Monitoring of crystallization processes during synthesis of zeolite A by in situ 27Al NMR spectroscopy

Seed- and solvent-free synthesis of ZSM-5 with tuneable Si/Al ratios for biomass hydrogenation

“…41,42 Interactions between F and Al atoms in the various intermediates species formed during the crystallization process were further studied by a 2D 19 F- 27 Al heteronuclear correlation (HETCOR) NMR technique ( Figure 5c). 39,43 At the initial stage of the crystallization process no correlation was detected, as shown in Figure 5c (t = 0 h). However, when the crystallization time was extended to 4 h, a very weak correlation peak at ca.…”

“…79 ppm can be assigned to anionic Al(OH)4 − species in the Al-containing raw materials. 39,40 The additional resonances observed at ca. 52 ppm and 25 ppm are attributed to tetrahedral [AlO4]and pentacoordinated [AlO5] 2anions, respectively.…”

In situ ultrasonic monitoring of zeolite A crystallization from coal fly ash

“…A deeper understanding of the formation mechanism will not only help in controlling and predicting the best conditions for synthesis but will also unmask the cooperative phenomena dictating chemical-structure-physical property relationships. Many attempts to understand the zeolite formation processes have been based on the use of ex situ monitoring techniques [20,22]. These techniques rely on periodic quenching of the reaction mixture, i.e.…”

“…The challenge with this approach is that it is not so reliable since there could be artifacts caused by the quenching process. Recently, in situ monitoring methods have been applied by different researchers [20][21][22] and most of these developments are described in a recent review by Pienack and Bensch [23] who have classified the different in situ methods as; (i) in situ scattering techniques, (ii) in situ spectroscopy, (iii) in situ mass spectrometry, (iv) in situ transmission electron microscopy and (v) combination methods. In addition to the list, the in situ ultrasonic technique reported first by Toufar [24] and Schmachtl et al [25] has also elicited great interest to contribute to the understanding of the complexity of the zeolite formation process.…”

Controlled Release Kinetics in Hydroxy Double Salts: Effect of Host Anion Structure

“…The coefficient (Avrami exponent) potentially contains information about the mechanism of the reaction [39]. The Avrami-Erofe' ev model has been applied successfully to solution phase anion exchange reactions in layered materials, and other fluid phase reactions [2,10,40,41]; we have also shown that values of parameters obtained from analysis of both solid state transformations and solution phase processes, employing the Avrami model, are comparable indicating that there is correlation between solid state transformation and fluid phase processes [21]. The Avrami exponent is usually obtained by taking double logarithm of the Avrami-Erofe' ev equation obtaining (4), which was popularized by Sharp and Hancock in 1972 [42].…”