CS197891B1 - Method for isolating pentaerythritol and / or calcium formate - Google Patents

Abstract

The invention relates to a method for isolating pentaerythritol and/or calcium formate from mother liquors from the production of pentaerythritol. It solves the problem of reducing the content of pentaerythritol and calcium formate by treating mother liquors from this production. The principle is that the solution is concentrated to a water content of 25 to 50 wt., while the solid phase is separated after possible dilution, e.g. with alcohols to a liquid phase content of 30 to 70 ¢. It can be used in the production of pentaerythritol preparations.

Description

The invention relates to a method of isolating pentaerythritol and/or calcium formate from aqueous solutions from the production of pentaerythritol. It solves the reduction of pentaerythritol etrate and calcium formate by processing the mother bottles from this production. The principle of epoóíve is that the solution is concentrated to a water content of 25 to 50 wt., while the solid phase is separated after possible dilution, e.g. with alcohols to a liquid phase content of 30 to 70 ¢. It can be used in the production of pentaerythritol.

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The invention solves an economically and technologically undemanding method of isolating pentaerythritol and/or calcium formate from mother solutions from the production of pentaerythritol.

UPIMWIIM WMB& ΒβΜΜΡΜΡΚΟΙΙΙ .10 1110018118 III (COIlQiniIGll ΙΟΜΙΙΟΙΠΪΠη 8 ΙΟβΐ&Ιπ aldehyde in an alkaline environment. Sodium hydroxide or calcium hydroxide are most often used as alkali.

Procedures for the isolation of pentaerythritol from the reaction solution depending on the type of use of the condensation catalyst. In the case that calcium hydroxide is used as a catalyst, such methods of processing the reaction solutions £e are possible. Berlow, R.H. Barth, J.E. Snow: The Pentaerythritols, Reinhold Publ. Corp., New York, (l958)j. Sulfuric or sulfuric acid is added to the reaction solution, which precipitates calcium in the form of slightly soluble to insoluble salts. After filtering off the insoluble part, the aqueous solution is concentrated and pentaerythritol is allowed to crystallize from the solution. After filtering out the crude pentaerythritol, the Sálej mother liquors are not processed. Although a high amount of pentaerythritol can be obtained from the Sa solution in this way, calcium sulfate is an unused waste. For significantly diluted solutions of around 3 5" by weight, formic acid is not obtained from aqueous solutions directly, but by azeotropic distillation or extraction.

Another way to isolate pentaerythritol is neutralization of the reaction solution with formic or acetic acid to a pH of 5.5 to 6.5, followed by centrifugation at a higher temperature until the solution is converted to pentaerythritol. After separation of solid calcium formate, the solution does not tend to crystallize by cooling to 15 to 25 °C,

A variation of this process is also concentration of the reaction solution and cooling in order to obtain a mixture of calcium formate and pentaerythritol. After separating the mixture, pentaerythritol is dissolved in a hot concentrated calcium formate solution, from which pentaerythritol is obtained after cooling.

Other methods use the precipitation of calcium formate by adding glycerin, ethylene glycol, benzyl alcohol or aqueous acetone.

In the case of using sodium hydroxide as a catalyst, after neutralization to pH 7 to 8, the solution is concentrated to a Specific weight* of 1,250 to 1,290 kg/m^ at a temperature of 50°C.

After cooling to a temperature of 10 to 25 °C, pentaerythritol is obtained with a minimum amount of impurities. Sodium formate is obtained from the mother solution by mixing the solutions with ethanol or propanol.

Pentaerythritol is obtained from the mother solution after evaporation of water to dryness by extraction with secondary or tertiary aliphatic alcohol or with moderately concentrated alkalis by extraction with formaldehyde.

There are also known methods of obtaining a mixture of pentaerythritol and calcium formate from the mother solution by concentrating the mother solutions ooa to 20 water content.

By extraction with methanol, syrups and a solid mixture of calcium formate and pentaerythritol are separated from the solution and poured into the refrigerator (No. Pat. 151 303).

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The mentioned methods have significant disadvantages in that, during extraction and organic substances, a substance is introduced into the environment, which needs to be separated and recycled for economic reasons.

In addition, in the case that aa works and by complete evaporation of water, when losses of pentaerythritol and added formate are minimized, the aa process is difficult to continue and, in addition, it is necessary to divide the ternary* into individual components. In addition to formate and pentaerythritol, a certain amount of substances can be found in the mother solutions and this is due to parallel or subsequent reactions. These aa are most often referred to as syrups.

According to this invention, the isolation of pentaerythritol and/or calcium formate from the mother solutions obtained after the separation of mixed salts in the first stage after the crystallization of raw pentaerythritol from the reaction mixture formed by the condensation of formaldehyde and aoethaldehyde in the presence of calcium hydroxide is carried out by thickening in such a way that the mother solution is then thickened to the water content in at least one step at least in one stage 25 to 50 5° wt., whereby after each thickening, pentaerythritol and calcium formate are separated from the suspension, preferably after addition of alcohols with 1 to 4 carbon atoms to a liquid phase content of 30 to 70 ji, and the solid phase ea is usually washed with water or aqueous solutions obtained during the production of pentaerythritol before Salžim spraying.

The advantage of the mentioned method of obtaining pentaerythritol and calcium formate is a high percentage of isolated products and minimal losses in waste liquor. In addition to this advantage, the above-mentioned method achieved the separation of the above-mentioned substances from the adjacent syrupy parts, which are formed during the condensation reaction of formaldehyde with aoethaldehyde, but also by subsequent reactions of formaldehyde. It is also a great advantage that if the conditions according to this invention and the process of isolation of the main products are followed, it can advantageously be continuous. In addition, the danger of pipe fouling caused by the introduction of solid substances and syrups will also be reduced, which will significantly extend the period of conformity of operation from one to the types of teohnological paragraph.

The mother solution after the first separation of pentaerythritol and calcium formate after the first crystallization contains about 7% by mass. of pentaerythritol, 12 of calcium formate and about 5 5" of auxiliary substances, so-called syrups.

The mentioned solution is subjected to Salčia processing, which consists in thickening by evaporation of water to a content of about 35% in the residue.

It is important to observe the specified amount of water, or when thickening to a higher degree, add* syrup solvent, as much as below the specified amount leads to aggrieved separation of the solid phase. Since the evaporation is carried out at an elevated temperature of 80 to 105 °C, it is necessary to cool the solution before separating the solid phase in order to obtain as much suspension as possible. The temperature of the mixture after filtration should be around 25 °C. At this temperature, the solubility* of pentaerythritol in water is 6.7 ?» mass. At a higher temperature, losses of the product would increase (at 66 °C the solubility is already 21.0% by mass)·

The mentioned first evaporation yields 215 kg of filtrate II from 1000 kg of mother liquor I

197,891 with an average circulation of 7.5 5» wt. of pentaerythritol, 11.7 wt· of calcium formate and a filter cake containing 90 kg of calcium formate and 54 kg of pentaerythritol. In 215 kg of filtrate II there are still 16 kg of pentaerythritol and 25.0 kg of calcium formate and about 60 fy of water. The filtrate II is concentrated again to a water content of 35% by weight and after cooling to a temperature of 25°C, the solid phase is collected again. The second filtration gives a solid phase containing 6 kg of pentaerythritol and 10 kg of calcium formate. The following is isolated from the filtrate I: after I concentration 77% by mass PE and 80% calcium formate and after II concentration 85.7% by mass PE and 88.3% calcium formate During the third concentration due to the considerable content of syrups in the residue It is advantageous after concentration to about 20% water to add solvent to the residue in such an amount that the solid phase and the syrups made up a maximum of 65% by mass. The solvent should be a substance that dissolves good syrups, but does not dissolve, or only to a limited extent, pentaerythritol. Alcohols, e.g. methanol, also meet the requirements. After mixing, the pentaerythritol and calcium formate are filtered off. In this way, the losses of pentaerythritol and calcium formate are reduced to ooa 5 fy, considering the content in the mother liquor I or to less than 2 fy, due to the calcium formate and pentaerythritol produced. Usually, however, the first two concentrations of the mother liquor I are sufficient, because already after the second aaparéoia of the solid phase, losses of pentaerythritol are within 5% ^of the produced amount.

Also, the first and second thickening can be carried out by thickening to a water content lower than 35 fy. Here, before separating the solid phase, it is important to add to the suspension a suitable solvent for cold use, or syrup solvent, e.g. methanol. As a result, losses of pentaerythritol in the mother solutions are reduced to ooa 2 fy per produced pentaerythritol during the first two concentrations. Since the solid phase obtained after separating the mother liquors still contains syrups contained as moisture in the solvent, it is advantageous to wash it. For washing, it is advisable to use pure water or better solutions obtained, for example, from the pure pentaerythritol department. At the same time, the content of syrups in the primary washing solution must be lower than the content in the mother liquor after the separation of the solid phase.

Although the invention only presents a method for isolating pentaerythritol, prepared by condensation of formaldehyde and acetaldehyde in an alkaline medium, the method can also be used for isolating other di- or polyols prepared in a similar manner.

The advantage of the above-mentioned procedure is the achievement of a high amount of isolated product with full process continuity and the elimination of the causes of frequent breakdowns in operation and reasons for moving the pipeline and the thickened product.

Other combination possibilities, as well as a specific implementation of the procedure, are given in the examples.

Example 1

000 g of mother liquors I after removal of part of the calcium formate and pentaerythritol contains 7.66 wt. parts of pentaerythritol, 11.56 wt. parts of calcium formate and 5.0 wt. parts of syrup. The solution contained 7h wt. parts of water, 383 g of pentaerythritol, 578 g of calcium formate and 250 β eirups.

The solution ea was concentrated to a water content of 40 ^c ,° wt. at 80 °C under reduced pressure. After cooling the solution to 25°C, the solid phase was separated. After removal of the solid phase, comprising 286 s of pentaerythritol, 428 e of calcium formate and 50 e of siinxpov, 1260 g of mother solution 11 containing 7.72 µl by mass was obtained. of pentaerythritol, 13.0 wt. of calcium formate, 15.2 J. mass. eirupov and 64 > mass. liquid shares.

We subjected the filtrate II of the mentioned composition to processing in order to find a suitable methodology and in order to obtain the maximum amount of pentaerythritol, and therefore minimal losses. 1000 g of filtrate II was evaporated to euoh. Evaporation gave 358 β of solid product. This eme was extracted with two doses of methanol, first 500 β of then 216 (33 fi of dry matter in eume methanol). After filtering and drying the suspension, we obtained 154 e of a solid fraction with a content of 28.6 wt. of pentaerythritol (determined gravimetrically), 67.6 fi wt. of calcium formate and 2.7 fi wt. eirupov. We also determined pentaerythritol, calcium formate and syrups in the filtrate. The eu results shown in Table 1.

Table 1 Mother liquor II evaporated to dryness and extracted with methanol (solvent content 66 wt.%).

Pentaerythritol (β) Calcium formate (β) Syrups (β) The approach 77.2 130.0 151.8 Crystalline fraction 4l ,2 io4,i 4.2 Filtrate 36.0 14.9 147

Next, we proceeded by concentrating mother liquors II 1000 g to different water contents and after adding methanol to different solvent contents, we separated the solid phase from the liquid by filtration. EU results shown in other tables.

Tab. 2 Mother liquor II concentrated to 10.0 wt. fi water and supplemented with methanol (from 1,000 g batch)

Solvent content hmo i.e. solid composition M Composition of the filtrate :id PE Café Sl PE Café You 35 61.1 110.7 30.9 16.1 20.8 116 52.6 49.7 104.1 15.8 18.2 18.3 123 64.1 41.8 100.6 9.5 28.4 17.4 132

Tab. 3 Mother liquor II concentrated to 15.2 wt. % water and supplemented with methanol (from 1,000 g of batch)

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Solvent content by mass.J Solid fraction composition M Filtrate composition M PE Café You PE Café You 36.3 55.8 102.4 18.2 18.0 27.7 137.1 bo,b b9.8 99.9 17.8 18.0 25.9 149.5 5b,i b2.9 103.8 13.5 22.5 32.0 139.5 ?7.6 oh, oh 104.3 9.2 23.6 23.0 144.0 65.0 32.2 104, i 6.6 30.1 > 25.2 157.4

Tab. b Mother liquor II concentrated to a water content of 26.3% by weight (i 000 β batch)

Solvent content p _z u luuotlj Solid fraction composition w Filtrate composition w PE Café You PE Café , Yes 35.8 56.0 99.0 19.1 17.9 29.7 137.8 41.0 49.7 100.0 16.4 18.6 26.6 140.0 48.0 46.8 102.6 12.8 21.7 25.2 141.0 59.6 37.3 100.0 10.8 29.7 25.3 146.0 67.0 30.6 103.9 8.4 33.3 25.2 152.0

Tab. 5 Mother liquor II concentrated to a water content of 3b.9 fi wt. (i 000 g batch)

Solvent Content Eat limot^ Solid fraction composition w Composition of the filtrate feL PE Café You PE caf You 34.9 48.7 80.8 19.7 20.6 41.9 131.8 39.0 43.3 93.8 17.5 23.8 42.3 140.0 52.3 30.5 88.7 14.5 33.3 41.0 142.0 62.3 20.1 91.0 9.6 43.9 38.0 146.0 68.8 13.4 95.0 7.5 54.5 35.0 146.0

Regarding the results shown in tables a to 5, we state that the proportion of up to 35% by mass. of the solvent content was difficult to separate on the filter!. Until the share with this content aa let filter'. For these reasons, we supplemented the solution with different water content with methanol.

For clarity, we present the percentages of pentaerythritol and calcium formate obtained depending on the different water content at a constant amount of solvent.

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Tab. 6 Effect of water content in concentrated mother liquor 11 on the amount of obtained pontaerythritol and formate supplemented with methanol at a solvent content of 35% lunot.

Water content by mass.J Insulation PE Café 10 79.1 85.1 15.2 72.3 78.8 26.3 72.5 76.1 34.9 63.1 62.1

Tab. 7 Effect of water content in concentrated mother liquor II on the amount of obtained pentaerythritol and formate supplemented with methanol at a solvent content of 67% by mass. (handle 1000 g)

Water content by mass.J Product isolation M PE Café - 53.4 80.0 10.0 54.1 77.4 15.2 41.7 80.0 26.3 39.6 79.9 3*1.9 17.4 73.1

As can be seen from the above results, as well as from the observation that it is very difficult for the solid phase to separate the highest amount of pentaerythritol obtained from the product containing more than 30% solvent and 1 water is achieved with the lowest amount of solvent. From the point of view of mass transport 1 from the point of view of separating the solid substrate from the liquid, it is advantageous to work with a solvent content of around 35% at a temperature of 25 °C.

According to the above results, it is advisable to make the thickening with solvents up to 26% water content, with the addition of methanol to 35 5% of the solvent on the filter attachment before cold separation.

Example 2

For spraying, we used mother solution II with a content of 7.5% by mass. of pentaerythritol, 11.7 & wt. calcium formate, 20.1 wt.% of syrups and 59.2% by mass. water

For thickening, we took 500 g of mother liquor samples, which we evaporated on a vacuum rotary evaporator at a temperature of 65 °C so that the residue after evaporation contained 35% by mass. water. For comparison, in some cases we evaporated the sample to dryness and dissolved 197 89 in pure methanol in different amounts in order to obtain a comparison with the possibilities of separation of solid products. After concentration, the product was cooled to 22 °C and filtered after dilution with methanol.

The amounts of isolated products were as follows:

Water content of the product before separation Methanol content in the product Isolated product PE 5» Café 34.9 34.9 34.9 0.0 0.0 0.0 0.0 0.0 6.0 25.0 64.0 64.0 64.0 (6o °c) 50.0 34.9 55.0 56.0 42.0 77.0 75.0 56.5 75.6 85.9 48.0 51.0 59.0 ’ 91.0 87.2 86.0 80.0 90.3

Example 3

500 g of mother liquors II. containing 8.6 l '6 wt. pentaerythritol, 10.0 5» wt. calcium formate and 22.5 /□ wt. syrups were evaporated to dryness at a temperature of 80 C under reduced pressure. Methanol was added to the residue so that the methanol content in the product was 60 Je. 64.7 pentaerythritol and 88% calcium formate were obtained. When 50 # methanol was used, 67.4 % pentaerythritol and 87 % formate were obtained. When 33 $ methanol was used, 70.9 pentaerythritol and 85 5» calcium formate were obtained from the original batch.

Claims (1)

OBJECT OF THE INVENTION Process for isolating pentaerythritol and / or calcium formate from mother liquors obtained after separating the mixed salts in the first step after crystallization of the crude pentaerythritol from the reaction mixture formed by condensation of formaldehyde and acetaldehyde in the presence of calcium hydroxide by concentration, characterized in that at least it is concentrated to a water content of at least one stage of 25 to 50 wt. As a rule, it is washed with water or aqueous solutions obtained in the preparation of pentaerythritol before further treatment.