JP2595071B2 - Gas chromatograph - Google Patents

Description

The present invention relates to a gas chromatograph. More particularly, the present invention relates to a gas chromatograph suitable for continuous separation and analysis of lower hydrocarbons, and particularly useful as an automatic analyzer in the fields of fuel chemistry and catalytic chemistry.

(B) Conventional technology In the fields of fuel chemistry and catalytic chemistry, hydrocarbon
Lower hydrocarbons separation analysis of C ₁ -C ₅ is quality control is important in the evaluation of catalyst performance.

Conventionally, such lower hydrocarbons have been separated and analyzed by gas chromatography. In particular, a so-called packed column [PC (Packed column)] in which a stationary phase packing material is packed is used as a separation column. A gas chromatograph in which a flow path is formed by combining ordinary precut columns and the like in series is generally used. In a gas chromatograph using such a packed column, the separation and analysis of C _{1 to} C ₅ lower hydrocarbons is about
Performed in a 50 minute analysis cycle.

(C) Problems to be Solved by the Invention However, in such a conventional method, the analysis cycle is long as described above, and it is difficult to perform a quick analysis. For example, when the analysis cycle is shortened, the separability is reduced, so that qualitative and quantitative problems are significantly disadvantageous.

Therefore, instead of the packed column, a porous open tube column (PLOT (Porous layer open tubular) column) that is excellent in separation of lower hydrocarbons is used.
By using as a separation column, the analysis cycle can be shortened.

However, another problem arises when analyzing hydrocarbons using such an open tubular column. In other words, not only the lower hydrocarbons mentioned above but also high-boiling hydrocarbons often coexist with other hydrocarbons in the hydrocarbon sample to be analyzed. It is always the case. When such a sample is separated and analyzed using the above-mentioned open tubular column, the coexisting high-boiling components are adsorbed to the column and cause deterioration of the column in a short time, thereby continuously analyzing lower hydrocarbons. Difficult to do,
Nor could it be adapted to the automation of the device. Also, the washing could not be carried out as easily as in a packed column. In addition, since the open tubular column has a small separation capacity, there are many restrictions on the concentration and amount of a sample to be analyzed, and there is a disadvantage that preparation of the sample is troublesome.

The present invention has been made under such circumstances, and it is an object of the present invention to provide a gas chromatograph which can rapidly separate and analyze lower hydrocarbons and is suitable for continuous analysis and automatic analysis.

(D) Means for Solving the Problems Thus, according to the present invention, a carrier gas supply unit, a sample introduction unit, and a micro-packed column are provided in this order, and the sample introduction unit and the micro-packed column are connected to each other. A first gas splitter is interposed in a flow path formed between the first gas splitter and a separation flow path connected to a gas discharge path of the first gas splitter. A first gas separation flow path in which a micro-packed type column is configured such that a carrier gas can flow backward by switching the flow path; and a gas introduction path switchably connected to the first gas separation flow path downstream of the packed type column. Having a flow path connected from the gas introduction path to a gas chromatograph detector through a porous open tubular type capillary column,
A second gas splitter is interposed between the gas introduction path and the porous open tubular capillary column, and a variable flow resistance is provided in a separation flow path connected to a gas discharge path of the second gas splitter. A gas chromatograph comprising: a second separation channel to which a pipe is connected is provided.

As the packed column in the first gas separation channel of the present invention, a partitioning filler (for example, silica beads, glass beads, porous polymer beads, or the like) serving as a stationary phase is used as a carrier, and a liquid phase is added thereto as necessary. (A coated or surface-treated one) is packed in a column container or tube, and a so-called micro-packed column is preferably used. Further, the gas splitter provided in the first gas separation channel can be configured by branch-connecting a flow resistance pipe extending to the gas discharge channel to the separation channel. The flow resistance of the resistance tube can be set by reducing the size of the conduit or the like, and it is usually appropriate to adjust the ratio between the supply flow rate and the discharge flow rate to be 1:10 to 1: 100.

On the other hand, as the porous open tubular column in the second gas separation channel, a tube (in which the liquid phase is porous if necessary) in which a porous layer such as porous silica, porous glass, and porous alumina is coated on the inner surface is used. (Which may be coated on the surface of the porous layer), of which a fused silica capillary tube is preferred. Also, the gas splitter provided in the second gas separation channel can be configured by branch-connecting a flow resistance tube as described above. However, the ratio between supply flow rate and discharge flow rate is 1: 1 to 1:10
It is suitable to adjust so that In addition, as a gas chromatograph detector, those known in the art can be applied, but it is preferable to use FID. As the carrier gas, various types used for hydrocarbon separation analysis can be applied.

As the sample introduction means in the first gas separation channel of the present invention, a device configured to introduce a sample by switching channels, that is, a loop type device is suitable. Switching of the flow path in introducing such a sample can be performed using a multi-port switching valve such as a six-way valve or an eight-way valve. In this case, the other ports of the multi-port switching valve are connected to the first gas separation flow path. It is preferable in terms of simplification of the apparatus configuration that the switching operation can be performed in conjunction with the switching of the connection between the and the second gas separation channel.

In a state where the first gas separation channel and the second gas separation channel are not connected, it is suitable that both channels are configured such that a carrier gas flows therethrough. It is preferable that the separation flow path is configured such that the carrier gas flows in the reverse direction when not connected, that is, in the direction from the separation column to the gas splitter. Such a flow path configuration can be simply configured by using the above-described multi-port switching valve.

(E) Action The hydrocarbon-containing sample injected into the first gas separation channel by the sample introducing means is introduced into the packed column only in a required amount by the splitter, where the high-boiling components are strongly retained, and the low-boiling components are strongly retained. In particular, C _{1 to} C ₅ hydrocarbons are extruded from the column in a short time because of relatively low retention. On this occasion,
The required amount of low-boiling components is introduced into the porous open tubular column via the splitter by connecting the second gas separation flow path, where each low-boiling component is separated and detected by the detector. Becomes Then, after the low-boiling component is introduced into the second gas separation channel, the first gas separation channel and the second gas separation channel are disconnected from each other, so that the low-boiling component stays in the packed column. The introduction of the high boiling point component into the second gas separation channel can be prevented, and the deterioration of the porous open tubular column can be prevented.

Furthermore, since high boiling components retained in the packed column can be removed to the outside of the system by introducing a carrier gas, the removal operation is performed in parallel with the separation and analysis in the second gas separation flow path, so that each analysis can be performed. The cycle can be shortened.

(F) Embodiment 1 shown in FIG. 1 is a structural explanatory view showing a basic state of a gas chromatograph according to an embodiment of the present invention.

As shown in the figure, the gas chromatograph 1 includes, from the carrier gas supply unit 2, pipes 4 and 5, a sample loop 7 (0.2 ml) provided with a sample measuring pipe 6 serving as a sample introduction means, a pipe 8, a gas splitter. 9. A first gas separation flow path in which the packed column 10 and the pipeline 12 are connected in this order is connected via a 10-port switching valve 19. Further, a second gas separation flow path connecting a gas introduction path 20, a gas splitter 21, a porous open tubular column 23, and an FID detector 24 is further provided in a pipe 12 downstream of the first gas separation flow path. It is switchably connected via a 10-port switching valve 19.

Each of the gas splitters 9 and 21 is formed of a three-way branch pipe. Each of the gas splitters 9 and 21 is connected to a flow resistance pipe 11, 22 whose flow rate can be controlled by a valve so that a predetermined amount of gas can be exhausted.

Further, the 10-port switching valve 19 is provided with a sample gas supply pipe composed of the carrier gas supply unit 2, the sample injector 3, the pipe 18 and the pipe 17, and by switching the switching valve 19, the sample is supplied. The sample gas injected from the injector 3 is configured to be introduced into the sample loop 7.

Further, in the drawing, the pipes 14 and 15 are pipes which can be configured to be able to switch a carrier gas supply path for performing initial setting, washing, etc. of each column. It is separated from the two-gas separation channel. Reference numerals 13 and 16 denote flow resistance columns for preventing fluctuations in the flow rate of the carrier gas at the time of switching.

In this example, as the packed column 10,
A column was used in which FFAP (10%) and 0V-101 (10%) were applied to Chromosolve W and filled with a usual partitioning agent in a column tube having an inner diameter of 1.0 mm and a length of 0.6 m. The porous open tubular column 23 has an inner diameter of 0.3 mm and a length of 5 mm.
A column in which alumina was coated on the inner surface of a 0-m fused silica capillary tube was used. Although not shown, the gas chromatograph 1 has a separation temperature of 50% for each column.
Two constant temperature baths are additionally provided so that the temperature is 50 ° C and 50 to 150 ° C.

A procedure for separating and analyzing lower hydrocarbons in a general hydrocarbon sample using the gas chromatograph 1 will be described. The sequence is controlled by a microcomputer controller (not shown).

First, an initial setting state of the gas chromatograph 1 before the analysis is shown in FIG. As shown in this figure, the 10-port switching valve 19 is set at a position where each port ab, cd, ef, gh, ij is connected. In this state, the carrier gas is discharged through the pipe 5 → the pipe 12 → the column 10 → the splitter 9 → the pipe 8 → the pipe 15 and also the pipe 14 → the gas introduction path 20 → the splitter 21 → the column 23 → FID detection. The gas is discharged through the vessel 24, whereby the initial setting state of the first gas separation channel and the second gas separation channel is secured.

In this state, the sample gas (hydrocarbon-containing sample) is injected from the sample injector 3 to introduce the sample gas into the sample loop 7, and the inside of the measuring tube 6 is replaced with the sample gas. Here, by switching the 10-port switching valve 19, introduction of the sample gas into the first gas separation channel and connection of the first gas separation channel and the second gas separation channel are performed as shown in FIG.

Thereby, the sample gas in the sample loop 7 is transferred to the splitter 9 by the carrier gas, and a part of the sample gas is supplied to the column 10 and subjected to the first-stage separation.
Here, as described above, the low-boiling components, particularly the C _{1 to} C ₅ components, are transferred to the gas introduction path 20 through the pipe 12 in a short time.

At this time, the switching valve 19 is switched to the state shown in FIG. 2 so that the first gas separation flow path and the second gas separation flow path are separated, and the second gas separation of the high boiling point component in the column 10 is performed. Although introduction into the flow path is prevented, the low-boiling components brought into the gas introduction path 20 are transferred to the splitter 21 by the carrier gas, and a part thereof is introduced into the column 23, where the separation property is high. Separation is performed, and each separated peak is
24 will be detected. On the other hand, by the switching, the carrier gas is supplied from the opposite direction to the column 10 in parallel with the above detection, so that the high boiling components retained in the column (or the pipe) are discharged out of the system through the pipes 8 and 15. Will be done. Therefore, at the end of the analysis, the first gas separation channel is ready for the next analysis.

In such a gas chromatograph, since low-boiling components are separated by the porous open tubular column 23, separation with high separability can be performed and analysis time can be shortened. And high boiling point column
Since the introduction into column 23 can be easily prevented, the characteristics of this column can be stabilized for a long time, and continuous analysis and automated analysis can be performed. Moreover, as described above, the first
Since the initial setting of the gas separation channel is also performed in parallel with the separation analysis, the analysis cycle can be further shortened.

The gas using a chromatographic 1 were selective separation analysis of the low-boiling components of fuel gas samples containing 15 different hydrocarbons and no more high-boiling hydrocarbons of C ₁ -C ₄ as a target. The carrier gas used was helium, the flow rate of the carrier gas was 12 ml / min in the pipe 4, and the splitters 9 and 2 were used.
The split ratio of 1 was 1:10 and 1: 1 respectively. The temperature of the column 23 was set to 50 to 130 ° C.

The result is shown in FIG. In the figure, is methane, is ethane, is ethylene, is propane, is propylene,
Is isobutane, is n-butane, is trans-2-
Butene, is 1-butene, is isobutene, is cis-
2-butene, is propylene, is iso-pentane,
Represents a peak of 1,3-butadiene, and represents a peak of n-pentane.

Thus, for each of C ₁ -C ₅ lower hydrocarbons, 10
It can be seen that a clear peak is obtained within a short time of less than one minute. This is equivalent to 1/5 of the analysis time when a conventional packed column is used as a separation column, and it can be confirmed that the analysis time and the analysis cycle are significantly reduced.

(G) Effects of the Invention According to the gas chromatograph of the present invention, separation and analysis of lower hydrocarbons can be performed more quickly and accurately than in the past, and long-term continuous analysis can be performed.

Therefore, the gas chromatograph of the present invention is extremely useful as an apparatus for analyzing lower hydrocarbons in the fields of fuel chemistry and catalytic chemistry, and is also convenient for automation.

[Brief description of the drawings]

FIG. 1 is a structural explanatory view showing a gas chromatograph of one embodiment of the present invention, FIG. 2 is a structural explanatory view showing a flow path switching state, and FIG. 3 is a lower hydrocarbon using the gas chromatograph of the present invention. FIG. 7 is a graph illustrating an analysis result of a class. 1 ... gas chromatograph, 2 ... carrier gas supply unit, 4,5,8,12,14,15,17,18 ... line, 3 ... sample injector, 6 ... sample measuring tube, 7 ... … Sample loop, 9,21… Gas splitter, 10… Packed column, 11,22… Flow resistance tube, 13,16… Flow resistance column, 19… 10-port switching valve, 20… Gas introduction , 23 …… porous open tubular column, 24 …… FID detector.

Claims (1)

(57) [Claims] 1. A flow path which can connect a carrier gas supply section, a sample introduction means and a micro-packed column in this order, and a first flow path formed between the sample introduction means and the micro-packed column. A gas splitter is interposed, a variable flow resistance tube is connected to a separation flow path connected to a gas discharge path of the first gas splitter, and a carrier gas is supplied to the micro-packed type column by switching the flow path. A first gas separation flow path configured to be capable of backflow; and a gas introduction path switchably connected downstream of the packed column of the first gas separation flow path. A second gas is constituted by a flow path connected to a gas chromatograph detector via a tubular type capillary column, and is provided between the gas introduction path and the porous open tubular type capillary column. Splitter is interposed, the second second separating channel and a gas chromatograph consisting comprises a flow path resistance tube of variable flow rate to the separation channel is connected leading to the gas discharge path of the gas splitter.