The method of determination of paraffin hydrocarbons in-olefins

 

(57) Abstract:

The method is designed to determine paraffin hydrocarbons in the olefin. The inventive method involves dilution of the sample heptane in a volume ratio of the sample : heptane equal to (1-1,2):5, passing the sample through chemical sorbent fractions of 0.06 to 0.1 mm at a volume ratio test : chemical sorbent equal to 1:(45-50), collecting the first portion of the eluate, drying to constant weight, and determination of the mass balance. As the use of chemical sorbent silica gel, treated with silver nitrate. The volume of the first portion of the eluate is not less than 2.5 times the size of the volume of solution taken for the chromatography was carried out.

The invention relates to the field of analytical chemistry, namely the chromatic method of determination of paraffin hydrocarbons in the olefin fraction C20-26.

There is a method of determining the paraffin hydrocarbons in the olefin fraction C20-26[1] by subtracting from 100% the content of olefins, a specific method synthesized.

The disadvantage of this method is high (up to 100 Rel.%) the measurement error that is associated with low paraffin content (about 5 wt.%) compared with the content of the result is a method of determining the paraffin-olefin fraction C16-18[2] by separating paraffins from olefins by liquid chromatography, according to which 2 g of the analyzed sample is mixed 0,03-0,04 g pentadecane ("label"), then 1 g of the sample with the "label" is served on top of a column containing 20 g of sorbent AgNO3/SiO2with faction 0,06-0,16 mm Paraffin hydrocarbons elute with hexane, the eluate containing the label, and contained in the sample paraffins analyzed by gas chromatography.

The disadvantages of the method are its high cost associated with a high consumption of silver nitrate (2,22 g on one definition), high uncertainty associated with the complexity contained paraffins (20 species), when the error in the determination of each component contributes to the definition of the total content of paraffin hydrocarbons, as well as the unacceptability for more analysis of high molecular weight olefins (C20-26) solidifying at room conditions.

The essence of the invention is a method for the determination of paraffin hydrocarbons in the olefin, in which the sample is diluted with heptane in a volume ratio of the sample: heptane (1-1,2):5 (to ensure the temperature of solution turbidity not exceeding 20oC) and injected into a column with a diameter of 10 the next volume ratio of the sample olefins:chemical sorbent 1: (45-50), elute with heptane until the volume of the eluate consisting of not less than 2.5 times the volume of the aliquot (solution of the sample introduced into the column), the eluent is evaporated, and determine the mass balance.

Dilution of the sample heptane to provide the cloud point of the solution not exceeding 20oC allows to avoid overstatement of the results of determination by eliminating overshoot undissolved olefins, and the use of the silica gel fractions of 0.06 to 0.1 mm allows to reduce the consumption of chemical sorbent containing silver nitrate, and also to facilitate its preparation (to carry out the drying at atmospheric pressure).

Determination of paraffin hydrocarbons in the olefin by dilution with heptane in a volume ratio of the sample:heptane (1-1,2):5 and passing through a column with a diameter of 10-11 mm, filled with silica gel fractions of 0.06 to 0.1 mm, treated with nitrate of silver, with a volumetric ratio test of olefins: chemical sorbent 1: (45-50), elution with heptane to achieve the volume of eluent consisting of not less than 2.5 times the volume entered in the column of solution samples, is a distinguishing characteristic, not found in similar technical solutions allows to reduce the error to define the characteristics and the achieved effect confirms the compliance of the proposed technical solution criteria invention of "novelty" and "inventive step".

The simplicity of the analysis, the availability, accuracy, the ability to implement on an industrial scale confirm compliance with a criterion of "industrial applicability".

The invention is carried out as follows. 1 g of sample was diluted with 5 cm3heptane, stirred until complete disappearance of turbidity, 1.4 to 1.5 g of the obtained solution contribute in column 7 g of chemical sorbent, representing the silica gel fractions of 0.06 to 0.1 mm, treated with a solution of silver nitrate (15 g of salt dissolved in 50 cm3water, put on 135 g of silica gel and dried for 15 hours at a temperature of 120-125oC and atmospheric pressure, or 7 hours at a temperature of 105oC and a residual pressure of 50 mm RT.cent.), paraffins elute with heptane until the volume of the eluate 5 cm3in suspended tube, the eluate blow a current of air at room temperature, the residue is dried at 105oC for 1 h and weighed. The difference of the masses determine the mass of paraffin hydrocarbons.

Mass fraction of paraffin hydrocarbons are calculated according to the formula

< / BR>
where

X - mass fraction of paraffin hydrocarbons in wt.%;

m is the mass selected paraffins, g;

M1is the mass of the original sample taken for analysis, g;

M2

A sample of olefins is heated in a water bath with a temperature of 50-70oC to obtain a transparent mass, make a 1 cm3samples suspended in Erlenmeyer flask 50 cm3and again weighed. The difference of the masses determine the mass of a sample (0,9172 g). Poured 5 cm3heptane and thoroughly stirred to obtain a clear solution. Into the flask insert a cork inserted in her pipette with a capacity of 2 cm3and weighed. Selected 2 cm3solution and applied to a column with chemical sorbent dropwise. The flask with a pipette and the remaining solution is still being weighed. The difference of the masses determine the mass introduced into the column in solution (1,4265 g). After soaked made solution sample, in column contribute heptane portions, so that the height of the layer of heptane over the sorbent was 0.5 to 2.0, see the Eluate is collected in a weighed glass tube with a diameter of 1.5-2.0 cm labeled 5 cm3. Upon reaching the volume of the eluate 5 cm3tube with eluate put under current cleaned from mechanical impurities of nitrogen or air and evaporate heptane. Tube with the remainder placed in an oven with a temperature of 105oC and continue drying for 60 minutes Then cooled tube and weighed. The difference of the masses determine the Mac is Rabinovich hydrocarbons in the olefin by liquid chromatography was carried out using as the chemical sorbent silica gel, processed silver nitrate, characterized in that the analyzed sample is diluted with heptane in a volume ratio of the sample : heptane equal to (1 - 1,2) : 5, is passed through a chemical sorbent fractions of 0.06 to 0.1 mm at a volume ratio test : chemical sorbent equal to 1 : 45 - 50, the first portion of the eluate volume, constituting not less than 2.5 times the size of the volume of solution samples taken from the chromatography was carried out, dried to constant mass and determine the mass balance.

 

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