CS208294B1 - A method of purifying di- to polyols - Google Patents

Abstract

The invention relates to the field of organic chemistry and technology. The invention provides a method for purifying di- to polyols by absorbing substances polluting the final product, especially those that worsen the APHA color test. The invention can be used in removing impurities from di- to polyols prepared especially by condensation of formaldehyde with another aldehyde and/or ketone in an alkaline environment. The invention is characterized by removing pollutants, especially after the removal of cations by trapping substances of an acidic nature, especially on anions.

Description

(54) Method for purifying di- to polyols

The invention relates to the field of organic chemistry and technology. The invention provides a method for purifying di- to polyols by absorbing substances polluting the final product, especially those that impair the APHA color test.

The invention can be used in the removal of impurities from di- to polyols prepared in particular by condensation of formaldehyde with another aldehyde and/or ketone in an alkaline environment. The invention is characterized by the removal of pollutants, in particular after the removal of cations by the capture of substances of an acidic nature, in particular on anions.

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The invention describes a method for purifying dl- to polyols prepared by condensation of formaldehyde with another aldehyde and/or ketone in an alkaline environment, while substantially reducing or eliminating the use of activated carbon.

In the production of di- to polyhydroxy compounds by condensation of formaldehyde and other aldehydes and/or ketones in an alkaline environment, in addition to the desired products, by-products are also formed, which reduce the quality of the final product ^E.Berlow, R.H. Barth, J.E, Snow s The Pentaerythritols, Reinhold Publishing Corp., New York (1958), J. F. Walker, Formaldehyde, Reinhold Publishing Corp., London (1964)^,

Undesirable products are mainly formed by condensation reactions of formaldehyde itself, or of higher aldehydes or ketones themselves. The products of internal condensation of formaldehyde and other carbonyl compounds are mostly not very thermally stable, which significantly affects the thermal stability of the final products and worsens the standardized color so-called ΑΡΚΑ phthalate test. ^Malek, Trnka: Skousení náměrových hmot a náměru, SNTL, Prague (1959), 1970-Annual Book of OSTM Standards American Society for Testing and Materials p. 550, Printed in Easton USA J· The APHA test of the so-called raw di- to polyols is therefore usually above 500. Commercial products are required to have an APHA test of around 100 for reasons of preparing colorless products.

The reduction of the APHA test is most often done by physical adsorption methods, especially by adsorption of impurities on activated carbon. £H. Mouren, P. Chorin, R. Sebourin i Mam. poudres 32. 89, (1950jj. Since the above method is economically very demanding and is also associated with handling difficulties. A chemical method of obtaining products with the required APHA test has also been proposed. In this case, oxidizing and reducing substances are used for the chemical conversion of impurities and subsequent binding of impurities by chemical or physical methods. /Czech. author, certificate 184 381/. Although the above method significantly reduced the consumption of activated carbon from 3 to 5% by weight to 0.5 to 1 # by weight, it was still required to use additions of chemical oxidizing and reducing agents. A simplification of the above method is the method according to this invention.

According to the present invention, the method of purifying di- to polyols prepared by condensation of formaldehyde with other aldehydes and/or ketones in an alkaline medium, preferably after separation from the reaction solution, is carried out in such a way that the di- to polyols in the liquid phase are fed to a substance capturing anions, especially anions in the OH cycle, preferably after preliminary removal of cations chemically or by sorption on cations, optionally using activated carbon, while the di- to polyol is obtained from the thus purified liquid phase in a conventional manner, e.g. by crystallization.

Based on the finding that the impurities causing the increase in the APHA test are mainly products of formaldehyde autocondensation, which are very easily oxidized to the corresponding acids in an alkaline environment even in the presence of atmospheric oxygen, the above substances can be very advantageously captured on alkaline adsorbents, especially anion exchange resins. A whole range of ion exchangers of our and foreign production was tested, while it is important that the ion exchanger is in the OH cycle,

208 294 which is achieved by its activation with alkali solutions, e.g. sodium hydroxide solution, etc.

Since it has been shown that especially acidic substances cause the formation of di- and polyols during the preparation of the resin, expressed in units of the APHA scale, the inclusion of these in the anions significantly improves the APHA test to the required values. The use of activated carbon is not required, which is of great importance from an economic and laborious point of view.

However, this does not limit the scope of use, as a certain amount of activated carbon is not harmful, but can further improve the APHA test.

The preparation of di- to polyol solutions for recrystallization (pure crystallization node) is most often done by a known procedure, where a washed crude di- to polyol compound (e.g. pentaerythritol) is added to technologically pure, deionized water at an elevated temperature, most often at a temperature of 90 to 105 °C. After dissolving the di- to polyol, purification is preferably done by removing the cations formed in the condensation reaction stage from the solution in the first stage, or by neutralizing the solution. Thus, in a condensation reaction using calcium hydroxide as a condensing agent and a substance necessary for the mixed Cannizzaro reaction to occur, where one mole of an aldehyde or ketone formed by condensation of formaldehyde with another carbonyl compound by replacing hydrogens on the -carbon to the carbonyl carbon with a methyl group and from formaldehyde in the presence of a molar equivalent of a base, the corresponding di- to polyol and formate of the base - calcium formate are formed. Since it is soluble in water, it reacts with the raw di- to polyol to pure crystallization. Its primary removal, binding is important for the reason that it does not create an alkaline environment in which it could lead to subsequent syrup reactions, e.g. polycondensation, while the syrups formed in this way would reduce the regenerability of the adsorbent and sorbent due to their limited solubility in water. Cations can be removed using cationic ion exchangers in the H cycle or, for example, by chemically binding the cation to an insoluble compound. In the case of calcium removal, the use of phosphoric acid has proven to be effective. The resulting calcium phosphate, together with limitedly soluble polycompounds (e.g. tri- to tetrapentaerythritol in the preparation of pentaerythritol), is removed from the solution, for example, by centrifugation or filtration. The solution thus prepared is fed to the anion ion exchanger anex in the OH cycle. The chemical reaction on the ion exchangers is very rapid, so that the volumetric rate of the solution can be very high (in the laboratory, work was carried out with a loading of 2 to 20 l of solution/ 1 anex.h),

Various types of annexes were tested, both Czechoslovak products Ostion type AU, AMP, AT, AD, SC, and foreign products from the Federal Republic of Germany Levratit M-60 and MP-500A and the GDR Vofatity SBV and EA-60 and others.

Although the mentioned anions were of different activity in terms of life and regenerability, it can be said that when they were converted to OH, they all had an effect on reducing formaldehyde syrups in the pure oak solution, which was reflected in a significant reduction in the APHA test value, i.e. an improvement in product quality.

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The anion was stored in towers with a height to diameter ratio of 3 to 10 ! 1, with the solution being injected from the top, and the product being siphoned from the bottom. The towers were heated to 70 to 90 °C. The anion was regenerated after washing out the residues of di- to polyols with distilled water and 4% sodium hydroxide solution. After washing out the residues of sodium hydroxide with water, the anion was ready for further use.

Although only artificially prepared ion exchangers were tested, it is obvious that natural alkaline substances capable of binding acidic syrupy components from the solution will also perform a similar function.

For example, calcium hydroxide also fulfills this function, but due to the difficult handling and problems with its removal from the solution, its use is not optimal.

From the solution thus treated after the removal of cations and anions, di- to polyols are obtained, for example, by crystallization after cooling the solution or by evaporation of the solvent. In some cases, when substances with a low melting point are involved, such as trimethylolpropane or neopentyl glycol, or substances that are completely miscible with water, a solvent other than water can be used, such as alcohol, etc., or the ions can be removed directly without a solvent.

The advantages of using the method according to the present invention are the elimination of the use of activated carbon from the production process, which is a significant improvement and simplification of the process from the point of view of costs and handling.

Not only do problems with dosing activated carbon disappear when using more efficient powdered carbon, its removal from the solution, disposal of used activated carbon, removal of dust, etc., but also the costs of its purchase are significantly reduced. While when using activated carbon, the consumption of the agent is 20 to 50 kg/ton of polyol produced, when using anex, even after 3θ regenerations, its reduced activity did not appear. This means that the consumption per 1 ton is max. 4 kg. At the same time, the anex is filled in towers, in which it is also regenerated, so that after charging the anex, handling it in subsequent cycles is practically eliminated.

The method is also advantageous from the point of view of environmental protection, as a result of the removal of dustiness of activated carbon. The method can be used in the purification of di- to polyols from the preparation of formaldehyde or in general for binding or. separation of syrups formed by internal condensation of formaldehyde. Other advantages of using the method according to this invention, which, however, do not exhaust all methods of use, are summarized in the examples.

Example 1

Testing of the anion exchange efficiency was performed in 1.5 om cross-section columns with 15 ml of anion exchange. The columns were jacketed and thermostatically controlled to 70 °C.

A 20% by weight aqueous solution of crude pentaerythritol with a composition of crude pentaerythritol (PE-C) and a hydroxyl group content of 40.5% by weight was tested.

208 294 monopentaerythritol determined by the benzaldehyde method formaldehyde content formalin content calcium content moisture' % H ₂ 0 syrup content determined as vioinal diols

$82.4 wt. 0.025% by weight, 0.54% by weight. $0.09 mass·

14.5 $ wt. 2.32 mg/g

For comparison, the solution was refined with a small amount of activated carbon, the activated carbon was filtered off, the filtrate was contacted with 3% by weight of pentol cation exchange resin, and after filtering off the cation exchange resin, pentaerythritol did not crystallize.

The results of the APHA test of the dried final pentaerythritol are shown in Table 1.

Table 1 Effect of activated carbon amount on the APHA test of final pentaerythritol

Amount of activated carbon per pentaerythritol ($ mass») 0 θ»5 1.0 2.0 3.0 5.0 APHA test >500 >500 500 400 300 250

Before use, the anion was activated by OH cycling with 150 ml - 4% by weight aqueous sodium hydroxide solution for 1 h, then rinsed with 150 ml of distilled water to a neutral reaction.

A 20 wt. solution of pentaerythritol heated to 90 °C was added to individual towers filled with anion exchange using a separating funnel in an amount of 160 g of solution over 1.5 h. The results are summarized in Table 2.

Table 2 Effect of the type of anion used on the APHA pentaerythritol staining test

Batch: 15 ml of anex, 20% solution of crude pentaerythritol in water, dosing rate

107 g/h. Dosing 1.5 h, without activated carbon and with 0.5% wt. activated carbon.

Type of annex Wofatit Ostion Lewatite SBW EA-óO AU AMP AT AD SC M-600 MP-500A APHA test without activated carbon 150 150 >500 250 150 150 175 175 250 APHA test with 0.5% wt. activated carbon 150 150 200 125 150 125 125 200

The application of activated carbon was done before feeding the solution to the anion exchange towers.

Example 2

Through anex Ostion SC 14 ml, in a column with a diameter of 1 cm, we dosed a 20% solution of pentaerythritol in water, with the proviso that after every 200 ml of solution, the sample was cooled, the pentaerythritol was filtered off and dried. The stock solution of pentaerythritol was pre-applied

208,294 filtered to the annex tower.

The results of the APHA test are listed in Table 3.

Tab. 3 Influence of the amount of solution of 20 wt. pentaerythritol in water and regeneration on the APHA of the final product. Used anion SC - 14 ml. Flow rate of 20 wt. % solution 200 ml/h. Regeneration of anion - 4 with NaOH solution 200 ml, flow rate during regeneration 100 ml/h.

After regeneration, rinse with 100 ml/h of distilled water.

Amount of solution (ml) 200 200 200 200 200 200 200 200 200 APHA 100 125 125 150 250 100 175 200 350 Regeneration to the Olympic cycle I. II.

Amount of solution 200 200 200 200 200 200 200 APHA 125 400 500 300 450 500 500 Regeneration to the OH cycle III. IV. V.

As can be seen from the above, the activity of the anion after regeneration, although initially higher after filtering the solution than without filtration in Example 1, gradually decreased so that after repeated regeneration the anion was practically not active in reducing the APHA of the final product.

Example 3

To test the effectiveness of the anions, we used columns arranged according to example 1 and 20, a solution of raw pentaerythritol with the composition of raw pentaerythritol /PE-D/, moisture content 16.3% by weight, formaldehyde syrups 0.15% by weight, calcium 0.03% by weight, % OH groups 40.6, free formaldehyde 0.04% by weight, bound formaldehyde 0.5% by weight, pentaerythritol content by the benzaldehyde method 82.1% by weight, APHA >500. The consumption of activated carbon for the purification of pentaerythritol is summarized in Table 4.

Table 4 Effect of activated carbon amount on APHA test of final pentaerythritol from PE-D

Amount of activated carbon (1 wt.) PE-D 0 θ»5 1.0 2.0 3.0 5.0 7.0 10 APHA test 500 500 400 300 200 175 125 100

After preparing a 20% aqueous solution of pentaerythritol at a temperature of 80 °C, we added

208,294 per 1 kg of raw pentaerythritol 1 ml of 85% phosphoric acid for calcium binding.

After 1 h, the resulting suspension was removed by filtration under reflux and the filtrate was used for anion exchange testing.

Flow rate 200 ml solution/h. Column filling - 125 g anion, volume 14 ml. Regeneration of anions, unlike example 2, took place after saturation of anions with syrups by rinsing with 100 ml distilled water, 100 ml 1% hydrochloric acid, 200 ml 4% sodium hydroxide and 200 ml distilled water. We tested anions: Ostion SC, Wofatit SBW, Lewatit M-600, Lewatit ΜΡ-5θθ A. The results of regeneration cycles of anions for the APHA test of the final product are summarized in Table 5.

Tab. 5 Effect of regeneration cycles on the activity of anions in the treatment of 20% wt. solution of crude pentaerythritol -D after removal of calcium. After passing the pentM-erythritol solution through the anion, the APHA test is achieved a after 3.5 g PE/l g anion, b after 7.0 g PE/l g anion. Flow rate 200 ml/h, 14.3 vol/vol.h.

APHA test Dinrh of the annex MP-500 A ** Note SC SBW * M-óOO ³ Regenerate 1 and 150 150 200 150 ratchet b 250 250 250 175 oykly 2 and 100 150 250 100 b 125 150 450 100 and 150 150 450 175 3 b 250 250 250 250 and 100 100 250 125 4 b 150 100 400 125 and 125 125 4oo 200 5 b 125 150 500 200 and 150 150 4oo 150 6 b 200 350 500 200 and 200 250 500 150 7 b 250 250 >500 150 and 250 200 500 200 8 b 250 250 >500 200 and 200 200 250 9 b 250 250 SC-3 250 10 and 250 250 >500 250 SC-3 regeneration b 250 200 >500 250 and 250 250 >500 350 and NaCl 11 b 250 175 >500 250 and 175 175 >500 175 12 b 350 200 >500 175

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APHA test Type of annex Note SC ¹ SBW ² M-600 ³ MP-500 A ⁴ and 300 175 300 13 b 125 175 350 and 125 175 175 lb b 300 300 200 and 125 250 250 15 b 125 250 300 and 200 200 250 250 SC-3 from 16 16 b 200 250 25Ο 250 regenerate methanol and 175 175 175 200 and NaOH solution 17 b 175 175 175 200 and 200 350 25Ο 200 18 b 250 200 200 250 and 200 250 200 300 19 b 250 175 200 350 and 200 300 175 175 20 b 300 200 175 200 and 250 ·. 200 regeneraola SC-3 and b boo 250 350 - only NaOH and 350 300 200 200 22 b - 250 350 300 and 175 200 350 175 23 b 175 200 125 175 and 200 175 25Ο 200 Collection b 200 300 250 200 and 175 175 150 200 25 b 200 175 125 175 and 150 200 250 250 26 b 200 350 350 350 from reg.oyklu 27 and 125 350 25Ο 200 regeneráola anechoic 27 b 200 200 350 - only NaOH and 150 200 250 150 annex 1,2,4 150 ml 28 b 200 200 200 200 3-100ml and 125 200 175 175 from 28 reg.1,2,4 100 ml 29 b 200 300 250 350 3- 50 ml and 200 200 200 200 30 b 250 250 200 350

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The measured results in Table 5 show that

- anex in the Cl cycle is not effective,

- regeneration does not require the flushing of anions with acids,

- for regeneration, a sufficient amount of 3.6 volumes/volume of 4% NaOH is required,

- the removal of calcium allowed the regeneration to be extended from 5 cycles to more than 30 cycles.

When flushing the anion exchangers with water before regeneration, countercurrent flushing is advantageous to remove sediments from the anion exchanger.

Example 4

A combination of cation and anion exchange towers was used to remove syrups from the final product during the purification of tetramethylcyclohexanol prepared from formaldehyde and cyclohexanone under sodium hydroxide catalysis.

2 3

For purification, 10 cm diameter columns were used, packed with 100 cm of Ostion S and 100 cm of Ostion AT. A 25% by weight solution of tetramethylcyclohexanol in butanol was fed to the columns at a temperature of 100 °C at a rate of 10 volumes per volume of anion exchange. The content of formaldehyde syrups in the solution before cation exchange and anion exchange was 0.36 mg/ml, ash content 0.025% by weight, after anion exchange 0.00 mg/ml, ash content 0.001% by weight.

Example 5

3 3

The Ostion SC ion exchanger was tested in a plated column with an internal cross-section of 10 om with a filling of 100 om, 200 and 300 om^.

Calcium was removed from a solution of 28% by weight of crude pentaerythritol PE-E at a temperature of 95 °C by precipitation with acetic acid. After filtering the precipitate from the solution, the solution was passed to an anion exchange column. Composition of crude pentol: % by weight ash 0.07%,

5» wt. calcium 0.034, formaldehyde syrups 0.13 wt. %, water -16.5 # wt., free formaldehyde 0.05 5 wt., pentaerythritol determined by benzaldehyde 83.8 β wt., APHA 500. The dependence of APHA on the amount of activated carbon during recrystallization was as follows:

% wt/PE-E of activated carbon 0 0.5 1.0 1.5 2.0 2.5 3.0 5.0 7.0 10.0 APHA test >500 300 250 200 200 200 150 150 100 100

The results are summarized in Table 6.

Tab.6 APHA of the final product depending on the amount of Ostion SC anion, when loading the anion with 28 wt. of pentaerythritol C solution in a multiplicity of 10 volumes/anion volume, after the first regeneration of the anion with 7.5 volumes of 4.0 g NaOH per anion volume.

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Quantity of annex Amount of solution flowed [taij APHA isolated pentaerythritol 100 360 150 360 125 360 125 360 150 360 150 360 250 200 720 200 720 200 720 175 720 175 720 175 720 150 300 1,080 150 1,080 150 1,080 100 1,080 175 1,080 150 1,080 150

Example 6

In the column according to Example 5, a solution of pentaerythritol after precipitation of calcium with phosphoric acid in an amount of 1 om^ 85 $ acid per 1 kg of pentaerythritol E was fed through 200 cm^ of Ostion SC 30 $ anex.

The experiment was performed continuously for 4 hours at a flow rate of 200 ml of solution per 1 hour. The anion was transferred to the OH cycle with 7.5 times the volume of 4% NaOH solution per volume of the anion for 2 hours, and rinsed with water at 800 ml/hour.

After 26 hours, the APHA test of the final crystallized and dried pentaerythritol was from 100 to 150, from 27 to 30 h 250, and up to 41 h 350.

Claims (1)

9 208 294 Anion Exchange Amount Amount of Overflow Solution [tha APHA Isolated Pentaerythritol 100 360 150 360 125 360 125 360 150 360 150 360 250 200 720 200 720 200 720 175 720 175 720 175 720 150 300 1 080 150 1,080 150 1,080 100 1 Example 6 In a column according to Example 5, a 30% solution of pentaerythritol after the precipitation of calcium with phosphoric acid in an amount of 1% 85% of acid per kg of pentaerythritol E was fed through a 200 µm anion exchanger Ostion SC. An experiment was done to keep 4 L Hours at a flow rate of 200 mL of solution per hour. Anexbol converted to OH Cycle 7 by 5 times the volume of U% NaOH solution to anion exchange volume for 2 h, and rinsed with 800 mL / hr. After 26 hours, the APHA assay of the final crystallized and dried pentaerythritol was from 100 to 150, from 27 to 30 h, 250, to 350 h, respectively, for the purification of di- to polyols prepared by condensation of formaldehyde with other aldehydes and / or ketones in the base The environment advantageous after being separated from the reaction solution, characterized in that the di- to polyols in the liquid phase are fed to the substance, even the anion exchange resin, in the OH cycle, preferably after the predetermined removal of 10,208,294 cationic or cation exchange resins. optionally using activated charcoal, the precipitate and the di- to polyol from the thus purified liquid phase is obtained in a conventional manner, e.g. crystallization. Printed by Moravské tiskařské závody, provoz 12, Leninova 1S, Olomouc Price: 2,40 Kčs