Development of an electrochemical cell for efficient hydrogen production through the IS process

Abstract

Abstract The Bunsen reaction (SO 2 + I 2 + 2H 2 O = H 2 SO 4 + 2HI) was examined by an electrochemical cell featuring a cation‐exchange membrane as the separator, using sulfuric acid dissolving sulfur dioxide as the anolyte and hydriodic acid dissolving iodine as the catholyte. In galvanostatic electrolysis, the molality of H 2 SO 4 in the anolyte and that of HI in the catholyte were increased up to 17.8 and 14.9 mol kg H2O −1 , respectively. These concentrations were far higher than those that were obtained by the Bunsen reaction carried out in the presence of a large amount of iodine (such as I 2 /HI = 4). I 2 concentration after the concentration procedure was at I 2 /HI = 0.95, which is lower than the reported value. I 2 is one of the recycling agents in the IS process. HI and H 2 SO 4 were successfully concentrated under low I 2 concentration. The concentration of HI agreed with the calculated value, based on the amount of electricity consumed, indicating high current efficiency. Heat/mass balance using this type of electrochemical cell through the IS process is discussed for evaluation of the reactor. The thermal efficiency to produce hydrogen was calculated at 42.1%, without heat recovery for electricity, by optimizing HI and H 2 SO 4 concentrations after application of the electrochemical cell. © 2004 American Institute of Chemical Engineers AIChE J, 50: 1991–1998, 2004