JP2606113B2 - Method for producing cyclohexene - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. 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 material such as a raw material of polyamide such as lactams and dicarboxylic acids, a raw material of lysine, a medicine and an agricultural chemical.

[0002]

2. Description of the Related Art Various processes for producing cyclohexene are known. Among them, a monocyclic aromatic hydrocarbon is prepared in the presence of an aqueous solution containing a ruthenium catalyst and an additive such as an alkali agent or a metal salt. The method of partial reduction with hydrogen is preferred because the selectivity of the corresponding cycloolefin is high (JP-B-56-22850, JP-A-577-130926, JP-B-57-7607, JP-A-61-7607). 40226, JP-A-62-45544).

[0003]

When cyclohexene is continuously produced from benzene by the above method, an oil phase consisting of a reaction product and an unreacted raw material is extracted from an aqueous phase consisting of a ruthenium catalyst and water. . In this case, in the case of industrial implementation, it is necessary to pass through a filter in order to reliably prevent solids present in a reaction solution such as a catalyst in the oil phase from being mixed into the oil phase. It is. However, according to the study of the present inventors, when the reaction is carried out for a long time, the filter is unexpectedly quickly clogged,
It has been found that it is difficult to stably produce cyclohexene. Such problems are more severe than expected, as it is not practical to change filters frequently.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide an industrially advantageous method for producing cyclohexene. To achieve this goal, the present inventors have conducted intensive studies and, as a result, have surprisingly found that there is a close relationship between filter blockage and trace impurities contained in benzene, and have reached the present invention.

That is, the gist of the present invention is to partially reduce benzene with hydrogen at a high temperature and a high pressure in a liquid phase in the presence of a ruthenium catalyst and water to convert an oil phase comprising a reaction product and unreacted raw materials into A method for separating cyclohexene from 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.

Hereinafter, the present invention will be described in detail. As the benzene as a raw material used in the present invention, the concentration of methylvinylbenzene in benzene is 10 ppm or less, preferably 5 ppm.
ppm or less, particularly preferably 1 ppm or less. If benzene containing methylvinylbenzene at a concentration higher than this concentration is used as a raw material, the filter will be clogged at an early stage, making it difficult to stably produce cyclohexene.

According to detailed studies by the present inventors, it has been confirmed that the composition of impurities in various industrially obtained benzenes is considerably different depending on each benzene.
This is considered to be due to the method of producing benzene or the difference in the origin of benzene. And, since the standard of benzene does not specify the concentration of methylvinylbenzene, which is a substance causing the clogging of such a filter, if industrial benzene is used easily, the filter may be removed by the existing methylvinylbenzene. Blockage occurs, making it difficult to produce stable cyclohexene.

The method for reducing the concentration of methylvinylbenzene in benzene to 10 ppm or less is not particularly limited, and industrial raw material benzene having a methylvinylbenzene content of a predetermined amount or less may be selected and used. Purification may be carried out by known means such as. The mechanism by which methylvinylbenzene present in benzene causes blockage of the filter is not clear, but it is thought 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 during or after the preparation thereof, such as zinc, chromium, molybdenum, cobalt, manganese,
It is a catalyst mainly composed of ruthenium to which nickel, iron, gold, copper and the like are added. The addition of these metal components generally increases the selectivity, although the reaction rate is somewhat lower than that of ruthenium alone. When another metal is used together with ruthenium, it is usually selected in the range of 0.1 to 10 in atomic ratio to ruthenium.

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

[0011] 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 usually 0.01 to 20 times the weight of benzene, and preferably 0.1 to 5 times the amount of benzene. Too little or too much water reduces the effect of coexistence. Further, with a preferable amount of water, the reaction solution taken out of the reaction system is separated into an organic phase and an aqueous phase, and the recovery of the target cyclohexene contained in the organic phase becomes easy.

In the reaction system of the present invention, a metal salt may coexist in water. Such metal salts include IU
The addition of metal salts such as Group 1 element, Group 2 element, zinc, iron, manganese, and cobalt in the Periodic Table of the PAC inorganic compound nomenclature (1989 edition) is effective, and particularly preferred is the addition of zinc salts. Achieve results. Here, as the salts of various metals, for example, weak acid salts such as carbonate and acetate, and strong acid salts such as hydrochloride, sulfate and nitrate are used. The amount of metal salt used is usually 1 × 1
It is 0 ^-5 to 1 times by weight.

The reaction of the present invention usually has a reaction temperature of 50 to 2
The reaction is carried out at a high temperature and 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 raw materials such as benzene, water, and a catalyst are suspended, and the hydrogen gas is supplied into the liquid reaction mixture via a nozzle opening.

[0014]

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

Example 1 Precision distillation was carried out to reduce the content of methylvinylbenzene to 0.1.
Using benzene of 1 ppm or less, benzene 3
3.9% by weight, ruthenium catalyst supporting silica 1.4
64.7% by weight of a 6% by weight aqueous zinc sulfate solution
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 stirring at a high speed to perform a partial hydrogenation reaction of benzene. (Average residence time of the oil phase 35 minutes). Further, a stationary tank is installed in the reactor, the oil phase and the 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. After 500 hours from the start of the reaction, the filter was closed and the oil phase could not be removed. Filter
When taken out and observed, sediment was accumulated.

[0017]

Industrial Applicability According to the method of the present invention, it is possible to suppress clogging of a filter for separating a reaction solution, which is an obstacle in the industrial production of cyclohexene by partially reducing benzene, so that cyclohexene can be stabilized for a long time. Can be manufactured.

Claims (1)

(57) [Claims] 1. A partial reduction of benzene with hydrogen at a high temperature and a high pressure in a liquid phase in the presence of a ruthenium catalyst and water to convert an oil phase composed of a reaction product and unreacted raw materials into a water composed of a catalyst slurry. A method for separating cyclohexene from an oil phase and continuously recovering cyclohexene from the oil phase, wherein the concentration of methylvinylbenzene in the raw material benzene is 10 ppm or less.