Antioxidants and Stabilisers Additives

Fuels and Biofuels may contain unstable species that can lead to the formation of undesirable compounds. These undesirable compounds (gums or insolubles) transported through the fuel system can lead to malfunction and breakdown. In order to stabilise fuels, antioxidants and stabilisers have been developed and used.

Gasoline can contain unstable species such as olefins and dienes and these can polymerise to form gums. In the fuel system, gums can be responsible for injection system fouling and are involved in intake valve deposit formation.

Unstable species in gasoline produce free radicals which combine with oxygen to produce further free radicals in a chain reaction and react with olefinic compounds to form gums. Uncontained, this oxidative chain reaction increases at an exponential rate producing increasing amounts of free radical and/or peroxide species. Antioxidants work by disrupting the chain propagating steps, by decomposing peroxides and by acting as free radical traps. Hindered phenols, for example intercept free radicals to form stable hindered radicals which do not propagate further. Typical treat rates are in the range 8 - 100 mg/kg.

Diesel fuel or Heating Fuels may be stored for prolonged periods, and it is of prime importance that the fuel remains fit for use throughout this time. Refinery processes to increase the proportion of diesel fuel obtained from a barrel of crude oil have utilised cracked material which contains olefins and more nitrogen and sulphur compounds than straight run distillates. Inclusion of unstable species such as olefins can result in polymerisation to form gums, whilst nitrogen and sulphur compounds and organic acids can combine to form sediments. Due to extensive desulphurisation of fuels at the refinery, reactions involving nitrogen and sulphur species have been significantly reduced, although those same refinery processes have resulted in diesel fuel being potentially susceptible to peroxidation, with consequent gum formation. Introduction of biodiesel (Fatty Acid Methyl Ester) is also a factor of instability linked to the presence of unsatured fatty acids.
As for gasoline, gums are generally undesirable and in diesel fuel systems, sediments can result in fuel filter blockage with implications for vehicle operability.

Stability improvers interfere with the acid-base reactions which occur between nitrogen and sulphurcompounds and organic acids, reacting preferentially to produce soluble reaction products and preventing sediment formation. As with gasoline, unstable species in diesel fuel produce free radicals which combine with oxygen to produce further free radicals in a chain reaction and react with olefinic compounds to form gums. Antioxidants inhibit chain-branching reactions or intercept free radicals to form stable hindered radicals which do not propagate further. Typical treat rates are in the range 20 - 200 mg/kg.

This TEAFS additive range has been developed to treat Gasoline; Diesel Fuels and Heating oils containing or not bio components like for example Fatty Acid Methyl Ester in Diesel Fuels. AOB series based on hindered phenol chemistry is particularly efficient to stabilize Diesel Fuels containing Fatty Acid Methyl Ester or pure Fatty acid Methyl Ester (B100). Methods used to evaluate oxidation stability are referenced as Rancimat (EN 15751) and ISO-12205 (ASTM D2274). It can also be used to stabilize gasoline.
BB series based on hindered phenol chemistry and dispersant. This series has been developed in order to maintain long-term oxidation stability properties of biodiesel, but also allows to bring back into specifications biodiesel with poor stability characteristics.
BB series based on hindered phenol chemistry and dispersant. This series has been developed in order to maintain long-term oxidation stability properties of biodiesel, but also allows to bring back into specifications biodiesel with poor stability characteristics.

TotalEnergies AFS antioxidant and stabiliser additives do not interfere with other fuel properties (cold flow properties, cetane number, lubricity, etc).