JP4041952B2 - Gold ultrafine particle support and catalyst comprising the support - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gold ultrafine particle carrier, a method for producing the same, and a catalyst comprising the carrier.
[0002]
[Prior art]
A gold ultrafine particle carrier in which gold ultrafine particles are supported on various carriers is used as a highly active catalyst in various applications such as an oxidation reaction catalyst and a hydrogenation reaction catalyst.
[0003]
Conventionally, as a method for producing a gold ultrafine particle carrier, a gold compound-containing aqueous solution is dropped into an oxide-containing aqueous solution having a pH of about 7 to 11, and a gold compound is precipitated on the oxide surface, followed by firing ( Precipitation / precipitation method): A method in which a reducing agent is dropped into an oxide-containing aqueous solution having a pH of about 7 to 11 in which a gold compound is dissolved to reduce and precipitate gold (reduction method); A method is disclosed in which carbon dioxide is blown into an aqueous solution, or an acidic aqueous solution is added to lower the pH to precipitate gold hydroxide, followed by firing, etc. No. 252908). )
In these methods, when a carrier having a small specific surface area is used, if a large amount of gold is supported, the gold particle size becomes large and cannot be supported as ultrafine particles, and gold is supported as ultrafine particles. For this purpose, there is a restriction that the amount of the load must be reduced. Therefore, in order to support gold as ultrafine particles and increase the amount supported, the specific surface area by the BET method is 50 m.²It is necessary to use a carrier having a high specific surface area exceeding about / g.
[0004]
However, a support in which ultrafine gold particles are supported on a carrier having a high specific surface area is useful as a catalyst having high activity. However, since it usually contains a lot of extra active sites such as acid sites, it is used as a catalyst. In this case, there is a harmful effect that the side reaction increases and the selectivity of the main reaction decreases.
[0005]
Therefore, if a large amount of ultrafine gold particles can be supported on a carrier having a small specific surface area and low activity, it is expected that side reactions can be suppressed and the selectivity of the main reaction can be improved. The
[0006]
[Problems to be solved by the invention]
The present invention has been made in view of the current state of the prior art described above, and its main object is to enable a large amount of ultrafine gold particles to be supported on a carrier having a small specific surface area and low activity. It is an object of the present invention to provide a novel ultrafine gold particle support useful as a reaction catalyst having various activities and excellent selectivity.
[0007]
[Means for Solving the Problems]
The present inventor has intensively studied to achieve the above-described object. As a result, a so-called precipitation method is adopted as a method for supporting the gold ultrafine particles, and the pH of the solution containing the inorganic oxide carrier and the gold compound is set to a specific pH range lower than the pH range in the conventional precipitation method. In some cases, it was surprisingly found that a large amount of ultrafine gold particles can be supported on an oxide carrier having a low specific surface area, and the present invention has been completed.
[0008]
  That is, the present invention supports gold ultrafine particlesBody, andAnd a catalyst comprising the support.
1. Specific surface area by BET method is 30m²Supporting ultrafine gold particles comprising 3 parts by weight or more of ultrafine gold particles having an average particle diameter of 25 nm or less with respect to 100 parts by weight of the inorganic oxide as a carrier.body.
2. An oxidation reaction catalyst comprising the ultrafine gold particle support according to Item 1.
3. A catalyst for hydrogenation reaction comprising the gold ultrafine particle support according to Item 1.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Gold ultrafine particle carrier
The ultrafine gold particle carrier of the present invention has a specific surface area of 30 m by the BET method.²3 parts by weight or more of gold ultrafine particles having an average particle diameter of 25 nm or less are supported on 100 parts by weight of an inorganic oxide of / g or less.
[0010]
The ultrafine gold particle carrier has a specific surface area of 30 m as measured by the BET method.²/ G or less of an inorganic oxide carrier having a low specific surface area to which a large amount of ultrafine gold particles are supported. Such a gold ultrafine particle carrier has a large amount of gold ultrafine particles supported and high catalytic activity, and the carrier has a small surface area and is inactive, and has few extra active sites such as acid sites. Therefore, it is useful as a highly selective catalyst with few side reactions.
[0011]
The carrier has a specific surface area of 30m by the BET method.²/ G or less is necessary, preferably 10 m²/ G or less is used.
[0012]
There are no particular limitations on the type of carrier, but inorganic oxides are preferable. Among them, the intended ultrafine gold particles are supported particularly when inorganic oxides having an isoelectric point of pH 7 or higher are used. The body is easy to obtain. On the other hand, when an inorganic oxide having an isoelectric point lower than pH 7 is used as a carrier, the amount of gold supported in the resulting gold carrier is increased, and the particle size of the gold is reduced to obtain ultrafine particles. It will be difficult to achieve both at the same time. Specific examples of inorganic oxides having a surface isoelectric point of pH 7 or higher include aluminum, iron, cobalt, nickel, copper, zinc, gallium, alkaline earths (magnesium, calcium, barium, etc.), lanthanoids (lanthanum) Inorganic oxides containing at least one element such as cerium and the like are preferred. Among these, an inorganic oxide containing zinc is preferable, and it is particularly preferable to use zinc oxide as a carrier.
[0013]
In the gold ultrafine particle carrier, the particle size of the supported gold ultrafine particle is not limited, but is preferably an ultrafine particle having an average particle size of about 25 nm or less, and an average particle size of about 20 nm or less. More preferably, the average particle size is more preferably about 10 nm or less. By supporting such gold ultrafine particles on a support, a support having high catalytic activity can be obtained. The lower limit of the average particle diameter is not particularly limited, but may be about 1 nm from the viewpoint of physical stability. The average particle size of the metal fine particles in the catalyst is an arithmetic average value of 100 particle sizes arbitrarily selected by observing the metal fine particles on the carrier with a transmission electron microscope (TEM).
[0014]
The amount of gold ultrafine particles supported can be about 3 parts by weight or more with respect to 100 parts by weight of the carrier by the production method of the present invention described later. Specific surface area by BET method is 30m²A support formed by supporting such a large amount of gold ultrafine particles on an inorganic oxide support of about / g or less is a novel gold ultrafine particle support that has not been obtained so far. The upper limit of the loading amount may be appropriately determined according to the use of the final product, the type of the carrier, etc., but the loading amount is usually in the range of about 3 to 20 parts by weight with respect to 100 parts by weight of the carrier. preferable.
Method for producing gold ultrafine particle carrier
In the present invention, the inorganic oxide carrier is dispersed in an aqueous solution in which a gold compound is dissolved, and the gold-containing precipitate is deposited on the surface of the inorganic oxide, and then the inorganic oxide on which the gold-containing precipitate is deposited is fired. That is, it is necessary to employ a precipitation method. In the precipitation method, the gold-containing precipitate is precipitated in a state in which the pH of the gold compound-containing aqueous solution in which the inorganic oxide carrier is dispersed is maintained in a specific range of 4 to 6.8. Surface area is 30m²It becomes possible to support a large amount of ultrafine gold particles of 3 parts by weight or more with respect to 100 parts by weight of the inorganic oxide support having a low specific surface area of / g or less.
[0015]
The water-soluble compound containing gold used in the method of the present invention is not limited as long as it is a water-soluble gold compound. For example, tetrachloroauric (III) acid “H [AuCl_Four], Sodium tetrachloroaurate (III) "Na [AuCl_Four], Potassium dicyanoaurate (I) "K [Au (CN)₂], Diethylamine gold (III) trichloride "(C₂H_Five)₂NH [AuCl_Three]; And gold compounds such as gold (C) cyanide. These compounds can be used individually by 1 type or in mixture of 2 or more types.
[0016]
The gold concentration of the aqueous solution varies depending on the type of compound used, but is usually about 0.1 to 100 mmol / l.
[0017]
The inorganic oxide carrier to be mixed with the aqueous solution may be used in any form such as a granular form or a granulated body. The amount of the carrier used may be an amount that can uniformly disperse the carrier in water, and may be set as appropriate according to the concentration of the aqueous solution, the type of carrier used, etc., but is usually about 10 to 200 g / l. Is appropriate.
[0018]
A surfactant may be added to the aqueous solution as necessary. The surfactant may be appropriately selected from known or commercially available products according to the aqueous solution. For example, anionic surfactants such as long-chain alkyl sulfonic acids and salts thereof, long-chain alkyl benzene sulfonic acids and salts thereof, long-chain alkyl carboxylic acids and salts thereof, aryl carboxylic acids and salts thereof; long-chain alkyl quaternary ammonium salts And the like; and nonionic surfactants such as polyalkylene glycol and polyoxyethylene nonylphenol. These surfactants can be used singly or in combination of two or more. In the present invention, anionic surfactants and nonionic surfactants are preferred, and anionic surfactants are particularly preferred. Among anionic surfactants, in particular, long-chain alkyl sulfonic acids having 8 or more carbon atoms and salts thereof, long-chain alkyl benzene sulfonic acids and salts thereof having 8 or more carbon atoms, long-chain alkyl carboxylic acids having 8 or more carbon atoms and their salts More preferred are salts, arylcarboxylic acids and salts thereof.
[0019]
The amount of the surfactant used can be appropriately determined depending on the desired dispersibility, the type of the surfactant used, and the like, but usually the surfactant concentration may be about 0.1 to 10 mmol / l.
[0020]
The gold compound-containing aqueous solution in which the carrier is dispersed needs to be in the range of about pH 4 to 6.8, and preferably in the range of about pH 5 to 6.5. By setting the pH of the gold compound-containing aqueous solution within this range, the particle size of gold supported on the resulting gold support is reduced and the amount of gold supported is increased. Obtainable. On the other hand, when the pH of the gold compound-containing aqueous solution is smaller than 4, the gold particle diameter of the obtained gold carrier becomes large, and gold ultrafine particles cannot be supported. On the other hand, when the pH exceeds 6.8, the average particle size of gold becomes small and it becomes easy to obtain ultrafine particles, but gold cannot be supported in a large amount.
[0021]
In this way, by adjusting the pH of the gold compound-containing aqueous solution to the specific range described above, 30 m²It becomes possible to carry a large amount of ultrafine gold particles on an inorganic oxide carrier having a low specific surface area of about / g or less. The pH of the aqueous solution can be adjusted with an alkali such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, or ammonia. If necessary, an acid such as hydrochloric acid can be used. These alkalis or acids may be used in the form of an aqueous solution as necessary.
[0022]
The liquid temperature of the gold compound-containing aqueous solution in which the carrier is dispersed is not particularly limited, but is usually about 10 to 100 ° C.
[0023]
The mixing time of the aqueous solution in which the carrier is dispersed can be appropriately changed depending on the type and shape of the carrier, but it is usually within a range of about 1 minute to 24 hours, preferably 10 minutes to 3 hours. What is necessary is just to set so that the deposit containing this may precipitate on a support | carrier.
[0024]
After mixing and stirring the aqueous solution in which the carrier is dispersed, an inorganic oxide in which a gold-containing precipitate is precipitated can be obtained by collecting the solid content. The solid content can be recovered by recovering the supernatant or according to a known solid-liquid separation method. The recovered solid content is preferably washed with ion-exchanged water or the like until residual ions are substantially eliminated.
[0025]
Subsequently, baking of solid content is performed. In this case, firing refers to heat treatment at a high temperature. Furthermore, if necessary, prior to firing, heating and drying may be performed. The drying temperature may usually be less than 150 ° C. The firing temperature is usually about 150 to 800 ° C, preferably 200 to 700 ° C, more preferably 250 to 600 ° C. The firing atmosphere is not particularly limited, and may be in air (air) or an oxidizing atmosphere, or in an inert gas atmosphere such as nitrogen, argon gas, or helium, in a reducing atmosphere such as hydrogen gas or carbon monoxide. There may be. The firing time may be appropriately determined according to the firing temperature, the size of the solid content, and the like. By firing, a gold ultrafine particle carrier in which gold is firmly fixed to the surface of the carrier can be obtained.
[0026]
According to the method of the present invention, the specific surface area is 30 m.²A large amount of ultrafine gold particles of 3 parts by weight or more per 100 parts by weight of the inorganic oxide support having a specific surface area as low as about / g or less can be supported.
[0027]
The obtained ultrafine gold particle support is useful for various reactions as a catalyst for oxidation reaction or hydrogenation reaction as a catalyst having high activity and excellent selectivity. As the oxidation reaction, it is useful for an oxidation reaction of an organic compound, is suitably used for an oxidation reaction of alcohols, aldehydes, etc., and is particularly useful for these oxidation reactions using molecular oxygen as an oxidizing agent. The hydrogenation reaction is useful for hydrogenation reactions of organic compounds, and is suitably used for hydrogenation reactions of carbonyl groups such as ketones and aldehydes. In particular, these hydrogens using molecular hydrogen as a hydrogenating agent. It is useful for chemical reaction.
[0028]
Hereinafter, examples of use of the gold ultrafine particle support of the present invention as an oxidation reaction catalyst or a hydrogenation reaction catalyst will be specifically described.
Catalyst for oxidation reaction
Production of carboxylic acid esters from aldehydes and alcohols
The gold ultrafine particle support of the present invention can be suitably used as a highly active and highly selective catalyst in the production of a carboxylic acid ester from an aldehyde and an alcohol in the presence of oxygen. In particular, when the above reaction is carried out in the presence of the ultrafine gold particle support of the present invention, by-products such as acetals that are produced in a relatively large amount under normal conditions are greatly suppressed, and the carboxylic acid has good selectivity. Esters can be produced.
[0029]
Examples of the aldehyde include aliphatic aldehydes having 1 to 10 carbon atoms such as formaldehyde, acetaldehyde, propionaldehyde, isobutyraldehyde, glyoxal, and pyrualdehyde; Saturated aldehydes: In addition to aromatic aldehydes having 6 to 20 carbon atoms such as benzaldehyde, p-methoxybenzaldehyde, tolualdehyde and phthalaldehyde, derivatives of these aldehydes can be used. Preferably, aliphatic aldehydes, α, β-unsaturated aldehydes and the like can be used. These aldehydes can be used singly or in combination of two or more.
[0030]
Examples of the alcohol include aliphatic alcohols having 1 to 10 carbon atoms such as methanol, ethanol, isopropanol and octanol; diols having 2 to 10 carbon atoms such as ethylene glycol and butanediol; and 3 to 3 carbon atoms such as allyl alcohol and methallyl alcohol. 10 aliphatic unsaturated alcohols; aromatic alcohols such as benzyl alcohol can be used. Preferably, a C1-C10 aliphatic alcohol etc. can be used. These alcohols can be used singly or in combination of two or more.
[0031]
In the production method of the present invention, the aldehyde and alcohol as raw materials may be appropriately selected according to the type of the target carboxylic acid ester. For example, when synthesizing methyl methacrylate, methacrolein may be used as the aldehyde and methanol may be used as the alcohol.
[0032]
Although the reaction ratio of aldehyde and alcohol is not particularly limited, the molar ratio of aldehyde / alcohol is preferably about 10 to 1/200, and more preferably in the range of 1/2 to 1/50. If it is in the said range, it will become possible to synthesize | combine carboxylic acid ester more efficiently.
[0033]
In the present invention, a carboxylic acid ester can be obtained by performing a reaction between an aldehyde and an alcohol in the presence of a catalyst comprising the gold ultrafine particle support of the present invention and oxygen (molecular oxygen).
[0034]
The reaction may be any of a liquid phase reaction and a gas phase reaction. Oxygen (oxygen gas) may be diluted with an inert gas such as nitrogen gas, argon gas, helium gas or carbon dioxide gas. Air can also be used as the oxygen-containing gas. The method for supplying oxygen to the reaction system is not particularly limited, and a known method can be applied.
[0035]
The form of the reaction may be any of continuous type, batch type, semi-batch type, etc., and is not particularly limited. In the case of adopting a batch system as a reaction form, the catalyst may be charged into the reaction apparatus together with the raw materials. Further, when a continuous type is adopted as the reaction form, the catalyst may be charged in advance in the reaction device, or the catalyst may be continuously charged together with the raw material in the reaction device. The catalyst may be in any form such as a fixed bed, a fluidized bed, and a suspended bed.
[0036]
What is necessary is just to determine the usage-amount of a catalyst suitably according to the combination of an aldehyde and alcohol, the kind of catalyst, reaction conditions, etc. The reaction time is not particularly limited and varies depending on the set conditions. Usually, the reaction time or residence time (retention liquid amount in the reactor / liquid supply amount) may be about 0.5 to 20 hours.
[0037]
Various conditions such as reaction temperature and reaction pressure may be appropriately determined according to the combination of aldehyde and alcohol, the type of catalyst, and the like. The reaction temperature is usually about 0 to 180 ° C, preferably 20 to 150 ° C. By setting the temperature within this range, the reaction can proceed more efficiently. The reaction pressure may be any of reduced pressure, normal pressure or increased pressure, but is preferably in the range of about 0.05 to 2 MPa (gauge pressure). Further, the total pressure may be set so that the oxygen concentration of the reactor effluent gas does not exceed the explosion range (8%). The pH of the reaction system is preferably about pH 6 to 9 from the viewpoint of byproduct suppression. In order to adjust the pH, for example, an alkali metal compound or an alkaline earth metal compound (carboxylate) can be used as an additive to the reaction system.
[0038]
After the above reaction, after separating the catalyst from the reaction system, the produced carboxylic acid ester may be recovered using a known separation and purification means. The separation method of the catalyst may follow a known method. For example, when the reaction system comprises a catalyst (solid content) and a reaction product (liquid component), the catalyst and the reaction product can be separated using a known solid-liquid separation method such as filtration or centrifugation.
[0039]
The carboxylic acid ester obtained by the method of the present invention can be used for the same application as the carboxylic acid ester obtained by the prior art. For example, carboxylic acid esters such as acrylic acid esters and methacrylic acid esters are useful as polymerization monomers that are raw materials for various acrylic resins.
Catalyst for hydrogenation reaction
Production of alcohols from carbonyl compounds
The ultrafine gold particle carrier of the present invention selectively hydrogenates a carbonyl group when an alcohol is produced by contacting a carbonyl compound with a hydrogenating agent in the presence of a hydrogenation reaction catalyst comprising the carrier. It has high selectivity and high activity for the reaction to make alcohol.
[0040]
In the method for producing an alcohol of the present invention, the raw material is not particularly limited as long as it is a compound having a carbonyl group. For example, a saturated carbonyl compound or an unsaturated carbonyl compound can be used, and these may be used in combination.
[0041]
Among these, as the saturated carbonyl compound, aldehydes such as acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, n-hexyl aldehyde, n-octyl aldehyde, 2-ethylhexyl aldehyde, glyoxal, pyruvic aldehyde, Examples include ketones such as acetone, methyl ethyl ketone, and cyclohexanone.
[0042]
As the unsaturated carbonyl compound, unsaturated carbonyl compounds such as α, β-unsaturated carbonyl compounds and aromatic carbonyl compounds can be used, and in particular, acrolein, methacrolein, crotonaldehyde, 3-methyl-2-butenal, [Alpha], [beta] -unsaturated aldehydes having about 3 to 10 carbon atoms such as cinnamyl aldehyde, aromatic aldehydes having about 6 to 20 carbon atoms such as benzaldehyde, anisaldehyde, p-hydroxybenzaldehyde, terephthalaldehyde, and furfural When used as a raw material, the corresponding unsaturated alcohol can be produced with high selectivity and high yield, and acrolein, methacrolein, benzaldehyde, terephthalaldehyde and the like are particularly preferable.
[0043]
The hydrogenation reaction of the carbonyl compound can be performed as a gas phase reaction or a liquid phase reaction.
[0044]
When the hydrogenation reaction of the carbonyl compound is performed as a liquid phase reaction, it is particularly preferable to perform the hydrogenation reaction in a solvent. By performing a hydrogenation reaction in a solvent in the presence of the catalyst of the present invention, only the carbonyl group of the carbonyl compound can be hydrogenated with high selectivity, and the corresponding alcohol can be obtained with high selectivity. Moreover, the target alcohol can be produced with a high selectivity and a high conversion rate even under mild conditions of relatively low temperature and low pressure without requiring high pressure or high temperature.
[0045]
Any solvent can be used without particular limitation as long as it can dissolve the carbonyl compound as a raw material and does not participate in the hydrogenation reaction. Specific examples of such solvents include water; alcohols such as methanol, ethanol, 2-propanol, 1-butanol, 1-octanol and 1,2-ethanediol; esters such as methyl acetate and ethyl acetate; And saturated hydrocarbons such as hexane and cyclohexane; aromatic hydrocarbons such as benzene, toluene and xylene; halogen compounds such as dichloromethane, 1,2-dichloroethane and benzene chloride. Among these, it is particularly preferable to use aliphatic saturated alcohols such as methanol and 2-propanol and water alone or in combination of two or more.
[0046]
The carbonyl compound used as a raw material is dissolved in a solvent and used for the reaction. The concentration of the carbonyl compound is not particularly limited, but is usually preferably about 0.1 to 60% by weight, more preferably about 1 to 30% by weight.
[0047]
The hydrogenation reaction of the carbonyl compound may be performed according to a known method in a solvent using a metal hydride, molecular hydrogen or the like as a hydrogenating agent. Among these hydrogenating agents, examples of the metal hydride include sodium borohydride, aluminum hydride, lithium aluminum hydride and the like. Among these hydrogenating agents, particularly when molecular hydrogen is used, the hydrogenation reaction can be carried out most easily and economically.
[0048]
The method for the hydrogenation reaction is not particularly limited, and it may be performed by any of continuous, batch, and semi-batch methods, and the reaction may be performed with stirring as necessary.
[0049]
The method for using the catalyst is not particularly limited as long as the carbonyl compound as a raw material and hydrogen can sufficiently contact the catalyst during the reaction.
[0050]
For example, when the reaction is carried out batchwise, the catalyst may be charged together with the raw materials in a solvent and the reaction may be carried out with stirring. In addition, when the reaction is carried out continuously, the catalyst is charged together with the raw material in a solvent, and this is continuously supplied to the reaction device, or the catalyst is charged in advance in the reaction device, and the solvent containing the raw material here May be supplied continuously. When the catalyst is charged into the reaction apparatus, the reaction apparatus may be in any form such as a fixed bed, a fluidized bed, and a suspension bed.
[0051]
The amount of the catalyst used is not particularly limited, and may be appropriately determined according to the type of raw material, the type of catalyst, the type of polar solvent, reaction conditions, and the like. For example, when the catalyst is charged together with the raw material in the solvent, the amount of the catalyst used is not particularly limited, but it is usually preferably about 0.01 to 50% by weight with respect to the total solution amount. More preferably, it is about 1 to 20% by weight. Also, a method of continuously supplying a solution containing raw materials and hydrogen to a reactor charged with a catalyst, for example, continuously supplying a solution containing raw materials and hydrogen to a reactor where the catalyst is fixed or filled by some method. In this method, the average residence time or contact time of the solution in the catalyst layer is preferably about 1 second to 2 hours, and more preferably about 10 seconds to 30 minutes.
[0052]
As a method for supplying molecular hydrogen, when the reaction is carried out batchwise, hydrogen is supplied into the reactor so that the hydrogen pressure is about 0.1 to 10 MPa, preferably about 0.2 to 2 MPa. Furthermore, hydrogen may be added as necessary so that the hydrogen pressure can be maintained during the reaction period. When the reaction is performed continuously, hydrogen may be continuously supplied into the reaction apparatus so that the hydrogen pressure is about 0.1 to 10 MPa, preferably about 0.2 to 2 MPa.
[0053]
Regarding the reaction temperature, the target alcohol can be obtained with a high conversion and high selectivity at a relatively low temperature of about 220 ° C. or less, and particularly about 150 ° C. or less in terms of suppressing side reactions. The temperature is preferably about 120 ° C. or less. Further, the lower limit of the reaction temperature is not particularly limited, but in order to obtain sufficient activity, it is suitably about 0 ° C. or higher, preferably about 20 ° C. or higher, preferably about 50 ° C. or higher. More preferably.
[0054]
The reaction time is not particularly limited and may vary depending on various reaction conditions, but is usually within the range of 0.5 to 20 hours as the reaction time or residence time (retention liquid amount / liquid supply amount in the reactor). That's fine.
[0055]
After performing the reaction by the above-described method, if necessary, the catalyst is separated using a known solid-liquid separation method such as filtration or centrifugation, and then the produced alcohol compound using a known separation and purification means. The desired alcohol can be obtained by recovering.
[0056]
【The invention's effect】
According to the present invention, the specific surface area by the BET method is 30 m.²It is possible to obtain a carrier in which an unprecedented amount of ultrafine gold particles, such as 3 parts by weight or more per 100 parts by weight of the carrier, is supported on a carrier having a small surface area of less than / g and low activity.
[0057]
Since the obtained support has a small surface area and is inactive, it is highly useful as an oxidation reaction catalyst, a hydrogenation reaction catalyst, etc. as a highly selective catalyst capable of suppressing side reactions.
[0058]
In particular, the carrier can be used effectively as a catalyst having high activity and excellent selectivity in, for example, the production of carboxylic acid esters using aldehydes and alcohols as raw materials, and the production of alcohols by hydrogenation of carbonyl compounds.
[0059]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples.
[0060]
Example 1
While maintaining 1 liter of an aqueous solution of 0.01 mol / l chloroauric acid at 65 to 70 ° C., the pH was adjusted to 5 using a 0.5N aqueous sodium hydroxide solution.
[0061]
In this aqueous solution, zinc oxide as a carrier (1 type JIS standard zinc oxide, specific surface area 4 m)²/ G) 20 g was added, and stirring was continued for 1 hour while maintaining the pH at 5 to 6 at a temperature of 65 to 70 ° C. Then, this aqueous solution was allowed to stand to remove the supernatant, and 0.5 liters of ion-exchanged water was newly added, followed by washing with water by stirring for 5 minutes at room temperature. This was repeated three times and then filtered. .
[0062]
The obtained solid was dried in air at 120 ° C. for 10 hours and further calcined in air at 400 ° C. for 3 hours.
[0063]
The gold carrier thus obtained was examined for the content of Au by fluorescent X-rays and found to be 9.7 parts by weight with respect to 100 parts by weight of the carrier. Further, when the gold particles were observed with an electron microscope, it was found that most of the particles were ultrafine particles in the range of about 5 to 25 nm and were supported on the surface of zinc oxide at a very high density.
[0064]
Example 2
Gold was supported on zinc oxide in the same manner as in Example 1 except that the pH of the solution in which zinc oxide was dispersed was adjusted to 6 to 6.8.
[0065]
With respect to the obtained gold carrier, the content of Au was examined by fluorescent X-rays. As a result, it was 5.6 parts by weight with respect to 100 parts by weight of the carrier. Further, when the gold particles were observed with an electron microscope, it was found that most of the particles were ultrafine particles having a size of about 3 to 20 nm and were supported on the surface of zinc oxide at a very high density.
[0066]
Comparative Example 1
Gold was supported on zinc oxide in the same manner as in Example 1 except that the pH of the solution in which zinc oxide was dispersed was adjusted to 7-8.
[0067]
When the gold content of the obtained gold carrier was examined by fluorescent X-rays, it was 0.8 parts by weight with respect to 100 parts by weight of the carrier. Moreover, when the gold particles were observed with an electron microscope, the size of the particles was almost ultrafine particles in the range of about 1 to 20 nm.
[0068]
Example 3
A 100 ml autoclave with rotary stirring was charged with 1.5 ml of methacrolein, 15 ml of methanol, and 0.5 g of the ultrafine gold particle support obtained in Example 1 and sealed. Next, after pressurizing the system to 0.3 MPa with oxygen, the system was heated to 80 ° C. with stirring and kept at the same temperature for 2 hours.
[0069]
Thereafter, the product was cooled and opened, and the contents were analyzed by gas chromatography. As a result, the methacrolein conversion rate was 82% and methyl methacrylate selectivity was 92%. Moreover, the selectivity of methacrolein dimethyl acetal, which is a by-product produced by the conventional method, was less than 1%.
[0070]
Example 4
A 100 ml autoclave with rotary stirring was charged with 2 g of a 40 wt% glyoxal aqueous solution, 15 ml of methanol, and 0.5 g of the ultrafine gold particle support obtained in Example 2 and sealed. Next, after pressurizing the system to 0.3 MPa with oxygen, the system was heated to 80 ° C. with stirring and maintained at the same temperature for 3 hours.
[0071]
After cooling and opening, the contents were analyzed by gas chromatography. The conversion rate of glyoxal was 92%, the selectivity for methyl glyoxylate was 82%, and the selectivity for dimethyl oxalate was 17%. Moreover, the selectivity of acetals which are by-products generated by the conventional method was less than 1%.
[0072]
Example 5
A 100 ml autoclave with rotary stirring was charged with 1.5 g of crotonaldehyde, 15 ml of 2-propanol, and 0.5 g of the ultrafine gold particle support obtained in Example 2 and sealed. Next, the inside of the system was purged with nitrogen, pressurized to 1 MPa with hydrogen, heated to 70 ° C. with stirring, and kept at the same temperature for 4 hours.
[0073]
After cooling and opening, the contents were analyzed by gas chromatography. The conversion of crotonaldehyde was 52% and the selectivity for crotyl alcohol was 74%.

Claims (3)

Gold ultrafine particles obtained by supporting 3 parts by weight or more of gold ultrafine particles having an average particle diameter of 25 nm or less with respect to 100 parts by weight of the inorganic oxide, using an inorganic oxide having a specific surface area of 30 m ² / g or less by the BET method as a carrier. Carrier. An oxidation reaction catalyst comprising the ultrafine gold particle support according to claim 1. A catalyst for hydrogenation reaction comprising the ultrafine gold particle support according to claim 1.