Extraction of Phenolic compounds from lignin pyrolysis bio oil using Switchable Hydrophilicity Solvents

Abstract

Lignin is one of the three basic components of wood. So far its use is just limited to produce energy from it by burning, unlike other two components, cellulose and hemicellulose. Lignin is an aromatic polymer byproduct from paper pulping industry. Char and lignin oil are the byproducts after the pyrolysis of lignin in a fluidized bed reactor. Within the oil are valuable phenolic compounds such as phenol, guaiacol and catechol. In this work Switchable Hydrophilicity solvents (SHS) are used to extract phenols as mixture from lignin-pyrolysis oil at the scale of 10 g of bio-oil. The three solvents used to extract the phenolic aromatic compounds were N,N-dimethylcyclohexylamine(hexyl amine), Diisopropylaminoethanol(propyl amine) and Dibutylaminoethanol(butyl amine). Lignin pyrolysis was performed under two temperature conditions, 600°C and 800°C. The bio oil used in the experiments was the one obtained from pyrolysis at 800°C. Total guaiacol found in 600°C bio oil was 2.6 g/L and in 800°C was 5.3 g/L. By using Hexyl Amine, Propyl amine and Butyl Amine we extracted 0.7, 0.6 and 0.2 (g/L) of guaiacol respectively from 0.1g of bio oil. By doing the qualitative analysis of the bio oil, it has been found out that hexyl amine extracted mostly guaiacol, Propyl Amine has equal portions of Guaiacol, Creosol, and other phenolic compounds whereas, Hexyl Amine has equal portions of Guaiacol and 4-ethyl, 2 methoxy phenol. Another parameter that we analyzed during the experiments was the times of extraction from the organic solvent. 2 and 4 times extraction parameters have been analyzed in which 4 times was found to be the most effective with 8 percent higher extraction efficiency than 2 times extraction. With two times extraction using ethyl acetate as an organic solvent we extracted 0.35, 0.30 and 0.10 g/L of guaiacol from N, N-dimethylcyclohexylamine(hexyl amine), Diisopropylaminoethanol(propyl amine) and Dibutylaminoethanol(butyl amine).Whereas, with 4 times extraction we obtained 0.7 , 0.6 and 0.2 (g/L) of guaiacol from N,N-dimethylcyclohexylamine(hexyl amine), Diisopropylaminoethanol(propyl amine) and Dibutylaminoethanol(butyl amine). respectively.