JPH07179367A - Production of cyclohexene - Google Patents

Abstract

PURPOSE:To provide a production method capable of preventing clogging of a filter for separation of a reaction solution, i.e., an obstruction in industrial production of cyclohexene by partial reduction of benzene and stably producing cyclohexene for a long period. CONSTITUTION:This production method is to partly reduce benzene with hydrogen in the presence of a ruthenium catalyst and water in a liquid phase at a high temperature and a high pressure, separate the oil phase composed of reactional products and unreacted raw materials from the aqueous phase composed of a catalyst slurry and continuously recover cyclohexene from the oil phase. The characteristic of this method for production of cyclohexene is that the concentration of methylvinylbenzene in benzene as the raw material is controlled to <=10ppm.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing cyclohexene by partially reducing benzene. Cyclohexene is a compound useful as an important intermediate raw material for polyamide raw materials such as lactams and dicarboxylic acids, lysine raw materials, pharmaceuticals and agricultural chemicals.

[0002]

2. Description of the Related Art Various methods for producing cyclohexene are known. Among them, in the presence of an aqueous solution containing a ruthenium catalyst containing a monocyclic aromatic hydrocarbon and an additive such as an alkali agent or a metal salt. The method of partial reduction with hydrogen is a preferable method because of high selectivity of the corresponding cycloolefin (Japanese Patent Publication No. 56-22850, Japanese Patent Publication No. 577-130926, Japanese Patent Publication No. 57-7607, Japanese Patent Publication No. 61-607-). 40226, JP-A-62-45544 and the like).

[0003]

When cyclohexene is continuously produced from benzene by the above method, an oil phase consisting of a reaction product and unreacted raw materials is taken out from an aqueous phase consisting of a ruthenium catalyst and water. . In this case, in industrial practice, it is necessary to pass a filter in order to reliably prevent the solid content present in the reaction liquid such as a catalyst in the oil phase from being mixed in the oil phase. Is. However, according to the study of the present inventors, when the reaction is carried out for a long time, the filter is blocked unexpectedly quickly,
It became clear that it was difficult to produce cyclohexene stably. This problem is more severe than expected, as frequent filter replacements are not practical.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and to provide an industrially advantageous method for producing cyclohexene. As a result of earnest studies to achieve this goal, the present inventors have unexpectedly found that there is a close relationship between the filter clogging and trace impurities contained in benzene, and arrived at the present invention.

That is, the gist of the present invention is to perform partial reduction of benzene with hydrogen in the presence of a ruthenium catalyst and water in a liquid phase at high temperature and high pressure to obtain an oil phase consisting of a reaction product and an unreacted raw material. A method for producing cyclohexene, which comprises phase-separating an aqueous phase comprising a catalyst slurry and continuously recovering cyclohexene from the oil phase, wherein the concentration of methylvinylbenzene in the raw material benzene is 10 ppm or less. Exist.

The present invention will be described in detail below. As the raw material benzene used in the present invention, the concentration of methylvinylbenzene in benzene is 10 ppm or less, preferably 5
It is necessary to set it to be ppm or less, particularly preferably 1 ppm or less. When benzene containing methylvinylbenzene at a concentration above this concentration is used as a raw material, the filter is clogged early, making it difficult to stably produce cyclohexene.

According to a detailed study by the present inventors, it has been confirmed that the composition of impurities in various industrially available benzenes varies considerably depending on each benzene.
This is considered to be due to the difference in the benzene production method or the source of benzene. Since the standard of normal benzene does not specify the concentration of methylvinylbenzene, which is the causative agent of the clogging of the filter, if industrial benzene is used easily, the presence of methylvinylbenzene causes the filter- Blockage occurs, which makes stable production of cyclohexene difficult.

The method for reducing the concentration of methylvinylbenzene in benzene to 10 ppm or less is not particularly limited, but industrial raw material benzene having a methylvinylbenzene content of not more than a predetermined amount may be selected and used, or distilled. You may refine | purify by well-known means, such as. The mechanism by which methylvinylbenzene present in benzene causes blockage of the filter is not clear, but it is considered to be due to the following mechanism. That is, it is presumed that methylvinylbenzene is polymerized in the reaction system and accumulates on the filter.

As the ruthenium catalyst in the present invention,
Those obtained by reducing various ruthenium compounds, or other metals such as zinc, chromium, molybdenum, cobalt, manganese at or after the preparation stage thereof.
It is a catalyst mainly composed of ruthenium containing nickel, iron, gold and copper. By adding these metal components, the reaction rate is generally slightly lower than that of ruthenium alone, but the selectivity can be increased. When another metal is used together with ruthenium, the atomic ratio to ruthenium is usually selected in the range of 0.1 to 10.

The various ruthenium compounds are not particularly limited, but for example, chlorides, bromides, iodides, nitrates, hydrochlorides, hydroxides, oxides, or complexes containing various rutheniums can be used. . As the reduction method, reduction with hydrogen gas or a chemical reduction method with formalin, sodium borohydride, hydrazine or the like can be performed. The ruthenium catalyst may be supported on a carrier, and examples of the carrier include silica, alumina, silica-alumina, zeolite, activated carbon, or general metal oxides, complex oxides, hydroxides, sparingly water-soluble metal salts and the like. To be done. Ruthenium is a method in which various ruthenium compounds are usually used as a carrier, for example, an ion exchange method,
It is supported by an adsorption method, a coprecipitation method, a dry solidification method, or the like. As the supported ruthenium compound, a ruthenium chloride, bromide, iodide, nitrate, hydrochloride, hydroxide, oxide, or complex containing various ruthenium, or in these compounds, reduced ruthenium to a metal state. It is a thing. Further, other metals may be co-supported after the preparation of these catalysts. The amount of ruthenium supported is usually 0.0
It is 1 to 10% by weight.

The reaction system of the present invention requires the presence of water. The amount of water varies depending on the reaction mode, but is usually 0.01 to 20 times by weight, preferably 0.1 to 5 times the amount of benzene. If there is too little water or too much water, the effect of coexistence decreases. Further, with a preferable amount of water, the reaction liquid taken out from the reaction system is separated into an organic phase and an aqueous phase, and the target cyclohexene contained in the organic phase is easily recovered.

Further, in the reaction system of the present invention, a metal salt may coexist in water. As such a metal salt, IU
It is effective to add a metal salt of Group 1 element, Group 2 element, zinc, iron, manganese, cobalt, etc. of the periodic table of PAC inorganic compound nomenclature (1989 version), and particularly preferable reaction by addition of zinc salt. You will get a grade. Here, as salts of various metals, for example, weak acid salts such as carbonates and acetates, and strong acid salts such as hydrochlorides, sulfates and nitrates are used. The amount of metal salt used is usually 1 × 1 with respect to coexisting water.
0 ^-5 to 1 times by weight.

In the reaction of the present invention, the reaction temperature is usually 50 to 2
The reaction is carried out at a high temperature and a high pressure of 50 ° C., preferably 100 to 220 ° C. and a reaction pressure of usually 0.1 to 20 MPa.
The reaction can be carried out batchwise or continuously, but industrially it is usually carried out continuously. The reaction is carried out by supplying hydrogen gas to a liquid reaction mixture in which the raw materials benzene, water, a catalyst and the like are suspended, and hydrogen gas is supplied into the liquid reaction mixture through a nozzle opening.

[0014]

EXAMPLES Examples will be described below, but the present invention is not limited to these examples.

Example 1 Precise distillation was carried out to obtain a methyl vinylbenzene content of 0.
Using benzene that is 1 ppm or less, benzene 3
3.9% by weight, silica-supported ruthenium catalyst 1.4
Wt% and 64.7 wt% zinc sulfate aqueous solution 64.7 wt%
Hydrogen gas was supplied to the slurry from the nozzle opening, and benzene was continuously supplied at a reaction pressure of 5.0 MPa and a temperature of 150 ° C. while performing high-speed stirring to carry out a partial hydrogenation reaction of benzene. (Average residence time of oil phase 35 minutes). Furthermore, a stationary tank is installed in the reactor, an oil phase and an aqueous phase are separated in the stationary tank, and the oil phase is filtered with a filter having a diameter of 5 μm.
And then collected. 500 hours after the start of the reaction, the filter was taken out and observed, and no accumulation was observed.

Comparative Example 1 A partial hydrogenation reaction of benzene was carried out in the same manner as in Example 1 except that benzene containing 20 ppm of methylvinylbenzene was used. 500 hours after the start of the reaction, the filter was clogged and the oil phase could not be extracted. Filter-
When taken out and observed, deposits had accumulated.

[0017]

Industrial Applicability According to the method of the present invention, it is possible to suppress clogging of the reaction solution separation filter, which is an obstacle when industrially producing cyclohexene by partially reducing benzene. Can be manufactured.

Claims (1)

[Claims] 1. Benzene is partially reduced with hydrogen at high temperature and high pressure in a liquid phase in the presence of a ruthenium catalyst and water, and an oil phase composed of a reaction product and unreacted raw material is converted into a water composed of a catalyst slurry. A method for producing cyclohexene, which comprises phase-separating phases and continuously recovering cyclohexene from the oil phase, wherein the concentration of methylvinylbenzene in the raw material benzene is 10 ppm or less.