Process for hydrogen production from water
AssigneeGeneral Atomic Company
InventorsJohn H. Norman, Thomas S. Roemer, Bruce E. Kirstein, Karol J. Mysels
Life of this patent
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Abstract
Hydrogen is produced from water by first reacting I.sub.2, SO.sub.2 and H.sub.2 O to make hydrogen iodide and sulfuric acid. A substantial molar excess of SO.sub.2 and I.sub.2 in the reaction zone creates a lighter sulfuric acid-bearing phase and a heavier polyiodic-acid-bearing phase. The heavier phase is separated, degassed and then contacted with phosphoric acid to permit distillation of HI of low water content and recovery of I.sub.2 as a separate fraction. Hydrogen is recovered from HI vapor, as by thermal decomposition.
Claims20
In a process for the production of hydrogen from water, wherein H.sub.2 O, SO.sub.2 and I.sub.2 are reacted in the presence of an excess amount of I.sub.2 and SO.sub.2 to produce sulfuric acid and hydrogen polyiodides in the form of a two-phase liquid system and wherein the heavier phase containing the major portion of the hydrogen polyiodides, which are complexes of HI and I.sub.2, is separated from the two-phase liquid system, degassed to remove unreacted SO.sub.2 and treated for hydrogen recovery, the improvement comprising
- treating said separated heavier phase with phosphoric acid that contains at least about 50 weight percent H.sub.3 PO.sub.4 to bind H.sub.2 O in said separated phase and precipitate I.sub.2 therefrom and distilling said phosphoric acid-treated liquid phase to separate hydrogen iodide therefrom and
- passing said separated hydrogen iodide to a hydrogen recovery zone.
A process for the thermochemical production of hydrogen from water comprising the steps of
- reacting H.sub.2 O, SO.sub.2 and I.sub.2 in the presence of an excess amount of I.sub.2 and SO.sub.2 to produce sulfuric acid and hydrogen polyiodides and create a two-phase liquid system wherein the heavier phase contains the major portion of said hydrogen polyiodides, which are complexes of HI and I.sub.2,
- separating the heavier phase from the two-phase liquid system,
- degassing said heavier phase to remove unreacted SO.sub.2,
- subjecting said degassed liquid to extractive distillation in the presence of phosphoric acid that contains at least about 50 w/o H.sub.3 PO.sub.4 so as to remove a substantial fraction of the HI present as gaseous HI in an overhead stream, to precipitate I.sub.2 as one fraction of the bottoms and to create another bottom fraction containing aqueous phosphoric acid,
- decomposing said gaseous hydrogen iodide to recover hydrogen and iodine, and
- processing said lighter phase to produce SO.sub.2, H.sub.2 O and O.sub.2.
A process for separating the components of a liquid consisting essentially of iodine and HI in the form of polyiodic acids and water in subazeotropic proportions, which process comprises
- treating said liquid with phosphoric acid that contains at least about 50 weight percent H.sub.3 PO.sub.4 so as to precipitate and separate iodine therefrom and reduce the activity of the water therein to the point that the vapor pressure of the HI exceeds the vapor pressure of the water and subsequently distilling said treated liquid to produce gaseous HI.
Dependencies are inferred from the claim text.