Methodology for Extraction of Phenolic Compounds of Bio-oil from Agricultural Biomass Wastes

Abstract

Bio-oil is a mixture of nearly 300 types of organic compounds, including phenols. Phenols are produced during oil refinement and are usually used as fuel additives, food antioxidants and in the synthesis of other chemicals. This study is mainly focused on the extraction of phenolic compounds from bio-oil produced during the pyrolysis of agroindustrial wastes. Bio-oil samples were produced by intermediated pyrolysis of oil from palm empty fruit bunch at 578 °C for 45.6 s using a fixed bed reactor. Under these conditions, the phenol fraction was 13.14 wt%. Two different extraction methodologies were used to obtain a higher phenol fraction of bio-oil: liquid–liquid extraction and reactive extraction. In the first method, an initial liquid–liquid extraction was performed to solubilize the bio-oil in a liquid phase. A second liquid–liquid extraction was subsequently performed with three different organic solvents to maximize the phenolic composition of the fraction. In contrast, the reactive extraction methodology was performed using a NaOH solution to produce phenolates, which are more soluble in water, and thus favor phenol extraction. The resulting phenol extraction yields were not higher than 30 wt% (i.e., a ratio of 1:3.5 of bio-oil and NaOH solution) for the reactive extraction; in contrast, for the liquid–liquid extraction, these yields rose above 68 wt%. The operating conditions favoring this extraction yield included a first extraction with a 5:1 dichloromethane/bio-oil mixture followed by a second extraction with a 10:1 ethyl acetate/concentrated dichloromethane bio-oil mixture.