Solvent free continuous hydrogenation of chloronitrobenzene over Pt/amide group grafted AC catalysts

Abstract

Solvent-free hydrogenation of chloronitrobenzene is considered as the most efficient and cleanest method for the production of chloroanilines which are important intermediates in the medicine, pigment and dye industry. However, it is difficult to suppress the side reaction of dechlorination in the solvent-free hydrogenation process. Herein, a novel Pt /amide group grafted AC catalyst was prepared by covalently grafting N-containing groups on commercial activated carbon which forms amide bond for solvent-free hydrogenation of chloronitrobenzene. Several Pt /amide group grafted AC catalysts grafted with different N-containing groups were prepared and experimental results indicate that Pt /amide group grafted AC catalysts covalently grafted with 1,3-cyclohexanediamine exhibit excellent performance on the suppression of dechlorination. The characterization results reveal that Pt/C catalyst grafted with 1,3-cyclohexanediamine has a narrower particle size distribution and smaller average size in comparison with Pt/C. The catalyst was evaluated in the solvent-free continuous hydrogenation of o-CNB to o-CAN and no dechorinated products was detected and high yield of o-CAN (more than 99.9%) was obtained in the range of 50∼120 ℃ compared with the severe dechlorination using Pt/C catalyst (yield of dechlorinated products≥70%). Additionally, no catalyst deactivation was observed in 200 h and turnover number per mole active metal (12290) is higher than the catalysts reported in the literatures (364∼9280) exhibiting the remarkable stability of Pt/C-N catalyst.