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2017 Volume 38 Issue 11
2017, 38(11):
Abstract:
2017, 38(11): 1781-1783
doi: 10.1016/S1872-2067(17)62966-8
Abstract:
2017, 38(11): 1784-1793
doi: 10.1016/S1872-2067(17)62908-5
Abstract:
2017, 38(11): 1794-1803
doi: 10.1016/S1872-2067(17)62905-X
Abstract:
Heterogeneous semiconductor photocatalysis is a promising green technology solution to energy and environmental problems. Traditional photocatalyst TiO2, with a wide band gap of 3.2 eV, can only be excited by UV light and utilizes less than 4% of solar energy. Silver phosphate (Ag3PO4) is among the most active visible-light-driven photocatalysts reported. Unfortunately, unwanted pho-tocorrosion is the main obstacle to the practical application of Ag3PO4. Much effort has been made in recent years to address this issue and further enhance the photocatalytic performance of Ag3PO4. The construction of Z-scheme photocatalytic systems that mimic natural photosynthesis is a prom-ising strategy to improve the photocatalytic activity and stability of Ag3PO4. This brief review con-cisely summarizes and highlights recent research progress in Ag3PO4-based all-solid-state Z-scheme photocatalytic systems with or without a solid-state electron mediator, focusing on their construc-tion, application, and reaction mechanism. Furthermore, the challenges and future prospects of Ag3PO4-based Z-scheme photocatalytic systems are discussed.
Heterogeneous semiconductor photocatalysis is a promising green technology solution to energy and environmental problems. Traditional photocatalyst TiO2, with a wide band gap of 3.2 eV, can only be excited by UV light and utilizes less than 4% of solar energy. Silver phosphate (Ag3PO4) is among the most active visible-light-driven photocatalysts reported. Unfortunately, unwanted pho-tocorrosion is the main obstacle to the practical application of Ag3PO4. Much effort has been made in recent years to address this issue and further enhance the photocatalytic performance of Ag3PO4. The construction of Z-scheme photocatalytic systems that mimic natural photosynthesis is a prom-ising strategy to improve the photocatalytic activity and stability of Ag3PO4. This brief review con-cisely summarizes and highlights recent research progress in Ag3PO4-based all-solid-state Z-scheme photocatalytic systems with or without a solid-state electron mediator, focusing on their construc-tion, application, and reaction mechanism. Furthermore, the challenges and future prospects of Ag3PO4-based Z-scheme photocatalytic systems are discussed.
2017, 38(11): 1804-1811
doi: 10.1016/S1872-2067(17)62912-7
Abstract:
The photocatalytic reduction of aqueous Cr(VI) to Cr(Ⅲ) was preliminarily studied using porous g-C3N4 as a photocatalyst under acidic conditions. The observed synergistic photocatalytic effect of porous g-C3N4 on a Cr(VI)/4-chlorophenol (4-CP) composite pollution system was further studied under different pH conditions. Compared with single-component photocatalytic systems for Cr(VI) reduction or 4-CP degradation, the Cr(VI) reduction efficiency and 4-CP degradation efficiency were simultaneously improved in the Cr(VI)/4-CP composite pollution system. The synergistic photo-catalytic effect in the Cr(VI)/4-CP composite pollution system can be attributed to the accelerated redox reaction between dichromate and 4-CP by electron transfer with porous g-C3N4.
The photocatalytic reduction of aqueous Cr(VI) to Cr(Ⅲ) was preliminarily studied using porous g-C3N4 as a photocatalyst under acidic conditions. The observed synergistic photocatalytic effect of porous g-C3N4 on a Cr(VI)/4-chlorophenol (4-CP) composite pollution system was further studied under different pH conditions. Compared with single-component photocatalytic systems for Cr(VI) reduction or 4-CP degradation, the Cr(VI) reduction efficiency and 4-CP degradation efficiency were simultaneously improved in the Cr(VI)/4-CP composite pollution system. The synergistic photo-catalytic effect in the Cr(VI)/4-CP composite pollution system can be attributed to the accelerated redox reaction between dichromate and 4-CP by electron transfer with porous g-C3N4.
2017, 38(11): 1812-1817
doi: 10.1016/S1872-2067(17)62921-8
Abstract:
In this study, we fabricated a NiOx film by electrodeposition of an ethanediamine nickel complex precursor (pH=11) on a fluorine-doped tin oxide substrate. The resulting film is robust and exhib-its high catalytic activity for electrochemical water oxidation. Water oxidation is initiated with an overpotential of 375 mV (1 mA/cm2) and a steady current density of 8.5 mA/cm2 is maintained for at least 10 h at 1.3 V versus the normal hydrogen electrode. Kinetic analysis reveals that there is a 2e-/3H+ pre-equilibrium process before the chemical rate-determining step. The low-cost preparation, robustness, and longevity make this catalyst competitive for applications in solar energy conversion and storage.
In this study, we fabricated a NiOx film by electrodeposition of an ethanediamine nickel complex precursor (pH=11) on a fluorine-doped tin oxide substrate. The resulting film is robust and exhib-its high catalytic activity for electrochemical water oxidation. Water oxidation is initiated with an overpotential of 375 mV (1 mA/cm2) and a steady current density of 8.5 mA/cm2 is maintained for at least 10 h at 1.3 V versus the normal hydrogen electrode. Kinetic analysis reveals that there is a 2e-/3H+ pre-equilibrium process before the chemical rate-determining step. The low-cost preparation, robustness, and longevity make this catalyst competitive for applications in solar energy conversion and storage.
2017, 38(11): 1818-1830
doi: 10.1016/S1872-2067(17)62910-3
Abstract:
SiO2-supported monometallic Ni and bimetallic Ni-In catalysts were prepared and used for hydro-deoxygenation of anisole, which was used as a model bio-oil compound, for BTX (benzene, toluene, and xylene) production. The effects of the Ni/In ratio and Ni content on the structures and perfor-mances of the catalysts were investigated. The results show that In atoms were incorporated into the Ni metal lattice. Although the Ni-In bimetallic crystallites were similar in size to those of mono-metallic Ni at the same Ni content, H2 uptake by the bimetallic Ni-In catalyst was much lower than that by monometallic Ni because of dilution of Ni atoms by In atoms. Charge transfer from In to Ni was observed for the bimetallic Ni-In catalysts. All the results indicate intimate contact between Ni and In atoms, and the In atoms geometrically and electronically modified the Ni atoms. In the hy-drodeoxygenation of anisole, although the activities of the Ni-In bimetallic catalysts in the conver-sion of anisole were lower than that of the monometallic Ni catalyst, they gave higher selectivities for BTX and cyclohexane as a result of suppression of benzene ring hydrogenation and C-C bond hydrogenolysis. They also showed lower methanation activity. These results will be useful for en-hancing carbon yields and reducing H2 consumption. In addition, the lower the Ni/In ratio was, the greater was the effect of In on the catalytic performance. The selectivity for BTX was primarily de-termined by the Ni/In ratio and was little affected by the Ni content. We suggest that the perfor-mance of the Ni-In bimetallic catalyst can be ascribed to the geometric and electronic effects of In.
SiO2-supported monometallic Ni and bimetallic Ni-In catalysts were prepared and used for hydro-deoxygenation of anisole, which was used as a model bio-oil compound, for BTX (benzene, toluene, and xylene) production. The effects of the Ni/In ratio and Ni content on the structures and perfor-mances of the catalysts were investigated. The results show that In atoms were incorporated into the Ni metal lattice. Although the Ni-In bimetallic crystallites were similar in size to those of mono-metallic Ni at the same Ni content, H2 uptake by the bimetallic Ni-In catalyst was much lower than that by monometallic Ni because of dilution of Ni atoms by In atoms. Charge transfer from In to Ni was observed for the bimetallic Ni-In catalysts. All the results indicate intimate contact between Ni and In atoms, and the In atoms geometrically and electronically modified the Ni atoms. In the hy-drodeoxygenation of anisole, although the activities of the Ni-In bimetallic catalysts in the conver-sion of anisole were lower than that of the monometallic Ni catalyst, they gave higher selectivities for BTX and cyclohexane as a result of suppression of benzene ring hydrogenation and C-C bond hydrogenolysis. They also showed lower methanation activity. These results will be useful for en-hancing carbon yields and reducing H2 consumption. In addition, the lower the Ni/In ratio was, the greater was the effect of In on the catalytic performance. The selectivity for BTX was primarily de-termined by the Ni/In ratio and was little affected by the Ni content. We suggest that the perfor-mance of the Ni-In bimetallic catalyst can be ascribed to the geometric and electronic effects of In.
2017, 38(11): 1831-1841
doi: 10.1016/S1872-2067(17)62897-3
Abstract:
An Fe/TiO2 catalyst with uniform mesopores was synthesized using Pluronic F127 as a struc-ture-directing agent. This catalyst was used for selective catalytic reduction of NO with NH3. The catalytic activity and resistance to H2O and SO2 of Fe/TiO2 prepared by a template method were better than those of catalysts synthesized using impregnation and coprecipitation. The samples were characterized using N2-physisorption, transmission electron microscopy, ultraviolet-visible spectroscopy, X-ray photoelectron spectroscopy, and in situ diffuse reflectance infrared Fouri-er-transform spectroscopy. The results showed that Pluronic F127 acted as a structural and chemi-cal promoter; it not only promoted the formation of a uniform mesoporous structure, leading to a higher surface area, but also improved dispersion of the active phase. In addition, the larger number of Lewis acidic sites, indicated by the presence of coordinated NH3 species (1188 cm-1) and the N-H stretching modes of coordinated NH3 (3242 and 3388 cm-1), were beneficial to mid-temperature selective catalytic reduction reactions.
An Fe/TiO2 catalyst with uniform mesopores was synthesized using Pluronic F127 as a struc-ture-directing agent. This catalyst was used for selective catalytic reduction of NO with NH3. The catalytic activity and resistance to H2O and SO2 of Fe/TiO2 prepared by a template method were better than those of catalysts synthesized using impregnation and coprecipitation. The samples were characterized using N2-physisorption, transmission electron microscopy, ultraviolet-visible spectroscopy, X-ray photoelectron spectroscopy, and in situ diffuse reflectance infrared Fouri-er-transform spectroscopy. The results showed that Pluronic F127 acted as a structural and chemi-cal promoter; it not only promoted the formation of a uniform mesoporous structure, leading to a higher surface area, but also improved dispersion of the active phase. In addition, the larger number of Lewis acidic sites, indicated by the presence of coordinated NH3 species (1188 cm-1) and the N-H stretching modes of coordinated NH3 (3242 and 3388 cm-1), were beneficial to mid-temperature selective catalytic reduction reactions.
2017, 38(11): 1842-1850
doi: 10.1016/S1872-2067(17)62914-0
Abstract:
CuCl/Phen can catalyze the C-N coupling between arylboronic acid and benzofurazan 1-oxide. This reaction occurred under mild and redox-neutral conditions with benzofurazan 1-oxide as an ami-nating reagent via ring scission, leading to a bifunctionalized aminonitrobenzene.
CuCl/Phen can catalyze the C-N coupling between arylboronic acid and benzofurazan 1-oxide. This reaction occurred under mild and redox-neutral conditions with benzofurazan 1-oxide as an ami-nating reagent via ring scission, leading to a bifunctionalized aminonitrobenzene.
2017, 38(11): 1851-1859
doi: 10.1016/S1872-2067(17)62929-2
Abstract:
We report a colloidal process to coat a layer of TiO2 onto SiO2 composite nanofibers containing em-bedded CdS and upconversion nanoparticles (UCNPs). The SiO2 composite nanofibers were fabri-cated by electrospinning. To improve the energy transfer efficiency, UCNPs and CdS nanoparticles were bound in close proximity to each other within the SiO2 matrix. β-NaYF4:Yb(30%),Tm(0.5%)@NaYF4:Yb(20%),Er(2%) core-shell nanoparticles were used as na-notransducers for near infrared light. These nanoparticles exhibited enhanced upconversion fluo-rescence compared with β-NaYF4:Yb(30%),Tm(0.5%) or β-NaYF4:Yb(30%),Tm(0.5%)@NaYF4 nanoparticles. The morphologies, size and chemical compositions have been extensively investi-gated using field emission scanning electron microscopy (FESEM), transmission electron microsco-py (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectra (XPS), respectively. The TEM images showed that the TiO2 composite nanotubes were embedded with a large amount of UCNPs and CdS nanoparticles. The composite TiO2 nanotubes degraded more than 90% of rhodamine B (RhB) dye during 20 min of irradiation by simulated solar light. In particular, more than 50% of RhB was decomposed in 70 min, under irradiation of near infrared light (NIR). This high degradation was attributed to the full spectrum absorption of solar light, and the enhanced transfer efficiency for near infrared light. The as-prepared nanostructures can harness solar energy, and provide an alter-native to overcome energy shortages and environmental protection.
We report a colloidal process to coat a layer of TiO2 onto SiO2 composite nanofibers containing em-bedded CdS and upconversion nanoparticles (UCNPs). The SiO2 composite nanofibers were fabri-cated by electrospinning. To improve the energy transfer efficiency, UCNPs and CdS nanoparticles were bound in close proximity to each other within the SiO2 matrix. β-NaYF4:Yb(30%),Tm(0.5%)@NaYF4:Yb(20%),Er(2%) core-shell nanoparticles were used as na-notransducers for near infrared light. These nanoparticles exhibited enhanced upconversion fluo-rescence compared with β-NaYF4:Yb(30%),Tm(0.5%) or β-NaYF4:Yb(30%),Tm(0.5%)@NaYF4 nanoparticles. The morphologies, size and chemical compositions have been extensively investi-gated using field emission scanning electron microscopy (FESEM), transmission electron microsco-py (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectra (XPS), respectively. The TEM images showed that the TiO2 composite nanotubes were embedded with a large amount of UCNPs and CdS nanoparticles. The composite TiO2 nanotubes degraded more than 90% of rhodamine B (RhB) dye during 20 min of irradiation by simulated solar light. In particular, more than 50% of RhB was decomposed in 70 min, under irradiation of near infrared light (NIR). This high degradation was attributed to the full spectrum absorption of solar light, and the enhanced transfer efficiency for near infrared light. The as-prepared nanostructures can harness solar energy, and provide an alter-native to overcome energy shortages and environmental protection.
2017, 38(11): 1860-1869
doi: 10.1016/S1872-2067(17)62898-5
Abstract:
Composite solid base catalysts derived from Ca-M-Al (M=Mg, La, Ce, Y) layered double hydroxides (LDH) were synthesized, characterized and applied to the transesterification of methanol with pro-pylene carbonate. X-ray diffraction analyses of the catalysts show that all of the catalysts were in the form of composite oxides. Compared with the Ca-Al LDH catalyst, the specific surface areas and pore volumes of the catalysts were increased with the introduction of Mg, La or Ce. The catalytic perfor-mance of these catalysts increases in the order of Ca-Y-Al < Ca-Al < Ca-Ce-Al < Ca-La-Al < Ca-Mg-Al, which is consistent with the total surface basic amounts of these materials and the formation of especially strong basic sites following modification with Mg and La. The Ca-Mg-Al catalyst shows the highest (Ca+Mg):Al atomic ratio, indicating that it likely contains more unsaturated O2- ions, providing it with the highest concentration of very strong basic sites. The recyclability of these cat-alysts is improved following the addition of Mg, La, Ce or Y, with the Ca-Mg-Al maintaining a high level of activity after ten recycling trials. X-ray diffraction analyses of fresh and used Ca-Mg-Al demonstrate that this catalyst is exceptionally stable, which could be of value in practical applica-tions related to heterogeneous catalysis.
Composite solid base catalysts derived from Ca-M-Al (M=Mg, La, Ce, Y) layered double hydroxides (LDH) were synthesized, characterized and applied to the transesterification of methanol with pro-pylene carbonate. X-ray diffraction analyses of the catalysts show that all of the catalysts were in the form of composite oxides. Compared with the Ca-Al LDH catalyst, the specific surface areas and pore volumes of the catalysts were increased with the introduction of Mg, La or Ce. The catalytic perfor-mance of these catalysts increases in the order of Ca-Y-Al < Ca-Al < Ca-Ce-Al < Ca-La-Al < Ca-Mg-Al, which is consistent with the total surface basic amounts of these materials and the formation of especially strong basic sites following modification with Mg and La. The Ca-Mg-Al catalyst shows the highest (Ca+Mg):Al atomic ratio, indicating that it likely contains more unsaturated O2- ions, providing it with the highest concentration of very strong basic sites. The recyclability of these cat-alysts is improved following the addition of Mg, La, Ce or Y, with the Ca-Mg-Al maintaining a high level of activity after ten recycling trials. X-ray diffraction analyses of fresh and used Ca-Mg-Al demonstrate that this catalyst is exceptionally stable, which could be of value in practical applica-tions related to heterogeneous catalysis.
2017, 38(11): 1870-1879
doi: 10.1016/S1872-2067(17)62904-8
Abstract:
The solvent-free oxidation of benzyl alcohol was studied using supported Pd-Ni bimetallic nanopar-ticles. Compared with monometallic Pd, the addition of Ni to Pd was found to be effective in sup-pressing the nondesired product toluene, thereby enhancing the selectivity towards benzaldehyde. This result was attributed to a dual effect of Ni addition:the weakening of dissociative adsorption of benzyl alcohol and the promotion of oxygen species involved in the oxidation pathway.
The solvent-free oxidation of benzyl alcohol was studied using supported Pd-Ni bimetallic nanopar-ticles. Compared with monometallic Pd, the addition of Ni to Pd was found to be effective in sup-pressing the nondesired product toluene, thereby enhancing the selectivity towards benzaldehyde. This result was attributed to a dual effect of Ni addition:the weakening of dissociative adsorption of benzyl alcohol and the promotion of oxygen species involved in the oxidation pathway.
2017, 38(11): 1880-1887
doi: 10.1016/S1872-2067(17)62906-1
Abstract:
The synthesis of ferrierite (FER) zeolite using piperidine as an organic structure-directing agent was investigated. X-ray diffraction, X-ray fluorescence, N2-adsorption, and scanning electron microscopy were used to characterize the crystal phases, textural properties, and particle morphologies of the zeolite samples. The crystallization behavior of the FER zeolite was found to be directly related to crystallization temperature. At 150 ℃, pure FER phase was observed throughout crystallization. At 160-170 ℃, MWW phase appeared first and gradually transformed into FER phase over time, indi-cating that the FER phase was thermodynamically favored. In the piperidine-Na2O-H2O synthetic system, alkalinity proved to be the crucial factor determining the size and textural properties of FER zeolite. Furthermore, the obtained FER samples exhibited good catalytic performance in the skeletal isomerization of 1-butene.
The synthesis of ferrierite (FER) zeolite using piperidine as an organic structure-directing agent was investigated. X-ray diffraction, X-ray fluorescence, N2-adsorption, and scanning electron microscopy were used to characterize the crystal phases, textural properties, and particle morphologies of the zeolite samples. The crystallization behavior of the FER zeolite was found to be directly related to crystallization temperature. At 150 ℃, pure FER phase was observed throughout crystallization. At 160-170 ℃, MWW phase appeared first and gradually transformed into FER phase over time, indi-cating that the FER phase was thermodynamically favored. In the piperidine-Na2O-H2O synthetic system, alkalinity proved to be the crucial factor determining the size and textural properties of FER zeolite. Furthermore, the obtained FER samples exhibited good catalytic performance in the skeletal isomerization of 1-butene.
2017, 38(11): 1888-1898
doi: 10.1016/S1872-2067(17)62909-7
Abstract:
Gold clusters and small nanoparticles supported on metal oxides could be prepared by deposi-tion-precipitation followed by microwave irradiation as a drying method and then calcination. The drying method influenced the size of the Au particles. Au(Ⅲ) was partly reduced during conven-tional oven drying, resulting in Au aggregates. In contrast, Au(Ⅲ) was preserved during microwave drying owing to rapid and uniform heating, and the Au diameter was minimized to 1.4 nm on Al2O3. This method can be applied to several metal oxide supports having different microwave absorption efficiencies, such as MnO2, Al2O3, and TiO2. These catalysts exhibited higher catalytic activities for CO oxidation at low temperature and for selective aerobic oxidation of sulfide than those prepared by conventional methods.
Gold clusters and small nanoparticles supported on metal oxides could be prepared by deposi-tion-precipitation followed by microwave irradiation as a drying method and then calcination. The drying method influenced the size of the Au particles. Au(Ⅲ) was partly reduced during conven-tional oven drying, resulting in Au aggregates. In contrast, Au(Ⅲ) was preserved during microwave drying owing to rapid and uniform heating, and the Au diameter was minimized to 1.4 nm on Al2O3. This method can be applied to several metal oxide supports having different microwave absorption efficiencies, such as MnO2, Al2O3, and TiO2. These catalysts exhibited higher catalytic activities for CO oxidation at low temperature and for selective aerobic oxidation of sulfide than those prepared by conventional methods.
2017, 38(11): 1899-1908
doi: 10.1016/S1872-2067(17)62924-3
Abstract:
CaMg(CO3)2 microspheres were prepared and used as hard templates to fabricate a series of CaMg(CO3)2@Ag2CO3 composite microspheres via a fast and low-cost ion exchange process. The effects of ion exchange time and temperature on the physicochemical properties and photocatalytic activities of the composite microspheres were studied through photocatalytic degradation of Acid Orange Ⅱ under xenon lamp irradiation. The obtained samples were analyzed by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, UV-vis diffuse reflectance spectroscopy, N2 physical adsorption, and photocurrent tests. The CaMg(CO3)2@Ag2CO3 sample with the highest activity was obtained with an ion exchange time of 4 h and temperature of 40℃. The degradation rate of Acid Orange Ⅱ by this sample reached 83.3% after 15 min of light irradiation, and the sample also performed well in phenol degradation. The CaMg(CO3)2@Ag2CO3 produced under these ion exchange conditions showed a well-ordered hierarchical morphology with small particle sizes, which was beneficial to light absorption and the transfer of photoelectrons (e-) and holes (h+) to the catalyst surface. Moreover, the separation of photogenerated carriers over the composites was greatly improved relative to bare CaMg(CO3)2. Despite the very low content of Ag2CO3 (2.56%), excellent photocatalytic performance was obtained over the CaMg(CO3)2@Ag2CO3 microspheres.
CaMg(CO3)2 microspheres were prepared and used as hard templates to fabricate a series of CaMg(CO3)2@Ag2CO3 composite microspheres via a fast and low-cost ion exchange process. The effects of ion exchange time and temperature on the physicochemical properties and photocatalytic activities of the composite microspheres were studied through photocatalytic degradation of Acid Orange Ⅱ under xenon lamp irradiation. The obtained samples were analyzed by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, UV-vis diffuse reflectance spectroscopy, N2 physical adsorption, and photocurrent tests. The CaMg(CO3)2@Ag2CO3 sample with the highest activity was obtained with an ion exchange time of 4 h and temperature of 40℃. The degradation rate of Acid Orange Ⅱ by this sample reached 83.3% after 15 min of light irradiation, and the sample also performed well in phenol degradation. The CaMg(CO3)2@Ag2CO3 produced under these ion exchange conditions showed a well-ordered hierarchical morphology with small particle sizes, which was beneficial to light absorption and the transfer of photoelectrons (e-) and holes (h+) to the catalyst surface. Moreover, the separation of photogenerated carriers over the composites was greatly improved relative to bare CaMg(CO3)2. Despite the very low content of Ag2CO3 (2.56%), excellent photocatalytic performance was obtained over the CaMg(CO3)2@Ag2CO3 microspheres.
2017, 38(11): 1909-1917
doi: 10.1016/S1872-2067(17)62917-6
Abstract:
Iron catalysis has attracted a wealth of interdependent research for its abundance, low price, and nontoxicity. Herein, a convenient and stable iron oxide (Fe2O3)-based catalyst, in which active Fe2O3 nanoparticles (NPs) were embedded into carbon films, was prepared via the pyrolysis of iron-polyaniline complexes on carbon particles. The obtained catalyst shows a large surface area, uniform pore channel distribution, with the Fe2O3 NPs homogeneously dispersed across the hybrid material. Scanning electron microscopy, Raman spectroscopy and X-ray diffraction analyses of the catalyst prepared at 900℃ (Fe2O3@G-C-900) and an acid-pretreated commercial activated carbon confirmed that additional carbon materials formed on the pristine carbon particles. Observation of high-resolution transmission electron microscopy images also revealed that the Fe2O3 NPs in the hybrid were encapsulated by a thin carbon film. The Fe2O3@G-C-900 composite was highly active and stable for the direct selective hydrogenation of nitroarenes to anilines under mild conditions, where previously noble metals were required. The synthetic strategy and the structure of the iron oxide-based composite may lead to the advancement of cost-effective and sustainable industrial processes.
Iron catalysis has attracted a wealth of interdependent research for its abundance, low price, and nontoxicity. Herein, a convenient and stable iron oxide (Fe2O3)-based catalyst, in which active Fe2O3 nanoparticles (NPs) were embedded into carbon films, was prepared via the pyrolysis of iron-polyaniline complexes on carbon particles. The obtained catalyst shows a large surface area, uniform pore channel distribution, with the Fe2O3 NPs homogeneously dispersed across the hybrid material. Scanning electron microscopy, Raman spectroscopy and X-ray diffraction analyses of the catalyst prepared at 900℃ (Fe2O3@G-C-900) and an acid-pretreated commercial activated carbon confirmed that additional carbon materials formed on the pristine carbon particles. Observation of high-resolution transmission electron microscopy images also revealed that the Fe2O3 NPs in the hybrid were encapsulated by a thin carbon film. The Fe2O3@G-C-900 composite was highly active and stable for the direct selective hydrogenation of nitroarenes to anilines under mild conditions, where previously noble metals were required. The synthetic strategy and the structure of the iron oxide-based composite may lead to the advancement of cost-effective and sustainable industrial processes.
2017, 38(11): 1918-1924
doi: 10.1016/S1872-2067(17)62920-6
Abstract:
Recyclable CuO nanoparticles were successfully employed to catalyze the microwave-assisted (3+2) cycloaddition reaction between nitriles and NaN3 to efficiently synthesize 5-substituted 1H-tetrazoles. The salient features associated with this protocol are its cost effectiveness, rapid synthesis, stability, reusability, mild reaction conditions without any additives, high tolerance to various func-tional groups, and excellent yields under microwave irradiation. This environmentally friendly, microwave-assisted, nanoparticle-catalyzed synthetic methodology is seen as an alternative to conventional procedures that involve Lewis acid catalysts and a simple operation to the privileged scaffold.
Recyclable CuO nanoparticles were successfully employed to catalyze the microwave-assisted (3+2) cycloaddition reaction between nitriles and NaN3 to efficiently synthesize 5-substituted 1H-tetrazoles. The salient features associated with this protocol are its cost effectiveness, rapid synthesis, stability, reusability, mild reaction conditions without any additives, high tolerance to various func-tional groups, and excellent yields under microwave irradiation. This environmentally friendly, microwave-assisted, nanoparticle-catalyzed synthetic methodology is seen as an alternative to conventional procedures that involve Lewis acid catalysts and a simple operation to the privileged scaffold.
2017, 38(11): 1925-1934
doi: 10.1016/S1872-2067(17)62922-X
Abstract:
α-, β-, δ-, and γ-MnO2 nanocrystals are successfully prepared. We then evaluated the NH3 selective catalytic reduction (SCR) performance of the MnO2 catalysts with different phases. The NOx conversion efficiency decreased in the order:γ-MnO2 > α-MnO2 > δ-MnO2 > β-MnO2. The NOx conversion with the use of γ-MnO2 and α-MnO2 catalysts reached 90% in the temperature range of 140-200℃, while that based on β-MnO2 reached only 40% at 200℃. The γ-MnO2 and α-MnO2 nanowire crystal morphologies enabled good dispersion of the catalysts and resulted in a relatively high specific surface area. We found that γ-MnO2 and α-MnO2 possessed stronger reducing abilities and more and stronger acidic sites than the other catalysts. In addition, more chemisorbed oxygen existed on the surface of the γ-MnO2 and α-MnO2 catalysts. The γ-MnO2 and α-MnO2 catalysts showed excellent performance in the low-temperature SCR of NO to N2 with NH3.
α-, β-, δ-, and γ-MnO2 nanocrystals are successfully prepared. We then evaluated the NH3 selective catalytic reduction (SCR) performance of the MnO2 catalysts with different phases. The NOx conversion efficiency decreased in the order:γ-MnO2 > α-MnO2 > δ-MnO2 > β-MnO2. The NOx conversion with the use of γ-MnO2 and α-MnO2 catalysts reached 90% in the temperature range of 140-200℃, while that based on β-MnO2 reached only 40% at 200℃. The γ-MnO2 and α-MnO2 nanowire crystal morphologies enabled good dispersion of the catalysts and resulted in a relatively high specific surface area. We found that γ-MnO2 and α-MnO2 possessed stronger reducing abilities and more and stronger acidic sites than the other catalysts. In addition, more chemisorbed oxygen existed on the surface of the γ-MnO2 and α-MnO2 catalysts. The γ-MnO2 and α-MnO2 catalysts showed excellent performance in the low-temperature SCR of NO to N2 with NH3.
