JP3498102B2 - Catalyst for carboxylic acid ester production with excellent strength - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a palladium-containing catalyst used for producing a carboxylic acid ester from an aldehyde and an alcohol and a method for producing the carboxylic acid ester.

[0002]

2. Description of the Related Art An industrially useful method for producing methyl methacrylate or methyl acrylate is an oxidative esterification method for directly producing methyl methacrylate or methyl acrylate by reacting methacrolein or acrolein with methanol. Proposed. This method is carried out by reacting methacrolein or acrolein with molecular oxygen in methanol, and the presence of a catalyst containing palladium is essential.

Palladium, which is a kind of noble metal, is expensive, and when it is used as a catalyst component, it is usually supported and dispersed on a carrier, and in that case, the selection of the carrier is extremely important. Japanese public Sho 57-35856, the same 5
7-35857, 57-35858, 57-3
No. 5859, No. 57-35860, the method of producing a carboxylic acid ester by reacting an aldehyde and an alcohol with a catalyst containing palladium in the presence of oxygen, activated carbon, silica, alumina, carbonic acid. Calcium and the like are exemplified as the catalyst carrier.

However, these catalysts are not necessarily satisfactory from the viewpoint of catalyst life as a result of studying palladium catalysts supported on these carriers on the premise of practical application as an industrial process. Became clear. That is, when it is assumed that the catalyst is reacted in a slurry state in a stirred tank reactor or a bubble column reactor which is often used industrially, activated carbon has insufficient mechanical strength. In addition, although alumina has high mechanical strength, the strength of the carrier decreases due to corrosion by an acidic substance represented by methacrylic acid or acrylic acid, which is a by-product unique to this reaction, and as a result, the expensive palladium component peels off. It has the fatal drawback of being easy. Calcium carbonate is more apt to be corroded by acidic substances than alumina and is not suitable for industrial use. On the other hand, with respect to silica, a part of the silica is gradually eroded by the water brought along with the process or the water by-produced in the reaction, and the silica as the carrier is eluted. For this reason, there is concern about stable long-term use. Further, it has lower mechanical strength than the above-mentioned alumina. As described above, a catalyst which has high mechanical strength, is physically stable, is resistant to corrosion by an acidic substance and water, and is chemically stable has not been proposed so far.

On the other hand, silica-magnesium, silica-alumina and the like are known as solid acid catalysts containing magnesium or aluminum. However, when these were used as carriers, it was considered to be unsuitable as a carrier for this reaction because by-products such as acetal are produced due to their acid nature. Therefore, in order to improve the mechanical strength and the corrosion resistance, which are the drawbacks of silica, which is almost neutral as a carrier, a study on a method for producing silica gel and a study on modification of silica gel by high temperature firing and the like have been reported.

However, no example has been found in which the mechanical strength and hydrolysis stability were successfully improved without impairing the original performance of the catalyst. For example, it is known that quartz, which is one of silica-based substances, is hard and has high mechanical strength and corrosion resistance. However, although the mechanical strength and corrosion resistance have been dramatically improved, the specific surface area has decreased (1 m ² / g
The following is caused, and since the metal catalyst cannot be supported in the form of fine particles in a highly dispersed state, the reaction activity of the catalyst obtained when quartz is used as a carrier is extremely low, and it is not possible to use it as a catalyst carrier. Therefore, assuming the use as a catalyst carrier, it is necessary to maintain a high specific surface area to some extent, and yet to satisfy the mechanical strength and the corrosion resistance to the liquid property inherent in this reaction. Not previously known.

[0007]

DISCLOSURE OF THE INVENTION The present invention is used for producing a carboxylic acid ester from an aldehyde and an alcohol in the presence of oxygen, has a high specific surface area and is excellent in mechanical strength and corrosion resistance, and It is intended to provide a palladium-containing supported catalyst which is stable for a long period of time and a method for producing a carboxylic acid ester using the supported catalyst.

[0008]

DISCLOSURE OF THE INVENTION In order to improve the mechanical strength and corrosion resistance of silica gel, the present inventors have focused on the unique structure of the silica chain (-Si-O-) constituting silica gel. Then, we conducted intensive research on the correlation between these structures and physical properties. As a result, surprisingly, the carrier in which silica, alumina, and magnesia are combined in a certain specific ratio overcomes the drawbacks observed in the case of silica alone and alumina alone, and satisfies the above-mentioned problems aimed at by the present invention. I found a thing.

That is, the present invention is as follows. 1. In a palladium-containing supported catalyst used for the production of a carboxylic acid ester in which an aldehyde is reacted with an alcohol in the presence of oxygen, aluminum is used as Al ₂ O ₃
A catalyst for the production of carboxylic acid ester, characterized by using as a carrier silica-alumina-magnesia containing -40 to 40% by weight, magnesium in the range of 3 to 30% by weight as MgO and silicon in the range of 50 to 92% by weight as SiO _2. . 2. A method for producing a carboxylic acid ester using the catalyst for producing a carboxylic acid ester according to the above 1 in the production of a carboxylic acid ester in which an aldehyde is reacted with an alcohol in the presence of oxygen. 3. The aldehyde is acrolein or methacrolein,
The method for producing a carboxylic acid ester according to the above 2, wherein the alcohol is methanol.

In the present invention, aluminum is Al ₂ O _{3 in an amount} of 5 to 40% by weight, and magnesium is MgO in an amount of _{3 to 3} %.
It is important to use silica-alumina-magnesia containing 0% by weight and silicon in the range of 50 to 92% by weight as SiO ₂ as a carrier for a palladium-supported catalyst for producing a carboxylic acid ester from an aldehyde and an alcohol.

It is insufficient to analyze whether the corrosion resistance such as the acid resistance and the water resistance is improved and the mechanical strength is improved by any reason. However, according to the inference by the present inventors,
By adding aluminum (Al) to the uncrosslinked silica (Si-O) chain of silica gel, Si-O-Al-O-
A new Si bond is formed, the stability of the Si-O chain to the original acidic substance is not lost, and the Al cross-linked structure is formed to strengthen the Si-O bond and dramatically improve the hydrolysis resistance stability. It is supposed to do. Also, Si
It is considered that when the -O-Al-O-Si crosslinked structure is formed, the number of Si-O uncrosslinked chains is reduced and the mechanical strength is greatly improved as compared with the case of silica gel alone. That is, S
It is presumed that the amount of the i-O-Al-O-Si crosslinked structure formed is correlated with the improvement in mechanical strength and corrosion resistance of the resulting silica gel.

The coexistence of magnesium (Mg) is Si-
Si (tetravalent) due to formation of O-Al-O-Si crosslinked structure
Magnesium (divalent) compensates and neutralizes the difference in charge caused by the difference in valence between Al and trivalent, and neutralizes the charge to promote stabilization of the charge. It is speculated that the stability of the structure is enhanced because the charge balance is achieved by the ternary system. The carrier containing magnesia-silica-alumina of the present invention shows acidity in silica-alumina, whereas it is almost neutral, that is, acetal which is prominently acidified in the production of carboxylic acid ester using the carrier. It is also inferred from the fact that there are few. In the carboxylic acid ester production reaction of the present invention, it is preferable to carry out while maintaining the pH of the reaction solution at 6 to 9, and the silica-alumina-magnesia of the present invention reacts under neutral conditions in the carboxylic acid ester production reaction of the present invention. From the reaction characteristics of carrying out, it has been clarified that a catalyst satisfying both of the effects of improving the catalyst strength and corrosion resistance can be obtained.

The palladium-supported catalyst having silica-alumina-magnesia as a carrier of the present invention will be described below. The silica-alumina-magnesia carrier of the present invention contains aluminum as Al ₂ O _{3 in an amount} of 5 to 40% by weight, preferably 7 to 30% by weight, and magnesium in an amount of 3 to 3 as MgO.
30% by weight, preferably 3 to 20% by weight, silicon in SiO
It is important that the content of ₂ is 50 to 92% by weight, preferably 55 to 88% by weight. Outside of this range, the effect of improving mechanical strength and water resistance is small. It is speculated that this is because magnesium, aluminum and silicon form a specific stable bond structure only within this range.

The specific surface area of the silica-alumina-magnesia carrier of the present invention is 10 to 700 as measured by the nitrogen adsorption method.
It is preferably m ² / g, more preferably 20 to
350 m ² / g, particularly preferably 50 to 300 m ² / g
Is. If the specific surface area is less than 10 m ² / g, the palladium component is difficult to support, and even if it is supported, it is easily peeled off, which is not preferable. Also, the reaction activity of the obtained catalyst is low. From the viewpoint of catalyst preparation, there is no particular problem with the large specific surface area of the carrier. However, when the specific surface area is large, the mechanical strength and the corrosion resistance tend to decrease. For this reason,
Most preferably, the specific surface area is selected from the range of 50 to ²⁰⁰ m ² / g.

The silica-alumina-magnesia carrier of the present invention is preferably used after being calcined at a suitable temperature so that the above specific surface area can be obtained before and during the preparation of the catalyst. Generally, it is selected from the range of 200 to 800 ° C.
Firing at a temperature above 800 ° C. is not preferable because the specific surface area is significantly reduced. The firing atmosphere is not particularly limited, but firing is generally performed in air or nitrogen. The firing time can be determined according to the specific surface area after firing.

A method for obtaining the silica-alumina-magnesia carrier of the present invention having the above physical properties will be described.
(1) A product obtained by forming a silica-alumina gel in advance and adding magnesium oxide to react, (2)
A solution obtained by reacting a solution of silica sol or the like with a solution of an aluminum compound and a magnesium compound,
(3) A product obtained by reacting a silica sol with a water-insoluble aluminum compound and a magnesium compound,
(4) Obtained by reacting silica gel with an aqueous solution of a water-soluble aluminum compound and magnesium compound, (5) Obtained by solid-phase reaction of silica gel with an aluminum compound and magnesium compound. The magnesium-, aluminum-, and silicon-containing composition thus obtained can be used as the silica-alumina-magnesia carrier of the present invention by firing at a suitable firing temperature and time as described above.

The methods for obtaining (1) to (5) will be described in detail below. As the silica raw material, silica sol, water glass or silica gel can be used. It suffices that the silica gel has an uncrosslinked silica site that reacts with aluminum, and the length of the Si—O chain is not particularly limited. The aluminum raw material is preferably sodium aluminate, aluminum chloride hexahydrate, aluminum perchlorate hexahydrate, aluminum sulfate, aluminum nitrate nonahydrate, water-soluble compounds such as aluminum diacetate, Even water-insoluble compounds such as aluminum and aluminum oxide can be used as long as they are compounds that react with uncrosslinked silica in silica sol or silica gel.

Magnesium oxide is used as a magnesium raw material.
Um, magnesium hydroxide, magnesium acetate, magnesium nitrate
Gnesium, magnesium chloride, magnesium sulfate, etc.
Can be used. Made from silica-alumina gel
In step (1), sulfuric acid is added to water glass in advance and p
A silica hydrogel of H8-10.5 was made and
l₂(SO_Four) ₃Add solution (pH 2 or above)
Below), sodium aluminate is further added (pH 5 to 5.
5), preparing the resulting silica-alumina hydrogel,
After adjusting the water content, etc., obtain MgO by hydrothermal reaction
be able to. Using a solution such as silica sol as a starting material
In the case of (2) and (3), a solution such as silica sol and
After mixing the minium compound and magnesium compound, hydrothermal
Synthesized by reaction, or silica, alumina and
Co-precipitate Gnesia or mixed sols
Use a spray dryer to atomize the rally, yes
Silica-alumina having desired particle size by granulation
It is also possible to use a magnesia carrier.

Particularly in the case of (3), the silica sol is reacted with a water-insoluble aluminum compound and a magnesium compound. At this time, the aluminum compound and the magnesium compound are pulverized to a predetermined particle size in advance, or It is also possible to preliminarily coarsely crush. Silica sol,
A water-insoluble aluminum compound and a magnesium compound are mixed, reacted, dried, and then calcined at a temperature of 800 ° C. or lower. The silica-alumina-magnesia after firing may be pulverized to a predetermined particle size without preliminarily pulverizing the aluminum compound and the magnesium compound. In the case of (4) using silica gel as a starting material, the silica gel is reacted with an aqueous solution of a water-soluble aluminum compound and a magnesium compound. You may crush it. Silica gel and an aqueous solution of a water-soluble aluminum compound and a magnesium compound are mixed, reacted, dried, and then calcined at a temperature of 800 ° C. or lower. The silica-alumina-magnesia after firing may be pulverized to a predetermined particle size without preliminarily pulverizing silica gel.

Similarly, (5) using silica gel as a starting material is prepared by solid-phase reaction of silica gel with an aluminum compound and a magnesium compound.
Aluminum and magnesium are reacted with uncrosslinked silica in the solid state. The silica gel, aluminum compound and magnesium compound may be pulverized to a predetermined particle size in advance, or may be preliminarily coarsely pulverized. The pulverization may be performed for each substance alone, or the three may be mixed and pulverized. The firing is preferably performed at a temperature of 800 ° C. or lower.

The reaction atmosphere is not particularly limited, but it is common to react in air or nitrogen. The reaction time can be determined according to the specific surface area after the reaction. It is also possible to use the silica gel, the aluminum compound and the magnesium compound without crushing them in advance and crushing them to a desired particle size after the reaction. In the present invention, silica-alumina-containing aluminum in the range of 5 to 40% by weight as Al ₂ O ₃ , magnesium in the range of 3 to 30% by weight as MgO, and silicon as SiO _{2 in} the range of 50 to 92% by weight.
It is important to use magnesia as a catalyst support.

As the catalyst component, palladium alone or other heterogeneous elements such as lead, mercury, thallium, bismuth, tellurium, nickel, chromium, cobalt, indium, tantalum, copper, zinc, zirconium, hafnium, tungsten, manganese. , Silver, rhenium, antimony, tin, rhodium, ruthenium, iridium, platinum,
It may contain gold, titanium, aluminum, boron, silicon or the like. Further, it may contain an alkali metal compound or an alkaline earth metal compound. Preferably with palladium,
It is preferable to use a catalyst containing at least one element selected from lead, mercury, thallium and bismuth and, if necessary, containing at least one member selected from alkali metal compounds and alkaline earth metal compounds. At this time, palladium may form an alloy or an intermetallic compound with different elements such as lead, mercury, thallium, and bismuth, and this is preferable in some cases. By using a catalyst containing these catalyst components, generation of carbon dioxide gas or hydrocarbon due to the cleavage reaction of the C—C bond of the raw material aldehyde or its oxidation reaction intermediate is prevented, and the desired carboxylic acid with a high selectivity is obtained. Esters can be produced.

On the other hand, by using silica-alumina-magnesia as a carrier, which is the main point of the present invention, the mechanical strength, acid resistance and hydrolysis resistance of the carrier are dramatically improved. , The catalyst deterioration due to the elution of the carrier component has been dramatically improved, and the catalyst has a practically high value, which is extremely stable physically and chemically without losing the catalyst life stably for a long period of time. Examples of the palladium compound that can be used include carboxylates such as palladium acetate and formate, inorganic salts such as hydrochlorides, nitrates, sulfates and phosphates, and complexes such as palladium phthalocyanine.

Examples of the lead compound include lead acetate,
Examples thereof include carboxylates such as lead formate, lead oxide, lead hydroxide and lead nitrate. Further, as the thallium compound, thallium acetate, thallium nitrate, thallium sulfate, thallium chloride, thallium oxide and the like can be used. Examples of the mercury compound include mercury acetate, mercury nitrate, mercuric chloride, and mercury oxide, and examples of the bismuth compound include bismuth fatty acid salts such as bismuth acetate and bismuth stearate, bismuth chloride, and nitric acid. Examples include bismuth.

Examples of the alkali metal salts include hydroxides such as sodium hydroxide and potassium hydroxide, carboxylates such as sodium formate, sodium acetate and potassium acetate, and carbonates such as sodium carbonate. As the alkaline earth metal salt, magnesium hydroxide, calcium hydroxide, barium hydroxide, strontium hydroxide,
Beryllium oxide, magnesium oxide, calcium oxide,
Examples thereof include barium oxide and strontium oxide.

These components other than palladium can be added during catalyst preparation and / or to the reaction system. Further, components other than palladium can be included in advance when producing silica-alumina-magnesia. The catalyst may be prepared according to a usual method for preparing a noble metal catalyst. For example, a method of adsorbing palladium by ion exchange on a carrier, or impregnating a carrier with a solution of palladium chloride or the like, followed by a method of reducing with hydrogen in a gas phase, formalin, formic acid, using a reducing agent such as hydrazine, a liquid A palladium metal supported catalyst can be obtained by reduction in the phase. A catalyst component other than palladium can be added at the time of catalyst preparation or under reaction conditions. The alkali metal and the alkaline earth metal may be present together during the catalyst preparation, or may be added during the catalyst preparation or in the reaction system.

The amount of the palladium-supported catalyst used in the present invention is not particularly limited, but is usually 0.1 to 0.1 with respect to the weight of the carrier.
It is 20% by weight, preferably 1 to 10% by weight, and the amount of lead, thallium, bismuth and mercury supported is usually 0.1 to 20.
%, Preferably 1 to 10% by weight, and the amount of the alkali metal compound or alkaline earth metal compound supported on the carrier is usually 0.5 to 30% by weight, preferably 1 to
It is 15% by weight. Other elements are usually 5% by weight,
It can be contained preferably in a range not exceeding 1% by weight.
The amount of the catalyst used can be widely changed depending on the kind and amount of the reaction raw material, the composition and preparation method of the catalyst, the reaction conditions, etc., but is not particularly limited, but generally 1/1000 to 20 relative to the raw material aldehyde. Use in double amount (weight ratio). 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 solution.

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. β-unsaturated aldehyde; benzaldehyde, tolylaldehyde, benzylaldehyde,
Aromatic aldehydes such as phthalaldehyde; and derivatives of these aldehydes. These aldehydes can be used alone or as a mixture of two or more kinds.

Examples of the alcohol used in the production of the carboxylic acid ester of the present invention include saturated aliphatic alcohols such as methanol, ethanol, isopropanol and octanol; diols such as ethylene glycol and butanediol; allyl alcohol and methallyl alcohol. Aliphatic unsaturated alcohols; aromatic alcohols such as benzyl alcohol and the like. Particularly, lower alcohols such as methyl alcohol and ethyl alcohol are preferred because of quick reaction. 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 aldehyde and alcohol used in the carboxylic acid ester production reaction of the present invention. For example, the molar ratio of aldehyde / alcohol is 10 /
Although it can be carried out in a wide range of 1 to 1/1000, it is generally preferable that the amount of aldehyde is small, and for example, the ratio is preferably in the range of 1/2 to 1/50. The oxygen used in the carboxylic acid ester production reaction of the present invention may be molecular oxygen, that is, oxygen gas itself or a mixed gas in which oxygen gas is diluted with a diluent inert to the reaction, such as nitrogen or carbon dioxide. Yes, air can also be used. The amount of oxygen present in the reaction system is sufficient if it is at least the stoichiometric amount necessary for the reaction, preferably at least 1.2 times the stoichiometric amount.

The carboxylic acid ester production reaction of the present invention comprises
It can be carried out by any method such as a gas phase reaction, a liquid phase reaction, an irrigation reaction, etc. by either a batch system or a continuous system. The reaction can be carried out without solvent, but a solvent inert to the reaction components,
For example, it can be carried out using hexane, decane, benzene, dioxane or the like. The reactor type is also fixed bed type,
It may be of any conventionally known type such as a fluidized bed type or a stirring tank type. Since the catalyst of the present invention has high mechanical strength,
It can be stably used in fluidized bed reactors, bubble column reactors, and stirred tank reactors.

The particle size of the silica-alumina-magnesia carrier of the present invention can be appropriately selected according to the reaction type of the catalyst and is not particularly limited, but when used in a liquid phase suspension state, it depends on the method of separating the catalyst. , For example, 20 to 20 in natural sedimentation
In many cases, it is 500 μm, preferably 20 to 200 μm, more preferably 20 to 100 μm. In the method using the filter separation, fine particles of 0.1 to 20 μm may be used.

When the reaction process for producing a carboxylic acid ester of the present invention is carried out in a liquid phase or the like, the reaction system contains an alkali metal or alkaline earth metal compound (eg, oxide, hydroxide, carbonate, carboxylic acid). It is preferable to maintain the pH of the reaction system at 6 to 9 by adding a salt or the like). By maintaining the pH of the reaction solution at 6 to 9, it is possible to effectively suppress a part of the raw material aldehyde from changing to an acetal due to the influence of the acid property. Generally, as the pH of the reaction system exceeds 9, side reactions such as aldehyde as a raw material become more prominent, and the selectivity of the desired carboxylic acid ester tends to decrease. PH tends to become noticeable and undesirable, so pH
Is preferably maintained at 6 to 9 for the reaction. Further, when the catalyst contains a compound of an alkali metal or an alkaline earth metal, it also has an action of preventing the compound from flowing out of the system. These alkali metal or alkaline earth metal compounds can be used alone or in combination of two or more.

The carboxylic acid ester production reaction of the present invention comprises
It can be carried out at high temperature of 100 ℃ or more,
It has the outstanding feature that the desired carboxylic acid ester can be produced with a high reaction rate and a high selectivity even at low temperatures. The reaction can be carried out in any wide pressure range from reduced pressure to increased pressure.

[0035]

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 hydrolysis resistance stability of the carrier was measured by the following method for accelerated evaluation and used as an index of the hydrolysis resistance stability. Also, Mg, A
l and Si were analyzed by the following method. <Evaluation of Hydrolysis Stability of Carrier> 0.2 g of a solid substance to be evaluated was weighed in a 100 ml SUS (stainless steel) container, 20 g of water was added, and the container was sealed and heated at a temperature of 180 ° C. for 1 hour. Thereafter, the concentration of Si ions eluted in water was measured and compared with an ICP (plasma emission spectrophotometer) (manufactured by Nippon Jarrell Ash Co., Ltd., ICAP-575 Mark II). <How to determine the contents of Mg, Al and Si> Mg is dissolved in aqua regia, Al and Si are dissolved in alkali molten salt, and ICP is used.
(Plasma emission spectrophotometer), and each element was converted into an oxide of MgO, Al ₂ O ₃ , and SiO ₂ to determine the content.

[0036]

Example 1 In a 50-liter stainless steel container, 3.75 kg of aluminum nitrate nonahydrate, 2.56 kg of magnesium nitrate hexahydrate, 540 g of 60% nitric acid, and water 4.6.
7 kg was added and stirred. Then, silica sol solution (SiO ₂ 30%) manufactured by Nissan Chemical Industries, Ltd. Snowtex N-
20.0 kg of 30 was added little by little and mixed. After thoroughly mixing, spray drying was performed with a spray dryer set at a temperature of 130 ° C. to obtain a solid. Next, the obtained solid material was filled into a stainless steel container having an open upper portion to a thickness of about 1 cm, and the temperature was raised from room temperature to 300 ° C. over 2 hours and then maintained for 3 hours in an electric furnace. After heating to 600 ° C in 2 hours, 3
After holding for a while, it was gradually cooled. MgO, Al ₂ O ₃ , SiO
₂ was 5.8% by weight, 7.4% by weight and 86.8% by weight, respectively. Specific surface area by nitrogen adsorption method is 148m ²
/ G, electron microscope (SEM) (S, manufactured by Hitachi, Ltd.
-2700), the average particle size is about 60 μm.
Then, it was almost spherical, and it was harder than the commercially available silica gel when the pulverization was examined with a mortar. When an accelerated evaluation of the hydrolysis resistance stability of the obtained silica-alumina-magnesia was carried out, the concentration of Si ions eluted by hydrolysis was 42 ppm.

[0037]

Comparative Example 1 A carrier having a specific surface area of 188 m ² / g was obtained in the same manner as in Example 1 except that the magnesium compound and the aluminum compound were not added. When the water resistance of the carrier was evaluated for acceleration, the concentration of eluted Si ions was 210 ppm.

[0038]

Comparative Example 2 Commercially available silica gel (Carriact 10 manufactured by Fuji Silysia Ltd.) was calcined at 600 ° C. for 3 hours. The specific surface area of the obtained silica by the nitrogen adsorption method is 300 m ² / g.
Met. When the accelerated evaluation of water resistance was performed, the concentration of eluted Si ions was 244 ppm.

[0039]

Example 2 The amount of magnesium in MgO was 3% by weight and the amount of aluminum in Al ₂ O ₃ was 12% by weight.
A carrier having a specific surface area of 155 m ² / g was obtained in the same manner as in Example 1 except that magnesium nitrate and aluminum nitrate were added and the firing temperature was 700 ° C. When the water resistance of the carrier was evaluated for acceleration, the concentration of eluted Si ions was 48 ppm.

[0040]

Example 3 The content of magnesium was 4% by weight as MgO and the content of aluminum was 20% by weight as Al ₂ O ₃ ,
A carrier having a specific surface area of 138 m ² / g was obtained in the same manner as in Example 1 except that magnesium nitrate and aluminum nitrate were added and the firing temperature was changed to 800 ° C. When the water resistance of the carrier was evaluated for acceleration, the concentration of eluted Si ions was 40 ppm.

[0041]

Example 4 Magnesium nitrate and aluminum nitrate were added to the magnesium source so that MgO was 13% by weight and aluminum was 35% by weight as Al ₂ O ₃ , and the firing temperature was 800 ° C. By the same operation as in Example 1, a carrier having a specific surface area of 123 m ² / g was obtained. Acceleration evaluation of the water resistance of the carrier revealed that the concentration of eluted Si ions was 70 pp.
It was m.

[0042]

Example 5 10 kg of water glass No. 3 (SiO ₂ : 28 to 30% by weight, Na ₂ O: 9 to 10% by weight), pH: 9
Sulfuric acid was added until Al ₂ (SO ₄ ) ₃ was added,
The pH was 2. Further add sodium aluminate pH:
5 to 5.5, part of which is dehydrated and silica / alumina is about 1
It was 0% by weight of hydrogel. After spray drying by spray drying at 130 ° C., Na ₂ O: 0.02% by weight, S
O ₄ : washed to 0.5% by weight or less. This was mixed in a slurry form with 300 g of MgO, treated at 80 ° C. for 3 hours, filtered and washed, then dried at 110 ° C. for 6 hours, and then 7
After heating to 00 ° C for 3 hours, hold for 3 hours, and then remove by cooling
4.4% by weight as gO, 13% by weight as Al ₂ O ₃
The carrier was obtained. The specific surface area of the obtained compound by the nitrogen adsorption method was 223 m ² / g. As a result of accelerated evaluation of water resistance, the concentration of eluted Si ions was 38 ppm.

[0043]

Example 6 Magnesium hydroxide and aluminum nitrate were added so that the amount of magnesium was 5% by weight as MgO and the amount of aluminum was 9% by weight as Al ₂ O ₃ , and the firing temperature was 600 ° C. By the same operation as in Example 1, a carrier having a specific surface area of 167 m ² / g was obtained. Accelerated evaluation of the water resistance of the carrier revealed a dissolved Si ion concentration of 41 pp.
It was m.

[0044]

Example 7 Aluminum nitrate was added to the magnesium source so that MgO was 30% by weight and aluminum was 15% by weight as Al ₂ O ₃ , and the firing temperature was 65.
A specific surface area of 134 is obtained by the same operation as in Example 1 except that the temperature is 0 ° C.
A carrier of m ² / g was obtained. When the water resistance of the carrier was accelerated and evaluated, the concentration of eluted Si ions was 65 ppm. Table 1 summarizes the composition, specific surface area, and eluted Si ion concentration of Examples 1 to 7 and Comparative Examples 1 and 2.

[0045]

[Example 8] Carrier of Example 1 100 g of the carrier was mixed with 50 parts of distilled water.
Add to a glass container containing 0 ml, and while stirring at 60 ° C., add a diluted hydrochloric acid solution of palladium chloride and an aqueous lead nitrate solution to Pd.
And Pb is rapidly added dropwise in an amount corresponding to 2.5% by weight. Then, the mixture is kept for 1 hour, and 1.2 times the stoichiometric amount of hydrazine is added for reduction. After reduction, decant the supernatant,
Wash with distilled water until no Cl ions are detected, 6
It was vacuum dried at 0 ° C. to obtain a catalyst carrying 2.5% by weight of Pd and Pb. To a 300 ml stainless steel autoclave equipped with an electromagnetic induction stirrer, 20 g of catalyst and 150 ml of methanol having a methacrolein concentration of 20% by weight as a raw material were added, and the methacrolein concentration was adjusted to 20 hours so that the residence time was 3 hours.
By continuously supplying wt% of methanol, a temperature of 80 ° C., a pressure of 4 kg / cm ² , a rotation speed of 1000 rpm (stirring tip speed: 1.2 m / s), and NaOH / so that the pH was 7 were obtained.
Air and nitrogen were supplied to the methanol solution so that the outlet oxygen concentration was 8%, and continuous reaction was performed. After reacting for 200 hours and analyzing the reaction product by gas chromatography, the conversion of methacrolein was 62.3% and the selectivity of methyl methacrylate (MMA) was 88.4%. Moreover, when the Pd and Si ion concentrations in the reaction solution were measured by ICP, Pd was below the detection limit, and Si
Was 1 ppm or less. After reacting for 1000 hours, the catalyst was taken out and examined by an electron microscope (SEM). As a result, the catalyst was hardly cracked or chipped.

[0046]

[Comparative Example 3] Silica gel (Carrieract 10 manufactured by Fuji Silysia Ltd.) was used as a carrier and impregnated with an aqueous magnesium acetate solution so as to contain 4% by weight of magnesium.
A continuous reaction was carried out by the same operation as in Example 8 except that the carrier calcined at 0 ° C was replaced. After reacting for 200 hours and analyzed by gas chromatography, the conversion of methacrolein was 59.3% and the selectivity of methyl methacrylate (MMA) was 87.5%. In addition, Pd and S in the reaction solution
When the i ion concentration was measured by ICP, Pd was 0.3 ppm and Si was 10 ppm. 10
After reacting for 00 hours, the catalyst was extracted and electron microscope (SEM)
As a result of examination with, the catalyst was found to have cracks and chips.

[0047]

Comparative Example 4 γ-Alumina as a carrier (manufactured by Mizusawa Chemical Co., Ltd.
A continuous reaction was carried out in the same manner as in Example 8 except that neo beads were used and the carrier was impregnated with an aqueous magnesium acetate solution so as to contain 4% by weight of magnesium and then the carrier was calcined at 600 ° C. P in the reaction solution reacted for 200 hours
d and Al ion concentration were measured by ICP.
d was 1 ppm and Al was 20 ppm. 100
After the reaction for 0 hour, the catalyst was taken out and examined by an electron microscope (SEM). As a result, a part of the catalyst was cracked, chipped and roughened on the surface.

[0048]

Comparative Example 5 As a carrier, the carrier composition of Example 3 is such that aluminum is 50% by weight in terms of Al ₂ O ₃ and magnesium is M.
A continuous reaction was carried out by the same operation as in Example 8, using the carrier obtained by the same operation except that the carrier was changed to 5% by weight in terms of gO. Two
When the Pd and Si ion concentrations in the reaction solution reacted for 00 hours were measured by ICP, Pd was 0.2 ppm, Si was 1 ppm or less, and Al was 10 ppm.
After reacting for 1000 hours, the catalyst was taken out, and an electron microscope (SE
When examined in M), cracks and chips were found in a part of the catalyst.

[0049]

Example 9 100 g of the carrier of Example 1 was ion-exchanged with 0.1 N ammonia water in an amount corresponding to 3 to 4 times the amount of acid sites. 100 ml of distilled water is added, and 0.01 mol of [Pd [NM ₃ ] ₄ ] Cl ₂ aqueous solution is slowly added dropwise at 60 ° C. with stirring in an amount corresponding to 2.5% by weight of palladium. Then, it is filtered, washed with distilled water until Cl ions are not detected, and dried at 110 ° C. The catalyst was reduced in a hydrogen stream at 300 ° C. for 4 hours, and further, a catalyst in which bismuth acetate as bismuth was impregnated and supported in an amount equivalent to 2.5% by weight was obtained. To a 300 ml stainless steel autoclave equipped with an electromagnetic induction stirrer, 20 g of catalyst and 150 ml of methanol having an acrolein concentration of 20% by weight as a raw material were added, and methanol having an acrolein concentration of 20% by weight was continuously supplied so that a residence time was 3 hours. , Temperature 80 ℃, pressure 4kg
/ Cm ² , rotation speed 1000 rpm (stirring tip speed:
1.2m / s), pH / 7, NaOH / methanol solution was supplied, and air and nitrogen were supplied so that the outlet oxygen concentration was 8% to carry out continuous reaction. When the reaction was carried out for 200 hours and analyzed by gas chromatography, the conversion of acrolein was 63.0% and the selectivity of acrylate was 8
It was 8.3%. After reacting for 1000 hours, the catalyst was taken out and examined by an electron microscope (SEM).
Almost no chipping was seen.

[0050]

Example 10 A catalyst was obtained by the same operation as in Example 9 except that thallium was used instead of bismuth. The catalyst 20 was placed in a 300 ml stainless steel autoclave equipped with an electromagnetic induction stirrer.
g, 150 ml of methanol having a benzaldehyde concentration of 20% by weight was added as a raw material, and methanol having a benzaldehyde concentration of 20% by weight was continuously supplied so that the residence time was 3 hours, and the temperature was 80 ° C., the pressure was 4 kg / cm ² , and the rotation was Several thousand rpm (stirring tip speed: 1.2 m / s), p
A NaOH / methanol solution was supplied to H7, and air and nitrogen were supplied so that the outlet oxygen concentration was 8% to carry out a continuous reaction. When the reaction was carried out for 200 hours and analyzed by gas chromatography, the conversion of benzaldehyde was 6
At 4.7%, the selectivity for methyl benzoate was 85.5%. After the reaction for 1000 hours, the catalyst was taken out and examined by an electron microscope (SEM). As a result, the catalyst was hardly cracked or chipped.

[0051]

[Table 1]

[0052]

The silica-based carrier of the present invention is a catalyst carrier having a high specific surface area and improved mechanical strength and corrosion resistance. A palladium-based supported catalyst using the catalyst carrier is excellent. The catalyst performance can be stably maintained for a long period of time. Further, since the catalyst life is greatly improved, the frequency of catalyst replacement is reduced, resulting in good operability and great economic effect.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI C07C 69/54 C07C 69/54 Z (58) Fields investigated (Int.Cl. ⁷ , DB name) B01J 21/06-38 / 74 C07C 67/00-67/62 JSTPlus (JOIS) CAplus (STN)

Claims (3)

(57) [Claims] 1. A palladium-containing supported catalyst used in the production of a carboxylic acid ester, which comprises reacting an aldehyde with an alcohol in the presence of oxygen, wherein aluminum is Al ₂ O.
₃ as 5 to 40 wt%, 3 to 30 wt% of magnesium as MgO, silica containing a range of silicon as SiO ₂ of 50 to 92 wt% - of alumina - carboxylic acid ester, which comprises using a magnesia carrier Production catalyst. 2. A method for producing a carboxylic acid ester which comprises reacting an aldehyde with an alcohol in the presence of oxygen.
A process for producing a carboxylic acid ester using the catalyst for producing a carboxylic acid ester described. 3. The method for producing a carboxylic acid ester according to claim 2, wherein the aldehyde is acrolein or methacrolein and the alcohol is methanol.