Computer-simulated degradation of CF₃Cl, CF₂Cl₂, and CFCl₃ under electron beam irradiation

Abstract

Electron beam treatment technologies should be versatile in the removal of chlorofluorocarbons (CFCs) owing to their exceptional cross sections for the thermal electrons generated in the radiolysis of air. Humidity, dose rates, O2 concentration, and CFC concentration influence the efficiency of the destruction process under electron beam treatment. Computer simulations have been used to theoretically demonstrate the destruction of chlorotrifluoromethane (CF3Cl), dichlorodifluoromethane (CF2Cl2), and trichlorofluoromethane (CFCl3) in the air (N2 + O2: 80% + 20%) in room temperature up to a dose of 13 kGy. Under these conditions, it is predicted that the removal efficiency is in the order CF3Cl (0.1%) < CF2Cl2 (7%) < CFCl3 (34%), which shows the dependence of the process on the number of substituted Cl atoms. Dissociative electron attachment with the release of Cl– is the primary process initiating the destruction of CFCs from the air stream. Reactions with the first excited state of oxygen, namely, O(1D), and charge-transfer reactions further promote the degradation process. The degradation products can be further degraded to CO2, Cl2, and F2 by prolonged radiation treatment. Other predicted products can also be removed through chemical processes.