SU781196A1 - Method of preventing styrene thermal polymerization - Google Patents

Description

  . 1, the invention relates to the field of styrene synthesis, and specifically to methods for preventing the thermopolymerization of styrene i, and is aimed at improving the technology for the isolation and purification of styrene by multi-stage distillation.

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

The production of styrene by catalytic dehydrogenation of ethylbenzene at high temperatures is the main industrial method of separating styrene from unreacted ethylbenzene, light by-products (benzene, toluene) and high-boiling impurities by 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 - 136 ° C, respectively), has a significant drawback, which is the thermal spontaneous polymerization of the monomer, which leads to the precipitation of difficult-to-remove polymers in heat exchange apparatus and on plates of the distillation columns, which causes loss of styrene.

Known methods predotvrascheyi thermal polymerization of styrene during its separation in distillation systems by administration of inhibitors such as mono- and dyalkilkatehiny, N-alkyl-N-arnlgidroksilaminy, N-tsyklogeksilgiDroksilamin, dialkiloksiaminovye salts, hydroxylammonium acetate, semicarbazide, tiosemikprbazidy

5 and their derivatives, furnace black in combination with organic peroxides, N, M-di- (lower alkyl) -hydroxylgmino salts of aliphatic carboxylic acids, t-aminonaphthols, hydroquinone, phenontazane, p-methoxyphenol, benzophenone triazine, and quinto-ianine diphols, hydroquinone, phenontazane, p-methoxyphenol, benzophenone triazine, hydrophinone, phenonthiazane, p-methoxyphenol, benzophenone triazine, and hydrophinone, phenonthiazane, p-methoxyphenol, benzophenone triazine, and hydrophinone, phenonthiazane, p-methoxyphenol, benzophenone triazine, and hydrophinone, phenonthiazane, p-methoxyphenol, benzophenone triazine, and hydrophinone, phenonthiazane, p-methoxyphenol, benzophenone, and p-methoxyphenol; , copper salts, di-2- (2-ethylhexyl) dithiophosphoric acid, dioxim-P-quinone-a and others.

25 Of these, only hydroquinone, mon6oxim-P hinbna, p-nitrophenol and sulfur or a mixture of sulfur with tert-butylpyrocate 1 was used industrially. However, the use of these was indicated.

30 inhibitors do not exclude clogging of distillation columns, ia material pipelines of other equipment, and 1 dissolving resin-based resins, the removal of which takes a lot of time and more time, So when using sulfur, there is a poor inhibition of the polymerization of divinylbenzene, which is due to the presence of ethyl strips, as a result of the presence of sulfur, and an amount of strips; volatile sulfur compounds

in the interaction of sulfur with styrene. In addition, the presence of sulfur in styrene above 0.001%, sharply affects the properties of polystyrene.

I The closest to the present invention is a method of preventing the thermopolymerization of styrene in the process of its isolation by distillation by introducing a thermopolymerization inhibitor, in which hydroquinone 2 is used.

However, at high temperatures, the indicated inhibitor is sulphide-effective and its use does not ensure the prevention of blockage by the equipment. R

faK, in the process of distillation of styrene at a bottom temperature of the column 80-90 ° C in the presence of 0.3-0.5% hydroquinone, more than 3% of the bottoms, consisting mainly of styrene polymers, are formed. Hydrbhinon is also sparingly soluble in styrene, which causes an uneven distribution of the inhibitor S. Reaction: yasee, complicates the technology and

achieving the required inhibitor concentration. . In addition, hydroquinone is prone to

Because of the fact that it is removed from the zone of high temperature and does not interfere with the thermal polymerization.

The purpose of the invention is to reduce the formation of thermopolymer and equipment plugging.

The goal is achieved by the fact that in the method of preventing thermo 781196

polymerization of styrene in the process of its isolation by distillation by introducing an inhibitor of thermopolymerization, as an inhibitor, bis (o-isopropyl-thionocarbonylhydrazone) N-naphthoquinone (BIKN) is used in an amount of 0, by weight of styrene.

The effectiveness of the developed method for preventing the thermal polymerization of styrene is illustrated by examples.

Example 1. A 50 ml glass ampoule, pre-washed with alcohol and dried with purified nitrogen, is loaded with 30 ml directly before loading of distilled styrene with a basic substance content of 99.7-99.8% and 0, gb (0.05% of weight of styrene) BIKN. The ampoule is sealed and placed in a silicone bath, where it is maintained for 15 hours. After tempering, the polymer is precipitated from the ampoule with methyl alcohol and centrifuged (p-2500 rpm) for 20 minutes. After decanting, the liquid is evacuated from the polymer to a constant weight, and residues are removed. solvent. The amount of polymer per monomer loaded is 28.06% with an average pulp mass of 143900 formed polymer.

Example 2. Thermal polymerization of styrene was carried out analogously to example 1, but instead of hydroquinone, a ZR MP of styrene-rectified and 0.272 (1.0% with respect to styrene) BIKN were loaded into a glass ampoule. Education is not happening.

Under similar conditions, thermopolymerization of styrene is carried out in the presence of various concentrations of NIR and hydroquinone.

The effect of the nature and concentration of the inhibitor on the amount of polymer formed upon heat treatment of styrene with and D 15 h is given in Table. one.

24.03 7.59 2.34

85110 22180 10840 Hydroquinone Content of POLYMER, yass.% 52.5 39.6 29.6 Molecular pH. :.; mass polymer .; 27990.0 ..; .. 101500 183200

| gve vd & ®Eg 1sh h5 hell about; Yes

Table

1.12 Ots. 6900 Ots. 25.7 12.4 3.9 135800 128500 42000

In the presence of BNCH, the thermopolymerization of styrene proceeds to a much lesser extent, moreover, with the formation of low molecular weight reaction products. This indicates that this compound, along with the manifestation of an effective inhibition, is at the same time the molecular weight regulator of the resulting thermopolymer, thereby eliminating the clogging of equipment with high molecular weight crosslinked polymers

wicked

The content of polymer, wt.% Ots.

Molecule

polymer mass Ots.

Hydroquinone Polymer content, wt.% 4.0

Molecule

Claims (2)

polymer weight 30,000 The use of NIRTs to prevent styrene from being thermopolymerized during its rectification release allows reducing the monomer losses for the formation of insoluble polymeric compounds by a factor of 3–4, increasing equipment utilization rates and improving technical and economic indicators of styrene production as a whole. The use of the proposed method in production does not require a change in the existing technology, replacement of equipment and can be carried out on existing technological schemes. The estimated economic effect of using this method in industry will not be 200 tr. in year. The invention method for preventing thermopolymer; meridization of styrene in the process of its development. As a result of its highly effective action against chain radical BIKN reactions, it inhibits the development of the process of thermopolymerization of styrene, largely preventing it during long-term heat treatment. The dependence of the amount of polymer formed and its molecular weight on the nature of the inhibitor during heat treatment of styrene (t) and the inhibitor concentration of 0.3 wt.% Are presented in Table. 2, Table 2 by fractionation by introducing a thermopolymerization inhibitor, characterized in that, in order to reduce the formation of thermopolymers and equipment, the bis- (o-isopropylthionocarbonylhydrazone) N-naphthochin is used as an inhibitor in an amount of 0.05-1.0% by weight styrene. Sources of information taken into account in the examination 1.Rezova AK et al. Preparation of styrene and inhibition of its spontaneous polymerization, M., TsNIITEneftekhim, 1974, p. 28 2. USSR author's certificate number 64313, cl. C 07 C 7/18, 1939 (prototype).