制备方法对Co-MOR催化剂CH_4选择还原NO性能的影响

Effects of Preparation Methods on the Catalytic Performance of Selective Catalytic Reduction of NO with CH_4 over Co-MOR Catalysts

采用离子交换法、浸渍法制备一系列的Co-MOR催化剂,并将其用于CH4选择性催化还原NOx(CH4-SCR)反应.运用X射线衍射(XRD)、X射线荧光光谱(XRF)、扫描电子显微镜(SEM)、紫外-拉曼(UV-Raman)光谱、X射线光电子能谱(XPS)、NO程序升温脱附(NO-TPD)等手段对催化剂进行了表征.结果表明,浸渍法制备的催化剂,Co以Co3O4形式存在;而离子交换法制备的催化剂,Co以离子形式进入丝光沸石(MOR)骨架之中,在催化剂上形成更多的Co2+和[Co-O-Co]2+,形成更均匀NO吸附中心和CH4-SCR反应活性中心.催化剂活性评价表明离子交换法制备的催化剂具有更宽的活性温度区间,Co(0.30)-MOR催化剂在327-450°C温度范围内NO转化率大于50%.

A series of Co-mordenite （MOR） catalysts prepared by ion-exchange or impregnation methods were used in the selective catalytic reaction of NO with methane （CH4-SCR）. The structure and physicochemical properties of the catalysts were examined by X-ray diffraction （XRD）, X-ray fluorescence （XRF）, scanning electron microscopy （SEM）, UV-Raman spectroscopy, X-ray photoelectron spectroscopy （XPS）, and temperature-programmed desorption of NO （NO-TPD）. The Co species in the catalyst prepared by impregnation is present as Co3O4, whereas in the catalyst prepared by an ion-exchange method, the Co species enter in the mordenite skeleton with the ion form, and the more Co2＋ and [Co-O-Co]2＋ formed in the catalysts, the more uniform the adsorption of NO centers and the active centers of CH4-SCR. The catalysts prepared by different methods exhibited different activities for CH4-SCR. The catalysts prepared by ion-exchange exhibited activity over a wide activity temperature region, and NO conversion was over 50% at 327-450 ℃ on the Co（0.30）-MOR catalyst.