RU2340590C1 - Method of separating multi-atom alcohols, neopentylglycol and sodium formiate - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method of separating multi-atom alcohols, for instance, neopentylglycol and sodium formiate, includes evaporation and cooling of reaction mixture, addition of organic solvent, crystallisation of sodium formiate, separation of sodium formiate from saturated solution of multi-atom alcohol, for instance, by filtration, and crystallisation of multi-atom alcohol. Reaction mixture is evaporated until two liquid layers are formed, which are separated into light phase - water-multi-atom alcohol and heavy phase -water-salt, separated water-salt fraction of solution is cooled until sodium formiate contained in it in form of cryslallohydrate is crystallised, sodium formiate crystals are separated, and remaining mother-solution is returned to process head, to evaporation stage, then separated light phase - water-multi-atom alcohol is additionally evaporated until 70% of contained in it sodium formiate is crystallised, then cooled to 25-30°C and subjected to processing with organic solvent from line of single-atom saturated alcohols, for instance, methane, for removal of remaining admixtures, with further crystallisation of multi-atom alcohol from remaining mother-solution.

EFFECT: reduction of amount of used organic solvent, elimination of high-temperature stage of extraction, preservation of yield of pure target products.

2 cl, 2 dwg, 1 ex

Description

The invention relates to the field of chemistry, and in particular to a method for the separation of polyhydric alcohols, for example neopentyl glycol, and sodium formate.

Polyhydric alcohols: 1,1,1-trimethylol ethane (metriol), 1,1,1-trimethylol propane (ethriol), 2,2-dimethylol propane (neopentyl glycol), etc. - find wide industrial use in the production of high-quality synthetic oils, alkyd and epoxy resins, varnishes, plastics, plasticizers, surfactants and other valuable products.

The synthesis of neopentyl glycol proceeds by the reaction of aldol condensation of isobutyric aldehyde with formaldehyde. The process is fast enough and does not require complex technological design. The main problem in the synthesis is the isolation of neopentyl glycol from the reaction mixture. Several methods are known in the industry for the extraction of neopentyl glycol from synthesis products: removal of sodium formate on ion-exchange resins; sublimation of neopentyl glycol; azeotropic distillation of water by aliphatic, cycloaliphatic or aromatic hydrocarbons, followed by extraction of neopentyl glycol with water from anhydrous syrup; extraction of neopentyl glycol with solvents on a countercurrent column. Each of the methods has its own advantages and disadvantages (see Rudkovsky D.M., Ketslakh M.M., Eppel F.A. Polyhydric alcohols. L .: Chemistry, 1972, p.122-138).

A known method for the separation of polyhydric alcohols, for example neopentyl glycol or ethriol, and sodium or calcium formate, comprising adding an organic solvent to the mixture of the substances to be separated, in which the polyol is dissolved, crystallization of sodium or calcium formate, separation of sodium or calcium formate from a solution of polyhydric alcohol in an organic solvent , for example, by filtration, recycling an organic solvent, cooling the solution and crystallizing a polyhydric alcohol, moreover, as organic A solvent of an aromatic series, for example, toluene, is used, and after adding an organic solvent to the mixture of separable substances, the resulting mixture is heated to boiling point and produced at this temperature simultaneously: sodium or calcium formate and dissolution of a polyhydric alcohol in an organic solvent. The method allows to increase the yield of well-purified target products (see US Pat. RF No. 2230729, publ. 06/20/2004, IPC С07С 31/20). This method is taken as a prototype for the proposed technical solution.

The disadvantages of the prototype method is the multi-stage process, the use of a large volume of solvent and heating it to a high temperature.

The objective of the invention is to develop a method for the separation of polyhydric alcohols, for example neopentyl glycol, and sodium formate in one cycle, reducing the amount of organic solvent used, eliminating the high-temperature stage of extraction while maintaining the yield of pure target products.

The technical result is a simplification of the process, conducting it under milder conditions.

The problem is solved using the characteristics specified in the 1st claim that are common with the prototype, such as a method for the separation of polyhydric alcohols, for example neopentyl glycol, and sodium formate using an organic solvent, crystallization of substances and their separation from the solution, and distinctive, significant signs, such as, the reaction mixture is evaporated to the formation of two liquid layers, which are separated into a light phase - water-polyhydric alcohol and a heavy phase - water-salt, separated water-salt part p the solution is cooled to crystallize the sodium formate contained in it in the form of a crystalline hydrate, the sodium formate crystals are separated, and the remaining mother liquor solution is returned to the process head to the evaporation stage, and then the separated light phase water-polyhydric alcohol is additionally evaporated to crystallize 70% of the formate contained in it sodium, then cooled to 25-30 ° C and subjected to treatment with an organic solvent from a number of monohydric saturated alcohols, for example methanol, to remove the remaining impurities, the precipitate from they are separated from the solution, for example by filtration, and polyhydric alcohol crystallizes from the remaining mother liquor.

According to paragraph 2 of the claims, the crystallization of a polyhydric alcohol, for example neopentyl glycol, is carried out by evaporation (removal) of the remaining aqueous solution of a monohydric saturated alcohol, for example methanol.

The above set of features, both known and new, allows the process of separation of substances described in paragraphs 1-2 of the claims to be obtained, to obtain separable substances of a sufficiently high degree of purity in one cycle, to reduce the amount of organic solvent used, to exclude the high-temperature stage of extraction while maintaining the yield of pure target products.

The above distinguishing features each individually and all together are aimed at solving the problem and are significant. The use of the proposed combination of significant distinguishing features in the prior art is not found, therefore, the proposed technical solution meets the patentability criterion of "novelty."

A single set of new essential features with common known provides a solution to the problem, is not obvious to specialists in this field of technology and indicates the compliance of the claimed technical solution (for the method) with the patentability criterion of "inventive step".

To determine the temperature and concentration conditions of the process of fractional crystallization of neopentyl glycol and sodium formate, the solubility in multicomponent aqueous-organic systems containing neopentyl glycol, sodium formate, methanol and water was studied (Figs. 1, 2).

The following is an example embodiment of the invention.

Example.

The polyhydric alcohol - neopentyl glycol is synthesized in a known manner, by reacting isobutyric aldehyde with formaldehyde in the presence of caustic soda, followed by neutralization of the reaction mixture with formic acid. The resulting synthesized is evaporated in two-thirds of the volume until the solution is divided into two layers and divided into two parts: the light phase - water-glycol and the heavy phase - water-salt and then process each part separately.

Processing of water-glycol part. The water-glycol part of one stripped off synthesis containing 79.4% of neopentyl glycol, 5.4% of sodium formate, 3.0% of impurities (C ₁₂ ...) and 12.2% of water, after separation of the layers is additionally evaporated until crystallization of 70% contained in it sodium formate (Fig.1, 2). Then, for each 100 parts by weight of the water-glycol portion evaporated and cooled to 30 ° C, 1.7 parts by weight of methanol are taken, crystalline sodium formate is separated from a solution of neopentyl glycol in an aqueous solution of methanol, for example, by filtration at a temperature of about 30 ° C.

From an aqueous methanol solution of neopentyl glycol, neopentyl glycol is crystallized by evaporation (removal) of the remaining aqueous methanol solution.

The result is for every 100 wt. parts of the mixture obtained by evaporation of the synthesis, 63.2 wt. parts of neopentyl glycol containing not more than 0.3% sodium, product yield 69.3% and 4.39 wt. parts of sodium formate, with a basic substance content of at least 99.2%.

Water-salt treatment. After separation of the layers, the water-salt portion of the stripped off synthesis is cooled to 0 ° С until crystallization of sodium formate crystalline hydrate and salt crystals are separated, for example, by filtration. The remaining solution - mother liquor is returned to the head of the process at the stage of evaporation.

As a result, for every 100 mass parts of the taken solution, 63.64 parts of sodium or calcium formate with a basic substance content of 99.0 are obtained, the yield of operations is 77.59%. The spent methanol solution formed in the process is used repeatedly in the processing of the water-glycol part of one stripped off synthesis (see above).

From the description and practical application of the present invention, other particular forms of its implementation will be apparent to those skilled in the art. This description and examples are considered as material illustrating the invention, the essence of which and the scope of patent claims are defined in the following claims, a combination of essential features and their equivalents.

Claims (2)

1. The method of separation of polyhydric alcohols, for example neopentyl glycol, and sodium formate, including evaporation and cooling of the reaction mixture, adding an organic solvent, crystallization of sodium formate, separating sodium formate from a saturated solution of polyhydric alcohol, for example, by filtration and crystallization of polyhydric alcohol, characterized in that the reaction mixture is evaporated to form two liquid layers, which are separated into a light phase - water - polyhydric alcohol and a heavy phase - water-salt, separated water the o-salt part of the solution is cooled to crystallize the sodium formate contained in it in the form of crystalline hydrate, sodium formate crystals are separated, and the remaining mother liquor is returned to the process head to the evaporation stage, and then the separated light phase - water - polyhydric alcohol is further evaporated until crystallization 70 % of the sodium formate contained in it, then cooled to 25-30 ° C and subjected to treatment with an organic solvent from a number of monohydric saturated alcohols, for example methanol, to remove remaining impurities the precipitated precipitate is separated from the solution, for example, by filtration, and polyhydric alcohol crystallizes from the remaining mother liquor. 2. The method according to claim 1, characterized in that the crystallization of a polyhydric alcohol, for example neopentyl glycol, is carried out by evaporation (removal) of the remaining aqueous solution of a monohydric saturated alcohol, for example methanol.

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