Hydrogen release through catalyzed methanolysis of solid sodium borohydride

Abstract

Methanolysis of sodium borohydride (NaBH 4 ) is a way of recovering the hydrogen stored in the hydride. Though the reaction is spontaneous, it can be accelerated by virtue of Co-TiO 2 or Ru-TiO 2 catalysts. Under our experimental conditions, Co-TiO 2 shows high catalytic performances, higher than those of Ru-TiO 2 . Hydrogen generation rates of 144 to 644 L(H 2 ) min À1 g À1 (Co) were measured as the Co content was decreased. The kinetic parameters of the catalyzed reaction were determined. The Co-TiO 2 -catalyzed methanolysis follows a power law, i.e. r 20 ¼ k$[NaBH 4 ] 1.3 $[CH 3 OH] 0.9 with k ¼ 1.8 Â 10 À2 s À1 . The Langmuir-Hinshelwood bimolecular mechanism accounts for the kinetics. The apparent activation energy was found to be 20.4 kJ mol À1 whereas that of the catalyzed hydrolysis was 49.4 kJ mol À1 . 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 NaBH 4 -CH 3 OH has been optimized. Under our experimental conditions, it was found that the highest capacity that can be achieved is 3.4 wt%.

Brønsted and Lewis Base Behavior of Sodium Amidotrihydridoborate (NaNH2BH3)

“…The THF was removed from the filtrate under dynamic vacuum to leave NaB(OCH 3 ) 4 as a white solid (0.703 g, 89 %). FTIR and 11 B NMR spectroscopic data were in good agreement with those for NaB(OCH 3 ) 4 in the literature …”

“…NaNH 2 BH 3 reacted directly with CH 3 OH to produce NaB(OCH 3 ) 4 , H 2 , and NH 3 in THF at room temperature (Table , entry 9). The product NaB(OCH 3 ) 4 was confirmed by 11 B NMR and FTIR spectroscopy (Figure S9), and the gaseous product was confirmed to be to be NH 3 .…”

“…A pungent‐smelling gas was released during the reaction and GC analysis indicated that the gas was a mixture of H 2 and NH 3 . THF and residual CH 3 OH were removed from the filtrate under dynamic vacuum to leave a white solid (0.729 g, 91 %), which was proved to be NaB(OCH 3 ) 4 by FTIR spectroscopy …”

“…FTIR and 11 B NMR spectroscopic data were in good agreement with those for NaB(OCH 3 ) 4 in the literature. [12] Reaction of NH 3 BH 3 with CH 3 ONa and CH 3 OH: NH 3 BH 3 (0.155 g, 5 mmol) and CH 3 ONa (0.27 g, 5 mmol) were placed in a two-necked 50 mL flask with a magnetic stir bar, and THF (15 mL) was injected into the flask at room temperature. CH 3 OH (10 mL, 247 mmol) was injected into the solution with stirring.…”

Highly efficient CoB catalyst using a support material based on Spirulina microalgal strain treated with ZnCl 2 for hydrogen generation via sodium borohydride methanolysis

“…Recently, the methanol solvent present in the alcohols is of interest in the use of SB instead of water in the HP. In these studies, it was stated that the preference of methanol solvent instead of water was more effective in the HP . The acidity value of the methanol in the alcohol is higher than the acidity value of the water, which may be the possible cause of this result.…”