Organosolv Treatment Using 1-Butanol and Degradation of Extracted Lignin Fractions into Phenolic Compounds over Iron Oxide Catalyst

Abstract

Organosolv treatment of Japanese cedar wood with silica–alumina catalyst in a water/1-butanol mixture and conversion of the recovered lignin fractions into phenolic compounds by catalytic cracking over an iron oxide catalyst were investigated. Organosolv for separation of lignin fractions from solid cellulose was carried out in an autoclave reactor at 423-523 K with/without silica–alumina catalyst. The average molecular weights of the lignin fractions obtained with/without the catalyst were 2060 and 2501, respectively, indicating that the catalyst was effective for depolymerization of lignin. Cellulose was significantly decomposed over 503 K with the catalyst, increasing the difficulty of separating lignin and cellulose. Therefore, the optimum treatment temperature was determined around 473 K to separate lignin fractions from solid cellulose. Moreover, the lignin fractions were extracted predominantly into the 1-butanol phase based on analyses of the molecular weight distributions and pyrolysis-GC-MS of the liquid products. Next, catalytic cracking of the obtained 1-butanol phase, which was rich in the lignin fractions, was performed over an iron oxide catalyst using a high-pressure fixed-bed flow reactor at 673 K. Consequently, degradation of the lignin was observed and the carbon yield of phenolic compounds after the reaction improved to 9.6 C-mol% based on the lignin fractions.