Biodiesel – analytical methodsPart 2 (to follow Synthesis)

Dr Robert Elliott(Dr) David Schaller

Ms Anna PaicePrimary Industry Centre for Science Education

Presented at CONASTA 59 2010

Does my biodiesel have soap in it?

No direct ASTM standard for soap

500 ppm is a good rule of thumb

Shake test – how long does water take to settle

Titration test (in acetone or alcohol)

Titrating soap in a biodiesel-acetone (or biodiesel-isopropanol) solution

Image adapted from http://www.chemguide.co.uk/physical/acidbaseeqia/indicators.html

Residual NaOH

Soap

AOCS method “soap in oil” cc17-79 www.nrel.gov/docs/fy04osti/36240.pdf

How do I get rid of soap?Use cleaner reagents and do it again...

Water washing removes the soap [Be careful: wash gently in the early stages to prevent the formation of an emulsion

(unless you are doing a salt wash or a vinegar wash)].

Water washing removes the alcohol, which helps the soap to stay in the biodiesel

(also helps get rid of glycerol, which can make your biodiesel cloudy)

Let the biodiesel stand and clarify

Did your reaction go to completion?Assaying glycerides in your biodiesel

Monoglycerides, diglycerides, trigylcerides

9/1 Test - solubility in alcohol

Re-reaction test – reaction at ~100ℴC for 10‘ Viscosity test

0

10

20

30

40

50

60

Corn oilCottonseed oilLinseed oilPeanut oilSafflower oilSesame oilSoybean oilSunflower oilTallow (Beef)PetrodieselMethy ricinoleateEthyl octanoate

kine

mat

ic v

isco

sity

Viscosity of biodiesels from different oils

See slide notes for data sources

Oils

FAMEs

40˚C

Viscosity as a proxy for completion

Fillipis et al., 1995

FAMEs

40˚C

http://www.pharmainfo.net/free-books/pharmaceutical-suspensionsa-review

Ostwald Viscometer

Relative viscosity by pipette draining

Image from http://www.glassware-manufacturers.com/pipettes.html

Data collection with mobile phones(Large bore pipettes are too fast on hot days)

Relative Viscosity by Pipette Drain Time

Water

24 hour reaction

20 minute reaction

10 minute reaction

5 minute reaction

Canola

Sunflower

Paraffin oil

0 20 40 60 80 100 120 140

Time (secs)