RU2189965C2 - Method of chemical treatment of monomer-containing (c7-c9)-fractions - Google Patents

Abstract

FIELD: chemical technology. SUBSTANCE: invention relates to a chemical treatment of monomer- -containing C₇-C₉-fractions that are used in the process of producing film-forming substances used for preparing drying oils and lacquers by method of cationic co-oligomerization of unsaturated hydrocarbons. The treatment of the parent fraction is carried out with a chemical reagent that presents a mixture of an aqueous solution of oxygen- and sulfur-containing Lewis bases and acetic acid taken in the following mass ratio: Lewis base : acetic acid = (0.005-0.0010) : (0.001-0.014) taken in the amount 2.5-50.0% of the reaction mixture mass. After separation of an aqueous layer the remaining hydrocarbon reaction mixture is subjected for azeotropic drying. EFFECT: improved method of treatment, increased yield of end product. 2 tbl, 1 dwg

Description

The invention relates to the chemical purification of monomer-containing fractions of C ₇ -C ₉ , which are used in the process of producing film formers for the preparation of drying oils and varnishes by cationic co-oligomerization of unsaturated hydrocarbons contained in them, such as: dimers of (methyl-) cyclopentadiene, its copolymers with isoprene and piperylene ( DCPD), (methyl-) styrenes, vinyl toluene, divinylbenzenes, indene and other vinyl aromatic hydrocarbons, isoolefins, conjugated dienes and acetylene hydrocarbons.

C ₇ -C ₉ fractions, ethylene by-products isolated from pyrocondensate obtained in synthetic ethanol plants often contain cycloesters (paraldehyde and metaldehyde), in amounts of 3-7 wt.% Mixed with other oxygen- and sometimes and sulfur-containing Lewis bases. When these fractions are used as raw materials for the production of film-forming agents (petroleum resin or liquid rubbers by cationic co-oligomerization of unsaturated hydrocarbons in the environment of alkylbenzenes contained in them, non-aromatic saturated and naphthenic, and non-cationophilic unsaturated hydrocarbons in the presence of Friedel-Crafts acids), the maximum permissible concentration of oxygen-containing bases is <0.05 wt.%.

 A known method of purification of monomer-containing pyrolysis hydrocarbon fractions by washing them with water at temperatures close to room temperature (Polymerization of isoprene, catalyzed by acids. Collection of articles VNIISK. M. - L. "Chemistry", 1964, S. 156). However, due to the low distribution coefficient of the above cycloesters between water and hydrocarbons, under normal operating conditions of the wash column, their residual content in the fraction cannot be reduced to less than 1 wt.%.

(где Х - алкил С₂-С₆ или галоид; Х - тиоалкил С₂-С₆, Me S АlR₂-, R₁ и R₂ - алкил С₂-С₇, Me - щелочной металл) или его смесью с Х А1 R₃R₄ (где Х - алкил С₂-С₆ или галоид, R₃ и R₄ - алкил С₂-С₆) при их массовом соотношении 1: 1-2 с последующим отделением и сжиганием смеси (НО)_3-nAlХ_n с продуктами осмоления непредельных углеводородов (авт. св. СССР, 732225, кл. С 07 С 7/01, 1980).The closest technical solution, prototype, is a method for the chemical purification of monomer-containing C ₇ -C ₉ hydrocarbon fractions from Lewis bases to their residual content not exceeding the maximum permissible level, by treating the fraction at elevated temperature with an organoaluminum compound of the general formula

(where X is C ₂ -C ₆ alkyl or halogen; X is C ₂ -C ₆ thioalkyl, Me S AlR ₂ -, R ₁ and R ₂ is C ₂ -C ₇ alkyl, Me is an alkali metal) or its mixture with X A1 R ₃ R ₄ (where X is C ₂ -C ₆ alkyl or halogen, R ₃ and R ₄ is C ₂ -C ₆ alkyl) with a mass ratio of 1: 1-2, followed by separation and combustion of the mixture (HO) _3-n AlX _n with resins of unsaturated hydrocarbons (ed. St. USSR, 732225, class С 07 С 7/01, 1980).

 The yield of monomers is 92-95% of their mass in the initial fraction.

 The disadvantage of this method is the danger of production, as a result of the use of fire and explosive organoaluminum compounds, and the insufficient yield of purified raw materials for the production of cationic film formers.

 The aim of the invention is to reduce the risk of production and increase the yield of purified raw materials.

 This goal is achieved in that the initial fraction is purified by a chemical reagent, which is used as an aqueous solution of oxygen and sulfur-containing Lewis bases with acetic acid with a mass ratio of Lewis base: acetic acid equal to 0.005-0.0010: 0.001-0.014, in the amount of 2.5-50.0% by weight of the reaction mixture, followed by separation of the aqueous layer and azeotropic drying of the purified fraction.

We found that under these conditions, with ordinary stirring, water forms an emulsion in the monomer-containing fraction with a dispersion of 10 ^-5 -10 ^-8 cm, that is, sufficient to reach the interface, providing a quantitative course of this reaction, most likely by the mechanism of interphase acid catalysis . Due to the unlimited solubility of acetaldehyde in water and its low boiling point (20.8 ^o C), it is automatically removed from the reaction phase, and, in accordance with the principle of Le Chatelier, the reaction is shifted to the right. Probably, all this ensures the achievement of a deep degree of purification of the fraction: the total content of cycloesters and other Lewis bases in it does not exceed 0.007 wt.%.

 For the purification of monomer-containing fractions according to the invention, an alloy steel plant shown in the drawing is used.

A heat carrier heated to 97-160 ^° C is fed into the shirt of the cube of stripping column 2 with an efficiency of 5 theoretical plates with a useful volume of 1 m ^3. Downstream of stream 1, a crude C ₇ -C ₉ fraction is fed. “Return water” (an aqueous solution of oxygen and sulfur-containing Lewis bases extracted from the fraction mixed with hydrocarbons and acetic acid) fed with fresh water supplied by stream 5 and water is supplied to stream 3 from settler 4.

Mixtures of acetaldehyde with azeotropes of hydrocarbons with water and other oxygen-containing substances coming from the top of the column by stream 7 are cooled to 75-80 ^° C in the refrigerator 8 and sent to the sump 4. The non-condensed acetaldehyde from the top of the refrigerator by stream 8a is taken off for mixing with the return water flowing 6 for incineration or disposal. Hydrocarbons leaving the cube of the stripping column by stream 9 and from the top of the sump by stream 10 are combined and sent to column 11 of azeotropic drying with an efficiency of 15 theories. plates. Heteroseaseotropes of water with hydrocarbons are withdrawn from the top of this column by stream 12 and, after cooling to 75-80 ^° C in the refrigerator 13, they are sent to the settling tank 14. The upper hydrocarbon layer is returned by stream 15 to the column, and the lower aqueous stream to stream 16. Dried, usually to a residual moisture content of 0.001-0.005 wt.% Fraction containing 0.5-1.9 wt.% Light thermo-oligomers that do not interfere with the cationic co-oligomerization of the unsaturated hydrocarbons contained in it and do not reduce the quality of the resulting film former, is diverted by stream 17.

 Thus, the yield of raw materials for producing a cationic film former in the composition of the purified monomer-containing pyrolysis fraction is 100% by weight of the monomers contained in the "dirty" fraction.

 The foregoing is illustrated by the following examples.

Example 1. In the cube of the stripper column 2 (see drawing) serves superheated to 160 ^o With water vapor. Actually, in the working zone of the cube, the temperature is set at 125 ^o C. To this stream 1 at a speed of 800 kg / h serves C ₇ -C ₉ -fraction of flexible pyrolysis of petroleum products in ethylene mode, containing, wt.%, In the amount of: 7.4 DCPD, 25.5 vinyl aromatic hydrocarbons, 2.9 conjugated dienes and acetylene hydrocarbons, 59.8 alkylbenzenes and other ballast hydrocarbons, 4.3 cycloesters and less than 0.1 other oxygen and sulfur-containing impurities. To this stream 3, at a speed of 83.4 kg / h, fresh return water is fed, fed with stream 5, containing, wt.%: 74.2 water, 25.0 acetaldehyde, in total, 0.8 hydrocarbons and other oxygen, as well sulfur-containing compounds, including 0.04 acetic acid.

In the reaction mixture, on average, the concentration is established, wt.%: 9.4 return water (including 7.0 actual water), as well as 0.005 acetic acid. From the top of the column with a stream of 7 at a speed of 154.5 kg / h flies a mixture containing, by weight. %: 40.0 water, 36.2 acetaldehyde, 23.2 C ₇ -C ₉ hydrocarbons and 0.5 other oxygen- as well as sulfur-containing trace elements. A stream of 6 at a rate of 37.9 kg / h for combustion is used to return a mixture of return water with non-condensed acetaldehyde. Stream 5 at a speed of 0.8 kg / h serves fresh water. A semi-purified monomer-containing fraction containing 0.5 wt% of a thermo-oligomer with a number average molecular weight of 304 is mixed with a C ₇ -C ₉ fraction exiting from the top of the settling tank 4 by stream 10 from a cube of the stripping column with stream 9 at a speed of 728.0 kg / h at a speed of 35.9 kg / h. The mixture enters the azeotropic drying column 11. Non-condensed acetaldehyde flies from the top of the refrigerator 8 with a stream of 8a at a speed of 36.0 kg / h to mix with the return water discharged for combustion. Stream 17 at a speed of 764 kg / h leaves a purified C ₇ -C ₉ fraction containing, wt.%: 7.5 DCPD, 26.4 vinyl aromatic hydrocarbons, 3.0 conjugated dienes and acetylene hydrocarbons, 62.5 alkylbenzenes and others "ballast" hydrocarbons, 0.5 thermo-oligomers, 0.003 cycloesters and 0.002 water. The yield of purified raw materials to obtain a cationic film former is 100% by weight of the monomers fed by stream 1 as part of a "dirty" C ₇ -C ₉ fraction.

 The results of purification from cycloesters of other monomer-containing pyrolysis hydrocarbon fractions according to Example 1 under the other claimed conditions are presented in Table 1 (Examples 2-3).

 The composition of the "dirty" fraction, the content, in fact, of water, return water and acetic acid in the total flow directed to the bottom of the stripping column, the temperature and residence time in the latter, vary.

If the content of return water in the total stream to the bottom of the stripping column is reduced to less than 2.5 wt.% (Example 4, presented in comparative table 2), the content of acetic acid in this stream to less than 0.002 wt.% (Example 5 table . 2), the residence time in the stripping column is less than 25 minutes (example 6) and / or the temperature of the bottom of this column is reduced to less than 92 ^o C (example 7), the residual concentration of cycloesters and other Lewis bases in the purified fraction increases more than 0.005 wt.%.

If the temperature of the bottom of the stripping column is raised above 128 ^o С (example 8) and / or the residence time in column 2 is increased to more than 100 minutes (example 9), the degree of purification remains almost at the same level, but energy consumption increases and productivity decreases installation.

 If the concentration of acetic acid in the total flow to the bottom of the stripping column is increased to more than 0.012 wt.% (By artificially introducing Example 10), the degree of purification of the fraction decreases, probably due to the excessive occurrence of consonant cationic oligomerization in statu nascendi of acetaldehyde.

 If the content of return water in the total flow to the stripping column is increased to more than 50 wt.% (Example 11), the degree of purification of the fraction remains at the same level, but the productivity of the installation decreases.

As follows from table 1, the purification of fractions from cycloesters by their monomerization at a temperature of 92-128 ^o With in the presence of 2.5-50.0 wt.% Return water (1.1-18.9 wt.%, In fact, water) and 0.002-0.012 wt.% Acetic acid for 25-100 min can reduce the residual oxygen content in them to a level lower than the maximum permissible.

 From comparative examples 4-11 presented in table. 2, it follows that when carrying out purification of fractions in modes beyond the scope of the claimed, the purpose of the invention is not achieved in full.

 The application of the invention will reduce the risk of production and the cost of the purified fractions by eliminating the loss of monomers in the waste.

Claims (1)

The method of chemical purification of monomer-containing (C ₇ -C ₉ ) - fractions from impurities that interfere with the cationic co-oligomerization of unsaturated hydrocarbons contained in them by treating with a chemical reagent at elevated temperature, characterized in that an aqueous solution of oxygen and sulfur-containing Lewis bases is used as a chemical reagent with acetic acid in a mass ratio of Lewis base: acetic acid 0.005-0.0010: 0.001-0.014 in an amount of 2.5-50.0% by weight of the reaction mixture, followed by separation of the aqueous layer and azeotro hydrochloric drying the fraction.

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