Mechanism of seeding in hydrothermal synthesis of zeolite Beta with organic structure-directing agent-free gel

Engineering of zeolite BEA crystal size and morphology via seed-directed steam assisted conversion

“…Similar tendency was observed in the case of seeded OSDA-free synthesis under hydrothermal conditions. 31 However, in that case the authors observed also the inuence of seed crystal size, which was much stronger than the effect of SAR.…”

“…There are several hypotheses in the literature on the fate of seeds during hydrothermal synthesis of zeolite BEA and on the mechanism of seeding. 20,31,35,36 Xiao et al 35 proposed core-shell mechanism, according to which BEA seeds introduced during the gel preparation remain intact during the hydrothermal synthesis and provide a surface for crystal growth. Kamimura et al 36 suggested that BEA seeds are partially dissolved and disaggregated into small pieces during the initial step of hydrothermal treatment and the new BEA is crystallized on the surface of these species exposed and/or dispersed in the interface of the amorphous aluminosilicate and the liquid phase.…”

Understanding Commonalities and Interplay Between Organotemplate‐Free Zeolite Synthesis, Hierarchical Structure Creation, and Interzeolite Transformation

“…Prior to this report, beta zeolites were believed to be only synthesized in the presence of appropriate organic templates. Due to the importance of beta zeolites in several industrially‐relevant applications, this approach attracted great attention and numerous follow‐on studies on the optimization of synthesis conditions, as well as on the identification of parameters affecting the product characteristics and yields . The OSDA‐free beta zeolites (OF‐beta) exhibit unique characteristics in terms of Al contents and structural integrity as compared to the conventional beta zeolites synthesized with tetraethylammonium hydroxide (TEAOH) (TEA‐beta) as the structure‐directing agent.…”

Preparationand Characterizationof High Performance Zeolite T Membranes from Clear Solutions

“…晶种液的配制: 自制颗粒尺寸为 2 μm 的 T 型分 子筛 [11] 加去离子水配制成浓度为 2wt%大晶种液, 自制 400 nm 的 T 型分子筛 [11] 体有取向生长趋势, 这与文献报道一致 [9] 。 从截面图 可看出, 随着晶化时间的增加, 膜层的厚度逐渐增 加。这与图 4 中随晶化时间延长, T 型分子筛膜衍射 特征峰强度逐渐增强相一致。 研究发现采用清液体系晶种诱导制备 T 型分子 筛膜的过程十分复杂。晶种在晶化过程中引发二次 成核, 以及表面生长机制共同促进了沸石晶体的快 速生长 [13][14][15]…”