Improving catalytic activity and stability of ZrO2 and CeO2 in the vapor-phase intramolecular aldol condensation of 2,5-hexanedione to 3-methyl-2-cyclopentenone

Improving catalytic stability by reducing the coke formation is still important in ensuring the longevity of the catalyst, especially in acid-base sites catalyzed reactions. In this work, we successfully improved the catalytic activity and stability of ZrO 2 and CeO 2 catalysts in the aldol condensation of 2,5-hexanedione (HDO) to 3-methyl-2-cyclopentenone (MCP) by the Ag modification and operation in H 2 flow. ZrO 2 poorly catalyzed aldol condensation of HDO and was severely deactivated regardless of the reaction conditions. Similarly, the CeO 2 was also deactivated during aldol condensation of HDO even though it has a milder deactivation rate than ZrO 2 catalyst. The modification of ZrO 2 and CeO 2 with Ag and the operation in H 2 flow reduced the catalyst deactivation by reducing the coke accumulation on the catalyst, while still maintaining high selectivity to MCP. Consequently, the modified ZrO 2 and CeO 2 catalyst could maintain their high activity under prolonged time on stream. • Aldol condensation of 2,5-hexanedione was catalyzed by ZrO 2 and CeO 2 . • Both ZrO 2 and CeO 2 were deactivated regardless of the reaction conditions. • The Ag-modified ZrO 2 and CeO 2 maintained their high performance in H 2 flow. • The improvement of stability was due to the reduction of coke accumulation. • The modified CeO 2 gave a 3-methyl-2-cyclopentenone yield of 92 % at a TOS of 10 h.