Catalytic Conversion of Pyrolysis Oil to Alcohols and Alkanes in Supercritical Methanol over the CuMgAlO<i>_x</i> Catalyst

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.