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2018 Volume 39 Issue 1
2018, 39(1):
Abstract:
2018, 39(1): 1-3
doi: 10.1016/S1872-2067(17)63002-X
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2018, 39(1): 4-7
doi: 10.1016/S1872-2067(17)62944-9
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2018, 39(1): 8-15
doi: 10.1016/S1872-2067(17)62933-4
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The construction of novel inorganic-organic hybrid nanomaterials for synchronous photocatalytic removal of heavy metal ions and organic pollutants has received significant attention. We successfully synthesized gold-loaded graphene oxide/PDPB (polymer poly(diphenylbutadiyne)) composites (Au-GO/PDPB) through a facile mechanical agitation and photoreduction method. The composites were characterized by XPS and TEM images, which confirmed the presence of GO and Au nanoparticles on the PDPB. The as-prepared Au-GO/PDPB composites displayed enhanced photocatalytic activity compared with that of pure PDPB for the synchronous photoreduction of hexavalent chromium (Cr(VI)) and photo-oxidation of phenol. We also determined the optimal loading mass of GO and Au nanoparticles on the PDPB; the Au1-GO2/PDPB (2.0 wt% GO and 1.0 wt% Au) composite displayed the best photocatalytic activity among all the catalysts. Our study provides a facile way to prepare inorganic-organic composites for the synchronous photocatalytic removal of heavy metal ions and organic pollutants.
The construction of novel inorganic-organic hybrid nanomaterials for synchronous photocatalytic removal of heavy metal ions and organic pollutants has received significant attention. We successfully synthesized gold-loaded graphene oxide/PDPB (polymer poly(diphenylbutadiyne)) composites (Au-GO/PDPB) through a facile mechanical agitation and photoreduction method. The composites were characterized by XPS and TEM images, which confirmed the presence of GO and Au nanoparticles on the PDPB. The as-prepared Au-GO/PDPB composites displayed enhanced photocatalytic activity compared with that of pure PDPB for the synchronous photoreduction of hexavalent chromium (Cr(VI)) and photo-oxidation of phenol. We also determined the optimal loading mass of GO and Au nanoparticles on the PDPB; the Au1-GO2/PDPB (2.0 wt% GO and 1.0 wt% Au) composite displayed the best photocatalytic activity among all the catalysts. Our study provides a facile way to prepare inorganic-organic composites for the synchronous photocatalytic removal of heavy metal ions and organic pollutants.
2018, 39(1): 16-26
doi: 10.1016/S1872-2067(17)62979-6
Abstract:
Growing concern regarding the sustainability of the chemical industry has driven the development of more efficient catalytic reactions. First-generation estimates of catalyst viability are based on crustal abundance, which has severe limitations. Herein, we propose a second-generation approach to predicting the viability of novel catalysts prior to industrial implementation to benefit the global chemical industry. Using this prediction, we found that a correlation exists between catalyst consumption and the annual production or price of the catalyst element for 11 representative industrial catalytic processes. Based on this correlation, we have introduced two new descriptors for catalyst viability, namely, catalyst consumption to availability ratio per annum (CCA) and consumed catalyst cost to product value ratio per annum (CCP). Based on evaluations of CCA and CCP for selected industrial reactions, we have grouped catalysts from the case studies according to viability, allowing the identification of general limits of viability based on CCA and CCP. Calculating the CCA and CCP and their comparing with the general limits of viability provides researchers with a novel framework for evaluating whether the cost or physical availability of a new catalyst could be limiting. We have extended this analysis to calculate the predicted limits of economically viable production and product cost for new catalysts.
Growing concern regarding the sustainability of the chemical industry has driven the development of more efficient catalytic reactions. First-generation estimates of catalyst viability are based on crustal abundance, which has severe limitations. Herein, we propose a second-generation approach to predicting the viability of novel catalysts prior to industrial implementation to benefit the global chemical industry. Using this prediction, we found that a correlation exists between catalyst consumption and the annual production or price of the catalyst element for 11 representative industrial catalytic processes. Based on this correlation, we have introduced two new descriptors for catalyst viability, namely, catalyst consumption to availability ratio per annum (CCA) and consumed catalyst cost to product value ratio per annum (CCP). Based on evaluations of CCA and CCP for selected industrial reactions, we have grouped catalysts from the case studies according to viability, allowing the identification of general limits of viability based on CCA and CCP. Calculating the CCA and CCP and their comparing with the general limits of viability provides researchers with a novel framework for evaluating whether the cost or physical availability of a new catalyst could be limiting. We have extended this analysis to calculate the predicted limits of economically viable production and product cost for new catalysts.
2018, 39(1): 27-36
doi: 10.1016/S1872-2067(17)62986-3
Abstract:
Mangenese oxides were synthesized using two new methods, a novel solvent-free reaction and a reflux technique, that produced cryptomelane-type products (K-OMS-2). Oxides were also synthesized using conventional methods and all specimens were applied to the oxidation of ethyl acetate and butyl acetate, acting as models for the volatile organic compounds found in industrial emissions. The catalysts were also characterized using N2 adsorption, X-ray diffraction, scanning electron microscopy, temperature programmed reduction and X-ray photoelectron spectroscopy. Each of the manganese oxides was found to be very active during the oxidation of both esters to CO2, and the synthesis methodology evidently had a significant impact on catalytic performance. The K-OMS-2 nanorods synthesized by the solvent-free method showed higher activity than K-OMS-2 materials prepared by the reflux technique, and samples with cryptomelane were more active than those prepared by the conventional methods. The catalyst with the highest performance also exhibited good stability and allowed 90% conversion of ethyl and butyl acetate to CO2 at 213 and 202℃, respectively. Significant differences in the catalyst performance were observed, clearly indicating that K-OMS-2 nanorods prepared by the solvent-free reaction were better catalysts for the selected VOC oxidations than the mixtures of manganese oxides traditionally obtained with conventional synthesis methods. The superior performance of the K-OMS-2 catalysts might be related to the increased average oxidation state of the manganese in these structures. Significant correlations between the catalytic performance and the surface chemical properties were also identified, highlighting the K-OMS-2 properties associated with the enhanced catalytic performance of the materials.
Mangenese oxides were synthesized using two new methods, a novel solvent-free reaction and a reflux technique, that produced cryptomelane-type products (K-OMS-2). Oxides were also synthesized using conventional methods and all specimens were applied to the oxidation of ethyl acetate and butyl acetate, acting as models for the volatile organic compounds found in industrial emissions. The catalysts were also characterized using N2 adsorption, X-ray diffraction, scanning electron microscopy, temperature programmed reduction and X-ray photoelectron spectroscopy. Each of the manganese oxides was found to be very active during the oxidation of both esters to CO2, and the synthesis methodology evidently had a significant impact on catalytic performance. The K-OMS-2 nanorods synthesized by the solvent-free method showed higher activity than K-OMS-2 materials prepared by the reflux technique, and samples with cryptomelane were more active than those prepared by the conventional methods. The catalyst with the highest performance also exhibited good stability and allowed 90% conversion of ethyl and butyl acetate to CO2 at 213 and 202℃, respectively. Significant differences in the catalyst performance were observed, clearly indicating that K-OMS-2 nanorods prepared by the solvent-free reaction were better catalysts for the selected VOC oxidations than the mixtures of manganese oxides traditionally obtained with conventional synthesis methods. The superior performance of the K-OMS-2 catalysts might be related to the increased average oxidation state of the manganese in these structures. Significant correlations between the catalytic performance and the surface chemical properties were also identified, highlighting the K-OMS-2 properties associated with the enhanced catalytic performance of the materials.
2018, 39(1): 37-46
doi: 10.1016/S1872-2067(17)62918-8
Abstract:
A novel route involving self-metathesis of 1-butene under mild conditions that gave high yields of ethene and hexene was proposed. The results of thermodynamic analysis revealed that the Gibbs energy of the target Metathesis I reaction (1-butene → ethene + 3-hexene) was much higher than that of the main side Metathesis II (1-butene + 2-butene → propene + 2-pentene). Suppression of 1-butene double-bond isomerization was the key step to increase the selectivity for the target olefin in the reaction network. The relationship between the catalytic performance and support nature was investigated in detail. On basis of H2-TPR, UV-Vis spectra and HRTEM results, an alumina (Al2O3) support with large surface area was beneficial for the dispersion of molybdenum (Mo) species. Both suitable acidity and sufficient Mo dispersion were important to selectively promote the self-metathesis reaction of 1-butene. On the optimal 6Mo/Al2O3 catalyst, 1-butene conversion reached 47% and ethene selectivity was as high as 42% on the premise of good catalytic stability (80℃, 1.0 MPa, 3 h-1).
A novel route involving self-metathesis of 1-butene under mild conditions that gave high yields of ethene and hexene was proposed. The results of thermodynamic analysis revealed that the Gibbs energy of the target Metathesis I reaction (1-butene → ethene + 3-hexene) was much higher than that of the main side Metathesis II (1-butene + 2-butene → propene + 2-pentene). Suppression of 1-butene double-bond isomerization was the key step to increase the selectivity for the target olefin in the reaction network. The relationship between the catalytic performance and support nature was investigated in detail. On basis of H2-TPR, UV-Vis spectra and HRTEM results, an alumina (Al2O3) support with large surface area was beneficial for the dispersion of molybdenum (Mo) species. Both suitable acidity and sufficient Mo dispersion were important to selectively promote the self-metathesis reaction of 1-butene. On the optimal 6Mo/Al2O3 catalyst, 1-butene conversion reached 47% and ethene selectivity was as high as 42% on the premise of good catalytic stability (80℃, 1.0 MPa, 3 h-1).
2018, 39(1): 47-53
doi: 10.1016/S1872-2067(17)62934-6
Abstract:
Paramagnetic polymer microspheres were synthesized by the inverse suspension polymerization method through polymerization of glycidyl methacrylate, ally glycidyl ether and methacrylamide on the surface of silica-coated Fe3O4 nanoparticles using N,N'-methylene-bis(acrylamide) as a cross-linking agent. Penicillin G acylase (PGA) was covalently immobilized on the surface of the paramagnetic microspheres by reacting the amino groups of the PGA molecules with the epoxy groups of the paramagnetic polymer microspheres. The effect of the SiO2 coating and the amount of paramagnetic Fe3O4 nanoparticles on the initial activity and the operational stability of the immobilized PGA was investigated. The results indicated that SiO2 played an important role in the polymerization process and paramagnetic polymer microspheres with a SiO2-coated Fe3O4 nanoparticles mass content of 7.5% are an optimal support material for PGA immobilization. Immobilized PGA on the paramagnetic polymer microspheres shows a high initial activity of 430 U/g (wet) and retains 99% of its initial activity after recycling 10 times. Furthermore, immobilized PGA exhibits high thermal stability, pH stability and excellent reusability, which can be rapidly recycled by the aid of magnet.
Paramagnetic polymer microspheres were synthesized by the inverse suspension polymerization method through polymerization of glycidyl methacrylate, ally glycidyl ether and methacrylamide on the surface of silica-coated Fe3O4 nanoparticles using N,N'-methylene-bis(acrylamide) as a cross-linking agent. Penicillin G acylase (PGA) was covalently immobilized on the surface of the paramagnetic microspheres by reacting the amino groups of the PGA molecules with the epoxy groups of the paramagnetic polymer microspheres. The effect of the SiO2 coating and the amount of paramagnetic Fe3O4 nanoparticles on the initial activity and the operational stability of the immobilized PGA was investigated. The results indicated that SiO2 played an important role in the polymerization process and paramagnetic polymer microspheres with a SiO2-coated Fe3O4 nanoparticles mass content of 7.5% are an optimal support material for PGA immobilization. Immobilized PGA on the paramagnetic polymer microspheres shows a high initial activity of 430 U/g (wet) and retains 99% of its initial activity after recycling 10 times. Furthermore, immobilized PGA exhibits high thermal stability, pH stability and excellent reusability, which can be rapidly recycled by the aid of magnet.
2018, 39(1): 54-62
doi: 10.1016/S1872-2067(17)62977-2
Abstract:
Well-aligned zinc oxide (ZnO) nanotube arrays loaded with tungsten trioxide (WO3) nanoparticles were synthesized by a process involving chemical bath deposition in combination with pyrolysis. The prepared ZnO-WO3 composites were characterized by X-ray diffraction, energy dispersive spectrometer, field emission scanning electron microscopy, X-ray photoelectron spectroscopy, photoluminescence spectroscopy, Fourier transform infrared spectroscopy and UV-vis diffuse reflectance spectroscopy. The photocatalytic activities of the ZnO-WO3 composite photocatalysts with different WO3 contents for the degradation of the herbicide chlorinated phenoxyacetic acid (MCPA-Na) under simulated sunlight irradiation were systematically evaluated. It was found that the WO3 content had a great effect on the photocatalytic activity of the ZnO-WO3 composites. The composite with 3% WO3 showed the highest photocatalytic activity, with a degradation rate of chlorinated phenoxyacetic acid of 98.5% after 200 min with 20 mg of photocatalyst. This photodegradation rate was about twice that of the pristine ZnO nanotube array. The recombination of photogenerated electrons and holes was increasingly suppressed with the addition of WO3 to ZnO. The high relative content of defects on the surface of the ZnO-WO3 composites was beneficial to their photocatalytic activity in the degradation of chlorinated phenoxyacetic acid.
Well-aligned zinc oxide (ZnO) nanotube arrays loaded with tungsten trioxide (WO3) nanoparticles were synthesized by a process involving chemical bath deposition in combination with pyrolysis. The prepared ZnO-WO3 composites were characterized by X-ray diffraction, energy dispersive spectrometer, field emission scanning electron microscopy, X-ray photoelectron spectroscopy, photoluminescence spectroscopy, Fourier transform infrared spectroscopy and UV-vis diffuse reflectance spectroscopy. The photocatalytic activities of the ZnO-WO3 composite photocatalysts with different WO3 contents for the degradation of the herbicide chlorinated phenoxyacetic acid (MCPA-Na) under simulated sunlight irradiation were systematically evaluated. It was found that the WO3 content had a great effect on the photocatalytic activity of the ZnO-WO3 composites. The composite with 3% WO3 showed the highest photocatalytic activity, with a degradation rate of chlorinated phenoxyacetic acid of 98.5% after 200 min with 20 mg of photocatalyst. This photodegradation rate was about twice that of the pristine ZnO nanotube array. The recombination of photogenerated electrons and holes was increasingly suppressed with the addition of WO3 to ZnO. The high relative content of defects on the surface of the ZnO-WO3 composites was beneficial to their photocatalytic activity in the degradation of chlorinated phenoxyacetic acid.
2018, 39(1): 71-78
doi: 10.1016/S1872-2067(17)62870-5
Abstract:
Silicon carbide (SiC) was used as a support for SSZ-13 zeolite in an attempt to improve the high-temperature stability and activity of Cu/SSZ-13 in the selective catalytic reduction (SCR) of NO with NH3. SSZ-13 was grown via a hydrothermal method using the silicon and silica contained in SiC as the source of silicon, which led to the formation of a chemically bonded SSZ-13 layer on SiC. Characterization using X-ray diffraction, scanning electron microscopy, and N2 adsorption-desorption isotherms revealed that the alkali content strongly affected the purity of zeolite and the crystallization time affected the coverage and crystallinity of the zeolite layer. Upon ion exchange, the resulting Cu/SSZ-13@SiC catalyst exhibited enhanced activity in NH3-SCR in the high-temperature region compared with the unsupported Cu/SSZ-13. Thus, the application temperature was extended with the use of SiC as the support.
Silicon carbide (SiC) was used as a support for SSZ-13 zeolite in an attempt to improve the high-temperature stability and activity of Cu/SSZ-13 in the selective catalytic reduction (SCR) of NO with NH3. SSZ-13 was grown via a hydrothermal method using the silicon and silica contained in SiC as the source of silicon, which led to the formation of a chemically bonded SSZ-13 layer on SiC. Characterization using X-ray diffraction, scanning electron microscopy, and N2 adsorption-desorption isotherms revealed that the alkali content strongly affected the purity of zeolite and the crystallization time affected the coverage and crystallinity of the zeolite layer. Upon ion exchange, the resulting Cu/SSZ-13@SiC catalyst exhibited enhanced activity in NH3-SCR in the high-temperature region compared with the unsupported Cu/SSZ-13. Thus, the application temperature was extended with the use of SiC as the support.
2018, 39(1): 79-87
doi: 10.1016/S1872-2067(17)62925-5
Abstract:
A highly efficient and reusable plane-curved and interlayer-expanded MoS2 nanocatalyst with increased exposure of active sites was prepared. The catalyst was used for the heterogeneous hydrogen transfer reaction of nitroarenes with hydrazine monohydrate as a reductant under mild reaction conditions without pressure and base, which was different from other hydrogen transfer systems that require the presence of a base (e.g., propan-2-ol/KOH). The sandwiching of carbon between the MoS2 nanosheets increased the distance between the layers of MoS2 and exposed more Mo sites, resulting in superior catalytic performance compared with that of bulk MoS2 catalyst. The active hydrogen (H*) generated from N2H4 could directly transfer to the -NO2 groups of nitrobenzene to form aniline followed by N2 emission, which was confirmed by detecting the gas emission with mass spectrometry during the decomposition of hydrazine or the co-existence of nitrobenzene and hydrazine.
A highly efficient and reusable plane-curved and interlayer-expanded MoS2 nanocatalyst with increased exposure of active sites was prepared. The catalyst was used for the heterogeneous hydrogen transfer reaction of nitroarenes with hydrazine monohydrate as a reductant under mild reaction conditions without pressure and base, which was different from other hydrogen transfer systems that require the presence of a base (e.g., propan-2-ol/KOH). The sandwiching of carbon between the MoS2 nanosheets increased the distance between the layers of MoS2 and exposed more Mo sites, resulting in superior catalytic performance compared with that of bulk MoS2 catalyst. The active hydrogen (H*) generated from N2H4 could directly transfer to the -NO2 groups of nitrobenzene to form aniline followed by N2 emission, which was confirmed by detecting the gas emission with mass spectrometry during the decomposition of hydrazine or the co-existence of nitrobenzene and hydrazine.
2018, 39(1): 88-98
doi: 10.1016/S1872-2067(17)62928-0
Abstract:
The CO2 reforming of CH4 is studied over MgO-promoted Ni catalysts, which were supported on alumina prepared from hydrotalcite. This presents an improved stability compared with non-promoted catalysts. The introduction of the MgO promoter was achieved through the "memory effect" of the Ni-Al hydrotalcite structure, and ICP-MS confirmed that only 0.42 wt.% of Mg2+ ions were added into the Ni-Mg/Al catalyst. Although no differences in the Ni particle size and basicity strength were observed, the Ni-Mg/Al catalyst showed a higher catalytic stability than the Ni/Al catalyst. A series of surface reaction experiments were used and showed that the addition of a MgO promoter with low concentration can promote CO2 dissociation to form active surface oxygen arising from the formation of the Ni-MgO interface sites. Therefore, the carbon-resistance promotion by nature was suggested to contribute to an oxidative environment around Ni particles, which would increase the conversion of carbon residues from CH4 cracking to yield CO on the Ni metal surface.
The CO2 reforming of CH4 is studied over MgO-promoted Ni catalysts, which were supported on alumina prepared from hydrotalcite. This presents an improved stability compared with non-promoted catalysts. The introduction of the MgO promoter was achieved through the "memory effect" of the Ni-Al hydrotalcite structure, and ICP-MS confirmed that only 0.42 wt.% of Mg2+ ions were added into the Ni-Mg/Al catalyst. Although no differences in the Ni particle size and basicity strength were observed, the Ni-Mg/Al catalyst showed a higher catalytic stability than the Ni/Al catalyst. A series of surface reaction experiments were used and showed that the addition of a MgO promoter with low concentration can promote CO2 dissociation to form active surface oxygen arising from the formation of the Ni-MgO interface sites. Therefore, the carbon-resistance promotion by nature was suggested to contribute to an oxidative environment around Ni particles, which would increase the conversion of carbon residues from CH4 cracking to yield CO on the Ni metal surface.
2018, 39(1): 99-108
doi: 10.1016/S1872-2067(17)62932-2
Abstract:
A series of indium oxide-modified Cu/SiO2 catalysts were synthesized and used to produce ethanol via methyl acetate hydrogenation. In-Cu/SiO2 catalyst containing 1.0 wt% In2O3 exhibited the best catalytic activity and stability. The physicochemical properties of the synthesized catalysts were investigated using several characterization methods and the results showed that introducing suitable indium to Cu/SiO2 increased the copper dispersion, diminished the copper crystallite size, and enriched the surface Cu+ concentration. Furthermore, the Cu/SiO2 catalyst gradually deactivated during the stability test, which was mainly attributed to copper sintering and the valence change in surface copper species. In contrast, indium addition can inhibit the thermal transmigration and accumulation of copper nanoparticles to stabilize the catalyst.
A series of indium oxide-modified Cu/SiO2 catalysts were synthesized and used to produce ethanol via methyl acetate hydrogenation. In-Cu/SiO2 catalyst containing 1.0 wt% In2O3 exhibited the best catalytic activity and stability. The physicochemical properties of the synthesized catalysts were investigated using several characterization methods and the results showed that introducing suitable indium to Cu/SiO2 increased the copper dispersion, diminished the copper crystallite size, and enriched the surface Cu+ concentration. Furthermore, the Cu/SiO2 catalyst gradually deactivated during the stability test, which was mainly attributed to copper sintering and the valence change in surface copper species. In contrast, indium addition can inhibit the thermal transmigration and accumulation of copper nanoparticles to stabilize the catalyst.
2018, 39(1): 118-127
doi: 10.1016/S1872-2067(17)62983-8
Abstract:
Two series of Mn/beta and Mn/ZSM-5 catalysts were prepared to study the influence of how different Mn precursors, introduced to the respective parent zeolites by wet impregnation, affected the selective catalytic reduction (SCR) of NO by NH3 across a low reaction temperature window of 50-350℃. In this study, the catalysts were characterized using N2 adsorption/desorption, X-ray diffraction, X-ray fluorescence, H2 temperature-programmed reduction, NH3 temperature-programmed desorption and X-ray photoelectron spectroscopy. As the manganese chloride precursor only partially decomposed this primarily resulted in the formation of MnCl2 in addition to the presence of low levels of crystalline Mn3O4, which resulted in poor catalytic performance. However, the manganese nitrate precursor formed crystalline MnO2 as the major phase in addition to a minor presence of unconverted Mn-nitrate. Furthermore, manganese acetate resulted principally in a mixture of amorphous Mn2O3 and MnO2, and crystalline Mn3O4. From all the catalysts screened, the test performance data showed Mn/beta-Ac to exhibit the highest NO conversion (97.5%) at 240℃, which remained >90% across a temperature window of 220-350℃. The excellent catalytic performance was ascribed to the enrichment of highly dispersed MnOx (Mn2O3 and MnO2) species that act as the active phase in the NH3-SCR process. Furthermore, together with a suitable amount of weakly acidic centers, higher concentration of surface manganese and a greater presence of surface labile oxygen groups, SCR performance was collectively enhanced at low temperature.
Two series of Mn/beta and Mn/ZSM-5 catalysts were prepared to study the influence of how different Mn precursors, introduced to the respective parent zeolites by wet impregnation, affected the selective catalytic reduction (SCR) of NO by NH3 across a low reaction temperature window of 50-350℃. In this study, the catalysts were characterized using N2 adsorption/desorption, X-ray diffraction, X-ray fluorescence, H2 temperature-programmed reduction, NH3 temperature-programmed desorption and X-ray photoelectron spectroscopy. As the manganese chloride precursor only partially decomposed this primarily resulted in the formation of MnCl2 in addition to the presence of low levels of crystalline Mn3O4, which resulted in poor catalytic performance. However, the manganese nitrate precursor formed crystalline MnO2 as the major phase in addition to a minor presence of unconverted Mn-nitrate. Furthermore, manganese acetate resulted principally in a mixture of amorphous Mn2O3 and MnO2, and crystalline Mn3O4. From all the catalysts screened, the test performance data showed Mn/beta-Ac to exhibit the highest NO conversion (97.5%) at 240℃, which remained >90% across a temperature window of 220-350℃. The excellent catalytic performance was ascribed to the enrichment of highly dispersed MnOx (Mn2O3 and MnO2) species that act as the active phase in the NH3-SCR process. Furthermore, together with a suitable amount of weakly acidic centers, higher concentration of surface manganese and a greater presence of surface labile oxygen groups, SCR performance was collectively enhanced at low temperature.
2018, 39(1): 128-137
doi: 10.1016/S1872-2067(17)62990-5
Abstract:
This study investigates the photodegradation of the organic dye rhodamine B by Ag-nanoparticle-containing BiVO4 catalysts under different irradiation conditions. The catalysts consist of Ag nanoparticles deposited on oxygen-vacancy-containing BiVO4. The morphology of the BiVO4 is olive shaped, and it has a uniform size distribution. The BiVO4 possesses a high oxygen vacancy density, and the resulting Ag nanoparticle-BiVO4 catalyst exhibits higher photocatalytic activity than BiVO4. The RhB degradation by the Ag nanoparticle-BiVO4 catalyst is 99% after 100 min of simulated solar irradiation. BiVO4 containing oxygen vacancies as a rationally designed support extends the catalyst response into the near-infrared region, and facilitates the trapping and transfer of plasmonic hot electrons. The enhanced photocatalytic efficiency is attributed to charge transfer from the BiVO4 to Ag nanoparticles, and surface plasmon resonance of the Ag nanoparticles. These insights into electron-hole separation and charge transfer may arouse interest in solar-driven wastewater treatment and water splitting.
This study investigates the photodegradation of the organic dye rhodamine B by Ag-nanoparticle-containing BiVO4 catalysts under different irradiation conditions. The catalysts consist of Ag nanoparticles deposited on oxygen-vacancy-containing BiVO4. The morphology of the BiVO4 is olive shaped, and it has a uniform size distribution. The BiVO4 possesses a high oxygen vacancy density, and the resulting Ag nanoparticle-BiVO4 catalyst exhibits higher photocatalytic activity than BiVO4. The RhB degradation by the Ag nanoparticle-BiVO4 catalyst is 99% after 100 min of simulated solar irradiation. BiVO4 containing oxygen vacancies as a rationally designed support extends the catalyst response into the near-infrared region, and facilitates the trapping and transfer of plasmonic hot electrons. The enhanced photocatalytic efficiency is attributed to charge transfer from the BiVO4 to Ag nanoparticles, and surface plasmon resonance of the Ag nanoparticles. These insights into electron-hole separation and charge transfer may arouse interest in solar-driven wastewater treatment and water splitting.
2018, 39(1): 138-145
doi: 10.1016/S1872-2067(17)62915-2
Abstract:
A novel nitrogen-centered radical-induced 1,2-carbon migration reaction of allylic alcohols has been developed. This method provides easy access to a variety of α-quaternary-β-amino ketones under mild reaction conditions. The reaction has a wide substrate scope and operational simplicity. Mechanistic studies suggest that 1,2-carbon migration is induced by regioselective nitrogen-centered radical addition to the alkene unit.
A novel nitrogen-centered radical-induced 1,2-carbon migration reaction of allylic alcohols has been developed. This method provides easy access to a variety of α-quaternary-β-amino ketones under mild reaction conditions. The reaction has a wide substrate scope and operational simplicity. Mechanistic studies suggest that 1,2-carbon migration is induced by regioselective nitrogen-centered radical addition to the alkene unit.
2018, 39(1): 146-156
doi: 10.1016/S1872-2067(17)62958-9
Abstract:
The carbonization process of a sucrose-RuCl3/SBA-15 composite towards a Ru-containing ordered mesoporous carbon (Ru-OMC) catalyst was studied by in situ temperature-programmed infrared spectroscopy to identify the stabilization role of organic carbon precursors during the formation of highly dispersed Ru nanoparticles. The results show that the formation of metal carbonyl species results in the formation of homogeneously distributed Ru nanoparticles, and the rigid silica support and carbon matrix around the Ru(CO)x complex can significantly avoid the sintering and agglomeration of Ru metal particles during elevated temperature thermal treatment. These results ultimately demonstrate that sucrose plays important roles in the formation of homogeneously distributed Ru nanoparticles in a porous carbon matrix.
The carbonization process of a sucrose-RuCl3/SBA-15 composite towards a Ru-containing ordered mesoporous carbon (Ru-OMC) catalyst was studied by in situ temperature-programmed infrared spectroscopy to identify the stabilization role of organic carbon precursors during the formation of highly dispersed Ru nanoparticles. The results show that the formation of metal carbonyl species results in the formation of homogeneously distributed Ru nanoparticles, and the rigid silica support and carbon matrix around the Ru(CO)x complex can significantly avoid the sintering and agglomeration of Ru metal particles during elevated temperature thermal treatment. These results ultimately demonstrate that sucrose plays important roles in the formation of homogeneously distributed Ru nanoparticles in a porous carbon matrix.
2018, 39(1): 157-166
doi: 10.1016/S1872-2067(17)62967-X
Abstract:
A series of Ru/FeOx catalysts were synthesized for the selective hydrogenation of CO2 to CO. Detailed characterizations of the catalysts through X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and temperature-programmed techniques were performed to directly monitor the surface chemical properties and the catalytic performance to elucidate the reaction mechanism. Highly dispersed Ru species were observed on the surface of FeOx regardless of the initial Ru loading. Varying the Ru loading resulted in changes to the Ru coverage over the FeOx surface, which had a significant impact on the interaction between Ru and adsorbed H, and concomitantly, the H2 activation capacity via the ability for H2 dissociation. FeOx having 0.01% of Ru loading exhibited 100% selectivity toward CO resulting from the very strong interaction between Ru and adsorbed H, which limits the desorption of the activated H species and hinders over-reduction of CO to CH4. Further increasing the Ru loading of the catalysts to above 0.01% resulted in the adsorbed H to be easily dissociated, as a result of a weaker interaction with Ru, which allowed excessive CO reduction to produce CH4. Understanding how to selectively design the catalyst by tuning the initial loading of the active phase has broader implications on the design of supported metal catalysts toward preparing liquid fuels from CO2.
A series of Ru/FeOx catalysts were synthesized for the selective hydrogenation of CO2 to CO. Detailed characterizations of the catalysts through X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and temperature-programmed techniques were performed to directly monitor the surface chemical properties and the catalytic performance to elucidate the reaction mechanism. Highly dispersed Ru species were observed on the surface of FeOx regardless of the initial Ru loading. Varying the Ru loading resulted in changes to the Ru coverage over the FeOx surface, which had a significant impact on the interaction between Ru and adsorbed H, and concomitantly, the H2 activation capacity via the ability for H2 dissociation. FeOx having 0.01% of Ru loading exhibited 100% selectivity toward CO resulting from the very strong interaction between Ru and adsorbed H, which limits the desorption of the activated H species and hinders over-reduction of CO to CH4. Further increasing the Ru loading of the catalysts to above 0.01% resulted in the adsorbed H to be easily dissociated, as a result of a weaker interaction with Ru, which allowed excessive CO reduction to produce CH4. Understanding how to selectively design the catalyst by tuning the initial loading of the active phase has broader implications on the design of supported metal catalysts toward preparing liquid fuels from CO2.
2018, 39(1): 167-180
doi: 10.1016/S1872-2067(17)62984-X
Abstract:
Hierarchical zeolite materials were prepared via one-pot synthesis of ZSM-11 zeolites with different molar ratios (R) of a mesoporogen, i.e., cetyltrimethylammonium bromide template (CTAB), to a microporogen, i.e., tetra-n-butylammonium bromide (TBABr). The structures, morphologies, and textural properties of the resultant materials were investigated. Initially, with increasing R, the crystal size of the synthesized product decreased, the number of intercrystalline mesopores increased, and a pure ZSM-11 zeolite phase was present. Then an MCM-41-like phase was produced and embedded in the ZSM-11 zeolite phase. Finally, an MCM-41-like phase was obtained. The alkalinity had important effects on the physicochemical and textural properties of the prepared samples. A possible mechanism of formation of the hierarchical ZSM-11 zeolite was proposed on the basis of a combination of various characterization results. The role of CTAB varied depending on the R value, and it showed a capping effect, micellar effect, and template effect. These effects of CTAB were synergetic in ZSM-11 synthesis, but they were competitive with the structure-directing effect of TBABr. In addition, the impact of the acidic properties and porosities of the hierarchical ZSM-11 catalysts on their performances in the alkylation of benzene with dimethyl ether was investigated.
Hierarchical zeolite materials were prepared via one-pot synthesis of ZSM-11 zeolites with different molar ratios (R) of a mesoporogen, i.e., cetyltrimethylammonium bromide template (CTAB), to a microporogen, i.e., tetra-n-butylammonium bromide (TBABr). The structures, morphologies, and textural properties of the resultant materials were investigated. Initially, with increasing R, the crystal size of the synthesized product decreased, the number of intercrystalline mesopores increased, and a pure ZSM-11 zeolite phase was present. Then an MCM-41-like phase was produced and embedded in the ZSM-11 zeolite phase. Finally, an MCM-41-like phase was obtained. The alkalinity had important effects on the physicochemical and textural properties of the prepared samples. A possible mechanism of formation of the hierarchical ZSM-11 zeolite was proposed on the basis of a combination of various characterization results. The role of CTAB varied depending on the R value, and it showed a capping effect, micellar effect, and template effect. These effects of CTAB were synergetic in ZSM-11 synthesis, but they were competitive with the structure-directing effect of TBABr. In addition, the impact of the acidic properties and porosities of the hierarchical ZSM-11 catalysts on their performances in the alkylation of benzene with dimethyl ether was investigated.
2018, 39(1): 181-189
doi: 10.1016/S1872-2067(17)62985-1
Abstract:
A ceria-modified hierarchical Hβ zeolite was prepared by a desilication-dealumination procedure followed by ceria modification. The catalytic performance of the ceria-modified and unmodified hierarchical Hβ zeolite catalysts for alkenylation of p-xylene with phenylacetylene was investigated. Various characterization techniques, including X-ray diffraction, X-ray fluorescence, nitrogen adsorption-desorption, and NH3 temperature-programmed desorption, were used to examine the structure-performance relationships. Our results show that the optimized ceria-modified hierarchical Hβ zeolite catalyst demonstrated higher catalytic activity, selectivity, and stability for alkenylation of p-xylene with phenylacetylene than those of pristine Hβ zeolite. This performance was attributed to more acidic sites and improved accessibility to active sites through larger pores, together with a higher mesoporous surface area and volume resulting from the hierarchical pore architecture and ceria modification. Thus, our 5 wt% CeO2-Hβ-B0.2A0.2 catalyst shows great potential for producing alkenyl aromatics through solid acid catalyzed alkenylation.
A ceria-modified hierarchical Hβ zeolite was prepared by a desilication-dealumination procedure followed by ceria modification. The catalytic performance of the ceria-modified and unmodified hierarchical Hβ zeolite catalysts for alkenylation of p-xylene with phenylacetylene was investigated. Various characterization techniques, including X-ray diffraction, X-ray fluorescence, nitrogen adsorption-desorption, and NH3 temperature-programmed desorption, were used to examine the structure-performance relationships. Our results show that the optimized ceria-modified hierarchical Hβ zeolite catalyst demonstrated higher catalytic activity, selectivity, and stability for alkenylation of p-xylene with phenylacetylene than those of pristine Hβ zeolite. This performance was attributed to more acidic sites and improved accessibility to active sites through larger pores, together with a higher mesoporous surface area and volume resulting from the hierarchical pore architecture and ceria modification. Thus, our 5 wt% CeO2-Hβ-B0.2A0.2 catalyst shows great potential for producing alkenyl aromatics through solid acid catalyzed alkenylation.
