Continuous and Selective Hydrodeoxygenation of Lignin Phenolics to Cycloalkanes Under Moderate Conditions

Abstract

We report a continuous selective hydrodeoxygenation (HDO) process of guaiacol conversion to cycloalkanes under 180 °C/1 MPa, which results in improved HDO chemistry for lignin-based jet fuel production. The incipient wetness impregnation method was modified to prepare an HY zeolite-supported Ru catalyst with better metal dispersion and acid site uniformity, which overcomes the low conversion and selectivity of previous literature. The modified catalyst (Ru-HY-60-MI) was tested in a continuous fixed bed reactor, resulting in increased HDO conversion of guaiacol to cycloalkanes compared to the unmodified catalyst. Pressure, temperature, and weight hourly space velocity-dependent tests validate guaiacol HDO over Ru-HY-60-MI catalyzed ring hydrogenation of guaiacol to 2-methoxycyclohexanol, acid-catalyzed demethoxylation and dehydration to cyclohexene, and further hydrogenation of cyclohexene to cyclohexane. These experiments enable exploring a continuous HDO process, demonstrate effectiveness for other β-β and α-O-4 lignin representatives and real lignin bio-oil, and pave the way towards commercialization of lignin-based jet fuel.

Keywords: Continuous hydrodeoxygenation, Engeenired catalyst, Cycloalkanes, Lignin bio-oil, Moderate conditions, Sustainable biorefinery