Enhanced Dichlorodifluoromethane Decomposition with Selective Fluorine Absorption by Acidic Fluorinated Magnesium Oxide

CCl2F2 decomposition with simultaneous halogen absorption by partially fluorinated MgO (MgF2–MgO) was studied, focusing on the effects of the acidity of the surface. CCl2F2 decomposition by MgF2–MgO was greatly promoted by fluorination of MgO at 10 mol% or higher. CCl2F2 decomposition was not a catalytic process over MgF2–MgO but basically a selective fluorine absorption reaction with MgO to form MgF2. Chlorine was released in the form of CCl4 regardless of reaction temperature and degree of fluorination of MgO due to low reactivity to CCl4. NH3-TPD and pyridine adsorption experiments were carried out to characterize the acid sites on MgF2–MgO samples. The amount of acid sites became maximum for 10% MgF2–MgO and the strength of acid sites increased as fluorination proceeded. CCl2F2 decomposition was revealed to be initiated by Lewis acid sites on MgF2–MgO formed by CCl2F2 decomposition as well as by fluorination with hydrofluoric acid aqueous solution. Thus, formation of the Lewis acid sites was considered to be the key step for efficient CCl2F2 decomposition with selective fluorine absorption.