Organic colloidal dispersion of iron particles, method for preparing same and use thereof as fuel additive for internal combustion engines

A process for preparing a dispersion comprising:

• a) reacting in a reaction medium either an iron salt in the presence of an iron complexing agent or an iron complex with a base, maintaining the pH of the reaction medium at a value of at most 8 to obtain a precipitate, the iron complexing agent being selected from hydrosoluble carboxylic acids with a complexing constant K such that the pK is at least 3 and the iron complex being selected from the products of reacting iron salts with said acids;
• and
• adding to an organic phase in the presence of an amphiphilic agent, either:
• b1) the precipitate directly obtained from step a) and separated from the reaction medium;
• b2) the precipitate in suspension in the reaction medium;
• or
• b3) the precipitate directly obtained from reaction step a) separated from the reaction medium and taken up in aqueous suspension;
• and
• c) recovering from step b) said dispersion comprising particles consisting essentially of iron oxide, iron hydroxide or iron oxyhydroxide in an organic phase.