10-35: Lignin degradation of yellow poplar (Liriodendron tulipifera) by acid catalyzed organosolv pretreatment

This study was focused on the effect of acid catalyzed organosolv pretreatment (ACOP) on lignin degradation of yellow poplar. Stems of twenty years old yellow poplar (chemical composition: glucan: 36.18±0.01, xylan: 18.00±0.17, Klason lignin: 25.99±0.46, acid soluble lignin: 3.34±0.04) were dried and milled to a particle size of < 0.5 mm. ACOP was conducted in a 500 ml reactor at various conditions (reaction temperature: 100~200°C, acid concentration: 0.5, 1, 2%, reaction time: 10 min, S/L ratio: 1/10). 

After ACOP, water insoluble solid (WIS, solid fraction) recovery rates decreased with increased reaction temperatures, and these results were accelerated in case of higher acid concentration. Total lignin contents of WIS decreased gradually and minimized at 150°C (0.5%: 12.10±0.56, 1%: 13.87±1.36, 2%: 12.63±1.88). However above 170°C, those were significantly increased because of serious degradation of cellulose. Dissimilar to lower conditions, at 200°C, WIS recovery rate with 2% acid concentration was the highest. This result was probably due to re-condensation of degraded lignin fractions to WIS at high temperature. Yields of organosolv lignin obtained by precipitation of liquid fraction were reached over 12% based on initial input amount, and showed similar aspect to WIS recovery rates. Especially increment rate of yields were insignificant after 150°C, and declined after 190°C.

Further analysis of structural properties of WIS and organosolv lignin will be carried out to accomplish the lignin degradation mechanism of yellow poplar by ACOP.