JP2925129B2 - Method for producing cycloolefin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for producing cycloolefins by partially reducing a monocyclic aromatic hydrocarbon. In particular, the present invention relates to a method for producing cyclohexene by partially reducing benzene. Cyclohexene is widely used as an intermediate material for organic chemical products, for example, a polyamide material.

[0002]

2. Description of the Related Art Various processes for producing cycloolefins, particularly cyclohexene, are known. Among them, a monocyclic aromatic hydrocarbon is generally used in the presence of a ruthenium catalyst and water, generally with an alkali agent or a metal salt. The method of partial reduction with hydrogen by adding an additive such as such is known as a preferable method because the selectivity and yield of the corresponding cycloolefin are high (Japanese Patent Publication No. 56-22850, etc.).

[0003] In such a method, the anion or alkali of the additive causes corrosion of the material in a liquid contact portion of the reactor or the like, and the activity or selectivity of the catalyst decreases due to the metal eluted from the reactor. It is known that the phenomenon occurs. For this reason, the liquid contact portion of the reactor is coated with a fluororesin (Japanese Patent Publication No. 56-22850), coated with nickel (Japanese Patent Application Laid-Open No. 62-67033), or using titanium or zirconium as a material (Japanese Patent Application Laid-Open No. No. 62-81331).

[0004]

However, all of these methods have some problems and are not necessarily industrially advantageous. Materials coated with a fluororesin have problems in strength at high temperatures and high pressures, and are not suitable for industrial use. In addition, titanium and zirconium have a problem of causing hydrogen embrittlement during long-term use, and are still insufficient. Further, although the nickel coating method improves corrosion resistance to some extent, it has been confirmed by the present inventors that the catalytic performance is significantly reduced by nickel eluted with time.

[0005]

The present inventors have intensively studied to improve the above-mentioned drawbacks of the prior art and to provide a more industrially advantageous method for producing cycloolefins. By reacting while maintaining the concentration at 50 ppm or less, and found that the desired cycloolefin can be produced with high selectivity and high yield over a long period of time,
As a result of further study, the present invention has been reached.

That is, the gist of the present invention is to provide a method for continuously producing cycloolefin by partially reducing a monocyclic aromatic hydrocarbon with hydrogen in the coexistence of a ruthenium catalyst and water to form a liquid in a liquid contact portion of a reactor. using a nickel-containing material, and the aqueous phase of the reaction solution be acidic, low of a reaction solution aqueous phase
Replace at least part with an aqueous solution containing no nickel
To reduce the nickel concentration in the aqueous phase of the reaction solution to 50 ppm
The present invention resides in a method for producing a cycloolefin, characterized in that the reaction is carried out while maintaining the following.

Hereinafter, the present invention will be described in more detail. The monocyclic aromatic hydrocarbon used as a raw material in the present invention is benzene or benzene usually substituted with a lower alkyl group having about 4 or less carbon atoms such as toluene and xylene. Examples of the ruthenium catalyst include those obtained by reducing various ruthenium compounds, or other metals after or after the preparation thereof, such as zinc, chromium, molybdenum, tungsten, manganese, cobalt, nickel, iron, and copper. It is mainly composed of added ruthenium. Various ruthenium compounds are not particularly limited, for example, chloride, bromide, iodide,
Nitrate, sulfate, hydroxide, oxide, and various ruthenium-containing complexes can be used. Reduction methods include reduction with hydrogen gas, or formalin,
It can be performed by a chemical reduction method using sodium borohydride, hydrazine or the like.

The ruthenium catalyst may be used by being supported on a carrier. The carrier may be silica, alumina, silica-alumina, zeolite, activated carbon, or a common metal oxide, composite oxide, hydroxide, or poorly water-soluble catalyst. Metal salts and the like. Ruthenium is a method commonly used for various ruthenium compounds on a carrier, for example, an ion exchange method, an adsorption method,
It is supported by an immersion method, a coprecipitation method and a dry method. As the supported ruthenium compound, ruthenium chloride,
It is bromide, iodide, nitrate, sulfate, hydroxide, oxide, or a complex containing various ruthenium, or a compound obtained by reducing ruthenium to a metal state in these compounds. After the preparation of these catalysts, other metal species such as chromium, molybdenum, tungsten, manganese, cobalt, nickel, iron, copper, silver and the like may be co-supported. The supported amount of ruthenium is usually 0.01 to 10% by weight.

[0009] The reaction system of the present invention requires the presence of water. Although the amount of water varies depending on the reaction mode, it is generally 0.1 to 20 times by weight, preferably 0.5 to 5 times by weight of the monocyclic aromatic hydrocarbon. Under these conditions, two phases are formed: an organic liquid phase (oil phase) containing the raw materials and products as main components, and a liquid phase (water phase) containing water.
When the ratio between the oil phase and the aqueous phase is extreme, it is difficult to form two phases, and liquid separation is difficult. Also, even if the amount of water is too small,
If the amount is too large, the effect of coexistence decreases, and if the amount is too large, it is not preferable because the size of the reactor needs to be increased.

In the reaction system of the present invention, the reaction solution
The pH of the aqueous phase is acidic, since a high reaction rate can be expected.
Der is, the combined use of metal salts as in the conventional known manner, it is possible to the aqueous phase acidic. Examples of the kind of the metal salt include a Group 1 metal, a Group 2 metal, and a Group 12 metal in the periodic table (the group number is IUPAC revised edition of inorganic chemical nomenclature (198).
9)) or nitrates, chlorides, sulfates, acetates, phosphates and the like of metals such as manganese and cobalt, and it is particularly preferable to use zinc sulfate in combination. The amount of the metal salt used is usually about 1 × 10 ⁻⁵ to 1 times by weight based on the water of the reaction system.

When the partial reduction reaction is carried out for a long time under the above reaction conditions, the requirements for selecting the material of the liquid contact portion of the reactor are that hydrogen embrittlement does not occur and that the material can be used under high temperature and high pressure. The purpose is to select a material that has sufficient strength and does not easily cause corrosion, and a nickel-containing material is most suitable for satisfying such conditions. Examples of the nickel-containing material include chromium steel, stainless steel, nickel-chromium-molybdenum alloy, nickel-molybdenum alloy, and the like.

However, according to the study of the present inventors, when it is assumed that the partial reduction reaction is carried out particularly continuously over a long period of time on an industrial scale, the material of the material in the liquid contact part has a small amount. It has been found that the catalyst is eluted in the liquid phase of the reaction solution, and further the nickel eluted among the components of the material significantly reduces the performance of the catalyst. Therefore, in order to produce cycloolefins with high selectivity and high yield while ensuring the safety of the equipment over a long period of time, use a nickel-containing material and nickel in the aqueous phase. It is necessary to manufacture in a system that does not accumulate.

When the cycloolefin is produced industrially, particularly continuously, an aqueous phase containing a catalyst component and the like is usually used repeatedly, so that the eluted nickel accumulates in the aqueous phase and the reaction proceeds. The effect of this will also increase. In order to reduce such an effect, the nickel concentration in the aqueous phase used repeatedly should be kept at a low level, specifically, the nickel concentration in the aqueous phase should be 50 ppm or less, preferably 30 pp.
m or less. This is because when the nickel concentration in the aqueous phase exceeds 50 ppm, the catalytic activity is significantly reduced.

In the present invention, the nickel concentration in the aqueous phase is 50
ppm is a method of holding the following, small reaction solution aqueous phase
Replace at least part with an aqueous solution containing no nickel
That the method is intended to take, preferably not extracting at least a portion of the aqueous solution containing nickel from the aqueous phase used repeatedly performed in the process of replacing the aqueous solution containing no nickel. The rate or frequency of extracting the nickel-containing aqueous solution is preferably set as appropriate according to the nickel elution rate of the nickel-containing material used.

As the reaction conditions of the present invention, the reaction temperature is as follows:
It is usually 50 to 250 ° C, preferably 100 to 220 ° C. When the temperature exceeds 250 ° C., the selectivity of cycloolefin decreases, and when the temperature is lower than 50 ° C., the reaction rate remarkably decreases, which is not preferable. The pressure of hydrogen during the reaction is usually 0.1 to 20.
MPa, preferably in the range of 0.5 to 10 MPa. Usually, if it exceeds 20 MPa, it is industrially disadvantageous,
On the other hand, if it is less than 0.1 MPa, the reaction rate is remarkably reduced, which is uneconomical in equipment. Reaction type must be continuous
It is.

[0016]

The present invention will be described below with reference to examples, but the present invention is not limited to the examples unless it exceeds the gist. Reference Example 1 Using zirconium silicate (manufactured by Mitsui Chemicals) as a carrier, a ruthenium chloride aqueous solution containing a predetermined amount of ruthenium and a zinc chloride aqueous solution containing a predetermined amount of zinc were mixed with the above carrier, and the mixture was heated at 60 ° C. After impregnation for 1 hour, water was distilled off using a rotary evaporator and the product was dried. 0.5% Ru-0.5% Zn / ZrSiO thus obtained
₄ was reduced and activated in a hydrogen stream at 200 ° C. for 3 hours.

In a 0.5 L batch reactor using a nickel-chromium-molybdenum alloy in the liquid contact part, water (nickel
ppm), zinc sulfate heptahydrate (ZrSiO _4.
7HO) and 80 ml of benzene were charged. Further, hydrogen gas was introduced, the reaction pressure was 5.0 MPa, and the temperature was 1
The partial reduction reaction was carried out at 50 ° C. while stirring at a high speed. Table 1 shows the reaction time, benzene conversion, and cyclohexene selectivity. Reference Comparative Example 1 Reference example except that water containing 100 ppm of nickel was used.
A partial hydrogenation reaction was carried out in the same manner as in Example 1 . Table 1 shows the reaction time, benzene conversion, and cyclohexene selectivity.

[0018]

[Table 1]

Reference Example 2 After impregnating SiO ₂ with an aqueous solution of zirconyl nitrate and drying,
ZrO ₂ —SiO ₂ heat treated at 00 ° C. (weight ratio 1: 1)
9) was used as a carrier. Carrying ruthenium <br/> arm及beauty zinc in the same manner as in Reference Example 1, further reduced with 3 hours hydrogen stream at 200 ° C., it was activated.

Using a nickel-chromium-molybdenum steel as a liquid contact part, 250 ml of water (0 ppm of nickel), 30 g of zinc sulfate heptahydrate, and 24 g of the above catalyst were placed in a 1 L continuous flow reactor equipped with an oil / water separation tank. Was charged. Further, hydrogen gas was introduced, the reaction pressure was set to 50 MPa, the temperature was set to 150 ° C., benzene was supplied at 300 L / Hr, and the partial reduction reaction was continuously performed while stirring at a high speed. The average residence time of benzene is 35 minutes. Table 2 shows the reaction time, benzene conversion, and cyclohexene selectivity. Further, after 87.5 hours, the reactor was cooled and the concentration of nickel in the aqueous phase of the reaction solution was measured to be 33.3 ppm.

[0021]

[Table 2]

Example 1 A partial reduction reaction of benzene was carried out under the same conditions as in Reference Example 2 . 100 hours after the start of the reaction, the stirring was stopped, 200 ml of the aqueous phase portion of the reaction solution was taken out, and instead, a zinc sulfate solution (0 pp nickel) having the same concentration as the aqueous phase solution was used.
m). Thereafter, the reaction results when the reaction was restarted are shown in Table-3.

[0023]

[Table 3]

Reference Comparative Example 2 A partial reduction reaction of benzene was carried out under the same conditions as in Reference Example 2 . Analysis of the reaction mixture 300 hours after the start of the reaction revealed that the benzene conversion was 15%, the cyclohexene selectivity was 67%, and the nickel concentration in the aqueous phase was 118%.
ppm.

[0025]

According to the method of the present invention, a cycloolefin can be stably produced from a monocyclic aromatic hydrocarbon for a long period of time.

Claims (1)

(57) [Claims] 1. A method for continuously producing cycloolefin by partially reducing a monocyclic aromatic hydrocarbon with hydrogen in the presence of a ruthenium catalyst and water, wherein a nickel-containing material is used in a liquid contact part of a reactor. The aqueous phase of the reaction solution is acidic, and at least a part of the aqueous phase of the reaction solution contains nickel.
A method for producing a cycloolefin, characterized in that the reaction is carried out while maintaining the nickel concentration in the aqueous phase of the reaction solution at 50 ppm or less by replacing the aqueous solution with no aqueous solution .