Multivariate approach for the optimization of sucrose ethanolysis: Paving the way to the exploitation of sucrose-rich by-products

The depletion of fossil resources is making the synthesis of renewable compounds urgent. Ethyl levulinate (EL) represents a strategic compound within the biorefinery process, being a valuable intermediate, solvent and biofuel additive of renewable origin. The one-pot ethanolysis is the preferred route for its synthesis, but the proper optimization of the reaction conditions to maximize the EL yield and minimize the critical by-products formation, diethyl ether (DEE) and humins, is still a challenge. In this regard, the present work aims at the optimization of sucrose ethanolysis through the multivariate approach, adopting H₂SO₄ as catalyst and following the high gravity approach (10.5 wt% sucrose loading), which allows the obtaining of concentrated EL streams, increasing productivity and making downstream operations easier and cheaper. The optimization allowed a compromise between the highest EL yield and the lowest DEE production, thus simplifying EL purification and consuming less solvent that can be recycled in the following run. Under these conditions, the humins formation was also kept low and, for the first time, not only the solid humins were characterized, proving to be suitable as solid fuel turning into a co-product of the process, but also the chemical structure of the soluble ones was investigated. For the first time, a preliminary study regarding the ethanolysis of thick juice was also performed, thus opening the way to the employment of low-cost sucrose-rich feedstocks as substrate for the synthesis of EL. Thus, this work contributes to making the synthesis of a strategic renewable compound as EL more sustainable.