Recyclable synthesis of Cs-ABW zeolite nanocrystals from non-reacted mother liquors with excellent catalytic henry reaction performance

Nanoscale zeolites are very attractive for advanced applications such as in catalysis, adsorption, supports, sensors and carriers. Green synthesis of these materials is highly appreciated aiming to increase product yield while chemical waste and production cost can be reduced. Here we report high-yield, low-cost and green synthesis of nanosized Cs-ABW zeolite by recycling and using the non-reacted mother liquors waste solutions produced from the hydrothermal Cs-ABW zeolite synthesis. The nanocrystalline Cs-ABW solid product of each successive batch was collected and characterized while the non-reacted mother liquors were recovered and re-used for subsequent synthesis of nanozeolites. The synthesized Cs-ABW zeolite nanocrystals from three subsequent cycles possessed fairly similar properties and they exhibited excellent catalytic performance in Henry (nitroaldol) reaction of benzaldehyde and nitroethane thanks to their basic sites, (Si-O-Al)-Cs⁺, located at the external surface of the zeolite. This approach hence suggests a low-cost and eco-friendly preparation of Cs-ABW zeolite nanocrystals since less chemical waste is disposed while the product yield can be significantly improved which are ideal for industrial scale-up process.