Highly selective hydrogenation of aromatic chloronitro compounds to aromatic chloroamines with ionic-liquid-like copolymer stabilized platinum nanocatalysts in ionic liquids

Abstract

Platinum nanoparticles (PtNPs stabilized by an ionic-liquid-like-copolymer (IP) immobilized in various ionic liquids (ILs)) effectively catalyze the selective hydrogenation of aromatic chloronitro compounds to aromatic chloroamines, a reaction of considerable commercial significance. The preparation of 2,4-dichloro-3-aminophenol (DAP) has been primarily studied due to its important industrial applications. DAP is usually prepared from 2,4-dichloro-3-nitrophenol (DNP) by reduction with hydrogen using Ni- or Pt-based catalysts. Compared to reactions in molecular (organic) solvents, the ILs system provides superior selectivity with functionalized ILs containing an alcohol group demonstrating the best recyclability, and ultimately achieving a turnover number of 2025 which is 750 fold higher than Raney nickel catalyst. A universal catalyst–ionic liquid system for the conversion of aromatic chloronitro compounds to aromatic chloroamines was also established. TEM, XPS, IR spectroscopy were used to characterize the morphology of the nanocatalysts allowing their structure to be correlated to their activity.