Thermochemical hydrogen production with the sulfur dioxide-iodine cycle by utilization of dipraseodymium dioxymonosulfate as a recycle reagent

Abstract

Insoluble, dipraseodymium oxide-sulfite monosulfate hydrates were prepared by reaction of dipraseodymium dioxymonosulfate with sulfur dioxide in aqueous media at 340 K. These compositions reacted with iodine to yield sulfate in the solid phase and hydrogen iodide in the gas phase. High yields of hydrogen iodide were measured at 770 K for a reaction time of ten minutes. Yields also depended on the sulfite content of the hydrate compositions, and were highest when the dipraseodymium dioxymonosulfate was 60% neutralized with sulfurous acid. An increased yield of hydrogen iodide was obtained by a second iodine oxidation after separation of the first gaseous products. A water splitting thermochemical cycle utilizing these reactions is described in which hydrogen is produced by catalytic decomposition of hydrogen iodide, and oxygen results from thermal decomposition of the solid product, that also yields sulfur dioxide and dipraseodymium dioxymonosulfate for recycle.