Study of a new complex method for extraction of phenolic compounds from bio-oils
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This paper reports a new extraction method on phenolic compounds separation from bio-oil. Through adding appropriate amount of calcium hydroxide into the bio-oil, using ammonia solution to adjust pH > 7 of the bio-oil, the complex was gradually generated in the bio-oil. Then the complex is filtered, and further dissolved by hydrochloric acid. High purity phenolic compounds collected from the dissolving solution are considered as crude products. In order to investigate the mechanism of the phenolic compounds extraction, a model bio-oil was prepared. In the process of phenol extraction from the model bio-oil, the complex formed was characterized by FT-IR and the phenols collected were detected by GC/MS. The results demonstrated that a complex formed instead of a salt of calcium guaiacol in the extraction process. Parameters investigated were the concentration of ammonia solution (1-6 mol/L), reaction temperature (20-70 °C) and reaction time (5-35 min). On the basis of the model bio-oil test, 4 mol/L of ammonia solution, 40°C of the reaction temperature, and 20 min of the reaction time were chosen as optimum reaction conditions. Testing of these conditions for 40 g of the crude bio-oil showed that the complex method extracted 2.9 g of phenolic compounds with the purity of 93.07%. Meanwhile, the whole extraction process does not discharge pollutants into the surrounding environment. ? 2014 Elsevier B.V. All rights reserved.