Hydrogen synthesizer part 1
1,904 views · Published 5 January 2018 · 51:14 · Indexed 29 October 2026
Channel: NOBOX7 · 2018 · Science & Technology
This video contains Paid links that gives me a 6% commission if you click and buy any product on that website . Check out my web site http://www.nobox7.com/ Check out my store front https://www.amazon.com/shop/nobox7 Support this channel on Patreon https://www.patreon.com/user?u=3620781 The following are possible reactions of aluminum with water: 2Al + 6H2O = 2Al(OH)3 + 3H2 (1) 2Al + 4H2O = 2AlO(OH) + 3H2 (2) 2Al + 3H2O = Al2O3 + 3H2 (3) The first reaction forms the aluminum hydroxide bayerite (Al(OH)3) and hydrogen, the second reaction forms the aluminum hydroxide boehmite (AlO(OH)) and hydrogen, and the third reaction forms aluminum oxide and hydrogen. All these reactions are thermodynamically favorable from room temperature past the melting point of aluminum (660 o C). All are also highly exothermic. From room temperature to 280 o C, Al(OH)3 is the most stable product, while from 280-480 o C, AlO(OH) is most stable. Above 480 o C, Al2O3 is the most stable product (3). See the Appendix I for a more thorough review of the thermodynamics of aluminum-water reactions. Version 1.0 - 2008 Page 5 of 26 Table I: Thermodynamics of the aluminum-water reaction. [The thermodynamic parameters as a function of temperature were calculated using HSC Thermodynamic Software, Version 4.1.] 2/3Al + 2H2O = 2/3Al(OH)3 + H2(g) T ΔH ΔS ΔG o C kJ/mol H2 J/K kJ/mol H2 0 -277 26.2 -284 100 -284 3.29 -285 200 -291 -12.1 -285 The reaction thermodynamics shown in Table I indicate that aluminum should spontaneously react with water. However, in practice a piece of aluminum dropped into water will not react under room temperature conditions, or even with boiling water. This is because the aluminum has a thin coherent, adhering layer of aluminum oxide, Al2O3, on its surface and this alumina layer prevents the reaction. So the key to inducing and maintaining the reaction of aluminum with water at room temperature is the continual removal and/or disruption of the hydrated alumina layer. Organizations that are currently involved with the development of aluminum-water systems for the production of hydrogen are listed in Appendix II. Reaction-Promoting Approaches: Hydroxide Promoters: A number of U.S. patents describe the use of hydroxides, primarily sodium hydroxide (NaOH), to promote aluminum-water reactions (4-8). There are two pertinent technical references on this subject. The first is by Belitskus (9). Here, experiments were described in which aluminum specimens including a cylindrical block, uncompacted powders, and pellets of various densities were reacted with aqueous solutions of sodium hydroxide at different concentrations to produce hydrogen gas at temperatures near room temperature. The formation of sodium aluminate was observed, as well as the regeneration of sodium hydroxide via the precipitation of aluminum hydroxide. Stockburger et.al. (10) described hydrogen generators in which aluminum was reacted with an aqueous solution of 5.75 M sodium hydroxide. The types of reactions found to occur between aluminum, sodium hydroxide, and water are shown below: 2Al + 2NaOH + 2H2O = Na2Al2O4 + 3H2 (4) 2Al + 6NaOH + xH2O = Na6Al2O6 + xH2O + 3H2 (5) Version 1.0 - 2008 Page 6 of 26 2Al + 2NaOH + 6H2O = 2NaAl(OH)4 + 3H2 (6) 2NaAl(OH)4 = 2NaOH + 2Al(OH)3
