RU2723974C1 - Method of determining content of anti-wear additives based on fatty acids in diesel fuel - Google Patents

Abstract

FIELD: quality control.SUBSTANCE: invention relates to the field of diesel fuel quality control mainly for determination of anti-wear additives based on fatty acids. Method for determining the amount of an anti-wear additive based on fatty acids in diesel fuels involves sampling, infrared spectrometry and subsequent determination of the concentration of the additive on a calibration curve plotted in coordinates of the height of the peak at the wave number of 1,710 cmis the concentration of the additive, before infrared spectrometry, a chromatographic column is filled with 1 g of sorbent, which is silica gel with particle size of 40–100 mcm, pore diameter of 60, is wetted with hexane and 50 cmof fuel sample is passed, creating vacuum of 13–40 mbar, followed by additionally successively passing through sorbent 2 cmof hexane, then 10 cmof ethanol, collecting the extracts in different containers, ethanol extract after transmission is maintained at temperature of 50–60 °C and vacuum of 10–15 mbar for 5 minutes, after which the volume was adjusted to 5 cmof tetrachloromethane, and the resulting solution was subjected to IR spectrometry.EFFECT: wider range of methods for determining additives in diesel fuel.1 cl, 1 dwg, 10 tbl

Description

The invention relates to the field of quality control of diesel fuels using IR spectrometry, mainly for determining the content of anti-wear additives in diesel fuels (hereinafter - DT), and can find application in analytical laboratories, laboratories of petroleum product supply enterprises.

The need for hydrotreatment of diesel fuels has led to the deterioration of some operational properties, one of which is the lubricity. The use of fuels as a lubricant for rubbing pairs of plunger fuel pumps, locking needles, pins, etc., avoids the construction of an additional oil system on diesel engines, provides lubrication of fuel supply and fuel control equipment (TPA), where it is very difficult to apply lubricating oils.

Antiwear additives are used to restore the lubricating properties of diesel fuel. The use of anti-wear additives in the composition of the diesel fuel allows to reduce wear of the TPA friction pairs.

At present, antiwear additives for diesel engines are approved for use in both domestic production: GT-16 (Gamma Additive LLC), Complex-ECO "D", etc., and foreign production: Kerokorr LA 99C (BASF), Hitec 4140A (Afton Chemical Corporation), KOLTEK DS 7739, etc. Most of the foreign and domestic antiwear additives contain fatty acids of tall oils with various additives as active components (1 - E. Burov. Study of the effectiveness of functional additives in diesel fuels of various hydrocarbon composition : Candidate of Chemical Sciences: 02.00.13. M., 2015. p. 18). The content of fatty acids in additives can vary from 50 to 80% (2 - Pat. RF 2401861 C01L 1/08 publ. 20.10.2010.)

Fatty acids are organic compounds with the general formula RCOOH, where R - represents an alkyl or alkenyl group. The most common fatty acids are palmitic, stearic, oleic and linoleic acids (Roberte J., Caserio M. Fundamentals of Organic Chemistry. Translated from English by Yu.G. Bundel. Publisher: Mir. M. 1978. p. 537.).

Effective concentrations of antiwear additives depend on the composition of the fuel and range from 0.005 to 0.05% wt. The amount of additive is increased as the sulfur content of the fuel decreases (2 - Danilov A.M. Reading book on oil refining. St. Petersburg: Khimizdat, 2012, p. 217).

However, an excess of fatty acids added to diesel fuel as part of anti-wear additives negatively affects the oxidative stability of the fuel, contributing to the acceleration of the oxidation process, which in turn leads to an increase in the formation of deposits (2 - Zinin V.D., Romanovskaya AB, Zinina N .D., Shchepalov AA, Grishin DF The influence of some heteroatomic organic compounds on the thermooxidizing properties of highly hydrotreated diesel fuel // Vestnik Nizhegorodskogo universiteta. 2012. V. 7, No. 5. P. 75-81.).

In this regard, to increase the reliability of TPA operation, it is necessary to control the quantitative content of antiwear additives based on FA in diesel fuel with an error of not more than 0.0015% of the mass

The authors were faced with the task of developing a method for determining the amount of antiwear additives based on FAs in diesel fuel that meets the following requirements:

- repeatability limit of not more than 0.0010% wt .;

- the minimum detection limit of antiwear additives of 0.005% wt.

When analyzing the sources of patent and scientific and technical information, to date, no methods have been identified for determining the antiwear additives based on fatty acids in diesel fuel with a repeatability of not more than 0.0010% wt. and with a minimum detection limit of not more than 0.005% wt.

A known method of determining the anti-wear additive Hitec 4140 in diesel fuel, which is determined by IR spectrometry using cuvettes with windows of potassium bromide 0.57 mm thick, according to the intensity of stretching vibrations of the carboxyl group in the region of 1710 cm ^-1 , with a minimum concentration of anti-wear additive 0, 0185% wt. (3 - Nechaev A.N., Tolstykh O.V., Martynova M.V. Determination of the content of depressant-dispersing, anti-wear and cetane-enhancing additives in diesel fuel by infrared spectrometry // Oil Refining and Petrochemicals 2008. No. 8. P. 42-44. )

However, this method is insensitive to the content of antiwear additives less than 0.018% wt. due to limitations in the detection limit of IR spectrometers using cuvettes 0.57 mm thick.

There is also a method for determining the antiwear additive Hitec 580 in jet fuels, in which the active components of the additive, dimers of fatty acids, are concentrated by vacuum distillation of 95-98% of fuel (4 - RF Pat. 2593767 G01N 21/35 publ. 10.08.16 .)

However, this method has a limitation - only for fuels for jet engines. It is not possible to concentrate FA antiwear additives in diesel fuel by vacuum distillation of the fuel, since the boiling points of FA are close to the boiling temperatures of hydrocarbons of diesel fuel.

The closest in technical essence and taken as a prototype is a method for determining the anti-wear additive Baykat in diesel fuel by IR spectrometry, including alkaline extraction of the LCD anti-wear additive from diesel oil with a solution of potassium hydroxide with a concentration of 1 mol / dm ³ , subsequent neutralization of the aqueous layer with a solution of hydrochloric acid and repeated extraction carbon tetrachloride, evaporation of the solvent and IR spectrometric determination of the concentration of the additive by optical density in the absorption band of 1710 cm ^-1 . (5 - Volegova A.Yu., Glazkova M. S. Determination of antiwear, cetane enhancing and depressant dispersing additives in diesel fuel by IR spectrometry // Oil Refining and Petrochemicals. 2019. No. 3. P. 29-33. - prototype).

The disadvantage of this method is the formation, at the stage of alkaline extraction, of a stable emulsion of diesel fuel with an aqueous alkaline solution under the action of potassium salts of fatty acids. The separation of this emulsion requires a long time, especially at concentrations of antiwear additives more than 0.02% wt. in DT.

The technical result of the invention is the expansion of the range of methods for determining antiwear additives based on FAs in diesel fuel with the elimination of the possibility of the formation of a stable emulsion through the use of a combination of solid phase extraction and IR spectrometry.

, смачивают гексаном и пропускают 50 см³ пробы топлива, создавая разрежение 13-40 мбар, после чего дополнительно последовательно пропускают через сорбент 2 см³ гексана, затем 10 см³ этанола, собирая экстракты в разные емкости, экстракт после пропускания этанола выдерживают при температуре 50-60°С и вакууме 10-15 мбар в течение 5 мин, по окончании которых доводят до объема 5 см³ тетрахлорметаном и полученный раствор подвергают ИК-спектрометрированию.The specified technical result is achieved by the fact that in the known method for determining the amount of anti-wear additives based on fatty acids in diesel fuels, including sampling, IR spectrometry and subsequent determination of the concentration of the additive according to a calibration graph constructed in coordinates of the peak height on the wave number of 1710 cm ^-1 - the concentration of the additive, according to the invention, before IR spectrometry, the chromatographic column is filled with 1 g of sorbent, which is used as silica gel, with a particle size of 40-100 μm, pore diameter 60

, moistened with hexane and passed 50 cm ³ fuel samples, creating a vacuum of 13-40 mbar, then additionally sequentially passed through a sorbent 2 cm ³ hexane, then 10 cm ³ ethanol, collecting the extracts in different containers, the extract after passing ethanol is kept at a temperature of 50 -60 ° C and a vacuum of 10-15 mbar for 5 min, after which they are brought to a volume of 5 cm ^{3 with} carbon tetrachloride and the resulting solution is subjected to IR spectrometry.

, количество сорбента - 1 г, элюент для десорбции жирных кислот - этанол, объем элюента, необходимый для десорбции 99±3% жирных кислот - 10 см³) и ИК-спектрометрирование на волновом числе 1710 см^-1. Определение количества противоизносной присадки на основе жирных кислот осуществляется по градуировочному графику.The technical essence of the invention lies in the fact that they use a combination of solid-phase extraction to isolate and concentrate FA (type of sorbent is silica gel with a particle size of 40-100 μm and a pore diameter of 60

, the amount of sorbent is 1 g, the eluent for desorption of fatty acids is ethanol, the volume of eluent required for the desorption of 99 ± 3% fatty acids is 10 cm ³ ) and IR spectrometry at a wave number of 1710 cm ^-1 . The determination of the amount of antiwear additives based on fatty acids is carried out according to the calibration schedule.

The figure 1 shows a calibration graph in coordinates: the height of the peak on the wave number of 1710 cm ^-1 h, is the concentration of antiwear additives (C), based on the results of testing artificially prepared samples, 1 - for additives Complex-ECO "D", 2 - KOLTEK DS 7739.

To confirm the achievement of the indicated technical result, samples (Table 1) of diesel fuels were prepared on the basis of a hydrotreated fraction of 180-320 ° C with the addition of an anti-wear additive, as a variant of GT-16, the amount of which corresponded to the concentration limits admissible by the production technology.

The obtained samples (table. 1) were tested to justify the set of essential features of the method set forth in the claims, namely:

, количество сорбента - 1 г, элюент для десорбции жирных кислот -этанол, объем элюента, необходимый для десорбции 99±3% жирных кислот - 10 см³, температура и вакуум, при котором проводят концентрирование этанольного экстракта - 50°С и 10-15 мбар, время нагревания этанольного экстракта 5 мин.optimal parameters of solid-phase extraction and additive concentration: type of sorbent - silica gel with a particle size of 40-100 μm and a pore diameter of 60

, the amount of sorbent is 1 g, the eluent for desorption of fatty acids is ethanol, the volume of eluent required for the desorption of 99 ± 3% fatty acids is 10 cm ³ , the temperature and vacuum at which the ethanol extract is concentrated are 50 ° C and 10-15 mbar, the heating time of the ethanol extract is 5 minutes

The optimal parameters of TFE and additive concentration were established experimentally.

Sorbent selection

Studies on the selection of sorbent for solid phase extraction (TFE) were carried out using concentrated solutions of 0.5% wt. GT-16 anti-wear additive in diesel fuel, which made it possible to record a change in the concentration of LC on an IR spectrometer; the sample volume in this case was 10 cm ³ .

(активность I), оксид алюминия с размером частиц 40-100 μм диаметром пор 60

(активность I), силикагель с размером частиц 40-100 μм и диаметром пор 60

оптимальным сорбентом является силикагель с размером частиц 40-100 μм и диаметром пор 60

(табл. 2 настоящего описания).As the sorbents were investigated: aluminum oxide with a particle size of 250-500 μm and a pore diameter of 60

(activity I), alumina with a particle size of 40-100 μm pore diameter 60

(activity I), silica gel with a particle size of 40-100 μm and a pore diameter of 60

the best sorbent is silica gel with a particle size of 40-100 μm and a pore diameter of 60

(table. 2 of the present description).

1.5 g of adsorbent was poured into a glass chromatographic column with a diameter of 10 mm, 200 mm high, and a porous plate to retain the stationary phase (adsorbent) and compacted with a light tap on a cork or rubber stopper for 5 min. A layer of glass wool 2-3 mm high was introduced on top of the sorbent, which was sealed with a glass rod to prevent swelling of the sorbent when pouring the eluent (according to standard method 6 - GOST 15886-70. Petroleum oils. Method for determination of resins).

To determine the degree of adsorption of fatty acids, 10 cm ³ test fuel containing 0.5% wt. GT-16 antiwear additives were passed through a chromatographic column filled with a sorbent according to the method described above. The IR spectrum of the fuel passing through the sorbent was recorded on a Nikolet 6700 IR spectrometer (Thermo Scientific), with a spectral range from 4000 to 450 cm ^-1 , a resolution of 1 cm ^-1 and a photometric error of not more than 1%, using an absorption tight cuvettes with potassium bromide windows and a nominal path length of 0.5 mm.

The concentration dependence of the determined fatty acid concentration in the fuel. The degree of adsorption was calculated by the formula 1:

C ₁ is the concentration of fatty acids in the original fuel,

C ₂ is the concentration of fatty acids in the fuel passed through the sorbent.

To determine the degree of desorption of fatty acids, 10 cm ^{3 of the} test fuel was passed through a chromatographic column filled with a sorbent. Then the sorbent was washed with 15 cm ^{3 of} methanol, the methanol extract was collected and methanol was distilled from it on a rotary evaporator at a temperature of 50 ° C and a vacuum of 10-15 mbar. The distillation residue was transferred to a 10 cm ³ volumetric flask and brought to standard volume with carbon tetrachloride. Conducted IR spectrometry of the resulting solution. The concentration dependence of the determined fatty acid concentration. The degree of desorption was calculated by the formula 2:

C ₁ is the concentration of fatty acids in the original fuel,

C ₂ is the concentration of fatty acids in the fuel passed through the sorbent.

C ₃ is the concentration of fatty acids in the solution obtained after desorption of FA from the sorbent, brought to a standard volume (10 cm ³ ) with carbon tetrachloride.

The results are presented in table 2.

All studied sorbents exhibit high adsorption ability with respect to FA; adsorption of 100% FA occurs. However, it is easier to desorb FAs from silica gel (Table 2, line 4, column 4).

Conclusion: the best sorbent is silica gel with a particle size of 40-100 μm and a pore diameter of 60

Determination of the minimum amount of sorbent necessary for the adsorption of antiwear additives from diesel fuel.

Since the fatty acid composition of antiwear additives can vary depending on the raw material, studies have been conducted to determine the degree of adsorption of saturated and unsaturated acids using stearic and oleic acids as examples.

. 10 см исследуемое топливо пропускали через хроматографическую колонку. Полученным топливом заполняли кювету с окнами из бромида калия, номинальной длиной пути 0,5 мм и снимали ИК-спектр.The chromatographic column was filled with the required amount of silica gel with a particle size of 40-100 μm and a pore diameter of 60

. 10 cm of test fuel was passed through a chromatographic column. The resulting fuel was filled into a cuvette with potassium bromide windows with a nominal path length of 0.5 mm and the IR spectrum was recorded.

The concentration dependence of the determined fatty acid concentration in the fuel. The degree of adsorption was calculated by the formula 1. The results are presented in table 3.

As can be seen from the test results, the minimum amount of adsorbent that allows to achieve 100% adsorption of FA from DT is 1 g of silica gel (Table 3, column 5). An increase in the amount of sorbent does not change the indicator of the degree of adsorption of FAs, but leads to an overrun.

Selection of eluent for desorption of antiwear additives from the sorbent.

In order to achieve the maximum degree of FA desorption, a number of solvents with different eluting forces were investigated: dichloromethane — eluting force on silica gel 0.30-0.32, isopropanol 0.60, ethanol 0.65, methanol 0.70-0 , 73.

. Затем промывали сорбент 15 см³ исследуемого элюента, собирали полученный экстракт и отгоняли из него элюент на ротационном испарителе при температуре 50°С и вакууме 10-15 мбар. Остаток после отгонки переносили в мерную колбу на 10 см³ и доводили до стандартного объема тетрахлорметаном.To determine the degree of desorption of fatty acids by elution with various solvents, 10 cm ^{3 of the} test fuel was passed through a chromatographic column filled with 1 g of silica gel with a particle size of 40-100 μm and a pore diameter of 60

. Then the sorbent was washed with 15 cm ^{3 of the} studied eluent, the obtained extract was collected and the eluent was distilled off from it on a rotary evaporator at a temperature of 50 ° C and a vacuum of 10-15 mbar. The distillation residue was transferred to a 10 cm ³ volumetric flask and brought to standard volume with carbon tetrachloride.

Spent IR spectrometry of the resulting solution. According to the calibration dependence, the concentration of fatty acids was determined. The degree of desorption was calculated by formula 2.

The results are presented in table 4.

Conclusion: the maximum degree of desorption is achieved using methanol and ethanol. Since methanol belongs to substances of hazard class 3, and ethanol belongs to substances of hazard class 4, ethanol was selected to isolate FAs (Table 4, column 4).

Determination of the minimum amount of eluent necessary for the desorption of antiwear additives from the sorbent.

. Затем промывали сорбент различным объемом этанола (5, 10, 15 и 20 см³), собирали полученный экстракт и отгоняли из него этанол на ротационном испарителе при температуре 50°С и вакууме 10-15 мбар. Остаток после отгонки переносили в мерную колбу на 10 см³ и доводили до стандартного объема тетрахлорметаном. Проводили ИК-спектрометрирование, полученного раствора. По градуировочной зависимости определяли концентрацию жирных кислот. Степень десорбции рассчитывали по формуле 2.To determine the degree of desorption of fatty acids during elution with various volumes of ethanol, 10 cm ^{3 of the} test fuel was passed through a chromatographic column filled with 1 g of silica gel with a particle size of 40-100 μm and a pore diameter of 60

. Then the sorbent was washed with a different volume of ethanol (5, 10, 15, and 20 cm ³ ), the obtained extract was collected and ethanol was distilled from it on a rotary evaporator at a temperature of 50 ° С and a vacuum of 10-15 mbar. The distillation residue was transferred to a 10 cm ³ volumetric flask and brought to standard volume with carbon tetrachloride. Conducted IR spectrometry of the resulting solution. The concentration dependence of the determined fatty acid concentration. The degree of desorption was calculated by formula 2.

The results are presented in table 5.

As can be seen from the test results, 10 cm ^{3 of} ethanol is sufficient to isolate 100% FA antiwear additives from diesel fuel (Table 4, column 3). A decrease in the amount of eluent can lead to a decrease in the degree of release of saturated acids, for example, poorly soluble stearic acid, and an increase in the amount of eluent is not economically feasible.

The influence of the speed of passage of the sample and eluent through the sorbent on the degree of release of FA.

To reduce the time spent on TFE, the influence of the speed of passage of the sample and eluent through the sorbent was studied (Table 6).

и вакуумный насос. Для создании вакуума 13-40 мбар использовали водоструйный насос, для создания вакуума 5-10 мбар использовали насос PC 3001 VARIO pro (Vacuubrand). При заданном вакууме через хроматографическую колонку пропускают 50 см³ исследуемого топлива с концентрацией противоизносной присадки ГТ-16 - 0,05% мас. После чего дополнительно пропускают через сорбент 2 см гексана. Отключают вакуум и меняют колбу Бунзена на чистую аналогичную колбу. Включают насос и при заданном вакууме пропускают через сорбент 10 см³ этанола. Этанольный экстракт переносили в отгонную колбу ротационного испарителя и отгоняют этанол при вакууме 15 мбар и температуре 50°С. После завершения отгонки, остаток из разгонной колбы количественно переносят в мерную колбу объемом 5 см³, доводят до стандартного объема тетрахлорметаном, закрывают колбу пробкой и перемешивают. Полученным раствором заполняют кювету толщиной 0,5 мм и подвергают ИК-спектрометрированию.The tests were carried out as follows. A chromatographic column filled with 1 g of silica gel with a particle size of 40-100 μm and a pore diameter of 60 was tightly connected to a Bunsen flask with a volume of 100 cm ³

and a vacuum pump. To create a vacuum of 13-40 mbar, a water-jet pump was used; to create a vacuum of 5-10 mbar, a PC 3001 VARIO pro pump (Vacuubrand) was used. At a given vacuum, 50 cm ^{3 of the} test fuel is passed through a chromatographic column with a concentration of anti-wear additive GT-16 - 0.05% wt. Then an additional 2 cm of hexane is passed through the sorbent. Turn off the vacuum and change the Bunsen flask to a clean, similar flask. The pump is turned on and, under a given vacuum, 10 cm ^{3 of} ethanol is passed through a sorbent. The ethanol extract was transferred to a distillation flask of a rotary evaporator and ethanol was distilled off under vacuum of 15 mbar and a temperature of 50 ° C. After completion of the distillation, the residue from the booster flask is quantitatively transferred to a 5 cm ³ volumetric flask, adjusted to standard volume with carbon tetrachloride, close the flask with a stopper and mix. The resulting solution is filled in a cuvette with a thickness of 0.5 mm and subjected to IR spectrometry.

The calibration dependence determines the concentration of fatty acids in the fuel. The degree of separation is calculated by the formula 3:

With ₁ - the concentration of FA in the original fuel,% wt.,

With ₄ - the concentration of FA in 5 cm ³ solution (isolated from the sorbent),% wt.,

V _to - volumetric volumetric flask, 5 cm ³ .

V _ol - the volume of the fuel sample, 50 cm ³ .

The results are presented in table 6.

It was found that an increase in the speed of passage of the fuel and eluent samples through the sorbent due to the vacuum (13-40 mbar) created by the water-jet pump does not reduce the degree of release of FA, but reduces the time of TFE from 4 hours to ~ 30 min, a further increase in the speed of passage Samples through the sorbent are not advisable, since it leads to a decrease in the degree of release of FA.

Selection of parameters for the distillation of ethanol and water from an ethanol extract of FA.

To increase the concentration of FA in the ethanol extract, it is necessary to distill off the solvent — ethanol and the water contained in it.

Unsaturated FAs are able to oxidize in air, the reaction rate increases with increasing temperature, so it is advisable to distill ethanol and water with minimal heating and for a short time, this requires the use of vacuum. Most vacuum rotary evaporators allow you to create a vacuum of 10-15 mbar, this is enough to drive ethanol and water from the extract without raising the temperature above 60 ° C.

Using the method (6 - EH NSO 12937-2000 Determination of water. Coulometric Karl Fischer titration method), the water content in the residue after distillation of ethanol was determined (Table 7, column 5).

As can be seen from the test results, 5 minutes is enough to distill the ethanol and water contained in the extract. An increase in time is not advisable.

Metrological processing of results.

The technical result relating to the accuracy of the method was obtained by mathematical processing of the results obtained during testing of model mixtures, which are compositions of diesel fuel with various concentrations of additives. For each studied antiwear additives (Table 8), a metrological examination was carried out using six solutions with a concentration of 0.005% wt., 0.010% wt., 0.020% wt., 0.040% wt., 0.050% wt., 0.06% wt. ., as for the GT-16 (table. 1), and idle experience - fuel does not contain antiwear additives. The diesel fraction of the hydrotreatment unit was used as fuel. The accuracy indicators of the method, calculated according to (7 - RMG 61-2010 State system for ensuring the uniformity of measurements. The accuracy, accuracy of precision methods of quantitative chemical analysis) are given in table 8.

Thus, the method for determining the content of antiwear additives based on fatty acids in diesel fuels allows to obtain a technical result only with the totality of existing features set forth in the claims.

The method is implemented as follows:

, уплотняли его легким постукиванием о корковую или резиновую пробку в течение 5 мин. Сверху сорбента вносили слой стекловаты высотой 2-3 мм, который уплотняли стеклянной палочкой для предотвращения взмучивания сорбента. Пропускали через сорбент 2 см³ гексана для смачивания, затем 50 см³ пробы топлива, создавая разрежение 13-40 мбар насосом, как вариант - водоструйным насосом, после чего дополнительно пропускают через сорбент 2 см³ гексана. Затем пропускали через сорбент 10 см³ этанола, собирая экстракт в другую емкости. Этанольный экстракт переносили в отгонную колбу ротационного испарителя. В нагревательную емкость наливают теплоноситель так, чтобы его уровень был не ниже уровня раствора в разгонной колбе. Устанавливают вращение разгонной колбы со скоростью (100±5) об/мин. Включают вакуумный насос и устанавливают вакуум на уровне от 15 мбар. Устанавливают температуру нагревательной емкости 50°С. После выхода ротационного испарителя на заданный режим продолжают отгонку в течение 5 минут. После завершения отгонки, остаток из разгонной колбы количественно переносят в мерную колбу объемом 5 см³. Отгонную колбу дважды промывают 1 см³ тетрахлорметаном, который так же переносят в мерную колбу, доводят содержимое мерной колбы до метки тетрахлорметаном, закрывают колбу пробкой и перемешивают. Полученным раствором заполняют кювету толщиной 0,5 мм и подвергают ИК-спектрометрированию. Определяют высоту пика на волновом числе 1710 см^-1. Определяют концентрацию присадки по градуировочному графику, построенному в координатах высота пика на волновом числе 1710 см^-1 - концентрация присадки.In a glass chromatographic column with a diameter of 10 mm and a height of 200 mm, with a porous plate to retain the stationary phase (adsorbent), 1 g of silica gel with a particle size of 40-100 μm and a pore diameter of 60

, compacted with a light tapping on the cortical or rubber plug for 5 minutes. A layer of glass wool 2-3 mm high was introduced on top of the sorbent, which was sealed with a glass rod to prevent the sorbent from swelling. 2 cm ^{3 of} hexane was passed through the sorbent for wetting, then 50 cm ^{3 of} fuel sample, creating a vacuum of 13-40 mbar with a pump, or, alternatively, with a water-jet pump, after which 2 cm ^{3 of} hexane was additionally passed through the sorbent. Then, 10 cm ^{3 of} ethanol was passed through the sorbent, collecting the extract in another container. The ethanol extract was transferred to a distillation flask of a rotary evaporator. The coolant is poured into the heating tank so that its level is not lower than the level of the solution in the booster flask. Set the rotation of the booster flask at a speed of (100 ± 5) rpm. Turn on the vacuum pump and set the vacuum at a level of 15 mbar. Set the temperature of the heating vessel to 50 ° C. After the rotary evaporator reaches the preset mode, distillation is continued for 5 minutes. After completion of the distillation, the residue from the booster flask is quantitatively transferred to a 5 cm ³ volumetric flask. The distillation flask is washed twice with 1 cm ^{3 of} carbon tetrachloride, which is also transferred to a volumetric flask, the contents of the volumetric flask are brought to the mark with carbon tetrachloride, the flask is closed with a stopper and stirred. The resulting solution is filled in a cuvette with a thickness of 0.5 mm and subjected to IR spectrometry. The height of the peak at the wave number of 1710 cm ^{-1 is} determined. The concentration of the additive is determined according to the calibration graph plotted in the coordinates of the peak height on the wave number of 1710 cm ^-1 - the concentration of the additive.

Example 1

It is necessary to determine the content of anti-wear additive in DT-L-K5, grade C, according to GOST 32511-2013 (Bashneft-Ufaneftekhim), in which, according to regulatory documents, the content of anti-wear additive Complex-ECO “D” is 0.045% wt.

Testing the fuel sample was carried out as described above.

The concentration of antiwear additives was determined according to the calibration schedule (Fig. 1, line 1)

The results of determining the height of the peak at the wave number of 1710 cm ^-1 and the concentration of antiwear additives Complex-ECO "D" by the claimed method are shown in table 9.

Conclusion: The content of the anti-wear additive Complexal-ECO "D" in DT-L-K5, grade C, within the accuracy of the method, corresponds to the concentration stated in the regulatory documents.

Example 2

It is necessary to determine the content of the anti-wear additive KOLTEK DS 7739 in DT-L-K5, Grade C, type III according to GOST R 52368-2005 (Khabarovsk Oil Refinery), in which, according to regulatory documents, the content of anti-wear additive is 0.050% wt.

Testing the fuel sample was carried out as described above.

The concentration of antiwear additives was determined according to the calibration schedule (Fig. 1, line 2)

The results of determining the concentration of antiwear additives KOLTEC DS 7739 of the claimed method are shown in table 10.

Conclusion: The content of the anti-wear additive KOLTEK DS 7739 in DT-L-K5, grade C exceeds the concentration stated in the regulatory documents, which can help accelerate oxidation processes during long-term storage of fuel.

Claims (1)

The method for determining the amount of antiwear additives based on fatty acids in diesel fuels, including sampling, IR spectrometry and subsequent determination of the additive concentration according to the calibration graph constructed in the coordinates of the peak height on the wave number of 1710 cm ^-1 - additive concentration, characterized in that before IR spectrometry chromatographic column is filled with 1 g of sorbent, which is used as silica gel, with a particle size of 40-100 μm, a pore diameter of 60

, moistened with hexane and passed 50 cm ³ fuel samples, creating a vacuum of 13-40 mbar, then additionally sequentially passed through a sorbent 2 cm ³ hexane, then 10 cm ³ ethanol, collecting the extracts in different containers, the extract after passing ethanol is kept at a temperature of 50 -60 ° C and a vacuum of 10-15 mbar for 5 min, after which they are brought to a volume of 5 cm ^{3 with} carbon tetrachloride and the resulting solution is subjected to IR spectrometry.

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