Tailoring of Hydrogen Generation by Hydrolysis of Magnesium Hydride in Organic Acids Solutions and Development of Generator of the Pressurised H[sub.2] Based on this Process

Hydrolysis of light metals and hydrides can potentially be used for the generation of hydrogen on-board fuel cell vehicles, or, alternatively, for refilling their fuel tanks with H[sub.2] generated and pressurised without compressor on site, at near-ambient conditions. Implementation of this approach requires solution of several problems, including the possibility of controlling H[sub.2] release and avoiding thermal runaway. We have solved this problem by developing the apparatus for the controlled generation of pressurised H[sub.2] using hydrolysis of Mg or MgH[sub.2] in organic acid solutions. The development is based on the results of experimental studies of MgH[sub.2] hydrolysis in dilute aqueous solutions of acetic, citric, and oxalic acids. It was shown that the hydrogen yield approaches 100% with a fast hydrolysis rate when the molar ratio acid/MgH[sub.2] exceeds 0.9, 2.0, and 2.7 for the citric, oxalic, and acetic acids, respectively. In doing so, the pH of the reaction solutions after hydrolysis corresponds to 4.53, 2.11, and 4.28, accordingly, testifying to the buffer nature of the solutions “citric acid/magnesium citrate” and “acetic acid/magnesium acetate”. We also overview testing results of the developed apparatus where the process rate is effectively controlled by the control of the acid concentration in the hydrolysis reactor.