|Dunn, Robert - Bob|
|HAAS, MICHAEL - Retired ARS Employee|
Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/19/2015
Publication Date: 4/11/2015
Publication URL: http://handle.nal.usda.gov/10113/62250
Citation: Dunn, R.O., Lew, H.N., Haas, M.J. 2015. Branched-chain fatty acid methyl esters as cold flow improvers for biodiesel. Journal of the American Oil Chemists' Society. 92(6):853-869. DOI: 10.1007/s11746-015-2643-2.
Interpretive Summary: This research contributed to the development of new additives that effectively improve the cold flow properties of biodiesel.Biodiesel is an alternative fuel for compression-ignition engines that is made from plant oils, animal fat, and waste cooking oils. It has cold flow properties that cause it to gel and plug fuel systems at higher temperatures than conventional diesel fuel (petrodiesel), even when it is blended in the petrodiesel. Additives are a convenient and inexpensive means to improve these properties. This study examined new compounds synthesized from oleic acid, a material that itself is obtained from plant oils and animal fats. These compounds have specialized chemical structures that modify the temperature where biodiesel begins to form solid particles (the cloud point). Under certain conditions, they decreased the cloud point of biodiesel made from three feedstocks: canola, palm, and soybean oils. This research will directly benefit scientists and engineers seeking to develop additives that can improve the cold flow properties and other performance factors related to biodiesel.
Technical Abstract: Biodiesel is an alternative diesel fuel derived mainly from the transesterification of plant oils with methanol or ethanol. This fuel is generally made from commodity oils such as canola, palm, or soybean and has a number of properties that make it compatible in compression-ignition engines. Despite its many advantages, biodiesel has poor cold flow properties that may impact its deployment during cooler months in moderate temperature climates. This work is a study on the use of skeletally branched-chain fatty acid methyl esters (BC-FAME) as additives and diluents to decrease the cloud point (CP) and pour point (PP) of biodiesel. Two BC-FAME, methyl iso-oleate and methyl iso-stearate isomers (Me iso-C18:1 and Me iso-C18:0), were tested in mixtures with canola oil fatty acid methyl esters (CaME), palm oil fatty acid methyl esters (PME), and soybean oil fatty acid methyl esters (SME). Results showed that mixing linear FAME with up to 2 mass% BC-FAME did not greatly affect CP, PP, or kinematic viscosity (KV) relative to the unmixed biodiesel fuels. In contrast, higher concentrations of BC-FAME, namely between 20 and 39 mass%, significantly improved CP and PP without raising KV in excess of limits specified in biodiesel fuel standard ASTM D6751. Furthermore, it is shown that biodiesel/Me iso-C18:0 mixtures matched or exceeded the performance of biodiesel/Me iso-C18:1 mixtures in terms of decreasing CP and PP under certain conditions. This was taken as evidence that additives or diluents with chemical structures based on long-chain saturated chains may be more effective at reducing the cold flow properties of mixtures with biodiesel than structures based on long-chain unsaturated chains.