RU2304281C1 - Method for determining amount of detersol-140 additive in motor oils for automobiles - Google Patents

Abstract

FIELD: technology for controlling quality of motor oils using optical means, in particular, detection of additives in motor oils.

SUBSTANCE: method includes taking a sample, measuring optical density in absorption bands 1604 and 2000 cm^-1 during spectrophotometry and following calculation of additive concentration using an experimentally derived formula.

EFFECT: expanded nomenclature of motor oil additives detectable by infrared spectroscopy, and also, possible identification of Detersol-140 only and determining of its amount only, as opposed to total content of all additives present in motor oil.

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Description

The invention relates to the field of quality control of motor oils using optical means, in particular to methods for determining the quantitative composition, mainly for determining additives in motor oils, and may find application in analytical laboratories, laboratories of oil refineries, and forensic science.

Due to the fact that in modern internal combustion engines of automotive vehicles more tense conditions have appeared than before (high boost, heavy loading, etc.), stringent requirements are imposed on engine oils for their operational properties, to ensure which the engine oil add a certain amount of various functional additives (antioxidant, detergent-dispersant, etc.). When the concentration of the additive decreases, the oil quality level decreases.

Determining not only the presence, but also the amount of additives is an important task, since they determine the reliability of the engine. One of the additives that improve the washing-dispersing properties of motor oil is Detersol-140, the amount of which in the oil should be from 2 to 3.5 wt.%. Additive Detersol-140 is a solution of carbonated calcium alkyl salicylate obtained by treating calcium alkyl salicylate with gaseous carbon dioxide in the presence of a promoter and an excess (against stoichiometry) of calcium hydroxide. (Fuels, lubricants, technical fluids. Assortment and application. Handbook / I.G. Anisimov, K.M. Badyshtova, S.A. Bnatov et al .; edited by V.M. Shkolnikov. Ed. 2nd . - M .: Publishing Center "Techinform", 1999 S. 450-451).

The authors were faced with the task of developing a method for determining the amount of Detersol-140 additive in motor oils for automotive vehicles. When viewing patent information and scientific and technical literature, the following was revealed.

There is a method of determining additives in oils by the value of the "alkaline number", including potentiometric titration with an alcoholic solution of potassium hydroxide (GOST 11362-96. Petroleum products and lubricants. The number of neutralization. Potentiometric titration method).

The disadvantages of this method is that the additives are determined not deferred, but in total, and their content is judged indirectly, based on the fact that the higher the alkaline number, the higher the concentration of additives.

There is also a method for determining the active elements (barium, calcium and zinc) that are part of oil additives in the form of metal salts, including the decomposition of metal salts with hydrochloric acid and complexometric titration of barium, calcium and zinc (GOST 13538-68 Additives and oils with additives. Method determination of barium, calcium and zinc by complexometric titration).

The disadvantage of this method is that only the active elements of the additives are determined, while the additives also consist of the organic part (for example, carbonated alkyl salicylates).

It is known that all alkyl salicylates in the IR spectrum are characterized by the presence of an absorption band in the range of 1640-1530 cm ^-1 (Kazitsina L.A., Kupletskaya M. B. Application of UV, IR, NMR spectroscopy in organic chemistry. M.: Moscow State University Lomonosov, Khimfak. 1968, p.105). Given that Detersol-140 contains carbonated calcium alkyl salicylate in its composition, the authors, when studying the quality of motor oils with this additive, revealed an absorption band for it of 1604 cm ^-1 , which is in a known range.

The closest in technical essence and taken as a prototype is an IR spectroscopic method for determining the content of polyalkyl methacrylates in depressant additives to petroleum products, including the preparation of samples with a known ratio of polymer, monomer and diesel fuel, the content of which in all artificial mixtures is 50 wt.%.

The infrared spectrum of the analyzed sample is removed in the range of 1850-1050 cm ^-1 and optical densities are measured on the bands of 1735 cm ^-1 and 1170 cm ^-1 . Passing the baseline through the points of 1735 cm ^-1 and 1170 cm ^{-1 of the} zero line of the spectrum and measuring the corresponding segments, calculate the concentration of the additive:

With _P = 6731lgD ₁₇₃₅ / D ₁₁₇₀ -85 (for With _P from 0 to 60 wt.%) Or

With _P = 2051lgD ₁₇₃₅ / D ₁₁₇₀ +18.2 (for With _P from 60 to 100 wt.%).

(Methods of analysis, research and testing of oils and petroleum products (non-standard methods), part 2, Moscow: VNIINP, 1984, p. 285-287).

The disadvantage of this method is the limited list of additives, the determination of which is possible. In addition, the method is long because of the intermediate calculation of optical densities and the use of different numerical coefficients in determining the concentration of the additive in two ranges.

The technical result of the invention is the expansion of the range determined by infrared spectroscopy additives for motor oils.

The specified technical result is achieved by the fact that in the method for determining the amount of detergent Detersol-140 in motor oils for automotive vehicles, including sampling, spectrophotometry, measuring optical density at given wavelengths and subsequent calculation of the concentration of the additive according to the mathematical dependence, according to the invention, the value of optical the density is measured in the absorption bands of 1604 cm ^-1 and 2000 cm ^-1 , and the concentration of the additive is determined by the following relationship

,

,

where C is the concentration of the additive, wt.%;

ΔD = D ₁₆₀₄ -D ₂₀₀₀ , the difference in optical density;

D ₁₆₀₄ is the optical density of the absorption band of 1604 cm ^-1 ;

D ₂₀₀₀ is the optical density of the absorption band of 2000 cm ^-1 ;

a = 0.1643 constant experimentally obtained coefficient;

b = 0.0225 constant experimentally obtained coefficient.

To substantiate the distinguishing feature, samples were prepared that were engine oil compositions with various concentrations of Detersol-140 additive (Table 1).

All artificially prepared samples are examined on an AF-1 IR Fourier spectrometer with a resolution of 2 cm ^-1 , in the wavelength range from 4000 to 450 cm ^-1 in a KCl cuvette with a thickness of 0.1 mm at a temperature of 20 ± 2 ° C of the sample.

Table 1 The composition of the samples, wt.% Components Sample No. 1 Number 2 Number 3 Number 4 Number 5 Additive Detersol-140, wt.% 2 2,5 3 3,5 four M-6z / 10V brand engine oil: I-40a, wt.% 91.5 91.0 90.5 90.0 89.5 With additives: DF-11, wt.% 2 2 2 2 2 PMA "D", wt.% 1,5 1,5 1,5 1,5 1,5 KND, wt.% 3 3 3 3 3

Optical densities D ₁₆₀₄ and D _{2000 are} measured. An absorption band of 2000 cm ⁻¹ is taken to determine the background of the sample. The difference in the optical densities of the absorption bands of 1604 cm ^-1 and 2000 cm ^{-1 is} determined for each sample. Build a graph of the dependence of the difference in optical density on the concentration of the additive. For the Detersol-140 additive, the graph of the dependence of the difference in optical densities on its concentration has the form of a straight line and can be represented by the equation: ΔD = a + bC, where ΔD = D ₁₆₀₄ -D ₂₀₀₀ . By mathematical processing of experimental data, the authors obtained the values of constant coefficients: a = 0.1643; b = 0.0225, which made it possible to obtain the formula for calculating the concentration of Detersol-140 additive in engine oil:

Substituting the numerical values of the constant coefficients “a” and “b” determine the concentration of the additive in the engine oil.

The data obtained are in good agreement with the Bouguer-Lambert-Beer law, which expresses the relationship between the optical density and the concentration of the absorbing substance (Kazitsina L.A., Kupletskaya MB, Application of UV, IR, NMR spectroscopy in organic chemistry. M.: Lomonosov Moscow State University Khimfak. 1968, p. 10).

Having determined the characteristic absorption band of 1604 cm ^{-1 of the} Detersol-140 additive and obtained the mathematical dependence of its concentration on the difference in optical densities, the authors investigated samples of M-6z / 10-V motor oil, into which the Detersol-140 additive was added in a certain amount, samples No. 6, 7, 8 (a portion of the additive was weighed on a VLR-200 balance with a division value of 0.05 mg, providing a measurement error of 0.010 mg). The results are presented in table.2.

table 2 The results of the study of samples of motor oil M-6z / 10-B with the introduced additive Detersol-140. Engine oil sample Number 6 Number 7 Number 8 The concentration of engine oil M-6z / 10-B, wt.% 97.9575 96.9605 95.9562 Detersol-140 additive concentration in the sample, wt.% 2,0425 3,0395 4,0438 Measured
options D ₁₆₀₄ 0.261 0.282 0,308 D ₂₀₀₀ 0,050 0.051 0,052 Asked
options but 0.1643 b 0.0225 Estimated
options ΔD 0.211 0.231 0.256 C, wt.% 2,0755 2,9644 4.0755

The obtained concentration values of the claimed method provide the necessary accuracy of measuring the concentration of the additive Detersol-140. Deviations in the concentration of the additive are within the acceptable range.

Thus, the invention extends the range of additives determined by infrared spectroscopy of additives for motor oils and allows only the Detersol-140 additive in motor oils for automotive vehicles to be identified and its quantity, not the total content of all additives present in the motor oil, and not its active elements. Given that the performance of the additive in engine oil is affected not only by the content of active elements, but also by the organic part of the additive (alkyl salicylate), the content of which has not been previously taken into account, the invention is relevant for assessing the performance of engine oils containing the Detersol-140 additive.

Claims (1)

A method for determining the amount of Detersol-140 additive in motor oils for automotive vehicles, including sampling, spectrophotometry, measuring optical density at certain wavelengths and then calculating the concentration of the additive by mathematical dependence, characterized in that the optical density is measured in absorption bands 1604 during spectrophotometry cm ^-1 and 2000 cm ^-1 , and the concentration of the additive is calculated according to the following relationship:

, where C is the concentration of the additive, wt.%; ΔD = D ₁₆₀₄ -D ₂₀₀₀ , the difference in optical density; D ₁₆₀₄ is the optical density of the absorption band of 1604 cm ^-1 ; D ₂₀₀₀ is the optical density of the absorption band of 2000 cm ^-1 ; a = 0.1643 constant experimentally obtained coefficient; b = 0.0225 constant experimentally obtained coefficient.