The method of separation of anhydrous sodium formate from aqueous solutions

 

(57) Abstract:

Usage: anhydrous sodium formate from aqueous solutions in the production of polyhydric alcohols with the use of azeotropic distillation with aromatic hydrocarbons. Essence: for dehydration of salt as azeotroping agent used benzene, toluene or xylene. The aqueous layer obtained azeotropic mixture is directed to the main stage of obtaining alcohol, and the organic layer is repeatedly used in the refining process. The volumetric ratio of aqueous solution of salt and azeotropically equal to (1-1,5) : 2.

The invention relates to the field of production of anhydrous sodium formate used in leather, textile and construction, which is a byproduct in the synthesis of polyhydric alcohols, condensation of the aldehyde in an alkaline medium. The specified method in the industry get pentaerythritol, atrial (trimethylolpropane), neopentylglycol (2,2-DIMETHYLPROPANE-1,3). When this method is used for 1 mol of the organic alcohol produces 1 mol of salt. In this regard, to obtain commercial sodium formate from the reaction solution remaining after separation of the alcohol, is an important task. the capacity of the salt in water at low temperatures. In addition, aqueous solutions of sodium formate falls in the form of a hydrate dehydration which is carried out at elevated temperatures.

There is a method of separation and drying of sodium formiate method evaporative crystallization in a fluidized bed using flue gases with a temperature of 300-350o(Y. A. Kaganovich, A., Slabinski "Industrial installations for drying in a fluidized bed", L. Chemistry, 1970, page 175). The disadvantages of this method are complex instrumentation process, high energy costs and low quality of formate sodium contaminated flue gases and the products of oxidation at high temperatures by-products of the synthesis of alcohols, which are present in the solutions received for processing.

Prototypes to this application are the following.

In the patent Poland 131946, class C 07 C 53/06//C 07 C 31/24 applied to the synthesis of pentaerythritol on anion exchangers offer the following scheme of producing sodium formate. The aqueous solution after regeneration of the anion exchange resin containing 2.1 to 3.9% of sodium formate, 0,9 2,1% sodium hydroxide concentrate, removing up to 90% of water, mixed with 25-50% methanol, boiled for 30-60 min, cooled and produce sodium formate. Methanol return tov, obtained by condensation of aldehydes in the presence of sodium hydroxide, proposed a similar approach, but expanded the range of solvents. In this case, use solvents, miscible with water, methanol, ethanol, dioxane). They are administered in an aqueous solution in an amount up to 60% salt produce crystallization. The solvent to be regenerated before reuse in the process. Salt is subjected to drying.

The drawback of both methods is the need of the organization phase of regeneration of organic solvents from aqueous solutions containing sodium formate. The last you want to retrieve from still bottoms and recycle them into marketable products.

As to how the selection of sodium formiate in the synthesis of neopentyl glycol, they have not been studied, because most often, the synthesis is carried out only with a catalytic amount of base type tertiary amines, and restore aldos conduct a hydrogenation catalyst.

An object of the invention is to develop a method of producing anhydrous sodium formiate in the synthesis of polyhydric alcohols with the exception of the operation of the regeneration of the solvent, increasing the purity of the salt and simplified the s from solutions of sodium formate is carried out in the form of an azeotropic mixture, and the solvent is selected based on the requirements of having a separate azeotropic mixtures and minimum solubility in water. These requirements satisfy, for example, aromatic hydrocarbons benzene, toluene, xylene, etc. giving azeotropic mixture with water, divided ambient temperature in aqueous and organic layers. The developed method consists in the following.

To aqueous solution of sodium formiate, obtained after extraction of polyhydric alcohols (atrial, pentaerythritol, neopentyl glycol), add solvent (benzene, toluene, xylene and others). The resulting mixture is heated with stirring, providing a constant boiling and distillation of water. After condensing the azeotropic mixture is sent to the divider, where the solvent back into the process, and water is collected in the collection. After distillation of the water suspension of anhydrous sodium formiate is filtered, the product is dried, and the solvent is sent without regeneration for the next process. Water, distilled from formate, used in the synthesis of polyhydric alcohols without any additional training. The amount of solvent required for the operation of distillation, is determined by the amount of equipment and technological properties of p is hladiny. Hot filtering allows you to further purify the sodium formate impurities alcohol if present in the solution.

The essence of the above proposals is illustrated by examples.

Example 1. In a flask equipped with stirrer, thermometer and a trap Dean-stark connected with a reflux condenser, pour 150 ml of an aqueous solution of sodium formiate, (density 1,272 g/cm) obtained after the extraction of neopentyl glycol and 200 ml of toluene. Carry out the distillation of water in the form of an azeotropic mixture with toluene, carrying out the temperature control in pairs and measuring the amount of water in the trap. At the end of the process, the suspension is cooled, the sodium formate is filtered off and dried. The product yield and water is practically quantitative. The melting point of salt 260-265oC. Content of sodium formiate of 99.1% content neopentyl glycol 0.4% Results with other similar solvents.

Example 2. Conditions of experience as in example 1. Taken 100 ml of solution with a density of 1.27 g/cm, obtained in the synthesis of pentaerythritol, and 200 ml of toluene. The resulting sodium formate with a melting point 247 - 250oWith, the product yield and water settlement. The content of sodium formate 97%

Example 3. Conditions of experience as in example 1. Taken 150 ml rozvody quantitative. The melting point of the obtained sodium formate 258-260oC. the Content of sodium formiate 98,7%

The method of separation of anhydrous sodium formate from the aqueous solution after extraction of polyols obtained by the condensation of aldehydes with formaldehyde, by removing water by azeotropic distillation, characterized in that the dehydration salts are using benzene, toluene or xylene as azeotroping agent and the aqueous layer azeotropic mixture is directed to the main stage of obtaining alcohol, and the organic layer is repeatedly used in the refining process.

 

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