JP2022155470A - Method for producing catalyst for producing acrolein and acrylic acid, and method for producing acrolein and acrylic acid using the catalyst - Google Patents

Abstract

To provide a method for producing a catalyst having excellent catalytic activity and yield, which is used in a method for producing acrolein and acrylic acid by catalytic gas phase oxidation of propylene.SOLUTION: Provided is a method for producing a catalyst for producing acrolein and acrylic acid by catalytic gas phase oxidation of propylene, comprising a step of mixing a raw material mixture including a raw material compound of molybdenum, a raw material compound of bismuth, and a raw material compound of cobalt, where the raw material compound of cobalt is cobalt nitrate hexahydrate and a mass loss rate L1 in thermogravimetry of the cobalt nitrate hexahydrate from 25°C to 105°C is 11 to 16 mass%.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a method for producing a catalyst for producing acrolein and acrylic acid, and a method for producing acrolein and acrylic acid using the catalyst.

Many proposals have been made for catalysts used in the industrial production of acrolein and acrylic acid by catalytic vapor phase oxidation of propylene with molecular oxygen. For example, in Patent Document 1, molybdenum, bismuth and iron are essential catalytically active components as catalysts for producing unsaturated aldehydes and unsaturated carboxylic acids, and molybdenum having an endothermic peak temperature within a predetermined temperature range is disclosed as a molybdenum raw material. A mixed metal oxide catalyst is disclosed which provides for the use of ammonium acid tetrahydrate.

JP 2018-153773 A

However, although the yield of acrolein and acrylic acid is improved by the catalyst described in Document 1, the catalyst performance such as catalytic activity and yield when acrolein and acrylic acid are produced on an industrial scale is further improved. Improvement is desired.

Accordingly, an object of the present invention is to provide a method for producing a catalyst excellent in catalytic activity and yield, which is used in a method for producing acrolein and acrylic acid by catalytic vapor phase oxidation of propylene. Another object of the present invention is to catalytically oxidize propylene with a molecular oxygen-containing gas in the presence of a catalyst having excellent catalytic activity and yield produced by the production method to produce acrolein and acrylic acid in a high amount. The object is to provide a method of manufacturing with high yield.

In order to solve the above-described problems, the present inventors have made extensive studies, paying particular attention to the properties of raw material compounds used in the production of catalysts. As a result, a process for producing a catalyst for producing acrolein and acrylic acid by catalytic gas-phase oxidation of propylene comprises mixing a raw material mixture containing a molybdenum raw material compound, a bismuth raw material compound and a cobalt raw material compound. wherein the raw material compound of cobalt is cobalt nitrate hexahydrate, and the mass loss rate L1 from 25°C to 105°C in thermogravimetric measurement of the cobalt nitrate hexahydrate is ₁₁ to 16% by mass. The present inventors have found that the above problems can be solved by a method for producing a catalyst.

According to the present invention, a catalyst for producing acrolein and acrylic acid with excellent catalytic activity and yield can be produced on an industrial scale. In addition, acrolein and acrylic acid can be produced in high yields by catalytic gas-phase oxidation of propylene using the obtained catalyst.

Embodiments of the present invention will be described below, but the present invention is not limited only to the following embodiments. In this specification, "X to Y" indicating a range means "X or more and Y or less".

One embodiment of the present invention is a method for producing a catalyst for producing acrolein and acrylic acid by catalytic vapor phase oxidation of propylene (hereinafter sometimes referred to as "catalyst for producing acrolein and acrylic acid"), , a molybdenum source compound, a bismuth source compound and a cobalt source compound, wherein the cobalt source compound is cobalt nitrate hexahydrate represented by the following formula (a): , the weight loss rate L ₁ from 25° C. to 105° C. in thermogravimetry (TG) of the cobalt nitrate hexahydrate is 11 to 16% by weight.
L ₁ (% by mass) = (W ₁ - W ₂ )/W ₁ × 100 (a)
here,
Cobalt nitrate hexahydrate substance amount (mg) at W ₁ = 25°C
W ₂ = Cobalt nitrate hexahydrate substance amount (mg) when reaching 105°C.

A method of producing a catalyst for producing acrolein and acrylic acid according to the present invention includes a step of mixing a raw material mixture containing a raw material compound for molybdenum, a raw material compound for bismuth, and a raw material compound for cobalt. Therefore, the catalyst for producing acrolein and acrylic acid according to the present invention contains molybdenum, bismuth and cobalt. include.

The catalyst for producing acrolein and acrylic acid according to the present invention contains molybdenum, bismuth and cobalt as essential components, and preferably further contains iron and/or nickel. Further, the catalyst for producing acrolein and acrylic acid according to the present invention preferably contains a composite oxide represented by the following general formula (1) (where general formula (1) excludes oxygen representing the oxidation state): . That is, the catalytically active component of the catalyst for producing acrolein and acrylic acid according to the present invention is a composite oxide represented by the following general formula (1) (wherein general formula (1) excludes oxygen representing the oxidation state): preferably included.
_{Mo12BiaCobAcBdCeDf ( 1 ) _ _ _}
In formula (1), Mo is molybdenum, Bi is bismuth, Co is cobalt, A is at least one element selected from the group consisting of iron and nickel, and B is an alkali metal or alkaline earth. At least one element selected from the group consisting of metals and thallium, C is at least one element selected from the group consisting of tungsten, silicon, aluminum, zirconium and titanium, and D is phosphorus, tellurium, and antimony. , tin, cerium, lead, niobium, manganese, arsenic, boron and zinc, and a, b, c, d, e and f are Bi, Co, A, B, represents the number of atoms of C and D, 0<a≤10, 0<b≤20, 0<c≤20, 0≤d≤10, 0≤e≤30, 0≤f≤4.

The catalyst for producing acrolein and acrylic acid according to the present invention preferably contains element A (at least one element selected from iron and nickel) as a catalyst component because it improves catalytic activity and yield.

In formula (1), a preferably satisfies 0<a≦10, more preferably 0.2≦a≦8, and still more preferably 0.4≦a≦6. In formula (1), b preferably satisfies 0<b≦20, more preferably 0.5≦b≦15, and still more preferably 1≦b≦12. In one embodiment, b in formula (1) is preferably 1.5<b≦20, more preferably 2≦b≦15, even more preferably 2.5≦b≦12. In formula (1), c preferably satisfies 0<c≦20, more preferably 0.2≦c≦15, and still more preferably 0.4≦c≦12. In formula (1), d preferably satisfies 0≦d≦10, more preferably 0≦d≦6, and still more preferably 0≦d≦4. In formula (1), e preferably satisfies 0≦e≦30, more preferably 0≦e≦20, even more preferably 0≦e≦15. In formula (1), f preferably satisfies 0≦f≦4, more preferably 0≦f≦3, and still more preferably 0≦f≦2.

Here, in the method for producing the catalyst for producing acrolein and acrylic acid according to the present invention, the raw material compound of cobalt used is cobalt nitrate hexahydrate. That is, in the catalyst for producing acrolein and acrylic acid according to the present invention, the cobalt raw material compound contained as an essential catalytically active component is cobalt nitrate hexahydrate. The mass loss rate L ₁ from 25° C. to 105° C. in thermogravimetric measurement of this cobalt nitrate hexahydrate (hereinafter referred to as “mass loss rate L ₁ of cobalt nitrate hexahydrate”) is 11 to 16 mass %. be. This mass reduction rate L1 is represented by the above formula ( _a ). By using such cobalt nitrate hexahydrate as a raw material for the catalyst for producing acrolein and acrylic acid, the catalytic activity and yield of the obtained catalyst for producing acrolein and acrylic acid can be significantly improved.

Here, the mass loss rate L1 of cobalt nitrate hexahydrate is the mass change accompanying dehydration and thermal decomposition of moisture _- absorbed water and crystal water caused by temperature change (heating) from 25°C to 105°C in thermogravimetry. It is a numerical value to represent. Of these, the mass change due to dehydration of crystal water and the mass change due to thermal decomposition in the temperature change from 25°C to 105°C of cobalt nitrate hexahydrate are values unique to cobalt nitrate hexahydrate. Conceivable. Therefore, in the thermogravimetric measurement, if there is a change in the numerical value of the mass reduction rate L1 of cobalt nitrate hexahydrate for _each measurement sample of cobalt nitrate hexahydrate, the amount of change (difference) in the numerical value is mainly cobalt nitrate It is believed that this is due to the amount of water absorbed by the hexahydrate. Theoretically considering the mass change due to dehydration of water of crystallization, the mass loss rate L1 of cobalt nitrate hexahydrate is _about 6 to 37%. The mass loss rate L ₁ of the hydrate can take a wider range of values. Incidentally, the mechanism of the weight loss of cobalt nitrate hexahydrate from 25° C. to 105° C. is merely speculation, and does not limit the technical scope of the present invention. The catalyst for producing acrolein and acrylic acid according to the present invention is effective when it is produced using, as a raw material, cobalt nitrate hexahydrate having a weight loss rate L1 within _a specific range.

Nitrates such as cobalt nitrate hexahydrate, which is commonly used as a raw material compound for catalysts, are known to absorb moisture easily. As a result, the mass loss rate L1 of cobalt nitrate hexahydrate also varies over _a wide range. However, until now, the water content and storage method of cobalt nitrate hexahydrate as a raw material used in catalysts for producing acrolein and acrylic acid have not been studied in detail.

_The present inventors have found that the higher the water content of cobalt nitrate hexahydrate, the higher its weight loss rate L1, and the production of acrolein and acrylic acid using cobalt nitrate hexahydrate with _a high weight loss rate L1. It has been found that the yield of acrolein and acrylic acid is low when propylene is catalytically oxidized using the catalyst for acrolein and acrylic acid production. In addition, when the water content of cobalt nitrate hexahydrate decreases, its weight loss rate L1 decreases, and _a catalyst for producing acrolein and acrylic acid is produced using cobalt nitrate hexahydrate with _a low weight loss rate L1. It was also found that the yield of acrolein and acrylic acid is similarly lowered when propylene is catalytically oxidized using the catalyst for producing acrolein and acrylic acid.

As a result of various investigations, it was found that the catalytic activity and yield of the obtained catalyst for producing acrolein and acrylic acid are significantly improved when the weight loss rate L1 of the cobalt nitrate hexahydrate used as _a raw material is 11 to 16% by weight. I found what I can do. That is, in the present invention, the mass loss rate L1 of cobalt nitrate hexahydrate varies over _a wide range by changing the water content of cobalt nitrate hexahydrate depending on the storage conditions of cobalt nitrate hexahydrate. , the performance of the resulting catalyst for producing acrolein and acrylic acid, such as catalytic activity and yield, fluctuates over a wide range, making it impossible to stably produce high-performance catalysts for producing acrolein and acrylic acid. This is what I discovered. According to the present invention, a catalyst for the production of acrolein and acrylic acid with excellent catalytic activity and yield can be stably produced industrially by using cobalt nitrate hexahydrate with _a specific weight loss rate L1. can be done. As a result, acrolein and acrylic acid can be produced industrially stably and in high yield using the catalyst. Although the reason why the configuration of the present invention produces the above effects is not necessarily clear, it is considered as follows.

Although it is not clear _what factors influence the mass loss rate L1 of cobalt nitrate hexahydrate _on the catalytic activity and yield, the difference in the mass loss rate L1 of cobalt nitrate hexahydrate when dissolved in water Co ²⁺ , Co ²⁺ and OH ⁻ bonding species (e.g., CoOH ⁺ , Co(OH) ₂ , Co ₂ OH ³⁺ , etc.) generated in It is thought that the reactivity of molybdenum and cobalt is changed.

When the mass loss rate L1 of cobalt nitrate hexahydrate is low (for example, when the mass loss rate L1 of cobalt nitrate hexahydrate from 25° _C to 105°C obtained by thermogravimetry is _less than 11 mass% ), and among the chemical species generated when cobalt nitrate hexahydrate is dissolved in water, the abundance ratio of dissolved species other than Co ²⁺ such as CoOH ⁺ , Co(OH) ₂ , and Co ₂ OH ³⁺ compared to Co ²⁺ is It is presumed that the increase reduces the abundance of Co ²⁺ and lowers the reactivity between molybdenum and cobalt. Further, when the mass loss rate L1 of cobalt nitrate hexahydrate is high (for example, the mass loss rate L1 of cobalt nitrate hexahydrate from 25° _C to 105° _C obtained by thermogravimetry is 16% by mass). exceeding), it is presumed that among the chemical species generated when cobalt nitrate hexahydrate is dissolved in water, the concentration of Co ²⁺ decreases and the reactivity between molybdenum and cobalt decreases. However, it goes without saying that such a mechanism is merely speculation and does not limit the technical scope of the present invention.

Nitrates are generally known to have high hygroscopicity, but nitrates other than cobalt (for example, nitrates of bismuth, iron and nickel) do not _affect the performance of the catalyst even if the mass loss rate L1 is controlled. The following examples (Examples 6 to 8) prove that the improvement effect is not exhibited. Although the reason for this is unknown, it can be said that only cobalt nitrate hexahydrate has _a significant effect on catalytic performance in correlation with the weight loss rate L1.

As described above, in the production of acrolein and acrylic acid production catalysts, by using cobalt nitrate hexahydrate having _a mass loss rate L1 of 11 to 16% by mass as a cobalt raw material, acrolein and The catalytic activity and yield of the catalyst for producing acrylic acid can be significantly improved.

11. _The weight loss rate L1 of cobalt nitrate hexahydrate is preferably greater than 11% by mass, more preferably 11.1% by mass or more, even more preferably greater than 11.1% by mass. It is even more preferably 3% by mass or more, particularly preferably 11.5% by mass or more, and most preferably 12% by mass or more. In addition, the weight loss rate L1 of cobalt nitrate hexahydrate is preferably _less than 16% by mass, more preferably 15.5% by mass or less, still more preferably 15% by mass or less, and even more preferably is 14.5% by mass or less, particularly preferably 14.3% by mass or less, and most preferably less than 14.1% by mass. In _a preferred embodiment, the weight loss rate L1 of cobalt nitrate hexahydrate is 14.0% by weight or less.

Here, _a method for measuring the mass loss rate L1 of cobalt nitrate hexahydrate will be described. As a measurement sample, an aluminum pan in which 20 mg of cobalt nitrate hexahydrate is accurately weighed is prepared. After setting the measurement sample in the sample holder of the thermogravimetric analysis (TG) device, the measurement was performed from 25 ° C. to 300 ° C. at a temperature increase rate of 2 ° C./min, and the mass loss rate L ₁ from 25 ° C. to 105 ° C. Calculate The thermogravimetric analysis (TG) equipment used for analysis may be of general specifications, and thermogravimetric differential thermal analysis configured so that thermogravimetric analysis (TG) and differential thermal analysis (DTA) can be measured simultaneously. It may be an analyzer (TG-DTA).

In addition, from the results of the thermogravimetric analysis, the mass loss rate L ₂ from 105 ° C. to 300 ° C. (hereinafter, "mass loss rate L ₂ of cobalt nitrate hexahydrate") and from 25 ° C. to 300 ° C. Mass loss rate L ₃ of cobalt nitrate hexahydrate (hereinafter, “mass loss rate L ₃ of cobalt nitrate hexahydrate”) is calculated. In the present invention, the mass loss rate L ₃ of cobalt nitrate hexahydrate is preferably 62 to 75 mass %, more preferably 65 to 73 mass %, still more preferably 66 to 72 mass %, Still more preferably 66.3 to 71.0% by mass, particularly preferably 66.5 to 70.5% by mass, most preferably 66.8 to 70.0% by mass. The catalytic activity of the catalyst for producing acrolein and acrylic acid obtained by using cobalt nitrate _hexahydrate having a mass loss rate L3 within the above range as the cobalt raw material in the production of the catalyst for producing acrolein and acrylic acid. and yield can be significantly improved.

Further, from the results of the thermogravimetric analysis _, the mass loss rate L1 of cobalt nitrate hexahydrate from 25°C to 105°C with respect to the mass loss rate L3 of cobalt nitrate hexahydrate from 25°C to 300° _C . (hereinafter referred to as “mass loss rate L of cobalt nitrate hexahydrate: ratio R of ₁ ”) is also calculated.

In one embodiment of the present invention, the ratio R of the mass loss rate L ₁ of cobalt nitrate hexahydrate is between 0.147 and 0.258. In the present invention, the _ratio R of the mass reduction rate L1 of cobalt nitrate hexahydrate is preferably 0.163 to 0.225, more preferably 0.164 to 0.210, and even more preferably is from 0.165 to 0.205, more preferably from 0.165 to 0.202, particularly preferably from 0.166 to 0.201, and most preferably from 0.166 to less than 0.201. In _one embodiment, the ratio R of the mass weight loss rate L1 of cobalt nitrate hexahydrate is 0.170 or more and less than 0.201. Acrolein and acrylic acid production obtained by using cobalt nitrate hexahydrate having a mass reduction rate L1 _ratio R in the above range as a raw material compound of cobalt in the production of acrolein and acrylic acid production catalysts. The catalytic activity and yield of the catalyst for use can be significantly improved.

The method for producing the catalyst for producing acrolein and acrylic acid according to the present invention includes a step of mixing a raw material mixture containing a raw material compound for molybdenum, a raw material compound for bismuth and a raw material compound for cobalt. The source compound of molybdenum is a compound containing molybdenum, the source compound of bismuth is a compound containing bismuth, and the source compound of cobalt is a compound containing cobalt. Therefore, the method for producing a catalyst for producing acrolein and acrylic acid according to the present invention essentially uses a molybdenum-containing compound, a bismuth-containing compound, and a cobalt-containing compound as raw materials, and the cobalt raw material compound has a mass reduction rate of L Except that ₁ is cobalt nitrate hexahydrate in a specific range, it can be produced according to a method generally used for producing a known catalyst for producing acrolein and acrylic acid. Preferred embodiments of the method for producing the catalyst for producing acrolein and acrylic acid according to the present invention are described below.

For example, the method for producing a catalyst for producing acrolein and acrylic acid according to the present invention includes: (1) mixing raw material compounds containing elements constituting catalytically active components (hereinafter referred to as "catalyst component elements") to obtain a raw material mixture; Raw material mixing step; (2) Drying step of heat-treating the raw material mixture to obtain a dried product; (3) Pulverizing step of pulverizing the dried product to obtain a pulverized product; (4) Molding the pulverized product to obtain a compact molding step; (5) supporting step of supporting the pulverized material on an inert carrier; and (6) firing step of firing the molded body or support; including one and Also, after the drying step (2) or the pulverizing step (3), the first firing step may be added, and firing may be performed twice in combination with (6). The step of mixing a raw material mixture containing a raw material compound of molybdenum, a raw material compound of bismuth and a raw material compound of cobalt is referred to as "(1) Mixing raw materials to obtain a raw material mixture by mixing raw material compounds containing catalyst component elements. corresponds to "process".

Furthermore, in a preferred embodiment, the method for producing a catalyst for producing acrolein and acrylic acid according to the present invention includes the following steps before the raw material mixing step; (A1) mass loss rate L of cobalt nitrate hexahydrate ₁ is measured by TG or TG-DTA; (B1) In the check step, if the mass loss rate L1 of cobalt nitrate hexahydrate is _less than 11% by mass or more than 16% by mass, cobalt nitrate hexahydrate An adjustment step of adjusting the mass reduction rate L ₁ of the cobalt nitrate hexahydrate so that the mass reduction rate L ₁ of the hydrated product is 11 to 16% by mass.

(A1) Checking step The checking step is a step of performing TG or TG-DTA measurement on cobalt nitrate hexahydrate used as a raw material to confirm the mass loss rate L1, ₁₀ to 3 hours before the raw material mixing step. It is preferable to do In addition, if it is confirmed in the checking step that the mass reduction rate L1 of the cobalt nitrate hexahydrate is ₁₁ to 16% by mass, the cobalt nitrate hexahydrate used as the raw material is removed until the raw material mixing step. , is preferably stored so that the mass reduction rate _L1 does not change. The storage method is not particularly limited, and _any known method may be used as long as the mass reduction rate L1 does not change. For example, as a storage method, the necessary amount or more of cobalt nitrate hexahydrate to be used as a raw material is filled in a hopper, and after purging with nitrogen, it is sealed and stored, or the necessary amount or necessary amount as a raw material is stored. A method of dissolving cobalt nitrate hexahydrate in an amount equal to or greater than the amount in an aqueous solution and sealing and storing the solution as an aqueous solution may also be used.

(B1) Adjustment step In the adjustment step, when it is confirmed in the check step that the mass reduction rate L1 of cobalt nitrate hexahydrate is _less than ₁₁ % by mass or exceeds 16% by mass, In this step, cobalt nitrate hexahydrate used as a raw material is treated accordingly.

As the processing performed in the adjustment process, for example, when cobalt nitrate hexahydrate is stored, the humidity of the storage location, the storage amount (the amount filled in the container), and the storage period are appropriately adjusted. are mentioned. These treatments may be performed singly or in combination. Here, in the adjustment step, when the mass reduction rate L1 of cobalt nitrate hexahydrate is _less than 11% by mass and when the mass reduction rate L1 of cobalt nitrate hexahydrate exceeds ₁₆ % by mass, The above processes are performed under different conditions.

For example, when the mass reduction rate L1 of cobalt nitrate hexahydrate is _less than 11% by mass, it is preferable to subject cobalt nitrate hexahydrate to moisture absorption treatment. As a treatment method for absorbing moisture, in the above treatment, the treatment is performed under conditions for absorbing moisture. For example, as a treatment method for moisture absorption, the necessary amount or more of the necessary amount of cobalt nitrate hexahydrate used as a raw material is placed in a covered warehouse at a temperature of -10 to 50 ° C. and a relative humidity of 40 to 100% RH. It may be stored for up to 24 hours, or left in the air for 1 to 24 hours after being filled in a hopper. _The storage period may be appropriately adjusted according to the mass loss rate L1 of the cobalt nitrate hexahydrate. In addition, the time required for processing can be arbitrarily changed by increasing or decreasing the storage amount (the amount filled in the container).

Further, for example, when the mass reduction rate L1 of cobalt nitrate hexahydrate exceeds ₁₆ mass%, it is preferable to perform a drying process on the cobalt nitrate hexahydrate. As a treatment method for drying, in the above treatment, the treatment is performed under drying conditions. For example, as a drying method, the necessary amount or more of the cobalt nitrate hexahydrate used as a raw material is placed in a covered warehouse at a temperature of -10 to 40 ° C. and a relative humidity of 0 to 60% RH. It may be stored for up to 24 hours, or may be vacuum dried for 1 to 24 hours after being filled in a hopper. _The storage period may be appropriately adjusted according to the mass loss rate L1 of the cobalt nitrate hexahydrate. In addition, the time required for processing can be arbitrarily changed by increasing or decreasing the storage amount (the amount filled in the container).

After the cobalt nitrate hexahydrate is treated in the adjustment step according to the mass loss rate _L1 confirmed in the check step, (A1) the mass loss rate _L1 of the cobalt nitrate hexahydrate is adjusted again. , TG or TG-DTA is preferably performed. That is, it is preferable to repeat (A1) the checking step and (B1) the adjusting step until the mass reduction rate L1 of the cobalt nitrate hexahydrate reaches ₁₁ to 16% by mass. In addition, when adjusting the mass reduction rate L1 of cobalt nitrate hexahydrate to ₁₁ to 16% by mass, by acquiring and collecting data at the time of adjustment to some extent, based on that data, It is possible to estimate the numerical value of the mass loss rate L ₁ to be used.

When it is confirmed through the check step or the check step and the adjustment step that the mass reduction rate L1 of the cobalt nitrate hexahydrate is ₁₁ to 16 mass%, using the cobalt nitrate hexahydrate, ( 1) raw material mixing step; (2) drying step; (3) pulverizing step; (4) molding step; (5) supporting step; ) are performed. Each step will be described below.

(1) Raw material mixing step In the present invention, the raw material mixing step refers to a raw material compound containing one or more of each catalyst component element constituting the catalyst for producing acrolein and acrylic acid (for example, a raw material compound of molybdenum, a raw material compound of bismuth, cobalt raw material compound, iron raw material compound and nickel raw material compound) to obtain a raw material mixture containing all the catalytic component elements. In the raw material mixing step of the present invention, at least a raw material compound of molybdenum, a raw material compound of bismuth, and a raw material compound of cobalt are mixed to obtain a raw material mixture. Source compounds containing catalyst component elements other than the molybdenum source compound, the bismuth source compound and the cobalt source compound may be included.

The raw material compounds of the catalyst component elements that can be used in the present invention are essentially a molybdenum raw material compound, a bismuth raw material compound, and a cobalt raw material compound, and the cobalt raw material compound has _a specified mass reduction rate L1. There is no particular limitation other than cobalt nitrate hexahydrate in the range of , chlorides, salts such as organic acid salts, their aqueous solutions, sols, etc., or mixtures thereof can be used in combination. Among them, ammonium salts and nitrates are preferably used as raw materials for each catalytic component element.

Examples of molybdenum raw material compounds include ammonium paramolybdate, ammonium dimolybdate, ammonium tetramolybdate, and molybdenum trioxide, among which ammonium paramolybdate is preferred. Examples of bismuth starting compounds include bismuth chloride, bismuth nitrate, bismuth sulfate, bismuth acetate, bismuth oxide, and bismuth subcarbonate, among which bismuth nitrate is preferred. Examples of the raw material compound of iron include iron chloride, iron nitrate, iron sulfate, iron acetate, iron oxide, and iron carbonate, among which iron nitrate is preferred. Examples of nickel raw material compounds include nickel chloride, nickel nitrate, nickel sulfate, nickel acetate, nickel oxide, and basic nickel carbonate, among which nickel nitrate is preferred.

The raw material mixture may be prepared by a method generally used for this type of catalyst. Each of the above raw material compounds may be dissolved or suspended in a solvent such as water to form a solution or slurry, and these may be sequentially mixed. . Also, one raw material compound can be divided into a plurality of solutions or slurries and mixed. Furthermore, each raw material compound can be added directly to the solution or slurry without being dissolved, and mixed. There are no particular restrictions on the mixing conditions (mixing order, temperature, pressure, pH, etc.) of the raw material compounds. The resulting solution or slurry may be concentrated to form a cake, if necessary, so as to apply the drying method in the subsequent drying step.

In the production method of the present invention, cobalt nitrate hexahydrate having a weight loss rate L ₁ from 25° C. to 105° C. of 11 to 16% by mass in thermogravimetric measurement is used as a raw material compound of cobalt. Here, as described above, cobalt nitrate hexahydrate has hygroscopicity, so the mass weight loss rate L1 _slightly fluctuates with time under normal storage conditions. Therefore, when mixing raw material compounds so as to obtain _a desired catalyst component composition in the raw material mixing step, cobalt nitrate hexahydrate is preferably weighed and used in consideration of the value of the mass reduction rate L1. . In addition, when producing a catalyst on an industrial scale, it is necessary to perform the raw material mixing process multiple times and adjust the catalyst component composition _each time to be the same, but the value of the mass reduction rate L1 should be considered. As a result, the amount of cobalt nitrate hexahydrate used may vary slightly each time. In that case, considering the amount of cobalt nitrate hexahydrate used and the value of its mass reduction rate L1, it is used when preparing the solution or slurry so that the _total amount of water in the system of the raw material mixture is the same. The amount of water may be adjusted, but as long as cobalt nitrate hexahydrate with _a weight loss rate L1 of 11 to 16% by weight is used, the total amount of water in the system should not be adjusted to be the same each time. may

In the production method of the present invention, when each nitrate is used as _a raw material compound of bismuth, iron, or nickel, the mass reduction rate L1 of these nitrates hardly affects the performance of the catalyst as described above. Therefore, it is not particularly necessary to adjust the _total water content in the system based _on the mass loss rate L1 of these nitrates, but it may be adjusted as appropriate in consideration of these mass loss rates L1.

(2) Drying step The drying step in the present invention refers to the raw material mixture obtained in the raw material mixing step, the pulverized product obtained in the pulverizing step described later, the molded product obtained in the molding step described later, or the supporting step described later. It is a step of heat-treating at least one of the obtained supports at a temperature in the range of preferably 100 to 300°C, more preferably 150 to 200°C.

In the drying step, when the raw material mixture obtained in the raw material mixing step is heat-treated to obtain a dried product, the heat treatment method for obtaining the dried product is not particularly limited, and is appropriately applied to the form of the raw material mixture. You can choose. For example, when the raw material mixture is in the form of a solution or a slurry, a spray dryer, a drum dryer, etc. may be used to obtain a granular or powdery dried product, or the solution or slurry may be placed in a vat or the like and placed in a box-type dryer. It can be dried with If the raw material mixture is in the form of a cake obtained by concentrating a solution or slurry, use a box dryer, tunnel dryer, etc., in an air stream, an inert gas stream such as nitrogen, etc., under gas flow or A block-like or flake-like dried product may be obtained by heat treatment in an atmosphere. For example, when using a box-type dryer or a tunnel-type dryer, the drying time is preferably 3 to 30 hours, more preferably 5 to 20 hours. When drying the solution or slurry of the raw material mixture in a vat or the like, or when drying the cake-like raw material mixture, any method that can obtain a dried product that can be pulverized in the subsequent pulverization step as necessary. good.

In addition, when heat-treating the pulverized product obtained in the pulverizing step described later, the molded product obtained in the molding step described later, or the supported product obtained in the supporting step described later, a box type dryer, a tunnel type drying Using a machine or the like, heat treatment can be performed in an atmosphere such as an air stream or an inert gas stream such as nitrogen to obtain a dried product.

(3) Pulverization step The pulverization step in the present invention is a step of pulverizing, if necessary, the dried product obtained by heat-treating the raw material mixture. In the production method of the present invention, it is preferable to pulverize the dried product obtained in the above-described drying step so as to obtain a desired particle size.

In the pulverization step, the pulverization method is not particularly limited, and may be selected so as to be applied to the form of the dried product. For example, the dried product may be pulverized using various hammer mills, jet mills, ball mills, etc. to obtain a pulverized product having a desired particle size that can be used in the subsequent molding step or carrying step. This pulverized material is used as a catalyst precursor. Further, the powder may be dried or calcined after pulverization. In this case, the catalyst precursor is dried or calcined after pulverization.

The particle size of the pulverized product (catalyst precursor) obtained through the pulverization step is not particularly limited, but is in the range of 0.1 to 500 μm in order to maintain good moldability or supportability in the molding step or supporting step described later. , preferably in the range of 10 to 300 μm.

(4) Forming step or (5) Supporting step The forming step in the present invention means that the pulverized product obtained in the pulverizing step as a catalyst precursor, the dried product obtained by re-drying the pulverized product, or the calcined product thereof is formed into a certain shape. It is a process of molding into. In addition, the supporting step in the present invention is a step of supporting the pulverized product obtained in the pulverizing step as a catalyst precursor, the dried product obtained by drying the pulverized product again, or the calcined product thereof on an inert carrier having a certain shape. is.

Examples of the method for molding the catalyst include a method for molding a catalyst precursor into a predetermined shape by an extrusion method, a tableting method, or the like. These methods can be appropriately selected and used in combination. Also, the catalyst precursor can be mixed with a powdery inert material and used in the molding process.

As a method for supporting the catalyst, for example, the catalyst precursor can be supported on an inert carrier according to the methods described in JP-A-6-381, JP-A-10-28877, and the like.

Examples of the inert carrier for supporting the catalyst precursor include alumina, silica, silica-alumina, titania, magnesia, steatite, cordierite, silica-magnesia, silicon carbide, silicon nitride and zeolite. There are no particular restrictions on the shape thereof, and known shapes such as spherical, ring, pellet, and irregular shapes can be used. When the carrier is spherical, the diameter is preferably in the range of 2 to 10 mm, and the amount of the catalytically active component supported on the inert carrier is preferably in the range of 20 to 300% by mass.

The shape of the catalyst is not particularly limited, and may be spherical, cylindrical, ring-shaped, irregular, or the like. When the shape of the catalyst is spherical, the diameter is preferably in the range of 4 to 12 mm. Of course, in the case of a spherical shape, it is not necessary to be a perfect sphere as long as it is substantially spherical. Similarly, in the case of a columnar shape and a ring shape, the cross-sectional shape does not have to be a perfect circle, and it is sufficient if it is substantially circular.

In the molding step and the carrying step, a molding aid for improving moldability, a carrying aid for improving carrying state, a binder, and the like can be used. Specific examples include organic compounds such as ethylene glycol, glycerin, propionic acid, maleic acid, benzyl alcohol, propyl alcohol, butyl alcohol, phenols, nitric acid, ammonium nitrate and ammonium carbonate.

In addition, for the purpose of improving the mechanical strength of the catalyst, glass fiber, ceramic fiber, metal fiber, mineral fiber, carbon fiber, silica, alumina, titanium oxide, silicon carbide, silicon nitride, etc., which are generally known as reinforcing materials, are added to the catalyst. of inorganic fibers may be added.

The method for adding these inorganic fibers is not particularly limited, and any method can be used as long as the inorganic fibers can be uniformly dispersed and contained in the catalyst. For example, inorganic fibers may be added to a raw material mixture containing catalyst component elements, or inorganic fibers may be added to a catalyst precursor obtained after drying and pulverizing a raw material mixture containing catalyst component elements.

A pore-forming agent may also be added for the purpose of forming appropriate pores in the catalyst. The pore-forming agent is not particularly limited, and starch, cellulose, urea, polyvinyl alcohol, melamine cyanurate and the like can be used.

(6) Firing Step In the present invention, the firing step is a step of heat-treating the compact obtained in the molding step or the carrier obtained in the carrying step at a high temperature.

The firing furnace used in the firing step is not particularly limited, and a generally used box-type firing furnace, tunnel-type firing furnace, or the like may be used. The firing temperature is 350 to 600°C, preferably 400 to 550°C, more preferably 420 to 500°C, and the firing time is 1 to 15 hours, preferably 2 to 10 hours. The firing atmosphere may be an oxidizing atmosphere, but a molecular oxygen-containing gas atmosphere is preferable. Air is preferably used as the molecular oxygen-containing gas.

Next, the method for producing acrolein and acrylic acid of the present invention will be described. The method for producing acrolein and acrylic acid of the present invention is a method of catalytic gas-phase oxidation of propylene using the catalyst obtained by the production method of the present invention. and catalytic gas-phase oxidation of propylene using the catalyst. In the method for producing acrolein and acrylic acid of the present invention, the catalyst obtained by the production method of the present invention is filled in a reaction tube in a reactor, and a source gas containing propylene and molecular oxygen is introduced into the reaction tube. Therefore, it is preferable to carry out a catalytic gas-phase oxidation reaction.

The reactor used for producing acrolein and acrylic acid by catalytic gas-phase oxidation of propylene in the present invention is not particularly limited as long as it is a fixed bed reactor, but generally used fixed bed multi-tube reactors A reactor, a plate reactor, or the like can be used, and a fixed bed multitubular reactor is preferred. The inner diameter of the reaction tube in the fixed-bed multitubular reactor is usually 15-50 mm, more preferably 20-40 mm, still more preferably 22-38 mm.

Each reaction tube of the fixed-bed multitubular reactor does not necessarily need to be filled with a single catalyst, and each layer of a plurality of known catalysts (hereinafter sometimes referred to as a "reaction zone") is used. It is also possible to fill so as to form For example, a method of filling catalysts with different loading ratios so that the loading ratio increases from the raw material gas inlet side to the outlet side, a method of diluting a portion of the catalyst with an inert carrier, or a combination of these methods. may be adopted. At this time, the number of reaction zones is appropriately determined according to the reaction conditions and the scale of the reactor. is desirably from 2 to 6.

The reaction conditions in the present invention are not particularly limited, and any conditions generally used for this type of reaction can be carried out. For example, as a raw material gas, preferably 1 to 15% by volume, more preferably 4 to 12% by volume of propylene; preferably 0.5 to 25% by volume, more preferably 2 to 20% by volume of molecular oxygen; 0 to 30% by volume, more preferably 0 to 25% by volume of water vapor; and the balance being an inert gas such as nitrogen; The catalyst may be contacted at a space velocity of 300 to 5,000 Hr ^-1 (standard conditions) under pressure.

There are no particular restrictions on the grade of propylene used as the raw material gas for the reaction, and polymer grade or chemical grade propylene can be used. Also, a propylene-containing mixed gas obtained by oxidative dehydrogenation of propane can be used, and if necessary, air or oxygen can be added to this mixed gas before use.

The present invention will be described in more detail with the following examples and comparative examples. However, the technical scope of the present invention is not limited only to the following examples. Unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass" respectively. Also, in the following examples, unless otherwise specified, the operations were carried out at room temperature (20 to 25° C.). Also, the conversion rate and yield in the examples and comparative examples were determined by the following equations.

Conversion rate [mol%]
= (number of moles of propylene reacted)/(number of moles of supplied propylene) x 100
Yield [mol%]
= (total moles of acrolein produced and acrylic acid produced)/(moles of supplied propylene) x 100.

[Experiment 1 Experiment on Cobalt Raw Material Compound]
[Preparation of cobalt nitrate hexahydrate]
Cobalt nitrate hexahydrate is treated in the above adjustment step (humidity of the storage location, storage amount (amount filled in the container), storage period) in combination as appropriate to reduce the mass shown in Table 1. Cobalt nitrate hexahydrate of rate L ₁ was prepared.

[Measurement of mass weight loss rate]
As a sample for measuring the mass reduction rate, an amount (about 20 mg) of cobalt nitrate hexahydrate required for thermogravimetric analysis was accurately weighed in an aluminum pan (W ₁ : amount of cobalt nitrate hexahydrate at room temperature). A measurement sample was prepared. After that, the measurement sample was placed in a sample holder of a thermogravimetric analysis (TG) device (device name: 2000S, manufactured by MacScience), and then the temperature was raised from room temperature of 25°C or lower to 300°C at a rate of 2°C per minute. , the mass of the sample was measured as a function of temperature. From the measured mass change of the sample, the mass loss rate L ₁ of cobalt nitrate hexahydrate and the mass loss rate L ₂ of cobalt nitrate hexahydrate are calculated by the following formulas (a) and (b). Also, the _ratio R of the mass reduction rate L1 of cobalt nitrate hexahydrate is calculated by the following formula (c). _The mass loss rate L3 of cobalt nitrate _hexahydrate is the _sum of the mass loss rate L1 of cobalt nitrate hexahydrate and the mass loss rate L2 of cobalt nitrate hexahydrate.

L ₁ (% by mass) = (W ₁ - W ₂ )/W ₁ × 100 (a)
L ₂ (% by mass) = (W ₂ - W ₃ )/W ₁ × 100 (b)
R=L1 _/ (L1 ₊ L2)= _{L1 /} L3 ( _c )
where, W ₁ = Cobalt nitrate hexahydrate substance amount (mg) at 25°C
Cobalt nitrate hexahydrate substance amount (mg) when W ₂ = reached 105°C
W ₃ = Cobalt nitrate hexahydrate substance amount (mg) when reaching 300°C.

[Catalyst Production Example 1: Preparation of catalyst (1)]
A Co and Ni aqueous solution was prepared by dissolving 340 parts of cobalt (II) nitrate hexahydrate and 82 parts of nickel (II) nitrate hexahydrate in 400 parts of ion-exchanged water. _The mass loss rate L1 of cobalt nitrate hexahydrate calculated by thermogravimetric analysis of the cobalt nitrate hexahydrate used at this time was 11.2 mass% _, and the mass loss rate L3 of cobalt nitrate hexahydrate was 66.9% by mass, and the _ratio R of the mass weight loss rate L1 of cobalt nitrate hexahydrate was 0.167. _In addition, the mass loss rate L1 of nickel nitrate hexahydrate from 25 ° C. to 105 ° C. calculated by thermogravimetric analysis of the nickel nitrate hexahydrate used was 14.7 mass%, from 25 ° C. to 300 ° C. The mass loss rate L ₃ of nickel nitrate hexahydrate is 41.4 mass%, and the mass loss rate L ₃ of nickel nitrate hexahydrate from 25 ° C to 300 ° C from 25 ° C to 105 ° C _The ratio R of the mass loss rate L1 of nickel nitrate hexahydrate was 0.355. For nitrates other than cobalt nitrate hexahydrate, similar thermogravimetric measurements were performed to determine W ₁ = mass (mg) of nitrate at 25°C, W ₂ = mass of nitrate when reaching 105°C ( mg), the mass (mg) of nitrate when W ₃ = 300 ° C. is measured, and the mass loss rate L ₁ of nitrate from 25 ° C. to 105 ° C., from 105 ° C. Ratio R of mass loss rate L1 of nitrate from 25° _C to 105°C to mass loss rate L2 _of nitrate up to ₃₀₀ °C and mass loss rate L3 of nitrate from 25°C to 300°C are calculated respectively. can.

Next, 99 parts of ferric nitrate (iron (III) nitrate nonahydrate) and 119 parts of bismuth (III) nitrate pentahydrate are mixed with 65 parts by mass of 65% by mass nitric acid and 300 parts of ion-exchanged water. An aqueous solution of Fe and Bi was prepared by dissolving in an aqueous nitric acid solution. _The mass loss rate L1 of ferric nitrate from 25 ° C. to 105 ° C. calculated by thermogravimetric analysis of the ferric nitrate used at this time was 28.5 mass%, and the ferric nitrate from 25 ° C. to 300 ° C. The mass loss rate L3 of iron is 63.5% by mass _, and the mass loss rate of ferric nitrate from 25 ° C to 105 ° C with respect to the mass loss rate L3 of ferric nitrate from 25 ° C to ₃₀₀ ° C _The ratio R of L1 was 0.449. Further, the weight loss rate L1 of bismuth (III) nitrate pentahydrate from 25° _C to 105°C calculated by thermogravimetric analysis of the bismuth (III) nitrate pentahydrate used was 13.0% by mass, The weight loss rate L3 of bismuth(III) nitrate pentahydrate from 25°C to ₃₀₀ °C is 53.2% by weight, and the weight loss of bismuth(III) nitrate pentahydrate from 25°C to 300°C is 53.2% by weight. _The ratio R of the weight loss rate L1 of bismuth( _III ) nitrate pentahydrate from 25° C. to 105° C. to the ratio L3 was 0.244. Separately, 400 parts of ammonium paramolybdate (VI) tetrahydrate was added to 1500 parts of ion-exchanged water and dissolved with stirring to prepare an aqueous Mo solution. The separately prepared Fe and Bi aqueous solution and the Mo aqueous solution were added dropwise to the Co and Ni aqueous solution and mixed, then 3 parts of titanium oxide were mixed, and then an aqueous solution of 1.9 parts of potassium nitrate dissolved in 30 parts of ion-exchanged water was added. to obtain a suspension (raw material mixture). The obtained suspension was heated and stirred until it became cake-like, and then naturally cooled to obtain a lumpy solid.

The lumpy solid matter was carried into a tunnel dryer, dried at 170° C. for 14 hours, and pulverized to 500 μm or less to obtain a catalyst precursor powder. 300 parts of alumina spherical carriers having an average particle diameter of 5.0 mm are charged into a tumbling granulator, and then the catalyst precursor powder is gradually added together with a 20% by mass aqueous solution of ammonium nitrate as a binder to obtain a catalyst precursor. After being supported on a carrier, it was calcined at 470° C. for 6 hours in an air atmosphere to obtain catalyst (1). The metal element composition of this catalyst ( ₁ ) excluding _oxygen and the _{carrier was " Mo12Bi1.3Co6.1Ni1.5Fe1.3Ti0.2K0.1 "} .

Further, the support rate of catalyst (1) calculated by the following formula (d) was 130% by mass.
Support rate (mass%) = (mass of catalyst - mass of support) / (mass of support) x 100
Formula (d).

[Catalyst Production Example 2: Preparation of catalyst (2)]
In Catalyst Production Example ₂ , the mass loss rate L1 of cobalt nitrate hexahydrate calculated by thermogravimetric analysis of the cobalt nitrate hexahydrate used was 13.0 mass%. The rate L ₃ was 68.8% by weight and the rate R of the mass loss rate L ₁ of cobalt nitrate hexahydrate was 0.189.

In Catalyst Production Example 2, 346 parts of cobalt nitrate hexahydrate was used in consideration of the value of L1 so that the cobalt composition in the resulting catalyst would be the same as in catalyst ( ₁ ), and the Co and Ni aqueous solution was being prepared. Considering the amount of cobalt nitrate hexahydrate and its L1 value, the amount of water used in the preparation of the Co and Ni aqueous solution was set to 394 parts so that the _total amount of water in the system was the same. Except for this, a catalyst was prepared in the same manner as in Catalyst Production Example 1 to obtain Catalyst (2).

[Catalyst Production Example 3: Preparation of catalyst (3)]
In Catalyst Production Example ₃ , the mass loss rate L1 of cobalt nitrate hexahydrate calculated by thermogravimetric analysis of the cobalt nitrate hexahydrate used was 14.0 mass%. The rate L ₃ was 69.9% by weight and the rate R of the mass loss rate L ₁ of cobalt nitrate hexahydrate was 0.200.

In Catalyst Production Example 3, 349 parts of cobalt nitrate hexahydrate was used in consideration of the value of L1 so that the cobalt composition in the obtained catalyst was the same as that of catalyst ( ₁ ), and the Co and Ni aqueous solution was being prepared. Considering the amount of cobalt nitrate hexahydrate and its L1 value, the amount of water used in the preparation of the Co and Ni aqueous solution was set to 391 parts so that the _total amount of water in the system was the same. Except for this, a catalyst was prepared in the same manner as in Catalyst Production Example 1 to obtain Catalyst (3).

[Catalyst Production Example 4: Preparation of catalyst (4)]
In Catalyst Production Example ₄ , the mass loss rate L1 of cobalt nitrate hexahydrate calculated by thermogravimetric analysis of the cobalt nitrate hexahydrate used was 14.2 mass%. The rate L ₃ was 70.1% by weight and the rate R of the mass loss rate L ₁ of cobalt nitrate hexahydrate was 0.203.

In Catalyst Production Example 4, 350 parts of cobalt nitrate hexahydrate was used in consideration of the value of L1 so that the cobalt composition in the obtained catalyst was the same as that of catalyst ( ₁ ), and the Co and Ni aqueous solution was being prepared. Considering the amount of cobalt nitrate hexahydrate and its L1 value, the amount of water used in the preparation of the Co and Ni aqueous solution was set to 390 parts so that the _total amount of water in the system was the same. Except for this, a catalyst was prepared in the same manner as in Catalyst Production Example 1 to obtain a catalyst (4).

[Catalyst Production Example 5: Preparation of catalyst (5)]
In Catalyst Production Example ₅ , the mass loss rate L1 of cobalt nitrate hexahydrate calculated by thermogravimetric analysis of the cobalt nitrate hexahydrate used was 15.8 mass%. The rate L ₃ was 70.9% by weight and the rate R of the mass loss rate L ₁ of cobalt nitrate hexahydrate was 0.223.

In Catalyst Production Example 5, 355 parts of cobalt nitrate hexahydrate was used in consideration of the value of L1 so that the cobalt composition in the resulting catalyst would be the same as that of catalyst ( ₁ ), and an aqueous solution of Co and Ni was being prepared. Considering the amount of cobalt nitrate hexahydrate and its L1 value, the amount of water used in the preparation of the Co and Ni aqueous solution was set to 385 parts so that the _total amount of water in the system was the same. A catalyst was prepared in the same manner as in Catalyst Production Example 1, except that Catalyst (5) was obtained.

[Catalyst Production Example 6: Preparation of catalyst (6)]
In Catalyst Production Example ₆ , the mass loss rate L1 of cobalt nitrate hexahydrate calculated by thermogravimetric analysis of the cobalt nitrate hexahydrate used was 10.7 mass%. The rate L ₃ was 66.2% by weight and the rate R of the mass loss rate L ₁ of cobalt nitrate hexahydrate was 0.162.

In Catalyst Production Example 6, 338 parts of cobalt nitrate hexahydrate was used in consideration of the value of L1 so that the cobalt composition in the resulting catalyst would be the same as in catalyst ( ₁ ), and the Co and Ni aqueous solution was being prepared. Considering the amount of cobalt nitrate hexahydrate and its L1 value, the amount of water used in the preparation of the Co and Ni aqueous solution was set to 402 parts so that the _total amount of water in the system was the same. Except for this, a catalyst was prepared in the same manner as in Catalyst Production Example 1 to obtain catalyst (6).

[Catalyst Production Example 7: Preparation of catalyst (7)]
In Catalyst Production Example ₇ , the mass loss rate L1 of cobalt nitrate hexahydrate calculated by thermogravimetric analysis of the cobalt nitrate hexahydrate used was 16.5 mass%. The rate L ₃ was 72.1% by weight and the rate R of the mass loss rate L ₁ of cobalt nitrate hexahydrate was 0.229.

In Catalyst Production Example ₇ , 358 parts of cobalt nitrate hexahydrate was used in consideration of the value of L1 so that the cobalt composition in the resulting catalyst would be the same, and the total amount of cobalt nitrate hexahydrate in the system during the preparation of the Co and Ni aqueous solutions was adjusted to 358 parts. Considering the amount of cobalt nitrate hexahydrate and its _L1 value, the amount of water used in the preparation of the Co and Ni aqueous solution was set to 382 parts so that the amount of water was the same. A catalyst was prepared in the same manner as in 1 to obtain catalyst (7).

[Experiment 2 Experiment on raw material compounds of iron, bismuth and nickel]
Next, with regard to the raw materials of iron, bismuth and nickel, catalysts (8) to (10) were prepared by adjusting the amounts of the raw materials of _each element based on the mass reduction rate L1 in the same manner as the raw materials of cobalt in Experiment 1. manufactured. In the same manner as cobalt nitrate hexahydrate in Experiment 1, the raw material of each element was adjusted by appropriately combining the humidity of the storage location, the storage amount (the amount filled in the container), and the storage period. Raw materials (iron nitrate nonahydrate, bismuth (III) nitrate pentahydrate, and nickel nitrate hexahydrate) having a mass reduction rate L ₁ shown in Table 2 were prepared.
[Catalyst Production Example 8: Preparation of catalyst (8)]
In Catalyst Production Example ₈ , the weight loss rate L1 of iron nitrate nonahydrate from 25° C. to 105° C. calculated by thermogravimetric analysis of the iron nitrate nonahydrate used was 38.2% by mass, 25° C. The mass loss rate L ₃ of iron nitrate nonahydrate from 25 ° C. to 300 ° C. is 81.0 mass %, and the mass loss rate L ₃ of iron nitrate nonahydrate from 25 ° C. to 300 ° C. _The ratio R of the mass loss rate L1 of iron nitrate nonahydrate up to 105° C. was 0.472.

In Catalyst Production Example 8, 109 parts of iron nitrate nonahydrate was used in consideration of the value of L1 so that the Fe composition in the obtained catalyst was the same as that of catalyst ( ₁ ), and the total water content in the system was Considering the amount of iron nitrate nonahydrate and its L1 value, the amount of water used in the preparation of the Fe and Bi aqueous solution was 291 parts as in Catalyst Production Example ₁ . A catalyst was prepared in the same manner to obtain catalyst (8).

[Catalyst Production Example 9: Preparation of catalyst (9)]
In Catalyst Production Example 9, the mass loss rate L1 of bismuth (III) nitrate pentahydrate from 25° _C to 105°C calculated by thermogravimetric analysis of the bismuth (III) nitrate pentahydrate used was 18. 6% by weight, weight loss rate L3 of bismuth(III) nitrate pentahydrate from 25°C to ₃₀₀ °C is 59.4% by weight, bismuth(III) nitrate pentahydrate from 25°C to 300°C _The ratio R of the mass loss rate L1 of bismuth( _III ) nitrate pentahydrate from 25°C to 105°C to the mass loss rate L3 of the product was 0.313.

In Catalyst Production Example 9, 126 parts of bismuth (III) nitrate pentahydrate was used in consideration of the value of L1 so that the Bi composition in the obtained catalyst was the same as that of catalyst ( ₁ ), and Considering the amount of bismuth (III) nitrate pentahydrate and its L1 value so that the _total water content is the same, except that the amount of water used in the preparation of the Fe and Bi aqueous solution was 294 parts. prepared a catalyst in the same manner as in Catalyst Production Example 1 to obtain Catalyst (9).

[Catalyst Production Example 10: Preparation of catalyst (10)]
In Catalyst Production Example ₁₀ , the mass loss rate L1 of nickel nitrate hexahydrate from 25°C to 105°C calculated by thermogravimetric analysis of the nickel nitrate hexahydrate used was 19.9% by mass, 25°C The mass loss rate L ₃ of nickel nitrate hexahydrate from 25 ° C. to 300 ° C. is 47.6 mass %, and the mass loss rate L ₃ of nickel nitrate hexahydrate from 25 ° C. to 300 ° C. _The rate R of the mass loss rate L1 of nickel nitrate hexahydrate up to 105° C. was 0.418.

In Catalyst Production Example 10, nickel nitrate hexahydrate was added to 86 parts in consideration of the value of L1 so that the resulting catalyst had the same Ni composition as that of catalyst ( ₁ ), and the total water content in the system was Considering the amount of nickel nitrate hexahydrate and its _L1 value, the amount of water used in the preparation of the Co and Ni aqueous solution was 397 parts. A catalyst was prepared in the same manner to obtain catalyst (10).

[Reactor]
A reactor consisting of a stainless steel reaction tube with a total length of 3000 mm and an inner diameter of 25 mm and a shell for flowing a heat medium covering it was prepared in the vertical direction, and each catalyst (1) to (10) obtained from the upper part of the reaction tube was added. It was dropped and packed so that the layer length was 2500 mm.

[Oxidation reaction]
In Examples 1 to 5 and Comparative Examples 1 and 2, 7.0% by volume of propylene, 13% by volume of oxygen, and 8.5% by volume of steam were supplied from the bottom of the reactors filled with catalysts (1) to (7), respectively. % and the balance being nitrogen was introduced at a space velocity of 1600 hr ^-1 (standard conditions), and a propylene oxidation reaction was carried out at a heat medium temperature of 310°C. Table 1 shows the results. Further, in Examples 6 to 8, catalysts (8) to (10) were charged, respectively, and the propylene oxidation reaction was carried out under the same conditions. Table 2 shows the results.

From the results of Experiment 1 (Table 1), in Examples 1 to 5 using catalysts (1) to (5) having a mass loss rate L ₁ of 11 to 16% by mass, the propylene conversion rate was 97.0 mol%. As mentioned above, it is shown that the yield of acrolein and acrylic acid is 91.5 mol % or more. On the other hand, in Comparative Examples 1 and 2 using the catalysts (6) and (7) having a mass loss rate L1 of _less than 11% by mass or greater than 16% by mass, the propylene conversion rate was less than 97.0 mol%, acrolein and The yield of acrylic acid is shown to be less than 91.5 mol%. Therefore, the catalysts (1) to (5) produced using cobalt nitrate hexahydrate with _a mass loss rate L1 of 11 to 16% by mass are excellent in catalytic activity and yield in the production of acrolein and acrylic acid. It was found that acrolein and acrylic acid can be produced in high yields by using the catalyst.

From the results of Experiment 2 (Table 2), it was found that the mass loss rate L1 of the nitrates of the raw materials _other than cobalt did not affect the propylene conversion rate and the yields of acrolein and acrylic acid. It was found that the effect is smaller _than that of the mass reduction rate L1.

This application is based on Japanese Patent Application No. 2021-057249 filed on March 30, 2021, the disclosure of which is incorporated herein by reference in its entirety.

Claims (3)

A method for producing a catalyst for producing acrolein and acrylic acid by catalytic gas-phase oxidation of propylene, comprising:
mixing a source mixture comprising a molybdenum source compound, a bismuth source compound and a cobalt source compound;
The raw material compound of cobalt is cobalt nitrate hexahydrate,
A method for producing a catalyst, wherein the cobalt nitrate hexahydrate has a weight loss rate L ₁ from 25° C. to 105° C. in thermogravimetry of 11 to 16% by mass, represented by the following formula (a).
L ₁ (% by mass) = (W ₁ - W ₂ )/W ₁ × 100 (a)
here,
Cobalt nitrate hexahydrate substance amount (mg) at W ₁ = 25°C
Cobalt nitrate hexahydrate substance amount (mg) when W ₂ = reached 105°C The catalyst has the following general formula (1):
_{Mo12BiaCobAcBdCeDf ( 1 ) _ _ _}
(In formula (1), Mo is molybdenum, Bi is bismuth, Co is cobalt, A is at least one element selected from the group consisting of iron and nickel, and B is an alkali metal, alkali At least one element selected from the group consisting of earth metals and thallium, C is at least one element selected from the group consisting of tungsten, silicon, aluminum, zirconium and titanium, D is phosphorus, tellurium, at least one element selected from the group consisting of antimony, tin, cerium, lead, niobium, manganese, arsenic, boron and zinc; a, b, c, d, e and f are Bi, Co, A, B , represents the number of atoms of C and D, and is 0 < a ≤ 10, 0 < b ≤ 20, 0 < c ≤ 20, 0 ≤ d ≤ 10, 0 ≤ e ≤ 30, 0 ≤ f ≤ 4 (where Equation (1) excludes oxygen, which represents the oxidation state.)
2. The method for producing a catalyst according to claim 1, comprising a composite oxide represented by A method for producing acrolein and acrylic acid, comprising catalytic gas-phase oxidation of propylene using the catalyst obtained by the production method according to claim 1 or 2.