摘要
用XPS考察了USY和FSY超稳Y型沸石及其起始原料NH_4Y沸石的表面组成,并结合Ar^+刻蚀技术与其体相组成进行了比较。结果表明,NH_4Y沸石的铝分布基本均匀一致,经超稳化处理后,沸石表面组成发生了很大的变化。用(NH_4)_2SiF_6液相脱铝补硅法制备的FSY表面呈缺铝特征,其表面铝原子浓度比体相低8～10％;而用传统水热法制备的USY具有典型的富铝表面,其表面铝原子浓度比体相高30％左右。USY表面富铝主要是由于USY“次表面”(Subsurface)附近的非骨架铝类迁移到表面所致。内层的非骨架铝类在常规水热超稳处理条件下一般则很难迁移,仍然留有在USY晶体内部。
The surface and bulk compositions (Si/Al or Al/(Al + Si)) of ultra-stable Y zeolites, FSY, USY and the original zeolite NH4Y were studied by X-ray pbotoelectron spectroscopy with Ar+ ion etching technique. The surface and bulk composition of NH4Y zeolite are basically the same. After the ultra-stabilized treatment, the surface composition of the zeolites is no longer equivalent to that of the bulk. For FSY zeolite obtained by dealumination of NH4Y zeolite with aqueous solution of(NH4)2-SiF6,the surface is obviously deficient in Al, and the Al atom concentration is 8-10% lower than that of the bulk. On the contrary, USY zeolite obtained by the traditional bydrotbermal treatment is typically Al-enri-ched in the surface. The surface Al atom concentration of USY zeolite is about 30% higher than that of its bulk. It was also found that the Al enriched in the surface of USY zeolite originated mainly from the migration of the non-framework Al of the "subsurface" of zeolite, and not the total bulk.
关键词
超稳Y沸石
铝分布
XPS
沸石
Ultrastable Y zeolite
surface composition
bulk composition
aluminium distribution
X-ray pbotoelectron speclroscopy
