NaBH4hydrolysis performance and kinetic evaluation of synthetic Co-Mn-Pt catalyst prepared with different supports

Abstract

Purpose: In this study, it was aimed to determine the hydrolysis and hydrogen generation rate of NaBH4 with TiO2 and Al2O3supported Co0.92-xMn0.08Ptxcatalysts. The determination of the effects of NaOH, catalyst and NaBH4amounts on the reaction was achieved by using kinetic methods and this constitutes a part of the study. Theory and Methods: Hydrogen production with high rates were studied with three different precursors supported on TiO2and Al2O3by wet impregnation technique. Precursors were arranged to constitute (x=0.03, 0.07 and 0.15) catalyst. 40 mg of catalyst were tested at 22°C, in alkaline medium and produced hydrogen volume was measured by inverse burette system and graphed with time. Transmission and scanning electron microscopies, X-ray diffraction, BET analysis and energy dispersion X-ray spectroscopy techniques are used to determine the catalyst properties. Different NaOH, NaBH4and temperatures were investigated to obtain kinetis data. Arrhenius equation was used calculate the activation energy and order of the reactions. Results: It was observed that the support type changes the morphology of the catalyst surface and activity. TiO2supported Co0.85Mn0.08Pt0.07catalyst gave the highest hydrogen generation rate with 6, 250 mL H2/min.gcatat 22°C. Optimum NaOH amount was determined as 0.15 M for both supports. Hydrolysis experiments showed that at high NaBH4concentration the reaction could not produce the expected hydrogen amount due to increased viscosity and decreased solubility. Kinetic studies reveal that the hydrolysis reaction happens according to zero order kinetics for NaBH4and catalyst amount is main parameter on rate. Activation energy of the reaction was calculated as 34.19 and 40.02 kJ/mol for the TiO2and Al2O3supports. Conclusion: Precursors were strongly embedded on supports and provide satisfactory hydrogen generation rates. It may be suggested to increase the catalyst amount and temperature to further increase production.