Crystal growth study of K-F nanozeolite and its catalytic behavior in Aldol condensation of benzaldehyde and heptanal enhanced by microwave heating

Hierarchical Cs–Pollucite Nanozeolite Modified with Novel Organosilane as an Excellent Solid Base Catalyst for Claisen–Schmidt Condensation of Benzaldehyde and Acetophenone

“…In order to confirm that TPOAC was chemically bound to the Cs-pollucite framework, as-synthesized CP-0 and CP-2.0 were selected and characterized with 29 Si MAS + DEC nmR spectroscopy. For CP-0, a broad signal is shown in the range of −72.9 to −104.1 ppm, where this band is due to the Q 1 : Si(OAl) 4 and Q 2 : Si(OSi)(OAl) 3 ) species originating from the Cs-pollucite framework (Figure 2a) [18]. On the other hand, CP-2.0 also exhibits the same nmR band at this region and a weak additional broad peak is also observed from −55 to −75 ppm, where this peak is contributed by the T n species (T n = RSi(OH) 3−n , n = 2 and 3) of TPOAC ( Figure 2b) [31].…”

“…The IR bands at 1014 and 1035 cm −1 are assigned to the internal vibrations of Si-O-T (T = Si, Al) asymmetric stretching modes while the signals resonated at 774, 720, and 631 cm −1 are the characteristics of distorted eight-membered ring sub-units present in the pollucite framework [18]. Furthermore, the IR band at 441 cm −1 is due to the bending vibration of TO 4 . On the other hand, two signals detected at 3458 and 1646 cm −1 are assigned to the stretching and bending vibrations of O-H groups of water, respectively [34].…”

“…Zeolites are crystalline aluminosilicate microporous minerals and are considered widely used in many potential applications, such as adsorption, ion exchange, drug delivery, and catalysis [1][2][3][4][5][6][7][8][9]. 2 of 16 In particular, Cs-pollucite is interesting because it has strong basic sites due to the presence of the alkali Cs + cation [10,11].…”

“…In addition, it has a three-dimensional open channel with an eight-membered ring pore size (pore opening 2.43 Å) forming a high thermally stable ANA framework structure [12]. However, the existence of small micropores in this zeolite provokes a barrier of diffusion limitation for guest molecules either from reactants or products [13]. In order to overcome the diffusion limitation of bulky molecules in Cs-pollucite, a viable approach has recently been proposed by downsizing the crystallite size to the nanometer range (<100 nm), with the aim of enhancing the external surface area of the zeolite [14][15][16].…”

Effects of Synthesis Parameters on Crystallization Behavior of K-MER Zeolite and Its Morphological Properties on Catalytic Cyanoethylation Reaction

“…Indeed, the pattern showed major peaks at 2θ = 8.96°, 10.84°, 12.46°, 16.58°, 17.80°, 27.50°, 28.10°, 30.28° and 32.88° which were characteristics of the MER framework topology [27]. Further increasing the heating time to 20 h showed no change in the framework composition and framework type but the XRD peaks with higher intensity and narrower peaks were recorded (Figure 1d: W-4), indicating Ostwald ripening and crystal growth were dominating the crystallization process [28]. This was supported by the FESEM microscopy showing that the crystalline K-MER zeolite nanorods further agglomerated and transformed into larger MER crystals (>1 μm) with bullet-shape morphology.…”