Investigation of the performance and deactivation behavior of Raney-Ni catalyst in continuous dehydrogenation of cyclohexane under multiphase reaction conditions

Abstract

The performance and deactivation behavior of Raney-Ni catalyst in continuous dehydrogenation of cyclohexane under multiphase reaction conditions were investigated in this paper. The experimental results showed that Raney-Ni had excellent catalytic activity for dehydrogenation of cyclohexane. Without assistance of any sweeping or carrier gas, the highest hydrogen evolution rate per unit reaction area could reach 0.20mmolcm−2min−1 at 322°C with a cyclohexane feeding rate of 8.5mmolmin−1 and Raney-Ni catalyst dosage of 3g. However, the deactivation of Raney-Ni catalyst was also observed during the course of reaction. The deactivation kinetics of Raney-Ni was studied, and the orders of deactivation at different reaction temperatures were determined, which showed that the decay of Raney-Ni catalyst was parallel deactivation. The equations of hydrogen evolution rates at different reaction temperatures were deduced from the deactivation kinetic equations. Due to the strong purging effect caused by the rapid evaporation of liquid organics on the catalyst surface under multiphase reaction conditions, the dehydrogenation reaction was confined to the outer layers of catalyst pallet and an ultralow apparent activation energy of 20.60kJmol−1 was obtained.