Ruthenium immobilized on Al ₂O ₃ pellets as a catalyst for hydrogen generation from hydrolysis and methanolysis of sodium borohydride

Ru immobilized Al ₂O ₃ pellets were synthesized as a catalyst for hydrogen generation in NaBH ₄ solutions. Under the Ru/Al ₂O ₃ catalysis, the hydrogen generation rate from the hydrolysis and methanolysis of NaBH ₄ in alkaline solution was explored as a function of NaBH ₄ concentration and temperature. Meanwhile, the borate byproducts derived from the NaBH ₄ hydrolysis were characterized by XRD and NMR. The results showed that the hydrogen generation rate depended on NaBH ₄ concentration for the hydrolysis, but did not for the methanolysis. 10 wt% NaBH ₄ hydrolysis containing 1 wt% NaOH catalyzed with 0.5 g Ru/Al ₂O ₃ 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 NaBH ₄ hydrolysis were 93% and 41.8 kJ mol ^-1, and from the NaBH ₄ 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 NaBH ₄ concentration could be the borax (Na ₂B ₄O ₇·H ₂O) and sodium borate hydrate (NaBO ₂·H ₂O).