Support effect of Rh catalysts on the hydrogenation of m-dinitrobenzene

MARTÍNEZ, JOSÉ J.; AGUILERA, EDNA X.; CUBILLOS, JAIRO; ROJAS, HUGO; GÓMEZ-CORTÉS, ANTONIO; DÍAZ, GABRIELA

Molecular Catalysis

Elsevier B.V.

Año: 2019 vol. 465 p. 54 - 60

2468-8231

The effect of the support (ZrO 2 , Al 2 O 3 , and TiO 2 ) 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, N 2 Adsorption, H 2 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/TiO 2 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 k 1 ) is faster than the second one (m-NA to m-PDA, kinetic constant k 2 ) and this depending on the catalyst. m-DNB preferentially adsorbs on electron deficient sites provided by Rh n+ species present in Rh/Al 2 O 3 and Rh/TiO 2 catalysts and depending on the relative amount of this sites the m-DNB is partially hydrogenated to m-NA. A direct correlation of k 2 /k 1 ratio with the amount of Rh° was found.