Support Effects for Pt and Rh-Based Catalysts for Partial Oxidation of n-Tetradecane

Catalytic partial oxidation (CPOX) of liquid fuels is an attractive option for producing a hydrogen-rich gas stream for fuel cell applications. However, the high sulfur content along with aromatic compounds present in liquid fuels may deactivate reforming catalysts. Deactivation of these catalysts by carbon deposition and sulfur poisoning is a key technical challenge. The relationship between catalyst supports and deactivation have been studied here for three catalysts (Rh/Ce_0.5Zr_0.5O₂, Pt/Ce_0.5Zr_0.5O₂, and Pt/Al₂O₃) in a fixed bed catalytic reactor using a mixture of n-tetradecane, 1-methylnaphthalene, and dibenzothiophene to simulate logistic fuels. Carbon production during CPOX reforming was directly related to olefin formation. Olefins, which are known coke precursors, were observed on the Pt catalysts during CPOX of n-tetradecane with no sulfur (particularly from Pt/Al₂O₃), but not on Rh/Ce_0.5Zr_0.5O₂. For the Rh/Ce_0.5Zr_0.5O₂, yields of H₂ and CO dropped to a stationary level after the introduction of sulfur-containing feed (1000 ppm sulfur) or aromatic-containing feed (5 wt%), however, the catalyst activity was restored after removing the sulfur or aromatics from the feed. For the Pt catalysts, H₂ and CO yields dropped continuously over time in the presence of sulfur or aromatics in feed. The superior performance of Rh/Ce_0.5Zr_0.5O₂ can be attributed to the higher oxygen-ion conductivity of the Ce_0.5Zr_0.5O₂ support as well as the activity of the Rh sites.