Microexplosion under Microwave Irradiation: A Facile Approach to Create Mesopores in Zeolites

Abstract

A facile microexplosion approach has been successfully developed to produce an interwoven mesopore network in zeolite crystals via the rushing-out of gases generated by decomposition of H 2 O 2 under microwave irradiation. This "gas imprint" method creates the mesopores from the interior crystal toward the exterior, in line with the direction of the pristine microporous channels, and is different from the previous methods in which the reagent starts an attack from the crystal surface and perforates inward. The created mesopores extend throughout the whole crystal and highly blend into the intrinsic micropores around. The acidity of zeolite is also well preserved due to this unique mechanism of pore creation. The continuous high quality hierarchical architecture with intact acidity leads to a notable increase both in the conversion of 2-methoxynaphthalene acylation and in the selectivity to the target molecule of 2-acetyl-6-methoxynapthalene. This microexplosion approach offers an efficient synthesis protocol of zeolitic hierarchy integrating intersected mesoporosity and zeolitic microporosity and opens the way to the rational organization of meso-and microporosity for maximal advantage in applications.

Synthesis of highly active ETS-10-based titanosilicate for heterogeneously catalyzed transesterification of triglycerides

“…It was suggested that exposure of the ETS-10 framework to H 2 O 2 solution leads to its partial removal either by the disruption of Ti–O–Ti chains and partial leaching of Ti atoms [26] or by microexplosions if elevated temperatures are used [39]. At the same time, the measured specific micropore volume either does not change (for 30 and 45 min of treatment time) or slightly increases from 0.110 cm 3 g −1 for the parent titanosilicate to 0.131 cm 3 g −1 after 60 min of treatment.…”

“…In such a case, it is expected that a significant portion of the mesopores might be not accessible for bulky reactants, such as triolein, being too large to diffuse through the micropores. In the case of treatment of ETS-10 titanosilicates with H 2 O 2 at elevated temperatures, if accompanied by microexplosions [39], the appearance of such domains is possible. To address this, a number of NMR experiments with adsorbed Xe possessing a polarizability that is high enough to distinguish between micro-, meso-, and macropores were conducted [60].…”

Combined solid-state NMR, FT-IR and computational studies on layered and porous materials

“…)to minimize the intra-and intermolecular electrostatic interactions. As the sitting position of Al atom (one of the 24 possible tetrahedral crystallographic sites) changes, and is responsible for changes in the C-N-C angles in TPA and a deviation from Td symmetry, very different sets of 14 N quadrupolar parameters were obtained.Tang et al successfully employed micro-explosion method by microwave assisted decomposition of H2O2 to create mesopores from the interior zeolite crystal toward the exterior 297. The effects of the micro-explosion process on the properties of the zeolites were investigated by ssNMR and IR spectroscopies.…”

“…Al MAS NMR spectra (B) of BEA zeolite before (a) and after (b) microwave treatment, showing the formation of two additional tetrahedral framework27 Al. Adapted with permission from ref 297…”

Hierarchically‐Ordered Zeolites: A Critical Assessment

“…Even combinations of both methods are reported as design option. [ 163 ] The breaking of the bonds can be initiated by additional, preparatory process, a hydrothermal [ 164 ] (e.g., steaming), or physical (e.g., an exposure to radiation [ 165 ] ) processes. The extractive demetallation step has to be performed in the second additional process after attacking the T‐O‐T bonds of the framework in the first, the demetallation initiating step.…”