JP2735755B2 - Method for producing chloroform - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing chloroform by reacting carbon tetrachloride with hydrogen.

[0002]

2. Description of the Related Art A method for producing chloroform by reacting carbon tetrachloride with hydrogen in a liquid phase is well known. For example, in Spanish Patent No. 2,018,748,
At a pressure of less than 8000 KPa and at a temperature of less than 250 ° C., carbon tetrachloride is converted into a liquid phase without dilution, a powdery catalyst is suspended in the liquid phase, and reacted with gaseous hydrogen or a gas containing hydrogen molecules to form a continuous system. Alternatively, a method for producing chloroform in a batch system is disclosed.

[0003]

According to the above-mentioned method, when the reaction time is 4 hours, the selectivity of chlorohom is at most 88 mol%, and chloroform can be produced with relatively high selectivity. However, as a result of the inventors repeating the above method in a continuous manner, when the reaction time was further increased, the performance of the catalyst evaluated by the selectivity of chloroform began to decrease, and the reaction time reached 12 hours. It has been found that the selectivity of chloroform sometimes deteriorates to 41 mol%.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted various studies with the aim of developing a method for preventing the performance of the catalyst from being deteriorated over a long period of time. By conducting the reaction while maintaining the concentration of carbon chloride in a specific range, it has been found that chloroform can be produced with high selectivity while preventing a decrease in the performance of the catalyst for a long time, and the present invention has been proposed. .

That is, the present invention relates to a method for producing chloroform by continuously supplying carbon tetrachloride and hydrogen into a reactor in the presence of a catalyst and reacting in the liquid phase to produce chloroform. 0.01 to 20% by weight of carbon tetrachloride
Is a method for producing chloroform.

In the present invention, known catalysts used in hydrogenation reactions can be used without any limitation. Active ingredient, presence or absence of carrier, carrier type, loading method, etc. are particularly limited
Although not required , a catalyst supported on a carrier can be suitably used in the present invention because the conversion of carbon tetrachloride increases.

The active components of the catalyst include, for example, platinum,
Platinum group metals such as palladium, rhodium and ruthenium can be suitably used. In the present invention, platinum and rhodium are particularly preferred, and platinum is most preferred. When using a carrier, the carrier particularly has a specific surface area of 10 to 2000 m ^2.
/ G, preferably 100 to 1500 m ² / g, and a carrier having a pore volume of 0.1 ml / g or more is suitably employed. Examples of such a carrier include activated carbon, alumina, silica, zeolite and the like, and activated carbon is particularly preferred. The amount of the active ingredient supported on the carrier is preferably 0.01% by weight or more in order to expect good catalytic action.
Usually, for economic reasons, the range is 0.01 to 50% by weight.
Preferably it is in the range of 0.1 to 10% by weight.

[0008] As a method of supporting the active ingredient on the carrier, a known method is employed without any limitation, and usually, an impregnation method, a coprecipitation method, an ion exchange method, or the like is employed. For example, as the impregnation method, the above-mentioned metal chloride, ammonium chloride, organic complex salt, nitrate, or a salt prepared by dissolving a metal in an appropriate solvent is used as a precursor of the active ingredient, and the precursor is used as a carrier. And left at room temperature for several hours.
The carrier is heated at a temperature of about 00 to 150 ° C. for a predetermined time to remove moisture remaining in the carrier, then calcined at a temperature of 100 to 500 ° C. for a predetermined time, and further in the presence of a reducing gas such as hydrogen or hydrazine. The method of reducing the precursor of the active component to a metal state at a temperature of 100 to 500 ° C. can be suitably adopted.

[0009] The catalyst used in the present invention, by which to reduce the particle size to increase the liquid contact area and extend the catalyst life while improving the conversion of carbon tetrachloride
Wear. If the particle size is too large, the life of the catalyst may be adversely affected.
３3 mm, preferably 0.03-1 mm.

The catalyst is used after being dispersed in a liquid phase. The amount of the catalyst used is not particularly limited, but is preferably in the range of 0.01 to 50% by weight in the liquid phase. In the present invention, the production efficiency of the intended chloroform may be reduced in order to dilute the carbon tetrachloride as a raw material as described later, but in such a case, the amount of the catalyst used is increased. As a result, it is possible to prevent a decrease in the production efficiency of chloroform.

In the present invention, the raw materials carbon tetrachloride and hydrogen are continuously supplied into a reactor, and the reaction is performed in a continuous manner. Here, the continuous supply means that carbon tetrachloride or a diluted solution thereof and hydrogen are supplied into the reactor in a continuous flow and intermittently supplied into the reactor at appropriate intervals. Say.

In the present invention, the reaction is performed in a liquid phase.
Hydrogen may be supplied to either the gas phase or the liquid phase,
Usually, it is preferable to supply to the liquid phase because the reaction can be rapidly performed by increasing the dissolution rate of hydrogen in the liquid phase.

In the present invention, the concentration of carbon tetrachloride in the liquid phase in the steady state is maintained at 0.01 to 20% by weight, preferably 0.1 to 10% by weight, more preferably 0.1 to 2% by weight. It is important to. When the concentration of carbon tetrachloride is lower than the above range, the selectivity of chloroform can be kept high, but it is not practical because the production amount of chloroform per unit time decreases. Also,
If the concentration of carbon tetrachloride is higher than the above range, it is not preferable because the performance of the catalyst deteriorates in a short time.

In order to set the concentration of carbon tetrachloride within the above range, it is usually sufficient to dilute the solvent with a solvent compatible with carbon tetrachloride in the above-mentioned concentration range of carbon tetrachloride. The solvent used for dilution is preferably, for example, a chlorinated hydrocarbon such as methylene chloride, chloroform, trichloroethane, perchloroethylene, or the like. As the reaction proceeds, a product mainly composed of chloroform is generated and mixed in the liquid phase. In the present invention, such a product is also included as a diluting solvent for carbon tetrachloride. Therefore, the concentration of carbon tetrachloride in the present invention is always the concentration of carbon tetrachloride in the liquid phase.

[0015] The concentration of carbon tetrachloride at the start of the reaction is not particularly limited and can be employed in the range of 0 to 100% by weight. Preferably, the concentration is in the range of about to 20% by weight, and more preferably, it is close to the concentration in a steady state.

The reaction temperature is set at 1 to increase the conversion of carbon tetrachloride and to suppress the formation of by-products such as hexachloroethane to improve the selectivity of chloroform.
The range is preferably from 0 to 250 ° C, particularly preferably from 50 to 200 ° C, more preferably from 50 to 150 ° C, from the viewpoint of the life of the catalyst. The reaction pressure may be any pressure at which a liquid phase can be maintained, and is generally preferably in the range of normal pressure to 200 kg / cm ² . The reaction pressure may be maintained by supplying hydrogen, or may be maintained by supplying a mixed gas of hydrogen and a gas other than hydrogen that does not participate in the reaction.

The catalyst is generally used by dispersing it in a liquid phase. The method for dispersing the catalyst is not particularly limited, and may be stirring by a stirrer, or a bubble column method in which hydrogen is blown into a liquid phase to disperse the catalyst in a turbulent state of a reaction solution forming a liquid phase.

As the reaction operation in the present invention, the following operation method can be exemplified. For example, as the reactor, a reactor such as an autoclave reactor with a stirrer or a tube reactor of a bubble column type can be suitably used. Carbon tetrachloride, diluent solvent and catalyst are fed into the reactor in appropriate proportions and the required amount of hydrogen is continuously fed. Then, the reaction temperature and pressure are adjusted. The supply of carbon tetrachloride may be performed by any method as long as the concentration of carbon tetrachloride in the liquid phase in the steady state is maintained at 0.01 to 20% by weight. For example, the method is previously charged in a reactor. Carbon tetrachloride may be continuously supplied to the solvent at a low flow rate without dilution, or a solution in which carbon tetrachloride is adjusted to a certain concentration by a diluting solvent may be continuously supplied to the reactor at a predetermined flow rate. .

The gas and the reaction solution in the reactor are continuously withdrawn. Since the extracted reaction liquid contains the dispersed catalyst, it is preferable to recover the catalyst using a liquid cyclone or a filter. The main product, chloroform, is separated from the reaction solution after the catalyst is separated by a known method such as a distillation method. The unreacted carbon tetrachloride separated at that time is preferably recycled to the reactor. On the other hand, hydrogen chloride contained in the reaction gas extracted from the reactor can be separated by distillation under high pressure or removed by passing through a water absorption column.
Thereafter, the chlorine compound contained therein can be condensed by cooling the reaction gas to an appropriate temperature.
In the above-described treatment of the reaction gas, the order of separation of hydrogen chloride and condensation of chlorine compounds can be reversed.

In the present invention, the method for isolating and purifying chloroform, which is the desired product, from the reaction system is not particularly limited, and known methods such as filtration and distillation can be employed.

[0021]

According to the present invention, chloroform can be obtained at a high selectivity without reducing the performance of the catalyst over a long period of time. Therefore, according to the method of the present invention, chloroform can be industrially advantageously produced.

[0022]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 Activated carbon prepared by supporting platinum at 0.5% by weight (specific surface area: 1
300 m ² / g, pore volume 0.6 cc / g) was used as a catalyst (average particle size 0.1 mm). 1.5 g of the catalyst was placed in an autoclave reactor (hereinafter, abbreviated as “reactor”) having an inner diameter of 50 mm and a height of 200 mm in the vessel, and 120 g of a methylene chloride solution in which the concentration of carbon tetrachloride was adjusted to 0.2% by weight.
After charging, the reactor was closed. After removing the air in the reactor, hydrogen was charged to 30 kg / cm ² at room temperature. In order to disperse the catalyst in the liquid phase, 100 r. p.
m. Stirred to the extent. The inside of the reactor was heated to 125 ° C., and thereafter, a methylene chloride solution having a carbon tetrachloride concentration of 8% by weight was continuously supplied into the reactor at a rate of about 0.5 g / min by a quantitative pump. Supply of hydrogen is 30 kg once an hour
/ Cm ² and vented to 45 kg / cm ^{2 with} hydrogen
Pressure. The withdrawal of the reaction solution was performed once every four hours by stopping the stirring, allowing the catalyst to settle, and then using a solution withdrawal pipe inserted into the reactor. The pressure reduced by extraction was pressurized to 45 kg / cm ^{2 with} hydrogen.

The analysis of the reaction product was performed using a FID type gas chromatograph. During the period from the start of the reaction to the elapse of 72 hours, the concentration of carbon tetrachloride in the liquid phase in the reactor in a steady state was 0.5% by weight, and the reaction was able to be performed stably. Table 1 shows the results of the reaction after 72 hours.

Examples 2, 3 and Comparative Example 1 In Example 1, the concentration of continuously supplied carbon tetrachloride was 15% by weight in Example 2, 20% by weight in Example 3, and 100% in Comparative Example 1. %, The same procedure as in Example 1 was carried out except that the concentration of carbon tetrachloride in the liquid phase in the steady state was changed as shown in Table 1, and the results are shown in Table 1.

Example 4 A reaction was carried out in the same manner as in Example 3 except that the amount of the catalyst was changed to 5.0 g.
It was shown to.

[0027]

[Table 1]

Examples 5 to 7 The same procedures as in Example 1 were carried out except that the amount of the catalyst was 2.0 g and the reaction temperature was the temperature shown in Table 2, and the results are shown in Table 2. . The lower the reaction temperature, the longer the catalyst life.

[0029]

[Table 2]

Claims (1)

(57) [Claims] 1. A method for producing chloroform by continuously supplying carbon tetrachloride and hydrogen into a reactor in the presence of a catalyst and reacting in a liquid phase to produce chloroform. A method for producing chloroform, wherein the concentration is maintained at 0.01 to 20% by weight.