Method of producing pentaerythritol using paraformaldehyde

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing pentaerythritol, involving condensation of formaldehyde with acetyldehyde in the presence of sodium hydroxide, rectification and evaporation of the condensed solution, vacuum crystallisation, filtration, washing the obtained technical pentaerythritol, recrystallisation, filtration and drying the pentaerythritol. The formaldehyde is used in form of a mixture of formalin and paraformaldehyde, where the paraformaldehyde constitutes up to 1/5 of the total amount of formaldehyde in the reaction mixture, the components being in the following molar ratio: acetaldehyde 1; formaldehyde 8.4-8.5; sodium hydroxide 1.15-1.20; water 70-72.

EFFECT: method increases efficiency of the process while ensuring high quality of the ready product.

1 ex

 

The present invention relates to the field of chemistry, in particular to the technology of organic synthesis, and can be used to produce pentaerythritol.

A known method of producing pentaerythritol in A.S. No. 77536, which consists in the condensation of acetaldehyde and formaldehyde in solution in the presence of caustic soda, cleaning solutions pentaerythritol, including other organic impurities, such as sodium formate, dipentaerythritol, polypentaerythritols, ion-exchange resins after separation of the unreacted aldehydes.

The disadvantage of this method is the low output of commodity pentaerythritol due to insufficient content of formaldehyde in the reaction mixture to ensure complete flow of synthesis and improve the quality of the obtained pentaerythritol.

A known method of producing pentaerythritol (Patent SU 300018, C07C 31/24, 1971), including the condensation of formaldehyde with acetaldehyde in the presence of a hydroxide of an alkaline or alkaline earth metals when heated with subsequent isolation of the target product by known methods.

The disadvantage is the low quantity and quality of pentaerythritol.

A known method of producing pentaerythritol (RF Patent No. 2078073, C07C 31/07, C07C 29/38, 1997), which consists in the interaction of acetaldehyde with formaldehyde in the presence of hydroxide intothree is, distillation and evaporation of the reaction solution, vacuum crystallization, filtration, washing and drying of the finished product.

The drawback is that, despite the intensification of the process, the yield of the obtained pentaerythritol is not high enough.

The closest analogue of the present invention is a method of producing pentaerythritol with a basic substance content of more than 98 wt.% and pentaerythritol, enriched dipentaerythritol in the amount of 5-20% (RF Patent No. 2208009, C07C 31/24, C07C 31/18, C07C 29/38, 2003). The known method involves the condensation of acetaldehyde with formaldehyde in an aqueous alkaline medium, rectification, evaporation, vacuum crystallization at 45-55°C and density of a suspension of 1.3-1.35 g/cm3, filtration, washing of the obtained technical pentaerythritol, further recrystallization in hot water, filtering at 45-55°C and drying with the release of pentaerythritol with a basic substance content of about 98 wt.%.

The known method significantly enhances the yield of pentaerythritol. However, the disadvantage of the prototype is the lack of performance of the process of obtaining pentaerythritol.

The technical object of the present invention is to improve the performance of the process of obtaining pentaerythritol, while ensuring a high quality finished product.

T is khnicheskie result when the task is to accelerate the process of obtaining pentaerythritol.

The method of producing pentaerythritol, which consists in the condensation of formaldehyde with acetaldehyde in the presence of sodium hydroxide, distillation and evaporation of the condensation solution, vacuum crystallization, filtration, washing of the obtained technical pentaerythritol, recrystallization, filtration and drying of pentaerythritol, characterized in that the formaldehyde used in the form of a mixture of formalin and paraformaldehyde, and paraformaldehyde is up to 1/5 of the total amount of formaldehyde in the reaction mixture, the molar ratio of components:

acetaldehyde1
formaldehyde8,4-8,5
sodium hydroxide1,15-1,20
water70-72.

The technical result is ensured by the fact that not more than 1/5 part of the formaldehyde used in the process of producing pentaerythritol is paraformaldehyde. Up to 1/5 part of the formaldehyde in the form of paraformaldehyde possible to increase the concentration of the condensation solution, which is explained by the higher content of formaldehyde in paraformaldehyde compared with formalin. In pairs the formaldehyde contains not less than 91% of formaldehyde, in formalin (aqueous solution of formaldehyde) - up to 55%. Increasing the concentration of the condensation solution accelerates the process of obtaining pentaerythritol by reducing the duration of the stage of evaporation. Reducing the total amount of methanol formed during the synthesis of pentaerythritol, reduces the time of the stage rectification and reduces the amount of impurities (usinternational pentaerythritol) in the finished product, which ensures high quality of pentaerythritol.

Using more than 1/5 parts of paraformaldehyde in a mixture of formaldehyde complicates the process of obtaining pentaerythritol and therefore lengthens the process, as it requires a loading device for loading paraformaldehyde in the reactor, installed inside the reactor mixing devices, the implementation of additional allotment of excess heat. In addition, for the dissolution of more than 1/5 parts of paraformaldehyde requires more water, which also leads to complicate and lengthen the process of preparation of pentaerythritol. At the same time, it is experimentally found that the use of less 1/280 parts of paraformaldehyde from the total amount of formaldehyde in the reaction mixture has no significant impact on the technical result and therefore naselenie is different.

Increasing the concentration of the condensation solution leads to increased output of finished product with a high content of the basic substance of monopentaerythritol, owing to the fact that the increase in the content of formaldehyde in the reaction mixture provides a more complete course of synthesis of pentaerythritol. Experiments have shown that the proposed method can be used to obtain pentaerythritol, including to schedule rate is now 99.14% monopentaerythritol.

Therefore, implementation of the proposed method of producing pentaerythritol with up to 1/5 of the total amount of formaldehyde in the reaction mixture with the claimed molar ratio of the components speeds up the process of obtaining pentaerythritol, while maintaining the high quality of the finished product.

The method of producing pentaerythritol using paraformaldehyde as follows.

To obtain pentaerythritol use:

acetic aldehyde technical with mass fractions of the basic substance - 99,79%, formaldehyde is in the form of a mixture of formalin (aqueous formaldehyde), with a basic substance content of 55% and paraformaldehyde with a basic substance content of more than 90%, for example, the brand "Granuform 91" produced by German company Ineos Paraform with formaldehyde 91%;

the caustic soda technical (sodium hydroxide), with mass fractions of the main substances - 48,63%;

formic acid content of the basic substance - 86%;

demineralized water.

Synthesis of pentaerythritol is carried out at a molar ratio of the components in the reaction mixture:

acetaldehyde - 1;

formaldehyde (including paraformaldehyde) - 8,4-8,5;

sodium hydroxide - 1,15-1,20;

water - 70-72

as the most optimal for obtaining the greatest quantity of the finished product - PENTAERYTHRITE.

For the process of condensation of formaldehyde and acetaldehyde in the presence of sodium hydroxide, paraformaldehyde loaded into the reactor simultaneously with formalin. This paraformaldehyde can be used in the form of powder or granules. Preferably the use of paraformaldehyde pellets because of their better solubility. In addition, paraformaldehyde pellets better stored and transported. Next, the process of obtaining pentaerythritol lead, using the known operations: distillation, evaporation, vacuum crystallization, filtration and washing of the obtained technical pentaerythritol. And time for the distillation and evaporation is reduced due to the increased concentration of formaldehyde in the condensation solution and reduce the amount of methanol due to the use of parts of formaldehyde in the form of paraformaldehyde. Then technical pentaerythritol cleaned by rastvorenii refining, subjected to vacuum crystallization with receipt and drying commodity pentaerythritol.

The proposed method is illustrated by a concrete example.

Charged to the reactor 26434,12 kg technical formalin solution containing 55% formaldehyde, 23,59 kg of paraformaldehyde brand "Granuform 91"that is 1/280 part of the total amount of formaldehyde, 2863,06 kg of sodium hydroxide containing 42.5% of NaOH, 12219,74 kg of demineralised water. The resulting mixture is stirred. Then gradually metered acetaldehyde in the number 1146,29 kg thus receive the total amount of the mixture 42686,80 kg After completion of the synthesis of pentaerythritol and the finished product is analyzed by its quality. The quality of the finished product is determined by the content of monopentaerythritol. The content of monopentaerythritol determine net identifiable components: derivatives of pentaerythritol, water and ash content related to sodium formate. Identification of impurities derived from pentaerythritol, carried out with application of gas chromatographic method for the chromatograph Color-800". Analysis of the quality of the finished product on the contents of monopentaerythritol, as the main identifiable substances, confirmed that the product obtained in the synthesis of pentaerythritol using 1/280 parts of formaldehyde as paraformaldehyde brand "Granuform 91 contains the schedule rate is now 99.14% monopentaerythritol. This analysis showed that in the finished product, obtained in a known manner without the use of paraformaldehyde, contains 99,12% monopentaerythritol. Therefore, the results of the comparative analysis has shown that the implementation of the proposed method the quality of the finished product is not only maintained, but improved.

Thus, the present invention improves the performance of the process of obtaining pentaerythritol, by acceleration, while improving the quality of the finished product.

The method of producing pentaerythritol, which consists in the condensation of formaldehyde with acetaldehyde in the presence of sodium hydroxide, distillation and evaporation of the condensation solution, vacuum crystallization, filtration, washing of the obtained technical pentaerythritol, recrystallization, filtration and drying of pentaerythritol, characterized in that the formaldehyde used in the form of a mixture of formalin and paraformaldehyde, and paraformaldehyde is up to 1/5 of the total amount of formaldehyde in the reaction mixture, the molar ratio of components:

acetaldehyde1
formaldehyde8,4-8,5
Hydra is xed sodium 1,15-1,20
water70-72



 

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1 tbl, 1 ex

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