Petroleum marker dyes synthesized from cardanol and aniline derivatives

Marker dyes 1-15 for petroleum products were synthesized by coupling reaction of a naturally occurring n-alkylphenol, cardanol, with aniline and its derivatives. These synthetic marker dyes provided invisible color in gasoline and high-speed diesel fuel at an effective usable level (2-5 ppm), but gave visible colors when detected by extraction with 50% (v/v) 1,2-diaminoethane in a solution containing ethane-1,2-diol and methanol (1:1, v/v). Dye contents in fuel oils could be simply quantified with a vis spectrophotometer. The ASTM test methods revealed that the general physical properties of the dyed fuel oils were similar to those of the undyed fuel oils. These synthetic dyes were found to be stable in fuel oils up to at least 3 months, suggesting that these marker dyes could be readily applied as markers for commercial fuel oils.