The method of purification of the pyrolysis of acetylene from diacetylene

 

(57) Abstract:

Purification of acetylene obtained by oxidative pyrolysis of methane from impurities diacetylene lead by sorption of diacetylene 30-35 wt.%. aqueous solution of the secondary amine with the addition of 8-10 wt.% of ethylene glycol. After heating the absorption solution at 60-70oC for 1.5-2 h the mixture is subjected to fractional distillation. The result is a 4-dialkylamino-3-butene-2-ones with the release of 65-75%. Contained in the exhaust gases and purified from diacetylene methylacetylene-allene fraction used for the production of isopropenylacetate, 2-aloxiprin and receive valuable commodity intermediates of organic synthesis - 4-dialkylamino-3-butene-2-ones.

The invention relates to the field of organic chemistry, in particular, to methods of purification of hydrocarbon gases from diacetylene.

In the process of obtaining diacetylene the pyrolysis of methane produced hydrocarbon mixture in addition to acetylene and its homologues contain 6-8 % by volume of diacetylene. Cleaning pyrolysis gases from diacetylene is extremely important technological challenge, complicated by the explosion of diacetylene and its homologues, as well as significant by its tendency to polymerization. This scrap.

A known number of domestic and foreign methods of cleaning pyrolysis gases from diacetylene, which can be divided into two groups of methods.

1. Methods based on selective absorption of components of hydrocarbon gases in selective solvents.

This group should include the method proposed by G. Thodos and L. Stutsman (U.S. Pat. USA, N 2.753.012, CL 183-115, 3.07.1956) and consisting in the sequential transmission of gases through the absorber containing a selective liquid solvent, for example acetone, diethylcarbamyl, DMF, N-methyl-2-pyrrolidone, carbitol and others After the absorption of the extract is heated and the resulting vapor containing low-boiling components, in contact with pure solvent. The resulting solution is used to highlight individual volatile components.

In other cases, the solvent used is N-methyl - 2-pyrrolidone (U.S. Pat. UK N 1051764, CL 5 E, publ. 1973), liquid ammonia (A. C. USSR N 570580 from 30.08.1977, IPC 6 07 With 7/11; A. S. USSR N 791713 from 30.12.1980, IPC 6 07 With 7/11; A. S. USSR N 1188154 from 30.10.1985, IPC 6 07 With 7/11), derivatives of pyridine (U.S. Pat. Romania N 67093 from 30.10.1979, class C 07 C 11/24).

These methods have several disadvantages. The required regeneration RA is small, that is not possible after desorption to obtain pure components of hydrocarbon gases and, consequently, hinders their further use. These methods involve desorption and allocation diacetylene after its absorption, which in itself is unsafe due to the explosion of diacetylene and his propensity for polymerization.

2. Methods based on chemical bonding diacetylene obtaining practically valuable products.

These methods are based on the absorption of diacetylene from a mixture of hydrocarbons pyrolysis of methane solutions or pure substances capable of selectively reacting with diacetylenes with the formation of low volatile products.

If the solvent-adsorbent to use methanol or a solution of methanol in dioxane (A. C. USSR N 785292 from 7.12.1980, class C 07 C 43/14), in the presence of catalytic amounts of potassium hydroxide is formed 1-methoxy-1-butene-3-in released in the following from the solution and which is the marketable product.

Diacetylene can be selected from diacetyltartaric gases dissolved in 3(5)-methylpyrazole, formed in the system of concentration due to the reaction of diacetylene with hydrazine (A. C. USSR N 391157, CL 10 H 23/00).

As a prototype of the proposed method is selected USSR author's certificate N 701981 from 5.12.1979, IPC C 07 C 7/11 (BI. N 45, 1979), in which diacetylene from a mixture of hydrocarbons absorbed utililization ether formed directly in the absorber due to the interaction of diacetylene with n-butanol in the presence of 1-3 wt.% potassium hydroxide. The accumulation ethynilesrtadiol ether part of the last displayed on the rectification to obtain pure ether.

The disadvantage of this method is the fact that formed vysokoperedelnyh product - amenitiesbalcony ether is prone to polymerization, has a sharp odor, toxic and environmental point of view, does not meet modern requirements. Use ethynilesrtadiol ether in further syntheses also inconvenient because of its instability. In ethynylbenzocrown ether solubility of acetylene is quite large: at 20oC in 1 g of the ether-soluble 2.1 cm3acetylene. Given that the content of the acetylene in the cleaned gases in 40-50 times greater than the concentration of diacetylene, such solubility leads to additional difficulties in the regeneration of the air.

The purpose of this sobrien practically valuable commodity product and educt for the synthesis of heterocyclic compounds 4 dialkylamino-3-butene-2 - ones.

This objective is achieved in that the gases of pyrolysis of acetylene after extraction, the product is passed into the absorber 30-35 wt.% an aqueous solution of the secondary amine with the addition of ethylene glycol to saturation of the solution diacetylenes and its penetrations through the absorber. After absorption, the absorbent incubated 2 hours at a temperature of 60-70oC and subjected to rectification, highlighting the product - 4-dialkylamino-3-butene-2-it.

As secondary amines is possible to use dimethyl - or diethylamino, research and other amines. The interaction is carried out according to the scheme:

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The use of secondary amine as absorbent has a number of important advantages.

1. Allows you to use to clean the products of large-scale production, for example, aqueous solution of dimethylamine with mass fractions of the main substance of 33%.

2. Leads to hydration of the triple bond of the product attaching amine to diacetylene with the formation of stable to oxidation and polymerization - aminophenylamino.

3. Absorbent non-flammable, non-toxic, non-explosive, minimally carried away by the stream of cleaned gas.

4. The composition of the absorber is, depending on the type of the secondary amine from 65 to 80 l diacetylene.

The concentration of amine is selected based on optimal saturation of the reaction mixture with diacetylene. At lower concentration of amine is lower than 30 wt.% reduced capacity of the adsorbent for diacetylene and increase energy cost allocation 4 dialkylamino-3-butene-2-it. With increasing amine concentration above 35 wt.% increases the removal of the amine from the absorber.

Adding ethylene glycol reduces the loss of amine, thus reducing its volatility, and ensuring the homogeneity of the reaction mass with increasing concentration of the product.

At the stage of absorption diacetylene from a hydrocarbon mixture is joining amine to diacetylene with the formation of 1 - dialkylamino-1-butene-3-in. Hydration innovage amine occurs after saturation of the solution diacetylenes by heating the mixture at 60-70oC for 2 hours. This temperature corresponds to the optimal reaction rate with a minimum flow rate of oxidative processes.

Fractionation solution of 4-dialkylamino-3-butene-2-it is in the vacuum allows, in addition to produce a marketable product to return in the process of absorption of ethylene glycol.

The invention is illustrated by the following examples.

the aqueous solution of dimethylamine, 15 ml of ethylene glycol and through the bubbler at 8-10oC missed 120L model mixtures containing 10% diacetylene, 42% of acetylene, 10% vinylacetylene, 18% methylacetylene and 20% argon (volume percent). By passing the gas mixture is heating the reaction mass. The temperature in the flask was maintained above 20oC by external cooling.

Gases, unreacted, was condensed in two successive coiled traps at the temperature of -60oC. Condensate, according to GC, contained methylacetylene, vinylacetylene, impurity Allen. Diacetylene within the sensitivity of the device was missing.

After passing a mixture of the reaction mass was heated up to 1.5 hours at a temperature of 70oC, and then cooled. The organic layer was vysalivanie potash, was separated and subjected to distillation without pre-drying. Received 14 g of 4-dimethylamino-3-butene-2-it. Yield 70%, so Kip. 80oC (1 mm RT. Art.), nD20at 1.5585; d2400,9718. The physical constants of the reaction product corresponds to the literature data (Zhur.org.chem., 1984. So 20. Vol.5. S. 962-968).

According to PMR spectroscopy is transconfiguration product relative to the double C=C bond.>13,2 Hz.

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The signal of the methyl group of acetyl fragment is located in the region of 1.9 M. D. (HD), the protons dimethylaminopropyl form a singlet at 2,86 M. D. (HC).

Example 2. In a three-neck flask equipped with stirrer, bubbling tube and a thermometer, were placed 130 ml of 35 wt.% an aqueous solution of diethylamine and 15 ml of ethylene glycol. At a temperature of 202oC through the solution to pass 100 liters of gas mixture composition (volume %): 9.6 diacetylene, 62,0 acetylene, 9.3 methylacetylene, 18.0 vinylacetylene, 1.1 phenylacetylene. After passing a mixture of hydrocarbons, the reaction mass was heated at a temperature of 65oC for 2 hours. The resulting mass was distilled in a vacuum, separating the low-boiling fraction containing diethylamine, water, ethylene glycol, and the target product - 4-diethylamino-3-butene-2-it. Yield 76%, so Kip. 145oC (10 mm RT. Art.).

The physical constants of the product are in accordance with literature data (Zhur.org.chem., 1984. So 20. Vol.5. S. 962-968). Analysis of gas condensate after the reaction showed complete absence of diacetylene. Product structure interaction proved by NMR1H and13C, IR-spectroscopy.

Example 3. After cooled to 15oC 30 logichnogo example 2. The reaction mixture was heated for 2 hours at a temperature of 60oC, the reaction product was isolated by direct rectification of the mixture. Output 4-N - morpholino-3-butene-2-it was 64%, so Kip. 120oC (1 mm RT. Art.), nD201,5760, d2401,1040, which corresponds to literature data. In the spectrum of TMR observed doublets ethylene protons at 7,86 and 5.45 M. D. (JHHto 13.6 Hz - transformation); the protons morpholino rings appear as multiplets in the region of 3.85 and 4,05 M. D.; the signal of the protons of the methyl group - a singlet at 2,05 m D. Analysis of gas condensate after passing through the reaction mass showed a complete lack of diacetylene.

In addition to secondary amines as a binder diacetylene agents can be used primary amines (n-Propylamine, aniline), but in this case, the yield of the target product is reduced to 40-50% and marked the breakthrough of diacetylene at the same speed ozonation.

Diacetylene is obtained as a by-product in an amount of about 5 % by volume of the produced acetylene method of oxidative pyrolysis of methane, and on all existing CIS production is burned due to the lack of methods of its purposeful use. The presence of ene-allene fractions for the production of isopropenylacetate, 2-alkoxyimino, acetone.

As shown in the above examples, the proposed method allows to almost completely clean gases of the pyrolysis of methane from diacetylene in addition. with high outputs to obtain valuable products 4 dialkylamino-3-butene-2-ones. The highest outputs are obtained by using lower secondary aliphatic amines (70-76%). 4 Dialkylamino-3-butene-2-ones are used as components in the textile, aniline dye industry, as antiknock additives. 4 Diethylamino-3-butene-2-it is a valuable source product to obtain a number of aromatic and heterocyclic dyes, pharmaceuticals, production of vitamins, inhibitors, plasticizers, accelerators of vulcanization of rubber.

The method of purification of the pyrolysis of acetylene from diacetylene by sorption of diacetylene absorbent material, characterized in that the sorption of diacetylene carried out using as the absorbent aqueous solution of a secondary amine with a mass fraction amine 30 - 35% with the addition of glycol to the saturation of the absorbent diacetylenes, at the end of the sorption absorbent is maintained at a temperature of 60 - 70oC for 1.5 - 2 h and under the

 

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