AMMONIA CATALYZED ORGANOSOLV DELIGNIFICATION OF POPLAR

A parametric investigation of NH₄OH catalyzed solvent delignification of poplar was conducted to define pretreatment conditions which would yield an optimal separation of the biomass components and an enzymatic susceptible solid carbohydrate phase. Delignification parameters of interest included concentration of NH₄OH, time and temperature of the reaction, and type of solvent. The addition of 0.82 M NH₄OH to the delignification liquor increased lignin removal and decreased carbohydrate degradation, but increasing NH₄OH concentration had no additional effect. At lower reaction temperatures, the extent of delignification increased with reaction time; at higher temperatures, a “relignification” of the pretreated wood was observed. The delignification and hemicellulose solubilization were modelled and rate constants reported. No major difference between three potential pulping solvents—ethanol, butanol, phenol—was observed. The enzymatic susceptibility of pretreated wood samples was approximately 6-fold greater than that of the untreated poplar. UV absorbance was used to qualitatively characterize the soiubilized lignins.