Dicarboxylic acids derived from lignin in yellow poplar during peracetic acid pretreatment

Peracetic acid (PAA) pretreatment has been used for production of fermentable sugar and ethanol, since the treatment has an advantage for removing lignin selectively under low temperature condition. Therefore, it has facilitated efficient separation of cellulose and lignin from biomass, and reduction of process cost. Meanwhile, most researches related to PAA treatment have focused on enhancement of enzymatic digestibility. PAA is known for a powerful oxidizing agent, and quite selective toward the lignin structure to oxidize aromatics in lignin generating dicarboxylic acids by aromatic ring cleavage. Production of valued chemical from the liquid hydrolysates after PAA treatment is also possible

The purpose of this study is to identify dicarboxylic acids derived from lignin in liquid fraction after PAA pretreatment. Yellow poplar (Liriodendron tulipifera) was used as a starting material. Peracetic acid was prepared by reaction of acetic acid and 30% hydrogen peroxide with volume ratio 1.5:1 at room temperature for 72 h. 1.5% sulfuric acid (w/w) was added as a catalyst. The reaction was conducted under the various conditions, which depend on liquid/solid ratio, reaction time, and temperature. After reaction, solid and liquid fractions were separated by filtration. The liquid fraction was extracted with organic solvent (dichloromethane and ethyl acetate) to obtain the lignin derived compounds, and then GC/MS analysis was carried out.   

The main compounds detected by GC/MS were followed as; glycolic acid, dimethylsuccinic acid, phthalic acid, oxalic acid, and lignin monomers (vanillic acid, and syringic acid). The quantitative analysis and the yield enhancement experiments will also carry out.