.5 g CH4/m^2/hr and 17.4 g CH4/m^2/hr,respectively.Activated carbon membranes proved to be very effective on H2S adsorption.Furthermore,carbonyl sulphide,ethyl mercaptan and isopropyl mercaptan seemed to be easily absorbed by the filling materials.
基金Project supported by the Knowledge Innovation Project in Resource and Environment Fields, Chinese Academy of Sciences (No. KZCX3-SW-128), the Open Foundation of the State Key Laboratory of Gas Geochemistry (SJJ-01-07), and the National Key Basic Research
文摘In a series of laboratory incubations using soils of two contrasting sitesfrom a temperate marsh on the Qinghai-Tibet Plateau, potential methane (CH_4) oxidation rates weremeasured to study the effects of inorganic N inputs on CH_4 oxidation. For adrained site, subsurfacepeat (5--15 cm) at an initial 20 mu L CH_4 L^(-1) showed a significantly different (P < 0.05) CH_4oxidation rate compared to other soil depths, with a maximal rate of 20.9 ng CH_4 gDW (dryweight)^(-1) h^(-1); the underlying mineral soil layers (15--30 and 30--50 cm) also had a strongCH_4 oxidation capacity at about an initial 2 000 mu L CH_4 L^(-1). With a waterlogged site, theCH_4 oxidation rate in an aerobic incubation was significantly greater (P < 0 05) in the surfacesoil layer (0--5 cm) compared to the 15--30 and 30--50 cm depths. There was generally no or a veryweak effect from addition of NO_3^- on CH_4 oxidation. In marked contrast, NH_4^+ salts, such as(NH_4)_2SO_4, NH_4Cl and NH_4NO_3, exhibited strong inhibitions, which varied as a function of theadded salts and the initial CH_4 level Increasing NH_4^+ usually resulted in greater inhibition andincreasing initial CH_4 concentrations resulted in less NH_4^+ inhibition on CH4 oxidation innatural high-altitude, low-latitude wetlands could be as important as has been reported foragricultural and forest soils. The NH_4^+ effects on the CH_4 oxidation rate need to be furtherinvestigated in a wide range of natural wetland soil types.
基金jointly supported by the National Natural Science Foundation of China (42106052)Shandong Provincial Natural Science Foundation (ZR2020QD070)the project of China Geological Survey (DD20190221)。
文摘Large amounts of gas hydrate are distributed in the northern slope of the South China Sea,which is a potential threat of methane leakage.Aerobic methane oxidation by methanotrophs,significant methane biotransformation that occurs in sediment surface and water column,can effectively reduce atmospheric emission of hydrate-decomposed methane.To identify active aerobic methanotrophs and their methane oxidation potential in sediments from the Shenhu Area in the South China Sea,multi-day enrichment incubations were conducted in this study.The results show that the methane oxidation rates in the studied sediments were 2.03‒2.36μmol/gdw/d,which were higher than those obtained by sediment incubations from other areas in marine ecosystems.Thus the authors suspect that the methane oxidation potential of methanotrophs was relatively higher in sediments from the Shenhu Area.After the incubations family Methylococcaea(type I methanotrophs)mainly consisted of genus Methylobacter and Methylococcaea_Other were predominant with an increased proportion of 70.3%,whereas Methylocaldum decreased simultaneously in the incubated sediments.Collectively,this study may help to gain a better understanding of the methane biotransformation in the Shenhu Area.
文摘Palladium based catalysts are the most active for methane oxidation. The tuning of their composition, structure and morphology at macro and nanoscale can alter significantly their catalytic behavior and robustness with a strong impact on their overall performances. Among the several combinations of supports and promoters that have been utilized, Pd/CeO2 has attracted a great attention due to its activity and durability coupled with the unusually high degree of interaction between Pd/Pd O and the support. This allows the creation of specific structural arrangements which profoundly impact on methane activation characteristics. Here we want to review the latest findings in this area, and particularly to envisage how the control(when possible) of Pd-CeO2 interaction at nanoscale can help in designing more robust methane oxidation catalysts.
文摘To reduce greenhouse gas emission from oil and gas production,it is essential to better convert methane to useful chemicals(rather) than to flare it.Conversion of methane to liquid oxygenates(mainly methanol) has attracted extensive attention and countless efforts have been made;however,running this reaction in a green,efficient,and practical way has remained elusive.The novel catalyst and oxidants play a critical role in activating methane and converting it to oxygenates(methanol).In this review,the work of commonly used oxidants for methane partial oxidation have been summarized,in which,earth abundant oxidants,O;and H;O are promising.Moreover,H;or CO can activate O;to produce H;O;that catalyzes methane partial oxidation more efficiently and selectively than O;or H;O.Therefore,the work of using reducing agent,such as CO and H;have been reviewed,focusing on rational catalyst design that features multifunction(H;O;production and CH;activation).The novel catalyst design has advanced this reaction towards practicality with green oxidants and H;using zeolites-based catalyst.Environmentally friendly zeolite preparation methods and novel two-dimensional(2 D) zeolites that can reduce waste,improve synthesis and catalytical performance substantially are also reviewed in this work to provide insights for a more comprehensive approach to meet the environment protection needs.
基金supported by the National Natural Science Foundation of China(Grant Nos.41977037,42377116,and 42077086)the 333 High-level Talents Training Project of Jiangsu Province(Grant No.BRA2022023)Fujian Natural Science Foundation(Grant No.2021J06019).
文摘Nitrite-dependent anaerobic methane oxidation (n-damo), performed by the bacteria associated with Candidatus Methylomirabilis oxyfera, acts as a novel methane sink in coastal wetlands. Conversion of coastal wetlands into paddy fields is a common land-use change that has profound effects on methane emissions, but its impact on n-damo process is nearly unknown. Our study adopted a space-for-time substitution method to compare n-damo activity and community of Methylomirabilis-like bacteria between natural vegetation covered by Phragmites australis, Kandelia candek, or Bruguiera sexangula and adjacent converted paddy fields in six China’s coastal wetlands. Generalized linear mixed model indicated that the activity of n-damo significantly increased by 43.6% and 165.8% after conversion of K. candek and B. sexangula wetlands into rice paddies, respectively, while the activity exhibited no significant change after conversion of P. australis wetlands. Furthermore, the abundance of Methylomirabilis-like bacteria significantly increased by 90.2%, 210.0%, and 110.1% following the conversion in wetlands covered by K. candek, B. sexangula, and P. australis, respectively. Principal co-ordinates analysis revealed significant changes in community structure of Methylomirabilis-like bacteria among vegetation types, with K. candek and B. sexangula showing a greater divergence than P. australis when compared to respective paddy fields. Path analysis indicated that land conversion resulted in changes in soil moisture content, organic carbon content, bulk density, and salinity and further affected the abundance of Methylomirabilis-like bacteria and ultimately n-damo activity. Overall, this is the first study to reveal the impact of conversion of coastal wetlands into paddy fields on n-damo activity and Methylomirabilis-like bacteria, and the impact was closely associated with the original native plant types. The results can enhance our understanding of the microbial-driven mechanisms of the impact of land conversion on methane emissions.
基金This work was supported by the DGAPA-UNAM(PAPIIT project,No.IN102721)the support from CONAHCYT through the Investigadoras e Investigadores por Mexico program(Researcher ID 6407,Project 265).
文摘Anaerobic oxidation of methane(AOM)can contribute to reducing methane emissions in landfills;however,the AOM rates vary depending on the inoculum source.This study addressed the capacity of AOM of a fermentative microbial community derived from a reactor treatingmunicipal solidwastes.First,the inoculum’s autotrophic capacitywas verified using a gasmixture of 75% CO_(2) and 25% H_(2).Results demonstrated that the fermentative microbial community reached amaximum CO_(2) consumption rate of 22.5±1.2 g CO_(2)/(m^(3)·h),obtaining acetate as the main product.Then,the inoculum was grown on a gas mixture of 50%CH_(4),35%CO_(2),and 15%N_(2),using iron(Fe^(3+))as the electron acceptor.The AOM rates increased over time and peaked at 3.1±0.9 g CH_(4)/(m^(3)·h)by 456 h with the simultaneous consumption of CO_(2).Acetate was the main product,with amaximum concentration of 180±9mg/L.By 408 h,a bacterial cluster of indicator species correlated with the AOM rates,including to Rhodobactereceae(r=0.80),Oceanicola(r=0.80),Propionicicella(r=0.77),Christensenellaceae(r=0.58),Oscillospiraceae(r=0.53),Mobilitalea(r=0.66),Hungateiclostridiaceae(r=0.46),and Izemoplasmatales(r=0.77).Methanosarcina,Methanobacterium,and Methanoculleus correlated with the AOM and CO_(2) consumption rates.A co-occurrence network analysis showed that Methanosarcina positively interacted with syntrophic bacteria like Christensenellaceae and Acinetobacter and diverse heterotrophic bacteria.This study demonstrated the feasibility of obtaining a CH_(4)-oxidizing microbial community in 16 days,exhibiting AOM rates higher than those reported for soils.
基金Project supported by the National Key Technologies R&D Program of China(2022YFE0114800)National Natural Science Foundation of China(22172032,U22A20431)。
文摘The direct activation of methane under mild condition to achieve highly selective of oxygenates is a challenging project.In this study,a well dispersed silver supported ZnTiO_(3) catalyst was prepared to achieve selective preparation of methanol from methane and water under mild condition.X-ray diffraction,transmission electron microscopy and X-ray photoelectron spectroscopy characterizations demonstrate that silver species are uniformly dispersed on ZnTiO_(3) surface in the form of metallic silver nanoparticles.The photoelectric characterizations reveal that the addition of silver species enhances light absorption and promotes charge separation of the catalysts.Under the reaction conditions of 50℃and 3 MPa,the methanol is obtained as the only liquid product over the designed Ag/ZnTiO_(3) catalyst under light irradiation.In this photocatalytic process,the holes generated by ZnTiO_(3) activate water to produce intermediate·OH,which further reacts with methane to synthesize methanol.The silver species as co-catalysts extend the light absorption range of ZnTiO_(3) as well as promote charge separation.
基金supported by the National Natural Science Foundation of China(22208290,22288102,22078288,22225802)the key R&D Program Projects in Zhejiang Province(2021C03005).
文摘Selective photocatalytic aerobic oxidation of methane to value-added chemicals offers a promising pathway for sustainable chemical industry,yet remains a huge challenge owing to the consecutive overoxidation of primary products.Here,a type II heterojunction were constructed in Ag-AgBr/ZnO to reduce the oxidation potential of stimulated holes and prevent the undesirable CH_(4) overoxidation side reactions.For photocatalytic oxidation of methane under ambient temperature,the products yield of 1499.6μmol gcat^(-1) h^(-1) with a primary products selectivity of 77.9%was achieved over Ag-AgBr/ZnO,which demonstrate remarkable improvement compared to Ag/ZnO(1089.9μmol gcat^(-1) h^(-1) ,40.1%).The superior activity and selectivity result from the promoted charge separation and the redox potential matching with methane activation after introducing AgBr species.Mechanism investigation elucidated that the photo-generated holes transferred from the valence band of ZnO to that of AgBr,which prevent H_(2)O oxidation and enhance the selective generation of•OOH radical.
基金This research was supported by"Regional Innovation Strategy"(2023RIS-008)and"C1 Gas Refinery Program"(NRF-2015M3D3D3A1A01064876)through the National Research Foundation of Koreafunded by the Ministry of Education(NRF-2017R1A6A1A03015876).
文摘Methane(CH_(4))has a higher heat capacity(104.9 kcal/mol)than carbon dioxide(CO_(2)),and this has inspired research aimed at reducing methane levels to retard global warming.Hydroxylation under ambient conditions through methanotrophs can provide crucial information for understanding the harsh C-H activation of methane.Soluble methane monooxygenase(sMMO)belongs to the bacterial multi-component monooxygenase superfamily and requires hydroxylase(MMOH),regulatory(MMOB),and reductase(MMOR)components.Recent structural and biophysical studies have demonstrated that these components accelerate and retard methane hydroxylation in MMOH through protein-protein interactions.Complex structures of sMMO,including MMOH-MMOB and MMOH-MMOD,illustrate how these regulatory and inhibitory components orchestrate the di-iron active sites located within the four-helix bundles of MMOH,specifically at the docking surface known as the canyon region.In addition,recent biophysical studies have demonstrated the role of MmoR,aσ54-dependent transcriptional regulator,in regulating sMMO expression.This perspective article introduces remarkable discoveries in recent reports on sMMO components that are crucial for understanding sMMO expression and activities.Our findings provide insight into how sMMO components interact with MMOH to control methane hydroxylation,shedding light on the mechanisms governing sMMO expression and the interactions between activating enzymes and promoters.
基金the National Key R&D Program of China(No.2021YFA1500800)National Natural Science Foundation of China(No.22072106).
文摘Methane chemistry is one of the“Holy Grails of catalysis”.It is highly desirable but challenge to transform methane into value-added chemicals,because of its high C-H bonding energy(435 kJ/mol),lack ofπbonding or unpaired electrons.Currently,commercial methane conversion is usually carried out in harsh conditions with enormous energy input.Photocatalytic partial oxidation of methane to liquid oxygenates(PPOMO)is a future-oriented technology towards realizing high efficiency and high selectivity under mild conditions.The selection of oxidant is crucial to the PPOMO performance.Hence,attentions are paid to the research progress of PPOMO with various oxidants(O_(2),H_(2)O,H_(2)O_(2)and other oxidants).Moreover,the activation of the selected oxidants is also highly emphasized.Meanwhile,we summarized the methane activation mechanisms focusing on the C-H bond that was broken mainly by·OH radical,O-specie or photogenerated hole(h+).Finally,the challenges and prospects in this subject are briefly discussed.
基金supported by the National Key Research and Development Program (Nos.2020YFA0210903)the National Natural Science Foundation of China (Grant Nos.22225807,21961132026,22021004)DFG within joint Sino-German project (KO 2261/11-1)。
文摘Oxidative coupling of methane (OCM) is one of the most promising approaches to produce ethylene and ethane (C_(2)-hydrocarbons) in the post-oil era.The MnO_(x)-Na_(2)WO_(4)/SiO_(2) system shows promising OCM performance,which can be further enhanced by cofed steam.However,the positive effect of steam on C_(2)-hydrocarbons selectivity practically disappears above 800℃.In the present study,we demonstrate that the use of SiC as a support for MnO_(x)-Na_(2)WO_(4) is beneficial for achieving high selectivity up to 850℃.Our sophisticated kinetic tests using feeds without and with steam revealed that the steam-mediated improvement in selectivity to C_(2)-hydrocarbons is due to the inhibition of the direct CH_(4) oxidation to carbon oxides because of the different enhancing effects of steam on the rates of CH_(4) conversion to C_(2)H_(6) and CO/CO_(2).Other descriptors of the selectivity improvement are MnO_(x) dispersion and the catalyst specific surface area.The knowledge gained herein may be useful for optimizing OCM performance through catalyst design and reactor operation.
基金supported by the Hi-Tech Research and Development Program (863) of China (No. 2007AA06Z349)the Science and Technology Commission of Shanghai Municipality (No. 09DZ2251700)
文摘Aged refuse from waste landfills closed for eight years was examined and found to contain rich methanotrophs capable of biooxidation for methane. Specially, community structure and methane oxidation capability of methanotrophs in the aged refuse were studied. The amount of methanotrophs ranged 61.97×10^3-632.91×10^3 cells/g （in dry basis） in aged refuse from Shanghai Laogang Landfill. Type I and II methanotrophs were found in the aged refuse in the presence of sterilized sewage sludge and only Type I methanotrophs were detected in the presence of nitrate minimal salt medium （NMS）. The clone sequences of the pmoA gene obtained from the aged refuse were similar to the pmoA gene of Methylobacter, Methylocaldum, and Methylocystis, and two clones were distinct with known genera of Type I methanotrophs according to phylogenetic analysis. Aged refuse enriched with NMS was used for methane biological oxidation and over 93% conversions were obtained.
基金Project supported bythe National Research Laboratory Programof the Korea Ministry of Science and Technology
文摘A 1% Fe-30% Hf over yttria-stabilized zirconia catalyst in combination with novel plasma-assisted activation techniques for a direct partial oxidation of methane to methanol was tested using dielectric barrier discharge plasma at ambient temperature and atmospheric pressure. However, instead of methanol, the reaction products were dominated by HE, CO, CO2, C2, and H2O. A catalytically activated plasma process increased the production of methanol compared with a noncatalytic plasma process. The maximum selectivity of methanol production was achieved using a catalyst that was treated at higher applied power.
文摘Ba0.5Sr0.5Co0.8Fe0.2O3-delta and Ba0.5Sr0.5Co0.8Ti0.2O3-delta oxides were synthesized by a combined EDTA-citrate complexing method. The catalytic behavior of these two oxides with the perovskite structure was studied during the reaction of methane oxidation. The pre-treatment with methane has different effect on the catalytic activities of both the oxides. The methane pre-treatment has not resulted in the change of the catalytic activity of BSCFO owing to its excellent reversibility of the perovskite structure resulting from the excellent synergistic interaction between Co and Fe in the oxide. However, the substitution with Ti on Fe-site in the lattice makes the methane pre-treatment have an obvious influence on the activity of the formed BSCTO oxide.
基金the National Natural Science Foundation of China (50574046)National Natural Science Foundation of Major Research Projects (90610035)+1 种基金Natural Science Foundation of Yunnan Province (2004E0058Q)High School Doctoral Subject Special Science and Re- search Foundation of Ministry of Education (20040674005)
文摘A series of Ce1-xFexO2 （x=0, 0.2, 0.4, 0.6, 0.8, 1） complex oxide catalysts were prepared using the coprecipitation method. The catalysts were characterized by means of XRD and H2-TPR. The reactions between methane and lattice oxygen from the complex oxides were investigated. The characteristic results revealed that the combination of Ce and Fe oxide in the catalysts could lower the temperature necessary to reduce the cerium oxide. The catalytic activity for selective CH4 oxidation was strongly influenced by dropped Fe species. Adding the appropriate amount of Fe2O3 to CeO2 could promote the action between CH4 and CeO2. Dispersed Fe2O3 first returned to the original state and would then virtually form the Fe species on the catalyst, which could be considered as the active site for selective CH4 oxidation. The appearance of carbon formation was significant and the oxidation of carbon appeared to be the rate-determining step; the amounts of surface reducible oxygen species in CeO2 were also relevant to the activity. Among all the catalysts, Ce0.6Fe0.402 exhibited the best activity, which converted 94.52% of CH4 at 900 ℃.
基金supported by the Open Foundation of State Key Laboratory of Physical Chemistry of Solid Surfaces, Xiamen University (No.200906)the Natural Science Foundation of Jiangxi Province (No.2010GZH0048)+1 种基金the National Natural Science Foundation of China (No. 21067004)the Young Science Foundation of Jiangxi Province Education Office (No. GJJ10150)
文摘Nano-sized γ-alumina （γ-Al2O3） was first prepared by a precipitation method. Then, active component of cobalt and a series of alkaline- earth metal promoters or nickel （Ni） with different contents were loaded on the γ-Al2O3 support. The catalysts were characterized by N2 adsorption-desorption, X-ray diffraction （XRD） and thermogravimetry analysis （TGA）. The activity and selectivity of the catalysts in catalytic partial oxidation （CPO） of methane have been compared with Co/γ-Al2O3, and it is found that the catalytic activity, selectivity, and stability are enhanced by the addition of alkaline-earth metals and nickel. The optimal loadings of strontium （Sr） and Ni were 6 and 4 wt%, respectively. This finding will be helpful in designing the trimetallic Co-Ni-Sr/γ-Al2O3 catalysts with high performance in CPO of methane
