Thermochemistry of valence changes in sulfur by decomposition of dipraseodymium oxide-sulfite monosulfate hydrates as reactants in thermochemical cycles

摘要

Diprasecondymium oxide-sulfite monosulfate hydrates were prepared by reaction of a suspension of dipraseodynmium dioxymonosulfate in aqueous sulfur dioxide at 340 K. Removal of excess sulfur dioxide precipitated the hydrates. These compositions dehydrated completely at 700K without appreciable sulfur dioxide loss. At 860 K, decomposition products (in the absence of water) were: sulfur dioxide, sulfur, oxide, sulfate and thiosulfate. Consistently, only 4 percent of sulfite remained unreacted after 50 minutes. Redox yields were (by disproportionation) in the range of 32 to 56 percent. Gibbs energy changes at 860K for three reactions were calculated from yield of gaseous products and gas quotients. There reactionsa re undesireable in the sulfur dioxide-iodine process for thermochemical hydrogen production.