Potassium-modified bifunctional MgAl-SBA-15 for aldol condensation of furfural and acetone

Abstract

The aldol condensation of furfural and acetone followed by hydrodeoxygenation into bio-jet fuel range alkanes and bio-polyester diols has attracted intensive interest in recent years. Such sequential reactions require a careful tailoring of one or more catalysts consisting of metal and acid–base active sites that can efficiently promote the two step cascade aldol condensation and hydrodeoxygenation. Here, we have begun developing a prominent base catalyst for mild aldol condensation of furfural and acetone by synthesizing acid–base bifunctional MgAl-SBA-15 and further modifying it with potassium. The catalyst with the highest basic site loading of 0.27 mmol g⁻¹ showed a furfural conversion of 83% and 99% total selectivity to products comprising 54% 4-(2-furyl)-4-hydroxy-butan-2-one (FAc-OH, a C₈ alcohol intermediate) and 23% of each 4-(2-furyl)-3-buten-2-one (FAc) and 1,4-pentadiene-3-one,1,5-di-2-furanyl (F₂Ac) (C₈ and C₁₃ aldol condensation products, respectively) after 3 hours of reaction, at 50 °C. Though a higher loading of potassium causes severe blockages of mesopores and inaccessible acid sites, the catalyst could still be regenerated by open-air calcination and be re-used for considerable cycles with fair catalytic performances. Overall, the present study can be the stepping stone for future investigations on further tuning of non-interfering active sites in SBA-15 to promote an efficient one-pot transformation of furfural and acetone via the two-step cascade aldol condensation and hydrodeoxygenation.