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Oxidative dehydrogenation of ethane in short contact time reactors

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Chapter 1 Introduction 14 The models proposed until now are useful tools to fit the experimental data in a limited range of conditions, but with hundreds of surface and homogeneous reactions, the physical meaning of the events occurring in the reactor may be easily lost. In the present study, a new approach will be used to model such complicated system. First of all, homogeneous and heterogeneous reaction rates will be compared with respect to the transport phenomena. Nevertheless, it is difficult under the conditions of reaction to obtain surface kinetic data due to the over-imposition of the homogeneous and heterogeneous reactions. Thus we preferred to conduct a comparison between the intrinsic gas-phase kinetics and the transport fluxes, to provide insights into the real reaction path of ethane towards the production of ethylene. The catalytic reactions are controlled by mass transport to the surface. Thus, above a certain temperature, mass fluxes to the surface are too slow and the catalytic reactions become negligible. We aim at developing a mathematical model of a monolithic reactor in which homogeneous reactions are coupled to the heterogeneous catalytic combustion of ethane. The kinetic model we think to use for the homogeneous reactions is the mechanism proposed by Marinov et al. (1996) or by Mims-Dean (1994), for fuel-rich conditions. Instead, on the surface we assumed that only the total oxidation of ethane occurs. Only one channel of the monolithic reactor will be modeled by means of a two- dimensional model, where mass and energy balance equations will be coupled with the Navier-Stokes equations, with the only simplification of the boundary-layer assumption. The system of partial differential equations will be solved by means of the module CRESLAF of the CHEMKIN3.6.2 package (Kee et al., 1990). This model will be considered a useful tool to determine the optimal conditions of operation and the properties required in an optimal catalyst.

Anteprima della Tesi di Francesco Donsì

Anteprima della tesi: Oxidative dehydrogenation of ethane in short contact time reactors, Pagina 14

Tesi di Dottorato

Dipartimento: Ingegneria Chimica

Autore: Francesco Donsì Contatta »

Composta da 194 pagine.


Questa tesi ha raggiunto 1055 click dal 04/11/2004.


Consultata integralmente 5 volte.

Disponibile in PDF, la consultazione è esclusivamente in formato digitale.