Excessive emissions of nitrogen oxides from flue gas have imposed various detrimental impacts on environment,and the development of deNO_(x) catalysts with low-cost and high performance is an urgent requirement.Iron o...Excessive emissions of nitrogen oxides from flue gas have imposed various detrimental impacts on environment,and the development of deNO_(x) catalysts with low-cost and high performance is an urgent requirement.Iron oxide-based material has been explored for promising deNO_(x) catalysts.However,the unsatisfactory low-temperature activity limits their practical applications.In this study,a series of excellent low-temperature denitrification catalysts(Ha-FeO_(x)/yZS)were prepared by acid treatment of zinc slag,and the mass ratios of Fe to impure ions was regulated by adjusting the acid concentrations.Ha-FeO_(x)/yZS showed high denitrification performance(>90%)in the range of 180–300℃,and the optimal NO conversion and N2 selectivity were higher than 95%at 250℃.Among them,the Ha-FeO_(x)/2ZS synthesized with 2 mol/L HNO3 exhibited the widest temperature window(175–350℃).The excellent denitrification performance of Ha-FeO_(x)/yZS was mainly attributed to the strong interaction between Fe and impurity ions to inhibit the growth of crystals,making Ha-FeO_(x)/yZS with amorphous structure,nice fine particles,large specific surface area,more surface acid sites and high chemisorbed oxygen.The in-situ DRIFT experiments confirmed that the SCR reaction on the Ha-FeO_(x)/yZS followed both Langmuir-Hinshelwood(L-H)mechanism and Eley-Rideal(E-R)mechanism.The present work proposed a high value-added method for the preparation of cost-effective catalysts from zinc slag,which showed a promising application prospect in NO_(x) removal by selective catalytic reduction with ammonia.展开更多
TiO_(2)-supported V_(2)O_(5)catalysts are commonly used in NO_(x)reduction with ammonia due to their robust catalytic performance.Over these catalysts,it is generally considered that the active species are mainly deri...TiO_(2)-supported V_(2)O_(5)catalysts are commonly used in NO_(x)reduction with ammonia due to their robust catalytic performance.Over these catalysts,it is generally considered that the active species are mainly derived from the vanadia species rather than the intrinsic structure of V-O-Ti entities,namely the interface sites.To reveal the role of V-O-Ti entities in NH_(3)-SCR,herein,we prepared TiO_(2)/V_(2)O_(5)catalysts and demonstrated that V-O-Ti entities were more active for NO_(x)reduction under wet conditions than the V sites(V=O)working alone.On the V-O-Ti entities,kinetic measurements and first principles calculations revealed that NH_(3)activation exhibited a much lower energy barrier than that on V=O sites.Under wet conditions,the V-O-Ti interface significantly inhibited the transformation of V=O to V-OH sites thus benefiting NH_(3)activation.Under wet conditions,meanwhile,the migration of NH_(4)^(+)from Ti site neighboring the V-O-Ti interface to Ti site of the V-O-Ti interface was exothermic;thus,V-O-Ti entities together with neighboring Ti sites could serve as channels linking NH_(3)pool and active centers for activation of NH_(4)^(+).This finding reveals that the V-O-Ti interface sites on V-based catalysts play a crucial role in NO_(x)removal under realistic conditions,providing a new perspective on NH_(3)-SCR mechanism.展开更多
Low-temperature selective catalytic reduction(SCR)is important for the elimination of NOfrom stationary sources.In the present study,the loading of Ce and W onα-Fe_(2)O_(3)was achieved through the integration of sing...Low-temperature selective catalytic reduction(SCR)is important for the elimination of NOfrom stationary sources.In the present study,the loading of Ce and W onα-Fe_(2)O_(3)was achieved through the integration of single-mode microwave and incipient wetness impregnation(IWI)methods.The scanning electron microscopy(SEM)and transmission electron microscopy(TEM)images reveal that the structure ofα-Fe_(2)O_(3)is spindle-like,and the structure remains unchanged after the introduction of Ce and/or W.The results of NH-SCR investigation demonstrate that NOconversion over Ce-W/α-Fe_(2)O_(3)is more than85%at 300℃,which is much higher than that over Ce/a-Fe_(2)O_(3)andα-Fe_(2)O_(3),Our studies illustrate that the addition of Ce can significantly increase the amount of surface oxygen vacancies as well as sites of moderate basicity.On the other hand,the addition of W can obviously decrease the amount of basic sites and increase the number of Br?nsted acid sites.The synergistic effect of Ce and W addition on balancing acidity/basicity properties accounts for the high activity of CeW/α-Fe_(2)O_(3)for NOremoval at low temperatures.The study provides insight into the relationship between acidity/basicity properties and catalytic performance of Ce-W/α-Fe_(2)O_(3)catalysts,which is beneficial to the design of high-performance NH-SCR catalyst for NOremoval at low temperatures.展开更多
Green and efficient NO_(x)removal at low temperature is still desired.NO_(x)removal via non-thermal plasma(NTP)reduction is one of such technique.This work presents the experimental and theoretical study on the NO_(x)...Green and efficient NO_(x)removal at low temperature is still desired.NO_(x)removal via non-thermal plasma(NTP)reduction is one of such technique.This work presents the experimental and theoretical study on the NO_(x)removal via NTP reduction(NTPRD)in dielectric barrier discharge reactor(DBD).The effect of O_(2)molar fraction on NO_(x)species in the outlet of DBD,and effects of NH_(3)/NO_(x)molar ratio and discharge power of DBD on NO_(x)removal efficiency are investigated.Results indicate that anaerobic condition and higher discharge power is beneficial to direct removal of NO_(x),and the NO_(x),removal efficiency can be up to 98.5%under the optimal operating conditions.It is also found that adding NH_(3)is favorable for the reduction of NO_(x),to N_(2)at lower discharge power.In addition,the NO_(x)removal mechanism and energy consumption analysis for the NTPRD process are also studied.It is found that the reduced active species(N^(+),N^(-),N^(+),N_(2)^(*),NH_(2)^(+),etc.)generated in the NTPRD process play important roles for the reduction of NO_(x),to N_(2).Our work paves a novel pathway for NO_(x)removal from anaerobic gas in industrial application.展开更多
We first present preparation of MnOx–CeO_2–Al_2O_3 catalysts with varying Mn contents through a self-propagating high-temperature synthesis(SHS) method, and studied the application of these catalysts to the selectiv...We first present preparation of MnOx–CeO_2–Al_2O_3 catalysts with varying Mn contents through a self-propagating high-temperature synthesis(SHS) method, and studied the application of these catalysts to the selective catalytic reduction of NOxwith NH3(NH_3-SCR).Using the catalyst with 18 wt.% Mn(18 MnCe1Al2), 100% NO conversion was achieved at 200°C and a gas hourly space velocity of 15384 hr-1, and the high-efficiency SCR temperature window, where NO conversion is greater than 90%, was widened to a temperature range of 150–300°C. 18 MnCe1Al2 showed great resistance to SO_2(100 ppm)and H_2O(5%) at 200°C. The catalysts were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller(BET) analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, and H_2 temperature programmed reduction. The characterization results showed that the surface atomic concentration of Mn increased with increasing Mn content, which led to synergism between Mn and Ce and improved the activity in the SCR reaction. 18 MnCe1Al2 has an extensive pore structure,with a BET surface area of approximately 135.4 m^2/g, a pore volume of approximately 0.16 cm^3/g, and an average pore diameter of approximately 4.6 nm. The SCR reaction on 18 MnCe1Al2 mainly followed the Eley-Rideal mechanism. The performances of the MnOx–CeO_2–Al_2O_3 catalysts were good, and because of the simplicity of the preparation process,the SHS method is applicable to their industrial-scale manufacture.展开更多
To study the infl uence of the preparation method on Cu active sites and the reaction pathway in NO reduction by NH 3 over Cu-SSZ-13, three kinds of catalysts (Cu ion-exchanged SSZ-13 1 , one-pot synthesis Cu-SSZ-13 2...To study the infl uence of the preparation method on Cu active sites and the reaction pathway in NO reduction by NH 3 over Cu-SSZ-13, three kinds of catalysts (Cu ion-exchanged SSZ-13 1 , one-pot synthesis Cu-SSZ-13 2 , and Ce 0.017 -Fe 0.017 /Cu- SSZ-13 [Ce and Fe ion exchange on the basis of Cu-SSZ-13 2 ]) were prepared. In situ diff use refl ectance infrared Fourier transform spectroscopy and H 2 temperature program reduction were used to study the diff erences in the reaction pathways and Cu active sites over the three kinds of catalysts. Density functional theory was employed to study the eff ect of active sites on the reaction pathway. In situ DRIFTS showed that the reaction pathway on Cu-SSZ-13 1 during NO oxidation was diff erent from that on Cu-SSZ-13 2 and Ce 0.017 -Fe 0.017 /Cu-SSZ-13. The diff erence was that intermediate NO 2 was involved in the selective catalytic reduction reaction on Cu-SSZ-13 1 , whereas NO 2 was not found during the reaction process on Cu-SSZ-13 2 and Ce 0.017 -Fe 0.017 /Cu-SSZ-13. H 2 -TPR studies revealed that the three catalysts had diff erent Cu active sites, which were located in the six-membered ring, eight-membered ring, and CHA cage. On the basis of DFT studies, NO and O 2 were more conducive to form nitrate when the Cu species was on the six- and eight-membered rings;by contrast, NO and O 2 were more conducive to form NO 2 in the cage. These results showed that diff erent preparation methods led to various Cu active sites, and varying Cu active sites could lead to diff erent NO oxidation processes.展开更多
基金National Natural Science Foundation of China(21676209)Natural Science Basic Research Program of Shaanxi(2022JQ-328)Postdoctoral Research Foundation of the Xi’an University of Architecture and Technology(19603210120).
文摘Excessive emissions of nitrogen oxides from flue gas have imposed various detrimental impacts on environment,and the development of deNO_(x) catalysts with low-cost and high performance is an urgent requirement.Iron oxide-based material has been explored for promising deNO_(x) catalysts.However,the unsatisfactory low-temperature activity limits their practical applications.In this study,a series of excellent low-temperature denitrification catalysts(Ha-FeO_(x)/yZS)were prepared by acid treatment of zinc slag,and the mass ratios of Fe to impure ions was regulated by adjusting the acid concentrations.Ha-FeO_(x)/yZS showed high denitrification performance(>90%)in the range of 180–300℃,and the optimal NO conversion and N2 selectivity were higher than 95%at 250℃.Among them,the Ha-FeO_(x)/2ZS synthesized with 2 mol/L HNO3 exhibited the widest temperature window(175–350℃).The excellent denitrification performance of Ha-FeO_(x)/yZS was mainly attributed to the strong interaction between Fe and impurity ions to inhibit the growth of crystals,making Ha-FeO_(x)/yZS with amorphous structure,nice fine particles,large specific surface area,more surface acid sites and high chemisorbed oxygen.The in-situ DRIFT experiments confirmed that the SCR reaction on the Ha-FeO_(x)/yZS followed both Langmuir-Hinshelwood(L-H)mechanism and Eley-Rideal(E-R)mechanism.The present work proposed a high value-added method for the preparation of cost-effective catalysts from zinc slag,which showed a promising application prospect in NO_(x) removal by selective catalytic reduction with ammonia.
基金supported by the National Natural Science Foundation of China (Nos.U20B6004,22072179,and 22276202)the Strategic Priority Research Program of the Chinese Academy of Sciences (No.XDA23010200)+1 种基金the Special project of eco-environmental technology for peak carbon dioxide emissions and carbon neutrality (No.RCEES-TDZ2021-2)the Youth Innovation Promotion Association of the Chinese Academy of Sciences (No.2019045)。
文摘TiO_(2)-supported V_(2)O_(5)catalysts are commonly used in NO_(x)reduction with ammonia due to their robust catalytic performance.Over these catalysts,it is generally considered that the active species are mainly derived from the vanadia species rather than the intrinsic structure of V-O-Ti entities,namely the interface sites.To reveal the role of V-O-Ti entities in NH_(3)-SCR,herein,we prepared TiO_(2)/V_(2)O_(5)catalysts and demonstrated that V-O-Ti entities were more active for NO_(x)reduction under wet conditions than the V sites(V=O)working alone.On the V-O-Ti entities,kinetic measurements and first principles calculations revealed that NH_(3)activation exhibited a much lower energy barrier than that on V=O sites.Under wet conditions,the V-O-Ti interface significantly inhibited the transformation of V=O to V-OH sites thus benefiting NH_(3)activation.Under wet conditions,meanwhile,the migration of NH_(4)^(+)from Ti site neighboring the V-O-Ti interface to Ti site of the V-O-Ti interface was exothermic;thus,V-O-Ti entities together with neighboring Ti sites could serve as channels linking NH_(3)pool and active centers for activation of NH_(4)^(+).This finding reveals that the V-O-Ti interface sites on V-based catalysts play a crucial role in NO_(x)removal under realistic conditions,providing a new perspective on NH_(3)-SCR mechanism.
基金Project supported by the National Natural Science Foundation of China(21703037,22108037)the Natural Science Foundation of Fujian(2018J10691)。
文摘Low-temperature selective catalytic reduction(SCR)is important for the elimination of NOfrom stationary sources.In the present study,the loading of Ce and W onα-Fe_(2)O_(3)was achieved through the integration of single-mode microwave and incipient wetness impregnation(IWI)methods.The scanning electron microscopy(SEM)and transmission electron microscopy(TEM)images reveal that the structure ofα-Fe_(2)O_(3)is spindle-like,and the structure remains unchanged after the introduction of Ce and/or W.The results of NH-SCR investigation demonstrate that NOconversion over Ce-W/α-Fe_(2)O_(3)is more than85%at 300℃,which is much higher than that over Ce/a-Fe_(2)O_(3)andα-Fe_(2)O_(3),Our studies illustrate that the addition of Ce can significantly increase the amount of surface oxygen vacancies as well as sites of moderate basicity.On the other hand,the addition of W can obviously decrease the amount of basic sites and increase the number of Br?nsted acid sites.The synergistic effect of Ce and W addition on balancing acidity/basicity properties accounts for the high activity of CeW/α-Fe_(2)O_(3)for NOremoval at low temperatures.The study provides insight into the relationship between acidity/basicity properties and catalytic performance of Ce-W/α-Fe_(2)O_(3)catalysts,which is beneficial to the design of high-performance NH-SCR catalyst for NOremoval at low temperatures.
基金supported by the National Natural Science Foundation of China(Grant Nos.21878009 and 21725601).
文摘Green and efficient NO_(x)removal at low temperature is still desired.NO_(x)removal via non-thermal plasma(NTP)reduction is one of such technique.This work presents the experimental and theoretical study on the NO_(x)removal via NTP reduction(NTPRD)in dielectric barrier discharge reactor(DBD).The effect of O_(2)molar fraction on NO_(x)species in the outlet of DBD,and effects of NH_(3)/NO_(x)molar ratio and discharge power of DBD on NO_(x)removal efficiency are investigated.Results indicate that anaerobic condition and higher discharge power is beneficial to direct removal of NO_(x),and the NO_(x),removal efficiency can be up to 98.5%under the optimal operating conditions.It is also found that adding NH_(3)is favorable for the reduction of NO_(x),to N_(2)at lower discharge power.In addition,the NO_(x)removal mechanism and energy consumption analysis for the NTPRD process are also studied.It is found that the reduced active species(N^(+),N^(-),N^(+),N_(2)^(*),NH_(2)^(+),etc.)generated in the NTPRD process play important roles for the reduction of NO_(x),to N_(2).Our work paves a novel pathway for NO_(x)removal from anaerobic gas in industrial application.
基金supported by the National High Technology Research and Development Program of China (863 program) (No.2015AA03A401)the Program for Changjiang Scholars and Innovative Research Team in University (No.IRT_15R46)the program of Science and Technology Innovation Team in Bingtuan (No.2015BD003)
文摘We first present preparation of MnOx–CeO_2–Al_2O_3 catalysts with varying Mn contents through a self-propagating high-temperature synthesis(SHS) method, and studied the application of these catalysts to the selective catalytic reduction of NOxwith NH3(NH_3-SCR).Using the catalyst with 18 wt.% Mn(18 MnCe1Al2), 100% NO conversion was achieved at 200°C and a gas hourly space velocity of 15384 hr-1, and the high-efficiency SCR temperature window, where NO conversion is greater than 90%, was widened to a temperature range of 150–300°C. 18 MnCe1Al2 showed great resistance to SO_2(100 ppm)and H_2O(5%) at 200°C. The catalysts were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller(BET) analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, and H_2 temperature programmed reduction. The characterization results showed that the surface atomic concentration of Mn increased with increasing Mn content, which led to synergism between Mn and Ce and improved the activity in the SCR reaction. 18 MnCe1Al2 has an extensive pore structure,with a BET surface area of approximately 135.4 m^2/g, a pore volume of approximately 0.16 cm^3/g, and an average pore diameter of approximately 4.6 nm. The SCR reaction on 18 MnCe1Al2 mainly followed the Eley-Rideal mechanism. The performances of the MnOx–CeO_2–Al_2O_3 catalysts were good, and because of the simplicity of the preparation process,the SHS method is applicable to their industrial-scale manufacture.
文摘To study the infl uence of the preparation method on Cu active sites and the reaction pathway in NO reduction by NH 3 over Cu-SSZ-13, three kinds of catalysts (Cu ion-exchanged SSZ-13 1 , one-pot synthesis Cu-SSZ-13 2 , and Ce 0.017 -Fe 0.017 /Cu- SSZ-13 [Ce and Fe ion exchange on the basis of Cu-SSZ-13 2 ]) were prepared. In situ diff use refl ectance infrared Fourier transform spectroscopy and H 2 temperature program reduction were used to study the diff erences in the reaction pathways and Cu active sites over the three kinds of catalysts. Density functional theory was employed to study the eff ect of active sites on the reaction pathway. In situ DRIFTS showed that the reaction pathway on Cu-SSZ-13 1 during NO oxidation was diff erent from that on Cu-SSZ-13 2 and Ce 0.017 -Fe 0.017 /Cu-SSZ-13. The diff erence was that intermediate NO 2 was involved in the selective catalytic reduction reaction on Cu-SSZ-13 1 , whereas NO 2 was not found during the reaction process on Cu-SSZ-13 2 and Ce 0.017 -Fe 0.017 /Cu-SSZ-13. H 2 -TPR studies revealed that the three catalysts had diff erent Cu active sites, which were located in the six-membered ring, eight-membered ring, and CHA cage. On the basis of DFT studies, NO and O 2 were more conducive to form nitrate when the Cu species was on the six- and eight-membered rings;by contrast, NO and O 2 were more conducive to form NO 2 in the cage. These results showed that diff erent preparation methods led to various Cu active sites, and varying Cu active sites could lead to diff erent NO oxidation processes.
