RU2560156C1 - Method of ethriol obtaining - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method includes the preparation of a reaction mixture by the introduction of n-butyral and water solution of NaOH into the water solution of formaldehyde in the presence of NaOH, the following extraction of the target product from the reaction mixture by extraction with an organic extragent and purification by vacuum-distillation. The reaction mixture is prepared during 1.5 h at a temperature of 30-46°C and pH of the mixture of 9-10.5, as the extragent applied are ethers of the general formula R-O-R', where R and R' are the same or different aliphatic linear, branched or cyclic monovalent hydrocarbon radicals with the number of carbon atoms from 1 to 6; extraction is carried out under excessive pressure at a temperature of 10-100°C higher than the temperature of the extragent boiling point under atmospheric pressure.

EFFECT: method makes it possible to obtain the target product of high purity with high output by the application of the simple technology.

10 cl, 1 dwg, 2 tbl, 18 ex

Description

The invention relates to basic organic and petrochemical synthesis and relates to a method for producing ethriol by condensation of n-butyral with formaldehyde, isolation of the target product from the reaction mixture and its purification.

The range of applications of ethriol in the chemical industry is extremely wide. Structural features (the presence of a Quaternary carbon atom) give its derivatives a number of unique properties - high thermal stability, moisture resistance, strength, chemical resistance. It serves as a raw material for the production of ester lubricants, alkyd and epoxy resins, enamels, polyesters and polyurethanes, plasticizers, polymers, adhesives for metals and other products.

Ethriol is synthesized by condensation of n-butyral with formaldehyde in the presence of a basic catalyst, which can be alkali and alkaline earth metal hydroxides, anion exchange resins, amines, hydrotalcites and other basic substances. In the first stage of the reaction, after the addition of two formaldehyde molecules to the α-carbon atom of n-butyral, 2,2-dimethylolbutyral (DMB) is formed by the aldol condensation mechanism:

where B is the main catalyst.

Further conversion of 2,2-dimethylolbutyral to ethriol can be carried out in two ways:

1) catalytic hydrogenation of a carbonyl group:

where cat are hydrogenation catalysts: nickel (Ni-Cr / SiO ₂ ; Ni / Al ₂ O ₃ ), copper (Cu-Zn / Al ₂ O ₃ ; Cu-Cr / Cr ₂ O ₃ ) or platinum group metals (Ru- Pd / C; Ru / C; Pt-Pd / C; Pt / C).

2) interaction with formaldehyde through the cross-reaction of Cannizzaro-Tischenko in the presence of an alkali metal hydroxide, for example, sodium hydroxide with the formation of the corresponding formate:

In the case of using anion-exchange resins, amines, and hydrotalcites, the synthesis of ethriol is at least two-stage, consisting of aldol condensation and hydrogenation of the aldol on heterogeneous catalysts of complex composition, and due to differences in process conditions, these stages cannot be carried out in the same reaction apparatus. Hydrogenation on the most popular nickel-containing catalysts is carried out under rather severe conditions at temperatures up to 200-250 ° С and hydrogen pressure up to 25 MPa. All this creates increased requirements for equipment and process safety, leads to significant costs of energy, materials and coolants. In addition, when using amines soluble in the reaction mass as a catalyst, they are also present in the solution at the hydrogenation stage, while catalyzing undesirable side reactions. Severe hydrogenation conditions inevitably cause a gumming of the reaction masses, which in turn complicates the isolation and reduces the yield of the target product.

The most widespread in practice was the second version of the process. In this case, the formation of the aldol and the reduction of the carbonyl group by the Cannizzaro-Tischenko reaction with the production of ethriol proceed at a high speed in one reactor, which greatly simplifies the hardware design of the synthesis stage. However, in this process, along with ethriol, a stoichiometric amount of sodium formate is formed. It is known that even an insignificant content (0.2-0.5 wt.%) Of sodium formate impurity in the crude ethriol leads to a sharp increase in the rate of ethriol decomposition during vacuum distillation purification with the formation of a volatile by-product, 2-ethyl acrolein. Intensive decomposition of ethriol in this case begins at temperatures above 170 ° C. In industrial plants, it is extremely difficult to maintain a high vacuum during distillation, and at an available residual pressure of about 40 Torr, efficient cleaning of ethriol requires heating to a temperature of the order of 210 ° C or more. Studies have been conducted to find substances that increase the stability of ethriol when heated with sodium formate. Two types of additives have been tested - reducing the basic nature of the environment and antioxidant. Decay inhibitors were calcium or barium carbonates, ammonium sulfate and antioxidant additives - hydroquinone, dicresylolpropane and α-naphthol (Vysotsky M.P., Ketslakh M.M., Rudkovsky D.M. On the thermal stability of trimethylolpropane (ethriol), in collection of "Oxosynthesis", L .: Gostoptekhizdat, 1963, p. 170-174). But, it is obvious that the use of additional substances increases the cost of the process and can lead to a decrease in the purity of the resulting commodity ethriol. Therefore, the main task consists in the most complete removal of ethriol-decomposing impurities of sodium formate before vacuum distillation at the maximum degree of extraction of the target product from an aqueous solution of condensation products.

A known method of producing ethriol by condensation of n-butyral with formaldehyde in an aqueous alkaline medium using a three-stage temperature regime: a) 10-25 ° C; b) 25-40 ° C; c) 40-60 ° C with exposure at each stage for 40-50 minutes. The synthesis is carried out at a molar ratio of n-butyral: formaldehyde: NaOH = 1: 3.5: 1.2, the mass ratio of water: n-butyral = 6: 1, and the concentration of added alkali is 40 mass. % (the addition of a solution of sodium hydroxide and n-butyral is carried out simultaneously). Isolation of ethriol is carried out by distillation of water from the reaction mass to dryness, followed by dissolution of the residue in isopropanol, filtration of insoluble inorganic salts and distillation of the crude ethriol in vacuum. SU 1553527 A1, 03/30/1990.

The disadvantage of this method is the relatively high residual content of sodium formate in the crude etriol (2-6 wt.%), Which leads to the decomposition of a significant part of the target product during vacuum rectification (up to 25 wt.%). Various modifications of this method do not bring fundamental improvements.

A known method of separating ethriol from aqueous solutions of the condensation products of n-butyral with formaldehyde in the presence of alkalis by extraction in a countercurrent packed column, in which the extractant is a mixture of ethyl acetate and ethyl alcohol in a ratio from 90:10 to 99: 1, which allows to increase the degree of extraction of etriol. The ratio of the extractant and the aqueous solution is 2: 1, the temperature is 50-65 ° C, the solvent flow into the column is 1.5 l / h. For one operating cycle, 81-84% of crude ethriol with an ash content of 0.2% is extracted from the aqueous solution, which corresponds to a sodium formate content of 0.44 mass. % SU 173738 A1, 08/06/1965.

The disadvantages of this method are the incomplete extraction of ethriol and a high content of formate impurity, in which the degree of decomposition of ethriol during its further purification by vacuum distillation remains high.

A known method for the isolation and purification of ethriol obtained by condensation of n-butyral with formaldehyde in the presence of an alkaline catalyst, according to which the extraction of ethriol from the reaction mass is carried out twice (by volume) of isobutanol at atmospheric pressure and a temperature of 65 ° C, followed by dilution of the extract with a second solvent (xylene) in a ratio of 1: 1 by volume, distillation of the first extractant, cooling the mixture of ethriol and xylene and separation of the layers. After decanting the xylene layer, ethriol is obtained with a basic substance content of about 90 mass. % and the presence of impurities of sodium formate in an amount of up to 0.16 mass. % US 3956406 A, 05/11/1976.

A significant disadvantage of this method is the use of mixtures of various solvents for the isolation of ethriol, which complicates their separation, purification and reuse as extractants. In addition, in the resulting commodity ethriol, in addition to organic impurities, it also contains a certain amount of salt - sodium formate, which can negatively affect the subsequent use of ethriol as a raw material in various processes, contaminating the target products or leading to their partial decomposition.

The closest technical solution to the proposed one is the method according to which ethriol is obtained by condensation of n-butyral and formaldehyde in the presence of NaOH. To a 13 wt.% Aqueous formaldehyde solution, n-butyral is simultaneously added over 70-120 minutes and a 48% aqueous NaOH solution over 70-90 minutes. The molar ratio of n-butyral: formaldehyde: NaOH is 1: (3.0-5.0) :( 1.0-1.5). The synthesis of ethriol is carried out at a temperature of 20-70 ° C for 90-180 minutes The reaction mass is neutralized with formic acid to a pH of 5-7 and concentrated to an ethriol content of 40-50 wt.%. Etriol from the reaction mass is isolated by extraction at atmospheric pressure with C ₆ -C ₁₀ alcohols, mainly 2-ethylhexanol (C ₈ ), at a temperature of 30-80 ° C (mainly 60 ° C) for 30-90 min, followed by washing the extract with water in the ratio of 5-20 hours of water per 100 hours of extract at a temperature of 30-80 ° C for 30-90 minutes to remove the residual amount of sodium formate and purification of ethriol by vacuum distillation. At the stages of extraction and washing with water according to this method, multiband (plate) columns of the Scheibel type are used. The purity of the final product is 99.5 mass. % US 7,253,326 B1, August 7, 2007.

The disadvantages of the method include the use of viscous high-boiling extractants, which significantly complicates the complete removal of the solvent from the extract during purification of ethriol and increases the cost of the process. In addition, the high affinity of ethriol and C ₆ -C ₁₀ aliphatic alcohols, as well as their partial miscibility with water, lead to an increased content of sodium formate impurity in the crude ethriol after extraction. The need to wash the extract with water significantly complicates the technological design of the separation stage, increases energy costs and leads to additional losses of the target product in the aqueous phase.

The technical problem solved by the invention is to create an effective method for producing ethriol, which provides a significant simplification of the technology of the synthesis process, isolation and purification, increasing the yield of the target product of high purity.

The technical result from the implementation of the invention is to simplify the process technology and increase the yield of target ethriol of high purity due to a more complete separation of etriol from an aqueous solution of condensation products and a decrease in the content of ethriol-decomposing impurities of sodium formate in crude ethriol. The simplification of the technology consists in increasing the efficiency of extraction of ethriol synthesis from the reaction mixture and obtaining crude ethriol with a low content of sodium formate without using the stage of washing the extract with water, causing loss of the target product or leading to the need for additional laborious operations for its reextraction from the aqueous phase after washing

The technical result is achieved in that the reaction mixture is prepared for 1.5 hours at a temperature of 30-46 ° C and the pH of the mixture is 9-10.5, then kept for 1-1.5 hours, ethers of the general formula are used as extractant ROR ′, where R and R ′ are the same or different aliphatic linear, branched or cyclic monovalent hydrocarbon radicals with the number of carbon atoms from 1 to 6, and the extraction is carried out under excess pressure that prevents boiling of the extractant, and at a temperature above the boiling point of the extractant in the atmosphere pressure. In particular, the extractants used in the invention include methyl tert-butyl, methyl n-butyl, methyl tert-amyl, methyl n-hexyl, diethyl, di-n-propyl, di-iso-propyl, di-n -butyl and other aliphatic ethers.

The solubility of sodium formate in the selected extractants is very low, which allows you to abandon any additional procedures for removing its residues from extracts of ethriol. However, at temperatures equal to or lower than the boiling point of the extractant at atmospheric pressure, the solubility of ethriol in it is also low. Therefore, the extraction is carried out at a higher temperature, which is ensured by carrying out the process at elevated pressure.

In accordance with the invention, a method for producing ethriol using n-butyral as a feedstock consists of three main steps: 1) condensation of butyral with formaldehyde in the presence of sodium hydroxide; 2) the selection of ethriol from the reaction mass by extraction under elevated pressure; 3) purification of the product by vacuum distillation.

The condensation of n-butyral with formaldehyde is carried out in an aqueous solution in the presence of NaOH. Technological formalin, an aqueous solution containing 35-37 wt.% Formaldehyde and 10-15 wt.% Methanol, is widely used in practice as a source of formaldehyde. The addition of methanol is necessary to stabilize the solution. However, in the synthesis of ethriol, methanol causes adverse reactions, for example, the formation of ethriol monomethylformal (a difficult to separate impurity). So, when using formalin with a methanol content of more than 6-7 mass. The% yield of ethriol is reduced by an average of 10%, therefore, before using formalin, its purification is required. The "demethanolation" of formalin is a technically complex and time-consuming task, and the resulting product cannot be stored and must be immediately used in the synthesis, which also causes certain inconveniences. An alternative source of formaldehyde is paraformaldehyde (paraform), from which a "methanol-free" aqueous solution of almost any concentration can easily be obtained. This facilitates the storage of raw materials, their delivery to the reactor and loading. Unlike formalin, paraform produced in advance and stored in stock can be used to produce ethriol.

In FIG. a schematic diagram of the process for producing ethriol in accordance with the invention. In the implementation of the invention, all operating procedures are as follows. In the reactor with external or internal heating (1) load water, the estimated amount of paraformaldehyde and carry out its depolymerization in the presence of 0.01-1.0 mol. % NaOH as a catalyst at a temperature of 40-80 ° C to obtain a "methanol-free" aqueous formaldehyde solution with a concentration of 13-20 mass. %

To increase the reaction rate of the synthesis of ethriol and increase the yield of the target product, the intensity of mixing the reaction mass is of fundamental importance. Since n-butyral has limited solubility in water, it is necessary to accelerate its diffusion into the aqueous phase. In addition, during the synthesis of ethriol, the viscosity of the reaction mass increases. In this regard, the invention uses high-speed mechanical mixing elements at the stage of a chemical reaction, capable of creating the necessary hydrodynamic regime of a developed turbulent flow in the reactor (1) (criterion Re> 10 ⁴ ), for example, blade, propeller, turbine (open and closed) and etc.

To the obtained aqueous solution of formaldehyde in the reactor (1) in an argon atmosphere at a constant or variable speed using n-feed devices (e.g. pumps), n-butyral and an aqueous solution of NaOH are added. For the implementation of the invention, preferably 3-4 mol of formaldehyde and 1-1.5 mol of NaOH per 1 mol of n-butyral are used. The condensation of n-butyral with formaldehyde is carried out at a molar ratio of n-butyral: formaldehyde: NaOH = 1: (3.0-4.0) :( 1.0-1.5). A typical molar ratio of n-butyral: formaldehyde: NaOH is close to the stoichiometry of the reaction (1: 3: 1). The concentration of added alkali is 20-50 mass. % A low initial concentration of formaldehyde - 13-20% - and its excess with respect to n-butyral contributes to a high yield of ethriol, otherwise the proportion of undesirable by-products increases. When a formaldehyde solution with a concentration below 13% is used for the synthesis of ethriol, the water consumption for the process increases and the reaction rate decreases due to greater dilution.

If the upper limit of the specified pH range is exceeded, the alkali supply is stopped and resumed after reaching the lower limit, and the entire unspent NaOH solution is introduced within 10-30 minutes after the completion of dosing of n-butyral. The progress of the condensation of n-butyral with formaldehyde is monitored by gas-liquid chromatography (GLC).

After condensation, the reaction mixture typically contains a small amount of unreacted NaOH. In addition, sodium formate, which is formed in stoichiometric amounts upon reduction of 2,2-dimethylolbutyral with formaldehyde, also has an alkaline reaction due to hydrolysis. The presence of hydroxide anions during the isolation of ethriol causes a number of undesirable side reactions, leads to the appearance of colored impurities, reduces the yield and affects the quality of the target product. To neutralize the reaction mixture, formic, acetic, sulfuric, hydrochloric, phosphoric and other acids can be used, which are added at the end of the reaction to the reactor (1) until pH 5-7 is reached. When formic acid is used to neutralize the mass, no additional anions are introduced into the reaction mixture, and pure sodium formate can be isolated as a conjugated commercial product without additional complex equipment and special reagents.

Unreacted formaldehyde is distilled off from the neutralized reaction mixture at atmospheric pressure without introducing additional water and the mixture is concentrated to an ethriol content of 30-45 wt. % Along with formaldehyde, impurities of volatile components such as formic acid, 2-ethyl acrolein and methanol are also removed from the mixture. Formaldehyde is distilled off at atmospheric pressure, since water-formaldehyde azeotrope is destroyed by evaporation in vacuum, and insoluble polymer products (linear polyoxymethylene) are formed and, instead of formaldehyde removal, its resistance to distillation increases. To minimize the cost of raw materials, distillate, which is mainly an aqueous solution of formaldehyde, after purification can be returned to the synthesis stage and reused.

The above operations of condensation, neutralization and concentration of the reaction mixture can be carried out sequentially in the same reactor, or separately in several different devices.

Isolation of ethriol from a concentrated aqueous solution of condensation products of n-butyral with formaldehyde (ethriol syrup) is carried out by the extraction method. Extraction of ethriol from incompletely dehydrated syrups is more promising than the use of azeotropic distillation of water. All technological procedures of the separation stage are carried out in the liquid phase without precipitation. Upon extraction, two well-separable liquid phases are formed: the aqueous phase containing sodium formate, and the organic phase in which ethriol is located.

Among the existing organic solvents which are miscibly limited to water, branched aliphatic ketones, as well as esters and ethers, are most suitable for ethriol extraction. At the same time, the use of such reactive compounds as esters and ketones for extraction is undesirable, since side reactions can occur: transesterification and formation of acetals with ethriol. In addition, ketones and esters (for example, ethyl acetate) are more "hydrophilic" solvents and, together with water, they transfer a large amount of sodium formate to the extract. For these reasons, less labile ethers in which the solubility of water is low and, therefore, the sodium formate content in the resulting extract will also be low, are more preferred for the extraction of ethriol.

To carry out the invention, the extraction of ethriol from a concentrated aqueous solution of condensation products is carried out by extraction using ethers of the general formula ROR ′ as an extractant, where R and R ′ are the same or different aliphatic linear, branched or cyclic monovalent hydrocarbon radicals with the number of carbon atoms from 1 to 6, and the extraction process is carried out under excess pressure at a temperature above the boiling point of the extractant at atmospheric pressure. If ethers with a hydrocarbon radical length of more than 6 carbon atoms are used as the extractant for the implementation of the invention, the efficiency of extraction of ethriol is reduced.

The solubility of etriol in ethers, for example, in MTBE and diisopropyl ether, at a temperature of 20 ° C is 2.1 and 0.7 g per 100 g of solvent, respectively, and at a boiling point of 55 and 68.5 ° C it increases several times . But, despite this, the rate of extraction of ethriol at these temperatures is still low. To increase the speed and completeness of the isolation of the target ethriol, the extraction is carried out under excess pressure at temperatures that are 10-100 ° C higher than the boiling point of the extractants at atmospheric pressure. Ethriol extraction is carried out under an excess pressure of 0.1-3 MPa, which prevents the extractant from boiling. For example, the partial pressure of saturated MTBE vapors at a temperature of 55 ° C is 0.1 MPa, therefore, to prevent boiling of the extractant, the process should be carried out at an overpressure not less than this value. The use of pressures above 3 MPa is impractical, since this complicates the hardware design of the process and imposes increased requirements on equipment and the safety of technological operations. To create pressure in the system, any available methods can be applied, for example, installing a check valve at the outlet of the extractor, pumping inert gas under pressure into the extraction system, etc.

As an extractor (2) in the practice of the invention, an apparatus with external or internal heating, with or without a mixing device, is used. Perhaps the use for the extraction of ethriol dish-shaped, packed, hollow (asexual) and other devices. The process of extraction of ethriol can be carried out both in batch and continuous mode. In the first case, the extractant is fed into the apparatus through a fixed layer of a concentrated aqueous solution of the condensation products of n-butyral with formaldehyde. In this case, the extractant (ether R-O-R ′) is a dispersed phase, the aqueous solution of condensation products is a continuous phase (dispersion medium). Due to the difference in density between the extractant and the aqueous solution in the extractor, the phases are separated: the upper (light) layer is a solution of ethriol in the extractant, which is removed from the extractor at a constant or variable speed, and the lower (heavy) layer is an aqueous solution of sodium formate.

In the second case, both liquid phases — a concentrated aqueous solution of the condensation products of n-butyral with formaldehyde and an extractant — are fed continuously into the apparatus in countercurrent flow and the extract and aqueous solution of sodium formate are removed separately.

The ethriol extract at the outlet of the extractor is cooled to or below the boiling point of the extractant at atmospheric pressure, then the pressure is reduced to atmospheric. The stream of ethriol extract from the extractor (2) is directed to an evaporator (3) connected to a condenser (4), after which the extractant is partially or completely separated by distillation and returned to the extraction stage. The evaporator (3) can be equipped with a mixing device to ensure uniform boiling during distillation of the extractant, or be used without it. To carry out the extraction in accordance with the invention, for each operating cycle, a fresh extractant can be used or distilled after the previous extraction operation and accumulated in the collection (5). Pure extractant from the collector (5) is continuously supplied to the extractor (2) by means of a pump (6).

The completeness of extraction of ethriol from an aqueous solution of condensation products during the implementation of the invention is 100% of its initial content in the solution, there is no loss of the target product in the aqueous phase. Ethriol extraction with ethers of the general formula ROR ′, where R and R ′ are hydrocarbon radicals with the number of carbon atoms from 1 to 6, under the conditions specified in the invention, allows to obtain crude ethriol with a low content of sodium formate impurity - 0.06-0 11 mass. % This greatly simplifies the technology of the process of obtaining ethriol, since the need to additionally wash the extract with water to remove salt impurities is eliminated.

Ethriol extract without further purification from sodium formate and after distillation of the solvent is subjected to vacuum distillation, and the aqueous phase from the extractor can be directed to the allocation of commodity sodium formate. Vacuum distillation of the crude ethriol during the implementation of the method is carried out in two stages. First, without performing fractionation and with a minimum residence time in a vacuum distillation apparatus (7), all volatile products, including ethriol, are driven away from inorganic impurities. Then, by vacuum distillation in the following apparatus (8), the target fraction of pure commodity ethriol is separated from both low-boiling and heavy by-products. In this case, low-boiling impurities include extractant residues, water, 2-ethyl acrolein, traces of the cyclic formal of ethriol. The main components of the bottom residue after distillation of ethriol are ditrimethylolpropane (ethriol dimer) and the linear formaldehyde of ethriol (in a smaller amount). To carry out the vacuum distillation of ethriol, devices of various devices can be used, and the process conditions depend on the type of equipment used. It is most preferable to carry out vacuum distillation at a residual pressure in the apparatus of 10-50 torr and a temperature of 170-250 ° C, the process is carried out both in continuous and in batch mode.

This approach when implementing the method can significantly reduce the amount of bottoms and achieve a total yield of high-purity ethriol of 84-87% per loaded n-butyral. By reducing the contact time with inorganic impurities, the formation of by-products of the process of obtaining ethriol (in particular, 2-ethyl acrolein) is minimized. The purity of the ethriol obtained by the implementation of the invention is 99.5-99.7 mass. %

The implementation of the present invention is illustrated by the following examples, which do not limit the scope of the claims presented in the claims.

Example 1

62.51 g (2.09 mol) of paraformaldehyde, 0.09 g (2.25 mmol; 0.11 mol.% Based on paraformaldehyde) NaOH and 414 are charged into a thermostatically controlled jacketed reactor equipped with a reflux condenser and a mechanical stirrer. ml of distilled water. The mixture is stirred at a temperature of 60 ° C for 1 h. The resulting aqueous solution with a formaldehyde concentration of 13 wt. % cooled to a temperature of 45 ° C. Then, with vigorous stirring, 46.86 g (0.65 mol) of n-butyral and 71.46 g of 40 mass are fed into the reactor using metering pumps. % aqueous NaOH solution (0.72 mol), molar ratio of n-butyral: formaldehyde: NaOH = 1: 3.2: 1.1. Dosing of reagents is carried out for 1.5 hours so that the temperature of the reaction mass does not rise above a temperature of 45 ° C, and the pH value is in the range of 9-10.5. If the upper limit of the specified pH range is exceeded, the alkali supply is stopped and resumed after reaching the lower limit, and the unspent NaOH solution is introduced within 10 minutes after the completion of dosing of n-butyral. After adding the entire amount of n-butyral and the alkali solution, the mass in the reactor is heated to a temperature of 50 ° C and stirred for 1 h. After the exposure is complete, the reaction mass is cooled to room temperature and acidified with formic acid to pH 5.5 with stirring. The conversion of n-butyral is 100%, the yield of ethriol is 94.3 mass. % calculated on the loaded n-butyral (according to GLC, the internal standard is isopropanol).

A typical reaction mixture after neutralization contains 77 mass. % water, 0.1 mass. % free formic acid, 0.6 mass. % formaldehyde, 0.1 mass. % 2-ethyl acrolein and traces of methanol. The rest is non-volatile compounds, including: about 13.8 mass. % ethriol, 7.8 wt. % sodium formate and about 0.5 wt. % heavy by-products.

Examples 2-7

The synthesis of ethriol is carried out analogously to example 1 by varying the molar ratio and concentration of the reactants, the temperature of the reaction mixture and the duration of exposure. Moreover, in cases where an aqueous solution of formaldehyde with a higher concentration is used for condensation (Examples 4-7), a more dilute NaOH solution is used to maintain the final mass ratio of n-butyral: water in the reaction mass approximately constant.

Table 1 shows the implementation conditions of examples 1-7, the conversion of n-butyral and the yield of ethriol.

a) The concentration of an aqueous solution of formaldehyde before adding n-butyral and NaOH.

b) The concentration of an aqueous solution of NaOH.

c) The temperature of the reaction mass with the addition of reagents.

g) The temperature of the reaction mass during exposure.

d) According to GLC, the internal standard is isopropanol.

Example 8

From the reaction mass obtained under the conditions of Example 1, 410 g of distillate are distilled off at atmospheric pressure. The resulting concentrated aqueous solution with a volume of 180 ml (density 1.15 g / ml) with an etriol content of 41 wt. % load using a pump into the extractor, which is a steel vertical column (overall dimensions 17 × 1000 mm, volume 230 ml) with a thermostatic jacket. External heating of the extractor is realized using a circulation thermostat. As the extractant used methyl tert-butyl ether (MTBE). The temperature inside the apparatus during extraction is 90 ° C, and the pressure is 2.7 MPa. The pressure is set using a check valve on the outlet pipe of the extract. The extractant from the receiving container using a high-pressure metering pump is continuously supplied to the lower part of the apparatus through a distribution device in the form of a perforated disk with 11 holes with a diameter of 0.5 mm, passing through a fixed layer of an aqueous solution of condensation products.

The stream of ethriol extract after reducing the pressure to atmospheric is directed to an evaporator connected to a condenser. The evaporator is heated using an oil bath with a temperature of 110 ° C and with stirring, the extractant is distilled off, which is collected in a receiver tank and returned to the extractor. The intensity of the distillation of the extractant from the evaporator and its supply to the extractor is kept constant. Etriol extraction progress is monitored by GLC. The criterion for the end of the process is the absence of a peak of ethriol in the sample of the extract from the outlet pipe, after which the supply of the extractant to the extraction column is stopped, the contents of the extractor are cooled to room temperature. The aqueous layer is directed to the allocation of sodium formate. MTBE is completely distilled off from the evaporator at atmospheric pressure. The content of sodium formate in the obtained crude ethriol 0.09 mass. % (according to atomic absorption spectrometry). The completeness of extraction of ethriol from an aqueous solution of condensation products is 100 mass. %

The product without further purification from sodium formate is sent to vacuum distillation, which is carried out in two stages. First, without performing fractionation at a temperature of a heating bath of 210-250 ° C and a residual pressure of 19 torr (vacuum of a water-jet pump), all volatile products, including ethriol, are driven away from inorganic impurities. Then, the desired fraction of ethriol is isolated by repeated vacuum distillation at a temperature of 210-220 ° C and a residual pressure of 19 torr. The total yield of pure etriol 86.8 mass. % calculated on loaded n-butyral, T _pl = 57-58 ° C, the content of the main substance 99.7 mass. %

Examples 9-18

The conditions for the synthesis of ethriol and the neutralization of the reaction mass are similar to example 1. The mass is concentrated to obtain an aqueous solution of condensation products with an etriol content of 41 mass. % The hardware design of the stages of extraction at elevated pressure and vacuum distillation of the crude ethriol are similar to Example 8, the type of extractant and the temperature of extraction are subjected to variation. In all examples, the degree of extraction of ethriol is 100 mass. %, there is no loss of the target product in the aqueous phase. The purity obtained after vacuum distillation of commodity ethriol is 99.6-99.7 mass. % Table 2 shows the conditions and results of extraction for examples 8-18.

a) The boiling point of the pure extractant at atmospheric pressure.

b) The temperature inside the extractor.

c) Overpressure inside the extractor.

d) The total (total) yield of pure commodity ethriol calculated on loaded n-butyral.

Explanations for the figure:

1 - reactor; 2 - extractor; 3 - evaporator; 4 - capacitor; 5 - collection of extractant; 6 - pump; 7, 8 - vacuum distillation apparatuses;

I is paraformaldehyde;

II - water;

III - an aqueous solution of sodium hydroxide;

IV - n-butyral;

V is water with the remainder of unreacted formaldehyde;

VI - concentrated aqueous solution of condensation products (ethriol syrup);

VII - etriol extract;

VIII - an aqueous solution of sodium formate;

IX — vapors of pure extractant;

X is the extractant distillate;

XI - fresh or regenerated extractant;

XII - raw ethriol;

XIII - the main fraction containing ethriol;

XIV - inorganic impurities;

XV - low-boiling impurities (pre-etriol fraction);

XVI - pure commodity ethriol;

XVII - VAT residue of heavy by-products.

Claims (10)

1. A method of producing ethriol, comprising preparing the reaction mixture by introducing n-butyral and an aqueous solution of NaOH into an aqueous solution of formaldehyde, condensing n-butyral with formaldehyde in the presence of NaOH, then isolating the target product from the reaction mixture by extraction with an organic extractant and purifying by vacuum distillation, characterized in that the reaction mixture is prepared for 1.5 hours at a temperature of 30-46 ° C and a pH of 9-10.5, ethers of the general formula ROR ′ are used as extractant, where R and R ′ are the same or different sistent aliphatic linear, branched or cyclic, monovalent hydrocarbon radicals of carbon number 1 to 6 and extraction is carried out under excess pressure at a temperature 10-100 ° C above the boiling point at atmospheric pressure of the extractant. 2. The method according to p. 1, characterized in that the aqueous formaldehyde solution is obtained by depolymerization of paraformaldehyde in the presence of 0.01-1.0 mol. % NaOH as a catalyst at a temperature of 40-80 ° C. 3. The method according to p. 1, characterized in that the condensation of n-butyral with formaldehyde is carried out at a molar ratio of n-butyral: formaldehyde: NaOH = 1: (3.0-4.0) :( 1.0-1.5 ), the initial concentration of formaldehyde solution is 13-20 mass. %, alkali solution concentration of 20-50 mass. % at a reaction mass temperature of 46-55 ° C with exposure for 1-1.5 hours 4. The method according to p. 1, characterized in that before carrying out the extraction from the reaction mixture at atmospheric pressure without introducing an additional amount of water, unreacted formaldehyde is distilled off and the mixture is concentrated to an ethriol content of 30-45 wt. % 5. The method according to p. 1, characterized in that the extractant is selected from the range: methyl tert-butyl, methyl n-butyl, methyl tert-amyl, methyl n-hexyl, diethyl, di-n-propyl, di -isopropyl, di-n-butyl and other aliphatic ethers. 6. The method according to p. 1, characterized in that the extraction is carried out under excess pressure in the extractor 0.1-3 MPa, which prevents boiling of the extractant. 7. The method according to p. 1, characterized in that the extractant is fed through a fixed bed of concentrated aqueous solution of condensation products of n-butyral with formaldehyde. 8. The method according to p. 1, characterized in that the concentrated aqueous solution of the condensation products of n-butyral with formaldehyde and the extractant is fed continuously countercurrently. 9. The method according to p. 1, characterized in that the ethriol extract is cooled to or below the boiling point of the extractant at atmospheric pressure, then the pressure is reduced to atmospheric pressure, after which the extractant is partially or completely separated by distillation and returned to the extraction stage. 10. The method according to p. 1, characterized in that the ethriol extract without further purification from sodium formate and after distillation of the solvent is subjected to vacuum distillation.

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