Review A review of catalytic sulfur (VI) oxide decomposition experiments Nicholas R. Brown a , Shripad T. Revankar a,b, * a School of Nuclear Engineering, Purdue University, West Lafayette IN 47907, United States b Division of Advanced Nuclear Engineering, POSTECH, Pohang, 790-784, Republic of South Korea article info Article history: Received 8 August 2011 Received in revised form 23 September 2011 Accepted 1 October 2011 Available online 13 November 2011 Keywords: Sulfur (VI) oxide Decomposition Sulfuric acid Thermochemical hydrogen Sulfur iodine abstract Sulfur (VI) oxide, also known as sulfur trioxide or SO 3 , decomposition is an oxygen- generating decomposition reaction that proceeds in the gaseous system SO 3 /SO 2 /O 2 /H 2 O at temperatures above 500 K. Maximum decomposition yield of SO 3 to SO 2 and O 2 is best achieved at temperatures of over 1000 K with an appropriate catalyst. According to the literature, noble metals and some transition metal oxides are highly effective catalysts in the laboratory environment. Sulfur (VI) oxide decomposition is the energetic and temperature limiting step of several endothermic hydrogen generating chemical process heat plants. In particular, the General Atomics Sulfur Iodine cycle and the Westinghouse Hybrid Sulfur cycle are candidates for thermal coupling to a high temperature nuclear reactor. Therefore the sulfur (VI) oxide decomposition reaction is a potential heat sink for a high temperature nuclear reactor. Thus, optimization of catalyst selection is required, both for operational efficiency and safety. In this paper, reaction mechanisms and catalyst composition for sulfur (VI) oxide decomposition are reviewed. Chemical kinetics data from previous sulfur (VI) oxide decomposition experiments are extracted from archival journal papers or other open literature. The available experimental database suggests that Pt- based catalysts have the highest stable activity among the noble metals and Fe 2 O 3 -based catalysts have the highest stable activity among the transition metal oxides. The decom- position temperature of the corresponding metal sulfate dictates the catalytic activity of a given transition metal oxide. Copyright ª 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. 1. Introduction The U.S. Department of Energy Office of Nuclear Energy, Science and Technology has prioritized the Very-High- Temperature Reactor (VHTR) amongst the novel nuclear reactor designs dubbed Generation IV (Gen IV). The VHTR is a candidate for utilization of nuclear process heat for novel applications, such as hydrogen generation via thermo- chemical water splitting. Hydrogen is the least polluting fuel of all natural or synthetic fuels [1]. Additionally hydrogen can be stored, transported, metered, and restricted by conven- tional means [1]. * Corresponding author. School of Nuclear Engineering, Purdue University, West Lafayette IN 47907, United States. Tel.: þ1 765 496 1782; fax: þ 1 765 494 9570. E-mail address: shripad@ecn.purdue.edu (S.T. Revankar). Available online at www.sciencedirect.com journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy 37 (2012) 2685 e2698 0360-3199/$ e see front matter Copyright ª 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.ijhydene.2011.10.054