Catalytic hydrogenation of m-dinitrobenzene over Pt/TiO2-Al2O3 catalysts was investigated. The effect of the enrichment of TiO2 was analyzed. The results showed that the increase in TiO2 content produced an enhancement in the activity of the catalyst. In these consecutive reactions, both rate constants (k(1) and k(2)) were determined and it whatever the catalyst, k(1) is higher than k(2). The limiting step of the reaction was the transformation of m-nitroaniline to m-phenylenediamine. This behavior was explained by the modification in the acceptor-donor electron character of the group in the meta position.