SU893852A1 - Method of hydrogen chloride purification - Google Patents

Description

one

The invention relates to the purification of hydrogen chloride and can be used in the production of high purity hydrogen chloride used in the technology of epitaxial structures.

A known method of purification of hydrogen chloride, which consists in cooling the hydrogen chloride to -OC. In this case, the purity of organochlorine impurities m 1 is achieved.

The disadvantage of this method is the high content of carbon dioxide, acetylene, moisture and other impurities in hydrogen chloride.

The closest to the proposed technical essence and the achieved result is the method of purification of hydrogen chloride from chlorine, moisture, carbon dioxide and hydrocarbons, consisting in the rectification of pre-liquefied gas at a temperature of from -80 to. The known method allows to obtain a product with a hydrocarbon content of 7.6-10-5%, € 0, -1.10-5%, CU5-10% and 2-10-4% 2.

However, achieving this degree of purity is associated with large losses of hydrogen chloride, the product yield is only 50-56%.

The purpose of the invention is to increase the spin of the fraction containing 0,

ten

C02.

The goal is achieved by the fact that in the method of purification of hydrogen chloride by means of distillation of liquefied gas, the rectification is carried out at a temperature of from -k to S.

Before rectification, hydrogen chloride is purified with activated carbon, pretreated with hydrogen chloride, and then dehydrated

20 fractional condensation at temperatures from -5 to -80C.

To ensure that the heat of adsorption of hydrogen chloride itself does not dissolve

it heated activated carbon and thus did not reduce its adsorption capacity with respect to organochlorine impurities, the adsorbent was pre-treated with hydrogen chloride. Raising the temperature of fractional condensation above does not allow achieving the maximum yield of this fraction, lowering the temperature below is accompanied by partial condensation of gaseous hydrogen chloride, dissolving precipitated crystalline hydrates and their entrainment by gas flow, which in turn leads to loss of hydrogen chloride during purification. Fractional condensation, together with pre-treatment on activated carbon, allows to obtain a maximum yield of the product after rectification.

The method is carried out as follows.

Hydrogen chloride gas containing about nitrogen and oxygen, C0, j ,, k moisture, 8igI organochlorine impurities and about 1-1 (G of hydrocarbons, is purified by passing through activated carbon. Then hydrogen chloride is subjected to detoxification at a temperature from -b to 5. Chloride hydrogen after the described operations contains organochlorine impurities f, 6-10-5 | and moisture,. Hydrogen chloride is then liquefied at 2-6 at and temperature from TO and subjected to rectification, selection of the fraction containing (0.9-1) -10 carbon dioxide. B (carbon dioxide, ethane, ethylene, nitrogen and oxygen) are removed from the reflux condenser, and nonvolatile (acetylene, organic chlorine and crystalline hydrates H O-xHCI) - from the column bottom.

Example 1. 5 kg of synthetic hydrogen chloride without prior purification on activated carbon and dehydration is subjected to rectification at. The yield of the product containing (0.9-1) 1 (G

CO is 68%.

Example 2. Same as in example 1, but the gas is pre-dehydrated at. The yield of the pure product is 77.

Example 3. Same as in example 2, but the gas is first purified with activated carbon, previously saturated with hydrogen chloride. The product yield is 9%.

the table shows data illustrating the dependence of the yield of pure hydrogen chloride on the purification mode.

Activated carbon

Same ||

Known method

91 89 56 82 68

-70 .1,5

-80 -60

51-56

-80

58

As can be seen from the table, additional purification with coal and condensation at temperatures from -65 to -SoC does not allow to achieve the purpose of the invention, if the distillation is carried out as in a known method. On the other hand, carrying out the rectification at a temperature ranging from -5 to allows, without preliminary purification of hydrogen chloride, to increase the yield of the fraction with a low content of carbon dioxide. The combination of these cleaning techniques allows to achieve the maximum yield of purified hydrogen chloride.

The implementation of the proposed method will increase the yield of pure hydrogen chloride by 1.5-1.6 times as compared with the known method. At the same time, there is a stabilization of the technological mode of operation of the distillation column, an increase in the efficiency of separation of the distillation stage and, as a consequence, a decrease in product loss, as well as the prevention of the ingress of atmospheric gases into the purified product.

Claims (3)

1. A method for purifying hydrogen chloride by distillation of liquefied gas, characterized in that, in order to increase the yield of the fraction containing carbon dioxide in the amount of F, the rectification is carried out at a temperature from to. 2. Method pop. 1, distinguished by the fact that before distillation hydrogen chloride is passed through activated carbon, and then dehydrated by fractional condensation. at temperatures from -65 to -80 ° C. 3. The method according to claim 2, I differ by the fact that the activated carbon is pretreated with hydrogen chloride. Sources of information taken into account in the examination 1. Yakimenko L.M. Production of chlorine, caustic soda and inorganic chlorine products. M., 197. s, L90. 2. USSR author's certificate number 51939, cl. C 01 8 7/08, 1975.