DOMINO REACTION FOR THE PRODUCTION OF GAMMA-VALEROLACTONE FROM FURFURAL TRIGGERED BY ZEOLITES WITH BR0NSTED AND LEWIS ACID SITES

摘要

Development of more carbon-efficient and economically viable lignocellulosic biomass conversion technologies is critical for the sustainable production of liquid transportation fuels and chemicals.1 The platform molecule y-valerolactone (GVL) has recently gained attention due to its capacity to be used as a fuel additive, be further processed into liquid alkenes, or be used as a polymer precursor. Here, we report an integrated catalytic process for the efficient production of GVL from furfural (Fur) via sequential transfer hydrogenation (TH) and hydrolysis reactions triggered by zeolites with Bransted and Lewis acid sites (Scheme 1). Our investigation uses Fur as a starting material because several well-established methods already exist for the production of Fur from hemicellulose.5 First, Fur is converted into furfural alcohol (FA) via a transfer hydrogenation reaction promoted by a Lewis acid catalyst and a hydrogen donor (e.g., 2-butanol). In the presence of an acid catalyst and 2-butanol, a fraction of FA is converted to furfuryl sec-butyl ether (FE). Next, a Bransted acid converts FA and FE into a mixture of LA and butyl levulinate (BL) via hydrolytic ring-opening reactions. Finally, both LA and BL undergo a second TH step to produce 4-hydroxypentanoates (4-HP) that spontaneously lactonize into GVL. In this work, a GVL yield of 78 mol% was obtained under optimal reaction conditions using a Zr-Beta as the Lewis acid and an aluminosilicate with MFI topology and nanosheet morphology (Al-MFI-ns) as the Bronsted acid. Both TH steps result in the oxidation of the hydrogen donor, which can be readily separated from the products and regenerated using inexpensive catalysts.6 Importantly, the catalysts, solvents, and mild reaction conditions used herein are compatible with those required to convert hemicellulose into Fur in high yields. Therefore, this catalytic system offers an attractive streamlined strategy for the production of GVL from lignocellulosic biomass without the use of precious metals or high pressures of molecular H2.