Cold flow properties of biodiesel from waste cooking oil and a new improvement method

Biodiesel despite its positive advantages when using it as a fuel in replacement of diesel, suffers a major drawback in the cold flow properties (CFP). During winters, plugging of the filters as well as crystallization of the fatty acid are two of the leading problems that makes the fuel to not reach injectors and the combustion chamber and therefore the engine does not start. Cold flow properties of waste cooking oil biodiesel (WCOB) through the reduction of cloud point (CP), pour point (PP) and the cold filter plugging point (CFPP) where investigated in this work. The effectiveness of an approaches using the combination of two techniques, controlled winterization and addition of fatty acids 2-ethylhexyl esters (FAEhE) to reduce CP, PP and CFPP was studied. The change in CP, PP and CFPP corresponded to a decrease in the saturated ethyl esters content. A reduction of the palmitic and stearic acid ethyl esters content of 20,63 % and 8.64 % respectively was found. There was not significant effect on the fuel properties due to changes in the chemical composition of liquid fractions. However, using a Factorial Design and Response Surface Methodology optimization, the lowest CP, PP and CFPP for WCOB biodiesel could be obtained working with a winterization temperature of -5 °C, adding a 10 % of FAEhE and cooling during 30 min.