JP3445957B2 - Residue analysis in liquefied gas - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for analyzing a residue content in a liquefied gas, which can easily and quickly measure and quantify the residue content contained in the liquefied gas such as liquefied petroleum gas.

[0002]

2. Description of the Related Art Liquefied petroleum gas (hereinafter, also referred to as "LP gas") contains butane as a main component. If oil (residue) is contained in the LP gas, for example, soot is deposited on the surface of the nickel catalyst to deteriorate the catalyst, block the vaporizer of a taxi, or generate power when the shift gas is produced and reacted. It is also a cause of troubles in pipes and equipment by blocking nozzles such as turbines. Therefore, at present, it is generally practiced to control various residual components contained in the LP gas to be below a certain amount.

At present, liquefied petroleum gas (hereinafter, "LP gas")
Say. ) For the quality standard and test method of the residue in
It is not specified by JIS, which is a domestic standard. On the other hand, JLPGA has become a practical standard in Japan.
The standard is 60 massppm or less (348K), 10
It is specified to be less than massppm (378K), and J
The LPGA-S-05T evaporation residue test method (mass method) is used as a quantitative method.

However, this test method requires an analysis time of 5 to 6 hours and requires a sample amount of 1 k for analysis.
g, which is difficult to carry out in a small-scale test, and is not suitable for research and development in which many small-scale experiments are conducted. Also, in terms of analytical operations, pretreatment and analytical processing are complicated and diversified, so the labor required for them is large, and since the sample is released into the atmosphere, environmental and safety measures are also required. Furthermore, the detection limit of the above-mentioned JLPGA-S-05T evaporation residue test method is 1 massppm, and although the accuracy is also defined in the JLPGA standard, the accuracy of analysis is not always high due to instrumental errors and human error of analytical instruments. I couldn't say that.

Against this background, in 1995,
The provisional standard test method JLPGA-S-05T-95 has been established as a provisional standard for the evaporation residue in the LP gas. Then, a measuring instrument conforming to the same test method, for example, "Shimadzu LP
A gas evaporation residue analysis system "(manufactured by Shimadzu Corporation) has also been developed. This system is a gas chromatography system using a capillary column and a hydrogen flame ionization detector (FID), which enables highly accurate and highly sensitive analysis, and the above-mentioned problems of detection limit and analysis accuracy are improved. .

[0006]

However, in this system, the vaporized carbon content in the LP gas is quantified as the total amount of the hydrocarbon component having 6 to 30 carbon atoms, so that the hydrocarbon containing more than 30 carbon atoms is contained. It is not suitable for the analysis of residual components. In addition, in the same system, it is necessary to separate and quantify hydrocarbons having 6 carbon atoms for each carbon number, and to introduce into the sample column in a pressurized state. Oven temperature, for example 2
It was still not a simple analytical method because it needed to be cooled to 58K.

Therefore, an object of the present invention is to solve the above-mentioned problems and to easily and easily remove a trace amount of a residue in LP gas.
It is to provide a method for performing a quick and accurate analysis.

[0008]

From the above-mentioned conventional technical background, as a new analytical method for trace residues in liquefied gas such as LP gas, (1) sampling is easy and necessary for the test. A small amount of sample is required (2)
The operation of the analysis test is simple, (3) continuous stable analysis is possible in the mass ppm order,
(4) It is required that the analysis operation be safe and environmentally friendly, and (5) that the analysis result be easily analyzed.

Based on the above matters, the present inventor has studied various methods for reproducibly analyzing a residue having a measurement object concentration of several mass ppm to several tens of mass ppm. As a result, the gas chromatographic method (hereinafter, also referred to as “GC method”) is the most general and applicable method among the established existing analytical techniques. The present invention has been completed by paying attention to what is satisfied.

That is, according to the present invention, the residue contained in the liquefied gas is extracted into a liquid organic solvent at room temperature and pressure, and the residue in the organic solvent is measured by a gas chromatograph method to obtain the above-mentioned substance. A method for analyzing a residue content in a liquefied gas, characterized by measuring and quantifying a residue content in the liquefied gas.

The present invention is also a method for analyzing a residue content in a liquefied gas, wherein the organic solvent is a hydrocarbon having 5 or more and less than 18 carbon atoms.

According to the present invention, it is possible to measure and quantify the residue content contained in liquefied gas, particularly liquefied petroleum gas, simply, quickly and accurately.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The present invention relates to a method for analyzing a residue content in a liquefied gas such as LP gas. In the present invention, the residue content in the liquefied gas is generally a substance that forms a drain remaining in the facility where the liquefied gas such as LP gas is consumed, and for example, hydrocarbons having 6 or more carbon atoms, Lubricating oils including mineral oils and greases, free water, sulfur compounds containing non-volatile sulfur, general chemical substances containing amine compounds, iron rust, and impurities such as dust. Of these, the residue content to be analyzed in the present invention is generally so-called hydrocarbon-based oil content that is contained in a small amount in liquefied gas such as LP gas.

The organic solvent that can be used in the present invention is a liquid at normal temperature and pressure, and since both LP gas and residue are saturated aliphatic hydrocarbons (paraffins), they can be mixed well with both. Desired. Therefore, a hydrocarbon-based organic solvent is desirable. In addition, since it is a liquid at room temperature and pressure, it is separated from the oil detection peak by GC, and LP gas is vaporized preferentially.
The vapor pressure needs to be lower than that of P gas. Since the LP gas, that is, propane and butane has 3 or 4 carbon atoms, and the oil component is composed of about 18 or more carbon atoms, paraffin is an organic solvent for extracting oil component having 5 or more carbon atoms 18 or more. Less than saturated hydrocarbons are preferred.

Further, unsaturated hydrocarbons such as hexene, cyclic hydrocarbons such as cyclohexane, and aromatic hydrocarbons such as benzene can be used as the organic solvent for extraction as long as they satisfy the above conditions. Furthermore, normal,
Isomers such as iso are not limited at all. Of these, normal paraffins of the same family are considered because of their miscibility with LP gas and oil content, the size of their effects on human health, the availability of samples, especially high-purity products, the price, and the ease of handling. Is preferred, and normal hexane is more preferred.

According to the present invention, (1) LP gas having a high vapor pressure is extracted by thoroughly mixing the LP gas with a liquid organic solvent at room temperature and atmospheric pressure to extract the residue contained in the LP gas into the organic solvent. A step of obtaining an organic solvent solution containing a residue of LP gas obtained by evaporating the gas (residue extraction step), (2)
The obtained organic solvent solution comprises a step of analyzing and quantifying the residue content in the LP gas by a gas chromatography method (hereinafter, also referred to as “GC method”) (residue content analysis step).

1) Residue Extraction Step The outline of each operation step of the residue extraction step is shown in FIG. This step is performed by the following procedures (1) to (4). (1) A predetermined volume (V1) of an organic solvent for extracting a residue is put in a container in advance (the volume may be arbitrary). The container is required to have the ability to withstand the pressure of LP gas. When measuring by volume, it is convenient to use a pressure proof glass container that can read the scale directly. (2) Predetermined volume (V2) in a container containing the organic solvent
Add LP gas and seal. (3) Mix the mixed solution in the container sufficiently. Mixing is performed by shaking the sealed container. (4) Utilizing the fact that the LP gas having a high vapor pressure is preferentially evaporated, the container is opened and the LP gas therein is evaporated.
At this time, it may be considered that the LP gas has evaporated when the volume of the solution reaches V1. In this operation, it suffices that the organic solvent finally remains when the LP gas evaporates and disappears. Therefore, if the evaporation amount is smaller than that of the LP gas, the organic solvent may be evaporated together, and in order to accelerate the evaporation of the LP gas, a suitable amount of a high-purity inert gas such as N ₂ or He is aerated to evaporate it. It can also be promoted. However, it is necessary to make sure that the organic solvent is not completely evaporated. In this case, the evaporation amount of the organic solvent is preferably as small as possible in order to suppress measurement error.

2) Residual Content Quantifying Step Next, the residual content in the LP gas extracted into the organic solvent is measured and quantified. This is done as follows. (1) The volume (V3) of the remaining solution is measured. (2) The solution of (1) above is measured by the GC method to determine the residual concentration (C) of the solution. Since the residue does not evaporate during the operation (4) of the above 1) residue extraction step,
The oil concentration (C1) in the LP gas can be calculated by the following equation (i).

C1 = C '× V3 / V2 (i)

At this time, the unit of C1 is "residual mass / L
P gas capacity ", eg g-oil / ml-LP gas, C'unit is" residue mass / organic solvent capacity ", eg g-oil / ml
-Becomes an organic solvent.

When the amount of solution is measured by mass, the measured volumes V1, V2 and V3 are respectively measured masses W1, W2 and
If W3 is set, the residual concentration (C2) in the LP gas can be calculated by the following equation (ii).

C2 = C '× W3 / W2 (ii)

At this time, the unit of C2 is "residual mass / L
P gas mass ", for example, g-oil / g-LP gas, C'unit is" residue mass / organic solvent mass ", for example, g-oil / g-organic solvent. Also, the correlation between C1 and C2 is , Where the density of the LP gas is d, it can be obtained from the equation (iii).

C1 = C2 × d (iii)

(3) Qualitative / quantitative analysis of the residue is carried out using the GC method. The various conditions of GC are JIS distillation test method (J
Follow the reference test method of IS-K2254). This method is based on or in accordance with the contents described as a gas chromatography distillation test method for petroleum fractions.

The residue extracted in the organic solvent need not be separated / qualified / quantified for each carbon number as long as the detection peak in GC can be clearly separated from that in the organic solvent and the total amount can be identified. As long as the above detection conditions are satisfied, the GC conditions of (1) above, such as the column tank temperature, the carrier flow rate, and the column type, the properties of the organic solvent and oil used,
Alternatively, changes and improvements can be made according to the analysis environment.

(4) Residual amount is quantified from the amount of GC detected.
The calculation method includes an absolute calibration curve method, a one-inspection calibration curve method, an internal standard method, etc., but it is not particularly limited as long as it does not hinder the qualitative and quantitative determination of oil and maintains the quantitative accuracy. Further, the residue used for the standard solution is preferably the residue contained in the LP gas to be actually measured, but if the composition distributions are similar and the detection ranges in GC are similar,
It is not particularly limited. As described above, LP
The residue in the gas can be easily and quickly analyzed.

[0028]

EXAMPLES Next, the present invention will be described in more detail by way of examples. Example 1 6.0 ml of LP gas (sample 1) was placed in a pressure-resistant glass container in which 5.0 ml (V1 = 5.0) of n-hexane had been put in advance.
(V2 = 6.0), sealed and mixed well. Next, the container was opened, the LP gas in the container was evaporated, the liquid amount in the container was adjusted to 5.0 ml (V3 = 5.0), and the residual content of this solution was measured by GC. As a result, the residue was 11.
5 ppm (g-oil / ml-n-hexane), 19.
It was 0 massppm (g-oil / g-LP gas).
The density of Sample 1 is 0.505 (g / ml, 15 ° C)
Met. The test time was 1 hour including the GC measurement time.

Table 1 shows the measurement conditions of GC. Further, the quantification of the residue was carried out by the absolute calibration curve method using the three standard solutions. The standard solution is an n-hexane solution, and as a residue, model oil (JIS K-2213 ISO VG3
2 turbine oil) was used. In addition, the residue concentration of the standard solution is 12.0, 53.0, 154ppm (g-oil / ml
-n-hexane).

[0030]

[Table 1]

The residue in the above model oil was extracted with n-hexane and analyzed by the GC method. The results are shown in FIG.
As shown in FIG. 2, the detection peaks of GC of the organic solvent, n-hexane, the model oil, and the additive of the model oil were completely separated and each was detected as one peak. A calibration curve with a correlation coefficient of 0.9992 was obtained from the oil concentration of each standard solution and the GC peak area, and was used to determine the residual content in the LP gas.

Example 2 As in Example 1, 5.0 ml of n-hexane (V
(1 = 5.0) The pressure-resistant glass container was charged with 5.5 ml (V2 = 5.5) of LP gas (Sample 2) containing no residue, and the mixture was sealed and sufficiently mixed. The container was opened and the liquid amount in the container was adjusted to 5.0 ml (V3 = 5.0). As a result of measuring the oil content of this solution by GC, the oil content was 0 ppm (g-o
il / ml-n-hexane), and 0 massppm
(G-oil / g-LP gas). The density of Sample 2 was 0.508 (g / ml, 15 ° C). Also, G
The measurement conditions for C, the standard solution, and the calibration curve are the same as in Example 1.

Example 3 2000 mg of model oil was mixed with 2000 g of sample 2,
This was designated as Sample 3. Then, as in Example 1,
5.8 ml (V2 = 5.8) of sample 3 was placed in a pressure resistant glass container containing 5.0 ml (V1 = 5.0) of n-hexane in advance.
Put in, seal and mix well. After opening the container, the liquid volume in the container was adjusted to 4.9 ml (V3 = 4.9). As a result of measuring the oil content of this solution by GC, the residual content was 60.5 p.
pm (g-oil / ml-n-hexane), 100 ma
It was ssppm (g-oil / g-LP gas). In addition,
The density of Sample 3 was 0.509 (g / ml, 15 ° C). The GC measurement conditions, standard solution, and calibration curve are the same as in Example 1.

Example 4 To 2000 g of sample 2, 100 mg of the model oil shown above was added.
Were mixed and this was designated as Sample 4. Then, Example 1
In the same manner as above, 5.2 ml of n-hexane (V1 = 5.
2) 4.9 ml of sample 4 (V
2 = 4.9), put in tightly and mixed well. The container was opened and the liquid volume in the container was adjusted to 5.0 ml (V3 = 5.0). As a result of measuring the residue of this solution by GC, the residue was 25.0 ppm (g-oil / ml-n-hexane),
It was 50.1 massppm (g-oil / g-LP gas). The density of Sample 4 was 0.509 (g / ml, 1
5 ° C.). The GC measurement conditions, standard solution, and calibration curve are the same as in Example 1.

Example 5 As in Example 1, 5.0 ml of n-hexane (V1
= 5.0), 5.4 ml (V2 = 5.4) of LP gas (Sample 5) was placed in a pressure resistant glass container, and after mixing well, the liquid volume in the container was 5.0 ml (V3 = 5. 0). As a result of measuring the oil content of this solution by GC, the oil content was 18.
4 ppm (g-oil / ml-n-hexane), 2
It was 9.2 massppm (g-oil / g-LP gas). The density of Sample 5 was 0.583 (g / ml, 15
℃). The GC measurement conditions and standard solution were the same as in Example 1, but a calibration curve with a correlation coefficient of 0.9994 was newly created and used.

Example 6 As in Example 1, 5.0 ml of n-hexane (V1
= 5.0), another 5.5 ml (V2 = 5.5) of LP gas (Sample 6) was placed in a pressure-resistant glass container, which was sealed and sufficiently mixed. Open the container and adjust the amount of liquid in the container to 5.1 m.
1 (V3 = 5.1). As a result of measuring the oil content of this solution by GC, the oil content was 0.2 ppm (g-oil / ml-n
-Hexane) and 0.3 mass ppm (g-oil
/ G-LP gas). The density of sample 6 is 0.5
It was 77 (g / ml, 15 degreeC). The GC measurement conditions, standard solution, and calibration curve are the same as in Example 5.

Example 7 In the same manner as in Example 1, 5.0 ml (V
Into a pressure resistant glass container (1 = 5.0), 5.2 ml (V2 = 5.2) of LP gas (Sample 7) containing no residue was charged, sealed, and thoroughly mixed. The container was opened and the liquid volume in the container was adjusted to 5.1 ml (V3 = 5.1). As a result of measuring the oil content of this solution by GC, the oil content was 0 ppm (g-oil /
ml- n-hexane), and 0 massppm (g-oi
1 / g-LP gas). The density of the sample 7 is 0.
It was 584 (g / ml, 15 degreeC). The GC measurement conditions, standard solution, and calibration curve are the same as in Example 5.

Example 8 2000 mg of sample 6 was mixed with 200 mg of the above model oil, and this was used as sample 8. Then, in the same manner as in Example 1, 5.2 ml (V2 = V2 = Sample 8) of the sample 8 was placed in a pressure-resistant glass container in which 5.0 mL (V1 = 5.0) of n-hexane was previously placed.
5.2) Put in, seal and mix well. The container was opened and the liquid volume in the container was adjusted to 5.0 ml (V3 = 5.0). As a result of measuring the oil content of this solution by GC, the oil content was 5
9.7 ppm (g-oil / ml-n-hexane) and 99.3 massppm (g-oil / g-LP gas)
Met. The density of Sample 8 is 0.578 (g / m
1, 15 ° C.). The GC measurement conditions, standard solution, and calibration curve are the same as in Example 5.

Example 9 To 2000 g of sample 6, 100 mg of the above model oil was mixed, and this was designated as sample 9. As in Example 1, the LP gas of Sample 9 was placed in a pressure-resistant glass container in which 4.9 ml (V1 = 4.9) of n-hexane had been placed in advance. ml (V2
= 5.5), put, sealed, and mixed well. The container was opened and the liquid volume in the container was adjusted to 5.0 ml (V3 = 5.0). As a result of measuring the oil content of this solution by GC, the oil content was 3
2.9 ppm (g-oil / ml-n-hexane) and 51.8 mass ppm (g-oil / g-LP gas)
Met. The density of Sample 9 was 0.577 (g / m
1, 15 ° C.). The GC measurement conditions, standard solution, and calibration curve are the same as in Example 5.

Example 10 To 2000 g of sample 7, 100 mg of the above model oil was mixed, and this was designated as sample 10. Then, in the same manner as in Example 1, 5.0 ml of n-hexane was previously prepared (V1 = 5.0).
5.8 with the LP gas of the sample 10 in the pressure resistant glass container.
ml (V2 = 5.8) was added, sealed and mixed well.
The container was opened and the liquid amount in the container was 5.0 ml (V3 = 5.
0). As a result of measuring the oil content of this solution by GC, the oil content was 33.2 ppm (g-oil / ml-n-hexane).
And was 49.0 mass ppm (g-oil / g-LP gas). The density of the sample 10 is 0.584 (g
/ Ml, 15 ° C). The GC measurement conditions, standard solution, and calibration curve are the same as in Example 5.

Example 11 In the same manner as in Example 1, 5.0 ml (V
1 = 5.0) in a pressure-resistant glass container, 5.0 ml (V2 = 5.0) of LP gas (Sample 11), and sealed.
Mix well. Open the container and adjust the amount of liquid in the container to 5.
It was set to 0 ml (V3 = 5.0). The oil content of this solution is
The oil content was 8.4 ppm (g-oil / ml)
-n-hexane), 15.8 massppm (g-
oil / g-LP gas). The density of Sample 11 was 0.530 (g / ml, 15 ° C). Also, G
The measurement conditions for C, the standard solution, and the calibration curve are the same as in Example 5.

Example 12 In the same manner as in Example 1, 3.00 g (W of n-hexane was previously prepared.
1 = 3.00) Put the LP of sample 6 in a pressure-resistant glass container.
Add 3.25 g of gas (W2 = 3.25), seal,
Mix well. Open the container and adjust the amount of liquid in the container to 3.0.
It was set to 2 g (W3 = 3.02). The oil content of this solution is
The oil content was 0 massppm (g-oil /
g-LP gas). The GC measurement conditions were the same as in Example 1, but the oil concentrations were 15.5, 58.0, 1
A calibration curve having a correlation coefficient of 0.9990 was newly prepared and used for three standard solutions having 55 mass ppm.

Example 13 In the same manner as in Example 1, 3.01 g (W
1 = 3.01) Put the LP of sample 8 in a pressure resistant glass container.
3.40g of gas (W2 = 3.40) was charged, sealed and mixed well. Open the container and adjust the amount of liquid in the container to 2.99.
g (W3 = 2.99). As a result of measuring the oil content of this solution by GC, the oil content was 101 massppm (g-oil /
g-LP gas). The GC measurement conditions, standard solution, and calibration curve are the same as in Example 12.

Example 14 As in Example 1, 10.0 ml of n-hexane was previously prepared.
89.5 ml (V2 = 89.5) of the LP gas of sample 6 in Table 1 was put into a pressure-resistant glass container containing (V1 = 10.0), mixed well, and then the liquid amount in the container was 10.0 ml ( V
3 = 10.0). As a result of measuring the oil content of this solution by GC, the oil content was 1.7 ppm (g-oil / ml-n-hexane) and 0.33 massppm (g-oil / g-L).
P gas). The test time was 1.3 hours. Although it takes a long time to evaporate the LP gas, the lower limit of the measured value could be lowered by one digit by adding the LP gas in an excessive amount as compared with the organic solvent, n-hexane in this example, and performing the concentrating operation. . The GC measurement conditions, standard solution, and calibration curve are the same as in Example 5. The measurement results of Examples 1 to 13 above are summarized in Table 2.

[0045]

[Table 2]

Comparative Example 1 Based on JLPGA-S-05T-86, a method for testing LP gas evaporation residue content specified by the Japan LP Gas Association, the residue content in the LP gas of Sample 1 was measured (measurement sample amount is 1000g, test time 6 hours). Residue is measured temperature 7
21 massppm at 5 ° C, 20 massp at 105 ° C
It was pm. Furthermore, the residue at the measurement temperature of 105 ° C.
When added to 200 g of -hexane, the amount of the component that did not dissolve in n-hexane was 0 mg. When the oil content of the n-hexane in which the residue was dissolved was measured by the same method as in Example 1, it was 98.5 mass ppm (g-oil / g-n-hexane), and most of the residue at the measurement temperature of 105 ° C. It was confirmed that the oil content was measured.

Comparative Examples 2 to 11 In the same manner as in Comparative Example 1, the residues in the LP gas of Samples 2 to 11 were measured. The results of measurement of the residue are shown in Table 3 including Comparative Example 1.
Are shown together.

[0048]

[Table 3]

In the comparative example, almost the same analysis result as that of the example was given, but a large amount of sample was required and the measurement time was as long as 6 hours as compared with the example.

[0050]

As described above, according to the present invention,
The residue contained in the liquefied gas can be easily and quickly measured and quantified accurately.

[Brief description of drawings]

FIG. 1 is a conceptual diagram illustrating a residue extraction step of a residue analysis method of the present invention.

FIG. 2 is an example in which a residue in liquefied petroleum gas was extracted with n-hexane and then the extract was analyzed by gas chromatography. The horizontal axis represents the retention time and the vertical axis represents the count of detected peaks.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuhiro Kato 1134-2, Gongendo, Satte City, Saitama Prefecture (72) Inventor Takeshi Kawanobe 1310, Kamitekobayashi, Hanyu City, Saitama Prefecture (72) Inventor, Sho Izumi, Canada Saint Catha Lins Hillside Drive 5-1 (56) Reference JP-A-4-318458 (JP, A) JP-A-57-142558 (JP, A) JP-A-61-161453 (JP, A) JP-A-7-270390 (JP, A) JP-A-3-115857 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01N 30/06 G01N 1/10 G01N 30/88

Claims (2)

(57) [Claims] 1. The liquefied gas is extracted by extracting the residue contained in the liquefied gas into an organic solvent that is a liquid at room temperature and atmospheric pressure, and measuring the residue in the organic solvent by a gas chromatograph method. A method for analyzing a residue in a liquefied gas, which comprises measuring and quantifying the residue of. 2. The method for analyzing a residue in a liquefied gas according to claim 1, wherein the organic solvent is a hydrocarbon having 5 or more and less than 18 carbon atoms.