Free Hydrogen, free in the sense of it being uncombined with other elements and existing as elemental, molecular, "H2", is not, strictly speaking, required by many of the Coal hydrogenation and Carbon Dioxide recycling technologies we've documented for you, since Hydrogen supplied in compounded form, such as Water or Methane, i.e., H2O or CH4, can in many cases be utilized.
And, since our National Aeronautics and Space Administration is the focus of this dispatch, please recall:
NASA Recycles CO2 to Methane at Room Temp | Research & Development | News; wherein, via their article, "Electrocatalytic Reduction of Carbon Dioxide to Methane; 2008; Lyndon B. Johnson Space Center"; NASA explains that, through a "room-temperature electrocatalytic process" they can, in fact, accomplish such transmutations as "CO2 + 2H2O → CH4 + 2O2" in a fairly straightforward way, and with a relatively low energy demand.
And, the CH4, Methane, thus formed from Carbon Dioxide can then be used to hydrogenate even more Carbon Dioxide, via "reforming" reactions, as have been known for a long time by our petroleum industry, and which have been undergoing continuous improvement, as illustrated, for example, by:
1939 CO2 + CH4 = Hydrocarbons | Research & Development; concerning: "US Patent 2,180,672 - Process for Converting Gaseous Hydrocarbons; 1939; Assignee: Phillips Petroleum; Abstract: This invention relates to processes for the conversion of normally gaseous hydrocarbons into organic products of higher molecular weight and more specifically to the conversion of methane ... into ... hydrocarbons suitable for motor fuel ... by reacting (it) with oxides of carbon ... (including) carbon dioxide"; and, by:
Exxon 2010 CO2 + Methane = Liquid Hydrocarbons | Research & Development; concerning: "US Patent 7,772,447 - Production of Liquid Hydrocarbons from Methane; 2010; Assignee: ExxonMobil; Abstract: (A) process for converting methane to liquid hydrocarbons ... (by) contacting ... methane and ... CO2 with a (specified) catalyst under conditions effective to convert said methane to aromatic hydrocarbons".
However, elemental Hydrogen does have great utility in alternative processes, such as the original Sabatier reaction, which won the Nobel Prize for Chemistry in 1912, and, about which more can be learned via:
Sabatier reaction - Wikipedia, the free encyclopedia; which actually discusses NASA's Carbon Dioxide recycling plans in some detail, and, which presents the Sabatier reaction as: "CO2 + 4H2 = CH4 + 2H2O".
And, elemental Hydrogen can be utilized to great good effect in processes designed to convert our abundant Coal into liquid hydrocarbon replacements for anything we now derive from increasingly unattractive sources of natural petroleum, as disclosed, for one example, in:
WVU Hydrogenates Coal Tar | Research & Development; where Hydrogen is seen to be required for the hydrogenation of the primary Coal oil, Naphthalene, which can be extracted from Coal via more traditional coking processes, to form the substance, "Tetralin", a Hydrogen donor solvent key to WVU's "West Virginia Process" for the direct liquefaction of Coal.
Such needed elemental Hydrogen can be generated via a number of process, even a few that are, somewhat surprisingly, based on Coal itself, as seen in:
Morgantown, WV, USDOE Hydrogen from Coal | Research & Development | News; concerning: "United States Patent 4,976,940 - Method for Producing H2; 1990; Inventor: Leland Paulson, Morgantown, WV; Assignee: The USA as represented by the DOE; Abstract: A method of producing hydrogen by an endothermic steam-carbon reaction".
Other H2 production schemes rely on the use of freely-available environmental energy to extract such valuable Hydrogen from Water; and, that is the focus of the NASA invention we report herein.
Comment follows excerpts from the initial link in this dispatch to:
"United States Patent 4,045,315 - Solar Photolysis of Water
Date: August, 1977
Inventors: James Fletcher (pro-forma, we believe), Administrator, NASA; and, Porter R. Ryason
Abstract: Hydrogen is produced by the solar photolysis of water in a first photo-oxidation vessel with a transparent wall in the presence of a water soluble photo-oxidizable reagent and an insoluble hydrogen recombination catalyst. Simultaneously oxygen is produced in a second photo-reduction reactor with a transparent wall in the presence of an insoluble photo-reduction reagent catalyst. When spent, the solution from the first reactor is fed into the second reactor. A reaction occurs in the dark in which the redox reagents are regenerated, and the regenerated photo-oxidation reagent solution is recycled to the first reactor. The photo-oxidation reagent is preferably a europium salt, and the first reactor also contains a hydrogen recombination catalyst such as platinum supported on glass beads. The photo-reduction catalyst is a bifunctional reagent catalyst including a transition metal salt such as a manganese oxychloride salt covalently bonded to the surface of a high area support such as glass fibers, together with a hydroxyl or chlorohydroxyl decomposition catalyst of high area.
(Sounds complicated as all get-out, we know. And, the "europium salt", especially, is likely an expensive bit of unpleasantly radioactive exotica. But, it does help in the production of cheap Hydrogen; and, we must emphasize, of pure Oxygen, a by-product herein that would have commercial value which could help to offset the costs of manufacturing Hydrogen for use in the various Coal and CO2 hydrogenation processes.)
Claims: A method of photolyzing water comprising the steps of: applying solar radiation to a first vessel containing an aqueous solution of a water soluble photo-oxidizable reagent and generating hydrogen gas therefrom while forming a spent solution containing oxidized, spent reagent;
(And) applying solar radiation to a second vessel containing water and a water insoluble photoreducible reagent catalyst and generating oxygen gas therefrom while forming spent, reduced photoreducible reagent catalyst;
(And) combining the spent solution containing oxidized photo-oxidizable reagent with the spent reduced photo-reducible reagent catalyst and regenerating said reagents in the dark to form a solution of regenerated photo-oxidizable reagent containing water-insoluble, regenerated photo-reducible reagent catalyst.
A method ... in which the soluble photo-oxidizable reagent is a material which absorbs strongly in the solar range at ground level and is capable of photolyzing water to produce hydrogen ... .
(The sunlight which reaches the ground, in other words, can get the job done. We don't have to put these things on the highest mountain tops, or hang them from big kites, to get enough solar energy.)
An apparatus for the photolysis of water comprising in combination: a first vessel for receiving an aqueous solution of photo-oxidizable reagent and having at least one wall portion transparent to solar radiation, said first vessel containing an immobilized, insoluble hydrogen recombination catalyst, and having a hydrogen gas outlet;
(And) a second vessel having at least one wall portion transparent to solar radiation and containing an immobilized photo-reduction reagent-catalyst, and having an oxygen gas outlet;
A method ... in which the first vessel further contains an insoluble, hydrogen recombination catalyst immobilized on a support (and) in which the recombination catalyst is selected from Platinum, Rhodium, Palladium, Iridium, Osmium and Nickel.
(Thank Goodness we finally got to plain ole' "Nickel"! The debit card was beginning to smoke.)
A method ... in which the (catalyst) support is non porous glass beads or fibers.
A method ... in which the insoluble photo-reducible reagent catalyst contains a first component capable of decomposing OH radicals ... .
(And) in which the first component comprises Platinum, Manganese Oxide, Lead Oxide, Iron Oxide or Zinc Oxide.
(And) in which the second component comprises a water stable oxychloride of a metal selected from Manganese, Titanium, Vanadium, Copper, Nickel, ... or Iron.
(And) in which both components are supported on a high area support.
Background and Field: The present invention relates to solar photolysis of water to produce pure hydrogen and to various methods and apparatus for conducting such a process.
Summary: A cyclic photo-redox process having water and sunlight as reactants and hydrogen and oxygen as products has been developed in accordance with the invention. Though long recognized as inexhaustible and abundant, sunlight is both a diffuse and an intermittent source of energy. The initial photo-redox step results in harvesting and storing the sun's rays during the daylight hours. At night a dark reaction is conducted in which the spent oxidation and reduction reagents are combined and the reaction proceeds to regenerate the reagents for the following daylight production sequence."
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One point that shouldn't be missed is that this process actually takes advantage of the fact that the sun doesn't always shine; with sunlight being especially "intermittent" in the often-cloudy environs of, even more especially, the Appalachian division of US Coal Country.
Periods of darkness enable a "reaction" that "regenerate(s) the reagents".
It can be seen, thus, as a fairly self-sustaining process that does it's business of making Hydrogen without a whole lot of fiddling around with, or expensive extra raw materials, or energy, needed.
And, note again that, although our Government-funded rocket scientists, who are fond of sending packages up into the sky gift-wrapped in Gold foil, do specify some very-expensive catalysts, such as Platinum and Osmium, they also identify some acceptable, and more economically palatable, substitutes from the "generics" shelf, such as Iron, Copper, Manganese and Nickel.