Roles of Lewis and BrªÛnsted acid sites in NO reduction with ammonia on CeO₂-ZrO₂-NiO-SO₄^2- catalyst

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State Key Laboratory of New Ceramics & Fine Process, Department of Materials Science and Engineering, Tsinghua University

Õª Òª£ºNickel and sulfate co-modified CeO2-ZrO2 catalysts were prepared by sol-gel method. The catalysts were characterized by XRD, FTIR, XPS, NH3 chemisorption and NH3-SCR activity tests. The results showed that the enhanced acidity of CeO2-ZrO2 catalysts by nickel and sulfate co-modification was responsible for the broadened temperature window and improved the selectivity to N2 in NH3-SCR deNOx. The introduction of nickel to CeO2-ZrO2 solid solutions resulted in more Ce3+ on surface of catalyst, leading to an increased Lewis acidity of catalyst. Higher Lewis acidity of catalyst facilitated ammonia activation at low temperature £¨<300 oC£© and thereby improved the NH3-SCR activity. The enhanced high-temperature £¨>300 oC£© activity and selectivity of catalysts arose from the introduction of BrªÛnsted acid sites £¨less oxidative than Lewis acid sites£© by sulfate modification.

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