ASABE Technical Library - Abstract

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Improving the Fuel Properties of Soy Biodiesel

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Transactions of the ASABE. 53(6): 1853-1858. (doi: 10.13031/2013.35794) @2010
Authors:   P. S. Wang, J. Thompson, T. E. Clemente, J. H. Van Gerpen
Keywords:   Biodiesel, Cold flow performance, Ethyl esters, Isopropyl esters, NOx emissions, Oleic acid, Soy methyl esters, Storage stability

Certain undesirable characteristics are associated with the use of soy methyl esters as a direct replacement for petroleum diesel fuel. When compared to petroleum diesel, soy methyl esters have higher NOx emissions, poorer cold flow, and a shorter shelf life. This article investigates whether the careful choice of alcohol and triglyceride feedstocks can improve these fuel properties. Three different triglyceride feedstocks with three different levels of oleic acid were examined. It was determined that a high amount of oleic acid in the triglyceride feedstock eliminates the tradeoff between cold flow and oxidative stability. The study also examined the role of three different alkyl groups (methyl, ethyl, and isopropyl) on the high-oleic feedstock. In NOx emissions testing, no significant difference was found between the alkyl groups. Isopropyl esters had the best cold flow properties, while methyl esters had the poorest cold flow properties for the three different alkyl groups. The induction periods for the methyl and ethyl esters from the high-oleic feedstock were 14 and 26 h, respectively, according to the Rancimat method. These numbers are in close agreement with the oxidative stability index. Isopropyl esters from the high-oleic feedstock had an induction period of less than an hour, which was unexpected. Further investigation revealed that the high-oleic isopropyl esters had no vitamin E in the form of a-tocopherol, and it was speculated that the washing step in the manufacture of the fuel removed all vitamin E content.

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