Baynox® is the LANXESS brand name for phenolic antioxidants which are used for the stabilisation of fuels, especially biodiesel and blends thereof with petro diesel. Baynox® increases the shelf life of fuels and protects against engine damage. Depending on the type of biodiesel (PME, RME, SME, UCOME) and the storage conditions, different products are available:

Baynox® Molten und  Baynox® EU are used as highly concentrated active ingredients, while Baynox® Solution and  Baynox® Cargo are solutions of these antioxidants in biodiesel / aromatic solvent. For applications with even higher requirements, the products  Baynox Plus® (solid),  Baynox® Plus Solution and Baynox® Ultra (solutions) can be used. The dosage depends on the natural stability of the (biodiesel) fuel which can vary. The resulting fuel has to comply with the (inter)national standards. 

Baynox® 44PD is an aminic antioxidant which is mainly used for the stabilization of gazoline. Typically it is used in lower dosage compared to the phenolic types. 

Baynox Solution - Patent granted (EP 1563041) for Baynox Solutions in Biodiesel





LANXESS is Silver Partner at the 18th International Conference on Renewable Mobility 1-22 January 2021, Fuels of the Future 




18th International Conference on Renewable Mobility - Digital and internationally networked

More Information: >>



What is biodiesel?

In these times of rising fuel prices an increasing number of private and commercial drivers who use diesel are changing to biodiesel.
Not only is biodiesel considerably better value for money than the mineral-based variant, it is also environmentally friendly and can be "home grown".
Biodiesel is produced chemically through transesterifcation of vegetable oils with methanol. Native vegetable oil is primarily rapeseed oil in Europe; used fats from the food industry and animal fats can also be used. The one thing all of these have in common is that the raw materials are renewable energy sources.

Where can I find out more about biodiesel?

Detailed information about the production, cost-effectiveness of biodiesel and which types of vehicle have been approved for its use is available from the following links:


and generally on the Internet via the usual search engines.

Does biodiesel have any disadvantages?

The "natural" fuel does have one disadvantage. As is the case with natural vegetable oils, it oxidizes more easily by atmospheric oxygen than mineral diesel.
The consequences of oxidation are firstly that biodiesel decomposes to form short-chain fatty acids, and secondly that insoluble polymers (gums) are formed. If nothing is done to counteract this, it is possible that the engine may become damaged as a result.
The oxidation of oils and fats by atmospheric oxygen is known as rancidity. Rancid oils and fats are unusable.

Can biodiesel become rancid?

In principle, yes. Specifically, it is the unsaturated fatty acid structures which are easily oxidized by atmospheric oxygen. These are the same in vegetable oils and biodiesel, it is only in the alcohol part that the two products differ.

What exactly happens when the biodiesel becomes rancid or oxidized?

When exposed to heat, light and stress, the fatty acid methyl ester forms a radical, usually directly next to the double bond. This radical quickly binds with the oxygen in the air, which is a diradical. A peroxide radical is formed.

Now the rapid radical destruction cycle begins. This peroxide radical immediately creates a new radical from the fatty acid methyl ester, which in turn binds with oxygen in the air. The destructive radical auto-oxidation cycle begins. During this process, up to 100 new radicals are created quickly from one single radical, meaning that decomposition occurs at an exponentially rapid rate, and the oil spoils and becomes rancid very quickly.

It is easy to identify rancid oils in the home from their typically unpleasant odor. The smell comes from the short-chain degradation products produced by the unsaturated fatty acids such as butyric acid.

What does nature do to prevent this?

In addition to the oils, oil-yielding plants produce vitamin E or tocopherol. which is a natural antioxidant.
A variety of different tocopherol isomers exist with differing effective strengths, but they all have the same basic chemical structure. A hindered aromatic phenol structure is bonded to a long-chain phythyl group. This is the actual active chemical structure of the antioxidant.

As animals and people are unable to produce vitamin E themselves, they have to take it in with their food, in order to protect their body fat against oxidation.

How does vitamin E work?

Before the peroxide radical creates another radical from the fatty acid group in the auto-oxidation mechanism, it is intercepted by vitamin E. The vitamin E binds the peroxide radical to the hindered phenol and prevents any further reaction taking place. No more new radicals are created and the decomposition of the fatty acids to short-chain degradation products is prevented.
Nevertheless, it must be noted that vitamin E is gradually used up in this process.

Does biodiesel contain vitamin E?

Yes, if there was vitamin E in the vegetable oil which served as the raw material, then it will also be passed into the biodiesel, depending on the production process used. This is why, for example, biodiesel made from rapeseed oil is very stable in terms of oxidation. According to our measurements the vitamin E content in rapeseed methyl ester is very high, that is at least in terms of the amount which can be expected to be found in natural vegetable oils.

How is the stability of biodiesel tested?

The natural stability of biodiesel is measured using the Rancimat method (DIN EN 14214).
This involves pumping the air through biodiesel which has been heated to a temperature of 110°C using a piece of equipment which meets the required standards. If short-chain fatty acids are present in the distillate as cleavage products of the fatty acid oxidation, this indicates that the biodiesel is unstable. The DIN EN 14214 standard stipulates that biodiesel must remain stable and undecomposed in the Rancimat for at least 6 hours.
Biodiesel has to fulfill this requirement not only at the production plant but at the pump when refueling vehicles.

What does stability mean in practice?

A stable and non "rancid" biodiesel is suitable as a fuel as recommended by manufacturers. A "rancid" biodiesel on the other hand may damage the engine and the fuel injection system.
To find out how quickly biodiesel ages after its production, a number of tests were carried out in our laboratories.
A fresh biodiesel (rapeseed methyl ester) from a recognized producer was aged in the laboratory. To do this, the biodiesel was agitated in an open 500 ml glass bottle at 40 °C in a temperature-controlled cupboard. Every few days a sample was taken and the stability was tested according to the Rancimat test.

This graph (see fig. 2 of 6) shows that the stability constantly decreases. After approximately 10 days it has fallen by one hour and is consequently outside of the limits permitted by the DIN EN 14214 standard. After two months the biodiesel is completely unstable and oxidation can take place unimpeded in a chain reaction, in other words it oxidizes quickly and is unusable.

During this laboratory test in a glass bottle other influences which may have accelerated the aging process of the biodiesel were ruled out. For example, heavy metals such as copper from equipment and fittings can speed up aging considerably.

When you consider that fuel in the tank of a car is very likely to reach temperatures of up to 40 °C and, more notably, that car drivers do not always completely empty the tank within 10 days, it is obvious that to ensure the operational safety of biodiesel it is essential that it has sufficient stability when it leaves the plant, and, where possible, that this is even above the standard.

Is there a connection between vitamin E content and stability?

Yes, the vitamin E content of the biodiesel was tested during the same test. It was observed that the stability decreases as the vitamin E content drops. (see fig. 3 of 6)

This means it is essential for the stability of biodiesel that the level of oxidation protection is just as high as that produced by the naturally occurring vitamin E.

How is it possible to recognize oxidation in biodiesel?

The answer is: from the oxygen consumption. The same amount of oxygen is removed from the air as oxidizes the biodiesel to form compounds containing oxygen.
This process can be clearly seen if a bottle filled with biodiesel is left standing for a long time. As soon as the antioxidant has been used up and the induction time is over, the oxygen is used and negative pressure builds up.

This effect can be seen on a plastic bottle in the way it becomes deformed. (see fig. 4 of 6)

How is possible to increase the natural stability of biodiesel?

It is possible to increase the natural stability of biodiesel by adding the antioxidant Baynox. The active ingredient in Baynox is a chemical simulation of vitamin E. This means that chemically it is also a hindered phenol. Just like vitamin E, Baynox intercepts the peroxide radicals and stops the autocatalytic oxidation of the unsaturated fatty acids.

Increasing amounts of Baynox were added to biodiesel (RME) which had a stability of 8.2 hours in the Rancimat. The figure (see fig. 5 of 6) shows the increase in the stability in relation to the quantity of Baynox.

With approximately 1,000 ppm Baynox it is possible to reach a value of approximately 10 hours in the Rancimat. This gives the biodiesel sufficient protection for transportation and a long period of storage at the gas station and in the tank of a diesel-fuelled vehicle.

How much Baynox needs to be added?

The required quantities for use are based on the natural stability of the type of biodiesel being used. This can be subject to considerable fluctuations. As a rule, amounts between 0.1 and 0.5 vol. % (equivalent to 1-5 l Baynox to 1,000 l biodiesel) are recommended. The dosage and tolerance with the customer-specific biodiesel must be ascertained in tests.

Experience shows that a different dose is recommended for biodiesel made from old cooking fat and oils and animal fats and oils than for biodiesel made from rapeseed oil or other types of vegetable oil.

How is Baynox added?

Baynox is the formulation of the high-purity antioxidant active ingredient dissolved in biodiesel. Baynox has almost the same viscosity and density as pure biodiesel and can simply be mixed with biodiesel. A static mixer or a pipeline of appropriate length are recommended for adding the stabilizer. Please don't hesitate to ask us if you require any further information on using Baynox.

Is Baynox compatible with additives used in winter?

Baynox has been tested for its compatibility with the most common winter additives. Even at high doses, no interactions with the winter additive occurred. Nor was the effectiveness of either the winter additive or Baynox impaired.

Where is it possible to get specialist and analytical support on antioxidants and biodiesel?

Bayer Industry Services (BIS) offers analytical tests for ascertaining the stability of biodiesel using the Rancimat test and the content of Baynox and vitamin E in biodiesel. These can be arranged by us on request.

BIS conducts tests with increasing amounts of Baynox and can show you by means of a diagram exactly which improvements are produced by adding which quantities of Baynox.

With this as a basis, you will always know exactly how much stabilizer you require for what use and thereby avoid unnecessary costs caused by adding too much and/or not adhering to the standard.

Additionally, Bayer Industry Services offers a broad range of analytical testing methods and expert know-how that can also be requested for other chemically related questions concerning biodiesel.

Please contact us if you have any chemical or technical queries.

How safe is Baynox to use?

Baynox is a 20 % solution of the distilled high-purity active ingredient dissolved in biodiesel (RME). The quality of every single batch is checked. If required, we can prepare the Baynox Biodiesel stabilizing solution using your own biodiesel.

Apart from the active ingredient and biodiesel (RME), Baynox does not contain any alcohol or mineral-based solubility promoters or other auxiliary agents. The active ingredient combusts in the vehicle's engine without leaving any residue. This is checked with every single batch.

Baynox is not a hazardous substance and has the same water hazard class as Biodiesel. Baynox is non-toxic and does not pose a risk in wastewater.

Does Baynox have any other effects?

During the oxidation process of the fatty acids a few oligomer or polymer components form in the biodiesel. These precipitate as gum if they are over a particular molecular weight.

In one of our tests on a used fat biodiesel, there was definite clouding after approximately 4-6 weeks' storage with a large surface area. This precipitation (gum) consisted of polymer biodiesel. With 500 ppm Baynox no precipitation occurred. (see fig. 6 of 6)

Adding Baynox stops the formation of oligomer or polymer components in biodiesel.

What size containers is Baynox available in?

Baynox is available in several different types of container, depending on customer requirements:

  • 1,000 l IBC: 20 % active ingredient dissolved in biodiesel (RME compliant with DIN EN 14214)
  • 10-18,000 l tanker or container: 20 % active ingredient dissolved in Biodiesel (RME compliant with DIN EN 14214) or in customer's own supplied biodiesel on request.
  • A sample may be requested for test purposes