Lignin-first biorefinery: a reusable catalyst for lignin depolymerization and application of lignin oil to jet fuel aromatics and polyurethane feedstock†
Lignin-first biorefinery is a novel concept, which was developed recently with great potential. This paper addresses two important issues in the lignin-first biorefinery: catalyst regenerability and lignin depolymerized product application. It was found that SiC is an effective and regenerable catalyst support, and the catalytic performance of Ru/SiC is comparable to the state-of-the-art results obtained from Ru/C used in the lignin-first biorefinery under identical conditions. Furthermore, the Ru/SiC catalyst can be regenerated by calcination without decrease in the catalytic performance. The resulting lignin oil from Ru/SiC catalyzed lignin depolymerization was then extracted by hexane, which is an optimized solvent for lignin oil upgradation based on model compound screening, and around 50 wt% of the hexane extract was obtained. The hexane extract was converted into aromatic hydrocarbons by ambient pressure hydrodeoxygenation over MoO3 catalyst. With a 15% blend of the resulting aromatic hydrocarbons, the jet fuel from the hydroprocessed ester and fatty acid (HEFA) meets the density requirements of the ASTM 7566 standard without compromising other required properties. The residue from hexane extraction was successfully used for preparation of rigid polyurethane foam (RPF) as an alternative to polyols of up to 50 wt%. The lignin based RPF not only reduced the use of fossil derived polyols, but also resulted in better water and flame resistance based on tentative LOI assessments. A biorefinery system was then proposed based on the technology developed in the present study.