Enrichment Of The Phenolic Constituents From Bio-oil And Their Bio-activities

Bio-oil is one of the products formed in the fast pyrolysis of biomass in the absence (orpoor) of oxygen. It can substituete for fossile fuels to be used in boiler, turbine, and dieselengine. On the other hand, because it is rich in chemical constituents, it is a kind of rawmaterial to extract value-added chemicals that can be widely used in the industries ofchemical engineering, food, and pharmaceutics.In this paper, phenolic constituents that are the main components in bio-oil wereenriched by chemical methods. The obtained products were analyzed by GC-MS, and itsbioactivities, including antioxidant activity and antimicrobial activity were investigated. Theobjective of this study was to provide theoretical basis for the further development andutilization of bio-oil.The results are reported as follows.1. The water in bio-oil could be removed satisfactorily by vacuum distillation (50℃,0.015MPa), and aging problems of the bio-oil could be avoided.2. Among the4solvents applied to extract phenolic constituents from bio-oil, i.e., ether,dichloromethane, ethyl acetate, and methanol, highest phenolic content (360mg/g) was foundin ether and ethyl acetate extracts. Their antioxidant activities were also stronger than othertwo extracts. Stongest antimicrobial activity was observed in ethyl acetate extract.3. The enrichment of phenolic constituents were realized by pH gradient extractionmethod. Response surface methodology was used for optimization. The ethyl acetate extractfrom bio-oil was washed three times with an aqueous4%NaHCO3. The residue was furtherextracted three times with5%NaOH with the ratio of1:0.45solvent/aqueous phase. Thecombined aqueous phases were collected and the pH of aqueous phases was adjusted to7with50%sulfuric acid to free the phenolic constituents. The total phenols content of thephenol-rich fraction was more than800mg/g and its antioxidant activity was similar to that ofascorbic acid. After pH gradient extraction, the antibacterial and antifungal ability ofphenol-rich fraction was obviously stronger than original ethyl acetate. The phenol-richfraction was analysed by GC-MC. The main composition of phenol-rich fraction was phenols(71.04%), aldehydes and ketones (5.77%), esters (4.5%), alcohols (1.54%), et al. Catechol isthe principal compound. The infrared spectrum confirms this result.4. Three fractions were obtained by column chromatography (F1, F2and F3). The total phenols content of F2is1137.68mg/g, which was more than that of others. Antioxidantactivity and antibacterial ability of F2was the strongest among all testing samples. Theanalysis result of F2by GC-MC shows that phenols (83.62%) was the main composition,including phenol (14.15%),4-methylphenol (13.99%),4-ethylphenol (14.58%) and catechol(14.88%).