Stability of supported platinum sulfuric acid decomposition catalysts for use in thermochemical water splitting cycles

The activity and stability of several metal oxide supported platinum catalysts were explored for the sulfuric acid decomposition reaction. The acid decomposition reaction is common to several sulfur based thermochemical water splitting cycles. Reactions were carried out using a feed of concentrated liquid sulfuric acid (96 wt%) at atmospheric pressure at temperatures between 800 and 850∘C and a weight hour space velocity of 52 g acid/g catalyst/h. Reactions were run at high space velocities such that variations in kinetics were not masked by surplus catalyst. The influence of exposure to reaction conditions was explored for three catalysts; 0.1–0.2 wt% Pt supported on alumina, zirconia and titania. The higher surface area Pt/Al2O3Pt/Al2O3 and Pt/ZrO2Pt/ZrO2 catalysts had the highest activity but deactivated rapidly. A low surface area Pt/TiO2Pt/TiO2 catalyst had good stability in short term tests, but slowly lost activity for over 200 h of continuous operation.