Properties of aluminum-fluoride catalysts prepared by the fluoridation of aluminum oxide with trifluoromethane

Abstract

High-purity AlF 3 has been prepared by allowing γ-Al 2O 3 to react with gaseous trifluoromethane at 670–770 K under 101 kPa total pressure. The use of gaseous trifluoromethane is a new, general method for preparing metal fluorides from metal oxides. AlF 3 prepared using this procedure retained the physical form of the starting γ-Al 2O 3. A 1 16 -in. γ-Al 2O 3 extrudate, for example, yielded an AlF 3 extrudate with comparable physical dimensions and crush strengths. X-Ray diffraction, BET surface area, pore volume, and surface acidity measurements were employed to characterize various AlF 3 samples. Significant decreases in surface area and pore volume as well as surface acidity occurred upon increasing the concentration of AlF 3 from 90 to 100%. This behavior presumably results from the fluoridation of residual γ-Al 2O 3. AlF 3 extrudates were utilized as supports for Pt and Pd catalysts. Specific benzene hydrogenation activities of these catalysts are comparable to those of Pt and Pd on γ-Al 2O 3. In a unique application, Pd AlF 3 was used to hydrogenate m-diethylbenzene in superacid ( HF TaF 5 ) solution.