WO2012131703A2 - Cyclic thermochemical dissociation of carbon dioxide and water. - Google Patents

Cyclic thermochemical dissociation of carbon dioxide and water. Download PDF

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WO2012131703A2
WO2012131703A2 PCT/IN2012/000170 IN2012000170W WO2012131703A2 WO 2012131703 A2 WO2012131703 A2 WO 2012131703A2 IN 2012000170 W IN2012000170 W IN 2012000170W WO 2012131703 A2 WO2012131703 A2 WO 2012131703A2
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metal
halogen
polar solvent
mixture
heating
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PCT/IN2012/000170
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French (fr)
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WO2012131703A4 (en
WO2012131703A3 (en
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Abhishek Chandrashekhar MALVE
Umesh Surendra TAMBOLI
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Malve Abhishek Chandrashekhar
Tamboli Umesh Surendra
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Publication of WO2012131703A2 publication Critical patent/WO2012131703A2/en
Publication of WO2012131703A3 publication Critical patent/WO2012131703A3/en
Publication of WO2012131703A4 publication Critical patent/WO2012131703A4/en

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
    • C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
    • C01B3/06—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of inorganic compounds containing electro-positively bound hydrogen, e.g. water, acids, bases, ammonia, with inorganic reducing agents
    • C01B3/08—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of inorganic compounds containing electro-positively bound hydrogen, e.g. water, acids, bases, ammonia, with inorganic reducing agents with metals
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B13/00—Oxygen; Ozone; Oxides or hydroxides in general
    • C01B13/02—Preparation of oxygen
    • C01B13/0203—Preparation of oxygen from inorganic compounds
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B13/00—Oxygen; Ozone; Oxides or hydroxides in general
    • C01B13/02—Preparation of oxygen
    • C01B13/0203—Preparation of oxygen from inorganic compounds
    • C01B13/0207—Water
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
    • C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
    • C01B3/06—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of inorganic compounds containing electro-positively bound hydrogen, e.g. water, acids, bases, ammonia, with inorganic reducing agents
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/40—Carbon monoxide
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B9/00—General methods of preparing halides
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B9/00—General methods of preparing halides
    • C01B9/06—Iodides
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis

Definitions

  • This invention pertains to a cyclic process to thermochemically dissociate oxides using metals or metal derivatives as catalysts. More particularly the invention comprises thermochemical dissociation of Carbon Dioxide into carbon and oxygen or into carbon monoxide and oxygen, or water into hydrogen and oxygen and to a process of extracting metals from their oxides or hydroxides or halides and recycling the metals and halogen.
  • the invention also relates to reacting metal oxides and/or hydroxides with halogens.
  • the invention also relates to reacting metal oxides with metal halides to give metal halide and metal oxyhalide in presence of polar solvent or combination of polar solvents, excluding pure water when metal is Magnesium.
  • the invention also relates to reacting metal hydroxides with metal halides to give metal halide, metal oxyhalide and water in presence of polar solvent or combination of polar solvents, excluding pure water when metal is Magnesium.
  • the invention also relates to reacting metal oxides with halogens to give metal halide and metal oxyhalide in presence of polar solvent or combination of polar solvents, excluding pure water when metal is Magnesium.
  • the invention also relates to reacting metal hydroxides with halogens to give metal halide, metal oxyhalide and water in presence of polar solvent or combination of polar solvents, excluding pure water when metal is magnesium.
  • This invention also pertains to use common ion effect to reduce the solubility of metal oxyhalides in the cyclic reaction process.
  • the invention also pertains to use of mixed metal oxides or mixed metal hydroxides or a mixture of metal oxide and metal hydroxide for the process of thermochemical decomposition of oxides or for the recovery of metal from its oxide or hydroxide.
  • the invention also pertains particularly to conversion of magnesium oxide to anhydrous magnesium iodide and further regenerating elemental Mg and Iodine.
  • the invention also pertains particularly to conversion of zinc oxide to zinc iodide and further regenerating elemental Zn and Iodine.
  • C0 2 is important to nature as is oxygen, but excess C0 2 may be contributing in global warming. All the organic fuels when oxidized give out C0 2 . On account of a rapid increase in global consumption of organic fuels, there is net rapid increase in CO 2 in the atmosphere. The equilibrium between CO 2 and O 2 is shifting and nature is responding by global rise in temperature as one of its responses. Since C0 2 shall be available in abundance and bringing down its current level of concentration in atmosphere is also desired, utilizing the same for creating energy rich organic molecules is highly desirable. Further, hydrogen is considered as an alternative to organic fuels as the energy carrier in future but for that to happen hydrogen must be prepared using green source of energy.
  • This cycle has a disadvantage of requirement of very high peak temperature, about 2000°C to split ZnO into Zn and 0 2 and 1700°C to convert Fe30 4 to FeO.
  • Product separation in order to avoid recombination which are essentially gases at such a high temperature is very difficult.
  • the invention comprises a process of cyclic thermochemical dissociation of oxides catalysed by a metal compound of general structural formula MX, wherein M is a metal; X is none or oxygen or halogen, the said oxygen or halogen present in moles equivalent to M; comprising at least a step of recovering anhydrous metal halide from a process stream and recycling the metal halide or thermally decomposing the same to metal and halogen for recycling.
  • the oxide selected for dissociation may be carbon-dioxide or water.
  • the invention comprises thermochemical dissociation of carbon dioxide comprising a step of reacting the same with MX, where M is Mg or Zn and X is none, to produce metal oxide and carbon monoxide or carbon; or MX, where M is Mg or Zn and X is halogen, to produce metal oxide, carbon and halogen.
  • the invention comprises thermochemical dissociation of water comprising a step of reacting the same with MX, where M is Mg or Zn and X is none, comprising step of reacting M with water to produce metal oxide and hydrogen or metal hydroxide and hydrogen.
  • the process of thermochemical dissociation comprises a step of reaction in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when M is Mg, of (a) metal oxide with a halogen with heating, to produce metal halide and metal oxyhalide, or (b) reacting metal hydroxide and halogen with heating to produce metal halide, metal oxyhalide and water, or (c) reacting mixture of metal oxide and metal hydroxide with halogen with heating to produce metal halide, metal oxyhalide and water, or (d) reacting mixture of metal oxides with halogen with heating to produce metal halide, metal oxyhalide and water, or (e) reacting mixture of metal hydroxides with halogen with heating, to produce metal halide, metal oxyhalide and water, or (f) reacting metal oxide and metal halide with halogen with heating to produce metal halide, metal oxyhalide and water, or (g) reacting metal oxide and metal halide
  • the said metal oxyhalide obtained from steps a to e mentioned above are decomposed by heating to get metal oxide, oxygen and halogen or the metal oxyhalide obtained from steps f and g mentioned above by heating to get metal halide and oxygen.
  • the oxygen thus produced is collected or liberated, and metal oxide or metal halide and halogen thus produced are recycled for further reaction to make metal oxyhalide and metal halide.
  • the metal halide dissolved in a polar solvent or a mixture of polar solvent is recovered separate from the polar solvent or the mixture of polar solvent; and the recovered solvent or solvent mixture is recycled for use as reaction medium for reacting metal oxide with halogen, or for reacting metal hydroxide with halogen, or for reacting mixture of metal hydroxide and metal oxide with halogen ,or for reacting mixture of metal oxide and metal halide with halogen, or for reacting mixture of metal hydroxide and metal halide with halogen; and the metal halide recovered free from the polar solvent or from the mixture of polar solvents by heating is thermally decomposed to recover metal and halogen, recycling halogen for reaction with (i) metal oxide, or (ii) metal hydroxide, or (iii) both, or (iv) metal oxide and metal halide, or (v) metal hydroxide and metal halide, and recycling metal to the reaction with carbon dioxide or water.
  • M is magnesium (Mg)
  • halogen is Iodine (I)
  • reactions between Magnesium oxide or magnesium iodide on one hand and the Iodine on other is done by heating the reaction up to a temperature of about 150 degrees celcius.
  • emetal may be chosen from the group of Mg, Zn, Cs, Cu, In, K, Li, Na, Rb, Tl, Ba, Ca, Mg, Sr, Be, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Ra, Sn, Zn, Al, Bi, Ce, Cr, Dy, Er, Fe, Ga, Gd, Ho, In, La, Lu, Nd, Pr, So, Sm, Tm, Y, Yb, Ge, Th, U and Zr.
  • Most preferred metals are Magnesium and Zinc and Magnesium iodate formed in such a reaction is thermally decomposed by heating up to a temperature of about 600 degrees celcius.
  • the invention comprises a process, wherein M is magnesium (Mg) and the halogen is Iodine (I), comprising a step of heating Magnesium Iodide for decomposition up to about 634 degrees celcius.
  • Invention also comprises an apparatus for MX catalysed thermochemical dissociation of oxides, wherein M is a metal; X is none, oxygen or halogen, the said oxygen or halogen present in moles equivalent to M; the said apparatus comprising at least a means for recovering anhydrous metal halide from a process stream and recycling the metal halide or thermally decomposing the same to metal and halogen for recycling; wherein M is selected from the group Mg, Zn, Cs, Cu, In, K, Li, Na, Rb, Tl, Ba, Ca, Mg, Sr, Be, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Ra, Sn, Zn, Al, Bi, Ce, Cr, Dy, Er, Fe, Ga, G
  • the apparatus or a device comprises at least following components: (a) a source of an oxide (C2), (b) a regulator to control quantity of the oxide to be fed to reaction chamber C1 and a means to avoid reverse flow of oxide from chamber C1 , (c) a source of polar solvent or a mixture thereof (C3), a means to add the polar solvent or mixture thereof to the reaction chamber C1 , a means for separation (F1 ) of metal oxide or metal hydroxide from reduced form of the oxide formed in chamber C1 , a reaction chamber for reaction between reactants in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when M is Mg, the said reactants comprise: (a) reacting metal oxide with a halogen with heating to produce metal halide and metal oxyhalide, or, (b) reacting metal hydroxide and halogen with heating to produce metal halide, metal oxyhalide and water, or (c) reacting mixture of metal oxide
  • this invention comprises a process for extracting metals from their oxides or hydroxides comprising steps of a reaction in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when the metal is Mg of: (a) (i) reacting metal oxide with a halogen with heating to produce metal halide and metal oxyhalide, or (ii) reacting metal hydroxide and halogen with heating to produce metal halide, metal oxyhalide and water, or (iii) reacting mixture of metal oxide and metal hydroxide with halogen with heating to produce metal halide, metal oxyhalide and water, or (iv) reacting mixture of metal oxides with halogen with heating, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when the metal Mg, to produce metal halide, metal oxyhalide and water, or (v) reacting mixture of metal hydroxides with halogen with heating to produce metal halide
  • this invention comprises a process of reacting metal oxides and/or hydroxides with halogens, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when the metal is Mg, comprising steps of (i) reacting metal oxide with a halogen with heating to produce metal halide and metal oxyhalide, or (ii) reacting metal hydroxide and halogen with heating to produce metal halide, metal oxyhalide and water, or (iii) reacting mixture of metal oxide and metal hydroxide with halogen with heating to produce metal halide, metal oxyhalide and water, or (iv) reacting mixture of metal oxides with halogen with heating, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when the metal g, to produce metal halide, metal oxyhalide and water, or (v) reacting mixture of metal hydroxides with halogen with heating to produce metal halide,
  • This invention also comprises a process to make anhydrous iodide of a metal comprising the steps of reacting in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when the metal is Mg, comprising steps of (i) reacting metal oxide with a halogen with heating to produce metal halide and metal oxyhalide, or (ii) reacting metal hydroxide and halogen with heating to produce metal halide, metal oxyhalide and water, or (iii) reacting mixture of metal oxide and metal hydroxide with halogen with heating to produce metal halide, metal oxyhalide and water, or (iv) reacting mixture of metal oxides with halogen with heating, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when the metal Mg, to produce metal halide, metal oxyhalide and water, or (v) reacting mixture of metal hydroxides with halogen with heating to produce metal halide,
  • This invention comprises cyclic process to thermochemically dissociate Carbon Dioxide (CO2) into carbon(C) and oxygen (0 2 ) or into CO(carbon monoxide) and O2, or a cyclic process to thermochemically dissociate water (H 2 0) into hydrogen(H2) and oxygen(C>2), or a process for extraction of metals from their oxides or hydroxides.
  • the process of invention comprises: (1 ) a first step of reacting (i) metals with carbon dioxide to produce metal oxide and carbon monoxide or carbon, or (ii) reacting metal halides with carbon dioxide to produce metal oxide, carbon and halogen or metal oxide, carbon monoxide and halogen, or (iii) metals with water to produce metal oxides/metal hydroxides and hydrogen,
  • the preferred halogen may be iodine.
  • the invention also comprises conversion of metal oxide or hydroxide to anhydrous Metal halide in a polar solvent or combination of polar solvents.
  • This anhydrous metal halide splits into metal and halogen which are recycled and makes a cyclic process possible, the said cyclic process being a further embodiment of this invention.
  • the said metal oxides or hydroxides may also be mixed metal oxides or mixed metal hydroxides or mixtures of oxides and hydroxides or mixture of oxide and metal halide or mixture of hydroxide and metal halide.
  • Source of energy could be anything until energy is provided at temperature required by the cycle.
  • Source of energy for instance could be from a conventional source comprising coal, electricity, natural gas etc. or an unconventional source such as exhaust of (light/heavy) vehicles or waste heat from nuclear reactor or industrial chimney exhaust or solar energy or combination of any of the above etc. but is not limited to the said sources.
  • a further embodiment of this invention comprises a process to reduce CO2.
  • the said CO2 may be, without limitation, from vehicular exhaust, from industries or atmosphere etc. and a combination thereof.
  • sources could be used comprising, without limitation, rain water, surface water, underground water, waste water and the like.
  • Metals react with water to release hydrogen and with carbon dioxide to release carbon or carbon monoxide.
  • reaction 1.1 If water is present in excess in reaction 1.1 , then instead of metal oxide metal hydroxide will form.
  • Metal halide + C0 2 - Metal oxide + C + halogen 1 .3
  • Magnesium iodide (which was used in our experiments) reacts with carbon dioxide and reduces it to carbon.
  • Reaction spontaneity of metal oxide depends on how much reactive the metal is or how much stable its oxide is, alternatively it depends upon Gibbs energy of the reaction.
  • metal oxides are so stable that recovery of metal from its oxide by direct heating requires very, very high temperature, which is a problem that needs a solution.
  • metal oxide is converted to a compound that readily reacts with carbon dioxide and water and again forms oxide.
  • a metal oxide is converted to a compound which can be split by direct heating.
  • the compound is such that it itself could be used to reduce carbon dioxide without any need to extract metal from it, but to reduce to water, metal should be extracted from it by direct heating.
  • This invention is illustrated by conversion of a metal oxide to a metal halide, particularly to a metal iodide.
  • the invention is illustrated by conversion of magnesium oxide (MgO) to anhydrous magnesium iodide (Mgl 2 ), its decomposition temperature being 634°C at NTP and it doesn't melt or boil in the process.
  • MgO magnesium oxide
  • Mgl 2 anhydrous magnesium iodide
  • the added advantage is, magnesium vigorously reacts with water and carbon dioxide.
  • Mg dissolves in the solvent
  • some fraction of Mg(l0 3 )2 too dissolves in it. Separation of Mgl 2 and (dissolved)Mg(l03)2 is necessary and difficult. While the un-dissolved Mg(l0 3 )2 can be separated from solvent by simple filtration and then Mgl 2 can be extracted by boiling off the solvent in an inert atmosphere but while boiling off the solvent the dissolved Mg(l0 3 ) 2 reacts with Mgl 2 to form MgO and l 2 .
  • reaction 2 never goes to completion, it establishes equilibrium, and the equilibrium point depends on the proportions of reactants and solvent taken and the reaction temperature.
  • the extracted Mgl 2 is anhydrous, heating it to above 634°C in an inert atmosphere decomposes it into Mg and I2 while filtered Mg(l03) 2 is decomposed into MgO, l 2 and 0 2 at about 600°C.
  • the reactions are as follows;
  • reaction 3 the fact that one fifth mole of iodate reacts with one mole of iodide (reaction 3) necessitates its separation, even small quantity of iodate lowers reaction completion percentage.
  • reaction 3 the fact that one fifth mole of iodate reacts with one mole of iodide (reaction 3) necessitates its separation, even small quantity of iodate lowers reaction completion percentage.
  • CaS0 4 is more soluble than Ca(l0 3 ) 2 in polar solvents, iodate sparingly dissolves in it due to the common ion Ca ++ which is already present due to CaS0 4 . Moreover, CaS0 4 is inert to the reaction.
  • Common ion donor could be anything that is more soluble than Ca(l0 3 ) 2 and is inert in the reaction, like CaS0 4l Cal 2 etc..
  • Common ion effect can also be used with single metal oxide to reduce solubility of metal iodate, but since the common ion donor will have to be a 'Mg' compound, it will also affect (reduce) the solubility of the iodide (formed by reaction) and hence will reduce percentage reaction completion. This is overcome by increasing the amount of solvent; this seems to be the drawback for single metal oxide,
  • M A metal selected from the group: Mg, Cs, Cu, In, K, Li, Na, b, Tl, Ba,
  • M" A metal selected from the group Mg, Cs, Cu, In, K, Li, Na, Rb, Tl, Ba,
  • G F, CI, Br, I - unless otherwise stated.
  • Reaction could be done in any solvent that dissolves M G 2 and is preferably insoluble to oxyhalides (such a solvent could be polar solvent such as an alcohol, water etc.). Henceforth, such solvents collectively will be called solvents.
  • Common ion donor could be anything that is more soluble than M (G0 3 ) x and is inert in the reaction, like M x (S0 4 ) y , M G x .
  • Metal iodide can be formed with varying efficiency by using mixed metal oxides. Efficiency depends on what metal oxides are used. Mixed metal oxides have an advantage that the solubility of the metal oxyhalide can be controlled with common ion effect.
  • M Ba, Ca, Mg, Sr, Be, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Ra, Sn, Zn, Al, Bi, Ce, Cr, Dy, Er, Fe, Ga, Gd, Ho, In, La, Lu, Nd, Pr, So, Sm, Tm, Y, Yb, Ge, Th, U, Zr
  • metal iodides can be prepared using mixed metal hydroxides with varying efficiency. Efficiency depends on what metal hydroxides are used. Mixed metal hydroxides have an advantage that the solubility of the metal oxyhalide can be controlled with common ion effect.
  • M “ Cs, Cu, In, K, Li, Na, Rb, Tl, Ba, Ca, Mg, Sr, Be, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Ra, Sn, Zn, Al, Bi, Ce, Cr, Dy, Er, Fe, Ga, Gd, Ho, In, La, Lu, Nd, Pr, So, Sm, Tm, Y, Yb, Ge, Th, U, Zr
  • M “ Cs, Cu, In, K, Li, Na, Rb, Tl, Ba, Ca, Mg, Sr, Be, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Ra, Sn, Zn, Al, Bi, Ce, Cr, Dy, Er, Fe, Ga, Gd, Ho, In, La, Lu, Nd, Pr, So, Sm, Tm, Y, Yb, Ge, Th, U, Zr
  • M " Ba, Ca, Mg, Sr, Be, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Ra, Sn, Zn, Al, Bi, Ce, Cr, Dy, Er, Fe, Ga, Gd, Ho, In, La, Lu, Nd, Pr, So, Sm, Tm, Y, Yb, Ge, Th, U, Zr
  • M " Cs, Cu, In, K, Li, Na, Rb, Tl, Ba, Ca, Mg, Sr, Be, Cd, Co, Cr, Cu, Hg,
  • metal halide After extracting metal halide from the solvent it is decomposed into metal and halogen in an inert atmosphere at its decomposition point when heated.
  • M (G03)(2y/x) is filtered from solvent it is decomposed when heated, into metal oxide, halogen and oxygen at its decomposition point.
  • M “ Cs, Cu, In, K, Li, Na, Rb, Tl, Ba, Ca, Mg, Sr, Be, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Ra, Sn, Z, Al, Bi, Ce, Cr, Dy, Er, Fe, Ga, Gd, Ho, In, La, Lu, Nd, Pr, So, Sm, Tm, Y, Yb, Ge, Th, U, Zr
  • Figure 1 Mass flow diagram of the process of thermochemical decomposition of oxides illustrated for carbon dioxide and water
  • M' and M" are selected from the group: Mg, Cs, Cu, In, K, Li, Na, Rb, Tl, Ba, Ca, Mg, Sr, Be, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Ra, Sn, Z, Al, Bi, Ce, Cr, Dy, Er, Fe, Ga, Gd, Ho, In, La, Lu, Nd, Pr, So, Sm, Tm, Y, Yb, Ge, Th, U, Zr; wherein M' is less reactive than M".
  • Reaction in box 3 is done in polar solvent or mixture of polar solvents at about 150C, wherein polar solvent is not pure water when M - Mg.
  • Figure 3 Schematic representation of the device for carrying out the process of thermochemical decomposition of oxides illustrated for carbon dioxide and water.
  • C1 Reaction chamber, L1 : line L1 , P1 : Pump, L2: line L2, V1 and V2: not return valves, C3: chamber C3, L3: line L3, P2: pump P2, L4: line L4, C4: chamber C4, L5: line L5, C5: chamber C5.
  • the process could be used for batch as well as continuous processing.
  • the net input energy to the cycle may come from a conventional energy source such as coal, electricity, natural gas etc. or from unconventional source such as exhaust of (light/heavy) vehicles or waste heat from nuclear reactor or industrial chimney exhaust or solar energy or combination of any of the above etc. till it is provided at a temperature above 700°C.
  • This energy goes into line 3.
  • the energy from line 3 then goes to line 1 and line 2 in the proportion that is required by the reactions in chambers connected to line 1 (chamber 22 and chamber 23) and reactions in chambers connected to line 2 (chamber 24 and chamber 20). For exothermic reactions (chambers 20 and 22), energy goes into lines 2 and 3 respectively.
  • Yellow and red lines are heat exchanger lines/pipes while blue lines are conveyer belts (is case solid is to be carried) or pipes(in case gas is to be carried). Chambers are placed in such a way that high temperature high energy requiring reactions(chamber 23 and 24) are closest to the line 3 and line 4(line 4 too carries energy at high temperature, it comes from the highly exothermic reaction from chamber 20), they are the first ones to get energy while reactions requiring low temperature low energy are away from lines 3 and 4(chambers 21 , 22 and 24).
  • MgO and C formed in chamber 20 are carried to chamber 21 using conveyer
  • MgO and C are separated in chamber 21 due to the difference in there densities. Density of MgO is more than that of C. A liquid is present in chamber 21 that is denser than C and less denser than MgO and it is such that both MgO and C do not dissolve or react with it, therefore, when mixture of MgO and C is put into chamber 21 carbon (C) floats in the liquid while
  • the liquid may be ethanol. Density of ethanol is 0.789gm/cm 3 . Its density is increased by addition of Znl 2 . In general, the liquid could be anything till its density is between the densities of MgO and C and it does not react or dissolve MgO and/or C.
  • lodide/lodate formation chamber (22) MgO is carried to chamber 22 from chambers 21 and 23 through conveyers 13 and 16 respectively. Iodine comes from chambers 23 and 24 through pipes 15 and 18 respectively while n-pentanol comes from chamber 24 through pipe 18. Same pipe(18) is used to carry iodine and n-pentanol from chamber 24 to chamber 22 since both are in the gaseous form when they are carried to chamber 22 and both are required at the same time and for the same reaction.
  • Trigger energy is required for the reaction at a temperature of 150°C, it is provided through line 7. As the reaction is exothermic heat is extracted from it (line 6). Chamber 22 is further from line 3 (from which it is getting energy) as compared to chamber 23 while it is closer to line 3 as compared to chamber 20.
  • Mg(l0 3 )2 is carried from chamber 22 to chamber 23 using conveyer 14. Here it is decomposed into MgO, l 2 and 0 2 . The reaction is endothermic and requires a temperature of 600°C. The chamber is closest to line 3, it gets its required energy through line 8. Oxygen is removed through line 25.
  • Mg decomposition/Mg extraction chamber(24) Once Mg(IO 3 ) 2 is removed through chamber 22 then the solvent is drained through line 17 into chamber 24. It contains dissolved Mgl 2 . The reaction taking place in this chamber is very endothermic and requires a temperature of 634°C. It gets its energy from line 4 and line 3 through line 9. Energy is taken by 2 process; one - boiling off n-pentanol, two - decomposition of Mgl 2 into Mg and l 2 .
  • the invention may have several uses and applications.
  • One such application could be reduction of carbon di-oxide to reduce the load of green-house gases.
  • Other application could be to convert a waste source of heat into a combustible fuel such as hydrogen by thermochemical splitting of water.
  • Operating this invention covering entire scope of all the alternatives of the oxides eligible for thermochemical dissociation, including specifically, without limitation, the carbon dioxide and water, and use of all metals, all metal oxides and all metal halides to catalyse the process of this invention and a device for achieving the functions set by the process of instant invention as its objective shall be possible for a person skilled in the art upon the illustration of how the core steps 2 and 3 described above are achieved.
  • Mgl 2 was taken in a round bottom flask of 500ml. Air from the flask was removed by upward displacement using C0 2 . The flask was then sealed and CO2 at 1 bar was maintained in the flask. The flask was then heated using heating mantle to about 230°C. At this temperature all Mgl 2 reacted with CO2 and formed MgO(white, powder like), l 2 (brown, small particles) and C(black, small particles) in the flask. pH of the products was measured at 10.3.
  • MgO : l 2 : Kl : Water : Pentanol 1 : 4 : 0.33 : 28 : 26 is used as a preferred molar ratio.
  • Reaction 19.1 is done in reaction chamber C1 , this chamber is Polytetrafluoroethylene coated in order to avoid reaction of iodine or of Mgl 2 with the chamber.
  • the reaction temperature is about 230°C.
  • Dissolved Mgl 2 is pumped into chamber C1 through line L1 using pump P1.
  • Chamber C1 is maintained at 1 bar C0 2 pressure. This pressure is maintained by connecting chamber C1 through line L2 to CO2 chamber C2 which has pressure regulator PR set at 1 bar. Reverse flow through lines L1 and L2 are avoided by not return valves Vi and V 2 respectively.
  • Once dissolved Mgl 2 enters chamber C1 it is heated so that all the solvent vapors go to chamber 03 through line L3 where they are cooled, the solvent then is in liquid state in chamber 03.
  • the solute(Mgl 2 ) remains in chamber 01 where it reacts with C0 2 .
  • solvent from chamber 03 is pumped to chamber 01 through line L3 using pump P2.
  • Solvent helps move the products of reaction 19.1 towards filter F1 through line L4.
  • Filter is a mesh(sieve) of 40microns which allows solvent, MgO and iodine to go through it while Carbon remains over the filter.
  • the filtrate so obtained goes to chamber C4 through line L5. Potassium iodide required for the reaction is already present in chamber C5 since reaction 19.3 is done in the chamber C4.
  • Reaction 19.2 is done in chamber C4 (same chamber where reaction 19.3 is done). Chamber C4 has a filter(sieve) F2. Once reaction 9.2 completes then the solvent containing Mgl2 is pumped to chamber C1 through line L1 and using pump P1. The residue iodine and KI03 are heated. Iodine boils early (184C) as compared to KI03 decomposition(450C), iodine is collected in chamber 05 while oxygen from KI03 is vented out through line L6.

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Abstract

The invention comprises a process of cyclic thermochemical dissociation of oxides catalysed by a metal compound of general structural formula MX, wherein M is a metal; X is none or oxygen or halogen, the said oxygen or halogen present in moles equivalent to M; comprising at least a step of recovering anhydrous metal halide from a process stream and recycling the metal halide or thermally decomposing the same to metal and halogen for recycling. The oxide selected for dissociation may be carbon-dioxide or water. After dissociation of oxides, the products of the reaction undergo a series of reactions comprising a reaction with a halogen, formation of metal halides and oxyhalides as intermediates, thermal decomposition of metal oxyhalides to recover metal oxides and Iodine for recycle, recovery of metal halides for recycle and thermal decomposition of metal halides to metal and halogen for recycle in the said cyclic process.

Description

Title :
CYCLIC THERMOCHEMICAL DISSOCIATION OF CARBON DIOXIDE AND WATER.
Field of Invention:
This invention pertains to a cyclic process to thermochemically dissociate oxides using metals or metal derivatives as catalysts. More particularly the invention comprises thermochemical dissociation of Carbon Dioxide into carbon and oxygen or into carbon monoxide and oxygen, or water into hydrogen and oxygen and to a process of extracting metals from their oxides or hydroxides or halides and recycling the metals and halogen. The invention also relates to reacting metal oxides and/or hydroxides with halogens. The invention also relates to reacting metal oxides with metal halides to give metal halide and metal oxyhalide in presence of polar solvent or combination of polar solvents, excluding pure water when metal is Magnesium. The invention also relates to reacting metal hydroxides with metal halides to give metal halide, metal oxyhalide and water in presence of polar solvent or combination of polar solvents, excluding pure water when metal is Magnesium. The invention also relates to reacting metal oxides with halogens to give metal halide and metal oxyhalide in presence of polar solvent or combination of polar solvents, excluding pure water when metal is Magnesium. The invention also relates to reacting metal hydroxides with halogens to give metal halide, metal oxyhalide and water in presence of polar solvent or combination of polar solvents, excluding pure water when metal is magnesium. This invention also pertains to use common ion effect to reduce the solubility of metal oxyhalides in the cyclic reaction process. The invention also pertains to use of mixed metal oxides or mixed metal hydroxides or a mixture of metal oxide and metal hydroxide for the process of thermochemical decomposition of oxides or for the recovery of metal from its oxide or hydroxide. The invention also pertains particularly to conversion of magnesium oxide to anhydrous magnesium iodide and further regenerating elemental Mg and Iodine. The invention also pertains particularly to conversion of zinc oxide to zinc iodide and further regenerating elemental Zn and Iodine.
BACKGROUND OF INVENTION
C02 is important to nature as is oxygen, but excess C02 may be contributing in global warming. All the organic fuels when oxidized give out C02. On account of a rapid increase in global consumption of organic fuels, there is net rapid increase in CO2 in the atmosphere. The equilibrium between CO2 and O2 is shifting and nature is responding by global rise in temperature as one of its responses. Since C02 shall be available in abundance and bringing down its current level of concentration in atmosphere is also desired, utilizing the same for creating energy rich organic molecules is highly desirable. Further, hydrogen is considered as an alternative to organic fuels as the energy carrier in future but for that to happen hydrogen must be prepared using green source of energy.
CO2 splitting is a very widely researched subject. M. E. Ga'lvez et al(C02 Splitting via Two-Step Solar Thermochemical Cycles with Zn/ZnO and FeO/Fe304 Redox Reactions: Thermodynamic Analysis - Energy Fuels, 2008, 22 (5), pp 3544-3550, DOI: 10.1021 /ef800230b, Publication Date (Web): August 13, 2008) describe a method to thermochemically split C02. The method uses Zn or FeO to reduce C02. ZnO or Fe304 thus formed are converted back to Zn or FeO by thermal dissociation. This cycle has a disadvantage of requirement of very high peak temperature, about 2000°C to split ZnO into Zn and 02 and 1700°C to convert Fe304 to FeO. Product separation (in order to avoid recombination) which are essentially gases at such a high temperature is very difficult.
Y. Shindo et al (Thermal efficiency of the magnesium-iodine cycle for thermochemical hydrogen production - International Journal of Hydrogen Energy, Volume 8, Issue 7, 1983, Pages 509-513) describe a method to thermochemically dissociate H2O into hydrogen and oxygen using MgO and iodine. The method converts MgO to hydrous Mgl2 which is then hydrolyzed into HI and MgO. HI is then separated and decomposed into H2 and l2. The equilibrium of hydrogen generation step (decomposition of HI) tends to be more on the reactant side, therefore yielding less hydrogen. Moreover, gas separation(HI and H2) is difficult.
C. F. V. Mason (The reaction of the alkaline earth metal oxides with iodine in the presence of water as part of a thermochemical hydrogen cycle - Journal of Inorganic and Nuclear Chemistry, Volume 42, Issue 6, 1980, Pages 799- 803) describe a process to thermochemically dissociate H20 into hydrogen and oxygen using metal oxides of group II elements of Periodic Table (except BeO and RaO) and iodine. Metal oxides and hydroxides are used single or in combination. The method converts MgO to hydrous Mgl2 which is then hydrolyzed into HI and MgO. HI is then separated and decomposed into H2 and l2. The equilibrium of hydrogen generation step(decomposition of HI) tends to be more on the reactant side, therefore yielding less hydrogen. Moreover, gas separation (HI and H2) is difficult.
SUMMARY OF THE INVENTION
The invention comprises a process of cyclic thermochemical dissociation of oxides catalysed by a metal compound of general structural formula MX, wherein M is a metal; X is none or oxygen or halogen, the said oxygen or halogen present in moles equivalent to M; comprising at least a step of recovering anhydrous metal halide from a process stream and recycling the metal halide or thermally decomposing the same to metal and halogen for recycling. The oxide selected for dissociation may be carbon-dioxide or water.
In one embodiment, the invention comprises thermochemical dissociation of carbon dioxide comprising a step of reacting the same with MX, where M is Mg or Zn and X is none, to produce metal oxide and carbon monoxide or carbon; or MX, where M is Mg or Zn and X is halogen, to produce metal oxide, carbon and halogen.
In another embodiment, the invention comprises thermochemical dissociation of water comprising a step of reacting the same with MX, where M is Mg or Zn and X is none, comprising step of reacting M with water to produce metal oxide and hydrogen or metal hydroxide and hydrogen.
In a further embodiment of the invention, the process of thermochemical dissociation comprises a step of reaction in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when M is Mg, of (a) metal oxide with a halogen with heating, to produce metal halide and metal oxyhalide, or (b) reacting metal hydroxide and halogen with heating to produce metal halide, metal oxyhalide and water, or (c) reacting mixture of metal oxide and metal hydroxide with halogen with heating to produce metal halide, metal oxyhalide and water, or (d) reacting mixture of metal oxides with halogen with heating to produce metal halide, metal oxyhalide and water, or (e) reacting mixture of metal hydroxides with halogen with heating, to produce metal halide, metal oxyhalide and water, or (f) reacting metal oxide and metal halide with halogen with heating to produce metal halide, metal oxyhalide and water, or (g) reacting metal hydroxide and metal halide with halogen with heating to produce metal halide, metal oxyhalide and water. One further embodiment of this reaction comprises a step of adding a compound with common ion of metal oxyhalide, where the said compound is more soluble in the solvent than the oxyhalide.
In a further embodiment of the invention, the said metal oxyhalide obtained from steps a to e mentioned above are decomposed by heating to get metal oxide, oxygen and halogen or the metal oxyhalide obtained from steps f and g mentioned above by heating to get metal halide and oxygen. The oxygen thus produced is collected or liberated, and metal oxide or metal halide and halogen thus produced are recycled for further reaction to make metal oxyhalide and metal halide.
In a still further embodiment of this invention, the metal halide dissolved in a polar solvent or a mixture of polar solvent is recovered separate from the polar solvent or the mixture of polar solvent; and the recovered solvent or solvent mixture is recycled for use as reaction medium for reacting metal oxide with halogen, or for reacting metal hydroxide with halogen, or for reacting mixture of metal hydroxide and metal oxide with halogen ,or for reacting mixture of metal oxide and metal halide with halogen, or for reacting mixture of metal hydroxide and metal halide with halogen; and the metal halide recovered free from the polar solvent or from the mixture of polar solvents by heating is thermally decomposed to recover metal and halogen, recycling halogen for reaction with (i) metal oxide, or (ii) metal hydroxide, or (iii) both, or (iv) metal oxide and metal halide, or (v) metal hydroxide and metal halide, and recycling metal to the reaction with carbon dioxide or water. The inventive experiment, M is magnesium (Mg), halogen is Iodine (I) and reactions between Magnesium oxide or magnesium iodide on one hand; and the Iodine on other is done by heating the reaction up to a temperature of about 150 degrees celcius.
In a reaction h emetal may be chosen from the group of Mg, Zn, Cs, Cu, In, K, Li, Na, Rb, Tl, Ba, Ca, Mg, Sr, Be, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Ra, Sn, Zn, Al, Bi, Ce, Cr, Dy, Er, Fe, Ga, Gd, Ho, In, La, Lu, Nd, Pr, So, Sm, Tm, Y, Yb, Ge, Th, U and Zr. Most preferred metals are Magnesium and Zinc and Magnesium iodate formed in such a reaction is thermally decomposed by heating up to a temperature of about 600 degrees celcius.
In another embodiment, the invention comprises a process, wherein M is magnesium (Mg) and the halogen is Iodine (I), comprising a step of heating Magnesium Iodide for decomposition up to about 634 degrees celcius. Invention also comprises an apparatus for MX catalysed thermochemical dissociation of oxides, wherein M is a metal; X is none, oxygen or halogen, the said oxygen or halogen present in moles equivalent to M; the said apparatus comprising at least a means for recovering anhydrous metal halide from a process stream and recycling the metal halide or thermally decomposing the same to metal and halogen for recycling; wherein M is selected from the group Mg, Zn, Cs, Cu, In, K, Li, Na, Rb, Tl, Ba, Ca, Mg, Sr, Be, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Ra, Sn, Zn, Al, Bi, Ce, Cr, Dy, Er, Fe, Ga, Gd, Ho, In, La, Lu, Nd, Pr, So, Sm, Tm, Y, Yb, Ge, Th, U and Zr. The oxides for dissociation may comprise either carbon dioxide or water.
In an embodiment of this invention, the apparatus or a device comprises at least following components: (a) a source of an oxide (C2), (b) a regulator to control quantity of the oxide to be fed to reaction chamber C1 and a means to avoid reverse flow of oxide from chamber C1 , (c) a source of polar solvent or a mixture thereof (C3), a means to add the polar solvent or mixture thereof to the reaction chamber C1 , a means for separation (F1 ) of metal oxide or metal hydroxide from reduced form of the oxide formed in chamber C1 , a reaction chamber for reaction between reactants in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when M is Mg, the said reactants comprise: (a) reacting metal oxide with a halogen with heating to produce metal halide and metal oxyhalide, or, (b) reacting metal hydroxide and halogen with heating to produce metal halide, metal oxyhalide and water, or (c) reacting mixture of metal oxide and metal hydroxide with halogen with heating to produce metal halide, metal oxyhalide and water, or (d) reacting mixture of metal oxides with halogen with heating to produce metal halide, metal oxyhalide and water, or (e) reacting mixture of metal hydroxides with halogen with heating to produce metal halide, metal oxyhalide and water, or (f) reacting metal oxide and metal halide with halogen with heating to produce metal halide, metal oxyhalide and water, or (g) reacting metal hydroxide and metal halide with halogen with heating to produce metal halide, metal oxyhalide and water; a means for separating solid products of the reaction from liquid products (F2), separating metal oxyhalide from metal halide dissolved in polar solvent or a mixture thereof, a means for thermally decomposing metal oxyhalide to form metal oxide, oxygen and halogen or to form metal halide and oxygen, and recycling metal oxide or metal halide to reaction chamber C4; and a means for separating polar solvent or mixture thereof from dissolved metal halide, recycling the recovered polar solvent or mixture thereof to reaction chamber C4 and recycling metal halide to reaction chamber C1 or thermally splitting the metal halide in chamber C6 for recycling metal to reaction chamber C1 and halogen to reaction chamber C4.
In one embodiment, this invention comprises a process for extracting metals from their oxides or hydroxides comprising steps of a reaction in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when the metal is Mg of: (a) (i) reacting metal oxide with a halogen with heating to produce metal halide and metal oxyhalide, or (ii) reacting metal hydroxide and halogen with heating to produce metal halide, metal oxyhalide and water, or (iii) reacting mixture of metal oxide and metal hydroxide with halogen with heating to produce metal halide, metal oxyhalide and water, or (iv) reacting mixture of metal oxides with halogen with heating, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when the metal Mg, to produce metal halide, metal oxyhalide and water, or (v) reacting mixture of metal hydroxides with halogen with heating to produce metal halide, metal oxyhalide and water, or (vi) reacting metal oxide and metal halide with halogen with heating to produce metal halide, metal oxyhalide and water, or (vii) reacting metal hydroxide and metal halide with halogen with heating to produce metal halide, metal oxyhalide and water; and (b) a process of (i) decomposing the said metal oxyhalide, obtained from steps (i) or (ii) or (iii) or (iv) or (v) by heating to get metal oxide, oxygen and halogen, or (ii) decomposing the said metal oxyhalide, obtained from steps (vi) or (vii), by heating to get metal halide and oxygen, recovering metal halide free from the polar solvent or the mixture of polar solvent from its solution, and decomposing the metal halide recovered free from the polar solvent or the mixture of polar solvent by heating to recover the metal and halogen.
In yet another embodiment, this invention comprises a process of reacting metal oxides and/or hydroxides with halogens, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when the metal is Mg, comprising steps of (i) reacting metal oxide with a halogen with heating to produce metal halide and metal oxyhalide, or (ii) reacting metal hydroxide and halogen with heating to produce metal halide, metal oxyhalide and water, or (iii) reacting mixture of metal oxide and metal hydroxide with halogen with heating to produce metal halide, metal oxyhalide and water, or (iv) reacting mixture of metal oxides with halogen with heating, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when the metal g, to produce metal halide, metal oxyhalide and water, or (v) reacting mixture of metal hydroxides with halogen with heating to produce metal halide, metal oxyhalide and water, or (vi) reacting metal oxide and metal halide with halogen with heating to produce metal halide, metal oxyhalide and water, or (vii) reacting metal hydroxide and metal halide with halogen with heating to produce metal halide, metal oxyhalide and water.
This invention also comprises a process to make anhydrous iodide of a metal comprising the steps of reacting in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when the metal is Mg, comprising steps of (i) reacting metal oxide with a halogen with heating to produce metal halide and metal oxyhalide, or (ii) reacting metal hydroxide and halogen with heating to produce metal halide, metal oxyhalide and water, or (iii) reacting mixture of metal oxide and metal hydroxide with halogen with heating to produce metal halide, metal oxyhalide and water, or (iv) reacting mixture of metal oxides with halogen with heating, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when the metal Mg, to produce metal halide, metal oxyhalide and water, or (v) reacting mixture of metal hydroxides with halogen with heating to produce metal halide, metal oxyhalide and water, or (vi) reacting metal oxide and metal halide with halogen with heating to produce metal halide, metal oxyhalide and water, or (vii) reacting metal hydroxide and metal halide with halogen with heating to produce metal halide, metal oxyhalide and water. A preferred metal for this reaction is Mg.
DETAILED DESCRIPTION OF THE INVENTION
This invention comprises cyclic process to thermochemically dissociate Carbon Dioxide (CO2) into carbon(C) and oxygen (02) or into CO(carbon monoxide) and O2, or a cyclic process to thermochemically dissociate water (H20) into hydrogen(H2) and oxygen(C>2), or a process for extraction of metals from their oxides or hydroxides. The process of invention comprises: (1 ) a first step of reacting (i) metals with carbon dioxide to produce metal oxide and carbon monoxide or carbon, or (ii) reacting metal halides with carbon dioxide to produce metal oxide, carbon and halogen or metal oxide, carbon monoxide and halogen, or (iii) metals with water to produce metal oxides/metal hydroxides and hydrogen,
(2) a second step of reacting, in presence of a polar solvent or mixture of polar solvents and at an elevated temperature, preferably at about 150 degrees celcius, (i) metal oxide with a halogen to produce metal halide and metal oxyhalide, or (ii) metal hydroxide and halogen to produce metal halide, metal oxyhalide and water, or (iii) metal oxide, metal hydroxide and halogen to produce metal halide, metal oxyhalide and water, or (ivj a mixture of metal oxides, and halogen to produce metal halide and metal oxyhalide, or (v) a mixture of metal hydroxides and halogen to produce metal halide, metal oxyhalide and water, or (vi) metal oxide, metal halide and halogen to produce metal halide and metal oxyhalide, or (vii) metal hydroxide, metal halide and halogen to produce metal halide, metal oxyhalide and water, and
(3) a third step of decomposing the said metal oxyhalide to metal oxide and oxygen and halogen; or into metal halide and oxygen.
and
(4) a fourth step of decomposing the said metal halide by heating to recover metal and halogen; if metal halide is used in the said first step then fourth step is unnecessary, the said fourth step becomes necessary only if metal is used in the first step.
The preferred halogen may be iodine.
The invention also comprises conversion of metal oxide or hydroxide to anhydrous Metal halide in a polar solvent or combination of polar solvents. This anhydrous metal halide splits into metal and halogen which are recycled and makes a cyclic process possible, the said cyclic process being a further embodiment of this invention. The said metal oxides or hydroxides may also be mixed metal oxides or mixed metal hydroxides or mixtures of oxides and hydroxides or mixture of oxide and metal halide or mixture of hydroxide and metal halide.
All the reagents in the process of this invention are recovered at the end of the cycle.
Source of energy could be anything until energy is provided at temperature required by the cycle. Source of energy, for instance could be from a conventional source comprising coal, electricity, natural gas etc. or an unconventional source such as exhaust of (light/heavy) vehicles or waste heat from nuclear reactor or industrial chimney exhaust or solar energy or combination of any of the above etc. but is not limited to the said sources. A further embodiment of this invention comprises a process to reduce CO2. The said CO2 may be, without limitation, from vehicular exhaust, from industries or atmosphere etc. and a combination thereof. To reduce water, several sources could be used comprising, without limitation, rain water, surface water, underground water, waste water and the like.
Metals react with water to release hydrogen and with carbon dioxide to release carbon or carbon monoxide.
2xM + y(C02/2H20) -» 2MxOy + y(C/2H2) 1.1
If water is present in excess in reaction 1.1 , then instead of metal oxide metal hydroxide will form.
xM + yC02 -> MxOy + yCO 1.2M
= metal
Metal halide reaction with carbon dioxide to reduce it to carbon or carbon monoxide.
Metal halide + C02 -» Metal oxide + C + halogen 1 .3
Metal halide + C02 -> Metal oxide + CO + halogen 1 .4
Magnesium iodide (which was used in our experiments) reacts with carbon dioxide and reduces it to carbon.
2Mgl2 + C02 -» 2MgO + C + 2I2 1.5
Reaction spontaneity of metal oxide depends on how much reactive the metal is or how much stable its oxide is, alternatively it depends upon Gibbs energy of the reaction. To reduce water or carbon dioxide with just the input of water or carbon dioxide and energy the process should be cyclic; i.e. recovery of metal from its oxide is necessary. Generally, metal oxides are so stable that recovery of metal from its oxide by direct heating requires very, very high temperature, which is a problem that needs a solution.
In one aspect of this invention, metal oxide is converted to a compound that readily reacts with carbon dioxide and water and again forms oxide. In another aspect of the invention, a metal oxide is converted to a compound which can be split by direct heating. The compound is such that it itself could be used to reduce carbon dioxide without any need to extract metal from it, but to reduce to water, metal should be extracted from it by direct heating. This invention is illustrated by conversion of a metal oxide to a metal halide, particularly to a metal iodide. The invention is illustrated by conversion of magnesium oxide (MgO) to anhydrous magnesium iodide (Mgl2), its decomposition temperature being 634°C at NTP and it doesn't melt or boil in the process. The added advantage is, magnesium vigorously reacts with water and carbon dioxide.
Following reaction converts magnesium oxide to anhydrous magnesium iodide;
Polar solvent or their
6MgO(s) + 6l2(s,i) com 'nat'on ► 5Mglz(dis8.) + Mg(l03)2(s) 2 wherein s = solid, I = liquid, diss. = dissolved
For the above reaction to work it must be done in a solvent other than pure water that dissolves Mg^ and is preferably insoluble to magnesium iodate. Such a solvent could be polar solvent such as an alcohol or mixture of alcohol and water. Though the reaction works in pure water, it creates hydrous Mgl2 upon boiling off water which is undesirable since hydrous Mgl2 decomposes into HI and MgO upon heating. Pure water may be used as a solvent if anhydrous Mgl2 can be recovered from it by some technique that is not used here.
While Mg dissolves in the solvent, some fraction of Mg(l03)2 too dissolves in it. Separation of Mgl2 and (dissolved)Mg(l03)2 is necessary and difficult. While the un-dissolved Mg(l03)2 can be separated from solvent by simple filtration and then Mgl2 can be extracted by boiling off the solvent in an inert atmosphere but while boiling off the solvent the dissolved Mg(l03)2 reacts with Mgl2 to form MgO and l2.
5Mgl2 + (dissolved) Mg(l03)2 6MgO + 6I2 3
Therefore, percentage completion of reaction depends on the quantity of undissolved Mg(l03)2. Moreover reaction 2 never goes to completion, it establishes equilibrium, and the equilibrium point depends on the proportions of reactants and solvent taken and the reaction temperature.
The extracted Mgl2 is anhydrous, heating it to above 634°C in an inert atmosphere decomposes it into Mg and I2 while filtered Mg(l03)2 is decomposed into MgO, l2 and 02 at about 600°C. The reactions are as follows;
Mgl2(S) - Mg(S) + l2(g) @ 634°C and inert atmosphere 4
Mg(l03)2(8) -> gO(s) + l2(g) + (5/2)02(g) @ 600°C 5 wherein s = solid, g = gas The reactions that constitute the cycle are as follows; (wherein s = solid, I = liquid, g = gas, diss. = dissolved)
C02(g) + 2Mg(S) - 2MgO(S) + C(s) ,.6.1.1
C02(g) + 2Mgl2(s) -> 2MgO(S) + C(s) + 2I2(S) 6.1.2 2H20(,,g) + 2Mg(s) 2MgO(s) + 2H2(g) 6.2
(12/5)MgO(s) + (12/5)l2(s,,) (2/5)Mg(l03)2(s) + 2Mgl2(diSs.) 7
2Mgl2(s) - > 2Mg(S) + 2l2(g) 8
(2/5)Mg(l03)2(s) (2/5)MgO(s) + (2/5)l2(g) + 02(g) .9
Mg(l03)2 solubility:
Though solubility of iodate is quite low, the fact that one fifth mole of iodate reacts with one mole of iodide (reaction 3) necessitates its separation, even small quantity of iodate lowers reaction completion percentage. The problem is solved by using mixed oxides and common ion effect as follows;
(wherein s = solid, I = liquid, diss. = dissolved)
5MgO(S) + CaO(s) + 6l2(s,i) + xCaS04(diss.) -> 5Mgl2(diss.) + Ca(l03)2(s) + xCaS04
(diss.) - in polar solvent 10.1
or
5MgO(S) + CaO(s) + 6l2(s,i) + xCa++ + xS04 ~~ -» 5Mgl2(dlss.) + Ca(l03)2(s) + xCa++
+ xS04 " - in polar solvent 10.2
As CaS04 is more soluble than Ca(l03)2 in polar solvents, iodate sparingly dissolves in it due to the common ion Ca++ which is already present due to CaS04. Moreover, CaS04 is inert to the reaction.
Common ion donor could be anything that is more soluble than Ca(l03)2 and is inert in the reaction, like CaS04l Cal2 etc.. Common ion effect can also be used with single metal oxide to reduce solubility of metal iodate, but since the common ion donor will have to be a 'Mg' compound, it will also affect (reduce) the solubility of the iodide (formed by reaction) and hence will reduce percentage reaction completion. This is overcome by increasing the amount of solvent; this seems to be the drawback for single metal oxide,
(wherein s = solid, I = liquid, diss. = dissolved)
6MgO(S) + 6l2(s,i) + xMgG2(diss.) -» 5Mgl2(diss.) + Mg(l03)2(s) + xMgG2(diss.) - in polar solvent 11.1
or
6MgO(S) + 6l2(s,i) + xMg++ + 2xG" 5Mgl2(diss.) + Mg(l03)2(8) + xMg++ + 2xG' - in a polar solvent 11.2
G = F, CI, Br, I
Generalizing the cycle:
M = A metal selected from the group: Mg, Cs, Cu, In, K, Li, Na, b, Tl, Ba,
Ca, Mg, Sr, Be, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Ra, Sn, Z, Al, Bi, Ce, Cr, Dy,
Er, Fe, Ga, Gd, Ho, In, La, Lu, Nd, Pr, So, Sm, Tm, Y, Yb, Ge, Th, U, Zr.
M" = A metal selected from the group Mg, Cs, Cu, In, K, Li, Na, Rb, Tl, Ba,
Ca, Mg, Sr, Be, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Ra, Sn, Z, Al, Bi, Ce, Cr, Dy, Er, Fe, Ga, Gd, Ho, In, La, Lu, Nd, Pr, So, Sm, Tm, Y, Yb, Ge, Th, U, Zr, wherein, M" is more reactive than M\
G = F, CI, Br, I - unless otherwise stated.
J = F, CI, Br, I - unless otherwise stated. C02/H20 reduction:
2M" + C02 -» 2M O + C
2M' + 2C02 - 2M O + 2CO
2M G2 + C02 - 2M O + C + 2G
M G2 + C02 - M O + CO + G2
2M' + 2H20 - 2M O + 2H2
General reactions for single and mixed metal oxide/hydroxide to metal halide conversion:
Reaction could be done in any solvent that dissolves M G2 and is preferably insoluble to oxyhalides (such a solvent could be polar solvent such as an alcohol, water etc.). Henceforth, such solvents collectively will be called solvents.
Water cannot be used as solvent where M Gx will form hydrates and upon decomposition will not yield metal and halogen. Therefore, water as a solvent cannot be used with 'Mg' but could be used with 'Zn'. Though as stated earlier it is possible to use water as a solvent if recovery of anhydrous Mgl2 is possible from it.
Common ion donor could be anything that is more soluble than M (G03)x and is inert in the reaction, like M x(S04)y, M Gx.
'J' equal to 'G' when M is not equal to M (mixed metal oxides/hydroxides) 1) Mixed metal oxides:
Metal iodide can be formed with varying efficiency by using mixed metal oxides. Efficiency depends on what metal oxides are used. Mixed metal oxides have an advantage that the solubility of the metal oxyhalide can be controlled with common ion effect.
5yM O + M'xOy + 6yG2 -» 5yMG2 + xM"(G03) (2y/x) 13.1 or
5yMO + M'xOy + 6yG2 + ZM'J (2yx) -» 5yMG2 + x M"(G03) (2y,x) + zM'J
(2y/x)---13.2
or
5yM'0 + M" xOy + 6yG2 + zM"(2y/x)+ + z(2y/x)J" -> 5yM G2 + xM "(G03) (2y/x) + zM"(2y/x)+ + z(2y/x)J- 13.3 M" = Ba, Ca, Mg, Sr, Be, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Ra, Sn, Zn, Al, Bi, Ce, Cr, Dy, Er, Fe, Ga, Gd, Ho, In, La, Lu, Nd, Pr, So, Sm, Tm, Y, Yb, Ge, Th, U, Zr
2) Mixed metal hydroxides:
Similar to mixed metal oxides metal iodides can be prepared using mixed metal hydroxides with varying efficiency. Efficiency depends on what metal hydroxides are used. Mixed metal hydroxides have an advantage that the solubility of the metal oxyhalide can be controlled with common ion effect.
5xM'(OH)2 + 2M"(OH)x + 6xG2 -» 5xMG2 + 2M"(G03)X +
6xH20 14.1
or
5xM(OH)2 + 2M"(OH)x + 6xG2 + zM"jx -» 5xMG2 + 2M"(G03)X + 6xH20 + zM"Jx 14.2 or 5xM'(OH)2 + 2M"(OH)x + 6xG2 + zM"x+ + zxJ" - 5xM G2 + 2M"(G03)X + 6xH20
+ zM "x+ + zxJ" 14.3
M" = Cs, Cu, In, K, Li, Na, Rb, Tl, Ba, Ca, Mg, Sr, Be, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Ra, Sn, Zn, Al, Bi, Ce, Cr, Dy, Er, Fe, Ga, Gd, Ho, In, La, Lu, Nd, Pr, So, Sm, Tm, Y, Yb, Ge, Th, U, Zr
3) Metal oxide and metal hydroxide:
This is very similar to mixed metal oxides or hydroxides with respect to everything.
5xM O + 2M"(OH)x + 6xG2 - 5xM G2 + 2M"(G03)X + xH20 15.1.1
or
5xM O + 2M"(OH)x + 6xG2 + zM"jx -» 5xM G2 + 2M "(G03)X + xH20 +
ZM"Jx 15.1.2 or
5xM O + 2M"(OH)x + 6xG2 + zM"x+ + zxJ" 5xM G2 + 2M"(G03)X + xH20 + zM "x+ + zxJ- 15.1 .3
M" = Cs, Cu, In, K, Li, Na, Rb, Tl, Ba, Ca, Mg, Sr, Be, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Ra, Sn, Zn, Al, Bi, Ce, Cr, Dy, Er, Fe, Ga, Gd, Ho, In, La, Lu, Nd, Pr, So, Sm, Tm, Y, Yb, Ge, Th, U, Zr
5yM'(OH)2 + M"xOy + 6yG2 -> 5yM G2 + xM"(G03) (2y/x) +
5yH20 15.2.1
or
5yM (OH)2 + M"xOy + 6yG2 + zM' j (2y/x)→ 5yM G2 + xM"(G03) (2y/x) + 5yH20 + zM"j (2y/x) 15.2.2 or
5yM (OH)2 + M" xOy + 6yG2 + zM"(2y/x>+ + z(2y/x)J' 5yM G2 + xM"(G03)(2y/x) +
5yH20 +zM"(2y/x)+ + z(2y/x)J- 15.2.3
M" = Ba, Ca, Mg, Sr, Be, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Ra, Sn, Zn, Al, Bi, Ce, Cr, Dy, Er, Fe, Ga, Gd, Ho, In, La, Lu, Nd, Pr, So, Sm, Tm, Y, Yb, Ge, Th, U, Zr
4) Metal oxide and metal halide:
3xM O + M 'GX + 3xG2 -> 3xM G2 + M '(G03)x 16.1 or
3xM O + M"Gx + 3xG2 + zM"j2 -» 3xM G2 + M"(G03)x + zM"j2 16.2
or
3xM O + M"Gx + 3xG2 + zM"x+ + zxJ" - 3xM G2 + M"(I03)X + zM"x+ + zxJ- 16.3
M" = Cs, Cu, In, K, Li, Na, Rb, Tl, Ba, Ca, Mg, Sr, Be, Cd, Co, Cr, Cu, Hg,
Mn, Ni, Pb, Ra, Sn, Zn, Al, Bi, Ce, Cr, Dy, Er, Fe, Ga, Gd, Ho, In, La, Lu, Nd,
Pr, So, Sm, Tm, Y, Yb, Ge, Th, U, Zr
Same goes for metal hydroxide and metal halide.
Metal extraction from its halide:
After extracting metal halide from the solvent it is decomposed into metal and halogen in an inert atmosphere at its decomposition point when heated.
M G2 ^ M' + G2 17 M (G03)(2y/X) decomposition:
Once M (G03)(2y/x) is filtered from solvent it is decomposed when heated, into metal oxide, halogen and oxygen at its decomposition point.
2xM "(G03)(2y/x) -> 2M" xOy + 2yG2 + 5y02 18
M" = Cs, Cu, In, K, Li, Na, Rb, Tl, Ba, Ca, Mg, Sr, Be, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Ra, Sn, Z, Al, Bi, Ce, Cr, Dy, Er, Fe, Ga, Gd, Ho, In, La, Lu, Nd, Pr, So, Sm, Tm, Y, Yb, Ge, Th, U, Zr
BRIEF DESCRIPTION OF FIGURES AND LEGENDS
Figure 1 : Mass flow diagram of the process of thermochemical decomposition of oxides illustrated for carbon dioxide and water
M = M'
Wherever two metals are involved in a same reaction, M' and M" are selected from the group: Mg, Cs, Cu, In, K, Li, Na, Rb, Tl, Ba, Ca, Mg, Sr, Be, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Ra, Sn, Z, Al, Bi, Ce, Cr, Dy, Er, Fe, Ga, Gd, Ho, In, La, Lu, Nd, Pr, So, Sm, Tm, Y, Yb, Ge, Th, U, Zr; wherein M' is less reactive than M".
X: F, CI, Br, I.
Reactions are not stoichiometrically balanced.
Reaction in box 3 is done in polar solvent or mixture of polar solvents at about 150C, wherein polar solvent is not pure water when M - Mg.
(s) - solid.
(I) - liquid.
(g) - gas.
(diss.) - dissolved in the solvent used. Figure 2: Mass and energy flow diagram of the process of thermochemical decomposition of oxides illustrated for carbon dioxide and water.
Figure 3: Schematic representation of the device for carrying out the process of thermochemical decomposition of oxides illustrated for carbon dioxide and water.
C1 : Reaction chamber, L1 : line L1 , P1 : Pump, L2: line L2, V1 and V2: not return valves, C3: chamber C3, L3: line L3, P2: pump P2, L4: line L4, C4: chamber C4, L5: line L5, C5: chamber C5. F2: a filter (sieve) F2, L6: line L6, C6: reaction chamber 6.
Figure 1 : Mass flow:
Explains cyclic flow of mass. The Figure helps understand how each step interacts with the other step. All the reactions in the Figure are for reduction of 1 mole C02 or 2mole H20.
Single metal oxide reaction is considered just to show the flow but similar flow applies to all other reactions defined above in the 'general reactions' section.
Figure 2: Mass and energy flow:
Explains mass and energy flow from one step/reaction/chamber to other. Single metal oxide reaction is considered just to show the flow but similar flow applies to all other reactions defined above in the 'general reactions' section.
Energy is extracted from the exothermic step and given to the endothermic step. Net energy input (as net reaction decomposes carbon dioxide, hence net cycle is endothermic) could be from any source having temperature above 700°C. Follow diagram (Figure 2)
The process could be used for batch as well as continuous processing.
Input energy/Line 3:
The net input energy to the cycle may come from a conventional energy source such as coal, electricity, natural gas etc. or from unconventional source such as exhaust of (light/heavy) vehicles or waste heat from nuclear reactor or industrial chimney exhaust or solar energy or combination of any of the above etc. till it is provided at a temperature above 700°C. This energy goes into line 3. The energy from line 3 then goes to line 1 and line 2 in the proportion that is required by the reactions in chambers connected to line 1 (chamber 22 and chamber 23) and reactions in chambers connected to line 2 (chamber 24 and chamber 20). For exothermic reactions (chambers 20 and 22), energy goes into lines 2 and 3 respectively. Yellow and red lines are heat exchanger lines/pipes while blue lines are conveyer belts (is case solid is to be carried) or pipes(in case gas is to be carried). Chambers are placed in such a way that high temperature high energy requiring reactions(chamber 23 and 24) are closest to the line 3 and line 4(line 4 too carries energy at high temperature, it comes from the highly exothermic reaction from chamber 20), they are the first ones to get energy while reactions requiring low temperature low energy are away from lines 3 and 4(chambers 21 , 22 and 24).
C02/H20 reduction chamber(20): C02/H20(line 10) goes into the chamber 20 and reacts vigorously with the magnesium powder that is present in it. Magnesium comes from chamber 24 to chamber 20 through conveyer 19. Though the reaction requires trigger energy (line 5), the reaction is very exothermic releasing (line 4) 808kJ of energy per mole of C02 reduced and 632kJ of energy for 2mole of H20 reduced. Chamber 20 is furthest from line 3 since the reaction taking place in it is highly exothermic and the reaction requires only very small amount of trigger energy.
C02 + 2Mg 2MgO + C - dH = -808kJ
2H20 + 2Mg 2MgO + 2H2 - dH = -632kJ
MgO/C filter chamber(21):
MgO and C formed in chamber 20 are carried to chamber 21 using conveyer
11. MgO and C are separated in chamber 21 due to the difference in there densities. Density of MgO is more than that of C. A liquid is present in chamber 21 that is denser than C and less denser than MgO and it is such that both MgO and C do not dissolve or react with it, therefore, when mixture of MgO and C is put into chamber 21 carbon (C) floats in the liquid while
MgO settles down. C is removed using conveyer (12).
The liquid may be ethanol. Density of ethanol is 0.789gm/cm3. Its density is increased by addition of Znl2. In general, the liquid could be anything till its density is between the densities of MgO and C and it does not react or dissolve MgO and/or C.
lodide/lodate formation chamber (22): MgO is carried to chamber 22 from chambers 21 and 23 through conveyers 13 and 16 respectively. Iodine comes from chambers 23 and 24 through pipes 15 and 18 respectively while n-pentanol comes from chamber 24 through pipe 18. Same pipe(18) is used to carry iodine and n-pentanol from chamber 24 to chamber 22 since both are in the gaseous form when they are carried to chamber 22 and both are required at the same time and for the same reaction.
Trigger energy is required for the reaction at a temperature of 150°C, it is provided through line 7. As the reaction is exothermic heat is extracted from it (line 6). Chamber 22 is further from line 3 (from which it is getting energy) as compared to chamber 23 while it is closer to line 3 as compared to chamber 20.
The products of this reaction - Mg(l03)2 precipitates in the solvent while Mgl2 dissolves in it.
(12/5)MgO(S) + ( 2/5)l2(s,,) - (2/5)Mg(l03)2(s) + 2Mgl2(diss.) - dH = -74.56kJ (wherein s = solid, I = liquid, diss. = dissolved)
Mg(IC>3)2 decomposition chamber:
Mg(l03)2 is carried from chamber 22 to chamber 23 using conveyer 14. Here it is decomposed into MgO, l2 and 02. The reaction is endothermic and requires a temperature of 600°C. The chamber is closest to line 3, it gets its required energy through line 8. Oxygen is removed through line 25.
(2/5)Mg(l03)2(s) -» (2/5)MgO(S) + (2/5)l2(g) + 02(g) - dH = 148.12
(wherein s = solid, I = liquid, g = gas)
Mg decomposition/Mg extraction chamber(24): Once Mg(IO3)2 is removed through chamber 22 then the solvent is drained through line 17 into chamber 24. It contains dissolved Mgl2. The reaction taking place in this chamber is very endothermic and requires a temperature of 634°C. It gets its energy from line 4 and line 3 through line 9. Energy is taken by 2 process; one - boiling off n-pentanol, two - decomposition of Mgl2 into Mg and l2.
2Mgl2(diss.) -> 2Mgl2(s) + n-pentanol - dH = 427kJ
2Mgl2(s) -> 2Mg(S) + 2l2(g) - dH = 853kJ
(wherein s = solid, diss. = dissolved, g = gas)
The invention may have several uses and applications. One such application could be reduction of carbon di-oxide to reduce the load of green-house gases. Other application could be to convert a waste source of heat into a combustible fuel such as hydrogen by thermochemical splitting of water. Operating this invention covering entire scope of all the alternatives of the oxides eligible for thermochemical dissociation, including specifically, without limitation, the carbon dioxide and water, and use of all metals, all metal oxides and all metal halides to catalyse the process of this invention and a device for achieving the functions set by the process of instant invention as its objective shall be possible for a person skilled in the art upon the illustration of how the core steps 2 and 3 described above are achieved. If the core steps 2 and 3 can be achieved, practicing any aspect of the disclosed invention is possible by making routine experimentation, although all the aspects may not be illustrated here. In the following are given non- limiting examples on how to achieve the core steps 2 and 3 for the purpose of illustration. All equivalents and alternatives obvious to a person skilled in the art are included within the scope of this disclosure and are considered to be within the scope of the claims.
EXAMPLES EXAMPLE 1
0.15gm magnesium oxide (MgO) and 2.54gm iodine(l2) were put into 10ml n- pentanol. This mixture was then heated to 120°C for 20 minutes. The mixture was allowed to cool down to room temperature. It was then titrated using 0.03M Ethylenediaminetetraacetic acid(EDTA). The result of titration suggested 80% reaction completion.
2.78gm Mgl2 was taken in a round bottom flask of 500ml. Air from the flask was removed by upward displacement using C02. The flask was then sealed and CO2 at 1 bar was maintained in the flask. The flask was then heated using heating mantle to about 230°C. At this temperature all Mgl2 reacted with CO2 and formed MgO(white, powder like), l2(brown, small particles) and C(black, small particles) in the flask. pH of the products was measured at 10.3.
EXAMPLE 2
Design of an illustrative device and performing the key steps:
A preferred design is illustrated in Figure 3 and explained below. However, any equivalent or improvement of the design illustrated below can be used. Reactions:
C02 + 2Mgl2 C + 2MgO +
2I2 19.1 2MgO + (2/3)KI + 2I2 2Mgl2 + (2/3)KI03 - solvent water and pentanol....19.2
(2/3)KI03 - (2/3)KI +
C-2 19.3
The actual molar ratios of reactants:
Reaction 19.1
Pressure of 1bar CO2 for any quantity of Mgl2.
Reaction 19.2
MgO : l2 : Kl : Water : Pentanol = 1 : 4 : 0.33 : 28 : 26 is used as a preferred molar ratio.
Reaction 19.1 is done in reaction chamber C1 , this chamber is Polytetrafluoroethylene coated in order to avoid reaction of iodine or of Mgl2 with the chamber. The reaction temperature is about 230°C. Dissolved Mgl2 is pumped into chamber C1 through line L1 using pump P1. Chamber C1 is maintained at 1 bar C02 pressure. This pressure is maintained by connecting chamber C1 through line L2 to CO2 chamber C2 which has pressure regulator PR set at 1 bar. Reverse flow through lines L1 and L2 are avoided by not return valves Vi and V2 respectively. Once dissolved Mgl2 enters chamber C1 it is heated so that all the solvent vapors go to chamber 03 through line L3 where they are cooled, the solvent then is in liquid state in chamber 03. The solute(Mgl2) remains in chamber 01 where it reacts with C02.
After reaction 19.1 completes, solvent from chamber 03 is pumped to chamber 01 through line L3 using pump P2. Solvent helps move the products of reaction 19.1 towards filter F1 through line L4. Filter is a mesh(sieve) of 40microns which allows solvent, MgO and iodine to go through it while Carbon remains over the filter. The filtrate so obtained goes to chamber C4 through line L5. Potassium iodide required for the reaction is already present in chamber C5 since reaction 19.3 is done in the chamber C4.
Reaction 19.2 is done in chamber C4 (same chamber where reaction 19.3 is done). Chamber C4 has a filter(sieve) F2. Once reaction 9.2 completes then the solvent containing Mgl2 is pumped to chamber C1 through line L1 and using pump P1. The residue iodine and KI03 are heated. Iodine boils early (184C) as compared to KI03 decomposition(450C), iodine is collected in chamber 05 while oxygen from KI03 is vented out through line L6.

Claims

1. A process of cyclic thermochemical dissociation of oxides catalysed by a metal compound of general structural formula MX, wherein M is a metal; X is none or oxygen or halogen, the said oxygen or halogen present in moles equivalent to M; comprising at least a step of recovering anhydrous metal halide from a process stream and recycling the metal halide or thermally decomposing the same to metal and halogen for recycling.
2. A process of claim 1 wherein the oxide selected for dissociation is carbon-dioxide.
3. A process of claim 2 comprising a step of reacting carbon dioxide with: a. MX, where M is Mg or Zn and X is none, to produce metal oxide and carbon monoxide or carbon, or
b. MX, where M is Mg or Zn and X is halogen, to produce metal oxide, carbon and halogen.
4. A process of claim 1 wherein the said oxide selected for dissociation is water.
5. A process of claim 4 wherein M is Mg or Zn and X is none, comprising step of reacting M with water to produce metal oxide and hydrogen or metal hydroxide and hydrogen.
6. A process of claim 3 or claim 5 comprising step of:
a. reacting metal oxide with a halogen with heating, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when M is Mg, to produce metal halide and metal oxyhalide, or
b. reacting metal hydroxide and halogen with heating, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when M is Mg, to produce metal halide, metal oxyhalide and water, or
c. reacting mixture of metal oxide and metal hydroxide with halogen with heating, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when M is Mg, to produce metal halide, metal oxyhalide and water, d. reacting mixture of metal oxides with halogen with heating, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when M is Mg, to produce metal halide, metal oxyhalide and water.
e. reacting mixture of metal hydroxides with halogen with heating, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when M is Mg, to produce metal halide, metal oxyhalide and water.
f. reacting metal oxide and metal halide with halogen with heating, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when M is Mg, to produce metal halide, metal oxyhalide and water.
g. reacting metal hydroxide and metal halide with halogen with heating, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when M is Mg, to produce metal halide, metal oxyhalide and water.
A process of claim 6 comprising step of:
a. decomposing the said metal oxyhalide, obtained from steps 6a, 6b, 6c,6d or 6e by heating to get metal oxide, oxygen and
• halogen, or
b. decomposing the said metal oxyhalide, obtained from steps 6f and, 6g, by heating to get metal halide and oxygen,
c. collecting or liberating oxygen thus produced, and
d. recycling metal oxide or metal halide, and halogen thus produced for further reaction to make metal oxyhalide and metal halide.
A process of claim 6 further comprising steps of:
a. recovering metal halide dissolved in a polar solvent or a mixture of polar solvent,
b. recycling the polar solvent or a mixture of polar solvent for use as reaction medium for:
i. reacting metal oxide with halogen, or for
ii. reacting metal hydroxide with halogen, or for iii. reacting mixture of metal hydroxide and metal oxide with halogen ,or for
iv. reacting mixture of metal oxide and metal halide with halogen, or for v. reacting mixture of metal hydroxide and metal halide with halogen; and
c. decomposing the metal halide recovered free from the polar solvent or from the mixture of polar solvents by heating to recover metal and halogen,
d. recycling halogen for reaction with (i) metal oxide, or (ii) metal hydroxide, or (iii) both, or (iv) metal oxide and metal halide, or (v) metal hydroxide and metal halide, and
e. recycling metal to the reaction with carbon dioxide or water.
9. A process of claim 6 wherein M is magnesium (Mg), halogen is Iodine (I) and comprising step of heating the reaction up to a temperature of about 150 degrees celcius.
10. A process of claim 6 wherein the metal is selected from a group of Mg, Zn, Cs, Cu, In, K, Li, Na, Rb, Tl, Ba, Ca, Mg, Sr, Be, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Ra, Sn, Zn, Al, Bi, Ce, Cr, Dy, Er, Fe, Ga, Gd, Ho, In, La, Lu, Nd, Pr, So, Sm, Tm, Y, Yb, Ge, Th, U and Zr
11. A process of claim 7 wherein M is magnesium (Mg), halogen is Iodine (I) and comprising step of heating up to a temperature of about 600 degrees celcius.
12. A process of claim 8 wherein M is magnesium (Mg), halogen is Iodine (I) and comprising step of heating Magnesium Iodide for decomposition up to about 634 degrees celcius.
3. An apparatus or device for MX catalysed thermochemical dissociation of oxides, wherein M is a metal; X is none, oxygen or halogen, the said oxygen or halogen present in moles equivalent to M; the said apparatus comprising at least a means for recovering anhydrous metal halide from a process stream and recycling the metal halide or thermally decomposing the same to metal and halogen for recycling.
14. An apparatus or a device of claim 13 wherein M is selected from the group Mg, Zn, Cs, Cu, In, K, Li, Na, Rb, Tl, Ba, Ca, Mg, Sr, Be, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Ra, Sn, Zn, Al, Bi, Ce, Cr, Dy, Er, Fe, Ga, Gd, Ho, In, La, Lu, Nd, Pr, So, Sm, Tm, Y, Yb, Ge, Th, U and Zr.
15. An apparatus or a device of claim 14 wherein oxides selected for dissociation comprise either carbon dioxide or water.
16. An apparatus or a device of claim 13 comprising at least following components:
a. a source of an oxide (C2),
b. a regulator to control quantity of the oxide to be fed to reaction chamber C1 and a means to avoid reverse flow of oxide from chamber C1 ,
c. a source of polar solvent or a mixture thereof (C3),
d. a means to add the polar solvent or mixture thereof to the reaction chamber C1 ,
e. a means for separation (F1) of metal oxide or metal hydroxide from reduced form of the oxide formed in chamber C1 , f. a reaction chamber for reaction between reactants in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when M is Mg, the said reactants comprise: (a) reacting metal oxide with a halogen with heating to produce metal halide and metal oxyhalide, or, (b) reacting metal hydroxide and halogen with heating to produce metal halide, metal oxyhalide and water, or (c) reacting mixture of metal oxide and metal hydroxide with halogen with heating to produce metal halide, metal oxyhalide and water, or (d) reacting mixture of metal oxides with halogen with heating to produce metal halide, metal oxyhalide and water, or (e) reacting mixture of metal hydroxides with halogen with heating to produce metal halide, metal oxyhalide and water, or (f) reacting metal oxide and metal halide with halogen with heating to produce metal halide, metal oxyhalide and water, or (g) reacting metal hydroxide and metal halide with halogen with heating to produce metal halide, metal oxyhalide and water, means for separating solid products of the reaction from liquid products (F2), separating metal oxyhalide from metal halide dissolved in polar solvent or a mixture thereof,
means for thermally decomposing metal oxyhalide to form metal oxide, oxygen and halogen or to form metal halide and oxygen; and recycling metal oxide or metal halide to reaction chamber C4,
means for separating polar solvent or mixture thereof from dissolved metal halide, recycling the recovered polar solvent or mixture thereof to reaction chamber C4 and recycling metal halide to reaction chamber C1 or thermally splitting the metal halide in chamber C6 for recycling metal to reaction chamber C1 and halogen to reaction chamber C4.
17. A process for extracting metals from their oxides or hydroxides comprising steps of:
a.
i. reacting metal oxide with a halogen with heating, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when the metal is Mg, to produce metal halide and metal oxyhalide, or ii. reacting metal hydroxide and halogen with heating, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when the metal is Mg, to produce metal halide, metal oxyhalide and water, or iii. reacting mixture of metal oxide and metal hydroxide with halogen with heating, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when the metal is Mg, to produce metal halide, metal oxyhalide and water,
iv. reacting mixture of metal oxides with halogen with heating, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when the metal is Mg, to produce metal halide, metal oxyhalide and water. v. reacting mixture of metal hydroxides with halogen with heating, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when the metal is Mg, to produce metal halide, metal oxyhalide and water.
vi. reacting metal oxide and metal halide with halogen with heating, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when the metal is Mg, to produce metal halide, metal oxyhalide and water.
vii. reacting metal hydroxide and metal halide with halogen with heating, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when the metal is Mg, to produce metal halide, metal oxyhalide and water.,
(i) decomposing the said metal oxyhalide, obtained from steps 17a(i), 17a(ii), 17a(iii),17a(iv) or 17a(v) by heating to get metal oxide, oxygen and halogen, (ii) decomposing the said metal oxyhalide, obtained from steps 6f and, 6g, by heating to get metal halide and oxygen,
recovering metal halide free from the polar solvent or the mixture of polar solvent from its solution, d. decomposing the metal halide recovered free from the polar solvent or the mixture of polar solvent by heating to recover the metal and halogen.
18. A process of reacting metal oxides and/or hydroxides with halogens comprising steps of:
i. reacting metal oxide with a halogen with heating, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when the metal is Mg, to produce metal halide and metal oxyhalide, or ii. reacting metal hydroxide and halogen with heating, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when the metal is Mg, to produce metal halide, metal oxyhalide and water, or iii. reacting mixture of metal oxide and metal hydroxide with halogen with heating, in a polar. solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when the metal is Mg, to produce metal halide, metal oxyhalide and water,
iv. reacting mixture of metal oxides with halogen with heating, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when the metal is Mg, to produce metal halide, metal oxyhalide and water. v. reacting mixture of metal hydroxides with halogen with heating, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when the metal is Mg, to produce metal halide, metal oxyhalide and water.
vi. reacting metal oxide and metal halide with halogen with heating, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when the metal is Mg, to produce metal halide, metal oxyhalide and water.
vii. reacting metal hydroxide and metal halide with halogen with heating, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when the metal is Mg, to produce metal halide, metal oxyhalide and water.
19. A process to make anhydrous iodide of a metal comprising the steps of:
a. reacting a metal oxide with a halogen with heating, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when the metal is Mg, to produce metal halide and metal oxyhalide, or
b. reacting a metal hydroxide and halogen with heating, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when the metal is Mg, to produce metal halide, metal oxyhalide and water, or
c. reacting mixture of a metal oxide and a metal hydroxide with halogen with heating, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when the metal is Mg, to produce metal halide, metal oxyhalide and water,
d. reacting mixture of metal oxides with halogen with heating, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when the metal is Mg, to produce metal halide, metal oxyhalide and water.
e. reacting mixture of metal hydroxides with halogen with heating, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when the metal is Mg, to produce metal halide, metal oxyhalide and water.
f. reacting metal oxide and metal halide with halogen with heating, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when the metal is Mg, to produce metal halide, metal oxyhalide and water.
g. reacting metal hydroxide and metal halide with halogen with heating, in a polar solvent or in a mixture of polar solvents wherein the polar solvent is not pure water when the metal is Mg, to produce metal halide, metal oxyhalide and water.
rocess of claim 19 wherein the metal is Mg.
21. A process of claim 6 comprising a step of adding a compound with common ion of metal oxyhalide, where the said compound is more soluble in the solvent than the oxyhalide.
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