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
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
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
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.
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.
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.
