SU1237657A1 - Method of producing chloromethanes - Google Patents

Description

The invention relates to a method for the oxychlorination of methane in order to obtain chloromethanes used as solvents and starting materials for the production of various products in the industry of basic organic synthesis.

The purpose of the invention is to reduce the formation of side carbon oxides in the process of acidifying chlorination, methane by reducing the rate of the side reaction of burning methane or chloromethanes.

In this process, at a higher temperature, the reaction mixture consisting of methane and / or chloromethanes, hydrogen chloride and / or chlorine, oxygen and / or oxygen-containing gas and gaseous diluent is passed through the catalyst at an increased temperature, and carbon dioxide is used as the diluent. gas, taken in the amount of 10-50% of the total volume of the gas mixture.

In this case, the reaction gas exiting the oxychloride reactor of the research institute of methane is treated, water and hydrogen chloride (in the form of hydrochloric acid) and chloromethanes are extracted from it, and the condensed mixture of methane, methyl chloride and carbon dioxide is re-circulated . in such a quantity that the concentration of carbon dioxide in the volume of the inlet gas mixture is 10-15%. In this case, an excess amount of carbon dioxide is withdrawn from the process as a blowout of a small portion of the circulating gas.

In the case of the preparation of chloromethanes by the C-balance scheme by direct chlorination of methane, followed by oxychlorination of the reaction mixture from the chlorination stage. A carbon dioxide gas that is recycled with unreacted methane after the oxidation stage and is recycled to the direct chlorination stage is used.

Significant differences in the method are the implementation of the oxychlorination process. methane in the presence of a gaseous diluent, carbon dioxide, taken in pre-; its concentration in the initial mixture of reagents is 10-50% by volume, as well as the use of carbon dioxide formed during oxychlorination and is found to be recycled.

PRI and MER 1-6. In the reactor, I presented a tube of nickel

alloy with an inner diameter of 32 mm and a height of 5 m, serves methane, hydrogen chloride, oxygen and carbon dioxide.

A 4 liter of methane oxychlorination catalyst is loaded into the reactor, which is a supported catalyst mixture containing chlorine, copper, potassium chloride and lanthanum chloride, taken in a molar ratio of 1: 1: 0.1-0.3. The copper chloride content is 3-6% of the total catalyst weight.

Alumina-sh oxide with a specific surface area of 1–3 is used as the catalyst carrier for methane oxychlorination. However, it is also possible to use carriers such as silica gel and aluminosilicate with a specific surface area of up to 10-40.

The oxidative chlorination of methane is carried out at almost constant feeds of methane (0.36 - 0.42 nm / h), hydrogen chloride (0.37-0.40) and oxygen (0.20-0.23), varying the flow carbon dioxide from 0., 05 to 1.44 and the total flow of gas 1 to 2.4 (examples 2-6).

At the outlet of the reactor, the reaction mixture is analyzed on two xpo-i matographs to determine (the composition of the reaction gas and the efficiency and selectivity of the reaction.

For comparison, the methane oxychlorination is carried out under the conditions of the prototype, passing 0.12 methane through the catalyst, 1.06. HC1 and 0.15 oxygen (example 1).

Data on the reaction temperature, the composition of the reaction mixtures before and after the reactor, the conversion of reactants and the formation of side carbon oxides. in the calculation of the reacted methane (the selectivity of the process), as well as the removal of chemical metanes obtained in experiments with different supply of carbon dioxide, are given in the table.

Example 7. To obtain chloromethanes, an installation consisting of direct and oxidative chlorination of methane and also processing units of the reaction gas to remove hydrogen chloride and carbon dioxide in the amount of 638 im / h is used to cool and mix it with oxygen supplied to quantity

81 nm / h, and fed to the shelving oxychlorination reactor, with a diameter of 800 mm, on the shelves of which the catalyst for the oxychlorination of methane is preloaded in an amount of 1,470 liters of a composition similar to that described in Example 1.

The oxychlorination reactor contains seven shelves between which heat exchangers are located to cool the gas leaving the catalyst bed at a temperature of 420 ° C to a temperature of 300 ° C at the entrance to the next catalyst bed. Hydrochloric acid is condensed from the vapor-gas mixture obtained at the outlet of the reactor for the oxidation of chlorine gas, the reaction gas is further neutralized, dried and compressed, and then chloromethanes are condensed. Non-condensed gas is returned to the chlorination reactor. A certain amount of circulation gas is blown off to remove excess carbon dioxide.

Data on temperature, composition of the reactor.

the cyoink mixtures before and after the oxychlorinator, the formation of collateral carbon oxides per methane reacted, and also the removal of chloromethanes are given in the table (Example 7). As can be seen from the table, in the production of chloromethanes by the oxidative chlorination of methane in the presence of a carbon dioxide basin, taken in an amount of 50.30 and 10% of the volume of the reaction mixture (examples 3, 4, 5), the formation of side carbon oxides is respectively 4.7 5.7 and 6.8%. At the same time, removal of chloromethanes from 1 l of catalyst amounted to 180 g / h.

When using carbon dioxide recirculated from the oxychlorination stage in the amount of 20.6% of the volume of the reaction mixture, 6% of the reactive methane is converted to carbon oxides when removing chloromethanes 185 g / l cat. H. (example 7).

At the same time, under the conditions of the prototype, the formation of carbon oxides is noticeably higher than 7.6%, and the removal of chloromethanes is only 120 g / l cat.

In the case of a decrease in the concentration of 1 {and carbon dioxide to 5% (Example 6)

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the formation of carbon oxides increases to 17.7%, which is significantly higher compared to the prototype.

An increase in the concentration of carbon dioxide gas above 50 vol% does not allow reducing the formation of carbon oxides and at the same time reduces the removal of chlorine methane. Thus, at a carbon dioxide concentration of 60% (Example 2), the formation of carbon oxides is 4.7% chloromethane removal 1.64 g / l cat. B. At the same time, at a CO concentration of 50%, the same formation of carbon oxides (4, 7%) is achieved simultaneously with a higher removal of chloromethanes of 180 g / l cat.

The table shows that carrying out the oxychlorination process under the conditions described in examples 3-5 and 7, in comparison with the prototype, leads to a decrease in the formation of side carbon oxides due to carrying out the process in the presence of carbon dioxide. The same effect is observed when using carbon dioxide gas formed at the oxychlorination stage and directed to dilute the initial oxychlorination mixture in the composition of the circulating gas.

The preparation of chloromethanes by the proposed method makes it possible to reduce the formation of side carbon oxides by. unit of reacting methane compared with the prototype from 7.6-16.7% to 4.7-6.8%.

An additional advantage of the method is a higher removal of chloromethanes per unit volume of catalyst, amounting to 180-185 g / l cat. against 120 g / l cat. under the conditions of the prototype.

Another advantage is a simpler process and instrumentation process with carbon dioxide recycle. In this case, the site of separation of hydrogen chloride and water is excluded, and special corrosion protection of communications and compressors is not required, which is necessary in case of recirculating hydrogen chloride during the process under the conditions of the prototype.

Claims (2)

1. METHOD FOR PRODUCING CHLOROMETHANES by oxidizing chlorination of methane by passing at a higher temperature a reaction mixture consisting of methane and / or chloromethanes, hydrogen chloride and / or chlorine, oxygen and / or an oxygen-containing gas and a gaseous diluent through a fixed bed of an oxychlorination catalyst, which is copper chloride , potassium and lanthanum on a carrier, characterized in that, in order to reduce the formation of carbon oxides, carbon dioxide taken in col honors 10-50% of the total gas mixture. 2. The method of pop. 1, the fact that they use <g carbon dioxide formed during methane oxychlorination. SU „„ 1237657 A