Deposit Forming Tendency of Gasoline Polar Compounds 932742

In order to evaluate the deposit-forming tendency produced by polar compounds in gasoline, acidic and basic compounds were isolated from four 190°C+ fractions of cracked Venezuelan components. These compounds were isolated from each component by aqueous sodium hydroxide and hydrochloric acid extractions, respectively. The remaining organic layer was then passed through a silica gel chromatography column on which the polar compounds were retained; the non-polar compounds were eluted directly. In order to elute the polar compounds from the silica column, four solvents were used (hexane, toluene, ethyl acetate and methanol). Each solvent fraction was characterized by IR, NMR-¹H and -¹³C, and FIA, sulfur, and total nitrogen were determined. Tests were performed with an ISD apparatus to evaluate deposit forming tendency of the different fractions. The non-polar material eluted directly from the column showed decreases (67-100%) in ISD deposits in comparison to the initial 190+°C fractions. The different polar fractions eluted from the silica column, and the basic and acidic compounds isolated by extraction were also tested. The basic, ethyl acetate and methanol fractions showed a high deposit-forming tendency. The hexane and toluene fractions showed no significant changes in deposit levels in spite of high sulfur contents. A decrease in the deposit-forming tendency was found for two of the acidic fractions, with respect to that of the original 190+°C fraction; for the others, no significant change in deposit levels was observed. Relations between chemical structures and possible mechanisms are discussed.