Efficient Route for the Production of Isoprene via Decarboxylation of Bioderived Mevalonolactone

Abstract

Isoprene production from biomass via solely biochemical processes is inherently limited by the low yields of the biological pathways. In this work, we demonstrate that isoprene can be efficiently produced via a hybrid bio/thermochemical process, combining the efficient fermentation of cellulosic sugars to mevalonolactone (MVL) with the acid-catalyzed MVL decarboxylation to isoprene. We report herein the thermochemical conversion of MVL to isoprene over inexpensive amorphous SiO2/Al2O3. A detailed investigation into the reaction conditions and the Si/Al ratio shows that isoprene formation is maximized over high-SiO2-content samples at mild temperatures (225-250 °C) that prevent its secondary oligomerization to alkylated aromatics and cyclic olefins. The highest isoprene yield is attained over SiO2/Al2O3 with 90 wt % SiO2 at 250 °C and 1.4 h-1, corresponding to ∼60% of the theoretical maximum. Acidity-performance correlations reveal the key role of Brønsted acidity in the reaction.