JP2000154164A - Manufacture of carboxylate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a carboxylate in high yield, with reduced use of catalyst quantity, reducing the deactivation of catalyst, useful as monomer for manufacture of synthetic resin by using a catalyst supporting gold on a carrier. SOLUTION: The reaction of (A) an aldehyde and (B) an alcohol (methanol or ethanol is preferred) in the presence of the oxygen including gas is carried out in the presence of (C) a catalyst carrying gold. The preferable component (A) is (meth)acrolein and the subject ester is (meth)acrylate or the component (A) is gyloxal and the subject ester is gyloxyl acid ester, and the carrier supporting gold is activated carbon, hydrophobic carrier or a hydrophilic carrier modified into hydrophobic carrier, the reaction is carried out at room temperature to 200 deg.C, under atmospheric pressure to 50 atm., for 1 to 20 hrs.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a carboxylic acid ester by directly reacting an aldehyde and an alcohol in the presence of oxygen in the presence of oxygen, and more particularly, to a catalyst which has been improved in carrying out the reaction. The present invention relates to a method for producing a carboxylic acid ester using the same. Acrylates or methacrylates obtained by reacting acrolein or methacrolein as aldehydes with alcohol in the presence of oxygen are widely used as polymerization monomers for producing various synthetic resins, and are very important in large quantities. Compound.

[0002]

2. Description of the Related Art Conventionally, as a method for producing a carboxylic acid ester from an aldehyde, a method has been widely practiced in which an aldehyde is first oxidized to form a carboxylic acid, which is further reacted with an alcohol to obtain a desired product. This method involves two reaction steps, not only increasing the construction cost of the production facility, but also has a problem that the yield of the aldehyde oxidation step is not sufficient. In particular, in the process of producing methacrylic acid by oxidizing methacrolein, the selectivity is at most about 80%, the space-time yield of the target product is low, and a multitubular, extremely large reactor is required. There is.

Various attempts have been made to react aldehydes and alcohols in the presence of oxygen in order to solve the above-mentioned problems. It has long been known that when ethanol is oxidized in the presence of a metal palladium catalyst, ethyl acetate is produced (Koka Journal, Vol. 71, 1515, (1968)).
This report shows a reaction mechanism in which acetaldehyde produced by oxidation of ethanol reacts with ethanol and oxygen by a palladium catalyst to give ethyl acetate. Similarly, it has been reported that when methanol is reacted with oxygen in the presence of a palladium catalyst, formaldehyde, which is a reaction intermediate, is converted to methyl formate by an oxidative esterification reaction (Kogaku, Vol. 71, 1638, (1968)). )).
The report also states that when the carboxylic acid ester synthesis by oxidative esterification is carried out in a liquid phase, the activity of the palladium catalyst used is reduced.

[0004] These oxidative esterification reactions are carried out using α, β
A method for producing an α, β unsaturated acid ester by applying to an unsaturated aldehyde has also been proposed (JP-A-57-3585).
6, -35857, -35860). These proposals disclose a method for improving the yield of the desired α, β unsaturated acid ester by combining a palladium with a base metal such as lead, mercury, and thallium or a compound of a base metal as a palladium catalyst to be used. Have been. In general, when a palladium is used as a catalyst in a heterogeneous oxidation reaction in a liquid phase, a base metal such as lead or a compound of a base metal is combined with the palladium to improve the yield of the target product,
A method for reducing the amount of catalyst used has also been disclosed (JP-A-54-138886).

[0005] However, even if such a method is used, the yield of the carboxylic acid ester obtained is not sufficient,
Further, the amount of the catalyst used is large, and it is problematic to carry out an industrial large-scale operation. For example, Japanese Patent Application Laid-Open No. 57-35856 discloses a catalyst in which 5 g% of paradium and 5.3 wt% of lead oxide are supported on calcium carbonate for reacting 3.3 g of methacrolein in 100 cc of methanol in a batch reactor. An example using 4 g is shown. That is, there is a problem that the amount of the catalyst used is larger than the charged amount of the raw material to be subjected to the reaction. Further, when such a noble metal catalyst is used in a liquid phase at a relatively low temperature, there is an unsolved problem such as a marked decrease in catalytic activity.

[0006]

In the production of a carboxylic acid ester by reacting an aldehyde and an alcohol in the presence of an oxygen-containing gas, as described above, the yield of the desired product is not sufficient, and the amount of the catalyst used is small. This is enormous, and there is a problem that the activity of the catalyst is reduced. A first object of the present invention is to produce a carboxylic acid ester by reacting an aldehyde and an alcohol in the presence of oxygen to obtain a carboxylic acid ester in a high yield and to use a small amount of a catalyst. It is to provide. A second object of the present invention is to provide a method for reducing the activity of a catalyst which promotes the reaction in producing a carboxylic acid ester by reacting an aldehyde and an alcohol in the presence of oxygen.

[0007]

Means for Solving the Problems The present inventors have conducted various studies on a method for reacting the above-mentioned problem-free aldehyde and alcohol in the presence of oxygen. As a result, it was found that the use of a gold catalyst in which gold was supported on a carrier as the catalyst used in the reaction yielded the desired product at a high yield, and that the amount of the catalyst used could be reduced as compared with the conventionally known palladium catalyst. The invention has been completed. In addition, the present inventors have found that the activity of the gold catalyst can be reduced by making the gold catalyst hydrophobic, thereby completing the present invention. That is, the gist of the present invention is a method of reacting an aldehyde and an alcohol in the presence of oxygen to produce a carboxylic acid ester in the presence of a gold catalyst.

[0008]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a carboxylic acid ester derived from an aldehyde using an aldehyde and an alcohol in the presence of oxygen using a gold catalyst, which is characterized by the gold catalyst used. The catalyst used in the present invention is a catalyst in which gold is supported on a carrier, and the carrier used is activated carbon, silica, alumina, silica-alumina, titania, zirconia, calcium carbonate and zeolite.
In particular, activated carbon is frequently used. The activated carbon used is coconut shell charcoal,
Any of a wood type such as charcoal or a coal type may be used.

Further, in order to make the catalyst hydrophobic, Teflon (manufactured by Dupont, USA), silicalite (manufactured by UCC, USA), high silica zeolite having a silica-alumina ratio of 30 or more, or graphite fluoride is used as a carrier. Use Alternatively, a gold catalyst using a normal hydrophilic carrier is treated with a polytetrafluoroethylene dispersion slurry,
A spray of a fluorinated graphite dispersion or the like is sprayed, dried and calcined to make the catalyst hydrophobic.

By making the catalyst hydrophobic, it is possible to prevent the activity of the catalyst from being reduced by the water produced by the reaction, and to allow the catalyst to work stably for a long time. The shape of the carrier is powder, crushed or tablet, and an appropriate shape is selected according to the type of the reactor.

The gold catalyst used in the method of the present invention has fine particles of gold supported on a carrier, and it is usually appropriate to adjust it by the following method. (A) An aqueous solution containing a gold compound obtained by dissolving a water-soluble gold compound such as chloroauric acid, a gold halide or a gold complex in water is prepared on a carrier, and the above-mentioned carrier is charged into the aqueous solution to be impregnated. The concentration of the gold compound aqueous solution is 0.01 to 0.5 Mo.
1 / L is an appropriate range. Next, the gold salt-impregnated carrier is reduced in an aqueous solution with a reducing agent such as formaldehyde, formate or hydrazine to prepare a catalyst. The reduction temperature in the range of room temperature to 100 ° C. is frequently used.
The reduction treatment may be a method of reducing using hydrogen gas in a gas phase. The gas phase reduction is carried out at 100-200 ° C. The amount of gold carried on the carrier is in the range of 0.01 to 10%, more preferably 0.1 to 3%. When the amount of gold carried is below the above range, the catalytic activity is low, and when it is above the above range, the particle size of gold on the carrier becomes excessive and the activity of the catalyst decreases. The particle size of gold on the carrier prepared by the method (A) is in the range of 10 to 30 nm as calculated from the peak width of X-ray diffraction.

(B) An aqueous alkali solution such as potassium carbonate or sodium bicarbonate is added to a gold aqueous solution in which a gold salt such as a gold halide or chloroauric acid is dissolved with stirring to adjust the pH of the aqueous solution to 9 to 9.
In step 11, gold fine particles are precipitated. The concentration of the aqueous solution in which the gold salt is dissolved is often in the range of 0.01 to 1 mol / L. The precipitated gold fine particles are colloidal and hardly settle even when left. The above-described carrier is introduced into the aqueous solution in which the obtained gold fine particles are dispersed, and the precipitated gold fine particles are adsorbed. Next, gold is reduced with a reducing agent such as formalin or hydrazine to prepare a catalyst. The loading amount of the fine gold particles on the carrier is often in the range of 0.1 to 3% as in the case of (A). The diameter of the fine gold particles on the carrier prepared by the method (B) is usually in the range of 7 to 15 nm, and the diameter of the fine gold particles is generally determined according to the method of the preparation of the method (A) according to the method of the preparation (B). Less than.

The aldehyde of the present invention includes aliphatic aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, glyoxal and methylglyoxal; unsaturated aldehydes such as acrolein, methacrolein and crotonaldehyde; benzaldehyde, tolylaldehyde, benzylaldehyde and the like. And aromatic aldehydes such as phthalaldehyde.

The alcohol of the present invention includes aliphatic alcohols such as methanol, ethanol, propanol, 2-ethylhexanol, n-octanol, ethylene glycol, butanediol and allyl alcohol; and aromatic alcohols such as benzyl alcohol and phenol.

The molar ratio of aldehyde to alcohol used in the reaction of the present invention is often in the range of 1: 3 to 1: 200 for aldehyde to alcohol. As the oxygen-containing gas to be used, air, oxygen, or a mixed gas obtained by diluting oxygen with nitrogen, carbon dioxide, or the like is used. The amount of the catalyst to be used is, for example, a case where the reaction is carried out in a batch system.
The range of t% is frequently used.

The reaction according to the invention is carried out at room temperature to 200 ° C., in particular at 40 ° C.
~ 150 ° C is frequently used as a suitable temperature range. The reaction pressure is often in the range of from atmospheric pressure to 50 atm, and is higher than the pressure necessary for maintaining a liquid layer at the reaction temperature generally used by the alcohol or aldehyde used. The time required for the reaction varies depending on the reaction temperature, amount of catalyst used, oxygen partial pressure, etc.
For example, in the case of a batch reaction, it is in the range of 1 to 20 hours. The type of the reactor is often a suspension bed, fixed bed or trickle bed.

In the method of the present invention, the temperature of the reaction system increases due to the heat of reaction due to the oxidation reaction. Therefore, when the reaction is carried out on an industrial scale, sufficient consideration must be given to the removal of the heat of reaction. In order to make the temperature constant, cooling means by a conventional method is required. After separating the catalyst from the solution after the reaction, the target carboxylic acid ester is isolated by a conventional method such as distillation.

[0018]

The present invention will be described in more detail with reference to the following examples. Example 1 25 ml of deionized water was diluted with 5 ml of a 0.1 mol / L aqueous solution of chloroauric acid. To this solution, 10 g of powder of activated carbon (Centau) manufactured by Calgon was added, and impregnated with chloroauric acid. Next, a solution of 1.5 g of sodium formate in 40 ml of deionized water was added to the above suspension, and the mixture was heated and stirred at 90 ° C. The gold-supported activated carbon was washed with water, filtered and dried to prepare a catalyst. The resulting catalyst had a gold loading of 1.1 w%,
The average particle size of gold obtained from the half width of X-ray diffraction was 15
nm. Stirrer, reflux condenser, gas injection pipe,
A 500 ml separable flask equipped with a thermocouple was used as a reactor, and the reaction temperature was externally adjusted with a water bath. 250 ml of methanol, 10 g of methacrolein, and 5 g of a catalyst were charged into a reactor, and air was blown into the reactor while stirring to react at 45 ° C. Four hours after the start of the reaction, the conversion of methacrolein was 95%, and the selectivity to methyl methacrylate was 8%.
It was 8 mol%.

Example 2 5 ml of a 0.2 mol / l chloroauric acid aqueous solution was taken, diluted with deionized water to 50 ml, and an aqueous sodium carbonate solution was added with stirring to adjust the pH of the gold chloride solution to 10.5. A colloidal suspension of was obtained. A suspension prepared by suspending 10 g of activated carbon powder in 50 g of deionized water was added thereto, and fine precipitates of gold were collected and deposited on the activated carbon. The suspension was heated to 70 ° C., an aqueous formalin solution was added and stirred, and a reduction treatment of a gold salt was performed. The activated carbon was filtered off, washed with water and dried to prepare a catalyst. The amount of gold supported on the catalyst was 1.03 w%, and the average particle size of gold obtained from the half width of the X-ray diffraction peak was 11 nm. Using the same reactor as in Example 1, ethanol 2
50 ml, 10 g of acrolein, and 4 g of the catalyst were charged into a reactor, and air was blown at 45 ° C. for 5 hours to cause a reaction. As a result of analyzing the reaction solution, the conversion of acrolein was 94% and the selectivity of ethyl acrylate was 90 mol%.

Example 3 A reaction was carried out in the same reactor using the same catalyst as in Example 2. 10 g of an aqueous glyoxal solution having a content of 40% in 250 ml of methanol and 3 g of a catalyst were added and reacted at 45 ° C. for 5 hours while blowing air. The catalyst was separated from the reaction solution, and the product was analyzed by high performance liquid chromatography. As a result, the conversion of glyoxal was 90% and the selectivity of methyl glyoxylate was 84 mol%.

Example 4 The same catalyst as in Example 2 was used except that the carrier was changed to hydrophobic fluorinated graphite. 0.98wt% gold loading
It was. 10 g of 2-phenylpropionaldehyde and 4.5 g of the catalyst were charged into 250 ml of ethanol in the same reactor as in Example 1 while blowing air at 60 ° C.
Allowed to react for hours. The reaction mixture from which the catalyst had been separated was analyzed by high performance liquid chromatography. As a result, the conversion of 2-phenylpropionaldehyde was 92%, and the selectivity for ethyl 2-phenylpropionate was 87 mol%.

Example 5 The same catalyst as in Example 2 was sprayed with a polyfluoroethylene dispersion and dried at 200 ° C. under reduced pressure to prepare a hydrophobic catalyst. 250 ml of methanol was placed in the same reactor as in Example 1,
10 g of methacrocrolein and 5 g of catalyst were charged at 55 ° C.
And reacted while blowing oxygen. Nitrogen was introduced into the gas phase of the reactor from another gas introduction pipe to keep the gas phase outside the explosion range. After reacting for 3 hours, the conversion of methacrolein was 92% and the selectivity to methyl methacrylate was 8
It was 8 mol%. The same reaction was repeated four times using the separated and recovered catalyst. Second conversion rate 88%, third conversion rate 86%, fourth conversion rate 87%, selectivity 88m
At ol%, no significant reduction in conversion and selectivity was observed, and almost no reduction in catalyst activity was observed.

[0023]

As described above, the use of a gold-supported catalyst makes it possible to reduce the amount of the catalyst used in comparison with a conventionally known palladium-based catalyst, and to efficiently produce a carboxylic acid ester from an aldehyde and an alcohol in good yield. Can be manufactured.
Further, by making the catalyst hydrophobic, it is possible to prevent a rapid decrease in the catalytic activity even when the catalyst is used repeatedly.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI theme coat ゛ (reference) // C07B 61/00 300 C07B 61/00 300 F term (reference) 4G069 AA01 AA03 BA08A BA08B BB02A BB02B BC33A BC33B BD15B CB75 DA08 EA01Y EC15Y 4H006 AA02 AC48 BA05 BA55 BA56 BA82 BE30 BQ10 KA35 4H039 CA66 CC30 CD10 CD40

Claims (7)

[Claims] 1. A method for producing a carboxylic acid ester, which comprises reacting an aldehyde and an alcohol in the presence of an oxygen-containing gas to produce a carboxylic acid ester, wherein the reaction is carried out in the presence of a catalyst having gold supported on a carrier. Method. 2. The method according to claim 1, wherein the aldehyde is acrolein and the carboxylate is an acrylate. 3. The aldehyde is methacrolein,
The method according to claim 1, wherein the carboxylate is a methacrylate. 4. The method according to claim 1, wherein the aldehyde is glyoxal and the carboxylate is glyoxylate. 5. The method according to claim 1, wherein the alcohol is methanol or ethanol. 6. The method according to claim 1, wherein the carrier supporting gold is activated carbon. 7. The method according to claim 1, wherein the gold-supporting carrier is a hydrophobic carrier or a hydrophilic carrier made hydrophobic.