John M. Watkins

A NEW LOOK AT THE MECHANISMS OF OXIDATIVE SEDIMENT FORMATION IN FUELS

ABSTRACT Alkylpyrroles have been known to promote sediment formation and discoloration of petroleum distillates for over thirty years. There has been much effort directed towards understanding the detailed mechanism of alkylpyrrole promoted sediment formation in petroleum distillates. In addition, recent studies have investigated the mechanism of alkylpyrrole sediment formation in shale derived synfuels. It is the intent of this article to critically review some of the postulated mechanisms for alkylpyrrole promoted sediment formation in fuels and then to comment on the significance of these mechanisms to our overall understanding of the field of oxidative fuel stability.

Liquid phase oxidation of thiophenol and indene by t-butyl hydroperoxide and oxygen

ABSTRACT The tert-butyl hydroperoxide (tBHP) or oxygen initiated oxidation of thiophenol in the presence of the active olefin indene was examined in benzene at 120C. The reaction is kinetically complex, but it was possible to relate the product distribution to a few competing reactions. The product mix was determined for several reaction time periods. The product slate was similar for all time periods, but yields of the individual components varied significantly with increasing reaction time. Gaseous products included isobutylene and a trace of methane. The major product from tBHP was t-butanol. The major product observed from thiophenol was phenyl disulfide. Addition products included the major product 2-phenylthiyl indan. Oxidation products included: indanols, indanones, and the sulfoxide and sulfone of the major product 2-phenylthiyl indan. Solvent participtation was noted by trace amounts of toluene.

CHEMICAL FACTORS AFFECTING INSOLUBLES FORMATION IN SHALE DERIVED DIESEL FUEL

ABSTRACT Detrimental changes in fuel properties with time have been a continuing problem in the use of middle distillate fuels. Instability of diesel fuels is usually defined by the formation of insoluble sediments and gums. Gravimetric stability tests have been conducted at 43° and 80°C, respectively, using three model nitrogen heterocycles, 2-methylpyridine, 2,6-di methyl quinoline, and dodecahydrocarbazole, as dopants in an otherwise stable shale diesel fuel. Potential interactive effects have been defined for these three model nitrogen heterocycles in the stable fuel in the presence of a second model dopant, t-butyl hydroperoxide. 2-Methyl pyridine and 2,6-dimethyl quinoline were inactive and only 2-methyl pyridine showed slight positive interactive effects. Dodecahydro-carbazole formed large amounts of insolubles by itself and exhibited positive interactive effects.

LIQUID PHASE CO-OXIDATION OF THIOPHENOL AND STYRENE BY OXYGEN AND t-BUTYL HYDROPEROXIDE

ABSTRACT Instability problems in both shale and petroleum derived middle distillate jet fuels have been correlated with the presence of peroxidic species. Although a good body of knowledge exists concerning the formation of peroxides in the liquid phase, relatively little is known about the reaction/ decomposition pathways available when other functional groups are present, since sulfur is the most abundant heteroatam present in jet fuels, the reaction of t-butyl hydroperoxide (tBKP) and/or oxygen with thiophenol in the presence of the active olefin, styrene, was examined in deaerated benzene at 120°C. The complex product mixture was analyzed by combined capillary column GC/MS. Major products included acetone, t-butanol and isdbutylene from the tBHP. Thiophenol and styrene combined to form addition products. Phenyl disulfide was observed from the thiophenol. The results indicated that although the product slate was complex, it was possible to explain the product mix in terms of a few competing reactions.