The effects of gel aging on the synthesis of NaY zeolite from colloidal silica

Hydrothermal synthesis of zeolite L in a Na+/K+ mixed alkali system

“…9 shows the morphology of zeolite L crystals obtained from the gel aged for 1 day by using Ludox and Zeosil as silica source under static conditions. For both of the silica sources, aging of the initial gel prior to crystallization also led to a decrease in the average crystal size of zeolite L. Numerous studies have been conducted in which the synthesis gel was aged at low temperature prior to crystallizing at elevated temperatures [38][39][40]. It is believed that the aging treatment offers the time required to achieve the formation of nuclei with dissolution of silica sources.…”

Nucleation and growth of zeolites and inorganic mesoporous solids: Molecular insights from magnetic resonance spectroscopy

“…NMR spectroscopy has provided valuable molecular-level insights concerning the influence of gel aging on the nucleation and growth of zeolites. One example is the crystallization of zeolites with technologically important faujasite-type (FAU) structures, for which the crystallization rates and composition of the zeolite products depend strongly on the aging of the initial hydrogels formed by mixing sodium aluminate and colloidal silica in aqueous sodium hydroxide solutions [39,40]. Recent ex situ 29 Si MAS NMR experiments [41] on hydrogel samples extracted after different aging periods indicate that, during aging of the gel, colloidal silica is dissolved, and with increasing aging time, aluminosilicate species are formed consisting exclusively of Q 4 (4Al) silicon units that are connected to four aluminum atoms via bridging oxygen atoms.…”

Changes of medium-range structure in the course of crystallization of zeolite omega from magadiite

“…Understanding the crystallization mechanisms of zeolites can conduct to exploit efficient routes to synthesize them. Although numerous works have attempted to understand the mechanisms of zeolites and solution transport and solid phase transformation mechanisms are proposed [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18], relatively few studies have been performed on the elucidation of the mediumrange structures and their changes during zeolite crystallization. As it is reported in the previous study, the short-range order is represented by the local coordination polyhedra, while the medium-range structure can be regarded as the next highest level of structural organization beyond the short-range order [19].…”