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Oxidative dehydrogenation of ethane in short contact time reactors

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Chapter 1 Introduction 12 a marked activity towards CO 2 formation may be highly beneficial to the process and perform better than Pt or no catalyst at all. Perovskite-based catalysts show quite peculiar catalytic properties both in being good catalysts of CO oxidation to CO 2 as reported by Cimino et al. (2002), Ciambelli et al. (2001 and 2002) and in being able to produce ethylene in mild oxidative conditions (Dai et al., 2000, Lee et al., 2001) and we reckon they can be suitable to the process. Nevertheless, our goal is to provide a deeper understanding of the properties required to be an optimal catalyst in the ODH process. Thus, we intend to extend the investigation to different active phases, having in mind the catalytic properties but also the properties of thermal stability. In particular, perovskites are extremely stable and we think that their lack of activity may be compensated by the dispersion of a noble metal, which is stabilized in the oxide matrix and used in lower amount since finely dispersed. Also other oxides, stable at high temperature, such as CeO 2 , may be suitable for the applications of ODH. The investigation of the catalyst may be pursued also focusing on the effect of other parameters of the catalytic reactor affecting the performance of the system. In particular, structured catalysts are often coated with a washcoat layer for a number of reasons. The washcoat increases the surface area, helps in preventing sintering of the active phase, improves the adhesion of the catalyst to the support and definitely changes the catalytic system. Another aspect that requires careful attention is the morphology of the support. Many supports are available on the market, but we will limit our investigation to ceramic supports, especially to foam and honeycomb morphology. Foam and honeycomb monoliths are different in the degree of randomness and vorticity, affecting dispersion both in radial and axial direction and consequently heat and mass transfer. They are different also in the ratio between homogeneous volume and geometric surface, which can influence the extent of reaction in the homogeneous phase and on the catalytic surface. A low homogeneous volume and a large geometric surface can yield to the quenching of the gas phase reactions and then to mainly oxidation products. Nevertheless, a large geometric surface per unit of volume is important to hold the heat produced on the catalyst, above all in the lab scale reactor. After considering the main issues regarding the catalyst and the catalytic reactor, this research will face the optimization of the process, and the effect of the main parameters of operation. A good regulation of these parameters would allow tuning the process towards the desired products and conversions.

Anteprima della Tesi di Francesco Donsì

Anteprima della tesi: Oxidative dehydrogenation of ethane in short contact time reactors, Pagina 12

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.