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Method of producing hydrogen gas from water

10994994 · 2021-05-04

    Inventors

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    Abstract

    The invention is a method for coproducing Hydrogen and certain metals by reducing a metal oxide(s) with MgH.sub.2 or with metal and water, wherein the non-water oxides used in the method include SiO.sub.2, Cr.sub.2O.sub.3, TiO.sub.2, SnO.sub.2, ZrO.sub.2, CuO, ZnO, WO.sub.3, Ta.sub.2O.sub.5, Cs.sub.2Cr.sub.2O.sub.7 or CsOH. The method reacts the MgH.sub.2 with a metal oxide or directly uses metal and water instead of a hydride, and initiates a reaction with the metal oxide. The reaction releases Hydrogen and reduces the subject oxide to metal.

    Claims

    1. A method of co-producing hydrogen and metal comprising the steps of: reacting Magnesium hydride and a compound A, selected from a group consisting of metal oxide and metal sulphide, in a fluidized bed reactor wherein a reaction is performed in sealed inert gas flushed reaction chamber and heated between 25° C. and 1000° C.; collecting hydrogen gas evolved; and collecting and separating metal and MgO thus produced.

    2. The method of co-producing hydrogen and metal of claim 1, wherein the compound A is at least one from the group consisting of SiO.sub.2, Al.sub.2O.sub.3, Cr.sub.2O.sub.3, TiO.sub.2, SnO.sub.2, ZrO.sub.2, CuO, CuS, CuFeS.sub.2, ZnO, WO.sub.3, Ta.sub.2O.sub.5, MnO.sub.2, Cs.sub.2Cr.sub.2O.sub.7 and CsOH.

    3. A method of co-producing hydrogen and metal comprising the steps of: reacting a metal P comprising Magnesium and, optionally, one or more of Calcium, Aluminium and Silicon, and metal oxide Q with water in a fluidized bed reactor in a sealed inert gas flushed reaction chamber and heating between 25° C. and 1000° C.; collecting hydrogen gas produced; and collecting and separating the metal and MgO thus produced.

    4. The method of coproducing hydrogen and metal of claim 3, wherein the metal oxide Q is selected from a group consisting of SiO.sub.2, Cr.sub.2O.sub.3, TiO.sub.2, SnO.sub.2, ZrO.sub.2, CuO, ZnO, WO.sub.3, Ta.sub.2O.sub.5, Cs.sub.2Cr.sub.2O.sub.7 or CsOH.

    5. The method of producing hydrogen of claim 1, wherein such method is carbon emission free.

    6. The method of producing hydrogen of claim 3, wherein such method is carbon emission free.

    7. The method of co-producing hydrogen and metal of claim 2, wherein the reaction is MgH.sub.2+0.5 SnO.sub.2=MgO+0.5 Sn+H.sub.2.

    Description

    BRIEF DESCRIPTION OF THE DRAWINGS

    (1) FIG. 1 is a phase diagram depicting the stability of MgH.sub.2 formed by combining different proportion of Mg and water at various temperatures.

    (2) FIG. 2 is a line drawing evidencing a diagram of a reactor used to produce hydrogen from the direct method.

    (3) FIG. 3 is a line drawing evidencing an alternate embodiment of the reactor shown in FIG. 2, this time for using the hydride method.

    DETAILED DESCRIPTION OF THE INVENTION

    (4) The present invention is a method of producing hydrogen from water, either via already-produced Magnesium hydride (MgH.sub.2) or via a reaction of water and magnesium. Magnesium hydride is a convenient and easily storable solid which contains hydrogen. Hydrogen can be generated by coproducing MgH.sub.2 with certain metals. The process is accomplished by reacting Magnesium hydride with a metal oxide or sulfide. Hydrogen can also be coproduced with metal by reaction of a metal such as Mg, Al, Si, or Ca with water and a metal oxide (oxide ore). The coproduction of metals and hydrogen makes hydrogen a by-product and therefore there is no specific cost involved and hence the process is highly profitable. The method is largely carbon emission free depending on mode of production of Magnesium.

    (5) The Magnesium required as a reactant in the process is obtained by electrolytic reduction of MgO by the solid oxide membrane (SOM) technique. This process requires close to 12 kWh of electricity and results in the generation of 11.28 kg of CO.sub.2 for each kg of Mg when thermal power is used. This emission is reduced to almost zero if alternate forms of energy (hydro, nuclear, solar, wind) are used.

    (6) When one mole of Mg reacts with one mole of H.sub.2 Magnesium hydride is obtained according to equation (1) shown below:
    Mg(s)+H.sub.2(g).fwdarw.MgH.sub.2(s)ΔH=−6.2E-02 kW T=300 K  (1)

    (7) When a metal such as Mg is reacted with water, we get the reaction as shown in (3) and not the hydride producing reaction as shown in (4):
    Mg+H.sub.2O.fwdarw.MgO+H.sub.2  (3)
    Mg+H.sub.2O.fwdarw.MgH.sub.2+0.5O.sub.2  (4)

    (8) The two-step process of reactions (1) and (3) can be changed to one step by using different proportions of Mg and water in reaction (3) to get the following reaction (5):
    2Mg+H.sub.2O.fwdarw.MgH.sub.2+MgO  (5)

    (9) There is an important difference between the hydride produced from reactions (1) and (3) and reaction (5). The hydride in reaction (5) is produced without involvement of any fossil fuel, except if Mg production leads to some carbon emission.

    (10) On heating, the hydride produces hydrogen according to equation (6):
    MgH.sub.2(s).fwdarw.Mg+H.sub.2 T=566 K ΔH=1.2E4 J  (6)

    (11) The price of the hydrogen produced will depend on the price of Mg used in the overall process.

    (12) Coproduction of Metal and Hydrogen:

    (13) There are two ways of coproducing hydrogen and the metal. The two disclosed methods are as follows:

    (14) 1. The Hydride Method:

    (15) This method to generate hydrogen is to carry the hydride to any site where it is required and apply some heat (reaction 6). MgH.sub.2 releases hydrogen on reacting with an oxide, usually with H.sub.2O. Other oxides which react with the hydride are CuO or CuFeS.sub.2, Fe.sub.2O.sub.3, Fe.sub.3O.sub.4, SiO.sub.2, SnO.sub.2, ZrO.sub.2, Al.sub.2O.sub.3 and Cr.sub.2O.sub.3. In each case MgO forms along with hydrogen and the added oxide is reduced to the corresponding metal.

    (16) The metals which are produced in the process are very expensive and their production along with hydrogen is very profitable. Further hydrogen being a byproduct is produced at no cost. The overall cost of production is reduced since the recycling cost of MgO will be easily recovered by the sale of the products namely the metal and hydrogen. The reactions of metal oxides with Magnesium Hydride presented below occur at a temperature of 300 K to 400 K. The temperature can be higher if kinetics are slow. All reactions are exothermic except (9). All ΔH values are in Joules.
    MgH.sub.2(s)+H2O.fwdarw.MgO+H.sub.2ΔH=−2.39E5  (7)
    MgH.sub.2(s)+SiO.sub.2.fwdarw.0.5Si+0.5Mg2SiO.sub.4+H.sub.2ΔH=−1.02E5  (8)
    MgH.sub.2(s)+0.34Al2O.sub.3.fwdarw.MgO+0.68Al+H.sub.2+(minor spinel),ΔH=3.6E4  (9)
    MgH.sub.2(s)+0.34Cr.sub.2O.sub.3.fwdarw.MgO+0.68Cr+H.sub.2+(minor spinel),ΔH=−1.41E5  (10)
    MgH.sub.2(s)+0.5TiO.sub.2.fwdarw.MgO+0.5TiH.sub.2+0.5H.sub.2ΔH=−1.25E5  (11)
    (TiH.sub.2=Ti+H2ΔH=2e5,T=1155 K)
    MgH.sub.2(s)+0.5SnO.sub.2.fwdarw.MgO+0.5Sn+H.sub.2ΔH=−2.37E5  (12)
    MgH.sub.2+0.5ZrO.sub.2.fwdarw.0.5ZrH.sub.2+MgO+0.5H.sub.2ΔH=−5.41E4  (13)
    (ZrH.sub.2=Zr+H2,T=1139K)
    MgH.sub.2+CuS.fwdarw.MgS+Cu+H.sub.2T=400ΔH=−5.8E5  (14)
    MgH.sub.2+CuO.fwdarw.MgO+Cu+H.sub.2T=400ΔH=−3.6E5  (15)
    MgH.sub.2+CuFeS.sub.2.fwdarw.FeS+MgS+Cu+H.sub.2ΔH=−1.87E5  (16)
    MgH.sub.2+ZnO.fwdarw.MgO+Zn+H.sub.2ΔH=−1.75E5  (17)
    3MgH.sub.2+WO.sub.3.fwdarw.3 MgO+W+3H.sub.2ΔH=−7.33E5  (18)
    MgH.sub.2+0.2Ta2O.sub.5.fwdarw.MgO+0.4Ta+H.sub.2ΔH=−1.16E5  (19)
    MnO.sub.2+2MgH.sub.2.fwdarw.2MgO+Mn+2H.sub.2ΔH=−3.6E5  (20)
    7MgH.sub.2+Cs.sub.2Cr.sub.2O.sub.7.fwdarw.2Cs+7MgO+2Cr+7H.sub.2ΔH=−1.59E6  (21)
    MgH.sub.2+CsOH.fwdarw.Cs+MgO+1.5H.sub.2ΔH=−1.087E5  (22)

    (17) Reactions (7) to (22) are thermo-chemically possible. The kinetic barrier in these reactions may be overcome by using higher temperatures if needed. Hence, these reactions proceed even in the absence of catalysts.

    (18) 2. the Direct Method:

    (19) In this method metal and hydrogen are produced without the use of hydride by the direct reaction of Metals such as Magnesium, Silicon, Aluminium or Calcium with water and metal-oxide. A few examples of such reactions are as follows:
    3Mg+SiO.sub.2+H.sub.2O=Si+3MgO+H.sub.2ΔH=−6.01E5  (23)

    (20) (The reaction not useful because Mg is higher in price than Si)
    2Al+SiO.sub.2+H.sub.2O=Si+Al.sub.2O.sub.3+H.sub.2ΔH=−5.23E5  (24)
    4Mg+Cr.sub.2O.sub.3+H.sub.2O=4MgO+2Cr+H.sub.2ΔH=−1.04E6  (25)
    3Mg+TiO.sub.2+H.sub.2O=3MgO+TiH.sub.2ΔH=−7.47E5  (26)
    2Al+TiO.sub.2+H.sub.2O=Al2O.sub.3+TiH.sub.2ΔH=−5.9E5  (27)
    3Ca+TiO.sub.2+H.sub.2O=3CaO+TiH.sub.2ΔH=−8.27E5  (28)
    3Mg+SnO.sub.2+H.sub.2O=3MgO+Sn+H.sub.2ΔH=−9.85E5  (29)
    3Ca+SnO.sub.2+H.sub.2O=3CaO+Sn+H.sub.2−1.086E6  (30)
    2Al+SnO.sub.2+H.sub.2O=Al.sub.2O.sub.3+Sn+H.sub.2ΔH=−8.62E5  (31)
    Mg+CuO+H2O=2MgO+Cu+H.sub.2T=400ΔH=−8.05E5  (32)
    Ca+CuO+H.sub.2O=2CaO+Cu+H.sub.2T=400ΔH=−8.75E5  (33)
    1.34Al+CuO+H.sub.2O=Cu+0.67Al.sub.2O.sub.3+H.sub.2ΔH=−71.19E5  (34)
    1.5Si+SnO.sub.2+H.sub.2O=1.5SiO.sub.2+Sn+H.sub.2ΔH=−5.46E5  (35)
    2Mg+0.5ZrO.sub.2+H.sub.2O=0.5ZrH.sub.2+2MgO+0.5H.sub.2ΔH=−4.861E4  (36)
    3Ca+ZrO.sub.2+H.sub.2O=3CaO+ZrH.sub.2ΔH=−7.35E5  (37)
    2Al+ZrO.sub.2+H.sub.2O=Al.sub.2O.sub.3+ZrH.sub.2ΔH=−5.05E5  (38)
    2Mg+ZnO+H.sub.2O=2MgO+Zn+H.sub.2ΔH=−6.15E5  (39)
    2Ca+ZnO+H.sub.2O=2CaO+Zn+H.sub.2ΔH=−6.77E5  (40)
    1.334Al+ZnO+H.sub.2O=Zn+0.667Al.sub.2O.sub.3+H.sub.2ΔH=−5.24E5  (41)
    Si+ZnO+H.sub.2O=Zn+SiO.sub.2+H.sub.2ΔH=−3.19E5  (42)
    2Si+WO.sub.3+H.sub.2O=2SiO.sub.2+W+H.sub.2ΔH=−7.37E5  (43)
    4Mg+WO.sub.3+H.sub.2O=4MgO+W+H.sub.2ΔH=−1.45E6  (44)
    3Al+WO.sub.3+H.sub.2O=1.333Al2O.sub.3+W+H.sub.2ΔH=−1.15E5  (45)
    6Mg+Ta.sub.2O.sub.5+H.sub.2O=6MgO+2Ta+H.sub.2ΔH=−1.32E6  (46)
    6Ca+Ta.sub.2O.sub.5+H.sub.2O=6CaO+2Ta+H.sub.2ΔH=−1.52E6  (47)
    4Al+Ta.sub.2O.sub.5+H.sub.2O=2Al2O3+2Ta+H.sub.2ΔH=−1.064E5  (48)
    4Si+Ta.sub.2O.sub.5+H.sub.2O=3SiO2+Ta.sub.2Si+H2ΔH=−5.7E5  (49)
    8Mg+Cs.sub.2Cr.sub.2O.sub.7+H.sub.2O=2Cs+8MgO+2Cr+H.sub.2ΔH=−2.48E  (50)
    8Ca+Cs.sub.2Cr.sub.2O.sub.7+H.sub.2O=2Cs+8CaO+2Cr+H2ΔH=−2.75E6  (51)
    5.5Al+Cs.sub.2Cr.sub.2O.sub.7+H.sub.2O=2Cs+2.67Al2O.sub.3+2Cr+H.sub.2ΔH=−2.14E6  (52)
    5.5Si+Cs.sub.2Cr.sub.2O.sub.7+H.sub.2O=2Cs+4SiO.sub.2+0.75CrSi+0.25Cr.sub.5Si.sub.3+H.sub.2  (53)
    ΔH=−1.42E6
    Mg+CsOH+H.sub.2O=Cs+MgO+1.5H.sub.2ΔH=−1.087E5  (54)
    Si+CsOH+H.sub.2O=Cs+SiO.sub.2+1.5H.sub.2ΔH=−2.53E5  (55)
    2Ca+CsOH+H.sub.2O=Cs+2CaO+H.sub.2ΔH=−6.12E5  (56)
    2Al+CsOH+2H.sub.2O=Cs+Al.sub.2O.sub.3+2.5H.sub.2ΔH=−7.75E5  (57)

    (21) The reactions (23) to (57) are thermo-chemically possible and the kinetic barrier is overcome by the temperature conditions of the reaction. The reactions therefore proceed to completion.

    (22) Reactors:

    (23) Fluidized bed reactors made of iron-alloy are used for these reactions. The finely ground charge consists of one of the metals including Magnesium, Silicon, Aluminum and Calcium. The metal oxides include SiO.sub.2, Cr.sub.2O.sub.3, TiO.sub.2, SnO.sub.2, ZrO.sub.2, CuO, ZnO, WO.sub.3, Ta.sub.2O.sub.5, Cs.sub.2Cr.sub.2O.sub.7 and CsOH. The grinding of the charge is done in inert gas sealed metal jars in a planetary ball mill. The reactor is maintained at a homogeneous temperature between 25° C. and 1000° C. All reactions consist of reacting one of the four elements Magnesium, Aluminum, Silicon or Calcium with water and the metal-oxides as mentioned above. The molar proportions of the reactants as shown in the equations are used as the reactant proportion. The detailed design of the reactors may require additional features to remove any difficulties due to the exothermic nature of the reactants.

    DETAILED DESCRIPTION OF THE FIGURES

    (24) FIG. 1 is a graph depicting the stability of MgH.sub.2 formed by combining different proportion of Mg and water at various temperatures. The figure shows that below T=566 K, MgH.sub.2 is stable and therefore can be synthesized directly from water and Mg.

    (25) FIG. 2 is a line drawing showing a fluidized bed reactor 10 used to co-produce hydrogen with metal. FIG. 2 shows first inlet 1 of the reactor wherein a mixture of the metal and metal oxide is fed. Hot steam is fed through the second inlet 2. The reaction chamber 3 containing fluidized bed of metal oxide and metal is the place where the reaction takes place. The outlet 4 is where the products MgO and metal are collected. The hydrogen evolved through the anterior outlet 6 is collected for use. The high temperature membrane 5 allows only hydrogen to pass through it preventing the outflow of other undesirable gases.

    (26) FIG. 3 is a line drawing showing another embodiment of the reactor 10 shown in FIG. 2. The first inlet 1 is used to feed MgH.sub.2 and metal oxide. Hot inert gas is fed through second inlet 2. The reaction chamber 3 contains fluidized bed of MgH.sub.2, metal oxide and hot inert gas where the reaction takes place. The outlet 4 is used to collect MgO and reduced metal. The hot temperature membrane 5 allows only hydrogen to pass through it. The evolved hydrogen is collected through anterior outlet 6.

    (27) Evaluation of the production cost and the sales cost of the obtained products reveal that the overall process is highly cost effective and economically beneficial. The process is very profitable as the price of magnesium used in the reaction is more than offset by the cost of metal obtained as the byproduct.

    (28) The present invention is a method of co-producing hydrogen and metal, the method comprises of the steps of reacting Magnesium hydride and metal oxide or Magnesium hydride and metal sulphide in a fluidized bed reactor, collecting the hydrogen gas evolved, collecting and separating the metal and MgO produced. The reaction occurs in a sealed inert gas flushed reaction chamber which is heated between 25° C. and 1000° C.

    (29) The metal oxide or metal sulphide used in the process include H.sub.2O, SiO.sub.2, Al.sub.2O.sub.3, Cr.sub.2O.sub.3, TiO.sub.2, SnO.sub.2, ZrO.sub.2, CuO, CuS, CuFeS.sub.2, ZnO, WO.sub.3, Ta.sub.2O.sub.5, MnO.sub.2, Cs.sub.2Cr.sub.2O.sub.7 and CsOH.

    (30) The invention also pertains to a method of co-producing hydrogen and metal, the method comprises the steps of reacting a metal and metal oxide with water in a fluidized bed reactor, collecting the hydrogen gas evolved, collecting and separating the metal and MgO. The reaction occurs in a sealed inert gas flushed reaction chamber which is heated between 25° C. and 1000° C.

    (31) The metal used in the process is one of Magnesium, Calcium, Aluminium or Silicon. The metal oxide used in the process is one of SiO.sub.2, Cr.sub.2O.sub.3, TiO.sub.2, SnO.sub.2, ZrO.sub.2, CuO, ZnO, WO.sub.3, Ta.sub.2O.sub.5, Cs.sub.2Cr.sub.2O.sub.7 or CsOH.

    (32) An example of the present invention is when tin oxide is added to magnesium hydride it gives us magnesium oxide, tin and hydrogen as in the equation represented below:
    MgH.sub.2+0.5SnO.sub.2.fwdarw.MgO+0.5Sn+H.sub.2

    (33) Production cost per mole of MgH.sub.2 works to 36-38 dollars by using electrolytic or Steam Methane Reformation method with Solid Oxide Membrane. The produced hydride when reacted with CuS by the hydride method of the invention results in producing hydrogen and copper yielding a net profit of 176 dollars (per mole) in the overall process.

    (34) When hydrogen is produced by reacting the hydride with a metal oxide, for some oxides, a kilogram of hydrogen results in production of metals worth many hundred dollars. The calculations are based on the prices of metal and hydride only, costs of oxides and energy are ignored.

    (35) In various embodiments of the reaction, production cost using MgH.sub.2 and SiO.sub.2, Cr.sub.2O.sub.3, TiO.sub.2, ZrO.sub.2 and CsOH as the metal oxide reactant have also revealed the process to be economically beneficial and viable.

    (36) The cost analysis of the direct method also indicates that the process is highly profitable and carbon emission free as long as the method of isolating the metal used in the reaction are obtained by using non-fossil sources of energy.

    (37) The invention has been explained based on preferred exemplary embodiments without being limited to these exemplary embodiments. The features of individual embodiments can be freely combined with features of other embodiments in order to form new embodiments to the extent compatibility is given. One trained in the art knows numerous deviations and embodiments of the device according to the invention, without here leaving the concept of the invention.

    LIST OF REFERENCE NUMERALS

    (38) 1 first inlet 2 second inlet 3 reaction chamber 4 outlet 5 membrane 6 anterior outlet 10 reactor