JP2005238226A - Method for producing noble metal-containing catalyst - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a noble metal-containing catalyst which is highly active and productive. <P>SOLUTION: The method for producing the noble metal-containing catalyst is characterized by immersing a product obtained by the reduction of at least noble metal compounds in a solution containing a reducing agent for three days or more. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a noble metal-containing catalyst having high activity and productivity.

  As described in Non-Patent Document 1, the precious metal-containing catalyst is used for various purposes such as environmental conservation use including purification of exhaust gas from automobiles, chemical use such as petroleum refining, petrochemistry, medicine, fragrance and food. in use. In chemical applications, it is used as a catalyst for synthesizing and producing various compounds by various chemical reactions such as hydrogenation, dehydrogenation, oxidation, carbonylation, hydroformylation and the like. Many of these have already been established industrially, but some of them are still under development and development for industrialization is underway.

  One method under development includes a method of producing an α, β-unsaturated carboxylic acid by oxidizing an olefin or α, β-unsaturated aldehyde with molecular oxygen. For example, Patent Document 1 discloses a method for producing an α, β-unsaturated carboxylic acid by liquid phase oxidation of an olefin with molecular oxygen using a palladium-containing catalyst containing palladium which is a noble metal. .

On the other hand, the precious metal itself is generally not easily oxidized even in the air as used for jewelry, and is easy to handle. It is easily oxidized and may be deactivated if left in the air. Therefore, it is generally stored after being dampened or immersed in water.
JP 60-155148 A By Muroi Takagi, industrial precious metal catalyst, published by JETI

  When the present inventor produced acrylic acid from propylene using a palladium-containing catalyst produced in accordance with the method described in the Examples of Patent Document 1, by-products (acetaldehyde, acetone described in Patent Document 1) In addition to acrolein, acetic acid, carbon dioxide), it was found that a large amount of various polymers and oligomers were by-produced, and it was found that the productivity of acrylic acid calculated including these by-products was low. As described above, the catalyst produced by the method described in Patent Document 1 does not yet have sufficient performance when used for the production of α, β-unsaturated carboxylic acid, and the α, β-unsaturated carboxylic acid having higher activity and productivity. There has been a demand for a method for producing a noble metal-containing catalyst that can be used as a catalyst for acid production.

  It is an object of the present invention to provide a method for producing a noble metal-containing catalyst having high activity and productivity.

  That is, the first gist of the present invention is a method for producing a noble metal-containing catalyst characterized in that at least a product obtained by reducing a noble metal compound is immersed in a solution containing a reducing agent for 3 days or more. is there.

  The concentration of the reducing agent in the solution is 0.01 to 50% by mass, the mass ratio of the solution to the product is 0.1 to 100, and the temperature of the solution is 0 to 40 ° C. Each is preferred.

  The reducing agent is one selected from the group consisting of ethanol, 2-propanol, hydrazine, formaldehyde, formic acid, oxalic acid, sodium borohydride, hydrogen, ethylene, propylene, 1-butene, 2-butene, and isobutylene. The above is preferable.

  Furthermore, you may have the process of carrying | supporting the said product on a support | carrier.

  The noble metal-containing catalyst can be suitably used as a catalyst for producing an α, β-unsaturated carboxylic acid by oxidizing an olefin or an α, β-unsaturated aldehyde with molecular oxygen.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of a noble metal containing catalyst with high activity and productivity can be provided.

  First, the manufacturing method of the noble metal containing catalyst of this invention is demonstrated in detail.

  In the present invention, the noble metal refers to palladium, platinum, rhodium, ruthenium, iridium, gold, silver, rhenium, or osmium. These precious metals contained in the precious metal-containing catalyst of the present invention may be used alone or as a mixture of two or more. Of these, palladium, platinum, rhodium, ruthenium, iridium and gold are preferable, and palladium is particularly preferable.

  The noble metal compound used as the raw material for the noble metal used in the production of the noble metal-containing catalyst is not particularly limited, and examples thereof include noble metal chlorides, oxides, acetates, nitrates, sulfates, tetoamine complexes, and acetylacetonate complexes. Compounds containing a noble metal atom in an oxidized state are preferred, and among them, noble metal chlorides, acetates and nitrates are more preferred.

  The noble metal-containing catalyst of the present invention may contain any metal other than the noble metal. When a metal other than a noble metal is contained, a noble metal compound and a metal compound of the metal may be used in combination. For example, as described later, when the reduction is performed in a liquid phase, a method in which a metal compound is dissolved in the solvent can be used. From the viewpoint of catalytic activity, it is preferable that the amount of the metal other than the noble metal in the noble metal-containing catalyst is 50 atomic% or less.

In the method for producing a noble metal-containing catalyst of the present invention, in order to improve the surface area of the noble metal in the product obtained by reducing at least the noble metal compound and realize high dispersion, and to control the acid point and base point, You may have the process which makes the support | carrier carry | support the product. As the method, for example, when the reduction is performed in a liquid phase as described later, a method of dispersing a carrier in the solvent can be used. As the carrier, for example, activated carbon, carbon black, silica, alumina, magnesia, calcia, titania, zirconia, and the like can be used, and any of activated carbon, silica, and alumina is preferably used. The specific surface area of the preferred support varies depending on the type of the support and the like, but it cannot be generally stated. In the case of activated carbon, it is usually 100 m ² / g or more, preferably 300 m ² / g or more, usually 5000 m ² / g or less, preferably 4000 m. ² / g or less. The smaller the specific surface area of the support is, the more the useful component is supported on the surface. The larger the lower limit is, the more the useful component is supported. In the case of using a carrier, the precious metal loading is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 1% by mass or more with respect to the mass of the carrier. Moreover, it is 40 mass% or less normally, Preferably it is 30 mass% or less, More preferably, it is 20 mass% or less.

  In the method for producing a noble metal-containing catalyst of the present invention, these raw materials are mixed to reduce at least the noble metal compound. The reduction may be performed in the gas phase, but is preferably performed in the liquid phase. When performing in a liquid phase, after dissolving a noble metal compound in a solvent, at least the noble metal compound is reduced using a reducing agent.

  The reduction temperature varies depending on the precious metal compound, the reducing agent, etc. used, but is usually −5 ° C. or higher, preferably 15 ° C. or higher. Moreover, it is normally performed at 150 ° C. or lower, preferably 80 ° C. or lower. The reduction time is usually 0.1 hour or longer, preferably 0.25 hour or longer, more preferably 0.5 hour or longer. Moreover, it is 4 hours or less normally, Preferably it is 3 hours or less, More preferably, it is 2 hours or less.

  The solvent used in the reduction in the liquid phase is preferably water, but depending on the solubility of the noble metal compound and the reducing agent and the dispersibility of the carrier when the carrier is used, ethanol, 1-propanol, 2- Alcohols such as propanol, n-butanol and t-butanol; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; organic acids such as acetic acid, n-valeric acid and iso-valeric acid; carbonization such as heptane, hexane and cyclohexane An organic solvent such as hydrogen can be used alone or in combination. Moreover, it is preferable to use the mixed solvent of these organic solvents and water. In particular, when palladium chloride is used as the noble metal compound, a mixed solvent of ethanol and water, a mixed solvent of acetone and water, or a mixed solvent of acetic acid and water is preferable.

  The reducing agent is selected from the group consisting of methanol, ethanol, 2-propanol, hydrazine, formaldehyde, formic acid, sodium formate, oxalic acid, sodium borohydride, hydrogen, ethylene, propylene, 1-butene, 2-butene and isobutylene. 1 or more selected from the group consisting of ethanol, 2-propanol, hydrazine, formaldehyde, sodium borohydride, hydrogen, ethylene, propylene, 1-butene, 2-butene and isobutylene. And most preferably one or more selected from the group consisting of hydrazine, formaldehyde, hydrogen and propylene.

  When the reducing agent is a gas, it is preferably carried out in a pressurizing apparatus such as an autoclave in order to increase the solubility in the solution. 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, there is no restriction | limiting in the apparatus which reduces a noble metal compound, It can carry out by adding a reducing agent in a noble metal compound solution. Although the usage-amount of a reducing agent at this time is not specifically limited, It is about 1-100 mol normally with respect to 1 mol of noble metal compounds.

  The method of the present invention includes a step of immersing the product obtained by reducing at least the noble metal compound by the above method in a solution containing a reducing agent for 3 days or more, preferably 7 days or more. This is particularly important, and the activity and productivity of the resulting noble metal-containing catalyst is low unless immersed for more than 3 days. Moreover, there is no restriction | limiting in particular about an upper limit, Even if it immerses over a long period of time, the activity and productivity of a noble metal containing catalyst will hardly fall. For example, there is no problem in principle even if immersion is performed for one year. However, in reality, it is rare that the produced noble metal-containing catalyst is used over a long period of time, and the above immersion period is usually within 6 months, preferably within 3 months.

  The reason why the activity and productivity of the resulting noble metal-containing catalyst is improved by immersion for 3 days or more is not clear, but a mild reducing atmosphere such as immersion causes new active sites that cannot be generated by normal reduction. It seems to increase on the surface.

  The solution containing the reducing agent used here can be prepared by selecting from the same reducing agent and solvent as in the case of reducing at least the noble metal compound in the liquid phase. As described above, when at least the reduction of the noble metal compound is performed in the liquid phase, the solution may be used as it is without preparing a solution containing the reducing agent separately. When the reducing agent used at that time is a gas and is pressurized during the reduction, the pressure may be returned to normal pressure. Moreover, since immersion may be left still, you may transfer to a different storage container etc.

  The temperature of the solution is preferably 0 to 40 ° C., that is, normal temperature. If it is too low, the activity of the precious metal-containing catalyst that may be difficult to exhibit the effect of immersion may be lowered. On the other hand, even if it is too high, the activity of the noble metal-containing catalyst that can make the effect of immersion difficult to appear may be lowered.

  The concentration of the reducing agent in the solution used for the immersion is usually 0.01% by mass or more, preferably 0.05% by mass or more, and more preferably 0.1% by mass or more. Moreover, it is 50 mass% or less normally, Preferably it is 10 mass% or less, More preferably, it is 5 mass% or less. If it is too low, the activity of the precious metal-containing catalyst that may be difficult to exhibit the effect of immersion may be lowered. On the other hand, if it is too high, the activity of the noble metal-containing catalyst obtained because the reducing agent is too strong may decrease.

  Furthermore, it is preferable that the mass ratio of the solution used at the time of immersion and the product immersed therein (at least obtained by reducing a noble metal compound) is 0.1 to 100. More preferably, it is 0.5 or more, More preferably, it is 1 or more. Further, it is more preferably 50 or less, and further preferably 20 or less. If the surface is too small, the surface of the noble metal may be oxidized. Conversely, if the surface is too large, the effect is hardly changed, and the solution is likely to be wasted.

  And after washing | cleaning and filtering the noble metal containing catalyst which was immersed suitably, it uses for reaction. For washing, water, warm water or a reaction solvent is used. Filtration is preferably performed in an inert gas atmosphere such as nitrogen, carbon dioxide, or argon. By washing, for example, impurities derived from raw material salts such as chloride, acetate radical, nitrate radical, and sulfate radical are removed. The cleaning method and the number of times are not particularly limited. However, depending on the impurities, the reaction may be hindered. Therefore, it is preferable that the cleaning is performed to such an extent that the impurities can be sufficiently removed.

  When storing the noble metal-containing catalyst obtained by such a method, it is preferable to store it by immersing it in a solution containing a reducing agent. It is particularly preferred to store in this state until use in the reaction. By immersing and storing in a solution containing a reducing agent in this way, oxidation of the noble metal-containing catalyst can be prevented and stable storage is possible. The solution containing the reducing agent used at this time may be the solution used when the above immersion is performed, or may be a solution prepared separately. Further, this storage method is applicable not only to the noble metal-containing catalyst obtained by the above-described method, and in any case, the effect that the activity and productivity of the noble metal-containing catalyst are hardly lowered is exhibited. The precious metal-containing catalyst that has been soaked and stored in this manner is appropriately washed and filtered before use in the reaction.

  The thus-prepared noble metal-containing catalyst can be used for various reactions. In particular, a catalyst for producing an α, β-unsaturated carboxylic acid by oxidizing an olefin or an α, β-unsaturated aldehyde with molecular oxygen. It is effective when used as. Here, a method for producing an α, β-unsaturated carboxylic acid by liquid phase oxidation of olefin or α, β-unsaturated aldehyde with molecular oxygen will be described.

  Examples of the raw material olefin include propylene, isobutylene, and 2-butene. Among these, propylene and isobutylene are preferable. Examples of the raw α, β-unsaturated aldehyde include acrolein, methacrolein, crotonaldehyde (β-methylacrolein), and cinnamaldehyde (β-phenylacrolein). Among these, acrolein and methacrolein are preferable. Is preferred. The raw material olefin or α, β-unsaturated aldehyde may contain a small amount of saturated hydrocarbon and / or lower saturated aldehyde as impurities.

  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 noble metal-containing 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.

  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.

  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.

  Examples of the reaction solvent for the liquid phase oxidation reaction include tertiary butanol, cyclohexanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, acetic acid, propionic acid, n-butyric acid, iso-butyric acid, n-valeric acid, iso-valeric acid, It is preferable to use at least one compound selected from the group consisting of ethyl acetate and methyl propionate. Among these, at least one compound selected from the group consisting of tertiary butanol, methyl isobutyl ketone, acetic acid, propionic acid, n-butyric acid, iso-butyric acid, n-valeric acid and iso-valeric acid is more preferable. Further, in order to produce an α, β-unsaturated carboxylic acid with high selectivity, it is preferable to coexist water in these organic solvents. The amount of water to coexist is not particularly limited, but is usually 2% by mass or more, preferably 5% by mass or more, based on the total mass of the organic solvent and water. Moreover, it is 70 mass% or less normally, Preferably it is 50 mass% or less. The mixture of the organic solvent and water is desirably in a uniform state, but may be in a non-uniform state.

  The concentration of the olefin or α, β-unsaturated aldehyde which is a raw material for the reaction is usually 0.1% by mass or more, preferably 0.5% by mass or more, based on the solvent present in the reactor. Moreover, it is 20 mass% or less normally, Preferably it is 10 mass% or less.

  The amount of molecular oxygen to be used is usually 0.1 mol or more, preferably 0.3 mol or more, more preferably 0.5 mol or more with respect to 1 mol of the raw material olefin or α, β-unsaturated aldehyde. is there. Moreover, it is 20 mol or less normally, Preferably it is 15 mol or less, More preferably, it is 10 mol or less.

  Usually, the noble metal-containing catalyst is used in a state of being suspended in the reaction solution, but may be used in a fixed bed. The amount of the noble metal catalyst used is usually 0.1% by mass or more, more preferably 0.5% by mass or more, and further preferably 1% by mass or more with respect to the solution present in the reactor. Moreover, it is 30 mass% or less normally, 20 mass% or less is more preferable, and 15 mass% or less is further more preferable.

  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. The reaction rate of isobutylene, the methacrolein (MAL), the selectivity of methacrylic acid (MAA) and polymer / oligomer, and the productivity of MAA are defined as follows.

Reaction rate of isobutylene (%) = (B / A) × 100
Selectivity of methacrolein (MAL) (%) = (C / B) × 100
Methacrylic acid (MAA) selectivity (%) = (D / B) × 100
Selectivity of polymer / oligomer (%) = (E / B) × 100
MAA productivity (g / g-Me / h) = F / (G × H)
here,
A is the number of moles of isobutylene supplied,
B is the number of moles of reacted isobutylene,
C is the number of moles of methacrolein produced,
D is the number of moles of methacrylic acid produced,
E is the number of moles of polymer and oligomer in terms of isobutylene calculated by dividing the total weight (unit: g) of the produced polymer and oligomer by the molecular weight of the supplied isobutylene,
F is the mass of the generated methacrylic acid (unit: g),
G is the mass of the noble metal contained in the noble metal-containing catalyst (unit: g-Me),
H is the reaction time (unit: h).

[Example 1]
(Preparation of precious metal-containing catalyst)
1.1 parts of palladium acetate (manufactured by NE Chemcat) was dissolved by heating in 60 parts of an 88 mass% n-valeric acid aqueous solution. To this solution, 5.0 parts of activated carbon (specific surface area of 780 m ^{2 /} g) was added, charged in an autoclave and sealed. Stirring was started, the internal liquid temperature was cooled to 10 ° C. or lower, propylene gas was introduced to an internal pressure of 0.5 MPa, and the mixture was held at 50 ° C. for 1 hour. After 1 hour, the temperature of the internal liquid was lowered to 20 ° C. or lower, and then the internal pressure was released. Thereafter, the solid-liquid mixture of the catalyst in the autoclave and the valeric acid aqueous solution in which propylene was dissolved was put in another container and capped. The propylene concentration in the liquid at this time was 2.0% by mass. Immersion was performed for 4 days, and suction filtration was performed immediately before the start of the reaction, followed by washing with tertiary butanol several times to obtain an activated carbon-supported palladium catalyst. The palladium loading rate of this catalyst was 10% by mass.

(Reaction evaluation)
The autoclave was sealed with 5.5 parts of an activated carbon-supported palladium catalyst obtained by the above method and 75 parts of a 75% by weight tertiary butanol aqueous solution as a reaction solvent, and the autoclave was sealed. Next, 2.0 parts of isobutylene was introduced, stirring (rotation speed: 100 rpm) was started, and the temperature was raised to 90 ° C. After completion of the temperature increase, nitrogen was introduced into the autoclave to an internal pressure of 2.4 MPa, and then compressed air was introduced to an internal pressure of 4.8 MPa. When the internal pressure decreased by 0.1 MPa during the reaction (internal pressure 4.7 MPa), the operation of introducing 0.1 MPa of oxygen was repeated. The pressure immediately after introduction is 4.8 MPa. The reaction was performed for 80 minutes.

  After completion of the reaction, the inside of the autoclave was ice-cooled in an ice bath. A gas collection bag was attached to the gas outlet of the autoclave, and the pressure in the reactor was released while collecting the gas that was opened by opening the gas outlet. The reaction solution containing the catalyst was taken out from the autoclave, the catalyst was separated by a membrane filter, and only the reaction solution was recovered. The collected reaction liquid and the collected gas were analyzed by gas chromatography. The results are shown in Table 1. It was found that the reaction rate and MAA productivity of isobutylene were high, and the activity and productivity of the resulting noble metal-containing catalyst were high.

[Example 2]
The same operation as in Example 1 was performed except that the immersion days were 8 days and the reaction time was 60 minutes. The results are shown in Table 1. It was found that the reaction rate and MAA productivity of isobutylene were high, and the activity and productivity of the resulting noble metal-containing catalyst were high.

[Example 3]
The same operation as in Example 1 was carried out except that the immersion days were 13 days and the reaction time was 50 minutes. The results are shown in Table 1. It was found that the reaction rate and MAA productivity of isobutylene were high, and the activity and productivity of the resulting noble metal-containing catalyst were high.

[Example 4]
The same operation as in Example 1 was carried out except that an immersion liquid having a propylene concentration of 0.1% by mass was used, the immersion period was 11 days, and the reaction time was 70 minutes. The results are shown in Table 1. It was found that the reaction rate and MAA productivity of isobutylene were high, and the activity and productivity of the resulting noble metal-containing catalyst were high.

[Comparative Example 1]
The same operation as in Example 2 was performed except that the number of days of immersion was set to 1. The results are shown in Table 1. The reaction rate of isobutylene and MAA productivity were low.

[Comparative Example 2]
The same operation as in Example 2 was performed except that an 88 mass% n-valeric acid aqueous solution in which the reducing agent was not dissolved was used as the immersion liquid. The results are shown in Table 1. The reaction rate of isobutylene and MAA productivity were low.

[Comparative Example 3]
The same operation as in Comparative Example 1 was performed except that the reaction time was 130 minutes. The results are shown in Table 1. Since the reaction time was increased, the reaction rate of isobutylene was the same as in the examples, but the MAA productivity was low.

[Comparative Example 4]
The same operation as in Comparative Example 1 was performed except that the reduction time was 300 minutes and the reaction time was 160 minutes. The results are shown in Table 1. Since the reaction time was increased, the reaction rate of isobutylene was the same as in the examples, but the MAA productivity was low.

[Comparative Example 5]
The same operation as in Comparative Example 1 was performed except that the reduction temperature was 80 ° C. and the reaction time was 120 minutes. The results are shown in Table 1. Since the reaction time was increased, the reaction rate of isobutylene was the same as in the examples, but the MAA productivity was low.

Claims (7)

  A method for producing a noble metal-containing catalyst, comprising a step of immersing a product obtained by reducing at least a noble metal compound in a solution containing a reducing agent for 3 days or more.   The method for producing a noble metal-containing catalyst according to claim 1, wherein the concentration of the reducing agent in the solution is 0.01 to 50% by mass.   The mass ratio of the said solution and the said product is 0.1-100, The manufacturing method of the noble metal containing catalyst of Claim 1 or 2 characterized by the above-mentioned.   The temperature of the said solution is 0-40 degreeC, The manufacturing method of the noble metal containing catalyst of any one of Claims 1-3 characterized by the above-mentioned.   The reducing agent is selected from the group consisting of methanol, ethanol, 2-propanol, hydrazine, formaldehyde, formic acid, sodium formate, oxalic acid, sodium borohydride, hydrogen, ethylene, propylene, 1-butene, 2-butene and isobutylene. The method for producing a noble metal-containing catalyst according to any one of claims 1 to 4, wherein the catalyst is one or more.   The method for producing a noble metal-containing catalyst according to any one of claims 1 to 5, further comprising a step of supporting the product on a support. 7. The catalyst according to claim 1, wherein the noble metal-containing catalyst is a catalyst for producing an α, β-unsaturated carboxylic acid by oxidizing an olefin or an α, β-unsaturated aldehyde with molecular oxygen. A method for producing a noble metal-containing catalyst.