Catalytic Conversion of Pyrolysis Oil to Alcohols and Alkanes in Supercritical Methanol over the CuMgAlO<i><sub>x</sub></i> Catalyst
Peter H. Galebach, Micaela Beussman, Jillian Johnson, Thomas Fredriksen, Chengrong Wang, Michael P. Lanci, George W. Huber
Abstract
Pyrolysis oil (PO) is an inexpensive biofuel produced via the fast pyrolysis of lignocellulosic biomass. However, PO is unstable and has low energy density, making it unsuitable as a fuel in conventional engines without upgrading. Supercritical methanol depolymerization and hydrodeoxygenation were used to convert PO to a mixture of alkanes and alcohols in a continuous packed-bed reaction using the CuMgAlOx catalyst. The PO was pretreated at low temperature to convert acids, aldehydes, and ketones. The pretreated PO was converted continuously for 11 h until the packed bed plugged from coke formation. The catalyst deactivated over time from the deposition of high molecular weight pyrolytic lignin (PL) species. Oxygenates and anhydrosugars in the sugar-rich aqueous fraction of PO were converted to C2-C6 alcohols, esters, and ethers through a mixed hydrodeoxygenation and Guerbet coupling reaction pathway. PL was converted to a mixture of oxygenated aromatics including naphthenes and cyclohexanols.