Hydrogen production via methanolysis of sodium borohydride using acetic acid as a catalyst

This study investigates hydrogen production through the methanolysis of sodium borohydride (NaBH₄) using acetic acid (CH₃COOH) as a catalyst, focusing on how temperature, catalyst concentration, methanol volume, and NaBH₄ concentration influence hydrogen generation rates. Parameters explored were: temperature from 20 to 50 °C, CH₃COOH concentration from 0.555 to 16.650 mM, methanol volume from 2 to 20 mL, and NaBH₄ concentration from 0.176 to 0.881 M. The power law model revealed a reaction order of 0.396 and an activation energy of 37.29 kJ mol⁻¹. Activation energies according to Michaelis-Menten and Langmuir-Hinshelwood kinetics were 34.32 and 31.67 kJ mol⁻¹, respectively. The ΔH_ads value was 0.12 ± 0.01 kJ mol⁻¹, and the ΔS° value was 10.33 ± 0.01 kJ mol⁻¹ K⁻¹. ΔG° decreases from −3025 kJ mol⁻¹ to −3335.44 kJ mol⁻¹ with an increase in temperature. The hydrogen generation rate (HGR) recorded was 168 L min⁻¹ g cat⁻¹ at 30 °C with 0.555 mM CH₃COOH, 0.528 M NaBH₄, and 15 mL of methanol. The study highlights that lower acetic acid concentration is more effective, avoiding steric hindrance that can occur with higher concentrations due to equilibrium reaction with excess alcohol. This insight underscores the potential of acetic acid as a cost-effective and environmentally friendly catalyst for hydrogen production, suggesting further optimization could enhance its performance.