RU2677827C1 - Method of gas chromatographic analysis of inorganic gases and hydrocarbons and device for its implementation - Google Patents

Abstract

FIELD: chemistry.SUBSTANCE: invention relates to analytical chemistry, specifically to gas chromatography, and can be used to analyze gas mixtures in various industries: chemical, oil, gas, petrochemical, and ecology. Claimed method for gas chromatography analysis of inorganic gases and hydrocarbons consists in simultaneously feeding inorganic gases and hydrocarbons with three metering valves to two, successively connected to the precolumns, packed columns and one capillary column, in the separation of inorganic gases on packed columns and hydrocarbons on a capillary column, as well as in the subsequent determination of the content of inorganic gases by a thermal conductivity detector and a hydrocarbon content by a flame ionization detector. Moreover, in the columns sorbents are used, namely, molecular sieve in one packed column, porous polymer in another packed column, and functionalized poly(1-trimethylsilyl-1-propyne) in a capillary column, which allows for the analysis of inorganic gases and hydrocarbons under isothermal conditions. Claimed device for gas chromatography analysis of inorganic gases and hydrocarbons includes a source of carrier gas, two metering valves connected in series with the pre-columns and packed columns, the third metering valve connected in series with the capillary column, thermal conductivity detector, flame ionization detector. Moreover, packed columns, successively blocking by pressure, are located on one arm of the detector by thermal conductivity.EFFECT: creation of a method and device for gas chromatographic analysis of the content of impurities, such as inorganic gases and hydrocarbons, in the process of dehydrogenation of isobutane, in isothermal conditions of chromatography, and reducing the time of analysis.2 cl, 4 dwg, 1 tbl

Description

The invention relates to analytical chemistry, specifically to gas chromatography and can be used to analyze gas mixtures in various industries: chemical, petroleum, gas, petrochemical, ecology.

In modern gas chromatography, various methods of gas chromatographic analysis of the content of impurities in gas samples are used, implemented using various chromatographs. For example, a method for chromatographic analysis of C ₁ -C ₆ hydrocarbons contained in oil by gas-liquid chromatography followed by their registration by a thermal conductivity detector, which consists in separating C ₁ -C ₅ hydrocarbons into alumina modified with paraffin oil and C ₂ -C ₆ on spherochrome modified with dibutyl phthalate [GOST 13379 - 82. Oil. Determination of C ₁ -C ₆ hydrocarbons by gas chromatography].

Another method [GOST 52714-2007. Gasolines Automotive. Determination of individual and group hydrocarbon composition by capillary gas chromatography] is used to determine the individual composition of hydrocarbons (up to C ₉ inclusive) and to determine individual hydrocarbons (up to C ₁₂ inclusive) and groups of n-paraffinic, isoparaffinic, aromatic, naphthenic, olefinic hydrocarbons and oxygenates .

The disadvantages of these methods are that inorganic gases and methane are not separated, the total time of direct analysis and reverse purge is 25-30 minutes.

Three more methods are known [GOST 31371.3 - 2008 (ISO 6974 - 6: 2002) Natural gas. Determination of composition by gas chromatography with an estimate of uncertainty. Part 3. Determination of hydrogen, helium, oxygen, nitrogen, carbon dioxide and C ₁ -C ₈ hydrocarbons using two packed columns]; [GOST 31371.4 - 2008 (ISO 6974 - 6: 2002) Natural gas. Determination of composition by gas chromatography with an estimate of uncertainty. Part 4. Determination of nitrogen, carbon dioxide and C ₁ -C ₅ and C ₆ hydrocarbons in the laboratory and using the built-in measuring system using two columns] and [GOST 31371.5 - 2008 (ISO 6974 - 6: 2002) Natural gas. Determination of composition by gas chromatography with an estimate of uncertainty. Part 5. Determination of nitrogen, carbon dioxide and C ₁ -C ₅ and C ₆ hydrocarbons in the laboratory and under continuous monitoring using three columns].

The disadvantages of these methods are that the sample is introduced into columns sequentially and for the separation of inorganic gases an additional cooling device for the column thermostat is required [GOST 31371.3 - 2008 (ISO 6974 - 6: 2002) Natural gas. Determination of composition by gas chromatography with an estimate of uncertainty. Part 3. Determination of hydrogen, helium, oxygen, nitrogen, carbon dioxide and C ₁ -C ₈ hydrocarbons using two packed columns]. Inorganic gases and methane are not separated, the total time of direct analysis and reverse purge is 25-30 minutes.

There is a method of gas chromatographic determination of sulfur-containing compounds in hydrocarbon products and a device for its implementation [RU 2426112, G01N 30/02, 08/10/2011]. The method of gas chromatographic determination of sulfur-containing compounds in hydrocarbon products consists in simultaneously supplying the analyzed product under pressure to the first path of the chromatograph to determine hydrogen sulfide at a concentration of more than 0.1% of the mass, and also to the second path of the chromatograph to determine hydrogen sulfide at a concentration of less than 0.1% mass The first tract includes piston-type metering valves installed in a heated thermostat and packed columns filled with a polymer adsorbent — a pre-column 0.1–1.5 m long and a main column 0.5–5 m long, as well as a thermal conductivity detector . The second path includes a piston-type metering tap in series, capillary columns installed in a heated thermostat — a pre-column 0.1–1.5 m long and a main column 15–50 m long, whose inner diameter is 0.23–0.32 mm, as well as a sulfur selective detector. Dosing valves of the first and second paths are arranged sequentially in the direction of the sample supply line.

The disadvantage is that inorganic gases (oxygen, nitrogen, carbon monoxide) are not separated by this method. Analysis of sulfur-containing hydrocarbon products proceeds in the temperature programming mode.

The closest technical solution to the invention according to the set of essential features is the method of simultaneous dosing and subsequent joint analysis on three capillary columns with a fixed amount of three different gas phases in volume [GOST 31371.6 - 2008 (ISO 6974 - 6: 2002) Natural gas. Determination of composition by gas chromatography with an estimate of uncertainty. Part 6. Determination of hydrogen, helium, oxygen, nitrogen, carbon dioxide and C ₁ -C ₈ hydrocarbons using three capillary columns]. To implement the method, it is necessary to use three columns installed in two gas chromatographs. To determine hydrogen, helium, oxygen, nitrogen, carbon dioxide and C ₁ -C ₈ hydrocarbons, gas chromatography using three capillary columns is used. Columns can be placed in one chromatograph with two thermostats or in two separate chromatographs. The temperature in both thermostats of the columns of one chromatograph should be independently controlled. Use a preliminary PoraPLOT U fused silica capillary column with a porous sorbent Porapak U deposited on the inner surface to separate air, CO ₂ , C ₂ H ₂ , C ₂ H ₄ , C ₂ H ₆ and C ₃ H ₈ , a capillary PLOT column of fused silica with a molecular sieve for the separation of He, H ₂ , O ₂ , N ₂ , CH ₄ and CO; and a capillary WCOT column of fused silica with a non-polar phase (methyl silicone) for the separation of C ₃ -C ₈ hydrocarbons.

The disadvantage of this method is the use of two thermostats or two chromatographs to accommodate three capillary columns, as well as a long analysis time of 30-60 minutes in the conditions of the temperature programming mode.

The objective of the present invention is to provide a method and device for gas chromatographic analysis of impurities, such as inorganic gases and hydrocarbons in the process of isobutane dehydrogenation, in isothermal chromatographic conditions, reducing analysis time.

The problem is solved due to the fact that in the method of gas chromatographic analysis of inorganic gases and hydrocarbons, the inorganic gases and hydrocarbons are simultaneously supplied by three metering taps into two packed columns and one capillary column connected in series with pre-columns, separation of inorganic gases on packed columns and hydrocarbons - on a capillary column, the subsequent determination of the content of inorganic gases by the detector by thermal conductivity and the content of hydrocarbon flame ionization sorbents, namely, a molecular sieve in one packed column, a porous polymer in another packed column, and functionalized poly (1-trimethylsilyl-1-propine) in a capillary column, which allows the analysis of inorganic gases and hydrocarbons under isothermal conditions.

The problem is solved due to the fact that the device for gas chromatographic analysis of inorganic gases and hydrocarbons contains a source of carrier gas, two metering valves connected in series with pre-columns and packed columns, a third metering valve connected in series with the capillary column, thermal conductivity detector, flame an ionization detector, and the packed columns are sequentially blocked by pressure and located on one arm of the detector in terms of thermal conductivity. The problem is also solved due to the fact that sorbents are used in the device, namely, a molecular sieve in one packed column, a porous polymer in another packed column, and functionalized poly (1-trimethylsilyl-1-propine) in the capillary column

In FIG. 1 shows a diagram of a device for gas chromatographic analysis — sampling, FIG. 2 is a diagram of a device for gas chromatographic analysis of a sample.

The device includes gas flow controllers 1, 2; pressure regulator 3; metering taps with sampling loops of fixed volumes 4, 5, 6; adsorption filter for carrier gas 7; pre-columns 8, 9; molecular sieve packing column 10; a packed column with a porous polymer 11; functionalized poly (1-trimethylsilyl-1-propine) capillary column 12; gas flow regulator 13; throttle 14; thermal conductivity detector 15; flame ionization detector 16; gas flow regulators 17, 18; adsorption filter for hydrogen 19; adsorption filter for air 20.

The device operates as follows:

The carrier gas passes through the sampling loops of fixed volumes of metering valves 4, 5, 6, pre-columns, nozzle and capillary columns.

Two nozzle columns 10 and 11 connected to each other through a tee are located on one arm of the detector for thermal conductivity 15, and on the second arm of the detector for thermal conductivity 15 there is a throttle (air resistance) 14. A gas sample is simultaneously dosed to two subcolumns 8 and 9, connected in series with nozzle columns 10 and 11, and one capillary column 12. Blocking by pressure (reducing flow to a minimum) for 6-9 minutes on a gas line connected to a metering valve 5 and a loop of a fixed volume, a pre-column 9 and nozzle column with a porous polymer 11 and the delay switching its supply allows you to bring the pressure in the metering loop to the pressure at the inlet of the nozzle column with a molecular sieve 10 to analyze the gas sample. The content of a gas sample of hydrogen, oxygen, nitrogen, methane and carbon monoxide is determined on a packed column with a molecular sieve 10.

Conversely, blocking by pressure (reducing flow to a minimum) for 4.5 min on a gas line connected to a metering valve 4 and a loop of a fixed volume, a pre-column 8 and a nozzle column with a molecular sieve 10 and a delay in switching its supply allows the pressure to dosing loop to the pressure at the inlet to the packed column with a porous polymer 11 for analyzing a gas sample. On a packed column with a porous polymer 11, the content of methane, carbon dioxide and the total value of hydrogen, oxygen, nitrogen, carbon monoxide in the gas sample, which are present in the chromatogram as unseparated peaks, are determined. The analysis is carried out sequentially, first on a packed column with a molecular sieve 10, and then on a packed column with a porous polymer 11. The analysis of hydrocarbons C ₁ -C ₄ on a capillary column with functionalized poly (1-trimethylsilyl-1-propine) is carried out in parallel with the analysis on two packed columns. This combination of chromatographic columns allows the analysis of a gas sample of isobutane dehydrogenation products under isothermal conditions.

This method of delaying the switching of metering valves is used to bring the pressure in the metering loops to the pressure at the entrance to the chromatographic columns and to conduct a sequential analysis of the gas sample on a packed column with a molecular sieve and then on a packed column with a porous polymer.

An example of a specific implementation of the method and device for its implementation.

The experiment is carried out on a Chromoe 1000 chromatograph with a thermal conductivity detector and a flame ionization detector.

Use pre-columns made of stainless steel with a size of 0.5 m × 3 mm × 2 mm (length, outer and inner diameters), a nozzle column made of stainless steel with a size of 2 m × 3 mm × 2 mm (length, outer and inner diameters) with a porous polymer Chromosorb 106 (80/100 mesh), stainless steel packing column 3 m × 3 mm × 2 mm (length, outer and inner diameters) with a NaX molecular sieve (45/60 mesh), quartz capillary column measuring 30 m × 0 , 32 mm × 0.5 μm (length, outer diameter and film thickness of functionalized poly (1-trimethylsilyl-1-propine). Ha Booster -. helium (argon), the space velocity at the outlet of the column of 30 cm / min for ² packed columns volumetric flow rate of the carrier gas (helium, argon) for the capillary column is 0.6 kgf / cm ² Oven temperature chromatograph 50 °. FROM.

As an example, sorbates were used: hydrogen, oxygen, nitrogen, air, carbon monoxide, carbon dioxide, methane, acetylene, ethylene, ethane, propylene, propane, 1,3-butadiene, isobutylene, isobutane, n-butane.

The retention times t _R were determined, the degree of separation R _s for the pairs of compounds and the asymmetry factor F _as peaks were calculated by the following formulas:

,

,

,

,

where t _R is the retention time, min; t ₁ , t ₂ - uncorrected retention times of two compounds, min; α ₁ , α ₂ - the width of the peaks of these compounds; F _as - asymmetry factor; AB - the width of the frontal section of the peak at the level of 0.1 of its height; BC - the width of the rear portion of the peak at the level of 0.1 of its height.

The results of the experiment are presented in the table.

Chromatograms of the separation of dehydrogenation products are shown in FIG. 3 (A) and FIG. 3 (B). In FIG. 3 (A) - separation of 1 - hydrogen, 2 - oxygen, 3 - nitrogen, 4 - methane, 5 - carbon monoxide, 6 - carbon dioxide, in FIG. 3 No. (B) - separation of hydrocarbons 7 - acetylene, 8 - ethylene, 9 - ethane, 10 - propylene, 11 - propane, 12 - 1,3-butadiene, 13 - isobutylene, 14 - isobutane, 15 - n-butane.

Thus, from the table and FIG. 3 (A), FIG. 3 (B) it is seen that the analysis time of the mixture of all sorbates is 13 minutes The degree of separation R _s determines both the sharpness of the peaks and the distance between the maxima. If R _s = 1, then the peak separation is approximately 98% of the total separation. If R _s > 1, then almost complete (without overlapping) peak separation is achieved (99.7% of the total separation).

The retention times of the components may differ from the above, it depends on the preparation conditions of the used chromatographic columns and the conduct of the dehydrogenation reaction, on the conditions for observing the temporary operating conditions of metering valves.

When solving this problem, a result is created that consists in the simultaneous introduction, removal of interfering components for the analysis of inorganic gases in a gas sample, the subsequent parallel analysis of the gas sample in two nozzle columns successively blocked by pressure and one capillary column. Sequential blocking by pressure for a fixed time ensures that the pressure in the dosing loop is brought to the pressure at the inlet to the packed columns and effectively separates the components of the isobutane dehydrogenation gas sample. The combination of sorbents (molecular sieves and a porous polymer) in packed columns and functionalized poly (1-trimethylsilyl-1-propine) in a capillary column allows analyzing a gas sample of dehydrogenation products under isothermal conditions for 10-15 minutes.

Claims (2)

1. The method of gas chromatographic analysis of inorganic gases and hydrocarbons, which consists in the simultaneous supply of inorganic gases and hydrocarbons by three metering taps into two nozzle columns and one capillary column connected in series with pre-columns, in the separation of inorganic gases on nozzle columns and hydrocarbons on a capillary column, in the subsequent determination of the inorganic gas content by the thermal conductivity detector and the hydrocarbon content by the flame ionization detector, The fact that sorbents are used in the columns, namely, a molecular sieve in one packed column, a porous polymer in another packed column, and functionalized poly (1-trimethylsilyl-1-propine) in a capillary column, which allows the analysis of inorganic gases and hydrocarbons in isothermal conditions. 2. Device for gas-chromatographic analysis of inorganic gases and hydrocarbons, including a carrier gas source, two metering valves connected in series with pre-columns and nozzle columns, a third metering valve connected in series with a capillary column, thermal conductivity detector, flame ionization detector characterized in that the packed columns, successively blocked by pressure, are located on one arm of the detector for thermal conductivity and sorbents are used in the columns, namely molecular sieve in one packed column, porous polymer in another packed column, and functionalized poly (1-trimethylsilyl-1-propine) in a capillary column.

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