Promoting effect of MoO3/Al2O3 catalysts fluorination on their reactivity in propylene metathesis

Supported MoO3/Al2O3-F catalysts were synthesized and characterized by Raman, IR, and NMR spectroscopy. It was shown that support fluorination leads to partial substitution of surface OH groups with F which is accompanied by increases the strength of both LAS (Lewis Acid Sites) and residual bridging OH groups. But the change in the acidity doesn't affect the structure of surface molybdenum forms. An increase of the fluorine content on γ-Al2O3 up to 6 wt% leads to 4.7-fold increase of the propylene conversion in metathesis reaction (WHSV = 11 h−1, T = 100 °C, p = 9 atm.) with selectivity above 95 %. The results prove that the support acidity plays an important role in the propylene metathesis. The catalyst modification method proposed here opens new opportunities for the improvement of classical metathesis catalysts.