WO2022161960A1

WO2022161960A1 - A method of marking fuels

Info

Publication number: WO2022161960A1
Application number: PCT/EP2022/051657
Authority: WO
Inventors: Hans Reichert; Leonhard Feiler; Rene Fischer; Oliver Seeger; Korinna Dormann
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2021-01-29
Filing date: 2022-01-25
Publication date: 2022-08-04
Anticipated expiration: 2023-07-29

Abstract

The present invention relates to a method of marking fuels comprising the steps of a) adding at least one photochromic compound of the formula (I) to the fuel, and b) converting the compound of formula (I) from an original stable state into a metastable state by photonic induction, whereby i) a change in an optical property and/or ii) detection of the time temperature dependent re-conversion from the metastable state to the original stable state act as an identification marker for the fuel.

Description

A method of marking fuels

The present invention relates to a method for marking fuels, and to compounds of formula (I) for use in the method.

Fuel samples are generally required to be labelled for a variety of purposes such as to distinguish between taxed and untaxed fuel oils or as brand identification for organic based liquids. Conventionally, fuels have been differentiated by means of colour, for example by including an appropriate dyestuff in the fuel, since colour is the simplest way of identifying fuel either by eye or quantitatively using a spectrophotometer.

The fuel is ideally marked with trace amounts of material (< 50ppm) such that the properties conferred by the marker chemical do not affect the bulk liquid. It should also be possible to detect concentrations as low as 5% of the marker in fuel in cases were the fuel has been diluted with unmarked fuel.

A variety of compounds have been described for marking fuels in the aforementioned manner. Often the fuel is marked with a chemical which is initially colourless but which becomes coloured upon the addition of a "developer" compound. US5498808, WO96/02613, W095/07460, EP0438734, W095/00606, US5205840 and WO95/10581.

GB2344599A relates to a method of marking liquids comprising the steps of adding a photochromic compound, such as, for example, spirooxazines (particularly but not exclusively spiro (indolino) oxazines) and heterocyclochromenes, in particular benzopyrans or napthopyrans, to the liquid and exposing the liquid to ultraviolet light to increase the visibility of the photochromic compound whereby the colour or intensity of the compound after exposure to ultraviolet light acts as an identification marker for the liquid. The dichromophoric compounds of formula (I) used according to the invention differ fundamentally from the monochromophoric compounds disclosed in GB2344599A. They exhibit a higher colour strength and their discoloration process is more pronounced and, hence, easier and faster to be observed and measured.

WO2010/039152A1 relates to a method comprising: testing a fuel for a presence of a first marker in the fuel in a predetermined concentration range; and testing the fuel for a presence of a second marker in the fuel, wherein: the presence of the first marker in the fuel in the predetermined concentration range and an absence of the second marker in the fuel is indicative that the fuel is unaltered, the presence of the first marker in the fuel in a concentration less than the predetermined concentration range is indicative that the fuel is altered, and the presence of the second marker in the fuel is indicative of an altered fuel.

EP2524812A2 relates to a remote marking system comprising at least one marker unit and at least one target, wherein: said marker unit comprises at least one emitter configured to emit at least one tracer signal; and said target comprises at least one receiving medium configured to change its state upon reception of said tracer signal thereby recording the position at which said tracer signal is received. In addition, EP2524812A2 relates to a photochromic solution comprising a photochromic material selected from the consisting of a spiro-oxazine compound, a naphthopyran compound, a spiropyrans compound, a triarylmethane compound, a stilbene compound, an azastilbene compound, a nitrone compound, a fulgide compound, a diarylethylene compound, a quinine compound and any combination thereof; and a solvent. US20110059545A1 provides photochromic oligomeric spiropyran compounds as well as methods for their preparation and use as active ingredients of time temperature indicators (TTIs). By virtue of its photochromic properties, the compound of formula (I) can undergo photo- induced coloration by irradiation with photons of a specific energy range, the coloration being followed by a time- and temperature-dependent decoloration; i.e. offers two detection possibilities which can be observed with the naked eye, or detected with a simple spectrometer. Due to the photochromic properties a high protection against counterfeit is possible, making the element ideally suitable for fuel marking. Accordingly, the present invention provides a method of marking liquids, in particular fuels, comprising the steps of a) adding at least one photochromic compound of the formula

the liquid, wherein R₁ to R₄ are independently of each other hydrogen, C₁-C₆alkoxy, halogen, CF₃, -C₁-C₆alkyl, or -NO₂, R₅ is hydrogen, halogen, -C₁-C₆alkoxy, -COOH, -COO-C₁-C₈alkyl, -CF₃, or phenyl; R₁₁ is hydrogen, or R₁₁ and R₅ form together a phenyl ring; R_a is -C₁-C₆alkyl, R_b is -C₁-C₆alkyl, or together with R_a form a 5-6 membered ring; and L is a divalent linker; and b) converting the compound of formula (I) from an original stable state into a metastable state by photonic induction, whereby i) a change in an optical property and/or ii) detection of the time temperature dependent re-conversion from the metastable state to the original stable state act as an identification marker for the liquid.

Preferably, the compound of formula (I) is added to the liquid, in particular the fuel, to be marked at a concentration that imparts no visible colour to the liquid.

Preferably, the photochromic compound becomes visible upon exposure to light, preferably blue light, or UV light.

The liquid is preferably a fuel. The term "fuel" refers to products having a predominantly hydrocarbon composition, although they may contain minor amounts of oxygen, nitrogen, sulfur or phosphorus. As used herein, the term “fuel” includes crude oils, as well as products derived from petroleum refining processes. Preferably, a “fuel” includes without limitation crude oil, lubricating oil, hydraulic fluid, brake fluid, gasoline, diesel fuel, kerosene, jet fuel, heating oil and heavy fuel oil. More preferably, the petroleum hydrocarbon is selected from the group consisting of gasoline, diesel fuel, kerosene, and jet fuel, and even more preferably from the group consisting of gasoline and diesel fuel.

The present invention is particularly suitable for marking fuels as the compounds recommended show stability therein and may be detected at ppm, or sub-ppm levels.

The absorbance of the photochromic compound used in the present invention is such that the absorbance on exposure to UV light under the appropriate temperature conditions is greater than 0.1 , more preferably greater than 0.2.

The marked liquid, in particular fuel, is preferably illuminated by an ultraviolet source or a flash lamp, such as a photographic flash lamp. Preferably, the marked liquid is illuminated at a constant distance for a constant length of time at a specified temperature to ensure reproducibility of the colour formation thereby ensuring the correct identification of the liquid from the detected marker.

Preferably, the sample of liquid, in particular fuel, to be identified is stored in a light free environment prior to exposure to ultraviolet light to ensure that any change in colour that has occurred in the marker during its exposure to ambient light is reversed prior to testing. Alternatively, the sample may be heated in a sealed vial to reverse the colour change prior to illumination. The increased visibility of the compound by exposure to the UV light may be reversed by the removal of the UV light source. For example, the method may comprise taking a sample of the liquid from the bulk liquid in a vial, if necessary cooling to a specified temperature, exposing the sample to UV light to enable the detection of the compound and thereby identify the liquid and returning the sample back to the bulk liquid. The change to the colourless state will then occur in the bulk liquid especially if it is in a light free environment. The photochromic compound is preferably provided as a liquid, in particular fuel, concentrate for addition to the liquid to be marked. Preferably, a concentrate of between 1% to 10% of the marker in an organic solvent is used. Organic solvents suitable for this purpose are, for example, alkyl benzenes, alkylnaphthalenes or a proprietary blend of such compounds. Polar organic solvents may be included to increase the solubility of the marker compound in the concentrate, such as formamide, N,N-dimethylformamide and N- methylpyrrolidone. Preferably, the solvents are a mixture of aromatic and aprotic solvents. These solvents may be used singly or in blends but must be miscible with the liquid, in particular the fuel, being marked. Preferably, the final concentration of the marker in the liquid, in particular in the fuel, is between 1 ppm and 30 ppm (w/vol) but the level will be dependent upon the inherent colour of the solvent used. The method and compounds of the present invention may be provided in combination with other markers. For example, the photochromic compounds may be used in conjunction with existing solvent dyes, such as mono- and bis-azo dyes, quinoline, methine, xanthene, perylene and anthraquinone based dyes. Alternatively, the photochromic compounds may be used in combination with colourless marker chemicals often found in fuels which require alkaline conditions for the formation of colour in an extracted aqueous layer, such as quinizarin, coumarin and those covered by WO96/32462 with both types of compound being detectable independently of one other. The photochromic compounds may also be used in combination with, or added as a mixture with, colourless marker chemicals which require acidic conditions for the formation of colour, such as basic azo dyes. The present invention also provides a number of compounds for use in the method. The compounds of formula (I) used in the method possess the ability to change colour or shade reversibly in light of a particular frequency or intensity. In a preferred embodiment in the compounds of the formula (I) R1 is hydrogen, C₁-C₆alkoxy, halogen, C₁-C₆alkyl, or -NO₂ ; R₂ is hydrogen or C₁-C₆ alkoxy; R₃ is NO2, or halogen; R₄ is hydrogen, C₁-C₆alkoxy, or halogen; R₅ is hydrogen, halogen, methoxy or –COOH R₁₁ is hydrogen, R_a is methyl or ethyl, R_b is methyl or ethyl, L is a divalent linker. The term "divalent linker" as used herein refers to any divalent capable of linking two spiropyran moieties together. Examples of divalent linker groups are selected from C₁-C₁₂alkylene, C₁-C₁₂alkenylene, C₁-C₁₂alkynylene,

, , ,

, wherein R₆ is hydrogen, halogen, C₁-C₆alkoxy, CF₃, NO₂, preferably methoxy, or hydrogen. s is 1 to 4, preferably 1 or 2. C₁-C₆ alkoxy is preferably methoxy. The term “halogen” refers to fluoro, chloro, bromo or iodo. More preferred: R₁ is hydrogen or methoxy. R₂ is hydrogen or methoxy. R₃ is nitro. R₄ is hydrogen. R₅ is hydrogen, halogen, methoxy or -COOH, R_a is methyl. R_b is methyl. Examples of compounds of the formula (I), wherein R₃ is NO₂, R₄ is H, are presented in Table 1. Table 1.

Best results have been obtained with the following compounds of the formula (I):

The compounds of formula (I) are reversibly photochromic (Scheme 1).

By virtue of its photochromic properties, the indicator compound can undergo photo-induced coloration by irradiation with photons of a specific energy range (conversion of the second isomeric form, thermodynamically more stable) into the first isomeric form (open form) the coloration being followed by a time- and temperature-dependent decoloration (conversion of the first isomeric form into the second isomeric form).

Suitable active materials exhibit the following characteristics:

(1) the system has at least one thermal process leading from one metastable state to one stable state, where the two states of the spiroaromatic compounds are characterized by a distinctly different color and/or any other measurable physical parameter such as luminescence, refraction index, conductivity and the like.

(2) the stable state may be converted into the metastable state using one or any combination of stimuli, among others the following processes: a) photonic induction, or b) thermal induction, and

(3) other than temperature and photoinduction (in the visible light range), the metastable state is substantially not affected by anyone or any combination of stimuli such as a) photo induction, b) piezo induction, c) electro induction, d) chemo induction.

Photoinduction means that the initially colourless compound of formula (I) is irradiated with light, preferably in the UV or near-UV range, as a result a reversible internal valence isomerisation from a colourless inactivated state to a coloured activated one is induced. A reverse discolouration process then proceeds at a rate that is time and temperature dependent.

Example 1

A concentrate of 1% by weight of the photochromic compound 127, 8-methoxy-1'-[[4-[(8- methoxy-3',3'-dimethyl-6-nitro-spiro[chromene-2,2'-indoline]-T-yl)methyl]phenyl]methyl]- 3',3'-dimethyl-6-nitro-spiro[chromene-2,2'-indoline], was prepared using a blend of aromatic solvents and a polar aprotic solvent. The compound was added to fuels at a level of 1-15 ppm (w/vol) and exhibited an absorbance of up to 0.3 by irradiation of the solution with a standard ultraviolet LED torch

Immediately after irradiation the decoloration can be followed by eye, or by the use a photospectrometer. Under ambient conditions the decoloration is nearly completed after 60 seconds.

The table below shows the decay at the absorption maximum of the compound dissolved in toluene (normalized for t =0 sec) after activation with UV light:

Claims

Claims 1. A method of marking fuels, comprising the steps of a) adding at least one photochromic compound of the formula

(I) to the fuel, wherein R1 to R4 are independently of each other hydrogen, -C1-C6alkoxy, halogen, CF3, -C1- C6alkyl, or -NO2, R5 is hydrogen, halogen, -C1-C6alkoxy, -COOH, -COO-C1-C8alkyl, -CF3, or phenyl; R11 is hydrogen, or R11 and R5 form together a phenyl ring; Ra is -C1-C6alkyl, Rb is -C1-C6alkyl, or together with Ra form a 5-6 membered ring; and L is a divalent linker; and b) converting the compound of formula (I) from an original stable state into a metastable state by photonic induction, whereby i) a change in an optical property and/or ii) detection of the time temperature dependent re-conversion from the metastable state to the original stable state act as an identification marker for the fuel. 2. The method according to claim 1, wherein the at least one compound formula (I) is selected from the group consisting of the following structural formulae

3. The method according to claim 1 or 2, wherein a color change is detected based on the color difference between said metastable and original state.

4. The method according to any of claims 1 to 3, wherein the absorbance of the photochromic compound on exposure to ultraviolet light, under the appropriate temperature conditions, is greater than 0.1 , especially greater than 0.2.

5. The method according to any of claims 1 to 4, wherein the fuel is illuminated at a constant distance for a constant length of time at a specified temperature to ensure reproducibility of the colour formation thereby ensuring the correct identification of the fuel from the detected marker.

6. The method according to any of claims 1 to 5, wherein a sample of the fuel to be identified is stored in a light free environment prior to exposure.

7. The method according to any of claims 1 to 6, wherein the compound of formula (I) is provided as a liquid concentrate of between 1% to 10% of the marker in an organic solvent.

8. The method according to claim 7, wherein the organic solvent is an alkyl benzene, alkylnaphthalene, or a proprietary blend of such compounds, optionally in admixture with a polar organic solvent to increase the solubility of the compound of formula (I) in the concentrate.

9. The method according to any of claims 1 to 8, wherein the final concentration of the compound of formula (I) in the fuel to be marked is between 1 ppm and 30 ppm (w/vol).

10. The method according to any of claims 1 to 9, wherein the compounds of formula (I) are used in conjunction with solvent dyes.

11. The method according to any of claims 1 to 10, wherein the fuel is selected from the group consisting of crude oil, lubricating oil, hydraulic fluid, brake fluid, gasoline, diesel fuel, kerosene, jet fuel, heating oil and heavy fuel oil.

12. Use of the compounds of formula (I) defined in claim 1 for use in marking fuels.

13. Use according to claim 12, wherein the fuel is selected from the group consisting of crude oil, lubricating oil, hydraulic fluid, brake fluid, gasoline, diesel fuel, kerosene, jet fuel, heating oil and heavy fuel oil.