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methane emission via sediment and water interface in the Bohai Sea,China

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Journal of Environmental Sciences 2022年第4期34卷 465-474页

作者： Kunpeng Zang Gen Zhang Xuemei Xu Nan Zheng Haoyu Xiong Haixiang Hong Kai Jiang Miao Liang College of Environment Zhejiang University of TechnologyHangzhou 310014China State Key Laboratory of Severe Weather&Key Laboratory of Atmospheric Chemistry of China Meteorological Administration Chinese Academy of Meteorological SciencesBeijing 100081China Key Laboratory for Ecological Environment in Coastal Areas National Marine Environmental Monitoring CenterDalian 116023China Meteorological Observation Center China Meteorological AdministrationBeijing 100081China

Sediment is recognized as the largest reservoir and source of methane(CH_(4))in the ocean,especially in the shallow coastal areas.To date,few data of CH_(4)concentration in sediment have been reported in the China shelf seas.In this study,we measured CH_(4)concentration in sediment and overlying seawater columns,and conducted an incubation experiment in the Bohai Sea in May 2017.CH_(4)concentration was found to be ranged from 3.075 to 1.795μmol/L in sediment,which was 2 to 3 orders of magnitude higher than that in overlying seawater columns.The surface sediment was an important source of CH_(4),while bottom seawater acted as its sink.Furthermore,the net emission rate via sediment water interface(SWI)was calculated as 2.45μmol/(m^(2)·day)based on the incubation experiment at station73,and the earthquake may enhance CH_(4)release from sediment to seawater column in the eastern Bohai Sea.

关键词： methane Porewater Sediment-water interface Rhizon sampler Earthquake

methane hydrate crystal growth on shell substrate

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Chinese Journal of Chemical Engineering 2022年第3期35卷 50-61页

作者： Xin Jiang Baojiang Sun Zhiyuan Wang Wantian Zhou Jiakai Ji Litao Chen School of Petroleum Engineering China University of Petroleum(East China)Qingdao 266580China Key Laboratory of Unconventional Oil and Gas Development China University of Petroleum(East China)Qingdao 266580China

Hydrate crystals growth on the surface of methane bubble(hydrate film)in pure water was studied by using a high-pressure visible microscope under the conditions of subcoolingΔT=5.44-13.72 K and methane concentration differenceΔC=2.92-8.19 mol·L^(-1).It was found the hydrate film is porous and the hydrate crystals grow towards the liquid phase on the film substrate.The crystal morphology and growth rate are affected byΔT andΔC.WhenΔT8.82 K orΔC>4.12 mol·L^(-1),the hydrate crystals grow in dendritic shape,and the axial growth rate increases first and then decreases.The perimeter and area of the growing hydrate crystals were measured,and the fractal dimension of hydrate crystal under differentΔC andΔT was calculated.The results show that the fractal dimension of columnar hydrate crystal is greater than 3.When3.87 mol·L^(-1)4.77 mol·L^(-1),ΔT<8.52 K,the fractal dimension of dendritic hydrate crystal is less than 2.

关键词： methane Hydrate Crystal growth Morphology Fractal dimension

methane in the Yellow Sea and East China Sea: dynamics, distribution, and production

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Journal of Oceanology and Limnology 2022年第2期40卷 530-550页

作者： Wangwang YE Guanxiang DU Honghai ZHANG Guiling ZHANG Frontiers Science Center for Deep Ocean Multispheres and Earth System and Key Laboratory of Marine Chemistry Theory and TechnologyMinistry of EducationOcean University of ChinaQingdao 266100China Key Laboratory of Global Change and Marine-Atmospheric Chemistry Third Institute of OceanographyMinistry of Natural ResourcesXiamen 361005China Laboratory for Marine Ecology and Environmental Science Pilot National Laboratory for Marine Science and Technology(Qingdao)Qingdao 266237China

The Yellow Sea(YS)and East China Sea(ECS)are important marginal seas of the western Pacific.Understanding the dynamics of methane(CH_(4))in the YS and ECS are essential to evaluate the role of coastal seas in global warming.We measured dissolved CH_(4) at various depths in the water column of the YS and ECS during a cruise from March to April 2017.The concentrations of CH_(4) varied greatly in different water masses,suggesting that the hydrographic conditions can substantially aff ect the CH_(4) distribution.The CH_(4) budget in the shelf of the ECS,which was estimated with a box model,suggests CH_(4) consumption in the water column was the major sink(>95%),followed by a loss with a total of 2.2%CH_(4) released to the atmosphere.Overall a local CH_(4) production of 0.28 nmol/(L·d)was needed to maintain the CH_(4) excess.Results from laboratory incubations showed an increase in CH_(4)(1.5 times higher than the value of the control)after the addition of dimethylsulfoniopropionate(DMSP).Field incubations result in a CH_(4) production rate of 1.2 nmol/(L·d)under a N-stressed conditions(N꞉P<1),indicates that the DMSP-dependent CH_(4) production prefer to occur in the oligotrophic seawaters,where nitrogen is depleted.This study demonstrates that the marginal seas of China is a hotspot for CH_(4) dynamics,and the cycling of methylated sulfur compounds(such as DMSP)may contribute importantly to locally formed CH_(4).This may have further implication to carbon and sulfur biogeochemical cycles in the western Pacific.

关键词： methane East China Sea Yellow Sea aerobic production dimethylsulfi de(DMS) dimethylsulfoniopropionate(DMSP)

Effect of dissolved oxygen on methane production from bottom sediment in a eutrophic stratified lake

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Journal of Environmental Sciences 2023年第3期125卷 61-72页

作者： Yasuyuki Maruya Keisuke Nakayama Masafumi Sasaki Katsuaki Komai Graduate School of Engineering Kyushu University744 MotookaNishi-KuFukuoka 819-0395Japan Graduate School of Engineering Kobe UniversityRokkodai-Cho 1-1Nada-KuKobe 657-8501Japan Department of Engineering Kitami Institute of TechnologyKohen-Cho 165Kitami 090-8507Japan

Clarifying the role of sulfate and dissolved oxygen (DO) in methane production may allow for precise and accurate modeling of methane emissions in eutrophic lakes.We conducted field observations of sulfate,methane,and DO concentrations in Lake Abashiri,a typical brackish and eutrophic lake in a cold region,to develop a DO-based method for quantitively estimating methane production in a eutrophic lake and analyzed the results.We found that sulfate concentrations decreased rapidly from 900.0 mg/L in water overlying the sediments to nearly 0.0 mg/L in the bottom sediment.methane production was almost uniform across sediment depths of 0.05 to 0.25 m,ranging from 1400 to 1800μmol/m^(2)/day.Also,methane production was found to be a function of DO concentrations in water overlying the bottom and could be modeled by a logistic function:constant production at 1,400μmol/m^(2)/day for DO concentrations of 0.0 to 3.0 mg/L,rapidly decreasing to 0μmol/m^(2)/day for DO concentrations of 3.0 to 6.0 mg/L.This methane model was verified using a simple one-dimensional numerical model that showed good agreement with field observations.Our results thus suggest that the proposed methane model reduces uncertainty in estimating methane production in a eutrophic lake.

关键词： Dissolved oxygen(DO) Stratification methane Anoxia Numerical simulation

Influence of NO_(x) on the activity of Pd/θ-Al_(2)O_(3) catalyst for methane oxidation: Alleviation of transient deactivation

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Journal of Environmental Sciences 2022年第2期34卷 38-47页

作者： Chang Cui Yan Zhang Wenpo Shan Yunbo Yu Hong He State Key Joint Laboratory of Environment Simulation and Pollution Control Research Center for Eco-Environmental SciencesChinese Academy of SciencesBeijing 100085China University of Chinese Academy of Sciences Beijing 100049China Center for Excellence in Regional Atmospheric Environment and Key Laboratory of Urban Pollutant Conversion Institute of Urban EnvironmentChinese Academy of SciencesXiamen 361021China Ningbo Research Center for Urban Environment Chinese Academy of SciencesNingbo 315800China Ganjiang Innovation Academy Chinese Academy of SciencesGanzhou 341000China

Alumina supported Pd catalyst(Pd/Al_(2)O_(3)) is active for complete oxidation of methane, while often suffers transient deactivation during the cold down process. Herein, heating and cooling cycle tests between 200 and 900 ℃ and isothermal experiments at 650 ℃ were conducted to investigate the influence of NO_(x) on transient deactivation of Pd/θ-Al_(2)O_(3) catalyst during the methane oxidation. It was found that the co-fed of NO alleviated transient deactivation in the cooling ramp from 800 to 500 ℃, which was resulted from the in situ formation of NO_(2) during the process of methane oxidation. Over the Pd/θ-Al_(2)O_(3), thermogravimetric analysis and O_(2) temperature programmed oxidation measurements confirmed that transient deactivation was due to the decomposition of Pd O particles and the hysteresis of Pd reoxidation, while the metal Pd entities were less active for methane oxidation than the Pd O ones. CO pulse chemisorption and scanning transmission electron microscopy characterizations rule out the NO_(2) effect on Pd size change. Powder X-ray diffraction and X-ray photoelectron spectroscopy characterizations were used to obtain palladium status of Pd/θ-Al_(2)O_(3) before and after reactions, indicating that in lean conditions at 650 ℃, the presence of NO_(2) increases the content of active Pd O on the catalyst surface, thus benefits methane oxidation. Homogeneous reaction between CH 4, O_(2), and NO_(x) may be partially responsible for the alleviation above 650 ℃. The interesting research of alleviation in transient deactivation by NO_(x), the components co-existing in exhausts, are of great significance for the application.

关键词： methane Catalytic oxidation Palladium NO_(x)influence

Decreasing ruminal methane production through enhancing the sulfate reduction pathway

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Animal Nutrition 2022年第2期9卷 320-326页

作者： Yuchao Zhao Guangyong Zhao State Key Laboratory of Animal Nutrition College of Animal Science and TechnologyChina Agricultural University100193 BeijingChina

methane(CH4)production from ruminants accounts for 16%of the global greenhouse gas emissions and represents 2%to 12%of feed energy.Mitigating CH_(4) production from ruminants is of great importance for sustainable development of the ruminant industry.H_(2) is the primary substrate for CH_(4) production in the processes of ruminal methanogenesis.Sulfate reducing bacteria are able to compete with methanogens for H_(2) in the rumen,and consequently inhibit the methanogenesis.Enhancing the ruminal sulfate reducing pathway is an important approach to mitigate CH_(4) emissions in ruminants.The review summarized the effects of sulfate and elemental S on ruminal methanogenesis,and clarified the related mechanisms through the impacts of sulfate and elemental S on major ruminal sulfate reducing bacteria.Enhancing the activities of the major ruminal sulfate reducing bacteria including Desulfovibrio,Desulfohalobium and Sulfolobus through dietary sulfate addition,elemental S and dried distillers grains with solubles can effectively decrease the ruminal CH_(4) emissions.Suitable levels of dietary addition with different S sources for reducing the ruminal CH_(4) production,as well as maintaining the performance and health of ruminants,need to be investigated in the future.

关键词： methane Rumen Sulfur Sulfate reduction pathway

Reaction characteristics of maximizing light olefins and decreasing methane in C_(5) hydrocarbons catalytic pyrolysis

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Petroleum Science 2023年第3期20卷 1909-1921页

作者： Mei-Jia Liu Gang Wang Shun-Nian Xu Tao-Ran Zheng Zhong-Dong Zhang Sheng-Bao He State Key Laboratory of Heavy Oil Processing China University of PetroleumBejing102249China Petrochemical Research Institute PetroChinaBejing102206China

When converting C_(5) hydrocarbons to light olefins by catalytic pyrolysis,the generation of low value-added methane will affect the atomic utilization efficiency of C_(5) hydrocarbons.To improve the atomic utilization efficiency,different generation pathways of light olefins and methane in the catalytic pyrolysis of C_(5) hydrocarbons were analyzed,and the effects of reaction conditions and zeolite types were inves-tigated.Results showed that light olefins were mainly formed by breaking the C_(2)-C_(3) bond in the middle position,while methane was formed by breaking the C_(1)-C_(2) bond at the end.Meanwhile,it was discovered that the hydrogen transfer reaction could be reduced by about 90%by selecting MTT zeolite with 1D topology and FER zeolite with 2D topology under high weight hourly space velocity(WHSV)and high temperature operations,thus leading to the improvement of the light olefins selectivity for the catalytic pyrolysis of n-pentane and 1-pentene to 55.12% and 74.60%,respectively.Moreover,the fraction ratio of terminal C_(1)-C_(2) bond cleavage was reduced,which would reduce the selectivity of methane to 6.63%and 1.83%.Therefore,zeolite with low hydrogen transfer activity and catalytic pyrolysis process with high WHsV will be conducive to maximize light olefins and to decrease methane.

关键词： n-Pentane 1-Pentene Catalytic pyrolysis Light olefins methane

客体溶剂导向策略构筑异构的金属有机框架材料实现二氧化碳和甲烷的动力学分离

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Engineering 2023年第4期23卷 64-72,M0004页

作者：赖丹陈富强郭立东陈俐吭陈洁杨启炜张治国杨亦文任其龙鲍宗必 Key Laboratory of Biomass Chemical Engineering of the Ministry of Education College of Chemical and Biological EngineeringZhejiang UniversityHangzhou 310027China Institute of Zhejiang University-Quzhou Quzhou 324000China

利用吸附分离技术实现二氧化碳和甲烷的分离是提高天然气品质的一种有效手段。然而,基于热力学分离的吸附剂对二氧化碳往往表现出很强的亲和力,因此再生过程会产生巨大的能耗。相较而言,尽管精准调控吸附剂孔径以实现吸附质扩散速率的... 详细信息

利用吸附分离技术实现二氧化碳和甲烷的分离是提高天然气品质的一种有效手段。然而,基于热力学分离的吸附剂对二氧化碳往往表现出很强的亲和力,因此再生过程会产生巨大的能耗。相较而言,尽管精准调控吸附剂孔径以实现吸附质扩散速率的巨大差异仍具有巨大挑战,动力学分离技术仍是变压吸附(PSA)过程的首选。本文报道了一种用于在亚埃尺度精准调控吸附剂孔径的客体溶剂导向策略,实现了二氧化碳和甲烷的高效动力学分离。基于4,4-(六氟异丙基亚甲基)-双(苯甲酸)和双核铜的轮桨型结构单元,我们构筑了一系列异构的金属有机框架材料。结果表明,得益于周期性扩张和收缩的孔道以及理想的孔径尺寸,CuFMOF·CH_(3)OH(CuFMOF-c)能够有效地捕获二氧化碳并阻碍甲烷的扩散,从而表现出优异的动力学分离性能,其具有极高的动力学选择性(273.5)和平衡-动力学综合选择性(64.2)。分子动力学(MD)模拟阐明了分离机制,固定床穿透实验验证了材料优异的分离性能。

关键词： Guest solvent-directed strategy Metal-organic frameworks Carbon dioxide methane Kinetic separation

Atomic Cu Sites Engineering Enables Efficient CO_(2)Electroreduction to methane with High CH_(4)/C_(2)H_(4)Ratio

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Nano-Micro Letters 2023年第12期15卷 361-375页

作者： Minhan Li Fangzhou Zhang Min Kuang Yuanyuan Ma Ting Liao Ziqi Sun Wei Luo Wan Jiang Jianping Yang Institute of Functional Materials State Key Laboratory for Modification of Chemical Fibers and Polymer MaterialsCollege of Materials Science and EngineeringDonghua UniversityShanghai 201620People’s Republic of China College of Materials Science and Engineering Zhengzhou UniversityZhengzhou 450001People’s Republic of China School of Mechanical Medical and Process EngineeringSchool of Chemistry and PhysicsQueensland University of Technology2 George StreetBrisbaneQLD 4001Australia

Electrochemical reduction of CO_(2)into high-value hydrocarbons and alcohols by using Cu-based catalysts is a promising and attractive technology for CO_(2)capture and utilization,resulting from their high catalytic activity and selectivity.The mobility and accessibility of active sites in Cubased catalysts significantly hinder the development of efficient Cu-based catalysts for CO_(2)electrochemical reduction reaction(CO_(2)RR).Herein,a facile and effective strategy is developed to engineer accessible and structural stable Cu sites by incorporating single atomic Cu into the nitrogen cavities of the host graphitic carbon nitride(g-C_(3)N_(4))as the active sites for CO_(2)-to-CH_(4)conversion in CO_(2)RR.By regulating the coordination and density of Cu sites in g-C_(3)N_(4),an optimal catalyst corresponding to a one Cu atom in one nitrogen cavity reaches the highest CH_(4)Faraday efficiency of 49.04%and produces the products with a high CH_(4)/C_(2)H_(4)ratio over 9.This work provides the first experimental study on g-C_(3)N_(4)-supported single Cu atom catalyst for efficient CH_(4)production from CO_(2)RR and suggests a principle in designing highly stable and selective high-efficiency Cu-based catalysts for CO_(2)RR by engineering Cu active sites in 2D materials with porous crystal structures.

关键词： CO_(2)RR Cu single-atom catalyst g-C_(3)N_(4) methane CH_(4)/C_(2)H_(4)ratio