Technique for analysis of biodiesel

The manufacture and use of fatty acid methyl esters (Fame), has huge implications for the environment; biodiesel is the name of a clean burning alternative fuel, produced from renewable resources

Biodiesel contains no petroleum, but it can be blended at any level with petroleum diesel to create a biodiesel blend.

It can be used in compression-ignition (diesel) engines with little or no modifications.

Biodiesel is simple to use, biodegradable, nontoxic, and essentially free of sulphur and aromatics.

Biodiesel is made through a chemical process called transesterification whereby the glycerin is separated from the fat or vegetable oil.

The process leaves behind two products - methyl esters (the chemical name for biodiesel) and glycerin (a valuable byproduct usually sold to be used in soaps and other products).

Fuel-grade biodiesel must be produced to strict industry specifications (ASTM D6751) in order to insure proper performance.

Biodiesel is the only alternative fuel to have fully completed the health effects testing requirements of the 1990 Clean Air Act Amendments.

Biodiesel that meets ASTM D6751 and is legally registered with the US Environmental Protection Agency is a legal motor fuel for sale and distribution.

Metrohm can offer a solution to many of the analytical requirements listed in Euopean Standard EN14214, namely, .

oxidative stability Rancimat method.

Acid value potentiometric titration.

Iodine value potentiometric titration.

Water content Karl Fischer.

Oxidative stability.

The Metrohm Rancimat 743 method for measuring the oxidative stability of fatty acid methyl esters is determined according to DIN EN 14112.

In this method the highly volatile organic acids produced by autoxidation are absorbed in water and used to indicate induction time.

With the simple to use 743 Rancimat, the determination takes place at a highly sophisticated level, eight measuring positions in two independent heating blocks.

Individual start on each position.

Comprehensive control by PC.

Up to four Rancimat measuring blocks per PC - and therefore up to 32 samples at up to eight different temperatures.

Integrated GLP test.

Titrations for biodiesel.

As listed in Euopean Standard EN14214, Biodiesel manaufacturers are required to determine acid value and iodine number by titration.

Using Metrohm autititrators these methods have been perfected over the years and can be found in Metrohm Application Bulletin 141- Analysis of Edible Oils and Fats.

Iodine number.

For this anlysis the following are required.

Metrohm Autotitrator, either a Titrando or a Titrino model.

Combined platinum electrode, eg Pt Titrode or Pt ring electrodes.

The titration is a dynamic (Det U) back titration with 0.1M sodium thiosulphate.

The sample is dissolve sample in glacial acetic acid.

And added are 25ml of reaction solution and 10ml catalyst.

(specified in Bulletin).

Store on dark for five minutes.

Add 15ml KI solution, DI water and back-titrate to excess of iodine with 0.1M Na2S2O3.

At same time run a blank without sample.

The titrator automatically carries out the calculation.

g iodine/100g =(ml of thiosulphate for blank - ml thiosulphate for sample) x 1.269/ sample size.

(1.269=equivalent weight of iodine).

Acid number.

You will need.

Autotitrator- Titrando or Titrino models.

Solvotrode Non-aqueous pH electrode with LiCl sat in ethanol electrolyte.

0.1M KOH in isopropanol.

Solvent mixture ethanol/diethyl ether 1:1.

Weigh out 5-10 g sample, dissolve in 50ml solvent mixture.

Dynamic (DET U) Titration with KOH.

AN mgKOH/g = ml 0.1M KOH x 5.61/ sample size.

(5.61=equivalent weight KOH).

Karl Fischer moisture analysis.

EN14214/ EN ISO 12937 states that water determination should be by coulometric KF titration method.

Metrohmcan offer a choice of two coulometers.

either the 831 or the 756 models.

In some cases the addition of a solubility promoter (chloroform or propanol) is recommeded to improve solubilty.

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