JPWO2019013116A1 - Method for producing catalyst, method for producing unsaturated carboxylic acid, method for producing unsaturated aldehyde and unsaturated carboxylic acid, and method for producing unsaturated carboxylic acid ester - Google Patents

Abstract

A catalyst capable of producing a target product with high selectivity is provided. The present invention relates to a method for producing a catalyst containing at least molybdenum and phosphorus, which is used for producing an unsaturated carboxylic acid by subjecting an unsaturated aldehyde to gas-phase catalytic oxidation with molecular oxygen, comprising a catalyst containing a nitrogen-containing component. The present invention relates to a method for producing a catalyst, comprising a step of exposing a precursor to a pressure exceeding atmospheric pressure and calcining the precursor.

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.

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

  As the firing, for example, Patent Documents 1 to 3 describe a gas containing ammonia or 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. I have. Patent Document 6 describes a firing method including a plurality of steps in which the gas used and the firing temperature are changed. Patent Document 7 describes a gas flow rate for a catalyst precursor.

JP-A-58-61833 JP-A-58-67643 JP-A-58-79545 JP-A-59-66349 JP-A-59-69148 JP 2012-245432 A JP 2009-213969 A

  However, the catalysts produced by the methods described in Patent Literatures 1 to 7 are used in a reaction for producing an unsaturated carboxylic acid by subjecting an unsaturated aldehyde to gas-phase catalytic oxidation with molecular oxygen, or propylene, isobutylene, primary Gas phase catalytic oxidation of at least one selected from the group consisting of butyl alcohol, tertiary butyl alcohol and methyl tertiary butyl ether with molecular oxygen to produce the corresponding unsaturated aldehyde and unsaturated carboxylic acid, respectively. When used in such reactions, there is a problem that the selectivity of the target product is not sufficient. Therefore, development of a method for producing a catalyst capable of producing a target product with higher selectivity has been desired. 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 at a high selectivity.

  The object is achieved by the following present inventions [1] to [16].

  [1] A method for producing a catalyst containing at least molybdenum and phosphorus, which is used in producing an unsaturated carboxylic acid by subjecting an unsaturated aldehyde to gas-phase catalytic oxidation with molecular oxygen, comprising a catalyst precursor containing a nitrogen-containing component. A method for producing a catalyst, comprising a step of exposing a body to a pressure exceeding atmospheric pressure and calcining the body.

  [2] At least one selected from the group consisting of propylene, isobutylene, primary butyl alcohol, tertiary butyl alcohol and methyl tertiary butyl ether is subjected to gas-phase catalytic oxidation with molecular oxygen to correspond to each. A method for producing a catalyst containing at least molybdenum and bismuth, which is used when producing unsaturated aldehydes and unsaturated carboxylic acids, wherein a catalyst precursor containing a nitrogen-containing component is exposed to a pressure exceeding atmospheric pressure and calcined. A method for producing a catalyst comprising a step.

  [3] The method for producing a catalyst according to [1] or [2], wherein the unsaturated aldehyde is acrolein or methacrolein.

  [4] The production of the catalyst according to any one of [1] to [3], wherein the catalyst precursor is calcined under at least one kind of gas flow selected from an oxygen-containing gas and an inert gas when calcining the catalyst precursor. Method.

  [5] The method for producing a catalyst according to any one of [1] to [4], wherein the pressure is 10 kPa (G) or more and 100 kPa (G) or less.

  [6] The method for producing a catalyst according to [5], wherein the pressure is 20 kPa (G) or more and 80 kPa (G) or less.

  [7] The method for producing a catalyst according to any one of [1] to [6], wherein the maximum value of the temperature in the calcination is 300 ° C or more and 700 ° C or less.

  [8] The method for producing a catalyst according to [7], wherein the maximum value of the temperature in the calcination is 350 ° C or more and 400 ° C or less.

  [9] The method for producing a catalyst according to any one of [1] to [8], wherein the nitrogen-containing component is at least one selected from the group consisting of ammonium radicals and nitrate radicals.

  [10] The method for producing a catalyst according to [1], wherein the catalyst precursor contains a heteropolyacid structure.

[11] The method for producing a catalyst according to [10], wherein the heteropolyacid structure is a Keggin-type heteropolyacid structure.
[12] A method for producing an unsaturated carboxylic acid, comprising producing an unsaturated carboxylic acid by subjecting an unsaturated aldehyde to gas-phase catalytic oxidation with molecular oxygen in the presence of the catalyst produced by the method according to [1].

[13] Production of an unsaturated carboxylic acid by producing a catalyst by the method according to [1], and producing an unsaturated carboxylic acid by subjecting an unsaturated aldehyde to gas-phase catalytic oxidation with molecular oxygen in the presence of the catalyst. Method.
[14] At least one selected from the group consisting of propylene, isobutylene, primary butyl alcohol, tertiary butyl alcohol, and methyl tertiary butyl ether in the presence of the catalyst produced by the method of [2]. Is produced by gas phase catalytic oxidation with molecular oxygen to produce corresponding unsaturated aldehydes and unsaturated carboxylic acids, respectively.

  [15] A catalyst is produced by the method according to [2], and is selected from the group consisting of propylene, isobutylene, primary butyl alcohol, tertiary butyl alcohol and methyl tertiary butyl ether in the presence of the catalyst. A method for producing an unsaturated aldehyde and an unsaturated carboxylic acid, wherein at least one kind is gaseous catalytically oxidized with molecular oxygen to produce a corresponding unsaturated aldehyde and an unsaturated carboxylic acid.

  [16] A method for producing an unsaturated carboxylic acid ester, wherein the unsaturated carboxylic acid produced by the method according to any one of [12] to [15] is esterified.

  ADVANTAGE OF THE INVENTION According to this invention, the catalyst which can produce a target product with high selectivity can be provided.

[Catalyst production method]
The first embodiment of the method for producing a catalyst according to the present invention is used for producing an unsaturated carboxylic acid by subjecting an unsaturated aldehyde to gas-phase catalytic oxidation with molecular oxygen, and a catalyst containing at least molybdenum and phosphorus. It is a manufacturing method. The method includes a step of exposing a catalyst precursor containing a nitrogen-containing component to a pressure exceeding atmospheric pressure and calcining the catalyst precursor.

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

  In the method according to the present invention, paying attention to the pressure at the time of calcination of the catalyst precursor, the catalyst precursor containing a nitrogen-containing component is calcined by exposing it to a pressure exceeding atmospheric pressure, whereby the target product is produced with a high selectivity. A manufacturable catalyst can be obtained. The reason is considered as follows. That is, the structure of the catalyst precursor changes in the course of the elimination of the nitrogen-containing component during the calcination, and a catalyst active site suitable for the intended reaction is formed. At this time, the desorption of the nitrogen-containing component is suppressed by exposing the catalyst precursor to a pressure higher than the atmospheric pressure. As a result, it is presumed that the structural change of the catalyst occurs at a slower rate than in the case of firing at a pressure lower than the atmospheric pressure, and a more uniform active site structure is formed on the catalyst surface. In addition, in the prior art, the influence of the pressure at the time of firing was not studied in detail.

  The method according to the present invention provides a catalyst containing at least molybdenum and phosphorus (hereinafter referred to as a catalyst for producing unsaturated carboxylic acid), which is used in producing an unsaturated carboxylic acid by subjecting an unsaturated aldehyde to gas-phase catalytic oxidation with molecular oxygen. Also shown). By performing the reaction using the catalyst, an unsaturated carboxylic acid can be produced with a higher selectivity. The unsaturated aldehyde is preferably acrolein or methacrolein because acrylic acid or methacrylic acid can be produced with higher selectivity. Further, the catalyst preferably contains a heteropolyacid structure, particularly a Keggin-type heteropolyacid structure, because an unsaturated carboxylic acid can be produced with a higher selectivity.

  Further, the method according to the present invention comprises subjecting at least one selected from the group consisting of propylene, isobutylene, primary butyl alcohol, tertiary butyl alcohol and methyl tertiary butyl ether to gas phase catalytic oxidation with molecular oxygen. Used for producing a catalyst containing at least molybdenum and bismuth (hereinafter also referred to as a catalyst for producing unsaturated aldehydes and unsaturated carboxylic acids) which is used when producing the corresponding unsaturated aldehydes and unsaturated carboxylic acids. Can be By performing the reaction using the catalyst, unsaturated aldehyde and unsaturated carboxylic acid can be produced with higher selectivity. The unsaturated aldehyde is preferably acrolein or methacrolein, and the unsaturated carboxylic acid is preferably 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.However, when the catalyst is the above-mentioned catalyst for producing an unsaturated carboxylic acid, from the viewpoint of producing an unsaturated carboxylic acid at 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 the 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, and α5 = 0 to 3, preferably 0. .01-3, α6 = 0.01-3, α7 = 0-4, and α8 is the atomic ratio of oxygen necessary 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 unsaturated aldehyde and unsaturated carboxylic acid, from the viewpoint of producing unsaturated aldehyde and unsaturated carboxylic acid with 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 the formula (2), Mo, Bi, Fe, Si and O are element symbols representing 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. When α9 = 12, α10 = 0.01 to 3, α11 = 0.01 to 5, α12 = 1 to 12, α13 = 0 to 8, and α14 = 0 to 5. , Α15 = 0.001-2, α16 = 0-20, and α17 is the atomic ratio of oxygen necessary 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 calcining (hereinafter, also referred to as a calcining step). However, the method includes a step of preparing a raw material liquid containing each element constituting the catalyst (hereinafter, also referred to as a raw material liquid preparing step) and a step of drying the raw material liquid to obtain a catalyst precursor (hereinafter, a drying step) ) And a calcination step are preferred from the viewpoint of obtaining a catalyst that can produce the target product with a higher selectivity. In addition, the method may include a step of forming a catalyst precursor (hereinafter, also referred to as a forming step) between the drying step and the firing step, if necessary.

(Raw material liquid 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 catalyst for producing an unsaturated carboxylic acid, the raw material liquid contains at least molybdenum and phosphorus. In the production of the catalyst for producing unsaturated aldehyde and unsaturated carboxylic acid, 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 or a catalyst for producing an unsaturated aldehyde and an unsaturated carboxylic acid having a high selectivity for a target product can be produced. When the catalyst is a catalyst for producing an unsaturated carboxylic acid, the type and the ratio of each element constituting the catalyst may be, for example, the element and the atomic ratio represented by the formula (1). When the catalyst is a catalyst for producing an unsaturated aldehyde and an unsaturated carboxylic acid, for example, the element and the atomic ratio represented by the formula (2) can be used.

  There is no particular limitation on the method of preparing the raw material liquid, but a method in which the raw material of each element is charged into water, heated to 30 to 100 ° C. and stirred to prepare a raw material liquid in a slurry state is preferable. The amount of water used is preferably 200 to 1000 parts by mass with respect to 100 parts by mass 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, molybdenum, molybdenum trioxide, ammonium paramolybdate, and the like can be used as molybdenum raw materials, and molybdenum acid and molybdenum trioxide are preferable. As a raw material of phosphorus, orthophosphoric acid, phosphorus pentoxide, ammonium phosphate and the like can be used. As a raw material of vanadium, ammonium metavanadate, divanadium pentoxide and the like can be used. In addition, as a raw material of copper, copper nitrate, copper sulfate, copper carbonate and the like can be used. Further, as a raw material of bismuth, bismuth nitrate, bismuth oxide, bismuth acetate, bismuth hydroxide and the like can be used. These materials may be used alone or in combination of two or more.

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 radicals, nitrate radicals, and nitrogen-containing heterocycles. At least one selected from the group consisting of ammonium radicals and nitrate radicals is preferred in view of the selectivity of the target product. Is preferred. Here, the ammonium root in the present invention is a general term for ammonia (NH ₃ ) that can be an ammonium ion (NH ₄ ⁺ ) and ammonium contained in an ammonium-containing compound such as an ammonium salt. Examples of the ammonium-containing compound include ammonium carbonate, ammonium bicarbonate, ammonium nitrate, ammonium acetate, ammonium vanadate, and ammonium salts of catalyst constituent elements. The term “nitrate” in the present invention is a general term for nitrogen oxide ions such as nitrate ion (NO ₃ ⁻ ) and nitrite ion (NO ₂ ⁻ ). Examples of the nitrate include nitrate ions contained in a nitrate of a catalyst constituent element. These may be used alone or in combination of two or more. The raw material liquid may contain a nitrogen-containing component by using an ammonium salt or a nitrate of each element as a raw material for each element.

  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, more preferably 1 kg or more. The upper limit is preferably 10 t or less, more preferably 1 t or less. By using 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 to dryness method, a spray drying method, a drum drying method, and a flash drying method. There is no particular limitation on the type and model of the dryer used for drying, the temperature at the time of drying, the atmosphere, and the like. For example, conditions for drying at 100 to 180 ° C in an air atmosphere for 0.1 to 20 hours can be mentioned. By changing the drying conditions, physical properties such as fluidity and moldability of the catalyst precursor can be controlled. Therefore, it is preferable to set 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. And a Keggin-type heteropolyacid structure. Whether the catalyst precursor contains a heteropolyacid structure (Keggin-type heteropolyacid structure) can be confirmed by measuring the catalyst precursor by infrared absorption analysis. For example, when the catalyst precursor contains a Keggin-type heteropolyacid structure, the obtained infrared absorption spectrum has characteristic peaks around 1060, 960, 870, and 780 cm ^-1 .

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

(Molding process)
In the forming step, the catalyst precursor obtained in the drying step is formed. There is no particular limitation on the molding method, and known dry and wet molding methods can be applied. For example, tablet molding, press molding, extrusion molding, granulation molding and the like can be mentioned. The shape of the molded product is not particularly limited, and examples include a columnar shape, a ring shape, and a spherical shape. In addition, 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. However, if necessary, a known additive such as graphite or talc may be added.

(Firing process)
In the firing step, the catalyst precursor containing the obtained nitrogen-containing component is fired by exposing it to a pressure exceeding atmospheric pressure. The pressure at which the catalyst precursor is exposed is preferably 10 kPa (G) or more, more preferably 20 kPa (G) or more, and even more preferably 30 kPa (G) or more. 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 the nitrogen-containing component is suppressed, and a more uniform active site structure is formed on the catalyst surface. When the pressure is 100 kPa (G) or less, desorption of the nitrogen-containing component from the catalyst precursor is not excessively inhibited, and a reduction in the reaction rate of the catalyst can be suppressed. Note that “kPa (G)” indicates a gauge pressure, and the atmospheric pressure + the gauge pressure is the actual pressure.

  In addition, the pressure is a pressure in a process of maintaining a constant temperature from a temperature increasing process in a firing process. The pressure value is a value obtained by measuring an arbitrary point in the container when firing is performed in a container having no spatial distribution of pressure. In a system having a spatial distribution of 焼 成, the value is at the lowest portion in the system, such as the pressure at the firing gas outlet. The term “in the system” as used herein means a range from the firing gas inlet to the firing gas outlet of the firing vessel. There is no particular limitation on the method of measuring the pressure in the system. For example, the pressure can be measured by providing a pressure gauge upstream of the firing gas outlet and as close as possible to the firing gas outlet. In addition, although there is no particular limitation on the method of increasing the pressure, when firing is performed under gas flow as described below, for example, a gas outlet pipe is extended, and a pressure control valve is provided at the gas outlet. This can be achieved by, for example, squeezing the valve or connecting the gas outlet to a trap tank filled with water or the like.

  There are no particular restrictions on the type of atmosphere gas used for firing the catalyst precursor, but an oxygen-containing gas such as air or an inert gas is preferred. 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 include water vapor. It is preferable that water vapor is contained in an amount of 0.01 to 5% by volume based on the whole gas to be circulated, and it is more preferable that the lower limit is 0.05% by volume or more and the upper limit is 2% by volume or less. The method of supplying the atmosphere gas during firing is not particularly limited, and the firing vessel may be filled with the atmosphere gas, and then the vessel may be sealed and fired. Although calcination may be carried out under a gas flow, calcination under gas flow is preferred from the viewpoint of catalytic activity.

  The lower limit of the maximum value of the firing temperature is preferably 300 ° C. or higher, more preferably 320 ° C. or higher, even more preferably 350 ° C. or higher, and particularly preferably 370 ° C. or higher. The upper limit of the maximum value of the 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 calcination temperature is 300 ° C. or higher, desorption of the nitrogen-containing component is promoted, and when the calcination temperature is 700 ° C. or lower, a decrease in specific surface area due to thermal decomposition and sintering of the catalyst can be suppressed. Here, the maximum value of the temperature refers to the temperature of a portion having the maximum value among the temperatures of the inner wall surface of the firing vessel in contact with the catalyst precursor. 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 is 0.001 to 1 mmol / g per unit mass of the catalyst, depending on the usage of the catalyst and the like.

The shape of the firing vessel is not particularly limited, and may be box-shaped or tubular. It is particularly preferable to use a tubular firing vessel 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 generation of hot spots can be suppressed.

[Method for producing unsaturated carboxylic acid]
The unsaturated aldehyde is subjected to gas-phase catalytic oxidation with molecular oxygen in the presence of the catalyst produced by the method according to the present invention. That is, the method for producing an unsaturated carboxylic acid according to the present invention includes a step of producing a catalyst by the method of the present invention and a step of subjecting an unsaturated aldehyde to gas-phase catalytic oxidation 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 preferred, and methacrolein is more preferred. Hereinafter, the case where methacrolein is used as the unsaturated aldehyde will be described. In this method, for example, by bringing a raw material gas containing methacrolein and molecular oxygen into contact with a catalyst, methacrolein is oxidized in a gas phase with 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 an arbitrary concentration. The molecular oxygen concentration in the source gas is preferably from 0.5 to 4.0 mol per 1 mol of the source 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 may be added to the source gas for dilution, or steam may be added. The reaction pressure can be set within a range from atmospheric pressure to several hundred kPa (G). The reaction temperature is preferably 230 to 450 ° C from the viewpoint of the yield of the target product, and the lower limit is more preferably 250 ° C or higher, and the upper limit is more preferably 400 ° C or lower.

[Method for producing unsaturated aldehyde and unsaturated carboxylic acid]
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 reacted with molecular oxygen. Performs gas phase catalytic oxidation. That is, the method for producing an unsaturated aldehyde and 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 propylene, isobutylene, primary butyl alcohol, Subjecting at least one selected from the group consisting of tert-butyl alcohol and methyl tertiary butyl ether to gas-phase catalytic oxidation 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 for the gas phase catalytic oxidation reaction can be the same as those for the method for producing an unsaturated carboxylic acid.

[Method for producing unsaturated carboxylic acid ester]
In the method for producing an unsaturated carboxylic acid ester according to the present invention, the unsaturated carboxylic acid obtained by the method according to the present invention is esterified. According to the method, gas phase catalytic oxidation of unsaturated aldehyde or at least one gas phase selected from the group consisting of propylene, isobutylene, primary butyl alcohol, tertiary butyl alcohol and methyl tertiary butyl ether An unsaturated carboxylic acid ester can be obtained using an unsaturated carboxylic acid obtained by catalytic oxidation. Examples of the alcohol to be reacted with the unsaturated carboxylic acid include methanol, ethanol, isopropanol, n-butanol and isobutanol. 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 performed in the presence of an acidic catalyst such as a sulfonic acid type cation exchange resin. The reaction temperature is preferably from 50 to 200C.

  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 a component obtained by dissolving the catalyst in aqueous ammonia by ICP emission spectrometry.

  The analysis of the raw material gas and the product 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 equations.

Conversion of methacrolein (%) = (R / F) × 100
Methacrylic acid selectivity (%) = (P / R) × 100
In the formula, F is the number of moles of methacrolein supplied per unit time, R is the number of moles of methacrolein reacted per unit time, and P is the number of moles of methacrylic acid generated per unit time.

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

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

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

(3) Forming Step The obtained catalyst precursor was formed 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 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 an air flow at a space velocity of 370 h ^-1 . A catalyst was obtained. 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 16 hours. In the firing, the maximum value of the temperature was 380 ° C. From the obtained catalyst, 0.001 to 1.0 mmol / g of a nitrogen-containing component per unit mass of the catalyst was detected.

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

(Reaction conditions)
Reaction gas: mixed gas of 4% by volume of methacrolein, 10% by volume of oxygen, 15% by volume of steam 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 from that in 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. The reaction was carried out in the same manner as in Example 1 except that the obtained catalyst was used and the contact time was changed to 1.5 seconds. Table 1 shows the results.

[Comparative Example 2]
The catalyst was prepared in the same manner as in Example 1 except that the pressure in the firing step was set to 0 kPa (G) by reducing the amount of water in the exhaust gas component trap tank connected to the firing gas outlet from that in Example 1. Manufactured. The reaction was carried out in the same manner as in Example 1 except that the obtained catalyst was used and the contact time was changed to 1.2 seconds. Table 1 shows the results.

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

[Example 3]
By reducing the amount of water in the exhaust gas component trap tank connected to the firing gas outlet from that in 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. The reaction was carried out in the same manner as in Example 1 except that the obtained catalyst was used and the contact time was changed to 1.7 seconds. Table 1 shows the results.

[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 a pressure control valve and the catalyst precursor was fired at 380 ° C for 16 hours. The reaction was carried out in the same manner as in Example 1 except that the obtained catalyst was used and the contact time was changed to 1.4 seconds. Table 1 shows the results.

[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 a pressure control valve. The reaction was carried out in the same manner as in Example 1 except that the obtained catalyst was used and the contact time was changed to 1.5 seconds. Table 1 shows the results.

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

Claims (16)

A method for producing a catalyst containing at least molybdenum and phosphorus, which is used for producing an unsaturated carboxylic acid by subjecting an unsaturated aldehyde to gas-phase catalytic oxidation with molecular oxygen,
A method for producing a catalyst, comprising a step of exposing a catalyst precursor containing a nitrogen-containing component to a pressure exceeding atmospheric pressure and calcining it. At least one selected from the group consisting of propylene, isobutylene, primary butyl alcohol, tertiary butyl alcohol, and methyl tertiary butyl ether is subjected to gas-phase catalytic oxidation with molecular oxygen to form a corresponding unsaturated aldehyde. And a method for producing a catalyst containing at least molybdenum and bismuth, which is used when producing an unsaturated carboxylic acid,
A method for producing a catalyst, comprising a step of exposing a catalyst precursor containing a nitrogen-containing component to a pressure exceeding atmospheric pressure and calcining the catalyst precursor.   3. The method according to claim 1, wherein the unsaturated aldehyde is acrolein or methacrolein.   The method for producing a catalyst according to any one of claims 1 to 3, wherein when the catalyst precursor is fired, the catalyst precursor is fired under at least one kind of gas flow selected from an oxygen-containing gas and an inert gas.   The method for producing a catalyst according to any one of claims 1 to 4, wherein the pressure is 10 kPa (G) or more and 100 kPa (G) or less.   The method for producing a catalyst according to claim 5, wherein the pressure is 20 kPa (G) or more and 80 kPa (G) or less.   The method for producing a catalyst according to any one of claims 1 to 6, wherein a maximum value of the temperature in the calcination is 300 ° C or more and 700 ° C or less.   The method for producing a catalyst according to claim 7, wherein the maximum value of the temperature in the calcination is 350 ° C or more and 400 ° C or less.   The method for producing a catalyst according to any one of claims 1 to 8, wherein the nitrogen-containing component is at least one selected from the group consisting of ammonium radicals and nitrate radicals.   The method for producing a catalyst according to claim 1, wherein the catalyst precursor has a heteropolyacid structure.   The method for producing a catalyst according to claim 10, wherein the heteropolyacid structure is a Keggin-type heteropolyacid structure.   A method for producing an unsaturated carboxylic acid, comprising producing an unsaturated carboxylic acid by subjecting an unsaturated aldehyde to gas-phase catalytic oxidation with molecular oxygen in the presence of the catalyst produced by the method according to claim 1.   A method for producing an unsaturated carboxylic acid, comprising producing a catalyst by the method according to claim 1, and producing an unsaturated carboxylic acid by subjecting an unsaturated aldehyde to gas-phase catalytic oxidation with molecular oxygen in the presence of the catalyst.   At least one selected from the group consisting of propylene, isobutylene, primary butyl alcohol, tertiary butyl alcohol and methyl tertiary butyl ether in the presence of a catalyst produced by the method of claim 2 A method for producing an unsaturated aldehyde and an unsaturated carboxylic acid, wherein a gas-phase catalytic oxidation with oxygen is performed to produce a corresponding unsaturated aldehyde and an unsaturated carboxylic acid.   A catalyst is produced by the method according to claim 2, and at least one selected from the group consisting of propylene, isobutylene, primary butyl alcohol, tertiary butyl alcohol and methyl tertiary butyl ether in the presence of the catalyst. Is produced by gas phase catalytic oxidation with molecular oxygen to produce corresponding unsaturated aldehydes and unsaturated carboxylic acids, respectively.   A method for producing an unsaturated carboxylic acid ester by esterifying the unsaturated carboxylic acid produced by the method according to any one of claims 12 to 15.