Hydrogen production via methanolysis of sodium borohydride using acetic acid as a catalyst
Muhammed Bora Akın, Ömer Şahin
Abstract
This study investigates hydrogen production through the methanolysis of sodium borohydride (NaBH 4 ) using acetic acid (CH 3 COOH) as a catalyst, focusing on how temperature, catalyst concentration, methanol volume, and NaBH 4 concentration influence hydrogen generation rates. Parameters explored were: temperature from 20 to 50 °C, CH 3 COOH concentration from 0.555 to 16.650 mM, methanol volume from 2 to 20 mL, and NaBH 4 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 CH 3 COOH, 0.528 M NaBH 4 , 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.