RU2139859C1 - Method of preparing inhibitor of polymerization of unsaturated hydrocarbons - Google Patents

Abstract

FIELD: chemical industry, more particularly preparation of inhibitor of polymerization of unsaturated hydrocarbons based on 2,2′,6,6′-tetramethyl-4- oxopiperidin-1-oxyl. SUBSTANCE: method comprises oxidizing 2,2′,6,6′-tetramethyl-4-oxopiperidine with organic hydroperoxide in the presence of variable valency metal compounds as catalyst. Method makes it possible to increase yield of the desired product and improve its inhibiting activity. EFFECT: more efficient preparation method. 5 cl, 7 ex, 2 tbl

Description

 The invention relates to the field of production of polymerization inhibitors of unsaturated hydrocarbons, in particular an inhibitor based on the stable iminoxyl radical 2,2 ', 6,6'-tetramethyl-4-oxopiperidin-1-oxyl.

 Known methods for producing individual stable iminoxyl radicals by oxidation of spatially hindered piperidines with hydrogen peroxide in the presence of catalysts / E. G. Rozantsev. Free iminoxyl radicals, Chemistry, 1970, 54, 182 /.

 These methods have a research preparative purpose, require the use of expensive and scarce products and are characterized by very low yields of the target product. Their industrial application would be associated with extremely high costs. In these methods, hydrogen peroxide is used as an oxidizing agent, which has a tendency to spontaneous decomposition and explosive properties, which complicates its use in industrial production. There is also the problem of treating wastewater containing hydrogen peroxide / U.Shamb and others, "Hydrogen peroxide", "Inlit", 1958, 132, 153-154 /.

Closest to our proposed invention is a method for producing a polymerization inhibitor of unsaturated hydrocarbons - 2,2 ', 6,6'-tetramethyl-4-oxopiperidin-1-oxyl - including the oxidation of 2,2', 6,6'-tetramethyl-4- oxopiperidine with hydrogen peroxide in the presence of catalytic amounts of salts of vanadium, molybdenum or tungsten acids and Trilon "B". / A.s. USSR N 166032, C 07 D, B.I. N 21, 1964./
The target product is isolated by saturation of the reaction mixture with potassium carbonate and extraction with ether, followed by distillation of the ether and recrystallization of the target product from hexane.

The disadvantages of this method are:
the use of expensive catalysts, the complexity of isolating an individual iminoxyl radical used as an inhibitor, low yields upon its production, and the use of hydrogen peroxide as an oxidizing agent.

 The objective of the present invention is to simplify the method of producing the inhibitor and increase its effectiveness.

 We propose a method for producing an unsaturated hydrocarbon polymerization inhibitor based on 2,2 ', 6,6'-tetramethyl-4-oxopiperidin-1-oxyl, including the oxidation of 2,2', 6,6'-tetramethyl-4-oxopiperidine (triacetonamine) organic hydroperoxides using variable valence metal compounds as a catalyst.

 The resulting oxidation product is preferably subjected to separation without isolation of the individual 2,2 ', 6,6'-tetramethyl-4-oxopiperidin-1-oxyl. However, this does not exclude the isolation of individual 2,2 ′, 6,6′-tetramethyl-4-oxopiperidin-1-oxyl by known methods.

 As a raw material for oxidation, a mixture of organic substances containing at least 85 wt.% Triacetonamine can be used.

 The oxidation product can be obtained in an organic solvent. To simplify the process technology, the inhibitor can be obtained in the form of a solution in alcohol formed during oxidation or in a mixture of alcohol with an organic solvent.

 Alcohols, aromatic, aliphatic hydrocarbons, ketones, esters, etc. are used as solvents. Preferably, the solvent is used in an amount of 20-80 wt.%.

It is possible to carry out the oxidation with strengthened oxides obtained during the oxidation of hydrocarbons and containing preferably ≈ 20-40% hydrocarbon hydroperoxides. For oxidation, concentrated organic hydroperoxides may also be used. Secondary and tertiary alkyl or arylalkyl hydroperoxides, for example, ethylbenzene, tert-butyl, tertamyl, isopropylbenzene and others, are used as hydroperoxides. The molar ratio of hydroperoxide to triacetonamine is usually 1-3: 1. The oxidation process can be carried out at a temperature of 50-90 ^o C. Oxidation can be carried out in the presence of an organic solvent.

 Compounds of Mo, V, Ti, W, Nb, Ta, Co, etc. can be used as a catalyst. It is preferable to use compounds of Mo, V or Ti. The amount of catalyst is usually 0.05-2 wt.% On 2,2 ', 6,6'-tetramethyl-4-oxopiperidine. Naphthenates, oxalates, resinates, glycolates, acetylacetonates, hexacarbonyls, chlorides, oxychlorides, oxides of these metals, metal compounds with alcohols and / or hydroperoxides can be used.

 In the case of incomplete conversion of hydroperoxide during oxidation, the reaction mixture after oxidation can be washed with a 30-35% alkali solution and then used as an inhibitor of polymerization of unsaturated hydrocarbons. The mass ratio of the reaction mixture: alkali = 1: 0.1 - 0.5.

 The target product (inhibitor) can be obtained either directly after the oxidation process without separation of the reaction mass, or including the separation stage by, for example, complete or partial distillation under vacuum of the alcohol and, possibly, an organic solvent that forms during the oxidation process.

In the proposed method, preferably no individual 2,2 ', 6,6'-tetramethyl-4-oxopiperidin-1-oxyl is isolated. After oxidation and isolation of the solvent and / or alcohol, a product is obtained that is used as an inhibitor of the polymerization of unsaturated hydrocarbons and having a composition, wt.%:
2,2 ', 6,6'-tetramethyl-4-oxopiperidin-1-oxyl (TAA-oxyl) - 50-90
2,2 ', 6,6'-tetramethyl-4-oxopiperidine (TAA) - 5-35
Impurities - 1-15.

 In terms of inhibitory activity, the new inhibitor is not inferior to the prototype TAA-oxyl, and in some cases even surpasses it.

 The differences of the proposed method from the prototype are: the use of organic hydroperoxides as an oxidizing agent, as a catalyst for metal compounds of variable valency, the possible exception of the stage of isolation of an individual 2,2 ', 6,6'-tetramethyl-4-oxopiperidin-1-oxyl, it is possible to use as a raw material for the oxidation of a mixture of organic substances containing at least 85 wt.% triacetonamine, the possible use of an inhibitor in the form of a solution in an organic solvent, the possible use as an oxidizing agent I strengthened oxidates obtained during the oxidation of hydrocarbons and containing preferably ≈ 20-40% hydroperoxides of hydrocarbons.

 As a result, through the use of a new oxidizing agent - organic hydroperoxides, eliminating the stage of isolation of an individual radical, increasing the yield of the target product and increasing its inhibitory activity, the economic efficiency of the method is increased.

 Hydroperoxides of hydrocarbons are significantly more stable products in comparison with hydrogen peroxide / BD Kruzhalov and others. "Joint production of phenol and acetone", M., 1963, 51 /, which simplifies their use as an oxidizing agent in industrial production. In addition, the oxidation of triacetonamine with organic hydroperoxides proceeds without the formation of water, unlike hydrogen peroxide, which significantly increases the economic efficiency of the process. Under new oxidation conditions, a mixture of products of a certain composition is obtained in high yield, which, as shown by tests, can be directly used as an inhibitor of polymerization of unsaturated hydrocarbons.

 When using as a raw material a mixture of organic substances containing triacetonamine in an amount of at least 85 wt.%, The yield of the target product is further increased without reducing its inhibitory activity.

 The invention is illustrated by the following examples.

 For convenience in the examples, the proposed inhibitor is indicated by the term "Inhibitor".

 Example 1

A solution of 10 g of triacetonamine (TAA) in 20 ml of toluene is heated to 70 ^° C, then 0.1 g of molybdenyl methylbutylene glycolate MoO ₂ (C ₅ H ₁₁ O ₂ ) ₂ is added and 10 ml of isopropylbenzene hydroperoxide (hyperysis) is added in a stream of nitrogen. The molar ratio of TAA: hyperysis = 1: 1. The mixture is stirred at a temperature of 70 ^o C for 3 hours. Then washed with 20% NaOH solution. After distillation under vacuum 20-40 mm RT. Art. and a temperature of 30-40 ^o C toluene receive a solution of the inhibitor in dimethylphenylcarbinol (DMF) of the composition shown in table. 1 at the end of the description.

 Example 2

50 g of TAA is heated to 50 ^° C., 0.1 g of vanadyl acetylacetonate VO (acac) ₂ is added and 37.5 ml of hydroperoxide tert are added in a stream of nitrogen. amyl (GPTA). The molar ratio of TAA: GPTA = 1: 1. The mixture is stirred at a temperature of 50 ^o C for 5 hours. After distillation under vacuum 40-50 mm RT.article and a temperature of 30-40 ^o C the resulting tert.-amyl alcohol receive an inhibitor of the following composition:
TAA-Oxyl - 76
TAA - 18
Impurities - 6
Example 3

A solution of 10 g of triacetonamine in 20 ml of tert-butyl alcohol (TBS) is heated to a boil (86 ^° C), 0.01 g of vanadium pentoxide V ₂ O ₅ is added and 10 ml of tert-butyl hydroperoxide (GPTB) are added in a stream of nitrogen. . The molar ratio of TAA: GPTV = 1: 1.3. The mixture is stirred for 1 hour. Get a solution of the inhibitor in TBS composition shown in the table. 2 at the end of the description.

 Example 4

The oxidation of TAA is carried out with a strengthened oxidate obtained by the oxidation of ethylbenzene and having the composition, wt.%:
Ethylbenozole hydroperoxide (HPEB) - 25-27
Ethylbenzene - 67-72
Impurities (acetophenone, methylphenylcarbinol, benzaldehyde) - 3-6
10 g of TAA is heated to 70 ^° C., 0.01 g of molybdenum hexacarbonyl Mo (CO) ₆ is added and 150 ml of an oxidate containing ≈ 25% HPEB are added in a stream of nitrogen. The molar ratio of TAA: HPEB = 1: 3. The mixture is stirred for 2 hours. Then washed with a 25-35% alkali solution. After distillation under vacuum 20-25 mm RT. Art. and a temperature of 40-45 ^o C ethylbenzene receive a solution of the inhibitor of the composition shown in table. 3 at the end of the description.

 Example 5

 The oxidation of TAA is carried out with a strengthened oxidate obtained by oxidation of isopentane and having a composition, wt.%.

GPTA - 35-40
Tertiary amyl alcohol - 57-63
Impurities - 2-3
A solution of 10 g of TAA in 10 ml of tert-amyl alcohol (TAS) is heated to 60 ^° C, 0.005 g of MoCl ₅ molybdenum chloride is added, and 20 ml of an oxidate containing ≈40% HPA are added in a stream of nitrogen. The mixture is stirred for 2 hours. After distillation under vacuum 40-50 mm RT.article and a temperature of 30-40 ^o C solvent (TAS) get an inhibitor of the following composition:
TAA-Oxyl - 63
TAA - 30
Impurities - 7
Example 6

A solution of 10 g of the hydrocarbon fraction isolated from the products of triacetonamine synthesis and containing 85 wt.% Triacetonamine in 25 ml of toluene is heated to 70 ^° C, 0.01 g of Mo (CO) ₆ are added in a stream of nitrogen, 9.5 ml of hyperis are added. The molar ratio of TAA: hyperysis = 1: 1. The mixture is stirred for 2 hours. Get a solution of the inhibitor of the composition shown in table. 4 at the end of the description.

 Example 7

 The determination of the inhibitory activity of an inhibitor under conditions of isolation of isoprene by distillation is carried out as follows.

In a 100 ml ampoule, carbon steel metal plates are loaded, purged with nitrogen, and weighed. Then, 30 ml of isoprene, containing or not containing an inhibitor, was charged and weighed again. The ampoule is placed in a cooling mixture of acetone + solid carbon dioxide, the gas space of the ampoule is blown over the liquid with nitrogen at a speed of 20 l / h for 1 min and sealed in a stream of nitrogen. Ampoules are placed in a thermostat and incubated at a temperature of 100 ^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 to constant weight and weighed again.

где C₁ - разность массы ампулы до и после прогрева в контрольном опыте;
C₂ - разность массы ампулы до и после прогрева в опыте с ингибитором.The inhibitory effect, wt.%, Is 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 the mass of the ampoule before and after heating in the experiment with the inhibitor.

 The results of the experiments are given in table. 5 (see the end of the description).

 The inhibitory activity of inhibitor samples during the separation of vinyl aromatic hydrocarbons, for example styrene, by distillation is determined as follows.

The essence of the method is thermostating of styrene, placed in a 4-neck round-bottom flask, in the presence of inhibitors at a temperature of 100-120 ^o C for 4 hours. The flask is heated by immersing it in an ultra-thermostat bath. The unit operates under vacuum. Residual pressure is created depending on the conditions of the experiment. Mixing the contents of the flask is carried out by boiling styrene. Nitrogen containing not more than 0.05-0.1 vol% oxygen or air is used as the gas phase. The determination of the polymer with a content of less than 1 wt.% Is carried out by the nephelometric method, with a polymer content of more than 1 wt.%, Use the gravimetric method.

 The results of the experiments are given in table. 6 (see the end of the description).

Claims (5)

 1. A method of producing an unsaturated hydrocarbon polymerization inhibitor based on 2,2 ', 6,6'-tetramethyl-4-oxopiperidin-1-oxyl by oxidation of 2,2', 6,6'-tetramethyl-4-oxopiperidine with an oxidizing agent in the presence of a catalyst, characterized in that organic hydroperoxide is used as an oxidizing agent, and compounds of metals of variable valency are used as a catalyst.  2. The method according to p. 1, characterized in that the resulting oxidation product is subjected to separation without isolation of individual 2,2 ', 6,6'-tetramethyl-4-oxopiperidin-1-oxyl.  3. The method according to PP. 1 and 2, characterized in that as a raw material for oxidation using a mixture of organic products containing at least 85 wt.% 2,2 ', 6,6'-tetramethyl-4-oxopiperidine.  4. The method according to PP. 1 to 3, characterized in that the oxidation product is obtained in an organic solvent.  5. The method according to PP. 1 to 4, characterized in that the oxidation is carried out with strengthened oxidates obtained from the oxidation of hydrocarbons and preferably containing ~ 20-40% hydrocarbon hydroperoxides.

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