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  • Hydrogen release through ca...
    Hannauer, J.; Demirci, U. B.; Pastor, G.; Geantet, C.; Herrmann, J. M. Null; Miele, P.

    Energy (Oxford), 01/2010, Letnik: 3, Številka: 11
    Journal Article

    Methanolysis of sodium borohydride (NaBH4) is a way of recovering the hydrogen stored in the hydride. Though the reaction is spontaneous, it can be accelerated by virtue of Co-TiO2 or Ru-TiO2 catalysts. Under our experimental conditions, Co-TiO2 shows high catalytic performances, higher than those of Ru-TiO2. Hydrogen generation rates of 144 to 644 L(H-2) min(-1) g(-1)(Co) were measured as the Co content was decreased. The kinetic parameters of the catalyzed reaction were determined. The Co-TiO2- catalyzed methanolysis follows a power law, i.e. r(20) k center dotNaBH4(1.3)center dotCH3OH(0.9) with k = 1.8 x 10(-2) s(-1). The Langmuir-Hinshelwood bimolecular mechanism accounts for the kinetics. The apparent activation energy was found to be 20.4 kJ mol(-1) whereas that of the catalyzed hydrolysis was 49.4 kJ mol(-1). Indeed, the catalyzed methanolysis was compared to the catalyzed hydrolysis as well as the catalyzed ethanolysis. For instance, it was remarked that water in methanol has a detrimental effect on the H-2 release kinetics. In parallel, the gravimetric hydrogen density of the system NaBH4-CH3OH has been optimized. Under our experimental conditions, it was found that the highest capacity that can be achieved is 3.4 wt%.