RU2681665C1 - Method of chromatographic analysis of mixture of hydrocarbons and gas chromatography for its implementation - Google Patents

Abstract

FIELD: oil and gas industry.SUBSTANCE: invention relates to gas chromatography and can be used in the analysis of complex mixtures of liquid petroleum products. Method of chromatographic analysis of mixtures of substances and a chromatograph for carrying out this method include the use of two serially connected chromatographic columns, wherein a sample of the analyzed mixture is introduced into the carrier gas stream at the inlet of the first column and after passing light components of the mixture of interest for analysis, the carrier gas stream is transferred to the second column at the inlet of the second column, the first column is blown with a part of the carrier gas stream containing heavy components of the sample from the inlet of the first column to the atmosphere and detect the separated light components of the mixture coming out of the second column, then after the outlet of light components that are of interest for analysis, from the second column to the detector and their registration, the volumetric rate of a part of the carrier gas stream used to blowing the first column is increased 10–50 times compared to the initial velocity of the blowing. carrier for light and heavy components, the light and heavy components are then transferred and separated into an additional third column, then they go into an additional detector and are recorded, after that, the valves located at the inlet are closed and the first and second columns with the sample components contained in them are part of the sample gas stream passing between the first and second columns, the velocity of the carrier gas during blowing is 2–3 times more than during analysis time.EFFECT: technical result is the simultaneous analysis of the light and heavy components of the analyzed sample, as well as the complete purification of all chromatographic columns from the residues of the analyzed sample.2 cl, 8 dwg

Description

The invention relates to gas chromatography and may find application in the analysis of complex mixtures of liquid petroleum products. Basically, the invention is intended to determine the distribution of components over the boiling range of oil fractions, then the analyzed sample, providing a simulated distillation mode, as well as determining the detailed hydrocarbon composition of gasoline fractions, further light sample components mixed with kerosene-gas oil fractions, then heavy sample components. The invention can be applied to the analysis of oil products of secondary processes, such as catalytic cracking, hydrocracking, coking.

A known method of chromatographic analysis of complex mixtures of organic compounds (SU, copyright certificate No. 1744646 A1, 1990) [1], which includes introducing the analyzed mixture into a composite cross-shaped column, separation in the flow of carrier gas in sections of the column filled with sorbents of different polarity, and recording signals at least two detectors, as well as in order to increase the reliability of identification by ensuring the possibility of obtaining multidimensional chromatographic spectra, the analysis is carried out repeatedly with sequential and changing the relationship between the pressures in the sections.

The disadvantage of this method [1] of chromatographic analysis is that it is not possible to purge the chromatographic columns from the remains of the analyzed sample. Also, the method requires complex hardware design, which consists of a cross-shaped column and two dispensers for the analyzed sample.

A chromatograph is also known (SU, copyright certificate No. 1718111 A1, 1990) [2], which contains a serially connected carrier gas preparation unit, a batcher, a flow divider made in the form of a tee with two chokes, and is additionally equipped with a differential flow controller and two detectors connected through pipelines of a single volume with the corresponding outputs of the differential detector, and the differential flow detector has three electrical inputs, the first of which is connected to the output of the differential detectors, the other two with outputs of additional detectors, and the output of the differential flow controller is connected to an adjustable throttle.

A disadvantage of the known device [2] is that the remains of the analyzed sample, which did not come out of the chromatographic columns during the analysis, will affect the accuracy of subsequent analyzes. The light components of the sample pass through the chromatographic column, almost without delay and without separation with the heavy components of the sample, which entails low accuracy in determining the detailed hydrocarbon composition.

The closest in technical essence and the achieved result to the invention is a device and method (RF patent No. 20188821, 1991) [3] chromatographic analysis of mixtures of substances using two series-connected chromatographic columns, in which a sample of the analyzed mixture is introduced into the carrier gas stream at the inlet the first column and after the transition of the light components of the mixture of interest for analysis to the second column, the carrier gas stream is transferred to the inlet of the second column, the first column is purged with a part of the gas flow an analyzer with the heavy components of the sample contained in it from the inlet of the first column into the atmosphere and detect the separated light components of the mixture emerging from the second column, additionally after the light components of interest for analysis exit from the second column into the detector and register their volume velocity of the gas flow the carrier used for backflushing the first column is increased 10-50 times compared with the initial purge rate. Also, with an increase in the flow rate of the carrier gas used for backflushing the first column, the temperature of the first column is increased.

The disadvantage of this method and device [3] is that there is no possibility of simultaneous analysis of the analyzed samples and light components of the analyzed samples. Also, purging does not ensure complete purification of all chromatographic columns from the remains of the analyzed sample.

The aim of the invention is the selection of light components from the sample and their subsequent analysis on a high-performance chromatographic column to more accurately determine the detailed hydrocarbon composition. At the same time, an analysis of the heavy components contained in the analyzed sample is performed by separating them on another chromatographic column to determine the distribution of the components over the boiling range. Purge all chromatographic columns from sample residues.

The invention is illustrated by the drawing, which shows a General view of a gas chromatograph for implementing the method of chromatographic analysis of a mixture of light and heavy components of the sample.

The achieved result is ensured by the fact that the method of chromatographic analysis of mixtures of substances using two chromatographic columns connected in series, in which a sample of the analyzed mixture is introduced into the carrier gas stream at the inlet of the first column and after the transition of light components of the mixture of interest for analysis to the second column, flow carrier gas is transferred to the inlet of the second column, the first column is purged with a part of the carrier gas stream with the heavy sample components contained in it from the inlet of the first column atmosphere and detect the separated light components of the mixture emerging from the second column, then after the light components of interest for analysis exit the second column into the detector and register them, the volumetric velocity of a portion of the carrier gas stream used for backflushing the first column is increased by 10- 50 times compared with the initial purge rate, it differs in that the introduced sample of the analyzed mixture is vaporized in the evaporator and separated on the first column by the carrier gas stream into light and heavy components entents, then light and heavy components pass and separate on an additional third column, then enter an additional detector and register, then close the valves located at the inlet and purge the first and second column with the components of the sample contained in them, a part of the carrier gas flow passing between the first and second column, the speed of the carrier gas during the purge time is 2-3 times greater than during the analysis.

A gas chromatograph comprising an injector connected in series, first and second chromatographic columns and a detector, pipelines for supplying carrier gas to the injector and at the entrance of the second column with controlled shut-off valves installed on them, as well as a pipeline for dumping part of the carrier gas stream into the atmosphere, connected to the inlet of the first column, then the pipeline for discharging part of the carrier gas stream into the atmosphere has two output channels, one of which has a controlled shut-off valve, and the other has a pneumatic shutter otivlenie, characterized in that the evaporator and the first column are located sequentially at the inlet in front of the shutoff valves, and an additional third column is located at the outlet of the shutoff valves and the inlet of the second column, an additional detector is located at the outlet of the additional third column, on the pipeline to discharge part of the carrier gas stream into the atmosphere, which is connected to the inlets of the second chromatographic and additional third chromatographic column, is installed parallel to the shut-off valve and pneumatic resistance.

The invention is illustrated by drawings, where in FIG. 1, 2 and 3, various operating positions of a gas chromatograph concept are presented for implementing a method of chromatographic analysis of a mixture of hydrocarbons.

The proposed gas chromatograph contains a common pipe 12, a flow regulator of the carrier gas 13, an evaporator 1 designed to evaporate the liquid sample introduced into it of the analyzed mixture of substances, the first chromatographic column 3, the second chromatographic column 4, the input of which is connected to the outlet shut-off valves 8 and 9, and the input of an additional third column 15, an additional detector 18 connected to the output of an additional third column, a detector 5 connected to the output of the second column, pipe 2 and pipe 6 for chi carrier gas connected to the inlet of the second column and the third column, and further output of the first column, and a conduit 7 for supplying a carrier gas during purge, connected to the inlet of the first column and second column and outputs the stop valves 8 and 9.

In pipelines 2 and 6 for supplying carrier gas to columns 15 and 4, controlled shut-off valves 8 and 9 are installed, which serve as shut-off elements of the carrier gas flow switch, by which the carrier gas flow is transferred to the input of an additional third column 15 and second column 4. Parallel to the shut-off valves 8 and 9, pneumatic resistors 10 and 11 are connected. The inlet of the pipeline 2 and 6 for supplying the carrier gas is combined into a common pipeline 12, in which the carrier gas flow controller 13, the evaporator 1 and the first chromatographic device are installed column 3. In the pipeline 7 for supplying a carrier gas stream 14 to the purge, a controlled shut-off valve 16 and pneumatic resistance 17 are installed.

In accordance with the proposed method, the described device operates as follows.

At the point in time preceding the start of the analysis, the gas circuit of the chromatograph is in the position shown in FIG. one.

In this position, valve 8 is open, and valves 9 and 16 are closed. The carrier gas stream passes through a common pipe 12 and the flow rate controller 13 enters the internal volume of the evaporator 1 and from it passes through a pipe 2 to an additional third column 15 and a second chromatographic column 4, respectively, enters the detector 18 and 5. A small part of the gas stream -carrier from the output of the regulator 13 through the pipeline 6, bypassing the closed valve 9 by shunting its pneumatic resistance 11, is fed to the input of the chromatographic column 4. This ensures the occurrence of non-blown volume in place connecting the pipeline 6 to the inlet of column 4. The flow rate of the carrier gas through columns 15 and 4 is optimal for chromatographic separation of light and heavy components of the sample.

A sample of the analyzed mixture containing light and heavy components of interest for analysis is introduced using a microsyringe into the evaporator 1, sample vapors picked up by the carrier gas flow entering the evaporator through pipeline 12 are transferred to column 3, where they are preliminarily separated into light and heavy components that pass through the pipe 2 enter the separation of columns 15 and 4 and detection using detectors 18 and 5, respectively. After a certain period of time (selected experimentally), when the light components passed through column 4 by switching valves 8 and 9, the gas circuit of the chromatograph is transferred to the position shown in FIG. 2. In this position, valve 8 is closed and valve 9 is open. Valve 16 continues to remain closed. The entire flow of carrier gas from the regulator 13 through the pipeline 6 is supplied to the input of the column 4, where it is divided into two parts. Most of the flow enters column 4, continuing to move the separated light components along the column, and a smaller part of the flow enters the outlet of column 15, moving the heavy components of the mixture cut off in it.

After exiting from columns 15 and 4 of all analyzed light and heavy components and registering them in detectors 18 and 5, respectively, the gas circuit of the chromatograph is transferred from the position shown in FIG. 2 to the position shown in FIG. 3. In this position, valve 8 remains closed, valve 9 and 16 opens in channel 14 for purging. At the same time, part of the carrier gas stream 14 purges an additional third column 15 and second chromatographic column 4, thereby purging all columns with detectors.

The increase in the flow rate of the carrier gas by 10-50 times, purging the columns 15 and 4, helps to reduce the time of the full analysis cycle. During purging, the signal level at the detector is monitored, when it begins to decline, the gas circuit of the chromatograph is returned to its initial state. After that, the next sample of the analyzed mixture is introduced and analyzed in the described sequence.

The analyzes were carried out on a gas chromatograph brand Chromos GH-1000.

Example 1. Based on the proposed method, a detailed hydrocarbon analysis of the C1-C12 gasoline fraction is carried out and simulated distillation of the C1-C44 kerosene-gas oil fractions included in the catalytic cracking product of vacuum gas oil is simulated.

As the first column 3 for the preliminary light and heavy component, a DB-1 capillary column of 1 m length and an internal diameter of 0.18 mm was used. In the evaporator for working with capillary columns there is a liner that is packed with calcined glass wool to hold mechanical impurities, resins and asphaltenes contained in the sample. The second separation column 4 was a capillary column with a length of 50 m and an inner diameter of 0.25 mm, the thickness of the liquid phase or adsorbent 0.5 μm grade HP-1. An additional third column 15 was a packed column 25 m long and 0.32 mm inner diameter. Using electronic gas flow controllers, the carrier gas speed is set at 250 ml / min. A flame ionization detector (PID) with an air flow rate of 400 ml / min and a hydrogen flow rate of 40 ml / min was used as detectors. The evaporator temperature was 360 ° C, the temperature of detector 5 was set to 250 ° C, the temperature of detector 18 was set to 350 ° C, the temperature of the column thermostat was programmed to an initial temperature of 35 ° C for 30 minutes, then heating 2 ° C / min for 58.50 min to 152 ° C with a 0 min incubation, then at a speed of 30 ° C / min for 4.27 min to 280 ° C with a 30 min incubation, the total analysis time was 123 min. A detailed hydrocarbon analysis analysis time was 75 minutes.

After entering the analyzed sample of the catalytic cracking product with a volume of 5 μl into the evaporator after a certain period of time (under the specified conditions was 3-5 s) by switching valves 8 and 9 of the carrier gas flow switch, it is directed to the inlet of column 4 (Fig. 2). At the same time, part of the carrier gas stream (120-140 ml / min) enters column 4 and transfers the analyzed light components of the mixture to detector 5, and part of the 110-130 ml / min stream is directed to column 15 and transfers the analyzed light and heavy components to detector 18.

After all analyzed components exit column 4 and 15 to detector 5 and 18, respectively, under the indicated conditions, valve 16 opens after 123 minutes and column 3 and 15 are purged with an accelerated flow of 2500 ml / min of carrier gas to release sample components. The purge time of columns 3 and 15 was determined by reducing the signal of the detectors and amounted to 13 minutes After purging is completed, columns 3 and 15 of the gas chromatograph are reset (Fig. 1).

The obtained chromatogram of a detailed hydrocarbon analysis C1-C12 is shown in FIG. 4 and simulated distillation C1-C44 are shown in FIG. 5 oil fractions present in the analyzed sample. The end of boiling of the catalytic cracking product of vacuum gas oil is not higher than C37, the components of the sample reached C37 in 123 minutes, the purge mode in this case lasted 13 minutes, shown in FIG. 6.

Example 2. The proposed method and device was used to determine the detailed hydrocarbon gasoline fraction C1-C12 and simulated distillation C1-C44 of oil components boiling up to 560 ° C. The analysis was carried out on the device described in example 1.

After entering the analyzed sample of the catalytic cracking product with a volume of 5 μl into the evaporator after a certain period of time (under the specified conditions was 3-5 s) by switching valves 8 and 9 of the carrier gas flow switch, it is directed to the inlet of column 4 (Fig. 2). At the same time, part of the carrier gas stream (120-140 ml / min) enters column 4 and transfers the analyzed light components of the mixture to detector 5, and part of the 110-130 ml / min stream is directed to column 15 and transfers the analyzed light and heavy components to detector 18.

After all analyzed components exit column 4 and 15 to detector 5 and 18, respectively, under the indicated conditions, valve 16 opens 32 minutes later and columns 3 and 15 are purged with an accelerated flow of 500 ml / min of carrier gas to release sample components. The purge time of columns 3 and 15 was determined by the decrease in the signal of the detectors and amounted to 6 minutes After purging is completed, columns 3 and 15 of the gas chromatograph are reset (Fig. 1).

The obtained chromatogram of a detailed hydrocarbon analysis C1-C12 is shown in FIG. 7 and simulated distillation C1-C44 are shown in FIG. 8 fractions of oil present in the analyzed sample. The components boiling up to C36 (495 ° C) exited in 32 minutes, then the components boiling above C36 (495 ° C) in the purge mode in this case went out in 6 minutes. Components C37 through C44 were not identified, therefore, they are not taken into account in the calculations.

Claims (2)

1. The method of chromatographic analysis of mixtures of substances using two series-connected chromatographic columns, in which a sample of the analyzed mixture is introduced into the carrier gas stream at the inlet of the first column and after the transition of light components of the mixture that are of interest for analysis, the carrier gas stream is transferred to the second column at the inlet of the second column, the first column is purged with a portion of the carrier gas stream with the heavy sample components contained in it from the inlet of the first column into the atmosphere and the second the first column, the separated light components of the mixture, then after the light components of interest for analysis exit the second column into the detector and register them, the volumetric velocity of a portion of the carrier gas stream used to purge the first column is increased 10–50 times compared to the initial purge rate, characterized in that the introduced sample of the analyzed mixture is vaporized in the evaporator and is separated on the first column by the flow of carrier gas into light and heavy components, then the light and heavy components pass and are separated on an additional third column, then they enter an additional detector and are registered, then the valves located at the inlet are closed and the first and second columns are blown with the components of the sample contained in them, part of the carrier gas flow passing between the first and second columns, carrier gas during purging is 2-3 times more than during analysis. 2. A gas chromatograph comprising an injector connected in series, first and second chromatographic columns and a detector, pipelines for supplying carrier gas to the injector and at the inlet of the second column with controlled shut-off valves installed on them, as well as a pipeline for dumping part of the carrier gas stream into the atmosphere connected to the inlet of the first column, then the pipeline for discharging part of the carrier gas stream into the atmosphere has two outlet channels, one of which has a controlled shut-off valve, and the other has a pneumatic resistance, characterized in that the evaporator and the first column are located sequentially at the inlet in front of the shut-off valves, and an additional third column is located at the outlet of the shut-off valves and the inlet of the second column, an additional detector is located at the outlet of the additional third column, on the pipeline to discharge part of the carrier gas stream in the atmosphere, which is connected to the inlets of the second chromatographic and additional third chromatographic column, a stopcock and pneumatic resistance are installed in parallel.

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