Examining biodiesel oxidation

Date: 3/10/2009 10:03 am

 Article taken from the March 2009 issue of TRIBOLOGY & LUBRICATION TECHNOLOGY

Examining biodiesel oxidation

A new study reveals the impact of an antioxidant in a lubricant during long-term storage.

Even with volatility in the pricing of crude oil, work is continuing to improve the viability of biodiesel as an alternative. As discussed in TLT, the many challenges in working with biodiesel include suitable feedstocks, cost-effective processing and preparing a final product that meets industry specifications.

In a previous TLT article, we discussed the use of a solid catalyst to reduce free fatty acid content and an ion exchange resin that can reduce impurities such as residual sodium methylate catalyst, soaps and glycerin. These steps all help to produce acceptable biodiesel that meets industry requirements.

But minimization of contaminants in biodiesel does not eliminate the problem with oxidation inherent in the actual vegetable oil. For example, one common feedstock for biodiesel is soybean oil. The largest fatty acid chain incorporated into soybean oil is linoleic acid at a concentration of approximately 55%. Linoleic acid is an example of a polyunsaturated fatty acid which is readily known to oxidize, leading to the breakdown of biodiesel and formation of higher concentrations of engine deposits.

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