JPH05163201A - Production of carboxylic acid butyl ester - Google Patents

Abstract

PURPOSE:To provide an extremely effective process for producing a carboxylic acid butyl ester from a carboxylic acid and ethylene in one step in a good yield. CONSTITUTION:A process for producing a carboxylic acid butyl ester by reacting ethylene with a carboxylic acid in one step comprises employing a heteropolyacid produced by substituting with palladium cations a part of protons contained in the heteropolyacid consisting mainly of a tungsten oxide represented by phosphotungstic acid or silicotungstic acid as a catalyst. Therein, when the content of the crystal water contained in the heteropolyacid in which a part of the protons is substituted with the palladium cations is to <=3.0 molecules per molecule of the heteropolyacid, an extremely active catalyst is obtained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing carboxylic acid butyl ester. More specifically, the present invention relates to a method for producing a carboxylic acid butyl ester by reacting a carboxylic acid with ethylene in the presence of a heteropoly acid mainly containing tungsten oxide.

[0002]

2. Description of the Related Art Conventionally, as a method for producing a carboxylic acid butyl ester, it has long been known that it is produced by an esterification reaction between a carboxylic acid and butyl alcohols and a reaction between a butyl alcohol and a carboxylic acid anhydride. There is.
However, these methods use butanols as a raw material.Butanols are raw materials obtained by further chemically changing olefins such as hydroformylation of propylene and hydration reaction of butenes, and are economically disadvantageous. is there. Further, the production method from butanols and carboxylic acid is a method by an esterification reaction, and since the esterification reaction is an equilibrium reaction, it is difficult to produce the ester in a high reaction yield, and a further by-product is produced. Measures need to be taken to remove the water. Further, in the method using a carboxylic acid anhydride, the yield of the ester is high, but the carboxylic acid anhydride used is expensive, and in addition, one molecule of the carboxylic acid is released, and this carboxylic acid is converted into an anhydride. It has various drawbacks such as being extremely difficult.

Further, as a method for solving these problems, as a method for producing a carboxylic acid butyl ester by addition reaction of butenes and carboxylic acid, addition reaction of carboxylic acid and butenes in the presence of an acid catalyst is old. Known from. For example, in World Patent No. 88-02216, tert-butyl acetate is produced from isobutene and acetic acid using N, N-dialkylalkanamide as a catalyst. Further, in WO 87/06244, sec-butyl acetate is produced from 1-butene and acetic acid by using a polymer catalyst having a sulfonic acid group. In Japanese Patent Publication No. 56-30334,
Sec-Butyl acetate is produced from 1-butene and acetic acid using tungsten heteropolyacid as a catalyst.

However, all of these methods use butenes as olefins. Butenes have an extremely small amount of production worldwide compared to ethylene, and their supply amount is not comparable to that of ethylene, and is unstable. Here, it can be said that the production of the butyl ester of a carboxylic acid from ethylene and a carboxylic acid is an extremely desirable method from the viewpoint of raw material circumstances and economy. Regarding the method for producing a carboxylic acid butyl ester from ethylene and a carboxylic acid, it is shown as a cited document in the prior art in the specification of Japanese Patent Publication No. 56-30334 (Japanese Patent Publication No. 47-42808, ) Examined these patents in detail, but there is no example in which a butyl ester is produced from carboxylic acid such as ethylene and acetic acid. Therefore, an example of producing a carboxylic acid butyl ester from ethylene and a carboxylic acid in a usual acid-catalyzed reaction has not yet been known.

[0005]

The object of the present invention is to produce a butyl carboxylic acid ester in a short time with a high selectivity and a high conversion rate by the reaction of ethylene with a carboxylic acid and to stabilize the reaction even in a high temperature region. The purpose of the present invention is to provide a catalyst that can be carried out.

[0006]

Means for Solving the Problems The inventors of the present invention investigated an efficient method for producing carboxylic acid butyl ester, and paid attention to the fact that the reaction between ethylene and carboxylic acid is an excellent production method. As a result, it was found that the reaction proceeded extremely efficiently by allowing the reaction system to have a catalyst obtained by substituting a part of protons of the heteropolyacid mainly composed of tungsten oxide as a catalyst with a palladium cation, and completed the method of the present invention. Came to do. That is, characterized in that the aliphatic carboxylic acid or aromatic carboxylic acid and ethylene are reacted in the presence of a heteropolyacid in which a part of the protons of the heteropolyacid mainly composed of an oxide of tungsten is replaced with a palladium cation. Carboxylic acid butyl ester
(Especially sec-butyl carboxylic acid) is a production method,
General formula: (M ₁ ) a (M ₂ ) b (W) c (O) d (H) ef (Pd) f / 2 (where M ₁ and M ₂ represent a metal atom, W is a tungsten atom, Pd represents a palladium atom, O represents an oxygen atom, and H represents a hydrogen atom.
Is an integer of 1 or 2, b is an integer of 0, 1 or 2, c is a positive integer of 20 or less, d is a positive integer of 100 or less, and e is a positive integer of 10 or less. Integer, f is 1
It is a positive real number less than 0. ) Is used as a catalyst. In these general formulas, M ₁ is an element symbol and is an element represented by any of P, Si, Co, Mn, Ni, As, Ti, Fe, V and B, and M ₂ is an element symbol V. It is preferable to use an element, and it is particularly preferable to use an element in which a part of protons of tungstosilicic acid and / or molybdosilicic acid is replaced with a palladium cation.

Further, these heteropolyacids may be those containing an amorphous water and / or water of crystallization of the acid, but the amount of water of crystallization of these heteropolyacids is 3 on average per molecule of the heteropolyacid. A heteropoly acid adjusted to 0.0 molecule or less is a more preferable catalyst. Furthermore, by heat-treating these heteropolyacids in the temperature range of 150 ° C. to 500 ° C. or by heat-treating them under the flow of an inert gas, the amount of water of crystallization contained on average per molecule of the heteropolyacid is A method for producing a heteropoly acid adjusted to 3.0 molecules or less as a catalyst is preferable as a dehydration adjusting method.

The method of the present invention will be described in detail below. The carboxylic acids and ethylene used in the method of the present invention do not need to be particularly purified, and carboxylic acids and ethylene of general reagent purity can be used as they are. It is more preferable to remove water. Here, the carboxylic acids used in the method of the present invention are aliphatic carboxylic acids and aromatic carboxylic acids, and specific examples of the aliphatic carboxylic acids include formic acid, acetic acid, propionic acid, butyric acid and the like having 1 to 15 carbon atoms. Aliphatic unsaturated carboxylic acids having 3 to 15 carbon atoms such as aliphatic saturated carboxylic acids, acrylic acid and methacrylic acid, and halogen atoms, cyano groups, nitro groups, hydroxyl groups,
1 to 15 carbon atoms partially substituted with amino group and sulfone group
Aliphatic saturated carboxylic acids of 3 to 15 carbon atoms, aliphatic unsaturated carboxylic acids of 3 to 15 carbon atoms, in addition to monocarboxylic acid,
Also included are polycarboxylic acids such as di- and tri-carboxylic acids.

The aromatic carboxylic acids are aromatic mono- and polycarboxylic acids, specifically, benzoic acid, naphthalenecarboxylic acids, phthalic acids and the like, and halogen atoms, hydroxyl groups, cyano groups, nitro groups and amino groups. With 7 carbon atoms, substituted with sulfone, sulfone, alkyl, allyl, etc.
~ 25 aromatic mono- and polycarboxylic acids.

The catalyst used in the method of the present invention is a heteropolyacid, and has the general formula (M ₁ ) a (M ₂ ) b (W) c (O) d (H) ef (Pd) f / 2 (provided that M ₁ Is the element symbol
P, Si, Co, Mn, Ni, As, Ti, Fe, V, B, etc., M ₂ is an element represented by the symbol V, etc., W is a tungsten atom, Pd is Palladium atom, O is oxygen atom, H
Represents a hydrogen atom, a is 1 or 2, b is 0, 1 or 2,
c is a positive integer of 20 or less, d is a positive integer of 100 or less,
e is a heteropolyacid represented by a positive integer of 10 or less and f is a positive real number of less than 10. Specifically, dodecatungstosilicic acid (SiW ₁₂ O ₄₀ H ₄ ), dodecatungstophosphoric acid (PW
₁₂ O ₄₀ H ₃ ), and a heteropoly acid having a structure in which one or more of these tungsten atoms are replaced by vanadium atoms, and a part of the protons of the heteropoly acid is replaced by a palladium cation, etc. are most available. Mentioned as a heteropoly acid. However, the method of the present invention is not limited to these heteropolyacids. Here, a method for preparing a heteropoly acid in which a part of protons of the heteropoly acid mainly composed of an oxide of tungsten used in the method of the present invention is replaced with a palladium cation will be described.

The method for preparing the above-mentioned palladium cation-exchanged heteropolyacid in the method of the present invention is not particularly limited, and any method may be used as long as a compound having the above general formula is prepared. However, there is no problem, but as a method that is generally easy to carry out, a commercially available heteropoly acid mainly composed of tungsten oxide (dodecatungstophosphoric acid, dodecatungstosilic acid) and palladium acetate are mixed and dissolved. Can be easily prepared. Usually, the heteropolyacid used in the present invention contains water of crystallization. Here, the water of crystallization of the heteropolyacid is a general term for water contained in the heteropolyacid at the time of commercial production or preparation, and specifically, when the heteropolyacid is prepared in a water-containing solvent, these are nonsolvents, etc. Water attached or incorporated in the heteropolyacid crystal when precipitated by, or water incorporated with the heteropolyacid by adsorption, deliquescence or the like. For example, in commercial dodecatungstophosphoric silicic acid, represented by the general formula _{H 4 SiW 12 O 40 · nH} 2 O, also commercially available dodecatungstophosphoric acid represented by the general formula _{H 3 PW 12 O 40 · nH} 2 O Is nH ₂ O shown in these above formulas,
It refers to water molecules incorporated in or adsorbed or contained in the crystal structure of the heteropolyacid. Therefore, in the method of the present invention, it is meant that the heteropolyacid represented by the above general formula has n molecules of water of crystallization. n
Is an average value, so it is not necessarily an integer, but a real number.
The value of n in the above formula is usually about 25 to 30 for commercially available heteropolyacids. Further, the value may be more than this value due to the adsorption of water or the like. It is possible to easily set the value of n to 0 in the water of crystallization that these have by performing dehydration treatment such as heating. In addition, the dehydrated heteropolyacid can easily increase the value of n again by a method such as adsorbing water.

A method for making the water of crystallization contained in the heteropolyacid as a catalyst used in the present invention an average of 3.0 molecules or less per molecule of the heteropolyacid will be described. Usually, the readily available heteropoly acid is heteropoly acid 1 as described above.
It contains several tens of molecules of crystal water per molecule. When a heteropoly acid used in the present invention in which a part of protons is substituted with a palladium cation is prepared from these heteropoly acid and a palladium compound such as palladium acetate, 4 to 30 molecules of crystal water are generally added to the heteropoly acid 1 Hold per molecule. The method of making the crystal water of these heteropolyacids on average 3.0 molecules or less per one molecule of the heteropolyacid is not particularly limited in the method of the present invention, but a heating dehydration operation is mentioned as a method that is easy to carry out.

As the heating and dehydrating operation, for example, heating in an ordinary electric furnace (muffle furnace) is recommended. Of course, the method of the present invention is not limited to this apparatus and method. The heating temperature is not particularly limited,
As long as the water of crystallization becomes 3.0 molecules or less on average per molecule of the heteropolyacid, it may be carried out at any temperature, but in order to carry out it more effectively, it should be 80 ° C or higher and 500 ° C
It is preferable to carry out at the following temperature, and it is more preferable to carry out at 200 ° C. or higher and 450 ° C. or lower. At low temperature, it is difficult to dehydrate, and at 550 ° C. or higher, it may become a heteropolyanhydride. At this time, the heating time required is not particularly limited, and if the amount of water of crystallization is in the above range, there is no problem, but it is in the range of 10 minutes to 24 hours. For example, if an ordinary electric furnace is used and dehydration operation is performed at about 300 ° C., the above range of water of crystallization is sufficiently reached in about 3 hours.

A catalyst for a heteropoly acid adjusted to an average of 3.0 molecules or less per molecule of the heteropolyacid by performing a heating dehydration operation under a flow condition of a gas inert to the heteropolyacid at a heating dehydration temperature. When used as, the catalytic activity is further improved. This operation makes it possible to provide a very effective catalyst. Here, the gas that is circulated during the heating and dehydration operation may be any gas that is inert to the heteropolyacid at the heating temperature. Further, even if it is a liquid or a solid at room temperature, it can be used if it is a gas at the heating temperature and is inert to the heteropolyacid. Specific examples thereof include air, argon, nitrogen, helium, hydrogen, aliphatic hydrocarbons and aromatic hydrocarbons, but the method of the present invention is not limited to these gases. Further, the flow rate of the inert gas is not particularly limited, but it is preferably in the range of 0.2 to 20 vol / Hr * vol as the space velocity in the apparatus in terms of gas volume at the heating temperature.

The catalyst used in the method of the present invention is one in which a part of the protons possessed by the heteropolyacid mainly composed of an oxide of tungsten is replaced with a palladium cation. At this time, in the method of the present invention, the substitution rate with palladium is based on the heteropolyacid or the protons possessed before the substitution, and the heteropolyacid in which 1 to 99% of the protons are substituted with palladium cations is used as a catalyst. Is preferred. More preferably, 10 to 90% of all protons are replaced with palladium cations. The reaction of carboxylic acid and ethylene in the method of the present invention is carried out as a liquid-gas phase or solid-gas phase heterogeneous system. The method of the present invention can be carried out under any conditions of normal pressure, reduced pressure and increased pressure. Normally, a gas-liquid mixed phase reaction occurs in a pressurized state. Further, although the reaction system is not particularly limited,
It can be carried out in a continuous system, a batch system or a semi-batch system.

In carrying out the method of the present invention, it is possible to add a solvent or an additive which is inactive to the catalyst and the reaction reagent (raw material and product). Specifically, n-
Butane, n-pentane, n-hexane, n-heptane,
Aliphatic saturated hydrocarbons such as n-octane, n-nonane, and n-decane, aromatic hydrocarbons such as benzene, toluene, ethylbenzene, xylene, anisole, cumene, and nitrobenzene, cyclopentane, alkyl-substituted cyclopentanes , Alkoxy-substituted cyclopentanes,
Nitro-substituted cyclopentanes, cyclohexane, alkyl-substituted cyclohexanes, alkoxy-substituted cyclohexanes, nito-substituted cyclohexanes, cycloheptane, alkyl-substituted cycloheptanes, alkoxy-substituted cycloheptanes, nitro-substituted cycloheptanes, cyclooctane, alkyl-substituted cyclohexanes It is also possible to use alicyclic saturated hydrocarbons such as octanes, alkoxy-substituted cyclooctanes and nitro-substituted cyclooctanes, and nitrogen, argon, air, helium and the like as a solvent or a diluent.

The quantitative relationship between carboxylic acid and ethylene charged when carrying out the reaction in the method of the present invention is not particularly limited. Carboxylic acid / ethylene amount ratio is 0.1-100
(Molar ratio). For example, in order to achieve a high conversion rate of carboxylic acid, it is desirable to carry out the molar ratio of ethylene to carboxylic acid at 1 or more. Further, in order to achieve a high conversion rate of ethylene, carboxylic acid of ethylene to It is desirable that the molar ratio be 1 or more.
In carrying out the method of the present invention, the amount of the catalyst to be added is not particularly limited, but, for example, when the reaction is carried out in a batch system, it is 0.1 to 100% by weight based on the weight of acetic acid charged. %, Preferably 1 to 50% by weight is recommended. If the amount is less than this, the reaction proceeds slowly, and if the amount is more than this, the reaction proceeds sufficiently, but it is hard to say that it is preferable from the economical point of view. However, it goes without saying that the method of the present invention can be carried out outside this range.

In carrying out the method of the present invention, the method of charging the catalyst and the reaction reagent is not particularly limited, and the catalyst, carboxylic acid, cyclohexene and the like may be charged at the same time, and the catalyst may be dissolved in another solvent or the like. It can be suspended and prepared. The reaction temperature to be carried out in the method of the present invention is not particularly limited, and it can be carried out in a wide temperature range, but is preferably 30.
It is recommended to carry out in the range of 70 ° C to 200 ° C, more preferably 70 ° C to 400 ° C. If it is carried out at an excessively low temperature, the reaction rate will be lowered, and if it is carried out at an excessively high temperature, the thermal stability of the reaction agent such as ethylene will be deteriorated, which is not economical. The reaction time depends on the amount of catalyst or the reaction temperature, but if the amount of catalyst is large and the temperature is high, it is extremely short (about 0.1 seconds or less), and if the amount of catalyst is small and the temperature is low, it is long (24 seconds). It is about time). After completion of the reaction, the target product can be obtained by a separation operation such as a normal distillation operation.

A specific mode for carrying out the method of the present invention will be described. The method for carrying out the method of the present invention is not particularly limited, but the following methods are mentioned as methods that can be easily carried out. Of course, the method of the present invention is not limited to these methods. (1) A method in which a predetermined amount of a catalyst, acetic acid and ethylene are put into an autoclave together with a medium such as nitrogen or argon if necessary, and then a reaction with heating and stirring is performed. (2) A method in which a predetermined amount of catalyst, ethylene, and acetic acid are continuously introduced together with a diluent such as a solvent, if necessary, into a reactor previously kept at a predetermined temperature and a predetermined pressure to carry out the reaction.

[0020]

EXAMPLES The method of the present invention will be described more specifically below with reference to examples. (1) Quantification of reaction product After the reaction product is reacted at a predetermined temperature for a predetermined time,
After cooling to room temperature, the reaction solution was quantified by gas chromatography. The yields of ethers in the examples were all calculated based on the charged carboxylic acid. (2) A method of substituting a part of protons of the heteropolyacid with a palladium cation. Commercially available heteropolyacids (dodecatungstosilicic acid, dodecatungstophosphoric acid) were dissolved in water, and a predetermined amount of an aqueous solution of palladium acetate was added thereto, and the mixture was stirred and replaced. (3) Calculation of Palladium Cation Substitution Amount The amount of protons possessed by 1 mol of this heteropolyacid = m in the number of moles of the charged heteropolyacid = f (for example, 3 in the case of dodecamolybdophosphoric acid), and further charged palladium acetate When the number of moles is k, the palladium cation substitution rate L (%) of this heteropoly acid is calculated by the following formula. L = 100 (2k) / (fm) (4) Quantification of water of crystallization contained in catalyst Water of crystallization contained in heteropolyacid in which part of heteropolyacid mainly composed of oxide of tungsten is replaced with palladium cation The amount of the heteropoly acid used for the substitution operation was heated and dehydrated at 500 ° C., and the weight of the heteropoly acid became constant and no longer decreased. The amount of water of crystallization of the heteropolyacid to be charged into the base for the substitution operation was determined, and the substitution operation and the like thereafter were calculated by weight conversion based on this. (5) Decrystallization water method of catalyst a. 350 in a normal muffle furnace (8 liters internal volume)
The amount of water of crystallization was adjusted by heating and dehydrating at ℃ for a predetermined time. b. In the above method b, except that the circulating gas was changed to argon, heating and dehydration were performed by the same operation, and the amount of water of crystallization was reduced to 0.
And

Example 1 In a 200 ml autoclave equipped with a magnetic stirrer, 3 protons (3 atoms per mol) possessed by dodecatungstophosphoric acid were prepared by the dehydration method a with the amount of water of crystallization held to 0.
3.0 g of catalyst substituted with 0% palladium cation, 60.4 g (1 mol) of commercially available acetic acid (special grade manufactured by Kokusan Kagaku Co.)
And commercial ethylene (99.5%) manufactured by Takachiho Shoji Co., Ltd. (0.68 mol) was charged, heated to 140 ° C. and pressurized for 5 hours, cooled to room temperature, then gas was released and returned to normal pressure. The reaction solution was taken out and quantified. As a result, sec-butyl acetate was produced in the reaction solution at a yield of 43.5%.
At this time, ethyl acetate was not produced at all.

Comparative Example 1 The reaction was carried out under the same reaction conditions as in Example 1 except that the catalyst was changed to dehydrated dodecatungstophosphoric acid. As a result, the production of butyl acetate was not confirmed at all, and only ethyl acetate was produced.

Comparative Example 2 The reaction was carried out under the same conditions as in Example 1 except that no catalyst was added. As a result, only raw materials were collected, and no reaction product was confirmed.

Example 2 The reaction was carried out under the same conditions as in Example 1 except that the reaction time was changed to 3 hours in Example 1. The result is acetic acid sec-
Butyl was produced in a yield of 31.7%.

Example 3 The reaction was carried out under the same conditions as in Example 1 except that the reaction time was 1 hour. As a result, sec-butyl acetate yield 1
Produced at 4.3%. From this result, even in an extremely short time,
It can be seen that butyl acetate is produced in good yield.

Example 4 All catalyst weights, etc., except that 30% of the protons possessed by dodecatungstosilicic acid in which the water of crystallization retained by the dehydration method a was set to 0 and the catalyst was replaced by one substituted with a palladium cation, Other conditions were the same as in Example 3, and the reaction was carried out. As a result, sec-butyl acetate was produced in a yield of 17.5%.

Examples 5 to 7 are heteropolyacids obtained by substituting palladium cations for 30% of the protons possessed by dodecatungstosilicic acid in the water of crystallization by the dehydration method a, and the amount of each is 0.4 per molecule of heteropolyacid. The reaction was conducted under the same conditions as in Example 1 except that the amount of catalyst used was 1.7, 2.9, 7.8 and 17.2 molecules of water of crystallization. I went. The results are as shown in Table 1.
Each produced sec-butyl acetate.

[0028]

[Table 1] Table 1 ─────────────────────────────────── sec-butyl acetate per molecule of catalyst Yield of water of crystallization (molecule) Yield (%) ─────────────────────────────────── Example 5 0.4 44.9 Example 6 1.7 45.1 Example 7 2.9 38.1 Example 8 7.8 15.3 Example 9 17.2 16.8 ─────── ────────────────────────────

Example 10 The reaction was carried out under the same conditions as in Example 3 except that the amount of catalyst was 1.0 g and the reaction temperature was 190 ° C. As a result, sec-butyl acetate was obtained in a yield of 40.7%. Examples 11 to 12 The reaction was carried out under the same conditions as in Example 1 except that the reaction temperatures were changed to 100 ° C and 120 ° C, respectively. The results are shown in Table 2.
As shown in, even if the reaction temperature was lowered, sec-butyl acetate was produced in good yield.

[0030]

[Table 2] Table 2 ────────────────────────────────── Reaction temperature (℃) sec-Butyl acetate yield Rate% ────────────────────────────────── Example 11 100 21.5 Example 12 120 33.4 ───────────────────────────────────

Example 13 The reaction was carried out under the same conditions as in Example 1 except that the amount of acetic acid charged was 90.0 g. As a result, sec-butyl acetate was produced in a yield of 31.6%.

Examples 14 to 17 In Example 3, partial palladium substitution which does not have water of crystallization, wherein the substitution rates of protons by palladium cations are 10.0, 20.0, 50.0 and 80.0%, respectively. The reaction was carried out under the same conditions as in Example 3 except for the use of dodecatungstophosphoric acid and other conditions such as the amount of catalyst used. As a result, sec-butyl acetate was produced in good yield as shown in Table 3.

[0033]

[Table 3] Table 3 ─────────────────────────────────── Acetate sec- by the Pd cation of the proton Substitution ratio (%) Yield (%) ──────────────────────────────────── Example 14 10.0 8.9 Example 15 20.0 12.4 Example 16 50.0 13.5 Example 17 80.0 6.2 ────────────────── ──────────────────

Example 18 The reaction was carried out under the same conditions as in Example 1 except that the catalyst dehydration method was changed to b. As a result, sec-butyl acetate was produced at a yield of 46.7%.

Examples 19 to 22 The reaction was carried out under the same conditions as in Example 4 except that carboxylic acid was replaced with propionic acid, butyric acid, formic acid and dichloroacetic acid (1 mol). The results are as shown in Table 4.
The carboxylic acid sec-butyl ester was produced in good yield in each case.

[0036]

[Table 4] Table 4 ─────────────────────────────────── Carboxylic acid sec-butyl carboxylic acid Yield (%) ─────────────────────────────────── Example 19 Propionic acid 15.8 Example 20 Butyric acid 14.2 Example 21 Formic acid 17.9 Example 22 Dichloroacetic acid 21.3 ───────────────────────────────── ───

[0037]

EFFECTS OF THE INVENTION According to the method of the present invention, by using as a catalyst a heteropoly acid in which a part of protons possessed by a heteropoly acid mainly composed of an oxide of tungsten is replaced by a palladium cation, it is possible to obtain a surprising effect from ethylene and carboxylic acid. Not surprisingly, the carboxylic acid butyl ester can be produced in a single step. Here, the activity of the catalyst in the method of the present invention is remarkably improved by adjusting the amount of water of crystallization held by the catalyst to an average of 3.0 molecules or less per one molecule of the heteropolyacid which is the catalyst. Further, as a method for dehydrating the heteropoly acid,
Higher catalytic activity is achieved by adjusting the amount of water of crystallization of the heteropolyacid to 3.0 molecules or less on average per molecule of the heteropolyacid under the flow of gas inert to the heteropolyacid such as air and argon. It is also found that carboxylic acid butyl esters can be obtained in a very mild and short time with a high selectivity and a high conversion rate, and in addition, the method of the present invention can be stably and effectively performed even in a high temperature state. It has become possible.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location C07C 69/02 8018-4H // C07B 61/00 300

Claims (8)

[Claims] 1. A carboxylic acid characterized by reacting carboxylic acid and ethylene in the presence of a heteropoly acid in which a part of protons possessed by a heteropoly acid mainly composed of tungsten oxide is replaced by a palladium cation. Method for producing butyl esters 2. A heteropolyacid mainly composed of tungsten oxide is represented by the general formula: (M ₁ ) a (M ₂ ) b (W) c (O) d (H) e (wherein M ₁ and M ₂ are metals. Represents an element, W represents a tungsten atom, O represents an oxygen atom, H represents a hydrogen atom, a is an integer of 1 or 2, b is an integer of 0, 1 or 2, and c Is a positive integer of 20 or less, d is a positive integer of 100 or less, and e
Is a positive integer of 10 or less. The method according to claim 1, which is a heteropoly acid represented by the formula (1). 3. M ₁ is an element symbol of P, Si, Co, Mn, Ni, A
The method according to claim 2, wherein the element represented by any one of s, Ti, Fe, V and B, and M ₂ is an element represented by V in the element symbol. 4. The heteropoly acid in which the amount of water of crystallization contained in the heteropoly acid in which a part of the protons are replaced by palladium cations is adjusted to an average of 3.0 molecules or less per molecule of the heteropoly acid. Method. 5. The amount of water of crystallization contained in a heteropolyacid in which a part of protons is substituted with a palladium cation is heat-treated in the temperature range of 150 ° C. to 500 ° C. so that the average amount of water of crystallization is 3 per molecule of the heteropolyacid. The method according to claim 4, wherein the number is adjusted to 0.0 molecule or less. 6. The method according to claim 5, wherein the heteropolyacid is heated and dehydrated under the flow of a gas inert to the heteropolyacid. 7. The method according to claim 1, wherein the heteropoly acid mainly composed of tungsten oxide is tungstophosphoric acid, tungstosilicic acid and a mixture thereof. 8. The method according to claim 1, wherein the carboxylic acid is an aliphatic carboxylic acid other than acetic acid or an aromatic carboxylic acid.