Microstructural characterization of doped-Pd/C catalysts for the selective hydrogenation of 2,4-dinitrotoluene to arylhydroxylamines

Pd/C catalysts doped with Fe, Sn and Ca for the selective hydrogenation of 2,4-dinitrotoluene (2,4-DNT) have been characterized by CO chemisorption, X-ray diffraction (XRD) and electron microscopy techniques (TEM-EDX). The promoters modify the microstructural and chemisorption properties of the noble metal particles with respect the undoped-Pd/C catalyst depending on the promoter nature and loading. Particles smaller than those observed on the monometallic catalysts were detected on Fe- and Sn-doped catalysts whereas larger particles were observed on the Ca-promoted samples. The promoters are located on the palladium particles, covering them and/or forming alloys with palladium. The role of the promoters in the selective hydrogenation of 2,4-DNT is discussed on the basis of the characterization results.