RU2395805C2 - METHOD FOR SIMULTANEOUS DETERMINATION OF TOTAL CONTENT OF F-, Cl-, Br-, I- S- AND P-ORGANIC COMPOUNDS IN OIL AND OIL REFINING PRODUCTS - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention discloses a method for simultaneous determination of total content of F-, Cl-, Br-, I-, S- and P-organic compounds in oil and oil refining products. The method involves putting a sample into a reactor and high-temperature oxidative conversion using oxygen, absorption of the conversion products with deionised water which is free from the elements under analysis and analysis of the obtained solution through ion chromatography.

EFFECT: improved method.

5 cl, 5 tbl, 4 ex

Description

The invention relates to the field of quality control of oil and oil products, in particular high-quality motor fuels, lubricating oils of catalytic processes and individual hydrocarbons and other high-purity chemicals.

Monitoring the total content of F-, Cl-, Br-, I-, and S-organic compounds in oil and especially in the corresponding products of its processing is necessary due to the fact that the corresponding inorganic conversion products of these compounds poison many of the catalysts used in the processes oil refining. Along with this, corrosion of the corresponding equipment used in these processes occurs.

Along with this, control over the continuous supply of low concentrations of organochlorine compounds to reforming catalysts is necessary. The total chlorine content at the outlet of the catalysts should be at the level of n · 10 ^-4 %.

In some cases, for example in lubricating oils, the determination of the total content of organophosphorus compounds is required.

The requirements for reducing the total content of organosulfur in motor fuels (10 ^-4 -10 ³ %) and in catalytic processes (below 10 ^-4 %) are increasing more and more.

Standardized methods, such as the American Standard Material Testing Methods - ASTM (see "A5TM, General Testing Methods"), used to determine the total content of S- and Cl-organic compounds (such as the total S and Cl) in petroleum products and various hydrocarbons are used for sequential, but not simultaneous determination of these elements and the selective determination of total O, Br and I is impossible - the results are calculated as total Cl, which is generally not true.

ASTM methods (D5808) based on high-temperature oxidative conversion and microcoulometric titration of the resulting HCl are used to determine the total Cl in oil and in refined products. A significant limitation of this method is the instability of the characteristics of the titration cell and the difficulty of working with it.

ASTM methods (D3961, D324) used to determine the total S in the same objects, based on high-temperature oxidative conversion and microcoulometric titration of SO ₂ , are even more complex compared to the corresponding methods used to determine the total Cl. Additional difficulties arise in connection with the formation, along with SO ₂ and SO ₃ , which is not titrated and not determined, the SO ₂ / SO ₃ ratio does not remain constant and depends on the matrix, conversion conditions, and the rate of introduction of the sample into the reactor. The concentration limits of detection in determining the total S and O are (0.5-1) · 10 ^-4 %.

Known ASTM method (D6428) for the determination of total sulfur in oil, motor fuels, based on high-temperature oxidative conversion and electrochemical detection, the detection limit is 5 · 10 ^-6 %. Known ASTM method (D5453), based on the high-temperature oxidative conversion to SO ₂ , and its determination using UV fluorescence. The detection limit of the method is (2-5) · 10 ^-6 %, depending on the source of UV radiation.

A review of the literature and existing ASTM methods showed that currently only one method is known that allows the simultaneous determination of the total content of F-, Cl-, Br- and S-organics in oil and its refined products. The method is the basis of ASTM method WK2513, which has not yet received practical application. It is based on high-temperature conversion in a stream of a mixture of argon, oxygen and water vapor (added to ensure the complete conversion of halogen-containing compounds). The conversion products are absorbed in the absorber with deionized water and a small part of the absorbate (2-5%) is analyzed by gradient chromatography ion chromatography. The volume of sample introduced into the reactor is 80-240 μl, with a detection limit of 5 · 10 ^-10 -10 ^-4 %. An advertisement for the AQF-100 device (sample preparation and high-temperature conversion unit for combination with an ion chromatograph) mentions the possibility of simultaneously determining the total content of F-, Cl-, Br-, I- and S-organic compounds in oils and refined products, however, the combination results with ion chromatograph not shown. This method can serve as a prototype of our proposed method. There are no known works or ASTM methods for determining the total content of phosphorus-containing compounds in oil products and other mixtures of hydrocarbons and along with the total content of F-, Cl-, Br-, I-, S- and P-organic compounds. Significant disadvantages of the prototype are the introduction into the reactor of large volume samples (80-240 μl) into the stream of a mixture of argon and oxygen (flow rates of 200 and 500 ml, respectively) and water vapor and selection for ion chromatographic analysis of only 2-5% of the absorbate. As a result, the detection limits for such large analyzed samples are substantially increased, and there is a risk of soot formation in the reactor due to pyrolysis in a mixture of argon and oxygen. In addition, the use of gradient elution significantly increased the analysis time, compared with the possible isocratic elution. Apparently for these reasons, the ASTM method (WK2513) has not found practical application until now, although it was approved in 2002. For the above reasons, it is very relevant to develop a simultaneous determination of the total content of F-, Cl-, Br-, I-, S- and P-organic compounds in petroleum refined products and various hydrocarbons at an ultralow level and oils.

The aim of this study was to develop a highly sensitive method for simultaneously determining the total content of F-, Cl-, Br-, I-, S- and P-organic compounds in oil refining products and oils. When implementing the method, the detection limit of the total content of the elements in question is reduced and the analysis time is reduced.

A method for simultaneously determining the total content of F-, Cl-, Br-, I-, S- and P-organic compounds in oil and oil refining products according to the present invention includes introducing a sample into a reactor and carrying out a high-temperature oxidative conversion using oxygen, absorption of conversion products deionized water, free from detectable elements, and analysis of the resulting solution by ion chromatography. The difference between the proposed method and the known one is that the high-temperature oxidative conversion is carried out in a stream of pure oxygen, after absorption of the conversion products in the absorber by deionized water, the oxygen formed in the CO ₂ process is blown away by a stream of oxygen or by supplying an inert gas to the absorber, which is additionally supplied to the absorber. The entire volume of absorbate is introduced through a protective column and a concentration column connected to it, most of the water is displaced by eluent from both columns, and then the anion concentrate formed as a result of absorption of the conversion products by water is transferred to the analytical column by the same eluent, and water and anions corresponding to elements by ion chromatography in isocratic conditions.

In order to increase the accuracy of determination, an organic compound containing an element that is absent in the analyzed sample is added at a known concentration to a sample of the analyzed sample before entering it into the rector, if necessary.

In order to ensure a more complete determination of the total content of F-, Cl-, Br-, I-, S- and P-organic compounds after absorption of the conversion products of F-, Cl-, Br-, I- and S- organic compounds in the absorber in if necessary, the reactor is injected with a sample of deionized water, free of the elements to be determined, the products of phosphorus oxidation are washed off the walls of the reactor into the absorber, the obtained absorbate is purged with inert gas in order to accelerate the blowing of CO ₂ and the resulting absorbate is analyzed by ion chromatography. In order to simplify the process, a disposable syringe, for example a microsyringe, is used as an absorber.

It is desirable to maintain the feed rate of the sample and oxygen flows such that the formation of soot on the walls of the reactor is excluded and the conversion products are completely transferred to the absorber and absorbed therein.

The analysis procedure and its features

1. A brief description of the installation, which determines the total content of F-, Cl-, Br-, I-, S- and P-organic compounds in oil products

The installation consists of a high-temperature furnace, a flowing quartz reactor with a removable absorber at its outlet, an ion chromatograph with a protective and concentrating column.

2. The procedure for determining the total content of F-, Cl-, Br-, I-, S- and P-organic compounds in oil products and oil

A liquid sample of the corresponding oil product is taken using a microsyringe, a sample is introduced into the reactor in a continuous stream of pure oxygen. The temperature inside the reactor is about 950 ° C. When an analyte in a known concentration of an organic substance containing an element that is not present in the sample is added to the sample before being introduced into the reactor, the accuracy of the determination increases further. The usual sample volume is 1 μl. The products of high-temperature oxidative conversion are absorbed with deionized water, which is free of the elements to be determined in the absorber, supplied with an inert gas stream or increased oxygen flow in order to accelerate the blowing off of dissolved CO ₂ . At this time, a sample of deionized water is introduced into the reactor and residues of phosphorus oxidation products are adsorbed from the walls of the reactor into the adsorber. After the purge is completed, the entire absorbate volume is passed through a protective column and a concentration column connected to it, most of the water is displaced from both columns with an eluent and the whole concentrate of anions formed as a result of absorption of the products of oxidative conversion is transferred to the analytical column, and water and anions are separated corresponding to the determined elements by ion chromatography under isocratic conditions.

In the case of analysis of gaseous oil products, an analyzed sample is taken with a syringe and introduced into the reactor in an oxygen stream. The usual sample volume is 5-10 cm, then the above operations are carried out. When analyzing solid refined petroleum products or oils, the sample taken and suspended in the boat is introduced into the colder zone of the reactor in an oxygen stream, followed by the boat moving to the hot zone and the operation described above is carried out.

In the analysis of oils, the injection of the sample is also carried out using a microsyringe into the cold zone of the reactor in an oxygen stream, followed by moving the reactor to the hot zone of the furnace.

At the same time, the feed rate of the sample and oxygen flows are monitored to prevent the formation of soot on the walls of the reactor and to ensure the complete transfer of the conversion products to the absorber and their absorption in it. Before starting experiments on high-temperature oxidative conversion, the ion chromatograph is calibrated using the determined anions F-, Cl-, Br-, I-, SO ₄ ^2- and НРО ₄ ^2- .

The invention can be illustrated by the following specific examples.

Example 1

In accordance with the described procedure, the degree of conversion of a number of fluorine, chlorine, bromine, iodine, sulfur, and phosphorus-containing organic compounds was studied. The study was carried out using model solutions in hexane and methanol (depending on the substance). The volume of sample introduced into the reactor left 1 μl and the analyte concentration in the solution was 10 ^-9 -10 ^-6 g / μl.

The data obtained for a number of compounds studied are shown in Table 1.

Table 1 Title The degree of conversion,% 10 ^-6 g 10 ^-8 g Heptafluorobutanol 97 ± 5 95 ± 6 Tetrafluorobromobenzene 95 ± 6 97 ± 5 Hexafluorobenzene 99 ± 6 96 ± 5 Carbon tetrachloride 99 ± 4 97 ± 5 Tetrachloroethane 96 ± 4 99 ± 5 Hexachlorobenzene (HCB) 96 ± 8 102 ± 6 Dibromomethane 97 ± 5 98 ± 5 Bromoform 99 ± 5 101 ± 4 Tetrabromoethane 100 ± 5 95 ± 6 Triethyl phosphate 95 ± 7 98 ± 6 Tributyl phosphonate 95 ± 6 95 ± 5 Tributyl phosphate 105 ± 6 95 ± 7 Octyl mercaptan 96 ± 7 96 ± 6 Dihexyl sulfide 96 ± 6 95 ± 5 Thiophene 98 ± 4 95 ± 6 4-iodophenol 97 ± 3 96 ± 5 1,4-diiodobenzene 98 ± 4 97 ± 5 Iodoacetic acid 96 ± 5 97 ± 6

As can be seen from the data in Table 1, the degree of conversion is about 100% for both 10 ^-6 g and 10 ^-8 g.

Example 2

In accordance with the described procedure, the analysis of 4 samples of diesel fuel. The sample volume is 1 μl.

The results are shown in Table 2.

table 2 Analysis of diesel fuel samples for the total content of F-, C1-, Br-, I-, S- and P-organic compounds (n = 3-5, P = 0.95, Sr 7-10%) Sample The content of elements in the original sample,% F Cl Br R S I one ≤1.3 × 10 ^-6 4.7 × 10 ^-4 ≤5.1 × 10 ^-6 ≤2.0 × 10 ^-5 3.4 × 10 ^-2 ≤1.9 × 10 ^-5 2 ≤1.3 × 10 ^-6 3.2 × 10 ^-4 ≤5.1 × l0 ^-6 ≤2.0 × 10 ^-5 0.3 × 10 ^-2 ≥1.9 × 10 ^-5 3 ≤1.3 × 10 ^-6 2.4 × 10 ^-4 ≤5.1 × 10 ^-6 ≤2.0h10- ⁵ 2.3 × 10 ^-2 ≤1.9 × 10 ^-5 four ≤1.3 × 10 ^-6 3.6 × 10 ^-4 ≤5.1 × 10 ^-6 ≤2.0 × 10 ^-5 0.9 × 10 ^-2 ≤1.9 × l0 ^-5

As can be seen from the table, the total content of organo-sulfur was (0.3-3.4) · 10 ^-2 %, and organochlorine was (2.4-4.7) · 10 ^-4 %, depending on the sample.

Example 3

Using the same analysis procedure, a number of benzene samples of various degrees of purity were studied for the content of F-, Cl-, Br-, I-, S- and P-organics. The data obtained are shown in Table 3.

Table 3 Analysis of benzene samples for the total content of halide, S and P organic compounds (n = 3-5, P = 0.95, Sr 7-10%) Sample The content of elements in the original sample,% F Cl Br R S I Benzene <1.3 × 10 ^-6 ≤2.1 × 10 ^-6 ≤5.1 × 10 ^-6 ≤2.0 × 10 ^-5 3.7 × 10 ^-4 ≤1.9 × 10 ^-5 one <1.3 × 10 ^-6 ≤2.1 × 10 ^-6 ≤5.1 × 10 ^-6 ≤2.0 × 10 ^-5 1.9 × l0 ^-4 ≤1.9 × 10- ⁵ 2 <1.3 × 10 ^-6 ≤2.1 × 10 ^-6 ≤5.1 × 10 ^-6 ≤2.0 × 10 ^-5 1.3 × 10 ^-4 ≤1.9 × 10 ^-5 3 <1.3 × 10 ^-6 ≤2.1 × 10 ^-6 ≤5.1 × 10 ^-6 ≤2.0 × 10 ^-5 0.6 × 10 ^-4 ≤1.9 × 10 ^-5

From the above data it can be seen that the total sulfur content was (0.6-3.7) -10 ^-4 % depending on the sample.

Example 4

The assessment of the correctness of the proposed method was carried out by the "entered-found" method using artificial mixtures prepared using the studied samples of diesel fuel (Table 4) and benzene (Table 5). The analysis of artificial mixtures was carried out in accordance with the described analysis procedure.

Table 4 Verification of the analysis of the proposed method by the method of "entered-found" for artificial mixtures based on diesel fuel The content of elements in the artificial mixture, 10 ^-2 % Introduced Found F Cl Br R S I F Cl Br R S I 3.0 4.2 5.7 10.2 8.1 9.3 2.9 4.1 5.7 10.5 7.9 8.8 2.1 4.5 4.9 12.3 3.6 10.5 2.0 4.5 5.0 12.4 3.9 9.9 4.2 4.5 4.9 8.9 6.7 9.8 4.1 4.7 5.0 8.6 6.5 10.0 2.5 2.5 2.6 9.8 4.9 9.9 2.4 2.5 27 9.9 5.2 9.9

As can be seen from table 4, the definition is correct, since the discrepancy does not exceed the experimental error.

Table 5 Verification of the analysis of the proposed method by the method of "entered-found" artificial mixtures based on the studied samples of benzene The content of elements in the artificial mixture, 10 ^-4 % Introduced Found F Cl Br R S I F Cl Br R S I 2.0 3.2 9.5 19.1 9.5 1.9 3.2 9.8 19.9 9.8 2.8 2.9 10.3 7.7 8.8 2.6 2.8 10.1  7.9 8.7 4.3 4.5 9.8 9.3 10.2 4.4 4.3 9.8 9.1 10.9 2.5 3.5 9.9 8.5 11.4 2.6 3.6 9.8 8.5 8.7

From the above data it can be seen that the definition is correct, since the discrepancy between the "entered-found" is within the experimental error.

Claims (5)

1. A method for simultaneously determining the total content of F-, Cl-, Br-, I-, S- and P-organic compounds in oil and oil refining products, based on the introduction of a sample into the reactor, high-temperature oxidative conversion using oxygen, absorption of conversion products deionized water, free from analyte elements, and analysis of the resulting solution by ion chromatography, characterized in that the high-temperature oxidative conversion is carried out in a stream of pure oxygen after absorption in the product absorber of conversion of deionized water, blow off the oxygen formed during the CO ₂ process or by supplying an additional inert gas stream to the absorber, the entire volume of absorbate is introduced through the protective column and the concentrating column connected to it, most of the water is eluated from both columns and then transferred with the same eluent in the analytical column, a concentrate of anions formed as a result of the absorption of the conversion products by water is used to separate water and anions corresponding to the elements being determined by the ion XP method omatography in isocratic conditions. 2. The method according to claim 1, characterized in that an organic compound containing an element that is not present in the analyzed sample is added to the sample of the analyzed sample before entering it into the reactor. 3. The method according to claim 2, characterized in that the feed rate of the sample and oxygen flows are such that the formation of soot on the walls of the reactor is excluded and the complete transfer of the conversion products to the absorber and their absorption in it is ensured. 4. The method according to claim 1, characterized in that after absorption of the products of the conversion of P-, Cl-, Br-, I- and S-organic compounds in the absorber, a sample of deionized water free of the elements to be determined is introduced into the reactor, washed from the walls of the reactor phosphorus oxidation products into the absorber, purge the obtained absorbate with an inert gas in order to accelerate the blowing of CO ₂ and the resulting absorbate is analyzed by ion chromatography. 5. The method according to claim 4, characterized in that a disposable syringe is used as an absorber.