Effects of monoacylglycerols on kinematic viscosity and cold filter plugging point of methyl soyate

Authors: Dunn, Robert - Bob

Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/4/2013
Publication Date: 11/24/2013
Citation: Dunn, R.O. 2013. Effects of monoacylglycerols on kinematic viscosity and cold filter plugging point of methyl soyate. Journal of the American Oil Chemists' Society. 90(12):1883-1894.

Interpretive Summary: This research determined that the effects of contaminants on the stability of biodiesel may be detected by measuring the low temperature filterability and viscosity (relative flowability). Monoglyceride contaminants are a side product from conversion of soybean oil into biodiesel. Even at very small concentrations, their presence is known to cause the formation of solid residues that can affect the operability of vehicles fueled with biodiesel and biodiesel/petro-diesel blends. This study determined that problems with monoacylglycerides could be identified by separately measuring the low temperature filterability and viscosity of biodiesel doped with added monoacylglycerols and mathematically comparing the data. Results from this research may be directly utilized in the development of procedures for fuel producers, distributors, and terminal operators to monitor the stability of biodiesel while it is stored during cold weather.

Technical Abstract: Biodiesel is an alternative fuel composed of mono-alkyl fatty acid esters made from the transesterification of plant oils or animal fats with methanol or ethanol. After conversion, biodiesel may contain trace concentrations of unconverted monoacylglycerols (MAG). These MAG have low solubility in biodiesel and may form solid residues when stored at cold temperatures. The present study evaluates the measurement of kinematic viscosity (v) and cold filter plugging point (CFPP)-time to filter (dt) as parameters that predict the temperature where small concentrations of MAG may lead to the formation of solids or other phase transitions that restrict the flow of soybean oil fatty acid methyl esters (SME) through filters and fuel lines. Mixtures of SME doped with MAG were prepared and v and dt were measured as the temperature decreased from 20 to below 0°C. Results showed a correlation between v and dt that held for neat SME (SME without added MAG) and SME-MAG mixtures as the temperature decreased to the threshold temperature (Tth). Sharp increases in dt disrupted the correlation as the temperature decreased below Tth. Furthermore, Tth generally increased as added MAG concentration increased in the mixtures.