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.

The authors acknowledge FEDER/Ministerio de Ciencia, Innovación y Universidades – Agencia Estatal de Investigación (CTM2017-85498-R), Comunidad de Madrid/UAM (SI1/PJI/2019-00487) and Junta de Andalucía (P20_00968) for financial support. The authors acknowledge the ALBA Synchrotron facility and Dr. Carlo Marini for beamtime at CLAESS (experiment 2016021666-2) and the contribution of the group of Professor Núria López at Institut Català d'Investigació Química (Tarragona, Spain). Maria Martin-Martinez acknowledges a postdoctoral grant (2017-T2/AMB-5668) from the Comunidad de Madrid “Atracción de Talento” program. Sichen Liu acknowledges Ministerio de Ciencia e Innovación for his research grant (PRE2018-084424).

Peer reviewed