JP2006081974A - Method for producing a catalyst for methacrylic acid production - Google Patents

Abstract

The present invention relates to a method for producing a methacrylic acid production catalyst for use in the production of methacrylic acid by vapor phase catalytic oxidation of methacrolein with molecular oxygen, and a catalyst having a high methacrolein conversion rate even under conditions of high methacrylic acid selectivity. To provide a method for obtaining
In a method for producing a methacrylic acid production catalyst having a composition represented by the following formula (1), a step of mixing at least a catalyst raw material in a solvent to obtain a catalyst raw material mixed solution, and the catalyst raw material mixed solution The method for producing a catalyst for producing methacrylic acid, comprising: a step of filtering the solid content contained in the product; a step of drying the filtered solid content under reduced pressure; and a step of firing the obtained dried product. Method.
_{P a Mo b V c Cu d} X e Y f Z g O h (1)
[Selection figure] None

Description

  The present invention relates to a method for producing a catalyst for producing methacrylic acid, which is used for producing methacrylic acid by gas phase catalytic oxidation of methacrolein.

As a catalyst for producing methacrylic acid by vapor-phase catalytic oxidation of methacrolein, Patent Document 1 mixes a solution or slurry containing at least molybdenum, phosphorus and vanadium and a solution or slurry containing an ammonia compound, A method is described in which a solution or slurry containing potassium or the like is mixed into the obtained mixed solution or slurry, and the resulting catalyst raw material mixture is dried and calcined to produce a catalyst for methacrylic acid production. It is described that the drying in this method is performed in order to obtain a solid from the catalyst raw material mixture, and evaporative drying methods such as drum drying are performed.
JP 2000-296336 A

  However, the catalyst obtained by this method tended to have a low methacrolein conversion rate under conditions of high methacrylic acid selectivity. Therefore, the present invention provides a method for producing a catalyst for producing methacrylic acid having a high methacrolein conversion rate even under conditions with a high methacrylic acid selectivity.

  That is, the present invention relates to a method for producing a catalyst for producing methacrylic acid having a composition represented by the following formula (1), which is used in producing methacrylic acid by vapor-phase catalytic oxidation of methacrolein with molecular oxygen. A step of mixing at least a catalyst raw material in a solvent to obtain a catalyst raw material mixture, a step of filtering solids contained in the catalyst raw material mixture, a step of filtering and drying the solids under reduced pressure, And a step of firing the obtained dried product. The present invention relates to a method for producing a catalyst for producing methacrylic acid.

_{P a Mo b V c Cu d} X e Y f Z g O h (1)
(Wherein P, Mo, V, Cu and O represent phosphorus, molybdenum, vanadium, copper and oxygen, respectively, X represents antimony, bismuth, arsenic, germanium, zirconium, tellurium, silver, selenium, silicon, tungsten, And Y is at least one element selected from the group consisting of iron, zinc, chromium, magnesium, tantalum, cobalt, manganese, barium, gallium, cerium, and lanthanum. Z represents at least one element selected from the group consisting of potassium, rubidium, cesium, and thallium, a, b, c, d, e, f, and g represent the atomic ratio of each element. And when b = 12, a = 0.5-3, c = 0.01-3, d = 0.01-2, e = 0-3, f = 0-0 A g = 0.01 to 3, h is an oxygen atom ratio required for satisfying the valency of each component.)

  According to the present invention, a catalyst having a high methacrolein conversion rate can be obtained even under conditions of high methacrylic acid selectivity, that is, an improvement in methacrylic acid yield can be achieved.

  First, the composition of the catalyst for methacrylic acid production produced by the method of the present invention and the catalyst raw material to be used will be described, and the production method of the present invention will be described below step by step.

(Composition of methacrylic acid production catalyst)
The catalyst produced by the method of the present invention is a catalyst for producing methacrylic acid used for producing methacrylic acid by vapor-phase catalytic oxidation of methacrolein with molecular oxygen and is represented by the following formula (1). It has a composition.

_{P a Mo b V c Cu d} X e Y f Z g O h (1)
(Wherein P, Mo, V, Cu and O represent phosphorus, molybdenum, vanadium, copper and oxygen, respectively, X represents antimony, bismuth, arsenic, germanium, zirconium, tellurium, silver, selenium, silicon, tungsten, And Y is at least one element selected from the group consisting of iron, zinc, chromium, magnesium, tantalum, cobalt, manganese, barium, gallium, cerium, and lanthanum. Z represents at least one element selected from the group consisting of potassium, rubidium, cesium, and thallium, a, b, c, d, e, f, and g represent the atomic ratio of each element. And when b = 12, a = 0.5-3, c = 0.01-3, d = 0.01-2, e = 0-3, f = 0-0 A g = 0.01 to 3, h is an oxygen atom ratio required for satisfying the valency of each component.)
The catalyst component is composed of phosphorus, molybdenum, vanadium, copper, Z element and oxygen as essential components, and the X element and Y element are optional components. a is preferably from 0.5 to 2. c is preferably from 0.01 to 1. As for g, 0.5-2 are preferred. The element Z is preferably cesium. The atomic ratio (a and c to g) of each element in the target catalyst for methacrylic acid production can be arbitrarily set within the above range by appropriately adjusting the blending ratio of each raw material to be described later. The composition of the produced catalyst for producing methacrylic acid can be analyzed for a composition other than oxygen, for example, by analyzing a catalyst dissolved in aqueous ammonia by ICP emission spectrometry and atomic absorption spectrometry.

(Catalyst materials used)
The raw material for producing the catalyst for producing methacrylic acid of the present invention is not particularly limited, and nitrates, carbonates, acetates, ammonium salts, oxides, halogens of each element (other than oxygen) contained in the target catalyst composition A combination of chemicals and the like can be used. For example, ammonium paramolybdate, molybdenum trioxide, molybdic acid, molybdenum chloride, etc. can be used as the molybdenum raw material, and ammonium metavanadate, vanadium pentoxide, vanadium chloride, etc. can be used as the vanadium raw material. As the phosphorus raw material, for example, orthophosphoric acid, phosphorus pentoxide, or phosphates such as ammonium phosphate and cesium phosphate can be used. As a copper raw material, for example, copper sulfate, copper nitrate, copper acetate, cuprous chloride, cupric chloride and the like can be used. As a raw material for the X element, for example, arsenic acid, arsenous acid, antimony acetate, antimony chloride, copper telluride, telluric acid, and the like can be used. As a raw material for Y element, for example, nitrate, carbonate, sulfate, ammonium salt, halide, hydroxide, etc. of Y element can be used. As a raw material for the Z element, for example, a nitrate, carbonate, hydroxide or the like of the Z element can be used.

(Process for obtaining catalyst raw material mixture)
First, at least a catalyst raw material is mixed in a solvent to prepare a catalyst raw material mixture. A glass container, a stainless steel reaction tank, etc. can be used for the container which prepares a catalyst raw material liquid mixture. Various cooling pipes such as a Liebig cooler may be attached on the container. The size of the container is not particularly limited.

  The catalyst raw material to mix can be suitably selected from the raw material of the said illustration, for example so that it may become the composition of the target catalyst for methacrylic acid manufacture. The raw material for each element may be one type or a combination of two or more types. The blending ratio of each raw material can also be appropriately set so as to obtain the composition of the target methacrylic acid production catalyst.

  As the solvent, water is preferably used. Although the usage-amount of a solvent is not specifically limited, It is preferable that it is 1: 3 to 1: 4 by the content ratio (mass ratio) of the total amount of the raw material to be used, and a solvent.

  The method for mixing the catalyst raw material and the solvent is not particularly limited, but a method of adding the catalyst raw material to the solvent while stirring the solvent is preferable. There is no restriction | limiting in particular about the order and temperature to add, According to the composition of the target catalyst, it can set suitably.

  In addition, it is preferable to add ammonia or an ammonia compound, or an alkali metal salt such as a cesium salt (hereinafter referred to as ammonia or the like if necessary) to the catalyst raw material mixture. By adding ammonia or the like, a solid (precipitate) can be deposited in the catalyst raw material mixture, and the filtration step described later is facilitated. This solid contains a heteropolyacid and / or a salt thereof, and its main structure is called Keggin type and / or Dawson type. There is no particular limitation on the timing of adding ammonia or the like, it may be added to the solvent from the beginning, may be added after mixing a part of the catalyst raw material, and finally mixed after mixing all the catalyst raw materials. May be. Those previously mixed with other catalyst raw materials can also be added. In particular, it is preferable to add ammonia or the like after mixing the phosphorus raw material, the molybdenum raw material, and the vanadium raw material.

  It does not specifically limit as ammonia or an ammonia compound, For example, ammonia (ammonia water), ammonium carbonate, ammonium hydrogencarbonate, ammonium nitrate etc. are mentioned. Examples of the cesium salt include cesium carbonate, cesium nitrate, cesium hydroxide and the like, and cesium nitrate is preferable. Examples of alkali metal salts other than cesium salts include rubidium nitrate, rubidium carbonate, rubidium acetate, and potassium nitrate. Ammonia may be used alone or in combination of two or more. When an alkali metal salt such as a cesium salt is used as the catalyst raw material, the same effect can be obtained without adding ammonia or the like separately, but ammonia or the like selected separately may be added.

  The addition amount of ammonia or the like is preferably 7 to 12 moles, more preferably 9 to 11 moles per mole of phosphorus atoms.

  After mixing at least the catalyst raw material and the solvent as described above, it is preferable to continue stirring at 40 ° C. or higher for 1 to 50 hours (hereinafter, this step is referred to as heating and stirring). The temperature of the catalyst raw material mixture during heating and stirring is preferably 40 ° C or higher and 98 ° C or lower. An electric heater, an oil bath heater, steam, etc. can be used for heating. A stirrer bar, a stirring blade, a stirring blade, or the like can be used for stirring.

  The state of the catalyst raw material mixture obtained as described above is not particularly limited as long as the solid content can be separated by filtration in the filtration step described later, and may be a slurry in which the solid content is suspended in the solvent, and may be precipitated. The thing may have settled.

(Step of filtering solids)
In the manufacturing method of the catalyst of this invention, since it manufactures by baking the solid content contained in the catalyst raw material liquid mixture obtained above, it is necessary to remove water from a catalyst raw material liquid mixture. In the prior art, a method of removing water by a heating process such as evaporation to dryness has been employed. In contrast, the present invention is characterized by removing water by filtration. According to the method of the present invention, since the solid content can be separated without applying heat, the change in the surface structure of the solid content due to heating can be prevented. The solid content includes not only a solid catalyst raw material not dissolved in the solvent but also a precipitate generated by mixing the ammonia and the like.

  Filtration may be any of natural filtration, pressure filtration, and vacuum filtration. The filtration pressure is preferably 10 to 30 Torr (0.0013 to 0.0040 MPa) in the case of reduced pressure, and preferably 1500 to 2000 Torr (0.20 to 0.27 MPa) in the case of pressurization. It is preferable to carry out for a minute. When filtering, a filter paper is used, but it is preferable to use a filter paper having a crystal retention particle diameter of 1 to 5 μm.

(Step of drying the filtered solid content under reduced pressure)
In the present invention, the filtered solid is dried under reduced pressure. The drying pressure is not particularly limited as long as it is under reduced pressure, but preferably 1 Torr (0.00013 MPa) or more. The drying temperature is preferably 100 ° C. or lower, and more preferably 30 to 50 ° C. A lower drying temperature is preferred because there is less change in the structure of the catalyst precursor due to heat. The drying time is preferably 12 to 24 hours. The drying atmosphere is preferably an air atmosphere, but may be dried in an inert gas atmosphere such as nitrogen gas. The reason why vacuum drying is preferable is not clear, but it is presumed that it has an effect of preventing changes in the catalyst surface structure due to normal heat drying.

(Molding)
The obtained dried product can be molded using a dry molding machine such as a tableting molding machine, an extrusion molding machine, or a rolling granulator, if necessary. Examples of the molded shape include a spherical shape, a ring shape, and a columnar shape. In molding, a small amount of known additives such as graphite and talc may be added. Molding may be performed after the next firing.

(Step of firing)
Next, the dried product is calcined to form a catalyst. As the firing method and firing conditions, known methods and conditions can be used. The optimum heat treatment conditions vary depending on the catalyst raw material, catalyst composition, production method, flow gas, etc., but preferably under a flow of oxygen-containing gas (oxygen concentration 10-30%) such as air, preferably 350-450 ° C., more preferably The method of baking by the temperature conditions of 350-380 degreeC is mentioned. The firing time is preferably 0.5 hours or more, more preferably 1 to 40 hours.

(Method for producing methacrylic acid)
Next, a method for producing methacrylic acid using the catalyst for producing methacrylic acid obtained by the method of the present invention as described above will be described. The method for producing methacrylic acid is a method for producing methacrylic acid by vapor-phase catalytic oxidation of methacrolein with molecular oxygen in the presence of the catalyst for producing methacrylic acid.

  The gas phase catalytic oxidation reaction can be performed in a fixed bed or a fluidized bed. Preference is given to a fixed bed. At this time, the catalyst layer may be one layer or two or more layers, and may be a catalyst-only layer, a layer in which a catalyst is supported on a carrier, or a layer in which other additive components are mixed.

  When producing methacrylic acid using the above-described catalyst for producing methacrylic acid of the present invention, a raw material gas containing methacrolein and molecular oxygen is brought into contact with the catalyst.

  The concentration of methacrolein in the raw material gas can be varied within a wide range, but is preferably 1% by volume or more, and more preferably 3% by volume or more. Moreover, 20 volume% or less is preferable and 10 volume% or less is more preferable.

  Although it is economical to use air as the molecular oxygen source, air or the like enriched with pure oxygen can also be used if necessary. The molecular oxygen concentration in the raw material gas is preferably 0.3 mol or more, more preferably 0.4 mol or more with respect to 1 mol of methacrolein. Moreover, 4 mol or less is preferable with respect to 1 mol of methacrolein, and 2.5 mol or less is more preferable.

  Moreover, it is preferable that source gas contains water vapor | steam. When the reaction is carried out in the presence of water, methacrylic acid is obtained in a higher yield. The concentration of water vapor in the raw material gas is preferably 0.1% by volume or more, and more preferably 1% by volume or more. Moreover, 50 volume% or less is preferable and 40 volume% or less is more preferable.

  The source gas may contain a small amount of impurities such as a lower saturated aldehyde, but the amount is preferably as small as possible. Moreover, inert gas, such as nitrogen and a carbon dioxide gas, may be included.

  The flow rate of the raw material gas is not particularly limited, and can be appropriately set so as to have an appropriate contact time. The contact time is preferably 1.5 seconds or longer, and more preferably 2 seconds or longer. Moreover, 15 seconds or less are preferable and 5 seconds or less are more preferable.

  The reaction pressure for the methacrylic acid production reaction is from atmospheric pressure (atmospheric pressure) to several atmospheres. The reaction temperature is preferably 230 ° C or higher, more preferably 250 ° C or higher. Moreover, 450 degrees C or less is preferable and 400 degrees C or less is more preferable.

Hereinafter, the manufacturing method of the catalyst by this invention and the example of methacrylic acid manufacturing reaction using the obtained catalyst are demonstrated concretely. In the description, “parts” means parts by mass. The product of the methacrylic acid production reaction was analyzed by gas chromatography. The reaction rate of methacrolein, the selectivity of the produced methacrylic acid and the single flow yield are defined as follows.
Reaction rate of methacrolein (%) = A / B × 100
Methacrylic acid selectivity (%) = C / A x 100
Single stream yield of methacrylic acid (%) = C / B × 100
Here, A represents the number of moles of reacted methacrolein, B represents the number of moles of methacrolein supplied, and C represents the number of moles of methacrylic acid produced.

Example 1
100 parts of molybdenum trioxide, 6.67 parts of 85 mass% phosphoric acid aqueous solution and 2.71 parts of ammonium metavanadate were mixed with 370 parts of pure water, heated to 100 ° C. and stirred for 2 hours. After cooling to 50 ° C., 11.3 parts of cesium nitrate was added. After heating to 70 ° C., 36.3 parts of 28% by mass aqueous ammonia was added. After cooling to 50 ° C., the mixture was stirred for 90 minutes. After adding 1.4 parts of copper nitrate and stirring for 15 minutes, 1.17 parts of iron nitrate was added and further stirred for 15 minutes. The mixture was further heated to 100 ° C. and stirred for 15 minutes to obtain a catalyst raw material mixture.

The solid content in the catalyst raw material mixture was filtered under pressure at 1500 Torr (0.20 MPa) to obtain a solid. The solid was dried under reduced pressure at 10 Torr (0.0013 MPa). The obtained dried product was compressed and crushed at 200 kgf / cm ² (20 MPa) to obtain a crushed product. The crushed product was calcined at 377 ° C. for 5 hours in an air atmosphere (flow rate 20 L / h) to obtain a catalyst for producing methacrylic acid. The composition of elements other than oxygen in the obtained catalyst was Mo ₁₂ P _0.92 V _0.46 Cu _0.08 Fe _0.06 Cs _1.2 .

  This catalyst was charged into a reaction tube, and a mixed gas of 5% methacrolein, 10% oxygen, 30% water vapor, and 55% nitrogen (volume%) was passed at a reaction temperature of 285 ° C. and a contact time of 3.6 seconds. Gas phase catalytic oxidation reaction (methacrylic acid production reaction) was performed. When the product was collected and analyzed by gas chromatography, the reaction rate of methacrolein was 70.4%, the selectivity of methacrylic acid was 89.3%, and the single flow rate of methacrylic acid was 62.9%.

(Comparative Example 1)
A catalyst raw material mixture was prepared using 110 parts of molybdenum trioxide, 3.39 parts of ammonium metavanadate, 1.26 parts of copper nitrate, 1.64 parts of iron nitrate, and 14.7 parts of cesium nitrate. A catalyst for methacrylic acid production was obtained in the same manner as in Example 1 except that the solid was obtained by evaporation to dryness by heating to 100 ° C. The composition of elements other than oxygen in the obtained catalyst was Mo ₁₂ P _0.92 V _0.46 Cu _0.08 Fe _0.06 Cs _1.2 .

  Using this catalyst, the gas phase catalytic oxidation reaction of methacrolein was performed in the same manner as in Example 1. As a result, the methacrolein reaction rate was 62.5%, the methacrylic acid selectivity was 90.0%, and the methacrylic acid single stream yield was 56. 3%.

(Comparative Example 2)
A catalyst for methacrylic acid production was obtained in the same manner as in Example 1 except that the catalyst raw material mixture was evaporated to dryness by heating to 100 ° C. to obtain a solid. The composition of elements other than oxygen in the obtained catalyst was Mo ₁₂ P ₁ V _0.4 Cu _0.1 Fe _0.043 Cs _1.2 .

  Using this catalyst, the gas phase catalytic oxidation reaction of methacrolein was carried out in the same manner as in Example 1. As a result, the methacrolein reaction rate was 63.7%, the methacrylic acid selectivity was 90.3%, and the single flow rate of methacrylic acid was 57. It was 5%.

(Example 2)
A catalyst for methacrylic acid production was obtained in the same manner as in Example 1 except that the catalyst raw material mixture was suction filtered at 20 Torr (0.0027 MPa) to obtain a solid. The composition of elements other than oxygen in the obtained catalyst was Mo ₁₂ P _0.92 V _0.37 Cu _0.09 Fe _0.06 Cs _1.2 .

  Using this catalyst, the gas phase catalytic oxidation reaction of methacrolein was carried out in the same manner as in Example 1. As a result, the methacrolein reaction rate was 70.1%, the methacrylic acid selectivity was 89.1%, and the single flow rate of methacrylic acid was 62. It was 5%.

(Comparative Example 3)
A catalyst raw material mixture was prepared by changing to 110 parts of molybdenum trioxide, 7.34 parts of 85 mass% phosphoric acid aqueous solution and 2.17 parts of ammonium metavanadate, and the catalyst raw material mixture was heated to 100 ° C to evaporate to dryness. A catalyst for methacrylic acid production was obtained in the same manner as in Example 1 except that it was solidified to obtain a solid. The composition of elements other than oxygen in the obtained catalyst was Mo ₁₂ P _0.92 V _0.37 Cu _0.09 Fe _0.06 Cs _1.2 .

  Using this catalyst, the gas phase catalytic oxidation reaction of methacrolein was carried out in the same manner as in Example 1. As a result, the methacrolein reaction rate was 63.0%, the methacrylic acid selectivity was 89.1%, and the single flow rate of methacrylic acid was 56. 1%.

(Example 3)
Production of methacrylic acid was carried out in the same manner as in Example 1 except that ammonia water was added as it was at 50 ° C. without heating to 70 ° C., and the catalyst raw material mixture was naturally filtered to obtain a solid. A catalyst was obtained. The composition of elements other than oxygen in the obtained catalyst was Mo ₁₂ P _0.92 V _0.46 Cu _0.09 Fe _0.06 Cs _1.2 .

  Using this catalyst, the gas phase catalytic oxidation reaction of methacrolein was carried out in the same manner as in Example 1. As a result, the methacrolein reaction rate was 70.2%, the methacrylic acid selectivity was 89.2%, and the methacrylic acid single stream yield was 62. It was 6%.

(Comparative Example 4)
The catalyst raw material mixture was prepared by increasing the amount to 110 parts of molybdenum trioxide and 7.34 parts of 85 mass% phosphoric acid aqueous solution, and the catalyst raw material mixture was heated to 100 ° C to evaporate to dryness to obtain a solid. A catalyst for methacrylic acid production was obtained in the same manner as in Example 1 except that. The composition of elements other than oxygen in the obtained catalyst was Mo ₁₂ P _0.92 V _0.46 Cu _0.09 Fe _0.06 Cs _1.2 .

  Using this catalyst, the gas phase catalytic oxidation reaction of methacrolein was carried out in the same manner as in Example 1. As a result, the methacrolein reaction rate was 63.2%, the methacrylic acid selectivity was 89.0%, and the single flow rate of methacrylic acid was 56. 2%.

  The above results are summarized in Table 1. By obtaining a solid from the catalyst raw material mixture by filtration as in the present invention, a catalyst for producing methacrylic acid having a high methacrolein conversion rate can be obtained even under conditions with a high methacrylic acid selectivity, and the yield of methacrylic acid can be improved. I understand that.

Claims (1)

In the method for producing a methacrylic acid production catalyst having a composition represented by the following formula (1), which is used in producing methacrylic acid by vapor phase catalytic oxidation of methacrolein with molecular oxygen:
A step of mixing at least a catalyst raw material in a solvent to obtain a catalyst raw material mixture,
Filtering the solids contained in the catalyst raw material mixture,
Drying the filtered solid content under reduced pressure;
A step of firing the obtained dried product;
A process for producing a catalyst for producing methacrylic acid, comprising:
_{P a Mo b V c Cu d} X e Y f Z g O h (1)
(Wherein P, Mo, V, Cu, and O represent phosphorus, molybdenum, vanadium, copper, and oxygen, respectively, X represents antimony, bismuth, arsenic, germanium, zirconium, tellurium, silver, selenium, silicon, tungsten , And at least one element selected from the group consisting of boron, Y is at least one selected from the group consisting of iron, zinc, chromium, magnesium, tantalum, cobalt, manganese, barium, gallium, cerium, and lanthanum Z represents at least one element selected from the group consisting of potassium, rubidium, cesium and thallium, a, b, c, d, e, f and g represent the atomic ratio of each element. When b = 12, a = 0.5-3, c = 0.01-3, d = 0.01-2, e = 0-3, f = 0-0 A g = 0.01 to 3, h is an oxygen atom ratio required for satisfying the valency of each component.)