Costin D. Nenitzescu Institute of Organic Chemistry, 71141 Bucharest, P.O. Box 15-254, Romania. The transesterification of vegetable oil with short-chain alcohols, in the presence of base-catalyst, by means of low frequency ultrasound (28 and 40 kHz) in order to obtain biodiesel fuel was studied. By using ultrasounds the reaction time is much shorter (10-40 min) than for mechanical stirring. The quantity of required catalyst is 2 or 3 times lower. The molar ratio of alcohol/oil used is only 6:1. Normal chain alcohols react fast, while secondary and tertiary alcohols show some or no conversion after 60 min of reaction. Surprisingly, 40 kHz ultrasounds are much more effective in the reduction of the reaction time (10-20 min). Twenty eight kilohertz give slightly better yields (98-99%), but longer reaction time, while higher frequencies are not useful at all for the transesterification of fatty acids. The future is coming on..here... we need to put it together and win once and for all... One-step lipid extraction and fatty acid methyl esters preparation from fresh plant tissues.. another link.. i dont want to simply repost information but at least organize it into a timeline

at density of oil = 0.894 g/ml and of MeOH = 0.792 "normal" base catalyzed stoichiometry is [code] liters moles OIL 1 1.24 MeOH 0.22 5.44 ratio 4.4 [/code] It does not add credibility to exaggerate

So, what are we really saying here, guys?

In another thread (which I can;t find right now) similar claims of dramatic improvements using ultrasound are made. Trouble is, they claim their replacing a reacton that take 5 to 10 hours and their using 6 W/square cm intensity. a. base catalyzed TE at 50C is over in less than an hour. Some say the mixing part need only be 10 minutes and an isothermal settling tanl will finish it off. b. that amount of ultrasound energy (who knows what depth) is probably leathal. If the energy was heat being trasfered by radiation the radiating surface would be at least 740C [code] sigma 5.67E-08 W/mK4 q = sigma A (Th^4 - Tc^4) q/A = 6 W/cm^2 60000 W/m^2 Tc 300 K 27 C Th = (q/sigma A + Tc^4)^(1/4) Th = 1016 K 743 C [/code] Now, you could align the wave guide and the reactor and be a bit more efficient ANd it is appealing that there could be a cold TE reaction But they should do an apples to apples comparison or state why they think conventional BCTE takes 5+hours

Its a very interesting investigation,also I read that seperation between glycerine and biodiesel can be done by ultrasonic Does anyone have the process on seperation?Also ýs there any ýndustrial design of this technology

@bmenergy, we are a manufacturer of industrial ultrasonic processing systems for all kind of liquids. You may want to have a look at our website at: [url]http://www.hielscher.com/ultrasonics/biodiesel_transesterification_01.htm[/url] For the transesterification of biodiesel - much like for for other liquid processes - we can scale up linear from a small pilot plant (e.g. 4kW) to a system running 3000bpd.

 For those interested in experimenting with ultrasonic and have the hobbyist bent and simple and inexpensive ultrasound generator can be made from materials available at the local Radio Shack for a few bucks.

 The following article from Mother Earth contains the base schematic for an ultrasonic generator using  an inexpensive integrate circuit and a tweeter.

http://www.motherearthnews.com/Alternative-Energy/1984-05-01/Ultrasonic-Plant-Stimulation.aspx

 The schematic is located in the image gallery. The frequency of this design can be tuned by changing the capacitor.

The chip is available from Radio Shack for $1.49:

http://www.radioshack.com/product/index.jsp?productId=2062598&cp 

This design uses the LM386 Low Voltage Power Amplifer from National Semi. This chip will produce frequencies in the 28 and 40 kHz range. The application notes from them contain circuit designs which provide the basis for far more sophisticated designs.

 http://www.national.com/an/AN/AN-263.pdf

  Enjoy and good luck.