Hydrogenation–dechlorination of 2-chloro-4,6-dinitroresorcinol over Pd/C catalysts

Pd catalysts supported on active carbon (Pd/C) prepared by impregnation–deposition were used in catalytic hydrogenation and hydrodechlorination (HDC) of 2-chloro-4,6-dinitroresorcinol (CDNR). Characterization by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy, and transmission electron microscopy revealed Pd species in the form of ~3.0-nm Pd nanoparticles composed of Pd0 and Pdn+ dispersed highly on active carbon. Pd/C catalysts with high Pd0/(Pd0 + Pdn+) exhibited high active for hydrogenation of CDNR, while the yield of the target product 4,6-diaminoresorcinol (DAR) largely depended on the solvent media. The correlations of the dielectric constants of the solvents with the activity and selectivity were obtained. Alkanol or acetic acid aqueous solutions were favorable for HDC. No 2-chloro-4,6-diaminoresorcinol product was detected when the reaction was carried out using 80 % ethanol/water media. XPS, energy-dispersive spectroscopy, and high-resolution transmission electron microscopy revealed that strong Cl adsorption caused the decrease in activity and selectivity for DAR of the Pd/C catalysts.