Temperature-Dependent Halogen-Exchange Activity Studies of Zeolite-Derived Aluminum Trifluoride

A high-surface-area (190 m 2 /g) amorphous aluminum trifluoride material (“plasma-AlF 3 ”) was synthesized by plasma decomposition of zeolite, and its structural and reactivity properties were investigated. High-resolution transmission electron microscopy of plasma-AlF 3 indicates morphological features on the nanometer-scale, whereas temperature-programmed X-ray diffraction is used to determine the phase-transition temperatures of plasma-AlF 3 to β- and α-AlF 3 . Halogen-exchange reactivity is studied by temperature-programmed reaction (TPR) techniques using the dismutation of CCl 2 F 2 as a model reaction. Plasma-AlF 3 is found to possess an unexpected low-temperature (>315 °C) activity not observed with the well-known halogen-exchange catalyst β-AlF 3 . Supporting TPR studies on aluminum trifluoride hydrates are performed to correlate this new activity with an amorphous AlF 3 structure, and a simple Lewis acid model is presented to explain the reactivity data.