Catalytic semi-continuous operation modes for hydrogen generation from carbon derivatives of ammonia boranes

Abstract

In the present study, the semi-continuous regime is evaluated for generating hydrogen (H-2) from carbon derivatives of ammonia borane (AB) via hydrolysis in presence of cobalt-doped activated carbon catalyst (Co-AC). Methylamine borane (MeAB) and ethane 1,2 diamine borane (EDAB) is used as an H-2 storage medium. At first, catalytic activity tests are performed between 20 degrees C and 80 degrees C. 0.2 M MeAB, EDAB, and also AB are hydrolyzed with - Co-AC catalyst, and the results are compared in two temperature regions. EDAB shows the lowest hydrogen generation rate at 64.38 mLH(2)/min.g(Co-AC) of all carbon derivatives of AB due to its higher thermal stability. The power-law model is used to describe the kinetic rate and activation energy (E-a) for all the reactants in the catalytic hydrolysis reaction and the reaction kinetics studied in two temperature regions as the low-temperature region (20-50 degrees C) and the high-temperature region (60-80 degrees C). The zero-order kinetic model describes each temperature region for each reactant. The E-a values of AB, MeAB, and EDAB are calculated as in the range of 48-65 kJ mol(-1) for the low-temperature region and in the range of 33-51 kJ mol(-1) for the high temperature region. The semi-continuous regimes were performed at 60 degrees C with the same amount of AB, MeAB, EDAB, and Co-AC catalyst used for catalytic activity tests. The hydrogen generation rates for the semi-continuous regime are calculated to be 2.46 L/h, 0.86 L/h, and 0.17 L/h for AB, MeAB, and EDAB, respectively. The used catalysts and the exhaust solutions are also characterized. After the semicontinuous regime, the characterization results show that Co-AC is stable and Co species does not leach into the exhaust solution. Also, boron is accumulated on the catalyst observed due to by-product formation during the hydrolyses. (c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.