Accelerating Effects of Diluents on the Pyrolysis Rates of Chlorodifluoromethane

Abstract

The acceleration effects of diluents (steam and/or nitrogen) on the pyrolysis of chlorodifluoromethane (R 22) have been examined. The reaction was carried out under atmospheric pressure by a flow method in the temperature range from 640 to 850° C. The residence time in the adiabatic tank reactors was less than 1 s. The diluents-R 22 molar ratio was varied from 0.2 to 9.0. Temperature dependence of the over-all 1 st-order rate constants in the absence of a diluent was given by equation (1).
k₀=10^9.82, exp{-467001500R(ca1)T}SeC-1(1)
The activation energy was not affected by the kind and concentrations of the diluents (Fig.7). The pyrolysis rate of R 22 in the presence of nitrogen was expressed by equation (2), which was found to be applicable to the reported data for the pyrolysis of R 22 under the conditions of
k=k₀exp{0.92p_D/(p_R)} (2)
reduced pressure and in the presence of helium (Fig.3). Acceleration effect of steam was shown by equation (3) (Figs.4, 5 and 6).
k=k₀(1+p_W/p_R)^0.82 (3)
Effects of dilution by nitrogen or helium, and of reduced pressure are attributed to the catalytic effect of wall surfaces, whereas the acceleration by steam seems to be caused by the association of the H₂O and HCl molecules in the gas phase.