Abstract:

The efficient, environmentally friendly, and cost-effective synthesis of zeolites holds significant importance in both academic and industrial applications. Traditionally, the synthesis of pure silicon MFI zeolite (Silicalite-1) through hydrothermal methods employing non-organic amine systems posed substantial challenges due to weak directing abilities and competitive growth of impure phases. In this study, Silicalite-1 zeolite was successfully synthesized in a methanol system, and particular attention was paid to the role of methanol and the crystallization conditions (water-to-silica ratio, alcohol-to-silica ratio, etc.) during the hydrothermal synthesis process. Computational and characterization techniques such as Monte Carlo simulations, XRD, SEM, TG, N₂ adsorption-desorption, and NH₃-TPD were employed. The results indicated that the introduction of seed crystals significantly improved the initial nucleation difficulties in the methanol system; a pure phase of Silicalite-1 with high crystallinity was directly synthesized when the seed crystal input was 3% and the alcohol-to-silica ratio was 3.3, showing excellent catalytic activity in the MTP reaction. Lastly, the low-cost synthesis strategy for Silicalite-1 proposed in this paper has notable research value and industrial application prospects.

Key words: molecular sieves, synthesis, Monte Carlo simulation, catalyst, stability

摘要：

分子筛的高效、环保和合成廉价在学术及工业应用领域都具有重要的意义。传统水热合成法中非有机胺体系因其弱导向性和杂晶相的竞争生长导致纯硅MFI分子筛（Silicalite-1）的合成极具挑战性。本文在甲醇体系中成功合成出Silicalite-1分子筛，并重点考察了水热合成过程中甲醇的作用和晶化条件（水硅比、醇硅比等）对分子筛合成的影响。使用蒙特卡罗模拟、X射线衍射（XRD）、扫描电子显微镜（SEM）、热重（TG）、N₂-吸附脱附和NH₃-程序升温脱附（NH₃-TPD）等方法进行了计算与表征。结果表明：引入晶种可以明显改善甲醇体系在晶化初期成核困难的问题，当晶种投入量为3%（质量分数）、醇硅比为3.3时可以直接合成出高结晶度的纯相Silicalite-1分子筛，该分子筛表现出优异的甲醇制丙烯（MTP）反应催化活性。最后，本文提出的Silicalite-1分子筛低成本合成策略具有显著的科研价值和工业化应用前景。

关键词: 分子筛, 合成, 蒙特卡罗模拟, 催化剂, 稳定性