RU2186764C1 - Method of synthesis of methylenecyclobutane carbonitrile - Google Patents

Abstract

FIELD: organic chemistry, chemical technology. SUBSTANCE: invention relates to the improved method of synthesis of methylenecyclobutane carbonitrile that is an intermediate substance used for synthesis of special polymers, rocket fuel, biologically active compounds and different organic compounds comprising cyclobutane moieties in their molecules. Method involves interaction of allene with acrylonitrile at increased temperature and pressure in the presence of inhibitor of polymerization. Allene fraction is subjected for absorption or extractive rectification using acrylonitrile as a retarder and absorbent or extractant. Obtained allene solution in acrylonitrile is fed in continuous regime to cascade of reverse mixing reactors, pressure is decreased in outlet of reactors, unreacted allene and part of acrylonitrile are separated from reaction products. Methylenecyclobutane carbonitrile and a mixture of unreacted allene and acrylonitrile are separated by rectification and inhibitor of polymerization is added to latter and recovered to absorption stage or extractive rectification where the measured amount of fresh allene and acrylonitrile is fed for preparing the reaction mixture of required composition that is fed to cascade of reactors. EFFECT: improved method of synthesis. 5 cl, 3 tbl, 4 ex

Description

 The invention relates to the petrochemical industry and more specifically to a method for producing methylenecyclobutanecarbonitrile.

 Methylenecyclobutanecarbonitrile, which is a mixture of 2- and 3-methylenecyclobutanecarbonitriles, can be used as a starting or intermediate compound for the production of special polymers, rocket fuels, biologically active substances and various organic compounds with cyclobutane fragments in molecules.

A known method of producing methylenecyclobutanecarbonitrile (ICBCN) by cycloaddition of acrylonitrile to an allene in the liquid phase by heating in an autoclave in the presence of a polymerization inhibitor - hydroquinone or fentiazine (US Patent 2,914,541, CL 549-240, 1959) [1]. The synthesis is carried out in a batch mode, at a temperature of 175-250 ^o C and a time of ~ 16 hours. Along with the target products, substituted octahydronaphthalene carbodinitriles (OGNDKN) are formed, the yield of which depends on the ratio of allen: acrylonitrile, and resinous products. The highest yield of ICBCN ~ 45% is obtained when using at least a twofold excess of acrylonitrile. In this case, the yield of octahydronaphthalenedicarbonitrile reaches ~ 24%, counting on the loaded allen. The rest of the allen is consumed unproductively and irrevocably.

 The process is thus characterized by insufficiently high yield of the target products, the formation of a significant amount of by-products of solid solids and resins that impede the isolation of commercial ICBM. The frequency and duration of the process in accordance with [1] make it unsuitable for implementation in industry due to low technology. Blow-offs of unreacted allen lead to environmental pollution and thus create environmental problems.

There is also known a method for producing methylenecyclobutanecarbonitrile from allene and acrylonitrile under more stringent conditions than in the previous method (F. Caserio, et al, J. Am. Chem. Soc., 80, p. 5507-5513, 1958) [2]. The synthesis is carried out in toluene at a temperature of 260-270 ^o With the yield of the target product ~ 60%. The process is accompanied by significant gum formation, which leads to unproductive consumption of reagents and complicates the selection of the target product.

More acceptable results, almost the same ICBCN yield as in [2], with a simultaneous decrease in the process temperature and a decrease in gum formation up to 12.8% based on loaded allen, are achieved in the well-known technical solution described in the article by HN Cripps, JK Williams , WH Sharkey, J. Am. Chem. Soc., 81, 2723 (1959) [3]. The process temperature is maintained no higher than 200 ^o C. However, the method in accordance with [3], as well as the previous one, is not technologically advanced due to the unproductive consumption of raw materials - allene (~ 3.4%) and acrylonitrile (~ 19, 0%). The method is not sufficiently high selectivity for MCCBN and low reactor productivity ~ 2.7 g / l • h Unproductive losses of raw materials associated with resin formation and the formation of OGNDKBN, lead to the deposition of solid precipitation on the walls of the reactor, and in the cube of distillation columns, and ultimately to their clogging. In addition, the process uses pure, almost 100% allen, which is extremely explosive and fire hazard, which is possible only in laboratory conditions, and even then with small reactor loads.

The use of concentrated allen fractions, for example, with an allen content of ~ 87%, due to its explosion and fire hazard, is associated with a number of safety measures. So, according to the current rules for storage and transportation of allen fractions, the temperature should not exceed + 4 ^o C, and pressure - 4.7 kg / cm ² , in addition, explosive decomposition phlegmatizers — propane and propylene — are included in their composition.

 The use of such allen fractions, although it reduces the risk of explosion and fire hazard, nevertheless creates difficulties of a technological nature, since inert will accumulate in the unreacted allen during the process, the separation of which is inevitably associated with the loss of allen. In addition, the use of allen fractions instead of pure allen leads to a noticeable decrease in the rate of cycloaddition of acrylonitrile to allen, and, accordingly, to a significant decrease in the yield of the target product.

 All this, along with the frequency and duration of the process, makes it impossible to use the method [3] for organizing large-scale production of methylene cyclobutanecarbonitrile.

 An object of the present invention thus was to provide a more technologically advanced, explosion and fireproof method for producing methylene cyclobutanecarbonitrile with increased yield and productivity of a process suitable for the production of methylene cyclobutanecarbonitrile on an industrial scale.

It was found that the problem was solved by a method for producing methylenecyclobutanecarbonitrile, including the interaction of allene with acrylonitrile at elevated temperature and pressure, in the presence of a polymerization inhibitor, characterized in that the allene fraction is subjected to absorption or extractive rectification using acrylonitrile as a phlegmatizer and absorbent or extractant, the solution of allene in acrylonitrile is continuously introduced into the cascade of reverse mixing reactors, at the outlet of which they reduce the pressure, unreacted allen and acrylonitrile are separated from the reaction products, methylenecyclobutanecarbonitrile and a mixture of unreacted allene and acrylonitrile are isolated from the reaction mass by rectification, the polymerization inhibitor is introduced into the latter and the amount of fresh allene fraction is returned to the absorption stage, and the fresh calculation is additionally submitted. acrylonitrile for the preparation of the reaction mixture of a given composition, which is then sent to the cascade of reverse reactors eniya. It should be noted that the allene fraction with an allen content of at least 75 wt.% Is subjected to absorption, and a mixture of return and fresh acrylonitrile in the ratio of 3.76-4.04: 1 is used as absorbent; extractive distillation is subjected to an allene fraction with an allen content of at least 25 wt.%, a mixture of return and fresh acrylonitrile in the ratio of 3.5-10: 1 is used as an extractant; unreacted allen and acrylonitrile are separated from the reaction products by lowering the pressure of the reaction mixture from 28-50 to 1.3-1.5 kg / cm ² . As a polymerization inhibitor, neosone D, α-naphthylamine, β-naphthylamine, ionol, pyrocatechol, o-aminophenol or p-quinondioxime are used.

 The implementation of the method for producing methylenecyclobutanecarbonitrile in accordance with the present invention allows to organize a continuous process of interaction of allen with acrylonitrile with increased selectivity. The performance of the reactor increases by about 6 times.

 A significant improvement of the technology is also achieved due to the fact that the separation of almost pure allen from the allen fraction is carried out immediately before entering the reactor and thus the risk of transportation and storage of highly concentrated allen is eliminated.

 The use of acrylonitrile, which is a reagent, also as a phlegmatizer, allows not only to prevent explosive decomposition of allen, but also to further simplify the process technology. In addition, due to the absorption of unreacted allen by acrylonitrile, allen blow-offs are eliminated and thus the loss of allen is significantly reduced and the environmental safety of the process is increased.

 The introduction of a polymerization inhibitor into the mixture of recycle allen and acrylonitrile before entering the absorber significantly reduces gum formation, and thus the deposition of solid and gummy products on heating surfaces is reduced. This effect is not achieved if the inhibitor is introduced directly into the reactor.

 For a better understanding of the invention, Figs. 1 and 2 show flow charts for preparing a reaction mixture of a solution of allen in acrylonitrile: Fig. 3 is a diagram for producing methylene cyclobutanecarbonitrile.

 The preparation of a solution of allen in acrylonitrile by absorption of the allen fraction is shown in FIG. 1. The allen fraction is sent to the absorption column 3, where allen and some of the impurities propane and propylene are absorbed from it by fresh acrylonitrile supplied to the top of this column. In addition, return acrylonitrile containing unreacted allen is introduced into the absorption column below the fresh acrylonitrile entry point. Before entering the absorption column in the stream of return acrylonitrile and unreacted allen serves inhibitor. Unabsorbed gases from the top of the absorption column 3 are sent for disposal. The bottoms product of the absorption column 3, which is a solution of allen in acrylonitrile of a predetermined composition, is sent by pump 4 to the cascade of methylenecyclobutanecarbonitrile synthesis reactors.

 Figure 2 shows a diagram of the preparation of a solution of highly concentrated allen in acrylonitrile by extractive distillation of the allen fraction using acrylonitrile as an extractant. The raw material for the preparation of the allen solution is the propane-propylene pyrolysis fraction containing significant amounts of propane and propylene, which are absorbed by acrylonitrile along with allen. The preparation of a solution of allen in acrylonitrile from such raw materials is carried out under conditions of extractive distillation. Before entering into the condenser 1, fresh acrylonitrile is introduced into the feedstock as a phlegmatizer and pump 2 is fed into the column 3 operating in the extractive rectification mode. Such a scheme makes it possible to increase the pressure in the column and thereby reduce the flow of refrigerant to the condenser 6. Acrylonitrile is introduced into the concentration part of the extractive distillation column 3 as an extractant — fresh through condenser 4, and return, containing unreacted allen — through condenser 5, respectively. Before entering the column 3, an inhibitor is introduced into the mixture of return acrylonitrile and unreacted allen.

 Part of the propane and propylene withdrawn from the top of the column 3, condensed in the reflux condenser 6, is returned to the column as reflux, the other is sent for disposal. The temperature of the cube of column 3 is maintained by the heat transfer agent circulating through the boiler 7. The bottoms product of column 3 — a solution of allene in acrylonitrile of a given composition — is sent to the cascade of methylenecyclobutanacrylonitrile synthesis reactors.

 Figure 3 shows a diagram of the reaction unit, which is a cascade of reverse mixing reactors and stage distillation separation of the reaction products of the cycloaddition of acrylonitrile to allen. Prepared in an absorption column (figure 1) or azeotropic distillation column (figure 2), the reaction mixture — a solution of allene in acrylonitrile of a given composition — is sent to the first in the course of the reactor 8 of the cascade of reverse mixing reactors. Stirring of the reaction mixture in the reactor 8 is carried out by the pump 9. An excess amount of the reaction mixture from the reactor 8 is transferred to the second reactor 10, the mixing of which is carried out by the pump 11. The excess of the reaction mixture from the reactor 10 is sent to the third reactor 12, where it is mixed by the pump 13. Obtained in cascade of reactors, a reaction mass containing methylenecyclobutanecarbonitrile, substituted octahydronaphthalenedicarbonitriles, unreacted allen and acrylonitrile, as well as high melting by-products of pressure throttle They are evaporated through a control valve (not shown in the diagram) with the evaporation of a part of allen and acrylonitrile and sent to distillation column 14. In column 14, unreacted allen and acrylonitrile are isolated as distillate, to which a polymerization inhibitor is added, and then sent to absorption column 3 ( figure 1) or azeotropic distillation column 3 (Fig. 2) for the preparation of the reaction mixture.

 The bottoms product of the column 14 is sent to a distillation column 15, in which the remaining acrylonitrile is isolated as distillate and sent to irrigate the column 14. From the bottoms product of the column 15 in column 16, methylene cyclobutanecarbonitrile is isolated. From the bottom product of column 16 in the drying unit 17, residual methylenecyclobutanecarbonitrile is returned to column 16 and high melting by-products are recovered.

 It was found that such a scheme of the process, namely the preliminary preparation of the reaction mixture - a solution of allen in acrylonitrile, the use of fresh and return acrylonitrile with an inhibitor added to it to prepare this solution, the use of reverse mixing techniques, the use of throttling at the stage prior to the distillation separation of products the reaction of cycloaddition of acrylonitrile to allen, as well as the use of acrylonitrile not only as a reagent and extractant, but also in As a phlegmatizer, it allowed to significantly simplify the technology for methylenecyclobutanecarbonitrile. The use of an explosion and fireproof method for preparing solutions of highly concentrated allen in acrylonitrile immediately before the process eliminated the difficult task of transporting and storing allen. The latter, along with the found techniques and the order of operations, made it possible to organize a continuous process for the production of methylenecyclobutanecarbonitrile, not only suitable for implementation on an industrial scale, but also with a significant increase in selectivity and productivity. At the same time, a reduction in gum formation was achieved, blow-offs were excluded and the environmental safety of the process was increased.

 The invention is illustrated by the following examples of specific performance.

Examples 1-4
Allen fraction is sent to the lower part of the absorption column 3 with a diameter of 400 mm with a height of the nozzle rings Raschig 10 x 10 x 1.8 mm - 16 m (figure 1).

 To prevent heat input from the ambient air and heat removal of allen absorption, the surface of the column is cooled by the refrigerant entering the coil mounted on the column.

 Chilled fresh acrylonitrile is fed to the top of the absorption column, and an inhibited solution of acrylonitrile and allene recycle to a height of 14 m.

 Unabsorbed gases, mainly consisting of propylene and propane, are removed from the top of the column for disposal.

 The bottoms product of column 3, which is a solution of allen in acrylonitrile of a given composition, is sent by pump 4 to the first reactor 8 of the cascade of reverse mixing reactors (Fig. 3).

 Stirring of the reaction mixture in the reactor 8 is carried out by the pump 9. An excess amount of the reaction mixture from the reactor 8 is transferred to the second reactor 10, the mixing of which is carried out by the pump 11. The excess of the reaction mixture from the reactor 10 is sent to the third reactor 12, where it is mixed by the pump 13.

 Reactors 8, 10, 12 are coil-type reverse mixing reactors with a diameter of 100 mm. The heating of the reactors is carried out by the coolant entering the jacket.

 The reaction mass obtained in the cascade of reactors containing methylenecyclobutanecarbonitrile, substituted octahydronaphthalenedicarbonitriles, unreacted allen and acrylonitrile after throttling is sent to rectification, where a mixture of unreacted acrylonitrile and allene is isolated to which the polymerization inhibitor is added and re-cyclized to 3 times.

 The results of the experiments are shown in tables 1 and 3.

Examples 5-14
The allen fraction is mixed with a portion of fresh acrylonitrile, cooled in the refrigerator 1 and pump 2 is fed into the lower part of the extractive rectification column 3 with a diameter of 400 mm and a nozzle height of 10.3 x 10 x 1.8 mm - 12 m. (Fig. 2). The rest of the fresh acrylonitrile cooled in the refrigerator 4 is fed to the top of the column. An inhibited solution of allen recycle in acrylonitrile is fed to a height of 10 m.

On top of the extractive distillation column 3, a propane-propylene fraction containing traces of allene, which is condensed in the reflux condenser 6, is selected as distillate. Part of the condensate is returned to column 3 as reflux (reflux number ≈25), the other part is sent for disposal. The temperature of the cube of the column 2 is supported by the coolant circulating through the boiler 7, in the range of 29-45 ^o C.

 The bottoms product of column 3 — a solution of allene in acrylonitrile of a given composition — is sent to the cascade of reverse mixing reactors for the synthesis of methylenecyclobutanecarbonitrile, as described in examples 1-4 (Fig. 3).

 The results are shown in tables 2 and 3.

Example 15 (comparative)
The method of obtaining methylenecyclobutanecarbonitrile is carried out in accordance with the prototype method [3].

 Allen, acrylonitrile and an inhibitor are charged into a steel autoclave in the ratio shown in table 3. The process conditions are shown in table 3.

 As can be seen from the data of table 3, the yield of the target product in accordance with the present invention is approximately 10% greater than in the prototype method. The performance of the process increases by an order of magnitude.

 For the implementation of the present invention on an industrial scale can be used serial equipment mounted in any petrochemical plant at low capital costs.

Claims (5)

 1. A method of producing methylene cyclobutanecarbonitrile, comprising reacting allene with acrylonitrile at elevated temperature and pressure, in the presence of a polymerization inhibitor, characterized in that the allene fraction is subjected to absorption or extractive distillation using acrylonitrile as a phlegmatizer and absorbent or extractant, the resulting solution of allene in acrylonitrile is continuously introduced into the cascade of reverse mixing reactors, at the outlet of which the pressure is reduced, the non-reactant is separated the allene and part of acrylonitrile that were reacted from the reaction products, methylenecyclobutanecarbonitrile and a mixture of unreacted allene and acrylonitrile were isolated from the reaction mass by distillation, the polymerization inhibitor was introduced into the latter and returned to the absorption or extractive rectification stage of the allene fraction, and the calculated amount of fresh acrylonitrile the reaction mixture of a given composition, which is then sent to the cascade of reverse mixing reactors.  2. The method according to claim 1, characterized in that the reaction mixture is prepared by absorption of an allen fraction with an allen content of at least 75 wt.% Or extractive distillation of an allen fraction with an allen content of at least 25 wt.%.  3. The method according to claims 1 and 2, characterized in that a mixture of recycle and fresh acrylonitrile in a molar ratio of 3.76-4.04: 1 is used for the absorption separation of allen from the allen fraction, or a mixture is used to isolate allen from the allen fraction by extractive distillation return and fresh acrylonitrile in a molar ratio of 3.5-10: 1. 4. The method according to claim 1, characterized in that the unreacted allen and acrylonitrile are separated from the reaction products by lowering the pressure of the reaction mixture from 28-50 to 1.3-1.5 kg / cm ² .  5. The method according to claims 1 to 4, characterized in that as a polymerization inhibitor, neozone D, α-naphthylamine, β-naphthylamine, ionol, pyrocatechol, o-aminophenol or p-quinondioxim are used.

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