JP2010155198A - Method for regenerating catalyst for producing methacrylic acid and method for producing the methacrylic acid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for regenerating a catalyst for producing methacrylic acid, with which both of the conversion ratio and selectivity coefficient of the catalyst can be excellently recovered. <P>SOLUTION: The method for regenerating the catalyst for producing methacrylic acid from the deteriorated one of the new catalyst consisting of a heteropolyacid compound having the composition containing phosphorus, molybdenum and an alkali metal, comprises the steps of: mixing a phosphorus compound and water in the deteriorated catalyst; drying the obtained mixture; and firing the dried mixture. In the method, the amount of the phosphorus compound to be mixed in the deteriorated catalyst is adjusted so that the atomic ratio of the phosphorus to the alkali metal in the heteropolyacid compound constituting the regenerated catalyst is made larger than that of the phosphorus to the alkali metal in the heteropolyacid compound constituting the new catalyst. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention provides a method for regenerating a catalyst for production of methacrylic acid by regenerating a deteriorated catalyst comprising a heteropolyacid compound having a composition containing phosphorus, molybdenum and an alkali metal element, and using the regenerated catalyst obtained by this method. And a method for producing methacrylic acid.

  A catalyst for producing methacrylic acid comprising a heteropolyacid compound having a composition containing phosphorus, molybdenum and an alkali metal element can be used for a long time in a gas phase catalytic oxidation reaction using, for example, methacrolein, etc. It is known that the catalyst activity is reduced by scattering or disappearing from the catalyst, or by absorbing moisture or receiving a heat load for some reason.

  As a method for regenerating such a deteriorated catalyst, for example, a catalyst that is regenerated by mixing an amount of a phosphorus compound corresponding to the amount of disappearance with water and treating the deteriorated catalyst in which phosphorus is partially scattered and disappeared. A method is reported in which the atomic ratio of phosphorus to the alkali metal element in the heteropolyacid compound is the same as that of the new catalyst before use in the reaction (Patent Documents 1 and 2).

JP 2001-286762 A JP 2001-286863 A

  However, although the conversion rate of the catalyst can be recovered satisfactorily by the conventional regeneration method, it cannot always be recovered to a satisfactory level in terms of selectivity.

  Accordingly, an object of the present invention is to provide a method for regenerating a catalyst for methacrylic acid production that can satisfactorily recover both the conversion rate and selectivity of the catalyst. Furthermore, an object of the present invention is to provide a method for producing methacrylic acid with a good conversion and selectivity using the regenerated catalyst obtained by this method.

  The present inventor has intensively studied to solve the above problems. As a result, when the phosphorous compound and water are mixed with the deteriorated catalyst and processed, the heteropolyacid compound in which the atomic ratio of phosphorus to the alkali metal element of the heteropolyacid compound constituting the regenerated catalyst constitutes the new catalyst before deterioration The inventors have found that the above problems can be solved by adjusting the amount of the phosphorus compound mixed with the deterioration catalyst so as to be larger than the atomic ratio of phosphorus with respect to the alkali metal element, and have completed the present invention.

That is, this invention consists of the following structures.
(1) A method for regenerating a catalyst for producing methacrylic acid from a deteriorated catalyst obtained by deteriorating a new catalyst comprising a heteropolyacid compound having a composition containing phosphorus, molybdenum and an alkali metal element, wherein the deteriorated catalyst includes a phosphorus compound and water. And then drying and calcining, and the atomic ratio of phosphorus to the alkali metal element of the heteropolyacid compound constituting the regenerated catalyst is an alkali of the heteropolyacid compound constituting the new catalyst. A method for regenerating a catalyst for methacrylic acid production, comprising adjusting a mixing amount of a phosphorus compound with respect to the deterioration catalyst so as to be larger than an atomic ratio of phosphorus with respect to a metal element.
(2) The new catalyst is represented by the following formula (I)
PaMobVcXdYeOx (I)
(In the formula (I), P, Mo and V represent phosphorus, molybdenum and vanadium, respectively, X represents at least one alkali metal element selected from the group consisting of potassium, rubidium and cesium, Y represents copper, arsenic Represents at least one element selected from the group consisting of antimony, boron, silver, bismuth, iron, cobalt, lanthanum, cerium and thallium, O represents oxygen, and when b = 12, 0 <a ≦ 3 0 ≦ c ≦ 3, 0 <d ≦ 3, 0 ≦ e ≦ 3, and x is a value determined by the oxidation state of each element)
The regeneration method of the catalyst for methacrylic acid manufacture as described in said (1) which consists of heteropoly acid compound shown by these.
(3) When the atomic ratio of phosphorus to the alkali metal element of the heteropolyacid compound constituting the new catalyst is α and the atomic ratio of phosphorus to the alkali metal element of the heteropolyacid compound constituting the regenerated catalyst is β, The method for regenerating a catalyst for methacrylic acid production according to the above (1) or (2), wherein the value of β / α is 1.2 or less.
(4) The method for regenerating a catalyst for methacrylic acid production according to any one of the above (1) to (3), wherein a nitric acid radical and an ammonium radical are also mixed when the phosphorus compound and water are mixed with the deteriorated catalyst.
(5) The method for regenerating a catalyst for methacrylic acid production according to any one of (1) to (4), wherein the deterioration catalyst is subjected to a heat treatment at 350 ° C. or higher before the phosphorus compound and water are mixed with the deterioration catalyst.
(6) A compound selected from the group consisting of methacrolein, isobutyraldehyde, isobutane and isobutyric acid in the presence of the catalyst for producing methacrylic acid regenerated by the method according to any one of (1) to (5). A method for producing methacrylic acid, which is subjected to a gas phase catalytic oxidation reaction.

  According to the present invention, when the catalyst for producing methacrylic acid is regenerated, both the conversion rate and selectivity of the catalyst can be recovered satisfactorily. Moreover, if the regenerated catalyst regenerated by this method is used, methacrylic acid can be produced with good conversion and selectivity.

Hereinafter, the present invention will be described in detail.
The method for regenerating a catalyst for producing methacrylic acid according to the present invention obtains a regenerated catalyst by subjecting a deteriorated catalyst obtained by deterioration of a new catalyst for producing methacrylic acid (hereinafter also referred to as “new catalyst”) to regeneration. Is the method.
The catalyst for production of methacrylic acid (new catalyst) in the present invention is composed of a heteropolyacid compound having a composition essentially including phosphorus, molybdenum and an alkali metal element, and may be composed of a free heteropolyacid, It may consist of a salt of a heteropolyacid. Especially, what consists of an acidic salt (partially neutralized salt) of heteropolyacid is preferable, More preferably, it consists of an acidic salt of Keggin type heteropolyacid.

  Preferred examples of the alkali metal element contained in the heteropolyacid compound as an essential constituent element include potassium, rubidium, cesium and the like. Further, the heteropolyacid compound preferably contains vanadium as an element other than phosphorus, molybdenum and alkali metal elements, and also includes copper, arsenic, antimony, boron, silver, bismuth, iron, cobalt, lanthanum, cerium and It is desirable to contain at least one element selected from the group consisting of thallium (hereinafter also referred to as “Y element”).

A preferred composition of the heteropolyacid compound constituting the methacrylic acid production catalyst (new catalyst) is shown by the following formula (I).
PaMobVcXdYeOx (I)
(In the formula (I), P, Mo and V represent phosphorus, molybdenum and vanadium, respectively, X represents at least one alkali metal element selected from the group consisting of potassium, rubidium and cesium, Y represents copper, arsenic Represents at least one element selected from the group consisting of antimony, boron, silver, bismuth, iron, cobalt, lanthanum, cerium and thallium (that is, the Y element), O represents oxygen, and b = 12. (0 <a ≦ 3, 0 ≦ c ≦ 3, 0 <d ≦ 3, 0 ≦ e ≦ 3, and x is a value determined by the oxidation state of each element)

  The catalyst for producing methacrylic acid (new catalyst) includes, for example, a compound containing each of the above-described elements constituting a heteropolyacid compound (for example, oxoacid, oxoacid salt, oxide, nitrate, carbonate, hydroxide of each element) Products, halides, etc.), formed into a desired shape, and then fired. For example, phosphoric acid, phosphate and the like are used as the compound containing phosphorus, and molybdate such as molybdic acid and ammonium molybdate, molybdenum oxide, molybdenum chloride and the like are used as the compound containing molybdenum. As the compound containing a metal element, an oxide, nitrate, carbonate, hydroxide, halide, or the like is used. In addition, as the compound containing vanadium, vanadate, vanadate (metavanadate) such as ammonium vanadate (ammonium metavanadate), vanadium oxide, vanadium chloride, etc. are used. Oxo acids, oxo acid salts, oxides, nitrates, carbonates, hydroxides, halides and the like are used.

  Such a methacrylic acid production catalyst (new catalyst) is used for the production of methacrylic acid, for example, part of phosphorus scatters or disappears from the catalyst, or absorbs moisture or receives a heat load for some reason. Depending on the case, the catalytic activity may decrease. In the regeneration method of the present invention, the deteriorated catalyst having the reduced catalyst activity is used as a target for regeneration treatment.

In the regeneration method of the present invention, a mixing step in which a phosphorus compound and water are mixed with the deteriorated catalyst is essential, and then a regenerated catalyst is obtained through a drying step and a calcination step.
In the mixing step, it is important to adjust the mixing amount of the phosphorus compound based on the composition of the deteriorated catalyst used for regeneration and the composition of the new catalyst. That is, the mixing amount of the phosphorus compound with respect to the deterioration catalyst is such that the atomic ratio of phosphorus to the alkali metal element of the heteropolyacid compound constituting the regenerated catalyst is phosphorus atoms relative to the alkali metal element of the heteropolyacid compound constituting the new catalyst. Adjust to be greater than the ratio. For example, when using a deteriorated catalyst in which a part of phosphorus is scattered and disappeared, instead of adding an amount of phosphorus corresponding to the lost amount and returning it to the same atomic ratio as the new catalyst, an amount of phosphorus larger than the lost amount is added. By adding, the atomic ratio of phosphorus to the alkali metal element in the obtained regenerated catalyst is adjusted to be larger than that of the new catalyst. On the other hand, even when using a deteriorated catalyst that has deteriorated due to moisture absorption, etc., although there is no scattering or disappearance of phosphorus, by adding a phosphorus compound, the atomic ratio of phosphorus to the alkali metal element in the regenerated catalyst obtained is that of a new catalyst (this In this case, the deterioration catalyst is adjusted to be larger than the same atomic ratio. Thereby, both the conversion rate and the selectivity of the catalyst can be recovered satisfactorily.
In particular, in the regeneration method of the present invention, the atomic ratio of phosphorus to the alkali metal element of the heteropolyacid compound constituting the new catalyst is α, and the atomic ratio of phosphorus to the alkali metal element of the heteropolyacid compound constituting the regenerated catalyst. When β is β, the value of β / α is preferably 1.2 or less from the viewpoint of conversion and selectivity.

  Specifically, the mixing amount of the phosphorus compound in the mixing step is determined by examining the catalyst composition (type and amount of constituent components) of the new catalyst and the deteriorated catalyst used for regeneration by fluorescent X-ray analysis, ICP emission analysis, etc. From the difference in the composition of the catalyst, the type and amount of the element disappeared in the production of methacrylic acid, etc. are grasped, and based on the result, the regenerated catalyst obtained has a specific composition (the atomic ratio of phosphorus to the alkali metal element described above) What is necessary is just to determine so that it may have a composition which becomes a range. The catalyst composition of the obtained regenerated catalyst can be analyzed and confirmed by fluorescent X-ray analysis, ICP emission analysis, or the like, as described above.

As the phosphorus compound to be mixed in the mixing step, one or two or more types may be appropriately selected from compounds containing phosphorus that can be used for manufacturing a new catalyst, such as phosphoric acid and phosphate.
As the water to be mixed in the mixing step, ion exchange water is usually used. The amount of water mixed is 1 part by weight of molybdenum atoms in the mixture obtained in the mixing step (total of molybdenum contained in the deterioration catalyst and molybdenum contained in the molybdenum compound added in the mixing step as described later). The amount is usually 1 to 20 parts by weight.

  In the mixing step, a compound containing a molybdenum compound and other catalyst constituent elements can be mixed with the above-described phosphorus compound and water in the deterioration catalyst. That is, when the methacrylic acid production catalyst (new catalyst) comprising the heteropoly acid compound is used for the production of methacrylic acid, not only phosphorus but also molybdenum and other catalyst constituent elements are scattered and lost from the catalyst. This may cause a decrease in catalyst activity. Therefore, when the phosphorus compound is mixed, the catalytic activity can be effectively recovered by mixing the molybdenum compound or the like and supplementing the lost molybdenum or the like.

  For example, when a molybdenum compound is mixed, the amount of the mixture is usually determined so that the atomic ratio of molybdenum to the alkali metal element of the heteropolyacid compound constituting the regenerated catalyst is the alkali metal element of the heteropolyacid compound constituting the new catalyst. So that the atomic ratio of molybdenum is the same (in other words, an amount corresponding to the disappearance of molybdenum is added to return to the same atomic ratio as that of the new catalyst). However, in order to improve the catalyst life, the mixing amount of the molybdenum compound is such that the atomic ratio of molybdenum to the alkali metal element of the heteropolyacid compound constituting the regenerated catalyst is the alkali metal of the heteropolyacid compound constituting the new catalyst. It is preferable to adjust so as to be smaller than the atomic ratio of molybdenum to the element.

Specifically, the amount of the molybdenum compound mixed is determined so that the atomic ratio of molybdenum to the alkali metal element of the obtained regenerated catalyst falls within a desired range based on the amount of disappearance lost in the production of methacrylic acid as in the case of the phosphorus compound. do it.
As the molybdenum compound to be mixed in the mixing step, one or more compounds selected from molybdenum-containing compounds that can be used for production of a new catalyst, such as molybdic acid, molybdate such as ammonium molybdate, molybdenum oxide, and molybdenum chloride. Two or more kinds may be appropriately selected.
In addition, when the compound containing the other catalyst constituent elements (elements other than phosphorus and molybdenum) is mixed, the amount of the mixture is within a range in which almost the same conversion rate, selectivity and catalyst life are exhibited in the regenerated catalyst. If not, the atomic ratio of the element to the alkali metal element of the heteropolyacid compound constituting the regenerated catalyst is not particularly limited, the atomic ratio of the element to the alkali metal element of the heteropolyacid compound constituting the new catalyst Or the atomic ratio of the element to the alkali metal element of the heteropolyacid compound constituting the regenerated catalyst may be adjusted to be equivalent to the alkali metal element of the heteropolyacid compound constituting the new catalyst. It is also possible to adjust so as to be larger or smaller than the atomic ratio of the element to.

The deterioration catalyst to be subjected to the mixing step is preferably subjected to heat treatment at 350 ° C. or higher as a pretreatment before mixing the phosphorus compound and water. Thereby, the conversion rate and selectivity in the regenerated catalyst obtained can be further improved.
The upper limit of the treatment temperature of the heat treatment performed as a pretreatment for the deteriorated catalyst is not particularly limited, but is preferably 600 ° C. or less, more preferably 550 ° C. or less. The treatment time for heat treatment is not particularly limited, but is usually 0.1 to 24 hours, preferably 0.5 to 10 hours.

  The heat treatment performed as a pretreatment for the deteriorated catalyst may be performed in an oxidizing gas atmosphere or a non-oxidizing gas atmosphere, but may be performed in an oxidizing gas atmosphere. preferable. The oxidizing gas here is a gas containing an oxidizing substance, and examples thereof include an oxygen-containing gas. In the case of using an oxygen-containing gas, the oxygen concentration is usually about 1 to 30% by volume. As the oxygen source, air or pure oxygen is usually used, and diluted with an inert gas as necessary. . The oxidizing gas may contain moisture as required, but the concentration is usually 10% by volume or less. Of these, air is preferable as the oxidizing gas.

When the deterioration catalyst to be used in the mixing step is a molded body, it may be used as it is, but if necessary, it can be pulverized by a conventionally known method before mixing the phosphorus compound and water. However, if the molded product (degraded catalyst) contains fibers that develop the strength of the catalyst, there is a concern that the strength may be reduced if the fibers are cut, so that the fibers are not cut. It is preferable to adjust the degree.
In addition, when performing both the grinding | pulverization process and the said heat processing performed as pre-processing to the deterioration catalyst provided to the said mixing process, the order of both processing is not restrict | limited especially, However, Usually, after performing a pulverization process, it heat-processes. .

In the mixing step, it is preferable to mix a nitrate group and an ammonium group when mixing the phosphorus compound and water with the deterioration catalyst. Thereby, the conversion rate and selectivity in the regenerated catalyst obtained can be further improved.
In order to mix the nitrate root, as a nitrate root supply source, for example, nitric acid or a nitrate such as ammonium nitrate may be mixed. On the other hand, to mix the ammonium root, as an ammonium root supply source, for example, Ammonia and ammonium salts such as ammonium nitrate, ammonium carbonate, ammonium hydrogen carbonate, and ammonium acetate may be mixed. Preferably, nitric acid and ammonium nitrate are used as the nitrate radical source, and ammonia and ammonium nitrate are preferably used as the ammonium radical source. The ratio of the nitrate radical supply source and the ammonium radical supply source can be adjusted as appropriate, but it is effective to adjust the molar ratio of the ammonium radical to the nitrate radical to be 1.3 or less. In addition, when an ammonium radical and a nitrate radical are contained in the phosphorus compound etc. which are mixed at a mixing process, those amounts are also considered and it adjusts so that it may become the said ratio.

  In the mixing step, the order of mixing the components described above is not particularly limited, and may be set as appropriate.

  The mixture obtained in the mixing step is then subjected to a drying step, but before being subjected to the drying step, it is preferable to subject the mixture to aging by heating at 100 ° C. or higher in a closed container. . By subjecting the mixture obtained in the mixing step to such aging treatment, the catalytic activity can be effectively recovered. The upper limit of the heating temperature in the aging treatment is preferably 200 ° C. or less, and more preferably 150 ° C. or less. In order to obtain a sufficient activity recovery effect, the heating time in the aging treatment is usually 0.1 hour or longer, preferably 2 hours or longer, and 10 hours or shorter from the viewpoint of productivity.

  The drying method carried out in the drying step is not particularly limited, and for example, a method usually used in this field such as an evaporation to dryness method, a spray drying method, a drum drying method, and an airflow drying method may be adopted. it can. Further, the drying conditions may be set as appropriate so that the water content in the mixture is sufficiently reduced, and is not particularly limited.

  The dried product obtained in the drying step is then subjected to a firing step, but before being subjected to the firing step, a desired shape (ring shape, pellet shape, spherical shape, cylindrical shape, etc.) is necessary. A forming process for forming the film can be performed. The molding process may be performed by a method usually used in this field, such as tableting molding or extrusion molding. In the molding treatment, water, a molding aid, a pore agent and the like can be added to the dried product as necessary. Examples of the molding aid include ammonium nitrate as well as ceramic fiber and glass fiber. In particular, ammonium nitrate has not only a function as a molding aid but also a function as a pore agent.

  It is preferable that the molded body obtained by the molding process is subsequently subjected to a temperature and humidity control process. A more stable catalyst can be obtained by subjecting the temperature and humidity control treatment to the firing step. Specifically, the temperature control and humidity control treatment is performed by exposing the molded body for about 0.5 to 10 hours in an atmosphere of 40 to 100 ° C. and a relative humidity of 10 to 60%. The treatment may be performed, for example, in a temperature-controlled and humidity-controlled tank or by spraying a temperature-controlled and humidity-controlled gas on the molded body. In addition, air is usually used as the atmospheric gas for the treatment, but an inert gas such as nitrogen may be used.

  The firing step can be performed by a method usually used in this field, and is not particularly limited. For example, it may be performed in an atmosphere of an oxidizing gas such as oxygen, or may be performed in an atmosphere of a non-oxidizing gas such as nitrogen, and the firing temperature is usually 300 ° C. or higher. Preferably, a two-stage firing method is employed in which the first-stage firing is performed in an oxidizing gas atmosphere and then the second-stage firing is performed in a non-oxidizing gas atmosphere. Thus, by carrying out calcination in two stages, the catalyst life can be recovered more favorably.

  When firing is performed in two stages, the oxidizing gas used in the first stage firing is a gas containing an oxidizing substance, and examples thereof include an oxygen-containing gas. In the case of using an oxygen-containing gas, the oxygen concentration is usually about 1 to 30% by volume. As the oxygen source, air or pure oxygen is usually used, and diluted with an inert gas as necessary. . The oxidizing gas may contain moisture as required, but the concentration is usually 10% by volume or less. Of these, air is preferable as the oxidizing gas. The first stage firing is usually performed under such an oxidizing gas stream. Moreover, the temperature of 1st step | paragraph baking is 360-410 degreeC normally, Preferably it is 380-400 degreeC.

  When firing is performed in two stages, the non-oxidizing gas used in the second stage firing is a gas that does not substantially contain an oxidizing substance such as oxygen. For example, nitrogen, carbon dioxide, helium, argon, etc. An active gas is mentioned. The non-oxidizing gas may contain moisture as required, but the concentration is usually 10% by volume or less. Of these, nitrogen is preferable as the non-oxidizing gas. The second-stage firing is usually performed under such a non-oxidizing gas stream. Moreover, the temperature of 2nd-stage baking is 420-500 degreeC normally, Preferably it is 420-450 degreeC.

  In addition, it is preferable to perform the heat processing hold | maintained at the temperature of about 180-300 degreeC in the atmosphere of oxidizing gas or non-oxidizing gas as pre-baking prior to the said baking process.

  Thus, it is possible to obtain a regenerated catalyst in which both the conversion rate and selectivity of the catalyst have been successfully recovered. This regenerated catalyst is made of a heteropolyacid compound, like a new catalyst, and may be made of a free heteropolyacid or a salt of a heteropolyacid. Especially, what consists of an acidic salt of heteropolyacid is preferable, and what consists of acidic salt of a Keggin type heteropolyacid is more preferable.

  The method for producing methacrylic acid of the present invention comprises a compound selected from the group consisting of methacrolein, isobutyraldehyde, isobutane and isobutyric acid in the presence of the catalyst for producing methacrylic acid regenerated by the regeneration method of the present invention (hereinafter referred to as “ Is sometimes referred to as a “raw material compound”). Thus, by using the regenerated catalyst of the present invention, methacrylic acid can be produced with good conversion and selectivity.

  The production of methacrylic acid is usually carried out by filling a fixed bed multi-tubular reactor with a catalyst and supplying a raw material gas containing the raw material compound and oxygen to the reactor, but is not limited thereto. It is also possible to adopt a reaction format such as a fluidized bed or a moving bed. Air is usually used as the oxygen source. The source gas may contain nitrogen, carbon dioxide, carbon monoxide, water vapor and the like as components other than the source compound and oxygen.

  The raw material compound contained in the raw material gas is not necessarily a high-purity purified product. For example, as methacrolein, a reaction containing methacrolein obtained by a gas phase catalytic oxidation reaction of isobutylene or t-butyl alcohol. Product gas can also be used. In addition, only 1 type may be sufficient as the raw material compound contained in the said raw material gas, and 2 or more types may be sufficient as it.

What is necessary is just to set the reaction conditions in manufacture of methacrylic acid suitably according to the kind etc. of the raw material compound contained in raw material gas. For example, when methacrolein is used as the raw material compound, the concentration of methacrolein in the raw material gas is usually 1 to 10% by volume, the water vapor concentration is 1 to 30% by volume, the molar ratio of oxygen to methacrolein is 1 to 5, space. The reaction is carried out under conditions where the speed is 500 to 5000 h ⁻¹ (standard condition standard), the reaction temperature is 250 to 350 ° C., and the reaction pressure is 0.1 to 0.3 MPa. On the other hand, when isobutane is used as the raw material compound, the isobutane concentration in the raw material gas is usually 1 to 85% by volume, the water vapor concentration is 3 to 30% by volume, the molar ratio of oxygen to isobutane is 0.05 to 4, and the space velocity Is carried out under the conditions of 400 to 5000 h ⁻¹ (standard condition standard), reaction temperature of 250 to 400 ° C., and reaction pressure of 0.1 to 1 MPa. In addition, when isobutyraldehyde or isobutyric acid is used as the raw material compound, generally the same reaction conditions as when methacrolein is used as the raw material are employed.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not restrict | limited to these.

The air used below contains 2% by volume of moisture (corresponding to the atmosphere), and nitrogen used below contains substantially no moisture.
The analysis and evaluation of the catalyst obtained in each of the following examples were performed as follows.

<Catalyst composition (ratio of constituent elements)>
Using a fluorescent X-ray analyzer (“ZSX Primus II” manufactured by Rigaku Corporation), the catalyst was determined by fluorescent X-ray analysis.

<Catalyst activity test>
9 g of catalyst was filled in a glass microreactor having an inner diameter of 16 mm, and a raw material gas prepared by mixing methacrolein, air, steam and nitrogen (composition: methacrolein 4 vol%, molecular oxygen 12 vol%, Steam 17 vol%, Nitrogen 67 vol%) was supplied at a space velocity of 670 h ⁻¹ and reacted at a furnace temperature (furnace temperature for heating the microreactor) of 280 ° C. for 1 hour. The temperature was raised to 0 ° C. and reacted for 1 hour, and then the reaction was again carried out at a furnace temperature of 280 ° C. for 1 hour. Then, the outlet gas (the gas after the reaction) at the end of the reaction (that is, when 1 hour has passed since the furnace temperature was again set to 280 ° C.) was sampled and analyzed by gas chromatography, and the conversion rate ( %), Selectivity (%) and yield (%).

Conversion rate (%) = [number of moles of reacted methacrolein ÷ supplied methacrolein
Number of moles] × 100
Selectivity (%) = [number of moles of methacrylic acid produced ÷ reacted methacrolein
Number of moles] × 100
Yield (%) = [conversion (%) × selectivity (%)] ÷ 100

(Reference Example 1-Preparation of a new catalyst)
In 224 kg of ion-exchanged water heated to 40 ° C., 38.2 kg of cesium nitrate [CsNO ₃ ], 27.4 kg of 75 wt% orthophosphoric acid, and 25.2 kg of 70 wt% nitric acid were dissolved, and this was designated as solution A. On the other hand, after 297 kg of ammonium molybdate tetrahydrate [(NH ₄ ) ₆ Mo ₇ O ₂₄ · 4H ₂ O] was dissolved in 330 kg of ion-exchanged water heated to 40 ° C., ammonium metavanadate [NH ₄ VO ₃ ] 8.19kg was suspended and this was made into the B liquid.

While maintaining the temperature of the liquid A and the liquid B at 40 ° C., the liquid A was dropped into the liquid B with stirring, and the mixed liquid after the dropping was stirred at 120 ° C. for 5.8 hours in a sealed container. Next, 10.2 kg of antimony trioxide [Sb ₂ O ₃ ] and 10.2 kg of copper nitrate trihydrate [Cu (NO ₃ ) ₂ .3H ₂ O] are added to ion-exchanged water with respect to the obtained mixed liquid. It added in the state suspended in 23 kg, and it stirred at 120 degreeC after that for 5 hours within the airtight container. Next, the slurry-like mixture thus obtained is dried with a spray dryer, and 4 parts by weight of ceramic fibers, 13 parts by weight of ammonium nitrate, and ion-exchanged water are added to 100 parts by weight of the obtained dry powder. After adding 7 parts by weight and kneading, it was extruded into a cylindrical shape having a diameter of 5 mm and a height of 6 mm. The obtained molded body was dried at a temperature of 90 ° C. and a relative humidity of 30% for 3 hours, and then heat treated in the order of 22 hours at 220 ° C. in an air stream and 1 hour at 250 ° C. in an air stream (before Firing). Next, the temperature was raised to 435 ° C. in a nitrogen stream and held at the same temperature for 3 hours. After cooling to 300 ° C. in the nitrogen stream, the air stream was switched from nitrogen to air, and again 390 ° C. in the air stream. The mixture was heated up to 3 hours and held at the same temperature for 3 hours to fire. Then, after cooling to 70 degreeC in airflow, the molded object was taken out and this was made into the new catalyst.

  The resulting new catalyst is a Keggin type composition comprising phosphorus, molybdenum, vanadium, antimony, copper and cesium in atomic ratios of 1.5, 12, 0.5, 0.5, 0.3 and 1.4, respectively. It consisted of an acid salt of a heteropolyacid. The atomic ratio α of phosphorus to cesium in the new catalyst was 1.07 (≈1.5 / 1.4). When this new catalyst was subjected to the activity test, the results shown in Table 1 were obtained.

(Reference Example 2-Preparation of deteriorated catalyst)
The new catalyst obtained in Reference Example 1 was subjected to methacrolein catalytic gas phase oxidation reaction for a long time to obtain a deteriorated catalyst.

  The acid salt of the heteropolyacid constituting the obtained deterioration catalyst is 1.3, 9.6, 0.5, 0.5, 0.3 and 1.3 for phosphorus, molybdenum, vanadium, antimony, copper and cesium, respectively. The composition contained at an atomic ratio of 4. When this deteriorated catalyst was subjected to the activity test, the results shown in Table 1 were obtained.

Example 1
200 g of the deteriorated catalyst obtained in Reference Example 2 was heat-treated at 450 ° C. for 5 hours in an air atmosphere. The obtained heat-treated catalyst (deteriorated catalyst) was added to 400 g of ion-exchanged water and stirred, and then 31.5 g of molybdenum trioxide [MoO ₃ ] and 3.7 g of 75 wt% orthophosphoric acid were added. At this time, the amount of orthophosphoric acid added was determined by comparing the composition of the acid salt of the heteropolyacid in the new catalyst obtained in Reference Example 1 with the composition of the acid salt of the heteropolyacid in the deteriorated catalyst obtained in Reference Example 2. The amount of phosphorus decreased in the deteriorated catalyst was grasped, and the amount of phosphorus atoms added was determined within a range that is larger than this amount of decrease. Further, the amount of molybdenum trioxide added was determined in the same manner as described above so that the amount of molybdenum reduced in the deterioration catalyst was grasped and the amount of molybdenum atoms added was the same as this amount of reduction.

Subsequently, after 69.2 g of ammonium nitrate [NH ₄ NO ₃ ] was added, the temperature was raised to 70 ° C. and held at the same temperature for 1 hour, and then 12.5 g of 25% by weight aqueous ammonia was added to reach 70 ° C. For 1 hour and then stirred at 120 ° C. for 5 hours in a sealed container to obtain a slurry mixture. The molar ratio of ammonium radicals to nitrate radicals in this slurry mixture was 1.2.

  Next, the obtained slurry-like mixture was dried at 120 ° C., and 5 parts by weight of ammonium nitrate and 7 parts by weight of ion-exchanged water were added to and kneaded with 100 parts by weight of the obtained dried product. Extruded into a 6 mm long cylinder. The obtained molded body was dried at a temperature of 90 ° C. and a relative humidity of 30% for 3 hours, and then heat treated in the order of 22 hours at 220 ° C. in an air stream and 1 hour at 250 ° C. in an air stream (before Firing). Next, the temperature is raised to 390 ° C. in an air stream and held at the same temperature for 3 hours, then the air stream is switched from air to nitrogen, the temperature is raised to 435 ° C. in the nitrogen stream and held at the same temperature for 4 hours. And fired. Then, after cooling to 70 degreeC in nitrogen stream, the molded object was taken out and this was made into the reproduction | regeneration catalyst (1).

  The obtained regenerated catalyst (1) contains phosphorus, molybdenum, vanadium, antimony, copper and cesium in atomic ratios of 1.58, 12, 0.5, 0.5, 0.3 and 1.4, respectively. The acid salt of a Keggin type heteropolyacid. In this regenerated catalyst (1), the atomic ratio β of phosphorus to cesium is 1.13 (≈1.58 / 1.4), and the value of β / α is 1.05 (≈ (1.58 / 1). 4) / (1.5 / 1.4)). When this regenerated catalyst (1) was subjected to the activity test, the results shown in Table 1 were obtained.

(Example 2)
A regenerated catalyst (2) was obtained in the same manner as in Example 1 except that the addition amount of 75 wt% orthophosphoric acid was changed from 3.7 g to 3.3 g in Example 1.
The obtained regenerated catalyst (2) contains phosphorus, molybdenum, vanadium, antimony, copper and cesium in atomic ratios of 1.55, 12, 0.5, 0.5, 0.3 and 1.4, respectively. The acid salt of a Keggin type heteropolyacid. In this regenerated catalyst (2), the atomic ratio β of phosphorus to cesium is 1.11 (≈1.55 / 1.4), and the value of β / α is 1.03 (≈ (1.55 / 1). 4) / (1.5 / 1.4)). When this regenerated catalyst (2) was subjected to the activity test, the results shown in Table 1 were obtained.

(Comparative Example 1)
A comparative regenerated catalyst (C1) was obtained in the same manner as in Example 1, except that the amount of 75 wt% orthophosphoric acid added was changed from 3.7 g to 2.7 g.
The obtained regenerated catalyst (C1) contains phosphorus, molybdenum, vanadium, antimony, copper and cesium in atomic ratios of 1.5, 12, 0.5, 0.5, 0.3 and 1.4, respectively. The acid salt of a Keggin type heteropolyacid. In this regenerated catalyst (C1), the atomic ratio β of phosphorus to cesium is 1.07 (≈1.5 / 1.4), and the value of β / α is 1.00 (= (1.5 / 1 4) / (1.5 / 1.4)). When this regenerated catalyst (C1) was subjected to the activity test, the results shown in Table 1 were obtained.

(Comparative Example 2)
A comparative regenerated catalyst (C2) was obtained in the same manner as in Example 1 except that the amount of 75 wt% orthophosphoric acid added was changed from 3.7 g to 2.1 g in Example 1.
The obtained regenerated catalyst (C2) contains phosphorus, molybdenum, vanadium, antimony, copper and cesium in atomic ratios of 1.46, 12, 0.5, 0.5, 0.3 and 1.4, respectively. The acid salt of a Keggin type heteropolyacid. In this regenerated catalyst (C2), the atomic ratio β of phosphorus to cesium is 1.04 (≈1.46 / 1.4), and the value of β / α is 0.97 (≈ (1.46 / 1). 4) / (1.5 / 1.4)). When this regenerated catalyst (C2) was subjected to the activity test, the results shown in Table 1 were obtained.

Claims (6)

A method for regenerating a catalyst for methacrylic acid production from a deteriorated catalyst obtained by deteriorating a new catalyst composed of a heteropolyacid compound having a composition containing phosphorus, molybdenum and an alkali metal element,
Including the steps of mixing a phosphorus compound and water with the deterioration catalyst, then drying and firing, and
The ratio of phosphorus to the alkali metal element of the heteropolyacid compound constituting the regenerated catalyst is larger than the atomic ratio of phosphorus to the alkali metal element of the heteropolyacid compound constituting the new catalyst. A method for regenerating a catalyst for producing methacrylic acid, comprising adjusting a mixing amount of a phosphorus compound. A new catalyst is represented by the following formula (I)
PaMobVcXdYeOx (I)
(In the formula (I), P, Mo and V represent phosphorus, molybdenum and vanadium, respectively, X represents at least one alkali metal element selected from the group consisting of potassium, rubidium and cesium, Y represents copper, arsenic Represents at least one element selected from the group consisting of antimony, boron, silver, bismuth, iron, cobalt, lanthanum, cerium and thallium, O represents oxygen, and when b = 12, 0 <a ≦ 3 0 ≦ c ≦ 3, 0 <d ≦ 3, 0 ≦ e ≦ 3, and x is a value determined by the oxidation state of each element)
The regeneration method of the catalyst for methacrylic acid production of Claim 1 which consists of heteropoly acid compound shown by these.   When the atomic ratio of phosphorus to the alkali metal element of the heteropolyacid compound constituting the new catalyst is α and the atomic ratio of phosphorus to the alkali metal element of the heteropolyacid compound constituting the regenerated catalyst is β, β / α The method for regenerating a catalyst for methacrylic acid production according to claim 1 or 2, wherein the value of is not more than 1.2.   The method for regenerating a catalyst for methacrylic acid production according to any one of claims 1 to 3, wherein a nitrate radical and an ammonium radical are also mixed when the phosphorus compound and water are mixed with the deterioration catalyst.   The method for regenerating a catalyst for methacrylic acid production according to any one of claims 1 to 4, wherein the deterioration catalyst is subjected to heat treatment at 350 ° C or higher before the phosphorus compound and water are mixed with the deterioration catalyst.   A compound selected from the group consisting of methacrolein, isobutyraldehyde, isobutane and isobutyric acid is subjected to a gas phase catalytic oxidation reaction in the presence of the catalyst for producing methacrylic acid regenerated by the method according to claim 1. A process for producing methacrylic acid, characterized in that: