Dilute-acid conversion of cotton straw to sugars and levulinic acid via 2-stage hydrolysis

Systemic study on thermal dilute-acid hydrolysis of cotton straw has been conducted. The process of sequential two-step reaction has been established, which can greatly improve the utilization efficiency of lignocellulosic biomass. The hydrolyses were carried out in an 1 L erlenmeyer flask placed in the pressure steam sterilizer, where the hydrolysis retention time (0–60 min), liquid to solid ratio (8–14:1) and acid concentration (0–1 mol/L) were examined for the first stage. Optimization of first stage hydrolysis is desirable to achieve the highest yield of the sugars from hemicellulose and also as a pretreatment for the second acid hydrolysis. The solid residuals were further dilute-acid (0.2 mol/L) hydrolyzed in this study. This second-stage hydrolysis mainly completed the conversion of cellulose to levulinic acid and formic acid. At last, dilute-acid conversion of cotton straw to sugars (in the first stage), levulinic acid and formic acid (in the second stage) was completed.

► Dilute-acid hydrolysis of cotton stalk.
► The variables examined were temperature, retention time, liquid to solid ratio and sulfuric acid concentration.
► The hemicellulose fraction of cotton stalk was converted to sugars.
► The cellulose section to levulinic acid subsequently.