EP1537193A1

EP1537193A1 - Low-sulphur odorants for liquid gas

Info

Publication number: EP1537193A1
Application number: EP03747924A
Authority: EP
Inventors: Gerd Mansfeld; Dirk MÜLLER; Nadine Tacke
Original assignee: Symrise AG
Current assignee: Symrise AG
Priority date: 2002-08-27
Filing date: 2003-08-22
Publication date: 2005-06-08
Anticipated expiration: 2023-08-22
Also published as: DE50311017D1; DE10240028A1; WO2004024852A1; JP2005537381A; EP1537193B1; US20060009372A1; AU2003267007A1; ATE419320T1

Abstract

New mixture comprises: (1) at least two C1-C6 alkyl acrylates; (2) compound(s) selected from C1-C8 mercaptans, C4-C12 thiophenes, C2-C8 sulfides or C2-C8 disulfides; (3) compound(s) selected from norbornenes, C1-C5 carboxylic acids, C1-C8 aldehydes, C6-C14 phenols, C7-C14 anisoles or C4-C14 pyrazines; and (4) optionally an antioxidant. An Independent claim is included for liquefied gas containing a mixture as above.

Description

Low sulfur odorant for liquefied gas

The present invention relates to acrylic acid alkyl ester mixtures containing a small proportion of sulfur-containing compounds, the use thereof for

Odorization of liquid gas, a process for the odorization of liquid gas and liquid gas containing these mixtures.

The areas of application for liquefied gas are diverse. Examples are the use as fuel gas (for example as camping gas, as motor fuel and

LPG, in gas lighters, in households and industry), as a propellant (e.g. for sprays) and as a chemical raw material.

Gas odorization means the addition of odor-intensive substances (odorants) that act as warning or alarm substances to gases that do not have their own odor, i.e. to otherwise essentially or completely odorless gases.

Liquid gas is generally understood to be gases which can be converted into the liquid state at low pressures and at 20 ° C. In the narrower sense, liquefied petroleum gas (LPG) essentially consists of propane,

Propene, butane and bμten. In the narrower sense, liquid gas is understood to mean propane and n-butane or mixtures thereof, which also contain proportions of unsaturated and / or branched hydrocarbons such as propene, isobutane, 1-butene, cis-2-butene, trans-2-butene, or May contain isobutene. The requirements for the composition of liquid gas are described in DFN 51622 and DVGW worksheet G 280 (DVGW = German Gas and Water Association).

Due to its high degree of purity, the liquefied gas used today is almost odorless. If leaks are not noticed in time, explosive gas / air mixtures with a high risk potential quickly build up.

For safety reasons, liquefied gas is therefore odorized by adding odor-intensive substances. The odorants can also be perceived in great dilution and, due to their exceptionally unpleasant smell, can cause an alarm association in humans as desired. The odorant must not only smell unpleasant and unmistakable, but above all must clearly represent a warning smell. Therefore, the smell of the odorized gas must not be removed from everyday life, e.g. from the kitchen and the household.

Odorants customary for liquid gas usually consist of individual substances or mixtures of individual substances from the group of mercaptans or sulfides such as, for example, ethyl mercapto, n-propyl mercaptan, isopropyl mercaptan, tert-butyl mercaptan (TBM), tetrahydrothiophene, dimethyl sulfide, diethyl sulfide.

Ethyl mercaptan is the most widely used odorant for liquid gas.

Mercaptans are ideal for reliable odorization of liquid gas. In the course of a more sensitive handling of the environment, however, it should be noted that the combustion of gases odorized in this way produces sulfur oxides as combustion products - several hundred tons per year nationwide. Other known problems of mercaptans or sulfides are corrosion, interaction with metal surfaces (e.g. adsorption on container walls) or the incompatibility of metal catalysts with these compounds.

Since the aim is to reduce sulfur compounds, attempts have already been made to develop low-sulfur odorants.

JP-A 55-104393 describes that odorant containing an alkyne and at least 2 compounds selected from a group consisting of methyl acrylate,

Ethyl acrylate, methyl methacrylate, allyl methacrylate, ethyl propionate, methyl n-butyrate, Methyl iso-butyrate and prenyl acrylate, and optionally tert-butyl mercaptan, are suitable for the odorization of fuel gases. The amount of odorant is 50 ppm by weight (mg / kg gas), preferably greater than or equal to 100 ppm. The best results in LPG were obtained with mixtures comprising TBM. A better odor effect was achieved by adding 2-butyne (50 ppm) to a mixture of methyl acrylate (50 ppm), allyl acrylate (100 ppm) and TBM (5 ppm). The best result showed a mixture of 2-butyne (50 ppm), allyl methacrylate (20 ppm), methyl acrylate (20 ppm), methyl n-butyrate (20 ppm), methyl iso-butyrate (20 ppm), ethyl propionate (20 ppm) and TBM (5 ppm).

JP-B 51-034841 describes that ethyl acrylate or n-valeric acid used alone, because of their olfactory properties, do not have a sufficiently odorant effect. The optimized mixture comprised 50-90% by weight of ethyl acrylate, 10-50% by weight of n-valeric acid and optionally triethylamm. A mixture consisting of 60% by weight of ethyl acrylate and 20% by weight of n-valeric acid and triethylamine was added to a gaseous fuel gas at 10 mg / m.

Odorants for fuel gases consisting of ethyl acrylate (70% by weight) and tert-butyl mercaptan (30% by weight) are known from JP-B 51-021402. This mixture was added to a gaseous fuel gas in an amount of 5 mg / m.

Odorants for odorization of heating gases consisting of a) 30-70% by weight of CrC ₄ alkyl mercaptans, b) 10-30% by weight of n-valeraldehyde and or isovaleraldehyde, n-butyric acid and / or isobutyric acid and optionally c) up to 60% by weight of tetrahydrothiophene are described in DE-A 31 51 215. These odorants were added to heating gas in amounts of 5-40 mg / m ³ .

Mixtures containing) 1 part by weight of dimethyl sulfide, b) 0.8-3 parts by weight of tert-butyl mercaptan and c) 0.1-0.2 parts by weight of tert-heptyl mercaptan or 0.05-0.3 parts by weight of tert-hexyl mercaptan for the odorization of Fuel gases are out JP-A 61-223094 known. These mixtures had an odor of tert-butyl mercaptan, which is associated with the odor of city gas.

The use of norbornene derivatives for fuel gas odorization is known from JP-A 55056190. LPG was at 40 mg / kg with a mixture of equal parts

5-ethylidene-2-norbornene and 5-vinyl-2-norbornene or 50 mg / kg with a mixture of 80% by weight of 5-ethylidene-2-norbornene and 20% by weight of ethyl acrylate.

Mixtures for the odorization of town gas containing norbornene. or a norbornen

Derivative and a diluent are described in DE-A 100 58 805.

Mixtures of C ₄ -C aldehydes and sulfur compounds are described as odorants in JP-A 50-126004. The odorization of 1 kg of propane was carried out with 50 mg of a mixture of 60% by weight of valeraldehyde and 40% by weight of n-butyl mercaptan. Valeraldehyde enhances the smell of n-butyl mercaptan. Similarly, 2-methylvaleraldehyde was used.

It is known from US-A 2,430,050 and DE-A 198 37 066 that antioxidants, in particular phenol derivatives, are suitable for stabilizing mercaptan-containing or alkyl acrylate-containing gas odorants.

Alternative low-sulfur odorants for the odorization of liquefied gas were sought.

The present invention relates to mixtures containing

A) at least two different acrylic acid -C ₆ alkyl esters; B) at least one compound from the group of the -Cs mercaptans, the C ₄ -C ₁₂ thiophene, the C ₂ -C ₈ sulfide or the C ₂ -C ₈ disulfide; C) at least one compound from the group of the norbornenes, the CrC ₅ carboxylic acids, the C ₈ -C aldehydes, the C ₆ -C ₄ phenols, the C -C ₁₄ anisoles or the C ₄ -C ₁₄ pyrazines;

D) optionally an antioxidant

for odorization of liquid gas.

Another subject of the present. The invention is the use of the mixtures according to the invention for the odorization of liquid gas, a process for the odorization of liquid gas and liquid gases containing the mixtures according to the invention.

The acrylic acid -CC ₆ alkyl esters are advantageously selected from the group comprising acrylic acid methyl ester, acrylic acid ethyl ester, acrylic acid n-propyl ester, acrylic acid isopropyl ester, acrylic acid n-butyl ester, acrylic acid isobutyl ester, acrylic acid tert. -butyl ester, acrylic acid-n-pentyl ester, acrylic acid-isopentyl ester and acrylic acid-n-hexyl ester.

Preferred are C ₁ -C ₄ -alkyl acrylates, in particular methyl acrylates, ethyl acrylates, n-propyl acrylates, isopropyl acrylates, n-butyl acrylates and isobutyl acrylates. Very particularly preferred acrylic acid -CC ₄ alkyl esters are methyl acrylate, ethyl acrylate and n-butyl acrylate.

The mixtures according to the invention contain the low molecular weight acrylic acid alkyl ester and the higher molecular weight acrylic acid alkyl ester preferably in a weight ratio of 9: 1 - 1: 9, preferably 7: 3 - 3: 7, in particular 3: 1 - 1: 3.

The compounds from group A) are advantageously contained in the mixtures according to the invention to 60-97% by weight, preferably to 70-95% by weight and particularly preferably to 80-95% by weight. The mercaptans were, for example, ethyl mercaptan, n-propyl mercaptan, isopropyl mercaptan, n-butyl mercaptan, sec-butyl mercaptan, isobutyl mercaptan, tert.-butyl mercaptan, n-penthencaptan, isopentyl mercaptan, neopentyl mercaptan, n-hexyl Isohexyl mercaptan, sec-hexyl mercaptan, neohexyl mercaptan, tert.-hexyl mercaptan, n-heptyl mercaptan, isoheptyl mercaptan, sec.-heptyl mercaptan, tert.-heptyl mercaptan, n-octyl mercaptan, isooctyl mercaptan, sec.-octyl mercaptan or

The thiophenes are advantageously thiophenes which are substituted by 1 to 4, preferably by one or two, C 1 -C 4 -alkyl and / or alkoxy groups. The thiophenes can also be hydrogenated thiophenes, with tetrahydrothiophene being preferred.

The sulfides can be, for example, dimethyl sulfide, diethyl sulfide, di-n-propyl sulfide, diisopropyl sulfide, di-n-butyl sulfide, diisobutyl sulfide, ethyl methyl sulfide, methyl n-propyl sulfide, methyl isopropyl sulfide, methyl isobutyl sulfide, isyl sulfide, or ethyl isopropyl sulfide. Dimethyl sulfide, diethyl sulfide, di-n-propyl sulfide, diisopropyl sulfide, di-n-butyl sulfide and diisobutyl sulfide are preferred.

The disulfides can be, for example, dimethyl disulfide, diethyl disulfide, di-n-propyl disulfide, diisopropyl disulfide, di-n-butyl disulfide, diisobutyl disulfide, ethyl methyl disulfide, methyl n-propyl disulfide, methyl isopropyl disulfide, methyl isobutyl disulfide disidyl disulfide, ethyl disulfide, ethyl disulfide. Dimethyl disulfide, diethyl disulfide, di-n-propyl disulfide, diisopropyl disulfide, di-n-butyl disulfide and diisobutyl disulfide are preferred.

The compounds from group B) are typically contained in the mixtures according to the invention to 1-40% by weight, advantageously to 2-30% by weight, preferably to 3-15% by weight. The norbomenes are advantageously those with a molecular weight of less than or equal to 130; norbornene, 2,5-norbornadiene, 5-ethylidene-2-norbornene and 5-vinyl-2-norbornene are preferred.

The carboxylic acids are advantageously acetic acid, propionic acid, n-butyric acid, isobutyric acid, n-valeric acid, isovaleric acid, n-caproic acid, isocaproic acid or 2-methylvaleric acid.

The aldehydes are advantageously acetaldehyde, propional dehyde, n-butyraldehyde, isobutyraldehyde, n-valeraldehyde, isoväleraldehyde, n-

Capronaldehyde, isocapronaldehyde or 2-methylvaleraldehyde.

The phenols are advantageously substituted phenols having a total of one or two C 1 -C ₄ alkyl and / or CrC ₄ alkoxy groups. Preferred phenols are 3-methylphenol, 2-ethylphenol, 4-ethylphenol, 2-isopropylphenol, 2-tert-butylphenol, 2-tert-butyl-4-methylphenol, 2-methoxyphenol, 2-methoxy-4-methylphenol and 2 methyl-5-isopropyl phenol. C1-C4 monoalkylated phenols are particularly preferred.

Advantageous anisoles are anisole, 2-methylanisole, 4-allylanisole or 4-methylanisole.

The pyrazines are advantageously alkylated and / or acylated pyrazines. Examples of advantageous pyrazines are 2-methylpyrazine, 2-ethylpyrazine, 2,3-dimethylpyrazine, 2,3-diethylpyrazine, 2,6-dimethylpyrazine, 2,3-methylethylpyrazine, 5,2-methylethylpyrazine, 2,3,5- Trimethylpyrazine, 3,5,2-dimethylethylpyrazine, 3,6,2-dimethylethylpyrazine, 5,2,3-methyldiethylpyrazine, tetramethylpyrazine, 2,3-methylacetylpyrazine or 2-acetylpyrazine. Pyrazines with a total of one to three, particularly preferably with a total of one or two, C ₁ -C ₄ -alkyl and / or C] are preferred _. -C ₄ acyl groups. The acylated pyrazines are preferably monoacylated and particularly preferably have an acetyl or propionyl group, preference being given to monoacetylated pyrazines, in particular 2-acetylpyrazine.

The compounds from group C) are typically contained in the mixtures according to the invention to 1-40% by weight, advantageously to 2-30% by weight, preferably to 3-15% by weight.

A weight ratio of components B) to components C) in the range from 3: 1 to 1: 3, preferably in the range 2: 1 to 1: 2 and particularly preferably 1.2: 1-1: 1.2 is advantageous.

Common antioxidants can be added, for example, to the stability of the odorant according to the invention. Examples include vitamin C and derivatives (e.g. ascorbyl palmitate, ascorbyl acetate), tocopherols and

Derivatives (e.g. vitamin E, vitamin E - acetate), vitamin A and derivatives (vitamin A - palmitate) phenolic benzylamines, formic acid, acetic acid, benzoic acid, sorbic acid, hexamethylenetetramine, tert.-butylated hydroxytoluene, tert.-butylated hydroxyanisole, - hydroxy acids (e.g. citric acid , Lactic acid, malic acid), hydroquinone monomethyl ether. Preferred antioxidants are tert-butylated hydroxytoluene (BHT, Jonol), tert-butylated hydroxyanisole and hydroquinone monomethyl ether.

The addition of antioxidants in particular results in a high storage stability of the mixtures according to the invention and of the odorized liquefied gas. Storage stability tests have shown that the warning smell of the invention

Mixtures remain largely the same over a period of 3 months at 20 ° C or 14 days at 40 ° C (incubator).

Several antioxidants can also be added to an odorant. The odorants advantageously contain one, two or three antioxidants, and one or two antioxidants are preferred. The total amount of antioxidants in the odorant is usually in the loading _. rich 0.05-2% by weight, preferably in the range 0.1-1% by weight, particularly preferably in the range 0.3-0.8% by weight. ^■ .

The amount of odorant according to the invention, based on the liquid gas to be odorized, is typically in the range 5-100 mg / kg, preferably 5-50 mg / kg, particularly preferably 10-40 mg / kg and very particularly preferably 12-30 mg / kg.

The warning smell of the liquid gas odorized according to the invention was from a

Test group clearly perceived even with a dilution of liquid gas in air in the range 1: 200 - 1: 2000.

Due to the presence of components C) in the mixtures according to the invention, a better warning smell was achieved compared to mixtures which only contained components A) and B).

Mixtures containing are preferred according to the invention

A) at least two different acrylic acid -CC ₄ alkyl esters;

B) at least one compound from the group of -C ₈ mercaptans, of C ₄ - C ₈ -thiophenes, C ₂ -C ₈ sulfides or disulfides C ₂ -C _8;

C) at least one compound from the group of norbomene, the C ₂ -C ₅ -

Carboxylic acids, the C ₂ -C ₅ aldehydes, the C ₆ -Cιo phenols, the C -C ₀ anisoles or the C ₄ -C ₁₀ pyrazines;

D) at least one antioxidant.

Mixtures containing are particularly preferred according to the invention A) methyl acrylate, ethyl acrylate, and optionally a further C-C acrylic acid alkyl ester _ö;

B) at least one compound from the group of thiophene, tetrahydrothiophene, dimethyl sulfide, diethyl sulfide, di-n-propyl sulfide, diisopropyl sulfide, dimethyl disulfide, diethyl disulfide, di-n-propyl disulfide, diisopropyl disulfide or the mercaptans of the formula (I)

in which

R ^{1 is} hydrogen, methyl or ethyl, preferably methyl, and

R> 2 is an alkyl group with 1 to 4 carbon atoms, preferably methyl, ethyl, isopropyl, isobutyl or tert-butyl;

C) at least one compound from the group norbornene, 2,5-norbornadiene, the C ₂ -C ₅ carboxylic acids, the C ₂ -C ₅ aldehydes, the C ₁ -C ₄ monoacylated pyrazines, the C ₁ -C ₄ -monoalkylated phenols;

D) at least one antioxidant.

Very particularly preferred mixtures essentially consist of

A) methyl acrylate and ethyl acrylate;

B) tert-butyl mercaptan; C) at least one compound from the group norbornene, propionaldehyde, isovaleraldehyde, isovaleric acid, 2-ethylphenol, 4-ethylphenol, 2-acetylpyrazine;

D) at least one antioxidant.

The following examples illustrate the invention:

Unless otherwise stated, all information is based on weight.

Me-Ac: methyl acrylate; Et-Ac: ethyl acrylate; Bu-Ac: n-butyl acrylate; DEP: diethyl phthalate; EtSH: ethyl mercaptan; iPrSH: isopropyl mercaptan, TBM: tert-butyl mercaptan, THM: tert-hexyl mercaptan; THT: tetrahydrothiophene, DES: diethyl sulfide, - Norb: norbornene, prop: propionaldehyde, IsoVS: isovaleric acid, IsoVA: isovalerianaldehyde, 2-EtPh: 2-ethylphenol; 4-EtPh: 4-ethylphenol, AcPyr: 2-

Acetylpyrazm, BHT: tert-butylated hydroxytoluene; BHA: tert-butylhydroxyanisole.

example 1

The odorants were evaluated in concentrations of 10, 25 and 50 mg / kg liquefied petroleum gas (20.3% propane, 78.6% butane, 1.1% other hydrocarbons) with regard to their warning smell and their warning intensity against liquefied petroleum gas contained the same concentrations of ethyl mercaptan or odorless diethyl phthalate (blank value). These concentrations correspond to the typical concentrations of odorant in the liquid gas.

The evaluation was carried out on a scale of 0-10, with 0 (odorless), 1 (very weak / very little warning) and 10 (very strong warning). The values given are mean values. The industry standard ethyl mercaptan was given the value 10, diethyl phthalate the value 0.

An aerosol can was filled with liquid gas of the above composition and an appropriate amount of odorant. After a rest period of about 24 hours, the odorized liquid gases were assessed in terms of smell. The test was carried out at room temperature (about 20 ° C.) in such a way that the gas phase of the odorized liquid gas was sprayed from the aerosol can into a smelling cup and the gas space in this smelling cup by a group of trained inspectors

(8 to 12 people) was assessed in terms of smell.

, The results for the 3 examined concentrations (10, 25 and 50 mg / kg liquid gas) were largely the same. The ratings given below were determined for a concentration of 35 mg / kg liquid gas.

Table 1 shows references and components of the mixtures according to the invention in comparison. Table 1:

Example 2

Table 2 shows the ratings for propionaldehyde (prop) as component C), the procedure was as described in Example 1.

Table 2:

Example 3

Table 3 shows the ratings for norbornene (Norb) as component C), the procedure was as described in Example 1.

Table 3:

Example 4

Table 4 shows the evaluations for isovaleric acid (IsoVS) as component C), the procedure was as described in Example 1.

Table 4:

Example 5

Table 5 shows the evaluations for 2-ethylphenol (2-EtPh) as component C), the procedure was as described in Example 1.

Table 5:

Example 6

Table 6 shows the ratings for 4-ethylphenol (4-EtPh) as component C), the procedure was as described in Example 1.

Table 6:

Example 7

Table 7 shows the evaluations for 2-acetylpyrazine (AcPyr) as component C), the procedure was as described in Example 1.

Table 7:

Example 8

Table 8 shows the evaluations for isovaleraldehyde (IsoVA) as component C), the procedure was as described in Example 1.

Table 8:

Example 9

Table 9 shows odorants according to the invention, each with a component C). The proportion of component C) in the odorant was 5%, and the mixtures contained 0.5% BHT as an antioxidant.

Table 9:

Example 10

Table 10 shows odorants according to the invention containing ethyl acrylate, methyl acrylate, at least one component C) from the group Prop, Norb, IsoVS, 2-EtPh and at least one further component C), and an antioxidant. The odorants contained 50% of ethyl acrylate and 36% of methyl acrylate from components A) and 3.3% of components C) of the first column. The mixtures contained 0.7% hydroquinone monomethyl ether as an antioxidant.

Table 10:

Example 11

Table 11 shows odorants according to the invention containing ethyl acrylate, methyl acrylate, at least one component C) from the group AcPyr, IsoVA, 4-EfPh and at least one further component C), and an antioxidant. The odorants contained 50% of ethyl acrylate and 36% of methyl acrylate from components A) and 3.3% of components C) of the first column. The mixtures contained 0.7% BHA as an antioxidant.

Table 11:

Example 12

To check the thermal stability, the odorized liquefied gases were assessed odorally after 24 hours at 20 ° C. (fresh batch) and after 14 days at 40 ° C. storage (storage) as described in Example 1. The amount of odorant added to the liquid gases was 35 mg / kg. Table 12 shows the results in comparison of ethyl mercaptan and a mixture A according to the invention consisting of 34% Me-Ac, 55.5% Et-Ac, 5% TBM, 5% Prop and 0.5% BHT.

Table 12:

After storage, the odorized liquefied petroleum gas had changed a lot with EtSH. The smell no longer caused an alarm association because it reminded of cooked cabbage vegetables.

Even after a storage period of 6 months at 20 ° C, the warning smell was the

Mixture A in the propane / n-butane mixtures is still very noticeable.

In the propane / n-butane mixtures with the addition of EtSH was also in the

Storage at 20 ° C after a few weeks, a clear smell of cabbage.

Claims

Patentansprflche

1. Containing mixtures

A) at least two different acrylic acid ~ CrC ₆ alkyl esters;

B) at least one compound selected from the group consisting of Cι-C ₈ mercaptans, the C ₄ -C ₁₂ -thiophenes, the C ₈ -C sulfides or disulfides C ₂ -C _8;

C) at least one compound from the group of the norbornene, the C _\ -

C-carboxylic acids, the CrC ₈ aldehydes, the C ₆ -C ₁₄ phenols, the C ₇ -C ₁₄ "anisoles or the C ₄ -C ₁₄ pyrazines;

D) optionally an antioxidant.

2. Mixtures according to claim 1, characterized in that they contain:

A) at least two different acrylic acid CrC ₄ alkyl esters;

B) at least one compound from the group of the -Cs mercaptans, the C ₄ -C ₈ thiophene, the C ₂ -C ₈ sulfide or the C -C ₈ disulfide;

C) at least one compound selected from the group consisting of norbornenes, the C ₂ - C ₅ carboxylic acids, C ₂ -C ₅ aldehydes, C ₆ -Cιo phenols, the C - CIO anisoles or C ₄ -Cι ₀ pyrazines ;

D) at least one antioxidant.

3. Mixtures according to claim 1, characterized in that they contain: A) acrylic acid methyl ester, acrylic acid ethyl ester and optionally a further acrylic acid C j -C ₆ alkyl ester;

in which

R ^{1 is} hydrogen, methyl or ethyl, preferably methyl, and

R ^{2 is} an alkyl group having 1 to 4 carbon atoms, preferred

Is methyl, ethyl, iso-propyl, iso-butyl or tert-butyl;

C) at least one compound from the group norbornene, 2,5-norbornadiene, the C ₂ -C ₅ carboxylic acids, the C ₂ -Cs aldehydes, the C \ - C ₄ -monoacylated pyrazines, the -C-C ₄ -monoalkylated phenols;

D) at least one antioxidant.

4. Mixtures according to claim 1, characterized in that they contain:

A) methyl acrylate and ethyl acrylate;

D) at least one antioxidant.

5. Mixtures according to at least one of claims 1 to 4, characterized in that they contain an antioxidant selected from tert-butylated hydroxytoluene, tert-butylated hydroxyanisole or hydroquinone mono- _. methyl ether.

6. Mixtures according to at least one of claims 1 to 5, characterized in that the mixtures contain:

60-97% by weight of components A),

1-40% by weight of components B), 1-40% by weight of components C) and 0.05-2% by weight of components D).

7. Mixtures according to at least one of claims 1 to 5, characterized in that the mixtures contain:

70-95% by weight of components A), 2-30% by weight of components B), 2-30% by weight of components C) and 0.1-1% by weight of components D).

8. Mixtures according to at least one of claims 1 to 7, characterized in that the weight ratio of components B) to components C) is in the range from 3: 1 to 1: 3.

9. Use of mixtures according to at least one of claims 1 to 8 for odorization of liquid gas.

10. LPG containing mixtures according to at least one of claims 1 to 8.

11. A process for the odorization of liquid gas, characterized in that a mixture according to at least one of claims 1 to 8 is added to the liquid gas.

12. The method according to claim 11, characterized in that the mixture is added to the liquid gas in an amount of 5-100 mg / kg liquid gas.