In the present study,two Ni/YSZ anodes with different volume ratios of Ni and YSZ,30:70 and 45:55 vol%,are operated in dry methane under open circuit and polarized conditions.Three-dimensional(3D)Ni/YSZ microstructure...In the present study,two Ni/YSZ anodes with different volume ratios of Ni and YSZ,30:70 and 45:55 vol%,are operated in dry methane under open circuit and polarized conditions.Three-dimensional(3D)Ni/YSZ microstructures after carbon deposition are reconstructed by the focused ion beam-scanning electron microscopy(FIB-SEM)with the help of machine learning segmentation.From the reconstructed mircostructures,volume fraction,connectivity,three phase boundary(TPB)density,and tortuosity are quantified.In addition,local carbon microstructures are quantitatively reconstructed,and the effect of polarization on carbon morphology is investigated.It is demonstrated that Ni surface in the vicinity of active TPB near the electrolyte is free from carbon formation,while remaining Ni surface at some distances from TPB exhibits severe carbon deposition.In average,total amount of carbon deposition is larger near the electrolyte.These observations imply complex interplay between the electrochemical steam generation and methane cracking on Ni surface which take place very locally near the active TPB.展开更多
In order to further improve the catalytic performance of zeolite catalyst for methanol to aromatics(MTA)technology, the double-tier SAPO-34/ZSM-5/quartz composite zeolite films were successfully synthesized via hydrot...In order to further improve the catalytic performance of zeolite catalyst for methanol to aromatics(MTA)technology, the double-tier SAPO-34/ZSM-5/quartz composite zeolite films were successfully synthesized via hydrothermal crystallization. The Si/Al ratio of SAPO-34 film was used as the only variable to study this material. The composite zeolite material with 0.6Si/Al ratio of SAPO-34 has the largest mesoporous specific surface area and the most suitable acid distribution. The catalytic performance for the MTA process showed that 0.6-SAPO-34/ZSM-5/quartz film has as high as 50.3% benzene-toluenexylene selectivity and 670 min lifetime. The MTA reaction is carried out through the path we designed to effectively avoid the hydrocarbon pool circulation of ZSM-5 zeolite, so as to improve the aromatics selectivity and inhibit the occurrence of deep side reactions to a great extent. The coke deposition behavior was monitored by thermogravimetric analysis and gas chromatograph/mass spectrometer, it is found that with the increase of Si/Al ratio, the active intermediates changed from low-substituted methylbenzene to high-substituted methylbenzene, which led to the rapid deactivation of the catalyst. This work provides a possibility to employ the synergy effect of composite zeolite film synthesizing anti-carbon deposition catalyst in MTA reaction.展开更多
Toluene methylation with methanol to produce para-xylene has been extensively and intensively studied.However,the methanol-to-hydrocarbons(MTH)side reaction in this reaction is difficult to be inhibited,which will cau...Toluene methylation with methanol to produce para-xylene has been extensively and intensively studied.However,the methanol-to-hydrocarbons(MTH)side reaction in this reaction is difficult to be inhibited,which will cause a mass of carbon deposition and cover the catalyst surface,resulting in catalyst deactivation.Here,a dual-functional Ru@HZSM-5 catalyst with high para-selectivity and low carbon deposition was prepared by encapsulating Ru metal with HZSM-5.According to catalytic performance studies,the Ru@HZSM-5 catalyst produced xylene selectivity of 98%and para-xylene selectivity of 96%.Meanwhile,we find that carbon precursors(e.g.ethylene)were very little when Ru catalyst was used,but the results of HZSM-5 catalyst were completely opposite.Ru@HZSM-5 catalyst achieves a lower carbon deposition rate of only 6%of HZSM-5.The main possible reason for this is that the initial C-C bond between methanol and the olefin is difficult to form.展开更多
The East China Sea(ECS),which is located in the transitional zone between land and ocean,is the main site for the burial of sedimentary organic carbon.Despite good constraints of the modern source to the sinking proce...The East China Sea(ECS),which is located in the transitional zone between land and ocean,is the main site for the burial of sedimentary organic carbon.Despite good constraints of the modern source to the sinking process of organic carbon,its fate in response to changes in climate and sea level since the last deglaciation remains poorly understood.We aim to fill this gap by presenting a high-resolution sedimentary record of core EC2005 to derive a better understanding of the evolution of the depositional environment and its control on the organic deposition since 17.3 kyr.Our results suggest that sedimentary organic carbon was deposited in a terrestrial environment before the seawater reached the study area around 13.1 kyr.This significant transition from a terrestrial environment to a marine environment is reflected by the decrease in TOC/TN and TOC/TS ratios,which is attributed to deglacial sea level rise.The sea level continued to rise until it reached its highstand at approximately 7.3 kyr when the mud depocenter was developed.Our results further indicate that the deposition of the sedimentary organic carbon could respond quickly to abrupt cold events,including the Heinrich stadial 1 and the Younger Dryas during the last deglaciation,as well as‘Bond events'during the Holocene.We propose that the rapid response of the organic deposition to those cold events in the northern hemisphere is linked to the East Asian winter monsoon.These new findings demonstrate that organic carbon deposition and burial on the inner shelf could effectively document sea level and climatic changes.展开更多
The deactivation mechanism of Co/MgO catalyst for the reforming of methane with carbon dioxide was investigated. The conversion of CH4 displayed a significant decrease in the initial stage caused by carbon deposition....The deactivation mechanism of Co/MgO catalyst for the reforming of methane with carbon dioxide was investigated. The conversion of CH4 displayed a significant decrease in the initial stage caused by carbon deposition.There were two types of cokes, carbon nanotubes(CNTs) and carbon nano-onions(CNOs). The number of the CNO layers that coated on the surface of Co nanoparticles(NPs) increased rapidly in the initial reforming time,which was responsible for the deactivation of the Co/MgO catalyst. The deposition of CNOs was attributed to the oxidation of Co NPs. Therefore, the deactivation of the Co/MgO catalyst was originated from the first oxidization of the Co NPs into Co3 O4 by O species(OH intermediate, CO_2, H2 O) during the reforming reaction,which accelerates the formation of coke that blocked the active metal, thus led to catalyst deactivation.展开更多
This paper gives an overview of the current understanding of the observations of black carbon(BC) in snow and ice, and the estimates of BC deposition and its radiative forcing over the Arctic. Both of the observations...This paper gives an overview of the current understanding of the observations of black carbon(BC) in snow and ice, and the estimates of BC deposition and its radiative forcing over the Arctic. Both of the observations and model results show that, in spring, the average BC concentration and the resulting radiative forcing in Russian Arctic > Canadian and Alaskan Arctic > Arctic Ocean and Greenland. The observed BC concentration presented a signi?cant decrease trend from the Arctic coastal regions to the center of Arctic Ocean. In summer, due to the combined effects of BC accumulation and enlarged snow grain size, the averaged radiative forcing per unit area over the Arctic Ocean is larger than that over each sector of the Arctic in spring. However, because summer sea ice is always covered by a large fraction of melt ponds, the role of BC in sea ice albedo evolution during this period is secondary. Multi-model mean results indicate that the annual mean radiative forcing from all sources of BC in snow and ice over the Arctic was ~0.17 W m^(-2). Wet deposition is the dominant removal mechanism in the Arctic, which accounts for more than 90% of the total deposition. In the last part, we discuss the uncertainties in present modeling studies, and suggest potential approaches to reduce the uncertainties.展开更多
Nitrogen doped carbons are an important family of materials with ideal activity for oxygen reduction reaction(ORR). It is always interesting to search functional carbons with high heteroatom contents and desirable str...Nitrogen doped carbons are an important family of materials with ideal activity for oxygen reduction reaction(ORR). It is always interesting to search functional carbons with high heteroatom contents and desirable structure for ORR. Within this study, the surface modification of carbon nanotubes(CNTs) via hydrothermal carbonization(HTC) technique in the presence of glucose and urea was reported, where the surface of CNTs is successfully coated by nitrogen containing hydrothermal carbon layers. The resulting composite combines both advantages of the outstanding electrical conductivity of CNTs and the effective ORR active sites provided by doped nitrogen in the HTC carbon layers. By controlling the ratio of glucose and urea, the nitrogen contents coated on the surface of CNTs can reach up to 1.7 wt%. The resulting materials show outstanding electrochemical activity towards ORR in alkaline electrolyte, making it one of the valuable metal-free electrode materials and a competent alternative to the state-of-the-art Pt/C catalyst.展开更多
The effect of temperature and hydrogen addition on undesired carbonaceous deposit formation during methane coupling was studied in DBD-plasma catalytic-wall reactors with Pd/Al2 O3, using electrical power to drive the...The effect of temperature and hydrogen addition on undesired carbonaceous deposit formation during methane coupling was studied in DBD-plasma catalytic-wall reactors with Pd/Al2 O3, using electrical power to drive the reaction.Experiments with thin catalyst layers allowed comparison of the performance of empty reactors and catalytic wall reactors without significantly influencing the plasma properties.The product distribution varies strongly in the temperature window between 25 and 200℃Minimal formation of deposits is found at an optimal temperature around 75℃ in the catalytic-wall reactors.The selectivity to deposits was c.a.10% with only 9 mg of catalyst loading instead of 45% in the blank reactor,while decreasing methane conversion only mildly.Co-feeding H2 to an empty reactor causes a similar decrease in selectivity to deposits,but in this case methane conversion also decreased significantly.Suppression of deposits formation in the catalytic-wall reactor at 75℃ is due to catalytic hydrogenation of mainly acetylene to ethylene.In the empty reactor,H2 co-feed decreases conversion but does not change the product distribution.The catalytic-wall reactors can be regenerated with H2-plasma at room temperature,which produces more added-value hydrocarbons.展开更多
The catalytic performance of methane partial oxidation was investigated on Pd/CeO2-ZrO2 and Pd/α-Al2O3 catalysts.The catalysts were characterized by XRD,Raman spectra,and TG-DTA techniques.The results show that CeO2-...The catalytic performance of methane partial oxidation was investigated on Pd/CeO2-ZrO2 and Pd/α-Al2O3 catalysts.The catalysts were characterized by XRD,Raman spectra,and TG-DTA techniques.The results show that CeO2-ZrO2 support is more advantageous for the catalytic activity and stability of catalysts compared to α-Al2O3.TG-DTA and Raman spectra results indicated that carbon deposited on the catalysts was in the form of graphite,which is the main reason for the deactivation of catalysts after a 24-hour reaction.Moreover,CeO2-ZrO2 had positive effect on inhibiting carbon deposition.展开更多
In this paper, the properties of carbon deposited on hexaaluminate LaNiAl11O19 catalyst were characterized by X-ray photoelectron spectroscopy (XPS), and in the meantime, the amount of carbon deposited on the catalyst...In this paper, the properties of carbon deposited on hexaaluminate LaNiAl11O19 catalyst were characterized by X-ray photoelectron spectroscopy (XPS), and in the meantime, the amount of carbon deposited on the catalyst, after both CH4 decomposition and CO2 reforming of CH4, was determined by means of thermogravimetric analysis (TGA), respectively. The rates of carbon deposited on the catalyst were also investigated and the apparent kinetic equation of CO2 reforming of CH4:carbon and the pressure ratio of CH4 and CO2.展开更多
Deposition of organic carbon forms the final net effect of the ocean carbon sink at a certain time scale. Organic carbon deposition on the Arctic shelves plays a particularly important role in the global carbon cycle ...Deposition of organic carbon forms the final net effect of the ocean carbon sink at a certain time scale. Organic carbon deposition on the Arctic shelves plays a particularly important role in the global carbon cycle because of the broad shelf area and rich nutrient concen tration. To determine the organic carbon deposition flux at the northern margin of the Chukchi Sea shelf, the 210Pb dating method was used to analyze the age and deposition rate of sediment samples from station R17 of the third Chinese National Arctic Research Expedition. The results showed that the deposition rate was 0.6 mm·a-1, the apparent deposition mass flux was 0.72 kg·m-2·a-1, and the organic carbon deposition flux was 517 mmol C·m-2·a-1,.It was estimated that at least 16% of the export organic carbon flux out of the euphotic zone was transferred and chronically buried into the sediment, a value which was much higher than the average ratio (-10%) for lowto mid-latitude regions, indicating a highly effective carbon sink at the northern margin of the Chukchi Sea shelf. With the decrease of sea ice coverage caused by wanning in the Arctic Ocean, it could be inferred that the Arctic shelves will play an increasingly important role in the global carbon cycle.展开更多
Carbon deposition on nickel powders in methane involves three stages in different reaction temperature ranges. Temperature programing oxidation test and Raman spectrum results indicated the formation of complex and or...Carbon deposition on nickel powders in methane involves three stages in different reaction temperature ranges. Temperature programing oxidation test and Raman spectrum results indicated the formation of complex and ordered carbon structures at high deposition temperatures. The values of I(D)/I(G) of the deposited carbon reached 1.86, 1.30, and 1.22 in the first, second, and third stages, respectively. The structure of carbon in the second stage was similar to that in the third stage. Carbon deposited in the first stage rarely contained homogeneous pyrolytic deposit layers. A kinetic model was developed to analyze the carbon deposition behavior in the first stage. The rate-determining step of the first stage is supposed to be interfacial reaction. Based on the investigation of carbon deposition kinetics on nickel powders from different resources, carbon deposition rate is suggested to have a linear relation with the square of specific surface area of nickel particles.展开更多
Ni/CeO_(2) catalysts(nCeO_(2):n_(Ni)=0,1,4,7,10)supported on SiC porous ce ramics for ethanol steam reforming(ESR)were investigated with respect to hydrogen production performance and growth of carbon deposition.The o...Ni/CeO_(2) catalysts(nCeO_(2):n_(Ni)=0,1,4,7,10)supported on SiC porous ce ramics for ethanol steam reforming(ESR)were investigated with respect to hydrogen production performance and growth of carbon deposition.The oxygen released from CeO_(2) enables the oxidation of CH_(x) species to serve as carbon precursors,thus providing Ni/CeO_(2) catalysts with stronger resistance to carbon deposition compared with Ni catalysts.The Ni/CeO_(2) catalysts prepared by inverse microemulsion and impregnation methods exhibit regular semicircular spherical shape on SiC porous ceramics.Under 500℃for 25 h of ESR reaction,the ethanol conversion rate over Ni/CeO_(2) catalysts(n_(CeO_(2)):n_(Ni)=7)is sustained up to 100%and H_(2) selectivity is essentially kept at 74%.The by-product selectivity declines stepwise with increasing content of CeO_(2),which is attributed to the adsorption and oxidation of CO and of CH_(x) species as CH_4 precursor from CeO_(2).The scanning electron microscopy(SEM)and transform electron microscopy(TEM)results reveal that further loading of CeO_(2) on the surface of Ni catalysts can alleviate both migration and sintering of Ni particles.Furthermore,carbon deposition on Ni/CeO_(2) catalysts preferentially outgrow filamentous rather than amorphous carbon,with a tendency for the latter to be more deactivated.展开更多
As an important component of carbonaceous matters,dissolved organic carbon(DOC)can absorb and scatter the solar radiation at ultraviolet and blue wavelengths.The wet deposition process has great impact on the con-cent...As an important component of carbonaceous matters,dissolved organic carbon(DOC)can absorb and scatter the solar radiation at ultraviolet and blue wavelengths.The wet deposition process has great impact on the con-centration and light absorption ability of precipitation DOC,affecting the climatic effect caused by DOC in the atmosphere.In this study,light absorption and fluorescence characteristics of precipitation DOC was investigated in the central Tibetan Plateau(TP).The results showed that the mean DOC concentration and mass absorption cross-section measured at 365 nm(MAC_(365)) in Tanggula(TGL)station were 0.59±0.42 mg/L and 0.37±0.19 m^(2)/g,respectively,while both values showed much higher volatilities than those of aerosols.DOC concentrations had significant negative correlation with the precipitation amount,while MAC_(365) values increase with the precipitation amount in TGL station.Therefore,DOC with high light-absorbing ability was preferred to be retained in the atmosphere during wet deposition.In this study,precipitation DOC contained three fluorescent components(one humic-like component and two tyrosine-like components)mainly from local biomass burning sources.DOC concentration showed a negative relationship with MAC_(365) value in TGL station.The wet deposition of DOC with low light-absorbing ability can reduce the strong negative radiative forcing caused by secondary organic aerosol due to high proportion of DOC in secondary organic carbon.Similar phenomenon was also found in Nam Co,Lulang and Everest stations of previous study,which may have a potential impact on radiative forcing in the atmosphere of TP.展开更多
The metal-organic framework(MOF)derived Ni–Co–C–N composite alloys(NiCCZ)were“embedded”inside the carbon cloth(CC)strands as opposed to the popular idea of growing them upward to realize ultrastable energy storag...The metal-organic framework(MOF)derived Ni–Co–C–N composite alloys(NiCCZ)were“embedded”inside the carbon cloth(CC)strands as opposed to the popular idea of growing them upward to realize ultrastable energy storage and conversion application.The NiCCZ was then oxygen functionalized,facilitating the next step of stoichiometric sulfur anion diffusion during hydrothermal sulfurization,generating a flower-like metal hydroxysulfide structure(NiCCZOS)with strong partial implantation inside CC.Thus obtained NiCCZOS shows an excellent capacity when tested as a supercapacitor electrode in a three-electrode configuration.Moreover,when paired with the biomass-derived nitrogen-rich activated carbon,the asymmetric supercapacitor device shows almost 100%capacity retention even after 45,000 charge–discharge cycles with remarkable energy density(59.4 Wh kg^(-1)/263.8μWh cm^(–2))owing to a uniquely designed cathode.Furthermore,the same electrode performed as an excellent bifunctional water-splitting electrocatalyst with an overpotential of 271 mV for oxygen evolution reaction(OER)and 168.4 mV for hydrogen evolution reaction(HER)at 10 mA cm−2 current density along with 30 h of unhinged chronopotentiometric stability performance for both HER and OER.Hence,a unique metal chalcogenide composite electrode/substrate configuration has been proposed as a highly stable electrode material for flexible energy storage and conversion applications.展开更多
Tin-based materials are very attractive anodes because of their high theoretical capacity,but their rapid capacity fading from volume expansions limits their practical applications during alloying and dealloying proce...Tin-based materials are very attractive anodes because of their high theoretical capacity,but their rapid capacity fading from volume expansions limits their practical applications during alloying and dealloying processes.Herein,the improved binder-free tin-copper intermetallic/carbon nanotubes(Cu6Sn5/CNTs)alloy thin-film electrodes are directly fabricated through efficient in situ electrodeposition from the leaching solution of treated waste-printed circuit boards(WPCBs).The characterization results show that the easily agglomerated Cu6Sn5 alloy nanoparticles are uniformly dispersed across the three-dimensional network when the CNTs concentration in the electrodeposition solution is maintained at 0.2 g·L−1.Moreover,the optimal Cu6Sn5/CNTs-0.2 alloy thin-film electrode can not only provide a decent discharge specific capacity of 458.35 mAh·g^(−1)after 50 cycles at 100 mA·g^(−1)within capacity retention of 82.58%but also deliver a relatively high reversible specific capacity of 518.24,445.52,418.18,345.33,and 278.05 mAh·g^(−1)at step-increased current density of 0.1,0.2,0.5,1.0,and 2.0 A·g^(−1),respectively.Therefore,the preparation process of the Cu6Sn5/CNTs-0.2 alloy thin-film electrode with improved electrochemical performance may provide a cost-effective strategy for the resource utilization of WPCBs to fabricate anode materials for lithium-ion batteries.展开更多
Porous carbon sheets have wide application prospects in many fields,especially in energy storage of supercapacitor due to the features combining both 2D structure and porous architectures.Herein,a self-deposition appr...Porous carbon sheets have wide application prospects in many fields,especially in energy storage of supercapacitor due to the features combining both 2D structure and porous architectures.Herein,a self-deposition approach is proposed to obtain N-doped mesoporous carbon nanosheets (N-MCNs),using 3-aminophenol (3-AF) as precursor and Mg(OH)_(2) sheet as hard template.This process realizes the direct carbon formation using 3-AF monomer as carbon precursor under the catalysis of hard template avoiding the polymerization and utilization of solvent.The mass ratio of 3-AF to Mg(OH)_(2) plays an important role in determining the pore structures and the resulting capacitance behavior.The results show that N-MCNs with a mass ratio of 3-AF and Mg(OH)_(2) of 1:1 have good electrochemical behavior for supercapacitors.This N-MCNs based electrode exhibits a high capacitance of 240 F·g^(-1)at 1 A·g^(-1),good rate performance(75.4%retention ratio at 20 A·g^(-1)),and high cycling stability with 98.3% initial capacitance retained after 10000 cycles.Symmetric supercapacitors on N-MCNs achieve energy density of 18.2 W·h·kg^(-1) and power density of 0.4 kW·kg^(-1) operated within a wide potential range of 0–1.6 V in 1.0 mol·L^(-1) Na_(2)SO_(4) solution,exhibiting its potential for electrode materials with high performance.展开更多
The strength development law of γ-type dicalcium silicate (γ-C_(2)S) under different carbonation processes was investigated,and the carbonation mechanism of γ-C_(2)S under the action of NH_(4)HCO_(3) was clarified ...The strength development law of γ-type dicalcium silicate (γ-C_(2)S) under different carbonation processes was investigated,and the carbonation mechanism of γ-C_(2)S under the action of NH_(4)HCO_(3) was clarified by using a wide range of test methods,including XRD and SEM.A method of saturated NH_(4)HCO_(3) solution as a curing agent was identified to improve the carbonation efficiency and enhance the carbonation degree of γ-C_(2)S,and then a high-strength carbonated specimen was obtained.Microhardness analysis and SEM morphology analysis were conducted on the carbonised specimens obtained under atmospheric pressure carbonisation conditions using the curing agent.It was found that γ-C_(2)S could perform carbonisation well under atmospheric pressure,which promoted the carbonisation efficiency and decreased the carbonisation cost simultaneously.Therefore,a new carbonisation process solution was proposed for the rapid carbonisation of γ-C_(2)S.展开更多
基金partly supported by the New Energy and Industrial Technology Development Organization(NEDO)by the Japan Society for the Promotion of Science KAKENHI(21K14090)+3 种基金the National Key R&D Program of China(2019YFE0122000)the Scientific Research Foundation of Graduate School of Southeast University(YBPY2106)the China Scholarship Councilby the Advanced Research Infrastructure for Materials and Nanotechnology in Japan(ARIM Japan)sponsored by the Ministry of Education,Culture,Sport,Science and Technology(MEXT),Japan。
文摘In the present study,two Ni/YSZ anodes with different volume ratios of Ni and YSZ,30:70 and 45:55 vol%,are operated in dry methane under open circuit and polarized conditions.Three-dimensional(3D)Ni/YSZ microstructures after carbon deposition are reconstructed by the focused ion beam-scanning electron microscopy(FIB-SEM)with the help of machine learning segmentation.From the reconstructed mircostructures,volume fraction,connectivity,three phase boundary(TPB)density,and tortuosity are quantified.In addition,local carbon microstructures are quantitatively reconstructed,and the effect of polarization on carbon morphology is investigated.It is demonstrated that Ni surface in the vicinity of active TPB near the electrolyte is free from carbon formation,while remaining Ni surface at some distances from TPB exhibits severe carbon deposition.In average,total amount of carbon deposition is larger near the electrolyte.These observations imply complex interplay between the electrochemical steam generation and methane cracking on Ni surface which take place very locally near the active TPB.
基金supported by the National Natural Science Foundation of China (51974312, 51974308)the National Key Research & Development Program of China (2019YFE0100100)。
文摘In order to further improve the catalytic performance of zeolite catalyst for methanol to aromatics(MTA)technology, the double-tier SAPO-34/ZSM-5/quartz composite zeolite films were successfully synthesized via hydrothermal crystallization. The Si/Al ratio of SAPO-34 film was used as the only variable to study this material. The composite zeolite material with 0.6Si/Al ratio of SAPO-34 has the largest mesoporous specific surface area and the most suitable acid distribution. The catalytic performance for the MTA process showed that 0.6-SAPO-34/ZSM-5/quartz film has as high as 50.3% benzene-toluenexylene selectivity and 670 min lifetime. The MTA reaction is carried out through the path we designed to effectively avoid the hydrocarbon pool circulation of ZSM-5 zeolite, so as to improve the aromatics selectivity and inhibit the occurrence of deep side reactions to a great extent. The coke deposition behavior was monitored by thermogravimetric analysis and gas chromatograph/mass spectrometer, it is found that with the increase of Si/Al ratio, the active intermediates changed from low-substituted methylbenzene to high-substituted methylbenzene, which led to the rapid deactivation of the catalyst. This work provides a possibility to employ the synergy effect of composite zeolite film synthesizing anti-carbon deposition catalyst in MTA reaction.
基金financial support from the Hongliu Outstanding Young Talents Funding Program of Lanzhou University of Technology(02/062214)。
文摘Toluene methylation with methanol to produce para-xylene has been extensively and intensively studied.However,the methanol-to-hydrocarbons(MTH)side reaction in this reaction is difficult to be inhibited,which will cause a mass of carbon deposition and cover the catalyst surface,resulting in catalyst deactivation.Here,a dual-functional Ru@HZSM-5 catalyst with high para-selectivity and low carbon deposition was prepared by encapsulating Ru metal with HZSM-5.According to catalytic performance studies,the Ru@HZSM-5 catalyst produced xylene selectivity of 98%and para-xylene selectivity of 96%.Meanwhile,we find that carbon precursors(e.g.ethylene)were very little when Ru catalyst was used,but the results of HZSM-5 catalyst were completely opposite.Ru@HZSM-5 catalyst achieves a lower carbon deposition rate of only 6%of HZSM-5.The main possible reason for this is that the initial C-C bond between methanol and the olefin is difficult to form.
基金the National Natural Science Foundation of China(No.41976053)and the Shandong Province Funds for Excellent Young Scholars(No.ZR2021YQ26)。
文摘The East China Sea(ECS),which is located in the transitional zone between land and ocean,is the main site for the burial of sedimentary organic carbon.Despite good constraints of the modern source to the sinking process of organic carbon,its fate in response to changes in climate and sea level since the last deglaciation remains poorly understood.We aim to fill this gap by presenting a high-resolution sedimentary record of core EC2005 to derive a better understanding of the evolution of the depositional environment and its control on the organic deposition since 17.3 kyr.Our results suggest that sedimentary organic carbon was deposited in a terrestrial environment before the seawater reached the study area around 13.1 kyr.This significant transition from a terrestrial environment to a marine environment is reflected by the decrease in TOC/TN and TOC/TS ratios,which is attributed to deglacial sea level rise.The sea level continued to rise until it reached its highstand at approximately 7.3 kyr when the mud depocenter was developed.Our results further indicate that the deposition of the sedimentary organic carbon could respond quickly to abrupt cold events,including the Heinrich stadial 1 and the Younger Dryas during the last deglaciation,as well as‘Bond events'during the Holocene.We propose that the rapid response of the organic deposition to those cold events in the northern hemisphere is linked to the East Asian winter monsoon.These new findings demonstrate that organic carbon deposition and burial on the inner shelf could effectively document sea level and climatic changes.
基金Supported by the National Natural Science Foundation of China(21736010,U1462128,91334108)the State Key Development Program for Basic Research of China(2015CB251402)
文摘The deactivation mechanism of Co/MgO catalyst for the reforming of methane with carbon dioxide was investigated. The conversion of CH4 displayed a significant decrease in the initial stage caused by carbon deposition.There were two types of cokes, carbon nanotubes(CNTs) and carbon nano-onions(CNOs). The number of the CNO layers that coated on the surface of Co nanoparticles(NPs) increased rapidly in the initial reforming time,which was responsible for the deactivation of the Co/MgO catalyst. The deposition of CNOs was attributed to the oxidation of Co NPs. Therefore, the deactivation of the Co/MgO catalyst was originated from the first oxidization of the Co NPs into Co3 O4 by O species(OH intermediate, CO_2, H2 O) during the reforming reaction,which accelerates the formation of coke that blocked the active metal, thus led to catalyst deactivation.
基金funded by the Ministry of Science and Technology of China (2013CBA01804)the National Nature Science Foundation of China (41425003, Y51101P1A1)+1 种基金the key project of CAMS: Research on the key processes of Cryospheric rapid changes (KJZD-EW-G03-04)the Opening Founding of State Key Laboratory of Cryospheric Sciences (SKLCS-OP-2016-03)
文摘This paper gives an overview of the current understanding of the observations of black carbon(BC) in snow and ice, and the estimates of BC deposition and its radiative forcing over the Arctic. Both of the observations and model results show that, in spring, the average BC concentration and the resulting radiative forcing in Russian Arctic > Canadian and Alaskan Arctic > Arctic Ocean and Greenland. The observed BC concentration presented a signi?cant decrease trend from the Arctic coastal regions to the center of Arctic Ocean. In summer, due to the combined effects of BC accumulation and enlarged snow grain size, the averaged radiative forcing per unit area over the Arctic Ocean is larger than that over each sector of the Arctic in spring. However, because summer sea ice is always covered by a large fraction of melt ponds, the role of BC in sea ice albedo evolution during this period is secondary. Multi-model mean results indicate that the annual mean radiative forcing from all sources of BC in snow and ice over the Arctic was ~0.17 W m^(-2). Wet deposition is the dominant removal mechanism in the Arctic, which accounts for more than 90% of the total deposition. In the last part, we discuss the uncertainties in present modeling studies, and suggest potential approaches to reduce the uncertainties.
基金The Award Program for Fujian Minjiang Scholar Professorship is acknowledged for financial supportfinancial support from the National Natural Science Foundation of China(NSFC Grant number 21571035)
文摘Nitrogen doped carbons are an important family of materials with ideal activity for oxygen reduction reaction(ORR). It is always interesting to search functional carbons with high heteroatom contents and desirable structure for ORR. Within this study, the surface modification of carbon nanotubes(CNTs) via hydrothermal carbonization(HTC) technique in the presence of glucose and urea was reported, where the surface of CNTs is successfully coated by nitrogen containing hydrothermal carbon layers. The resulting composite combines both advantages of the outstanding electrical conductivity of CNTs and the effective ORR active sites provided by doped nitrogen in the HTC carbon layers. By controlling the ratio of glucose and urea, the nitrogen contents coated on the surface of CNTs can reach up to 1.7 wt%. The resulting materials show outstanding electrochemical activity towards ORR in alkaline electrolyte, making it one of the valuable metal-free electrode materials and a competent alternative to the state-of-the-art Pt/C catalyst.
基金supported by the Innovation Fund for Chemistry of NWO,grant number 731.014.303by SASOL。
文摘The effect of temperature and hydrogen addition on undesired carbonaceous deposit formation during methane coupling was studied in DBD-plasma catalytic-wall reactors with Pd/Al2 O3, using electrical power to drive the reaction.Experiments with thin catalyst layers allowed comparison of the performance of empty reactors and catalytic wall reactors without significantly influencing the plasma properties.The product distribution varies strongly in the temperature window between 25 and 200℃Minimal formation of deposits is found at an optimal temperature around 75℃ in the catalytic-wall reactors.The selectivity to deposits was c.a.10% with only 9 mg of catalyst loading instead of 45% in the blank reactor,while decreasing methane conversion only mildly.Co-feeding H2 to an empty reactor causes a similar decrease in selectivity to deposits,but in this case methane conversion also decreased significantly.Suppression of deposits formation in the catalytic-wall reactor at 75℃ is due to catalytic hydrogenation of mainly acetylene to ethylene.In the empty reactor,H2 co-feed decreases conversion but does not change the product distribution.The catalytic-wall reactors can be regenerated with H2-plasma at room temperature,which produces more added-value hydrocarbons.
基金Project supported by the National‘973’Project(2004CB719503)Petro China(W050509-01-05)
文摘The catalytic performance of methane partial oxidation was investigated on Pd/CeO2-ZrO2 and Pd/α-Al2O3 catalysts.The catalysts were characterized by XRD,Raman spectra,and TG-DTA techniques.The results show that CeO2-ZrO2 support is more advantageous for the catalytic activity and stability of catalysts compared to α-Al2O3.TG-DTA and Raman spectra results indicated that carbon deposited on the catalysts was in the form of graphite,which is the main reason for the deactivation of catalysts after a 24-hour reaction.Moreover,CeO2-ZrO2 had positive effect on inhibiting carbon deposition.
文摘In this paper, the properties of carbon deposited on hexaaluminate LaNiAl11O19 catalyst were characterized by X-ray photoelectron spectroscopy (XPS), and in the meantime, the amount of carbon deposited on the catalyst, after both CH4 decomposition and CO2 reforming of CH4, was determined by means of thermogravimetric analysis (TGA), respectively. The rates of carbon deposited on the catalyst were also investigated and the apparent kinetic equation of CO2 reforming of CH4:carbon and the pressure ratio of CH4 and CO2.
基金supported by the Scientific Research Foundation of the Third Institute of Oceanography, SOA (Grant nos. 2011024 and 2011025)the Marine Science Youth Fund of SOA (Grant no. 2012107)
文摘Deposition of organic carbon forms the final net effect of the ocean carbon sink at a certain time scale. Organic carbon deposition on the Arctic shelves plays a particularly important role in the global carbon cycle because of the broad shelf area and rich nutrient concen tration. To determine the organic carbon deposition flux at the northern margin of the Chukchi Sea shelf, the 210Pb dating method was used to analyze the age and deposition rate of sediment samples from station R17 of the third Chinese National Arctic Research Expedition. The results showed that the deposition rate was 0.6 mm·a-1, the apparent deposition mass flux was 0.72 kg·m-2·a-1, and the organic carbon deposition flux was 517 mmol C·m-2·a-1,.It was estimated that at least 16% of the export organic carbon flux out of the euphotic zone was transferred and chronically buried into the sediment, a value which was much higher than the average ratio (-10%) for lowto mid-latitude regions, indicating a highly effective carbon sink at the northern margin of the Chukchi Sea shelf. With the decrease of sea ice coverage caused by wanning in the Arctic Ocean, it could be inferred that the Arctic shelves will play an increasingly important role in the global carbon cycle.
基金financially supported by the National Program on Key Basic Research Project of China (973 Program, No. 2012CB215405)the National Natural Science Foundation of China (No. 51174022)
文摘Carbon deposition on nickel powders in methane involves three stages in different reaction temperature ranges. Temperature programing oxidation test and Raman spectrum results indicated the formation of complex and ordered carbon structures at high deposition temperatures. The values of I(D)/I(G) of the deposited carbon reached 1.86, 1.30, and 1.22 in the first, second, and third stages, respectively. The structure of carbon in the second stage was similar to that in the third stage. Carbon deposited in the first stage rarely contained homogeneous pyrolytic deposit layers. A kinetic model was developed to analyze the carbon deposition behavior in the first stage. The rate-determining step of the first stage is supposed to be interfacial reaction. Based on the investigation of carbon deposition kinetics on nickel powders from different resources, carbon deposition rate is suggested to have a linear relation with the square of specific surface area of nickel particles.
基金This work was supported by the National Basic Research Program of China （No.2012CB215405）, the National Natural Science Foundation of China （No.11374272）, and the Specialized Research Fund for the Doctoral Program of Higher Education （No.20123402110064）.
基金Project supported by the Natural Science Foundation of Hunan Province,China (2022JJ30133)。
文摘Ni/CeO_(2) catalysts(nCeO_(2):n_(Ni)=0,1,4,7,10)supported on SiC porous ce ramics for ethanol steam reforming(ESR)were investigated with respect to hydrogen production performance and growth of carbon deposition.The oxygen released from CeO_(2) enables the oxidation of CH_(x) species to serve as carbon precursors,thus providing Ni/CeO_(2) catalysts with stronger resistance to carbon deposition compared with Ni catalysts.The Ni/CeO_(2) catalysts prepared by inverse microemulsion and impregnation methods exhibit regular semicircular spherical shape on SiC porous ceramics.Under 500℃for 25 h of ESR reaction,the ethanol conversion rate over Ni/CeO_(2) catalysts(n_(CeO_(2)):n_(Ni)=7)is sustained up to 100%and H_(2) selectivity is essentially kept at 74%.The by-product selectivity declines stepwise with increasing content of CeO_(2),which is attributed to the adsorption and oxidation of CO and of CH_(x) species as CH_4 precursor from CeO_(2).The scanning electron microscopy(SEM)and transform electron microscopy(TEM)results reveal that further loading of CeO_(2) on the surface of Ni catalysts can alleviate both migration and sintering of Ni particles.Furthermore,carbon deposition on Ni/CeO_(2) catalysts preferentially outgrow filamentous rather than amorphous carbon,with a tendency for the latter to be more deactivated.
基金supported by the National Natural Science Foundation of China(42201158,42177366)the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(2019QZKK0605)+1 种基金Natural Science Foundation of Gansu Province,China(23JRRA656)the State Key Laboratory of Cryospheric Science(SKLCS-ZZ-2022).
文摘As an important component of carbonaceous matters,dissolved organic carbon(DOC)can absorb and scatter the solar radiation at ultraviolet and blue wavelengths.The wet deposition process has great impact on the con-centration and light absorption ability of precipitation DOC,affecting the climatic effect caused by DOC in the atmosphere.In this study,light absorption and fluorescence characteristics of precipitation DOC was investigated in the central Tibetan Plateau(TP).The results showed that the mean DOC concentration and mass absorption cross-section measured at 365 nm(MAC_(365)) in Tanggula(TGL)station were 0.59±0.42 mg/L and 0.37±0.19 m^(2)/g,respectively,while both values showed much higher volatilities than those of aerosols.DOC concentrations had significant negative correlation with the precipitation amount,while MAC_(365) values increase with the precipitation amount in TGL station.Therefore,DOC with high light-absorbing ability was preferred to be retained in the atmosphere during wet deposition.In this study,precipitation DOC contained three fluorescent components(one humic-like component and two tyrosine-like components)mainly from local biomass burning sources.DOC concentration showed a negative relationship with MAC_(365) value in TGL station.The wet deposition of DOC with low light-absorbing ability can reduce the strong negative radiative forcing caused by secondary organic aerosol due to high proportion of DOC in secondary organic carbon.Similar phenomenon was also found in Nam Co,Lulang and Everest stations of previous study,which may have a potential impact on radiative forcing in the atmosphere of TP.
基金supported by the Basic Science Research Program through the National Research Foundation of Korea(NRF)grant funded by the Korean government(MSIT)(2021R1A4A2000934).
文摘The metal-organic framework(MOF)derived Ni–Co–C–N composite alloys(NiCCZ)were“embedded”inside the carbon cloth(CC)strands as opposed to the popular idea of growing them upward to realize ultrastable energy storage and conversion application.The NiCCZ was then oxygen functionalized,facilitating the next step of stoichiometric sulfur anion diffusion during hydrothermal sulfurization,generating a flower-like metal hydroxysulfide structure(NiCCZOS)with strong partial implantation inside CC.Thus obtained NiCCZOS shows an excellent capacity when tested as a supercapacitor electrode in a three-electrode configuration.Moreover,when paired with the biomass-derived nitrogen-rich activated carbon,the asymmetric supercapacitor device shows almost 100%capacity retention even after 45,000 charge–discharge cycles with remarkable energy density(59.4 Wh kg^(-1)/263.8μWh cm^(–2))owing to a uniquely designed cathode.Furthermore,the same electrode performed as an excellent bifunctional water-splitting electrocatalyst with an overpotential of 271 mV for oxygen evolution reaction(OER)and 168.4 mV for hydrogen evolution reaction(HER)at 10 mA cm−2 current density along with 30 h of unhinged chronopotentiometric stability performance for both HER and OER.Hence,a unique metal chalcogenide composite electrode/substrate configuration has been proposed as a highly stable electrode material for flexible energy storage and conversion applications.
基金supported by the National Natural Science Foundation of China(Nos.52274292 and 51874046)the Outstanding Youth Foundation of Hubei Province,China(No.2020CFA090)the Young Topnotch Talent Cultivation Program of Hubei Province,China.
文摘Tin-based materials are very attractive anodes because of their high theoretical capacity,but their rapid capacity fading from volume expansions limits their practical applications during alloying and dealloying processes.Herein,the improved binder-free tin-copper intermetallic/carbon nanotubes(Cu6Sn5/CNTs)alloy thin-film electrodes are directly fabricated through efficient in situ electrodeposition from the leaching solution of treated waste-printed circuit boards(WPCBs).The characterization results show that the easily agglomerated Cu6Sn5 alloy nanoparticles are uniformly dispersed across the three-dimensional network when the CNTs concentration in the electrodeposition solution is maintained at 0.2 g·L−1.Moreover,the optimal Cu6Sn5/CNTs-0.2 alloy thin-film electrode can not only provide a decent discharge specific capacity of 458.35 mAh·g^(−1)after 50 cycles at 100 mA·g^(−1)within capacity retention of 82.58%but also deliver a relatively high reversible specific capacity of 518.24,445.52,418.18,345.33,and 278.05 mAh·g^(−1)at step-increased current density of 0.1,0.2,0.5,1.0,and 2.0 A·g^(−1),respectively.Therefore,the preparation process of the Cu6Sn5/CNTs-0.2 alloy thin-film electrode with improved electrochemical performance may provide a cost-effective strategy for the resource utilization of WPCBs to fabricate anode materials for lithium-ion batteries.
基金the Natural Science Foundation of Hebei (B02020208088)S&T Program of Hebei (20544401D, 20314401D, 206Z4406G, 21314402D, B2021208074, 21344601D)Tianjin Science and Technology Project (19YFSLQY00070)。
文摘Porous carbon sheets have wide application prospects in many fields,especially in energy storage of supercapacitor due to the features combining both 2D structure and porous architectures.Herein,a self-deposition approach is proposed to obtain N-doped mesoporous carbon nanosheets (N-MCNs),using 3-aminophenol (3-AF) as precursor and Mg(OH)_(2) sheet as hard template.This process realizes the direct carbon formation using 3-AF monomer as carbon precursor under the catalysis of hard template avoiding the polymerization and utilization of solvent.The mass ratio of 3-AF to Mg(OH)_(2) plays an important role in determining the pore structures and the resulting capacitance behavior.The results show that N-MCNs with a mass ratio of 3-AF and Mg(OH)_(2) of 1:1 have good electrochemical behavior for supercapacitors.This N-MCNs based electrode exhibits a high capacitance of 240 F·g^(-1)at 1 A·g^(-1),good rate performance(75.4%retention ratio at 20 A·g^(-1)),and high cycling stability with 98.3% initial capacitance retained after 10000 cycles.Symmetric supercapacitors on N-MCNs achieve energy density of 18.2 W·h·kg^(-1) and power density of 0.4 kW·kg^(-1) operated within a wide potential range of 0–1.6 V in 1.0 mol·L^(-1) Na_(2)SO_(4) solution,exhibiting its potential for electrode materials with high performance.
基金Funded by Hubei Technology Innovation Key Program (No.2018AAA004)。
文摘The strength development law of γ-type dicalcium silicate (γ-C_(2)S) under different carbonation processes was investigated,and the carbonation mechanism of γ-C_(2)S under the action of NH_(4)HCO_(3) was clarified by using a wide range of test methods,including XRD and SEM.A method of saturated NH_(4)HCO_(3) solution as a curing agent was identified to improve the carbonation efficiency and enhance the carbonation degree of γ-C_(2)S,and then a high-strength carbonated specimen was obtained.Microhardness analysis and SEM morphology analysis were conducted on the carbonised specimens obtained under atmospheric pressure carbonisation conditions using the curing agent.It was found that γ-C_(2)S could perform carbonisation well under atmospheric pressure,which promoted the carbonisation efficiency and decreased the carbonisation cost simultaneously.Therefore,a new carbonisation process solution was proposed for the rapid carbonisation of γ-C_(2)S.
