Submitted to: Commercialization of Biodiesel Producing a Quality Fuel
Publication Type: Proceedings
Publication Acceptance Date: 7/10/1997
Publication Date: N/A
Citation: N/A Interpretive Summary: Methyl soyate, a form of biodiesel derived from soybean oil, is attractive as an alternative fuel for combustion in compression ignition (diesel) engines. However, methyl soyate has shown the propensity for developing cold weather start-up and operability problems at much higher temperatures than conventional diesel fuel. The cold weather operability temperature limit of biodiesel may be substantially reduced by a process called winterization. Winterization is the refrigeration of biodiesel to deliberate cause formation of small wax crystals followed by filtration to remove those crystals. This work shows that winterization substantially improves the cold weather operability limit of methyl soyate. On the other hand, winterization affects other important fuel properties. For example, winterized biodiesel may require special storage and handling procedures to preventing rancidity from oxidation. Nevertheless, this work demonstrates that biodiesel can be safely improved with respect to cold weather operability without diminishing fuel quality with respect to the standard specification for biodiesel. Such an improvement should help reduce obstacles to widespread commercialization of biodiesel fuel and extenders. Finally, results from this work support exclusion of iodine number as a parameter for evaluating biodiesel fuel quality.
Technical Abstract: Methyl esters from vegetable oils are attractive as alternative fuels or extenders for combustion in direct injection compression ignition (diesel) engines. However, methyl esters have low-temp flow properties that may preclude their deployment during periods of cold weather in moderate-temperature climates. Winterization of methyl soyate can reduce this limit by 10-20C and that this process can be engineered to deliver product yields as high as 87% with respect to starting material. This work examines the benefits of winterization against effects on overall fuel quality of methyl soyate. Results showed that winterization significantly decreases cloud point (CP), pour point and low temperature filterability of methyl soyate. In contrast, winterization increases acid value, peroxide value and viscosity, and reduces specific gravity. Iodine number was slightly increased by winterization. Analytical techniques were developed to evaluate oxidative stability of methyl soyate at 50C. Not surprisingly, winterization significantly decreased induction periods of neat methyl soyate and soyate/distillate blends. No direct correlation was found to exist between iodine number and CP or between iodine number and induction period. Overall, this work supports the notion that iodine number should not be included as a parameter for evaluating biodiesel fuel quality.