Ce-encapsulated Beta zeolite was synthesized by a one-pot hydrothermal method with citric acid complexing Ce in the absence of Na species.Additional citric acid can effectively prevent the deposition of Ce species dur...Ce-encapsulated Beta zeolite was synthesized by a one-pot hydrothermal method with citric acid complexing Ce in the absence of Na species.Additional citric acid can effectively prevent the deposition of Ce species during the hydrothermal synthesis of zeolites,leading to uniform distribution of Ce cluster in the framework of Beta zeolites.Moreover,the sodium-free synthesis system resulted that the Brønsted acid sites were mainly located on the straight channels and external surface of Beta zeolites,improving the utilization of Brønsted acid sites.In addition,Ce encapsulated Beta zeolites showed enhanced activity and robust stability in the alkylation of benzene with 1-dodecene based on the synergistic effect between Ce species and Brønsted acid sites,which pave the way for its practical application in the production of alkylbenzene.展开更多
Y zeolites have moderate microporous pore size, large specific surface area, and good hydrothermal stability, which were widely used in industrial adsorption of volatile organic compounds (VOCs), but the performance o...Y zeolites have moderate microporous pore size, large specific surface area, and good hydrothermal stability, which were widely used in industrial adsorption of volatile organic compounds (VOCs), but the performance of Y zeolites in adsorption of VOCs under high humidity conditions is terrible. In this paper, Y zeolites with different silica-alumina ratios were hydrophobically modified by organosilane and characterized by XRD, FTIR, SEM, BET, NMR. In the experiments of static and dynamic adsorption of VOCs by modified Y zeolites, it can be concluded that the static water adsorption capacity of Y zeolites with silica-aluminum ratio of 5 and 40 after silica modification decreased by 62 wt% and 53 wt%, under the conditions of high humidity, GHSV = 15,000 h<sup>-1</sup>, T = 35°C and initial concentration of toluene C<sub>0</sub> = 5000 mg·m<sup>-3</sup>. The saturation adsorption capacity of toluene was increased from 0.06 g·g<sup>-1</sup>, 0.09 g·g<sup>-1</sup> to 0.15 g·g<sup>-1</sup>, 0.21 g·g<sup>-1</sup>, the adsorption selectivity of Y zeolites for water was reduced and that for toluene was increased after Vapor phase silanization overlay modification. The present modification method might carry out targeted modification of zeolites surface, provide research ideas and guidance under high humidity conditions.展开更多
Novel organo-inorganic hybrid materials(MTW-x-SO_(3)H) have been fabricated by immobilizing 3-mercap topropyltriethoxysilane onto mesopore MTW zeolites, which is treated via a simple oxidation process with hydrogen pe...Novel organo-inorganic hybrid materials(MTW-x-SO_(3)H) have been fabricated by immobilizing 3-mercap topropyltriethoxysilane onto mesopore MTW zeolites, which is treated via a simple oxidation process with hydrogen peroxide as the oxidant to transform sulfhydryl group into sulfonic acid group. The organic sulfhydryl groups are covalently bonded to the external surface of MTW zeolites through the condensation between siloxane arising from organic fragments with silanol groups on the surface of MTW zeolites, the hybrids contain sulfonic acid group within the external surface of MTW zeolites and an opened mesoporous system in the matrix of MTW zeolites, which provide enough accessible Brùnsted acid sites for the alkylation between phenol with tert-butyl alcohol. Through this methodology it's possible to prepare multifunctional materials where the plenty of mesopores are benefit for the introduction of larger numbers of sulfonic acid groups that contributes to activity during reactions, resulting in high activity(>55%) of MTW-4-SO_(3)H and desired selectivity(>56%) of 2-TBP(2-tert-butyl phenol) in the alkylation between phenol with tert-butyl alcohol.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
Furfuryl ethers have been considered to be a promising fuel additive.One step reduction etherification of furfural over supported Pd catalysts provides a facile way for the preparation of furfuryl ether.However,the pr...Furfuryl ethers have been considered to be a promising fuel additive.One step reduction etherification of furfural over supported Pd catalysts provides a facile way for the preparation of furfuryl ether.However,the preparation of a reusable Pd catalyst for reductive etherification remains to be a great challenge.In this study,a series of Si O_(2)supported Pd catalysts with particle size ranging from 2.2 nm to 28 nm were prepared.Their textural properties and catalytic performance in furfural reductive etherification have been systematically studied.The results herein shed light on the particle size effect on the competition between hydrogenation/hydrogenolysis of C=O in furfural over Pd surface.We found out that Pd nanoparticles larger than 3 nm are preferred for one step reductive etherification.Based on this finding,we prepared a Pd/ZSM-5 bifunctional catalyst comprising Pd nanoparticles larger than 3 nm and decreased acidity in presence of amino organosilane,which served as a bifunctional catalyst succeeding in one-pot synthesis of ether via reductive-etherification and direct-etherification.This strategy showed significant advantage in efficiently converting furfuryl acohol,a major side-product,into ether,while suppressing the undesired side-reactions.展开更多
Syngas to ethanol, consisting of dimethyl ether(DME) carbonylation to methyl acetate(MA) over zeolites and MA hydrogenation to ethanol on copper catalyst, has been developed in recent years.DME carbonylation over zeol...Syngas to ethanol, consisting of dimethyl ether(DME) carbonylation to methyl acetate(MA) over zeolites and MA hydrogenation to ethanol on copper catalyst, has been developed in recent years.DME carbonylation over zeolites, a key step in this new process, has attracted increasing attention due to the high reaction efficiency and promising industrial application.In recent years, continuous efforts have been made on improving the activity and stability of the zeolites.From a mechanistic point of view, DME carbonylation to MA, involving the formation of C–C bond, is achieved via the Koch-type CO insertion into DME within the 8-member ring(8-MR) pores of zeolites, typically HMOR and HZSM-35.The unique geometric configuration of the 8-MR pore endowed the formation of the key intermediate(acetyl, CH3CO^*), possibly by a spatial confinement of the transition state during CO insertion into the surface O–CH3 group.This review article summarizes the main progress on zeolite-catalyzed DME carbonylation, including reaction kinetics and mechanism, theoretical calculations, and experimental strategies developed for populating acid sites and engineering pore structure of the zeolites in order to enhance the overall performance.展开更多
Selectivity control is a difficult scientific and industrial challenge in methanol-to-olefins(MTO)conversion.It has been experimentally established that the topology of zeolite catalysts influenced the distribution of...Selectivity control is a difficult scientific and industrial challenge in methanol-to-olefins(MTO)conversion.It has been experimentally established that the topology of zeolite catalysts influenced the distribution of products.Besides the topology effect on reaction kinetics,the topology influences the diffusion of reactants and products in catalysts as well.In this work,by using COMPASS force-field molecular dynamics method,we investigated the intracrystalline diffusion of ethene and propene in four different zeolites,CHA,MFI,BEA and FAU,at different temperatures.The self-diffusion coefficients and diffusion activation barriers were calculated.A strong restriction on the diffusion of propene in CHA was observed because the self-diffusion coefficient ratio of ethene to propene is larger than 18 and the diffusion activation barrier of propene is more than 20 kJ/mol in CHA.This ratio decreases with the increase of temperature in the four investigated zeolites.The shape selectivity on products from diffusion perspective can provide some implications on the understanding of the selectivity difference between HSAPO-34 and HZSM-5 catalysts for the MTO conversion.展开更多
The exhaust gases, including SO_2,NH_3, H_2S, NO_2, NO, and CO, are principal air pollutants due to their severe harms to the ecological environment.Zeolites have been considered as good absorbent candidates to captur...The exhaust gases, including SO_2,NH_3, H_2S, NO_2, NO, and CO, are principal air pollutants due to their severe harms to the ecological environment.Zeolites have been considered as good absorbent candidates to capture the six exhaust gases.In this work, we performed grand canonical ensemble Monte Carlo(GCMC) simulations to examine the capability of 95 kinds of all-silica zeolites in the removal of the six toxic gases, and to predict the adsorption isotherms of the six gases on all the zeolites.The simulation results showed that, H_2S, NO, NO_2, CO and NH_3 are well-captured by zeolite structures with accessible surface area of 1600–1800 m^2·g^(-1) and pore diameter of 0.6–0.7 nm, such as AFY and PAU, while SO_2 is well-adsorbed by zeolites containing larger accessible surface area(1700–2700 m^2·g^(-1)) and pore diameter(0.7–1.4 nm) at room temperature and an atmospheric pressure.However, at saturated adsorption, zeolites RWY, IRR, JSR, TSC, and ITT are found to exhibit better abilities to capture these gases.Our study provides useful computational insights in choosing and designing zeolite structures with high performance to remove toxic gases for air purification, thereby facilitating the development and application of exhaust gas-processing technology in green industry.展开更多
In this study,selective dealumination of Beta zeolites was performed through partially removing the templating agent in Beta zeolites by calcination and then removing the aluminum on the external surface of Beta zeoli...In this study,selective dealumination of Beta zeolites was performed through partially removing the templating agent in Beta zeolites by calcination and then removing the aluminum on the external surface of Beta zeolites with acid treatment.Hydrocracking catalysts were prepared by loading WO_(3)onto these dealuminated Beta zeolites.It was shown that the surface SiO_(2)/Al_(2)O_(3)of selectively dealuminated Beta zeolites was higher than that of conventionally dealuminated samples for the same bulk SiO_(2)/Al_(2)O_(3),and the hydrogenation activity of the catalyst of the selectively dealuminated Beta zeolites was lower than that of conventionally dealuminated Beta zeolites.The experimental results for tetralin hydrocracking to BTX showed that the catalysts based on the selectively dealuminated Beta zeolites had higher BTX selectivity and lower coke formation rate than that the catalysts based on the conventionally dealuminated Beta zeolites.展开更多
With the increasingly stringent standards for limiting sulfide content in liquid fuels,oxidative desulfurization(ODS)has become a promising ultra-deep desulfurization process in fuel desulfurization.TS-1 zeolites show...With the increasingly stringent standards for limiting sulfide content in liquid fuels,oxidative desulfurization(ODS)has become a promising ultra-deep desulfurization process in fuel desulfurization.TS-1 zeolites show great potential as catalysts for ODS reactions,due to its remarkable oxidation activity at low temperatures and pressure.However,the inherent microporous structure of conventional TS-1 zeolites restricts the mass transportation and renders the active sites in the microporous space of TS-1 zeolites inaccessible for bulky aromatic organosulfur compounds.Fabrication of hierarchical TS-1 zeolites by incorporating meso-/macropores into microporous TS-1 zeolites is an effective strategy to improve mass transportability.In recent years,abundant efforts have been dedicated to developing synthetic strategies of hierarchical TS-1 zeolite,thereby improving its catalytic performance in the ODS process.This mini-review addresses the synthetic methods of hierarchical TS-1 catalysts and their catalytic performance in the ODS reactions.In addition,some current problems and prospects of synthesis routes for constructing hierarchical TS-1 catalysts have also been revised.We expect this mini-review to shed light on the more efficient preparation strategies of hierarchical TS-1 zeolites for the ODS process.展开更多
A novel technology of preparing zeolites based on solid-solid mass transformation mechanism is developed for the first time. By employing this technology, three different types of highly crystallized pentasil zeolites...A novel technology of preparing zeolites based on solid-solid mass transformation mechanism is developed for the first time. By employing this technology, three different types of highly crystallized pentasil zeolites, ZSM-35 (FER-type), Silicalite-1(MFI-type) and Mordenite(MOR-type), are successfully synthesized in the solid system. In terms of commercial production, the technology-could simplify synthesis procedure and make the continuous production of zeolites possible, so as to improve the productivity. Additionally, it is environmentally friendly because the crystallization occurs in solid phase where there exists no pollution caused by waste liquid. Therefore, this technique provides us with a new industrial process for the clean and continuous production of zeolites. The characteristics in synthesis chemistry and the crystallization mechanism involved in the technology are also discussed.展开更多
Adsorptive separation of light hydrocarbons by porous solids provides an energy-efficient alternative to state-of-the-art cryogenic distillation.However,an optimal balance between the cost,performance and stability of...Adsorptive separation of light hydrocarbons by porous solids provides an energy-efficient alternative to state-of-the-art cryogenic distillation.However,an optimal balance between the cost,performance and stability of the sorbent material is yet to be achieved for industrial applications.Here,we report the efficient separation of C2 and C3 hydrocarbons by a faujasite zeolite(Na-X,Si/Al=1.23).A tandem configuration of two fixed-beds packed with Na-X affords complete dynamic separation of the ternary mixture of C_(2)H_(2)/C_(2)H_(4)/C_(2)H_(6)(1/49.5/49.5;v/v/v)under ambient conditions.Pressure-swing desorption on the latter fixed-bed gives ethylene(>99.50%,1.80 mmol g^(-1))and ethane(>99.99%,1.41 mmol g^(-1)).In situ synchrotron X-ray powder diffraction revealed the binding sites for C_(2)H_(2)and C_(2)H_(4)in Na-X.This study highlights the potential application of commercial zeolites for challenging industrial separations.展开更多
Tailoring the Ti coordination states in titanosilicate zeolites to simultaneously improve feedstock conversion and maximize the target product selectivity remains a challenge in the pursuit of high-performance catalys...Tailoring the Ti coordination states in titanosilicate zeolites to simultaneously improve feedstock conversion and maximize the target product selectivity remains a challenge in the pursuit of high-performance catalysts for selective oxidation reactions.Herein,we provide a facile strategy to synthesize hierarchical anatase-free TS-1(MFI-type)zeolites with tetrahedrally coordinated(TiO_(4))and octahedrally coordinated Ti species(TiO_(6)).The TiO_(4)species provide high epoxide selectivity,while the TiO_(6)species afford improved alkene conversion.This strategy is achieved by synergistically using an L-lysine-assisted approach and a two-step crystallization;the two-step crystallization approach prevents the formation of anatase TiO_(2),while L-lysine stabilizes the TiO_(6)species and ensures efficient incorporation of TiO_(6)into the anatase-free TS-1 zeolites.Compared with their conventional counterparts,which only contain TiO_(4)species,the as-prepared TS-1 zeolites(Si/Ti=36.9)result in a higher 1-hexene conversion(33%),higher TON value(153),and comparable epoxide selectivity(95%).This synthetic strategy provides avenues to tailor the amount and distribution of Ti species in titanosilicate zeolites to achieve high catalytic performances in various processes.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
H-type zeolites（ HY, Hβ, and HM） were synthesized and characterized by XRD, NH3-TPD, and Py-IR. Selectively catalytic alkylation of naphthalene with n-hexanol to hexyl-naphthalene over the zeolites was carried out....H-type zeolites（ HY, Hβ, and HM） were synthesized and characterized by XRD, NH3-TPD, and Py-IR. Selectively catalytic alkylation of naphthalene with n-hexanol to hexyl-naphthalene over the zeolites was carried out. The experimental results show that the catalytic activities of the zeolites are mainly determined by their acid properties and pore structures. The larger the pore diameter is, the higher the catalytic activity is. NH3-TPD profiles show that Hβ and HM have lower acid strengths than HY. HY has both the highest activity and highest selectivity for the hexylnaphthalene. Higher reaction temperatures and longer reaction time are beneficial to the production of β-hexyl-naphthalene over the HY zeolite.展开更多
The roles of acidity and micropore structure of zeolite were studied in the hydrolysis of the model oligosaccharide of cellulose–cellobiose. HZSM-5, HY, HMOR and Hβ zeolites were selected as model catalysts for the ...The roles of acidity and micropore structure of zeolite were studied in the hydrolysis of the model oligosaccharide of cellulose–cellobiose. HZSM-5, HY, HMOR and Hβ zeolites were selected as model catalysts for the hydrolysis of cellobiose. The effect of acidity of zeolite, including the strength, type and location, on its catalytic activity was investigated. The strong Br？nsted acid sites located in micropores are the active sites for the hydrolysis of cellobiose to glucose. Meanwhile, the catalytic performance of zeolite is also dependent on the micropore size of zeolite.展开更多
Developing effective iron-incorporated zeolites and determining their active centers for the direct oxidation of CH_4 to oxygenates have remained challenging topics so far.In this paper,we successfully prepare the hig...Developing effective iron-incorporated zeolites and determining their active centers for the direct oxidation of CH_4 to oxygenates have remained challenging topics so far.In this paper,we successfully prepare the highly-dispersed iron supported Y zeolites by a facile solid-state ion-exchange method with ferrocene,which was conducted under water-free conditions followed by a series of calcination.Moreover,extra-framework dinuclear Fe^(2+)complexes are identified as so-called activeα-iron sites on zeolites.ICP-OES,N_2 adsorption–desorption test,X-ray diffraction,solid-state^(27)Al NMR,N_2O titration,TEM,EPR and^(57)Fe M?ssbauer spectra were carried out to characterize properties of sample structure,acid sites,as well as the supported iron species.Characterization results indicate that high-temperature treatments have no effect on the typical structure feature of zeolites.Compared with catalysts synthesized by conventional impregnation,the samples prepared by the facile approach possess abundant dinuclear Fe^(2+)complexes but no Fe_2O_3 bulks and show weak acidity.These lead to a higher oxygenate selectivity in CH_4 oxidation to oxygenates.Remarkably,the oxygenate(HCHO and CH_3OH)selectivity of 6.5% at 375°C can be eventually obtained.展开更多
Basic zeolites have shown great potential as efficient catalysts for biodiesel production in the transesterification reactions.However,conventional three-dimensional(3D)basic zeolites generally suffer from limited bas...Basic zeolites have shown great potential as efficient catalysts for biodiesel production in the transesterification reactions.However,conventional three-dimensional(3D)basic zeolites generally suffer from limited base sites and severe mass-transfer restriction,thereby suppressing their catalytic activity.Herein,2D basic zeolites with large external surface areas,hierarchical characteristics,and abundant accessible and stable base sites are prepared by expansion,delamination and subsequent solid-state ion-exchange(SSIE)approach.The facile SSIE method provides more advantages in stabilizing and dispersing high concentration of strong basic sites than the conventional liquid-phase ion-exchange(LIE)approach.Due to the excellent mass transportation and stable basic sites,the 2D Na/ITQ-2 prepared by the SSIE approach shows remarkably enhanced activity and recyclability in the transesterification of triglycerides to produce biodiesel,compared to 3D zeolites and other reported basic zeolites.This work will open the boulevard to the rational design of 2D basic catalysts and expand the potential application of 2D zeolites to biodiesel production and other industrial reactions involving bulky molecules.展开更多
In this work,n-pentane catalytic cracking over HZSM-5 zeolites was studied at 650°C under atmosphere pressure.A particular attention was paid to the measurement of n-pentane conversion,light olefins production,pr...In this work,n-pentane catalytic cracking over HZSM-5 zeolites was studied at 650°C under atmosphere pressure.A particular attention was paid to the measurement of n-pentane conversion,light olefins production,product distribution,coke deposit,etc.Several indexes were defined to evaluate the effects of operating conditions on the catalytic performance of HZSM-5 zeolites.It was found that decreasing the weight hourly space velocity,increasing the reactant partial pressure,and increasing the carrier gas flow rate could inhibit C-H bond breaking and enhance the C-C bond breaking and hydride transfer reactions,leading to reduced alkenes selectivity,which suppressed the formation of external coke and alleviated the deactivation of HZSM-5 zeolites.It was deduced that the catalytic stability of HZSM-5 zeolites was improved at the cost of alkenes selectivity.Compared with decreasing the weight hourly space velocity and increasing the reactant partial pressure,increasing the carrier gas flow rate could enhance the diffusion process and protect alkenes from being consumed in coke formation in order to improve the catalytic stability of HZSM-5 zeolites with less reduction of alkenes selectivity.展开更多
A single adsorption isothermal study was performed over HY and BEA zeolites in order to determine their adsorption capacities for phenol, ortho-nitrophenol and para-nitrophenol. The experiments were realized in batch ...A single adsorption isothermal study was performed over HY and BEA zeolites in order to determine their adsorption capacities for phenol, ortho-nitrophenol and para-nitrophenol. The experiments were realized in batch reactor and the isotherms were modelized by the Fowler-Guggenheim equation. During the adsorption process weak zeolite-sorbate interactions and more significant sorbate-sorbate attractions were identified. The adsorption was not linked to the molecular size of the sorbates and a strong correlation was established between the adsorption compound was the best adsorbed. The removal performances capacities and the dipole moments of the sorbates. The most polar of the zeolites depended on their hydrophobicity.展开更多
基金supported by the National Natural Science Foundation of China(22278090,21978055)Natural Science Foundation of Guangdong Province,China(2022A1515012088)the Science and Technology Planning Project of Guangdong Province,China(2022A0505030073,2022A0505030013).
文摘Ce-encapsulated Beta zeolite was synthesized by a one-pot hydrothermal method with citric acid complexing Ce in the absence of Na species.Additional citric acid can effectively prevent the deposition of Ce species during the hydrothermal synthesis of zeolites,leading to uniform distribution of Ce cluster in the framework of Beta zeolites.Moreover,the sodium-free synthesis system resulted that the Brønsted acid sites were mainly located on the straight channels and external surface of Beta zeolites,improving the utilization of Brønsted acid sites.In addition,Ce encapsulated Beta zeolites showed enhanced activity and robust stability in the alkylation of benzene with 1-dodecene based on the synergistic effect between Ce species and Brønsted acid sites,which pave the way for its practical application in the production of alkylbenzene.
文摘Y zeolites have moderate microporous pore size, large specific surface area, and good hydrothermal stability, which were widely used in industrial adsorption of volatile organic compounds (VOCs), but the performance of Y zeolites in adsorption of VOCs under high humidity conditions is terrible. In this paper, Y zeolites with different silica-alumina ratios were hydrophobically modified by organosilane and characterized by XRD, FTIR, SEM, BET, NMR. In the experiments of static and dynamic adsorption of VOCs by modified Y zeolites, it can be concluded that the static water adsorption capacity of Y zeolites with silica-aluminum ratio of 5 and 40 after silica modification decreased by 62 wt% and 53 wt%, under the conditions of high humidity, GHSV = 15,000 h<sup>-1</sup>, T = 35°C and initial concentration of toluene C<sub>0</sub> = 5000 mg·m<sup>-3</sup>. The saturation adsorption capacity of toluene was increased from 0.06 g·g<sup>-1</sup>, 0.09 g·g<sup>-1</sup> to 0.15 g·g<sup>-1</sup>, 0.21 g·g<sup>-1</sup>, the adsorption selectivity of Y zeolites for water was reduced and that for toluene was increased after Vapor phase silanization overlay modification. The present modification method might carry out targeted modification of zeolites surface, provide research ideas and guidance under high humidity conditions.
基金supported by the National Natural Science Foundation of China (21978055, 22278090)Natural Science Foundation of Guangdong Province, China (2022A1515012088)+2 种基金the Science and Technology Planning Project of Guangdong Province, China (22A0505050073, 2022A0505030013)the Guangdong Provincial Key Laboratory of Plant Resources Biorefinery, China (2021GDKLPRB10)the "High-level Talents Program" of the Pearl River, China (2017GC010080)。
文摘Novel organo-inorganic hybrid materials(MTW-x-SO_(3)H) have been fabricated by immobilizing 3-mercap topropyltriethoxysilane onto mesopore MTW zeolites, which is treated via a simple oxidation process with hydrogen peroxide as the oxidant to transform sulfhydryl group into sulfonic acid group. The organic sulfhydryl groups are covalently bonded to the external surface of MTW zeolites through the condensation between siloxane arising from organic fragments with silanol groups on the surface of MTW zeolites, the hybrids contain sulfonic acid group within the external surface of MTW zeolites and an opened mesoporous system in the matrix of MTW zeolites, which provide enough accessible Brùnsted acid sites for the alkylation between phenol with tert-butyl alcohol. Through this methodology it's possible to prepare multifunctional materials where the plenty of mesopores are benefit for the introduction of larger numbers of sulfonic acid groups that contributes to activity during reactions, resulting in high activity(>55%) of MTW-4-SO_(3)H and desired selectivity(>56%) of 2-TBP(2-tert-butyl phenol) in the alkylation between phenol with tert-butyl alcohol.
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.
基金financial support from the National Natural Science Foundation of China(21773067)the Open Research fund of Shanghai Key Laboratory of Green Chemistry and Chemical Processes。
文摘Furfuryl ethers have been considered to be a promising fuel additive.One step reduction etherification of furfural over supported Pd catalysts provides a facile way for the preparation of furfuryl ether.However,the preparation of a reusable Pd catalyst for reductive etherification remains to be a great challenge.In this study,a series of Si O_(2)supported Pd catalysts with particle size ranging from 2.2 nm to 28 nm were prepared.Their textural properties and catalytic performance in furfural reductive etherification have been systematically studied.The results herein shed light on the particle size effect on the competition between hydrogenation/hydrogenolysis of C=O in furfural over Pd surface.We found out that Pd nanoparticles larger than 3 nm are preferred for one step reductive etherification.Based on this finding,we prepared a Pd/ZSM-5 bifunctional catalyst comprising Pd nanoparticles larger than 3 nm and decreased acidity in presence of amino organosilane,which served as a bifunctional catalyst succeeding in one-pot synthesis of ether via reductive-etherification and direct-etherification.This strategy showed significant advantage in efficiently converting furfuryl acohol,a major side-product,into ether,while suppressing the undesired side-reactions.
基金supported by the National Natural Science Foundation of China(Grant no.20973166)
文摘Syngas to ethanol, consisting of dimethyl ether(DME) carbonylation to methyl acetate(MA) over zeolites and MA hydrogenation to ethanol on copper catalyst, has been developed in recent years.DME carbonylation over zeolites, a key step in this new process, has attracted increasing attention due to the high reaction efficiency and promising industrial application.In recent years, continuous efforts have been made on improving the activity and stability of the zeolites.From a mechanistic point of view, DME carbonylation to MA, involving the formation of C–C bond, is achieved via the Koch-type CO insertion into DME within the 8-member ring(8-MR) pores of zeolites, typically HMOR and HZSM-35.The unique geometric configuration of the 8-MR pore endowed the formation of the key intermediate(acetyl, CH3CO^*), possibly by a spatial confinement of the transition state during CO insertion into the surface O–CH3 group.This review article summarizes the main progress on zeolite-catalyzed DME carbonylation, including reaction kinetics and mechanism, theoretical calculations, and experimental strategies developed for populating acid sites and engineering pore structure of the zeolites in order to enhance the overall performance.
基金supported by the National Basic Research Program of China (2009CB623504)the National Science Foundation of China (21103231)Shanghai Science Foundation (11ZR1449700)
文摘Selectivity control is a difficult scientific and industrial challenge in methanol-to-olefins(MTO)conversion.It has been experimentally established that the topology of zeolite catalysts influenced the distribution of products.Besides the topology effect on reaction kinetics,the topology influences the diffusion of reactants and products in catalysts as well.In this work,by using COMPASS force-field molecular dynamics method,we investigated the intracrystalline diffusion of ethene and propene in four different zeolites,CHA,MFI,BEA and FAU,at different temperatures.The self-diffusion coefficients and diffusion activation barriers were calculated.A strong restriction on the diffusion of propene in CHA was observed because the self-diffusion coefficient ratio of ethene to propene is larger than 18 and the diffusion activation barrier of propene is more than 20 kJ/mol in CHA.This ratio decreases with the increase of temperature in the four investigated zeolites.The shape selectivity on products from diffusion perspective can provide some implications on the understanding of the selectivity difference between HSAPO-34 and HZSM-5 catalysts for the MTO conversion.
基金Supported by the National Natural Science Foundation of China(21406172)the Natural Science Foundation of Hubei Province,China(2016CFB388 and 2013CFA091)
文摘The exhaust gases, including SO_2,NH_3, H_2S, NO_2, NO, and CO, are principal air pollutants due to their severe harms to the ecological environment.Zeolites have been considered as good absorbent candidates to capture the six exhaust gases.In this work, we performed grand canonical ensemble Monte Carlo(GCMC) simulations to examine the capability of 95 kinds of all-silica zeolites in the removal of the six toxic gases, and to predict the adsorption isotherms of the six gases on all the zeolites.The simulation results showed that, H_2S, NO, NO_2, CO and NH_3 are well-captured by zeolite structures with accessible surface area of 1600–1800 m^2·g^(-1) and pore diameter of 0.6–0.7 nm, such as AFY and PAU, while SO_2 is well-adsorbed by zeolites containing larger accessible surface area(1700–2700 m^2·g^(-1)) and pore diameter(0.7–1.4 nm) at room temperature and an atmospheric pressure.However, at saturated adsorption, zeolites RWY, IRR, JSR, TSC, and ITT are found to exhibit better abilities to capture these gases.Our study provides useful computational insights in choosing and designing zeolite structures with high performance to remove toxic gases for air purification, thereby facilitating the development and application of exhaust gas-processing technology in green industry.
文摘In this study,selective dealumination of Beta zeolites was performed through partially removing the templating agent in Beta zeolites by calcination and then removing the aluminum on the external surface of Beta zeolites with acid treatment.Hydrocracking catalysts were prepared by loading WO_(3)onto these dealuminated Beta zeolites.It was shown that the surface SiO_(2)/Al_(2)O_(3)of selectively dealuminated Beta zeolites was higher than that of conventionally dealuminated samples for the same bulk SiO_(2)/Al_(2)O_(3),and the hydrogenation activity of the catalyst of the selectively dealuminated Beta zeolites was lower than that of conventionally dealuminated Beta zeolites.The experimental results for tetralin hydrocracking to BTX showed that the catalysts based on the selectively dealuminated Beta zeolites had higher BTX selectivity and lower coke formation rate than that the catalysts based on the conventionally dealuminated Beta zeolites.
基金supported by the National Natural Science Foundation of China(21971082)the Jilin Province Science and Technology Development Plan(20200201096JC and 20190201229JC)+1 种基金the China Postdoctoral Science Foundation(2019T120235 and 2018M640280)for supporting this workthe 111 Project(B17020)。
文摘With the increasingly stringent standards for limiting sulfide content in liquid fuels,oxidative desulfurization(ODS)has become a promising ultra-deep desulfurization process in fuel desulfurization.TS-1 zeolites show great potential as catalysts for ODS reactions,due to its remarkable oxidation activity at low temperatures and pressure.However,the inherent microporous structure of conventional TS-1 zeolites restricts the mass transportation and renders the active sites in the microporous space of TS-1 zeolites inaccessible for bulky aromatic organosulfur compounds.Fabrication of hierarchical TS-1 zeolites by incorporating meso-/macropores into microporous TS-1 zeolites is an effective strategy to improve mass transportability.In recent years,abundant efforts have been dedicated to developing synthetic strategies of hierarchical TS-1 zeolite,thereby improving its catalytic performance in the ODS process.This mini-review addresses the synthetic methods of hierarchical TS-1 catalysts and their catalytic performance in the ODS reactions.In addition,some current problems and prospects of synthesis routes for constructing hierarchical TS-1 catalysts have also been revised.We expect this mini-review to shed light on the more efficient preparation strategies of hierarchical TS-1 zeolites for the ODS process.
基金Supported by the National Natural Science Foundation of China (No.20173039) and by China National Petroleum Corporation (No.2002B50501)
文摘A novel technology of preparing zeolites based on solid-solid mass transformation mechanism is developed for the first time. By employing this technology, three different types of highly crystallized pentasil zeolites, ZSM-35 (FER-type), Silicalite-1(MFI-type) and Mordenite(MOR-type), are successfully synthesized in the solid system. In terms of commercial production, the technology-could simplify synthesis procedure and make the continuous production of zeolites possible, so as to improve the productivity. Additionally, it is environmentally friendly because the crystallization occurs in solid phase where there exists no pollution caused by waste liquid. Therefore, this technique provides us with a new industrial process for the clean and continuous production of zeolites. The characteristics in synthesis chemistry and the crystallization mechanism involved in the technology are also discussed.
基金supported by the National Natural Science Fund of China(22121005,22025203)the University of Manchester,and Haihe Laboratory of Sustainable Chemical Transformations,Tianjin。
文摘Adsorptive separation of light hydrocarbons by porous solids provides an energy-efficient alternative to state-of-the-art cryogenic distillation.However,an optimal balance between the cost,performance and stability of the sorbent material is yet to be achieved for industrial applications.Here,we report the efficient separation of C2 and C3 hydrocarbons by a faujasite zeolite(Na-X,Si/Al=1.23).A tandem configuration of two fixed-beds packed with Na-X affords complete dynamic separation of the ternary mixture of C_(2)H_(2)/C_(2)H_(4)/C_(2)H_(6)(1/49.5/49.5;v/v/v)under ambient conditions.Pressure-swing desorption on the latter fixed-bed gives ethylene(>99.50%,1.80 mmol g^(-1))and ethane(>99.99%,1.41 mmol g^(-1)).In situ synchrotron X-ray powder diffraction revealed the binding sites for C_(2)H_(2)and C_(2)H_(4)in Na-X.This study highlights the potential application of commercial zeolites for challenging industrial separations.
文摘Tailoring the Ti coordination states in titanosilicate zeolites to simultaneously improve feedstock conversion and maximize the target product selectivity remains a challenge in the pursuit of high-performance catalysts for selective oxidation reactions.Herein,we provide a facile strategy to synthesize hierarchical anatase-free TS-1(MFI-type)zeolites with tetrahedrally coordinated(TiO_(4))and octahedrally coordinated Ti species(TiO_(6)).The TiO_(4)species provide high epoxide selectivity,while the TiO_(6)species afford improved alkene conversion.This strategy is achieved by synergistically using an L-lysine-assisted approach and a two-step crystallization;the two-step crystallization approach prevents the formation of anatase TiO_(2),while L-lysine stabilizes the TiO_(6)species and ensures efficient incorporation of TiO_(6)into the anatase-free TS-1 zeolites.Compared with their conventional counterparts,which only contain TiO_(4)species,the as-prepared TS-1 zeolites(Si/Ti=36.9)result in a higher 1-hexene conversion(33%),higher TON value(153),and comparable epoxide selectivity(95%).This synthetic strategy provides avenues to tailor the amount and distribution of Ti species in titanosilicate zeolites to achieve high catalytic performances in various processes.
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H-type zeolites（ HY, Hβ, and HM） were synthesized and characterized by XRD, NH3-TPD, and Py-IR. Selectively catalytic alkylation of naphthalene with n-hexanol to hexyl-naphthalene over the zeolites was carried out. The experimental results show that the catalytic activities of the zeolites are mainly determined by their acid properties and pore structures. The larger the pore diameter is, the higher the catalytic activity is. NH3-TPD profiles show that Hβ and HM have lower acid strengths than HY. HY has both the highest activity and highest selectivity for the hexylnaphthalene. Higher reaction temperatures and longer reaction time are beneficial to the production of β-hexyl-naphthalene over the HY zeolite.
基金supported by the National Natural Science Foundation of China(Grant:U1304209,J1210060)the Undergraduate Innovation Education Project of Zhengzhou University for the financial support(Grant:2014sjxm008)
文摘The roles of acidity and micropore structure of zeolite were studied in the hydrolysis of the model oligosaccharide of cellulose–cellobiose. HZSM-5, HY, HMOR and Hβ zeolites were selected as model catalysts for the hydrolysis of cellobiose. The effect of acidity of zeolite, including the strength, type and location, on its catalytic activity was investigated. The strong Br？nsted acid sites located in micropores are the active sites for the hydrolysis of cellobiose to glucose. Meanwhile, the catalytic performance of zeolite is also dependent on the micropore size of zeolite.
基金Support by the National Key R&D Program of China(2016YFA0202900)the National Natural Science Foundation of China(21622606)+2 种基金the Natural Science Foundation of Zhejiang Province(LR18B060001)Basic Research Project of Sinopec Group(415025)the Fundamental Research Funds for the Central Universities
文摘Developing effective iron-incorporated zeolites and determining their active centers for the direct oxidation of CH_4 to oxygenates have remained challenging topics so far.In this paper,we successfully prepare the highly-dispersed iron supported Y zeolites by a facile solid-state ion-exchange method with ferrocene,which was conducted under water-free conditions followed by a series of calcination.Moreover,extra-framework dinuclear Fe^(2+)complexes are identified as so-called activeα-iron sites on zeolites.ICP-OES,N_2 adsorption–desorption test,X-ray diffraction,solid-state^(27)Al NMR,N_2O titration,TEM,EPR and^(57)Fe M?ssbauer spectra were carried out to characterize properties of sample structure,acid sites,as well as the supported iron species.Characterization results indicate that high-temperature treatments have no effect on the typical structure feature of zeolites.Compared with catalysts synthesized by conventional impregnation,the samples prepared by the facile approach possess abundant dinuclear Fe^(2+)complexes but no Fe_2O_3 bulks and show weak acidity.These lead to a higher oxygenate selectivity in CH_4 oxidation to oxygenates.Remarkably,the oxygenate(HCHO and CH_3OH)selectivity of 6.5% at 375°C can be eventually obtained.
基金supported by the National Natural Science Foundation of China(Grant Nos.21835002,21621001 and 22001090)the 111 Project(B17020)Yang acknowledges the Jilin Province Science and Technology Development Plan(Grant 20200201096JC).
文摘Basic zeolites have shown great potential as efficient catalysts for biodiesel production in the transesterification reactions.However,conventional three-dimensional(3D)basic zeolites generally suffer from limited base sites and severe mass-transfer restriction,thereby suppressing their catalytic activity.Herein,2D basic zeolites with large external surface areas,hierarchical characteristics,and abundant accessible and stable base sites are prepared by expansion,delamination and subsequent solid-state ion-exchange(SSIE)approach.The facile SSIE method provides more advantages in stabilizing and dispersing high concentration of strong basic sites than the conventional liquid-phase ion-exchange(LIE)approach.Due to the excellent mass transportation and stable basic sites,the 2D Na/ITQ-2 prepared by the SSIE approach shows remarkably enhanced activity and recyclability in the transesterification of triglycerides to produce biodiesel,compared to 3D zeolites and other reported basic zeolites.This work will open the boulevard to the rational design of 2D basic catalysts and expand the potential application of 2D zeolites to biodiesel production and other industrial reactions involving bulky molecules.
基金The authors gratefully acknowledge the financial support from the National Natural Science Foundation of China(Grant No.21908010)the Education Department of Jilin Province(Grant No.JJKH20191314KJ)the Changchun University of Technology.
文摘In this work,n-pentane catalytic cracking over HZSM-5 zeolites was studied at 650°C under atmosphere pressure.A particular attention was paid to the measurement of n-pentane conversion,light olefins production,product distribution,coke deposit,etc.Several indexes were defined to evaluate the effects of operating conditions on the catalytic performance of HZSM-5 zeolites.It was found that decreasing the weight hourly space velocity,increasing the reactant partial pressure,and increasing the carrier gas flow rate could inhibit C-H bond breaking and enhance the C-C bond breaking and hydride transfer reactions,leading to reduced alkenes selectivity,which suppressed the formation of external coke and alleviated the deactivation of HZSM-5 zeolites.It was deduced that the catalytic stability of HZSM-5 zeolites was improved at the cost of alkenes selectivity.Compared with decreasing the weight hourly space velocity and increasing the reactant partial pressure,increasing the carrier gas flow rate could enhance the diffusion process and protect alkenes from being consumed in coke formation in order to improve the catalytic stability of HZSM-5 zeolites with less reduction of alkenes selectivity.
文摘A single adsorption isothermal study was performed over HY and BEA zeolites in order to determine their adsorption capacities for phenol, ortho-nitrophenol and para-nitrophenol. The experiments were realized in batch reactor and the isotherms were modelized by the Fowler-Guggenheim equation. During the adsorption process weak zeolite-sorbate interactions and more significant sorbate-sorbate attractions were identified. The adsorption was not linked to the molecular size of the sorbates and a strong correlation was established between the adsorption compound was the best adsorbed. The removal performances capacities and the dipole moments of the sorbates. The most polar of the zeolites depended on their hydrophobicity.
