Effect of reaction conditions on hydrothermal degradation of cornstalk lignin

Cornstalk lignin was hydrothermally depolymerized at mild conditions in ethanol–water for producing value-added phenolics. The effects of residence time (from 30 min to 180 min), reaction temperature (from 498 K to 573 K) and concentration of ethanol (from 0% to 95% vol.) on yields of liquid products and phenolic compounds were studied in detail. The optimal conditions of 523 K, 90 min and 65% vol. ethanol–water resulted in the highest yield of liquid products (∼70 wt.%). The liquid products were analyzed by gas chromatography–mass spectrometry (GC–MS) to confirm the presence of primarily heterocycle (2,3-dihydrobenzofuran) and phenolics (such as ethylphenol, guaiacol, ethylguaiacol and syringol). Reaction conditions had significant effects on yield and composition of liquid products.

► Lignin was hydrothermally depolymerized in ethanol–water at mild conditions.
► High yield of liquid products was obtained (∼70 wt.%).
► The liquid products were mainly composed of phenolics.