C4 hydrocarbon fraction separation process

FIELD: petrochemical processes.

SUBSTANCE: C4-hydrocarbon fractions obtained by cracking and/or pyrolysis of hydrocarbon feedstock in presence of amine-type extractant are subjected to rectification additionally involving butylene-isobutylene fraction resulting from butylene-to-isobutylene isomerization and containing 30-70% butylenes, 25-65% isobutylene, and 3-8% butanes. Weight ratio of C4-hydrocarbon fractions to added butylene-isobutylene fraction is 1:(3-7).

EFFECT: increased separation efficiency.

3 ex

 

The invention relates to the field of petrochemical industry, specifically to the division With4hydrocarbon fraction by extractive distillation, and can be used in the synthetic rubber industry.

The known method of separation of butane-butenova fractions by means of extractive distillation using as the extractant acetone or acetonitrile (Pasiecznik, Van, Limpopo "Album of technological schemes of the main production of the synthetic rubber industry". L., "Chemistry", 1986, p.14-16). Separation is butane-butenova fraction isolated from contact gas of the first stage dehydrogenation of butane and butene recycle-butadiene fraction.

The method is designed to separate4hydrocarbon fractions with a low content of isobutylene and aims to obtain butadiene-1,3.

Closest to the present invention is a method of separation4hydrocarbon fractions of catalytic cracking, which are characterized by the absence of butadiene and a relatively low content of isobutylene (12-16 wt. -%), or4hydrocarbon fractions of pyrolysis gasoline containing up to 45% of the mass. butadiene by extractive distillation (Shuvalov "isolation and purification of monomers for synthetic rubber. L., "Chemistry", 1987, str-170).

The drawback described what about the method is incomplete extraction of butane partial fractions, which affects their further processing. In addition, the method allows for the separation or pyrolysis or cracking of fractions, and is not intended for the processing of fractions having different composition.

The objective of the invention is to develop a way to share With4hydrocarbon fractions of different composition to achieve a high degree of separation.

The problem is solved by providing a method of separation4hydrocarbon fractions obtained by cracking and/or pyrolysis of hydrocarbons by distillation in the presence of amine extractant type, with rectification additionally served butylene-isobutilene fraction obtained by isomerization of butylenes in the isobutylene containing 30-70 wt%. butylenes, 25-65% of the mass. of isobutylene and 3-8% of the mass. butane, while the mass ratio of the mixture of hydrocarbon fractions With4: butylene-isobutilene fraction withstand equal to 1:3-7.

The difference of the proposed method from the closest is that separation With4hydrocarbon fractions additionally serves obtained by isomerization of butylenes in the isobutylene fraction containing 30-70 wt%. butylenes, 25-65% of the mass. of isobutylene and 3-8% of the mass. butane, maintaining the mass ratio of the fraction of uglevodorov the s 4: butylene-isobutilene fraction equal to 1:3-7.

Rectification can be carried out in the presence of an extractant containing, for example, acetonitrile, dimethylformamide, dimethylacetamide, etc.

The proposed method is as follows.

With4the hydrocarbon fraction obtained by cracking and/or pyrolysis of hydrocarbons, and butylene-isobutilene fraction obtained by isomerization of butylenes in the isobutylene containing 30-70 wt%. butylenes, 25-65% of the mass. of isobutylene and 3-8% of the mass. butane, is fed into the extractive distillation column. The mass ratio of the fraction of hydrocarbons With4: butylene-isobutilene fraction withstand equal to 1:3-7. In the extractive distillation column in the presence of amine extractant type is the separation of hydrocarbon fractions on butane-isobutane and butylene-isobutilene fraction. From the top of the extractive distillation column select pairs butane-isobutane fraction, which after condensation is directed to washing from the extractant and further processing. VAT product of the extractive distillation column is sent to the desorption column. To reduce the number of process equipment the bottom of the column extractive distillation can be connected with the column desorption. In the desorption column is proishodit selection butylene-isobutilene fraction of the extractant. From the top of the desorption column to select pairs butylene-isobutilene fraction, which after condensation is directed to washing from the extractant and further processing.

The implementation of the method of separation4hydrocarbon fractions are illustrated in the following examples.

Example 1

With4the hydrocarbon fraction obtained by cracking hydrocarbon feedstock having a composition, % wt.: hydrocarbons With3- 2,61, ∑ butane - 31,85, butylene - 23,72, isobutylene - 41,82, and the fraction obtained from the isomerization of butylenes in the isobutylene containing % mass.: hydrocarbons With3is 2.01, butylene - 55,23, isobutylene - 39,48, ∑ butane (butane+isobutane) of 3.28, is fed into the extractive distillation column, where as extractant serves a 10%aqueous solution of acetonitrile. The mass ratio of the fraction of hydrocarbons With4: butylene-isobutilene fraction withstand equal to 1:3.

From the top of the extractive distillation column select pairs butane-isobutane fraction, which after condensation is directed to washing from the extractant and further processing, the following composition, % wt.: hydrocarbons With3- 1,95, ∑ butane (butane+isobutane) - 97,05, butylene - 0,4, isobutylene - 0,6.

VAT product of the extractive distillation column is sent to the desorption column. From the top of the desorption column to select the ary butylene-isobutilene fraction, after condensation is directed to washing from the extractant and further processing, the following composition,% wt.: ∑ butane - 0,45, butylene - 51,74, isobutylene - 47,81.

Example 2

With4the hydrocarbon fraction obtained in the pyrolysis of hydrocarbons, having a composition, % wt.: hydrocarbons With3- 1,51, ∑ butane - 36,18, butadiene-1,3 - 1,0, butylene - 30,54, isobutylene - 30,77, and the fraction obtained from the isomerization of butylenes in the isobutylene containing% mass.: hydrocarbons With3is 2.01, butylene - 30,53, isobutylene - 59,46, ∑ butane (butane+isobutane) to 8.0, is fed into the extractive distillation column, where as extractant serves 8%aqueous solution of acetonitrile. The mass ratio of the fraction of hydrocarbons With4: butylene-isobutilene fraction withstand equal to 1:7.

From the top of the extractive distillation column select pairs butane-isobutane fraction, which after condensation is directed to washing from the extractant and further processing, the following composition, % wt.: hydrocarbons With3- 1,95, ∑ butane (butane+isobutane) - 97,05, butylene - 0.3, the isobutylene - 0,7.

VAT product of the extractive distillation column is sent to the desorption column. From the top of the desorption column to select pairs butylene-isobutilene fraction, which after condensation sent for laundering oakstreet and further processing, the following composition, % wt.: ∑ butane - 2,45, butylene - 49,74, isobutylene - 47,81, butadiene-1,3 is 1.0.

Example 3

With4the hydrocarbon fraction obtained by cracking hydrocarbon feedstock having a composition, % wt.: ∑ butane - 61,28, butylene - 23,72, isobutylene - 15,0, C4the hydrocarbon fraction obtained in the pyrolysis of hydrocarbons, having a composition, % wt.: hydrocarbons With3- 1,51, ∑ butane - 30,18, butadiene-1,3 - 0,5, butylene - 37,04, isobutylene - 30,77, and the fraction obtained from the isomerization of butylenes in the isobutylene containing % mass.: hydrocarbons With3- 1,01, butylene - 69,53, isobutylene - 25,18, ∑butane (butane+isobutane) - 4,28, is fed into the extractive distillation column, where as extractant serves a 10%aqueous solution of acetonitrile. The mass ratio of the fraction of hydrocarbons With4: butylene-isobutilene fraction withstand equal to 1:5.

From the top of the extractive distillation column select pairs butane-isobutane fraction, which after condensation is directed to washing from the extractant and further processing, the following composition, % wt.: hydrocarbons With3- 1,95, ∑ butane (butane+isobutane) - 97,05, butylene - 0,5, isobutylene and 0.5.

VAT product of the extractive distillation column is sent to the desorption column. From the top of the desorption column select p is the market butylene-isobutilene fraction, after condensation is directed to washing from the extractant and further processing, the following composition, % wt.: ∑ butane - 0,45, butylene - 51,74, isobutylene - 47,81.

As seen from the above examples, the proposed method allows to separate4hydrocarbon fractions of different composition and to achieve a high degree of separation.

The method of separation4hydrocarbon fractions obtained by cracking and/or pyrolysis of hydrocarbons by distillation in the presence of amine extractant type, characterized in that the rectification additionally served butylene-isobutilene fraction obtained by isomerization of butylenes in the isobutylene containing 30-70 wt.% butylenes, 25-65 wt.% of isobutylene and 3-8 wt.% butane, while the mass ratio of the mixture of hydrocarbon fractions With4:butylene-isobutilene fraction withstand equal to 1:3-7.



 

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