Physicochemical Characterization of Silicalite-1 Nanophase Material

Abstract

A silicalite-1 nanophase material with an elementary particle size of 18-100 nm is synthesized from clear solution and isolated and purified using supercentrifugation. The nanopowder is characterized in detail using scanning electron microscopy, high-resolution transmission electron microscopy, attenuated force microscopy, 29 Si magic angle spinning NMR, 13 C cross polarization magic angle spinning NMR, X-ray diffraction, dinitrogen physisorption, and thermogravimetric analysis and compared with micrometer-sized silicalite-1. The nanosized and micrometer-sized materials have many common properties including the refined structure and the nature and concentrations of tetrapropylammonium species incorporated during the synthesis. Unique properties of the nanophase are a splitting of the characteristic framework vibration at 550 cm -1 into a doublet at 555 and 570 cm -1 , a high concentration of defect sites, and a strain in the crystallites along the "a" crystallographic direction. The nanophase exhibits a two-stage dinitrogen physisorption in the low-pressure region, ascribed to adsorptions in micropores created by the stacking of the nanoparticles in addition to adsorptions in the intracrystalline micropores.

Synthesis of hierarchical porous materials with ZSM-5 structures via template-free sol–gel method

“…4 shows FTIR spectra of different samples. Compared with the IR spectrum of DCX, those of the samples after recrystallization contain silanol stretching band [14] at 950-960 cm À1 and double ring vibrations band [15] at 550-560 cm À1 (positions marked by black arrows). For HPM-80 the appearance of the 550-560 cm…”

Biomorphic Cellular SiSiC/Zeolite Ceramic Composites: From Rattan Palm to Bioinspired Structured Monoliths for Catalysis and Sorption

“…The isotherm of the SiSiC/ZSM-5 composite showed a step in the range P/P 0 = 0.1±0.4, related to the presence of inter-/intracrystalline mesopores. The Barrett±Joyner±Halenda (BJH) method was used in order to evaluate the mesopore distribution [33] (mesopore volumẽ 0.0013 cm 3 g ±1 and an average mesopore size of 2.2 nm). The stereological image analyses for the pore size distribution in the biomorphic ceramic composite show that the average pore size shifts from~300 lm in the SiSiC ceramic composite tõ 250 lm in the Silicalite-1/SiSiC (Fig.…”

Ordered Porous Nanomaterials: The Merit of Small

“…One of the most recent and detailed studies on the crystallization mechanism of zeolites is owed to the group of Martens and Jacobs at the Catholic University of Leuven [62][63][64][65][66], where they described the zeolite formation originating from "nanoslabs" with very small dimensions which contained one SDA molecule each. More recent studies [67,68] pointed towards a type of silicate oligomer as the primary constituent for the nanoslabs.…”