Login In
2014 Volume 35 Issue 12
2014, 35(12):
Abstract:
2014, 35(12): 1911-1916
doi: 10.1016/S1872-2067(14)60208-4
Abstract:
The catalytic conversion of non-activated primary aliphatic alcohols to aldehydes is a challenge, and monometallic Cu-based catalysts loaded on different supports have often been used for these reactions. Cu-Ni/γ-Al2O3 bimetallic catalysts were prepared and used for anaerobic dehydrogenation of 3,3-dimethyl-1-butanol to 3,3-dimethyl-1-butanal. These catalysts exhibited higher activity than Cu/γ-Al2O3 under the same reaction conditions, and a wide range of primary aliphatic alcohols were efficiently converted to the corresponding aldehydes over Cu-Ni/γ-Al2O3 under mild conditions.
The catalytic conversion of non-activated primary aliphatic alcohols to aldehydes is a challenge, and monometallic Cu-based catalysts loaded on different supports have often been used for these reactions. Cu-Ni/γ-Al2O3 bimetallic catalysts were prepared and used for anaerobic dehydrogenation of 3,3-dimethyl-1-butanol to 3,3-dimethyl-1-butanal. These catalysts exhibited higher activity than Cu/γ-Al2O3 under the same reaction conditions, and a wide range of primary aliphatic alcohols were efficiently converted to the corresponding aldehydes over Cu-Ni/γ-Al2O3 under mild conditions.
2014, 35(12): 1917-1920
doi: 10.1016/S1872-2067(14)60216-3
Abstract:
The use of athermoregulated phase-transfer Rh nanoparticle catalyst for the selective hydrogenation of ortho-chloronitrobenzene (o-CNB) to ortho-chloroaniline (o-CAN) in an aqueous/1-pentanol biphasic system was studied. Under the optimized reaction conditions, the conversion of o-CNB and the selectivity for o-CAN were 100% and 98%, respectively. The catalyst was easily separated from the product by phase separation and reused eight times without evident loss of activity and selectivity.
The use of athermoregulated phase-transfer Rh nanoparticle catalyst for the selective hydrogenation of ortho-chloronitrobenzene (o-CNB) to ortho-chloroaniline (o-CAN) in an aqueous/1-pentanol biphasic system was studied. Under the optimized reaction conditions, the conversion of o-CNB and the selectivity for o-CAN were 100% and 98%, respectively. The catalyst was easily separated from the product by phase separation and reused eight times without evident loss of activity and selectivity.
2014, 35(12): 1921-1926
doi: 10.1016/S1872-2067(14)60224-2
Abstract:
A palladium nanoparticle (PdNPs) catalyst was synthesized in halogen-free anion ionic liquid (1-buthyl-3-methylimidazolium lactate, [Bmim]Lac) by a simple chemical approach. The transmission electron microscopy analysis confirmed the presence of highly dispersed PdNPs in [Bmim]Lac with small average particle size distribution from 2.2 to 3.1 nm. The size of the PdNPs increases with decreasing molar ratio of [Bmim]Lac to Pd(OAc)2 and increasing temperature. The activity of PdNPs@[Bmim]Lac catalyst was tested by the Heck-Mizoroki reaction, and the conditions were optimized. The catalyst can efficiently catalyze couplings of various aryl bromides and iodides with different olefins, giving good yields of products under the optimal conditions and be recycled up to six consecutive times.
A palladium nanoparticle (PdNPs) catalyst was synthesized in halogen-free anion ionic liquid (1-buthyl-3-methylimidazolium lactate, [Bmim]Lac) by a simple chemical approach. The transmission electron microscopy analysis confirmed the presence of highly dispersed PdNPs in [Bmim]Lac with small average particle size distribution from 2.2 to 3.1 nm. The size of the PdNPs increases with decreasing molar ratio of [Bmim]Lac to Pd(OAc)2 and increasing temperature. The activity of PdNPs@[Bmim]Lac catalyst was tested by the Heck-Mizoroki reaction, and the conditions were optimized. The catalyst can efficiently catalyze couplings of various aryl bromides and iodides with different olefins, giving good yields of products under the optimal conditions and be recycled up to six consecutive times.
2014, 35(12): 1927-1936
doi: 10.1016/S1872-2067(14)60129-7
Abstract:
Hydroxyapatite (HAP) was modified by adding various organic molecules, such as cetyltrimethylammonium bromide, sodium dodecyl sulfate, and sodium citrate, during the precipitation of HAP. Sodium citrate-modified HAP displayed the best activity for formaldehyde oxidation, achieving complete conversion at 240 ℃. The influence of the organic modifiers on the structure of HAP was assessed by X-ray diffraction, Fourier transform infrared spectroscopy, N2 adsorption- desorption, scanning electron microscopy, and thermogravimetry/derivative thermogravimetry. The higher specific surface area and pore volume, and smaller pores, owing to modification with sodium citrate, favored adsorption, mass transfer, and interaction process during formaldehyde oxidation. Furthermore, the higher hydroxyl group content observed in sodium citrate- modified HAP enhanced interactions between formaldehyde and HAP, thus resulting in higher catalytic activity.
Hydroxyapatite (HAP) was modified by adding various organic molecules, such as cetyltrimethylammonium bromide, sodium dodecyl sulfate, and sodium citrate, during the precipitation of HAP. Sodium citrate-modified HAP displayed the best activity for formaldehyde oxidation, achieving complete conversion at 240 ℃. The influence of the organic modifiers on the structure of HAP was assessed by X-ray diffraction, Fourier transform infrared spectroscopy, N2 adsorption- desorption, scanning electron microscopy, and thermogravimetry/derivative thermogravimetry. The higher specific surface area and pore volume, and smaller pores, owing to modification with sodium citrate, favored adsorption, mass transfer, and interaction process during formaldehyde oxidation. Furthermore, the higher hydroxyl group content observed in sodium citrate- modified HAP enhanced interactions between formaldehyde and HAP, thus resulting in higher catalytic activity.
2014, 35(12): 1937-1943
doi: 10.1016/S1872-2067(14)60169-8
Abstract:
We present here a density functional theory plus U study of NO reduction with CO, catalyzed by a single transition metal atom (TM1 = Zr1, Tc1, Ru1, Rh1, Pd1, Pt1)-doped CeO2(111). The catalytic center was identified as the TM dopant in combination with lattice oxygen. The investigation into N2 selectivity focused on three key elementary steps: gaseous N2O formation, subsequent re-adsorption, and N-O bond scission to produce N2. In these steps, Rh1, Pd1, and Pt1/CeO2(111) exhibit a higher selectivity, whereas the other systems (Zr1, Tc1, Ru1) TM1/CeO2 show a lower selectivity. The higher selectivity displayed by Pt1, Pd1, and Rh1 dopants arises from the availability of valence d electrons, which permit the formation of strong chemical bonds with the reactants and intermediates. Calculated results agree well with experimental findings, and the insights gained can be used to guide the rational design of the doped oxides for catalysis.
We present here a density functional theory plus U study of NO reduction with CO, catalyzed by a single transition metal atom (TM1 = Zr1, Tc1, Ru1, Rh1, Pd1, Pt1)-doped CeO2(111). The catalytic center was identified as the TM dopant in combination with lattice oxygen. The investigation into N2 selectivity focused on three key elementary steps: gaseous N2O formation, subsequent re-adsorption, and N-O bond scission to produce N2. In these steps, Rh1, Pd1, and Pt1/CeO2(111) exhibit a higher selectivity, whereas the other systems (Zr1, Tc1, Ru1) TM1/CeO2 show a lower selectivity. The higher selectivity displayed by Pt1, Pd1, and Rh1 dopants arises from the availability of valence d electrons, which permit the formation of strong chemical bonds with the reactants and intermediates. Calculated results agree well with experimental findings, and the insights gained can be used to guide the rational design of the doped oxides for catalysis.
2014, 35(12): 1944-1954
doi: 10.1016/S1872-2067(14)60181-9
Abstract:
Mixed Ga-Zn oxynitrides were synthesized using coprecipitation, wet-precipitation, and solid-solution methods. The oxynitrides were used as supports for Rh nanoparticle catalysts in photocatalytic water splitting, CO oxidation, and H2 oxidation. Mixed Ga-Zn oxynitrides produced by wet precipitation and nitridation had good visible-light-absorption properties and high surface areas, so they were used to support uniformly sized poly(vinylpyrrolidone)-stabilized Rh nanoparticles. The nanoparticle size range was 2-9 nm. These catalysts had negligible activity in photocatalytic H2 production by water splitting with methanol as a sacrificial agent. Other mixed Ga-Zn oxynitrides were also inactive. A reference sample provided by Domen also showed very low activity. The influence of particle size on Rh-catalyzed oxidation of CO and H2 was investigated. For CO oxidation, the activities of small particles were higher for particles with higher Rh oxidation degrees. The opposite holds for H2 oxidation.
Mixed Ga-Zn oxynitrides were synthesized using coprecipitation, wet-precipitation, and solid-solution methods. The oxynitrides were used as supports for Rh nanoparticle catalysts in photocatalytic water splitting, CO oxidation, and H2 oxidation. Mixed Ga-Zn oxynitrides produced by wet precipitation and nitridation had good visible-light-absorption properties and high surface areas, so they were used to support uniformly sized poly(vinylpyrrolidone)-stabilized Rh nanoparticles. The nanoparticle size range was 2-9 nm. These catalysts had negligible activity in photocatalytic H2 production by water splitting with methanol as a sacrificial agent. Other mixed Ga-Zn oxynitrides were also inactive. A reference sample provided by Domen also showed very low activity. The influence of particle size on Rh-catalyzed oxidation of CO and H2 was investigated. For CO oxidation, the activities of small particles were higher for particles with higher Rh oxidation degrees. The opposite holds for H2 oxidation.
2014, 35(12): 1955-1971
doi: 10.1016/S1872-2067(14)60171-6
Abstract:
Ni-Mg-Al solid basic catalysts for CO2 reforming of CH4 were prepared using a surfactant-assisted coprecipitation method. The preferred orientations of the surfactants on the Ni(111) and Ni(200) crystal planes were investigated. The catalytic performance of the surfactant-modified catalysts was tested at 800 ℃. The cetyltrimethylammonium bromide (CTAB)-modified catalyst (CB-LDO; LDO = layered double oxide) was further studied at various reaction temperatures. All the catalysts were characterized using Fourier-transform infrared spectroscopy, X-ray diffraction, temperature- programmed reduction, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and temperature-programmed oxidation. The results show that growth of the Ni(200) plane is promoted by tetrapropylammonium hydroxide and restrained by P123, PVP, and CTAB. The crystallinity degree of Ni(200) plays a key role in the activation of CH4. The CB-LDO catalysts retain high activities and stabilities, because of the crystal phase transformation at high temperature during the reaction; this leads to the formation of spinel NiAl2O4 and exposure of the Ni(200) crystal plane.
Ni-Mg-Al solid basic catalysts for CO2 reforming of CH4 were prepared using a surfactant-assisted coprecipitation method. The preferred orientations of the surfactants on the Ni(111) and Ni(200) crystal planes were investigated. The catalytic performance of the surfactant-modified catalysts was tested at 800 ℃. The cetyltrimethylammonium bromide (CTAB)-modified catalyst (CB-LDO; LDO = layered double oxide) was further studied at various reaction temperatures. All the catalysts were characterized using Fourier-transform infrared spectroscopy, X-ray diffraction, temperature- programmed reduction, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and temperature-programmed oxidation. The results show that growth of the Ni(200) plane is promoted by tetrapropylammonium hydroxide and restrained by P123, PVP, and CTAB. The crystallinity degree of Ni(200) plays a key role in the activation of CH4. The CB-LDO catalysts retain high activities and stabilities, because of the crystal phase transformation at high temperature during the reaction; this leads to the formation of spinel NiAl2O4 and exposure of the Ni(200) crystal plane.
2014, 35(12): 1972-1981
doi: 10.1016/S1872-2067(14)60184-4
Abstract:
The effects of aggregated Fe oxo (FeOx) species on N2O decomposition activity of aqueous ion-exchanged Fe/ZSM-5 were investigated. Aggregation of FeOx species was achieved by thermal treatment of the Fe/ZSM-5 catalysts at different temperatures (600-900 ℃) in pure Ar. The characterizations were carried out using X-ray diffraction, N2 physisorption, UV-Vis diffuse reflectance spectroscopy, X-ray absorption fine structure spectroscopy, pulse-response analysis, and O2-temperature-programmed desorption. The FeOx species on the external framework of the ZMS-5 zeolite played a dominant role in N2O decomposition over Fe/ZSM-5. By studying the relationship between the contents of the various existing iron species and activity of the different catalysts, polynuclear FeOx appeared to be the main active phase for N2O decomposition. Additionally, Fe-O with a long bond length ((Fe-O)2) in amorphous polynuclear FeOx was positively correlated to the activity of the catalysts, indicating that (Fe-O)2 was the active species for N2O decomposition.
The effects of aggregated Fe oxo (FeOx) species on N2O decomposition activity of aqueous ion-exchanged Fe/ZSM-5 were investigated. Aggregation of FeOx species was achieved by thermal treatment of the Fe/ZSM-5 catalysts at different temperatures (600-900 ℃) in pure Ar. The characterizations were carried out using X-ray diffraction, N2 physisorption, UV-Vis diffuse reflectance spectroscopy, X-ray absorption fine structure spectroscopy, pulse-response analysis, and O2-temperature-programmed desorption. The FeOx species on the external framework of the ZMS-5 zeolite played a dominant role in N2O decomposition over Fe/ZSM-5. By studying the relationship between the contents of the various existing iron species and activity of the different catalysts, polynuclear FeOx appeared to be the main active phase for N2O decomposition. Additionally, Fe-O with a long bond length ((Fe-O)2) in amorphous polynuclear FeOx was positively correlated to the activity of the catalysts, indicating that (Fe-O)2 was the active species for N2O decomposition.
2014, 35(12): 1982-1989
doi: 10.1016/S1872-2067(14)60185-6
Abstract:
Copper zirconium phosphate nanoparticles have been used as an efficient catalyst for the acetylation of a wide range of alcohols and phenols with acetic anhydride in good to excellent yields under solvent-free conditions. The steric and electronic properties of the different substrates had a significant influence on the reaction conditions required to achieve the acetylation. The catalyst used in the current study was characterized by inductively-coupled plasma optical emission spectroscopy, energy dispersive spectroscopy, X-ray diffraction, N2 adsorption-desorption, scanning electron microscopy, and transmission electron microscopy. These analyses revealed that the interlayer distance in the catalyst increased from 7.5 to 8.0 Å when Cu2+ was intercalated between the layers, whereas the crystallinity of the material was reduced. This nanocatalyst could also be recovered and reused at least six times without any discernible decrease in its catalytic activity. This new method for the acetylation of alcohols and phenols has several key advantages, including mild and environmentally friendly reaction conditions, as well as good to excellent yields and a facile work-up.
Copper zirconium phosphate nanoparticles have been used as an efficient catalyst for the acetylation of a wide range of alcohols and phenols with acetic anhydride in good to excellent yields under solvent-free conditions. The steric and electronic properties of the different substrates had a significant influence on the reaction conditions required to achieve the acetylation. The catalyst used in the current study was characterized by inductively-coupled plasma optical emission spectroscopy, energy dispersive spectroscopy, X-ray diffraction, N2 adsorption-desorption, scanning electron microscopy, and transmission electron microscopy. These analyses revealed that the interlayer distance in the catalyst increased from 7.5 to 8.0 Å when Cu2+ was intercalated between the layers, whereas the crystallinity of the material was reduced. This nanocatalyst could also be recovered and reused at least six times without any discernible decrease in its catalytic activity. This new method for the acetylation of alcohols and phenols has several key advantages, including mild and environmentally friendly reaction conditions, as well as good to excellent yields and a facile work-up.
2014, 35(12): 1990-1996
doi: 10.1016/S1872-2067(14)60190-X
Abstract:
Pd nanoparticles were immobilized on a tubular ceramic membrane support. The support surface was functionalized by N-(β-aminoethyl)-γ-aminopropyl trimethoxy silane (AAPTS), which contains two amino groups. The Pd-immobilized ceramic membrane support was characterized by X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, inductively coupled plasma emission spectroscopy, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. Its catalytic properties were investigated by the liquid phase hydrogenation of p-nitrophenol to p-aminophenol. The Pd-immobilized ceramic membrane support was compared with the Pd nanoparticles immobilized on a similar support functionalized by γ-amino-propyltriethoxy silane (3-APTS), which contains one amino group. Higher catalytic activity and stability were observed for the AAPTS-functionalized support. AAPTS contains twice as many amino groups as 3-APTS, and consequently exhibited a stronger electron-donating effect toward Pd. The AAPTS-functionalized ceramic membrane support contained more immobilized Pd nanoparticles, which were bound more strongly. This led to a higher catalytic activity and stability.
Pd nanoparticles were immobilized on a tubular ceramic membrane support. The support surface was functionalized by N-(β-aminoethyl)-γ-aminopropyl trimethoxy silane (AAPTS), which contains two amino groups. The Pd-immobilized ceramic membrane support was characterized by X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, inductively coupled plasma emission spectroscopy, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. Its catalytic properties were investigated by the liquid phase hydrogenation of p-nitrophenol to p-aminophenol. The Pd-immobilized ceramic membrane support was compared with the Pd nanoparticles immobilized on a similar support functionalized by γ-amino-propyltriethoxy silane (3-APTS), which contains one amino group. Higher catalytic activity and stability were observed for the AAPTS-functionalized support. AAPTS contains twice as many amino groups as 3-APTS, and consequently exhibited a stronger electron-donating effect toward Pd. The AAPTS-functionalized ceramic membrane support contained more immobilized Pd nanoparticles, which were bound more strongly. This led to a higher catalytic activity and stability.
2014, 35(12): 1997-2005
doi: 10.1016/S1872-2067(14)60198-4
Abstract:
Scale-like copper oxide (CuO)/tetrapod-like ZnO whisker (T-ZnOw) nanocomposites were fabricated using poly(ethylene glycol) (PEG; Mw = 400) as a soft template by a simple and environmentally friendly method without the use of hydroxide reagents at low temperatures. The structures and morphologies of the samples were investigated in detail, and the photocatalytic properties of the samples were determined using photoluminescence (PL) detection and the photocatalytic degradation of cationic pollutant (methylene blue, MB) and anionic pollutant (methyl orange, MO) aqueous solutions under ultraviolet (UV) irradiation. Large numbers of scale-like CuO nanoparticles were deposited on the T-ZnOw surfaces in an ordered fashion; the amount of scale-like CuO nanoparticles increased, and the arrangement became more ordered with increasing PEG 400 content. The PL emission peak intensities of the samples changed with increasing PEG 400 content. All the CuO/T-ZnOw nanocomposites showed excellent photocatalytic activities in the degradation of MB and MO aqueous solutions under UV irradiation when the PEG 400 concentration was less than or equal to 0.60 mol/L. The photocatalytic properties of the samples improved with increasing PEG400 concentration, but deteriorated when the PEG 400 concentration was increased further; this was reflected by the emission peak intensities in the PL spectra. The nanocomposites showed better efficiency for MB degradation than for MO degradation under the same conditions.
Scale-like copper oxide (CuO)/tetrapod-like ZnO whisker (T-ZnOw) nanocomposites were fabricated using poly(ethylene glycol) (PEG; Mw = 400) as a soft template by a simple and environmentally friendly method without the use of hydroxide reagents at low temperatures. The structures and morphologies of the samples were investigated in detail, and the photocatalytic properties of the samples were determined using photoluminescence (PL) detection and the photocatalytic degradation of cationic pollutant (methylene blue, MB) and anionic pollutant (methyl orange, MO) aqueous solutions under ultraviolet (UV) irradiation. Large numbers of scale-like CuO nanoparticles were deposited on the T-ZnOw surfaces in an ordered fashion; the amount of scale-like CuO nanoparticles increased, and the arrangement became more ordered with increasing PEG 400 content. The PL emission peak intensities of the samples changed with increasing PEG 400 content. All the CuO/T-ZnOw nanocomposites showed excellent photocatalytic activities in the degradation of MB and MO aqueous solutions under UV irradiation when the PEG 400 concentration was less than or equal to 0.60 mol/L. The photocatalytic properties of the samples improved with increasing PEG400 concentration, but deteriorated when the PEG 400 concentration was increased further; this was reflected by the emission peak intensities in the PL spectra. The nanocomposites showed better efficiency for MB degradation than for MO degradation under the same conditions.
2014, 35(12): 2006-2013
doi: 10.1016/S1872-2067(14)60195-9
Abstract:
The development of an economic and simple heterogeneous oyster shell waste supported CuCl2 catalyst for the aldehyde-alkyne-amine (A3) coupling reaction was reported. The waste oyster shell powder (OSP) supported CuCl2 (OSP-CuCl2) catalyst was prepared by a simple method from waste OSPs and CuCl2, which was shown to be a highly active and recyclable catalyst for the A3-coupling reaction. A range of propargylamines were obtained in good to excellent yields (85%-97%) under solvent-free and microwave-heated conditions. The OSP-CuCl2 catalyst can be simply recovered by filtration and reused for at least six runs. Propargylamine can be produced in 87% yield even when the scale of the A3-coupling reaction was increased to 150 mmol.
The development of an economic and simple heterogeneous oyster shell waste supported CuCl2 catalyst for the aldehyde-alkyne-amine (A3) coupling reaction was reported. The waste oyster shell powder (OSP) supported CuCl2 (OSP-CuCl2) catalyst was prepared by a simple method from waste OSPs and CuCl2, which was shown to be a highly active and recyclable catalyst for the A3-coupling reaction. A range of propargylamines were obtained in good to excellent yields (85%-97%) under solvent-free and microwave-heated conditions. The OSP-CuCl2 catalyst can be simply recovered by filtration and reused for at least six runs. Propargylamine can be produced in 87% yield even when the scale of the A3-coupling reaction was increased to 150 mmol.
2014, 35(12): 2014-2019
doi: 10.1016/S1872-2067(14)60210-2
Abstract:
A nanocomposite UV-visible light-responsive multiwalled carbon nanotube (MWCNT)/titanium dioxide (TiO2) nanophotocatalyst was successfully synthesized by a modified sol-gel method using titanium isopropoxide and functionalized MWCNTs as the starting precursors. The photocatalytic activity of the TiO2 and the nanohybrid material was investigated through the photodegradation of Reactive Black 5 dye under ultraviolet light irradiation. X-ray diffraction analysis indicated that anatase phase was obtained for both the pure TiO2 and the MWCNT/TiO2 composite, while Raman spectroscopy confirmed the presence of MWCNTs in the composite. Field emission scanning electron microscopy revealed that TiO2 nanoparticles with an individual diameter of about 10-20 nm were coated on the surface of the MWCNTs. The specific surface areas of the samples were found to be 80 and 181 m2/g for the pure TiO2 and MWCNT/TiO2, respectively. As a result, MWCNT/TiO2 showed better photocatalytic performance than pure TiO2 because the high surface area of MWCNTs enabled them to function as good electron acceptors for the retardation of electron-hole pair recombination.
A nanocomposite UV-visible light-responsive multiwalled carbon nanotube (MWCNT)/titanium dioxide (TiO2) nanophotocatalyst was successfully synthesized by a modified sol-gel method using titanium isopropoxide and functionalized MWCNTs as the starting precursors. The photocatalytic activity of the TiO2 and the nanohybrid material was investigated through the photodegradation of Reactive Black 5 dye under ultraviolet light irradiation. X-ray diffraction analysis indicated that anatase phase was obtained for both the pure TiO2 and the MWCNT/TiO2 composite, while Raman spectroscopy confirmed the presence of MWCNTs in the composite. Field emission scanning electron microscopy revealed that TiO2 nanoparticles with an individual diameter of about 10-20 nm were coated on the surface of the MWCNTs. The specific surface areas of the samples were found to be 80 and 181 m2/g for the pure TiO2 and MWCNT/TiO2, respectively. As a result, MWCNT/TiO2 showed better photocatalytic performance than pure TiO2 because the high surface area of MWCNTs enabled them to function as good electron acceptors for the retardation of electron-hole pair recombination.
2014, 35(12): 2020-2028
doi: 10.1016/S1872-2067(14)60218-7
Abstract:
V2O5/WO3-TiO2 catalysts were prepared by conventional impregnation (VWTi-con) and ultrasound-assisted impregnation methods (VWTi-HUST). Their catalytic performance was tested for the selective catalytic reduction (SCR) of NO with NH3. The effects of the preparation methods on the catalyst properties were studied. The catalysts were characterized by X-ray diffraction, scanning electron microscopy, Raman and X-ray photoelectron spectroscopy. Both structural investigation and NH3-SCR activity showed that the preparation method had a strong effect on the thermal behavior of the V2O5/WO3-TiO2 catalysts. After a hydrothermal treatment, a significant loss of NO reduction activity was observed for the VWTi-con catalyst, which suffered severe sintering and even formed a rutile VxTi1-xO2 solid solution, while the VWTi-HUST catalyst had the same good hydrothermal stability as a commercial catalyst, indicating that the VWTi-HUST catalyst can be used in a commercial diesel after-treatment system. The ultrasound-assisted impregnation method produced a stronger interaction between the vanadium species and WTi support, which stabilized the vanadium species in the reduced state.
V2O5/WO3-TiO2 catalysts were prepared by conventional impregnation (VWTi-con) and ultrasound-assisted impregnation methods (VWTi-HUST). Their catalytic performance was tested for the selective catalytic reduction (SCR) of NO with NH3. The effects of the preparation methods on the catalyst properties were studied. The catalysts were characterized by X-ray diffraction, scanning electron microscopy, Raman and X-ray photoelectron spectroscopy. Both structural investigation and NH3-SCR activity showed that the preparation method had a strong effect on the thermal behavior of the V2O5/WO3-TiO2 catalysts. After a hydrothermal treatment, a significant loss of NO reduction activity was observed for the VWTi-con catalyst, which suffered severe sintering and even formed a rutile VxTi1-xO2 solid solution, while the VWTi-HUST catalyst had the same good hydrothermal stability as a commercial catalyst, indicating that the VWTi-HUST catalyst can be used in a commercial diesel after-treatment system. The ultrasound-assisted impregnation method produced a stronger interaction between the vanadium species and WTi support, which stabilized the vanadium species in the reduced state.
2014, 35(12): 2029-2037
doi: 10.1016/S1872-2067(14)60232-1
Abstract:
Ultrafine and homogenously dispersed Pt3Co alloy nanoparticles were fabricated on reduced graphene oxide (RGO) in a few minutes under microwave irradiation. Characterization results confirmed that microwave irradiation was important for higher metal utilization, the easy control of alloy composition, improved dispersion of the Pt3Co particles and minimizing the re-graphitization of the parent RGO by comparison with conventional solvent-thermal and impregnation methods. This Pt3Co/RGO-MW catalyst was extremely active and selective during the hydrogenation of cinnamaldehyde to cinnamyl alcohol. The calculated specific activity of each Pt atom in the Pt3Co/RGO-MW at 70 ℃ was 23.8 min-1.
Ultrafine and homogenously dispersed Pt3Co alloy nanoparticles were fabricated on reduced graphene oxide (RGO) in a few minutes under microwave irradiation. Characterization results confirmed that microwave irradiation was important for higher metal utilization, the easy control of alloy composition, improved dispersion of the Pt3Co particles and minimizing the re-graphitization of the parent RGO by comparison with conventional solvent-thermal and impregnation methods. This Pt3Co/RGO-MW catalyst was extremely active and selective during the hydrogenation of cinnamaldehyde to cinnamyl alcohol. The calculated specific activity of each Pt atom in the Pt3Co/RGO-MW at 70 ℃ was 23.8 min-1.
