Research Of Separating And Upgrading Phenolic Compounds From Bio-oil

Biomass is acknowledged as an abundant of renewable and clean energy source and can be transformed into a liquid fuel called bio-oil. Biomass with low energy density can be converted to high energy density bio-oil via pyrolysis which contains a number of important chemical raw materials, can also provide a lot of chemicals, which improves the utilization efficiency of the bio-oil effectively. However, the property of bio-oil prepared by the fast pyro lysis technology is unstable for its aging reaction after long home later, which limits its application. Therefore, it must be refined before used directly as fuel, and extraction of high value compounds from bio-oil is also an important research direction.In the first chapter, the status and trends of the the world’s energy development was described at begin, and the significance of biomass energy development and prospects were summarized. The development history of biomass energy was described in detail by introducing the classification and utilization technology of biomass. At last, some of the physical and chemical refining methods, and the status of the application of bio-oil were discussed and compared.In the second chapter, based on the physical and chemical properties of bio-oil, improving the quality of bio-oil is efficient use of the premise, and the techniques of extraction of high value compounds from bio-oil and upgrading methods of bio-oil were then reviewed. At last, the phenolic compounds of bio-oil and their application, as well as the separation and extraction techniques of these phenolic compounds, were briefly described.In the third chapter, the main physical and chemical properties of the low-temperature fraction(25～100℃), middle-temperature fraction(100～170℃) and high-temperature fraction(10～250℃) were studied, the results show that the high temperature fraction does exist a large number of phenolic compounds(56%). The moisture content of the bio-oil is the highest (24.7%), and the distillate fractions are all very low in moisture content, which is 2.34% of the low-temperature fraction, and the fraction of middle-temperature(1.98%) and high-temperature(0.77%) fraction are lower; The heating value of low-temperature fraction(16.3 MJ/kg) was compared to bio-oil(14.8 MJ/kg) increased most significantly, which shows that the more saturated compounds and less oxygenate compounds in low-temperature fraction, and high boiling point of oxygen-containing compounds are present in the other two fractions.In the fourth chapter, based on metal ions will generate precipitate with phenolic compounds under alkaline conditions, the recovery process of phenolic compounds in high-temperature fraction of bio-oil were studied and discussed. Many phenols have the effect of extraction from high-temperature fraction by Mg2+, but most extraction results are not satisfactory, with the exception of 4-ethylphenol extraction efficiency is better whose relative peak area more than 20%; Few phenols have the effect of extraction from high-temperature fraction by Al3+, but most extraction results are not satisfactory; Many phenols have the effect of extraction from high-temperature fraction by Zn2+, only with the exception of 4-ethylphenol extraction efficiency is better whose relative peak area more than 10%; Many phenols have the effect of extraction from high-temperature fraction by Fe3+, but most extraction results are not satisfactory, with the exception of 4-ethylphenol extraction efficiency is better but the extraction rate is not high.In the fifth chapter, in order to investigate the recovery of phenolic compounds in high-temperature fraction of bio-oil by Mg2+,25℃of the reaction temperature, 2.5mol/L of sodium hydroxide solution and 20 min of the reaction time were chosen as the optimum reaction condition. The results demonstrated that although most of the relative content of phenolic compounds is not high but separating phenolic compounds from high-temperature fraction of bio-oil by Mg2+ is a simple and effective method. In this condition, the recovery of 4-ethylphenol in high-temperature bio-oil fractions reaches 34.97%. However, due to mixing of other ingredients in the distillation process of the formation of insolubles, resulting in purity of the desired product is not high enough. Although the extraction rate of 4-ethylphenol is higher relative to other phenols, but compared to some of the more mature technologies, this approach needs further study and improvement.Chapter VI is the summary and outlook of the paper.In this paper, in order to investigate the recovery of phenolic compounds in high-temperature fraction by metal ion precipitation,25℃ of the reaction temperature, 2.5mol/L of sodium hydroxide solution and 20 min of the reaction time were chosen as the optimum reaction condition. The results demonstrated that although most of the relative content of phenolic compounds is not high but this method has good enrichment of phenolic compounds. In this condition, the recovery of 4-ethylphenol in high-temperature bio-oil fractions reaches 34.97%.However, the purity and the extraction rate of objective product is not high enough which needs further study. Although most extraction results are not satisfactory by Fe3+ and the extraction rate is not high, either. But with the exception of 4-ethylphenol extraction efficiency is better whose relative peak area more than 20%. So, extraction of phenolic compounds from bio-oil by Fe3+ has a certain research value which needs further research and discuss.