Investigation on fluorinated alumina catalysts prepared by the fluorination of γ-Al₂O₃ with CHF₃ for the isomerization of E-1-chloro-3,3,3-trifluoropropene

As an environmentally friendly cleaning agent, Z-1-chloro-3,3,3-trifluoropropene (HCFO-1233zd(Z)) can realize industrial production by the isomerization of HCFO-1233zd(E). Herein, various isomerization catalysts with different structures, compositions and acid properties were prepared through the fluorination of γ-Al₂O₃ with CHF₃ by controlling the activation conditions. For the first time, the catalysts for HCFO-1233zd(E) isomerization were systematically studied by XRD, N₂ physisorption, XPS, SEM, MAS NMR spectroscopy, NH₃-TPD and py-IR. The active site of this reaction was revealed and the catalyst deactivation mechanism was proposed. It turned out that HCFO-1233zd(E) isomerization prefers to occur at Lewis acid sites with moderate density and strength. The amorphous particles composed of γ-Al₂O₃, Al₂O₃(F) and α-AlF₃ (R3¯c) at 450 °C exhibit highly catalytic activity for HCFO-1233zd(E) isomerization. After 100 h evaluation, it was found that residual γ-Al₂O₃ can be fluorinated by HCFO-1233zd(E) to form needle-like structures which could induce the amorphous Al₂O₃(F) particles to reorganize and give cubic structures, where the Lewis acid properties were enhanced, leading to catalyst deactivation.