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2015 Volume 36 Issue 7
2015, 36(7):
Abstract:
2015, 36(7): 915-924
doi: 10.1016/S1872-2067(14)60303-X
Abstract:
The dry reforming of coke oven gas (COG) to produce syngas was performed over La0.6Sr0.4NixCo1-xO3 catalysts in a fixed-bed reactor at 800 ℃. These perovskite-type oxides were synthesized using a sol-gel method and characterized using X-ray diffraction (XRD), N2 adsorption-desorption, temperature-programmed reduction of H2, scanning electron microscopy, transmission electron microscopy, and thermogravimetry-differential scanning calorimetry. XRD results showed that the La0.6Sr0.4NixCo1-xO3 perovskite-type oxides formed quaternary solid solutions. The effects of the degree of Ni substitution (x) and the catalyst calcination temperature on the dry reforming of COG were investigated. XRD analysis of the tested catalysts showed the formation of Ni0, Co0, and La2O2CO3, of which the latter is the main active phase responsible for the high activity and stability, and the suppression of coke formation under severe reaction conditions. COG rich in H2 can also reduce the formation of carbon deposits by inhibiting CH4 decomposition.
The dry reforming of coke oven gas (COG) to produce syngas was performed over La0.6Sr0.4NixCo1-xO3 catalysts in a fixed-bed reactor at 800 ℃. These perovskite-type oxides were synthesized using a sol-gel method and characterized using X-ray diffraction (XRD), N2 adsorption-desorption, temperature-programmed reduction of H2, scanning electron microscopy, transmission electron microscopy, and thermogravimetry-differential scanning calorimetry. XRD results showed that the La0.6Sr0.4NixCo1-xO3 perovskite-type oxides formed quaternary solid solutions. The effects of the degree of Ni substitution (x) and the catalyst calcination temperature on the dry reforming of COG were investigated. XRD analysis of the tested catalysts showed the formation of Ni0, Co0, and La2O2CO3, of which the latter is the main active phase responsible for the high activity and stability, and the suppression of coke formation under severe reaction conditions. COG rich in H2 can also reduce the formation of carbon deposits by inhibiting CH4 decomposition.
2015, 36(7): 925-932
doi: 10.1016/S1872-2067(15)60866-X
Abstract:
Rh-catalyzed redox-neutral coupling between N-aryl nitrones and alkynes has been achieved under relatively mild conditions. The reaction proceeded via C-H activation at the N-aryl ring with subsequent O-atom transfer, affording trisubstituted indolines in good chemoselectivity and moderate to good diasteroselectivity.
Rh-catalyzed redox-neutral coupling between N-aryl nitrones and alkynes has been achieved under relatively mild conditions. The reaction proceeded via C-H activation at the N-aryl ring with subsequent O-atom transfer, affording trisubstituted indolines in good chemoselectivity and moderate to good diasteroselectivity.
2015, 36(7): 933-942
doi: 10.1016/S1872-2067(15)60870-1
Abstract:
Cr-free bi-metallic SBA-15-supported Co-Cu catalysts were examined in the conversion of biomass-derived α-, β-unsaturated aldehyde (furfural) to value-added chemical furfuryl alcohol (FOL). Co-Cu/SBA-15 catalysts with a fixed Cu loading of 10 wt% and varying Co loadings (2.5, 5, and 10 wt%) were prepared by the impregnation method. The catalysts were characterized by X-ray diffraction, N2 sorption, H2 temperature-programmed reduction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, CO chemisorption, and inductively coupled plasma mass spectrometry. The influence of different reaction parameters such as temperature, pressure, catalyst dosage, and furfural concentration on the catalyst performance was evaluated. Relative to catalysts supported on amorphous silica, the current SBA-15-supported Co-Cu catalysts displayed higher performance, attaining a furfural conversion of 99% and furfuryl alcohol selectivity of 80%. The catalytic reactions were conducted in a 100-mL autoclave at 170 ℃ and 2 MPa H2 pressure for 4 h.
Cr-free bi-metallic SBA-15-supported Co-Cu catalysts were examined in the conversion of biomass-derived α-, β-unsaturated aldehyde (furfural) to value-added chemical furfuryl alcohol (FOL). Co-Cu/SBA-15 catalysts with a fixed Cu loading of 10 wt% and varying Co loadings (2.5, 5, and 10 wt%) were prepared by the impregnation method. The catalysts were characterized by X-ray diffraction, N2 sorption, H2 temperature-programmed reduction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, CO chemisorption, and inductively coupled plasma mass spectrometry. The influence of different reaction parameters such as temperature, pressure, catalyst dosage, and furfural concentration on the catalyst performance was evaluated. Relative to catalysts supported on amorphous silica, the current SBA-15-supported Co-Cu catalysts displayed higher performance, attaining a furfural conversion of 99% and furfuryl alcohol selectivity of 80%. The catalytic reactions were conducted in a 100-mL autoclave at 170 ℃ and 2 MPa H2 pressure for 4 h.
2015, 36(7): 943-951
doi: 10.1016/S1872-2067(15)60863-4
Abstract:
Pd-based nanomaterials have been considered as an effective catalyst for formic acid electrooxidation reaction (FAOR). Herein, we reported two types of polyaniline (PANI)-promoted Pd catalysts. One was an nPANI/Pd electrocatalyst prepared by the electropolymerization of aniline and the electrodeposition of Pd. The other was a Pd/C/nPANI catalyst prepared by the direct electropolymerization of aniline on a commercial Pd/C catalyst. The results show that PANI alone has no catalytic activity for FAOR; however, PANI can exhibit a significant promoting effect to Pd. The current densities of FAOR on the Pd catalysts with a PANI coating show a significant increase compared with that of the Pd reference catalyst without PANI as a promoter. The promoting effects of PANI are strongly dependent on the electropolymerization potential cycles (n). The highest catalytic activities for FAOR of all the nPANI/Pd and Pd/C/nPANI catalysts were those of 15PANI/Pd and Pd/C/20PANI. The mass-specific activity (MSA) of Pd in 15PANI/Pd was 7.5 times that of the Pd catalyst, and the MSA and intrinsic activity of Pd/C/20PANI were 2.3 and 3.3 times that of the Pd/C catalyst, respectively. The enhanced performance of Pd catalysts is proposed as an electronic effect between Pd nanoparticles and PANI.
Pd-based nanomaterials have been considered as an effective catalyst for formic acid electrooxidation reaction (FAOR). Herein, we reported two types of polyaniline (PANI)-promoted Pd catalysts. One was an nPANI/Pd electrocatalyst prepared by the electropolymerization of aniline and the electrodeposition of Pd. The other was a Pd/C/nPANI catalyst prepared by the direct electropolymerization of aniline on a commercial Pd/C catalyst. The results show that PANI alone has no catalytic activity for FAOR; however, PANI can exhibit a significant promoting effect to Pd. The current densities of FAOR on the Pd catalysts with a PANI coating show a significant increase compared with that of the Pd reference catalyst without PANI as a promoter. The promoting effects of PANI are strongly dependent on the electropolymerization potential cycles (n). The highest catalytic activities for FAOR of all the nPANI/Pd and Pd/C/nPANI catalysts were those of 15PANI/Pd and Pd/C/20PANI. The mass-specific activity (MSA) of Pd in 15PANI/Pd was 7.5 times that of the Pd catalyst, and the MSA and intrinsic activity of Pd/C/20PANI were 2.3 and 3.3 times that of the Pd/C catalyst, respectively. The enhanced performance of Pd catalysts is proposed as an electronic effect between Pd nanoparticles and PANI.
2015, 36(7): 952-956
doi: 10.1016/S1872-2067(15)60835-X
Abstract:
The simultaneous wet air oxidation of nitrobenzene (NB) and phenol with homogenous catalyst was carried out in a stainless autoclave in a temperature range of 150-210 ℃ and at a partial oxygen pressure of 1.0 MPa. Compared with the non-catalytic co-oxidation of NB and phenol, the presence of the homogeneous catalyst greatly improved the conversion of both compounds. The transition metal ions Cu2+, Co2+ and Ni2+ were found to be effective catalysts, with Cu2+ affording the best results. How phenol was added to the autoclave was investigated and was found to affect the conversion of NB. Adding phenol in smaller portions can help to degrade NB more effectively. As an example, two additions of phenol with Cu2+ as the homogenous catalyst allowed 95% conversion of NB at 200 ℃ in 1 h. This catalytic co-oxidation method incorporating the addition of phenol initiator batches therefore provides an alternative and effective means of removing persistent organic pollutants from the environment.
The simultaneous wet air oxidation of nitrobenzene (NB) and phenol with homogenous catalyst was carried out in a stainless autoclave in a temperature range of 150-210 ℃ and at a partial oxygen pressure of 1.0 MPa. Compared with the non-catalytic co-oxidation of NB and phenol, the presence of the homogeneous catalyst greatly improved the conversion of both compounds. The transition metal ions Cu2+, Co2+ and Ni2+ were found to be effective catalysts, with Cu2+ affording the best results. How phenol was added to the autoclave was investigated and was found to affect the conversion of NB. Adding phenol in smaller portions can help to degrade NB more effectively. As an example, two additions of phenol with Cu2+ as the homogenous catalyst allowed 95% conversion of NB at 200 ℃ in 1 h. This catalytic co-oxidation method incorporating the addition of phenol initiator batches therefore provides an alternative and effective means of removing persistent organic pollutants from the environment.
2015, 36(7): 957-960
doi: 10.1016/S1872-2067(15)60860-9
Abstract:
The production of octahydrocoumarin, which can serve as a replacement for toxic coumarin, was investigated using 5% Ru on active carbon (Ru/C) as the catalyst for the hydrogenation of coumarin. The hydrogenation was studied by optimizing the reaction conditions (pressure, solvent and coumarin concentration). The activity and selectivity of the Ru/C catalyst were compared for different solvents. The mechanism of coumarin hydrogenation was deduced. The formation of side products was explained. The optimal hydrogenation reaction conditions were: 130 ℃, 10 MPa, 60 wt% coumarin in methanol, and 0.5 wt% (based on coumarin) of Ru/C catalyst. At the complete conversion of coumarin, the selectivity to the desired product was 90%.
The production of octahydrocoumarin, which can serve as a replacement for toxic coumarin, was investigated using 5% Ru on active carbon (Ru/C) as the catalyst for the hydrogenation of coumarin. The hydrogenation was studied by optimizing the reaction conditions (pressure, solvent and coumarin concentration). The activity and selectivity of the Ru/C catalyst were compared for different solvents. The mechanism of coumarin hydrogenation was deduced. The formation of side products was explained. The optimal hydrogenation reaction conditions were: 130 ℃, 10 MPa, 60 wt% coumarin in methanol, and 0.5 wt% (based on coumarin) of Ru/C catalyst. At the complete conversion of coumarin, the selectivity to the desired product was 90%.
2015, 36(7): 961-968
doi: 10.1016/S1872-2067(15)60856-7
Abstract:
Magnetic Fe3O4 nanoparticles were successfully deposited on graphene oxide sheets by ultrasound-assisted coprecipitation. The nanoparticles were characterized using transmission electron microscopy, vibrating sample magnetometry, and X-ray photoelectron spectroscopy. The synthesized material was used as a support for the immobilization of horseradish peroxidase (HRP). The removals of 2-chlorophenol, 4-chlorophenol, and 2,4-dichlorophenol using the immobilized HRP were investigated. Batch degradation studies were used to determine the effects of the initial solution pH values, reaction temperature, reaction time, H2O2 and chlorophenol concentrations, and immobilized enzyme dosage on the removal of chlorophenols. The different numbers and positions of electron-withdrawing substituents affected the chlorophenol removal efficiency; the order of the removal efficiencies was 2-chlorophenol < 4-chlorophenol < 2,4-dichlorophenol. The oxidation products formed during chlorophenol degradation were identified using gas chromatography-mass spectrometry. The biochemical properties of the immobilized HRP were investigated; the results indicated that the storage stability and tolerance to changes in pH and temperature of the immobilized HRP were better than those of free HRP. The nanoparticles were recovered using an external magnetic field, and the immobilized HRP retained 66% of its initial activity for the first four cycles, showing that the immobilized HRP had moderate stability. These results suggest that the immobilized enzyme has potential application in wastewater treatment.
Magnetic Fe3O4 nanoparticles were successfully deposited on graphene oxide sheets by ultrasound-assisted coprecipitation. The nanoparticles were characterized using transmission electron microscopy, vibrating sample magnetometry, and X-ray photoelectron spectroscopy. The synthesized material was used as a support for the immobilization of horseradish peroxidase (HRP). The removals of 2-chlorophenol, 4-chlorophenol, and 2,4-dichlorophenol using the immobilized HRP were investigated. Batch degradation studies were used to determine the effects of the initial solution pH values, reaction temperature, reaction time, H2O2 and chlorophenol concentrations, and immobilized enzyme dosage on the removal of chlorophenols. The different numbers and positions of electron-withdrawing substituents affected the chlorophenol removal efficiency; the order of the removal efficiencies was 2-chlorophenol < 4-chlorophenol < 2,4-dichlorophenol. The oxidation products formed during chlorophenol degradation were identified using gas chromatography-mass spectrometry. The biochemical properties of the immobilized HRP were investigated; the results indicated that the storage stability and tolerance to changes in pH and temperature of the immobilized HRP were better than those of free HRP. The nanoparticles were recovered using an external magnetic field, and the immobilized HRP retained 66% of its initial activity for the first four cycles, showing that the immobilized HRP had moderate stability. These results suggest that the immobilized enzyme has potential application in wastewater treatment.
2015, 36(7): 969-974
doi: 10.1016/S1872-2067(15)60858-0
Abstract:
NaBiO3 and Bi(NO3)3 were used to synthesize Bi-doped NaTaO3. The influence of the Bi chemical state on the photocatalytic activity was investigated using X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and diffused reflectance spectroscopy to study the structure, chemical state and light absorption characteristics, respectively. The photocatalytic activity was evaluated by the H2 evolution water splitting reaction. The monoclinic phase of NaTaO3 remained intact for the two Bi-doped samples, but the Ta-O-Ta bond was distorted from 180° after Bi doping. XPS results indicated that Bi3+ was doped into NaTaO3 with the Bi(NO3)3 precursor, while Bi5+ and Bi3+ were doped into NaTaO3 with the NaBiO3 precursor. The two samples showed identical light absorption, where doping with Bi extended the light absorption to long wavelength light as expected. However, Bi3+ doping did not promote the photocatalytic activity of NaTaO3, while Bi5+ and Bi3+ doping did. The distorted Ta-O-Ta bond from 180° due to doping with Bi was detrimental for charge carrier transfer in the photocatalytic process. In contrast, the vacancies or defects in the NaTaO3 lattice induced by Bi doping for charge balance were beneficial for charge carrier separation. The opposing action of these two factors resulted in the activity of the Bi3+-doped sample being comparable with pristine NaTaO3. For Bi5+- and Bi3+-doped NaTaO3, a high concentration of defects was induced by the high valence Bi5+ ion and this led to its higher photocatalytic activity. Our results indicated that charge carrier transfer is a priority factor in the photocatalytic process and the doping of a high valence ion in the ABO3 structure is a way to promote the separation of charge carriers.
NaBiO3 and Bi(NO3)3 were used to synthesize Bi-doped NaTaO3. The influence of the Bi chemical state on the photocatalytic activity was investigated using X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and diffused reflectance spectroscopy to study the structure, chemical state and light absorption characteristics, respectively. The photocatalytic activity was evaluated by the H2 evolution water splitting reaction. The monoclinic phase of NaTaO3 remained intact for the two Bi-doped samples, but the Ta-O-Ta bond was distorted from 180° after Bi doping. XPS results indicated that Bi3+ was doped into NaTaO3 with the Bi(NO3)3 precursor, while Bi5+ and Bi3+ were doped into NaTaO3 with the NaBiO3 precursor. The two samples showed identical light absorption, where doping with Bi extended the light absorption to long wavelength light as expected. However, Bi3+ doping did not promote the photocatalytic activity of NaTaO3, while Bi5+ and Bi3+ doping did. The distorted Ta-O-Ta bond from 180° due to doping with Bi was detrimental for charge carrier transfer in the photocatalytic process. In contrast, the vacancies or defects in the NaTaO3 lattice induced by Bi doping for charge balance were beneficial for charge carrier separation. The opposing action of these two factors resulted in the activity of the Bi3+-doped sample being comparable with pristine NaTaO3. For Bi5+- and Bi3+-doped NaTaO3, a high concentration of defects was induced by the high valence Bi5+ ion and this led to its higher photocatalytic activity. Our results indicated that charge carrier transfer is a priority factor in the photocatalytic process and the doping of a high valence ion in the ABO3 structure is a way to promote the separation of charge carriers.
2015, 36(7): 975-981
doi: 10.1016/S1872-2067(15)60851-8
Abstract:
A Ti/α-PbO2/β-PbO2 electrode with high stability was prepared and examined toward the electrochemical degradation of 2-chlorophenol. Scanning electron microscopy analysis revealed that Ti/α-PbO2/β-PbO2 had a cauliflower morphology comprising small β-PbO2 crystals. The 2-chlorophenol removal rate using the Ti/α-PbO2/β-PbO2 electrode was 100% after 180 min of electrolysis under optimal conditions, which were selected based on the orthogonal test method, i.e., initial concentration of 2-cholorophenol = 50 mg/L, concentration of Na2SO4 = 0.1 mol/L, temperature = 35 ℃, and anode current density = 20 mA/cm2. Kinetic analyses demonstrated that the electrochemical oxidation of 2-chlorophenol on the Ti/α-PbO2/β-PbO2 electrode followed pseudo-first order kinetics.
A Ti/α-PbO2/β-PbO2 electrode with high stability was prepared and examined toward the electrochemical degradation of 2-chlorophenol. Scanning electron microscopy analysis revealed that Ti/α-PbO2/β-PbO2 had a cauliflower morphology comprising small β-PbO2 crystals. The 2-chlorophenol removal rate using the Ti/α-PbO2/β-PbO2 electrode was 100% after 180 min of electrolysis under optimal conditions, which were selected based on the orthogonal test method, i.e., initial concentration of 2-cholorophenol = 50 mg/L, concentration of Na2SO4 = 0.1 mol/L, temperature = 35 ℃, and anode current density = 20 mA/cm2. Kinetic analyses demonstrated that the electrochemical oxidation of 2-chlorophenol on the Ti/α-PbO2/β-PbO2 electrode followed pseudo-first order kinetics.
2015, 36(7): 982-986
doi: 10.1016/S1872-2067(15)60852-X
Abstract:
Quaternary ammonium Brönsted acid surfactant-combined dicationic ionic liquids (BASDILs) based on zwitterionic 1,2-bis[N-methyl-N-(3-sulfopropyl)-alkylammonium]ethane betaines and various anions were prepared and characterized. BASDILs possess properties similar to those of phase-separated catalysts and were applied to the catalytic synthesis of biodiesel from free fatty acids and alcohols. Several factors were investigated and the results indicated that [C12Sb][p-CH3C6H4SO3] was the optimal catalyst, with good catalytic performance and reusability under mild conditions.
Quaternary ammonium Brönsted acid surfactant-combined dicationic ionic liquids (BASDILs) based on zwitterionic 1,2-bis[N-methyl-N-(3-sulfopropyl)-alkylammonium]ethane betaines and various anions were prepared and characterized. BASDILs possess properties similar to those of phase-separated catalysts and were applied to the catalytic synthesis of biodiesel from free fatty acids and alcohols. Several factors were investigated and the results indicated that [C12Sb][p-CH3C6H4SO3] was the optimal catalyst, with good catalytic performance and reusability under mild conditions.
2015, 36(7): 987-993
doi: 10.1016/S1872-2067(15)60849-X
Abstract:
Bi2WO6 microspheres with a diameter of 1.5-2 μm were prepared by a hydrothermal method, and then coated with different contents of AgCl to form heterostructured AgCl/Bi2WO6 microspheres. The prepared Bi2WO6 and AgCl/Bi2WO6 photocatalysts were characterized by X-ray diffraction, N2 physical adsorption, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and ultraviolet-visible diffuse reflectance spectroscopy. The photocatalytic activity of the catalysts was evaluated by photocatalytic degradation of rhodamine B under ultraviolet and visible light irradiation. Results showed that the deposition of AgCl had no obvious effect on the light absorption and surface properties of Bi2WO6. However, the heterostructured AgCl/Bi2WO6 photocatalysts exhibited considerably higher activity than the pure AgCl and Bi2WO6 catalysts. With the optimal AgCl content of 20 wt%, the photocatalytic activity of the heterostructured AgCl/Bi2WO6 catalyst was increased under both ultraviolet and visible light compared with that of Bi2WO6. The main reason for the enhanced photocatalytic activity is attributed to the formation of AgCl/Bi2WO6 heterostructures effectively suppressing the recombination of photogenerated electrons and holes.
Bi2WO6 microspheres with a diameter of 1.5-2 μm were prepared by a hydrothermal method, and then coated with different contents of AgCl to form heterostructured AgCl/Bi2WO6 microspheres. The prepared Bi2WO6 and AgCl/Bi2WO6 photocatalysts were characterized by X-ray diffraction, N2 physical adsorption, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and ultraviolet-visible diffuse reflectance spectroscopy. The photocatalytic activity of the catalysts was evaluated by photocatalytic degradation of rhodamine B under ultraviolet and visible light irradiation. Results showed that the deposition of AgCl had no obvious effect on the light absorption and surface properties of Bi2WO6. However, the heterostructured AgCl/Bi2WO6 photocatalysts exhibited considerably higher activity than the pure AgCl and Bi2WO6 catalysts. With the optimal AgCl content of 20 wt%, the photocatalytic activity of the heterostructured AgCl/Bi2WO6 catalyst was increased under both ultraviolet and visible light compared with that of Bi2WO6. The main reason for the enhanced photocatalytic activity is attributed to the formation of AgCl/Bi2WO6 heterostructures effectively suppressing the recombination of photogenerated electrons and holes.
2015, 36(7): 994-1000
doi: 10.1016/S1872-2067(15)60850-6
Abstract:
The influence of a nickel promoter on the catalytic behavior of a modified alumina supported Pd close-coupled catalyst was investigated. Doping with nickel improved the catalytic activity for the reactions of C3H8, especially over the aged catalyst. T50 and T90 of the aged Pd catalyst were decreased by 31 and 30 ℃, respectively. The single reaction results revealed that doping with Ni promoted the catalytic activity for the C3H8 + NO reaction. The fresh and aged catalysts were characterized by H2-temperature-programmed reduction, CO chemisorption, high resolution transmission electron microscopy, and X-ray photoelectron spectroscopy, which revealed that the doping with Ni inhibited the sintering of active PdOx species and the formation of undesired metallic Pd0, and led to improved reducibility of active PdOx and increased the surface area of PdOx species.
The influence of a nickel promoter on the catalytic behavior of a modified alumina supported Pd close-coupled catalyst was investigated. Doping with nickel improved the catalytic activity for the reactions of C3H8, especially over the aged catalyst. T50 and T90 of the aged Pd catalyst were decreased by 31 and 30 ℃, respectively. The single reaction results revealed that doping with Ni promoted the catalytic activity for the C3H8 + NO reaction. The fresh and aged catalysts were characterized by H2-temperature-programmed reduction, CO chemisorption, high resolution transmission electron microscopy, and X-ray photoelectron spectroscopy, which revealed that the doping with Ni inhibited the sintering of active PdOx species and the formation of undesired metallic Pd0, and led to improved reducibility of active PdOx and increased the surface area of PdOx species.
2015, 36(7): 1001-1008
doi: 10.1016/S1872-2067(15)60855-5
Abstract:
This work demonstrates an improved (NH4)2SiF6 treatment to enhance the hydrothermal stability of mesoporous SBA-15 zeolite. In this treatment, Al3+ ions are incorporated into SBA-15 zeolite first, then it is treated with 5% (NH4)2SiF6 solution according to 1% SiO2 of SBA-15 and finally washed with HCl (2 mol/L) to remove the pre-incorporated Al3+ ions. The obtained SBA-15 exhibits higher hydrothermal stability than that without pre-incorporated Al3+. Compared with the latter, the sample maintains a better ordered mesostructure and a larger surface area (271 m2/g) after hydrothermal treatment at 800 ℃ for 12 h in 100% steam. The results show that incorporating Al3+ ions into SBA-15 zeolite before (NH4)2SiF6 treatment obviously promotes the stabilization effect of (NH4)2SiF6 treatment. The mechanism suggests that the incorporated Al3+ ions can effectively capture F- ions that have been released from (NH4)2SiF6, and thus reduce their etching into the SBA-15 zeolite framework. This ensures that the positive factors of (NH4)2SiF6 treatment, such as silicon insertion and surface hydrophobization by F- ions, play effective roles in the improvement of the hydrothermal stability of SBA-15 zeolite. This promoting effect of the Al3+ ions is closely related to the method that is used to introduce the Al3+ and the SBA-15 zeolite processing temperature.
This work demonstrates an improved (NH4)2SiF6 treatment to enhance the hydrothermal stability of mesoporous SBA-15 zeolite. In this treatment, Al3+ ions are incorporated into SBA-15 zeolite first, then it is treated with 5% (NH4)2SiF6 solution according to 1% SiO2 of SBA-15 and finally washed with HCl (2 mol/L) to remove the pre-incorporated Al3+ ions. The obtained SBA-15 exhibits higher hydrothermal stability than that without pre-incorporated Al3+. Compared with the latter, the sample maintains a better ordered mesostructure and a larger surface area (271 m2/g) after hydrothermal treatment at 800 ℃ for 12 h in 100% steam. The results show that incorporating Al3+ ions into SBA-15 zeolite before (NH4)2SiF6 treatment obviously promotes the stabilization effect of (NH4)2SiF6 treatment. The mechanism suggests that the incorporated Al3+ ions can effectively capture F- ions that have been released from (NH4)2SiF6, and thus reduce their etching into the SBA-15 zeolite framework. This ensures that the positive factors of (NH4)2SiF6 treatment, such as silicon insertion and surface hydrophobization by F- ions, play effective roles in the improvement of the hydrothermal stability of SBA-15 zeolite. This promoting effect of the Al3+ ions is closely related to the method that is used to introduce the Al3+ and the SBA-15 zeolite processing temperature.
2015, 36(7): 1009-1016
doi: 10.1016/S1872-2067(15)60844-0
Abstract:
A hybrid catalyst of g-C3N4 (graphitic carbon nitride)/rGO (reduced graphene oxide) was prepared by directly heating a mixture of melamine and GO in air. g-C3N4 in the hybrid retained the structure of pristine g-C3N4, and the heterojunction between g-C3N4 and rGO was formed by π-π interaction. The highest photocatalytic efficiency for the degradation of rhodamine B (RhB) was with the melamine/GO mass ratio of 800/1, with a first order rate constant 2.6 times that of pristine g-C3N4. The enhanced photocatalytic activity was assigned to the rGO-promoted separation of photo-generated electron (e-)-hole (h+) pairs. In addition, the photocatalytic activity of g-C3N4/rGO was pH sensitive with a much increased photodegrading rate at low pH values. The first order rate constant was 8.6 times that of pristine g-C3N4 at pH = 1.98. The pH sensitive behavior resulted from the promoted oxidation of h+ with RhB by the consumption of e- with the reaction of proton (H+) in which rGO acted as a good platform for transferring e- through its atomic sheets.
A hybrid catalyst of g-C3N4 (graphitic carbon nitride)/rGO (reduced graphene oxide) was prepared by directly heating a mixture of melamine and GO in air. g-C3N4 in the hybrid retained the structure of pristine g-C3N4, and the heterojunction between g-C3N4 and rGO was formed by π-π interaction. The highest photocatalytic efficiency for the degradation of rhodamine B (RhB) was with the melamine/GO mass ratio of 800/1, with a first order rate constant 2.6 times that of pristine g-C3N4. The enhanced photocatalytic activity was assigned to the rGO-promoted separation of photo-generated electron (e-)-hole (h+) pairs. In addition, the photocatalytic activity of g-C3N4/rGO was pH sensitive with a much increased photodegrading rate at low pH values. The first order rate constant was 8.6 times that of pristine g-C3N4 at pH = 1.98. The pH sensitive behavior resulted from the promoted oxidation of h+ with RhB by the consumption of e- with the reaction of proton (H+) in which rGO acted as a good platform for transferring e- through its atomic sheets.
2015, 36(7): 1017-1022
doi: 10.1016/S1872-2067(15)60842-7
Abstract:
Periodic density functional theory calculations have been conducted using the DMol3 package to investigate the geminal methylation of a series of methylbenzenes as hydrocarbon pool species trapped within the framework of a catalyst for the conversion of methyl halides to light olefins. The adsorption energies of CH3Cl (-18 kJ/mol) and CH3Br (-22 kJ/mol) into a SAPO-34 catalyst were calculated, and the results revealed that these methylating agents were not being accurately distinguished because of similarities in the electronegativities of their halogen atoms. The reaction energies and energy barriers were also obtained for the geminal methylation reactions of a series of methylbenzenes using CH3Cl and CH3Br. The results of these calculations suggested that the geminal methylation of hexamethylbenzene (HMB) was exothermic based on the negative reaction energies, whereas the geminal methylation reactions of all of the other methylbenzenes were endothermic. Furthermore, the energy barriers for the geminal methylation of HMB with CH3Cl and CH3Br were lower than those of the other methylbenzenes evaluated in the current study, which indicated that HMB was forming strong electrostatic interactions within the structural framework of the molecular sieves, and that the reactivity of the methylbenzene substrate increased as the number of methyl groups increased.
Periodic density functional theory calculations have been conducted using the DMol3 package to investigate the geminal methylation of a series of methylbenzenes as hydrocarbon pool species trapped within the framework of a catalyst for the conversion of methyl halides to light olefins. The adsorption energies of CH3Cl (-18 kJ/mol) and CH3Br (-22 kJ/mol) into a SAPO-34 catalyst were calculated, and the results revealed that these methylating agents were not being accurately distinguished because of similarities in the electronegativities of their halogen atoms. The reaction energies and energy barriers were also obtained for the geminal methylation reactions of a series of methylbenzenes using CH3Cl and CH3Br. The results of these calculations suggested that the geminal methylation of hexamethylbenzene (HMB) was exothermic based on the negative reaction energies, whereas the geminal methylation reactions of all of the other methylbenzenes were endothermic. Furthermore, the energy barriers for the geminal methylation of HMB with CH3Cl and CH3Br were lower than those of the other methylbenzenes evaluated in the current study, which indicated that HMB was forming strong electrostatic interactions within the structural framework of the molecular sieves, and that the reactivity of the methylbenzene substrate increased as the number of methyl groups increased.
2015, 36(7): 1023-1028
doi: 10.1016/S1872-2067(15)60846-4
Abstract:
The one-pot eight-component reaction between Meldrum's acid, an aromatic aldehyde, and an aryl amine was achieved in the presence of citric acid catalyst. The corresponding dispirohydroquinolines were obtained in good yields with excellent diastereoselectivity. This method is a combination of the Knoevenagel and Michael reactions.
The one-pot eight-component reaction between Meldrum's acid, an aromatic aldehyde, and an aryl amine was achieved in the presence of citric acid catalyst. The corresponding dispirohydroquinolines were obtained in good yields with excellent diastereoselectivity. This method is a combination of the Knoevenagel and Michael reactions.
2015, 36(7): 1029-1034
doi: 10.1016/S1872-2067(15)60841-5
Abstract:
An electrochemical approach to fabricate a nanostructured Fe/Pt-Fe catalyst through electrodeposition followed by galvanic replacement is presented. An Fe/Pt-Fe nanostructured electrode was prepared by deposition of Fe-Zn onto a Fe electrode surface, followed by replacement of the Zn by Pt at open-circuit potential in a Pt-containing alkaline solution. Scanning electron microscopy and energy-dispersive X-ray techniques reveal that the Fe/Pt-Fe electrode is porous and contains Pt. The electrocatalytic activity of the Fe/Pt-Fe electrode for oxidation of methanol was examined by cyclic voltammetry and chronoamperometry. The electrooxidation current on the Fe/Pt-Fe catalyst is much higher than that on flat Pt and smooth Fe catalysts. The onset potential and peak potential on the Fe/Pt-Fe catalyst are more negative than those on flat Pt and smooth Fe electrodes for methanol electrooxidation. All results show that this nanostructured Fe/Pt-Fe electrode is very attractive for integrated fuel cell applications in alkaline media.
An electrochemical approach to fabricate a nanostructured Fe/Pt-Fe catalyst through electrodeposition followed by galvanic replacement is presented. An Fe/Pt-Fe nanostructured electrode was prepared by deposition of Fe-Zn onto a Fe electrode surface, followed by replacement of the Zn by Pt at open-circuit potential in a Pt-containing alkaline solution. Scanning electron microscopy and energy-dispersive X-ray techniques reveal that the Fe/Pt-Fe electrode is porous and contains Pt. The electrocatalytic activity of the Fe/Pt-Fe electrode for oxidation of methanol was examined by cyclic voltammetry and chronoamperometry. The electrooxidation current on the Fe/Pt-Fe catalyst is much higher than that on flat Pt and smooth Fe catalysts. The onset potential and peak potential on the Fe/Pt-Fe catalyst are more negative than those on flat Pt and smooth Fe electrodes for methanol electrooxidation. All results show that this nanostructured Fe/Pt-Fe electrode is very attractive for integrated fuel cell applications in alkaline media.
2015, 36(7): 1035-1041
doi: 10.1016/S1872-2067(15)60836-1
Abstract:
The different amounts of [5,10,15,20-tetrakis-(pentafluorophenyl)porphyrin] manganese chloride (TF20PPMnCl) were immobilized on amino-functionalized MCM-41 for catalysis of the hydroxylation of naphthalene. The samples were characterized by X-ray powder diffraction, N2 adsorption/ desorption isotherms, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, diffuse reflectance ultraviolet-visible spectroscopy, thermogravimetric and differential scanning calorimetry, and inductively coupled plasma mass spectrometry. The results indicated that the manganese porphyrins were axially coordinated on amino-functionalized MCM-41. The prepared samples showed remarkable catalytic activity in the hydroxylation of naphthalene with meta-chloroperbenzoic acid as the oxidant. The catalyst could be reused several times without loss of its activity.
The different amounts of [5,10,15,20-tetrakis-(pentafluorophenyl)porphyrin] manganese chloride (TF20PPMnCl) were immobilized on amino-functionalized MCM-41 for catalysis of the hydroxylation of naphthalene. The samples were characterized by X-ray powder diffraction, N2 adsorption/ desorption isotherms, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, diffuse reflectance ultraviolet-visible spectroscopy, thermogravimetric and differential scanning calorimetry, and inductively coupled plasma mass spectrometry. The results indicated that the manganese porphyrins were axially coordinated on amino-functionalized MCM-41. The prepared samples showed remarkable catalytic activity in the hydroxylation of naphthalene with meta-chloroperbenzoic acid as the oxidant. The catalyst could be reused several times without loss of its activity.
2015, 36(7): 1042-1046
doi: 10.1016/S1872-2067(15)60853-1
Abstract:
A novel, biochemical, and eco-friendly method has been developed for the synthesis of Ag nanoparticles using an aqueous leaf extract of readily accessible Cinnamomum tamala as reducing and stabilizing agents. These Ag nanoparticles were used to catalyze the synthesis of pyranopyrazoles. The green nature and ease of recovery and reusability of the catalyst, together with high yields of products, make this protocol attractive and useful.
A novel, biochemical, and eco-friendly method has been developed for the synthesis of Ag nanoparticles using an aqueous leaf extract of readily accessible Cinnamomum tamala as reducing and stabilizing agents. These Ag nanoparticles were used to catalyze the synthesis of pyranopyrazoles. The green nature and ease of recovery and reusability of the catalyst, together with high yields of products, make this protocol attractive and useful.
2015, 36(7): 1047-1053
doi: 10.1016/S1872-2067(15)60837-3
Abstract:
An oxime-derived palladacycle was synthesized using 4-bromobenzoxime and pyridine in CHCl3, and characterized by FT-IR and 1H NMR spectroscopy. This Pd complex was supported on Fe3O4/oleic acid and shown to be an efficient catalyst for the copper-free Sonogashira cross-coupling reaction of various aryl halides with phenylacetylene in air and in ethanol or mixed aqueous medium. The oxime-derived palladacycle gave highly active palladium nanoparticles for the organic synthesis. The coupling products were obtained in high yields with low Pd loading and the heterogeneous catalyst can be separated by an external magnet and reused six times without loss of its activity. The characterization of the catalyst was carried out by XRD, SEM and TEM. Both TEM and XRD revealed that the palladium nanoparticles were well dispersed with diameters from 5 to 10 nm and average size 9.97 nm.
An oxime-derived palladacycle was synthesized using 4-bromobenzoxime and pyridine in CHCl3, and characterized by FT-IR and 1H NMR spectroscopy. This Pd complex was supported on Fe3O4/oleic acid and shown to be an efficient catalyst for the copper-free Sonogashira cross-coupling reaction of various aryl halides with phenylacetylene in air and in ethanol or mixed aqueous medium. The oxime-derived palladacycle gave highly active palladium nanoparticles for the organic synthesis. The coupling products were obtained in high yields with low Pd loading and the heterogeneous catalyst can be separated by an external magnet and reused six times without loss of its activity. The characterization of the catalyst was carried out by XRD, SEM and TEM. Both TEM and XRD revealed that the palladium nanoparticles were well dispersed with diameters from 5 to 10 nm and average size 9.97 nm.
2015, 36(7): 1054-1059
doi: 10.1016/S1872-2067(15)60830-0
Abstract:
The one-pot three-component cyclocondensation has been developed involving the reaction of benzil with an aromatic aldehydes and ammonium acetate under thermal solvent-free conditions in the presence of a KSF supported 10-molybdo-2-vanadophosphoric acid catalyst. 10-Molybdo-2-vanadophosphoric acid was immobilized on KSF with a 20% loading, which showed the highest catalytic activity. The catalyst was fully characterized using FT-IR spectroscopy, thermal analysis, XRD and SEM analysis techniques. There are several distinct advantages to this protocol, including high yields, short reaction time, operational simplicity and a recyclable catalyst with a facile work-up procedure.
The one-pot three-component cyclocondensation has been developed involving the reaction of benzil with an aromatic aldehydes and ammonium acetate under thermal solvent-free conditions in the presence of a KSF supported 10-molybdo-2-vanadophosphoric acid catalyst. 10-Molybdo-2-vanadophosphoric acid was immobilized on KSF with a 20% loading, which showed the highest catalytic activity. The catalyst was fully characterized using FT-IR spectroscopy, thermal analysis, XRD and SEM analysis techniques. There are several distinct advantages to this protocol, including high yields, short reaction time, operational simplicity and a recyclable catalyst with a facile work-up procedure.
2015, 36(7): 1060-1067
doi: 10.1016/S1872-2067(15)60839-7
Abstract:
V2O5/MO-Al2O3 (M = Mg, Ca, Sr, Ba) catalysts with different V2O5 loading were prepared by impregnation with ammonium metavanadate as the V precursor and characterized and tested for the selectively oxidative dehydrogenation of n-butane to butenes. Characterization by BET, XRD, FTIR, H2-TPR and Raman spectra showed that the catalysts doped with different alkaline earth metals had different structure and catalytic activity. The catalysts doped with Ca, Sr or Ba had the orthovanadate phase that was difficult to reduce, so their redox cycles could not be established and they exhibited low activity. The catalysts doped with Mg showed high catalytic activity and selectivity. The catalyst with 5% V2O5 loading exhibited the highest n-butane conversion (30.3%) and total butene selectivity (64.3%) at 600 ℃. This was due to the well dispersed VOx species and the existence of the MgO crystalline phase, which were both present at a V2O5 loading of 5%.
V2O5/MO-Al2O3 (M = Mg, Ca, Sr, Ba) catalysts with different V2O5 loading were prepared by impregnation with ammonium metavanadate as the V precursor and characterized and tested for the selectively oxidative dehydrogenation of n-butane to butenes. Characterization by BET, XRD, FTIR, H2-TPR and Raman spectra showed that the catalysts doped with different alkaline earth metals had different structure and catalytic activity. The catalysts doped with Ca, Sr or Ba had the orthovanadate phase that was difficult to reduce, so their redox cycles could not be established and they exhibited low activity. The catalysts doped with Mg showed high catalytic activity and selectivity. The catalyst with 5% V2O5 loading exhibited the highest n-butane conversion (30.3%) and total butene selectivity (64.3%) at 600 ℃. This was due to the well dispersed VOx species and the existence of the MgO crystalline phase, which were both present at a V2O5 loading of 5%.
2015, 36(7): 1068-1076
doi: 10.1016/S1872-2067(15)60833-6
Abstract:
Electricity production from brewery wastewater using dual-chamber microbial fuel cells (MFCs) with a tin-coated copper mesh in the anode was investigated by changing the hydraulic retention time (HRT). The MFCs were fed with wastewater samples from the inlet (inflow, MFC-1) and outlet (outflow, MFC-2) of an anaerobic digester of a brewery wastewater treatment plant. Both chemical oxygen demand removal and current density were improved by decreasing HRT. The best MFC performance was with an HRT of 0.5 d. The maximum power densities of 8.001 and 1.843 µW/cm2 were obtained from reactors MFC-1 and MFC-2, respectively. Microbial diversity at different conditions was studied using PCR-DGGE profiling of 16S rRNA fragments of the microorganisms from the biofilm on the anode electrode. The MFC reactor had mainly Geobacter, Shewanella, and Clostridium species, and some bacteria were easily washed out at lower HRTs. The fouling characteristics of the MFC Nafion membrane and the resulting degradation of MFC performance were examined. The ion exchange capacity, conductivity, and diffusivity of the membrane decreased significantly after fouling. The morphology of the Nafion membrane and MFC degradation were studied using scanning electron microscopy and attenuated total reflection-Fourier transform infrared spectroscopy.
Electricity production from brewery wastewater using dual-chamber microbial fuel cells (MFCs) with a tin-coated copper mesh in the anode was investigated by changing the hydraulic retention time (HRT). The MFCs were fed with wastewater samples from the inlet (inflow, MFC-1) and outlet (outflow, MFC-2) of an anaerobic digester of a brewery wastewater treatment plant. Both chemical oxygen demand removal and current density were improved by decreasing HRT. The best MFC performance was with an HRT of 0.5 d. The maximum power densities of 8.001 and 1.843 µW/cm2 were obtained from reactors MFC-1 and MFC-2, respectively. Microbial diversity at different conditions was studied using PCR-DGGE profiling of 16S rRNA fragments of the microorganisms from the biofilm on the anode electrode. The MFC reactor had mainly Geobacter, Shewanella, and Clostridium species, and some bacteria were easily washed out at lower HRTs. The fouling characteristics of the MFC Nafion membrane and the resulting degradation of MFC performance were examined. The ion exchange capacity, conductivity, and diffusivity of the membrane decreased significantly after fouling. The morphology of the Nafion membrane and MFC degradation were studied using scanning electron microscopy and attenuated total reflection-Fourier transform infrared spectroscopy.
2015, 36(7): 1077-1085
doi: 10.1016/S1872-2067(15)60827-0
Abstract:
Carbon-coated CdS (CdS@C) nanoparticles were conveniently prepared by a one-step hydrothermal carbonization method at temperature as low as 130 ℃, in which cadmium acetate and glucose were used as the cadmium and carbon sources, respectively, and thiourea was used as the sulfur source and catalyst for the hydrothermal carbonization of glucose. The prepared CdS@C particles possess a smaller size, better dispersion, and more uniform distribution than pure CdS particles prepared under the same conditions. Furthermore, the hydrothermal carbonization of glucose easily induces the prior formation of metastable cubic CdS crystals. In addition, the carbonaceous species coated on the surface of CdS expands the range of absorption light and slightly decreases the band gap of CdS, as well as reduces the recombination of the photogenerated electron-hole pairs of CdS and its photo-oxidative corrosion, which can improve the photocatalytic activity and stability of CdS for the photo-oxidative degradation of methyl orange in aqueous solution under visible light irradiation.
Carbon-coated CdS (CdS@C) nanoparticles were conveniently prepared by a one-step hydrothermal carbonization method at temperature as low as 130 ℃, in which cadmium acetate and glucose were used as the cadmium and carbon sources, respectively, and thiourea was used as the sulfur source and catalyst for the hydrothermal carbonization of glucose. The prepared CdS@C particles possess a smaller size, better dispersion, and more uniform distribution than pure CdS particles prepared under the same conditions. Furthermore, the hydrothermal carbonization of glucose easily induces the prior formation of metastable cubic CdS crystals. In addition, the carbonaceous species coated on the surface of CdS expands the range of absorption light and slightly decreases the band gap of CdS, as well as reduces the recombination of the photogenerated electron-hole pairs of CdS and its photo-oxidative corrosion, which can improve the photocatalytic activity and stability of CdS for the photo-oxidative degradation of methyl orange in aqueous solution under visible light irradiation.
2015, 36(7): 1086-1092
doi: 10.1016/S1872-2067(14)60319-3
Abstract:
A vanadium doped graphitic carbon nitride catalyst has been prepared and used for the direct hydroxylation of arenes with O2. Substituted arenes with electron-withdrawing groups such as CN, NO2, COOH, CF3, and COCH3 were oxygenated to the corresponding phenols in moderate yields. The catalyst also proved applicable for the hydroxylation of aromatic halides (F, Cl, and Br) with O2.
A vanadium doped graphitic carbon nitride catalyst has been prepared and used for the direct hydroxylation of arenes with O2. Substituted arenes with electron-withdrawing groups such as CN, NO2, COOH, CF3, and COCH3 were oxygenated to the corresponding phenols in moderate yields. The catalyst also proved applicable for the hydroxylation of aromatic halides (F, Cl, and Br) with O2.
2015, 36(7): 1093-1100
doi: 10.1016/S1872-2067(14)60317-X
Abstract:
Stereoselective synthesis by an aldol reaction between chloroacetone and aldehyde was studied using a synthesized chiral organocatalyst and triethylamine. The reaction gave α-chloro-β-hydroxy ketones in excellent yield with high anti selectivity and enantioselectivity. The chiral organocatalyst was also used in the Knoevenagel reaction, which gave α-cyano-β-hydroxy ketones at a low temperature and the usual Knoevenagel product at a high temperature. Both products were obtained in good to moderate yield with good anti selectivity in the case of α-cyano-β-hydroxy ketone derivatives.
Stereoselective synthesis by an aldol reaction between chloroacetone and aldehyde was studied using a synthesized chiral organocatalyst and triethylamine. The reaction gave α-chloro-β-hydroxy ketones in excellent yield with high anti selectivity and enantioselectivity. The chiral organocatalyst was also used in the Knoevenagel reaction, which gave α-cyano-β-hydroxy ketones at a low temperature and the usual Knoevenagel product at a high temperature. Both products were obtained in good to moderate yield with good anti selectivity in the case of α-cyano-β-hydroxy ketone derivatives.
2015, 36(7): 1101-1108
doi: 10.1016/S1872-2067(14)60318-1
Abstract:
Three complexes containing 2-pyrazinecarboxylate (pzca-), including [Ni(pzca)2(H2O)2], [Co(pzca)2(H2O)2], and [Cu(pzca)2(H2O)2], have been synthesized and characterized using physicochemical and spectroscopic methods. Furthermore, the structure of each complex was determined by single-crystal X-ray diffraction. All three complexes have an octahedral geometry, where the metal ion chelated by two carboxylate oxygens, two nitrogen atoms belonging to pyrazinic acid molecules, and two oxygen atoms of two water molecules. The catalytic activities of these complexes were also investigated in the green synthesis of 2H-indazolo[2,1-b]phthalazine-triones by the reaction of hydrazine hydrate with an arylaldehyde, phthalic anhydride, and dimedone in acetic acid.
Three complexes containing 2-pyrazinecarboxylate (pzca-), including [Ni(pzca)2(H2O)2], [Co(pzca)2(H2O)2], and [Cu(pzca)2(H2O)2], have been synthesized and characterized using physicochemical and spectroscopic methods. Furthermore, the structure of each complex was determined by single-crystal X-ray diffraction. All three complexes have an octahedral geometry, where the metal ion chelated by two carboxylate oxygens, two nitrogen atoms belonging to pyrazinic acid molecules, and two oxygen atoms of two water molecules. The catalytic activities of these complexes were also investigated in the green synthesis of 2H-indazolo[2,1-b]phthalazine-triones by the reaction of hydrazine hydrate with an arylaldehyde, phthalic anhydride, and dimedone in acetic acid.
2015, 36(7): 1109-1116
doi: 10.1016/S1872-2067(14)60315-6
Abstract:
Nickel zirconium phosphate nanoparticles were found to function as efficient catalysts for the selective oxidation of a wide range of alcohols to their corresponding ketones and aldehydes using H2O2 as an oxidizing agent and without any organic solvents, phase transfer catalysts, or additives. The steric and electronic properties of various substrates had significant influence on the reaction conditions required to achieve acetylation. The results showed that this method can be applied for the chemoselective oxidation of benzyl alcohols in the presence of aliphatic alcohols. The catalyst used in the current study was characterized by ICP-OES, XRD, NH3-TPD, Py-FTIR, N2 adsorption-desorption, SEM and TEM. These analyses revealed that the interlayer distance in the catalyst increased from 0.75 to 0.98 nm when Ni2+ was intercalated between the layers, whereas the crystallinity of the material was reduced. The nanocatalyst could also be recovered and reused at least seven times without any discernible decrease in its catalytic activity. This new method for the oxidation of alcohols has several key advantages, including mild and environmentally friendly reaction conditions, short reaction time, excellent yields and a facile work-up.
Nickel zirconium phosphate nanoparticles were found to function as efficient catalysts for the selective oxidation of a wide range of alcohols to their corresponding ketones and aldehydes using H2O2 as an oxidizing agent and without any organic solvents, phase transfer catalysts, or additives. The steric and electronic properties of various substrates had significant influence on the reaction conditions required to achieve acetylation. The results showed that this method can be applied for the chemoselective oxidation of benzyl alcohols in the presence of aliphatic alcohols. The catalyst used in the current study was characterized by ICP-OES, XRD, NH3-TPD, Py-FTIR, N2 adsorption-desorption, SEM and TEM. These analyses revealed that the interlayer distance in the catalyst increased from 0.75 to 0.98 nm when Ni2+ was intercalated between the layers, whereas the crystallinity of the material was reduced. The nanocatalyst could also be recovered and reused at least seven times without any discernible decrease in its catalytic activity. This new method for the oxidation of alcohols has several key advantages, including mild and environmentally friendly reaction conditions, short reaction time, excellent yields and a facile work-up.
2015, 36(7): 1117-1123
doi: 10.1016/S1872-2067(14)60310-7
Abstract:
Gold (Au) nanoparticle (NP)-mesoporous silica (SiO2) composite nanotubes were prepared by a bottom-up approach, in which Au NPs were anchored to the inner wall of mesoporous SiO2 tubular shells. In this composite, the agglomeration, exfoliation, and grain growth of Au NPs were restricted, and the loading and size of the catalyst NPs were easily tuned. The mesoporous shell, open ends, and one-dimensional passage of the SiO2 nanotubes all promote the diffusion of reactants, which enhanced the catalytic efficiency of this composite in the reduction of 4-nitrophenol. The Au NP-mesoporous SiO2 composite nanotubes also demonstrated good reusability, and no leaching or agglomeration of the Au NPs was observed during the catalytic reaction.
Gold (Au) nanoparticle (NP)-mesoporous silica (SiO2) composite nanotubes were prepared by a bottom-up approach, in which Au NPs were anchored to the inner wall of mesoporous SiO2 tubular shells. In this composite, the agglomeration, exfoliation, and grain growth of Au NPs were restricted, and the loading and size of the catalyst NPs were easily tuned. The mesoporous shell, open ends, and one-dimensional passage of the SiO2 nanotubes all promote the diffusion of reactants, which enhanced the catalytic efficiency of this composite in the reduction of 4-nitrophenol. The Au NP-mesoporous SiO2 composite nanotubes also demonstrated good reusability, and no leaching or agglomeration of the Au NPs was observed during the catalytic reaction.
2015, 36(7): 1124-1130
doi: 10.1016/S1872-2067(14)60308-9
Abstract:
A series of coumarin-chalcone hybrid compounds and coumarins linked to pyrazoline was synthesized in good yield and short time using a simple and efficient method. This method involved the one-pot reaction of salicylaldehyde, an α-ketoester and an aromatic aldehyde (in the case of the coumarin-chalcone derivatives) in addition to hydrazine hydrate (in the case of the pyrazolyl coumarins) in the presence of a catalytic amount of bismuth triflate [Bi(OTf)3, 5 mol%]. The synthesized compounds showed scavenging activity towards the free radical 2,2-diphenyl-1-picrylhydrazyl. All compounds were characterized using IR, 1H NMR and 13C NMR spectroscopy.
A series of coumarin-chalcone hybrid compounds and coumarins linked to pyrazoline was synthesized in good yield and short time using a simple and efficient method. This method involved the one-pot reaction of salicylaldehyde, an α-ketoester and an aromatic aldehyde (in the case of the coumarin-chalcone derivatives) in addition to hydrazine hydrate (in the case of the pyrazolyl coumarins) in the presence of a catalytic amount of bismuth triflate [Bi(OTf)3, 5 mol%]. The synthesized compounds showed scavenging activity towards the free radical 2,2-diphenyl-1-picrylhydrazyl. All compounds were characterized using IR, 1H NMR and 13C NMR spectroscopy.
2015, 36(7): 1131-1135
doi: 10.1016/S1872-2067(14)60297-7
Abstract:
Direct conversion of syngas into hydrocarbons with high selectivity remains a challenge. Herein, we report the synthesis of a core-shell-structured catalyst constituting Cr-Zn oxide as the core and SAPO-34 as the shell for the conversion of syngas into hydrocarbons with high selectivity. A SiO2 layer was sandwiched between the core and the shell to prevent damage to the core during shell synthesis. Furthermore, the intermediate SiO2 layer acted as a Si source for the formation of the shell. The prepared catalyst displayed considerably higher selectivity toward the production of C2-C4 hydrocarbons (66.9%) than that of methanol and methane. The findings show the potential of the prepared core-shell-structured catalyst in the one-step production of hydrocarbons, such as liquefied petroleum gas, from syngas. However, further optimization of the catalyst is necessary to achieve higher performance.
Direct conversion of syngas into hydrocarbons with high selectivity remains a challenge. Herein, we report the synthesis of a core-shell-structured catalyst constituting Cr-Zn oxide as the core and SAPO-34 as the shell for the conversion of syngas into hydrocarbons with high selectivity. A SiO2 layer was sandwiched between the core and the shell to prevent damage to the core during shell synthesis. Furthermore, the intermediate SiO2 layer acted as a Si source for the formation of the shell. The prepared catalyst displayed considerably higher selectivity toward the production of C2-C4 hydrocarbons (66.9%) than that of methanol and methane. The findings show the potential of the prepared core-shell-structured catalyst in the one-step production of hydrocarbons, such as liquefied petroleum gas, from syngas. However, further optimization of the catalyst is necessary to achieve higher performance.
2015, 36(7): 1136-1141
doi: 10.1016/S1872-2067(14)60309-0
Abstract:
A mild and efficient protocol for the alkali carbonate-catalyzed one-pot synthesis of dimethyl carbonate (DMC) from epoxide, CO2 and methanol was developed. The reaction conditions for the one-pot synthesis of DMC were investigated. Under the optimized conditions of initial pressure 0.5 MPa, 120 ℃ and catalyst loading of 7.5 mol%, 63.5% yield of DMC was achieved using ethylene oxide as the starting material. A mechanism for the catalysis by the alkali carbonate was proposed.
A mild and efficient protocol for the alkali carbonate-catalyzed one-pot synthesis of dimethyl carbonate (DMC) from epoxide, CO2 and methanol was developed. The reaction conditions for the one-pot synthesis of DMC were investigated. Under the optimized conditions of initial pressure 0.5 MPa, 120 ℃ and catalyst loading of 7.5 mol%, 63.5% yield of DMC was achieved using ethylene oxide as the starting material. A mechanism for the catalysis by the alkali carbonate was proposed.
2015, 36(7): 1142-1154
doi: 10.1016/S1872-2067(14)60312-0
Abstract:
CeO2 nanotubes (CeO2-NT) were synthesized using carbon nanotubes as template by a liquid phase deposition and hydrothermal method. X-ray diffraction, transmission electron microscopy, and N2 adsorption-desorption were used to characterize the CeO2-NT. The wall of CeO2-NT was composed of small interconnected nanocrystallites ranging from 4 to 9 nm in size. The specific surface area of CeO2-NT was 108.8 m2/g with an outer diameter of 25 nm and length > 300 nm. Supported Pd catalyst, Pd-O/CeO2-NT, was prepared using CeO2-NT as the support. Temperature-programmed reduction analysis showed that the surface oxygen on Pd-O/CeO2-NT could be reduced at low temperature, therefore it showed high activity in the reaction. Pd-O/CeO2-NT was used as the catalyst for the oxidative carbonylation of phenol. It has better activity and DPC selectivity than Pd-O/CeO2-P, which was prepared by supporting Pd on zero dimensional CeO2 particles. Under the optimized conditions, phenol conversion was 67.7% with 93.3% DPC selectivity with Pd-O/CeO2-NT. However, its catalytic activity decreased when the catalyst was used for the second time. This was attributed to the destruction of the tubular structure of Pd-O/CeO2-NT and Pd leaching during the reaction.
CeO2 nanotubes (CeO2-NT) were synthesized using carbon nanotubes as template by a liquid phase deposition and hydrothermal method. X-ray diffraction, transmission electron microscopy, and N2 adsorption-desorption were used to characterize the CeO2-NT. The wall of CeO2-NT was composed of small interconnected nanocrystallites ranging from 4 to 9 nm in size. The specific surface area of CeO2-NT was 108.8 m2/g with an outer diameter of 25 nm and length > 300 nm. Supported Pd catalyst, Pd-O/CeO2-NT, was prepared using CeO2-NT as the support. Temperature-programmed reduction analysis showed that the surface oxygen on Pd-O/CeO2-NT could be reduced at low temperature, therefore it showed high activity in the reaction. Pd-O/CeO2-NT was used as the catalyst for the oxidative carbonylation of phenol. It has better activity and DPC selectivity than Pd-O/CeO2-P, which was prepared by supporting Pd on zero dimensional CeO2 particles. Under the optimized conditions, phenol conversion was 67.7% with 93.3% DPC selectivity with Pd-O/CeO2-NT. However, its catalytic activity decreased when the catalyst was used for the second time. This was attributed to the destruction of the tubular structure of Pd-O/CeO2-NT and Pd leaching during the reaction.
