A simple strategy of Cu modification was proposed to broaden the operation temperature window for NbCe catalyst.The best catalyst Cu0.010/Nb1Ce3 presented over 90%NO conversion in a wide temperature range of 200-400℃...A simple strategy of Cu modification was proposed to broaden the operation temperature window for NbCe catalyst.The best catalyst Cu0.010/Nb1Ce3 presented over 90%NO conversion in a wide temperature range of 200-400℃and exhibited an excellent H_(2)O or/and SO_(2) resistance at 275℃.To understand the promotional mechanism of Cu modification,the correlation among the"activity-structure-property"were tried to establish systematically.Cu species highly dispersed on NbCe catalyst to serve as the active component.The strong interaction among Cu,Nb and Ce promoted the emergence of NbO4 and induced more Bronsted acid sites.And Cu modification obviously enhanced the redox behavior of the NbCe catalyst.Besides,EPR probed the Cu species exited in the form of monomeric and dimeric Cu^(2+),the isolated Cu^(2+)acted as catalytic active sites to promote the reaction:Cu^(2+)-NO_(3)^(-)+NO(g)→Cu^(2+)-NO_(2)^(-)+NO_(2)(g).Then the generated NO_(2) would accelerate the fast-SCR reaction process and thus facilitated the lowtemperature deNO_(x) efficiency.Moreover,surface nitrates became unstable and easy to decompose after Cu modification,thus providing additional adsorption and activation sites for NH3,and ensuring the improvement of catalytic activity at high temperature.Since the NH3-SCR reaction followed by E-R reaction pathway efficaciously over Cu_(0.010)/Nb_(1)Ce_(3) catalyst,the excellent H_(2)O and SO_(2) resistance was as expected.展开更多
The sulfated CeO_(2)/Al_(2)O_(3) catalysts with different sizes of CeO_(2)nanoparticles were prepared by using pure H_2O or acetic acid solution as impregnation solvent, and the influence of sizes of CeO_(2) nanoparti...The sulfated CeO_(2)/Al_(2)O_(3) catalysts with different sizes of CeO_(2)nanoparticles were prepared by using pure H_2O or acetic acid solution as impregnation solvent, and the influence of sizes of CeO_(2) nanoparticles on the catalytic performances of the sulfated CeO_(2)/Al_(2)O_(3) catalyst was studied. The catalytic performance tests show that the sulfated CeO_(2)/Al_(2)O_(3) catalyst using acetic acid solution as impregnation solvent has better catalytic activity and the resistance to K+poisoning than the sulfated CeO_(2)/Al_(2)O_(3) catalyst using pure H_(2)O as impregnation solvent. The excellent catalytic performances can be ascribed to the smaller sizes of CeO_(2) nanoparticles in CeO_(2)/Al_(2)O_(3) catalyst using acetic acid solution, which results in larger amount of adsorbed sulfate species, surface acid sites, surface active oxygen species and excellent redox property. These features are helpful for improving the catalytic performances of sulfated CeO_(2)/Al_(2)O_(3) catalyst using smaller amount of CeO_(2) to cut the costs.展开更多
Understanding the influence of sulfates over catalysts for selective catalytic reduction of NO with NH_(3)(NH_(3)-SCR)is crucial due to the universal presence of SO_(2)in exhaust gas.Depending on the degree of sulfati...Understanding the influence of sulfates over catalysts for selective catalytic reduction of NO with NH_(3)(NH_(3)-SCR)is crucial due to the universal presence of SO_(2)in exhaust gas.Depending on the degree of sulfation,there mainly exist surface and bulk sulfates and NH_(3)-SCR activity is generally considered to suffer more from bulk sulfates.Herein,the unique function of bulk sulfates over Ce O_(2)in promoting hightemperature SCR reaction is revealed.Notably,compared with CeO_(2)dominated with surface sulfates(S-CeO_(2)-4h)and commercial V_2O_5-WO_(3)/TiO_(2),CeO_(2)with bulk sulfates(S-Ce O_(2)-72h)exhibits admirable NO conversion at the temperature range of 400-550℃.Bulk sulfates provide more Br?nsted acid sites with stronger strength for NH_(3)adsorption.Moreover,the oxidation ability of Ce O_(2)is significantly inhibited due to electron-withdrawing effect from bulk sulfates,which alleviates NH_(3)oxidation at high temperatures.More NH_(3)adsorption with high stability and limited NH_(3)oxidation capacity ensure the excellent catalytic performance for S-CeO_(2)-72h in high-temperature denitration.This work provides new insight of bulk sulfates in promoting SCR activity and open a new avenue to design de NO_xcatalysts employed at high temperatures.展开更多
A series of supported CeO2/TiO2 catalysts were prepared to explore the influence of CeO2 loading on these catalysts for the selective catalytic reduction of NO3 by NH3(NH3-SCR).The catalysts were investigated in detai...A series of supported CeO2/TiO2 catalysts were prepared to explore the influence of CeO2 loading on these catalysts for the selective catalytic reduction of NO3 by NH3(NH3-SCR).The catalysts were investigated in detail by means of XRD,Raman,H2-TPR,NH3-TPD,XPS,in situ DRIFTS,and NH3-SCR reaction.The activity of the catalyst is closely related to the content of CeO2.When the loading of CeO2 is near the dispersion capacity(1.16 mmol Ce4+/100 m^2 TiO2),the catalytic activity is better.This may be because that the dispersed CeO2 is the active species and the catalyst has appropriate redox property,along with the larger amounts of surface Ce content and surface adsorbed oxygen species.Finally,a possible reaction mechanism via the Langmuir-Hinshelwood(L-H)mechanism is tentatively proposed to further understand the NH3-SCR reaction.展开更多
For CO catalytic oxidation,Cu and Ce species are of great importance,between which the synergistic effect is worth investigating.In this work,CeO_(2)/Cu_(2)O with Cu_(2)O {111} and {100} planes were comparatively expl...For CO catalytic oxidation,Cu and Ce species are of great importance,between which the synergistic effect is worth investigating.In this work,CeO_(2)/Cu_(2)O with Cu_(2)O {111} and {100} planes were comparatively explored on CO catalytic oxidation to reveal the effects of interfacial electronic interactions and oxygen defects.The activity result demonstrates that CeO_(2)/o-Cu_(2)O {111} has superior performance compared with CeO_(2)/c-Cu_(2)O {100}.Credit to the coordination unsaturated copper atoms(Cu_(CUS)) on oCu_(2)O {111} surface,the interfacial electronic interactions on CeO_(2)/o-Cu_(2)O {111} are more obvious than those on CeO_(2)/c-Cu_(2)O {100},leading to richer oxygen defect generation,better redox and activation abilities of CO and O_(2) reactants.Furthermore,the reaction mechanism of CeO_(2)/o-Cu_(2)O {111} on CO oxidation is revealed,i.e.,CO and O_(2) are adsorbed on the Cucus on Cu_(2)O {111} and oxygen defect of CeO_(2),respectively,and then synergistically promote the CO oxidation to CO_(2).The work sheds light on the designing optimized ceria and copper-based catalysts and the mechanism of CO oxidation.展开更多
Active species loss owing to reactant stream washing is a general problem which industrial catalysts suffer from.In case of catalysts synthesized by co-precipitation method,which have active species unused in bulk pha...Active species loss owing to reactant stream washing is a general problem which industrial catalysts suffer from.In case of catalysts synthesized by co-precipitation method,which have active species unused in bulk phase,can be regenerated by a simple thermal treatment that leads to active species in bulk phase migration to surface of the deactivated catalysts.In this work,the influence of regeneration temperature was investigated by employing ammonium hydroxide washing to simulate reactant stream washing of CeCoxO2 catalysts for NO+CO reaction.It is found that the deactivated catalyst can be regenerated by simple thermal treatment and increasing calcination temperature could accelerate the Co species migration from the bulk phase to surface of catalysts.展开更多
CeO_(2)/TiO_(2)(denoted as Ce Ti) catalysts obtained by solid-phase impregnation behaved better in lowtemperature selective catalytic reduction of NO_(x)with NH_(3)(NH_(3)-SCR) than that by conventional wet impregnati...CeO_(2)/TiO_(2)(denoted as Ce Ti) catalysts obtained by solid-phase impregnation behaved better in lowtemperature selective catalytic reduction of NO_(x)with NH_(3)(NH_(3)-SCR) than that by conventional wet impregnation.To explore the main factors for activity distinction,the texture property,CeO_(2)dispersion and structure changes of TiO_(2)were comprehensively analyzed.It was found that surface changes of TiO_(2)had a significant impact on the improved activity.From results of inductively coupled plasma atomic emission spectrometer (ICP-AES),diffuse reflectance UV-vis spectroscopy (UV-vis-DRS) and Raman,it was inferred that Ce ions were partially incorporated into TiO_(2)lattice,accompanied with the formation of defects and vacancies during solid-phase impregnation.Accordingly,Ce Ti catalysts from solid-phase impregnation exhibited superiority in adsorption and activation of reactants.Further result from monitoring the preparation process indicated that the evolved NO played an important role in promoting Ce doping through depriving oxygen atoms on TiO_(2)surface.The interaction between Ce and Ti was enhanced.The catalyst performed better in NH_(3)-SCR,especially at low temperature,which testified the solid-phase impregnation could be an effective method to modulate interface structure for designing efficient catalyst.展开更多
Sulfate adsorption is one of the factors that cause the poisoning of catalyst in the low-temperature NH_(3) selective catalytic reduction reaction(NH_(3)-SCR).In this paper,by controlling the co-adsorption time of SO_...Sulfate adsorption is one of the factors that cause the poisoning of catalyst in the low-temperature NH_(3) selective catalytic reduction reaction(NH_(3)-SCR).In this paper,by controlling the co-adsorption time of SO_(2) and O_(2) at 150℃,a range of sulfated MnCeOx catalysts with different contents of metal sulfate species were prepared to reveal the influence of metal sulfate species content on the catalytic performances and reaction mechanisms at low temperature.The catalytic activity below 250℃rapidly decreases with increasing metal sulfate species content.The results of characterizations shed light on the reduction of specific surface area,Mn^(4+)and Ce^(3+)content,and redox ability of MnCeOx owing to the formation of metal sulfate species.Further experiments reveal that metal sulfate species preferentially absorb on MnOx domains rather than on CeO_(2) domains,and the adsorbed metal sulfate species can suppress the Eley-Rideal and the Langmuir-Hinshelwood reaction mechanisms over the sulfated MnCeOx.All the above results are detrimental to the activity of sulfated MnCeOx in the low-temperature NH3-SCR reaction.展开更多
基金supported by the National Natural Foundation of China(21607019,21503115)the Open Project Program of Jiangsu Key Laboratory of Vehicle Emissions Control(OVEC013)the Talent Introduction Project of Chongqing Three Gorges University~~
基金Financial support from the National Natural Science Foundation of China,China(Nos.21972062,21976081,21976111)。
文摘A simple strategy of Cu modification was proposed to broaden the operation temperature window for NbCe catalyst.The best catalyst Cu0.010/Nb1Ce3 presented over 90%NO conversion in a wide temperature range of 200-400℃and exhibited an excellent H_(2)O or/and SO_(2) resistance at 275℃.To understand the promotional mechanism of Cu modification,the correlation among the"activity-structure-property"were tried to establish systematically.Cu species highly dispersed on NbCe catalyst to serve as the active component.The strong interaction among Cu,Nb and Ce promoted the emergence of NbO4 and induced more Bronsted acid sites.And Cu modification obviously enhanced the redox behavior of the NbCe catalyst.Besides,EPR probed the Cu species exited in the form of monomeric and dimeric Cu^(2+),the isolated Cu^(2+)acted as catalytic active sites to promote the reaction:Cu^(2+)-NO_(3)^(-)+NO(g)→Cu^(2+)-NO_(2)^(-)+NO_(2)(g).Then the generated NO_(2) would accelerate the fast-SCR reaction process and thus facilitated the lowtemperature deNO_(x) efficiency.Moreover,surface nitrates became unstable and easy to decompose after Cu modification,thus providing additional adsorption and activation sites for NH3,and ensuring the improvement of catalytic activity at high temperature.Since the NH3-SCR reaction followed by E-R reaction pathway efficaciously over Cu_(0.010)/Nb_(1)Ce_(3) catalyst,the excellent H_(2)O and SO_(2) resistance was as expected.
基金Project supported by the National Natural Science Foundation of China(21607019)the Scientific and Technological Research Program of Chongqing Municipal Education Commission(KJQN202101242,KJQN202001227)the Open Project Program of Key Laboratory of Water Environment Evolution and Pollution Control in the Three Gorges Reservoir(WEPKL2019ZD-04)。
文摘The sulfated CeO_(2)/Al_(2)O_(3) catalysts with different sizes of CeO_(2)nanoparticles were prepared by using pure H_2O or acetic acid solution as impregnation solvent, and the influence of sizes of CeO_(2) nanoparticles on the catalytic performances of the sulfated CeO_(2)/Al_(2)O_(3) catalyst was studied. The catalytic performance tests show that the sulfated CeO_(2)/Al_(2)O_(3) catalyst using acetic acid solution as impregnation solvent has better catalytic activity and the resistance to K+poisoning than the sulfated CeO_(2)/Al_(2)O_(3) catalyst using pure H_(2)O as impregnation solvent. The excellent catalytic performances can be ascribed to the smaller sizes of CeO_(2) nanoparticles in CeO_(2)/Al_(2)O_(3) catalyst using acetic acid solution, which results in larger amount of adsorbed sulfate species, surface acid sites, surface active oxygen species and excellent redox property. These features are helpful for improving the catalytic performances of sulfated CeO_(2)/Al_(2)O_(3) catalyst using smaller amount of CeO_(2) to cut the costs.
基金The financial supports from the National Natural Science Foundation of China(Nos.21976081,21972062)Major Scientific and Technological Project of Bingtuan(No.2018AA002),are greatly acknowledged。
文摘Understanding the influence of sulfates over catalysts for selective catalytic reduction of NO with NH_(3)(NH_(3)-SCR)is crucial due to the universal presence of SO_(2)in exhaust gas.Depending on the degree of sulfation,there mainly exist surface and bulk sulfates and NH_(3)-SCR activity is generally considered to suffer more from bulk sulfates.Herein,the unique function of bulk sulfates over Ce O_(2)in promoting hightemperature SCR reaction is revealed.Notably,compared with CeO_(2)dominated with surface sulfates(S-CeO_(2)-4h)and commercial V_2O_5-WO_(3)/TiO_(2),CeO_(2)with bulk sulfates(S-Ce O_(2)-72h)exhibits admirable NO conversion at the temperature range of 400-550℃.Bulk sulfates provide more Br?nsted acid sites with stronger strength for NH_(3)adsorption.Moreover,the oxidation ability of Ce O_(2)is significantly inhibited due to electron-withdrawing effect from bulk sulfates,which alleviates NH_(3)oxidation at high temperatures.More NH_(3)adsorption with high stability and limited NH_(3)oxidation capacity ensure the excellent catalytic performance for S-CeO_(2)-72h in high-temperature denitration.This work provides new insight of bulk sulfates in promoting SCR activity and open a new avenue to design de NO_xcatalysts employed at high temperatures.
基金Project supported by the National Natural Science Foundation of China(21773106,21677069,51674002,21307001)the Open Project Program of Jiangsu Key Laboratory of Vehicle Emissions Control(OVEC037)。
文摘A series of supported CeO2/TiO2 catalysts were prepared to explore the influence of CeO2 loading on these catalysts for the selective catalytic reduction of NO3 by NH3(NH3-SCR).The catalysts were investigated in detail by means of XRD,Raman,H2-TPR,NH3-TPD,XPS,in situ DRIFTS,and NH3-SCR reaction.The activity of the catalyst is closely related to the content of CeO2.When the loading of CeO2 is near the dispersion capacity(1.16 mmol Ce4+/100 m^2 TiO2),the catalytic activity is better.This may be because that the dispersed CeO2 is the active species and the catalyst has appropriate redox property,along with the larger amounts of surface Ce content and surface adsorbed oxygen species.Finally,a possible reaction mechanism via the Langmuir-Hinshelwood(L-H)mechanism is tentatively proposed to further understand the NH3-SCR reaction.
基金Project supported by the National Natural Science Foundation of China (21707066,21677069)。
文摘For CO catalytic oxidation,Cu and Ce species are of great importance,between which the synergistic effect is worth investigating.In this work,CeO_(2)/Cu_(2)O with Cu_(2)O {111} and {100} planes were comparatively explored on CO catalytic oxidation to reveal the effects of interfacial electronic interactions and oxygen defects.The activity result demonstrates that CeO_(2)/o-Cu_(2)O {111} has superior performance compared with CeO_(2)/c-Cu_(2)O {100}.Credit to the coordination unsaturated copper atoms(Cu_(CUS)) on oCu_(2)O {111} surface,the interfacial electronic interactions on CeO_(2)/o-Cu_(2)O {111} are more obvious than those on CeO_(2)/c-Cu_(2)O {100},leading to richer oxygen defect generation,better redox and activation abilities of CO and O_(2) reactants.Furthermore,the reaction mechanism of CeO_(2)/o-Cu_(2)O {111} on CO oxidation is revealed,i.e.,CO and O_(2) are adsorbed on the Cucus on Cu_(2)O {111} and oxygen defect of CeO_(2),respectively,and then synergistically promote the CO oxidation to CO_(2).The work sheds light on the designing optimized ceria and copper-based catalysts and the mechanism of CO oxidation.
基金Project supported by the Opening Foundation of Jiangsu Key Laboratory of Vehicle Emissions Control(OVEC041)Major Scientific and Technological Project of Bingtuan(2018AA002)。
文摘Active species loss owing to reactant stream washing is a general problem which industrial catalysts suffer from.In case of catalysts synthesized by co-precipitation method,which have active species unused in bulk phase,can be regenerated by a simple thermal treatment that leads to active species in bulk phase migration to surface of the deactivated catalysts.In this work,the influence of regeneration temperature was investigated by employing ammonium hydroxide washing to simulate reactant stream washing of CeCoxO2 catalysts for NO+CO reaction.It is found that the deactivated catalyst can be regenerated by simple thermal treatment and increasing calcination temperature could accelerate the Co species migration from the bulk phase to surface of catalysts.
基金financial supports from the National Natural Science Foundation of China (Nos.21976081,21773106)。
文摘CeO_(2)/TiO_(2)(denoted as Ce Ti) catalysts obtained by solid-phase impregnation behaved better in lowtemperature selective catalytic reduction of NO_(x)with NH_(3)(NH_(3)-SCR) than that by conventional wet impregnation.To explore the main factors for activity distinction,the texture property,CeO_(2)dispersion and structure changes of TiO_(2)were comprehensively analyzed.It was found that surface changes of TiO_(2)had a significant impact on the improved activity.From results of inductively coupled plasma atomic emission spectrometer (ICP-AES),diffuse reflectance UV-vis spectroscopy (UV-vis-DRS) and Raman,it was inferred that Ce ions were partially incorporated into TiO_(2)lattice,accompanied with the formation of defects and vacancies during solid-phase impregnation.Accordingly,Ce Ti catalysts from solid-phase impregnation exhibited superiority in adsorption and activation of reactants.Further result from monitoring the preparation process indicated that the evolved NO played an important role in promoting Ce doping through depriving oxygen atoms on TiO_(2)surface.The interaction between Ce and Ti was enhanced.The catalyst performed better in NH_(3)-SCR,especially at low temperature,which testified the solid-phase impregnation could be an effective method to modulate interface structure for designing efficient catalyst.
基金Project supported by the National Natural Science Foundation of China(21607019)the Scientific andTechnological Research Program of Chongqing Municipal Education Commission(KJQN202101242,KJQN202001227)+2 种基金the Science andTechnology Project of Wanzhou(wzstc-2019034)the Open Project Program of Key Laboratory of Water Environment Evolution andPollution Control in the Three Gorges Reservoir(WEPKL2019ZD-04)the Project Program of Chongqing Postgraduate Research andInnovation(CYS21489)。
文摘Sulfate adsorption is one of the factors that cause the poisoning of catalyst in the low-temperature NH_(3) selective catalytic reduction reaction(NH_(3)-SCR).In this paper,by controlling the co-adsorption time of SO_(2) and O_(2) at 150℃,a range of sulfated MnCeOx catalysts with different contents of metal sulfate species were prepared to reveal the influence of metal sulfate species content on the catalytic performances and reaction mechanisms at low temperature.The catalytic activity below 250℃rapidly decreases with increasing metal sulfate species content.The results of characterizations shed light on the reduction of specific surface area,Mn^(4+)and Ce^(3+)content,and redox ability of MnCeOx owing to the formation of metal sulfate species.Further experiments reveal that metal sulfate species preferentially absorb on MnOx domains rather than on CeO_(2) domains,and the adsorbed metal sulfate species can suppress the Eley-Rideal and the Langmuir-Hinshelwood reaction mechanisms over the sulfated MnCeOx.All the above results are detrimental to the activity of sulfated MnCeOx in the low-temperature NH3-SCR reaction.