INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, cilt.38, ss.2824-2835, 2013 (SCI İndekslerine Giren Dergi)
In this study, a novel perspective has been proposed as "Ultrasonic Hydrolysis" for hydrogen generation from ammonia borane (NH3BH3) with cobalt-boron (Co-B) catalysts. The Co-B catalysts are prepared by the sol-gel reaction of boron oxide (B2O3) with cobalt(II) chloride hexahydrate (CoCI2 center dot 6H(2)O) in the presence of citric acid (C6H8O7). Two types of Co-B catalysts, amorphous and crystalline, are obtained after calcination at 500 and 700 degrees C respectively. The hydrolysis reactions are carried out in a batch reactor under ultrasonic conditions (frequency of irradiation of 35 kHz) at temperatures of 22, 40, 60 and 80 degrees C using 0.12 M NH3BH3 solution with amorphous and crystalline Co-B catalysts. The experimental data is fitted to zero-, first-, and second-order kinetic models and zero model gives good behavior description of the hydrogen generation rate. The maximum hydrogen generation rate is observed with amorphous Co-B catalyst (9157.20 ml.min(-1).g cat(-1)) and amount optimization, reusability and recyclability test are performed; TOF values for catalytic reactions were calculated. The corresponding activation energy (Ea) is only 47.50 kJ.mol(-1) under ultrasonic conditions. In conclusion, the hydrogen generation rate has been increased by 37.79, 21.99, and 21.85% under ultrasonic conditions when the results are compared with 500, 750, and 1000 rpm magnetic stirring hydrolysis, respectively. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.