New method of total acid number (TAN) determination in biooils

摘要

Fast pyrolysis oil is one source of renewable liquid fuels, which is promising in satisfying environmental concerns over fossil fuels. The ASTM D664 method is used to determine the acidic constituents in petroleum products, lubricants, and biodiesel requiring mixtures of 2‐propanol and toluene as solvent. The ASTM method also uses large quantities of solvents for the total acid number (TAN) determination. The ASTM D664 method has been adopted for the determination of TAN for bio‐oils data published in literature. However, the properties of fast pyrolysis bio‐oils are different from those of petroleum products and biodiesel, because bio‐oils are soluble in polar solvents and partially soluble in water whereas petroleum products and biodiesel are insoluble in water and are more non‐polar. An alternative method which is more suitable for TAN determination of pyrolysis bio‐oil has been developed and validated. Aqueous potassium hydroxide (0.1 M KOH) was used as standard titrant instead of 0.1M KOH in alcoholic solution, and acetone was used as titration solvent instead of mixtures of toluene and 2‐propanol as specified in the ASTM method. Four bio‐oil samples were analyzed for determination of TAN with the new method and the ASTM method, respectively. The results showed that TAN of bio‐oil samples obtained by the new method are in good agreement with the one obtained by the ASTM method. It was confirmed that the new method was simpler and relatively cheaper and more suitable for TAN determination of the pyrolysis oils than the ASTM D664 method.