Biodiesel – analytical methods
Part 2 (to follow Synthesis)
Dr Robert Elliott
(Dr) David Schaller
Ms Anna Paice
Primary 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
Titration test (in acetone or alcohol)
Titrating soap in a biodiesel-acetone
(or biodiesel-isopropanol) solution
AOCS method “soap in oil” cc17-79 www.nrel.gov/docs/fy04osti/36240.pdf
Image adapted from http://www.chemguide.co.uk/physical/acidbaseeqia/indicators.html
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 of biodiesels from different oils
See slide notes for data sources
Viscosity as a proxy for completion
et al., 1995
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