Method for treatment of butadiene flow by removal of by-side products formed at stage for selective impurity hydrogenation

FIELD: organic chemistry, chemical technology.

SUBSTANCE: invention relates to technology for isolation and purification of butadiene prepared by thermal cracking of hydrocarbons followed by removing heavy by-side products from crude butadiene flow after the selective hydrogenation of undesirable impurities. The flow outgoing from the reaction zone of the selective hydrogenation is fed into evaporator with fraction zone for extraction of butadiene wherein this zone is sprayed with the raffinate flow from the zone of butadiene extraction. From the evaporator the vapor phase containing butadiene with reduced concentration of by-side products is removed and fed to the stage for isolating the concentrated liquid phase comprising heavy by-side products of the reaction. Butadiene-containing vapor phase is recovered to the zone for extraction of butadiene. The fraction zone comprises from 3 to 7 theoretical plates. The temperature in evaporator is maintained in the range from 27°C to 93°C under the pressure value from 375 to 790 kPa. Invention provides the improved technology in preparing the purified butadiene.

EFFECT: improved method for treatment.

5 cl

 

The technical field to which the invention relates.

The technical field to which the invention relates, for the removal of high molecular weight by-products of the reaction of selective hydrogenation of leaving the reaction zone of the stream.

The level of technology

Methods of preparation, isolation and purification of butadiene known, and the butadiene used in the manufacture of synthetic rubber. The crude butadiene get by thermal and catalytic cracking of hydrocarbons. Upon receipt of the crude butadiene also produces undesirable side products, such as ETHYLACETYLENE and vinylacetylene. The explosive nature of the acetylenes and the tendency to the formation and deposition of polymers requires special considerations when working with hydrocarbons containing acetylene. In addition, when enriched with butadiene stream is used to produce synthetic rubber, the presence of acetylene is very undesirable and should be removed. In order to minimize the difficulties caused by the presence of acetylenes, crude butadiene is subjected to selective hydrogenation in a special reaction zone, in which acetylene is converted into diolefine. However, when selective hydrogenation of acetylene formed trace amounts of heavy by-products, generally referred to as the polymer is, or "green oil". In structurally independent methods of selective hydrogenation of acetylenes resulting green oil is removed from the resulting butadiene using fractional column, equipped with all standard equipment including kettle-reboiler, the upper condenser with receiver and pump fill.

In US-A-4,049,742 described the way in which 1,3-butadiene allocate using selective solvent from the mixture With4-hydrocarbons containing 1,3-butadiene, hydrocarbons are more soluble in the selective solvent than 1,3-butadiene, including acetylene and possibly 1,2-butadiene and C5-hydrocarbons, and hydrocarbons, less soluble in the selective solvent than 1,3-butadiene. The crude mixture With4-share hydrocarbons with one or more extractive distillation zone a distillate containing the less soluble hydrocarbons, a fraction consisting of 1,3-butadiene, and the fraction containing the more soluble hydrocarbons, including higher acetylene and 1,3-butadiene.

In accordance with the present invention it was found that, when the selective hydrogenation emerging from the reaction zone a liquid stream containing crude butadiene and trace amounts of by-products, is subjected to evaporation in preparation for the subsequent extraction of butadiene in selek is active solvent, you can allocate a fraction enriched in heavy by-products of the reaction. In the present invention is applied evaporator containing fractional area that is irrigated process liquid raffinate from the extraction solvent.

The invention

It was discovered that an improved method of removing heavy side products of the reaction of selective hydrogenation of leaving the reaction zone of the flow can be achieved by the introduction of this exit stream in the evaporator for solvent extraction of butadiene containing fractional area that is irrigated by a stream of the raffinate from the solvent extraction of butadiene. This forms a vapor phase containing butadiene with a low concentration of heavy by-products, and the concentrated liquid phase containing heavy side reaction products.

One of the embodiments of the present invention relates to a method for removal of heavy by-products of the reaction of selective hydrogenation of the output from the reaction zone a stream containing butadiene and trace amounts of heavy by-products, which includes: (a) the filing of the exit stream from the reaction zone selective hydrogenation in the evaporator for solvent extraction of butadiene containing fractional area; (b) irrigation fractional area flow of raffinate from the extraction zone b is Tatiana; (C) allocating a vapor phase containing butadiene with a low concentration of heavy by-products from the evaporator; (d) the allotment and allocation of concentrated liquid phase containing heavy side reaction products, from the evaporator; (e) feeding the vapor phase containing butadiene, in the area of extraction of butadiene.

Other embodiments of the present invention encompass other aspects such as the structure and mode of operation of fractional zone.

Brief description of figures

The figure represents a simplified scheme of the technological operations of the preferred embodiment of the invention. The figure is intended for schematic illustration of the present invention and not to limit.

Detailed disclosure of the invention

The starting material for the method of the present invention is an output stream from the reaction zone selective hydrogenation containing butadiene and trace amounts of heavy by-products. The source material is introduced into the evaporator for solvent extraction of butadiene containing fractional area. The evaporator for the extraction of butadiene is preferably equipped with a kettle-reboiler, and fractional area preferably contains from 3 to 7 theoretical plates. The evaporator preferably operates at conditions including a temperature from 27 to 93°and pressure from 375 to 790 kPa.

Detailed description of figures

In the figure, the method of the present invention is disclosed using a simplified scheme of technological operations, where equipment such as pumps, devices, circuits, heat transfer and heat sink, compressors and similar equipment are not as unimportant for understanding the method. The use of such equipment is the responsibility of specialists in this field.

Let us turn now to the drawing. The original thread With untreated4-hydrocarbons and hydrogen enters the process through line 1 and enters the zone selective hydrogenation of 2. Out of the zone selective hydrogenation of 2 stream with a reduced concentration of acetylene compounds is on line 3 and enters the evaporator for solvent extraction of butadiene 4, equipped with a fractional area 5. The flow of raffinate from the solvent extraction of butadiene is fed in will evaporate the eh for the extraction of butadiene 4 through line 6. Waste fluid is drained from the evaporator for solvent extraction of butadiene 4 through line 8, and part of its on line 10 flows into the heat exchanger 11. The heated fluid exits the heat exchanger 11 through line 12 and enters the evaporator for solvent extraction of butadiene 4. At least one part of the bottom liquid passing through the line 8, issued on lines 9 and comes to recycling. Containing butadiene in the vapor phase with a low concentration of heavy by-products is removed from the evaporator for solvent extraction of butadiene 4 through line 7 and enters the area of extraction of butadiene.

Next, the method of the present invention is disclosed in the following example. This example, however, is not intended unjustified limitation of the method of the invention, but serves merely to illustrate the advantages of the method described above. These data should be considered as probable and satisfactory revealing the expected efficiency of the invention.

Example

The original thread With untreated4-hydrocarbons in the number and characteristics shown in table 1, enters the zone selective hydrogenation containing catalyst for selective hydrogenation containing copper. The original stream of hydrogen is also supplied to the zone selective hydrogenation with a speed of 11 kg/HR out of the zone selective hydrogenation stream postupaet evaporator for solvent extraction of butadiene, equipped with a fractional area. Fractional area is irrigated with liquid raffinate from the solvent extraction of butadiene in the number and characteristics given in table 1. The flow of the evaporated distillate in the amount of 21882 kg/h, the characteristics of which are given in table 1, is removed from the evaporator for solvent extraction of butadiene and enters the area of extraction of butadiene. Waste liquid containing hard polymer compound, is removed from the evaporator for solvent extraction of butadiene in the amount of 54 kg/h and goes for recycling.

Table 1

The balance mass (kg/h)
ComponentThe original neocis. With4The original hydrogenThe flow of raffinate in the evaporatorThe distillate from the evaporatorWaste liquid from the evaporator
Hydrogen111,6
Propane2,22,2
Propene6,5the 15.6
PROPADIENE6,56,5
8,70,02
i-butaneto 136.44,51450,1
n-butane482,9the 15.6503,21,0
1-Butene3402,2112,03604,75,3
i-Butene3989,1127,54107,35,3
CIS-2-Butene913,929,2939,42,8
TRANS-2-Butene112435,911562,7
1,3-Butadiene11317,611367,818,4
1,2-Butadiene6,50,26,7
ETHYLACETYLENE45,50,04
Vinylacetylene132,10,01
With5+26 25,40,6
Green oil0,317,4
Total kg/h21600113252188254

The preceding description, the figure and the example clearly reveals the advantages inherent in the method of the present invention and obtained by its application benefits.

1. Method of removing heavy side products of the reaction of selective hydrogenation of the output from the reaction zone a stream containing butadiene and trace amounts of heavy by-products, including:

(a) the filing of the exit stream from the reaction zone selective hydrogenation in the evaporator for solvent extraction of butadiene containing fractional area;

(b) irrigation fractional area flow of raffinate from the solvent extraction of butadiene;

(c) allocating a vapor phase containing butadiene with a low concentration of heavy by-products from the evaporator;

(d) the allotment and allocation of concentrated liquid phase containing heavy side reaction products, from the evaporator;

(e) introducing a vapor phase containing butadiene, in the area of extraction of butadiene.

2. The method according to claim 1, in which the fractional area contains from 3 to 7 theoretical plates.

3. The way p is 1, in which the molar ratio of irrigation in the fractional area is from 0.01 to 0.02.

4. The method according to claim 1, in which the concentrated liquid phase containing heavy side reaction products, is given in the amount of less than 0.5% by weight of the effluent stream from the reaction zone selective hydrogenation.

5. The method according to claim 1, in which the evaporator for solvent extraction of butadiene operates at a temperature of 27-93°and the pressure 375-790 kPa.



 

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