Using photoelectrocatalytic CO_(2) reduction reaction(CO_(2)RR)to produce valuable fuels is a fascinating way to alleviate environmental issues and energy crises.Bismuth-based(Bi-based)catalysts have attracted widespr...Using photoelectrocatalytic CO_(2) reduction reaction(CO_(2)RR)to produce valuable fuels is a fascinating way to alleviate environmental issues and energy crises.Bismuth-based(Bi-based)catalysts have attracted widespread attention for CO_(2)RR due to their high catalytic activity,selectivity,excellent stability,and low cost.However,they still need to be further improved to meet the needs of industrial applications.This review article comprehensively summarizes the recent advances in regulation strategies of Bi-based catalysts and can be divided into six categories:(1)defect engineering,(2)atomic doping engineering,(3)organic framework engineering,(4)inorganic heterojunction engineering,(5)crystal face engineering,and(6)alloying and polarization engineering.Meanwhile,the corresponding catalytic mechanisms of each regulation strategy will also be discussed in detail,aiming to enable researchers to understand the structure-property relationship of the improved Bibased catalysts fundamentally.Finally,the challenges and future opportunities of the Bi-based catalysts in the photoelectrocatalytic CO_(2)RR application field will also be featured from the perspectives of the(1)combination or synergy of multiple regulatory strategies,(2)revealing formation mechanism and realizing controllable synthesis,and(3)in situ multiscale investigation of activation pathways and uncovering the catalytic mechanisms.On the one hand,through the comparative analysis and mechanism explanation of the six major regulatory strategies,a multidimensional knowledge framework of the structure-activity relationship of Bi-based catalysts can be constructed for researchers,which not only deepens the atomic-level understanding of catalytic active sites,charge transport paths,and the adsorption behavior of intermediate products,but also provides theoretical guiding principles for the controllable design of new catalysts;on the other hand,the promising collaborative regulation strategies,controllable synthetic paths,and the in situ multiscale characterization techniques presented in this work provides a paradigm reference for shortening the research and development cycle of high-performance catalysts,conducive to facilitating the transition of photoelectrocatalytic CO_(2)RR technology from the laboratory routes to industrial application.展开更多
Against the background of“carbon peak and carbon neutrality,”it is of great practical significance to develop non-blast furnace ironmaking technology for the sustainable development of steel industry.Carbon-bearing ...Against the background of“carbon peak and carbon neutrality,”it is of great practical significance to develop non-blast furnace ironmaking technology for the sustainable development of steel industry.Carbon-bearing iron ore pellet is an innovative burden of direct reduction ironmaking due to its excellent self-reducing property,and the thermal strength of pellet is a crucial metallurgical property that affects its wide application.The carbon-bearing iron ore pellet without binders(CIPWB)was prepared using iron concentrate and anthracite,and the effects of reducing agent addition amount,size of pellet,reduction temperature and time on the thermal compressive strength of CIPWB during the reduction process were studied.Simultaneously,the mechanism of the thermal strength evolution of CIPWB was revealed.The results showed that during the low-temperature reduction process(300-500℃),the thermal compressive strength of CIPWB linearly increases with increasing the size of pellet,while it gradually decreases with increasing the anthracite ratio.When the CIPWB with 8%anthracite is reduced at 300℃for 60 min,the thermal strength of pellet is enhanced from 13.24 to 31.88 N as the size of pellet increases from 8.04 to 12.78 mm.Meanwhile,as the temperature is 500℃,with increasing the anthracite ratio from 2%to 8%,the thermal compressive strength of pellet under reduction for 60 min remarkably decreases from 41.47 to 8.94 N.Furthermore,in the high-temperature reduction process(600-1150℃),the thermal compressive strength of CIPWB firstly increases and then reduces with increasing the temperature,while it as well as the temperature corresponding to the maximum strength decreases with increasing the anthracite ratio.With adding 18%anthracite,the thermal compressive strength of pellet reaches the maximum value at 800℃,namely 35.00 N,and obtains the minimum value at 1050℃,namely 8.60 N.The thermal compressive strength of CIPWB significantly depends on the temperature,reducing agent dosage,and pellet size.展开更多
In response to the new mechanism of direct vortex melting reduction of vanadium–titanium magnetite,the reaction control mechanism and the migration regularity of valuable components in the process of direct melting r...In response to the new mechanism of direct vortex melting reduction of vanadium–titanium magnetite,the reaction control mechanism and the migration regularity of valuable components in the process of direct melting reduction were investigated using kinetic empirical equation by fitting and combining with X-ray diffraction,X-ray fluorescence,scanning electron microscopy,energy-dispersive spectrometry,and optical microscopy.The results show that iron reduction is controlled by the mass transfer process of(FeOx)in the slag,while vanadium reduction is controlled by both the mass transfer of(VOx)in the slag and the mass transfer of[V]in the molten iron,and the slag–metal interfacial reaction is the only pathway for vanadium reduction.The reduction of iron and vanadium is an obvious first-order reaction,with activation energy of 101.6051 and 197.416 kJ mol^(−1),respectively.Increasing the vortex rate and reaction temperature is beneficial to improving the reaction rate and reduction efficiency.The mineral phase variation of iron and vanadium in the slag during the reduction process is Fe_(2)O_(3)→Fe_(3)O_(4)/FeV_(2)O_(4)→FeTiO_(3) and FeV_(2)O_(4)→MgV_(2)O_(5);titanium in slag is mainly in the form of Mg_(x)Ti_(3−x)O_(5)(0≤x≤1)and CaTiO_(3).As the reaction time went on,the molar ratio(nTi/nMg)in Mg_(x)Ti_(3−x)O_(5)(0≤x≤1)and the Ti2O_(3) content in the slag gradually went up,while the area proportion of Mg_(x)Ti_(3−x)O_(5)(0≤x≤1)went up and then down,and the porosity of the slag and the grain size of Mg_(x)Ti_(3−x)O_(5)(0≤x≤1)got smaller.展开更多
The experiment explored the Fe_(2)O_(3) reduction process with H_(2)/CO mixed gas and confirmed a promoting effect from CO when its volume proportion in mixed gas is 20% at 850℃.The ReaxFF molecular dynamics(MD)simul...The experiment explored the Fe_(2)O_(3) reduction process with H_(2)/CO mixed gas and confirmed a promoting effect from CO when its volume proportion in mixed gas is 20% at 850℃.The ReaxFF molecular dynamics(MD)simulation method was used to observe the reduction process and provide an atomic-level explanation.The accuracy of the parameters used in the simulation was verified by the density functional theory(DFT)calculation.The simulation shows that the initial reduction rate of H_(2) is much faster than that of CO(from 800 to 950℃).As the reduction proceeds,cementite,obtained after CO participates in the reduction at 850℃,will appear on the iron surface.Due to the active properties of C atoms in cementite,they are easy to further react with the O atoms in Fe_(2)O_(3).The generation of internal CO may destroy the dense structure of the surface layer,thereby affecting the overall reduction swelling of Fe_(2)O_(3).However,excess CO is detrimental to the reaction rate,mainly because of the poor thermodynamic conditions of CO in the temperature range and the molecular diffusion capacity is not as good as that of H_(2).Furthermore,the surface structures obtained after H_(2) and CO reduction have been compared,and it was found that the structure obtained by CO reduction has a larger surface area,thus promoting the sub sequent reaction of H_(2).展开更多
Electrochemical nitrate reduction(NO_(3)RR)offers a promising avenue for treating nitrate-contaminated water and recovering ammonia(NH_(3)),yet the complexities of direct electron transfer(DET)and hydrogen atom transf...Electrochemical nitrate reduction(NO_(3)RR)offers a promising avenue for treating nitrate-contaminated water and recovering ammonia(NH_(3)),yet the complexities of direct electron transfer(DET)and hydrogen atom transfer(HAT)mechanisms crucial for efficiency remain elusive.This study bridges the gap with a combined experimental and theoretical approach,elucidating the impact of catalyst structure on NO3RR pathways.We discover that catalysts favoring strong NO_(3^(-))adsorption and efficient water dissociation were more inclined towards DET,enhancing denitrification.The Fe@Fe_(3)O_(4)/FF cathode,leveraging the synergistic interplay between metallic Fe and Fe_(3)O_(4),excelled in NO3RR via DET,achieving an NH3yield of 0.28 mmol h-1cm-2and a Faradaic efficiency of 95.7%for NH3at-1.6 V(vs.SCE),with minimal nitrite accumulation at 100 mmol/L nitrate.Conversely,the Fe/FF and Fe_(3)O_(4)/CC cathodes showed reduced NH3production and increased nitrite levels,attributed to the lack of Fe_(3)O_(4)and metallic Fe,respectively,resulting in a dominant HAT mechanism.Moreover,Fe@Fe_(3)O_(4)/FF facilitated complete denitrification in real wastewater treatment by harnessing Cl^(-)for electrochemically mediated breakpoint chlorination.This research not only deepens our understanding of NO3RR mechanisms but also paves the way for designing superior nitrate reduction catalysts.展开更多
The increasing demand for magnesium as a next-generation structural material highlights the significance of incorporating CaF_(2)as a catalyst to enhance the efficiency of vacuum carbothermal reduction of magnesium(VC...The increasing demand for magnesium as a next-generation structural material highlights the significance of incorporating CaF_(2)as a catalyst to enhance the efficiency of vacuum carbothermal reduction of magnesium(VCTRM).This study investigates the thermodynamic theory and catalytic mechanism of CaF_(2)in the VCTRM process.Catalytic reduction experiments and molecular dynamics simulations were conducted to gain a comprehensive understanding of the process.Thermodynamic calculations indicate that in vacuum carbothermal reduction,the primary reaction occurs between MgO and C.Analysis shows that CaF_(2)'s catalytic action primarily involves F^(-),Ca^(2+),and melt eutectic.Our experiments demonstrate that the addition of CaF_(2)significantly increases the reduction rate.Furthermore,the mass loss rate increases with both the quantity of CaF_(2)added and the holding time,stabilizing at additions over 5%.Experiments conducted at temperatures above the melting point of CaF_(2)exhibited a pronounced catalytic effect.The resultant magnesium showed optimal structure and crystallization,with a purity of 87.84%.Notably,while CaF_(2)remained in the residue,it was not detected in the condensate,confirming its catalytic role.Molecular dynamics simulations revealed that molten CaF_(2)sabotages the structure of magnesium oxide,with F^(-)dispersing onto the surface of MgO,thus enhancing the reaction between MgO and C to form CO.However,no chemical reaction was observed between C,MgO,and CaF_(2).The occurrence of the carbothermal reduction reaction at high temperatures depends on the concentration of the reducing agent C,with CaF_(2)influencing the reaction rate.This research elucidates the theoretical and mechanistic foundations of CaF_(2)-catalyzed VCTRM,aligning with the green energy-saving concept and significantly advancing the green and efficient VCTRM process.展开更多
Platinum(Pt) nanoparticle catalysts remain the most popular cathode materials for oxygen reduction reaction(ORR) in proton exchange membrane fuel cells. Non-metallic alloying of Pt has become an emerging strategy to i...Platinum(Pt) nanoparticle catalysts remain the most popular cathode materials for oxygen reduction reaction(ORR) in proton exchange membrane fuel cells. Non-metallic alloying of Pt has become an emerging strategy to improve electrocatalytic performance, however, the electrocatalytic ORR mechanisms still need to be understood for further improvement toward practical application. Herein, a rapid microwave reduction method is employed for alloying phosphorous(P) into Pt to form a carbon supported phosphorus-alloyed Pt nanoparticle catalyst(P-Pt/C), which demonstrates the ability to replace commercial Pt/C. By a combination of density functional theory calculations and in-situ electrochemical Raman spectroscopy, the regulation role of P-alloying in the electrocatalytic mechanisms is revealed. It is found that the nearby Pt atoms can convert the ORR pathway from associative one to dissociative one, exhibiting a spontaneous dissociation of*OOH intermediate to*OH and*O species as well as a change of potential determining step to*O protonation. Furthermore, the strategy of large-scale economic synthesis of such alloying Pt-based catalyst is also established, demonstrated by a gram-level synthesis per batch.This study puts insight into the electrocatalytic ORR fundamentals of Pt-alloying with non-metals and provides a basis for the reasonable design and synthesis of efficient nonmetals-alloyed Pt catalysts.展开更多
To explore the denitration mechanism of iron-vanadium/activated carbon(Fe-V/AC)catalysts in ammonia-selective catalytic reduction(NH_(3)-SCR),the physicochemical properties of Fe-V/AC catalysts were characterized.The ...To explore the denitration mechanism of iron-vanadium/activated carbon(Fe-V/AC)catalysts in ammonia-selective catalytic reduction(NH_(3)-SCR),the physicochemical properties of Fe-V/AC catalysts were characterized.The denitration activities of the Fe-V/AC catalysts in the range of 150-300℃ were evaluated.The increase in denitration temperature leads to the highest and fastest recovery rate of NO conversion in the 10Fe-15V/AC catalyst.However,more metal oxides were attached to the catalyst surface as the V loading increased,and the accumulation occurred.The surface-active components are FeO,Fe_(2)O_(3),Fe_(3)O_(4),VO_(2),and V_(2)O_(5).In addition,the increase in the V loading induced a series of modification effects.A large amount of Fe^(3+)was reduced to Fe^(2+),and a large amount of V^(4+)was oxidized to V^(5+).The surface oxygen species(O_(α))were transformed into lattice oxygen(O_(β)).The presence of a large amount of V species deteriorated the pore-structure parameters and destroyed the oxygen-containing functional groups.Increasing the V loading can effectively increase the Lewis acid sites,thereby promoting NH_(3) adsorption and NO reduction and increasing the stretching vibration of weakly adsorbed ammonia species on the catalyst.The NH_(3) adsorption process produces a notable increase in the concentration of monodentate nitrite(NH_(4)^(+)).The NH_(3)-SCR denitration mechanism of the Fe-V/AC catalyst includes reaction gas adsorption,catalytic denitration of metal active components,and gas desorption.展开更多
The process of aluminothermic reduction of a mixture of calcined dolomite and calcined magnesite had been developed. The mechanism of the process was studied by SEM and EDS. The reduction process was divided into thre...The process of aluminothermic reduction of a mixture of calcined dolomite and calcined magnesite had been developed. The mechanism of the process was studied by SEM and EDS. The reduction process was divided into three stages:0≤ηt/ηf≤0.43±0.06, 0.43±0.06≤ηt/ηf≤0.9±0.02 and 0.9±0.02≤ηt/ηf<1, whereηt andηf are the reduction ratio at time t and the final reduction ratio obtained in the experiment at temperature T, respectively. The first stage included the direct reaction between calcined dolomite or calcined magnesite and Al with 12CaO·7Al2O3 and MgO·Al2O3 as products. The reaction rate depended on the chemical reaction. The CA phase was mainly produced in the second stage and the overall reaction rate was determined by both the diffusion of Ca2+ with molten Al and the chemical reaction. The CA2 phase was mainly produced in the third stage and the reaction process was controlled by the diffusion of Ca2+.展开更多
A low-grade nickel laterite ore was reduced at different reduction temperatures. The morphology of metallic particles was investigated by scanning electron microscopy （SEM） and energy dispersive spectroscopy （EDS）...A low-grade nickel laterite ore was reduced at different reduction temperatures. The morphology of metallic particles was investigated by scanning electron microscopy （SEM） and energy dispersive spectroscopy （EDS）. Experimental results indicate that the metallic nickel and iron gradually assemble and grow into larger spherical particles with increasing temperature and prolonging time. After reduction, the nickel laterite ore obviously changes into two parts of Fe-Ni metallic particles and slag matrix. An obvious relationship is found between the reduction of iron magnesium olivine and its crystal chemical properties. The nickel and iron oxides are reduced to metallic by reductant, and the lattice of olivine is destroyed. The entire reduction process is comprised of oxide reduction and metallic phase growth.展开更多
V2O5/TiO2-ZrO2 catalysts containing various amounts of WO3 were synthesized.The catalyst morphologies,catalytic performances,and reaction mechanisms in the selective catalytic reduction of NOx by NH3 were investigated...V2O5/TiO2-ZrO2 catalysts containing various amounts of WO3 were synthesized.The catalyst morphologies,catalytic performances,and reaction mechanisms in the selective catalytic reduction of NOx by NH3 were investigated using in situ diffuse-reflectance infrared Fourier-transform spectroscopy,temperature-programmed reduction（TPR）,X-ray diffraction,and the Brunauer-Emmett-Teller（BET） method.The BET surface area of the triple oxides increased with increasing ZrO2 doping but gradually decreased with increasing WO3 loading.Addition of sufficient WO3 helped to stabilize the pore structure and the combination of WO3 and ZrO2 improved dispersion of all the metal oxides.The mechanisms of reactions using V2O5-9%WO3/TiO2-ZrO2 and V2O5-9%WO3/TiO2were compared by using either a single or mixed gas feed and various pretreatments.The results suggest that both reactions followed the Eley-Ridel mechanism;however,the dominant acid sites,which depended on the addition of WO3 or ZrO2,determined the pathways for NOx reduction,and involved[NH4^＋-NO-Bronsted acid site]^＊ and[NH2-NO-Lewis acid site]^＊ intermediates,respectively.NH3-TPR and H2-TPR showed that the metal oxides in the catalysts were not reduced by NH3 and O2did not reoxidize the catalyst surfaces but participated in the formation of H2O and NO2.展开更多
The electrochemical reduction of carbon dioxide(CO_(2))into value-added chemicals and fuels has been extensively studied as a promising strategy for mitigating environmental issues and achieving sustainable energy con...The electrochemical reduction of carbon dioxide(CO_(2))into value-added chemicals and fuels has been extensively studied as a promising strategy for mitigating environmental issues and achieving sustainable energy conversion.Substantial efforts have been made to improve the understanding of CO_(2)reduction reaction(CO_(2)RR)mechanisms by computational and spectroscopic studies.An in-depth understanding of CO_(2)RR mechanism can provide the guidance and criteria for designing high-efficiency catalysts,and hence,steering CO_(2)RR to desired products.This review systematically discusses the formation mechanisms and reaction pathways of various CO_(2)RR products,including C_(1)products(CO,HCOOH,and CH_(4)),C_(2)products(C_(2)H_(4),C_(2)H_(5)OH,and CH_(3)COOH),and C_(3+)products(C_(3)H_(6),C_(3)H_(7)OH,and others).The reaction pathways are elucidated by analyzing the adsorption behavior,energy barriers,and intermediate coupling steps involved in the generation of each product.Particular emphasis is placed on the key intermediates,such as^(*)OCHO,^(*)COOH,^(*)CO,^(*)OCCOH,and^(*)CCO,which play crucial roles in determining the product selectivity.The effects of catalyst composition,morphology,and electronic structure on the adsorption and activation of these intermediates are also discussed.Moreover,advanced characterization techniques,including in-situ spectroscopy and isotopic labeling experiments,are highlighted for their contributions to unraveling the reaction mechanisms.The review aims to provide critical insights to reveal the activity-determining para meters and underlying CO_(2)RR mechanisms,which will guide the rational design of next-generation electrocatalysts for selective CO^(2)RR towards high-value products.展开更多
Bionic non-smooth surfaces （BNSS） can reduce drag. Much attention has been paid to the mechanism of shear stress reduction by riblets. The mechanism of pressure force reduction by bionic non-smooth surfaces on bodie...Bionic non-smooth surfaces （BNSS） can reduce drag. Much attention has been paid to the mechanism of shear stress reduction by riblets. The mechanism of pressure force reduction by bionic non-smooth surfaces on bodies of revolution has not been well investigated. In this work CFD simulation has revealed the mechanism of drag reduction by BNSS, which may work in three ways. First, BNSS on bodies of revolution may lower the surface velocity of the medium, which prevents the sudden speed up of air on the cross section. So the bottom pressure of the model would not be disturbed sharply, resulting in less energy loss and drag reduction. Second, the magnitude of vorticity induced by the bionic model becomes smaller because, due to the sculpturing, the growth of tiny air bubbles is avoided. Thus the large moment of inertia induced by large air bubble is reduced. The reduction of the vorticity could reduce the dissipation of the eddy. So the pressure force could also be reduced. Third, the thickness of the momentum layer on the model becomes less which, according to the relationship between the drag coefficient and the momentum thickness, reduces drag.展开更多
The reduction of vanadium titano-magnetite pellets by H_2-CO at temperatures from 850 to 1050°C was investigated in this paper. The influences of pre-oxidation treatment, reduction temperature, and V_（H_2）/（V_...The reduction of vanadium titano-magnetite pellets by H_2-CO at temperatures from 850 to 1050°C was investigated in this paper. The influences of pre-oxidation treatment, reduction temperature, and V_（H_2）/（V_（H_2） ＋ VCO） on the metallization degree were studied. The results showed that pre-oxidation played a substantial role in the reduction of vanadium titano-magnetite pellets. During the reduction process, the metallization degree increased with increasing temperature and increasing V_（H_2） /（V_（H_2） ＋ VCO）. The phase transformation of pre-oxidized vanadium titano-magnetite pellets during the reduction process under an H_2 atmosphere and a CO atmosphere was discussed, and the reduced samples were analyzed by scanning electron microscopy（SEM） in conjunction with back scatter electron（BSE） imaging. The results show that the difference in thermodynamic reducing ability between H_2 and CO is not the only factor that leads to differences in the reduction results obtained using different atmospheres. Some of Fe_（3-x）Ti_xO_4 cannot be reduced under a CO atmosphere because of the densification of particles＇ structure and because of the enrichment of Mg in unreacted cores. By contrast, a loose structure of particles was obtained when the pellets were reduced under an H_2 atmosphere and this structure decreased the resistance to gas diffusion. Moreover, the phenomenon of Mg enrichment in unreacted cores disappeared during H_2 reduction. Both the lower resistance to gas diffusion and the lack of Mg enrichment facilitated the reduction of vanadium titano-magnetite.展开更多
The reduction of the nitrobenzene compounds （NBCs） by the catalyzed Fe-Cu process and the relationship between the electrochemical reduction characteristics of NBCs at copper electrode and reduction rate were studie...The reduction of the nitrobenzene compounds （NBCs） by the catalyzed Fe-Cu process and the relationship between the electrochemical reduction characteristics of NBCs at copper electrode and reduction rate were studied in alkaline medium（pH=11）. The catalyzed Fe-Cu process was found more effective on degradation of NBCs compared to Master Builder＇s iron. The reduction rate by the catalyzed Fe-Cu process decreased in the following order： nitrobenzene 〉4-chloro-nitrobenzene ≥m-dinitrobenzene ：〉 4-nitrophenol ≥2,4-dinitrotoluene 〉2-nitrophenol. The reduction rate by Master Builder＇s iron decreased in the following order： m-dinitrobenzene ≥4-chloro-nitrobenzene 〉4-nitrophenol 〉2,4-dinitrotoluene ≈nitrobenzene 〉2-nitrophenol. NBCs were reduced directly on the surface of copper rather than by the hydrogen produced at cathode in the catalyzed Fe-Cu process. The reduction was realized by the hydrogen produced at cathode and Fe（OH）2 in Master Builder＇s iron, It is an essential difference in reaction mechanisms between these two technologies. For this reason, the reduction by the catalyzed Fe-Cu depended greatly on NBC＇s electron withdrawing ability.展开更多
The influences of the time, temperature and atmosphere on the reduction swelling of oxidized pellets were investigated by single factor experiments. The mechanisms of reduction swelling of oxidized pellets were analyz...The influences of the time, temperature and atmosphere on the reduction swelling of oxidized pellets were investigated by single factor experiments. The mechanisms of reduction swelling of oxidized pellets were analyzed and investigated by SEM （scanning electron microscopy） and XRD （X-ray diffractometer） analysis. The results show that the change rules of reduction swelling index of oxidized pellets in different reduction atmospheres are very similar. With the increase of reduction time, the reduction swelling index moves up firstly and then down. When the reduction temperature is above 900 ℃, α-quartz turns into α-tridymite, and the transition generates additional volume expansion effect. The reduction swelling index changes faster in H2 atmosphere than in CO atmosphere. Increasing Ha content in the reduction atmosphere is useful to decrease the reduction swelling index, but it is also easy to cause oxidized pellets cracking.展开更多
As one of the three major components of woody biomass,lignin is a kind of natural organic polymer and the only abundant natural renewable resource with aromatic nucleus.Chemical catalysis induced depolymerization is a...As one of the three major components of woody biomass,lignin is a kind of natural organic polymer and the only abundant natural renewable resource with aromatic nucleus.Chemical catalysis induced depolymerization is an important and effective approach for lignin utilization.In particular,photocatalysis and electrocatalysis show great potential in accurately activating C-O/C-C bonds,which is a critical point of selective cleavage of lignin.In this contribution,we focus on radical and(photo)electron transfer induced reaction mechanisms of the photo(electro)catalytic depolymerization of lignin.Primarily,the general situation of Carbon-centered radicals and active oxygen species mediated lignin conversion has been discussed.Then the mechanisms for(photo)electron transfer mediated lignin depolymerization have been summarized.At the end of this review,the challenges and opportunities of photo(electro)catalysis in the applications of lignin valorization have been forecasted.展开更多
Hongge vanadium titanomagnetite（HVTM）pellets were reduced by H2-CO gas mixture for simulating the reduction processes of Midrex and HYL-III shaft furnaces.The influences of reduction temperature,ratio ofφ（H2）toφ...Hongge vanadium titanomagnetite（HVTM）pellets were reduced by H2-CO gas mixture for simulating the reduction processes of Midrex and HYL-III shaft furnaces.The influences of reduction temperature,ratio ofφ（H2）toφ（CO）,and pellet size on the reduction of HVTM pellets were evaluated in detail and the reduction reaction kinetics was investigated.The results show that both the reduction degree and reduction rate can be improved with increasing the reduction temperature and the H2 content as well as decreasing the pellet size.The rational reduction parameters are reduction temperature of 1050℃,ratio ofφ（H2）toφ（CO）of 2.5,and pellet diameter in the range of 8-11 mm.Under these conditions（pellet diameter of 11mm）,final reduction degree of 95.51% is achieved.The X-ray diffraction（XRD）pattern shows that the main phases of final reduced pellets under these conditions（pellet diameter of 11 mm）are reduced iron and rutile.The peak intensity of reduced iron increases obviously with the increase in the reduction temperature.Besides,relatively high reduction temperature promotes the migration and coarsening of metallic iron particles and improves the distribution of vanadium and chromium in the reduced iron,which is conducive to subsequent melting separation.At the early stage,the reduction process is controlled by interfacial chemical reaction and the apparent activation energy is 60.78kJ/mol.The reduction process is controlled by both interfacial chemical reaction and internal diffusion at the final stage,and the apparent activation energy is 30.54kJ/mol.展开更多
The conventional linkage mechanisms with compliant joint have been widely studied and implemented for increasing the adaptability of the mechanism to external contacts. However, the analysis of how compliant joints in...The conventional linkage mechanisms with compliant joint have been widely studied and implemented for increasing the adaptability of the mechanism to external contacts. However, the analysis of how compliant joints in linkage mechanism can reduce the energy consumption isn＇t still studied deeply. In a mobile service robot head, the actions of blinking the eyes and moving the eyeballs are realized by the planar linkage mechanism respectively. Therefore, minimizing the driving torques through motion trajectories for the linkage mechanism, which will be beneficial to extend the working time for mobile service robots. The dynamic modeling of the linkage mechanism with springs-loaded compliant joint is established. An optimization procedure for obtaining the optimal parameters of springs is proposed for minimizing the max value of driving torques within a range of desired operating conditions. The Simulations prove that the linkage mechanism with compliant joints can effectively reduce the driving torques, and reduce the energy consumption consequently. The framework can also be applied in other similar applications to reduce the driving torque and save energy. Compared with previous efforts, this is the first attempt that the linkage mechanism with complaint joint is applied in the robot head for reducing the driving torque.展开更多
Non-thermal plasma has been proved to be an effective and competitive technology for removing NO in flue gas since 1970. In this paper, the NO reduction mechanism of the non-thermal plasma reaction in NO/N_2/O_2 syste...Non-thermal plasma has been proved to be an effective and competitive technology for removing NO in flue gas since 1970. In this paper, the NO reduction mechanism of the non-thermal plasma reaction in NO/N_2/O_2 system was investigated using the method of spectral analysis and quantum chemistry. By the establishment of NO reduction and gas discharge plasma emission spectrum measuring system, the NO reduction results, gas discharge emission spectra of NO/N_2/O_2 and pure N_2 were obtained, and then the model of molecular orbit of N_2 either in ground state or its excited state was worked out using the method of molecular orbit Ab initio in Self-Consistent Field(SCF). It was found that NO reduction in NO/N_2 gas discharge plasma was achieved mainly through a series of fast elementary reactions and the N(E6) at excited state was the base for NO reduction.展开更多
基金supports from the National Natural Science Foundation of China(Grant Nos.12305372 and 22376217)the National Key Research&Development Program of China(Grant Nos.2022YFA1603802 and 2022YFB3504100)+1 种基金the projects of the key laboratory of advanced energy materials chemistry,ministry of education(Nankai University)key laboratory of Jiangxi Province for persistent pollutants prevention control and resource reuse(2023SSY02061)are gratefully acknowledged.
文摘Using photoelectrocatalytic CO_(2) reduction reaction(CO_(2)RR)to produce valuable fuels is a fascinating way to alleviate environmental issues and energy crises.Bismuth-based(Bi-based)catalysts have attracted widespread attention for CO_(2)RR due to their high catalytic activity,selectivity,excellent stability,and low cost.However,they still need to be further improved to meet the needs of industrial applications.This review article comprehensively summarizes the recent advances in regulation strategies of Bi-based catalysts and can be divided into six categories:(1)defect engineering,(2)atomic doping engineering,(3)organic framework engineering,(4)inorganic heterojunction engineering,(5)crystal face engineering,and(6)alloying and polarization engineering.Meanwhile,the corresponding catalytic mechanisms of each regulation strategy will also be discussed in detail,aiming to enable researchers to understand the structure-property relationship of the improved Bibased catalysts fundamentally.Finally,the challenges and future opportunities of the Bi-based catalysts in the photoelectrocatalytic CO_(2)RR application field will also be featured from the perspectives of the(1)combination or synergy of multiple regulatory strategies,(2)revealing formation mechanism and realizing controllable synthesis,and(3)in situ multiscale investigation of activation pathways and uncovering the catalytic mechanisms.On the one hand,through the comparative analysis and mechanism explanation of the six major regulatory strategies,a multidimensional knowledge framework of the structure-activity relationship of Bi-based catalysts can be constructed for researchers,which not only deepens the atomic-level understanding of catalytic active sites,charge transport paths,and the adsorption behavior of intermediate products,but also provides theoretical guiding principles for the controllable design of new catalysts;on the other hand,the promising collaborative regulation strategies,controllable synthetic paths,and the in situ multiscale characterization techniques presented in this work provides a paradigm reference for shortening the research and development cycle of high-performance catalysts,conducive to facilitating the transition of photoelectrocatalytic CO_(2)RR technology from the laboratory routes to industrial application.
基金support of the National Natural Science Foundation of China(52074080,52004001,and 51574002).
文摘Against the background of“carbon peak and carbon neutrality,”it is of great practical significance to develop non-blast furnace ironmaking technology for the sustainable development of steel industry.Carbon-bearing iron ore pellet is an innovative burden of direct reduction ironmaking due to its excellent self-reducing property,and the thermal strength of pellet is a crucial metallurgical property that affects its wide application.The carbon-bearing iron ore pellet without binders(CIPWB)was prepared using iron concentrate and anthracite,and the effects of reducing agent addition amount,size of pellet,reduction temperature and time on the thermal compressive strength of CIPWB during the reduction process were studied.Simultaneously,the mechanism of the thermal strength evolution of CIPWB was revealed.The results showed that during the low-temperature reduction process(300-500℃),the thermal compressive strength of CIPWB linearly increases with increasing the size of pellet,while it gradually decreases with increasing the anthracite ratio.When the CIPWB with 8%anthracite is reduced at 300℃for 60 min,the thermal strength of pellet is enhanced from 13.24 to 31.88 N as the size of pellet increases from 8.04 to 12.78 mm.Meanwhile,as the temperature is 500℃,with increasing the anthracite ratio from 2%to 8%,the thermal compressive strength of pellet under reduction for 60 min remarkably decreases from 41.47 to 8.94 N.Furthermore,in the high-temperature reduction process(600-1150℃),the thermal compressive strength of CIPWB firstly increases and then reduces with increasing the temperature,while it as well as the temperature corresponding to the maximum strength decreases with increasing the anthracite ratio.With adding 18%anthracite,the thermal compressive strength of pellet reaches the maximum value at 800℃,namely 35.00 N,and obtains the minimum value at 1050℃,namely 8.60 N.The thermal compressive strength of CIPWB significantly depends on the temperature,reducing agent dosage,and pellet size.
基金supported by the National Natural Science Foundation of China(U1908225)the Fundamental Research Funds for Central Universities(N2225012 and N232405-06).
文摘In response to the new mechanism of direct vortex melting reduction of vanadium–titanium magnetite,the reaction control mechanism and the migration regularity of valuable components in the process of direct melting reduction were investigated using kinetic empirical equation by fitting and combining with X-ray diffraction,X-ray fluorescence,scanning electron microscopy,energy-dispersive spectrometry,and optical microscopy.The results show that iron reduction is controlled by the mass transfer process of(FeOx)in the slag,while vanadium reduction is controlled by both the mass transfer of(VOx)in the slag and the mass transfer of[V]in the molten iron,and the slag–metal interfacial reaction is the only pathway for vanadium reduction.The reduction of iron and vanadium is an obvious first-order reaction,with activation energy of 101.6051 and 197.416 kJ mol^(−1),respectively.Increasing the vortex rate and reaction temperature is beneficial to improving the reaction rate and reduction efficiency.The mineral phase variation of iron and vanadium in the slag during the reduction process is Fe_(2)O_(3)→Fe_(3)O_(4)/FeV_(2)O_(4)→FeTiO_(3) and FeV_(2)O_(4)→MgV_(2)O_(5);titanium in slag is mainly in the form of Mg_(x)Ti_(3−x)O_(5)(0≤x≤1)and CaTiO_(3).As the reaction time went on,the molar ratio(nTi/nMg)in Mg_(x)Ti_(3−x)O_(5)(0≤x≤1)and the Ti2O_(3) content in the slag gradually went up,while the area proportion of Mg_(x)Ti_(3−x)O_(5)(0≤x≤1)went up and then down,and the porosity of the slag and the grain size of Mg_(x)Ti_(3−x)O_(5)(0≤x≤1)got smaller.
基金financial support from the National Natural Science Foundation of China(Nos.52204335 and 52374319)the National Nature Science Foundation of China(No.52174291)the Central Universities Foundation of China(No.06500170)。
文摘The experiment explored the Fe_(2)O_(3) reduction process with H_(2)/CO mixed gas and confirmed a promoting effect from CO when its volume proportion in mixed gas is 20% at 850℃.The ReaxFF molecular dynamics(MD)simulation method was used to observe the reduction process and provide an atomic-level explanation.The accuracy of the parameters used in the simulation was verified by the density functional theory(DFT)calculation.The simulation shows that the initial reduction rate of H_(2) is much faster than that of CO(from 800 to 950℃).As the reduction proceeds,cementite,obtained after CO participates in the reduction at 850℃,will appear on the iron surface.Due to the active properties of C atoms in cementite,they are easy to further react with the O atoms in Fe_(2)O_(3).The generation of internal CO may destroy the dense structure of the surface layer,thereby affecting the overall reduction swelling of Fe_(2)O_(3).However,excess CO is detrimental to the reaction rate,mainly because of the poor thermodynamic conditions of CO in the temperature range and the molecular diffusion capacity is not as good as that of H_(2).Furthermore,the surface structures obtained after H_(2) and CO reduction have been compared,and it was found that the structure obtained by CO reduction has a larger surface area,thus promoting the sub sequent reaction of H_(2).
基金support from the National Natural Science Foundation of China(Nos.U21A2034 and 21876052)the Guangdong Special Support Plan for Innovation Teams(No.2019BT02L218)+1 种基金the Guangdong Special Support Plan for Young Top-notch Talents(No.2019TQ05L179)the Natural Science Foundation of Guangdong Province,China(No.2021B1515120077)。
文摘Electrochemical nitrate reduction(NO_(3)RR)offers a promising avenue for treating nitrate-contaminated water and recovering ammonia(NH_(3)),yet the complexities of direct electron transfer(DET)and hydrogen atom transfer(HAT)mechanisms crucial for efficiency remain elusive.This study bridges the gap with a combined experimental and theoretical approach,elucidating the impact of catalyst structure on NO3RR pathways.We discover that catalysts favoring strong NO_(3^(-))adsorption and efficient water dissociation were more inclined towards DET,enhancing denitrification.The Fe@Fe_(3)O_(4)/FF cathode,leveraging the synergistic interplay between metallic Fe and Fe_(3)O_(4),excelled in NO3RR via DET,achieving an NH3yield of 0.28 mmol h-1cm-2and a Faradaic efficiency of 95.7%for NH3at-1.6 V(vs.SCE),with minimal nitrite accumulation at 100 mmol/L nitrate.Conversely,the Fe/FF and Fe_(3)O_(4)/CC cathodes showed reduced NH3production and increased nitrite levels,attributed to the lack of Fe_(3)O_(4)and metallic Fe,respectively,resulting in a dominant HAT mechanism.Moreover,Fe@Fe_(3)O_(4)/FF facilitated complete denitrification in real wastewater treatment by harnessing Cl^(-)for electrochemically mediated breakpoint chlorination.This research not only deepens our understanding of NO3RR mechanisms but also paves the way for designing superior nitrate reduction catalysts.
基金supported by the Leading Talents of Industrial Technology in Yunnan Province[grant number 618820190024]the Yunnan Province Nonferrous Metal Vacuum Metallurgy Top Team[grant number 202305AS350012].
文摘The increasing demand for magnesium as a next-generation structural material highlights the significance of incorporating CaF_(2)as a catalyst to enhance the efficiency of vacuum carbothermal reduction of magnesium(VCTRM).This study investigates the thermodynamic theory and catalytic mechanism of CaF_(2)in the VCTRM process.Catalytic reduction experiments and molecular dynamics simulations were conducted to gain a comprehensive understanding of the process.Thermodynamic calculations indicate that in vacuum carbothermal reduction,the primary reaction occurs between MgO and C.Analysis shows that CaF_(2)'s catalytic action primarily involves F^(-),Ca^(2+),and melt eutectic.Our experiments demonstrate that the addition of CaF_(2)significantly increases the reduction rate.Furthermore,the mass loss rate increases with both the quantity of CaF_(2)added and the holding time,stabilizing at additions over 5%.Experiments conducted at temperatures above the melting point of CaF_(2)exhibited a pronounced catalytic effect.The resultant magnesium showed optimal structure and crystallization,with a purity of 87.84%.Notably,while CaF_(2)remained in the residue,it was not detected in the condensate,confirming its catalytic role.Molecular dynamics simulations revealed that molten CaF_(2)sabotages the structure of magnesium oxide,with F^(-)dispersing onto the surface of MgO,thus enhancing the reaction between MgO and C to form CO.However,no chemical reaction was observed between C,MgO,and CaF_(2).The occurrence of the carbothermal reduction reaction at high temperatures depends on the concentration of the reducing agent C,with CaF_(2)influencing the reaction rate.This research elucidates the theoretical and mechanistic foundations of CaF_(2)-catalyzed VCTRM,aligning with the green energy-saving concept and significantly advancing the green and efficient VCTRM process.
基金sponsored by the Natural Science Foundation of Shanghai (No. 23ZR1423900)the National Natural Science Foundation of China (No. 22272105)。
文摘Platinum(Pt) nanoparticle catalysts remain the most popular cathode materials for oxygen reduction reaction(ORR) in proton exchange membrane fuel cells. Non-metallic alloying of Pt has become an emerging strategy to improve electrocatalytic performance, however, the electrocatalytic ORR mechanisms still need to be understood for further improvement toward practical application. Herein, a rapid microwave reduction method is employed for alloying phosphorous(P) into Pt to form a carbon supported phosphorus-alloyed Pt nanoparticle catalyst(P-Pt/C), which demonstrates the ability to replace commercial Pt/C. By a combination of density functional theory calculations and in-situ electrochemical Raman spectroscopy, the regulation role of P-alloying in the electrocatalytic mechanisms is revealed. It is found that the nearby Pt atoms can convert the ORR pathway from associative one to dissociative one, exhibiting a spontaneous dissociation of*OOH intermediate to*OH and*O species as well as a change of potential determining step to*O protonation. Furthermore, the strategy of large-scale economic synthesis of such alloying Pt-based catalyst is also established, demonstrated by a gram-level synthesis per batch.This study puts insight into the electrocatalytic ORR fundamentals of Pt-alloying with non-metals and provides a basis for the reasonable design and synthesis of efficient nonmetals-alloyed Pt catalysts.
基金financially supported by National Natural Science Foundation of China(No.52264043).
文摘To explore the denitration mechanism of iron-vanadium/activated carbon(Fe-V/AC)catalysts in ammonia-selective catalytic reduction(NH_(3)-SCR),the physicochemical properties of Fe-V/AC catalysts were characterized.The denitration activities of the Fe-V/AC catalysts in the range of 150-300℃ were evaluated.The increase in denitration temperature leads to the highest and fastest recovery rate of NO conversion in the 10Fe-15V/AC catalyst.However,more metal oxides were attached to the catalyst surface as the V loading increased,and the accumulation occurred.The surface-active components are FeO,Fe_(2)O_(3),Fe_(3)O_(4),VO_(2),and V_(2)O_(5).In addition,the increase in the V loading induced a series of modification effects.A large amount of Fe^(3+)was reduced to Fe^(2+),and a large amount of V^(4+)was oxidized to V^(5+).The surface oxygen species(O_(α))were transformed into lattice oxygen(O_(β)).The presence of a large amount of V species deteriorated the pore-structure parameters and destroyed the oxygen-containing functional groups.Increasing the V loading can effectively increase the Lewis acid sites,thereby promoting NH_(3) adsorption and NO reduction and increasing the stretching vibration of weakly adsorbed ammonia species on the catalyst.The NH_(3) adsorption process produces a notable increase in the concentration of monodentate nitrite(NH_(4)^(+)).The NH_(3)-SCR denitration mechanism of the Fe-V/AC catalyst includes reaction gas adsorption,catalytic denitration of metal active components,and gas desorption.
基金Project(MYF2011-34)supported by High-tech R&D Projects of Liaoning Province Magnesia Materials Industry,ChinaProject(2011221002)supported by Industrial Research Projects of Liaoning Province,ChinaProject(N100302009)supported by the Fundamental Research Funds for the Central Universities,China
文摘The process of aluminothermic reduction of a mixture of calcined dolomite and calcined magnesite had been developed. The mechanism of the process was studied by SEM and EDS. The reduction process was divided into three stages:0≤ηt/ηf≤0.43±0.06, 0.43±0.06≤ηt/ηf≤0.9±0.02 and 0.9±0.02≤ηt/ηf<1, whereηt andηf are the reduction ratio at time t and the final reduction ratio obtained in the experiment at temperature T, respectively. The first stage included the direct reaction between calcined dolomite or calcined magnesite and Al with 12CaO·7Al2O3 and MgO·Al2O3 as products. The reaction rate depended on the chemical reaction. The CA phase was mainly produced in the second stage and the overall reaction rate was determined by both the diffusion of Ca2+ with molten Al and the chemical reaction. The CA2 phase was mainly produced in the third stage and the reaction process was controlled by the diffusion of Ca2+.
基金Project(51134002)supported by the National Natural Science Foundation of ChinaProject(2012BAB14B02)supported by the Ministry of Science and Technology of ChinaProject(12120113086600)supported by Ministry of Land and Resources of China
文摘A low-grade nickel laterite ore was reduced at different reduction temperatures. The morphology of metallic particles was investigated by scanning electron microscopy （SEM） and energy dispersive spectroscopy （EDS）. Experimental results indicate that the metallic nickel and iron gradually assemble and grow into larger spherical particles with increasing temperature and prolonging time. After reduction, the nickel laterite ore obviously changes into two parts of Fe-Ni metallic particles and slag matrix. An obvious relationship is found between the reduction of iron magnesium olivine and its crystal chemical properties. The nickel and iron oxides are reduced to metallic by reductant, and the lattice of olivine is destroyed. The entire reduction process is comprised of oxide reduction and metallic phase growth.
基金supported by the National Natural Science Foundation of China(51306034)Key Research&Development Projects of Jiangsu Province(BE2015677)the National Basic Research Program of China(2013CB228505)~~
文摘V2O5/TiO2-ZrO2 catalysts containing various amounts of WO3 were synthesized.The catalyst morphologies,catalytic performances,and reaction mechanisms in the selective catalytic reduction of NOx by NH3 were investigated using in situ diffuse-reflectance infrared Fourier-transform spectroscopy,temperature-programmed reduction（TPR）,X-ray diffraction,and the Brunauer-Emmett-Teller（BET） method.The BET surface area of the triple oxides increased with increasing ZrO2 doping but gradually decreased with increasing WO3 loading.Addition of sufficient WO3 helped to stabilize the pore structure and the combination of WO3 and ZrO2 improved dispersion of all the metal oxides.The mechanisms of reactions using V2O5-9%WO3/TiO2-ZrO2 and V2O5-9%WO3/TiO2were compared by using either a single or mixed gas feed and various pretreatments.The results suggest that both reactions followed the Eley-Ridel mechanism;however,the dominant acid sites,which depended on the addition of WO3 or ZrO2,determined the pathways for NOx reduction,and involved[NH4^＋-NO-Bronsted acid site]^＊ and[NH2-NO-Lewis acid site]^＊ intermediates,respectively.NH3-TPR and H2-TPR showed that the metal oxides in the catalysts were not reduced by NH3 and O2did not reoxidize the catalyst surfaces but participated in the formation of H2O and NO2.
基金financially supported by the National Natural Science Foundation of China(Grants 22225901,21975237 and 51702312)the Fundamental Research Funds for the Central Universities(Grant WK2340000101)+5 种基金the USTC Research Funds of the Double First-Class Initiative(Grant YD2340002007 and YD9990002017)the Open Funds of the State Key Laboratory of Rare Earth Resource Utilization(Grant RERU2022007)the China Postdoctoral Science Foundation(Grants 2023M733371,2024M750006 and 2023T160617)Postdoctoral Fellowship Program(Grade C)of China Postdoctoral Science Foundation(GZC20230008)the Natural Science Foundation Youth Project of Anhui Province(2408085QB065)the Postdoctoral Research Funding Project of Anhui Province(2023B727)。
文摘The electrochemical reduction of carbon dioxide(CO_(2))into value-added chemicals and fuels has been extensively studied as a promising strategy for mitigating environmental issues and achieving sustainable energy conversion.Substantial efforts have been made to improve the understanding of CO_(2)reduction reaction(CO_(2)RR)mechanisms by computational and spectroscopic studies.An in-depth understanding of CO_(2)RR mechanism can provide the guidance and criteria for designing high-efficiency catalysts,and hence,steering CO_(2)RR to desired products.This review systematically discusses the formation mechanisms and reaction pathways of various CO_(2)RR products,including C_(1)products(CO,HCOOH,and CH_(4)),C_(2)products(C_(2)H_(4),C_(2)H_(5)OH,and CH_(3)COOH),and C_(3+)products(C_(3)H_(6),C_(3)H_(7)OH,and others).The reaction pathways are elucidated by analyzing the adsorption behavior,energy barriers,and intermediate coupling steps involved in the generation of each product.Particular emphasis is placed on the key intermediates,such as^(*)OCHO,^(*)COOH,^(*)CO,^(*)OCCOH,and^(*)CCO,which play crucial roles in determining the product selectivity.The effects of catalyst composition,morphology,and electronic structure on the adsorption and activation of these intermediates are also discussed.Moreover,advanced characterization techniques,including in-situ spectroscopy and isotopic labeling experiments,are highlighted for their contributions to unraveling the reaction mechanisms.The review aims to provide critical insights to reveal the activity-determining para meters and underlying CO_(2)RR mechanisms,which will guide the rational design of next-generation electrocatalysts for selective CO^(2)RR towards high-value products.
基金National Natural Science Foundation of China （Grant No.50635030） the International Cooperation key Project of Ministry of Science and Technology of China （Grant No. 2005DFA00850）+2 种基金 The key project about ministry of education of science and technology （Grant No. 105059） the international cooperative of Jilin Province （Grant No.20040703-1） Specialized Research fund for the Doctoral Program of higher Education （Grant No. 20050183064）.
文摘Bionic non-smooth surfaces （BNSS） can reduce drag. Much attention has been paid to the mechanism of shear stress reduction by riblets. The mechanism of pressure force reduction by bionic non-smooth surfaces on bodies of revolution has not been well investigated. In this work CFD simulation has revealed the mechanism of drag reduction by BNSS, which may work in three ways. First, BNSS on bodies of revolution may lower the surface velocity of the medium, which prevents the sudden speed up of air on the cross section. So the bottom pressure of the model would not be disturbed sharply, resulting in less energy loss and drag reduction. Second, the magnitude of vorticity induced by the bionic model becomes smaller because, due to the sculpturing, the growth of tiny air bubbles is avoided. Thus the large moment of inertia induced by large air bubble is reduced. The reduction of the vorticity could reduce the dissipation of the eddy. So the pressure force could also be reduced. Third, the thickness of the momentum layer on the model becomes less which, according to the relationship between the drag coefficient and the momentum thickness, reduces drag.
基金financially supported by the Fundamental Research Funds for the Central Universities(2014zzts273)
文摘The reduction of vanadium titano-magnetite pellets by H_2-CO at temperatures from 850 to 1050°C was investigated in this paper. The influences of pre-oxidation treatment, reduction temperature, and V_（H_2）/（V_（H_2） ＋ VCO） on the metallization degree were studied. The results showed that pre-oxidation played a substantial role in the reduction of vanadium titano-magnetite pellets. During the reduction process, the metallization degree increased with increasing temperature and increasing V_（H_2） /（V_（H_2） ＋ VCO）. The phase transformation of pre-oxidized vanadium titano-magnetite pellets during the reduction process under an H_2 atmosphere and a CO atmosphere was discussed, and the reduced samples were analyzed by scanning electron microscopy（SEM） in conjunction with back scatter electron（BSE） imaging. The results show that the difference in thermodynamic reducing ability between H_2 and CO is not the only factor that leads to differences in the reduction results obtained using different atmospheres. Some of Fe_（3-x）Ti_xO_4 cannot be reduced under a CO atmosphere because of the densification of particles＇ structure and because of the enrichment of Mg in unreacted cores. By contrast, a loose structure of particles was obtained when the pellets were reduced under an H_2 atmosphere and this structure decreased the resistance to gas diffusion. Moreover, the phenomenon of Mg enrichment in unreacted cores disappeared during H_2 reduction. Both the lower resistance to gas diffusion and the lack of Mg enrichment facilitated the reduction of vanadium titano-magnetite.
文摘The reduction of the nitrobenzene compounds （NBCs） by the catalyzed Fe-Cu process and the relationship between the electrochemical reduction characteristics of NBCs at copper electrode and reduction rate were studied in alkaline medium（pH=11）. The catalyzed Fe-Cu process was found more effective on degradation of NBCs compared to Master Builder＇s iron. The reduction rate by the catalyzed Fe-Cu process decreased in the following order： nitrobenzene 〉4-chloro-nitrobenzene ≥m-dinitrobenzene ：〉 4-nitrophenol ≥2,4-dinitrotoluene 〉2-nitrophenol. The reduction rate by Master Builder＇s iron decreased in the following order： m-dinitrobenzene ≥4-chloro-nitrobenzene 〉4-nitrophenol 〉2,4-dinitrotoluene ≈nitrobenzene 〉2-nitrophenol. NBCs were reduced directly on the surface of copper rather than by the hydrogen produced at cathode in the catalyzed Fe-Cu process. The reduction was realized by the hydrogen produced at cathode and Fe（OH）2 in Master Builder＇s iron, It is an essential difference in reaction mechanisms between these two technologies. For this reason, the reduction by the catalyzed Fe-Cu depended greatly on NBC＇s electron withdrawing ability.
基金Sponsored by National Natural Science Foundation of China(51104014)National Natural Science Foundation of China and Baosteel(51134008)National Basic Research Program(973Program)of China(2012CB720401)
文摘The influences of the time, temperature and atmosphere on the reduction swelling of oxidized pellets were investigated by single factor experiments. The mechanisms of reduction swelling of oxidized pellets were analyzed and investigated by SEM （scanning electron microscopy） and XRD （X-ray diffractometer） analysis. The results show that the change rules of reduction swelling index of oxidized pellets in different reduction atmospheres are very similar. With the increase of reduction time, the reduction swelling index moves up firstly and then down. When the reduction temperature is above 900 ℃, α-quartz turns into α-tridymite, and the transition generates additional volume expansion effect. The reduction swelling index changes faster in H2 atmosphere than in CO atmosphere. Increasing Ha content in the reduction atmosphere is useful to decrease the reduction swelling index, but it is also easy to cause oxidized pellets cracking.
基金financial support of the National Natural Science Foundation of China,China(Grant No.21736003,21975082)the Guangdong Basic and Applied Basic Research Foundation(Grant Number:2019A1515011472)the Science and Technology Program of Guangzhou(Grant Number:202102080479)。
文摘As one of the three major components of woody biomass,lignin is a kind of natural organic polymer and the only abundant natural renewable resource with aromatic nucleus.Chemical catalysis induced depolymerization is an important and effective approach for lignin utilization.In particular,photocatalysis and electrocatalysis show great potential in accurately activating C-O/C-C bonds,which is a critical point of selective cleavage of lignin.In this contribution,we focus on radical and(photo)electron transfer induced reaction mechanisms of the photo(electro)catalytic depolymerization of lignin.Primarily,the general situation of Carbon-centered radicals and active oxygen species mediated lignin conversion has been discussed.Then the mechanisms for(photo)electron transfer mediated lignin depolymerization have been summarized.At the end of this review,the challenges and opportunities of photo(electro)catalysis in the applications of lignin valorization have been forecasted.
基金financially supported by National Natural Science Foundation of China(Grant No.51574067)
文摘Hongge vanadium titanomagnetite（HVTM）pellets were reduced by H2-CO gas mixture for simulating the reduction processes of Midrex and HYL-III shaft furnaces.The influences of reduction temperature,ratio ofφ（H2）toφ（CO）,and pellet size on the reduction of HVTM pellets were evaluated in detail and the reduction reaction kinetics was investigated.The results show that both the reduction degree and reduction rate can be improved with increasing the reduction temperature and the H2 content as well as decreasing the pellet size.The rational reduction parameters are reduction temperature of 1050℃,ratio ofφ（H2）toφ（CO）of 2.5,and pellet diameter in the range of 8-11 mm.Under these conditions（pellet diameter of 11mm）,final reduction degree of 95.51% is achieved.The X-ray diffraction（XRD）pattern shows that the main phases of final reduced pellets under these conditions（pellet diameter of 11 mm）are reduced iron and rutile.The peak intensity of reduced iron increases obviously with the increase in the reduction temperature.Besides,relatively high reduction temperature promotes the migration and coarsening of metallic iron particles and improves the distribution of vanadium and chromium in the reduced iron,which is conducive to subsequent melting separation.At the early stage,the reduction process is controlled by interfacial chemical reaction and the apparent activation energy is 60.78kJ/mol.The reduction process is controlled by both interfacial chemical reaction and internal diffusion at the final stage,and the apparent activation energy is 30.54kJ/mol.
基金Supported by National Natural Science Foundation of China(Grant No.51105089)Shenzhen Engineering Laboratory of Industrial Robots and Systems(Grant No.A224412028)Shenzhen Engineering Laboratory of Performance Robots at Digital Stage(Grant No.[2014]1507)
文摘The conventional linkage mechanisms with compliant joint have been widely studied and implemented for increasing the adaptability of the mechanism to external contacts. However, the analysis of how compliant joints in linkage mechanism can reduce the energy consumption isn＇t still studied deeply. In a mobile service robot head, the actions of blinking the eyes and moving the eyeballs are realized by the planar linkage mechanism respectively. Therefore, minimizing the driving torques through motion trajectories for the linkage mechanism, which will be beneficial to extend the working time for mobile service robots. The dynamic modeling of the linkage mechanism with springs-loaded compliant joint is established. An optimization procedure for obtaining the optimal parameters of springs is proposed for minimizing the max value of driving torques within a range of desired operating conditions. The Simulations prove that the linkage mechanism with compliant joints can effectively reduce the driving torques, and reduce the energy consumption consequently. The framework can also be applied in other similar applications to reduce the driving torque and save energy. Compared with previous efforts, this is the first attempt that the linkage mechanism with complaint joint is applied in the robot head for reducing the driving torque.
基金The National Basic Research Program(973) of China(No. G19990222909)
文摘Non-thermal plasma has been proved to be an effective and competitive technology for removing NO in flue gas since 1970. In this paper, the NO reduction mechanism of the non-thermal plasma reaction in NO/N_2/O_2 system was investigated using the method of spectral analysis and quantum chemistry. By the establishment of NO reduction and gas discharge plasma emission spectrum measuring system, the NO reduction results, gas discharge emission spectra of NO/N_2/O_2 and pure N_2 were obtained, and then the model of molecular orbit of N_2 either in ground state or its excited state was worked out using the method of molecular orbit Ab initio in Self-Consistent Field(SCF). It was found that NO reduction in NO/N_2 gas discharge plasma was achieved mainly through a series of fast elementary reactions and the N(E6) at excited state was the base for NO reduction.
