RU2713166C1 - Method of preparing samples of oil-field chemicals for determining organochlorine compounds and organically bound chlorine - Google Patents

Abstract

FIELD: chemistry.SUBSTANCE: invention relates to analytical chemistry and specifically to a method for preparing samples of oil-field reagents. Method of preparing samples of oil-field chemicals for determining organochlorine compounds and organically bound chlorine involves separating salts of quaternary ammonium compounds to eliminate the effect of products of their thermal decomposition, wherein analyzed sample, polar and non-polar solvents are extracted in equal proportions, extraction of mixture with transition of quaternary ammonium compounds to polar phase, and organochlorine compounds in a nonpolar phase with subsequent extraction of an aliquot of an extract of a nonpolar solvent for analysis.EFFECT: high accuracy and reliability of determining quantitative content of organochlorine compounds present in reagents.5 cl, 7 dwg, 1 tbl

Description

The invention relates to the field of analytical chemistry, and in particular to a method for preparing samples of oilfield reagents for the determination of organochlorine compounds and organically bound chlorine.

Currently, the oil industry uses a huge number of different oil field reagents: clay stabilizers, surfactants, emulsifiers, demulsifiers, viscosity modifiers, corrosion inhibitors, paraffin inhibitors, detergents, bactericides, etc. Many reagents contain organochlorine compounds either as a constituent component or as impurities remaining in them as a result of a violation of the technology for their production.

 Organochlorine compounds (ChOS) are organic compounds in which one or more atoms are replaced by chlorine atoms. Volatile organochlorine compounds (LHOS) are a COS group, the boiling point of which is below 204 ° C. Of the halogens contained in oil, it is CWS that creates the greatest problems, since they are an additional source of inorganic chlorides (in some cases very significant) of hydrochloric corrosion in oil refining plants. When oil is refined at high temperatures, they are often destroyed with the formation of corrosive hydrogen chloride, and partly with the formation of lighter “fragments” distributed over the fractions of oil.

The greatest activity of HOS is observed in pre-hydrotreatment plants for raw materials, diesel fuel, gas fractionation and reforming. The limits of boiling of COS mainly coincide with the limits of boiling of gasoline fractions; therefore, the main damage is observed in catalytic reforming plants due to the high corrosion rate due to the formation of HCl and partial deactivation of the catalysts. Hydrochloric acid is the strongest corrosive agent, in addition, hydrogen chloride interacts with ammonia formed during the hydrogenation of nitrogen compounds, which are traditionally present in oil. The result is ammonium chloride (NH ₄ Cl), a white, powdery substance that clogs equipment. As a result, the equipment of hydrotreatment plants, as well as preliminary hydrotreatment units for raw materials of catalytic reforming and isomerization units, undergo additional wear due to hydrochloric corrosion and become clogged with ammonium chloride deposits.

GOST R 51858 for oil [1], prescribes a mandatory definition, in addition to traditional physicochemical parameters (density, content of solids, water, chloride salts, hydrogen sulfide and mercaptans, saturated vapor pressure), as well as the content of organochlorine compounds (COS). GOST established the norm of organic chlorides in the oil fraction boiling up to 204 ° С - not more than 10 ppm.

According to the ANO GTSSS Neftepromkhim, HOSs are most often found in large quantities in organic solvents (for example, toluene), hydrophobizing agents based on N-alkyl dimethylbenzylammonium chloride, lubricant additives for drilling fluids based on used oils, and also acids that are waste products in technological processes of which organochlorine compounds are present. In small amounts, LXOC is found in corrosion inhibitors, bactericides, and complex inhibitors containing salts of quaternary ammonium compounds (QUAS).

In the methods of GOST R 52247 and ASTM D4929, as a preliminary operation, distillation of naphtha (fraction boiling off up to 204 ° С) is provided, in the method of GOST 20242 burning of a sample in a bomb, in the method of GOST 14618.1 destruction of chemical substances by boiling with sodium in xylene. When analyzing samples of reagents containing salts of quaternary ammonium bases, this method yields false results due to thermal degradation of QAS (alkyl dimethylbenzylammonium chloride) during tests with the formation of a secondary organochlorine - benzyl chloride. In direct chromatography of such chemical products, a peak characteristic of the retention time for benzyl chloride is present on the chromatogram, which is a consequence of the destruction of the HOUR under chromatographic conditions (evaporator temperature 220 ° C).

When analyzing chemicals using GOST R 52247 methods, the presence of inorganic compounds of chlorine and other halogens, as well as sulfur, also affects the reliability of the results. By X-ray fluorescence analysis, all chlorine (including inorganic) is determined, and not only in the form of an organochlorine compound.

When adapting the methods of GOST R 52247 for application to oilfield products, a problem also arises with the inability to distill chemicals like oil.

A known method for determining the content of volatile organochlorine compounds in complex mixtures (RF patent No. 22199541 C1). In this case, the analyzed mixture is passed in a carrier gas stream through an evaporator at 220-350 ° С, then it is separated in a capillary column of a chromatograph at 50-320 ° С, detected at 220-350 ° С in an electron capture detector, to which an additional carrier gas is supplied with a speed of 20 cm ³ / min and the quantitative and individual composition of volatile organochlorine compounds establish a specific source of pollution. The disadvantage of this method is also the receipt of false results in the analysis of samples containing HOUR.

When analyzing samples of reagents in the form of acids and acid compositions by gas-liquid chromatography, the introduction of acids into the device causes corrosion of the metal elements of the device, and the introduction of hydrofluoric acid leads to the dissolution of the glass parts of the device. In addition, in the process of analysis, the reliability of the results is also affected by the presence of inorganic chlorine compounds.

The technical task of the invention is to reduce the risk of the formation of volatile organochlorine compounds in marketable oil due to high-precision control of the applied chemicals.

EFFECT: high accuracy and reliability of determining the quantitative content of organochlorine compounds present in reagents.

The technical result is achieved by the fact that the method of preparing samples of oilfield chemicals for the determination of organochlorine compounds and organically bound chlorine involves the separation of salts of quaternary ammonium compounds to exclude the effects of their thermal degradation products, and the test sample, polar and non-polar solvents are taken in equal proportions, the mixture is extracted with the transition of quaternary ammonium compounds to the polar phase, and organochlorine compounds to the non-polar phase with the last blowing selection nonpolar solvent extract aliquots for analysis.

The technical result is also achieved by the fact that the method of preparing samples of oilfield chemicals, which are compositions of organic and inorganic compounds in water-based solutions of increased aggressiveness, for determining organochlorine compounds and organically bound chlorine involves sampling the test sample and non-polar solvents, extracting the mixture with the passage of inorganic compounds chlorine in the polar phase, and organochlorine compounds in the non-polar phase, followed by selection of an aliquot of tract nonpolar solvent for analysis.

HOUR salts are organic derivatives of the ammonium ion NH4 +, in which the hydrogen atoms are completely or partially replaced by organic radicals [R4-nNHn] + An-, where the anion An is the residue of an organic or inorganic acid, n = 0-3. In HOUR, the chlorine atom is not in the covalent, but in the ionic state.

Salts of Quaternary ammonium compounds are components of effective corrosion inhibitors and are characterized by a functional group (positively charged nitrogen atom) and a lipophilic residue. The most commonly used compound is alkyldimethylbenzylammonium chloride, which in itself is not LHOS, because in this case there is no Cl-Cl bond (a sign of an organochlorine compound), but there is an R-NH4 + Cl- ionic bond. However, compounds of this class can be thermally unstable and undergo degradation when heated to 204 ° С with the formation of benzyl chloride, which belongs to the class of LHOS. GOST R 52247 regulates the methods for determining LHOS in relation to oil, and not to chemical products, and provides for the mandatory stage of distillation of the oil fraction. It is at this stage that the destruction of HOURs occurs with the formation of benzyl chloride. The benzyl chloride resulting from the thermal decomposition of HOURs after the conversion of organically bound chlorine to inorganic chloride will be detected after distillation of oil by any method proposed in GOST R 52247. When chromatographic products are directly chromatographed, there is a peak in the chromatogram characteristic of the retention time for benzyl chloride, which is also a consequence destruction of the HOUR under chromatographic conditions (evaporator temperature 220 ° C).

To exclude a false peak of benzyl chloride if it is detected on the chromatogram of the studied chemical product, it is necessary to perform a repeated measurement, confirming either the initial presence of BC in the chemical product or its formation as a result of the destruction of the HOUR.

Preliminary preparation of a sample of the studied chemical reagent, presumably containing an HOUR, including the selection of the test sample, the introduction of polar and non-polar solvents in equal proportions, the extraction of the mixture with subsequent separation, the selection of an aliquot of the extract of the non-polar organic solvent for subsequent analysis, is proposed. In this case, the HOUR salts, upon extraction, pass into the polar phase, while the volatile organochlorine compounds pass into the nonpolar phase (organic solvent). Thus, in the presence of an HOUR in the test sample, a false peak of benzyl chloride is not recorded on the chromatogram. This indicates that initially benzyl chloride is not present in the chemical product and does not appear as a result of thermal destruction of HOURs, as HOUR remains in the aqueous (polar) phase. In the case when benzyl chloride is initially present in the chemical product, upon extraction as a non-polar compound, it passes into the non-polar phase - an organic solvent.

Analysis of samples containing reagents in the form of aqueous solutions of acids or acidic compounds gives results on the content of total chlorine, whereas the volatile organochlorine compounds and organically bound chlorine represent the danger. To accurately determine the ChOS content in aggressive liquids, the method of sample preparation includes sampling the test sample, assessing the pH value, introducing a non-polar solvent at pH≤4, performing extraction of the mixture with subsequent stratification of the sample, and taking an aliquot of the non-polar organic solvent extract used for further analysis.

The quantitative ratio of the test sample and non-polar solvent is determined on the basis of the specified boundaries of the calibration graph and involves the concentration or dilution of the sample (after the initial determination of the COS, if the result is outside the calibration chart, it is possible to dilute or concentrate the COS in the extract, respectively, to get within the graph , in the future, the obtained mass fraction of HOS is recalculated depending on the degree of dilution),

If the test reagent is presented in the form of a dry or viscous chemical product, the sample preparation method includes dissolving it in a suitable solvent (for example, indicated in the technical specifications for the test reagent), introducing a mixture of polar and non-polar solvent, performing extraction of the mixture followed by separation of the sample, selection aliquots of an extract of a non-polar organic solvent used for further analysis.

In a particular case, it is possible to introduce a prepared sample of a chemical reagent into a sample of oil, a model of oil or an oil product, followed by distillation of the resulting mixture. This method of sample preparation allows you to simulate the process of oil preparation, thereby providing reliable results for the determination of organochlorine compounds in oil in as close as possible to real conditions. The sample thus obtained is further examined for the quantitative content of ChOS.

After sample preparation, the content of cholesterol or organically bound chlorine is determined by any of the known methods: gas, gas-liquid chromatography, X-ray fluorescence analysis, mass spectrometry, etc.

Examples of the invention:

Example 1

Samples of a corrosion inhibitor and a paraffin scale inhibitor were taken in an amount of 1 l each.

A chromato-mass spectrometric study of these samples was carried out. The resulting spectrum of the corrosion inhibitor is presented in figure 1, the spectrum of the inhibitor of paraffin deposits - in figure 2.

Identification of the components was carried out using a library of mass spectra.

The following organochlorine components were found in the corrosion inhibitor sample: C ₇ H ₇ Cl, C ₁₁ H ₂₃ Cl, C ₁₈ H ₃₁ ClO. In a paraffin scale inhibitor sample: C ₇ H ₇ Cl, C ₁₁ H ₂₃ Cl, C ₁₄ H ₂₉ Cl.

The boiling points of C ₁₁ H ₂₃ Cl, C ₁₄ H ₂₉ Cl, C ₁₈ H ₃₁ ClO exceed the temperature of 204 ° C and are not classified as volatile organochlorine compounds, determined according to GOST P52247. Based on this, these components are excluded from further research.

Figure 3 presents the spectrum of the volatile organochlorine compounds of benzyl chloride With ₇ H ₇ Cl.

The large amount determined (as a result of the tests) (about 70,000 ppm in terms of the chemical product) of benzylchloride in the samples can be caused both by the presence of the substance in the chemical product and by the thermal degradation of the QAS (alkyl dimethylbenzylammonium chloride) during the tests with the formation of a secondary organochlorine - benzyl chloride.

To determine the source of LHOS in the samples of chemicals, additional studies were carried out on a gas chromatograph with an electron capture detector (Figs. 4-5).

On the chromatograms (Fig. 4 - corrosion inhibitor, Fig. 5 - paraffin scale inhibitor) peaks of benzyl chloride were also observed.

The samples were extracted with isooctane and water in 1: 1: 1 ratios.

For this, 4 cm ^{3 of the} test sample, isooctane and water were pipetted into the measuring cylinder. The extraction was carried out by shaking the mixture for 3-10 minutes and holding for 3-10 hours to separate it. After that, an aliquot of an extract of non-polar solvent with a volume of 1 μl was selected. Analysis of the sample was carried out by gas chromatography.

After extraction, peaks of benzyl chloride were not observed in the obtained chromatograms (Fig. 6 - corrosion inhibitor, Fig. 7 - paraffin deposition inhibitor). On the one hand, this testifies to the transition of the QAS to the aqueous phase, and, on the other hand, that previously discovered (during the tests by GOST R 52247, chromatography-mass spectrometry and gas chromatography without preliminary sample preparation, benzyl chloride appeared as a result of thermal destruction of the QAS.

Example 2

A sample of the test sample in the form of a loose powder weighing 5-10 g, weighed with an accuracy of ± 0.001 g, was placed in the bottle, the minimum amount of the selected solvent was added to the bottle with a pipette so that the resulting solution could be taken out with a microsyringe. The dissolved sample was held for 2 hours, after which the preparation was carried out analogously to example 1.

On the example of this experiment, the possibility of research including viscous and bulk products was confirmed.

Example 3

A sample was taken of 20% hydrochloric acid, which was dosed into the oil model (kerosene 50%, Nefras C 3-80-120 30%, Petroleum ether 20%) at a concentration of 1%. Then, the resulting mixture was distilled according to the method of GOST R 52247, and the value of organic chlorides was determined according to the method B of GOST 52247.

By means of X-ray fluorescence spectrometry, 2025 ppm chlorides were detected in the sample.

After that, the sample was prepared according to the claimed invention:

In a separatory funnel with 100 cm ³ cylinder was added using 50 cm ³ sample to be measured and 15 cm ³ of isooctane, the selected pipette capacity of 20 cm ^3. The extraction was performed by shaking the sample for 5 minutes and waiting for the mixture to separate. The aqueous part was transferred to a beaker, and the isooctane extract was transferred to a volumetric flask with a ground stopper with a capacity of 50 cm ³ . The aqueous part was returned to a separatory funnel and was again extracted with 15 cm ³ isooctane taken with the same pipette. After phase separation, the aqueous portion of the sample was discarded, and the isooctane extract was combined with the first extract. The separatory funnel was rinsed with a 10 cm ³ solvent, pipetted, and the resulting solution was transferred to a volumetric flask with the combined extract, the solution was brought to the mark with isooctane, closed with a stopper and mixed. A sample was taken, followed by its dosing into an oil model. The resulting mixture was distilled according to GOST R 52247. By the method of X-ray fluorescence spectrometry (according to method B GOST 52247) 1.2 ppm of organic chlorides were detected in the sample.

The sample was also analyzed for COS content by gas-liquid chromatography; 1.4 ppm chloroform was detected in the sample.

Table 1 compares the results of the determination of organic chlorides and ChOS in hydrochloric acid with and without sample preparation.

Thus, without sample preparation, hydrochloric acid is distilled along with the oil model; in the distilled fraction, all chlorine, including inorganic, is determined by X-ray fluorescence spectrometry. After sample preparation according to the claimed invention, the content of organic chlorides is determined.

The advantages of the claimed invention:

- the ability to accurately and reliably determine the source of contamination of commercial oil in the form of volatile organic compounds and organically bound chlorine;

- the ability to control chemicals for volatile organochlorine compounds and salts of Quaternary ammonium compounds capable of forming volatile organochlorine compounds.

- the ability to analyze chemical reagents presented in various physical forms (liquid, powder, viscous substance, etc.).

Claims (5)

1. A method of preparing samples of oilfield chemicals for the determination of organochlorine compounds and organically bound chlorine, including the separation of salts of quaternary ammonium compounds to exclude the influence of products of their thermal degradation, while taking the test sample, polar and non-polar solvents in equal proportions, extracting the mixture with the transition of the Quaternary ammonium compounds in the polar phase, and organochlorine compounds in the non-polar phase, followed by selection of an aliquot of the extract lar solvent for analysis. 2. The method of preparing samples according to claim 1, characterized in that the samples of the test product in a viscous or loose form are pre-dissolved in a suitable solvent. 3. The method of preparing samples according to claim 1, characterized in that it includes the distillation of the extract with oil, a model of oil or oil product. 4. A method of preparing samples of oilfield chemicals, which are compositions of organic and inorganic compounds in water-based solutions of increased aggressiveness, for determining organochlorine compounds and organically bound chlorine, including sampling the test sample and non-polar solvents, extracting the mixture with the transition of inorganic chlorine compounds to the polar phase , and organochlorine compounds in the non-polar phase, followed by selection of an aliquot of the non-polar solvent extract for analysis. 5. The method of preparing samples according to claim 4, characterized in that it involves the distillation of the extract with oil, oil model or oil product.

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