Kinetics Analysis Of Liquid-Phase Benzene Hydrogenation In A Slurry System Formed By MINi₅ And C₆H₆

Hydride slurry is a novel technology of hydrogen storage, which shows great potentialities in hydrogen storage and utilities of fuel cells in hydrogen vehicles.In this paper, the kinetics of hydrogen absorption of a typical hydride slurry system formed by Lanthanum-rich misch metal Nickel-Jive (MlNis) particles suspended in liquid benzene was studied by investigating the influence of the reaction temperature, system pressure, alloy concentration and stirring speed on the mass transfer-reaction processes inside the slurry. The kinetic model of liquid-phase hydrogenation of benzene was developed, and the hydrogen absorption behaviors of Lanthanum Nickel-five (LaNi5)-Benzene and Raney Ni-Benzene slurry system were also investigated as a comparison.The research shows that the liquid-phase hydrogenation of benzene in MlNi5-C6H6 slurry system is a process controlled by the reaction conducted on the surface of the catalyst particles. The mass transfer resistance at gas-liquid interface and that from the bulk liquid phase to the surface of the catalyst particles can be ignored. The apparent reaction rate is zero order for benzene concentration and first order for hydrogen concentration in the liquid phase. MlNis alloy can be the catalyst of the hydrogenation reaction of benzene in liquid-phase and the conversion of benzene can reach 100%, and the saturated hydrogen absorption capacity of 50wt% MNi5-C6H6 slurry reaches 4.12wt%. In the temperature range of 393K~513K, the activation energy of the hydrogen absorption reaction of MlNi5-C6H6 slurry system is 42.16KJ/mol, and the apparent kinetic model can be expressed as follow:The experimental researches on LaNi5-C6H6 slurry system and Raney Ni-C6H6 slurry system shows that LaNi5 and Raney Ni can also be the catalyst ofhydrogenation of benzene in liquid-phase, and the conversion of benzene can reach 100%. The catalytic activity of Raney Ni is much higher than those of LaNis and MINis, and the catalytic activities of LaNis and MlNi5 are similar. The saturated hydrogen capacities of 50wt% LaNi5-C6H6 and 50wt% MNi5-C6H6 slurry systems reach 4.12wt%. However the saturated hydrogen capacity of 0.5wt% Raney Ni-C6H6 slurry system is about 7.15%, which is quite close to the saturated hydrogen capacity of benzene. The apparent activation energies of the hydrogen absorption reactions of MNi5-C6H6, LaNi5-C6H6 and RaneyNi-C6H6 slurry systems are 42.16KJ/mol, 52.50kJ/mol and 72.21kJ/mol, respectively.