Phosgene formation via carbon monoxide and dichlorine reaction over an activated carbon catalyst: Towards a reaction model.

• The relative magnitude of reagent & product adsorption coefficients is determined. • Chlorine adsorption measurements indicate a distribution of active sites. • Desorption profiles indicate the presence of retained species post-reaction. • A reaction model is proposed to account for experimental observables. The reaction of carbon monoxide and dichlorine over an activated carbon (Donau Supersorbon K40) to produce phosgene is examined. Individual reagent and product breakthrough measurements over the clean catalyst establish the magnitude of adsorption coefficients (K) to follow the trend: K Cl2 > K COCl2 >> K CO. Chlorine adsorption measurements indicate a distribution of active sites that conforms to a two-site model, with the sites classified according to their enthalpy of adsorption. At 323 K, Type-I and Type-II sites exhibit respective adsorption capacities of 2.8 ± 0.3 and 1.5 ± 0.4 mmol Cl 2 g−1 cat. Post-reaction temperature-programmed desorption measurements alongside elemental analysis (SEM-EDAX) confirm the presence of retained chlorine moieties at the catalyst surface. These observations are rationalised within a postulated reaction scheme that accounts for sustained phosgene synthesis over the selected activated carbon. [ABSTRACT FROM AUTHOR]