Direct Solid Lewis Acid Catalyzed Wood Liquefaction into Lactic Acid: Kinetic Evidences that Wood Pretreatment Might Not be a Prerequisite

The objective of the present work was to determine if wood sawdust can be used instead of isolated cellulose in the general solid-acid-catalyzed production of chemicals. The kinetics of model cellulose and pine-wood sawdust liquefaction into lactic acid were determined in the presence of a solid Lewis acid, ZrW. The catalytic hydrolysis of pine wood was performed at 190 °C in a large-scale batch reactor (2.5 L). Similar kinetic curves of lactic formation were obtained for cellulose and wood as substrates. Moreover, the initial lactic acid production rate of pine-wood sawdust was higher than that of model cellulose, proving that, in spite of the presence of lignin/hemicellulose, the catalyst drives the transformation towards lactic acid formation. However, our results give also evidence of solid-catalyst deactivation for both cellulose and wood substrates. This result indicates that if wood pretreatment can be bypassed, the bottleneck will be the solid-catalyst regeneration and recycling.