SU706020A3 - Method of inhibiting polymerization of vinylaromatic hydrocarbons - Google Patents

Description

(54) METHOD FOR INHIBITING POLYMERIZATION OF VINYLAROMATIC HYDROCARBONS

: The polymerization of vinyl aromatic compounds can vary widely over various factors of the distillation process, such as temperature, the amount of reflux, if any, pressure, duration, treatment. It was found, however. ; iT.o usually amount within 5 ppm - 200 chppm (ppm-parts per million) of phenothiazine and within

1 ppm - 100 ppm of phenolic. Condensed Neuve Expression) 1 residual for practically complete retardation of the polymerization of vinyl aromatic soy-7: ffpii dineny; norm conditions x dg stilc tion, for example at.

During the operation of the technology proposed for the proposed method, the degree of pyrimerization inside the distillation unit is significantly lower than that observed with the use of known technology options. This product, which, it is desirable to expose the distill cy, rises. at the exit of the installation is proportional to the decrease in the amount of polymer formed. The speed of the work of distillers - usb aybvki can be increased by using RoriW4ecTBa.

formed by the polymer. .Material, on a yaplyivayuschys - at the bottom or in the zone of the boiler of the distillation unit, you can re-use your equipment as a fuel or for recycling. You can also use THIS when using the proposed one. any way. PL: The immense material, which is inevitably formed in the DISTILLATION.RTM process, has such properties under which there are almost no conditions for disrupting the operating mode of the follow-up installation or the installation itself.

The distillation process can be a wide range of parameters, including distillation under reduced pressure (vacuum distillation) and distillation at atmospheric pressure (when the distiller communicates with the atmosphere) and a rather wide range, temperatures from about to about 150 ° C .

The main component of the β-PO inhibitor of the proposed method Phenotgyasin C (2 HgNS (cf. 7th edition, bn, B & H) Grand Reynold, is a powder, granules or flakes ranging from sulfur-green to green-yellow , tasteless, but with a slight odor. It is insoluble in ether and water, BUT dissolves in acetone, its melting point is in the range l75-185 ° C, and its boiling point,., Oxygen, used in combination with phenothiazine, can be in the form itself oxygen or in the form of an oxygen-containing gas, Kohli Oxygenated gas is used i, the remaining components of this gas must be inert with respect to the vinyl aromatic compounds under distillation conditions. The most convenient, practical and least expensive source of oxygen is air, JcoTopOMy and preferred, The amount of oxygen used

0 can vary widely, but usually it is the amount contained in the air.

The polymerization inhibitor according to the proposed method. A hybrid installation can be introduced by any

in a convenient way that allows - to achieve an effective distribution of the inhibitor throughout the installation. Inhibitor can. add to the recess

Q jets of styrenic material, inside the distillation reboiler zone

Others, or .v yy.brm friend convenient. Mayte; . i v As soon as | iVitor gradually loses its properties in the process of exploitation, it is necessary to maintain the necessary amount of the igniter in the distillation unit. Moreover, the inhibitor may be added to the distillation process both continuously and periodically. The inhibitor concentration can {be supported by any means, it is only important that it

was above the minimum required. level,

- The use of the inhibitor polymerization system according to the proposed method makes it possible to operate the installation at a higher speed, since the proposed inhibitor

40 is more effective than the known, and therefore provides an opportunity for ymeimeni. distillation temperatures are higher at higher pressures. Thus, the rate

45 distillation can be increased

without increasing the volume of polymerization which is defined as acceptable

in existing distillation products. cess, ......,

50 Using the proposed method, materials that accumulate during the distillation process can be removed and used as fuel or for

55 recycling,

Upon the yield of the distillation product obtained by the proposed method, a large percentage of pure easily polymerizable vinyl aromatic compound is obtained in an unpolymerized form: i the used g inhibitor does not impair the properties of the monomer obtained,. Example: Three 100 ml reaction flasks were prepared:

 the first contains 50 h of distilled styrene without TVS, to which 100 ppm phenothiazine is added, the second 50 g of finished styrene containing approximately 8 ppm of TVS, and a third contains 50 g of distilled styrene, to which 10 ppm of TVS and 100 ppm are added phenothiazine. Each of the flasks is installed in a magnetic stirrer, closed with a septum, and heated in a stirred oil bath to 115 ± Ic. Periodically, samples are removed from each flask using a syringe and tested for turbidity in methanol. The results are shown in Table 1. Table. The duration of a slowness sample of laziness, hours 1.0–1.5, is less than 0.5–4.0–4.5. Thus, neither TVS nor phenothiazine alone can provide the degree of retardation observed when they are used together. are synthetic as styrene polymerization inhibitor. EXAMPLE 2. As in Example 1, four reaction flasks were prepared, each of which was charged with 50 g of distilled styrene that did not contain TVS. 25 ppm of phenothiazine and 10 p of TVS are added to the first flask, 25 ppm of phenothiazi and 20 ppm of TVS are added to the second, 50 ppm of phenothiazine and 10 ppm of TVS are added to the third, 50 ppm of phenothiazine and 40 ppm of TVS, which molar ratio 1: 1. Each flask was heated in an oil bath of up to 115 and periodically samples were taken for turbidity testing in methanol. The results obtained are shown in Table 2. Table2 Thus, the optimal relative amounts of phenothiazine and TBC are 1: 1 molar ratio. SampleZ, Distillation column with a diameter of 30.5 cm is filled with a packing. Styrene is continuously fed to the column, and distillate is continuously withdrawn from its upper part; bottom residues are discharged hourly to maintain reboiler level. A styrene monomer is fed to the column at a continuous feed rate of 400 ml / min, which corresponds to a processing time of approximately 6.3 hours. The steam jacket is heated to maintain the average reboiler temperature. The reflux ratio ranges from 3: 1 to 20: 1. An inhibitor of 50 ppm of phenothiazine and 30 ppm of TBC is added to styrene feed in which it contains 10 ppm of TBC, resulting in a 1: 1 molar ratio of the inhibitor components. Air is introduced into the area of the reboiler at a rate of 1.2 l / mi. After 7.5 hours the speed is blown, the speed was increased to 2.0 l / min. After 14.5 hours, the concentration of the inhibitor injected into the feed stream was up to 75 ppm phenothiazine and 45 ppm TVS. The process is stabilized after approximately 18 hours and the experiment continues for approximately 23.5 hours. The bottom remains periochdically are discharged as experience progresses. concentrated to dryness using a rotary dryer to determine the percentage of polymer content. When operating in a stabilized mode using a Brockfield viscometer, the viscosity of the reboiler liquid is determined (the viscosity is 0). At the end of the cycle, only 7.2% of the polymer was detected. The results of this cycle are given in Table 3. T a b, l and c a 3

0.591

thirty

1.2

50

0.3

4 I I

1.099 0.2

1.5104

2.5106 0.3 770602 Continuation of table 3.

A d.stillation column according to Example 3 is prepared; the temperature of the reboiler is maintained at an average level of 104.8 ° C; an inhibitor is introduced into the feed: 75 ppm phenothiaine and 45 ppm TVS 5

Table4

Note: The + sign indicates that the sample was not 65. was taken. 0 (added), the speed of air blowing varies from 2.0 l / min to 0, and then restored to 0.50 l / min. The duration of the experiment, approximately 23 hours, the bottom residues are periodically removed and concentrated to determine their amount (this is an indicator of polymer formation). The results of this cycle are shown in table 4.

Example 5. A distillation column was prepared as described in Example 3. Crude synthetic styrene consisting of 60% styrene and 40% ethylbeneol is fed to this column. Both the amount of inhibitor and the air flow rate vary during the course of the experiment, which is carried out in those:

A period of approximately 70 hours with a cutout of approximately 6.3 hours for dosg / gzheni conditions. stable operation; Bottom residues are periodically withdrawn and the amount of residues after vani is fixed. The results of this experiment are shown in Table 5.

Table

Claims (1)

Invention Formula 1. A method of inhibiting the polymerization of vinyl aromatic hydrocarbons: in the process of their isolation from a carbon-hydrogen mixture by distillation by introducing an inhibitor based on tert. Butylcatechol., So that, in order to reduce polymerization, as the inhibitor uses a mixture of tertbutylcatechol and phenothiazium at a molar ratio of 10 to 1: 1. The inhibition process is carried out in the presence of oxygen. 2, the method according to Claim 1, from which the inhibitor is used in an amount of from 6 to 300 parts per million parts of the vinyl aromatic hydrocarbon or hydrocarbon mixture that is subjected to rectification,. . . .. .3. The method according to Claims 1 and 2, that is, that the rectification is carried out at a temperature of 65150 ° C, preferably 90-148 ° C. 4. The method according to claim 1, characterized in that the process is carried out in the presence of 0.07-0.13% by weight. oxygen. Sources of information taken into account in the examination 1. Patent of Great Britain No. 569412 published. 1945 - the prototype.