Catalytic Performance for the Conversion of Potent Fluorinated Greenhouse Gases by Aluminium Fluorides with Different Morphology

The AlF 3 catalysts with controlled morphology (cubic, hexahedron and octahedron) were synthesized via hydrothermal method using different solvents. The dehydrofluorination of 1,1,1,3,3-pentafluoropropane (HFC-245fa) was used as the model reaction to evaluate the catalytic performance of the AlF 3 catalysts with different morphology. Results showed that surface area, crystal structure, surface acidic properties together with the chemical composition of the AlF 3 catalyst were substantially influenced by the different morphology. XRD results showed that κ-AlF 3 crystalline structure was formed when using ethanol as solvent while β-AlF 3 crystalline structure was formed when using water as solvent. Among the three prepared AlF 3 samples, the AlF 3 -C catalyst with cubic shape demonstrated not only largest surface area but also most amount of medium-strength surface acid sites, resulting in enhanced reaction activity towards the dehydrofluorination reaction. The characteristic high Miller index crystal planes of (402) and (321) exposed on the cubic shaped AlF 3 -C catalyst is believed to be the main reason accounting for the high catalytic performance as there are equal amount of Al and F atoms exposed. Moreover, a reaction mechanism describing dedehydrofluorination of HFC-245fa on AlF 3 catalyst with equal amount of Al and F atoms exposed on certain crystal planes was proposed. Graphic Abstract