Improving Acid Number Testing of Biodiesel Feedstock and Product

• Published in: Journal of the American Oil Chemists' Society 2012-03, Vol.89 (3), p.409-417
• Main Authors: Kovács, A, Czinkota, I, Tóth, J
• Format: Article
• Language: English
• Subjects: Acid number; Acidity; Acid–base titration; Agriculture; Aluminum; aluminum foil; Biodiesel; Biodiesel fuels; Biological and medical sciences; Biomaterials; Biotechnology; Chemistry; Chemistry and Materials Science; Electrodes; Fat industries; Fatty acids; feedstocks; Fluctuations; Food industries; Food Science; Fundamental and applied biological sciences. Psychology; Industrial Chemistry/Chemical Engineering; Magnetic fields; Original Paper; Raw materials; Repeatability; Solvent; Solvents; titration
• ISSN: 0003-021X; 1558-9331
• DOI: 10.1007/s11746-011-1929-2

The acidity of low and high free fatty acid containing feedstock varieties and biodiesel production intermediary products were tested using a variety of standard methods by the use of manual and automatic titration apparatus. The objective was to select the optimal test method for intermediary products in biodiesel processing and to optimize the selected technique by reducing the extent of bias. We found that there are two major reasons for variations in electrode potential readings. Colloid chemistry has an impact on the initial phase of titration by breakage and reformulation of the partially disperse system. Electric and magnetic fields in the titration beaker were the main reasons for sensitive fluctuations in electrode potentials in the potential range of interest for acid number readings. Refluxing the analyte with the diluting solvent proved to be an efficient technique to offset the influence of colloid processes. Addition of a filter electrolyte to the titration solvent allowed the filter fluctuations to be related to changes in uniformity of electric and magnetic fields in the titration beaker. Addition of filter electrolyte improved signal reliability than shading the external noises by wrapping the titration beaker in aluminium foil. Mathematical interpretation of potential readings revealed the extent of improvement in electrode potential fluctuation by the techniques employed. Both the aqueous and non-aqueous titration are suitable for accurate testing the acid number of biodiesel feedstock and intermediary products.