Catalytic partial oxidation of n-tetradecane in the presence of sulfur or polynuclear aromatics: Effects of support and metal

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 and aromatic content present in these fuels increases the propensity towards deactivation of noble metal-based catalysts used in this reaction. The relationship between catalyst supports and deactivation has been studied here for three catalysts (Rh/Ce0.56Zr0.44O2−x, Pt/Ce0.56Zr0.44O2−x and Pt/Al2O3) in a fixed-bed catalytic reactor using various mixtures of n-tetradecane with 1-methylnaphthalene or dibenzothiophene to simulate logistic fuels. Carbon deposition during CPOX reforming was shown to be directly related to the concentration of unsaturated products formed. Unsaturates (olefins + aromatics), which are known coke precursors, were observed on both platinum catalysts during CPOX of n-tetradecane with no sulfur (particularly from Pt/Al2O3), but not on Rh/Ce0.56Zr0.44O2−x. For the Rh/Ce0.56Zr0.44O2−x, yields of hydrogen and carbon monoxide 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 platinum catalysts, hydrogen and carbon monoxide yields dropped continuously over time in the presence of sulfur or aromatics in feed. The superior performance of Rh/Ce0.56Zr0.44O2−x can be attributed to the higher oxygen-ion conductivity of the Ce0.56Zr0.44O2−x support as well as the higher activity of rhodium compared to platinum.