Hydrodynamics and Mass Transfer of Multiphase Packed-Bed Microreactors
Lead Research Organisation:
University College London
Department Name: Chemical Engineering
Abstract
Laboratory studies of catalyst and reaction performance are routinely performed in reactors that are orders of magnitude smaller than those in commercial practice. Reducing the scale of experimentation has several advantages, such as lower equipment costs, lower material amounts and intrinsically lower safety risks. When scaling down three-phase reactors, the hydrodynamics change significantly to those in industrial and laboratory reactors due to a shift in the dominant forces to viscous and surface tension forces. As a result, the hydrodynamics and correlations available in the literature for conventional scale trickle-bed reactors cannot be extrapolated. To this end, this project seeks to develop continuous flow microfluidic systems for the investigation of hydrodynamic and mass transfer behaviour in multiphase packed bed reactors. Novel on-chip analytical technologies for reactor characterisation will be developed and used to characterise reactor performance. This will involve the use of spectroscopy to determine residence time distributions, the results of which can be used determine axial and radial dispersion characteristics as well as develop mass transfer correlations applicable to micro-packed bed reactors. Simulation tools will also be used to effectively design micro-reactors for hydrodynamic and mass transfer purposes.
Organisations
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| EP/N509577/1 | 01/10/2016 | 24/03/2022 | |||
| 1808457 | Studentship | EP/N509577/1 | 14/11/2016 | 13/02/2021 | Baldassarre Venezia |
| Description | The use of reactors with a packed-bed of catalyst may suffer from low catalyst efficiency and non-uniform temperature conditions. Liquid-solid slurry reactors can overcome these problems by allowing the use of small particles and enhancing the mixing properties between the catalyst and the liquid reactants. In our project we faced the issue related to the aerobic oxidation of alcohols to aldehydes. This is commonly avoided in industry due to the risk of mixing the substrate with a gaseous oxidant. A solution to overcome this hazard is to use membrane contactors that are able to separate the two reacting phases. The development of a novel reactor configuration that combines the advantages of using a slurry tubular reactor in a loop configuration and a tubular membrane contactor for the safe oxygen delivery was realised. This was demonstrated to be an effective and safe reactor for the catalytic aerobic oxidation of benzyl alcohol. The reactor is flexible, as any powdered catalyst can be used in batch or continuous operation. Experiments performed in collaboration with Cardiff University, showed that the reactor operated in batch mode had comparable performance to that of a conventional autoclave which used pure oxygen bubbled in the substrate. The addition of a crossflow filter to the reactor loop allowed to keep the catalyst confined inside the loop and operate in a continuous production mode. Due to its effective oxygen delivery and the use of a catalyst powder in a slurry form, this reactor showed superior performance in terms of compared to a flat membrane packed-bed reactor. Other reactions can be performed in this reactor involving a wider spectrum of catalysts, including those that are difficult to pelletize, with the additional benefits of having small mass transport resistances and the possibility of operating safely if a gaseous oxidant is to be employed. The development of this novel reactor allowed us to improve mechanical design skills for designing reactors for alcohol oxidation applications. However, many problems arose during the design of such reactor. Clogging of the catalyst particles inside the loop was one of them. In order to overcome this, another new reactor design was conceived as outcome of this project. |
| Exploitation Route | This novel reactor concept can be employed in research in the chemical or pharmaceutical industry or academia. Due to the low mass transfer resistances to the catalyst sites, studies on the intrinsic kinetics in oxidation and hydrogenation reactions can be performed. Furthermore, its plug-and-play configuration and the use of a membrane make this reactor easy and safe to use. |
| Sectors | Chemicals,Pharmaceuticals and Medical Biotechnology |
| Description | The slurry loop tubular membrane reactor is part of the family of membrane reactors. These can be employed in the aerobic oxidation of alcohols. In pharmaceutical industry potent and toxic inorganic oxidants are traditionally employed to oxidize alcohols. However, our novel reactor uses only molecular oxygen. The atom efficiency that arises from using oxygen and the environment-friendly catalysts employed in reaction satisfy the principles of green chemistry. Further development of this type of reactors should be considered in the future in order to establish efficient green chemical processes. |
| Sector | Chemicals,Pharmaceuticals and Medical Biotechnology |
| Impact Types | Societal,Policy & public services |