挤出成型对硅铝酸盐沸石催化剂酸性影响的研究进展

Research Progress in Influence of Extrusion on Acidity of Aluminosilicate Zeolite Catalysts

工业使用的沸石催化剂通常需要成型,在此过程中引入的成型组分会与沸石发生相互作用,从而使成型沸石催化剂的酸性和催化活性发生改变。笔者从硅铝酸盐沸石酸性入手,明确了沸石酸性的来源,讨论了沸石脱铝行为与其结构的关系以及抑制沸石脱铝的手段。进一步地,深入探讨了成型过程中各类常用黏结剂与沸石之间的相互作用,包括沸石脱铝、拟薄水铝石黏结剂中向沸石的铝迁移、SiO_(2)黏结剂向沸石的硅迁移、黏土黏结剂与沸石间碱金属离子交换等;并从原理上阐释了上述作用对催化剂酸性的影响,明确了催化剂酸性的变化主要在于分子筛脱铝与酸位点生成的平衡。在此认识基础上,总结并阐释了胶溶剂及其他成型助剂对沸石催化剂酸性的影响及其作用机理。最后,对成型过程中保留并进一步提高沸石催化剂酸性和催化活性的方向进行了展望。

Zeolite catalysts used in industry usually need to be shaped;during the molding process,the interactions between molding component and zeolite will change the acidity and catalytic activity of the shaped zeolite catalysts.Based on the acidity of silicoaluminate zeolite,the authors clarify the origin of the acidity of zeolite,and discuss the relationship between the dealumination behavior of zeolite and its structure,as well as the means of inhibiting the dealuminization of zeolite.Furthermore,the interactions between various common binders and zeolites during the molding process are deeply explored,including the dealuminization of zeolite,Al migration from pseudo boehmite binders to zeolites,Si migration from SiO_(2) binders to zeolites,and the exchange of alkali metal ions between clay binders and zeolites.The above effects on catalyst acidity were explained in theory.Moreover,it has been clarified that the change in catalyst acidity mainly lies in the balance between the dealuminization of zeolite and the generation of acid sites.Based on these understandings,the paper summarizes and explains the influence and effective mechanism of peptizers and other molding additives on the acidity of zeolite catalysts,and finally looks forward to the prospects of retaining and further improving the acidity and catalytic activity of zeolite catalysts during the molding process.