氨水改性催化环己酮肟Beckmann重排反应的研究

为研究氨水改性对具有MFI结构的Silicalite-1分子筛催化环己酮肟气相Beckmann重排反应性能的影响,选用两种水热合成工艺合成了单斜和正交两种晶系的Silicalite-1分子筛,并用氨水分别对其进行改性处理。通过XRD和IR表征考察了不同合成方法、不同的处理温度、时间等因素对催化剂晶体结构、表面硅羟基的影响。表征结果说明氨水处理时间和温度可能会改变分子筛的晶系、表面硅羟基的强度和种类。改性前后Silicalite-1催化Beckmann重排反应评价的结果说明重排反应的主活性中心是硅羟基窝,但活性中心和MFI结构的晶系没有关系。碱处理能够减弱副反应活性中心末端硅羟基,提高催化剂的稳定性和产物己内酰胺的选择性。

Study on the Beckmann rearrangement of cyclohexanone oxime over Silicalite-1 modified with ammonia solution

Silicalite-1 samples were synthesized by two hydrothermal methods and modified with ammonia solution under different temperature and length of time respectively.The characterization researched by XRD,FTIR indicated that ammonia solution could change the crystal form and silanol type on Silicalite-1.The results of vapor Beckmann rearrangement of cyclohexanone oxime indicated that nest silanol were the main active sites,but the crystal form was not related to the silanol type and catalytic performance.Ammonia solution treatment could also eliminate the side reaction site of terminal silanol group of Silicalite-1 so as to improve the Beckmann rearrangement performance.