JP6798617B2 - A method for producing a catalyst, a method for producing an unsaturated carboxylic acid, a method for producing an unsaturated aldehyde and an unsaturated carboxylic acid, and a method for producing an unsaturated carboxylic acid ester. - Google Patents

Description

The present invention relates to a method for producing a catalyst, a method for producing an unsaturated carboxylic acid, a method for producing an unsaturated aldehyde and an unsaturated carboxylic acid, and a method for producing an unsaturated carboxylic acid ester.

Numerous studies have been made on methods for producing catalysts. The catalyst is generally produced by preparing a raw material solution such as an aqueous solution or an aqueous slurry containing each element constituting the catalyst, and drying and firing the raw material solution.

As the firing, for example, Patent Documents 1 to 3 describe a gas containing ammonia and water vapor, Patent Document 4 describes a non-oxidizing gas, and Patent Document 5 describes a firing using a gas containing an oxygen-containing organic compound. There is. Further, Patent Document 6 describes a firing method including a plurality of steps in which the gas used and the firing temperature are changed. Further, Patent Document 7 describes the gas flow rate with respect to the catalyst precursor.

Japanese Unexamined Patent Publication No. 58-61833 JP-A-58-67643 JP-A-58-79545 JP-A-59-66349 JP-A-59-69148 Japanese Unexamined Patent Publication No. 2012-245432 Japanese Unexamined Patent Publication No. 2009-213969

However, the catalyst produced by the methods described in Patent Documents 1 to 7 is a reaction for producing an unsaturated carboxylic acid by vapor-phase catalytic oxidation of an unsaturated aldehyde with molecular oxygen, or propylene, isobutylene, or primary. At least one selected from the group consisting of butyl alcohol, tertiary butyl alcohol and methyl tertiary butyl ether is vapor-phase catalytically oxidized with molecular oxygen to produce the corresponding unsaturated aldehydes and unsaturated carboxylic acids. When used in the reaction, there is a problem that the selectivity of the target product is not sufficient. Therefore, it is desired to develop a method for producing a catalyst capable of producing the target product with a higher selectivity. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a catalyst capable of producing a target product with a high selectivity.

The above problems are solved by the following inventions [1] to [ 12 ].

[1] Production of a catalyst having a composition represented by the following formula (1), which contains at least molybdenum and phosphorus and is used when unsaturated aldehyde is vapor-phase catalytically oxidized with molecular oxygen to produce an unsaturated carboxylic acid. It ’s a method,
A method for producing a catalyst, which comprises a step of exposing a catalyst precursor containing a nitrogen-containing component to a pressure of 10 kPa (G) or more and 80 kPa (G) or less in a gas flow containing an oxygen-containing gas and firing.
P _α1 Mo _α2 V _α3 Cu _α4 A _α5 E _α6 G _α7 O _α8 (1)
[In formula (1), P, Mo, V, Cu and O are element symbols indicating phosphorus, molybdenum, vanadium, copper and oxygen, respectively. A represents at least one element selected from the group consisting of antimony, bismuth, arsenic, germanium, zirconium, tellurium, silver, selenium, silicon, tungsten and boron. E represents at least one element selected from the group consisting of potassium, rubidium, cesium, thallium, magnesium and barium. G is at least one selected from the group consisting of iron, zinc, chromium, calcium, strontium, tantalum, cobalt, nickel, manganese, titanium, tin, lead, niobium, indium, sulfur, palladium, gallium, cerium and lanthanum. Indicates an element. α1 to α8 represent the atomic ratio of each element, and when α2 = 12, α1 = 0.5 to 3, α3 = 0.01 to 3, α4 = 0.01 to 2, α5 = 0 to 3, α6 = 0. .01 to 3 and α7 = 0 to 4, where α8 is the atomic ratio of oxygen required to satisfy the valence of each element. ].

[2] The method for producing a catalyst according to [1], wherein the pressure is 20 kPa (G) or more.
[3] The method for producing a catalyst according to [2], wherein the pressure is 30 kPa (G) or more and 70 kPa (G) or less.
[4] The method for producing a catalyst according to any one of [1] to [3], wherein the unsaturated aldehyde is acrolein or methacrolein.
[5] The method for producing a catalyst according to any one of [1] to [4], wherein the maximum temperature in the firing is 300 ° C. or higher and 700 ° C. or lower.
[6] The method for producing a catalyst according to [5], wherein the maximum temperature in the firing is 350 ° C. or higher and 400 ° C. or lower.
[7] The method for producing a catalyst according to any one of [1] to [6], wherein the nitrogen-containing component is at least one selected from the group consisting of ammonium roots and nitrate roots.
[8] The method for producing a catalyst according to [1], wherein the catalyst precursor contains a heteropolyacid structure.
[9] The method for producing a catalyst according to [8], wherein the heteropolyacid structure is a kegin-type heteropolyacid structure.

[ 10 ] In the presence of the catalyst produced by the method according to any one of [1] to [9] , unsaturated aldehydes are vapor-phase catalytically oxidized with molecular oxygen to produce unsaturated carboxylic acids. A method for producing an unsaturated carboxylic acid.

[ 11 ] A catalyst is produced by the method according to any one of [1] to [9] , and in the presence of the catalyst, unsaturated aldehyde is vapor-phase catalytically oxidized with molecular oxygen to produce an unsaturated carboxylic acid. A method for producing an unsaturated carboxylic acid.

[ 12 ] A method for producing an unsaturated carboxylic acid ester that esterifies an unsaturated carboxylic acid produced by the method according to [ 10] or [11] .

According to the present invention, it is possible to provide a catalyst capable of producing a target product with a high selectivity.

[Catalyst manufacturing method]
The first embodiment of the method for producing a catalyst according to the present invention is a catalyst containing at least molybdenum and phosphorus, which is used when unsaturated aldehyde is vapor-phase catalytically oxidized with molecular oxygen to produce an unsaturated carboxylic acid. It is a manufacturing method. The method comprises the step of firing a catalyst precursor containing a nitrogen-containing component by exposing it to a pressure exceeding atmospheric pressure.

In addition, in the second embodiment of the method for producing a catalyst according to the present invention, at least one selected from the group consisting of propylene, isobutylene, primary butyl alcohol, tertiary butyl alcohol and methyl tertiary butyl ether is used. It is a method for producing a catalyst containing at least molybdenum and bismuth, which is used in producing unsaturated aldehydes and unsaturated carboxylic acids corresponding to each by vapor-phase catalytic oxidation with molecular oxygen. The method comprises the step of firing a catalyst precursor containing a nitrogen-containing component by exposing it to a pressure exceeding atmospheric pressure.

In the method according to the present invention, attention is paid to the pressure at the time of firing the catalyst precursor, and the catalyst precursor containing a nitrogen-containing component is exposed to a pressure exceeding atmospheric pressure and fired to obtain a target product with a high selectivity. A manufacturable catalyst can be obtained. The reason for this is considered as follows. That is, the structure of the catalyst precursor changes in the process of desorbing the nitrogen-containing component during calcination, and a catalytic active site preferable for the desired reaction is formed. At this time, the catalyst precursor is exposed to a pressure higher than the atmospheric pressure, so that the desorption of the nitrogen-containing component is suppressed. As a result, it is presumed that the structural change of the catalyst occurs at a slower rate than in the case of firing under atmospheric pressure or less, and a homogeneous active site structure is formed on the catalyst surface. In the prior art, the influence of pressure during firing has not been studied in detail.

The method according to the present invention is a catalyst containing at least molybdenum and phosphorus (hereinafter, a catalyst for producing unsaturated carboxylic acid), which is used when unsaturated aldehyde is vapor-phase catalytically oxidized with molecular oxygen to produce unsaturated carboxylic acid. Also shown). By carrying out the reaction using the catalyst, an unsaturated carboxylic acid can be produced with a higher selectivity. It is preferable that the unsaturated aldehyde is acrolein or methacrolein because acrylic acid or methacrylic acid can be produced with a higher selectivity. Further, it is preferable that the catalyst contains a heteropolyacid structure, particularly a kegin-type heteropolyacid structure, because an unsaturated carboxylic acid can be produced with a higher selectivity.

Further, in the method according to the present invention, at least one selected from the group consisting of propylene, isobutylene, primary butyl alcohol, tertiary butyl alcohol and methyl tertiary butyl ether is vapor-phase catalytically oxidized with molecular oxygen. Therefore, it is used in the production of a catalyst containing at least molybdenum and bismuth (hereinafter, also referred to as a catalyst for producing unsaturated aldehyde and unsaturated carboxylic acid), which is used in producing the corresponding unsaturated aldehyde and unsaturated carboxylic acid. Be done. By carrying out the reaction using the catalyst, unsaturated aldehydes and unsaturated carboxylic acids can be produced with higher selectivity. It is preferable that the unsaturated aldehyde is acrolein or methacrolein and the unsaturated carboxylic acid is acrylic acid or methacrylic acid from the viewpoint of selectivity.

The composition of the catalyst obtained by the method according to the present invention is not particularly limited, but when the catalyst is the catalyst for producing unsaturated carboxylic acid, the unsaturated carboxylic acid can be produced with a higher selectivity. The catalyst preferably has a composition represented by the following formula (1).

P _α1 Mo _α2 V _α3 Cu _α4 A _α5 E _α6 G _α7 O _α8 (1)
In formula (1), P, Mo, V, Cu and O are element symbols indicating phosphorus, molybdenum, vanadium, copper and oxygen, respectively. A represents at least one element selected from the group consisting of antimony, bismuth, arsenic, germanium, zirconium, tellurium, silver, selenium, silicon, tungsten and boron. E represents at least one element selected from the group consisting of potassium, rubidium, cesium, thallium, magnesium and barium. G is at least one selected from the group consisting of iron, zinc, chromium, calcium, strontium, tantalum, cobalt, nickel, manganese, titanium, tin, lead, niobium, indium, sulfur, palladium, gallium, cerium and lanthanum. Indicates an element. α1 to α8 represent the atomic ratio of each element, and when α2 = 12, α1 = 0.5 to 3, α3 = 0.01 to 3, α4 = 0.01 to 2, α5 = 0 to 3, preferably 0. .01-3, α6 = 0.01-3, α7 = 0-4, and α8 is the atomic ratio of oxygen required to satisfy the valence of each element.

Further, when the catalyst obtained by the method according to the present invention is the catalyst for producing the unsaturated aldehyde and the unsaturated carboxylic acid, the unsaturated aldehyde and the unsaturated carboxylic acid can be produced with a higher selectivity. The catalyst preferably has a composition represented by the following formula (2).

_{Mo α9 Bi α10 Fe α11 X α12} A 'α13 E' α14 G 'α15 Si α16 O α17 (2)
In formula (2), Mo, Bi, Fe, Si and O are element symbols indicating molybdenum, bismuth, iron, silicon and oxygen, respectively. X represents at least one element selected from the group consisting of cobalt and nickel. A'represents at least one element selected from the group consisting of chromium, lead, manganese, calcium, magnesium, niobium, silver, barium, tin, tantalum and zinc. E'represents at least one element selected from the group consisting of phosphorus, boron, sulfur, selenium, tellurium, cerium, tungsten, antimony and titanium. G'represents at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, cesium and thallium. α9 to α17 represent the atomic ratio of each element, and when α9 = 12, α10 = 0.01-3, α11 = 0.01 to 5, α12 = 1 to 12, α13 = 0 to 8, α14 = 0 to 5. , Α15 = 0.001 to 2, α16 = 0 to 20, and α17 is the atomic ratio of oxygen required to satisfy the valence of each element.

The method for producing a catalyst according to the present invention is not particularly limited as long as it includes a step of exposing a catalyst precursor containing a nitrogen-containing component to a pressure exceeding atmospheric pressure and firing (hereinafter, also referred to as a firing step). However, the method includes a step of preparing a raw material solution containing each element constituting the catalyst (hereinafter, also referred to as a raw material solution preparation step) and a step of drying the raw material solution to obtain a catalyst precursor (hereinafter, a drying step). It is also preferable to include (also shown) and a firing step from the viewpoint of obtaining a catalyst capable of producing the target product with a higher selectivity. Further, the method may include, if necessary, a step of molding the catalyst precursor (hereinafter, also referred to as a molding step) between the drying step and the firing step.

(Ingredient solution preparation process)
In the raw material liquid preparation step, a raw material liquid containing each element constituting the catalyst is prepared. In the production of the unsaturated carboxylic acid production catalyst, the raw material liquid contains at least molybdenum and phosphorus. Further, in the production of the unsaturated aldehyde and unsaturated carboxylic acid production catalyst, the raw material liquid contains at least molybdenum and bismuth. When the raw material liquid contains these elements, a catalyst for producing an unsaturated carboxylic acid having a high selectivity of a target product, or a catalyst for producing an unsaturated aldehyde and an unsaturated carboxylic acid can be produced. Regarding the type and ratio of each element constituting the catalyst, when the catalyst is an unsaturated carboxylic acid production catalyst, for example, the element and atomic ratio represented by the above formula (1) can be used. When the catalyst is a catalyst for producing unsaturated aldehydes and unsaturated carboxylic acids, the element and atomic ratios represented by the formula (2) can be used, for example.

The method for preparing the raw material liquid is not particularly limited, but a method in which the raw materials of each element are added to water, heated to 30 to 100 ° C. and stirred to prepare a slurry-like raw material liquid is preferable. The amount of water used is preferably 200 to 1000 parts by mass with respect to 100 parts by mass in total of the raw materials of each element.

The raw material of each element is not particularly limited, and oxides, nitrates, carbonates, ammonium salts and the like of each element can be appropriately selected and used. For example, as a raw material for molybdenum, molybdic acid, molybdenum trioxide, ammonium paramolybdate and the like can be used, and molybdic acid and molybdenum trioxide are preferable. As a raw material for phosphorus, orthophosphoric acid, phosphorus pentoxide, ammonium phosphate and the like can be used. As a raw material for vanadium, ammonium metavanadate, divanadium pentoxide and the like can be used. Further, as a raw material for copper, copper nitrate, copper sulfate, copper carbonate and the like can be used. Further, as a raw material for bismuth, bismuth nitrate, bismuth oxide, bismuth acetate, bismuth hydroxide and the like can be used. One of these raw materials may be used, or two or more of these raw materials may be used in combination.

In the method according to the present invention, since the catalyst precursor contains a nitrogen-containing component, the raw material liquid preferably contains a nitrogen-containing component. Examples of the nitrogen-containing component include ammonium roots, nitrate roots, nitrogen-containing heterocycles, and the like, and at least one selected from the group consisting of ammonium roots and nitrate roots is the viewpoint of the selectivity of the target product. Is preferable. Here, the ammonium radical in the present invention, ammonia (NH 3) can become an ammonium ion (NH 4 ^_+), and is a generic name of ammonium contained in the ammonium-containing compounds such as ammonium salts. Examples of the ammonium-containing compound include ammonium carbonate, ammonium bicarbonate, ammonium nitrate, ammonium acetate, ammonium vanadate, and ammonium salts of catalyst constituent elements. Further, the nitrate of the present invention, nitrate ions (NO ₃ ^-), nitrite (NO ₂ ^-) is a general term for nitrogen oxide ion such. Examples of the nitrate root include nitrate ions contained in the nitrate of the catalyst constituent element. These may be used alone or in combination of two or more. By using an ammonium salt or a nitrate of each element as a raw material of each element, a nitrogen-containing component may be contained in the raw material liquid.

The preparation scale of the raw material liquid is not particularly limited, but the lower limit of the amount of the raw material of the main element is preferably 100 g or more, and more preferably 1 kg or more. The upper limit is preferably 10 tons or less, and more preferably 1 tons or less. With such a scale, a good raw material liquid can be stably prepared.

(Drying process)
In the drying step, the raw material liquid obtained in the raw material liquid preparation step is dried to obtain a catalyst precursor. The method for drying the raw material liquid is not particularly limited, and examples thereof include an evaporation drying method, a spray drying method, a drum drying method, and an air flow drying method. The type and model of the dryer used for drying, the temperature at the time of drying, the atmosphere, and the like are not particularly limited, and examples thereof include conditions for drying at 100 to 180 ° C. for 0.1 to 20 hours in an air atmosphere. Since physical properties such as fluidity and moldability of the catalyst precursor can be controlled by changing the drying conditions, it is preferable to set the conditions according to the purpose.

When the method according to the present invention is used for producing the catalyst for producing an unsaturated carboxylic acid, the obtained catalyst precursor preferably contains a heteropolyacid structure from the viewpoint of producing an unsaturated carboxylic acid with a higher selectivity. , It is more preferable to contain a kegin-type heteropolyacid structure. Whether or not the catalyst precursor contains a heteropolyacid structure (Kegin-type heteropolyacid structure) can be confirmed by measuring the catalyst precursor by infrared absorption analysis. For example, when the catalyst precursor contains a kegin-type heteropolyacid structure, the obtained infrared absorption spectrum has a characteristic peak near 1060, 960, 870, 780 cm- ¹ .

The amount of the nitrogen-containing component contained in the obtained catalyst precursor is not particularly limited, but can be, for example, 0.5 to 7.0% by mass.

(Molding process)
In the molding step, the catalyst precursor obtained in the drying step is molded. The molding method is not particularly limited, and known dry and wet molding methods can be applied. For example, tableting molding, press molding, extrusion molding, granulation molding and the like can be mentioned. The shape of the molded product is also not particularly limited, and examples thereof include a columnar shape, a ring shape, and a spherical shape. Further, at the time of molding, it is preferable to mold only the catalyst precursor without adding a carrier or the like to the catalyst precursor, but if necessary, a known additive such as graphite or talc may be added.

(Baking process)
In the firing step, the obtained catalyst precursor containing a nitrogen-containing component is exposed to a pressure exceeding atmospheric pressure and fired. The pressure to which the catalyst precursor is exposed is preferably 10 kPa (G) or higher, more preferably 20 kPa (G) or higher, and even more preferably 30 kPa (G) or higher. The pressure is preferably 100 kPa (G) or less, more preferably 80 kPa (G) or less, and even more preferably 70 kPa (G) or less. When the pressure is 10 kPa (G) or more, desorption of nitrogen-containing components is suppressed, and a homogeneous active site structure is formed on the catalyst surface. Further, when the pressure is 100 kPa (G) or less, the desorption of the nitrogen-containing component from the catalyst precursor is not excessively inhibited, and the decrease in the reaction rate of the catalyst can be suppressed. In addition, "kPa (G)" indicates gauge pressure, and atmospheric pressure + gauge pressure is the actual pressure.

The pressure is defined as the pressure from the heating process of the firing step to the constant temperature holding process. Further, the pressure value is a value obtained by measuring an arbitrary point in the container when firing in a container having no spatial distribution of pressure, and is a pressure when firing by flowing gas in a tubular firing container. In a system with a spatial distribution of, it is the value at the lowest part in the system, such as the pressure at the calcined gas outlet. Further, the inside of the system here means a range from the firing gas inlet to the firing gas outlet of the firing container. The method for measuring the pressure in the system is not particularly limited, but for example, it can be measured by providing a pressure gauge upstream of the firing gas outlet and as close as possible to the firing gas outlet. The method of increasing the pressure is not particularly limited, but when firing is performed under gas flow as described later, for example, a pressure control valve is provided at the gas outlet to extend the gas outlet pipe. This can be achieved by closing the valve, connecting the gas outlet to a trap tank filled with water or the like.

The type of atmospheric gas used for firing the catalyst precursor is not particularly limited, but an oxygen-containing gas such as air or an inert gas is preferable. Here, the inert gas refers to a gas that does not reduce the catalytic activity, and examples thereof include nitrogen, carbon dioxide, helium, and argon. As the gas, air, nitrogen, a mixed gas of oxygen and air, or a mixed gas thereof is more preferable, and air is further preferable. Further, the gas may contain water vapor. It is preferable that 0.01 to 5% by volume of water vapor is contained in the entire gas to be circulated, and in particular, the lower limit is 0.05% by volume or more and the upper limit is 2% by volume or less. There is no particular limitation on how to supply the atmospheric gas at the time of firing, and the firing container may be filled with the atmospheric gas and then the container may be closed and fired, and the atmospheric gas is constantly supplied into the firing container. Although it may be fired below, it is preferable to fire it under gas flow from the viewpoint of catalytic activity.

The lower limit of the maximum temperature in the firing is preferably 300 ° C. or higher, more preferably 320 ° C. or higher, further preferably 350 ° C. or higher, and particularly preferably 370 ° C. or higher. The upper limit of the maximum temperature is preferably 700 ° C. or lower, more preferably 450 ° C. or lower, further preferably 400 ° C. or lower, and particularly preferably 390 ° C. or lower. When the firing temperature is 300 ° C. or higher, desorption of nitrogen-containing components is promoted, and when the firing temperature is 700 ° C. or lower, a decrease in specific surface area due to thermal decomposition of the catalyst or sintering can be suppressed. Here, the maximum value of the temperature means the temperature of the portion of the inner wall surface of the firing container in contact with the catalyst precursor, which is the maximum value. The method for measuring the temperature is not particularly limited, but a method using a thermocouple is preferable.

The preferable range of the residual amount of the nitrogen-containing component in the obtained catalyst can be, for example, 0.001 to 1 mmol / g per unit mass of the catalyst, although it depends on the method of using the catalyst and the like.

The shape of the firing container is not particularly limited and may be box-shaped or tubular, but it is particularly preferable to use a tubular firing container having a cross-sectional area of ² to 100 cm ² . When the cross-sectional area is 2 cm ² or more, industrial productivity is improved. Further, when the cross-sectional area is 100 cm ² or less, temperature control becomes easy and the generation of hot spots can be suppressed.

[Method for producing unsaturated carboxylic acid]
In the presence of the catalyst produced by the method according to the present invention, unsaturated aldehyde is vapor-phase catalytically oxidized with molecular oxygen. That is, the method for producing an unsaturated carboxylic acid according to the present invention comprises a step of producing a catalyst by the method according to the present invention and a step of vapor-phase catalytic oxidation of unsaturated aldehyde with molecular oxygen in the presence of the catalyst. Have. By using the catalyst produced by the method according to the present invention, an unsaturated carboxylic acid can be produced with a higher selectivity than before. As the unsaturated aldehyde, acrolein or methacrolein is preferable, and methacrolein is more preferable. Hereinafter, a case where methacrolein is used as the unsaturated aldehyde will be described. In this method, for example, by bringing methacrolein and a raw material gas containing molecular oxygen into contact with a catalyst, methacrolein is vapor-phase contact oxidized by molecular oxygen to obtain methacrylic acid.

The concentration of the raw material compound in the raw material gas is not limited and can be set to any concentration, but 1 to 20% by volume is preferable, the lower limit is 3% by volume or more, and the upper limit is 10% by volume or less. The molecular oxygen concentration in the raw material gas is preferably 0.5 to 4.0 mol with respect to 1 mol of the raw material compound, and particularly preferably the lower limit is 1.0 mol or more and the upper limit is 3.0 mol or less. Further, an inert gas such as nitrogen or carbon dioxide gas may be added to the raw material gas for dilution, or water vapor may be added. The reaction pressure can be set in the range from atmospheric pressure to several hundred kPa (G). From the viewpoint of the yield of the target product, the reaction temperature is preferably 230 to 450 ° C., particularly preferably the lower limit is 250 ° C. or higher and the upper limit is 400 ° C. or lower.

[Method for producing unsaturated aldehydes and unsaturated carboxylic acids]
In the presence of the catalyst produced by the method according to the present invention, at least one selected from the group consisting of propylene, isobutylene, primary butyl alcohol, tertiary butyl alcohol and methyl tertiary butyl ether is prepared by molecular oxygen. Gas-phase contact oxidation. That is, the method for producing an unsaturated aldehyde and an unsaturated carboxylic acid according to the present invention includes a step of producing a catalyst by the method according to the present invention, and in the presence of the catalyst, propylene, isobutylene, primary butyl alcohol, and third. It comprises a step of gas-phase catalytic oxidation of at least one selected from the group consisting of tertiary butyl alcohol and methyl tertiary butyl ether with molecular oxygen. By using the catalyst produced by the method according to the present invention, unsaturated aldehydes and unsaturated carboxylic acids can be produced with higher selectivity than before. The unsaturated aldehyde is preferably acrolein or methacrolein, more preferably methacrolein. The unsaturated carboxylic acid is preferably acrylic acid or methacrylic acid, more preferably methacrylic acid. The conditions of the vapor-phase catalytic oxidation reaction can be the same as the method for producing the unsaturated carboxylic acid.

[Method for producing unsaturated carboxylic acid ester]
The method for producing an unsaturated carboxylic acid ester according to the present invention esterifies the unsaturated carboxylic acid obtained by the method according to the present invention. According to the method, vapor phase catalytic oxidation of unsaturated aldehydes, or at least one vapor phase selected from the group consisting of propylene, isobutylene, primary butyl alcohols, tertiary butyl alcohols and methyl tertiary butyl ethers. An unsaturated carboxylic acid ester can be obtained using the unsaturated carboxylic acid obtained by catalytic oxidation. Examples of the alcohol to react with the unsaturated carboxylic acid include methanol, ethanol, isopropanol, n-butanol, isobutanol and the like. Examples of the obtained unsaturated carboxylic acid ester include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and butyl (meth) acrylate. The reaction can be carried out in the presence of an acidic catalyst such as a sulfonic acid type cation exchange resin. The reaction temperature is preferably 50 to 200 ° C.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. “Parts” in Examples and Comparative Examples means parts by mass. The molar ratio of the catalyst composition was calculated by analyzing the components of the catalyst dissolved in aqueous ammonia by ICP emission spectrometry.

Analysis of the source gas and products in the production of methacrylic acid was performed using gas chromatography. From the results of gas chromatography, the reaction rate of methacrolein and the selectivity of methacrylic acid were determined by the following formulas.

Methacrolein reaction rate (%) = (R / F) x 100
Methacrylic acid selectivity (%) = (P / R) x 100
In the formula, F is the number of moles of methacrolein supplied in a unit time, R is the number of moles of methacrolein reacted in a unit time, and P is the number of moles of methacrylic acid produced in a unit time.

The selectivity of methacrylic acid changes depending on the reaction rate of methacrolein. Therefore, it is preferable that the selectivity of methacrylic acid in the gas-phase catalytic oxidation reaction using each catalyst is compared by aligning the reaction rates of methacrolein to the same value. Therefore, in the following Examples and Comparative Examples, the contact time was changed by appropriately adjusting the amount of the catalyst used in the reaction under a constant reaction gas flow rate, and the reaction rate of methacrolein was adjusted to about 40%. Is shown.

[Example 1]
(1) Raw material solution preparation step 100 parts of molybdenum trioxide, 4.06 parts of ammonium metavanadate, 6.67 parts of 85% by mass phosphoric acid, 0.84 parts of diantimony trioxide and 2.80 parts of copper nitrate in 400 parts of pure water. Added a part. This was stirred to form a slurry, and the obtained slurry was heated at 90 ° C. for 3 hours. While keeping this at 90 ° C., a solution prepared by dissolving 11.3 parts of cesium carbonate in 40.3 parts of pure water was added and held for 30 minutes. Then, a solution prepared by dissolving 8.34 parts of ammonium carbonate in 37.5 parts of pure water was added. Then, the raw material solution was obtained by holding at 90 ° C. for 30 minutes.

(2) Drying Step The obtained raw material liquid was heated at 101 ° C., evaporated and dried while stirring. Then, the obtained solid material was dried at 90 ° C. for 16 hours to obtain a catalyst precursor. The resulting catalyst precursor contained a kegin-type heteropolyacid structure. The oxygen-excluded composition of the catalyst precursor was Mo ₁₂ V _0.6 P _1.0 Sb _0.1 Cu _0.2 Cs _1.2 (NH ₄ ) _3.0 .

(3) Molding Step The obtained catalyst precursor was molded into a ring shape having an outer diameter of 5 mm, an inner diameter of 2 mm, and a length of 5 mm by a tableting molding machine.

(4) Firing step The obtained molded product of the catalyst precursor is filled in a stainless steel pipe having an inner diameter of 27.5 mm and a length of 6 m, and the catalyst precursor is fired at 380 ° C. under air flow at a space velocity of 370 h- ¹ . Obtained a catalyst. At this time, the firing gas outlet was connected to an exhaust gas component trap tank filled with water, and the pressure in the main firing step was set to 64 kPa (G). The holding time at 380 ° C. during firing was set to 16 hours. In firing, the maximum temperature was 380 ° C. From the obtained catalyst, a nitrogen-containing component of 0.001 to 1.0 mmol / g per catalyst unit mass was detected.

The obtained catalyst was filled in a reaction tube, a reaction gas was introduced, and methacrylic acid was produced by vapor phase catalytic oxidation under the following reaction conditions. The results are shown in Table 1.

(Reaction condition)
Reaction gas: Mixed gas of 4% by volume of methacrolein, 10% by volume of oxygen, 15% by volume of water vapor and 71% by volume of nitrogen Reaction temperature: 310 ° C.
Reaction pressure: 101 kPa (G)
Contact time: 1.8 seconds.

[Comparative Example 1]
By reducing the amount of water in the exhaust gas component trap tank connected to the firing gas outlet as compared to Example 1, the pressure in the firing step was set to 0 kPa (G), and the catalyst precursor was fired at 380 ° C. for 12 hours. Except for the above, a catalyst was produced in the same manner as in Example 1. Further, using the obtained catalyst, the reaction was carried out in the same manner as in Example 1 except that the contact time was changed to 1.5 seconds. The results are shown in Table 1.

[Comparative Example 2]
The catalyst was used in the same manner as in Example 1 except that the pressure in the firing step was set to 0 kPa (G) by making the amount of water in the exhaust gas component trap tank connected to the firing gas outlet smaller than that in Example 1. Manufactured. Further, using the obtained catalyst, the reaction was carried out in the same manner as in Example 1 except that the contact time was changed to 1.2 seconds. The results are shown in Table 1.

[Example 2]
A catalyst was produced in the same manner as in Example 1 except that a pressure control valve was provided at the firing gas outlet, the pressure in the firing step was 64 kPa (G), and the catalyst precursor was fired at 382 ° C. for 16 hours. Further, using the obtained catalyst, the reaction was carried out in the same manner as in Example 1 except that the contact time was changed to 1.7 seconds. The results are shown in Table 1.

[Example 3]
By reducing the amount of water in the exhaust gas component trap tank connected to the firing gas outlet as compared to Example 1, the pressure in the firing step was set to 54 kPa (G), and the catalyst precursor was fired at 382 ° C. for 14 hours. Except for the above, a catalyst was produced in the same manner as in Example 1. Further, using the obtained catalyst, the reaction was carried out in the same manner as in Example 1 except that the contact time was changed to 1.7 seconds. The results are shown in Table 1.

[Example 4]
A catalyst was produced in the same manner as in Example 2 except that the pressure in the firing step was set to 10 kPa (G) by the pressure control valve and the catalyst precursor was fired at 380 ° C. for 16 hours. Further, using the obtained catalyst, the reaction was carried out in the same manner as in Example 1 except that the contact time was changed to 1.4 seconds. The results are shown in Table 1.

[Example 5]
A catalyst was produced in the same manner as in Example 4 except that the pressure in the firing step was set to 30 kPa (G) by the pressure control valve. Further, using the obtained catalyst, the reaction was carried out in the same manner as in Example 1 except that the contact time was changed to 1.5 seconds. The results are shown in Table 1.

As shown in Table 1, in Examples 1 to 5 in which the catalyst was produced by the method according to the present invention, methacrylic acid could be produced with a higher selectivity than in Comparative Examples 1 and 2.

Claims (12)

A method for producing a catalyst having a composition represented by the following formula (1), which contains at least molybdenum and phosphorus and is used when unsaturated aldehyde is vapor-phase catalytically oxidized with molecular oxygen to produce an unsaturated carboxylic acid. hand,
A method for producing a catalyst, which comprises a step of exposing a catalyst precursor containing a nitrogen-containing component to a pressure of 10 kPa (G) or more and 80 kPa (G) or less in a gas flow containing an oxygen-containing gas and firing.
P _α1 Mo _α2 V _α3 Cu _α4 A _α5 E _α6 G _α7 O _α8 (1)
[In formula (1), P, Mo, V, Cu and O are element symbols indicating phosphorus, molybdenum, vanadium, copper and oxygen, respectively. A represents at least one element selected from the group consisting of antimony, bismuth, arsenic, germanium, zirconium, tellurium, silver, selenium, silicon, tungsten and boron. E represents at least one element selected from the group consisting of potassium, rubidium, cesium, thallium, magnesium and barium. G is at least one selected from the group consisting of iron, zinc, chromium, calcium, strontium, tantalum, cobalt, nickel, manganese, titanium, tin, lead, niobium, indium, sulfur, palladium, gallium, cerium and lanthanum. Indicates an element. α1 to α8 represent the atomic ratio of each element, and when α2 = 12, α1 = 0.5 to 3, α3 = 0.01 to 3, α4 = 0.01 to 2, α5 = 0 to 3, α6 = 0. .01 to 3 and α7 = 0 to 4, where α8 is the atomic ratio of oxygen required to satisfy the valence of each element. ]. The method for producing a catalyst according to claim 1, wherein the pressure is 20 kPa (G) or more. The method for producing a catalyst according to claim 2, wherein the pressure is 30 kPa (G) or more and 70 kPa (G) or less. The method for producing a catalyst according to any one of claims 1 to 3, wherein the unsaturated aldehyde is acrolein or methacrolein. The method for producing a catalyst according to any one of claims 1 to 4 , wherein the maximum temperature in the firing is 300 ° C. or higher and 700 ° C. or lower. The method for producing a catalyst according to claim 5 , wherein the maximum temperature in the firing is 350 ° C. or higher and 400 ° C. or lower. The method for producing a catalyst according to any one of claims 1 to 6 , wherein the nitrogen-containing component is at least one selected from the group consisting of ammonium roots and nitrate roots. The method for producing a catalyst according to claim 1, wherein the catalyst precursor contains a heteropolyacid structure. The method for producing a catalyst according to claim 8 , wherein the heteropolyacid structure is a kegin-type heteropolyacid structure. An unsaturated carboxylic acid produced by vapor-phase catalytic oxidation of unsaturated aldehyde with molecular oxygen in the presence of a catalyst produced by the method according to any one of claims 1 to 9 . Production method. An unsaturated carboxylic acid is produced by producing a catalyst by the method according to any one of claims 1 to 9 , and vapor-phase catalytic oxidation of unsaturated aldehyde with molecular oxygen in the presence of the catalyst. Method for producing carboxylic acid. A method for producing an unsaturated carboxylic acid ester, which esterifies an unsaturated carboxylic acid produced by the method according to claim 10 or 11 .