A series of Co/γ-Al_2O_3 catalysts were prepared with the impregnation method and characterized by means of the BET specific surface area, X-ray diffraction(XRD), thermogravimetric analysis(TGA) and Laser Raman spect...A series of Co/γ-Al_2O_3 catalysts were prepared with the impregnation method and characterized by means of the BET specific surface area, X-ray diffraction(XRD), thermogravimetric analysis(TGA) and Laser Raman spectroscopy. The Co/γ-Al_2O_3 catalysts were activated by using H_2, 20%CH_4/H_2 or CH_4, respectively. There was no obvious difference between the activities of the Co/γ-Al_2O_3 catalyst activated by using the different activation methods for methane dry reforming. The catalytic properties of the Co/γ-Al_2O_3 catalysts with different Co loadings were also investigated. The optimized Co loading for the Co/γ-Al_2O_3 catalyst pretreated with 20% CH_4/H_2 is around 12%(mass fraction).展开更多
The activity and thermal stability of Pd/Al2O3 and Pd/（Al2O3＋MOx） （M=Ca, La, Ce） palladium catalysts in the reaction of complete oxidation of methane are presented in this study. The catalyst supports were prepar...The activity and thermal stability of Pd/Al2O3 and Pd/（Al2O3＋MOx） （M=Ca, La, Ce） palladium catalysts in the reaction of complete oxidation of methane are presented in this study. The catalyst supports were prepared by sol-gel method and they were dried either conventionally or with supercritical carbon dioxide. Then they were impregnated with palladium nitrate solution. The catalysts with unmodified alumina had a high surface area. The activity and thermal stability of the aluminasupported catalyst was also very high. The introduction of calcium, lanthanum, or cerium oxide into alumina support caused a decrease of the surface area in the way dependent on the support precursor drying method. These modifiers decreased the activity of palladium catalysts, and they required higher temperatures for the complete oxidation of methane than unmodified Pd/Al2O3. The improvement of the palladium activity by lanthanum and cerium support modifier was observed only at low temperatures of the reaction.展开更多
One-step synthesis of n-butanol from bimolecular condensation of ethanol was firstlyachieved over nickel supported gamma alumina catalyst. A mechanism of dehydration path for thegrowth of carbon chain by eliminating a...One-step synthesis of n-butanol from bimolecular condensation of ethanol was firstlyachieved over nickel supported gamma alumina catalyst. A mechanism of dehydration path for thegrowth of carbon chain by eliminating a hydroxy group from one ethanol molecule with a α-H ofother ethanol molecule rather than aldol condensation was verified.展开更多
The pore structure of spherical alumina supports is closely related to the dispersion of catalytically active components and the diffusion of reactants.Maintaining excellent pore structure under strict reaction condit...The pore structure of spherical alumina supports is closely related to the dispersion of catalytically active components and the diffusion of reactants.Maintaining excellent pore structure under strict reaction conditions is of utmost importance.In this work,sphericalγ-Al_(2)O_(3)support with a bimodal pore structure,composed of macropores and mesopores,was successfully synthesized using dodecane as the pore-forming agent through the oil–ammonia column-shaping method.The morphology and internal pore structure of the alumina were found to be influenced by the amount of surfactant added and ultrasound treatment conditions.Notably,when concentration of surfactant was 4‰and ultrasound voltage of 20 V was applied,the resultingγ-Al_(2)O_(3)-4‰-20 displayed a highly concentrated distribution of macropores with an average pore size of 100 nm,resulting in an impressive porosity of 69.21%.In contrast,the untreated sample ofγ-Al_(2)O_(3)-0-0 only exhibited a mesoporous distribution with a porosity of 54.03%.Moreover,after being subjected to a hydrothermal treatment in a high temperature(600°C)and high humidity(water vapor)environment for 120 h,theγ-Al_(2)O_(3)-4‰-20 sample maintained a high BET specific surface area of 170.9 m^(2)g^(−1)and mercury intrusion porosimetry specific surface area of 263.3 m^(2)g^(−1).展开更多
Volatile organic compounds(VOCs)are among the major sources of air pollution.Catalytic ozonation is an efficient process for removing VOCs at lower reaction temperature compared to catalytic oxidation.In this study,a ...Volatile organic compounds(VOCs)are among the major sources of air pollution.Catalytic ozonation is an efficient process for removing VOCs at lower reaction temperature compared to catalytic oxidation.In this study,a series of alumina supported single and mixed manganese and cobalt oxides catalysts were used for ozonation of acetone at room temperature.The influence of augmenting the single Mn and Co catalysts were investigated on the performance and structure of the catalyst.The manganese and cobalt single and mixed oxides catalysts of the formula Mnl0%-CoX and Co10%-MnX(where X=0,2.5%,5%,or 10%)were prepared.It was found that addition of Mn and Co at lower loading levels(2.5%or 5%)to single metal oxide catalysts enhanced the catalytic activity.The mixed oxides catalysts of(Mnl0%-Co2.5%)and(Mn10%-Co5%)led to acetone conversion of about 84%.It is concluded that lower oxidation state of the secondary metal improves ozone decomposition and oxidation of acetone.展开更多
A mesoporous MCM-48 membrane was synthesized on a coarse-pore α-alumina ceramic tube by hydrothermal treatment by using a cationic surfactant as the structure-directing agent under basic conditions. The products were...A mesoporous MCM-48 membrane was synthesized on a coarse-pore α-alumina ceramic tube by hydrothermal treatment by using a cationic surfactant as the structure-directing agent under basic conditions. The products were characterized by small-angle X-ray diffraction, SEM measurements and N_2 adsorption experiments. The X-ray diffraction(XRD) results show that the membrane possesses a periodic mesostructure, which is typical for an MCM-48 material. The results of the SEM measurements indicate that MCM-48 grew in the pores of the support and formed a continuous membrane. The N_2 adsorption and desorption isotherms also show that the membrane is a typical mesoporous material with pore channel size of about 2.74 nm.展开更多
文摘A series of Co/γ-Al_2O_3 catalysts were prepared with the impregnation method and characterized by means of the BET specific surface area, X-ray diffraction(XRD), thermogravimetric analysis(TGA) and Laser Raman spectroscopy. The Co/γ-Al_2O_3 catalysts were activated by using H_2, 20%CH_4/H_2 or CH_4, respectively. There was no obvious difference between the activities of the Co/γ-Al_2O_3 catalyst activated by using the different activation methods for methane dry reforming. The catalytic properties of the Co/γ-Al_2O_3 catalysts with different Co loadings were also investigated. The optimized Co loading for the Co/γ-Al_2O_3 catalyst pretreated with 20% CH_4/H_2 is around 12%(mass fraction).
文摘The activity and thermal stability of Pd/Al2O3 and Pd/（Al2O3＋MOx） （M=Ca, La, Ce） palladium catalysts in the reaction of complete oxidation of methane are presented in this study. The catalyst supports were prepared by sol-gel method and they were dried either conventionally or with supercritical carbon dioxide. Then they were impregnated with palladium nitrate solution. The catalysts with unmodified alumina had a high surface area. The activity and thermal stability of the aluminasupported catalyst was also very high. The introduction of calcium, lanthanum, or cerium oxide into alumina support caused a decrease of the surface area in the way dependent on the support precursor drying method. These modifiers decreased the activity of palladium catalysts, and they required higher temperatures for the complete oxidation of methane than unmodified Pd/Al2O3. The improvement of the palladium activity by lanthanum and cerium support modifier was observed only at low temperatures of the reaction.
文摘One-step synthesis of n-butanol from bimolecular condensation of ethanol was firstlyachieved over nickel supported gamma alumina catalyst. A mechanism of dehydration path for thegrowth of carbon chain by eliminating a hydroxy group from one ethanol molecule with a α-H ofother ethanol molecule rather than aldol condensation was verified.
基金National Key R&D Program of China(grant No.2022YFA1503400)Lanzhou Petrochemical Research Center project,and Programs for Foreign Talent(grant No.G2021106012L).
文摘The pore structure of spherical alumina supports is closely related to the dispersion of catalytically active components and the diffusion of reactants.Maintaining excellent pore structure under strict reaction conditions is of utmost importance.In this work,sphericalγ-Al_(2)O_(3)support with a bimodal pore structure,composed of macropores and mesopores,was successfully synthesized using dodecane as the pore-forming agent through the oil–ammonia column-shaping method.The morphology and internal pore structure of the alumina were found to be influenced by the amount of surfactant added and ultrasound treatment conditions.Notably,when concentration of surfactant was 4‰and ultrasound voltage of 20 V was applied,the resultingγ-Al_(2)O_(3)-4‰-20 displayed a highly concentrated distribution of macropores with an average pore size of 100 nm,resulting in an impressive porosity of 69.21%.In contrast,the untreated sample ofγ-Al_(2)O_(3)-0-0 only exhibited a mesoporous distribution with a porosity of 54.03%.Moreover,after being subjected to a hydrothermal treatment in a high temperature(600°C)and high humidity(water vapor)environment for 120 h,theγ-Al_(2)O_(3)-4‰-20 sample maintained a high BET specific surface area of 170.9 m^(2)g^(−1)and mercury intrusion porosimetry specific surface area of 263.3 m^(2)g^(−1).
基金Authors would like to thank the University of Saskatchewan and the Natural Sciences and Engineering Research Council of Canada for their financial support of this research.
文摘Volatile organic compounds(VOCs)are among the major sources of air pollution.Catalytic ozonation is an efficient process for removing VOCs at lower reaction temperature compared to catalytic oxidation.In this study,a series of alumina supported single and mixed manganese and cobalt oxides catalysts were used for ozonation of acetone at room temperature.The influence of augmenting the single Mn and Co catalysts were investigated on the performance and structure of the catalyst.The manganese and cobalt single and mixed oxides catalysts of the formula Mnl0%-CoX and Co10%-MnX(where X=0,2.5%,5%,or 10%)were prepared.It was found that addition of Mn and Co at lower loading levels(2.5%or 5%)to single metal oxide catalysts enhanced the catalytic activity.The mixed oxides catalysts of(Mnl0%-Co2.5%)and(Mn10%-Co5%)led to acetone conversion of about 84%.It is concluded that lower oxidation state of the secondary metal improves ozone decomposition and oxidation of acetone.
文摘A mesoporous MCM-48 membrane was synthesized on a coarse-pore α-alumina ceramic tube by hydrothermal treatment by using a cationic surfactant as the structure-directing agent under basic conditions. The products were characterized by small-angle X-ray diffraction, SEM measurements and N_2 adsorption experiments. The X-ray diffraction(XRD) results show that the membrane possesses a periodic mesostructure, which is typical for an MCM-48 material. The results of the SEM measurements indicate that MCM-48 grew in the pores of the support and formed a continuous membrane. The N_2 adsorption and desorption isotherms also show that the membrane is a typical mesoporous material with pore channel size of about 2.74 nm.
