Pentaerythritol and dipentaerythritol synthesis method

FIELD: chemistry.

SUBSTANCE: present invention relates to a method for synthesis of pentaerythritol and dipentaerythritol, involving reaction of acetaldehyde with formaldehyde in the presence of sodium hydroxide, purification of the reaction solution through distillation of excess formaldehyde, evaporation and crystallisation of technical pentaerythritol, washing the residue, recrystallisation of technical pentaerythritol, separation of the residue from the solution and drying commercial-grade pentaerythritol and treatment of the product after drying. After drying the product is treated through separation, thereby extracting the pentaerythritol fractions most contaminated with non-volatile impurities of dipentaerythritol and cyclic formalin, and the extracted fractions are processed by leaching pentaerythritol with demineralised water at 10-80C and ratio of liquid phase to solid phase equal to (5.5-8)/1, and subsequent separation of the formed pentaerythritol solution and dipentaerythritol precipitate and taking the pentaerythritol solution to the technical pentaerythritol recrystallisation step.

EFFECT: method enables to obtain pentaerythritol with low content of dipentaerythritol and cyclic formalin impurities, as well as recycling of dipentaerythritol.

6 cl, 1 tbl, 7 ex

 

The invention relates to the technology of organic synthesis, in particular to a technology for production of pentaerythritol and dipentaerythritol used in paint and other industries.

A known method of producing pentaerythritol and dipentaerythritol /1/, which includes the interaction of acetaldehyde with formaldehyde in the presence of sodium hydroxide, evaporating the reaction solution, crystallization, filtration, washing and drying of the finished product, characterized in that the evaporation of the reaction solution is carried out fractionally, first made by evaporation to a certain specific gravity, crystallization and release dipentaerythritol, the remaining mother liquor is subjected to further evaporation followed by crystallization and release of pentaerythritol. Thus interaction of acetaldehyde with formaldehyde is carried out at the excess of formaldehyde up to 50% of the stoichiometric until complete conversion of the aldehyde, the reaction solution is subjected to evaporation to a specific gravity of 1.05-1.12 g/cm3, cooled to a temperature of 10-20C. and filtered and washed with water fallen dipentaerythritol. The interaction of acetaldehyde with formaldehyde is carried out in the presence of boric acid or borax in the amount of 0.015 to 0.02 mol per mol of acetaldehyde. Evaporation of the reaction solution is carried out under vacuum. Nedostatkami.mne are the complexity and energy technology, associated with carrying additional allocation of dipentaerythritol during fractional crystallization, by necessity after the separation of dipentaerythritol repeatedly heating and cooling a saturated solution of pentaerythritol.

Also known is a method of obtaining pure pentaerythritol with a basic substance content of more than 98 wt.% and pentaerythritol, enriched dipentaerythritol /2/, namely, that carry out the condensation of acetaldehyde with formaldehyde in aqueous-alkaline medium with subsequent neutralization of the reaction mixture, the desorption of excess formaldehyde, evaporation, vacuum crystallization at 45-55C and density of a suspension of 1.30-1.35 g/cm3, filtering, washing the obtained technical pentaerythritol, its subsequent recrystallization in hot water, filtering at 45-55C and drying emitting pentaerythritol. Next, the filtrate of the suspension of technical pentaerythritol and the filtrate from the stage of recrystallization unite, evaporated, and subjected to vacuum crystallization at 38-45C. filter the resulting suspension, the precipitate is washed again it is recrystallized in hot water, filtered the precipitate at 45-55C and dried to obtain a product containing pentaerythritol and enriched dipentaerythritol in the amount of 5-20 wt.%. And washing the precipitate obtained after stage vacuum crystal is saved at 38-45C. and filtering, provide demineralized water and/or filtrate enriched with pentaerythritol, taken from the stage of recrystallization. At the stages of receipt of pentaerythritol with a basic substance content of more than 98% of the last isolated in the number of 55-74 wt.% from its content in the initial solution. The disadvantage of this method is the pollution of pentaerythritol impurities dipentaerythritol and that the method does not allow for obtaining trademark dipentaerythritol.

The closest technical solution to the claimed method is a method of producing pentaerythritol /3/, including the synthesis of pentaerythritol, purification reaction solution, evaporation and crystallization of technical pentaerythritol, sediment washing, recrystallization of technical pentaerythritol, separating the precipitate from the solution and drying commodity pentaerythritol, handling of the product after drying by crushing lumps of dry product to a particle size of particles of 1-2 mm and additional heat treatment by the heat carrier heated to a temperature of 160-180C and moving at a speed of 20-30 m/s Method reduces the mass fraction of moisture and volatile impurities in the finished product from 0.3 to 0.07 to 0.08%. The disadvantage is that the method does not allow to reduce the content of non-volatile impurities in the pentaerythritol (type dipentaerythritol and cyclic formula) and does not include disposal deep is enteritica.

The aim of the invention is to reduce the impurity content of dipentaerythritol and cyclic formula in pentaerythritol and disposal of dipentaerythritol.

This objective is achieved in that in the method of producing pentaerythritol, including the interaction of acetaldehyde with formaldehyde in the presence of sodium hydroxide, purification of the reaction solution by distillation of excess formaldehyde, evaporation and crystallization of technical pentaerythritol, sediment washing, recrystallization of technical pentaerythritol, separating the precipitate from the solution and drying commodity pentaerythritol, handling of the product after drying, the product after drying is carried out by separation, allocating a fraction of pentaerythritol, the most contaminated non-volatile impurities dipentaerythritol and cyclic formula, and the selected fraction is processed by leaching pentaerythritol demineralized water at a temperature of 10-80C., and the ratio of liquid and solid phase, equal (5,5-8)/1, with subsequent separation of the resulting solution of pentaerythritol and sludge dipentaerythritol, and applying the solution of pentaerythritol to the stage recrystallization of technical pentaerythritol. Moreover, separation of the product after drying produce pneumocephaly in cyclones and/or mechanically on the shale shakers; separating the resulting solution of pentaerythrit is and sludge dipentaerythritol carried out on filters or centrifuges; the precipitate of dipentaerythritol washed with demineralized water and dried; the leaching is carried out at temperatures of 40-50 with a ratio of liquid and solid phases, is equal to (5,5-6)/1.

Treatment of the product after drying by separation with the separation of fractions of pentaerythritol, the most contaminated non-volatile impurities dipentaerythritol and cyclic formula (mostly fine class 0-0,125 mm), can significantly reduce the content of impurities of dipentaerythritol and cyclic formula in pentaerythritol with a low cost of operation and full utilization of selected fractions.

Carrying out processing of selected fractions by leaching pentaerythritol demineralized water followed by separation of the resulting solution of pentaerythritol and sludge dipentaerythritol on filters or centrifuges, a feed solution of pentaerythritol to the stage recrystallization of technical pentaerythritol allows a simple way to remove the impurity of dipentaerythritol of the product and send the resulting solution into the existing technological scheme of production of pentaerythritol.

The operation of the leaching of pentaerythritol demineralized water from selected contaminated fractions at temperatures of 10-80C., preferentially at temperatures of 40-50C at the ratios of the liquid and solid phases (5,5-8)/, mainly when the ratio (5,5-6)/1 provides the most complete removal of sludge dipentaerythritol impurities of sodium formate, pentaerythritol obtaining a concentrated solution of pentaerythritol which are further processed in the pentaerythritol.

The use of leaching nudemaniladating water leads to an increase in the content of impurities in the solution of pentaerythritol coming on crystallization, with subsequent contamination of the commodity pentaerythritol.

The leaching at temperatures below 10C will lead to a deterioration of leaching and increased impurity content of pentaerythritol in dipentaerythritol.

When the temperature of the leaching above 80C is dissolved dipentaerythritol that leads to accumulation of impurities in the solution of pentaerythritol, subsequent contamination emitted from a solution of crystalline pentaerythritol and lower output dipentaerythritol.

The leaching when the ratio of the liquid and solid phases below 5.5/1 leads to a low degree of leaching and accumulation of impurities pentaerythritol in the sediment of dipentaerythritol, and maintaining the ratio of the liquid and solid phases above 8/1 leads to strong dilution of the resulting solution of pentaerythritol and the need for further concentrating the solution by evaporation, which increases energy consumption.

Obtained by leaching the precipitate of dipentaerythritol washed and transported to the drying for the production of commodity dipentaerythritol.

Examples of the method.

Example 1. Treatment of the product (pentaerythritol) after drying by separation

The original crude pentaerythritol received /2/ JSC "Metafrax" using stages of the synthesis of pentaerythritol of formaldehyde and acetaldehyde in the presence of sodium hydroxide, followed by neutralization of the reaction medium formic acid, purification of the reaction solution by distillation of formaldehyde, evaporation and crystallization of technical pentaerythritol with a final temperature of 50C., filtering and washing the precipitate filtrate from the stage of recrystallization, dissolution of the precipitate in water, cleaning solution, ion-exchange resin and recrystallization of the precipitate technical pentaerythritol, the precipitate from the solution in the centrifuge and drying of the finished product. Source pentaerythritol contained (%): monopentaerythritol - 95,67; dipentaerythritol - 3,96; cyclic nonformal - 0,360.

The product of pentaerythritol after drying (to remove from the product of dipentaerythritol and cyclic nonformula) was performed by separation of the source of pentaerythritol in the air cyclone. When this occurred the separation of the fraction class 0-0,125, the most contaminated of dipenta is a retreat. As a result of separation of the obtained pentaerythritol containing (%): monopentaerythritol - 98,05; dipentaerythritol - 1,837; cyclic nonformal - 0,100. By separating the content of monopentaerythritol in commodity product grew 2,383%, and the content of impurities of dipentaerythritol decreased by 2,123% (2.15 times), impurities CMP - 0,260% (3.6 times).

Example 2. Treatment of the product (pentaerythritol) after drying by separation

The original crude pentaerythritol was obtained analogously to example 1, with the difference that was obtained from a cleaner solutions. Source pentaerythritol contained (%): monopentaerythritol - 97,99; dipentaerythritol - 1,74; cyclic nonformal - 0,250.

Department of pentaerythritol from dipentaerythritol (DEP) and cyclic nonformula (CMP) was performed by separation of the source pentaerythritol on the vibrating screen. After treatment, the obtained pentaerythritol containing (%): monopentaerythritol - 98,92; dipentaerythritol - 0,917; cyclic nonformal - 0,136. By separating the content of monopentaerythritol in commodity product increased by 0.93%, and the content of impurities of dipentaerythritol decreased by 0,823% (1.9 times), impurities CMP - 0.114% (1.84%).

Example 3. The processing sub-standard pulverulent fraction of pentaerythritol in dipentaerythritol and the solution of pentaerythritol

Powdered non-conforming product (cyclone dust) pentaerythritol obtained in example 1, with Ergal (wt.%): the monopentaerythritol - 85,109; dipentaerythritol - 16,52; cyclic nonformal - 1,366. Sieve analysis of cyclone dust pentaerythritol showed that the cyclone dust contains 92,6% fraction size 0-0,125 mm

Recycling cyclone dust pentaerythritol was carried out as follows. A portion of the cyclone dust pentaerythritol (50 g) were placed in a thermostatted at 50C. the reactor with 250 ml of distilled water. After adding water to the cyclone dust suspension was intensively stirred for 30 minutes. When leaching was supported by the correlation of phases W/T=5. Then the suspension was filtered to make vacuum light filter at a temperature of 50C, the filtrate was analyzed for content of monopentaerythritol, which was 14,09%. The precipitate was washed on the filter 22 ml of distilled water with a temperature of 25C. Then the precipitate was dried and tested. The output of sediment (from the original cyclone dust) was 23,34%. The output of dipentaerythritol (%) was calculated as the ratio of the number of received dipentaerythritol to the amount of the original cyclone dust. The content of dipentaerythritol and cyclic formula in the Deposit amounted to 46%of monopentaerythritol - 54,0%. This product does not meet the commercial quality of dipentaerythritol.

Example 4. The processing sub-standard pulverulent fraction of pentaerythritol in dipentaerythritol and the solution of pentaerythritol

Processed cyclone dust of the same composition similarly p is the iMER No. 3 with the difference, that leaching was filed more water 275 ml the ratio of liquid and solid phases in the leaching amounted to W/T=5,5. The concentration of monopentaerythritol in the filtrate was 12,97%. The sediment yield was 11,54%. The content of dipentaerythritol in the sediment was of 97.78%monopentaerythritol and cyclic formula - 2,22%. The resulting product meets the commodity as dipentaerythritol, and the concentration of monopentaerythritol 12,97% in the filtrate acceptable for processing solution pentaerythritol with a little cost to evaporation.

Example 5. The processing sub-standard pulverulent fraction of pentaerythritol in dipentaerythritol and the solution of pentaerythritol.

Processed cyclone dust of the same composition as in example 3 with the difference that the ratio of the liquid and solid phases in the leaching amounted to W/T=6. The concentration of monopentaerythritol in the filtrate was 12,02%. The output of sediment (from the original cyclone dust) amounted 9,10%. The content of dipentaerythritol in the sediment was of 97.78%monopentaerythritol and cyclic formula - 2,15%. The resulting product meets the commodity as dipentaerythritol, and the concentration of monopentaerythritol 12,02% in the filtrate acceptable for processing solution pentaerythritol with a little cost to evaporation.

Example 6. The processing sub-standard pulverulent fraction of the pentaerythritol is in dipentaerythritol and the solution of pentaerythritol

Processed cyclone dust of the same composition as in example 3 with the difference that the ratio of the liquid and solid phases in the leaching amounted to W/T=8. The concentration of monopentaerythritol in the filtrate amounted to 9.3%. The output of sediment (from the original cyclone dust) was 8.5%. The content of dipentaerythritol in the sediment was 98,03%monopentaerythritol and cyclic formula - of 1.97%. The resulting product meets the commodity as dipentaerythritol, and the concentration of monopentaerythritol 9.3% in the filtrate acceptable for processing solution pentaerythritol with a little cost to evaporation.

Example 7. The processing sub-standard pulverulent fraction of pentaerythritol in dipentaerythritol and the solution of pentaerythritol

Processed cyclone dust of the same composition as in example 3 with the difference that the ratio of the liquid and solid phases in the leaching amounted to W/T=9. The concentration of monopentaerythritol in the filtrate was 8.3%. The output of sediment (from the original cyclone dust) amounted to 8.0%. The content of dipentaerythritol in the sediment was 98,03%monopentaerythritol and cyclic formula - 1,90%. By leaching with a higher dilution of the concentration of monopentaerythritol in the filtrate significantly decreased to 8.3%, which is unacceptable for processing solution pentaerythritol, as rising costs for evaporation.

For sravnenie the data of the experiments in examples 3-7 are shown in the table.

Table
The rates of recycling cyclone dust pentaerythritol in dipentaerythritol and the solution of pentaerythritol
no experience34567
The ratio W/T in the leaching55,5689
The concentration of pentaerythritol in R-re after leaching, %14,0912,9712,02of 9.308,30
The content of monopentaerythritol and cyclic formula in dry sediment, %54,02,222,151,971,90
The content of dipentaerythritol in dry sediment, %46,0of 97.7897,8598,03 98,1
The output of dipentaerythritol, %23,3411,549,108,508,00

Analysis of the data the table shows that the most preferred is carrying out processing of particulate fractions in examples 4-5. When these modes is achieved by a high content in the resulting precipitate of dipentaerythritol (of 97.78-97,85%) and acceptable concentrations of pentaerythritol in the solution after leaching (12,97-12,02%), which will require low cost evaporation of the solution during processing it in crystalline pentaerythritol.

Advantages of the proposed method are the simplicity, the absence of toxic reagents, the possibility of obtaining pure pentaerythritol higher quality (the content of monopentaerythritol that 98.9%) with simultaneous utilization and obtaining a new product - commodity dipentaerythritol containing 98% of the basic substance.

List of used sources

1. RF patent 2181353, IPC SS 31/24. The method of producing pentaerythritol. / Narrogin V.B. have been, Kabakov SI, Tailakov S.N., Sedov L.L., Matsuev SV, Vasil EV, Prokhorov VP - Appl. 24.04.00. Publ. 20.04.02.

2. RF patent 2208009, IPC SS 31/24, 31/18, s/38. The method of producing pentaerythritol with the content of the basic substance bol is e 98 wt.% and pentaerythritol, enriched with dipentaerythritol in the amount of 5-20 wt.%. Daut, VA, Mayer, V., burns A., Semerikov A.B., Shadrin D.V., Postonogov E.A. JSC "Metafrax". Appl. 2002.04.11. Published. 2003.07.10.

3. RF patent 2053215, IPC SS 31/24. The method of producing pentaerythritol. Zagidullin AGRICULTURAL, Daut, VA, burns V., Meyer CENTURIES, Covers E.E. JSC "Methanol" Stated 1992.11.11. Publ. 1996.01.27.

1. The method of producing pentaerythritol and dipentaerythritol, including the interaction of acetaldehyde with formaldehyde in the presence of sodium hydroxide, purification of the reaction solution by distillation of excess formaldehyde, evaporation and crystallization of technical pentaerythritol, sediment washing, recrystallization of technical pentaerythritol, separating the precipitate from the solution and drying commodity pentaerythritol, handling of the product after drying, characterized in that the processing of the product after drying is carried out by separation, allocating a fraction of pentaerythritol, the most contaminated non-volatile impurities dipentaerythritol and cyclic formula, and the selected fraction is processed by leaching pentaerythritol demineralized water at a temperature of 10-80C., and the ratio of liquid and solid phase, equal to 5.5-8)/1, with subsequent separation of the resulting solution of pentaerythritol and sludge dipentaerythritol, and applying the solution of pentaerythritol to the stage of recrystallization-the th pentaerythritol.

2. The method according to claim 1, characterized in that the separation of the product after drying produce pneumocephaly in cyclones and/or mechanically on the shale shakers.

3. The method according to claim 1, characterized in that the separation of the resulting solution of pentaerythritol and sludge dipentaerythritol carried out on filters or centrifuges.

4. The method according to claim 1, characterized in that the precipitate of dipentaerythritol washed with demineralized water and dried.

5. The method according to claim 1, characterized in that the leaching is carried out at temperatures of 40-50C.

6. The method according to claim 1, characterized in that the leaching is carried out at a ratio of liquid and solid phases, is equal to (5,5-6)/1.



 

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