Continuous catalytic hydrodechlorination of polychlorinated biphenyls (PCBs) in transformer oil

Abstract

Continuous catalytic hydrodechlorination of polychlorinated biphenyls (PCBs) in the presence of transformer oils was carried out in a fixed bed reactor using a 57.6 wt% Ni on silicon oxide-aluminum oxide (SiO₂-Al₂O₃) catalyst. Reaction temperatures ranging 150–300°C, PCBs concentrations ranging 50–200 ppm, and reaction times ranging 1–8 h were tested. At a higher reaction temperature or at a lower PCBs concentration, catalytic activity was higher and complete dechlorination of PCBs resulted even at long reaction time. Catalyst regeneration using hexane and 0.1 M sodium hydroxide (NaOH) was effective to restore the catalytic activity. Fresh, spent and regenerated catalysts were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis. XRD analysis revealed growth of Ni crystallite size of the spent and the regenerated catalysts. XPS analysis showed that a considerable amount of chlorine and carbon species were deposited on the surface of the spent catalyst, which may play a role in the catalysts deactivation.

Keywords:

• Transformer oil
• PCBs
• continuous hydrodechlorination

Acknowledgments

This work has been supported by the Ministry of Environment, Republic of Korea.