A Hierarchically Micro-Meso-Macroporous Zeolite CaA for Methanol Conversion to Dimethyl Ether

Abstract

Abstract:A hierarchical zeolite CaA with microporous, mesoporous and macroporous structure was hydrothermally synthesized by a "Bond-Blocking" method using organo-functionalized mesoporous silica (MS) as a silica source. The characterization by XRD, SEM/TEM and N 2 adsorption/desorption techniques showed that the prepared material had well-crystalline zeolite Linde Type A (LTA) topological structure, microspherical particle morphologies, and hierarchically intracrystalline micro-meso-macropores structure. With the Bond-Blocking principle, the external surface area and macro-mesoporosity of the hierarchical zeolite CaA can be adjusted by varying the organo-functionalized degree of the mesoporous silica surface. Similarly, the distribution of the micro-meso-macroporous structure in the zeolite CaA can be controlled purposely. Compared with the conventional microporous zeolite CaA, the hierarchical zeolite CaA as a catalyst in the conversion of methanol to dimethyl ether (DME), exhibited complete DME selectivity and stable catalytic activity with high methanol conversion. The catalytic performances of the hierarchical zeolite CaA results clearly from the micro-meso-macroporous structure, improving diffusion properties, favoring the access to the active surface and avoiding secondary reactions (no hydrocarbon products were detected after 3 h of reaction).

Preparation and Potential Catalytic Applications of Hierarchically Structured Zeolites with Macropores

“…Reproduced under the terms of the Creative Commons CC‐BY license. [ 18 ] Copyright 2016, The Authors. Published by MDPI.…”

“…Templating with Organo‐Functionalized Mesoporous Silica : Wang and co‐workers used organic modified mesoporous silica in a bottom‐up approach as silica source during hydrothermal crystallization. [ 18 ] The mesoporous fumed silica was modified with an organosilane (phenylaminopropyl‐trimethoxysilane) resulting in the formation of CaA zeolites of spherical morphology with additional meso and macropores as shown in Figure 3c. In the transmission electron microscopy micrographs, the intact crystals did not show macropores, which indicates a limited connectivity of the macropore system to the external surface.…”

“…Hierarchical CaA zeolites with intracrystalline meso and macropores showed a higher dimethyl ether (DME) selectivity, conversion and catalytic stability in the conversion of methanol to DME. [ 18 ] However, due to the presence of mesopores the enhanced catalytic performance cannot be directly attributed to the presence of macropores.…”

Sustainable Route for Synthesis of All-Silica SOD Zeolite

“…Zeolites, which are constructed by AlO 4 or SiO 4 tetrahedra, have been widely applied in gas adsorption and separation, ion exchange, and shape-selective catalysis [1][2][3][4][5][6][7][8]. To date, there are many zeolites that have been successfully synthesized including silicate, aluminosilicate, germanosilicate, and so on [1][2][3][4][5][6][7][8].…”

First-Principles Study on Hydrogen Storage Performance of Transition Metal-Doped Zeolite Template Carbon

“…Although the zeolites for commercial use at present do not meet the standard of hydrogen storage materials, its rich and diverse structural characteristics will provide much broad development in the future energy storage. Therefore, it is of great significance to study the underlying adsorption and diffusion mechanism of hydrogen molecules in zeolites and predict the physical and chemical properties of synthetic materials for the molecular design of new materials in the future [8][9][10].…”