RU2372616C1 - Definition method of content of resins in oils - Google Patents

Abstract

FIELD: oil and gas production.

SUBSTANCE: oil is deasphalted, prepared 0.5% solution of asphalt-free oil in toluol, photocolorimetered it at length of wave 510 nm, it is defined transmission density, by its value there are calculated absorption of light coefficient (K_la) of solution of asphalt-free oil from correlation: K_la= 100%*D/0.4343CL [cm^-1], where D - value of transmission density at absorption band 510 nm; C - concentration of asphalt-free oil in toluol, %; L - absorption layer thickness of solution of asphalt-free oil in used liquid measuring cavity, cm; and by value K_la it is calculated content of resins in oil by empirically established formula:

EFFECT: simplicity and acceleration of analysis.

1 ex, 1 dwg

Description

The invention relates to methods for determining the component composition of oils using the photocolorimetric method in the visible part of the spectrum, in particular to methods for determining the tar content in oil, and can be used in field and research laboratories in the complex analysis of oils and oil products ..

A known method for the determination of resins in oil using the chromatographic method GOST 11868-66 [see Bogomolov A.I., Temyanko M.B., Khotintseva L.I. Modern oil research methods. - L .: Nedra, 1984, p.182-192]. In accordance with this method, the deasphaltedate obtained after precipitation, washing and filtering of asphaltenes is poured into a prepared chromatographic column filled with silica gel. After the initial product is completely absorbed into the silica gel, desorption is started. For desorption of oils, petroleum ether is poured into the column tank, and the selection of the eluent begins simultaneously from the bottom of the column. To isolate the resins, elute with an alcohol-benzene mixture. The solvents are distilled off in a water bath. After distillation of the bulk of the solvent, the resins are transferred to tared cups and dried to constant weight. The resin content (X) in wt.% Is found by the formula:

X = 100 × m ₁ / m ₂ ,

where m ₁ is the mass of resins, g; m ₂ - oil sample, g.

The disadvantage of this method, based on the adsorption-desorption of oil deasphalting on silica gel, is the complexity and duration of the procedure.

A known method for determining the content of resinous-asphaltene substances in oil [RU 2001131939, publ. 08/10/2003], including their adsorption followed by washing the adsorbate with a solvent, desorption of resins with a solvent, and determination of the amount of resins and asphaltenes. The method is based on the fact that a sample of the analyzed oil is adsorbed on a superthin quartz fiber, after which the adsorbate is washed with a solvent in two steps, resinous asphaltene substances deposited on a superthin quartz fiber are burned in a stream of air with the formation of carbon dioxide, and the total amount is initially determined from the carbon content the content of resins and asphaltenes, then the content of asphaltenes, and the content of resins is determined by the difference.

The disadvantage of this method is the complexity and duration of the determination process (not fundamentally different from the classical method). In addition, the use of various complex analytical procedures can lead to a decrease in the accuracy of determination.

Known photocolorimetric method for determining asphaltenes in oil [Collection N.T. Physicochemistry and oilfield development. Issue 30, 1975, 177 pp.]. In accordance with this method, the concentration curve of asphaltenes in oil is determined from the calibration curve of the dependence of the optical density of the oil solution on the concentration of asphaltenes in benzene. A graph is used between the light absorption coefficient of degassed oil and the oil asphaltenes content. The correlation coefficient is rather high and amounts to 0.916, which indicates a close relationship between the studied parameters, close to functional. To determine the coefficient of light absorption, a solution is prepared from 0.2 ml of degassed oil in 50 ml of benzene. Measurements are performed on standard photocolorimeters with a neutral filter in a 5 mm wide cuvette.

Thus, to find the content of asphaltenes in oil, it is sufficient to determine the light absorption coefficient of degassed oil, then, according to the schedule or formula, find the weight content of asphaltenes.

The disadvantage of this invention is the incorrect use of direct photocolorimetry of oil to determine the content of asphaltenes, since the presence of asphaltenes in oil is, although significant, but not the only factor in the light absorption of oils. It is known that resins also make a significant contribution to the overall oil absorption coefficient. Thus, the accuracy of determining the content of asphaltenes is reduced. In addition, this method is not applicable for determining the content of resins in oils.

Known photocolorimetric methods for determining the actual resins in hydrocarbon fuels and gasolines [RU 2018121 C1, publ. 08/15/1994; RU 2007711 C1, publ. 02/15/1994]. The essence of the invention is that a sample of gasoline (hydrocarbon fuel) is applied to chromatographic paper, dried, impregnated paper, washed with n-heptane, then dried again and finely cut chromatographic paper with actual resins is placed in an acetone-toluene mixture, the solution is shaken, and the optical density of the solution is measured , and the actual resin content is determined by the formula: C _f.s. = K · D, where C _f.s. - concentration of actual resins in gasoline, mg per 100 cm ^{3 of} gasoline (hydrocarbon fuel); K is an empirical coefficient; D is the optical density.

However, this method is not suitable for determining the tar content in oils.

The objective of the invention is a new simple method for determining the resin content in oil, expanding the arsenal of known methods and allowing to reduce the time of research.

The technical result of the invention is the determination of the concentration of resins in oils based on the empirically established dependence of the authors.

The objective is achieved by a method of determining the resin content in oils, lies in the fact that after the standard deasphalting process, 0.5% solution in toluene deasphalting fotokolorimetriruyut in the visible spectrum at 510 nm and determined its absorbance, optical density, calculate K _sp deasphalting according to the formula determined from the law of Bouguer-Lambert-Bera:

To _sp = 100% · D / 0.4343CL [cm ^-1 ],

where K _sp the light absorption coefficient of a 0.5% solution of deasphalting agent in toluene at 510 nm, cm ^-1 ;

D is the optical density with an absorption band of 510 nm;

C is the concentration of deasphalting agent in toluene,%;

L is the thickness of the absorbing layer of the deasphalting solution in the used liquid measuring cell, see

The resin content in oil in mass% is calculated by the formula:

The formula expresses the empirical dependence of K _cn on the tar content in oils. The drawing shows a calibration curve of the value of K _SP from the resin content. The correlation coefficient (R) of the dependence is 0.978, which indicates a close relationship between the studied parameters. The resin content in various oils was determined by the classical chromatographic method according to GOST 11868-66.

The invention is illustrated by the following specific embodiment.

Example. To precipitate asphaltenes to the oil sample (oil of the Zyuzeyevsky field, density 0.9144 g / cm ³ ) in an amount of 4-5 g, placed in a flat-bottomed flask, add 200 ml of petroleum ether (40-70 ° C). After vigorous stirring, the mixture was left to stand for 24 hours. The asphaltene precipitate is filtered off and washed repeatedly with fresh portions of petroleum ether. The filtrate is distilled off to the volume of the original oil by distillation of petroleum ether to obtain deasphalting agent. 0.25 ml deasphalting agent is diluted in 50 ml of toluene and the resulting solution is placed in a measuring liquid cuvette with an absorbing layer thickness of 1 cm. The optical density of the solution is measured at a KFK-3 photometer at a wavelength of 510 nm. By the value of optical density (D = 0.912), K _c is calculated using the formula:

To _sp = 100% · D / 0.4343CL [cm ^-1 ].

The light absorption coefficient is equal to 420 cm ^-1 and the resin content calculated by the formula

equal to 21.18 wt.%.

In the control experiment to determine the tar content in the oil sample of the Zyuzeyevskoye field, the standard method according to GOST 11868-66 obtained a value of 21.66 wt.%

Thus, the claimed invention allows you to easily, quickly and with high accuracy to determine the content of resins in oils.

Claims (1)

The method for determining the tar content in oils, which consists in the fact that the oil is deasphalted, a 0.5% solution of deasphalting solution in toluene is prepared, photocolorimetric it at a wavelength of 510 nm, the optical density is determined, the light absorption coefficient (K _c ) of the deasphalted solution is calculated from its value ratios:
To _sp = 100% · D / 0, 4343 CL, [cm ^-1 ],
where D is the optical density with an absorption band of 510 nm;
C is the concentration of deasphalting agent in toluene,%;
L is the thickness of the absorbing layer of the deasphalting solution in the used liquid measuring cell, cm;
and the value of K _sp calculate the resin content in oil according to an empirically established formula:

Images