SU1718055A1 - Method of determination of softening point of high-molecular petroleum distillates - Google Patents

Abstract

The invention relates to the rheological properties of substances and relates to methods for determining the softening temperature from absorption spectra in the visible region. In order to simplify the determination of the softening temperature of petroleum fractions, expanding the temperature range of the determination, the ability to work with trace amounts of the sample, the test sample dissolved in toluene is irradiated, a specific absorption rate is determined in the range of 350-600 nm and the dependences Tp AI + Aa Kjv, where T2 is the softening temperature, amp ° C; K is the specific absorption rate, g / l-cm; AI, Aa are wavelength dependent coefficients. 4 tab.

Description

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with

The invention relates to the determination of the rheological properties of a substance, in particular, to a method for determining the softening temperature of high molecular weight petroleum fractions, and can be used to determine the softening temperature of cracking residues, tar, bitumen / high molecular weight products of coal tar processing.

The softening point is an important rheological indicator of petroleum product, characterizing the ability of a substance to transfer from a non-crystalline to a highly elastic or into a flowing state. The softening temperature is defined as the temperature at which the sample of petroleum product under study begins to deform under the influence of a constant load.

A known method for determining the softening temperature of heavy petroleum products is that the sample of the petroleum product is ground and pressed into a ring, which is placed in a vessel equipped with a thermometer. Then the sample of oil is heated at a rate of 5 deg / min. In this case, the temperature at which the deformation of the sample ends when the ball is lowered to the bottom of the vessel is taken to be the softening temperature of the oil product. This method is used as a standard ring and ball method (TISC).

The disadvantage of this method is the complexity and difficulty of a clear op00.

o ate

the softening temperature of substances that have this index below 20-30 ° C, and substances that are in a fluid state at room temperature, since in this case the substance leaks out of the ring and the sample needs to be frozen, besides , the method is not applicable to samples with low ring adhesion, it is impossible to work with small (less than 3g) sample weights, it is also impossible to apply the KISH method to unstable oil fractions that destruct or boil away at low heat.

The closest in technical essence and the achieved result is the nuclear magnetic resonance method for determining the softening temperature of high molecular weight petroleum fractions.

Its essence is as follows.

The distillate fraction formed during the processing is selected using a special probe located in front of the NMR spectrometer. The volume of the probe is 10–20 cm3, therefore the consumption of the sample under study reaches 10–20 g and more. After the sample is cooled, it is exposed to electromagnetic radiation, the NMR spectrum of the nuclear magnetic resonance is recorded, the integral intensities of the spectral lines are measured, the softening temperature of the heavy oil product Tp is determined according to

TP A + B-R,

where A, B are coefficients depending on the type of oil product, calculated using the least squares method;

R C + p + y

I

relative intensity, which is determined by the spectrum of H;

at the same time, the U, I /, y - integral intensities of protons in the a -, {$ -, and - positions with respect to the aromatic ring;

lar is the integral intensity of the protons of the aromatic ring in the H-spectra.

The disadvantages of this method are the use of a difficult-to-use NMR spectrometer and the laboriousness of the method, since the softening temperature is judged indirectly - by influencing the radiation in the midrange of the spectrum not on the sample itself, but on the distillate that is formed during its processing, what

determines the impossibility of controlling the softening temperature of a substance in processes not related to the distillate fraction. In addition, the spectrometer is rigidly connected to the reactor in which the sample to be studied is to be placed. Hence the fundamental impossibility of working with individual samples in small quantities. NMR spectrometer application

makes the method practically impossible for widespread introduction into laboratory practice because of the difficulty in operating a production line, the need for special probes, flow rate controllers, etc. The method is limited by the fact that it is impossible in principle to apply it to paramagnetic substances. Upon transition to paramagnetic fractions, the absorption lines in the NMR spectra are broadened and (in the limit) merge with the background.

In addition, the method involves analyzing substances whose softening temperatures are much higher than room temperature (it reaches several tens or even hundreds

° C). For substances whose softening temperature is in the range of 0 - 30 ° C, the method cannot be used.

The purpose of the invention is to simplify the method for determining the softening temperature of high molecular weight oil fractions, reducing the mass of the analyzed sample, expanding the range of detected temperatures.

The goal is achieved by the fact that

according to the method for determining the softening temperature of high molecular weight oil fractions, which consists in preparing the sample for spectrometry, measurements are made in the spectrum

absorption and determine the softening temperature according to the calibration dependence, sample preparation is carried out, its solution in toluene and diluted the resulting solution to a predetermined integrated optical density, measurements in the absorption spectrum are carried out in the range of 350 - 600 nm, the specific absorption coefficient K is determined on one of the wavelengths, and the softening temperature Tp is determined by

calibration dependence

Tp Ai + A2 KA,

where AI, Az are the calibration coefficients depending on the wavelength.

The sample of the test substance is prepared for spectrometry, its solution in toluene and diluted the resulting solution to a given integrated optical density.

A solvent, toluene, is used to prepare the solutions of the test substances. The need to dilute the solutions is primarily due to the tendency of the molecules of the high molecular weight components of the oil to associate, which leads to a deviation from the basic law of light absorption;

Measurements in the absorption spectrum are carried out in the range of 350-600 nm.

The visible range of the spectrum for determining the softening (solidification) temperature was chosen because it contains the smallest deviations of the determination results (see Tables 1, 3, 4).

Tables 3 and 4 present data to substantiate the boundaries of the spectral range for determining the softening (solidification) temperature for two types of substances, namely, the softening temperature was determined experimentally using absorption (extinction) coefficients. For the study, those substances that have the best and worst indicators of softening temperature with respect to the substance of positions 3 and 7 (see table 1) were selected.

The absorption coefficient together with the coefficients AI and Aa (Table 2) are the determining factor in determining the softening temperature of the high molecular weight petroleum fractions. You can define the boundaries of the spectral range. From tab. 3 and 4, it follows that the operating wavelength range is 350 nm and 600 nm, since the determination error drastically increases beyond the limits of this range (see Table 3 and 4). The left boundary of the range is 350 nm, since at this wavelength, Cd increases sharply and all Tp at H 350 nm have a large error, which reaches 17% and above. The right boundary of the range of the spectrum is limited to I 600 nm, since a change in Cd (absorption coefficient) occurs at I 600 nm, but very slowly (a change in tenths and hundredths of nm). The relative determination error outside 600 nm increases to 18% and higher when determining the softening temperature, i.e. It is evident (see Table 3 and 4) that A 600 nm may be the right boundary for determining the softening temperature of high molecular weight petroleum fractions. According to the available experimental data, the substances that cause the absorption of radiation in the considered spectral range are aromatic

hydrocarbons and high molecular weight petroleum compounds such as resins and asphalt concrete.

The specific absorption coefficient K is determined at one of the wavelengths, and the softening temperature Tr is determined by the calibration dependence

ten

TP AI + A2-Cd,

where AI, Aa are calibration coefficients depending on the wavelength.

In each case, the wavelength is chosen arbitrarily, which facilitates

5 research and does not impose certain conditions on the method. You can also use measurements at the same wavelengths. But measurements for different substances need to be made at such a wavelength, where the maximum absorption optical density is observed, which can be considered as working. Obviously, in such an optimal region near the working wavelength, the error in determining the softening temperature will be minimal. But since the researcher, as a rule, does not know the optimal region or optimal wavelength of the test substance, as well as the optical density of similar in nature to the high molecular weight oil fractions coincides at the same wavelength, it is therefore recommended to make measurements at several wavelengths in near ultraviolet and visible region (350 - 600 nm) of the spectrum. A solution is prepared for each test substance. The spectrum of the prepared solution of a substance is calculated at a certain wavelength corresponding value.

0 absorption coefficient. According to the proposed equation, Tr AI + A2-K3, using the coefficients AI and Aa (Table 2) or extrapolating according to Table 2 (if the coefficients AI and A2 are not in the table), determine the softening temperature for each of the wavelengths. Find the average value, which is taken as the softening temperature of the test substance.

The coefficients AI and A2 (table 2) get

0 by the method of least squares (OLS). To do this, use the experimental data (the substance of position 1, Table 1) and obtained by the method of the Ring and the ball (CIT) for the remaining nine samples (Table 1). The absorption coefficients K are determined at specific wavelengths. At a fixed wavelength for several types of samples, the coefficients AI, A2 are determined by the least squares statistical method. Regression ratios At and

A2 are common to all substances and are summarized in Table 2.

The correlation coefficients of the parameters of the softening temperature Tp and the absorption coefficient K are also preliminarily evaluated (Table 2).

Using this method, it is possible to determine the softening temperature of high molecular weight petroleum fractions that exhibit both diamagnetic and paramagnetic properties, which provides a spectrophotometric method of analysis.

In addition, the application of the spectrophotometric data to determine the softening temperature of the sample under study makes it possible to obtain results for substances whose softening temperature is in the range of room temperature from 20 to 30 ° C and below.

The softening temperature is determined as follows.

The test substance in an amount of 0.1-0.2 or less is weighed on an analytical balance, then the weight of the oil product is dissolved in an aromatic solvent (toluene), while fixing the concentration of the oil product solution. The solution is poured into the working cell of the spectrophotometer. A paired cuvette with an aromatic solvent (toluene) is placed in the comparison channel, a spectrum is taken in the visible region of 350-600 nm, after which the specific absorption coefficient of the oil product is determined at one of the wavelength values for high molecular weight oil fractions. Using the dependence of the softening temperature on the specific absorption rate, determine the softening temperature from the ratio

Tp Ai + A2 KL,

where Tp is the softening temperature ° С;

Ah, wavelength dependent coefficients;

CD is the specific absorption rate, g / l-cm;

PRI me R 1. Determination of tar softening temperature of West Siberian commercial oil (see table 1).

A sample of 0.1895 g. Into a flask with a weighed sample, 15 - 30 ml of toluene is poured. After the sample is completely dissolved in toluene, the solution is weighed and the concentration of the solution Ci is calculated.

Ci sample weight. g x 1000

solution weight, solution sample density, g, g / l.

5 Then an additional dilution is carried out so that the solution has a pale yellow color (the volume of toluene can vary 5-50 ml), and the solution is weighed again. The concentration of solution C after

10 additional dilutions are calculated by the formula

WITH

sample solution with a concentration of Ci, g

solvent weight, g

x Ci, g / l;

With e zzzz x 104596 ° 1003 g / l

20 The specific absorption rate K is determined at a single wavelength of I 526 nm according to the Lambert-Beer formula.

25

I / „-;

14 Lg.

E- D

where C is the concentration of the test sample, g / l;

E is the thickness of the cuvette, cm;

D is the optical density of the test solution, equal to 0.026, then

., 0.1003 ° C / / h Kd 1 x 0.026 398 (g / l Sm}

Hence, the softening temperature is determined by the equation

Tr - 14.01 + 23.83 x 3.98 "81.84 ° C

The coefficients AI -14.01 A2 23.83 (see tab, 2).

The softening point of a sample of the same type is 80.5 ° C. Relative error of 1.5%

4581.84 -80.50

81.84

x 100 1.5%.

EXAMPLE 2 The softening temperature of tar of mangyshlak oil, TKip, is determined. 450 ° C (see tab.1).

A sample of 0.12 g of sample was taken. 15 - 30 ml of toluene was added to the flask. After the sample is dissolved in toluene, the solution is weighed (the weight of the solution is equal to 17.3200 g). Calculate the concentration of the solution Ci

„0.1200.pppp,

C1 1T3200 a866 x1000 6g / L

After additional dissolution to a pale yellow color, the concentration C is calculated. If the weight of the solution with the concentration Ci is equal to 0.0102 g, and the weight of the diluted solution is 1.1457 g, then

with x 6 0.0534 g / l.

1,14b

The optical density of the sample under study at 420 nm is 0.017, then

K 1 0TG 3-16g / L-SM

The softening temperature Tp -17.68 + + 7.96-3.16 7.5 ° C.

The coefficient Ai -17.68 A2 7.96 obtained by extrapolation from the table.2.

As can be seen, for various high molecular weight petroleum fractions, this relationship is fulfilled with good accuracy and adequacy. This is evidenced by high correlation coefficients (0.90 - 0.95) and an average absolute error,

which is ± 2.0 in the test interval (see tab.1 and 2).

Claims (1)

The invention The method of determining the softening temperature of high molecular weight oil fractions, which consists in preparing the sample in spectrometry, measuring in the absorption spectrum and determining the temperature softening according to the calibration dependence, characterized in that, in order to simplify the method, reduce the mass of the analyzed sample and expand the range of detected temperatures, sample preparation is carried out, its solution in toluene and diluted the resulting solution to a given integral optical density, measurement in the absorption spectrum is carried out in the range of 350 - 600 nm, the specific absorption coefficient KA is determined at one of the wavelengths, and the softening temperature Tp is determined by the calibration dependence Tp AI + Kjv x Yes, where AI, Aa - calibration coefficients depending on the wavelength. T a and Experience Wavelength, Empirical Values: nm Coefficients table 2 Linear coefficients Table 3 Table