JP2007112969A - Odorant for fuel gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an odorant for a fuel gas without increasing the content of sulfur, hardly affected by temperature change or the like, and having excellent odor quality and odor intensity. <P>SOLUTION: The odorant for the fuel gas contains mercaptanes and cyclohexene as essential components regulated so that the mixed ratio of the mercaptanes to the cyclohexene by mass may be (85:15)-(25:75). The mixture of tert-butylmercaptane with the cyclohexene in the ratio of (85:15)-(50:50) by mass is especially preferable. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an odorant for fuel such as liquefied natural gas (LNG), city gas, and LP gas.

  Conventionally, liquefied natural gas (LNG), city gas, and LP gas have been used to prevent accidents such as fuel gas poisoning, ignition or explosion, so that if the fuel gas leaks, it can be detected quickly and easily by smelling it. A fuel gas odorant is added to the fuel gas. As such odorants for fuel gas, mercaptans, sulfides and the like are known, and these are used alone or in combination of several kinds. The sulfur-containing compounds currently used have a small amount and a high odor effect, and the odor chamber is generally perceived as a gas odor.

  However, sulfur compounds are not preferable because they are a source of generation of sulfur dioxide, which is an air pollutant, as fuel is burned. In recent years, as city gas based on liquefied natural gas containing no sulfur content has become widespread, a gas odorant containing no sulfur content has been demanded.

  Among fuel cells that are currently being developed, stationary fuel cells that have already been supplied with city gas using hydrogen as a feedstock have begun to spread before other systems. . When city gas is used as the hydrogen source, hydrogen is generated by the reformer. However, it is necessary to remove sulfur from the necessity of preventing poisoning of the reforming catalyst. For this reason, desulfurization of sulfur compounds derived from odorants contained in fuel gas is currently being carried out, and the sulfur content in fuel gas is reduced as much as possible in order to omit the desulfurization device or extend the life of the desulfurization device. There is a need to reduce it.

In recent years, various means have been proposed as means for achieving the above-described object. For example, instead of a sulfur compound, a mixture of valeric acid and an acrylate ester (see Patent Document 1 below), cyclohexene (see Patent Document 2 below) ), An odorant containing 5-ethylidene-2-norbornene as an essential component (see Patent Document 3 below), and odorant containing 2-methoxy-3-isobutylpyrazine as a non-sulfur component and a combination of mercaptan and sulfide. It is suggested that an agent (see Patent Document 4 below), pyrazine (see Patent Document 5 below) and the like are used as non-sulfur odorants.
JP-A-48-79804 JP 54-58701 A JP-A-55-56190 JP-A-60-92396 JP 55-59190 A JP-A-8-60167

  Non-sulfur odorants proposed in recent years as odorants used in fuel gas are weaker in odor intensity than mercaptans and have different odor qualities, so they can be used satisfactorily as replacements for mercaptans. The fact is that it has not been found.

  On the other hand, mercaptans have problems such as solidification at low temperatures, relatively low soil permeability and possible delays in detection when leaked in buried facilities, and depending on the situation, it may be difficult to handle when used alone. . On the other hand, methods such as mixing with other sulfur-containing compounds and non-sulfur odorants have also been proposed.

  However, sulfur-containing compounds other than mercaptans have a problem in that the amount of sulfur compound used increases because the odor intensity as high as that of mercaptans cannot be obtained. In addition, as for the mixture of mercaptans and non-sulfur compounds, for example, as seen in Patent Document 2, only a method of using a mixture of non-sulfur compounds and mercaptans is suggested. No consideration has been given to the ratio characteristics.

  The problem to be solved by the present invention is to provide an odorant for fuel gas that is not easily affected by temperature fluctuations and the like, and has excellent odor quality and odor intensity without increasing the sulfur content.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have completed a fuel gas odorant containing mercaptans as an active ingredient, which limits the amount of sulfur and is easy to handle. It came. That is, the present invention provides an odorant for fuel gas, which contains mercaptans and cyclohexene as essential components, and the mixing ratio of mercaptans and cyclohexene is in the range of 85:15 to 25:75. is there.

  The odorant of the present invention is economical because it has a sensing effect even at a low concentration relative to the fuel gas. Further, since mercaptans do not solidify even in a relatively low temperature environment, they can be easily used without performing an operation such as keeping the odorizing device warm.

  Hereinafter, the odorant of the present invention will be described. According to the present invention, mercaptans and cyclohexene are contained as essential components, and by mixing mercaptans and cyclohexene in a mass ratio of 85:15 to 25:75, the sulfur content is not increased and handled at low temperatures. Therefore, it is possible to obtain an odorant for fuel gas which is easy and has good soil permeability. Furthermore, blending mercaptans and cyclohexene in a mass ratio in the range of 85:25 to 50:50 prevents coagulation of mercaptans at low temperatures and has a recognition threshold that is almost equivalent to that of mercaptans alone. Since it is obtained, it is particularly preferable.

  If the ratio of mercaptans to cyclohexene exceeds 85% by mass, it tends to solidify at low temperatures, and the handling method must be changed depending on the environment. On the other hand, if the amount of cyclohexene exceeds 75% by mass, the recognition threshold of the odorant increases, and the required amount of mercaptans per unit amount of fuel gas increases.

  Examples of mercaptans in the present invention include ethyl mercaptan, n-propyl mercaptan, isopropyl mercaptan, n-butyl mercaptan, isobutyl mercaptan, secondary butyl mercaptan, tertiary butyl mercaptan, n-pentyl mercaptan, 2-pentyl mercaptan, 3-pentyl mercaptan, Pentyl mercaptan, 2-methylbutyl mercaptan, 3-methylbutyl mercaptan, 1,1-dimethylpropyl mercaptan, 2,2-dimethylpropyl mercaptan, 1,2-dimethylpropyl mercaptan, n-hexyl mercaptan, 2-hexyl mercaptan, 3 -Hexyl mercaptan, 1-methylpentyl mercaptan, 2-methylpentyl mercaptan, 3-methylpentyl mercaptan, 1-methylpentyl Lucaptan, 3-methyl-2-pentyl mercaptan, 4-methyl-2-pentyl mercaptan, 2-methyl-3-pentyl mercaptan, 3-methyl-3-pentyl mercaptan, 1,1-dimethylbutyl mercaptan, 2,2- Dimethylbutyl mercaptan, 3,3-dimethylbutyl mercaptan, 1,2-dimethylbutyl mercaptan, 1,3-dimethylbutyl mercaptan, 2,3-dimethylbutyl mercaptan, 1,1,2-trimethylpropyl mercaptan, 1,2, Examples thereof include 2-trimethylpropyl mercaptan and furfuryl mercaptan. Among them, ethyl mercaptan, n-propyl mercaptan, isopropyl mercaptan, tertiary butyl mercaptan, and furfuryl mercaptan are preferable from the viewpoint of odor.

  In the odorant for fuel gas of the present invention, sulfides can be blended in order to further improve chemical stability or soil permeability. Examples of sulfides include dimethyl sulfide, diethyl sulfide, methyl ethyl sulfide, di-n-propyl sulfide, n-propyl isopropyl sulfide, diisopropyl sulfide, methyl n-propyl sulfide, methyl isopropyl sulfide, ethyl n-propyl sulfide, ethyl isopropyl sulfide. , Di n-butyl sulfide, diisobutyl sulfide, ditertiary butyl sulfide, n-butyl methyl sulfide, n-butyl ethyl sulfide, n-butyl n-propyl sulfide, n-butyl isopropyl sulfide, isobutyl methyl sulfide, isobutyl ethyl sulfide, isobutyl n-propyl sulfide, isobutyl isopropyl sulfide, tertiary butyl methyl sulfide, tertiary Methyl ethyl sulfide, tertiary butyl n- propyl sulfide, tertiary butyl isopropyl sulfide, tetrahydrothiophene, and the like. Among them, dimethyl sulfide and tetrahydrothiophene are preferable from the viewpoint of odor.

  The fuel gas odorant of the present invention can also be blended with a non-sulfur odorant for the purpose of reducing the sulfur content. Examples of the non-sulfur odorant include nitrogen-containing compounds such as lower fatty acids, pyrazines, pyridines and pyrimidines. More specific examples of these non-sulfur odorants include 2-alkoxy-3-alkylpyrazine. Among them, 2-methoxy-3-iso-propylpyrazine or 2-methoxy-3-iso-butylpyrazine is preferable from the viewpoint of odor quality and odor intensity.

  The mixing ratio of the sulfides of the present invention is not particularly limited as long as the odor effect is exhibited. However, it is preferable that the mixing ratio is as low as possible in order to reduce the sulfur content.

The addition ratio of the odorant of the present invention to the fuel gas is not particularly limited as long as the odor effect is exhibited, but is preferably as low as possible from the viewpoint of economy. Specifically, in the range of 0.1-100 mg / Nm ^3, and more preferably in a 5 to 50 mg / Nm ^3.

  The fuel gas to which the odorant for fuel gas of the present invention is applied is not particularly limited. Specifically, fuel gas such as liquefied natural gas (LNG), industrial gas, or liquefied petroleum gas is used. Can be mentioned.

  Next, although an Example demonstrates this invention concretely, this invention is not restrict | limited to a following example. In the following examples, the recognition threshold of odorants was evaluated by the following test method.

(Odor chamber evaluation)
The odor intensity and odor quality, which are the most basic characteristics of a gas odorant, were measured by the odorless chamber method in accordance with the “Measurement Method of Gas Odor Concentration” of the Japan Gas Association. That is, the odor intensity and odor quality were evaluated by stirring and leaving the test substance in an 8 m ³ odorless room until the concentration of the test substance in the atmosphere was constant, and then leaving the room. The determination of odor intensity was measured by the following 6-step odor intensity display method using five skilled panels, the average value was taken as the measurement value, and the odorant concentration at which the odor intensity was 2 was taken as the recognition threshold value.
"6-level odor intensity display method"
0: Odorless 1: I don't know what it smells, but I can feel it at last 2: I can understand what it smells, I feel it easily 3: Smells I feel clearly 4: Strong smell 5: I can't stand it

Example 1
Tertiary butyl mercaptan (TBM) and cyclohexene were stirred and mixed at a weight ratio of 5:95 to 100: 0 to prepare an odorant solution. This solution was added so as to be 0.1 to 100 mg / Nm ³ with respect to liquefied natural gas. The cognitive threshold concentration of this sample was evaluated by the test method. From the results, the amount of TBM blended in the mixture of TBM and cyclohexene (mass%) was compared with the amount of TBM added (μg / Nm ³ ) necessary to reach the recognition threshold for the fuel gas. The result is shown in FIG.

  From the test results, it was found that the absolute amount of TBM in the fuel gas tends to increase rapidly in the region where the TBM content is less than 25% by mass. Thereby, when using the composition which consists of TBM and cyclohexene as an odorant, it was judged that it is preferable that the TBM compounding quantity in a composition is 25% or more.

(Physical property test)
In order to be put into practical use as an odorant for fuel gas, it is basic but has a low freezing point and is easy to handle. TBM has a freezing point of 1 ° C. and is difficult to use alone in cold regions. Therefore, a mixed solution with cyclohexene was prepared, and the freezing point was confirmed with a -20 ° C freezer. Moreover, in order to be put into practical use as an odorant for fuel gas, it is necessary to be chemically stable. It was confirmed that the fuel gas odorant according to the present invention satisfies these conditions.

(Chemical stability)
Add 20 g of odorant and 0.2 g of ferric oxide powder to a 30 mL glass sealed container, heat at 50 ° C. for 10 days, measure by gas chromatography and check for changes in composition of the sample before and after heating. If no new peak was detected by chromatography in any reaction, it was judged stable. The test results are shown in Table 1.

  From this result, it was confirmed that the composition composed of TBM and cyclohexane satisfies various usage conditions. However, when the amount of TBM is 85% or less, there is no deterioration in operability due to the climatic environment. Therefore, it was judged preferable.

  The odorant for fuel gas of the present invention is excellent in odor quality and odor intensity, which is not easily affected by temperature fluctuations without increasing the sulfur content, and can be added to various fuel gases.

The graph of the TBM compounding quantity (mass%) in the mixture of TBM and cyclohexene, and the addition amount (microgram / Nm < ³ >) of TBM required to reach the recognition threshold with respect to fuel gas. Example 1

Claims (4)

An odorant for fuel gas, comprising mercaptans and cyclohexene as essential components, wherein the mixing ratio of mercaptans and cyclohexene is in the range of 85:15 to 25:75. An odorant for fuel gas, comprising a mercaptan and cyclohexene, wherein a mixing ratio of the mercaptan and cyclohexene is in a range of 85:15 to 25:75. The odorant for fuel gas according to claim 1 or 2, wherein the mercaptan is tertiary butyl mercaptan. The fuel gas odorant according to any one of claims 1 to 3, wherein the mixing ratio of tertiary butyl mercaptan and cyclohexene is in the range of 85:15 to 50:50 by mass ratio.

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