General Atomic Company

Ga Technologies, Inc.

Hi-z Technology, Inc.

Biotechnetics

John H Norman

Karol J Mysels

John L Russell, Jr

Thomas S Roemer

Norbert B Elsner

Barry W McQuillan

John T Porter, Ii

Wolfgang A Wrasidlo

Dennis R O'Keefe

Kenneth H McCorkle

David G Williamson

Susan A Stowell

Robert Sharp

Bruce E Kirstein

A process and related compositions for lowering the electrical resistivity of ZrB.sub.2 are described. In a preferred embodiment, ZrH.sub.2 or Zr powder is blended with the ZrB.sub.2 powder and the composite is vacuum hot pressed at 2100.degree. C. The elemental Zr so formed can be beneficial by gettering impurities such as oxygen, nitrogen, and carbon, and by altering the overall ZrB.sub.2 stoichiometry, e.g., to ZrB.sub.1.97. Excess Zr is present in the matrix as a finely dispersed material. A variety of dopant materials can also be used to alter the electrical, thermal, and mechanical properties. Samples exhibiting this Zr-rich second phase exhibit lower electrical resistivities, higher thermal conductivities, better thermal shock resistance.

ZrB.sub.2 phase with enhanced electrical and thermal conductivities and

A method and generator for preparing the radioisotope of lead, .sup.212 Pb, whereby .sup.228 Th, in a closed chamber, is allowed to decay to gaseous .sup.220 Rn which is then readily separated from the thorium and other decay products by diffusing the .sup.220 Rn gas into a second chamber, where it decays to .sup.212 Pb which can then be collected from the second chamber. The .sup.228 Th preferably is amorphous, such as thorium stearate. Collection of .sup.212 Pb occurs in a medium of high and open porosity into which the .sup.220 Rn diffuses so that the decay products recoil into the medium. The .sup.212 Pb can be recovered from this medium by dissolving the medium or by reacting it with an antibody-chelating complex solution to entrap it in the antibody-chelating complex.

Method and generator for producing radioactive lead-212

Water is decomposed to molecular hydrogen and molecular oxygen in a thermochemical cycle which comprises (i) reacting Cl.sub.2, Br.sub.2 or BrCl with water to obtain oxygen and hydrogen halide; (ii) forming a graphite intercalation compound with a hydrogen halide from step (i) and a metal halide selected from MBr.sub.i Cl.sub.3-i, wherein M is aluminum, gallium or indium and i is 0, 1, 2 or 3, and thereby obtaining hydrogen; (iii) decomposing by heating the graphite intercalation compound formed in step (ii); (iv) recycling the halogen produced in step (iii) for use in step (i); and (v) recycling the metal halide and graphite produced in step (iv) for use in step (ii).

Water-splitting cycle with graphite intercalation compounds

Hydrogen is produced from hydrogen sulfide by coupling, in a single reaction zone, the partial oxidation of hydrogen sulfide to water and sulfur with the thermal decomposition of hydrogen sulfide to hydrogen and sulfur. When one mole of hydrogen sulfide is burned with a stoichiometric deficiency of oxygen, enough thermal energy is generated by the exothermic partial oxidation to effect the thermal dissociation of about two moles of hydrogen sulfide. The gas mixture exiting from the reaction zone is substantially instantaneously cooled by quenching with cooler gas of substantially the same composition to prevent significant recombination of hydrogen and sulfur. The thermal energy in the gas following the quench step is used to preheat the H.sub.2 S and to cause some dissociation before entry into the reaction zone.

Hydrogen production from in situ partial burning of H.sub.2 S

A method of storing heat is provided utilizing a chemical cycle which interconverts sulfuric acid and sulfur. The method can be used to levelize the energy obtained from intermittent heat sources, such as solar collectors. Dilute sulfuric acid is concentrated by evaporation of water, and the concentrated sulfuric acid is boiled and decomposed using intense heat from the heat source, forming sulfur dioxide and oxygen. The sulfur dioxide is reacted with water in a disproportionation reaction yielding dilute sulfuric acid, which is recycled, and elemental sulfur. The sulfur has substantial potential chemical energy and represents the storage of a significant portion of the energy obtained from the heat source. The sulfur is burned whenever required to release the stored energy. A particularly advantageous use of the heat storage method is in conjunction with a solar-powered facility which uses the Bunsen reaction in a water-splitting process. The energy storage method is used to levelize the availability of solar energy while some of the sulfur dioxide produced in the heat storage reactions is converted to sulfuric acid in the Bunsen reaction.

Sulfuric acid-sulfur heat storage cycle

Liquid hydrogen iodide is decomposed to form hydrogen and iodine in the presence of water using a soluble catalyst. Decomposition is carried out at a temperature between about 350.degree. K. and about 525.degree. K. and at a corresponding pressure between about 25 and about 300 atmospheres in the presence of an aqueous solution which acts as a carrier for the homogeneous catalyst. Various halides of the platinum group metals, particularly Pd, Rh and Pt, are used, particularly the chlorides and iodides which exhibit good solubility. After separation of the H.sub.2, the stream from the decomposer is countercurrently extracted with nearly dry HI to remove I.sub.2. The wet phase contains most of the catalyst and is recycled directly to the decomposition step. The catalyst in the remaining almost dry HI-I.sub.2 phase is then extracted into a wet phase which is also recycled. The catalyst-free HI-I.sub.2 phase is finally distilled to separate the HI and I.sub.2. The HI is recycled to the reactor; the I.sub.2 is returned to a reactor operating in accordance with the Bunsen equation to create more HI.

Hydrogen iodide decomposition

A method of extraction of HI from an aqueous solution of HI and I.sub.2. HBr is added to create a two-phase liquid mixture wherein a dry phase consists essentially of HBr, I and HI and is in equilibrium with a wet phase having a far greater HBr:HI ratio. Using a countercurrent extractor, two solutions can be obtained: a dry HBr--HI--I.sub.2 solution and a wet essentially HBr solution. The dry and wet phases are easily separable, and HI is recovered from the dry phase, after first separating I.sub.2, as by distillation. Alternatively, the HI-HBr liquid mixture is treated to catalytically decompose the HI. HBr is recovered from the wet phase by suitable treatment, including high-pressure distillation, to produce an H.sub.2 O--HBr azeotrope that is not more than 25 mole percent HBr. The azeotrope may be returned for use in an earlier step in the overall process which results in the production of the aqueous solution of HI and I.sub.2 without major detriment because of the presence of HBr.

Recovery of hydrogen iodide

A two-stage process for the catalytic decomposition of H.sub.2 SO.sub.4 wherein H.sub.2 SO.sub.4 in vapor form is contacted in a first stage with a platinum group metal catalyst at temperatures between about 700.degree. K. and 970.degree. K. The platinum group metal catalyst is supported on a substrate of titania, barium sulfate, zirconia, silica, zirconium silicate or a mixture thereof, and at least about 40 percent of the H.sub.2 SO.sub.4 is decomposed to SO.sub.2. Vapors from the first stage enter a second stage where they contact a copper oxide and iron oxide catalyst at a temperature above 970.degree. K. The second stage catalyst is supported on a substrate of barium sulfate, zirconium oxide or titanium oxide.

Catalytic decomposition of H.sub.2 SO.sub.4

Substantially pure O.sub.2 is recovered from a gaseous mixture containing O.sub.2 and another gas, such as SO.sub.2 or NH.sub.3. An O.sub.2 --SO.sub.2 mixture is injected into a substantially vertical reaction zone to which I.sub.2 and H.sub.2 O are continuously supplied at an upper location. By injecting the gas mixture at a lower location and at a preselected rate, substantially all of the SO.sub.2 in the mixture either reacts chemically or is dissolved in the H.sub.2 O. I.sub.2 may be supplied in particulate form and in substantial excess with respect to water so that the intermediate zone resembles a packed bed of wet iodine, in which case the gaseous mixture flows in the interstices of the packed bed. Electrolysis or an other chemical reaction wherein O.sub.2 does not take part can also be used.

Oxygen recovery from gas mixtures

A continuous reaction is carried out between gaseous SO.sub.2, I.sub.2 and liquid H.sub.2 O in a substantially vertical reaction zone. H.sub.2 O plus I.sub.2 in a substantial excess are supplied to an upper location at preselected rates. SO.sub.2 is injected into the zone at a lower location, and a desired temperature is maintained at an intermediate location where the reaction proceeds to produce sulfuric acid and hydrogen iodide. The reaction products are removed from a location near the bottom at a rate proportional to the preselected rates to cause a continuous downward flow within the reaction zone. The SO.sub.2 flow rate assures that substantially all of the SO.sub.2 either reacts or is absorbed by the downward traveling nongaseous reactants.

Method of reacting I.sub.2 with a liquid and a gas

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.

Process for hydrogen production from water

Hydrogen is produced from water by reacting I.sub.2 SO.sub.2 and H.sub.2 O to make hydrogen iodide and sulfuric acid. SO.sub.2 is present in a substantial molar excess with respect to the available H.sub.2 O and I.sub.2 is also present in excess to cause the formation of a lighter sulfuric acid-bearing phase and a heavier hydrogen iodide-bearing phase. The heavier phase is separated from the lighter phase, degassed to remove SO.sub.2 and then treated with additional HI and I.sub.2 to cause the formation of a light immiscible fraction containing sulfuric acid and water which is removed to substantially reduce the sulfur content of the degassed phase. Finally, the hydrogen iodide product is separated and decomposed to produce hydrogen.

Process for the production of hydrogen from water

Hydrogen is thermochemically produced from water in a cycle wherein a first reaction produces hydrogen iodide and H.sub.2 SO.sub.4 by the reaction of iodine, sulfur dioxide and water under conditions which cause two distinct aqueous phases to be formed, i.e., a lighter sulfuric acid-bearing phase and a heavier hydrogen iodide-bearing phase. After separation of the two phases, the heavier phase containing most of the hydrogen iodide is treated, e.g., at a high temperature, to decompose the hydrogen iodide and recover hydrogen and iodine. The H.sub.2 SO.sub.4 is pyrolyzed to recover sulfur dioxide and produce oxygen.

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La Jolla, CA, United States of America

John H Norman