JP2005224657A - PALLADIUM-CONTAINING CARRYING CATALYST, ITS PRODUCTION METHOD AND METHOD FOR PRODUCING alpha,beta-UNSATURATED CARBOXYLIC ACID - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a palladium-containing carrying catalyst for producing α,β-unsaturated carboxylic acid from olefin or α,β-unsaturated aldehyde at high yield, its production method and a method for producing α,β-unsaturated carboxylic acid at high yield. <P>SOLUTION: The catalyst for producing α,β-unsaturated carboxylic acid by oxidizing olefin or α,β-unsaturated aldehyde by molecular oxygen in a liquid phase is made to the palladium-containing carrying catalyst in which a carrier is carried with palladium having an average particle diameter in a range of 1-8 nm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a palladium-containing supported catalyst for producing an α, β-unsaturated carboxylic acid from an olefin or an α, β-unsaturated aldehyde, a method for producing the same, and an α, β-unsaturated carboxylic acid using the catalyst. The present invention relates to a method for producing an acid.

Palladium-containing catalysts are widely used as catalysts for obtaining α, β-unsaturated carboxylic acids by liquid phase oxidation of olefins or α, β-unsaturated aldehydes with molecular oxygen. For example, Patent Documents 1 to 3 describe a palladium-containing supported catalyst in which palladium is supported on a support such as activated carbon, but there is no description regarding the particle size of palladium contained therein.
JP 56-59722 A JP 60-155148 A JP 60-139341 A

  When the present inventor produced acrylic acid from propylene using a palladium-containing supported catalyst produced according to the method described in Examples of Patent Documents 1 to 3, a by-product described in Patent Documents 1 to 3 was obtained. In addition to the products (acetaldehyde, acetone, acrolein, acetic acid, carbon dioxide), it was found that a large number of various polymers and oligomers were by-produced. In Patent Documents 1 to 3, these polymers and oligomers are not captured, and the selectivity of the actual acrylic acid including these by-products is lower than those described in the Examples of Patent Documents 1 to 3. It has been found. Therefore, the yield of α, β-unsaturated carboxylic acid in the method for producing α, β-unsaturated carboxylic acid using the catalyst described in Patent Documents 1 to 3 is not yet sufficient, and α, β can be obtained at a higher yield. -Catalysts capable of producing unsaturated carboxylic acids are desired.

  Accordingly, an object of the present invention is to provide a palladium-containing supported catalyst for producing α, β-unsaturated carboxylic acid in high yield from an olefin or an α, β-unsaturated aldehyde, a method for producing the same, and an α, β-unsaturated catalyst. The object is to provide a method for producing a saturated carboxylic acid in a high yield.

  The present invention is a catalyst for producing an α, β-unsaturated carboxylic acid by oxidizing an olefin or α, β-unsaturated aldehyde with molecular oxygen in a liquid phase, and has an average particle size of 1 to 8 nm. This is a palladium-containing supported catalyst in which palladium in the above range is supported on a carrier.

  The present invention also relates to a method for producing the palladium-containing supported catalyst, wherein the palladium compound is reduced with a reducing agent in the presence of a carrier.

  Furthermore, the present invention is a method for producing an α, β-unsaturated carboxylic acid in which an olefin or an α, β-unsaturated aldehyde is oxidized in the liquid phase with molecular oxygen in the presence of the palladium-containing supported catalyst.

  According to the present invention, when α, β-unsaturated carboxylic acid is produced from olefin or α, β-unsaturated aldehyde, the amount of by-product polymer and oligomer is small, and α, β-unsaturated A palladium-containing supported catalyst capable of producing carboxylic acid in high yield and a method for producing the same can be provided, and α, β-unsaturated carboxylic acid can be produced in high yield by using the catalyst.

  The catalyst of the present invention is a catalyst for producing an α, β-unsaturated carboxylic acid by oxidizing α, β-unsaturated aldehyde with molecular oxygen in a liquid phase, and has an average particle diameter of 1 to 8 nm. This is a palladium-containing supported catalyst in which palladium in the above range is supported on a carrier. By setting the average particle diameter of palladium within the above range, a palladium-containing supported catalyst capable of producing an α, β-unsaturated carboxylic acid from an α, β-unsaturated aldehyde in a high yield is obtained.

  The average particle diameter of palladium in the present invention is measured with a transmission electron microscope for palladium in the palladium-containing supported catalyst, and is specifically a value calculated as follows. An observation image of a transmission electron microscope was printed at an equal magnification, and 50 particles of palladium in the field of view were randomly picked up and each particle size was measured. Since the shape of the palladium region was almost circular, it was measured by approximating that it was all circular. This operation was carried out for three visual fields, and the average of the measured values was taken as the average particle diameter. The observation with a transmission electron microscope is performed at an observation magnification capable of measuring the particle diameter of palladium.

  The lower limit value of the average particle diameter of palladium calculated as described above is 1 nm or more, preferably 1.2 nm or more, more preferably 1.4 nm or more, and the upper limit value of the average particle diameter of palladium is 8 nm or less. It was found that 7 nm or less is preferable and 6 nm or less is more preferable. When the average particle diameter of palladium is outside the predetermined range, the activity of the palladium-containing supported catalyst containing the palladium tends to decrease, and the yield of the α, β-unsaturated carboxylic acid tends to decrease.

  Although the manufacturing method of the palladium containing supported catalyst of this invention is not specifically limited, The method of reduce | restoring a palladium compound with a reducing agent in presence of a support | carrier can be taken. Specifically, for example, a liquid phase reduction method in which a reducing agent is added to a palladium compound solution in which a carrier is dispersed to reduce, or a carrier in which a palladium compound solution is impregnated is dried and reduced in a reducing atmosphere. It can be produced by a phase reduction method or the like. Of these, the liquid phase reduction method is preferred. Hereinafter, the manufacturing method of the palladium containing supported catalyst by a liquid phase reduction method is demonstrated.

  The average particle diameter of palladium in the palladium-containing supported catalyst is the type and specific surface area of activated carbon used, the type of solvent used for the preparation of the palladium-containing supported catalyst and the mixing ratio in the case of a mixed solvent, and the raw material of the palladium-containing supported catalyst. It varies depending on various conditions such as the kind and concentration of a certain palladium compound, the temperature and time for reducing the palladium compound, and the like. In the present invention, it is necessary to appropriately select and set those conditions, and to set the average particle diameter of palladium in the obtained palladium-containing supported catalyst within the above range.

  The palladium compound used for the production of the palladium-containing supported catalyst by the liquid phase reduction method is not particularly limited, but examples thereof include palladium chloride, oxide, acetate, nitrate, sulfate, tetraammine complex, and acetylacetonate complex. Palladium chloride, oxide, acetate, nitrate, or sulfate is more preferable, and palladium chloride, acetate, or nitrate is particularly preferable. These can be used alone or in combination.

  As a solvent for dissolving the palladium compound, water, alcohol, ketone, organic acid, hydrocarbon, or a mixed solvent of two or more selected from these groups can be used. The solvent is appropriately selected depending on the solubility of the palladium compound and the reducing agent, the dispersibility of the carrier, and the like, and among them, a mixed solvent of one or two or more solvents selected from organic acids and water is preferable. The organic acid is preferably at least one selected from the group consisting of acetic acid, propionic acid, n-butyric acid, iso-butyric acid, n-valeric acid and iso-valeric acid. Of these, n-valeric acid is particularly preferred. The amount of water at that time is not particularly limited, but is usually 5% by mass or more, preferably 8% by mass or more with respect to the mass of the mixed solvent. Moreover, it is 60 mass% or less normally, Preferably, it is 40 mass% or less. In the case of a mixed solvent, a uniform state is desirable, but a non-uniform state may be used.

  When the target palladium-containing supported catalyst contains a metal other than palladium, a method in which the metal compound of the metal is dissolved in a palladium compound solution can be used. From the viewpoint of catalytic activity, the amount of the metal other than palladium in the palladium-containing supported catalyst is preferably 50 atomic% or less.

Examples of the carrier used in the present invention include activated carbon, silica, alumina, titania, and zirconia. Of these, activated carbon is preferred. The raw material of the activated carbon is not particularly limited, and examples thereof include wood, coconut shell, coal, and synthetic resin. The shape of the activated carbon is not particularly limited, and examples thereof include powder, crushed, granular, tablet, and fiber. The activation method of activated carbon is not particularly limited, and examples thereof include water vapor activation, carbon dioxide activation, zinc chloride activation, phosphate activation, and alkali activation. The specific surface area of the activated carbon is preferably at least 300 meters ² / g, and particularly preferably equal to or greater than 600m ² / g. Moreover, 4000 m < ² > / g or less is preferable and 2500 m < ² > / g or less is especially preferable.

  The carrier and the palladium compound are added to the solvent in the desired order or simultaneously to prepare a palladium compound solution in which the carrier is dispersed. The density | concentration of a palladium compound is 0.1 mass% or more normally, Preferably it is 0.2 mass% or more, Most preferably, it is 0.5 mass% or more. Moreover, it is 20 mass% or less normally, Preferably it is 10 mass% or less, Most preferably, it is 7 mass% or less. Next, a reducing agent is added to the palladium compound solution in which the carrier is dispersed to reduce palladium, and a palladium-containing supported catalyst in which the reduced palladium is supported on the carrier is obtained.

  The reducing agent to be used is not particularly limited, and examples thereof include hydrazine, formalin, sodium borohydride, hydrogen, formic acid, formic acid salt, ethylene, propylene, and isobutylene. Of these, propylene and isobutylene are preferable.

  When the reducing agent is a gas, the reduction of palladium is preferably performed in a pressure device such as an autoclave. At that time, the inside of the pressurizer is pressurized with a reducing agent. The pressure is usually 0.1 to 1.0 MPa (gauge pressure; hereinafter, all pressures are expressed as gauge pressures).

  Moreover, when a reducing agent is a liquid or solid, a reduction process can be performed by adding a reducing agent in a palladium compound solution. The amount of reducing agent used is usually about 1 to 50 moles per mole of palladium compound.

  The temperature of the system and the reduction time during the reduction vary depending on the reduction method, the palladium compound used, the solvent, the reducing agent, etc., but cannot generally be said, but in the case of the liquid phase reduction method, the reduction temperature is usually 0 to 100 ° C. The time is 0.5 to 24 hours.

  After the reduction, a carrier on which palladium is supported (hereinafter referred to as “palladium-containing supported catalyst” or simply “catalyst”) is separated from the dispersion. Although this method is not specifically limited, For example, methods, such as filtration and centrifugation, can be used. The separated catalyst is appropriately dried. The drying method is not particularly limited, and various methods can be used.

  The concentration of palladium contained in the solution separated from the catalyst after the reduction is preferably 10 mg / l or less. This amount can be adjusted by the palladium compound concentration before reduction, the reduction conditions, and the like. Presence or absence of palladium in the solution can be easily confirmed by adding a reducing agent such as hydrazine, and the amount of palladium in the solution can be quantified by elemental analysis such as ICP.

  The palladium loading ratio of the catalyst is usually 0.1 to 40% by mass with respect to the support. The lower limit of the loading rate is preferably 1% by mass or more, and more preferably 4% by mass or more. The upper limit of the loading rate is preferably 30% by mass or less, more preferably 20% by mass or less, and particularly preferably 15% by mass or less. The loading rate can be determined from the mass of the carrier used for catalyst preparation, the mass of palladium in the palladium compound, and the mass of palladium contained in the solution separated from the catalyst after reduction.

  As described above, the palladium-containing supported catalyst of the present invention can be produced.

  The catalyst may be activated before being subjected to liquid phase oxidation. The activation method is not particularly limited, and various methods can be used. As a method of activation, a method of heating in a reducing atmosphere in a hydrogen stream is common.

  Next, a method for producing an α, β-unsaturated carboxylic acid by oxidizing an olefin or α, β-unsaturated aldehyde with molecular oxygen in a liquid phase will be described.

  Examples of the olefin as a raw material for liquid phase oxidation include propylene, isobutylene, 1-butene, and 2-butene. Examples of the raw α, β-unsaturated aldehyde include acrolein, methacrolein, crotonaldehyde (β-methylacrolein), and cinnamaldehyde (β-phenylacrolein).

  The α, β-unsaturated carboxylic acid produced by liquid phase oxidation is an α, β-unsaturated carboxylic acid having the same carbon skeleton as the olefin when the raw material is an olefin. When the raw material is an α, β-unsaturated aldehyde, it is an α, β-unsaturated carboxylic acid in which the aldehyde group of the α, β-unsaturated aldehyde is changed to a carboxyl group.

  The catalyst of the present invention is suitable for liquid phase oxidation for producing acrylic acid from propylene or acrolein, and methacrylic acid from isobutylene or methacrolein.

  The raw material olefin or α, β-unsaturated aldehyde may contain a small amount of saturated hydrocarbon, lower saturated aldehyde and the like as impurities.

  Air is economical as the molecular oxygen source used in the reaction, but pure oxygen or a mixed gas of pure oxygen and air can also be used. If necessary, air or pure oxygen is converted into nitrogen, carbon dioxide, water vapor. It is also possible to use a mixed gas diluted with the same.

  Although the solvent used for liquid phase oxidation is not specifically limited, For example, Water; Alcohol, such as tertiary butanol and cyclohexanol; Ketone, such as acetone, methyl ethyl ketone, methyl isobutyl ketone; Acetic acid, propionic acid, n-butyric acid, iso-butyric acid, an organic acid such as n-valeric acid and iso-valeric acid; an organic acid ester such as ethyl acetate and methyl propionate; a hydrocarbon such as hexane, cyclohexane and toluene; or a mixed solvent of two or more selected from these groups Can be used. Especially, the mixed solvent of 1 type, or 2 or more types of solvent chosen from the group which consists of alcohol, a ketone, an organic acid, and organic acid ester, and water is preferable. The amount of water at that time is not particularly limited, but is usually 2% by mass or more, preferably 5% by mass or more with respect to the mass of the mixed solvent. Moreover, it is 70 mass% or less normally, Preferably it is 50 mass% or less. Although the solvent is desirably uniform, it may be used in a non-uniform state.

  The liquid phase oxidation reaction may be carried out in either a continuous type or a batch type, but in view of productivity, the continuous type is preferred industrially.

  The amount of the olefin or α, β-unsaturated aldehyde used as a raw material is usually 0.1 parts by mass or more, preferably 0.5 parts by mass or more with respect to 100 parts by mass of the solvent. Moreover, it is 20 mass parts or less normally, Preferably it is 10 mass parts or less.

  The amount of molecular oxygen used is usually 0.1 mol or more, preferably 0.3 mol or more, particularly preferably 0.5 mol, per 1 mol of the raw material olefin or α, β-unsaturated aldehyde. That's it. Moreover, it is 20 mol or less normally, Preferably it is 15 mol or less, Most preferably, it is 10 mol or less.

  Usually, the catalyst is used in a state suspended in the reaction solution, but may be used in a fixed bed. The amount of the catalyst used is usually 0.1 parts by weight or more, preferably 0.5 parts by weight or more, particularly preferably 1 part by weight as the catalyst present in the reactor with respect to 100 parts by weight of the solution present in the reactor. More than a part. Moreover, it is 30 mass parts or less normally, Preferably it is 20 mass parts or less, Most preferably, it is 15 mass parts or less.

  The reaction temperature and reaction pressure are appropriately selected depending on the solvent used and the reaction raw materials. The reaction temperature is generally 30 to 200 ° C, preferably 50 ° C or higher, and preferably 150 ° C or lower. The reaction pressure is generally atmospheric pressure (0 MPa) to 10 MPa, preferably 0.5 MPa or more, and preferably 5 MPa or less.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited to an Example. In the following Examples and Comparative Examples, “part” means “part by mass”.

(Analysis of raw materials and products)
Analysis of raw materials and products was performed using gas chromatography. In addition, reaction rate of olefin or α, β-unsaturated aldehyde, selectivity of α, β-unsaturated aldehyde to be produced, selectivity of polymer / oligomer to be produced, selectivity of α, β-unsaturated carboxylic acid to be produced And the yield is defined as follows:

Reaction rate of olefin or α, β-unsaturated aldehyde (%)
= (B / A) x 100
Selectivity of α, β-unsaturated aldehyde (%) = (C / B) × 100
Selectivity of α, β-unsaturated carboxylic acid (%) = (D / B) × 100
Selectivity of polymer / oligomer (%) = (E / B) × 100
Yield of α, β-unsaturated carboxylic acid (%) = (D / A) × 100
Here, A is the number of moles of olefin or α, β-unsaturated aldehyde supplied, B is the number of moles of reacted olefin or α, β-unsaturated aldehyde, and C is the mole of α, β-unsaturated aldehyde produced. Number, D is the number of moles of α, β-unsaturated carboxylic acid produced, E is calculated by dividing the total mass (unit: g) of the polymer and oligomer by the molecular weight of the olefin or α, β-unsaturated aldehyde supplied. The number of moles of olefin or polymer and oligomer in terms of α, β-unsaturated aldehyde. Here, in the case of the α, β-unsaturated aldehyde oxidation reaction, C / B = 0.

(Average particle diameter of palladium in the palladium-containing supported catalyst)
The average particle diameter of palladium in the palladium-containing supported catalyst was measured with a transmission electron microscope. Specifically, the calculation was performed as follows. The observation image of the transmission electron microscope was printed at the same magnification, and 50 palladium particles in the field of view were picked up and the particle diameters were measured. Since the shape of the palladium particles was almost circular, it was approximated to be circular and measured. This operation was carried out for three visual fields, and the average of the measured values was taken as the average particle diameter.

<Example 1>
(Preparation of palladium-containing supported catalyst)
1.16 parts of palladium acetate was added to 60 parts of an 88% by mass n-valeric acid aqueous solution and dissolved by heating and stirring at 80 ° C. for 1 hour. The obtained solution was transferred to an autoclave, and 5.4 parts of activated carbon (specific surface area 840 m ^{2 /} g) produced from a coal raw material was added, stirring was started at a rotation speed of 400 rpm, and introduction and release of nitrogen gas were started. The inside of the apparatus was purged with nitrogen several times. After introducing propylene gas to 0.5 MPa, the temperature was raised to 50 ° C. (reduction temperature) and held for 1 hour (reduction time). After completion of the reaction, the mixture was cooled to 20 ° C., and the internal gas was released. Then, the autoclave was opened. The suspension was filtered to obtain a palladium-containing supported catalyst having a loading rate of 10 mass% (palladium mass relative to the mass of the carrier).

  The average particle diameter of palladium in the obtained palladium-containing supported catalyst was 1.5 nm (observation magnification of transmission electron microscope: 1,000,000 times).

(Catalyst performance evaluation)
An autoclave equipped with a stirrer was charged with 69 parts of an 88% by mass acetic acid aqueous solution containing 200 ppm of p-methoxyphenol and 3 parts of the above palladium-containing supported catalyst. Further, 2.5 parts of methacrolein was added. After sealing the autoclave, stirring was started at a stirring speed of 820 rpm, and the temperature was raised to 90 ° C. by a heater. When the temperature reached 90 ° C., air was introduced up to 3.2 MPa and maintained for 20 minutes (reaction time). After completion of the reaction, it was cooled to 20 ° C. Further, an absorption tube filled with cold water and a gas collection bag were attached in this order to the gas outlet of the autoclave. The gas outlet was opened and the pressure in the reactor was released while collecting the gas. The reaction solution was transferred to a centrifuge tube, and the catalyst was precipitated by centrifugation. The supernatant was collected through a PTFE membrane filter (pore size: 0.5 μm).

  As a result, methacrolein conversion was 93.6%, methacrylic acid selectivity was 79.9%, polymer / oligomer selectivity was 8.5%, and methacrylic acid yield was 74.8%.

<Example 2>
A catalyst was prepared in the same manner as in Example 1 except that activated carbon produced from a coconut shell raw material having a specific surface area of 988 m ² / g was used as a carrier. The average particle diameter of palladium in the obtained palladium-containing supported catalyst (supporting rate: 10% by mass) was 2.6 nm (observation magnification with a transmission electron microscope: 300,000 times).
The catalyst performance was evaluated in the same manner as in Example 1. As a result, the methacrolein reaction rate was 89.7%, the methacrylic acid selectivity was 84.7%, the polymer / oligomer selectivity was 4.3%, and the methacrylic acid yield was 76.0. %Met.

<Comparative Example 1>
A catalyst was prepared in the same manner as in Example 1 except that a 96% by mass acetic acid aqueous solution was used as the catalyst preparation solvent. The average particle diameter of palladium in the obtained palladium-containing supported catalyst (supporting rate: 10% by mass) was 8.4 nm (observation magnification with a transmission electron microscope: 300,000 times).

  As a result of evaluating the catalyst performance in the same manner as in Example 1, the methacrolein reaction rate was 46.4%, the methacrylic acid selectivity was 71.5%, the polymer / oligomer selectivity was 15.4%, and the methacrylic acid yield was 33.2. %Met.

<Comparative example 2>
A catalyst was prepared in the same manner as in Example 1 except that n-valeric acid was used as the catalyst preparation solvent. The average particle diameter of palladium in the obtained palladium-containing supported catalyst (supporting rate: 10% by mass) was 10.1 nm (observation magnification with a transmission electron microscope: 300,000 times).

  The catalyst performance was evaluated in the same manner as in Example 1. As a result, the methacrolein reaction rate was 45.4%, the methacrylic acid selectivity was 65.2%, the polymer / oligomer selectivity was 21.3%, and the methacrylic acid yield was 30.0. %Met.

<Comparative Example 3>
A catalyst was prepared in the same manner as in Example 1 except that the amount of palladium acetate was 0.11 part, the reduction temperature was 25 ° C., and the reduction time was 18 hours. The average particle diameter of palladium in the obtained palladium-containing supported catalyst (supporting rate: 10% by mass) was 0.8 nm (observation magnification with a transmission electron microscope: 1,000,000 times).

  The catalyst performance was evaluated in the same manner as in Example 1 except that the methacrolein reaction time was 3 hours. As a result, the methacrolein reaction rate was 42.5%, the methacrylic acid selectivity was 59.8%, and the polymer / oligomer selectivity was 29. The yield was 6% and the yield of methacrylic acid was 25.4%.

  The above results are summarized in Table 1. Thus, it was found that α, β-unsaturated carboxylic acid can be produced from olefin or α, β-unsaturated aldehyde in high yield by using the palladium-containing supported catalyst of the present invention.

Claims (3)

  A catalyst for producing an α, β-unsaturated carboxylic acid by oxidizing an olefin or α, β-unsaturated aldehyde in the liquid phase with molecular oxygen, and having an average particle size in the range of 1 to 8 nm. A palladium-containing supported catalyst in which palladium is supported on a carrier.   The method for producing a palladium-containing supported catalyst according to claim 1, wherein the palladium compound is reduced with a reducing agent in the presence of a carrier.   A process for producing an α, β-unsaturated carboxylic acid in which an olefin or an α, β-unsaturated aldehyde is oxidized in the liquid phase with molecular oxygen in the presence of the palladium-containing supported catalyst according to claim 1.