Efficient Continuous Production of the Biofuel Additive 5-(t-Butoxymethyl) Furfural from 5-Hydroxymethylfurfural

Abstract

The catalytic etherification of 5-hydroxymethylfurfural (HMF) with t-butanol to a biofuel additive 5-(t-butoxymethyl) furfural (t-BMF) is studied by screening 27 heterogeneous protic and/or Lewis acids. Preyssler heteropolyacid H14[NaP5W30O110] and Montmorillonite-based CLOI_CSP catalysts are identified as the most efficient ones, allowing the etherification to reach the t-BMF/HMF equilibrium faster (≈1:1), thus promoting minimum side reactions. Further optimization of the batch experimental conditions, namely catalyst loading, temperature, HMF concentration, time, t-BMF stability, and additives, allows the t-BMF/HMF equilibrium to be reached in less than 3 h with outstanding selectivity >95%. Under optimized conditions, CLOI_CSP is reused for four cycles without significant loss of efficiency. In addition, it exhibits high efficiency under flow conditions, allowing continuous production of t-BMF up to 0.7 g t-BMF g−1 catalyst min−1 at high concentrations of HMF.