Depolymerization of Kraft lignin into liquid fuels over a WO3 modified acid-base coupled hydrogenation catalyst

Abstract

Lignin depolymerization to prepare valuable liquid fuels and phenolics is an important route to improve its efficient utilization, whereas some intractable challenges remain on account of the recalcitrant three-dimensional structure and the depolymerized intermediates are apt to condensation. Although some catalysts can work on lignin model compounds, the depolymerization rate is unable to compete effectively with the condensation reaction in the actual lignin depolymerization process. Based on this, the selective adsorption and activation of the C-O and C–C bonds, as well as the stabilization of depolymerization intermediates are essential to achieving efficient lignin depolymerization. Herein, a novel W-modified acid-base coupled hydrogenation catalyst was reported for the effective lignin conversion to generate liquid fuels. The Lewis acid sites WOx and TiO2 as well as the base sites MgO were favorable for adsorption and polarization of C–C and C-O bonds, promoting the cleavage of C–C and C-O bonds, while the hydrogenation site NiO activated the H2 molecular and inhibits the condensation reaction of reactive intermediates. Thereby, the cleavage of C-O and C–C bonds was facilitated by selective hydrodeoxygenation, leading to enhanced yields in petroleum ether solubilities and monomers. After reacting at 300 °C for 24 h, 63.03% petroleum ether solubles yield (mainly monomers and dimers) and 21.56% monophenol yield obtained with the HHV increased from 25.41 MJKg−1 to 33.90 MJKg−1, and the reusability was accredited.