RU2616004C1 - Method for processing of high-boiling by-products of trimethylpropane production process - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method for processing of high-boiling by-products of trimethylolpropane production process by condensation of n-butyraldehide with formaldehyde. Di-TMP with a purity of 98 wt % or higher is recovered by successive crystallisation of bottom products of raw TMP vacuum distillation, first using ethyl acetate at a mass ratio of 1:1-1.5, then using acetone at a mass ratio of 1:2-5. Formal-rich and oily di-TMP combined residue, unsuitable for the recovery of 98 wt % or higher di-TMP, is converted into TMP and di-TMP esters by esterification process, using C1-C18 carboxylic acid or a mixture of acids in the presence of 0.05-20.0 wt % of acid catalyst at a temperature of 70-250°C. The resulting esters are separated from the traces of carboxylic acid and acid catalyst. The produced in the process water, formaldehyde and methanol are removed from the reaction mix as their azeotropes with hydrocarbons or as a vapour phase.

EFFECT: improved efficiency and completeness of processing of high-boiling by-products, remaining in the bottoms of raw TMP vacuum distillation; as a result, produced a number of sought after industrial substances, reducing thereby the total amount of process waste.

3 cl, 2 tbl, 15 ex

Description

The invention relates to basic organic and petrochemical synthesis and relates to a method for processing by-products, namely high-boiling by-products of the process of producing ethriol, condensation of n-butyral with formaldehyde.

Etriol is a large-capacity product of organic synthesis and is used as a raw material for the production of ester lubricants, alkyd resins, enamels, polyesters and polyurethanes, plasticizers, adhesives for metals and other products. Ethriol is synthesized by condensation of n-butyral with formaldehyde in the presence of a basic catalyst. The use of sodium hydroxide as a catalyst provides a good yield of the target product (85-90%) and satisfactory processability.

However, during the condensation of n-butyral with formaldehyde in the presence of sodium hydroxide, along with the target ethriol, up to 10-15% (based on the initial n-butyral) of high-boiling by-products are formed, which form the basis of the bottom residue of vacuum distillation of the crude ethriol. Their appearance is due to the interaction in various combinations of the target ethriol with formaldehyde, intermediate substances, low-boiling by-products and traces of methanol present in the reaction medium. The high boiling bottoms of the crude ethriol vacuum distillation consists of approximately 15 different substances, mainly polyols and their formulas, which have similar boiling points and solubility. Due to the high mutual affinity of ethriol and high boiling point by-products, its complete isolation from the bottom residue is an extremely difficult task. Therefore, in the composition of the bottom residue of the vacuum distillation of the crude ethriol, ethriol itself is also present in an amount of up to 25-35 wt.%. In addition, bottoms by-products contain a fragment of chemically bound ethriol in their structure and are potentially valuable substances. In particular, they include commercially demanded di-trimethylolpropane (di-TMP, structure 1), the content of which in the high-boiling fraction can reach 50 wt.%.

Di-TMP is formed by the interaction of ethriol and formaldehyde with side 2-ethyl acrolein in the presence of a basic catalyst. Individual purified di-TMP is used as a raw material in the production of chemical products for various purposes: acrylic monomers and oligomers, varnishes and paints, components of PVC stabilizers, polyesters, polyurethane foams, alkyd resins, and also as a component for the production of high-index synthetic ester oils and greases with a wide temperature range of operation. Esters of di-TMP and carboxylic acids (by analogy with etriol esters) are characterized by a low pour point, have high chemical resistance, thermal stability and good viscosity-temperature properties, as well as sufficient compatibility with various plastic materials.

Along with di-TMP, the high-boiling by-products of the ethriol preparation process are also represented by the linear formaldehyde formaldehyde (structure 2), the methylpolyformal formaldehyde (structure 3), the cyclic formaldehyde di-TMP (structure 4) and other formulas of a similar nature resulting from the interaction of ethriol and di- TMP with formaldehyde and methanol present in the reaction mixture at the synthesis stage.

The total fraction of formals in the bottom residue of vacuum distillation of the crude ethriol is 20-30 wt.%. These compounds contain bound ethriol and di-TMP, but do not find commercial use and greatly complicate the isolation of the substances in demand. For this reason, the bottom residue of vacuum distillation of crude ethriol in its unprocessed form is not marketed, which negatively affects the economy and the manufacturability of the synthesis of ethriol as a whole. Therefore, the search for ways of rational use and non-waste processing of high-boiling by-products of the process of obtaining ethriol is an urgent task with great practical significance.

A known method of decomposition of linear and cyclic formulas of polyols in an aqueous solution containing also formates of alkali or alkaline earth metals. The method consists in hydrogenating a mixture of high boiling point by-products in the presence of a heterogeneous catalyst at pH <7 to obtain the desired polyhydric alcohol. The hydrogenation catalyst is Ru / C (5 wt.% Ruthenium). Hydrogenolysis of formals can be carried out at a hydrogen pressure of 1-3 MPa in the presence of substances with acidic functional groups. To eliminate the effect of catalyst poisoning by impurities of sodium formate (usually always present in the bottom residue after separation of the polyol), a temperature of 200 to 280 ° C is required. The conversion of the formulas is 90-98% with the selectivity for the corresponding polyol 89-98% (US 6265623 B1, 07.24.2001).

The disadvantages of this method are the high process temperature, the use of hydrogen under high pressure up to 3 MPa, as well as the use of an expensive heterogeneous catalyst, the activity of which is irreversibly reduced in the presence of sodium formate. In addition, as a result of hydrogenolysis, a mixture is obtained containing both the polyol itself and its dimer. The isolation of individual substances from such a mixture is still difficult.

A known method of increasing the yield of ethriol by decomposition of by-products containing formali. According to this method, low-boiling impurities are distilled off from the crude ethriol, then the remaining product is separated into a fraction containing the main amount of ethriol and a fraction of high-boiling products. The high boiling fraction is treated with an aqueous solution of formic acid. 3 parts of water and 1 wt.% Acid are added to 1 part of bottoms, while the water content in the reaction mixture should be 20-90 wt.%. The mixture is stirred at atmospheric pressure in a stream of nitrogen for 6 hours at a temperature of 100 ° C. When implementing the method, the content of ethriol in a mixture of high-boiling by-products can be increased from 10 to 35 wt.%. In addition, up to 10 wt.% 2,2-dimethylolbutyral is formed, which must be hydrogenated to produce ethriol (US 7301058 B2, 11.27.2007).

The disadvantages of the method include the need for an additional stage of hydrogenation of the carbonyl group of 2,2-dimethylolbutyral, which complicates the process. The issue of further efficient isolation of ethriol from an aqueous solution of a mixture of high-boiling by-products and the use of the residue has not been resolved.

A known method of decomposition of ethriol formulas by treating the bottom residue of vacuum distillation with acid in the presence of an oxidizing agent in order to increase the yield of ethriol. The formaldehyde released during this oxidizes to formic acid. An intermediate product, ethriol formate, is hydrolyzed in the presence of alkali, which also binds formic acid. The resulting ethriol is subsequently separated from potassium formate using multi-stage extraction with ethyl acetate. Formic acid or cation exchange resins may be used as the acid. Acid is added to the aqueous solution of high boiling formals in such an amount that the pH of the mixture is 1.5-3. As the oxidizing agent, it is preferable to use hydrogen peroxide. The process is carried out at a temperature of 70-90 ° C for 4 hours (US 8759593 B2, 06.24.2014).

The disadvantages of this method are the formation along with ethriol of secondary 2,2-dimethylolbutyral (up to 9 wt.%) And etriol formate (up to 14 wt.%), An increase in the content of unidentified impurities, while the concentration of commercially valuable di-TMP is reduced by 2-6 % The ethriol content in the final mixture is 50-60% and its separation from a large number of other by-products is difficult.

A known method of processing high-boiling by-products regarding the production of di-TMP and an additional amount of ethriol from the bottom residue of vacuum distillation containing ethriol (5-30 wt.%), Di-TMP (10-30 wt.%), Linear formaldehyde (25 -60 wt.%) And sodium formate (less than 1 wt.%). The mixture is dissolved in water at a temperature of 60-80 ° C to obtain a 60-80% solution. Then, under a hydrogen pressure of 1-30 MPa and a temperature of 160-280 ° C at pH = 1-3, the mixture is hydrogenated in the presence of a heterogeneous Ru / C catalyst (5 wt.% Ruthenium). To maintain pH, protic inorganic or organic acids C1-C4 are used, as well as solids of an acidic nature. As a result of hydrogenation, the ethriol content in the residue increases from 19 to 75 wt.%, While the linear formaldehyde completely decomposes. After this, the catalyst and acid are removed, the residue is successively passed through layers of anion exchange resin and cation exchange resin and double vacuum rectification is carried out in a batch mode. The best purity of di-TMP obtained after vacuum distillation was 97.4 wt.% By GLC (US 2013/0131391 A1, 05.23.2013).

The disadvantages of the method include the multi-stage and complexity of the process, the high cost of the ruthenium catalyst, the process at elevated temperature and pressure of hydrogen, as well as the relatively low purity of the resulting product.

A known method for the separation of di-TMP, according to which the bottom residue after separation of ethriol is re-distilled with superheated steam at a temperature of 160-220 ° C and a residual pressure of 4.0-13.3 kPa. In this case, the target di-TMP is distilled off together with the distillate. After distillation of water from the distillate, technical di-TMP is obtained with a melting point of 98-105 ° C. Purified di-TMP is obtained by recrystallization of a technical product from water or a suitable organic solvent. On average, 15 g of a technical product containing di-TMP is isolated from 39 g of the bottom residue by steam distillation, which is recrystallized three times from acetone to obtain 10 g of pure di-TMP with a melting point of 108-109 ° C (US 3740322 A, 19.06. 1973).

The disadvantages of the method include the fact that di-TMP is distilled off with steam simultaneously with other undesirable by-products contained in the bottom residue and close to di-TMP in chemical structure and boiling point (in particular, the linear formaldehyde). This degrades the quality of the target di-TMP. Vacuum stripping with steam requires specific equipment and is associated with significant energy consumption. In addition, additional purification, such as recrystallization, is still required to obtain high purity di-TMP.

Theoretically, di-TMP can be isolated from the bottom residue of distillation of the crude ethriol by repeated distillation. However, the target product has a very high boiling point, therefore, during rectification, intense thermal decomposition of di-TMP will occur even in the presence of an insignificant amount of sodium formate. Di-TMP can also be isolated by treating the bottom residue with acetic anhydride, followed by vacuum-distillation of the acylated product and its decomposition in the presence of alkali.

However, such a multi-stage method, requiring a significant amount of additional reagents, is not economically suitable for industrial implementation.

The closest technical solution to the proposed method is the decomposition of the linear formal etriol with obtaining an additional amount of ethriol. According to this method, an acid catalyst (inorganic acid, organic sulfonic acid, cation exchange resin) and a solvent are preferably added to the residue of vacuum distillation of ethriol containing up to 40 wt.% Linear formaldehyde, up to 5 wt.% Water and methanol cyclohexane. The mixture is stirred at an elevated temperature, preferably 90-220 ° C, for 0.5-8 hours, which leads to the conversion of the linear formal to the target ethriol, increasing its total content in the mixture from 10 to 32 wt.%. During the process, a cyclic formaldehyde of ethriol is also formed, the concentration of which in the reaction mixture reaches 46 wt.% (US 6096905 A, 08/01/2000).

The disadvantage of this method is the occurrence of parallel adverse reactions of the formation of the cyclic formal of ethriol and other undesirable impurities, the total mass of which in the resulting mixture exceeds the mass of the formed ethriol. At the same time, the content of etriol itself increases slightly - from 10 to 35 wt.%, And valuable di-TMP is consumed. The decomposition of the formed cyclic formal of ethriol and the separation of ethriol from the mixture require additional chemical and technological operations, which ultimately leads to an increase in the cost of production. After distillation of the additional amount of ethriol, by-products still remain in the residue, which in this case are unused waste. In addition, in addition to the linear formaldehyde formaldehyde, the crude vacuum ethriol distillation residue also contains methylpolyformal ethriol, cyclic and linear di-TMP formalins, which must also be processed.

Thus, most of the known approaches to the processing of high-boiling by-products of ethriol synthesis relate to methods of their decomposition by chemical methods in order to increase the yield of the desired etriol or to recover commercial di-TMP. However, the result of this treatment is often the formation of difficult to separate multicomponent mixtures. Isolation of additional individual ethriol from this mixture by vacuum distillation is associated with significant difficulties due to the high mutual affinity of ethriol with impurities of other by-products. In addition, the content of undesirable impurities of non-volatile sodium formate in the bottom residue during the distillation of the main amount of ethriol increases up to 1.5 wt.%, Which dramatically affects the further separation of the residues of ethriol and di-TMP. In the presence of such an amount of sodium formate at temperatures above 170 ° C, the intensive decomposition of valuable ethriol and di-TMP begins with the formation of 2-ethyl acrolein, methanol and water, which makes the process of additional vacuum distillation impractical. Separated in this case, the ethriol fraction differs from the commodity ethriol in terms of melting temperature and requires additional energy and materials for subsequent purification, which significantly increases the cost of the whole process of obtaining ethriol.

The technical problem solved by the invention is to create an effective method for processing high-boiling by-products of ethriol synthesis, converting them into valuable chemical products, and reducing unused waste.

The technical result from the implementation of the invention is to increase the efficiency and completeness of the processing of high-boiling by-products of the synthesis of ethriol contained in the bottom residue of vacuum distillation of the crude ethriol, to obtain from them a series of substances demanded by the industry and thereby reduce waste in general.

The technical result is achieved by isolating di-TMP with a purity of 98 wt.% And higher by sequential recrystallization of the bottom residue of vacuum distillation of the crude ethriol, first from ethyl acetate in a mass ratio of 1: 1-1.5, then from acetone in a mass ratio of 1: 2 -5, after which the crystallization solvents are evaporated from the mother liquors, the residues are combined, the resulting combined residue is enriched with formals, from which the isolation of di-TMP with a purity of at least 98 wt.% Becomes impossible, turn into ethriol and di-trimester esters ilolpropane by esterification with C1-C18 carboxylic acid or a mixture of acids in the presence of 0.05-20.0 wt.% acid catalyst at a temperature of 70-250 ° C followed by purification of esters from traces of carboxylic acid and acid catalyst, moreover, water released during the conversion , formaldehyde and methanol are removed from the reaction mass in the form of azeotropes with hydrocarbons or in the form of a gas-vapor mixture.

Under optimal conditions for the synthesis of ethriol, the amount of di-TMP formed is comparable to or exceeds the mass of high-boiling formals.

It was found that twofold recrystallization of the bottom residue of vacuum distillation of the crude ethriol allows one to efficiently isolate di-TMP with a purity of 98.0-99.5 wt.% With minimal costs of organic solvents. First, recrystallization is carried out from ethyl acetate, isolating the product with a purity of about 80 wt.%, Then from acetone. These solvents are available, low toxicity, large-capacity produced by the chemical industry and have a low cost. Recrystallization is carried out by standard methods, including dissolving the substance at the boiling point of the solution, cooling and crystallizing at ambient temperature or lower temperature, filtering and drying the precipitate of the purified substance, evaporating the mother liquor to regenerate the solvent and concentrate the residue in order to transfer it to the complex stage ethers. The reduced crystallization temperature increases the degree of separation of di-TMP from the initial bottom residue of the vacuum distillation of the crude ethriol. During the process, the mass ratio of recrystallized substance and ethyl acetate should be in the range of 1: 1-1.5, and the mass ratio of recrystallized substance and acetone should be in the range of 1: 2-5. A decrease in the amount of ethyl acetate or acetone below the specified limits leads to incomplete dissolution, a decrease in the degree of isolation of di-TMP due to the mutual solubility of the separated components, and a deterioration in the purity of the product to a less significant value of 98 wt.%. High dilution improves the quality of the product, but reduces the degree of di-TMP release, increases the consumption rates of solvents and the energy consumption for their regeneration. Since the purity of commercial di-TMP is usually about 98 wt.%, An increase in the amount of solvent above the stated limits is practically impractical. Within the claimed limits, the degree of extraction of di-TMP reaches 75%, and the purity of 99.5 wt.%.

In the industrial implementation of the invention, recrystallization can be carried out periodically or continuously using known equipment. It is advisable to regenerate the solvents from the mother liquors by evaporation at elevated temperature or under vacuum, avoiding mixing the solutions from recrystallization from different solvents in order to avoid the additional stage of separation of ethyl acetate and acetone by distillation. Drying of the solid product can also be carried out by known methods: heating below the melting point and keeping under vacuum, passing gas through the product layer, or a combination of these methods. To accelerate crystallization in the solution, it is advisable to make a seed of pre-purified di-TMP.

Ethriol and di-TMP esters are widely used in industry as synthetic lubricants and plasticizers with attractive viscous-temperature characteristics and low pour point, the corresponding acrylates and methacrylates are used in the production of various polymer coatings, films, fibers, etc. At the same time, to improve the properties preferably mixed compositions of the esters of both polyols, which are usually obtained from individual ethriol and di-TMP.

In this regard, the present invention proposes the use of high-boiling by-products of the synthesis of ethriol to obtain such ester compositions, excluding any separation of the individual components of the formats-enriched combined residue after the isolation of di-TMP. Moreover, by selecting the degree of extraction of part of di-TMP before conversion to esters, the composition of the resulting ester product can be widely controlled.

It was found that, when interacting with carboxylic acids under conditions of acid catalysis, both free ethriol and di-TMP, and their formalins contained in the combined residue, can be quantitatively converted into esters of ethriol and di-trimethylolpropane. The conversion of free polyols proceeds with the release of water, and in the case of formals formaldehyde or methanol and formaldehyde are additionally formed. The decomposition of formals occurs as a result of hydrolysis with water, which occurs during the esterification of HO groups or as a result of direct interaction with carboxylic acid. In total, reactions occur leading to the formation of esters, for example:

Thus, in contrast to the known methods of processing high-boiling by-products of ethriol synthesis, the use of the invention eliminates complex technological operations and makes it possible, using raw materials from the production of ethriol after separation of di-TMP, with high yield and in one chemical stage to obtain valuable complex esters of ethriol and di-trimethylolpropane.

The reaction with carboxylic acids, accompanied by the decomposition of formals, is carried out at a temperature of 70-250 ° C. At temperatures below 70 ° C, the reaction slows down significantly, the yield of the desired esters decreases and complete conversion of the formals is not achieved. At temperatures above 250 ° C, an undesirable resinification of the reaction mass occurs, and the quality of the ester product, which is contaminated with intensely colored impurities, decreases.

Transformation catalysts can be any compounds with pronounced acidic properties, in particular strong inorganic acids and their anhydrides, alkyl and arylsulfonic acids, activated natural minerals and clays (for example, montmorillonite, mordenite, acidic zeolites, kaolinite, beidellite, etc.), acidic salts and oxides (aluminum, tin, titanium, zirconium, etc.), as well as cation exchange resins in the H-form. The load of the acid catalyst is from 0.05 to 20 wt.% Of the total reaction mass. With a smaller amount of catalyst, the reaction rate decreases markedly, its duration increases, and complete conversion is not achieved. The use of more than 20 wt.% Of the catalyst does not fundamentally affect the reaction rate, but at the same time, the costs of the catalyst, its subsequent neutralization are increased, and at high temperatures the risk of resinification of the reaction mass increases.

The conversion of the combined residue enriched with formals to esters is carried out with carboxylic acids with the number of carbon atoms from 1 to 18 or their mixtures in various mass ratios. By selecting the appropriate carboxylic acids, the physicochemical properties necessary for the targeted use of esters can be achieved. The use of carboxylic acids with carbon atoms in excess of 18 is limited by purely practical considerations: the cost of such acids, the lack of a sufficient raw material base for their production, the high viscosity of the resulting esters, which limits their scope, the high boiling point of the starting carboxylic acid and ester product, which makes it difficult to clean the latter .

The esterification reaction is an equilibrium reaction, therefore, to shift the equilibrium towards the final products, the resulting water is removed as a gas-vapor mixture or as an azeotrope with a suitable solvent inert to the components of the reaction mixture, preferably a hydrocarbon. Water removal can be accelerated by passing gas through the reaction mass. It is fundamentally important that formaldehyde released during the decomposition of formals is also discharged from the reaction zone in the form of a gas-vapor mixture or azeotropes with reaction water, methanol and hydrocarbon. Thus, the occurrence of other by-products of the formaldehyde-class formaldehyde is excluded.

Depending on the amount of acid and reaction conditions, both full esters and partial esterification products containing free hydroxyl groups can be obtained. Unreacted carboxylic acids can be separated from the reaction mass by distillation at atmospheric pressure or in vacuum and reused. Residues of carboxylic acids and acid catalyst are removed by any available means: washing with a dilute aqueous solution of bases, alkali metal carbonates or by adsorption treatment, for example, with various clays or ion exchange resins, etc. If necessary, the ester product can be further purified by fractional distillation, preferably under reduced pressure due to high boiling points. The yield of transformation products reaches 98% of theory. The acid number according to GOST 5985-79 does not exceed 0.1 mg KOH / g.

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

In a glass vessel for recrystallization with a volume of 150 ml with a jacket (heating and cooling using a thermostat), a reflux condenser and a mechanical stirring device, 30 g of the bottom residue of vacuum distillation of crude ethriol containing: 33 wt.% Ethriol, 40 wt.% Di- TMP and 27 wt.% Other impurities, including formal. The contents of the container are dissolved with stirring and heating to a temperature of 80 ° C in 40 ml of ethyl acetate (weight ratio bottoms: ethyl acetate = 1: 1.2), after which the stirring device is turned off, a coolant is fed into the jacket and kept at a temperature of 10 ° C within 10 hours. The colorless precipitate formed is filtered off on a glass porous filter and dried. Obtain 10.3 g of a crystalline substance with a content of di-TMP by GLC 80.1 wt.%. The obtained crystalline substance is dissolved in 27 ml of acetone (mass ratio of substance: acetone = 1: 3.3) with stirring and heating to a temperature of 56 ° C, after which the stirring device is turned off, the solution is cooled to a temperature of 10 ° C and recrystallization is carried out for 10 h. The precipitate formed is filtered off and dried. 7.6 g of di-TMP are obtained with a GLC purity of 98.8% by weight; boiling point 202 ° C / 266.6 Pa; melting point 108-109 ° C.

IR spectrum (ν, cm ^-1 ): 3254 (O-H), 2960, 2930, 2875 (С-Н), 1254, 1130, 1024 (С-О-С). ¹ H NMR Spectrum δ _H (D ₂ O, 300 MHz): 3.36-3.28 (m, 8H), 3.15 (s, 4H, -CH ₂ -O-), 1.13 (q, J = 7.51; 7.38 Hz, 4H, CH ₂ ), 0.65 (t, J = 7.55 Hz, 6H, CH ₃ ).

The spectral data correspond to an authentic di-TMP sample. The degree of di-TMP recovery is 63%, calculated on its initial content in the bottom residue of the vacuum distillation of crude ethriol taken for recrystallization (table 1).

After two crystallizations, the mother liquors are evaporated on a rotary evaporator in a vacuum of a water-jet pump, the residues are combined and 22.4 g of the enriched combined residue of the composition are obtained: ethriol 43.7 wt.%, Di-TMP 20.4 wt.%, The rest are impurities, including formali, 35.9 wt.%. The combined residue was charged into a 250 ml glass flask equipped with a mechanical stirrer and a Dean-Stark reflux nozzle. 59.1 g (0.58 mol) of n-pentanoic acid, 110 ml of toluene and 5.0 g of Amberlyst 15 dry cation exchange resin were added to the flask as an acid catalyst. The mass is boiled for 20 hours in an argon atmosphere with vigorous stirring. Water, formaldehyde and methanol released during the conversion are taken off as an azeotrope with toluene. Upon completion of the reaction, the catalyst is filtered off, washed with 30 ml of toluene on a filter, and the filtrates are combined. The toluene is distilled off at atmospheric pressure, the excess pentanoic acid is removed in vacuo, the residue is washed with a 2% aqueous NaHCO ₃ solution, dried with anhydrous MgSO ₄ and distilled in vacuo, taking a fraction of the complete esters of ethriol and di-TMP boiling in the range 189-240 ° C / 13.3 Pa. Obtain 42.82 g of esters with a mass ratio of ethriol trivalerate: di-TMP tetravalerate = 66.5: 33.5 wt.% (Approximately 2: 1). Yield 96.2 wt.% Of theoretical, acid value 0.06 mg KOH / g (table 2).

Examples 2-5 (illustrate the isolation of di-TMP from the bottom residue of vacuum distillation of the crude ethriol by recrystallization)

Isolation of di-TMP from the bottom residue of vacuum distillation of the crude ethriol is carried out analogously to example 1 by varying the mass ratio of the amount of substance taken for recrystallization to solvent, temperature and crystallization time.

The results obtained are summarized in table 1.

The examples 1-5 (table 1) show that with a decrease in the amount of solvent supplied to the recrystallization, the total degree of di-TMP release increases, however, the purity of the resulting product decreases.

Examples 6-11 (illustrate the conversion of the format-enriched combined residue after the separation of di-TMP into esters with the allocation of water, formaldehyde and methanol released in the process of conversion as azeotropes with hydrocarbon).

The separation of di-TMP from the bottom residue of vacuum distillation of the crude ethriol is carried out analogously to example 1. Further conversion of the format-enriched combined residue to obtain esters and their purification is carried out analogously to example 1, varying the type of carboxylic acid, hydrocarbon, catalyst, as well as the temperature of the reaction mass. The results are shown in table 2. In the described examples, the conversion of high-boiling by-products of ethriol synthesis is 98-99.5%, the yield of esters is 95.9-98.2 wt.%. The content of impurities in ester products does not exceed 1 wt.%.

Example 12 (illustrates the conversion of a formaldehyde-combined residue after separation of di-TMP into esters with the allocation of water, formaldehyde and methanol released in the process of conversion as a gas-vapor mixture)

In a glass bottle for recrystallization with a volume of 100 ml with a jacket (heating and cooling with a thermostat), a reflux condenser and a mechanical stirring device, 10.3 g of the bottom residue of vacuum distillation of the crude ethriol containing: 33 wt.% Ethriol, 40 wt.% di-TMP, and 27 wt.% other impurities, including formal. The isolation of di-TMP by recrystallization is carried out analogously to example 1. After recrystallization, 2.60 g of di-TMP are obtained with a GLC purity of 98.7 wt.%, As well as 7.67 g of a formaldehyde-containing combined residue, which is loaded into a 100 ml round-bottom flask equipped with a bubbler, mixing device and Dean-Stark nozzle with reflux condenser. 25.16 g (0.25 mol) of n-pentanoic acid and 0.1 g (0.57 mmol) of p-toluenesulfonic acid (p-TSC) are added to the flask. The mixture is heated at a temperature of 140 ° C with vigorous stirring and bubbling of dry nitrogen through a layer of the reaction mass for 6 hours. After that, the temperature of the reaction mass is increased to 160 ° C and held for 4 hours until the reaction is complete (control by GLC). The water, formaldehyde and methanol released during the reaction are taken off as a gas-vapor mixture and collected in a Dean-Stark nozzle.

At the end of the reaction, excess n-pentanoic acid was distilled off in vacuo, the residue was washed with a 2% aqueous solution of NaHCO ₃ , dried with anhydrous MgSO _4, and the desiccant was filtered off. The filtrate was distilled in vacuo, collecting a fraction of the complete esters of ethriol and dimethylolpropane boiling in the range 189-239 ° C / 13.3 Pa. Yield 15.33 g (95.1 wt.% Of theoretical), weight ratio of ethriol trivalerate: di-TMP tetravalerate = 66.9: 33.1 wt.%. The acid value is 0.1 mg KOH / g (table 2).

Examples 13-15

The conversion of the formaldehyde-bound combined residue after the isolation of di-TMP into esters is carried out analogously to example 12, varying the type of carboxylic acid, the catalyst and the temperature of the reaction mass. The results are shown in table 2.

Thus, the implementation of the invention provides the separation of commercially demanded and expensive di-TMP with a purity of at least 98 wt.% From the bottom residue of vacuum distillation of the crude ethriol and processing of the combined residue remaining after this enriched with formulas into C1-C18, etriol and di-trimethylolpropane, which are in demand in various fields of technology. When implementing the invention, a high depth of processing of high-boiling by-products of the process of obtaining ethriol is achieved and the amount of unclaimed waste is reduced almost completely.

Claims (3)

1. The method of processing high-boiling by-products of the process of obtaining ethriol, which consists in the fact that carry out sequential recrystallization of the bottom residue of vacuum distillation of the crude ethriol by dissolving it in ethyl acetate at a mass ratio of 1: 1-1.5 at a boiling point of the solution, cooling and aging, separation separated crystalline substance and dissolving it in acetone at a mass ratio of 1: 2-5 at the boiling point of the solution, cooling and aging, after which the trimethylolpropane is separated in the form of an individual compound with a purity of not less than 98 wt.%, crystallization solvents are evaporated from the mother liquors, the residues are combined, the resulting combined residue, enriched with formals, is converted into ethriol and dimethylolpropane esters by etherification with C1-C18 carboxylic acid or a mixture of acids in the presence of 0.05-20.0 wt.% Acid catalyst at a temperature of 70-250 ° C, followed by purification of esters from traces of carboxylic acid and acid catalyst, and water, formaldehyde released during the conversion guide and the methanol is removed from the reaction mass. 2. The method according to p. 1, characterized in that the water, formaldehyde and methanol released during the conversion are removed as azeotropes with a hydrocarbon selected from the group: benzene, toluene, o-xylene or p-xylene. 3. The method according to p. 1, characterized in that the water, formaldehyde and methanol released during the conversion are removed in the form of a gas-vapor mixture.