Reusability of Mg/Al catalysts for the aldol condensation of furfural and acetone in a continuous flow reactor

Hydrotalcite catalysts with a Mg: Al ratio of 3:1 were assessed for the aldol condensation of furfural with acetone on a continuous packed bed reactor. The as-prepared (FHT), calcined (CHT), and rehydrated (RHT) hydrotalcites were characterized and their activity was tested at 100 °C and 12 bar(a) with an acetone:furfural ratio of 10:1 at a furfural WHSV of 5.77 h −1 . FHT showed low conversion and deactivated fast. CHT and RHT exhibited complete conversion during 2 and 4 h, respectively, and deactivated to a 20 % conversion after 8–11 h. The main products were ( E )-4-(furan-2-yl)but-3-en-2-on (C8) and (1 E ,4 E )-1,5-di(furan-2-yl)penta-1,4-dien-3-one (C13). Small amounts of higher molar mass products formed by ketonization were observed, and they were linked to the deposition of insoluble oligomers. Reuse of the spent catalysts by recalcination to remove the organic deposits was evaluated for a total of four reaction tests. A gradual loss of performance was seen after each reactivation treatment. • The aldol condensation of furfural and acetone was tested with 3:1 Mg:Al hydrotalcite catalysts in a packed bed reactor. • The deposition of large oligomers deactivated the catalysts. Products up to 21 carbons were present in the liquid product. • The reuse of the catalysts was investigated in four consecutive cycles of activation and activity measurement. • The activity of the catalysts decreased and the selectivity of the different products shifted with each reuse cycle.