Patent ID: 6977177
Filing Date: 2005-12-20
Classification: C10L,Y10T

Abstract:
1. A method for marking a liquid petroleum hydrocarbon; said method comprising adding to the liquid petroleum hydrocarbon at least one substituted anthraquinone dye having formula (I) wherein R 1 and R 2 independently are hydrogen, hydroxy, OR 11 , amino or NR 11 R 12 ; R 3 and R 5 independently are alkyl, aryl, aralkyl, heteroalkyl or heterocyclic; R 4 and R 6 independently are hydrogen or alkyl; R 7 , R 8 , R 9 and R 10 independently are cyano, nitro or hydrogen, provided that at least two of R 7 , R 8 , R 9 and R 10 are cyano or nitro; R 11 is alkyl, aryl, aralkyl, heteroalkyl, heterocyclic or alkanoyl; R 12 is hydrogen or alkyl; and wherein said at least one substituted anthraquinone dye has an absorption maximum in the range from 690 nm to 1000 nm.