用于NH_3-SCR的锰铈基催化剂的改性研究

Modification of Manganese Cerium-based Catalysts for NH_3-SCR

为了拓宽锰铈基催化剂的中高温段活性窗口,采用共沉淀法制备了锰铈基催化剂(MnCe3Ox)及一系列掺杂不同过渡金属M的改性催化剂(MnCe3MOx,其中M可以是W,Fe,Cu),分别对它们进行了SCR活性及选择性测试,发现通过掺杂W可以拓宽锰铈基催化剂的高温段活性窗口,提高其N2的选择性;对优选出的MnCe3WOx催化剂进行了抗硫性测试,发现其在中高温段具有优良的抗硫性,而在低温段抗硫性有待提高;分别利用BET比表面积分析仪和X射线衍射仪(XRD)对催化剂的比表面积和晶型进行表征;使用原位漫反射傅里叶变换技术(insitu DRIFTS)进行反应机理研究,发现W的加入提高了催化剂表面Lewis酸的酸量,同时促进催化剂表面在吸附NO和O2时生成更多的单齿硝酸盐,从而拓宽了催化剂高温段窗口。

In order to improve the performance of manganese cerium-based catalysts in high temperature,the manganese ceri- um-based catalysts （MnCe3 OX ） and a series of modified catalysts doped with different transition metal M （MnCe3 MOx, M may be W, Fe or Cu） were prepared with the method of coprecipitation. The activity and selectivity of each catalyst was evaluated respectively. The experimental results showed that doping tungsten broadened the high temperature activity window of manga- nese cerium-based catalysts and improved its N2 selectivity. The sulfur resistance test of optimized MnCe3 WOx catalyst showed the excellent resistance ability in middle and high temperature and the insufficient resistance in low temperature. With BET spe- cific surface area analyzer and X-ray diffraction （XRD）, the specific surface area and crystal type of catalysts were character- ized. The reaction mechanism research of in situ DRIFTS found that the introduction of tungsten increased the amount of Lewis acid in the surface of catalyst and promoted more monodentate nitrate by the adsorption of NO and O2, and hence the high tem- perature activity window was broadened.