DE1673233A1 - Method and device for the gas chromatographic separation of hydrocarbons - Google Patents

Description

VEB Leuna-Werke »Walter Ulbricht" Leuna, ²³ · ^{8> 66}

Patent department. S / DC.Hi / Ry

L.P. .672

Method and device for the gas chromatographic separation of hydrocarbons

The invention relates to a method and an apparatus for gas chromatographic group analysis of hydrocarbons on molecular sieves.

It is known to detect hydrocarbons by means of partition gas chromatography due to the different boiling points and the different polar behavior of the Hydrocarbons in special distribution liquids in the Separate carrier gas flow.

It is also known to remove non-volatile compounds from the chromatography column by backwashing after the more volatile compounds have been separated off by gas chromatography. For this purpose, the gas chromatograph is equipped with a secondary column in addition to the main column. The gas path of the secondary column can be reversed independently of the main column. - ^ ·

It is also known for adsorption gas chromatography of gases and low-boiling hydrocarbons Apply molecular sieves.

It is also known to use normal paraffins of branched, naphthenic and aromatic hydrocarbons prior to gas chromatographic analysis by molecular sieves to be separated from type 5 A. Here the normal paraffins are completely adsorbed by the molecular sieve »while the isoparaffins, naphthenes and aromatics pass the sieve and then more or more on an impregnated carrier material are less well separated. The n-paraffin content is determined by subtractive gas chromatography.

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ORlGfNAL INSPECTED

As the adsorption capacity of the molecular sieves gradually, exhausted, the sieves have to be subjected to desorption after a more or less long running time. This is done, for example, by periodically heating the molecular sieves or by desorption with lower paraffins. Further disadvantages are the complexity of the apparatus Methods and their time requirement, which is 15 to 30 minutes per analysis.

The purpose of the invention is to avoid these disadvantages.

The object was therefore to provide a method for gas chromatographic Group analysis of hydrocarbons on molecular sieves to develop a separation of Hydrocarbon molecules made possible within a few minutes without subsequent desorption of the molecular sieve.

According to the invention, this object is achieved by separating the hydrocarbon groups by means of Molecular sieving takes place at temperatures that affect the adsorptive capacity reduce the molecular sieve so far that the molecules retained in the pores of the molecular sieve are desorbed from the carrier gas during the analysis, and that the entire gas mixture immediately after the registration of the molecules not retained by a Switching of the carrier gas path in the opposite direction from the molecular sieve column is rinsed.

The temperatures are determined empirically because they depend on the composition and the boiling range the sample to be analyzed.

A further object was to create a device in which the method according to the invention is simple Way can be done.

According to the invention, this object is achieved by a device solved, in which the thermostat room except for a detector with a heatable to 300 to 550 ° 0 Molecular sieve column, and at the detector,

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Dosing device and Molefcularaiebsäule with suitably arranged and gas path switches that can be controlled according to a program that can be determined in advance are coupled.

The principle of the method and the device will be explained in more detail using the flow diagram.

The process takes place in two phases.

Phase 1

The sample is fed into the dosing device by means of an automatic autosampler or a suitable dosing syringe 1 and the cooling device 2 in the evaporator chamber injected. The vaporized sample flows together with the carrier gas, which flows through line 4 via the gas path switch 5 is guided to the metering device 1, by means of the gas path switch 6 via the molecular sieve column 7. This can be regulated separately from the thermostat room Heater 8 surround. The gas then flows through the detector 9, which is equipped with a recording device (recorder) is coupled, and is finally passed into the exhaust line 12 by means of the gas path switch 11, - With the help the automatic control 13> which is connected to the gas path switches 5j 6 and 11 and the metering device is, the gas path is switched and phase 2 is initiated.

Phase 2

The carrier gas now flows, coming from the line 4, via the gas path switch 5 and 11 and the detector 9 to the molecular sieve column 7 and flushes the already registered hydrocarbons together with the unregistered ones Hydrocarbons via the gas path switch 6 into the Exhaust pipe 12.

After a preselected time, the gas path is switched by means of the automatic control 13 and thus the Phase 1 initiated. * - '. ,

The method and the device according to the invention allow a quantitative determination of hydrocarbon groups in hydrocarbon mixtures η of all settlements,

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as long as these evaporate sufficiently at normal pressure leave, with all molecules not retained forming a uniform narrow peak, the height of which corresponds to percentage of the hydrocarbon group present in the Mixture is proportional.

Furthermore, they can be purified by gas chromatography Hydrocarbons still determine compounds that are normally associated with the main peak in gas chromatography coincide. Since these compounds migrate as a narrow peak with the carrier gas front, the ventilation method is very sensitive.

In addition, the invention allows a very quick registration of the 'analysis result, since the registration Coming compounds leave the separation column practically with the carrier gas front just a few seconds after the sample has been dispensed. The next dose of sample can be made as required and substance mixture take place about 0.5 to 3 minutes after the previous dosage.

Furthermore, the components to be determined are without an additional device when the paper feed is low registered on the recorder in clear bar graph notation. After calibration of the recorder paper, the analysis result can be read from the line length on the recorder will·

The analysis device developed according to the invention is particularly suitable for automatic process control in distillation plants, n-paraffin extraction plants, hydro splitting plants and others, whereby an almost continuous control is guaranteed.

Eventually, the life of the molecular sieves significantly increased.

Example 1:

5 / ti each of a mixture of 2,2,4-trimethylpentane, 3-ethylheptane, ethylcyclohexane, 2-benzylbutane, n-hexane and n-Nonane were dosed into the evaporation chamber at one-minute intervals using an automatic autosampler

1 09818/0469 '

The hydrocarbon gas mixture was passed through a molecular sieve column of the ^{5 A type, which had been heated to 400 ° C., by means of hydrogen.} The detector had a temperature of 140 ^° C. The gas mixture contained 20, 40, 90 or 95 % η-paraffins. These analysis results were already available 10 seconds after dosing.

Example 2:

5 Al each of a hydrocracking gasoline, which consisted of η-paraffins, olefins, aromatics, isoparaffins and eaphthens, were injected into the vaporizer chamber at one-minute intervals by means of an automatic autosampler. The hydrocarbon gas mixture was passed by means of hydrogen over a molecular sieve of the type 5 A, which had been heated to 400 ⁰ G. The detector had a temperature of 140 ⁰ O, The analysis results with 30% n ~ paraffins was "η already jevjsils 10 lake after dosing

Example 3i

Per 10 ^ 1 of a paraffin concentrate having a boiling range of 320 ⁰ C 230.bis were dosed at intervals of two minutes by means of an automatic sample injector into the evaporator chamber. The hydrocarbon gas mixture was passed through a 5A molecular sieve column together with hydrogen. The detector had a temperature of 220 ⁰ O.

The analysis results with 90 or 96 % n-paraffinia were already available 10 seconds after dosing,

Example 4: ■

10 / l each of a product enriched with paraffins with a boiling range from 300 to 410 ⁰ O, which consisted of η-paraffins, isoparaffins, naphthenes, olefins and aromatics, were dosed into the evaporation chamber at two-minute intervals by means of an automatic sampler. The gas mixture was passed through a molecular sieve column of the ^{3 A type, which had been heated to 500 0 O, by means of hydrogen.} The detector had a temperature of 300 ⁰ O. The analysis results with 37% n-Paraffineri U ^ e * ^ e ^ aiLs 15 aec after dosing

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Example 5:

To test the purity of "pure" n-paraffins, 10 and 1 n-octane were injected into the vaporizer chamber using a DOA syringe. The vaporized n-Oetan became! by means of hydrogen via a molecular sieve column of the type. 5 A, which ^{had been heated to 400 0} G, passed. The detector was a katharometer of the Oow Mao type, which worked with sensitivity level 2 and a cell current of 200 mA * and had a temperature of 140.degree.

After every 10 seconds, a 11.4 cm long line was recorded by the recorder as the analytical result, which corresponded to a total contamination in the n-octane of 0.27%. A calibration was carried out by adding 0.13 % each of isocontane and metering this mixture, and it was found that in this way it was still possible to determine 0.01 % of total impurities without difficulty.

Example 6;

Depending iqU 1 of a Cg-Kchlenwasserstoffgeiaisehes were dosed at intervals of 90 se ζ by a automatis3hen Probengeberβ in the evaporator chamber, "The hydrocarbon was hydrogen gas mixture is passed by means of hydrogen over a Mclekularsiebßäule type 10 X, which had been heated to 470 ^C G. The detector had a temperature of 220 ^° C. '

The analysis results with 99 or 75 % aromatics were available after every 8 seconds.

All samples could be dosed as often as desired without affecting the accuracy of the analysis or the adsorption capacity the molecular sieve column subsided. Desorption of the molecular weight is not necessary.

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Claims (2)

672. -7- 1873233 claims: 1. A method for gas chromatographic group analysis of hydrocarbons on molecular sieves, characterized in that the hydrocarbon groups are separated by means of Mclekularsiefcen at temperatures which reduced the absorption capacity of the molecular sieves to such an extent that ate in the pores of the molecular sieves .retained molecules during the analysis of the carrier gas deserted, since the entire gas mixture is flushed immediately after the registration of the molecules not retained by switching the carrier gas path in the opposite direction from the molecular sieve column, 2. Apparatus for carrying out the method according to claim 1, characterized in that the Thermostatenrauin is equipped with a detector and a ^{heatable to 300 to 550 0} C molecular sieve column, and that the detector, Molelcularsiebsäule and dosing device with suitably arranged and according to a previously determinable program controllable gas path switches are coupled. 10981 8/0469 Empty page