Catalytic hydroxyalkylation/alkylation of 2‑methylfuran with butanal to form a biodiesel precursor using acidic ion-exchange resins

Abstract

The catalytic hydroxyalkylation/alkylation of 2-methylfuran (2MF) with butanal has been investigated over several acidic ion-exchange resins within the temperature range 50−90 °C and at a stoichiometric reactant molar ratio of 2MF/butanal (2:1). Butanal conversion increases with temperature and also the formation of undesired 2-methylfuran oligomers, leading to a decrease in yield to the target product. The highest butanal conversion (90%) is achieved at 50 °C over Dowex 50Wx2 with a negligible formation of 2-methylfuran oligomers. The observed catalytic activity and final yield to the target product have been rationalized on the basis of morphological properties of resins and their dynamic behavior within the present reaction medium. The findings reveal that gel-type resins are more active and render higher product yields than their macroreticular congeners due to the enhanced accessibility to acid centers because of their improved ability to swell throughout the reaction. Macroreticular resins with a low cross-linking degree, e.g., Amberlyst 39, also produce interesting catalytic results. The stability of the most promising catalyst has been evaluated after three reaction cycles, and the full reusability outcome speaks for its appropriateness as a potential catalyst for the studied process.