Kinetic models of concentrated NaBH4 hydrolysis

• New experimental data at temperatures to 80 °C and concentrations to 20 wt.%.
• Two kinetic models for NaBH4 self-hydrolysis are presented.
• The rate constant is affected by Cl− anion in solution.

The hydrolysis of NaBH4 in liquid solution has been extensively studied in the past few years; however, data on the kinetics of self-hydrolysis in concentrated solution are few. This work reports the kinetic modeling of self-hydrolysis of 10–20 wt.% NaBH4 at 25–80 °C. Also, pH data were obtained independently of the reaction kinetics data. The data obtained from Boron-11 NMR measurements and pH are used to determine kinetic parameters. An empirical power law model is evaluated over a wide pH range. The effects of temperature, pH and initial sodium borohyride concentration are reported. The power law model reproduced the trends of the kinetics of the hydrolysis reaction. In addition, a pseudo first order model derived from a proposed reaction mechanism is evaluated. The behavior of the pseudo first order rate constant k is interpreted in terms of the effect of pH.