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作者(2019)在《Effect of Preparation Method on Cu Active Sites and the Reaction Pathway in NO Reduction by NH3 over Cu–SSZ-13》一文中研究指出:To study the influence of the preparation method on Cu active sites and the reaction pathway in NO reduction by NH 3over Cu–SSZ-13,three kinds of catalysts(Cu ion-exchanged SSZ-13 1,one-pot synthesis Cu–SSZ-13 2,and Ce 0.017–Fe0.017/Cu–SSZ-13[Ce and Fe ion exchange on the basis of Cu–SSZ-13 2])were prepared.In situ diffuse reflectance infrared Fourier transform spectroscopy and H 2temperature program reduction were used to study the differences in the reaction pathways and Cu active sites over the three kinds of catalysts.Density functional theory was employed to study the effect of active sites on the reaction pathway.In situ DRIFTS showed that the reaction pathway on Cu–SSZ-13 1during NO oxidation was different from that on Cu–SSZ-13 2and Ce 0.017–Fe0.017/Cu–SSZ-13.The difference was that intermediate NO 2was involved in the selective catalytic reduction reaction on Cu–SSZ-13 1,whereas NO 2was not found during the reaction process on Cu–SSZ-13 2and Ce 0.017–Fe0.017/Cu–SSZ-13.H2–TPR studies revealed that the three catalysts had different 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 2were more conducive to form nitrate when the Cu species was on the six-and eight-membered rings;by contrast,NO and O 2were more conducive to form NO 2in the cage.These results showed that different preparation methods led to various Cu active sites,and varying Cu active sites could lead to different NO oxidation processes.
Abstract
To study the influence of the preparation method on Cu active sites and the reaction pathway in NO reduction by NH 3over Cu–SSZ-13,three kinds of catalysts(Cu ion-exchanged SSZ-13 1,one-pot synthesis Cu–SSZ-13 2,and Ce 0.017–Fe0.017/Cu–SSZ-13[Ce and Fe ion exchange on the basis of Cu–SSZ-13 2])were prepared.In situ diffuse reflectance infrared Fourier transform spectroscopy and H 2temperature program reduction were used to study the differences in the reaction pathways and Cu active sites over the three kinds of catalysts.Density functional theory was employed to study the effect of active sites on the reaction pathway.In situ DRIFTS showed that the reaction pathway on Cu–SSZ-13 1during NO oxidation was different from that on Cu–SSZ-13 2and Ce 0.017–Fe0.017/Cu–SSZ-13.The difference was that intermediate NO 2was involved in the selective catalytic reduction reaction on Cu–SSZ-13 1,whereas NO 2was not found during the reaction process on Cu–SSZ-13 2and Ce 0.017–Fe0.017/Cu–SSZ-13.H2–TPR studies revealed that the three catalysts had different 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 2were more conducive to form nitrate when the Cu species was on the six-and eight-membered rings;by contrast,NO and O 2were more conducive to form NO 2in the cage.These results showed that different preparation methods led to various Cu active sites,and varying Cu active sites could lead to different NO oxidation processes.
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