JP3035641B2 - Method for producing acetic acid by carbonylation of methanol - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing acetic acid by carbonylation of methanol.

[0002]

2. Description of the Related Art As a method for producing acetic acid by carbonylation of methanol, a method is known in which methanol is reacted with carbon monoxide in a water-containing acetic acid solvent in which a rhodium compound and methyl iodide are dissolved. (Japanese Patent Publication No. 47-3334). This method was developed by the Monsanto Company and is widely practiced worldwide as the so-called "Monsanto method".
Although this Monsanto process is very good in that acetic acid can be produced in high yield from methanol, it has some essential disadvantages. For example, the Monsanto method uses a catalyst solution prepared by dissolving a catalyst with low solubility in acetic acid, so that the reaction is performed uniformly, so a large amount of acetic acid is required to uniformly dissolve the catalyst, and as a result, In addition, the reactor and the processing equipment for the obtained reaction liquid are inevitably large, and the amount of catalyst liquid circulated from the reaction liquid processing equipment to the reactor is also increased, thus increasing the construction cost of the acetic acid production plant. However, there is a disadvantage that the operation cost of the plant is also increased. In addition, in this method, it is necessary to keep a high concentration of water in the catalyst solution in order to keep the carbonylation reaction rate of methanol and the acetic acid selectivity high, and to prevent catalyst deposition in the circulating catalyst solution. But,
Due to the high concentration of water, there is also a disadvantage that methyl iodide used as a reaction accelerator undergoes hydrolysis to produce a large amount of hydrogen iodide. And this hydrogen iodide not only corrodes the equipment system but also mixes into the product acetic acid,
Reduce the quality of the product acetic acid. Further, the Monsanto method has a disadvantage that a large apparatus is required for separating and recovering the catalyst from the catalyst solution, regenerating the catalyst, and circulating the catalyst in the reaction system.

In order to overcome the disadvantages of the Monsanto method, several methods have been proposed so far, representative examples of which are described in JP-A-60-26943. There is a method described in JP-A-63-2553047. The method described in the former publication is a method in which lithium iodide and methyl acetate are present in a catalyst solution, and methanol is carbonylated under a condition of a lower water content than in the case of the Monsanto method. However, this method
From the point that a catalyst solution in which the catalyst is uniformly dissolved in a large amount of acetic acid is used, and in order to keep the water content in the catalyst solution low, it is necessary to increase the concentration of lithium iodide and methyl acetate, The processing of the reaction solution has become complicated, and has not been able to overcome the essential disadvantages of the Monsanto method. On the other hand, the method described in the latter publication discloses a method in which rhodium is supported on an insoluble resin containing a pyridine ring at a ratio of less than 10 wt% in the presence of a solid catalyst, a partial pressure of carbon monoxide: 65 to 80 bar, and a temperature: 170 This is a method of carbonylating methanol at -200 ° C. Since this method uses a solid catalyst to carry out the reaction in a heterogeneous system, it overcomes the essential disadvantages of the Monsanto method in which the reaction is carried out in a homogeneous system using a catalyst solution containing a large amount of added water. Is an effective method. However, since this method uses a high carbon monoxide partial pressure of 65 to 85 bar at a reaction temperature of 170 to 200 ° C. in order to obtain a high reaction rate, the total reaction pressure is necessarily 95 kg / cm ^2. The pressure becomes higher than G, and it is necessary to make the reactor large in pressure resistance. As a result, there is a problem that the reactor cost is inevitably increased. This publication also discloses side reactions that occur with the carbonylation reaction of methanol, such as an esterification reaction in which acetic acid reacts with methanol to produce methyl acetate and water, and a dehydration condensation reaction in which dimethyl ether and water form by the reaction between methanol. It does not describe reactions and the like, and does not suggest any means for controlling these side reactions. When these side reactions occur at a high rate, the reaction solution contains an undesirably large amount of water and by-products, making it impossible to obtain an economical acetic acid process. Also, Hjortkjaer et al. (A
applied Catalysis, 67, 269-2
78, (1991)), using an insoluble resin containing a pyridine group, at a reaction temperature of 140 ° C. and a reaction pressure of 20 kg /
cm ² G (CO partial pressure is 20 kg / cm ² or less)
In, the carbonylation of the raw material consisting of methanol and methyl iodide using a fixed bed flow reactor,
In this case, the dissociation of rhodium from the catalyst resin occurs at the beginning of the reaction, the reaction activity is reduced, and only a low activity of about 1/5 of the homogeneous catalyst is obtained.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a method for reacting methanol with carbon monoxide in the presence of a rhodium-containing solid catalyst and in the presence of methyl iodide. It is an object of the present invention to provide a highly economical acetic acid production method capable of controlling the side reaction and efficiently obtaining acetic acid having a low content of by-products as a product. And

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have completed the present invention. That is, according to the present invention, acetic acid is produced by reacting methanol and carbon monoxide in a reaction solvent containing an organic solvent selected from acetic acid and methyl acetate in the presence of a rhodium-containing solid catalyst and methyl iodide. (I) a rhodium-containing solid catalyst having a degree of crosslinking of 10%
As described above, the one in which rhodium is supported on an insoluble resin containing a pyridine ring in the resin structure is used, (ii) the degree of carbonylation Ac (I) of the solution in the reactor is 0.15 or more, and (iii) the reaction The water content Cw (II) of the product liquid is 0.5 to
(Iv) The carbon monoxide partial pressure in the reaction system is 7 to 30 kg / cm ² and the total reaction pressure is 15 to
60 kg / cm ² G, (v) reaction temperature is 14
A process for producing acetic acid by carbonylation of methanol, wherein the temperature is 0 to 250 ° C.

The catalyst used in the present invention is obtained by fixing rhodium to an insoluble resin containing a pyridine ring in the resin structure. In this case, the pyridine ring includes a substituted or unsubstituted pyridine ring and a pyridine ring forming a condensed ring such as a quinoline ring. Further, examples of the substituent in the substituted pyridine ring include substituents such as an alkyl group and an alkoxy group that are inactive to a carbonylation reaction. As a typical example of such an insoluble resin containing a pyridine ring in the resin structure, for example, by reacting vinyl pyridine with a divinyl monomer, or with vinyl pyridine,
It can be obtained by reacting a vinyl monomer containing a divinyl monomer. Specific examples of such a pyridine ring-containing insoluble resin include, for example, 4-vinylpyridine / divinylbenzene copolymer, 2-vinylpyridine / divinylbenzene copolymer, styrene / vinylpyridine / divinylbenzene copolymer, vinyl Methylpyridine / divinylbenzene copolymer, vinylpyridine / methyl acrylate / ethyl diacrylate copolymer and the like can be mentioned.

In the insoluble resin containing a pyridine ring in the resin structure used in the present invention (hereinafter simply referred to as insoluble resin), the degree of crosslinking is 10% or more, preferably 15 to 40%.
It is. If the degree of crosslinking is lower than 10%, the resin structure becomes susceptible to swelling and shrinkage by a reaction solvent such as acetic acid, which is not preferable. On the other hand, the upper limit of the degree of crosslinking is 40
%, The higher the degree of crosslinking, the lower the content of the pyridine ring in the insoluble resin becomes too low. As a result, the content of the rhodium in the resin also becomes low, and a catalyst with high catalytic efficiency cannot be obtained. . The pyridine ring content in the resin is represented by a basic equivalent, 2 to 10 meq /
g, preferably in the range of 3.5 to 6.5 meq / g. In the present specification, the degree of crosslinking referred to for an insoluble resin containing a pyridine ring in the resin structure is represented by the content (% by weight) of a divinyl monomer which forms the crosslinking contained in the resin.

[0008] In the catalyst used in the present invention, the pyridine ring may be free basic, or may be a quaternary pyridinium salt in which the basic nitrogen atom is previously quaternized, or an oxidized one. It may be a certain N-oxide or the like. The insoluble resin containing a pyridine ring is used as a granular material having a particle size of 0.01 to 2 mm, preferably 0.1 to 1 mm, more preferably 0.25 to 0.7 mm, and the preferred shape is a spherical body. . Insoluble resins containing a pyridine ring in the resin structure are already commercially available, for example, “Reillex-425” (Reilly Tar Chemicals), “KEX-316”, “KEX-50”
1 "and" KEX-212 "(both by Koei Chemical Co., Ltd.). In the present invention, these commercially available products can be used as an insoluble resin for supporting rhodium.

As a method for supporting and fixing rhodium on an insoluble resin containing a pyridine ring in the resin structure, a conventionally known method is employed. For example, by contacting the insoluble resin with a rhodium salt in a solvent containing methyl iodide under carbon monoxide pressure, an insoluble resin carrying and fixing rhodium can be obtained. Generally, the rhodium salt may be brought into contact with the insoluble resin under the conditions of the carbonylation reaction of methanol. In the rhodium-containing catalyst thus obtained, the pyridine ring contained in the insoluble resin is quaternized by methyl iodide to form a pyridinium salt, and the pyridinium salt is reacted with a rhodium salt, methyl iodide and carbon monoxide. It is considered that the rhodium carbonyl complex ([RhI ₂ (CO) ₂ ] ⁻ ) generated by the above has a structure ionically bonded. In the insoluble resin contacted with the rhodium salt, the pyridine ring can be a free base or a quaternized pyridinium salt or an N oxide, but in any case, the basic nitrogen atom is used in the carbonylation reaction of methanol. Is considered to be quaternized by methyl iodide.

Examples of the rhodium salt include rhodium chloride and rhodium halides such as rhodium bromide and rhodium iodide. The use ratio of methyl iodide to rhodium salt is 2 to 2 moles of methyl iodide per mole of rhodium salt.
The proportion is 2,000 mol, preferably 50 to 500 mol. The carbon monoxide pressure when the rhodium salt is brought into contact with methyl iodide is 7 to 30 kg / cm ² G, preferably 10 to 20 kg / cm ² G. Preferred rhodium-containing insoluble resin used in the present invention, from the viewpoint of effectively preventing the dissociation of rhodium from the insoluble resin during the reaction, rhodium in the resin, in terms of rhodium metal, 0.2 to 0.2.
The content is 15 wt%, preferably 0.3 to 8 wt%, more preferably 0.5 to 1 wt%.

The carbonylation reaction of methanol in the present invention can be carried out using various reactors.
Examples of the type of such a reactor include a fixed bed, a mixing tank, and an expansion bed. The amount of rhodium-immobilized insoluble resin in the reactor is generally 2 to the solution in the reactor.
-40 wt%, but in the case of a mixing tank reactor, it is 2-25 wt%.
It is good to choose to weight%. In the fixed bed reactor, 20 to
It is good to choose 40 wt% and 2-25 wt% in an expanded bed reactor.

In the present invention, the above-mentioned rhodium-immobilized insoluble resin is used as a catalyst, and a reaction solvent containing acetic acid and / or methyl acetate is used. The amount of the reaction solvent used in the present invention depends on the degree of carbonylation A defined below.
It is defined by c (I). Further, water can be added to the reaction solvent of the present invention. In this case, the amount of the water added is determined by the water content Cw defined later in the reaction product solution.
The amount is such that (II) is in the range of 0.5 to 10 wt%. In the present invention, the degree of carbonylation Ac (I) of the solution in the reactor is maintained at 0.15 or more, and the water content Cw (II) of the reaction product liquid is 0.5 to 10% by weight, preferably 1 to 5% by weight. The reaction is carried out while maintaining the percentage. By carrying out the reaction under such conditions, the reaction activity of the rhodium carbonyl complex ([RhI ₂ CO ₂ ] ⁻ ), which is the active center of the rhodium-immobilized insoluble resin catalyst, is increased, and the pyridinium salt and the rhodium carbonyl complex are reacted with each other. Is improved, the dissociation of rhodium from the insoluble resin is effectively prevented at a high reaction rate, and the carbonylation reaction of methanol can proceed smoothly. More importantly, the degree of carbonylation Ac in the solution in the reactor is Ac
By keeping (I) in the above range, 7 kg / cm
^The rhodium carbonyl complex is stably present even under the extremely low CO partial pressure condition of ^{2, and} the carbonylation reaction of methanol can proceed at a high reaction rate. This means that there is no need to use a special pressure vessel as a reactor, so that the cost of the reactor can be greatly reduced and a practical and economical acetic acid process can be obtained. As can be seen in the above-mentioned JP-A-63-253047, it is considered that a pressure of 65 to 85 bar as a CO partial pressure is essential for a methanol carbonylation reaction to proceed at a high reaction rate. However, as mentioned above,
It is an unexpected fact that the present inventors have first found that the carbonylation reaction of methanol proceeds at a high reaction rate at a low CO partial pressure of 7 kg / cm ^{2 according to} the present invention.

In the present invention, the partial pressure of CO (partial pressure of carbon monoxide) may be 7 kg / cm ² or more, preferably 10 kg / cm ² or more. Even if the CO partial pressure is particularly increased, the reaction rate is not improved, and no particular advantage in reaction is obtained. From an economic viewpoint, the upper limit of the CO partial pressure is 30 kg / kg.
It is better to be about cm ² . Therefore, C in the present invention
O partial pressure is 7-30 kg / cm ² , preferably 10-2
It is better to define it in the range of 0 kg / cm ² . By maintaining the CO partial pressure in such a range, the total reaction pressure can be reduced to an economical 15-60 kg / cm ² G, particularly 15-40 kg / cm ² G.
cm ² G, more preferably 15-30 kg / cm ² G.

The reaction temperature in the carbonylation reaction of the present invention is from 140 to 250 ° C., preferably from 160 to 230 ° C. The upper limit is appropriately selected according to the heat resistance of the insoluble resin used. The amount of methyl iodide in the reaction system is 1 to 40% by weight, preferably 5 to 30% by weight in the solution in the reactor. Further, the rhodium concentration defined below in the reaction system is 5% in the solution in the reactor.
0 wtppm or more, preferably 300 wtppm or more, more preferably 500 wtppm or more.

The most advantageous feature of the present invention is that, as described above, the carbonylation degree Ac (I) of the solution in the reactor is kept high, the catalyst activity is kept high, and the carbonylation reaction rate of methanol is increased. While holding in range
Carbon monoxide partial pressure: 7-30 kg / cm ² , total reaction pressure: 6
The carbonylation reaction of methanol is performed under low pressure conditions of 0 kg / cm ² G or less, and the water content Cw (II) is 0.5 to 10
An object of the present invention is to obtain a reaction product liquid of wt%, preferably 1 to 5 wt%. As a result, the cost of a reactor including a reactor and the cost of acetic acid purification such as water separation are significantly reduced, and a practical acetic acid process can be obtained. This is a surprising fact that the present inventors first found.

The degree of carbonylation Ac (I) of the solution in the reactor using the rhodium-containing insoluble resin catalyst affects the carbonylation reaction rate of methanol and the stability of the catalyst. The stability of the catalyst is determined by the water content C of the solution in the reactor.
It is also affected by w (I), and shows a tendency for rhodium to be easily detached from the catalyst as the water content Cw (I) increases. According to the study of the present inventors, when the carbonylation degree Ac (I) of the solution in the reactor is 0.15 or more, a high methanol carbonylation reaction rate can be obtained while keeping the stability of the catalyst high. It was found that The degree of carbonylation Ac (I) of the solution in the reactor is 0.1
If it is less than 5, the carbonylation rate of methanol will be too low to obtain acetic acid with good productivity, and the amount of rhodium released from the catalyst will increase, deteriorating the stability of the catalyst. Preferred degree of carbonylation Ac of the solution in the reactor
(I) is 0.55 or more, especially 0.7 or more. Further, in the present invention, as described above, a small amount of water coexists in the solution in the reactor, but the presence of this small amount of water increases the stability of the catalyst and reduces the reaction rate to an economical value. And other effects can be obtained. The water content of the solution in the reactor is equal to or lower than the water content of the reaction product solution. The degree of carbonylation Ac (I) of the solution in the reactor was set at 0.1.
It is maintained at 15 or more, preferably 0.55 or more, more preferably 0.7 or more, and the water content Cw (II) of the reaction product liquid is 0.5 to 10 wt%, preferably 1 to 5 w
By maintaining the content at t%, the detachment of rhodium from the catalyst can be substantially completely prevented, and acetic acid can be efficiently produced under a stable and highly active catalyst. This water content C
If w (II) exceeds 10 wt%, the cost of separating acetic acid and water increases, the amount of rhodium dissociated from the catalyst increases, and the amount of rhodium discharged out of the reaction system together with the reaction product increases.

In the present invention, the water content C of the reaction product solution
w (II) is 0.5 to 10% by weight, preferably 1 to
In order to keep in the range of 5 wt%, at least the total feed to the reactor is defined by the moisture content Aw (I)
Is maintained at 0.30 or less, and the degree of carbonylation Ac (II) of the reaction product at the end of the reaction, defined as follows, is 0.1.
It is necessary to carry out the reaction so as to be 8 or more.

In the carbonylation reaction of methanol of the present invention, the degree of carbonylation Ac of the reaction product liquid at the end of the carbonylation reaction of methanol using the specific catalyst described above.
As the value of (II) increases, the conversion of methanol increases and the rate of formation of by-products such as water, methyl acetate, and dimethyl ether decreases. In the present invention, the carbonylation degree Ac (II) of the reaction product solution is preferably maintained at 0.8 or more. The carbonylation degree Ac (I
When I) is 0.8 or more, the conversion of methanol is usually 90% or more. Further, as the degree of carbonylation Ac (II) of the reaction product increases, the amount of by-products decreases and the concentration of water in the reaction product decreases.

In the carbonylation reaction of methanol, side reactions of the following reaction formulas (2) and (3) are generated together with a main reaction of the following reaction formula (1). CH ₃ OH + CO → CH ₃ COOH (1) CH ₃ COOH + CH ₃ OH → CH ₃ COOCH ₃ + H ₂ O (2) 2CH ₃ OH → CH ₃ OCH ₃ + H ₂ O (3) These side reactions (2) and (3) ) Produces water as a by-product,
As described above, since this by-product water hydrolyzes methyl iodide to generate highly corrosive hydrogen iodide, it is important to suppress the by-product water as low as possible.
According to the study of the present inventors, the water content Aw (I) of the total feed to the reactor is kept at 0.3 or less, and the carbonylation degree Ac (II) of the reaction product liquid is 0.8 or more. By maintaining the temperature, the side reaction is suppressed, the generation of by-product water is effectively prevented, and the water content Cw (II) in the reaction product liquid is reduced to 10%.
It has been found that it can be suppressed to not more than wt%. In the present invention, by maintaining the water content Aw (I) of the entire feed to the reactor at 0.20 or less and maintaining the carbonylation degree of the reaction product liquid at 0.80 or more, The water content Cw (II) can be suppressed to 5.0 wt% or less. The fact that the water content Cw (II) in the reaction product liquid can be maintained at such a low value has great significance in the acetic acid production process by the carbonylation reaction of methanol, and has various advantages as described below. Can be obtained.

(1) Since the production of hydrogen iodide due to the hydrolysis of methyl iodide present in the reaction system can be suppressed, the corrosion of the apparatus system by hydrogen iodide can be remarkably suppressed. (2) In an acetic acid purification system of an acetic acid production plant, it is necessary to separate and remove hydrogen iodide and water, which are mixed as impurities and are difficult to separate, in order to obtain acetic acid of high purity. Since the water content of the reaction product solution according to the present invention is low, it is easy to separate and remove water and methyl iodide from acetic acid, and the cost for separating and purifying acetic acid is significantly reduced. (3) Dissociation of rhodium from the rhodium-immobilized insoluble resin that comes into contact with the solution in the reactor is prevented, and rhodium is prevented from leaking out of the reactor together with the reaction product liquid. Since rhodium has a high value, if it leaks out of the reactor, a separation and recovery step from the reaction product liquid is required, and the recovery cost will be very expensive. By keeping the water content low as described above, rhodium is not dissociated from the rhodium-immobilized insoluble resin, so that it is not necessary to provide such a rhodium separation / recovery step.

In the present invention, the reaction rate at which methanol is converted to another substance, that is, the above-mentioned reaction formula (1),
The reaction rate at which methanol is consumed by (2) and (3) is large in the initial stage of the reaction, and decreases as the reaction proceeds, in other words, as the conversion of methanol increases. The present inventors have surprisingly found that the conversion rate of methanol gradually decreases as the reaction proceeds as described above, but the carbonylation reaction rate of methanol, that is, the reaction formula (1) The indicated reaction production rate is almost constant when the water content Cw (II) of the reaction product liquid is 0.5 wt% or more. In order to maintain the economical acetic acid reactor yield, the reaction product liquid contains water. It is advantageous to carry out the carbonylation reaction of methanol while maintaining the concentration Cw (II) at 0.5 wt% or more and the carbonylation degree Ac (II) of the reaction product at 0.80 or more. I found it.

In this specification, the degree of carbonylation Ac, the degree of water content Aw, the concentration of water Cw, and the concentration of rhodium C
r is defined as follows. (Degree of carbonylation) The degree of carbonylation Ac is defined by the following equation.

[0023]

(Equation 1)

In the above formula, Ci represents the molar concentration (mol / l) of each component Mi present in the solution, Zi represents the carbonylation coefficient of each component Mi, and Xi represents the raw material coefficient of each component Mi. n indicates the total number of all components Mi present in the solution.
The carbonylation coefficient Zi and the raw material coefficient Xi of each component Mi are as shown in the following table.

[0025]

[Table 1]

(Water content) The water content Aw is defined by the following equation.

[0027]

(Equation 2)

In the above formula, Yi is the water content coefficient of each component Mi. Ci, Xi and n have the same meaning as given above for the degree of carbonylation. Water content coefficient Yi of each component Mi
Is as follows. Methyl iodide: 0 Methanol: 0 Acetic acid: 0 Methyl acetate: -1 Water: 1 dimethyl ether: -1 Carbon monoxide: 0 Other organic compounds: 0

(Water content) The water content Cw is wt% of water contained in the solution. (Rhodium concentration) The rhodium concentration Cr is expressed by wt. Of the amount of rhodium metal in the solution excluding the rhodium-immobilized insoluble resin.
%.

The degree of carbonylation Ac (I) of the solution in the reactor referred to in the present specification is defined as follows according to the type of the reactor. In a batch reactor, it is defined as the degree of carbonylation of the raw material solution charged in the reactor. In a mixed tank flow reactor, it is defined as the degree of carbonylation of the solution present in the reactor. In this reactor, since the solution in the reactor is uniformly mixed, the degree of carbonylation of the solution in the reactor,
The degree of carbonylation of the reaction product solution is the same. In a piston flow reactor, it is defined as the degree of carbonylation of the total feed to the reactor. The feed in this case includes methanol, methyl iodide, and reaction solvent newly introduced into the reactor, as well as unreacted methanol, dimethyl ether, methyl acetate, reaction solvent, methyl iodide, and the like circulated from the separation system. Included.

The carbonylation degree Ac (II) of the reaction product solution in the carbonylation reaction of methanol referred to in the present specification.
Is defined as follows according to the type of the reactor. In a batch reactor, it is defined as the carbonylation degree of the reaction product obtained at the end of the carbonylation reaction of methanol.
In a mixing tank flow type reactor and a piston flow type reactor,
It is defined as the degree of carbonylation of the reaction product discharged from the reactor outlet.

The water content Aw (I) of the total feed to the reactor referred to herein is defined as follows depending on the type of the reactor. In a batch type reactor, it is defined as the water content of the raw material solution charged in the reactor. In mixed tank flow reactors and piston flow reactors, it is defined as the water content of the total feed supplied to the reactor. The feed in this case includes methanol newly supplied to the reactor, methyl iodide, carbon monoxide, unreacted methanol circulated from the separation system, methyl acetate, dimethyl ether, a reaction solvent, methyl iodide, The reaction solution and the like which are withdrawn from the reactor and circulated to the reactor through an external cooler are included.

The water content C of the solution in the reactor referred to in this specification
w (I) is defined as follows depending on the type of the reactor. In a batch reactor, it is defined as wt% of water contained in a raw material solution filled in the reactor. In a mixed tank flow reactor, the weight of water contained in the solution present in the reactor
Defined as%. For a piston flow reactor, it is defined as the wt% of water contained in the total feed to the reactor.

The water content Cw of the reaction product solution referred to in this specification
(II) is defined as follows according to the type of the reactor. In a lift batch reactor, it is defined as wt% of water contained in a reaction product liquid obtained after completion of the reaction. In a mixing tank flow type reactor and a piston flow type reactor, it is defined as wt% of water contained in a reaction product liquid discharged from the reactor.

The carbonylation reaction of methanol in the present invention is advantageously carried out using a flow reactor. The flow reactor includes a mixed tank flow reactor and a piston flow reactor. Hereinafter, examples of acetic acid production by carbonylation of methanol of the present invention using these reactors will be described in detail. FIG. 1 shows an example of a flow sheet of the acetic acid production method of the present invention using a mixed tank flow reactor. In FIG. 1, R-1 is a mixing tank flow type reactor, 7 is a cooler, and S is a separation system. Reactor R-1 was charged with acetic acid as a reaction solvent, a rhodium-containing insoluble resin as a catalyst, and methyl iodide as a reaction accelerator, and these fillers were provided in the reactor. The mixture is uniformly stirred and mixed by the stirrer. Methanol containing methyl iodide was introduced into the reactor R-1 from the bottom via lines 1 and 2, and carbon monoxide was introduced from line 3 via a gas disperser attached to the reactor. To introduce. Reactor R
The methanol and carbon monoxide introduced into -1 react here in the presence of a rhodium-containing insoluble resin and methyl iodide to produce acetic acid. A reaction product liquid containing acetic acid generated by this reaction is withdrawn through line 4, a part of which is introduced into separation system S through line 5, and another part passes through line 6 and is provided with a cooler. 7, after being cooled here, is circulated through line 2 to reactor R-1. By circulating a part of the reaction product liquid to the reactor through the cooler in this way, the reaction heat generated in the reactor can be removed. Gaseous material containing unreacted carbon monoxide is withdrawn through line 8 and discharged through flow valve 9 and line 10. From this gaseous substance, low-boiling substances such as methyl iodide contained therein are separated and circulated to the reactor.

The reaction product liquid containing acetic acid introduced into the separation system S is subjected to a separation treatment including distillation here, acetic acid is recovered through the line 11, and the acetic acid obtained after separating acetic acid from the reaction product liquid is recovered. The residual liquid of the reaction product solution containing organisms is supplied to lines 12 and 13
To the methanol line 1 and circulated through line 2 to the reactor R-1. Part of the residual liquid is discharged to the outside of the system through the line 14 as necessary. This circulating liquid contains by-products such as methyl iodide, water, hydrogen iodide, methyl acetate and dimethyl ether, as well as unreacted methanol, methyl acetate and the like. Further, a part of the separated acetic acid can be mixed into the circulating liquid. Rhodium concentration in the solution in the reactor is 50 wtppm or more, preferably 300 wtppm or more, more preferably 500 wtppm.
ppm or more. Rhodium concentration in the solution in the reactor is
It can be controlled by adjusting the amount of the insoluble resin charged into the reactor and the amount of rhodium supported on the insoluble resin. For example, by mixing 0.05% by weight of an insoluble resin carrying 1% by weight of rhodium with respect to 100 parts by weight of a solution in a reactor, 500 wt ppm is obtained.
Can be obtained. By mixing 0.07 parts by weight of the insoluble resin carrying 3 wt% of rhodium with respect to 100 parts by weight of the solution in the reactor, a solution in the reactor having a rhodium concentration of 2100 wt ppm can be obtained. .

In the present invention, the degree of carbonylation Ac (I) of the solution in the reactor 1 is maintained at 0.15 or more, the partial pressure of carbon monoxide is 7 to 30 kg / cm ² , and the reaction temperature is 140 to 250. ℃, the water content C of the reaction product solution
w (II) is maintained at 0.5 to 10 wt%. By performing the carbonylation reaction under such conditions, the carbonylation reaction of methanol can be rapidly performed while maintaining a high catalytic activity at a reduced total reaction pressure of 15 to 60 kg / cm ² G. be able to. In this mixed tank flow type reactor, the degree of carbonylation Ac of the solution in the reactor is Ac.
(I) can be adjusted by the residence time of the solution in the reactor.

In this mixing tank flow type reactor, since the contents of the reactor are uniformly mixed, the carbonylation degree Ac (I) of the solution in the reactor and the reaction product liquid discharged from the reactor outlet are determined. The degree of carbonylation Ac (II) is substantially the same. In this reactor, the methanol introduced is immediately dispersed throughout the reactor and reacts quickly. As described above, in this mixed-tank flow reactor, methanol is carbonylated at a carbonylation degree Ac (I) of the solution in the reactor which is as high as the carbonylation degree Ac (II) of the reaction product solution, and is converted to acetic acid. Can be done.

The carbonylation reaction of methanol in the present invention is an exothermic reaction, and it is necessary to remove the heat of reaction in order to maintain the reaction temperature at a predetermined temperature. As a typical method for removing this heat of reaction, as shown in FIG.
A method of extracting a part of the solution in the reactor to the outside, indirectly cooling the solution with a cooler, and returning the solution to the reactor can be shown. In addition to such a method, various methods are available for removing the heat of reaction. For example, the solution in the reactor may be introduced into a flasher to vaporize a part of the solution, adiabatically cool the solution, and circulate the cooled solution to the reactor.

The solution in the reactor R-1 can be stirred by a method other than the stirrer. For example, the solution in the reactor is fluidized and stirred by carbon monoxide gas introduced into the reactor. Alternatively, fluid stirring can be performed using a circulating liquid flow into the reactor.

Next, a method for producing acetic acid by a carbonylation reaction of methanol using a piston flow reactor according to the present invention will be described. FIG. 2 shows an example of a flow sheet of a method for producing acetic acid using a piston flow reactor. In FIG. 2, R-2 is a piston flow type reactor,
21 is a gas-liquid separator, and S is a separation system.

The piston flow reactor R-2 has a structure in which a plurality of catalyst tubes are erected inside. The catalyst tube in this case has a structure in which a rhodium-containing insoluble resin is filled therein as a catalyst, and may be a fixed bed type in which the catalyst is filled so that the catalyst does not flow. It may be a floor type.

The catalyst tube in the reactor R-2 is cooled by bringing a refrigerant into contact with the outer surface thereof. Steam is preferably used as the refrigerant. The steam is extracted from the reactor and used as a heat source for the distillation column. The raw material methanol containing methyl iodide is introduced into the inlet of the reactor R-2 through the line 1 together with the circulating liquid circulated from the line 13 and the carbon monoxide supplied through the line 3. A gas-liquid mixture composed of carbon monoxide and a liquid containing methanol and acetic acid introduced into the bottom of the inlet of the reactor R-2 is sufficiently dispersed in gas at the inlet of the reactor, and is supplied to a plurality of catalyst tubes. And the gas is supplied uniformly. In the catalyst tube, methanol and carbon monoxide react in acetic acid as a reaction solvent in the presence of a catalyst and methyl iodide to be converted to acetic acid. The reaction product liquid containing acetic acid is withdrawn through line 20 and introduced into a gas-liquid separator 22, where gaseous matter containing unreacted carbon monoxide is withdrawn through line 23,
Discharged through flow valve 24 and line 25. Low-boiling substances such as methyl iodide are separated from this gaseous substance and circulated to the reactor R-2. After the gaseous matter containing unreacted carbon monoxide is separated, the reaction product liquid is supplied to line 2
2 to the separation system S, where the acetic acid is separated, and the separated acetic acid is recovered through the line 26.
In the separation system S, the residual liquid after the acetic acid is separated from the reaction product liquid passes through the lines 12 and 13 and the methanol line 1
And circulated through line 2 to reactor R-2. Part of the circulating residual liquid is discharged out of the system through the line 14 as necessary. This circulating liquid contains by-products such as methyl iodide, water, hydrogen iodide, methyl acetate, and dimethyl ether, as well as unreacted methanol and methyl acetate.
Further, one part of the separated acetic acid can be mixed therein.

In the present invention, the total carbonylation degree Ac (I) of methanol, acetic acid and circulating liquid fed into the reactor R-2 is 0.15 or more, especially 0.5
While maintaining the water content Aw (I) at 5 or more, preferably 0.7 or more and 0.30 or less, particularly 0.20 or less,
The carbon monoxide partial pressure is 7 to 30 kg / cm ² , and the reaction temperature is 1
Hold at 40-250 ° C. By performing the carbonylation reaction under such conditions, the reaction pressure is increased to 15 to 60.
kg / cm ² G, particularly 15~40kg / cm ² G the lowered pressure that can be performed quickly methanol carbonylation reaction. In the present invention, the reactor R
-2 degree of carbonylation Ac of the reaction product liquid extracted from -2
The carbonylation reaction of methanol is performed so that (II) is 0.8 or more, preferably 0.90 or more.

In the present invention, the water content Aw (I) of the whole feed to the reactor R-2 is not more than 0.30, especially 0.1.
The carbonylation degree Ac (II) of the reaction product liquid discharged from the reactor is kept at 0.8 or more, especially at 0.8 or less.
By maintaining the concentration at 9 or more, the side reaction is suppressed, the generation of by-product water is effectively prevented, and the water content Cw (II) in the reaction product liquid discharged from the reactor is 10 wt% or less, especially 5 wt%.
wt% or less. Further, in the present invention, the water content Cw (II) of the reaction product liquid is adjusted to 0.5 to 10
By keeping the wt%, a high carbonylation reaction rate of methanol can be obtained, and acetic acid can be produced with high production efficiency. In the present invention, if necessary, at least a part of the reaction product liquid residual liquid containing by-products after separating acetic acid from the reaction product liquid can be circulated to the reactor.

[0045]

According to the present invention, the methanol carbonylation reaction, under conditions of low reaction pressure of low carbon monoxide partial pressure of 7~30kg / cm ² and 15~60kg / cm ² G, stabilized Acetic acid having a low by-product content can be obtained with good productivity and economical by selectively performing the reaction at a high reaction rate under a high activity catalyst.

[0046]

Next, the present invention will be described in more detail with reference to examples. Example 1 6.8 g of sufficiently dried poly-4-vinylpyridine / divinylbenzene copolymer resin (trade name "Reillex")
425 ", 25% cross-linking degree, Reilly company), is impregnated with methanol for a sufficient time, and then methyl iodide is made up to 140 g of a solution consisting of 8 wt% of methyl iodide, 40 wt% of methanol and 52 wt% of acetic acid. And acetic acid, and the mixture was charged into a 250 cc titanium-made autoclave reactor equipped with a stirrer, and 0.07 g of RhCl ₃ .3H ₂ O was added.
After degassing the mixture several times with carbon monoxide, when the temperature was increased to 190 ° C., the total pressure of the autoclave was about 40 kg / c.
CO was supplied through a self-regulating control valve so that m ² G (the initial partial pressure of CO was 15 kg / cm ² G). After 60 minutes, the reactor was cooled, and after purging with nitrogen, the reaction product was removed by decantation, and washing with methanol was repeated several times. Rh in the reaction product was analyzed by atomic absorption spectroscopy, but Rh was hardly detected. When the Rh-supported catalyst resin thus prepared was analyzed, most of the added RhCl ₃ .3H ₂ O was immobilized on the resin, the amount was 0.4 wt%, and most of the pyridine ring was It was found that an equivalent amount of iodine was fixed.

Next, the catalyst thus prepared was added with 8
wt% methyl iodide, 40 wt% methanol, 52w
Methyl iodide, acetic acid, and methanol were added to make 140 g of a solution containing t% acetic acid, and the mixture was charged in a 250 cc titanium autoclave reactor, and degassed several times with CO. The mixture (Ac (I) = 0.40, Aw (I) = 0.0
Was heated to 190 ° C, and the total pressure of the autoclave was about 40 kg.
/ Cm ² G (initial CO partial pressure: 15 kg / cm ² ), CO was supplied by a control valve by a self-powered system, and the reaction was carried out. After 180 minutes, the reaction product solution was sampled from the reactor under a reaction condition by a high-pressure sampler and analyzed. The product was a product having the composition shown in Table 2, and its carbonylation degree Ac
(II) = 0.84, water content Cw (II) = 4.1 wt
%, And the concentration of Rh released from the catalyst into the reaction solution was 0.1%.
It was 3 ppm or less. Further, the carbonylation reaction rate of methanol in this reaction was 3.1 mol / l · h.

Example 2 A poly-4-vinylpyridine resin having a degree of crosslinking of about 10
% KEX-316 (Koei Chemical Co., Ltd.), 0.14 g
KEX-316 in which 0.8 wt% of Rh was immobilized on a resin in the same manner as in Example 1 except that RhCl ₃ .3H ₂ O was added.
A resin catalyst was prepared. Using this catalyst, a reaction was carried out in the same manner as in Example 1, and sampling was carried out 120 minutes later. As a result, a reaction product liquid having the composition shown in Table 2 was obtained.
I) = 0.87, Cw (II) = 3.4 wt%, and the concentration of Rh released into the reaction solution was 0.3 ppm or less. The carbonylation reaction rate in this reaction was 4.7 mol / l · h.

Example 3 As a poly-4-vinylpyridine resin, the degree of crosslinking was about 20%.
Of KEX-212 (Koei Chemical Co., Ltd.) and 0.14 g of RhCl ₃ .3H ₂ O were added in the same manner as in Example 1 except for adding 0.14 g of RhCl ₃ .3H ₂ O.
8 wt% Rh was supported and immobilized to prepare a KEX-212 resin catalyst, and the catalyst was adjusted to 140 g of a reaction solution consisting of 39.5 wt% methyl iodide, 39.5 wt% methanol, and 51 wt% acetic acid. Then, the reaction was carried out in the same manner as in Example 1 except that this solution (Ac (I) = 0.40, Aw (I) = 0.0) was used. Is obtained, and Ac (II) = 0.94 and Cw (II) = 1.6 w
and the Rh concentration dissociated in the reaction product solution was 0.3%.
wtppm or less. The carbonylation reaction rate of methanol in this reaction was 3.6 mol / lh.

Example 4 KEX-501 as poly-4-vinylpyridine resin
KEX- with 0.8 wt% Rh supported and immobilized in exactly the same manner as in Example 2 except that (crosslinking degree: about 30%) was used.
A 501 resin catalyst was obtained. Using this catalyst, a reaction was carried out in the same manner as in Example 2. After sampling for 180 minutes, a reaction product liquid having the composition shown in Table 2 was obtained, and the Ac (II) =
0.91 and Cw (II) = 2.3 wt%, and the concentration of Rh released into the reaction solution was 0.3 wt ppm or less. The carbonylation reaction rate of methanol in this reaction was 3.4 mol / l · h.

Example 5 The catalyst used in Example 1 was used again for the next reaction after washing with methanol. A reaction solution (Ac (I) = 0.70, Aw (I) = 0.0) consisting of 8.0% by weight of methyl iodide, 16% by weight of methanol and 76% by weight of acetic acid was added to the catalyst.
Methyl iodide, methanol and acetic acid were added so as to obtain 40 g, and the reaction temperature was 175 ° C. in a 250 cc titanium reactor.
The reaction was carried out in the same manner as in Example 1 and sampling was performed 150 minutes later. As a result, a reaction product solution having the composition shown in Table 2 was obtained. Its carbonylation degree Ac (II) was 0.94, and the carbonylation rate of methanol was Was 2.0 mol / l · h.

Example 6 The reaction was carried out in the same manner as in Example 5 except that the reaction temperature was changed to 205 ° C. As a result, a reaction product liquid having the composition shown in Table 2 was obtained, and its Ac (II) was 0.94 and the carbonylation rate of methanol was 3.3 mol / l · h.

Example 7 Other than adding 0.70 g of RhCl ₃ .3H ₂ O,
When a catalyst was prepared in the same manner as in Example 1, 2.0 wt%
A catalyst in which Rh was immobilized on a pyridine resin was obtained.
In this case, unlike in Examples 1 to 6, the total amount of rhodium used was not fixed, and only about 1/2 was fixed. A reaction solution comprising 8.0 wt% of methyl iodide, 16 wt% of methanol and 76 wt% of acetic acid (Ac (I) = 0.70, Aw (I) =
0.0) 140 g of methyl iodide, methanol, and acetic acid were added, and the mixture was charged into a 250 cc titanium autoclave reactor, degassed several times with CO, heated to 190 ° C., and the total pressure of the autoclave was about 30 kg. / Cm ² G (15 kg / cm ² in initial CO partial pressure), and CO was supplied by a self-acting control valve to carry out the reaction. After 50 minutes, the reaction product was sampled from the reactor under high pressure and sampled under high pressure.
As a result of analysis, the reaction product liquid had the composition shown in Table 1. The carbonylation degree Ac (II) was 0.95, and the water content Cw (II) was 1.1 wt%. The carbonylation reaction rate of methanol was 5.1 mol / l · h.

Example 8 A catalyst having 5.0 wt% of Rh immobilized thereon was prepared in the same manner as in Example 7. The catalyst thus prepared was reacted in the same manner as in Example 7, and after 30 minutes, the sample was analyzed by sampling. The carbonylation degree Ac (II) of the reaction product solution was 0.95, and the water content Cw was 1 .2wt
%, And the composition was almost the same as that of Example 7. At this time, the carbonylation reaction rate of methanol was 9.
It was 4 mol / l · h.

Example 9 A catalyst carrying 0.8 wt% Rh was prepared in the same manner as in Example 1 except that 0.14 g of RhCl ₃ .3H ₂ O was used. To the catalyst thus obtained, methyl iodide, methanol and acetic acid were added so as to obtain 70 g of the reaction solution having the same concentration as in Example 7, and the reaction was carried out in the same manner as in Example 7.
After sampling for 35 minutes, the carbonylation degree Ac (II) of the reaction product solution was 0.95, and the water content Cw (II)
Was 1.1 wt%, and the composition was almost the same as that of Example 7. In this case, the carbonylation reaction rate of methanol was 7.8 mol / l · h.

Example 10 After washing the catalyst used in Example 7 with methanol, the catalyst was added with 9.1 wt% of methyl iodide and 12.1 w of methanol.
t%, acetic acid 45.8wt%, methyl acetate 23.1wt
%, Water 9.9 wt% solution (Ac (I) = 0.60, Aw
Each raw material was added so that (I) = 0.14), and the reaction was carried out in the same manner as in Example 1. The carbonylation degree Ac (II) of the reaction product liquid after 90 minutes was 0.94, and the carbonylation degree Ac (II) of the reaction liquid after 180 minutes was 0.98. The reaction product liquid had the composition shown in Table 2. The carbonylation rate of methanol at Ac (II) = 0.94 was 3.7 mol / l.
H, and the carbonylation rate of methanol at Ac (II) = 0.98 was 3.2 mol / l · h.

Comparative Example 1 A catalyst was prepared in the same manner as in Example 1 by using Reilex 402 (trade name: 2%) as a vinylpyridine resin and subjected to a reaction. Did not rise at all and remained at 0.40. After the reaction, the resin was crushed into a tar-like shape.

Comparative Example 2 Using the catalyst prepared in Example 1, the total pressure of the autoclave was about 29 kg / cm ² G (4 kg / c at the initial CO partial pressure).
m ² ), except that the reaction was carried out in the same manner as in Example 1. The reaction product was sampled and analyzed in 200 minutes. Ac (II) = 0.48, Cw (II) = 12.8 w
t%, rhodium concentration = 2.6 wtppm, a large amount of water was generated, and dissociation of rhodium into the reaction product solution was observed. At this time, the methanol carbonylation reaction rate was 0.5 mol / l · h, which was 2.9 mol in Example 1.
/ L · h.

Comparative Example 3 Using the catalyst of Example 1, the total pressure of the autoclave was increased to about 65 k.
g / cm ² G (40 kg / cm ² in initial CO partial pressure) except that the reaction was carried out in the same manner as in Example 1,
When the reaction solution was analyzed at 00 minutes, Ac (II) = 0.
88, Cw (II) = 3.2 wt%, the concentration of rhodium dissociated in the reaction product solution was 0.3 wt ppm or less, but the carbonylation reaction rate at this time was 2.9 mol / l.
H, which is exactly the same as in Example 1, and the effect of improving the reaction rate by increasing the partial pressure of CO was not observed.

COMPARATIVE EXAMPLE 4 The catalyst of Example 9 was prepared by adding 7.6 wt% of methyl iodide, 32 wt% of methanol, 45 wt% of acetic acid and 16 wt% of water (Ac (I) = 0.40, Aw (I) = 0). .51), and the total pressure of the autoclave was increased to about 40 kg / c.
The reaction was carried out in the same manner as in Example 1 except that m ² G (initial CO partial pressure was 19 kg / cm ² G). The carbonylation reaction rate of methanol is 4.4 mol / l · h, and the carbonylation degree Ac (II) of the reaction product liquid after the reaction after 120 minutes is 0.1 mol / l · h.
89, the composition of the reaction product liquid was as shown in Table 2, and 14.9% by weight of water was present. Further, Rh dissociated into the reaction solution was 4.5 wtppm.

Comparative Example 5 A solution of 7.5 wt% of methyl iodide, 74.5 wt% of methanol and 11.9 wt% of acetic acid (Ac
(I) = 0.05, Aw (I) = 0.27), and the total pressure of the autoclave was adjusted to about 50 kg / cm.
^The reaction was carried out in the same manner as in Example 1, except that the pressure became ² G (initial CO partial pressure: 16 kg / cm ² ). The carbonylation degree Ac (II) of the reaction product liquid after 60 minutes was 0.05, and the carbonylation reaction rate of methanol was as low as 0.9 mol / l · h.

Example 11 A reaction was carried out in the same manner as in Example 1 except that the catalyst of Example 9 was used. Sampling analysis of a reaction product liquid was performed at 50 minutes, 80 minutes, 140 minutes, and 240 minutes. The water content Cw (II) in each reaction product solution decreased to 9.9, 8.5, 1.8 and 0.2 wt% with the progress of the reaction. The carbonylation rate is 140 minutes Ac (II)
Up to 0.93, a constant rate of 4.5 mol / l · h was shown. On the other hand, with Ac (II) 0.98 after 240 minutes, the carbonylation rate was 0.3 mol / l · h, and the water content Cw (I
I) was 0.2 wt%. 2 from the beginning of this reaction
Average carbonylation reaction rate up to 40 minutes is 2.3 mol
/ L · h. Further, in this reaction, the concentration of Rh dissociated in the reaction product solution was 0.3 wtppm or less.

Example 12 Using an autoclave of a mixing tank flow type in which the internal liquid volume was controlled to 120 cc, (Ac (I) = 0.81, Aw (I) =
0.0) under the condition of 0.0).
In a continuous test of 100 hours, the degree of carbonylation Ac
(II) A reaction product liquid having 0.81 and a rhodium concentration dissociated into the reaction product liquid of 0.3 wtppm or less could be continuously obtained. In this experiment, 5.8 g of the catalyst of Example 9 was used at a dry weight, and this catalyst was previously charged in an autoclave together with acetic acid and methyl iodide. The reaction temperature is 190 ° C and the reaction pressure is CO
And kept at 30 kg / cm ² G as a total pressure. The raw materials supplied to the reactor were CO: 18 Nl / Hr, methanol: 15 g / Hr, methyl iodide: 2 g / Hr, dimethyl ether: 0.1, methyl iodide 8.3,
Methanol: 0.4, acetic acid 63.2, methyl acetate: 2
A reaction solution consisting of 2.4, water: 5.6 (wt%) could be continuously obtained.

Example 13 Following Example 12, the raw materials supplied to the reactor with the same apparatus were as follows: CO: 13.2 Nl / hr, methanol: 22 g / h
r, acetic acid 95 g / hr, methyl iodide 13 g / hr, carbonylation reaction was carried out continuously for 100 hours, Ac (II) = 0.87, Aw (II) = 0.0, rhodium concentration A reaction product liquid of 0.3 wtppm or less was continuously obtained. Table 2 shows the composition of the solution.

[0065]

[Table 2- (1)]

[0066]

[Table 2- (2)]

Next, Table 3 summarizes the reaction conditions and the reaction results in Examples 1 to 13 and Comparative Examples 1 to 5.

[0068]

[Table 3]

[Brief description of the drawings]

FIG. 1 shows an example of a flow sheet of the acetic acid production method of the present invention using a mixed tank flow reactor.

FIG. 2 shows an example of a flow sheet of the method for producing acetic acid of the present invention using a piston flow type reactor.

[Explanation of symbols]

 R-1 Mixing tank flow type reactor R-2 Piston flow type reactor S Separation system

Continued on the front page (72) Inventor Sachio Asaoka 2-1-1, Tsurumichuo, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture Inside Chiyoda Kako Construction Co., Ltd. No. 1 Inside Chiyoda Kako Construction Co., Ltd. (56) References JP-A-63-253047 (JP, A) JP-B-47-47237 (JP, B1) JP-B-47-3331 (JP, B1) -503808 (JP, A) Chemical Abstracts, 105 (1986), 210768. (58) Fields investigated (Int. Cl. ⁷ , DB name) C07C 53/08 C07C 51/12 CAPLUS (STN) REGISTRY (STN) WPIDS (STN)

Claims (3)

(57) [Claims] A method for producing acetic acid by reacting methanol and carbon monoxide in a reaction solvent containing an organic solvent selected from acetic acid and methyl acetate in the presence of a rhodium-containing solid catalyst and methyl iodide. (I) a rhodium-containing solid catalyst having a degree of cross-linking of 10% or more and insoluble resin containing a pyridine ring in the resin structure and supporting rhodium; (ii) a degree of carbonylation of the solution in the reactor. Ac
(I) is 0.15 or more, (iii) the water content Cw (II) of the reaction product liquid is 0.5 to 10 wt%,
(Iv) The carbon monoxide partial pressure in the reaction system is 7 to 30 kg /
cm ² and the total reaction pressure is 15-60 kg / cm ² G, (v) the reaction temperature is 140-250 ° C.,
A process for producing acetic acid by carbonylation of methanol, characterized by the following. 2. The water content Aw of the total feed to the reactor.
2. The reaction product solution according to claim 1, wherein (I) is 0.30 or less, the carbonylation degree Ac (II) of the reaction product solution is 0.80 or more, and the water content Cw (II) of the reaction product solution is 1 to 5 wt%. Method. 3. The reactor according to claim 1, wherein the rhodium concentration in the reactor is 500 wt ppm or more in the solution in the reactor.
the method of.