Low‐temperature selective catalytic reduction(SCR)of NO with NH3 was tested over Ho‐doped Mn–Ce/TiO2 catalysts prepared by the impregnation method.The obtained catalysts with different Ho doping ratios were charact...Low‐temperature selective catalytic reduction(SCR)of NO with NH3 was tested over Ho‐doped Mn–Ce/TiO2 catalysts prepared by the impregnation method.The obtained catalysts with different Ho doping ratios were characterized by Brunauer‐Emmett‐Teller(BET),X‐ray diffraction(XRD),temperature‐programmed reduction(H2‐TPR),temperature‐programmed desorption of NH3(NH3‐TPD),X‐ray photoelectron spectroscopy(XPS),and scanning electron microscopy(SEM).The catalytic activities were tested on a fixed bed.Their results indicated that the proper doping amount of Ho could effectively improve the low‐temperature denitrification performance and the SO2 resistance of Mn–Ce/TiO2 catalyst.The catalyst with Ho/Ti of 0.1 presented excellent catalytic activity,with a conversion of more than 90%in the temperature window of 140–220°C.The characterization results showed that the improved SCR activity of the Mn–Ce/TiO2 catalyst caused by Ho doping was due to the increase of the specific surface area,higher concentration of chemisorbed oxygen,higher surface Mn4+/Mn3+ratio,and higher acidity.The SO2 resistance test showed that the deactivating influence of SO2 on the catalyst was irreversible.The XRD and XPS results showed that the main reason for the catalyst deactivation was sulfates that had formed on the catalyst surface and that Ho doping could inhibit the sulfation to some extent.展开更多
Series of Mn/TiO2 catalysts modified with various contents of Nd for low-temperature SCR were synthesized.It can be found that the appropriate amount of Nd can markedly reduce the take-off temperature of Mn/TiO2 catal...Series of Mn/TiO2 catalysts modified with various contents of Nd for low-temperature SCR were synthesized.It can be found that the appropriate amount of Nd can markedly reduce the take-off temperature of Mn/TiO2 catalyst to 80℃and NOx conversion is stabilized over 90%in the wide temperature range of 100-2600 C.0.1 Nd-Mn/Ti shows higher N2 selectivity and better SO2 resistance than Mn/Ti catalyst.The results reveal that Nd-doped Mn/TiO2 catalyst exhibits larger BET surface area and better dispersion of active component Mn2O3.XPS results indicate that the optimal 0.1 Nd-Mn/Ti sample possesses higher concentration of Mn4+and larger amount of adsorbed oxygen at the surface compared with the unmodified counterpart.In situ DRIFTS show that the surface acidity is evidently increased after adding Nd,especially,the Lewis acid sites,and the intermediate(-NH2)is more stable.The reaction mechanism over Mn/Ti and 0.1 Nd-Mn/Ti catalysts obey the Eley-Rideal(E-R)mechanisms under low temperature reaction conditions.H2-TPR results show that Nd-Mn/TiO2 catalyst exhibits better lowtemperature redox properties.展开更多
为进一步提高Mn-TiO_2/分子筛催化剂和等离子体协同的催化活性,增加CO2选择性,减少O3产量。以5A分子筛为催化剂载体,采用浸渍法并利用Ag改性制备了Ag-Mn-TiO_2/分子筛催化剂,并运用XRD、SEM、EDS和FT-IR等技术对催化剂进行了表征。在针...为进一步提高Mn-TiO_2/分子筛催化剂和等离子体协同的催化活性,增加CO2选择性,减少O3产量。以5A分子筛为催化剂载体,采用浸渍法并利用Ag改性制备了Ag-Mn-TiO_2/分子筛催化剂,并运用XRD、SEM、EDS和FT-IR等技术对催化剂进行了表征。在针-板式高压脉冲反应器中研究了Ag的负载量与焙烧温度对Ag-Mn-TiO_2/分子筛催化剂的催化活性、CO2选择性和O3的产量的影响。结果表明:掺杂Ag后,促进Mn价态向+4价转变,提高了Mn-TiO_2/分子筛催化剂活性;焙烧温度为500℃时,Ag和Mn在分子筛上分布均匀,有利于Ag和Mn氧化物晶粒成长。当脉冲电压20 k V,Ag负载量为4%时,Ag-Mn-TiO_2/分子筛催化剂的甲醛去除率达到97.6%,O3浓度为99.4 mg·m-3,CO2选择性为50.2%。展开更多
A series of Mn-doped TiO2 nanowires(NWs) were prepared by hydrothermal method at the mole fraction of Mn changing from 0 to 12.0%.X-ray powder diffraction(XRD) analysis shows that all the samples have pure anatase str...A series of Mn-doped TiO2 nanowires(NWs) were prepared by hydrothermal method at the mole fraction of Mn changing from 0 to 12.0%.X-ray powder diffraction(XRD) analysis shows that all the samples have pure anatase structure.SEM and TEM studies show that the diameter and the length of the Mn-doped TiO2 NWs are larger than those of the undoped TiO2 NWs.Energy dispersive X-ray spectroscopy(EDX) reveals that the samples are composed of Ti,Mn and O.According to magnetization measurements,all samples show ferromagnetic behavior,but only the undoped TiO2 NWs are completely ferromagnetic with a saturated magnetization about 1.0 mA·m2/kg.Mn-doped TiO2 samples exhibit antiferromagnetic and ferromagnetic(AF-FM) behaviors simultaneously.Photoluminescence(PL) spectra demonstrate the existence of MnO2 sublattice.These observations indicate that an AF-WF crossover is induced by the coexistence of TiO2 sublattice and MnO2 sublattice.展开更多
摘要Low‐temperature selective catalytic reduction(SCR)of NO with NH3 was tested over Ho‐doped Mn–Ce/TiO2 catalysts prepared by the impregnation method.The obtained catalysts with different Ho doping ratios were characterized by Brunauer‐Emmett‐Teller(BET),X‐ray diffraction(XRD),temperature‐programmed reduction(H2‐TPR),temperature‐programmed desorption of NH3(NH3‐TPD),X‐ray photoelectron spectroscopy(XPS),and scanning electron microscopy(SEM).The catalytic activities were tested on a fixed bed.Their results indicated that the proper doping amount of Ho could effectively improve the low‐temperature denitrification performance and the SO2 resistance of Mn–Ce/TiO2 catalyst.The catalyst with Ho/Ti of 0.1 presented excellent catalytic activity,with a conversion of more than 90%in the temperature window of 140–220°C.The characterization results showed that the improved SCR activity of the Mn–Ce/TiO2 catalyst caused by Ho doping was due to the increase of the specific surface area,higher concentration of chemisorbed oxygen,higher surface Mn4+/Mn3+ratio,and higher acidity.The SO2 resistance test showed that the deactivating influence of SO2 on the catalyst was irreversible.The XRD and XPS results showed that the main reason for the catalyst deactivation was sulfates that had formed on the catalyst surface and that Ho doping could inhibit the sulfation to some extent.
基金Project supported by the Key Research and Development Projects of Jiangsu Province(BE2017716)National Key R&D Program of China(2017YFB0603201)Environmental Nonprofit Industry Research subject(2016YFC0208102)。
摘要Series of Mn/TiO2 catalysts modified with various contents of Nd for low-temperature SCR were synthesized.It can be found that the appropriate amount of Nd can markedly reduce the take-off temperature of Mn/TiO2 catalyst to 80℃and NOx conversion is stabilized over 90%in the wide temperature range of 100-2600 C.0.1 Nd-Mn/Ti shows higher N2 selectivity and better SO2 resistance than Mn/Ti catalyst.The results reveal that Nd-doped Mn/TiO2 catalyst exhibits larger BET surface area and better dispersion of active component Mn2O3.XPS results indicate that the optimal 0.1 Nd-Mn/Ti sample possesses higher concentration of Mn4+and larger amount of adsorbed oxygen at the surface compared with the unmodified counterpart.In situ DRIFTS show that the surface acidity is evidently increased after adding Nd,especially,the Lewis acid sites,and the intermediate(-NH2)is more stable.The reaction mechanism over Mn/Ti and 0.1 Nd-Mn/Ti catalysts obey the Eley-Rideal(E-R)mechanisms under low temperature reaction conditions.H2-TPR results show that Nd-Mn/TiO2 catalyst exhibits better lowtemperature redox properties.
摘要为进一步提高Mn-TiO_2/分子筛催化剂和等离子体协同的催化活性,增加CO2选择性,减少O3产量。以5A分子筛为催化剂载体,采用浸渍法并利用Ag改性制备了Ag-Mn-TiO_2/分子筛催化剂,并运用XRD、SEM、EDS和FT-IR等技术对催化剂进行了表征。在针-板式高压脉冲反应器中研究了Ag的负载量与焙烧温度对Ag-Mn-TiO_2/分子筛催化剂的催化活性、CO2选择性和O3的产量的影响。结果表明:掺杂Ag后,促进Mn价态向+4价转变,提高了Mn-TiO_2/分子筛催化剂活性;焙烧温度为500℃时,Ag和Mn在分子筛上分布均匀,有利于Ag和Mn氧化物晶粒成长。当脉冲电压20 k V,Ag负载量为4%时,Ag-Mn-TiO_2/分子筛催化剂的甲醛去除率达到97.6%,O3浓度为99.4 mg·m-3,CO2选择性为50.2%。
基金Project(06JJ2031) supported by Natrual Science Foundation of Hunan Province, ChinaProject(06A065) supported by Education Department of Hunan Province, China
摘要A series of Mn-doped TiO2 nanowires(NWs) were prepared by hydrothermal method at the mole fraction of Mn changing from 0 to 12.0%.X-ray powder diffraction(XRD) analysis shows that all the samples have pure anatase structure.SEM and TEM studies show that the diameter and the length of the Mn-doped TiO2 NWs are larger than those of the undoped TiO2 NWs.Energy dispersive X-ray spectroscopy(EDX) reveals that the samples are composed of Ti,Mn and O.According to magnetization measurements,all samples show ferromagnetic behavior,but only the undoped TiO2 NWs are completely ferromagnetic with a saturated magnetization about 1.0 mA·m2/kg.Mn-doped TiO2 samples exhibit antiferromagnetic and ferromagnetic(AF-FM) behaviors simultaneously.Photoluminescence(PL) spectra demonstrate the existence of MnO2 sublattice.These observations indicate that an AF-WF crossover is induced by the coexistence of TiO2 sublattice and MnO2 sublattice.