Hierarchical ZSM-5 beads composed of zeolite nanosheets obtained by pseudomorphic transformation

Abstract

The concept of pseudomorphic transformation was used to transform amorphous mesoporous silica beads with different size (20, 50 and 75 µm) into hierarchical MFI-type zeolite beads composed of ZSM-5 nanosheets. The beads were synthesized under hydrothermal conditions at different temperatures and treatment times, with and without mechanical stirring? (à quelle étape?). The influence of the different synthesis parameters was investigated by X-Ray Diffraction, Scanning Electron Microscopy, Transmission Electron Microscopy, X-Ray Fluorescence, Nitrogen adsorption-desorption measurements, 27 Al solid-state Nuclear Magnetic Resonance, Energy-Dispersive X-Ray analysis and Thermogravimetric analysis.Well-crystallized 20 µm ZSM-5 nanosheets beads similar in size and shape to the original mesoporous amorphous silica beads were obtained after a hydrothermal treatment at 150 °C for 5 days in a tumbling oven and 2 days in static at 120 °C. The influence of the bead size on the pseudomorphic transformation was studied in order to prepare well-crystallized ZSM-5 nanosheets beads of 50 and 75 µm. Results showed that the required time of the static treatment at 120°C increases when the size of the parent silica spheres increases. This is explained by the fact that crystallization starts from the outer bead surface toward the center.

State of the Art and Perspectives of Hierarchical Zeolites: Practical Overview of Synthesis Methods and Use in Catalysis

“…Mesopores with an average diameter of 3.9-4.7 nm were obtained. [223] In another study, Yan et al used TPAOH and an ammonium surfactant, viz. C 6 H 5 C 6 H 4 OC 10 H 20 N(CH 3 ) 2 C 6 H 13 , in a dual templating synthesis method to create various bodies of ZSM-5 nanosheets (e.g., ultrathin ZSM-5 nanosheets, splitlike nanosheets and condensed packing plates), depending on the precise ratios of the templates.…”

“…Mesopores with an average diameter of 3.9–4.7 nm were obtained. [ 223 ] In another study, Yan et al. used TPAOH and an ammonium surfactant, viz.…”

Controlled Crystallization of Hierarchical Monoliths Composed of Nanozeolites

“…The resulting LTA monoliths showed high adsorption capacities for decontamination radioactive aqueous effluents in continuous flow thanks to their fast ion-exchange kinetics 56 . Our group has recently described the one-step synthesis of ZSM-5 nanosheets beads with different sizes by using the pseudomorphism concept 57 . Here, we describe the pseudomorphic transformation of two types of amorphous silica monoliths having bimodal micro/macro and meso/macro porosity, into ZSM-5 nanosheets monoliths.…”

Guided Crystallization of Zeolite Beads Composed of ZSM-12 Nanosponges

“…This concept was successfully used by Anne Galarneau's team to synthesize micrometric beads and zeolite monoliths of the LTA, SOD and FAU type with low Si/Al ratios [43][44][45][46]. Our group has recently reported the direct synthesis of hierarchical ZSM-5 beads [47] and monoliths with nanosheets morphology [48], and also plain and hollow purely silica beads of silicalite-1 nanosheets by using the pseudomorphic transformation method [49]. Here, we report the use of the pseudomorphic transformation concept to elaborate hierarchical ZSM-12 zeolite beads with nanosponges morphology thanks to the use of a dual-porogenic surfactant as a template and growth inhibitor, which was used for zeolite *BEA nanosponge synthesis [9,21,25].…”