JPWO2010052909A1 - Method for producing methacrylic acid and catalyst for producing methacrylic acid - Google Patents

Abstract

In the present invention, when isobutylene is oxidized by a direct-coupled two-stage contact gas phase oxidation method to produce methacrylic acid, the reaction is performed at a conversion of isobutylene of 95 to 98% in the former stage, and molybdenum, vanadium, phosphorus, and the like in the latter stage. By using a catalyst obtained by calcining a catalyst composition containing one or two kinds selected from the group consisting of potassium, rubidium, cesium and ammonium components, particularly a catalyst containing ammonium components, for a long period of time. The present invention relates to a method for producing methacrylic acid capable of producing a stable methacrylic acid in a high yield and a catalyst for producing methacrylic acid for a direct-coupled two-stage contact gas phase oxidation method.

Description

 In the first stage, the present invention oxidizes isobutylene to methacrolein in the presence of an oxidation catalyst to obtain methacrolein, and in the second stage, oxidizes methacrolein in the presence of an oxidation catalyst. The present invention relates to a method for producing methacrylic acid by a direct-coupled two-stage contact gas phase oxidation method for obtaining methacrylic acid and a second-stage (for methacrolein oxidation) oxidation catalyst therefor.

  Many methods for producing methacrylic acid by catalytic gas phase oxidation reaction of methacrolein and catalysts used in the reaction have been proposed (for example, Patent Documents 1 to 5), some of which are used for industrial scale production. Yes.

  As one method for producing methacrylic acid, in the first stage, isobutylene is oxidized to methacrolein, and the resulting reaction product gas is supplied to the second stage to oxidize methacrolein. Thus, a direct-coupled two-stage contact gas phase oxidation method for obtaining methacrylic acid has been studied (Non-patent Document 1).

  In the method of producing methacrylic acid from isobutylene by the direct-coupled two-stage contact gas phase oxidation method, if the reaction is performed by directly coupling the first and second stages, the unreacted isobutylene adversely affects the activity of the subsequent catalyst. In order to reduce unreacted isobutylene, the conversion of isobutylene in the first stage reaction is generally operated at over 98%.

Japanese Patent Laid-Open No. 50-101316 JP-A-57-177347 JP-A-4-63139 JP-A-5-31368 JP-A-6-91172

Masahiro Wada, Catalyst, Vol. 32, 4, 223 (1990)

However, compared with the production of acrylic acid by the catalytic gas phase oxidation reaction of acrolein using a molybdenum-vanadium catalyst, the methacrylic acid production method and the catalyst for methacrylic acid production by the catalytic gas phase oxidation reaction of methacrolein are partially industrialized. However, since the reaction yield (activity and selectivity) is low and the catalyst life is short, there is a need for improvement. In particular, in the production of methacrylic acid by direct-coupled two-stage gas phase oxidation from isobutylene, in order to avoid reduction in catalyst activity due to unreacted isobutylene in the second stage reaction and shortening of catalyst life, isobutylene exceeding 98% Reaction at conversion is considered preferred.
On the other hand, when the reaction at the first stage reaction is carried out at a conversion rate of 99% or more, the reaction at a high temperature is required, the life of the first stage catalyst is shortened, and the selectivity to methacrolein and methacrylic acid. (Effective selection rate) also tends to decrease. Therefore, it is desirable to carry out the reaction at an isobutylene conversion rate of about 95 to 98 mol% with little thermal load on the catalyst and high effective selectivity. For this reason, there is a demand for the development of a catalyst with little adverse effect on unreacted isobutylene even when the residual ratio of unreacted isobutylene is a relatively high value of 2 to 5%.

Formation of methacrolein by catalytic gas phase oxidation reaction of isobutylene or formation of methacrolein by catalytic gas phase oxidation reaction of isobutylene generated by dehydration reaction of tertiary butyl alcohol, and methacrylic acid by catalytic gas phase oxidation reaction of the methacrolein In the methacrylic acid production method by the direct-coupled two-stage contact gas phase oxidation method for producing the product, by using a specific catalyst as the latter catalyst, there is little adverse effect on isobutylene even in the presence of relatively high unreacted isobutylene. The present inventors have found that a relatively high methacrolein conversion rate and methacrylic acid selectivity can be maintained, thereby completing the present invention.

That is, the present invention relates to the following.
(1) (a) isobutylene is oxidized to methacrolein in the gas phase with molecular oxygen or a molecular oxygen-containing gas in the presence of an oxidation catalyst (step (a)),
(B) The obtained reaction product gas containing unreacted isobutylene and methacrolein is oxidized in the gas phase with molecular oxygen or a molecular oxygen-containing gas in the presence of an oxidation catalyst to produce methacrylic acid. (Step (b)),
A method,
The reaction is performed at a conversion rate of isobutylene in the step (a) of 95 mol% or more and 98 mol% or less, and the oxidation catalyst of the step (b) is molybdenum, vanadium, phosphorus, potassium, rubidium, cesium and ammonia components. A method for producing methacrylic acid, which is a catalyst obtained by molding and firing a catalyst composition containing one or two kinds selected from the group consisting of:
(2) The oxidation catalyst in step (b) is represented by the general formula (1)
_{Mo 10 V a P b (NH} 4) c X d Y e O f (1)
(Wherein Mo is molybdenum, V is vanadium, P is phosphorus, (NH ₄ ) is an ammonium group, X is at least one element selected from K, Rb, and Cs, Y is Sb, As, Cu, Ag, Mg) Represents at least one element selected from the group consisting of Zn, Al, B, Ge, Sn, Pb, Ti, Zr, Cr, Re, Bi, W, Fe, Co, Ni, Ce, and Th; f represents the atomic ratio of each element, a is a positive number of 0.1 ≦ a ≦ 6.0, b is a positive number of 0.5 ≦ b ≦ 6.0, and c is 0.1 ≦ c ≦ A positive number of 10.0, d is a positive number of 0.1 ≦ d ≦ 3.0, and e is a positive number of 0 ≦ e ≦ 3.0. Production of methacrylic acid according to the above (1), which is a catalyst for producing methacrylic acid obtained by molding and firing a product Law.

(3) The above (1) using the catalyst for methacrylic acid production obtained by calcining the catalyst composition having the active ingredient composition represented by the general formula (1) at a temperature of 300 to less than 400 ° C. Or the manufacturing method of methacrylic acid as described in (2).
(4) The method for producing methacrylic acid according to any one of (2) to (3) above, wherein Y is at least two elements selected from the group consisting of Sb, As and Cu.
(5) The method for producing methacrylic acid according to the above (4), wherein Y is both As and Cu.
(6) The catalyst composition is molded by coating the dried slurry of the composition with a strength improver and water or an alcohol having 1 to 4 carbon atoms on a spherical carrier to form a spherical coated catalyst. The manufacturing method of methacrylic acid of any one of said (1)-(5) which is what.
(7) The catalyst composition is formed by coating the dried slurry of the composition with a strength improver and a pore-forming agent on a spherical carrier using water or an alcohol having 1 to 4 carbon atoms as a binder. The method for producing methacrylic acid according to any one of the above (1) to (5), which is a spherical coating catalyst.
(8) The method for producing methacrylic acid according to any one of (1) to (7), wherein a bismuth-molybdenum-containing composite oxide catalyst is used in step (a).
(9) The bismuth-molybdenum-containing composite oxide catalyst is selected from the group consisting of molybdenum, bismuth, iron and cobalt, and the group consisting of nickel, tin, zinc, tungsten, chromium, manganese, magnesium, antimony, cerium, and titanium. The method for producing methacrylic acid according to (8) above, wherein a composite oxide catalyst containing at least one kind of alkali metal or thallium is used.
(10) The above (1) to (9), wherein the reaction product gas containing unreacted isobutylene and methacrolein in step (b) contains 2 to 5 mol% of unreacted isobutylene in the total amount of reaction product gas. The method for producing methacrylic acid according to any one of the above.

(11) General formula (1)
_{Mo 10 V a P b (NH} 4) c X d Y e O f (1)
(Wherein Mo is molybdenum, V is vanadium, P is phosphorus, (NH ₄ ) is an ammonium group, X is at least one element selected from K, Rb, and Cs, Y is Sb, As, Cu, Ag, Mg) Represents at least one element selected from Zn, Al, B, Ge, Sn, Pb, Ti, Zr, Cr, Re, Bi, W, Fe, Co, Ni, Ce, Th, Represents the atomic ratio of each element, a is a positive number of 0.1 ≦ a ≦ 6.0, b is a positive number of 0.5 ≦ b ≦ 6.0, and c is 0.1 ≦ c ≦ 10.0. A positive number of 0.1 ≦ d ≦ 3.0, e represents a positive number of 0 ≦ e ≦ 3.0, and a slurry of a catalyst composition having an active component composition represented by: The dried product is combined with a strength improver and a pore forming agent, and water or an alcohol having 1 to 4 carbon atoms as a binder, Coated with, formed into spherical coated catalyst, 100 to 450 steps in the above (1) obtained by firing ° C. (b) for producing methacrylic acid oxidation catalyst.

(12) The catalyst for producing methacrylic acid for step (b) according to claim 11, wherein Y is at least two elements selected from the group consisting of Sb, As and Cu.
(13) Molding a catalyst composition having an active component composition represented by the general formula (1), wherein Y is at least one element selected from the group consisting of As and Cu, and then firing at 250 to 400 ° C. The oxidation catalyst for methacrylic acid production for the step (b) according to the above (11) or (12) obtained by the method.
(14) The oxidation catalyst for producing methacrylic acid for the step (b) according to the above (11) to (13), wherein the ratio of the active ingredient to the whole spherical coated catalyst is 10 to 60% by mass.
(15) The oxidation catalyst for producing methacrylic acid for the step (b) according to the above (11) to (14), wherein the ratio of the pore forming agent is 1 to 40% by mass with respect to the active ingredient.
(16) The catalyst obtained by molding and firing the catalyst composition for the step (b) is represented by the following general formula (a′-1)
_{Mo 10 V a P b (NH} 4) c 'X dd Y e O f (a'-1)
(Wherein Mo is molybdenum, V is vanadium, P is phosphorus, (NH ₄ ) is an ammonium group, X is at least one element selected from K, Rb, and Cs, Y is Sb, As, Cu, Ag, Each represents at least one element selected from Mg, Zn, Al, B, Ge, Sn, Pb, Ti, Zr, Cr, Re, Bi, W, Fe, Co, Ni, Ce, and Th; c ′, dd, g and f represent the atomic ratio of each element, a is a positive number of 0.1 ≦ a ≦ 6.0, b is a positive number of 0.5 ≦ b ≦ 6.0, c 'Represents a positive number of 0 ≦ c' ≦ 10, dd represents a positive number of 0 ≦ dd ≦ 3.0, and e represents a positive number of 0 ≦ e ≦ 3.0.)
The manufacturing method of methacrylic acid as described in said (1) which is a catalyst which has an active ingredient composition represented by these.
(17) The catalyst composition is formed by coating the dried slurry of the composition on a spherical carrier with water or an alcohol having 1 to 4 carbon atoms as a binder together with a strength improver and a pore-forming agent. The method for producing methacrylic acid according to the above (16), which is a spherical coating catalyst.
(18) The method for producing methacrylic acid according to the above (16) or (17), wherein Y is at least two elements selected from the group consisting of Sb, As and Cu.
(19) The method for producing methacrylic acid according to the above (16) to (18), wherein c ′ is a positive number of 0.01 ≦ c ′ ≦ 5.
(20) The method for producing methacrylic acid according to any one of (16) to (19), wherein dd is a positive number satisfying 0.1 ≦ dd ≦ 3.0.

  According to the present invention, even in the production of methacrylic acid by direct-coupled two-stage gas phase oxidation of isobutylene, the conversion of isobutylene does not need to be as high as 98 mol% or more, particularly 99% or more, and optimal conversion is achieved. The reaction temperature of the first stage (step (a) in the present invention) can be lowered because the isobutylene conversion is not required to be carried out at a high rate. Since the thermal load on the eye catalyst is small, the life of the first stage catalyst is extended, and a catalyst strong against isobutylene poisoning is used in the second stage, so that stable operation for a long period of time becomes possible. In addition, since it is possible to operate the pre-stage reaction in a range where the yield of active ingredients is high, it is possible to increase the yield of methacrylic acid with respect to isobutylene.

Hereinafter, the present invention will be described in detail. The object of the present invention is a methacrylic acid production method for producing methacrylic acid from isobutylene via methacrolein. The oxidation reactor in the first stage (step (a)) and the second stage (step) This is a method for producing methacrylic acid by directly coupled two-stage contact gas phase oxidation without providing a purification apparatus between the oxidation reactors of (b)).
The raw material isobutylene may be isobutylene directly used or may be isobutylene produced by a dehydration reaction of tertiary butyl alcohol.
In the method for producing methacrylic acid by the direct-coupled two-stage contact gas phase oxidation method of the present invention, the isobutylene catalytic gas phase oxidation reaction in the previous stage (step (a)) is conducted at a conversion rate of isobutylene (mol%: the same applies hereinafter) of 95. % Or more and 98% or less, more preferably 96 or more and less than 98%, still more preferably 97% or more and less than 98%. In addition, the final yield of methacrylic acid is improved by reacting so that the total selectivity of methacrolein and methacrylic acid (hereinafter also referred to as pre-stage effective selectivity) is 80% or more, more preferably 84% or more. Preferred above. The upper limit of the total selectivity is most preferably 100%, but in practice it is 95% or less, more usually 90% or less.
The isobutylene conversion rate in the preceding step (a) can be adjusted to the above range depending on the catalyst used, the reaction temperature, the gas flow rate, and the like. These can be easily determined by those skilled in the art by appropriately conducting preliminary tests in consideration of the performance of the pre-reaction catalyst and the shape of the pre-reactor.

The catalyst used for the catalytic gas phase oxidation of isobutylene in step (a) is generally a catalyst known as a catalyst for the production of methacrolein in the catalytic gas phase oxidation of isobutylene and achieves the above performance. Any can be used. Many such catalysts are generally known.
For example, it is most commonly a bismuth-molybdenum-containing composite oxide catalyst. Examples thereof include the catalysts disclosed in JP 2007-61763 A, JP 10-216523 A, JP 2009-114119 A, and the like. Examples of preferred catalysts include molybdenum, bismuth and iron, and cobalt, nickel (Ni), tin (Sn), zinc (Zn), tungsten (W), chromium (Cr), manganese (Mn), magnesium (Mg), antimony (Sb), cerium (Ce), at least one selected from the group consisting of titanium (Ti) (preferably one or two of cobalt and nickel), and an alkali metal (preferably potassium , At least one selected from the group consisting of rubidium and cesium) or composite oxide catalysts containing thallium.

As an example of the composite oxidation catalyst, the following general formula (2)
Mo ₁₃ Bi _aa Fe _bb Co _cc XX _{d ′} YY _{e ′ Of '} (2)
(Wherein Mo is molybdenum, Bi is bismuth, Fe is iron, Co is cobalt, XX is an alkali metal (preferably at least one selected from potassium, rubidium and cesium) or thallium, YY is nickel (Ni), tin ( At least selected from the group consisting of Sn), zinc (Zn), tungsten (W), chromium (Cr), manganese (Mn), magnesium (Mg), antimony (Sb), cerium (Ce), and titanium (Ti). Aa, bb, cc, d ′, e ′, and f ′ represent the atomic ratio of each element, aa is a positive number of 0.1 ≦ aa ≦ 10, and bb is 0.1 ≦ bb ≦ 10.0 positive number, cc is 1 ≦ cc ≦ 10.0 positive number, d ′ is 0.01 ≦ d ′ ≦ 2 positive number, e ′ is 0 ≦ e ′ ≦ 2.0 positive number Each represents a number, and f ′ is the acid of each element by firing Represents a value determined by the degree.) Represented by may be mentioned composite oxide catalyst. As XX, cesium is more preferable, and as YY, nickel is more preferable.
As a more preferable catalyst, in the above formula (2), XX is at least one selected from potassium, rubidium and cesium (preferably cesium), and YY is nickel.

The catalyst for producing methacrylic acid used in the step (b) of the method for producing methacrylic acid by direct-coupled two-stage contact gas phase oxidation of the present invention comprises catalyst active components (molybdenum, phosphorus, vanadium, ammonia, potassium, rubidium and An aqueous solution containing a compound containing one or more of at least one element selected from cesium) or an aqueous dispersion of the compound so that all active ingredients are contained (hereinafter, both are referred to as a slurry) Can be obtained by molding and baking the obtained dry powder.
In addition to the above active components (molybdenum, phosphorus, vanadium, and at least one element selected from ammonia, potassium, rubidium and cesium), the catalyst used in the present invention includes antimony, arsenic, copper, silver , Magnesium, zinc, aluminum, boron, germanium, tin, lead, titanium, zirconium, chromium, rhenium, bismuth, tungsten, iron, cobalt, nickel, cerium, thorium may be included as an optional component .

The composition of the active component element excluding oxygen before firing of the preferred catalyst used in the step (b) of the present invention can be represented by the following general formula (a-1) from the addition ratio of the raw material compounds.
_{Mo 10 V a P b (NH} 4) c X dd Y e (a-1)
(In the formula, the same symbols as in general formula (1) all have the same meaning as in general formula (1), and dd represents 0 ≦ d ≦ 3.0.)
In the above catalyst, X is more preferably Cs, and Y is more preferably at least two elements selected from the group consisting of Sb, As and Cu. In some cases, a catalyst in which Y is two types of As and Cu in the formula (a-1) is also preferable.
The catalyst used in the subsequent step (b) is preferably prepared by adding an ammonium group-containing compound during slurry preparation to prepare a slurry and having a composition represented by the formula (a-1). Therefore, a catalyst obtained by molding and calcining a dry composition having this elemental composition is preferable as a catalyst used in the subsequent step (b) of the present invention.
The catalyst composition after calcination has the following general formula (a′-1)
_{Mo 10 V a P b (NH} 4) c 'X dd Y e O f (a'-1)
(Where c ′ represents a positive number of 0 ≦ c ′ ≦ 10, f represents a value determined by the degree of oxidation of each element by firing, and the other symbols have the same meaning as in the general formula (a-1)). Represents
Can be expressed as
In the above formula, preferable c ′ is a positive number of 0.01 ≦ c ′ ≦ 5, and preferable dd is a positive number of 0.1 ≦ d ≦ 3.0.
Further, a catalyst in which the calcination temperature is set to 400 ° C. or lower so that an ammonium component is contained in the baked catalyst is more preferable.

One of the more preferable embodiments of the catalyst used in the step (b) of the present invention is represented by the general formula (1) when the catalyst composition after calcination is expressed from the addition ratio of the active ingredient-containing compound.
_{Mo 10 V a P b (NH} 4) c X d Y e O f (1)
(Wherein Mo is molybdenum, V is vanadium, P is phosphorus, (NH ₄ ) is an ammonium group, X is at least one element selected from K, Rb, and Cs, Y is Sb, As, Cu, Ag, Mg) Represents at least one element selected from Zn, Al, B, Ge, Sn, Pb, Ti, Zr, Cr, Re, Bi, W, Fe, Co, Ni, Ce, Th, Represents the atomic ratio of each element, a is 0.1 ≦ a ≦ 6.0, preferably 0.3 ≦ a ≦ 2.0, and b is 0.5 ≦ b ≦ 6.0, preferably 0.7 ≦ b ≦ 2.0, c is 0.1 ≦ c ≦ 10.0, preferably 0.5 ≦ c ≦ 5.0, d is 0.1 ≦ d ≦ 3.0, preferably 0.4 ≦ d ≦ 1.5, e is 0 ≦ e ≦ 3.0, preferably 0.01 ≦ e ≦ 0.5, f is a value determined by the oxidized state after firing)
It is represented by

However, it is known that when the catalyst is calcined, the ammonium component is considerably lost when calcined at a high temperature of about 300 to 400 ° C. and almost completely lost when calcined at a temperature exceeding 420 ° C. 4-63139), the amount of the ammonium component in the catalyst after the actual firing is in the range of 0 to 10 in the above formula (1) depending on the firing conditions. A preferable value of c after firing is from about a trace (0.001) to about 5, and most preferably about 0.01 to 1.
Therefore, the composition after firing in the more preferred embodiment has the following general formula (1 ′).
_{Mo 10 V a P b (NH} 4) c 'X d Y e O f (1')
(In the formula, c ′ represents a positive number of 0 ≦ c ′ ≦ 10, and other symbols represent the same meaning as in the general formula (1)).
It is more preferable when c ′ is 0.01 to 5 and more preferable when c ′ is 0.01 to 1.
In the catalysts of the above formulas (1) and (1 ′), X is more preferably Cs, and Y is more preferably at least two elements selected from the group consisting of Sb, As and Cu. In some cases, a catalyst in which Y is two types of As and Cu in the formula (a-1) is also preferable.

In any catalyst represented by any of the above formulas, a slurry dry powder is formed and then calcined to provide a catalyst for use in the step (b) of the present invention. Molding may be in any form that can be used as a catalyst. As a preferred form, a coated catalyst obtained by coating a granular simple substance with a slurry dry powder is preferred.
Moreover, it is preferable to use the binder mentioned later in the above coating.
Furthermore, a coated catalyst obtained by blending a catalyst strength improver and a pore forming agent is more preferred as the catalyst for step (b) of the present invention. In particular, a catalyst using a pore-forming agent is less susceptible to poisoning with unreacted isobutylene and is suitable for the production of methacrylic acid by direct-coupled two-stage contact gas phase oxidation, and improves the yield of methacrylic acid, and the catalyst It is preferable for extending the life.
If the catalyst used in the step (b) of the present invention is a catalyst that satisfies the above conditions, it is less poisoned even in the presence of unreacted isobutylene, and the preceding step (a) is performed under the optimum conditions described above. Even if the reaction is carried out, the reduction in methacrolein conversion due to unreacted isobutylene poisoning is small, and the yield of methacrylic acid can be improved.
When the specific oxidation catalyst as described above is used in step (b), the reduction in methacrolein conversion rate due to poisoning with unreacted isobutylene is less than when other catalysts are used. The yield of the catalyst can be increased and the catalyst life due to poisoning can be reduced, so that the catalyst life can be extended.

For example, adverse effects (also called poisoning) due to the presence of unreacted isobutylene,
(1) a reaction product gas in a state where there is almost no unreacted isobutylene obtained by reacting the preceding step (a) at a conversion rate of isobutylene higher than 99%;
(2) The reaction of the preceding step (a) with an isobutylene conversion rate higher than 96% and a conversion rate lower than 98, using a reaction product gas containing more than 2% unreacted isobutylene and less than 4%, As a result of conducting a direct-coupled two-stage contact gas phase oxidation reaction under the same conditions, and examining the difference in the methacrolein conversion rate and the selectivity of methacrylic acid, the following facts were found.
1. Even when the oxidation catalyst for the above step (b) is used, except for the most preferable Example 2, in Examples 1 and 3 to 4, when a reaction product gas containing unreacted isobutylene is used, the presence of unreacted isobutylene Although the selectivity of methacrylic acid is slightly increased as compared with the case where the reaction product gas is not used, the methacrolein conversion rate is further decreased.
That is, when a reaction product gas in which unreacted isobutylene is present in an amount of more than 2% and less than 3% is used, the methacrolein conversion is reduced by 8 to 12% and the selectivity of methacrylic acid is increased by 1 to 2% Then, it is a decrease that cannot be compensated for. Furthermore, the more unreacted isobutylene, the greater the reduction in methacrolein conversion. When a reaction product gas in which unreacted isobutylene is present in an amount of more than 3% and less than 4% is used, the methacrolein conversion is reduced by 19 to 23%, and the selectivity of methacrylic acid is increased by 4 to 8%. This is a decline that cannot be compensated for.

Thus, even if the specific catalyst used in the present invention is used, the adverse effect (poisoning) of unreacted isobutylene cannot be avoided. However, in the meantime, the reduction in the conversion rate is within 25%. Can be evaluated. On the other hand, in the catalyst of Example 4, the rate of decrease of the catalyst of Examples 1 and 3 was about 19%, staying within 20%, whereas it decreased to 23%, exceeding 20%. Therefore, it was found that the unreacted isobutylene is susceptible to adverse effects (poisoning) as compared with other catalysts of the present invention. That is, even in the catalyst used in the step (b) of the present invention, a catalyst that does not use an ammonium component during catalyst preparation is considered to be more poisonous than a catalyst that uses an ammonium component.
The atomic ratio of the catalytically active component described in the present invention is calculated from the raw material charge unless otherwise specified. Further, f of oxygen in the general formula (1) is a value that is naturally determined depending on the firing conditions and the like.

Hereinafter, embodiments will be described according to the above-described steps. These are common to all the catalysts for the step (b).
Step 1: Preparation of Slurry In the present invention, the active ingredient-containing compound used for catalyst preparation includes chloride, sulfate, nitrate, oxide or acetate of the active ingredient element. Specific examples of preferred compounds include nitrates such as potassium nitrate and cobalt nitrate, oxides such as molybdenum oxide, vanadium pentoxide, antimony trioxide, cerium oxide, zinc oxide and germanium oxide, and acetates such as cesium acetate and ammonium acetate. , Hydroxides such as cesium hydroxide and ammonium hydroxide, and acids (or salts thereof) such as orthophosphoric acid, phosphoric acid, boric acid, aluminum phosphate or 12 tungstophosphoric acid. The compounds containing these active ingredients may be used alone or in combination of two or more. The slurry can be obtained by uniformly mixing each active ingredient-containing compound and water. The order of addition of the active ingredient-containing compound in preparing the slurry is selected from the group consisting of potassium, rubidium and cesium after sufficiently dissolving the compound containing molybdenum, vanadium, phosphorus and other metal elements as required. It is preferable to add a compound containing at least one element and an ammonium compound to the slurry. As a metal compound other than the essential active component in this case, for example, as a copper compound, copper acetate (cuprous acetate, cupric acetate, basic copper acetate, etc., preferably cupric acetate) or copper oxide (oxidized oxide) When using cuprous, cupric oxide), a preferable effect may be obtained.
For the ammonium component, any compound having an ammonium group may be used, but ammonium hydroxide, ammonium acetate and the like are preferable, and ammonium acetate is most preferable.

  The temperature at which the slurry is prepared is preferably heated to a temperature at which molybdenum, phosphorus, vanadium and, if necessary, a compound containing another metal element can be sufficiently dissolved. The temperature when adding the compound containing at least one element selected from the group consisting of potassium, rubidium and cesium and the ammonium compound is usually in the range of 0 to 35 ° C, preferably about 10 to 30 ° C. In this case, the resulting catalyst tends to be highly active. The amount of water used in the slurry is not particularly limited as long as the total amount of the compound used can be completely dissolved or mixed uniformly. The amount of water used may be appropriately determined in consideration of the drying method and drying conditions. Usually, it is about 200-2000 mass parts with respect to 100 mass parts of total mass of the compound for slurry preparation. The amount of water may be large, but if it is too large, the energy cost of the drying process becomes high, and there are many disadvantages such as the case where it cannot be completely dried.

Step 2: Drying Next, the slurry obtained above is dried to obtain a dry powder (composite oxide). The drying method is not particularly limited as long as the slurry can be completely dried. Examples thereof include drum drying, freeze drying, spray drying, and evaporation to dryness. Among these, in the present invention, spray drying which can be dried from a slurry state into powder or granules in a short time is particularly preferable.
The drying temperature of spray drying varies depending on the slurry concentration, the liquid feeding speed, etc., but the temperature at the outlet of the dryer is generally 70 to 150 ° C. Moreover, it is preferable to dry so that the average particle diameter of the slurry dry body obtained in this case may be 30-700 micrometers.

Step 3: Molding The dry powder (active ingredient powder) obtained in Step 2 is used after being molded into a columnar shape, tablet, ring shape, spherical shape, etc., in order to reduce the pressure loss of the reaction gas in the oxidation reaction. . Of these, it is particularly preferable to coat an inert carrier to form a coated catalyst, since selectivity can be improved and reaction heat can be removed.
This coating step is preferably the rolling granulation method described below. In this method, for example, in a device having a flat or uneven disk at the bottom in a fixed container, the support in the container is vigorously stirred by repeated rotation and revolution movements by rotating the disk at high speed. In this method, the carrier is coated with a binder, a dry powder, and a coating mixture to which other additives such as a molding aid, a strength improver, and a pore-forming agent are added if necessary. The method of adding the binder is as follows: 1) Preliminarily mix with the coating mixture 2) Add at the same time as adding the coating mixture into the fixed container 3) Add after adding the coating mixture into the fixed container 4) Addition of the coating mixture before it is added to the fixed container, 5) Dividing the coating mixture and the binder, respectively, and combining 2) to 4) as appropriate, and adding the total amount, etc. can be arbitrarily adopted. . Of these, in 5), for example, the coating rate is adjusted by using an auto feeder or the like so that a predetermined amount is supported on the carrier without adhesion of the coating mixture to the fixed container wall and aggregation of the coating mixture. Is preferred.
The binder is not particularly limited as long as it is at least one selected from the group consisting of water and an organic compound having a boiling point of 150 ° C. or less at 1 atm. Specific examples of binders other than water include alcohols such as methanol, ethanol, propanols and butanols, preferably alcohols having 1 to 4 carbon atoms, ethers such as ethyl ether, butyl ether or dioxane, and esters such as ethyl acetate or butyl acetate. , Ketones such as acetone or methyl ethyl ketone, and aqueous solutions thereof, and ethanol is particularly preferable. When ethanol is used as the binder, ethanol / water = 10/0 to 0/10 (mass ratio), preferably 9/1 to 1/9 (mass ratio) by mixing with water. The usage-amount of these binders is 2-60 mass parts normally with respect to 100 mass parts of coating mixtures, Preferably it is 10-50 mass parts.

Specific examples of the carrier in the coated catalyst include a spherical carrier having a diameter of 1 to 15 mm, preferably 2.5 to 10 mm, such as silicon carbide, alumina, silica alumina, mullite and alundum. These carriers are usually those having a porosity of 10 to 70%. The ratio of the carrier to the coating mixture is usually used in such an amount that the coating mixture / (coating mixture + carrier) = 10 to 75% by mass, preferably 15 to 60% by mass.
When the ratio of the coating mixture is large, the reaction activity of the coated catalyst increases, but the mechanical strength tends to decrease. On the contrary, when the ratio of the coating mixture is small, the mechanical strength is large, but the reaction activity tends to be small.
In addition, silica gel, diatomaceous earth, an alumina powder etc. are mentioned as a shaping | molding adjuvant used as needed in the above. The usage-amount of a shaping | molding adjuvant is 1-60 mass parts normally with respect to 100 mass parts of dry powder.
Further, if necessary, the use of inorganic fibers (for example, ceramic fibers or whiskers) inert to the catalytically active component and the reaction gas as a strength improver is useful for improving the mechanical strength of the catalyst, and is preferable. . The amount of these fibers used is usually 1 to 30 parts by mass with respect to 100 parts by mass of the dry powder.
Examples of the pore-forming agent used as necessary in the above include organic polymer compounds such as wheat flour, purified starch, and cellulose, and those having a decomposition point or a transition point of less than 430 ° C. are preferably used. More preferred are wheat flour and starches such as purified starch, and most preferred is wheat flour. The amount of the pore forming agent used is usually 1 to 40 parts by mass, preferably 1 to 30 parts by mass with respect to 100 parts by mass of the dry powder (active ingredient powder).
The catalyst calcined with the pore-forming agent added is preferably any of the above-mentioned catalysts because it is less susceptible to adverse effects even in the presence of unreacted isobutylene.
In this way, the dry powder is coated on the carrier, and the coated product obtained at this time usually has a diameter of about 3 to 15 mm.

Step 4: Calcination The coated catalyst obtained as described above can be directly used for the catalytic gas phase oxidation reaction as a catalyst, but calcination is preferred because the catalyst activity may be improved. The firing temperature in this case is usually 100 to 450 ° C., preferably 250 to 420 ° C., more preferably 250 to less than 400 ° C., more preferably 300 to less than 400 ° C. in order to leave the ammonium component. The firing time is 1 to 20 hours.
The ratio of the active component to the entire coated catalyst obtained as described above is 10 to 60% by mass.

Hereafter, the manufacturing method of methacrylic acid by the direct connection two-stage contact gas phase reaction of this invention is demonstrated.
In the method for producing methacrylic acid by the direct-coupled two-stage contact gas phase reaction of the present invention, the reactor in the former stage (step (a)) is charged with an oxidation catalyst for oxidizing isobutylene to methacrolein, and the latter stage ( The reactor of the step (b)) is filled with the catalyst for the latter stage, and a mixed gas of isobutylene, oxygen and a dilution gas is supplied to the reactor of the former stage, and the preceding oxidation reaction and the latter stage oxidation reaction are performed. Thus, the desired methacrylic acid can be produced.
Examples of the oxygen include pure oxygen gas and gas containing oxygen such as air. Examples of the dilution gas include nitrogen, carbon dioxide, water vapor, and a mixed gas thereof.
The preceding catalytic gas phase oxidation reaction comprises a mixed gas of isobutylene, oxygen and diluent gas, for example, isobutylene: oxygen: water vapor: nitrogen in a molar ratio of isobutylene 1: oxygen 2-5: water vapor 1: nitrogen 10-20. The mixed gas is supplied to the pre-stage reactor, and prepared and reacted at the pre-stage reaction bath temperature of 200 ° C. to 450 ° C. so that the conversion of isobutylene is 95 to 98%. In this case, it is preferable to carry out the reaction so that the pre-stage effective selectivity is 80% or more. The source gas may be supplied at a normal space velocity of 400 to 4000 / hr [normal temperature and normal pressure (NTP) conditions] to maintain the isobutylene conversion rate. Next, the reaction product gas is supplied as it is to the subsequent reactor. The reaction product gas contains 2% to 5% unreacted isobutylene.
The subsequent oxidation reaction is performed at a reaction bath temperature of 200 to 450 ° C., preferably 250 to 400 ° C., more preferably about 260 ° C. to 360 ° C. It is preferable to carry out the reaction at a methacrolein conversion rate of 50% to 85%, preferably 60% to 85%, more preferably 70% to 85%.
In addition, the catalytic gas phase oxidation reaction in the preceding stage and the subsequent stage can be performed under pressure or under reduced pressure, but generally a pressure around atmospheric pressure is suitable.

The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to the examples.
In the following, the conversion rate, selectivity and yield are defined as follows.
Isobutylene conversion rate = (number of moles of reacted isobutylene / number of moles of supplied isobutylene) × 100
Conversion rate of methacrolein = (number of moles of methacrolein reacted in the latter stage / number of moles of methacrolein supplied in the latter stage) × 100
First stage effective selectivity = {(number of moles of methacrolein produced in the first stage + number of moles of methacrylic acid produced in the first stage) / number of moles of reacted isobutylene} × 100
Subsequent methacrylic acid selectivity = (number of moles of methacrylic acid produced in the latter stage / number of moles of methacrolein reacted in the latter stage) × 100
Methacrylic acid yield = (total number of moles of methacrylic acid produced in the former and latter stages / number of moles of isobutylene supplied) x 100
The catalyst composition in the following examples is an active component composition excluding oxygen.

Example 1
1) Preparation of catalyst To 5680 ml of pure water, 800 g of molybdenum trioxide, 40.43 g of vanadium pentoxide, 73.67 g of 85 mass% normal phosphoric acid and 26.29 g of 60 mass% arsenic acid aqueous solution were added, and the mixture was heated and stirred at 92 ° C. for 3 hours. A clear reddish brown solution was obtained. Subsequently, the solution was cooled to 15 to 20 ° C., and 944.8 g of a 9.1% by mass cesium hydroxide aqueous solution was gradually added with stirring, and aged at 15 to 20 ° C. for 1 hour to give a yellow slurry Got.
Subsequently, 89.87 g of ammonium acetate was further added to the slurry, and further aged at 15 to 20 ° C. for 30 minutes.
Subsequently, 44.37 g of cupric acetate was further added to the slurry and further aged at 15 to 20 ° C. for 30 minutes.
Subsequently, this slurry was spray-dried to obtain a composite oxide. The composition of the obtained composite oxide was Mo ₁₀ V _0.8 P _1.15 As _0.2 Cu _0.4 Cs _1.0 (NH ₄ ) _2.1
It is.
Next, 144 g of the composite oxide and 24 g of the strength improver (ceramic fiber) were uniformly mixed, and 166 g of a spherical porous alumina support (particle size: 4.0 mm) was coated and molded using about 80 g of a 90% by mass ethanol aqueous solution as a binder. Subsequently, the obtained molded product was calcined at 360 ° C. for 5 hours under an air flow to obtain a target coated catalyst. The composition of the obtained catalyst is the same as the above composition except that the ammonium component is largely lost by calcination and is considered to be about 0.01 to 1.0.

2) Two-stage oxidation reaction of isobutylene Two reaction tubes are arranged in series, each filled with a catalyst for producing methacrolein and a catalyst for producing methacrylic acid, and a reaction for obtaining methacrylic acid by supplying a raw material gas is performed. It was. Details are shown below.
A coated catalyst obtained by molding a bismuth-molybdenum-based composite oxide in the same manner as the catalyst of Example 1 was used as a catalyst for the preceding oxidation reaction. The active component composition of this catalyst is Mo ₁₂ Bi _1.7 Fe _1.8 Co _7.0 Ni _0.8 Cs _0.1
It is. 17 ml of a stainless steel reaction tube having an inner diameter of 22.2 mm is filled with the catalyst, and a raw material gas (composition (molar ratio); isobutylene: oxygen: water vapor: nitrogen = 1: 2.2: 1: 12.5) is a space velocity (SV). The oxidation reaction of isobutylene was performed under conditions of 1200 h ⁻¹ .
In the pre-stage oxidation reaction, the isobutylene conversion rate was first adjusted to exceed about 99%, and the reaction was carried out by sequentially lowering the conversion rate to the 97% level and the 96% level. In this case, the reaction bath temperature is 360 to 370 ° C. when the isobutylene conversion rate is 99% or more, 345 to 350 ° C. when the isobutylene conversion rate is 97%, and the isobutylene conversion rate is 96%. 340-342 ° C.
The catalyst prepared in 1) above was used for the latter stage oxidation reaction. The catalyst was filled in 25 ml of a stainless steel reaction tube having an inner diameter of 18.4 mm, and the product gas of the above-mentioned pre-stage oxidation reaction was introduced to carry out the post-stage oxidation reaction. The post-reaction bath temperature was constant at 275 ° C., and the reaction gas composition produced in the pre-stage oxidation reaction was changed depending on the difference in the conversion of isobutylene in the pre-stage oxidation reaction. The reaction results were measured to determine how the methacrolein conversion rate and methacrylic acid selectivity change in the latter stage due to the difference in conversion rate (difference in the amount of unreacted isobutylene).
The results are shown in Table 1.

Example 2
A coated catalyst was prepared in the same manner as in Example 1 except that 144 g of the composite oxide, 24 g of the strength improver (ceramic fiber) and 14 g of the pore forming agent (wheat flour) were mixed in Example 1. The active component composition in the composite oxide before firing is Mo ₁₀ V _0.8 P _1.15 As _0.2 Cu _0.4 Cs _1.0 (NH ₄ ) _2.1
It is.
The composition of the catalyst after calcination is the same as the above composition except that the ammonium component is largely lost by calcination and is considered to be about 0.01 to 1.0.
A two-stage oxidation reaction of isobutylene was carried out in the same manner as in Example 1 except that this coated catalyst was used and the reaction bath temperature of the latter stage oxidation reaction was 280 ° C. The results are shown in Table 1.

Example 3
To 5680 ml of pure water, 800 g of molybdenum trioxide, 40.43 g of vanadium pentoxide and 73.67 g of 85% by mass orthophosphoric acid were added and stirred at 92 ° C. for 3 hours to obtain a reddish brown transparent solution. Subsequently, this solution was cooled to 15 to 20 ° C., and 283.4 g of a 9.1 mass% cesium hydroxide aqueous solution was gradually added thereto while stirring. The obtained mixture was aged at 15 to 20 ° C. for 1 hour to obtain a yellow slurry.
Subsequently, 89.87 g of ammonium acetate was further added to the slurry, and further aged at 15 to 20 ° C. for 30 minutes.
Subsequently, 44.37 g of cupric acetate was further added to the slurry and further aged at 15 to 20 ° C. for 30 minutes.
Subsequently, this slurry was spray-dried to obtain a composite oxide. The composition of the obtained composite oxide was Mo ₁₀ V _0.8 P _1.15 As _0.2 Cu _0.4 Cs _0.3 (NH ₄ ) _2.1
It is.
Next, this composite oxide granule was fired at 310 ° C. for 5 hours under air flow to obtain a pre-fired granule. There was a mass loss of about 4% due to pre-firing. To 131 g of the pre-fired granules, 10 g of antimony trioxide and 7 g of a strength improver (ceramic fiber) were uniformly mixed. The obtained granule was coated and molded on 179 g of a spherical porous alumina carrier (particle size: 4.0 mm) using about 70 g of a 50% by mass ethanol aqueous solution as a binder. The resulting molded product was then calcined at 380 ° C. for 5 hours under air flow to obtain the desired coated catalyst. The composition of the obtained catalyst is the same as the above composition except that the ammonium component is largely lost by calcination and is considered to be about 0.01 to 1.0.
A two-stage oxidation reaction of isobutylene was carried out in the same manner as in Example 1 except that this coated catalyst was used and the reaction bath temperature of the latter stage oxidation reaction was set to 300 ° C. The results are shown in Table 1.

Example 4
800 g of molybdenum trioxide, 40.43 g of vanadium pentoxide, 73.67 g of 85 mass% normal phosphoric acid and 65.73 g of 60 mass% arsenic acid aqueous solution were added to 5680 ml of pure water, and the mixture was heated and stirred at 92 ° C. for 3 hours to obtain a reddish brown transparent solution Got.
Subsequently, 44.37 g of cupric acetate was further added to the solution, followed by further aging at 92 ° C. for 30 minutes.
Subsequently, this slurry was spray-dried to obtain a composite oxide. The composition of the obtained composite oxide was Mo ₁₀ V _0.8 P _1.15 Cu _0.4 As _0.5
It is.
Next, 214 g of the composite oxide and 30 g of the strength improver (ceramic fiber) were uniformly mixed, and 200 g of a spherical porous alumina support (particle size: 4.0 mm) was coated and molded using about 50 g of a 90% by mass ethanol aqueous solution as a binder. Next, the obtained molded product was calcined at 310 ° C. for 5 hours under an air flow to obtain a target coated catalyst. The composition of the obtained catalyst is the same as described above.
A two-stage oxidation reaction of isobutylene was carried out in the same manner as in Example 1 except that this coated catalyst was used and the reaction bath temperature of the latter stage oxidation reaction was 305 ° C.
The results are shown in Table 1.

From the above results, the following matters were found.
It can be said that a catalyst having a lower decrease in methacrolein conversion rate by lowering the isobutylene conversion rate is less susceptible to the adsorption poisoning of isobutylene.
As in Example 1, the catalyst in which the addition amount of the X component is 0.4 to 1.5 with respect to molybdenum 10 is not easily affected by the adsorption poisoning of isobutylene.
By appropriately adding a pore forming agent as in Example 2, the influence of the adsorption poisoning of isobutylene is greatly reduced.
Further, as in Example 3, the catalyst satisfying the composition described in claim 2 has an effect of reducing the influence of the adsorption poisoning of isobutylene.
In the above table, the yield of methacrylic acid in the above examples is not shown because the unreacted residual isobutylene has an adverse effect on the methacrolein conversion rate, but the methacrylic acid yield is not shown. The combined methacrylic acid and methacrylic acid produced in the latter stage were 48 mol% to slightly less than 59 mol% based on the supplied isobutylene. In any of Examples 1, 3 and 4, the highest methacrylic acid yield was achieved when the isobutylene conversion rate was 99% or more. However, when the isobutylene conversion rate was 99% or more, the first stage catalyst was thermally Considering that the catalyst life is shortened due to the large load, it is considered that the reaction at an isobutylene conversion of 95 mol% or more and 98 mol% or less, particularly 96 mol% or more and less than 98 mol% is most preferable.
In particular, in Example 2, there was no adverse effect due to the presence of unreacted isobutylene, and the conversion of isobutylene was 97.92 mol% and 96.43 compared with the case where the conversion of isobutylene was 99.01 mol%. In the case of mol%, the methacrolein conversion rate in the latter stage is rather improved. That is, the yields of methacrylic acid were also 54.65 mol% (when the isobutylene conversion was 99.01 mol%) and 56.10 mol% (when the isobutylene conversion was 97.92 mol%), respectively. And 55.41 mol% (when the conversion of isobutylene is 96.43 mol%), the coexistence of an ammonium component and a pore forming agent indicates that it is particularly preferable.

Industrial applicability

  In the direct-coupled two-stage contact gas phase oxidation method, when the specific catalyst used in the present invention is used, even if it is unreacted isobutylene-containing methacrolein gas, the reduction in the conversion rate of methacrolein to methacrylic acid is small. Even when the conversion rate of the pre-stage isobutylene in the reaction product gas is lowered and the reaction is carried out under favorable conditions that improve the pre-stage effective selectivity, methacrylic acid can be obtained in a high yield, and as a result, the conversion rate of the pre-stage isobutylene is lowered. The temperature is low, the heat load on the catalyst is reduced, and the life of the first stage catalyst can be extended. In addition, the catalyst life can be extended because both the second stage catalyst and the catalyst have little unreacted isobutylene poisoning. The methacrylic acid production method of the present invention using a specific catalyst in the direct-coupled two-stage catalytic gas phase oxidation method is very useful for improving the yield of methacrylic acid in the direct-coupled two-stage catalytic gas phase oxidation method. .

Claims (20)

(A) oxidizing isobutylene to methacrolein in the gas phase with molecular oxygen or a molecular oxygen-containing gas in the presence of an oxidation catalyst (step (a)),
(B) The obtained reaction product gas containing unreacted isobutylene and methacrolein is oxidized in the gas phase with molecular oxygen or a molecular oxygen-containing gas in the presence of an oxidation catalyst to produce methacrylic acid. (Step (b)),
A method,
The reaction is performed at a conversion rate of isobutylene in the step (a) of 95 mol% or more and 98 mol% or less, and the oxidation catalyst of the step (b) is molybdenum, vanadium, phosphorus, potassium, rubidium, cesium and ammonium components. A method for producing methacrylic acid, which is a catalyst obtained by molding and firing a catalyst composition containing one or two kinds selected from the group consisting of: In step (b), the oxidation catalyst is represented by the general formula (1).
_{Mo 10 V a P b (NH} 4) c X d Y e O f (1)
(Wherein Mo is molybdenum, V is vanadium, P is phosphorus, (NH ₄ ) is an ammonium group, X is at least one element selected from K, Rb, and Cs, Y is Sb, As, Cu, Ag, Mg) Represents at least one element selected from the group consisting of Zn, Al, B, Ge, Sn, Pb, Ti, Zr, Cr, Re, Bi, W, Fe, Co, Ni, Ce, and Th; h represents an atomic ratio of each element, a is a positive number of 0.1 ≦ a ≦ 6.0, b is a positive number of 0.5 ≦ b ≦ 6.0, and c is 0.1 ≦ c ≦ A positive number of 10.0, d is a positive number of 0.1 ≦ d ≦ 3.0, and e is a positive number of 0 ≦ e ≦ 3.0. The method for producing methacrylic acid according to claim 1, which is a catalyst for producing methacrylic acid obtained by molding and firing a product. .   The methacrylic acid according to claim 2, wherein a catalyst for producing methacrylic acid obtained by calcining the catalyst composition having the active ingredient composition represented by the general formula (1) at a temperature of 300 to less than 400 ° C is used. Acid production method.   The method for producing methacrylic acid according to claim 2, wherein Y is at least two elements selected from the group consisting of Sb, As and Cu.   The method for producing methacrylic acid according to claim 4, wherein Y is both As and Cu.   Molding of the catalyst composition having the active ingredient composition represented by the general formula (1) is carried out by using a slurry dried body of the composition together with a strength improver and water or an alcohol having 1 to 4 carbon atoms as a binder. The method for producing methacrylic acid according to claim 2, wherein the catalyst is coated on top to form a spherical coating catalyst.   Molding of the catalyst composition having the active ingredient composition represented by the general formula (1) is carried out by adding water or an alcohol having 1 to 4 carbon atoms together with a strength improving agent and a pore forming agent to the slurry dried body of the composition. The method for producing methacrylic acid according to claim 2, wherein the catalyst is coated on a spherical carrier as a binder to form a spherical coated catalyst.   The method for producing methacrylic acid according to claim 1 or 2, wherein a bismuth-molybdenum-containing composite oxide catalyst is used in step (a).   The bismuth-molybdenum-containing composite oxide catalyst is at least one selected from the group consisting of molybdenum, bismuth and iron, and cobalt, nickel, tin, zinc, tungsten, chromium, manganese, magnesium, antimony, cerium, and titanium. Furthermore, the manufacturing method of methacrylic acid of Claim 8 which uses the complex oxide catalyst containing an alkali metal or thallium.   The methacrylic acid solution according to claim 1 or 2, wherein the reaction product gas containing unreacted isobutylene and methacrolein in step (b) contains 2 to 5 mol% of unreacted isobutylene in the total amount of the reaction product gas. Production method. General formula (1)
_{Mo 10 V a P b (NH} 4) c X d Y e O f (1)
(Wherein Mo is molybdenum, V is vanadium, P is phosphorus, (NH ₄ ) is an ammonium group, X is at least one element selected from K, Rb, and Cs, Y is Sb, As, Cu, Ag, Mg) Represents at least one element selected from Zn, Al, B, Ge, Sn, Pb, Ti, Zr, Cr, Re, Bi, W, Fe, Co, Ni, Ce, Th, Represents the atomic ratio of each element, a is a positive number of 0.1 ≦ a ≦ 6.0, b is a positive number of 0.5 ≦ b ≦ 6.0, and c is 0.1 ≦ c ≦ 10.0. A positive number of 0.1 ≦ d ≦ 3.0, e represents a positive number of 0 ≦ e ≦ 3.0, and a slurry of a catalyst composition having an active component composition represented by: On the spherical carrier, the dried product, together with a strength improver and a pore-forming agent, water or an alcohol having 1 to 4 carbon atoms as a binder Coated with, formed into spherical coated catalyst, 100 to 450 steps in claim 1 obtained by firing ° C. (b) for producing methacrylic acid oxidation catalyst.   The catalyst for producing methacrylic acid for step (b) according to claim 11, wherein Y is at least two elements selected from the group consisting of Sb, As and Cu.   It is obtained by molding a catalyst composition having an active component composition represented by the general formula (1), wherein Y is at least one element selected from the group consisting of As and Cu, and then firing at 250 to 400 ° C. A catalyst for producing methacrylic acid for step (b) in claim 12.   The catalyst for methacrylic acid production according to claim 11 or 13, wherein the ratio of the active ingredient to the entire spherical coated catalyst is 10 to 60% by mass.   The catalyst for producing methacrylic acid for step (b) according to claim 11, wherein the ratio of the pore forming agent is 1 to 40% by mass with respect to the active ingredient. The catalyst obtained by molding and firing the catalyst composition for the step (b) is represented by the following general formula (a′-1)
_{Mo 10 V a P b (NH} 4) c 'X dd Y e O f (a'-1)
(Wherein Mo is molybdenum, V is vanadium, P is phosphorus, (NH ₄ ) is an ammonium group, X is at least one element selected from K, Rb, and Cs, Y is Sb, As, Cu, Ag, Each represents at least one element selected from Mg, Zn, Al, B, Ge, Sn, Pb, Ti, Zr, Cr, Re, Bi, W, Fe, Co, Ni, Ce, and Th; c ′, dd, g and f represent the atomic ratio of each element, a is a positive number of 0.1 ≦ a ≦ 6.0, b is a positive number of 0.5 ≦ b ≦ 6.0, c 'Represents a positive number of 0 ≦ c' ≦ 10, dd represents a positive number of 0 ≦ dd ≦ 3.0, and e represents a positive number of 0 ≦ e ≦ 3.0.)
The method for producing methacrylic acid according to claim 1, wherein the catalyst has an active ingredient composition represented by:   When the catalyst composition is molded, the dried slurry of the composition is coated on a spherical carrier with water or an alcohol having 1 to 4 carbon atoms as a binder together with a strength improver and a pore forming agent. The method for producing methacrylic acid according to claim 16.   The method for producing methacrylic acid according to claim 17, wherein Y is at least two elements selected from the group consisting of Sb, As and Cu.  The method for producing methacrylic acid according to claim 16, wherein c ′ is a positive number satisfying 0.01 ≦ c ′ ≦ 5.   The method for producing methacrylic acid according to claim 16, wherein dd is a positive number satisfying 0.1 ≦ d ≦ 3.0.