Robust dehydrofluorination of HFC-245fa to HFO-1234ze via in situ VOFx formation over a non-oxalic acid assisted V2O5/γ-Al2O3 catalyst.

Abstract

The demand for trans-1,3,3,3-tetrafluoropropene [HFO-1234ze(E)] as a next-generation, low-global-warming-potential (GWP) refrigerant is rising due to international restrictions on high-GWP refrigerants like chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs). Catalytic dehydrofluorination of HFC-245fa offers a viable synthesis route for the production of HFO-1234ze(E), but the catalyst degradation under harsh acidic conditions remains a major challenge. In this study, a highly stable γ-Al₂O₃ supported catalyst was developed for efficient dehydrofluorination with vanadium species exhibiting the highest activity among the screened metal ions Ni²⁺, V⁵⁺, Zn²⁺, La³⁺, Fe³⁺, Mn²⁺ and Cu²⁺. The optimized 15 wt% V₂O₅/γ-Al₂O₃ catalyst, prepared without oxalic acid assistance, exhibited strong metal-support interactions and demonstrated superior catalytic performance achieving ∼95% HFC-245fa conversion. The catalyst activity increased from 1.3 to 2.1 μmol s^-1 g_cat^-1 due to the formation of in situ VOFx species generated through the interaction between V₂O₅ and HF, as confirmed from NH₃-TPD and XPS analysis. The catalyst also exhibited ∼81% selectivity towards HFO-1234ze(E) at 350 °C. It is noteworthy that the catalyst maintained a stable performance up to 74 h, without significant deactivation. Overall, these results highlight the importance of rational metal selection, loading optimization, and interface engineering in developing robust catalysts for industrial hydrofluoroolefin production.