The use of carbon black to catalyze the reduction of nitrobenzenes by sulfides.

Using carbon black (CB) as catalyst, the reduction of nitrobenzenes (NBs) to anilines by sulfides at room temperature was studied. In the reactions, CB serves as an intermedium to accelerate the reduction of NBs by sulfides. In the presence of 0.3g/L CB and 3.0 mM sulfides at pH 7.0 and 25°C, our results showed that CB-catalyzed reduction of NBs were pseudo-first order. The reduction rate constant of nitrobenzene was 0.0367 h(-1) in the presence of CB-1, which was 10 times more than the reduction rate constant in the absence of CB-1. Other experiments of different CB samples produced by different methods and different raw materials indicated that some active oxygenated functional groups on CB surface should be the reactive sites and play the dominant role in catalyzing the reduction of NBs. The catalytic reactions of different NBs by sulfides indicated that the reduction rate constants of chloronitrobenzenes to chloroanilines were greater than those of methylnitrobenzenes to methylanilines. And due to the effect of different substituent positions, the nitro group with meta substituent was reduced most easily while the nitro group with ortho substituent was reduced most difficulty.