(253j) Continuous Selective Hydrodeoxygenation (HDO) of Guaiacol to Cycloalkanes Under Near-Ambient Conditions

Many parallel efforts are underway to produce next-generation clean fuels from lignin in order to reduce reliance on petroleum feedstock. In this work, we developed a continuous selective hydrodeoxygenation (HDO) process of guaiacol conversion to cycloalkanes under near-ambient conditions, leading to deeper understanding of HDO chemistry of lignin conversion. Previous reports of guaiacol conversion under near-ambient conditions (<200 ^oC and 4 MPa) suffers from low conversion and low selectivity of HDO products in addition to catalytic site poisoning. In order to overcome these challenges, the typical incipient wetness impregnation method was modified to improve HY zeolite-supported Ru catalyst synthesis. Results showed that metal dispersion and acid site uniformity were improved. The modified catalyst (Ru-HY-60-MI) was then tested in a continuous fixed bed reactor, resulting in increased HDO reaction of guaiacol to cycloalkanes at 180 ^oC and 1 MPa compared to the original catalyst. Pressure, temperature and WHSV dependent tests validated guaiacol HDO mechanism over Ru-HY-60-MI through metal-catalyzed ring hydrogenation of guaiacol to 2-methoxy-cyclohexanol followed by acid-catalyzed demethoxylation and dehydration to cyclohexene and subsequent metal-catalyzed hydrogenation of cyclohexene to cyclohexane. This insightful understanding of continuous guaiacol HDO is key to improve the efficiency of the continuous HDO of lignin to jet fuel hydrocarbons and enable the process scale-up for a more sustainable biorefinery.