Kinetic Study of the Oxychlorination Process

Abstract

The aim of this paper is to investigate the performance and stability of the non-promoted, potassium, cerium and mixed potassium/cerium promoted CuCl2/gamma-Al2O3 during oxychlorination of ethylene using mass spectroscopy and in situ operando UV-Vis spectrophotometry.

In addition, two novel investigative methods was used and evaluated with respect to accuracy and reproducibility. Most important, a novel approach combining in situ operando time and spatial resolved UV-Vis spectrophotometry and mass spectroscopy to map and quantify the oxidation state and kinetics of the catalyst during catalytic cycles. Secondly, a method of rational catalytic design combining transient kinetic data to predict the catalytic performance and oxidation state at reaction conditions approaching steady state.

It was found that as the system approaches steady state conditions, cuprous copper chloride dominates the catalyst surface of the non-promoted catalyst as a result of the transient oxidation being rate determining. Promoting the catalyst was able to shift the rate determining step causing copper species to reside as mainly cupric copper and hence increasing the overall activity.

Experimental results demonstrated that potassium and cerium provides different, and possibly incompatible routes to an increased fraction of cupric copper as the effect of the individual promoter are not additive in the mixed catalyst. As cerium increases both transient rates while potassium decreases the reduction rate and increases the oxidation rate, cerium promotion resulted the highest activity in a reasonably oxidized catalyst while potassium promotion resulted in the most oxidized catalysts at moderate activity level.