Thermochemical Splitting Research Articles

Thermochemical splitting cycles of sodium chloride

Download Hi-Res ImageDownload to MS-PowerPointCite This:Ind. Eng. Chem. Proc. Des. Dev. 1985, 24, 1, 223-226

Thermochemical splitting of sulfur dioxide with cerium(IV) oxide

Ce/sub 2/(SO/sub 3/)/sub 2/SO/sub 4/.4H/sub 2/O thermally decomposes in several steps to yield H/sub 2/O, sulfur, SO/sub 2/, and O/sub 2/ as gaseous products, plus Ce/sub 2/O(SO/sub 4/)/sub 2/, Ce/sub 2/O/sub 2/SO/sub 4/, CeOSO/sub 4/, and CeO/sub 2/ as intermediate products. The terminal solid product above 1250 K is CeO/sub 2/. Reaction pathways are described in detail. A thermochemical cycle for splitting SO/sub 2/ into sulfur and oxygen with CeO/sub 2/ is described, in which sulfur and/or oxygen and/or cerium all change valence in four different reactions.

Thermochemical splitting of water and carbon dioxide with cerium compounds

Cerium(IV) oxide reacts with solid or molten Na 4P 2O 7 at 750–950 °C to form sodium cerium(III) phosphate, Na 3Ce(PO 4) 2(s), Na 3PO 4(s), and O 2(g). The mixture of Na 3Ce(PO 4) 2(s) with Na 3PO 4(s) reacts at similar temperatures with Na 2CO 3(l) and steam to produce CeO 2(s), NaPO 4(s), CO 2(g), and H 2(s). In the absence of steam, carbon monoxide forms instead of H 2(g). Treatment of aqueous Na 3PO 4 with CO 2(aq) at 0–50 °C yields solutions of Na 2HPO 4 and NaHCO 3, which are separated by crystallization. These salts condense at ⪡200 °C to form Na 4P 2O 7(s) and Na 2CO 3(s), respectively, thus completing the thermochemical cycle. The cycle splits either H 2O or CO 2, depending upon whether steam is used in the reaction of Na 2CO 3 with Na 3Ce(PO 4) 2.