Methanol-to-hydrocarbons(MTH)reaction comprises a set of crucial catalytic processes to produce light olefins,gasoline,or aromatics.MTH reaction is a classic example of reaction complexity in zeolite catalysis.The mol...Methanol-to-hydrocarbons(MTH)reaction comprises a set of crucial catalytic processes to produce light olefins,gasoline,or aromatics.MTH reaction is a classic example of reaction complexity in zeolite catalysis.The molecular understanding of reaction routes and deactivation mechanisms still encounters many challenges.Herein,we chose HZSM-22 zeolite with the simple one-dimensional 10-membered ring(10-MR)channel as a prototypical system,leveraging the spatial nanoconfinement effect of its unique pore architecture to minimize reaction complexity.The identification of the molecular structures of coke species with acene-,biphenyl-,or fluorene-typed structures was made possible through a combination of the advanced matrix-assisted laser desorption/ionization Fourier-transform ion cyclotron resonance mass spectrometry(MALDI FT-ICR MS)with the gas chromatography-mass spectrometer(GC-MS)technique.With this,we uncovered two modes of growth mechanism of coke molecules,i.e.,a stepwise route and a dehydrogenative coupling route.The findings deepen the mechanistic understanding of zeolite deactivation and provide a theoretical foundation for designing coke-resistant catalysts.展开更多
Stem cell therapy shows promise for treating brain injuries;neural stem cells in particular are capable of repairing damage by forming new nerve cells and supporting recovery.However,optimizing the implantation and fu...Stem cell therapy shows promise for treating brain injuries;neural stem cells in particular are capable of repairing damage by forming new nerve cells and supporting recovery.However,optimizing the implantation and functionality of these cells in damaged brain regions remains challenging.Silk fibroin,a natural protein derived from silkworm silk,is a biocompatible material with exceptional properties that are useful for tissue engineering.Its biodegradability,mechanical robustness,and ability to promote cell growth make it particularly valuable for biomedical applications.Silk fibroin nanomaterials,which comprise silk fibroin processed into nanostructures,offer enhanced surface area,improved loading capacity for bioactive molecules,and superior nanoscale interactions with cells compared with bulk silk fibroin materials.In this study,we first extracted human-derived neural stem cells from a 14-week-old human fetus.Then,neural stem cells were loaded with 1%silk fibroin nanomaterials,which was identified as the optimal concentration to support human-derived neural stem cell growth and release of neurotrophic factors.Finally,1%silk fibroin nanomaterials were implanted into a rat model of hypoxic-ischemic brain injury.The results showed that,compared with the treatment with human-derived neural stem cells alone,silk fibroin hydrogel carrying human-derived neural stem cells was significantly more effective at alleviating brain tissue damage,increasing neurotrophic factor secretion in the brain microenvironment,and promoting motor and cognitive function recovery.These findings suggest that silk fibroin nanomaterials loaded with human-derived neural stem cells could be used to treat hypoxic-ischemic encephalopathy.However,the mechanisms and related signaling pathways by which hydrogels combined with cells exert their reparative effects still require further in-depth investigation.展开更多
A 10%Ni/γ-Al_(2)O_(3)catalyst was prepared for dry reforming of methane.Sphericalγ-Al_(2)O_(3)particles having an average particle size of 60μm were used as the support and an iso-volume impregnation method was emp...A 10%Ni/γ-Al_(2)O_(3)catalyst was prepared for dry reforming of methane.Sphericalγ-Al_(2)O_(3)particles having an average particle size of 60μm were used as the support and an iso-volume impregnation method was employed for the preparation.All activity-evaluation tests were conducted in a fluidized-bed quartz reactor at 0.1 MPa and variable temperatures and space velocities for 600 min.The results of the tests revealed that at 750℃ the catalyst activity showed an obviously accelerated decrease trend with the increase of space velocity.Ther-mogravimetric analysis of the spent catalysts revealed,however,that little carbon deposit formed in those spent samples that had experienced faster decreases in activity at higher space velocities.While these two facts together deny the possibility of carbon deposition leading to the accelerated activity decline at 750℃and high space velocities,increasing the CO_(2)/CH_(4)ratio of the feed was demonstrated to further accelerate the activity decrease.Meanwhile,XRD and XPS analyses of the spent catalyst samples revealed that oxidative transformation of metallic Ni in catalyst to Ni_(x)O(x≤1)species did occur in the reforming in the feed of CO_(2)/CH_(4)=1.5.All these results together have strongly revealed,for the first time,a conclusion as follows:it was the gradual oxidative transformation of active Ni sites in 10%Ni/γ-Al_(2)O_(3)catalyst to inactive Ni oxide species to cause a continuous decline of its dry reforming activity in fluidized-bed operation mode and at 750℃ and high space velocity condition.展开更多
The metal oxide promoter decisively influences the overall performance of Fe catalysts in the direct hydrogenation of CO_(2)to C_(5+)hydrocarbons.However,the roles of metal oxide promoter for Fe catalysts,particularly...The metal oxide promoter decisively influences the overall performance of Fe catalysts in the direct hydrogenation of CO_(2)to C_(5+)hydrocarbons.However,the roles of metal oxide promoter for Fe catalysts,particularly ZrO_(2),have rarely been investigated.To plug this knowledge gap,a new Fe catalyst promoted with Na and partially reduced ZrO_(x)(Na-FeZrO_(x-9))was developed in this study;the catalyst helped produce C_(5+)hydrocarbons in remarkably high yield(26.3%at 360℃).In contrast to ZrO_(x)-free Fe-oxide,NaFeZrO_(x)-9 exhibited long-term stability for CO_(2)hydrogenation(750 h on-stream).The findings revealed multiple roles of ZrO_(x).Notably,ZrO_(x)decorated the Fe-oxide particles after calcination,thereby suppressing excess particle aggregation during the reaction,and acted as a"coke remover"to eliminate the carbon deposited on the catalyst surface.Additionally,oxygen vacancy(O_(v))sites in ZrO_(x)and electron transfer from ZrO_(x)to Fe sites facilitated the adsorption of CO_(2)at the Zr-Fe interface.展开更多
Autocatalysis from the by-product metal sulfides plays a critical role in the residual oil hydrotreating(RHT)process.However,it has not been considered to build the catalyst deactivation models,which probably is one i...Autocatalysis from the by-product metal sulfides plays a critical role in the residual oil hydrotreating(RHT)process.However,it has not been considered to build the catalyst deactivation models,which probably is one important reason that the widely used S-type deactivation models are inaccurate in predicting some RHT processes'deactivation profiles.A three-stage catalyst deactivation model was first developed to fill this gap based on the mechanism inferred from the experimental and literature data.This model accounts for active site formation from by-product metal sulfides,deactivation due to active site coverage by coke formation and metal deposition,active site poisoning by highly-adsorbed species,active phase sintering,and diffusion resistance from the pore blockage at the same time,resulting in a function of dimensionless metals-on-catalyst.Then,the effectiveness of the proposed model was evaluated using the industrial data of an RHT unit and the experimental data from the literature,either in combination with reaction kinetics or independently.Results showed that RHT processes with clear autocatalytic effects may display different types of deactivation profiles from the traditional"S"shape.However,the proposed model was able to accurately track the entire deactivation curve of the RHT process and well predict the product properties.This approach yields valuable insights into the intricate autocatalytic effect that remarkably contributes to the performance modification of RHT catalysts.It is highly recommended that further research should be conducted on this topic,as it shows great potential to significantly advance catalyst and process development.展开更多
Coke formation is the primary cause of zeolite deactivation in industrial catalysis,yet the structural identity,spatial location and molecular routes of polycyclic aromatic hydrocarbons(PAHs)within confined zeolite po...Coke formation is the primary cause of zeolite deactivation in industrial catalysis,yet the structural identity,spatial location and molecular routes of polycyclic aromatic hydrocarbons(PAHs)within confined zeolite pores remain elusive.Here,by coupling matrix-assisted laser desorption/ionization Fourier-transform ion cyclotron resonance mass spectrometry with multi-dimensional chemical imaging,we unveil a channel-passing growth mechanism for PAHs in ZSM-5 zeolites during methanol conversion through identifying the molecular fingerprints of larger PAHs,pinpointing and visualizing their 3D location and spatiotemporal evolution trajectory with atomic resolution and at both channel and single-crystal scales.Confined aromatic entities cross-link with each other,culminating in multicore PAH chains as the both thermodynamically favorable and kinetically trapped host-vip entanglement wrought and templated by the defined molecular-scale constrained microenvironments of zeolite.The mechanistic concept proves general across both channel-and cage-structured zeolite materials.Our multiscale deactivating model based on the full-picture coke structure-location correlations—spanning atom,molecule,channel/cage and single crystal scales—would shed new light on the intertwined chemical and physical processes in catalyst deactivation.This work not only resolves long-standing puzzles in coke formation but also provides design principles for coke-resistant zeolites.The methods and insights would rekindle interest in confinement effects and host-vip chemistry across broader chemistry fields beyond catalysis and carbon materials.展开更多
In this study,we investigated Mo-impregnated H-MCM-22 catalysts(denoted Mo/M)for methanedehydroaromatization(MDA)to produce aromatics such as benzene and toluene(BT).We attemptedto improve the performance of the MDA c...In this study,we investigated Mo-impregnated H-MCM-22 catalysts(denoted Mo/M)for methanedehydroaromatization(MDA)to produce aromatics such as benzene and toluene(BT).We attemptedto improve the performance of the MDA catalysts by reducing the amount of Brönsted acidsites(BAS)of the H-MCM-22 supports via hydrothermal dealumination.Among the prepared catalysts,an optimal hydrothermal treatment(HT)of H-MCM-22 supports at 400℃,followed by Moimpregnation(denoted Mo/M_400),resulted in a reduced and optimal amount of BAS,along with acomparable Mo distribution to Mo/M.Further,Mo/M_400 enhanced BT formation rates(maximumBT formation rate of 5.23 vs.4.73 mmolBT·g^(−1)·h^(−1) for Mo/M);it appears that dealumination-inducedreduction in the quantity of BAS altered their spatial interaction with active Mo species,promotingBT and naphthalene formation.Interestingly,the lifetime of intermediate C_(2)(ethane and ethylene)formation was also improved for Mo/M_400.Rigorous coke analyses revealed that the decreasedcoke content in the aromatic-selective 10-membered-ring(10-MR)pores,as well as the ability ofthe 12-MR pores to accommodate coke deposits over a longer reaction time,improved the stabilityof Mo/M_400.Nonetheless,for all catalysts,the deactivations of BAS,and subsequently,the activeMo sites were mainly ascribed to coke deposition.The overall enhancement in MDA performance byMo/M_400 was attributed to the advantages of the optimally reduced BAS,allowing such performanceto surpass those of previously reported Mo-based catalysts.展开更多
Electrocatalytic carbon dioxide reduction(ECO_(2)RR)serves as a promising approach for converting CO_(2)into energy-dense fuels and high-value chemicals,garnering substantial interest across academic and industrial se...Electrocatalytic carbon dioxide reduction(ECO_(2)RR)serves as a promising approach for converting CO_(2)into energy-dense fuels and high-value chemicals,garnering substantial interest across academic and industrial sectors.Copper(Cu)-based electrocatalysts are widely acknowledged as highly effective for ECO_(2)RR,primarily due to their optimal adsorption energy for*CO.Nonetheless,significant challenges remain to be addressed in transitioning Cu-based catalysts from research settings to industrial applications,including the low stability and unavoidable side reactions.This article aims to i)systematically examine the deactivation mechanisms of Cu-based catalysts,including changes in valence states,surface poisoning,and restructuring(agglomeration,dissolution,Ostwald ripening);ii)provide a timely overview of cutting-edge strategies to enhance the stability of Cu-based catalysts,such as ligand effects,heteroatom doping,support optimization,size effect,and restructuring;iii)highlight critical areas and prospective development directions that warrant further exploration to expedite the industrial adoption of Cu-based catalysts in ECO_(2)RR.展开更多
In this study,the commonly used Cu or Mn-based low-temperature SCR catalysts were employed to investigate their different reaction behaviors in the presence of high-content water vapor.Experimental results reveal that...In this study,the commonly used Cu or Mn-based low-temperature SCR catalysts were employed to investigate their different reaction behaviors in the presence of high-content water vapor.Experimental results reveal that CuCeTi sample possesses superior water re sistance at low temperature compared with MnCeTi catalyst.Upon the introduction of water vapor,both catalysts exhibit a quick loss in deNOxefficiency,while that is more pronounced on MnCeTi sample.In addition,unlike CuCeTi sample,MnCeTi catalyst also shows a gradual deactivation tendency after initial quick activity loss.Characterization and simulation results indicate that H_(2)O is more easily adsorbed and dissociated on MnCeTi catalyst,showing stronger suppression on NH3adsorption,causing more serious initial deactivation.Furthermore,more abundant hydroxyl groups derived from dissociative adsorption of water on MnCeTi catalyst will lead to more NH4NO3deposition and the decrease in redox capacity.This is the main reason of gradual deactivation of MnCeTi catalyst at high-content water vapor.Such findings could pave a new way for development of highly efficient SCR catalysts with good water resistance for real application.展开更多
The implementation of embedded selective catalytic reduction(SCR)denitration in chain grate during iron ore pelletizing process obviates additional flue gas heating.However,the influence of gas components and alkali m...The implementation of embedded selective catalytic reduction(SCR)denitration in chain grate during iron ore pelletizing process obviates additional flue gas heating.However,the influence of gas components and alkali metal on SCR denitration requires attention.The SCR denitration behavior in the preheating section of chain grate was investigated,and the combined influence mechanisms of H_(2)O(g),SO_(2),and potassium were revealed.The results show that the presence of H_(2)O(g)and SO_(2) in the flue gas decreases the NO conversion rate of the catalyst from 96.3%to 79.5%,while potassium adsorbed on the catalyst surface further reduces the NO conversion rate to 74.1%.H_(2)O(g),SO_(2),and potassium in the flue gas form sulfate and potassium salt on the catalyst surface,blocking the pore structure,thereby decreasing the gas adsorption capacity of the catalyst.Moreover,SO_(2) and potassium engage in competitive adsorption and reaction with NH_(3) and NO at the active sites on the catalyst surface,reducing the content and activity of the catalyst effective component.Increasing the flue gas temperature can promote the decomposition of ammonium sulfate and ammonium bisulfate on the catalyst surface,but it has little effect on potassium.Additionally,potassium will exacerbate sulfur poisoning of the catalyst.Hence,the embedded SCR denitration process requires electrostatic precipitation to eliminate the adverse impacts of potassium and thermal regime optimization to raise flue gas temperature to 350℃,thereby increasing NO conversion rate exceeding 85%.展开更多
Cu-SSZ-13 small-pore zeolites have been commercialized for NO_(x) abatement in diesel engines,while they still suffer fromhydrothermal deactivation.To identify the changes occurring in catalysts during the whole hydro...Cu-SSZ-13 small-pore zeolites have been commercialized for NO_(x) abatement in diesel engines,while they still suffer fromhydrothermal deactivation.To identify the changes occurring in catalysts during the whole hydrothermal aging(HTA)process,the selective catalytic reduction by ammonia(NH3-SCR)performance of hydrothermally aged catalysts was investigated until total deactivation occurred.Through precisely identifying the alterations in the zeolite framework and active Cu sites during HTA,three stages were distinguished under progressively more severe HTA conditions,which were dealumination/transformation of active Cu species,CuO_(x) accumulation,and structural collapse.These three stages were found to cause a slight decrease,serious attenuation,and total deactivation of the deNO_(x) efficiency,which stemmed from the loss of Bronsted acid sites,reduction in the number of active Cu ion sites and structural collapse,respectively.This work also depicted simulated deactivation curves of Cu-SSZ-13 with various compositions during the HTA process,which helps in understanding the hydrothermal aging limits of catalysts with various Si/Al ratios and Cu loadings.展开更多
The reduction of carbon emissions in the steel industry is a significant challenge,and utilizing CO_(2) from carbon intensive steel industry off-gases for methanol production is a promising strategy for decarbonizatio...The reduction of carbon emissions in the steel industry is a significant challenge,and utilizing CO_(2) from carbon intensive steel industry off-gases for methanol production is a promising strategy for decarbonization.However,steelwork off-gases typically contain various impurities,including H_(2)S,which can deactivate commercial methanol synthesis catalysts,Cu/ZnO/Al_(2)O_(3)(CZA).Reverse water-gas shift(RWGS)reaction is the predominant side reaction in CO_(2) hydrogenation to methanol which can occur at ambient pressure,enabling the decouple of RWGS from methanol production at high pressure.Then,a series of activated CZA catalysts has been in-situ pretreated in 400 ppm H_(2)S/Ar at 250℃and tested for both RWGS reaction at ambient pressure and CO_(2) hydrogenation to methanol at high pressure.An innovative decoupling strategy was employed to isolate the RWGS reaction from the methanol synthesis process,enabling the investigation of the evolution of active site structures and the poisoning mechanism through elemental analysis,X-ray Diffraction,X-ray Photoelectron Spectroscopy,Fourier Transform Infrared Spectroscopy,Temperature Programmed Reduction and CO_(2) Temperature Programmed Desorption.The results indicate that there are different dynamic migration behaviors of ZnO_(x) in the two reaction systems,leading to different poisoning mechanisms.These interesting findings are beneficial to develop sulfur resistant and durable highly efficient catalysts for CO_(2) hydrogenation to methanol,promoting the carbon emission reduction in steel industry.展开更多
Catalyst deactivation due to coking is microscopically analyzed,then a model is presented,based upon the analogy between coke deposition and solid aggregation.The Monte Carlo simulation results show that the model ca...Catalyst deactivation due to coking is microscopically analyzed,then a model is presented,based upon the analogy between coke deposition and solid aggregation.The Monte Carlo simulation results show that the model can fit the experimental data in all cases.With this model,the mechanism of formation of coke with different shapes is derived and the relation between the catalytic activity and coke shape is theoretically demonstrated.In addition,the model described in this paper can also be used to simulate the catalyst preparation so as to make more useful and efficient catalysts.The model in this paper is very simple,with only two parameters that indicate the nature of catalyst deactivation.The extension of the model to more complicated systems is also discussed.展开更多
In industrial catalytic processes,coke deposition can cause catalyst deactivation by covering acid sites and/or blocking pores.The regeneration of deactivated catalysts,thereby removing the coke and simultaneously res...In industrial catalytic processes,coke deposition can cause catalyst deactivation by covering acid sites and/or blocking pores.The regeneration of deactivated catalysts,thereby removing the coke and simultaneously restoring the catalytic activity,is highly desired.Despite various chemical reactions and methods are available to remove coke,developing reliable,efficient,and economic regeneration methods for catalytic processes still remains a challenge in industrial practice.In this paper,the current progress of regeneration methods such as oxidation(air,ozone and oxynitride),gasification(carbon dioxide and water steam),and hydrogenation(hydrogen)is reviewed,which hopefully can shed some light on the design and optimization of catalysts and the related processes.展开更多
Recently, H_(2) has attracted increasing attention as green energy carrier holding the possibility to replace fossil fuel-based energy sources and thereby reduce CO_(2) emissions. Green hydrogen can be generated by wa...Recently, H_(2) has attracted increasing attention as green energy carrier holding the possibility to replace fossil fuel-based energy sources and thereby reduce CO_(2) emissions. Green hydrogen can be generated by water electrolysis using renewable energies like wind and solar power. When it is combusted, only water forms as by-product. However, the efficiency of water electrolysis is hampered by the anodic oxygen evolution reaction(OER) because of the slow kinetics which leads to a high overpotential. Therefore, many catalysts have been developed for OER to facilitate the kinetics and reduce the overpotential. In addition to electrocatalytic activity, the stability of the catalysts is imperative for industrial application and has been intensively studied. In this review, we cover recent findings on the stability and deactivation mechanisms of OER catalysts. We discuss the correlation between OER activity and stability, methodologies and experimental techniques to study the stability and deactivation as well as the deactivation mechanisms, together with factors influencing stability. Furthermore, strategies for stabilizing and regenerating OER catalysts as well as methods to predict stability are summarized. Finally, the review highlights emerging methodologies yet to be explored and future directions of stability studies and the design of highly stable OER catalysts.展开更多
Increasingly stringent regulations in many countries require effective reduction and control of NOx emissions. To meet these limits, various methods have been exploited, among which the selective catalytic reduction o...Increasingly stringent regulations in many countries require effective reduction and control of NOx emissions. To meet these limits, various methods have been exploited, among which the selective catalytic reduction of NOx using ammonia as the reduc- rant （NH3-SCR） is the most favored technology. High catalytic activity, N2 selectivity and resistance to deactivation by sulfur, alkaline metals and hydrothermal conditions are the optimal properties of a successful SCR catalyst. Rare earth oxides, particularly CeO2, have been increasingly used to improve the catalytic activity and resistance to deactivation of deNOx catalysts, both modifying tradi- tional vanadium catalysts, and also developing novel catalysts, especially for low temperature applications. This review summarized the open literature concerning recent research and development progresses in the application of rare earths for NH3-SCR of NOx. Additionally, the roles of rare earths in enhancing the performance of NH3-SCR catalyst were reviewed.展开更多
SO2 poisoning and regeneration of Mn-Ce/TiO2 catalyst prepared by a novel co-precipitation method for low temperature selective catalytic reduction （SCR） of NOx with ammonia were investigated in this study. When 700...SO2 poisoning and regeneration of Mn-Ce/TiO2 catalyst prepared by a novel co-precipitation method for low temperature selective catalytic reduction （SCR） of NOx with ammonia were investigated in this study. When 700 ppm SO2 was fed in, the Mn-Ce/TiO2 catalyst had good resistance to SO2, but the deactivation of Mn-Ce/TiO2 poisoned by SO2 still occurred. The NO conversion of Mn-Ce/TiO2 （the molar ra-tio of Ce to Ti is 0.075） catalyst decreased from 92.5% to 34.6% in 13 h. Characterizations of fresh and SO2-poisoned Mn-Ce/TiO2 catalysts were carried out by Brunauer-Emmett-Teller method （BET）, ion chromatography （IC）, X-ray photoelectron spectroscopy （XPS）, and X-ray diffraction （XRD）. The characterized results indicated that the deposition of sulfates and nitrates on the surface made the catalyst deactivated. Water washing, thermal regeneration and reductive regeneration were used to regenerate the deactivated Mn-Ce/TiO2. And water washing showed best performance on the regeneration of poisoned catalysts, especially with ultrasonic vibration. The Mn-Ce/TiO2 catalyst showed high stability under a series of deactivation-regeneration experiments for ten cycles.展开更多
The coking kinetics and reaction-regeneration on Zn/HZSM-5 （Zn/HZ） catalyst in the conversion of methanol to aromatics were investigated. The highest initial benzene, toluene and xylene （BTX） yield of ca. 67.7% wa...The coking kinetics and reaction-regeneration on Zn/HZSM-5 （Zn/HZ） catalyst in the conversion of methanol to aromatics were investigated. The highest initial benzene, toluene and xylene （BTX） yield of ca. 67.7% was obtained on fresh Zn/HZ catalyst, which showed the worst catalytic stability. The cycle of reaction-regeneration significantly modified the texture and acidity of Zn/HZ catalyst, which in turn affected its catalytic performance and coking behavior in methanol conversion to BTX. The residual carbon located on the surface of Zn/HZ catalyst led to the decrease of acid sites and the change on the acid sites distribution, which played an important roles on its activity and deactivation. It was found that the high B/L ratio and the low total acid sites concentration of the Zn/HZ catalyst favored to the high BTX yield and good catalytic stability in methanol conversion.展开更多
基金financially supported by the National Key R&D Program of China(2024YFB4105401)the National Natural Science Foundation of China(22372164,22288101 and 22072148)。
文摘Methanol-to-hydrocarbons(MTH)reaction comprises a set of crucial catalytic processes to produce light olefins,gasoline,or aromatics.MTH reaction is a classic example of reaction complexity in zeolite catalysis.The molecular understanding of reaction routes and deactivation mechanisms still encounters many challenges.Herein,we chose HZSM-22 zeolite with the simple one-dimensional 10-membered ring(10-MR)channel as a prototypical system,leveraging the spatial nanoconfinement effect of its unique pore architecture to minimize reaction complexity.The identification of the molecular structures of coke species with acene-,biphenyl-,or fluorene-typed structures was made possible through a combination of the advanced matrix-assisted laser desorption/ionization Fourier-transform ion cyclotron resonance mass spectrometry(MALDI FT-ICR MS)with the gas chromatography-mass spectrometer(GC-MS)technique.With this,we uncovered two modes of growth mechanism of coke molecules,i.e.,a stepwise route and a dehydrogenative coupling route.The findings deepen the mechanistic understanding of zeolite deactivation and provide a theoretical foundation for designing coke-resistant catalysts.
基金Dalian Science and Technology Talent Innovation Support Policy Implementation Plan High-Level Talent Team,No.2022RG18(to JL)the Science and Technology Plan Orientation of Liaoning Province,No.[2021]49(to JL)+1 种基金Dalian High-Level Talent Innovation Support Plan,No.2021RQ028(to CH)Natural Science Foundation of Liaoning Province,No.2022-BS-238(to CH).
文摘Stem cell therapy shows promise for treating brain injuries;neural stem cells in particular are capable of repairing damage by forming new nerve cells and supporting recovery.However,optimizing the implantation and functionality of these cells in damaged brain regions remains challenging.Silk fibroin,a natural protein derived from silkworm silk,is a biocompatible material with exceptional properties that are useful for tissue engineering.Its biodegradability,mechanical robustness,and ability to promote cell growth make it particularly valuable for biomedical applications.Silk fibroin nanomaterials,which comprise silk fibroin processed into nanostructures,offer enhanced surface area,improved loading capacity for bioactive molecules,and superior nanoscale interactions with cells compared with bulk silk fibroin materials.In this study,we first extracted human-derived neural stem cells from a 14-week-old human fetus.Then,neural stem cells were loaded with 1%silk fibroin nanomaterials,which was identified as the optimal concentration to support human-derived neural stem cell growth and release of neurotrophic factors.Finally,1%silk fibroin nanomaterials were implanted into a rat model of hypoxic-ischemic brain injury.The results showed that,compared with the treatment with human-derived neural stem cells alone,silk fibroin hydrogel carrying human-derived neural stem cells was significantly more effective at alleviating brain tissue damage,increasing neurotrophic factor secretion in the brain microenvironment,and promoting motor and cognitive function recovery.These findings suggest that silk fibroin nanomaterials loaded with human-derived neural stem cells could be used to treat hypoxic-ischemic encephalopathy.However,the mechanisms and related signaling pathways by which hydrogels combined with cells exert their reparative effects still require further in-depth investigation.
基金financially supported by National Natural Science Foundation of China(U21A20316).
文摘A 10%Ni/γ-Al_(2)O_(3)catalyst was prepared for dry reforming of methane.Sphericalγ-Al_(2)O_(3)particles having an average particle size of 60μm were used as the support and an iso-volume impregnation method was employed for the preparation.All activity-evaluation tests were conducted in a fluidized-bed quartz reactor at 0.1 MPa and variable temperatures and space velocities for 600 min.The results of the tests revealed that at 750℃ the catalyst activity showed an obviously accelerated decrease trend with the increase of space velocity.Ther-mogravimetric analysis of the spent catalysts revealed,however,that little carbon deposit formed in those spent samples that had experienced faster decreases in activity at higher space velocities.While these two facts together deny the possibility of carbon deposition leading to the accelerated activity decline at 750℃and high space velocities,increasing the CO_(2)/CH_(4)ratio of the feed was demonstrated to further accelerate the activity decrease.Meanwhile,XRD and XPS analyses of the spent catalyst samples revealed that oxidative transformation of metallic Ni in catalyst to Ni_(x)O(x≤1)species did occur in the reforming in the feed of CO_(2)/CH_(4)=1.5.All these results together have strongly revealed,for the first time,a conclusion as follows:it was the gradual oxidative transformation of active Ni sites in 10%Ni/γ-Al_(2)O_(3)catalyst to inactive Ni oxide species to cause a continuous decline of its dry reforming activity in fluidized-bed operation mode and at 750℃ and high space velocity condition.
基金financial support from the National Research Council of Science&Technology(NST)grant funded by the Ministry of Science and ICT,Republic of Korea(CAP21012-100)the Korea Institute of Energy Technology Evaluation and Planning(KETEP),under the Ministry of Trade,Industry&Energy(MOTIE),Republic of Korea(20224C10300010)the KETEP grant funded by the MOTIE(20224000000440,Sector coupling energy industry advancement manpower training program)。
文摘The metal oxide promoter decisively influences the overall performance of Fe catalysts in the direct hydrogenation of CO_(2)to C_(5+)hydrocarbons.However,the roles of metal oxide promoter for Fe catalysts,particularly ZrO_(2),have rarely been investigated.To plug this knowledge gap,a new Fe catalyst promoted with Na and partially reduced ZrO_(x)(Na-FeZrO_(x-9))was developed in this study;the catalyst helped produce C_(5+)hydrocarbons in remarkably high yield(26.3%at 360℃).In contrast to ZrO_(x)-free Fe-oxide,NaFeZrO_(x)-9 exhibited long-term stability for CO_(2)hydrogenation(750 h on-stream).The findings revealed multiple roles of ZrO_(x).Notably,ZrO_(x)decorated the Fe-oxide particles after calcination,thereby suppressing excess particle aggregation during the reaction,and acted as a"coke remover"to eliminate the carbon deposited on the catalyst surface.Additionally,oxygen vacancy(O_(v))sites in ZrO_(x)and electron transfer from ZrO_(x)to Fe sites facilitated the adsorption of CO_(2)at the Zr-Fe interface.
基金supports by the National Key Research and Development Program of China(2021YFA1501204)the project of SINOPEC RIPP Co.Ltd(PR20230230).
文摘Autocatalysis from the by-product metal sulfides plays a critical role in the residual oil hydrotreating(RHT)process.However,it has not been considered to build the catalyst deactivation models,which probably is one important reason that the widely used S-type deactivation models are inaccurate in predicting some RHT processes'deactivation profiles.A three-stage catalyst deactivation model was first developed to fill this gap based on the mechanism inferred from the experimental and literature data.This model accounts for active site formation from by-product metal sulfides,deactivation due to active site coverage by coke formation and metal deposition,active site poisoning by highly-adsorbed species,active phase sintering,and diffusion resistance from the pore blockage at the same time,resulting in a function of dimensionless metals-on-catalyst.Then,the effectiveness of the proposed model was evaluated using the industrial data of an RHT unit and the experimental data from the literature,either in combination with reaction kinetics or independently.Results showed that RHT processes with clear autocatalytic effects may display different types of deactivation profiles from the traditional"S"shape.However,the proposed model was able to accurately track the entire deactivation curve of the RHT process and well predict the product properties.This approach yields valuable insights into the intricate autocatalytic effect that remarkably contributes to the performance modification of RHT catalysts.It is highly recommended that further research should be conducted on this topic,as it shows great potential to significantly advance catalyst and process development.
文摘Coke formation is the primary cause of zeolite deactivation in industrial catalysis,yet the structural identity,spatial location and molecular routes of polycyclic aromatic hydrocarbons(PAHs)within confined zeolite pores remain elusive.Here,by coupling matrix-assisted laser desorption/ionization Fourier-transform ion cyclotron resonance mass spectrometry with multi-dimensional chemical imaging,we unveil a channel-passing growth mechanism for PAHs in ZSM-5 zeolites during methanol conversion through identifying the molecular fingerprints of larger PAHs,pinpointing and visualizing their 3D location and spatiotemporal evolution trajectory with atomic resolution and at both channel and single-crystal scales.Confined aromatic entities cross-link with each other,culminating in multicore PAH chains as the both thermodynamically favorable and kinetically trapped host-vip entanglement wrought and templated by the defined molecular-scale constrained microenvironments of zeolite.The mechanistic concept proves general across both channel-and cage-structured zeolite materials.Our multiscale deactivating model based on the full-picture coke structure-location correlations—spanning atom,molecule,channel/cage and single crystal scales—would shed new light on the intertwined chemical and physical processes in catalyst deactivation.This work not only resolves long-standing puzzles in coke formation but also provides design principles for coke-resistant zeolites.The methods and insights would rekindle interest in confinement effects and host-vip chemistry across broader chemistry fields beyond catalysis and carbon materials.
文摘In this study,we investigated Mo-impregnated H-MCM-22 catalysts(denoted Mo/M)for methanedehydroaromatization(MDA)to produce aromatics such as benzene and toluene(BT).We attemptedto improve the performance of the MDA catalysts by reducing the amount of Brönsted acidsites(BAS)of the H-MCM-22 supports via hydrothermal dealumination.Among the prepared catalysts,an optimal hydrothermal treatment(HT)of H-MCM-22 supports at 400℃,followed by Moimpregnation(denoted Mo/M_400),resulted in a reduced and optimal amount of BAS,along with acomparable Mo distribution to Mo/M.Further,Mo/M_400 enhanced BT formation rates(maximumBT formation rate of 5.23 vs.4.73 mmolBT·g^(−1)·h^(−1) for Mo/M);it appears that dealumination-inducedreduction in the quantity of BAS altered their spatial interaction with active Mo species,promotingBT and naphthalene formation.Interestingly,the lifetime of intermediate C_(2)(ethane and ethylene)formation was also improved for Mo/M_400.Rigorous coke analyses revealed that the decreasedcoke content in the aromatic-selective 10-membered-ring(10-MR)pores,as well as the ability ofthe 12-MR pores to accommodate coke deposits over a longer reaction time,improved the stabilityof Mo/M_400.Nonetheless,for all catalysts,the deactivations of BAS,and subsequently,the activeMo sites were mainly ascribed to coke deposition.The overall enhancement in MDA performance byMo/M_400 was attributed to the advantages of the optimally reduced BAS,allowing such performanceto surpass those of previously reported Mo-based catalysts.
基金support from the Technology Project of the State Grid Zhejiang Electric Power Company,Ltd.(No.B311DS230005).
文摘Electrocatalytic carbon dioxide reduction(ECO_(2)RR)serves as a promising approach for converting CO_(2)into energy-dense fuels and high-value chemicals,garnering substantial interest across academic and industrial sectors.Copper(Cu)-based electrocatalysts are widely acknowledged as highly effective for ECO_(2)RR,primarily due to their optimal adsorption energy for*CO.Nonetheless,significant challenges remain to be addressed in transitioning Cu-based catalysts from research settings to industrial applications,including the low stability and unavoidable side reactions.This article aims to i)systematically examine the deactivation mechanisms of Cu-based catalysts,including changes in valence states,surface poisoning,and restructuring(agglomeration,dissolution,Ostwald ripening);ii)provide a timely overview of cutting-edge strategies to enhance the stability of Cu-based catalysts,such as ligand effects,heteroatom doping,support optimization,size effect,and restructuring;iii)highlight critical areas and prospective development directions that warrant further exploration to expedite the industrial adoption of Cu-based catalysts in ECO_(2)RR.
基金Project supported by National Key R&D Program of China(2022YFC3701600)National Natural Science Foundation of China(22276162 and 22306072)+1 种基金China Postdoctoral Science Foundation(2023M731441)Young Talent Fund of Jiaxing Science and Technology Project(2023AY40030)。
文摘In this study,the commonly used Cu or Mn-based low-temperature SCR catalysts were employed to investigate their different reaction behaviors in the presence of high-content water vapor.Experimental results reveal that CuCeTi sample possesses superior water re sistance at low temperature compared with MnCeTi catalyst.Upon the introduction of water vapor,both catalysts exhibit a quick loss in deNOxefficiency,while that is more pronounced on MnCeTi sample.In addition,unlike CuCeTi sample,MnCeTi catalyst also shows a gradual deactivation tendency after initial quick activity loss.Characterization and simulation results indicate that H_(2)O is more easily adsorbed and dissociated on MnCeTi catalyst,showing stronger suppression on NH3adsorption,causing more serious initial deactivation.Furthermore,more abundant hydroxyl groups derived from dissociative adsorption of water on MnCeTi catalyst will lead to more NH4NO3deposition and the decrease in redox capacity.This is the main reason of gradual deactivation of MnCeTi catalyst at high-content water vapor.Such findings could pave a new way for development of highly efficient SCR catalysts with good water resistance for real application.
基金financially supported by the National Key Research and Development Program of China(No.2023YFC3707002)Hunan Provincial Innovation Foundation for Postgraduate(No.QL20220069)Postgraduate Innovative Project of Central South University(No.1053320214756).
文摘The implementation of embedded selective catalytic reduction(SCR)denitration in chain grate during iron ore pelletizing process obviates additional flue gas heating.However,the influence of gas components and alkali metal on SCR denitration requires attention.The SCR denitration behavior in the preheating section of chain grate was investigated,and the combined influence mechanisms of H_(2)O(g),SO_(2),and potassium were revealed.The results show that the presence of H_(2)O(g)and SO_(2) in the flue gas decreases the NO conversion rate of the catalyst from 96.3%to 79.5%,while potassium adsorbed on the catalyst surface further reduces the NO conversion rate to 74.1%.H_(2)O(g),SO_(2),and potassium in the flue gas form sulfate and potassium salt on the catalyst surface,blocking the pore structure,thereby decreasing the gas adsorption capacity of the catalyst.Moreover,SO_(2) and potassium engage in competitive adsorption and reaction with NH_(3) and NO at the active sites on the catalyst surface,reducing the content and activity of the catalyst effective component.Increasing the flue gas temperature can promote the decomposition of ammonium sulfate and ammonium bisulfate on the catalyst surface,but it has little effect on potassium.Additionally,potassium will exacerbate sulfur poisoning of the catalyst.Hence,the embedded SCR denitration process requires electrostatic precipitation to eliminate the adverse impacts of potassium and thermal regime optimization to raise flue gas temperature to 350℃,thereby increasing NO conversion rate exceeding 85%.
基金supported by the National Key R&D Program of China(No.2023YFC3707201)the National Natural Science Foundation of China(No.52270112)the National Energy-Saving and Low-Carbon Materials Production and Application Demonstration Platform Program(No.TC220H06N).
文摘Cu-SSZ-13 small-pore zeolites have been commercialized for NO_(x) abatement in diesel engines,while they still suffer fromhydrothermal deactivation.To identify the changes occurring in catalysts during the whole hydrothermal aging(HTA)process,the selective catalytic reduction by ammonia(NH3-SCR)performance of hydrothermally aged catalysts was investigated until total deactivation occurred.Through precisely identifying the alterations in the zeolite framework and active Cu sites during HTA,three stages were distinguished under progressively more severe HTA conditions,which were dealumination/transformation of active Cu species,CuO_(x) accumulation,and structural collapse.These three stages were found to cause a slight decrease,serious attenuation,and total deactivation of the deNO_(x) efficiency,which stemmed from the loss of Bronsted acid sites,reduction in the number of active Cu ion sites and structural collapse,respectively.This work also depicted simulated deactivation curves of Cu-SSZ-13 with various compositions during the HTA process,which helps in understanding the hydrothermal aging limits of catalysts with various Si/Al ratios and Cu loadings.
基金supported by the National Natural Science Foundation of China(Nos.22276060 and 21976059)Guangdong Basic and Applied Basic Research Foundation(No.2024A1515012636)China Scholarship Council Scholarship(No.201906155006)。
文摘The reduction of carbon emissions in the steel industry is a significant challenge,and utilizing CO_(2) from carbon intensive steel industry off-gases for methanol production is a promising strategy for decarbonization.However,steelwork off-gases typically contain various impurities,including H_(2)S,which can deactivate commercial methanol synthesis catalysts,Cu/ZnO/Al_(2)O_(3)(CZA).Reverse water-gas shift(RWGS)reaction is the predominant side reaction in CO_(2) hydrogenation to methanol which can occur at ambient pressure,enabling the decouple of RWGS from methanol production at high pressure.Then,a series of activated CZA catalysts has been in-situ pretreated in 400 ppm H_(2)S/Ar at 250℃and tested for both RWGS reaction at ambient pressure and CO_(2) hydrogenation to methanol at high pressure.An innovative decoupling strategy was employed to isolate the RWGS reaction from the methanol synthesis process,enabling the investigation of the evolution of active site structures and the poisoning mechanism through elemental analysis,X-ray Diffraction,X-ray Photoelectron Spectroscopy,Fourier Transform Infrared Spectroscopy,Temperature Programmed Reduction and CO_(2) Temperature Programmed Desorption.The results indicate that there are different dynamic migration behaviors of ZnO_(x) in the two reaction systems,leading to different poisoning mechanisms.These interesting findings are beneficial to develop sulfur resistant and durable highly efficient catalysts for CO_(2) hydrogenation to methanol,promoting the carbon emission reduction in steel industry.
基金Supported by the National Natural Science Foundation of China(No.2 97760 38)
文摘Catalyst deactivation due to coking is microscopically analyzed,then a model is presented,based upon the analogy between coke deposition and solid aggregation.The Monte Carlo simulation results show that the model can fit the experimental data in all cases.With this model,the mechanism of formation of coke with different shapes is derived and the relation between the catalytic activity and coke shape is theoretically demonstrated.In addition,the model described in this paper can also be used to simulate the catalyst preparation so as to make more useful and efficient catalysts.The model in this paper is very simple,with only two parameters that indicate the nature of catalyst deactivation.The extension of the model to more complicated systems is also discussed.
文摘In industrial catalytic processes,coke deposition can cause catalyst deactivation by covering acid sites and/or blocking pores.The regeneration of deactivated catalysts,thereby removing the coke and simultaneously restoring the catalytic activity,is highly desired.Despite various chemical reactions and methods are available to remove coke,developing reliable,efficient,and economic regeneration methods for catalytic processes still remains a challenge in industrial practice.In this paper,the current progress of regeneration methods such as oxidation(air,ozone and oxynitride),gasification(carbon dioxide and water steam),and hydrogenation(hydrogen)is reviewed,which hopefully can shed some light on the design and optimization of catalysts and the related processes.
基金support by the German Federal Ministry of Education and Research (BMBF) (H2Giga QT1.1 PrometH2eusFKZ 03HY105A)the China Scholarship Council for financial support。
文摘Recently, H_(2) has attracted increasing attention as green energy carrier holding the possibility to replace fossil fuel-based energy sources and thereby reduce CO_(2) emissions. Green hydrogen can be generated by water electrolysis using renewable energies like wind and solar power. When it is combusted, only water forms as by-product. However, the efficiency of water electrolysis is hampered by the anodic oxygen evolution reaction(OER) because of the slow kinetics which leads to a high overpotential. Therefore, many catalysts have been developed for OER to facilitate the kinetics and reduce the overpotential. In addition to electrocatalytic activity, the stability of the catalysts is imperative for industrial application and has been intensively studied. In this review, we cover recent findings on the stability and deactivation mechanisms of OER catalysts. We discuss the correlation between OER activity and stability, methodologies and experimental techniques to study the stability and deactivation as well as the deactivation mechanisms, together with factors influencing stability. Furthermore, strategies for stabilizing and regenerating OER catalysts as well as methods to predict stability are summarized. Finally, the review highlights emerging methodologies yet to be explored and future directions of stability studies and the design of highly stable OER catalysts.
基金supported by National Natural Science Foundation of China(51202126)Postdoctoral Science Foundation of China(2012M520266)Strategic Emerging Industry Development Funds of Shenzhen(JCYJ20120619152738634)
文摘Increasingly stringent regulations in many countries require effective reduction and control of NOx emissions. To meet these limits, various methods have been exploited, among which the selective catalytic reduction of NOx using ammonia as the reduc- rant （NH3-SCR） is the most favored technology. High catalytic activity, N2 selectivity and resistance to deactivation by sulfur, alkaline metals and hydrothermal conditions are the optimal properties of a successful SCR catalyst. Rare earth oxides, particularly CeO2, have been increasingly used to improve the catalytic activity and resistance to deactivation of deNOx catalysts, both modifying tradi- tional vanadium catalysts, and also developing novel catalysts, especially for low temperature applications. This review summarized the open literature concerning recent research and development progresses in the application of rare earths for NH3-SCR of NOx. Additionally, the roles of rare earths in enhancing the performance of NH3-SCR catalyst were reviewed.
基金financially supported by the Research Project of China Guodian Corporation (No.D11T22)
文摘SO2 poisoning and regeneration of Mn-Ce/TiO2 catalyst prepared by a novel co-precipitation method for low temperature selective catalytic reduction （SCR） of NOx with ammonia were investigated in this study. When 700 ppm SO2 was fed in, the Mn-Ce/TiO2 catalyst had good resistance to SO2, but the deactivation of Mn-Ce/TiO2 poisoned by SO2 still occurred. The NO conversion of Mn-Ce/TiO2 （the molar ra-tio of Ce to Ti is 0.075） catalyst decreased from 92.5% to 34.6% in 13 h. Characterizations of fresh and SO2-poisoned Mn-Ce/TiO2 catalysts were carried out by Brunauer-Emmett-Teller method （BET）, ion chromatography （IC）, X-ray photoelectron spectroscopy （XPS）, and X-ray diffraction （XRD）. The characterized results indicated that the deposition of sulfates and nitrates on the surface made the catalyst deactivated. Water washing, thermal regeneration and reductive regeneration were used to regenerate the deactivated Mn-Ce/TiO2. And water washing showed best performance on the regeneration of poisoned catalysts, especially with ultrasonic vibration. The Mn-Ce/TiO2 catalyst showed high stability under a series of deactivation-regeneration experiments for ten cycles.
基金supported by the National Ministry of Education(NCET-10-878)Shaanxi"13115"Innovation Project(2009ZDKJ-70)Shaanxi Key Innovation Project(2011ZKC4-08)
文摘The coking kinetics and reaction-regeneration on Zn/HZSM-5 （Zn/HZ） catalyst in the conversion of methanol to aromatics were investigated. The highest initial benzene, toluene and xylene （BTX） yield of ca. 67.7% was obtained on fresh Zn/HZ catalyst, which showed the worst catalytic stability. The cycle of reaction-regeneration significantly modified the texture and acidity of Zn/HZ catalyst, which in turn affected its catalytic performance and coking behavior in methanol conversion to BTX. The residual carbon located on the surface of Zn/HZ catalyst led to the decrease of acid sites and the change on the acid sites distribution, which played an important roles on its activity and deactivation. It was found that the high B/L ratio and the low total acid sites concentration of the Zn/HZ catalyst favored to the high BTX yield and good catalytic stability in methanol conversion.
