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

摘要

Pd-Fe/SiO2 bimetallic catalysts with a constant amount ofudPd and a different Fe/Pd ratio were prepared by sequential wetudmpregnation and the hydrogenation of 2,4-dinitrotoluene wasudarried out at 25'C in a batch reactor. The presence of Feudnhances the Pd catalytic activity. The formation of a disperseudPd-Fe alloy was evidenced through X-ray powder diffractionudnd is consistent with the data observed by FTIR analysis, TPR,udnd chemisorption features. The increase of the Fe total contenudf the catalysts results in the increase of the dispersion of theudmetallic phase and in the presence of partially oxidized Feudpecies. FTIR analysis shows that nitrocompounds chemisorbudmainly on the support rather than on the metal surface. It isuduggested that the Pd-Fe alloy formation is responsible for theudncrease of the catalytic activity because of a cooperative effectudof Fe in the hydrogen transfer step.