Catalytic decomposition of sulfuric acid using metal oxides as the oxygen generating reaction in thermochemical water splitting process

Abstract

The catalytic activity of metal oxides was studied in an attempt to find some suitable catalysts for the decomposition of sulfuric acid as the oxygen-generating reaction in thermochemical water splitting process. Measurements were performed for oxides of Ce(IV), Cr(III), Fe(III), Al, Ni and Cu and Pt in the range 600–950°C, at space velocities of 4300 to 20000 h −1 in a fixed bed reactor. The order of the activities at the initial concentration of SO 3 of 4.0 mol% was as follows: Pt ≈ Cr 2O 3 > Fe 2O 3 > (CuO) > CeO 2 > NiO > Al 2O 3. The activity of Cr 2O 3 above 700°C was nearly the same as the Pt catalyst. For NiO and CuO, there was a discrepancy between conversions determined from high to low temperature and conversions from low to high temperature. It was found that the catalytic activity for metal oxides was closely related with their thermodynamic properties: the higher the unstability of the sulfate, the higher the catalytic activity of the oxide.