Method of recovering aromatic hydrocarbons from non- condensed styrene production gases

FIELD: petrochemical processes.

SUBSTANCE: method provides for three-stage isolation of aromatic hydrocarbons in the separation, absorption, and separation stages using, as absorbent, ethylbenzene rectification bottom residue. Loaded absorbent containing diethylbenzene isomer mixture serves as starting material for production of alkylaromatic hydrocarbons including divinylbenzene.

EFFECT: reduced loss of aromatic hydrocarbons and improved economical efficiency of styrene production process.

2 dwg, 1 tbl, 5 ex

 

The present invention relates to the production of styrene, in particular to the method of separation of aromatic hydrocarbons from nscontainerbox gases for styrene, and can be used in the petrochemical industry in the production of styrene and other aromatic hydrocarbons.

The known method (ed. St. USSR №1168545, class C 07 C 15/46, 1985) release of aromatic hydrocarbons from nscontainerbox gases, which as absorbent use the distillation residues of the distillation of styrene, when the high viscosity of the absorbent requires the introduction of a diluent and, as a consequence, the additional energy consumption by Stripping and distillation products absorption.

The known method (U.S. Pat. U.S. No. 4288234, CL 01 D 47/00, 1981) selection of aromatic hydrocarbons from nscontainerbox gases of the catalytic dehydrogenation of ethylbenzene by means of absorption neskondensirovannyh gas. Removals are heavy by-products of the production of ethylbenzene containing diphenylethan and polyalkylbenzene, including o-m-p-diethylbenzene at a temperature 17-52° and a pressure of 1-8 ATA. Desorption of aromatic hydrocarbons from saturated technical absorbents provide steam at a temperature of 52-149° and the pressure of 0.07 to 2.8 ATA. According to this method, the volume fraction remaining in nscontainerframe aromatic hydrocarbons is 0.2%.

The known method has drawbacks:

1. High residual content of aromatic hydrocarbons in neskondensirovannyh gas.

2. Use as an absorbent for processing exhaust gases polyalkylbenzenes resin containing o-m-p-diethylbenzene that requires thorough cleaning released by desorption of aromatic hydrocarbons.

3. Recycling in the scheme of obtaining styrene desorbed aromatic hydrocarbons containing diethylbenzene who enter the system for the allocation of styrene, where return ethylbenzene sent to the dehydrogenation, where from diethylbenzene formed divinylbenzene, causing intensive driving cross-linked polymer, which reduces the capacity of the plant and leads to the loss and deterioration of the quality of the target product is styrene. In addition, desorption of aromatic hydrocarbons from saturated heavy absorbent, as under vacuum and at a pressure in the desorption column requires greater consumption of power.

The closest in technical essence and the achieved result of the present invention is a method for separating aromatic hydrocarbons from neskondensirovannyh gases styrene production (Patent RF №2063950, class C 07 C 15/46, 7/11, 20.07.1996). The method involves the selection aromatizes the x hydrocarbons from neskondensirovannyh gases styrene production in three stages. The first stage - pre-selection of aromatic hydrocarbons separation. The second stage is the absorption of aromatic hydrocarbons, etilbenzene charge. The third separation unabsorbed gas drop entrainment.

Absorbent - ethylbenzene mixture is a mixture of direct and return ethylbenzene, with a mass fraction, %: benzene 0,1; toluene 0,8; ethylbenzene 98,6; styrene of 0.5. The rich absorbent is again applied to the dehydrogenation of ethylbenzene to styrene.

According to prototype selection aromatic hydrocarbons carried out according to the following scheme (Graphic images. Figure 1).

Neskondensirovannyh gas, volume fraction of aromatic hydrocarbons in which a 1.46-3,80%coming from the Department of condensing gas contact process for the catalytic dehydrogenation of ethyl benzene from line 1 enters the drop entrainment 2, where at a temperature of 1-5° and pressure of 1,2-5,0 ATA allocated mechanically gone hydrocarbons and water. Speed tangentially introduced into the drop entrainment on line 1 gas flow of 50 m/S. the Use of drop entrainment can reduce the content of aromatic hydrocarbons and water, and thereby to reduce the load on the stage of absorption.

Neskondensirovannyh gas of drop entrainment 2 line 5 enters the absorber 6, where line 7 is absorbent. As the absorbent used is to ethylbenzene charge - a mixture of straight run and return benzene containing a mass fraction, %: benzene - 0,1; toluene - 0,8; ethylbenzene - 98,6; styrene and 0.5. The absorption process is carried out at a temperature of minus 10 - +1° and a pressure of 1.2-5 ATA. Speed neskondensirovannyh gas on the free section of 0.22 m/s, density of coverage not less than 5 m3/m2·including the Rich absorbent from the absorber 6 through line 8 flows into the collector 4.

Neskondensirovannyh gas containing no water from the absorber 6 through line 9 is sent to the drop entrainment 10, at a temperature of minus 10 to minus 15° and pressure of 1,2-5,0 ATA additionally allocated hydrocarbons. Speed tangentially introduced into the drop entrainment on line 9 flow neskondensirovannyh gas 50 m/s, the drop entrainment equipped agglomerated device.

After the selection in the drop entrainment 10 volume fraction of aromatic hydrocarbons in neskondensirovannyh gas in line 12 is 0,008%.

Nscontainerframe hydrocarbons from the drop entrainment 10 through line 12 is directed or burning is used as fuel, or for generation of hydrogen gas. Selected hydrocarbons from the drop entrainment 10 line 11 enter the collector 4. Aromatic hydrocarbons with water from collector 4 through line 13 serves as a component of raw materials, in the dehydrogenation of ethylbenzene.

The disadvantage of this method is:

2. In the presence of styrene in raw materials for the dehydrogenation under the influence of high temperature non-catalytic reaction zones by free radical mechanism is the formation of impurities which adversely affect the quality of commercial styrene:

The aim of the invention is to reduce losses of aromatic hydrocarbons, the improvement of technical and economic indicators of the production of styrene by increasing the selectivity of the target response and avoiding contamination of the raw materials dehydrogenation products of side reactions that adversely affect the catalyst and the properties of the commodity styrene. At the same time rich absorbent containing o-m-p-diethylbenzene used as a valuable component of the process feedstock Ave is in the production of polystyrene.

This objective is achieved in that the aromatic hydrocarbons are allocated from nscontainerbox gases styrene production in three stages:separation, absorption and separation, and as absorbent under absorption using the VAT residue of ethylbenzene obtained in the production of ethylbenzene and hydrocarbon having the following composition, mass fraction of component,%:

- ethylbenzene 11,17-30,40

- o-m-p-xylene 0,03-0,10

- diethylbenzene 80,50-63,10

- polyalkylbenzene 8,30-6,40

Comparative analysis of the proposed method with the prototype allows to conclude that the claimed method differs from the known use as an absorbent for absorption of aromatic hydrocarbons from nscontainerbox gases styrene production of the cubic residue of ethylbenzene, which, after saturation is used in the process of getting divinylbenzene.

Analysis of the known methods of extraction of aromatic hydrocarbons from nscontainerbox gases styrene production showed that the method of separation of aromatic hydrocarbons from nscontainerbox gas production of styrene, which includes three stages: separation, absorption and separation are known. Known facts and use as absorbents, recirculating in the process of obtaining styrene ethylbenzene the charge and heavy by-products of the production of ethylbenzene, containing diphenylethan and polyalkylbenzene. However, only the fact that the use as absorbent VAT residue of ethylbenzene, which, after saturation derived from the process of obtaining styrene and used as raw materials for the production of divinylbenzene, allows deep to extract aromatic hydrocarbons from nscontainerbox gases and at the same time not impair the properties of the target product is styrene.

The essence of the method consists in the following.

Selection of aromatic hydrocarbons is carried out on the following concept (Graphic images. 2).

Neskondensirovannyh the gas separation dehydrogenation of ethylbenzene after condensation from line 1 enters the drop entrainment 2, from which liquid aromatic hydrocarbons and water lines 3 are merged into the collector 4. Separation of hydrocarbons and water in the drop entrainment 2 is carried out at a temperature of 1-5° and pressure of 1,2-5,0 ATA. The use of drop entrainment can reduce the content of aromatic hydrocarbons and water in the stream arriving at the stage of absorption.

Neskondensirovannyh gas of drop entrainment 2 line 5 enters the absorber 6, where line 7 is absorbent. As absorbent under absorption using the VAT residue of ethylbenzene with the following hydrocarbon is left, mass fraction of component, %:

- ethylbenzene 11,17-30,40

- o-m-p-xylene 0,03-0,10

- diethylbenzene 80,50-63,10

- polyalkylbenzene 8,30-6,40

The absorbance of aromatic hydrocarbons is carried out at a temperature of minus 10 - +1° and pressure of 1,2-5,0 ATA. The density of irrigation in the absorber is not less than 5 m3/m2·including the process of absorption in sub-zero temperatures implies the density of irrigation atmospheric distillation, providing complete solubility of water in the absorbent material.

The rich absorbent from the absorber 6 through line 8 flows into the collector 4. Neskondensirovannyh gas containing no water from the absorber 6 through line 9 is sent to the drop entrainment 10, at a temperature of minus 10 to minus 15° and pressure of 1,2-5,0 ATA additionally allocated hydrocarbons. The drop entrainment 10 equipped agglomerated device.

Nscontainerframe hydrocarbons from the drop entrainment 10 through line 12 is directed or burning is used as fuel, or for generation of hydrogen gas. Selected hydrocarbons from the bump 10 on line 11 enter the collector 4. Aromatic hydrocarbons and water from the collector 4 through line 13 serves for the production of polystyrene.

The use of the proposed method of separation of aromatic hydrocarbons from nscontainerbox gases styrene production will reduce materialisation, to improve technical and economic performance of the production of styrene by increasing the selectivity of the target response and avoiding contamination of the raw products of side reactions that adversely affects the performance of the catalyst and the properties of the commodity styrene. At the same time rich absorbent containing o-m-p-diethylbenzene, serves as raw material for polystyrene.

The invention is explained with the following examples.

Example 1 (the prototype).

Selection of aromatic hydrocarbons from neskondensirovannyh gas coming from the Department of condensing gas contact process for the catalytic dehydrogenation of ethylbenzene, is carried out in three stages. Neskondensirovannyh gas, volume fraction of aromatic hydrocarbons in which 1,46%, is fed to the first stage in the drop entrainment 2, where at a temperature of 1° and a pressure of 1.2 ATA allocated mechanically gone aromatic hydrocarbons and water. Speed tangentially introduced through line 1 flow neskondensirovannyh gas in the drop entrainment 50 m/S.

In the second stage absorption are etilbenzene the charge composition, mass fraction, %: benzene -0,03; -of-0.7 toluene; ethylbenzene -98,66; styrene - 0,61 at a temperature of 1° and a pressure of 1.2 ATA. Speed neskondensirovannyh gas on the free section of 0.22 m/s gravity irrigation 5 m3/m2· PM

In the third stage, the aromatic hydrocarbons are separated from neskondensirovannyh gas drop entrainment 10 at a temperature of minus 10° and a pressure of 1.2 ATA. Speed tangentially introduced through line 9 flow neskondensirovannyh gas in the drop entrainment 50 m/s, the drop entrainment equipped agglomerated device.

After selecting the volume fraction of aromatic hydrocarbons in neskondensirovannyh gas in line 12 is 0,008%.

Data material balance flow given in the table.

Example 2.

The process is conducted according to the proposed method. Selection of aromatic hydrocarbons from neskondensirovannyh gas coming from the Department of condensing gas contact process for the catalytic dehydrogenation of ethylbenzene, is carried out in three stages. Neskondensirovannyh gas volume fraction of aromatic hydrocarbons 1,46% is applied to the first stage in the drop entrainment 2, where at a temperature of 1° and a pressure of 1.2 ATA allocated mechanically gone aromatic hydrocarbons and water. Speed tangentially introduced through line 1 flow neskondensirovannyh gas in the drop entrainment 50 m/S.

In the second stage absorption are kubovy balance of ethylbenzene, hydrocarbon having the following composition, mass fraction of component, %:

- ethylbenzene 11,17-30,40

- o-m-p-xylene 0,03-0,10

di is tevenson 80,50-63,10

- polyalkylbenzene 8,30-6,40

Temperature absorption 1° C, a pressure of 1.2 ATA. Speed neskondensirovannyh gas on the free section of 0.22 m/s gravity irrigation 5 m3/m2·PM

In the third stage, the aromatic hydrocarbons are separated from neskondensirovannyh gas drop entrainment 10 at a temperature of minus 10° and a pressure of 1.2 ATA. Speed tangentially introduced through line 9 flow neskondensirovannyh gas in the drop entrainment 50 m/s, the drop entrainment equipped agglomerated device.

After selecting the volume fraction of aromatic hydrocarbons in neskondensirovannyh gas in line 12 is 0,0015% (table).

Example 3.

The process is conducted according to the proposed method. Selection of aromatic hydrocarbons from neskondensirovannyh gas coming from the Department of condensing gas contact process for the catalytic dehydrogenation of ethylbenzene, is carried out in three stages. Neskondensirovannyh gas volume fraction of aromatic hydrocarbons 2,90% line 1 is the drop entrainment 2, where at a temperature of 3° and a pressure of 3 ATA allocated mechanically gone aromatic hydrocarbons and water. Speed tangentially introduced through line 1 flow neskondensirovannyh gas in the drop entrainment 50 m/S.

In the second stage absorption are kubovy balance of ethylbenzene as in example 2) at a temperature of absorption minus 2° C and a pressure of 3 ATA. Speed neskondensirovannyh gas on the free section of 0.22 m/s gravity irrigation 5 m3/m2PM

In the third stage, the aromatic hydrocarbons are separated from neskondensirovannyh gas drop entrainment 10 at a temperature of minus 12° and a pressure of 3 ATA. Speed tangentially introduced through line 9 flow neskondensirovannyh gas in the drop entrainment 50 m/s, the drop entrainment equipped agglomerated device.

After selecting the volume fraction of aromatic hydrocarbons in neskondensirovannyh gas in line 12 is 0,0015% (table).

Example 4.

The process is conducted according to the proposed method. The volume fraction of aromatic hydrocarbons in neskondensirovannyh gas of 3.6%. Process conditions similar to those suggested in example 3. Balance sheet data in the table.

Example 5.

The process is conducted according to the proposed method. The volume fraction of aromatic hydrocarbons in neskondensirovannyh gas of 3.8%. Process conditions similar to those suggested in example 3. Balance sheet data in the table.

The method of separation of aromatic hydrocarbons from nscontainerbox gases styrene production, including phase separation, absorption and separation, characterized in that the absorbent under absorption using the VAT residue of rectifica the AI ethylbenzene, after saturation as the raw material for the production of alkylaromatic hydrocarbons, including divinylbenzene and hydrocarbon having the following composition, mass fraction, %:

Ethylbenzene 11,17 - 30,40

Automatomatically 0,03 - 0,10

Diethylbenzene 80,50 - 63,10

Polyalkylbenzene 8,30 - 6,40



 

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