Catalytic Performance Of Ni/γ-Al₂O₃ For Hydrogen Carrier Methylcyclohexane Dehydrogenation

Hydrogen is considered to be a promising clean fuel in the future, characterized by abundant resource, renewability, high energy density and zero contamination. There are some important issues need to be resolved for hydrogen energy's scale industrial application, which are Low-cost hydrogen production, safe storage and efficient transmission, and the scale of hydrogen energy industrial application. And the most important issue need to be resolved is hydrogen storage technology.Hydrogen storage with organic liquid hydrides achieved by a pair of reversible reaction between unsaturated organic liquid and hydrogen(i.e., hydrogenation and dehydrogenation reactions). Hydrogenation reaction is used to achieve the hydrogen storage (chemical bonding reaction); dehydrogenation is used to achieve the release of hydrogen. This paper focuses on the dehydrogenation of hydrogen energy carrier methylcyclohexane, and we wish to provide a valuable reference for hydrogen storage process with organic liquid hydrides.During the preparation process ofγ-Al₂O₃, adding the ultrasonic means that significantly increased surface area ofγ-Al₂O₃. Catalysts with different Ni content supported on activated alumina,γ-Al₂O₃ with surface area of 241㎡/g, were prepared via traditional volume impregnation method under ammonia or ethanol conditions. The catalysts Ni/γ-Al₂O₃ were characterized by XRD,SEM and BET.This study compares the characterization data of catalysts and the catalyst performance of methylcyclohexane dehydrogenation. The results show that the catalysts which preparation under the ammonia system has the optimum performance for methylcyclohexane dehydrogenation, we believe that the different precursor forms of catalyst have a major impact on catalyst performance.Dehydrogenation of methylcyclohexane (MCH) catalyzed by Ni/γ-Al₂O₃ was performed under a fixed-bed micro reactor. Experimental results showed that the dehydrogenation conversion of MCH can be reached to 94.58% and the selectivity to toluene formation is 100% by using 20% Ni/γ-Al₂O₃ catalyst of ammonia system at reaction temperature of 653K and reaction pressure of 0.5Mpa with MCH/N₂ of 7/12 and the volume gas space velocity of 212 h^-1. This experiment compares the catalyst performance of methylcyclohexane dehydrogenation between 20% Ni/γ-Al₂O₃ catalyst with 3% Pt/C catalyst. The results show that both 20% Ni/γ-Al₂O₃ catalyst and 3% Pt/C catalyst have the high catalytic activity for methylcyclohexane dehydrogenation under the high temperature, but 3% Pt/C catalyst has the high catalytic activity under the low-temperature than 20% Ni/γ-Al₂O₃ catalyst. For example, use 20% Ni/γ-Al₂O₃ catalyst and 3% Pt/C catalyst to make the conversion rate of MCH above 90%, 20% Ni/γ-Al₂O₃ catalyst need more 40℃temperature than 3% Pt/C catalyst. This experiment also shows that these nickel-based catalysts are feasible to replace platinum and other noble metal catalysts.