Kinetics of the direct chlorination of carbon

Abstract

Carbon, in the form of a wood char activated by treatment with air and chlorine, has been chlorinated directly at temperatures between 600º and 800º and at chlorine pressures between 3.5 and 20 atm in a flow apparatus to produce carbon tetrachloride as sole reaction product. The rate of formation R of carbon tetrachloride can be expressed by the equation R = ⁱlp_a where il is the rate constant for the chemisorption of chlorine on carbon and p_a is the partial pressure of chlorine. The rate is also dependent on the nature of the carbon, high temperature carbons being less reactive. The energy of activation for the process is 25 kcal mole^-1. When carbon tetrachloride is decomposed in a carbon bed, tetrachloroethylene, hexachloroethane, chlorine, and carbon are formed as products, the predominant species depending on the conditions. This indicated that the overall reaction is not given by the simple equation C + 2Cl₂ + CCl₄ (I) and, on prolonged reaction times, yields of carbon tetrachloride well below the amount expected at equilibrium for this reaction confirm the finding. p_a denotes the partial pressure of Cl₂, pb that of CCl₄, pc that of C₂C1₄, and p_a that of C_zCl₆.The subscript numerals to i and j refer to the equation numbers in the text.