JP5019586B2 - Process for producing α, β-unsaturated carboxylic acid - Google Patents

Description

  The present invention relates to a method for producing an α, β-unsaturated carboxylic acid from an olefin or an α, β-unsaturated aldehyde with high selectivity and high productivity.

As a noble metal-containing supported catalyst for producing an α, β-unsaturated carboxylic acid by liquid phase oxidation of olefin or α, β-unsaturated aldehyde with molecular oxygen, for example, in Patent Document 1, palladium and tellurium are used in a predetermined manner. Catalysts containing a molar ratio have been proposed.
International Publication No. 2005/118134 Pamphlet

  However, when a catalyst containing palladium and tellurium was used, the selectivity and productivity decreased with time, and there was a problem in industrial production.

  The present invention provides a method for obtaining an α, β-unsaturated carboxylic acid from an olefin or an α, β-unsaturated aldehyde with high selectivity and high productivity over a long period of time using a catalyst containing palladium and tellurium. With the goal.

The present invention provides a step of obtaining a catalyst precursor in which a palladium salt and a tellurium raw material are supported on a support, and a flow gas in which the concentration of water vapor is controlled to 20 to 90% by volume, while introducing the catalyst precursor to palladium. Α, β-unsaturation in which metal fine particles containing palladium and tellurium are supported on a support by a method comprising a step of heat-treating at a temperature equal to or higher than the thermal decomposition temperature of the salt and a step of reducing the heat-treated catalyst precursor A method for producing an α, β-unsaturated carboxylic acid, comprising preparing a catalyst for carboxylic acid synthesis and oxidizing an olefin or an α, β-unsaturated aldehyde in a liquid phase in the presence of the catalyst , -When the Te / Pd atom number ratio in the bulk composition of the unsaturated carboxylic acid synthesis catalyst is A and the Te / Pd atom number ratio in the surface layer composition of the metal fine particles is B, B / A is greater than 1 and 5. 0 or less, Preferably, it is a method for producing an α, β-unsaturated carboxylic acid, which is controlled to be 1.2 to 4.5.

  In the present invention, the number of metal fine particles having a diameter of 1 to 8 nm is preferably 70% by number or more among the metal fine particles. In the present invention, the carrier preferably has a volume ratio of a pore diameter of 2 to 10 nm to a total pore volume of 70% by volume or more.

  In the present invention, the bulk composition of the α, β-unsaturated carboxylic acid synthesis catalyst is preferably represented by the following general formula (1).

Pd _a Te _b C _c D _d (EO _x ) _e (1)
(Wherein Pd, Te and O represent palladium, tellurium and oxygen, respectively, C is at least one element selected from the group consisting of platinum, rhodium, ruthenium, iridium, gold, lead and silver, and D is lead. , At least one element selected from the group consisting of bismuth, antimony, thallium and mercury, E is at least one element selected from the group consisting of silicon, aluminum, titanium, zirconium, magnesium, carbon and calcium EO _x is an oxide of the group of element E and is expected to function as a carrier, and x is an atomic ratio of oxygen necessary to satisfy the valence of element E. a, b , C, d and e represent the mass ratio of each element or carrier, and when e = 100, 0.1 ≦ a ≦ 40, 0 ≦ c ≦ 12, 0 ≦ d ≦ 12, and palladium The atomic ratio of tellurium for is a b satisfying 0.005 ≦ tellurium / palladium ≦ 0.3.)

  In the present invention, during the reaction, at least a part of the catalyst for synthesizing α, β-unsaturated carboxylic acid can be exchanged with another catalyst for synthesizing α, β-unsaturated carboxylic acid. Moreover, in this invention, reaction can be performed continuously for 25 hours or more.

Furthermore, the present invention is a method for producing a catalyst for synthesizing α, β-unsaturated carboxylic acid in which metal fine particles containing palladium and tellurium are supported on a carrier, wherein the carrier carries a palladium salt and a tellurium raw material. A step of obtaining the catalyst precursor, a step of heat-treating the catalyst precursor at a temperature equal to or higher than a thermal decomposition temperature of the palladium salt while introducing a flow gas whose water vapor concentration is controlled to 20 to 90% by volume, and the heat treatment And a step of reducing the produced catalyst precursor. A method for producing a catalyst for synthesizing an α, β-unsaturated carboxylic acid.

  Here, the above-mentioned A and B, the number ratio of the metal fine particles having a diameter of 1 to 8 nm, and the volume ratio of the pore diameter of 2 to 10 nm with respect to the total pore volume are values measured by the method defined below.

(A: Bulk composition ratio (Te / Pd))
To 0.5 g of catalyst, 5 ml of 36% by mass hydrochloric acid, 10 ml of 57% by mass hydroiodic acid and 2.5 ml of 47% by mass hydrofluoric acid are successively added and heated in a sealed state to be completely dissolved. Thereafter, the solution is transferred to a polypropylene measuring flask and diluted to the marked line with pure water to obtain a sample solution. Next, after appropriately diluting the sample solution, Te and Pd were quantified using an ICP issuing spectroscopic analyzer (manufactured by Thermo Elemental Co., Ltd., IRIS-advantage (trade name)), and the atomic ratio A was determined as a bulk composition ratio ( (Te / Pd).

(B: Surface layer composition ratio (Te / Pd))
Grind the catalyst in an agate mortar. This is applied to a conductive carbon tape and installed in a place where X-rays of an X-ray photoelectron spectrometer (manufactured by VG, ESCA LAB220iXL (trade name)) are irradiated. This sample is irradiated with AlKα rays at an area of 250 μm × 1000 μm at a 10 kV output by a monochrome radiation source, and photoelectrons emitted from the sample are collected to obtain an XPS spectrum. Using analysis software (Eclipse (trade name)), the atomic percentage of Te and Pd is estimated from the XPS peak area ratio for each element, and the atomic ratio B is calculated as the surface layer composition ratio (Te / Pd).

(Measurement of metal particle diameter)
The catalyst is embedded in a polypropylene capsule by the Suppr Resin method, and an ultrathin section is prepared by a microtome (Leica, ULTRACUT-S (trade name)). This is examined with a transmission electron microscope (manufactured by HITACHI, H-7600 (trade name)), and an image is taken. The photographed image is measured by using image analysis software Image Pro Plus (trade name), and for each sample, the metal particle diameter is measured for each particle diameter (diameter) from 10 fields of view to 200 or more. From the obtained number distribution of the metal particle diameter, the ratio of the number of metal fine particles having a diameter of 1 to 8 nm is determined.

(Pore diameter distribution and pore volume of catalyst support)
0.1 g of the carrier is collected and measured with a specific surface area / pore diameter distribution measuring device (manufactured by Micromeritics, TriStar 3000 (trade name)). The sample is degassed at 200 ° C. for 3 hours. The BJH method pore diameter distribution is analyzed from the nitrogen gas desorption isotherm under the liquid nitrogen temperature, and the volume ratio of pores having a pore diameter (diameter) of 2 to 10 nm is determined.

  According to the production method of α, β-unsaturated carboxylic acid of the present invention, olefin is liquid-phase oxidized with molecular oxygen to stably produce α, β-unsaturated carboxylic acid with high selectivity and high productivity. can do.

  In the conventional method for producing an α, β-unsaturated carboxylic acid using a catalyst for synthesizing α, β-unsaturated carboxylic acid containing metal fine particles containing palladium and tellurium in the carrier, the selectivity and Productivity decreased and there was a problem in industrial production.

  As a result of diligent investigations to solve this problem, B / A when the Te / Pd atomic ratio in the bulk composition of the catalyst is A and the Te / Pd atomic ratio in the surface layer composition of the metal fine particle is B is determined as time passes during the reaction. It was found that it increased.

  Furthermore, as a result of comparing B / A and reaction performance, the following was found. That is, when B / A is 1 or less as in the conventional catalyst, the reactivity of the olefin or α, β-unsaturated aldehyde is high but unstable, a lot of complete oxidation occurs, and α, β- The selectivity and productivity of unsaturated carboxylic acids are low. In addition, as B / A increases with time, complete oxidation decreases, but the reactivity of olefins or α, β-unsaturated aldehydes is low, so the selection of the target product α, β-unsaturated carboxylic acid is selected. Rate and productivity are low.

  And when B / A was controlled in a certain range, it turned out that (alpha), (beta) -unsaturated carboxylic acid continues being obtained with high selectivity and high productivity. Specifically, B / A may be controlled to be greater than 1 and 5.0 or less. The lower limit of B / A is preferably 1.2 or more, and more preferably 1, 4 or more. The upper limit of B / A is preferably 4.5 or less, and more preferably 4.0 or less.

  Conventionally, attention has been focused on the value of the bulk composition ratio A, but it may not be possible to control the catalyst performance to a desired level. However, it was found that the catalyst performance can be stably controlled to a desired level by controlling B / A within a predetermined range.

  As a method for controlling so as to satisfy such a condition, it can be performed by setting a liquid phase oxidation reaction condition, a catalyst composition or a production condition described later, and a method as described in JP-A-2006-289264. In the middle of the reaction, all or part of the catalyst may be extracted and another catalyst may be added to replace the catalyst. Simply, a method of adding another catalyst may be used. The catalyst to be replaced or added is not necessarily a new catalyst or a regenerated catalyst, and a single product or a mixture of a plurality of types of catalysts having different compositions, production methods, and usage histories may be applied. In order to control the catalyst as a whole within the range that satisfies the conditions of the present invention, a catalyst that does not satisfy the conditions of the present invention alone may be applied. By performing such control, it is possible to produce an α, β-unsaturated carboxylic acid with high selectivity and high productivity more stably than when it is performed without control.

  Hereinafter, α, β-unsaturated carboxylic acid is obtained by liquid phase oxidation of olefin or α, β-unsaturated aldehyde with molecular oxygen using a catalyst in which metal fine particles containing palladium and tellurium are supported in a carrier. A method of manufacturing the will be described.

  Examples of the raw material olefin include propylene, isobutylene, and 2-butene. Among these, propylene and isobutylene are preferable. The raw material olefin may contain a small amount of saturated hydrocarbon and / or lower saturated aldehyde as impurities. The α, β-unsaturated carboxylic acid produced is an α, β-unsaturated carboxylic acid having the same carbon skeleton as the olefin. Specifically, acrylic acid is obtained when the raw material is propylene, and methacrylic acid 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. 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 is an α, β-unsaturated carboxylic acid in which the aldehyde group of the α, β-unsaturated aldehyde is changed to a carboxyl group. Specifically, acrylic acid is obtained when the raw material is acrolein, and methacrylic acid is obtained when the raw material is methacrolein.

  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. The liquid phase oxidation reaction is preferably carried out in a fluidized bed instead of a fixed bed.

  As the source of molecular oxygen used in the liquid phase oxidation reaction, air is economical and preferable. However, 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, A mixed gas diluted with carbon dioxide, water vapor or the like can also be used. This gas such as air is usually 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 water to be coexisted 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 preferably in a uniform state, but may be in a non-uniform state.

  The concentration of the olefin or α, β-unsaturated aldehyde that is a raw material for the liquid phase oxidation reaction is 0.1% by mass or more, more preferably 0.5% by mass or more, with respect to the solvent present in the reactor. It is 30 mass% or less, More preferably, it is 20 mass% or less.

  The amount of molecular oxygen used is preferably at least 0.1 mol, more preferably at least 0.2 mol, even more preferably at least 0.3 mol, based on 1 mol of the raw material olefin or α, β-unsaturated aldehyde. It is preferably 20 mol or less, more preferably 15 mol or less, still more preferably 10 mol or less.

  A catalyst is used in the state suspended in the reaction liquid which performs liquid phase oxidation. The amount of the catalyst used is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, still more preferably 1% by mass or more, and 30% by mass or less with respect to the solution present in the reactor. More preferably, it is 20 mass% or less, More preferably, it is 15 mass% or less.

  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. The reaction temperature is preferably 200 ° C. or lower, more preferably 150 ° C. or lower. The reaction pressure is preferably 0 MPa (gauge pressure; hereinafter, pressure notation unless otherwise specified), more preferably 0.5 MPa or more. The reaction pressure is preferably 10 MPa or less, more preferably 5 MPa or less.

  According to the method of the present invention, it is possible to carry out the reaction continuously for 25 hours or more.

  The catalyst used for the liquid phase oxidation reaction is a catalyst in which fine metal particles containing palladium and tellurium are supported on a carrier. In addition to palladium and tellurium, other atoms such as platinum, rhodium, ruthenium, iridium, gold, lead, bismuth, thallium, mercury, and carbon can be contained. From the viewpoint of expressing high catalytic activity, it is preferable that 50% by mass or more of the components other than the carrier contained in the catalyst is palladium.

  In particular, the bulk composition of the catalyst used in the liquid phase oxidation reaction is preferably represented by the following general formula (1).

Pd _a Te _b C _c D _d (EO _x ) _e (1)
(Wherein Pd, Te and O represent palladium, tellurium and oxygen, respectively, C is at least one element selected from the group consisting of platinum, rhodium, ruthenium, iridium, gold, lead and silver, and D is lead. , At least one element selected from the group consisting of bismuth, antimony, thallium and mercury, E is at least one element selected from the group consisting of silicon, aluminum, titanium, zirconium, magnesium, carbon and calcium EO _x is an oxide of the group of element E and is expected to function as a carrier, and x is an atomic ratio of oxygen necessary to satisfy the valence of element E. a, b , C, d and e represent the mass ratio of each element or carrier, and when e = 100, 0.1 ≦ a ≦ 40, 0 ≦ c ≦ 12, 0 ≦ d ≦ 12, and palladium Against a b where the atomic ratio of tellurium satisfies 0.005 ≦ tellurium / palladium ≦ 0.3.)
In addition, it is preferable that all or a part of palladium contained in the catalyst is in a metal state from the viewpoint of developing high catalytic activity. Tellurium contained in the catalyst may be in an oxidized state, a reduced state or a metallic state.

  The type of the carrier is not particularly limited, and typical carriers such as activated carbon, carbon black, silica, alumina, magnesia, calcia, zirconia, and titania can be used, and among them, activated carbon, silica, and zirconia are preferable. The shape of the carrier is not particularly limited. For example, in the case of activated carbon, various types such as powder, sphere, pellet and fiber can be used. A carrier having a diameter or length of 1 μm to 10 mm can be used.

Although the specific surface area of a preferable support varies depending on the type of the support and the like, it cannot be generally stated. In the case of activated carbon, the specific surface area is preferably 100 to 5000 m ² / g, more preferably 300 to 4000 m ² / g. For silica, the specific surface area is preferably 50~1500m ² / g, more preferably 100~1000m ² / g. The smaller the specific surface area of the support is, the more the catalyst having a useful component (palladium atom / tellurium atom) supported on the surface can be produced, and the larger the specific surface area of the carrier, the more the useful component can be produced.

  The total pore volume of the carrier measured by the nitrogen gas adsorption method is preferably 0.40 to 1.50 cc / g. The average pore diameter (diameter) of the support is preferably 2 to 10 nm.

  The palladium loading ratio in the catalyst is preferably from 0.1 to 40 mass%, more preferably from 0.5 to 30 mass%, still more preferably from 1 to 20 mass%, based on the carrier before loading. The supported ratio of tellurium in the catalyst is preferably 0.005 to 0.3 (atomic ratio) times, more preferably 0.01 to 0.25 times, and more preferably 0.03 to 0.20 times the amount of palladium supported. Further preferred.

  Here, it is known that the diameter of the metal fine particles supported on the carrier increases (sinters) with time. It was found that the catalyst activity and product distribution change as the diameter of the metal fine particles changes. As a result of the examination, it has been found that among the fine metal particles supported on the carrier, it is preferable to maintain the fine metal particles having a diameter of 1 to 8 nm at 70% by number or more. The number ratio is more preferably 80% by number or more, and still more preferably 90% by number or more. Conventionally, the distribution was not checked by paying attention only to the average particle diameter (diameter) of the metal fine particles. However, by using the control of the number ratio of the metal fine particles having a diameter of 1 to 8 nm in combination, α, β at a higher level. -It has been found that unsaturated carboxylic acids continue to be obtained with high selectivity and high productivity.

  From this viewpoint, the volume ratio of the pore diameter of 2 to 10 nm to the total pore volume of the support is preferably 70% by volume or more, and more preferably 80% by volume or more. That is, the metal fine particles do not grow beyond the size of the pore diameter of the carrier even if they are sintered, and the preferred size can be maintained. Furthermore, it is more preferable that the support has pores communicating in all directions through a plurality of routes, since it is difficult for the fine particles to obstruct the pore blockage. Conventionally, the distribution was not checked by paying attention only to the average pore diameter of the carrier, but as a result, the volume ratio of the pore diameter of 2 to 10 nm with respect to the total pore volume of the carrier was controlled within the above range, resulting in high It has been found that α, β-unsaturated carboxylic acids continue to be obtained with high selectivity and high productivity.

  Hereinafter, the preferable manufacturing method of the catalyst used for liquid phase oxidation reaction is demonstrated.

  First, a method for producing a catalyst in which fine metal particles containing palladium and tellurium are supported on a carrier will be described.

  Examples of the palladium raw material used for the catalyst production include palladium salts, palladium oxide, palladium oxide alloys, palladium black and the like, and among them, palladium salts are preferable. Examples of the palladium salt include palladium chloride (thermal decomposition temperature: 650 ° C.), palladium acetate (thermal decomposition temperature: 230 ° C.), palladium nitrate (thermal decomposition temperature: 120 ° C.), tetraammine palladium chloride (thermal decomposition temperature: 300 ° C.). ), Tetraamminepalladium nitrate (thermal decomposition temperature: 220 ° C), bis (acetylacetonato) palladium (thermal decomposition temperature: 210 ° C), among others, palladium chloride, palladium acetate, palladium nitrate, tetraamminepalladium. Chloride is preferred.

  The thermal decomposition temperature of the palladium salt can be measured by thermogravimetry. In the present invention, when a palladium salt was heated from room temperature to 5.0 ° C./min in an air stream using a thermogravimetric apparatus (manufactured by Shimadzu Corporation, trade name: TGA-50), the weight decreased by 10%. The temperature was defined as the pyrolysis temperature of the palladium salt.

  Examples of the tellurium raw material used in the production of the catalyst include tellurium salt, telluric acid and its salt, telluric acid and its salt, tellurium oxide, tellurium oxide alloy, etc., among which tellurium salt, telluric acid and its salt. , Tellurite and its salts, and tellurium oxide are preferred. 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.

  First, a palladium raw material and a tellurium raw material are supported on a carrier. As a method for supporting the palladium raw material and the tellurium raw material on the carrier, a method of evaporating the solvent after immersing the carrier in a solution or dispersion of the palladium raw material and the tellurium raw material may be used. A so-called pore filling method is preferred, in which a solution or dispersion of a tellurium raw material is absorbed by a carrier and then the solvent is evaporated. The solvent used when the palladium raw material and the tellurium raw material are supported on the carrier is not particularly limited, but a solvent capable of dissolving the palladium raw material and the tellurium raw material is preferable from the viewpoint of the dispersibility of palladium and tellurium on the carrier. The palladium raw material and the tellurium raw material may be supported simultaneously or sequentially. In the case of carrying sequentially, drying, baking, and reducing operations may be inserted between them.

  When using a palladium salt as the palladium raw material, it is preferable to heat-treat the catalyst precursor having at least the palladium raw material supported on the carrier at a temperature equal to or higher than the thermal decomposition temperature of the palladium salt. By performing the heat treatment, at least a part of the palladium salt on the support is decomposed into palladium oxide. The carrier may be in a state where the tellurium raw material is also supported, or may be in a state before the tellurium raw material is supported. As for the heat treatment method, for example, a heat treatment method in which the catalyst precursor is placed on a calcining vat for stationary firing, or a heat treatment method using a conveyor type continuous firing furnace or the like can be performed.

  Furthermore, in order to facilitate the control of the composition ratio (Te / Pd) of the surface layer of the metal fine particles and the particle size distribution of the metal fine particles, the heat treatment is performed while circulating a gas containing water vapor in air or nitrogen in the firing furnace. Preferably it is done. The total gas flow rate is preferably equal to or higher than the catalyst precursor capacity / min. However, immediately after the start of steam flow, the flow rate may be adjusted so that water vapor flows in the furnace. And it is preferable to introduce | transduce the distribution | circulation gas by which the density | concentration of water vapor | steam was controlled to 20-90 volume%. The concentration of the water vapor is preferably controlled to 40 to 60% by volume. In this way, the B / A of the catalyst and the particle size of the metal fine particles obtained during the reaction can be obtained by heat treatment at a temperature equal to or higher than the thermal decomposition temperature of the palladium salt while introducing a flow gas whose water vapor concentration is controlled. It will be difficult to change. The reason for this is that decomposition and oxidation are promoted by sufficiently flowing water vapor so that the surface / bulk composition of the metal fine particle precursor is easily controlled, and the dispersibility of the metal fine particle precursor is not uniform and high. I think.

  The heat treatment temperature is preferably equal to or higher than the thermal decomposition temperature of the palladium raw material, but if the heat treatment temperature is too high in the presence of water vapor, the support may be sintered and decomposed, or the dispersibility of the metal fine particle precursor may deteriorate. The heat treatment temperature is preferably slightly higher than the thermal decomposition temperature. Specifically, the thermal decomposition temperature is preferably 700 ° C. or lower, more preferably 500 ° C. or lower. The method for raising the temperature up to the predetermined heat treatment temperature is not particularly limited, but the temperature raising rate is preferably 1 to 10 ° C./min in order to obtain a good dispersion state of the metal fine particle precursor in the catalyst containing palladium and tellurium. The holding time after reaching the predetermined heat treatment temperature is not particularly limited as long as the palladium salt is decomposed, but 1 to 12 hours is preferable.

  The concentration of water vapor may be controlled at least during the heat treatment, but it is effective to perform the heat treatment from the time when the palladium salt thermal decomposition temperature is reached to the completion of the heat treatment when the temperature is raised to a predetermined heat treatment temperature.

  Next, the heat-treated catalyst precursor is reduced with a reducing agent. When a palladium raw material other than the palladium salt is used, it may be reduced without heat treatment. The reduction method is not particularly limited, and may be performed in a gas phase, but is preferably performed in a liquid phase. Hereinafter, a method for reducing the catalyst precursor in the liquid phase and a liquid phase reduction method will be described.

  In the liquid phase reduction method, first, a catalyst precursor is dispersed in a solvent, and then a reducing agent is added to the dispersion to reduce the catalyst precursor.

  As a solvent used in the liquid phase reduction method, water is generally used, but alcohols such as 1-propanol, n-butanol, and t-butanol are used depending on the solubility of the reducing agent and the dispersibility of the catalyst precursor; Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; organic acids such as acetic acid, n-valeric acid and iso-valeric acid; organic solvents such as hydrocarbons such as heptane, hexane and cyclohexane; A mixed solvent with water can also be used.

  Any reducing agent used in the liquid phase reduction method can be used as long as it has at least the ability to reduce palladium oxide. Examples include ethanol, 2-propanol, formaldehyde, hydrazine, formic acid, oxalic acid, sodium borohydride, lithium aluminum hydride, calcium hydride, hydrogen, ethylene, propylene, 1-butene, 2-butene, and isobutylene. . Among these, at least one compound selected from the group consisting of ethanol, 2-propanol, formaldehyde, hydrazine, sodium borohydride, hydrogen, ethylene, propylene, 1-butene, 2-butene and isobutylene is preferable. Two or more reducing agents may be used in combination.

  Although the addition method of a reducing agent is not specifically limited, For example, the method of reducing while dripping a reducing agent, the method of reducing after adding all the reducing agents, etc. are mentioned. The temperature and reduction time of the system at the time of reduction vary depending on the reduction method, the solvent used, the reducing agent, etc., but cannot be generally stated, but the reduction temperature may be 0 to 100 ° C. and the reduction time may be 0.5 to 24 hours. preferable.

  As described above, the catalyst precursor can be reduced using the reducing agent. By this reduction, most of the palladium atoms contained in the catalyst precursor change from the oxidized state to the metal state. The tellurium raw material may or may not be subjected to the heat treatment and reduction treatment.

  Catalysts containing atoms other than palladium and tellurium are obtained by supporting the raw materials of other atoms such as corresponding metal salts and oxides on a support, and performing the heat treatment, reduction, etc. as necessary. Can do. There are no particular limitations on the method of supporting the raw materials of other atoms at that time, but it can be carried out in the same manner as the method of supporting the palladium raw material and the tellurium raw material. In addition, the raw materials of other atoms can be supported before the palladium raw material and the tellurium raw material are supported, or can be supported after the palladium raw material and the tellurium raw material are supported. You can also.

  The obtained catalyst is preferably washed with water, a solvent or the like. By washing with water, a solvent, etc., impurities derived from palladium raw materials such as chloride, acetate radical, nitrate radical, sulfate radical, unreacted reducing agent, and the like are removed. The washing method and number of times are not particularly limited, but depending on the impurities and unreacted reducing agent, the liquid phase oxidation reaction of olefins or α, β-unsaturated aldehydes may be hindered. Is preferred. The washed catalyst may be used in the reaction as it is after being recovered by filtration or centrifugation.

  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.

(A: Bulk composition ratio (Te / Pd))
To 0.5 g of the catalyst, 5 ml of 36% by mass hydrochloric acid, 10 ml of 57% by mass hydroiodic acid and 2.5 ml of 47% by mass hydrofluoric acid were sequentially added and heated in a sealed state to be completely dissolved. Thereafter, the solution was transferred to a polypropylene volumetric flask and diluted with pure water up to the marked line to obtain a sample solution. Next, after appropriately diluting this sample solution, Te and Pd were quantified using an ICP emission spectroscopic analyzer (manufactured by Thermo Elemental Co., Ltd., IRIS-advantage (trade name)), and the atomic ratio A was determined as the bulk composition ratio. Calculated as (Te / Pd).

(B: Surface layer composition ratio (Te / Pd))
The surface layer composition ratio of the metal fine particles in the present invention is measured by X-ray photoelectron spectroscopy (XPS), and the atomic number% of Te and Pd is estimated from the area of the obtained spectrum. The ratio B was calculated as the surface layer composition ratio (Te / Pd).

  Examples of more specific measurement methods are shown below. First, the catalyst was pulverized in an agate mortar. This was applied to a conductive carbon tape and installed in a place where X-rays of an X-ray photoelectron spectrometer (manufactured by VG, ESCA LAB220iXL (trade name)) are irradiated. Then, the sample was irradiated with AlKα rays by a monochrome source at an output of 10 kV to an area of 250 μm × 1000 μm, and photoelectrons emitted from the sample were condensed to obtain an XPS spectrum.

  From the peak area ratio of the XPS spectrum, the ratio of tellurium and palladium metal present in the surface layer of the catalyst was estimated. Specifically, atomic% was calculated from the peak area ratio for each element using analysis software (Eclipse (trade name)). At this time, the total of the atomic percentage of the elements contained in the catalyst was 100. From the calculated atomic%, the ratio of atomic% of tellurium and palladium was taken to obtain the atomic ratio B.

  XPS is generally referred to as surface analysis, but actually detects depth information of up to several nanometers. This is comparable to the metal fine particle size. However, since the surface information is detected more strongly than inside the metal fine particles, it can be used as a relative measure of the surface composition.

(Measurement of metal particle diameter)
The measurement of the metal particle diameter in the present invention was performed with a transmission electron microscope (TEM), the metal particle diameter was estimated from the obtained image, and the average particle diameter was calculated.

  Examples of more specific measurement methods are shown below. First, the catalyst was embedded in a polypropylene capsule by the Suppr Resin method, and an ultrathin section was prepared by a microtome (Leica, ULTRACUT-S (trade name)). This was examined with a transmission electron microscope (manufactured by HITACHI, H-7600 (trade name)), and an image was taken. The photographed images were measured using image analysis software Image Pro Plus (trade name), and the metal particle diameters were measured for each sample from 10 fields of view to 200 or more particle diameters. And the average value of the obtained metal particle diameter was made into the average particle diameter which represents a sample, and the number ratio of the metal fine particles with a diameter of 1-8 nm was calculated | required from the number distribution of the obtained metal particle diameter.

(Pore diameter distribution and pore volume of catalyst support)
0.1 g of the carrier was collected and measured with a specific surface area / pore diameter distribution measuring apparatus (manufactured by Micromeritics, TriStar 3000 (trade name)). The sample was degassed at 200 ° C. for 3 hours. Analyzing the BET specific surface area from the nitrogen gas adsorption isotherm under liquid nitrogen temperature and the BJH method pore size distribution from the desorption isotherm, the pore volume, the volume ratio of pores having a diameter of 2 to 10 nm, and the average pore diameter are obtained. It was.

(Liquid-phase oxidation reaction of isobutylene)
As a reaction vessel for conducting the liquid phase oxidation reaction, a jacketed stainless steel stirred tank reactor having an inner diameter of 126 mm and a capacity of 4 liters was used. The raw material is supplied from the upper part of the reaction vessel together with the solvent, and the reaction liquid is continuously extracted from the system while keeping the liquid surface of the liquid phase part constant. The oxygen concentration in the exhaust gas was constantly monitored with a magnetic oxygen meter (manufactured by Yokogawa Electric).

  A catalyst corresponding to a palladium mass of 50 g and a 75% by mass tertiary butanol aqueous solution as a solvent were previously introduced into the reaction vessel so as to reach the control liquid level (the liquid level was adjusted so that the liquid volume was 3 liters). Nitrogen gas was supplied to the liquid phase part of the reaction vessel through a sparger made of sintered metal at a rate of about 2000 g / hr to increase the pressure to 4.9 MPa (absolute pressure), and this pressure was maintained by a pressure controller thereafter. . After the liquid phase temperature was raised to 110 ° C. and stabilized for about 10 minutes, 461 g / hr of liquefied isobutylene and a solvent (75 mass% tertiary butanol aqueous solution was added with 200 ppm of p-methoxyphenol as a polymerization inhibitor). Prepared at a rate of 1844 g / hr. The average residence time at this time was 1.0 hour. Next, while maintaining the gas phase pressure, the nitrogen gas supply amount is gradually replaced with air (commercial compressed air cylinder; oxygen concentration 21 vol%), and finally supplied continuously at 2000 g / hr. The reaction was started. When the oxygen concentration in the gas phase exceeded 5% by volume, priority was given to controlling the amount of air supplied so that the oxygen concentration was maintained at 5% by volume or less.

(Analysis of reactants)
The reaction solution and exhaust gas were sampled and analyzed. Analysis of raw materials and products was performed using gas chromatography (manufactured by Shimadzu Corporation) equipped with an FID or TCD detector. In addition, the selectivity of the produced | generated methacrylic acid and the productivity of the produced | generated methacrylic acid are defined as follows.
Selectivity of methacrylic acid (%) = (B / A) × 100
Productivity of methacrylic acid (g-MAA / (g-Pd · hr)) = (B × MwM) / PD
Here, A is the molar flow rate (mol / h) of the disappeared isobutylene, B is the molar flow rate (mol / h) of the produced methacrylic acid, MwM is the molecular weight of methacrylic acid, PD is the mass of palladium used in the reaction (g ).

[Example 1]
(Catalyst preparation)
10.8 parts of telluric acid (Te / Pd charged atomic ratio is 0.10) dissolved in 195.3 parts (Pd 50 parts) of palladium nitrate solution (Pd content 25.60% by mass) with a small amount of pure water; A mixed solution to which 500 parts of pure water was added was prepared. The above mixed solution was added to 250 parts of zirconia support (specific surface area 80 m ² / g, pore volume 0.25 cc / g, average pore diameter 7.6 nm, pore diameter 2 to 10 nm is 75% by volume of pore volume). After soaking, the solvent was evaporated using an evaporator under reduced pressure at 70 ° C. for 2 hours. Thereafter, heat treatment was performed in air at 200 ° C. for 3 hours. During the temperature increase from 120 ° C. to 200 ° C. and heat treatment at 200 ° C., a gas whose water vapor concentration was controlled to 40% by volume was circulated. To the obtained catalyst precursor, 500 parts of a 37% by mass aqueous formaldehyde solution was added. The mixture was heated to 70 ° C., held for 2 hours with stirring, suction filtered and washed with pure water to obtain a palladium-containing supported catalyst.

(Reaction evaluation)
The liquid phase oxidation reaction of isobutylene was performed using the produced palladium containing supported catalyst. The analysis values of the reaction products are shown in Table 1 for 5 hours, 25 hours and 43 hours after the start of the reaction.

(Catalyst evaluation)
The bulk composition ratio A, surface composition ratio B, and metal particle size distribution of the palladium-containing supported catalyst were measured. The catalyst sample is a pre-reaction product and a sample collected at the time of analyzing each product. Table 1 shows B / A, the average particle diameter of the metal fine particles, and the ratio of the metal fine particles in the range of 1 to 8 nm in each catalyst sample.

[Example 2]
(Catalyst preparation)
5.4 parts of telluric acid (Te / Pd charged atomic ratio is 0.05) dissolved in a small amount of pure water in 195.3 parts (Pd 50 parts) of a palladium nitrate solution (Pd content 25.60% by mass); A mixed solution to which 1000 parts of pure water was added was prepared. The above mixed solution is added to 1000 parts of silica support (specific surface area 520 m ² / g, pore volume 0.73 cc / g, average pore diameter 4.7 nm, pore diameter 2 to 10 nm is 90% by volume of pore volume). After soaking, the solvent was evaporated using an evaporator under reduced pressure at 70 ° C. for 2 hours. Thereafter, heat treatment was performed in air at 200 ° C. for 3 hours. During the temperature increase from 120 ° C. to 200 ° C. and during the heat treatment at 200 ° C., a gas whose water vapor concentration was controlled to 50% by volume was circulated. To the obtained catalyst precursor, 500 parts of a 37% by mass aqueous formaldehyde solution was added. The mixture was heated to 70 ° C., held for 2 hours with stirring, suction filtered and washed with pure water to obtain a palladium-containing supported catalyst.

(Reaction evaluation)
The liquid phase oxidation reaction of isobutylene was performed using the produced palladium containing supported catalyst. The analytical values of the reaction products are shown in Table 2 for 5 hours, 25 hours and 43 hours after the start of the reaction.

(Catalyst evaluation)
Evaluation of the palladium-containing supported catalyst (pre-reaction product and collected product at the time of analyzing each product) was carried out in the same manner as in Example 1. Table 2 shows the B / A, the average particle diameter of the metal fine particles, and the ratio of the metal fine particles in the range of 1 to 8 nm in each catalyst sample.

[Comparative Example 1]
(Catalyst preparation)
5.4 parts of telluric acid (Te / Pd charged atomic ratio is 0.05) dissolved in a small amount of pure water in 195.3 parts (Pd 50 parts) of a palladium nitrate solution (Pd content 25.60% by mass); A mixed solution to which 1000 parts of pure water was added was prepared. The above mixed solution is added to 500 parts of silica support (specific surface area of 430 m ² / g, pore volume of 0.71 cc / g, average pore size of 5.3 nm, and pores of 2 to 10 nm are 90% by volume of the pore volume). After soaking, the solvent was evaporated using an evaporator under reduced pressure at 70 ° C. for 2 hours. Thereafter, heat treatment was performed in air at 300 ° C. for 3 hours. In addition, during the temperature increase to 300 ° C. and the heat treatment at 300 ° C., a gas having a water vapor concentration of substantially 0% by volume was introduced. To the obtained catalyst precursor, 500 parts of a 37% by mass aqueous formaldehyde solution was added. The mixture was heated to 70 ° C., held for 2 hours with stirring, suction filtered and washed with pure water to obtain a palladium-containing supported catalyst.

(Reaction evaluation)
The liquid phase oxidation reaction of isobutylene was performed using the produced palladium containing supported catalyst. The analysis values of the reaction products are shown in Table 3 for 5 hours, 25 hours and 43 hours after the start of the reaction.

(Catalyst evaluation)
Evaluation of the palladium-containing supported catalyst (pre-reaction product and collected product at the time of analyzing each product) was carried out in the same manner as in Example 1. Table 3 shows B / A, the average particle diameter of the metal fine particles, and the ratio of the metal fine particles in the range of 1 to 8 nm in each catalyst sample.

[Example 3]
(Catalyst preparation)
10.8 parts of telluric acid (Te / Pd charged atomic ratio is 0.10) dissolved in 195.3 parts (Pd 50 parts) of palladium nitrate solution (Pd content 25.60% by mass) with a small amount of pure water; A mixed solution to which 1000 parts of pure water was added was prepared. The above mixed solution is immersed in 500 parts of a silica support (specific surface area 140 m ² / g, pore volume 0.25 cc / g, average pore diameter 11 nm, pores having a pore diameter of 2 to 10 nm are 50% by volume of the pore volume). After that, the solvent was evaporated using an evaporator under reduced pressure at 70 ° C. for 2 hours. Thereafter, heat treatment was performed in air at 200 ° C. for 3 hours. During the temperature increase from 120 ° C. to 200 ° C. and during the heat treatment at 200 ° C., a gas whose water vapor concentration was controlled to 50% by volume was circulated. To the obtained catalyst precursor, 500 parts of a 37% by mass aqueous formaldehyde solution was added. The mixture was heated to 70 ° C., held for 2 hours with stirring, suction filtered and washed with pure water to obtain a palladium-containing supported catalyst.

(Reaction evaluation)
The liquid phase oxidation reaction of isobutylene was performed using the produced palladium containing supported catalyst. The analytical values of the reaction products are shown in Table 4 for 5 hours, 25 hours and 43 hours after the start of the reaction.

(Catalyst evaluation)
Evaluation of the palladium-containing supported catalyst (pre-reaction product and collected product at the time of analyzing each product) was carried out in the same manner as in Example 1. Table 4 shows B / A, the average particle diameter of the metal fine particles, and the ratio of the metal fine particles in the range of 1 to 8 nm in each catalyst sample.

[Example 4]
(Reaction evaluation)
After performing the reaction evaluation in Example 1 for 46 hours, 10% by mass of the catalyst inside the reactor was replaced with a new catalyst produced in Example 1, and the liquid phase oxidation reaction of isobutylene was continued. The analytical values of the reaction product are shown in Table 5 for 72 hours and 99 hours after the start of the reaction in Example 1.

(Catalyst evaluation)
Evaluation of the palladium-containing supported catalyst (collected product at the time of analyzing each product) was carried out in the same manner as in Example 1. Table 5 shows the B / A, the average particle diameter of the metal fine particles, and the ratio of the metal fine particles in the range of 1 to 8 nm in each catalyst sample.

  By controlling the B / A value within an appropriate range as in Examples 1 to 3, the selectivity and productivity of methacrylic acid can be maintained high. In particular, in Examples 1 and 2 in which the ratio of metal particles having a diameter of 1 to 8 nm is also in an appropriate range, the selectivity and productivity of methacrylic acid can be maintained at a higher level. On the other hand, when the B / A value is not controlled within an appropriate range as in Comparative Example 1, there is a tendency that the selectivity of methacrylic acid and the productivity decrease range increase from outside the range. .

As in Example 4, the selectivity and productivity of methacrylic acid can be maintained high also by partially exchanging the catalyst during the reaction and controlling the B / A value within an appropriate range .

Claims (8)

Obtaining a catalyst precursor in which a palladium salt and a tellurium raw material are supported on a carrier;
A step of heat-treating the catalyst precursor at a temperature equal to or higher than the thermal decomposition temperature of the palladium salt while introducing a flow gas in which the concentration of water vapor is controlled to 20 to 90% by volume;
Reducing the heat-treated catalyst precursor;
And a catalyst for synthesizing α, β-unsaturated carboxylic acid in which metal fine particles containing palladium and tellurium are supported on a carrier, and an olefin or α, β-unsaturated aldehyde in the presence of the catalyst. A process for producing an α, β-unsaturated carboxylic acid wherein
When the Te / Pd atom number ratio in the bulk composition of the α, β-unsaturated carboxylic acid synthesis catalyst is A and the Te / Pd atom number ratio in the surface layer composition of the metal fine particles is B, B / A is 1 A method for producing an α, β-unsaturated carboxylic acid, wherein the production is controlled to be greater than 5.0.   2. The method for producing an α, β-unsaturated carboxylic acid according to claim 1, wherein the number of metal fine particles having a diameter of 1 to 8 nm is 70% by number or more among the metal fine particles.   The method for producing an α, β-unsaturated carboxylic acid according to claim 1 or 2, wherein the carrier has a volume ratio of a pore diameter of 2 to 10 nm to a total pore volume of 70% by volume or more. The bulk composition of the catalyst for synthesizing the α, β-unsaturated carboxylic acid is represented by the following general formula (1), and the α, β-unsaturated carboxylic acid according to any one of claims 1 to 3 is characterized. Acid production method.
Pd _a Te _b C _c D _d (EO _x ) _e (1)
(Wherein Pd, Te and O represent palladium, tellurium and oxygen, respectively, C is at least one element selected from the group consisting of platinum, rhodium, ruthenium, iridium, gold, lead and silver, and D is lead. , At least one element selected from the group consisting of bismuth, antimony, thallium and mercury, E is at least one element selected from the group consisting of silicon, aluminum, titanium, zirconium, magnesium, carbon and calcium EO _x is an oxide of the group of element E and is expected to function as a carrier, and x is an atomic ratio of oxygen necessary to satisfy the valence of element E. a, b , C, d and e represent the mass ratio of each element or carrier, and when e = 100, 0.1 ≦ a ≦ 40, 0 ≦ c ≦ 12, 0 ≦ d ≦ 12, and palladium The atomic ratio of tellurium to b is 0.005 ≦ tellurium / palladium ≦ 0.3.) In the course of the reaction, the alpha, beta-at least a portion of the unsaturated carboxylic acid catalyst for synthesizing, another alpha, according to claim 1-4, characterized in that to replace the beta-unsaturated carboxylic acid catalyst for synthesizing The manufacturing method of the alpha, beta-unsaturated carboxylic acid in any one. The method of alpha, of β- unsaturated carboxylic acid production according to claim 1-5 which continuously and performing the reaction over 25 hours. A method for producing a catalyst for synthesizing an α, β-unsaturated carboxylic acid in which metal fine particles containing palladium and tellurium are supported on a carrier,
Obtaining a catalyst precursor having a palladium salt and a tellurium raw material supported on the carrier;
A step of heat-treating the catalyst precursor at a temperature equal to or higher than the thermal decomposition temperature of the palladium salt while introducing a flow gas in which the concentration of water vapor is controlled to 20 to 90% by volume;
And a step of reducing the heat-treated catalyst precursor. A method for producing a catalyst for synthesizing an α, β-unsaturated carboxylic acid. As the carrier, a method of alpha, of β- unsaturated carboxylic acid synthesis for catalyst preparation according to claim 7 in which the volume ratio of the pore size 2~10nm to the total pore volume used 70% by volume or more carriers.