Method and apparatus for obtaining a mixture for producing H2, corresponding mixture

Abstract

A method for obtaining a mixture for producing H.sub.2, the mixture comprising a metal borohydride, Me(BH.sub.4).sub.n, a metal hydroxide, Me(OH).sub.n, and H.sub.2O, in which Me is a metal and n is the valance of the metal ion. The H.sub.2O is provided in ultrapure water, UPW, the UPW having an electrical conductance below 1 μS/cm. The method comprises dissolving the metal borohydride and the metal hydroxide in UPW to obtain the mixture for producing H.sub.2 comprising an amount of borohydride, BH.sub.4, groups of the metal borohydride in the range of 45 to 55% mol of the mixture, an amount of hydroxide, OH, groups of the metal hydroxide in the range of 2 to 5% mol of the mixture, and at least substantially UPW for the remainder of the mixture.

Claims

1. A method for obtaining a mixture for producing H.sub.2, the mixture comprising a metal borohydride, Me(BH.sub.4).sub.n, a metal hydroxide, Me(OH).sub.n, and H.sub.2O, in which Me is a metal and n is the valance of the metal ion, wherein H.sub.2O is provided as ultrapure water, UPW, the UPW having an electrical conductance below 0.06 μS/cm, and the method comprises dissolving the metal borohydride and the metal hydroxide in UPW to obtain the mixture for producing H.sub.2 comprising an amount of borohydride, BH.sub.4, groups of the metal borohydride in the range of 45 to 55% mol of the mixture, an amount of hydroxide, OH, groups of the metal hydroxide in the range of 2 to 5% mol of the mixture, and UPW substantially for the remainder of the mixture.

2. The method according to claim 1, wherein the method comprises the steps of dissolving an amount of the metal hydroxide in H.sub.2O to provide an auxiliary mixture of metal hydroxide dissolved in H.sub.2O; and dissolving an amount of the metal borohydride in the auxiliary mixture of metal hydroxide dissolved in H.sub.2O to provide the mixture for producing H.sub.2.

3. The method according to claim 1, wherein the mixture for producing H.sub.2 comprises an amount of hydroxide groups of the metal hydroxide in the range of 3 to 4% mol.

4. The method according to claim 1, wherein the mixture for producing H.sub.2 comprises an amount of borohydride groups of the metal borohydride in the range of 48 to 53% mol.

5. A mixture for producing H.sub.2, wherein the mixture comprises a metal borohydride, Me(BH.sub.4).sub.n, and a metal hydroxide, Me(OH).sub.n, dissolved in H.sub.2O, in which Me is a metal and n is the valance of the metal ion, wherein H.sub.2O is provided as ultrapure water, UPW, the UPW having an electrical conductance below 0.06 μS/cm, and the mixture comprises an amount of borohydride, BH.sub.4, groups of the metal borohydride in the range of 45 to 55% mol of the mixture, an amount of hydroxide, OH, groups of the metal hydroxide in the range of 2 to 5% mol of the mixture, and UPW substantially for the remainder of the mixture.

6. A mixture for producing H.sub.2, wherein the mixture comprises a metal borohydride, Me(BH.sub.4).sub.n, and a metal hydroxide, Me(OH).sub.n, dissolved in H.sub.2O, in which Me is a metal and n is the valance of the metal ion, wherein H.sub.2O is provided as ultrapure water, UPW, the UPW having an electrical conductance below 0.06 μS/cm, and the mixture comprises an amount of borohydride, BH.sub.4, groups of the metal borohydride in the range of 45 to 55% mol, of the mixture, an amount of hydroxide, OH, groups of the metal hydroxide in the range of 2 to 5% mol, of the mixture, and UPW substantially for the remainder of the mixture, wherein the mixture is obtained by the method according to claim 1.

7. The method according to claim 1, wherein the UPW satisfies having an Electronics and Semiconductor Grade Water ASTM Type E-1 classification or better.

8. The method according to claim 1, wherein the metal, Me, is at least one of lithium, Li; sodium, Na; and potassium, K.

9. The method according to claim 1, wherein the metal, Me, is sodium, Na, and the mixture for producing H.sub.2 comprising an amount of sodium borohydride, NaBH.sub.4, in the range of 58 to 72% wt of the mixture, and an amount of sodium hydroxide, NaOH, in the range of 3 to 7% wt of the mixture.

10. The mixture of claim 5, wherein the mixture comprises an amount of borohydride, BH.sub.4, groups of the metal borohydride in the range of the range of 48 to 53% mol, of the mixture.

11. The mixture of claim 5, wherein the mixture comprises an amount of hydroxide, OH, groups of the metal hydroxide in the range of 3 to 4% mol, of the mixture.

12. The method of claim 9, wherein the mixture for producing H.sub.2 comprises an amount of sodium borohydride, NaBH.sub.4, in the range of 62 to 69% wt, of the mixture.

13. The method of claim 9, wherein the mixture for producing H.sub.2 comprises an amount of sodium hydroxide, NaOH, in the range of 4 to 6% wt, of the mixture.

14. The method according to claim 2, wherein the mixture for producing H.sub.2 comprises an amount of hydroxide groups of the metal hydroxide in the range of 3 to 4% mol.

15. The method according to claim 2, wherein the mixture for producing H.sub.2 comprises an amount of borohydride groups of the metal borohydride in the range of 48 to 53% mol.

16. The method according to claim 3, wherein the mixture for producing H.sub.2 comprises an amount of borohydride groups of the metal borohydride in the range of 48 to 53% mol.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features and advantages of the invention will become apparent from the description of the invention by way of non-limiting and non-exclusive embodiments. These embodiments are not to be construed as limiting the scope of protection. The person skilled in the art will realize that other alternatives and equivalent embodiments of the invention can be conceived and reduced to practice without departing from the scope of the present invention. Embodiments of the invention will be described with reference to the accompanying drawings, in which like or same reference symbols denote like, same or corresponding parts, and in which

(2) FIG. 1 shows a graph of the influence of the pH value of a stabilized mixture of NaBH.sub.4 and NaOH in UPW on the half-time decay value of NaBH.sub.4;

(3) FIG. 2 shows a graph of the influence of the amounts of NaOH and NaBH.sub.4 added to UPW on the freezing point T.sub.F of the mixture;

(4) FIG. 3 shows a graph of the dependence of the volume required to store a certain amount of hydrogen on the concentration of NaBH.sub.4 (sodium borohydride);

(5) FIG. 4 shows a schematic representation of an acid reactor type;

(6) FIG. 5 shows a schematic representation of a catalyst reactor type;

(7) FIG. 6 shows a schematic representation of a dual reactor type;

(8) FIG. 7 shows a schematic representation of an acid reactor type process flow;

(9) FIG. 8 shows a schematic representation of a catalyst reactor type process flow;

(10) FIG. 9 shows a schematic representation of a dual reactor type process flow;

(11) FIGS. 10 and 11 show a schematic representation of a generalized reactor type;

(12) FIG. 12 shows an overview of various process parameters and their influence on the process;

(13) FIG. 13 schematically depicts the reaction setup of experiments carried out;

(14) FIGS. 14, 15 and 16 show pictures of the reaction setup of experiments carried out;

(15) FIGS. 17, 18 and 19 show graphs of temperatures and pressure monitored for three experiments carried out;

(16) FIG. 20 shows solid residue obtained in an experiment;

(17) FIG. 21 shows a gas chromatography (GC) graph from a GC measurement carried out on the gas produced in an experiment; and

(18) FIG. 22 shows an x-ray diffraction (XRD) graph from an XRD measurement carried out on the residue shown in FIG. 20.

DETAILED DESCRIPTION OF EMBODIMENTS

(19) The present description takes the technology and apparatus as disclosed in WO 2010/087698 A2, which is incorporated herein by reference, as a starting point. The international publication discloses a production process for H.sub.2, in which a metal boron hydride, MeBH.sub.4, is dissolved in water having a conductance of <0.5 μS/cm. The quality of water having such low conductance is qualified as ASTM Type E-1 grade water (Electronics and Semiconductor Grade Water), which is in this description referred to as ultrapure water, UPW. UPW in this description refers to water satisfying the above quality grade and/or water having a conductance of <1 μS/cm, especially <0.5 μS/cm, more especially <0.1 μS/cm, and more especially <0.06 μS/cm. Water having a conductance of <0.06 μS/cm is also being specified as having a resistivity of 18.2 MΩ/cm or larger at 25° C. Further, such solution and such use of a boron hydride fuel is generally in a nitrogen environment to avoid any reaction with moisture and CO.sub.2 in ambient air. Below some important parameters for the production of H.sub.2 using a metal boron hydride fuel will be discussed.

(20) The present description primarily refers to sodium borohydride (NaBH.sub.4) as a metal borohydride. Other examples of a metal borohydride are lithium borohydride (LiBH.sub.4) and potassium borohydride (KBH.sub.4). However, the method according to the invention is applicable to any metal borohydride, which can be referred to as Me(BH.sub.4).sub.y, in which Me is a metal having a number y of borohydride groups BH.sub.4 attached to it. A metal includes any material generally referred to as a metal, including alkali metals, transition metals and complex metals.

(21) Acidity and Reaction Rate

(22) The reaction rate in the production of H.sub.2 is dependent on the acidity level (pH value) of the borohydride water solution. The Arizona State University has published in 2005 experiments on the reaction rate of NaBH.sub.4 with water (Don Gervasio, Michael Xu and Evan Thomas; Arizona State University; Tempe, Ariz.; 26 Jul. 2005; http://fsl.npre.illinois.edu/Project%20Presentation/fuel%20cell%20project_files/July%20workshop%20presentations/uiuc-talk-25July2005.pdf), and results are shown in FIG. 1. The figure has been made based on a table of results published by the Arizona State University. FIG. 1 shows the influence of the pH value of a stabilized solution of NaBH.sub.4 in water on the half-time decay value t.sub.1/2 of NaBH.sub.4 in the solution. A metal hydroxide (Me hydroxide) has been used as a stabilizer. The stability of the solution increases with increasing pH value and shows a logarithmic (.sup.10 log) dependence of the half-time decay value on the pH value. Along the vertical axis the half-time is shown in seconds (s) while in the graph the measurement points have been identified by their half-time value in seconds (s), minutes (m), hours (h) and days (d).

(23) These results show support that for long-term storage a metal borohydride is preferably stored in dry form, so not dissolved in water. For use within days or weeks the liquid metal borohydride can be prepared by dissolving MeBH.sub.4 in water, preferably shortly before actual use. Upon use of the fuel within the order of seconds the pH value of the aqueous metal borohydride is to be decreased, preferably at about pH=7 for the pH value. A mixture having such pH value can be referred to as being in the release reaction regime RR shown in FIG. 1. A mixture having a high pH value before it is being transferred to a reaction can be referred to as being in the pre-reaction regime PR as shown in FIG. 1. The RR and PR regimes indicated in FIG. 1 are for illustrative purposes only. The actual pH ranges tied to such regimes will depend on the specific application. This can be done in a space just before the fuel enters a reactor space, where the H.sub.2 already being formed can be passed to the outlet.

(24) Solubility and Temperature

(25) The solubility of a metal borohydride, for instance, NaBH.sub.4, in ultrapure water, UPW, is, inter alia, dependent on the temperature (https://en.wikipedia.org/wiki/Solubility_table (sodium borohydride)). The following table provides the solubility of NaBH.sub.4 in grams per 100 gram UPW:

(26) TABLE-US-00001 Temperature Solubility  0° C. 25.0 gram 20° C. 55.0 gram 40° C. 88.5 gram

(27) This implies for the borohydride fuel that the fuel may be a slurry, dependent on the temperature and even at a concentration of 33⅓% wt. The fuel will always be a slurry at a concentration of 66⅔% wt.

(28) This option of 66⅔% wt is preferred since the fuel should be suitable for various types of fuel cells, having in mind the water that is being formed during the reaction in the fuel cell. H.sub.2O produced by the fuel cell can be mixed with the fuel to arrive at a desired amount of H.sub.2O in the fuel mixture. It is required that the fuel be prepared in a suitable manner for the application, for instance a mobile application, in which it is going to be used.

(29) Frost Protection

(30) Frost protection of the aqueous metal borohydride fuel for a borohydride concentration to be employed can be provided by applying an appropriate metal borohydride to stabilizer ratio in the aqueous fuel (in this description the fuel is also referred to as fuel mixture or fuel solution). One should generally consider a stabilizer concentration that is higher than necessary for the pH value required (Progress in the catalysts for H.sub.2 generation from NaBH.sub.4 fuel; V. I. Simagina; https://www.google.nl/webhp?sourceid=chrome-instant&rlz=1C1CHWA_nINL615NL615&ion=1&espv=2&ie=UTF-8#q=Progress+in+the+catalysts+for+H2+generation+from+NaBH4+fuel+V.I.+Simagine%2C+O.V.+Netskine%2C+O.V.+Komova+and+A.M.+Ozerova). The temperature range specified by the US Department of Energy (US DoE) is from −40° C. to 60° C.

(31) A decrease in freezing point temperature can be calculated using

(32) $\Delta T=K*\frac{m}{M}$
in which K=−1.86 for water;

(33) M=39.99711 g/mol for NaOH, the solubility of NaOH at 20° C. being 1,070 g/I;

(34) M=37,833 g/mol for NaBH.sub.4, the solubility of NaBH.sub.4 at 20° C. being 550 g/I.

(35) By at least one of adding an amount of NaOH and controlling the fraction by weight of the NaOH that is present in the mixture due to the reaction by controlling the discharge rate, the fraction of UPW decreases in the same amount as the NaOH increases. As a result the fraction by weight of NaBH.sub.4 increases as well, which causes a decrease of the freezing point temperature as is shown in FIG. 2. The figure shows the decrease in freezing temperature by adding an x % wt amount of NaOH to water, to a 33.3% wt NaBH.sub.4 in water solution, and to a solution of NaBH.sub.4 in water while maintaining 33.3% wt NaBH.sub.4 in the final mixture.

(36) This fluctuating amount of MeOH present in the aqueous borohydride fuel implies that the reactor requires an active control on the pH value to maintain the pH value at a required level.

(37) The borohydride fuel, for instance a sodium borohydride fuel, can be used in a 33% mixture with a concentration of about 33% wt NaBH.sub.4, which, for instance, can be written as (all percentages in relation to the concentration or mixture being percentages by weight (% wt))

(38) 33.33% NaBH4+5% NaOH+61.67% UPW

(39) or which can be written as

(40) 33.33% NaBH4+10% NaOH+56.67% UPW.

(41) A borohydride fuel mixture of MeBH.sub.4, MeOH and UPW (H.sub.2O) can be optimized such that the mixture has a predetermined freezing point. The ratio of components can be defined as follows for use at higher temperatures:

(42) a NaBH4+b NaOH+c UPW, in which 30%<a<37%, 3%<b<7% and 60%<c<63%, and a+b+c=100%, preferably a=33%, b=5% and c=62%,
and the ratio may defined as follows for use at lower temperatures, for instance, down to −40° C.:

(43) d NaBH4+e NaOH+f UPW, in which 30%<d<37%, 7%<e<13% and 50%<f<63%, and d+e+f=100%, preferable: a=33%, b=10% and c=57%.

(44) More concentrated 67% mixtures of the fuel are envisioned with a concentration of about 67%. They may, for example, have the following composition:

(45) 67% NaBH.sub.4+5% NaOH+28% UPW

(46) or:

(47) 67% NaBH.sub.4+10% NaOH+23% UPW.

(48) Some examples of 33% and 67% mixtures are as follows:

(49) TABLE-US-00002 NaBH.sub.4 NaOH H.sub.2O (UPW) pH value 33% mixtures 33.33%  3% 63.67% 13.929 33.33%  5% 61.67% 13.693 33.33% 10% 56.67% 13.929 33.33% 15% 51.67% 13.693 67% mixtures 66.67%  3% 30.33% 13.607 66.67%  5% 28.33% 13.693 66.67% 10% 23.33% 13.607 66.67% 15% 18.33% 13.355

(50) The half-time value t.sub.1/2, at about pH=13 is about 42.6 days according to FIGS. 1 and 2. Increasing to pH=13.5 gives a half-time value of about t.sub.1/2=213 days, which involves the following losses of NaBH.sub.4 from the fuel in dependence of the time lapsed after preparation of the fuel:

(51) TABLE-US-00003 time loss .sup. 1 hour 0.014%  4 hours 0.054%  8 hours 0.094% 24 hours 0.325% 25 hours 0.338% 29 hours 0.392% 33 hours 0.446% 48 hours 0.649% .sup. 3 days 0.972% .sup. 4 days 1.293% .sup. 5 days 1.394% .sup. 7 days 2.252%

(52) The above table shows that about 2¼% of the amount of NaBH.sub.4 is lost from the fuel within about a week after its preparation. It is therefore advantageous to only prepare the fuel shortly before it will be used in the reactor. Just a smaller quantity of fuel may be prepared for immediate use. One can prepare a mixture of UPW and MeOH, for instance, NaOH, beforehand.

(53) Above only some examples are provided. Very suitable mixtures for producing H.sub.2 appear to have an amount of sodium borohydride, NaBH.sub.4, in the range of 58 to 72% wt, optionally in the range of 62 to 69% wt, of the mixture, and an amount of sodium hydroxide, NaOH, in the range of 3 to 7% wt, optionally in the range of 4 to 6% wt, of the mixture. The remainder of the fuel mixture is ultrapure water. For a general metal borohydride this can be written in terms of molar percentages (% mol). Generally, a very suitable mixture for producing H.sub.2 comprises an amount of borohydride, BH.sub.4, groups of the metal borohydride in the range of 45 to 55% mol of the mixture, an amount of hydroxide, OH, groups of the metal hydroxide in the range of 2 to 5% mol of the mixture, and at least substantially UPW for the remainder of the mixture.

(54) The reaction rate can be accelerated by decreasing the pH value of the fuel mixture or by passing the fuel mixture over a catalyst. The reaction can be slowed down by increasing the pH value of the fuel mixture.

(55) Volumetric Storage

(56) FIG. 3 shows the volume of sodium borohydride (SBH, NaBH.sub.4) required at various SBH concentrations to store various amounts of hydrogen according to results by Ying Wu (Hydrogen Storage via Sodium Borohydride, Current status, Barriers and R&D roadmap; Ying Wu; 14 Apr. 2005; https://gcep.stanford.edu/pdfs/hydrogen_workshop/Wu.pdf). The results show the volumetric ratio against the gravimetric storage for sodium borohydride. 30% wt NaBH.sub.4 mixture is about 63 g H.sub.2/liter. For comparison, liquid H.sub.2 is about 71 g H.sub.2/liter, and compressed H.sub.2 is about 23 g H.sub.2/liter and 39 g H.sub.2/liter at pressures of 5,000 psi and 10,000 psi, respectively. A 33.3% wt NaBH.sub.4 mixture is therefore about equivalent to liquid H.sub.2 in stored amount of H.sub.2. The advantage of the NaBH.sub.4 fuel mixture is that it does not require cooling and does not require high pressures. The above assumes the stoichiometric ratio in the following reaction:

(57) ##STR00001##
One should realize that NaBO.sub.2 is a dry residue, which is hard to remove during the process.
Accelerators

(58) Various accelerators can be employed for accelerating the reaction of the metal borohydride with water.

(59) Accelerating Catalyst

(60) When NaBH.sub.4 is dissolved into ultrapure water (UPW) then the UPW needs to be buffered to obtain a basic solution before the NaBH.sub.4 is mixed in. The NaBH.sub.4 solution is circulated over a catalyst to release H.sub.2 from the NaBH.sub.4. In this process NaBH.sub.4 is converted to sodium boric oxide (NaB.sub.xO.sub.y) by release of H.sub.2. Preferably, a catalyst is employed which has a carrier, for example, Al.sub.2O.sub.3, covered with a surface layer comprising platinum, cobalt, ruthenium or a combination thereof.

(61) Accelerating Acid

(62) Preferably, an acid is employed to accelerate the hydrolysis reaction that occurs with UPW (MFTH_110805_DPElectronicS; Phys. Chem. Chem. Phys., 2011, 13, 17077-17083) Hydrochloric acid (HCl) can be used when sodium is the base metal since it is a rather cheap, efficient and widely used acid. HCl dissolved in UPW provides H.sup.+ and Cl.sup.− ions. The chemical reaction with the borohydride can be as follows:
BH.sub.4.sup.−+H.sup.++3H.sub.2O.fwdarw.B(OH).sub.3+4H.sub.2
In case of a stoichiometric ratio this could read:
2BH.sub.4.sup.−+2H.sup.++3H.sub.2O.fwdarw.B.sub.2O.sub.3+8H.sub.2
This leaves Na.sup.+ and Cl.sup.− ions in the same amounts in the solution. The remainder of the UPW in the solution may evaporate due to the reaction heat that is released in the chemical reaction to provide NaCl together with various boron oxides.

(63) Some scientists (Progress in the catalysts for H.sub.2 generation from NaBH.sub.4 fuel; V.I. Simagina; https://www.google.nl/webhp?sourceid=chrome-instant&rlz=1C1CHWA_nINL615NL615&ion=1&espv=2&ie=UTF-8#q=Progress+in+the+catalysts+for+H2+generation+from+NaBH4+fuel+V.I.+Simagine%2C+O.V.+Netskina%2C+O.V.+Komova+and+A.M.+Ozerova) indicate that BH.sub.3 can be formed, which is converted into B.sub.2H.sub.6. B.sub.2H.sub.6 reacts with water to release H.sub.2 and to form boron acid, which provides another reason to use an excess amount of water in the reaction.

(64) The pH value of the mixture can be made neutral in the reactor in which an acid is employed, after which the acid is added to further reduce the reaction time. The amount of acid to be added is basically equal to the amount of MeOH in the mixture.

(65) Comparison of the Use of an Acid and a Catalyst

(66) Employing an acid provides a rather high reaction rate as an advantage, while the disadvantages are having an additional element in the process, an increase in costs and weight, and a more difficult reuse of materials. Employing a catalyst advantageously saves on costs and weight, while the disadvantage is having a slower reaction rate. By employing both a catalyst and an acid the advantage of having a higher reaction rate can be balanced against the disadvantages of having an additional element in the process, an increase in costs and weight, and a more difficult reuse of materials.

(67) Per application a desired selection is made, balancing the pros and cons. In relation to WO 2010/087698 A2, the selection will have an impact on the amount of gas stored.

(68) Reaction Products

(69) Reaction products from the reaction of the metal borohydride end of in a so-called spent fuel. In case of an abundance of UPW the following reaction products are present (Don Gervasio, Michael Xu and Evan Thomas; Arizona State University; Tempe, Ariz.; 26 Jul. 2005; http://fsl.npre.illinois.edu/Project%20Presentation/fuel%20cell%20project_files/July%20workshop%20presentations/uiuc-talk-25July2005.pdf):

(70) TABLE-US-00004 H.sub.2O mole oxygen required (add on volume of (per NaBH.sub.4) 30% solution) H.sub.2O boron oxide [moles] [moles] [millilitre] *NaB(OH).sub.4 4 32 576 NaBO.sub.2—xH.sub.2O** 2 + x 16 288 Na.sub.2B.sub.4O.sub.7  7/2 28 504 Na.sub.2B.sub.4O.sub.7—10H.sub.2O 17/2 68 1224 Na.sub.2B.sub.4O.sub.6(OH).sub.2—3H.sub.2O 11/2 44 792 Na.sub.2B.sub.4O.sub.7—5H.sub.2O 12/2 48 864 NaB.sub.4O.sub.5(OH).sub.4—3H.sub.2O 12/2 48 864 NaB.sub.4O.sub.5(OH).sub.4—8H.sub.2O 17/2 68 1224 *X-ray diffraction data of the Arizona State University indicate that NAB(OH).sub.4 is the by-product of the hydrolysis reaction (Don Gervasio, Michael Xu and Evan Thomas; Arizona State University; Tempe, AZ; 26 Jul. 2005). **Progress in the catalysts for H.sub.2 generation from NaBH.sub.4 fuel; V. I. Simagina (Hydrogen on Demand)
Reaction Process

(71) The maximum reaction is at a process in which the ratio of H.sub.2O to borohydride groups (BH.sub.4) in the metal borohydride (Me(BH.sub.4).sub.y), for instance, NaBH.sub.4, is at least 5 to 2. This has been described in a Dutch patent application filed on 6 Mar. 2016 and invoking priority of Dutch patent application NL 2015742. Preferably, a larger amount of water is used to keep the mixture after the reaction in a liquid state. As an example 1 kg of H.sub.2 is used in NaBH.sub.4. A possible borohydride fuel composition of 33.33% wt NaBH.sub.4 and 5% wt NaOH consists of:

(72) 9.38 kg NaBH.sub.4, which is 248.05 mole

(73) 1.41 kg NaOH, which is 35.19 mole

(74) 17.36 kg UPW, which is 936.69 mole

(75) For a ratio of H.sub.2O:NaBH.sub.4 of 2:1 the 17.36 kg of UPW is sufficient. To have a ratio of H.sub.2O:NaBH.sub.4 of 5:1 an amount of 22.34 kg UPW is required. To obtain such amount the UPW provided should be supplemented with 70% of the theoretically produced water from the fuel cell, being 6.25 kg. In a stationary application this will not pose a problem.
Reactor

(76) Various reactor embodiments can be employed for the reaction of metal borohydride yielding hydrogen gas. The metal borohydride fuel (MeBH.sub.4/MeOH/UPW mixture) is also referred to as H2Fuel in the description and the drawings.

Reactor Embodiment 1: A Reactor Embodiment Having an Accelerating Acid

(77) FIGS. 4 and 7 show a schematic representation of a first exemplary reaction in which an acid Ac, for instance, HCl, is supplied. The acid may be supplied together with water. The fuel is mixed in the reactor Ra with the accelerator comprising an acid Ac, HCL in the example, and UPW. The maximum mixing ratio, providing a fast response, of an Na, containing molecule to 1 Cl+H.sup.++OH.sup.−; 3H.sub.2O is producing a low overall weight percentage of Hz. This will not be a disadvantage in a stationary application, but it will raise costs. The minimum mixing ratio, providing a response equal to the half-time at the pH value of the mixture, is NaOH:HCL=1:1, and releasing at least 2.5H.sub.2O.

(78) To allow correctly dosing the amount of water added part of the water is recaptured from the liquid from the fuel cell FC. Mixing is done in a mixing chamber to obtain a proper mixing and to obtain a heat yield at a concentrated location so that the heat can be better discharged. Heat is generated in the reactor in the amount of 53.8 MJ per kgH.sub.2, which is discharged by a cooling fluid. The heat discharged can be used in another application or in the synthesis. Boron oxide is discharged together with other reaction products in a spent fuel mixture SF1.

(79) FIGS. 4 and 7 depict a schematic representation of an embodiment of the acid reactor process. FIG. 7 shows a stock of an acid/UPW mixture 10 (mixture of an acid Ac and UPW); a stock of dry MeBH.sub.4 20; a stock of MeOH 30; a stock of an MeOH/UPW mixture 40; a first mixing chamber M1 for providing a mixture of MeOH and UPW; a second mixing chamber M2 for providing a mixture of MeBH.sub.4, MeOH and UPW from separate supplies of dry MeBH.sub.4 and MeOH/UPW mixture into the second mixing chamber M2 to provide an MeBH.sub.4/MeOH/UPW fuel mixture having selected percentages (by weight) of MeBH.sub.4 and MeOH; an acid reactor chamber Ra having respective buffer chambers for H.sub.2 gas and spent fuel SF1; a storage tank 51 for spent fuel SF1; and a fuel cell FC. Alternatively, all separate stocks of UPW, acid and metal hydroxide may also be employed and mixed during use to arrive at desired mixing ratios.

(80) In a semi-direct use the mixing of MeOH, UPW and MeBH.sub.4 may also take place at the “gas” (fuelling) station. FIG. 4 generally shows that an acid Ac, a metal borohydride (NaBH.sub.4 in the example), H.sub.2O and a metal hydroxide (NaOH in the example) are supplied to the reactor Ra, which can be provided into reaction process as required. The acid can be supplied to promote and accelerate the H2 production process, and the metal hydroxide can be supplied to slow down or stop the process. They may also be supplied for yielding desired other reaction products. The embodiment of the acid reactor process of FIG. 7 is provided with a reactor chamber Ra in which the acid/UPW mixture is mixed with the MeBH.sub.4/MeOH/UPW fuel mixture H2Fuel. The resulting mixture is circulated within the reactor chamber. The pH value of the MeBH.sub.4/MeOH/UPW fuel mixture is decreased by mixing with the acid/UPW mixture to a pH value of, for instance, pH=6-7, such that reaction times for generating H.sub.2 are sufficiently fast in line with the half time values applicable, as discussed earlier.

(81) The H.sub.2 generated is passed to the fuel cell FC for the production of electrical energy by reaction with O.sub.2 to H.sub.2O. The H.sub.2O resulting from the chemical reaction in the fuel cell generally qualifies as ultrapure water (UPW) and is passed to the first mixing chamber M1 to provide an MeOH/UPW mixture having a selected percentage (by weight) of MeOH. In case the H.sub.2O produced would not be UPW, it can be filtered or otherwise treated to become UPW. By using the H.sub.2O from the fuel cell it is not required to keep a separate storage of UPW, which saves weight, space and costs.

(82) Spent fuel SF1 is passed from the reactor chamber Ra to a spent fuel storage tank 51 that can be part of a larger tank 50. The spent fuel can be recycled.

Reactor Embodiment 2: A Reactor Embodiment Having an Accelerating Catalyst

(83) FIGS. 5 and 8 shows a schematic representation of a second exemplary reaction process in which a catalyst is employed as an accelerator. The reactor comprises a reaction chamber Rc in which the actual reaction takes place. The reaction occurs over a catalyst that releases hydrogen gas from the metal borohydride. In order to increase the reaction rate it is preferred that the pH value of the fuel mixture H2Fuel is lowered in accordance with FIG. 1. Each component is discharged in its own appropriate manner. A supply of acid Ac is therefore available.

(84) A continuous mixing occurs over the catalyst in the reaction chamber by circulating the H2Fuel. A pressure decrease to the open discharge of the spent fuel SF2 to the receiving chamber is measured, powered and monitored. Each part may have its own measurement and control. Discharge of hydrogen gas is realized at another higher level, as is discussed in WO 2010/087698 A2.

(85) FIG. 8 depicts a schematic representation of an embodiment of a catalytic reactor process. The catalytic reactor process embodiment shares quite a few elements with the acid reactor process embodiment of FIG. 7, as is obvious from the figures, the functioning of which is the same. The catalytic reactor process comprises a catalytic reactor chamber Rc. The MeBH.sub.4/MeOH/UPW fuel mixture H2Fuel is mixed in-line in mixer M3 with the acid/UPW mixture to obtain a desired pH value of, for instance, pH=7-9, preferable 7, of the fuel mixture and is subsequently provided into the catalytic reaction chamber Rc. The MeOH/UPW mixture is also provided into the (relatively slow) catalytic reaction chamber Rc to allow slowing down the reaction rate by adding additional metal hydroxide. The embodiment of the catalytic reactor process of FIG. 8 is provided with a catalytic reactor chamber Rc having a catalyst based on a carrier with, for example, cobalt. The fuel mixture with MeBH.sub.4 should be circulated a sufficient amount of time over the catalyst, for instance, by passing the fuel mixture several times over the catalyst, to obtain H.sub.2. By decreasing the pH value of the fuel mixture to, for instance, pH=7, the total process time is reduced. A different composition of spent fuel SF2 will result as compared to the spent fuel from an acid type reactor. The spent fuel SF2 from the catalytic reactor Rc is collected in a spent fuel storage tank 52 that may be part of a larger tank 50.

Reactor Embodiment 3: A Reactor Embodiment Having a Combination of an Acid and a Catalyst as Accelerators

(86) FIGS. 6 and 9 show a schematic representation of a combination or dual type of reactor Rd, which is a combination of reactor embodiments 1 and 2 above. The 3.sup.rd reactor process embodiment comprises two separate mixers at the inlets, which is not actually shown as such. The hydrogen gas outlets of both mixers discharge in a common gas storage having one outlet. The spent fuel of both mixers can be channelled to two separate spent fuel storage chambers 51, 52, each with its own outlet, or to one common spent fuel storage chamber 50.

(87) FIG. 9 depicts a schematic representation of a dual reactor type comprising a dual reactor Rd having two reaction chambers, an acid reaction chamber and a catalytic reaction chamber. Such a dual reactor type can be advantageous to compensate for the slow response time of the catalytic reactor as compared to the acid reactor. The dual reactor type embodiment again shares quite a few elements with the acid reactor type embodiment of FIG. 7 and the catalytic reactor type embodiment of FIG. 8, as is obvious from the figures, the functioning of which is the same as already described.

(88) The relatively slow response time can be compensated for by having a larger Hz gas storage in between reactor Rc and its use, for instance, in a fuel cell. The slow response can also be compensated for by employing a dual rector system Rd as shown in FIG. 9. In a catalytic process in the catalytic reactor a hydrogen atom is being replaced by a hydroxide from H.sub.2O, which causes an increase of the pH value of the fuel mixture. This will cause an increase in the half-time value of the reaction rate (see FIG. 1), leading to slowing down of the reaction. Further, the pH value will increase due to a reaction between H.sub.2O and MeBH.sub.4., which may result in an increase of the pH value from about pH=7 to about pH=11. Both mechanism thus cause an increase in pH value of the fuel mixture H2Fuel and thus a slowing down of the reaction rate. The reaction rate can be kept at a constant level or be controlled to a desired reaction by adding an amount of acid for decreasing the pH value again to a level to obtain a desired reaction rate. A decrease of the pH value from, for instance, pH=11 to pH=9 will already have a large influence on the reaction rate. An acid can also be employed to increase the response time of the reactor when a sudden increase in H.sub.2 generation is required.

(89) Various catalysts can be employed in the catalytic and dual reactor types. Some examples are Indanthrene Gold Orange, Perylene TCDA, Perylene diimide, Co powder, Indanthrene Yellow, Zn phtalocyanine, Indanthrene Black, Quinacridone, Pyranthrenedione, Isoviolantrone, Indigo, Indanthrene, Ni phthalocyanine, No catalyst, Cu phthalocyanine, Ditridecyl-3,4,9,10-perylenetetracarboxylic diimide, Dimethoxyviolanthrone, Poly(methylmethacrylate), 1,4-Di-keto-pyrrolr(3,4-C)pyrrole, 3,4,9,10-perylenetetracarboxylic dianhydride, Perylenetetracarboxylic diimide, and Phosphate buffer pH 11. However, this list is far from complete.

(90) The dual reactor may have respective buffer chambers for hydrogen gas and spent fuel. The storage tank 50 for spent fuel SF1, SF2 of the dual reactor type may have separate tanks 51, 52 or a common tank 50 for storing spent fuel from the acid and catalytic reactions, respectively.

(91) FIGS. 10 and 11 show more generalized reactors and supply of reactants. The reactor R can be an acid type reactor Ra, catalyst type reactor Re or dual type reactor Rd. The metal borohydride, NaBH.sub.4 as an example in FIG. 10, may be supplied as such as shown in FIG. 10, but may also be supplied in a mixture indicated as H2Fuel in FIG. 11. H2Fuel may be any suitable mixture of the metal borohydride, for example in a mixture of the metal borohydride and H.sub.2O stabilized with a metal hydroxide, such as a NaBH.sub.4/NaOH/H.sub.2O fuel mixture. The acid AC and metal hydroxide, NaOH in FIGS. 10 and 11, may also be supplied in a mixture with, for instance, H.sub.2O.

(92) Fuel Mixture Preparation

(93) FIG. 12 shows an overview of various parameters that have an impact on the reaction to produce Hz, from a metal borohydride. A dry storage of MeBH.sub.4 is preferred for the longer term since it can be stored in dry form for years while no deterioration will occur in case it is kept under humid free conditions. Further, in the dry state it can be easily supplied to a location for actual use. At the location of actual use the fuel mixture can be prepared according to the desired requirements.

(94) Taking a dry metal borohydride as a starting point, a first step would be to mix ultrapure water, UPW, with a metal hydroxide, so as to obtain a mixture with a desired pH value. The purity level of the water plays an important role, as has been disclosed in WO 2010/087698 A2, in the release of H.sub.2 in the reaction of the hydrogen atom in the hydride and a hydrogen atom of the water. The desired pH value of the mixture is chosen in dependence of, inter alia, the desired reaction rate RR and reaction time, storage time before use in the reaction, temperature at use and in storage, and/or stationary or mobile use of the fuel mixture. The metal hydroxide is to be added to and mixed with UPW in such a manner that the solution does not contain any particles or flakes. A choice of the form of metal hydroxide will also dependent on its cost level.

(95) The metal hydroxide acts as a stabilizer for the metal borohydride that is added at a later moment to the mixture. The amounts of metal hydroxide and metal borohydride added to the UPW determine a freezing point of the fuel mixture, and therefore its suitability of use under summer-like, winter-like or other types of conditions. The amount of metal borohydride added is also to be determined based on its solubility S.

(96) The pH value (level of acidity) can be changed by adding an appropriate acid. HCl can be a good choice, but any other suitable acid may be employed. One may store all constituents of the fuel mixture separate and prepare the fuel mixture from the separate constituents metal borohydride, metal hydroxide, acid and UPW when required. When using a catalyst one preferably does not use an acid in a steady state since it increases costs and may deteriorate the catalyst. FIG. 12 further shows the parameters that are of influence in the reactor. The temperature T.sub.R of the reactor at which the reaction takes place has its influence on the reaction rate. The temperature T is also shown as a parameter for the reaction in dependence of the pH level and the solubility S.

(97) The metal, Me, in the metal borohydride and the metal hydroxide is most preferably the same metal. The description mostly refers to NaBH.sub.4, NaOH and NaCl. However, Na can be replaced by any other metal, which metal is generally referred to as Me in the chemical formulas in the description. The metal Me refers to any material usually referred to as a metal, including alkali metals, transition metals, complex metals, etc. Further examples of such metals are, for instance, lithium (Li), potassium (K), magnesium (Mg) and aluminum (Al).

EXPERIMENTS

(98) Below experiments and experimental results are discussed on the preparation of a fuel mixture for producing H.sub.2 and the production of H.sub.2 from the fuel mixture. Details are provided of the materials used, the reaction setup, the experiments and the results thereof.

(99) Materials

(100) All chemicals were purchased from Sigma-Aldrich except for the ultrapure water (UPW), which was obtained from the Pure Water Group. The following chemicals were used to prepare fuel and activator solutions:

(101) TABLE-US-00005 Chemical Grade Purity Order no. Batch no. sodium borohydride granular,  98% 452874 MKBR3579V 10-40 mesh sodium hydroxide reagent grade, ≥98% S5881 SZBF0550V pellets hydrochloric acid for 1 L standard solution, 38285 SZBF0560V concentrate 0.5M HCl (0.5N) ultrapure water (UPW) ASTM type E-1

(102) The alkaline solution was prepared by taking 30.837 gram UPW in a beaker and adding 2.505 gram of NaOH and stirring the resulting mixture until all NaOH pellets were dissolved completely.

(103) The activator solution was prepared by mixing hydrochloric acid concentrate with the same amount of ultrapure water. 75.637 gram of hydrochloric acid concentrate was weighed in a beaker. 75.633 gram of UPW was weighed in another (different) beaker, and the hydrochloric acid was added to the UPW. Both beakers were flushed with the solution to ensure a homogeneous solution.

(104) 5 gram of fuel (also referred to as fuel mixture or fuel solution) was prepared by mixing 3.331 gram of alkaline solution with 1.666 gram of sodium borohydride. The mixture was stirred until no solids remained in solution. A short heating (a few seconds on a heating plate) of the mixture helped dissolving the solid. The pH value of the fuel solution was determined to be pH=13.5. The final composition of the H.sub.2 generating fuel used in the experiments is given below:

(105) TABLE-US-00006 Compound Amount (gram) % wt NaBH.sub.4 1.666 33.34 NaOH 0.250 5.00 UPW 3.081 61.66 Total: 4.997 100.00
Reaction Setup

(106) The reaction setup is shown in FIGS. 13 to 16. The reactor setup comprises a stainless steel reaction vessel 1 (having a volume of 182.4±1.5 ml) with a Teflon insert 2. The Teflon insert 2 is the actual reaction mixture container and is replaced with a new one in each reaction. On top of the reaction vessel are provided a pressure sensor 3, temperature sensors 4, 5 (thermocouples) for gas and liquid phases, respectively, a septum 6 and a valve 7. The sensor 3, 4 and 5 were connected to a data acquisition computer.

(107) The specifications of the pressure sensor and the temperature sensors used are given below:

(108) TABLE-US-00007 Calibrated Designation Sensor type Range range Accuracy Pressure AE sensors ATM 0-2.5 bara 0-2.4 bara 0.0125 bara 2.5 bar abs Temperature Omega engineering −250-350° C. 0-100° C. 1.4° C. reaction medium Type T Temperature gas Omega engineering −250-350° C. 0-100° C. 1.4° C. medium Type T

(109) The sensors were calibrated and the calibration logs are given in the tables below:

(110) TABLE-US-00008 Pressure sensor Results of polynomial fit of input data set. Fitted to function: Y = a + b .Math. X a = −3.33977748360518E+0001 CC = 0.999993998801983 b = 2.51274942241271E+0004 Linearity: +0.169%; −0.185% STATISTICS input: 10 points output: 10 points minimal X value: 7.69999E−01 maximal error 0.44010720% LSO: maximal X value: 9.5990000 average error 0.16192703% LSO: minimal Y value: 1.92600E+04 maximal error 0.18505821% FSO: maximal X value: 2.40960E+05 average error 0.07577616% FSO: standard 261.38961904 deviation:

(111) TABLE-US-00009 Temperature liquid reaction medium (T.sub.liq) thermocouple signal amplifier Results of polynomial fit of input data set. Fitted to function: Y = a + b .Math. X a = 2.73696307682517E+0002 CC = 0.999978525273946 b = 1.50113170585922E+0001 Linearity: +0.047%; −0.146% STATISTICS input: 11 points output: 11 points minimal X value: 0.00000E+00 maximal error 0.19960360% LSO: maximal X value: 6.6420000 average error 0.04954811% LSO: minimal Y value: 273.1500000 maximal error 0.14630571% FSO: maximal X value: 373.1500000 average error 0.04024681% FSO: standard 0.22911342 deviation:

(112) TABLE-US-00010 Temperature gas reaction medium (T.sub.gas) thermocouple signal amplifier Results of polynomial fit of input data set. Fitted to function: Y = a + b .Math. X a = 2.72150413620245E+0002 CC = 0.999999761705112 b = 1.50265967609884E+0001 Linearity: +0.012%; −0.006% STATISTICS input: 11 points output: 11 points minimal X value: 6.55000E−02 maximal error 0.01282300% LSO: maximal X value: 6.7220000 average error 0.00551510% LSO: minimal Y value: 273.1500000 maximal error 0.01179027% FSO: maximal X value: 373.1500000 average error 0.00469818% FSO: standard 0.02412944 deviation:

(113) The valve 7 is connected to a quadruple connector 8. Two gas chromatography (GC) vials 9, 10 of 50 ml each are connected to the quadruple connector 8 with respective valves in between vial and connector. Further, another valve 11 is connected to the quadruple connector 8 for enabling the addition and evacuation of gases to and from the reaction vessel 1.

(114) Before experiments were started, tubing and GC vials were under vacuum. Once the insert with the fuel in it was placed in the reaction vessel 1, the tubing and the reaction vessel were filled with nitrogen (purity grade N50, Air Liquide) at atmospheric pressure. Air was removed by alternatingly adding nitrogen (5 bar) and applying vacuum for three consecutive times, then pressurizing with nitrogen (5 bar) and finally open the gas evacuation valve until the pressure inside the vessel equalled ambient pressure. With the reaction setup containing fuel and being filled with nitrogen, the setup is ready for activator injection by a syringe 12 passing through the septum 6 into the insert 2 inside the reaction vessel 1.

(115) Execution of Experiments

(116) The H.sub.2 generation experiment was performed three times on 29 Oct. 2015 following the protocol 15EM/0678 of the institute TNO in the Netherlands. Fuel is inserted in the insert 2, and the reactor 1 is filled with nitrogen as described previously. To add the activator solution, the following steps were executed. First, a clean, disposable syringe 12 (having a volume of 2 ml) was equipped with a disposable stainless steel needle (having an inner diameter of 0.9 mm). The syringe was flushed with the activator solution, leaving no air in the syringe or needle. The mass of the flushed syringe was determined. The balance was tared with the syringe, and the syringe was filled with the required amount of activator (also referred to as activator solution or activator mixture). The mass of syringe plus activator was determined. Next, the syringe was emptied slowly (in the course of 20-40 seconds) into the Teflon insert 2 by injecting it through the septum 6, without letting any gas enter the syringe or needle. When addition of the activator was complete the syringe was removed and weighed. The exact amount of activator added was determined by subtracting the weight of the emptied syringe from the combined mass of syringe and activator. The exact amounts of fuel and activator added in the experiments are given below:

(117) TABLE-US-00011 Experiment reference Fuel [gram] Activator [gram] YPEvG119 0.2008 0.3352 YPEvG120 0.1993 0.3331 YPEvG121 0.2001 0.3554

(118) The GC vials were filled with the gas mixture from the reaction vessel about 30 minutes after the pressure in the vessel was considered stable (typically about 15 minutes after addition of the activator was completed). Experiment YPEvG119 was terminated earlier due to a malfunction of the data acquisition software. The total data recording time from the moment of addition of the activator was 1,610 seconds (26.7 minutes). The experiment showed a stable pressure in the reaction vessel and hence the experiment was considered successful. The GC vials were filled by opening the valves connecting the vials to the quadruple connector and the reaction vessel. Due to the maintained vacuum in the vials, they quickly filled with the gas phase when their respective valves were opened. The filled vials were allowed to equilibrate for 5 minutes, then their respective valves were closed and the vials were sent to be analyzed by gas chromatography (GC).

(119) After filling the GC vials, any excess pressure in the reaction vessel was released and the vessel was opened. The Teflon insert was removed. The solid left behind in the insert 2 was dried in a vacuum stove at 30° C.

(120) Pressure and Temperature Profiles

(121) The pressure and temperature profiles of experiments YPEvG119, YPEvG120 and YPEvG121 are given in FIGS. 17 to 19, respectively. The reaction started when the activator solution was added, which is indicated by S together with the time in seconds after start of the taking measurements in FIGS. 17 to 19. It is followed by a rapid increase in temperature of the liquid (T.sub.liq), which peaks at 75-77° C. Simultaneously, the gas pressure showed a rapid increase indicating the production of gas. The resulting stable pressure and corresponding temperature, as well as the starting pressure and temperature are given below:

(122) TABLE-US-00012 Experiment reference P.sub.start [bara] T.sub.start.sup.1 [° C.] P.sub.end [bara] T.sub.end [° C.] YPEvG119 1.03 25.3 1.92 24.8 YPEvG120 1.03 26.2 1.96 25.0 YPEvG121 1.04 25.8 1.97 25.1 .sup.1T.sub.start was higher due to the preflushing with nitrogen and applying a vacuum

(123) The increase in gas temperature (T.sub.gas) is much less pronounced due to the rapid cooling through interaction with the reactor vessel walls.

(124) Gas Chromatography (GC) Results

(125) The gas chromatography (GC) analysis plot for experiment YPEvG-121 is given in FIG. 21 as an example. The analysis is reported in report 15EM/0712 of institute TNO in the Netherlands. The following table shows the results form analyzing the plot of FIG. 21:

(126) TABLE-US-00013 RetTime Area Amount [min] Type [25 μV s] Amt/Area [% vol] Name 2.932 — carbon dioxide (CO.sub.2) 4.527 — ammonia (NH.sub.3) 22.217 BB 1319.35925 3.44871e−2 45.50090 hydrogen (H.sub.2) 23.572 BB 652.65613 8.44455e−4 5.51139e−1 oxygen (O.sub.2) 26.146 BB 6.81704e4 7.76071e−4 52.90504 nitrogen (N.sub.2) 28.397 — methane (NH.sub.4) 31.683 — carbon monoxide (CO) Total: 98.95708

(127) The hydrogen (H.sub.2) and nitrogen (N.sub.2) concentrations derived from the gas chromatography measurements are given in the table below:

(128) TABLE-US-00014 Experiment reference H.sub.2 gas [% vol] N.sub.2 gas [% vol] Other [% vol] YPEvG119 45.3 53.2 1.5 YPEvG120 45.2 52.9 1.9 YPEvG121 45.5 52.8 1.7

(129) Because the setup is flushed with nitrogen before each test, other gases in the analyses mostly result from the reaction inside the vessel. As can be seen from the above table, the GC measurement detected almost exclusively hydrogen gas and nitrogen gas. Small amounts of water and oxygen were also detected. The oxygen and to a potentially lesser extent the water were already present before combining the fuel and the activator solution and are therefore included in the starting pressure.

(130) X-Ray Diffraction (XRD) Results

(131) The residue from the reaction before drying is a grey solid. After drying in vacuum a white solid is obtained. The solid obtained from experiment YPEvG119 is shown in FIG. 20. This white residue from experiment YPEvG119 was analyzed using x-ray diffraction (XRD).

(132) The solid residues of the experiments were qualitatively evaluated by XRD. XRD is limited to the identification of crystalline compounds. None of the diffractograms pointed towards large amounts of amorphous compounds. The XRD diffractogram pattern measured is given in FIG. 22. Three library patterns are found to overlap well with the measured pattern. The crystalline solids corresponding to these library patterns identified are given in the table below:

(133) TABLE-US-00015 Pattern reference Chemical formula Substance name 1 PDF 00-007-0277 Na.sub.2B.sub.4O.sub.7•5H.sub.2O Tincalconite, syn 2 PDF 00-005-0628 NaCl Halite, syn 3 PDF 01-075-2259 Na.sub.2ClB(OH).sub.4 Teepleite, syn
The integer number in the first column of the table above is used to identify peaks of the corresponding pattern in FIG. 22. The peaks identified with ‘2’ thus correspond with pattern PDF 00-005-0628 corresponding to NaCl. The analysis report of the XRD analysis is also reported in report 15EM/0712 of institute TNO in the Netherlands.

DISCUSSION

(134) The GC results indicate that the gas produced is almost completely hydrogen gas in all experiments. Therefore, the pressure increase can be used to determine the absolute value of hydrogen gas produced (applying the ideal gas law, which is applicable due to the low pressures). The molar quantities of hydrogen gas, as well as the starting molar quantities of nitrogen gas are calculated. Both are translated to their respective volume percentages and compared with the GC results. These calculated molar quantities and volume percentages of hydrogen and nitrogen are given in the table below:

(135) TABLE-US-00016 Pressure based Pressure based GC results Experiment [mol] [% vol] [% vol] reference N.sub.2 H.sub.2 N.sub.2 H.sub.2 N.sub.2 H.sub.2 YPEvG119 0.0076 0.0066 53 47 53 45 YPEvG120 0.0075 0.0069 52 48 53 45 YPEvG121 0.0076 0.0069 53 47 53 46

(136) The calculated volume percentages results are consistent with the measured volume percentages the GC experiments. The GC results on hydrogen show a lower concentration of hydrogen gas. The calculated amounts of hydrogen from the pressure values should therefore be seen as maximum values.

(137) In the table below the calculated amounts of hydrogen are compared to the theoretical maximum amounts of hydrogen which can be produced from sodium borohydride according to the reaction formula using the mass of NaBH.sub.4 employed in the fuel (the ratio is designated as yield):
NaBH.sub.4+2H.sub.2O.fwdarw.NaBO.sub.2+4H.sub.2
This is the ideal reaction formula of the decomposition reaction of sodium borohydride. The actual reaction could be different (as also indicated by the XRD results). However, for comparison in relation to the theoretical maximum this is an appropriate reaction equation. The table below also gives the ratio of the mass of hydrogen gas produced and the total mass of the fuel and activator solution applied (designated as efficiency):

(138) TABLE-US-00017 Theo- Acti- Effi- Experiment H.sub.2 retical Yield Fuel vator ciency reference [mol] H.sub.2 [mol] [% mol] [gram] [gram] [% wt] YPEvG119 0.0066 0.0071 93 0.2008 0.3352 2.5 YPEvG120 0.0069 0.0070 98 0.1993 0.3331 2.6 YPEvG121 0.0069 0.0071 98 0.2001 0.3554 2.5 Average: — — 96 — — 2.5

(139) The yields obtained are close to the theoretical maximum of 100%. Experiment YPEvG119 has a lower yield than the other two experiments. No direct reason can be found, but leakage of some H.sub.2 seems likely. It is not likely that it is related to the shorter measurement time because the pressure was already constant (and the reaction completed) for a considerable amount of time as can also be seen in FIG. 14.

CONCLUSIONS

(140) The objective of the experiments was to validate whether the fuel mixture H2Fuel produces hydrogen gas when brought in contact with the activator solution.

(141) The GC analysis indicates that predominately hydrogen gas is produced. Nitrogen and hydrogen gas are detected with small amounts of oxygen and water. The pressure increase can be attributed to the H.sub.2 production and therewith used to quantify the amount of H.sub.2 produced. The resulting values should be seen as maximum values.

(142) The fuel in reaction with the activator solution produces hydrogen gas with an average of 96% mol of the theoretical maximum, while the maximum in practice is 98% mol due to specifications of NaBH.sub.4, and in an efficiency of 2.5% wt in relation to the total mass of fuel and activator solution combined. In this case an overdose is provided to the acid and water in order to obtain the maximum of hydrogen conversion in the shortest possible period of time after injection.

(143) XRD analysis indicate that no sodium borohydride or other crystalline borohydrides remained after reaction. Minerals detected were predominately kitchen salt and sodium borates. This indicates the reaction reached completion.