Preparation,Characterization And Ammonia Oxidation Performance Of Supported ZrO₂ Catalysts

As one of the common air pollutants,leaked ammonia can cause serious harm to human health and break ecological balance.It is believed that selective catalytic oxidation?SCO?of ammonia to N2 and H2 O is an effective way to remove the low-concentration ammonia from the atmosphere.In the field of environmental catalysis,considerable attention has recently been drawn on developing more efficient heterogeneous catalyst for NH3-SCO process.In this paper,a series of supported Zr O₂ catalysts were prepared by surfactanttemplated method.The physicochemical properties of these catalysts were studied by a series of characterization means.The catalytic performance of the catalysts was investigated for the reaction of NH3-SCO.In addition,a small amount of noble metal Ru or Pt was supported on CuO-ZrO₂ by impregnation method to prepare noble metal supported catalysts.The effects of noble metal loading and pretreatment conditions on the catalytic performance were studied.The relationship between the composition,structure and surface properties of the catalysts and their catalytic properties were discussed.The main contents and the results are as follows:A series of CuO-ZrO₂ catalysts with different copper contents?6.0-14 wt%?were prepared by using cetyltrimethylammonium bromide?CTAB?as template.The effects of calcination temperature and other factors on the catalytic performance of the catalysts were investigated.Compared with the CuO-ZrO₂ catalysts prepared by impregnation and mechanochemical methods,the 10 wt%CuO-ZrO₂ catalyst?calcined at 720 ??prepared by surfactant-templated method shows higher catalytic activity for NH3-SCO.It can completely oxidize ammonia at 270 ?,at this time N2 selectivity is 93%.A variety of characterization results show that the catalyst prepared by surfactant-templated method has higher specific surface area,larger pore volume,and more highly dispersed active copper oxide species,thus resulting in the high catalytic activity for NH3-SCO reaction.The noble metal supported Pt/CuO-ZrO₂ and Ru/CuO-ZrO₂ catalysts were prepared by impregnation method.The effects of noble metal loading and pretreatment conditions on the catalytic performance of NH3-SCO were studied.NH3 could be completely oxidized at 220 ? over the 1.0 wt%Ru/CuO-ZrO₂ catalyst pretreated under O₂ atmosphere at 600 ?.The 1.0 wt%Pt/CuO-ZrO₂ catalyst pretreated under H2 atmosphere at 600 ? could completely oxidize NH3 at 200 ?.The catalytic performance of the noble metal modified CuO-ZrO₂ catalysts is significantly better than the CuO-ZrO₂ catalyst.The characterization results show that the Pt0 and RuO₂ species introduced into the catalysts should be the main active centers for the oxidation of NH3 at low-temperature.The existence of the relatively strong interaction between the noble metal nanoparticles and the CuO-ZrO₂ support could improve the dispersity and the structure stability of the noble metal nanoparticles,thus resulting in the formation of highly active and stable catalysts for low-temperature oxidation of NH3.