RU2114154C1 - Method of inhibiting process of thermopolymerization and resin formation of unsaturated hydrocarbons - Google Patents

Abstract

FIELD: chemical industry. SUBSTANCE: claimed method is useful in process of thermopolymerization of resin formation of unsaturated hydrocarbons in deethanization and depropanization columns in the process of separation of products of pyrolysis of hydrocarbons by multi-step rectification by adding inhibitor. The inhibitor includes product resulting from oxidizing 2,2′,6,6′- tetramethyl-4-oxopiperidine and comprising 55-92% 2,2′,6,6′ tetramethyl-4-oxopiperidine-1-oxyl; 4-35 % 2,2′,6,6′- tetramethyl-4-oxopiperidine; 1-8% 2,2′,6,6′-tetramethyl-1- hydroxy-4-oxopiperidine; and 1-9% admixtures. Inhibitor is used in amount of 0.005-0.3% (preferably 0.01-0.1%) by weight on initial hydrocarbon mixtures admitted into depropanization and deethanization columns. The inhibitor includes solution of said oxidation product in organic solvent. EFFECT: more efficient method and improved economic characteristics. 2 cl, 1 tbl

Description

 The invention relates to methods for inhibiting the thermopolymerization and gum formation of unsaturated hydrocarbons, specifically in deethanization and de-propanization columns during the separation of hydrocarbon pyrolysis products by multi-stage distillation.

 Known methods for preventing the thermopolymerization of diene hydrocarbons by introducing inhibitors, among which the most widely used are hydroquinone, o-nitrophenol, wood-resin antioxidant (DSA), N-phenyl-N-propyl-p-phenylenediamine (4010 NA). However, these inhibitors are not effective enough when using in the process of processing mixtures of unsaturated hydrocarbons that are prone to the formation of compaction products (gum formation) (Karakuleva GI et al. Inhibition of the polymerization of diolefins in the processes of their isolation and storage. 1974, p.24-25) .

 A known method of inhibiting the spontaneous polymerization of unsaturated monomers by the introduction of polymer inhibitors, for example polyhydroquinone or poly-α-naphthol. However, the known method does not allow to exclude the formation of polymer (ed. St. USSR N 1073239, class C 08 F 2/42, 1982).

 A known method of inhibiting the radical polymerization of vinyl monomers by introducing into them as a polymerization inhibitor 2,2 ', 6,6'-tetramethyl-1-hydroxy-4-oxopiperidine.

 The disadvantage of this method is the complexity of the technology for producing and isolating the inhibitor and its insufficiently high efficiency.

 Closest to the proposed invention in technical essence is a method for stabilizing vinyl monomers, which consists in introducing 2.2 ', 6,6'-tetramethyl-4-oxopiperidin-1-oxyl as an inhibitor of the stable iminoxyl radical (Inhibitory effect 2.2 ', 6,6'-tetramethyl-4-oxo-piperidin-1-oxyl in radical polymerization. 160, 1972, 244-249).

 The disadvantage of this method is the complexity of the technology for producing and isolating the used inhibitor, low yields upon receipt thereof, as well as inhibitory activity insufficient to solve a number of specific practical problems of inhibition.

 The objective of the invention is to increase the efficiency of the process of inhibition of thermopolymerization and gum formation of unsaturated hydrocarbons while improving economic performance through the use of a more affordable and cheap inhibitor with a high inhibitory effect.

A method is proposed for inhibiting the process of thermopolymerization and gum formation of unsaturated hydrocarbons by introducing an inhibitor, which is used as a product obtained by the oxidation of 2,2 '6,6'-tetramethyl-4-oxopiperidine (triacetonamine-TAA) and having a composition, wt. %:
2,2 ', 6,6'-Tetramethyl-4-oxopiperidin-1-oxyl (TAA-oxyl) - 55-92
2,2 ', 6,6'-Tetramethyl-4-oxopiperidine (TAA) - 4-35
2,2 ', 6,6'-Tetramethyl-1-hydroxy-4-oxopiperidine (TAA-hydroxy) - 1-8
Impurities - 1-9
(IPON inhibitor).

 The specified inhibitor is used in an amount of 0.005-0.3% (preferably 0.01-0.1%) for the initial hydrocarbon mixtures entering the separation in the columns of deethanization and depropanization.

 In the new method, a solution of the above oxidation product in an organic solvent, for example, n-butanol, toluene, xylene, ethylbenzene, etc., preferably with a mass fraction of 5-40%, can also be used as an inhibitor, which simplifies the technology of the inhibition process.

To obtain an inhibitor, the oxidation of triacetonamine can be carried out at 20-50 ^o C in a solvent medium (water, alcohols, etc.). As an oxidation catalyst, tungstates and sodium molybdates, alkali metal carbonates or bicarbonates, CO _2, and other known secondary amine oxidation catalysts can be used. The IPON inhibitor can be isolated from the reaction mixture, for example, by extraction with an organic solvent (alcohols, aromatic hydrocarbons, esters, ketones, etc.), followed by distillation of the solvent under vacuum, preferably at 10-40 mm RT. Art. at a temperature not exceeding 100 ^o C, preferably not higher than 70 ^o C.

The initial triacetonamine or its solution can be obtained in a known manner - the interaction of acetone with ammonia at a temperature of 50-90 ^o C and a molar ratio of acetone: ammonia of 15-2.5: 1 in the presence of acidic catalysts (application Germany No. 2916471, class C 07 B 211/74, 1979).

 The difference between the proposed method and the prototype is the use of an oxidation product of 2,2 ', 6,6'-tetramethyl-4-oxopiperidine of the above composition or a solution of this product in an organic solvent as an inhibitor of polymerization of unsaturated hydrocarbons.

 As a result, the economic efficiency of the new inhibition method is significantly increased by simplifying the technology for producing and isolating the used inhibitor and increasing its yields.

 In addition, the inhibitor used in the proposed method has a higher inhibitory efficacy than each of its constituent components. This indicates that a mixture of components is formed, which has a synergistic effect with respect to inhibiting the polymerization of various unsaturated hydrocarbons.

 The use of a new method of inhibition in the separation of pyrolysis products by multi-stage distillation can significantly reduce the formation of polymers and resins under severe operating conditions, which increases the mileage of boilers of deethanization and de-propanization columns before cleaning and significantly increases the economic efficiency of the processes.

Example 1. To a solution of 100 g of triacetonamine in 100 ml of water, 165 ml of a 30% hydrogen peroxide solution are added with stirring in a stream of CO ₂ . The mixture was kept at a temperature of 40 ^° C. for 5 hours. Then, 300 ml of toluene were extracted in a separatory funnel. The hydrocarbon (oil) layer is separated, dried by azeotropic distillation under vacuum of 20-40 mm RT.article at 30-40 ^o C. Get 375 ml of a solution of IPON inhibitor with wt. share of 30%. Yield 97% of theory.

 The inhibitor composition is given in table. one.

 The resulting solution of IPON inhibitor is used to inhibit the polymerization of diolefin hydrocarbons according to the procedure described after example 4.

Example 2. In the conditions of example 1 from the resulting solution of the IPON inhibitor in toluene is distilled off under vacuum 20-40 mm RT.article at 40-70 ^o C solvent. Get the IPON inhibitor in the form of a viscous resin of the following composition, wt.%:
2,2 ', 6,6'-Tetramethyl-4-oxopiperidin-1-oxyl - 85
2,2 ', 6,6'-Tetramethyl-4-oxopiperidine - 4
2,2 ', 6,6'-Tetramethyl-1-hydroxy-4-oxopiperidine - 3
Impurities - 8
Example 3. To a solution of 15 g of triacetonamine in 150 ml of water add 15 ml of 30% hydrogen peroxide and 0.02 g of sodium tungstate and trilon B. The mixture is heated for 3 hours at 50 ^o C, cooled, extracted with 150 ml of xylene. Get a solution of the IPON inhibitor in xylene with wt. share of 10%. Yield 92% of theory. After distillation of the solvent under vacuum, an IPON inhibitor is obtained in the form of a viscous resin of the following composition, wt.%:
2,2 ', 6,6'-Tetramethyl-4-oxopiperidin-1-oxyl - 55
2,2 ', 6,6'-Tetramethyl-4-oxopiperidine - 35
2,2 ', 6,6'-Tetramethyl-1-hydroxy-4-oxopiperidine - 1
Impurities - 9
Example 4. To a solution of 20 g of triacetonamine in 40 ml of n-butanol, 30 ml of 30% hydrogen peroxide was added under stirring in a stream of CO ₂ . The mixture was stirred at 30-40 ^° C. for 5 hours. The oil layer was separated, dried by azeotropic distillation under vacuum of 20-40 mm Hg. at 40-50 ^o C. Get a solution of IPON in butanol with wt. share of 40%. Yield 90% of theory.

 The inhibitor composition is given in table.2.

 The obtained samples of the IPON inhibitor were used to inhibit the polymerization and gum formation of unsaturated hydrocarbons in the separation of distillation pyrolysis products. The tests were carried out as follows.

A mixture of hydrocarbons with or without an inhibitor is loaded into the ampoule, which is the feed of the depropanizer column of the following composition, wt.%:
1. Propadiene + propylene - 2.22
2. Propylene - 61.35
3. Propane - 2.36
4. 1,3-Butadiene - 9.25
5. Butenes - 11.07
6. Bhutans - 1.13
7. C ₅ -components - 9.73
8. C ₆ -C ₈ non-aromatic - 0.90
9. Benzene - 1.87
10. Toluene - 0.12
11. Xylenes + Ethylbenzene - Traces
or columns of a deethanizer of the following composition, wt.%:
1. Methane - 0.02
2. Acetylene - 0.74
3. Ethylene - 49.75
4. Ethan - 17.74
5. Propadiene + propylene - 0.63
6. Propylene - 19.69
7. Propane - 0.74
8. 1,3-Butadiene - 2.98
9. Butenes - 3.50
10. Bhutans - 0.35
11. C ₅ components - 3.08
12. C ₆ -C ₈ non-aromatic - 0.15
13. Benzene - 0.60
14. Toluene - 0.03
15. Xylenes + Ethylbenzene - Traces
The ampoule with the initial mixture is cooled with solid carbon dioxide in acetone.

The mixture is purged with nitrogen for 10 minutes at a rate of 0.03 L / min, then the ampoule is poured and placed in a thermostat. The tests are carried out at 90 ^o C for 24 hours. At the end of the temperature control, the ampoules are removed, cooled with solid carbon dioxide, opened and dried with nitrogen at 100 ^o C, and again weighed on an analytical balance.

где C₁ - разность массы ампулы до и после прогрева в контрольном опыте;
C₂ - разность массы ампулы до и после прогрева в опыте с ингибитором ИПОН.The inhibitory effect, wt.%, Calculated by the formula

where C ₁ - the difference in the mass of the ampoule before and after heating in the control experiment;
C ₂ is the difference in weight of the ampoule before and after heating in the experiment with an IPON inhibitor.

 The results of the experiments are given in table.3.

 The use of an IPON inhibitor to inhibit the polymerization and gum formation of unsaturated hydrocarbons in an amount of more than 0.1 wt.% Is impractical, since it leads to an increase in the load on the column, and therefore to an increase in energy consumption and increased consumption of the inhibitor. The introduction of an IPON inhibitor in an amount of less than 0.01 wt.% On hydrocarbon mixtures does not give the desired result.

 With an increase in the content of triacetonamine in the IPON inhibitor over 35% and a decrease in wt. the proportion of TAA-oxyl is less than 55%, a synergistic effect is not observed and the inhibitory activity of IPON decreases.

Claims (2)

1. The method of inhibiting the process of thermopolymerization and gum formation of unsaturated hydrocarbons in columns of deethanization and depropanization during the separation of the products of the pyrolysis of hydrocarbons by multi-stage rectification by introducing an inhibitor based on 2,2 ', 6,6'-tetramethyl-4-oxopiperidin-1-oxyl, characterized in that as an inhibitor use the product obtained by the oxidation of 2,2 ', 6,6'-tetramethyl-4-oxopiperidine and having a composition, wt.%:
2,2 ', 6,6'-Tetramethyl-4-oxopiperidin-1-oxyl - 55 - 92
2,2 ', 6,6'-Tetramethyl-4-oxopiperidine - 4 - 35
2,2 ', 6,6'-Tetramethyl-1-hydroxy-4-oxopiperidine - 1 - 8
Impurities - 1 - 9
in an amount of 0.005 to 0.3 wt.% (preferably 0.01 to 0.1 wt.%) to the initial hydrocarbon mixtures entering the separation in the columns of depropanization and deethanization.  2. The method according to claim 1, characterized in that as an inhibitor use a solution of the product obtained by the oxidation of 2,2 ', 6,6'-tetramethyl-4-oxopiperidine in an organic solvent.

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