JP5188034B2 - Gold-supported particles with excellent wear resistance - Google Patents

Description

  The present invention relates to gold-supported particles used as a catalyst.

  Many methods for producing carboxylic acid esters in one step from aldehydes and alcohols have been proposed for a long time. For example, Japanese Patent Publication No. 57-35856 (Patent Document 1), Japanese Patent Publication No. 4-72578 (Patent Document 2), Japanese Patent Application Laid-Open No. 57-50545 (Patent Document 3), and the like, JP-A-61-243044 (Patent Document 4) discloses a palladium-tellurium-based catalyst, JP-B-57-35860 (Patent Document 5) discloses a palladium-thallium-mercury-based catalyst, and JP-B-57-19090. (Patent Document 6) includes a palladium-alkaline earth metal-zinc-cadmium catalyst, and Japanese Patent Publication No. 62-7902 (Patent Document 7), Japanese Patent Application Laid-Open No. 10-158214 (Patent Document 8), and the like. A production method using a system catalyst is described.

  In addition, as a prior document characterized by the carrier, Japanese Patent Laid-Open No. 5-148184 (Patent Document 9) uses a hydrophobic Teflon (registered trademark) carrier, a graphite fluoride carrier, a high silica zeolite carrier, and the like. JP-A-8-332383 (Patent Document 10) discloses a silica-alumina carrier, JP-A-9-52044 (Patent Document 11) describes a silica-alumina-magnesia carrier, and JP-A-9-192495 (Patent Document 12). ), A crystalline metallosilicate carrier, Japanese Patent Application Laid-Open No. 2003-305366 (Patent Document 13), describes a method of using a carrier containing zirconium, silicon, and aluminum as essential components. However, conventional metal-supported particles are generally easily worn, and a carrier having higher durability is required.

  Further, most of the catalysts used in the liquid phase reaction reported so far contain palladium, but recently there have been reported examples of using a metal other than palladium as a component, for example, JP-A-2000-154164. No. (Patent Document 14) discloses a catalyst in which a hydrophobic carrier and gold are combined.

  However, the catalyst in which the gold fine particles are supported on the carrier is liable to be peeled off from the carrier when the slurry is stirred, resulting in a problem that the reactivity is lowered. On the other hand, Japanese Patent Application Laid-Open No. 2002-361866 (Patent Document 15), Japanese Patent Application Laid-Open No. 2004-181357 (Patent Document 16), Japanese Patent Application Laid-Open No. 2004-181358 (Patent Document 17), and Japanese Patent Application Laid-Open No. 2004-181359. (Patent Document 18) proposes a method of improving the peelability from a carrier by using ultrafine gold particles of 6 nm or less.

However, when gold is used as a catalyst component, a technique for further improving the reactivity and durability is required.
Japanese Patent Publication No.57-35856 Japanese Examined Patent Publication No. 4-72578 JP-A-57-50545 JP-A-61-243044 Japanese Patent Publication No.57-35860 Japanese Patent Publication No.57-19090 Japanese Examined Patent Publication No. 62-7902 JP-A-10-158214 JP-A-5-148184 JP-A-8-332383 JP-A-9-52044 JP 9-192495 A JP 2003-305366 A JP 2000-154164 A JP 2002-361886 A JP 2004-181357 A JP 2004-181358 A JP 2004-181359 A

  The present invention is a gold-supported fine particle used as a catalyst in the production of a carboxylic acid ester from an aldehyde and alcohol or alcohols in the presence of oxygen, and has gold peeling resistance and wear resistance as a catalyst component. It aims at providing the particle | grains which are excellent in a point and can maintain high reactivity stably.

  As a result of intensive studies to solve the above problems, the present inventors have found that gold-supported particles in which gold is supported on a carrier containing a predetermined component at a predetermined atomic ratio are substantially gold on the outermost shell. It has been found that gold is difficult to peel off from the gold-supporting particles having such a structure and has excellent wear resistance, and the present invention has been completed.

[1] A particle in which gold is supported on a carrier containing silica having a particle size of 20 to 150 μm,
(I) The carrier includes silica, Al, alkali metal and / or alkaline earth metal, and the atomic ratio is represented by the following formulas (I) and (II):
Al / Si = 0.02 to 0.25 (I)
(Alkali metal + 0.5 × Alkaline earth metal) /Al≧0.5 (II)
Meet or
(ii) The carrier includes silica, Al, zirconia, and alkali metal and / or alkaline earth metal, and the atomic ratio is represented by the following formulas (III) to (V):
(Alkali metal + 0.5 × Alkaline earth metal) /Al≧0.5 (III)
Al / Si = 0.02 to 0.8 (IV)
Zr / Si = 0.5-10.0 (V)
A gold-carrying particle having a substantially gold-free layer with a thickness within 5 μm from the outermost surface of the particle;
[2] The gold-carrying particle according to [1], wherein the highest frequency of the pore diameter of the particle determined from a nitrogen desorption spectrum by a nitrogen adsorption method is in the range of 3 nm to 50 nm;
[3] The gold-carrying particle according to any one of [1] and [2] above, wherein the pore volume of the particle is in a range of 0.1 ml / g to 0.5 ml / g;
[4] The method for producing gold-supported particles according to any one of [1] to [3], wherein the gold is supported on a carrier and reduced, and the carrier is subjected to ultrasonic cleaning treatment at least once. Comprising the steps of:
[5] A method for producing a carboxylic acid ester comprising a step of reacting aldehyde, alcohol and oxygen in the presence of a catalyst in a liquid phase, wherein the catalyst is any one of [1] to [3] above Using a gold-supported particle of
[6] The group in which the carboxylic acid ester is an acrylic ester, the aldehyde is acrolein, and the alcohol is methanol, ethanol, butanol , 2-ethylhexanol, cyclohexanol, ethylene glycol, propylene glycol, and butanediol. The method according to [5] above, which is at least one alcohol selected from:
[7] The carboxylic acid ester is a methacrylic acid ester, the aldehyde is methacrolein, and the alcohol is selected from the group consisting of methanol, ethanol, butanol , 2-ethylhexanol, cyclohexanol, ethylene glycol, propylene glycol, and butanediol. The method according to [5] above, which is at least one selected alcohol;
[8] A method for producing a carboxylic acid ester comprising a step of reacting one or two kinds of alcohol and oxygen in the presence of a catalyst in a liquid phase, wherein the catalyst is any one of the above [1] to [3] A method using the gold-supported particles according to Item;
[9] The carboxylic acid ester is selected from the group consisting of methyl oxycarboxylate, ethyl oxycarboxylate, methyl carboxylate and ethyl carboxylate, and the one or two kinds of alcohols are ethylene glycol, propylene glycol, butanediol. The method according to [8] above, wherein the alcohol is one or two alcohols selected from the group consisting of methanol and ethanol;
[10] The method according to [9] above, wherein the carboxylic acid ester is ethyl acetate and the alcohol is ethanol.

  According to the present invention, by controlling the gold distribution in the gold-carrying particles, it is possible to realize a high peeling suppression function. In the method for producing a carboxylic acid ester in the presence of oxygen, when the gold-supported particles according to the present invention are used as a catalyst, the carboxylic acid ester can be produced stably and in a high yield over a long period of time.

  The present invention relates to a gold-supporting particle characterized by a gold-supporting structure and a carrier component composition, physical properties, and production method, and produces a carboxylic acid ester from an aldehyde and alcohol or from alcohols in the presence of oxygen. When used as a catalyst in the method, the present inventors have found a catalyst that is excellent in peeling resistance, wear resistance, etc. and can stably obtain high reactivity.

  The present invention was created by fusing new ideas. Gold has been widely used as a precious metal for decoration materials since ancient times. On the other hand, as petrochemistry has developed as a catalyst, it has started to be reported to have activity, and research has been particularly actively conducted in recent years. However, when gold is actually prepared as a catalyst, the behavior differs greatly from palladium. As an example, in the case of palladium atoms, reduction of palladium ions to metal requires reduction using a reducing agent such as hydrogen gas, alcohol or hydrazine which is active hydrogen. Unless the above high temperature treatment is performed, oxygen cannot be desorbed from the palladium oxide to obtain metallic palladium. On the other hand, gold ions are known as monovalent and trivalent ions. However, if treated in air at a temperature of about 200 ° C. or higher, oxygen is released to form metallic gold, and metal can be used without using a reducing agent in the solution. It has been reported that even gold can be reduced. Thus, since the chemical properties such as redox behavior and compound solubility are greatly different between palladium and gold, the knowledge of the palladium catalyst cannot be utilized as it is when gold is used as a catalyst.

  The present inventors have studied in detail the properties of the metals used, and devised the most effective method for producing gold-supported particles from the viewpoint of durability performance and catalyst performance. That is, the present inventors have found that the characteristics of the support and the support structure are important for obtaining metal-supported particles that exhibit an effective function when used in a reaction as a catalyst. More specifically, as a first factor, it was found that the supporting structure is particularly important for suppressing gold peeling, and secondly, the combination of carriers used is extremely important. By controlling the gold support structure, the releasability can be greatly improved even by using a conventionally commonly used carrier such as silica, Al, activated carbon or the like. However, it is preferable not only to control the gold support structure but also to use a mechanically and chemically highly durable carrier for suppressing long-term peeling. Examples of such carriers include two types of carriers that have been found by the present inventors and are excellent in long-term use. Specifically, a system containing silica, Al, and an alkali metal and / or alkaline earth metal, and another, zirconium, silica, Al, an alkali metal and / or alkaline earth metal. It is a carrier of the system containing. A system containing silica, Al, and an alkali metal and / or alkaline earth metal is harder than silica, excellent in mechanical strength, and excellent in water resistance. A system containing zirconium, silica, Al, and an alkali metal and / or alkaline earth metal is characterized in that chemical stability such as acidity and alkalinity estimated to be derived from zirconia is further imparted. . Therefore, these can be selected and used according to the reaction field to be used. Furthermore, it was found that the specific pore diameter and pore volume are important factors for achieving mechanical strength, and realized long-term durability that was difficult to achieve with the prior art.

  Hereinafter, the present invention will be described in detail.

  The gold-carrying particles according to the present invention are particles in which gold is supported on a carrier containing silica having a particle diameter of 20 to 150 μm, and the layer has a thickness within 5 μm from the outermost surface of the particle and does not substantially contain gold. Is formed. The inventors of the present invention have conducted detailed investigations on the support of gold and the improvement of peelability using several types of carriers. As a result, the metal supported even when the metal-supported particles are packed and fixed in a packed tower and a liquid is allowed to flow. However, when dissolved in a solution, it was confirmed that the gold supported from the particles could be peeled off depending on the loading method when stirred vigorously in a container with a stirring blade in a slurry state. Furthermore, as a result of observing and measuring the cross section of the gold-carrying particles using an analyzer such as EPMA, the gold peeling phenomenon is closely related to the gold distribution structure, and the peeling caused by the stirring and mixing of the slurry is caused on the outer surface of the particle. It was confirmed that this was remarkable when the supported gold particles were present. That is, when the gold solution and the carrier are brought into contact with each other, the gold solution diffuses from the surface of the single particle to the inside and is fixed inside the particle. On the other hand, it was found that with the supported particles in which the gold particles are not attached to the outer surface of the particles, gold peeling caused by stirring and mixing in a slurry state is suppressed. Furthermore, according to the particle cross-sectional analysis of EPMA, the gold-supported particles have a layer that does not substantially support gold up to 5 μm from the outer surface, and in the particles in which gold is supported, the slurry is stirred and mixed. As a result of the peelability test and the analysis results of the reaction experiment, it was confirmed that the gold concentration in the solution was below ppm to ppb level and was hardly detectable. In the present invention, “substantially free of gold” is a measure based on EPMA measurement used for analysis. Under the condition that Au can be detected by the EPMA measurement method, the intensity of Au atoms is almost equal to the background. An indistinguishable level.

  Regarding the wear resistance, since the degree of wear of the particles varies depending on the period of use and the mixed state, the thickness of the layer on which the gold is not supported is an optimum depth within the range of 5 μm from the outer surface of the particles based on the use conditions. The thickness in the vertical direction can be selected. From the reaction characteristics and release characteristics, the thickness of the layer on which gold is not supported is more preferably 3 μm from the outer surface, and in the reaction system with little wear, the thickness of the outer surface to 2 μm is preferably selected.

  As the carrier for the gold-carrying particles according to the present invention, a carrier containing silica, Al, alkali metal and / or alkaline earth metal and having an atomic ratio satisfying the following formula (I) and formula (II): Can be mentioned.

Al / Si = 0.02 to 0.25 (I)
(Alkali metal + 0.5 × Alkaline earth metal) /Al≧0.5 (II)
Further, another embodiment of the carrier for gold-supported particles according to the present invention includes silica, Al, zirconia, an alkali metal and / or an alkaline earth metal, and the atomic ratio is represented by the following formula (III). Examples of the carrier satisfying-(V).
(Alkali metal + 0.5 × Alkaline earth metal) /Al≧0.5 (III)
Al / Si = 0.02 to 0.8 (IV)
Zr / Si = 0.5-10.0 (V)
When the carrier composition is within this range, sufficient hardness and mechanical strength can be obtained, and excellent chemical stability can be seen in the zirconia-containing system. Such an effect is presumed to be due to the endurance performance being improved because each element crosslinks with oxygen interposed.

  For example, in a system containing silica, Al, and an alkali metal and / or alkaline earth metal, the above effect can be obtained by effectively forming a bond of O—Al—O—Si—O—. Inferred. In this system, it is important that Al / Si = 0.02 to 0.25. If it is 0.25 or more, the properties of aluminum alone tend to develop. More preferably, Al / Si is in the range of 0.03 to 0.2. Alkali metals and alkaline earth metals are presumed to contribute to structural stability by the action of neutralizing the solid acid sites generated by the silica-alumina bond. Therefore, (alkali metal + 0.5 × alkaline earth metal) /Al≧0.5 is preferable. If it is 0.5 or less, there is a tendency that a solid acid point due to a silica-alumina bond is developed. The upper limit is not particularly limited, but is usually set from a range of 3 times or less of Al atoms.

  On the other hand, in a system containing silica, Al, zirconia, and an alkali metal and / or alkaline earth metal, -Zr-O-Al-O-Si- is obtained by further combining zirconia with a silica-alumina bond. It is presumed that a bond such as O- is newly formed. From the same relationship as silica and Al (alkali metal + 0.5 × alkaline earth metal) /Al≧0.5, Al / Si = 0.02 to 0.8, and the composition ratio of zirconia to silica is Zr / Si = 0.5-10.0 is preferable. By satisfying this range, it is considered that the chemical property of zirconia that is stable to acids and bases is imparted. That is, it is considered that by forming a metal oxane structure in which silica, Al or zirconia, silica, and Al are combined, mechanical strength is improved and chemical resistance is expressed as compared with physical properties such as silica gel. Alkali metals and alkaline earth metals are considered to be important components for stabilizing the balance of charges generated when the crosslinked structure is formed, in addition to the auxiliary effect of increasing the durability of the carrier. Outside the composition range of the present invention, the characteristics of each component itself appear, and it is presumed that the composite effect is reduced.

  To date, silica gel has been reported in many cases as a carrier material that is stable under acidic and neutral conditions. However, when silica gel is used as a carrier in water, about several ppm of silica ion dissolution is observed in a gentle stirring experiment. Since the saturated solubility of silica gel in water is 400 ppm, it seems to be a level that does not cause a problem in normal use, but when used over a long period of 1 year or 2 years, 10% or more of the silica gel is dissolved. Can be. Then, naturally, peeling of the metal supported on the silica carrier occurs slowly but surely. As described above, by controlling the gold support structure, a large improvement effect is imparted to the suppression of peeling in the short term. However, when used as an industrial catalyst, since long-term stability in the order of years is important, in addition to controlling the gold support structure, the use of a support having a stable composition is also an important factor. I understand that.

  Moreover, it is preferable that the gold | metal support particle | grains which concern on this invention have the maximum frequency of the pore diameter of the said particle | grains calculated | required from the nitrogen desorption spectrum by the nitrogen adsorption method in the range of 3-50 nm. The pore structure of the carrier is one of the extremely important physical properties from the viewpoint of supporting characteristics of metal components other than strength, long-term stability including peeling, and reaction characteristics. The pore diameter of the present invention is a necessary physical property value for expressing these characteristics. For pores smaller than 3 nm, the supported metal tends to be difficult to exfoliate. However, if the pore diameter is too small, the diffusion resistance in the pores is reduced when used as a catalyst in a liquid phase reaction or the like. In many cases, the reaction activity becomes low because the diffusion process of the reaction substrate becomes rate-determining and becomes rate-limiting. On the other hand, when pores larger than 50 nm are present, the diffusion of the reactant is facilitated and the mass transfer is less likely to be a rate-determining process, but the supported metal tends to peel off and the catalyst tends to crack, and as a result It becomes easier for the metal to be peeled off when carrying. Therefore, the range is preferably 3 nm to 50 nm, and more preferably 3 nm to 30 nm.

  The gold-supporting particles according to the present invention preferably have a pore volume in the range of 0.1 ml / g to 0.5 ml / g. The pore volume is necessary as a space for supporting a noble metal. However, when the pore volume increases, the strength tends to decrease rapidly. Therefore, the range of 0.1 ml / g to 0.5 ml / g is preferable in terms of the balance between strength and carrying characteristics. More preferably, it is the range of 0.1 ml / g-0.4 ml / g.

  Such gold-supported particles can be produced, for example, by the following production method.

  The carrier of the gold-supported particles according to the present invention is spray-dried silica, Al, alkali metal and / or alkaline earth gold, or a slurry in which silica, Al, zirconium, alkali metal and / or alkaline earth gold is mixed, It can be manufactured by firing. If each constituent element can react to form a crosslinked structure, a conventionally known technique for producing a spherical carrier can be used.

  As the zirconia sol and the silica sol, a zirconia sol having a colloidal particle diameter of 0.5 to 50 nm and a silica sol having a colloidal particle diameter of 0.5 to 80 nm can be used, respectively, and these sols are prepared according to generally known production methods. In addition, commercially available sols may be used as they are. For example, in the case of zirconia sol, it can be obtained by heating an aqueous solution of a water-soluble zirconium salt at a temperature of about 120 ° C. or less to hydrolyze, or neutralizing with an alkali agent such as ammonia. On the other hand, as the silica sol, a sol obtained by neutralizing water glass with a mineral acid such as sulfuric acid or a sol obtained by treating water glass with an ion exchange resin can be used. However, in order to form a spherical durable carrier, the particle diameter of these sols should be within the range of 0.5 nm to 80 nm, more preferably 0.5 nm to 50 nm. preferable. When the particle diameter of the colloid is reduced, the specific surface area tends to increase and the crush resistance tends to improve, but the shape tends to deteriorate, which is not preferable for obtaining spherical particles. On the other hand, when the particle size of the colloid is too large, the pore diameter and the pore volume tend to increase, which affects the decrease in specific surface area and the chemical resistance and crush resistance. Therefore, the sol particle diameter may be selected in accordance with the physical property requirements of the carrier as required in the range of 0.5 nm to 80 nm, more preferably 0.5 nm to 50 nm. Combining sols having different particle diameters tends to show an effect of improving the strength, which is more preferable from the viewpoint of strength.

  As Al, alumina sol or a general commercially available aluminum compound can be used. As the alumina sol, an ordinary commercially available sol can be applied in the same manner as the zirconia sol and the silica sol. Examples of the aluminum compound include sodium aluminate, aluminum chloride hexahydrate, aluminum perchlorate hexahydrate, aluminum sulfate, aluminum nitrate nonahydrate, and aluminum diacetate. A water-soluble aluminum compound is preferable, and aluminum nitrate is more preferable. The reason why aluminum nitrate is preferable is that, in the process of firing the carrier formed into a spherical shape, other than aluminum vaporizes and disappears as nitrogen oxides, so that an operation for removing impurities later is not necessary. Similarly, alumina sol has the advantage that no other impurities remain. The reason why the water-soluble one is preferable is that the mixed slurry with zirconia sol and silica sol is easily dispersed uniformly.

  As a raw material for the alkali metal or alkaline earth metal, a common commercially available compound can be used in the same manner as the aluminum raw material. Preferred are water-soluble compounds, and more preferred are hydroxides, carbonates, nitrates and acetates.

  Further, in the present invention, characteristics such as control of slurry properties and pore structure of the product, and physical properties of the obtained carrier are obtained in a mixed slurry of zirconia, silica, aluminum compound or (alkali metal and / or alkaline earth metal) compound. It is possible to add inorganic and / or organic substances in order to fine tune. Inorganic substances used include mineral acids such as nitric acid, hydrochloric acid and sulfuric acid, metal salts such as alkali metals such as Li, Na, K, Rb and Cs, alkaline earth metals such as Mg, Ca, Sr and Ba, and ammonia. In addition to water-soluble compounds such as ammonium nitrate, clay minerals that are dispersed in water to form a suspension can be used. As the organic substance, polymers such as polyethylene glycol, methyl cellulose, polyvinyl alcohol, polyacrylic acid, polyacrylamide, and the like can be used.

  The effect of adding inorganic and organic substances varies, but it is possible to control the formation of the spherical carrier, the pore diameter and the pore volume. Specifically, the liquid quality of the mixed slurry is an important factor for obtaining a spherical carrier. It becomes. By adjusting the viscosity and solid content concentration with an inorganic or organic substance, it is possible to obtain a liquid quality in which a spherical carrier is easily formed. The pore diameter and pore volume can be controlled by selecting an optimal organic compound that remains in the carrier during the molding step and can be removed by baking and washing operations after molding. By selecting and adding an inorganic substance or an organic substance, the effect of promoting spheroidization and fine-tuning the physical property value is great.

  The carrier of the present invention can be produced by spray-drying the mixed slurry of various raw materials and additives described above, and the method for forming the mixed slurry into droplets is a rotating disk method, a two-fluid nozzle method, a pressure nozzle. Examples thereof include a method using a known spraying device such as a method.

  The liquid to be sprayed must be used in a well-mixed state. When the mixed state is poor, the performance of the carrier is affected, for example, the durability is lowered due to the uneven distribution of the composition. Especially when preparing raw materials, the viscosity of the slurry may increase and some gelation (condensation of colloids) may occur, and there is a concern that non-uniform particles may be formed. In addition to the above considerations, it may be preferable to control the metastable region of silica sol near pH 2, for example, by adding an acid or an alkali.

  Further, the liquid to be sprayed needs to have a certain degree of viscosity and solid content concentration. If the viscosity or the solid content concentration is too low, the porous body obtained by spray drying does not become a true sphere, but many depressed spheres are generated. If it is too high, the dispersibility between the porous bodies may be adversely affected, and depending on the properties, droplets cannot be formed stably. Therefore, the viscosity is preferably in the range of 5 cp to 10000 cp as long as spraying is possible. From the shape, a higher sprayable viscosity tends to be preferable, and from the balance with operability, more preferably 10 cp to A range of 1000 cp can be selected. Moreover, it is preferable from a shape and a particle diameter that solid content concentration exists in the range of 10 wt%-50 wt%, and can select suitable concentration. In addition, as a standard as spray drying conditions, the hot air temperature at the entrance of the drying tower of the spray dryer is preferably in the range of 200 ° C. to 280 ° C., and the outlet temperature of the drying tower is preferably in the range of 110 ° C. to 140 ° C.

  Next, the carrier formed into a particle shape by spray drying is fired. The firing temperature of the porous carrier of the present invention is preferably in the range of 300 to 800 ° C. Since the physical properties of the carrier such as porosity change as the firing conditions, it is necessary to select appropriate temperature conditions and temperature raising conditions. When the firing temperature is low, it is difficult to maintain durability as a composite oxide, and when it is too high, the pore volume is reduced. Further, it is preferable that the temperature rise condition is gradually raised using a program temperature rise or the like. Baking at a high temperature condition is not preferable because gasification and combustion of inorganic and organic substances become intense, and are exposed to a high temperature state higher than a set value or cause pulverization.

  After calcination, a porous carrier having a predetermined particle size can be appropriately selected according to the reaction mode. The particle diameter when used as a catalyst is preferably in the range of 20 to 150 μm. If it is 20 μm or less, there is a tendency that application of a simple separation method such as sedimentation separation becomes difficult when used in the reaction, and the catalyst tends to be washed away. On the other hand, when the thickness is 150 μm or more, when used in a liquid phase reaction, the diffusion resistance in the pores increases, and the tendency to settle easily and maintain the slurry state is observed. This particle range is most preferable from the balance of separability, reactivity, and slurry state maintenance characteristics. When the sedimentation time is desired to be shortened or when the particle sedimentation rate is sufficiently faster than the flow rate of the extracted liquid, it can be set narrower from the range of 20 μm to 150 μm.

  In addition, about the method of making a support | carrier contain an alkali metal and an alkaline-earth metal compound in a support | carrier, the method of spray-drying simultaneously with another component and the method of adsorb | sucking an alkali metal and an alkaline-earth metal later can also be used. . For example, a method using an immersion method, such as adding a carrier to a solution in which an alkali metal or alkaline earth metal compound is dissolved, and performing a drying treatment, soaking the carrier with a pore volume of alkali metal or alkaline earth metal compound. A method using an impregnation method such as a drying treatment can also be applied. However, the method for adsorbing alkali metals and alkaline earth metal compounds later requires careful attention such as liquid drying treatment under mild conditions in order to highly disperse alkali metals and alkaline earth metal compounds on the carrier. is there.

  The gold-supported particles according to the present invention can be produced by bringing the carrier thus obtained into contact with a solution containing gold. Examples of the gold raw material include tetrachloroauric acid, sodium tetrachloroaurate, potassium dicyanoaurate, diethylaminegold trichloride, gold cyanide and the like.

  When gold alone is supported, it can be made metal gold by firing at 200 ° C. to 800 ° C. or higher. It can also be reduced to a metal gold by using a general reducing agent. As the reducing agent, formalin, formic acid, hydrazine, molecular hydrogen, sodium borohydride and the like can be used.

  Subsequently, a typical method for controlling the distribution of gold so that an outer layer substantially free of gold is formed will be described by taking as an example the case of using a carrier containing magnesium as a base component. For example, a solution in which aluminum nitrate is dissolved is heated and stirred, and a carrier is put into the solution in a short time. In this step, the base component in the depth direction from the surface of the carrier particles is equivalent to aluminum and consumed by adsorption neutralization. Then, when added to an aqueous solution in which a gold aqueous solution such as tetrachloroauric acid prepared at pH 2 or lower is dissolved, the base in the vicinity of the particle surface is consumed by aluminum, so that the gold ions diffuse into the particle and the internal base. And fixed by the neutralization reaction. At this stage, internal fixation of the gold carrier is completed.

  Subsequently, it is washed with water, dried, fired at a temperature of 200 ° C. to 800 ° C., further dispersed in water and subjected to ultrasonic cleaning, whereby particles carrying metal gold are obtained. On the other hand, as a reduction step, particles reduced with hydrazine or the like at a temperature of 5 to 100 ° C., and then decanted, washed with water, and subjected to ultrasonic cleaning, and then vacuum dried to obtain particles carrying gold. According to the method of the present invention, by changing the amount of aluminum nitrate to be added before adding gold, the thickness of the layer on which gold is not supported can be arbitrarily controlled. In addition, as a result of comparison between the case where ultrasonic cleaning was performed and the case where it was not performed, it was confirmed that the ultrasonic cleaning effectively removed gold adhering to the outer surface which could not be removed by a normal cleaning operation. The preparation method incorporating ultrasonic cleaning of the present invention is a very effective method.

  The temperature condition for supporting gold can be performed at a temperature of room temperature to 200 ° C., but the lower the temperature, the higher the gold distribution, for example, 70 ° C. or higher is preferable. More preferably, the temperature is in the vicinity of 100 ° C to 100 ° C.

  The reduction method can also be carried out by adding formalin and formic acid while heating the catalyst precursor after supporting gold in water or methanol. Reduction can also be performed using molecular hydrogen. Formalin, formic acid, and hydrazine are generally used in an amount of 0.5 to 100 times mol and practically 1 to 10 times mol of the gold loading. Moreover, there is no particular problem even if this amount is exceeded. In the reduction treatment with molecular hydrogen, pure hydrogen gas or a material diluted with an inert gas such as nitrogen or methane can be used. The hydrogen concentration is 0.1 vol% or more, and the pressure is normal pressure or several tens of atmospheres, for example, by blowing into the dispersion during the production of the catalyst. When the temperature and pressure conditions for the reduction are from 160 ° C. to a low temperature at which the solution does not freeze, the pressure is preferably from normal pressure to several atmospheres. Furthermore, although the reduction treatment time varies depending on the catalyst type and treatment conditions, it is roughly several minutes to 100 hours. It is convenient to set the conditions so that the processing is completed within a few hours.

  The gold loading amount in the present invention is not particularly limited, but is preferably 0.1 wt% to 20 wt%, more preferably 1 wt% to 10 wt%, based on the weight of the carrier. At a high loading amount outside this range, gold aggregates and the activity per catalytic metal is low, and when it is too low, the activity per catalyst tends to be low.

  In addition, the gold-supported particles in the present invention can contain a different element in addition to gold. For example, palladium, silver, mercury, thallium, bismuth, tellurium, nickel, chromium, cobalt, indium, tantalum, copper, zinc, zirconium, hafnium, tungsten, manganese, silver, rhenium, antimony, tin, rhodium, ruthenium, iridium, Platinum, titanium, aluminum, boron, silicon and the like can be included. These dissimilar elements are preferably 0.01 wt% to 20 wt%, preferably 0.1 wt% to 10 wt% per catalyst. Further, the catalyst may contain at least one metal salt selected from alkali metal compounds, alkaline earth metal compounds, and rare earth compounds. The content of alkali metal, alkaline earth metal, and rare earth is selected from a range of 15 wt% or less per catalyst. These different elements or alkali metals and alkaline earth metal compounds and rare earth compounds may be contained in the catalyst during the production and reaction of the gold-supported particles, or a method of previously containing them in the support is also used. be able to.

  The gold-supported particles in the present invention can be suitably used for a reaction for producing a carboxylic acid ester by reacting with an aldehyde, alcohol and molecular oxygen. The amount of the catalyst used can be changed greatly depending on the type of reaction raw material, the composition and preparation method of the catalyst, reaction conditions, reaction type, etc., but there is no particular limitation, but when reacting the catalyst in a slurry state, The solid concentration in the slurry is preferably 4 to 50 wt / vol%, preferably 4 to 30 wt / vol%, more preferably 10 to 25 wt / vol%.

  Aldehydes used as raw materials are aliphatic saturated aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, isobutyraldehyde and glyoxal, aliphatic α and β-unsaturated aldehydes such as acrolein, methacrolein and crotonaldehyde, benzaldehyde, tolylaldehyde and benzylaldehyde. , Aromatic aldehydes such as phthalaldehyde, and derivatives of aldehydes. These aldehydes can be used alone or as a mixture of two or more kinds.

  On the other hand, as alcohols, aliphatic saturated alcohols such as methanol, ethanol, isopropanol and octanol, aliphatic cyclic alcohols such as cyclohexanol, diols such as ethylene glycol, propylene glycol and butanediol, allyl alcohol, methallyl alcohol, etc. And an aliphatic alcohol such as benzyl alcohol. The corresponding carboxylic acid ester can be synthesized from the aldehyde and the alcohol, and the alcohol can be used alone or in any two or more kinds, for example, synthesis of ethyl acetate from ethanol or synthesis of methyl glycolate from a mixture of ethylene glycol and methanol. It can be used as a reaction.

  Further, as oxygen, molecular oxygen, that is, oxygen diluted in oxygen gas or inert gas, and air can be used.

  In the reaction for producing a carboxylic acid ester, the ratio of the amount of aldehyde to alcohol used is, for example, in the range of 2/1 to 1/50 in terms of (aldehyde or alcohol) / alcohol molar ratio. It can be set according to. For example, in the reaction of producing methacrolein / methanol to methyl methacrylate and glycols / methanol to methyl glycolate, the range of 1/2 to 1/10 is preferably selected. The amount of oxygen present in the reaction system may be at least the stoichiometric amount necessary for the reaction, preferably at least 1.2 times the stoichiometric amount.

  In addition, the carboxylic acid ester production reaction of the present invention can be carried out by any method such as gas phase reaction, liquid phase reaction, irrigation reaction or the like, either batchwise or continuously. The reaction can be carried out without solvent, but a solvent inert to the reaction components, for example, hexane, decane, benzene, dioxane and the like may be used. As the reactor type, conventionally known types such as a fixed bed type, a fluidized bed type, and a stirring tank type can be adopted. In addition, since the catalyst of this invention has crushing resistance, it can be used stably also in a fluidized bed reactor, a bubble column reactor, and a stirred tank reactor.

  The particle diameter of the catalyst in the present invention can be appropriately selected according to the reaction mode. For example, when used in a liquid phase suspension state, it varies depending on the separation method of the catalyst, and in the natural sedimentation separation, it is preferably 20 to 150 μm, more preferably 20 to 100 μm.

  When the carboxylic acid ester production reaction process of the present invention is carried out in a liquid phase or the like, an alkali metal or alkaline earth metal compound (for example, oxide, hydroxide, carbonate, carboxylate, etc.) is used in the reaction system. Is preferably added to maintain the pH of the reaction system at 6-8. Varies depending on the partial pressure of oxygen at the reactor outlet side, reaction raw materials such as aldehyde species and alcohol species to be reacted, reaction conditions or reactor type, but in practice, the oxygen partial pressure at the reactor outlet is below the lower limit of the explosion range. For example, the reaction pressure can be controlled in any wide pressure range from reduced pressure to increased pressure, but usually at a pressure of 0.05 to 2 MPa. Is done. From the viewpoint of safety, it is preferable to set the total pressure so that the oxygen concentration of the reactor effluent gas does not exceed the explosion range (8%). Moreover, although reaction temperature can be implemented even at the high temperature of 100 degreeC or more, Preferably it is 30-100 degreeC. The reaction time is preferably set to an optimum time depending on the behavior of the reaction products and by-products, and productivity, and is not uniquely determined, but is usually 1 to 20 hours.

EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to those Examples. First, various processes used in this embodiment will be described below.
(Shape observation)
Observation was performed using an X-650 scanning electron microscope manufactured by Hitachi, Ltd.
(Physical property measurement: pore diameter, specific surface area, pore volume)
Measurement was performed with a Yuasa Ionics / Autosorb 3MP apparatus using nitrogen as an adsorbed gas. The BET method was used for the surface area, the BJH method was used for the pore diameter and pore distribution, and the adsorption amount was P / P ₀ , Max for the pore volume.
(EPMA analysis)
The analysis of the cross section of the particles obtained by embedding and polishing the gold-carrying particles in a resin was measured using Shimadzu Corporation EPMA1600 at an acceleration voltage of 15 KeV. Analyzes in the depth direction from the outer surface of Au from reflected electron image and line analysis (Au analysis is wavelength: 5.8419, spectral crystal: PET, Si analysis is wavelength: 7.1224, spectral crystal ADP is used) It was.
(Ultrasonic cleaning)
The ultrasonic cleaning apparatus used was IUC-3011 manufactured by Tokyo Ultrasonic Technology Co., Ltd., and the output was 600 W / L, power density 20 W / L, and oscillation frequency 27 KHz.
(ICP-MS analysis)
The analysis of the Au concentration in the solution was performed using an X7ICP / MS type manufactured by Tnermo Elemental.

First, according to carrier production examples 1 to 3, three types of carriers were produced and used for examples and comparative examples.
[Carrier Production Example 1]
An aqueous solution prepared by dissolving 3.75 kg of aluminum nitrate nonahydrate (manufactured by Wako Pure Chemical Industries) and 2.56 kg of magnesium nitrate hexahydrate (manufactured by Wako Pure Chemical Industries) in 4.67 kg of pure water was maintained at 15 ° C. Silica sol having a colloidal particle diameter of 10 to 20 nm in a stirred state (trade name: TX11561 made by Nalco Co., Ltd., adjusted aqueous solution with SiO ₂ content of 30 wt%) is gradually dropped into 20.0 kg and mixed with silica sol, aluminum nitrate and magnesium nitrate. A slurry was obtained. Thereafter, the mixed slurry was kept at 50 ° C. for 24 hours and aged. After cooling to room temperature, the mixture is spray-dried with a spray dryer set at an outlet temperature of 130 ° C. in the air using a spray dryer apparatus with stirring, then baked at 400 ° C., and then subjected to a classification treatment to obtain particles of 30 μm or less and Particles having an average particle diameter of 60 μm were obtained by removing particles of 150 μm or more. Baking was performed again at 580 ° C. to obtain a white silica / alumina / magnesia carrier. As for the pore diameter of the obtained carrier, the value obtained from nitrogen desorption was 3 nm to 15 nm, the maximum frequency diameter was 8 nm, and the pore volume was 0.29 ml / g.

In this production example,
(Alkali metal + 0.5 × Alkaline earth metal) /Al=0.5 and Al / Si = 0.10.
[Carrier Production Example 2]
An aqueous solution prepared by dissolving 0.83 kg of aluminum nitrate nonahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) and 0.95 kg of magnesium nitrate hexahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) in pure water was stirred for a colloidal particle diameter of 10 nm to 20 nm silica sol (trade name: TX11561 made by Nalco Co., Ltd., adjusted aqueous solution with SiO ₂ content of 30 wt%) was gradually dropped into 1.20 kg to prepare a mixed solution of silica sol, aluminum nitrate, and magnesium nitrate. Next, the mixed liquid was mixed with 1.50 kg of colloidal average particles having a colloidal particle diameter of 50 nm under stirring and a zirconia sol (manufactured by Daiichi Rare Elemental Chemical Co., Ltd., trade name: ZSL-20N, ZrO ₂ content 20 wt%). A zirconia sol having a diameter of 10 nm (trade name: ZSL-10T, manufactured by Daiichi Rare Elemental Chemical Co., Ltd., ZrO2 content 10 wt%) 11.8 kg was added little by little to obtain a mixed white slurry. A small amount of nitric acid and aqueous ammonia were added to this slurry, and then 1.5 kg of ammonium nitrate was added and stirred for 2 hours. Subsequently, the mixed slurry is spray-dried in the air using a spray dryer while stirring, and then fired at 400 ° C., followed by classification to remove particles of 30 μm or less and particles of 150 μm or more. Particles having an average particle diameter of 60 μm were obtained. Baking was performed again at 580 ° C. to obtain a white silica / alumina / zirconia / magnesia carrier. The pore diameter obtained from nitrogen desorption was 3 to 5 nm, the maximum frequency diameter was 4 nm, and the pore volume was 0.15 ml / g.

In this production example,
(Alkali metal + 0.5 × Alkaline earth metal) /Al=0.84, Al / Si = 0.37, and Zr / Si = 2.01.
[Carrier Production Example 3]
Aluminum nitrate nonahydrate (made by Wako Pure Chemical Industries, Ltd.) 4.86 kg, rubidium nitrate (manufactured by Wako Pure Chemical Industries, Ltd.) 3.05 kg dissolved in pure water (5.0 kg) in an agitation colloidal particle kept at 15 ° C. Silica sol having a diameter of 10 nm to 20 nm (manufactured by Nalco Co., Ltd., trade name: TX11561, adjusted aqueous solution with SiO ₂ content of 30 wt%) was gradually dropped into 20.0 kg to obtain a mixed slurry of silica sol, aluminum nitrate, and rubidium nitrate. Thereafter, the mixed slurry was kept at room temperature for 24 hours and aged. Spray-drying with a spray dryer set at an outlet temperature of 130 ° C in air using a spray dryer device while stirring at room temperature, followed by calcination at 400 ° C and classification treatment to obtain particles of 30 µm or less and particles of 150 µm or more Removal gave particles with an average particle size of 60 μm. Baking was performed again at 580 ° C. to obtain a white silica / alumina / rubidium carrier. The pore diameter obtained from nitrogen desorption was 3 nm to 15 nm, the maximum frequency diameter was 7 nm, and the pore volume was 0.27 ml / g.

In this production example,
(Alkali metal + 0.5 × Alkaline earth metal) /Al=0.77 and Al / Si = 0.13.
[Example 1: Production of gold-supported particles]
The aluminum nitrate aqueous solution of 0.35 parts by weight as aluminum with respect to 100 parts by weight of the carrier was maintained at 90 ° C., and the carrier of the carrier production example 1 was immediately added thereto and stirred for 10 minutes. Next, 100 parts by weight of the carrier On the other hand, a solution containing 3 parts by weight of tetrachloroauric acid aqueous solution and a small amount of nitric acid as metal gold was added instantaneously and stirred at 90 ° C. for 10 minutes. The supernatant was decanted and removed, washed with distilled water at room temperature, dried, and calcined at 400 ° C. Subsequently, the gold carrier was dispersed in water and ultrasonic cleaning was performed for 30 minutes. Thereafter, washing with water was performed until the supernatant became transparent, followed by vacuum drying at 80 ° C. to obtain gold-carrying particles. As a result of the EPMA analysis, it was confirmed that the gold supported layer had a layer in which no gold was supported in the depth direction of 2 μm from the outer surface of the particle.
[Comparative Example 1: Production of gold-supported particles]
Gold-carrying particles were obtained in the same manner as in Example 1, except that the water was not added with aluminum nitrate and ultrasonic cleaning was not performed. As a result of EPMA analysis, it was confirmed that the gold was supported on the outer surface of the particle and in a range up to a depth of 5 μm.
[Comparative Example 2: Production of gold-supported particles]
Gold-supported particles were obtained by the same operation except that the ultrasonic cleaning of Example 1 was not performed. As a result of the EPMA analysis, a layer not supporting gold was formed to a depth of 2 μm from the surface of the particles, but gold particles adhered to the outer surface.
[Example 2: Esterification reaction]
Using 200 g of the gold-carrying particles of Example 1 as a catalyst, the liquid phase part equipped with a catalyst separator was charged into a 1.2 liter stirring-type slenless reactor, and the contents were stirred at a tip speed of the stirring blade of 4 m / s. However, an oxidative ertellation reaction between aldehyde and alcohol was carried out. A 36.7% by weight methacrolein / methanol solution was supplied at 0.6 liter / hr, and the reaction was performed by blowing air at 80 ° C. and 0.4 Mpa pressure so that the outlet oxygen concentration was 0.02 Mpa or less. The product was withdrawn at a constant rate and analyzed by gas chromatography to check for reactivity. Further, the production rate of methyl methacrylate (MMA) for 20 hours from the start of the reaction was 5.9 mol / h · KgCat, and the selectivity was 92.6%. The reactivity at the time point of 100 hours and 500 hours hardly changed. Further, when the concentration of gold in the reaction solution was measured using ICP-MS, the gold concentration in the reaction solution at each time point of 20, 100, and 500 hours was 1 ppb or less, and gold peeling and the like were complete. It was confirmed that it was suppressed.
[Comparative Example 3: Esterification reaction]
The esterification reaction was performed in the same manner as in Example 2 except that the gold-supported particles obtained in Comparative Example 1 were used as a catalyst. The production rate of MMA for 20 hours from the start of the reaction was 6.0 mol / h · KgCat, and the selectivity was 92.3%. At the 100th hour, the MMA production rate was 5.6 mol / h · KgCat and the selectivity was 92.4%, and the MMA production rate after 500 hours was 4.9 mol / h · KgCat and the selectivity was 92.5%. There was a decrease in activity. In addition, when the concentration of gold in the reaction solution was measured using ICP, it was 22 ppm for 20 hours, 4 ppm for 100 hours, and 1 ppm at 500 hours, and the activity decreased due to peeling of gold, etc. It was estimated.
[Comparative Example 4: Esterification reaction]
The esterification reaction was performed in the same manner as in Example 2 except that the gold-supported particles obtained in Comparative Example 2 were used as a catalyst. The production rate of MMA for 20 hours from the start of the reaction was 6.2 mol / h · KgCat, and the selectivity was 92.1%. At the 100th hour, the MMA production rate is 5.7 mol / h · KgCat, the selectivity is 92.3%, the MMA production rate after 500 hours is 5.6 mol / h · KgCat, and the selectivity is 92.4%. A large decrease in activity was observed at the beginning of the reaction. Further, when the concentration of gold in the reaction solution was measured by ICP, it was 19 ppm at 20 hours, 0.5 ppm at 100 hours, and 0.2 ppm at 500 hours, and the activity decreased due to peeling of gold or the like. It was estimated.
[Example 3: Production of gold-supported particles]
The carrier was maintained at 90 ° C. in a state where 0.50 parts by weight of an aluminum nitrate aqueous solution was stirred as aluminum with respect to 100 parts by weight of the carrier. On the other hand, a solution obtained by adding 4 parts by weight of tetrachloroauric acid aqueous solution and a small amount of nitric acid as metal gold was added instantaneously and stirred at 90 ° C. for 10 minutes. The supernatant was decanted and removed, washed with distilled water at room temperature, dried, and calcined at 400 ° C. Subsequently, the gold carrier was dispersed in water and ultrasonic cleaning was performed for 30 minutes. Thereafter, washing with water was performed until the supernatant became transparent, followed by vacuum drying at 80 ° C. to obtain gold-carrying particles. As a result of EPMA analysis, it was confirmed that the particles were gold-carrying particles having a layer in which gold was not carried in the depth direction of 3 μm from the outer surface of the particles.
[Example 4: Esterification reaction]
Using 200 g of the gold-carrying particles of Example 3 as a catalyst, the liquid phase part equipped with a catalyst separator was charged into a 1.2 liter stirring type slurless reactor, and the tip speed of the stirring blade was 4 m / s. The alcohol was oxidatively esterified with stirring. A 25.0 wt% ethylene glycol / methanol solution was supplied at 0.6 liter / hr, and the reaction was performed by blowing air at 90 ° C. and 0.4 Mpa pressure so that the outlet oxygen concentration was 0.02 Mpa or less. The product was withdrawn at a constant rate and analyzed by gas chromatography to check for reactivity. The production rate of methyl glycolate (GM) for 20 hours from the start of the reaction was 4.6 mol / h · KgCat, and the selectivity was 79.3%. At 500 hours, the reactivity was as follows. Methyl glycolate (GM) production rate was 4.5 mol / h · KgCat, and selectivity was 79.6%, almost unchanged. In addition, when the gold concentration in the reaction solution was measured using ICP-MS, the gold concentration in the reaction solution at each time point of 20,500 hours was 1 ppb or less, and gold peeling and the like were completely suppressed. It was confirmed that
[Comparative Example 5: Production of gold-supported particles and esterification reaction]
600 g of titanium isopropoxide (Wako Pure Chemical Industries) was dissolved in 1.0 kg of a commercially available silica carrier (Fuji Silysia Chemical Carrieract Q-10, average particle size 65 μm, average pore size 10 nm, pore volume 1.23 ml / g). 2 L of 2-propanol solution was added, heated to distill off the solvent, and impregnated with a titanium-containing compound. After drying at 110 ° C. for 10 hours, it was calcined in air at 600 ° C. for 4 hours. Next, while maintaining 4.5 L of 20 mMol chloroauric acid aqueous solution at 60 ° C., 0.5 N sodium hydroxide aqueous solution was added to adjust the pH to 10. After adding 10 ml of tetraamminepalladium hydroxide aqueous solution (Pd content 20 g / L) to this solution, 200 g of the above titanium-containing silica support was added and stirred at 70 ° C. for 1 hour. Thereafter, the washing operation of removing the supernatant by removing the supernatant and adding 4 L of distilled water to the remaining gold immobilized and stirring for 5 minutes was repeated three times. After filtration, it was dried at 110 ° C. for 10 hours, and calcined in air at 400 ° C. for 3 hours to obtain particles having gold supported on titanium-containing silica.

  The esterification reaction was performed in the same manner as in Example 4 except that these particles were used as a catalyst.

The production rate of methyl glycolate (GM) for 20 hours from the start of the reaction was 5.0 mol / h · KgCat, and the selectivity was 78.5%. The production rate of methyl glycolate (GM) after 100 hours was 4.6 mol / h · KgCat, and the selectivity was 78.6%. Moreover, when the gold concentration in the reaction solution was measured using ICP-MS, the gold concentration in the reaction solution at each time point of 20, 100 hours was 4.5 ppm and 0.2 ppm, the reaction was reduced, and the gold concentration Peeling was observed.
[Example 5: Production of gold-supported particles and esterification reaction]
Particles carrying gold were obtained by the operation method of Example 1 except that the carrier was changed to the carrier of Carrier Production Example 3, aluminum was changed to 0.50 parts by weight, and metal gold was changed to 4.5 parts by weight.

  As a result of EPMA analysis, it was confirmed that the particles were gold-carrying particles having a layer in which gold was not carried in the depth direction of 3 μm from the outer surface of the particles. Using 200 g of the obtained particles as a catalyst, the liquid phase part equipped with a catalyst separator was charged into a 1.2 liter stirring-type slenless reactor, and the contents were stirred while stirring the contents with a stirring blade tip speed of 4 m / s. The oxidative esterification reaction of was carried out. Ethanol was supplied at 0.6 liter / hr, and the reaction was performed by blowing air so that the outlet oxygen concentration was 0.02 Mpa or less at 80 ° C. and 0.5 Mpa pressure. The product was withdrawn at a constant rate and analyzed by gas chromatography to check for reactivity. The production rate of ethyl acetate for 30 hours from the start of the reaction was 3.1 mol / h · KgCat, and the selectivity was 84.3%. As for the reactivity after 300 hours, the production rate of ethyl acetate was 3.2 mol / h · KgCat, and the selectivity was 84.5%. Moreover, when the gold concentration in the reaction solution was measured using ICP-MS, the gold concentration in the reaction solution at each time point of 30 and 300 hours was 1 ppb or less, the reaction efficiency was not lowered, and gold was peeled off. Etc. were confirmed to be completely suppressed.

Claims (10)

Particles in which gold is supported on a carrier containing silica having a particle size of 20 to 150 μm,
(I) The carrier includes silica, Al, alkali metal and / or alkaline earth metal, and the atomic ratio is represented by the following formulas (I) and (II):
Al / Si = 0.02 to 0.25 (I)
(Alkali metal + 0.5 × Alkaline earth metal) /Al≧0.5 (II)
Meet or
(ii) The carrier includes silica, Al, zirconia, and alkali metal and / or alkaline earth metal, and the atomic ratio is represented by the following formulas (III) to (V):
(Alkali metal + 0.5 × Alkaline earth metal) /Al≧0.5 (III)
Al / Si = 0.02 to 0.8 (IV)
Zr / Si = 0.5-10.0 (V)
A gold-carrying particle having a substantially gold-free layer with a thickness within 5 μm from the outermost surface of the particle.   2. The gold-supported particle according to claim 1, wherein the maximum frequency of the pore diameter of the particle determined from a nitrogen desorption spectrum by a nitrogen adsorption method is in the range of 3 nm to 50 nm.   The gold-carrying particles according to claim 1 or 2, wherein the pore volume of the particles is in the range of 0.1 ml / g to 0.5 ml / g.   4. The method for producing gold-supported particles according to claim 1, comprising a step of supporting and reducing gold on a carrier, and a step of subjecting the carrier to ultrasonic cleaning at least once. ,Method.   A method for producing a carboxylic acid ester comprising a step of reacting an aldehyde, alcohol and oxygen in the presence of a catalyst in a liquid phase, wherein the gold-supported particles according to any one of claims 1 to 3 are used as the catalyst. ,Method. The carboxylic acid ester is an acrylic acid ester;
The aldehyde is acrolein;
Wherein the alcohol is methanol, ethanol, butanol, 2 an ethyl hexanol, cyclohexanol, at least one alcohol ethylene glycol, it is selected from the group consisting of propylene glycol and butanediol, The method of claim 5. The carboxylic acid ester is a methacrylic acid ester, the aldehyde is methacrolein,
6. The method of claim 5, wherein the alcohol is at least one alcohol selected from the group consisting of methanol, ethanol, butanol , 2-ethylhexanol, cyclohexanol, ethylene glycol, propylene glycol, and butanediol.   A method for producing a carboxylic acid ester, comprising a step of reacting one or two kinds of alcohol and oxygen in the presence of a catalyst in a liquid phase, wherein the catalyst carries the gold support according to any one of claims 1 to 3. A method using particles.   The carboxylic acid ester is selected from the group consisting of methyl oxycarboxylate, ethyl oxycarboxylate, methyl carboxylate and ethyl carboxylate, and the one or two alcohols are ethylene glycol, propylene glycol, butanediol, methanol and The method according to claim 8, wherein the alcohol is one or two alcohols selected from the group consisting of ethanol.   The method of claim 9, wherein the carboxylic acid ester is ethyl acetate and the alcohol is ethanol.