JP5110939B2 - Gas odorant - Google Patents

Description

  The present invention relates to a gas odorant for imparting a warning odor necessary for gas leak recognition to gas.

  In recent years, fuel gas has become indispensable for daily life, and its use is expanding in many fields. By the way, as this fuel gas, for example, hydrocarbon gas such as propane and butane (liquefied petroleum gas), motor gas (fuel for taxi), LNG (liquefied natural gas), city gas, industrial gas (acetylene, etc.), fuel cell Gas, hydrogen gas, DME (dimethyl ether), etc. are all flammable and explosive, but they have very little odor and may not be noticed even if leaked as they are. Sufficient measures to prevent disasters such as ignition and explosion are necessary.

  Therefore, conventionally, the simplest method of this countermeasure is to add a compound having a specific odor to the fuel gas as an odorant (odorant), so that if such gases leak, It has been done to make it easily perceivable. As these odorants, mercaptans and sulfides have been used.

  However, mercaptans and sulfides, which are general odorants used in the past, contain sulfur, so sulfur oxides are produced by the combustion of the gas, and the sulfur oxides remain in the atmosphere. Was a cause of environmental pollution.

  In addition, when the above conventional odorant is used for fuel gas (for example, city gas, DME) used in the fuel cell, the odorant contains sulfur, so the performance of the catalyst used in the fuel cell There are problems such as lowering the cell voltage and lowering the cell voltage. Further, since the nitrogen content contained in the odorant is reformed and changed to ammonia, there are problems such as lowering the performance of the catalyst and lowering the cell voltage.

  In addition, when the conventional odorants (mercaptans and sulfides) are used for liquefied petroleum gas (LP gas), mercaptans and sulfides have properties different from LP gas in terms of physical properties. Even if LP gas in the gas container is used and reduced, the degree of remaining in the gas container is high. Therefore, when the amount of LP gas remaining in the gas container decreases, the concentration of the odorant in the LP gas becomes extremely high. For example, when 99% of LP gas is consumed, the concentration of the odorant in the LP gas in the gas container is increased. The odorant concentration is 77 times higher than the initial concentration. As described above, when the concentration of the odorant in the gas container is increased, there is a problem that an abnormally strong odor occurs when the gas leaks to the outside.

On the other hand, in order to solve the various problems described above, in recent years, development of an odorant containing no sulfur content has been promoted (for example, see Patent Documents 1 and 2 below), but further improvement is desired. Yes. In other words, environmental pollution can be further reduced, and even in a small amount, the detected concentration is high, and it is good for fuel cells. Even if the fuel gas in the gas container is low, the residual concentration of the odorant hardly changes and abnormal odor problem The appearance of odorants for fuel gas that do not generate odors is expected.
JP 2002-294261 A JP 2002-356688 A

  Furthermore, not only fuel gas but also other gases that can hardly sense the odor even when leaked, for example, oxygen gas, nitrogen gas, argon gas, or toxic gas, it can be recognized if leaked. Therefore, there is an increasing demand for imparting odors because it consumes gas wastefully and is dangerous to life, and odorants that can impart odors even with trace amounts are being studied. .

  The present invention has been proposed in view of the above, and an object of the present invention is to provide a gas odorant which does not generate sulfur oxides even when burned and does not pollute the environment.

  It is another object of the present invention to provide a gas odorant that can increase the sensed concentration even when added in a small amount.

  It is another object of the present invention to provide a gas odorant that does not cause any problems even when used in a fuel cell.

  It is another object of the present invention to provide a gas odorant in which the residual concentration of the odorant hardly changes even when the fuel gas in the gas container is low and the abnormal odor problem does not occur.

  In order to achieve the above object, the invention according to claim 1 is a gas odorant for imparting a warning odor necessary for gas leak recognition to a gas, wherein the odorant is composed of butyl isocyanide. It is a feature.

  The invention described in claim 2 is the invention described in claim 1, wherein the butyl isocyanide is n-butyl isocyanide.

  The invention according to claim 3 is the invention according to claim 1 or 2, wherein the butyl isocyanide is added to the gas in a state dissolved in a solvent.

  The invention described in claim 4 is the invention described in claim 3, wherein the solvent is n-hexane.

Further, the invention according to claim 5, in the invention described in any one of the four claims 1 described above, the gas, propane, hydrocarbon gas (liquefied petroleum gas) pig down, Motagasu ( fuel taxis), LNG (liquefied natural gas), town gas, industrial gas (acetylene), a fuel cell gas, in which either a fuel gas of hydrogen gas, and DME.

The present invention as described in claim 6 is the invention according to any one of the 4 claims 1 described above, the gas, in which oxygen, nitrogen, argon gas, a toxic gas.

  In this invention, since butyl isocyanide is used as the gas odorant (gas odorant), the gas odorant can be configured not to contain a sulfur component. In the case of gas, sulfur oxides are not generated even when the fuel gas is burned, and environmental pollution can be reliably prevented.

  In addition, by using butyl isocyanide as a gas odorant, the detection concentration can be greatly increased even with the addition of a small amount, such as hydrocarbon gas (liquefied petroleum gas) such as propane and butane, motor gas (fuel for taxi) , LNG (liquefied natural gas), city gas, industrial gas (acetylene, etc.), fuel cell gas, hydrogen gas, DME fuel gas, oxygen, nitrogen, argon gas, toxic gas, etc. Can be accurately applied to the required gas.

  In addition, since the gas odorant can be configured not to contain sulfur, even if it is added to natural gas or DME used in a fuel cell, the performance of the fuel cell catalyst is reduced, or the cell There is no problem of lowering the voltage, and a good fuel gas odorant for a fuel cell can be provided. Moreover, since the nitrogen content contained in the gas odorant can be significantly reduced, it is possible to reliably prevent the catalyst performance and cell voltage from being reduced by changing to ammonia by reforming.

  Further, since butyl isocyanide is added to the gas odorant in a solvent state, when the gas is a fuel gas, it is easily vaporized together with the fuel gas. For this reason, even if the remaining amount of fuel gas in the gas container is reduced, the residual concentration of the odorant is hardly changed, and is significantly lower than the conventional case. Therefore, the abnormal odor problem that has conventionally occurred does not occur.

  Embodiments of the present invention will be described in detail below.

である。 In the embodiment of the present invention, n-butyl isocyanide (BIC) is used as a gas odorant (gas odorant) that gives a gas a warning odor necessary for gas leak recognition. The general formula of n-butyl isocyanide is

It is.

  The gas used here is hydrocarbon gas such as propane or butane (liquefied petroleum gas), motor gas (fuel for taxi), LNG (liquefied natural gas), city gas, industrial gas (acetylene, etc.), fuel cell It is a gas that needs to be given a warning odor such as gas, hydrogen gas, DME fuel gas, oxygen, nitrogen, argon gas, toxic gas, and the like.

  The fuel gas is finally used in a vaporized state, but at the stage leading to the fuel gas, it may be a solid or a liquid, and here it is referred to as a fuel gas regardless of the state.

As can be seen from the above general formula, n-butyl isocyanide (hereinafter simply referred to as “butyl isocyanide”) used as a gas odorant does not contain sulfur but is usually used as a fuel gas odorant. Odor is more than twice as strong as that of tertiary butyl mercaptan (TBM ((CH ₃ ) ₃ CSH)).

When the odor intensity is compared with the perception threshold, TBM is 7.3 × 10 ⁻⁵ mol ppm, whereas butyl isocyanide is 3.3 × 10 ⁻⁵ mol ppm, which is 45% of TBM. The cognitive threshold is reached at a concentration of. Therefore, the amount of butyl isocyanide added can be reduced to 45% of the conventionally used TBM. Note that the recognition threshold means a level of stage 2 (a weak odor that can be understood as to what kind of odor) in the odor intensity display method in which the odor level felt by the sense of smell is displayed by its intensity (odor intensity).

  The case where this butyl isocyanide is added to propane gas of liquefied petroleum gas (LP gas) will be described below.

  When butyl isocyanide is added to propane gas, butyl isocyanide is not directly mixed with propane gas but separated, so in this embodiment, butyl isocyanide is once dissolved in a solvent and mixed with propane gas in that state.

Here, n-hexane (CH ₃ (CH ₂ ) ₄ CH ₃ ) was used as the solvent. When butyl isocyanide is dissolved in n-hexane (hereinafter, simply referred to as “hexane”) and added to propane gas in that state, it is mixed almost uniformly. When hexane is mixed with propane gas, it dissolves in propane gas and is easily converted into fuel.

  Butyl isocyanide is suitably dissolved in 1 to 6 times the molar ratio of hexane. When dissolved in hexane with a molar ratio of 1 or less, the amount of hexane relative to butyl isocyanide decreases, and accordingly, butyl isocyanide is less likely to vaporize and the gas concentration of butyl isocyanide in the vaporized propane gas becomes too low. The phenomenon that the smell becomes weak occurs, which is inconvenient. In addition, when dissolved in hexane at a molar ratio of 6 times or more, the amount of hexane relative to butyl isocyanide increases, and accordingly butyl isocyanide is easily vaporized. As a result, the gas concentration of butyl isocyanide in the vaporized propane gas The phenomenon that the odor becomes too high and the odor is too strong occurs, and the amount of hexane used increases, resulting in a high cost, which is also inconvenient.

  1 and 2 are graphs showing the concentration of butyl isocyanide in a propane gas container when butyl isocyanide is dissolved in hexane at a molar ratio of 4 times and mixed with propane gas, and FIG. 1 shows the concentration in the gas phase. FIG. 2 shows the concentration in the liquid phase.

  In FIG. 1, the horizontal axis indicates the liquid level height of propane gas, and the vertical axis indicates the molar concentration in the gas phase. As can be seen from this figure, when the liquid level is 430 mm (100% level), the concentration of butyl isocyanide in the gas phase is 31 mol ppm, and after that, when propane gas is used and the liquid level drops, the level slightly increases or decreases. However, when the liquid level is 80% or less, the liquid level decreases stably and gradually, and even if the liquid level is close to 0, it is almost constant at about 6.5 mol ppm.

  In FIG. 2, the horizontal axis indicates the liquid level height of propane gas, and the vertical axis indicates the molar concentration in the liquid phase. As can be seen from this figure, the concentration of butyl isocyanide in the liquid phase when the liquid surface height is 430 mm (100% level) is 230 mol ppm, and then increases to 1300 mol ppm when propane gas is used. However, after that, when the liquid level is 80% or less, the liquid level is generally stabilized at about 200 to 500 mol ppm, and when the liquid level is almost 0 (2 mm), it is close to 850 mol ppm. .

  From FIG. 1 and FIG. 2, when propane gas is used and vaporized, butyl isocyanide is easily vaporized along with it, and the ratio of butyl isocyanide mixed in the vaporized propane gas is almost zero. Even so, it is about 6.5 mol ppm and is stable.

  In this way, when butyl isocyanide is used as the odorant, even when the propane gas in the gas container is low, the phenomenon that the concentration of the odorant in the vaporized propane gas becomes abnormally high does not occur, Therefore, the problem of abnormal odor that has occurred when the remaining fuel gas in the gas container is reduced is solved.

  1 and 2, the butyl isocyanide dissolved in propane gas was 157 mol ppm, and the overall average concentration of butyl isocyanide in the gas phase was 10.2 mol ppm. Therefore, the vapor-liquid equilibrium ratio was 10.2 / 157 = 0.07. This value is almost the same as the vapor-liquid equilibrium ratio (0.07) of TBM used in the past, which indicates that the vaporization of butyl isocyanide from the liquid phase to the gas phase is performed quickly. This point also shows that butyl isocyanide is effective as an odorant.

  Butyl isocyanide has a normal boiling point of 124 ° C., whereas TBM has a normal boiling point of 65 ° C., and the vapor-liquid equilibrium ratio of butyl isocyanide is usually expected to be lower than TBM, but is used by dissolving in an organic solvent. This is considered to improve the actual vapor-liquid equilibrium ratio.

  The appropriate amount of butyl isocyanide added is as follows. Conventionally, TBM added as an odorant in an LPG manufacturing company is 8.5 ppm by weight. In order to exert the same odor intensity as TBM, it is sufficient to add 8.5 × 45/100 = 3.84 ppm by weight of butyl isocyanide considering that the recognition threshold is 45% of TBM. When converted to mol ppm, 3.84 × (90 (molecular weight of TBM) / 83 (molecular weight of butyl isocyanide)) = 4.16≈4 mol ppm. Considering that the vapor-liquid equilibrium ratio is 0.07, the concentration of butyl isocyanide in propane gas is 4 × 0.07 = 0.28 mol ppm.

  Butyl isocyanide does not contain sulfur as described above. Therefore, even if it is added to city gas, DME, etc. used in fuel cells, the performance of the fuel cell catalyst is lowered or the cell voltage is lowered. Therefore, a good fuel gas odorant for a fuel cell can be provided. In addition, the amount of butyl isocyanide added can be reduced to less than half that of the conventional TBM, so that the nitrogen content in the gas odorant can be greatly reduced. Thus, it is possible to reliably prevent a decrease in catalyst performance and a decrease in cell voltage.

On the other hand, since butyl isocyanide contains N atoms, when the fuel gas burns, it becomes nitrogen oxide (Fuel NO _x ) and its influence is considered. However, as described above, the concentration of butyl isocyanide is 0. 28 mol ppm is less than half of the TBM used in the past. When all N of this butyl isocyanide is combined with oxygen and burned, the concentration of NO _x is 0.28 in consideration of expansion during combustion. /26=0.01 mol ppm, so that it is almost unnecessary to consider the influence. Note that the denominator of the value "26", to the propane 1 mol air ratio 1 is due to the combustion exhaust gas 26 mol, 26 mol of breakdown, CO ₂ = 3 moles, H ₂ O = 4 mol, N ₂ = 19 mol.

Further, considering combustion when the fuel gas is hydrogen, hydrogen has a small amount of oxygen, and considering the expansion during combustion, the concentration of NO _x is 0.28 / 3 = 0.09 mol ppm. However, the effect of this level is almost negligible. The numerical value “3” in the denominator is based on the fact that the combustion exhaust gas becomes 3 moles with respect to 1 mole of propane at an air ratio of 1, and the breakdown of 3 moles is H ₂ O = 1 mole, N ₂ = 3 moles.

  As described above, in this invention, since butyl isocyanide is used as a gas odorant (gas odorant), the gas odorant can be configured not to contain sulfur. Therefore, when the gas is a fuel gas, sulfur oxides are not generated even when the fuel gas is burned, and environmental pollution can be reliably prevented.

  In addition, by using butyl isocyanide as a gas odorant, it is possible to significantly increase the sensed concentration even with a small amount of addition, and not only in the case of the above propane gas, but also hydrocarbon gases such as butane other than propane gas (Liquefied petroleum gas), motor gas (fuel for taxi), LNG (liquefied natural gas), city gas, industrial gas (acetylene, etc.), fuel cell gas, hydrogen gas, DME fuel gas, oxygen It can be applied to gases that need to be given a warning odor, such as nitrogen, argon gas, and toxic gas.

  In addition, since the gas odorant can be configured not to contain sulfur, even if it is added to city gas, DME, etc. used in fuel cells, the performance of the fuel cell catalyst may be reduced, There is no problem of lowering the voltage, and a good gas odorant for a fuel cell can be provided. Moreover, since the nitrogen content contained in the gas odorant can be significantly reduced, it is possible to reliably prevent the catalyst performance and cell voltage from being reduced by changing to ammonia by reforming.

  Further, since butyl isocyanide is added to the gas odorant in a solvent state, when the gas is a fuel gas, it is easily vaporized together with the fuel gas. For this reason, even if the remaining amount of fuel gas in the gas container is reduced, the residual concentration of the odorant is hardly changed, and is significantly lower than the conventional case. Therefore, the abnormal odor problem that has conventionally occurred does not occur.

It is a graph which shows the density | concentration in the gaseous phase of the butyl isocyanide in a propane gas container at the time of melt | dissolving butyl isocyanide in hexane 4 times in molar ratio, and mixing with propane gas. It is a graph which shows the density | concentration in the liquid phase of the butyl isocyanide in a propane gas container at the time of melt | dissolving butyl isocyanide in hexane 4 times in molar ratio, and mixing with propane gas.

Claims (6)

In gas odorants that give gas a warning odor necessary for gas leak recognition,
A gas odorant, wherein the odorant comprises butyl isocyanide.   The gas odorant according to claim 1, wherein the butyl isocyanide is n-butyl isocyanide.   The gas odorant according to claim 1 or 2, wherein the butyl isocyanide is added to the gas in a state dissolved in a solvent.   The gas odorant according to claim 3, wherein the solvent is n-hexane. The gas is propane, hydrocarbon gas (liquefied petroleum gas) pig down, Motagasu (fuel taxis), LNG (liquefied natural gas), town gas, industrial gas (acetylene), a fuel cell gas, hydrogen The gas odorant according to any one of claims 1 to 4, wherein the gas odorant is a gas for fuel of either gas or dimethyl ether (DME). The gas is oxygen, nitrogen, argon gas, which is toxic gas, gas odorant according to any one of claims 1 to 4.

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