María H. Brijaldo

LIQUID-PHASE HYDROGENATION OF m-DINITROBENZENE OVER PLATINUM CATALYSTS

The m-dinitrobenzene hydrogenation to m-phenylenediamine in liquid phase was studied with platinum supported on SiO 2 , TiO 2 , Al 2 O 3 and Nb 2 O 5 catalysts. Incipient impregnation method was used to prepare the catalysts with 1wt% of Pt. The effect of the support and the reduction temperature (473 K or 773 K) were analyzed. The materials were characterized by X-ray diffraction (XRD), nitrogen physisorption (77 K), hydrogen chemisorption (298 K), transmission electron microscopy (TEM), temperature programmed reduction (H 2 -TPR) and temperature programmed desorption of ammonia (NH 3 -TPD). The results showed that Pt/ TiO 2 (HT) catalyst had a higher yield (60%) toward m- phenylenediamine and conversion level (98.2%) of m-dinitrobenzene. This behavior can be attributed to the reduction of PtO x crystallites to metallic Pt, small particle size and the strong metal-support interaction due to the migration of TiO x species on the Pt crystallites.

Hydrogenation of m-Dinitrobenzene Over Pt Supported Catalysts on TiO2–Al2O3 Binary Oxides

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 (k1 and k2) were determined and it whatever the catalyst, k1 is higher than k2. 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.Graphical Abstract