RU2398756C2 - DI-(β-CHLOROETHYL)FORMAL SYNTHESIS METHOD - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method for synthesis of di-(β-chloroethyl)formal, which is the basic material in synthesis of polysulphide oligomers (thiocols), capable of cold curing to obtain sealants with unique properties. Method involves reacting ethylene chlorohydrin with formaldehyde in molar ratio (2.25-2.7):1, in the presence of dry gaseous hydrogen chloride as an acid catalyst with subsequent azeotropic distillation of the reaction water in the presence of 1,2-dichloroethane as a resolving agent.

EFFECT: method enables to obtain an end product with high output and selectivity.

6 cl, 1 tbl, 12 ex

Description

The invention relates to a technology for the production of di- (β-chloroethyl) formal, which is the main raw material in the synthesis of polysulfide oligomers (thiocols), characterized by the ability to cold vulcanize to obtain sealants that are unique in their properties.

A known method of producing di- (β-chloroethyl) formal by condensation of ethylene chlorohydrin with formaldehyde in the presence of acidic catalysts by reaction

To shift this equilibrium system towards the formation of the target product, water-removing agents are used, such as: sodium sulfate, calcium chloride (Yu.V. Pokonova. Haloesters. Khimiya Publishing House, M.-L., 1966, p.20- 21) or concentrated sulfuric acid (Chemical Industry, vol. 84, No. 2, 2007, p. 97-100). However, the use of sulfuric acid in the technology for the production of di- (β-chloroethyl) formal is associated with the formation of a significant amount of waste - diluted sulfuric acid contaminated with organic impurities and therefore difficult to utilize. The use of calcium chloride as a water-taking agent leads to a complex hardware design of the process, as well as to significant losses of the target product with spent calcium chloride.

More modern methods of removing water from the reaction mixture for the synthesis of di- (β-chloroethyl) formal include its distillation in the form of an azeotropic mixture with a suitable separating agent, for example, dichloroethane, diisopropyl ether, nitromethane (S.K. Ogorodnikov. Formaldehyde. Publishing house " Chemistry ", L., 1984, p.199) or ethylene chlorohydrin taken for the reaction in stoichiometric excess (J. Orlowski, H. Czerwinska, L. Klar. Przem. Chem., 1957, 13, No. 9, 520-523, D.M. Vinokurov, "University proceedings. Chemistry and chemical technology", 1961, 4, No. 6, 988-991).

The known method (RF Patent No. 2143419, filed 07/07/98, op. 12/27/99) for the preparation of di- (β-chloroethyl) formal by reacting 1-chloromethyl-2'-chloroethyl ether with ethylene oxide in the presence of a catalytic amount of zinc chloride at a temperature from minus 10 to plus 10 ° C with a yield of the target product of 99%. But 1-chloromethyl-2'-chloroethyl ether belongs to the class of highly toxic compounds. In addition, during the synthesis of di- (β-chloroethyl) formal from this ether and ethylene oxide, characterized by the release of a significant amount of heat, the possibility of local overheating of the reaction mass, accompanied by the formation of ethylene oxide polymers, was noted.

Closest to the claimed method for producing di- (β-chloroethyl) formal the method used in the patent (German Patent No. 4214847, application 05.05.92, op. 11.11.93) and consisting in the interaction of paraformaldehyde - a polymer form of formaldehyde (FA) and ethylene chlorohydrin (ECG) taken in a molar ratio of FA: ECG equal to 1: (2.7 ÷ 6), preferably 1: (3 ÷ 4.5), in the presence of concentrated hydrochloric acid. The role of the azeotropically forming agent in this method is carried out by ethylene chlorohydrin taken in synthesis in large excess. Since hydrochloric acid brings water into the reaction system that inhibits the condensation of ethylene chlorohydrin with formaldehyde, the authors achieve a high degree of conversion of the starting reagents to the target product of 98-99% and high yields of di- (β-chloroethyl) formal - 98% (by FA ) and 97% (according to ECG) due to a significant amount of excess ethylene chloride and high synthesis temperatures - 80-125 ° C. Since the withdrawal of reaction water from the system is due to excess ethylene chlorohydrin, this method of producing di- (β-chloroethyl) formal is characterized by large losses of the feedstock (ethylene chlorohydrin), which constitute at least 10% by weight of the target product obtained. In addition, in this process, a special step is required to separate the return ethylene chlorohydrin from the reaction water, which is not mentioned in the patent description.

The task of the invention is to increase the yield of di- (β-chloroethyl) formal, increase the selectivity of the process for the target product and reduce the loss of raw materials.

The authors propose to obtain di- (β-chloroethyl) formal by reacting ethylene chlorohydrin (ECG) with paraformaldehyde (FA) in the presence of an acid catalyst - anhydrous hydrogen chloride (HCl). The synthesis of di- (β-chloroethyl) formal proceeds in two stages. First, paraformaldehyde is dissolved in ethylene chloride hydrochloride pre-acidified with hydrogen chloride at a temperature of 40-60 ° C and the reaction mixture is kept at a temperature of 40-85 ° C for 20-30 minutes. The concentration of hydrogen chloride in the reaction mixture in the range of 0.3-1.0 wt.%. The molar ratio of ECG: FA corresponds to (2.25 ÷ 2.7): 1, mainly 2.6: 1. The total duration of the first stage of the synthesis does not exceed 40 minutes The yield of di- (β-chloroethyl) formal at the end of the first synthesis step is from 80 to 90.2%. The selectivity for the target product is from 95.8 to 99.7% (according to formaldehyde) and from 98.0 to 99.8% (according to ECG).

The proposed conditions already at the first stage of synthesis provide a high conversion of the starting reagents (at least 80%) while at the same time a high selectivity of the process for the target product and a slight formation of side oligomeric formulas.

To achieve the yields of the desired di- (β-chloroethyl) formal in the claimed method, the second synthesis step is carried out with simultaneous distillation of the reaction water in the form of an azeotropic mixture with 1,2-dichloroethane (DCE) added for this purpose in an amount of 2.04 mol per 1 mol the resulting di- (β-chloroethyl) formal. Distillation of the azeotropic mixture DCE-H ₂ O from the reaction mixture is carried out on a distillation column at atmospheric pressure and a temperature of the column cube 84-95 ° C, top - 72-85 ° C. 1,2-Dichloroethane is loaded into the cube of the distillation column either completely at the rate of 201.73 g (2.04 mol) per 1 mol of the obtained di- (β-chloroethyl) formal, or first one third of the required amount of 1,2-dichloroethane is charged, and the remaining 1,2-dichloroethane is metered into the cube of the column continuously during the entire process of distillation of the reaction water. At the end of the second stage of the synthesis, the yield of di- (β-chloroethyl) formal reaches 95.0-99.6%, while the process is highly selective for the target product, 97.0-99.7% (for formaldehyde) and 98.5- 99.8% (according to ECG). The distilled azeotropic mixture of DCE-H ₂ O with impurities of ECG, HCl and formaldehyde is stratified into an organic dichloroethane layer, which is recycled for the subsequent operation to obtain di- (β-chloroethyl) formal, and to the aqueous layer.

The distillation residue obtained after distillation of the reaction water with the content of di- (β-chloroethyl) formaldehyde on average 80% (the rest is mainly excess ECG) is subjected to distillation under vacuum (P _ost = 230 mm Hg). After distillation of the excess ECG, the di- (β-chloroethyl) formaldehyde containing oligomeric formals in an amount of 0.32-1.73 wt% is used for the synthesis of thiocol.

The distilled ECG is recycled to the first step in the synthesis of di- (β-chloroethyl) formal.

Obtaining di- (β-chloroethyl) formal by the proposed method is illustrated by examples 1-12, the conditions for the synthesis and distillation and the results are shown in the table.

Example 1. In a glass reactor equipped with a stirrer, reflux condenser, thermometer and tube for loading the starting components and sampling the reaction mass for analysis, load 185.187 g (2.3 mol) of ethylene chloride (containing 0.037 g of H ₂ O), pre-acidified with gaseous hydrogen chloride. The mass of hydrogen chloride dissolved in the ECG is 1.5 g. The contents of the reactor are heated with a water bath to a temperature of 60 ° C and 30.597 g of paraformaldehyde containing 0.597 g of H ₂ O as an impurity are loaded. The mass fraction of the catalyst (hydrogen chloride) in the total mass of the loaded starting reagents (ECG and formaldehyde) is 0.7%. The reaction mixture was kept at a temperature of 60 ° C and with stirring for 30 minutes

The mass fraction of di- (β-chloroethyl) formal in the reaction mixture after the specified time is 63.7%, which corresponds to the formation of 80% of the target product from the theoretically possible. The process selectivity for the di- (β-chloroethyl) formal is 97.1% (for consumed formaldehyde), 98.6% (for consumed ECG).

The reaction mixture obtained in the first stage of the synthesis is transferred to a distillation column cube with an efficiency of 5 tons, where 201.73 g (161 ml) of DCE are also charged as an azeotropically for distilling reaction water. The azeotropic mixture of DCE-H ₂ O is distilled off at atmospheric pressure and at a column bottom temperature of 84-95 ° C, top - 72-85 ° C. The total mass of the distilled liquid is 230.2 g, with the separation of which receive 210.75 g of the organic (dichloroethane layer) and 19.45 g of the aqueous layer. The duration of the acceleration is 45 minutes.

The composition of the obtained dichloroethane layer, wt.%:

formaldehyde 0.04 1,2-dichloroethane 93.87 ethylene chlorohydrin 5.65 water 0.37 Hcl 0,07

The composition of the aqueous layer, wt.%:

formaldehyde 2.06 1,2-dichloroethane 2.88 ethylene chlorohydrin 5.24 water 84,99 Hcl 4.83

After separation of the reaction water, 188.81 g of di- (β-chloro-ethyl) formaldehyde, a crude material containing in its composition, wt.%, Remained in the cube of the column:

formaldehyde 0.06 1,2-dichloroethane 1.77 ethylene chlorohydrin 9.01 di- (β-chloroethyl) formal 87.05 T ₁ 1.26 T ₂ 0.28 water 0.35 Hcl 0.22

where T ₁ and T ₂ are homologues of di- (β-chloroethyl) formal having the formula:

The yield of di- (β-chloroethyl) formal after distillation of the reaction water is 95% of theoretical. The selectivity of the whole process of obtaining the target product, calculated by the consumed formaldehyde, is 97%, by the consumed ethylene chlorohydrin - 98.6%.

Residual ethylene chloride and other boiling impurities (formaldehyde, DCE, HCl, H ₂ O) are removed from the di- (β-chloroethyl) formaldehyde by distillation on a distillation column under vacuum (residual pressure - 230 mm Hg) at the temperature of the cube column 112-130 ° С, top - 84-90 ° С. The mass of the distilled fraction is 21.46 g. Composition, wt.%:

formaldehyde 0.47 1,2-dichloroethane 15,56 ethylene chlorohydrin 75.44 di- (β-chloroethyl) formal 3.96 water 2.75 Hcl 1.82

The liquid remaining in the cube of the column and representing a commodity di- (β-chloroethyl) formal weight of 167.35 g, has the following composition, wt.%:

formaldehyde 0.01 ethylene chlorohydrin 0.50 di- (β-chloroethyl) formal 97.70 T ₁ 1.42 T ₂ 0.31 water 0.05 Hcl 0.02

Using a simple vacuum distillation method, di- (β-chloroethyl) formal of improved quality can be obtained with a basic substance content of at least 99 wt.%.

Example 2. The synthesis of di- (β-chloroethyl) formal is carried out as in example 1, but with a molar ratio of ECG: FA equal to 2.6: 1, in the presence of 0.5 wt.% Hydrogen chloride at a temperature of 60 ° C. The yield of di- (β-chloroethyl) formal in the first stage of synthesis is 89% of the theoretical. The selectivity of the target product is 99% (for formaldehyde) and 99.5% (for ECG). After the second stage of synthesis with distillation of the reaction water in a mixture with DCE added in the same amount as in Example 1, 211.43 g of di- (β-chloroethyl) formal formaldehyde is obtained, which contains 80.27% of the main substance (the rest - residual ECG and other impurities). The yield of di- (β-chloroethyl) formal at this stage is 98.1%. The total content of formulas - homologs in the di- (β-chloroethyl) formaldehyde - crude is 0.51%. The process selectivity for the target product is 98.9% (for formaldehyde) and 99.5% (for ECG). After separation of the azeotropic mixture distilled off in the second stage of synthesis, 212.11 g of an organic (dichloroethane) layer containing 93% DCE (197.26 g) is obtained and must be returned to the cycle to the stage of distillation of reaction water during another synthesis synthesis of di- (β- chloroethyl) formal. As a result of separation of the residual ECG from the obtained di- (β-chloroethyl) formaldehyde, crude by distillation on a distillation column at a pressure of 230 mmHg, column cube temperature 112-129 ° С, top 84-90 ° С get 170.53 g di- (β-chloroethyl) technical formal, the content of the main substance of which is 98.69%, and the total concentration of formulas - homologues of 0.62%. The fraction of residual ethylene chlorohydrin in an amount of 40.9 g distilled at the distillation column containing 83.86% ECG (34.3 g) is to be returned to the cycle for subsequent synthesis operations of di- (β-chloroethyl) formaldehyde to replace part of the initial ECG

Example 3. The synthesis of di- (β-chloroethyl) formal is carried out as in Example 2, but first, the third part (of the calculated amount) of the azeotropically forming agent - DCE 67.23 g (53.7 ml) is loaded into the cube of the rectification column to distill the reaction water. , the remaining mass of DCE - 134.5 g (107.3 ml) is fed into the cube of the column continuously during the distillation of the azeotropic mixture. The distillation of a mixture of DCE-H ₂ O and residual DCE is carried out for 1 hour at atmospheric pressure at a temperature of the bottom of the column in the range 89-95 ° C, top - 72-85 ° C. The result is 211.38 g of di- (β-chloroethyl) formal - crude, containing 80.21% of the basic substance (169.54 g). The yield of the target product is 98%. The selectivity of the process according to the di- (β-chloroethyl) formula is 98.8% (according to formaldehyde) and 99.4% (according to ECG).

Example 4-10 The synthesis of di- (β-chloroethyl) formal is carried out under the conditions of example 1.

Example 11. The synthesis of di- (β-chloroethyl) formal is carried out under the conditions of example 1. As an azeotropically for distillation of the reaction water using return DCE in the amount of 212.11 g obtained during the synthesis in example 2, with the addition of 4.47 g of fresh DCE. Returnable DCE contains 93% (197.26 g) of the main substance, the rest: ECG - 6.76%, H ₂ O - 0.19%, HCl - 0.05%. Upon completion of the distillation of the reaction water with DCE, carried out analogously to example 1, the yield of di- (β-chloroethyl) formal is 97.8% with a selectivity calculated by the consumed formaldehyde of 98.5%, by ECG - 99.3%. The dichloroethane layer (212.62 g) obtained after separation of the distilled azeotropic mixture, having the following composition, wt.%: DCE - 92.63, ECG - 7.11, H ₂ O - 0.21, HCl - 0.05, may be recycled again.

Example 12. The synthesis of di- (β-chloroethyl) formal is carried out under the conditions of example 1, but at the same time as pure ECG (175.0 g), return ethylene chlorohydrin in an amount of 40.9 g distilled from di- (β-chloroethyl) formal is used - raw in example 2 and containing in its composition 83.86% (34.3 g) ECG, the rest, wt.%: FA - 0.22, DCE - 9.85, di- (β-chloroethyl) formal - 3, 45, H ₂ O 1.74 and HCl 0.88 (0.36 g). The hydrogen chloride present in the return ethylene chlorohydrin replaces a part of the catalyst, therefore, a smaller amount of gaseous hydrogen chloride — 1.0 g — is consumed for preliminary acidification of the initial ethylene chlorohydrin. The total content of the catalyst in the reaction mixture is 0.55 wt.%. As a result of subsequent rectification of 214.22 g of di- (β-chloroethyl) formal formaldehyde, obtained in order to isolate the di (β-chloroethyl) formal formaldehyde, residual ethylene chlorohydrin and other low-boiling impurities are distilled off under vacuum (P _ost = 230 mm Hg) at a temperature regime similar to Example 1. Stripping, which amounted to 42.64 g, containing ECG in an amount of 82.86%, rest, wt.%: formaldehyde - 0.26, DCE - 10.39, di - (β-chloroethyl) formal - 3.68, H ₂ O - 1.88, HCl - 0.94, can be recycled to the following operations for the synthesis of di- (β-chloroethyl) formal.

The composition of the di- (β-chloroethyl) technical formal obtained as a result of rectification is as follows, wt.%:

formaldehyde 0.006 ECG 0.57 di- (β-chloroethyl) formal 98.72 T ₁ 0.43 T ₂ 0.20 H ₂ O 0.06 Hcl 0.01

Claims (6)

1. The method of obtaining di- (β-chloroethyl) formal by reacting ethylene chlorohydrin with formaldehyde in the presence of an acid catalyst, characterized in that the reaction of ethylene chlorohydrin with formaldehyde is carried out in a molar ratio (2.25-2.7): 1, in the presence of dry hydrogen chloride gas as a catalyst, followed by azeotropic distillation of the reaction water in the presence of 1,2-dichloroethane as a separating agent. 2. The method according to claim 1, characterized in that the dry gaseous hydrogen chloride is used in an amount of 0.3-1.0 wt.%. 3. The method according to claim 1, characterized in that 1,2-dichloroethane is fed to completely distill off the reaction water. 4. The method according to claim 1, characterized in that 1,2-dichloroethane is supplied to distill off the reaction water, at least at least one third of the total amount, and the remaining 1,2-dichloroethane is fed continuously during the entire process of distillation of the reaction water. 5. The method according to claim 1, characterized in that after distillation of the reaction water, the residual ethylene chloride is distilled off, which is returned to the synthesis stage. 6. The method according to claim 1, characterized in that 1,2-dichloroethane after azeotropic distillation and subsequent separation from the water layer is returned to the cycle.