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
The effect of ammonia on the catalytic performance for 1-methylnaphthalene(1-MN) selective hydrogenation saturation was studied with Co-Mo/γ-Al_2O_3, Ni-W/γ-Al_2O_3, Ni-Mo/γ-Al_2O_3, and Ni-Mo-W/γ-Al_2O_3 catalyst...The effect of ammonia on the catalytic performance for 1-methylnaphthalene(1-MN) selective hydrogenation saturation was studied with Co-Mo/γ-Al_2O_3, Ni-W/γ-Al_2O_3, Ni-Mo/γ-Al_2O_3, and Ni-Mo-W/γ-Al_2O_3 catalysts. The results indicated that Ni-Mo-W/γ-Al_2O_3 catalyst exhibited the best performance for saturation of 1-MN. The introduction of NH3 remarkably inhibited the hydrogenation of 1-MN in the dynamic control area, but it had no effect in the thermodynamic control area. Besides, the mono-aromatics selectivity on the Ni-Mo-W and Ni-Mo catalysts was enhanced. However, it had little effect on the Ni-W and Co-Mo catalysts.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
Constructing heterojunctions and hollow multi-shelled structures can render materials with fascinating physicochemical properties,and have been regarded as two promising strategies to overcome the severe shuttling and...Constructing heterojunctions and hollow multi-shelled structures can render materials with fascinating physicochemical properties,and have been regarded as two promising strategies to overcome the severe shuttling and sluggish kinetics of polysulfide in lithium-sulfur(Li-S)batteries.However,a single strategy can only take limited effect.Modulating catalytic hosts with synergistic effects are urgently desired.Herein,Mn_(3)O_(4)-MnS heterogeneous multi-shelled hollow spheres are meticulously designed by controlled sulfuration of Mn2O3 hollow spheres,and then applied as advanced encapsulation hosts for Li-S batteries.Benefiting from the separated spatial confinement by hollow multi-shelled structure,ample exposed active sites and built-in electric field by heterogeneous interface,and synergistic effects between Mn_(3)O_(4)(strong adsorption)and MnS(fast conversion)components,the assembled battery achieves prominent rate capability and decent cyclability(0.016%decay per cycle at 2 C,1000 cycles).More crucially,satisfactory areal capacity reaches up to 7.1 mAh cm^(-2)even with high sulfur loading(8.0 mg cm^(-2))and lean electrolyte(E/S=4.0 pL mg^(-1))conditions.This work will provide inspiration for the rational design of hollow multi-shelled heterostructure for various electrocatalysis applications.展开更多
Understanding chemical transformations of contaminants and the resulting products is extremely important in devising proper monitoring methods for such contaminants and in assessing potential human exposure to the tra...Understanding chemical transformations of contaminants and the resulting products is extremely important in devising proper monitoring methods for such contaminants and in assessing potential human exposure to the transformation products in the environment. Ultraviolet (UV) light from the sun can induce various photochemical transformations of contaminants in the environment. Alkylnaphthalenes are light-molecular-weight polycyclic aromatic hydrocarbons (PAHs) which are one of the most widespread organic pollutants present in ambient air as a result of a variety of incomplete combustion sources. In this study, 1-methylnapthalene,a typical example of an alkylnaphthalene, was subjected to UV irradiation to investigate its transformation in the presence and absence of air. Twenty-one products were detected in the reaction mixtures. Some photo-oxidation products were identified, including both ring-opened and ring-retained oxygenated compounds, such as 1-naphthaldehyde, 1-naphthoic acid, 1-naphthalenemethanol and phthalic anhydride. Although dimeric products were observed in the presence of air, more were found in the presence of helium or argon gas, indicating a different photo-oxidation pathway from those commonly observed in other media, such as water. Under just 48 hours of exposure to the UV light in the presence of air, three major products were formed with a production yield of about 10% each. Compared to 1-methylnapthalene, the UV induced transformation products observed in this study are more volatile, acidic, water soluble or toxic. The formation of these products may significantly change our understanding of the risks assessed solely from the parent compound in contaminants research and supports the inclusion of airborne transformations of the parent compound in risk assessment.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.
文摘The effect of ammonia on the catalytic performance for 1-methylnaphthalene(1-MN) selective hydrogenation saturation was studied with Co-Mo/γ-Al_2O_3, Ni-W/γ-Al_2O_3, Ni-Mo/γ-Al_2O_3, and Ni-Mo-W/γ-Al_2O_3 catalysts. The results indicated that Ni-Mo-W/γ-Al_2O_3 catalyst exhibited the best performance for saturation of 1-MN. The introduction of NH3 remarkably inhibited the hydrogenation of 1-MN in the dynamic control area, but it had no effect in the thermodynamic control area. Besides, the mono-aromatics selectivity on the Ni-Mo-W and Ni-Mo catalysts was enhanced. However, it had little effect on the Ni-W and Co-Mo catalysts.
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.
基金The support from the National Natural Science Foundation of China(No.51971083)the Natural Science Foundation of Heilongjiang Province,China(YQ 2020E007)is gratefully acknowledgedfinancially sponsored by Heilongjiang Touyan Team Program.
文摘Constructing heterojunctions and hollow multi-shelled structures can render materials with fascinating physicochemical properties,and have been regarded as two promising strategies to overcome the severe shuttling and sluggish kinetics of polysulfide in lithium-sulfur(Li-S)batteries.However,a single strategy can only take limited effect.Modulating catalytic hosts with synergistic effects are urgently desired.Herein,Mn_(3)O_(4)-MnS heterogeneous multi-shelled hollow spheres are meticulously designed by controlled sulfuration of Mn2O3 hollow spheres,and then applied as advanced encapsulation hosts for Li-S batteries.Benefiting from the separated spatial confinement by hollow multi-shelled structure,ample exposed active sites and built-in electric field by heterogeneous interface,and synergistic effects between Mn_(3)O_(4)(strong adsorption)and MnS(fast conversion)components,the assembled battery achieves prominent rate capability and decent cyclability(0.016%decay per cycle at 2 C,1000 cycles).More crucially,satisfactory areal capacity reaches up to 7.1 mAh cm^(-2)even with high sulfur loading(8.0 mg cm^(-2))and lean electrolyte(E/S=4.0 pL mg^(-1))conditions.This work will provide inspiration for the rational design of hollow multi-shelled heterostructure for various electrocatalysis applications.
文摘Understanding chemical transformations of contaminants and the resulting products is extremely important in devising proper monitoring methods for such contaminants and in assessing potential human exposure to the transformation products in the environment. Ultraviolet (UV) light from the sun can induce various photochemical transformations of contaminants in the environment. Alkylnaphthalenes are light-molecular-weight polycyclic aromatic hydrocarbons (PAHs) which are one of the most widespread organic pollutants present in ambient air as a result of a variety of incomplete combustion sources. In this study, 1-methylnapthalene,a typical example of an alkylnaphthalene, was subjected to UV irradiation to investigate its transformation in the presence and absence of air. Twenty-one products were detected in the reaction mixtures. Some photo-oxidation products were identified, including both ring-opened and ring-retained oxygenated compounds, such as 1-naphthaldehyde, 1-naphthoic acid, 1-naphthalenemethanol and phthalic anhydride. Although dimeric products were observed in the presence of air, more were found in the presence of helium or argon gas, indicating a different photo-oxidation pathway from those commonly observed in other media, such as water. Under just 48 hours of exposure to the UV light in the presence of air, three major products were formed with a production yield of about 10% each. Compared to 1-methylnapthalene, the UV induced transformation products observed in this study are more volatile, acidic, water soluble or toxic. The formation of these products may significantly change our understanding of the risks assessed solely from the parent compound in contaminants research and supports the inclusion of airborne transformations of the parent compound in risk assessment.
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.
