In the past decade,dry reforming of methane(DRM)has garnered increasing interest as it converts CH_(4)and CO_(2),two typical greenhouse gases,into synthesis gas(H_(2)and CO)for the production of high-value-added chemi...In the past decade,dry reforming of methane(DRM)has garnered increasing interest as it converts CH_(4)and CO_(2),two typical greenhouse gases,into synthesis gas(H_(2)and CO)for the production of high-value-added chemicals and fuels.Nickel-based DRM catalysts,renowned for their high activity and low cost,however,encounter challenges such as severe deactivation from sintering and carbon deposition.Herein,a surrounded NiO@NiAlO precursor derived from Ni(OH)_(2)nanosheets was modified at both the core and shell interfaces with MgO via wet impregnation.The obtained 0.8MgO^(WI)/Ni@NiAlO catalyst achieved a high CH_(4)reaction rate of~177 mmol gNi^(-1)min^(-1)and remained stable for 50 h at 600℃without coke formation.In sharp contrast,other Mg-doped catalysts(MgO modified the core or shell interfaces)and the catalyst without Mg-doping deactivated within 10 h due to coking or Ni particle sintering.The Ni/MgNiO_(2)interfaces and abundant oxygen vacancies(O_(v))generated by Mg-doping contributed to the outstanding resistance to sintering&coking as well as the superior activity and stability of the 0.8MgO^(WI)/Ni@NiAlO catalyst.In-situ investigation further unveiled the reaction mechanism:the activation of CO_(2)via adsorption on O_(v)generates active oxygen species(O^(*)),which reacts with CH_(x)^(*)intermediates formed by the dissociation of CH_(4)on Ni sites,yielding CO and H_(2).This work not only fabricates coke-free and high-stability Ni-based DRM catalysts via interface engineering but also provides insights and a new strategy for the design of high-efficiency and stable catalysts for DRM.展开更多
Dry reforming of methane(DRM)has gained significant attention as a promising route to convert two major greenhouse gases(CO_(2) and CH4)to syngas.The development of efficient catalysts is critical for the engineering ...Dry reforming of methane(DRM)has gained significant attention as a promising route to convert two major greenhouse gases(CO_(2) and CH4)to syngas.The development of efficient catalysts is critical for the engineering applications.In this study,the Ce_(x)Zr_(1-x)O_(2)/ZSM-5 composites with different oxygen vacancy concentrations were synthesized by tuning the Ce/Zr ratio,followed by the deposition of metal Ni to island-like Ce_(x)Zr_(1-x)O_(2)on ZSM-5,forming a variety of Ni-Ce_(x)Zr_(1-x)O_(2)/ZSM-5 catalysts,which were applied for the DRM reaction under 750◦C.Combined with various characterizations,it was found that the oxygen vacancy concentration illustrated the volcanic tendency with the decreased Ce/Zr ratio,and the interaction between metal Ni and Ce_(x)Zr_(1-x)O_(2)exhibited a positive relationship with oxygen vacancy concentration.The enhanced between Ni and Ce_(x)Zr_(1-x)O_(2)interaction could improve the strength and amount of Ni-O-M(M=Ce/Zr)species,making the d-band centers of catalysts closer to the Fermi energy level,which was beneficial to the CH4 and CO_(2) activation,along with the improved capacity to resist sintering and coking.Especially,the C1Z3(Ni-Ce0.25Zr0.75O_(2)/ZSM-5)catalyst with the Ce/Zr ratio of 1/3 demonstrated the optimal catalytic performance with 91.9%CH4 and 93.8%CO_(2) conversions within 50 h,accompanied by the best structural and catalytic stability after 100 h.In-situ DRIFTS was employed to study the reaction path and mechanism,discovering that significant amounts of strengthened Ni-O-M species were conducive to activating adsorbed CH4 and CO_(2),and desorbing the linear CO species.展开更多
The thermal protection of rocket engines is a crucial aspect of rocket engine design.In this paper,the gas film/regenerative composite cooling of the liquid oxygen/liquid methane(LOX/LCH4)rocket engine thrust chamber ...The thermal protection of rocket engines is a crucial aspect of rocket engine design.In this paper,the gas film/regenerative composite cooling of the liquid oxygen/liquid methane(LOX/LCH4)rocket engine thrust chamber was investigated.A gas film/regenerative composite cooling model was developed based on the Grisson gas film cooling efficiency formula and the one-dimensional regenerative cooling model.The accuracy of the model was validated through experiments conducted on a 6 kg/s level gas film/regenerative composite cooling thrust chamber.Additionally,key parameters related to heat transfer performance were calculated.The results demonstrate that the model is sufficiently accurate to be used as a preliminary design tool.The temperature rise error of the coolant,when compared with the experimental results,was found to be less than 10%.Although the pressure drop error is relatively large,the calculated results still provide valuable guidance for heat transfer analysis.In addition,the performance of composite cooling is observed to be superior to regenerative cooling.Increasing the gas film flow rate results in higher cooling efficiency and a lower gas-side wall temperature.Furthermore,the position at which the gas film is introduced greatly impacts the cooling performance.The optimal introduction position for the gas film is determined when the film is introduced from a single row of holes.This optimal introduction position results in a more uniform wall temperature distribution and reduces the peak temperature.Lastly,it is observed that a double row of holes,when compared to a single row of holes,enhances the cooling effect in the superposition area of the gas film and further lowers the gas-side wall temperature.These results provide a basis for the design of gas film/regenerative composite cooling systems.展开更多
Electrocatalytic CO_(2)reduction(ECR)to produce value-added fuels and chemicals using renewable electricity is an emerging strategy to mitigate global warming and decrease reliance on fossil fuels.Among various ECR pr...Electrocatalytic CO_(2)reduction(ECR)to produce value-added fuels and chemicals using renewable electricity is an emerging strategy to mitigate global warming and decrease reliance on fossil fuels.Among various ECR products,liquid oxygenates(Oxys)are especially attractive due to their high energy density,high safety and transportability that could be adapted to the existing infrastructure and transportation system.However,efficiently generating these highly reduced oxygen-containing products by ECR remains challenging due to the complexity of coupled proton and electron transfer processes.In recent years,in-depth studies of reaction mechanisms have advanced the design of catalysts and the regulation of reaction systems for ECR to produce Oxys,Here,by focusing on the production of typical Oxys,such as methanol,acetic acid,ethanol,acetone,n-propanol,and isopropanol,we outline various reaction paths and key intermediates for the electrochemical conversion of CO_(2)into these target products.We also summarize the current research status and recent advances in catalysts based on their elemental composition,and consider recent studies on the change of catalyst geometry and electronic structure,as well as the optimization of reaction systems to increase ECR performance.Finally,we analyze the challenges in the field of ECR to Oxys and provide an outlook on future directions for high-efficiency catalyst prediction and design,as well as the development of advanced reaction systems.展开更多
The development of highly active catalyst in pH-neutral media for oxygen evolution reaction(OER)is critical in the field of renewable energy storage and conversion.Nevertheless,the slow kinetics of proton-coupled elec...The development of highly active catalyst in pH-neutral media for oxygen evolution reaction(OER)is critical in the field of renewable energy storage and conversion.Nevertheless,the slow kinetics of proton-coupled electron transfer(PCET)hinders the overall OER efficiency.Herein,we report an ionic liquid(IL)modified CoSn(OH)_(6)nanocubes(denoted as CoS-n(OH)_(6)-IL),which could be prepared through a facile strategy.The modified IL would not change the structural character-istics of CoSn(OH)_(6),but could effectively regulate the local proton activity near the active sites.The CoSn(OH)_(6)-IL exhibited higher intrinsic OER performances than the pristine CoSn(OH)_(6)in neutral media.For example,the current density of CoS-n(OH)_(6)-IL at 1.8 V versus reversible hydrogen electrode(RHE)was about 4 times higher than that of CoSn(OH)_(6).According to the pH-dependent kinetic investigations,operando electrochemical impedance spectroscopic,chemical probe tests,and deuterium kinetic isotope effects,the interfacial layer of IL could be utilized as a proton transfer mediator to promote the proton transfer,which enhances the surface coverage of OER intermediates and reduces the activation barrier.Consequent-ly,the sluggish OER kinetics would be efficiently accelerated.This study provides a facile and effective strategy to facilitate the PCET processes and is beneficial to guide the rational design of OER electrocatalysts.展开更多
It is urgent to develop catalysts with application potential for oxidative coupling of methane(OCM)at relatively lower temperature.Herein,three-dimensional ordered macro porous(3 DOM)La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)(...It is urgent to develop catalysts with application potential for oxidative coupling of methane(OCM)at relatively lower temperature.Herein,three-dimensional ordered macro porous(3 DOM)La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)(A_(2)B_(2)O_(7)-type)catalysts with disordered defective cubic fluorite phased structure were successfully prepared by a colloidal crystal template method.3DOM structure promotes the accessibility of the gaseous reactants(O2and CH4)to the active sites.The co-doping of Ca and Sr ions in La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)catalysts improved the formation of oxygen vacancies,thereby leading to increased density of surface-active oxygen species(O_(2)^(-))for the activation of CH4and the formation of C2products(C2H6and C2H4).3DOM La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)catalysts exhibit high catalytic activity for OCM at low temperature.3DOM La1.7Sr0.3Ce1.7Ca0.3O7-δcatalyst with the highest density of O_(2)^(-)species exhibited the highest catalytic activity for low-temperature OCM,i.e.,its CH4conversion,selectivity and yield of C2products at 650℃are 32.2%,66.1%and 21.3%,respectively.The mechanism was proposed that the increase in surface oxygen vacancies induced by the co-doping of Ca and Sr ions boosts the key step of C-H bond breaking and C-C bond coupling in catalyzing low-temperature OCM.It is meaningful for the development of the low-temperature and high-efficient catalysts for OCM reaction in practical application.展开更多
Natural gas is widely regarded as an efficient,relatively clean,and economically viable energy source.Its safe operation and continuous supply through pipeline infrastructure has led to its prominence in the energy se...Natural gas is widely regarded as an efficient,relatively clean,and economically viable energy source.Its safe operation and continuous supply through pipeline infrastructure has led to its prominence in the energy sector.Methanol plays an important role in the natural gas industry,typically serving as a solvent or hydrate inhibitor.Therefore,the accurate estimation of thermodynamic properties for methane/methanol binary is extremely important to optimise the operating parameter,maximise the dehydration effect,and reduce the cost.As the Helmholtz energy equation of state is expected to offer high accuracy in predicting the vapour-liquid equilibrium of methane/methanol binary,four reducing parameters were derived based on collected experimental data.Additionally,the sensitivities of various reducing parameter combinations were simultaneously investigated.The results demonstrated a strong agreement between predicted fractions and experimental data,with the UMADs(uncertainty-weighted mean absolute deviation)of 3.484 and 0.665 for liquid and vapour phases,respectively.Meanwhile,it is deemed“very likely”,“likely”,and“unlikely”to achieve acceptable prediction for 3-parameter optimisation,2-parameter optimisation and,1-parameter optimisation,respectively.展开更多
Unconventional natural gas has become an important supplement to conventional energy sources,and the process of enrichment and purification of methane from low concentration coalbed methane is crucial.To this end,we r...Unconventional natural gas has become an important supplement to conventional energy sources,and the process of enrichment and purification of methane from low concentration coalbed methane is crucial.To this end,we report a copper-based metal-organic framework(MOF),ZJNU-119Cu,featuring two methane traps constructed with uncoordinated carboxylic acid oxygens and open metal sites.ZJNU-119Cu exhibits a high methane adsorption capacity(58.2 cm^(3)·g^(-1))at 298 K and 0.1 MPa and excellent CH_(4)/N_(2) separation performance under dynamic conditions.Densityfunctional theory calculations combined with grand canonical Monte Carlo simulation theory reveal the interaction mechanism for the uncoordinated carboxylic acid oxygen atoms and open metal sites in ZJNU-119Cu with CH4.The gas adsorption isotherms,heat of adsorption calculations,and breakthrough separation experiments indicate that this MOF is a very promising adsorbent for CH_(4)/N_(2) separation.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
Engineering the morphology of the support is effective in tuning the redox properties of active metals for efficient catalytic methane combustion via tailoring the metal-support interaction.Herein,uniform Ir nanoparti...Engineering the morphology of the support is effective in tuning the redox properties of active metals for efficient catalytic methane combustion via tailoring the metal-support interaction.Herein,uniform Ir nanoparticles supported on anatase TiO_(2)with different morphologies predominantly exposing{100},{101},and{001}planes were synthesized and tested for methane combustion.The CH_(4) catalytic activity shows a remarkable TiO_(2)-facet-dependent effect and follows the order of Ir/TiO_(2)-{100}>Ir/TiO_(2)-{101}>>Ir/TiO_(2)-{001}.Detailed characterizations and DFT calculations reveal that compared with Ir-TiO_(2)-{101}and Ir-TiO_(2)-{001}interfaces,the superior Ir-TiO_(2)-{100}interface facilitates the generation of electron-rich Ir species through more profound charge transfer from TiO_(2)-{100}to Ir atoms.The electron-rich Ir structure,featuring abundant defect oxygen vacancies,significantly enhances the redox properties of active Ir species and reduces the activation energy for breaking the initial C-H bond in CH_(4),resulting in the superior catalytic activity for methane combustion.These findings deepen fundamental insights into the TiO_(2)-facet-dependent reactivity of different Ir/TiO_(2)nanomaterials in methane oxidation and pave the way for designing efficient Ir-based methane oxidation catalysts.展开更多
Palladium-based catalysts have long been considered the benchmark for methane combustion;however,the authentic phase of catalytic active sites remains a subject of ongoing debate.Additionally,challenges like water-poi...Palladium-based catalysts have long been considered the benchmark for methane combustion;however,the authentic phase of catalytic active sites remains a subject of ongoing debate.Additionally,challenges like water-poisoning and long-term stability need to be addressed to advance catalyst performance.Herein,we investigate Pd on Co_(3)O_(4) nanorods as a highly effective catalyst for catalytic oxidation of methane,demonstrating long-term stability and water tolerance during a 100-h continuous operation at 350℃.Comprehensive characterizations reveal the presence of an active Pd-oxygen vacancy(Ov)-cobalt interface in Pd/Co_(3)O_(4),which effectively adsorbs molecular O_(2).The absorbed oxygen species on this interface are activated and directly participate in methane combustion.Moreover,near-ambient pressure X-ray photoelectron spectroscopy demonstrates that Pd nanoparticles undergo a rapid phase transition and predominantly remain in the metallic state during the reaction.This behavior is attributed to the electronic metal-support interaction between Pd and Co_(3)O_(4).Furthermore,in situ Fourier transformed infrared spectrum reveals that under reaction conditions,HCO3*species are formed initially and subsequently transformed into formate species,indicating that the formate pathway is the dominant mechanism for CH_(4) oxidation.展开更多
Clean and O-(2√2×√2)R45°Cu(100) surfaces were prepared to study the impact of surface oxygen on the activation of methane dissociation.Auger electron spectroscopy,low energy electron diffraction,infrared r...Clean and O-(2√2×√2)R45°Cu(100) surfaces were prepared to study the impact of surface oxygen on the activation of methane dissociation.Auger electron spectroscopy,low energy electron diffraction,infrared reflection absorption spectroscopy,scanning tunneling microscope,and a quadrupole mass-spectrometer for temperature programmed desorption were used to explore the behavior of CH_(4) on the two surfaces.The dissociative adsorption of CH_(4) was observed on oxygen-pre-covered Cu(100) but not on the clean surface indicating surface oxygen promotes the dissociation of the C-H bond.This study can be a reference for the conversion of methane into other high-value-added products with high efficiency and low energy consumption.展开更多
Pr0.7Zr0.3O2-δ solid solution was prepared by co-precipitation method and used as an oxygen carrier in the selective oxidation of methane to syngas(methane/air redox process). The evolution on the physicochemical pro...Pr0.7Zr0.3O2-δ solid solution was prepared by co-precipitation method and used as an oxygen carrier in the selective oxidation of methane to syngas(methane/air redox process). The evolution on the physicochemical properties of Pr0.7Zr0.3O2-δ during the redox process was studied by means of X-ray diffraction(XRD), H2 temperature-programmed reduction(H2-TPR), O2temperature-programmed desorption(O2-TPD), Brunauer-Emmett-Teller(BET) surface area measurement and X-ray photoelectron spectroscopy(XPS) technologies. The results indicated that Pr0.7Zr0.3O2-δ solid solution showed the high activity for the methane conversion to syngas with a high CO selectivity in the range of 83.5%-88.1%. Though Pr-Zr solid solution possessed high thermal stability, lattice oxygen was obviously reduced for the recycled sample due to decreased surface oxygen which promoted oxygen vacancies. The increased oxygen vacancies seemed to enhance the oxygen transfer ability in the redox process and provided sufficient oxygen for the methane selective oxidation, resulting in a satisfactory activity. The problem of hot pot was avoided by comparing fresh, aged and recycle sample in the reaction.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
Anthropogenic methane emissions are a leading cause of the increase in global averagetemperatures,often referred to as global warming.Flooded soils play a significant role in methaneproduction,where the anaerobic cond...Anthropogenic methane emissions are a leading cause of the increase in global averagetemperatures,often referred to as global warming.Flooded soils play a significant role in methaneproduction,where the anaerobic conditions promote the production of methane by methanogenicmicroorganisms.Rice fields contribute a considerable portion of agricultural methane emissions,as riceplants provide both factors that enhance and limit methane production.Rice plants harbor both methaneproducingand methane-oxidizing microorganisms.Exudates from rice roots provide source for methaneproduction,while oxygen delivered from the root aerenchyma enhances methane oxidation.Studies haveshown that the diversity of these microorganisms depends on rice cultivars with some genes characterizedas harboring specific groups of microorganisms related to methane emissions.However,there is still aneed for research to determine the balance between methane production and oxidation,as rice plantspossess the ability to regulate net methane production.Various agronomical practices,such as fertilizerand water management,have been employed to mitigate methane emissions.Nevertheless,studiescorrelating agronomic and chemical management of methane with productivity are limited.Moreover,evidences for breeding low-methane-emitting rice varieties are scattered largely due to the absence ofcoordinated breeding programs.Research has indicated that phenotypic characteristics,such as rootbiomass,shoot architecture,and aerenchyma,are highly correlated with methane emissions.This reviewdiscusses available studies that involve the correlation between plant characteristics and methaneemissions.It emphasizes the necessity and importance of breeding low-methane-emitting rice varieties inaddition to existing agronomic,biological,and chemical practices.The review also delves into the idealphenotypic and physiological characteristics of low-methane-emitting rice and potential breeding techniques,drawing from studies conducted with diverse varieties,mutants,and transgenic plants.展开更多
Oxygen vacancies have been widely concerned with the facilitation effects of CO_(2)activation for CO_(2)methanation.However,little attention has been paid to the generation of active intermediate species induced by en...Oxygen vacancies have been widely concerned with the facilitation effects of CO_(2)activation for CO_(2)methanation.However,little attention has been paid to the generation of active intermediate species induced by enriched oxygen vacancies.Herein,we discovered that CeNiO_(3−δ)catalyst enriched oxygen vacancies can efficiently activate CO_(2)and realize high activity for photothermal CO_(2)methanation.In situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)proved that oxygen vacancies are beneficial to the formation of reactive intermediate species of polydentate carbonate over CeNiO_(3−δ),which is crucial for efficient CO_(2)methanation.These results revealed mechanistic insights into how effective CO_(2)activation induced by oxygen vacancies can be manipulated by adjusting the adsorption intermediate species.展开更多
The Ce-Fe-O mixed oxide with a ratio of Ce/Fe=7:3, which was prepared by coprecipitation method and employed as oxygen carrier, for direct partial oxidation of methane to syngas in the absence of gaseous oxygen was ex...The Ce-Fe-O mixed oxide with a ratio of Ce/Fe=7:3, which was prepared by coprecipitation method and employed as oxygen carrier, for direct partial oxidation of methane to syngas in the absence of gaseous oxygen was explored. The mixed oxide was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), and the catalytic performances were studied in a fixed-bed quartz reactor and a thermogravimetric reactor, respectively. Approximately 99.4% H2 se...展开更多
Two-step steam reforming of methane (SRM) is a novel chemical looping process towards the production of pure hydrogen and syngas (synthesis gas), consisting of a syngas production step and a water-splitting step. Rene...Two-step steam reforming of methane (SRM) is a novel chemical looping process towards the production of pure hydrogen and syngas (synthesis gas), consisting of a syngas production step and a water-splitting step. Renewable energy can be used to drive this process for hydrogen production, especially solar energy. CeO2-Fe2O3 complex oxide oxygen carrier was prepared by the impregnation method and characterized by means of X-ray diffractometer (XRD), Raman spectroscopy (Raman) and hydrogen programmed reduction (H2-TPR). CH4 temperature programmed and isothermal reactions were adopted to test syngas production reactivity, and water splitting reaction was employed to investigate water-splitting activity. Moreover, two-step SRM performance was evaluated by a successive redox cycle. The results showed that CO-uncontaminated H2 and highly selective syngas (with H2/CO ratio close to 2) could be respectively obtained from two steps, and CeFeO3 formation was found in the first redox cycle and proved to be enhanced by the redox treatment. After 10 successive cycles, obvious CeFeO3 phase was detected, which may be responsible for favorable successive redox cycle performances.展开更多
In this paper, the partial oxidation of methane to synthesis gas using lattice oxygen of La1- SrxMO3-λ (M=Fe, x ...In this paper, the partial oxidation of methane to synthesis gas using lattice oxygen of La1- SrxMO3-λ (M=Fe, x Mn) perovskite oxides instead of molecular oxygen was investigated. The redox circulation between 11% O2/Ar flow and 11% CH4/He flow at 900℃ shows that methane can be oxidized to CO and H2 with a selectivity of over 90.7% using the lattice oxygen of La1- SrxFeO3-λ (x≤0.2) perovskite oxides in an appropriate reaction condition, while the lost lattice x oxygen can be supplemented by air re-oxidation. It is viable for the lattice oxygen of La1- SrxFeO3-λ (x≤0.2) perovskite x oxides instead of molecular oxygen to react with methane to synthesis gas in the redox mode.展开更多
Direct conversion of methane using a metal-loaded ZSM-5 zeolite prepared viaacidic ion exchange was investigated to elucidate the roles of metal and acidity in the formation ofliquid hydrocarbons. ZSM-5 (SiO_2/Al_2O_3...Direct conversion of methane using a metal-loaded ZSM-5 zeolite prepared viaacidic ion exchange was investigated to elucidate the roles of metal and acidity in the formation ofliquid hydrocarbons. ZSM-5 (SiO_2/Al_2O_3=30) was loaded with different metals (Cr, Cu and Ga)according to the acidic ion-exchange method to produce metal-loaded ZSM-5 zeolite catalysts. XRD,NMR, FT-IR and N_2 adsorption analyses indicated that Cr and Ga species managed to occupy thealuminum positions in the ZSM-5 framework. In addition, Cr species were deposited in the pores ofthe structure. However, Cu oxides were deposited on the surface and in the mesopores of the ZSM-5zeolite. An acidity study using TPD-NH_3, FT-IR, and IR-pyridine analyses revealed that the totalnumber of acid sites and the strengths of the Broensted and Lewis acid sites were significantlydifferent after the acidic ion exchange treatment. Cu loaded HZSM-5 is a potential catalyst fordirect conversion of methane to liquid hydrocarbons. The successful production of gasoline via thedirect conversion of methane depends on the amount of aluminum in the zeolite framework and thestrength of the Broensted acid sites.展开更多
文摘In the past decade,dry reforming of methane(DRM)has garnered increasing interest as it converts CH_(4)and CO_(2),two typical greenhouse gases,into synthesis gas(H_(2)and CO)for the production of high-value-added chemicals and fuels.Nickel-based DRM catalysts,renowned for their high activity and low cost,however,encounter challenges such as severe deactivation from sintering and carbon deposition.Herein,a surrounded NiO@NiAlO precursor derived from Ni(OH)_(2)nanosheets was modified at both the core and shell interfaces with MgO via wet impregnation.The obtained 0.8MgO^(WI)/Ni@NiAlO catalyst achieved a high CH_(4)reaction rate of~177 mmol gNi^(-1)min^(-1)and remained stable for 50 h at 600℃without coke formation.In sharp contrast,other Mg-doped catalysts(MgO modified the core or shell interfaces)and the catalyst without Mg-doping deactivated within 10 h due to coking or Ni particle sintering.The Ni/MgNiO_(2)interfaces and abundant oxygen vacancies(O_(v))generated by Mg-doping contributed to the outstanding resistance to sintering&coking as well as the superior activity and stability of the 0.8MgO^(WI)/Ni@NiAlO catalyst.In-situ investigation further unveiled the reaction mechanism:the activation of CO_(2)via adsorption on O_(v)generates active oxygen species(O^(*)),which reacts with CH_(x)^(*)intermediates formed by the dissociation of CH_(4)on Ni sites,yielding CO and H_(2).This work not only fabricates coke-free and high-stability Ni-based DRM catalysts via interface engineering but also provides insights and a new strategy for the design of high-efficiency and stable catalysts for DRM.
基金the following financial supports:National Natural Science Foundation of China(22075225 and 22038011)Innovative Scientific Program of CNNC,State Key Laboratory of Clean and Efficient Coal Utilization,Taiyuan University of Technology(MJNYSKL202401,MJNYSKL202404).
文摘Dry reforming of methane(DRM)has gained significant attention as a promising route to convert two major greenhouse gases(CO_(2) and CH4)to syngas.The development of efficient catalysts is critical for the engineering applications.In this study,the Ce_(x)Zr_(1-x)O_(2)/ZSM-5 composites with different oxygen vacancy concentrations were synthesized by tuning the Ce/Zr ratio,followed by the deposition of metal Ni to island-like Ce_(x)Zr_(1-x)O_(2)on ZSM-5,forming a variety of Ni-Ce_(x)Zr_(1-x)O_(2)/ZSM-5 catalysts,which were applied for the DRM reaction under 750◦C.Combined with various characterizations,it was found that the oxygen vacancy concentration illustrated the volcanic tendency with the decreased Ce/Zr ratio,and the interaction between metal Ni and Ce_(x)Zr_(1-x)O_(2)exhibited a positive relationship with oxygen vacancy concentration.The enhanced between Ni and Ce_(x)Zr_(1-x)O_(2)interaction could improve the strength and amount of Ni-O-M(M=Ce/Zr)species,making the d-band centers of catalysts closer to the Fermi energy level,which was beneficial to the CH4 and CO_(2) activation,along with the improved capacity to resist sintering and coking.Especially,the C1Z3(Ni-Ce0.25Zr0.75O_(2)/ZSM-5)catalyst with the Ce/Zr ratio of 1/3 demonstrated the optimal catalytic performance with 91.9%CH4 and 93.8%CO_(2) conversions within 50 h,accompanied by the best structural and catalytic stability after 100 h.In-situ DRIFTS was employed to study the reaction path and mechanism,discovering that significant amounts of strengthened Ni-O-M species were conducive to activating adsorbed CH4 and CO_(2),and desorbing the linear CO species.
基金supported by the National Science Fund Project(No.2019-JCJQ-ZQ-019)the Innovative Research Group Project of National Natural Science Foundation of China(No.T2221002).
文摘The thermal protection of rocket engines is a crucial aspect of rocket engine design.In this paper,the gas film/regenerative composite cooling of the liquid oxygen/liquid methane(LOX/LCH4)rocket engine thrust chamber was investigated.A gas film/regenerative composite cooling model was developed based on the Grisson gas film cooling efficiency formula and the one-dimensional regenerative cooling model.The accuracy of the model was validated through experiments conducted on a 6 kg/s level gas film/regenerative composite cooling thrust chamber.Additionally,key parameters related to heat transfer performance were calculated.The results demonstrate that the model is sufficiently accurate to be used as a preliminary design tool.The temperature rise error of the coolant,when compared with the experimental results,was found to be less than 10%.Although the pressure drop error is relatively large,the calculated results still provide valuable guidance for heat transfer analysis.In addition,the performance of composite cooling is observed to be superior to regenerative cooling.Increasing the gas film flow rate results in higher cooling efficiency and a lower gas-side wall temperature.Furthermore,the position at which the gas film is introduced greatly impacts the cooling performance.The optimal introduction position for the gas film is determined when the film is introduced from a single row of holes.This optimal introduction position results in a more uniform wall temperature distribution and reduces the peak temperature.Lastly,it is observed that a double row of holes,when compared to a single row of holes,enhances the cooling effect in the superposition area of the gas film and further lowers the gas-side wall temperature.These results provide a basis for the design of gas film/regenerative composite cooling systems.
基金financial supports from the National Natural Science Foundation of China(52201237)the Talent Introduction Project of Chinese Academy of Sciences(E344011)+4 种基金the Shenzhen High Level Talent Team Project(KQTD2022110109364705)the Joint Research Project of China Merchants Group and SIAT(E2Z1521)the Cross Institute Joint Research Youth Team Project of SIAT(E25427)National Natural Science Foundation of China(52402136)the China Postdoctoral Science Foundation(E325281005)。
文摘Electrocatalytic CO_(2)reduction(ECR)to produce value-added fuels and chemicals using renewable electricity is an emerging strategy to mitigate global warming and decrease reliance on fossil fuels.Among various ECR products,liquid oxygenates(Oxys)are especially attractive due to their high energy density,high safety and transportability that could be adapted to the existing infrastructure and transportation system.However,efficiently generating these highly reduced oxygen-containing products by ECR remains challenging due to the complexity of coupled proton and electron transfer processes.In recent years,in-depth studies of reaction mechanisms have advanced the design of catalysts and the regulation of reaction systems for ECR to produce Oxys,Here,by focusing on the production of typical Oxys,such as methanol,acetic acid,ethanol,acetone,n-propanol,and isopropanol,we outline various reaction paths and key intermediates for the electrochemical conversion of CO_(2)into these target products.We also summarize the current research status and recent advances in catalysts based on their elemental composition,and consider recent studies on the change of catalyst geometry and electronic structure,as well as the optimization of reaction systems to increase ECR performance.Finally,we analyze the challenges in the field of ECR to Oxys and provide an outlook on future directions for high-efficiency catalyst prediction and design,as well as the development of advanced reaction systems.
基金supported by the National Natural Science Foundation of China(22209040,22202063).
文摘The development of highly active catalyst in pH-neutral media for oxygen evolution reaction(OER)is critical in the field of renewable energy storage and conversion.Nevertheless,the slow kinetics of proton-coupled electron transfer(PCET)hinders the overall OER efficiency.Herein,we report an ionic liquid(IL)modified CoSn(OH)_(6)nanocubes(denoted as CoS-n(OH)_(6)-IL),which could be prepared through a facile strategy.The modified IL would not change the structural character-istics of CoSn(OH)_(6),but could effectively regulate the local proton activity near the active sites.The CoSn(OH)_(6)-IL exhibited higher intrinsic OER performances than the pristine CoSn(OH)_(6)in neutral media.For example,the current density of CoS-n(OH)_(6)-IL at 1.8 V versus reversible hydrogen electrode(RHE)was about 4 times higher than that of CoSn(OH)_(6).According to the pH-dependent kinetic investigations,operando electrochemical impedance spectroscopic,chemical probe tests,and deuterium kinetic isotope effects,the interfacial layer of IL could be utilized as a proton transfer mediator to promote the proton transfer,which enhances the surface coverage of OER intermediates and reduces the activation barrier.Consequent-ly,the sluggish OER kinetics would be efficiently accelerated.This study provides a facile and effective strategy to facilitate the PCET processes and is beneficial to guide the rational design of OER electrocatalysts.
基金supported by the National Key Research and Development Program of China(Nos.2022YFB3504100,2022YFB3506200)the National Natural Science Foundation of China(Nos.22208373,22376217)+1 种基金the Beijing Nova Program(No.20220484215)the Science Foundation of China University of Petroleum,Beijing(No.2462023YJRC030)。
文摘It is urgent to develop catalysts with application potential for oxidative coupling of methane(OCM)at relatively lower temperature.Herein,three-dimensional ordered macro porous(3 DOM)La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)(A_(2)B_(2)O_(7)-type)catalysts with disordered defective cubic fluorite phased structure were successfully prepared by a colloidal crystal template method.3DOM structure promotes the accessibility of the gaseous reactants(O2and CH4)to the active sites.The co-doping of Ca and Sr ions in La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)catalysts improved the formation of oxygen vacancies,thereby leading to increased density of surface-active oxygen species(O_(2)^(-))for the activation of CH4and the formation of C2products(C2H6and C2H4).3DOM La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)catalysts exhibit high catalytic activity for OCM at low temperature.3DOM La1.7Sr0.3Ce1.7Ca0.3O7-δcatalyst with the highest density of O_(2)^(-)species exhibited the highest catalytic activity for low-temperature OCM,i.e.,its CH4conversion,selectivity and yield of C2products at 650℃are 32.2%,66.1%and 21.3%,respectively.The mechanism was proposed that the increase in surface oxygen vacancies induced by the co-doping of Ca and Sr ions boosts the key step of C-H bond breaking and C-C bond coupling in catalyzing low-temperature OCM.It is meaningful for the development of the low-temperature and high-efficient catalysts for OCM reaction in practical application.
基金supported financially by the National Natural Science Foundation of China(52202434)the National Natural Science Foundation of Ningbo(2023J275).
文摘Natural gas is widely regarded as an efficient,relatively clean,and economically viable energy source.Its safe operation and continuous supply through pipeline infrastructure has led to its prominence in the energy sector.Methanol plays an important role in the natural gas industry,typically serving as a solvent or hydrate inhibitor.Therefore,the accurate estimation of thermodynamic properties for methane/methanol binary is extremely important to optimise the operating parameter,maximise the dehydration effect,and reduce the cost.As the Helmholtz energy equation of state is expected to offer high accuracy in predicting the vapour-liquid equilibrium of methane/methanol binary,four reducing parameters were derived based on collected experimental data.Additionally,the sensitivities of various reducing parameter combinations were simultaneously investigated.The results demonstrated a strong agreement between predicted fractions and experimental data,with the UMADs(uncertainty-weighted mean absolute deviation)of 3.484 and 0.665 for liquid and vapour phases,respectively.Meanwhile,it is deemed“very likely”,“likely”,and“unlikely”to achieve acceptable prediction for 3-parameter optimisation,2-parameter optimisation and,1-parameter optimisation,respectively.
基金financial support from the National Natural Science Foundation of China(22408258 and 22378287)the Joint Founds of the National Natural Science Foundation of China(U20B6004)the Natural Science Foundation of Shanxi Province(202303021222012).
文摘Unconventional natural gas has become an important supplement to conventional energy sources,and the process of enrichment and purification of methane from low concentration coalbed methane is crucial.To this end,we report a copper-based metal-organic framework(MOF),ZJNU-119Cu,featuring two methane traps constructed with uncoordinated carboxylic acid oxygens and open metal sites.ZJNU-119Cu exhibits a high methane adsorption capacity(58.2 cm^(3)·g^(-1))at 298 K and 0.1 MPa and excellent CH_(4)/N_(2) separation performance under dynamic conditions.Densityfunctional theory calculations combined with grand canonical Monte Carlo simulation theory reveal the interaction mechanism for the uncoordinated carboxylic acid oxygen atoms and open metal sites in ZJNU-119Cu with CH4.The gas adsorption isotherms,heat of adsorption calculations,and breakthrough separation experiments indicate that this MOF is a very promising adsorbent for CH_(4)/N_(2) separation.
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.
文摘Engineering the morphology of the support is effective in tuning the redox properties of active metals for efficient catalytic methane combustion via tailoring the metal-support interaction.Herein,uniform Ir nanoparticles supported on anatase TiO_(2)with different morphologies predominantly exposing{100},{101},and{001}planes were synthesized and tested for methane combustion.The CH_(4) catalytic activity shows a remarkable TiO_(2)-facet-dependent effect and follows the order of Ir/TiO_(2)-{100}>Ir/TiO_(2)-{101}>>Ir/TiO_(2)-{001}.Detailed characterizations and DFT calculations reveal that compared with Ir-TiO_(2)-{101}and Ir-TiO_(2)-{001}interfaces,the superior Ir-TiO_(2)-{100}interface facilitates the generation of electron-rich Ir species through more profound charge transfer from TiO_(2)-{100}to Ir atoms.The electron-rich Ir structure,featuring abundant defect oxygen vacancies,significantly enhances the redox properties of active Ir species and reduces the activation energy for breaking the initial C-H bond in CH_(4),resulting in the superior catalytic activity for methane combustion.These findings deepen fundamental insights into the TiO_(2)-facet-dependent reactivity of different Ir/TiO_(2)nanomaterials in methane oxidation and pave the way for designing efficient Ir-based methane oxidation catalysts.
文摘Palladium-based catalysts have long been considered the benchmark for methane combustion;however,the authentic phase of catalytic active sites remains a subject of ongoing debate.Additionally,challenges like water-poisoning and long-term stability need to be addressed to advance catalyst performance.Herein,we investigate Pd on Co_(3)O_(4) nanorods as a highly effective catalyst for catalytic oxidation of methane,demonstrating long-term stability and water tolerance during a 100-h continuous operation at 350℃.Comprehensive characterizations reveal the presence of an active Pd-oxygen vacancy(Ov)-cobalt interface in Pd/Co_(3)O_(4),which effectively adsorbs molecular O_(2).The absorbed oxygen species on this interface are activated and directly participate in methane combustion.Moreover,near-ambient pressure X-ray photoelectron spectroscopy demonstrates that Pd nanoparticles undergo a rapid phase transition and predominantly remain in the metallic state during the reaction.This behavior is attributed to the electronic metal-support interaction between Pd and Co_(3)O_(4).Furthermore,in situ Fourier transformed infrared spectrum reveals that under reaction conditions,HCO3*species are formed initially and subsequently transformed into formate species,indicating that the formate pathway is the dominant mechanism for CH_(4) oxidation.
基金This work is supported by the National Key R&D Program of China(No.2022YFB4101201)the Na-tional Natural Science Foundation of China(No.21972162).
文摘Clean and O-(2√2×√2)R45°Cu(100) surfaces were prepared to study the impact of surface oxygen on the activation of methane dissociation.Auger electron spectroscopy,low energy electron diffraction,infrared reflection absorption spectroscopy,scanning tunneling microscope,and a quadrupole mass-spectrometer for temperature programmed desorption were used to explore the behavior of CH_(4) on the two surfaces.The dissociative adsorption of CH_(4) was observed on oxygen-pre-covered Cu(100) but not on the clean surface indicating surface oxygen promotes the dissociation of the C-H bond.This study can be a reference for the conversion of methane into other high-value-added products with high efficiency and low energy consumption.
基金Projects(51374004,51174105,51204083,51104074,51306084)supported by the National Natural Science Foundation of ChinaProjects(2012FD016,2014HB006)supported by the Applied Basic Research Program of Yunnan Province,ChinaProject(2010241)supported by the Analysis and Testing Foundation of Kunming University of Science and Technology,China
文摘Pr0.7Zr0.3O2-δ solid solution was prepared by co-precipitation method and used as an oxygen carrier in the selective oxidation of methane to syngas(methane/air redox process). The evolution on the physicochemical properties of Pr0.7Zr0.3O2-δ during the redox process was studied by means of X-ray diffraction(XRD), H2 temperature-programmed reduction(H2-TPR), O2temperature-programmed desorption(O2-TPD), Brunauer-Emmett-Teller(BET) surface area measurement and X-ray photoelectron spectroscopy(XPS) technologies. The results indicated that Pr0.7Zr0.3O2-δ solid solution showed the high activity for the methane conversion to syngas with a high CO selectivity in the range of 83.5%-88.1%. Though Pr-Zr solid solution possessed high thermal stability, lattice oxygen was obviously reduced for the recycled sample due to decreased surface oxygen which promoted oxygen vacancies. The increased oxygen vacancies seemed to enhance the oxygen transfer ability in the redox process and provided sufficient oxygen for the methane selective oxidation, resulting in a satisfactory activity. The problem of hot pot was avoided by comparing fresh, aged and recycle sample in the reaction.
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 Improvement of Green Rice Plant Type Using Genetic Information Program, Rural Development Administration, Korea (Grant No. PJ01699202)
文摘Anthropogenic methane emissions are a leading cause of the increase in global averagetemperatures,often referred to as global warming.Flooded soils play a significant role in methaneproduction,where the anaerobic conditions promote the production of methane by methanogenicmicroorganisms.Rice fields contribute a considerable portion of agricultural methane emissions,as riceplants provide both factors that enhance and limit methane production.Rice plants harbor both methaneproducingand methane-oxidizing microorganisms.Exudates from rice roots provide source for methaneproduction,while oxygen delivered from the root aerenchyma enhances methane oxidation.Studies haveshown that the diversity of these microorganisms depends on rice cultivars with some genes characterizedas harboring specific groups of microorganisms related to methane emissions.However,there is still aneed for research to determine the balance between methane production and oxidation,as rice plantspossess the ability to regulate net methane production.Various agronomical practices,such as fertilizerand water management,have been employed to mitigate methane emissions.Nevertheless,studiescorrelating agronomic and chemical management of methane with productivity are limited.Moreover,evidences for breeding low-methane-emitting rice varieties are scattered largely due to the absence ofcoordinated breeding programs.Research has indicated that phenotypic characteristics,such as rootbiomass,shoot architecture,and aerenchyma,are highly correlated with methane emissions.This reviewdiscusses available studies that involve the correlation between plant characteristics and methaneemissions.It emphasizes the necessity and importance of breeding low-methane-emitting rice varieties inaddition to existing agronomic,biological,and chemical practices.The review also delves into the idealphenotypic and physiological characteristics of low-methane-emitting rice and potential breeding techniques,drawing from studies conducted with diverse varieties,mutants,and transgenic plants.
基金Financial support from the National Natural Science Foundation of China(Nos.22025202,51572191,and 21633004)the Jiangsu Funding Program for Excellent Postdoctoral Talent is gratefully acknowledged.
文摘Oxygen vacancies have been widely concerned with the facilitation effects of CO_(2)activation for CO_(2)methanation.However,little attention has been paid to the generation of active intermediate species induced by enriched oxygen vacancies.Herein,we discovered that CeNiO_(3−δ)catalyst enriched oxygen vacancies can efficiently activate CO_(2)and realize high activity for photothermal CO_(2)methanation.In situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)proved that oxygen vacancies are beneficial to the formation of reactive intermediate species of polydentate carbonate over CeNiO_(3−δ),which is crucial for efficient CO_(2)methanation.These results revealed mechanistic insights into how effective CO_(2)activation induced by oxygen vacancies can be manipulated by adjusting the adsorption intermediate species.
基金Project supported by the National Natural Science Foundation of China (50574046, 50774038)the Research Fund for the Doctoral Program of Higher Education of China (20095314120005)+1 种基金the Natural Science Foundation of Yunnan Province (2008E030M) the Foundation of Kun-ming University of Science and Technology (KKZ3200927010)
文摘The Ce-Fe-O mixed oxide with a ratio of Ce/Fe=7:3, which was prepared by coprecipitation method and employed as oxygen carrier, for direct partial oxidation of methane to syngas in the absence of gaseous oxygen was explored. The mixed oxide was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), and the catalytic performances were studied in a fixed-bed quartz reactor and a thermogravimetric reactor, respectively. Approximately 99.4% H2 se...
基金Project support by the National Natural Science Foundation of China (50574046, 50774038)the Natural Science Foundation of Yunnan Prov-ince (2008E030M)+1 种基金the Research Fund for the Doctoral Program of Higher Education of China (20095314120005)2010 Innovation Fund of Kunming University of Science and Technology
文摘Two-step steam reforming of methane (SRM) is a novel chemical looping process towards the production of pure hydrogen and syngas (synthesis gas), consisting of a syngas production step and a water-splitting step. Renewable energy can be used to drive this process for hydrogen production, especially solar energy. CeO2-Fe2O3 complex oxide oxygen carrier was prepared by the impregnation method and characterized by means of X-ray diffractometer (XRD), Raman spectroscopy (Raman) and hydrogen programmed reduction (H2-TPR). CH4 temperature programmed and isothermal reactions were adopted to test syngas production reactivity, and water splitting reaction was employed to investigate water-splitting activity. Moreover, two-step SRM performance was evaluated by a successive redox cycle. The results showed that CO-uncontaminated H2 and highly selective syngas (with H2/CO ratio close to 2) could be respectively obtained from two steps, and CeFeO3 formation was found in the first redox cycle and proved to be enhanced by the redox treatment. After 10 successive cycles, obvious CeFeO3 phase was detected, which may be responsible for favorable successive redox cycle performances.
文摘In this paper, the partial oxidation of methane to synthesis gas using lattice oxygen of La1- SrxMO3-λ (M=Fe, x Mn) perovskite oxides instead of molecular oxygen was investigated. The redox circulation between 11% O2/Ar flow and 11% CH4/He flow at 900℃ shows that methane can be oxidized to CO and H2 with a selectivity of over 90.7% using the lattice oxygen of La1- SrxFeO3-λ (x≤0.2) perovskite oxides in an appropriate reaction condition, while the lost lattice x oxygen can be supplemented by air re-oxidation. It is viable for the lattice oxygen of La1- SrxFeO3-λ (x≤0.2) perovskite x oxides instead of molecular oxygen to react with methane to synthesis gas in the redox mode.
文摘Direct conversion of methane using a metal-loaded ZSM-5 zeolite prepared viaacidic ion exchange was investigated to elucidate the roles of metal and acidity in the formation ofliquid hydrocarbons. ZSM-5 (SiO_2/Al_2O_3=30) was loaded with different metals (Cr, Cu and Ga)according to the acidic ion-exchange method to produce metal-loaded ZSM-5 zeolite catalysts. XRD,NMR, FT-IR and N_2 adsorption analyses indicated that Cr and Ga species managed to occupy thealuminum positions in the ZSM-5 framework. In addition, Cr species were deposited in the pores ofthe structure. However, Cu oxides were deposited on the surface and in the mesopores of the ZSM-5zeolite. An acidity study using TPD-NH_3, FT-IR, and IR-pyridine analyses revealed that the totalnumber of acid sites and the strengths of the Broensted and Lewis acid sites were significantlydifferent after the acidic ion exchange treatment. Cu loaded HZSM-5 is a potential catalyst fordirect conversion of methane to liquid hydrocarbons. The successful production of gasoline via thedirect conversion of methane depends on the amount of aluminum in the zeolite framework and thestrength of the Broensted acid sites.
