JPH10324664A - Production of unsaturated carboxylic acid ester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an α,β-unsaturated carboxylic acid ester in high selectivity and yield by the vapor-phase alkyl esterification of an α,β-unsaturated carboxylic acid with alcohol in the presence of a specific catalyst. SOLUTION: This method uses an oxide containing an alkaline metal element as the catalyst for the vapor-phase esterification of an α,β-unsaturated carboxylic acid with alcohol to produce the α,β-unsaturated carboxylic acid ester. The oxide as the catalyst preferably comprises an alkali metal element and at least one element selected from the group consisting of the groups IIIb, IVb, IIIa, IVa, and Va elements, more preferably from the group consisting of silicon, titanium and zirconium. The oxide is particularly preferably shown by the formula (M is an alkaline metal; X is Si, Ti or Zr; Q is Y, La, Ce, B or the like; (a) to (d) are each an atomic number of each element).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing α, β-unsaturated carboxylic acid esters. α, β-
Unsaturated carboxylic acid esters, particularly alkyl esters of acrylic acid and methacrylic acid are industrially very useful compounds as raw materials for synthetic resins, synthetic fibers and the like.

[0002]

2. Description of the Related Art Heretofore, as a method of esterifying an α, β-unsaturated carboxylic acid and an alcohol, a liquid phase method using a mineral acid catalyst such as a sulfuric acid catalyst or a phosphoric acid catalyst or a strongly acidic ion exchange resin as a catalyst has been known. Alternatively, a gas phase method using a solid acid catalyst is known.

An example of a gas phase method which is more excellent in productivity is a method using a solid phosphoric acid catalyst (Japanese Patent Publication No. Sho 42-5).
No. 222), a method using a molybdenum sulfide catalyst (Japanese Patent Publication No. 44-9885, etc.) and a method using a silica-titania catalyst (Japanese Patent Publication No. 55-33702, etc.) have been proposed.

[0004] However, both methods use α, β-
Although the ester selectivity based on unsaturated carboxylic acid is considerably increased, the strong solid acidity of the catalyst used causes a decrease in the esterification selectivity due to the Michael adduct of the starting alcohol to the double bond and a decrease in the molecular weight of the starting alcohol. There was a problem that by-products of dialkyl ether due to inter-water dehydration and by-products of olefins due to intra-molecular dehydration occurred, resulting in a decrease in esterification selectivity based on alcohol.

[0005] The generation of these by-products has caused various problems such as separation and purification in industrial processes, adverse effects on product quality, and deterioration of catalyst activity.

For example, in the synthesis of butyl acrylate, the boiling point of dibutyl ether as a by-product (142 ° C.) is the same as the boiling point of acrylic acid as a raw material (139 ° C.) and the boiling point of butyl acrylate as a product (145 ° C.). Because the difference is small, dibutyl ether is mixed into the product butyl acrylate, which causes a decrease in the purity of the product, and the known catalysts are all caused by deposition of carbonaceous substances on the catalyst. Due to the remarkable deterioration of the activity with time, it was not endurable for industrial practice.

As described above, the conventional methods for producing alkyl esters of α, β-unsaturated carboxylic acids from α, β-unsaturated carboxylic acids and alcohols by a gas phase method are industrially satisfactory. Rather, there has been a strong demand for a process for producing alkyl esters of α, β-unsaturated carboxylic acids having high selectivity using a catalyst having stable catalytic activity over a long period of time.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above situation, and an object of the present invention is to provide:
When α, β-unsaturated carboxylic esters are produced in the gas phase from α, β-unsaturated carboxylic acids and alcohols, the amount of by-products such as dialkyl ethers and olefins derived from the raw material alcohol is small, and An object of the present invention is to provide a method for producing an α, β-unsaturated carboxylic acid ester with a high recovery rate of a reaction alcohol, a high selectivity and a high yield.

[0009]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and have found that when α, β-unsaturated carboxylic acids and alcohols are used for alkyl esterification in the gas phase. In addition, they have found that the use of an oxide containing an alkali metal element as a catalyst produces an alkyl ester with an extremely high selectivity than ever before.

That is, the present invention relates to a process for producing an α, β-unsaturated carboxylic acid ester by subjecting an α, β-unsaturated carboxylic acid and an alcohol to an alkyl esterification reaction in the gas phase in the presence of a catalyst. , Wherein the catalyst is an oxide containing an alkali metal element.
The present invention relates to a method for producing an unsaturated carboxylic acid ester.

Another invention of the present invention relates to a method for producing an alkyl ester of an α, β-unsaturated carboxylic acid by subjecting an α, β-unsaturated carboxylic acid and an alcohol to alkylesterification reaction in a gas phase. The present invention relates to a catalyst used for alkyl esterification of α, β-unsaturated carboxylic acids, which is an oxide containing an alkali metal element.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The α, β-unsaturated carboxylic acids which are one of the raw materials in the method of the present invention are not particularly limited, but include, for example, acrylic acid and methacrylic acid.

The alcohol used as the other raw material in the present invention is not particularly limited, but is preferably a monohydric aliphatic alcohol in terms of reactivity. Examples thereof include methanol, ethanol, n-propyl alcohol, and iso-propyl. Alcohol, n-butyl alcohol, iso-butyl alcohol, 2-ethylhexyl alcohol and the like can be mentioned.

The catalyst used in the method of the present invention is not particularly limited as long as it is an oxide containing an alkali metal element, but the alkali metal element and the periodic table IIIb, IVb, I
An oxide containing at least one element selected from the group consisting of elements of groups IIa, IVa and Va is preferred. More preferably, it is an oxide containing an alkali metal element and at least one element selected from the group consisting of silicon, titanium and zirconium, and further preferably, the following general formula (1):

[0015]

Embedded image

(Wherein M represents an alkali metal element, X
Represents one or more elements selected from the group consisting of silicon, titanium and zirconium, and Q represents Y, La, Ce,
Represents one or more elements selected from the group consisting of B, Al, Ge, Sn, Pb, P, Sb and Bi, O represents oxygen, and a, b, c and d are the number of atoms of each element. When a is 1, b is 1 to 500 and c is 0 to 1, and d is a numerical value determined by the values of a, b and c and the bonding state of various constituent elements. ).

By using the catalyst, the alkyl esterification of the α, β-unsaturated carboxylic acid proceeds at an extremely high selectivity, and the Michael addition reactant as a by-product is hardly formed, and The alcohols used are selectively consumed for the alkyl esterification of α, β-unsaturated carboxylic acids, and the dialkyl ethers are formed by their own intermolecular dehydration.
This is excellent in that olefination due to tellurization and its own intramolecular dehydration hardly occurs. Further, even if the catalyst is used continuously for a long period of time under severe reaction conditions and its catalytic activity is reduced due to coking or the like, the catalytic activity can be recovered by burning the coke through air. It is.

In particular, in the oxide represented by the general formula (2), which is one of the preferred embodiments of the catalyst according to the present invention, when a is 1 and b is less than 1, the effectiveness of the catalyst is reduced. When the surface area becomes extremely small, the catalytic activity may decrease. When b exceeds 500, the catalytic activity may decrease extremely.

Oxide catalysts consisting of silicon alone without alkali metals, ie, silica alone, have a low activity due to a very weak solid acid, so that they are strongly resistant to the selective alkyl esterification of α, β-unsaturated carboxylic acids. It has been reported that a solid acid is effective and a titania-silica catalyst is optimal (Japanese Patent Publication No. 55-33702). However, in the reaction using such a catalyst, a strong acid point (about -1) is used.
0 <H ₀ <−5) Dialkyl ether of alcohols
Loss of alcohol recovery due to tellurization and olefination of alcohols, reduction in activity due to coking, and the like are inevitable. On the other hand, the catalyst of the present invention containing an alkali metal has a weaker acid strength than that of silica alone (H ₀ about +3) (for example, H ₀ ≧ about +3).
5, preferably H ₀ ≧ about +8), the activity is increased, giving alkyl esters with a much higher selectivity than previously known catalysts. The reason why the catalyst of the present invention provides such an advantage is that the addition of the solid basicity makes it easier for the raw material α, β-unsaturated carboxylic acid to be adsorbed and the activity is improved. Therefore, it is presumed that dialkyl etherification or olefination of the alcohol itself hardly occurs.

The method for preparing the catalyst of the present invention is not particularly limited, and any conventionally known method can be applied.

The method for preparing the catalyst of the present invention will be described below with reference to an oxide containing an alkali metal element and silicon, which is a particularly preferred embodiment of the catalyst of the present invention.

As the raw material of the alkali metal element, oxides, hydroxides, halides, salts (nitrates, carbonates, carboxylates, phosphates, sulfates, etc.) and metals are used. As a raw material of silicon, silicon oxide, silicic acid, silicates (such as alkali metal silicate and alkaline earth metal silicate), and organic silicate ester are used. In addition, as a raw material of an optional component element, for example, a component element represented by Q in the general formula (1),
Oxides, hydroxides, halides, salts (carbonate, nitrate, carboxylate, phosphate, sulfate, etc.), metals and the like are used.

The catalyst may be prepared by dissolving or suspending an alkali metal element source and a silicon source in water, heating and concentrating under stirring, drying, molding and calcining to obtain a catalyst. A method in which a silicon oxide molded body is immersed in an aqueous solution of an alkali metal element source, heated to dryness, dried and calcined to obtain a catalyst. There is a method in which an aqueous solution of an alkali metal element source is added to various silicates or silicon-containing oxides, mixed, dried, molded, calcined, and used as a catalyst. In order to make the catalyst contain the optional component element, a method using an alkali metal element source and / or a silicon source containing the component element, a method of adding the raw material of the optional component element during catalyst preparation, and the like are adopted. Can be.

The catalyst according to the present invention can be used by being supported on or mixed with a known carrier (for example, alumina, silicon carbide, etc.).

The calcination temperature for preparing the catalyst according to the present invention is 300 to 100, although it depends on the type of the catalyst raw material used.
A wide range of 0 ° C can be adopted, and a range of 400 to 800 ° C is preferable.

In the production method of the present invention, any type of fixed bed flow type or fluidized bed type reactor can be used as long as it can be carried out by a gas phase reaction.

The α, β-unsaturated carboxylic acids and alcohols used as raw materials in the production method of the present invention are usually α, β-unsaturated carboxylic acids and alcohols.
Molar ratio of unsaturated carboxylic acids to alcohols of 1: 1
-20, preferably 1: 1-10
used.

In the production method of the present invention, the raw materials α, β-
A reaction temperature and a reaction pressure at which unsaturated carboxylic acids and alcohols can maintain a gaseous state are employed. The reaction pressure is usually normal pressure or reduced pressure, but pressurization is also possible. The reaction temperature varies depending on the type of the raw material α, β-unsaturated carboxylic acid and other reaction conditions.
A range of 0 ° C, preferably 200-350 ° C, is suitable. When the reaction temperature is lower than 150 ° C., the conversion of the raw material α, β-unsaturated carboxylic acid is greatly reduced, and the reaction temperature is 350 ° C.
If the temperature is higher than ℃, the selectivity of the target alkyl ester is remarkably reduced due to polymerization of the raw material α, β-unsaturated carboxylic acid or product ester. The raw material gas mixture of α, β-unsaturated carboxylic acids and alcohols can be used without dilution.
Alternatively, nitrogen, helium, argon, hydrocarbons, etc.
It is diluted with a substance inert to the target reaction and supplied to the catalyst layer under normal pressure or reduced pressure. Space velocity of mixed gas of raw material α, β-unsaturated carboxylic acid and alcohol (GHS
V) varies depending on the type of raw materials and other reaction conditions, but is ^{1 to} 2000 h ^-1 , preferably 100 to 1000 h ^-1 .
h- ¹ .

[0029]

EXAMPLES The present invention will now be described specifically with reference to examples, but the present invention is not limited to these examples.

The conversion, selectivity, and single-stream yield in the examples and comparative examples follow the following definitions.

[0031]

(Equation 1)

Example 1 (Preparation of catalyst) In a solution of 2.71 g of cesium carbonate dissolved in 40 g of water, spherical silica gel (5-10 mesh) 3
0 g was immersed for 2 hours. After that, heat to dryness in a hot water bath,
After drying at 120 ° C in air for 20 hours,
After calcination for a time, a catalyst having a composition of Cs ₁ Si _{30 in} atomic ratio excluding oxygen was prepared.

(Reaction) 20 ml of this catalyst was used with an inner diameter of 20 m.
m, was immersed in a molten salt bath at 330 ° C., and a mixed solution of acrylic acid and methanol (molar ratio 1: 3) was fed into the reaction tube with a metering pump. A raw material gas consisting of 50% by volume of nitrogen and 50% by volume of nitrogen is supplied to a space velocity of 400 h ^{-1 of a} mixed gas of acrylic acid and methanol
And the reaction was carried out at normal pressure. As a result of analyzing the reaction product one hour after the start of the supply by gas chromatography,
The conversion of acrylic acid was 98.0 mol%, and the selectivity for methyl acrylate was 99.8 mol% (single-stream yield: 97.8 mol%). No dimethyl ether was produced, and unreacted methanol was almost quantitatively recovered.

Example 2 A reaction was carried out under the same conditions as in Example 1 except that the catalyst of Example 1 was replaced with ethanol instead of methanol. The reaction product one hour after the start of the supply was analyzed by gas chromatography, and as a result, the conversion of acrylic acid was 6%.
The selectivity for ethyl acrylate was 99.6 mol% (single-stream yield: 68.1 mol%). No production of diethyl ether or ethylene was observed, and unreacted ethanol was almost quantitatively recovered.

Example 3 A reaction was carried out under the same conditions as in Example 1 except that the catalyst of Example 1 was used and n-butanol was used instead of methanol for alcohol. One hour after the start of the supply, the reaction product was analyzed by gas chromatography. As a result, the conversion of acrylic acid was 43.0% by mole, and the selectivity of butyl acrylate was 99.5% by mole (single-stream yield: 42.8% by mole). Met. Further, no production of dibutyl ether and butene was observed, and unreacted butanol was almost quantitatively recovered.

Example 4 Example 1 was repeated except that the catalyst of Example 1 was used and 2-ethylhexyl alcohol was used instead of methanol for alcohol.
The reaction was carried out under the same conditions as described above. One hour after the start of the supply, the reaction product was analyzed by gas chromatography. As a result, the conversion of acrylic acid was 40.0 mol% and the selectivity for 2-ethylhexyl acrylate was 99.7 mol% (single-stream yield: 39.9 mol%). %)Met. Further, no generation of dioctyl ether and olefin was observed, and unreacted 2-ethylhexyl alcohol was almost quantitatively recovered.

Example 5 A reaction was carried out under the same conditions as in Example 1 except that the catalyst of Example 1 was used and methacrylic acid was used instead of acrylic acid. One hour after the start of the supply, the reaction product was analyzed by gas chromatography. As a result, the conversion of methacrylic acid was 77.0 mol%, and the selectivity of methyl methacrylate was 99.9 mol% (single-stream yield: 76.9 mol%). Met. No dimethyl ether was generated, and unreacted methanol was almost quantitatively recovered.

Example 6 (Preparation of catalyst) Spherical silica gel (5-10 mesh) was added to a solution of 1.76 g of sodium carbonate dissolved in 40 g of water.
30 g was immersed for 2 hours. Then, it is dried by heating in a hot water bath and dried in air at 120 ° C. for 20 hours.
For 2 hours to prepare a catalyst having a composition of Na ₁ Si _{30 in an} atomic ratio excluding oxygen.

(Reaction) Using this catalyst, a reaction was carried out under the same conditions as in Example 1. One hour after the start of the supply, the reaction product was analyzed by gas chromatography. As a result, the conversion of acrylic acid was 20.0 mol% and the selectivity of methyl acrylate was 9
It was 9.9 mol% (single-stream yield: 20.0 mol%). No dimethyl ether was generated, and unreacted methanol was almost quantitatively recovered.

Example 7 (Preparation of catalyst) Spherical silica gel (5-10 mesh) 3 was prepared by dissolving 2.03 g of potassium carbonate in 40 g of water.
0 g was immersed for 2 hours. After that, heat to dryness in a hot water bath,
After drying at 120 ° C in air for 20 hours,
After calcination for a time, a catalyst having a composition of K ₁ Si _{30 in} atomic ratio excluding oxygen was prepared.

(Reaction) Using this catalyst, a reaction was carried out under the same conditions as in Example 1. One hour after the start of the supply, the reaction product was analyzed by gas chromatography. As a result, the conversion of acrylic acid was 64.0 mol% and the selectivity of methyl acrylate was 9
It was 9.8 mol% (single-stream yield: 63.9 mol%). No dimethyl ether was generated, and unreacted methanol was almost quantitatively recovered.

Example 8 (Preparation of catalyst) Spherical silica gel (5-10 mesh) was placed in a solution obtained by dissolving 7.38 g of rubidium nitrate in 50 g of water.
30 g was immersed for 2 hours. Then, it is dried by heating in a hot water bath and dried in air at 120 ° C. for 20 hours.
For 2 hours to prepare a catalyst having a composition of Rb ₁ Si _{30 in} atomic ratio excluding oxygen.

(Reaction) Using this catalyst, a reaction was carried out under the same conditions as in Example 1. One hour after the start of the supply, the reaction product was analyzed by gas chromatography. As a result, the conversion of acrylic acid was 84.5 mol% and the selectivity of methyl acrylate was 9
It was 9.8 mol% (single-stream yield: 84.3 mol%). No dimethyl ether was generated, and unreacted methanol was almost quantitatively recovered.

Example 9 (Preparation of catalyst) In a solution of 4.08 g of cesium carbonate dissolved in 50 g of water, 40 g of commercially available titanium dioxide (manufactured by Katayama Chemical) was added.
, And concentrated to dryness while heating and mixing on a hot water bath. Then, after drying in air at 120 ° C. for 20 hours, 500 ° C. in air
By sintering for 2 hours and crushing to 9-16 mesh,
A catalyst having a composition of Cs ₁ Ti _{20 in} atomic ratio excluding oxygen was prepared.

(Reaction) Using this catalyst, a reaction was carried out under the same conditions as in Example 1. One hour after the start of the supply, the reaction product was analyzed by gas chromatography. As a result, the conversion of acrylic acid was 78.7 mol% and the selectivity of methyl acrylate was 9
It was 9.5 mol% (single-stream yield: 78.3 mol%). No dimethyl ether was generated, and unreacted methanol was almost quantitatively recovered.

Example 10 (Preparation of catalyst) Commercially available zirconium oxide (manufactured by Norton) 5 was dissolved in a solution obtained by dissolving 6.61 g of cesium carbonate in 50 g of water.
0 g was immersed for 2 hours. After that, heat to dryness in a hot water bath,
After drying at 120 ° C in air for 20 hours,
By calcining for 9 hours and crushing to 9-16 mesh, a catalyst having a composition of Cs ₁ Zr _{10 in} atomic ratio excluding oxygen was prepared.

(Reaction) Using this catalyst, a reaction was carried out under the same conditions as in Example 1. One hour after the start of the supply, the reaction product was analyzed by gas chromatography. As a result, the conversion of acrylic acid was 87.5 mol% and the selectivity of methyl acrylate was 9
It was 9.5 mol% (single-stream yield: 87.1 mol%). No dimethyl ether was generated, and unreacted methanol was almost quantitatively recovered.

Example 11 (Preparation of catalyst) 50 g of zirconium silicate (manufactured by Wako Pure Chemical Industries) was added to a solution obtained by dissolving 2.22 g of cesium carbonate in 40 g of water, and concentrated while heating and mixing on a hot water bath. To dryness. Next, after drying in air at 120 ° C. for 20 hours, it is calcined in air at 500 ° C. for 2 hours and crushed to 9-16 mesh to prepare a catalyst having a composition of Cs ₁ Zr ₂₀ Si _{20 in an} atomic ratio excluding oxygen. did.

(Reaction) Using this catalyst, a reaction was carried out under the same conditions as in Example 1. One hour after the start of the supply, the reaction product was analyzed by gas chromatography. As a result, the conversion of acrylic acid was 76.3 mol% and the selectivity of methyl acrylate was 9
It was 9.5 mol% (single-stream yield: 75.9 mol%). Unreacted methanol was almost quantitatively recovered.

Example 12 (Preparation of catalyst) 2.34 g of cesium chloride and 1.80 g of lanthanum nitrate hexahydrate were dissolved in 50 g of water.
25 g of spherical silica gel (5-10 mesh) was immersed for 2 hours. Then, heat to dryness in a hot water bath, and in air at 120 ° C.
And then calcined in air at 500 ° C. for 2 hours to prepare a catalyst having a composition of Cs ₁ Si ₃₀ La _{0.3 in} atomic ratio excluding oxygen.

(Reaction) Using this catalyst, a reaction was carried out under the same conditions as in Example 1. One hour after the start of the supply, the reaction product was analyzed by gas chromatography. As a result, the conversion of acrylic acid was 72.3 mol% and the selectivity of methyl acrylate was 9
It was 9.5 mol% (single-stream yield: 71.9 mol%). No dimethyl ether was generated, and unreacted methanol was almost quantitatively recovered.

Example 13 (Preparation of catalyst) 30 g of spherical silica gel (5-10 mesh) was immersed in a solution prepared by dissolving 2.03 g of cesium carbonate and 2.88 g of 85% orthophosphoric acid in 40 g of water for 2 hours. Thereafter, the mixture was heated to dryness on a hot water bath, dried in air at 120 ° C. for 20 hours, and calcined in air at 500 ° C. for 2 hours to prepare a catalyst having a composition of Cs ₁ Si ₄₀ P _{2 in an} atomic ratio excluding oxygen. .

(Reaction) Using this catalyst, a reaction was carried out under the same conditions as in Example 1. One hour after the start of the supply, the reaction product was analyzed by gas chromatography. As a result, the conversion of acrylic acid was 25.6 mol% and the selectivity of butyl acrylate was 9
It was 9.3 mol% (single-stream yield: 25.4 mol%). Also, no formation of dibutyl ether and butene was observed,
Unreacted butanol was recovered almost quantitatively.

Example 14 (Preparation of catalyst) 30 g of spherical silica gel (5-10 mesh) was immersed in a solution of 8.13 g of cesium carbonate and 6.24 g of aluminum nitrate nonahydrate in 40 g of water for 2 hours. . Then, heat and dry on a hot water bath,
After drying at 0 ° C. for 20 hours, it was calcined in air at 500 ° C. for 3 hours to prepare a catalyst having a composition of Cs ₁ Si ₁₀ Al _{0.33 in} atomic ratio excluding oxygen.

(Reaction) Using this catalyst, a reaction temperature of 30
The reaction was carried out under the same conditions as in Example 1 except that the temperature was changed to 0 ° C. One hour after the start of the supply, the reaction product was analyzed by gas chromatography. As a result, the conversion of acrylic acid was 82.5 mol% and the selectivity for methyl acrylate was 99.7 mol% (single-stream yield: 82.3 mol%). Met. No dimethyl ether was generated, and unreacted methanol was almost quantitatively recovered.

Example 15 (Preparation of catalyst) 8.13 g of cesium carbonate and 1. boric acid
30 g of spherical silica gel (5-10 mesh) was immersed in a solution of 03 g in 40 g of water for 2 hours. Thereafter, the mixture was heated to dryness on a hot water bath, dried in air at 120 ° C. for 20 hours, and calcined in air at 500 ° C. for 2 hours to prepare a catalyst having a composition of Cs ₁ Si ₁₀ B _{0.33 in an} atomic ratio excluding oxygen. .

(Reaction) Using this catalyst, a reaction was carried out under the same conditions as in Example 1. One hour after the start of the supply, the reaction product was analyzed by gas chromatography. As a result, the conversion of acrylic acid was 88.6 mol% and the selectivity for methyl acrylate was 9
It was 9.6 mol% (single-stream yield: 88.2 mol%). No dimethyl ether was generated, and unreacted methanol was almost quantitatively recovered.

Example 16 10 ml of the catalyst of Example 1 was charged into a stainless steel reaction tube, and then immersed in a molten salt bath at 330 ° C. Then, the pressure inside the reaction tube was reduced by a vacuum pump, and a mixed liquid of acrylic acid and methanol (molar ratio 1: 3) was sent by a quantitative pump, and the outlet pressure of the mixed gas was 380 mmHg, and the space velocity was 400 h ^-1 . Supplied. One hour after the start of the supply, the reaction product was analyzed by gas chromatography. As a result, the conversion of acrylic acid was 68.0 mol%, and the selectivity for methyl acrylate was 99.5 mol% (single-stream yield: 67.7 mol%). Met. No dimethyl ether was produced, and unreacted methanol was almost quantitatively recovered.

Example 17 10 ml of the catalyst of Example 1 was filled in a stainless steel reaction tube, and then immersed in a molten salt bath at 300 ° C. Next, a mixed solution of acrylic acid and methanol (molar ratio 1: 3) was fed at a normal pressure by a metering pump and supplied to the reaction tube at a space velocity of 400 h ^-1 . After the reaction was continuously carried out for 50 hours, the supply of the raw material was stopped, and then the air was passed at 400 ° C. for 24 hours to burn the substances on carbon deposited on the catalyst, thereby regenerating the catalyst. Thereafter, the reaction conditions were returned to the above-described reaction conditions, and the reaction was performed. The conversion of acrylic acid and the selectivity of methyl acrylate were as shown in Table 1 as a result of analyzing the reaction products by gas chromatography after each time from the start of the supply of the raw materials and after the regeneration of the catalyst.

[0060]

[Table 1]

Comparative Example 1 (Preparation of catalyst) 52.0 g of ethyl orthosilicate was dissolved in 200 ml of an ethanol-water (4: 1) solution. Separately, 57.4 g of titanium tetrachloride was ice-cooled and diluted with 200 ml of dilute hydrochloric acid.
The solution was added slowly to make a homogeneous solution. These two solutions were mixed and neutralized with a 1: 5 dilution of aqueous ammonia with vigorous stirring, adjusted to pH 7 by adding 1.6 L of water, stirred for 2 hours, and allowed to stand overnight for common use. Sinked. After that, the generated precipitate was separated by filtration, sufficiently washed with water, dried in air at 120 ° C., calcined at 400 ° C. in air for 2 hours, crushed to 9-16 mesh, and titania-silica solid acid catalyst. Was prepared. (The above was carried out according to the method described in JP-B-55-33702.) (Reaction) Using this catalyst, a reaction was carried out in the same manner as in Example 1 except that n-butanol was used instead of methanol. Was. One hour after the start of the supply, the reaction product was analyzed by gas chromatography.
It was 0 mol% and the selectivity for butyl acrylate was 91.0 mol% (single-stream yield: 53.7 mol%). The conversion of acrylic acid based on n-butanol was 85.2 mol%, and the selectivity for butyl acrylate was 11.9 mol%. Butene and dibutyl ether were generated as by-products.

Comparative Example 2 (Reaction) A reaction was carried out in the same manner as in Example 1 using spherical silica gel (calcined at 500 ° C. for 2 hours). One hour after the start of the supply, the reaction product was analyzed by gas chromatography. As a result, the conversion of acrylic acid was 49.0 mol% and the selectivity for methyl acrylate was 99.5%.

[0063]

As is clear from the above Examples and Comparative Examples, when the catalyst of the present invention is used, α, β-unsaturated carboxylic acids are formed in a gas phase from α, β-unsaturated carboxylic acids and alcohols. In the production of the alkyl ester of α, β-unsaturated carboxylic acids, an alkyl ester of an α, β-unsaturated carboxylic acid can be stably obtained over a long period of time with extremely high selectivity and yield. In addition, since there are almost no by-products such as dialkyl ethers and olefins from the starting alcohol, the effect of recovering the unreacted alcohol is high. Therefore, it can be said that the method of the present invention is excellent as a method for industrially producing alkyl esters of α, β-unsaturated carboxylic acids.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // C07B 61/00 300 C07B 61/00 300

Claims (5)

[Claims] 1. The method according to claim 1, wherein the α, β-unsaturated carboxylic acid is reacted with an alcohol in the gas phase in the presence of a catalyst to produce an α, β-unsaturated carboxylic acid ester. Is an oxide containing an alkali metal element, wherein α, β-unsaturated carboxylic acid esters are produced. 2. The catalyst according to claim 1, wherein the catalyst is an oxide containing an alkali metal element and at least one element selected from the group consisting of elements of the periodic table IIIb, IVb, IIIa, IVa and Va. The method according to claim 1. 3. The catalyst according to claim 1, wherein the catalyst is an oxide containing an alkali metal element and at least one element selected from the group consisting of silicon, titanium and zirconium.
Or the production method according to 2. 4. The catalyst according to claim 1, wherein the catalyst has the general formula (1): (Wherein M represents an alkali metal element, X represents one or more elements selected from the group consisting of silicon, titanium and zirconium, and Q represents Y, La, Ce, B, Al, G
e, at least one element selected from the group consisting of Sn, Pb, P, Sb and Bi, O represents oxygen, a,
b, c and d are the numbers of each element, and when a is 1,
b is 1 to 500 and c is 0 to 1, and d is a numerical value determined by the values of a, b and c and the bonding state of various constituent elements. The method according to any one of claims 1 to 3, which is an oxide represented by the formula: 5. An α, β-unsaturated carboxylic acid and an alcohol are subjected to alkyl esterification in a gas phase to form an α, β-unsaturated carboxylic acid and an alcohol.
A catalyst for use in producing an alkyl ester of an unsaturated carboxylic acid, wherein the catalyst is an oxide containing an alkali metal element.
Catalyst for alkyl esterification of unsaturated carboxylic acids.