Cu-SSZ-13/堇青石整体式催化剂的原位合成及其NH3选择性催化还原NO性能

采用水热合成技术, 在堇青石蜂窝陶瓷载体上原位合成了SSZ-13分子筛, 并借助X射线衍射(XRD)和场发射扫描电子显微镜(FESEM)等手段对其进行表征. 在此基础上, 研究了合成时间对催化剂结构和机械性能的影响. 另外, 使用固定床反应器测试了离子交换度为50%的Cu-SSZ-13/堇青石催化剂和Cu-SSZ-13催化剂水热老化前后的氨气选择性催化还原(NH₃-SCR) NO性能. 结果表明, 通过原位合成法制备的Cu-SSZ-13/堇青石催化剂在200-500 ℃ 的窗口温度内能达到80%以上的转化率, 并在300 ℃ 时达到96.4%的转化率. 在850 ℃水热老化12 h后, Cu-SSZ-13催化剂完全丧失了催化性能, 而Cu-SSZ-13/堇青石催化剂在300 ℃时仍然保持91%的转化率. 使用XRD和固体27Al 核磁共振(²⁷Al NMR)的方法, 研究了水热老化前后两种催化剂结构的变化, 结果表明, 当水热老化12 h 后, Cu-SSZ-13 基本丧失了SSZ-13 结构特征峰, 而Cu-SSZ-13/堇青石仍然保持了一定的SSZ-13 骨架结构. 证明了通过原位合成法制备的Cu-SSZ-13/堇青石催化剂具有较好的抗水热老化性能.

In situ Synthesis of Cu-SSZ-13/Cordierite Monolithic Catalyst for the Selective Catalytic Reduction of NO with NH3

SSZ-13 molecular sieves were synthesized in situ on the surface of a honeycomb-shaped cordierite support using a hydrothermal method, and the resulting material was characterized by X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM). The process for preparing SSZ-13/cordierite was optimized in detail. Furthermore, the ion exchange levels of the 50% Cu-SSZ-13/cordierite and Cu-SSZ-13 catalysts were tested in the ammonia-selective catalytic reduction (NH₃-SCR) of NO both before and after the hydrothermal treatment process using a fixed-bed reactor. The results of these experiments showed that the Cu-SSZ-13/cordierite prepared in situ by hydrothermal synthesis had good catalytic activity, and gave an NO conversion of more than 80% at temperatures in the range of 200-500 ℃, with the highest NO conversion of 96.4%being reached at 300 ℃. After being aged hydrothermally at 850 ℃ for 12 h, the SCR activity of the Cu- SSZ-13 catalyst was significantly reduced, whereas that of Cu-SSZ-13/cordierite remained largely unchanged with an NO conversion of 91% at 300 ℃. Analysis of the catalysts framework both before and after the hydrothermal treatment by X-ray diffraction and solid state ²⁷Al NMR revealed a significant reduction in the intensities of the X-ray diffraction and tetrahedral aluminumpeaks for Cu-SSZ-13, whereas those of the Cu-SSZ- 13/cordierite material remained unchanged. These results indicated that the Cu-SSZ-13/cordierite prepared by in situ hydrothermal synthesis was less prone to deactivation by hydrothermal aging.