JP2007185633A - PALLADIUM-CONTAINING CATALYSTS, METHOD OF PRODUCING THE SAME AND METHOD OF PRODUCING alpha, beta-UNSATURATED CARBOXYLIC ACID - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a palladium-containing catalyst for producing an α, β-unsaturated carboxylic acid from an olefin or an α, β-unsaturated aldehyde with high selectivity and preventing carbon dioxide from occurring, a method of producing the catalyst, and a method of producing the α, β-unsaturated carboxylic acid using the catalyst. <P>SOLUTION: The palladium-containing catalyst contains 0.001-0.25 moles of a silver element to one mole of a palladium element. The palladium-containing catalyst may preferably be produced by a method having the process of reducing a compound containing an oxidized palladium element with a reducing agent and the process of reducing a compound containing an oxidized silver element with a reducing agent. The above palladium-containing catalyst may preferably used in the method of producing the α, β-unsaturated carboxylic acid wherein the olefin or the α, β-unsaturated aldehyde is oxidized with a molecular oxygen in a liquid phase. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

Many α, β-unsaturated carboxylic acids are industrially useful. For example, acrylic acid and methacrylic acid are used in extremely large quantities for applications such as synthetic resin raw materials. As a method for producing an α, β-unsaturated carboxylic acid, a method for producing an olefin or α, β-unsaturated aldehyde by liquid phase oxidation with molecular oxygen has been studied. As a catalyst for producing α, β-unsaturated carboxylic acid by liquid phase oxidation of olefin or α, β-unsaturated aldehyde with molecular oxygen, for example, Patent Document 1 proposes a palladium-containing catalyst. Further, as a catalyst for producing an α, β-unsaturated carboxylic acid by liquid phase oxidation of olefin with molecular oxygen, for example, in Patent Document 2, an intermetallic compound of palladium and lead, bismuth, thallium or mercury is used. Palladium-containing catalysts containing compounds have been proposed.
JP 2004-141863 A JP 56-59722 A

  However, in the liquid phase oxidation using the palladium-containing catalysts of Patent Documents 1 and 2, the selectivity of the target product α, β-unsaturated carboxylic acid is not sufficient, and further improvement of the selectivity is desired. It was. In particular, when the selectivity of by-product carbon dioxide increases, the selectivity of α, β-unsaturated carboxylic acid decreases, so a catalyst that can suppress the selectivity of carbon dioxide has been desired.

  An object of the present invention is to produce an α, β-unsaturated carboxylic acid from an olefin or an α, β-unsaturated aldehyde with high selectivity, and a catalyst for suppressing the selectivity of by-product carbon dioxide, and the catalyst And a method for producing an α, β-unsaturated carboxylic acid using the catalyst.

  The present invention relates to a palladium-containing catalyst for producing an α, β-unsaturated carboxylic acid from an olefin or an α, β-unsaturated aldehyde, and 0.001 to 0.25 silver element per 1 mol of palladium element. Palladium-containing catalyst containing moles. It is preferable to use a supported palladium-containing catalyst in which the palladium element and the silver element are supported on a carrier.

  The present invention is also a method for producing a palladium-containing catalyst, comprising a step of reducing a compound containing palladium element in an oxidized state with a reducing agent, and a step of reducing a compound containing silver element in an oxidized state with a reducing agent. It is a manufacturing method of a palladium containing catalyst. In the case of producing a supported palladium-containing catalyst, it is preferable to perform the two reduction steps in the presence of a carrier.

  Furthermore, the present invention is a method for producing an α, β-unsaturated carboxylic acid in which an olefin or an α, β-unsaturated aldehyde is subjected to liquid phase oxidation with molecular oxygen using the palladium-containing catalyst.

  According to the present invention, a palladium-containing catalyst capable of obtaining an α, β-unsaturated carboxylic acid from an olefin or an α, β-unsaturated aldehyde with high selectivity and suppressing the selectivity of carbon dioxide produced as a by-product. , A method for producing the same, and a method for producing an α, β-unsaturated carboxylic acid using the same.

  The palladium-containing catalyst of the present invention (hereinafter also referred to as “catalyst” for short) produces α, β-unsaturated carboxylic acid by liquid phase oxidation of olefin or α, β-unsaturated aldehyde with molecular oxygen. (Hereinafter, also referred to as “liquid phase oxidation” for short), which contains 0.001 to 0.25 mol of silver element per 1 mol of palladium element. The catalyst preferably further contains 0.001 to 0.4 mol of tellurium element with respect to 1 mol of palladium element.

  The palladium element contained in the palladium-containing catalyst is preferably in a zero-valent metal state. The silver element contained in the palladium-containing catalyst is preferably in a zero-valent metal state. The tellurium element optionally contained in the palladium-containing catalyst is preferably in a + 6-valent, + 4-valent oxidized state or a zero-valent metal state.

  In the present specification, the number of moles of silver element relative to 1.0 mole of palladium element in the catalyst, that is, the molar ratio of silver element to palladium element may be abbreviated as Ag / Pd. Similarly, the molar ratio of tellurium element and palladium element may be abbreviated as Te / Pd. By setting Ag / Pd and Te / Pd in such predetermined ranges, a catalyst capable of producing α, β-unsaturated carboxylic acid with high selectivity from olefin or α, β-unsaturated aldehyde is obtained. It is done. Ag / Pd is preferably 0.005 to 0.25, and more preferably 0.01 to 0.23. Te / Pd is preferably 0.005 to 0.35, and more preferably 0.01 to 0.3. The Ag / Pd and Te / Pd can be adjusted by the blending ratio of the palladium compound, silver compound, and tellurium compound used for the production of the palladium-containing catalyst.

Ag / Pd and Te / Pd can be calculated from the mass and atomic weight of each element contained in the catalyst. The mass of each element contained in the catalyst can be quantified by elemental analysis. As a method for quantifying the mass of each element in the catalyst by elemental analysis, the following A treatment liquid and B treatment liquid are prepared and analyzed.
Preparation of treatment solution A: 0.2 g of catalyst and a predetermined amount of concentrated nitric acid, concentrated sulfuric acid, and hydrogen peroxide water were placed in a Teflon (registered trademark) decomposition tube, and a microwave thermal decomposition apparatus (CEM, MARS5 (product) Name)). The sample is filtered, and the filtrate and washing water are combined, and the volume is made up in a volumetric flask to obtain the treatment solution A.
Preparation of B treatment liquid: The filter paper in which the insoluble parts in the A treatment were collected was transferred to a platinum crucible, heated and incinerated, and then added with lithium metaborate and melted with a gas burner. After cooling, add hydrochloric acid and a small amount of water in a crucible and dissolve, then add up to a volumetric flask to make the B treatment solution.
The mass of silver and palladium contained in the obtained A treatment liquid and B treatment liquid was quantified with an ICP emission analyzer (manufactured by Thermo Elemental Co., Ltd., IRIS-Advantage (trade name)), and the mass of each element in both treatment liquids was determined. The mass of each element in the catalyst can be determined from the total mass.

  In addition, when a catalyst is produced by a method in which the catalyst contains substantially all of the metal elements contained in the raw material, such as the pore filling method, the content of each element and the blending amount of the raw material used are determined. The mass may be calculated.

  The catalyst of the present invention as described above may be a non-supported type, but a supported type in which palladium element and silver element or palladium element, silver element and tellurium element are supported on a support is preferable. Examples of the carrier include activated carbon, carbon black, silica, alumina, magnesia, calcia, titania and zirconia. Among these, silica, alumina, magnesia, calcia, titania and zirconia are more preferable, and silica, titania and zirconia are particularly preferable. One type of carrier may be used, but two or more types may be used. When using 2 or more types, for example, a mixture such as a mixed oxide obtained by mixing silica and alumina, a composite such as silica-alumina which is a composite oxide, and the like can be given.

The preferred specific surface area of the support varies depending on the type of the support and the like and cannot be generally stated. In the case of silica, it is preferably 50 m ² / g or more, more preferably 100 m ² / g or more. Moreover, 1500 m < ² > / g or less is preferable and 1000 m < ² > / g or less is more preferable. The smaller the specific surface area of the carrier is, the more the catalyst having a useful component (palladium, silver) supported on the surface can be produced, and the larger the specific surface area, the more the useful component can be produced.

  The pore volume of the carrier is not particularly limited, but is preferably 0.1 cc / g or more, and more preferably 0.2 cc / g or more. Moreover, 2 cc / g or less is preferable and 1.5 cc / g or less is more preferable.

  The shape and size of the carrier vary depending on the shape and size of the reaction apparatus and are not particularly limited. Examples thereof include various shapes such as powder, granules, spheres, and pellets. Among these, granular and spherical shapes are preferable because they are easy to operate such as filtration. When the carrier is powdery or granular, the particle size (median diameter) is preferably 0.5 μm or more, and more preferably 1 μm or more. Moreover, 200 micrometers or less are preferable and 100 micrometers or less are more preferable. The larger the particle size of the carrier, the easier the separation of the catalyst and the reaction solution, and the smaller the support, the better the dispersibility of the catalyst in the reaction solution.

  In the case of a supported catalyst, the loading ratio of palladium element to the support is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and further preferably 1% by mass or more with respect to the mass of the carrier before support. Moreover, 40 mass% or less is preferable, 30 mass% or less is more preferable, and 20 mass% or less is further more preferable.

  In the case of a supported catalyst, the loading rate can be calculated from the mass of each element contained in the catalyst determined by the above method and the like and the mass of the carrier used. The mass of the carrier can also be quantified by the following method. That is, the catalyst is placed in a platinum crucible and melted by adding sodium carbonate. Thereafter, distilled water is added to obtain a uniform solution, and a specific element in the sample solution is quantified by ICP emission analysis. For example, in the case of a silica carrier, Si element is quantified.

  The catalyst of the present invention may contain other metal elements in addition to palladium element, silver element and tellurium element. Examples of other metal elements include platinum, rhodium, ruthenium, iridium, gold, osmium, copper, lead, bismuth, thallium, mercury, antimony, and the like. One or more other metal elements can be contained. From the viewpoint of expressing high catalytic activity, the total of palladium element, silver element, and tellurium element is preferably 60% by mass or more, more preferably 80% by mass or more, among the metal elements contained in the catalyst. .

  The catalyst of the present invention can be preferably produced by a method having a step of reducing a compound containing an element in an oxidized state with a reducing agent. For example, a step of reducing a compound containing palladium element in an oxidized state with a reducing agent (hereinafter also referred to as “Pd reduction step”) and a step of reducing a compound containing silver element in an oxidized state with a reducing agent (hereinafter referred to as “ It can also be suitably produced by a method including an “Ag reduction step”. Further, in the case of producing a catalyst containing tellurium element, a Pd reduction step, an Ag reduction step, and a step of reducing a compound containing tellurium element in an oxidized state with a reducing agent (hereinafter also referred to as “Te reduction step”) are included. A method is mentioned. However, when producing a catalyst containing tellurium element, the Te reduction step is not necessarily essential. Hereinafter, the production of the catalyst by this method will be described.

  Examples of the palladium compound containing palladium element in the oxidized state (hereinafter also referred to as “Pd raw material”) include palladium salts, palladium oxides, palladium oxide alloys, etc. Among them, palladium salts are preferable. Examples of the palladium salt include palladium chloride, palladium acetate, palladium nitrate, palladium sulfate, tetraamminepalladium chloride and bis (acetylacetonato) palladium, among which palladium chloride, palladium acetate, palladium nitrate, tetraammine. Palladium chloride is preferred.

  Examples of the silver compound containing silver element in an oxidized state (hereinafter also referred to as “Ag raw material”) include silver salts and silver oxide. Specifically, silver acetate, silver acetylacetonate, silver benzoate, silver bromide, silver carbonate, silver chloride, silver citrate hydrate, silver fluoride, silver iodide, silver lactate, silver nitrate, silver nitrite, oxidation It may be silver, silver phosphate, or a silver solution in an aqueous inorganic acid, such as a solution in nitric acid.

  Examples of tellurium compounds containing tellurium elements (hereinafter also referred to as “Te raw materials”) include tellurium metal, tellurium salts, telluric acid and salts thereof, telluric acid and salts thereof, and tellurium oxide. Examples of tellurium salts include hydrogen telluride, tellurium tetrachloride, tellurium dichloride, tellurium hexafluoride, tellurium tetraiodide, tellurium tetrabromide, tellurium dibromide, and the like. Examples of tellurate include sodium tellurate and potassium tellurate. Examples of tellurite include sodium tellurite and potassium tellurite. Of these, telluric acid and its salt, telluric acid and its salt, and tellurium oxide are preferred. Since the Te reduction step is not always essential, the tellurium element contained in the Te raw material may be in an oxidized state, a reduced state, or a metal state.

In addition to the above compound, a compound containing two or more elements of palladium element, silver element and tellurium element can be used as a raw material for the two or more elements. Specifically, for example, palladium-tellurium complex or the like [PdX _n (TeRR ′) _4-n ] (wherein X is any one of fluorine, chlorine, bromine, and iodine, and TeRR ′ is an organic tellurium compound). ) As a Pd raw material and a Te raw material. A compound containing both palladium element in an oxidized state and silver element in an oxidized state can be used as the Pd raw material and the Te raw material.

  The Pd raw material and the Ag raw material as described above are appropriately selected and used as a raw material for producing the catalyst. The compounding amount of these compounds is appropriately selected so that the loading ratio of Ag / Pd or palladium element becomes a target value. When producing a catalyst containing tellurium element, the above Te raw material is appropriately selected and used as a raw material for producing the catalyst. The blending amount of the Te raw material is appropriately selected so that Te / Pd becomes a target value.

  In addition to palladium, silver and tellurium, in the case of producing a catalyst containing other metal elements, a compound containing other metal elements (hereinafter also referred to as “other raw materials”) may be used in combination. Examples of the other raw materials include metals, metal oxides, metal salts, metal oxyacids, and metal oxyacid salts containing other metal elements.

  The Pd reduction step and the Ag reduction step may be performed simultaneously or separately. When performed separately, the order of the Pd reduction step and the Ag reduction step is arbitrary. When performing the Te reduction step, the Te reduction step can be performed simultaneously with the Pd reduction step and / or the Ag reduction step, or in any order.

  Further, in the case of producing a catalyst containing other metal elements in addition to palladium, silver, and tellurium, and when a step of reducing other raw materials with a reducing agent is necessary, the reduction step includes a Pd reduction step and / or It can be performed simultaneously with the Ag reduction step and / or the Te reduction step, or in any order.

  A method of performing an Ag reduction step after the Pd reduction step is preferable. When performing the process of adding a tellurium compound, the process is preferably after the Pd reduction process.

  Examples of the reduction method for producing a supported catalyst include, for example, (1) a method in which a raw material containing a metal element in an oxidized state is supported on a carrier and then brought into contact with a reducing agent to reduce the metal element (2 A method of reducing and supporting the metal element in the solution or slurry by bringing a reducing agent into contact with the support in contact with the solution or slurry of the raw material containing the metal element in the oxidized state; Examples include a method of adding another raw material after the method is carried out. Among them, the reduction method (1) in which a catalyst having a high degree of metal element dispersion is easily obtained is preferable.

  As the reduction method (1), a solution obtained by dissolving one or more of Pd raw material, Ag raw material, Te raw material and other raw materials (hereinafter collectively referred to as “metal raw material”) in a solvent is used as a carrier. After impregnation, a method is preferred in which the oxide is reduced by contacting with a reducing agent after heat treatment and supporting it as a metal oxide.

  As the impregnation method for impregnating the carrier with the solution, a so-called pore filling method in which the carrier is absorbed by the carrier is preferable. The solvent of the solution is not particularly limited as long as it dissolves the metal raw material. Examples of the solvent for the metal raw material include water; organic carboxylic acids such as acetic acid and valeric acid; inorganic acids such as nitric acid and hydrochloric acid; alcohols such as ethanol, 1-propanol, 2-propanol, n-butanol, and t-butanol. Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; solvents such as hydrocarbons such as heptane, hexane, and cyclohexane can be used singly or in combination. From the viewpoint of the solubility of the metal raw material and the reducing agent or the dispersibility of the carrier, water and organic carboxylic acids are preferred.

  The operation of impregnating the carrier with the solution can be performed only once using a solution containing all the metal raw materials, but can also be performed a plurality of times using a plurality of solutions. When performing several times, you may perform impregnation operation after the 2nd time after either the last heat processing or a reduction process. The order in which the metal elements are supported is not particularly limited.

  It is preferable that the temperature of the heat treatment be equal to or higher than a decomposition temperature at which the metal raw material is changed to a metal oxide. The time for the heat treatment is not particularly limited as long as the metal raw material is changed to a metal oxide, but is preferably 1 hour or longer, and preferably 12 hours or shorter.

  Examples of the reduction method (2) include a method of reducing a metal raw material by contacting a reducing agent in a state in which a carrier is impregnated with a solution obtained by dissolving one or more metal raw materials in a solvent, and a solution. Examples thereof include a method of reducing a metal raw material by bringing a reducing agent into contact with the carrier dispersed therein.

  The operation of bringing the reducing agent into contact can be performed only once using a solution containing all metal raw materials, but can also be performed a plurality of times using a plurality of solutions. In the case of performing a plurality of times, the carrier subjected to the previous reduction treatment is used in the second and subsequent reduction treatments. The order in which the metal elements are supported is not particularly limited.

  As the reduction method of (3), for example, a solution or slurry obtained by reducing a metal raw material with a reducing agent in the presence of a carrier, or a solution obtained by dissolving or dispersing another metal raw material in a solvent such as water, or A method of adding a slurry is preferred. As a solvent of the solution or slurry to be added, water is generally used, but various organic solvents as described above may be used. After adding another metal raw material, you may reduce by adding a reducing agent again.

  When the reduction treatment is performed a plurality of times, the type of the reducing agent, the reduction temperature and time, the type of the solvent in the liquid phase, and the like can be appropriately set independently for each time.

  The reducing agent used in the reduction is not particularly limited. For example, hydrazine, formaldehyde, sodium borohydride, hydrogen, formic acid, formic acid salt, ethylene, propylene, 1-butene, 2-butene, isobutylene, 1,3- Examples include butadiene, 1-heptene, 1-hexene, 2-hexene, cyclohexene, allyl alcohol, methacryl alcohol, acrolein, and methacrolein. Of these, hydrazine, formaldehyde, hydrogen, formic acid, and formic acid salts are preferred. Two or more of these may be used in combination.

  The solvent used for reduction in the liquid phase is preferably water, but depending on the dispersibility of the carrier, alcohols such as ethanol, 1-propanol, 2-propanol, n-butanol, and t-butanol; acetone, Ketones such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; organic acids such as acetic acid, n-valeric acid and isovaleric acid; and organic solvents such as hydrocarbons such as heptane, hexane and cyclohexane may be used alone or in combination. it can. A mixed solvent of these and water can also be used.

  When the reducing agent is a gas, it is desirable to carry out in a pressure device such as an autoclave in order to increase the solubility in the solution. In that case, it is preferable to pressurize the inside of a pressurization apparatus with a reducing agent. The pressure is preferably 0.1 MPa (gauge pressure; hereinafter referred to as gauge pressure) or more, and preferably 1 MPa or less.

  In addition, when the reducing agent is a liquid, there is no limitation on the apparatus for performing the reduction, and the reduction can be performed by adding the reducing agent to the solution. The amount of the reducing agent used at this time is not particularly limited, but it is preferably 1 mol or more and 1 mol or less with respect to 1 mol of the raw material to be reduced.

  The reduction temperature and reduction time vary depending on the raw material to be reduced, the reducing agent, etc., but the reduction temperature is preferably −5 ° C. or higher, more preferably 15 ° C. or higher. Moreover, 150 degrees C or less is preferable and 80 degrees C or less is more preferable.

  The reduction time is preferably 0.1 hour or longer, more preferably 0.25 hour or longer, and further preferably 0.5 hour or longer. Moreover, 4 hours or less are preferable, 3 hours or less are more preferable, and 2 hours or less are more preferable.

  When producing a supported catalyst using a metal raw material that does not require reduction, the metal raw material may be supported on the carrier after the reduction.

  The obtained catalyst is preferably washed with water, an organic solvent or the like. By washing with water, an organic solvent or the like, impurities derived from metal raw materials such as chloride, acetate radical, nitrate radical, and sulfate radical are removed. The cleaning method and the number of times are not particularly limited. However, depending on the impurities, there is a possibility that the liquid phase oxidation reaction may be inhibited. The washed catalyst may be recovered by filtration or centrifugation and used for the reaction as it is. Moreover, when performing a Pd reduction process and an Ag reduction process by another process, it is also preferable to wash between the processes.

  Further, the recovered catalyst may be dried. Although a drying method is not specifically limited, It is preferable to dry in air or an inert gas using a dryer. The dried catalyst can also be activated before use in the reaction if desired. The activation method is not particularly limited, and examples thereof include a heat treatment method in a reducing atmosphere in a hydrogen stream. According to this method, an oxide film on the surface of palladium or silver and impurities that could not be removed by washing can be removed.

  Next, a method for producing an α, β-unsaturated carboxylic acid by liquid phase oxidation of olefin or α, β-unsaturated aldehyde with molecular oxygen using the palladium-containing catalyst of the present invention will be described.

  Only one of the raw material olefin and α, β-unsaturated aldehyde for liquid phase oxidation may be used, or a mixture of both may be used.

  Examples of the raw material olefin include propylene, isobutylene, and 2-butene. Among these, propylene and isobutylene are preferable. Two or more olefins can be used in combination. The raw material olefin may contain a small amount of saturated hydrocarbon and / or lower saturated aldehyde as impurities.

  An α, β-unsaturated carboxylic acid produced from an olefin is an α, β-unsaturated carboxylic acid having the same carbon skeleton as the olefin. For example, acrylic acid is obtained when the raw material is propylene, and methacrylic acid is obtained when the raw material is isobutylene. Usually, α, β-unsaturated aldehyde is simultaneously obtained from olefin. This α, β-unsaturated aldehyde is an α, β-unsaturated aldehyde having the same carbon skeleton as the olefin. For example, acrolein is obtained when the raw material is propylene, and methacrolein is obtained when the raw material is isobutylene.

  Examples of the raw α, β-unsaturated aldehyde include acrolein, methacrolein, crotonaldehyde (β-methylacrolein), and cinnamaldehyde (β-phenylacrolein). Of these, acrolein and methacrolein are preferable. Two or more α, β-unsaturated aldehydes can be used in combination. The raw α, β-unsaturated aldehyde may contain a small amount of saturated hydrocarbon and / or lower saturated aldehyde as impurities.

  The α, β-unsaturated carboxylic acid produced from the α, β-unsaturated aldehyde is an α, β-unsaturated carboxylic acid in which the aldehyde group of the α, β-unsaturated aldehyde is changed to a carboxyl group. For example, acrylic acid is obtained when the raw material is acrolein, and methacrylic acid is obtained when the raw material is methacrolein.

  In the liquid phase oxidation reaction, an α, β-unsaturated carboxylic acid anhydride may be obtained simultaneously with the α, β-unsaturated carboxylic acid. Since this anhydride can be decomposed into the target product α, β-unsaturated carboxylic acid by hydrolysis, it can be regarded as a useful product in the production of α, β-unsaturated carboxylic acid.

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

  As the molecular oxygen source used in the liquid phase oxidation reaction, air is economical and preferable, but pure oxygen or a mixed gas of pure oxygen and air can also be used. If necessary, air or pure oxygen is converted into nitrogen, dioxide. A mixed gas diluted with carbon, water vapor or the like can also be used. The gas such as air is preferably supplied in a pressurized state into a reaction vessel such as an autoclave.

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

  The total concentration of the olefin and α, β-unsaturated aldehyde that are raw materials for the liquid phase oxidation reaction is preferably 0.1% by mass or more, more preferably 0.5% by mass or more with respect to the solvent present in the reactor. . Moreover, 30 mass% or less is preferable, and 20 mass% or less is more preferable.

  The amount of molecular oxygen used is preferably 0.1 mol or more, more preferably 0.2 mol or more, and particularly preferably 0.3 mol or more with respect to 1 mol of the raw material olefin and α, β-unsaturated aldehyde. . Moreover, 20 mol or less is preferable, 15 mol or less is more preferable, and 10 mol or less is especially preferable.

  The catalyst is preferably used in a state suspended in a reaction solution for liquid phase oxidation, but may be used in a fixed bed. The amount of the catalyst used is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and particularly preferably 1% by mass or more with respect to the solution present in the reactor. Moreover, 40 mass% or less is preferable, 35 mass% or less is more preferable, and 30 mass% or less is especially preferable.

  The reaction temperature and reaction pressure are appropriately selected depending on the solvent and raw materials used. The reaction temperature is preferably 30 ° C or higher, more preferably 50 ° C or higher. Moreover, 200 degrees C or less is preferable and 150 degrees C or less is more preferable. The reaction pressure is preferably atmospheric pressure (0 MPa) or more, more preferably 2 MPa or more. Moreover, 10 MPa or less is preferable and 7 MPa or less is more preferable.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited to an Example. The “parts” in the following examples and comparative examples are parts by mass.

(Quantification of each element in the catalyst)
Ag / Pd, Te / Pd, and the mass of palladium element, silver element, and tellurium element used for calculation of palladium element loading are the palladium element content and blending amount of the Pd raw material used, and the silver element of the Ag raw material used. It was calculated from the content and blending amount, and the tellurium element content and blending amount of the Te raw material to be used.

  Further, the ratio of the mass of palladium element to the mass of carrier was defined as “palladium element loading ratio”. The carrier mass was quantified as follows.

(Quantification of support mass in catalyst)
The catalyst was taken up in a platinum crucible and melted by adding sodium carbonate. Distilled water was added to obtain a homogeneous solution, and the Si element in the sample solution was quantified with an ICP emission analyzer (manufactured by Thermo Elemental Co., Ltd., IRIS-Advantage (trade name)).

(Analysis of raw materials, products and by-products in the production of α, β-unsaturated carboxylic acids)
Analysis of raw materials and products in the production of α, β-unsaturated carboxylic acid was performed using gas chromatography. In addition, the reaction rate of an olefin, the selectivity of the produced α, β-unsaturated carboxylic acid and α, β-unsaturated carboxylic acid anhydride, and the selectivity of carbon dioxide produced as a by-product are defined as follows.

Olefin reaction rate (%) = (B / A) × 100
Selectivity of α, β-unsaturated carboxylic acid (%) = (C / B) × 100
Selectivity of α, β-unsaturated carboxylic anhydride (%) = (D × 2 / B) × 100
Carbon dioxide selectivity (%) = (E / F / B) x 100
Here, A is the number of moles of olefin supplied, B is the number of moles of reacted olefin, C is the number of moles of α, β-unsaturated carboxylic acid produced, and D is the α, β-unsaturated carboxylic acid anhydride produced. The number of moles of the product, E is the number of moles of carbon dioxide produced as a by-product, and F is the number of carbons of the raw material olefin.

  In addition, the total selectivity of the target product α, β-unsaturated carboxylic acid and the useful product α, β-unsaturated carboxylic acid anhydride is also used as an indicator of catalyst performance. is doing.

[Example 1]
(Catalyst preparation)
To a uniform aqueous solution obtained by adding 4.1 parts of a palladium nitrate nitric acid solution (made by Takanaka Tanaka, palladium element content 24.41 wt%) to an aqueous silver nitrate solution in which 0.08 part of silver nitrate is dissolved in 15 parts of pure water, After adding 5.0 parts of a granular silica carrier (specific surface area 450 m ² / g, pore volume 0.68 cc / g, median diameter 53.58 μm), water was removed by evaporation. The carrier impregnated with the metal salt by such an immersion method was baked in air at 450 ° C. for 3 hours to obtain a silica carrier on which palladium element and silver element were supported. The obtained silica carrier was added to 75 parts of a 37 mass% formaldehyde aqueous solution. A reduction treatment was performed by heating to 70 ° C. and stirring for 2 hours. Subsequently, after suction filtration, it was filtered and washed with 1000 parts of warm water. Furthermore, it was dried at 100 ° C. for 2 hours under a nitrogen flow to obtain a supported palladium-containing catalyst in which reduced palladium element and silver element were supported on a silica support.

  This catalyst had an Ag / Pd of 0.05 and a palladium element loading of 20% by mass.

(Reaction evaluation)
In the autoclave, 3 parts of the catalyst obtained by the above method and 75 parts of a 75 mass% t-butanol aqueous solution as a reaction solvent were put, and the autoclave was sealed. Next, 2.0 parts of isobutylene was introduced, stirring (revolution 1000 rpm) was started, and the temperature was raised to 90 ° C., which is the reaction temperature. After completion of the temperature increase, nitrogen was introduced into the autoclave to an internal pressure of 2.4 MPa, and then air was introduced to an internal pressure of 4.8 MPa to initiate the reaction. Every time when the internal pressure decreased by 0.1 MPa during the reaction (internal pressure 4.7 MPa), an operation of introducing 0.1 MPa of oxygen to make the internal pressure 4.8 MPa (hereinafter also referred to as oxygen introducing operation) was repeated 8 times. . The reaction was terminated when the internal pressure decreased to 4.7 MPa after the eighth oxygen introduction.

  After completion of the reaction, the autoclave was placed in an ice bath to cool the contents. A gas collection bag was attached to the gas outlet of the autoclave, and the pressure in the reactor was released while collecting the gas that was opened by opening the gas outlet. The reaction solution containing the catalyst was taken out from the autoclave, the catalyst was separated by a membrane filter, and the reaction solution was recovered. The recovered reaction solution and the collected gas were analyzed by gas chromatography, and the reaction rate and selectivity were calculated. The results are shown in Table 1.

[Example 2]
(Catalyst preparation)
To a uniform aqueous solution obtained by adding 4.1 parts of a palladium nitrate nitric acid solution (made by Takanaka Tanaka, palladium element content 24.41 wt%) to an aqueous silver nitrate solution in which 0.08 part of silver nitrate is dissolved in 15 parts of pure water, After adding 5 parts of a granular silica carrier (specific surface area 450 m ² / g, pore volume 0.68 cc / g, median diameter 53.58 μm), water was removed by evaporation. The carrier impregnated with the metal salt by such an immersion method was baked in air at 450 ° C. for 3 hours to obtain a silica carrier on which palladium element and silver element were supported. The obtained silica carrier was added to 75 parts of a 37 mass% formaldehyde aqueous solution. A reduction treatment was performed by heating to 70 ° C. and stirring for 2 hours. Next, after suction filtration, it was filtered and washed with 1000 parts of warm water to obtain a silica carrier carrying palladium element and silver element.

  The silica carrier carrying the palladium element and the silver element was dispersed in 50 parts of pure water, and an aqueous telluric acid solution in which 0.06 part of telluric acid was dissolved in 5 parts of pure water was dropped into the dispersion. The solution was heated to 70 ° C. and stirred for 2 hours. Subsequently, after suction filtration, it was filtered and washed with 1000 parts of warm water. Furthermore, it was dried at 100 ° C. for 2 hours under a nitrogen flow to obtain a supported palladium-containing catalyst in which reduced palladium element, silver element and tellurium element were supported on a silica carrier.

  This catalyst had an Ag / Pd of 0.05, Te / Pd of 0.05, and a palladium element loading of 20% by mass.

(Reaction evaluation)
The reaction was evaluated in the same manner as in Example 1 using 3 parts of the catalyst obtained above. The results are shown in Table 1.

[Example 3]
(Catalyst preparation)
A mixed solution of silver nitrate aqueous solution in which 0.16 part of silver nitrate is dissolved in 15 parts of pure water and telluric acid aqueous solution in which 0.324 part of telluric acid is dissolved in 20 parts of pure water is mixed with a palladium nitrate nitric acid solution (manufactured by Tanaka Kikinzoku). , Palladium element content 24.41 wt%) 4.10 parts was added to obtain a homogeneous aqueous solution. To this was added 5.0 parts of a granular silica carrier (specific surface area 450 m ² / g, pore volume 0.68 cc / g, median diameter 53.58 μm), and then water was removed by evaporation. The carrier impregnated with the metal salt by such an immersion method was baked in air at 450 ° C. for 3 hours to obtain a silica carrier on which palladium element, silver element and tellurium element were supported. The obtained silica carrier was added to 75 parts of a 37% by mass aqueous formaldehyde solution, heated to 70 ° C., and subjected to a reduction treatment in which the mixture was stirred for 2 hours. Subsequently, after suction filtration, it was filtered and washed with 1000 parts of warm water. Furthermore, it was dried at 100 ° C. for 2 hours under a nitrogen flow to obtain a supported palladium-containing catalyst in which reduced palladium element, silver element and tellurium element were supported on a silica carrier.

  This catalyst had an Ag / Pd of 0.1, Te / Pd of 0.15, and a palladium element loading of 20% by mass.

(Reaction evaluation)
The same procedure as in Example 1 was performed except that 3 parts of the catalyst obtained above was used and the reaction temperature was changed to 110 ° C. The results are shown in Table 1.

[Example 4]
(Catalyst preparation)
A supported palladium-containing catalyst was obtained in the same manner as in Example 3 except that 0.08 part of silver nitrate and 0.22 part of telluric acid were used. This catalyst had an Ag / Pd of 0.05, Te / Pd of 0.1, and a palladium element loading of 20% by mass.

(Reaction evaluation)
The same procedure as in Example 3 was performed using 3 parts of the catalyst obtained above. The results are shown in Table 1.

[Example 5]
(Catalyst preparation)
A supported palladium-containing catalyst was obtained in the same manner as in Example 3 except that 0.03 part of silver nitrate and 0.22 part of telluric acid were used. This catalyst had an Ag / Pd of 0.02, Te / Pd of 0.1, and a palladium element loading of 20% by mass.

(Reaction evaluation)
The same procedure as in Example 3 was performed using 3 parts of the catalyst obtained above. The results are shown in Table 1.

[Comparative Example 1]
(Catalyst preparation)
To a homogeneous aqueous solution obtained by adding 15 parts of pure water to 4.1 parts of a palladium nitrate nitric acid solution (made by Tanaka Kikinzoku, palladium element content 24.41 wt%), a granular silica support (specific surface area 450 m ² / g, fine After adding 5 parts (pore volume 0.68 cc / g, median diameter 53.58 μm), water was removed by evaporation. The carrier impregnated with the metal salt by such an immersion method was calcined in air at 450 ° C. for 3 hours to obtain a silica carrier carrying palladium element. The obtained silica carrier was added to 75 parts of a 37 mass% formaldehyde aqueous solution. A reduction treatment was performed by heating to 70 ° C. and stirring for 2 hours. Subsequently, after suction filtration, it was filtered and washed with 1000 parts of warm water. Furthermore, it was dried at 100 ° C. for 2 hours under a nitrogen flow to obtain a supported palladium-containing catalyst in which the reduced palladium element was supported on a silica carrier.

  The palladium element loading of this catalyst was 20% by mass.

(Reaction evaluation)
The reaction was evaluated in the same manner as in Example 1 using the catalyst obtained above. The results are shown in Table 1.

[Comparative Example 2]
(Reaction evaluation)
The reaction was evaluated in the same manner as in Example 3 using the catalyst obtained in Comparative Example 1. The results are shown in Table 1.

  As described above, when the palladium-containing catalyst of the present invention is used, α, β-unsaturated carboxylic acid can be produced with high selectivity, and carbon dioxide by-product can be suppressed at equivalent α, β-carboxylic acid selectivity. I understood.

Claims (6)

  A palladium-containing catalyst for producing an α, β-unsaturated carboxylic acid from an olefin or an α, β-unsaturated aldehyde, containing 0.001 to 0.25 mol of silver element per mol of palladium element. Palladium-containing catalyst.   Furthermore, the palladium containing catalyst containing 0.001-0.4 mol of tellurium elements with respect to 1 mol of palladium elements.   The palladium-containing catalyst according to claim 1 or 2, wherein the palladium element and the silver element are supported on a support.   A method for producing a palladium-containing catalyst according to claim 1 or 2, wherein a step of reducing a compound containing palladium element in an oxidized state with a reducing agent, and a step of reducing a compound containing silver element in an oxidized state with a reducing agent. A method for producing a palladium-containing catalyst comprising:   4. A method for producing a palladium-containing catalyst according to claim 3, wherein a compound containing palladium element in an oxidized state in the presence of the carrier is reduced with a reducing agent, and silver element in the oxidized state in the presence of the carrier. A method for producing a palladium-containing catalyst, comprising a step of reducing a compound containing a reducing agent with a reducing agent.   A process for producing an α, β-unsaturated carboxylic acid, wherein the olefin or α, β-unsaturated aldehyde is subjected to liquid phase oxidation with molecular oxygen using the palladium-containing catalyst according to claim 1.