Catalytic partial oxidation of n-butane over Rh catalysts for solid oxide fuel cell applications
✍ Scribed by Seyed-A. Seyed-Reihani; Gregory S. Jackson
- Publisher
- Elsevier Science
- Year
- 2010
- Tongue
- English
- Weight
- 840 KB
- Volume
- 155
- Category
- Article
- ISSN
- 0920-5861
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✦ Synopsis
Development of solid oxide fuel cell (SOFC) systems running on hydrocarbons including liquid fuels and light hydrocarbons such as n-butane is beginning to show the attractiveness of SOFCs for small-scale power applications of <5 kW. Although it has been shown that direct utilization of hydrocarbons in SOFCs is a possibility with internal reforming for certain operating conditions, SOFC anode materials and architectures [1,2], stable SOFC operation at higher power densities can be achieved with external reforming [3,4]. For small power SOFC applications, fuel reforming and adequate preheating of inlet flows must be done in a volumetrically efficient manner. As such, catalytic partial oxidation (CPOx) of hydrocarbon fuels has been considered attractive because the rapid kinetics permit volumetrically efficient syngas production without excessive amounts of fuel preheating [5][6][7][8][9]. In comparison to endothermic steam reforming of hydrocarbons, CPOx provides superior start-up and transient response and reduces the heat input to the fuel stream -both of which are critical in small-scale power applications. Improving fundamental understanding of CPOx reactors with higher hydrocarbons can provide a basis for designing/optimizing systems for size and operability in various small-scale SOFC systems.
To understand the unique demands of small-scale SOFCs on CPOx reactors, Fig. 1 provides a schematic of an idealized SOFC system with a tightly integrated CPOx fuel processor, which provides both a H 2 /CO-rich mixture for the anode flow and general heating for both incoming flows. In such a configuration, waste heat recovery from the anode exhaust combustor can provide preheated air temperatures of 300 8C or higher for the CPOx reactor depending on heat losses along the outer wall of the air passages. In addition, internal heat exchange will occur from the CPOx to the surrounding air flow as indicated in the expanded view of the CPOx reactor in Fig. 1. It is important to understand how non-adiabatic operating conditions of the CPOx reactor will influence fuel conversion and product selectivity.
Early studies by Schmidt and co-workers on CPOx of higher hydrocarbons focused primarily on supported Rh and Pt catalysts in short t res reactors under near adiabatic conditions [10][11][12]. Their work indicated Rh catalysts have superior selectivity to syngas, and as such, supported Rh is the focus of this study. These and other studies on CPOx of higher hydrocarbons on Rh catalysts [5,13,14] still leave uncertainties as to the coupling of thermal energy transport and reactor performance in terms of fuel conversion and H 2 and CO selectivities. This is particularly important because the Catalysis Today 155 (2010) 75-83