JPH07106995B2 - Method for producing methyl chloride - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing methyl chloride, and more particularly to economically producing methyl chloride from carbon tetrachloride and methanol without the presence of a difficult-to-separate mixed gas of carbon dioxide and methyl chloride in the reaction system. To the manufacturing method.

[0002]

2. Description of the Related Art In recent years, the depletion of the ozone layer has become a major social problem, and the London Conference in June 1990 decided to abolish ozone-depleting substances during this century. There is. One of the ozone depleting substances
One is carbon tetrachloride (CCl ₄ ). The most representative industrial production method of carbon tetrachloride is a chlorination method of methane or methyl chloride. This method uses CH _{4 as} shown below.
→ CH ₃ Cl → CH ₂ Cl ₂ → CCl ₄ is a sequential co-reaction reaction in which CCl ₄ is produced, and the product is unreacted methane or chloromethane from methyl chloride (CH ₃ Cl) to carbon tetrachloride. It becomes a mixture of kinds. CH ₄ + Cl ₂ → CH ₃ Cl + HCl CH ₃ Cl + Cl ₂ → CH ₂ Cl ₂ + HCl CH ₂ Cl ₂ + Cl ₂ → CHCl ₃ + HCl CHCl ₃ + Cl ₂ → CCl ₄ + HCl It is impossible to carry out this reaction without carbon by-products. However, since each partially chlorinated methane has a large and useful market, the influence on the others when this manufacturing method is abolished is extremely large. Therefore, a means for promptly converting carbon tetrachloride produced as a by-product into another harmless useful substance is desired.

Therefore, the present inventors have previously proposed, as one of the methods, a gas phase reaction method of carbon tetrachloride, methanol or the like using a catalyst in which a metal chloride such as zinc chloride is supported on activated carbon. When this reaction is expressed using a thermochemical reaction formula,
CCl ₄ ＋4 MeOH → 4CH ₃ Cl ＋ CO ₂ ＋ 2H ₂ O ＋ 70kcal / m
It becomes ol-CCl ₄ . However, if this method is performed all at once in a fixed bed reactor filled with a catalyst, the heat generated in the reactor may cause a high temperature region partially due to the poor heat transfer.

On the other hand, the most popular conventional method for separating carbon dioxide from the reaction product is as follows. 1) Alkanolamine method: This is a method in which alkanolamine [(HOR) _n NH _3-n ] and the absorbed gas are brought into contact with each other at 50 ° C. at about atmospheric pressure, and carbon dioxide and alkanolamine represented by the following chemical formula 1 are obtained. Is a method of removing carbon dioxide by using the chemical equilibrium.

[Chemical 1] In this method, methyl chloride reacts with alkanolamine to form methyl alkanol ammonium chloride [Me (HO
R) _n NH _{3 -n} Cl] is formed, and therefore cannot be applied to the absorption of carbon dioxide in this coexistence. 2) Hot potassium carbonate method: As shown in the following chemical formula ² , this is a method of removing carbon dioxide by contacting a potassium carbonate solution and an absorbed gas at 120 ° C. under a pressure of about 20 kg / cm ² G.

[Chemical 2] In the presence of high temperature alkali such as potassium carbonate, water reacts with methyl chloride. When carbon dioxide is absorbed at a low temperature, this reaction does not occur, but the absorption rate of carbon dioxide decreases, so that it is necessary to make the absorption tower extremely high, which is uneconomical. 3) Absorption by sodium hydroxide Methyl chloride and sodium hydroxide do not react at low temperature and low pressure, but the reaction between sodium hydroxide and carbon dioxide is an irreversible reaction. The amount of sodium hydroxide consumed will increase and the cost will increase. Thus, an inexpensive means for removing carbon dioxide in a system in which methyl chloride coexists has not been proposed so far.

[0005]

Therefore, the present invention suppresses the generation of high temperature locally in the reactor and does not generate a gas mixture of methyl chloride and carbon dioxide, which is difficult to separate, and is simple. It is intended to provide a method for producing methyl chloride from carbon tetrachloride and methanol, which enables removal of carbon dioxide in the process.

[0006]

The method for producing methyl chloride according to the present invention comprises: 1) a group 1B and 2A of the periodic table,
At least one of 2B, 6B, 7B and 8
First, using a catalyst in which a halide and / or an oxide of a certain element is supported on activated carbon, carbon tetrachloride is hydrolyzed in a gas phase and the resulting carbon dioxide and hydrogen chloride are separated.
And 2) a second step of producing methyl chloride by reacting the hydrogen chloride with methanol, preferably, the reaction in the second step is carried out in the presence of the same catalyst as in the first step. It is characterized by being performed in the gas phase.

Hereinafter, one embodiment of the process for producing methyl chloride of the present invention will be described with reference to FIG. In the first reaction step A, a raw material containing at least carbon tetrachloride and water (hereinafter referred to as the first raw material) is received, and carbon tetrachloride is hydrolyzed in the gas phase in the presence of the above catalyst to obtain a reaction gas. To separate carbon dioxide and hydrogen chloride. In the second reaction step B, methyl chloride is produced from the hydrogen chloride obtained in the first reaction step A and a raw material containing at least methanol (hereinafter referred to as the second raw material). The present invention divides the reaction into a hydrolytic reaction of carbon tetrachloride and a synthetic reaction of methyl chloride from hydrogen chloride and methanol without mixing carbon dioxide and methyl chloride, which are difficult to separate, to give a reactor. It is easy to control the temperature inside,
It is premised that the first raw material does not contain methanol. In addition, in the method of the present invention, hydrogen chloride produced in other steps in the second reaction step B can be reacted with methanol. The hydrogen chloride supplied in this case is gaseous hydrogen chloride,
Either concentrated hydrochloric acid or diluted hydrochloric acid can be used. Hydrogen chloride can be mixed and supplied with either the first raw material or the second raw material.

In the first reaction step A, carbon tetrachloride is hydrolyzed by a gas phase catalytic reaction. The catalyst used is one in which at least one halide and / or oxide of 1B group, 2A group, 2B group, 6B group, 7B group and 8 group of the periodic table is supported on activated carbon. It is desirable to keep the temperature inside the reactor at around 150 to 250 ° C. This is 150 ℃
If it is less than the above range, the reaction rate of carbon tetrachloride is reduced and the reaction rate is reduced. Above 250 ° C, the reaction rate increases, but as the temperature increases, the corrosiveness due to the reaction gas increases, making it difficult to select a permanent material. The higher the reaction pressure is, the smaller the capacity of the reactor is, but it is preferable to carry out the reaction at a pressure of about 5 kg / cm ² G or less in consideration of corrosion. The molar ratio of carbon tetrachloride and water to be supplied is H ₂ O / CCl ₄ = 2.0, because this reaction is carried out according to the following formula.
A slight excess of water to increase the reaction rate of carbon tetrachloride H ₂ O
It is preferable to supply at / CCl ₄ = 2.2 or more. CCl ₄ + 2H ₂ O → CO ₂ + 4HCl However, the supply of a large excess of water also supplies components that are not involved in the reaction, which leads to an increase in the size of the device and is economically disadvantageous. Under these conditions, the residence time in the process is 5-10
In a second, almost all the supplied carbon tetrachloride reacts. First
The reaction gas in the reaction step A consists of carbon dioxide, hydrogen chloride and water (excess), and carbon dioxide and other components may be separated by any known method. Most simply, hydrogen chloride is recovered as hydrochloric acid water and carbon dioxide is released as a gas, for example by using a condenser or condenser and a water scrubber.

Regarding the gas phase hydrolysis reaction of carbon tetrachloride, a method using an acid resistant molecular sieve described in US Pat. No. 4,423,024 is well known.
However, since the catalyst used here has lower activity than the catalyst used in the present invention, a temperature higher than that in the present invention (220 to 310 ° C. is preferable) is necessary in order not to reduce the reaction rate of carbon tetrachloride. Actually, the temperature is 240 to 332 ° C. in the example using carbon tetrachloride. This acid-resistant molecular sieve is used in the first reaction step A of the present invention, and the reaction temperature is set to about 200 ° C. in order to suppress the corrosion by the reaction gas as in the present invention. The hydrolysis reaction will not be completed. If the remaining reaction product obtained by removing carbon dioxide from this reaction gas is sent to the second reaction step B using the catalyst, the hydrolysis reaction of carbon tetrachloride in the second reaction step B, hydrogen chloride and methanol Simultaneously with the reaction of synthesizing methyl chloride from the above, the disadvantages such as the generation of mixed gas of carbon dioxide and C _{1 and} the difficulty of temperature control occur. When the second reaction step B is carried out by the following liquid phase non-catalytic reaction, the first reaction step A
The unreacted carbon tetrachloride from is not hydrolyzed here and is discharged as it is as an unreacted product.

In the second reaction step B, methyl chloride is produced from the hydrogen chloride and methanol obtained in the first reaction step A. Any conventionally known method for synthesizing methyl chloride from methanol and hydrogen chloride may be used for the reaction mode here. For example, this includes a gas phase reaction using the same catalyst as in the first reaction step A or a liquid phase non-catalytic reaction. Among these, the gas phase catalytic reaction is preferable from the viewpoint of reaction efficiency of methanol and hydrogen chloride. The supply form of hydrogen chloride obtained in the first reaction step A to the second reaction step B can be appropriately selected depending on the reaction mode in the second reaction step B. For example, when the gas phase catalytic method is used in the second reaction step B, hydrogen chloride may be diffused from the hydrochloric acid water obtained in the first reaction step A and supplied to the second reaction step B. May be completely evaporated and supplied to the second reaction step B. The reaction conditions in the second reaction step B are also appropriately selected according to the reaction mode here. For example, when the gas phase reaction using the same catalyst as in the first reaction step A is performed in the second reaction step B, it is desirable to keep the temperature in the reactor at about 150 to 250 ° C. This is
If the temperature is lower than 150 ° C, the reaction rate of methanol decreases and the reaction rate decreases. If the temperature exceeds 250 ° C, the reaction rate increases, but as the temperature increases, the corrosiveness of the reaction gas increases and it becomes difficult to select a permanent material. . The higher the reaction pressure is, the smaller the capacity of the reactor is. However, it is preferable to carry out the reaction at a pressure of about 5 kg / cm ² G or less in consideration of corrosion resistance. Regarding the ratio of methanol and hydrogen chloride to be supplied, the amount of dimethyl ether [(CH ₃ ) ₂ O] produced as a by-product increases when methanol is supplied in excess, so the supply ratio: HCl / MeOH (molar ratio) should be 1.01 or more. It is preferable to supply a slight excess of hydrogen chloride. If this amount is made too large, the amount of unreacted hydrogen chloride increases and the conversion of chlorine to methyl chloride becomes inefficient. Under the above conditions, 95% or more of the supplied methanol reacts with an average residence time of about 5 to 10 seconds. When a liquid phase non-catalytic reaction is used in the second reaction step B, the reaction temperature is preferably about 70 ° C or higher. If it is less than 70 ° C, the reaction rate of methanol decreases. The reaction pressure is preferably a pressurized state in order to improve the reaction results. The ratio of methanol to hydrogen chloride supplied is because the reaction rate of this system is slower than that of the gas phase reaction,
Good results are obtained with an excess of hydrogen chloride, for example HCl / MeOH> 2.0.

[0011]

EXAMPLES The present invention will be specifically described below with reference to examples. The following reactions were performed using the manufacturing process shown in FIG. First, carbon tetrachloride 7 as a raw material is put in the first vaporizer 1.
538 g / hour, hydrochloric acid water 8 returned from the water scrubber (composition: water 80.0% by weight, hydrogen chloride 20.0% by weight) were supplied at a rate of 709 g / hour, vaporized to 150 ° C., and heated. This is 50mm in diameter
It was supplied to the first reactor 2, which was made of glass with a φ × 1000 mm height and wound with an external heater and was filled with activated carbon supporting 30% by weight of zinc chloride. The molar ratio of H ₂ O / CCl ₄ supplied was 9.0, and the average residence time in the superficial column was 8.1 seconds.
The temperature inside the vessel was controlled at 195 to 225 ° C. The gas discharged from the first reactor 2 is condensed in the condenser 3, and the uncondensed portion 9 therein is guided to the water scrubber 4 which circulates hydrochloric acid water, and the dissolved portion is removed and discharged (12). . The condensate 10 in the condenser 3 was 629 g / hour, and its composition was 33.3% by weight of hydrogen chloride and 66.7% by weight of water. The water scrubber 4 supplies pure water 11 at 1779 g / hour and exhaust gas 12 at 185 g / hour.
By the time, its composition is 83.4% by weight carbon dioxide and 16.6% by weight water.
Met. The solution 13 in the water scrubber 4 is divided into two at 2213 g / hour (hydrogen chloride 20.0% by weight), and one 709 g / hour is sent to the first vaporizer 1 as water scrubber return hydrochloric acid water 8 and the other (14 ) Of 1504 g / hour is supplied to the second vaporizer 5 together with the condensate 10. Methanol 15 as another raw material was supplied to the second vaporizer 5 at 407 g / hour. In the second vaporizer 5, these accepted raw materials were heated to 150 ° C. and supplied to the second reactor 6. The second reactor 6 has a diameter of 70 mm
It is made of glass with a diameter of φ x 1600 mm wound with an external heater, and the same catalyst as in the first reactor 2 is filled inside. The molar ratio of hydrogen chloride and methanol supplied was HCl / MeOH = 1.1, and the average residence time was 8.5 seconds. The reaction temperature here is 200-220.
Controlled at ° C. The gas 16 discharged from the second reactor 6 is 25
At 40 g / hour, the composition is methyl chloride: 24.6% by weight, hydrogen chloride: 2.3% by weight, methanol: 0.3% by weight,
Dimethyl ether: 0.08% by weight, water: 72.7% by weight. Carbon tetrachloride was 100% reacted in the first reactor 2. The reaction rate of methanol is 98.2%, and the selectivity of methyl chloride is
It was 99.3%.

[0012]

According to the present invention, in the production of methyl chloride from carbon tetrachloride and methanol, a mixed gas of methyl chloride and carbon dioxide, which is difficult to separate, is not generated. Can be removed. Further, by dividing the reaction into two stages, it is possible to prevent the generation of a local high temperature part in the fixed bed catalytic reactor, which is difficult to remove heat.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an outline of reaction steps for carrying out the method of the present invention.

FIG. 2 is an explanatory view showing another embodiment of a reaction step for carrying out the method of the present invention.

[Explanation of symbols]

1 ... 1st vaporizer, 2 ... 1st reactor, 3 ... condenser,
4 ... Water scrubber, 5 ... 2nd vaporizer, 6 ... 2nd reactor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-59-184139 (JP, A) JP-A-58-27644 (JP, A) JP-A-63-91128 (JP, A) JP-B 6- 59331 (JP, B2) US Patent 4423024 (US, A)

Claims (2)

[Claims] 1. A 1B group, 2A group, 2B group of the periodic table,
Carbon dioxide obtained by hydrolyzing carbon tetrachloride in a gas phase using a catalyst in which a halide and / or oxide of at least one element of 6B group, 7B group and 8 group is supported on activated carbon. Methyl chloride from carbon tetrachloride and methanol comprising a first step of separating hydrogen chloride and hydrogen chloride and 2) a second step of reacting the hydrogen chloride with methanol to produce methyl chloride. Manufacturing method. 2. The method for producing methyl chloride according to claim 1, wherein the reaction in the second step is carried out in the gas phase in the presence of the same catalyst as in the first step.