Roles of Lewis and Brφnsted acid sites in NO reduction with ammonia on CeO2-ZrO2-NiO-SO42- catalyst

Nickel 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 ℃) and thereby improved the NH3-SCR activity.The enhanced high-temperature (＞300 ℃) activity and selectivity of catalysts arose from the introduction of Brφnsted acid sites (less oxidative than Lewis acid sites) by sulfate modification.