A review of recent researches on Bunsen reaction for hydrogen production via S-I water and H2S splitting cycles

The Bunsen reaction is the center reaction for both the sulfur-iodine water splitting cycle for hydrogen production and the novel hydrogen sulfide splitting cycle for hydrogen and sulfuric acid production from the sulfur-containing gases. This paper reviews the research progress of the Bunsen reaction in recent 10-15 years. Researches were initially focused on the optimization of the operating conditions of the conventional Bunsen reaction requiring excessive water and iodine to improve the products separation efficiency and to avoid the side reactions and iodine vapor deposition. Alternative methods including electrochemical methods, precipitation methods, and non-aqueous solvent methods had their respective advantages, but still faced challenges. In development of the technology of H2S splitting cycle, dissolving iodine in toluene solvent could render the Bunsen reaction to occur with the flowable I-2 stream at ambient temperature such that the side reactions and iodine vaporization can be avoided and the corrosion hazard lessened. It also prevented the Bunsen reaction from using excessive iodine and water. The products from the Bunsen reaction including HI, H2SO4, H2O, and toluene could be directly electrolyzed. (C) 2018 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.