Following the Crystallization of Microporous Solids Using EDXRD Techniques

Abstract

Energy dispersive X-ray diffraction (EDXRD) techniques are applied to study the development of crystalline phases during the synthesis of microporous materials. We present data for both zeolite A and AlPO-5 systems. We explore the effects of template concentration and of temperature. The measured activation energy for zeolite A of ∼58 kJ mol-1 accords well with that observed for other silicate systems. The kinetics revealed by our study accord with the nucleation/growth model of the Avrami−Erofeev treatment.

In‐situ Energy‐Dispersive X‐ray Diffraction Studies of Crystal Growth and Compound Conversion Under Solvothermal Conditions

“…The values are in a range similar to those calculated for the crystallisation of the DAP compound as well as for usual zeolite compounds reported in the literature. [9,39] For the reactions with changing mechanisms the k values for α Ͻ 0.8 were used. [38] Rate equation f(α) ϭ kt m Diffusion-controlled:…”

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

“…A commonly used version higher of in situ XRD is energy-dispersive X-ray diffraction (ED-XRD), which has a much time resolution higher than that of regular XRD. This approach makes use of a white (multiwavelength) X-ray beam, which is sent through the sample, and the scattered X-rays are detected as a function of energy at one or more fixed angles [42].…”

“…At higher alkalinity, these aggregates did not form, which suggests that precursors can self-assemble into a crystal structure, as with the secondary building unit (SBU) mechanism (Figure 12.2a) [43]. ED-XRD has until now not been applied to silicalite-1 synthesis, but has shown its capabilities in a range of other microporous materials, such as zeolite A [44] and AlPO-5 [42]. However, as soon as XRD is combined with simultaneously measured SAXS, the single-wavelength approach is more convenient [4].…”

Systematic study of the crystallization process of CrAPO-5 using in situ high resolution X-ray diffraction

“…On the other hand, the present methods used to investigate state of Cr ions heavily rely on ultraviolet/visible spectroscopy (UV-vis), electron paramagnetic resonance (EPR), 15,[18][19][20][21][22][23][24] X-ray absorption spectroscopy (XAS) [25][26][27] and nuclear magnetic resonance (NMR), 28 which all focused on the synthesized products. A large number of studies have been devoted to studying the transformation of gel to nanoporous materials using a variety of in situ techniques, like X-ray diffraction (XRD) methods, [29][30][31][32][33][34][35] small-angle X-ray scattering (SAXS) techniques 5 and X-ray absorption spectroscopy (XAS). 36,37 Although a combined technique approach using all these methods has been reported to derive mechanistic aspects of the crystallization process, 5,37 recent developments, particularly in the area of angular-dispersive high resolution powder X-ray powder diffraction (HRXRPD), make it possible to collect high-quality diffraction data in a very short time scale, which will not only determine the kinetics, but also the precise structural parameters, in particular the variation in lattice parameters of the reacting system.…”