Effects of various reaction conditions on the alcoholysis of borohydride compounds

In this thesis study, on Al2O3, TiO2 and activated carbon (AC) supports; single, double, triple and four active metal impregnation methods. Salts of transition metals such as NiCl2.6H2O, CoCl2.6H2O, CuCl2.2H2O, MnCl2.2H2O and FeCl3 were used to form the active structures of the catalyst. In the presence of these produced catalysts, the decomposition of sodium borohydride by alcoholysis and hydrogen production was achieved. Sodium borohydride (NaBH4), one of the chemical hydrogen storage materials, is an important storage alternative with a hydrogen content of 10.8% by mass. Hydrogen volumes produced at 230C were measured by the reverse burette method, and their amounts were recorded over time. Isopropyl alcohol (IPA) and Propylene Glycol (PG) were used in the alcoholization process. As a result of the studies, the best results were observed in the experiments with propylene glycol. It was determined that the catalyst with the best hydrogen production capability was Mn0,85Co0,08Cu0,07/TiO2 with a velocity of 4545 mL H2/gcat.min. In order to further increase the hydrogen production rate, ammonium borane was introduced in NaBH4 solution. The hydrogen production rates gave faster results when compared to only NaBH4 containing studies. Amonium borane and sodium borohydride mixture results in 7500 mL H2/gcat.min rate (HPS) with Mn0,85Co0,08Ni0,07/AC catalyst. Catalysts were divided into two groups as fresh and tested, and their characterizations were made by TEM (Transmission Electron Microscopy) and SEM (Scanning Electron Microscopy) analyzes. In SEM analyzes, it was understood that the channels on the surface became wider due to the gas-liquid mobility during the alcohollysis process, while in the TEM analyzes, the catalyst particles had a homogeneous and nano-sized distribution. The reaction degree and activation energy were calculated with the collected kinetic data. As a result of the calculation, it was found that the reaction was zeroth order and the activation energy of the Mn0,85Co0,08Cu0,07/TiO2 catalyst was 44 kJ/mol. In the retests, it was observed that the activity and conversion rate decreased with reuse.