Acid base phenomena in oxidative stability of distillate fuel

Military fuels are frequently stored for several years in strategic reserves. Over such extended periods of time, small but significant changes in fuel properties can occur. One important property which changes with time is insolubles content. Formation of insolubles is an indication of chemical reactions in a fuel, reactions which are triggered by air oxidation. Degradation of fuels in this manner is an important aspect of fuel instability. Stabilizing antioxidants may be used to reduce the extent of deposit formation in middle distillate fuels. Specific additives, such as phenylenediamines and hindered phenols, have been allowed in some military specification. Additive manufactures state that these antioxidants are ineffective for heavier distillates, however, and recommend other types of products. Their commercial experience with diesel fuels and home heating oils has led them to recommend alkyl amines as stability additives. Findings that free radical inhibitors were ineffective in controlling stability of middle distillate raised the question: Is free radical chemistry the key to distillate fuel instability with respect to deposit formation The effectiveness of organic amines suggests that acid/base phenomena are also involved in the chemical reactions producing deposits. The thrust of the work presented in this paper tests the acid/base thesis withmore » emphasis on fuels containing light cycle oil (LCO). The system was perturbed in several ways in an effort to diagnose the controlling chemistry. The bulk of the study dealt with the performance of a tertiary alkyl amine, duPont Fuel Oil Additive No.3 (FOA-3), which is used in commercial practice.« less