JP5149138B2 - Method for producing catalyst for synthesis of unsaturated carboxylic acid - Google Patents

Description

  The present invention relates to a method for producing an unsaturated carboxylic acid synthesis catalyst, and more particularly, to a methacrylic acid synthesis catalyst used for producing methacrylic acid by vapor-phase catalytic oxidation of methacrolein with molecular oxygen. Suitable for manufacturing method.

  As a catalyst for producing methacrylic acid by using methacrolein as an unsaturated aldehyde and gas-phase catalytic oxidation with molecular oxygen to produce methacrylic acid, those mainly composed of heteropolyacids such as molybdophosphoric acid and molybdophosphate or salts thereof are available. Are known.

  Numerous studies have been made on methods for producing these catalysts, and many of them first prepare a raw material liquid containing raw materials for each element constituting the catalyst, and then produce the catalyst by drying and firing it. doing.

  This raw material liquid is usually an aqueous slurry. The solid content contained in the slurry is a complex salt or a mixture of an alkali metal salt of a heteropoly acid and an ammonium salt, nitrogen-containing organic compound salt, or the like of the heteropoly acid. Among these, ammonium salts of heteropolyacids and nitrogen-containing organic compound salts are mostly decomposed by firing to become heteropolyacids, so the final main component of the catalyst is a composite of an alkali metal salt of a heteropolyacid and a heteropolyacid. It becomes a thing.

Nitrate is often used as the catalyst raw material. However, it is already known that nitrates, when mixed with ammonium roots, can have an undesirable effect when the catalyst is calcined. Patent Document 1 discloses the use of ammonium and sulfate radicals in order to adjust the pH to a range of 3 to 9, but one of the reasons is to avoid the mixing of nitrate and ammonium roots. The reduction of adverse effects during firing is mentioned. Moreover, in patent document 2, the catalyst is prepared on condition that the raw material containing a nitrate radical is not used at all, and the process of making the heteropolyacid salt of P: Mo = 1: 9 is included.
Japanese Patent Laid-Open No. 6-86933 JP 59-12758 A

  However, the catalyst obtained by the prior art is not sufficient in the selectivity and yield of unsaturated carboxylic acid, and the present situation is that further improvement is desired as an industrial catalyst.

  Nitrate is often used as a catalyst raw material in order to form a favorable chemical structure by adjusting pH fluctuation behavior. However, as described above, the nitrate radical may adversely affect the catalytic activity during calcination. It is possible to substitute nitrates with sulfates and carbonates, but sulfates and carbonates may also adversely affect catalyst activity during firing. That is, it is preferable not to include all of the nitrate, carbonate, and sulfate groups, but on the other hand, the conventional method of adding raw materials that do not include these is a problem in which a favorable chemical structure is not formed due to unfavorable pH fluctuation behavior. was there.

  An object of the present invention is to provide a method for producing an unsaturated carboxylic acid synthesis catalyst capable of synthesizing an unsaturated carboxylic acid with high selectivity and yield in the synthesis of an unsaturated carboxylic acid such as methacrylic acid and acrylic acid. To do.

The method for producing an unsaturated carboxylic acid synthesis catalyst of the present invention comprises phosphorous and molybdenum, potassium, rubidium, used when synthesizing an unsaturated carboxylic acid by vapor-phase catalytic oxidation of an unsaturated aldehyde with molecular oxygen. A method for producing an unsaturated carboxylic acid synthesis catalyst comprising at least one element of cesium and optionally containing at least one element of arsenic, antimony and tellurium,
Preparing an aqueous slurry or aqueous solution a containing a raw material of molybdenum;
Preparing an aqueous solution A containing a raw material of at least one element of potassium, rubidium and cesium and a raw material of at least one element of phosphorus, arsenic, antimony and tellurium;
Mixing the aqueous slurry or aqueous solution a and the aqueous solution A to prepare an aqueous slurry or aqueous solution b;
Preparing an aqueous solution B containing a raw material of ammonium ions and a raw material of at least one element of phosphorus, arsenic, antimony and tellurium;
Mixing the aqueous slurry or aqueous solution b and the aqueous solution B, preparing a raw material mixture in which all catalyst raw materials are charged, and drying the raw material mixture to obtain a catalyst precursor;
A step of firing the catalyst precursor and satisfying all of the following conditions (1) to (3).
(1) The pH of the raw material mixture is less than 3.
(2) The concentrations of nitrate radical, carbonate radical and sulfate radical in the raw material mixture are all 0.01 mol / l or less.
(3) The aqueous solution B contains phosphorus, arsenic, antimony, and tellurium in a molar equivalent of 0.1 to 10 times the molar equivalent of ammonium ions.

  The catalyst for synthesizing unsaturated carboxylic acid of the present invention is produced by the above production method.

  The method for producing an unsaturated carboxylic acid according to the present invention is characterized in that an unsaturated aldehyde is synthesized by vapor-phase catalytic oxidation of an unsaturated aldehyde with molecular oxygen using the unsaturated carboxylic acid synthesis catalyst described above. To do.

  ADVANTAGE OF THE INVENTION According to this invention, in the synthesis | combination of unsaturated carboxylic acids, such as methacrylic acid and acrylic acid, the manufacturing method of the catalyst for unsaturated carboxylic acid synthesis | combination with a high selectivity and yield of unsaturated carboxylic acid can be provided.

  Hereinafter, the present invention will be described in detail.

  The unsaturated carboxylic acid referred to in the present invention is, for example, an α, β-unsaturated carboxylic acid such as methacrylic acid or acrylic acid, and the unsaturated aldehyde is, for example, an α, β-unsaturated such as methacrolein or acrolein. It is a saturated aldehyde and is an unsaturated aldehyde corresponding to an unsaturated carboxylic acid.

[Production Method of Unsaturated Carboxylic Acid Synthesis Catalyst]
The method for producing an unsaturated carboxylic acid synthesis catalyst of the present invention comprises phosphorous and molybdenum, potassium, rubidium, used when synthesizing an unsaturated carboxylic acid by vapor-phase catalytic oxidation of an unsaturated aldehyde with molecular oxygen. A method for producing an unsaturated carboxylic acid synthesis catalyst comprising at least one element of cesium and optionally containing at least one element of arsenic, antimony and tellurium,
Preparing an aqueous slurry or aqueous solution a containing a raw material of molybdenum;
Preparing an aqueous solution A containing a raw material of at least one element of potassium, rubidium and cesium and a raw material of at least one element of phosphorus, arsenic, antimony and tellurium;
Mixing the aqueous slurry or aqueous solution a and the aqueous solution A to prepare an aqueous slurry or aqueous solution b;
Preparing an aqueous solution B containing a raw material of ammonium ions and a raw material of at least one element of phosphorus, arsenic, antimony and tellurium;
Mixing the aqueous slurry or aqueous solution b and the aqueous solution B, preparing a raw material mixture in which all catalyst raw materials are charged, and drying the raw material mixture to obtain a catalyst precursor;
A step of firing the catalyst precursor and satisfying all of the following conditions (1) to (3).
(1) The pH of the raw material mixture is less than 3.
(2) The concentrations of nitrate radical, carbonate radical and sulfate radical in the raw material mixture are all 0.01 mol / l or less.
(3) The aqueous solution B contains phosphorus, arsenic, antimony, and tellurium in a molar equivalent of 0.1 to 10 times the molar equivalent of ammonium ions.

  The unsaturated carboxylic acid synthesis catalyst produced by the production method of the present invention is preferably a catalyst represented by the following formula (I).

_{P a Mo b V c Cu d} X e Y f Z g O h (I)
(In the formula (I), P, Mo, V, Cu and O are element symbols indicating phosphorus, molybdenum, vanadium, copper and oxygen, respectively. X is at least one element of arsenic, tellurium and antimony. And Y may contain at least one element selected from the group consisting of bismuth, zirconium, silver, iron, zinc, chromium, magnesium, cobalt, manganese, barium, cerium and lanthanum. Z represents at least one element selected from the group consisting of potassium, rubidium and cesium, a to h represent the atomic ratio of each element, and when b = 12, a = 0.5 to 3, c = 0.01 to 3, d = 0.01 to 2, e = 0.01 to 3, f = 0 to 3, g = 0.01 to 3, h satisfies the valence of each component. Oxygen needed to do It is an atomic ratio).

  The method for producing an unsaturated carboxylic acid synthesis catalyst of the present invention can be generally used for producing an unsaturated carboxylic acid synthesis catalyst. In particular, it is suitable for a method for producing a catalyst for synthesizing methacrylic acid used when producing methacrylic acid by vapor phase catalytic oxidation of methacrolein with molecular oxygen.

  Details of each step in the method for producing an unsaturated carboxylic acid synthesis catalyst of the present invention will be described below.

  First, a catalyst raw material is mixed in water to prepare a raw material mixture. As a catalyst raw material, a raw material of each element constituting the catalyst (excluding hydrogen, nitrogen and oxygen) is used.

  As raw materials for each element, oxides, hydroxides, ammonium salts and the like of each element can be appropriately selected and used. As a raw material of molybdenum, molybdic acid, molybdenum trioxide, ammonium molybdate and the like can be used, but molybdic acid and molybdenum trioxide not containing ammonium ions are preferable. As a raw material of phosphorus, phosphoric acid, phosphorus pentoxide, ammonium phosphate, copper phosphate, or the like can be used. As a raw material for arsenic, arsenic acid, arsenous acid or the like can be used. As the raw material of antimony, antimony trioxide, ammonium antimonate and the like can be used. As a raw material for tellurium, tellurium trioxide, ammonium tellurate and the like can be used. As a raw material of vanadium, ammonium metavanadate, divanadium pentoxide, or the like can be used. As a raw material for copper, copper phosphate, copper hydroxide and the like can be used. Copper phosphate can also be used as a raw material for phosphorus.

  These hydroxides are preferred as raw materials for potassium, rubidium and cesium. In addition, phosphates, carboxylates and the like can also be used. Phosphate can also be used as a raw material for phosphorus. However, the raw materials of potassium, rubidium and cesium are mixed in advance with raw materials of at least one element of phosphorus, arsenic, antimony and tellurium. Therefore, especially when mixing with phosphoric acid or arsenic acid is used, carbonates and bicarbonates can be used in advance, so carbonates and bicarbonates can also be used. There is.

  In addition to the raw materials for each of these main elements, ammonium ions are required for the catalyst production method of the present invention. As a raw material for ammonium ions, aqueous ammonia is preferable. In addition to inorganic acid ammonium salts such as ammonium phosphate, ammonium arsenate, ammonium antimonate and ammonium tellurate, ammonium carboxylates such as ammonium acetate and diammonium oxalate can also be used. However, ammonium ions are mixed in advance with a raw material of at least one element of phosphorus, arsenic, antimony and tellurium. Therefore, especially when mixing with phosphoric acid and arsenic acid is premised, carbonate radicals can be removed in advance using ammonium carbonate or ammonium bicarbonate, so ammonium carbonate or ammonium bicarbonate can also be used. There is.

  In the present invention, first, an aqueous slurry or an aqueous solution a is prepared by adding a molybdenum raw material to water among the catalyst raw materials. It is not necessary to add all of the molybdenum raw material at this stage, and it is possible to add it in divided portions before adding the whole amount of ammonium ions.

  Moreover, the raw material of phosphorus, arsenic, and tellurium can also be added to the aqueous slurry or aqueous solution a. The total amount of phosphorus, arsenic and tellurium contained in the aqueous slurry or aqueous solution a is preferably 0.1 equivalent or more and 1 equivalent or less when the molar equivalent of all molybdenum used for catalyst preparation is 12. In addition, when using the raw material of antimony, it is preferable not to add the raw material of antimony at this stage but to add it together with the raw materials of potassium, rubidium and cesium, or after that. In addition, the amount of potassium, rubidium, cesium and ammonium ions is preferably smaller at this stage, and the total amount of potassium, rubidium, cesium and ammonium ions contained in the aqueous slurry or aqueous solution a is based on the total molybdenum used in the catalyst preparation. When the molar equivalent is 12, it is preferably 1 equivalent or less. Raw materials such as vanadium, bismuth, zirconium, silver, iron, zinc, chromium, magnesium, cobalt, manganese, barium, cerium, and lanthanum may be added at this stage or at a later stage.

  The aqueous slurry or aqueous solution a is preferably prepared by heating and stirring at 30 to 100 ° C. As for the usage-amount of water, 200-1000 mass parts is preferable with respect to a total of 100 mass parts of the molybdenum raw material used for catalyst preparation.

  On the other hand, an aqueous solution A containing a raw material of at least one element of potassium, rubidium and cesium and a raw material of at least one element of phosphorus, arsenic, antimony and tellurium is prepared. The total amount of phosphorus, arsenic, antimony and tellurium contained in this aqueous solution A is 0.1 to 10 times the molar equivalent of the total molar equivalent of potassium, rubidium and cesium contained in this aqueous solution A. It is more preferable that the molar equivalent is 0.2 times or more and 1 time or less.

  Next, the aqueous slurry or aqueous solution a and the aqueous solution A are mixed to prepare an aqueous slurry or aqueous solution b. Although there is no restriction | limiting in particular in a mixing method, It is preferable that the temperature at the time of mixing is 0 to 50 degreeC, and it is more preferable that it is 10 to 30 degreeC. When the above mixed solution is not used as the aqueous solution A, when the aqueous solution A is added to the aqueous slurry or aqueous solution a, the concentration of potassium, rubidium or cesium is high in the local area where the aqueous solution A contacts the aqueous slurry or aqueous solution a. This results in an excessive pH increase and an undesirable chemical structure. By using the above mixed solution as the aqueous solution A, this increase in local pH can be suppressed without adding nitrate, carbonate, and sulfate radicals.

  Next, an aqueous solution B containing an ammonium ion raw material and a raw material of at least one element of phosphorus, arsenic, antimony, and tellurium is prepared. It is essential that the total amount of phosphorus, arsenic, antimony and tellurium contained in this aqueous solution B is a molar equivalent of 0.1 to 10 times the molar equivalent of ammonium contained in this aqueous solution B, The molar equivalent is 0.2 times or more and 1 time or less.

However, the number of molar equivalents of all ammonium ions used for catalyst preparation is preferably 0.5 or more and 6 or less with respect to 12 molar equivalents of all molybdenum used for catalyst preparation. If the number of molar equivalents of ammonium ions is too small, a crystal structure that adversely affects catalyst performance may be generated. Further, if the number of molar equivalents of ammonium ions increases too much, the final pH of the slurry or aqueous solution becomes as high as 3 or more, and part of the Keggin structure collapses, for example, the Dawson structure that has a ratio of P ₂ Mo ₁₈ Therefore, a preferable chemical structure may not be obtained.

  Next, the aqueous slurry or aqueous solution b and aqueous solution B are mixed. Although there is no restriction | limiting in particular in a mixing method, It is preferable that the temperature at the time of mixing is 0 to 50 degreeC, and it is more preferable that it is 10 to 30 degreeC. When the mixed solution as described above is not used as the aqueous solution B, when the aqueous solution B is added to the aqueous slurry or the aqueous solution b, the concentration of ammonium ions becomes too high in the local area where the aqueous solution B contacts the aqueous slurry or the aqueous solution b. An increase in pH occurs and an undesirable chemical structure is generated. By using the above mixed solution as the aqueous solution B, this increase in local pH can be suppressed without adding nitrate, carbonate, and sulfate radicals.

This effect occurs by the same mechanism as in the case of the aqueous solution A, but the aqueous solution B plays a more important role than the aqueous solution A. When the above mixed solution is not used for the aqueous solution B, even if the pH of the whole slurry is less than 3, a part of the Keggin structure is broken, and for example, a Dawson structure having a ratio of P ₂ Mo ₁₈ is formed, which is preferable. The chemical structure cannot be obtained.

  Then, the remaining catalyst raw materials are mixed to prepare a raw material mixed solution in which all the catalyst raw materials are charged. In addition, before mixing the aqueous solution B, it is preferable that the other remaining raw materials are put into the aqueous slurry or the aqueous solution b.

  The pH of the raw material mixture needs to be less than 3. Since the Keggin structure is maintained when the pH of the raw material mixture is less than 3, the lower the pH, the better. On the other hand, since it is preferable that there are many ammonium ions, the pH of a raw material liquid mixture becomes a preferable area | region substantially 1 or more and 2.8 or less.

  In the catalyst preparation method in which the pH of the raw material mixture is less than 3, it has been conventionally considered that at least a part of phosphorus, which is an essential component, must be initially introduced. However, prior to the present invention, the timing of the addition of phosphorus, which is an essential component of the catalyst, is not important because it is not important, and it can be added at any timing in the raw material mixture preparation process without adversely affecting the catalyst performance. I found it.

  The gist of the present invention is to eliminate nitrate, carbonate and sulfate radicals as much as possible, and to suppress an increase in local pH when adding aqueous solution B (and aqueous solution A). For this purpose, phosphorus, which is essential and has a relatively large amount of added catalyst, is most easily used, but at least part of it can be replaced with arsenic, antimony and tellurium.

  Although there is no restriction | limiting in particular in the preparation scale of a raw material liquid mixture, From a viewpoint which can prepare a raw material liquid mixture stably, as the usage-amount of a molybdenum raw material, 100g-10t are preferable and 1kg-1t are more preferable.

  The raw material mixture thus obtained is dried at less than 300 ° C. to prepare a catalyst precursor. Although there is no restriction | limiting in particular in the specific method of a drying process, For example, the evaporative drying method, the spray drying method, the drum drying method, the airflow drying method etc. are mentioned.

  There is no restriction | limiting in particular in the kind of drying machine used for drying, a model, the temperature at the time of drying, atmosphere, etc. For example, the conditions etc. which dry at 100-180 degreeC by air atmosphere for 0.1 to 20 hours are mentioned. However, since the physical properties such as fluidity and moldability of the catalyst precursor can be controlled by changing the drying conditions, it is preferable to set conditions according to the purpose.

  Moreover, you may implement the shaping | molding process which shape | molds a catalyst precursor as needed after a drying process and before the baking process mentioned later. There is no restriction | limiting in particular in a shaping | molding method, A well-known dry type and wet shaping | molding method can be applied, For example, tableting shaping | molding, press molding, extrusion molding, granulation shaping | molding etc. are mentioned. The shape of the molded product is 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 a known additive such as graphite or talc may be added as necessary.

  Next, a firing process is performed in which the catalyst precursor is fired at a temperature of 300 ° C. or higher.

  Although there is no restriction | limiting in particular in the gas component distribute | circulated at a baking process, It is preferable to bake in oxygen-containing gas circulation, such as air, or inert gas circulation. Here, the inert gas refers to a gas that does not decrease the catalytic activity, and examples thereof include nitrogen, carbon dioxide gas, helium, and argon.

The shape of the firing container is not particularly limited, but it is preferable to use a tubular firing container having a cross-sectional area of 2 cm ² or more and 100 cm ² or less. Industrial productivity is improved by using a tubular firing container having a cross-sectional area of 2 cm ² or more. Further, by using a tubular firing container having a cross-sectional area of 100 cm ² or less, temperature control becomes easy and hot spots are less likely to occur during firing.

  The firing temperature may be selected from a temperature range of 300 ° C. or higher, and the maximum temperature is preferably 320 ° C. or higher. Moreover, 700 degreeC or less is preferable and the maximum temperature of a calcination temperature has more preferable 450 degreeC or less.

  Through the above-described steps, the unsaturated carboxylic acid synthesis catalyst of the present invention can be obtained.

[Method for producing unsaturated carboxylic acid]
Using the unsaturated carboxylic acid synthesis catalyst produced by the above production method, an unsaturated aldehyde is synthesized by vapor-phase catalytic oxidation of the unsaturated aldehyde with molecular oxygen. For example, by bringing a raw material gas containing methacrolein and molecular oxygen into contact with an unsaturated carboxylic acid synthesis catalyst, methacrolein is vapor-phase contact oxidized with molecular oxygen to obtain methacrylic acid.

  The reaction conditions for producing methacrylic acid using methacrolein as an unsaturated aldehyde are shown below.

  There is no restriction | limiting in the methacrolein density | concentration in source gas, Although it can set to arbitrary density | concentrations, 1-20 volume% is suitable, and 3-10 volume% is especially preferable.

  The molecular oxygen concentration in the raw material gas is preferably 0.5 to 4 mol, more preferably 1 to 3 mol, relative to 1 mol of methacrolein.

  In addition, an inert gas such as nitrogen or carbon dioxide may be added to the raw material gas for dilution, or water vapor may be added.

  The reaction pressure is usually set within a range from normal pressure (0 kPa-G; hereinafter, reaction pressure is expressed in gauge pressure) to 1000 kPa.

  The reaction temperature is usually set within the range of 230 to 450 ° C, and is preferably 250 to 400 ° C from the viewpoint of the yield of methacrylic acid.

  EXAMPLES Hereinafter, although an Example is given and this invention is concretely demonstrated about an oxidation of methacrolein, this invention is not limited to these Examples.

  Further, “parts” in the following examples and comparative examples are parts by mass. The composition of the catalyst was determined using ICP emission analysis and atomic absorption analysis.

  The analysis of the raw material gas and the product was performed using gas chromatography. In addition, the reaction rate of methacrolein, the selectivity of the methacrylic acid to produce | generate, and a single flow yield are defined as follows.

Reaction rate of methacrolein (%) = (B / A) × 100
Methacrylic acid selectivity (%) = (C / B) × 100
Single flow yield (%) of methacrylic acid = (C / A) × 100.

  Here, A is the number of moles of methacrolein supplied, B is the number of moles of reacted methacrolein, and C is the number of moles of methacrylic acid produced.

[Example 1]
To 600 parts of pure water, 100 parts of molybdenum trioxide, 3.16 parts of divanadium pentoxide, 6.85 parts of 60% by mass aqueous arsenic acid solution and 2.75 parts of 80% by mass copper phosphate aqueous solution were added, The mixture was stirred for 5 hours under reflux to obtain an aqueous slurry a. The total amount of phosphorus and arsenic contained in the aqueous slurry a is 0.6 equivalent when the molar equivalent of all molybdenum used for catalyst preparation is 12.

  An aqueous solution A was prepared by dissolving 10.11 parts of cesium bicarbonate in 30 parts of pure water, adding 2.00 parts of 85 mass% phosphoric acid aqueous solution, and heating to 50 ° C. for 1 hour to vaporize carbonate ions. The amount of phosphorus contained in the aqueous solution A is 0.33 times the molar equivalent of the cesium molar equivalent contained in the aqueous solution A.

  The aqueous solution A and the aqueous slurry a were both cooled to 25 ° C., and the aqueous solution A was added to the aqueous slurry a to obtain an aqueous slurry b.

  After adding 3.34 parts of 85 mass% phosphoric acid aqueous solution to 30 parts of pure water, it cooled to 5 degreeC, 14.06 parts of 14 mass% ammonia water was added little by little, and the aqueous solution B was prepared. Note that the amount of phosphorus contained in the aqueous solution B is 0.25 times the molar equivalent of the ammonium ion contained in the aqueous solution B.

  The aqueous solution B was added to the aqueous slurry b (25 ° C.) to obtain a raw material mixture. When a part of the raw material mixture was collected and analyzed by ion chromatography, nitrate, carbonate and sulfate radicals were not detected, and it was confirmed that the content was 0.01 mol / l or less. Moreover, pH was 2.1 and it confirmed that it was less than 3.

  This raw material mixture was heated to 101 ° C., evaporated to dryness with stirring, and further dried at 130 ° C. for 16 hours to obtain a catalyst precursor.

  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 machine.

The molded catalyst precursor was put into a cylindrical quartz glass baking vessel having an inner diameter of 3 cm. The catalyst was obtained by heating at 10 ° C./h under air flow and calcining at 380 ° C. for 2 hours. The composition of the obtained catalyst excluding hydrogen, nitrogen, and oxygen was P ₁ Mo ₁₂ V _0.5 Cu _0.3 As _0.5 Cs _0.9 . This catalyst was filled in a reaction tube, and methacrylic acid was produced by gas phase catalytic oxidation under the following conditions. The results are shown in Table 1.

(Reaction conditions)
Reaction gas: 5% by volume of methacrolein, 10% by volume of oxygen, 30% by volume of water vapor, 55% by volume of nitrogen Reaction temperature: 290 ° C.
Reaction pressure: 101 kPa
Contact time: 3.6 seconds.

[Comparative Example 1]
Aqueous slurry b was not prepared except that 3.34 parts of 85 mass% phosphoric acid aqueous solution was added to 30 parts of pure water and 14.06 parts of 14 mass% aqueous ammonia were separately added to aqueous slurry b. A catalyst was produced in the same manner as in Example 1. When a part of the raw material mixture was collected and analyzed by ion chromatography, nitrate, carbonate and sulfate radicals were not detected, and it was confirmed that the content was 0.01 mol / l or less. The pH was 2.1. The composition of the obtained catalyst excluding hydrogen, nitrogen, and oxygen was P ₁ Mo ₁₂ V _0.5 Cu _0.3 As _0.5 Cs _0.9 . The catalyst was filled in a reaction tube, and methacrylic acid was produced by gas phase catalytic oxidation under the same conditions as in Example 1. The results are shown in Table 1.

[Example 2]
A catalyst was produced in the same manner as in Example 1 except that 2.40 parts of tellurium trioxide was used instead of 6.85 parts of the 60 mass% arsenic acid aqueous solution. The total amount of phosphorus and tellurium contained in the aqueous slurry a is 0.35 equivalents when the molar equivalent of all molybdenum used for catalyst preparation is 12. When a part of the raw material mixture was collected and analyzed by ion chromatography, nitrate, carbonate and sulfate radicals were not detected, and it was confirmed that the content was 0.01 mol / l or less. The pH was 2.6. The composition of the obtained catalyst excluding hydrogen, nitrogen, and oxygen was P ₁ Mo ₁₂ V _0.5 Cu _0.3 Te _0.25 Cs _0.9 . The catalyst was filled in a reaction tube, and methacrylic acid was produced by gas phase catalytic oxidation under the same conditions as in Example 1. The results are shown in Table 1.

[Comparative Example 2]
Aqueous slurry b was not prepared except that 3.34 parts of 85 mass% phosphoric acid aqueous solution was added to 30 parts of pure water and 14.06 parts of 14 mass% aqueous ammonia were separately added to aqueous slurry b. A catalyst was produced in the same manner as in Example 2. When a part of the raw material mixture was collected and analyzed by ion chromatography, nitrate, carbonate and sulfate radicals were not detected, and it was confirmed that the content was 0.01 mol / l or less. The pH was 2.6. The composition of the obtained catalyst excluding hydrogen, nitrogen, and oxygen was P ₁ Mo ₁₂ V _0.5 Cu _0.3 Te _0.25 Cs _0.9 . The catalyst was filled in a reaction tube, and methacrylic acid was produced by gas phase catalytic oxidation under the same conditions as in Example 1. The results are shown in Table 1.

[Example 3]
A catalyst was produced in the same manner as in Example 1 except that 6.85 parts of 60 mass% arsenic acid aqueous solution was not used and 1.69 parts of antimony trioxide was added to the aqueous slurry b. The amount of phosphorus contained in the aqueous slurry a is 0.3 equivalent when the molar equivalent of all molybdenum used for catalyst preparation is 12. When a part of the raw material mixture was collected and analyzed by ion chromatography, nitrate, carbonate and sulfate radicals were not detected, and it was confirmed that the content was 0.01 mol / l or less. The pH was 2.6. The composition of the obtained catalyst excluding hydrogen, nitrogen, and oxygen was P ₁ Mo ₁₂ V _0.5 Cu _0.3 Sb _0.2 Cs _0.9 . The catalyst was filled in a reaction tube, and methacrylic acid was produced by gas phase catalytic oxidation under the same conditions as in Example 1. The results are shown in Table 1.

[Comparative Example 3]
A catalyst was produced in the same manner as in Example 3, except that 10.16 parts of cesium nitrate was used instead of 10.11 parts of cesium bicarbonate in the preparation of aqueous solution A. The amount of phosphorus contained in the aqueous solution A is 0.33 times the molar equivalent of the cesium molar equivalent contained in the aqueous solution A. When a part of the raw material mixture was collected and analyzed by ion chromatography, carbonate and sulfate radicals were not detected, and it was confirmed that both contents were 0.01 mol / l or less. As a result, it was confirmed that the content was about 0.08 mol / l. The pH was 1.8. The composition of the obtained catalyst excluding hydrogen, nitrogen, and oxygen was P ₁ Mo ₁₂ V _0.5 Cu _0.3 Sb _0.2 Cs _0.9 . The catalyst was filled in a reaction tube, and methacrylic acid was produced by gas phase catalytic oxidation under the same conditions as in Example 1. The results are shown in Table 1.

[Comparative Example 4]
Aqueous slurry b was not prepared except that 3.34 parts of 85% by mass phosphoric acid aqueous solution was added to 30 parts of pure water and 14.06 parts of 14% by mass ammonia water were separately added to aqueous slurry b. A catalyst was produced in the same manner as in Example 3. When a part of the raw material mixture was sampled and analyzed by ion chromatography, nitrate radical, carbonate radical and sulfate radical were not detected, and it was confirmed that the contents were all 0.01 mol / l or less. The pH was 2.6. The composition of the obtained catalyst excluding hydrogen, nitrogen, and oxygen was P ₁ Mo ₁₂ V _0.5 Cu _0.3 Sb _0.2 Cs _0.9 . The catalyst was filled in a reaction tube, and methacrylic acid was produced by gas phase catalytic oxidation under the same conditions as in Example 1. The results are shown in Table 1.

[Comparative Example 5]
A catalyst was produced in the same manner as in Example 3 except that 14 mass% aqueous ammonia added to the aqueous solution B was changed to 28.12 parts. The amount of phosphorus contained in the aqueous solution B is 0.175 times the molar equivalent of the molar equivalent of ammonium ions contained in the aqueous solution B. When a part of the raw material mixture was sampled and analyzed by ion chromatography, nitrate radical, carbonate radical and sulfate radical were not detected, and it was confirmed that the contents were all 0.01 mol / l or less. The pH was 3.5. The composition of the obtained catalyst excluding hydrogen, nitrogen, and oxygen was P ₁ Mo ₁₂ V _0.5 Cu _0.3 Sb _0.2 Cs _0.9 . The catalyst was filled in a reaction tube, and methacrylic acid was produced by gas phase catalytic oxidation under the same conditions as in Example 1. The results are shown in Table 1.

  As shown in Table 1, when the catalyst for synthesizing methacrylic acid obtained in each example is used, methacrylic acid can be produced with higher selectivity and higher yield than the comparative example.

Claims (4)

Used in the synthesis of unsaturated carboxylic acid by vapor-phase catalytic oxidation of unsaturated aldehyde with molecular oxygen, containing phosphorus and molybdenum and at least one element of potassium, rubidium, cesium, arsenic, antimony and A method for producing an unsaturated carboxylic acid synthesis catalyst which may contain at least one element of tellurium,
Preparing an aqueous slurry or aqueous solution a containing a raw material of molybdenum;
Preparing an aqueous solution A containing a raw material of at least one element of potassium, rubidium and cesium and a raw material of at least one element of phosphorus, arsenic, antimony and tellurium;
Mixing the aqueous slurry or aqueous solution a and the aqueous solution A to prepare an aqueous slurry or aqueous solution b;
Preparing an aqueous solution B containing a raw material of ammonium ions and a raw material of at least one element of phosphorus, arsenic, antimony and tellurium;
Mixing the aqueous slurry or aqueous solution b and the aqueous solution B, preparing a raw material mixture in which all catalyst raw materials are charged, and drying the raw material mixture to obtain a catalyst precursor;
And a step of calcining the catalyst precursor, which satisfies all the following conditions (1) to (3):
(1) The pH of the raw material mixture is less than 3.
(2) The concentrations of nitrate radical, carbonate radical and sulfate radical in the raw material mixture are all 0.01 mol / l or less.
(3) The aqueous solution B contains phosphorus, arsenic, antimony, and tellurium in a molar equivalent of 0.1 to 10 times the molar equivalent of ammonium ions.   The aqueous solution A contains phosphorus, arsenic, antimony and tellurium in a molar equivalent of 0.1 to 10 times the total molar equivalent of potassium, rubidium and cesium. A method for producing an unsaturated carboxylic acid synthesis catalyst.   An unsaturated carboxylic acid synthesis catalyst produced by the production method according to claim 1 or 2.   A method for producing an unsaturated carboxylic acid, comprising using the catalyst for synthesizing an unsaturated carboxylic acid according to claim 3 to synthesize an unsaturated carboxylic acid by vapor-phase catalytic oxidation of an unsaturated aldehyde with molecular oxygen. .