Hydrophobic Pd/Al2O3 catalyst intensified nitrobenzene hydrogenation in flow

Designing efficient catalysts and solvent system for the multiphase hydrogenation reaction is vital in continuous flow reactors. Herein, we prepare hydrophilic Pd/Al 2 O 3 and hydrophobic modified C 12 PA-Pd/Al 2 O 3 catalyst for nitrobenzene (NB) hydrogenation in micropacked bed reactors (μPBRs). By tuning the methanol-water volume ratio, reaction temperature, reaction pressure, liquid and gas superficial velocity, the NB conversion and aniline (AN) yield are optimized. The highest NB conversion of 97.1% and AN yield 95.6% are obtained in μPBRs with hydrophobic C 12 PA-Pd/Al 2 O 3 at the reaction temperature of 90 °C. The apparent kinetic model is developed in μPBRs with two types of catalysts, and activity energies of NB hydrogenation for Pd/Al 2 O 3 and C 12 PA-Pd/Al 2 O 3 are 7.944 kJ·mol -1 and 3.372 kJ·mol -1 , respectively. It indicates that the catalytic efficiency of C 12 PA-Pd/Al 2 O 3 is better than that of Pd/Al 2 O 3 in the methanol-water mixed solvent in μPBRs. The value of TOF for the hydrophobic modified C 12 PA-Pd/Al 2 O 3 catalyst is twice compared with the hydrophilic Pd/Al 2 O 3 catalyst. The value of STY for μPBRs is higher than that of stirred tank reactors (STRs) and fixed bed reactors (FBRs).