SU724489A1 - Method of preventing styrene thermal polymerization - Google Patents

Description

one

The invention relates to methods for preventing the thermal polymerization of styrene and can be used in the petrochemical industry.

Styrene is one of the most important monomers for the production of synthetic rubber and is widely used in chemical acidity, for example, for the production of polystyrene, styrene copolymers and styrene-butadiene rubbers.

In the production of styrene by catalytic dehydrogenation of ethylbenzene at high temperatures, the main method for separating styrene from unreacted ethylbenzene, light by-products (benzene, toluene) and high-boiling impurities is the method of multi-stage rectification.

However, this method, especially at the stage of separation of styrene and ethylbenzene - components with a close boiling point (145 and respectively), has a significant drawback, which is the thermal polymerization of the monomer, resulting in the deposition of difficult-to-remove polymers in heat exchangers.

. 2 -. .

the apparatus and on the plates of the rectification, secondly, to a significant loss of m styrene.

Methods are known for preventing the thermal polymerization of prostrate with the use of various inhibitors, for example, wAn pacTBOpoiB salts with electron-donor properties, c1 Dioxime-p-quinone mixture

0 with hydroquinone or aromatic nitrophenol, sulfur, p-oxydiphenylamine, p-tert-butylpyrocatechin and DR. II and 2.

However, the use of these

5 inhibitors do not exclude clogging of distillation columns, pipelines and other equipment with sparingly soluble resins.

The disadvantages of the process with the use of sulfur are the poor inhibition of the polymerization of divinylbenzene, which is formed due to the presence of diethylbenzene in ethylbenzene, as well as the formation of volatile sulfur compounds.

5 compounds in the interaction of sulfur with styrene.

Closest to the invention is a method of preventing the thermal polymerization of styrene in

0, the process of its isolation by rectification in the presence of an inhibitor, which is used as hydroquinone 3,

However, at high temperatures, this inhibitor is not sufficiently effective and its use does not prevent the equipment from becoming blocked by the polymer. Thus, in the process of distillation of styrene at a bottom temperature of 80-90 ° C, in the presence of O, 3-0.5% of hydroquinone, more than 3% of bottoms consisting mainly of styrene polymers are formed. In addition, hydroquinone is sparingly soluble in styrene, which causes uneven distribution of the inhibitor in the reaction mass, complicates the technology and the achievement of the required inhibitor concentration,

The purpose of the invention is to reduce the formation of a thermopolymer and prevent the equipment from being driven.

The delivered chain is achieved by the described method of preventing the thermal polymerization of styrene in the process of its isolation by rectifying in the presence of an inhibitor of 4-n-Intra-anthraquinone, taken in an amount of 0, 3, weight.

The use of 4-nitrsanthraquinone, together with a significant suppression of radical chain reactions causing the thermal (spontaneous) polymerization process, leads to the formation of low molecular weight reaction products, which are more soluble in styrene and related impurities than high molecular weight products ts continuously from

of the distillation column together with the bottoms, thus eliminating the clogging of the equipment.

Example 1. A glass vial with a capacity of 50 ivui, previously spilled with alcohol and dried with purified nitrogen, is charged with 30 ml of distilled styrene with a basic substance content of 99.7-99.8% and 0.0166 g (0.05% by weight of styrene) 4-nitroanthraquinone, Ampoule sealed and placed in a silicone bath where maintained for 15 hours. Then the polymer from the ampoule is precipitated with methyl alcohol and centrifuged (P 2500 rpm) for 20 minutes. After the liquid has been decanted, vacuuming the polymer from the polymer to constant weight removes residual solvent. The amount of polymer per monomer loaded is 27, .3 wt.%, With an average molecular weight of the resulting polymer of 163700.

Example 2 The tertary polymerization of styrene is carried out analogously to example 1. In this case, 30 ml of styrene-rectified and 0.0815 g are charged into a glass vial. (0.3% relative to the weight of styrene) 4-nitroanthraquinone. The amount of polymer formed and its molecular weight are 10.9%. and 40500 respectively

Under similar conditions, styrene is thermopolymerized in the presence of various concentrations of hydroquinone; and 4-nitroanthraquinone The results of the experiments are summarized in tabt, 1,

 .Tables a-D

The content of polymer, mass,% 52,5

Molecular weight

polymer279 900

polymer content, mass% 27.3

Molecular weight

polymer163 700

39.6 29.6 25.7

201 500 183 200 135 800

20.5, 15.5 10.9

97 000 59 800 40 500

As follows from the table. 1, in the presence of 4-nitroanthraquinone, the thermopolymerization of styrene proceeds with the formation of low molecular weight reaction products. Thus, this compound, along with the manifestation of an effective inhibitory effect, is at the same time the molecular weight regulator of the resulting thermopolymer, thereby eliminating the clogging of the equipment of high molecular weight cross-linked polymers.

. Example 3, Styrene raw material containing 35.5% ethylbenzene is fed to a continuous distillation column with a capacity of 1 l / h. The residual pressure of the top of the column is no more than 15 mmHg, st ,, the temperature of the cube is 90-95 0, the phlegmon number is 10, the superheated ethylbeneol vapor is removed from the upper part of the column, the styrene vapor is removed as a side fraction. The rectification of styrene is carried out in the presence of 4-nitro-anthraquinone, which is fed with the feed in the form of a solution a in the monomer at a rate of 0.3% based on the total weight of styrene fed to the rectification. Opening the column after 600 hours of continuous operation shows that there is no clogging of styrene polymerization products with its products.

Table 2

Due to the highly effective action with respect to the chain radical reactions, 4-nitroanthraquinone significantly inhibits the development of the process of thermal polymerization of styrene during prolonged heat treatment,.

five

The data given in table. 2 illustrates the dependence of the amount of polymer formed and its molecular weight on the nature of the inhibitor during heat treatment of styrene in

Claims (3)

1. USSR author's certificate number 298580, class, C 07 C 7/18, 1971. 2. USSR author's certificate number 441263, cl. C 07 S 7/18, 1974. 3. USSR author's certificate number 257496, cl. C 07 S 7/18, 1969 0 (prototype).