Course: BFM 202 Biodiesel Production

Lecture

Oxidative Stability of Biodiesel
Credits
BFM 202 Biodiesel Production Unit 1 Reading has been adapted from "ENGY 131 Unit 1 Commentary: What is biodiesel?" by Southeastern Illinois College.

ENGY 131 Biodiesel Production course content by Southeastern Illinois College is licensed under a Creative Commons Attribution 3.0 Unported License. Except where indicated otherwise.

Unit 8 Biodiesel Lubricity and Oxidative Stability

Oxidative Stability of Biodiesel

Oxidation occurs as biodiesel fuel degrades upon exposure to oxygen. Heat, water, and metals facilitate the process. Unrefined vegetable oils contain antioxidants which slow the oxidation process, however, production processes remove these protective antioxidants.

Biodiesel oxidation occurs while fuel is being stored, handled, or is in use. Oxidized fuel leads to excessive engine wear and fuel injector failure as a result of fuel deposits. Pressure drop across plugged filters and poor valve seating then occurs. This translates to poor engine performance and reduced fuel economy. Antioxidants assist in oxidation prevention. Standardized biodiesel tests indicate its oxidative stability and thus performance.

ASTM D7462 is the Standard Test Method for the Oxidative Stability for Biodiesel and its blends.

Biodiesel Oxidative Testing

The Rancimat test is the most common method for testing biodiesel oxidative stability. This test samples biodiesel fuel in the presence of air over a period of time. The reference created from the test is called the "induction period" and the time is specified in biodiesel standards ASTM D 6751 and EN 14214.

Oxidative tests of biodiesel stored for two years indicate that viscosity, peroxide value, acid value, and density increase while heat of combustion decreased. Results can be dependent upon the feedstock. Other oxidative tests of biodiesel are the oil stability index (OSI), wet chemical procedures (acid value and peroxide value), and pressurized differential scanning calorimetry (DSC).

Additional Resource

Weighing Oxidation Stability Tests for Biodiesel

http://www.biodieselmagazine.com/article.jsp?article_id=2478&q=fuel%20oxidation&category_id=23