Enhancement of furfural-cyclopentanone aldol condensation using binary water-ethanol mixtures as solvent

BACKGROUND: Cyclopentanone (CPO) - furfural (FFL) aldol condensation is a very interesting reaction for upgrading the furfural obtained in the depolymerization - dehydration reaction of cellulosic materials. Reaction is faster with cyclopentanone than with other ketones, and resulting condensation adducts are attractive for manufacturing drop-in fuels. However, the most important problem is that these adducts present low water solubility. RESULTS: Binary systems combining water (needed to promote aldol condensation) and ethanol (for enhancing the condensation adducts solubility) at different ratios have been tested. Operation parameters, such as water/ethanol ratio, temperature and reaction time, were optimized for this reaction. Best results (global yield to condensation adducts higher than 36%) were achieved using 1:2 water/ethanol ratio, and working at 303 K. Higher water ratios lead to the precipitation of condensation products, whereas higher ethanol concentrations hinder the catalyst performance. A reaction mechanism, considering a first-order kinetic model on cyclopentanone concentration, was proposed. Kinetic constants have been empirically correlated with ethanol concentration in the reaction medium. CONCLUSIONS: The use of binary ethanol-water binary mixtures with controlled solvent ratios can avoid the precipitation of condensation adducts. This precipitation leads to important operation problems in the reactor as well as to catalyst deactivation. The negative effect of the presence of ethanol on the reaction kinetics can be overcome by increasing reaction temperature. (C) 2017 Society of Chemical Industry