Abstract:The catalytic hydrogenation of 2,4-dinitroaniline with a 0.5 wt% Pt/TiO2 was investigated in a multiphase medium of tetrahydrofuran (THF) pressurized by CO2 at different pressures and at 323 K. When CO2 pressure was raised, the overall rate of hydrogenation simply decreased but the selectivity to the desired product of 4-nitro-1,2-phenylenediamine increased. The noticeable enhancement of the selectivity to 4-nitro-1,2-phenylenediamine can be explained by chemical actions of CO2 molecules.In situ high-pressure FTIR and molecular simulations demonstrate that the dissolved CO2 molecules may interact with amino group of the substrate and weaken the intra-hydrogen bonding between the amino and 2-nitro groups, which results in the change of the relative reactivity of the two nitro groups, yielding the desired product in a higher selectivity. The change of the intra-and inter-molecular interactions between the substrate and CO2 molecules was theoretically examined by DFT calculation.2
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