SU267625A1 - METHOD OF DEEP DRYING AND THIN CLEANING OF ACID ACID from ANT - Google Patents

Description

The proposed method relates to adsorption purification "to the separation of substances that differ slightly in molecular size.

The production of acetic acid by the oxidation of eye fractions is associated with the formation of formic acid and a number of other fatty acids, as well as water. When cleaning with acetic acid, the special task of separating a ternary azeotropic mixture — formic acid: acetic acid: water — arises. If water is removed from the system, for example, by the adsorption method, the remaining anhydrous mixture of low molecular weight fatty acids is easily separated by distillation.

High purity acetic acid is required to obtain viral citrate. It should contain no more than 0, water and 0.05% formic acid. In order to increase the efficiency and increase the service life of zinc-acetate catalysts for the synthesis of vinyl acetate, drying of acetic acid to the residual water content of OD% and lower is desirable.

Separating and drying a mixture of acetic and formic acids is a difficult task. If the differences in IB size of water molecules and acetic acid are relatively large and provide the possibility of deep drainage of the latter using a number of samples of porous glasses — molecular sieves, the difference between the sizes of water molecules and formic acid is much smaller moment) of acetic acid and water is much more than between acetic acid and formic.

The presence of formic acid in acetic acid contributes to the displacement of water from the sorption space, and its molecules block the entrance windows of the sorbent, inhibit the diffusion of water and reduce its sorption.

A known method of separating a mixture of acetic and formic acids by rectification. In this case, water is first separated, and then acetic acid is separated from formic acid. To obtain a pure product, a two-stage azeotropic distillation is necessary. However, even in this (best) case, it is possible to obtain acetic acid with a purity not higher than 99.80 / 0, as the limit is 99.9%.

In order to obtain high-purity acetic acid, a method has been proposed that accelerated acid is passed through synthetic mordenite or, first, through porous glass and then through synthetic mordenite. The proposed method makes it possible to obtain acetic acid with a purity higher than 99.9% with a residual water content of not more than 0.05o / o and m of favic acid no more than 0.01-0.02%.

The use of porous glasses for this purpose is advisable to the star of the low temperature of their desorption regeneration (120-130 ° C) and the efficiency of the process. The experiments also revealed the possibility of lowering the temperatures of desorption regeneration of mordenite to 150-250 ° C (depending on the desired depth of drying).

The results were obtained on a ternary mixture — acetic acid, containing impurities of water, and formic acid — about a percent — fractions of a percent each. This indicates the possibility of organizing technological processes for obtaining high-purity acetic acid using porous glasses — molecular sieves and mordenite.

Below are examples of the implementation of the proposed method. The initial triple mixture is acetic acid: formic acid: water In a ratio of 98.08: 0.6: 1.32 (weight fl / o).

Example 1. On a sample of porous glass obtained from erc. % SiO2) leached at 1N. HC1 at 95 ° C for 5 days, in one pass a mixture of acetic and formic acids with a water content of 0.030 / 0, was obtained. Such a mixture can be either easily rectified, or effectively purified from formic acid using mordenite.

Example 2. On a sample of porous glass prepared by leaching erkleza (granulate), sodium borosilicate glass of composition Na-9.5 / 28.5, in 0.5 n. HC1 at 95 ° C

for 5 days, in one pass, a mixture of acetic and formic acids with a water content of 0.03% was obtained.

Example 3. On a sample of porous glass obtained from erklez (granulated), sodium borosilicate glass of composition Na-12.2 / 35.3, leached in 3 liters. HC1 at 95 ° C for 5 days, in a single pass, a mixture of acetic and formic acids with a residual water content of 0.05VoPr and p 4 was obtained. -10/30 leached in 3 n. H2S04 at 95 ° C for 5 days, in one pass a mixture of acetic and formic acids was obtained with a residual em water content of 0.06%.

The full dynamic capacity of porous glasses — molecular sieves with respect to water reaches 4–6 wt. e / o.

Example 5. A sample of mordenite was obtained in one Pass. Acetic acid, completely purified of formic acid (residual content of 0.01%), dried to a residual water content of 0.02 V / o, t. A. acetic acid purity 99.93%. Full dynamic water capacity up to 4-6 wt. “/ O, for formic acid 2-4 wt. %

Subject invention

A method of deep drainage and fine purification of acetic acid from formic acid, characterized in that, in order to obtain high-purity acetic acid, acetic acid is passed through synthetic: mordenite or first through porous glass, and then through synthetic mordenite.