Phase Separation And Upgrading Of Bio-Oil

With the economic development and rapid growth of population, The demand forenergy is rising, and excessive exploitation and consumption of fossil fuel such ascoal, oil and gas, resulted in a series of questions including environmental pollution,global warming etal. Biomass was considered as one of the most promisingalternative renewable energy sources, which can be converted into liquid fuel (knownas bio-oil) through fast-pyrolysis. However, bio-oil is a complex liquid mixture, andmore than 400 organic compounds have been detected in the bio-oil. So bio-oilexhibits some undesired properties such as acidity, thermal instability, low heatingvalue, high viscosity, corrosiveness and so on, which limite its applications in energyand fuel. Therefore, it need to be separated and upgraded before using as the fuels andchemicals resources.In the preface, firstly, we stated the biomass utilization and meanings of study,analysed the properties and chemical composition of the bio-oil. Secondly,compared the methods on separating bio-oil. Finally, the upgrading techniques andPros and Cons of the treatments were discussed. Phase separation is one of the mosteffective pathway to realize initial separation of bio-oil, which can generate fractionswith similar polarity. By adding a little aqueous salt solution (10 wt% of bio-oil), thepyrolysis bio-oil of rice husk would fast form two phases. The main work includes thefour parts:(1) After addition a little aqueous salt solution, the bio-oil can be formed twophases. The higher of the concentration of salts solution, the better the phaseseparation can be achieved. For different kinds of salt solutions with the sameconcentration, the effect of phase separation mainly depends on the number of ionsand the charge of ions in the salts solution, phase separation is also affected by otherfactors.(2) The salts of raw materials is mainly resources of ash, the presence of ashhave great affect on the properity of bio-oil, if the ash content is higher, it canaccelerate aging and change the composition of the bio-oil. Ash ratio of theupper/bottom layers showed that the salts were mainly distributed in the upper layerafter adding aqueous salt solutions to the bio-oil. However, the salts distribution isvarious for the different salt solutions. (3) Five fractions can be obtained after extraction of the upper and bottom layer.Elemental composition, gas chromatography-mass spectrometry and infraredspectrum revealed that some similar compounds are rich in different fractions. Forexample, compounds levoglucosan (55), which is the highest proportion in thefraction A, up to 28.55%. lignin-derived such as guaiacol-derived sypringol-derived isenrich in the fraction B and/or C.(4) The organic acid on the upper layer was extracted by octyl alcohol. The octylalcohol can react with the organic acid by adding AlCl3as the catalyst, gaschromatography-mass spectrometry analysis showed that acetic acid, propanoic acidthat are abundant in the upper layers are transformed into acetic acid octyl ester,propionic acid octyl ester, respectively. Duo to the different boiling point betweenoctyl ester and octyl alcohol, octyl alcohol can be separated by distilled method andrecycling.