JPH0975740A - Catalyst for production of methacrylic acid and production of methacrylic acid using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a catalyst having higher reactivity and selectivity and a longer service life than the conventional catalyst. SOLUTION: This catalyst is a partially neutralized salt of a hetero-polyacid represented by the formula, Pa Mob Vc Sbd Cue Xf Og . Starting materials for this catalyst except starting material for V and/or starting material for Sb are mixed, dissolved or suspended in water and heated at 80-200 deg.C for 1-24hr in the presence of ammonium radicals, starting material for V and/or starting material for Sb is added, they are heated again at 80-200 deg.C for 1-24hr and then firing is carried out.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an improvement in a heteropolyacid catalyst used for the production of methacrylic acid by vapor phase catalytic oxidation. Specifically, it relates to improvement of a heteropolyacid catalyst used for producing methacrylic acid by vapor-phase catalytic oxidation of methacrolein, isobutane and the like with molecular oxygen.

[0002]

2. Description of the Related Art Many catalysts have been proposed for producing methacrylic acid by vapor-phase catalytic oxidation of methacrolein (for example, JP-A-50-101316 and JP-A-5-101316).
7-177347, JP-A-4-63139, JP-A-5-31368, and JP-A-5-3136.
No. 8, JP-A-6-91172, etc.), a part of which is already used for industrial scale production.

A catalyst for producing methacrylic acid by oxidative dehydrogenation of isobutyric acid (for example, JP-A-57-72936) and oxidation of isobutyraldehyde (for example, JP-A-57-144238). Is also well known. Further, a catalyst for producing methacrylic acid or methacrolein by oxidizing isobutylene or tertiary butanol (for example, JP-A-55-127328),
Recently, catalysts for directly oxidizing isobutane to produce methacrylic acid and methacrolein (JP-A-2-42032, etc.) have also been proposed.

The catalyst used in these reactions is
It is known that those having a structure of a heteropolyacid containing molybdenum and phosphorus as the main components and salts thereof are effective. Regarding the composition, partial replacement of molybdenum with vanadium, co-catalyst components such as copper, antimony and arsenic Regarding the addition and preparation method of the above, various improvements have been made such as the use of cyclic amine, heat aging (for example, JP-A-4-25739).

[0005]

However, these conventional catalysts do not necessarily satisfy both the reaction yield (activity and selectivity) and the catalyst life even in the oxidation of methacrolein that has already been put to practical use. Not a thing. For example, compared with a catalyst that produces acrylic acid from acrolein, not only the selectivity of the reaction is poor, but also the reaction activity and life are poor, and therefore a large amount of catalyst is required, and the burden of equipment cost and catalyst cost is large at present. is there. One of the main reasons why the performance of the catalyst is not sufficient is that it has not been industrialized even when using isobutane, isobutyric acid or the like as a raw material. An object of the present invention is to improve the existing catalyst and provide a catalyst having higher reaction activity, selectivity and long catalyst life.

[0006]

Means for Solving the Problems In order to achieve the above objects, the inventors of the present invention have made extensive studies on improvement of a heteropolyacid catalyst, and as a result, found that a catalyst having a specific catalyst composition and prepared by a specific method was used. The inventors have found that the above-mentioned objects are achieved and completed the present invention.

That is, the present invention has the general formula PaMobV
cSbdCueXfOg (in the formula, P, Mo, V, Sb,
Cu and O respectively represent phosphorus, molybdenum, vanadium, antimony, copper and oxygen, X represents at least one element selected from the group consisting of rubidium, cesium and thallium, and subscripts a, b, c and d. , E, f and g represent the atomic ratio of each element, and when b = 12,
a, c, d, e, f do not include 0 (zero) respectively 3
The following values are taken, and g represents a value determined by the valence and atomic ratio of other elements), which is a partially neutralized salt of a heteropoly acid, wherein a vanadium raw material and / or an antimony raw material are The catalyst raw material to be removed is dissolved or suspended in water, and in the presence of ammonium root, 80 to 2
After heat treatment at a temperature of 00 ° C. for 1 to 24 hours, a vanadium raw material and / or an antimony raw material is added, and the temperature is again 8
A catalyst for producing methacrylic acid, which is obtained by heat-treating at a temperature of 0 to 200 ° C. for 1 to 24 hours and calcining.

Further, the present invention provides a method for producing methacrylic acid, which comprises subjecting methacrolein to gas-phase catalytic oxidation with molecular oxygen in the presence of the above-mentioned catalyst for producing methacrylic acid.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The basic structure of the catalyst of the present invention is a conventionally well-known partially neutralized salt of phosphomolybdic acid with rubidium, cesium, and thallium. Further, vanadium and antimony are essential components. And contains copper. It is already known that these elements are effective, but as a result of various studies on the relationship between the combination of these compositions and the preparation method, the following has been found regarding the composition.

First, the catalyst containing antimony but not vanadium has a high reaction selectivity, but has a drawback that the reaction rate tends to decrease with use for a long time and is not durable for industrial use. On the other hand, a catalyst containing vanadium but not antimony can provide some degree of reaction selectivity and life with conventional preparation methods, but it is not sufficient. Further, even in the case of a catalyst containing both vanadium and antimony, only a catalyst having a poor reaction activity and a short life can be obtained by the conventional preparation method. In order to have the reaction selectivity, the activity and the lifetime, it is necessary to use both the vanadium and the antimony and to use the special preparation method of the present invention. Also, copper is essential in terms of improving reaction activity. In addition, arsenic, silver, iron, cobalt, lanthanum, cerium, etc. may be contained as optional components.

As the raw material used for preparing the catalyst, a combination of oxides, nitrates, carbonates, ammonium salts, hydroxides and halides of each element can be used.
For example, molybdenum raw materials include ammonium paramolybdate, molybdenum trioxide, molybdenum chloride, etc., vanadium raw materials include ammonium metavanadate, vanadium pentoxide, vanadium chloride, etc., and antimony raw materials include antimony trioxide, antimony pentoxide, etc. Can be used. Further, it is necessary to contain ammonium root at the stage of heat treatment of the suspension described later. Therefore,
Ammonia is required without ammonium salts.

The method of preparing a catalyst according to the present invention is carried out by first dissolving or suspending a catalyst raw material, excluding vanadium raw material and / or antimony raw material, in water and subjecting it to heat treatment in the presence of ammonium root. (First step),
Next, it is indispensable to add vanadium raw material and / or antimony raw material, and further perform heat treatment (second step). That is, the vanadium raw material and / or the antimony raw material may not be added to the catalyst raw material during the first heat treatment and may be added in the total amount during the second heat treatment, or vanadium may be added during the first heat treatment. Add either raw material or antimony raw material,
In the second heat treatment, a method of adding a vanadium raw material and / or an antimony raw material may be added, and further, a vanadium raw material and / or an antimony raw material may be added in each stage.
Alternatively, a method may be used in which the antimony raw material is added separately. More preferably during the first-stage heat treatment,
It is recommended to add vanadium raw material or antimony raw material to the catalyst raw material, and at the time of the second stage heat treatment, at least the non-added vanadium raw material or antimony raw material should be added in the first stage and heat treatment is recommended. It The water-soluble raw material may be separately dissolved in water before use, but it may be charged as a powder without any problem.

The heat treatment in both the first and second steps is about 80 to about 200 ° C., preferably about 100 to about 100 ° C.
About 150 ° C., about 1 to about 24 hours, preferably about 10
It takes about 20 hours. If the temperature is lower than about 80 ° C. or if the time is shorter than 1 hour, the reaction does not proceed sufficiently and the catalyst has a low methacrylic acid selectivity, which is not preferable. The temperature may exceed about 200 ° C. or the time may exceed about 24 hours, but the corresponding effect cannot be obtained.

When the suspension obtained by the heat treatment is evaporated to dryness, the solid obtained is found to be P: Mo from X-ray diffraction and infrared absorption.
It can be seen that a salt of so-called Dawson type heteropolyacid having a ratio of 1: 9 is formed. When this is heated to about 180 to 350 ° C. in an oxidizing gas such as air, an inert gas such as nitrogen, or a reducing gas such as hydrogen, a so-called Keggin-type heteropoly acid having a P: Mo ratio of 1:12 is obtained. Change to salt. Since it is prepared by containing the ammonium root, the solid at this stage is a mixed salt of the X component of the heteropolyacid (rubidium, cesium, etc.) and ammonium.
As it is, it does not have the property of a solid acid and its activity is low, so it is necessary to activate it by firing. Baking at a temperature of about 400 to 500 ° C., preferably about 420 to 450 ° C. in an inert gas such as nitrogen. As a result, almost all of the ammonium components are eliminated to form a protonic acid, which exhibits high activity. When firing in air, when the temperature exceeds 400 ° C, decomposition and sintering of the heteropolyacid occur and the activity decreases.
When the temperature is lower than ℃, the activity is low because many ammonium roots remain. After firing in inert gas, 400 ℃ in air
There is no problem in firing at a temperature below. When the X component is not present in the catalyst component, the thermal stability and surface area of the obtained catalyst are lowered.

The catalyst of the present invention thus obtained is used for the production of methacrylic acid by the oxidation of various raw materials including the oxidation of methacrolein. In use, the catalyst alone or alumina, silica, silicon carbide is used. It is used in the form of being supported on a carrier such as or being diluted and mixed, and in the case of a fixed bed, it is used after being formed into a columnar shape, a spherical shape, a ring shape or the like. A reaction type such as a fluidized bed or a moving bed can also be used.

When methacrolein is catalytically oxidized in the gas phase to produce methacrylic acid using the catalyst of the present invention, the raw material used does not necessarily have to be pure methacrolein, but isobutylene or tertiary butanol. A methacrolein-containing gas obtained by vapor-phase catalytic oxidation of methacrolein or a vaporized methacrolein obtained by a liquid phase method may be used. The oxygen source may be pure oxygen, but industrially air is used. As other diluent gas, nitrogen, carbon dioxide, carbon monoxide, steam or the like can be used. The methacrolein concentration in the reaction raw material gas is 1 to
10%, and a ratio of oxygen to methacrolein of about 1 to 5 is used. Space velocity of raw material gas is 500 to 5000
The range of h ⁻¹ and the reaction temperature are preferably about 250 to 350 ° C. The reaction pressure is usually around normal pressure or slightly elevated pressure.

When isobutane is directly oxidized to produce methacrylic acid or methacrolein using the catalyst of the present invention, the isobutane concentration in the raw material gas is 1 to 85%, and the oxygen source is pure oxygen or oxygen. Enriched air, air, etc. are used. A suitable ratio of oxygen to isobutane is 0.05 to 4. It is desirable that the reaction gas contains water vapor in the range of 3 to 30%. The raw material gas may contain nitrogen, carbon dioxide, carbon monoxide or the like as a diluent gas. Unreacted isobutane and optionally oxygen are recovered and recycled, as the activity cannot be very active in this reaction. By-product methacrolein is recycled or introduced into another reactor to oxidize methacrylic acid. Space velocity is 40
The reaction temperature is preferably 0 to 5000 h ^-1 , and the reaction temperature is preferably 270 to 400 ° C. The reaction pressure may be atmospheric pressure or increased pressure.

The catalyst of the present invention is oxidative dehydrogenation of isobutyric acid,
It can also be used for the production of methacrylic acid by the oxidation of isobutyraldehyde. It can also be used when producing methacrylic acid from isobutylene in a single step. In these reactions, the reaction conditions similar to the oxidation of methacrolein can be adopted.

[0019]

INDUSTRIAL APPLICABILITY The catalyst of the present invention has higher reaction activity, higher selectivity and longer catalyst life than conventional catalysts in the production of methacrylic acid.

[0020]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. The definitions of conversion rate and selectivity are as follows. Conversion rate of methacrolein (%) = (mol number of reacted methacrolein) / (mol number of supplied methacrolein) x
100 Methacrolein acid selectivity (%) = (number of moles of methacrolein produced) / (number of moles of reacted methacrolein)
× 100

Example 1 To 224 g of ion-exchanged water heated to 40 ° C., cesium nitrate was added.
Mu [CsNO_Three] 38.2 g, copper nitrate [Cu (NO_Three)₂・
3H₂O] 10.2 g, phosphoric acid aqueous solution [85% -H_ThreeP
O_Four] 24.2 g, nitric acid [70% -HNO_Three] 25.2
g was dissolved, and this was designated as solution A. Io heated to 40 ° C
Ammonium molybdate [(N
H_Four)₆Mo₇O_{twenty four}・ 4H₂O] 297 g is dissolved and meta
Ammonium vanadate [NH_FourVO_Three] 8.19 g
It was suspended and used as solution B. A to stirring liquid B
The liquid was dropped. The resulting suspension is placed in a sealed container at 120
The mixture was heated and stirred at ℃ for 17 hours. Trioxide is added to the obtained suspension.
Antimony [Sb₂O _Three] Add 10.2g and get more
Heat the resulting suspension in a sealed vessel at 120 ° C for 17 hours.
Stirred. The resulting suspension was evaporated to dryness at 120 ° C.
The obtained dried product has the structure of a Dawson type heteropolyacid salt.
doing. Dry solid is crushed to 1000μm or less
Add agent, add water and knead, diameter 5mm, height 5m
It was extruded and molded on a cylinder of m. This molded body is heated to 90 ° C.
After drying in, it is further baked at 250 ° C. for 3 hours. this
Baking at 435 ° C for 3 hours in a nitrogen stream, then air stream
A catalyst was obtained by calcining at 390 ° C. for 3 hours. Of this catalyst
The composition excluding oxygen is P_1.5Mo₁₂V_0.5Sb_0.5Cu_0.3
Cs_1.4It is.

9 g of this catalyst was filled in a glass reaction tube having an inner diameter of 15 mm, and 4 mol% of methacrolein and 12 m of oxygen were filled.
An activity test was carried out at a reaction temperature of 290 ° C. through a reaction tube with a raw material gas having a composition of ol%, water vapor 17 mol%, and the balance nitrogen at a space velocity (STP standard) of 670 h ⁻¹ . As a result, when the steady state was reached, the conversion of methacrolein was 97.3%, the selectivity of methacrylic acid was 77.8%, and the yield of methacrylic acid was 75.7%. The methacrylic acid selectivity when the methacrolein conversion rate was 90% was calculated by changing the conditions, and it was 80.8%.

As an accelerated life test, the obtained catalyst 4.5
g was filled in a glass reaction tube having an inner diameter of 15 mm, and a raw material gas having the same composition as described above was continuously operated at a reaction temperature of 320 ° C. through the reaction tube at a space velocity of 1300 h ⁻¹ . As a result, the methacrolein conversion rate was 93.1 15 hours after the start of the reaction.
%, Methacrylic acid selectivity 75.0%, methacrylic acid yield 69.8%, and 92.4% and 7 after 480 hours, respectively.
6.9%, 71.0%, 9 after 960 hours respectively
0.2%, 80.1%, 72.2%, and after 2400 hours were 74.7%, 86.0%, and 64.2%, respectively.

Comparative Example 1 A solution of phosphoric acid [85% -H ₃ P in 350 g of ion-exchanged water]
O ₄ ] 4.6g was added, and molybdovanadolinic acid was further added.
115 g of [H ₄ P ₁ Mo ₁₁ V ₁ O ₄₀ · 18H ₂ O] and 3.64 g of antimony trioxide [Sb ₂ O ₃ ] were added, and 10
Reflux for 14 hours at 0 ° C. to dissolve. This solution is cooled to 13 ° C. and designated as solution A. To 250 g of ion-exchanged water cooled to 13 ° C., cesium nitrate [CsNO ₃ ] 13.7
g, copper nitrate _{[Cu (NO 3) 2 ·} 3H2O] 3.62
g and 10.4 g of ammonium nitrate [NH ₄ NO ₃ ] are dissolved, and this is designated as solution B. Solution B is added dropwise to solution A, and the temperature is 65 ° C.
Concentrate under reduced pressure with. The obtained dried solid matter was placed in a stainless steel vat and dried at 120 ° C. in an electric furnace. The molding step and firing step were performed in the same manner as in Example 1. The composition of this catalyst excluding oxygen is P _1.5 Mo ₁₂ V _1.1 Sb _0.5 Cu _0.3 Cs _1.4 . In the same activity test as in Example 1, the conversion of methacrolein was 35.2%, the selectivity of methacrolein was 85.8%, and the yield of methacrylic acid was 30.2%.

Comparative Example 2 In 224 g of ion-exchanged water heated to 40 ° C., 38.2 g of cesium nitrate [CsNO ₃ ] and copper nitrate [Cu (NO ₃ ) ₂
· 3H ₂ O] 10.15g, aqueous solution of phosphoric acid [85% -H
₃ PO ₄ ] 24.21 g, nitric acid [70% -HNO ₃ ] 2
5.2g was melt | dissolved and this was made into the A liquid. Ammonium molybdate is added to 330 ml of deionized water heated to 40 ° C.
_{[(NH 4) 6 Mo 7} O 24 · 4H 2 O] was dissolved 297 g, ammonium metavanadate [NH ₄ VO _3] 8.
19 g was suspended and this was designated as solution B. Stirring B
Solution A was added dropwise to the solution. To the obtained suspension, 10.2 g of antimony trioxide [Sb ₂ O ₃ ] was added. The obtained suspension was heated and stirred at 120 ° C. for 17 hours in a sealed container. Example 1 for the drying process, the molding process, and the firing process
I went the same way. The composition of this catalyst excluding oxygen is P _1.5 M.
o ₁₂ V _0.5 Sb _0.5 Cu _0.3 Cs _1.4 . Example 1
In the same activity test as above, the conversion of methacrolein was 93.6.
%, The methacrylic acid selectivity was 81.1%, the methacrylic acid yield was 75.9%, and the methacrylic acid selectivity at a methacrolein conversion rate of 90% was 83.1%.

The results of the same accelerated life test as in Example 1 of the obtained catalyst were as follows: 15 hours after the start of the reaction, the conversion of methacrolein was 88.9%, the selectivity of methacrylic acid was 76.9%,
The methacrylic acid yields were 68.3% and 81.0%, 84.2%, and 68.2% after 480 hours, respectively.

Comparative Example 3 The same procedure as in Example 1 was performed except that 10.2 g of antimony trioxide [Sb ₂ O ₃ ] was added and no heat treatment was performed again. In the same activity test as in Example 1, the conversion of methacrolein was 94.0%, the selectivity of methacrylic acid was 75.6%,
Methacrylic acid yield 71.0%, methacrolein conversion 9
The methacrylic acid selectivity at 0% was 77.4%.

Example 2 Example 1 was repeated except that after heat treatment was performed at 135 ° C. for 17 hours, 10.2 g of antimony trioxide [Sb ₂ O ₃ ] was added and the heat treatment was performed again at 135 ° C. for 17 hours. I went the same way. In the same activity test as in Example 1, the methacrolein conversion rate was 92.6%, the methacrylic acid selectivity was 83.2%, the methacrylic acid yield was 77.0%, and the methacrylic acid selectivity was 90% when the methacrolein conversion rate was 90%. It was 0.2%.

Example 3 Example 3 was repeated except that 12.6 g of nitric acid [70% -HNO ₃ ] was added. In the same activity test as in Example 1, the methacrolein conversion rate was 89.9% and the methacrylic acid selectivity was 8
The methacrylic acid selectivity was 84.0% when the methacrylic acid yield was 4.0%, the methacrylic acid yield was 75.5%, and the methacrolein conversion rate was 90%.

Example 5 Example ₃ was repeated except that 12.6 g of nitric acid [70% -HNO ₃ ] was added. In the same activity test as in Example 1, the conversion of methacrolein was 90.2% and the selectivity of methacrylic acid was 8
The methacrylic acid selectivity was 84.6% at a methacrylic acid yield of 76.3% and a methacrolein conversion rate of 90%.

The results of the same accelerated life test as in Example 1 of the obtained catalyst were as follows: 15 hours after the start of the reaction, the conversion of methacrolein was 86.5%, the selectivity of methacrylic acid was 79.7%,
The yields of methacrylic acid were 68.9%, 81.8%, 83.3% and 68.1% after 480 hours, and 68.6%, 86.4% and 59.2% after 1440 hours, respectively. It was

Example 6 To 224 g of ion-exchanged water heated to 40 ° C., 38.2 g of cesium nitrate [CsNO ₃ ] and copper nitrate [Cu (NO ₃ ) ₂
· 3H ₂ O] 10.15g, aqueous solution of phosphoric acid [85% -H
₃ PO ₄ ] 24.21 g, nitric acid [70% -HNO ₃ ] 2
5.2g was melt | dissolved and this was made into the A liquid. Ammonium molybdate is added to 330 ml of deionized water heated to 40 ° C.
_{[(NH 4) 6 Mo 7} O 24 · 4H 2 O] was dissolved 297 g, which was used as a B solution. Solution A was added dropwise to solution B being stirred. This suspension contains antimony trioxide [Sb
₂ O ₃ ] 10.2 g was added. The obtained suspension was heated and stirred at 120 ° C. for 17 hours in a sealed container. Ammonium metavanadate [NH ₄ V] was added to the obtained suspension.
O _3] 8.19 g was added, further the resulting suspension in a sealed vessel was heated and stirred 17 hours at 120 ° C.. The drying process, molding process, and firing process were performed in the same manner as in Example 1. The composition of this catalyst excluding oxygen is P _1.5 Mo ₁₂ V _0.5 Sb _0.5.
Cu _0.3 Cs _1.4 . In the same activity test as in Example 1, the methacrolein conversion rate was 94.3%, the methacrylic acid selectivity was 81.7%, the methacrylic acid yield was 77.0%, and the methacrylic acid selectivity was 90% when the methacrolein conversion rate was 90%. ．
8%.

The results of the same accelerated life test as in Example 1 of the obtained catalyst were as follows: 15 hours after the start of the reaction, the conversion of methacrolein was 93.5%, the selectivity of methacrylic acid was 74.1%,
Methacrylic acid yield 69.2%, after 8 hours 89.5%, 80.8%, 72.3%, after 1440 hours 81.9%, 83.4%, 68.3%, respectively.
After 2400 hours, 74.5%, 85.1%,
It was 63.3%.

Example 7 In 224 g of ion-exchanged water heated to 40 ° C., 38.2 g of cesium nitrate [CsNO ₃ ] and copper nitrate [Cu (NO ₃ ) ₂
· 3H ₂ O] 10.15g, aqueous solution of phosphoric acid [85% -H
₃ PO ₄ ] 24.21 g, nitric acid [70% -HNO ₃ ] 2
5.2g was melt | dissolved and this was made into the A liquid. Ammonium molybdate is added to 330 ml of deionized water heated to 40 ° C.
_{[(NH 4) 6 Mo 7} O 24 · 4H 2 O] was dissolved 297 g, which was used as a B solution. Solution A was added dropwise to solution B being stirred. The resulting suspension is 1 at 120 ° C in a sealed container.
Heat and stir for 7 hours, and add antimony trioxide to this suspension.
[Sb ₂ O ₃ ] 10.2 g and ammonium metavanadate [NH ₄ VO ₃ ] 8.19 g were added, and the mixture was heated with stirring at 120 ° C. for 5 hours. The drying process, molding process, and firing process were performed in the same manner as in Example 1. The composition of this catalyst excluding oxygen is P _1.5 Mo ₁₂ V _0.5 Sb _0.5 Cu _0.3 Cs _1.4 .
In the same activity test as in Example 1, the conversion of methacrolein was 9
The methacrylic acid selectivity was 79.5% when the methacrylic acid selectivity was 79.1%, the methacrylic acid yield was 75.7%, and the methacrolein conversion rate was 90%.

The results of the same accelerated life test as in Example 1 of the obtained catalyst were as follows: 15 hours after the start of the reaction, the conversion of methacrolein was 95.8%, the selectivity of methacrylic acid was 70.1%,
The yields of methacrylic acid were 67.1%, and were 89.7%, 79.6%, and 71.4% after 480 hours.

Claims (6)

[Claims] 1. The general formula PaMobVcSbdCueX
fOg (In the formula, P, Mo, V, Sb, Cu, and O represent phosphorus, molybdenum, vanadium, antimony, copper, and oxygen, respectively, and X represents at least one selected from the group consisting of rubidium, cesium, and thallium. Representing elements, the subscripts a, b, c, d, e, f and g represent the atomic ratio of each element. When b = 12, a, c, d, e,
f takes a value of 3 or less that does not include 0 (zero),
g represents a value determined by the valences and atomic ratios of other elements), and is a partially neutralized salt of a heteropoly acid, wherein the catalyst raw material excluding the vanadium raw material and / or the antimony raw material is water. Dissolve or suspend, and in the presence of ammonium root at a temperature of 80-200 ℃ 1
A catalyst for methacrylic acid production, which is obtained by heating for 24 hours, then adding a vanadium raw material and / or an antimony raw material, heat treating again at a temperature of 80 to 200 ° C. for 1 to 24 hours, and calcining. 2. The heating treatment dissolves or suspends, in the catalyst raw material, the catalyst raw material excluding the vanadium raw material or the antimony raw material in water, and in the state where ammonium root is present, 80
After the heat treatment at a temperature of ˜200 ° C. for 1 to 24 hours, the vanadium raw material and / or the antimony raw material is added, and again heat treated at a temperature of 80 to 200 ° C. for 1 to 24 hours, followed by firing. Item 2. A catalyst for producing methacrylic acid according to item 1. 3. Heat treatment at 100 to 150 ° C. for 10 to 2
The catalyst for producing methacrylic acid according to claim 1 or 2, which has 0 hours. 4. The suspension obtained by heat treatment again is concentrated to dryness, and the dried solid is calcined at a temperature of 400 to 500 ° C. in an inert gas. 2. The catalyst for producing methacrylic acid according to 2. 5. A method for producing methacrylic acid, which comprises subjecting methacrolein to gas-phase catalytic oxidation with molecular oxygen in the presence of the catalyst for producing methacrylic acid according to any one of claims 1 to 4. 6. The methacrolein concentration in the reaction raw material gas is 1 to 10%, and the ratio of oxygen to methacrolein is 1 to
5, space velocity is 500 ~ 5000h ^-1 , reaction temperature is 25
It carries out at 0-350 degreeC, The manufacturing method of the methacrylic acid of Claim 5 characterized by the above-mentioned.