Dehydrofluorination of 1, 1, 1, 3, 3-pentafluoropropane over C-AlF3 composite catalysts: Improved catalyst stability by the presence of pre-deposited carbon

A series of C-AlF3 composite catalysts were prepared using a sol-gel method and different aluminum precursors (i.e. aluminum isopropoxide (Al(OiPr)3) and aluminum diacetate hydroxide (C4H7AlO5)). These catalysts were very active in gas-phase dehydrofluorination of 1, 1, 1, 3, 3-pentafluoropane. For example, a catalyst calcined at 400 °C with aluminum isopropoxide as the precursor (denoted as C-AlF3-AIP-400) gave a reaction rate of 8.30 μmol s−1 gcat-1 and a selectivity to 1, 3, 3, 3-tetrafluoropropene (HFO-1234ze) of above 99% at 340 °C. More importantly, the C-AlF3 catalysts showed excellent stability during 100 h reaction, while the pure AlF3 catalyst suffered severe deactivation owing to the coke deposition on the surface. In contrast, pre-deposited carbonaceous species formed in the catalyst due to the incomplete decomposition of organic precursors during the preparation procedure, which blocked strong acidic sites in the AlF3 and thus maintained the catalyst stability. Therefore, these findings provide useful information on the development of efficient catalyst for this reaction, particularly on the maintainance of catalyst stability.