V2O5/TiO2-ZrO2 catalysts containing various amounts of WO3 were synthesized.The catalyst morphologies,catalytic performances,and reaction mechanisms in the selective catalytic reduction of NOx by NH3 were investigated...V2O5/TiO2-ZrO2 catalysts containing various amounts of WO3 were synthesized.The catalyst morphologies,catalytic performances,and reaction mechanisms in the selective catalytic reduction of NOx by NH3 were investigated using in situ diffuse-reflectance infrared Fourier-transform spectroscopy,temperature-programmed reduction（TPR）,X-ray diffraction,and the Brunauer-Emmett-Teller（BET） method.The BET surface area of the triple oxides increased with increasing ZrO2 doping but gradually decreased with increasing WO3 loading.Addition of sufficient WO3 helped to stabilize the pore structure and the combination of WO3 and ZrO2 improved dispersion of all the metal oxides.The mechanisms of reactions using V2O5-9%WO3/TiO2-ZrO2 and V2O5-9%WO3/TiO2were compared by using either a single or mixed gas feed and various pretreatments.The results suggest that both reactions followed the Eley-Ridel mechanism;however,the dominant acid sites,which depended on the addition of WO3 or ZrO2,determined the pathways for NOx reduction,and involved[NH4^＋-NO-Bronsted acid site]^＊ and[NH2-NO-Lewis acid site]^＊ intermediates,respectively.NH3-TPR and H2-TPR showed that the metal oxides in the catalysts were not reduced by NH3 and O2did not reoxidize the catalyst surfaces but participated in the formation of H2O and NO2.展开更多
A series of H3PO4-modified CeO2 samples were prepared by impregnation of CeO2 with H3PO4solution,and evaluated for the selective catalytic reduction of NOx by NH3.The samples were characterized by X-ray diffraction,N2...A series of H3PO4-modified CeO2 samples were prepared by impregnation of CeO2 with H3PO4solution,and evaluated for the selective catalytic reduction of NOx by NH3.The samples were characterized by X-ray diffraction,N2 adsorption-desorption,infrared spectroscopy,Raman spectroscopy,X-ray photoelectron spectroscopy,temperature-programmed desorption of NH3,and temperature-programmed reduction of H2.The results showed that more than 80%NO conversion was achieved in the temperature range 250-550℃ over the H3PO4-CeO2 catalyst.The enhanced catalytic performance could be ascribed to the increase in acidic strength,especially Bronsted acidity,and reduction in redox properties of the CeO2 after H3PO4 modification.展开更多
Vanadium oxide （VOx） nanostructures, synthesized by hydrothermal treatment using dodecylamine as template, were evaluated for the selective catalytic reduction of NOx with ammonia （NH3-SCR）, The effect of solvent ...Vanadium oxide （VOx） nanostructures, synthesized by hydrothermal treatment using dodecylamine as template, were evaluated for the selective catalytic reduction of NOx with ammonia （NH3-SCR）, The effect of solvent type in the reaction mixture （EtOH/（EtOH ＋ H20）） and time of hydrolysis was studied. The obtained materials were characterized by XRD, SEM, TEM and BET, The VOx nanorods （80-120 nm diameter and 1-4 μm length） were synthesized in 25 vol% EtOH/（EtOH ＋ H20） and the open-ended multiwalled VOx nanotube （50-100 nm inner diameter, 110-180 nm outer diameter and 0,5-2 pm length） synthesized in 50 vol% EtOH/（EtOH ＋ H20）. VOx nanotuhes performed the superior NH3-SCR activity under a gas hourly space velocity of 12,000 h-1 at low temperature of 250 ~C （NOx conversion of 893g ＆ N2 selectivity of 100%）, while most of the developed Vanadia base catalysts are active at high temperature （〉350 ℃）. The superior NH3-SCR activity ofVOx nanotubes at low tem- perature is related to nanocrystalline structure, special nanotube morphology as well as high specific surface area.展开更多
MoVNbTe catalyst has been found to be the most active and selective catalyst in the ammoxidation of propane to ACN, the selective oxidation of propane to acrylic acid and in the oxidative dehydrogenation of ethane to ...MoVNbTe catalyst has been found to be the most active and selective catalyst in the ammoxidation of propane to ACN, the selective oxidation of propane to acrylic acid and in the oxidative dehydrogenation of ethane to ethylene. However, in our previous work, when 0.5 mL of MoVNbTe catalyst prepared using slurry method was tested in the propane ammoxidation to ACN, it only shows 1% conversion of propane with about 55% selectivity to CAN, thus giving only 0.6% yields to ACN. The poor catalyst activity is attributed to insufficient formation of crystalline phases essential for the propane activation process. In an attempt to improve the physicochemical properties of this catalyst, several preparation methods have been used, namely hydrothermal, reflux, changing the solvent and changing the calcinations temperature. The modified catalysts have been characterized using X-Ray Diffraction （XRD） and N2 physisorption （BET）. The MoVNbTe catalyst prepared by hydrothermal method shows a remarkable improvement in the formation of crystalline phases.展开更多
基金supported by the National Natural Science Foundation of China(51306034)Key Research&Development Projects of Jiangsu Province(BE2015677)the National Basic Research Program of China(2013CB228505)~~
文摘V2O5/TiO2-ZrO2 catalysts containing various amounts of WO3 were synthesized.The catalyst morphologies,catalytic performances,and reaction mechanisms in the selective catalytic reduction of NOx by NH3 were investigated using in situ diffuse-reflectance infrared Fourier-transform spectroscopy,temperature-programmed reduction（TPR）,X-ray diffraction,and the Brunauer-Emmett-Teller（BET） method.The BET surface area of the triple oxides increased with increasing ZrO2 doping but gradually decreased with increasing WO3 loading.Addition of sufficient WO3 helped to stabilize the pore structure and the combination of WO3 and ZrO2 improved dispersion of all the metal oxides.The mechanisms of reactions using V2O5-9%WO3/TiO2-ZrO2 and V2O5-9%WO3/TiO2were compared by using either a single or mixed gas feed and various pretreatments.The results suggest that both reactions followed the Eley-Ridel mechanism;however,the dominant acid sites,which depended on the addition of WO3 or ZrO2,determined the pathways for NOx reduction,and involved[NH4^＋-NO-Bronsted acid site]^＊ and[NH2-NO-Lewis acid site]^＊ intermediates,respectively.NH3-TPR and H2-TPR showed that the metal oxides in the catalysts were not reduced by NH3 and O2did not reoxidize the catalyst surfaces but participated in the formation of H2O and NO2.
基金supported by the National Natural Science Foundation of China(21177120)the Open Fund of Key Laboratory of Functional Inorganic Material Chemistry(Heilongjiang University),Ministry of Education~~
文摘A series of H3PO4-modified CeO2 samples were prepared by impregnation of CeO2 with H3PO4solution,and evaluated for the selective catalytic reduction of NOx by NH3.The samples were characterized by X-ray diffraction,N2 adsorption-desorption,infrared spectroscopy,Raman spectroscopy,X-ray photoelectron spectroscopy,temperature-programmed desorption of NH3,and temperature-programmed reduction of H2.The results showed that more than 80%NO conversion was achieved in the temperature range 250-550℃ over the H3PO4-CeO2 catalyst.The enhanced catalytic performance could be ascribed to the increase in acidic strength,especially Bronsted acidity,and reduction in redox properties of the CeO2 after H3PO4 modification.
基金the Iran Nanotechnology Initiative Council for the financial and other supports
文摘Vanadium oxide （VOx） nanostructures, synthesized by hydrothermal treatment using dodecylamine as template, were evaluated for the selective catalytic reduction of NOx with ammonia （NH3-SCR）, The effect of solvent type in the reaction mixture （EtOH/（EtOH ＋ H20）） and time of hydrolysis was studied. The obtained materials were characterized by XRD, SEM, TEM and BET, The VOx nanorods （80-120 nm diameter and 1-4 μm length） were synthesized in 25 vol% EtOH/（EtOH ＋ H20） and the open-ended multiwalled VOx nanotube （50-100 nm inner diameter, 110-180 nm outer diameter and 0,5-2 pm length） synthesized in 50 vol% EtOH/（EtOH ＋ H20）. VOx nanotuhes performed the superior NH3-SCR activity under a gas hourly space velocity of 12,000 h-1 at low temperature of 250 ~C （NOx conversion of 893g ＆ N2 selectivity of 100%）, while most of the developed Vanadia base catalysts are active at high temperature （〉350 ℃）. The superior NH3-SCR activity ofVOx nanotubes at low tem- perature is related to nanocrystalline structure, special nanotube morphology as well as high specific surface area.
文摘MoVNbTe catalyst has been found to be the most active and selective catalyst in the ammoxidation of propane to ACN, the selective oxidation of propane to acrylic acid and in the oxidative dehydrogenation of ethane to ethylene. However, in our previous work, when 0.5 mL of MoVNbTe catalyst prepared using slurry method was tested in the propane ammoxidation to ACN, it only shows 1% conversion of propane with about 55% selectivity to CAN, thus giving only 0.6% yields to ACN. The poor catalyst activity is attributed to insufficient formation of crystalline phases essential for the propane activation process. In an attempt to improve the physicochemical properties of this catalyst, several preparation methods have been used, namely hydrothermal, reflux, changing the solvent and changing the calcinations temperature. The modified catalysts have been characterized using X-Ray Diffraction （XRD） and N2 physisorption （BET）. The MoVNbTe catalyst prepared by hydrothermal method shows a remarkable improvement in the formation of crystalline phases.
