In the last decades, miniaturized flow chemistry has promised to bring the benefits of process intensification, continuous manufacturing and greener chemistry to the fine chemical industry. However, miniaturized catalytic processes where gas, liquid, and solids are involved have always been impeded by two main drawbacks: multiphase-flow maldistribution (i.e. gas channeling) and clogging of capillary reactors. In this thesis, first principle models have been used to capture the complexity of multiphase flow in micropacked-bed reactors, which can suffer from poor and unpredictable mass-transfer performance. When the particle size ranges 100 µm in diameter, capillary and viscous forces control the hydrodynamics. Under such conditions, the gas —and not the liquid— flows creating preferential channels that cause poor radial dispersion. Experimental observations from the literature were reproduced to validate a physical-based modeling approach, the Phase Field Method (PFM). This simulation strategy sheds light on the impact of the micropacked-bed geometry and wettability on the formation of preferential gas channels. Counterintuitively, to homogenize the two-phase flow hydrodynamics and reduce radial mass-transfer limitations, solvent wettability of the support needs to be restricted, showing best performance when the contact angle ranges 60° and capillary forces are still dominant. Visualization experiments showed that ultrasound irradiation can also be used to partially fluidized the bed and modify the hydrodynamics. Under sonication, residence time distributions (RTD) in micropacked-bed reactors revealed a two-order-of-magnitude reduction in dispersion, allowing for nearly plug-flow behavior at high gas and liquid flow rates. At a reduced scale, surfaces vibrating with a low amplitude were shown to fluidize, prevent and solve capillary tube blockage problems, which are commonly found in the fine chemical industry for continuous product synthesis. The modeling and simulation strategy used in this thesis, enables a fast prototyping methodology for the proper acoustic design of sonoreactors, whose scale-up was achieved by introducing slits in sonotrodes. In addition, a patent-pending helicoidal capillary sonoreactor has shown to transform longitudinal vibrating modes into radial and torsional modes, pioneering a new range of chemistry able to handle a high concentration of particles. The contributions of this thesis made in the fields of reaction engineering and process intensification have demonstrated how computational methods and experimental techniques in other areas of research can be used to foster innovation at a fast pace.
| Identifer | oai:union.ndltd.org:ua.es/oai:rua.ua.es:10045/90920 |
| Date | 20 September 2018 |
| Creators | Navarro-Brull, Francisco J. |
| Contributors | Gómez, Roberto, Universidad de Alicante. Departamento de Química Física |
| Publisher | Universidad de Alicante |
| Source Sets | Universidad de Alicante |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/doctoralThesis |
| Rights | Licencia Creative Commons Reconocimiento-NoComercial-SinObraDerivada 4.0, info:eu-repo/semantics/openAccess |
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