Catalytic decomposition of sulfur trioxide with metallic catalysts for the is cycle of thermochemical hydrogen production

Iodine-Sulfur (IS) thermochemical process is one promising method for hydrogen production by thermochemically splitting water at high temperature. It has been focused as a carbon-free hydrogen production process to overcome the global warming problem and positively expected for industrialization. The IS process is a continuous and closed-cycle system consisting of three steps; (i) Bunsen reaction (I₂ + SO₂ + 2H₂O = 2HI + H ₂SO₄ ; 293-373 K), (ii) HI decomposition (2HI = H ₂ I₂ ; 473-973 K), (iii) H₂SO₄ decomposition (H₂SO₄ = H₂O + SO₃ → H₂O + SO₂ + 0.5O₂ ; 1073-1173K). Among these, the catalytic decomposition of SO₃ to SO₂ and O₂ is a key reaction using the highest temperature generated from VHTR (very high temperature gas-cooled nuclear reactor). In this work, various metallic catalysts supported on Al₂O₃ or TiO₂ were prepared in various metal contents, and the catalytic activity and thermal durability of each catalyst were compared at the temperature range of 750-950°C in a fixed bed reactor. Concentrated analyses with Fe catalysts were performed since Fe on Al₂O₃ or TiO₂ showed interestingly high performance and thermal resistance.