WFU Biofuels

Wake Forest students, faculty, staff and associates making and testing vegetable-oil based fuels.

Monday, October 31, 2005

Molecular Scissors

A guy named Richard Carpenter has recently raised a question about B100 use in modern diesel engines on the Biofuels Interest Group (BIG). His observations have centered on the potential problems of using B100 in modern diesels given the differences in viscosities between B100 and petrol diesel. Here are the viscosities of petrol and B100 at 27 and 75C:

27C 75C
petrol 4.3 1.5 (mm^2/s)
B100 (soy) 11 4.3 (mm^2/s)

So B100 only approaches the viscosity of "cold" petrol diesel when heated to 75C. From what I understand the forces in the injection systems skyrocket given these differences. The fuel is injected at about 22,000 to 26,000 psi!!! In a nutshell, without software changes the engines run less efficiently. There are also increased stresses in the injection pump systems causing some "unconfirmed" premature failures. This does not help B100 acceptance but does create a need to blend.

I started looking for articles that address this problem in B100. I knew ozonlysis of FAME would produce shorter chain esters and that would produce a less viscous fuel. So I search and found this:

A recent paper by Ramani Narayan in Biomacromolecules 2005, 6, 1334-1344 looks at the ozonlysis of FAME. He is Chemical Engineer at Michigan State University. They treated methyl soyate (FAME) with ozone in a process called ozonlysis. The reaction will take double bonds cleave them by either oxidative or reductive pathways. The end result is the production of 9, 6 and 3 carbon chain esters from the UNSATURATED esters. They did not report any viscosities on the ozonized FAME but did report a change in volatilization temp of 135C to 73C (petrol diesel is ~76C). They also reported no change in temperature for the onset of crystallization in region 1 (long chain saturated esters) but a depression in region 2 (unsaturated esters) from -63C to -86C. They did not measure the viscosity of the ozonized product but I wager the numbers are lower.

Since the reaction is cheap and easy I bet we may see more about this. Especially for mono and polyunsaturated B100 derived from oils like Canola, Peanut and Soybean. I also wonder what effect we would see on the ozonlysis of SVO. So if and when we are able to measure viscosity we have some measuring to do.


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