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Highly ordered mesoporous materials with extremely high hydrothermal stability have been successfully synthesized by a novel and facile approach. Our method is built on the understanding that the hydrothermal treatment process plays an important role in the synthesis of mesoporous materials. It is proposed that in order to use high temperature hydrothermal treatment to increase the inorganic framework cross-linkage, an important requirement is that the organic surfactants must be retained as much as possible to maintain the preformed organic−inorganic composite mesostructure against framework shrinkage during the hydrothermal treatment process. This requirement can be achieved by enhancing the surfactant−silanol interaction at the organic−inorganic interface through adjusting the hydrothermal treatment pH and adding acetic acid (HAc) during the synthesis. When a high temperature (∼200 °C) hydrothermal treatment is employed, ordered mesoporous materials can only be obtained in a hydrothermal treatment pH range of 1−3. When the hydrothermal treatment pH is near the isoelectric point of silica, the highest silanol density on silica walls can entrap the largest amount of surfactants within pores, resulting in highly ordered mesostructured materials. Moreover, the disadvantage of the hydrothermal treatment under strong acidic conditions widely adopted in the literature has been revealed. Compared to previous reports, our approach is simple and does not involve environmentally unfriendly or expensive agents, thus is easy to be scaled up for industrial applications. Most strikingly, the highly ordered mesostructure of aluminosilicate synthesized by our approach can be maintained after steam treatment at 800 °C for 5 h with only a 4.9% decrease in the Brunauer−Emmett−Teller surface area. Our achievements have added new contributions to understanding the preparation of highly ordered and highly stable mesoporous materials, which sheds light on the practical applications of this new family of porous materials in the petroleum and petrochemical industry.

A modified 3D porous material with cage-like structure for efficient oil/water and emulsion separation.

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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).

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