JPH11139997A - Production of cycloolefin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a cyclohexene, capable of removing a reaction heat by a simple method, by using no heat removal method such as an external circulating method or reducing another heat removal method. SOLUTION: In this method for producing a cycloolefin by the partial hydrogenation of a monocyclic aromatic hydrocarbon in which at least a monocyclic aromatic hydrocarbon and a gaseous hydrogen are supplied to a reactor charged with water and a catalyst under acidic conditions and successively collecting a reaction product, the heat of the reactor is removed by using a gas which is fed to the reactor, not used in the reaction, and is discharged out of the reactor. Preferably, hydrogen in an amount more excessive than that required for the reaction and heat removal is used and the latent heat of a component which is accompanied by a gas to be discharged is utilized. More preferably, the discharged gas is condensed, at least a part of the condensed gas is recycled to the reaction system to remove heat by taking advantage of the latent heat of the condensed component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a cyclic olefin from a monocyclic aromatic hydrocarbon as a raw material, and particularly to a method for producing cyclohexene from a benzene as a raw material.
More specifically, the present invention relates to a method for continuously producing cyclohexene in which benzene and hydrogen are continuously supplied into a reactor under acidic conditions in which water and a catalyst are present, and a reaction product is continuously collected.

[0002]

2. Description of the Related Art It is known to produce cyclohexene by partially hydrogenating benzene under acidic conditions in the presence of water (for example, JP-A-60-247881). This reaction is a four-phase reaction of a gas phase containing hydrogen, an aqueous phase containing water, an oil phase containing benzene and cyclohexene, and a solid phase containing a catalyst.

[0003]

In the partial hydrogenation reaction of benzene, cyclohexane is also produced by the complete hydrogenation of benzene, in addition to the production of cyclohexene by the intended partial hydrogenation reaction of benzene. These reactions involve a large heat of reaction as in the following equation.

[0004]

C ₆ H ₆ + 2H ₂ → C ₆ H ₁₀ ΔH (423 K) = − 22.7 kcal / mol C ₆ H ₆ + 3H ₂ → C ₆ H ₁₂ ΔH (423 K) = − 51.4 kcal / mol

[0005] Therefore, in this reaction system, heat removal from the reactor is a major problem. As a general method of removing heat from the reactor, there is a so-called external circulation system in which a part of the content of the reactor is extracted, cooled, and then returned to the reactor. However, such an external circulation system has the following problems. That is, since this reaction system is under acidic conditions, there is a problem of corrosion of the reactor,
In some cases, a high-grade material such as Hastelloy or titanium may be used. If the above-described external circulation system is employed, the same problem as in the reactor occurs up to such an external circulation line. Thus, not only is it undesirable that corrosion occurs in the external circulation line, but also there is a problem in that the cost increases when high-grade materials are used up to the external circulation line in order to prevent corrosion. In addition, when the external circulation system is employed, the catalyst is also externally circulated, so that there is a problem that crushing occurs.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide a method for producing cyclohexene which can remove heat of reaction by a simple method. According to the study of the present inventors, the heat is supplied to the reactor, and the gas is discharged from the reactor to remove heat,
In particular, heat is removed by utilizing the fact that the substance in the reactor takes the latent heat from the reactor to change its state and is entrained by the gas, and more preferably to remove the heat as the gas. When hydrogen is supplied, the amount of hydrogen supplied is greater than the required amount of hydrogen determined from the reaction results, so that a large amount of water and organic substances are taken away by the latent heat in the exhaust gas from the reactor. It was found that the heat was removed from the vessel. In particular, it has been found that the latent heat is released by cooling the exhaust gas, and then the condensate is supplied to the reactor, whereby the reactor can be cooled using the exhaust gas from the reactor as a heat medium.

That is, the gist of the present invention is to continuously supply at least a monocyclic aromatic hydrocarbon (for example, benzene) and gaseous hydrogen into a reactor under an acidic condition in which water and a catalyst are present. In a process for producing cyclic olefins by partial hydrogenation of monocyclic aromatic hydrocarbons, in which the product is continuously collected, the reaction is carried out using gas that is supplied to the reactor and discharged from the reactor without being used for the reaction. The present invention resides in a method for producing a cyclic olefin, which comprises removing heat from a vessel.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described with reference to a method for producing cyclohexene by partial hydrogenation using benzene as a monocyclic aromatic hydrocarbon. The reaction system of the present invention requires the presence of water. As for the amount of water,
Although it varies depending on the reaction mode, generally, the benzene concentration is 0.1%.
It is 0.1 to 10 times by weight, preferably 0.1 to 5 times by weight. Under such conditions, an organic liquid phase (oil phase) mainly composed of raw materials and products and a liquid phase (water phase) containing water form two phases without stirring. 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, if the amount of water is too small or too large, the presence effect of water decreases. Further, in the present invention, a metal salt compound may be contained in water. Examples of the metal salt compound include sulfates, chlorides, acetates, phosphates, and the like of metals belonging to Group 1 and Group 2 of the periodic table, and metals such as zinc, manganese, and cobalt. It is a metal sulfate such as cobalt. The amount of the metal salt to be used is generally 1 × 10 ^-5 to 1 times, preferably 1 × 10 ^-4 to 0.1 times by weight of water in the reaction system.

The catalyst used in the reaction of the present invention is preferably a ruthenium catalyst. Raw materials for ruthenium catalysts include ruthenium halides, nitrates, hydroxides,
Further, complex compounds such as ruthenium carbonyl and ruthenium ammine complexes, and ruthenium alkoxides are exemplified. Among them, ruthenium chloride is preferably used. Ruthenium, which is the active component of the catalyst, can be used alone, but other metal components may be used in combination as co-catalyst components. By adding a co-catalyst, the effects of the present invention can be further exhibited. As the promoter component, zinc, iron, cobalt, manganese, gold, lanthanum, copper and the like are effective, and zinc is particularly preferable. As a raw material of the cocatalyst component, a halide, a nitrate, an acetate, a sulfate, and a complex compound containing each of the above metals are used. When a promoter metal is used, the atomic ratio of the promoter metal to ruthenium atoms is usually 0.01 to 20.
, Preferably in the range of 0.1 to 10.

The method for preparing the unsupported catalyst precursor includes the following:
Using a mixture of ruthenium and a compound as a raw material of a desired promoter metal component, it may be obtained as a solid by a general coprecipitation method such as an alkali precipitation method, or may be evaporated and dried in a homogeneous solution state. It may be solid.

Although a non-supported catalyst can be used as the ruthenium catalyst, generally, a carrier-supported catalyst is more likely to obtain an improvement in activity per catalyst component or an improvement in stability of catalyst activity. desirable. As a method for preparing a carrier-supported catalyst precursor, that is, a method for supporting a catalyst component on a carrier, a known method, for example, an evaporation to dryness method, a spray method,
An impregnation-supporting method, an ion-exchange method and the like are preferably used. In addition, as a solvent used for supporting the active component at the time of catalyst preparation, water or an organic solvent such as alcohol, acetone, tetrahydrofuran, hexane, and toluene is used. The supported amount of ruthenium is usually 0.001 to 10% by weight, preferably 0.1 to 5% by weight. Further, the co-catalyst component may be supported at the same time as ruthenium, or may be pre-supported and then support ruthenium,
Conversely, the ruthenium may be loaded after loading it in advance.

As the carrier used in the above-mentioned carrier-supported catalyst, those generally known as catalyst carriers can be mentioned. Examples of the carrier include silica, alumina, silica-alumina, zeolite, activated carbon, and metal oxides. Composite oxide,
Examples include hydroxides and poorly water-soluble metal salts. Specifically, barium sulfate, metal salts such as calcium sulfate, silica,
Examples thereof include oxides of alumina, zirconia, titania, chromia, and rare earth metals, or composite oxides such as silica-alumina, silica-zirconia, and zirconium silicate, and silica modified with a metal oxide such as zirconia. You.

[0013] Among the above carriers, carriers having the following properties can be suitably used. That is, when the pore volume and the pore distribution are measured by the mercury intrusion method, the pore diameter is 75 to 1
Total pore volume of 0.2000 Å
10 ml / g, preferably 0.3-5 ml / g,
In addition, 50% or more, preferably 70% or more of the pore volume having a pore diameter of usually 250 Å or more is based on the total pore volume of 75 to 100,000 Å.
% Of the carrier. If the proportion of the pores having a pore diameter of less than 250 angstroms is too large, the selectivity tends to decrease, which is not preferred.

As a method for activating the catalyst, 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 by hydrogen gas is preferred,
In a hydrogen-containing gas atmosphere, reduction activation is carried out by firing under conditions of usually 80 to 500 ° C, preferably 100 to 450 ° C. When the reduction temperature is lower than 80 ° C., the reduction ratio of ruthenium is remarkably reduced. When the reduction temperature is higher than 500 ° C., aggregation of ruthenium is liable to occur, and the yield of cyclohexene formation,
This causes the selectivity to decrease.

As the reaction conditions of the present invention, the reaction temperature is as follows:
It is usually selected from the range of 50 to 250 ° C, preferably 100 to 220 ° C. If the temperature is higher than 250 ° C., the selectivity of cyclohexene decreases, and if the temperature is lower than 50 ° C., the reaction rate is remarkably reduced, which is not preferable. The hydrogen pressure during the reaction is
Usually 0.1 to 20 MPa, preferably 0.5 to 10 MPa
It is selected from the range of a. 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 terms of equipment. The reaction is carried out continuously using one or two or more reaction vessels.

In the present invention, heat is removed from the reactor by supplying the gas supplied to the reactor in excess of the amount used for the reaction. That is, the gas supplied to the reactor only needs to include a gas discharged without being used in the reaction, and a gas inert to the reaction (for example, nitrogen, a rare gas, or the like) is used in combination with hydrogen as a reaction raw material. However, it is preferable that substantially all of the supplied gas is hydrogen, and the supply amount of hydrogen is larger than the amount of hydrogen required for the reaction. When an inert gas is used, it is not consumed in the reaction, and when the discharged gas is recycled, the inert gas accumulates in the reactor and becomes crowded. In order to prevent this, it is necessary to provide a purge line for discharging a part of the gas to be recycled out of the reaction system. Also, a purge line is required when the hydrogen gas contains a large amount of impurities. Therefore, in the present invention, it is industrially advantageous to supply an excess amount of hydrogen, which is one of the reaction source gases. However, as long as the amount of the inert gas is such that it is absorbed by the liquid in the reaction system and is removed outside the system, there is no problem even if it is treated in the same way as the case of an excessive amount of hydrogen.

In the method of the present invention, not only the "heat removal by gas" of the present invention but also other heat removal methods such as an external circulation method may be used. That is, it is usually at least 10%, preferably 30%, of the heat removal amount of the whole reaction.
% Or more, more preferably 50% or more, most preferably 80% or more, and in some cases, the entire amount of required heat removal may be removed by the method specified in the present invention.

Therefore, in a preferred embodiment, the amount of hydrogen when an excessive amount of hydrogen is used varies depending on the target heat removal ratio, but specifically, the amount of hydrogen to be supplied normally is 1.2 to the required amount. It is 50 times, preferably 1.5 to 20 times, and more preferably 2 to 10 times. If the supply amount of hydrogen is too small, the reaction temperature rises, and if it is too large, the reaction temperature lowers, and there is a problem that any of the reaction temperature conditions deviates. Here, “the amount of hydrogen required for the reaction” means not only the amount of hydrogen required for the production of cyclohexene,
The amount of hydrogen required for the production of cyclohexane is also taken into consideration, and in short, it means the amount of hydrogen required for the entire reaction obtained from the conversion of benzene and the selectivity of cyclohexene.

When the reactors are provided in multiple stages, the "hydrogen amount required for the reaction" is determined with respect to the hydrogen amount required in each reactor. And the amount of The amount of gas when hydrogen and an inert gas are used in combination also varies depending on the target heat removal ratio, but the gas hold-up in the present invention is usually 0.01 to 0.7, preferably 0.1 to 0.7. Since it is 1 to 0.4, the supply amount of the gas inert to the reaction may be determined from this value and the supplied hydrogen amount.

The gas supplied to the reactor is usually supplied to the liquid phase in the reactor, and the unreacted components are discharged from the upper part of the reactor. In the exhaust gas, benzene, together with unreacted gas,
Cyclohexene, cyclohexane and water are entrained. When these are entrained, the latent heat is removed from the reaction system and changed into a gas, thereby removing the heat. Further, the exhaust gas is cooled by cooling means such as a heat exchanger, and the latent heat is released. The number of cooling means such as a heat exchanger is not particularly limited, and one or more cooling means are used. When a metal salt or the like is present in the reaction system, a gas-liquid contact device such as a tray or a plate is provided in the gas phase of the reactor, and when the condensate and the exhaust gas are brought into contact, the exhaust gas contains the metal salt that accompanies the exhaust gas. The splash liquid can be removed, and the material of the heat exchanger can be reduced. Alternatively, a method may be employed in which two or more heat exchangers are provided, metal salts are removed by the first-stage heat exchanger, and the materials of the second- and subsequent-stage heat exchangers are reduced. Of course, 1
One heat exchanger may be provided for one reactor.

Examples of the heat exchanger include various heat exchangers such as a multi-tube heat exchanger, and among them, a kettle-type heat exchanger that can easily recover heat as a waste heat boiler is preferable. The temperature for cooling is not particularly limited and may be appropriately determined according to the required heat removal amount or the like, and is usually 100 ° C or lower, preferably 60 ° C or lower, more preferably 40 ° C or lower.

After the exhaust gas is cooled, a gas component (uncondensed component) containing unreacted hydrogen can be circulated to the reaction system and reused. For example, if the supplied gas is an excessive amount of hydrogen, the exhaust gas contains unreacted hydrogen, so it is possible to reduce the amount of hydrogen used by circulating it to the original reactor. it can. If multiple reactors are provided, reduce the amount of hydrogen in the circulated exhaust gas,
Feeding the remaining hydrogen to the next reactor is preferred in terms of reducing the number of compressors.

When the exhaust gas contains a large amount of impurities or inert gas, a part of the non-condensable components to be recycled is discharged to the outside of the reaction system in order to prevent the gas from being accumulated in the reaction system. Things are also done. Further, condensed components generated by cooling can be circulated to the reaction system and reused. Further, since the condensed component contains water, cyclohexene, cyclohexane, benzene and the like, it can be supplied to the original reactor or another reactor. In particular, when the condensed component is cooled to a temperature lower than the temperature of the reactor and circulated to the reaction system, the sensible heat also has an effect of removing heat from the reactor.

FIG. 1 is a schematic view showing one embodiment of the present invention. The figure shows an example of a continuous stirred tank reactor (two tanks). Each reactor contains an oil phase containing benzene, cyclohexene, cyclohexane, etc., an aqueous phase containing water in which metal salts such as zinc sulfate are dissolved, and a particulate Ru catalyst suspended in the aqueous phase. It is a four-phase reaction system consisting of a solid phase and a gas phase containing hydrogen gas. Benzene as a raw material is supplied to the first reactor R1 from line 1 and hydrogen is supplied from lines 2 and 14 to the first reactor R1. Water is supplied from the line 16 so that the oil-water ratio is constant. Each component is usually fed to the liquid phase of the reactor. Unreacted gas at the reactor outlet is line 3
It is further supplied to the heat exchanger E1 and condensed. The condensed liquid is returned to the reactor R1 from the line 5, and the gas not condensed is supplied to the heat exchanger E2 from the line 4. The liquid condensed in E2 is also returned to the reactor R1, and the uncondensed gas is used for the raw material and heat removal of the next reactor R2 from the line 7 together with the additional hydrogen supplied from the line 9. You. The liquid at the outlet of the reactor R1 is separated into oil and water by an oil / water separator S1, the aqueous phase is circulated to the reactor R1, and the oil phase is supplied to the next reactor R2. Oil-water separation can also be performed inside the reactor by providing a weir or the like at the back of the reactor. It is possible to supply the reaction product in the reactor R1 to the next reactor R2 without separating it from oil and water, but in this case, the amount of the aqueous phase circulating in the entire reaction system becomes large. There is.

In the second reactor R2, the first reactor R1
The same operation as is performed. The outlet liquid of the reactor R2 is further subjected to oil / water separation in an oil / water separator S2, and the oil phase is subjected to cyclohexene (CH) in a separation step such as an extractive distillation step (not shown).
E), cyclohexane (CHX) and benzene (BZ). The separated BZ is recycled to the reactor. On the other hand, the unreacted gas after condensing the organic matter is supplied to line 1
After passing through the compressor from 4, the fuel is returned to the first reactor R1. At this time, if there are many impurities in the hydrogen gas, it is preferable to provide a purge line. It is desirable that the heat exchanger E4 is set to a temperature at which the organic matter is sufficiently condensed in order to prevent the organic matter from being mixed into the compressor. Further, in the present invention, since the heat is removed by the supplied hydrogen gas, it is not necessary to circulate the liquid in the reactor to the outside to remove the heat. In this case, there is an effect that the amount circulating outside can be reduced.

When three or more reactors are provided, they can be carried out in the same manner as described above. In this case, the exhaust gas from the final reactor is preferably cooled and then returned to the preceding reactor, but more preferably the first exhaust gas.
Feed to the reactor at the stage.

[0027]

The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.
In the following, the conversion rate and the selectivity are determined as follows.

[0028]

(Equation 2)

[0029]

(Equation 3)

[0030]

EXAMPLE 1 A continuous partial hydrogenation reaction of benzene is performed according to the schematic diagram shown in FIG. The operating conditions were as follows: a continuous stirring tank reactor (two tanks), a reaction pressure of 5.0 MPa, and a reaction temperature of 15 MPa.
At 0 ° C. and an oil-water ratio (oil / water) of 0.1, the conversion of benzene (BZ) at the outlet of reactor A (line 8) was 37.7.
% And the selectivity of cyclohexene (CHE) is 78.8%.
The conversion of benzene (BZ) at the outlet of the reactor B is 60%, and the selectivity of cyclohexene (CHE) is 73%. The condition of the condensation heat exchanger is 80 ° C in the first stage (V),
The second stage (W) is set to 40 ° C. Further, BZ is supplied to the reactor A from the line 1 at 115 ° C. and 100 kmol / hr, and the oil phase separated at the outlet of the reactor A is supplied to the reactor B. The aqueous phase is recycled to the reactor A. The hydrogen supplied to the reactor A is a combination of newly supplied hydrogen and recycled hydrogen,
The amount is about 3.3 times the amount of hydrogen required for the reaction. On the other hand, for the reactor B, the amount of hydrogen supplied is about 4.3 times the amount required for the reaction.

When the above conditions are adopted, continuous operation is possible by the mass balance shown in Table 1. That is, by setting the supply of hydrogen to an excess amount of 3 to 5 times the amount required for the reaction, the heat of reaction can be removed only by the condensing heat exchanger, and an industrially excellent process can be provided. .

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

[Table 3]

[0035]

According to the present invention, it is an object of the present invention to provide a method for producing cyclohexene which can remove the heat of reaction by a simple method. That is, the heat supplied to the reactor and discharged from the reactor is used to remove heat from the reactor, in particular, the substance in the reactor takes latent heat from the reactor to change its state and be entrained by the gas. More preferably, when blowing gaseous hydrogen as one of the reaction raw materials as the gas, by supplying a larger amount of hydrogen than the required amount of hydrogen determined from the reaction results, The heat of the reactor can be removed. In particular, by cooling this exhaust gas and supplying condensed matter to the reactor, the reactor can be cooled using the exhaust gas from the reactor as a heat medium.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of the present invention, in which two continuous stirred tank reactors are provided.

[Explanation of symbols]

R1, R2: reactor, E1, E2, E3, E4: heat exchanger, S1, S2: oil / water separator, C1: compressor,
(1) to (17): Line (tube)

FIG. 2 is a schematic diagram of a reaction flow of Example 1 of the present invention.

[Explanation of symbols]

A, B: reactor, V, W, X, Y: heat exchanger, 1 to 17:
Line (tube)

Claims (13)

[Claims] 1. A monocycle for continuously supplying at least a monocyclic aromatic hydrocarbon and gaseous hydrogen to a reactor under an acidic condition in which water and a catalyst are present, and continuously collecting a reaction product. A method for producing a cyclic olefin by partial hydrogenation of an aromatic hydrocarbon, wherein the heat of the reactor is removed by using a gas supplied to the reactor and discharged from the reactor without being used for the reaction. For producing cyclic olefins. 2. The method according to claim 1, wherein the heat removal of the reactor is carried out by utilizing latent heat of a component supplied to the reactor and entrained in a gas discharged from the reactor without being used for the reaction. The method for producing a cyclic olefin according to claim 1, wherein 3. The method for producing a cyclic olefin according to claim 1, wherein the monocyclic aromatic hydrocarbon is benzene, and the obtained cyclic olefin is cyclohexene. 4. The cyclic olefin according to claim 1, wherein the gas supplied to the reactor and discharged from the reactor without being used for the reaction is mainly composed of hydrogen. Production method. 5. The method for producing a cyclic olefin according to claim 4, wherein the amount of supplied hydrogen is 1.2 to 50 times the amount of hydrogen required for the reaction. 6. The reactor according to claim 1, wherein the exhaust gas from the reactor is cooled and at least a part of the condensed components is circulated to the reactor.
The method for producing a cyclic olefin according to any one of the above. 7. The method for producing a cyclic olefin according to claim 1, wherein the exhaust gas from the reactor is cooled, and at least a part of the non-condensable components is circulated to the reactor. 8. The method for producing a cyclic olefin according to claim 7, wherein a part of the non-condensable component is discharged out of the reaction system. 9. The process for producing a cyclic olefin according to claim 1, wherein a Ru-containing catalyst is used as the catalyst. 10. The method for producing a cyclic olefin according to claim 1, wherein a metal salt is present in the stirring tank. 11. The method for producing a cyclic olefin according to claim 10, wherein a metal sulfate is used as the metal salt. 12. The method according to claim 1, wherein the heat removal using the gas supplied to and discharged from the reactor is 10% or more of the heat removal required for the entire reaction. A method for producing a cyclic olefin. 13. n under acidic conditions in the presence of water and a catalyst.
A single-ring aromatic hydrocarbon and gaseous hydrogen are continuously supplied into a reactor (n ≧ 2), and a reaction product is continuously collected by partial hydrogenation of the single-ring aromatic hydrocarbon. In the method for producing a cyclic olefin, (1) a monocyclic aromatic hydrocarbon and hydrogen are supplied to a first reactor, a reaction product is supplied to a second reactor, and the discharged gas is cooled. (2) supplying the reaction product from the former reactor to the latter reactor, cooling the gas discharged from the former reactor, and then reacting the latter reactor. Supplying (n-1) times to the container,
(3) Separating the reaction product from the final reactor into oil and water, extracting the oil phase separated from the oil and water, cooling the exhaust gas from the final reactor, and circulating the exhaust gas to an optional upstream reactor. , (4) The amount of hydrogen supplied to each reactor is made larger than the amount of hydrogen required for the reaction in the reactor, and the exhaust gas from the reactor is cooled.
The method for producing a cyclic olefin according to any one of the above.