JPS5817170B2 - Methanooxyensokahou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to chlorination processes, and more particularly to new and improved processes for producing chlorinated methanes.

A common method for producing chlorinated methane is to directly chlorinate methane, but a method of oxychlorinating methane to produce chlorinated methane is also known.

However, such an oxychlorination reaction usually produces a large amount of carbon oxides, various dimers, or mixtures thereof, and therefore has the drawback of low methane selectivity.

Furthermore, oxychlorination of methane necessarily produces four types of chlorinated methane selectivity, including undesirable chlorinated methane byproducts.

For example, the production of carbon tetrachloride is not desirable in terms of marketability.

Therefore, methane oxidation that maximizes methane selectivity to chlorinated methane (i.e., minimizes the production of carbon oxides and dimers) and minimizes the production of carbon tetrachloride. A chlorination process is desired in the art.

It is an object of the present invention to provide a new and improved process for producing chlorinated methane.

Another object of the present invention is to provide a new and improved method for oxychlorinating methane to produce chlorinated methanes.

Still another object of the present invention is to provide a method for oxychlorinating methane while minimizing the production of carbon oxides and various dimers.

Yet another object of the present invention is to provide a method for oxychlorinating methane while minimizing the formation of carbon tetracarbons.

Generally speaking, to achieve the objects of the present invention, chlorine or hydrogen chloride, or a mixture thereof, and methane are contacted with a molten mixture containing cupric chloride, cupric chloride, and copper oxychloride. As a result, chlorinated methane is obtained.

In this way, the amount of carbon oxides generated from methane can be reduced because methane does not come into direct contact with molecular oxygen as in conventional methods.

The copper chlorides are usually maintained in a molten state by using a melting point depressant consisting of a metal salt.

The melting point depressant is a chloride of a monovalent metal, that is, a metal in a monovalent positive valence state, which is non-volatile and does not react with oxygen under the reaction conditions.

The chlorides of monovalent metals are preferably chlorides of alkali metals, particularly potassium chloride and lithium chloride; Other chlorides and mixtures thereof can also be used, such as group (1) heavy metal chlorides, such as zinc chloride, silver chloride, and crilam chloride.

The amount of the metal salt melting point depressant added is such that the salt mixture of the copper chlorides and the melting point depressant can be maintained in a molten state at the reaction temperature, and at the same time the melting point of the molten salt mixture can be increased to about 315.
The amount should be sufficient to adjust the temperature to 6°C (below 600°C).

For example, if the salt mixture is copper chlorides and potassium chloride, the composition of the melt will be about 20 parts by weight to about 40 parts by weight, preferably 30 parts by weight of potassium chloride and the balance copper chlorides. .

However, if the catalyst is in a molten state under reaction conditions, the melting point of the catalyst melt will be 315.6°C (600°C).
It goes without saying that there is no problem even if the temperature is higher than 0.5°F.

Furthermore, other reaction promoters may be included in the catalyst melt.

As a representative example, when considering the reaction of producing chlorinated methane using methyl chloride, the reaction can be expressed by the following equation.

(1) 2CuCJI? 2-+2CuCl(J'2
(2) CH4+C12 → CH3C4+HCl (3) Cu
()CuC12+2HCl→2CuC,6+H20 Copper oxychloride can be obtained by contacting molecular oxygen with the above molten mixture in a separate reaction zone, and the reaction formula is expressed by the following formula.

(4) 2CuC12,000 Figure 02CuO・CuCl2 The total reaction for producing chlorinated methane is as follows: This is achieved by reducing oxides and at the same time reducing the formation of carbon tetrachloride and various dimers (chlorinated products having 2 or more carbon atoms).

In this way, the single stream selectivity for various chlorinated products can be increased while minimizing the amount of carbon tetrachloride produced.

Note that single-stream methane selectivity for various chlorinated products refers to the portion of the total converted methane that is converted to chlorinated methane, and the remainder is usually carbon oxides (carbon dioxide or carbon monoxide, or a mixture thereof). and represents the methane losses obtained in the form of various dimers.

According to the present invention, chlorinated methane can be obtained by oxychlorination of methane with a selectivity of at least about 75 moles, and the amount of carbon tetrachloride contained in the chlorinated methane product is about 17% by weight. Section below.

The oxychlorination reaction temperature was approximately 3.71.1°C (700°F).
) to about 460°C (below 860°C), preferably about 4267
Using chlorine as the sole chlorinating agent to control the single flow conversion of total methane (fresh feed and recycle streams) over a temperature range of 800°F to below 850°C It is believed that high selectivity of methane to chlorinated methane products can be achieved by setting the total single flow conversion to at most 30 parts when hydrogen chloride is used as the sole chlorinating agent and up to 15 parts when hydrogen chloride is used as the sole chlorinating agent. At the same time, the amount of carbon tetrachloride produced can be minimized.

The amount of carbon tetrachloride produced depends on the chlorinating agent and the conversion rate of methane.

Furthermore, if chlorine is used instead of hydrogen chloride, the amount of carbon tetrachloride produced is reduced, and if the total conversion rate of methane is reduced, the amount of carbon tetrachloride produced is also reduced.

When hydrogen chloride is used alone as a chlorinating agent, a large amount of carbon tetrachloride tends to be generated.Therefore, when hydrogen chloride is used as the sole chlorinating agent, the amount of carbon tetrachloride generated should be 17 parts or less. Therefore, it has been found that the methane conversion rate must be appropriately limited.

Therefore, when chlorine is used as the chlorinating agent, the methane conversion rate is limited to 30 parts or less, but when hydrogen chloride is used as the sole chlorinating agent, the methane conversion rate is limited to 15 parts or less.

Furthermore, when a mixture of hydrogen chloride and chlorine is used as the chlorinating agent, the conversion must be at an intermediate value depending on the relative proportions of the two types of chlorinating agents in the mixture.

When methane is oxychlorinated, the reaction stream from the oxychlorination reactor contains four types of chlorinated methane derivatives: methyl chloride, methylene chloride, chloroform, and carbon tetrachloride.

Net chlorinated methane product refers to chlorinated methane product that is not recycled to the oxychlorination reactor, and includes one or more chlorinated methane derivatives.

In addition, in the production of a net chlorinated methane product containing one or more chlorinated methane derivatives of methylene chloride, chloroform, and carbon tetrachloride, a portion of the methylene chloride present in the reaction stream is converted into a net chlorinated methane product. It goes without saying that the remaining amount may be recycled to the oxychlorination reactor.

As the ratio of chloroform to methylene chloride in the net product increases, the ratio of methylene chloride recycle stream to fresh methane feed stream also increases.

It has been found that the ratio of desired chlorinated methane product to carbon tetrachloride contained in the net chlorinated methane product is determined by the methane conversion rate.

That is, as the total single stream methane conversion decreases, the ratio of desired chlorinated methane product to carbon tetrachloride in the net product increases.

Economically, it is better to lower the methane conversion rate, but lowering the conversion rate increases the amount of recirculation flow, resulting in increased production costs.

Typically, methane conversion is not reduced below about 10%.

When producing chloroform as the desired chlorinated methane product, carbon tetrachloride is also usually produced as a net product, reducing the carbon tetrachloride contained in the net product by reducing the total methane single-stream conversion. The ratio of chloroform to chloroform can be increased.

Therefore, the amount of carbon tetrachloride in the net product can be reduced, if desired, by decreasing the total methane single-stream conversion.

For example, when using chlorine as the chlorinating agent, if the total methane single-stream conversion rate is reduced from about 30% to about 18%, the amount of carbon tetrachloride in the net product decreases from about 16% or less to about 10% or less. decreases to

Similarly, if methylene chloride and chloroform are the desired net chlorinated methane products, the ratio of the amphoteric to carbon tetrachloride can be increased by decreasing the methane conversion.

However, the amount of carbon tetrachloride produced at a given methane conversion rate varies depending on the type of chlorinated methane product in question.

That is, the amount of carbon tetrachloride produced is different when both chloroform and methylene chloride are the desired chlorinated methane product and when only chloroform is the desired product. Less carbon tetrachloride is produced when desired as a chlorinated methane product.

Also, as the methane conversion rate is decreased and the ratio of the desired chlorinated methane species (methylene chloride and chloroform) to carbon tetrachloride in the net chlorinated methane product is decreased, the chloroform in the net chlorinated methane product increases. The ratio of methylene chloride to methylene chloride also increases.

Therefore, the amount of carbon tetrachloride produced should be suppressed to about 5% by weight.

Like methane conversion, reaction temperature is also a factor that influences methane selectivity to chlorinated methanes.

According to the invention, the melt mixture for oxychlorination is used and the reaction temperature is set to 371.1. 'C (700°F) to 460°C (860°F), preferably 426.7°C (860°F)
00'F) to 454-. 4°C (850'F) and to limit the net production of carbon tetrachloride (no more than about 17 parts by weight carbon tetrachloride in the net product).
By limiting methane conversion, single stream methane selectivity for chlorinated methanes can be achieved at least about 75 moles.

In the present invention, the single-stream methane selectivity for chlorinated methane can be increased to about 90 molar ratios, but normally the selectivity is in the range of about 75 molar ratios to about 90 molar ratios.

The reaction temperature has a particularly significant effect on methane selectivity, and as the reaction temperature increases above 460°C (860°F), methane selectivity decreases.

By carrying out the oxychlorination method of the present invention, methane is oxychlorinated with a single flow methane selectivity of at least about 75 moles while limiting the net carbon tetrachloride production amount to about 17% by weight or less, thereby producing chlorinated methane. can be obtained.

Such results can be achieved without recycling carbon tetrachloride.

Although the process of the invention allows the production of methyl chloride, methylene chloride and chloroform as the desired net chlorinated methane products, the process of the invention is particularly suitable for the production of chloroform alone or a mixture of chloroform and methylene chloride. It is.

” = As shown, the oxychlorination reaction takes place at approximately 371.1°C (7
000F) to 460°C (860°F), preferably 4
267°C (800°F) to 4544°C'(850'
F).

The reaction temperature is a factor that greatly influences the single flow methane selective production.

Although the pressure and residence time used in carrying out the oxychlorination reaction can vary over a wide range, the reaction pressure is usually in the range of about 1 atm to about 10 atm, and the residence time is about 1 second. It ranges from about 60 seconds to about 60 seconds.

The ratio of chlorine or hydrogen chloride or mixtures thereof to the total methane (fresh and recycled methane) present in the oxychlorination reaction zone is a determining factor in methane conversion.

Therefore, it is difficult to determine the amount of chlorine or hydrogen chloride, or a mixture thereof, to be added to the oxychlorination reaction zone to achieve the desired single-stream methane conversion based on the total methane present and the recycled chlorinated methane. It is easy for those skilled in the art.

The molten mixture introduced into the oxychlorination reaction zone is typically about 2
From 0 to 55 wt. chlorinated steel sheet 1 to about 0.5 wt. to the maximum solubility of oxychloride in the melt (
Usually about 4% by weight of oxychloride is included.

The oxychloride is usually present in a range of about 1 part by weight to about 3 parts by weight.

Oxychloride is the source of oxygen, so a sufficient amount of oxine chloride must be present in the melt.

However, by adjusting the salt circulation rate, the amounts of various components in the melt can be varied without compromising reaction requirements.

To generate oxychloride, the molten mixture is heated with molecular oxygen in a separate reaction zone 1 at approximately 700°C.
F) to 510°C (950°F), preferably 426.
The contact may be made at a temperature in the range of 7°C (below 800°C) to 482.2°C (below 900°C).

Note that molecular oxygen is normally supplied using air.

In this case, the working pressure is usually between about 1 atmosphere and about 10 atmospheres and the residence time is between about 1 second and about 60 seconds, although shorter or longer residence times can be used. .

The invention will be further described in connection with examples of embodiments shown in the accompanying drawings, but it will be understood that the scope of the invention is not limited thereto.

It should be noted that molten copper chloride is highly corrosive and therefore the reaction equipment must be properly protected.

For example, various types of reactors may be lined with ceramic.

Similarly, if a pump is used to transport molten salts, the pump must also be protected.

However, the transfer of molten salts between reactors is preferably carried out using well-known lift gases.

FIG. 1 is a schematic flow sheet of an embodiment of the present invention.

In the drawing, the molten chloride salt, which is a mixture of potassium chloride, cupric chloride, and cupric chloride, in the flow path 10 is
As described above, the molten salt is introduced into the top of the reaction section of oxidizer 11, which is maintained at a temperature and pressure suitable for oxidation.

A compressed oxygen-containing gas, such as compressed gas, in flow path 12 is introduced into the bottom of oxidizer 11 and brought into countercurrent contact with the descending molten salt to oxidize the salt and form copper oxychloride.

This oxidation reaction is exothermic.

The effluent gas, consisting mainly of nitrogen introduced with the air, rises to the top of the oxidizer 11.

In the oxidizer 11, the effluent gas mixes with lift gas introduced through the flow path 13, as described below.

The effluent gas is brought into direct contact with droplets of a cooling liquid, such as hydrochloric acid, introduced through the flow path 14 at the top of the oxidizer 11 to cool and vaporize salts, and salts that have flowed out with the effluent gas. remove.

The effluent gas, which now contains vaporized cooling liquid, is then removed from the oxidizer 11 via flow path 15 and introduced into a direct contact cooling tower 16 of known type.

In said column 16, the effluent gas is cooled in direct contact with a suitable cooling liquid, in particular hydrogen chloride water, introduced via channel 17, so that vaporized cooling liquid can be removed from the gas stream.

The removed cooling liquid is taken out from the bottom of the column 18 through a flow path 18, and a portion thereof is introduced into the oxidizer 11 through a flow path 14 in order to cool the effluent in the oxidizer 11. Ru.

The remainder of the cooling liquid flows through channel 19 including cooler 21 and channel 17.
is introduced into the cooling tower 16 via the cooling tower 16.

The effluent gas, consisting mainly of nitrogen, is passed through the cooling tower 1 through a flow path 22.
6 and two parts thereof are discharged through the flow path 23.

The remainder of the nitrogen effluent gas is compressed in compressor 24 and the temperature of the compressed gas is adjusted in heat exchanger 63 before being sent through channels 25 and 26 and used as a lift gas for molten copper chloride as described below. do.

The molten salt containing copper oxychloride is removed from the bottom of oxidizer 11 via channel 31 and removed by lift gas in channel 25 to separator 3 adjacent to the top of the reaction section of reactor 33.
It can be raised to within 2.

In the separator 32, the molten salt is separated from the lift gas, and the separated lift gas is taken out via the flow path 35, mixed with the lift gas from the oxidizer, and transferred to the oxidizer 11 via the flow path 13. is introduced into the cooling section of the

A fresh methane feed stream in channel 44, a fresh feed stream consisting of chlorine or hydrogen chloride or a mixture thereof in channel 43, and methane and chlorinated methane or chlorinated methanes in channel 45 are fed to the bottom of reactor 33. is introduced into reactor 33 in contact with the descending molten salt to chlorinate the methane to yield the desired chlorinated methane product.

Reaction conditions within reactor 33 are controlled as described above to limit the formation of carbon oxides and carbon tetrachloride.

Chlorinated methane (the reaction effluent contains methyl chloride, methylene chloride, chloroform, and carbon tetrachloride independent of the desired net chlorinated methane product), unconverted methane, water vapor, and small amounts of hydrogen chloride. (usually in an amount corresponding to the equilibrium amount of hydrogen chloride) and carbon oxides is brought into direct contact with a coolant, such as a weight of chloroethane, introduced via flow path 53 to remove the effluent gas. and remove the vaporized salts and the salts that flowed out with the effluent stream.

At this stage, the effluent gas containing the vaporized cooling liquid flows through the flow path 5.
4 from the oxidizer 33 and then introduced into the separation and recovery area 101.

In separation and recovery zone 101, the net chlorinated methane product is recovered and removed via flow path 102.

Meanwhile, unreacted methane and chlorinated methane other than the desired chlorinated methane product are also recovered and recycled to the reactor 33 via the flow path 45.

Separation and recovery can be carried out using any of various known methods, and the method can be selected depending on the type of chlorinated methane to be recovered as a product.

Molten salt is removed from the bottom of reactor 33 via channel 61 and lifted by lift gas in channel 26 to separator 62 adjacent the top of reactor 11.

In the separator 62, the molten salt is separated from the lift gas and introduced into the oxidizer 11 via the flow path 10.

Lift gas, on the other hand, is removed from separator 62 via channel 64 and mixed with the lift gas present in channel 35.

This mixed lift gas is introduced via flow path 13 into the top cooling zone of the oxidizer.

The invention will now be described with reference to FIG.

FIG. 2 is a schematic flow sheet showing a representative example for recovering net chlorinated methane products such as methylene chloride, chloroform, and carbon tetrachloride.

In this example, the net product contains enough chloroform to require recycling of a small amount of methylene chloride; It is also possible to produce the net product without recycling.

In FIG. 2, the reaction effluent in channel 54 is cooled in compressor 110, mainly condensing a portion of water (if hydrogen chloride is present, the condensed water also contains hydrogen chloride). .

Due to the cooling, chlorinated hydrocarbons including chlorinated hydrocarbons used as a cooling liquid are also condensed.

The condensed water and condensed chlorinated hydrocarbons are separated in separator 111 , the aqueous phase being removed via channel 112 and the chlorinated hydrocarbon phase being removed via channel 113 .

A portion of the chlorinated hydrocarbons in channel 113 is recycled via channel 53 as a cooling liquid for reactor 33 .

Alternatively, all of these chlorinated hydrocarbons may be recycled as coolant if necessary.

In this case, the aqueous phase in channel 112 is separated from entrained and dissolved chlorinated hydrocarbons in a stripping column (not shown) by a stripping operation.

The recovered chlorinated hydrocarbons (recovered in the stopping tower) in the flow path 112a are mixed with the chlorinated hydrocarbons in the flow path 113.

Depending on the amount of hydrogen chloride present in the water, the water can also be processed to recover hydrogen chloride or a concentrated solution of hydrogen chloride.

The remainder of the gaseous effluent stream in flow path 114 may be passed to an alkaline wash zone 115 of well known type to remove residual hydrogen chloride.

If the gaseous effluent from alkaline wash zone 115 in flow path 116 is used, said effluent is further introduced into another cooling separation zone 117 for further condensation of water and chlorinated hydrocarbons. The carbon dioxide gas is removed by passing through a type of acid gas removal zone 118 and then introduced into a dryer 119 and further into a fractionating column 121.

Chlorinated hydrocarbons in flow path 113 and cooling separation zone 117
Dryer 1 combines the chlorinated hydrocarbons separated in
20 and introduced into a fractionating column 121.

If necessary, a portion of the chlorinated hydrocarbons recovered in the cooling separation zone may be recycled to the reactor 33 as a cooling liquid.

Furthermore, the water separated in the cooling separation zone 117 can be introduced into a stripping tower to recover chlorinated hydrocarbons.

The recovered chlorinated hydrocarbons are also introduced into the fractionator 121.

Fractionation column 121 is operated at a predetermined temperature and pressure to recover lighter components, ie, methane and methyl chloride, from methylene chloride as overhead oil.

The overhead oil from the fractionation column, 121, located in flow path 45 is recycled to reactor 33.

The bottom oil from the fractionation column 121 in the flow path 122 is introduced into a separation column 123 operated at a predetermined temperature and pressure to recover methylene chloride as top oil.

A portion of the methylene chloride overhead oil in the flow path 124 is transferred to the reactor 33.
and the remainder is recovered as net product.

The bottom oil from the fractionator 123 in the flow path 125 is introduced into the fractionator 126, which is operated at a predetermined temperature and pressure, and chloroform is recovered as top oil.

The chloroform overhead is recovered as net product via flow path 127.

The bottom oil from fractionator 126 in flow path 128 consists primarily of carbon tetrachloride.

The bottom oil may contain some dimer, and if carbon tetrachloride is marketable, the bottom oil may be fractionally distilled to recover carbon tetrachloride. do.

Additionally, the bottom oil in flow path 128, along with the oxygen-containing gas in flow path 131, may be introduced into combustion zone 129 to be combusted and recover the chlorine value in the form of hydrogen chloride and chlorine.

In this case, a combustion stream is removed from the combustion zone 129 and introduced into the reactor 11.

Chlorine and hydrogen chloride are recovered in reactor 11.

A general method for recovering chlorine values using combustion of chlorinated hydrocarbons is described in US Pat. No. 3,548,016.

The present invention will be explained below with reference to Examples, but the scope of the present invention is not limited by the Examples.

Examples In the following examples, methane and a chlorinating agent (chlorine and/or hydrogen chloride) were mixed with 30 parts by weight of potassium chloride, 39 parts by weight of potassium chloride,
parts by weight of cupric chloride, 31 parts by weight of cupric chloride, and 2.
Methane was oxychlorinated by countercurrent contact with a molten mixture consisting of 1 part by weight of copper oxychloride to obtain chlorinated methanes.

The oxychlorination reaction is carried out immediately at 4489°C (840'F).
and a residence time of 12 seconds.

In the table, the molar ratios of methyl chloride and methylene chloride to methane represent the recycled amounts of these components.

Table 1 shows the reaction conditions, and Table 2 shows the composition of the net product obtained.

A significant advantage of the present invention is that methane can be selected from 1'J
It is possible to obtain chlorinated methane by oxychlorination with E, and the high methane selectivity means that the amount of carbon oxides and various dimers produced can be minimized. do.

Furthermore, since the amount of carbon tetrachloride produced is suppressed, the advantages mentioned above can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a schematic flow sheet of one embodiment of the present invention, and FIG. 2 is a schematic flow sheet of one embodiment for recovering chlorinated methane products. 11... Oxidizer, 16... Direct contact cooling tower, 21... Cooler, 24... Compressor, 32... Separator, 33... Reactor, 62... Separator, 101... Separation and recovery area, 110... Compressor, 111...
... Separator, 115 ... Alkali cleaning area, 11
7... Cooling separation zone, 118... Acidic gas removal zone, 119... Dryer, 120...
・Dryer, 121... Fractional distillation column, 123...
... Fractional distillation column, 126... Fractional distillation column,
129... Combustion area.

Claims (1)

[Claims] 1. In an oxychlorination reaction zone, a chlorinating agent which is methane and hydrogen chloride or chlorine or a mixture thereof is brought into contact with a molten salt consisting of cuprous chloride, cupric chloride and copper oxychloride. When the chlorinating agent is chlorine alone, the contacting is carried out at 3711°C (700°F) to 460°C (8600°F), and the conversion rate of methane is kept below 30% when the chlorinating agent is chlorine alone. is controlled to less than 15% if hydrogen chloride alone, and the reaction effluent containing unreacted methane, methyl chloride, methylene chloride, chloroform and carbon tetrachloride is removed from the reaction zone and chloroform is removed as the net methane chlorination product. and carbon tetrachloride and optionally methylene chloride, wherein said carbon tetrachloride is less than 17 parts by weight of said net methane chlorination product and the methane selectivity is at least 75 parts or more; A process for oxychlorination of methane further characterized by recycling unreacted methane, methyl chloride and some residual methylene chloride to the oxychlorination reaction zone. 2. When bringing methane, hydrogen chloride, chlorine, or a mixture thereof into contact with a molten salt consisting of cuprous chloride, cupric chloride, and copper oxychloride in the oxychlorination reaction zone, 371.1°C (700°F)
or 460°G (860°F), and if the chlorinating agent is chlorine alone, the conversion rate of methane is reduced to 30 parts or less.
In addition, when the chlorinating agent is hydrogen chloride alone, it is controlled to 15% or less, and the reaction effluent containing unreacted methane, methyl chloride, methylene chloride, chloroform and carbon tetrachloride is taken out from the reaction zone, and the net methane chlorination is Chloroform and carbon tetrachloride and optionally methylene chloride are recovered as product j, where the carbon tetrachloride is less than 17% by weight of the net methane chlorination product and the methane selectivity is at least 75%. and further recycling unreacted methane, methyl chloride and any remaining methylene chloride to the oxychlorination reaction zone and contacting the molten salt removed from the oxychlorination reaction zone with oxygen in the oxidation zone. A process for the oxychlorination of methane characterized by producing copper oxychloride and introducing the molten salt removed from the oxidation reaction zone into the oxychlorination reaction zone.