Aldol Condensation of Biomass-Derived Levulinic Acid and Furfural over Acid Zeolites

Acid-catalyzed cross condensation between furfural and levulinic acid is presented in this work as an alternative for manufacturing C10 chemicals from renewable platform molecules. First experiments conclude that the neutralization of the carboxylic group of levulinic acid is required to prevent side reactions such as cyclization. Two C10 products are obtained, suggesting two parallel reaction mechanisms. Different reaction conditions (temperatures and initial reactants ratios) have been tested, and results were used to propose a kinetic model. The role of the properties of different catalysts is also studied, analyzing the activity, selectivity and acidities of different zeolites structures (ZSM-5, MOR, BETA), observing a clear correspondence between medium-strength acidity and the production of the most stable product. A high selectivity to this compound is required to reduce the permanent adsorption and oligomerization of the starting materials, the main deactivation cause identified in this process. Thus, the best results were obtained with ZSM-5 (23) at 423 K and a LA/FFL ratio 2:1, with 50% of product yield and almost negligible relevance of side reactions (carbon balance after 24 h: 91%), observing a good behavior after three reusability cycles without any regeneration.