Evaluation of oxy-organosolv pretreatment on lignin extraction from wheat straw

To develop a characteristic Lignin-first strategy, the oxy-organosolv delignification processes under mild conditions were comprehensively investigated. Results showed that lignin yield could achieve about 50 % under the optimum process conditions of ethanol concentration 80 %, temperature 90 degrees C, liquid to wheat straw ratio 25:1 for powdery-scale substrates, which was 65.0 % higher than that for rod-scale substrates under the same conditions. The lignin structural and carbohydrate component results demonstrated the employment of oxygen induced great quantities of lignin dissolving out on the premise of little carbohydrate component (<1 %) and lignin structural (mainly beta-O-4 units) changes. Moreover, based on the molecular weight and polydiversity comparison results, the aqueous oxygen could transfer homogeneously in mild organosolv system and result in lignin degradation uniformly. Besides, the employment of oxygen assisted in not only extending the massive lignin removal stage to 30 min and 50 min for P-OEEL and R-OEEL respectively, but also boost the delignification rate with comparison to P-EL and R-EL. Lastly, the excellent anti-oxidant properties of lignin from oxy-organosolv process were demonstrated by scavenging DPPH and ABTS radicals. The economic calculations showed that the cost for lignin production were about 1.58USD/g lignin from powdery-scale wheat straw, providing a competitive route for high-value utilize waste biomass.

Automated summary

A characteristic Lignin-first strategy was developed through comprehensive investigation of the oxy-organosolv delignification processes under mild conditions. The results showed that the lignin yield could reach about 50% under the optimized process conditions. The use of oxygen induced significant lignin dissolution without affecting the carbohydrate component and lignin structure, resulting in uniform lignin degradation. Additionally, the employment of oxygen extended the lignin removal stage and increased the delignification rate compared to conventional methods.