SU735992A1 - Adsorbent for gas chromatography - Google Patents

Description

(54) ADSORBENT FOR GAS -XPOMATOrPAOHH

I

The invention relates to a gas chromatographic separation method for mixtures of saturated and unsaturated normal and isostatic hydrocarbons and can be used in the chemical and petrochemical industries.

; -. "It is known to use as adsorbents or carriers for liquid phases in gas chromatography of various types: silica compounds, synthetic and natural zeolites, as well as porous polymeric materials of different polarities 1, 2 and 3.

In most cases, the aforementioned absorbents and carriers do not simultaneously have mechanical strength, high selectivity, thermal stability, and a sufficient desorption rate, which makes it difficult to quickly and completely separate substances with similar physicochemical properties.

In addition, many of them have noticeable adsorption and catalytic activity, which impairs their separation properties. As a rule, they require additional processing: modification, application of liquid and polymer phases, the use of binding, special installations for the granulation of Forming grains of the required size. This makes it difficult and expensive to prepare them.

A known method for separating mixtures of hydrocarbons Ci-C 7 by gas adsorption chromatography using industrial pink cobalt (II) 4 as an adsorbent.

The disadvantage of this method is the low temperature resistance of cobalt (II) hydroxide, which does not allow to increase the temperature of separation above 100 ° C, since in the range of 100-110 ° С Co (OH) g turns into oxide forms, which are much lower than the initial selectivity drug. Consequently, the use of cobalt hydroxide as an adsorbent in the analysis

15 higher boiling hydrocarbons (Cg-do) is practically impossible.

The purpose of the invention is to develop a method for the chromatographic separation of saturated and unsaturated normal hydrocarbons and the composition from Ci to Xu.

This goal is achieved by the use of cadmium (II) hydroxide as an adsorbent.

It has a sufficiently high mechanical strength and heat resistance (up to 150 ° C), which allows it to carry out the process of separating heavier hydrocarbons in the temperature range from 30 to 150 ° C.

In addition, the adsorbent does not require any pre-treatment, except sieving on a specific fraction (0.25-0.5 mm).

As shown by the experiments, when using cadmium (P) hydroxide, a sufficiently complete and precise separation of complex mixtures of hydrocarbons containing from 12 to 20 components is achieved. The use of a programmed increase in the temperature of the column shortens the analysis time, which for all mixtures does not exceed 20-30 minutes on average.

The separation process can be carried out on any chromatograph using a flame ionization detector or thermal conductivity detector. The length of the column varies from 1.0 to 4.0 m (d 0.4 cm); speed of carrier gas (gels) from 10 to 50 ml / min. The programmed temperature increase of the column was carried out at a rate of 3-10 ° C / min. The tests were carried out on a Tsvet-100 chromatograph.

The following are examples of the separation of mixtures of hydrocarbons using Cd (II) hydroxide as an adsorbent.

The peaks in the chromatograms, indicated by numbers, correspond to the components of the mixture to be separated.

Example 1. A model mixture of hydrocarbons of composition Ci € 7: 1 is methane, 2 is ethane,

3-member, 4 - propane, 5 - propylene,

6- isobutylene, 7 - n. butane, 8 - a-butylene,

9-trans-butylene, 10 - isobutylene, 11 - cis-butylene, 12 - isopentane, 13 - n. pentane, 14 - isohexane, 15 - n. hexane, 16 - isoheptane, 17 - n. heptane.

FIG. 1 shows the chromatogram of the mixture obtained under the following conditions: ionization-flame detector, column length 4.0 m, carrier gas rate 40 ml / min, test temperature 50-140 ° C, column temperature rise rate

10 ° C / min, sample size 0.2 μl, analysis time 25 min.

Example 2. Industrial mixture of composition Ci-Cg: 1 - methane, 2 - ethane, 3 - ethylene,

4 - propane, 5 - propylene, 6 - propadiene,

7- isobutane, 8 - n. butane, 9 - butene-1, 10 - isobutylene, 11 - tra c-butene-2, 12 - cis-butene-2, 13 - methylacetylene, 14 - divinyl, 15 - isopentane, 16 - n. pentane, 17 - 2,2-dimethylbutane, 18 - pentene-1, 19 - 2-methylbutene-1, 20 - trans-pentene-2, 21 - cis-pentene-2.

FIG. Figure 2 shows the chromatogram of the mixture obtained under the following conditions: column length 3.0 m, carrier gas (gels) speed 30 ml / min, test temperature 30-140 ° C, column rise temperature 7335992

ki 6 ° C / min, sample size 1.0 ml. Under these conditions, a clear separation of this mixture is achieved within 30 minutes.

In the practice of work of factory and research laboratories for this purpose, 5 commonly used combination columns up to 10 m in length, filled with sodium alumina modified with sodium hydroxide, which is then applied diethylene glycol or squalane. The preparation of this adsorbent includes the following stages: calcination at 300 ° С, treatment with 3% stretch with NaOH for 24 h, substance at 100 ° С, and then applying a 2% liquid phase. The speed of the carrier gas is 80 ml / min, the analysis time is 60-90 minutes. The disadvantage of the above method is also the high hygroscopicity of the alumino gel, which makes the chromatographic columns less durable (less than a month).

Example 3. Isomerizate Cj composition: 1 - n. heptane, 2 - 2,2,3,3-tetramethylbutane, 3. - 0, 2,2-dimethylhexane, 4 - 2,4-dimethylhexane, 5 - 2,2,3-trimethylpentane, 6 - 3,3-dimethylhexane, 7 - 2,3,3-trimethylpentane, 8 - 2,3 dimethylhexane, 9 - 2-methylheptane, 10 - 4-methylheptane, 11 - 3,4dimethylhexane, 123-ethylhexane, 13 - 3-methylheptane, 14 - n. octane.

FIG. 3 shows the chromatogram of the mixture obtained under the following conditions: detector – catarometer, column length 2.5 m, carrier gas speed 20 ml / min, test temperature 70-150 ° C, column temperature rise rate 6 ° C / min, value 7.0 μl samples, analysis time 17 min.

Example 4. Isomerizate C5 composition: 1 - n. octane, 2 - 2,3,5-trimethylhexane, 3 - 2,4-dimethylheptane, 4 - 2,6-dimethylheptane, 5 - 2,5-dimethylheptane, 6 - 3,3-dimethylheptane, 7 - 2,3- dimethylheptane, 8 - 4-ethylheptane, 9 - 3-ethylheptane, 10 - 2-methyloctane, II - 3-methyloctane, 12 - n. nonan.

FIG. 4 shows the chromatogram of the mixture obtained under the following conditions: detector — ionization-flame, column length 1.0 m, carrier gas speed 30 ml / min, test temperature 80–150 ° C, column temperature rise rate 6 ° C / min, sample size 0.5 μl, analysis time 20 min.

In practice, the separation of mixture No. 3 and No. 4 is carried out on a one-hundred-meter capillary column using squalane as the liquid phase.

Thus, the proposed adsorbent in the separation of complex hydrocarbon mixtures is characterized by high geometric uniformity (5lg 15-20, gef.po () 1000 A), mechanical strength and higher heat resistance compared to cobalt hydroxide (P), which makes it possible to carry out selective separation of higher-boiling hydrocarbon blends with Cg-Xu chain length.

Claims (4)

1. US Patent No. 3677938, cl. 73-23, published. 1972. 2. The patent of France No. 2091714, cl. G 01 N 31/08, published 1972. 3. USSR author's certificate number 481295, cl. G 01 N 31/08, 1975. 4. USSR author's certificate No. 442420, cl. G 01 N 31/08, 1974 (prototype). 30 of FIG. 2 I OMUH 15 go Oh min 10 .З .i; t zo ten O min ffl