Additives for Diesel Fuels
Filterability improver
If diesel is cooled, the paraffin separates in a crystalline form or as amorphous solids as soon as it goes below the specified temperature. The extent of the operational fault of the engine is not just influenced by the quantity, but also by the size of the paraffin crystal. Polymer additives hinder the crystal building due to the deposit reactions and consequently hinder the build-up of large crystals. There are two kinds of additives (see below):
| Additive | Effect | Comment |
| High-molecular chlorinated hydrocarbons | Filterability improver | 1.Main type e.g. condensates between napthalin and chlorinated paraffin Concentration: 0.01–0.1% (m/m) |
| Copolymerisates based on ethyl with acryl and methacryl acid esters, maleic acid diesters, alcohols or vinyl acetate | Filterability improver | 2.Main type Concentration: 0.01–0.1% (m/m) |
| saltpetre acid ester such as: Amylnitrate or Cyclohexynitrate | Ignition aid (increases cetane count) | The practical significance is low in today’s time. Concentration: 0.1–1% |
| See Petrol | Antioxidants / Metal-Deactivators | Very small concentration |
| See Petrol | Corrosion inhibitor | Rarely required, since diesel is very mildly corrosive very small concentrations, in some cases up to max. 100mg/kg |
| Detergents and/or antioxidants (see petrol under carburettor detergents, which ONLY prevents the deposits) | Anti-smoke additive | Prevents soot build-up. The effect is moderate; the soot content does not reduce much. Concentration: to 0.5% |
| Barium bonds (also calcium bonds) | Anti-smoke additive | e.g. Barium naphtasulphonate or Barium carbonate. Dissolved in spindle oil. Good effect (soot build-up reduces considerably) Due to the poison in the emitted Ba bonds (approx. 25% as barium carbonate, rest as non-poisonous BaSO4), probably not in use any more. |
| Lead-iron-manganese and cobalt bonds: lead-naphthenate, tetraethyl lead, calcium sulphonate, manganese naphthenate, nickel carbonyl, methylcyclopentaldienyl-manganese tricarbonyl, Ferrocen | Anti-smoke additive | Ba bonds display the best effect for diesel; Mn and Fe bonds not so much During the combustion, there are largely metal oxides and sulphates (they can be determined this way) Co, Ni, Cu bonds due to their poisonous properties are not available in the industry |
| Nitropropane, Nitroethane, Ethylnitrate (Salpetre acid ethylester CH3CH2-O-NO2) | Anti-smoke additive | |
| Butylhydroperoxide | Anti-smoke additive | Also reduces the build-up of carcinogenic benzopyrenes |
Compiled by Sandor Brandenberger
Literature
1): Volker Hoenig, Tests of the mechanisms of the action of additives for heavy fuel oil, VDI, 84, 1991