The Application of Enzymatic Pretreatment with Subsequent Pyrolysis to Improve the Production of Phenols from Selected Industrial (Technical) Lignins

The development of effective strategies for lignin valorization to valuable products is of high interest in various industries such as pulp and paper and the emerging bioenergy process. Indeed, the successful valorization of lignin could improve the profitability of these processes and their environmental performance. In this study, an original strategy involving the sequential application of enzymes and pyrolysis was explored for the conversion (i.e., valorization) of lignins to bio-oil rich in phenols. Methods Four technical lignins from different processes were pretreated for 24 h using the concerted depolymerization action of lignin peroxidase and quinone reductase enzymes. Pyrolysis was then performed on the pretreated and untreated (control) samples using a bench-scale tubular reactor at 550 ℃ for 30 min. Results Enzymatic pretreatment could contribute to a 17.5-82.3% increase in the bio-oil mass yield during subsequent pyrolysis. In some cases, enzymatic pretreatment also improved the production of total phenols in bio-oils by a maximum of 43%, with steam explosion (S-E) lignin showing the best performance. Of the four technical lignins, S-E and sodaanthraquinone lignins gave the highest production of monomeric phenols whereas the sulfite lignins were more challenging to valorize due to their high inorganic contents. Conclusion Enzymatic pretreatment could contribute to the valorization of some technical lignins to phenols during subsequent pyrolysis.