CS244273B1 - A method of refining glycerin - Google Patents

Abstract

The method of refining glycerin, produced by hydrolysis of fatty acid glycerides, containing organic nitrogenous impurities, consists in passing crude distilled glycerin through a layer of strongly acidic cation exchanger, preferably a copolymer of styrene with divinylbenzene, at a temperature of 20-120 ° C. The refining effect is increased if glycerin, purified on an acidic cation exchanger, is subsequently passed through a layer of strongly basic cation exchanger.

Description

The invention relates to the removal of organic nitrogen impurities from glycerin produced by hydrolysis of fatty acid glycerides by trapping on strongly acidic ion exchangers.

Glycerin is principally prepared either solely by a synthetic process from propylene, or by cleavage of natural organic materials, fatty acid glycerides, which is carried out with the primary aim of obtaining soaps, or fatty acids for other synthetic purposes.

Despite the original view that the preparation of glycerol by a purely synthetic route is fully predominant, the extraction of glycerin from natural materials remains important and is the only procedure for smaller economic units, since the preparation of synthetic glycerin is a source of enormous environmental pollution, or economically low profitable or unprofitable. In order to obtain natural glycerin, the raw material which can be considered as the so-called bottom lye (after soap preparation) or glycerine water (after fat breakdown) is freed from the ballasts by precipitation after prior pH adjustment and in the vapor phase the liquid fraction is vacuum thickened to contain about 80% glycerin. Upon concentration, inorganic salts possibly still present in the solution are also removed. The crude glycerin obtained is still distilled under vacuum and can optionally be freed from color by mixing with 3 - 1% hot activated carbon. This best part, respectively.

The process used exclusively in our country does not prevent a certain proportion of nitrogenous substances resulting from the degradation of organic materials during processing from getting into the final product and thus the resulting product is not equal in quality to the synthetic glycerin and is not suitable for all purposes.

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In another method, ballasts having the nature of acids, bases, or salts are removed prior to concentration to the crude glycerin by treatment with ion exchangers, i.e. granular polymers bearing strongly alkaline or acidic functional groups. (E. Kreicar, A. Kopecky, Chem. Avg. 11/36, 660, 1961). The method has not been adopted here, probably because of its high demands on labor, the necessity of frequent regeneration of ion exchange beds and the consequent generation of large amounts of waste water.

It has now been found that organic nitrogenous substances which can be detected after thin-layer chromatography, for example with ninhydrin, have a distinctly alkaline nature and can therefore be removed by treatment with acid-functional ion exchangers, cation exchangers. Furthermore, it was surprisingly found that the migration ability of alkaline impurities

V is so large that they are well removed from highly concentrated glycerin solutions (> 80%). This has the practical significance that refining can only be carried out with the final distillate, where other alkaline substances are not present, so that the capacity of the ion exchanger based on the amount of glycerine processed is large, which reduces the regeneration requirements and removes the above mentioned negative circumstances. At the same time, as has been found below, glycerin is also discolored, eliminating the need for possible discolouration by activated carbon ·

The present invention provides a process for refining glycerin produced by hydrolyzing fatty acid glycerides containing organic nitrogen impurities. It consists in passing the crude distilled glycerin through a layer of a strongly acidic ion exchanger, a cation exchanger based on a raacroretic acid polymer, preferably styrene-divinylbenzene copolymers whose exchange groups are, sulfonic acid groups at a temperature of 20 - 120 ° C, preferably at 40 - 80 ° C. Glycerin is passed through the bed until the charge efficiency is depleted, as determined by analytical assay.

The effect of the refining process is further enhanced if the refining product is subsequently passed through a basic anion exchange layer. This removes the trace acidity of the refined acid

- 3 244 273 glycerine purified solely by acid cation exchanger and foreign odors, also degrading the product.

Higher quality glycerin is used primarily in cosmetics, pharmacy and explosives.

The method of the invention is described in more detail in the following examples:

Example 1

A highly acidic cation exchanger based on the macroreticular styrene-divinylbenzene copolymers, the only exchange groups of which are the sulfone groups on the aromatic nucleus, trade name Ostion KSP, was used for refining. His volumetric capacity was

2.2 mval / ml. Before its use it was recycled several times ie it was alternately converted into H ⁺ and Na ⁺ cycle as usual in this technique, so the ion exchanger was alternately treated with dilute solution of hydrochloric acid (c = 2 mol.l-^) and sodium hydroxide (c The acid exchanger was thoroughly removed by washing with distilled water prior to the change of the reagent, and the ion exchanger was transferred to an H ⁺ cycle in the last pretreatment step and the cation exchanger slurry was introduced into a 13 mm diameter chromatography column. After the excess water had dripped down to the ion exchanger level, the cartridge was overlaid with technical glycerin, which contained nitrogenous substances on the chfomatogram as intense as the 0.9% solution, and was markedly yellow in color. Glycerin was left free for flow filling.

The refractive index was monitored in the effluent and, after stabilization, pure glycerin was collected, which contained less impurities than the method used to detect, i.e., a standard glue solution of 0.05% by mass, was clear-water-clear. At a temperature of 24 ° C, a proportional force equal to 15 cm of the height of the glycerin column above the ion exchanger layer was flowing through the device at a steady speed of 3.2 g / h. The experiment was terminated after treatment with 600 g of glycerin, with no sign of decreasing quality observed in the last batches of the product.

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After evaluating the quality of glycerin, the following procedure was performed:

The glycerin of interest was loaded onto the center of a Silufol UV 254 chromatography plate along with an equal amount of standard, which was a solution of Cl in glycerin at concentrations of 1f 0.5;

0.1 and 0.05%. The chromatogram was developed with a 3: 2: 1 mixture of isopropyl alcohol, pyridine and water. After removal and drying, the chromatogram was then sprayed with 0.3% ninhydrin in ethanol and developed by heating to 110 ° C for three minutes. The relative content of nitrogen impurities was determined by comparison with the color intensity of the standard substance solutions. The refinement of the impurity concentration was then performed with a narrower range of standards, eg in the range of 0.5 to 1.0%.

Example 2

The experiment in Example 1 was repeated except that the ion exchanger column and the glycerin column above it were tempered by a jacket in which the thermostat water was circulated to 50 ° C. The average glycerin flow rate at this temperature was 23 g / h. The first traces of coloring of the product, which were, however, much more noticeable than the raw material, appeared after the flow of 630 g of glycerin. This amount therefore determines the capacity of the ion exchanger for the given conditions.

Example 3

The spent ion exchanger charge of Example 2 was first freed of glycerin by washing with water and then recovered. Regeneration was achieved by mixing the cartridge with 40 ml of sodium hydroxide solution (c = 2 mol.l -1) at 95 ° C, removing the caustic solution by filtration and thoroughly washing it with distilled water directly on the filter, and transferring again to an H ⁺ cycle by stirring twice. ml of hydrochloric acid solution (c = 2 mol.I * ^-1 ), filtering and washing the acid traces with distilled water.

With this regenerated ion exchanger charge, the experiment described in Example 2 was repeated. The flow rate of the glycerin through the charge remained unchanged, until 620 g of glycerin were purified until the first traces of coloration appeared.

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The experiment described in Example 2 was repeated except that the apparatus was heated to 80 ° C. Each time after the first discolouration of the effluent product was observed, the experiment was discontinued and the cartridge was regenerated as described in Example 3.

, V cartridge Glycerin flow rate (g / h) filling capacity (G) original 67 620 I. regeneration 67 540 II. regeneration 66 510 III, regeneration 66 490

Example 5

The experiment described in Example 2 was repeated except that another Ostion KSP column was loaded with a strongly basic anion exchange resin based on a styrene divinylbenzene copolymer containing dimethylammonium functional groups, commercially available as Ostion AD, introduced into the OH cycle. The column diameter was 13 mm, the ion exchanger filling height was 5 cm. After passing the glycerine through both cartridges, the product had the same properties as described in Example 2, but did not exhibit trace acidity (at a level of 5.10 ^- val / kg) as was the case with products treated only by passage through an acidic ion exchanger. appeared after the passage of glycerin only through an acidic ion exchanger.

Example 6

The experiment described in Example 2 was repeated except that the ion exchanger column jacket was tempered with silicone oil during displacement of water at 90 ° C and after filling the column with glycerine up to 120 ° C. The first 300 ml of the flow-through cartridge were water-soluble and did not contain foreign substances detectable by thin-layer chromatography.

Claims (2)

A process for refining glycerin produced by hydrolyzing fatty acid glycerides containing organic nitrogen impurities using an ion exchanger, characterized in that the crude distilled glycerin is passed through a layer of a strongly acidic ion exchanger, a cation exchanger based on a macroreticular polymer, preferably copolymer, styrene and divinylbenzene. the exchange groups are sulfonic groups at a temperature of 20 - 120 ° C. 2. A process according to claim 1, characterized in that the glycerin purified on an acidic ion exchanger, cation exchanger, is subsequently passed through a layer of basic ion exchanger, an anion exchanger.