Larger amounts of alkalis, alkali earth metals and sulfides in flue gas from glass furnace were easier to deactivate selective catalytic reduction （SCR） catalyst compared to the flue gases from other stationary sour...Larger amounts of alkalis, alkali earth metals and sulfides in flue gas from glass furnace were easier to deactivate selective catalytic reduction （SCR） catalyst compared to the flue gases from other stationary sources. Catalyst regeneration has been an emerging research topic for flue gas denitrification in glass furnace. Regeneration of the deactivated TiO2-ZrO2-CeO2 /Al2TiO 5 -TiO2-SiO2 （ATS） complex phase ceramics catalysts used for NH3 -SCR of NO x in glass furnace was studied in this work. Effects of regeneration methods, including washing with different aqueous solutions and sulfuric acid, thermal regeneration, thermal reduction regeneration, and thermal regeneration with SO2 , on catalytic performance were comparatively investigated. In comparison of catalytic activities between the catalysts before and after regeneration, results showed that washing was the most effective regeneration method, and the sulfuric acid concentration of the washing solution was an important factor. Washing time directly affected catalyst regeneration efficiency and catalyst life. The regenerated TiO2-ZrO2 -CeO2 /ATS catalyst regained more than 90% NO conversion after being washed with 10 wt.% H2SO4 for 30 min.展开更多
In this paper, a low-cost activated carbon(AC) was prepared from deactivated resin catalyst(DRC) for methyl tert-butyl ether(MTBE) synthesis through carbonization and subsequent steam activation treatment. The activat...In this paper, a low-cost activated carbon(AC) was prepared from deactivated resin catalyst(DRC) for methyl tert-butyl ether(MTBE) synthesis through carbonization and subsequent steam activation treatment. The activated carbon was characterized in detail. After loading various transition metals, including Cu^(2+), Ag+, Co^(2+), Ni^(2+), Zn^(2+), and Fe^(3+) via the ultrasonic-assisted impregnation method, a series of metal-loaded adsorbents(xM-AC) were obtained and their dimethyl sulfide(DMS) adsorption performance was investigated in a batch system. Among these adsorbents, 15Cu-AC presented a superior DMS adsorption capacity equating to 58.986 mg/g due to the formation of S-M(σ) bonds between Cu^(2+) and sulfur atoms of DMS as confirmed by the Raman spectra and kinetic study.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
We compared the activities of functional regions of the brain in the Deqi versus non-Deqi state, as reported by physicians and subjects cludng acupuncture, Twelve healthy volunteers received sham and true needling at ...We compared the activities of functional regions of the brain in the Deqi versus non-Deqi state, as reported by physicians and subjects cludng acupuncture, Twelve healthy volunteers received sham and true needling at the Waiguan （TE5） acupoint. Real-time cerebral functional MRI showed that compared with non-sensation after sham needling, true needling activated Brodmann areas 3, 6, 8, 9, 10, 11, 13, 20, 21, 37, 39, 40, 43, and 47, the head of the caudate nucleus, the parahippocampal gyrus, thalamus and red nucleus. True needling also deactivated Brodmann areas 1,2, 3, 4, 5, 6, 7, 9. 10. 18.24.31.40 and 46.展开更多
Mercury-containing catalysts are widely used for acetylene hydrochlorination in China. Surface chemical characteristics of the fresh low-level mercury catalysts and spent low-level mercury catalysts were compared usin...Mercury-containing catalysts are widely used for acetylene hydrochlorination in China. Surface chemical characteristics of the fresh low-level mercury catalysts and spent low-level mercury catalysts were compared using multiple characterization methods. Pore blockage and active site coverage caused by chlorine-containing organics are responsible for catalyst deactivation. The reactions of chloroethylene and acetylene with chlorine free radical can generate chlorine-containing organic species. SiO_2 and functional groups on activated carbon contribute to the generation of carbon deposition. No significant reduction in the total content of mercury was observed after catalyst deactivation, while there was mercury loss locally. The irreversible loss of HgCl_2 caused by volatilization, reduction and poisoning of elements S and P also can lead to catalyst deactivation. Si, Al, Ca and Fe oxides are scattered on the activated carbon. Active components are still uniformly absorbed on activated carbon after catalyst deactivation.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 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
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
Molecular sieve catalysts,owing to their unique chemical properties,are widely used as catalysts among various catalytic reactions.Abundant Br?nsted acid sites in molecular sieve catalysts usually enable active compon...Molecular sieve catalysts,owing to their unique chemical properties,are widely used as catalysts among various catalytic reactions.Abundant Br?nsted acid sites in molecular sieve catalysts usually enable active components to disperse well on the catalyst surface,and help to adsorb a large number of gas molecules to achieve maximum catalytic performance.Therefore,a variety of molecular sieve catalysts have been developed and used in the selective catalytic reduction of NO_(x)by NH_(3)(NH_(3)-SCR).For example,Cu molecular sieve catalysts such as Cu-SSZ-13 and Cu-SAPO-34 with wide temperature windows and stable structure are considered and applied as commercial catalysts for NO_(x)removal in diesel vehicles for a long time.Although molecular sieve catalysts possess many advantages,they still cannot avoid the serious deactivation caused by various factors in practical applications.In this review,reasons leading to the deactivation of molecular sieve catalysts for NO_(x)reduction in actual working conditions were concluded.The deactivation mechanisms of molecular sieve catalysts for NO_(x)reduction were analyzed and the corresponding anti-deactivation strategies were summarized.Finally,challenges and prospects of molecular sieve catalysts for NO_(x)reduction were also proposed.展开更多
A series of model catalysts were obtained by treating commercial fresh and spent catalysts unloaded from the factory with different methods, including green oil dipping, extraction and high-temperature regeneration;fi...A series of model catalysts were obtained by treating commercial fresh and spent catalysts unloaded from the factory with different methods, including green oil dipping, extraction and high-temperature regeneration;finally, the deactivation behavior of the commercial catalyst for acetylene hydrogenation were studied. The influence of various possible deactivation factors on the catalytic performance was elucidated via detailed structural characterization, surface composition analysis, and activity evaluation.The results showed that green oil, carbon deposit and sintering of active metal were the main reasons for deactivation, among which green oil and carbon deposit led to rapid deactivation, while the activity could be recovered after regeneration by high-temperature calcination. The sintering of active metal components was attributed to the high-temperature regeneration in hydrothermal conditions, which was slow but irreversible and accounted for permanent deactivation. Thus, optimizing the regeneration is expected to extend the service life of the commercial catalyst.展开更多
Hydrogen(H_(2)) has been regarded as a promising alternative to fossil-fuel energy.Green H_(2) produced via water electrolysis(WE)powered by renewable energy could achieve a zero-carbon footprint.Considerable attentio...Hydrogen(H_(2)) has been regarded as a promising alternative to fossil-fuel energy.Green H_(2) produced via water electrolysis(WE)powered by renewable energy could achieve a zero-carbon footprint.Considerable attention has been focused on developing highly active catalysts to facilitate the reaction kinetics and improve the energy efficiency of WE.However,the stability of the electrocatalysts hampers the commercial viability of WE.Few studies have elucidated the origin of catalyst degradation.In this review,we first discuss the WE mechanism,including anodic oxygen evolution reaction(OER)and cathodic hydrogen evolution reaction(HER).Then,we provide strategies used to enhance the stability of electrocatalysts.After that,the deactivation mechanisms of the typical commercialized HER and OER catalysts,including Pt,Ni,RuO_(2),and IrO_(2),are summarized.Finally,the influence of fluctuating energy on catalyst degradation is highlighted and in situ characterization methodologies for understanding the dynamic deactivation processes are described.展开更多
Hydrogen sulfide(H_(2)S) not only presents significant environmental concerns but also induces severe corrosion in industrial equipment,even at low concentrations.Among various technologies,the selective oxidation of ...Hydrogen sulfide(H_(2)S) not only presents significant environmental concerns but also induces severe corrosion in industrial equipment,even at low concentrations.Among various technologies,the selective oxidation of hydrogen sulfide(SOH_(2)S) to elemental sulfur(S) has emerged as a sustainable and environmentally friendly solution.Due to its unique properties,iron oxide has been extensively investigated as a catalyst for SOH_(2)S;however,rapid deactivation has remained a significant drawback.The causes of iron oxide-based catalysts deactivation mechanisms in SOH_(2)S,including sulfur or sulfate deposition,the transformation of iron species,sintering and excessive oxygen vacancy formation,and active site loss,are thoroughly examined in this review.By focusing on the deactivation mechanisms,this review aims to provide valuable insights into enhancing the stability and efficiency of iron-based catalysts for SOH_(2)S.展开更多
It is well known that calcium oxide (CaO) has better catalytic efficiency than most heterogeneous catalysts in many transesterification reactions. However, the gradual deactivation problem prevents its large-scale app...It is well known that calcium oxide (CaO) has better catalytic efficiency than most heterogeneous catalysts in many transesterification reactions. However, the gradual deactivation problem prevents its large-scale application in industry. In this paper, the deactivation mechanism of CaO in a fixed-bed reactor is investigated based on the transesterification reaction of propylene carbonate and methanol. The leaching amount of CaO during the reaction was estimated by the concentration of Ca in the products. The pretreated and recovered catalysts were characterized by FT-IR, XRD, TG-MS and SEM-EDS. It is evident from experiments and characterization that the deactivation process of CaO is accompanied by the leaching of calcium species and the generation of CaCO3, which are also verified by DFT calculations. At high temperature and high weight hourly space velocity, the deactivation was attributed to the formation of dense CaCO3 shell, which prevents the contact between the feedstock and the active species inside.展开更多
Zeolites are a promising support for Pd catalysts in leanmethane(CH_(4))combustion.Herein,three types of zeolites(H-MOR,H-ZSM-5 and H-Y)were selected to estimate their structural effects and deactivation mechanisms in...Zeolites are a promising support for Pd catalysts in leanmethane(CH_(4))combustion.Herein,three types of zeolites(H-MOR,H-ZSM-5 and H-Y)were selected to estimate their structural effects and deactivation mechanisms in CH_(4)combustion.We show that variations in zeolite structure and surface acidity led to distinct changes in Pd states.Pd/H-MOR with external high-dispersing Pd nanoparticles exhibited the best apparent activity,with activation energy(Ea)at 73 kJ/mol,while Pd/H-ZSM-5 displayed the highest turnover frequency(TOF)at 19.6×10^(−3)sec^(−1),presumably owing to its large particles with more step sites providing active sites in one particle for CH_(4)activation.Pd/H-Y with dispersed PdO within pore channels and/or Pd2+ions on ion-exchange sites yielded the lowest apparent activity and TOF.Furthermore,Pd/H-MOR and Pd/H-ZSM-5 were both stable under a dry condition,but introducing 3 vol.%H_(2)O caused the CH_(4)conversion rate on Pd/H-MOR drop from 100%to 63%and that on Pd/H-ZSM-5 decreased remarkably from 82%to 36%.The former was shown to originate fromzeolite structural dealumination,and the latter principally owed to Pd aggregation and the loss of active PdO.展开更多
基金Project supported by National Natural Science Foundation of China(51272105,51172107,21106071)the New Teachers'Fund for Doctor Stations Sponsored by the Ministry of Education of China(20113221120004)+1 种基金the National Key Technology R&D Program of China(2012BAE01B03)the Supporting Program for Sci&Tech Research of Jiangsu Province of China(2011023)
文摘Larger amounts of alkalis, alkali earth metals and sulfides in flue gas from glass furnace were easier to deactivate selective catalytic reduction （SCR） catalyst compared to the flue gases from other stationary sources. Catalyst regeneration has been an emerging research topic for flue gas denitrification in glass furnace. Regeneration of the deactivated TiO2-ZrO2-CeO2 /Al2TiO 5 -TiO2-SiO2 （ATS） complex phase ceramics catalysts used for NH3 -SCR of NO x in glass furnace was studied in this work. Effects of regeneration methods, including washing with different aqueous solutions and sulfuric acid, thermal regeneration, thermal reduction regeneration, and thermal regeneration with SO2 , on catalytic performance were comparatively investigated. In comparison of catalytic activities between the catalysts before and after regeneration, results showed that washing was the most effective regeneration method, and the sulfuric acid concentration of the washing solution was an important factor. Washing time directly affected catalyst regeneration efficiency and catalyst life. The regenerated TiO2-ZrO2 -CeO2 /ATS catalyst regained more than 90% NO conversion after being washed with 10 wt.% H2SO4 for 30 min.
基金financially supported by the National Natural Science Foundation of China (No. 21276086)
文摘In this paper, a low-cost activated carbon(AC) was prepared from deactivated resin catalyst(DRC) for methyl tert-butyl ether(MTBE) synthesis through carbonization and subsequent steam activation treatment. The activated carbon was characterized in detail. After loading various transition metals, including Cu^(2+), Ag+, Co^(2+), Ni^(2+), Zn^(2+), and Fe^(3+) via the ultrasonic-assisted impregnation method, a series of metal-loaded adsorbents(xM-AC) were obtained and their dimethyl sulfide(DMS) adsorption performance was investigated in a batch system. Among these adsorbents, 15Cu-AC presented a superior DMS adsorption capacity equating to 58.986 mg/g due to the formation of S-M(σ) bonds between Cu^(2+) and sulfur atoms of DMS as confirmed by the Raman spectra and kinetic study.
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supported by the National Basic Research Program of China (973 Program), No. 2006CB504505,2012CB518504the Third Key Construction Program of"211 Project" of Guangdong Province
文摘We compared the activities of functional regions of the brain in the Deqi versus non-Deqi state, as reported by physicians and subjects cludng acupuncture, Twelve healthy volunteers received sham and true needling at the Waiguan （TE5） acupoint. Real-time cerebral functional MRI showed that compared with non-sensation after sham needling, true needling activated Brodmann areas 3, 6, 8, 9, 10, 11, 13, 20, 21, 37, 39, 40, 43, and 47, the head of the caudate nucleus, the parahippocampal gyrus, thalamus and red nucleus. True needling also deactivated Brodmann areas 1,2, 3, 4, 5, 6, 7, 9. 10. 18.24.31.40 and 46.
基金Supported by the National Science Fund for Excellent Young Scholars of China(No.51522405)
文摘Mercury-containing catalysts are widely used for acetylene hydrochlorination in China. Surface chemical characteristics of the fresh low-level mercury catalysts and spent low-level mercury catalysts were compared using multiple characterization methods. Pore blockage and active site coverage caused by chlorine-containing organics are responsible for catalyst deactivation. The reactions of chloroethylene and acetylene with chlorine free radical can generate chlorine-containing organic species. SiO_2 and functional groups on activated carbon contribute to the generation of carbon deposition. No significant reduction in the total content of mercury was observed after catalyst deactivation, while there was mercury loss locally. The irreversible loss of HgCl_2 caused by volatilization, reduction and poisoning of elements S and P also can lead to catalyst deactivation. Si, Al, Ca and Fe oxides are scattered on the activated carbon. Active components are still uniformly absorbed on activated carbon after catalyst deactivation.
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the support from the National Natural Science Foundation of China(No.22125604)the Chenguang Program supported by Shanghai Education Development Foundation and Shanghai Municipal Education Commission(No.22Z00354)。
文摘Molecular sieve catalysts,owing to their unique chemical properties,are widely used as catalysts among various catalytic reactions.Abundant Br?nsted acid sites in molecular sieve catalysts usually enable active components to disperse well on the catalyst surface,and help to adsorb a large number of gas molecules to achieve maximum catalytic performance.Therefore,a variety of molecular sieve catalysts have been developed and used in the selective catalytic reduction of NO_(x)by NH_(3)(NH_(3)-SCR).For example,Cu molecular sieve catalysts such as Cu-SSZ-13 and Cu-SAPO-34 with wide temperature windows and stable structure are considered and applied as commercial catalysts for NO_(x)removal in diesel vehicles for a long time.Although molecular sieve catalysts possess many advantages,they still cannot avoid the serious deactivation caused by various factors in practical applications.In this review,reasons leading to the deactivation of molecular sieve catalysts for NO_(x)reduction in actual working conditions were concluded.The deactivation mechanisms of molecular sieve catalysts for NO_(x)reduction were analyzed and the corresponding anti-deactivation strategies were summarized.Finally,challenges and prospects of molecular sieve catalysts for NO_(x)reduction were also proposed.
基金the financial support from the Sinopec Catalyst Co.Ltd.,China。
文摘A series of model catalysts were obtained by treating commercial fresh and spent catalysts unloaded from the factory with different methods, including green oil dipping, extraction and high-temperature regeneration;finally, the deactivation behavior of the commercial catalyst for acetylene hydrogenation were studied. The influence of various possible deactivation factors on the catalytic performance was elucidated via detailed structural characterization, surface composition analysis, and activity evaluation.The results showed that green oil, carbon deposit and sintering of active metal were the main reasons for deactivation, among which green oil and carbon deposit led to rapid deactivation, while the activity could be recovered after regeneration by high-temperature calcination. The sintering of active metal components was attributed to the high-temperature regeneration in hydrothermal conditions, which was slow but irreversible and accounted for permanent deactivation. Thus, optimizing the regeneration is expected to extend the service life of the commercial catalyst.
基金financially supported by the Science Foundation of Donghai Laboratory (Grant No.DH-2022ZY0010)the R&D Project of State Grid Corporation of China (No.5108-202218280A-2-439-XG).
文摘Hydrogen(H_(2)) has been regarded as a promising alternative to fossil-fuel energy.Green H_(2) produced via water electrolysis(WE)powered by renewable energy could achieve a zero-carbon footprint.Considerable attention has been focused on developing highly active catalysts to facilitate the reaction kinetics and improve the energy efficiency of WE.However,the stability of the electrocatalysts hampers the commercial viability of WE.Few studies have elucidated the origin of catalyst degradation.In this review,we first discuss the WE mechanism,including anodic oxygen evolution reaction(OER)and cathodic hydrogen evolution reaction(HER).Then,we provide strategies used to enhance the stability of electrocatalysts.After that,the deactivation mechanisms of the typical commercialized HER and OER catalysts,including Pt,Ni,RuO_(2),and IrO_(2),are summarized.Finally,the influence of fluctuating energy on catalyst degradation is highlighted and in situ characterization methodologies for understanding the dynamic deactivation processes are described.
基金supported by Thailand Science Research and Innovation Fund Chulalongkorn University,Thailand(IND66210014)。
文摘Hydrogen sulfide(H_(2)S) not only presents significant environmental concerns but also induces severe corrosion in industrial equipment,even at low concentrations.Among various technologies,the selective oxidation of hydrogen sulfide(SOH_(2)S) to elemental sulfur(S) has emerged as a sustainable and environmentally friendly solution.Due to its unique properties,iron oxide has been extensively investigated as a catalyst for SOH_(2)S;however,rapid deactivation has remained a significant drawback.The causes of iron oxide-based catalysts deactivation mechanisms in SOH_(2)S,including sulfur or sulfate deposition,the transformation of iron species,sintering and excessive oxygen vacancy formation,and active site loss,are thoroughly examined in this review.By focusing on the deactivation mechanisms,this review aims to provide valuable insights into enhancing the stability and efficiency of iron-based catalysts for SOH_(2)S.
基金supported by the Liaoning Provincial Natural Science Foundation Joint Fund for Innovation Capability Improvement(2021-NLTS-12-02)Key Research and Local Service Projects of the Liaoning Provincial Department of Education(LDB2019005).
文摘It is well known that calcium oxide (CaO) has better catalytic efficiency than most heterogeneous catalysts in many transesterification reactions. However, the gradual deactivation problem prevents its large-scale application in industry. In this paper, the deactivation mechanism of CaO in a fixed-bed reactor is investigated based on the transesterification reaction of propylene carbonate and methanol. The leaching amount of CaO during the reaction was estimated by the concentration of Ca in the products. The pretreated and recovered catalysts were characterized by FT-IR, XRD, TG-MS and SEM-EDS. It is evident from experiments and characterization that the deactivation process of CaO is accompanied by the leaching of calcium species and the generation of CaCO3, which are also verified by DFT calculations. At high temperature and high weight hourly space velocity, the deactivation was attributed to the formation of dense CaCO3 shell, which prevents the contact between the feedstock and the active species inside.
基金supported by the National Key R&D Program of China(No.2022YFC3701603)the National Natural Science Foundation of China(Nos.22106133,52070168)+1 种基金the Key R&D Plan of Zhejiang Province(No.2023C03127)the Fundamental Research Funds for the Central Universities(No.226-2022-00150).
文摘Zeolites are a promising support for Pd catalysts in leanmethane(CH_(4))combustion.Herein,three types of zeolites(H-MOR,H-ZSM-5 and H-Y)were selected to estimate their structural effects and deactivation mechanisms in CH_(4)combustion.We show that variations in zeolite structure and surface acidity led to distinct changes in Pd states.Pd/H-MOR with external high-dispersing Pd nanoparticles exhibited the best apparent activity,with activation energy(Ea)at 73 kJ/mol,while Pd/H-ZSM-5 displayed the highest turnover frequency(TOF)at 19.6×10^(−3)sec^(−1),presumably owing to its large particles with more step sites providing active sites in one particle for CH_(4)activation.Pd/H-Y with dispersed PdO within pore channels and/or Pd2+ions on ion-exchange sites yielded the lowest apparent activity and TOF.Furthermore,Pd/H-MOR and Pd/H-ZSM-5 were both stable under a dry condition,but introducing 3 vol.%H_(2)O caused the CH_(4)conversion rate on Pd/H-MOR drop from 100%to 63%and that on Pd/H-ZSM-5 decreased remarkably from 82%to 36%.The former was shown to originate fromzeolite structural dealumination,and the latter principally owed to Pd aggregation and the loss of active PdO.
