X-ray photoelectron spectroscopy studies on ethylene oxychlorination catalysts

Abstract

Copper chloride on alumina catalyst used for oxychlorination of ethylene represents a typical system where copper is in a dynamic equilibrium between Cu⁺ and Cu⁺⁺ oxidation states. Surface studies on redox, structural and compositional properties have been undertaken to monitor the changes that occur on the catalyst during use and pinpoint causes for its deactivation. For this, a fresh and a spent catalyst were been chosen for characterization. A core consisting of copper in Cu⁺ state and present as CuAlO₂ is formed at the centre of the catalyst sphere. Formation of such a nonreversible phase under reaction conditions upsets the redox equilibrium. XPS also shows the absence of potassium in the core and its precipitation as a new phase on use, probably KCl, formed by the decomposition of active component KCuCl₃. These factors facilitate deactivation.