U.S. patent application number 12/442074 was filed with the patent office on 2011-06-30 for low-sulfer odorants featuring improved stability.
This patent application is currently assigned to SYMRISE GmbH & Co KG. Invention is credited to Norbert Andreas Braun, Marcus Eh, Jorg Eilers, Adrian Henke, Fritz Henke, Ingo Wohrle.
Application Number | 20110155616 12/442074 |
Document ID | / |
Family ID | 37514119 |
Filed Date | 2011-06-30 |
United States Patent
Application |
20110155616 |
Kind Code |
A1 |
Eh; Marcus ; et al. |
June 30, 2011 |
LOW-SULFER ODORANTS FEATURING IMPROVED STABILITY
Abstract
The present invention relates to an odorant comprising or
consisting of (A) at least 75% by weight of acrylic acid methyl
ester and/or acrylic acid ethyl ester, (B) 2-19.5% by weight of
tetrahydrothiophene (THT), (C) 5-50 ppm of hydroquinone monomethyl
ether, and also neither, one or both components selected from the
group consisting of (D) 0.025-0.2% by weight of butylhydroxy
toluene and/or butyl hydroxyanisole and (E) 5-500 ppm of one or
more compounds of formula (I) ##STR00001## wherein R is selected
from the group consisting of H, --OH, --NH.sub.2, --O.sub.2CR.sup.1
and --NOCR.sup.1, wherein R.sup.1 represents an alkyl radical
containing 1 to 4 carbon atoms, based on the total weight of the
odorant.
Inventors: |
Eh; Marcus; (Holzminden,
DE) ; Eilers; Jorg; (Holzminden, DE) ; Wohrle;
Ingo; (Holzminden, DE) ; Braun; Norbert Andreas;
(Queens, SG) ; Henke; Fritz; (Hoxter, DE) ;
Henke; Adrian; (Hoxter, DE) |
Assignee: |
SYMRISE GmbH & Co KG
Holzminden
DE
|
Family ID: |
37514119 |
Appl. No.: |
12/442074 |
Filed: |
September 21, 2007 |
PCT Filed: |
September 21, 2007 |
PCT NO: |
PCT/EP2007/060057 |
371 Date: |
May 12, 2010 |
Current U.S.
Class: |
206/524.1 ;
44/338; 44/352 |
Current CPC
Class: |
C10L 3/006 20130101 |
Class at
Publication: |
206/524.1 ;
44/338; 44/352 |
International
Class: |
B65D 85/00 20060101
B65D085/00; C10L 1/22 20060101 C10L001/22; C10L 1/24 20060101
C10L001/24 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 22, 2006 |
DE |
20 2006 014 741.1 |
Claims
1. An odorant comprising or consisting of (A) at least 75% by
weight of acrylic acid methyl ester and/or acrylic acid ethyl
ester, (B) 2-19.5% by weight of tetrahydrothiophene (THT), (C) 5-50
ppm of hydroquinone monomethyl ether, and also neither, one or both
components are selected from the group consisting of (D) 0.025-0.2%
by weight of butylhydroxy toluene and/or butyl hydroxyanisole and
(E) 5-500 ppm of one or more compounds of formula (I) ##STR00010##
wherein R is selected from the group consisting of H, --OH,
--NH.sub.2, --O.sub.2CR.sup.1 and --NOCR.sup.1, wherein R.sup.1
represents an alkyl radical containing 1 to 4 carbon atoms, based
on the total weight of the odorant.
2. The odorant as claimed in claim 1, comprising (D) 0.025-0.2% by
weight of butylhydroxy toluene and/or butyl hydroxyanisole and/or
(E) 5-500 ppm of one or more compounds of formula (I) ##STR00011##
wherein R is selected from the group consisting of H, --OH,
--NH.sub.2, --O.sub.2CR.sup.1 and --NOCR.sup.1, wherein R.sup.1
represents an alkyl radical containing 1 to 4 carbon atoms.
3. The odorant as claimed in claim 1, comprising or consisting of
(A) at least 84% by weight of acrylic acid methyl ester and/or
acrylic acid ethyl ester, and/or (B) 5-15% by weight of
tetrahydrothiophene (THT), and/or (C) 10-20 ppm of hydroquinone
monomethyl ether, and/or (D) 0.05-0.15% by weight of butylhydroxy
toluene and/or butyl hydroxyanisole and/or (E) 10-200 ppm of one or
more compounds of formula (I).
4. The odorant as claimed in claim 1, comprising (A) at least 84%
by weight of acrylic acid methyl ester and/or acrylic acid ethyl
ester, (B) 5-15% by weight of tetrahydrothiophene (THT), and (C)
10-20 ppm of hydroquinone monomethyl ether and also neither, one or
both components selected from the group consisting of (D)
0.05-0.15% by weight of butylhydroxy toluene and/or butyl
hydroxyanisole and (E) 10-200 ppm of one or more compounds of
formula (I).
5. The odorant as claimed in claim 1, comprising in component (E)
one or more compounds of formula (I) ##STR00012## wherein R is
selected from the group consisting of H and --OH.
6. The odorant as claimed in claim 1, comprising (A) at least 84%
by weight of acrylic acid methyl ester and/or acrylic acid ethyl
ester, (B) 5-15% by weight of tetrahydrothiophene (THT), and (C)
10-20 ppm of hydroquinone monomethyl ether and also one or both
components selected from the group consisting of (D) 0.05-0.15% by
weight of butylhydroxy toluene and (E) 10-200 ppm of one or more
compounds of formula (I) ##STR00013## wherein R is selected from
the group consisting of H and --OH.
7. The odorant as claimed in claim 1, comprising neither tert-butyl
mercaptan (TBM) nor ethyl mercaptan.
8. The odorant as claimed in claim 1, wherein the odorant comprises
no mercaptan.
9. The odorant as claimed in claim 1, wherein the odorant
comprises, apart from tetrahydrothiophene (THT), no
sulfur-containing compound.
10. A fuel gas having a methane content of at least 60% by weight,
comprising an odorant as defined in claim 1.
11. The fuel gas as claimed in claim 10, wherein the fuel gas is
natural gas.
12. A vessel comprising (i) an odorant as claimed in claim 1,
comprising component (E), wherein the odorant is contacted in the
vessel with a metal or metal ions or another reactant which is
capable of reacting with component (E) or (ii) a fuel gas having a
methane content of at least 60% by weight, containing an odorant as
defined in claim 1 comprising component (E), wherein the fuel gas
is contacted in the vessel with a metal or metal ions or another
reactant which is capable of reacting with component (E).
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit of priority to
PCT/EP2007/060057, filed on Sep. 21, 2007, which asserts priority
to DE 20 2006 014 741.1, filed on Sep. 22, 2006, which are
incorporated herein by reference in their entireties.
[0002] The present invention relates to low-sulfur odorants
comprising or consisting of A) acrylic acid methyl ester and/or
acrylic acid ethyl ester, B) tetrahydrothiophene (THT) and C)
hydroquinone monomethyl ether in specific concentrations. The
content of hydroquinone monomethyl ether is in this case very low.
In addition to said components A), B) and C), an odorant according
to the invention can also comprise one, two or more components
having a stabilizing effect, cf. in this regard the information
given concerning components D) and E) below. The invention relates
also to a corresponding fuel gas (preferably natural gas) having a
methane content of at least 60% by weight, which comprises a
content of the odorant according to the invention.
[0003] A method for odorizing a fuel gas of this type is also
described.
[0004] The town and coke-oven gases used previously for the public
supply of gas contained components having an intensive smell and
therefore had a strong inherent smell, so that issuing gas could
easily be perceived.
[0005] The term "gas odorizing" refers to the addition of
substances (odorants) which have an intensive smell and act as
warning or alarm substances to gases having no significant inherent
smell, i.e. to otherwise substantially or completely odorless
gases.
[0006] Natural gas consists mainly of methane (typical methane
contents lie in the range of from 50 to 99% by weight, usually in
the range of from 60 to 99% by weight and conventionally 80 to 99%
by weight) and can, depending on their origin, additionally contain
differing contents of ethane, propane and hydrocarbons of
relatively high molecular weight. Natural gas H(H=high) has a
methane content of from 87 to 99.1% by volume, natural gas L
(L=low) contains generally 79.8 to 87% by volume of methane.
[0007] Owing to its high degree of purity, the gas, conventionally
obtained from natural gas, used today in the public mains network
is per se almost odorless.
[0008] If leakages are not noted in good time, explosive gas/air
mixtures having a high risk potential soon build up.
[0009] For safety reasons, gas is therefore odorized by adding
substances having an intensive smell. Thus, in Germany, for
example, all gases which do not have a sufficient inherent smell
and are distributed in the public supply of gas must be odorized in
accordance with DVGW Worksheet G 280 (DVGW=Deutscher Verein des
Gas- and Wasserfaches e.V. (German Technical and Scientific
Association for Gas and Water)). These odorants are perceptible
even when highly diluted and cause in a desired manner, owing to
their exceptionally unpleasant smell, an alarm association in
humans. The odorant must not only smell unpleasant and
unmistakable, but rather above all be unambiguously a warning
smell. Therefore, the smell of the odorized gas may not be a smell
with which humans are familiar from everyday life, for example from
cooking and the home. In Germany approximately 90% of service gas
is currently odorized with tetrahydrothiophene (THT) (12-25
mg/m.sup.3); in addition, odorizing with mercaptans is also
conventional.
[0010] It can be beneficial to add to the gas a relatively large
amount of odorant over a relatively long period of time. In the
case of what is known as shock odorizing, one to three times the
amount of odorant is supplied to the gas, compared to conventional
odorizing. Shock odorizing is applied for example during the
putting-into-operation of new networks or line portions in order
more rapidly to attain the minimum odorant concentration or else to
identify small leaks in the gas installation.
[0011] THT alone is ideal for reliable odorizing of gas. However,
with a view to sensitive treatment of the environment, it should be
noted that sulfur oxides are formed as combustion products to a
greater degree when gases odorized in this way are burned.
[0012] As efforts are generally made to reduce or avoid sulfur
compounds, attempts have already been made to develop low-sulfur or
sulfur-free odorants.
[0013] JP-B-51-007481 mentions that acrylic acid alkyl esters such
as methyl acrylate, ethyl acrylate and butyl acrylate are known to
have weak odorizing properties for fuel gases and to be almost
insignificant in this regard. The document describes and claims
allyl acrylate as an effective odorizing component.
[0014] JP-A 55-104393 describes that odorants 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 isobutyrate and prenyl
acrylate, and also if appropriate tert-butyl mercaptan, are
suitable for odorizing fuel gases. The amount of odorant is, based
on weight, 50 ppm (mg/kg of gas), preferably greater than or equal
to 100 ppm. The best results in the case of LPG (liquid gas) were
obtained with mixtures comprising tert-butyl mercaptan (TBM). By
adding 2-butyne (50 ppm) to a mixture of methyl acrylate (50 ppm),
allyl acrylate (100 ppm) and TBM (5 ppm), a better odorizing effect
was attained. The best result was displayed by a mixture of
2-butyne (50 ppm), allyl methacrylate (20 ppm), methyl acrylate (20
ppm), methyl-n-butyrate (20 ppm), methyl isobutyrate (20 ppm),
ethyl propionate (20 ppm) and TBM (5 ppm).
[0015] JP-B-51-034841 determined "odor threshold values" of various
substances, wherein n-valeric acid, n-butyric acid,
isobutyraldehyde and various methyl amines had low olfactory "odor
threshold values". Ethyl acrylate or n-valeric acid used alone did
not have a sufficiently odorizing effect. An optimized mixture
comprised 50-90% by weight of ethyl acrylate, 10-50% by weight of
n-valeric acid and optionally triethyl amine. The mixture which was
taken to be most effective comprised ethyl acrylate, n-valeric acid
and triethyl amine, wherein this mixture contained equal parts by
weight of n-valeric acid and triethyl amine and also 30 to 80% by
weight of ethyl acrylate; a corresponding mixture consisting of 60%
by weight of ethyl acrylate and 20% by weight of each of n-valeric
acid and triethyl amine was added to a gaseous fuel gas at 10
mg/m.sup.3.
[0016] 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.sup.3.
[0017] Odorous substances for odorizing heating gases consisting of
a) 30-70% by weight of C.sub.1-C.sub.4 alkyl mercaptans, b) 10-30%
by weight of n-valeraldehyde and/or isovaleraldehyde, n-butyric
acid and/or isobutyric acid and also if appropriate c) up to 60% by
weight of tetrahydrothiophene (THT) are described in DE-A 31 51
215. These odorants were added to heating gas in amounts of from
5-40 mg/m.sup.3.
[0018] In DE-A 198 37 066 the problem of sulfur-free gas odorizing
was solved by means of mixtures containing at least one acrylic
acid C.sub.1-C.sub.12 alkyl ester and a nitrogen compound having a
boiling point in the range of from 90 to 210.degree. C. and a
molecular weight of from 80 to 160, wherein mixtures containing at
least two different acrylic acid alkyl esters are preferred.
Alkyl-substituted 1,4-pyrazines are described as being particularly
suitable nitrogen compounds.
[0019] Mixtures containing a) 1 proportion by weight of dimethyl
sulfide, b) 0.8-3 proportions by weight of tert-butyl mercaptan and
c) 0.1-0.2 proportions by weight of tert-heptyl mercaptan or
0.05-0.3 proportions by weight of tert-hexyl mercaptan for
odorizing fuel gases are known from JP-A 61-223094. These mixtures
had a smell of tert-butyl mercaptan which is associated with the
smell of the town gas.
[0020] The use of norbornene derivatives for fuel gas odorizing is
known from JP-A55056190. LPG was mixed at 40 mg/kg with a mixture
of equal parts of 5-ethylidene-2-norbornene and
5-vinyl-2-norbornene or at 50 mg/kg with a mixture of 80% by weight
of 5-ethylidene-2-norbornene and 20% by weight of ethyl
acrylate.
[0021] Mixtures for odorizing town gas containing norbornene or a
norbornene derivative and a diluting agent are described in DE-A
100 58 805.
[0022] Mixtures of C.sub.4-C.sub.7 aldehydes and sulfur compounds
are described as odorants in JP-A 50-126004. The odorizing 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 strengthens in this case the smell of the n-butyl
mercaptan. 2-Methylvaleraldehyde was used in a similar manner.
[0023] U.S. Pat. No. 4,487,613 proposes odorants for fuel gases
having a high content of sulfur-containing compounds, which
additionally contain the warning smell-strengthening compounds
2-methoxy-3-isobutyl pyrazine and/or
4-methyl-4-mercapto-2-pentanone. The odorants disclosed in
accordance with U.S. Pat. No. 4,487,613 can also contain low
contents of acrylic acid methyl ester.
[0024] WO 2005/061680 describes the use of a mixture containing (a)
at least two different acrylic acid C.sub.1-C.sub.6 alkyl esters,
(b) at least one compound from the group of the C.sub.1-C.sub.8
mercaptans, the C.sub.4-C.sub.12 thiophenes, the C.sub.2-C.sub.8
sulfides or the C.sub.2-C.sub.8 disulfides and (c) at least one
compound from the group of the norbornenes, the C.sub.1-C.sub.6
carboxylic acids, the C.sub.1-C.sub.8 aldehydes, the
C.sub.6-C.sub.14 phenols, the C.sub.7-C.sub.14 anisoles or the
C.sub.4-C.sub.14 pyrazines and also if appropriate (d) an
antioxidant for odorizing fuel gas having a methane content of at
least 60% by weight.
[0025] WO 2005/103210 relates to odorants and accordingly odorized
gases comprising [0026] (i) 0.1-49.9% of a cyclic or open-chain
thioether containing at most 9 carbon atoms, [0027] (ii) 50-99.8%
of an acrylic acid C.sub.1-C.sub.12 ester, [0028] (iii) 0.001-0.1%
of specific nitroxides.
[0029] The mixtures proposed in accordance with WO 2005/103210 are
said to be allegedly improved odorants. WO 2005/103210 states in
this regard inter alia that the nitroxides proposed therein
effectively prevent the radical polarization, which is of course to
be avoided in the case of odorants, of the acrylic acid esters
contained therein. WO 2005/103210 regards mixtures comprising ethyl
acrylate and THT as being particularly preferred.
[0030] However, the nitroxides proposed in accordance with WO
2005/103210 alone do not cause completely sufficient stabilization
of the odorant in question. Thus, interactions can occur between
the nitroxides and the thioethers, in particular in the presence of
metals and metal surfaces, such as for example in the vessels for
storing the odorants, so that the warning smell of the odorants
proposed therein can change and become impaired. As a result of
interactions of the nitroxides with metals and metal surfaces,
consumption can also occur as a result of abreaction of the
nitroxides, so that comprehensive stabilization of the acrylic acid
esters is no longer ensured in each case. Thus, nitroxides can be
oxidized in the presence of copper ions (to form the corresponding
nitrons) or reduced in the presence of iron ions (to form the
corresponding N-hydroxy compounds).
[0031] Alternative low-sulfur odorants for odorizing natural gas or
fuel gases consisting mainly of methane, which are preferably
superior in their properties to the previously known odorants, were
therefore sought, wherein, in addition to the quality of the
warning smell, the stability in storage of the odorant is also
important, so that the quality of the warning smell can be ensured
even over a relatively long period of (storage) time.
[0032] The subject-matter of the present invention is a mixture
(referred to hereinafter as an "odorant") comprising or
(substantially) consisting of the following components: [0033] (A)
at least 75% by weight of acrylic acid methyl ester and/or acrylic
acid ethyl ester, [0034] (B) 2-19.5% by weight of
tetrahydrothiophene (THT), [0035] (C) 5-50 ppm of hydroquinone
monomethyl ether, and also neither, one or both components selected
from the group consisting of [0036] (D) 0.025-0.2% by weight of
butylhydroxy toluene and/or butyl hydroxyanisole and [0037] (E)
5-500 ppm of one or more compounds of formula (I)
##STR00002##
[0037] wherein R is selected from the group consisting of H, --OH,
--NH.sub.2, --O.sub.2CR.sup.1 and --NOCR.sup.1, wherein R.sup.1
represents an alkyl radical containing 1 to 4 carbon atoms, based
on the total weight of the odorant.
[0038] Also relevant in practice is a corresponding method for
odorizing fuel gases having a methane content of at least 60% by
weight (of preferably natural gas) using an odorant according to
the invention. In this case, an odorant according to the invention
is added to the fuel gas. With regard to preferred configurations,
reference is made to the information given concerning the preferred
odorants according to the invention and the uses thereof, which
applies accordingly.
[0039] A further subject-matter of the present invention is a fuel
gas having a methane content of at least 60% by weight comprising
an odorant according to the invention. With regard to the preferred
odorants for use in fuel gases according to the invention,
reference is made to the subsequent discussion of preferred
odorants.
[0040] The fuel gas to be odorized or the fuel gas according to the
invention has a methane content of at least 60% by weight,
preferably of at least 70% by weight and particularly preferably of
at least 75% by weight.
[0041] The total amount of acrylic acid methyl ester and acrylic
acid ethyl ester (component (A)) in the odorants according to the
invention is at least 75% by weight, preferably at least 84% by
weight.
[0042] In so far as the odorants according to the invention
comprise acrylic acid methyl ester and acrylic acid ethyl ester,
the preferred ratio by weight of acrylic acid methyl ester to
acrylic acid ethyl ester lies in the range of from 9:1-1:9,
preferably in the range of from 7:3-3:7, in particular in the range
of from 3:1-1:4. Most particularly preferably, the ratio by weight
of acrylic acid methyl ester to acrylic acid ethyl ester lies in
the range of from 1:1-1:3.
[0043] The compound tetrahydrothiophene (component (B)) is
contained in the odorants according to the invention at 2-19.5% by
weight, preferably at 5-15% by weight.
[0044] The compound hydroquinone monomethyl ether (4-methoxyphenol,
MeHQ) (component (C)) is contained in the odorants according to the
invention in very low amounts lying in the range of from 5-50 ppm,
preferably 10-20 ppm. The use of larger amounts of component (C) is
surprisingly not required to attain high stability of the odorant;
the use of the low amount provided in accordance with the invention
of component (C) is advantageous for stability reasons, in
particular if component (E) is present (cf. also the examples).
[0045] Odorants according to the invention preferably comprise
as component (D) 0.025-0.2% by weight of butylhydroxy toluene
and/or butyl hydroxyanisole and/or as component (E) 5-500 ppm of
one or more compounds of formula (I)
##STR00003##
wherein R is selected from the group consisting of H, --OH,
--NH.sub.2, --O.sub.2CR.sup.1 and --NOCR.sup.1, wherein R.sup.1
represents an alkyl radical containing 1 to 4 carbon atoms.
[0046] In so far as they are contained, the total amount of the
compounds of component (D) butylhydroxy toluene (BHT, ionol,
2,6-di-tert-butyl-p-cresol, E 321) and/or butyl hydroxyanisole
(BHA, E 320) in the odorants according to the invention lies in the
range of from 0.025-0.2% by weight, preferably in the range of from
0.05-0.15% by weight.
[0047] Owing to the presence of component (C), in particular in
combination with one or both further components (D) and/or (E),
there is attained in particular high stability in storage of the
odorants according to the invention and also of an odorized fuel
gas according to the invention. Stability in storage tests have
shown that the warning smell of odorants according to the invention
in a fuel gas remains substantially constant over a period of more
than 8 months at 40.degree. C. (incubator), cf. also the examples
below. Particularly high stability in storage is attained if
component (C) and one of components (D) and/or (E) are at the same
time present.
[0048] The total amount of component (E) in preferred odorants
according to the invention lies in the range of from 5-500 ppm,
preferably in the range of from 10-200 ppm. The compounds of
formula (I) are stable nitroxides.
[0049] The synthesis of stable nitroxides of formula (I) is
described in detail in the literature, for example in Chem. Rev.
1978, 78, 37, Synthesis 1971, 190 and "Synthetic Chemistry of
Stable Nitroxides", L. B. Volodarsky et al., CRC Press, 1993,
ISBN:0-8493-4590-1.
[0050] Preferred compounds which can be used in component (E)
correspond to formula (I) wherein R.dbd.H
(2,2,6,6-tetramethylpiperidin-1-oxyl of formula (Ia), known under
the abbreviation TEMPO) or wherein R.dbd.OH (corresponding to
formula (Ib)) and are commercially available.
##STR00004##
[0051] The amount of odorant based on the fuel gas to be odorized
lies typically in the range of from 2-100 mg/m.sup.3, preferably
3-50 mg/m.sup.3, particularly preferably 5-40 mg/m.sup.3 and most
particularly preferably 8-35 mg/m.sup.3.
[0052] Preferably, the odorants according to the invention and the
fuel gases, in particular natural gas, containing these mixtures
contain, in addition to THT (component (B)), neither tert-butyl
mercaptan (TBM) nor ethyl mercaptan. Preferably, the odorant
comprises no mercaptan at all. Particularly preferably, apart from
tetrahydrothiophene (component (B)), no further sulfur-containing
compound is contained in the odorant according to the
invention.
[0053] Preferred odorants according to the invention comprise or
consist of: [0054] (A) at least 84% by weight of acrylic acid
methyl ester and/or acrylic acid ethyl ester, and/or [0055] (B)
5-15% by weight of tetrahydrothiophene (THT), and/or [0056] (C)
10-20 ppm of hydroquinone monomethyl ether, and/or [0057] (D)
0.05-0.15% by weight of butylhydroxy toluene and/or butyl
hydroxyanisole and/or [0058] (E) 10-200 ppm of one or more
compounds of formula (I).
[0059] Particularly preferred odorants according to the invention
comprise: [0060] (A) at least 84% by weight of acrylic acid methyl
ester and/or acrylic acid ethyl ester, [0061] (B) 5-15% by weight
of tetrahydrothiophene (THT), and [0062] (C) 10-20 ppm of
hydroquinone monomethyl ether [0063] and also neither, one or both
components selected from the group consisting of [0064] (D)
0.05-0.15% by weight of butylhydroxy toluene and/or butyl
hydroxyanisole and [0065] (E) 10-200 ppm of one or more compounds
of formula (I).
[0066] Particularly preferably, an odorant according to the
invention comprises [0067] (A) at least 84% by weight of acrylic
acid methyl ester and/or acrylic acid ethyl ester, [0068] (B) 5-15%
by weight of tetrahydrothiophene (THT), and [0069] (C) 10-20 ppm of
hydroquinone monomethyl ether and also one or both components
selected from the group consisting of [0070] (D) 0.05-0.15% by
weight of butylhydroxy toluene and [0071] (E) 10-200 ppm of one or
more compounds of formula (I)
##STR00005##
[0071] wherein R is selected from the group consisting of H and
--OH.
[0072] The particularly preferred mixtures are distinguished by
particularly high stability in storage. Partly synergistic
stability improvements are observed in odorizings according to the
invention on combination of hydroquinone monomethyl ether
(component (C)) and at least one further component (D) and/or
(E).
[0073] In so far as one or more compounds of formula (I) are
contained as component (E) in an odorant according to the
invention, said compounds do not display the above-discussed
drawbacks of the odorants proposed in accordance with WO
2005/103210; presumably, this is due to the presence of component
(C), that is to say, the presence of the low amount of hydroquinone
monomethyl ether.
[0074] Most particularly preferred odorizings according to the
invention contain or consist of [0075] (A) at least 84% by weight
of acrylic acid methyl ester and/or acrylic acid ethyl ester,
[0076] (B) 5-15% by weight of tetrahydrothiophene, [0077] (C) 10-20
ppm of hydroquinone monomethyl ether, and [0078] (D) 0.05-0.15% by
weight of butylhydroxy toluene.
[0079] Alternative most particularly preferred odorizings according
to the invention contain or consist of [0080] (A) at least 84% by
weight of acrylic acid methyl ester and/or acrylic acid ethyl
ester, [0081] (B) 5-15% by weight of tetrahydrothiophene, [0082]
(C) 10-20 ppm of hydroquinone monomethyl ether, and [0083] (E)
10-200 ppm of one or more compounds of formula (Ia) or (Ib).
[0084] With these most particularly preferred odorants, the best
odorizing of the gas and in particular the highest stability of
odorants according to the invention and fuel gases according to the
invention were attained. The warning smell was most strongly
pronounced and was perceived still clearly and in substantially
unadulterated form even after a storage time of well over 8
months.
[0085] The present invention relates also to a vessel
comprising:
(i) an odorant according to the invention comprising component (E),
wherein the odorant or (ii) a fuel gas according to the invention,
containing an odorant comprising component (E), wherein the fuel
gas is contacted in the vessel with a metal or metal ions or
another reactant which is capable of reacting with component
(E).
[0086] With regard to the preferred configuration of the odorants
comprising component (E) to be used in this case, reference is made
to the foregoing discussion of odorants according to the invention
and fuel gases.
[0087] Methods which are in practice particularly relevant for
odorizing fuel gas having a methane content of at least 60% by
weight (preferably natural gas) correspond in their preferred
configurations to the particularly preferred odorants according to
the invention. Preferably, an odorant according to the invention is
added to a fuel gas to be odorized in an amount which causes a
warning smell. Amounts of odorant that are preferably to be used,
based on the amount of the fuel gas to be odorized, are specified
above.
[0088] Further aspects of the invention emerge from the appended
claims.
[0089] The following examples describe the invention. Unless
otherwise stated, all particulars relate to weight.
[0090] The abbreviations have the following meanings:
[0091] MeAc: methyl acrylate; EtAc: ethyl acrylate; THT:
tetrahydrothiophene; MeHQ=hydroquinone monomethyl ether;
BHT=2,6-di-tert-butyl-p-cresol;
TEMPO=2,2,6,6-tetramethylpiperidin-1-oxyl.
EXAMPLES
[0092] The odorants according to the invention of the following
table 1 were olfactorily assessed in concentrations of 10 and 25
mg/Nm.sup.3 of natural gas (natural gas L; methane content: approx.
85% by volume) with regard to their warning smell and their warning
intensity against unodorized natural gas (blank value). These
concentrations correspond to the typical concentrations of odorant
in natural gas under conventional conditions.
[0093] The test method was carried out at room temperature (about
20.degree. C.) in such a way that the odorant is introduced into a
gas flow in a tube. At the end of this 2 m-long tube (the
homogenization takes place within the tube), the issuing odorized
gas is olfactorily assessed by a group of trained examiners (8 to
12 persons). The assessment was carried out on a scale of from 1
(very weak/offering very little warning) to 10 (very stark/offering
a great deal of warning); the specified values are average
values.
[0094] In order to examine the stability in storage, the odorants
according to the invention were added to natural gas L and the
odorized natural gas was olfactorily tested after specific periods
of time in storage at 40.degree. C. as described. The criterion for
stability in storage was the significant olfactory correspondence
of the stored odorized gas to the original warning smell.
[0095] The results were substantially identical for the two
concentrations examined (10 and 25 mg/Nm.sup.3 Gas).
TABLE-US-00001 TABLE 1 EtAc MeAc THT BHT [% by [% by [% by [% by
Example weight of] weight of] weight of] MeHQ weight of] TEMPO
Assessmement 1 92.0 -- 7.9985 15 ppm -- -- 8.5 2 88.0 -- 11.9987 13
ppm -- -- 9.0 3 -- 90.0 9.9985 15 ppm -- -- 8.0 4 60.0 30.0 9.9985
15 ppm -- -- 9.5 5** 91.0 -- 8.8985 15 ppm 0.10 -- 9.5 6** 91.0 --
8.9900 15 ppm -- 85 ppm 9.5 **greatly improved stability in
storage
[0096] After a storage time of more than 8 months at 40.degree. C.,
the warning smell could still be perceived very clearly in all
examples 1 to 6.
[0097] The odorants according to examples 5 and 6, which comprised
BHT or TEMPO, had particularly high stability in storage in the
odorized natural gas. Even after a storage time of well over 8
months at 40.degree. C., the warning smell was almost unaltered
compared to the freshly odorized natural gas.
SPECIFIC EMBODIMENTS
[0098] Specific embodiment one comprises an odorant comprising or
consisting of [0099] (A) at least 75% by weight of acrylic acid
methyl ester and/or acrylic acid ethyl ester, [0100] (B) 2-19.5% by
weight of tetrahydrothiophene (THT), [0101] (C) 5-50 ppm of
hydroquinone monomethyl ether, and also neither, one or both
components selected from the group consisting of [0102] (D)
0.025-0.2% by weight of butylhydroxy toluene and/or butyl
hydroxyanisole and [0103] (E) 5-500 ppm of one or more compounds of
formula (I)
##STR00006##
[0103] wherein R is selected from the group consisting of H, --OH,
--NH.sub.2, --O.sub.2CR.sup.1 and --NOCR.sup.1, wherein R.sup.1
represents an alkyl radical containing 1 to 4 carbon atoms, based
on the total weight of the odorant.
[0104] Specific embodiment two comprises the odorant as in specific
embodiment one, comprising [0105] (D) 0.025-0.2% by weight of
butylhydroxy toluene and/or butyl hydroxyanisole and/or [0106] (E)
5-500 ppm of one or more compounds of formula (I)
##STR00007##
[0106] wherein [0107] R is selected from the group consisting of H,
--OH, --NH.sub.2, --O.sub.2CR.sup.1 and --NOCR.sup.1, wherein
R.sup.1 represents an alkyl radical containing 1 to 4 carbon
atoms.
[0108] Specific embodiment three comprises the odorant as in one of
the preceding specific embodiments, comprising or consisting of
[0109] (A) at least 84% by weight of acrylic acid methyl ester
and/or acrylic acid ethyl ester, and/or [0110] (B) 5-15% by weight
of tetrahydrothiophene (THT), and/or [0111] (C) 10-20 ppm of
hydroquinone monomethyl ether, and/or [0112] (D) 0.05-0.15% by
weight of butylhydroxy toluene and/or butyl hydroxyanisole and/or
[0113] (E) 10-200 ppm of one or more compounds of formula (I).
[0114] Specific embodiment four comprises the odorant as in one of
the preceding specific embodiments, comprising [0115] (A) at least
84% by weight of acrylic acid methyl ester and/or acrylic acid
ethyl ester, [0116] (B) 5-15% by weight of tetrahydrothiophene
(THT), and [0117] (C) 10-20 ppm of hydroquinone monomethyl ether
and also neither, one or both components selected from the group
consisting of [0118] (D) 0.05-0.15% by weight of butylhydroxy
toluene and/or butyl hydroxyanisole and [0119] (E) 10-200 ppm of
one or more compounds of formula (I).
[0120] Specific embodiment five comprises the odorant as in one of
the preceding specific embodiments, comprising in component (E) one
or more compounds of formula (I)
##STR00008##
wherein R is selected from the group consisting of H and --OH.
[0121] Specific embodiment six comprises the odorant as in one of
the preceding specific embodiments, comprising [0122] (A) at least
84% by weight of acrylic acid methyl ester and/or acrylic acid
ethyl ester, [0123] (B) 5-15% by weight of tetrahydrothiophene
(THT), and [0124] (C) 10-20 ppm of hydroquinone monomethyl ether
and also one or both components selected from the group consisting
of [0125] (D) 0.05-0.15% by weight of butylhydroxy toluene and
[0126] (E) 10-200 ppm of one or more compounds of formula (I)
##STR00009##
[0126] wherein R is selected from the group consisting of H and
--OH.
[0127] Specific embodiment seven comprises the odorant as in one of
the preceding specific embodiments, comprising neither tert-butyl
mercaptan (TBM) nor ethyl mercaptan.
[0128] Specific embodiment eight comprises the odorant as in one of
the preceding specific embodiments, wherein the odorant comprises
no mercaptan.
[0129] Specific embodiment nine comprises the odorant as in one of
the preceding specific embodiments, wherein the odorant comprises,
apart from tetrahydrothiophene (THT), no sulfur-containing
compound.
[0130] Specific embodiment ten comprises a fuel gas having a
methane content of at least 60% by weight, comprising an odorant as
defined in one of the preceding specific embodiments.
[0131] Specific embodiment eleven comprises the fuel gas as in
specific embodiment ten, characterized in that the fuel gas is
natural gas.
[0132] Specific embodiment twelve comprises a vessel comprising
(i) an odorant as in one of specific embodiments one to eight,
comprising component (E), wherein the odorant or (ii) a fuel gas as
in one of specific embodiments nine and ten, containing an odorant
comprising component (E), wherein the fuel gas is contacted in the
vessel with a metal or metal ions or another reactant which is
capable of reacting with component (E).
* * * * *