| All the governments give a high priority on the development of fuel cell since it is a high-performance and clean power generation device. Compared to other gas fuels, when the high purity hydrogen gas is applied as the fuel in the fuel cell, it will offer the advantages of high stability of catalysis process, high efficiency in power generation and high capacity for power generation. Therefore it is considered as the ideal fuel for the fuel cell under high temperature condition.Hydrogen Production from Sodium borohydride via hydrolysis/alcoholysis can deliver the benefits of high storage volume of hydrogen, high purity with the hydrogen generated, environment friendly and easy to control the hydrogen generation process, etc. It is one of the techniques widely discussed at the current time.In case of ambient temperature environment, the hydrogen generation via the hydrolysis of Sodium borohydride will require an environment with catalyst. In general, the current catalysts prepared are not suiTab. for large-scale application due to limitations such as their high costs, rigorous requirements on the environment, poor stability during the catalysis process and weak regeneration capability.Therefore, the development of the transition metal catalyst with low cost, high stability and high poisoning resistance in the application of hydrogen generation from Sodium borohydride via catalytic hydrolysis/alcoholysis will offer very important theoretical value and application value for the fuel cell with direct hydrolysis of Sodium borohydride. Within this thesis, the hydrogen generations in alcohol/water solution and actual water are studied with low-cost, high-performance transition metal catalysts.The followings are the main research content and results:1., The catalytic performances of Cobalt-based Catalysts on the hydrogen generation via the hydrolysis of Sodium borohydride are studied with transition metal Ni, Fe, Cu, Y, Ce and La as Catalyst promoter. It is found by the experiments that there is an optimal range for the doping content of Catalyst promoter against the activity of catalyst. The optimal contents of Ni, Fe, Cu, Y, Ce and La are20%,20%,10%,30%,30%and30%, respectively. With the catalyst promoters at their optimal contents, the order of the activity of each catalyst will be Ni>Y>Cu>La>Ce>Fe>no catalyst promoter. The one with the maximum activation energy is Co-Fe-B/Attapulgite catalyst with the value of64.85kJ/mol; the one with the minimum activation energy is Co-Y-B/At catalyst with the value of36.69kJ/mol.2、The impact of alcohol/water volume ratio on the hydrogen generation during the hydrogen generation process from the Sodium borohydride alcohol/water mixture solution is studied. It is found that the rate of hydrogen generation will be raised then lowered with the increase of alcohol/water volume ratio, and the maximum hydrogen generation rate will be achieved when the alcohol/water volume ratio is kept at75%. The possible causes for this kind of phenomenon are:Ethanol will compete with water within the reaction solution during the absorption process. Since O-H bond in the water is more readily to polarize, it is preferential to contact the surface of catalyst. However, due to the hydrophobicity induced by the-CH3group in ethanol, the contact between O-H in water and the surface of catalyst is reduced by the high concentration ethanol-water solution and the hydrogen generation rate is lowered. Meanwhile, the high concentration ethanol-water solution increased the viscosity of the solution and inhibited the diffusions of reactant ions to the surface of catalyst and product ions from the surface of catalyst to the liquid phase, thus the hydrogen generation rate was also reduced by somehow.3、The catalytic performances of the multiple components catalyst with TiO2, attapulgite and silica gel as the carrier are systemically studied. It is found by the experiments that the order of the catalyst activity from high to low is:TiO2> attapulgite> silica gel, and the average hydrogen generation rate is6.84L/(min.g),2.89L(min.g) and2.39L/(min.g), respectively. The catalyst stability of the supported catalyst is investigated with multiple circulation experiments, and it is indicated by the results that the best catalyst stability is achieved with the catalyst using attapulgite as the carrier. After10circulation experiments, the catalyst activity will be lowered to75%of the initial value, while it will be lowered to29.27%of the initial value after10circulation experiments for the catalyst using TiO2as the carrier. 4、The impact on the hydrogen generation rate catalyzed by Co-Y-B/TiO2by the factors such as the concentration of Sodium borohydride, the concentration of Sodium Hydroxide, and the content of Y within the catalyst is investigated. There is optimal range for these3factors on the hydrogen generation rate, and they are8%,8%and30%, respectively; both the load of the active ingredient and the reaction temperature will have a positive correlation with the hydrogen generation rate. A model of the reaction kinetics on the first-order catalysis is established by analyzing the catalytic behaviors of Co-Y-B catalysts with TiO2, attapulgite and silica gel as the carrier, and all of the catalysis reactions during the alcoholysis/hydrolysis of Sodium borohydride are consistent with first-order reaction kinetics model;5、When the nature river water is collected as the solvent in the hydrogen generation experiment, the corresponding average hydrogen generation rate is less than the one of distilled water, and the impact on the hydrogen generation process by the factors such as the concentration of Sodium borohydride, the concentration of Sodium Hydroxide and reaction temperature, etc. during the reaction process is similar to distilled water system; The ingredients of Ca(HCO3)2,CaCl2and NaHCO3within the river water have a large impact on the hydrogen generation, while the ingredients of KCl,MgSO4,Na2SO4and NaCI have a small impact on the hydrogen generation rate; The optimal average hydrogen generation rate can be achieved with the optimization of the concentration of Sodium borohydride, the concentration of Sodium Hydroxide, reaction temperature, type of carrier and doping amount of Y by Response surface analysis. A quadratic equation model can be obtained with regression. The gap between the model forecasting value and experiment data is small and this is a reliable experimental model. |
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