Method for marking mineral oils with amthraquinones

The invention discloses the use of anthraquinones of the formula ##STR1## where R.sup.3 is unsubstituted or substituted C.sub.1 -C.sub.18 -alkyl or unsubstituted or substituted phenyl for marking mineral oils. Also disclosed are the marked mineral oils and a method of detecting the anthraquinones in mineral oils.

This application is a 371 of PCT/EP94/00673, filed Mar. 7, 1994, published 
as WO94/21752, Sep. 29, 1994. 
The present invention relates to the use of anthraquinones of the formula 
Ia 
##STR2## 
where R.sup.3 is C.sub.1 -C.sub.18 -alkyl which is unsubstituted or 
substituted by hydroxyl, cyano or phenyl and may be interrupted by from 1 
to 3 ether oxygen atoms or from 1 to 3 N-(C.sub.1 -C.sub.4 -alkyl)-imino 
groups or is phenyl which is unsubstituted or substituted by C.sub.1 
-C.sub.4 -alkyl, hydroxyl, C.sub.1 -C.sub.4 -alkoxy, (C.sub.1 -C.sub.4 
-mono- or dialkylcarbamoyl)-C.sub.1 -C.sub.4 -alkoxy or C.sub.1 -C.sub.8 
-mono- or dialkylsulfamoyl, where the alkyl groups may be interrupted by 
from 1 to 3 ether oxygen atoms, for marking mineral oils, mineral oils 
marked with the abovementioned anthraquinones, and dye mixtures containing 
an oil-soluble dye and an abovementioned anthraquinone. 
The present invention furthermore relates to a method of detecting 
anthraquinones of the formula Ib 
##STR3## 
R.sup.1 is hydrogen, C.sub.1 -C.sub.18 -alkyl which is unsubstituted or 
substituted by cyano, or phenyl which is unsubstituted or substituted by 
C.sub.1 -C.sub.4 -alkyl, hydroxyl or C.sub.1 -C.sub.4 -alkoxy, and R.sup.2 
is hydrogen or a radical of the formula X--R.sup.3, where X is oxygen or 
sulfur and R.sup.3 has the abovementioned meanings, in mineral oils by 
treating the latter with an aqueous alkaline medium. 
EP-A-147 704 and EP-A-149 125 disclose 1,4-dihydroxyanthraquinones which 
have a substituted amino group in the ring position 2 as markers for 
mineral oils. However, it has been found that the compounds stated there 
have unsatisfactory performance characteristics. Thus, they exhibit, for 
example, insufficient stability to alkalis. 
U.S. Pat. No. 3,164,449 discloses dye mixtures comprising N-substituted 
1-hydroxy-4-aminoanthraquinones, suitable substituents being hexadecyl, 
octadecyl, octadecenyl and octadecadienyl. These dye mixtures, like the 
anthraquinones mentioned in GB-A-552 882, are used as dyes for dyeing 
mineral oils. There is no indication of the use as markers in either of 
these documents. 
It is an object of the present invention to provide novel agents for 
marking mineral oils. The novel agents should be easily obtainable and 
readily soluble in mineral oils. Moreover, they should be capable of being 
detected in a simple manner. Even very small amounts of marker should be 
capable of being rendered visible by a strong color reaction. Finally, the 
marker should have good stability in the alkaline detection reaction. 
We have found that this object is achieved and that the anthraquinones of 
the formula Ia which are defined at the outset are advantageous for 
marking mineral oils. 
All alkyl radicals occurring in the abovementioned formulae Ia and Ib may 
be either straight-chain or branched. 
If substituted alkyl groups occur in the abovementioned formulae Ia and Ib, 
they have, as a rule, 1 or 2 substituents. 
If phenyl groups occur in the abovementioned formulae Ia and Ib, they have, 
as a rule, from 1 to 3 substituents. 
R.sup.1 and R.sup.3 are each, for example, methyl, ethyl, propyl, 
isopropyl, butyl, isobutyl, sec-butyl, pentyl, isopentyl, neopentyl, 
tert-pentyl, hexyl, 2-methylpentyl, heptyl, octyl, 2-ethylhexyl, isooctyl, 
nonyl, isononyl, decyl, isodecyl, undecyl, dodecyl, tridecyl, 
3,5,5,7-tetramethylnonyl, isotridecyl (the above names isooctyl, isononyl, 
isodecyl and isotridecyl are trivial names and originate from the alcohols 
obtained by the oxo synthesis, cf. Ullmanns Encyklopadie der technischen 
Chemie, 4th Edition, Volume 7, pages 215 to 217, and Volume 11, pages 435 
and 436), tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, 
cyanomethyl, 2-cyanoethyl, 2- or 3-cyanopropyl, 2- or 4-cyanobutyl, 
5-cyanopentyl, 6-cyanohexyl, phenyl, 2-, 3-or 4-methylphenyl, 2-, 3- or 
4-ethylphenyl, 2,4-dimethylphenyl, 2-, 3- or 4-hydroxyphenyl, 
2,4-dihydroxyphenyl, 2-, 3- or 4-methoxyphenyl, 2-, 3- or 4-ethoxyphenyl 
or 2,4-dimethoxyphenyl. 
R.sup.3 may furthermore be, for example, 2-methoxyethyl, 2-ethoxyethyl, 
2-propoxyethyl, 2-isopropoxyethyl, 2-butoxyethyl, 2- or 3-methoxypropyl, 
2- or 3-ethoxypropyl, 2- or 3-propoxypropyl, 2- or 3-butoxypropyl, 2- or 
4-methoxybutyl, 2- or 4-ethoxybutyl, 2- or 4-propoxybutyl, 2- or 
4-butoxybutyl, 2-hydroxyethyl, 2-hydroxypropyl, 3-hydroxypropyl, 
2-hydroxybutyl, 4-hydroxybutyl, 5-hydroxypentyl, 6-hydroxyhexyl, 
5-hydroxy-3-oxapentyl, benzyl, 1-phenylethyl, 2-phenylethyl, 
3,6-dioxaheptyl, 3,6-dioxaoctyl, 4,8-dioxanonyl, 3,7-dioxaoctyl, 
3,7-dioxanonyl, 4,7-dioxaoctyl, 4,7-dioxanonyl, 4,8-dioxadecyl, 
3,6,8-trioxadecyl, 3,6,9-trioxaundecyl, 2-dimethylaminoethyl, 
2-diethylaminoethyl, 2- or 3-dimethylaminopropyl, 2- or 
3-diethylaminopropyl, 2- or 4-dimethylaminobutyl, 2- or 4 
-diethylaminobutyl, 3,6-dimethyl-3,6-diazaheptyl, 
3,6,9-trimethyl-3,6,9-triazadecyl, 2-(1-methoxyethoxy)ethyl, 
2-(1-ethoxyethoxy)ethyl, 2-(1-isobutoxyethoxy)ethyl, 2- or 
3-(1-methoxyethoxy)propyl, 2- or 3-(1-ethoxyethoxy)propyl, 2- or 
3-(1-isobutoxyethoxy)propyl, 4-mono- or dimethylsulfamoylphenyl, 4-mono- 
or diethylsulfamoylphenyl, 4-mono- or dipropylsulfamoylphenyl, 4-mono- or 
diisopropylsulfamoylphenyl, 4-mono- or dibutylsulfamoylphenyl, 
4-(mono-3-oxabutylsulfamoyl)phenyl, 4-(mono-3-oxapentylsulfamoyl)phenyl, 
4-(mono-4-oxapentylsulfamoyl)phenyl, 4-(mono-4-oxahexylsulfamoyl)phenyl, 
3-mono- or dimethylcarbamoylmethoxyphenyl, 3-mono- or 
diethylcarbamoylmethoxyphenyl, 3-(2-mono- or 
dimethylcarbamoylethoxy)phenyl or 3-(2-mono-or 
diethylcarbamoylethoxy)phenyl. 
Anthraquinones of the formula Ib, where R.sup.2 is hydrogen or a radical of 
the formula OR.sup.3, in which R.sup.3 has the abovementioned meanings, 
are preferably detected in mineral oils. 
Anthraquinones of the formula Ib, where R.sup.1 is hydrogen or C.sub.1 
-C.sub.18 -alkyl or is phenyl which is unsubstituted or substituted by 
C.sub.1 -C.sub.4 -alkyl, hydroxyl or C.sub.1 -C.sub.4 -alkoxy and R.sup.2 
is hydrogen, are particularly preferably detected in mineral oils. 
Anthraquinones of the formula Ib, where R.sup.1 is hydrogen and R.sup.2 is 
a radical of the formula OR.sup.3, in which R.sup.3 has the abovementioned 
meanings, are furthermore particularly preferably detected in mineral 
oils. 
The detection of anthraquinones of the formula Ib, where R.sup.1 is 
hydrogen, C.sub.1 -C.sub.4 -alkyl phenyl or methylphenyl and R.sup.2 is 
hydrogen, in mineral oils is very particularly noteworthy. 
The detection of anthraquinones of the formula Ib, where R.sup.1 is 
hydrogen and R.sup.2 is C.sub.1 -C.sub.4 -alkoxy or phenoxy, mineral oils 
is furthermore very particularly noteworthy. 
The use of anthraquinones of the formula Ia, where R.sup.3 is C.sub.1 
-C.sub.4 -alkyl or phenyl, for marking mineral oils is furthermore very 
particularly noteworthy. 
The present invention furthermore relates to mineral oils containing one or 
more of the anthraquinones of the formula Ia. 
For the purposes of the present invention, mineral oils are to be 
understood as meaning, for example, power fuels, such as gasoline, 
kerosene or diesel oils, or oils, such as fuel oil or engine oil. 
The anthraquinones of the formula Ia are particularly suitable for marking 
mineral oils for which identification is required, for example for tax 
reasons. In order to keep the costs of identification low, it is desirable 
to use very small amounts of marker. 
In order to mark mineral oil, anthraquinones of the formula Ia are used 
either as such or in the form of solutions. Preferred solvents are 
aromatic hydrocarbons, such as toluene, xylene, dodecylbenzene, 
diisopropylnaphthalene or a mixture of higher aromatics, which is 
commercially available under the name Shellsol.RTM. AB (from Shell). 
Further cosolvents, for example alcohols, such as methanol, ethanol, 
propanol, isopropanol, butanol, isobutanol, pentanol, hexanol, heptanol, 
octanol, 2-ethylhexanol or cyclohexanol, glycols, such as butylethylene 
glycol or methylpropylene glycol, amines, such as triethylamine, 
diisooctylamine, dicyclohexylamine, aniline, N-methylaniline, 
N,N-dimethylaniline, toluidine or xylidene, alkanolamines, such as 
3-(2-methoxyethoxy)propylamine, o-cresol, m-cresol or p-cresol, ketones, 
such as diethyl ketone or cyclohexanone, lactams, such as 
.gamma.-butyrolactone, carbonates, such as ethylene carbonate or propylene 
carbonate, phenols, such as tert-butylphenol or nonylphenol, esters, such 
as methyl phthalate, ethyl phthalate, 2-ethylhexyl phthalate, ethyl 
acetate, butyl acetate or cyclohexyl acetate, amides, such as 
N,N-dimethylformamide, N,N-diethylacetamide or N-methylpyrrolidone, or 
mixtures thereof, can usually be used for improving the solubility. In 
order to avoid a high viscosity of the resulting solutions, a 
concentration of anthraquinone Ia of from 1 to 50, preferably from 10 to 
50, % by weight, based in each case on the solution, is generally chosen. 
The present invention furthermore relates to dye mixtures containing an 
oil-soluble dye and an anthraquinone of the formula Ia. 
The novel dye mixtures are advantageously prepared and used in the form of 
solutions. Preferred solvents are the abovementioned products. However, in 
order to avoid an excessively high viscosity of the resulting solutions 
here too, the abovementioned concentrations of dye are also chosen. 
The anthraquinones of the formula Ia and the oil-soluble dye are 
advantageously dissolved in a weight ratio of from 10:1 to 1:10 in 
solvents. In principle, the ratio can of course be completely freely 
chosen. The novel mixtures may contain one or more oil-soluble dyes and 
one or more anthraquinones of the formula Ia. 
Oil-soluble dyes for the novel mixtures are, for example, the compounds 
which are stated under Solvent Dyes in the Color Index and which may 
originate from various dye classes. The choice of the oil-soluble dyes 
depends on the desired hue. Representative examples of oil-soluble dyes 
are the dyes of the formulae II to IX: 
##STR4## 
Further suitable oil-soluble dyes are, for example, C.I. Solvent Yellow 14 
(12,055), C.I. Solvent Yellow 16 (12,700), C.I. Solvent Yellow 56 
(11,021), C.I. Solvent Orange 102, C.I. Solvent Red 1 (12,150), C.I. 
Solvent Red 19, C.I. Solvent Red 24 (26,105), C.I. Solvent Red 215 or C.I. 
Solvent Blue 35 (61,554). 
The novel mixtures have the advantage that they are suitable for coloring 
mineral oils so that they are readily visible and at the same time can be 
used as marking substances. 
By means of the anthraquinones of the formula Ia which are to be used 
according to the invention, it is possible to detect marked mineral oils 
in a very simple manner even when the marking substances are present only 
in a concentration of about 10 ppm or lower. This also applies when the 
novel dye mixtures are used. 
As stated at the outset, the anthraquinones of the formula Ib which are 
used as markers can be advantageously detected if the mineral oil is 
treated with an aqueous alkaline medium. 
When an aqueous alkaline medium is added to the marked mineral oil, the 
result is a clearly visible color reaction with formation of a complex, 
the latter passing over into the aqueous phase. 
Suitable aqueous alkaline media for the detection reaction are in 
particular aqueous solutions of alkali metal carbonates or alkali metal 
hydroxides, for example aqueous sodium carbonate or potassium carbonate 
solutions or sodium hydroxide or potassium hydroxide solutions. The 
content of alkali metal carbonate or alkali metal hydroxide in the aqueous 
solution is as a rule from 1 to 10% by weight, based on the weight of the 
solution. 
In some cases, it may also be advantageous to add solubilizers, eg. 
N-methylpyrrolidone, methanol, ethanol, propanol, 1-methoxypropan-2-ol, 
glycerol, ethylene glycol, diethylene glycol, nonylphenol or 
water-miscible amines, for example alkanolamines, such as diethanolamine 
or triethanolamine, to the aqueous alkaline medium in minor amounts (in 
general up to 20%). 
The anthraquinones of the formulae Ia and Ib are known per se. They are 
dispersion dyes for coloring or printing textiles. Examples are C.I. 
Disperse Red 4 (60,755), C.I. Disperse Red 15 (60,710), C.I. Disperse Blue 
22 (60,715), C.I. Disperse Violet 13 (60,725) or C.I. Disperse Violet 27 
(60,724). Further information may be obtained from, for example, K. 
Venkataraman, The Chemistry of Synthetic Dyes, Vol. 2, page 805, or Vol. 
3, pages 391 to 396. 
The anthraquinones which are to be used according to the invention can be 
detected in a simple manner in mineral oils. They exhibit high alkali 
stability in the detection reaction taking place in an alkaline medium.

The Examples which follow illustrate the invention. 
EXAMPLE 1 
100 ml of mineral oil which contains 10 ppm of 
1-amino-2-methoxy-4-hydroxyanthraquinone was thoroughly shaken with 5 ml 
of a mixture of 10% strength by weight sodium hydroxide solution and 
N-methylpyrrolidone (5:1 v/v). The lower aqueous phase became violet while 
the organic phase was decolorized. 
After standing for two days at room temperature, 95% of the dye complex 
were still present in the aqueous phase, as shown by photometric 
measurements. 
The anthraquinones shown in the Table below can be detected in a similar 
manner. 
__________________________________________________________________________ 
Color of the 
Example no. 
Marker aqueous phase 
__________________________________________________________________________ 
##STR5## violet 
3 
##STR6## violet 
4 
##STR7## blue 
5 
##STR8## violet 
6 
##STR9## blue 
7 
##STR10## blue 
8 
##STR11## blue 
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