Ruthenium immobilized on Al2O3 pellets as a catalyst for hydrogen generation from hydrolysis and methanolysis of sodium borohydride

Abstract

Ru immobilized Al₂O₃ pellets were synthesized as a catalyst for hydrogen generation in NaBH₄ solutions. Under the Ru/Al₂O₃ catalysis, the hydrogen generation rate from the hydrolysis and methanolysis of NaBH₄ in alkaline solution was explored as a function of NaBH₄ concentration and temperature. Meanwhile, the borate byproducts derived from the NaBH₄ hydrolysis were characterized by XRD and NMR. The results showed that the hydrogen generation rate depended on NaBH₄ concentration for the hydrolysis, but did not for the methanolysis. 10 wt% NaBH₄ hydrolysis containing 1 wt% NaOH catalyzed with 0.5 g Ru/Al₂O₃ could generate hydrogen with a rate of about 65.5 ml min⁻¹ g⁻¹. The productivity and activation energy of hydrogen generation from the NaBH₄ hydrolysis were 93% and 41.8 kJ mol⁻¹, and from the NaBH₄ methanolysis were 97% and 51.0 kJ mol⁻¹, respectively. The XRD and NMR analyses showed that the species from the hydrolysis byproducts varied with the NaBH₄ concentration could be the borax (Na₂B₄O₇·H₂O) and sodium borate hydrate (NaBO₂·H₂O).