Kinetics of the High-Temperature Heterogeneous Reaction of Chlorine and Nickel between 1200 and 1700°K

The kinetics of the reaction of gaseous chlorine with metallic nickel has been investigated in a constant pressure flow system in the temperature range from 1200° to 1700°K, and at chlorine pressures between 0.08 and 0.4 mm Hg. Nickel chloride produced in the over-all reaction, Ni(s)+Cl2(g)→NiCl2(g), is highly volatile at these temperatures, and the reaction thus takes place on the exposed metal surface. The process whereby nickel is removed from the surface is first order in chlorine pressure, very rapid with a collision efficiency between 0.5 and 0.2, and is temperature independent, i.e., Eact<2 kcal. The rate constant for the removal of nickel is found to be 1.85 × 103 cm sec—1, the units corresponding to moles of nickel per cm2of surface per unit density (M/cm3) of chlorine. An experimental technique employing time lapse photography is described which is particularly well suited to the study of the kinetics of high temperature surface reactions with volatile reaction products.