JP3532668B2 - High Purity and High Quality Method for Carboxylic Acid Ester Production Catalyst - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for activating a catalyst used in producing a carboxylic acid ester from an aldehyde, an alcohol and molecular oxygen.

[0002]

2. Description of the Related Art As a method for producing industrially useful methyl methacrylate (hereinafter abbreviated as MMA) or methyl acrylate, a direct acid method for producing methacrylic acid from methacrolein and further converting it to MMA is known. The so-called manufacturing method has already been industrialized. However, although the yield of the process of oxidizing methacrolein to methacrylic acid has been improved to the lower 80% level due to many years of catalyst improvement, it is still low and there is much room for improvement. Further, the heteropolyacid catalyst to be used originally has a disadvantage in thermal stability, and the decomposition gradually proceeds under the reaction temperature condition. Although improvements in catalysts for improving heat resistance have been reported, it is said that the catalyst life is still insufficient as an industrial catalyst.

On the other hand, a new route for producing methyl methacrylate or methyl acrylate by reacting methacrolein or acrolein with methanol and molecular oxygen has recently been in the spotlight. The reaction is carried out by reacting methacrolein or acrolein with molecular oxygen in methanol, and the presence of a catalyst containing palladium is essential.

Heretofore, in this production method, hydrocarbons and carbon dioxide gas have been generated due to the decomposition reaction of aldehydes, and the yield of the desired carboxylic acid ester has been low. Heterogeneous aldehydes due to their own oxidation and heterogeneous carboxylate esters (eg, methyl formate when using methanol as alcohol, and ethyl acetate when using ethanol as alcohol) were poor in selectivity on the basis of alcohol. . In addition, there is a disadvantage that the catalyst activity cannot be maintained for a long time. In particular, when α / β-unsaturated aldehydes such as methacrolein and acrolein, which have high industrial practical value, are used as starting materials, a large amount of carbon dioxide or olefin ( Decomposition products such as propylene in the case of methacrolein) were generated, which was far from practical use.

The present inventors have disclosed JP-B-57-35856,
JP-B-57-35857 and JP-B-57-35859 propose catalyst systems containing palladium and lead, and significantly improve the selectivity to the methyl ester based on methacrolein or acrolein by 90%. However, the reaction temperature was up to 50 ° C. at most. Subsequently, Japanese Patent Publication No. 62-7902 proposes a catalyst containing an intermetallic compound in which palladium and lead are combined at a simple integer ratio, whereby the decomposition reaction of methacrolein or acrolein is almost completely inhibited, and the catalytic activity is also reduced. It has been shown that the catalyst system is not lost for a long time. As described above, the new production method using these new catalyst systems has the advantage that the process is shorter than the direct acid method, which has a feeling that the yield improvement and catalyst life improvement have reached a plateau. 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 practice, the MMA selectivity of the catalyst system decreases and methyl formate due to oxidation of the alcohol itself is reduced. The amount of by-products increases rapidly. That is, Japanese Patent Publication No. 62-7902 discloses that a high MMA selectivity exceeding 90% is obtained, and that methyl formate is formed only in a small amount of 0.03 to 0.06 mol / mol MMA. These were carried out under mild conditions with an aldehyde concentration of 10% or less and a reaction temperature of 40 to 60 ° C. Under these conditions, the amount of unreacted methanol recycled is large due to the low concentration of MMA generated, and as a result, the amount of steam used increases and the economic efficiency deteriorates. Moreover, the productivity is low and the reactor is large. To improve the economy, it is desirable to increase the aldehyde concentration and the reaction temperature as much as possible. Japanese Patent Publication No. 5-69813 discloses a reaction example at a methacrolein concentration of 20% and a reaction temperature of 80 ° C. However, under such high methacrolein concentration and high reaction temperature conditions, a high MMA selectivity exceeding 90% cannot be obtained. Moreover, methyl formate doubles to 0.0923 mol / mol MMA. Further, when the concentration of methacrolein is increased to 30% and the conditions are more severe, the decomposition reaction of the aldehyde is likely to occur and the MMA
It has been found that the selectivity of the compound worsens.

[0007] In order to improve economical efficiency, a catalyst system having a high MMA selectivity of more than 90% at a high temperature and a high aldehyde concentration and having a low by-product of methyl formate has been expected.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a method for producing a carboxylic acid ester by reacting an aldehyde and an alcohol with a catalyst containing palladium and lead. An object of the present invention is to provide an activation method for obtaining a catalyst having a high selectivity for a carboxylic acid ester and a small amount of by-products derived from alcohol such as methyl formate even under conditions.

[0009]

In view of such circumstances, 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 by-products such as methyl formate. The present inventors have intensively studied the catalyst system including the catalyst and completed the present invention. That is, the present invention is as follows. 1. Palladium and lead-containing supported catalyst for carboxylic acid ester prepared from aldehydes and alcohol and molecular oxygen, carrying the composition ratio of the palladium / lead atomic ratio Palladium
A method for producing a carboxylate ester-producing catalyst having high purity and high quality, comprising treating a catalyst containing 2.5 or more lead with a lower fatty acid in the case where the number of atoms is 3 atoms . 2. The palladium / lead supported composition ratio of the highly pure and high-grade supported palladium / lead containing catalyst has an atomic ratio of palladium.
When the number of atoms is 3, the lead is 0.7 to 1.3 , and the X-ray diffraction angle (2θ) of the (111) plane of the palladium-lead intermetallic compound is 38.55 to 38.70. A method for increasing the purity and quality of the carboxylic acid ester production catalyst according to claim 1. 3. 2. The carboxylic acid ester production catalyst according to claim 1, wherein the aldehyde is methacrolein, acrolein or a mixture thereof, and the alcohol is methanol.
High quality method.

Hereinafter, the present invention will be described in detail. The present inventors have focused on Pd ₃ Pb ₁ having an atomic ratio of 3/1, which is an intermetallic compound in which palladium and lead are combined at a simple integer ratio, proposed in Japanese Patent Publication No. 62-7902, _Three
More detailed research was conducted on the production of a supported catalyst having Pb ₁ supported thereon. As a result, the supported catalyst containing palladium and lead obtained by the preparation method described in Japanese Patent Publication No. 62-7902 has a low purity even though it contains a Pd ₃ Pb ₁ intermetallic compound as a catalyst species, and has a low palladium-lead intermetallic compound. It was clarified that the catalyst had many defects and the like in the crystal lattice. In particular, a catalyst in which the supported amount of lead is adjusted at an atomic ratio of 3/1, which is the stoichiometric composition of palladium / lead of the Pd ₃ Pb ₁ intermetallic compound, has a further increase in crystal lattice defects, and is economically advantageous. Under the conditions of high temperature and high aldehyde concentration,
The present inventors have also clarified that the MMA selectivity is rather low.

As a result of further research, it was found that the Japanese Patent Publication No. Sho 62-7
In the ordinary preparation method described in JP-A-902, a high-purity, high-grade Pd ₃ Pb ₁ intermetallic compound-supported catalyst cannot be obtained, and the supported palladium / lead composition proposed in the present invention When the atomic ratio is 3 atoms of palladium
By treating a palladium / lead-containing supported catalyst with 2.5 or more lead with a lower fatty acid, a supported catalyst containing a high-grade Pd ₃ Pb ₁ intermetallic compound with a high purity with few defects in the crystal lattice can be obtained. I found that. It was also revealed that the obtained catalyst exhibited high MMA selectivity even under severe reaction conditions such as the above-mentioned high aldehyde concentration and high reaction temperature.

When the palladium / lead carrying composition ratio (atomic ratio) to be subjected to a high-purity / high-quality method (hereinafter referred to as activation) is 2.5 or more when palladium is 3 atoms.
The palladium / lead-containing supported catalyst can be prepared by a known preparation method. A typical catalyst preparation method will be described. A carrier is added to an aqueous solution containing a soluble lead compound and a soluble palladium salt such as palladium chloride, and the mixture is heated and impregnated to impregnate palladium and lead. Next, reduction is carried out with formalin, formic acid, hydrazine or hydrogen gas. Lead may be loaded before loading palladium, and various production methods are possible, such as loading palladium and lead simultaneously as described above.

[0013] In addition to palladium and lead as a catalyst component, other elements such as mercury, thallium, bismuth, tellurium, nickel, chromium, cobalt, indium, tantalum, copper, zinc, zirconium, hafnium, tungsten, manganese, silver, rhenium , Antimony, tin, rhodium, ruthenium, iridium, platinum, gold, titanium, aluminum, boron, silicon, and the like. These different elements can usually be contained in an amount not exceeding 5% by weight, preferably not exceeding 1% by weight. Further, those containing at least one member selected from an alkali metal compound and an alkaline earth metal compound have the advantage that the reaction activity is high. Alkali metal and alkaline earth metal are usually 0.1.
It is selected from the range of 01 to 30% by weight, preferably 0.01 to 5% by weight. These different elements, such as alkali metal and alkaline earth metal compounds, may intrude in a small amount between crystal lattices, 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 preparing the catalyst and adsorbed or adhered to a carrier, or a carrier pre-loaded with these may be used. A catalyst can also be prepared. It is also possible to add to the reaction system under the reaction conditions.

The palladium compound or lead compound used for the preparation of the catalyst includes, for example, organic acid salts such as formate and acetate, inorganic acid salts such as sulfate, hydrochloride and nitrate, and organic salts such as ammine complex and benzonitrile complex. Metal complexes,
It is appropriately selected from oxides and hydroxides, but palladium compounds and palladium acetate are preferable as the palladium compound, and lead nitrate and lead acetate are preferable as the lead compound. 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 carried 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 carried is not particularly limited, and is usually 0.1 to 20% by weight, and preferably 1 to 10% by weight, based on the weight of the carrier. The ratio (atomic ratio) is important.

That is, when the supported composition ratio of palladium / lead is 3 atoms of palladium in atomic ratio, lead is more than 2.5.
A catalyst having a lead content is an object of the activation of the present invention. Preferably, when palladium is 3 atoms, lead is 2.5 to 1
0, more preferably 2.5-5 . These are low-purity catalysts containing particularly high amounts of lead impurities. Hereinafter, the method of activating the supported palladium / lead-containing catalyst of the present invention will be described.

In the activation, the supported composition ratio (atomic ratio) of palladium / lead prepared by a known preparation method is changed from palladium to 3 atoms.
In this case, the palladium / lead-supported catalyst in which lead has a lead carrying amount of more than 2.5 is treated with a lower fatty acid in a simple method. Specifically, for example, as illustrated in Example 1, a catalyst to be activated is dispersed in an aqueous solution containing 10% by weight of acetic acid, and the mixture is heated while stirring.

The lower fatty acid used in the present invention is selected from formic acid, acetic acid, propionic acid, butyric acid, maleic acid, methacrylic acid and the like. Acetic acid is industrially preferred because it is easily available. These lower fatty acids are preferably used as a 0.1 to 20% by weight aqueous solution or methanol solution. More preferably, it is 1 to 15% by weight. As long as the solvent is inert and stable to the catalyst, a solvent other than water and methanol can be selected, but it is simple to use as an aqueous solution. When the activation is performed using an inorganic acid such as a mineral acid or sulfuric acid or an acid such as paratoluenesulfonic acid, good catalytic performance cannot be obtained. It is preferred to use the above lower fatty acids in a concentration not exceeding 20% by weight.

The activation treatment may be carried out while continuously supplying the lower fatty acid to the reactor, or the lower fatty acid may be charged and treated together with a catalyst. For this reason, the amount of the lower fatty acid to be used is not uniquely determined, but as a guide, it is preferable to use the lower fatty acid in a range of 10 to 1000 times mol based on the amount of the supported palladium. The activation treatment temperature is preferably from room temperature to 200 ° C, more preferably from 40 to 160 ° C.

The activation treatment time varies depending on the treatment type, treatment temperature, and catalyst type, and thus cannot be determined. If the treatment time is too long, the catalyst performance may decrease. Usually, it is preferably selected from the range of 0.1 to 100 hours, more preferably from 0.5 to 20 hours. The activation treatment operation is performed by dispersing the catalyst in a slurry state using a stirring tank, a bubble tower, or the like. In this case, the catalyst concentration in the liquid is usually 0.04 to 0.5 kg per liter. Alternatively, the catalyst may be filled in a fixed bed and a solution containing a lower fatty acid may be allowed to flow.

[0021] The palladium / lead-bearing composition ratio (atomic ratio) path
When the amount of lead is 3 atoms, the amount of lead supported on the lead is 2.5 or more . Particularly, the palladium / lead supported catalyst of low purity is unexpectedly activated by the very simple activation treatment of the present invention. Composition ratio is 3 atoms of palladium in atomic ratio
When the lead is 0.7 to 1.3 and the X-ray diffraction angle (2) of the (111) plane of the palladium-lead intermetallic compound is
θ) is 38.55 to 38.70, and is a high-grade, high-purity supported catalyst composed of a high-grade Pd ₃ Pd ₁ compound with few lattice defects. More preferably, palladium metal (3d (3/2) + 3d (5/2)) / lead metal (4f
When the intensity ratio of the X-ray photoelectron spectrum of (7/2) × 1.75) is 1 for the palladium intensity, the lead intensity is 0.2 to 0.5.
7 range. When the catalyst is less than 38.55, the yield on the basis of alcohol is remarkably reduced, for example, the production of methyl formate increases, and when it exceeds 38.70, the decomposition of aldehyde becomes remarkable, and the yield on the basis of aldehyde is reduced. On the other hand, when the amount of supported lead exceeds 1.3 in terms of atomic ratio, formation of methyl formate becomes remarkable, and when it is less than 0.7, MMA selectivity is greatly reduced due to decomposition of aldehyde. The catalyst obtained by the activation method of the present invention has improved yields based on aldehyde and alcohol.

According to the method of the present invention, when the supported composition ratio (atomic ratio) of palladium / lead is 3 palladium atoms,
A catalyst whose lead is close to 0.7-1.3 and 3/1, and
This has made it possible to obtain a supported catalyst containing Pd ₃ Pb ₁ having a high purity without lattice defects. In principle, the amount of lead supported on the catalyst should be as small as possible in a palladium / lead supporting composition ratio (atomic ratio) of 3/1.
Can be obtained. According to a known production method, the palladium / lead supporting composition ratio (atomic ratio) is 3 /
Catalysts prepared with compositions close to 1 had low MMA selectivity. According to the method of the present invention, it has become possible to activate a catalyst having a palladium / lead carrying composition ratio (atomic ratio) of 3/1, which has heretofore been impossible. Not only the MMA selectivity is improved, but also a catalyst with very little by-product derived from alcohols such as methyl formate is obtained. In addition, a catalyst that does not cause lead to flow out into process wastewater because the catalyst contains few impurities including lead. This is advantageous in that it does not require a treatment cost for detoxifying lead in wastewater, and is extremely important when industrially implemented.

The palladium obtained by the activation method of the present invention
The lead-containing supported catalyst can be suitably used for a reaction for producing a carboxylic acid ester by reacting an aldehyde with an alcohol and molecular oxygen. The amount of the catalyst used can be largely changed depending on the type of the reaction raw materials, the composition and preparation method of the catalyst, the reaction conditions, the reaction type, etc., and is not particularly limited.When the catalyst is reacted in a slurry state, Reaction liquid 1
It is preferable to use 0.04 to 0.5 kg per liter.

Next, a method for producing a carboxylic acid ester in which the catalyst obtained by the activation method of the present invention is suitably used will be described. As the aldehyde used in the production of the carboxylic acid ester, for example, formaldehyde, acetaldehyde, propionaldehyde, isobutyraldehyde, aliphatic saturated aldehyde such as glyoxal,
Examples include aliphatic α-β-unsaturated aldehydes such as acrolein, methacrolein, and crotonaldehyde, aromatic aldehydes such as benzaldehyde, tolylaldehyde, benzylaldehyde, and 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 includes, for example, aliphatic saturated alcohols such as methanol, ethanol, isopropanol and octanol, diols such as ethylene glycol and butanediol, and aliphatic alcohols such as allyl alcohol and methallyl alcohol. And aromatic alcohols such as unsaturated alcohols and benzyl alcohol. These alcohols can be used alone or as a mixture of two or more kinds.

There is no particular limitation on the ratio of the aldehyde and the alcohol used in the production of the carboxylic acid ester.
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 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 performing in the liquid phase, a bubble column reactor, a draft tube reactor,
Any reactor type, such as a stirred tank reactor, can be used.

The oxygen used in the carboxylic acid ester production reaction 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 gas. And air can also be used. When the present reaction is continuously performed, the deterioration of the catalyst can be suppressed by performing the reaction while adding a substance containing lead to the reactor. At this time, by setting the oxygen partial pressure at the reactor outlet side to 0.8 kg / cm ² or less, the lead concentration in the raw material liquid supplied to the reactor can be reduced to suppress the deterioration of the catalyst. The amount of lead added and the oxygen partial pressure at the reactor outlet are difficult to determine to specific values depending on the reaction raw materials such as aldehyde species and alcohol species to be reacted, reaction conditions or reactor type, etc. Determined and supplied to the reactor to determine the supported palladium / lead composition ratio (atomic ratio)
Is 0.7 to 1.3 when palladium has 3 atoms.
The X-ray diffraction angle (2θ) of the (111) plane of the palladium-lead intermetallic compound is 38.55 to 38.70, and the palladium metal (3d (3/2) + 3d (5/2)) / lead metal ( 4
f (7/2) × 1.75) When the intensity ratio of the X-ray photoelectron spectrum is palladium intensity 1, the lead intensity is 0.2 to
0.7 and the state of the catalyst of the present invention can be stably maintained during the reaction. If the amount of lead to be added is large, the treatment cost for detoxifying the lead in the wastewater becomes high, and the amount of methyl formate, a by-product of the reaction, is not preferable. Partial pressure is 0.4 kg / cm ²
It is preferable to reduce the amount of lead supplied as follows. More preferably, the pressure can be reduced to 0.2 kg / cm ² or less. However, if the oxygen required for the reaction is not secured, oxygen becomes insufficient and the conversion of the raw material aldehyde is reduced, and undesired by-products are formed. You can choose within the range that is not.

The reaction can be carried out in a wide range of pressure from reduced pressure to increased pressure.
It is performed at a pressure of kg / cm ² . The total pressure may be set so that the oxygen concentration of the gas discharged from the reactor does not exceed the explosion range (8%). In the reaction of the present invention, a compound of an alkali metal or an alkaline earth metal (eg, oxide, hydroxide, carbonate, carboxylate, etc.) is added to the reaction system to maintain the pH of the reaction system at 6 to 9. Is preferred. Especially pH 6
This has the effect of preventing the 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.

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

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to Examples and Comparative Examples. The pressure used in the examples and the like is expressed as an absolute pressure and is shown in kg / cm ² . <Measurement of X-ray Diffraction Angle of (111) Plane of Pd / Pb Compound> The measurement was carried out using RAD-RA manufactured by Rigaku according to the usual measurement procedure of powder X-ray diffraction, and CuKα1 line (1.540598) was used.
Using 1), the diffraction angle 2θ of the (111) plane of the supported catalyst palladium-lead intermetallic compound was measured. The measurement must be performed with particularly high precision. For example, National Institute of
The (111) plane and the (200) plane of the LaB ₆ compound determined by Standards & Technology as the standard reference substance 660 were measured, and the respective values were 37.441 and 43.506.
It is standardized so that As a result, a result with high measurement accuracy and good reproducibility can be obtained. The catalyst is evacuated at 160 ° C. and treated for 3 hours to remove low molecular adsorbed / occluded components and then measured. <Measurement of X-ray photoelectron spectrum> The measurement was performed using ESCA LAB-200-X manufactured by VG. As shown in FIG. 2, after the peak separation process, the area of each peak was determined, and the palladium metal (3d (3/2) +3
d (5/2)) / lead metal (4f (7/2) × 1.75)
Area ratio and palladium metal (3d (3/2) + 3d
(5/2)) / charged lead (4f (7/2) + 4f (5
/ 2)) was determined, and this was defined as the peak intensity ratio.
1 and 2 show palladium (3d) and lead (4f), respectively.
An example of the measurement will be shown. <Pd, Pb elemental analysis> The palladium / lead-containing supported catalyst was heat-treated with aqua regia to completely extract the palladium and lead components, and the measurement was performed using Shimadzu A
The measurement was performed using an A-6400F type atomic absorption spectrophotometer. <Reference Production Example 1> Aluminum nitrate and magnesium nitrate were added to Snowtex N-30 (trade name: SiO _{2 for} Nissan Chemical Co., Ltd .: 30% by weight) as an aqueous silica sol solution, respectively, with Al / Si +
After adding and dissolving Al = 10 mol% and Mg / Si + Mg = 10 mol%, a spherical carrier having an average particle size of 60 μm was obtained by spray drying with a spray dryer set at a temperature of 130 ° C. After calcination at 300 ° C. and then at 600 ° C., palladium chloride and lead nitrate were used as carriers for each of palladium and 100 parts by weight of the carrier.
After being supported to 9.7 parts by weight, the catalyst was reduced with hydrazine to form a catalyst ( Pd _5.0 Pb _9.7 / Mg, Al-Si
Expressed as O ₂ . ) Got. The Pd /
The composition ratio of Pb is determined when the atomic ratio is 3 palladium atoms.
In this case, the lead is 2.98 and is expressed as 3 / 2.98, and the X-ray diffraction angle of the (111) plane of the palladium-lead intermetallic compound (2
θ) is 38.685 degrees, and the intensity ratio of the X-ray photoelectron spectrum of palladium (3d) / lead (4f) is palladium.
When the strength is 1, the lead strength is 1.94, and 1 / 1.94.
Was expressed.

[0031]

Example 1 2 kg of the catalyst of Reference Production Example 1 was charged into a 30 liter autoclave, and water containing 10% by weight of acetic acid was added to 1 autoclave.
0 liter / hr. 80 ° C while mixing and stirring catalyst
And activated for 15 hours. The resulting catalyst had a Pd / Pb carrying composition ratio (atomic ratio) of 3 palladium.
In the case of a palladium, the lead is 1.03 , and the X-ray diffraction angle (2θ) of the (111) plane of the palladium-lead intermetallic compound is 38.67.
8 degrees. Also, the intensity ratio of the X-ray photoelectron spectrum of palladium (3d) / lead (4f) is such that the palladium intensity is 1
In this case, the lead strength was 0.234 .

After the activation treatment, 240 g of the catalyst was charged into an externally circulating stainless steel bubble column reactor having a catalyst separator provided with a catalyst and having a liquid phase of 1.2 liters, and a reaction was carried out. In a reactor, 0.54 l / hr of a 36.7% by weight methacrolein / methanol solution in which lead acetate was dissolved so that the lead concentration in the feedstock solution became 50 ppm, and 0.06 l / hr of a NaOH / methanol solution were dissolved. hr was continuously supplied to the reactor (corresponding to an aldehyde concentration of about 33%), and the reaction temperature was set at 80.
At a reaction pressure of 5 kg / cm ² and an outlet oxygen concentration of 4.0%
The MMA generation reaction was performed while adjusting the amount of air so as to obtain an oxygen partial pressure of 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. When the reaction product was analyzed after 10 hours, the conversion of methacrolein was 6%.
1.1%, the selectivity of methyl methacrylate was 89.7%, and propylene was formed as a by-product at a selectivity of 2.5% and methyl formate was formed at 0.032 mol / mol MMA.

[0033]

Comparative Example 1 An activation treatment was carried out in exactly the same manner as in Example 1 except that the catalyst of Reference Production Example 1 was activated with a 5% by weight aqueous hydrochloric acid solution. The obtained catalyst had a Pd / Pb carrying composition ratio (atomic ratio) of 0.3% for lead when palladium was 3 atoms.
74 , X of (111) plane of palladium-lead intermetallic compound
The line diffraction angle (2θ) was 38.743 degrees. Further, the intensity ratio of the X-ray photoelectron spectrum of palladium (3d) / lead (4f) is such that the lead intensity is 0.1 when the palladium intensity is 1.
85 . This catalyst was subjected to an MMA formation reaction under exactly the same conditions as in Example 1, and the reaction product was analyzed 10 hours after the start of the reaction. The conversion of methacrolein was 56.8% and the selectivity of methyl methacrylate was 86.
Propylene as a by-product with a selectivity of 4.8%,
Methyl formate was produced at 0.043 mol / mol MMA. <Reference Production Example 2> 5.0 parts by weight of palladium was supported on silica gel (Carrierct 10) manufactured by Fuji Silysia Ltd. using a palladium ammine complex, and then 11.5 parts by weight of lead and 0.11 part by weight of thallium were continuously used. The catalyst before activation by supporting and reducing with formalin ( Pd _5.0 Pb _11.5 Tl _0.11 / SiO ₂
Notation. ) Got. The supported composition ratio (atomic ratio) of Pd / Pb of the obtained catalyst was as follows when palladium was 3 atoms.
3.54 lead and palladium-lead intermetallic compound (11
1) The X-ray diffraction angle (2θ) of the surface was 38.688 degrees. In addition, the intensity ratio of the X-ray photoelectron spectrum of palladium (3d) / lead (4f) is as follows:
The strength was 1.21 .

[0034]

Examples 2 to 6 The catalyst of Reference Production Example 2 was activated with various fatty acids shown in Table 1 instead of the acetic acid of Example 1.
~ 6 catalysts were obtained. The Pd / Pb carrying composition ratio (atomic ratio) of the obtained catalyst and the palladium-lead intermetallic compound (11
1) X-ray diffraction angle (2θ) of plane, palladium metal (3d)
Table 1 summarizes the intensity ratio of the X-ray photoelectron spectrum of the lead metal (4f) and the results of the reaction products. For comparison, the reaction was carried out under exactly the same conditions as in Example 1. XPS column in Table 1
Indicates the intensity of Pb, where the intensity of Pd is defined as 1.
You.

[0035]

[Table 1]

[0036]

Example 7 Pd _5.0 Pb _8.6 Bi _0.23 K
_2.0 / Al ₂ O ₃ (Pd / Pb loading composition ratio is atomic ratio.
The activation treatment similar to that in Example 1 was performed on the supported catalyst before activation having a composition of 2.65 ) of lead when palladium was 3 atoms . The Pd / Pb carrying composition ratio of the obtained catalyst was such that when the atomic ratio of palladium was 3 atoms, the amount of lead was 0.1% .
98 , X of (111) plane of palladium-lead intermetallic compound
The line diffraction angle (2θ) was 38.691 degrees. Further, the intensity ratio of the X-ray photoelectron spectrum of palladium (3d) / lead (4f) is 0.2 assuming that the palladium strength is 1.
32 .

In a stirred tank reactor having the same capacity as in Example 1, 200 g of the activated catalyst was charged, and lead acetate was dissolved in the reactor so that the lead concentration in the feed solution became 50 ppm. 36.7 wt% of acrolein / methanol solution 0.54 liters / hr, NaOH / methanol solution was fed to the 0.06 l / hr continuously, the outlet oxygen concentration at a reaction temperature of 80 ° C., a reaction pressure 5 kg / cm ² Was adjusted to 4.0% (corresponding to an oxygen partial pressure of 0.20 kg / cm ² ) while supplying air to the reactor while adjusting the amount of air to perform a methyl acrylate formation reaction. The pH of the reaction solution was 7.
The NaOH concentration supplied to the reactor was controlled so as to be 1. When the reaction product was analyzed after 10 hours, the conversion of acrolein was 58.3%, the selectivity for methyl acrylate was 88.8%, the selectivity for ethylene was 2.6%, and the formate was methyl formate. 0.035 mol / mol MMA was produced.

[0038]

Example 8 The same activation operation as in Example 1 was carried out except that the activation treatment time for 2 kg of the catalyst of Reference Production Example 1 was changed to 30 hours. The Pd / Pb carrying composition ratio (atomic ratio) of the obtained catalyst was 0.9 % for lead when palladium was 3 atoms.
5. The X-ray diffraction angle (2θ) of the (111) plane of the palladium / lead compound was 38.682 degrees. As for the intensity ratio of the X-ray photoelectron spectrum of palladium (3d) / lead (4f), when the palladium intensity was 1, the lead intensity was 0.183 .

An MMA generation reaction was carried out in the same manner as in Example 1 using 240 g of the catalyst after the activation treatment. When the reaction product was analyzed after 10 hours, the conversion of methacrolein was 57.3%, the selectivity of methyl methacrylate was 87.9%, the selectivity of propylene as a by-product was 3.1%, and the selectivity of formic acid was 3.1%. Methyl was produced at 0.031 mol / mol MMA.

[0040]

According to the activating method of the present invention, an aldehyde and an alcohol are reacted with molecular oxygen to produce a carboxylic acid ester. This also makes it possible to provide a catalyst which simultaneously improves the yield on aldehyde and alcohol basis.

[Brief description of the 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 Pb (4f) and a result of curve fitting.

[Explanation of symbols]

1 Pb4f _7/2 (Pb ⁰ ) 2 Pb 4f _5/2 (Pb ⁰ ) 3 Pb 4f _7/2 (Pb _OX ) 4 Pb 4f _5/2 (Pb _OX ) 5 X-ray satellite of Si2s (MgKα ₃ ) 6 X of Si2s Wire satellite (MgKα ₄ )

Continuation of the front page (58) Fields investigated (Int. Cl. ⁷ , DB name) B01J 21/00-38/74 C07C 67/00-67/62 JSPlus (JOIS) CAplus (STN)

Claims (3)

(57) [Claims] A palladium / lead-containing supported catalyst for producing a carboxylic acid ester from an aldehyde, an alcohol and molecular oxygen, wherein the supported composition ratio of palladium / lead is an atomic ratio.
A method for producing a catalyst for producing a carboxylic acid ester having high purity and high quality, comprising treating a catalyst containing 2.5 or more lead with a lower fatty acid when palladium has 3 atoms . 2. A carrier composition ratio of palladium / lead of the high-purity, high-definition palladium-lead-containing supported catalyst the atomic ratio
When palladium is 3 atoms, the lead is 0.7 to 1.3 , and the X of the (111) plane of the palladium-lead intermetallic compound is
The method for producing a carboxylate ester production catalyst according to claim 1, wherein the line diffraction angle (2θ) is 38.55 to 38.70. 3. The method of claim 1, wherein the aldehyde is methacrolein, acrolein or a mixture thereof, and the alcohol is methanol.