无有机胺模板剂法制备ZSM-5@Silicalite-1核壳材料

ZSM-5@Silicalite-1核壳材料由于其表面纯硅Silicalite-1分子筛能够有效覆盖ZSM-5分子筛表面的酸性位,从而抑制外表面积炭反应,提高其在甲醇转化、烯烃裂解、烷基化等反应中的稳定性及特定产物选择性.但是,ZSM-5@Silicalite-1核壳材料合成需使用有机胺模板剂导向合成,且合成体系采用较...

Preparation of ZSM-5@Silicalite-1 Core-Shell Material in the Absence ofOrganic Amine Template

ZSM-5@Silicalite-1 core-shell material can inhibit the carbon deposition reaction on the external surface and improve its stability in methanol conversion, olefin cracking and alkylation, and selectivity in other specific products, because the pure silicon Silicalite-1 molecular sieve on its surface can effectively cover the acidic sites on the surface of ZSM-5 molecular sieve. However, ZSM-5@Silicalite-1 core-shell material is synthesized using an organic amine template, and the synthesis system adopts a high H₂O/SiO₂ molar ratio (n(H₂O)/n(SiO₂)>120), which brings problems such as high cost, low yield and more waste water. Therefore, a new strategy has been proposed for the green synthesis of ZSM-5@Silicalite-1 without using any organic amine template. This method uses ZSM-5 zeolite molecular sieve as the seed crystal and ethanol as the channel filler to successfully prepare ZSM-5@Silicalite-1 core-shell material by grinding, adopts XRD, SEM, N₂ physical adsorption, XPS and other characterization means for analysis, and investigates the impact of such parameters as n(Na₂O)/n(SiO₂), n(C₂H₅OH)/nSiO₂), seed crystal type and crystallization time on the synthesis of ZSM-5@Silicalite-1. The results show that ZSM-5@Silicalite-1 molecular sieve synthesized in the absence of organic amine template is characterized not only by high sample yield, but also by high degree of crystallinity and regular morphology. When n(Na₂O)/n(SiO₂)=0.035, n(C₂H₅OH)/nSiO₂)=1.62, and the crystallization time is 48 h, the crystallinity degree of ZSM-5@Silicalite-1 hits the peak.