CS259585B1 - The preparation of pure 2-propanol - Google Patents

Abstract

The starting ternary. raw material, by discontinuous or continuous. distillation, is freed from the more volatile, components- and in the presence of. entrained. from it, water is separated by azeotropic distillation,. 2-propanol is then continuously or. discontinuously. distilled^ under reduced -or· atmospheric pressure. in. apparatus resistant; in-eye, corrosive·. in-effect. 2-propanol,. while. fraction is taken at. defined. moderate, temperature and the distillate is passed. through. a set. of. microfilters. with porosity. from 0.8-to·0;2 μm

Description

The invention "relates to the preparation of high-purity 2-propanol using physicochemical purification methods from a waste ternary mixture in a device made of a material that is resistant to the corrosive effects of 2-propanol and its accompanying impurities."

2-Propanol is used as a rinse aid in the production of electronic components. For this purpose, 2-propanol must meet strict purity criteria. 2-propanol produced by conventional refining in conventional equipment contains organic impurities — residues of unreacted input raw materials, products of side reactions, and inorganic impurities — metal ions due to equipment corrosion, dust particles from contamination of chemicals with ambient air.

The above-mentioned shortcomings are not addressed by the method of preparing high-purity 2-propanol from a waste ternary mixture consisting of 81% by weight of 2-propanol, 14% by weight of water and 5% by weight of ketones (mainly acetone), which consists in distilling 2-propanol under reduced or atmospheric pressure in an apparatus whose material is resistant to the corrosive effects of the distilled medium and the distillate is passed through a system of microfilters with decreasing pore size.

The preparation of high-purity 2-propanol takes place in the following technological stages:

1. distillation of acetone from the real raw material,

2. preparation of the azeotrope 2-propanol — water,

3. dewatering of the azeotropic mixture,

4. purification of anhydrous 2-propanol.

The whole process can be carried out continuously or discontinuously. The raw material is freed from acetone by rectification on a grate column. Acetone, as the most volatile component, is removed in the distillate, the remainder is alcohol containing water and higher volatile components.

In the next stage of the separation process, an azeotropic mixture of 2-propanol — water (88 % by weight of 2-propanol, 12 % by weight of water) is obtained. Further reduction of the water content is achieved by azeotropic distillation in the presence of an entrainer (benzene, toluene, methyl ethyl ketone, ethyl butyl ether, cyclohexanol). The formation of an entrainer — water azeotrope, or alternatively an entrainer — — water — 2-propanol, allows the destruction of the water content in the azeotropic mixture of 2-propanol — water.

Anhydrous 2-propanol is purified by distillation in an apparatus resistant to the corrosion effects of 2-propanol, under atmospheric or reduced pressure. A fraction is taken at a temperature of t ₀ + 0.5 °C, whereby

1359.473 6.86451 — log p

197.558 where t ₀ is the boiling point corresponding to the working pressure in °C and p is the working pressure in the apparatus in kPa. Further details on the method of preparing high-purity 2-propanol are given in the example.

Example

The starting raw material for the preparation of high-purity 2-propanol is a waste mixture of 2-propanol, water, ketones and other impurities. It was found by analysis to contain:

main component 81.0% by weight 99.7 % by weight water 14.0% 0.1 % ketones 5.0%/year. — evaporate 9.0 ppm 5.0 PPm About 0.6 ppm 0.5 PPm To 2.0 ppm 0.1 PPm Mg 20.0 ppm 0.1 PPm Cr 1.5 ppm 0.02 ppm Fe 0.3 ppm 0.1 PPm Data in to the second pinch represent a higher given values.

In the first stage, the raw material is stripped of acetone in a 20-tiered grate column. The reflux ratio is 30:1. The process is continuous, the feed is fed to

10th stage. Acetone leaves in the distillate, alcohol containing water and higher boiling components is taken from the bottom of the column. The bottom residue from the 1st rectification is fed as a feed to the next column (20th stage grate column), where the azeotropic mixture 2-propanol — water is prepared. This azeotropic mixture is taken as. distillate, the residue consists of water and higher boiling point impurities.

A 37-tray grate column is used for continuous dewatering of the obtained azeotropic mixture. Dewatering takes place during azeotropic distillation using benzene as a carrier. The raw material and carrier are fed to the 11th stage from the top of the column. The azeotropic mixture 2-propanol — water is charged into the reboiler. After the column is emptied and distillation starts, the carrier is added. The temperature at the top of the column drops to 66 to 67 °C, and an azeotrope with the following composition begins to separate: 43.8% benzene, 18.7% 2-propanol, 7.5% water.

The azeotrope is separated into an organic phase (containing predominantly benzene) and an aqueous phase (containing predominantly water). A distillate containing essentially only the aqueous phase is withdrawn — the reflux ratio is adjusted so that separation occurs at the top of the column. The organic phase is returned as reflux.

Since a significant part of the entrainer remains in the column, the amount of benzene added is reduced to a minimum. After separation of water from the 2-propanol azeotrope — water in the reboiler begins to feed another azeotrope as a feed into the column and at the same time withdraw the Friday residue — alcohol free from water. The column regime must be adjusted so that the withdrawn 2-propanol has the required composition: H2O content below 0.1%, without benzene.

The obtained anhydrous alcohol is further purified by the above method. The distillate is then fed to a disc or candle type filter device in a stainless steel housing. The filter membranes are made of a material resistant to the dissolving effects of 2-propanol. The porosity of the filters is 0.8 ₍ um, 0.4 μΐο and 0.2 μνα, while a microfilter with a porosity of 0.2 μΐη is included before the filtrate enters the shipping container.

The qualitative and quantitative parameters of the 2-propanol prepared in this way are listed in the table:

main content] components water content vapor

Ca

Fe

K

Cu

On

Mg

99.9% by weight.

0.1%

5.0 ppm 0.05 ppm 0.01 ppm 0.09 ppm 0.0.2 ppm 0.01 ppm 0.09 ppm dust particle content:

up to 5 .um 5 to 25 μΐη over 25 μπι

000 ^dm3 1,200 ^dm3

400 ^dm3

Claims (1)

Process for preparing high purity 2-propanol from waste ternary feedstock composition of 81 wt. 2-propanol, 14 wt. water and 5% ketones, characterized in that the raw material is subjected to multiple distillation refining under reduced or atmospheric pressure in an apparatus whose material is resistant to the corrosive effects of the distilled medium, taking a fraction from the last distillation stage at a temperature of t ₀ + 0,5 ° C, where t ₀ is the equilibrium temperature in ° C relative to the applied working pressure p in kPa given by 1359,473 6.86451 - log p 197.558 and the distillate thus obtained is passed directly through a microfilter system with a pore size of 0.8 to 0.2 μΐη.