Fast and Continuous Synthesis of 1-Methyl-2,4-cyclohexanediamine in a Micro-Packed Bed Reactor

1-methyl-2,4-cyclohexanediamine (2,4-MCHD) is the core raw material for the synthesis of high-grade polyurethane. Aiming at the problems of long reaction time and safety risks in batch reactors, a fast and safe synthesis scheme of 2,4-MCHD was proposed. The one-pot catalytic hydrogenation of 2, 4-dinitrotoluene (2, 4-DNT) to 2, 4-MCHD was investigated in a microfilled bed reactor (μPBR) over the 5%LiOH-5%Ru/γ-Al 2 O 3 catalyst. The effects of temperature, pressure, gas and liquid volumetric were investigated. Under the optimized condition (180 °C, 7 MPa H 2 pressure, 0.6 mL/min liquid flow rate, 40 mL/min gas flow rate), within a residence time of 144 s, the conversion of 2,4-DNT and the selectivity of 2,4-MCHD exceeded 99% and 80%, respectively. Compared to the conventional batch mode, an increase of one to two orders of magnitude in space-time-yield (STY) was realized under continuous flow mode. Furthermore, the inherent risks of high-pressure hydrogenation in batch processes are significantly mitigated in the μPBR due to its minimal hydrogen inventory and superior heat and mass transfer characteristics.