JP2522346B2 - Method and apparatus for analyzing hydrocarbon mixtures - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for analyzing a hydrocarbon mixture and an apparatus therefor. More specifically, a hydrocarbon mixture such as naphtha and gasoline is used as a saturated aliphatic hydrocarbon, an unsaturated aliphatic hydrocarbon,
The present invention relates to an analytical method for separating and quantifying aromatic hydrocarbons and an apparatus therefor.

(B) Conventional technology To separate and quantify hydrocarbon mixtures such as naphtha and gasoline according to the types of saturated aliphatic hydrocarbons, unsaturated aliphatic hydrocarbons and aromatic hydrocarbons contained in them, JI
The fluorescent indicator method described in S (JIS K-2536) is used. In this method, a sample containing a mixture of the above types is adsorbed on a specified adsorption tube filled with fine silica gel and a small amount of silica gel with a fluorescent dye, and then developed with isopropyl alcohol, based on the difference in adsorption affinity. The boundaries of each type that are separated into layers are quantitatively determined by using an ultraviolet lamp because the fluorescent dyes also selectively exist at the boundaries. Separately from this, gas chromatography (G
Although a method for analyzing hydrocarbons using C) is known, it is difficult to analyze by type of hydrocarbons as described above, since only the boiling point is analyzed in ordinary GC.

(C) Problems to be Solved by the Invention However, in the above-mentioned fluorescent indicator method, the band of silica gel with fluorescent dye that accumulates on the boundary surface is not sharp, which makes it easy to include individual errors by the measurer, and it is reliable or reproducible. The measured value is poor. Further, this method has a problem that the analysis time also becomes long.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a method and apparatus for analyzing a hydrocarbon mixture by type, which does not include the individual error of the measurer and can be measured in a short time.

(D) Means for Solving the Problems Thus, according to the present invention, a hydrocarbon mixture-containing sample is subjected to gas chromatography to obtain a carrier gas stream separated and contained in an aliphatic hydrocarbon and an aromatic hydrocarbon, respectively. This carrier gas stream is divided into two gas streams at a predetermined flow ratio, one of the gas streams is detected with a flame ionization detector for aliphatic hydrocarbons and aromatic hydrocarbons, and the other gas stream is combined with sulfuric acid. After removing the unsaturated aliphatic hydrocarbons and aromatic hydrocarbons through the contact treatment step, the saturated flame hydrocarbons are detected by a flame flame ionization detector, and the detection output of each flame flame ionization detector and the above flow rate are detected. Based on the ratio
There is provided a method for analyzing a hydrocarbon mixture, characterized by separately quantifying saturated aliphatic hydrocarbon, unsaturated aliphatic hydrocarbon and aromatic hydrocarbon in the sample.

In the method of the present invention, a hydrocarbon mixture-containing sample is first subjected to gas chromatography (hereinafter referred to as GC), and an aliphatic hydrocarbon (hereinafter referred to as () hydrocarbon) and aromatic hydrocarbon (hereinafter referred to as “hydrocarbon”) contained in the sample. It is separated into (a) hydrocarbons. Here, as the hydrocarbon mixture-containing sample, a saturated aliphatic hydrocarbon (hereinafter referred to as (s) hydrocarbon), an unsaturated aliphatic hydrocarbon (hereinafter referred to as (o) hydrocarbon) and (a) hydrocarbon are usually mixed. Can be tested. Examples thereof include gasoline and naphtha. In the method of the present invention, cycloalkanes are included in the above (s) hydrocarbon.

The () hydrocarbons (that is, containing (s) and (o) hydrocarbons) and (a) hydrocarbons separated above are contained in the GC carrier gas and are discharged as a gas stream. The flow is split into two flow paths at a predetermined flow rate ratio. Here, the predetermined flow rate ratio means a diversion ratio to the two flow paths. In the one gas stream divided here, () hydrocarbons ((s) and (o) are not distinguished from each other) and (a) hydrocarbons are detected by a hydrogen flame ionization detector (hereinafter referred to as FID), respectively. It One of the gas streams is subjected to contact treatment with sulfuric acid, (o) hydrocarbons and (a) hydrocarbons react with sulfuric acid and are collected in the trap, and the remaining (s) hydrocarbons are detected by FID. The Rukoto.

For the contact treatment with the sulfuric acid, sulfuric acid heated to a predetermined temperature is used. A suitable heating temperature is 80 to 120 ° C. If the temperature is 120 ° C or higher, it is not preferable in view of corrosion of equipment by sulfuric acid vapor, and if the temperature is 80 ° C or lower, removal is incomplete or insufficient, which is not preferable. The heated sulfuric acid is used for the purpose of contacting the gas phase of the components to be removed (that is, the hydrocarbons (o) and (a)) transferred by the carrier gas to sulphate these and convert them into a non-volatile substance. Even if a small amount of inorganic gas is generated due to the contact at this time, it is not detected by the FID, so there is no problem in the following quantification.

As described above, since the two divided gas flows have a predetermined flow rate ratio, this flow rate ratio (or split flow ratio: k)
From the correlation between the peak area (A) of the detected peak and the sample volume, the respective hydrocarbons (s), (o) and (a) will be quantified. For details, reference is made to the description of Examples below.

The present invention also provides, as an apparatus capable of performing the above analysis, a carrier gas supply unit, a sample introduction unit, and a separation column in this order, and is connected to a first FID that detects separated samples sequentially transferred from the separation column. 1 analysis channel, a sulfuric acid-containing trap that is connected between the separation column of the channel and the first FID and that contacts a carrier gas containing a separated sample transferred from the separation column to remove a predetermined substance in the sample It is possible to provide an analyzer for a hydrocarbon mixture, which comprises a second analysis flow path extending to the second FID via the above.

As the separation column used in the apparatus of the present invention, a column having a strong polarity used in ordinary GC is suitable, and for example, TCEP or the like is selected.

As the sulfuric acid-containing trap used in the device of the present invention,
It is used in such a form that the contact with the carrier gas containing the separated sample is sufficiently performed. As one preferable embodiment, a column in which sulfuric acid is impregnated or coated with a carrier or the like is packed and provided in a carrier gas channel. The carrier is used to increase the contact specific surface of sulfuric acid with respect to the gas phase of the removed component, and a diatomaceous earth carrier, for example, cimarite, which is used for a column packing of a general gas chromatograph is suitable. As a method of coating the above-mentioned sulfuric acid on the above carrier in an anhydrous state, water is added to a predetermined amount of carrier and a predetermined amount of sulfuric acid corresponding thereto, mixed and stirred, heated to remove water, and then packed in a column. Examples include aging at a temperature of about 120 ° C. for a predetermined time while flowing a carrier gas. The ratio of the carrier to sulfuric acid is not particularly limited, but it is suitable to use about 40% by weight of sulfuric acid with respect to the carrier. The carrier gas passage of this device may be provided with a purification trap that can collect water vapor and inorganic gas generated in the trap after the trap and prevent corrosion of the FID cell portion.

In the apparatus of the present invention, the carrier gas flow channel is branched downstream of the separation column. With such a flow channel configuration, one feature is that the carrier gas containing the separated component can be split and measured in parallel in each of the split channels, and thus the measurement time can be shortened. Also for this device,
Between the sample introduction part of the first analysis flow path and the separation column or at the connection part of the second analysis flow path to the first analysis flow path, the flow resistance is higher than that of either the first or second analysis flow path. By connecting a small carrier gas discharge conduit, it is possible to adopt a configuration in which the amount of the carrier gas containing the separated component transferred to each of the detectors of the first FID and the second FID can be detected in a small amount.
By connecting the carrier gas discharge conduit, the amount of sample passing through the sulfuric acid-containing trap can be reduced and the life of the trap can be extended. In addition, FI in high concentration range
It is also possible to prevent the saturation phenomenon of D (the linearity of the response is lost). For details, reference is made to the description of Examples below.

(E) Action According to the present invention, the hydrocarbon mixture-containing sample introduced into the carrier gas is first separated into the aliphatic hydrocarbon and the aromatic hydrocarbon by the separation column. The carrier gas contained in this separated state is then diverted at a predetermined flow rate ratio, and the above-mentioned aliphatic hydrocarbon and aromatic hydrocarbon are detected by the hydrogen flame ionization detector on one diverting channel, and the other 1 After the unsaturated aliphatic hydrocarbons and aromatic hydrocarbons are removed by coming into contact with sulfuric acid on the two branch channels, the remaining saturated aliphatic hydrocarbons are detected by a flame ionization detector. Then, based on the detection peaks obtained from the detectors and the predetermined flow rate ratio, the saturated aliphatic hydrocarbon, unsaturated aliphatic hydrocarbon and aromatic hydrocarbon in the sample are quantified respectively.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto.

(F) Embodiment FIG. 1 is a structural explanatory view of an embodiment of a gas chromatograph apparatus for carrying out the method of the present invention. In the figure, a gas chromatograph device (1) includes a sample separation tube connected from a carrier gas supply section (not shown) to a sample injection / vaporization chamber (2) and a separation column (3) in this order to a branch section (p). Road A first branch flow path (b) connected from the branching part (p) to a first hydrogen flame ionization detector (hereinafter FID-1) (4) via a resistance conduit (R ₁ ) and the branching part ( p) through the sulfuric acid-containing trap (5), the purification trap (6) and the resistance conduit (R ₂ ) in this order, and then the second hydrogen flame ionization detector (hereinafter
FID-2) (7) second branch flow path (c),
It mainly comprises a conduit and a carrier gas discharge conduit (d) extending from the branch portion (p) to the split vent via a resistance conduit (r).

TCEP is used for the separation column (3). Further, a column filled with a carrier coated with sulfuric acid is used as the sulfuric acid-containing trap (5). The separation column (3) and the sulfuric acid-containing trap (5) are usually placed in the same column oven. Also, the above FID-1 and FID
-2 is equipped with a recording device (not shown).

The sulfuric acid-containing trap (5) was manufactured by the following method. That is, water is added to and mixed with 10 g of cimarite and 4 g of sulfuric acid, and the mixture is stirred, heated at 80 to 90 ° C to remove water, and then packed in a column and placed in the gas chromatograph flow path as described above, and then the carrier. Aging was performed for 2 hours at a temperature of about 120 ° C. while flowing a gas.

The purification trap (6) is a sulfuric acid-containing trap (5).
The main purpose of this is to absorb the acidic gas and water generated in 1., and it is provided to prevent corrosion of the FID-2 cell connected in the subsequent stage.

The resistance conduits (R ₁ ) and (R ₂ ) are both set to have a resistance larger than that of the resistance conduit (r). Ratio between the first separation channel (b) and the sample separation conduit It is possible to adjust the split ratio between the second split flow path (c) and the second split flow path (c).

Further, another example of the construction of the apparatus for carrying out the method of the present invention is shown in FIG. In the apparatus shown in this figure, the carrier gas discharge line (d) in the apparatus shown in FIG. It is different in that it is provided between the sample injection / vaporization chamber (2) and the separation column (3), and this flow path configuration can also achieve the same purpose as the apparatus of FIG.

Next, using a gas chromatograph (1) having the configuration as shown in FIG. 1, for commercial gasoline, saturated aliphatic (hereinafter (s)) hydrocarbons and unsaturated aliphatic (hereinafter (o)) carbonization contained in the gasoline are carried out. The procedure for quantitative analysis for each type of hydrogen and aromatic (hereinafter (a)) hydrocarbon will be described.

-Analysis conditions are set to the following conditions, for example.

Conditions for gas chromatography Carrier gas: Helium Carrier gas flow rate: 40 ml / min Separation column: TCEP Garam temperature: 80-120 ° C Sulfuric acid-containing trap temperature: 120 ° C Split ratio: (b) / (d) = 1 / 10-1 / 100: (c) / (d) = 1/10 to 1/100 When performing the above quantitative analysis, either before or after this analysis, the diversion ratio between the first diversion channel and the second diversion channel and the FID- It is necessary to determine the correction coefficient indicating the correlation between the peak area and the capacity obtained in 1 and -2.
First, these decisions will be described.

Determination of flow splitting ratio (k) (o) Hydrocarbon-free naphtha as a standard sample (STD)
Then, when measured under the above conditions, for example, the chromatogram shown in the schematic diagram in FIG. 3 (a) is obtained from FID-1, and from FID-2 is shown in the schematic diagram in FIG. 3 (b). It is assumed that a chromatogram is obtained. In this case, the peak (s ₁ ) based on the hydrocarbon (s) and the peak group (a _m ) based on the other hydrocarbon (a) are obtained in FIG. Thus, a peak (s ₂ ) of only (s) hydrocarbons can be obtained. Thus the comparison between the area of the peak (s ₁₎ the area of (A _{s1 STD)} and peak _{(s 2) (A s2 STD} ), the first branch passage and (b) between the second branch passage (c) The diversion ratio (k) can be determined as k = A _{s1 STD} / A _{s2 STD} ....

Correction coefficient from peak area to volume (F _s , F _o , F _a ) (s), (o) and (a) Two standard samples with known volume% of hydrocarbons and different concentrations Was measured under the above-mentioned conditions using, for example, a chromatogram shown in the schematic diagram in FIG. 4 (a) was obtained from FID-1, and from FID-2 in the schematic diagram in FIG. 4 (b). Suppose that a chromatogram is obtained. That is, the same figure (a)
In the separation column (3), an aliphatic (hereinafter ()) hydrocarbon, that is, [(s) + (o)] hydrocarbon, and (a)
A peak pattern separated into hydrocarbons is obtained, and a peak based on only (s) hydrocarbons is obtained from FIG. Therefore, in Figure (a), the peak area for () hydrocarbons is represented by A _{s + o} , the peak area for (a) hydrocarbons is represented by A _a , and the peak area is represented by α _s in Figure (b). For example, first, the relationship of A _o = A _{s + o} −A _s is obtained, and further by using the diversion ratio (k),
The relationship of A _s = α _s × k will be obtained. Therefore
By measuring A _{s + o} , A _a , α _s , A _s , A _o , A _a can be obtained, and the correction coefficient (F _s , F _o , F _a ) can be obtained by associating these with the known capacity. You can decide.

Quantitative Analysis of Samples by Type Commercially available gasoline was analyzed by the apparatus of FIG. 1 under the same conditions as above, and the detection peaks obtained from FID-1 and FID-2 were determined as described above. Using (k) and (F _s , F _o , F _a ), the respective capacities of (s) hydrocarbons, (o) hydrocarbons, and (a) hydrocarbons in gasoline can be determined.

That is, the carrier gas containing the sample separated into the () hydrocarbons (that is, s + o) and the (a) hydrocarbons by the separation column (3) has a first branch flow path (depending on the split ratio of the branch portion (p) ( b), the second branch channel (c) and the split vent. From the carrier gas transferred to the first branch channel (b), FID-1 (4)
A chromatogram consisting of peaks based on (s + o) hydrocarbons and peak groups based on (a) hydrocarbons is obtained.
The carrier gas transferred to the second flow path (c) first comes into contact with heated sulfuric acid in the sulfuric acid-containing trap (5) to remove (o) hydrocarbons and (a) hydrocarbons,
FID-2 (7) gives a chromatogram consisting of peaks due to (s) hydrocarbons remaining in the carrier gas. Therefore, the peak area (A
s ₊ o) and (Aa) and the peak area (α _s ) obtained from FID-2, using the diversion ratio (k) and the correction coefficient (F _s , F _o , F _a ). Thus, the capacity can be calculated for each type of (s) hydrocarbon, (o) hydrocarbon, and (a) hydrocarbon.

(G) Effect of the Invention According to the present invention, the saturated aliphatic hydrocarbon, unsaturated aliphatic hydrocarbon, and aromatic hydrocarbon contained in the hydrocarbon mixture sample can be easily separated and quantified, respectively. In addition, since the measurement is performed in parallel flow channels, the analysis time can be shortened. Furthermore, since the measurement is performed based on the peak detected by the hydrogen flame ionization detector, the analytical method is reliable and reproducible without including individual error unlike the fluorescence method. Further, according to the configuration of the present invention, since the hydrogen flame ionization detector is used, even if the configuration absorbs the inorganic gas generated in the flow channel, the quantitative value is not affected, and more accurate analysis can be performed. . Further, by providing the apparatus of the present invention with a carrier gas discharge pipe, the amount of the sample introduced into the means for removing the predetermined component can be reduced, and the life of the removing means can be extended. In addition, the system can be built with one GC equipped with two FIDs.

[Brief description of drawings]

FIG. 1 is a structural explanatory view of an embodiment of a gas chromatograph apparatus for carrying out the method of the present invention, FIG. 2 is a structural explanatory view of another example of a device for carrying out the method of the present invention, and FIG. A schematic diagram of a chromatogram obtained when naphtha containing no unsaturated aliphatic hydrocarbon is used as a standard sample in the apparatus shown in FIG. 4, and FIG. 4 shows the capacity of each component by type in the apparatus shown in FIG. It is a schematic diagram of the chromatogram obtained using a standard sample. (2) …… Sample injection / vaporization chamber, (3) …… Separation column, (4) …… First hydrogen flame ionization detector, (5) …… Sulfuric acid-containing trap, (6) …… Purification trap, ( 7) ... Second flame ionization detector, (B) ...... first branch passage, (c) ...... second branch passage, (d) ...... carrier gas discharge _{line, (R 1) (R 2} ) (r) ...... resistance line.

Claims (2)

(57) [Claims] 1. A hydrocarbon mixture-containing sample is subjected to gas chromatography to obtain a carrier gas stream separated and contained in aliphatic hydrocarbons and aromatic hydrocarbons, and the carrier gas stream is divided into two gases at a predetermined flow rate ratio. And one of the gas streams is detected with a flame ionization detector to detect aliphatic hydrocarbons and aromatic hydrocarbons, and the other gas stream is subjected to a contact treatment step with sulfuric acid to produce unsaturated aliphatic hydrocarbons. After removing the aromatic hydrocarbons and saturated hydrocarbons, the saturated flame hydrocarbons are detected with a flame ionization detector, and the saturated aliphatic hydrocarbons in the sample are detected based on the detection output of each flame flame ionization detector and the flow rate ratio. A method for analyzing a hydrocarbon mixture, characterized by separating and quantifying hydrocarbons, unsaturated aliphatic hydrocarbons and aromatic hydrocarbons, respectively. 2. A first analysis flow path, which comprises a carrier gas supply section, a sample introduction section and a separation column in this order, and which is connected to a first hydrogen flame ionization detector for detecting separation samples sequentially transferred from the separation column. A sulfuric acid-containing trap that is connected between the separation column in the flow path and the first hydrogen flame ionization detector and that contacts a carrier gas containing the separated sample transferred from the separation column to remove a predetermined substance in the sample And a second analysis flow path extending to the second hydrogen flame ionization detector through the analysis device for a hydrocarbon mixture.