(33a) Novel Separation Process of Gaseous Mixture of SO2 and O2 with Ionic Liquid for Hydrogen Production in Thermochemical Sulfur-Iodine Water Splitting Cycle

Sulfur-Iodine cycle is the most promising thermochemical cycle for water splitting to produce hydrogen which can replace the fossil fuels in the future. As a sub-cycle in the thermochemical Sulfur-Iodine water splitting cycle, sulfuric acid (H2SO4) decomposes into oxygen (O2) and sulfur dioxide (SO2) which should be separated for the recycle of SO2 into the sulfuric acid generation reaction (Bunsen Reaction). Conventional gas separation processes are Pressure Swing Adsorption (PSA), Temperature Swing Adsorption (TSA), and solvent absorption. PSA and TSA are basically energy intensive processes to control the pressure and temperature in a large system. Absorption process is not attractive for the high temperature process because of the volatile property of the solvent. A novel separation process needs to be proposed to compensate the demerits of conventional gas separation methods for the high temperature-gaseous SO2/O2 mixture. Ionic Liquid is not volatile even at high temperature, which can improve absorption process utilizing organic solvents by eliminating the issue of volatility of the solvents. In addition, a continuous process can be realized by recycling non-volatile ionic liquid at high temperature. Cost of gas separation process can be reduced by avoiding PSA and TSA and by operating absorption system relatively at high temperature by ionic liquid process compared to the solvent absorption. In this study, absorption process of SO2 by ionic liquid is investigated. At first, the best ionic liquid for SO2 absorption is selected by combining anions and cations. With TGA/DTA analysis operating temperature windows of each ionic liquid are determined. After that, absorption and desorption properties of SO2 by each ionic liquid are examined. Moreover, IR analysis is executed before and after the absorption of SO2 to verify the absorption mechanism.