Zeolites with high external surface area allow diffusing reactants greater access to catalytically active sites, which has led to interest in the preparation of nanosized zeolites. In this study, a top-down approach has been used for zeolite synthesis by first milling the zeolite to produce nanoparticles. This technique destroys the outer portion of the zeolite framework, causing a significant decrease in its catalytic activity. To remedy this, the damaged part was recrystallized using a dilute silicate solution after bead milling. The combined bead milling and postmilling recrystallization yielded nano ZSM-5 (MFI type zeolite), approximately 60 nm in size, with high crystallinity, and the zeolite powder showed a higher catalytic activity in cumene cracking in comparison with the raw ZSM-5 zeolite. Furthermore, the decrease in crystal size suppresses catalyst deactivation through coke deposition during cumene cracking.
A systematic investigation has been carried out on cavitation erosion in solid-water mixtures using vibratory test facilities and some analytical devices. A mixture of distilled water and heterogeneous solid particles is used. It is shown in this work that solid particles play significant roles on acoustic cavitation erosion through two ways when present in liquids. They, aggravate the abrasive wear of materials owing to the effects of particle size, concentration, and hardness. In addition, they relieve the damage produced by the reduction of the collapse pressure of cavitation bubble because of the variation of the physical properties in mixtures. Total erosion is dependent on this governing factor.
A new device has been developed for sequential production of mm-sized solid spherical shells using liquid-liquid gas systems. This device comprises a cylindrical vessel, for containing two kinds of immiscible liquids, and a gas injection orifice, set at the center of the vessel’s bottom. Solid spherical shells are successfully and sequentially produced by solidifying rising liquid spherical shells, formed sequentially at the horizontal interface between two immiscible liquids.
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