无模板一段晶化法ZSM-5分子筛的制备与表征

Template-free synthesis and characterization of ZSM-5 zeolites by one-step method

无模板水热体系中,在摩尔组成12Na2O:(80、100)SiO2:2Al2O3:2500H2O条件下,室温动态老化24h后180℃晶化24~48h,成功制得ZSM-5分子筛,采用XRD和SEM等手段考察分子筛的结晶度和表观形貌随晶化时间的变化规律。结果表明,在硅铝比为40~50条件下,随晶化时间的延长,分子筛经历了从无定形前驱体、菜花状层片结构和结晶度较高的蛹状大单晶(20μm×10μm)等晶化阶段;采用Py-IR对比考察有机胺体系商品ZSM-5分子筛与本实验无模板ZSM-5的酸性,结果表明,无模板一段晶化法制得的ZSM-5分子筛B、L酸量较大,B/L比值较低。

ZSM-5 zeolites were hydrothermally synthesized in the template-free system by aging at room temperature for 24 h followed by crystallizing at 180°C for 24-48 h when the mole ratio was 12Na2O:(80 and 100)SiO2:2Al2O3:2500 H2O, and the effects of crystallization time on the structure and morphology of the zeolites were investigated by XRD and SEM. The results showed that the crystallization of ZSM-5 in template-free system experienced the process from amorphous precursor, cauliflower lamellar structure to pupal-like large crystal with higher crystallinity(20μm×10μm). Acidity of template-free ZSM-5 was characteriazed by Py-IR, and the results indicated that the amounts of B and L acids were higher and the ratio of B/L was lower compared with that of the commercial ZSM-5(n(SiO2)/n(Al2O3)=38) synthesized in the organic amine system.