Methods for in situ spectroscopic probing of the synthesis of a zeolite

Abstract

Unraveling the crystallization mechanism of zeolites remains an increasingly important challenge in chemistry. During the last decade, in situ spectroscopic methods have provided an unprecedented level of detail of the underlying molecular mechanisms and their kinetics. Magnetic resonance, vibrational and X-ray absorption techniques have emerged as principal tools for the in situ observation of crystallization. In this tutorial review, we discuss how these in situ methods have contributed to our understanding of the complex and diverse molecular processes that govern zeolite crystallization.

Probing ZnAPO-34 Self-Assembly Using Simultaneous Multiple in Situ Techniques

“…February 13,2011 ABSTRACT: The hydrothermal crystallization of ZnAPO-34 (CHA) molecular sieves has been studied for the first time using a combined in situ four technique setup utilizing SAXS/WAXS/XAFS/Raman to follow the various steps that occur during the complex transformation process of an amorphous precursor gel into a crystalline microporous material. These data are also supported by a detailed characterization of both the precursor gel (using Raman, NMR, XAFS, and TEM) and the final crystalline material (NMR, XRD, XAFS, TEM, and energy minimization calculations).…”

Recent Trends in Operando and In Situ Characterization: Techniques for Rational Design of Catalysts

“…The crystallization is initiated by heating the mixture in a sealed autoclave reactor. This usually takes place at a temperature between 50 and 200 • C and at autogeneous pressure [16][17][18]. The transformation of molecular precursors to micron-sized zeolite crystals involves several steps [19].…”

“…The transformation of molecular precursors to micron-sized zeolite crystals involves several steps [19]. A number of review and original articles are available on the possible mechanisms of silicalite-1 crystallization [16,[20][21][22][23][24]. Three possible mechanisms, as shown in Figure 12.2a [16], are distinguished and the crucial differences lie in two points: the size range in which the first ordered units are formed and the size range in which particles aggregate to form larger structures.…”

“…A number of review and original articles are available on the possible mechanisms of silicalite-1 crystallization [16,[20][21][22][23][24]. Three possible mechanisms, as shown in Figure 12.2a [16], are distinguished and the crucial differences lie in two points: the size range in which the first ordered units are formed and the size range in which particles aggregate to form larger structures. The parameters that influence the mechanism and thus the final structure are reaction mixture pH [25] and synthesis and crystallization temperatures [21,23].…”

“…During the synthesis stages of silicate-1, several intermediate crystallites of different size ranges are known to be involved and this difference in size necessitates [16].) (b) Schematic of the crystallization mechanisms as a function of particle size and in situ analysis techniques, as described in the text.…”