Furfural Upgrading by Aldol Condensation with Ketones over Solid-Base Catalysts
Aldol condensation reactions between furfural and various ketones were studied in a flow reactor at 373 K and 100 psi for application to upgrading of furfural. Specific rates for the reaction of acetone and furfural were measured on MgAl 2 O 4 , Al 2 O 3 , CaO/MgAl 2 O 4 and MgO/MgAl 2 O 4 and found to be highest on CaO/MgAl 2 O 4 . While the presence of CO 2 and H 2 O did not affect the stability of the CaO/MgAl 2 O 4 catalyst, the catalyst deactivated over a period of a few hours due to the production of 2-furoic acid formed by the Cannizzaro reaction. While aldol condensation rates between furfural and either 2-pentanone and decanal approached that of acetone, rates for 4-heptanone and 2,5-heptanedione were significantly lower because the α-hydrogens of the carbonyl compounds are less easily attacked in these molecules. The selectivity to aldol products is affected by the relative rates of the aldol-condensation and the Cannizzaro reactions. Possible strategies for maximizing production of the aldol products with larger ketones are discussed.