CS224840B1 - Pentaerythriol manufacturing process - Google Patents

Description

The present invention provides a process for the production of pentaerythritol and its recovery from reaction solutions.

In the preparation of pentaerythritol, the procedure for obtaining pentaerythritol from its reaction solutions is selected depending on the kind of the alkaline reagent used. When using sodium hydroxide after neutralization of the solution to pH 7.8 to 8.0 with formic acid, the solution is concentrated to a specific gravity of 1250 to 11.0 kg / kg at 50 ° C and crystallized at 10 to 25 ° C after crystallization. the crude pentaerythritol is separated from the mother liquor containing sodium formate. Lowenheira F, A ·, Moran Μ. K .: Industrie! Chemicals, John Wiley and Sous (USA) 1975} E. Berlow,

R.H. Barth, J.E. Snow: The Pentaerythritols Reinhold Publ.

Corp. New York (i958) J · If calcium hydroxide is used, the calcium ions are removed by precipitation with sulfuric or oxalic acid prior to thickening the solution, the resulting low-soluble calcium sulfate and / or calcium sulfate being formed. insoluble calcium oxalate is removed from the solutions by filtration. After separation,

Separates of Peters M. S, Quinu J. A., Ind. and Eng. Chom, 47, 1710 (1955)].

In the case where the use of calcium hydroxide is used to neutralize the acid, which forms more soluble calcium salts, e.g. formic acid, the solution is concentrated so as to terminate in pentaerythritol, the precipitated calcium formate is hot filtered, and after cooling the crystallized pentaerythritol is removed by filtration £1. Koudelka, P. Kl? U-

In this case, a possible pentaerythritol residue, respectively. to obtain a calcium formate as a mixture thereof by concentrating to the lowest possible water content at temperatures up to 80 ° C and after separating the syrups by extraction with a suitable solvent, for example methanol back into the reaction solution before concentration. This will increase both the isolated pentaerythritol and calcium tartrate.

Another method utilizes multiple fractional crystallization to obtain as large amounts as possible, progressively thickening the mother liquor. In the process of condensation of aldehydes with sodium hydroxide due to the high solubility of sodium tartrate (71 ° C at 15 ° C or 202 g at 100.5 ° C in 100 g of water), it is already possible to obtain at the first concentration step up to $ 75 of pentaerythritol produced, but the pentaerythritol produced contains an increased amount of dipentaerythritol. In the case of calcium hydroxide technologies, if the calcium ions are removed by precipitation, the efficiency of the isolation is also very high. However, in these cases, the formic acid released is diluted as it is not isolated from the condensate obtained from the evaporation of the solutions. If calcium ions are not removed by precipitation but calcium formate is present in the solution, because of its reduced solubility, isolation is most often done by concentrating the solution to a solution below the saturation limit to pentaerythritol, which is obtained after the insoluble calcium formate is separated. Hot, crystallized from the cooled solution.

When working with calcium hydroxide as a condensing agent, the last proportions of formaldehyde are removed by converting it into JTe forms. Berlow, Barth R. H., Snow J. "The Pentaerythritols Am. Chem. Soc. Mon. Reirih Publishing Corp ·

New York (1958) J Because the forraozes at elevated temperatures under these conditions are subject to variations affecting product quality parameters, in particular the APBA test, they are concentrated at temperatures of 50 to 80 ° C «For these reasons, pentaerythritol recovery is in one step relatively low so that the division needs to be repeated a number of times, which increases the labor demand for the machine, but also increases the energy consumption of the operator and the loss of product. These disadvantages are overcome by the process of our invention. _{224 M (J}

According to the present invention, a process for producing pentaerythritol using calcium hydroxide as a condensing agent, using condensation inhibitors from formaldehyde alone, preferably at least one boron and / or manganese compound, is effected by concentrating the solution and / or separating the calcium formate. at least one stage is carried out at a temperature of 81 to 110 ° C, preferably in the presence of oxygen.

The advantage of the method according to the invention is that already in one stage it is possible to achieve substantially higher amounts of isolated pentaerythritol and / or dipentaerythritol and calcium formate, reduce losses of the main and byproduct, high quality parameters of the final product, simpler process and equipment and higher efficiency of the separation process.

The condensation inhibitors of formaldehyde alone inhibit the formation of glycol aldehyde or its condensation products in the reaction portion, but their presence also suppresses the formation of syrups in the formaldehyde rectification process, where, in the presence of oxygen in particular, it suppresses the formation of color products by subsequent reactions of condensation products. In addition, in a continuous process .zaradením least one piston-type reactor before neutralization reaction can be ensured, when working with a small excess of formaldehyde, adjusting the reaction time, respectively, reaction temperature, reaction conditions such that _f originated so bright syrups, formaldehyde condensation products When using a higher excess of formaldehyde, it is again possible to degrade this by rectifying the solution after neutralization. The solution thus obtained is concentrated, preferably in a multi-stage evaporator, wherein either. the final evaporator step and / or the separation of the calcium formate from the suspensions is carried out at a temperature above 80 ° C, preferably 90-95 ° C. Upon concentration, especially at higher temperatures, it is convenient to introduce oxygen into the solution, e.g. in the form of air, which inhibits the formation of colored products.

-ί224 840

The advantages of said process for obtaining crude poutaorythritol and / or dipentaerythritol from its reaction solutions are already due to the water solubility of pentaerythritol and dipentacrythritol. Thus, while at a temperature of 80 DEG C., 44 g of tritol pentaery are dissolved in 100 .mu.g of water, so at a temperature of >

g, at a temperature of C95 ° C it is 72 g and at a temperature of 100 ° C 85 g. By subculture to 30 ° C, when the solubility of 8.4 g nu 100 g water, crystallizes from a solution saturated at 80 ° C 35.6 g, at 90 ° C 52.6 g at 95 ° 0 63 6.6 g and at 100 ° C 76.6 g of pentaerythritol with an equal content of 100 g of water. This is similar for dipentaerythritol where the solubility at 30 ° C is 0.3 g per 100 g water, at 80 ° C 3.9 g, at 90 ° C 6.01 and at 100 ° C 9.01 g per 100 g of water.

The advantage of this process is the higher amount of pentaerythritol obtained already in the first stage, which reduces the handling losses of the main and by-products. By isolating the products, it thereby makes it possible to reduce the losses of the product in the mother liquor from the manufacturing process while achieving the same or higher quality parameters of the final product.

The way of carrying out the process according to the invention can be seen from the examples of use which do not exhaust all possible combinations. The process can be used not only for the preparation of pentaerythritol but also for other di-polyols attached from formaldehyde.

Example 1

Pentaerythritol is prepared in a 5 L sulfonation flask equipped with a thermometer, stirrer and reflux condenser. The flask is immersed in a tempered bath where the reaction is carried out at 40 ° C - 1 ° C. 20 moles of formaldehyde, 0.2 g of manganese sulphate are added to the flask and after tempering to 35 ° C add

2.4 moles of calcium hydroxide in the form of 10 wt. sodium ,.

After the addition of formaldehyde, air is started to flow through the capillary through the bad condenser at a rate of 1 L per minute. After the metering of the hydroxide, 4 mol of acetaldehyde is metered in the form of a 50% solution

-224 840 within 4θ minutes. After the acetaldehyde dosing is complete, the reaction conditions are maintained for 20 minutes and the reaction solution is heated to 60 ° C. After the formaldehyde content was reduced to 0.1. the solution is neutralized with formic acid to pH 7 ·

Then the solution is concentrated at 100 ° C on a rotary evaporator with an inlet air to a pentaerythritol content of 35% by weight, the calcium formate is filtered at 100 ° C, washed with 80 ° C warm water 10 ° to formate and the filtrate is cooled to 30 ° C over 1 h. Crystallized pentaerythritol is filtered off *

After drying, the weight of the crude pentaerythritol is 3 ^ 5 e, i. 84% of the amount produced, the weight of the isolated calcium formate is 215 e, i. 68.9% of the amount produced (Pentaerythritol contains 88% mono- and 11-dipentaerythritol).

The mother liquor is concentrated to 20 [mu] l of water at 80 [deg.] C. and 226 g of methanol, i. to 55% dry matter. After cooling to 30 ° C, a mixture of pentaerythritol and calcium formate containing 37.5% of pentaerythritol and 86% of calcium formate, i.e. a pentaerythritol content, is obtained by filtration. 8.6% pentaerythritol and 27.6 $> formate made products.

In total, 92.6% of crude pentaerythritol is recovered from the amount produced and 96.5% of the calcium formate produced. If otherwise unchanged conditions, an attempt is made to reconcile according to the prior art, i.e. an inhibitor-free and air-purged experiment under otherwise the same conditions to achieve approximately the same pentaerythritol and calcium tin formulations, except that the reaction solution is brown after completion of the experiment. After concentrating the solution to a saturated solution of pen taerythritol at 80 ° C, at that temperature 156 e of calcium formate 50 are filtered off from the amount produced and, after cooling, the crystallized pentaerythritol is crystallized. The weight of the crude pentaerythritol is 321.7 e, i. 73.9% of the quantity produced.

The filtrate was further concentrated to 20 $ water content. Dilute with methanol to 55% dry matter. After cooling to 30 ° C, a mixture of calcium formate 143.5 a and 73.3 p pentaerythritol, i.e. the pentaerythritol, is filtered off. we get 90.8 $> from the raw foam produced-

224,840 erythritol, i. 1.8% less alce in the first case and 96% of the produced calcium formate, i. 0.5% less than in the first case.

Purification of the crude pentaerythritol consumes 2% of the activated carbon in the first case and 5% in the second case. activated carbon to achieve APHA 200 and the difference in pentaerythritol yields is increased by $ 4.8 in favor of the present invention.

Example 2

The reaction solution of pentaerythritol made with a molar ratio of formaldehyde-acetaldehyde 8: 1 at a temperature of 30 to 46 ° C, with an initial formaldehyde concentration of 20% by weight. in the presence of 0.001 wt. % manganese in the form of soluble manganese formate and 0.01 wt. % boron in the form of sodium tetraborate in the feed contains 8 wt. formaldehyde. Formaldehyde is distilled off under pressure on a 10-bar pressure rectification column at 140 ° C under. presence of oxygen. Solution from the pSty column outlet with formaldehyde content below 0.1 p. The mixture is further concentrated to a multi-column evaporator, the temperature in the last member of the evaporator being 95 ° C. The solution is saturated to pentacrythritol at 92 ° C. The calcium formate suspension is separated on a filter or centrifuge, the solution is next to the crystallizer, who after cooling to temperature. Penfcaerythritol crystallizes. The crude pentaoxy tritol is filtered off and dried and weighed. 83 g of pentaerythritol x 1000 g of the reaction solution are obtained, i. 86 ~! % of the quantity produced. In the case that the thick solution variation is made from the reaction solution without borax and raongunate formate in the rectification of formaldehyde, this is obtained by 10% by weight. less and the pentaerythritol obtained from the solution after concentration at 80 ° C is lived, i. of lower quality than in the first case, and 77 g of pentaerythritol are obtained, i. 79,9 $ quantity produced.

In the case where the concentration from the inhibitor-free solution is carried out under the same heating conditions as the '1224 840 in the first case, a pale to brown pentaerythltol is obtained, while purifying to the same ΛΡΤ1Λ requires 5 times the activated carbon and purified pentaerythritol. is 6 fu smaller than in the first case.

If, using formaldehyde condensation inhibitors, the concentration of the XObi solutions at 80 ° C to such a water content is such that 66 g of pentaerythritol remains in solution after concentration of 100 g of water and the solution is heated to 95 ° C before separating the calcium formate, neither pentaea tritol will change, nor does the quality of the final product decrease

Claims (1)

A process for the preparation of pentaerythritol using calcium hydroxide as a condensing agent using condensate formation inhibitors from formaldehyde alone, preferably at least one boron and / or rangoon compound, characterized in that the concentration of the solution and / or the separation of the calcium formers in at least one stage is done at a temperature of 81 ° to HO 0 _°, preferably in the presence _of oxygen