Gas phase selective catalytic oxidation of toluene to benzatdehyde was studied on V_2O_5-Ag_2O/η-Al_2O_3 catalyst prepared by impregnation. The catalyst was characterized by XRD, XPS, TEM, and FT-IR. The catalytic re...Gas phase selective catalytic oxidation of toluene to benzatdehyde was studied on V_2O_5-Ag_2O/η-Al_2O_3 catalyst prepared by impregnation. The catalyst was characterized by XRD, XPS, TEM, and FT-IR. The catalytic results showed that toluene conversion and selectivity for benzaldehyde on catalyst sample No.4 (V/(V+Ag)=0.68) was higher than other catalysts with different V/Ag ratios. This was attributed to the higher surface area, larger pore volume and pore diameter of the catalyst sample No. 4 than the other catalysts. The XRD patterns recorded from the catalyst before and after the oxidation reaction revealed that the new phases were developed, and this suggested that silver had entered the vanadium lattice. XPS results showed that the vanadium on the surface of No.4 and No.5 sample was more than that in the bulk, thus forming a vanadium rich layer on the surface. It was noted that when the catalyst was doped by potassium promoter, the toluene conversion and selectivity for benzaldehyde were higher than those on the undoped catalyst. This was attributed to the disordered structure of V_2O_5 lattice of the K-doped catalyst and a better interracial contact between the particles.展开更多
The selective catalytic oxidation of toluene with hydrogen peroxide over V-Mo-based catalysts under mild conditions was studied.The promotion effect of Mo on the catalysts was studied with V/Al2O3 and Mo/Al2O3 as refe...The selective catalytic oxidation of toluene with hydrogen peroxide over V-Mo-based catalysts under mild conditions was studied.The promotion effect of Mo on the catalysts was studied with V/Al2O3 and Mo/Al2O3 as reference samples.The catalysts were characterized by XRD,TPR,and XPS techniques.The results show that the addition of Mo to V/Al2O3 may change the distribution of V species on Al2O3 surface.Over V-Mo/Al2O3 catalyst,highly dispersed amorphous V species facilitates benzaldehyde formation,and crystalline V2O5 species increases the conversion of toluene but decreases the selectivity to benzaldehyde,while AlVMoO7 species favors both the conversion of toluene and the formation of cresols.The yield of benzaldehyde depends remarkably on the surface O/Al and Mo/V atomic ratios,and gets to a maximum value of 13.2% with a selectivity of 79.5% at an O/Al atomic ratio of 3.0 and Mo/V atomic ratio of 0.7.展开更多
Multi-walled carbon nanotubes (MWCNTs) were fabricated and oxidized by different concentrations of sodium hypochlorite (NaOC1) solutions. The untreated MWCNTs and modified MWCNTs were employed as adsorbents to stu...Multi-walled carbon nanotubes (MWCNTs) were fabricated and oxidized by different concentrations of sodium hypochlorite (NaOC1) solutions. The untreated MWCNTs and modified MWCNTs were employed as adsorbents to study their characterizations and adsorption performance of toluene, ethylbenzene and xylene isomers (TEX) in an aqueous solution. The physicochemical properties of MWCNTs were greatly affected after oxidation, which influences TEX adsorption capacity. The 3% NaOCl-oxidized MWCNTs shows the greatest enhancement in TEX adsorption, followed by the 30% NaOCl. More interestingly, the 15% NaOCl-oxidized MWCNTs has lower adsorption capacities than untreated MWCNTs. The adsorption mechanism of TEX on treated MWCNTs is attributed to the combined action of hydrophobic interaction, π-π bonding interaction between the aromatic ring of TEX and the oxygen-containing functional groups of MWCNTs and electrostatic interac- tion. 3% NaOCl solution could not only introduce much oxygen-containing functional groups on MWCNTs, but also lead to less damage for the pore structure. This suggests that the CNTs-3% NaOCl is efficient adsorbent for TEX and that they may possess good potential for TEX removal in wastewater treatment.展开更多
The key issues to improve the performance of photocatalysts for selective oxidation of toluene are promoting the migration and separation of charge carrier,and enhancing the generation of active oxygen species.It is k...The key issues to improve the performance of photocatalysts for selective oxidation of toluene are promoting the migration and separation of charge carrier,and enhancing the generation of active oxygen species.It is known that the construction of compact heterojunction is an efficient protocol to inhibit photogenerated electron-hole recombination.In this work,a 2D-2D[Bi_(6)O_(6)(OH)_(3)](NO_(3))3·1.5H2O-Bi_(2)MoO_(6)(denoted as BBN-BMO)composite heterojunction has been prepared by one-step hydrothermal method for the first time.The tetragonal phase BBN in the composite plays the role of transferring electrons from the visible light activated orthorhombic phase BMO and promoting the generation of active·O_(2)^(-),the holes left in BMO are used to activate toluene and produce benzyl radical,thus greatly improving the photocatalytic performance for selective oxidation of toluene.The toluene conversion rate of BBN-BMO is 3466μmol·g^(-1)·h^(-1),which is three times that of pure BMO.The selectivity to benzalde-hyde is 94.2%.In addition,reasonable mechanism has been speculated based on a series of control experiments.展开更多
Efficient selective oxidation of hydrocarbons to corresponding ketones has been a significant but challenging work in the past decades.Here,a nitrogen-doped bamboo-like carbon nanotubes encapsulating cobalt catalyst(N...Efficient selective oxidation of hydrocarbons to corresponding ketones has been a significant but challenging work in the past decades.Here,a nitrogen-doped bamboo-like carbon nanotubes encapsulating cobalt catalyst(NCNTs-X)using citric acid,melamine and CoCl_(2)·6H_(2)O as precursors was synthesized by a simple pyrolysis method.A series of characterization techniques were employed to investigate the physicochemical properties of samples.And the results show that the as-prepared catalysts achieve a high catalytic performance for selective ethylbenzene oxidation(78.3% ethylbenzene conversion)using molecular oxygen as oxidant,especially giving a high selectivity(93.8% selectivity to acetophenone).According to the investigation of the structure-activity relationship of the catalysts,it can be deduced that the Co-N_(x) sites have an obvious positive effect on catalytic performance thanks to the synergistic effect between metallic cobalt and pyridinic N.展开更多
The lanthanum molybdovanadophosphoric tetrabasic heteropoly complex was synthesized.Catalytic properties of the title heteropoly complex for selective oxidation of ethylbezene to acetonphenone was investigated.The sui...The lanthanum molybdovanadophosphoric tetrabasic heteropoly complex was synthesized.Catalytic properties of the title heteropoly complex for selective oxidation of ethylbezene to acetonphenone was investigated.The suitable reaction conditions was discussed.展开更多
A series of Ce-Mo oxide catalysts with different Ce/Mo atomic ratio were prepared and applied to selective oxidation of toluene to benzaldehyde. The structures and properties of the surfaces of catalysts were characte...A series of Ce-Mo oxide catalysts with different Ce/Mo atomic ratio were prepared and applied to selective oxidation of toluene to benzaldehyde. The structures and properties of the surfaces of catalysts were characterized by XRD, TPR and DR-UVS. The natures of oxygen species on the surfaces of these samples were studied by using temperature programmed desorption-mass spectrography(TPD-MS). The results showed that the oxygen species of multiple adsorption existed on the sample surface. And in the range of desorption temperature<900℃, for the Ce-Mo samples, not only the desorption peaks of O- species on surfaces of samples be discoved, but also the O2- species appeared. As the content of Ce in Ce-Mo oxides was changed, the activation energy of oxygen desorption(Ed) also changed. The Ed value of sample 3 (Ce/Mo=1/1) is the lowest and its selectivity of benzaldehyde in toluene oxidation is the highest. Thus, a Parallel relation between the Ed value and the selectivity for benzaldehyde existed in these Ce-Mo oxides.展开更多
文摘Gas phase selective catalytic oxidation of toluene to benzatdehyde was studied on V_2O_5-Ag_2O/η-Al_2O_3 catalyst prepared by impregnation. The catalyst was characterized by XRD, XPS, TEM, and FT-IR. The catalytic results showed that toluene conversion and selectivity for benzaldehyde on catalyst sample No.4 (V/(V+Ag)=0.68) was higher than other catalysts with different V/Ag ratios. This was attributed to the higher surface area, larger pore volume and pore diameter of the catalyst sample No. 4 than the other catalysts. The XRD patterns recorded from the catalyst before and after the oxidation reaction revealed that the new phases were developed, and this suggested that silver had entered the vanadium lattice. XPS results showed that the vanadium on the surface of No.4 and No.5 sample was more than that in the bulk, thus forming a vanadium rich layer on the surface. It was noted that when the catalyst was doped by potassium promoter, the toluene conversion and selectivity for benzaldehyde were higher than those on the undoped catalyst. This was attributed to the disordered structure of V_2O_5 lattice of the K-doped catalyst and a better interracial contact between the particles.
基金Supported by the National Natural Science Foundation of China(Nos.20502017and20072024)the Teaching and ResearchAward Program for Outstanding Young Teachers in Higher Education Institutions of Ministry of Education,Chinathe ScienceFoundation for Young Teachers of Sichuan University.
文摘The selective catalytic oxidation of toluene with hydrogen peroxide over V-Mo-based catalysts under mild conditions was studied.The promotion effect of Mo on the catalysts was studied with V/Al2O3 and Mo/Al2O3 as reference samples.The catalysts were characterized by XRD,TPR,and XPS techniques.The results show that the addition of Mo to V/Al2O3 may change the distribution of V species on Al2O3 surface.Over V-Mo/Al2O3 catalyst,highly dispersed amorphous V species facilitates benzaldehyde formation,and crystalline V2O5 species increases the conversion of toluene but decreases the selectivity to benzaldehyde,while AlVMoO7 species favors both the conversion of toluene and the formation of cresols.The yield of benzaldehyde depends remarkably on the surface O/Al and Mo/V atomic ratios,and gets to a maximum value of 13.2% with a selectivity of 79.5% at an O/Al atomic ratio of 3.0 and Mo/V atomic ratio of 0.7.
文摘Multi-walled carbon nanotubes (MWCNTs) were fabricated and oxidized by different concentrations of sodium hypochlorite (NaOC1) solutions. The untreated MWCNTs and modified MWCNTs were employed as adsorbents to study their characterizations and adsorption performance of toluene, ethylbenzene and xylene isomers (TEX) in an aqueous solution. The physicochemical properties of MWCNTs were greatly affected after oxidation, which influences TEX adsorption capacity. The 3% NaOCl-oxidized MWCNTs shows the greatest enhancement in TEX adsorption, followed by the 30% NaOCl. More interestingly, the 15% NaOCl-oxidized MWCNTs has lower adsorption capacities than untreated MWCNTs. The adsorption mechanism of TEX on treated MWCNTs is attributed to the combined action of hydrophobic interaction, π-π bonding interaction between the aromatic ring of TEX and the oxygen-containing functional groups of MWCNTs and electrostatic interac- tion. 3% NaOCl solution could not only introduce much oxygen-containing functional groups on MWCNTs, but also lead to less damage for the pore structure. This suggests that the CNTs-3% NaOCl is efficient adsorbent for TEX and that they may possess good potential for TEX removal in wastewater treatment.
基金National Natural Science Foundation of China(Nos.21975069,21725602,22108067,and 21938002)Innovative Research Groups of Hunan Province(No.2019JJ10001)Science and Technology Planning Project of Hunan Province(No.2019RS3010).
文摘The key issues to improve the performance of photocatalysts for selective oxidation of toluene are promoting the migration and separation of charge carrier,and enhancing the generation of active oxygen species.It is known that the construction of compact heterojunction is an efficient protocol to inhibit photogenerated electron-hole recombination.In this work,a 2D-2D[Bi_(6)O_(6)(OH)_(3)](NO_(3))3·1.5H2O-Bi_(2)MoO_(6)(denoted as BBN-BMO)composite heterojunction has been prepared by one-step hydrothermal method for the first time.The tetragonal phase BBN in the composite plays the role of transferring electrons from the visible light activated orthorhombic phase BMO and promoting the generation of active·O_(2)^(-),the holes left in BMO are used to activate toluene and produce benzyl radical,thus greatly improving the photocatalytic performance for selective oxidation of toluene.The toluene conversion rate of BBN-BMO is 3466μmol·g^(-1)·h^(-1),which is three times that of pure BMO.The selectivity to benzalde-hyde is 94.2%.In addition,reasonable mechanism has been speculated based on a series of control experiments.
基金financially supported by the National Natural Science Foundation of China(Nos.21975069 and 21872045)Key Project of Research and Development Plan of Hunan Province(Grant No.2019SK2071)+2 种基金the Innovative Research Groups of Hunan Province(Grant No.2019JJ10001)the Natural Science Foundation of Hunan Province,China(Grant No.2020JJ416)the Science and Technology Planning Project of Hunan Province(Grant No.2019RS3010).
文摘Efficient selective oxidation of hydrocarbons to corresponding ketones has been a significant but challenging work in the past decades.Here,a nitrogen-doped bamboo-like carbon nanotubes encapsulating cobalt catalyst(NCNTs-X)using citric acid,melamine and CoCl_(2)·6H_(2)O as precursors was synthesized by a simple pyrolysis method.A series of characterization techniques were employed to investigate the physicochemical properties of samples.And the results show that the as-prepared catalysts achieve a high catalytic performance for selective ethylbenzene oxidation(78.3% ethylbenzene conversion)using molecular oxygen as oxidant,especially giving a high selectivity(93.8% selectivity to acetophenone).According to the investigation of the structure-activity relationship of the catalysts,it can be deduced that the Co-N_(x) sites have an obvious positive effect on catalytic performance thanks to the synergistic effect between metallic cobalt and pyridinic N.
文摘The lanthanum molybdovanadophosphoric tetrabasic heteropoly complex was synthesized.Catalytic properties of the title heteropoly complex for selective oxidation of ethylbezene to acetonphenone was investigated.The suitable reaction conditions was discussed.
文摘A series of Ce-Mo oxide catalysts with different Ce/Mo atomic ratio were prepared and applied to selective oxidation of toluene to benzaldehyde. The structures and properties of the surfaces of catalysts were characterized by XRD, TPR and DR-UVS. The natures of oxygen species on the surfaces of these samples were studied by using temperature programmed desorption-mass spectrography(TPD-MS). The results showed that the oxygen species of multiple adsorption existed on the sample surface. And in the range of desorption temperature<900℃, for the Ce-Mo samples, not only the desorption peaks of O- species on surfaces of samples be discoved, but also the O2- species appeared. As the content of Ce in Ce-Mo oxides was changed, the activation energy of oxygen desorption(Ed) also changed. The Ed value of sample 3 (Ce/Mo=1/1) is the lowest and its selectivity of benzaldehyde in toluene oxidation is the highest. Thus, a Parallel relation between the Ed value and the selectivity for benzaldehyde existed in these Ce-Mo oxides.