The use of fossil fuels significantly contributes to excess CO_(2) emissions.Catalytic hydrogenation of CO_(2) to dimethyl ether(DME)is an effective method for CO_(2) recycling,offering both environmental and economic...The use of fossil fuels significantly contributes to excess CO_(2) emissions.Catalytic hydrogenation of CO_(2) to dimethyl ether(DME)is an effective method for CO_(2) recycling,offering both environmental and economic benefits.Zeolites,known for their efficiency as solid catalysts,are widely utilized in the chemical industries.Bifunctional catalysts based on zeolites have gained attention for their applications in CO_(2) hydrogenation to DME.This review discusses key factors affecting the catalytic performance of zeolites,including topologies,Si/Al ratio,crystal size,and the proximity of metallic species to the zeolite catalysts.Although bifunctional catalytic systems enhance the conversion of CO_(2) to DME,they also lead to high CO selectivity at elevated temperatures,which can limit both DME yield and selectivity.We present recent advancements in the development of bifunctional catalysts for the direct hydrogenation of CO_(2) to DME,providing insights for designing optimized catalysts for tandem reaction systems.展开更多
Direct converting carbon dioxide(CO_(2))and propane(C_(3)H_(8))into aromatics with high carbon utilization offers a desirable opportunity to simultaneously mitigate CO_(2)emission and adequately utilize C_(3)H_(8) in ...Direct converting carbon dioxide(CO_(2))and propane(C_(3)H_(8))into aromatics with high carbon utilization offers a desirable opportunity to simultaneously mitigate CO_(2)emission and adequately utilize C_(3)H_(8) in shale gas.Owing to their thermodynamic resistance,converting CO_(2)and C_(3)H_(8) respectively remains difficult.Here,we achieve 60.2%aromatics selectivity and 48.8%propane conversion over H-ZSM-5-25 via a zeolite-catalyzing the coupling of CO_(2)and C_(3)H_(8).Operando dual-beam FTIR spectroscopy combined with ^(13)C-labeled CO_(2)tracing experiments revealed that CO_(2)is directly involved in the generation of aromatics,with its carbon atoms selectively embedded into the aromatic ring,bypassing the reverse water-gas shift pathway.Accordingly,a cooperative aromatization mechanism is proposed.Thereinto,lactones,produced from CO_(2)and olefins,are proven to be the key intermediate.This work not only provides an opportunity for simultaneous conversion of CO_(2)and C_(3)H_(8),but also expends coupling strategy designing of CO_(2)and alkanes over acidic zeolites.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
Sulfur dioxide(SO_(2))frequently coexist with volatile organic compounds(VOCs)in exhaust gas.The competitive adsorption of SO_(2) and VOCs can adversely affect the efficiency of catalytic combustion,leading to catalys...Sulfur dioxide(SO_(2))frequently coexist with volatile organic compounds(VOCs)in exhaust gas.The competitive adsorption of SO_(2) and VOCs can adversely affect the efficiency of catalytic combustion,leading to catalyst poisoning and irreversible loss of activity.To investigate the impact of sulfur poisoning on the catalysts,we prepared the MnO_(2)/Beta zeolite,and a corresponding series of sulfur-poisoned catalysts through in-situ thermal decomposition of(NH_(4))_(2)SO_(4).The decrease in toluene catalytic activity of poisoned MnO_(2)/Beta zeolite primarily results from the conversion of the active species MnO_(2) to MnSO_(4).However,the crystal structure and the porous structure of MnO_(2)/Beta zeolite were stable,and original structure was still maintained when 1.6%(mass)sulfur species were introduced.Furthermore,the extra-framework Al of Beta zeolite could capture sulfur species to generate Al2(SO_(4))_(3),thereby reducing sulfur species from reacting with Mn^(4+) active sites.The combination of sulfur and Beta zeolite was found to directly produce new strong-acid sites,thus effectively compensating for the effect of reduced Mn4+active species on the catalytic activity.展开更多
Sodium Y(Na Y) zeolite is a promising adsorbent for carbon capture.The template-free synthesis of Na Y zeolite has gained considerable interests to minimize its costs and environmental effects.However,Na Y zeolites sy...Sodium Y(Na Y) zeolite is a promising adsorbent for carbon capture.The template-free synthesis of Na Y zeolite has gained considerable interests to minimize its costs and environmental effects.However,Na Y zeolites synthesized through template-free methods exhibited lower CO_(2) adsorption capacities(~4.07 mmol·g^(-1)) compared to template-assisted counterparts,often requiring longer crystallization time and higher energy penalty.This study systematically compared the microstructural characteristics and CO_(2) adsorption performance of Na Y zeolites synthesized with and without templates,including those from the commercial markets.Through process optimization,the CO_(2) adsorption capacity of the template-free Na Y zeolite was significantly enhanced,surpassing those template-assisted samples.Notably,it achieved CO_(2) adsorption capacities of 6.51 mmol·g^(-1) at 25℃ and 0.1 MPa,and 7.40 mmol·g^(-1) at 0℃ and 0.1 MPa,outperforming both commercial Na Y and template-assisted samples.The structural differences,including crystal integrity,pore size distribution and surface properties,were systematically discussed.The optimized synthesis method increased the specific surface area and the ratio of microporous structures.The template-free Na Y also showed superior CO_(2) capture capacity,moisture resistance,breakthrough performance and stability,indicating its application potential for carbon capture.展开更多
The direct oxidation of cyclohexane to adipic acid(AA)without the use of HNO_(3)is important but still challenging.Herein,hierarchical manganese-containing TS-1 zeolite(HMTS)was prepared using an improved direct synth...The direct oxidation of cyclohexane to adipic acid(AA)without the use of HNO_(3)is important but still challenging.Herein,hierarchical manganese-containing TS-1 zeolite(HMTS)was prepared using an improved direct synthesis method,in which titanium and manganese coexist within the zeolite matrix,as characterized by X-ray diffraction,X-ray photoelectron spectroscopy,transmission electron microscopy,ultraviolet,extended X-ray absorption fine structure etc.The introduction of matrix Mn species(Mn^(3+),Mn^(4+))not only increased the surface oxygen vacancies,but also generated medium-strong acid sites,which endowed HMTS catalysts with the ability to efficiently activate oxygen and facilitate substrate coordination.On HMTS-3,one-pot oxidation of cyclohexane at 140℃and 2 MPa O_(2)gave 81.6%conversion and 71.5%AA selectivity,the highest value obtained at present.Control experiments with single-component samples confirmed that matrix Ti^(4+)catalyzed the conversion of cyclohexane to a mixture of cyclohexanone and cyclohexanol(KA oil),and matrix Mn favored the conversion of KA oil to AA.The synergy between matrix Ti and Mn inside the hierarchical structure were the key factor for the superior activity.Specifically,the matrix Ti^(4+)might activate oxygen to form Ti-O_(2)2-which facilitated the activation of the C-H bond of cyclohexane.The activation of O_(2)on matrix Mn^(3+)formed Mn^(4+)-O_(2)-favoring the breaking of the C-C bond of cyclohexanone.The hierarchical structure not only exposed more active sites and promoted mass transfer,but also provided a better microenvironment for the matrix Mn to synergize with the matrix Ti,which facilitated the overall reaction.This work demonstrated the practical application potential of HMTS and provided useful insights into the direct oxidation of cyclohexane to AA.展开更多
Zeolite X was synthesized by a two-step hydrothermal method using natural stellerite zeolite as the silicon seed,and its adsorption performance for Cd^(2+)and Ni^(2+)ions was experimentally and comprehensively investi...Zeolite X was synthesized by a two-step hydrothermal method using natural stellerite zeolite as the silicon seed,and its adsorption performance for Cd^(2+)and Ni^(2+)ions was experimentally and comprehensively investigated.The effects of p H,zeolite X dosage,contact time,and temperature on adsorption performance for Cd^(2+)and Ni^(2+)ions over were studied.The adsorption process was endothermic and spontaneous,and followed the pseudo-second-order kinetic and the Langmuir isotherm models.The maximum adsorption capacitiesfor Cd^(2+)and Ni^(2+)ions at 298 K were 173.553 and 75.897 mg.g-1,respectively.Ion exchange and precipitation were the principal mechanisms for the removal of Cd^(2+)ions from aqueous solutions by zeolite X,followed by electrostatic adsorption.Ion exchange was the principal mechanisms for the removal of Ni^(2+)ions from aqueous solutions by zeolite X,followed by electrostatic adsorption and precipitation.The zeolite X converted from stellerite zeolite has a low n(Si/Al),abundant hydroxyl groups,and high crystallinity and purity,imparting a good adsorption performance for Cd^(2+)and Ni^(2+)ions.This study suggests that zeolite X converted from stellerite zeolite could be a useful environmentally-friendly and effective tool for the removal of Cd^(2+)and Ni^(2+)ions from aqueous solutions.展开更多
A versatile wet impregnation method was employed to conveniently and controllably deposit Fe_2O_3 nanoparticles on zeolites including commercial Y, mordenite and ZSM-5 with the similar framework Si/Al ratios and cryst...A versatile wet impregnation method was employed to conveniently and controllably deposit Fe_2O_3 nanoparticles on zeolites including commercial Y, mordenite and ZSM-5 with the similar framework Si/Al ratios and crystal sizes, respectively. The ultrafine Fe_2O_3 nanoparticles in size of 5 nm can be highly dispersed on zeolite Y matrix due to its much better wettability than ZSM-5 and mordenite. By using the obtained Fe_2O_3/zeolite composite as the heterogeneous Fenton-like catalysts, the degradation of phenol as a model reaction was systematically investigated, including the zeolite supports, particle size and dispersion of Fe_2O_3, and reaction conditions of H_2O_2 concentration, temperature, and pH value. The catalyst based on zeolite Y with Fe loading of 9% exhibited the best phenol degradation efficiency (> 90%)in neutral pH within 2 h. Its high catalytic activity in Fenton reaction can be attributed to the bifunctional properties of strong surface BrФnsted acidity and high reactivity of octahedral Fe^(3+) in the highlydispersed ultrafine Fe_2O_3 nanoparticles in size of 5 nm, which were the primary active centers to quickly decompose H_2O_2 into hydroxyl radicals. Since phenol degradation can be performed under mild conditions of ambient temperature (283-323 K) and a wide pH range (4.0-7.0), the catalysts can be easily recovered for recyclable use with stable degradation activity, which own the immense potential in deep treatment of organic pollutants in industrial wastewater.展开更多
A selective and efficient process for the electrophilic nitration is described using N_2O_5 as a green nitrating agent,Hβ zeolite as a solid acid catalyst and shape controlling agent under mild conditions.
Li4Si O4 has been regarded as one of the most promising high-temperature CO2 sorbents.However,for practical applications,its CO2sorption kinetics,cycling stability and sorption properties at lower temperatures or lowe...Li4Si O4 has been regarded as one of the most promising high-temperature CO2 sorbents.However,for practical applications,its CO2sorption kinetics,cycling stability and sorption properties at lower temperatures or lower CO2 concentrations have to be improved.In this contribution,four Li4Si O4 sorbents were synthesized from zeolite precursors MCM-41,MCM-48,TS-1,and ZSM-5.The CO2 uptake,cycling stability and the optimal CO2 sorption conditions were investigated.Among the samples,MCM-41-Li4Si O4 showed the best cycling stability at 650°C,with a stable reversible CO2 uptake of 29.1 wt%under 100 vol%CO2 during 20 cycles.But its sorption kinetics and CO2 uptakes at lower temperatures and lower CO2 concentrations need to be improved.We then demonstrated that the sorption kinetics can be improved by modifying the MCM-41 precursor with metals such as Al,Ti,Ca,and Na.The Na-MCM-41-Li4Si O4 sample exhibited the highest sorption rate,and reached the equilibrium sorption capacity close to the theoretical value of 36.7 wt%within 20 min.In addition,we proved that coating the MCM-41-Li4Si O4with Na2CO3and K2CO3can significantly increase the CO2uptakes at lower temperatures(e.g.550℃)and lower CO2concentrations(10–20 vol%).At 550℃ and under 20 vol%CO2,15 wt%K2CO3-MCM-41-Li4Si O4 and 10 wt%Na2CO3-MCM-41-Li4Si O4 sorbents resulted in a CO2 uptake of 32.2 wt%and 34.7 wt%,respectively,which are much higher than that of MCM-41-Li4Si O4(11.8 wt%).These two sorbents also showed good cycling stability.The promoiting mechasnim by alkali carbonate coating was discussed by a doubleshell model.展开更多
For the first time the preparation of the N-doped TiO2-coated NaY zeolite membrane（N-doped TiO2/NaY zeolite membrane） as an electrode material for photoelectrocatalysis has been achieved and reported.The XRD, SEM, U...For the first time the preparation of the N-doped TiO2-coated NaY zeolite membrane（N-doped TiO2/NaY zeolite membrane） as an electrode material for photoelectrocatalysis has been achieved and reported.The XRD, SEM, UV–vis and XPS techniques were used to characterize the structure of the N-doped TiO2/NaY zeolite membrane. The results verified that the surface of the N-doped TiO2/NaY zeolite membrane was coated by TiO2 nanoparticles of ca. 20 nm size and exhibited a distinct red-shift in the UV–vis spectra compared to N-doped TiO2. The photoelectrocatalysis performance of the N-doped TiO2/NaY zeolite membrane electrode was evaluated by phenol degradation. The results revealed it is a promising novel electrode material for application of photoelectrocatalysis in the removal of organic contaminants in waste water.展开更多
Artificial zeolite was modified by nano-Fe3O4 for development of functional adsorbents.Subsequently,adsorbents such as calcium cross-linked nano-Fe3O4 microspheres (Ca-MS),calcium cross-linked nano-Fe3O4 modified zeol...Artificial zeolite was modified by nano-Fe3O4 for development of functional adsorbents.Subsequently,adsorbents such as calcium cross-linked nano-Fe3O4 microspheres (Ca-MS),calcium cross-linked nano-Fe3O4 modified zeolite microspheres (Ca-MZS) and iron cross-linked nano-Fe3O4 modified zeolite microspheres (Fe-MZS) were prepared and compared for their adsorption performance.The effects of adsorbent dosage,solution pH,initial concentration and ion content on the removal of Cu^2+ from wastewater are investigated,and the adsorption kinetics and isotherms for the adsorbent materials were analyzed.The experimental results indicate that for the initial concentration of Cu^2+ of 30 mg/L,the adsorption is noted to be most stable.The optimal initial pH for adsorbing Cu^2+ is observed to be 5.5.At an optimal dosage of Ca-MZS of 900 mg/L,the adsorption capacity is measured to be 28.25 mg/g,along with the removal rate of 72.49%.The addition of Na+ and K+ affects the adsorption of Cu^2+.For the Na^+ and K^+ concentration of 0.2 mmol/L,the Cu^2+ removal rate by Ca-MZS drops to 11.94% and 22.12%,respectively.As compared with the adsorbents such as Natural Zeolite (NZ),Ca-MS and Fe-MZS,Ca-MZS demonstrates the best removal effect in solution,where the removal rate reaches 84.27%,with the maximum adsorption capacity of 28.09 mg/g.The Cu^2+ adsorption kinetics of Ca-MZS is observed to follow the Elovich kinetic model,with the adsorption isotherm data fitting the Freundlich isotherm model by using the non-linear method.展开更多
The intrinsically safe Zn||I_(2) battery,one of the leading candidates aiming to replace traditional Pb-acid batteries,is still seriously suffering from short shelf and cycling lifespan,due to the uncontrolled I_(3)^(...The intrinsically safe Zn||I_(2) battery,one of the leading candidates aiming to replace traditional Pb-acid batteries,is still seriously suffering from short shelf and cycling lifespan,due to the uncontrolled I_(3)^(−)-shuttling and dynamic parasitic reactions on Zn anodes.Considering the fact that almost all these detrimental processes terminate on the surfaces of Zn anodes,modifying Zn anodes’surface with protecting layers should be one of the most straightforward and thorough approaches to restrain these processes.Herein,a facile zeolite-based cation-exchange protecting layer is designed to comprehensively suppress the unfavored parasitic reactions on the Zn anodes.The negatively-charged cavities in the zeolite lattice provide highly accessible migration channels for Zn^(2+),while blocking anions and electrolyte from passing through.This low-cost cation-exchange protecting layer can simultaneously suppress self-discharge,anode corrosion/passivation,and Zn dendrite growth,awarding the Zn||I_(2) batteries with ultra-long cycle life(91.92%capacity retention after 5600 cycles at 2 A g^(−1)),high coulombic efficiencies(99.76%in average)and large capacity(203–196 mAh g^(−1) at 0.2 A g^(−1)).This work provides a highly affordable approach for the construction of high-performance Zn-I_(2) aqueous batteries.展开更多
In this work, the zeolite-Y was ion-exchanged by introducing silver cations into the framework of microsized nano-porous sodium zeolite-Y using a liquid-phase ion exchanged method. The Ag+ion-exchanged zeolite, was th...In this work, the zeolite-Y was ion-exchanged by introducing silver cations into the framework of microsized nano-porous sodium zeolite-Y using a liquid-phase ion exchanged method. The Ag+ion-exchanged zeolite, was then embedded into the Matrimid5218 matrix to form novel mixed matrix membranes(MMMs). The particles and MMMs were characterized by ultraviolet-visible diffuse reflectance spectroscopy(UV–vis DRS), N2adsorption–desorption isotherm, X-ray diffraction(XRD), Fourier transform infrared(FTIR) and scanning electron microscopy(SEM). Furthermore, the effects of filler content(0–20wt%) on pure and mixed gas experiments, feed pressure(2–20 bar) and operating temperature(35–75 oC)on CO2/CH4transport properties of Matrimid/Ag Y MMMs were considered. Characterization results confirmed an appropriate ion-exchange treatment of the zeolites. The SEM results confirmed the superior interfacial adhesion between polymer and zeolites, particularly in the case of Matrimid/Ag Y membranes.This is due to the proper silverous zeolite/Matrimid functional groups’ interactions. The gas permeation results showed that the CO2permeability increased about 123%, from 8.34 Barrer for pure Matrimid to18.62 Barrer for Matrimid/Ag Y(15 wt%). The CO2/CH4selectivity was improved about 66%, from 36.3 for Matrimid to 60.1 for Matrimid/Ag Y(15 wt%). The privileged gas separation performance of Matrimid/Ag Y(15 wt%) was the result of a combined effect of facilitated transport mechanism of Ag+ions as well as the intrinsic surface diffusion mechanism of Y-type zeolite. In order to survey the possibility of using the developed MMMs in industry, the CO2-induced plasticization effect and mixed gas experiment were accomplished. It was deduced that the fabricated MMMs could maintain the superior performance in actual operating conditions.展开更多
The adsorption method based on solid adsorbents is one of feasible ways to capture and store CO2. Using the ion exchange method, different zeolites Na KA varying in K＋content were produced. The adsorption isotherms a...The adsorption method based on solid adsorbents is one of feasible ways to capture and store CO2. Using the ion exchange method, different zeolites Na KA varying in K＋content were produced. The adsorption isotherms and kinetic uptakes were measured. The experimental results show that the optimal NaKA could adsorb significant quantities of CO2 and little N2. On the zeolite Na KA with 14.7 at.% K＋, the adsorption capacity for pure CO2 is over 3.10 mmol g^-1 and the CO2–N2 selectivity is about 149 at ambient pressure and temperature. The kinetic CO2–N2 selectivity could also achieved 200 within 3 min according to the uptake data. To demonstrate the separation effectiveness, breakthrough curves of pure components and binary mixtures were investigated experimentally and theoretically in a fixed bed. It is found that the breakthrough points of CO2 and N2 are almost at the same time under the atmospheric pressure at 348 K with the raw gas composition CO2/N2（20：80, v/v）. If the pressure has been increased higher than 0.1 MPa, CO2 would break through the bed much slower than N2. Therefore, the pressure may become the limiting factor for the separation performance of zeolites NaKA.展开更多
2,6-Dimethylnaphthalene (2,6-DMN) is a key intermediate for polyethylene naphthalate synthesis. The selective synthesis of 2,6-DMN from naphthalene and methanol was carried out over different zeolites (HZSM-5, Hβ, HU...2,6-Dimethylnaphthalene (2,6-DMN) is a key intermediate for polyethylene naphthalate synthesis. The selective synthesis of 2,6-DMN from naphthalene and methanol was carried out over different zeolites (HZSM-5, Hβ, HUSY and SAPO-11) modified by 0.1wt% PdO under atmospheric pressure. Among the adopted zeolites, SAPO-11 exhibits exceptional shape-selectivity and stability to synthesize 2,6-dimethylnaphthalene from methylation of naphthalene, due to the special pore structure of SAPO-11 which inosculated better with 2,6-dimethylnaphthalene than with 2,7-dimethylnaphthalene.展开更多
The effects of the initial framework SiO2/Al2O3 ratio and temperature on the structural changes of NaY zeolites during hydrothermal treatments are studied. Two samples with different framework SiO2/Al2O3 ratios are ...The effects of the initial framework SiO2/Al2O3 ratio and temperature on the structural changes of NaY zeolites during hydrothermal treatments are studied. Two samples with different framework SiO2/Al2O3 ratios are subjected to hydrothermal treatment at four different temperatures. For zeolite with a lower initial SiO2/Al2O3 ratio of 4.2, mesopores are easily formed because more framework aluminum is detached. Moreover, two kinds of mesopores are produced at a higher temperature due to the interconnection of vacancies and smaller mesopores. For zeolite with a higher initial SiO2/Al2O3 ratio of 6.0, there are less mesopores formed as compared with the lower initial SiO2/Al2O3 ratio sample, but there are some macropores formed. This may be attributed to the isolation of vacancies and the different distributions of aluminum in the crystal lattice of the zeolite. The experiment data show that NaY with the SiO2/Al2O3 ratio of 6.0 retains a high relative crystallinity during the hydrothermal treatment. This proves that a high framework SiO2/Al2O3 ratio benefits the stability of zeolite.展开更多
Ti02 coatings on natural feather zeolite are respectively prepared by a collosol （Sol-gel） method and two powder coating methods with deionizod water or dehydrated ethanol as a dispersant. During degradation of orth...Ti02 coatings on natural feather zeolite are respectively prepared by a collosol （Sol-gel） method and two powder coating methods with deionizod water or dehydrated ethanol as a dispersant. During degradation of orthomono- chlorphenol solutions by ultraviolet, the strong adsorption capability of the zeolite results in increased concentration of substrate on its surface. The Ti（h film coated on feather zeolite further enhances the photocatalytic activity. The TiO~ film on the zeolite prepared by the Sol-gel method is found more effective as a catalyst than that by two powder coating methods.展开更多
The low porosity of metal-organic framework glass makes it difficult to prepare membranes with high permeability.To solve this problem,we fabricated a series of self-supported zeolite glass composite membranes with di...The low porosity of metal-organic framework glass makes it difficult to prepare membranes with high permeability.To solve this problem,we fabricated a series of self-supported zeolite glass composite membranes with different 4A zeolite loadings using the abundant pore structure of the zeolite.The 4A zeolite embedded in the zeolite glass composite membrane preserved the ligand bonds and chemical structure.The self-supported zeolite glass composite membranes exhibited good interfacial compatibility.More importantly,the incorporation of the 4A zeolite significantly improved the CO_(2)adsorption capacity of the pure a_(g)ZIF-62 membranes.In addition,gas separation performance measurements showed that the(a_(g)ZIF-62)_(0.7)(4A)_(0.3)membrane had a permeability of 13,329 Barrer for pure CO_(2)and an ideal selectivity of 31.7 for CO_(2)/CH_(4),which exceeded Robeson's upper bound.The(a_(g)ZIF-62)_(0.7)(4A)_(0.3)membrane exhibited good operational stability in the variable pressure test and 48 h long-term continuous test.This study provides a method for preparing zeolite glass composite membranes.展开更多
Study of physisorbed and chemisorbed carbon dioxide (CO<sub>2</sub>) species was carried out on the NaX zeolite modified by cationic exchanges with bivalent cations (Ca<sup>2+</sup> and Ba<s...Study of physisorbed and chemisorbed carbon dioxide (CO<sub>2</sub>) species was carried out on the NaX zeolite modified by cationic exchanges with bivalent cations (Ca<sup>2+</sup> and Ba<sup>2+</sup>) by temperature-programmed desorption of CO<sub>2</sub> (CO<sub>2</sub>-TPD). Others results were obtained by infrared to complete the study. The results of this research showed, in the physisorption region (213 - 473 K), that the cationic exchanges on NaX zeolite with bivalent cations increase slightly the interactions of CO<sub>2</sub> molecule with adsorbents and/or cationic site. Indeed, the desorption energies of physisorbed CO<sub>2</sub> obtained on the reference zeolite NaX (13.5 kJ·mol<sup>-1</sup>) are lower than that of exchanged zeolites E-CaX and E-BaX (15.77 and 15.17 kJ·mol<sup>-1</sup> respectively). In the chemisorbed CO<sub>2</sub> region (573 - 873 K), the desorption energies related to desorbed species (bidentate carbonates: CO<sub>3</sub>2-</sup>) on the exchanged zeolites E-CaX and E-BaX are about 81 kJ·mol<sup>-1</sup>, higher than the desorbed species (bicarbonates: HCO<sub>3</sub>2-</sup>) on the reference R-NaX (62 kJ·mol<sup>-1</sup>). In addition, the exchanged E-BaX zeolite develops the secondary adsorption sites corresponding to bicarbonates species with desorption energies of 35 kJ·mol<sup>-1</sup> lower to desorption energies of bicarbonates noted on the reference zeolite NaX.展开更多
基金the National Key Research and Development Program of China(2021YFA1500401)the National Natural Science Foundation of China(22288101)the‘111 Center’(B17020)for supporting this work.
文摘The use of fossil fuels significantly contributes to excess CO_(2) emissions.Catalytic hydrogenation of CO_(2) to dimethyl ether(DME)is an effective method for CO_(2) recycling,offering both environmental and economic benefits.Zeolites,known for their efficiency as solid catalysts,are widely utilized in the chemical industries.Bifunctional catalysts based on zeolites have gained attention for their applications in CO_(2) hydrogenation to DME.This review discusses key factors affecting the catalytic performance of zeolites,including topologies,Si/Al ratio,crystal size,and the proximity of metallic species to the zeolite catalysts.Although bifunctional catalytic systems enhance the conversion of CO_(2) to DME,they also lead to high CO selectivity at elevated temperatures,which can limit both DME yield and selectivity.We present recent advancements in the development of bifunctional catalysts for the direct hydrogenation of CO_(2) to DME,providing insights for designing optimized catalysts for tandem reaction systems.
文摘Direct converting carbon dioxide(CO_(2))and propane(C_(3)H_(8))into aromatics with high carbon utilization offers a desirable opportunity to simultaneously mitigate CO_(2)emission and adequately utilize C_(3)H_(8) in shale gas.Owing to their thermodynamic resistance,converting CO_(2)and C_(3)H_(8) respectively remains difficult.Here,we achieve 60.2%aromatics selectivity and 48.8%propane conversion over H-ZSM-5-25 via a zeolite-catalyzing the coupling of CO_(2)and C_(3)H_(8).Operando dual-beam FTIR spectroscopy combined with ^(13)C-labeled CO_(2)tracing experiments revealed that CO_(2)is directly involved in the generation of aromatics,with its carbon atoms selectively embedded into the aromatic ring,bypassing the reverse water-gas shift pathway.Accordingly,a cooperative aromatization mechanism is proposed.Thereinto,lactones,produced from CO_(2)and olefins,are proven to be the key intermediate.This work not only provides an opportunity for simultaneous conversion of CO_(2)and C_(3)H_(8),but also expends coupling strategy designing of CO_(2)and alkanes over acidic zeolites.
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supported by the National Natural Science Foundation of China(21577094)the Zhejiang Public Welfare Technology Research Project(LGG19B070003).
文摘Sulfur dioxide(SO_(2))frequently coexist with volatile organic compounds(VOCs)in exhaust gas.The competitive adsorption of SO_(2) and VOCs can adversely affect the efficiency of catalytic combustion,leading to catalyst poisoning and irreversible loss of activity.To investigate the impact of sulfur poisoning on the catalysts,we prepared the MnO_(2)/Beta zeolite,and a corresponding series of sulfur-poisoned catalysts through in-situ thermal decomposition of(NH_(4))_(2)SO_(4).The decrease in toluene catalytic activity of poisoned MnO_(2)/Beta zeolite primarily results from the conversion of the active species MnO_(2) to MnSO_(4).However,the crystal structure and the porous structure of MnO_(2)/Beta zeolite were stable,and original structure was still maintained when 1.6%(mass)sulfur species were introduced.Furthermore,the extra-framework Al of Beta zeolite could capture sulfur species to generate Al2(SO_(4))_(3),thereby reducing sulfur species from reacting with Mn^(4+) active sites.The combination of sulfur and Beta zeolite was found to directly produce new strong-acid sites,thus effectively compensating for the effect of reduced Mn4+active species on the catalytic activity.
基金the financial support from the Selfdeployed Projects (E355F002 and E355F005) of Ganjiang Innovation Academyfinancial support by Bureau of Science and Technology,Taiyuan,entitled “the enrichment of coal bed methane using novel adsorbents via pressure swing adsorption”。
文摘Sodium Y(Na Y) zeolite is a promising adsorbent for carbon capture.The template-free synthesis of Na Y zeolite has gained considerable interests to minimize its costs and environmental effects.However,Na Y zeolites synthesized through template-free methods exhibited lower CO_(2) adsorption capacities(~4.07 mmol·g^(-1)) compared to template-assisted counterparts,often requiring longer crystallization time and higher energy penalty.This study systematically compared the microstructural characteristics and CO_(2) adsorption performance of Na Y zeolites synthesized with and without templates,including those from the commercial markets.Through process optimization,the CO_(2) adsorption capacity of the template-free Na Y zeolite was significantly enhanced,surpassing those template-assisted samples.Notably,it achieved CO_(2) adsorption capacities of 6.51 mmol·g^(-1) at 25℃ and 0.1 MPa,and 7.40 mmol·g^(-1) at 0℃ and 0.1 MPa,outperforming both commercial Na Y and template-assisted samples.The structural differences,including crystal integrity,pore size distribution and surface properties,were systematically discussed.The optimized synthesis method increased the specific surface area and the ratio of microporous structures.The template-free Na Y also showed superior CO_(2) capture capacity,moisture resistance,breakthrough performance and stability,indicating its application potential for carbon capture.
文摘The direct oxidation of cyclohexane to adipic acid(AA)without the use of HNO_(3)is important but still challenging.Herein,hierarchical manganese-containing TS-1 zeolite(HMTS)was prepared using an improved direct synthesis method,in which titanium and manganese coexist within the zeolite matrix,as characterized by X-ray diffraction,X-ray photoelectron spectroscopy,transmission electron microscopy,ultraviolet,extended X-ray absorption fine structure etc.The introduction of matrix Mn species(Mn^(3+),Mn^(4+))not only increased the surface oxygen vacancies,but also generated medium-strong acid sites,which endowed HMTS catalysts with the ability to efficiently activate oxygen and facilitate substrate coordination.On HMTS-3,one-pot oxidation of cyclohexane at 140℃and 2 MPa O_(2)gave 81.6%conversion and 71.5%AA selectivity,the highest value obtained at present.Control experiments with single-component samples confirmed that matrix Ti^(4+)catalyzed the conversion of cyclohexane to a mixture of cyclohexanone and cyclohexanol(KA oil),and matrix Mn favored the conversion of KA oil to AA.The synergy between matrix Ti and Mn inside the hierarchical structure were the key factor for the superior activity.Specifically,the matrix Ti^(4+)might activate oxygen to form Ti-O_(2)2-which facilitated the activation of the C-H bond of cyclohexane.The activation of O_(2)on matrix Mn^(3+)formed Mn^(4+)-O_(2)-favoring the breaking of the C-C bond of cyclohexanone.The hierarchical structure not only exposed more active sites and promoted mass transfer,but also provided a better microenvironment for the matrix Mn to synergize with the matrix Ti,which facilitated the overall reaction.This work demonstrated the practical application potential of HMTS and provided useful insights into the direct oxidation of cyclohexane to AA.
基金supported by the National Natural Science Foundation of China(51564008,41662005)Natural Science Foundation of Guangxi Province(2019GXNSFBA245083)。
文摘Zeolite X was synthesized by a two-step hydrothermal method using natural stellerite zeolite as the silicon seed,and its adsorption performance for Cd^(2+)and Ni^(2+)ions was experimentally and comprehensively investigated.The effects of p H,zeolite X dosage,contact time,and temperature on adsorption performance for Cd^(2+)and Ni^(2+)ions over were studied.The adsorption process was endothermic and spontaneous,and followed the pseudo-second-order kinetic and the Langmuir isotherm models.The maximum adsorption capacitiesfor Cd^(2+)and Ni^(2+)ions at 298 K were 173.553 and 75.897 mg.g-1,respectively.Ion exchange and precipitation were the principal mechanisms for the removal of Cd^(2+)ions from aqueous solutions by zeolite X,followed by electrostatic adsorption.Ion exchange was the principal mechanisms for the removal of Ni^(2+)ions from aqueous solutions by zeolite X,followed by electrostatic adsorption and precipitation.The zeolite X converted from stellerite zeolite has a low n(Si/Al),abundant hydroxyl groups,and high crystallinity and purity,imparting a good adsorption performance for Cd^(2+)and Ni^(2+)ions.This study suggests that zeolite X converted from stellerite zeolite could be a useful environmentally-friendly and effective tool for the removal of Cd^(2+)and Ni^(2+)ions from aqueous solutions.
基金sponsored by Shanghai Pujiang Program, China (No. 16PJ1401100)the Shanghai Committee of Science and Technology, China (No.15ZR1402000)+3 种基金Key Basic Research Program of Science and Technology Commission of Shanghai Municipality (No. 17JC1400100)the NSF of China(No. 21673048)National Youth Top Talent Support Program of National High-Level Personnel of Special Support Program (Youth Top-notch Talent Support Program)the State Key Laboratory of Transducer Technology of China (No. SKT1503)
文摘A versatile wet impregnation method was employed to conveniently and controllably deposit Fe_2O_3 nanoparticles on zeolites including commercial Y, mordenite and ZSM-5 with the similar framework Si/Al ratios and crystal sizes, respectively. The ultrafine Fe_2O_3 nanoparticles in size of 5 nm can be highly dispersed on zeolite Y matrix due to its much better wettability than ZSM-5 and mordenite. By using the obtained Fe_2O_3/zeolite composite as the heterogeneous Fenton-like catalysts, the degradation of phenol as a model reaction was systematically investigated, including the zeolite supports, particle size and dispersion of Fe_2O_3, and reaction conditions of H_2O_2 concentration, temperature, and pH value. The catalyst based on zeolite Y with Fe loading of 9% exhibited the best phenol degradation efficiency (> 90%)in neutral pH within 2 h. Its high catalytic activity in Fenton reaction can be attributed to the bifunctional properties of strong surface BrФnsted acidity and high reactivity of octahedral Fe^(3+) in the highlydispersed ultrafine Fe_2O_3 nanoparticles in size of 5 nm, which were the primary active centers to quickly decompose H_2O_2 into hydroxyl radicals. Since phenol degradation can be performed under mild conditions of ambient temperature (283-323 K) and a wide pH range (4.0-7.0), the catalysts can be easily recovered for recyclable use with stable degradation activity, which own the immense potential in deep treatment of organic pollutants in industrial wastewater.
基金the financial support from the National Natural Science Foundation of China-Academy of Engineering Physics(No.10976014)the Natural Science Foundation of Jiangsu Province(No.BK2011697)Independent Scientific Research Special Plan of NJUST(No.2011YBXM06)
文摘A selective and efficient process for the electrophilic nitration is described using N_2O_5 as a green nitrating agent,Hβ zeolite as a solid acid catalyst and shape controlling agent under mild conditions.
基金supported by the National Natural Science Foundation of China (51622801, 51572029)Beijing Excellent Young Scholar (2015000026833ZK11)the Beijing Natural Science Foundation (2184114)
文摘Li4Si O4 has been regarded as one of the most promising high-temperature CO2 sorbents.However,for practical applications,its CO2sorption kinetics,cycling stability and sorption properties at lower temperatures or lower CO2 concentrations have to be improved.In this contribution,four Li4Si O4 sorbents were synthesized from zeolite precursors MCM-41,MCM-48,TS-1,and ZSM-5.The CO2 uptake,cycling stability and the optimal CO2 sorption conditions were investigated.Among the samples,MCM-41-Li4Si O4 showed the best cycling stability at 650°C,with a stable reversible CO2 uptake of 29.1 wt%under 100 vol%CO2 during 20 cycles.But its sorption kinetics and CO2 uptakes at lower temperatures and lower CO2 concentrations need to be improved.We then demonstrated that the sorption kinetics can be improved by modifying the MCM-41 precursor with metals such as Al,Ti,Ca,and Na.The Na-MCM-41-Li4Si O4 sample exhibited the highest sorption rate,and reached the equilibrium sorption capacity close to the theoretical value of 36.7 wt%within 20 min.In addition,we proved that coating the MCM-41-Li4Si O4with Na2CO3and K2CO3can significantly increase the CO2uptakes at lower temperatures(e.g.550℃)and lower CO2concentrations(10–20 vol%).At 550℃ and under 20 vol%CO2,15 wt%K2CO3-MCM-41-Li4Si O4 and 10 wt%Na2CO3-MCM-41-Li4Si O4 sorbents resulted in a CO2 uptake of 32.2 wt%and 34.7 wt%,respectively,which are much higher than that of MCM-41-Li4Si O4(11.8 wt%).These two sorbents also showed good cycling stability.The promoiting mechasnim by alkali carbonate coating was discussed by a doubleshell model.
基金supported by the Talent Introduction Fund of Yangzhou University(2012),Jiangsu Province Science and Technology Support Project(No.BE2014613)Six Big Peak Talent in Jiangsu Province(No.2014-XCL-013)the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘For the first time the preparation of the N-doped TiO2-coated NaY zeolite membrane（N-doped TiO2/NaY zeolite membrane） as an electrode material for photoelectrocatalysis has been achieved and reported.The XRD, SEM, UV–vis and XPS techniques were used to characterize the structure of the N-doped TiO2/NaY zeolite membrane. The results verified that the surface of the N-doped TiO2/NaY zeolite membrane was coated by TiO2 nanoparticles of ca. 20 nm size and exhibited a distinct red-shift in the UV–vis spectra compared to N-doped TiO2. The photoelectrocatalysis performance of the N-doped TiO2/NaY zeolite membrane electrode was evaluated by phenol degradation. The results revealed it is a promising novel electrode material for application of photoelectrocatalysis in the removal of organic contaminants in waste water.
基金Funded by the Science Foundation of Hubei Province of China(2015CFB706)。
文摘Artificial zeolite was modified by nano-Fe3O4 for development of functional adsorbents.Subsequently,adsorbents such as calcium cross-linked nano-Fe3O4 microspheres (Ca-MS),calcium cross-linked nano-Fe3O4 modified zeolite microspheres (Ca-MZS) and iron cross-linked nano-Fe3O4 modified zeolite microspheres (Fe-MZS) were prepared and compared for their adsorption performance.The effects of adsorbent dosage,solution pH,initial concentration and ion content on the removal of Cu^2+ from wastewater are investigated,and the adsorption kinetics and isotherms for the adsorbent materials were analyzed.The experimental results indicate that for the initial concentration of Cu^2+ of 30 mg/L,the adsorption is noted to be most stable.The optimal initial pH for adsorbing Cu^2+ is observed to be 5.5.At an optimal dosage of Ca-MZS of 900 mg/L,the adsorption capacity is measured to be 28.25 mg/g,along with the removal rate of 72.49%.The addition of Na+ and K+ affects the adsorption of Cu^2+.For the Na^+ and K^+ concentration of 0.2 mmol/L,the Cu^2+ removal rate by Ca-MZS drops to 11.94% and 22.12%,respectively.As compared with the adsorbents such as Natural Zeolite (NZ),Ca-MS and Fe-MZS,Ca-MZS demonstrates the best removal effect in solution,where the removal rate reaches 84.27%,with the maximum adsorption capacity of 28.09 mg/g.The Cu^2+ adsorption kinetics of Ca-MZS is observed to follow the Elovich kinetic model,with the adsorption isotherm data fitting the Freundlich isotherm model by using the non-linear method.
基金The authors thank the National Natural Science Foundation of China(51502194,22133005,21973107,and 22103093)the Natural Science Foundation of Shandong(ZR2020ME024)+2 种基金the Science and Technology Commission of Shanghai Municipality(21ZR1472900)the Key Laboratory for Palygorskite Science and Applied Technology of Jiangsu Province(HPK202103)for financial supportOpen access funding provided by Shanghai Jiao Tong University
文摘The intrinsically safe Zn||I_(2) battery,one of the leading candidates aiming to replace traditional Pb-acid batteries,is still seriously suffering from short shelf and cycling lifespan,due to the uncontrolled I_(3)^(−)-shuttling and dynamic parasitic reactions on Zn anodes.Considering the fact that almost all these detrimental processes terminate on the surfaces of Zn anodes,modifying Zn anodes’surface with protecting layers should be one of the most straightforward and thorough approaches to restrain these processes.Herein,a facile zeolite-based cation-exchange protecting layer is designed to comprehensively suppress the unfavored parasitic reactions on the Zn anodes.The negatively-charged cavities in the zeolite lattice provide highly accessible migration channels for Zn^(2+),while blocking anions and electrolyte from passing through.This low-cost cation-exchange protecting layer can simultaneously suppress self-discharge,anode corrosion/passivation,and Zn dendrite growth,awarding the Zn||I_(2) batteries with ultra-long cycle life(91.92%capacity retention after 5600 cycles at 2 A g^(−1)),high coulombic efficiencies(99.76%in average)and large capacity(203–196 mAh g^(−1) at 0.2 A g^(−1)).This work provides a highly affordable approach for the construction of high-performance Zn-I_(2) aqueous batteries.
文摘In this work, the zeolite-Y was ion-exchanged by introducing silver cations into the framework of microsized nano-porous sodium zeolite-Y using a liquid-phase ion exchanged method. The Ag+ion-exchanged zeolite, was then embedded into the Matrimid5218 matrix to form novel mixed matrix membranes(MMMs). The particles and MMMs were characterized by ultraviolet-visible diffuse reflectance spectroscopy(UV–vis DRS), N2adsorption–desorption isotherm, X-ray diffraction(XRD), Fourier transform infrared(FTIR) and scanning electron microscopy(SEM). Furthermore, the effects of filler content(0–20wt%) on pure and mixed gas experiments, feed pressure(2–20 bar) and operating temperature(35–75 oC)on CO2/CH4transport properties of Matrimid/Ag Y MMMs were considered. Characterization results confirmed an appropriate ion-exchange treatment of the zeolites. The SEM results confirmed the superior interfacial adhesion between polymer and zeolites, particularly in the case of Matrimid/Ag Y membranes.This is due to the proper silverous zeolite/Matrimid functional groups’ interactions. The gas permeation results showed that the CO2permeability increased about 123%, from 8.34 Barrer for pure Matrimid to18.62 Barrer for Matrimid/Ag Y(15 wt%). The CO2/CH4selectivity was improved about 66%, from 36.3 for Matrimid to 60.1 for Matrimid/Ag Y(15 wt%). The privileged gas separation performance of Matrimid/Ag Y(15 wt%) was the result of a combined effect of facilitated transport mechanism of Ag+ions as well as the intrinsic surface diffusion mechanism of Y-type zeolite. In order to survey the possibility of using the developed MMMs in industry, the CO2-induced plasticization effect and mixed gas experiment were accomplished. It was deduced that the fabricated MMMs could maintain the superior performance in actual operating conditions.
文摘The adsorption method based on solid adsorbents is one of feasible ways to capture and store CO2. Using the ion exchange method, different zeolites Na KA varying in K＋content were produced. The adsorption isotherms and kinetic uptakes were measured. The experimental results show that the optimal NaKA could adsorb significant quantities of CO2 and little N2. On the zeolite Na KA with 14.7 at.% K＋, the adsorption capacity for pure CO2 is over 3.10 mmol g^-1 and the CO2–N2 selectivity is about 149 at ambient pressure and temperature. The kinetic CO2–N2 selectivity could also achieved 200 within 3 min according to the uptake data. To demonstrate the separation effectiveness, breakthrough curves of pure components and binary mixtures were investigated experimentally and theoretically in a fixed bed. It is found that the breakthrough points of CO2 and N2 are almost at the same time under the atmospheric pressure at 348 K with the raw gas composition CO2/N2（20：80, v/v）. If the pressure has been increased higher than 0.1 MPa, CO2 would break through the bed much slower than N2. Therefore, the pressure may become the limiting factor for the separation performance of zeolites NaKA.
文摘2,6-Dimethylnaphthalene (2,6-DMN) is a key intermediate for polyethylene naphthalate synthesis. The selective synthesis of 2,6-DMN from naphthalene and methanol was carried out over different zeolites (HZSM-5, Hβ, HUSY and SAPO-11) modified by 0.1wt% PdO under atmospheric pressure. Among the adopted zeolites, SAPO-11 exhibits exceptional shape-selectivity and stability to synthesize 2,6-dimethylnaphthalene from methylation of naphthalene, due to the special pore structure of SAPO-11 which inosculated better with 2,6-dimethylnaphthalene than with 2,7-dimethylnaphthalene.
文摘The effects of the initial framework SiO2/Al2O3 ratio and temperature on the structural changes of NaY zeolites during hydrothermal treatments are studied. Two samples with different framework SiO2/Al2O3 ratios are subjected to hydrothermal treatment at four different temperatures. For zeolite with a lower initial SiO2/Al2O3 ratio of 4.2, mesopores are easily formed because more framework aluminum is detached. Moreover, two kinds of mesopores are produced at a higher temperature due to the interconnection of vacancies and smaller mesopores. For zeolite with a higher initial SiO2/Al2O3 ratio of 6.0, there are less mesopores formed as compared with the lower initial SiO2/Al2O3 ratio sample, but there are some macropores formed. This may be attributed to the isolation of vacancies and the different distributions of aluminum in the crystal lattice of the zeolite. The experiment data show that NaY with the SiO2/Al2O3 ratio of 6.0 retains a high relative crystallinity during the hydrothermal treatment. This proves that a high framework SiO2/Al2O3 ratio benefits the stability of zeolite.
文摘Ti02 coatings on natural feather zeolite are respectively prepared by a collosol （Sol-gel） method and two powder coating methods with deionizod water or dehydrated ethanol as a dispersant. During degradation of orthomono- chlorphenol solutions by ultraviolet, the strong adsorption capability of the zeolite results in increased concentration of substrate on its surface. The Ti（h film coated on feather zeolite further enhances the photocatalytic activity. The TiO~ film on the zeolite prepared by the Sol-gel method is found more effective as a catalyst than that by two powder coating methods.
基金supported by the S&T Program of Hebei(no.22373709D).
文摘The low porosity of metal-organic framework glass makes it difficult to prepare membranes with high permeability.To solve this problem,we fabricated a series of self-supported zeolite glass composite membranes with different 4A zeolite loadings using the abundant pore structure of the zeolite.The 4A zeolite embedded in the zeolite glass composite membrane preserved the ligand bonds and chemical structure.The self-supported zeolite glass composite membranes exhibited good interfacial compatibility.More importantly,the incorporation of the 4A zeolite significantly improved the CO_(2)adsorption capacity of the pure a_(g)ZIF-62 membranes.In addition,gas separation performance measurements showed that the(a_(g)ZIF-62)_(0.7)(4A)_(0.3)membrane had a permeability of 13,329 Barrer for pure CO_(2)and an ideal selectivity of 31.7 for CO_(2)/CH_(4),which exceeded Robeson's upper bound.The(a_(g)ZIF-62)_(0.7)(4A)_(0.3)membrane exhibited good operational stability in the variable pressure test and 48 h long-term continuous test.This study provides a method for preparing zeolite glass composite membranes.
文摘Study of physisorbed and chemisorbed carbon dioxide (CO<sub>2</sub>) species was carried out on the NaX zeolite modified by cationic exchanges with bivalent cations (Ca<sup>2+</sup> and Ba<sup>2+</sup>) by temperature-programmed desorption of CO<sub>2</sub> (CO<sub>2</sub>-TPD). Others results were obtained by infrared to complete the study. The results of this research showed, in the physisorption region (213 - 473 K), that the cationic exchanges on NaX zeolite with bivalent cations increase slightly the interactions of CO<sub>2</sub> molecule with adsorbents and/or cationic site. Indeed, the desorption energies of physisorbed CO<sub>2</sub> obtained on the reference zeolite NaX (13.5 kJ·mol<sup>-1</sup>) are lower than that of exchanged zeolites E-CaX and E-BaX (15.77 and 15.17 kJ·mol<sup>-1</sup> respectively). In the chemisorbed CO<sub>2</sub> region (573 - 873 K), the desorption energies related to desorbed species (bidentate carbonates: CO<sub>3</sub>2-</sup>) on the exchanged zeolites E-CaX and E-BaX are about 81 kJ·mol<sup>-1</sup>, higher than the desorbed species (bicarbonates: HCO<sub>3</sub>2-</sup>) on the reference R-NaX (62 kJ·mol<sup>-1</sup>). In addition, the exchanged E-BaX zeolite develops the secondary adsorption sites corresponding to bicarbonates species with desorption energies of 35 kJ·mol<sup>-1</sup> lower to desorption energies of bicarbonates noted on the reference zeolite NaX.
