SU667555A1 - Method of separating trioxane - Google Patents

Description

I

The invention relates to an improved method for the isolation of trioxane, which is used for the preparation of polydems of maldehyde, and also as a pacj catalyst.

A known method for isolating grioxane from a water-formaldehyde solution obtained after synthesizing grioxane from aldehyde forms on an acidic catalyst by distillation with a trioxane content of 406O%, followed by treating the trioxane distillate with a low boiling solvent, which is not miscible with water and forming azeotropic mixture with it, is used as an example, a mixture that is not amenable to mixing with water and forming an azeotropic mixture with it, as described above, which was mixed with a mixture of water that is not miscible with water and azeotropic mixture forms with it, as exemplified by a solvent, which is not averaged with water and azeotropic mixture is formed, and the sample is mixed with a mixture of water and azeotropic mixture, which was mixed with a mixture of water and 406 O%. and rectification of the resulting solution, ll. The disadvantages of this method are the complexity of the instrumentation of the process: a distillation column — RK with the required number of theoretical plates 60, for separating trioxane distillate from the reaction mixture, and energy consumption (high steam consumption to maintain the hydrodynamic, RK operation mode).

In addition, 43.1-45.2% trioxane and 14.217, 8% formaldehyde are contained in the distillate selected. The presence in the distillate of such a significant amount of formaldehyde improves the process of further purification of trioxane, moreover, in the extraction of trioxane b (enzol formaldehyde goes into the aqueous layer, forming large amounts of weak formaldehyde diluents, which are loaded with benzene, which must be strengthened under pressure , which is associated with considerable difficulties (RK under pressure, high energy costs, etc.). During the rectification of weak solutions of formaldehyde under pressure, the reaction occurs. Cannicarro and in formalin according to L is formic acid, which is removed with the aid of ion exchangers. This is due to the advent of large amounts of wastewater.

Yzv1esten method of separation of trioxane from water-formaldehyde solution by distillation of the extrusion of the crystal, and the formaldehyde obtained after the synthesis of the trioxane from formaldehyde at 0 ° C; solvent, immiscible with water and forming with it azo-nitrogen mixture, for example dichloroethane, and distillation of azebtrbpa 2. The disadvantages of this method consist in the complexity of instrumentation a cooling and centrifuging process, associated with significant capital and large energy costs. Krbyo foro, dyo yo, and while centrifuging trioxane of the required purity, two are carried out; or triple washing of the crystals with ice water, which is associated with a significant consumption of water. OWN Two or three times queuing entails the presence of a large amount of mother liquor and industrial water, the content of trioxane in which reaches 10-12%, and the formaldehyde content of 7-8%, which is required for returning to the process cycle, formalin arises the need for it strengthening rectification under pressure, which is connected again with energy-efficient operation costs. Moreover, during rectification under pressure of weak formaldehyde solutions, formalin-acid forms accumulate in formalin You, which are removed by ion-exchangers, are associated with the occurrence of large quantities of wastewater. Isolation of rioksan from the mother liquor and other water entails great losses of the latter. In addition, the method does not allow trioxide 1 to be allowed to the required degree of purity for the melt polymerization, for which using trioxane with a formaldehyde content of not more than 0.0.03%. (preferably O, OO1%) and a water content of not more than 0.003% (preferably 0.001%). The known method provides the formaldehyde content in trioxane p, 004% and the water content of 0.006%. The aim of the invention is to improve the process and increase the purity of the target product. . The invention is dried in an EQM that the distillate containing trioxane, the aldehyde form, and the water obtained after ctra-, the formaldehyde trioxane with an acidic catalyst, is distilled at a residual pressure of 15-2 o-2 mm Hg. and a temperature of 60-7 ° C with the subsequent treatment of the wet crystalline trioxane with a low-boiling solvent, immiscible with water, which formed a hydrotropic mixture, and the subsequent distillation of the azeotrope. Benzene is preferably used as the low boiling solvent. The drawing shows the trioxane release scheme. . The trioxane synthesis reactor, 1, is loaded with concentrated formalin and a catalyst (sulfuric acid, basic acid or sucroic acid). The contents of the reactor are heated to 97-11 ° C, the vaporized trioxane, formaldehyde and water vapor pass through a heat exchanger (cooler) 2 and enter collection No. 3, equipped with a ypoBHsi 4 regulator, interlocked with the flow meter 5 so that constant value is maintained in collection No. 3 level. From collector 3, the trioxane distillate is pumped by vacuum through flow meter 5 to apparatus 6 equipped with a barometric tube, in which vacuum of 150–200 mm Hg is created. and the temperature is maintained corresponding to the vapor pressure of trioxane at given us and x. Trioxane vapor enters the annulus of the heat exchanger 7, where the trioxane crystallizes. Cold water is fed into the tube space to maintain the temperature of the heat exchanger. By filling the inter-tube space of the heat exchanger with trioxane, which is determined by a special device that regulates the resistance of the system, a switch is made to the 2nd similar heat exchanger, and in the heat exchanger filled with trioxane, the solvent 8 is pumped and circulated until complete dissolution of the crystalline trioxane. After that, the dissolved trioxane enters collection 9, from where it is fed to the stage of isolation of pure trioxane. The reflux condenser 10 is designed to completely capture the trioxane vapor from the solvent in order to eliminate vapor. In apparatus 6, formaldehyde is concentrated, which is collected by a 1 G collector through a barometric tube, from which pump 12 is fed through the flow meter 13 to the trioxane synthesis reactor. The implementation of the process according to the proposed method eliminates the formation of weak formaldehyde solutions and, therefore, the stage of strengthening of weak formalin or formic acid. , when trioxane is released from ice forms of the hydrochloric solutions under vacuum and at a temperature corresponding to the vapor pressure of the valve, a small amount of formaldehyde evaporates, the distillate is 44-55% trioxane, 5-6% formaldehyde and 50% water, This greatly simplifies the process of further purification. At the same time, in apparatus 6 there is a significant strengthening of forcitalin, which is fed to reactor 1. As a result, the process of synthesis of trioxane is intensified and the productivity of the synthesis reactor increases. . The release of trioxane under vacuum significantly slows the Cannitzarro reaction to form methanol and formic acid, which in turn facilitates further purification of trioxane and improves the quality of the target product. Example 1. In the reactor 1 load Yu kg 55% formalin and 3% by weight of sulfuric acid. The contents of the reactor are heated to 100-105 ° C, the resulting trioxane vapor passes through a direct cooler 2 and enters collector 3, in which regulator 4 maintains a constant level. Using a vacuum through the flow meter 5, the trioxane distillate at a rate of 4 kg / h is fed into the apparatus 6, in which a constant level is maintained by means of a barometric pipe and a barometric collector 11. In apparatus 6, a residual vacuum of 150 mm Hg is created. and the temperature is maintained at 6 ° -65 ° C, corresponding to the vapor pressure of trioxane. Evaporating trioxane vapor enters the intertubular space of the heat exchanger 7, in which the temperature is 10 10 C. At a given temperature, the trioxane crystallizes on the annulus walls. By filling the inter-tube space of the heat exchanger 7 with crystal trioxane, the vacuum from the heat exchanger is removed and the similar second heat exchanger is connected to work. Hot water is supplied to the tube space of heat eHHRxa 7 to maintain a temperature in the range of 45-50 ° C. Pump 8 feeds 4 kg / h into annulus benzene, which is circulated until complete dissolution of trioxane. The benzene solution of trioxane enters the collection, where. it separates from the aqueous layer. The benzene solution of trioxane is supplied to the Republic of Kazakhstan, in which the temperature is established, the mode: the temperature of the top of the column is not lower than 80 ° C, the temperature of the bottom of the COLUMN. 114-115 ° C. Benzene vapors from the RK enter the condenser, where they condense, part of the benzene is removed. Hia irrigation PK, the remaining benzene is recycled to dissolve the trioxane in heat exchanger 7. From the bottom of the column, 3.4 kg / h of trioxane are taken. Trioxane is characterized by so pl. 61-62 ° C, bp. 114115 C, trioxane content of 99.9%, formaldehyde content of 0.001%, moisture content of 0.001%. In apparatus 6, formaldehyde is strengthened to 70% concentration, which enters the barometric collector 11 through the barometric tube and feeds it into the reactor 1 at a speed of 2 kg / h via a flow meter 13 via pump 12. In reactor 1, formalin is strengthened to a concentration of 6O%. As a result, the removal of trioxane per unit volume of the reactor is increased. Example 2. In the reactor 1 load 10 kg 55% of formal formalin and 5% by weight of benzo-sulphonic acid. Synthesis lead. similarly to that described in example 1, so that the device 6 is maintained at a residual vacuum of 2OO mm Hg and a temperature of 70 C. After the distillation of benzene, 3.3 kg / h of trioxane with a melting point of 61-62 ° C are obtained, the temperature boiling point 114 C, which contains 99.99% of Grioxane, OH, 003% formaldehyde, and OH,% SS water. In apparatus 6, formaldehyde is strengthened to a concentration of 65%, which is returned to the p & actor 1, the concentration of which increases to 59%. Performance synthesis reactor 173 g / l.h. The table shows the characteristics of trioxane, obtained by known and proposed methods.

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Comparative Characterization of Trioxane Isolation Methods

Known61-62 114 99.9 Suggested

61-62 114 99.99 0.001

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Claims (2)

1. The method for isolating grioxane from water The solution / s is treated with a low boiling solvent and immiscible by treating the crystalline trioxane with crystalline trioxane. with water and forming a neazeotropic mixture, and then distilling off the azeotrope, characterized in that, in order to control the process and improve the quality of the target product, e 6 of the solvent treatment stage, the distillation of trioxane from the water P t 0,001180 Formal degenerate solution with a residual pressure of 150-20 O mmHg at “3070 s. .- - -. . - -,: -, 2. The method according to i. about aphids and yushchi it Shesheyyus 1us; Tv.ryrTel end up benzene. Sources of information understood in attention during examination 1. Avt6 | certificate of the USSR № 337383, cl. C 07 J) 323/06, 03.20.63.,: 2, Japan’s Patent No. 6490, cl. 16.E4, 16,03,67. /: V 0,0040, O06