The way physico-chemical analysis of materials

 

(57) Abstract:

Use: for the quantitative gas chromatographic separation of high-boiling components of crude oil. The essence: if you have a low residual pressure, ensuring compliance with proportion to the partial pressure of the analyzed component from its mole fraction in the separating liquid, under conditions of programmed temperature increase carry out the separation of high-boiling components of crude oil. The technical result of the invention consists in the expansion of the range separating liquids at high temperatures and reducing erosion of the chromatographic bands of the components of the analyzed material.

The invention relates to research or analysis of materials, in particular to gas chromatography for the quantitative determination of high-boiling components of crude oil.

There is a method for physical-chemical separation of the components of the mobile phase as it moves along the stationary phase. The method consists in the fact that through the column passed a steady stream virtually no adsorbiruyuschee (or not soluble in the stationary liquid) gas and the carrier gas at the entrance of the column enter naibolee adsorbiruya (or the least soluble component of this mixture, further pure carrier gas, then stronger adsorbiruya component, again the carrier gas, etc. of the Zone output (s) of the components in the chromatogram are separated carrier gas [1, 512 S., 2nd paragraph].

The disadvantage of this method is that its application is limited to separation of high-boiling components, which are strongly adsorbed on the surface of the carrier.

Closest to the proposed invention, where partially eliminated the above-mentioned disadvantage of the method is gas chromatography with programmable temperature. The known method of physico-chemical analysis of the materials, including the separation of components of the mobile phase as it moves along the stationary phase with programmable temperature used for the analysis of high-boiling petroleum products [2, S. 6, paragraph 2].

The known method also has its drawbacks associated mainly with volatility separating liquids at high temperatures [1, C. 513, last paragraph].

The task of the invention is the expansion of the range separating the liquid (stationary phase) at high temperatures and reducing erosion of the chromatographic bands of the analyzed mixture.

The main parameter of the chromatographic strip - characteristic retention is associated with values of thermodynamic functions of dissolution (or adsorption) of the analyzed component. Thermodynamic function of dissolution (adsorption), in turn, connected c pressure. It is known that in the area of low pressure (shares or more mm Hg) the shape of the curve isotherm dissolution approaching linear, that is observed is proportional to the dependence of the partial pressure of the analyzed component from its mole fraction in the separating fluid and the dissolution rate (evaporation) is constant for a given component [1, C. 418, last paragraph]. At a constant flow rate of gas in the column flow chromatographic bands is also constant. This speed is greater, the worse adsorbed (or dissolve) the analyzed component, and the less, the better it is adsorbed (or dissolves). Therefore, chromatographies the awns, that provides a clear separation. This is a significant advantage of the present invention from the known method in which the separation of components is carried out in the condensed state at a pressure slightly above atmospheric (800-850 mm Hg). At low residual pressures (three orders of magnitude below atmospheric share or more mm Hg) in the column of the chromatograph partial pressure of the dissolved component is determined only by the chemical nature of the analyzed component and does not depend on the nature of the separated liquid (stationary phase), which can significantly extend the range of these liquids. In this second essential difference of the present invention. Since each band in the gas phase moves along the column at a constant speed, the distribution of the partial pressure created at the entrance of the column at the inlet samples, will move to the exit from the column without changing the (overlapping strips of the other components) and the chromatographic strip the analyzed component will be recorded by the detector without dilution.

An example of the method. The implementation of the method is to pre-determine the equilibrium pressure at which PR is forest pressure, when observed proportional dependence of the partial pressure of the analyzed component from its mole fraction, use the curves of adsorption isotherms of the analyzed components. The corresponding isotherms are found in the literature or determined by the statistical method and the difference between the entered number of the analyzed component and remaining in the equilibrium gas phase (method of evaporation of liquids from the vacuum microburette, gas volumetric method). Statistical methods used in the study of adsorption of individual gases or vapors in vacuum installations in which the adsorbent pre-pumped by heating to remove the previously adsorbed components. The presence of extraneous components reduces the amount of adsorption and slows down the balance.

Installation to determine the equilibrium pressure with vacuum microburette from which the vapor of the liquid component is applied to the ampoule with the separating liquid. The amount of dissolved component is measured by the loss of this component in microburette minus the number of the component remaining in the gas space above the separating liquid. The volume of this space is pre-nomerami. In volumetric gas method uses the same principle, but the gas source is a gas burette [1, S. 432, last paragraph]. For example, low equilibrium pressure at which the observed proportional dependence of the partial pressure of the analyzed component from its mole fraction for benzene is 0.2 mm Hg), and carbon tetrachloride - 0.45 mm [1, C. 418, Fig. XVI.l].

Known design chromatograph [1, S. 514, Fig.1], in which the carrier gas from the cylinder through the valve enters the column, after exiting the column, the gas passes the detector. A detector that registers the change of thermal conductivity of the gas on the heated metal threads, is more sensitive and therefore more preferable [ibid, S. 514]. The volumetric rate of gas is measured after the output of the detector by the rheometer. For the quantitative determination of benzene and its homologues chromatographic column through the exit of the rheometer is connected to a vacuum pump that creates and supports the analysis vacuum (residual pressure) in the column equal to 0.2 mm Hg. The approximate conditions of the analysis (except pressure) different components of crude oil are shown in table [2, C. 134, PL.1]. In the rest of the course of the analysis area is the development of a chromatographic column to a residual pressure (fraction mm Hg) allows you to extend the range of the separating liquid (stationary phase) at high temperature and provides a more distinct separation of components by reducing erosion (overlay) of the chromatographic bands of the analyzed mixture.

Literature

1. J. I. Gerasimov, V. P. Drawing, E. N. Eremin, etc. a Course in physical chemistry. Volume 1. Edition 2. M.: Chemistry, 1969, 592 S.

2. M. S. Vigdergauz. Gas chromatography as a method of research oil. M.: Nauka, 1973, 256 S.

The way physico-chemical analysis of materials, including separation in the chromatographic column components of the mobile phase as it moves along the stationary phase with a programmable temperature, characterized in that the separation of the components produced at low residual pressure, ensuring compliance with proportion to the partial pressure of the analyzed component from its mole fraction in the separating liquid.

 

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