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2015 Volume 36 Issue 5
2015, 36(5):
Abstract:
2015, 36(5): 683-691
doi: 10.1016/S1872-2067(14)60298-9
Abstract:
2015, 36(5): 692-697
doi: 10.1016/S1872-2067(15)60838-5
Abstract:
2015, 36(5): 698-704
doi: 10.1016/S1872-2067(14)60320-X
Abstract:
A sol-gel method was used to prepare TiO2 and sulfur-TiO2 (S-TiO2) nanocomposites, which were characterized by N2 adsorption-desorption, X-ray diffraction, X-ray photoelectron spectroscopy, photoluminescene, ultraviolet visible and transmission electron microscopy measurements. The photocatalytic performance of TiO2 and S-TiO2 nanocomposites, with respect to the photocatalytic oxidation of cyanide under visible light irradiation, was determined. The results reveal that S is well dispersed on the surface of TiO2 nanoparticles. Additionally, the surface area of the S-TiO2 nanocomposites was observed to be smaller than that of the TiO2 nanoparticles because of blocked pores caused by doping with S. The S-TiO2 nanocomposite (0.3 wt% S) exhibited the lowest band gap and the highest photocatalytic activity in the oxidation of cyanide. The photocatalytic performance of S-TiO2 (0.3 wt% S) nanocomposites was stable, even after the fifth reuse of the nanoparticles for the oxidation of cyanide.
A sol-gel method was used to prepare TiO2 and sulfur-TiO2 (S-TiO2) nanocomposites, which were characterized by N2 adsorption-desorption, X-ray diffraction, X-ray photoelectron spectroscopy, photoluminescene, ultraviolet visible and transmission electron microscopy measurements. The photocatalytic performance of TiO2 and S-TiO2 nanocomposites, with respect to the photocatalytic oxidation of cyanide under visible light irradiation, was determined. The results reveal that S is well dispersed on the surface of TiO2 nanoparticles. Additionally, the surface area of the S-TiO2 nanocomposites was observed to be smaller than that of the TiO2 nanoparticles because of blocked pores caused by doping with S. The S-TiO2 nanocomposite (0.3 wt% S) exhibited the lowest band gap and the highest photocatalytic activity in the oxidation of cyanide. The photocatalytic performance of S-TiO2 (0.3 wt% S) nanocomposites was stable, even after the fifth reuse of the nanoparticles for the oxidation of cyanide.
2015, 36(5): 705-711
doi: 10.1016/S1872-2067(14)60316-8
Abstract:
We report the fabrication and characterization of a magnetically recyclable Fe3O4@Nico@Ag catalyst for reduction reactions in the liquid phase. Fe3O4 is a magnetic core and nicotinic acid was used as the linker for Ag. The characterization was done with X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, vibrating sample magnetometry (VSM), and ultraviolet-visible spectroscopy. VSM measurements proved the superparamagnetic property of the catalyst.
We report the fabrication and characterization of a magnetically recyclable Fe3O4@Nico@Ag catalyst for reduction reactions in the liquid phase. Fe3O4 is a magnetic core and nicotinic acid was used as the linker for Ag. The characterization was done with X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, vibrating sample magnetometry (VSM), and ultraviolet-visible spectroscopy. VSM measurements proved the superparamagnetic property of the catalyst.
2015, 36(5): 712-720
doi: 10.1016/S1872-2067(14)60313-2
Abstract:
Molybdenum-based catalysts supported on Al2O3 doped with Ni, Cu, or Fe oxide were synthesized and used in ethylbenzene dehydrogenation to produce styrene. The molybdenum oxide was supported using an unconventional route that combined the polymeric precursor method (Pechini) and wet impregnation on commercial alumina. The samples were characterized by X-ray diffraction (XRD), N2 adsorption-desorption isotherms, temperature-programmed reduction of H2 (H2-TPR), and thermogravimetric (TG) analysis. XRD results showed that the added metals were well dispersed on the alumina support. The addition of the metal oxide (Ni, Cu, or Fe) of 2 wt% by wet impregnation did not affect the texture of the support. TPR results indicated a synergistic effect between the dopant and molybdenum oxide. The catalytic tests showed ethylbenzene conversion of 28%-53% and styrene selectivity of 94%-97%, indicating that the addition of the dopant improved the catalytic performance, which was related to the redox mechanism. Molybdenum oxides play a fundamental role in the oxidative dehydrogenation of ethylbenzene to styrene by its redox and acid-base properties. The sample containing Cu showed an atypical result with increasing conversion during the reaction, which was due to metal reduction. The Ni-containing solid exhibited the highest amount of carbon deposited, shown by TG analysis after the catalytic test, which explained its lower catalytic stability and selectivity.
Molybdenum-based catalysts supported on Al2O3 doped with Ni, Cu, or Fe oxide were synthesized and used in ethylbenzene dehydrogenation to produce styrene. The molybdenum oxide was supported using an unconventional route that combined the polymeric precursor method (Pechini) and wet impregnation on commercial alumina. The samples were characterized by X-ray diffraction (XRD), N2 adsorption-desorption isotherms, temperature-programmed reduction of H2 (H2-TPR), and thermogravimetric (TG) analysis. XRD results showed that the added metals were well dispersed on the alumina support. The addition of the metal oxide (Ni, Cu, or Fe) of 2 wt% by wet impregnation did not affect the texture of the support. TPR results indicated a synergistic effect between the dopant and molybdenum oxide. The catalytic tests showed ethylbenzene conversion of 28%-53% and styrene selectivity of 94%-97%, indicating that the addition of the dopant improved the catalytic performance, which was related to the redox mechanism. Molybdenum oxides play a fundamental role in the oxidative dehydrogenation of ethylbenzene to styrene by its redox and acid-base properties. The sample containing Cu showed an atypical result with increasing conversion during the reaction, which was due to metal reduction. The Ni-containing solid exhibited the highest amount of carbon deposited, shown by TG analysis after the catalytic test, which explained its lower catalytic stability and selectivity.
2015, 36(5): 721-727
doi: 10.1016/S1872-2067(14)60314-4
Abstract:
The selective oxidation of styrene to benzaldehyde catalyzed by p-toluenesulfonic acid (p-TsOH) in the presence of activated carbon (AC) was investigated with H2O2 as the oxidant. The reaction parameters of reaction time, temperature, catalyst mass, and styrene/H2O2 molar ratios were evaluated. A strong promoting effect of AC on the p-TsOH/H2O2 system was observed. The appropriate ratio and amounts of AC and p-TsOH were an important factor. The acidity of p-TsOH does not play a significant role. p-TsOH reacted with H2O2 by a non-radical process to oxidize styrene. The function of the AC was to activate H2O2 and to help the p-TsOH/H2O2 system in styrene oxidation. The reduction of oxygen containing groups (-OH, -COOH) on AC by a high temperature treatment or introduction of -SO3H groups onto AC affected the styrene conversion. The -SO3H groups were more effective than the oxygen-containing groups on the AC in promoting styrene oxidation.
The selective oxidation of styrene to benzaldehyde catalyzed by p-toluenesulfonic acid (p-TsOH) in the presence of activated carbon (AC) was investigated with H2O2 as the oxidant. The reaction parameters of reaction time, temperature, catalyst mass, and styrene/H2O2 molar ratios were evaluated. A strong promoting effect of AC on the p-TsOH/H2O2 system was observed. The appropriate ratio and amounts of AC and p-TsOH were an important factor. The acidity of p-TsOH does not play a significant role. p-TsOH reacted with H2O2 by a non-radical process to oxidize styrene. The function of the AC was to activate H2O2 and to help the p-TsOH/H2O2 system in styrene oxidation. The reduction of oxygen containing groups (-OH, -COOH) on AC by a high temperature treatment or introduction of -SO3H groups onto AC affected the styrene conversion. The -SO3H groups were more effective than the oxygen-containing groups on the AC in promoting styrene oxidation.
2015, 36(5): 728-733
doi: 10.1016/S1872-2067(14)60307-7
Abstract:
4-(Succinimido)-1-butane sulfonic acid was shown to be an efficient and reusable Brönsted acid catalyst for the synthesis of pyrano[4,3-b]pyran derivatives using thermal and ultrasonic conditions. The catalyst was prepared by mixing succinimide and 1,4-butanesultone, which is simpler and safer than the preparation of succinimide sulfonic acid. This method has the advantages of high yield, clean reaction, simple methodology, and short reaction time. The catalyst can be recycled without loss of activity.
4-(Succinimido)-1-butane sulfonic acid was shown to be an efficient and reusable Brönsted acid catalyst for the synthesis of pyrano[4,3-b]pyran derivatives using thermal and ultrasonic conditions. The catalyst was prepared by mixing succinimide and 1,4-butanesultone, which is simpler and safer than the preparation of succinimide sulfonic acid. This method has the advantages of high yield, clean reaction, simple methodology, and short reaction time. The catalyst can be recycled without loss of activity.
2015, 36(5): 734-741
doi: 10.1016/S1872-2067(14)60304-1
Abstract:
A powerful and environmentally benign method has been developed for the one-pot synthesis of 4-substituted-1,5-benzodiazepines via the three-component reaction of a series of aldehydes with dimedone and o-phenylenediamine using [H-NMP][HSO4] as a Brönsted acidic ionic liquid catalyst under solvent-free conditions. The key benefits of this new method over existing techniques include high yields, the use of a green catalyst, short reaction times and facile catalyst separation.
A powerful and environmentally benign method has been developed for the one-pot synthesis of 4-substituted-1,5-benzodiazepines via the three-component reaction of a series of aldehydes with dimedone and o-phenylenediamine using [H-NMP][HSO4] as a Brönsted acidic ionic liquid catalyst under solvent-free conditions. The key benefits of this new method over existing techniques include high yields, the use of a green catalyst, short reaction times and facile catalyst separation.
2015, 36(5): 742-749
doi: 10.1016/S1872-2067(14)60305-3
Abstract:
Hollow microblocks of [Zn(anic)2], as a novel coordination compound, were synthesized using 2-aminonicotinic acid (Hanic) and zinc (II) nitrate tetrahydrate. The chemical composition of the zinc complex, ZnC12H10N4O4, was determined by Fourier transform infrared (FTIR) spectroscopy and elemental analysis. The synthesized zinc complex was used as a precursor to produce ZnO nanostructures by calcination at 550 ℃ for 4 h. Morphological studies by scanning electron microscopy and transmission electron microscopy revealed the formation of porous microbricks of ZnO nanoparticles. N2 adsorption-desorption analysis showed that the obtained ZnO microbricks possess a mesoporous structure with a surface area of 8.13 m²/g and a pore size of 22.6 nm. The X-ray diffraction pattern of the final product proved the formation of a pure ZnO composition with a hexagonal structure. Moreover, FTIR analyses showed that the 2-aminonicotinic acid ligand peaks were absent after the calcination step. Diffuse reflectance spectroscopy was used to determine the band gap energy of the produced ZnO and it was about 3.19 eV. To investigate the photocatalytic activity of the porous ZnO nanostructure, a series of photocatalytic tests were carried out to remove Congo red, as a representative toxic azo dye, from aqueous solution. The results show that the product can be used as an efficient photocatalyst for waste water treatment with high degradation efficiency.
Hollow microblocks of [Zn(anic)2], as a novel coordination compound, were synthesized using 2-aminonicotinic acid (Hanic) and zinc (II) nitrate tetrahydrate. The chemical composition of the zinc complex, ZnC12H10N4O4, was determined by Fourier transform infrared (FTIR) spectroscopy and elemental analysis. The synthesized zinc complex was used as a precursor to produce ZnO nanostructures by calcination at 550 ℃ for 4 h. Morphological studies by scanning electron microscopy and transmission electron microscopy revealed the formation of porous microbricks of ZnO nanoparticles. N2 adsorption-desorption analysis showed that the obtained ZnO microbricks possess a mesoporous structure with a surface area of 8.13 m²/g and a pore size of 22.6 nm. The X-ray diffraction pattern of the final product proved the formation of a pure ZnO composition with a hexagonal structure. Moreover, FTIR analyses showed that the 2-aminonicotinic acid ligand peaks were absent after the calcination step. Diffuse reflectance spectroscopy was used to determine the band gap energy of the produced ZnO and it was about 3.19 eV. To investigate the photocatalytic activity of the porous ZnO nanostructure, a series of photocatalytic tests were carried out to remove Congo red, as a representative toxic azo dye, from aqueous solution. The results show that the product can be used as an efficient photocatalyst for waste water treatment with high degradation efficiency.
2015, 36(5): 750-756
doi: 10.1016/S1872-2067(14)60294-1
Abstract:
Pt-Mo/SiO2 catalysts were prepared using impregnation-reduction methods. Mo-promoted Pt catalysts exhibit much higher water gas shift reaction activity at low temperatures than Pt/SiO2 catalysts. Various characterization methods including inductive coupled plasma atomic emission spectrometry, X-ray diffraction, transmission electron microscopy, X-ray absorption near edge spectrum, and X-ray photoelectron spectroscopy were applied to investigate the composition, structure and chemical state of the Pt-Mo/SiO2 catalysts. Our results indicate that the added Mo species effectively improves the dispersion of Pt nanoparticles and the synergistic effect between the Pt nanoparticles and surface MoOx species enhances the catalytic performance for the water gas shift reaction. Pt nanoparticles decorated with highly dispersed MoOx patches are found to be the active architecture.
Pt-Mo/SiO2 catalysts were prepared using impregnation-reduction methods. Mo-promoted Pt catalysts exhibit much higher water gas shift reaction activity at low temperatures than Pt/SiO2 catalysts. Various characterization methods including inductive coupled plasma atomic emission spectrometry, X-ray diffraction, transmission electron microscopy, X-ray absorption near edge spectrum, and X-ray photoelectron spectroscopy were applied to investigate the composition, structure and chemical state of the Pt-Mo/SiO2 catalysts. Our results indicate that the added Mo species effectively improves the dispersion of Pt nanoparticles and the synergistic effect between the Pt nanoparticles and surface MoOx species enhances the catalytic performance for the water gas shift reaction. Pt nanoparticles decorated with highly dispersed MoOx patches are found to be the active architecture.
2015, 36(5): 757-763
doi: 10.1016/S1872-2067(14)60302-8
Abstract:
Fructose was used as an efficient catalyst for three-component condensation reactions of aryl aldehydes, malononitrile, and dimedone in a mixture of EtOH and H2O as green solvents. The advantages of this method are a short reaction time, high yields, low cost, easy accesses, and simple work-up. The mechanism of the synthesis of a derivative of 4H-tetrahydrobenzo[b]pyran was clarified using spectroscopic kinetic methods. The activation energy (Ea = 65.34 kJ/mol) and related kinetic parameters (ΔG‡ = 69.14 kJ/mol, ΔS‡ = 20.99 J/(mol·K), and ΔH‡ = 62.89 kJ/mol) were calculated, based on the effects of temperature, concentration, and solvent. The first step in the proposed mechanism was identified as the rate-determining step (k1), based on the steady-state approximation.
Fructose was used as an efficient catalyst for three-component condensation reactions of aryl aldehydes, malononitrile, and dimedone in a mixture of EtOH and H2O as green solvents. The advantages of this method are a short reaction time, high yields, low cost, easy accesses, and simple work-up. The mechanism of the synthesis of a derivative of 4H-tetrahydrobenzo[b]pyran was clarified using spectroscopic kinetic methods. The activation energy (Ea = 65.34 kJ/mol) and related kinetic parameters (ΔG‡ = 69.14 kJ/mol, ΔS‡ = 20.99 J/(mol·K), and ΔH‡ = 62.89 kJ/mol) were calculated, based on the effects of temperature, concentration, and solvent. The first step in the proposed mechanism was identified as the rate-determining step (k1), based on the steady-state approximation.
2015, 36(5): 764-770
doi: 10.1016/S1872-2067(14)60293-X
Abstract:
The -ONNO- tetradentate Schiff base ligand N,N'-bis(2-hydroxy-3-methoxybenzaldehyde)benzene-1,2-diamine (HMBBD) has been synthesized. The ligand was attached to copper (Cu-HMBBD) in methanol under N2 atmosphere to give a mononuclear complex. The reactivity of this complex in the ring-opening polymerization (ROP) of lactide has been studied. The complex has a square planner geometry, as determined by X-ray diffraction studies. The copper complex is highly active towards the ring-opening polymerization of lactide, and the rate of polymerization is heavily dependent on the initiator used. The copper complex allows controlled ring-opening polymerization, as shown by the linear relationship between the percentage conversion and the number average molecular weight. Based on the literature, a mechanism for the ROP of lactide has been proposed.
The -ONNO- tetradentate Schiff base ligand N,N'-bis(2-hydroxy-3-methoxybenzaldehyde)benzene-1,2-diamine (HMBBD) has been synthesized. The ligand was attached to copper (Cu-HMBBD) in methanol under N2 atmosphere to give a mononuclear complex. The reactivity of this complex in the ring-opening polymerization (ROP) of lactide has been studied. The complex has a square planner geometry, as determined by X-ray diffraction studies. The copper complex is highly active towards the ring-opening polymerization of lactide, and the rate of polymerization is heavily dependent on the initiator used. The copper complex allows controlled ring-opening polymerization, as shown by the linear relationship between the percentage conversion and the number average molecular weight. Based on the literature, a mechanism for the ROP of lactide has been proposed.
2015, 36(5): 771-777
doi: 10.1016/S1872-2067(14)60282-5
Abstract:
A new heterogeneous catalyst composed of Pd nanoparticles immobilized within a HypoGel resin has been prepared in the absence of any ligands using an extensive cross-linking method. This newly developed nanocatalyst was characterized by N2 adsorption-desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Fourier transform infrared spectroscopy and inductively coupled plasma-mass spectrometer (ICP-MS) techniques. TEM and XRD results revealed that the Pd nanoparticles were well dispersed with diameters in the range of 4-12 nm, and an average size of about 8 nm. The cross-linked Pd catalyst demonstrated excellent catalytic activity towards the synthesis of a series of biaryl compounds by the reaction of various aryl halides (e.g., bromides andiodides) with phenylboronic acid in the presence of tetrabutylammonium bromide. ICP-MS analysis indicated that there was only 0.25% weight loss of Pd (0.55 ± 0.02 ppm) from the supported catalyst after the first cycle reaction. Furthermore, the catalyst showed excellent reusability (up to five uses) with consistently high levels of catalytic activity following its recovery by filtration.
A new heterogeneous catalyst composed of Pd nanoparticles immobilized within a HypoGel resin has been prepared in the absence of any ligands using an extensive cross-linking method. This newly developed nanocatalyst was characterized by N2 adsorption-desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Fourier transform infrared spectroscopy and inductively coupled plasma-mass spectrometer (ICP-MS) techniques. TEM and XRD results revealed that the Pd nanoparticles were well dispersed with diameters in the range of 4-12 nm, and an average size of about 8 nm. The cross-linked Pd catalyst demonstrated excellent catalytic activity towards the synthesis of a series of biaryl compounds by the reaction of various aryl halides (e.g., bromides andiodides) with phenylboronic acid in the presence of tetrabutylammonium bromide. ICP-MS analysis indicated that there was only 0.25% weight loss of Pd (0.55 ± 0.02 ppm) from the supported catalyst after the first cycle reaction. Furthermore, the catalyst showed excellent reusability (up to five uses) with consistently high levels of catalytic activity following its recovery by filtration.
2015, 36(5): 778-784
doi: 10.1016/S1872-2067(14)60281-3
Abstract:
Magnetite nanoparticles coated with sulfuric acid-functionalized mesoporous MCM-48 were synthesized and used as a catalyst in three-component domino reactions of indoles, arylglyoxal monohydrates and N-arylenaminones to furnish the desired 3,3'-bisindoles by formation of two C-C and one C-N bonds in a smooth cascade with good yields under mild reaction conditions. The catalyst was recovered easily and maintained activity in successive runs.
Magnetite nanoparticles coated with sulfuric acid-functionalized mesoporous MCM-48 were synthesized and used as a catalyst in three-component domino reactions of indoles, arylglyoxal monohydrates and N-arylenaminones to furnish the desired 3,3'-bisindoles by formation of two C-C and one C-N bonds in a smooth cascade with good yields under mild reaction conditions. The catalyst was recovered easily and maintained activity in successive runs.
