The Cyclohexane Dehydrogenation Technology Research And The Energy Analysis For The On-board Hydrogen Source System

Hydrogen-powered vehicle has many advantages comparing with the traditional gasoline-powered automobile, e.g., lower noise and lower pollution, it is a continuously developing energy mode in view of the utilization of the new energy sources and environmental protection. However, one of the main bottlenecks preventing the industrialization of hydrogen-powered vehicle is the development of a high efficient, safe and economical on-board hydrogen source system. In this paper, we studied the dehydrogenation process of cyclohexane, and made an energy analysis for the on-board hydrogen source system.The multiphase dehydrogenation of cyclohexane catalyzed by Raney-Ni in small glass equipment was studied. The model of energy balance was established, and the kinetics of the dehydrogenation of cyclohexane was discussed by investigating the influences of reaction temperature (523K-633K), the amounts of catalyst (lg-9g) and reactant (0.2mL-3.0mL) on the dehydrogenation conversion of cyclohexane. We developed the dehydrogenation equipment for the on-board hydrogen source system. The experiments showed that, the "wet-dry" multiphase condition formed on the catalyst surface was closely connected with reaction temperature, the amounts of reactant and the catalyst dosage. The control of the system energy balance was critically important, if the energy offered by catalyst was just equal to the total energy of the system needed, the dehydrogenation conversion of cyclohexane should be the highest. The results showed that under the reaction conditions of 593K, 0.5mL cyclohexane and 7g Raney-Ni, the dehydrogenation conversion of cyclohexane was up to 72.7%, the purity of the evolved hydrogen was 100% without any impurity component, the apparent activation energy of the cyclohexane dehydrogenation reaction was 54.55 kJ/mol.Considering the economical efficiency of the energy, we systematically analyzed the thermal efficiency of the slurry hydrogen storage system formed by C₆H₆/C₆H₁2 and LaNi₅/LaNi₅H₆. Two conceptual designs of the on-board hydrogen sources basedon the slurry hydrogen storage systems, dehydrogenation system and hydrogenation-dehydrogenation system, were proposed. The influences of the conversion rates of the dehydrogenation of cyclohexane and the utilization ratios of the exhausted waste heat produced in the systems to the systematic thermal efficiencies were also investigated. The total energy efficiencies of the hydrogen-powered vehicles, which were driven by the hydrogen engine or the fuel cell on board equipped with a slurry hydrogen storage source, were estimated. In terms of our systematic energy efficiency analyses, on-board slurry hydrogen storage system is economically practicable with a promising perspective in the near future.