JPS6160622A - Collection of t-butylstyrene - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] Kihika Hiroshi 1 is widely used;
t-butylstyrene (BEB) by oxydehydrogenation of
tBS), and in particular to a method for rigorously separating unreacted t-butyl ethylbenzene feed from the t-butylstyrene product.

T-Butylstyrene (tBS) is a compound advantageously produced by catalytic oxydehydrogenation of dobutylethylbenzene (tBEB). This product is, for example, a chemical intermediate,
It has many uses, such as as a monomer or copolymerizable monomer in the manufacture of polymeric materials and the like. T-butylstyrene is often used in place of styrene in several applications because it has desirable physical and chemical properties.

Styrene is also not suitable, although t-butylstyrene has methods that work well.

Since tBS belongs to the same class as styrene, there are similarities in chemical properties. One of their common properties is their tendency to polymerize whenever activated by chemicals or heat. Conventional methods for purifying styrene can be used to purify tBS.

However, since the boiling point of tBS is approximately 70° C. higher than styrene, the tendency of tBS to coalesce is much greater than that of styrene in any industrial method of purifying styrene.

Some of the differences between styrene and tBS derive from the presence of dialkenylbenzenes in tBS but not in styrene. These cross-linking compounds can polymerize and interfere with refinery operation. It produces similar polymers. Cross-linked polymer has a tendency to collect in the device and impede attempts to dissolve it.

Some other differences from styrene in separating tBS into pure products arise due to the existence of isomers of tBS and tBEB. Meta and paraisomers have been found to exist in tBEB and tBS. m-t
Bs has a boiling point intermediate between that of p-LBEB and p-tBs and is found in both the overhead and bottom products when a conventional distillation column is used to separate tBEB and tBS. be done.

When ethylbenzene and low-elevation point compounds are distilled from styrene and high-boiling point compounds, a conventional distillation column is right-handed for the separation. The distillation column is fed with crude styrene to which a polymerization inhibitor has been added at an intermediate point. The distillation column is operated at reduced pressure, with a portion of the overhead product being refluxed to improve separation. It is necessary to use a distillation column that has a low pressure drop and a high separation efficiency, thus reducing the actual number of plates required in the column. A typical industrial distillation column for separating ethylbenzene from styrene will be approximately 180 feet tall.

When distilling a tBs mixture in a distillation column, several chemical and physical relationships must be considered. Firstly, the distillation column must contain as many plates as necessary to separate the key compounds. The pressure drop required to move the vapor from the bottom to the top of the column must be of sufficient height, and the pressure at the bottom of the distillation column must be significantly higher than the pressure at the top. If the pressure drop is too large, the pressure at the bottom of the column can reach several times the pressure at the top. For every doubling of pressure, the corresponding temperature increases by approximately 20°C. If the pressure at the top of the column is too low, the velocity of vapor passing through the column will be too high, making operation dangerous due to liquid flooding in that part of the column. Even if the temperature at the top of the column is low enough to prevent excessive polymerization, the high pressure and concentration of polymerizable compounds will cause excessive polymerization to occur if the temperature at the bottom increases, making the operation dangerous. When ffi combination occurs, the viscosity of the liquid at the bottom of the distillation column increases and the efficiency of the number of plates in the distillation column is lost.

When the fluid in the distillation column becomes viscous, the film of liquid on the packing material becomes thicker, and the liquid is retained in the distillation column for a long time, causing further polymerization and becoming viscous. . Also, when the viscosity of the partially polymerized liquid in the distillation column increases,
The liquid level above the filler becomes a steady flow rather than a turbulent flow. The distillation column thus changes from being operationally efficient to inoperable.

The packing of modern distillation column packing materials relies on a large number of small holes that allow liquid and vapor to diverge and mix. ! I! Once coalescence begins, these pores tend to become clogged with viscous liquids or solids. I! To compensate for the low number of theoretical plates in the A column, 1t! ! The speed or feed rate must be regulated; a higher enema rate will increase the pressure drop within the distillation column and result in a higher temperature; a decreased feed rate will cause the material to stay longer in the heated distillation column; The amount of polymer per unit product is relatively high.

Since there is a potential for polymerization in the distillation column, the distillation column must be designed so that the residence time of the liquid is as short as possible and therefore there is little excess capacity for operation of the kettle. When separating the para isomers, the meta-tBS is the component that is not separated, part of it at the top of the column and the other part in the column.

Located at the bottom. When the amount of tBEB at the bottom of the column is very small, the concentration of m-tBS at the bottom of the column is also small; the presence of m-tBs in tBEB increases tBEB.
H recycle is adversely affected or signifies a significant loss of product from the process.

Therefore, the styrene purification method cannot be directly applied to the tBs purification method; the styrene purification method is a method of separating ethylbenzene from styrene by distillation, and also includes a method of separating high-boiling point compounds by distillation a. However, it is not easy to transfer this simple method to treat high-grade tBS and related compounds.

According to the invention, the effluent of the oxydehydrogenation zone is introduced as a feed stream into an extractive distillation zone, the feed stream is extractively distilled with sulforane as a solvent, and the butyl ethylbenzene is removed from the top of the column. - A method for separating t-butylstyrene from an oxydehydrogenation zone effluent containing dobutyl ethylbenzene and t-butylstyrene is provided, the method comprising removing sulforane containing -butylstyrene as the bottoms.

Traditionally, sulfolane has been used to separate aromatics from non-aromatic compounds such as paraffins, but according to the present invention, sulforane unexpectedly can be used to separate aromatics and their isomers, such as meta and tBEB. It has been found that it can be used to separate para isomer compounds from other aromatic and isomer compounds closely related to it, namely the meta and para isomers of tBS. It has also been found that if this separation is carried out under the conditions of extractive distillation, it can be carried out while minimizing the migration of tBS into the tBKB product stream, or conversely the migration of tBEB into tBS. It was brought out.

The invention will now be described with reference to the accompanying drawings, which show schematic illustrations of an apparatus for carrying out the method of the invention.

In a typical operation, t-butylethylbenzene (
feeding a crude feed stream containing tBEB), t-butylstyrene (tBs), intermediate boiling point aromatic divinyl impurities, and low and high point hydrocarbons to the midpoint of extractive distillation column 2 from line 1; The sulfolane is also fed through line 3 to the higher section of the distillation column together with the polymerization inhibitor that is usually added. The vapor 4 at the top of the column condenses in a reflux condenser 5, a portion 6 of the condensate being returned as column reflux, while a remaining portion 7 is taken off as distillation product. A portion 8 of the bottoms 8 is returned to the distillation column through a reconcentrator 10 to supply heat thereto, and the remaining bottoms are withdrawn into line 11.

The ff14j ratio of sulforane to t-butylstyrene introduced during the feed wave should be in the range of about 1 = 1 to about 10:1; the feed wave may be a liquid, vapor, or a mixture of liquid and vapor. Something can happen. Preferably, the feed stream is at least partially vaporized.

The polymerization inhibitor can be any effective to inhibit polymerization of tBs and aromatic divinyl compounds. Among suitable polymerization inhibitors are 2,4-dinitrophenol and 2,8-dinitro-cresol. The concentration of polymerization inhibitor in the liquid in the distillation column, which must be added near the top of the column, is about 100 to about 10,000 by weight.
It should be 0 ppm, preferably about 500 to about 5000 ppm.

The external reflux ratio, ie the weight ratio of the flows in lines 6 and 7, can vary considerably and is suitably kept in the range of about 1:1 to about 10:1.

The extractive distillation column must be operated at reduced pressure, tB
In order to minimize S incorporation, it is necessary to operate the distillation column at as low a temperature as possible while at the same time keeping the liquid retention as low as possible while still maintaining an adequate production rate. Therefore, the pressure is about 10 to about 100+n
) Ig; pressures lower than 10 mmHg reduce the capacity of the distillation column. Although the liquid retention j1 is unaffected by the lower pressure, a reduction in the throughput reduces the production in part in the form of an increased residence time, such as at low temperatures.

The temperature at the top of the distillation column generally ranges from about 80°C to about 140°C, and the temperature at the reboiler 2 ranges from about 140°C to about 180°C.

The distillation column's reflow basin must be designed to have a relatively short residence time; the boiling point of the bottom product is below the temperature at which tBs can be safely stored at IF7 without causing undue stagnation problems. Due to the high cost, the residence time in the reboiler must be kept as short as possible, while still maintaining good process control.The residence time of the combined liquid in the distillation column and reboiler is approximately 311! / and preferably no more than about 1 hour.

When operating an extractive distillation column, an overhead stream can be obtained that contains substantially all of the tBs isomer introduced into the distillation column with the feed stream. The overhead stream also contains any low temperature impurities present in the feed stream and very small amounts of m-tBS and p-tns, usually less than about 1% by weight. There is also a small amount of sulforane, typically 0.8 to about 5% by weight.
It exists in the top of the tower due to the distortion of . In order to remove the sulforane from the overhead stream 7, it is washed in the multi-stage extraction zone 12 with water entering through line 13 and exiting through line 14. Washed tBEB containing at most trace amounts of sulforane
is removed in line 15, which is suitable for circulation without further treatment to the oxydehydrogenation reactor used for the production of tBS.

The bottoms product of line 11 contains sulfo-lane solvent, a formal inhibitor, tBS and a very small amount of tBEB;
BEB is usually only in trace amounts, less than about 0.8111% by weight of p-tBEH, calculated without sulforane. The bottoms also contain divinyl aromatic impurities and high boiling hydrocarbons introduced with the feed. LB
The S product is recovered by any suitable method, such as mixing the bottoms with water to dilute the sulfuran and separating the hydrocarbon layer containing most of the tBS and some impurities (not shown). After 1) separation and further washing of the hydrocarbon layer to remove residual sulfuran, it is advantageous to feed the hydrocarbon stream to a distillation section where high-boiling impurities are removed from the tBS. If necessary, the tBS product can be further purified, for example, by the extraction 7/A distillation method described in the patent application No. can be made into a sulforane stream.

The following example illustrates this offer. These examples are merely illustrative and do not limit the invention.

Example 1 Crude t-butylstyrene (tBS) made by oxydehydrogenation of t-butylethylbenzene (tBEB)
) was extracted and distilled in a laboratory distillation column. The crude t-butylstyrene feed stream had the following component distribution:

Ingredients 1% Low point component 1.2m-tBEB
2.8ρ-tBEB
57.1m-tBs
1.4P-tBs
36.7 Width Kasuri point component
0.1 High bare point component 0.7 Total 100.0 Distillation column has a diameter of 2
The distillation column was approximately 8 feet tall, had a 0.16-inch metal saddle, and had a reflux condenser at the top and a reflux condenser at the bottom. A re-enema device is attached to the. A feed stream with a humidity of about 120" C enters the distillation column at a rate of about 10 cc/min about 8 feet from the bottom of the column.
5000 ppm by weight.
(Regarding t-BS heavy industry) 2,4-dinitrophenol is added to the sulfuran in the distillation column to inhibit polymerization. The reflux ratio was maintained at approximately 5:l and the bottom product was reboiled.
The pressure in the condenser is about 30g, and the temperature at the top of the column is about 110℃.
The temperature at the bottom of the column is approximately 150°C.

The overhead product, consisting primarily of t-BEB, contained 14$ of m-LBS and 2x of p-tBs fed to the distillation column. The overhead product also contains about 4.3% by weight in hydrocarbons.
It contained sulforane.

The bottom product, consisting primarily of [BS and sulforane] contained a small amount of tllEn. In sulforane-free hemlock, m-tBEB is less than 0.1% by weight, p
-tBEB was approximately 0.8% by weight.

Control Example Using the same distillation column as in Example 1, crude tBS was distilled without using sulforane. This experiment lasted for four days.
I went to the commander. During the 2-hour portion of this experiment, 811
ml of crude tBS was fed. 480 at of distillate was collected and 50 ml of distillate was returned to the top of the distillation column as a solvent for 2,4-dinitrophenol. The external reflux ratio was 3.5:1, the pressure was 32 ml/g, the temperature at the top of the column was 117°C, and the temperature at the bottom was 134°C. Bottom product 1f8.2g (7) p-tBE6,! = 1.
It included $23 + w-tBEB. The overhead product was 0.88Z p-tBEI3 and 1.38$ m-t[3
It included EB. The feed rate was reduced from 5 dews, 17 minutes to 417 minutes, while the heat feed was kept at the previous value. Approximately 1
After 2 hours, the operation of the distillation column became unstable. The distillation column retention varied, resulting in zero polymer with altered composition in the re-enema, rendering the distillation column inoperable and concomitantly reducing the rate of collection of the overhead product, leading to termination of the experiment. The behavior of the distillation column clearly indicated the formation of polymer. Experiments without sulforane cannot reach the speed and purity obtained using sulforane in the same distillation column.

Example 2 Crude tBs was extractively distilled using a 15 foot distillation column constructed from a steam jacket section of 3 inch diameter pipe. The top of the column is equipped with a condenser equipped with a reflux branch valve. An electrically heated flat bottom redistiller fitted with a level detector and control valve is provided at the bottom of the distillation column.

A crude LBS of the composition of Example 1 was preheated to t-135°C and fed to the distillation column at a rate of about 0.4 gallons/hour at a point 10 feet from the top of the column. Approximately 5000pp at the same time
m (with respect to tBs in the distillation column liquor) of 2,4-dinitrophenol is fed to the distillation column at 120 DEG C. one foot below the top of the column. Keep the thl flow ratio around 3=1,
The pressure (at the top of the column) was about 50 mm) Ig, and the temperature was about 120°C at the top and about 180°C at the bottom.

The distillation column was operated continuously for approximately two months at the average operating conditions described above. The amount of tBEH in the bottom product was usually less than $0.6 in the hydrocarbons therein. The concentration of sulfolane in the overhead product was approximately 2.5% by weight. It is contemplated by those skilled in the art that without departing from the spirit and scope of the invention as described in IJJJB for Wood and the claims below,
It is obvious that many variations can be made.

[Brief explanation of the drawing]

The accompanying drawings illustrate one embodiment of the extractive distillation process for Moku'A IJJ. Patent applicant L.Pan Products Company

Claims (1)

[Claims] 1. The effluent stream of the oxydehydrogenation zone is introduced as a feed stream into an extractive distillation zone, and the feed stream is extractively distilled with sulfolane as a solvent to remove t-butylethylbenzene from the top of the column. A process for separating t-butylstyrene from an oxydehydrogenation zone effluent containing t-butyl ethylbenzene and t-butylstyrene, characterized in that sulfolane containing t-butylstyrene is removed as the bottoms. 2. The weight ratio of sulfolane to t-butylstyrene introduced with the feed stream to the extractive distillation section is from about 1:1 to about 10:
1. The method according to claim 1, wherein: 3. The method of claim 1, wherein after condensation, a portion of the overhead is returned to the top of the extractive distillation section to provide a reflux ratio of about 1:1 to about 10:1. 4. The method of claim 1, wherein the pressure in the distillation zone is maintained at about 10-100 mmHg. 5. The method of claim 4, wherein the pressure is maintained at about 20-50 mmHg. 6. The method of claim 1, wherein the feed to the extractive distillation zone is partially or completely evaporated. 7. The method of claim 1, wherein the polymerization inhibitor is introduced into the extractive distillation zone and the concentration in the liquor in the zone is from about 100 to about 10,000 ppm by weight. 8. The method of claim 7, wherein the concentration is from about 500 to about 5,000 ppm. 8. The polymerization inhibitor is 2,4-dinitrophenol and 2.
8. The method of claim 7, wherein the compound is selected from the group consisting of 6-dinitro-m-cresol. 10. The method of claim 7, wherein the polymerization inhibitor is introduced into the extractive distillation zone near the point where the sulfolane feed stream is introduced.