Energy Sciences

While examining the heterogeneous reaction of chlorine atoms with alkenes, in the presence of Cl₂, we have observed an unexpectedly large enhancement of reactivity and the predominance of chlorinated reaction products even under high O₂ conditions, where Cl atom recycling is expected to be minimal. These observations cannot be explained by known free radical oxidation or cycling mechanisms, but rather we find evidence for the multiphase catalytic coupling of free radical oxidation with electrophilic Cl₂ addition. The mechanism entails the production of oxygenated reaction intermediates, which act as gas-liquid phase-transfer catalysts (gl-PTCs) by promoting the accommodation of gas-phase Cl₂ by the aerosol, thereby enhancing electrophilic addition. Although the majority of PTCs typically couple chemistry between two immiscible liquid phases (aqueous/organic), there are few examples of PTCs that couple gas-liquid reactions. This work shows how multiphase reaction schemes of aerosols can be reimagined for understanding catalytic reaction mechanisms.