Characterization and performance analysis of fuel flexible OSR-WGS catalysts

Abstract

This research study was conducted in order to acquire insight of an efficient fuel processor (FP) since FPs are believed to represent a key step of transition from conventional to decentralized energy production when combined with fuel cells (FC). Emphasis was first given to oxidative steam reforming (OSR) catalyst - namely Pt-Ni/Al2O3, by studing its surface characteristics, testing its performance under different hydrocarbon feed compositions and acquiring power-law kinetics of OSR reaction. Infrared CO adsorption studies revealed the possibility of a surface alloy formation. OSR experiments conducted with propane and/or methane feeds showed that addition of methane to the hydrocarbon feed enhanced hydrogen production rate and stability. Experimental results also underlined the fuel flexibility of Pt-Ni system when the methane content in the feed and the metal loadings of the bimetallic catalyst were adjusted carefully. In an effort to provide reliable rate laws to be used in the calculation of volume requirement of OSR and water-gas shift (WGS) reactors, the power-law type kinetics of OSR and reversible WGS reactions were determined over Pt-Ni/Al2O3 and Au-Re/CeO2 catalysts at 400 and 300°C, respectively. OSR and WGS reactors were connected in series and combined OSR-WGS experiments were conducted to investigate the response of the Au-Re/ZrO2 WGS catalyst to changes in the product stream of OSR reactor at different reaction temperatures. Additional hydrogen production in the WGS reactor was achieved at an OSR reactor temperature of 500°C with low C/O2 and W/F ratios. Lastly, an exergy analysis of a FP model was performed by using experimental results of OSR reactor operated at 400°C. The analysis showed that exergy efficiency of the combined FP-FC system can be increased by mixing part of the rejected stream by the FC with the fresh feed by introduction of a recycle stream to the system. OSR experiments that were conducted with feed streams obtained upon hypothetical mixing of fresh feed and recycle stream showed that Pt-Ni system adapts well to the changes in the feed composition.