This thesis presents a catalytic membrane reactor configuration (CMMR), which is intended for efficient conduction of the fluorination of toluene with respect to industrial production of mono-fluorinated products. The underlying paradigms for the development of this device are process intensification, simplification and synthesis. In this manner a reactor is created which addresses the problematic features of the direct fluorination of toluene reaction and also aims on high overall efficiency, e.g. by reducing downstream processing. Microreactors inherently facilitate high gradients of concentrations and temperatures due to small measures, which results in high material and energy fluxes. Additionally, a multifunctional catalytic membrane is used to supports the electrophilic attack of fluorine on organic compounds and improve heat management and process safety. A mathematical model of this process is developed, based on heat, mass and momentum conservation equations, and equations describing the reaction chemistry. The model is too complex to be solved analytically because of the fact that momentum, heat and mass conservation equations including alchemical reactions have to be solved simultaneously in a 3-dimensional modelling domain. The finite element method was found to be suitable to solve this specific problem, because its intrinsic structure facilitates efficient handling of boundary value problems and complex modelling domain geometries. A commercial package is employed which allows 3-dimensional simulations and features powerful post-processing tools. Results obtained Jähnisch et al.(2000) with the direct fluorination of toluene in a failing film microreactor (FFMR) are used to determine some model parameters and to verify the model. In a simulation study the process model is used to analyse heat and mass transfer processes and to determine the achievable performance of the CMMR with regard to the selectivity, the production rate, the conversion of toluene and process safety. As a benchmark for the effectiveness of the membrane, results obtained with the FFMR employed by Jähnisch et al. (2000) are used. In this connection the most important feature of the membrane under investigation are: support of the electrophilic reaction (with rate constant k<sub>1</sub>), decoupling of the momentum of the gas and the liquid flow, high heat conductivity and diffusion resistance imposed on reactants and intermediate products. Heat management with the CMMR is analysed in connection with the design of the integrated heat exchanger with the goal of minimising the temperature variations in the reactor cross-section and along the reactor as well as avoiding heat back-mixing which can potentially result in thermal run-away and unsafe operation. The results present a good basis for the design and experimental work with a pilot plant and optimisation of this process as well as scale-up in the course of plant design for the industrial production of mono-fluorinated toluene.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:661647 |
| Date | January 2005 |
| Creators | Schuster, Andreas |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/14361 |
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