CS259588B1 - Method of preparing pure methanol - Google Patents

Abstract

Distillation is carried out at pressures corresponding to the temperature range t0 = 11.3 to 64.5 degrees Celsius, where t0 is the temperature of distillate withdrawal. The methanol prepared in this way is further removed from heterogeneous impurities on a system of filters with pore openings, size 0.8 micrometers, 0.45 μτη, 0.2 μη, while the filters are connected one after the other in the order as mentioned above.

Description

The invention relates to the preparation of particularly pure methanol using physicochemical purification methods in equipment whose material resists the corrosive effects of methanol and its accompanying impurities.

Methanol is used as a rinse agent in the production of integrated circuits, therefore it must meet all purity criteria set by the consumer. The produced methanol of technically pure, pure, p. a., or chemically pure purity is unsuitable for the above-mentioned purposes, as it contains impurities that can be classified into two groups:

Group I — organic impurities that entered there as residues of unreacted input raw materials, impurities from these raw materials, and also products of side reactions.

Group II — impurities of inorganic nature, such as metal ions released from the material of the production equipment, dust particles originating from contamination of the chemical with the surrounding environment.

The above-mentioned shortcomings are not present in the method of preparing particularly pure methanol, the essence of which lies in the fact that from the raw material methanol pa, or pure methanol, or chemically pure methanol, or technical methanol, a fraction is taken at a temperature of t ₀ + 0.5 ^a C defined by the relationship using a process of continuous or discontinuous distillation under reduced or atmospheric pressure.

1615.59 ^Q ~ 7.26415 — log p

Table

242.713 where t ₀ is the boiling point in °C corresponding to the working pressure pv kPa at which the distillation is conducted.

The material of the distillation apparatus must be sufficiently resistant to the effects of methanol and its accompanying impurities.

The obtained distillate is then fed to the filtration unit. The filtration unit serves to remove unwanted heterogeneous particles. It consists of a system of several interconnected filters, with the pore size of the filter membranes decreasing in the direction of the flow of the filtered medium so as to ensure the required quality of the resulting product with respect to the number and distribution of particles and at the same time to prevent excessive clogging of the membranes with the smallest pore size. Filter systems with pore openings of 0.8 ₍ «m, 0.45 μΐη and 0.2 μΐη are used.

The method of preparation is illustrated by the following example.

Example

The input raw material — methanol of quality grade p. a. — was analyzed according to CSN 68 6484. The metal content was determined by the AAS method. Of the measured values, those whose concentration exceeds the value prescribed by the requirements for microelectronics are listed — — column A. Column B lists the concentration requirements for microelectronics.

A B

main component content 99.9% by weight vapor 12 ppm max. 5 ppm alkali (as NH3) 2 ppm max. 1 ppm aldehyde and ketone content '20 ppm max. 10 ppm free acid (HCOOHj 1.6 ppm max. 20 ppm specific resistance 0.3 MΩ. cm min. 3 MΩ . cm water content 0.44% wt. max. 0.1% by weight Pb 0.16 ppm max. 0.05 ppm To 0.7 ppm max. 0.1 ppm On 2.2 ppm max. 0.5 ppm Dust particles (heteropurities): 1 to 5 μm 25,800 max. 20,000 dm ^-3 5 to 25 μΐη 11,345 max. 3,000 ^dm3 over 25 one 830 max. 500 dm ^-3

239588

100 l of raw material was gradually dosed into the reboiler of a glass evaporator (SIMAX), the individual parts of which were sealed with PTFE seals. Pressure regulation in the apparatus was ensured by a vacuum regulator. The working pressure of the distillation was 26 kPa, the working temperature 34 + 1 ^C C. The feed rate of the raw material was 20 liters/h. The yield of the distillation process was 86% of the feed. The distillation product was dosed from the distillation head using a glass pump into a system of three series-connected filters with filter membranes, the pore size of which was 0.8 μm, 0.45 μm and 0.2 μm. The resulting product was analyzed. The analyses confirmed that the product obtained in this way meets the quality requirements for microelectronics.

Column A quality required for microelectronics.

Column B quality achieved by the above method.

A B

main component content 99.9 θ/o wt. 99.93% wt. vapor max. 5 ppm 1.3 ppm alkali (like HN3] max. 1 ppm 0.05 ppm aldehyde and ketone content max. 10 ppm 0.23 ppm free acids (HCOOH) max. 20 ppm 1.63 ppm specific resistance min. 3 MΩ . cm 5 MΩ. cm water content max. 0.01 %. wt. 0.009% wt. Pb max. 0.05 ppm 0.0045 ppm To max. 0.1 ppm 0.03 ppm On max. 0.5 ppm 0.04 ppm Heterogeneous impurities 1 to 5 times 20,000 dm ^-3 1,227 5 to 25 months 3,000 dm ^-3 1062 over 25 mτα 500 dm ^-3 459

SUBJECT OF THE INVENTION

Claims (1)

Process for preparing pure methanol from preformed methanol, characterized in that the methanol is distilled at atmospheric pressure or under vacuum in an apparatus whose material is resistant to the corrosive effects of the distilled medium, without air, taking a fraction at t ₀ + 0.5 ° C given 1,615.59 7,26415 - log p Where t ₀ is the boiling point in. ° C corresponding to the working pressure at which distillation is ap and the working pressure in the apparatus in kPa, and the distillate is passed through a set of filters with a porosity of 0,8 μΐη, 0,45 μτα and