不同WO3含量对CeO2-ZrO2-WO3催化剂在NH3选择性催化还原NO中的影响

采用水热法制备了CeO₂-ZrO₂-WO₃(CZW)催化剂,考察了WO₃含量对CZW催化剂上NH₃选择性催化还原NO_x性能的影响,并利用X射线衍射、N₂吸附-脱附、H₂程序升温还原、NH₃和NO程序升温脱附等方法对其进行了表征。结果表明,WO₃以无定形的形式存在于催化剂中,添加WO₃后显著提高了催化剂的表面酸性,并且在CZW催化剂上出现了强吸附的NO物种,从而有利于提高催化剂的活性。另外,适量的WO₃引入将增大催化剂的比表面积,促进催化剂的氧化还原性能,这将有利于提高SCR的催化活性。和CeO₂-ZrO₂催化剂相比,当WO₃的含量为20%时,CZW催化剂表现出良好的抗硫性能。此外,当空速为60 000 h^-1时,在200~463 ℃,该催化剂显示出了大于90% NO_x转化率。

Effect of WO3 content on the catalytic activity of CeO2-ZrO2-WO3 for selective catalytic reduction of NO with NH3

A series of CeO₂-ZrO₂-WO₃ catalysts (CZW) was prepared by the hydrothermal method. The effect of WO₃ content on their catalytic properties for selective reduction of NO_<em>x with NH₃ was investigated. The catalysts were characterized by X-ray diffraction, N₂ sorption, H₂ temperature-programmed reduction, NH₃ temperature-programmed desorption and NO temperature-programmed desorption techniques. It was shown that WO₃ existed as amorphous species in the CZW. Introduction of WO₃ in the CZW dramatically enhanced its surface acidity and gave rise to strongly adsorbed NO species, consequently increasing the catalytic activity. In addition, appropriate amounts of WO₃ also increased the surface area and improved the reduction behavior of the catalyst. Compared to the CeO₂-ZrO₂, the CZW with 20% WO₃ not only exhibited high resistivity to SO₂, but also had a wider reaction temperature window. It showed a NO_x conversion of> 90% at the space velocity of 60 000 h^-1 in the temperature range of 200~463 ℃.