EA039200B1 - Method for preparation of samples of oil-field chemicals for determination of organic chlorine compounds and organically binded chlorine - Google Patents

Abstract

The invention is related to the field of analytical chemistry, in particular, to a method for preparing samples of oilfield reagents for determination of organochlorine compounds and organically bound chlorine. The objective of the invention is to reduce the risk of formation of volatile organochlorine compounds in commercial oil by means of high-precision control of the chemicals used. The technical effect of the invention is high accuracy and reliability of determining the quantitative content of organochlorine compounds present in the reagents. The objective of the invention is achieved by provision of a method for preparing samples of oilfield chemicals for determination of organochlorine compounds and organically bound chlorine comprising separation of salts of quaternary ammonium compounds to exclude the influence of products of their thermal degradation comprising taking a test sample, polar and non-polar solvents in equal proportions, extracting the mixture with transition of quaternary ammonium compounds into the polar phase, and organochlorine compounds into the non-polar phase, followed by taking an aliquot of the non-polar solvent extract for analysis. The objective of the invention is also attained by provision of a method for preparing samples of oilfield chemicals that comprise highly corrosive compositions of organic and non-organic compounds in aqueous solutions for determination of organochlorine compounds and organically bound chlorine, comprising taking the test sample and non-polar solvents, extracting the mixture with transition of non-organic chlorine compounds into the polar phase, and organochlorine compounds into the non-polar phase, followed by taking an aliquot of the non-polar solvent extract for analysis.

Description

Technical field

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.

Prior Art

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

Organochlorine compounds (OCs) are organic compounds in which one or more atoms have been replaced by chlorine atoms. Highly volatile organochlorine compounds (LCOCs) are a group of OCs whose boiling point is below 204°C. Of the halogens contained in oil, it is COSs that create the greatest problems, since they are an additional (in some cases very significant) source of hydrochloric corrosion of oil refining units in addition to inorganic chlorides. During oil refining at high temperatures, they are often destroyed with the formation of corrosive hydrogen chloride, and partly with the formation of lighter fragments that are distributed over the oil fractions.

The highest activity of COS is observed at the plants for preliminary hydrotreatment of raw materials, diesel fuel, gas fractionation and reforming. The boiling range of COS is basically the same as the boiling range of gasoline fractions, therefore, the main damage is observed in catalytic reformers due to the high corrosion rate due to the formation of HCl and partial deactivation of catalysts. Hydrochloric acid is the strongest corrosive agent. In addition, hydrogen chloride interacts with ammonia, which is formed during the hydrogenation of nitrogen compounds that 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 the hydrotreating units, as well as the pre-hydrotreatment units of the feedstock of the catalytic reforming and isomerization plants, is subjected to additional wear due to hydrochloric corrosion and becomes clogged with ammonium chloride deposits.

GOST R 51858 for oil prescribes a mandatory determination, in addition to traditional physicochemical indicators (density, content of mechanical impurities, water, chloride salts, hydrogen sulfide and mercaptans, saturated vapor pressure), also the content of organochlorine compounds (OCs). In GOST, the norm of organic chlorides in the fraction of oil boiling up to 204 ° C is set - no more than 10 ppm.

According to the ANO GTSSS Neftepromkhim, COS are most often found in large quantities in organic solvents (for example, toluene), water repellents based on N-alkyldimethylbenzylammonium chloride, lubricating additives for drilling fluids based on used oils, as well as acids, which are production wastes, in the technological processes of which there are organochlorine compounds. In small quantities, LCOS is found in corrosion inhibitors, bactericides, and complex action inhibitors containing salts of quaternary ammonium compounds (QAC).

In the GOST R 52247 and ASTM D 4929 methods, naphtha is distilled off as a preliminary operation (a fraction that boils up to 204 ° C), in the GOST 20242 method, the sample is burned in a bomb, in the GOST 14618.1 method, the destruction of COS by boiling with sodium in xylene. When analyzing samples of reagents containing salts of quaternary ammonium bases, using this method, unreliable results are obtained at the output, due to thermal destruction of QAS (alkyldimethylbenzylammonium chloride) during tests with the formation of secondary organochlorine - benzyl chloride. During direct chromatography of such chemical products, a peak is present on the chromatogram, characteristic of the retention time for benzyl chloride, which is a consequence of the destruction of QAS under chromatographic conditions (evaporator temperature 220°C).

In the analysis of chemicals by the methods of GOST R 52247, the reliability of the results is also affected by the presence of inorganic compounds of chlorine and other halogens, as well as sulfur. The method of X-ray fluorescence analysis determines all chlorine (including inorganic), and not just 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 impossibility of distilling chemicals similarly to oil.

A known method for determining the content of volatile organochlorine compounds in complex mixtures (RF patent No. 2219541 C1). In this case, the analyzed mixture is passed in a flow of carrier gas through an evaporator at 220–350°C, then separated in a capillary column of a chromatograph at 50–320°C, detected at 220–350°C in an electron capture detector, into which carrier gas is additionally supplied at a speed of 20 cm ³ /min and the quantitative and individual composition of volatile organochlorine compounds determine the specific source of pollution. The disadvantage of this method is the obtaining of unreliable results in the analysis of samples containing QAS.

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, during the analysis, the reliability of the results is also affected by the presence of inorganic chlorine compounds.

The essence of the invention

The technical objective of the claimed invention is to reduce the risk of formation of volatile organochlorine compounds in commercial oil due to high-precision control of the chemicals used.

EFFECT: high accuracy and reliability of determining the quantitative content of organochlorine compounds present in the 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 includes the separation of salts of quaternary ammonium compounds to exclude the influence of their thermal degradation products, while taking the test sample, polar and non-polar solvents in equal proportions, extracting the mixture with the transition of quaternary ammonium compounds to the polar phase, and organochlorine compounds to the non-polar phase, followed by the selection of an aliquot of the extract of the non-polar solvent for analysis.

Also, the technical result is 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 the determination of organochlorine compounds and organically bound chlorine includes taking the test sample and non-polar solvent, extracting the mixture with the transition of inorganic compounds chlorine into the polar phase, and organochlorine compounds into the non-polar phase, followed by the selection of an aliquot of the extract of the non-polar solvent for analysis.

QAS salts are organic derivatives of the ammonium ion NH ₄ ⁺ , in which 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 QAS, the chlorine atom is not in a covalent, but in an 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 an LCOS, because. in this case, there is no C-Cl bond (a sign of an organochlorine compound), but there is an ionic bond R-NH ₄ +Cl-. However, compounds of this class can be thermally unstable and undergo degradation when heated to 204°C with the formation of benzyl chloride, which belongs to the LCOS class. GOST R 52247 regulates methods for determining LCOS in relation to oil, and not to chemical products, and provides for a mandatory stage of oil fraction distillation. It is at this stage that the destruction of QAS occurs with the formation of benzyl chloride. The benzyl chloride formed as a result of thermal decomposition of QAS after the conversion of organically bound chlorine into inorganic chloride will be detected after oil distillation by any method proposed in GOST R 52247. In direct chromatography of such chemical products, a peak is present on the chromatogram, characteristic of the retention time for benzyl chloride, which is also a consequence of QAS destruction under chromatographic conditions (evaporator temperature 220°C).

In order to exclude a false peak of benzyl chloride, if it is detected on the chromatogram of the chemical product under study, it is necessary to perform a repeated measurement, confirming either the initial presence of PC in the chemical product, or its formation as a result of the destruction of QAS.

It is proposed to carry out preliminary preparation of a sample of the chemical reagent under study, presumably containing QAS, 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, and the selection of an aliquot of the extract of the non-polar organic solvent for subsequent analysis. In this case, QAS salts during extraction pass into the polar phase, while highly volatile organochlorine compounds pass into the non-polar phase (organic solvent). Thus, in the presence of QAC 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 QAS, since At the same time, HAS remains in the aqueous (polar) phase. In the case when benzyl chloride is initially present in the chemical product, during extraction as a non-polar compound, it passes into a non-polar phase - an organic solvent.

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

The quantitative ratio of the test sample and the non-polar solvent is determined based on the specified boundaries of the calibration curve and involves concentrating or diluting the sample (after the initial determination of COS, if the result lies outside the calibration curve, it is possible to dilute or concentrate the COS in the extract accordingly to fall within the boundaries of the graph; in further, the resulting mass fraction of COS 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, specified in the specifications for the test reagent), introducing a mixture of polar and non-polar solvent, extracting the mixture, followed by stratification of the sample, sampling an aliquot of the non-polar organic solvent extract used for further analysis.

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

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

Information confirming the possibility of carrying out the invention

The following are examples of the invention.

Example 1

Samples of corrosion inhibitor and paraffin inhibitor were taken in the amount of 1 liter each.

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

The identification of components was carried out using a library of mass spectra.

The following organochlorine components were found in the corrosion inhibitor sample: C7H7Cl, StsH ₂₃ C1, C ₁₈ H ₃₁ ClO. In the paraffin inhibitor sample: C7H7Cl, StsN ₂₃ C1, C ₁₄ H ₂₉ Cl.

The boiling points of C11H ₂₃ Cl, C ₁₄ H ₂₉ Cl, C ₁₈ H ₃₁ ClO exceed 204°C and are not classified as highly volatile organochlorine compounds determined according to GOST R 52247. Based on this, these components were excluded from further study.

In FIG. Figure 3 shows the spectrum of the highly volatile organochlorine compound benzyl chloride C7H7C1.

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

To determine the source of LCOS in chemical samples, additional studies were carried out on a gas chromatograph with an electron capture detector (Fig. 4, 5).

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

Samples were extracted with isooctane and water in ratios of 1:1:1.

To do this, 4 ^cm3 of the test sample, isooctane, and water were pipetted into a graduated 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, a 1 μl aliquot of the non-polar solvent extract was taken. Sample analysis was carried out by gas chromatography.

After extraction, no benzyl chloride peaks were observed in the obtained chromatograms (Fig. 6 corrosion inhibitor, Fig. 7 wax inhibitor). This indicates, on the one hand, the transition of QAC to the aqueous phase, and, on the other hand, that the previously discovered (during tests by the methods of GOST R 52247, chromato-mass spectrometry and gas chromatography, without preliminary sample preparation, benzyl chloride appeared as a result of thermal destruction HOUR.

Example 2

A portion of the test sample in the form of a free-flowing powder weighing 5–10 g, weighed with an error of ± 0.001 g, was placed in a weighing bottle, and a minimum amount of the selected solvent was added to the weighing bottle using a pipette so that the resulting solution could be taken with a microsyringe. The dissolved sample was kept for 2 hours, after which the preparation was carried out similarly to example 1.

On the example of this experiment, the possibility of studying viscous and friable products, among other things, was confirmed.

Example 3

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

X-ray fluorescence spectrometry detected 2025 ppm chlorides in the sample.

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

In a separating funnel with a capacity of 100 cm ³ with the help of a cylinder was added 50 cm3 of the measured sample and 15 cm3 of isooctane, taken with a pipette with a capacity of 20 ^cm3 . Extraction was performed by shaking the sample for 5 min and waiting for the mixture to separate. The water 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 portion was returned to the separating funnel and extracted again with 15 cm ³ isooctane taken with the same pipette. After phase separation, the aqueous part of the sample was discarded, and the isooctane extract was combined with the first extract. The separating funnel was rinsed with a 10 cm ³ solvent measured with a pipette, and the resulting solution was transferred to a volumetric flask with the combined extract, the volume of the solution was brought to the mark with isooctane, closed with a stopper, and mixed. A sample was taken with its subsequent dosing into the oil model. The resulting mixture was distilled according to GOST R 52247. Using X-ray fluorescence spectrometry (by method B GOST 52247), 1.2 ppm of organic chlorides were found in the sample.

Also, the sample was analyzed for the content of CHOS by gas-liquid chromatography. The sample contained 1.4 ppm chloroform.

The table compares the results of the determination of organic chlorides and COS in hydrochloric acid with and without sample preparation.

Comparison of determination results

Sample Mass fraction of organic chlorides by X-ray fluorescence spectrometry, ppm Mass fraction of COS by GLC, ppm Oil model +1% hydrochloric acid 20% 2025 1.5 (chloroform) Oil model + 1% sample after sample preparation with hydrochloric acid 20% 1.2 1.4 (chloroform) 20% hydrochloric acid without sample preparation 205 015 -

Thus, without sample preparation, hydrochloric acid is distilled along with the model oil; 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 are the following:

the possibility of accurate and reliable determination of the source of commercial oil pollution in the form of volatile organic compounds and organically bound chlorine;

the possibility of monitoring chemical reagents for the content of volatile organochlorine compounds and salts of quaternary ammonium compounds capable of forming volatile organochlorine compounds;

the possibility of analyzing chemical reagents presented in various physical forms (liquid, powder, viscous substance, etc.).

Claims (5)

1. A method for 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 their thermal degradation products, while taking the test sample, polar and non-polar solvents in equal proportions, extracting the mixture with the transition of quaternary ammonium compounds into the polar phase, and organochlorine compounds into the non-polar phase, followed by the selection of an aliquot of the extract of the non-polar solvent for analysis. 2. Sample preparation method according to claim 1, characterized in that samples of the test product in viscous or free-flowing form are preliminarily dissolved in a suitable solvent. 3. Sample preparation method according to claim 1, characterized in that it includes distillation of the extract with oil, model oil or oil product. - 4 039200 4. A method for preparing samples of oilfield chemicals, which are compositions of organic and inorganic compounds in water-based solutions of increased aggressiveness, for the determination of organochlorine compounds and organically bound chlorine, including taking the test sample and a non-polar solvent, extracting the mixture with the transition of inorganic chlorine compounds to the polar phase , and organochlorine compounds into the non-polar phase, followed by the selection of an aliquot of the extract of the non-polar solvent for analysis. 5. Sample preparation method according to claim 4, characterized in that it includes distillation of the extract with oil, model oil or oil product.