JP2868968B2 - Method for producing chloroform - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing chloroform by reducing carbon tetrachloride with hydrogen and replacing chlorine atoms with hydrogen atoms.

[0002]

2. Description of the Related Art Production of a hydrogen-containing organic compound in which an organic halide is reduced with hydrogen and a halogen atom is replaced with a hydrogen atom is performed, for example, in the presence of a reduction catalyst mainly composed of platinum or the like.
The reaction can be performed by reacting an organic halide with hydrogen. For example, Japanese Unexamined Patent Publication No. 4-504728 discloses that an activated carbon-supported catalyst is suspended in a liquid phase composed of carbon tetrachloride at a pressure of 8000 KPa or less and a temperature of 250 ° C. or less, and reacted with hydrogen gas to form chloroform. A method of making is disclosed.

[0003]

According to this method, there is a problem that as the reaction time becomes longer, the catalytic activity expressed by the amount of chloroform formed per unit time per unit amount of catalytic metal decreases. That is, when the reaction time is compared between 2 hours and 4 hours, the catalyst activity is reduced by up to 34%. In order to pursue the cause of the deactivation of the catalyst with the lapse of reaction time, the present inventors carried out additional tests of the above method and analyzed the deactivated catalyst. It was found that a polymer was formed, and further, this polymer was found to be derived from hexachloroethane by-produced in the reduction reaction. It was also found that the catalyst once deactivated cannot be regenerated by solvent extraction, oxidation treatment, or reduction treatment.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on a method in which the performance of the catalyst does not decrease over a long period of time, and as a result, before loading a metal on a catalyst support made of carbon, a reducing agent, an oxidizing agent, an organic It has been found that the above object can be achieved by keeping the halide in contact with the halide, and the present invention has been proposed.

That is, the present invention provides a method for producing chloroform in which a chlorine atom is replaced by a hydrogen atom by reacting carbon tetrachloride with hydrogen in the presence of a catalyst, wherein a catalyst comprising carbon is used as a catalyst, A method for producing chloroform, which comprises using a catalyst that supports a Group 8 metal of the periodic table after contacting with an oxidizing agent or an organic halide.

[0006] As the carrier made of carbon in the present invention, known carriers can be used without any limitation. Specifically, for example, activated carbon and carbon black can be mentioned.

In the present invention, the carrier made of carbon must be brought into contact with a reducing agent, an oxidizing agent or an organic halide in advance before supporting a metal belonging to Group 8 of the periodic table described later. This makes it possible to maintain the catalytic activity in the reduction reaction of carbon tetrachloride for a long time. If the metal of Group 8 of the periodic table is supported on a carbon support and then brought into contact with these reducing agents, oxidizing agents or organic halides, the effects of the present invention cannot be obtained, which is not preferable. In other words, as described above, by previously treating carbon as a carrier with an organic halide such as hexachloroethane, which is a substance for deactivating the catalyst,
The catalyst life can be prolonged, and in the present invention, the timing of treating the support is important.

[0008] In the method of contacting with a reducing agent, the reducing agent is not particularly limited, and any known reducing agent can be used without any particular limitation.
Examples thereof include lower hydrocarbons having 5 and lower alcohols having 1 to 5 carbon atoms, and hydrogen and hydrazine are particularly preferable. The supplied reducing agent may be either gaseous or liquid.

As a contact method, a known solid-gas contact method or a solid-liquid contact method can be employed without any limitation. For example, when the reducing agent is in a gaseous state, after filling a carrier made of carbon into, for example, a container having an inlet and an outlet at both ends, after scavenging at the contact temperature using an inert gas such as nitrogen and helium from the inlet. The method of supplying the reducing agent can be suitably adopted. The supply amount of the reducing agent is 0.001 to 10 mol / hour per 1 g of the carrier, and the contact time is 30 minutes to 2 minutes.
0 hours is appropriate. The contact temperature is not particularly limited,
In consideration of the continuity of the catalytic activity, a range of 550 to 1500 ° C is preferable, and a range of 600 to 1100 ° C is more preferable. After the end of the supply of the reducing agent, it may be cooled to room temperature while flowing the above-mentioned inert gas.

When the reducing agent is in a liquid state, a carrier made of carbon may be immersed in the reducing agent and brought into contact therewith. As the contact method at this time, a method in which a carrier made of a reducing agent and carbon is added to a container with a cooling pipe and the container is brought into contact at a predetermined temperature is suitably adopted. The amount of the reducing agent used is 0.0
The contact temperature may be selected from a range of from 20 ° C. to the boiling point of the reducing agent. The contact pressure can be either normal pressure or pressurization, and the contact time is suitably in the range of 30 minutes to 50 hours. After the contact, the carrier is washed with water and then dried under reduced pressure to obtain a carrier suitable for the reaction.

Next, in the method of contacting with an oxidizing agent,
As the oxidizing agent, a known oxidizing agent can be used, but in order to exert the effects of the present invention, nitric acid and hydrogen peroxide are preferable, and nitric acid is particularly preferable. Nitric acid has a concentration of 13.5 to 1N, and hydrogen peroxide has a concentration of 3 to 60% by weight.
Aqueous solution can be suitably used. The conditions such as the contact method, the amount of the oxidizing agent used, the contact temperature, and the contact time can be the same as those described for the reducing agent.

The organic halide used in the method of contacting with an organic halide is not particularly limited, but halogenated alkanes having 1 to 4 carbon atoms can be suitably used. Specific examples include chloromethane, dichloromethane, chloroform, carbon tetrachloride, dichloroethane, hexachloroethane, 1,2-dichloropropane, and hexachlorobutadiene. Furthermore,
The use of perhalides such as carbon tetrachloride, hexachloroethane, and hexachlorobutadiene is preferable because good effects can be obtained. A liquid organic halide can be used as it is, and a solid organic halide can be used by dissolving it in a liquid organic halide.

As the contacting method, the above-mentioned method for contacting with a reducing agent can be employed as it is. The amount of the organic halide to be used is not particularly limited, but may be an amount sufficient to immerse the entire amount of the carrier. When the solid organic halide is used by dissolving it in a liquid organic halide, the concentration is usually selected from the range of 1 to 80% by weight, though it depends on the solubility of the solid organic halide. Contact temperature is 20 ~ 200 ℃,
The contact time may be selected from a range of 30 minutes to 50 hours. The pressure may be normal pressure or pressurization. Thereafter, washing with a low-boiling organic halide such as dichloromethane, chloroform, carbon tetrachloride, dichloroethane or the like or drying under reduced pressure can be employed as necessary.

The catalyst used in the present invention can be prepared by supporting a metal of Group 8 of the periodic table on the carbon support thus obtained. As the Group 8 metals of the periodic table, iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, platinum and the like can be mentioned. Of these, platinum, palladium, rhodium and ruthenium are highly active. And platinum and palladium are particularly preferred. Further, a metal of Group 1B of the periodic table consisting of gold, silver, and copper may be used in a range of 0.01 to 50% by weight based on the metal of Group 8 of the periodic table.

As a method for loading the Group VIII metal on the carrier, known methods can be employed without any limitation.
For example, an impregnation method, a coprecipitation method, an ion exchange method and the like can be mentioned. As an impregnation method, chloride, ammonium salt, ammine complex, organic complex salt, nitrate, acetate or a metal as a precursor of a metal belonging to Group 8 of the periodic table is dissolved in a suitable solvent, and the solution is impregnated into a carrier. After leaving at room temperature for several hours, it is heated at a temperature of about 100 to 150 ° C. to remove the solvent remaining in the carrier, and is further cycled at a temperature of 20 to 500 ° C. in the presence of a reducing agent such as hydrogen or hydrazine. Ritsuyo 8
A method of reducing the group metal precursor to a metal state can be suitably employed.

The content of the Group 8 metal of the periodic table in the catalyst used in the present invention is preferably 0.01% by weight or more in order to expect good catalytic action. , 0.01 to 50% by weight, preferably 0.1 to 10% by weight.

Using the catalyst thus obtained, carbon tetrachloride is reacted with hydrogen to produce chloroform in which a chlorine atom is replaced by a hydrogen atom.

The carbon tetrachloride is usually used as it is or after being diluted with a compatible solvent. As the solvent used for dilution, for example, chlorinated hydrocarbons such as dichloromethane and chloroform are preferable. The concentration is not particularly limited, but can be adopted in the range of 1 to 100% by weight.

The reaction can be carried out in any of a batch system, a continuous system, and a semi-continuous system. Further, any of a liquid phase and a gas phase can be carried out, but a liquid phase method is preferred from the viewpoint of selectivity and catalyst life. In the liquid phase method, hydrogen may be supplied to either the gas phase or the liquid phase, but usually, supplying it to the liquid phase is to increase the rate of dissolution of hydrogen in the liquid phase so that the reaction can be performed quickly. Is preferred because In the liquid phase method,
The reaction can employ either a fixed bed or a suspension bed. The amount of the catalyst used is not particularly limited, but is preferably in the range of 0.01 to 50 parts by weight based on 100 parts by weight of the organic halide as the raw material.

The reaction temperature is set to 10 to 250 to increase the conversion of the organic halide and suppress the generation of by-products.
° C is preferable, and especially from the viewpoint of catalyst life, it is 50 to 2 ° C.
It is preferably in the range of 00 ° C, more preferably 50 to 150 ° C. The reaction pressure may be either normal pressure or pressurization, but is generally preferably in the range of normal pressure to 200 kg / cm ² , and more preferably in the range of ^{2 to} 100 kg / cm ² .

The reaction molar ratio of hydrogen to carbon tetrachloride is not particularly limited. When the amount of hydrogen is increased, the reaction rate is increased, but the production rate of low-order chlorinated carbon in which hydrodechlorination has progressed is increased. Usually, hydrogen is added in an amount of 0.1 to 1 mol of carbon tetrachloride.
It is preferable to make 1 to 10 moles of the reaction.

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

The method of the present invention is suitable for a hydrodechlorination reaction in which one chlorine atom is replaced with a hydrogen atom from carbon tetrachloride as a raw material, and it is possible to obtain mainly chloroform using carbon tetrachloride as a raw material. it can. When chloroform is used as the raw material, methylene chloride may be mainly obtained.

[0024]

The mechanism of action of the present invention is not clear, but when it is brought into contact with a reducing agent and an oxidizing agent, the surface functional group of the carbon support is converted into an inactive group.
It is presumed that the properties of the surface of the carbon carrier changed and polymerization of by-products became difficult to occur. Further, when the organic halide is brought into contact with an organic halide, it is presumed that the polymerization active sites on the carrier made of carbon have been eliminated by the organic halide brought into contact in advance.

According to the present invention, the production of by-products can be reduced, the selectivity of the target product can be increased, and hydrodechlorination of carbon tetrachloride while maintaining high activity for 200 hours or more can be achieved. Can be. Therefore, the present invention is extremely useful industrially.

[0026]

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 (Preparation of a catalyst in which platinum is supported on a modified activated carbon carrier by hydrogen reduction) Activated carbon (specific surface area: 1300 m ² / g, pores) was placed in a quartz cylindrical container having an inlet and an outlet at both ends. Capacity: 0.87m ³
/ G, particle size: 780 to 340 μm) were fixed at both ends with quartz wool, and the temperature was raised to 1000 ° C. while flowing nitrogen gas at a flow rate of 400 ml / min, and the temperature was maintained for 1 hour. After 1 hour, switch the supply gas to hydrogen 400ml
After maintaining the same temperature for 1 hour while flowing at a flow rate of / min, the gas was switched to nitrogen gas and cooled to room temperature. The amount of the activated carbon modified by hydrogen reduction obtained was 45.5 g.

Next, 30 ml of water was added to 10 g of the modified activated carbon, and 30 g of an aqueous solution of chloroplatinic acid hexahydrate (platinum content: 1% by weight) was added thereto with stirring. For 12 hours to remove excess water. Thereafter, hydrogen was reduced at a flow rate of 200 ml / min under atmospheric pressure at a temperature of 300 ° C. for 3 hours. Furthermore, it cooled to room temperature under hydrogen stream. The catalyst contained 3% by weight of platinum.

Example 2 The same operation as in Example 1 was carried out except that the treatment temperature with hydrogen gas was set at 600 ° C. and the holding time at the same temperature was set at 10 hours, so that 3% by weight of platinum was supported on the modified activated carbon. A catalyst was obtained.

Example 3 (Preparation of catalyst in which palladium is supported on modified activated carbon by hydrogen reduction) Example 1 was repeated except that 5 g of an aqueous solution of palladium chloride (1% by weight of palladium) was used instead of chloroplatinic acid. The same operation was performed to obtain a catalyst in which 0.5% by weight of palladium was supported on the modified activated carbon.

Example 4 (Preparation of a catalyst in which platinum is supported on modified activated carbon by hydrazine reduction) In a glass container equipped with a stirrer equipped with a cooling tube, 200 ml of hydrazine monohydrate was used in the same manner as in Example 1. 50 g of activated carbon was added and heated to 120 ° C. with stirring. After maintaining at the same temperature for 3 hours and cooling to room temperature, the activated carbon was collected by filtration and washed with water until the filtrate became neutral. Then, 11
Vacuum dried at 0 ° C. The amount of the activated carbon modified by hydrazine reduction was 48.9 g.

Then, the same procedure as in Example 1 was carried out to obtain a catalyst in which platinum was supported on modified activated carbon obtained by hydrazine reduction. The catalyst contained 3% by weight of platinum.

Example 5 (Preparation of catalyst in which platinum is supported on modified activated carbon by 13.5N nitric acid oxidation) [0033] 200 ml of 13.5N nitric acid was used in Example 1 in a glass container equipped with a stirrer equipped with a cooling pipe. Similar activated carbon 50
g and heated to 86 ° C. with stirring. After maintaining at the same temperature for 1 hour and cooling to room temperature, the activated carbon was collected by filtration and washed with water until the filtrate became neutral. Then, it was vacuum-dried at 110 ° C. The obtained activated carbon modified by 13.5N nitric acid oxidation weighed 57.2 g.

Next, the same operation as in Example 1 was performed.
A catalyst in which platinum was supported on activated carbon modified by 5N nitric acid oxidation was obtained. The catalyst contained 3% by weight of platinum.

Example 6 (Preparation of a catalyst in which platinum is supported on modified activated carbon by 2N nitric acid oxidation) A process was performed in the same manner as in Example 5 except that 2N nitric acid was used and the treatment temperature was 100 ° C. The amount of the activated carbon modified by the 2N nitric acid oxidation was 56.2 g. Next, a catalyst in which platinum was supported on activated carbon modified by 2N nitric acid oxidation was obtained in the same manner as in Example 1. The catalyst contained 3% by weight of platinum.

Example 7 (Preparation of a catalyst in which platinum is supported on modified activated carbon by contact with carbon tetrachloride) In an autoclave equipped with a stirrer, 200 ml of carbon tetrachloride and 50 g of activated carbon similar to that used in Example 1 were placed and replaced with hydrogen. After sealing, the temperature was raised to 160 ° C. After maintaining at the same temperature for 16 hours and cooling to room temperature, the activated carbon was collected by filtration and sufficiently washed with carbon tetrachloride. Then, it was vacuum-dried at 110 ° C.
51.5 g of the modified activated carbon obtained by contact with carbon tetrachloride was obtained.
Met.

Then, the same procedure as in Example 1 was carried out to obtain a catalyst in which platinum was supported on modified activated carbon by contact with carbon tetrachloride. The catalyst contained 3% by weight of platinum.

Example 8 (Preparation of Catalyst Having Platinum Supported on Modified Activated Carbon by Contacting with Hexachloroethane) A procedure was carried out in the same manner as in Example 7, except that 200 ml of a 10% by weight hexachloroethane dichloromethane solution was used. The obtained activated carbon modified by contact with hexachloroethane is 5
2.5 g.

Next, the same procedure as in Example 1 was carried out to obtain a catalyst in which platinum was supported on modified activated carbon by contact with hexachloroethane. The catalyst contained 3% by weight of platinum.

Example 9 (Preparation of chloroform) 60 g of carbon tetrachloride was placed in an autoclave having an inner diameter of 50 mm and a height of 200 mm in a vessel, and 5.0 g of the catalyst prepared in Examples 1 to 8 was added. Was. After removing the air in the reactor, hydrogen was charged at room temperature at 35 kg / cm ² · G. 5 with a stirrer equipped with a disk turbine blade
While stirring at 00 rpm, the inside of the reactor was heated and controlled to 105 ° C., and then carbon tetrachloride was added to the reactor with a metering pump at 0.2
It was continuously fed into the reactor at 5 g / min. The supply of hydrogen is 1
Time once performs degassing to 30Kg / cm ² · G, was performed by supplying hydrogen to 45Kg / cm ² · G. Withdrawal of the reaction solution was performed with a liquid extraction pipe with a filter inserted into a reactor adjusted so that 36 ml of the reaction solution remained. The pressure reduced by the extraction was increased to 45 kg / cm ² · G with hydrogen. Table 1 shows the results of analyzing the reaction gas and the liquid and following the change over time.

[0041]

[Table 1]

Comparative Example 1 The same procedure as in Example 9 was carried out except that untreated activated carbon and a 3% by weight platinum-supported activated carbon catalyst prepared and operated in the same manner as in Example 1 were used. Was. The results are shown in Table 1.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-129130 (JP, A) JP-A-1-258632 (JP, A) JP-A 1-258631 (JP, A) JP-A-1- 132537 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C07C 19/04 C07C 17/23

Claims (1)

(57) [Claims] A method for producing chloroform in which a chlorine atom is replaced by a hydrogen atom by reacting carbon tetrachloride and hydrogen in the presence of a catalyst, wherein a catalyst comprising carbon is used as a catalyst as a reducing agent, an oxidizing agent or an organic compound. A method for producing chloroform, which comprises using a catalyst in which a metal of Group 8 of the periodic table is supported after contacting with a halide.