SSZ-13分子筛快速合成及其在SCR催化剂中的应用

Rapid synthesis of SSZ-13 zeolite and its application in SCR catalysts

采用快速合成法,引入促进剂,160℃晶化7 h制备形貌规整、结晶度高的微米级SSZ-13分子筛,考察其铜基分子筛催化剂高温水热老化、硫老化和碳氢老化前后的性能。结果表明,水热晶化(6~7)h是SSZ-13分子筛快速合成的关键时期,新鲜样Cu/SSZ-13-f的NOx起燃温度T_(50)=145℃,活性温度窗口T_(90)=(180~550)℃。高温水汽环境驱动下铜物种脱离分子筛交换位迁移聚集生长成氧化铜簇,导致高温性能明显劣化。硫中毒形成的硫酸盐/亚硫酸盐随着温度升高而分解,Cu/SSZ-13-s在达到活性温度窗口(250~325)℃后,催化活性逐渐恢复并在450℃后接近新鲜样。碳氢化合物对该催化剂影响较低,Cu/SSZ-13-hc的T_(50)=155℃、T_(90)=(165~525)℃,催化活性没有明显劣化。发动机台架测试结果显示,自制SCR样件在WHSC和WHTC循环工况下NOx排放量分别为0.19 g·(kW·h)^(-1)和0.23 g·(kW·h)^(-1),满足GB17691-2018相关限值要求。

Rapid synthesis method was used to prepare micron-sized SSZ-13 with regular morphology and high crystallinity by introducing accelerator at 160℃for 7 hours.The performance of copper based zeolite catalysts before and after high temperature hydrothermal aging,sulfur aging and hydrocarbon aging were systematically investigated.The results showed that hydrothermal crystallization for(6-7)h was the key period for rapid synthesis of SSZ-13.The NO_(X) ignition temperature of Cu/SSZ-13-f was 145℃,and the temperature window was(180-550)℃.Driven by high-temperature water vapor environment,copper species were forced to leave the molecular sieve,migrate and aggregate to grow into copper oxide clusters,resulting in obvious deterioration of its high-temperature performance.Sulfate/sulfite formed by SO_(2) poisoning was decomposed by heating.After reaching the temperature window(250-325)℃,catalytic activity of Cu/SSZ-13-s gradually approached that of fresh sample after 450℃.The catalyst was less affected by hydrocarbons.No significant deterioration in catalytic activity was observed for Cu/ssz-13-hc[T_(50)=155℃and T_(90)=(165-525)℃].Engine bench test results showed that NOx emissions of the as-prepared SCR sample under WHSC and WHTC cycle were 0.19 g·(kW·h)^(-1) and 0.23 g·(kW·h)^(-1) respectively,meeting the limitation requirements of GB 17691-2018.