CS259586B1 - A method of preparing pure xylene - Google Patents

Abstract

Xylene is discontinuously or continuously rectified under atmospheric pressure or vacuum, without access to air. A fraction is taken at a defined mean temperature, which is the equilibrium temperature with respect to the working pressure. The working pressure is from a pressure interval of 8 to 101.32 kPa. The distillate is directly passed through a system of microfilters with a porosity of 0.8 µm, 0.4 µm and 0.2 µm.

Description

259536

BACKGROUND OF THE INVENTION The present invention relates to the preparation of especially pure oxylene using physico-chemical purification methods.

Xylene is used as a rinse aid in the manufacture of integrated microelectronic circuits. The xylene used for this purpose must comply with the stringent purity criteria that conventional commercial purity products do not. The impurities found in these products can be classified in two groups: I. Group - impurities of organic character, which represent residues of feedstock, impurities of feedstock as well as products of side reactions. II. a group - impurities of an inorganic character, e.g., metal ions released by the corrosion of a manufacturing apparatus, dust particles in contact with ambient air.

The aforementioned drawbacks are not due to the preparation of particularly pure xylene, the essence of which is that the pure xylene produced, or pure, or "polymerized" is continuously or discontinuously distilled under reduced or atmospheric pressure in an apparatus of which the material is resistant to corrosion by xylene, taking off the fraction at a temperature of ± 1 ° C given that it is 1472,733, 6,14049 log p - 217,808 where the boiling point corresponds to the working pressure in ° C and is the working pressure in the distillation apparatus in kPa.

The distillate is subsequently passed through a system of microfilters which ensure that the product from the hillfort of the quantity and dispersion of the heterogeneous impurities is obtained as follows: particle size 1 to 5 μτα5 to 25 μίαnad 25 μία per 1 dm'max. 20 000max. 3 000max. 500 4 of the trikone shall be prepared from commercial species of oxylene as follows:

Xylene of commercial purity is pumped through the feeder and sprayed with a metering pump into the rectification device. Rectification can be conducted continuously or discontinuously. The pressure-temperature conditions in the distillation plant space are equilibrium, the working pressure being adjusted in the range from 8 kPa to 101.32 kPa. The product withdrawal temperature is = 1 ° C, with t0 equilibrating the xylene temperature at a given working pressure of the aforementioned working pressure range.

The distillate is trapped in the master by preventing air from entering the master. The distillate is subsequently passed to the filtration stage from the distillation master. The filtration is carried out in a multistage manner such that the filters are placed one behind the other and the size of the membranes decreases in the direction of the flow of the filter medium. The product after rectification and filtration is analyzed for chemical heterogeneous impurities. The filter and distillation apparatus must be made of materials resistant to the action of xylene and its accompanying additives. Example

The "polymerization" xylene was pumped into the reservoir at 100 liters and was subsequently fed through the glass pump at a rate of 18 liters / h into a SIMAX glass-bottom cooker with a short-refill packed column. The working pressure in the column was 101.32 kPa. The product was collected with distillation beginning t0 = 137.5 degrees Celsius and the end of distillation at t = 139.5 ° C. The product is distilled from the glass pump by three-stage filtration. Filter housings were made of steel grade 17. Filter membranes used to remove heterogeneous particles destilate pore sizes: 1st degree 0.8 μϊη 2nd degree 0.4 μϊη 3rd degree 0.2 μϊη

AND

Product analysis confirmed by comparison with raw material that the product conforms to ipre microelectronics:

The size of the pores of the pores of the membranes in the individual filtration stages is decreasing in proportion to the flow of the filtered medium.

High-purity xylene quality for microelements

Claims (1)

259586 Table Input Xylene by Xylene by Raw Material Method of Invention Microelectric Quality Requirements Main Ingredient Content - Total Isomers 99.1% 99.8% 99% Evaporation ppm 12.0 2.5 5.0 Water Content ppm 20.0 14.0 100.0 acidity (as HCl) ppm 6.5 1.3 5.0 lead ppm 0.15 0.02 0.05 arsenic ppm 0.15 0.01 0.01 sodium ppm 0.5 0, 19 0.5 calcium ppm 0.7 0.23 0.5 liters ppm 0.02 0.01 0.02 potassium ippm 0.2 0.1 0.1 content of heterogeneous particles 24 670 990 20 000 1 to 5 μτα 22 SUMMARY OF THE INVENTION A method for the preparation of pure xylene, characterized in that xylene is distilled at atmospheric pressure or vacuum in a distillation apparatus made of a material resistant to the corrosive effects of the distilled medium without air the mean temperature of the distillate withdrawal t0 + 1 ° C, depending on the chosen working pressure, is given by 1472.733 0 6.14049 - log p 217,808 where t0 is the boiling temperature corresponding to the working pressure in ° C and the working pressure in the distillation apparatus is in kPa, and the distillate thus collected is followed by a filter on a microfilter system with membrane porosity of 0.8 µm, 0.4 µm and 0.2 µm.