Due to the technology limitation and inferior deNO_(x) efficiency of urea selective catalytic reduction (SCR) catalysts at low temperatures, passive NO_(x) adsorber (PNA) for decrease of NO_(x), CO and hydrocarbons (H...Due to the technology limitation and inferior deNO_(x) efficiency of urea selective catalytic reduction (SCR) catalysts at low temperatures, passive NO_(x) adsorber (PNA) for decrease of NO_(x), CO and hydrocarbons (HCs) during “cold start” of vehicles was proposed to meet the further tighten NO_(x) emission regulations in future. Among them, Pd modified zeolite PNA materials have received more attention because of their excellent NO_(x) storage capacity, anti-poisoning and hydrothermal stability and since Pd/zeolite PNA was proposed, a variety of advanced characterization methods have been applied to investigate its adsorption behavior and structure-performance relationship. The comprehension of the active sites and adsorption chemistry of Pd/zeolite PNA was also significantly improved. However, there are few reviews that systematically summarize the recent progress and application challenges in atomic-level understanding of this material. In this review, we summarized the latest research progress of Pd/zeolite PNA, including active adsorption sites, adsorption mechanism, material physicochemical properties, preparation methods, storage and release performance and structure-performance relationships. In addition, the deactivation challenges faced by Pd/zeolite PNA in practical applications, such as chemical poisoning, high temperature hydrothermal aging deactivation, etc., were also discussed at the micro-level, and some possible effective countermeasures are given. Besides, some possible improvements and research hotspots were put forward, which could be helpful for designing and constructing more efficient PNA materials for meeting the ultra-low NO_(x) emission regulation in the future.展开更多
This study examined the impact of CeO_(2)addition on the sulfur tolerance of Pd/beta zeolite catalyst in toluene catalytic oxidation.By preparing and assessing Ce-modified beta zeolite-supported Pd catalysts,it is fou...This study examined the impact of CeO_(2)addition on the sulfur tolerance of Pd/beta zeolite catalyst in toluene catalytic oxidation.By preparing and assessing Ce-modified beta zeolite-supported Pd catalysts,it is found that the toluene complete conversion over Pd/7.5Ce-beta zeolite occurs at 190℃,with a minimal increase of 20℃even after sulfur poisoning.It is shown that Ce-doping markedly enhances sulfur tolerance besides catalytic activity.The underlying mechanism involves CeO_(2)sites capturing sulfur species,thus safeguarding active Pd species from sulfur poisoning.It can be observed that Pd0active sites,which are crucial in the catalytic high activity,are still present in the most severely poisoned catalyst.Furthermore,Ce-modified catalyst exhibits a more stable pore structure and increased acid strength after sulfur poisoning,all of which are beneficial to improving the sulfur tolerance.Consequently,Pd/Ce-beta zeolite is a promising solution for processing sulfur-containing volatile organic compounds,offering valuable insights for developing effective and sustainable catalysts for environmental remediation.展开更多
Recycling rare earth elements(REEs)from waste is necessary for an environmentally sustainable reuse and wastewater management approach.Na-A zeolite was synthesized from coal fly ash(CFA)and applied for Ce^(3+)adsorpti...Recycling rare earth elements(REEs)from waste is necessary for an environmentally sustainable reuse and wastewater management approach.Na-A zeolite was synthesized from coal fly ash(CFA)and applied for Ce^(3+)adsorption.Fourier transform infrared(FTIR)spectra show peaks at 790,500 and 467 cm^(-1),which are bond vibrations of Si-O-Si,Si with Al-O and Si-O-.The surface area is 15.88 m^(2)/g,with a pore size of 2.14 nm.SEM images show a cubic shape,which indicates the formation of zeolite.Field emission and energy disperse spectroscopy(EDS)shows the formation of Si,Al,Na,and O.Na-A zeolite was applied for Ce^(3+)adsorption.The optimum conditions for Ce^(3+)adsorption are 50 ppm concentration,360 min,and pH 6.The maximum adsorption capacity is 176.49 mg/g.Based on the results,it is found that the adsorption of Ce^(3+)by Na-A zeolite is pseudo-second-order.The desorption test using HNO_(3) is more effective than using HCl and H_(2)SO_(4).A desorption efficiency of 97.22%is obtained at 4 cycles.Adsorption test using real sample wastewater demonstrates an adsorption efficiency of 83.35%.展开更多
Zeolite nanosheets with a short b-axis thickness are highly desirable in lots of catalytic reactions due to their reduced diffusion resistance. Nevertheless, conventional synthesis methods usually require expensive st...Zeolite nanosheets with a short b-axis thickness are highly desirable in lots of catalytic reactions due to their reduced diffusion resistance. Nevertheless, conventional synthesis methods usually require expensive structure-directing agents(SDAs), pricey raw materials, and eco-unfriendly fluorine-containing additives. Here, we contributed a cost-effective and fluoride-free synthesis method for synthesizing high-quality MFI zeolite nanosheets through a Silicalite-1(Sil-1) seed suspension and urea cooperative strategy, only with inexpensive colloidal silica as the Si source. Our approach was effective for synthesizing both Sil-1 and aluminum-containing ZSM-5 nanosheets. By optimizing key synthesis parameters,including seed aging time, seed quantity, and urea concentration, we achieved precise control over the crystal face aspect ratio and b-axis thickness. We also revealed a non-classical oriented nanosheet growth mechanism, where Sil-1 seeds induced the formation of quasi-ordered precursor particles, and the(010)crystal planes of these particles facilitated urea adsorption, thereby promoting c-axis-oriented growth.The obtained ZSM-5 nanosheets exhibited exceptional catalytic performance in the benzene alkylation with ethanol, maintaining stability for over 500 h, which is 5 times longer than traditional ZSM-5 catalysts. Furthermore, large-scale production of ZSM-5 nanosheets was successfully carried out in a 3 L highpressure autoclave, yielding samples consistent with those from laboratory-scale synthesis. This work marks a significant step forward in the sustainable and efficient production of MFI nanosheets using inexpensive and environmentally friendly raw materials, offering the broad applicability in catalysis.展开更多
High-capacity LiBH_(4)is a promising solid hydrogen storage material.However,the large electron cloud density between the B-H bonds in LiBH_(4)induces high dehydrogenation temperatures and sluggish dehydrogenation kin...High-capacity LiBH_(4)is a promising solid hydrogen storage material.However,the large electron cloud density between the B-H bonds in LiBH_(4)induces high dehydrogenation temperatures and sluggish dehydrogenation kinetics.To solve the above problems,it is proposed to enhance the hydrogen storage properties of LiBH_(4)through the synergistic effect of Brønsted and Lewis acid in Hβzeolite.Composite hydrogen storage systems with different mass ratios were prepared by simple ball-milling.At a LiBH_(4)-to-Hβmass ratio of 6:4,the 6LiBH_(4)-4Hβsystem released hydrogen at 190℃and achieved a hydrogen release capacity of 7.0 wt%H_(2)upon heating to 400℃.More importantly,the hydrogen release capacity of the system reached 6.02 wt%at 350℃under isothermal conditions after 100 min and 7.2 wt%at 400℃under isothermal conditions after 80 min,whereas the pristine LiBH_(4)only achieved 2.2 wt%.The improvement in hydrogen storage performance of the system was mainly attributed to two factors:(i)Lewis acid sites with acceptable electrons in the Hβweaken the electron density of B-H bonds in LiBH_(4),and(ii)the H+proton from the Brønsted acid sites and H−of LiBH_(4)undergo a H^(+)+H^(−)=H_(2)reaction.Theoretical calculations revealed that the Lewis and Brønsted acid sites in the Hβzeolite are conducive to the weakening of B-H bonds and that storage charge transfer occurs near the Lewis acid sites.The present work provides new insights into improving the hydrogen storage performance of LiBH_(4)by weakening the B-H bonds in the LiBH_(4).展开更多
Nitrogen oxides(NO_(x))from diesel engine exhaust,is one of the major sources of environmental pollution.Currently,selective catalytic reduction with ammonia(NH_(3)-SCR)is considered to be the most effective protocol ...Nitrogen oxides(NO_(x))from diesel engine exhaust,is one of the major sources of environmental pollution.Currently,selective catalytic reduction with ammonia(NH_(3)-SCR)is considered to be the most effective protocol for reducing NO_(x)emissions.Nowadays,zeolitebased NH_(3)-SCR catalysts have been industrialized and widespread used in this field.Nevertheless,with the increasingly stringent environmental regulations and implementation of the requirement of“zero emission”of diesel engine exhaust,it is extremely urgent to prepare catalysts with superior NH_(3)-SCR activity and exceptional resistance to poisons(SO2,alkali metals,hydrocarbons,etc.).Core-shell structure zeolite-based catalysts(CSCs)have shown great promise in NH_(3)-SCR of NO_(x)in recent years by virtue of its relatively higher low-temperature activity,broader operation temperature window and outstanding resistance to poisons.This review mainly focuses on the recent progress of CSCs for NH_(3)-SCR of NO_(x)with three extensively investigated SSZ-13,ZSM-5,Beta zeolites as cores.The reaction mechanisms of resistance to sulfur poisoning,alkali metal poisoning,hydrocarbon poisoning,and hydrothermal aging are summarized.Moreover,the important role of interfacial effect between core and shell in the reaction of NH_(3)-SCR was clarified.Finally,the future development and application outlook of CSCs are prospected.展开更多
Methane’s complete catalytic oxidation process has been widely studied,but efficient catalytic oxidation of low-concentration methane(≤0.75%)remains a crucial problem in the coal chemical industry.How to prevent the...Methane’s complete catalytic oxidation process has been widely studied,but efficient catalytic oxidation of low-concentration methane(≤0.75%)remains a crucial problem in the coal chemical industry.How to prevent the sintering deactivation of the active component in Pd-based catalysts and achieve efficient and stable operation of sub-nanometer catalysts remains challenging.Here,we utilize the interaction between amine ligands and Pd nanoparticles to stabilize and encapsulate the Pd particles within the pores of a molecular sieve carrier,effectively promoting the high dispersion of Pd particles.By leveraging the low acidity,high hydrophobicity,and high hydrothermal stability of the zeolite carrier,the Pd@S-1 catalyst exhibits excellent activity and stability in the catalytic oxidation of methane at lowconcentrations.Finally,density functional theory is employed to investigate the reaction mechanism of low-concentration methane during the catalytic process.Encapsulating the active metal component in zeolite to improve catalytic activity and stability provides a theoretical basis and direction for preparing complete oxidation catalysts for low-concentration methane.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
The cerium-silicate pillared MWW zeolites are fabricated by introducing Ce species into the silica pillars within adjacent MWW layers through a liquid-phase pillaring method,and the multiple-layer structure of MWW zeo...The cerium-silicate pillared MWW zeolites are fabricated by introducing Ce species into the silica pillars within adjacent MWW layers through a liquid-phase pillaring method,and the multiple-layer structure of MWW zeolites is well maintained.However,it's found that these Ce^(3+)species can produce the Bronsted acid sites by the dissociation of water molecules owing to the electrostatic field of Ce^(3+)cations,the splitting of water molecules occurs following[Ce(H_2O)_n]^(3+)■Ce[(OH)(H_2O)_(n-1)]^(2+)+H^(+)equation based on the Plank-Hirschler mechanism,leading to superior activity of resultant cerium-silicate pillared MWW zeolites in the alkylation between benzene with 1-dodecene.Moreover,the additional Ce species located in the silica pillars can be easily accessed by vip molecules due to the presence of mesopores between neighboring MWW layers,which can strongly active benzene molecules by polarization effect,and dodecyl carbenium ions are preferred to attack the carbon atoms located in activated benzene molecules,resulting in the long lifetime of cerium-silicate pillared MWW zeolites since the oligomerization of long-chain olefins is suppressed.Under harsh reaction conditions(benzene/1-dodecene=10,WHSV=20 h^(-1)),the optimized cerium-silicate pillared MWW zeolite shows outstanding activity(>40%)and excellent selectivity(>85%)of 2-LAB in the alkylation of benzene with 1-dodecene.展开更多
Organic structure directingagents(OSDAs),suchas tetrapropylammonium(TPA)cations,serve as crucial templates for the formation of zeolite frameworks.These organic molecules interact with inorganic species,guiding the as...Organic structure directingagents(OSDAs),suchas tetrapropylammonium(TPA)cations,serve as crucial templates for the formation of zeolite frameworks.These organic molecules interact with inorganic species,guiding the assembly of the zeolite structure.In this study,we inves-tigate the complex interplay between boron species and TPA cations during the crystallization of[B,Al]-ZSM-5 zeolites.Two-dimensional(2D)11B-{1H}cross-polarization heteronuclear correlation(CP-HECTOR)NMRexperiments elucidate distinct interactions between two boron species,B(IV)-1 and B(IV)-2,and the propyl chain of the TPAs.Amorphous B(IV)-1 species exhibit a strong preference for proximity to the nitrogen cation center of the OSDAs,while framework B(IV)-2 species engage with components situated at greater distances from the cation center.Moreover,13C-{11B}symmetry-based resonance-echo saturation-pulse double-resonance(S-RESPDOR)experiments revealed that framework boron species preferentially occupy the straight channels of the MFI structure,as evidenced by their interaction with specificmethyl groups on the TPAmolecules.This observation provides valuable insights into the crystallization mechanism of boron-based zeolites,suggesting that the conformation and orientation of the OSDA molecules play a critical role in determining the location of boron atoms within the zeolite framework.展开更多
A combination of experimental and statistical analysis presents a comprehensive understanding of the microwave pyrolysis technique for catalytic deconstruction of mixed-density plastics.By optimizing the process param...A combination of experimental and statistical analysis presents a comprehensive understanding of the microwave pyrolysis technique for catalytic deconstruction of mixed-density plastics.By optimizing the process parameters and catalyst selection,it is possible to maximize the production of valuable solid and energy products,contributing to sustainable waste management.In this work,different mixed-density plastics were pyrolyzed with different catalysts and residence times to yield liquid fuel,syngas,and structured carbon residue.The effect of inputs on the product type,yield and composition was statistically evaluated using ANOVA,which showed an F value of 4.108 and a p-value of 0.098(>1.00).FTIR and GC-MS revealed that the oil product consisted of C13+fractions in the form of alkanes,alkenes,and aromatics.The microscopic analysis of the residue confirmed the formation of carbon nanotubes along with other amorphous products.The presence of impurities in the solid product was further analyzed through XRD analysis.The pyrolytic liquid fuel revealed the presence of conjugated aromatic structure and carbonyl group in their concentration.This research demonstrated that converting mixed-density plastics using sodium zeolite,aluminum oxide,and nickel oxide catalysts yields 84%valuable products,confirming wasted plastics as a lucrative energy feedstock for producing hydrogen and high-value carbon compounds.展开更多
Zeolite-loaded noble metal catalysts have demonstrated excellent performance in addressing cold-start automotive exhaust NOx emissions and catalytic oxidation of VOCs applications.Pd and Pt are the most commonly used ...Zeolite-loaded noble metal catalysts have demonstrated excellent performance in addressing cold-start automotive exhaust NOx emissions and catalytic oxidation of VOCs applications.Pd and Pt are the most commonly used active metals in PNA and VOC catalysts,respectively.However,despite the same metal/zeolite composition,the efficient active sites for PNA and VOC catalysts have been viewed as mainly Pd^(2+) and Pt^(0),respectively,both of which are different from each other.As a result,various methods need to be applied to dope Pd and Pt in zeolitic support respectively for different usages.No matter which type of metal species is needed,the common requirement for both PNA and VOC catalysts is that the metal species should be highly dispersed in zeolite support and stay stable.The purpose of this paper is to review the progress of synthetic means of zeolite-coated noble metals(Pd,Pt,etc.)as effective PNA or VOC catalysts.To give a better understanding of the relationship between efficient metal species and the introduced methods,the species that contributed to the NOx adsorption(PNA)and VOCs deep catalytic oxidation were first summarized and compared.Then,based on the above discussion,the detailed construction strategies for different active sites in PNA and VOC catalysts,respectively,were elaborated in terms of synthetic routes,precursor selection,and zeolite carrier requirements.It is hoped that this will contribute to a better understanding of noble metal adsorption/catalysis in zeolites and provide promising strategies for the design of adsorption/catalysts with high activity,selectivity and stability.展开更多
Precisely tailoring metal single-atoms within zeolite scaffolds and understanding the origin of the unique behavior of such atomically dispersed catalysts are pivotal and challenge in chemistry and catalysis.Herein,we...Precisely tailoring metal single-atoms within zeolite scaffolds and understanding the origin of the unique behavior of such atomically dispersed catalysts are pivotal and challenge in chemistry and catalysis.Herein,we have successfully fabricated Ni single-atoms within BEA zeolite(Ni_(1)@Beta)through a facile in situ two-step hydrothermal strategy,notably without using any chelating agent for stabilizing Ni species.With the aid of advanced characterization techniques,such as aberration-corrected high-angle annular dark-field scanning transmission electron microscopy,X-ray absorption spectroscopy,etc.,and combined with density functional theory calculations,the nature and micro-environment of isolated Ni species,which are incorporated within 6-membered rings and stabilized by four skeletal oxygens of Beta zeolite,have been identified.The as-obtained Ni1@Beta exhibits a superior performance in terms of activity(with a turnover frequency value up to 114.1 h^(-1))and stability(for 5 consecutive runs)in the selective hydrogenation of furfural,surpassing those of Ni nanoparticle analogues and previously reported Ni-based heterogeneous catalysts.This study provides an efficient strategy for the fabrication of non-noble metal single-atoms within zeolites,which could be of great help for the design of metal-zeolite combinations in the chemoselective reactions involved in biomass conversion and beyond.展开更多
The hydrothermal stability of zeolites is essential for their potential applications in biomass conversion,especially in processes involving elevated temperatures alongside the use or generation of H_(2)O.In this stud...The hydrothermal stability of zeolites is essential for their potential applications in biomass conversion,especially in processes involving elevated temperatures alongside the use or generation of H_(2)O.In this study,we employed F-ions as mineralizers to synthesize hydrothermally stable ZSM-5 zeolites under acidic conditions.The acidic synthesis system promotes zeolites with fewer silanol-terminated lattice defects(ZSM-5(A))compared to the traditional basic conditions(ZSM-5(B)),endowing materials with substantially higher structural integrity and hydrophobicity.After 10 days of autoclave treatment at 200℃ in aqueous phase,H-ZSM-5(A)demonstrated nearly unchanged reaction rates in the dehydration of cyclohexanol,while H-ZSM-5(B)lost>50%of the dehydration activity.Additionally,H-ZSM-5(A)delivered higher initial dehydration rates compared to H-ZSM-5(B).The different measured activation energies further revealed variations in reaction pathways during cyclohexanol dehydration,i.e.,the monomer-or dimer-mediated routes depending on the concentration of alcohol molecule within zeolite pores,providing additional evidence for the strengthened hydrophobic nature of H-ZSM-5(A).Beyond this,the zeolite surface properties and the strength of cyclohexanol-zeolite interactions may impose additional transport/adsorption barriers attributed to multi-phase phenomena on the more polar H-ZSM-5(B)zeolite surfaces.More importantly,the hydrothermal treatment did not induce significant desilication and dealumination in H-ZSM-5(A),thereby preserving its active acid sites and ensuring exceptional hydrothermal stability.The present work fundamentally studies the synthesis of hydrothermally stable zeolites in an acidic medium using fluorides and expands the understanding of polar interactions in catalysis,characterized by the dehydration of cyclohexanol,for future application in biomass conversion.展开更多
Propane dehydrogenation(PDH)has emerged as a key on-purpose technology for the production of propylene,but it often depends on toxic chromium and expensive platinum catalysts,highlighting the need for environmentally ...Propane dehydrogenation(PDH)has emerged as a key on-purpose technology for the production of propylene,but it often depends on toxic chromium and expensive platinum catalysts,highlighting the need for environmentally friendly and cost-effective alternatives.In this study,we developed a facile impregnation method to fabricate unsaturated Co single-atoms with a tricoordinated Co_(1)O_(3)H_(x) structure by regulating silanol nests in purely siliceous Beta zeolites.Detailed PDH catalytic tests and characterizations revealed a positive correlation between the presence of silanol nests and enhanced catalytic activity.Additionally,the unsaturated Co single-atoms exhibited a carbon deposition rate more than an order of magnitude slower than that of Co nanoparticles.Notably,the optimized Co_(0.3%)/deAl-meso-Beta catalyst achieved a record-high propylene formation rate of 21.2 mmol_(C3H6) g_(cat)^(-1) h^(-1),with an exceptional propylene selectivity of 99.1%at 550℃.Moreover,the Co_(0.3%)/deAl-meso-Beta catalyst demonstrated excellent stability,with negligible deactivation after 5 consecutive regeneration cycles.This study emphasizes the pivotal role of silanol nests of zeolites in stabilizing and modulating the coordination environment of metallic active sites,providing valuable insights for the design of high-activity,high-stability,and low-cost PDH catalysts.展开更多
A comparative study of products of thermal and thermocatalytic cracking of polypropylene(PP) in the presence of potassium polytitanate(PPT) synthesized by treatment of TiO_(2)(rutile) powder with molten mixture of KOH...A comparative study of products of thermal and thermocatalytic cracking of polypropylene(PP) in the presence of potassium polytitanate(PPT) synthesized by treatment of TiO_(2)(rutile) powder with molten mixture of KOH and KNO_(3) taken in a weight ratio of 30∶30∶40 has been carried out.It was shown that the studied type of PPT powder exhibits catalytic properties in the reaction of thermal decomposition of PP,compared to the effect of commercial zeolite catalyst CBV-780 traditionally used for this purpose.Based on the analysis performed,the differences in the mechanism of catalytic action of PPT and the zeolite were considered.The reasons for the observed differences in the composition of PP cracking products and in the rate of coke formation on the surface of studied catalysts were analyzed.Considering the obtained results,it has been proposed that the CBV-780 catalyst promoted more intensive production of the gaseous hydrocarbons compared to PPT,due to higher specific surface area(internal surface) accessible for relatively light and small-sized hydrocarbon products of cracking.However,intensive coke formation on the outer surface of the microporous zeolite contributes to the blocking of transport channels and the rapid loss of catalytic action.At the same time,PPT,which initially has a smaller specific surface area,retains its catalytic activity significantly longer due to slit-shaped flat pores and higher transport accessibility of the inner surface.展开更多
ITR zeolite could be potentially used as catalysts in methanol to propylene(MTP),where their performance is strongly related to its Al distribution.However,the control of Al distribution in ITR zeolite poses a signifi...ITR zeolite could be potentially used as catalysts in methanol to propylene(MTP),where their performance is strongly related to its Al distribution.However,the control of Al distribution in ITR zeolite poses a significant synthetic challenge.Herein,we demonstrate the possibility to control the Al distribution in ITR zeolites using zeolite A as an aluminum source(A-ITR).The A-ITR exhibited similar crystallinity,nanosheet morphology,textual parameters,and acidic concentration with those of conventional ITR made zeolites using aluminum isopropoxide as an aluminum source(C-ITR).Characterizations of the zeolite product with^(27)Al MQ.MAS NMR spectra,^(27)Al MAS NMR spectra,and 1-hexene cracking reveal that the A-ITR zeolites have more Al species distributed in T6 and T8 sites located in relatively smaller micropores of the framework than C-ITR.As a result,the A-ITR gave enhanced catalyst lifetime and propylene selectivity due to the suppression of the aromatic cycle in the MTP reaction,compared with the C-ITR.This work provides an alternative approach to prepare efficient ITR zeolites for MTP reaction.展开更多
The effectiveness of Elodea nuttallii combined with a mixture of hydrous ferric oxide,zeolite and calcite(HZC)to reduce the internal loading of phosphorus(P)from sediment and its mechanism were studied,and the effect ...The effectiveness of Elodea nuttallii combined with a mixture of hydrous ferric oxide,zeolite and calcite(HZC)to reduce the internal loading of phosphorus(P)from sediment and its mechanism were studied,and the effect of Elodea nuttallii combined with HZC on the composition and function of the microbial communities in the surface sediment was also investigated.The results showed that the combination utilization of Elodea nuttallii and HZC can decrease the risk of phosphorus liberation from sediment to the overlying water,and the controlling efficiency of Elodea nuttallii combined with HZCwas higher than that of Elodea nuttallii or HZC alone.The passivation of labile P measured by diffusive gradient in thin film device and mobile P played a crucial role in the control of internal P loading from sediment by the combined Elodea nuttallii+HZC treatment.HZC capping had a promoting effect on the growth of Elodea nuttallii.This was beneficial to the absorption of phosphorus from sediment by Elodea nuttallii.The combined application of Elodea nuttallii and HZC not only had a certain negative effect on the diversity of bacteria in the surface sediment,but also changed themicrobial compositions of the surface sediment at the levels of phylum and genus.However,the microbial communities in the surface sediment still can perform good ecological function.The above results suggest that the combined application of Elodea nuttallii and HZC has a high potential in the management of internal P loading from sediment.展开更多
Metal-support interactions and hydrogen spillover effects in heterogeneous catalysts play a crucial role in aromatic hydrogenation reactions;however,these effects are limited by the metal dispersion on the catalyst an...Metal-support interactions and hydrogen spillover effects in heterogeneous catalysts play a crucial role in aromatic hydrogenation reactions;however,these effects are limited by the metal dispersion on the catalyst and the number of acceptable H*receptors.This study prepares highly dispersed Ni nanoparticles(NPs)catalysts on a Beta substrate via precursor structure topology transformation.In contrast to traditional support materials,the coordination and electronic structure changes between the Ni NPs and the support were achieved,further optimizing the active interface sites and enhancing hydrogen activation and hydrogenation performance.Additionally,the-OH groups at the strong acid sites in zeolite effectively intensified the hydrogen spillover effect as receptors for H^(*)migration and anchoring,accelerating the hydrogenation rate of aromatic rings.Under solvent-free conditions,this catalyst was used for the hydrogenation reaction of aromatic-rich oils,directly producing a C_(8)-C_(14)branched cycloalkanes mixture with an aromatic conversion rate of>99%.The cycloalkanes mixture produced by this method features high density(0.92 g/mL)and a low freezing point(<-60℃),making it suitable for use as high-density aviation fuel or as an additive to enhance the volumetric heat value of conventional aviation fuels in practical applications.展开更多
Metal(oxide)-zeolite bifunctional catalysts have been the subject of considerable attention from researchers in both academic and industry,due to their superior activity and stability in various heterogeneous catalyti...Metal(oxide)-zeolite bifunctional catalysts have been the subject of considerable attention from researchers in both academic and industry,due to their superior activity and stability in various heterogeneous catalytic processes[1–3].Based on the different metal loading sites,these bifunctional catalysts can be categorized as follows:(a)metal species loaded on the outer surface of zeolite crystals,(b)metal species encapsulated within the channels or cavities of zeolites,and(c)metal species incorporated into the zeolite framework(Fig.1).Metal species in type(b)and(c)samples are stabilized by the zeolite frameworks,resulting in excellent thermal and hydrothermal stability during catalytic reactions,especially under harsh conditions,as well as unique shape-selectivity.However,the complex synthesis procedures make large-scale preparation of these catalysts impractical.In contrast,a type(a)sample can be achieved via the simple impregnation;nevertheless,migration of metal species and their aggregation into larger particles often occur during the calcination and reduction processes.展开更多
基金financial support from the National Natural Science Foundation of China (No. 52000084)the China Postdoctoral Science Foundation (No. 2019M662630)National Engineering Laboratory for Mobile Source Emission Control Technology (No. NELMS2018A08)。
文摘Due to the technology limitation and inferior deNO_(x) efficiency of urea selective catalytic reduction (SCR) catalysts at low temperatures, passive NO_(x) adsorber (PNA) for decrease of NO_(x), CO and hydrocarbons (HCs) during “cold start” of vehicles was proposed to meet the further tighten NO_(x) emission regulations in future. Among them, Pd modified zeolite PNA materials have received more attention because of their excellent NO_(x) storage capacity, anti-poisoning and hydrothermal stability and since Pd/zeolite PNA was proposed, a variety of advanced characterization methods have been applied to investigate its adsorption behavior and structure-performance relationship. The comprehension of the active sites and adsorption chemistry of Pd/zeolite PNA was also significantly improved. However, there are few reviews that systematically summarize the recent progress and application challenges in atomic-level understanding of this material. In this review, we summarized the latest research progress of Pd/zeolite PNA, including active adsorption sites, adsorption mechanism, material physicochemical properties, preparation methods, storage and release performance and structure-performance relationships. In addition, the deactivation challenges faced by Pd/zeolite PNA in practical applications, such as chemical poisoning, high temperature hydrothermal aging deactivation, etc., were also discussed at the micro-level, and some possible effective countermeasures are given. Besides, some possible improvements and research hotspots were put forward, which could be helpful for designing and constructing more efficient PNA materials for meeting the ultra-low NO_(x) emission regulation in the future.
基金Project supported by Zhejiang Public Welfare Technology Research Project(LGG19B070003)the National Natural Science Foundation of China(21902069)。
文摘This study examined the impact of CeO_(2)addition on the sulfur tolerance of Pd/beta zeolite catalyst in toluene catalytic oxidation.By preparing and assessing Ce-modified beta zeolite-supported Pd catalysts,it is found that the toluene complete conversion over Pd/7.5Ce-beta zeolite occurs at 190℃,with a minimal increase of 20℃even after sulfur poisoning.It is shown that Ce-doping markedly enhances sulfur tolerance besides catalytic activity.The underlying mechanism involves CeO_(2)sites capturing sulfur species,thus safeguarding active Pd species from sulfur poisoning.It can be observed that Pd0active sites,which are crucial in the catalytic high activity,are still present in the most severely poisoned catalyst.Furthermore,Ce-modified catalyst exhibits a more stable pore structure and increased acid strength after sulfur poisoning,all of which are beneficial to improving the sulfur tolerance.Consequently,Pd/Ce-beta zeolite is a promising solution for processing sulfur-containing volatile organic compounds,offering valuable insights for developing effective and sustainable catalysts for environmental remediation.
基金Project supported by Rumah Program 2023 and Net Zero Emission Program(1507/Ⅱ.7/HK.01.00/6/2023)a research facility from the National Research and Innovation Agency of Republic of Indonesia。
文摘Recycling rare earth elements(REEs)from waste is necessary for an environmentally sustainable reuse and wastewater management approach.Na-A zeolite was synthesized from coal fly ash(CFA)and applied for Ce^(3+)adsorption.Fourier transform infrared(FTIR)spectra show peaks at 790,500 and 467 cm^(-1),which are bond vibrations of Si-O-Si,Si with Al-O and Si-O-.The surface area is 15.88 m^(2)/g,with a pore size of 2.14 nm.SEM images show a cubic shape,which indicates the formation of zeolite.Field emission and energy disperse spectroscopy(EDS)shows the formation of Si,Al,Na,and O.Na-A zeolite was applied for Ce^(3+)adsorption.The optimum conditions for Ce^(3+)adsorption are 50 ppm concentration,360 min,and pH 6.The maximum adsorption capacity is 176.49 mg/g.Based on the results,it is found that the adsorption of Ce^(3+)by Na-A zeolite is pseudo-second-order.The desorption test using HNO_(3) is more effective than using HCl and H_(2)SO_(4).A desorption efficiency of 97.22%is obtained at 4 cycles.Adsorption test using real sample wastewater demonstrates an adsorption efficiency of 83.35%.
基金Joint Project of Dalian University of Technology-Dalian Institute of Chemical Physics (HX20230236)。
文摘Zeolite nanosheets with a short b-axis thickness are highly desirable in lots of catalytic reactions due to their reduced diffusion resistance. Nevertheless, conventional synthesis methods usually require expensive structure-directing agents(SDAs), pricey raw materials, and eco-unfriendly fluorine-containing additives. Here, we contributed a cost-effective and fluoride-free synthesis method for synthesizing high-quality MFI zeolite nanosheets through a Silicalite-1(Sil-1) seed suspension and urea cooperative strategy, only with inexpensive colloidal silica as the Si source. Our approach was effective for synthesizing both Sil-1 and aluminum-containing ZSM-5 nanosheets. By optimizing key synthesis parameters,including seed aging time, seed quantity, and urea concentration, we achieved precise control over the crystal face aspect ratio and b-axis thickness. We also revealed a non-classical oriented nanosheet growth mechanism, where Sil-1 seeds induced the formation of quasi-ordered precursor particles, and the(010)crystal planes of these particles facilitated urea adsorption, thereby promoting c-axis-oriented growth.The obtained ZSM-5 nanosheets exhibited exceptional catalytic performance in the benzene alkylation with ethanol, maintaining stability for over 500 h, which is 5 times longer than traditional ZSM-5 catalysts. Furthermore, large-scale production of ZSM-5 nanosheets was successfully carried out in a 3 L highpressure autoclave, yielding samples consistent with those from laboratory-scale synthesis. This work marks a significant step forward in the sustainable and efficient production of MFI nanosheets using inexpensive and environmentally friendly raw materials, offering the broad applicability in catalysis.
基金supported by the National Natural Science Foundation of China(No.52201274)the Project of Education Department of Shanxi Province(No.22JK0419).
文摘High-capacity LiBH_(4)is a promising solid hydrogen storage material.However,the large electron cloud density between the B-H bonds in LiBH_(4)induces high dehydrogenation temperatures and sluggish dehydrogenation kinetics.To solve the above problems,it is proposed to enhance the hydrogen storage properties of LiBH_(4)through the synergistic effect of Brønsted and Lewis acid in Hβzeolite.Composite hydrogen storage systems with different mass ratios were prepared by simple ball-milling.At a LiBH_(4)-to-Hβmass ratio of 6:4,the 6LiBH_(4)-4Hβsystem released hydrogen at 190℃and achieved a hydrogen release capacity of 7.0 wt%H_(2)upon heating to 400℃.More importantly,the hydrogen release capacity of the system reached 6.02 wt%at 350℃under isothermal conditions after 100 min and 7.2 wt%at 400℃under isothermal conditions after 80 min,whereas the pristine LiBH_(4)only achieved 2.2 wt%.The improvement in hydrogen storage performance of the system was mainly attributed to two factors:(i)Lewis acid sites with acceptable electrons in the Hβweaken the electron density of B-H bonds in LiBH_(4),and(ii)the H+proton from the Brønsted acid sites and H−of LiBH_(4)undergo a H^(+)+H^(−)=H_(2)reaction.Theoretical calculations revealed that the Lewis and Brønsted acid sites in the Hβzeolite are conducive to the weakening of B-H bonds and that storage charge transfer occurs near the Lewis acid sites.The present work provides new insights into improving the hydrogen storage performance of LiBH_(4)by weakening the B-H bonds in the LiBH_(4).
基金supported by the Key Technologies Research and Development Program(No.2022YFB3504102)the National Natural Science Foundation of China(Nos.22035009,22002050,and 22202087)+2 种基金the National Engineering Laboratory for Mobile Source Emission Control Technology(No.NELMS2020B01)Fuyang Normal University Open Fund(No.FSKFKT006D)the Postdoctoral Science Foundation of China(Nos.2022T150765 and 2020M683154).
文摘Nitrogen oxides(NO_(x))from diesel engine exhaust,is one of the major sources of environmental pollution.Currently,selective catalytic reduction with ammonia(NH_(3)-SCR)is considered to be the most effective protocol for reducing NO_(x)emissions.Nowadays,zeolitebased NH_(3)-SCR catalysts have been industrialized and widespread used in this field.Nevertheless,with the increasingly stringent environmental regulations and implementation of the requirement of“zero emission”of diesel engine exhaust,it is extremely urgent to prepare catalysts with superior NH_(3)-SCR activity and exceptional resistance to poisons(SO2,alkali metals,hydrocarbons,etc.).Core-shell structure zeolite-based catalysts(CSCs)have shown great promise in NH_(3)-SCR of NO_(x)in recent years by virtue of its relatively higher low-temperature activity,broader operation temperature window and outstanding resistance to poisons.This review mainly focuses on the recent progress of CSCs for NH_(3)-SCR of NO_(x)with three extensively investigated SSZ-13,ZSM-5,Beta zeolites as cores.The reaction mechanisms of resistance to sulfur poisoning,alkali metal poisoning,hydrocarbon poisoning,and hydrothermal aging are summarized.Moreover,the important role of interfacial effect between core and shell in the reaction of NH_(3)-SCR was clarified.Finally,the future development and application outlook of CSCs are prospected.
基金supported by the National Natural Science Foundation of China(No.52270114)the State key laboratory of coal mine disaster dynamics and control(No.2011DA105827-FW202210).
文摘Methane’s complete catalytic oxidation process has been widely studied,but efficient catalytic oxidation of low-concentration methane(≤0.75%)remains a crucial problem in the coal chemical industry.How to prevent the sintering deactivation of the active component in Pd-based catalysts and achieve efficient and stable operation of sub-nanometer catalysts remains challenging.Here,we utilize the interaction between amine ligands and Pd nanoparticles to stabilize and encapsulate the Pd particles within the pores of a molecular sieve carrier,effectively promoting the high dispersion of Pd particles.By leveraging the low acidity,high hydrophobicity,and high hydrothermal stability of the zeolite carrier,the Pd@S-1 catalyst exhibits excellent activity and stability in the catalytic oxidation of methane at lowconcentrations.Finally,density functional theory is employed to investigate the reaction mechanism of low-concentration methane during the catalytic process.Encapsulating the active metal component in zeolite to improve catalytic activity and stability provides a theoretical basis and direction for preparing complete oxidation catalysts for low-concentration methane.
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.
基金supported by the National Natural Science Foundation of China(22278090,21978055)Natural Science Foundation of Guangdong Province,China(2022A1515012088)。
文摘The cerium-silicate pillared MWW zeolites are fabricated by introducing Ce species into the silica pillars within adjacent MWW layers through a liquid-phase pillaring method,and the multiple-layer structure of MWW zeolites is well maintained.However,it's found that these Ce^(3+)species can produce the Bronsted acid sites by the dissociation of water molecules owing to the electrostatic field of Ce^(3+)cations,the splitting of water molecules occurs following[Ce(H_2O)_n]^(3+)■Ce[(OH)(H_2O)_(n-1)]^(2+)+H^(+)equation based on the Plank-Hirschler mechanism,leading to superior activity of resultant cerium-silicate pillared MWW zeolites in the alkylation between benzene with 1-dodecene.Moreover,the additional Ce species located in the silica pillars can be easily accessed by vip molecules due to the presence of mesopores between neighboring MWW layers,which can strongly active benzene molecules by polarization effect,and dodecyl carbenium ions are preferred to attack the carbon atoms located in activated benzene molecules,resulting in the long lifetime of cerium-silicate pillared MWW zeolites since the oligomerization of long-chain olefins is suppressed.Under harsh reaction conditions(benzene/1-dodecene=10,WHSV=20 h^(-1)),the optimized cerium-silicate pillared MWW zeolite shows outstanding activity(>40%)and excellent selectivity(>85%)of 2-LAB in the alkylation of benzene with 1-dodecene.
基金supported by the National Energy R&D Center of Petroleum Refining Technology(RIPP,SINOPEC),the National Natural Science Foundation of China(Grants 22161132028,22172177,22225205,22372191 and 22372178)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB0540000)+2 种基金the International Partnership Program of the Chinese Academy of Sciences(314GJH2022022FN)Natural Science Foundation of Hubei Province(2021CFA021)Hubei International Scientific and Technological Cooperation Program(2024EHA043)and Base(SH2303).
文摘Organic structure directingagents(OSDAs),suchas tetrapropylammonium(TPA)cations,serve as crucial templates for the formation of zeolite frameworks.These organic molecules interact with inorganic species,guiding the assembly of the zeolite structure.In this study,we inves-tigate the complex interplay between boron species and TPA cations during the crystallization of[B,Al]-ZSM-5 zeolites.Two-dimensional(2D)11B-{1H}cross-polarization heteronuclear correlation(CP-HECTOR)NMRexperiments elucidate distinct interactions between two boron species,B(IV)-1 and B(IV)-2,and the propyl chain of the TPAs.Amorphous B(IV)-1 species exhibit a strong preference for proximity to the nitrogen cation center of the OSDAs,while framework B(IV)-2 species engage with components situated at greater distances from the cation center.Moreover,13C-{11B}symmetry-based resonance-echo saturation-pulse double-resonance(S-RESPDOR)experiments revealed that framework boron species preferentially occupy the straight channels of the MFI structure,as evidenced by their interaction with specificmethyl groups on the TPAmolecules.This observation provides valuable insights into the crystallization mechanism of boron-based zeolites,suggesting that the conformation and orientation of the OSDA molecules play a critical role in determining the location of boron atoms within the zeolite framework.
基金supported by the Researchers Supporting Project(RSPD2025R985),King Saud University,Riyadh,Saudi Arabia.
文摘A combination of experimental and statistical analysis presents a comprehensive understanding of the microwave pyrolysis technique for catalytic deconstruction of mixed-density plastics.By optimizing the process parameters and catalyst selection,it is possible to maximize the production of valuable solid and energy products,contributing to sustainable waste management.In this work,different mixed-density plastics were pyrolyzed with different catalysts and residence times to yield liquid fuel,syngas,and structured carbon residue.The effect of inputs on the product type,yield and composition was statistically evaluated using ANOVA,which showed an F value of 4.108 and a p-value of 0.098(>1.00).FTIR and GC-MS revealed that the oil product consisted of C13+fractions in the form of alkanes,alkenes,and aromatics.The microscopic analysis of the residue confirmed the formation of carbon nanotubes along with other amorphous products.The presence of impurities in the solid product was further analyzed through XRD analysis.The pyrolytic liquid fuel revealed the presence of conjugated aromatic structure and carbonyl group in their concentration.This research demonstrated that converting mixed-density plastics using sodium zeolite,aluminum oxide,and nickel oxide catalysts yields 84%valuable products,confirming wasted plastics as a lucrative energy feedstock for producing hydrogen and high-value carbon compounds.
基金supported by Zhongtian Iron and Steel-University of Science and Technology Beijing Youth Science and Technology Innovation Fund(No.FZTNTC2024050005)National Engineering Laboratory for Mobile Source Emission Control Technology,China(No.NELMS2020A07)The Fundamental Research Funds for the Central Universities,China(No.FRF-AT-20-12)。
文摘Zeolite-loaded noble metal catalysts have demonstrated excellent performance in addressing cold-start automotive exhaust NOx emissions and catalytic oxidation of VOCs applications.Pd and Pt are the most commonly used active metals in PNA and VOC catalysts,respectively.However,despite the same metal/zeolite composition,the efficient active sites for PNA and VOC catalysts have been viewed as mainly Pd^(2+) and Pt^(0),respectively,both of which are different from each other.As a result,various methods need to be applied to dope Pd and Pt in zeolitic support respectively for different usages.No matter which type of metal species is needed,the common requirement for both PNA and VOC catalysts is that the metal species should be highly dispersed in zeolite support and stay stable.The purpose of this paper is to review the progress of synthetic means of zeolite-coated noble metals(Pd,Pt,etc.)as effective PNA or VOC catalysts.To give a better understanding of the relationship between efficient metal species and the introduced methods,the species that contributed to the NOx adsorption(PNA)and VOCs deep catalytic oxidation were first summarized and compared.Then,based on the above discussion,the detailed construction strategies for different active sites in PNA and VOC catalysts,respectively,were elaborated in terms of synthetic routes,precursor selection,and zeolite carrier requirements.It is hoped that this will contribute to a better understanding of noble metal adsorption/catalysis in zeolites and provide promising strategies for the design of adsorption/catalysts with high activity,selectivity and stability.
文摘Precisely tailoring metal single-atoms within zeolite scaffolds and understanding the origin of the unique behavior of such atomically dispersed catalysts are pivotal and challenge in chemistry and catalysis.Herein,we have successfully fabricated Ni single-atoms within BEA zeolite(Ni_(1)@Beta)through a facile in situ two-step hydrothermal strategy,notably without using any chelating agent for stabilizing Ni species.With the aid of advanced characterization techniques,such as aberration-corrected high-angle annular dark-field scanning transmission electron microscopy,X-ray absorption spectroscopy,etc.,and combined with density functional theory calculations,the nature and micro-environment of isolated Ni species,which are incorporated within 6-membered rings and stabilized by four skeletal oxygens of Beta zeolite,have been identified.The as-obtained Ni1@Beta exhibits a superior performance in terms of activity(with a turnover frequency value up to 114.1 h^(-1))and stability(for 5 consecutive runs)in the selective hydrogenation of furfural,surpassing those of Ni nanoparticle analogues and previously reported Ni-based heterogeneous catalysts.This study provides an efficient strategy for the fabrication of non-noble metal single-atoms within zeolites,which could be of great help for the design of metal-zeolite combinations in the chemoselective reactions involved in biomass conversion and beyond.
文摘The hydrothermal stability of zeolites is essential for their potential applications in biomass conversion,especially in processes involving elevated temperatures alongside the use or generation of H_(2)O.In this study,we employed F-ions as mineralizers to synthesize hydrothermally stable ZSM-5 zeolites under acidic conditions.The acidic synthesis system promotes zeolites with fewer silanol-terminated lattice defects(ZSM-5(A))compared to the traditional basic conditions(ZSM-5(B)),endowing materials with substantially higher structural integrity and hydrophobicity.After 10 days of autoclave treatment at 200℃ in aqueous phase,H-ZSM-5(A)demonstrated nearly unchanged reaction rates in the dehydration of cyclohexanol,while H-ZSM-5(B)lost>50%of the dehydration activity.Additionally,H-ZSM-5(A)delivered higher initial dehydration rates compared to H-ZSM-5(B).The different measured activation energies further revealed variations in reaction pathways during cyclohexanol dehydration,i.e.,the monomer-or dimer-mediated routes depending on the concentration of alcohol molecule within zeolite pores,providing additional evidence for the strengthened hydrophobic nature of H-ZSM-5(A).Beyond this,the zeolite surface properties and the strength of cyclohexanol-zeolite interactions may impose additional transport/adsorption barriers attributed to multi-phase phenomena on the more polar H-ZSM-5(B)zeolite surfaces.More importantly,the hydrothermal treatment did not induce significant desilication and dealumination in H-ZSM-5(A),thereby preserving its active acid sites and ensuring exceptional hydrothermal stability.The present work fundamentally studies the synthesis of hydrothermally stable zeolites in an acidic medium using fluorides and expands the understanding of polar interactions in catalysis,characterized by the dehydration of cyclohexanol,for future application in biomass conversion.
文摘Propane dehydrogenation(PDH)has emerged as a key on-purpose technology for the production of propylene,but it often depends on toxic chromium and expensive platinum catalysts,highlighting the need for environmentally friendly and cost-effective alternatives.In this study,we developed a facile impregnation method to fabricate unsaturated Co single-atoms with a tricoordinated Co_(1)O_(3)H_(x) structure by regulating silanol nests in purely siliceous Beta zeolites.Detailed PDH catalytic tests and characterizations revealed a positive correlation between the presence of silanol nests and enhanced catalytic activity.Additionally,the unsaturated Co single-atoms exhibited a carbon deposition rate more than an order of magnitude slower than that of Co nanoparticles.Notably,the optimized Co_(0.3%)/deAl-meso-Beta catalyst achieved a record-high propylene formation rate of 21.2 mmol_(C3H6) g_(cat)^(-1) h^(-1),with an exceptional propylene selectivity of 99.1%at 550℃.Moreover,the Co_(0.3%)/deAl-meso-Beta catalyst demonstrated excellent stability,with negligible deactivation after 5 consecutive regeneration cycles.This study emphasizes the pivotal role of silanol nests of zeolites in stabilizing and modulating the coordination environment of metallic active sites,providing valuable insights for the design of high-activity,high-stability,and low-cost PDH catalysts.
文摘A comparative study of products of thermal and thermocatalytic cracking of polypropylene(PP) in the presence of potassium polytitanate(PPT) synthesized by treatment of TiO_(2)(rutile) powder with molten mixture of KOH and KNO_(3) taken in a weight ratio of 30∶30∶40 has been carried out.It was shown that the studied type of PPT powder exhibits catalytic properties in the reaction of thermal decomposition of PP,compared to the effect of commercial zeolite catalyst CBV-780 traditionally used for this purpose.Based on the analysis performed,the differences in the mechanism of catalytic action of PPT and the zeolite were considered.The reasons for the observed differences in the composition of PP cracking products and in the rate of coke formation on the surface of studied catalysts were analyzed.Considering the obtained results,it has been proposed that the CBV-780 catalyst promoted more intensive production of the gaseous hydrocarbons compared to PPT,due to higher specific surface area(internal surface) accessible for relatively light and small-sized hydrocarbon products of cracking.However,intensive coke formation on the outer surface of the microporous zeolite contributes to the blocking of transport channels and the rapid loss of catalytic action.At the same time,PPT,which initially has a smaller specific surface area,retains its catalytic activity significantly longer due to slit-shaped flat pores and higher transport accessibility of the inner surface.
基金supported by the National Key Research and Development Program of China(2022YFA1503602)the National Natural Science Foundation of China(22288101,U21B20101 and 22172141)+1 种基金the BASF International Network of Centers of Excellence projectthe Zhejiang Provincial Natural Science Foundation of China(LR24B030001)。
文摘ITR zeolite could be potentially used as catalysts in methanol to propylene(MTP),where their performance is strongly related to its Al distribution.However,the control of Al distribution in ITR zeolite poses a significant synthetic challenge.Herein,we demonstrate the possibility to control the Al distribution in ITR zeolites using zeolite A as an aluminum source(A-ITR).The A-ITR exhibited similar crystallinity,nanosheet morphology,textual parameters,and acidic concentration with those of conventional ITR made zeolites using aluminum isopropoxide as an aluminum source(C-ITR).Characterizations of the zeolite product with^(27)Al MQ.MAS NMR spectra,^(27)Al MAS NMR spectra,and 1-hexene cracking reveal that the A-ITR zeolites have more Al species distributed in T6 and T8 sites located in relatively smaller micropores of the framework than C-ITR.As a result,the A-ITR gave enhanced catalyst lifetime and propylene selectivity due to the suppression of the aromatic cycle in the MTP reaction,compared with the C-ITR.This work provides an alternative approach to prepare efficient ITR zeolites for MTP reaction.
基金supported by the Capacity Building Project of Local University of Shanghai Municipal Science and Technology Commission(No.10230502900)the Program for Shanghai Collaborative Innovation Center for Cultivating Elite Breeds and Green-culture of Aquaculture animals(No.2021-KJ-02-12)the Innovation Project for Chongming Agriculture Industry from Chongming District Agriculture Commission of Shanghai(No.2022CNKC-01-05).
文摘The effectiveness of Elodea nuttallii combined with a mixture of hydrous ferric oxide,zeolite and calcite(HZC)to reduce the internal loading of phosphorus(P)from sediment and its mechanism were studied,and the effect of Elodea nuttallii combined with HZC on the composition and function of the microbial communities in the surface sediment was also investigated.The results showed that the combination utilization of Elodea nuttallii and HZC can decrease the risk of phosphorus liberation from sediment to the overlying water,and the controlling efficiency of Elodea nuttallii combined with HZCwas higher than that of Elodea nuttallii or HZC alone.The passivation of labile P measured by diffusive gradient in thin film device and mobile P played a crucial role in the control of internal P loading from sediment by the combined Elodea nuttallii+HZC treatment.HZC capping had a promoting effect on the growth of Elodea nuttallii.This was beneficial to the absorption of phosphorus from sediment by Elodea nuttallii.The combined application of Elodea nuttallii and HZC not only had a certain negative effect on the diversity of bacteria in the surface sediment,but also changed themicrobial compositions of the surface sediment at the levels of phylum and genus.However,the microbial communities in the surface sediment still can perform good ecological function.The above results suggest that the combined application of Elodea nuttallii and HZC has a high potential in the management of internal P loading from sediment.
基金financially supported by the National Natural Science Foundation of China(Grant 22278439,21776313)the Shandong Province Higher Education Youth Innovation Technology Support Program(Grant 2022KJ074)。
文摘Metal-support interactions and hydrogen spillover effects in heterogeneous catalysts play a crucial role in aromatic hydrogenation reactions;however,these effects are limited by the metal dispersion on the catalyst and the number of acceptable H*receptors.This study prepares highly dispersed Ni nanoparticles(NPs)catalysts on a Beta substrate via precursor structure topology transformation.In contrast to traditional support materials,the coordination and electronic structure changes between the Ni NPs and the support were achieved,further optimizing the active interface sites and enhancing hydrogen activation and hydrogenation performance.Additionally,the-OH groups at the strong acid sites in zeolite effectively intensified the hydrogen spillover effect as receptors for H^(*)migration and anchoring,accelerating the hydrogenation rate of aromatic rings.Under solvent-free conditions,this catalyst was used for the hydrogenation reaction of aromatic-rich oils,directly producing a C_(8)-C_(14)branched cycloalkanes mixture with an aromatic conversion rate of>99%.The cycloalkanes mixture produced by this method features high density(0.92 g/mL)and a low freezing point(<-60℃),making it suitable for use as high-density aviation fuel or as an additive to enhance the volumetric heat value of conventional aviation fuels in practical applications.
基金financially supported by the National Key R&D Program of China(2024YFE0101100)the National Natural Science Foundation of China(22475112,22305132,22305155)+1 种基金the China Postdoctoral Science Foundation(2023M732323)the Postdoctoral Fellowship Program of CPSF(GZC20231679).
文摘Metal(oxide)-zeolite bifunctional catalysts have been the subject of considerable attention from researchers in both academic and industry,due to their superior activity and stability in various heterogeneous catalytic processes[1–3].Based on the different metal loading sites,these bifunctional catalysts can be categorized as follows:(a)metal species loaded on the outer surface of zeolite crystals,(b)metal species encapsulated within the channels or cavities of zeolites,and(c)metal species incorporated into the zeolite framework(Fig.1).Metal species in type(b)and(c)samples are stabilized by the zeolite frameworks,resulting in excellent thermal and hydrothermal stability during catalytic reactions,especially under harsh conditions,as well as unique shape-selectivity.However,the complex synthesis procedures make large-scale preparation of these catalysts impractical.In contrast,a type(a)sample can be achieved via the simple impregnation;nevertheless,migration of metal species and their aggregation into larger particles often occur during the calcination and reduction processes.
