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With the growing global propylene demand, propane dehydrogenation (PDH) has attracted great attention for on-purpose propylene production. However, its industrial application is limited because catalysts suffer from rapid deactivation due to coke deposition and metal catalyst sintering. To enhance metal catalyst dispersion and coke resistance, Pt-based catalysts have been widely investigated with various porous supports. In particular, zeolite can benefit from large surface area and acid sites, which favors high metal dispersion and promoting catalytic activity. In this work, we investigated the PDH catalytic properties of Beta zeolites as a support for Pt-Sn based catalysts. In comparison with Pt-Sn supported over θ-Al2O3 and amorphous silica (Q6), Beta zeolite-supported Pt-Sn catalysts exhibited a different reaction trend, achieving the best propylene selectivity after a proper period of reaction time. The different PDH catalytic behavior over Beta zeolite-supported Pt-Sn catalysts has been attributed to their physicochemical properties and reaction mechanism. Although Pt-Sn catalyst supported over Beta zeolite with low acidity showed low Pt dispersion, it formed a relatively lower amount of coke on PDH reaction and maintained a high surface area and active Pt surfaces, resulting in enhanced stability for PDH reaction. This work can provide a better understanding of zeolite-supported Pt-Sn catalysts to improve PDH catalytic activity with high selectivity and low coke formation.

Emulsion solution crystallization can achieve a narrow and predictable crystal size distribution (CSD) when the emulsion droplets are uniform. The crystallization kinetics of emulsion solution crystallization are generally different from those of conventional bulk crystallization. This work characterizes the impact of temperature profile on emulsion solution cooling crystallization. The temperature is controlled by a tubular heat exchanger, and a membrane is used to create an emulsion with controllable droplet size distribution. The crystallization performance is characterized by the dynamic development of the crystal number density and the CSD, which are compared with those of bulk cooling crystallization. The crystal number density is highly sensitive to the cooling profile, and the process behavior is consistent with a system dominated by primary nucleation. Regardless of the cooling profile, secondary nucleation is suppressed in the emulsion with confined crystallization inside the droplets, which results in a narrow CSD. In contrast, secondary nucleation is dominant in bulk crystallization, leading to a broader CSD with a higher crystal number density. The mean crystal length decreases as the batch time increases with emulsion crystallization, which is different from bulk crystallization. A more predictable and narrower CSD can be obtained from emulsion crystallization, but a higher supersaturation or longer batch time is needed in emulsion crystallization to achieve a similar yield when compared to that in conventional bulk cooling crystallization.