The kinetics of the reverse deacon reaction

Abstract

The reverse Deacon reaction, Cl 2 + H 2O → 2HCl + 1 2 O 2 , is considered one of the most important steps in thermochemical water-splitting processes for production of hydrogen from water. The purpose for undertaking this research was to investigate the kinetics of the chlorination of water vapor at high temperatures. An eleven-pass glass reactor 4 mm ID and 511 mm long was used. Stimulus-response experiments showed the reactor could be analysed by plug flow procedures. The rate expression for the reverse Deacon reaction was developed from the experimental data at 879 K. Varying the partial pressures of the reactants, the rate data were collected, and these results were synthesized to formulate the rate law. The rate expression was verified by the integral approach and the results were extended to two other temperatures, 777 K and 983 K. The parameters of the rate expression were obtained by means of a linear-least-square fit. The frequency factor and the energy of activation were determined for the reverse Deacon reaction. An attempt was made to verify these parameters with the theoretical values from collision theory and activated complex theory. A mechanism consistent with one of the limiting conditions was postulated. A statistical study was also made to reveal the effects of the flow rates of the reactants and temperature on conversion of chlorine.