Cetane Improver Additives. One of the ways to improve diesel fuel cetane number is to mix it with cetane improver additives. These additives reduce ignition lag of the fuel mixture.
There are two types of cetane improver additives:
- alkyd
- peroxide.
The additives cause homolytic molecule breaking and formation of free radicals, which provoke fuel ignition. The additives are only effective in the first stages of combustion.
Adding of up to 1% cetane improver raises the cetane number by 10-12 units. Previously, alkyl nitrates were used for this purpose, but their efficiency was accompanied by significant drawbacks, such as corrosive properties, reduction of wear-protective additive efficiency and lubricity of the fuel. Storage of fuel with nitrate additives for over six months reduces additive concentration due to its oxidation reactions with hydrocarbons, dropping the cetane number by 4-6. The above limitations are why research into the development of cetane improvers is ongoing.
Organic compounds based on peroxides, such as diaryl and dialkyl peroxides, are of particular interest. Some of the advantages of these substances is stability in storage and at higher temperatures, as well as stability in contact with water and other materials present in diesel fuel in the market.
Today, the most popular peroxide is ditertiary butyl peroxide. The general advantages of peroxides are compatibility with antiwear additives, lower toxicity and explosion hazard, as well as no corrosion effects. Diesel fuel in the United States are expected to be produced with peroxides, due to the stricter requirements to nitric compound content in diesel fuel.