Kinetic Studies of Reaction between Sodium Borohydride and Methanol, Water, and Their Mixtures

Abstract

This paper reports the kinetics of hydrogen generation from the reaction between sodium borohydride and methanol, water, and their mixtures over a temperature range between -20 and +50 °C. Hydrogen generation was found to obey a first-order rate law with respect to sodium borohydride concentration for each of the four reacting mixtures of methanol, "nearly dry" methanol (2:1 water to sodium borohydride mole ratio), "wet" methanol (10:1 water to sodium borohydride ratio), and water, with activation energies of 53.0 ( 3.4, 52.3 ( 9.5, 36.1 ( 2.8, and 86.6 ( 8.0 kJ/mol, respectively. Methanolysis of sodium borohydride was shown to be a feasible method for low-temperature hydrogen generation. However, this noncatalytic reaction system exhibited large lag time and slow reaction kinetics at low temperatures. Our study indicates that the reaction system based on sodium borohydride and the nearly dry methanol can be a potential high gravimetric density hydrogen storage system.

Sodium Borohydride Hydrolysis as Hydrogen Generator: Issues, State of the Art and Applicability Upstream from a Fuel Cell

“…The second way is simply to by-pass the problem by changing the experimental approach. The latter way is what Lo et al [41] chose to do. To avoid the formation of the hydrated reaction product, an alternative to H 2 O utilisation as reactant is the use of a primary alcohol.…”

“…Indeed NaBH 4 is known to be reactive to e.g. methanol and ethanol [42] and methanol has the highest reactivity towards NaBH 4 [41]. The overall reaction between methanol and NaBH 4 can be described as:…”

“…Lo et al [41] assessed the H 2 generation in methanol and mixtures of methanol and water (H 2 O/NaBH 4 mole ratio of either 2 or 10). The best system was the mixture with a mole ratio of 10.…”

Chemistry, nanostructure and magnetic properties of Co–Ru–B–O nanoalloys

“…Sodium borohydride (SB) is one of the most studied because releases hydrogen safely through its hydrolysis reaction (1) with a high potential hydrogen storage capacity (10.8%, but usually lower in experimental conditions due to the formation and precipitation of hydrated borates) [3][4][5][6][7]. Also methanolysis (reaction of SB with methanol) and the use of methanol-water mixtures were proposed as efficient methods to produce hydrogen from sodium borohydride with promising hydrogen storage capacity [8]. NaBH 4 + 2 H 2 O → 4H 2 + NaBO 2 (1) Uncatalysed, reaction (1) is very slow.…”

“…Most proposed systems for hydrogen generation through (1) are based on the addition of stabilized (on sodium hydroxide) SB solutions to a certain catalyst or by addition of water to a mixture of solid SB and catalyst. [4][5][6]8] Cobalt is definitely the most studied metal catalyst because of its cost effectiveness [9][10][11]. Co based catalysts have been tested and/or prepared in a wide of range of forms, from the simplest CoCl 2 6H 2 O salt to metallic cobalt, cobalt oxides and also alloyed with another elements [12][13][14][15][16][17].…”