Naturally biodegradable polymer as an effective heterogeneous catalyst for synthesis of biofuels via Knoevenagel condensation strategy

Exploitation of natural biopolymers as heterogeneous catalysts for biomass valorization is highly attractive as it renders the production processes to be sustainable and increases the economic competitiveness of bio-refinery. Herein, sodium alginate was for the first time developed as heterogeneous base catalyst for Knoevenagel condensation of furfural and acetylacetone to produce high-quality fuel precursor. A furfural conversion rate as high as 89.58% along with 86.47% yield of 3-(furan-2-ylmethylene)pentane-2,4-dione was obtained in ethanol at 140 °C with 10 h. The excellent catalytic performance of sodium alginate in Knoevenagel condensation of furfural with acetylacetone was confirmed by the low value (10.8 kJ/mol) of as-obtained activation energy. In addition, a plausible reaction mechanism for Knoevenagel condensation of furfural with acetylacetone over sodium alginate was proposed. Moreover, sodium alginate almost sustained its original activity in consecutive six reuse experiments and the durability of sodium alginate was characterized by several techniques. Furthermore, other bio-based aldehydes such as 5-hydroxymethylfurfural and 5-methylfurfural were also applicable in the as-established system with producing the corresponding fuel precursor in excellent yields.