Separation and analysis of hydroxyaromatic species in liquid fuel. [Hydroxyaromatic compounds]

A combination of liquid chromatographic, chemical derivatization, and GC/MS methods has been used to isolate and analyze hydroxyaromatic (Ar-OH) compounds in fuels. Nonaqueous ion exchange chromatography is first used to obtain a concentrate of acidic compounds from the fuel. This concentrate is subsequently subfractionated into compound classes by HPLC using a silica column and a mobile phase containing a strong base, tetramethylammonium hydroxide. The subfraction containing ARUH is then either silylated with N,O-bis(trimethylsilyl)-trifluoroacetamide (10 percent trimethylchlorosilant catalyst) or acylated with trifluoroacetyl chloride (6:1 m/m triethylamine catalyst) and analyzed by GC/MS using a 30 m by 0.025 ..mu..m J and W DB-5 column. Silylated ArOH show prominent molecular ions and a fragment corresponding to (CH/sub 3/)/sub 3/-Si+ (m/e 73). In general, silylation increases the retention of ArOH on the GC column, whereas acylated ArOH elute faster than the unreacted ArOH. Acylkated ArOH yield very characteristic mass spectra which are far more useful for qualitative identification than those of silylated or underivatized ArOH. Considering the diverse sources of the fuels examined thus far, the distribution of ArOH species determined in each is surprisingly similar. All contain phenols and indanols/tetralinols as the most abundant classes. The overall abundance of ArOH in fuels generally more » decreases in the following order: coal liquids > shale oils Much greater than petroleum. In this report, results from application of the method to an SRC-II coal liquid, a Wilmington (CA) petroleum, and an in situ retorted OSCR shale oil are discussed in terms of structural variations in ArOH as a function of fuel type. For example, the two most distinguishing features of the coal liquid ArOH are their high concentration in the whole oil and presence of condensed ring species such as pyrenols and partially hydrogenated pyrenols. « less