JP3503777B2 - Surface-controlled supported catalyst containing palladium and lead - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a catalyst used for producing a carboxylic acid ester from an aldehyde, an alcohol and molecular oxygen, and a method for producing a carboxylic acid ester using the catalyst.

[0002]

2. Description of the Related Art As a method for industrially useful production of methyl methacrylate or methyl acrylate, a method called direct acid method for producing methacrylic acid from methacrolein and converting it to methacrylic acid methyl ester has already been industrialized. ing. However, although the yield of the step of oxidizing methacrolein to methacrylic acid has been improved to the low 80% range through many years of catalyst improvement, it is still low and there is a lot of room for improvement. Further, the heteropolyacid catalyst used has a difficulty due to thermal stability, and the decomposition thereof gradually progresses under reaction temperature conditions. Although catalyst improvements for improving heat resistance have been reported, it is said that the catalyst life is still insufficient for industrial catalysts.

On the other hand, a new method of reacting methacrolein or acrolein with methanol and molecular oxygen to produce methyl methacrylate or methyl acrylate all at once has been highlighted recently. It is carried out by reacting methacrolein or acrolein with molecular oxygen in methanol and the presence of a catalyst containing palladium is essential.

Conventionally, in this production method, hydrocarbons and carbon dioxide gas are produced by the simultaneous decomposition reaction of aldehydes, the yield of the desired carboxylic acid ester is low, and alcohol is produced in parallel with the carboxylic acid ester production reaction. Different aldehydes due to own oxidation and different carboxylic acid esters (for example, methyl formate when methanol was used as alcohol, ethyl acetate when ethanol was used) were by-produced from the aldehyde, and the selectivity based on alcohol was also poor. . Moreover, there is a drawback that the catalytic activity cannot be maintained for a long time. Particularly when α / β-unsaturated aldehydes such as methacrolein and acrolein, which are of high industrial practical value, are used as starting materials, the stability of these reaction intermediates is much lower, and therefore a large amount of carbon dioxide and olefins are generated during the reaction. Decomposition products such as (propylene in the case of methacrolein) were generated, which was far from the practical level.

The present inventors have found that Japanese Patent Publication No. 57-035856.
No. 57-35857 and 57-3535
In Japanese Patent No. 859, a catalyst system containing palladium and lead is proposed, and it is shown that the selectivity to methyl ester based on methacrolein or acrolein is significantly improved, and it becomes a high value exceeding 90%. , The reaction temperature is at most 50
It was up to ° C.

Subsequently, Japanese Patent Publication No. 62-007902 proposes a catalyst containing an intermetallic compound in which palladium and lead are bonded in a simple integer ratio, whereby the decomposition reaction of methacrolein or acrolein is almost completely suppressed, and It has been shown that the catalyst system does not lose its catalytic activity for a long time. As described above, the new production method using these new catalyst systems has advantages such as a shorter process than the direct acid method, which has a peak in improving yield and improving catalyst life. Industrialization is awaited as a manufacturing method.

However, if this reaction is carried out at a high temperature of 60 ° C. or higher, which is an economically advantageous reaction condition on the premise of industrial implementation, and a high concentration of aldehyde of 20% or more, the MMA selectivity of the catalyst system is lowered and A rapid increase in the amount of methyl formate by-product occurs due to the oxidation of alcohol itself. That is, in Japanese Examined Patent Publication No. 62-007902, a high M exceeding 90% is obtained.
MA selectivity is obtained, and methyl formate is 0.03-
Although it is exemplified that the amount is as small as 0.06 mol / mol MMA, these are carried out under mild conditions where the aldehyde concentration is 10% or less and the reaction temperature is 40 to 60 ° C. MMA generated under these conditions
Since the concentration is low, the amount of unreacted methanol recycled is large, and as a result, the amount of steam used increases and economic efficiency deteriorates. Moreover, the productivity is low and the reactor is large. In order to improve the economic efficiency, it is desirable to increase the aldehyde concentration and the reaction temperature as much as possible, and Japanese Patent Publication No. 06-9813 discloses a reaction example in which the methacrolein concentration is 20% and the reaction temperature is 80 ° C. However, under such a high methacrolein concentration and high reaction temperature conditions, a high MMA selectivity exceeding 90% cannot be obtained. Moreover, methyl formate is 0.0
Doubling to 923 mol / mol MMA. If the methacrolein concentration is increased to 30% under more severe conditions,
The decomposition reaction of the aldehyde is likely to occur, and the MMA selectivity is further deteriorated.

In order to improve the economical efficiency, the advent of a catalyst system having a high MMA selectivity of more than 90% at a high temperature and a high aldehyde concentration and a low methyl formate byproduct was awaited.

[0009]

DISCLOSURE OF THE INVENTION In the present invention, when an aldehyde, an alcohol, and molecular oxygen are reacted with a catalyst containing palladium and lead to produce a carboxylic acid ester, the concentration of the aldehyde and the reaction temperature are increased to improve the economical efficiency. And a catalyst enabling a method for producing a carboxylic acid ester having a high selectivity of a carboxylic acid ester and a small amount of by-products derived from an alcohol such as methyl formate, and a carboxylic acid ester using the catalyst. It provides a method.

[0010]

In view of the above situation, the present inventors have developed palladium and lead in order to develop a catalyst having a high carboxylate ester selectivity and a small amount of alcohol-derived byproducts such as methyl formate. Of the intermetallic compound species in which palladium and lead are bonded in a simple integer ratio proposed by the present inventors in Japanese Patent Publication No. 62-007902, Pd ₃ having an atomic ratio of 3/1 is studied. The present invention has been completed by paying attention to Pb type ₁ and conducting more detailed research.

That is, the present invention is as follows. 1. A catalyst for producing a carboxylic acid ester from an aldehyde, an alcohol, and molecular oxygen, which is a supported catalyst containing palladium and lead and satisfying the following (1) to (3). (1) The supported composition ratio of palladium / lead is 3/0.
7 to 3 / 1.3, the (111) plane X-ray diffraction angle (2θ) of the (2) palladium / lead intermetallic compound is 38.55 to 3
8.70, (3) supported catalyst palladium metal (3d (3
/ 2) + 3d (5/2)) / lead metal (4f (7/2) x
1.75) X-ray photoelectron spectrum intensity ratio is 1 / 0.2
~ 1 / 0.7, 2. A method for producing a carboxylic acid ester by reacting an aldehyde with an alcohol and molecular oxygen, which comprises reacting the aldehyde with the alcohol and the molecular oxygen in the presence of the supported catalyst according to the above 1. . 3. The method for producing a carboxylic acid ester according to the above 2, wherein the aldehyde is methacrolein, acrolein or a mixture thereof, and the alcohol is methanol.

The present invention will be described in detail below. Among the supported catalysts obtained by supporting high-quality Pd ₃ Pb ₁ species on a carrier with high purity, particularly palladium metal (3d (3/2) +
3d (5/2)) / lead metal (4f (7/2) x 1.7
X-ray photoelectron spectrum intensity ratio of 5) is 1 / 0.2 to 1
The catalyst whose surface structure and surface composition are precisely controlled to be /0.7 produces less methyl formate by-products even under severe reaction conditions such as high aldehyde concentration and high reaction temperature. The selectivity of the carboxylic acid ester is high. Moreover, they have found that the conversion rate of aldehyde is also high. Controlling the surface structure and surface composition of a catalyst containing Pd ₃ Pb ₁ as a catalyst species resulted in a completely unexpected result in that the reactivity with alcohol and aldehyde was significantly changed. It is extremely important to precisely control the structure and composition of the catalyst surface, and the catalyst is Pd ₃ Pb ₁ species, and the palladium metal (3d (3/2) + 3d (5
/ 2)) / lead metal (4f (7/2) x 1.75), so that the X-ray photoelectron spectrum intensity ratio is 1 / 0.2 to 1 / 0.7. The precise control makes it possible to solve the problems of the present invention.

According to the present invention, the surface structure and surface composition of a supported catalyst containing Pd ₃ Pb ₁ as a chemical species are defined as palladium metal (3
d (3/2) + 3d (5/2)) / lead metal (4f (7 /
2) × 1.75) X-ray photoelectron spectrum intensity ratio is 1 /
It is important to control so as to be 0.2 to 1 / 0.7. For whatever reason, it is still insufficient to analyze whether it is a catalyst that has a low methyl formate byproduct, a high selectivity of the carboxylic acid ester, and a high aldehyde conversion rate. Has succeeded in retaining the excellent characteristics of Pd ₃ Pb ₁ as a catalyst species by controlling the structure and composition of the catalyst surface more precisely because it is susceptible to redox and its state is unstable. Is believed to have produced an excellent effect.

The supported catalyst of the present invention contains palladium and lead. First, the supported composition ratio (atomic ratio) of palladium / lead must satisfy 3 / 0.7 to 3 / 1.3. It is preferably 3 / 0.9 to 3 / 1.1. When the amount of supported lead exceeds 1.3 by atomic ratio, the formation of methyl formate becomes remarkable.
When it is less than 0.7, the MMA selectivity is largely reduced due to the decomposition of aldehyde. More preferably, it is as close to 3/1 as possible.

Secondly, the palladium / lead intermetallic compound (1
The X-ray diffraction angle (2θ) of the 11) plane is 38.55 to 38.7.
The range is 0. If it is less than 38.55, the by-product of methyl formate is remarkable. If it exceeds 38.70, the decomposition of aldehyde becomes remarkable, and the MMA selectivity decreases. Third, palladium metal (3d (3/2) + 3d (5/2)) / lead metal (4
The X-ray photoelectron spectrum intensity ratio of f (7/2) × 1.75) is 1 / 0.2 to 1 / 0.7, preferably 1 / 0.3 to
It is necessary to control in the range of 1 / 0.6. When a catalyst satisfying these three conditions is used, the production of methyl formate is small, the MMA selectivity is high, and the aldehyde conversion is high. That is, when it exceeds 0.7, the by-product of methyl formate increases, and at the same time, the catalytic activity decreases. On the other hand, if it is less than 0.2, the catalytic activity is lowered. Furthermore, palladium metal (3d (3/2) + 3d (5 /
2)) / charged lead (4f (7/2) + 4f (5 /
By controlling the intensity ratio of 2)) within the range of 1/0 to 1 / 0.2, the by-product of methyl formate can be further suppressed. 1/0 as much as possible
Is most desirable.

In addition to palladium and lead as a catalyst component, different elements such as mercury, thallium, bismuth, tellurium, nickel, chromium, cobalt, indium, tantalum, copper, zinc, zirconium, hafnium, tungsten, manganese, silver and rhenium are used. , Antimony, tin, rhodium, ruthenium, iridium, platinum, gold, titanium, aluminum, boron, silicon and the like may be contained. These different elements can be contained in the range of usually 5% by weight, preferably 1% by weight. Further, compounds containing at least one member selected from alkali metal compounds and alkaline earth metal compounds are advantageous in that the reaction activity becomes high. Alkali metal and alkaline earth metal are usually 0.0
It is selected from the range of 1 to 30% by weight, preferably 0.01 to 5% by weight. These different elements, alkali metals and alkaline earth metals, etc. may penetrate into the crystal lattice in a small amount or may be substituted with a part of the crystal lattice metal. Further, the alkali metal and / or alkaline earth metal compound may be added to a solution containing a palladium compound or a lead compound at the time of catalyst preparation and may be adsorbed or attached to a carrier, or a carrier supporting these in advance may be used as a catalyst. Can also be prepared. It is also possible to add it to the reaction system under the reaction conditions.

The palladium compound and the lead compound used for preparing the catalyst include organic acid salts such as formate salts and acetate salts, inorganic acid salts such as sulfates, hydrochlorides and nitrates, ammine complexes, benzonitrile complexes and the like. It is appropriately selected from organic metal complexes, oxides, hydroxides and the like. Palladium compounds are preferably palladium chloride, palladium acetate and the like, and lead compounds are preferably lead nitrate, lead acetate and the like. The alkali metal compound and alkaline earth metal compound are also selected from organic acid salts, inorganic acid salts, hydroxides and the like.

The carrier can be widely selected from activated carbon, silica, alumina, silica-alumina, zeolite, magnesia, magnesium hydroxide, titania, calcium carbonate, activated carbon and the like. The amount of palladium supported on the carrier is not particularly limited, but is usually 0.1 to 20% by weight, preferably 1 to 10% by weight based on the weight of the carrier. The amount of lead supported is not particularly limited, but is usually selected from the range of 0.05 to 17% by weight, preferably 0.45 to 8.5, with respect to the weight of the carrier.
However, as mentioned above, the atomic ratio of supported palladium / supported lead is 3
It should be in the range of /0.7 to 3 / 1.3. It is preferably 3 / 0.9 to 3 / 1.1.

The production examples of the catalyst of the present invention will be described below.
First, a palladium / lead-containing supported catalyst is prepared according to a usual preparation method. At this time, the supported composition ratio of palladium / lead is usually selected from the atomic ratio range of 3 / 0.1 to 3/10. Practically 3 / 0.1 to 3/3, more preferably 3/0.
It is preferably set to 7 to 3 / 1.3. However, beyond this range, for example less than 3 / 0.1 or 3 /
Even if it exceeds 10, it is possible to additionally support lead or remove excess lead in the catalyst structure completion step and surface structure control step described below. It is not necessarily limited to (atomic ratio).

The most practical process for obtaining the catalyst of the present invention is
A catalyst structure-completing step of preparing a palladium / lead-containing supported catalyst having a palladium / lead supported composition ratio of 3 / 0.7 to 3 / 1.3 in atomic ratio prepared in advance according to a conventional preparation method, and It can be obtained through two steps of controlling the surface structure of the catalyst. That is, the supported composition ratio of palladium / lead obtained by the usual preparation method is 3 / atomic ratio.
0.7 to 3 / 1.3 palladium-and-lead-containing supported catalyst is subjected to the structure completion treatment which is the first step,
Palladium / lead intermetallic compound (1
11) plane X-ray diffraction angle (2θ) is 38.55 to 38.7.
By satisfying 0, a structure-completed catalyst satisfying the requirements (1) and (2) is obtained.

First, the step of completing the structure of the catalyst will be described. There are various methods for completing the structure, and all of them cannot be explained.However, for example, the catalyst obtained by the above-mentioned ordinary manufacturing method is further reacted with formalin, formic acid, hydrazine, methanol or molecular hydrogen in the presence of a lead compound. Complete. In addition, as another method, for example, it is possible to obtain the catalyst obtained by the usual production method by performing a series of redox operations consisting of oxidation with molecular oxygen and subsequent reduction with methanol at least once or more. However, it can also be obtained by simultaneously performing oxidation with molecular oxygen and reduction with methanol.

More specifically, according to the usual method shown in Reference Production Example 2, the atomic ratio of supported palladium / supported lead was 3 /.
After preparing a supported catalyst having a composition ratio of 0.98 in advance, the supported composition ratio (atomic ratio) of palladium / lead is, for example, 3 / 1.3.
So that the supported catalyst is dispersed in methanol in which lead acetate is dissolved, reaction temperature = 90 ° C., reaction pressure = 5 kg / c
m ² (hereinafter, the pressure is expressed as an absolute pressure and is shown in kg / cm ² ), and the outlet oxygen concentration is 2.0% (oxygen partial pressure 0.1 k
g / cm ² equivalent), supplying air to the reactor,
It is also possible to obtain a catalyst having a completed structure by activating it for about 20 hours.

Only the step of completing the structure (3)
Palladium metal (3d (3/2) + 3d (5/2)) /
The catalyst may satisfy the X-ray photoelectron spectrum intensity ratio of 1 / 0.2 to 1 / 0.7 of lead metal (4f (7/2) × 1.75), but the above (3) should be surely applied. In order to satisfy the above, a step of controlling the surface structure of the catalyst, which is the second step, is performed.

Next, the control of the surface structure of the catalyst, which is the second step, will be described. The most practical and easy method is to control the surface structure of the catalyst while producing the carboxylic acid ester, which is of high practical significance. That is, when a carboxylic acid ester is produced by reacting an aldehyde with an alcohol and molecular oxygen in the presence of a structure-completed catalyst containing palladium and lead, while a small amount of a substance containing lead is present in the reactor. The reaction is carried out at a specific oxygen partial pressure. By carrying out this step, a catalyst satisfying the above (3) can be surely obtained. It is difficult to determine the oxygen partial pressure and the amount of lead added to specific values depending on the reaction raw materials such as the aldehyde species and alcohol species to be reacted, the reaction conditions, the reactor type or the palladium and lead composition of the catalyst, etc. Oxygen partial pressure at the outlet is 0.02-
The concentration of lead added to the reactor is controlled at 0.8 kg / cm ² , and the reaction is performed in the range of 0.1 to 2000 ppm. Also,
When the amount of lead supplied to the reactor increases, the treatment cost for detoxifying the lead in the wastewater increases, which is not preferable. Practically, the necessary minimum amount is selected from the range of 1 to 200 ppm.

Further, without directly carrying out the step of structural completion as the first step, the structural completion of the catalyst and control of the surface structure are carried out by directly carrying out the production reaction of the carboxylic acid ester as the second step. It is also possible to do it at the same time. That is, when a catalyst containing palladium and lead is reacted with an aldehyde, an alcohol and molecular oxygen to produce a carboxylic acid ester, the reaction is carried out at a specific oxygen partial pressure while a small amount of a substance containing lead is present in the reactor. It is possible to complete the structure of the catalyst and also control the surface structure only by performing the above-described step of controlling the surface structure of the catalyst.
The oxygen partial pressure and the amount of lead added are difficult to determine to specific values depending on the reaction raw materials such as aldehyde species to be reacted, alcohol species, reaction conditions, reactor type or palladium and lead composition of the catalyst, but in the second step Similar to the step of controlling the surface structure of the catalyst, for example, the oxygen partial pressure at the reactor outlet is controlled to 0.02 to 0.8 kg / cm ² , and the lead concentration added to the reactor is 0.1 to 2000 ppm. It is preferable to carry out the reaction within the range.

Although the mechanism for completing the structure and controlling the surface of the catalyst is unknown, it is presumed by the present inventors that the active hydrogen present on the catalyst plays an important role under these conditions. It is presumed that it is necessary to reduce the oxygen partial pressure in order to enhance the function of. As the aldehyde and alcohol used in the step of completing the catalyst structure and the step of controlling the surface structure of the catalyst, it is convenient to use the aldehyde and alcohol that are the raw materials for the production of carboxylic acid ester using the present catalyst. . For example, when used as a catalyst for the production of methacrylic acid methyl ester, it is advantageous to select methacrolein as the aldehyde and methanol as the alcohol.

The catalyst whose structure is to be completed can be prepared by a known preparation method. To describe a typical catalyst preparation method, a carrier is added to an aqueous solution containing a soluble lead compound and a soluble palladium salt such as palladium chloride to impregnate palladium and lead. Then, it is reduced with a reducing agent such as formalin, formic acid, hydrazine, or hydrogen gas. The obtained supported catalyst containing palladium and lead, as disclosed by the present inventors in Japanese Patent Publication No. 62-007902, contains a Pd ₃ Pb ₁ intermetallic compound as a catalyst species, but its purity is low. For this reason, the catalyst supported on the carrier obtained by such a usual production method is the required composition ratio (atomic ratio) of palladium / lead and the (111) plane of the palladium / lead intermetallic compound, which are the requirements of the present invention. It cannot be a catalyst that simultaneously satisfies the X-ray diffraction angle and the X-ray photoelectron spectrum intensity ratio of palladium metal / lead metal. A catalyst satisfying the requirements of the present invention can be obtained only by completing the structure of the catalyst obtained by such a conventional production method and controlling the surface structure of the catalyst by the above method.

The catalyst of the present invention can be suitably used for the reaction of reacting an aldehyde with an alcohol and molecular oxygen to produce a carboxylic acid ester. The amount of the catalyst used depends on the types of reaction raw materials, the composition and preparation method of the catalyst, the reaction conditions,
The amount can be largely changed depending on the reaction type and the like, but is not particularly limited, but when the catalyst is reacted in a slurry state, it is preferable to use 0.04 to 0.5 kg in 1 liter of the reaction liquid.

Examples of the aldehyde used in the production of the carboxylic acid ester of the present invention include aliphatic saturated aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, isobutyraldehyde and glyoxal, and aliphatic α such as acrolein, methacrolein and crotonaldehyde. -Aromatic aldehydes such as β-unsaturated aldehyde, benzaldehyde, tolylaldehyde, benzylaldehyde, phthalaldehyde, and derivatives of these aldehydes. These aldehydes can be used alone or as a mixture of two or more kinds.

The alcohol used in the production of the carboxylic acid ester of the present invention is, for example, methanol,
Examples thereof include aliphatic saturated alcohols such as ethanol, isopropanol and octanol, diols such as ethylene glycol and butanediol, aliphatic unsaturated alcohols such as allyl alcohol and methallyl alcohol, and aromatic alcohols such as benzyl alcohol. These alcohols can be used alone or as a mixture of two or more kinds.

There is no particular limitation on the amount ratio of the aldehyde and the alcohol used in the production of the carboxylic acid ester of the present invention. For example, the molar ratio of aldehyde / alcohol is 10-1.
Although it can be carried out in a wide range such as / 1000, it is generally carried out in a range of 1/2 to 1/50. The production reaction of the carboxylic acid ester of the present invention can be carried out by any conventionally known method such as a gas phase reaction, a liquid phase reaction and a perfusion reaction. For example, when it is carried out in the liquid phase, it may be carried out in any reactor type such as a bubble column reactor, a draft tube type reactor and a stirred tank reactor.

The oxygen used in the reaction for producing the carboxylic acid ester of the present invention is molecular oxygen, that is, oxygen gas itself or a mixed gas obtained by diluting oxygen gas with a diluent inert to the reaction, such as nitrogen or carbon dioxide. It can be shaped and air can be used. When the present reaction is continuously carried out, the deterioration of the catalyst can be suppressed by carrying out the reaction while adding a substance containing lead to the reactor. At this time, by setting the oxygen partial pressure on the outlet side of the reactor to 0.8 kg / cm ² or less, it is possible to suppress the deterioration of the catalyst by reducing the lead concentration in the raw material liquid supplied to the reactor. It is difficult to determine the lead addition amount and oxygen partial pressure at the reactor outlet to a specific value depending on the reaction raw materials such as aldehyde species and alcohol species to be reacted, reaction conditions or reactor type, etc. The palladium / lead loading composition ratio of the catalyst was determined to be 3 / 0.7 to 3 / 1.3 in atomic ratio and the X-ray diffraction angle of the (111) plane of the palladium / lead compound was determined and supplied to the reactor. (2θ) is 38.5
5 to 38.70, palladium metal (3d (3/2) +3
d (5/2)) / lead metal (4f (7/2) × 1.75)
X-ray photoelectron spectrum intensity ratio of 1 / 0.2 to 1/0.
7 and the catalyst of the present invention can be stably maintained during the reaction.

When the amount of lead added is large, the treatment cost for detoxifying the lead in the waste water becomes high, and the amount of the reaction by-product, methyl formate, becomes large, which is not preferable. The oxygen partial pressure on the side is preferably 0.4 kg / cm ² or less to reduce the amount of lead supplied. More preferably, it can be set to 0.2 kg / cm ² or less, but if oxygen necessary for the reaction is not secured, oxygen deficiency will occur and the conversion rate of the raw material aldehyde will decrease, and inconvenient by-products will be generated. You can choose within the range.

The reaction pressure can be carried out in any wide pressure range from reduced pressure to increased pressure, but usually 0.5 to 20.
It is carried out at a pressure of kg / cm ² . The total pressure should be set so that the oxygen concentration in the gas discharged from the reactor does not exceed the explosion range (8%). In the reaction of the present invention, the pH of the reaction system is maintained at 6 to 9 by adding an alkali metal or alkaline earth metal compound (eg, oxide, hydroxide, carbonate, carboxylate, etc.) to the reaction system. It is preferable. Especially pH 6
With the above, there is an effect of preventing dissolution of the lead component in the catalyst. These alkali metal or alkaline earth metal compounds can be used alone or in combination of two or more.

The high aldehyde concentration reaction of the present invention can be carried out at a high temperature of 100 ° C. or higher, but is preferably 30 to 100 ° C. More preferably 60 to 90 ° C
Is. The reaction time is not particularly limited and cannot be uniquely determined because it varies depending on the set conditions, but it is usually 1 to 20 hours.

[0036]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below with reference to Examples and Comparative Examples. The pressure used in Examples and the like is expressed as an absolute pressure and is expressed as kg / cm ² . <Reference Production Example 1> As a silica sol aqueous solution, Snowtex N-30 (manufactured by Nissan Chemical Co., Ltd., trade name: SiO ₂ min: 3)
Aluminum nitrate and magnesium nitrate in Al / Si + Al = 10 mol%, Mg / Si + M
After adding and dissolving so that g = 10 mol%, 130
Spray drying was carried out with a spray dryer set to a temperature of ° C to obtain a spherical carrier having an average particle size of 60 µm. 300 ℃, then 600
After calcination at ℃, palladium chloride and lead nitrate were used as a carrier to support palladium and lead to 5 and 6.5 parts by weight, respectively, per 100 parts by weight of the carrier, and then reduced with hydrazine to reduce the catalyst. (Pd5.0Pb6.5
/ Mg, expressed as Al-SiO _2. ) Got. The Pd / Pb supported composition ratio of the obtained supported catalyst was 3/1.
95, X of (111) plane of palladium / lead intermetallic compound
The line diffraction angle (2θ) was 38.745 degrees, and the intensity ratio of the X-ray photoelectron spectrum of palladium metal (3d) / lead metal (4f) was 1 / 1.24. <Measurement of X-Ray Diffraction Angle of (111) Face of Pd / Pb Intermetallic Compound> The measurement was performed using RAD-RA manufactured by Rigaku Co., Ltd. according to the usual measurement procedure of powder X-ray diffraction, and CuKα1 ray (1.5
The diffraction angle 2θ of the (111) plane of the supported catalyst palladium / lead intermetallic compound was measured using 405981Å). The measurement must be performed with high precision. For example National I
Institute of Standards & Technology 66
(111) of the LaB ₆ compound defined as 0
Plane and (200) plane were measured and the respective values were 37.44.
Normalize to be 1,43.506. As a result, highly accurate measurement results with high reproducibility can be obtained. 1 catalyst
It is vacuum-evacuated at 60 ° C. and treated for 3 hours to remove low-molecular adsorption / occlusion components, and then measured. <Measurement of X-ray photoelectron spectrum> Measurement is made by VG ESCA
Performed using LAB-200-X. As shown in FIG. 2, after the peak separation treatment, the areas of the respective peaks were calculated, and the area of palladium metal (3d (3/2) + 3d (5/2)) / lead metal (4f (7/2) × 1.75) was calculated. The area ratio and the area ratio of palladium metal (3d (3/2) + 3d (5/2)) / charged lead (4f (7/2) + 4f (5/2)) were obtained, and this was calculated as the peak intensity ratio. And 1 and 2 show measurement examples of palladium (3d) and lead (4f), respectively.

[0037]

Example 1 An external circulation type stainless steel bubble column reactor having a catalyst separator and a liquid phase portion of 1.2 liters was charged with 300 g of the supported catalyst obtained in Reference Production Example 1 above to carry out a reaction. . 36.7% by weight of methacrolein /
0.54 liter / hr methanol solution, NaOH /
A methanol solution was continuously supplied at 0.06 liter / hr so that the outlet oxygen concentration would be 3.0% (oxygen partial pressure 0.15 kg / cm ² equivalent) at a reaction temperature of 80 ° C. and a reaction pressure of 5 kg / cm ^2. Air was supplied to the reactor while adjusting the amount of air to complete the structure of the catalyst. PH of reaction solution
Was controlled to 7.1 so that the concentration of NaOH supplied to the reactor was controlled, and the structure completion treatment was performed for 50 hours. Subsequently, in order to control the surface structure of the catalyst, the oxygen concentration at the outlet of the reactor was changed to 4.0% (corresponding to an oxygen partial pressure of 0.20 kg / cm ² ), and at the same time, 36.7 wt% of methacrolein / was supplied to the reactor. It was started to add lead acetate to the methanol solution so that the lead concentration in the feedstock liquid would be 20 ppm.
After a total of 100 hours including the structure completion treatment time, the catalyst was taken out from the reactor and analyzed. As a result, the Pd / Pb supported composition ratio was 3 / 1.08 by atomic ratio.
The X-ray diffraction angle (2θ) of the (111) plane of the palladium / lead intermetallic compound was 38.612 degrees, and the palladium metal (3
The intensity ratio of the X-ray photoelectron spectrum of d) / lead metal (4f) was changed to 1 / 0.49.

240 g of this catalyst was equipped in a catalyst separator, and the liquid phase portion was charged into an external circulation type bubble column reactor made of stainless steel to carry out MMA formation reaction. 0.54 liters / hr of a 36.7 wt% methacrolein / methanol solution and 0.06 liters of a NaOH / methanol solution were prepared by dissolving lead acetate in the reactor so that the lead concentration in the feedstock solution was 20 ppm. The reaction was carried out by continuously supplying the gas at a reaction temperature of 80 ° C. and a reaction pressure of 5 kg / cm ^{2 so} that the outlet oxygen concentration was 4.0% (corresponding to an oxygen partial pressure of 0.20 kg / cm ² ). Supply air to the vessel
The MA production reaction was carried out, and when the reaction product was analyzed after 10 hours, the methacrolein conversion rate was 61.
8%, methyl methacrylate selectivity is 91.6%,
Propylene had a selectivity of 1.23% and methyl formate was produced at 0.045 mol / mol MMA as a by-product.

[0039]

Example 2 The supported catalyst obtained in Reference Production Example 1 was subjected to the structure completion treatment under the same operation and conditions as in Example 1, and the feedstock solution was used as a control condition for the catalyst surface structure after 50 hours. The reaction was carried out under the same conditions as in Example 1 except that the lead concentration in the reactor was changed to 10 ppm, and after a total of 100 hours including the activation treatment time, the catalyst was extracted from the reactor and analyzed. The composition ratio of Pb supported is 3 / 1.02 in atomic ratio, the X-ray diffraction angle (2θ) of the (111) plane of the palladium / lead intermetallic compound is 38.609 degrees,
The intensity ratio of the X-ray photoelectron spectrum of palladium metal (3d) / lead metal (4f) was 1 / 0.32. Using this catalyst, an MMA producing reaction is carried out in the same manner as in Example 1, and 1
When the reaction product was analyzed at 0 hours,
The conversion of methacrolein was 60.9%, the selectivity of methyl methacrylate was 90.2%, propylene had a selectivity of 1.93%, and methyl formate produced 0.032 mol / mol MMA as by-products.

[0040]

Comparative Example 1 In Example 1, until the catalyst structure was completed, the reaction was performed for 50 hours in exactly the same manner as in Example 1, and then the catalyst was extracted from the reactor and analyzed. The atomic ratio was 3 / 1.24, and the X-ray diffraction angle (2θ) of the (111) plane of the palladium / lead intermetallic compound was 38.65.
The intensity ratio of the X-ray photoelectron spectrum of the palladium metal (3d) / lead metal (4f) twice was 1 / 0.89. Using this catalyst, an MMA forming reaction was carried out in the same manner as in Example 1, and the reaction product was analyzed after 10 hours. The conversion of methacrolein was 57.3% and the selectivity of methyl methacrylate was 90.7%. As a by-product, propylene has a selectivity of 1.72% and methyl formate is 0.08.
5 mol / mol MMA was produced.

[0041]

Examples 3 to 7 and Comparative Examples 3 to 7 The various catalysts listed in Table 1 as Examples 3 to 7 and Comparative Examples 3 to 7 were prepared according to Pd /
The composition ratio of Pb (atomic ratio), the X-ray diffraction angle (2θ) of the (111) plane of the palladium / lead intermetallic compound, and the intensity ratio of the X-ray photoelectron spectrum of palladium metal (3d) / lead metal (4f) are shown. The reaction results at the time are summarized. For comparison, the reaction results were evaluated by outlet oxygen concentration of 4.0% (oxygen partial pressure of 0.
20 kg / cm ² equivalent), the lead concentration in the feedstock liquid is 20
The reaction was carried out for 10 hours in ppm.

[0042]

[Table 1]

[0043]

[Embodiment 8] The catalyst separator used in Embodiment 1 is provided, and two external circulation type stainless steel bubble column reactors each having a liquid phase of 1.2 liter are connected in series. With the supported catalyst obtained in No. 1, 240 g of a catalyst for which the structure completion treatment had already been completed was charged and the reaction was carried out. In the first-stage reactor, 0.53 liter / hr of a 36.7 wt% methacrolein / methanol solution in which lead acetate was dissolved so that the lead concentration in the feedstock liquid was 20 ppm, NaOH / meta
Continuously supplying 0.06 liter / hr of the nol solution,
The reaction is performed by supplying air to the reactor while adjusting the amount of air so that the outlet oxygen concentration is 4.0% (oxygen partial pressure is 0.20 kg / cm2) at a reaction temperature of 80 ° C and a reaction pressure of 5 kg / cm2. I went. The catalyst suspension is liquid-solid separated, the catalyst is returned to the reactor, only the reaction liquid is sent to the second stage reactor together with NaOH / methanol solution 0.06 liter / hr, and the outflow gas of the first stage reactor is While venting to the two-stage reactor, the outlet oxygen concentration of the second-stage reactor was 2.2% (oxygen partial pressure 0.1
1 kg / cm2 equivalent), adding a shortage of air to the second stage reactor, reaction temperature 80 ° C, reaction pressure 4.6 kg
The reaction was carried out at / cm @ 2. Further, in both the first-stage reactor and the second-stage reactor, the concentration of NaOH supplied to the reactor was controlled so that the pH of the reaction solution was 7.1. When the reaction product was analyzed after 500 hours, the conversion of methacrolein was 61.6% and the selectivity of methyl methacrylate was 91.5.
%, Propylene has a selectivity of 1.36%, and methyl formate has a selectivity of 0.
It was 049 mol / mol MMA. At the same time, when a part of the catalyst was extracted from each of the first-stage reactor and the second-stage reactor and analyzed, it was found that the catalyst of the first-stage reactor was Pd / Pb.
The supported composition ratio was 3 / 1.05 in atomic ratio, and the X-ray diffraction angle (2θ) of the (111) plane of the palladium / lead intermetallic compound was 3
It is 8.602 degrees, and the intensity ratio of the X-ray photoelectron spectrum of palladium metal (3d) / lead metal (4f) is 1 / 0.4.
5, the second-stage reactor catalyst had an atomic ratio of Pd / Pb loading composition ratio of 3 / 0.98, and an X-ray diffraction angle (2θ) of the (111) plane of the palladium / lead intermetallic compound of 38.612 degrees. The intensity ratio of the X-ray photoelectron spectrum of palladium metal (3d) / lead metal (4f) was 1 / 0.45. The reaction was further carried out under these conditions for 500 hours. Reaction results and Pd / Pb supported composition ratio of catalysts in the first and second stage reactors, X-ray diffraction angle (2θ) of (111) plane of palladium / lead compound, and palladium metal (3d) / lead metal ( No significant change was observed in the intensity ratio of the X-ray photoelectron spectrum of 4f), but only methyl formate decreased to 0.039 mol / mol MMA.

[0044]

[Reference Production Example 2] Palladium was added to 100 parts by weight of silica gel (trade name: Carriact 10) manufactured by Fuji Silysia.
A catalyst carrying 0 parts by weight and 3.18 parts by weight of lead was obtained. The composition ratio of Pd / Pb supported on the obtained catalyst was 3/0.
98, X of (111) plane of palladium / lead intermetallic compound
The line diffraction angle (2θ) was 38.927 degrees, and the intensity ratio of the X-ray photoelectron spectrum of palladium (3d) / lead (4f) was 1 / 0.15.

[0045]

Example 9 In a stirred tank reactor having a liquid phase portion of 6 liters,
1 kg of the catalyst obtained in Reference Production Example 2 and Pd / of the catalyst
Methanol in which lead acetate corresponding to the lead content that is insufficient for setting the Pb supported composition ratio (atomic ratio) to 3 / 1.3 was dissolved was charged, and the outlet oxygen concentration was adjusted at a reaction temperature of 90 ° C. and a reaction pressure of 5 kg / cm ^2. Air was supplied to the reactor while adjusting the amount of air to 2.0% (corresponding to an oxygen partial pressure of 0.10 kg / cm ² ), and the catalyst structure completion treatment was performed for 20 hours. 200 g of this catalyst was charged into a stirred tank reactor having the same capacity as in Example 1, and 36.7 wt% of methacrolein was prepared by dissolving lead acetate in the reactor so that the lead concentration in the feedstock liquid was 20 ppm. / Methanol solution 0.54 l / h
r, NaOH / methanol solution 0.06 liter / h
r continuously supplied, reaction temperature 80 ° C, reaction pressure 5 kg /
The outlet oxygen concentration is 4.0% in cm ² (oxygen partial pressure 0.20 k
Air was supplied to the reactor while the amount of air was adjusted so that it became g / cm ² ) and the catalyst surface structure was controlled for 50 hours. The concentration of NaOH supplied to the reactor was controlled so that the pH of the reaction solution was 7.1. When the obtained catalyst was analyzed, the composition ratio of Pd / Pb supported was 3/1.
10. Palladium / lead intermetallic compound (111) plane X
The line diffraction angle (2θ) was 38.611 degrees, and the intensity ratio of the X-ray photoelectron spectrum of palladium metal (3d) / lead metal (4f) was 0.428. When the reaction product was analyzed by carrying out the reaction for 10 hours under the above surface structure control conditions, the conversion of methacrolein was 63.2%, the selectivity of methyl methacrylate was 91.3%, and the selectivity of propylene was 1. 1%, methyl formate 0.052 mol / mol MMA
Was being generated.

[0046]

Comparative Example 8 The Pd / Pb supported composition ratio of the catalyst which was subjected only to the catalyst structure completion treatment in Example 9 was 3 / 1.27 in atomic ratio,
The X-ray diffraction angle (2θ) of the (111) plane of the palladium / lead intermetallic compound was 38.691 degrees, and the intensity ratio of the X-ray photoelectron spectrum of palladium metal (3d) / lead metal (4f) was 0.763. Met. 200 g of this catalyst was charged into a stirred tank reactor having the same capacity as in Example 1, and the reactor was charged with 36.7 wt% of methacrolein / methanol solution at 0.54 liter / hr and NaOH / methanol solution at 0. 06 liter / hr continuously supplied, reaction temperature 80
℃, reaction pressure 5kg / cm ² outlet oxygen concentration 4.0%
The reaction was performed by supplying air to the reactor while adjusting the amount of air so that the oxygen partial pressure was equivalent to 0.20 kg / cm ² . The concentration of NaOH supplied to the reactor was controlled so that the pH of the reaction solution was 7.1. Further, lead acetate was added to a 36.7 wt% methacrolein / methanol solution supplied to the reactor so that the lead concentration in the feedstock liquid would be 20 ppm. When the reaction product was analyzed after 10 hours, the conversion of methacrolein was 57.2.
%, Methyl methacrylate selectivity was 89.3%, propylene had a selectivity of 2.03% and methyl formate was 0.152 mol / mol MMA as by-products.

[0047]

[Comparative Example 9] 1 kg of the catalyst of Reference Production Example 2 was added to a stirring tank having a liquid phase portion of 6 liters, and the lead content was insufficient to make the Pd / Pb supported composition ratio (atomic ratio) of the catalyst 3 / 1.3. Charge water with the corresponding lead acetate and heat to 90 ° C.
% Formalin aqueous solution formalin / supported palladium = 1
The mixture was added to 0 mol, and the mixture was heated with stirring for 1 hour. The composition ratio of Pd / Pb supported on the obtained catalyst was 3 / 1.27 in atomic ratio, and the palladium / lead intermetallic compound (1
The X-ray diffraction angle (2θ) of the 11) plane was 38.642 degrees, and the intensity ratio of the X-ray photoelectron spectrum of palladium metal (3d) / lead metal (4f) was 0.953.

240 g of this catalyst was placed in an external circulation type stainless steel bubble column reactor equipped with a catalyst separator and having a liquid phase portion of 1.2 liter, and the reaction was carried out. 0.54 liters / hr of a 36.7 wt% methacrolein / methanol solution in which lead acetate was dissolved so that the lead concentration in the feedstock solution was 20 ppm, and NaOH / methanol solution was 0.06 liters / hr continuously Is supplied to the reactor (corresponding to an aldehyde concentration of about 33%), the reaction temperature is 80 ° C., the reaction pressure is 5 kg /
The outlet oxygen concentration is 4.0% in cm ² (oxygen partial pressure 0.20 k
g / cm ² ) MMA while adjusting the air volume so that
When the production reaction was performed and the reaction product was analyzed after 10 hours, the conversion of methacrolein was 56.8.
%, Methyl methacrylate selectivity was 91.2%, propylene had a selectivity of 1.03% and methyl formate was 0.178 mol / mol MMA as by-products.

[0049]

[Example 10] The MMA production reaction of Example 1 was further conducted 50 times.
The reaction product was analyzed for 0 hours. The methacrolein conversion rate, methyl methacrylate selectivity and propylene selectivity were almost unchanged from the 100th hour, while methyl formate was reduced from 0.045 to 0.032 mol / mol MMA. When a part of the catalyst was extracted from the reactor and analyzed, the composition ratio (atomic ratio) supporting Pd / Pb, the X-ray diffraction angle (2θ) of the (111) plane of the palladium / lead compound, and the palladium metal (3d) / The intensity ratio of the X-ray photoelectron spectrum of the lead metal (4f) was almost the same as that at the 100th hour, but the intensity ratio of the X-ray photoelectron spectrum of the palladium metal (3d) / charged lead (4f) was 1 at the 100th hour. /0.1
From the 1st to the 500th hour, it changed greatly to 1/0.
The intensity ratio of the photoelectron spectrum of palladium metal (3d) / charged lead (4f) of the catalyst of Reference Production Example 1 used in Example 1 was 1 / 0.35.

[0050]

[Example 11] Using the catalyst of Example 4, a reaction product was analyzed by performing the reaction under the same operation and reaction conditions as in the MMA forming reaction of Example 9 except that acrolein was reacted instead of methacrolein. However, the acrolein conversion rate is 6
The selectivity was 1.2%, the methyl acrylate selectivity was 91.3%, ethylene was 1.2% as a byproduct, and 0.055 mol / mol MA of methyl formate was produced.

[0051]

INDUSTRIAL APPLICABILITY The supported catalyst of the present invention has a high carboxylic acid ester selectivity when reacting an aldehyde and an alcohol with molecular oxygen to produce a carboxylic acid ester, and reduces the by-product of an ester derived from an alcohol. Moreover, the conversion rate of aldehyde is increased. Therefore, it is possible to provide a highly economical production method of methacrylic acid methyl ester having a high industrial practical value, and it is industrially very useful.

[Brief description of drawings]

FIG. 1 is a spectrum diagram showing an example of an X-ray photoelectron spectrum of Pd (3d).

FIG. 2 is a spectrum diagram showing an X-ray photoelectron spectrum of Pd (4f) and an example of curve fitting.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-55-151533 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B01J 21/00-38/74 C07C 67 / 00-67/62 EUROPAT (QUESTEL) JSTPlus (JOIS) CAplus (STN)

Claims (7)

(57) [Claims] 1. A catalyst for producing a carboxylic acid ester from an aldehyde, an alcohol, and molecular oxygen, which is a supported catalyst containing palladium and lead and satisfying the following (1) to (3). (1) The supported composition ratio of palladium / lead is 3/0.
7 to 3 / 1.3, (2) X of (111) plane of palladium / lead intermetallic compound
Line diffraction angle (2θ) is 38.55 to 38.70, (3) Palladium metal (3d (3/2) +3) as a supported catalyst.
d (5/2)) / lead metal (4f (7/2) × 1.75)
X-ray photoelectron spectrum intensity ratio of 1 / 0.2 to 1/0.
7, 2. The loading composition ratio of palladium / lead is atomic ratio.
It is 3 / 0.9-3 / 1.1, It is characterized by the above-mentioned.
1. The supported catalyst according to 1. 3. Palladium metal (3d (3 /
2) + 3d (5/2)) / lead metal (4f (7/2) ×
1.75) X-ray photoelectron spectrum intensity ratio is 1 / 0.3
~ 1 / 0.6, claim 1 or 2 characterized in that
Loaded supported catalyst. 4. Palladium metal (3d (3 /
2) + 3d (5/2)) / charged lead (4f (7/2)
+ 4f (5/2)) X-ray photoelectron spectrum intensity ratio is 1
It is /0/1/0.2, It is characterized by the above-mentioned.
2. The supported catalyst according to 2. 5. An alkali metal or alkaline earth metal is added to
The content of 01 to 30% by weight.
Loaded supported catalyst. 6. A method for producing a carboxylic acid ester by reacting an aldehyde with an alcohol and molecular oxygen, wherein the aldehyde is reacted with the alcohol and the molecular oxygen in the presence of the supported catalyst according to claim 1. A method for producing a carboxylic acid ester, which comprises reacting. 7. The method for producing a carboxylic acid ester according to claim 6 , wherein the aldehyde is methacrolein, acrolein or a mixture thereof, and the alcohol is methanol.