New method accelerates stability testing of soy-based biofuel

Jan 13, 2009
New method accelerates stability testing of soy-based biofuel
NIST chemist Tom Bruno demonstrates sampling of biodiesel fuel for injection into a gas chromatograph-mass spectrometer, an instrument that separates and identifies the components of a mixture. Credit: Ost, NIST

The National Institute of Standards and Technology has developed a method to accelerate stability testing of biodiesel fuel made from soybeans and also identified additives that enhance stability at high temperatures. The results, described in a new paper,* could help overcome a key barrier to practical use of biofuels.

Both oxidation and heating can cause biodiesel to break down, adversely affecting performance. These two effects usually are analyzed separately, but NIST chemists developed a method to approximate both effects at the same time while also analyzing fluid composition. NIST’s “advanced distillation curve” method could accelerate and simplify testing of biodiesels, according to lead author Tom Bruno. NIST researchers used the new method to demonstrate the effectiveness of three additives in reducing oxidation of biodiesel at high temperatures, as would occur in aviation fuels.

Biodiesel—which can be prepared from vegetable oil, animal fats, used cooking oil, or microalgae—is a potential replacement or extender for petroleum-based diesel fuel. Biodiesel offers several advantages, including renewability, the potential for domestic production, biodegradability, and decreased emissions of carbon monoxide and particulate matter. Biodiesel also has several serious disadvantages, including increased nitrogen oxide emissions and chemical instability, especially at higher temperatures.

Antioxidants often are added to vegetable oils to retard oxidation during storage. The NIST work may be the first to enhance stability of biofuel at high temperatures, Bruno said. The study focused on three compounds, THQ, t-decalin and tetralin,** that help neutralize highly reactive “free radicals” formed at temperatures above 300 degrees C. Test results showed that all three compounds stabilized biodiesel. As expected from studies of aviation fuels, THQ and t-decalin perform similarly and outperform tetralin. For solutions containing 1 percent additive, THQ performed best overall.

A distillation curve charts the percentage of a mixture that evaporates as a sample is slowly heated. Because the different components of a complex mixture typically have different boiling points, a distillation curve gives a good measure of the relative amount of each component. NIST chemists enhanced the traditional technique by improving precision and control of temperature measurements and adding the capability to analyze the chemical composition of each boiling fraction.

To adapt the method for unstable fluids such as biodiesels, the authors made repeated distillation curves of samples and quantified the variation in parameters such as temperature for each distillate fraction across the different runs of the experiment. These data were averaged over the entire distillation curve to identify the range of variations that might occur. This range was extended to theoretically model the potential oxidative and thermal decomposition of the samples.

Notes:

* T.J. Bruno, A. Wolk and A. Naydich. Stabilization of biodiesel fuel at elevated temperature with hydrogen donors: Evaluation with the advanced distillation curve method. Energy & Fuels. Articles ASAP (Web), January 2, 2009. DOI: 10.1021/ef800740d.

** THQ: 1,2,3,4-tetrahydroquinoline; t-decalin: transdecahydronaphthalene; tetralin: 1,2,3,4-tetrahydronaphthalene.

Source: National Institute of Standards and Technology

Explore further: Repeated self-healing now possible in composite materials

add to favorites email to friend print save as pdf

Related Stories

Chemists Get Scoop on Crude ‘Oil’ from Pig Manure

Jun 11, 2008

After a close examination of crude oil made from pig manure, chemists at the National Institute of Standards and Technology (NIST) are certain about a number of things. Most obviously, “This stuff smells worse than manure,” ...

Recommended for you

Research offers 'promise' of improved food safety

22 hours ago

The issue of food safety has rocketed up the political agenda in recent years but despite huge improvements, some concerns and problems still persist. Fears about our food are moving away from issues about ...

Metals go from strength to strength

22 hours ago

To the human hand, metal feels hard, but at the nanoscale it is surprisingly malleable. Push a lump of metal with brute force through a right-angle mould or die, and while it might look much the same to the ...

Chemists achieve molecular first

23 hours ago

(Phys.org) —Chemists from Trinity College Dublin have achieved a long-pursued molecular first by interlocking three molecules through a single point. Developing interlocked molecules is one of the greatest ...

User comments : 0

More news stories

Chemists achieve molecular first

(Phys.org) —Chemists from Trinity College Dublin have achieved a long-pursued molecular first by interlocking three molecules through a single point. Developing interlocked molecules is one of the greatest ...

Metals go from strength to strength

To the human hand, metal feels hard, but at the nanoscale it is surprisingly malleable. Push a lump of metal with brute force through a right-angle mould or die, and while it might look much the same to the ...

ESO image: A study in scarlet

This new image from ESO's La Silla Observatory in Chile reveals a cloud of hydrogen called Gum 41. In the middle of this little-known nebula, brilliant hot young stars are giving off energetic radiation that ...

First direct observations of excitons in motion achieved

A quasiparticle called an exciton—responsible for the transfer of energy within devices such as solar cells, LEDs, and semiconductor circuits—has been understood theoretically for decades. But exciton movement within ...

Warm US West, cold East: A 4,000-year pattern

Last winter's curvy jet stream pattern brought mild temperatures to western North America and harsh cold to the East. A University of Utah-led study shows that pattern became more pronounced 4,000 years ago, ...

Patent talk: Google sharpens contact lens vision

(Phys.org) —A report from Patent Bolt brings us one step closer to what Google may have in mind in developing smart contact lenses. According to the discussion Google is interested in the concept of contact ...