Petroleum Markers Synthesized from n-Alkylbenzene and Aniline Derivatives

Petroleum markers 1−20 were synthesized either by a coupling reaction of n-alkylaniline (which was prepared from nitration and reduction reactions of n-alkylbenzene) with a diazonium salt of aniline derivatives or by a coupling reaction of a diazonium salt of n-alkylaniline with aniline or phenol derivatives. These synthetic markers provided invisible color in high-speed diesel fuel at an effective usable level (3−5 ppm), but gave visible colors when detected by extraction with 50% (v/v) 1,2-diaminoethane in a solution containing propane-1,3-diol and methanol (2:3, v/v). Marker contents in fuel oil could be successfully quantified with a VIS spectrophotometer. The markers did not alter the physical properties of the diesel fuel (as revealed by tests performed according to ASTM methods), and they were also stable in diesel fuel over a period of at least 3 months, suggesting that these synthetic dyes could readily be applied as petroleum markers in commercial fuel oils.