LAUSR

Abstract The effect of the support (ZrO2, Al2O3, and TiO2) of Rh (1 wt%) catalysts for the hydrogenation of m-dinitrobenzene (m-DNB) in liquid phase was studied. The catalysts were reduced at 300 °C and characterized by EDS, TPR, TEM, N2 Adsorption, H2 chemisorption, XPS and Pyr-FTIR. Occurrence of partially reduced Rh species and metallic Rh is different among catalysts as evidenced by XPS. A typical SMSI effect was observed in Rh/TiO2 catalyst according to comparison of Hydrogen chemisorption and TEM results. Kinetic analysis of the m-DNB hydrogenation showed that the first step hydrogenation rate (m-DNB to m-NA, kinetic constant k1) is faster than the second one (m-NA to m-PDA, kinetic constant k2) and this depending on the catalyst. m-DNB preferentially adsorbs on electron deficient sites provided by Rhn+ species present in Rh/Al2O3 and Rh/TiO2 catalysts and depending on the relative amount of this sites the m-DNB is partially hydrogenated to m-NA. A direct correlation of k2/k1 ratio with the amount of Rh° was found.