Reactivity and catalytic activity of copper chlorides. Part 1.—Kinetics of the reaction of CuCl with chlorine

Abstract

The reaction of solid CuCl of average particle radius 8.75 µm with Cl2 gas at pressures of a few cmHg has been followed manometrically in the temperature range 75 to 130°C. Up to about CuCl1.2, the reaction proceeds at constant rate and shows zero or slightly negative apparent activation energy. In this region, the product continuously recrystallizes exposing fresh CuCl surface. At higher extent of reaction, the product layer builds up on each crystallite and diffusion becomes rate-controlling. From CuCl1.25 to CuCl1.62, the rate law is the appropriate modification of the parabolic law (a modified Ginstling-Brounshtein equation integrated over the particle size distribution), with tarnishing constant 2.18 × 10–12 cm2 s–1 at 130°C and activation energy 11.3 kcal mol–1. These values are compatible with migration of a defect at concentrations of the order of 0.1 % of cation concentrations in CuCl2. Propane affects the reaction rate in a manner depending on solid phase composition according to a two-peaked curve.