A series of composite catalysts were prepared by the wet mixing method, and the mass ratio of CuO-ZnO-Al2O3-ZrO2 component to HZSM-5 zeolite （molar ratio of SiO2 to Al2O3 being 25） was 2：1. The CuO-ZnO-Al2O3-ZrO2 ...A series of composite catalysts were prepared by the wet mixing method, and the mass ratio of CuO-ZnO-Al2O3-ZrO2 component to HZSM-5 zeolite （molar ratio of SiO2 to Al2O3 being 25） was 2：1. The CuO-ZnO-Al2O3-ZrO2 （CuO/ZnO/Al2O3=3/6/1 by weight） component was prepared by a modified ＇two-step＇ co-precipitation method. The effects of ZrO2 on the performance of CuO-ZnO-Al2O3/HZSMo5 catalyst for dimethyl ether synthesis from CO2 hydrogenation were investigated. It was found that ZrO2 improved the properties of CuO-ZnO-Al2O3/HZSM-5 as a structural promoter.展开更多
A La-modified Al2O3 catalyst was prepared with deposition-precipitation method. The effect of calcination temperature on the reactivity for vapor phase hydrofluorination of acetylene to vinyl fluoride. The catalysts c...A La-modified Al2O3 catalyst was prepared with deposition-precipitation method. The effect of calcination temperature on the reactivity for vapor phase hydrofluorination of acetylene to vinyl fluoride. The catalysts calcined at different temperatures were characterized using NH3-TPD, pyridine-FTIR, X-ray diffraction, and Raman techniques. It was found that the calcination process could not only change the structure of these catalysts but also modify the amount of surface acidity on the catalysts. The catalyst calcined at 400 ℃ exhibited the highest conversion of acetylene （94.6%） and highest selectivity to vinyl fluoride （83.4%） and lower coke deposition selectivity （0.72%）. The highest activity was related to the largest amount of surface acidity on the catalyst, and the coke deposition was also related to the total amount of surface acidic sites.展开更多
The development of efficient systems for the catalytic oxidation of 2-nitro-4-methylsulfonyltoluene(NMST)to 2-nitro-4-methylsulfonyl benzoic acid(NMSBA)with atmospheric air or molecular oxygen in alkaline medium prese...The development of efficient systems for the catalytic oxidation of 2-nitro-4-methylsulfonyltoluene(NMST)to 2-nitro-4-methylsulfonyl benzoic acid(NMSBA)with atmospheric air or molecular oxygen in alkaline medium presents a significant challenge for the chemical industry.Here,we report the synthesis of FeOOH/Fe_(3)O_(4)/metal-organic framework(MOF)polygonal mesopores microflower templated from a MIL-88B(Fe)at room temperature,which exposes polygonal mesopores with atomistic edge steps and lattice defects.The obtained FeOOH/Fe_(3)O_(4)/MOF catalyst was adsorbed onto glass beads and then introduced into the microchannel reactor.In the alkaline environment,oxygen was used as oxidant to catalyze the oxidation of NMST to NMSBA,showing impressive performance.This sustainable system utilizes oxygen as a clean oxidant in an inexpensive and environmentally friendly NaOH/methanol mixture.The position and type of substituent critically affect the products.Additionally,this sustainable protocol enabled gram-scale preparation of carboxylic acid and benzyl alcohol derivatives with high chemoselectivities.Finally,the reactions can be conducted in a pressure reactor,which can conserve oxygen and prevent solvent loss.Moreover,compared with the traditional batch reactor,the self-built microchannel reactor can accelerate the reaction rate,shorten the reaction time,and enhance the selectivity of catalytic oxidation reactions.This approach contributes to environmental protection and holds potential for industrial applications.展开更多
A series of K-promoted Pt/Al2O3 catalysts were tested for CO oxidation. It was found that the addition of K significantly enhanced the activity. A detailed kinetic study showed that the activation energies of the K-co...A series of K-promoted Pt/Al2O3 catalysts were tested for CO oxidation. It was found that the addition of K significantly enhanced the activity. A detailed kinetic study showed that the activation energies of the K-containing catalysts were lower than those of the K-free ones, particularly for catalysts with high Pt contents （51.6 k）/mol for 0.42K-2.0Pt/Al2O3 and 6：3.6 kJ/mol for 2.0Pt/Al2O3 ）. The CO reaction orders were higher for the K-containing catalysts （about -0.2） than for the K-free ones （about -0.5）, with the former having much lower equilibrium constants for CO adsorption than the latter. In situ Fourier-transform infrared spectroscopy showed that surface CO desorption from the 0.42K-2.0Pt/Al2O3 catalyst was easier than from 2.0Pt/Al2O3. The promoting effect of K was therefore caused by weakening of the interactions between CO and surface Pt atoms. This decreased coverage of the catalyst with CO and facilitated competitive O2 chemisorption on the Pt surface, and significantly lowered the reaction barrier between chemisorbed CO and O2 species.展开更多
separation is an attractive alternative to filtration or centrifugation for separating solid catalysts from a liquid phase, Here, core-shell Fe3O4@UiO-66-NH2 nanohybrids with well-defined structures were constructed b...separation is an attractive alternative to filtration or centrifugation for separating solid catalysts from a liquid phase, Here, core-shell Fe3O4@UiO-66-NH2 nanohybrids with well-defined structures were constructed by dispersing magnets in a dimethylformamide （DMF） solution con- taining two metal-organic framework （MOF） precursors, namely ZrCI4 and 2-aminobenzenetricar- boxylic acid. This method is simpler and more efficient than previously reported step-by-step method in which magnets were consecutively dispersed in DMF solutions each containing one MOF precursor, and the obtained Fe304@UiO-66-NH2 with three assembly cycles has a higher degree of crystallinity and porosiW. The core-shell Fe3O4@UiO-66-NH2 is highly active and selective in Knoevenagel condensations because of the bifunctionality of UiO-66-NH2 and better mass transfer in the nano-sized shells. It also has good recycling stability, and can be recovered magnetically and reused at least four times without significant loss of catalytic activity and framework integrity. The effects of substitution on the reactivity of benzaldehyde and of substrate size were also investigated.展开更多
Silane coupling agent KH560 was used to modify the surface of nano-α-Al<sub>2</sub>O<sub>3</sub> in ethanol-aqueous solution with different proportions. The particle size of nano-α-Al<sub&...Silane coupling agent KH560 was used to modify the surface of nano-α-Al<sub>2</sub>O<sub>3</sub> in ethanol-aqueous solution with different proportions. The particle size of nano-α-Al<sub>2</sub>O<sub>3</sub> was determined by nano-particle size analyzer, and the effects of nano-α-Al<sub>2</sub>O<sub>3</sub> content, ethanol-aqueous solution ratio and KH560 dosage on the dispersion and particle size of nano-α-Al<sub>2</sub>O<sub>3</sub> were investigated. The material structure before and after modification was determined by Fourier transform infrared spectroscopy (FTIR). Aqueous polyurethane resin and inorganic components are combined with modified nano-α-Al<sub>2</sub>O<sub>3</sub> dispersion to form chromium-free passivation solution. The solution is coated on the galvanized sheet, the adhesion and surface hardness are tested, the bonding strength of the coating and the surface hardness of the substrate are discussed. The corrosion resistance and surface morphology of the matrix were investigated by electrochemical test, neutral salt spray test and scanning electron microscope test. The chromium-free passivation film formed after the modification of nano-α-Al<sub>2</sub>O<sub>3</sub> increases the surface hardness of galvanized sheet by about 85%. The corrosion resistance of the film is better than that of a single polyurethane film. The results show that the surface hardness and corrosion resistance of polyurethane resin composite passivation film are significantly improved by the introduction of nano-α-Al<sub>2</sub>O<sub>3</sub>.展开更多
Coral reef-like Ni/Al2O3 catalysts were prepared by co-precipitation of nickel acetate and aluminium nitrate with sodium carbonate aqueous solution in the medium of ethylene glycolye.Methanation of syngas was carried ...Coral reef-like Ni/Al2O3 catalysts were prepared by co-precipitation of nickel acetate and aluminium nitrate with sodium carbonate aqueous solution in the medium of ethylene glycolye.Methanation of syngas was carried out over coral reef-like Ni/Al2O3 catalysts in a continuous flow type fixed-bed reactor.The structure and properties of the fresh and used catalysts were studied by SEM,N2 adsorption-desorption,XRD,H2-TPR,O2-TPO,TG and ICP-AES techniques.The results showed that the coral reef-like Ni/Al2O3 catalysts exhibited better activity than the conventional Ni/Al2O3-H2O catalysts.The activities of coral reef-like catalysts were in the order of Ni/Al2O3-673Ni/Al2O3-573Ni/Al2O3- 473Ni/Al2O3-773.Ni/Al2O3-673-EG catalyst showed not only good activity and improved stability but also superior resistance to carbon deposition,sintering,and Ni loss.Under the reaction conditions of CO/H2（molar ratio）=1：3,593 K,atmospheric pressure and a GHSV of 2500 h-1,CH4 selectivity was 84.7%,and the CO conversion reached 98.2%.展开更多
In situ quick X-ray absorption spectroscopy(QXAFS) at the Cu and Zn K-edge under operando conditions has been used to unravel the Cu/Zn interaction and identify possible active site of CuO/ZnO/Al_2O_3 catalyst for met...In situ quick X-ray absorption spectroscopy(QXAFS) at the Cu and Zn K-edge under operando conditions has been used to unravel the Cu/Zn interaction and identify possible active site of CuO/ZnO/Al_2O_3 catalyst for methanol synthesis. In this work, the catalyst, whose activity increases with the reaction temperature and pressure, was studied at calcined, reduced, and reacted conditions. TEM and EDX images for the calcined and reduced catalysts showed that copper was distributed uniformly at both conditions. TPR profile revealed two reduction peaks at 165 and 195 °C for copper species in the calcined catalyst. QXAFS results demonstrated that the calcined form consisted mainly of a mixed Cu O and Zn O, and it was progressively transformed into Cu metal particles and dispersed Zn O species as the reduction treatment. It was demonstrated that activation of the catalyst precursor occurred via a Cu^+intermediate, and the active catalyst predominantly consisted of metallic Cu and Zn O evenunder higher pressures. Structure of the active catalyst did not change with the temperature or pressure, indicating that the role of the Zn was mainly to improve Cu dispersion.This indicates the potential of QXAFS method in studying the structure evolutions of catalysts in methanol synthesis.展开更多
Deactivation mechanism of Cr-Al2O3catalyst and the interaction of Cr-A1 in the dehydrogenation of isobutane, as well as the nature of the catalytic active center, were studied using XRD, SEM, XPS, H2-TPR, isobutane-TP...Deactivation mechanism of Cr-Al2O3catalyst and the interaction of Cr-A1 in the dehydrogenation of isobutane, as well as the nature of the catalytic active center, were studied using XRD, SEM, XPS, H2-TPR, isobutane-TPR and TPO techniques. The results revealed that the deactivation of Cr-Al2O3 catalyst was mainly caused by carbon deposition on its surface. The Cr3＋ ion could not be reduced by hydrogen but could be reduced to Cr2＋ by hydrocarbons and monoxide carbon. The active center for isobutane dehydrogenation could be Cr2＋/Cr3＋ produced from Cr6＋ by the on line reduction of hydrocarbon and carbon monoxide. The binding energy of Al3＋ was strongly affected by the state of chromium cations in the catalysts.展开更多
文摘A series of composite catalysts were prepared by the wet mixing method, and the mass ratio of CuO-ZnO-Al2O3-ZrO2 component to HZSM-5 zeolite （molar ratio of SiO2 to Al2O3 being 25） was 2：1. The CuO-ZnO-Al2O3-ZrO2 （CuO/ZnO/Al2O3=3/6/1 by weight） component was prepared by a modified ＇two-step＇ co-precipitation method. The effects of ZrO2 on the performance of CuO-ZnO-Al2O3/HZSMo5 catalyst for dimethyl ether synthesis from CO2 hydrogenation were investigated. It was found that ZrO2 improved the properties of CuO-ZnO-Al2O3/HZSM-5 as a structural promoter.
基金ACKNOWLEDGMENT This work was supported by the National Natural Science Foundation of China （No.20873125）,
文摘A La-modified Al2O3 catalyst was prepared with deposition-precipitation method. The effect of calcination temperature on the reactivity for vapor phase hydrofluorination of acetylene to vinyl fluoride. The catalysts calcined at different temperatures were characterized using NH3-TPD, pyridine-FTIR, X-ray diffraction, and Raman techniques. It was found that the calcination process could not only change the structure of these catalysts but also modify the amount of surface acidity on the catalysts. The catalyst calcined at 400 ℃ exhibited the highest conversion of acetylene （94.6%） and highest selectivity to vinyl fluoride （83.4%） and lower coke deposition selectivity （0.72%）. The highest activity was related to the largest amount of surface acidity on the catalyst, and the coke deposition was also related to the total amount of surface acidic sites.
基金supported by the National Natural Science Foundation of China(22078251)Hubei Province Key Research and Development Program(2023DJC167)the research project of Hubei Provincial Department of Education(D20191504).
文摘The development of efficient systems for the catalytic oxidation of 2-nitro-4-methylsulfonyltoluene(NMST)to 2-nitro-4-methylsulfonyl benzoic acid(NMSBA)with atmospheric air or molecular oxygen in alkaline medium presents a significant challenge for the chemical industry.Here,we report the synthesis of FeOOH/Fe_(3)O_(4)/metal-organic framework(MOF)polygonal mesopores microflower templated from a MIL-88B(Fe)at room temperature,which exposes polygonal mesopores with atomistic edge steps and lattice defects.The obtained FeOOH/Fe_(3)O_(4)/MOF catalyst was adsorbed onto glass beads and then introduced into the microchannel reactor.In the alkaline environment,oxygen was used as oxidant to catalyze the oxidation of NMST to NMSBA,showing impressive performance.This sustainable system utilizes oxygen as a clean oxidant in an inexpensive and environmentally friendly NaOH/methanol mixture.The position and type of substituent critically affect the products.Additionally,this sustainable protocol enabled gram-scale preparation of carboxylic acid and benzyl alcohol derivatives with high chemoselectivities.Finally,the reactions can be conducted in a pressure reactor,which can conserve oxygen and prevent solvent loss.Moreover,compared with the traditional batch reactor,the self-built microchannel reactor can accelerate the reaction rate,shorten the reaction time,and enhance the selectivity of catalytic oxidation reactions.This approach contributes to environmental protection and holds potential for industrial applications.
基金financially supported by the National Natural Science Foundation of China(21173195)~~
文摘A series of K-promoted Pt/Al2O3 catalysts were tested for CO oxidation. It was found that the addition of K significantly enhanced the activity. A detailed kinetic study showed that the activation energies of the K-containing catalysts were lower than those of the K-free ones, particularly for catalysts with high Pt contents （51.6 k）/mol for 0.42K-2.0Pt/Al2O3 and 6：3.6 kJ/mol for 2.0Pt/Al2O3 ）. The CO reaction orders were higher for the K-containing catalysts （about -0.2） than for the K-free ones （about -0.5）, with the former having much lower equilibrium constants for CO adsorption than the latter. In situ Fourier-transform infrared spectroscopy showed that surface CO desorption from the 0.42K-2.0Pt/Al2O3 catalyst was easier than from 2.0Pt/Al2O3. The promoting effect of K was therefore caused by weakening of the interactions between CO and surface Pt atoms. This decreased coverage of the catalyst with CO and facilitated competitive O2 chemisorption on the Pt surface, and significantly lowered the reaction barrier between chemisorbed CO and O2 species.
基金supported by the National Natural Science Foundation of China (21203017)Open Fund of State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences (N-11-3)+1 种基金Program for Liaoning Excellent Talents in University (LNET)the Funda-mental Research Funds for the Central Universities (DC201502020304)~~
文摘separation is an attractive alternative to filtration or centrifugation for separating solid catalysts from a liquid phase, Here, core-shell Fe3O4@UiO-66-NH2 nanohybrids with well-defined structures were constructed by dispersing magnets in a dimethylformamide （DMF） solution con- taining two metal-organic framework （MOF） precursors, namely ZrCI4 and 2-aminobenzenetricar- boxylic acid. This method is simpler and more efficient than previously reported step-by-step method in which magnets were consecutively dispersed in DMF solutions each containing one MOF precursor, and the obtained Fe304@UiO-66-NH2 with three assembly cycles has a higher degree of crystallinity and porosiW. The core-shell Fe3O4@UiO-66-NH2 is highly active and selective in Knoevenagel condensations because of the bifunctionality of UiO-66-NH2 and better mass transfer in the nano-sized shells. It also has good recycling stability, and can be recovered magnetically and reused at least four times without significant loss of catalytic activity and framework integrity. The effects of substitution on the reactivity of benzaldehyde and of substrate size were also investigated.
文摘Silane coupling agent KH560 was used to modify the surface of nano-α-Al<sub>2</sub>O<sub>3</sub> in ethanol-aqueous solution with different proportions. The particle size of nano-α-Al<sub>2</sub>O<sub>3</sub> was determined by nano-particle size analyzer, and the effects of nano-α-Al<sub>2</sub>O<sub>3</sub> content, ethanol-aqueous solution ratio and KH560 dosage on the dispersion and particle size of nano-α-Al<sub>2</sub>O<sub>3</sub> were investigated. The material structure before and after modification was determined by Fourier transform infrared spectroscopy (FTIR). Aqueous polyurethane resin and inorganic components are combined with modified nano-α-Al<sub>2</sub>O<sub>3</sub> dispersion to form chromium-free passivation solution. The solution is coated on the galvanized sheet, the adhesion and surface hardness are tested, the bonding strength of the coating and the surface hardness of the substrate are discussed. The corrosion resistance and surface morphology of the matrix were investigated by electrochemical test, neutral salt spray test and scanning electron microscope test. The chromium-free passivation film formed after the modification of nano-α-Al<sub>2</sub>O<sub>3</sub> increases the surface hardness of galvanized sheet by about 85%. The corrosion resistance of the film is better than that of a single polyurethane film. The results show that the surface hardness and corrosion resistance of polyurethane resin composite passivation film are significantly improved by the introduction of nano-α-Al<sub>2</sub>O<sub>3</sub>.
基金financially supported by Independent Research Subject from Ministry of Science and Technology of China(No.2008BWZ005)
文摘Coral reef-like Ni/Al2O3 catalysts were prepared by co-precipitation of nickel acetate and aluminium nitrate with sodium carbonate aqueous solution in the medium of ethylene glycolye.Methanation of syngas was carried out over coral reef-like Ni/Al2O3 catalysts in a continuous flow type fixed-bed reactor.The structure and properties of the fresh and used catalysts were studied by SEM,N2 adsorption-desorption,XRD,H2-TPR,O2-TPO,TG and ICP-AES techniques.The results showed that the coral reef-like Ni/Al2O3 catalysts exhibited better activity than the conventional Ni/Al2O3-H2O catalysts.The activities of coral reef-like catalysts were in the order of Ni/Al2O3-673Ni/Al2O3-573Ni/Al2O3- 473Ni/Al2O3-773.Ni/Al2O3-673-EG catalyst showed not only good activity and improved stability but also superior resistance to carbon deposition,sintering,and Ni loss.Under the reaction conditions of CO/H2（molar ratio）=1：3,593 K,atmospheric pressure and a GHSV of 2500 h-1,CH4 selectivity was 84.7%,and the CO conversion reached 98.2%.
基金supported by the National Basic Research Program of China(973 Program,2013CB933104)the National Natural Science Foundation of China(Nos.11275258 and 11135008)
文摘In situ quick X-ray absorption spectroscopy(QXAFS) at the Cu and Zn K-edge under operando conditions has been used to unravel the Cu/Zn interaction and identify possible active site of CuO/ZnO/Al_2O_3 catalyst for methanol synthesis. In this work, the catalyst, whose activity increases with the reaction temperature and pressure, was studied at calcined, reduced, and reacted conditions. TEM and EDX images for the calcined and reduced catalysts showed that copper was distributed uniformly at both conditions. TPR profile revealed two reduction peaks at 165 and 195 °C for copper species in the calcined catalyst. QXAFS results demonstrated that the calcined form consisted mainly of a mixed Cu O and Zn O, and it was progressively transformed into Cu metal particles and dispersed Zn O species as the reduction treatment. It was demonstrated that activation of the catalyst precursor occurred via a Cu^+intermediate, and the active catalyst predominantly consisted of metallic Cu and Zn O evenunder higher pressures. Structure of the active catalyst did not change with the temperature or pressure, indicating that the role of the Zn was mainly to improve Cu dispersion.This indicates the potential of QXAFS method in studying the structure evolutions of catalysts in methanol synthesis.
基金supported by the Natural Science Foundation of Shandong Provence of China(ZR2013BM008)
文摘Deactivation mechanism of Cr-Al2O3catalyst and the interaction of Cr-A1 in the dehydrogenation of isobutane, as well as the nature of the catalytic active center, were studied using XRD, SEM, XPS, H2-TPR, isobutane-TPR and TPO techniques. The results revealed that the deactivation of Cr-Al2O3 catalyst was mainly caused by carbon deposition on its surface. The Cr3＋ ion could not be reduced by hydrogen but could be reduced to Cr2＋ by hydrocarbons and monoxide carbon. The active center for isobutane dehydrogenation could be Cr2＋/Cr3＋ produced from Cr6＋ by the on line reduction of hydrocarbon and carbon monoxide. The binding energy of Al3＋ was strongly affected by the state of chromium cations in the catalysts.
