Upgrading of dichloromethane to olefins by hydrodechlorination: Improving process efficiency by the addition of Fe to carbon nanotubes-supported Pd catalyst

Abstract

Upgrading of waste dichloromethane to produce olefins has been performed by hydrodechlorination (HDC) using bimetallic catalysts consisting of Pd-Fe/CNT, Pd-Sn/CNT and Pd-Ag/CNT. Pd/CNT was also studied. Pd-Fe/CNT showed the best performance in terms of activity (X≈81 %) and stability, with the highest selectivity to olefins (>60 %, mainly C2H4), at 350 °C, which could be mainly attributed to the existence of stable Pd-Fe interaction. Characterization results and density functional theory calculations suggest that incorporating Fe atoms into the Pd lattice changes its electronic and geometrical properties. Fe atoms show stronger dissociative adsorption of CH2Cl2 than Pd ones, leading to lower activation energies for the dechlorination of CH2Cl2 on the studied Pd-Fe(1 1 1), which also favors the formation of C-C bond between two adjacent CH2*, promoting the formation of C2H4. Pd-Sn and Pd-Ag catalysts hinder olefins formation, due to the non-reactive Sn atoms and significant metal segregation in case of Pd-Ag.