JPH0987208A - Production of cycloolefin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably obtain over a long period of time with easy catalyst regeneration a cycloolefin useful as an intermediate for e.g. polyamide feedstocks by continuous partial hydrogenation of a monocyclic aromatic hydrocarbon under retaining the cobalt accumulation on the surface of a ruthenium catalyst at a specified level or lower. SOLUTION: This cycloolefin is obtained by continuous partial hydrogenation of (D) a monocyclic aromatic hydrocarbon through such a catalytic process that, in the presence of (A) a ruthenium catalyst, (B) a cobalt salt such as cobalt sulfate and (C) water, at least part of the component A in the reaction system is extracted, put to acid cleaning, washed with water, put to reduction treatment and then circulated in the reaction system to retain the cobalt accumulation on the surface of the component A in the reaction system at <=1 (esp. <=0.5) pt.wt. based on 1 pt.wt. of the ruthenium.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for partially hydrogenating a monocyclic aromatic hydrocarbon to produce cycloolefins. In particular, it relates to a method for partially hydrogenating benzene to produce cyclohexene. 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 methods are known for producing cycloolefins, especially cyclohexene. Among them, a monocyclic aromatic hydrocarbon is generally used in the presence of a ruthenium catalyst and water to produce an alkali agent or a metal salt. A method in which an additive such as the above is added to carry out partial hydrogenation is known as a preferable method because of high selectivity and yield of corresponding cycloolefin. Of these, a method of partial reduction in the presence of a catalyst in which ruthenium is mainly supported on a metal oxide such as silica or alumina, water and cobalt sulfate (JP-A-57-1309).
26), a ruthenium catalyst using barium sulfate as a carrier, a method of partial reduction in the presence of water and a sulfate salt selected from Li, Co, Fe and Zn (JP-A-61-2226), and the like. It is known to use a cobalt salt as a preferable metal salt.

On the other hand, generally, when a platinum group metal catalyst such as ruthenium is poisoned, it is washed with alkaline water, treated with a mineral acid, reduced, or burned with an oxygen-containing gas. It is known that the reproduction is performed by a method of doing so or a method of combining these methods. (Special notice Sho 5
6-24580, Japanese Patent Laid-Open No. 3-41216, JP-A-53-53.
39283, JP-A-57-132548, etc.)

[0004]

In a process for producing a cycloolefin, a monocyclic aromatic hydrocarbon is partially reduced with hydrogen in the liquid phase at high temperature and high pressure in the presence of a ruthenium catalyst, water and a metal salt compound. And / or in the case of regenerating a catalyst with reduced selectivity, the known methods described above
Catalyst regeneration is still not sufficient. In particular, when putting this reaction using an expensive ruthenium catalyst into practical use, establishing a more effective catalyst regeneration method is an important issue.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to improve these drawbacks of the prior art and to provide an industrially advantageous process for producing cycloolefin. In particular, no examples have been found in which the catalyst life in the presence of a cobalt salt in the reaction system has been examined in detail, and the cause of reduction in catalyst performance and catalyst regeneration technology have not been known. The present inventor has recognized that when a cobalt salt is present in a reaction system and a cycloolefin is continuously produced over a long period of time, the catalytic activity is decreased over time, and such a decrease in activity is caused on the catalyst. It was found to be due to the accumulation of cobalt in the. Furthermore, the present invention was accomplished by studying an effective regeneration method for a catalyst with reduced activity.

That is, the gist of the present invention is a method for producing a cycloolefin in which a monocyclic aromatic hydrocarbon is continuously partially hydrogenated in the presence of a ruthenium catalyst, a cobalt salt and water. The present invention will be described in detail below in the method for producing a cycloolefin, which is characterized in that the amount of accumulated cobalt is maintained at 1 or less with respect to 1 part by weight of ruthenium.

The ruthenium catalyst used in the present invention may be used as it is as the reduced metal particles containing ruthenium, or may be used as a supported catalyst supported on a carrier. Examples of the carrier include silica, alumina, silica-alumina, zeolite, activated carbon, general metal oxides, complex oxides, hydroxides, sparingly water-soluble metal salts and the like. Furthermore, as one of the preferred forms of the above carrier, a carrier obtained by modifying a silica carrier with a transition metal compound, particularly a carrier obtained by modifying zirconia with silica, and a carrier containing a zirconium silicate such as zirconium silicate are exemplified.

The ruthenium catalyst may be ruthenium alone or may contain a promoter metal component. As the promoter metal component, zinc, cobalt, manganese,
Examples are iron, lanthanum, gold, silver and copper. When using a promoter metal, the atomic ratio of the promoter metal to the ruthenium atom is usually 0.01 to 10, preferably 0.1 to 5.
And When each catalyst component is loaded on the carrier, it is usually used as a catalyst by loading 0.001 to 10% by weight, preferably 0.02 to 5% by weight on the carrier. Preparation of such a catalyst is carried out according to a commonly used method for preparing a supported metal catalyst. As a raw material compound for each metal component of the catalyst, a halide, nitrate, acetate, sulfate of each metal, a complex compound containing each metal, or the like is used. The co-supporting component with ruthenium may be supported on the carrier at the same time as the ruthenium raw material, or may be supported after supporting ruthenium in advance, or after supporting these metals first and then supporting ruthenium afterwards. Good.

As a preparation method, after dipping the carrier in the catalyst component liquid, the solvent is evaporated to evaporate the solvent to fix the active component, and the spray is used to spray the catalyst active component liquid while keeping the carrier dry. Or a known impregnation-supporting method such as a method of immersing the carrier in the liquid of the catalytically active component and then filtering it. Further, as the solvent used when supporting the active ingredient at the time of catalyst preparation, water or alcohol,
Organic solvents such as acetone, tetrahydrofuran, hexane and toluene are used. Of these, water and alcohol are preferable.

The prepared catalyst is used after being reduced and activated. As the reduction method, a catalytic reduction method using hydrogen gas or a chemical reduction method using formalin, sodium borohydride, hydrazine or the like is used. Of these, catalytic reduction with hydrogen gas is preferable, and usually 80 to 500.
The reductive activation is carried out under the condition of ℃, preferably 100 to 450 ℃. If the reduction temperature is lower than 80 ° C, the reduction rate of ruthenium is significantly reduced, and if it is higher than 500 ° C, agglomeration of ruthenium is likely to occur, which causes a decrease in cycloolefin production yield and selectivity.

In the present invention, the above-mentioned ruthenium reduced product is used as a catalyst. By subjecting such a catalyst to the water treatment described below, it is possible to obtain a catalyst having further improved cycloolefin selectivity. is there. The water treatment condition is usually 0.01 to 100 times by weight, preferably 0.1 to 100 times the amount of the above catalyst (ruthenium reduced product).
It is carried out by immersing in 10 to 10 times the weight of water. The treatment conditions are usually from normal pressure to under pressure, from room temperature to 250.
C., preferably room temperature to 200.degree. C., usually 10 minutes or longer, preferably 1 to 20 hours. The catalyst treatment atmosphere is usually an inert gas atmosphere or a hydrogen gas atmosphere, preferably a hydrogen gas atmosphere. Furthermore, the catalyst after the water contact treatment is usually dried and then subjected to a re-reduction treatment, particularly a contact treatment in a hydrogen gas atmosphere, whereby a ruthenium catalyst having a higher activity can be obtained.

The water used for the above contact treatment may be not only pure water but also an aqueous solution containing a metal salt. At least a part of the metal component in the aqueous metal salt solution binds to the catalyst, so that it functions as a co-catalyst component, and further improvement in catalytic activity can be expected, which is desirable. The concentration of the metal salt in the aqueous solution is usually 1 × 10 ⁻⁵ to 1 times the weight of water, preferably 1 × 10 ^{−4 to} 0.1%.
2 times the weight. The catalyst after the contact treatment is usually used after filtering a metal salt aqueous solution, washing with pure water, and drying. Further, after drying, it is desirable to perform re-reduction treatment under a hydrogen gas atmosphere or the like.

The present invention uses the above ruthenium catalyst. When the present invention is carried out, the monocyclic aromatic hydrocarbons used as the reaction raw materials are benzene, toluene, xylene, and lower ones having about 1 to 4 carbon atoms. Examples thereof include alkyl group-substituted benzenes. 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 0.01 to 10 times by weight, preferably 0.1 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. Further, if the amount of water is too small or too large, the effect of coexistence decreases, and if the amount of water is too large, it is necessary to enlarge the reactor, which is not preferable.

In the present invention, a cobalt salt is present in the reaction system. As the cobalt salt, cobalt sulfate,
Examples thereof include nitrates, chlorides and phosphates, and cobalt sulfate is particularly preferably used. The amount of the metal salt used is usually selected from the range of 1 × 10 ⁻⁵ or more to saturated solubility, preferably 1 × 10 ⁻² to 1 times the weight of water in the reaction system.

As the reaction conditions of the present invention, the reaction temperature is
It is usually selected from the range of 50 to 250 ° C, preferably 100 to 220 ° C. When the temperature is 250 ° C or higher, the selectivity of cycloolefin is lowered, and when the temperature is 50 ° C or lower, the reaction rate is remarkably lowered, which is not preferable. The hydrogen pressure during the reaction is usually selected from the range of 0.1 to 20 MPa, preferably 0.5 to 10 MPa. When it exceeds 20 MPa, it is industrially disadvantageous, while when it is less than 0.1 MPa, the reaction rate remarkably decreases and it is uneconomical in terms of equipment.

The effect of the present invention is particularly exerted by continuously carrying out the reaction. The continuous reaction is usually carried out in a state where the liquid phase is suspended by continuously supplying a monocyclic aromatic hydrocarbon and hydrogen to a reaction system in which a catalyst, a metal salt and water are present. Further, a suspension containing the reaction product is continuously taken out from the reaction system, and is separated into an aqueous phase containing the catalyst and an oil phase containing the reaction product, and the oil phase is taken out. The olefin will be refined. The type of the reactor is not particularly limited, and a general reactor such as a reactor having one tank or two or more continuous stirring tanks and a tube reactor can be used. The reaction time, that is, the residence time of the starting monocyclic aromatic hydrocarbon in the reaction system is arbitrary depending on the type of the reactor and the amount of catalyst, but is usually about 5 to 100 minutes.

An example of a method for separating the reaction liquid into an oil phase and an aqueous phase is a method in which an oil / water separation weir is provided in the reactor and only the oil phase is taken out. It is also conceivable to take out a part of the reaction liquid with a liquid circulation pump and supply it to an oil-water separation tank provided outside the reactor to separate it.The aqueous phase containing the separated catalyst is circulated to the reactor. Can be reused. Cycloolefin can be easily purified and recovered from the separated oil phase by a known method such as distillation. Further, at least a part of the catalyst in the aqueous phase may be appropriately extracted, a regeneration operation may be performed as described below, and the regenerated catalyst may be circulated in the reactor.

When the inventor continuously conducts the above reaction in which the cobalt salt is present, the cobalt metal component accumulates on the catalyst over time, and when the amount of accumulation increases to some extent, the catalytic activity rapidly increases. According to the present invention, the amount of cobalt accumulated on the surface of the ruthenium catalyst in the reaction system is 1 or less, preferably 0.5 or less, more preferably 0.2 or less relative to 1 part by weight of ruthenium. It is characterized by holding below.

Although there is a method of using cobalt as a co-catalyst for the purpose of improving the cycloolefin selectivity of the ruthenium catalyst, the cobalt accumulated in the ruthenium catalyst found in the present invention is a conventionally known co-catalyst. Unlike cobalt as a catalyst, it reduces activity but does not significantly improve selectivity (but cycloolefin selectivity is compared by cycloolefin selectivity at the same monocyclic aromatic-hydrocarbon conversion). .). Therefore,
Even in a ruthenium catalyst containing cobalt as a co-catalyst component, the activity of the catalyst is lowered due to the accumulation of the cobalt component mainly in the reaction system water.

The cause of the decrease in the activity of the ruthenium catalyst due to the accumulation of the cobalt salt is that when the reduction reaction with hydrogen is carried out in the presence of sulfate as in the present reaction system, the ruthenium catalyst which is the reduction catalyst is used. It is presumed that cobalt is likely to accumulate on the active sites. Further, it is presumed that the cobalt accumulated on the catalyst blocks the active site or reduces the activity of the ruthenium catalyst by an electronic effect.

In the present invention, the amount of cobalt accumulated on the surface of the ruthenium catalyst in the reaction system is 1 with respect to 1 part by weight of ruthenium.
Means for holding below is not particularly limited, but by carrying out one of the most preferable methods to acid-wash the catalyst whose activity is lowered by the above reaction, metal cobalt components accumulated on the catalyst, etc. The method of reducing the amount of and reusing it is illustrated. The method of acid washing can be carried out by washing the catalyst with an aqueous acid solution having a pH of 4 or less. As the acid used, mineral acids such as sulfuric acid, hydrochloric acid and nitric acid are preferably used, and sulfuric acid is particularly preferable. The washing temperature is usually room temperature to 300 ° C, preferably 40 to 100 ° C. Alternatively, the catalyst may be washed with water before the acid washing and then the acid washing.

Furthermore, after washing the catalyst with water after washing with the acid aqueous solution, it is usually desirable to wash with water until the pH of the washing liquid becomes about 6 to 7. By carrying out such water washing, it is possible to prevent the used acidic substance from being mixed into the reaction system and exerting a bad influence on the reaction. Further, it is also suitable to reduce the catalyst after such acid washing and water washing. The reduction is carried out by the above method, but the temperature condition can be lower than the condition for forming the metal ruthenium from the ruthenium raw material, and is usually selected from the room temperature to 500 ° C. The temperature is preferably room temperature to 300 ° C.

The catalyst regeneration method of the present invention can be carried out by extracting a part or the whole of the metal salt aqueous solution slurry containing the catalyst from the reaction system and performing the above-mentioned acid washing. By increasing the frequency of acid cleaning, it is possible to control the amount of cobalt accumulated in the catalyst in the reactor to be low. However, when the frequency is excessively increased, it is possible to maintain the catalyst activity at a high level, but there is a drawback that the cost involved in the regeneration treatment is industrially increased, and the type of cobalt salt used, It may be carried out at an appropriate frequency in consideration of the concentration, the type of material used, and the deterioration rate determined from the catalyst performance.

The cobalt concentration in the catalyst can be measured by the following method. After the reaction, a cobalt sulfate aqueous solution slurry of such a deteriorated catalyst was taken out, the catalyst was filtered off, resuspended in pure water, the catalyst was filtered off, and the cobalt content of the filtrate was analyzed by ICP emission spectroscopy. Measured.
The suspension in pure water and the filtration of the catalyst are repeated until the cobalt concentration of the filtrate becomes 1 ppm or less. The catalyst after washing with water is dried and the cobalt concentration is measured by a fluorescent X-ray analysis method.

[0025]

EXAMPLES Examples will be described below, but the present invention is not limited to these examples. The conversion rate and selectivity shown in Examples and Comparative Examples are defined by the following equations.

[0026]

[Equation 1]

Example 1 (Production of catalyst) Zirconium oxynitrate dihydrate 0.8
Silica (Fuji Silysia Chemical, trade name: CARIACT-Q-
50) 8.0 g was added, and after dipping at room temperature, water was distilled off and the residue was dried. Next, it was calcined at 1000 ° C. for 4 hours under air flow to prepare a silica carrier modified with 5% by weight of zirconia with respect to silica. The above-mentioned zirconia-modified silica carrier was added to an aqueous solution containing a predetermined amount of ruthenium chloride and zinc chloride, immersed at 60 ° C. for 1 hour, water was distilled off and dried. Furthermore, in a hydrogen stream, it was reduced and activated at 200 ° C. for 3 hours to be activated to obtain a ruthenium reduced product carrying ruthenium and zinc in an amount of about 0.5% by weight with respect to the carrier.

Next, 10 g of the reduced product of ruthenium and 200 ml of a 6% by weight zinc sulfate aqueous solution were added to an internal volume of 500 m.
1 t autoclave made of Ti, and stirred at a temperature of 200 ° C. and a pressure of 5.0 MPa at 600 rpm,
It was treated for 5 hours. After the treatment, the catalyst was taken out and washed with pure water. Washing was performed by adding 30 times the amount of pure water to the catalyst and mixing them sufficiently for 1 hour with stirring, etc., until the zinc concentration in the wash water at the time of substantially equilibrium became 0.1 ppm or less. Further, after drying the catalyst, it is dried in a hydrogen stream at 200
C. for 3 hours. The above catalyst in a hydrogen stream at 200 ° C
It was decided to use this reduced ruthenium as a new catalyst by activating it after reduction for 3 hours. .

(Partial Hydrogenation Reaction of Benzene) Titanium was used in the liquid contact part, and a continuous flow reactor having an oil volume of 1 L and an internal volume of 1 L was used.
1, hydrogen gas was supplied from the nozzle opening in the presence of 2.5 g of the above catalyst, and benzene was continuously supplied at a flow rate of 110 ml while performing high-speed stirring at a reaction pressure of 5.0 MPa and a temperature of 150 ° C. Then, a partial hydrogenation reaction of benzene was performed. The residence time of the oil phase is 90 minutes. Further, the oil phase was separated in a stationary tank in the reactor, and only the oil phase was continuously collected. The collected oil phase was analyzed by gas chromatography. Table 1 shows the reaction results 10 hours and 59 hours after the start of the reaction.

(Measurement of Cobalt Accumulation Amount) After 60 hours of continuous reaction, an aqueous slurry of cobalt sulfate as a catalyst for such deterioration was prepared.
It was taken out, the catalyst was filtered off, and then resuspended in pure water.
Further, the catalyst was filtered off, and the cobalt content of the filtrate was measured by ICP emission spectroscopy. Cobalt concentration of filtrate is 1pp
The suspension in pure water and the filtration of the catalyst were repeated until the amount became m or less. After such washing, the catalyst was dried and the cobalt concentration in the catalyst was measured by fluorescent X-ray analysis.
The cobalt concentration in the catalyst was 1 part by weight of ruthenium,
It was 0.12 parts by weight.

(Acid cleaning) Cobalt is ruthenium 1
0.12 parts by weight of the catalyst, which was accumulated with respect to parts by weight, was charged into a 1N aqueous sulfuric acid solution, and the mixture was stirred at 98 ° C. for 1 hour. After washing with sulfuric acid and thoroughly washing the catalyst with water, the cobalt concentration in the catalyst was similarly measured by fluorescent X-ray analysis. The cobalt concentration in the catalyst was 0.013 with respect to 1 part by weight of ruthenium.
It was part by weight.

(Reuse) The catalyst after washing with sulfuric acid and washing with water was reduced at 100 ° C. in a hydrogen stream. Using the regenerated catalyst, the benzene partial hydrogenation reaction was continuously carried out by the above method. Table 1 shows the reaction results 10 hours after the start of the reaction.

[0033]

[Table 1]

Comparative Example 1 The benzene partial hydrogenation reaction was continuously carried out by the method described in Example 1 except that a 1% aqueous solution of cobalt sulfate was used. Table 2 shows the reaction results 3 hours, 10 hours, and 19 hours after the start of the reaction. Furthermore, when the cobalt concentration accumulated in the catalyst was measured by the method described in Example 1, the cobalt concentration in the catalyst was found to be 1 part by weight of ruthenium.
It was 2.88 parts by weight.

[0035]

[Table 2]

Example 2 The regenerated catalyst after the new catalyst and various washing methods were carried out using a batch reaction was evaluated. (New catalyst) A titanium autoclave having an internal volume of 0.5 was charged with 0.1% zinc sulfate aqueous solution 150, 1.0 g of the unused catalyst described in Example 1, and 100 L of benzene at a reaction temperature of 150 ° C. Under the reaction pressure of 5.0 MPa, hydrogen is added to 5
It was supplied at 7 Nl / Hr and stirred at a rotation speed of 1000 rpm to carry out a partial hydrogenation reaction of benzene. Table 3 shows the reaction results 20 minutes after the start of the reaction.

(Sulfuric acid washed regenerated catalyst) The partial hydrogenation reaction of benzene was carried out under the reaction conditions carried out with the above new catalyst except that the same regenerated catalyst prepared by sulfuric acid washing as in Example 1 was used.
Table 3 shows the reaction results 20 minutes after the start of the reaction.

(Sulfuric acid washed regenerated catalyst) The above new catalyst except that a regenerated catalyst prepared by the same washing method as in Example 1 was used except that a 1N nitric acid aqueous solution was used instead of the sulfuric acid aqueous solution in the washing method of Example 1. A partial hydrogenation reaction of benzene was carried out under the reaction conditions used. Table 3 shows the reaction results 20 minutes after the start of the reaction.

(Water-washed regenerated catalyst) The partial hydrogenation reaction of benzene was carried out under the reaction conditions carried out with the above new catalyst except that the acid-washing was omitted in Example 1 and only the washing with pure water was carried out. did. Table 3 shows the reaction results 20 minutes after the start of the reaction.

[0040]

[Table 3]

[0041]

According to the present invention, a deteriorated catalyst can be appropriately and effectively regenerated, and a cycloolefin can be stably produced from a monocyclic aromatic hydrocarbon over a long period of time.

Claims (6)

[Claims] 1. A ruthenium catalyst containing a monocyclic aromatic hydrocarbon,
A method for producing a cycloolefin which is partially hydrogenated continuously in the presence of a cobalt salt and water, characterized in that the amount of cobalt accumulated on the surface of the ruthenium catalyst in the reaction system is maintained at 1 or less with respect to 1 part by weight of ruthenium. A method for producing a cycloolefin. 2. The method according to claim 1, wherein at least a part of the ruthenium catalyst in the reaction system is extracted, washed with an acid, and the ruthenium catalyst is circulated in the reaction system. 3. The method according to claim 2, wherein the ruthenium catalyst washed with water after the acid washing is circulated in the reaction system. 4. The method according to claim 2, wherein the ruthenium catalyst, which has been subjected to acid washing, water washing, and reduction treatment, is circulated in the reaction system. 5. The method according to claim 1, wherein the amount of cobalt accumulated on the surface of the ruthenium catalyst in the reaction system is maintained at 0.5 or less with respect to 1 part by weight of ruthenium. 6. The method according to claim 1, wherein the cobalt salt is cobalt sulfate.