Catalytic partial oxidation of n-butane over Rh catalysts for solid oxide fuel cell applications

Catalytic partial oxidation (CPOx) of n-butane in O2/Ar mixtures at ratios of 1/3.76 has been investigated over Rh catalysis impregnated in γ-Al2O3 washcoat supports coated on α-Al2O3 ceramic foam monoliths. The impact of heat loss on Rh-based CPOx reactor performance for small-scale SOFC application is tested here by varying reactor lengths, insulation, and flow conditions. Results for a C/O ratio = 1.0 and Tin = 300 °C indicate the n-butane conversion and H2 and CO selectivity depend strongly upon reactor temperature and thus heat lost through the external reactor walls. Because heat loss does not scale with flow rate, higher flow rates for catalyst contact times approaching 15 ms increase fuel conversion and syngas selectivity. Furthermore, shortening catalyst length (from 10 to 5 mm) also reduces heat loss and increases fuel conversion and H2 selectivity. CO selectivity, however, drops with the shorter length. These results suggest that for the conditions tested, butane conversion and H2 production occur rapidly within the first couple of mm in the reactor, whereas CO production occurs more broadly throughout the reactor length. This study provides valuable insight into the conditions needed for good CPOx performance for fuel processing in small-scale SOFC applications.