Statistical analysis of the effects of carbonization parameters on the structure of carbonized electrospun organosolv lignin fibers

Organosolv process is among the top choices for pretreatment of lignocellulosic biomass in cellulosic ethanol production. The lignin obtained as coproduct of this process is a low molecular weight biopolymer. Development of high-value application for this material enhances the economic viability of the bioethanol production process. In this study, aqueous sodium hydroxide solution of organosolv lignin/poly(ethylene oxide) (PEO) blend with 95/5 wt % ratio was electrospun. The fiber morphology and thermal properties were compared with organosolv lignin/PEO fibers electrospun from N, N-dimethylformamide (DMF) solution. Although organosolv lignin powder and fibers spun from DMF had a low T-g (similar to 100 degrees C), the fibers from alkaline aqueous solutions did not exhibit a glass transition point and could be carbonized without thermostabilization. The effects of carbonization heating rate, temperature, and time on the average fiber diameter, Raman peaks, and X-ray diffraction results of the carbonized electrospun fibers were statistically analyzed by using a two-level factorial design of experiments. Carbonization temperature, time, and interaction of these two parameters have the most significant effects. Formation of graphitized structures in the carbonized fibers was confirmed by transmission electron microscopy (TEM). The alkaline aqueous electrospinning of organosolv lignin has the advantages of using a green solvent, ability to increase the lignin content of fibers to more than 95 wt %, and removing the time and energy intensive step of thermostabilization before carbonization. (C) 2016 Wiley Periodicals, Inc.