JPH04297426A - Production of methyl chloride - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention provides a method for producing methyl chloride, and in particular, an economical method for producing methyl chloride from carbon tetrachloride and methanol without the presence of a mixed gas of carbon dioxide and methyl chloride, which is difficult to separate, in the reaction system. Relating to a method of manufacturing.

0002

[Background 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 completely eliminate ozone-depleting substances by the end of this century, and the industry is also proceeding with plans to follow this. There is. One of these ozone layer depleting substances is carbon tetrachloride (CCl4). The most typical industrial method for producing carbon tetrachloride is the chlorination method of methane or methyl chloride. This method is as shown in the formula below: CH4 → CH3Cl → CH2Cl2 → CCl4
It is a sequential simultaneous reaction in which CCl4 is produced via
It becomes a mixture of chloromethanes ranging from 3Cl) to carbon tetrachloride. CH4 + Cl2 → CH3Cl + HCl
CH3Cl + Cl2 → CH2Cl2
+ HClCH2Cl2 + Cl2 → C
HCl3+ HClCHCl3 + Cl2 →
CCl4+ HCl It is therefore impossible to carry out this reaction without the by-product of carbon tetrachloride. but,
Partially chlorinated methane each has a large and useful market, so the impact on others if this production method were abolished would be extremely large. Therefore, there is a need for a means to quickly convert the by-product carbon tetrachloride into other harmless useful substances.

[0003] As one of the methods, the present inventors have previously proposed a gas phase reaction method for carbon tetrachloride, methanol, etc. using a catalyst in which a metal chloride such as zinc chloride is supported on activated carbon. This reaction can be expressed using a thermochemical reaction equation:
CCl4+4MeOH → 4CH3Cl + C
O2+2H2O +70kcal/mol-CCl4
becomes. However, if this method is carried out all at once in a fixed bed reactor filled with catalyst, due to poor heat transfer within the reactor,
The heat generated may cause a high temperature region to occur in some areas.

On the other hand, the most conventional method for separating carbon dioxide from the reaction product is as follows. 1) Alkanolamine method: In this method, alkanolamine [(HOR)nNH3-n] and gas to be absorbed are heated at 50°C.
This is a method of removing carbon dioxide by bringing them into contact at approximately atmospheric pressure and using the chemical equilibrium between carbon dioxide and alkanolamine shown in Formula 1 below.

In this method, methyl chloride reacts with alkanolamine to form methylalkanol ammonium chloride [Me
(HOR)nNH3-nCl], so it cannot be applied to carbon dioxide absorption under this coexistence. 2) Thermal potassium carbonate method: As shown in formula 2 below, a potassium carbonate solution and an absorbed gas are heated at 120°C and 20kg/cm2.
This is a method of removing carbon dioxide by contacting under pressure of about G.

[Chemical 2] In the presence of alkali such as potassium carbonate at high temperature, water and methyl chloride react. When carbon dioxide is absorbed at low temperatures, this reaction does not occur, but the absorption rate of carbon dioxide decreases, making it necessary to make the absorption tower very high, which becomes uneconomical. 3) Absorption by sodium hydroxide Methyl chloride and sodium hydroxide do not react at low temperature and low pressure, but because the reaction between sodium hydroxide and carbon dioxide is an irreversible reaction, the amount of carbon tetrachloride used as a raw material increases. The amount of sodium hydroxide consumed also increases, resulting in higher costs. Thus far, no inexpensive means for removing carbon dioxide in a system in which methyl chloride coexists has been proposed.

[0005]

[Problems to be Solved by the Invention] Therefore, the present invention suppresses the generation of local high temperatures in the reactor, and also eliminates the generation of a mixed gas of methyl chloride and carbon dioxide, which is difficult to separate. The present invention provides a method for producing methyl chloride from carbon tetrachloride and methanol, which allows the removal of carbon dioxide in the process.

[0006]

[Means for Solving the Problems] The method for producing methyl chloride according to the present invention comprises: 1) groups 1B and 2A of the periodic table;
At least one of Group 2B, Group 6B, Group 7B and Group 8
The first step is to hydrolyze carbon tetrachloride in the gas phase using a catalyst in which halides and/or oxides of certain elements are supported on activated carbon, and to separate the resulting carbon dioxide and hydrogen chloride.
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 carried out in the gas phase.

[0007] An embodiment of the methyl chloride production process of the present invention will be described below with reference to FIG. 1 illustrating it. 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, carbon tetrachloride is hydrolyzed in the gas phase in the presence of the catalyst, and the resulting reaction gas is carbon dioxide and hydrogen chloride are separated. 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 a second raw material). The present invention enables the reaction to be separated into a hydrolysis reaction of carbon tetrachloride and a synthesis reaction of methyl chloride from hydrogen chloride and methanol without mixing carbon dioxide and methyl chloride, which are difficult to separate. This makes it easy to control the temperature inside.
It is assumed that the first raw material does not contain methanol. Furthermore, in the method of the present invention, hydrogen chloride produced in another step can be reacted with methanol in the second reaction step B. In this case, the hydrogen chloride to be supplied may be in the form of gaseous hydrogen chloride, concentrated hydrochloric acid, or diluted hydrochloric acid. Hydrogen chloride can be supplied mixed 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 groups 1B, 2A, 2B, 6B, 7B and 8 of the periodic table is supported on activated carbon. It is desirable to maintain the temperature inside the reactor at about 150 to 250°C. If the temperature is lower than 150°C, the reaction rate of carbon tetrachloride decreases, leading to a decrease in the reaction rate. When the temperature exceeds 250° C., the reaction rate increases, but as the temperature increases, the corrosivity caused by the reaction gas increases, making it difficult to select a permanent material. The higher the reaction pressure, the smaller the capacity of the reactor, but from the viewpoint of strength in consideration of corrosion, it is preferable to conduct the reaction at a pressure of about 5 kg/cm2G or less. Since this reaction is carried out according to the following formula, the molar ratio of carbon tetrachloride and water to be supplied is the stoichiometric ratio.
H2O/CCl4 = 2.0, but in order to increase the reaction rate of carbon tetrachloride, water is added in excess H2O/CCl4
=2.2 or more is preferable. CCl4 + 2H2O → CO2 + 4HCl However, supplying a large excess of water also supplies components that do not participate in the reaction, leading to an increase in the size of the apparatus, which is economically disadvantageous. Under these conditions, the residence time in the process is 5 to 10 seconds, and almost all of the supplied carbon tetrachloride reacts. The reaction gas in the first reaction step A consists of carbon dioxide, hydrogen chloride, and water (excess), and any known method may be used to separate the carbon dioxide and other components. . Most simply, the hydrogen chloride is recovered as aqueous hydrochloric acid and the carbon dioxide is released as a gas, for example using a condenser or condenser and 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, the catalyst used here has lower activity than the catalyst used in the present invention, so in order not to reduce the reaction rate of carbon tetrachloride, a temperature higher than that of the present invention (220 to 310°C) is required.
(preferably). In fact, in an example using carbon tetrachloride, the temperature is 240 to 332°C. When 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 corrosion by the reaction gas as in the present invention, carbon tetrachloride is removed in the first reaction step A. The hydrolysis reaction will not be completed. If the remaining reaction product after removing carbon dioxide from this reaction gas is sent to the second reaction step B using the catalyst,
In the second reaction step B, the hydrolysis reaction of carbon tetrachloride and the synthesis reaction of methyl chloride from hydrogen chloride and methanol occur simultaneously, resulting in the generation of a mixed gas of carbon dioxide and C1, making temperature control difficult, etc. causing inconvenience. In addition, when the second reaction step B is carried out in the liquid phase non-catalytic reaction described below, the unreacted carbon tetrachloride from the first reaction step A is not hydrolyzed here and is discharged as an unreacted product. Put it away.

In the second reaction step B, methyl chloride is produced from the hydrogen chloride obtained in the first reaction step A and methanol. Any of the conventional methods for synthesizing methyl chloride from methanol and hydrogen chloride may be used as the reaction method here. For example, this may include a gas phase reaction using the same catalyst as in the first reaction step A or a liquid phase non-catalytic reaction. Among these, gas phase catalytic reaction is preferred from the viewpoint of reaction efficiency of methanol and hydrogen chloride. The manner in which hydrogen chloride obtained in the first reaction step A is supplied to the second reaction step B can be appropriately selected depending on the reaction mode in the second reaction step B. For example, when a gas phase catalyst 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 then supplied to the second reaction step B. The entire amount may be evaporated and supplied to the second reaction step B. The reaction conditions in the second reaction step B are also appropriately selected depending on the reaction mode here. For example, when performing a gas phase reaction using the same catalyst as in the first reaction step A in the second reaction step B, it is desirable to maintain the temperature inside the reactor at about 150 to 250°C. If this temperature is lower than 150℃, the reaction rate of methanol decreases, leading to a decrease in the reaction rate, and if the temperature exceeds 250℃, the reaction rate increases, but as the temperature increases, the corrosivity of the reaction gas increases, making it difficult to select a permanent material. Become. The higher the reaction pressure, the smaller the capacity of the reactor, but from the viewpoint of strength considering corrosion, it is preferable to conduct the reaction at a pressure of about 5 kg/cm2G or less. Regarding the ratio of methanol and hydrogen chloride to be supplied, the supply ratio: HC
such as l/MeOH (molar ratio) of 1.01 or more,
It is preferable to supply a slight excess of hydrogen chloride. If this amount is too large, unreacted hydrogen chloride will increase, and the conversion of chlorine to methyl chloride will become inefficient. Under the above conditions, more than 95% of the supplied methanol reacts with an average residence time of about 5 to 10 seconds. Also, the second reaction step B
When liquid phase non-catalytic reaction is used, the reaction temperature is preferably about 70°C or higher. When this temperature is lower than 70°C, the reaction rate of methanol decreases. The reaction pressure is preferably a pressurized state in order to improve reaction results. Since the reaction rate of this system is slower than the above gas phase reaction, good results can be obtained by using an excess of hydrogen chloride, for example, HCl/MeOH > 2.0. .

[0011]

[Examples] The present invention will be specifically explained below using examples. The following reaction was carried out using the manufacturing process shown in FIG. First, 538 g/hour of raw material carbon tetrachloride 7 and 709 g/hour of hydrochloric acid water 8 (composition: water 80.0% by weight, hydrogen chloride 20.0% by weight) returned from the water scrubber were added to the first vaporizer 1.
They were each supplied at a rate of g/hour, and the temperature was vaporized and raised to 150°C. This was supplied to the first reactor 2, which was made of glass and was wrapped with an external heater and had a diameter of 50 mmφ and a height of 1000 mm, and was filled with activated carbon carrying 30% by weight of zinc chloride. The molar ratio of H2O/CCl4 supplied was 9.0, and the average residence time in the column was 8.1 seconds. The temperature inside the vessel was controlled at 195-225°C. The gas discharged from the first reactor 2 was condensed in a condenser 3, and the uncondensed content 9 there was led to a water scrubber 4 circulating hydrochloric acid water to remove dissolved content and exhaust (1
2). The condensate 10 in condenser 3 was 629 g/hour and had a composition of 33.3% by weight of hydrogen chloride and 66.7% by weight of water. Water scrubber 4 uses pure water 11 at 1779
The exhaust gas 12 is 185 g/hour and has a composition of 83.4% carbon dioxide and 16.6% water by weight.
Met. Dissolved solution 13 in water scrubber 4 is 2213g
/hour (hydrogen chloride 20.0% by weight), one 709g/hour is sent to the first vaporizer 1 as hydrochloric acid water 8 returned from the water scrubber, and the other (14) 1504g/hour is the condensed water. It is supplied to the second vaporizer 5 together with the liquid 10. The second vaporizer 5 has methanol 15 as another raw material.
was supplied at a rate of 407 g/hour. These raw materials received in the second vaporizer 5 were heated to 150° C. and supplied to the second reactor 6. The second reactor 6 is made of glass wrapped with an external heater and has a diameter of 70 mmφ and a height of 1600 mm, and is filled with the same catalyst as the first reactor 2. The molar ratio of hydrogen chloride and methanol supplied was HCl/MeOH=1.
1. Average residence time is 8.5 seconds. The reaction temperature here was controlled at 200-220°C. The gas 16 discharged from the second reactor 6 was 2540 g/hour, and its composition was methyl chloride: 24.6% by weight, hydrogen chloride: 2.
3% by weight, methanol: 0.3% by weight, dimethyl ether: 0.08% by weight, and water: 72.7% by weight. 100% of the carbon tetrachloride reacted in the first reactor 2. The methanol reaction rate was 98.2%, and the methyl chloride selectivity 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, so that carbon dioxide can be produced in a simple process. can be removed. Furthermore, by dividing the reaction into two stages, it is possible to prevent the generation of localized high temperature areas within the fixed bed catalytic reactor where heat removal is difficult.

[Brief explanation of drawings]

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

FIG. 2 is an explanatory diagram showing another embodiment of the reaction process for carrying out the method of the present invention.

[Explanation of symbols]

1... First vaporizer, 2... First reactor, 3... Condenser,
4...Water scrubber, 5...Second vaporizer, 6...Second reactor.

Claims (2)

[Claims] Claim 1: 1) Group 1B, Group 2A, Group 2B of the periodic table,
Carbon dioxide obtained by hydrolyzing carbon tetrachloride in the gas phase using a catalyst in which a halide and/or oxide of at least one element from Group 6B, Group 7B, and Group 8 is supported on activated carbon. and 2) a second step of producing methyl chloride by reacting the hydrogen chloride with methanol.Methyl chloride from carbon tetrachloride and methanol. 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.