SU487057A1 - The method of extraction of glycerol and glycols - Google Patents

Description

one

The invention relates to a method for isolating glycerol and glycols from the products of the hydrogenolysis of carbohydrates, which are widely used in various areas of the national economy.

A method is known for isolating glycerol and glycols from the hydrogenation product obtained by hydrogenolysis of carbohydrates by double evaporation of the hydrogenation product, treating it with an adsorbent, and distillation. First, the glycols are distilled off, and then from the bottom residue - glycerol with superheated steam.

The disadvantage of this method is a rather complicated technology, including two-stage evaporation, cleaning of adsorbents, filtration. In addition, the use of high temperatures — the release of glycerol and glycols and hydrogenation by distillation leads to a significant decomposition of the products, especially glycerol, pitch and, consequently, to an increase in losses and a decrease in the quality of the target products.

To simplify the process technology, improve the quality and reduce the loss of the target products, it has been suggested that one stripped off hydrogenated product be treated with acetone at 99-101 ° C and a pressure of 3-4 atm.

Glycerin and glycols are extracted from carbohydrate hydrogenolysis products with a threefold excess of acetone. Then a layer of acetone with dissolved glycols and glycerin in it is separated from the insoluble residue, the temperature is lowered, and a heterogeneous system is obtained consisting of two phases: pacTiBOpa acetone, glycerol and glycols, and a solution of glycerol and glycols in acetone. Separating these solutions is not difficult, since glycerin, glycols and acetone have a large difference in density. Ward off acetone from glycerin and

glycols are also easy due to the large (over 100 ° C) difference in their boiling points. The mixture of glycols and glycerol is divided into known substances into known methods. Due to the low solubility of higher

alcohols in acetone at 100 ° C they practically will not contaminate glycerol and glycols; therefore, special subsequent purification of the target products from higher alcohols is not required. Acetone after distillation without any

additional purification can be reused for extraction.

After two consecutive extractions with a three-fold excess of acetone, the glycols are extracted by almost 100% from the hydrogenate.

and up to 95% glycerol (from its initial content in the hydrogenation product), and after the first extraction, glycols are mainly removed (about 80%), and after the second - the acetone layer contains up to 70% glycerol, i.e.

a glycol rich fraction is obtained.

and a fraction enriched in glycerol. Such a distribution of glycol and glycerol by extraction steps greatly facilitates their subsequent separation into individual substances.

Example. SO g. Of hydrogenation produced by hydrogenolysis of carbohydrates containing (in%): 14 higher polyols (mainly sorbitol), 50 glycols (ethylene glycol and 1,2-propylene glycol) and 32 glycerol, twice successively mixed with a three-fold excess of acetone at 100 ° C and a pressure of 3-4 atm in a steel autoclave with a working volume of 250 ml for 1 hour. The upper layer, i.e., the acetone layer with the glycols and glycerin dissolved in it, each time after settling iB for b-10 min at 100 ° C is drained, while the undissolved higher alcohols remain in the raffinate. Then drained a-cetone layer was incubated for 1 hour at room temperature. In this case, two layers are formed (a layer of acetone containing 20-30% glycerol and glycols, and mixtures of glycecerin and glycols, comprising 3-5;% acetone), which are separated in a separating funnel. As a result of two repeated extractions with a threefold amount of acetone, practically polygly the glycols and up to 95% glycerol are extracted from the hydrogenate. The extractant is distilled off at atmospheric pressure and 70 ° C, after which the distilled adeton is reused for extraction. The mixture of glycerol and glycol is separated by vacuum distillation. Non-sparking, stranded residue of higher alcohols is returned to re-hydrogenolysis. Indicators of glycerol released:

Density at 20 ° С,, 2570

Content%

pure glycerin98,2

ash0,002

Non-volatile organic residue 0,015

a.krolein and other reducing substances are absent fatty acids are absent

Reactions, 1 ml 0.1 n. solution of HC1 whether KOH 0.20 ml of KOH

The saponification ratio (ester content) per 1 g of glycerin, KOH 0.54 mg

The yield of purified glycerin,% of the charge 70

Subject invention

The method of glycerol and glycol extraction from hydrogenation produced by hydrogenolysis of carbohydrates using evaporation and distillation, characterized in that, in order to simplify the process, improve Quality and reduce losses of the target products, one stripped off the hydrogenation product is treated with acetone at 99 ° C and pressure 3- 4 atm.