RU2510629C1 - Method of obtaining pentaerythrite trichlorohydrin - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: pentaerythrite is subjected to interaction with chloranhydrides of organic acids C₂-C₅ of normal and iso-structure. Reaction is realised at temperature 150-200°C, preferably 170-190°C, in closed reactor with obtaining monoether of pentaerythrite trichlorohydrin with the following removal of carboxyl group by alkaline or acid hydrolysis or transesterification with alcohols C₁÷C₃ in presence of catalysts - acids of Lewis and(or) Brensted. Obtained pentaerythrite trichlorohydrin is clarified by vacuum distillation.

EFFECT: method makes it possible to simplify the process and simultaneously increase its selectivity.

1 tbl, 12 ex

Description

The invention relates to methods for the synthesis of pentaerythritol chlorides, in particular to a method for producing pentaerythritol trichlorohydrin, which is used as an intermediate in organic synthesis processes. Trichlorohydrin pentaerythritol is widely used to produce chlorinated polyesters with valuable mechanical, dielectric and chemical properties, namely, reduced flammability and the ability to independently attenuate, in addition, they are characterized by high heat resistance.

A known method of producing pentaerythritol trichlorohydrin by reacting pentaerythritol with thionyl chloride in a pyridine medium with a molar ratio of pentaerythritol: thionyl chloride: pyridine 1: 4: 4, depending on the target product. The method is as follows.

In a reactor equipped with a stirrer, reflux condenser and a metering device, a predetermined amount of pentaerythritol and pyridine is stirred at a temperature of the reaction mixture 0-5 ° C. At a certain rate, 2/3 of the calculated amount of thionyl chloride is introduced into the reactor through a metering device. The remaining 1/3 part is introduced into the reactor at a rate that excludes crystallization of the contents of the reactor. After that, the reaction mass is heated until gas evolution ceases. After cooling, an equal volume of water is added to the reactor. The aqueous layer is decanted and extracted first 3 times with benzene and then 3 times with ether. The ether-benzene extract was combined with a water-insoluble layer, dried, ether and benzene were distilled off, and fractionated under reduced pressure. The yield of pentaerythritol chlorohydrins is 70% of theoretical [A. Moradien, J.B. Cloke, Am. Chem. Soc., 67, 942 (1945)].

The disadvantage of this method is the complexity of the synthesis, due to the need to conduct it at a low temperature, followed by the use of water to isolate the products of synthesis and organic volatile solvents to extract the target products, which requires additional technological operations associated with the regeneration of pyridine and solvents.

A known method of producing trichlorohydrin pentaerythritol, in which pentaerythritol, organic acid and a fraction of gasoline are charged into the reactor with so on. 60-185 ° C, necessary to remove water formed during the reaction. The mixture is heated to 120-130 ° C and then hydrogen chloride is passed through a Schott filter. At the same time, within 1-2 hours the temperature is raised to 200-220 ° C. The transmission rate of hydrogen chloride is 110 l / h per 1 kg of pentaerythritol, the consumption of hydrogen chloride is 200% of theoretical. As the esterification and hydrochlorination reactions proceed, the resulting water is removed from the reaction zone with gasoline, which is collected in a water separator.

Water containing approximately 30% hydrogen chloride is drained, and gasoline is sent back to the reactor. To remove dissolved hydrogen chloride, the resulting product is washed with water.

The molar ratio of pentaerythritol to organic acid is 1: 1 or 1: 0.75. Under these conditions, the yield of trichlorohydrin and pentaerythritol etherchlorohydrin is about 75% of the theoretical based on the initial amount of pentaerythritol. [D.M. Rudkovsky, E.K. Remiz, S.V. Katsman, Housing and communal services, No. 1, 1961, p.16].

The disadvantage of this method is the use of excess hydrogen chloride, part of which is irretrievably lost; high process temperatures; the formation of water and the need to withdraw it from the reaction zone, which requires the use of a solvent.

Closest to the claimed invention is a method for producing pentaerythritol chlorohydrins, where hydrogen chloride is passed into a mixture of acetic acid and water at 0 ° C until a calculated amount of HCl is adsorbed. The resulting mixture was loaded into an autoclave together with pentaerythritol. The autoclave is closed and heated to 160 ° C for 8 hours. Then the autoclave was cooled to room temperature and the reaction mixture was poured into water. The resulting pentaerythritol trichlorohydrin acetate was isolated by extraction with methylene chloride. The solvent was removed and the remaining oil was boiled overnight with 500 ml of methanol and 50 ml of concentrated hydrochloric acid. A mixture of methyl acetate and methanol is slowly distilled off. Pentaerythritol trichlorohydrin is fractionated or isolated from ethyl acetate by recrystallization. The product yield is 90% of theoretical [W. Serenson, T. Campbell. "Preparative methods of polymer chemistry", 1963, p.306].

The disadvantage of this method is the need for preliminary saturation of acetic acid with hydrogen chloride, high corrosiveness of the reaction medium, the need to isolate the synthesis products with wash water and extraction.

The objective of the invention is to simplify the process while increasing its selectivity.

The technical result from the use of the invention lies in the advantages of the proposed method, namely that in the synthesis process and in the isolation of products, water does not participate and does not form, and the need to use solvents for extraction is also eliminated.

The above technical result is achieved by the method of obtaining pentaerythritol trichlorohydrin from pentaerythritol, the peculiarity of which is that it is obtained by the interaction of pentaerythritol with organic acid chlorides C ₂ -C ₅ normal and iso-structure in an amount sufficient to replace OH groups in pentaerythritol, while the reaction is carried out at a temperature of 150-200 ° C, preferably 170-190 ° C, in a closed reactor to obtain pentaerythritol trichlorohydrin monoester followed by removal of the carboxyl group by local or acid hydrolysis or transesterification with C ₁ ÷ C ₃ alcohols in the presence of catalysts - Lewis and / or Bronsted acids, and by vacuum distillation of pentaerythritol trichohydrin.

The method is illustrated by the following examples.

Example 1. 120 g of pentaerythritol and 276 g of acetyl chloride are charged into a metal reactor. The reactor was closed and heated at 180 ° C for 12 hours. Then, the reactor was opened, unloaded and the acetic acid formed was distilled off. Thus, get pentaerythritol trichlorohydrin acetate, with a basic substance content of 98.5% of the mass. Next, the obtained product is subjected to transesterification according to one of the methods for removing the carboxyl group, for this purpose, pentaerythritol trichlorohydrin acetate, 150 g of ethanol and 3 g of p-toluenesulfonic acid are charged into a flask equipped with a distillation column 1000 mm high and 25 mm in diameter. The mixture is boiled with simultaneous distillation of ethyl acetate, the end of the reaction is judged by increasing the temperature of the distillate to 77-78 ° C. The crude trichlorohydrin obtained is clarified by vacuum distillation and the desired product is obtained with a content of 98-99%.

Examples 2-12 are carried out analogously to example 1. The obtained results of the method according to the examples are shown in table 1.

The interaction of pentaerythritol with acid chlorides of C ₂ -C ₅ acids of normal and structure, namely propionic, butyric, isobutyric, isomers of valerianic acid (n-pentanoic, 3-methylbutanoic, 2-methylbutanoic, 2,2-dimethylpropanoic), including chlorohydride acids according to examples 1-12, occurs by chemical reaction in accordance with the following formula

where R = C _n H _{2n + 1} - normal and iso-structure, n = 1 ÷ 4.

The conditions and sequence of carrying out technological methods when implementing the method for the interaction of pentaerythritol with carboxylic acid chlorides of C ₂ -C _{5 of} normal and iso-structure are within the scope of the claimed technical solution, and, therefore, this category of acid chlorides is fully included in the scope of claims in accordance with the formula inventions.

Table 1 Preparation of pentaerythritol trichlorohydrin from pentaerythritol Carboxylic acid chloride T reaction, ° C Reaction time, hour The concentration of ester of trichlorohydrin pentaerythritol,% wt. Concentration. pentaerythritol trichlorohydrin,% wt. The yield of trichlorohydrin pentaerythritol,% wt. one Acetyl chloride 180 fourteen 98.61 99.32 94.27 2 Propionyl chloride 180 fourteen 96.39 98.68 92.58 3 Butyryl chloride 180 fourteen 95.86 98.47 93.12 four Isobutyryl chloride 180 fourteen 96.54 97.98 92.61 5 Valeroyl chloride 180 fourteen 97.11 98.21 91.89 6 Isovaleryl chloride 180 fifteen 95,99 98.86 92.33 7 Acetyl chloride 150 eighteen 94.60 95.32 91.23 8 Propionyl chloride 190 12 95.40 97.58 90.58 9 Butyryl chloride 170 16 95.86 96.77 91.0 10 Isobutyryl chloride 160 17 94.64 95,99 89.61 eleven Valeroyl chloride 190 eleven 96.30 96.21 90.89 12 Isovaleryl chloride 200 9 96,99 96.81 90.13

Claims (1)

A method for producing pentaerythritol trichlorohydrin from pentaerythritol, characterized in that pentaerythritol is reacted with normal and iso-structure organic acids C ₂ -C ₅ , the reaction being carried out at a temperature of 150-200 ° C, preferably 170-190 ° C, in a closed reactor to produce pentaerythritol trichlorohydrin monoester followed by removal of the carboxyl group by alkaline or acid hydrolysis or transesterification with С ₁ ÷ С ₃ alcohols in the presence of catalysts - Lewis and (or) Bronsted acids - and clarified using the obtained trichlorohydrin pentaerythritol by vacuum distillation.