核壳结构Beta/MCM-22双微孔复合分子筛的合成与表征

以Beta分子筛为晶核,通过二步水热晶化法成功制备了形态良好的Beta/MCM-22核壳结构复合分子筛。采用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)及N2吸附-脱附技术等对分子筛进行了表征。结果表明,复合分子筛形态规整,Beta与MCM-22分别作为核壳而共生;Beta/MCM-22复合分子筛孔结构性质介于MCM-22、Beta分子筛之间。在酸性分布上,复合分子筛的中强酸及B酸所占比例显著增加(CB/CL=13.8)。通过Ar-H2等离子体对Beta分子筛进行处理,使其表面能提高并使表面正电荷富集、硅羟基增加,这是形成良好Beta/MCM-22核壳结构的内在原因。

Synthesis and characterization of core-shell Beta/MCM-22 micro-microporous composite zeolites

With Beta zeolite as the core crystals, core-shell Beta/MCM-22 composite zeolites with uniform morphology were synthesized by a two-step hydrothermal method. The composite zeolites were characterized by XRD, SEM, TEM, N₂-adsorption and FT-IR. The results showed the composite zeolites exhibit uniform structured morphology; Beta and MCM-22 zeolites act as core and shell, respectively. The pore structure of Beta/MCM-22 composite zeolites was between those of MCM-22 and Beta zeolites. The amounts of medium acidic sites and brnsted acidic sites are increased markedly (C_B/C_L = 13.80) in the composite zeolites. The surface energy, Si-OH groups and surficial positive charges of Beta zeolites are enriched through Ar-H₂ plasma surface treatment, which contributes to the formation of uniform core-shell Beta/MCM-22 composite zeolites.