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2014 Volume 35 Issue 7
2014, 35(7):
Abstract:
2014, 35(7): 981-982
doi: 10.1016/S1872-2067(14)60144-3
Abstract:
2014, 35(7): 983-988
doi: 10.1016/S1872-2067(14)60162-5
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2014, 35(7): 989-1007
doi: 10.1016/S1872-2067(14)60075-9
Abstract:
Photocatalysis is considered to be an effective solution for the current energy and environmental crises caused by industrial development. However, the practical application of conventional oxide photocatalysts is restricted by poor visible light adsorption because of their wide band gaps. The study of photocatalysts with a narrow band gap is thus a hot topic. Among oxide photocatalysts, Bi-based photocatalysts have attracted much interest because of their high visible light photocatalytic activity. This review summarizes recent advances into the type, preparation method, morphology control, composite construction, and properties of Bi-based photocatalysts. Finally, this review ends with a discussion on the future development of Bi-based photocatalysts in this exciting research area.
Photocatalysis is considered to be an effective solution for the current energy and environmental crises caused by industrial development. However, the practical application of conventional oxide photocatalysts is restricted by poor visible light adsorption because of their wide band gaps. The study of photocatalysts with a narrow band gap is thus a hot topic. Among oxide photocatalysts, Bi-based photocatalysts have attracted much interest because of their high visible light photocatalytic activity. This review summarizes recent advances into the type, preparation method, morphology control, composite construction, and properties of Bi-based photocatalysts. Finally, this review ends with a discussion on the future development of Bi-based photocatalysts in this exciting research area.
2014, 35(7): 1008-1011
doi: 10.1016/S1872-2067(14)60080-2
Abstract:
A series of amphiphilic proline-derived mercapto imidazole organic catalysts were synthesized and shown to be very effective with an acid cocatalyst for the asymmetric Michael addition reaction of ketones to nitroolefins with high diastereoselectivity (up to 99:1) and execellent enantioselectivity (up to 96%) using water as solvent.
A series of amphiphilic proline-derived mercapto imidazole organic catalysts were synthesized and shown to be very effective with an acid cocatalyst for the asymmetric Michael addition reaction of ketones to nitroolefins with high diastereoselectivity (up to 99:1) and execellent enantioselectivity (up to 96%) using water as solvent.
2014, 35(7): 1012-1016
doi: 10.1016/S1872-2067(14)60141-8
Abstract:
A novel Rh(III)-catalyzed direct amidation of aldehydes featuring Ag2CO3 as the oxidant is described. This selective procedure provides a variety of N-pyridinamides and imide derivatives in good yields.
A novel Rh(III)-catalyzed direct amidation of aldehydes featuring Ag2CO3 as the oxidant is described. This selective procedure provides a variety of N-pyridinamides and imide derivatives in good yields.
2014, 35(7): 1017-1023
doi: 10.1016/S1872-2067(14)60061-9
Abstract:
Poly(4-vinylpyridinium) perchlorate has been used as an efficient solid acid catalyst for the synthesis of 3,3'-(arylmethylene)bis(4-hydroxycoumarins) and bis(indolyl)methanes, with the products being formed in excellent yields over very short reaction times under mild and environmentally friendly conditions. This catalyst can be reused several times without any appreciable loss in its activity.
Poly(4-vinylpyridinium) perchlorate has been used as an efficient solid acid catalyst for the synthesis of 3,3'-(arylmethylene)bis(4-hydroxycoumarins) and bis(indolyl)methanes, with the products being formed in excellent yields over very short reaction times under mild and environmentally friendly conditions. This catalyst can be reused several times without any appreciable loss in its activity.
2014, 35(7): 1024-1029
doi: 10.1016/S1872-2067(14)60029-2
Abstract:
A facile and efficient method has been developed for the synthesis of 1-amidoalkyl-2-naphthols via the one-pot multi-component condensation of 2-naphthol with aromatic aldehydes and acetamide or thioacetamide in the presence of melamine-Br3 under solvent-free conditions. There are several advantages to this reaction, including high yields, short reaction time, and high catalytic efficiency.
A facile and efficient method has been developed for the synthesis of 1-amidoalkyl-2-naphthols via the one-pot multi-component condensation of 2-naphthol with aromatic aldehydes and acetamide or thioacetamide in the presence of melamine-Br3 under solvent-free conditions. There are several advantages to this reaction, including high yields, short reaction time, and high catalytic efficiency.
2014, 35(7): 1030-1035
doi: 10.1016/S1872-2067(14)60035-8
Abstract:
Ion exchange method was used to fabricate Cu-ETS-10 titanosilicate catalysts, which possessed high activity, N2 selectivity and SO2 resistance for NOx selective catalytic reduction (SCR). N2 sorption measurements indicated that the microporous catalysts had high surface areas of 288-380 m2/g. The Cu content and speciation were investigated by inductively coupled plasma atomic emission spectrometry, H2 temperature-programmed reduction, and diffuse reflectance infrared Fourier transform spectroscopy. Various Cu species coexisted within the catalyst. Isolated Cu2+ species were the active sites for NH3-SCR, the number of which initially increased and then decreased with increasing Cu content. The catalytic activity of Cu-ETS-10 depended on the isolated Cu2+ species content.
Ion exchange method was used to fabricate Cu-ETS-10 titanosilicate catalysts, which possessed high activity, N2 selectivity and SO2 resistance for NOx selective catalytic reduction (SCR). N2 sorption measurements indicated that the microporous catalysts had high surface areas of 288-380 m2/g. The Cu content and speciation were investigated by inductively coupled plasma atomic emission spectrometry, H2 temperature-programmed reduction, and diffuse reflectance infrared Fourier transform spectroscopy. Various Cu species coexisted within the catalyst. Isolated Cu2+ species were the active sites for NH3-SCR, the number of which initially increased and then decreased with increasing Cu content. The catalytic activity of Cu-ETS-10 depended on the isolated Cu2+ species content.
2014, 35(7): 1036-1042
doi: 10.1016/S1872-2067(14)60038-3
Abstract:
3-Methyl-1-sulfonic acid imidazolium hydrogen sulfate has been used as an efficient, halogen-free, and reusable Brönsted acidic ionic liquid catalyst for the synthesis of ethyl-4-aryl/heteryl-hexahydro-trimehtyl-5-oxoquinoline-3-carboxylates via the one-pot condensation of dimedone with aryl/heteryl aldehydes, ethyl acetoacetate, and ammonium acetate under solvent-free conditions. This method has the advantage of being clean and simple, as well as providing the desired product in high yield over a short reaction time. Furthermore, the catalyst could be recycled and reused four times without any discernible reduction in activity.
3-Methyl-1-sulfonic acid imidazolium hydrogen sulfate has been used as an efficient, halogen-free, and reusable Brönsted acidic ionic liquid catalyst for the synthesis of ethyl-4-aryl/heteryl-hexahydro-trimehtyl-5-oxoquinoline-3-carboxylates via the one-pot condensation of dimedone with aryl/heteryl aldehydes, ethyl acetoacetate, and ammonium acetate under solvent-free conditions. This method has the advantage of being clean and simple, as well as providing the desired product in high yield over a short reaction time. Furthermore, the catalyst could be recycled and reused four times without any discernible reduction in activity.
2014, 35(7): 1043-1053
doi: 10.1016/S1872-2067(14)60042-5
Abstract:
MoO3/SiO2 catalysts for the transesterification of dimethyl oxalate (DMO) with phenol were prepared by both the thermal spreading (TS) and incipient wetness impregnation methods. The results showed that the 10%MoO3/SiO2 catalyst prepared by TS (10%MoO3/SiO2-TS) exhibited higher catalytic performance compared with the 10%MoO3/SiO2 catalyst prepared by incipient wetness impregnation (10%MoO3/SiO2-C). The catalysts were characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, pyridine-IR spectroscopy, and NH3 temperature-programmed desorption. These analyses indicated that weak Lewis acid sites were formed on the catalyst surfaces and that the Mo species were present as monomeric MoO3 rather than as isolated molybdenum oxide or polymolybdate species on both catalysts, although the 10%MoO3/SiO2-TS exhibited better dispersion of MoO3 and a higher surface Mo content than the 10%MoO3/SiO2-C. Under the optimal transesterification reaction conditions (1.2 g 10%MoO3/SiO2-TS, T=180℃, n(DMO)/n(phenol)=2, t=4 h), the conversion of phenol was 70.9%, and the yields of methyl phenyl oxalate and diphenyl oxalate were 63.1% and 7.7%, respectively.
MoO3/SiO2 catalysts for the transesterification of dimethyl oxalate (DMO) with phenol were prepared by both the thermal spreading (TS) and incipient wetness impregnation methods. The results showed that the 10%MoO3/SiO2 catalyst prepared by TS (10%MoO3/SiO2-TS) exhibited higher catalytic performance compared with the 10%MoO3/SiO2 catalyst prepared by incipient wetness impregnation (10%MoO3/SiO2-C). The catalysts were characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, pyridine-IR spectroscopy, and NH3 temperature-programmed desorption. These analyses indicated that weak Lewis acid sites were formed on the catalyst surfaces and that the Mo species were present as monomeric MoO3 rather than as isolated molybdenum oxide or polymolybdate species on both catalysts, although the 10%MoO3/SiO2-TS exhibited better dispersion of MoO3 and a higher surface Mo content than the 10%MoO3/SiO2-C. Under the optimal transesterification reaction conditions (1.2 g 10%MoO3/SiO2-TS, T=180℃, n(DMO)/n(phenol)=2, t=4 h), the conversion of phenol was 70.9%, and the yields of methyl phenyl oxalate and diphenyl oxalate were 63.1% and 7.7%, respectively.
2014, 35(7): 1054-1058
doi: 10.1016/S1872-2067(14)60041-3
Abstract:
Cerium (IV) sulfate tetrahydrate, Ce(SO4)2·4H2O, is a novel inorganic solid acidic catalyst that efficiently catalyzes the synthesis of 2,3-dihydroquinazolin-4(1H)-ones via the one-pot three-component reaction of isatoic anhydride, aromatic aldehydes, and a nitrogen source (ammonium acetate, ammonium carbonate, ammonium chloride, or methylamine) under solvent-free conditions. The desired products are obtained in short reaction time with high yields. The catalyst is inexpensive and readily available and can be recovered conveniently and reused such that considerable catalytic activity can still be achieved after the fifth run. Easy work-up and avoiding the use of harmful organic solvents are other advantages of this simple procedure.
Cerium (IV) sulfate tetrahydrate, Ce(SO4)2·4H2O, is a novel inorganic solid acidic catalyst that efficiently catalyzes the synthesis of 2,3-dihydroquinazolin-4(1H)-ones via the one-pot three-component reaction of isatoic anhydride, aromatic aldehydes, and a nitrogen source (ammonium acetate, ammonium carbonate, ammonium chloride, or methylamine) under solvent-free conditions. The desired products are obtained in short reaction time with high yields. The catalyst is inexpensive and readily available and can be recovered conveniently and reused such that considerable catalytic activity can still be achieved after the fifth run. Easy work-up and avoiding the use of harmful organic solvents are other advantages of this simple procedure.
2014, 35(7): 1059-1067
doi: 10.1016/S1872-2067(14)60045-0
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Cyclopalladated ferrocenylimine dimers and cyclopalladated ferrocenylimine monomers were designed and prepared. They were characterized using 1H NMR, 13C NMR, and IR spectroscopies, and MS. The catalytic properties of these compounds in Heck and Suzuki coupling reactions in water or organic solvents were systematically investigated. The results showed that these catalysts could effectively catalyze Heck and Suzuki coupling reactions of aryl or heteroaryl halides in water or organic solvents.
Cyclopalladated ferrocenylimine dimers and cyclopalladated ferrocenylimine monomers were designed and prepared. They were characterized using 1H NMR, 13C NMR, and IR spectroscopies, and MS. The catalytic properties of these compounds in Heck and Suzuki coupling reactions in water or organic solvents were systematically investigated. The results showed that these catalysts could effectively catalyze Heck and Suzuki coupling reactions of aryl or heteroaryl halides in water or organic solvents.
2014, 35(7): 1068-1077
doi: 10.1016/S1872-2067(14)60047-4
Abstract:
Pr, N, and P tri-doped anatase TiO2 nanosheets (PrNPTO) were synthesized by a combined sol-gel solvothermal method and characterized by X-ray diffraction, transmission electron microscopy, N2 adsorption-desorption, X-ray photoelectron spectroscopy, UV-vis absorbance spectroscopy, and photoluminescence spectroscopy. When the Pr-doping concentration was 1.75 wt% and calcination temperature employed was 550℃, the resulting PrNPTO showed the highest photoactivity towards the degradation of methylene blue under visible and UV light irradiation. PrNPTO also displayed superior photoactivity towards the degradation of 4-chlorophenol under sunlight (kapp=3.90×10-2 min-1) over the non-doped, single-doped, and co-doped samples, and P25 TiO2 (kapp =1.17×10-2 min-1). The high photoactivity of PrNPTO was attributed to the increased UV and visible light absorption properties, reduced recombination of photogenerated carriers, increased surface hydroxyl content, and improved surface textural properties. PrNPTO was highly efficient and stable under simulated sunlight irradiation, which are essential attributes for practical application in environment-related remediation schemes.
Pr, N, and P tri-doped anatase TiO2 nanosheets (PrNPTO) were synthesized by a combined sol-gel solvothermal method and characterized by X-ray diffraction, transmission electron microscopy, N2 adsorption-desorption, X-ray photoelectron spectroscopy, UV-vis absorbance spectroscopy, and photoluminescence spectroscopy. When the Pr-doping concentration was 1.75 wt% and calcination temperature employed was 550℃, the resulting PrNPTO showed the highest photoactivity towards the degradation of methylene blue under visible and UV light irradiation. PrNPTO also displayed superior photoactivity towards the degradation of 4-chlorophenol under sunlight (kapp=3.90×10-2 min-1) over the non-doped, single-doped, and co-doped samples, and P25 TiO2 (kapp =1.17×10-2 min-1). The high photoactivity of PrNPTO was attributed to the increased UV and visible light absorption properties, reduced recombination of photogenerated carriers, increased surface hydroxyl content, and improved surface textural properties. PrNPTO was highly efficient and stable under simulated sunlight irradiation, which are essential attributes for practical application in environment-related remediation schemes.
2014, 35(7): 1078-1083
doi: 10.1016/S1872-2067(14)60044-9
Abstract:
A N-doped mesoporous carbon (NMC-1) has been synthesized at relatively low temperature using chitosan as a nitrogen and carbon source, tetraethoxysilane as a soft template, and nickel nitrate as a catalyst. NMC-1 has a porous structure and heteroatoms such as N and O atoms, indicating that NMC-1 can contribute to electrocatalysis, electric double-layer capacitance, and pseudocapacitance. Hence, NMC-1 was used as a bifunctional material which shows effective activity as an electrocatalyst for oxygen reduction reaction in alkaline solution, and a high specific capacitance as an ultracapacitor (252 F/g at 0.2 A/g). The results demonstrate that the presented NMC-1 has potential applications as a renewable and environmentally friendly material in fuel cells and supercapacitors.
A N-doped mesoporous carbon (NMC-1) has been synthesized at relatively low temperature using chitosan as a nitrogen and carbon source, tetraethoxysilane as a soft template, and nickel nitrate as a catalyst. NMC-1 has a porous structure and heteroatoms such as N and O atoms, indicating that NMC-1 can contribute to electrocatalysis, electric double-layer capacitance, and pseudocapacitance. Hence, NMC-1 was used as a bifunctional material which shows effective activity as an electrocatalyst for oxygen reduction reaction in alkaline solution, and a high specific capacitance as an ultracapacitor (252 F/g at 0.2 A/g). The results demonstrate that the presented NMC-1 has potential applications as a renewable and environmentally friendly material in fuel cells and supercapacitors.
2014, 35(7): 1084-1090
doi: 10.1016/S1872-2067(14)60054-1
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Catalytically active, stable, and mechanically durable solid K/Al2O3 catalysts for the transesterification of rapeseed oil with methanol was studied. In a batch reactor, high catalytic activity was accompanied by leaching of K species, caused by glycerol, and mechanical destruction of the solid catalyst as a result of contact with the stirrer. In a fixed-bed reactor, some leaching of K species into the liquid phases was also observed, but approached 0 during 30 h of time-on-stream; the activity of the K/Al2O3 catalyst (~83% ester yield) was stable for 100 h of time-on-stream and no mechanical destruction of the catalyst was observed. The populations of K2O and K-O-Al species for fresh and used K/Al2O3 catalysts were compared using Fourier transform infrared spectroscopy. It was found that some K2O species leached into the liquid phases at the beginning of the reaction.
Catalytically active, stable, and mechanically durable solid K/Al2O3 catalysts for the transesterification of rapeseed oil with methanol was studied. In a batch reactor, high catalytic activity was accompanied by leaching of K species, caused by glycerol, and mechanical destruction of the solid catalyst as a result of contact with the stirrer. In a fixed-bed reactor, some leaching of K species into the liquid phases was also observed, but approached 0 during 30 h of time-on-stream; the activity of the K/Al2O3 catalyst (~83% ester yield) was stable for 100 h of time-on-stream and no mechanical destruction of the catalyst was observed. The populations of K2O and K-O-Al species for fresh and used K/Al2O3 catalysts were compared using Fourier transform infrared spectroscopy. It was found that some K2O species leached into the liquid phases at the beginning of the reaction.
2014, 35(7): 1091-1097
doi: 10.1016/S1872-2067(14)60050-4
Abstract:
Focused on the optimization of the gas diffusion electrode (GDE) in an alkaline anion exchange membrane fuel cell (AAEMFC), PTFE content and catalyst loading in the catalyst layer (CL) were found to have a substantial effect on the cell performance and electrochemical kinetics. The i-V curves, open circuit voltage, cell resistance, in-situ electrochemical impedance spectroscopy and kinetics analysis have been used to evaluate the electrochemical properties of the fabricated GDEs. The results reveal that the optimum PTFE content in the CL of AAEMFC is 20%. Pt loading ranged from 0.2-1.0 mg/cm2 was also investigated as a vital parameter for three-phase boundary, CL conductivity and catalyst utilization. Ultimately, the highest peak power density of 213 mW/cm2 was achieved at 50℃ from the prepared GDE with Pt loading of 1.0 mg/cm2 on Pt/C and 20% PTFE in CL of AAEMFC. Considering the Pt-based catalyst effective utilization and cost, however, the platinum requirement can be diminished to close to 0.5 mg/cm2 in CLwithout significant performance loss.
Focused on the optimization of the gas diffusion electrode (GDE) in an alkaline anion exchange membrane fuel cell (AAEMFC), PTFE content and catalyst loading in the catalyst layer (CL) were found to have a substantial effect on the cell performance and electrochemical kinetics. The i-V curves, open circuit voltage, cell resistance, in-situ electrochemical impedance spectroscopy and kinetics analysis have been used to evaluate the electrochemical properties of the fabricated GDEs. The results reveal that the optimum PTFE content in the CL of AAEMFC is 20%. Pt loading ranged from 0.2-1.0 mg/cm2 was also investigated as a vital parameter for three-phase boundary, CL conductivity and catalyst utilization. Ultimately, the highest peak power density of 213 mW/cm2 was achieved at 50℃ from the prepared GDE with Pt loading of 1.0 mg/cm2 on Pt/C and 20% PTFE in CL of AAEMFC. Considering the Pt-based catalyst effective utilization and cost, however, the platinum requirement can be diminished to close to 0.5 mg/cm2 in CLwithout significant performance loss.
2014, 35(7): 1098-1104
doi: 10.1016/S1872-2067(14)60049-8
Abstract:
A polytyramine-copper oxalate nanocomposite modified copper (PTCOxNMC) electrode prepared by electropolymerization was examined for electrocatalytic activity towards the oxidation of methanol in alkaline solution using cyclic voltammetry and impedance spectroscopy. The prepared PTCOxNMC electrode showed a significantly high response for adsorbed methanol oxidation. The effects of various parameters such as potential scan rate and methanol concentration on the electrocatalytic oxidation at the surface of the PTCOxNMC electrode were investigated. Spectrometry techniques such as Fourier transform infrared spectroscopy and scanning electron microscopy were used to determine the surface physical characteristics of the modified electrode and revealed that the polytyramine-copper oxalate nanocomposite particles were highly dispersed on the surface of the copper electrode with a narrow size up to 40 nm. The very high current density obtained for the catalytic oxidation may have resulted from the high electrode surface area caused by modification with the poly-tyramine-copper oxalate nanocomposite.
A polytyramine-copper oxalate nanocomposite modified copper (PTCOxNMC) electrode prepared by electropolymerization was examined for electrocatalytic activity towards the oxidation of methanol in alkaline solution using cyclic voltammetry and impedance spectroscopy. The prepared PTCOxNMC electrode showed a significantly high response for adsorbed methanol oxidation. The effects of various parameters such as potential scan rate and methanol concentration on the electrocatalytic oxidation at the surface of the PTCOxNMC electrode were investigated. Spectrometry techniques such as Fourier transform infrared spectroscopy and scanning electron microscopy were used to determine the surface physical characteristics of the modified electrode and revealed that the polytyramine-copper oxalate nanocomposite particles were highly dispersed on the surface of the copper electrode with a narrow size up to 40 nm. The very high current density obtained for the catalytic oxidation may have resulted from the high electrode surface area caused by modification with the poly-tyramine-copper oxalate nanocomposite.
2014, 35(7): 1105-1112
doi: 10.1016/S1872-2067(14)60058-9
Abstract:
A series of NixCo1-xCo2O4 (0 ≤ x ≤ 1) spinel catalysts were prepared by the co-precipitation method and used for direct N2O decomposition. The decomposition pathway of the parent precipitates was characterized by thermal analysis. The catalysts were calcined at 500℃ for 3 h and characterized by powder X-ray diffraction, Fourier transform infrared, and N2 adsorption-desorption. Nickel cobaltite spinel was formed in the solid state reaction between NiO and Co3O4. The N2O decomposition measurement revealed significant increase in the activity of Co3O4 spinel oxide catalyst with the partial replacement of Co2+ by Ni2+. The activity of this series of catalysts was controlled by the degree of Co2+ substitution by Ni2+, spinel crystallite size, catalyst surface area, presence of residual K+, and calcination temperature.
A series of NixCo1-xCo2O4 (0 ≤ x ≤ 1) spinel catalysts were prepared by the co-precipitation method and used for direct N2O decomposition. The decomposition pathway of the parent precipitates was characterized by thermal analysis. The catalysts were calcined at 500℃ for 3 h and characterized by powder X-ray diffraction, Fourier transform infrared, and N2 adsorption-desorption. Nickel cobaltite spinel was formed in the solid state reaction between NiO and Co3O4. The N2O decomposition measurement revealed significant increase in the activity of Co3O4 spinel oxide catalyst with the partial replacement of Co2+ by Ni2+. The activity of this series of catalysts was controlled by the degree of Co2+ substitution by Ni2+, spinel crystallite size, catalyst surface area, presence of residual K+, and calcination temperature.
2014, 35(7): 1113-1125
doi: 10.1016/S1872-2067(14)60055-3
Abstract:
AgX (X=I, Br) nanoparticles-surface modified ZnO nanorod arrays (AgX/ZnO) were prepared using an impregnation method. The influence of impregnating solution concentration, immersion time, and UV light illumination pretreatment on the visible light-driven photocatalytic activity of AgX/ZnO was evaluated. The morphology, phase composition, band gap, and surface characteristics of the AgX/ZnO nanorod arrays were assessed by field-emission scanning electron microscopy, X-ray diffraction, diffuse reflectance UV-Vis absorption spectroscopy, and X-ray photoelectron spectroscopy. The AgBr nanoparticles were homogeneously distributed on the top and side surfaces of the ZnO nanorods, and connected to form a porous network structure. Following UV light illumination pretreatment, Ag nanoparticles were formed on the surface of the AgBr nanoparticles producing a Ag/AgBr/ZnO nanostructure. Methyl orange photodegradation study showed that the photocatalytic activity of AgBr/ZnO was higher than that of AgI/ZnO, synthesized under similar conditions, and was highly related to the impregnating solution concentration and immersion time. Owing to the high surface area of the ZnO nanorod arrays, the visible light sensitivity of AgBr, and surface plasmon resonance of Ag/AgBr, Ag/AgBr/ZnO exhibited the highest visible light-driven photocatalytic activity.
AgX (X=I, Br) nanoparticles-surface modified ZnO nanorod arrays (AgX/ZnO) were prepared using an impregnation method. The influence of impregnating solution concentration, immersion time, and UV light illumination pretreatment on the visible light-driven photocatalytic activity of AgX/ZnO was evaluated. The morphology, phase composition, band gap, and surface characteristics of the AgX/ZnO nanorod arrays were assessed by field-emission scanning electron microscopy, X-ray diffraction, diffuse reflectance UV-Vis absorption spectroscopy, and X-ray photoelectron spectroscopy. The AgBr nanoparticles were homogeneously distributed on the top and side surfaces of the ZnO nanorods, and connected to form a porous network structure. Following UV light illumination pretreatment, Ag nanoparticles were formed on the surface of the AgBr nanoparticles producing a Ag/AgBr/ZnO nanostructure. Methyl orange photodegradation study showed that the photocatalytic activity of AgBr/ZnO was higher than that of AgI/ZnO, synthesized under similar conditions, and was highly related to the impregnating solution concentration and immersion time. Owing to the high surface area of the ZnO nanorod arrays, the visible light sensitivity of AgBr, and surface plasmon resonance of Ag/AgBr, Ag/AgBr/ZnO exhibited the highest visible light-driven photocatalytic activity.
2014, 35(7): 1126-1135
doi: 10.1016/S1872-2067(14)60052-8
Abstract:
N-Sulfonic acid poly(4-vinylpyridinum) hydrogen sulfate has been developed as a recyclable solid acid catalyst for the acetylation of alcohols, phenols, thiols, and amines, as well as the 1,1-diacetylation of aldehydes under solvent-free conditions at room temperature. The acetylated products were formed in good to excellent yields over short reaction times, and the catalyst could be readily recovered by filtration and used several times without any discernible loss in activity. The hydrogen sulfate anion of the catalytic system was found to play a critical role in enhancing the reaction time and yield of the acetylation reaction.
N-Sulfonic acid poly(4-vinylpyridinum) hydrogen sulfate has been developed as a recyclable solid acid catalyst for the acetylation of alcohols, phenols, thiols, and amines, as well as the 1,1-diacetylation of aldehydes under solvent-free conditions at room temperature. The acetylated products were formed in good to excellent yields over short reaction times, and the catalyst could be readily recovered by filtration and used several times without any discernible loss in activity. The hydrogen sulfate anion of the catalytic system was found to play a critical role in enhancing the reaction time and yield of the acetylation reaction.
2014, 35(7): 1136-1147
doi: 10.1016/S1872-2067(14)60060-7
Abstract:
A facile synthesis of α-zirconium phosphate (ZP) nanoparticles as an effective, eco-friendly, and recyclable solid acid catalyst is reported. Polyvinylpyrrolidone (PVP) and polyvinyl alcohol (PVA) were used as organic matrix as dispersing agents and served as a template for the nanoparticles. Hydrogen bonds between ZP and PVA or PVP, along the polymer chains, appear to play an important role for improving the dispersion of in situ formed ZP. Following calcination of PVA/ZP or PVP/ZP, pure hexagonal ZP nanoparticles were obtained. The catalysts were characterized by nitrogen sorption, inductively coupled plasma optical emission spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy, and transmission electron microscopy. Pyridine-FTIR and temperature-programmed desorption of NH3 suggest the presence of Brönsted acid sites. The acidic properties of the catalyst were studied in Friedel-Crafts alkylation of phenol by tert-butanol, producing 2-tert-butylphenol, 4-tert-butylphenol, and 2,4-di-tert-butylphenol. The alkylation reaction was performed in the presence of catalysts P2O5/Al2O3, P2O5/SiO2, α-ZrP (prepared in the absence of the polymers), and various ionic liquids. The use of the hexagonal ZP nanoparticle catalyst afforded an excellent phenol conversion (86%) and selectivity towards 4-tert-butylphenol (83%) under optimized reaction conditions. The catalyst was easily recovered from the reaction mixture, regenerated, and reused at least four times without significant loss in the catalytic activity.
A facile synthesis of α-zirconium phosphate (ZP) nanoparticles as an effective, eco-friendly, and recyclable solid acid catalyst is reported. Polyvinylpyrrolidone (PVP) and polyvinyl alcohol (PVA) were used as organic matrix as dispersing agents and served as a template for the nanoparticles. Hydrogen bonds between ZP and PVA or PVP, along the polymer chains, appear to play an important role for improving the dispersion of in situ formed ZP. Following calcination of PVA/ZP or PVP/ZP, pure hexagonal ZP nanoparticles were obtained. The catalysts were characterized by nitrogen sorption, inductively coupled plasma optical emission spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy, and transmission electron microscopy. Pyridine-FTIR and temperature-programmed desorption of NH3 suggest the presence of Brönsted acid sites. The acidic properties of the catalyst were studied in Friedel-Crafts alkylation of phenol by tert-butanol, producing 2-tert-butylphenol, 4-tert-butylphenol, and 2,4-di-tert-butylphenol. The alkylation reaction was performed in the presence of catalysts P2O5/Al2O3, P2O5/SiO2, α-ZrP (prepared in the absence of the polymers), and various ionic liquids. The use of the hexagonal ZP nanoparticle catalyst afforded an excellent phenol conversion (86%) and selectivity towards 4-tert-butylphenol (83%) under optimized reaction conditions. The catalyst was easily recovered from the reaction mixture, regenerated, and reused at least four times without significant loss in the catalytic activity.
2014, 35(7): 1148-1156
doi: 10.1016/S1872-2067(14)60057-7
Abstract:
Zirconium phosphates were prepared by precipitation, hydrothermal synthesis, and impregnation methods and were characterized by X-ray diffraction, thermogravimetric analysis, nitrogen adsorption, Fourier transform infrared spectroscopy, and Hammett indicators. The different preparation methods have crucial effects on the texture and surface acidity of the zirconium phosphates. The zirconium phosphates were employed as catalysts for the gas phase dehydration of glycerol under mild reaction conditions. The zirconium phosphates from the precipitation method afforded the highest activity with the complete conversion of glycerol, 81% selectivity to acrolein, and no obvious deactivation over 24 h. Surface acidic sites played an important role in the activity, selectivity to acrolein, and life of catalysts.
Zirconium phosphates were prepared by precipitation, hydrothermal synthesis, and impregnation methods and were characterized by X-ray diffraction, thermogravimetric analysis, nitrogen adsorption, Fourier transform infrared spectroscopy, and Hammett indicators. The different preparation methods have crucial effects on the texture and surface acidity of the zirconium phosphates. The zirconium phosphates were employed as catalysts for the gas phase dehydration of glycerol under mild reaction conditions. The zirconium phosphates from the precipitation method afforded the highest activity with the complete conversion of glycerol, 81% selectivity to acrolein, and no obvious deactivation over 24 h. Surface acidic sites played an important role in the activity, selectivity to acrolein, and life of catalysts.
2014, 35(7): 1157-1165
doi: 10.1016/S1872-2067(14)60062-0
Abstract:
Mixed oxides obtained by adding varying amounts of ZnO into Zr0.5Al0.5O1.75 were used as supports to prepare 1.5% Pd catalysts. The catalyst activity and H2O tolerances of the catalysts were evaluated in a gas mixture simulating the exhaust of lean-burn natural gas-fueled vehicles. The catalysts were further characterized by N2 adsorption-desorption, X-ray diffraction, H2 temperature programmed reduction and X-ray photoelectron spectroscopy. The catalytic activity was greatly influenced by ZnO contents in Zr0.5Al0.5O1.75 support. The catalyst containing 15% ZnO exhibited a light-off temperature and complete conversion temperature for CH4 in the absence of H2O of 278 and 314℃, respectively; while these same values in the presence of H2O were 342 and 371℃, respectively. These results indicate that this combination of materials offers excellent catalytic activity at low temperature and also exhibits significant H2O tolerance.
Mixed oxides obtained by adding varying amounts of ZnO into Zr0.5Al0.5O1.75 were used as supports to prepare 1.5% Pd catalysts. The catalyst activity and H2O tolerances of the catalysts were evaluated in a gas mixture simulating the exhaust of lean-burn natural gas-fueled vehicles. The catalysts were further characterized by N2 adsorption-desorption, X-ray diffraction, H2 temperature programmed reduction and X-ray photoelectron spectroscopy. The catalytic activity was greatly influenced by ZnO contents in Zr0.5Al0.5O1.75 support. The catalyst containing 15% ZnO exhibited a light-off temperature and complete conversion temperature for CH4 in the absence of H2O of 278 and 314℃, respectively; while these same values in the presence of H2O were 342 and 371℃, respectively. These results indicate that this combination of materials offers excellent catalytic activity at low temperature and also exhibits significant H2O tolerance.
2014, 35(7): 1166-1172
doi: 10.1016/S1872-2067(14)60065-6
Abstract:
A highly sensitive electrochemical sensor was prepared for the determination of L-cysteine using a modified multiwall carbon nanotubes paste electrode in the presence of 3,4-dihydroxycinnamic acid (3,4-DHCA) as a mediator, based on an electrocatalytic process. The results indicate that the electrode is electrocatalytically efficient for the oxidation of L-cysteine in the presence of 3,4-DHCA. The interaction between the mediator and L-cysteine can be used for its sensitive and selective determination. Using chronoamperometry, the catalytic reaction rate constant was calculated to be 2.37×102 mol-1 L s-1. The catalytic peak current was linearly dependent on the L-cysteine concentration in the range of 0.4-115 μmol/L. The detection limit obtained by linear sweep voltammetry was 0.25 μmol/L. Finally, the modified electrode was examined as a selective, simple, and precise new electrochemical sensor for the determination of L-cysteine in real samples.
A highly sensitive electrochemical sensor was prepared for the determination of L-cysteine using a modified multiwall carbon nanotubes paste electrode in the presence of 3,4-dihydroxycinnamic acid (3,4-DHCA) as a mediator, based on an electrocatalytic process. The results indicate that the electrode is electrocatalytically efficient for the oxidation of L-cysteine in the presence of 3,4-DHCA. The interaction between the mediator and L-cysteine can be used for its sensitive and selective determination. Using chronoamperometry, the catalytic reaction rate constant was calculated to be 2.37×102 mol-1 L s-1. The catalytic peak current was linearly dependent on the L-cysteine concentration in the range of 0.4-115 μmol/L. The detection limit obtained by linear sweep voltammetry was 0.25 μmol/L. Finally, the modified electrode was examined as a selective, simple, and precise new electrochemical sensor for the determination of L-cysteine in real samples.
2014, 35(7): 1173-1188
doi: 10.1016/S1872-2067(14)60066-8
Abstract:
Covalent coupling between LaMnO3 nanoparticles and carbon black to produce a composite catalyst for oxygen reduction reaction (ORR) was achieved by physical mixing of modified carbon and perovskite-type LaMnO3 nanoparticles, followed by sintering at different temperatures. Perovskite-type LaMnO3 nanoparticles were first synthesized via chemical precipitation, and the carbon support (Vulcan XC-72) was modified using graphitization, followed by HNO3 and ammonia treatments. The morphology and electronic states of the carbon black-LaMnO3 hybrid catalyst were characterized by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The loaded LaMnO3 particles featured rod-like, three bars-like, and bamboo rod-like structures and were homogeneously dispersed in the carbon matrix that featured a hollow spherical structure. At a sintering temperature of about 300℃, C-O-M (M=La, Mn) bonds formed at the interface between the carbon and LaMnO3 nanoparticles. Electrochemical measurements in 1 mol/L NaOH showed that the carbon-LaMnO3 hybrid prepared at a LaMnO3/GCB mass ratio of 2:3 displayed the highest electrocatalytic activity towards ORR among all the synthesized hybrid catalysts. The electrocatalytic activity was comparable with that obtained by commercial Pt/C catalyst (E-TEK). The average electron transfer number of ORR was ~3.81, and the corresponding yield of the hydrogen peroxide intermediatewas ~9.5%. The remarkably improved electrocatalytic activity towards ORR was likely because of the formation of covalent bonds (C-O-M) between the LaMnO3 nanoparticles and carbon that can effectively enhance the ORR kinetics. This information is important to understand the physical origin of the electrocatalytic activity of carbon-supported rare earth oxides as catalysts for ORR.
Covalent coupling between LaMnO3 nanoparticles and carbon black to produce a composite catalyst for oxygen reduction reaction (ORR) was achieved by physical mixing of modified carbon and perovskite-type LaMnO3 nanoparticles, followed by sintering at different temperatures. Perovskite-type LaMnO3 nanoparticles were first synthesized via chemical precipitation, and the carbon support (Vulcan XC-72) was modified using graphitization, followed by HNO3 and ammonia treatments. The morphology and electronic states of the carbon black-LaMnO3 hybrid catalyst were characterized by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The loaded LaMnO3 particles featured rod-like, three bars-like, and bamboo rod-like structures and were homogeneously dispersed in the carbon matrix that featured a hollow spherical structure. At a sintering temperature of about 300℃, C-O-M (M=La, Mn) bonds formed at the interface between the carbon and LaMnO3 nanoparticles. Electrochemical measurements in 1 mol/L NaOH showed that the carbon-LaMnO3 hybrid prepared at a LaMnO3/GCB mass ratio of 2:3 displayed the highest electrocatalytic activity towards ORR among all the synthesized hybrid catalysts. The electrocatalytic activity was comparable with that obtained by commercial Pt/C catalyst (E-TEK). The average electron transfer number of ORR was ~3.81, and the corresponding yield of the hydrogen peroxide intermediatewas ~9.5%. The remarkably improved electrocatalytic activity towards ORR was likely because of the formation of covalent bonds (C-O-M) between the LaMnO3 nanoparticles and carbon that can effectively enhance the ORR kinetics. This information is important to understand the physical origin of the electrocatalytic activity of carbon-supported rare earth oxides as catalysts for ORR.
2014, 35(7): 1189-1195
doi: 10.1016/S1872-2067(14)60076-0
Abstract:
S-doped TiO2 (S-TiO2) films were immobilized on flexible low-cost aluminum sheets (S-TiO2-AS) using a sol-gel dipping process and low post-processing temperatures. The photocatalytic degradation of toxic organic vapors using the prepared films was evaluated using a continuous-flow glass tube under visible light exposure. The surface properties of the S-TiO2-AS and TiO2-AS films were examined by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and ultraviolet-visible spectroscopy. The photolysis of benzene, toluene, ethyl benzene, and xylene (BTEX) did not occur on the bare AS. In contrast, the photocatalytic degradation efficiencies of the target pollutants using S-TiO2-AS were higher than those obtained using reference TiO2-AS photocatalyst. In particular, the average photocatalytic degradation efficiencies of BTEX using S-TiO2-0.8-AS (S/Ti ratio=0.8) over a 3-h process were 34%, 78%, 91%, and 94%, respectively, whereas those of TiO2-AS were 2%, 11%, 21%, and 36%, respectively. The photocatalytic decomposition efficiencies of BTEX under visible irradiation using S-TiO2-AS increased with increasing S/Ti ratios from 0.2 to 0.8, but decreased when the ratio further increased to 1.6. Thus, S-TiO2-AS can be prepared using optimal S/Ti ratios. The degradation of BTEX over S-TiO2-AS depended on the air flow rates and initial concentrations of the target chemical. Overall, under optimal conditions, S-TiO2-AS can be effectively applied for the purification of toxic organic vapors.
S-doped TiO2 (S-TiO2) films were immobilized on flexible low-cost aluminum sheets (S-TiO2-AS) using a sol-gel dipping process and low post-processing temperatures. The photocatalytic degradation of toxic organic vapors using the prepared films was evaluated using a continuous-flow glass tube under visible light exposure. The surface properties of the S-TiO2-AS and TiO2-AS films were examined by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and ultraviolet-visible spectroscopy. The photolysis of benzene, toluene, ethyl benzene, and xylene (BTEX) did not occur on the bare AS. In contrast, the photocatalytic degradation efficiencies of the target pollutants using S-TiO2-AS were higher than those obtained using reference TiO2-AS photocatalyst. In particular, the average photocatalytic degradation efficiencies of BTEX using S-TiO2-0.8-AS (S/Ti ratio=0.8) over a 3-h process were 34%, 78%, 91%, and 94%, respectively, whereas those of TiO2-AS were 2%, 11%, 21%, and 36%, respectively. The photocatalytic decomposition efficiencies of BTEX under visible irradiation using S-TiO2-AS increased with increasing S/Ti ratios from 0.2 to 0.8, but decreased when the ratio further increased to 1.6. Thus, S-TiO2-AS can be prepared using optimal S/Ti ratios. The degradation of BTEX over S-TiO2-AS depended on the air flow rates and initial concentrations of the target chemical. Overall, under optimal conditions, S-TiO2-AS can be effectively applied for the purification of toxic organic vapors.
2014, 35(7): 1196-1205
doi: 10.1016/S1872-2067(14)60084-X
Abstract:
We prepared perovskite-type oxides La1-xSrxFeO3 (x =0, 0.3, 0.5, 0.9) by a combustion method and used these as oxygen carriers for the partial oxidation of methane. X-ray diffration, scanning electron microscopy and H2 temperature-programmed reduction techniques were used to characterize the samples. Their reduction and oxidation activities were investigated using a thermogravimetric analysis reactor and fixed-bed reaction equipment, respectively. The results showed that the lattice oxygen in La1-xSrxFeO3 was suitable for the partial oxidation of methane to produce syngas. Their capacity to provide oxygen was enhanced by the partial substitution of La3+ by Sr2+ and the synthesized materials have good regenerability. The optimal degree of Sr substitution was found to be x=0.3-0.5 for La1-xSrxFeO3 with regard to reactivity, selectivity, and oxygen-donating ability. CH4 conversion was higher than 70%, and the n(H2)/n(CO) ratio remained about 2:1 and no obvious decomposition of CH4 occurred.
We prepared perovskite-type oxides La1-xSrxFeO3 (x =0, 0.3, 0.5, 0.9) by a combustion method and used these as oxygen carriers for the partial oxidation of methane. X-ray diffration, scanning electron microscopy and H2 temperature-programmed reduction techniques were used to characterize the samples. Their reduction and oxidation activities were investigated using a thermogravimetric analysis reactor and fixed-bed reaction equipment, respectively. The results showed that the lattice oxygen in La1-xSrxFeO3 was suitable for the partial oxidation of methane to produce syngas. Their capacity to provide oxygen was enhanced by the partial substitution of La3+ by Sr2+ and the synthesized materials have good regenerability. The optimal degree of Sr substitution was found to be x=0.3-0.5 for La1-xSrxFeO3 with regard to reactivity, selectivity, and oxygen-donating ability. CH4 conversion was higher than 70%, and the n(H2)/n(CO) ratio remained about 2:1 and no obvious decomposition of CH4 occurred.
2014, 35(7): 1206-1211
doi: 10.1016/S1872-2067(14)60090-5
Abstract:
In(OTf)3 plays the role of a Lewis acid catalyst in the Pechmann condensation of phenols with β-ketoesters under solvent-free conditions to give coumarin derivatives. This novel and inexpensive method has advantages such as short reaction time, excellent product yields, and avoids the use of organic solvents in agreement with green chemistry principles. Catalyst loadings can be as low as 1 mol% to give high yields of the corresponding coumarins at 80℃. The catalyst can be recovered after the reaction, and reused with only a slight decrease in the yield.
In(OTf)3 plays the role of a Lewis acid catalyst in the Pechmann condensation of phenols with β-ketoesters under solvent-free conditions to give coumarin derivatives. This novel and inexpensive method has advantages such as short reaction time, excellent product yields, and avoids the use of organic solvents in agreement with green chemistry principles. Catalyst loadings can be as low as 1 mol% to give high yields of the corresponding coumarins at 80℃. The catalyst can be recovered after the reaction, and reused with only a slight decrease in the yield.
2014, 35(7): 1212-1223
doi: 10.1016/S1872-2067(14)60091-7
Abstract:
M/Al2O3-CeO2 (M=Pt-Ru, Ru, and Pt) catalysts were prepared using an impregnation method. Their catalytic performance in catalytic wet air oxidation (CWAO) of methylamine was compared. The catalysts were characterized using temperature-programmed reduction, X-ray photoelectron spectroscopy, X-ray diffraction, transmission electron microscopy, N2 adsorption, and CO chemisorption. The experimental results indicated that the dispersion of active species in the Pt-Ru/Al2O3-CeO2 catalyst was greatly improved by the introduction of Pt; therefore, its catalytic performance was significantly enhanced. Temperature-dependent activity showed hysteresis over the catalysts, indicating that CWAO of methylamine followed a chemisorption mechanism.
M/Al2O3-CeO2 (M=Pt-Ru, Ru, and Pt) catalysts were prepared using an impregnation method. Their catalytic performance in catalytic wet air oxidation (CWAO) of methylamine was compared. The catalysts were characterized using temperature-programmed reduction, X-ray photoelectron spectroscopy, X-ray diffraction, transmission electron microscopy, N2 adsorption, and CO chemisorption. The experimental results indicated that the dispersion of active species in the Pt-Ru/Al2O3-CeO2 catalyst was greatly improved by the introduction of Pt; therefore, its catalytic performance was significantly enhanced. Temperature-dependent activity showed hysteresis over the catalysts, indicating that CWAO of methylamine followed a chemisorption mechanism.
2014, 35(7): 1224-1234
doi: 10.1016/S1872-2067(14)60097-8
Abstract:
Several triethylamine (TEA) salts of phosphotungstic acid were synthesized by an acid-base reaction using a Keggin-type phosphotungstic acid and TEA, and used to catalyze the oxidation of benzyl alcohol to benzaldehyde in water with 30% aqueous hydrogen peroxide as oxidant. (TEAH)nH3-nPW12O40 (n=1, 2, 3) were excellent catalysts for the reaction and could be isolated and recycled. With (TEAH)H2PW12O40, the conversion of benzyl alcohol and selectivity to benzaldehyde were as high as 99.6% and 100%, respectively, under optimized reaction conditions. The catalysts and their transformation and distribution during the reaction were investigated by IR, 31P NMR and analysis of the reaction system, and the reaction mechanism was deduced. In this water-oil biphasic reaction, (PW12O40)3- was first oxidized and degraded into small (PO4(WO(O2)2)4)3- and free tungsten species that were soluble in the aqueous phase upon reaction with H2O2. Then (PO4(WO(O2)2)4)3-, as the actual oxidant, oxidized benzyl alcohol soluble in the aqueous phase to benzaldehyde, and was converted into a SAR (species after reaction) after losing its active oxygen. The catalytic cycle was completed by the polymerization of the SAR with the free tungsten species back to larger catalyst precursor (PW12O40)3-, which was soluble in the oil phase.
Several triethylamine (TEA) salts of phosphotungstic acid were synthesized by an acid-base reaction using a Keggin-type phosphotungstic acid and TEA, and used to catalyze the oxidation of benzyl alcohol to benzaldehyde in water with 30% aqueous hydrogen peroxide as oxidant. (TEAH)nH3-nPW12O40 (n=1, 2, 3) were excellent catalysts for the reaction and could be isolated and recycled. With (TEAH)H2PW12O40, the conversion of benzyl alcohol and selectivity to benzaldehyde were as high as 99.6% and 100%, respectively, under optimized reaction conditions. The catalysts and their transformation and distribution during the reaction were investigated by IR, 31P NMR and analysis of the reaction system, and the reaction mechanism was deduced. In this water-oil biphasic reaction, (PW12O40)3- was first oxidized and degraded into small (PO4(WO(O2)2)4)3- and free tungsten species that were soluble in the aqueous phase upon reaction with H2O2. Then (PO4(WO(O2)2)4)3-, as the actual oxidant, oxidized benzyl alcohol soluble in the aqueous phase to benzaldehyde, and was converted into a SAR (species after reaction) after losing its active oxygen. The catalytic cycle was completed by the polymerization of the SAR with the free tungsten species back to larger catalyst precursor (PW12O40)3-, which was soluble in the oil phase.
