Pd-Fe/SiO2 Catalysts in the Hydrogenation of 2,4-Dinitrotoluene

Pd-Fe/SiO2 bimetallic catalysts with a constant amount of Pd and a different Fe/Pd ratio were prepared by sequential wet mpregnation and the hydrogenation of 2,4-dinitrotoluene was arried out at 25'C in a batch reactor. The presence of Fe nhances the Pd catalytic activity. The formation of a disperse Pd-Fe alloy was evidenced through X-ray powder diffraction nd is consistent with the data observed by FTIR analysis, TPR, nd chemisorption features. The increase of the Fe total conten f the catalysts results in the increase of the dispersion of the metallic phase and in the presence of partially oxidized Fe pecies. FTIR analysis shows that nitrocompounds chemisorb mainly on the support rather than on the metal surface. It is uggested that the Pd-Fe alloy formation is responsible for the ncrease of the catalytic activity because of a cooperative effect of Fe in the hydrogen transfer step.