In this work,the catalytic performance of vanadia-molybdena loaded on TiO_(2),MgO,ZSM-5,NaY and Mordenite was investigated in the selective oxidation of 2-methylnaphthalene(2-MN)to 2-naphthaldehyde(2-NA).Results show ...In this work,the catalytic performance of vanadia-molybdena loaded on TiO_(2),MgO,ZSM-5,NaY and Mordenite was investigated in the selective oxidation of 2-methylnaphthalene(2-MN)to 2-naphthaldehyde(2-NA).Results show that strong interactions between supports(TiO2,ZSM-5)and active components can promote the dispersion of active component.Monolayer VOx and MoOx are the main form on the catalyst surface,which is beneficial to the 2-NA selectivity.However,the corresponding weak interactions between Mordenite and active components may lead to the production of oxide crystals and the separation of active components,thus reducing the 2-NA selectivity.Due to the high Na content,new crystal NaVMoO6 forms on the NaY surface,which is inactive in the reaction.For V-Mo/TiO2,V and Mo can be inserted into the TiO2 lattice,changing the electronic structures of active components and support and improving the activity of surface oxygen species.This investigation highlights an important consideration on supports properties when designing supported catalysts.展开更多
Shape-selective methylation of 2-methylnaphthalene (2-MN) was carried out over NH 4 F and Pt modified HZSM-5 (SiO 2 /Al 2 O 3 = 83) catalysts in a fixed-bed down-flow reactor using methanol as methylating agent and 1,...Shape-selective methylation of 2-methylnaphthalene (2-MN) was carried out over NH 4 F and Pt modified HZSM-5 (SiO 2 /Al 2 O 3 = 83) catalysts in a fixed-bed down-flow reactor using methanol as methylating agent and 1,3,5-trimethylbenzene (1,3,5-TMB) as a solvent. Pt promoted HZSM-5 catalysts showed low concentration of coke-like polycondensed aromatics, NH 4 F modification decreased non-shape-selective acid sites. After Pt and NH 4 F co-modification, both conversion of 2-MN and selectivity to 2,6-DMN were improved. 6%NH 4 F/0.5%Pt/HZSM-5 catalyst exhibited 13.8% of 2-MN conversion with 6.2% of 2,6-DMN yield after 7 h time on stream (TOS), and 2,6-/2,7-DMN ratio of 1.7 after 10 h of TOS.展开更多
Acylation of 2-methylnaphthalene(2-MN) is a very important reaction in organic synthesis,and the effiency of the continuous reactor is more than one of the batch reactor.Considering that the Friedel–Crafts acylation ...Acylation of 2-methylnaphthalene(2-MN) is a very important reaction in organic synthesis,and the effiency of the continuous reactor is more than one of the batch reactor.Considering that the Friedel–Crafts acylation is a rapid exothermic reaction,in this study,we perform the acylation of 2-MN in a stainless steel microchannel flow reactor,which is characterized by high mass and heat transfer rates.The effect of reactant ratio,mixing temperature,reaction temperature,and reaction time on product yield and selectivity were investigated.Under the optimal conditions,2-methyl-6-propionylnaphthalene(2,6-MPN) was obtained in 85.8% yield with 87.5% selectivity.Compared with the conventional batch system,the continuous flow microchannel reactor provides a more efficient method for the synthesis of 2,6-MPN.展开更多
β-Mn2V2O7 crystals with strip shape are successfully prepared by the molten salt method in a closed crucible, and are characterized by x-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission ele...β-Mn2V2O7 crystals with strip shape are successfully prepared by the molten salt method in a closed crucible, and are characterized by x-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, selected area of electron diffraction （SAED） and high-resolution transmission electron microscopy （HRTEM）. The results indicate that the sample is of the β-Mn2V2O7 crystal with monoclinic symmetry, level natural cleavage facets and directional growth. Magnetic properties are measured by vibration sample magnetometry （VSM） at room temperature, and the magnetic hysteresis loop indicates that the β-Mn2V2O7 has anti-ferromagnetic properties with low coercive force and remnant magnetization. The magnetic measurement results in different directions exhibit that the β-Mn2V2O7 has magnetic anisotropy, which is due to the fact that the magnetic interaction energy of the β-Mn2V2O7 is lowest only when the electron configuration is in a certain direction.展开更多
MnO-SiO_2-Al_2O_3-MnS oxysulfide system has been investigated by experimental phase diagram and activity measurement coupled with thermodynamic modeling.Phase equilibria of the MnO-MnS,MnO-SiO_2-MnS, MnO-Al_2O_3-MnS a...MnO-SiO_2-Al_2O_3-MnS oxysulfide system has been investigated by experimental phase diagram and activity measurement coupled with thermodynamic modeling.Phase equilibria of the MnO-MnS,MnO-SiO_2-MnS, MnO-Al_2O_3-MnS and MnO-SiO_2-Al_2O_3-MnS systems under low oxygen partial pressure have been experimentally investigated for the temperature range of 1 185 to 1 500℃using equilibration and quenching techniques. Equilibrium phases were analyzed by scanning electron microscope,electron probe X-ray microanalysis(EPMA), and differential thermal analysis(DTA ).Phase diagrams were successfully constructed for the systems investigated.Two ternary compounds in the MnO-SiO_2-MnS system were found.Activities of MnO and MnS in MnO-SiO_2-Al_2O_3-MnS liquid oxysulfide solution from very low sulfur concentration to high sulfur concentration at solid MnS saturation were investigated employing gas/liquid/Pt - Mn alloy under controlled atmosphere at 1 500℃.As X(SiO_2)/(X(MnO) + X(SiO_2)) increases in liquid oxysulfide solution,activity coefficient of MnO decreases while that of MnS increases.As X(AlO_(1.5)) increases,the activity coefficient of MnS increases while no remarkable change was observed for the activity coefficient of MnO.Quantitative analysis of the thermodynamic properties of the oxysulfide solution as well as phase diagram of the system was also earned out by employing the Modified Quasichemical Model in the quadruplet approximation.In view of inclusion utilization for free - cutting steel,it might have an advantage to decrease the Al_2O_3 content and increase the MnO/SiO_2 ratio.展开更多
We report the microwave synthesis and the doping effect of Mo_(3-)xRe_xAl_(2)C(0≤x≤0.3)superconductor.Re doping into Mo_(3)Al_(2)C results in a regular shrinkage of the lattice,marked by the linear decrease of latti...We report the microwave synthesis and the doping effect of Mo_(3-)xRe_xAl_(2)C(0≤x≤0.3)superconductor.Re doping into Mo_(3)Al_(2)C results in a regular shrinkage of the lattice,marked by the linear decrease of lattice parameter a from6.868(1)A(for Mo_(3)Al_(2)C)to 6.846(2)A(for Mo_(2.7)Re_(0.3)Al_(2)C).Upon Re doping,T_(c)of Mo_(3-x)Re_xAl_(2)C first increases and then decreases,with the maximum T_(c)=9.14 K at the optimal doping level of x=0.09.Our report provides a convenient method to synthesize Mo_(3-)xRe_xAl_(2)C within minutes,and also marks the first Re doping study with enhanced superconductivity on the non-centrosymmetric superconductor Mo_(3)Al_(2)C.展开更多
Aqueous Zinc-ion batteries(ZIB) are attracting immense attention because of their merits of excellent safety and quite cheap properties compared with lithium-ion batteries(LIB).Manganese oxide is one of the most impor...Aqueous Zinc-ion batteries(ZIB) are attracting immense attention because of their merits of excellent safety and quite cheap properties compared with lithium-ion batteries(LIB).Manganese oxide is one of the most important cathode materials of ZIB.In this paper,α-Mn2O3 used as cathode of ZIB is synthesized via Metal-Organic Framework(MOF)-derived method,which delivers a high specific capacity of225 mAh g^(-1) at 0.05 A g^(-1) and 92.7 mAh g^(-1) after 1700 cycles at 2 A g^(-1).The charge storage mechanism of α-Mn2O3 cathode is found to greatly depend on the discharge current density.At lower current density discharging,the H+ and Zn2+ are successively intercalated into the α-Mn2O3 before and after the "turning point" of discharge voltage and their discharging products present obviously different morphologies changing from flower-like to large plate-like products.At a higher current density,the low-voltage plateau after the turning point disappears due to the decrease of amount of Zn2+ intercalation and the H+intercalation is dominated in α-Mn2 O3.This study provides significant understanding for future design and research of high-performance Mn-based cathodes of ZIB.展开更多
The performance of BaC12-TiO2-SnO2 composite catalysts in oxidative coupling of methane reaction has been investigated. A series of BaC12-TiO2, BaC1E-SnO2, TiO2-SnO2, and BaC12-TiO2-SnO2 catalysts were prepared, and c...The performance of BaC12-TiO2-SnO2 composite catalysts in oxidative coupling of methane reaction has been investigated. A series of BaC12-TiO2, BaC1E-SnO2, TiO2-SnO2, and BaC12-TiO2-SnO2 catalysts were prepared, and characterized by BET, XRD, XPS, CO2-TPD and H2-TPR, respectively. The synergistic effect among BaC12, SnO2 and TiO2 compositions enhances the catalytic performance. The best C2 selectivity and ethylene yield are obtained on the catalyst with the equal molar amount of the three compositions （BaC12 ： TiO2 ： SnO2 molar ratio of 1 ： 1 ： 1）. The optimal reaction conditions are as follows： 800 ℃, 44 mL.min-1 for methane, 22 mL.min-1 for oxygen and a space velocity of 5000 mL-h-1 .g-1, and the C2H4 yield over the catalyst is 20.1% with the CH4 conversion of 43.8% and C2 selectivity of 53.3%.展开更多
The support γ-Al_2O_3 was treated with 1-methylnaphthalene as the model reactant by respectively using the chemical static adsorption method and the accelerated coking method to study the coking sites of γ-Al_2O_3 s...The support γ-Al_2O_3 was treated with 1-methylnaphthalene as the model reactant by respectively using the chemical static adsorption method and the accelerated coking method to study the coking sites of γ-Al_2O_3 surface. The carbon species formed on γ-Al_2O_3 surface were analyzed by CAT-CS, TG-MS, IR-OH, and Py-IR techniques. The results of characterization by CAT-CS and TG-MS techniques indicated that the carbon species formed during the chemical static adsorption process is mainly composed of the reversibly adsorbed coke precursors with a lowly-condensed state, while that formed after the accelerated coking process is probably related with the irreversibly adsorbed coke deposits with a highlycondensed state. The results of characterization by IR-OH and Py-IR techniques further implied that the formation of the two kinds of carbon species, i.e., coke precursors and coke deposits, are closely related with the basic hydroxyl groups and the strong Lewis acid sites on γ-Al_2O_3 surface. The results lead to a deep insight into the coking mechanism on the alumina surface.展开更多
基金Henan Province Science and Technology Research Project(232102321041).
文摘In this work,the catalytic performance of vanadia-molybdena loaded on TiO_(2),MgO,ZSM-5,NaY and Mordenite was investigated in the selective oxidation of 2-methylnaphthalene(2-MN)to 2-naphthaldehyde(2-NA).Results show that strong interactions between supports(TiO2,ZSM-5)and active components can promote the dispersion of active component.Monolayer VOx and MoOx are the main form on the catalyst surface,which is beneficial to the 2-NA selectivity.However,the corresponding weak interactions between Mordenite and active components may lead to the production of oxide crystals and the separation of active components,thus reducing the 2-NA selectivity.Due to the high Na content,new crystal NaVMoO6 forms on the NaY surface,which is inactive in the reaction.For V-Mo/TiO2,V and Mo can be inserted into the TiO2 lattice,changing the electronic structures of active components and support and improving the activity of surface oxygen species.This investigation highlights an important consideration on supports properties when designing supported catalysts.
基金Supported by the Program for New Century Excellent Talents in University (NCET-04-0268)the Expertise-Introduction Project for Disciplinary Innovation of Universities
文摘Shape-selective methylation of 2-methylnaphthalene (2-MN) was carried out over NH 4 F and Pt modified HZSM-5 (SiO 2 /Al 2 O 3 = 83) catalysts in a fixed-bed down-flow reactor using methanol as methylating agent and 1,3,5-trimethylbenzene (1,3,5-TMB) as a solvent. Pt promoted HZSM-5 catalysts showed low concentration of coke-like polycondensed aromatics, NH 4 F modification decreased non-shape-selective acid sites. After Pt and NH 4 F co-modification, both conversion of 2-MN and selectivity to 2,6-DMN were improved. 6%NH 4 F/0.5%Pt/HZSM-5 catalyst exhibited 13.8% of 2-MN conversion with 6.2% of 2,6-DMN yield after 7 h time on stream (TOS), and 2,6-/2,7-DMN ratio of 1.7 after 10 h of TOS.
基金Supported by the National Natural Science Foundation of China(91634101)The Project of Construction of Innovative Teams and Teacher Career Development for Universities and Colleges under Beijing Municipality(IDHT20180508)
文摘Acylation of 2-methylnaphthalene(2-MN) is a very important reaction in organic synthesis,and the effiency of the continuous reactor is more than one of the batch reactor.Considering that the Friedel–Crafts acylation is a rapid exothermic reaction,in this study,we perform the acylation of 2-MN in a stainless steel microchannel flow reactor,which is characterized by high mass and heat transfer rates.The effect of reactant ratio,mixing temperature,reaction temperature,and reaction time on product yield and selectivity were investigated.Under the optimal conditions,2-methyl-6-propionylnaphthalene(2,6-MPN) was obtained in 85.8% yield with 87.5% selectivity.Compared with the conventional batch system,the continuous flow microchannel reactor provides a more efficient method for the synthesis of 2,6-MPN.
文摘β-Mn2V2O7 crystals with strip shape are successfully prepared by the molten salt method in a closed crucible, and are characterized by x-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, selected area of electron diffraction （SAED） and high-resolution transmission electron microscopy （HRTEM）. The results indicate that the sample is of the β-Mn2V2O7 crystal with monoclinic symmetry, level natural cleavage facets and directional growth. Magnetic properties are measured by vibration sample magnetometry （VSM） at room temperature, and the magnetic hysteresis loop indicates that the β-Mn2V2O7 has anti-ferromagnetic properties with low coercive force and remnant magnetization. The magnetic measurement results in different directions exhibit that the β-Mn2V2O7 has magnetic anisotropy, which is due to the fact that the magnetic interaction energy of the β-Mn2V2O7 is lowest only when the electron configuration is in a certain direction.
文摘MnO-SiO_2-Al_2O_3-MnS oxysulfide system has been investigated by experimental phase diagram and activity measurement coupled with thermodynamic modeling.Phase equilibria of the MnO-MnS,MnO-SiO_2-MnS, MnO-Al_2O_3-MnS and MnO-SiO_2-Al_2O_3-MnS systems under low oxygen partial pressure have been experimentally investigated for the temperature range of 1 185 to 1 500℃using equilibration and quenching techniques. Equilibrium phases were analyzed by scanning electron microscope,electron probe X-ray microanalysis(EPMA), and differential thermal analysis(DTA ).Phase diagrams were successfully constructed for the systems investigated.Two ternary compounds in the MnO-SiO_2-MnS system were found.Activities of MnO and MnS in MnO-SiO_2-Al_2O_3-MnS liquid oxysulfide solution from very low sulfur concentration to high sulfur concentration at solid MnS saturation were investigated employing gas/liquid/Pt - Mn alloy under controlled atmosphere at 1 500℃.As X(SiO_2)/(X(MnO) + X(SiO_2)) increases in liquid oxysulfide solution,activity coefficient of MnO decreases while that of MnS increases.As X(AlO_(1.5)) increases,the activity coefficient of MnS increases while no remarkable change was observed for the activity coefficient of MnO.Quantitative analysis of the thermodynamic properties of the oxysulfide solution as well as phase diagram of the system was also earned out by employing the Modified Quasichemical Model in the quadruplet approximation.In view of inclusion utilization for free - cutting steel,it might have an advantage to decrease the Al_2O_3 content and increase the MnO/SiO_2 ratio.
基金the National Key Research and Development of China(Grant Nos.2018YFA0704200 and 2016YFA0300301)the National Natural Science Foundation of China(Grant Nos.12074414 and 11774402)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB25000000)。
文摘We report the microwave synthesis and the doping effect of Mo_(3-)xRe_xAl_(2)C(0≤x≤0.3)superconductor.Re doping into Mo_(3)Al_(2)C results in a regular shrinkage of the lattice,marked by the linear decrease of lattice parameter a from6.868(1)A(for Mo_(3)Al_(2)C)to 6.846(2)A(for Mo_(2.7)Re_(0.3)Al_(2)C).Upon Re doping,T_(c)of Mo_(3-x)Re_xAl_(2)C first increases and then decreases,with the maximum T_(c)=9.14 K at the optimal doping level of x=0.09.Our report provides a convenient method to synthesize Mo_(3-)xRe_xAl_(2)C within minutes,and also marks the first Re doping study with enhanced superconductivity on the non-centrosymmetric superconductor Mo_(3)Al_(2)C.
基金supported by the National Natural Science Foundation of China (51672156)Local Innovative Research Teams Project of Guangdong Pearl River Talents Program (No. 2017BT01N111)+2 种基金Guangdong Province Technical Plan Project (2017B010119001)Shenzhen Technical Plan Project (JCYJ20170817161221958 and JCYJ20170412170706047)Shenzhen Graphene Manufacturing Innovation Center (201901161513)。
文摘Aqueous Zinc-ion batteries(ZIB) are attracting immense attention because of their merits of excellent safety and quite cheap properties compared with lithium-ion batteries(LIB).Manganese oxide is one of the most important cathode materials of ZIB.In this paper,α-Mn2O3 used as cathode of ZIB is synthesized via Metal-Organic Framework(MOF)-derived method,which delivers a high specific capacity of225 mAh g^(-1) at 0.05 A g^(-1) and 92.7 mAh g^(-1) after 1700 cycles at 2 A g^(-1).The charge storage mechanism of α-Mn2O3 cathode is found to greatly depend on the discharge current density.At lower current density discharging,the H+ and Zn2+ are successively intercalated into the α-Mn2O3 before and after the "turning point" of discharge voltage and their discharging products present obviously different morphologies changing from flower-like to large plate-like products.At a higher current density,the low-voltage plateau after the turning point disappears due to the decrease of amount of Zn2+ intercalation and the H+intercalation is dominated in α-Mn2 O3.This study provides significant understanding for future design and research of high-performance Mn-based cathodes of ZIB.
文摘The performance of BaC12-TiO2-SnO2 composite catalysts in oxidative coupling of methane reaction has been investigated. A series of BaC12-TiO2, BaC1E-SnO2, TiO2-SnO2, and BaC12-TiO2-SnO2 catalysts were prepared, and characterized by BET, XRD, XPS, CO2-TPD and H2-TPR, respectively. The synergistic effect among BaC12, SnO2 and TiO2 compositions enhances the catalytic performance. The best C2 selectivity and ethylene yield are obtained on the catalyst with the equal molar amount of the three compositions （BaC12 ： TiO2 ： SnO2 molar ratio of 1 ： 1 ： 1）. The optimal reaction conditions are as follows： 800 ℃, 44 mL.min-1 for methane, 22 mL.min-1 for oxygen and a space velocity of 5000 mL-h-1 .g-1, and the C2H4 yield over the catalyst is 20.1% with the CH4 conversion of 43.8% and C2 selectivity of 53.3%.
基金support from the National Key Basic Research Program of China (Grant 2017YFB0306603)
文摘The support γ-Al_2O_3 was treated with 1-methylnaphthalene as the model reactant by respectively using the chemical static adsorption method and the accelerated coking method to study the coking sites of γ-Al_2O_3 surface. The carbon species formed on γ-Al_2O_3 surface were analyzed by CAT-CS, TG-MS, IR-OH, and Py-IR techniques. The results of characterization by CAT-CS and TG-MS techniques indicated that the carbon species formed during the chemical static adsorption process is mainly composed of the reversibly adsorbed coke precursors with a lowly-condensed state, while that formed after the accelerated coking process is probably related with the irreversibly adsorbed coke deposits with a highlycondensed state. The results of characterization by IR-OH and Py-IR techniques further implied that the formation of the two kinds of carbon species, i.e., coke precursors and coke deposits, are closely related with the basic hydroxyl groups and the strong Lewis acid sites on γ-Al_2O_3 surface. The results lead to a deep insight into the coking mechanism on the alumina surface.
