JP6653871B2 - Catalyst for producing methacrylic acid, method for producing the same, and method for producing methacrylic acid - Google Patents

Description

  The present invention relates to a catalyst for producing methacrylic acid having a novel structure, which is used for producing methacrylic acid by subjecting methacrolein to catalytic gas phase oxidation, a method for producing the catalyst, and a method for producing methacrylic acid. The present invention relates to a method for producing methacrylic acid from rain.

  Methacrylic acid can be produced by subjecting methacrolein, isobutyraldehyde, isobutyric acid, etc. to catalytic gas phase oxidation. It is known that a catalyst having the structure of a heteropolyacid and / or a salt thereof is effective as a catalyst used at this time, and many proposals have been made on the composition, physical properties, and production method thereof.

  These catalysts are usually produced by steps such as preparation, drying, molding, and calcination of a raw material mixture. With respect to the production of a catalyst that stably exhibits high performance, many reports have been made on the composition, adjustment method, and calcination method.

  For example, Patent Document 1 proposes a material containing molybdenum and phosphorus as main components and having a heteropolyacid and / or a salt thereof. Patent Document 2 discloses that in preparing a heteropolyacid catalyst, a heteropolyacid salt containing at least molybdenum, phosphorus and cesium is obtained, and a catalyst raw material containing at least molybdenum and phosphorus and containing no cesium is added to the heteropolyacid salt. , A method for preparing a catalyst characterized by being prepared in two steps. Patent Document 3 discloses that in preparing a molybdenum, phosphorus, vanadium, antimony, and copper-based catalyst, a catalyst material other than a vanadium material and / or an antimony material among catalyst materials is dissolved or suspended in water, and ammonium root is dissolved. Heat treatment at a temperature of 80 to 200 ° C. for 1 to 24 hours in the presence of, a vanadium raw material and / or an antimony raw material are added, and a heat treatment is again performed at a temperature of 80 to 200 ° C. for 1 to 24 hours, followed by firing. A method is described.

  On the other hand, Non-Patent Document 1 discloses an ε-Keggin-type polyacid containing molybdenum, vanadium, and bismuth as main components.

JP-A-06-91172 JP 05-177141 A Japanese Patent No. 3482476

Dalton Trans. , 2014, 43, 13584-13590

  However, these known heteropolyacid-based catalysts described in Patent Documents 1 to 3 all have an α-Keggin-type structure, but the reaction results of the method for producing methacrylic acid from methacrolein show similar reaction results. Was insufficient compared with the reaction results of the method for producing acrylic acid from acrolein. Despite long-term intensive studies, the improvement in the performance of conventional α-Keggin-type heteropolyacid catalysts can be seen as plateauing. Therefore, an object of the present invention is to provide a catalyst having a novel structure for producing methacrylic acid by catalytic vapor phase oxidation of methacrolein, a method for producing the catalyst, and the use of the catalyst to produce methacrylic acid from methacrolein. It is to provide a method for producing methacrylic acid.

  The present inventor has conducted intensive studies on a catalyst that can be suitably used for producing methacrylic acid from methacrolein in order to solve the above-mentioned problems. As a result, a heteropolyacid and / or ε-Keggin type structure satisfying a specific composition formula has been obtained. The inventors have found that methacrylic acid can be produced from methacrolein by using the salt, and have completed the present invention.

That is, the present invention
(1) A methacrylic acid production catalyst for producing methacrylic acid by catalytic gas phase oxidation of methacrolein in the presence of molecular oxygen or a molecular oxygen-containing gas,
Represented by the following general formula (I),
_{Mo a A b B c X d} Y e Z f O g (I)
(Where Mo is molybdenum,
A is at least one element selected from the group consisting of vanadium, zinc, manganese, iron, cobalt and nickel;
B is at least one element selected from the group consisting of bismuth, zinc, manganese, iron, cobalt and nickel;
X is at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, cesium and thallium;
Y is at least one element selected from the group consisting of phosphorus, arsenic, antimony, germanium, bismuth and selenium;
Z is at least one element selected from the group consisting of iron, chromium, nickel, cobalt, manganese, zinc, tin, silver, palladium, rhodium, ruthenium, tellurium, tungsten, silicon, aluminum, cerium, magnesium, boron and ammonium. Or ions,
a, b, c, d, e, and f respectively represent the atomic ratio of each element. When b = 1, 0 <a <5.0, 0 <c <2.0, and 0 ≦ d <3. 0, 0 ≦ e <1.0, 0 ≦ f <2.0, and g is a number determined by the oxidation state of each element.)
In the powder X-ray diffraction pattern using Cu-Kα ray, the value of 2θ was 7.7 ° ± 0.3 °, 23.2 ° ± 0.3 °, 25.4 ° ± 0.3 °, 26. A catalyst for producing methacrylic acid, having an ε-Keggin-type heteropolyacid structure, having diffraction peaks at 5 ° ± 0.3 ° and 29.8 ° ± 0.3 °,
(2) The catalyst for producing methacrylic acid according to (1), wherein A is vanadium,
(3) the catalyst for producing methacrylic acid according to (1) or (2), wherein B is bismuth;
(4) The method for producing a catalyst for producing methacrylic acid according to any one of (1) to (3), comprising the following steps:
Step (A): a compound containing molybdenum; a compound containing at least one element selected from the group consisting of vanadium, zinc, manganese, iron, cobalt and nickel; and bismuth, zinc, manganese, iron, cobalt and nickel A compound containing at least one element selected from the group consisting of; a compound containing at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, cesium and thallium, if necessary; phosphorus, arsenic, antimony, A compound containing at least one element selected from the group consisting of germanium, bismuth and selenium; and, if necessary, iron, chromium, nickel, cobalt, manganese, zinc, tin, silver, palladium, rhodium, ruthenium, tellurium, tungsten, Silicon, a Miniumu, cerium, magnesium, at least one element or compound containing ions selected from the group consisting of boron and ammonium, mixed with water to prepare an aqueous solution or aqueous dispersion of these compounds process,
Step (B): a step of obtaining a solid content by hydrothermal synthesis using the aqueous solution or aqueous dispersion obtained in step (A),
Step (C): a step of firing the solid content obtained in step (B),
(5) The method for producing a catalyst for producing methacrylic acid according to (4), wherein the temperature in the hydrothermal synthesis is 80 ° C to 200 ° C, and the pressure is a saturated vapor pressure at the temperature.
(6) A catalytic gas-phase oxidation reaction of methacrolein with molecular oxygen or a molecular oxygen-containing gas in the presence of the catalyst for producing methacrylic acid according to any one of (1) to (3). A method for producing methacrylic acid,
About.

  Methacrylic acid can be produced from methacrolein by using a heteropolyacid catalyst having an ε-Keggin type structure satisfying the specific composition formula of the present invention.

4 is a measurement result of powder X-ray diffraction of the catalyst according to Example 1 before calcination by Cu-Kα radiation. 4 is a measurement result of powder X-ray diffraction by Cu-Kα ray of the catalyst after firing according to Example 1 and Comparative Example 1.

  As the structure of the heteropoly acid and its salt, a plurality of structures such as Keggin type, Dawson type and Anderson type are known. A typical Keggin-type heteropolyacid refers to one in which three octahedrons share a vertex oxygen atom as a structural unit, and four structural units are coordinated in a tetrahedron centered on a hetero atom. In the α-Keggin-type heteropolyacid, four structural units share four oxygen atoms at the corners of a tetrahedron, respectively, and are coordinated at a position substantially symmetric to Td (Td is classified by the Schoenfries notation. One in which the molecule of interest forms a tetrahedral shape).

  On the other hand, the ε-Keggin-type heteropolyacid refers to one in which four structural units are each rotated by 60 ° about the C3 axis from the α-Keggin type. The ε-Keggin type heteropoly acid has a value of 2θ of 7.7 ° ± 0.3 °, 23.2 ° ± 0.3 °, 25.4 ° in a powder X-ray diffraction pattern using Cu-Kα ray. It can be confirmed by having diffraction peaks at ± 0.3 °, 26.5 ° ± 0.3 °, and 29.8 ° ± 0.3 °.

The catalyst of the present invention is a methacrylic acid production catalyst for producing methacrylic acid by subjecting methacrolein to catalytic gas phase oxidation in the presence of molecular oxygen or a molecular oxygen-containing gas,
Represented by the following general formula (I),
_{Mo a A b B c X d} Y e Z f O g (I)
(Where Mo is molybdenum,
A is at least one element selected from the group consisting of vanadium, zinc, manganese, iron, cobalt and nickel;
B is at least one element selected from the group consisting of bismuth, zinc, manganese, iron, cobalt and nickel;
X is at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, cesium and thallium;
Y is at least one element selected from the group consisting of phosphorus, arsenic, antimony, germanium, bismuth and selenium;
Z is at least one element selected from the group consisting of iron, chromium, nickel, cobalt, manganese, zinc, tin, silver, palladium, rhodium, ruthenium, tellurium, tungsten, silicon, aluminum, cerium, magnesium, boron and ammonium. Or ions,
a, b, c, d, e, and f respectively represent the atomic ratio of each element. When b = 1, 0 <a <5.0, 0 <c <2.0, and 0 ≦ d <3. 0, 0 ≦ e <1.0, 0 ≦ f <2.0, and g is a number determined by the oxidation state of each element.)
In the powder X-ray diffraction pattern using Cu-Kα ray, the value of 2θ was 7.7 ° ± 0.3 °, 23.2 ° ± 0.3 °, 25.4 ° ± 0.3 °, 26. A methacrylic acid production catalyst having an ε-Keggin-type heteropolyacid structure having diffraction peaks at 5 ° ± 0.3 ° and 29.8 ° ± 0.3 °.

  In the ε-Keggin-type heteropolyacid of the general formula (I), Mo is a constituent element of polyoxometalate, A is a constituent element of polyoxometalate, B is a linker, X is a cationic species, Y is a polyoxometalate constituent element (central element) and can also be a cationic species, and Z is a cationic species. A is preferably vanadium, and B is preferably bismuth.

The catalyst of the present invention can be prepared by a method including the following steps.
Step (A)
A compound containing molybdenum; a compound containing A (at least one element selected from the group consisting of vanadium, zinc, manganese, iron, cobalt and nickel); and B (bismuth, zinc, manganese, iron, cobalt and nickel) A compound containing at least X (at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, cesium and thallium); and optionally a Y ( A compound containing at least one element selected from the group consisting of phosphorus, arsenic, antimony, germanium, bismuth and selenium; and, if necessary, Z (iron, chromium, nickel, cobalt, manganese, zinc, tin, silver, palladium) , Rhodium, ruthenium, tellurium, tangs A compound containing at least one element or ion selected from the group consisting of silicon, aluminum, cerium, magnesium, boron and ammonium) with water to prepare an aqueous solution or dispersion of these compounds. Process,
Step (B)
A step of obtaining a solid content by hydrothermal synthesis using the aqueous solution or the aqueous dispersion obtained in the step (A),
Step (C)
Baking the solid matter obtained in the step (B).

  The starting material compound in the method for producing a catalyst of the present invention is not particularly limited, and examples of molybdenum-containing compounds include ammonium molybdate, molybdenum trioxide, molybdic acid, sodium molybdate and the like.

  Examples of the component A raw material include, but are not limited to, hydroxides, chlorides, sulfates, nitrates, oxides, and acetates of the component elements (vanadium, zinc, manganese, iron, cobalt, and nickel). Preferred are compounds containing vanadium, such as vanadic acid, vanadate (metavanadate) such as ammonium vanadate (ammonium metavanadate), vanadium oxide, and vanadium chloride, with vanadyl sulfate being particularly preferred.

  Examples of the component B raw material include, but are not limited to, hydroxides, chlorides, sulfates, nitrates, oxides, and acetates of the component elements (bismuth, zinc, manganese, iron, cobalt, and nickel). Preferred are compounds containing bismuth, particularly bismuth hydroxide and bismuth nitrate.

  When the X, Y and / or Z component raw materials are added, the step of addition is not particularly limited, and may be appropriately added before or after hydrothermal synthesis or during firing. Examples of the X, Y and Z component raw materials include hydroxides, chlorides, sulfates, nitrates, oxides and acetates of the component elements.

  Hydrothermal synthesis is a method of synthesizing a substance and growing a crystal in the presence of high-temperature and high-pressure water. In the present invention, hydrothermal synthesis is performed, for example, by charging a slurry liquid into an autoclave. The reaction can be carried out in air, but it is preferred to carry out the reaction in an autoclave before or after starting the reaction by replacing part or all of the inside of the autoclave with an inert gas such as nitrogen or helium instead of air. The reaction temperature of the hydrothermal synthesis is usually 80 ° C to 200 ° C, and the reaction time is usually 1 to 100 hours. The pressure in the autoclave is preferably a saturated vapor pressure, and stirring may be performed during hydrothermal synthesis. After the completion of the hydrothermal synthesis, the solid substance may be dried as it is, but the unreacted substance may have an adverse effect when producing methacrylic acid from methacrolein. Filtration and washing are more preferred. The product thus obtained can be used as it is as the catalyst of the present invention, but is preferably subjected to a calcination treatment. The firing treatment is performed in an inert gas such as nitrogen or helium at 200 ° C. or higher, preferably 300 to 500 ° C. for 0.5 to 10 hours.

  The catalyst of the present invention thus obtained can be used as it is as the catalyst of the present invention, but it is preferable to use it after pulverization. The catalyst of the present invention can be applied to any reaction mode such as a fixed bed, a fluidized bed, and a moving bed. The catalyst can be a coated catalyst in which a product is supported and molded, or a catalyst in which a powdery composite metal oxide is molded by a molding machine such as tablet molding. In the fluidized bed and moving bed reactors, it is advantageous to use a uniform catalyst of about several tens of microns prepared by further adding a silica component or the like in order to improve abrasion resistance.

The catalyst of the present invention is used for producing methacrylic acid from methacrolein by catalytic gas phase oxidation. The raw material gas composition in the catalytic gas phase oxidation reaction for producing methacrylic acid from methacrolein is not particularly limited, but methacrolein: oxygen: water vapor: diluent gas = 1: 0.1 to 10: 0 to 30: 0 to 60 ( (Molar ratio). Here, as the diluent gas, nitrogen, carbon dioxide gas and the like are preferable. The catalytic gas phase oxidation reaction may be carried out under increased or reduced pressure, but is generally preferably carried out at a pressure near atmospheric pressure. The reaction is carried out usually at a temperature of 200 to 400 ° C, preferably 220 to 350 ° C. The supply amount of the raw material gas is usually 100～100000Hr ^-1 in the space velocity (SV), preferably 400~30000hr ^-1.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples as long as the gist is not exceeded.
The conversion of methacrolein and the yield of methacrylic acid in the following examples are respectively defined as follows.
Conversion of methacrolein (mol%) = (moles of reacted methacrolein) / (moles of supplied methacrolein) × 100
Methacrylic acid yield (mol%) = (mol number of generated methacrylic acid) / (mol number of supplied methacrolein) × 100

Example 1
(Preparation of catalyst)
1.471 g of ammonium molybdate was dissolved in 20 ml of distilled water at room temperature. In another container, 0.5365 g of vanadyl sulfate n-hydrate was dissolved in 20 ml of distilled water, and the aqueous solution was added to the above-mentioned molybdenum aqueous solution and sufficiently stirred to change into a slurry. In another container, a solution prepared by dissolving 0.68 g of bismuth nitrate pentahydrate in 1.7 ml of a mixed solution of glycerin and distilled water (volume ratio 1: 1) was prepared. The aqueous solution was added to the slurry liquid which had been stirred for 3 minutes, and further stirred for 7 minutes. The pH of the slurry was adjusted to 4.0 using a 28% aqueous ammonia solution. After bubbling the slurry liquid with nitrogen gas for 10 minutes, the slurry liquid was transferred to an autoclave having an internal capacity of 100 mL while washing the beaker with distilled water so as to leave no residue, and heated and stirred at 175 ° C. for 48 hours. The obtained product was allowed to cool to room temperature, filtered, washed with water (20 mL × 3), and dried at 80 ° C. overnight to obtain a granular product.

The composition of the resulting granules was analyzed by X-ray fluorescence analysis and elemental analysis. The atomic ratio of molybdenum was 2.9 and the atomic ratio of bismuth was 0.1 when the atomic ratio of vanadium was 1.0. 7, the atomic ratio of nitrogen was 0.8, and the catalyst composition was Mo _9.8 V _3.6 Bi _2.5 (NH ₄ ) _2.9 O ₄₂ . FIG. 1 shows the results of X-ray diffraction (using Cu-Kα rays) measurement. It was confirmed that peaks appeared at 2θ values of 7.7 °, 23.2 °, 25.4 °, 26.5 ° and 29.8 °.
The resulting sample was fully baked at 300 ° C. for 6 hours under air flow, and the composition was analyzed by X-ray fluorescence analysis and elemental analysis. As a result, when the atomic ratio of vanadium was set to 1.0, molybdenum was determined. Is 3.1, the atomic ratio of bismuth is 0.9, the atomic ratio of nitrogen is 0.8, and the composition formula is Mo _11.2 V _3.6 Bi _3.2 (NH ₄ ) _2.9 O ₄₀ was found. FIG. 2 shows the results of X-ray diffraction (using Cu-Kα rays) measurement. It was confirmed that peaks appeared at 2θ values of 7.7 °, 23.5 °, 25.6 °, 26.8 ° and 30.1 °.

(Catalyst evaluation test)
3.45 g of the calcined granules were uniformly mixed with 6.90 g of crushed quartz sand. This was mixed with 20.6 g of a spherical porous alumina carrier (particle diameter: 4.0 mm), and then charged into a stainless steel reaction tube having an inner diameter of 18.4 mm, and the raw material gas composition (molar ratio) methacrolein: oxygen: water vapor: nitrogen = The reaction results were measured at a ratio of 1: 2: 4: 18.6, a space velocity (SV) of 1200 hr-1, and a reaction bath temperature of 290 ° C. Table 1 shows the results of the evaluation test.

Comparative Example 1
Raw materials having the same composition as in Example 1 (20.37 g of ammonium molybdate, 9.79 g of vanadyl sulfate n-hydrate, and 13.42 g of bismuth nitrate pentahydrate) were weighed to prepare physically mixed granules. When the composition of the obtained sample was analyzed by X-ray fluorescence analysis, the atomic ratio of molybdenum was 2.8 and the atomic ratio of bismuth was 0.6 when the atomic ratio of vanadium was 1.0. It was confirmed that the sample had almost the same composition as that of the sample obtained in Example 1. FIG. 2 shows the results of X-ray diffraction (using Cu-Kα rays) measurement. Since no peak could be confirmed at 2θ values of 7.7 °, 25.4 °, 26.5 °, and 29.8 °, it was confirmed that this comparative sample did not have an ε-Keggin-type heteropolyacid structure. confirmed.
(Catalyst evaluation test)
The catalyst evaluation test was performed under the same conditions as in Example 1. Table 1 shows the results of the evaluation test. From these results, it was confirmed that the structure of the ε-Keggin type heteropoly acid was significant in the methacrylic acid generation reaction.

Example 2
(Preparation of catalyst)
The preparation of the product, filtration, washing with water, and drying steps were performed in the same manner as in Example 1 except that the charged amount was 400 times. 13.3 g of a strength improver (ceramic fiber) is uniformly mixed with 125.0 g of the granules obtained in this step, and tumbling granulation is performed using 200 g of a spherical porous alumina carrier (4.5 mm in diameter) with pure water as a binder. It was covered and molded by the method. The obtained molded product was subjected to main firing at 300 ° C. for 6 hours under air flow to obtain a target coated catalyst. When the composition of this coated catalyst was analyzed by X-ray fluorescence analysis and elemental analysis, the atomic ratio of molybdenum was 3.2 and the atomic ratio of bismuth was 0.1 when the atomic ratio of vanadium was 1.0. 7, the atomic ratio of nitrogen was 1.1, and the composition formula was Mo _11.5 V _3.6 Bi _2.5 (NH ₄ ) _4.0 O ₄₀ . When the X-ray diffraction (using Cu-Kα ray) was measured, a graph similar to that of Example 1 shown in FIG. 2 was obtained, and as a 2θ value, 7.7 °, 23.2 °, 25.4 °, 26 Since peaks were confirmed at 0.5 ° and 29.8 °, it was confirmed that the sample of the present invention had an ε-Keggin-type heteropolyacid structure.

(Catalyst evaluation test)
A stainless steel reaction tube having an inner diameter of 18.4 mm was filled with 41.2 ml of the coated catalyst obtained in Example 2, and the raw material gas composition (molar ratio) methacrolein: oxygen: water vapor: nitrogen = 1: 2: 4: 18.6. The reaction results were measured at a space velocity (SV) of 300 hr-1 and a reaction bath temperature of 290 ° C. The results of the evaluation test are shown in Table 1 below. It was confirmed that coating and molding the granules having the ε-Keggin type heteropolyacid structure was significant by the methacrylic acid generation reaction.

Claims (4)

A catalyst for producing methacrylic acid for producing methacrylic acid by subjecting methacrolein to catalytic gas phase oxidation in the presence of molecular oxygen or a molecular oxygen-containing gas,
Represented by the following general formula (I),
_{Mo a A b B c X d} Y e Z f O g (I)
(Where Mo is molybdenum,
A is a vanadium,
B is a bismuth vinegar,
X is at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, cesium and thallium;
Y is at least one element selected from the group consisting of phosphorus, arsenic, antimony, germanium, bismuth and selenium;
Z is at least one element selected from the group consisting of iron, chromium, nickel, cobalt, manganese, zinc, tin, silver, palladium, rhodium, ruthenium, tellurium, tungsten, silicon, aluminum, cerium, magnesium, boron and ammonium. Or ions,
a, b, c, d, e, and f respectively represent the atomic ratio of each element. When b = 1, 0 <a <5.0, 0 <c <2.0, and 0 ≦ d <3. 0, 0 ≦ e <1.0, 0 ≦ f <2.0, and g is a number determined by the oxidation state of each element.)
In the powder X-ray diffraction pattern using Cu-Kα ray, the value of 2θ was 7.7 ° ± 0.3 °, 23.2 ° ± 0.3 °, 25.4 ° ± 0.3 °, 26. A methacrylic acid production catalyst having an ε-Keggin-type heteropolyacid structure having diffraction peaks at 5 ° ± 0.3 ° and 29.8 ° ± 0.3 °. The method for producing a catalyst for producing methacrylic acid according to claim 1 , comprising the following steps:
Step (A): compound containing molybdenum; compounds containing vanadium; and compounds containing bismuth scan; lithium necessary, sodium, potassium, rubidium, at least one element selected from the group consisting of cesium and thallium Compound containing; if necessary, a compound containing at least one element selected from the group consisting of phosphorus, arsenic, antimony, germanium, bismuth and selenium; and if necessary, iron, chromium, nickel, cobalt, manganese, zinc, tin, A compound containing at least one element or ion selected from the group consisting of silver, palladium, rhodium, ruthenium, tellurium, tungsten, silicon, aluminum, cerium, magnesium, boron and ammonium is mixed with water, and these compounds are mixed. Aqueous solution of Preparing a dispersion,
Step (B): a step of obtaining a solid content by hydrothermal synthesis using the aqueous solution or aqueous dispersion obtained in step (A),
Step (C): a step of firing the solid content obtained in step (B). The method for producing a catalyst for producing methacrylic acid according to claim 2 , wherein the temperature in the hydrothermal synthesis is from 80C to 200C, and the pressure is the saturated vapor pressure at the temperature. A method for producing methacrylic acid, comprising performing a catalytic gas-phase oxidation reaction of methacrolein with molecular oxygen or a molecular oxygen-containing gas in the presence of the catalyst for producing methacrylic acid according to claim 1 .

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