JPS5857409B2 - Method for producing chlorinated methane - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process for producing chlorinated hydrocarbons, and in particular to a process for producing salts of chlorinated methane.

In producing chlorinated methane from methane, the chlorinated methane effluent contains unreacted methane as well as chlorinated methane that is recycled into the chlorinated methane production process.

According to prior art processes, such unreacted methane and recycled chlorinated methane are recovered from the effluent by fractional distillation; however, such fractional distillation results in an increase in the overall cost of the process.

It is an object of the present invention to provide an improved method for producing chlorinated methane.

According to the invention, fresh feed methane, recycled unreacted methane and recycled chlorinated methane (including at least methyl chloride and generally also methylene chloride) are introduced into a chlorinated methane production zone where fresh feed By converting methane and recycled methane to chlorinated methane products,
A method of producing chlorinated methane is provided.

The chlorinated methane effluent containing unreacted methane, chlorinated methane (methyl chloride, methylene chloride, chloroform and carbon tetrachloride), water vapor and hydrogen chloride is removed from the chlorinated methane production zone and transferred therefrom to the aqueous hydrogen chloride and chlorinated Separate a portion of the methane product.

The remaining effluent containing unreacted methane, chlorinated methane, and water vapor is then compressed and cooled to condense another portion thereof, producing about 75 to about 100% of the required methano recycle material.
A residual gaseous recycle stream is created which preferably contains about 90% to about 100% and about 60% to about 90% of the required methyl chloride recycle material.

If methylene chloride is also recycled, the remaining gaseous recycle stream contains about 5 to about 50% of the required methylene chloride recycle material.
%.

Most of the recycled material required in this process is recovered without fractional distillation (and without the need for drying the effluent prior to fractional distillation).

The amount of recycled material required in this process depends on the desired product distribution among the four chlorinated methane products.

If the product distribution requires large amounts of heavy product, ie carbon tetrachloride, large amounts of lightly chlorinated methane must be recycled.

An advantage of the present invention is that regardless of the amount of recycle material required for each component to obtain the desired product, the majority of the recycle material required is removed without fractional distillation of the effluent and without drying the effluent. It's about what you get.

The invention will now be described with respect to embodiments thereof with reference to the accompanying drawings.

Although this embodiment is specifically described with respect to producing chlorinated methane by a molten salt process, the chlorinated methane effluent can be made by other methods than molten salt.

In the drawing, a molten salt mixture of high and low valence chlorides of polyvalent metals and melting point depressants, in particular cuprous chloride and cupric chloride condensed with a melting point depressant such as potassium chloride, is shown in line 10. Then, it is introduced into the oxidation reactor 12.

In the oxidation reactor, the molten salt is contacted with molecular oxygen, generally introduced as air, by line 11 to produce copper oxychloride.

Oxidation is generally carried out at temperatures between about 316°C and about 482°C (about 600°C and 900°C).
(lower) temperature.

Chlorine components in the form of hydrogen chloride and/or chlorine may also be introduced into the oxidation reactor.

Such chlorine components react with the molten salt to increase its high valent chloride content.

A molten salt mixture containing cuprous chloride, cupric chloride and copper oxychloride is removed from oxidation reactor 11 via line 13 and introduced into chlorinated methane production zone 14.

In the chlorinated methane production zone 14, the molten salt is passed through line 15.
fresh feed methane introduced by, hydrogen chloride, chlorine or mixtures thereof introduced by line 16;
and a recycle stream containing unreacted methane and chlorinated methane introduced by line 17 to effect the production of chlorinated methane.

Zone 14 generally operates at temperatures on the order of about 700 to about 100 ov, with lower temperatures being preferred.

Molten salt recovered from chlorinated methane production zone 14 is recycled to oxidation reaction zone 11 via line 10.

Chlorinated methane, particularly chlorinated methane containing methyl chloride, methylene chloride, chloroform and carbon tetrachloride, unreacted methane, water vapor, hydrogen chloride, carbon dioxide and non-condensables, is passed through line 21. from the chlorinated methane production zone 14 by passing the effluent into a condenser 22 where the effluent is indirectly cooled to a temperature that causes condensation of the aqueous hydrogen chloride solution and some additional chlorinated hydrocarbons.

To carry out such condensation, the effluent is passed through the condenser 22 to a concentration of 0.
703~7.03 kg/ca gauge (10~100
26.7 to approximately 121°C (80°C) at pressures in the range of
Cool to a temperature of ~250° C.

Cooling can also be achieved by methods other than indirect cooling.

The cooled effluent in line 23 is introduced into separator 24, where the condensed portion is separated into an organic phase consisting of heavy columnar methane and an aqueous phase of dilute hydrochloric acid.

The condensed organic phase is removed from separator 24 by line 25 and can be used as a cooling liquid in the chlorinated methane production zone if desired.

Alternatively, such condensed chlorinated methane can form part of the reaction product, if desired.

The condensed aqueous phase is removed from the separator 24 by line 26; such aqueous phase can be further processed to strip the chlorinated methane therefrom, which can then be condensed to recover a more concentrated aqueous hydrogen chloride solution. can.

Essentially all unreacted methane, chlorinated methane, water vapor,
The non-condensable portion of the chlorinated methane effluent containing some hydrogen chloride, carbon dioxide and non-condensables is removed from separator 24 by line 41 and introduced into a direct contact quench vessel 42 for further separation of the chlorinated methane. Do the following.

In the quench vessel 42, the chlorinated methane is further condensed at a pressure on the order of about 0.35 to about 7.03 kg/crrt gauge (about 5 to about 100 psig) and about 10.0 to about 66°C ( Cool the effluent to a temperature on the order of about 50 to about 150 degrees below.

Although the present invention has been specifically described using direct contact cooling in a quench vessel, other methods of providing effluent cooling to condense chlorinated methane can also be used.

In quench vessel 42, the chlorinated methane effluent is brought into direct contact with an aqueous quench liquid introduced via line 43 to directly cool the effluent and further condense water vapor and chlorinated methane therefrom.

The condensed portion forms an aqueous phase and an organic phase at the bottom of the quench bath vessel 42.

Condensed organics recovered from quench bath vessel 42 by line 44 form part of the chlorinated methane product.

The organics recovered by line 44 generally contain all four types of chlorinated methane.

Additionally, the cooling in vessel 42 is generally conducted in such a manner as to condense most of the chloroform and carbon tetrachloride from the effluent, such that the remaining gaseous effluent recovered from quench bath vessel 42 is essentially free of all unused effluent. Contains reactant methane, methyl chloride, small amounts of methylene chloride and small amounts of chloroform and carbon tetrachloride.

The condensed aqueous phase is removed from the quench bath vessel 42 by line 45 and is preferably combined with an alkali, such as sodium hydroxide, in line 46 to maintain alkaline conditions in the aqueous phase.

A first portion of the aqueous phase is passed through line 47, which line 4
Included in 7 is a quench cooler 48 in which the aqueous phase is cooled to a temperature suitable to provide the necessary cooling to the quench bath vessel 42.

The cooled effluent is transferred via line 43 to quench bath vessel 42.
Introduce it inside.

The aqueous phase removed from column vessel 42 by line 52 is then further processed to separate the chlorinated methane therefrom.

The stripped aqueous phase is then discarded as a waste stream.

The non-condensable product of the chlorinated methane production effluent, containing essentially all unreacted methane, chlorinated methane (primarily methyl chloride and methylene chloride), some water vapor, carbon dioxide and non-condensables, is quenched from line 49. It is taken out from the bath container 42.

The effluent in line 49 is compressed in compressor 61 and cooled by indirect heat exchange in cooler 62 for further condensation of chlorinated methane.

The cooled and compressed flow in line 63 is approximately 4.44
- a temperature of about 37.8°C (about 40 to about 100 below), preferably about 4.44 to about 15.6°C (about 40 to about 60 below);
and about 3.52 to about 21.09 kg/crft gauge (about 50 to about 300 psig) preferably about 7.03
to about 14.06 kg/crrt gauge (about 100 to about 200 psig).

The pressure and temperature of the stream in line 63 is such that it causes condensation of a portion of the effluent and reduces the required methane recycle material to 75 to 100%.
% preferably 90-100% (as will be appreciated, the total methane recycle material is such that the total methane recycle material is essentially 100% unreacted methane even if the gas recycle stream contains less than such 100% requirement. (as designed) and adjusted within the conditions described above to provide a residual gaseous recycle stream containing about 60-90% of the required methyl chloride recycle material.

When methylene chloride is recycled, the residual gaseous recycle stream provides 5 to 50% of the required methylene chloride recycle material.

The residual gaseous recycle stream may also contain small amounts of chloroform and carbon tetrachloride.

The mixed stream in line 63 is introduced into a gas-liquid separator 64 where the gaseous recycle stream is separated from the condensed aqueous phase and the condensed organic phase.

A gaseous recycle stream is removed from separator 64 by line 6T and transferred to chlorinated methane production zone 14 by line 17.
circulate.

A portion of the flow in line 67 may be removed as a slip stream by line 68 for carbon dioxide and non-condensable removal.

The chlorinated methane present in the stream in line 68 may be recovered as a reaction product and/or recycled to the chlorinated methane production zone.

The aqueous phase is removed from separator 64 by line 65;
Such aqueous phase may be further processed to strip the chlorinated hydrocarbons therefrom before it is disposed of.

The organic phase is recovered from separator 64 by line 66.
This forms part of the overall reaction product.

The remaining portion of the required recycle material (methane, if present; methyl chloride; methylene chloride, if present; and chloroform, if present) is recovered from stream 66 by fractionation.

Alternatively, all or a portion of such required residual circulating material is obtained from stream 44.

Remaining recycle requirements recovered from stream 66 and/or stream 44 (not shown) are added to recycle stream 67 by line 71.

The remaining portion of the non-condensable effluent is recycled by line 17 to the chlorinated methane production zone.

Chlorinated methane can also be made by methods other than the molten salt process, but such methods are preferred.

For example, chlorinated methane can be made by an oxychlorination process in which methane is brought into direct contact with oxygen and hydrogen chloride.

As a further modification, various cooling steps other than those specifically shown may be used.

The present invention will be explained below with reference to Examples.

EXAMPLE Shown below is a product distribution of methyl chloride: methylene chloride: chloroform carbon ditetrachloride of 20:30:40:1.
An example of the composition of the individual streams used in making the final product is 0% by weight.

The gaseous recycle stream in line 67 contains about 98% methane recycle material, about 64% methyl chloride recycle material, and about 10% methylene chloride recycle material.

The present invention is particularly advantageous in that the majority of the methane and chlorinated methane required for recycling to the chlorinated hydrocarbon production zone is recovered from the chlorinated methane effluent without the need for fractional distillation.

Furthermore, such recycle material is provided without drying the recycle stream.

[Brief explanation of drawings]

The drawings are process diagrams of one embodiment of the present invention. 11... Oxidation reactor, 14... Chlorinated methane production zone, 22... Condenser, 24...
... Separator, 42 ... Direct contact quenching vessel, 4
8...Quick chiller, 61"...Compressor.

Claims (1)

Claims: 1. A method for producing chlorinated methane in a chlorinated methane production zone comprising introducing into the chlorinated methane production zone a gaseous recycle stream containing unreacted methane and methyl chloride, comprising: ( a) unreacted methane from the chlorinated methane production zone;
removing a gaseous effluent containing methyl chloride, methylene chloride, chloroform, carbon tetrachloride, water vapor and hydrogen chloride; (b) cooling the effluent to condense a portion thereof; and discharging the effluent into the condensed portion; (e) recovering the organic and aqueous phases; and (d) collecting the non-condensed portion of the gaseous effluent. 52-2], 09'i/ct4 gauge (50-300 psig) and a temperature of 4.44-37.8°C (40-100°C) to separate the effluent by compression and cooling. a portion is condensed and the remaining gas stream containing 75-100% recycled unreacted methane and 60-90% recycled methyl chloride is introduced into the chlorinated methane production zone in the gaseous recycled stream. (e) recovering said organic phase and aqueous phase;
recovering the residual gas stream without drying and fractionation for recirculation to the chlorinated hydrocarbon production zone; (g) introducing said residual gas stream into the chlorinated hydrocarbon production zone as part of said gaseous recycle stream; A method for producing chlorinated methane, characterized by: 2 said gaseous recycle stream further contains methylene chloride;
The residual gas stream contains 5 to 50% methylene chloride introduced into the chlorinated methane production zone in the gaseous recycle stream.
A method according to claim 1 containing: 3 Cooling in step (b) at 0.35 to 7.03 kg/c
10 at i-gauge (5-100 psig) pressure
．． 4. The process of claim 2 carried out at a temperature of 55 to 150'F''. 4. In the chlorinated methane production zone, hydrogen chloride, chlorine and mixtures thereof. 5. The method of claim 1, wherein chlorinated methane is produced by contacting a molten mixture containing the materials and cuprous chloride, cupric chloride, and oxychloride steel with a fresh feed of methane. (d) Compression and cooling of 7.03 to 14.0
6ky/crA gauge (100-200psig)
2. The method according to claim 1, wherein the process is carried out at a pressure of 4.44 to 15.6° C. (below 40 to 60° C.).