The use of boric acid (H3BO3) and boron oxide (B2O3) for co-precipitation synthesis of cobalt-boron catalysts: Catalytic activity in hydrogen generation

摘要

The use of boric acid (H3BO3) and boron oxide (B2O3) for the synthesis of cobalt-based catalysts by the co-precipitation technique was investigated and catalytic activities in hydrogen generation were evaluated. Different cobalt salts [cobalt (II) chloride (CoCl2 center dot 6H(2)O), cobalt sulfate (CoSO4 center dot 5H(2)O) and cobalt(II) nitrate (Co(NO3)(2) center dot 7H(2)O)] were used with H3BO3 and B2O3 to prepare Co based catalysts. Crystalline, surface and chemical characteristics were clarified using X-ray diffraction (XRD); low temperature adsorption of nitrogen (BET), scanning electron microscopy (SEM), and inductively coupled plasma optical emission spectroscopy (ICP-OES). Three types of powder samples were obtained according to the different boron sources and cobalt salts, and it was found that an efficient Co based catalyst was obtained by co-precipitation of B2O3 and CoCl2 center dot 6H(2)O salt. Additionally, the effect of temperature, stabilizer ratio and NaBH4/catalyst ratio on parameters, characterizing the reaction of hydrogen generation was investigated. The zero order, first order and Langmuir-Hinshelwood kinetic models were used to identify the effect of Co based catalysts on the behavior of the catalytic system in hydrogen generation. Kinetic parameters of hydrogen generation for zero-order kinetic model were calculated for the following conditions: the rate of hydrogen generation is 0.93 L H-2 g(-1) catalyst min(-1), the activation energy is 43.55 kJ mol(-1) and the constant of Arrhenius equation is 11 min(-1).