Ordered Micro/Mesoporous Composite Prepared as Thin Films

Abstract

A new synthesis method for preparation of thin films and powders consisting of zeolite beta nanocrystals embedded in ordered mesoporous silica matrix is described. The final structures possessing bimodal porosity, i.e., high degree of mesophase order and spatially defined microporous zeolite nanocrystals are obtained via simultaneous solvent evaporation of preformed silica/surfactant/ethanol/nanosized zeolite beta assemblies. The films were characterized with grazing-incident diffraction (GID), nitrogen sorption based on gravimetric measurements with quartz crystal microbalance (QCM) devices, and transmission electron microscopy (TEM). It is shown that the incorporation of beta nanocrystals in the mesoporous silica matrix and the mesophase order itself can be controlled through the variation of the fractional amounts of the zeolite nanoparticles and silica/surfactant solutions. The HR-TEM measurements showed that the nanosized Beta microporous crystals are separated and at the same time connected through an ordered mesostructured matrix.

New Strategy to Synthesis of Hierarchical Mesoporous Zeolites

“…In fact, however, the two templating system worked in a competitive, rather than cooperative manner, which resulted in the formation of the bulk zeolite without any mesoporosity, the amorphous mesoporous material, or their physical mixtures. 20 To solve the phaseseparation problem, amphiphilic organosilanes 21,22 or silane-founctionalized polymers 23 were introduced into the silica-alumina sol-gel reaction mixture as the mesopore-directing agents, because the hydrolyzable methoxysilyl moiety, contained in the surfactant, could strongly interact with the growing crystal domains through the formation of covalent bonds with other SiO 2 and Al 2 O 3 sources to avoid phase separation. The resulting materials exhibited the interconnected mesopores with zeolitic pore walls, but their mesoporous volumes were relative small.…”

Bimodal micro‐mesoporous aluminosilicates for heavy oil cracking: Porosity tuning and catalytic properties

“…13,14 Nevertheless, the diffusion path length in the micropore channels of these composite materials is still quite long for diffusion-limited reactions, 15 because of the bulky and separate nature of microporous zeolites in these composite materials. 16 Such a quite long diffusion path length often results in much longer time for intermediate product molecules inside micropore channels to diffuse outward, leading to unwanted by-reactions such as excessive cracking in FCC processes. So, to fully take advantage of the unique adsorption performance and excellent shape-selectivity of microporous zeolites without suffering from diffusional limitations, micropore channels in zeolite phase should be short 17 and directly connected to more open mesopores, as described by the concept of pore continuum.…”

Formation of ZSM‐22 Zeolite Catalytic Particles by Fusion of Elementary Nanorods

“…Zeolite nanocrystals that have particle sizes smaller than 200 nm are useful for the preparation of zeolite films, [1][2][3] membranes [4,5] and hierarchical materials. [6][7][8][9][10][11][12] In the field of catalysis, particle size generally is considered to be an important parameter for tuning the activity and selectivity of a zeolite catalyst.…”