JP7532841B2 - Method for producing catalyst for synthesis of unsaturated carboxylic acid - Google Patents

Description

The present invention relates to a method for producing a catalyst for synthesizing an unsaturated carboxylic acid. More specifically, the present invention relates to a method for producing a catalyst for synthesizing an unsaturated carboxylic acid, which is used in producing an unsaturated carboxylic acid by catalytically oxidizing an unsaturated aldehyde with an oxygen-containing gas in the gas phase.

Catalysts that contain molybdenum as an essential component are generally used to produce unsaturated carboxylic acids by catalytically oxidizing unsaturated aldehydes with oxygen-containing gases in the gas phase. Specifically, improvements to catalysts and production methods used in the production of acrylic acid from acrolein and other raw materials, and methacrylic acid from methacrolein and other raw materials, are being vigorously pursued from various perspectives.

The process for producing unsaturated carboxylic acids comprises catalytically oxidizing an olefin and an oxygen-containing gas in the gas phase in a fixed bed reactor packed with a catalyst.
The catalyst packed in the fixed bed reactor is generally a catalyst in which powder of catalytic component elements is molded into a predetermined shape, or a catalyst in which catalytic component elements are supported on an inert carrier having a predetermined shape.

Patent Document 1 presents a method for producing a catalyst used in producing an unsaturated carboxylic acid or the like by catalytically oxidizing an unsaturated aldehyde in the gas phase, in which catalyst component elements, the essential component of which is molybdenum, are mixed, suspended, dried, and pulverized to obtain a powder, and the powder is then supported on a carrier to obtain a catalyst.

The catalyst described in Patent Document 1 can improve the catalytic performance and mechanical strength of the catalyst by using dry powder of the catalyst component elements whose weight loss rate in an air atmosphere at 300°C is within a specified range.

JP 2004-243213 A

However, even with this method, the desired raw material conversion rate and product selectivity were not necessarily satisfactory.

Therefore, the objective of this invention is to obtain a catalyst with improved raw material conversion and product selectivity.

That is, the present invention relates to the following.
[1] A method for producing a catalyst for synthesizing an unsaturated carboxylic acid, comprising: a drying step of drying and heating a starting material mixture liquid in which supply source compounds of each catalyst component element are integrated to obtain a dried product; a shaping step of forming the dried product into a powder for support or obtaining a powder for support from the dried product and supporting the powder on a granular support to obtain a catalyst precursor; and a calcination step of calcining the catalyst precursor to obtain a catalyst,
The weight loss rate of the support powder at 300°C is less than 5 mass%, and the difference between the weight loss rate of the support powder at 370°C and the weight loss rate of the support powder at 300°C is within a range of 1 mass% or more and 6 mass% or less.
The weight loss rate of the support powder is a value calculated from the mass of the support powder before and after heating at 300° C. or 370° C. in an air atmosphere until there is no change in mass, using the following formula:
Weight loss rate (mass %)=[(mass (g) of support powder before heating−mass (g) of support powder after heating)/mass (g) of support powder before heating)]×100

[2] A method for producing a catalyst for synthesizing an unsaturated carboxylic acid, comprising: a drying step of drying and heating a starting material mixture liquid in which source compounds of each catalyst component element are integrated to obtain a dried product; a shaping step of converting the dried product into a powder for support or obtaining a powder for support from the dried product and supporting it on a granular support to obtain a catalyst precursor; and a calcination step of calcining the catalyst precursor to obtain a catalyst, wherein the heat treatment conditions are as follows:
Heat treatment temperature: 270°C to 330°C Heat treatment temperature retention time: 30 minutes to 2 hours

[3] The method for producing a catalyst for synthesizing an unsaturated carboxylic acid according to [1], wherein the heat treatment is carried out under the following conditions:
Heat treatment temperature: 270° C. or higher and 330° C. or lower Heat treatment temperature retention time: 30 minutes or higher and 3 hours or lower [4] The method for producing a catalyst for synthesizing an unsaturated carboxylic acid according to any one of [1] to [3], wherein the starting material mixture contains a sulfate.
[5] The method for producing the catalyst for synthesizing an unsaturated carboxylic acid according to any one of [1] to [4], further comprising a step of pulverizing the dried product.

[6] The method for producing a catalyst for synthesizing an unsaturated carboxylic acid according to any one of [1] to [5], wherein the catalyst for synthesizing an unsaturated carboxylic acid is a catalyst represented by the following composition formula (1):
Mo ₁₂ V _a X _b Cu _c Y _d Sb _e Z _{f Sig} C _h O _i (1)
(In formula (1), X represents Nb and/or W, Y represents at least one element selected from the group consisting of Mg, Ca, Sr, Ba, and Zn, and Z represents at least one element selected from the group consisting of Fe, Co, Ni, and Bi. a to i represent atomic ratios of each element and are in the ranges of 0<a≦12, 0≦b≦12, 0<c≦12, 0≦d≦8, 0≦e≦500, 0≦f≦500, 0≦g≦500, and 0≦h≦500, and i is a value that satisfies the oxidation state of other elements.)

[7] A method for producing acrylic acid by gas-phase catalytic oxidation of acrolein with an oxygen-containing gas using a catalyst produced by the method for producing a catalyst for synthesizing an unsaturated carboxylic acid described in any one of [1] to [6].

The present invention uses a catalyst for synthesizing unsaturated carboxylic acids that has a specific weight loss ratio relationship for the supporting powder, so that in the production of unsaturated carboxylic acids from unsaturated aldehydes, the raw material conversion rate and product selectivity can be increased, and the yield can be improved.

The following describes in detail the embodiments of the present invention. Note that the present invention is not limited to the following description, and can be modified in various ways within the scope of the gist of the invention.

<Catalyst>
The catalyst for synthesizing an unsaturated carboxylic acid according to the present invention (hereinafter, may be simply referred to as the "catalyst") is a catalyst for synthesizing an unsaturated carboxylic acid, which uses an unsaturated aldehyde such as acrolein or methacrolein as a raw material and performs gas-phase catalytic oxidation with an oxygen-containing gas to produce an unsaturated carboxylic acid such as acrylic acid or methacrylic acid.
This catalyst contains molybdenum (Mo) as an essential catalytic component element, and preferably contains vanadium (V) and copper (Cu) as other catalytic component elements, and more preferably contains one or more of the following components: antimony (Sb), silicon (Si), carbon (C), niobium (Nb), tungsten (W), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), zinc (Zn), iron (Fe), cobalt (Co), nickel (Ni), bismuth (Bi), and the like.

An example of such a catalyst is a catalyst represented by the following composition formula (1).
Mo ₁₂ V _a X _b Cu _c Y _d Sb _e Z _{f Sig} C _h O _i (1)

In formula (1), X represents Nb and/or W, Y represents at least one element selected from the group consisting of Mg, Ca, Sr, Ba and Zn, and Z represents at least one element selected from the group consisting of Fe, Co, Ni and Bi. a to i represent the atomic ratio of each element, and are in the ranges of 0<a≦12, 0≦b≦12, 0<c≦12, 0≦d≦8, 0≦e≦500, 0≦f≦500, 0≦g≦500, 0≦h≦500, and i is a value that satisfies the oxidation state of the other elements.

<Catalyst manufacturing method>
Next, a method for producing the catalyst will be described.
The catalyst can be produced through a process including a liquid preparation step in which a predetermined compound having each of the component elements (hereinafter referred to as "catalyst component elements") constituting the catalyst is used as a compound serving as a catalyst source (hereinafter referred to as "source compound"), in which each of the source compounds having the catalyst component elements is added to a solvent or solution to be integrated and, if necessary, heated to obtain a starting material mixture, a drying step in which the starting material mixture is heat-treated to obtain a dried product, a molding step in which the dried product is made into a support powder or a support powder is obtained from the dried product and supported on a granular support to obtain a catalyst precursor, and a calcination step in which the catalyst precursor is calcined to obtain a catalyst.

[Liquid preparation process]
First, the respective source compounds containing one or more of the catalyst component elements to be used, such as molybdenum, are combined to obtain a starting material mixture, which may be in the form of a solution or a suspension.
The term "integration" means that the aqueous solutions or aqueous dispersions of the supply source compounds of the catalyst component elements are mixed or aged all at once or stepwise.
(A) A method of mixing the above-mentioned respective supply source compounds together at once;
(b) mixing the above-mentioned source compounds together and subjecting them to aging treatment;
(c) a method of mixing the respective supply source compounds stepwise;
(d) A method in which each of the supply source compounds is mixed and aged stepwise in a repeated manner;
and a combination of (a) to (d), all of which are included in the concept of integrating the respective supply source compounds of the catalyst component elements. Here, the aging refers to "the operation of treating industrial raw materials or semi-finished products under specific conditions such as a fixed time and a fixed temperature to obtain or increase the required physical or chemical properties or to promote a specified reaction" (Chemical Encyclopedia/Kyoritsu Shuppan). In this invention, the fixed time refers to a range of 10 minutes to 24 hours, and the fixed temperature refers to a range from room temperature to the boiling point of the aqueous solution or aqueous dispersion.

[Heat treatment]
The starting material mixture obtained by this integration can be used as it is or by heating to form a starting material mixture. The heat treatment refers to a treatment for forming individual metal oxides or composite metal oxides of each of the supply source compounds of the catalyst component elements, forming metal oxides or composite metal oxides of the composite compound produced by integration, forming the final composite metal oxide, etc. The heating is not necessarily limited to one time. That is, the heating can be performed at any of the integration stages shown in (a) to (d) above, and may be additionally performed after integration as necessary. The heating temperature is usually in the range of 200°C to 600°C.
Furthermore, the above-mentioned integration treatment and heat treatment may be carried out before, after or during the above-mentioned drying step, pulverization step or the like, if necessary.

[Source Compounds]
Examples of the molybdenum (Mo) supply source compound include ammonium paramolybdate, molybdenum trioxide, molybdic acid, ammonium phosphomolybdate, and phosphomolybdic acid.

Examples of the vanadium (V) supply source compound include ammonium vanadate, vanadium pentoxide, vanadium oxalate, vanadium sulfate, and the like.
In the composition formula (1), the vanadium is preferably added in an amount a of more than 0 and not more than 12 when the molybdenum is 12, more preferably, a is 0.1 or more and not more than 6, and even more preferably, a is 1 or more and not more than 5. When a is within the above range, a catalyst having excellent conversion rate and capable of producing an unsaturated carboxylic acid with high selectivity can be obtained.

Examples of the source compound of niobium (Nb) include niobium hydroxide, niobium pentoxide, etc. Examples of the source compound of tungsten (W) include tungstic acid or a salt thereof, etc.
In the composition formula (1), the amount b of at least one element selected from niobium and tungsten, which is X in this formula (1), is preferably added so that when molybdenum is 12, b is added so that b is 0 to 12, more preferably 0.1 to 6, and even more preferably 0.5 to 4. When b is within the above range, a catalyst excellent in conversion rate and capable of producing an unsaturated carboxylic acid with high selectivity can be obtained.

Examples of the copper (Cu) source compound include copper sulfate, copper nitrate, and cuprous chloride.
In the composition formula (1), the amount c of copper added in this formula (1) is preferably added so that when molybdenum is 12, c is more than 0 and not more than 12, more preferably c is 0.1 or more and not more than 6, and even more preferably c is 0.5 or more and not more than 4. When c is within the above range, a catalyst excellent in conversion rate and capable of producing an unsaturated carboxylic acid with high selectivity can be obtained.

The magnesium (Mg) source compound may be magnesium oxide, magnesium carbonate, magnesium sulfate, etc. The calcium (Ca) source compound may be calcium oxide, calcium carbonate, calcium hydroxide, etc. The strontium (Sr) source compound may be strontium oxide, strontium carbonate, strontium hydroxide, strontium nitrate, etc.
Examples of the source compound of barium (Ba) include barium oxide, barium carbonate, barium nitrate, barium acetate, barium sulfate, etc. Examples of the source compound of zinc (Zn) include zinc oxide, zinc carbonate, zinc hydroxide, zinc nitrate, etc.
In the composition formula (1), the amount d of at least one element selected from magnesium, calcium, strontium, barium and zinc, which is Y in this formula (1), is preferably added so that when molybdenum is 12, d is added so that d is 0 to 8, more preferably 0.1 to 6, and even more preferably 0.2 to 4. When d is within the above range, a catalyst excellent in conversion rate and capable of producing an unsaturated carboxylic acid with high selectivity can be obtained.

Examples of the antimony (Sb) supply source compound include antimony oxides such as antimony trioxide and antimony pentoxide.
In the composition formula (1), the amount e of antimony added in this formula (1) is preferably such that, when molybdenum is 12, e is from 0 to 500, more preferably from 0.1 to 100, and even more preferably from 0.2 to 50. When e is within the above range, a catalyst having excellent conversion rate and capable of producing an unsaturated carboxylic acid with high selectivity can be obtained.

Examples of the iron (Fe) source compound include ferric nitrate, ferric sulfate, ferric chloride, ferric acetate, etc. Examples of the cobalt (Co) source compound include cobalt nitrate, cobalt sulfate, cobalt chloride, cobalt carbonate, cobalt acetate, etc.
Examples of the nickel (Ni) source compound include nickel nitrate, nickel sulfate, nickel chloride, nickel carbonate, nickel acetate, etc. Examples of the bismuth (Bi) source compound include bismuth chloride, bismuth nitrate, bismuth oxide, bismuth subcarbonate, etc.
In the composition formula (1), the amount f of at least one element selected from iron, cobalt, nickel and bismuth, which is Z in this formula (1), is preferably added so that when molybdenum is 12, f is 0 or more and 500 or less, more preferably f is 0.1 or more and 400 or less, and even more preferably f is 1 or more and 300 or less. When f is within the above range, a catalyst excellent in conversion rate and capable of producing an unsaturated carboxylic acid with high selectivity can be obtained.

Examples of the silicon (Si) source compound include silica, granular silica, colloidal silica, and fumed silica.
In the composition formula (1), the amount g of silicon added in this formula (1) is preferably added so that when molybdenum is 12, g is from 0 to 500, more preferably from 0.1 to 400, and even more preferably from 1 to 300. When g is within the above range, a catalyst excellent in conversion rate and capable of producing an unsaturated carboxylic acid with high selectivity can be obtained.

Examples of the carbon (C) supply source compound include green silicon carbide and black silicon carbide in which carbon (C) and Si are integrated together, and silicon carbide is preferably in the form of a fine powder.
In the composition formula (1), the amount of carbon added, h, in this formula (1), is preferably added so that when molybdenum is 12, h is 0 or more and 500 or less, more preferably h is 0.1 or more and 400 or less, and even more preferably h is 1 or more and 300 or less. When h is within the above range, a catalyst having excellent conversion rate and capable of producing an unsaturated carboxylic acid with high selectivity can be obtained.

Of the above-mentioned source compounds used, it is preferable that one of the source compounds contains a sulfate. In other words, it is preferable that the starting material mixture contains a sulfate. When a source compound containing a sulfate is used, the dried product described below contains sulfate, and the supporting powder also contains sulfate, which can sufficiently contribute to improving the raw material conversion rate and product selectivity of the obtained catalyst.

[Drying process]
The drying step is a step of drying the starting material mixture obtained in the liquid preparation step, followed by a heat treatment to obtain a dried product.

There are no limitations to the drying method, but typical examples include drum drying and spray drying. For example, spray drying is a method that can be preferably applied to the present invention because it can obtain a dried product from the starting material mixture in a short time, and the obtained dried product is nearly spherical and has excellent fluidity.

The temperature during spray drying varies depending on the concentration of the source compound in the starting material mixture and the supply rate, but is usually between 90°C and 250°C, and preferably between 120°C and 200°C. Temperatures outside this range may result in problems such as the dried product containing a large amount of moisture or a low recovery rate of the dried product.

The heat treatment method is carried out by heating at a predetermined temperature for a predetermined period of time, preferably in the atmosphere.
The temperature of this heat treatment must be 270° C. or higher, and preferably 280° C. or higher. The heating temperature must be 330° C. or lower, and preferably 320° C. or lower. Outside this range, the raw material conversion rate and product selectivity of the resulting catalyst may not be sufficiently improved, or molding may become difficult.
The time for which the heat treatment temperature is maintained at this time must be 30 minutes or more, and preferably 45 minutes or more. The time for this heat treatment must be 3 hours or less, and preferably 2 hours or less. If the time is outside this range, the raw material conversion rate and product selectivity of the resulting catalyst may not be sufficiently improved, or molding may become difficult.
The apparatus used for the heat treatment may be a box-type heating furnace, a tunnel-type heating furnace, a hot air dryer, a rotary kiln, etc., with the hot air dryer or rotary kiln being preferred since the material to be dried can be heated uniformly.

[Crushing process]
The dried product obtained in the drying step may be used in the next step as it is, but since it is to be supported on a carrier in the next molding step, if the particle size of the dried product is large, a crushing step may be carried out to crush the dried product into a powdered crushed product. Examples of the crushing method include a stirring blade type crusher, a ball mill, a jet mill, a hammer mill, etc. Examples of the apparatus include Wonder Blender (model WB-1) and Wonder Crush/Mill (model D3V-10) imported and sold by Osaka Chemical Co., Ltd.

[Molding process]
The molding step is a step of obtaining a catalyst precursor by using the dried product obtained in the drying step or the pulverized product as a supporting powder.
When the dried material obtained in the drying step is a powder of a size that can be supported on a carrier, it is used as is as the powder for support. When the particle size of the dried material is large, the powder-like pulverized material pulverized in the pulverization step is used as the powder for support.

The support powder has catalytic activity as is, but catalysts are generally packed into fixed-bed reactors for use in gas-phase catalytic oxidation. Using the support powder as is can cause problems such as poor workability when loading and unloading from the reactor and increased pressure loss during gas-phase catalytic oxidation, so a shaped catalyst is used by supporting it on a granular carrier. The shaped catalyst preferably has a major axis diameter of 2 mm or more and 15 mm or less, and more preferably 3 mm or more and 10 mm or less.

This molding method is carried out by supporting the obtained support powder on a granular carrier. Additives such as binders, molding aids, and strength enhancers may be added to facilitate the support of the support powder on the granular carrier and to improve the strength of the produced catalyst. The granular carrier is preferably a carrier that is inactive to the reaction used as a catalyst, and examples of such carriers include silica, silicon carbide, alumina, alumina-silica, mullite, and alundum. It is also preferable to use a spherical carrier with a linear axis diameter of preferably 2.5 mm to 10 mm, and more preferably 2.5 mm to 6 mm. Furthermore, it is more preferable to use a porosity of 20% to 60% and a water absorption rate of 10% to 60%, since this makes it easier to support the catalyst component elements.

The additive is
(1) Adding the powder to the support after mixing it in advance;
(2) adding the support powder into the fixed container at the same time;
(3) Addition after the addition of the supporting powder;
(4) before adding the supporting powder;
(5) Add the supporting powder and the additive separately,
Methods such as adding the total amount of a suitable combination of (1) to (5) can be arbitrarily adopted. Among these, in (5), it is preferable to adjust the addition speed using an autofeeder or the like so that a predetermined amount of the supporting powder is supported on the carrier without adhesion of the supporting powder to the wall of a fixed container or aggregation of the supporting powder.

The ratio of the amount of the support powder to the amount of the carrier, expressed as the amount of the support powder/(the amount of the support powder+the amount of the carrier), is usually 10% by mass or more and 90% by mass or less, and preferably 20% by mass or more and 70% by mass or less.
The catalyst precursor obtained by the above method preferably has a major axis diameter of 3 mm or more and 12 mm or less, and more preferably 3 mm or more and 7 mm or less.

The binder may be an organic binder such as ethanol, glycerin, or polyvinyl alcohol, or an inorganic binder such as an aqueous solution of silica sol. An organic binder is preferred, and glycerin or polyvinyl alcohol is more preferred. The organic binder may be used as is, but from the viewpoint of ease of use, it is preferred to use it as an aqueous solution. The aqueous solution concentration is preferably 0.1% by mass or more. The amount of binder used is usually 0.1 parts by weight or more and 50 parts by weight or less, preferably 0.5 parts by weight or more and 30 parts by weight or less, based on 100 parts by weight of the supporting powder.

Examples of the molding aid include silica gel, diatomaceous earth, and alumina powder. The amount of the molding aid used is usually 1 part by weight or more and 20 parts by weight or less per 100 parts by weight of the support powder. Furthermore, if necessary, the use of a strength improver such as inorganic substances such as flake glass, ceramic fibers, and whiskers is useful for improving the mechanical strength of the catalyst. The amount of the strength improver used is usually 0.5 parts by weight or more and 20 parts by weight or less per 100 parts by weight of the support powder.

It is essential that the weight loss rate of the support powder when it is heat-treated at a specific temperature immediately before being supported on the granular carrier is within a specified range. That is, when the support powder is heat-treated under conditions of 300°C, the weight loss rate is less than 5% by mass, and preferably less than 4% by mass. If the weight loss rate at 300°C exceeds 5% by mass, molding may become difficult, and effective catalytic components may be lost from the supported powder during firing, resulting in a decrease in catalytic activity, particularly the raw material conversion rate.

In addition to this condition, the difference between the weight loss rate when the support powder is heat-treated under conditions of 370°C and the weight loss rate when the support powder is heat-treated under conditions of 300°C must be 1% by mass or more and 6% by mass or less, and preferably 2% by mass or more and 4% by mass or less. If the difference between the weight loss rate of the support powder at 370°C and the weight loss rate at 300°C is greater than 6% by mass, effective catalytic components are lost from the powder supported during firing, and as a result, the catalytic performance, particularly the raw material conversion rate, may decrease. On the other hand, if the difference between the weight loss rate of the support powder at 370°C and the weight loss rate at 300°C is less than 1% by mass, pores effective for reaction are unlikely to be formed in the catalyst, and the catalytic performance, particularly the raw material conversion rate, may decrease.

A support powder satisfying such conditions can be obtained by appropriately adjusting the drying conditions in the drying step, the heating temperature and heating time in the heat treatment, the conditions in the grinding step, and the environment (temperature, etc.) and time until the obtained support powder is supported on the granular carrier.
The weight loss rate of the support powder is a value calculated from the mass of the support powder before and after heating at 300° C. or 370° C. in an air atmosphere until there is no change in mass, using the following formula:
Weight loss rate (mass %)=[(mass (g) of support powder before heating−mass (g) of support powder after heating)/mass (g) of support powder before heating)]×100

[Firing process]
The calcination step is a step of calcining the catalyst precursor obtained in the molding step to form a catalyst.
The catalyst precursor obtained in the molding step is then calcined to obtain a catalyst. The calcination temperature is usually 250° C. to 800° C., preferably 300° C. to 600° C., and the calcination time is 1 hour to 50 hours.

By using the catalyst produced by this method, it is possible to efficiently produce unsaturated carboxylic acids such as acrylic acid and methacrylic acid with high conversion and high selectivity by catalytically oxidizing unsaturated aldehydes such as acrolein and methacrolein with an oxygen-containing gas in the gas phase.

The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples in any way as long as the gist of the present invention is not exceeded.
<Weight loss rate measurement>
Immediately before carrying out the process for supporting on a carrier, 1 g of the powder for support was weighed, placed in a crucible, and held in a muffle furnace in the presence of air at a predetermined temperature for 1 hour. The weight loss rate at a predetermined temperature was calculated based on the mass of the powder for support before and after heating.

<Calculation of conversion rate, selectivity, and yield>
The acrolein conversion, the acrylic acid selectivity, and the acrylic acid yield were calculated from the following formulas.
Acrolein conversion rate (mol%) = (number of moles of reacted acrolein / number of moles of acrolein supplied) x 100
Acrylic acid selectivity (mol%)=(moles of acrylic acid produced/moles of acrolein converted)×100
Acrylic acid yield (mol %)=(moles of acrylic acid produced/moles of acrolein supplied)×100

(Examples 1 to 3, Comparative Examples 1 to 4)
<Preparation of catalyst>
2281 ml of warm water was placed in a container, and 76 g of ammonium metavanadate was further added and dissolved in the water. Next, 568 g of ammonium molybdate was further added and dissolved to obtain a solution (hereinafter referred to as "Solution A").
Next, a solution prepared by dissolving 80 g of copper sulfate in 115 ml of warm water was added to the solution A and mixed uniformly. Next, 52 g of niobium hydroxide and 16 g of antimony trioxide were further added to this mixed solution and stirred to obtain a starting material mixed solution.
This mixture of starting materials was spray-dried at 150° C., and then heat-treated in the atmosphere using a hot air dryer at the heat treatment temperature and for the holding time shown in Table 1 to obtain a dried product.
The dried product was pulverized to 200 μm or less using a stirring blade type pulverizer to obtain a pulverized product. This pulverized product was used as a supporting powder. To this supporting powder, 1.5% by weight of scaly glass was added relative to the supporting powder, and the mixture was mixed uniformly to obtain a mixture. 100 g of a spherical inert carrier having a diameter of 4.9 mm and mainly composed of alumina-silica was charged into a pan-type granulator, and a 20% by weight aqueous solution of glycerin and the mixture were alternately added to the inert carrier to support the mixture so that the support rate was 40% by weight, thereby obtaining a catalyst precursor, which is a molded body. This catalyst precursor was calcined at 390° C. for 3 hours in an atmosphere of 5% by volume of oxygen in which air was diluted with nitrogen, to obtain a catalyst. The composition ratio of this catalyst was as follows.
Mo ₁₂ V _2.4 Cu _1.2 Nb ₁ Sb _0.4

<Gas-phase catalytic oxidation of acrolein>
A reaction tube with an inner diameter of 21 mm was filled with 33 ml of the catalyst. Oxygen and nitrogen were added to the gas obtained by gas-phase catalytic oxidation of propylene, and a raw material mixed gas having the following composition was introduced from the inlet of the reaction tube, and the reaction was evaluated at a space velocity of 1550/hr. The heat transfer medium temperature was 250° C. The reaction evaluation results are shown in Table 1.
The composition of the raw material mixed gas used is as follows:
Acrolein: 6% by volume, steam: 22% by volume, oxygen: 8% by volume, (nitrogen-containing inert gas + other gases): 64% by volume

Claims (7)

A method for producing a catalyst for synthesizing an unsaturated carboxylic acid, comprising: a drying step of drying and heating a starting material mixture liquid in which supply source compounds of each catalyst component element are integrated to obtain a dried product; a shaping step of forming the dried product into a powder for support or obtaining a powder for support from the dried product and supporting the powder on a granular support to obtain a catalyst precursor; and a calcination step of calcining the catalyst precursor to obtain a catalyst,
The catalyst for synthesizing an unsaturated carboxylic acid is a catalyst for producing an unsaturated carboxylic acid by gas-phase catalytic oxidation of an unsaturated aldehyde as a raw material with an oxygen-containing gas,
This catalyst for synthesizing an unsaturated carboxylic acid contains molybdenum (Mo) as an essential catalytic component element,
The weight loss rate of the support powder at 300°C is less than 5 mass%, and the difference between the weight loss rate of the support powder at 370°C and the weight loss rate of the support powder at 300°C is within a range of 1 mass% or more and 6 mass% or less.
The weight loss rate of the support powder is a value calculated from the mass of the support powder before and after heating at 300° C. or 370° C. in an air atmosphere until there is no change in mass, using the following formula:
Weight loss rate (mass %)=[(mass (g) of support powder before heating−mass (g) of support powder after heating)/mass (g) of support powder before heating)]×100 A method for producing a catalyst for synthesizing an unsaturated carboxylic acid, comprising: a drying step of drying and heating a starting material mixture liquid in which supply source compounds of each catalyst component element are integrated to obtain a dried product; a shaping step of forming the dried product into a powder for support or obtaining a powder for support from the dried product and supporting the powder on a granular support to obtain a catalyst precursor; and a calcination step of calcining the catalyst precursor to obtain a catalyst,
The catalyst for synthesizing an unsaturated carboxylic acid is a catalyst for producing an unsaturated carboxylic acid by gas-phase catalytic oxidation of an unsaturated aldehyde as a raw material with an oxygen-containing gas,
This catalyst for synthesizing an unsaturated carboxylic acid contains molybdenum (Mo) as an essential catalytic component element,
The heat treatment conditions are as follows:
Heat treatment temperature: 270°C to 330°C Heat treatment temperature retention time: 30 minutes to 3 hours 2. The method for producing a catalyst for synthesizing an unsaturated carboxylic acid according to claim 1, wherein the heat treatment is carried out under the following conditions:
Heat treatment temperature: 270°C to 330°C Heat treatment temperature retention time: 30 minutes to 3 hours The method for producing a catalyst for synthesizing an unsaturated carboxylic acid according to any one of claims 1 to 3, wherein the starting material mixture contains a sulfate. The method for producing a catalyst for synthesizing an unsaturated carboxylic acid according to any one of claims 1 to 4 further comprises a step of pulverizing the dried product. The method for producing a catalyst for synthesizing an unsaturated carboxylic acid according to any one of claims 1 to 5, wherein the catalyst for synthesizing an unsaturated carboxylic acid is a catalyst represented by the following composition formula (1):
Mo ₁₂ V _a X _b Cu _c Y _d Sb _e Z _{f Sig} C _h O _i (1)
(In formula (1), X represents Nb and/or W, Y represents at least one element selected from the group consisting of Mg, Ca, Sr, Ba, and Zn, and Z represents at least one element selected from the group consisting of Fe, Co, Ni, and Bi. a to i represent atomic ratios of each element and are in the ranges of 0<a≦12, 0≦b≦12, 0<c≦12, 0≦d≦8, 0≦e≦500, 0≦f≦500, 0≦g≦500, and 0≦h≦500, and i is a value that satisfies the oxidation state of other elements.) A method for producing acrylic acid, which comprises gas-phase catalytic oxidation of acrolein with an oxygen-containing gas using a catalyst produced by the method for producing a catalyst for synthesizing an unsaturated carboxylic acid according to any one of claims 1 to 6.