Synergy of Al2(SO4)3 and H3PO4 in co-solvents converts starch to 5-ethoxymethylfurfural

Efficient synthesis of promising biofuel 5-ethoxymethylfurfural (EMF) directly from starch was developed over a mixed-acid system composed of Al2(SO4)3 and H3PO4 in ethanol−DMSO co-solvent medium. The reaction proceeds through the depolymerization of starch to form glucose over Brønsted acidic H3PO4, which is then isomerized to fructose by Al2(SO4)3, a Lewis acid catalyst. The mixed-acid system then synergistically catalyzes the formation of EMF. At 170 °C, 36.9%, 39.8%, and 34.7% yields of EMF can be captured from corn starch, amylose and amylopectin, respectively. Moreover, the conversion of cellobiose and wood pulp cellulose produces 38.5% and 9.5% yields of EMF. [Display omitted] •Efficient synthesis of promising biofuel EMF from starch in one-pot model was invented.•H3PO4 and Al2(SO4)3 had a positive synergistic effect on starch valorization to EMF.•DMSO co-solvent promotes glucose transformation and stabilizes EMF synthesis.•EMF yields from corn starch, amylose and amylopectin were 36.9%, 39.8% and 34.7%.•Reaction mechanism was proposed to explain the role of catalysts and co-solvent.