JP2000086543A - Production of cyclic olefin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce the subject compound, suppressing the reduction of selectivity and in a good efficiency by partially hydrogenating a single ring aromatic hydrocarbon in the presence of a ruthenium catalyst, water and a metal sulfate salt, while changing the concentration of the metal sulfate salt dissolved in an aqueous phase in which the catalyst presents. SOLUTION: This method for producing a cyclic olefin is to perform a reaction of the partial hydrogenation of a single ring aromatic hydrocarbon (e.g.; benzene, toluene, xylene and a lower alkyl-substituted benzene) with hydrogen in the presence of a ruthenium catalyst (e.g.; consisting of metallic ruthenium obtained by reducing a ruthenium compound in advance), water and a metal sulfate salt (preferably containing at least zinc sulfate) by changing (preferably increasing or changing within 1×10-5 to 5.0 mol/l range) the concentration of the metal sulfate salt dissolved in an aqueous phase in which the catalyst presents.

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 a cycloolefin by hydrogenating a monocyclic aromatic hydrocarbon in the presence of a ruthenium catalyst. Cycloolefins, particularly cyclohexenes, have high value as intermediate materials for organic chemical products, and are particularly useful as polyamide materials, lysine materials, and the like.

[0002]

2. Description of the Related Art Various methods for producing cycloolefins are known, and among them, a method of partially hydrogenating a monocyclic aromatic hydrocarbon using a ruthenium catalyst is the most common method. As a method for improving the yield and yield, there have been reported many results of studies on types of catalyst components and supports, metal salts as additives to the reaction system, and the like.

[0003] Among them, in a reaction system in which water and zinc coexist with a relatively high yield of cycloolefin, for example, (1) monocyclic aromatic hydrocarbon is converted into water and at least 1
When partially reducing with hydrogen under neutral or acidic conditions in the coexistence of various zinc compounds, 30-200
(2) a method comprising using a catalyst in which particles mainly composed of metal ruthenium having an average crystallite diameter of 主 成分 are supported on a carrier (Japanese Patent Publication No. H8-25919); (2) a monocyclic aromatic compound in the presence of a ruthenium catalyst; In producing a cycloolefin by partially hydrogenating an aromatic hydrocarbon, in a reaction system, at least one of zinc oxide and zinc hydroxide is present in a dissolved state in an amount equal to or less than the saturation solubility. (3) When a monocyclic aromatic hydrocarbon is partially reduced with hydrogen in the presence of water, 200
方法 A method in which the reaction is carried out under neutral or acidic conditions in the presence of at least one kind of solid basic zinc using hydrogenation catalyst particles mainly composed of metal ruthenium having an average crystallite diameter of not more than Japanese Patent Publication No. Hei 8-19012), (4) Using a ruthenium catalyst obtained by reducing a ruthenium compound containing zinc in advance, a monocyclic aromatic hydrocarbon is produced under acidic conditions in the presence of water and a water-soluble zinc compound. A method of partial reduction with hydrogen (Japanese Patent Publication No. 2-16736) has been proposed.

Further, in a method of obtaining a cycloolefin by partially reducing a monocyclic aromatic hydrocarbon with hydrogen in the presence of water and zinc sulfate using a ruthenium catalyst, the concentration of zinc sulfate in the aqueous phase depends on the reaction results. Studies have already been conducted to determine whether or not it affects the concentration of zinc sulfate, and it is known that there is an optimum zinc sulfate concentration at which the selectivity of cycloolefin is the highest (Applied Catalysis A: General, 89 (19)
92) 77-102).

[0005] If a process for producing a cycloolefin by partially hydrogenating a monocyclic aromatic hydrocarbon with hydrogen partially using a ruthenium catalyst is to be carried out industrially, efficient production is hindered. It is preferable to use the catalyst for a long period of time because it is desired to reduce the frequency of replacing the catalyst as much as possible. However, it has been found that the cycloolefin selectivity then changes over time. After the reaction is started using the catalyst, the selectivity of cycloolefin generally increases in the very early stage, but thereafter, the selectivity of cycloolefin decreases. It is more efficient to avoid the decrease in the selectivity of the cycloolefin for the purpose of production as much as possible.

[0006] However, none of the above-mentioned prior art documents mentions a solution to the decrease in cycloolefin selectivity due to long-term use of the catalyst. There is no description.

[0007]

The object of the present invention is to reduce the selectivity of cycloolefin generated when a ruthenium catalyst is used for a long period of time by changing the concentration of metal sulfate in the aqueous phase in the reaction system. It is an object of the present invention to provide a method for efficiently producing a cycloolefin by hydrogenating a monocyclic aromatic hydrocarbon.

[0008]

Means for Solving the Problems The present inventors have found that a monocyclic aromatic hydrocarbon is partially hydrogenated and reacted with hydrogen in the presence of a ruthenium catalyst, water and metal sulfate to produce a cycloolefin. As a surprising fact, it has been found that the optimum concentration of the metal sulfate dissolved in the aqueous phase containing the catalyst changes with the use of the catalyst over a long period of time, and the metal sulfate is always adjusted to or close to the optimum concentration. By changing the sulfate concentration, the decrease in cycloolefin selectivity was successfully suppressed, and the present invention was completed.

That is, the present invention is as follows. 1) In the presence of a ruthenium catalyst, water and a metal sulfate, a monocyclic aromatic hydrocarbon is partially hydrogenated with hydrogen and reacted.
A method for producing a cycloolefin, comprising: performing a reaction while producing a cycloolefin while changing the concentration of a metal sulfate dissolved in an aqueous phase containing a catalyst.

2) The method according to the above 1, wherein the reaction is carried out while increasing the concentration of the metal sulfate. 3) The method according to 1 or 2, wherein the metal sulfate is a metal sulfate containing at least zinc sulfate. 4) The concentration of the metal sulfate in the aqueous phase is 1 × 10 ^{−5 to} 5.0.
4. The method according to any one of the above 1 to 3, wherein the concentration of the metal sulfate is changed within the range of mol / l.

5) The water is 0.5% of the monocyclic aromatic hydrocarbon.
The method according to any one of the above items 1 to 4, wherein the method is present in an amount of up to 20 times by weight. 6) The method according to any one of 1 to 5 above, wherein the ruthenium catalyst comprises a metal ruthenium obtained by previously reducing a ruthenium compound. (7) The method according to (6) above, wherein the ruthenium catalyst is an unsupported catalyst and the average crystallite size of the metal ruthenium is 200 ° or less.

(8) The method according to the above (7), wherein the ruthenium compound is a ruthenium compound containing a zinc compound, and contains 0.1 to 50% by weight of zinc based on ruthenium. Hereinafter, the present invention will be described in more detail. The monocyclic aromatic hydrocarbon in the present invention includes benzene, toluene, xylene, benzene usually substituted with a lower alkyl group having 1 to 4 carbon atoms, and the like.

The reaction pressure of the present invention is generally from 10 to 200 a.
tm is preferably 20 to 70 atm. If the reaction pressure is too low, the selectivity of the cycloolefin decreases, and if the reaction pressure is too high, the hydrogen and monocyclic aromatic hydrocarbon to be supplied to the reactor must be made high, which is both inefficient. In the present invention, the reaction temperature is generally 50 to
Although it is 250 ° C, it is preferably 100 to 200 ° C. If the reaction temperature is too low, the reaction rate will decrease, and if the reaction temperature is too high, the result will be to promote the growth of the average crystallite size of ruthenium as a catalyst.

The ruthenium catalyst used in the present invention is a catalyst comprising metal ruthenium obtained by previously reducing various ruthenium compounds. The ruthenium compounds include, for example, chlorides, bromides, halides such as iodides,
Alternatively, a nitrate, a sulfate, a hydroxide, or a complex containing various rutheniums, for example, a ruthenium carbonyl complex, a ruthenium acetylacetonate complex, a ruthenocene complex, a ruthenium ammine complex, and a compound derived from such a complex can be used. . Further, the use of a mixture of two or more of these ruthenium compounds can be used.

As a method for reducing these ruthenium compounds, a catalytic reduction method using hydrogen or carbon monoxide, or a chemical reduction method using formalin, sodium borohydride, hydrazine or the like is used. Of these, catalytic reduction with hydrogen is preferred, and reduction activation is usually performed at 50 to 450 ° C, preferably 100 to 400 ° C. If the reduction temperature is less than 50 ° C., it takes too much time to reduce,
If the temperature exceeds 50 ° C., the aggregation of ruthenium proceeds, which may adversely affect the activity and the selectivity. The reduction may be performed in a gas phase or a liquid phase, but is preferably a liquid phase reduction. By performing the reduction operation in the liquid phase, impurities that adversely affect the reaction can be removed at the same time.

Before or after the reduction of the ruthenium compound, other metals or metal compounds such as zinc, chromium, molybdenum, tungsten, manganese, cobalt, nickel, iron, copper, gold, platinum, and the like, A compound mainly composed of ruthenium obtained by adding a compound may be used. When such a metal or metal compound is used, it is usually selected in the range of 0.001 to 20 as the atomic ratio to the ruthenium atom. Among them, zinc and a zinc compound are preferable, and the zinc and the zinc compound are preferably added before the reduction of the ruthenium compound. Is particularly preferred.

The ruthenium catalyst may be used by being supported on a carrier. The carrier is not particularly limited, but may be magnesium, aluminum, silicon, calcium, titanium, vanadium, chromium, manganese, cobalt, iron, nickel, copper, zinc, zirconium, hafnium, tungsten or the like, or such a metal. Oxides, composite oxides, hydroxides, sulfates, poorly water-soluble metal salts,
Alternatively, compounds and mixtures in which two or more such carriers can be chemically or physically combined are exemplified. The method for supporting ruthenium is not particularly limited, and examples thereof include an adsorption method, an ion exchange method, an immersion method, a coprecipitation method, and a drying method. The amount of ruthenium supported is not particularly limited, but is usually 0.001 to 20% by weight based on the carrier. However, it is preferable that ruthenium is used as it is without being supported on a carrier.

Further, in the case where the ruthenium catalyst is a non-supported catalyst composed of metal ruthenium obtained by previously reducing a ruthenium compound, the average crystallite size of the metal ruthenium is preferably 200 ° or less. If the average crystallite diameter exceeds this, the surface area of the ruthenium catalyst in which the active site exists is reduced, and the catalytic activity is reduced, so that it is not efficient. The measurement of the average crystallite diameter of the ruthenium catalyst is calculated from the spread of the diffraction line width obtained by the X-ray diffraction method of the ruthenium catalyst to be used, according to Scherrer's formula.
Specifically, it is calculated from the spread of a diffraction line having a maximum at a diffraction angle (2θ) of around 44 ° using CuKα radiation as an X-ray source. Further, the lower limit of the average crystallite diameter is theoretically a value larger than the crystal unit, and is actually 10
Å or more.

In the present invention, the amount of the ruthenium catalyst used is determined by the amount of water present in the reaction system, and is defined by the weight of the ruthenium catalyst per unit volume of the aqueous phase formed by the water. Specifically, the ruthenium catalyst can be used in a ratio of 0.01 to 100 g with respect to 1000 ml of the aqueous phase. Water must be present in the reaction system of the present invention. The amount depends on the type of reaction,
0.001 to 1 based on the starting monocyclic aromatic hydrocarbon used
It is 00 weight times. If the amount of water is too small, the selectivity of cycloolefin is reduced, and if the amount of water is too large, there are adverse effects such as an increase in the size of the reactor. It is preferable that 0.5 to 20 times by weight coexist in the reactor. However, in any case, water must be present in such an amount that the organic liquid phase mainly containing the raw material and the product and the liquid phase containing water do not become one phase under the reaction conditions. In other words, there is an amount of water in which a raw material and a product are in an organic liquid phase as a main component, that is, an oil phase and a water phase in which water is a main component are in a phase separated state, that is, an oil phase and an aqueous phase are in a liquid two-phase state. Must be.
Here, the main component refers to a component which shows the maximum ratio in terms of moles among the components constituting the liquid phase.

The concentration of hydrogen ions in the aqueous phase formed by water coexisting in the reaction system, that is, the pH, must be 7.0 or less, acidic or neutral. Furthermore, in the present invention, it is necessary that the metal sulfate is present, and it is not particularly necessary that the entire amount of the metal sulfate is present in a solid form in the reaction system. Must be present in a dissolved state. The metal sulfate to be present in the reaction system is exemplified by zinc, iron, nickel, cadmium, gallium, indium, magnesium, aluminum, chromium, manganese, cobalt, copper, and the like, and two or more of these may be used in combination. A double salt containing such a metal sulfate may be used. In particular, it is preferable to use zinc sulfate as the metal sulfate. The amount of the metal sulfate used is such that the concentration in the aqueous phase existing in the reaction system is 1 × 10 ^{−5 to} 5.0 mo.
1 / l, preferably 1 × 10 ^{−3 to} 2.0 mol when zinc sulfate is used as the metal sulfate at least.
/ L is more preferred.

In the reaction system of the present invention, the following metal salts may be present as in a conventionally known method. Examples of the kind of the metal salt include Group 1 metals such as lithium, sodium and potassium in the periodic table, and Group 2 metals such as magnesium and calcium (the group numbers are based on the revised IUPAC inorganic chemical nomenclature (198).
9)), or zinc, manganese, cobalt,
Metal nitrates such as copper, cadmium, lead, arsenic, iron, gallium, germanium, vanadium, chromium, silver, gold, platinum, nickel, palladium, barium, aluminum,
Examples include chlorides, oxides, hydroxides, acetates, phosphates, and the like, or a mixture of two or more of them chemically and / or physically. Among these, the addition of zinc salts such as zinc hydroxide and zinc oxide is preferable, and particularly a double salt containing zinc hydroxide, for example, a general formula (ZnSO ₄ ) _m · (Zn
(OH) ₂₎ represented by _n m: _n = 1: _0.01~100
The presence of a double salt of is preferred.

The amount of the metal salt used is not particularly limited as long as the aqueous phase can be kept acidic or neutral, but is usually 1 × 10 ^-5 to 1 × 10 ⁵ weight times the used ruthenium.
These may be present anywhere in the reaction system, and the present form does not necessarily have to be completely dissolved in the aqueous phase. Further, in addition to water, one or more organic substances having one or more hydroxyl groups may be present in the reaction system, and the amount thereof is not particularly limited. For those capable of dissolving both cycloolefin and cycloparaffin to be reacted under the reaction conditions,
It is preferable that the aqueous phase and the oil phase existing in the reaction system are in a range that does not form a single liquid phase. That is, the amount of the organic substance to be added is preferably in a range that allows the reaction liquid to maintain the two-phase state of the aqueous phase and the oil phase.

An important feature of the present invention is that a ruthenium catalyst,
In the presence of water and a metal sulfate, a monocyclic aromatic hydrocarbon is partially hydrogenated with hydrogen to cause a reaction, and in producing a cycloolefin, the reaction is carried out by changing the metal sulfate concentration in an aqueous phase containing a catalyst. On the point. When a process for producing a cycloolefin by partially hydrogenating a monocyclic aromatic hydrocarbon with hydrogen partially using a ruthenium catalyst is to be carried out industrially, cycloparaffin which is a by-product of the reaction is produced. It is desirable to carry out the reaction under conditions that suppress the generation and increase the selectivity of the target compound, cycloolefin, as high as possible. For this purpose, the concentration of the metal sulfate in the aqueous phase in the reaction system should usually be carried out at a value at which the selectivity of cycloolefin is maximum or close to the value. However, heretofore, not only has there been no knowledge that the optimum concentration of the metal sulfate changes with the long-term use of the catalyst, and it was not generally expected that the optimum concentration would change.

From the experiments conducted by the inventors, it was found that, for the first time, a change in the optimum concentration of the metal sulfate due to the long-term use of the catalyst, that is, when the catalyst was used for a long time, the concentration of the metal sulfate in the aqueous phase at which the selectivity of the cycloolefin became maximum. It has been confirmed that the change in cycloolefin selectivity over time during long-term use of the catalyst has been clarified as one of the causes and succeeded in significantly suppressing the decrease in the selectivity. did.

That is, the selectivity of cycloolefin is changed by changing the concentration of the metal sulfate in the aqueous phase in which the reaction is carried out in accordance with the optimum concentration of the metal sulfate in the aqueous phase which changes with the long-term use of the catalyst. Can be produced at or near the maximum. The effect of improving the selectivity of cycloolefins is that the amount of cycloolefins is improved by several thousand tons per year, considering that the standard-scale facility for industrially producing cycloolefins is about 100,000 tons per year. It can be evaluated as a very large effect.

The concentration of the metal sulfate in the aqueous phase at which the selectivity of the cycloolefin becomes the maximum is determined by extracting a part of the catalyst slurry containing the ruthenium catalyst from the reaction system over time and using it in water or in the reaction. It can be confirmed by adjusting the catalyst slurry of the metal sulfate having different concentration by adding the metal sulfate, and evaluating the reaction by a batch experiment or the like.

As a result, the point at which the cycloolefin selectivity is maximized is found, and the concentration of the metal sulfate in the aqueous phase in the reaction system may be adjusted to approach that point. As a specific adjustment method, when increasing the metal sulfate concentration, a method of adding the metal sulfate to the reaction system is convenient. In that case, dissolve the metal sulfate in water,
Alternatively, it may be added to the reaction system by mixing. When it is desired to lower the concentration of the metal sulfate, a part of the catalyst slurry is withdrawn, allowed to settle, the supernatant in which the metal sulfate is dissolved is replaced with water, and then the catalyst slurry is returned to the reaction system. Good. For these methods, a simple method may be appropriately selected depending on the type of reaction to be used.

Although the phenomenon clarified in the present invention, that is, the phenomenon in which the concentration of metal sulfate at which the selectivity of cycloolefin is maximized occurs, it has not been fully elucidated, but the ruthenium catalyst used It is considered that the active site of has undergone some change due to prolonged exposure to the reaction conditions. According to the method of the present invention, the catalyst activity is usually improved, so it can be said that this is an extremely effective method. As shown in the examples, when the concentration of the metal sulfate is changed in the direction of increasing the cycloolefin selectivity according to the method of the present invention, the catalyst activity is also improved, and as a result, the use of the catalyst for a longer period of time is improved. Also becomes possible.

The production method of the present invention can be applied to both a batch reaction system and a continuous reaction system. In particular, this is an effective method in a continuous reaction system in which there is little opportunity for catalyst replacement.
When a continuous reaction system is used, the reaction conversion of the raw material is 1
It is appropriately selected in the range of 0 to 90 mol%, and more preferably in the range of 30 to 70 mol% from an economic viewpoint.

According to the method of the present invention, cycloolefins can be efficiently produced for a long time as long as 100 hours or more or for a long time. However, the time need not necessarily be continuous. The point is how much time the used catalyst has been exposed to under the reaction conditions.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on embodiments, but the present invention is not limited to the embodiments unless it exceeds the gist. The conversion of benzene and the selectivity of cyclohexene shown in the following examples are values calculated by the following formula based on the concentration analysis values of the experiment.

Cyclohexene selectivity (%) = [(moles of cyclohexene produced by the reaction) / P] × 100 P (moles) = (moles of cyclohexene produced by the reaction) + (moles of cyclohexane produced by the reaction) (The number of moles) Further, the conversion rate of benzene used as a raw material represents a conversion rate calculated from the following equation based on the concentration analysis value of the experiment.

Benzene conversion (%) = [(moles of benzene consumed by the reaction) / (moles of benzene supplied to the reactor)] × 100 In FIGS. 3 and 4, the catalytic activity is benzene. Conversion rate 4
The evaluation was performed at 0%, and the calculation formula was as shown below. Catalytic activity (1 / h) at 40% benzene conversion = [(grams of benzene reaction weight per hour at 40 mol% benzene conversion) / (grams of weight of ruthenium catalyst used for reaction)]

[0034]

Reference Example 1 (Experiment 1) While continuously supplying benzene and hydrogen to a reactor equipped with an electromagnetic induction stirrer, continuously extracting and separating a catalyst slurry and product oil containing unreacted benzene from the reactor. The separated catalyst slurry was subjected to a continuous reaction for 100 hours under high-speed stirring using a continuous reaction apparatus capable of continuously returning the catalyst slurry to the reactor again. The catalyst slurry after the continuous reaction was recovered, and five of them were separated from each other by 280 ml of the catalyst slurry.

Next, different amounts of zinc sulfate were added to and dissolved in the five catalyst slurries, or different amounts of water were added.
Catalyst slurries having different zinc sulfate concentrations in the catalyst slurries were prepared. Further, thereafter, in order to equalize the volumes of the catalyst slurries, these catalyst slurries were allowed to settle down and the supernatant was appropriately removed, and the volume of the catalyst slurries was all set to 280 ml under normal temperature and normal pressure. Then, these catalyst slurries were subjected to a batch reaction in the following manner, and the relationship between the concentration of zinc sulfate in the slurries and the selectivity of cyclohexene was examined.

In the batch reaction, 280 ml of the catalyst slurry was charged into an autoclave having an inner volume of 1 liter and the inside surface of which was coated with Teflon, the gas inside was sufficiently replaced with hydrogen, and the reaction vessel was sealed. After the temperature was raised to 50 ° C., 50 a
The pressure was increased to tm. Immediately after the completion of the pressure increase, 140 ml of liquid benzene at 130 ° C. was injected into the autoclave, and the reaction was performed at a reaction pressure of 50 atm and at 130 ° C. under high-speed stirring while injecting hydrogen.

During the batch reaction, a part of the reaction solution was withdrawn over time, and the composition of the oil was analyzed by gas chromatography. From the analytical values thus obtained, the selectivity of cyclohexene at a benzene conversion of 40 mol% was obtained by interpolation. Further, the catalyst slurry after the batch reaction was recovered, and zinc sulfate dissolved in the aqueous phase in the slurry at normal temperature and normal pressure was analyzed by an atomic absorption method. The result is shown in FIG.

Further, a result showing the same tendency as the results shown in FIGS. 1 and 2 was observed at a place other than the benzene conversion rate of 40 mol%. (Experiment 2) Only the reaction time in the continuous reactor was 1500
The operation was performed in the same manner as in Experiment 1 except for the time. The result is shown in FIG.

The catalyst slurry used in the continuous reactors of Experiments 1 and 2 of Example 1 was prepared by reducing the amount of zinc obtained by reducing ruthenium hydroxide containing zinc hydroxide in advance to 6%.
Weight percent ruthenium catalyst (average crystallite size of about 58
Å) 15 g, 70 g of zirconia as a dispersant (average crystallite diameter of about 200 Å), 1500 ml of water, ZnSO4.7H2O
(Wako Pure Chemicals special grade) is a catalyst slurry consisting of 265 g. Further, water contained in the produced oil separated during the continuous reaction is separated by cooling the oil and returned to the reactor again to prevent the water of the catalyst slurry and the dissolved zinc sulfate from decreasing. did.

Further, the internal volume of the continuous reaction apparatus was an autoclave having a 3 liter inner surface coated with Teflon, and the supply amount of benzene during the continuous reaction was 250 ml / liter.
h, the amount of catalyst oil and product oil containing unreacted benzene extracted from the reactor is 1000 ml / h. As a result of Reference Example 1, as shown in FIG. 1, the area where the selectivity of cyclohexene is highest at a benzene conversion rate of 40 mol% of the catalyst slurry after the continuous reaction for 100 hours has a zinc sulfate concentration of 0.4 to 0 in the aqueous phase. In the region where the selectivity of cyclohexene after 1500 hours is highest, the concentration of zinc sulfate in the aqueous phase is 0.7 to 0.9.
It turns out that it has moved between mol / l. This clearly shows that the zinc sulfate concentration in the aqueous phase at which the cyclohexene selectivity is highest is clearly changed. That is,
In order to maintain a high selectivity of cyclohexene, it is important to change the concentration of zinc sulfate.

[0041]

REFERENCE EXAMPLE 2 The same experiment as in Reference Example 1 was performed except that a ruthenium catalyst (average crystallite diameter: about 59 °) obtained by previously reducing ruthenium hydroxide containing no zinc was used as the ruthenium catalyst. The result is shown in FIG. As a result of Reference Example 2, as shown in FIG. 2, the region where the selectivity of cyclohexene is highest at a benzene conversion rate of 40 mol% of the catalyst slurry after continuous reaction for 100 hours has a zinc sulfate concentration of 0.3 to 0 in the aqueous phase. .5 mol / l,
The region where the selectivity of cyclohexene after 1500 hours is the highest is when the zinc sulfate concentration in the aqueous phase is 0.6 to 0.9 mol /.
It turns out that it is between 1 It can be seen that the concentration of zinc sulfate in the aqueous phase at which the cyclohexene selectivity is highest is clearly changed.

In the experiments of Reference Examples 1 and 2, all reactions were carried out under the condition that two liquid phases, ie, an oil phase and an aqueous phase, were present, and the pH in the aqueous phase was all acidic or neutral. . From the above results, in order to maintain a high cyclohexene selectivity when the ruthenium catalyst is used for a long time, it is extremely necessary to change the concentration of zinc sulfate in the aqueous phase, that is, the concentration of metal sulfate over time. It turns out to be important. In addition, in the vicinity of the metal sulfate concentration where the cycloolefin selectivity peaks, as shown in FIGS. 3 and 4, the higher the metal sulfate concentration, the more the catalytic activity is improved. If the metal sulfate concentration is increased to keep the concentration high, not only the selectivity of cycloolefin but also the catalytic activity is improved, and the cycloolefin can be produced more efficiently.

[0043]

Example 1 In a continuous reaction, an experiment was conducted to suppress the decrease in cyclohexene selectivity with time by changing the concentration of zinc sulfate in the aqueous phase. In the reactor, 5.0 g of the ruthenium catalyst used in Reference Example 1, 25 g of zirconia, and 1500 water
After charging and sealing the catalyst slurry composed of 0.1 ml of ZnSO4.7H2O (special grade manufactured by Wako Pure Chemical Industries, Ltd.), the air in the gas phase inside the reactor was sufficiently replaced with hydrogen. Thereafter, the temperature of the catalyst slurry in the reactor was raised to 130 ° C., and hydrogen was injected thereinto to adjust the pressure of the reactor to 50 atm. In this state, benzene was continuously supplied to the reactor, and the reaction was started under high-speed stirring. The required amount of hydrogen consumed during the reaction was continuously supplied to the reactor, and the reaction product oil containing unreacted benzene was continuously discharged out of the reactor. Water and a trace amount of metal salts contained in this oil were all recovered and returned to the reactor as appropriate. Further, the composition of the extracted oil was appropriately analyzed by gas chromatography, and the amount of benzene continuously supplied to the reactor was adjusted so that the concentration of benzene contained in the oil was 40 mol%. .

After 1500 hours from the start of the reaction, an appropriate amount of zinc sulfate was added to the reactor so that the concentration of zinc sulfate in the aqueous phase became 0.8 mol / l. FIG. 5 shows the results obtained in this experiment. In order to analyze the concentration of zinc sulfate in the aqueous phase present in the reactor during the reaction, a part of the catalyst slurry was removed from the reactor at 100 hours, 1400 hours and 1600 hours after the start of the reaction. It was extracted and analyzed for the concentration of zinc sulfate in the aqueous phase. Table 1 shows the results.

The continuous reaction experiment apparatus used in this example has a reactor having an inner surface coated with Teflon and having an inner volume of 3 liters. The apparatus for separating the reaction slurry containing catalyst slurries and unreacted benzene is used as a reactor. This is an experimental device incorporated inside, and the mechanism is such that product oil containing unreacted benzene can be taken out of the reactor. In order to prevent the water and the like of the catalyst slurry from dissolving and reducing in the oil taken out of the system, all of the water and the like in the oil were collected and returned to the reactor as appropriate.

[0046]

Example 2 An experiment was conducted in the same manner as in Example 1 except that the ruthenium catalyst used in Reference Example 2 was used as the ruthenium catalyst. FIG. 6 and Table 2 show the results of this example. From the results of Examples 1 and 2, it can be seen that by changing the concentration of zinc sulfate, the decrease in cyclohexene selectivity over time could be suppressed.

[0047]

[Table 1]

[0048]

[Table 2]

[0049]

According to the present invention, cycloolefin can be efficiently produced for a long time while suppressing a decrease in the selectivity of cycloolefin.

[Brief description of the drawings]

FIG. 1 shows the results of Experiments 1 and 2 performed in Reference Example 1.
It is a figure which shows the relationship between the concentration of zinc sulfate in an aqueous phase, and the cyclohexene selectivity at the time of a benzene conversion rate of 40 mol%.

FIG. 2 shows the results of Experiments 1 and 2 performed in Reference Example 2.
It is a figure which shows the relationship between the concentration of zinc sulfate in an aqueous phase, and the cyclohexene selectivity at the time of a benzene conversion rate of 40 mol%.

FIG. 3 shows the results of Experiments 1 and 2 performed in Reference Example 1.
It is a figure which shows the relationship between the zinc sulfate concentration in an aqueous phase, and the benzene weight consumption rate per unit catalyst weight at the time of the benzene conversion rate of 40 mol%, ie, a catalyst activity.

FIG. 4 shows the results of Experiments 1 and 2 performed in Reference Example 2.
It is a figure which shows the relationship between the zinc sulfate concentration in an aqueous phase, and the benzene weight consumption rate per unit catalyst weight at the time of the benzene conversion rate of 40 mol%, ie, a catalyst activity.

FIG. 5 is a diagram showing the change over time in benzene conversion and cyclohexene selectivity calculated from the composition analysis of the oil drawn out of the reactor in Example 1.

FIG. 6 is a graph showing changes over time in benzene conversion and cyclohexene selectivity calculated from the composition analysis of the oil drawn out of the reactor in Example 2.

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Claims (8)

[Claims] 1. A method in which a monocyclic aromatic hydrocarbon is partially hydrogenated and reacted with hydrogen in the presence of a ruthenium catalyst, water and a metal sulfate to produce a cycloolefin, the metal dissolved in an aqueous phase containing the catalyst. A method for producing a cycloolefin, wherein the reaction is carried out while changing the sulfate concentration. 2. The method according to claim 1, wherein the reaction is carried out while increasing the concentration of the metal sulfate. 3. The metal sulfate according to claim 1, wherein the metal sulfate is a metal sulfate containing at least zinc sulfate.
The described method. 4. The method according to claim 1, wherein the concentration of the metal sulfate in the aqueous phase is 1 × 10 5
The method according to any one of claims 1 to 3, wherein the concentration of the metal sulfate is changed in the range of ^{-5 to} 5.0 mol / l. 5. The method according to claim 1, wherein the water is from 0.5 to 0.5% of the monocyclic aromatic hydrocarbon.
The method according to any one of claims 1 to 4, which is present in an amount of 20 times by weight. 6. The method according to claim 1, wherein the ruthenium catalyst comprises a metal ruthenium obtained by previously reducing a ruthenium compound. 7. The method according to claim 6, wherein the ruthenium catalyst is an unsupported catalyst and the average crystallite size of the metal ruthenium is 200 ° or less. 8. The method according to claim 7, wherein the ruthenium compound is a ruthenium compound containing a zinc compound, and contains 0.1 to 50% by weight of zinc based on ruthenium.