Silicalite-1空心球材料制备及其在Beckmann重排反应中催化应用研究

以碳微球作为硬模板、纳米Silicalite-1分子筛作为壳层,采用水热法合成了Silicalite-1空心球材料。采用XRD、SEM、FT-IR、N_2吸附、29Si M AS NM R、TG、XPS等技术对催化剂的物相、形貌和性能等进行表征,发现该空心材料具有较高的结晶度、发达的多级孔道结构和丰富的表面羟基。与传统方法制备的Silicalite-1分子筛催化剂相比,Silicalite-1空心材料在环己酮肟Beckmann重排反应中表现出优异的催化性能,使环己酮肟的转化率达99%、己内酰胺的选择性达94%,同时催化剂保持极佳的稳定性。研究表明,Silicalite-1空心材料中具有的大量巢式硅羟基和末端硅羟基是Beckmann重排反应的主要活性位,且可通过简单焙烧再生实现羟基活性位的完全恢复。

Synthesis of Silicalite-1 hollow sphere catalyst and its application for Beckmann rearrangement reaction

Silicalite-1 zeolite hollow sphere structured material was hydrothermally synthesized via the aid of carbon microspheres as hard-template. The morphology, structure, textural and physicochemical properties of the material were characterized with XRD, SEM, FT-IR, N₂ adsorption-desorption isotherm, ²⁹Si MAS NMR, TG, and XPS techniques. It was suggested that the obtained Silicalite-1 hollow spheres were highly crystallized with developed multiple channel structure and abundant surface hydroxyl groups, which endowed the material with excellent catalytic properties in Beckmann rearrangement reaction of cyclohexanone-oxime. Compared with the Silicalite-1 catalyst prepared from conventional method, the Silicalite-1 hollow sphere catalyst showed much higher activity to the conversion of cyclohexanone-oxime (99%) and selectivity of caprolactam (94%), with excellent stability at the same time. The abundant nest silanols and terminal silanols in Silicalite-1 hollow sphere were main active sites for Beckmann rearrangement reaction, and could be easily recovered from the deactivated catalysts by calcination.