JP5335505B2 - Noble metal support and method for producing carboxylic acid ester using the same as catalyst - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a supported body of noble metal that can maintain a metallic component comprising palladium in a stably supported state, and can maintain high reactivity for a long period of time even when used as a catalyst. <P>SOLUTION: The supported body of noble metal includes a support constituted of a composite oxide comprising silicon, aluminum, at least one of the fourth period elements selected from the group consisting of iron, cobalt, nickel and zinc, and at least one alkaline element selected from the group consisting of alkali metal elements, alkali earth metal elements, and rare earth elements, each in the ranges of 42 to 90 mol%, 3 to 38 mol%, 0.5 to 20 mol%, and 2 to 38 mol% respectively relative to the aggregate mole amount of the silicon, the aluminum, the fourth period element and the alkaline element, and a metallic component comprising palladium supported by the support. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a noble metal support and a method for producing a carboxylic acid ester using the same as a catalyst.

  Palladium or palladium metal compounds are widely used industrially as catalysts. Palladium is used alone as a catalyst. However, in general, in view of the purpose of reducing the amount of active ingredient used and achieving high reactivity, when palladium is used as a catalyst component, in order to increase the specific surface area and increase the utilization efficiency. Usually, it is used by being dispersed and supported on a carrier. In chemical industrial processes, such palladium-supported catalysts are widely used for various reactions such as oxidation reaction, reduction reaction, reforming, CO addition, etc., as well as purification catalysts for automobile exhaust gas. Various types of carriers for supporting palladium are used depending on the characteristics and application of the reaction.

  Among them, silica-based carriers are widely used as carriers for palladium-supported catalysts because they can support various metal ions. If the physical properties such as a high specific surface area are to be satisfied in order to meet the requirements for the catalyst carrier, the silica carrier needs to be made porous, but in that case the mechanical strength is weakened. On the other hand, the specific surface area of a silica-based support obtained by firing at a high temperature in an attempt to satisfy the mechanical strength is small. Thus, it is difficult to obtain a silica-based carrier satisfying the contradicting physical properties of high mechanical strength and large specific surface area, and no silica-based material satisfying both requirements has been obtained.

It is known that quartz, which is one of silica-based materials, is hard and has high mechanical strength. However, although it is generally excellent in mechanical strength, the specific surface area is small (1 m ² / g or less) and it cannot be used for applications requiring a high specific surface area. In order to use it as a catalyst carrier, it may be synthesized by increasing the specific surface area of the silica-based carrier, but in that case, the mechanical strength is sacrificed, and an example having sufficient surface area and mechanical strength is Absent.

In JP-A-9-52044, as a carrier for a catalyst for producing a carboxylic acid ester, aluminum is 5 to 40% by weight as Al ₂ O ₃ , magnesium is 3 to 30% by weight as MgO, and silicon is 50 to 50% as SiO _2. Silica-alumina-magnesia containing in the range of 92% by weight is described.

JP-A-9-52044

  The silica-alumina-magnesia carrier described in Patent Document 1 has the characteristics of high mechanical strength, large specific surface area, high water resistance compared to silica, and high acid resistance compared to alumina. . However, when the carrier is used as a carrier for a catalyst for producing a carboxylic acid ester, the mechanical strength can be satisfied under normal use conditions, but conditions such as vigorous mixing between particles, particles and a stirring spring, etc. In the reaction under severe conditions in the turbid reaction, there may be a problem of cracking or chipping due to friction or the like.

  Further, according to the study by the present inventors, when the reaction is carried out over a long period of time using the catalyst having the carrier described in Patent Document 1, it is gradually caused by expansion of the pore diameter and particle growth. It has been found that the structure of the catalyst particles changes. The expansion of the pore diameter is due to the by-product of the reaction-specific acid component and the addition of the alkali component, whereby the catalyst particles are repeatedly exposed locally to acids and bases, and one of silicon and aluminum in the silica-alumina-magnesia support. This is considered to be caused by dissolution and precipitation of the part and rearrangement of the silica / alumina crosslinked structure. It was also found that the particle growth progressed by sintering of the supported palladium simultaneously with the expansion of the pore diameter, and as a result, the catalytic activity decreased.

  Thus, conventionally, it has been extremely difficult to obtain a carrier that stably supports a metal component containing palladium.

  Therefore, the present invention has been made in view of the above circumstances, can maintain a state in which a metal component containing palladium is stably supported, and can maintain high reactivity over a long period of time even when used as a catalyst. It is an object of the present invention to provide a noble metal support and a method for producing a carboxylic acid ester using the same as a catalyst.

  From the viewpoint of improving the chemical stability and mechanical strength of silica gel, the present inventors paid attention to the unique structure of silica chains (-Si-O-) constituting the silica gel, and these structures and physical properties. Research on the correlation with As a result, surprisingly, from at least one fourth periodic element selected from the group consisting of silicon, aluminum, iron, cobalt, nickel and zinc, an alkali metal element, an alkaline earth metal element, and a rare earth element. It has been found that a carrier comprising a complex oxide containing at least one basic element selected from the group can overcome the above-mentioned drawbacks found in conventional carriers and solve the above problems. Completed the invention.

That is, the present invention is as follows.
[1] Selected from the group consisting of at least one fourth periodic element selected from the group consisting of silicon, aluminum, iron, cobalt, nickel, and zinc, an alkali metal element, an alkaline earth metal element, and a rare earth element At least one basic element, 42 to 90 mol% and 3 to 38 mol, respectively, with respect to the total molar amount of the silicon, the aluminum, the fourth periodic element, and the basic element. %, 0.5 to 20 mol%, and 2 to 38 mol% in the presence of oxygen, containing a support made of a composite oxide, and a metal component containing palladium supported on the support A noble metal support used as a catalyst in an oxidative esterification reaction in which an aldehyde and an alcohol are reacted with each other .
[2] The noble metal support according to [1], wherein the composition ratio of the fourth periodic element to the aluminum in the support is 0.02 to 1.0 on a molar basis.
[3] The noble metal support according to [1] or [2], wherein the composition ratio of the fourth periodic element to the basic element in the carrier is 0.02 to 1.2 on a molar basis.
[4] The composite oxide is a composite oxide in which the fourth periodic element is nickel and the basic element is magnesium, with respect to the total molar amount of the silicon, the aluminum, the nickel, and the magnesium. The silicon is contained in the range of 42 to 90 mol%, the aluminum in the range of 3 to 38 mol%, the nickel in the range of 0.5 to 20 mol%, and the magnesium in the range of 2 to 38 mol%, [1] to The noble metal support according to any one of [3].
[5] The noble metal support according to any one of [1] to [4], wherein the metal component containing palladium is palladium and / or a palladium compound.
[6] The noble metal support according to [5], wherein the palladium compound is an intermetallic compound containing palladium and at least one element selected from the group consisting of lead, mercury, thallium and bismuth.
[7] A method for producing a carboxylic acid ester, wherein the noble metal support of any one of [1] to [6] is used as a catalyst, and an aldehyde and an alcohol are reacted in the presence of oxygen.
[8] The method for producing a carboxylic acid ester according to [7], wherein the aldehyde is selected from the group consisting of acrolein, methacrolein, and a mixture thereof.
[9] The method for producing a carboxylic acid ester according to [7] or [8], wherein the alcohol is methanol.

  The present invention can maintain a state in which a metal component containing palladium is stably supported, and can maintain a high reactivity over a long period of time even when used as a catalyst, and a carboxylic acid ester using the same as a catalyst It aims at providing the manufacturing method of.

  Hereinafter, the best mode for carrying out the present invention (hereinafter simply referred to as “the present embodiment”) will be described in detail. The present invention is not limited to the following embodiment, and can be implemented with various modifications within the scope of the gist.

[Precious metal support]
The noble metal carrier of this embodiment includes at least one fourth periodic element selected from the group consisting of silicon, aluminum, iron, cobalt, nickel, and zinc, an alkali metal element, an alkaline earth metal element, and a rare earth element. A carrier comprising a composite oxide containing at least one basic element selected from the group consisting of elements, and a metal component containing palladium carried on the carrier.

  Hereinafter, the characteristics of the carrier of this embodiment will be described. The carrier according to the present embodiment can greatly improve the chemical stability and the mechanical strength, and the inventor presumes the reason as follows. For example, the presence of aluminum (Al) in silica having an uncrosslinked silica (Si—O) chain allows a cross-linked structure of Si—O chains such as Si—O—Al—O—Si bonds (hereinafter, "Silica-alumina cross-linked structure") is newly formed. When this Al-linked structure is formed, it is considered that the Si—O bond is strengthened without losing the stability of the Si—O chain with respect to the original acidic substance. As a result, it is considered that the hydrolysis resistance (hereinafter also simply referred to as “water resistance”) of the composite oxide is remarkably improved. Moreover, when a silica-alumina crosslinked structure is formed, it is considered that Si—O uncrosslinked chains are reduced and mechanical strength is increased as compared with the case of silica alone. That is, it is presumed that the amount of silica-alumina crosslinked structure formed correlates with the improvement in mechanical strength and water resistance of the resulting silica.

  Further, with the generation of the silica-alumina crosslinked structure, the charge becomes unstable based on the difference in valence between Si (tetravalent) and Al (trivalent). Therefore, in the carrier according to this embodiment, in addition to silicon and aluminum, at least one basic element selected from alkali metal elements, alkaline earth metal elements, and rare earth metal elements coexists. Thereby, 1 to 3 basic elements are compensated and neutralized, and charge stabilization is promoted. Furthermore, since it becomes a three-component system, it is presumed that the stability of the structure can be further improved because a balance in charge can be achieved. One reason for this is that silica-alumina is acidic while silica-alumina-magnesia is almost neutral.

  The carrier containing at least one fourth periodic element selected from the group consisting of iron, cobalt, nickel, and zinc in addition to the above three component elements has a chemical structure compared with that not containing the fourth periodic element. Stability is increased. Therefore, even under pH swing conditions where the acid and base are repeatedly exposed, the structural stability is high, and the enlargement of the pore diameter and the reduction of the specific surface area are suppressed.

  According to the study by the present inventors, when a noble metal support using silica-alumina or silica-alumina-magnesia as a support is used as a catalyst for the synthesis reaction of carboxylic acid ester, it is gradually in a long-term reaction. However, it became clear that the structural change of the composite particles occurred. In this reaction, the particles of the support are repeatedly exposed to acids and bases locally in the above reaction, and a part of the aluminum in the carrier dissolves and precipitates, resulting in rearrangement of the silica / alumina crosslinked structure. This is considered to be due to the increase in the pore diameter of the particles of the supported material. It has also been found that, as the pore diameter increases, sintering of metal particles containing palladium occurs and the specific surface area decreases, whereby the catalytic activity decreases.

  The fourth periodic element contained in the carrier is considered to react with aluminum and / or a basic element, which are constituent elements of the carrier, to generate a composite oxide containing the fourth periodic element. As a result of the formation of such a compound acting on the stabilization of the silica / alumina crosslinked structure, it is considered that the chemical stability of the carrier is improved and the structural change is greatly improved.

  Here, the “composite oxide” in the present specification represents an oxide containing two or more metals. That is, the “composite oxide” is an oxide in which two or more kinds of metal oxides form a compound, and a double oxide in which an oxoacid ion does not exist as a structural unit (for example, perovskite oxidation of nickel). Products and spinel oxides). However, it is a concept wider than a double oxide, and includes all oxides in which two or more metals are combined. An oxide in which two or more metal oxides form a solid solution is also a category of “composite oxide”.

  For example, nickel is selected as the fourth periodic element, magnesium is selected as the basic element, and a carrier made of a composite oxide containing silicon-aluminum-nickel-magnesium is analyzed by double-crystal high-resolution X-ray fluorescence analysis (HRXRF). When the chemical state of nickel is analyzed, nickel in the support according to the present embodiment does not exist as nickel oxide which is a single compound. The nickel exists as a composite oxide containing nickel, such as a nickel oxide compound or a solid solution formed by combining nickel oxide and alumina and / or magnesia, or a mixture thereof.

  The double-crystal type high-resolution X-ray fluorescence analysis (HRXRF) has extremely high energy resolution, and can analyze the chemical state of an element from the energy position (chemical shift) and shape of the spectrum obtained. In particular, in the Kα spectrum of a 3d transition metal element, a chemical shift and a spectrum shape change due to a change in valence and electronic state, and the chemical state of the element can be analyzed in detail. In the carrier according to the present embodiment, the NiKα spectrum is different from that in the case of nickel oxide, and a chemical state of nickel different from nickel oxide which is a single compound is confirmed.

In the carrier according to the present embodiment, nickel is presumed to exist, for example, as nickel aluminate (NiAl ₂ O ₄ ), which is a spinel compound of nickel oxide and alumina, or as a solid solution of nickel oxide and magnesia (NiO · MgO). Is done. Similarly, for the fourth periodic element other than nickel, the oxide forms a solid solution with a spinel compound or basic metal oxide with alumina, which acts to stabilize the silica-alumina crosslinked structure. It is thought that the stability of the product has increased.

Carrier according to the present embodiment is preferably the specific surface area of 20 to 500 m ² / g, more preferably 50 to 400 m ² / g, particularly preferably 50~350m ² / g. When a support | carrier is used as a catalyst support | carrier, the pore diameter becomes like this. Preferably it is 3-50 nm, More preferably, it is 3-30 nm, More preferably, it is 3-10 nm. The pore volume of the carrier is preferably in the range of 0.1 to 1.0 mL / g, more preferably in the range of 0.1 to 0.5 mL / g. From the viewpoint of mechanical strength and water resistance, the carrier of this embodiment preferably has a specific surface area, pore diameter, and pore volume in the above ranges. Here, the specific surface area, pore diameter and pore volume of the carrier are measured according to the method described in [Measurement and analysis of physical properties] described later.

  The carrier composed of a composite oxide containing silicon, aluminum, the fourth periodic element and the basic element contains 42 to 90 silicon with respect to the total molar amount of silicon, aluminum, the fourth periodic element and the basic element. Mol%, aluminum is included in the range of 3 to 38 mol%, the fourth periodic element is included in the range of 0.5 to 20 mol%, and the basic element is included in the range of 2 to 38 mol%. Preferably, silicon is 70 to 90 mol%, aluminum is 5 to 30 mol%, the fourth periodic element is 0.5 to 10 mol%, basic element is 2 to 30 mol%, more preferably, silicon is 75 to 90 mol%, 5-15 mol% of aluminum, 0.5-5 mol% of the fourth periodic element, and 2-15 mol% of the basic element. When the amount of silicon, aluminum, the fourth periodic element and the basic element is within the above range, silicon, aluminum, the fourth periodic element, the basic element and the oxygen atom form a specific stable bond structure with each other, As a result, the chemical stability, mechanical strength and water resistance of the noble metal support tend to be good.

  Examples of basic alkali metal elements include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs). Examples of alkaline earth metal elements include beryllium ( Examples of rare earth elements include Be), magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba), and lanthanum (La), cerium (Ce), and praseodymium (Pr).

  There is a suitable range for the composition ratio between the fourth periodic element and the aluminum or basic element contained in the carrier according to the present embodiment. The composition ratio of the fourth periodic element to aluminum (fourth periodic element / aluminum) is preferably 0.02 to 1.0, more preferably 0.05 to 0.8, and still more preferably 0.04 on a molar basis. ~ 0.6. The composition ratio of the fourth periodic element to the basic element (fourth periodic element / basic element) is preferably 0.02 to 1.2, more preferably 0.05 to 1.0, on a molar basis. More preferably, it is 0.05-0.8. When the composition ratio between the fourth periodic element and aluminum or the basic element is within the above range, the effect of improving the elution of aluminum and the structural change of the noble metal support tends to increase. This is presumably because the fourth periodic element, aluminum, and the basic element form a specific composite oxide within this range to form a stable bond structure.

  When the fourth periodic element is nickel and the basic element is magnesium, the carrier made of a composite oxide containing silicon, aluminum, nickel, and magnesium has a total molar amount of silicon, aluminum, nickel, and magnesium. On the other hand, it preferably contains silicon in a range of 42 to 90 mol%, aluminum in a range of 3 to 38 mol%, nickel in a range of 0.5 to 20 mol%, and magnesium in a range of 2 to 38 mol%. More preferably, silicon is 70 to 90 mol%, aluminum is 5 to 30 mol%, nickel is 0.5 to 10 mol%, magnesium is 2 to 30 mol%, more preferably silicon is 75 to 90 mol%, It contains 5 to 15 mol% of aluminum, 0.5 to 5 mol% of nickel, and 2 to 15 mol% of magnesium. When the elemental composition of silicon, aluminum, nickel and magnesium is within the above range, silicon, aluminum, nickel and magnesium form a specific stable bond structure, and as a result, the chemical stability, mechanical strength and Water resistance tends to be good.

  The solid form of the carrier according to the present embodiment is not particularly limited as long as predetermined physical properties can be obtained, but it is amorphous so that a diffraction peak derived from a crystalline component is not observed by X-ray diffraction. It is preferable. By adopting such a solid form, the fourth periodic element in the carrier is dispersed to a high degree and acts strongly on the silica / alumina crosslinked structure, so that better chemical stability tends to be obtained.

  The carrier according to the present embodiment may have various shapes such as a substantial thickness or a particle size in the order of μm to cm. Specific examples of the carrier shape include a spherical shape, an elliptical shape, a cylindrical shape, a tablet shape, a hollow cylindrical shape, a plate shape, a rod shape, a sheet shape, and a honeycomb shape. When used as a catalyst carrier, the shape of the carrier according to the present embodiment can be appropriately changed depending on the reaction format used. For example, when the catalyst support is used for a fixed bed reaction, a hollow cylindrical shape or a honeycomb shape with a small pressure loss is preferable, and a spherical shape is generally preferable under the liquid phase slurry suspension conditions.

  In particular, when the carrier according to the present embodiment is used for the reaction as a catalyst carrier in a fluidized state, the shape is preferably spherical particles, and the particle size is preferably an average particle size of 1 to 200 μm, more preferably 10 to 10 μm. It is 200 micrometers, More preferably, it is 30-150 micrometers. By using the support as such particles, the catalyst performance can be maintained over a long period of time. The average particle size of the carrier is measured according to the method described in [Measurement and analysis of physical properties] described later.

  A carrier made of a composite oxide containing silicon, aluminum, the fourth periodic element and the basic element has higher water resistance than silica and higher acid resistance than alumina. In addition, the carrier has excellent physical properties such as higher mechanical strength than silica. In addition, the carrier has extremely high chemical stability compared to silica-alumina or silica-alumina-magnesia, and, for example, a part of silicon and aluminum dissolves under pH swing conditions that are repeatedly exposed to acids and bases. Structural changes such as expansion of pore diameter and reduction of specific surface area due to precipitation are suppressed.

  Next, a preferred method for preparing a carrier according to this embodiment having the above composition will be described.

There are no particular limitations on the method of preparing the carrier comprising the composite oxide containing silicon, aluminum, the fourth periodic element, and the basic element. For example, silica and aluminum are prepared by the following methods (1) to (6). A step of obtaining a composition comprising a compound, a compound of a fourth periodic element and a compound of a basic element, a step of drying the composition as necessary to obtain a dried product, and the dried product or the above composition And a step of firing under conditions described later.
(1) A commercially available silica-alumina composition is reacted with a compound of a fourth periodic element and a compound of a basic element.
(2) A silica-alumina gel is formed in advance, and a compound of a fourth periodic element and a compound of a basic element are added and reacted.
(3) The silica sol is reacted with an aluminum compound, a fourth periodic element compound, and a basic element compound.
(4) A silica sol is reacted with an aluminum compound insoluble in water, a compound of a fourth periodic element insoluble in water, and a compound of a basic element insoluble in water.
(5) The silica gel is reacted with an aqueous solution of a water-soluble aluminum compound, a water-soluble fourth periodic element compound, and a water-soluble basic element compound.
(6) Solid phase reaction of silica gel with an aluminum compound, a fourth periodic element compound, and a basic element compound.

  Below, the preparation method of the support | carrier using the method of said (1)-(6) is demonstrated in detail.

  In the method (1), a commercially available silica-alumina composition is mixed with a compound containing a fourth periodic element and a compound containing a basic element to obtain a slurry. The carrier can be prepared by drying the slurry and firing it under the conditions described below. As the compound containing the fourth periodic element and the compound containing the basic element, water-soluble compounds represented by chlorides, carbonates, nitrates and acetates are preferable. However, water-insoluble compounds such as hydroxides and oxides can also be used.

  In the methods (2) to (6), for example, silica sol, water glass, or silica gel is used as the silica source. As long as it has an uncrosslinked Si site | part which reacts with Al as silica gel, there is no restriction | limiting in particular about the length of a Si-O chain | strand. As the aluminum compound, water-soluble compounds represented by sodium aluminate, aluminum chloride hexahydrate, aluminum perchlorate hexahydrate, aluminum sulfate, aluminum nitrate nonahydrate, and aluminum diacetate are preferable. However, it may be a water-insoluble compound such as aluminum hydroxide or aluminum oxide, and any compound that reacts with uncrosslinked Si in silica sol or silica gel can be used for the preparation of the carrier. Examples of the compound containing the fourth periodic element or basic element include oxides, hydroxides, chlorides, carbonates, sulfates, nitrates, and acetates of these elements.

In the case of the method (2) using silica-alumina gel, sulfuric acid is previously added to water glass to prepare a silica hydrogel having a pH of 8 to 10.5, and Al ₂ (SO ₄ ) having a pH of 2 or lower. ₃ Add the solution, and further add sodium aluminate with a pH of 5 to 5.5 to prepare a silica-alumina hydrogel. Next, the moisture contained in the hydrogel is adjusted to 10 to 40% by spray drying or the like, and a compound of a fourth periodic element and a compound of a basic element are added thereto to obtain a composition. And after drying the composition, a support | carrier can be obtained by baking on the conditions mentioned later.

  In the case of the methods (3) and (4) using silica sol as a starting material, an aluminum compound, a fourth periodic element compound and a basic element compound are mixed in the silica sol, and the silica sol, aluminum compound and fourth period are mixed. A mixture sol which is a composition containing a compound of an element and a compound of a basic element is obtained, then the mixture sol is dried to obtain a gel, and the gel is fired at the temperature, time and atmospheric conditions described below. Alternatively, an alkaline aqueous solution is added to the mixture sol to coprecipitate silica, an aluminum compound, a fourth periodic element compound, and a basic element compound, and the coprecipitate is dried and then fired under the conditions described below. In addition, a carrier having a desired particle size can be obtained by passing the mixture sol as it is by using a spray dryer and pulverizing the mixture sol, or drying the mixture sol and granulating the gel. Is possible.

  In particular, in the case of the method (4), silica sol, an aluminum compound insoluble in water, a compound of a fourth periodic element insoluble in water, and a compound of a basic element insoluble in water are reacted. The fourth periodic element compound and the basic element compound may be pulverized to a predetermined particle diameter in advance or preliminarily or coarsely pulverized. Conditions after mixing the aluminum compound insoluble in water, the compound of the fourth periodic element insoluble in water and the compound of the basic element insoluble in water, and silica sol, and then drying the reaction product, and further described below Bake with. In addition, the composition of silica-alumina-fourth periodic element-basic element after firing without preliminarily pulverizing or preliminarily coarsely pulverizing the aluminum compound, the fourth periodic element compound, and the basic element compound. May be pulverized to a predetermined particle size.

  In the case of the method (5) using silica gel as a starting material, the silica gel is reacted with an aqueous solution of a water-soluble aluminum compound, a water-soluble fourth periodic element compound and a water-soluble basic element compound. You may grind | pulverize to a predetermined particle diameter, or you may coarsely grind | pulverize preliminary. In the case of the method (5), after obtaining a slurry in which silica gel is mixed with an aqueous solution of a water-soluble aluminum compound, an aqueous solution of a water-soluble fourth periodic element compound, and an aqueous solution of a water-soluble basic element compound, The slurry is dried and further baked for 1 to 48 hours under the conditions described below. Alternatively, the composition of calcined silica-alumina-fourth periodic element-basic element may be pulverized to a predetermined particle size without pre-pulverizing or preliminarily coarsely pulverizing silica gel.

  Similarly, the method (6) using silica gel as a starting material is a method in which a silica gel is reacted with an aluminum compound, a compound of a fourth periodic element and a compound of a basic element to obtain a reactant which is a composition. is there. In this case, Al is reacted with uncrosslinked Si in a solid state. Silica gel, an aluminum compound, a compound of the fourth periodic element, and a compound of the basic element may be pulverized to a predetermined particle size in advance, or may be preliminarily coarsely pulverized. At this time, each substance may be pulverized alone, or both may be mixed and pulverized. The reaction product obtained by the solid phase reaction is dried if necessary and then further baked. Firing is preferably performed under the temperature, time, and atmospheric conditions described below. Silica gel, aluminum compound, fourth period element compound, basic element compound are not pulverized in advance or preliminarily coarsely pulverized, and the reaction product obtained by the reaction is pulverized to a desired particle size. May be.

  As another method for preparing a composition containing silica, an aluminum compound, a compound of a fourth periodic element, and a compound of a basic element, the component of the basic element is added to a composite oxide containing silicon, aluminum, and the fourth periodic element. A method of adsorption can also be used. In this case, for example, a method using a dipping method such as adding a composite oxide containing silicon, aluminum, and a fourth periodic element to a solution in which a compound of a basic element is dissolved, or a pore volume, A method using an impregnation method in which a compound of a basic element is soaked in the composite oxide and subjected to a drying treatment can be applied.

  In addition, a method of adsorbing a component containing the fourth periodic element to a composite oxide containing silicon, aluminum, and the basic element can also be used. For example, a method using an immersion method such as adding the composite oxide to a solution in which a compound containing a fourth periodic element is dissolved and performing a drying treatment, or a compound containing a fourth periodic element corresponding to the pore volume is used. A method using an impregnation method in which a composite oxide is soaked and dried is applicable.

  However, as described above, the method of adsorbing the component containing the basic element or the component containing the fourth periodic element later highly disperses the component containing the basic element or the component containing the fourth periodic element on the carrier. Attention should be paid such as performing the liquid drying process under mild conditions.

  To the slurry containing various raw materials obtained as described above, an inorganic substance or an organic substance may be added in order to control the slurry properties, finely adjust the properties such as the pore structure of the product and the obtained physical properties.

  Specific examples of inorganic substances used include mineral acids such as nitric acid, hydrochloric acid, and sulfuric acid; alkali metals such as Li, Na, K, Rb, and Cs; and metal salts such as alkaline earth metals such as Mg, Ca, Sr, and Ba And water-soluble compounds such as ammonia and ammonium nitrate, and clay minerals that are dispersed in water to form a suspension. Specific examples of organic substances include polymers such as polyethylene glycol, methyl cellulose, polyvinyl alcohol, polyacrylic acid, and polyacrylamide.

  There are various effects obtained by adding an inorganic substance and an organic substance. Mainly, the support is formed into a spherical shape, and the pore diameter and pore volume are controlled. More specifically, the liquid quality of the mixed slurry is an important factor for obtaining a spherical carrier. By adding an inorganic substance or an organic substance and adjusting the viscosity and solid content concentration of the slurry, it can be changed to a liquid quality in which a spherical carrier can be easily obtained. In order to control the pore diameter and the pore volume, an optimal organic compound that remains in the inside of the carrier at the molding stage and can be removed by firing and washing operations after molding may be selected.

  Next, a composition such as a slurry, gel, or reactant containing the above-described various raw materials and additives is dried. The drying method is not particularly limited, but spray drying is preferable from the viewpoint of controlling the particle size of the carrier. In this case, as a method for forming the mixed slurry into droplets, a method using a known spraying device such as a rotating disk method, a two-fluid nozzle method, a pressure nozzle method, or the like can be given.

  The liquid to be sprayed (slurry) needs to 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. In particular, when each raw material is prepared, the viscosity of the slurry may increase and the gelation (condensation of the colloid) may occur, and there is a concern that uneven particles may be formed. Therefore, in addition to considering each material gradually mixed under stirring, etc., a mixed slurry is prepared by controlling the mixture in the metastable region of silica sol near pH 2, for example, by adding acid or alkali. May be preferred.

  The liquid to be sprayed preferably has a predetermined range of viscosity and solid content concentration. When the viscosity and the solid content concentration are lower than the predetermined range, the porous body obtained by spray drying does not become a true sphere, and a large number of depressed spherical porous bodies tend to be generated. Moreover, when they are higher than the predetermined range, the dispersibility between the porous bodies may be adversely affected, and depending on the properties, droplets cannot be stably formed. Therefore, the viscosity of the liquid to be sprayed is preferably in the range of 5 to 10000 cp at the spraying temperature as long as spraying is possible. Further, from the viewpoint of the shape, a tendency that a higher viscosity is preferable in a sprayable range is observed, and the viscosity is more preferably in the range of 10 to 1000 cp from the balance with operability. Moreover, it is preferable from a viewpoint of a shape and a particle diameter that solid content concentration exists in the range of 10-50 mass%. In addition, as a standard of spray drying conditions, it is preferable that the hot air temperature at the entrance of the drying tower of the spray dryer is in the range of 200 to 280 ° C and the outlet temperature of the drying tower is in the range of 110 to 140 ° C.

  Next, a solid substance is obtained by baking the composition after further drying through the methods (1) to (5) or the reaction product obtained by the method (6). The firing temperature is generally in the range of 200 to 800 ° C. When the composition is calcined at 800 ° C. or lower, the specific surface area of the carrier can be increased. When the composition is calcined at 200 ° C. or higher, dehydration or condensation reaction between gels becomes more sufficient, and the pore volume is increased. The bulkiness can be further suppressed. A firing temperature in the range of 300 to 600 ° C. is preferable from the viewpoint of balance of physical properties and operability. However, when the composition contains a nitrate, it is preferably fired at a temperature higher than the decomposition temperature of the nitrate. The physical properties of the carrier such as the porosity can be changed depending on the firing temperature and the temperature raising rate, and an appropriate firing temperature and temperature raising conditions may be selected in accordance with the target physical properties. That is, by setting the firing temperature to an appropriate condition, the durability of the composite oxide can be maintained well, and a decrease in pore volume can be suppressed. Further, it is preferable to gradually increase the temperature using a program temperature increase or the like as the temperature increase condition. As a result, the gasification and combustion of inorganic and organic substances become severe, and accordingly, it becomes easy to be exposed to a high temperature state higher than the setting, and cracking is likely to occur, and as a result, crushing is prevented as a result. be able to.

  In addition, the firing atmosphere is not particularly limited, but firing is generally performed in air or nitrogen. Moreover, although baking time can be determined according to the specific surface area of the support | carrier after baking, it is generally 1 to 48 hours. The physical properties of the carrier such as porosity can be changed also by these firing conditions, and each firing condition may be selected according to the target physical properties.

  Although the solid obtained through the baking process as described above may be used as the carrier according to the present embodiment, it is preferable to further hydrothermally treat the solid. Surprisingly, through the hydrothermal treatment process, the pore diameter of most of the pores has a uniform pore structure that exists in a narrow range of 3 to 5 nm, and the specific surface area and mechanical strength are also large. A carrier can be obtained.

  “Hydrothermal treatment” as used herein is an operation of immersing the solid in water or a solution containing water and holding the solid for a certain period of time while heating. As a result, the present inventors presume that sufficient water is present in the pores of the solid matter, mass transfer occurs using the water as a medium, and the reconstruction of the pores proceeds. Therefore, from the viewpoint of promoting rapid mass transfer, the hydrothermal treatment temperature is preferably 60 ° C. or higher, more preferably 70 ° C. or higher, still more preferably 80 ° C. or higher, and particularly preferably 90 ° C. or higher. The temperature of the hydrothermal treatment may be a high temperature of 100 ° C. or higher, but in that case, a pressure device is required so that moisture does not evaporate excessively. Even if the hydrothermal treatment temperature is as low as less than 60 ° C., the carrier according to the present embodiment can be obtained, but the treatment time tends to be long. Further, as is clear from the above, hydrothermal treatment at a temperature equal to or higher than the boiling point of the solution under pressure is advantageous in that the effect is manifested in a short time. However, from the viewpoint of ease of operation, it is usually preferable to perform a hydrothermal treatment at a high temperature in the range below the boiling point. The hydrothermal treatment time varies depending on conditions such as the type of metal constituting the solid, the amount of metal, the metal composition ratio, and the treatment temperature, but preferably 1 minute to 5 hours, more preferably 5 minutes to 3 hours, and even more preferably. Within 5 minutes to 1 hour.

  The reason why the pore distribution is narrowed by hydrothermal treatment is not clear, and detailed studies are insufficient. At present, the present inventors presume the reason as follows. That is, by subjecting the above-described composition containing silica to molding, drying, firing, and the like, a crosslinking reaction between particles in the composition proceeds, and first a structure having a pore distribution of 2 to 10 nm ( Solids) are formed. In the drying process and the baking process, dehydration reaction between gels and cross-linking reaction proceed by heating in a gas atmosphere, but these reactions are solid-phase reactions. There is no pore distribution. However, it is speculated that by subjecting the solid matter to further hydrothermal treatment, the reaction by the hydrolysis and re-crosslinking reaction of the solid matter proceeds and the rearrangement of the structure occurs. In addition, taking into account that the obtained pore volume is close to the porosity due to the close-packing of particles, the hydrothermal reaction by hydrothermal treatment changes to a thermodynamically stable packed structure, resulting in a pore diameter of 3 to 5 nm. It is presumed that a carrier having a pore distribution in a narrow range can be obtained.

  Next, another preferred method for preparing the carrier according to this embodiment will be described. This preparation method comprises a composition containing silica, an aluminum compound, and a compound of at least one basic element selected from the group consisting of alkali metal elements, alkaline earth metal elements, and rare earth elements, or a composition thereof A step (first step) of baking a dried product to obtain a solid, and the solid, and at least one fourth periodic element selected from the group consisting of iron, cobalt, nickel and zinc A step of neutralizing a mixture of the soluble metal salt with an acidic aqueous solution and precipitating a fourth periodic element on the solid (second step); and a step of hydrothermally treating the solid on which the fourth periodic element is precipitated ( (3rd process) and the process (4th process) which heat-processes the solid substance which passed through the process of hydrothermally treating.

  In the first step, a slurry further containing silica, an aluminum compound and a compound of the basic element is prepared, dried, and then fired to obtain a solid. What is necessary is just to mix | blend a slurry by the method similar to the above-mentioned embodiment except not containing the compound of a 4th period element. Moreover, the firing temperature should just be the same as the firing temperature in the above-mentioned embodiment.

  Next, in the second step, by neutralizing the mixture of the solid matter obtained in the first step and the acidic aqueous solution containing the fourth periodic element, a component containing the fourth periodic element is added to the solid matter. Precipitate. Under the present circumstances, the solid substance mixed with acidic aqueous solution may be in the state of the water slurry which disperse | distributed it to water. At this stage, due to the neutralization reaction between the ions of the fourth periodic element in the aqueous solution and the base, for example, in the state of the hydroxide of the fourth periodic element, the component containing the fourth periodic element precipitates on the solid and is immobilized. Is done.

  Examples of the base used when neutralizing in the second step include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and ammonia. Further, an alkali metal element (Li, Na, K, Rb, Cs), an alkaline earth metal element (Be, Mg, Ca, Sr, Ba) and a rare earth element (La, A component containing one or more basic elements selected from the group consisting of Ce and Pr) may be included. Examples of the component containing such a basic element include potassium hydroxide, rubidium hydroxide, magnesium oxide, strontium oxide, lanthanum oxide, and cerium oxide.

  In the second step, for example, an acidic aqueous solution of a soluble metal salt containing a fourth periodic element and a solid are mixed and neutralized with a base while stirring to precipitate a component of the fourth periodic element on the solid. To precipitate. When precipitating the component of the fourth periodic element, conditions such as the concentration of the acidic aqueous solution containing the fourth periodic element, the base, the pH of the aqueous solution, and the temperature may be selected as appropriate.

  The concentration of the fourth periodic element in the acidic aqueous solution (when two or more fourth periodic elements are contained, the concentration of each fourth periodic element) is preferably 0.0001 to 1.0 mol / L, more preferably The range is 0.001 to 0.5 mol / L, more preferably 0.005 to 0.2 mol / L.

  Further, when neutralizing with a base, the amount of the base may be adjusted so that the pH of the aqueous solution is preferably in the range of 5 to 10, more preferably 6 to 8. The temperature of the aqueous solution is preferably 0 to 100 ° C, more preferably 30 to 90 ° C, still more preferably 60 to 90 ° C.

  The time required for precipitating the component containing the fourth periodic element varies depending on conditions such as the content of alumina, the fourth periodic element and the basic element, and the temperature, but preferably 1 minute to 5 hours, more preferably 5 The range is from minutes to 3 hours, more preferably from 5 minutes to 1 hour.

  Next, in a 3rd process, the solid substance in which the component containing a 4th period element precipitated is hydrothermally processed, and a mixture is obtained. By subjecting the solid to hydrothermal treatment, the hydrolysis and re-crosslinking reaction of the silica gel proceed, and the rearrangement of the structure occurs, and at the same time, the compound of the fourth periodic element proceeds.

  The hydrothermal treatment may be the same as that in the above embodiment, and the neutralization liquid used in the second step may be heated as it is to perform the hydrothermal treatment. The hydrothermal treatment is preferably carried out at a temperature range of 60 ° C. or higher for 1 to 48 hours. Hydrothermal treatment is possible even at a low temperature of less than 60 ° C., but the treatment time becomes longer. From the viewpoint of operability, treatment time, etc., the hydrothermal treatment is preferably performed at 60 to 90 ° C.

  Furthermore, after the solid contained in the mixture obtained in the third step is washed with water and dried as necessary, heat treatment is performed in the fourth step. Thus, the carrier according to this embodiment can be obtained.

  The heat treatment temperature of the solid in the fourth step is preferably 40 to 900 ° C, more preferably 80 to 800 ° C, still more preferably 200 to 700 ° C, and particularly preferably 300 to 600 ° C.

  The atmosphere of the heat treatment is, for example, in the air (or in the air), in an oxidizing atmosphere (oxygen, ozone, nitrogen oxide, carbon dioxide, hydrogen peroxide, hypochlorous acid, inorganic / organic peroxide, etc.) And in an inert gas atmosphere (helium, argon, nitrogen, etc.). The heat treatment time may be appropriately selected according to the heat treatment temperature and the amount of solid matter.

  The noble metal-supported material of the present embodiment contains the above-mentioned carrier and a metal component containing palladium supported on the carrier. The metal component containing palladium is a metal or a metal compound containing at least palladium as a metal element. Specific examples thereof may be palladium alone, or palladium and other different elements such as lead, mercury, thallium, bismuth, tellurium, nickel, chromium, cobalt, indium, tantalum, copper, zinc, zirconium, It may contain one or more of hafnium, tungsten, manganese, silver, rhenium, antimony, tin, rhodium, ruthenium, iridium, platinum, gold, titanium, aluminum, boron and silicon. Further, the metal component may contain an alkali metal compound or an alkaline earth metal compound.

The metal component preferably contains palladium and at least one element selected from the group consisting of lead, mercury, thallium and bismuth, and if necessary, from the group consisting of alkali metal compounds and alkaline earth metal compounds It is also preferred to further comprise at least one selected compound. At this time, palladium may form an alloy or an intermetallic compound with a different element such as lead, mercury, thallium, or bismuth, and an alloy or an intermetallic compound is preferable in some cases. When such a noble metal support on which an alloy or an intermetallic compound is supported is used as a catalyst for the production of a carboxylic acid ester, carbon dioxide gas or hydrocarbons due to the C—C bond cleavage reaction of the raw aldehyde or its oxidation reaction intermediate The target carboxylic acid ester can be produced with high selectivity. Such an alloy or intermetallic compound is specified by a technique such as specifying a lattice constant by X-ray diffraction, for example. As an intermetallic compound, palladium (Pd) and one or more metal elements selected from the group consisting of lead (Pb), mercury (Hg), thallium (Tl), and bismuth (Bi) have a simple integer ratio. A compound having a new property different from that of the component metal element, which is bonded in the above is preferable. Examples of such intermetallic compounds include Pd ₃ Pb ₁ , Pd ₅ Pb ₃ , σ-Pd ₁ Hg ₁ , Pd ₂ Hg ₅ , Pd ₁ Tl ₂ , Pd ₂ Tl ₁ , Pd ₃ Bi ₁ , Pd ₁ Examples thereof include binary intermetallic compounds such as Bi ₁ and Pd ₁ Bi _2, and multicomponent intermetallic compounds of three or more components containing these elements. Furthermore, in addition to the above intermetallic compounds, a small amount of different elements such as tellurium, antimony, rhodium, ruthenium, iridium, platinum, nickel, and gold enter the crystal lattice, or the crystal lattice metal What was partially substituted is also exemplified as the intermetallic compound according to this embodiment.

  The amount of each metal component supported is not particularly limited. The supported amount of palladium is preferably 0.1 to 20% by mass, more preferably 1 to 10% by mass with respect to 100% by mass of the carrier. In the case where lead, thallium, bismuth, and mercury are supported, the supported amount is preferably 0.1 to 20% by mass, more preferably 1 to 10% by mass with respect to 100% by mass of the carrier. When a metal compound or an alkaline earth metal compound is supported, the amount supported is preferably 0.5 to 30% by mass and more preferably 1 to 15% by mass with respect to 100% by mass of the support. . The noble metal-supported material can contain other above-mentioned different elements in a total amount of preferably 5% by mass or less, more preferably 1% by mass or less with respect to 100% by mass of the support.

The specific surface area of the noble metal support of the present embodiment is preferably 20 to 500 m ² / g, more preferably, as measured by the BET nitrogen adsorption method, from the viewpoint of improving reaction activity and difficulty in detaching the active component. The range is 50 to 400 m ² / g, more preferably 100 to 350 m ² / g.

  The pore structure of the noble metal support of this embodiment is one of the extremely important physical properties from the viewpoint of the support characteristics of metal components, long-term stability including peeling, and reaction characteristics when used as a catalyst. The pore diameter is a physical property value that serves as an index for developing these characteristics. If the pore diameter is smaller than 3 nm, the release property of the supported metal component tends to be good, but when used as a catalyst in a liquid phase reaction or the like, the diffusion resistance in the pores of the reaction substrate increases, The diffusion process tends to be rate limiting and the reaction activity tends to decrease. Therefore, the pore diameter is preferably 3 nm or more. On the other hand, the pore diameter is preferably 50 nm or less from the viewpoint of difficulty of cracking of the supported material and difficulty of peeling of the supported metal particles. Therefore, the pore diameter of the noble metal support is preferably 3 nm to 50 nm, more preferably 3 nm to 30 nm, and still more preferably 3 nm to 10 nm. The pore volume is preferably in the range of 0.1 to 1.0 mL / g, more preferably 0.1 to 0.5 mL / g, and still more preferably 0.1 to 0. The range is 3 mL / g. The noble metal support of the present embodiment preferably has a pore diameter and a pore volume that satisfy the above ranges.

  The method for obtaining the noble metal support of the present embodiment by supporting the metal component on the support is not particularly limited as long as the noble metal support as described above is obtained, and a method for preparing a commonly used noble metal supported catalyst. Just follow. For example, a method of adsorbing palladium ion exchanged on the carrier, or hydrogen impregnation in the gas phase after impregnating the carrier with a solution of a palladium compound such as palladium chloride, or a reducing agent such as formalin, formic acid, hydrazine, etc. A noble metal support can be obtained by a method of reducing in a liquid phase. Each metal component other than palladium may be added during the preparation of the noble metal support, but when the noble metal support is used as a catalyst, it can also be added to the reaction system using the catalyst. Alkali metal compounds and alkaline earth metal compounds may also be previously present at the time of preparation of the noble metal support, or can be added to the reaction system at the time of preparation of the noble metal support.

  Examples of the palladium compound that is a raw material of palladium supported on a noble metal support include, for example, carboxylates such as palladium acetate and formate, inorganic acid salts such as hydrochloride, nitrate, sulfate, and phosphates, palladium phthalocyanine. And the like.

  Moreover, as a lead compound which is the raw material of the lead carry | supported by a noble metal carrying | support thing, carboxylates, such as lead acetate and lead formate, lead oxide, lead hydroxide, and lead nitrate are mentioned, for example. Furthermore, examples of the thallium compound that is a raw material of thallium supported on the noble metal support include thallium acetate, thallium nitrate, thallium sulfate, thallium chloride, and thallium oxide. Examples of the mercury compound that is a raw material of mercury supported on the noble metal support include mercury acetate, mercury nitrate, mercuric chloride, and mercury oxide. Examples of the bismuth compound that is a raw material of bismuth supported on the noble metal support include bismuth fatty acid salts such as bismuth acetate and bismuth stearate, bismuth chloride, and bismuth nitrate.

  Examples of the alkali metal salt that is a raw material of the alkali metal compound supported on the noble metal support include, for example, hydroxides such as sodium hydroxide and potassium hydroxide, carboxylates such as sodium formate, sodium acetate, and potassium acetate, and carbonic acid. Examples thereof include carbonates such as sodium. The alkaline earth metal salt that is the raw material of the alkaline earth metal compound supported on the noble metal support includes magnesium hydroxide, calcium hydroxide, barium hydroxide, strontium hydroxide, beryllium oxide, magnesium oxide, calcium oxide, oxidation Examples include barium and strontium oxide.

[Method for producing compound using noble metal support as catalyst]
The noble metal support of the present embodiment is widely used as a catalyst for chemical synthesis. This noble metal support is, for example, direct hydrogen peroxide synthesis from hydrogen and oxygen, catalytic combustion of VOC / CO / hydrocarbon, deodorization, oxidative esterification of aldehyde and alcohol, Wacker oxidation from alkene to aldehyde, from ethylene Direct oxidation to acetic acid, synthesis of vinyl acetate from ethylene and acetic acid, synthesis of dimethyl carbonate by oxidation of alkyl nitrite and CO, synthesis of dimethyl carbonate by oxidative carbonylation of methanol, unsaturated ester by oxidative carbonylation of alcohol and alkene Synthesis, synthesis of unsaturated ester by CO addition to alkene in the presence of alcohol, synthesis of diphenyl carbonate by oxidative carbonylation of phenol, synthesis of 1,4-diacetoxybutene from butadiene and acetic acid, direct synthesis of acetic acid by oxygen oxidation of ethylene, Carbonyl compounds of alcohols Oxidation to alcohol, oxidation of alcohols to carboxylic acids, oxidation of aldehydes to carboxylic acids, oxidation of propylene to acrylic acid, synthesis of dibutyl oxalate by CO coupling reaction, oxidation of carbon monoxide, various unsaturated compounds Hydrogenation, partial hydrogenation, nuclear hydrogenation of aromatic compounds, hydrodehalogenation of halides, hydrogenation of anthraquinone in hydrogen peroxide synthesis, selective hydrogenation of acetylene bond to double bond, nitrate ion in water Reduction to nitrogen and ammonia, hydroxylamine synthesis by nitrate ion hydrogen reduction, NOx reduction, gasoline engine exhaust gas purification, hydrogen synthesis gas by methanol steam reforming, cross-coupling reaction, hydroamine N-arylation or allylic alkylation It can be used as a catalyst for reactions such as

  Hereinafter, a method for producing a carboxylic acid ester by oxidative esterification reaction from an aldehyde and an alcohol in the presence of oxygen using the noble metal support of the present embodiment as a catalyst will be described as an example.

Examples of the aldehyde used as a raw material include C ₁ -C ₁₀ aliphatic saturated aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, isobutyraldehyde, glyoxal; C ₃ -C ₁₀ aliphatic α, such as acrolein, methacrolein, and crotonaldehyde. β- unsaturated aldehydes; include and derivatives thereof aldehydes; benzaldehyde, tolylaldehyde, benzylaldehyde, C ₆ -C ₂₀ aromatic aldehydes such as phthalaldehyde. These aldehydes are used alone or as a mixture of two or more. Among them, it is preferable that the aldehyde is selected from the group consisting of acrolein, methacrolein, and a mixture thereof because the noble metal support of the present embodiment can be used more effectively as a catalyst.

Examples of the alcohol include methanol, ethanol, isopropanol, butanol, 2-ethylhexanol, C ₁ -C ₁₀ aliphatic saturated alcohols of octanol; cyclopentanol, C ₅ -C ₁₀ alicyclic alcohols such as cyclohexanol, ; allyl alcohol, C ₃ -C ₁₀ aliphatic unsaturated alcohols such as methallyl alcohol;; C ₆ -C ₂₀ aromatic alcohols such as benzyl alcohol, ethylene glycol, propylene glycol, C ₂ -C ₁₀ diols such as butanediol; And hydroxyoxetanes such as 3-alkyl-3-hydroxymethyloxetane. These alcohols are used alone or as a mixture of two or more. Among them, it is preferable that the alcohol is methanol because the noble metal support of the present embodiment can be used more effectively as a catalyst.

  The amount ratio of aldehyde to alcohol is not particularly limited. For example, the ratio of aldehyde to alcohol (aldehyde / alcohol) may be in a wide range such as 10 to 1/1000 on a molar basis. Is 1/2 to 1/50.

  The amount of the catalyst used is not particularly limited, and can be changed greatly depending on the type of reaction raw material, the composition and preparation method of the catalyst, reaction conditions, reaction mode, and the like. When the catalyst is reacted in a slurry state, the catalyst is preferably 1 to 50 mass / volume%, more preferably 3 to 30 mass / volume%, still more preferably 10 to 25 mass / volume, as the solid content concentration in the slurry. % Range.

  The carboxylic acid ester can be produced by any method such as a gas phase reaction, a liquid phase reaction, and an irrigation reaction, either batchwise or continuously.

  The reaction can be carried out without solvent, but can also be carried out using a solvent inert to the reaction components (reaction substrate, reaction product and catalyst) such as hexane, decane, benzene, dioxane.

  The reaction format may be a conventionally known format such as a fixed bed type, a fluidized bed type, and a stirring tank type. For example, when reacting in the liquid phase, any reactor type such as a bubble column reactor, a draft tube reactor, a stirred tank reactor, etc. can be employed.

  The oxygen used in the production of the carboxylic acid ester is in the form of molecular oxygen, that is, oxygen gas itself or a mixed gas obtained by diluting the oxygen gas with a diluent inert to the reaction, such as nitrogen or carbon dioxide. Also good. As the oxygen raw material, air is preferably used from the viewpoints of operability and economy.

  The oxygen partial pressure varies depending on the reaction raw materials such as aldehyde species and alcohol species, the reaction conditions, or the reactor type, but practically, the oxygen partial pressure at the outlet of the reactor is in a range where the concentration is below the lower limit of the explosion range. For example, it is preferable to manage at 20 to 80 kPa. About reaction pressure, the arbitrary wide pressure range from pressure reduction to pressurization may be sufficient, for example, reaction pressure of the range of 0.05-2 Mpa. Further, it is preferable from the viewpoint of safety to set the total pressure (for example, oxygen concentration 8%) so that the oxygen concentration in the gas flowing out from the reactor does not exceed the explosion limit.

  When the production reaction of a carboxylic acid ester is carried out in the liquid phase or the like, an alkali metal or alkaline earth metal compound (eg, oxide, hydroxide, carbonate, carboxylate) is added to the reaction system. It is preferable to maintain pH of 6-9. These alkali metal or alkaline earth metal compounds are used singly or in combination of two or more.

  Although the reaction temperature at the time of manufacturing carboxylic acid ester may be high temperature exceeding 200 degreeC, Preferably it is 30-200 degreeC, More preferably, it is 40-150 degreeC, More preferably, it is 60-120 degreeC. The reaction time is not particularly limited and is not uniquely determined because it varies depending on the set conditions, but is usually 1 to 20 hours.

[Measurement and analysis of physical properties]
Determination of content of constituent elements of carrier and noble metal support, measurement of specific surface area, pore diameter and pore volume, measurement of average particle diameter, measurement of bulk density (CBD), measurement of wear resistance, analysis of crystal structure The chemical state analysis of the carrier, the shape observation, and the metal particle morphology observation can be carried out by the following methods.

(Determination of the content of constituent elements of the support and the noble metal support)
The concentrations of Si, Al, fourth periodic element and basic element in the support, and the concentration of each metal element in the noble metal support are the ICP emission analyzer (ICP-AES, MS) manufactured by Thermo Fisher Scientific Co., Ltd. It is quantified using “IRIS IntrepidII XDL type” (trade name).

  Samples are prepared as follows. First, a carrier or a noble metal support is weighed in a Teflon (registered trademark) decomposition vessel, and nitric acid and hydrogen fluoride are added thereto. The obtained solution is thermally decomposed by “ETHOS TC type” (trade name), which is a microwave decomposing apparatus manufactured by Milestone General, and then evaporated to dryness on a heater. Next, nitric acid and hydrochloric acid are added to the deposited residue, and pressure decomposition is performed with a microwave decomposition apparatus, and the obtained decomposition solution is made to have a constant volume with pure water as a sample.

  The sample is quantified by the internal standard method in the ICP-AES, and the contents of Si, Al, the fourth periodic element and the basic element in the support and the metal in the noble metal support are subtracted from the operation blank value simultaneously performed. The content of the element is obtained, and the composition ratio and the supported amount are calculated.

(Measurement of specific surface area, pore diameter and pore volume)
The specific surface area, pore diameter, and pore volume of the support and the noble metal support are measured by using a gas adsorption amount measuring device “Autosorb 3MP” (trade name) manufactured by Yuasa Ionics Co., Ltd. Adsorption method). The BET method is used as the specific surface area, the BJH method is used as the pore diameter and pore distribution, the P / P ₀ and the adsorption amount at Max are used as the pore volume.

(Measurement of average particle size)
The average particle diameter (volume basis) of the carrier and the precious metal carrier is measured using an LS230 laser diffraction / scattering particle size distribution analyzer manufactured by Beckman Coulter.

(Measurement of bulk density (CBD))
As a pretreatment, first, about 120 g of a carrier is collected in a stainless crucible and fired for 1 hour in a 500 ° C. muffle furnace. The carrier after baking is put into a desiccator (with silica gel) and cooled to room temperature. 100.0 g of the carrier thus pretreated is collected, transferred to a 250 mL graduated cylinder, and the carrier is tapped and filled in a graduated cylinder with a shaker for 15 minutes. Remove the graduated cylinder from the shaker, level the carrier surface in the graduated cylinder and read the filling volume. The bulk density is a value obtained by dividing the mass of the carrier by the filling volume.

(Measurement of wear resistance)
About 50 g of the carrier is precisely weighed into a vertical tube having an inner diameter of 1.5 inches and provided with a perforated disk having three orifices of 1/64 inch at the bottom. Air is blown from the outside through a perforated disk into a vertical tube at a speed of 15 CF (Cubic Feet) per hour, and the particles of the carrier in the tube are vigorously flowed. The ratio (mass%) of the total amount of carrier particles that have been refined within 5 to 20 hours from the start of air blowing and dissipated from the top of the vertical tube to the initially charged amount is expressed as “Abrasion resistance”. "

(Analysis of crystal structure)
X-ray source Cu tube (40 kV, 200 mA), measurement range 5 to 65 deg (0.02 deg / step), measurement speed using a powder X-ray diffractometer (XRD) “Rint 2500 type” (trade name) manufactured by Rigaku Corporation The crystal structure of the support and the noble metal support is analyzed under the conditions of 0.2 deg / min and slit width (scattering, divergence, light reception) of 1 deg, 1 deg, and 0.15 mm.
The measurement is performed by uniformly spreading the sample on a non-reflective sample plate and fixing it with neoprene rubber.

(Chemical state analysis of support)
The NiKα spectrum of the support was measured with XFRA190 double-crystal high-resolution X-ray fluorescence spectrometer (HRXRF) manufactured by Technos, and the obtained parameters were compared with those of the standard substance (nickel metal, nickel oxide). Estimate the chemical state such as the valence of nickel inside.

  As a measurement sample, the prepared carrier is used as it is. The measurement of the Ni Kα spectrum is performed in the partial spectrum mode. At this time, Ge (220) is used as the spectral crystal, and the slit has a vertical divergence angle of 1 °, and the excitation voltage and current are set to 35 kV and 80 mA, respectively. Then, filter paper is used as an absorber in the standard sample, and a counting time is selected for each sample in the carrier sample, and measurement is performed so that the peak intensity of the Kα spectrum is 3,000 cps or less and 10,000 counts or more. The measurement is repeated five times for each sample, and nickel metal is measured before and after the repeated measurement. After smoothing the measured spectrum (SG method 7 points-5 times), the peak position, full width at half maximum (FWHM), and asymmetry coefficient (AI) were calculated. The peak position was the nickel metal measured before and after the measurement of the sample. It is treated as a deviation from the measured value, chemical shift (ΔE).

(Shape observation)
The carrier and the precious metal carrier are observed using an X-650 scanning electron microscope (SEM) manufactured by Hitachi, Ltd.

(Metallic particle morphology observation)
Using JEOL 3100FEF transmission electron microscope / scanning transmission electron microscope apparatus (TEM / STEM) [acceleration voltage 300 kV, energy dispersive X-ray detector (EDX) attached], TEM bright field image, STEM A dark field image is observed, and STEM-EDS composition analysis (point analysis, mapping, line analysis) is performed.

  As data analysis software, TEM image, STEM image analysis (length measurement, Fourier transform analysis): Digital Micrograph (registered trademark) Ver. 1.70.16, Gatan, EDS data analysis (mapping image processing, composition quantitative calculation): NORAN System SIX ver. 2.0, Thermo Fisher Scientific is used.

  The measurement sample is obtained as a sample for TEM / STEM observation by crushing a noble metal-supported material in a mortar, dispersing it in ethanol, performing ultrasonic cleaning for about 1 minute, dropping on a Mo-made microgrit, and wind.

EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely, this invention is not limited at all by these. Those skilled in the art can implement various modifications as well as the following embodiments, and such modifications are also included in the scope of the claims of the present invention. In addition, the measurement of the physical property of an Example and a comparative example was implemented on the conditions as described in the above-mentioned [measurement of physical property, analysis].
[Example 1]

(1) Production of carrier 1.5 kg of aluminum nitrate nonahydrate, 0.24 kg of nickel nitrate hexahydrate, 0.98 kg of magnesium nitrate hexahydrate and 0.27 kg of 60% nitric acid were added to 3.0 L of pure water. A dissolved aqueous solution was prepared. Into 10.0 kg of a silica sol solution (manufactured by Nissan Chemical Co., trade name “Snowtex N-30”, SiO ₂ content: 30% by mass) with a colloidal particle diameter of 10 to 20 nm in a stirred state in which the aqueous solution is maintained at 15 ° C. The mixture was gradually added dropwise to obtain a mixed slurry of silica sol, aluminum nitrate, nickel nitrate and magnesium nitrate. Thereafter, the mixed slurry was spray-dried with a spray dryer apparatus whose outlet temperature was set to 130 ° C. to obtain a solid.

  Next, the obtained solid was filled in a stainless steel container having an open top with a thickness of about 1 cm, heated from room temperature to 300 ° C. over 2 hours in an electric furnace, and then held at 300 ° C. for 3 hours. Further, the temperature was raised to 600 ° C. in 2 hours, and then calcined by holding at 600 ° C. for 3 hours. Thereafter, it was gradually cooled to obtain a carrier made of a composite oxide containing silicon-aluminum-nickel-magnesium.

  The obtained support was 85.3 mol% silicon, 6.8 mol% aluminum, 1.4 mol% nickel, and 6. mol magnesium with respect to the total molar amount of silicon, aluminum, nickel and magnesium. 5 mol% was contained. The composition ratio of Ni (X) / Al was 0.21 on a molar basis, and the composition ratio of Ni (X) / Mg (B) was 0.22 on a molar basis.

The specific surface area determined by the nitrogen adsorption method was 223 m ² / g, the pore volume was 0.26 mL / g, and the average pore diameter was 5.1 nm. The bulk density was 0.97 CBD, and the wear resistance was 0.1% by mass. The average particle diameter was 62 μm from the result of measurement by laser / scattering particle size distribution measurement. Further, from observation with a scanning electron microscope (SEM), there was no crack or chipping, and the shape was almost spherical. As for the solid form, an amorphous pattern similar to that of silica gel was obtained from the results of powder X-ray diffraction (XRD).

  Regarding the chemical state of nickel in the support, it is presumed to be high spin divalent nickel from the results of double-crystal high-resolution X-ray fluorescence analysis (HRXRF), and is different from nickel oxide, which is a single compound, due to the difference in NiKα spectra. It was found to be in a chemical state. The full width at half maximum (FWHM) of the Ni Kα spectrum of the carrier obtained from the measured spectrum was 3.474 and the chemical shift (ΔE) was 0.331. The full width at half maximum (FWHM) of the Ni Kα spectrum of nickel oxide measured as a standard substance was 3.249, and the chemical shift (ΔE) was 0.344.

(2) Production of noble metal support 300 g of the carrier obtained above was added to a glass container containing 1 L of distilled water and stirred at 60 ° C., and palladium chloride in an amount corresponding to 2.5% by mass as Pd. Was quickly added dropwise. Thereafter, the contents of the glass container were held for 1 hour, and hydrazine was added to the stoichiometric amount 1.2 times and reduced. The supernatant is removed from the reduced content by decantation, and the precipitate is recovered. The precipitate is washed with distilled water until Cl ions are no longer detected, and further dried under vacuum at 60 ° C. A noble metal support (Pd / Si—Al—Ni—Mg composite oxide) supported by 5% by mass was obtained.

The noble metal support had a specific surface area of 241 m ² / g, a pore volume of 0.27 mL / g, and an average pore diameter of 3.9 nm according to the nitrogen adsorption method. The average particle diameter was 62 μm from the result of measurement by laser / scattering particle size distribution measurement. Further, from observation with a scanning electron microscope (SEM), the noble metal support was not cracked or chipped, and the shape was almost spherical.

  According to the result of powder X-ray diffraction (XRD) of the noble metal support, a diffraction peak attributed to Pd was observed. When the fine structure of the above-mentioned noble metal support was observed using a transmission electron microscope (TEM), Pd particles having a particle diameter of 5 to 6 nm were uniformly supported on the surface of the carrier. The number average particle diameter of the Pd particles was 5.2 nm (calculated number: 100).

Next, in order to evaluate the chemical stability of the noble metal support, a pH swing test was performed by the following method.
10 g of the noble metal support obtained as described above was added to 100 mL of a pH 4 buffer solution in a glass container, and after stirring at 90 ° C. for 10 minutes, the mixture was left to stand to remove the supernatant, washed with water, Decanted. The solid material thus obtained was added to 100 mL of a pH 10 buffer solution placed in a glass container, and stirring was continued at 90 ° C. for 10 minutes. Then, the solid was left to stand to remove the supernatant, washed with water, and decanted. The above operation was made into 1 cycle, and the pH swing process of 50 cycles in total was implemented. As a result, the specific surface area of the noble metal support after the pH swing treatment was 242 m ² / g, the pore volume was 0.27 mL / g, and the average pore diameter was 4.0 nm. Was not recognized. Moreover, the average particle diameter of Pd particles by a transmission electron microscope (TEM / STEM) was 5.3 nm (calculated number: 100), and almost no particle growth of Pd particles was observed.

[Example 2]
300 g of the carrier obtained in (1) of Example 1 was added to 1 L of distilled water in a glass container, and while stirring at 60 ° C., an amount of chloride corresponding to 2.5% by mass as Pd and Pb, respectively. A dilute hydrochloric acid solution of palladium and an aqueous lead nitrate solution were quickly added dropwise. Thereafter, the contents of the glass container were held for 1 hour, and hydrazine was added to the stoichiometric amount 1.2 times and reduced. The supernatant is removed from the reduced contents by decantation, and the precipitate is recovered. The precipitate is washed with distilled water until no Cl ions are detected, and further dried at 60 ° C. under vacuum to remove Pd and Pb. A noble metal support (PdPb / Si—Al—Ni—Mg composite oxide) supported by 2.5% by mass was obtained.

The noble metal support had a specific surface area of 240 m ² / g, a pore volume of 0.26 mL / g, and an average pore diameter of 4.0 nm as determined by the nitrogen adsorption method. The average particle diameter was 62 μm from the result of measurement by laser / scattering particle size distribution measurement. Further, from observation with a scanning electron microscope (SEM), the noble metal support was not cracked or chipped, and the shape was almost spherical.

According to the result of powder X-ray diffraction (XRD) of the above-mentioned noble metal support, diffraction peaks (2θ = 38.6 °, 44.8 °, 65.4 °, attributed to the intermetallic compound of Pd ₃ Pb ₁ , 78.6 °) was observed. When the fine structure of the above-mentioned noble metal support was observed using a transmission electron microscope (TEM), PdPb particles having a particle diameter of 5 to 6 nm were uniformly supported on the support surface. The number average particle diameter of the PdPb particles was 5.5 nm (calculated number: 100).

Next, in order to evaluate the chemical stability of the noble metal support obtained as described above, a pH swing test was performed in the same manner as in Example 1. As a result, the specific surface area of the noble metal support after the pH swing treatment was 241 m ² / g, the pore volume was 0.27 mL / g, the average pore diameter was 4.0 nm, and no structural change was observed due to the pH swing treatment. It was. Moreover, the average particle diameter of the PdPb particles by a transmission electron microscope (TEM) was 5.1 nm (calculated number: 100), and almost no particle growth of the PdPb particles was observed.

Example 3
Instead of aluminum nitrate 9 hydrate 1.5 kg, aluminum nitrate 9 hydrate 4.0 kg, nickel nitrate hexahydrate 0.24 kg, zinc nitrate hexahydrate 0.11 kg, magnesium nitrate hexahydrate Except that 1.1 kg of potassium nitrate was used instead of 0.98 kg, the same procedure as in (1) of Example 1 was performed, 69.7 mol% silicon, 15.0 mol% aluminum, and 0.5 mol% zinc. A carrier containing 14.9 mol% of potassium was obtained. The composition ratio of Zn (X) / Al was 0.03 on a molar basis, and the composition ratio of Zn (X) / K (B) was 0.03 on a molar basis.

The specific surface area determined by the nitrogen adsorption method was 170 m ² / g, the pore volume was 0.27 mL / g, and the average pore diameter was 5.3 nm. The bulk density was 0.95 CBD, and the wear resistance was 0.1% by mass. The average particle diameter was 64 μm from the result of measurement by laser / scattering particle size distribution measurement. Moreover, from observation with a scanning electron microscope (SEM), there was no crack or chipping, and the shape was almost spherical. As for the solid form, an amorphous pattern similar to that of silica gel was obtained from the results of powder X-ray diffraction (XRD).

  Next, 300 g of the carrier was added to 1 L of distilled water in a glass container, and while stirring at 60 ° C., a diluted hydrochloric acid solution of palladium chloride and bismuth acetate in an amount corresponding to 2.5% by mass as Pd and Bi, respectively. The aqueous solution was quickly added dropwise. Thereafter, the contents of the glass container were held for 1 hour, and hydrazine was added to the stoichiometric amount 1.2 times and reduced. The supernatant is removed from the reduced content by decantation, and the precipitate is recovered. The precipitate is washed with distilled water until Cl ions are no longer detected, and further dried at 60 ° C. under vacuum to remove Pd and Bi. A noble metal support (PdBi / Si—Al—Zn—K composite oxide) supported by 2.5% by mass was obtained.

The noble metal support had a specific surface area of 178 m ² / g, a pore volume of 0.28 mL / g, and an average pore diameter of 3.9 nm according to the nitrogen adsorption method. The average particle size was 64 μm from the result of measurement by laser / scattering particle size distribution measurement. Further, from observation with a scanning electron microscope (SEM), the noble metal support was not cracked or chipped, and the shape was almost spherical.

  According to the result of powder X-ray diffraction (XRD) of the above-mentioned noble metal support, the diffraction peaks (2θ = 38.9 °, 45.2 °, 65.8 °, 79.0) attributed to the intermetallic compound of PdBi. °) was observed. When the fine structure of the above-mentioned noble metal support was observed using a transmission electron microscope (TEM), PdBi particles having a particle diameter of 5 to 6 nm were uniformly supported on the support surface. The number average particle diameter of the PdBi particles was 5.1 nm (calculated number: 100).

Next, in order to evaluate the chemical stability of the noble metal support obtained as described above, a pH swing test was performed in the same manner as in Example 1. As a result, the specific surface area of the noble metal support after the pH swing treatment was 180 m ² / g, the pore volume was 0.27 mL / g, the average pore diameter was 3.9 nm, and no structural change was observed due to the pH swing treatment. It was. Moreover, the average particle diameter of the PdBi particle | grains by a transmission electron microscope (TEM) is 5.0 nm (calculated number: 100), and the particle growth of PdBi particle | grains was hardly observed.

Example 4
Except that 0.24 kg of nickel nitrate hexahydrate was used instead of 0.2 kg of iron nitrate nonahydrate, and 0.48 kg of lanthanum nitrate nonahydrate was used instead of 0.98 kg of magnesium nitrate hexahydrate. In the same manner as in Example 1 (1), a support containing 89.9 mol% silicon, 7.2 mol% aluminum, 0.9 mol% iron, and 2.0 mol% lanthanum was obtained. The composition ratio of Fe (X) / Al was 0.12 on a molar basis, and the composition ratio of Fe (X) / La (B) was 0.45 on a molar basis.

The specific surface area determined by the nitrogen adsorption method was 232 m ² / g, the pore volume was 0.28 mL / g, and the average pore diameter was 5.0 nm. The bulk density was 0.98 CBD, and the wear resistance was 0.1% by mass. The average particle diameter was 64 μm from the result of measurement by laser / scattering particle size distribution measurement. Moreover, from observation with a scanning electron microscope (SEM), there was no crack or chipping, and the shape was almost spherical. As for the solid form, an amorphous pattern similar to that of silica gel was obtained from the results of powder X-ray diffraction (XRD).

  Next, 300 g of the above carrier was added to 1 L of distilled water in a glass container, and while stirring at 60 ° C., a solution of palladium chloride in dilute hydrochloric acid and thallium acetate in an amount corresponding to 2.5% by mass as Pd and Tl, respectively. The aqueous solution was quickly added dropwise. Thereafter, the contents of the glass container were held for 1 hour, and hydrazine was added to the stoichiometric amount 1.2 times and reduced. The supernatant is removed from the reduced content by decantation, and the precipitate is recovered. The precipitate is washed with distilled water until Cl ions are no longer detected, and is dried in vacuo at 60 ° C. A noble metal support (PdTl / Si—Al—Fe—La composite oxide) supported by 2.5% by mass was obtained.

The noble metal support had a specific surface area of 251 m ² / g, a pore volume of 0.28 mL / g, and an average pore diameter of 3.9 nm according to the nitrogen adsorption method. The average particle size was 64 μm from the result of measurement by laser / scattering particle size distribution measurement. Further, from observation with a scanning electron microscope (SEM), the noble metal support was not cracked or chipped, and the shape was almost spherical.

  According to the result of powder X-ray diffraction (XRD) of the above-mentioned noble metal support, diffraction peaks (2θ = 38.5 °, 44.7 °, 65.0 °, 78.1) attributed to the intermetallic compound of PdTl. °) was observed. When the fine structure of the above-mentioned noble metal support was observed using a transmission electron microscope (TEM), PdTl particles having a particle diameter of 5 to 6 nm were uniformly supported on the surface of the carrier. The number average particle diameter of the PdTl particles was 5.2 nm (calculated number: 100).

Next, a pH swing test was performed by the same method as in Example 1 in order to evaluate the chemical stability of the noble metal support as described above. As a result, the specific surface area of the noble metal support after the pH swing treatment was 254 m ² / g, the pore volume was 0.27 mL / g, the average pore diameter was 4.0 nm, and no structural change was observed due to the pH swing treatment. It was. Moreover, the average particle diameter of the PdTl particles by a transmission electron microscope (TEM) was 5.2 nm (calculated number: 100), and almost no particle growth of the PdTl particles was observed.

Example 5
To 10 kg of water glass No. 3 (SiO ₂ : 28 to 30% by mass, Na ₂ O: 9 to 10% by mass), sulfuric acid was added until the pH reached 9, and then aluminum sulfate was added to adjust the pH to 2. . Further, sodium aluminate was added to adjust the pH to 5 to 5.5, and a part thereof was dehydrated to obtain a hydrogel containing about 10% by mass of silica-alumina. This hydrogel was spray-dried at 130 ° C. by spray drying, and then washed so that Na ₂ O was 0.02 mass% and SO ₄ was 0.5 mass% or less. To this, 0.83 kg of magnesium oxide and 1.8 kg of nickel oxide were added and mixed to obtain a slurry. The slurry was filtered, washed, dried at 110 ° C. for 6 hours, then heated to 700 ° C. over 3 hours, and held at 700 ° C. for 3 hours for firing. Then, it cooled and obtained the support | carrier.

  The obtained support was 42.2 mol% silicon, 20.4 mol% aluminum, 19.8 mol% nickel, and 17.6 mol magnesium with respect to the total molar amount of silicon, aluminum, nickel and magnesium. Contained mol%. The composition ratio of Ni (X) / Al was 0.97 on a molar basis, and the composition ratio of Ni (X) / Mg (B) was 1.13 on a molar basis.

The specific surface area determined by the nitrogen adsorption method was 73 m ² / g, the pore volume was 0.26 mL / g, and the average pore diameter was 5.4 nm. The bulk density was 1.05 CBD, and the wear resistance was 0.1% by mass. The average particle size was 63 μm from the result of measurement by laser / scattering particle size distribution measurement. Further, from observation with a scanning electron microscope (SEM), the carrier was not cracked or chipped, and the shape was almost spherical. As for the solid form, an amorphous pattern similar to that of silica gel was obtained from the results of powder X-ray diffraction (XRD).

  Next, a noble metal support (PdPb / Si—Al—) supporting 2.5% by mass of Pd and Pb, respectively, in the same manner as in Example 2 except that the support was replaced with the support obtained as described above. Ni-Mg composite oxide) was obtained.

The noble metal support had a specific surface area of 94 m ² / g, a pore volume of 0.27 mL / g, and an average pore diameter of 4.0 nm as determined by the nitrogen adsorption method. The average particle diameter was 62 μm from the result of measurement by laser / scattering particle size distribution measurement. Further, from observation with a scanning electron microscope (SEM), the noble metal support was not cracked or chipped, and the shape was almost spherical.

According to the result of powder X-ray diffraction (XRD) of the above-mentioned noble metal support, diffraction peaks (2θ = 38.6 °, 44.8 °, 65.4 °, attributed to the intermetallic compound of Pd ₃ Pb ₁ , 78.6 °) was observed. When the fine structure of the above-mentioned noble metal support was observed using a transmission electron microscope (TEM), PdPb particles having a particle diameter of 5 to 6 nm were uniformly supported on the support surface. The number average particle diameter of the PdPb particles was 5.3 nm (calculated number: 100).

Next, in order to evaluate the chemical stability of the noble metal support obtained as described above, a pH swing test was performed in the same manner as in Example 1. As a result, the specific surface area of the noble metal support after the pH swing treatment was 95 m ² / g, the pore volume was 0.26 mL / g, the average pore diameter was 4.0 nm, and no structural change was observed due to the pH swing treatment. It was. Moreover, the average particle diameter of the PdPb particles by a transmission electron microscope (TEM) was 5.2 nm (calculated number: 100), and almost no particle growth of the PdPb particles was observed.

Example 6
In place of 1.5 kg of aluminum nitrate nonahydrate, 4.4 kg of aluminum oxide, 0.93 kg of nickel oxide in place of 0.24 kg of nickel nitrate hexahydrate, and oxidized in place of 0.98 kg of magnesium nitrate hexahydrate Except for using 0.42 kg of magnesium and changing the firing temperature from 600 ° C. to 800 ° C., in the same manner as in (1) of Example 1, silicon was 42.9 mol%, aluminum was 37.0 mol%, nickel was A carrier containing 10.9 mol% and 9.1 mol% magnesium was obtained. The composition ratio of Ni (X) / Al was 0.30 on a molar basis, and the composition ratio of Ni (X) / Mg (B) was 1.20 on a molar basis. The specific surface area determined by the nitrogen adsorption method was 78 m ² / g, the pore volume was 0.27 mL / g, and the average pore diameter was 5.2 nm. The bulk density was 1.02 CBD, and the wear resistance was 0.1% by mass. The average particle diameter was 62 μm from the result of measurement by laser / scattering particle size distribution measurement. Further, from observation with a scanning electron microscope (SEM), the carrier was not cracked or chipped, and the shape was almost spherical. As for the solid form, an amorphous pattern similar to that of silica gel was obtained from the results of powder X-ray diffraction (XRD).

  Next, a noble metal support (PdPb / Si—Al—) supporting 2.5% by mass of Pd and Pb, respectively, in the same manner as in Example 2 except that the support was replaced with the support obtained as described above. Ni-Mg composite oxide) was obtained.

The noble metal support had a specific surface area of 105 m ² / g, a pore volume of 0.27 mL / g, and an average pore diameter of 3.9 nm according to the nitrogen adsorption method. The average particle diameter was 62 μm from the result of measurement by laser / scattering particle size distribution measurement. Further, from observation with a scanning electron microscope (SEM), the noble metal support was not cracked or chipped, and the shape was almost spherical.

According to the result of powder X-ray diffraction (XRD) of the above-mentioned noble metal support, diffraction peaks (2θ = 38.6 °, 44.8 °, 65.4 °, attributed to the intermetallic compound of Pd ₃ Pb ₁ , 78.6 °) was observed. When the fine structure of the above-mentioned noble metal support was observed using a transmission electron microscope (TEM), PdPb particles having a particle diameter of 5 to 6 nm were uniformly supported on the support surface. The number average particle diameter of the PdPb particles was 5.4 nm (calculated number: 100).

Next, in order to evaluate the chemical stability of the noble metal support obtained as described above, a pH swing test was performed in the same manner as in Example 1. As a result, the specific surface area of the noble metal support after the pH swing treatment was 107 m ² / g, the pore volume was 0.27 mL / g, the average pore diameter was 4.0 nm, and no structural change was observed due to the pH swing treatment. It was. Moreover, the average particle diameter of the PdPb particles by a transmission electron microscope (TEM) was 5.3 nm (calculated number: 100), and almost no particle growth of the PdPb particles was observed.

Example 7
Instead of aluminum nitrate 9 hydrate 1.5 kg, aluminum nitrate 9 hydrate 1.0 kg, nickel nitrate hexahydrate 0.24 kg, nickel hydroxide 0.23 kg, magnesium nitrate hexahydrate 0.98 kg Instead of using a predetermined amount of 1.9 kg of magnesium hydroxide and changing the firing temperature from 600 ° C. to 650 ° C. in the same manner as in (1) of Example 1, 57.6 mol% of silicon and aluminum were used. A carrier containing 3.1 mol%, 2.8 mol% nickel, and 36.6 mol% magnesium was obtained. The composition ratio of Ni (X) / Al was 0.91 on a molar basis, and the composition ratio of Ni (X) / Mg (B) was 0.08 on a molar basis. The specific surface area determined by the nitrogen adsorption method was 92 m ² / g, the pore volume was 0.28 mL / g, and the average pore diameter was 5.1 nm. The bulk density was 0.99 CBD, and the wear resistance was 0.1% by mass. The average particle diameter was 62 μm from the result of measurement by laser / scattering particle size distribution measurement. Further, from observation with a scanning electron microscope (SEM), the carrier was not cracked or chipped, and the shape was almost spherical. As for the solid form, an amorphous pattern similar to that of silica gel was obtained from the results of powder X-ray diffraction (XRD).

  Next, a noble metal carrier (PdPb / Si—Al—Ni) carrying 2.5% by mass of Pd and Pb, respectively, in the same manner as in Example 2 except that the carrier was replaced with the carrier obtained as described above. -Mg composite oxide).

The noble metal support had a specific surface area of 120 m ² / g, a pore volume of 0.28 mL / g, and an average pore diameter of 3.9 nm according to the nitrogen adsorption method. The average particle diameter was 62 μm from the result of measurement by laser / scattering particle size distribution measurement. From observation with a scanning electron microscope (SEM), the noble metal support was not cracked or chipped, and the shape was almost spherical.

According to the result of powder X-ray diffraction (XRD) of the above-mentioned noble metal support, diffraction peaks (2θ = 38.6 °, 44.8 °, 65.4 °, attributed to the intermetallic compound of Pd ₃ Pb ₁ , 78.6 °) was observed. When the fine structure of the above-mentioned noble metal support was observed using a transmission electron microscope (TEM), PdPb particles having a particle diameter of 5 to 6 nm were uniformly supported on the support surface. The number average particle diameter of the PdPb particles was 5.2 nm (calculated number: 100).

Next, in order to evaluate the chemical stability of the noble metal support obtained as described above, a pH swing test was performed in the same manner as in Example 1. As a result, the specific surface area of the noble metal support after the pH swing treatment was 118 m ² / g, the pore volume was 0.28 mL / g, the average pore diameter was 3.9 nm, and no structural change was observed due to the pH swing treatment. It was. Moreover, the average particle diameter of the PdPb particles by a transmission electron microscope (TEM) was 5.3 nm (calculated number: 100), and almost no particle growth of the PdPb particles was observed.

Example 8
An aqueous solution prepared by dissolving 2.0 kg of aluminum nitrate nonahydrate, 1.5 kg of magnesium nitrate, and 0.27 kg of 60% nitric acid in 3.0 L of pure water was prepared. Into 10.0 kg of a silica sol solution (manufactured by Nissan Chemical Co., trade name “Snowtex N-30”, SiO ₂ content: 30% by mass) with a colloidal particle diameter of 10 to 20 nm in a stirred state in which the aqueous solution is maintained at 15 ° C. The mixture was gradually added dropwise to obtain a mixed slurry of silica sol, aluminum nitrate and magnesium nitrate. Thereafter, the mixed slurry was aged by holding at 50 ° C. for 24 hours. The aged mixed slurry was cooled to room temperature and then spray-dried with a spray dryer apparatus whose outlet temperature was set to 130 ° C. to obtain a dried product.
Next, the obtained solid was filled in a stainless steel container having an open top with a thickness of about 1 cm, heated from room temperature to 300 ° C. over 2 hours in an electric furnace, and then kept at 300 ° C. for 3 hours. Furthermore, after heating up to 600 degreeC over 2 hours, it hold | maintained at 600 degreeC for 3 hours, and baked. Then, it annealed and obtained the silica-alumina-magnesia which is a solid substance.

Next, 1.0 L of an aqueous solution containing 27 g of nickel nitrate hexahydrate was heated to 90 ° C. Into this aqueous solution, 300 g of silica-alumina-magnesia, which was a solid obtained as described above, was added and kept at 90 ° C. for 1 hour with stirring to precipitate a nickel component on the solid. The mixture was then allowed to stand to remove the supernatant, washed several times with distilled water, filtered and the solid material was dried at 105 ° C. for 16 hours and further calcined in air at 600 ° C. for 5 hours. Thus, a support containing 80.3 mol% silicon, 8.7 mol% aluminum, 1.5 mol% nickel, and 9.5 mol% magnesium was obtained. The composition ratio of Ni (X) / Al was 0.18 on a molar basis, and the composition ratio of Ni (X) / Mg (B) was 0.16 on a molar basis.
The specific surface area determined by the nitrogen adsorption method was 245 m ² / g, the pore volume was 0.26 mL / g, and the average pore diameter was 4.0 nm. The bulk density was 0.99 CBD, and the wear resistance was 0.1% by mass. The average particle diameter was 62 μm from the result of measurement by laser / scattering particle size distribution measurement. Further, from observation with a scanning electron microscope (SEM), the carrier was not cracked or chipped, and the shape was almost spherical. As for the solid form, an amorphous pattern similar to that of silica gel was obtained from the results of powder X-ray diffraction (XRD).

  Next, a noble metal carrier (PdPb / Si—Al—Ni) carrying 2.5% by mass of Pd and Pb, respectively, in the same manner as in Example 2 except that the carrier was replaced with the carrier obtained as described above. -Mg composite oxide).

The noble metal support had a specific surface area of 242 m ² / g, a pore volume of 0.26 mL / g, and an average pore diameter of 3.9 nm according to the nitrogen adsorption method. The average particle diameter was 62 μm from the result of measurement by laser / scattering particle size distribution measurement. Further, from observation with a scanning electron microscope (SEM), the noble metal support was not cracked or chipped, and the shape was almost spherical.

According to the result of powder X-ray diffraction (XRD) of the above-mentioned noble metal support, diffraction peaks (2θ = 38.6 °, 44.8 °, 65.4 °, attributed to the intermetallic compound of Pd ₃ Pb ₁ , 78.6 °) was observed. When the fine structure of the above-mentioned noble metal support was observed using a transmission electron microscope (TEM), PdPb particles having a particle diameter of 5 to 6 nm were uniformly supported on the support surface. The number average particle diameter of the PdPb particles was 5.0 nm (calculated number: 100).

Next, in order to evaluate the chemical stability of the noble metal support obtained as described above, a pH swing test was performed in the same manner as in Example 1. As a result, the specific surface area of the noble metal support after the pH swing treatment was 245 m ² / g, the pore volume was 0.26 mL / g, the average pore diameter was 4.0 nm, and no structural change was observed due to the pH swing treatment. It was. Moreover, the average particle diameter of the PdPb particles by a transmission electron microscope (TEM) was 4.9 nm (calculated number: 100), and almost no particle growth of the PdPb particles was observed.

[Comparative Example 1]
Silica sol solution as a raw material is made by Nissan Chemical Co., Ltd., trade name “Snowtex N-30”, made by the company, trade name “Snowtex N-40” (SiO ₂ content: 40 mass%), aluminum nitrate, nickel nitrate A solid was obtained in the same manner as in Example 1 except that the composition of the silica alone was not added without adding magnesium nitrate until the mixed slurry was spray-dried with a spray dryer. Next, the obtained solid was heated from room temperature to 300 ° C. with a rotary kiln over 2 hours and then held at 300 ° C. for 1 hour. Further, the temperature was raised to 600 ° C. in 2 hours, and then held at 600 ° C. for 1 hour for firing. Thereafter, it was gradually cooled to obtain silica.
The specific surface area determined by the nitrogen adsorption method was 215 m ² / g, the pore volume was 0.26 mL / g, and the average pore diameter was 5.5 nm. The bulk density was 0.55 CBD, and the wear resistance was 3.3% by mass. The average particle diameter was 66 μm from the result of measurement by laser / scattering particle size distribution measurement. Moreover, from the observation with a scanning electron microscope (SEM), the silica was cracked or chipped. The shape of silica was almost spherical. For the solid form, an amorphous pattern was obtained from the results of powder X-ray diffraction (XRD).

Next, a noble metal support (PdPb / SiO ₂ ) supporting 2.5% by mass of Pd and Pb, respectively, was obtained in the same manner as in Example 2 except that the support was replaced with silica obtained as described above. It was.

The noble metal support had a specific surface area of 216 m ² / g, a pore volume of 0.26 mL / g, and an average pore diameter of 5.5 nm as determined by the nitrogen adsorption method. The average particle size was 66 μm from the result of measurement by particle size distribution measurement by laser / scattering method. Further, from observation with a scanning electron microscope (SEM), the noble metal support was not cracked or chipped, and the shape was almost spherical.

According to the result of powder X-ray diffraction (XRD) of the above-mentioned noble metal support, diffraction peaks (2θ = 38.6 °, 44.8 °, 65.4 °, attributed to the intermetallic compound of Pd ₃ Pb ₁ , 78.6 °) was observed. When the fine structure of the above-mentioned noble metal support was observed using a transmission electron microscope (TEM), PdPb particles having a particle diameter of 5 to 6 nm were uniformly supported on the support surface. The number average particle diameter of the PdPb particles was 5.1 nm (calculated number: 100).

Next, in order to evaluate the chemical stability of the noble metal support obtained as described above, a pH swing test was performed in the same manner as in Example 1. As a result, the specific surface area of the noble metal support after the pH swing treatment was 201 m ² / g, the pore volume was 0.27 mL / g, the average pore diameter was 8.8 nm, and structural changes due to the pH swing treatment were observed. . Moreover, the average particle diameter of PdPb by a transmission electron microscope (TEM) was 7.4 nm (calculated number: 100), and PdPb particle growth was observed.
[Comparative Example 2]
A silica-alumina composition containing 93.0 mol% silicon and 7.0 mol% aluminum was obtained in the same manner as (1) of Example 1 except that nickel nitrate and magnesium nitrate were not used. The specific surface area determined by the nitrogen adsorption method was 220 m ² / g, the pore volume was 0.30 mL / g, and the average pore diameter was 5.2 nm. The bulk density was 0.94 CBD, and the wear resistance was 0.2% by mass. The average particle size of the silica-alumina composition was 62 μm based on the results of laser / scattering particle size distribution measurement. Moreover, from the observation with a scanning electron microscope (SEM), the silica-alumina composition was not cracked or chipped, and the shape was almost spherical. For the solid form, an amorphous pattern was obtained from the results of powder X-ray diffraction (XRD).

Next, a noble metal support (PdPb / Si) supporting 2.5% by mass of Pd and Pb, respectively, in the same manner as in Example 2 except that the support was replaced with the silica-alumina composition obtained as described above. -A l double if oxide) was obtained.

The noble metal support had a specific surface area of 223 m ² / g, a pore volume of 0.29 mL / g, and an average pore diameter of 5.2 nm as determined by the nitrogen adsorption method. The average particle diameter was 62 μm from the result of measurement by laser / scattering particle size distribution measurement. Further, from observation with a scanning electron microscope (SEM), the noble metal support was not cracked or chipped, and the shape was almost spherical.

According to the result of powder X-ray diffraction (XRD) of the above-mentioned noble metal support, diffraction peaks (2θ = 38.6 °, 44.8 °, 65.4 °, attributed to the intermetallic compound of Pd ₃ Pb ₁ , 78.6 °) was observed. When the fine structure of the above-mentioned noble metal support was observed using a transmission electron microscope (TEM), PdPb particles having a particle diameter of 5 to 6 nm were uniformly supported on the support surface. The number average particle diameter of the PdPb particles was 5.0 nm (calculated number: 100).

Next, in order to evaluate the chemical stability of the noble metal support obtained as described above, a pH swing test was performed in the same manner as in Example 1. As a result, the specific surface area of the noble metal support after the pH swing treatment was 205 m ² / g, the pore volume was 0.27 mL / g, the average pore diameter was 8.5 nm, and structural changes due to the pH swing treatment were observed. . Moreover, the average particle diameter of PdPb by a transmission electron microscope (TEM) was 7.4 nm (calculated number: 100), and PdPb particle growth was observed.

[Comparative Example 3]
A silica-alumina-magnesia containing 86.5 mol% silicon, 6.9 mol% aluminum, and 6.6 mol% magnesium, except that nickel nitrate was not used. A composition was obtained. The specific surface area determined by the nitrogen adsorption method was 213 m ² / g, the pore volume was 0.27 mL / g, and the average pore diameter was 5.1 nm. The bulk density was 0.96 CBD, and the wear resistance was 0.1% by mass. The average particle size of the silica-alumina-magnesia composition was 62 μm from the result of laser / scattering particle size distribution measurement. Further, from the observation with a scanning electron microscope (SEM), the silica-alumina-magnesia composition had no cracks or chips, and the shape was almost spherical. As for the solid form, an amorphous pattern similar to that of silica gel was obtained from the results of powder X-ray diffraction (XRD).

Next, in the same manner as in Example 2 except that the support was replaced with the silica-alumina-magnesia composition obtained as described above, a noble metal support (PdPb) supporting 2.5% by mass of Pd and Pb, respectively. / Si-Al - Mg composite oxide).

The noble metal support had a specific surface area of 228 m ² / g, a pore volume of 0.28 mL / g, and an average pore diameter of 3.9 nm according to the nitrogen adsorption method. The average particle diameter was 62 μm from the result of measurement by laser / scattering particle size distribution measurement. Further, from observation with a scanning electron microscope (SEM), the noble metal support was not cracked or chipped, and the shape was almost spherical.

According to the result of powder X-ray diffraction (XRD) of the above-mentioned noble metal support, diffraction peaks (2θ = 38.6 °, 44.8 °, 65.4 °, attributed to the intermetallic compound of Pd ₃ Pb ₁ , 78.6 °) was observed. When the fine structure of the above-mentioned noble metal support was observed using a transmission electron microscope (TEM), PdPb particles having a particle diameter of 5 to 6 nm were uniformly supported on the support surface. The number average particle diameter of the PdPb particles was 5.0 nm (calculated number: 100).

Next, in order to evaluate the chemical stability of the noble metal support obtained as described above, a pH swing test was performed in the same manner as in Example 1. As a result, the specific surface area of the noble metal support after the pH swing treatment was 215 m ² / g, the pore volume was 0.27 mL / g, the average pore diameter was 8.1 nm, and structural changes due to the pH swing treatment were observed. . Moreover, the average particle diameter of the PdPb particles by a transmission electron microscope (TEM) was 7.2 nm (calculated number: 100), and particle growth of the PdPb particles was observed.

[Comparative Example 4]
Instead of aluminum nitrate nonahydrate 1.5 kg, aluminum nitrate nonahydrate 2.3 kg, nickel nitrate hexahydrate 0.24 kg instead of nickel nitrate hexahydrate 0.37 kg, magnesium nitrate hexahydrate Instead of 0.98 kg, magnesium nitrate hexahydrate 0.21 kg, silica sol solution (trade name “Snowtex N-30”, manufactured by Nissan Chemical Co., Ltd., SiO ₂ content: 30% by mass) instead of 10.0 kg Except for using 1.0 kg of the silica sol solution, the same procedure as in (1) of Example 1 was carried out, 37.3 mol% silicon, 46.2 mol% aluminum, 10.1 mol% nickel, 6 mg magnesium. A silica-alumina-nickel oxide-magnesia composition containing 5 mol% was obtained. The composition ratio of Ni (X) / Al was 0.22 on a molar basis, and the composition ratio of Ni (X) / Mg (B) was 1.56 on a molar basis. The specific surface area determined by the nitrogen adsorption method was 195 m ² / g, the pore volume was 0.3 mL / g, and the average pore diameter was 5.3 nm. The bulk density was 0.85 CBD, and the wear resistance was 0.5% by mass. The average particle diameter was 64 μm from the result of measurement by laser / scattering particle size distribution measurement. Moreover, from the observation with a scanning electron microscope (SEM), the silica-alumina-nickel oxide-magnesia composition was found to be cracked or chipped. The shape was almost spherical. About the solid form, the crystal pattern derived from an alumina was obtained from the result of the powder X-ray diffraction (XRD).
Next, a noble metal support in which 2.5% by mass of Pd and Pb was supported in the same manner as in Example 2 except that the support was replaced with the silica-alumina-nickel oxide-magnesia composition obtained as described above. The product (PdPb / SiO ₂ —Al ₂ O ₃ —NiO—MgO) was obtained.

The noble metal support had a specific surface area of 198 m ² / g, a pore volume of 0.29 mL / g, and an average pore diameter of 5.2 nm as determined by the nitrogen adsorption method. The average particle size was 64 μm from the result of measurement by laser / scattering particle size distribution measurement. Further, from observation with a scanning electron microscope (SEM), the noble metal support was not cracked or chipped, and the shape was almost spherical.

According to the result of powder X-ray diffraction (XRD) of the above-mentioned noble metal support, diffraction peaks (2θ = 38.6 °, 44.8 °, 65.4 °, attributed to the intermetallic compound of Pd ₃ Pb ₁ , 78.6 °) was observed. When the microstructure of the noble metal support was observed using a transmission electron microscope (TEM), PdPb particles having a particle diameter of 4 to 6 nm were uniformly supported on the support surface. The number average particle diameter of the PdPb particles was 4.9 nm (calculated number: 100).

Next, in order to evaluate the chemical stability of the noble metal support obtained as described above, a pH swing test was performed in the same manner as in Example 1. As a result, the specific surface area of the noble metal support after the pH swing treatment was 185 m ² / g, the pore volume was 0.28 mL / g, the average pore diameter was 8.2 nm, and structural changes due to the pH swing treatment were observed. . Moreover, the average particle diameter of the PdPb particles by a transmission electron microscope (TEM) was 7.4 nm (calculated number: 100), and particle growth of the PdPb particles was observed.

[Comparative Example 5]
Instead of aluminum nitrate 9 hydrate 1.5 kg, aluminum nitrate 9 hydrate 1.0 kg, nickel nitrate hexahydrate 0.24 kg, nickel nitrate hexahydrate 0.05 kg, magnesium nitrate hexahydrate Except for using 0.23 kg of magnesium nitrate hexahydrate instead of 0.98 kg, 93.1 mol% of silicon, 5.0 mol% of aluminum, nickel, and in the same manner as (1) of Example 1 A silica-alumina-nickel oxide-magnesia composition containing 0.3 mol% of magnesium and 1.6 mol% of magnesium was obtained. The composition ratio of Ni (X) / Al was 0.07 on a molar basis, and the composition ratio of Ni (X) / Mg (B) was 0.22 on a molar basis. The specific surface area determined by the nitrogen adsorption method was 210 m ² / g, the pore volume was 0.27 mL / g, and the average pore diameter was 5.4 nm. The bulk density was 0.9 CBD, and the wear resistance was 2.0 mass%. The average particle diameter was 65 μm from the result of measurement by laser / scattering particle size distribution measurement. Moreover, from the observation with a scanning electron microscope (SEM), the silica-alumina-nickel oxide-magnesia composition was found to be cracked or chipped. The shape was almost spherical. As for the solid form, an amorphous pattern similar to that of silica gel was obtained from the results of powder X-ray diffraction (XRD).
Next, a noble metal support in which 2.5% by mass of Pd and Pb was supported in the same manner as in Example 2 except that the support was replaced with the silica-alumina-nickel oxide-magnesia composition obtained as described above. The product (PdPb / SiO ₂ —Al ₂ O ₃ —NiO—MgO) was obtained.

The noble metal support had a specific surface area of 209 m ² / g, a pore volume of 0.28 mL / g, and an average pore diameter of 5.4 nm according to the nitrogen adsorption method. The average particle diameter was 65 μm from the result of measurement by laser / scattering particle size distribution measurement. Further, from observation with a scanning electron microscope (SEM), the noble metal support was not cracked or chipped, and the shape was almost spherical.

According to the result of powder X-ray diffraction (XRD) of the above-mentioned noble metal support, diffraction peaks (2θ = 38.6 °, 44.8 °, 65.4 °, attributed to the intermetallic compound of Pd ₃ Pb ₁ , 78.6 °) was observed. When the microstructure of the noble metal support was observed using a transmission electron microscope (TEM), PdPb particles having a particle diameter of 4 to 6 nm were uniformly supported on the support surface. The number average particle diameter of the PdPb particles was 5.0 nm (calculated number: 100).

Next, in order to evaluate the chemical stability of the noble metal support obtained as described above, a pH swing test was performed in the same manner as in Example 1. As a result, the specific surface area of the noble metal support after the pH swing treatment was 200 m ² / g, the pore volume was 0.27 mL / g, the average pore diameter was 8.4 nm, and structural changes due to the pH swing treatment were observed. . Moreover, the average particle diameter of the PdPb particles by a transmission electron microscope (TEM) was 7.2 nm (calculated number: 100), and particle growth of the PdPb particles was observed.

Table 1 shows the compositions and physical properties of the noble metal carriers of Examples 1 to 8 and Comparative Examples 1 to 5.

Example 9
As a catalyst, 240 g of the noble metal support (PdPb / Si—Al—Ni—Mg composite oxide) obtained in Example 1 was provided with a catalyst separator, and the liquid phase part was 1.2 liters of a stirring type stainless steel reaction. I put it in a vessel. The content of the stirring blade in the reactor was stirred at a speed of 4 m / sec, and the oxidative carboxylic acid ester was formed from the aldehyde and alcohol. A 36.7% by weight methacrolein / methanol solution was continuously supplied to the reactor at 0.6 liter / hour, and a 1-4% by weight NaOH / methanol solution was continuously supplied to the reactor at 0.06 liter / hour. Air was blown into the reactor such that the reaction temperature was 80 ° C., the reaction pressure was 0.5 MPa, and the outlet oxygen concentration was 4.0 vol% (corresponding to an oxygen partial pressure of 0.02 MPa). The supplied NaOH concentration was adjusted. The reaction product was continuously extracted through an overflow line from the reactor outlet, and its composition was analyzed by gas chromatography to examine the reactivity.

  The conversion rate of methacrolein after the elapse of 500 hours from the start of the reaction was 44.2%, the selectivity of methyl methacrylate was 91.5%, and the methyl methacrylate production activity per unit mass of the catalyst was 4.40 mol / hour / kg. -It was a catalyst. The methacrolein conversion rate after 1000 hours from the start of the reaction was 44.6%, the selectivity of methyl methacrylate was 91.3%, and the methyl methacrylate production activity was 4.43 mol / hour / kg-catalyst. The activity hardly changed.

When the catalyst was removed after 1000 hours from the start of the reaction and examined with a scanning electron microscope (SEM), the catalyst particles were hardly cracked or chipped. Further, the specific surface area of the catalyst as determined by the nitrogen adsorption method was 241 m ² / g, the pore volume was 0.27 mL / g, and the average pore diameter was 4.1 nm.

  Next, the catalyst after 1000 hours from the start of the reaction was observed with a transmission electron microscope (TEM / STEM). As a result, nanoparticles having a maximum distribution (number average particle size: 5.2 nm) at a particle size of 5 to 6 nm were obtained. It was confirmed that it was supported on a carrier, and sintering of PdPb particles was not observed.

[Comparative Example 6]
The reaction was conducted in the same manner as in Example 9 except that the noble metal support (PdPb / SiO ₂ —Al ₂ O ₃ —MgO) obtained in Comparative Example 3 was used as the catalyst. As a result, the methacrolein conversion after 500 hours from the start of the reaction was 41.4%, the methyl methacrylate selectivity was 90.5%, and the methyl methacrylate production activity per unit mass of the catalyst was 4.08 mol / Time / kg-catalyst. The methacrolein conversion rate after 1000 hours from the start of the reaction was 34.5%, the methyl methacrylate selectivity was 90.1%, and the methyl methacrylate production activity was 3.38 mol / hour / kg-catalyst. A decrease in activity was observed.

When the catalyst was removed after 1000 hours from the start of the reaction and examined with a scanning electron microscope (SEM), the catalyst particles were hardly cracked or chipped. Further, the specific surface area of the catalyst as determined by the nitrogen adsorption method was 210 m ² / g, the pore volume was 0.27 mL / g, the average pore diameter was 6.2 nm, and a change in the catalyst structure was observed.

  Next, when the catalyst after 1000 hours from the start of the reaction was observed with a transmission electron microscope (TEM), the number average particle diameter of the PdPb particles was 5.9 nm, and the sintering of the PdPb particles was performed simultaneously with the expansion of the pore diameter. Was observed.

  From the above results, when the noble metal support of the present invention is used as a catalyst for the above-mentioned carboxylic acid ester formation reaction, it efficiently generates a carboxylic acid ester with high selectivity, and the structure change of the catalyst even after a long time has passed. In addition, almost no sintering of metal particles was observed, and high reactivity was maintained. Therefore, the noble metal-supported material of the present invention can greatly improve the economy not only by this specific reaction but also by a wider number of reactions in general, as compared with the conventional noble metal-supported material.

Claims (9)

At least one fourth periodic element selected from the group consisting of silicon, aluminum, iron, cobalt, nickel and zinc, and at least selected from the group consisting of alkali metal elements, alkaline earth metal elements and rare earth elements One basic element is 42 to 90 mol%, 3 to 38 mol%, 0, respectively, with respect to the total molar amount of the silicon, the aluminum, the fourth periodic element, and the basic element. A carrier comprising a complex oxide containing in the range of 5 to 20 mol%, 2 to 38 mol%,
A metal component containing palladium supported on the carrier;
A noble metal support, which is used as a catalyst in an oxidative esterification reaction in which an aldehyde and an alcohol are reacted in the presence of oxygen .   The noble metal support according to claim 1, wherein a composition ratio of the fourth periodic element to the aluminum in the carrier is 0.02 to 1.0 on a molar basis.   The noble metal support according to claim 1 or 2, wherein a composition ratio of the fourth periodic element to the basic element in the carrier is 0.02 to 1.2 on a molar basis.   The composite oxide is a composite oxide in which the fourth periodic element is nickel and the basic element is magnesium, and the total amount of the silicon, the aluminum, the nickel, and the magnesium is 4. The composition according to claim 1, wherein silicon is contained in the range of 42 to 90 mol%, the aluminum in the range of 3 to 38 mol%, the nickel in the range of 0.5 to 20 mol%, and the magnesium in the range of 2 to 38 mol%. The noble metal support according to claim 1.   The noble metal carrier according to any one of claims 1 to 4, wherein the metal component containing palladium is palladium and / or a palladium compound.   The noble metal support according to claim 5, wherein the palladium compound is an intermetallic compound containing palladium and at least one element selected from the group consisting of lead, mercury, thallium and bismuth.   A method for producing a carboxylic acid ester, comprising reacting an aldehyde with an alcohol in the presence of oxygen, using the noble metal support according to any one of claims 1 to 6 as a catalyst.   The method for producing a carboxylic acid ester according to claim 7, wherein the aldehyde is selected from the group consisting of acrolein, methacrolein, and a mixture thereof.   The method for producing a carboxylic acid ester according to claim 7 or 8, wherein the alcohol is methanol.