The Chemistry of Deposit Formation in Distillate Fuels,

The chemistry of deposit formation in distillate fuels has been investigated at 65 and 80 C for time peroids equivalent to up to four years ambient storage. The chemical environment was varied by using different fuels, fuel blends, deposit promoters and stabilzers. Blends of light cycle oil LCO in straight run automotive distallate oil ADO were studied in most detail. A variety of carboxylic acids, a sulfonic acid, thiophenol, and caustic extract from LCO primarily phenols increased deposit formation some very dramatically. For the carboxylic acids, a linear relationship was found between the hydrogen ion concentration calculated from pK sub a values for water solutions and the amount of deposit formed. These acids enhanced deposit formation by catalytic action and are not incorporated into the deposit. Dodecylbenzenesulfonic acid and thiophenol were both strong deposit promoters, the latter deriving its major activity through partial conversion to benzenesulfonic acid during fuel stress. The phenols in the LCO caustic extract react via oxidative coupling to increase molecular size and develop low solubility in the fuel. A tertiary aliphatic amine stabilzer was effective for reducing the amounts of deposits from most stressed fuels and from all blends tested. Keywords Diesel fuels Storage stability Degradation Additives.