RU2537468C2 - Method for determining markers of transported oil and oil products, and device for its implementation - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: invention refers to gas chromatographic methods of analysis and may by used in oil industry and other industries for hidden marking of oil and oil products during various expertises in commercial and industrial enterprises. Essence of equipment consists in the following: volatile compounds (markers) are extracted from oil by airlift contact of gas flow with solution of volatile markers in low-volatile solvent (oil or oil products) with subsequent headspace analysis by method of gas chromatography. As volatile markers, used are aliphatic monobasic alcohols and their mixtures, and gas flow, saturated with volatile compounds (alcohol markers and petroleum hydrocarbons), are bubbled through non-polar solvent for removal of oil volatile hydrocarbons. Then gas flow saturated with volatile alcohol markers is bubbled through a small volume of distilled water to obtain concentrated aqueous solution of alcohol marker, which is dosed to gas chromatograph for analysis. Device for the method implementation includes series-connected unit for gas preparation and three series-connected bubble condensers, the first of which is filled with oil sample with volatile alcohol marker with volume V₁, the second - with non-polar solvent with volume V₂=V_i, and the third bubble condenser is filled with distilled water with volume V₃=0.01V₁.

EFFECT: increase of sensitivity of gas-chromatographic determination of volatile alcohol markers of transported oil and oil products.

2 cl, 1 dwg, 1 tbl

Description

The invention relates to gas chromatographic methods of analysis and can be used in the oil and other industries for covert labeling of oil and oil products during various types of examinations in commercial and industrial enterprises.

Known methods for determining special compounds for hidden labeling of substances, materials and products with the aim of identifying them, determining ways of their distribution on the market, establishing the place of manufacture and confirming the fact of contact interaction (see: Mitrichev BC Forensic examination of materials, substances and products. Saratov: Publishing house of Saratov University. 1980. S. 9-90).

Markers used in the oil industry can be either colored or colorless (invisible). For example, such petroleum products, diesel, or gasoline often contain visible labeling compounds (dyes or compounds) that indicate the purpose, price, or brand name of the product (see: Friswell MR, Hiuton MP Markers for petroleum method of tagging, and method of detection Patent USN 5205840. 1993).

The disadvantages of colored markers are, for example, that some of them lose their color properties over time, which makes it difficult to detect them during long-term storage.

Invisible markers can be divided into three classes:

A - appear in fuel by adding a special reagent;

B - are determined in the fuel using special equipment;

C - DNA markers.

Class A markers are extracted from petroleum or petroleum products and are developed using a specially selected reagent (see: Desai B., Smith MJ Colorless petroleum markers. Patent USN 6002056. 1999, also see: Oreiup RB Colored petroleum markers. Patent USN 4735631. 1988 )

Class B markers are determined using various physicochemical methods, for example, liquid and gas chromatography, spectrophotometry, or specialized detection devices (see: Combs George G. (US). Fluorescence or fluorescence-intensive markers for liquids or products. Patent RUN 2408612 of 27.11. 2008).

The disadvantage of class B markers is the impossibility of obtaining unambiguous conclusions from the analysis, since oil and some oil products are characterized by their own luminescence, which significantly complicates the identification of the introduced marker. In addition, oil contains a large number of substances that interfere with the chromatographic determination of markers. In this regard, before determining them, it is necessary to conduct special preparation of an oil sample for analysis.

The fuel labeling system using DNA technologies is based on the latest technological achievements and is the most advanced, providing 100% reliability of identification of oil and oil products (see: http://www.euromarker.ru/marker).

A significant disadvantage of DNA markers is the high cost and complexity of their preparation.

It is known to use aliphatic alcohols C ₁ -C ₅ for studying water and oil filtration processes in porous media to increase oil recovery in productive formations (see: Arutyunov Yu.I., Efremov A.O., Onuchak L.A., Dudikov BC Distribution study aliphatic monoalcohols C ₁ -C ₅ in the "produced water -dodekan." // Bulletin of the Samara state University. Natural Science series. 2012. №3 / 1. S.123-131).

Also known is a chemical marker containing homologues of n-alkanes C ₁₆ -C ₂₆ or mixtures thereof, which are determined in oils and petroleum products by gas chromatography with direct dosing of an oil sample into the chromatograph evaporator. The minimum concentration of the marker, determined in oil or petroleum products, lies in the range of 1.0-5.0 wt.% (See: Nekhoroshev S.V., Rubanik S.I., Nekhoroshev V.P., Turov Yu.P. Chemical marker Patent RU N. 2199574 dated 02.27.2003).

The closest to the claimed invention in terms of essential features is a method for obtaining constant microconcentrations of volatile compounds in a gas stream, in which the gas stream is saturated to a predetermined equilibrium concentration by bubbling contact of the gas stream with a solution of volatile compounds in a low-volatile solvent. Saturation of a gas stream to an equilibrium concentration by vapor of a volatile substance is carried out by successive contact of the gas stream with at least three fixed portions of a solution of volatile substances in a low-volatile solvent (see: Berezkin V.G., Platonov I.A., Onuchak L.A., Lepsky MV A method for producing constant microconcentrations of volatile compounds in a gas stream Patent RU N. 2213958 of 10/10/2003 // Bull. Inventory No. 28.2003).

Closest to the invention in terms of essential features is a device for implementing this method for obtaining constant microconcentrations of volatile compounds in a gas stream, containing a series-connected inert gas preparation unit and three bubblers filled with a solution of volatile compounds in a low-volatile solvent, the volume of solutions of the first bubbler exceeding the volumes of solutions in subsequent bubblers.

The disadvantage of this method and device is the low sensitivity of determining volatile markers of oil and oil products during gas chromatographic vapor-phase analysis (see: Ioffe B.V., Reznik T.L. // Journal of Analytical Chemistry. 1981. V.36. P.2191 -2198).

The objective of the invention is to increase the sensitivity of determining volatile markers of transported oil and petroleum products.

This problem is solved due to the fact that in the method for determining the markers of transported oil and oil products, in which volatile compounds (markers) are extracted with an inert gas stream by bubbling contact of the gas stream with a solution of volatile markers in a low-volatile solvent (oil and oil products) followed by vapor-phase analysis by gas chromatography, moreover, aliphatic monohydric alcohols with the number of carbon atoms in molecules from three to five or more or mixtures thereof are used as volatile markers, and the flow an inert gas saturated with volatile compounds (markers and petroleum hydrocarbons) is bubbled through a non-polar solvent to remove volatile hydrocarbons of oil and oil products, then an inert gas stream saturated with volatile alcohol markers is bubbled through a small volume of distilled water to obtain a concentrated solution of an alcohol marker, which is metered into a gas chromatograph for analysis.

This problem is also solved due to the fact that in the device for determining markers of transported oil and oil products, containing in series a unit for the preparation of inert gas and three bubblers filled with liquid substances, the volume of the solution of the first bubbler exceeding the volume of the subsequent ones, while the first bubbler is filled with a breakdown of oil or petroleum product with a volatile alcohol marker with a volume of V ₁ , the second bubbler is filled with a non-polar solvent, with a volume of V ₂ = V ₁ , and the third bubbler is filled with distilled water with a volume of V ₃ = 0.01V ₁ .

When solving this problem, a technical result is created that consists in increasing the sensitivity of the gas chromatographic determination of volatile alcohol markers of transported oil and oil products due to the additional liquid-phase concentration of alcohol markers in a small volume of distilled water. The volume of distilled water is chosen from the calculation so that the equilibrium concentration of alcohol markers is reached in a period of not more than 20 minutes at a given volumetric gas flow rate. At the same time, there is no need to use large quantities of alcohol for marking oil and oil products and the additional costs associated with this are eliminated.

All of the above allows us to conclude that the claimed invention is interconnected by a single inventive concept.

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

Figure 1 schematically shows a device for determining markers of transported oil and oil products. The device contains: an inert gas preparation unit 1, three sequentially connected bubblers 2, 3 and 4. The bubbler 2 is filled with a sample of oil or oil product with a volatile alcohol marker, the bubbler 3 is filled with a non-polar solvent - n-decane, the bubbler 4 is filled with distilled water.

The proposed device operates as follows. A sample of oil or oil product with a dissolved alcohol marker in an amount of 20 cm ³ is poured into bubbler 2, 20 cm ^{3 of} n-decane is poured into bubbler 3, and 0.2 cm ^{3 of} distilled water is poured into bubbler 4. The inert gas stream of nitrogen from the preparation unit 1 with a space velocity of not more than 10 cm ³ / min is bubbled through three series-connected bubblers 2, 3 and 4 for 20 minutes. After that, a sample of an aqueous solution of an alcohol marker is taken from a bubbler 4 with a microsyringe and dosed into an evaporator of a gas chromatograph. Injection volume = 5 V _pr ml.

The use of aliphatic monohydric alcohols with the number of carbon atoms in molecules from three to five as markers of transported oil and oil products is not described in the literature. The number of labeling options depends on the number of individual normal alcohols and isostructure in the marker. For example, the use of these six aliphatic alcohols as a marker allows you to get 33 marking options.

One of the main requirements for oil markers is to reduce their consumption during operation, which is associated with the sensitivity of the measuring device used. The concentration of markers in oil varies according to published data at the level of units and tens of parts per million. It is customary to evaluate such concentrations as impurities with all the ensuing problems associated with their gas chromatographic determination.

An experimental evaluation of the implementation of the proposed and known methods for determining the markers of transported oil and oil products was carried out using two types of oil with the code name Rodnikovka and Ponomarevka, in which a fixed amount of alcohol markers — butanol-1 and 2-methylpropanol-1 — was added.

In the known method, the gas stream is saturated to an equilibrium concentration with vapor of volatile alcohol markers by sequential contact of the gas stream with at least three fixed portions of a solution of volatile alcohol markers in a low-volatile oil sample, and the volume of the first portion must exceed the volume of subsequent portions. In a device for implementing the known method, an oil sample with a dissolved alcohol marker in an amount of 20 cm ³ is poured into the first of three consecutive bubblers, the same oil sample with a marker is poured in an amount of 15 cm ³ into two subsequent bubblers. A stream of inert nitrogen gas from the preparation unit with a bulk velocity of 10 cm ³ / min is bubbled through three bubblers for 20 minutes. After that, a gas sample is taken from the last bubbler with a syringe and dosed into the gas chromatograph evaporator for analysis. The volume of the injected sample V _CR = 5 cm

The experiment was carried out on a Tsvet-500 gas chromatograph with a flame ionization detector in isothermal mode. Column thermostat temperature T _c = 135 ° C. Evaporator temperature 160 ° C. The alcohol marker was separated from the peak of water and impurities of oil hydrocarbons on a chromatographic column with a length of 80 cm and an inner diameter of 3 mm filled with a polysorb-1 polymer sorbent with a grain size of 0.16-0.2 mm. The carrier gas is nitrogen. The pressure of the carrier gas at the inlet to the column ΔP _i = 70 kPa. The results of the chromatographic experiment were processed using the Multichrom software and hardware complex, version 1.5x.

To identify artifacts ("false peaks") in the chromatograms, a control experiment was performed before the analysis of labeled oil. To do this, pure oil without a marker was poured into the bubbler and gas extraction was carried out with nitrogen for 20 min at a flow rate of 10 cm ³ / min.

From the obtained chromatograms, the retention time of alcohol markers t _R (min), the peak area A _i (mV · s) were calculated, and the precision of measuring the peak area was estimated using the results of n = 5 consecutive measurements as the boundary of the confidence interval of measurement s in percent according to the equation:

$$\epsilon =\sqrt{\frac{{\displaystyle \sum _{\mathrm{one}}^n{(A_i-A_{cp})}^2}}{n(n-\mathrm{one})}}\cdot \frac{\mathrm{one}}{A_{cp}}\cdot t(P,f)\cdot \mathrm{one\; hundred}$$

where A _i is the unit measurement of the peak area in the sample; A _cp is the average peak area of n = 5 measurements; t (P, f) = 2.78 - Student's test at P = 0.95 and f = n-1 = 4.

The results of the experiment are presented in the table "Comparative data of the experimental verification of the known and proposed methods."

Comparative data of experimental verification of the known and proposed methods No. p / p Name Known method The proposed method t _R min A _cp , mV ε,% t _R min A _cp , mV ε,% one Pure oil Rodnikovka (blank experience) 2,442 5.39 39.7 2,437 4.03 38.5 3,177 5.43 48.9 3,171 4.05 39,4 2 Ponomarevka Pure Oil (idle experience) 2,422 4.12 53.5 2,417 3.08 52.8 3,073 3.77 44.8 3,067 3.27 43,4 3 Rodnikova labeled with butanol-1, 50 mg / kg 3,042 5.45 43.9 3,036 11.11 11.5 four Rodnikova labeled with butanol-1, 500 mg / kg 3,012 10.78 11.8 3,006 1166.55 1.4 5 “Ponomarevka” labeled with butanol-1, 50 mg / kg 3,125 3.83 44.3 3,115 8.03 12.8 6 “Ponomarevka” labeled with butanol-1, 500 mg / kg 3,018 7.77 12.7 3,014 843.15 1,5 7 Rodnikova labeled with 2-methylpropanol-1, 50 mg / kg 2,437 5.42 41.2 2,432 42.84 10.7 8 Rodnikova labeled with 2-methylpropanol-1, 500 mg / kg 2,418 43.57 12.5 2,413 4455.36 1,2 9 "Ponomarevka" labeled with 2-methylpropanol-1, 50 mg / kg 2,431 3.85 42,4 2,407 37.93 11.6 10 "Ponomarevka" labeled with 2-methylpropanol-1, 500 mg / kg 2,407 39.25 11.9 2,402 3944.72 1.3 eleven Rodnikova labeled with 2-methylpropanol-1, 50 mg / kg and butanol-1, 50 mg / kg 2,433 5.43 42.1 2,431 41.85 10,4 3,048 5.41 43,2 3,037 10,4 11.3

From the data in the table shows that:

1. The sensitivity of the determination of butanol-1 and 2-methylpropanol-1 in two oils "Rodnikovka" and "Ponomarevka" by the proposed method is an order of magnitude higher than the sensitivity of their determination in a known manner.

2. The minimum detectable concentration of butanol-1 and 2-methylpropanol-1 is 50 mg / kg. In this case, the output signal of the chromatograph (peak area of the alcohol marker) is more than twice the signal for the “blank” (control) experiment. The minimum detectable concentration of alcohol markers in a known manner is 500 mg / kg.

3. Butanol-1 and 2-methylpropanol-1 are recorded with different retention times t _R , therefore, can be determined in different oils independently of each other.

4. The quality of the oil does not affect the output of the chromatograph. Statistical processing of the signals of alcohol markers in the Rodnikovka and Ponomarevka oils showed that the samples are homogeneous and obey the law of normal distribution.

5. The measurement error of butanol-1 and 2-methylpropanol-1 in oil with a concentration of 50 mg / kg of the proposed method does not exceed 13%.

The appearance of “false” peaks of butanol-1 and 2-methylpropanol-1 on the chromatograms is associated with the peculiarities of the analysis of impurities and, above all, with the accumulation of these alcohols in the metering devices and gas channels of the chromatograph from previous analyzes and their gradual desorption in subsequent analyzes.

Using the proposed method for determining the markers of transported oil and oil products and devices for its implementation allows you to:

1. Significantly increase the sensitivity of the determination of volatile alcohol markers of transported oil and oil products.

2. Reduce the consumption of volatile alcohols for labeling oil and petroleum products.

3. The use of aliphatic monohydric alcohols with the number of carbon atoms in molecules from three to five normal and isostructures and their mixtures allows you to get 33 different labeling options.

Claims (2)

1. The method of determining the markers of transported oil and oil products, in which volatile compounds (markers) are extracted with an inert gas stream by bubbling contact of the gas stream with a solution of volatile markers in a low-volatile solvent (oil or oil products), followed by vapor-phase analysis by gas chromatography, characterized in that aliphatic monohydric alcohols with the number of carbon atoms in the molecules from three to five or more or mixtures thereof are used as volatile markers, and the inert gas stream saturates volatile compounds (alcohol markers and petroleum hydrocarbons) are bubbled through a non-polar solvent to remove volatile hydrocarbons of oil and oil products, then an inert gas stream saturated with volatile alcohol markers is bubbled through a small volume of distilled water to obtain a concentrated aqueous solution of an alcohol marker, which is metered into gas chromatograph evaporator for analysis. 2. A device for determining markers of transported oil and oil products, containing a series-connected inert gas preparation unit and three bubblers filled with liquid substances, the liquid volume of the first bubbler exceeding the liquid volume of the subsequent ones, characterized in that the first bubbler is filled with a sample of oil or oil product with volatile alcohol a marker with a volume of V ₁ , the second bubbler is filled with a non-polar solvent with a volume of V ₂ = V ₁ , and the third bubbler is filled with distilled water with a volume of V ₃ = 0.01V ₁ .