The use of additives to improve certain fuel properties – common practice for fossil fuels long since – has also gained increasing importance concerning Biodiesel. So far predominantly flow improvers and oxidation stabilizers are utilized; but additional additives are imaginable, too, and may play a part in the production and application of Biodiesel in the future.
The utilization of stabilizers for Biodiesel as blend component is called for more and more frequently in order to ensure sufficient oxidation stability of the final fuel; the European Standards for Diesel fuel and Biodiesel (EN 590, EN 14214 as well as the French national B7 specification) even expressly recommend additivation.
Apart from stabilizer BHT (3,5-di-tert-butyl-4-hydroxy-toluene) mostly utilized so far, there is meanwhile a variety of other products some of which show a significantly better effect and are also suitable for the use in Biodiesel. However, it is of great importance for the release of those substances for ‘Biodiesel’ as blend component that they do not show any unwanted interaction with the Diesel fuel, its additives or the engine oil. For a safe use – from blending to the application and combustion in the engine – negative impacts of such additives must be detected beforehand by means of suitable
In cooperation with the mineral oil industry a catalogue of test methods was defined by means of which oxidation stabilizers can be tested for possible unwanted side effects.
With the revision of EN 14214 (EN 14214:2010) in 2012, the requirements for the oxidation stability increased from 6 h as stipulated by the previous standard to 8 h according to the new standard EN 14214:2012. This alteration led to corresponding consequences regarding the required achievable oxidation stability for the No-harm Test. Since 2013 the requirement of the No-harm Test is that a minimum oxidation stability of 8 h +1 h must be achieved by additivation. The achievement of an extra hour is meant to provide the customer with a safe time reserve for any possible stability loss due to contact with oxygen during transport or prolonged storage times, for example.
However, since all products listed in the No-harm list had already achieved the required oxidation stability of 8 h prior to the alteration of the EN standard, those products were not re-tested especially with regard to the extra stability time reserve.
The test comprises the following test criteria:
In addition, further minimum requirements must be fulfilled such as unchanged safety-related properties of the Biodiesel (e.g. flash point, water hazard class); no impermissible alteration of the standard parameters according to EN 14214 for Biodiesel; submission of an explicit application descriptions for the additive.
Products which pass the test and fulfill the above criteria are listed and published on AGQM’s homepage. In addition, according to a defined method (Relative Efficiency Test – RET) and with four differing scenarios the dosages of the tested stabilizers effectively corresponding to the reference dosage of 200 mg BHT/kg are determined.
The evaluation of the tested additives refers to analysis carried out with conventional commercial Diesel fuel. Interactions with the specific additive packages of mineral oil companies were not analyzed in this context.
We would like to point out that upon request it is possible for interested parties to view the achieved no-harm results according to the test certificates. Please address the additive producer if you wish to obtain any information.
AGQM’s list is open for interested producers of additives.
You want to test one of your own products? Contact us.
The detailed report with the anonymus test results of all successfully tested oxidation stabilizers can be ordered here.