Process for producing a catalyst for producing acrolein and acrylic acid, and process for producing acrolein and acrylic acid using the catalyst

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

[0001] 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.

Background Art

[0002] Regarding the catalyst used in the industrial production of acrolein and acrylic acid by catalytic gas-phase oxidation of propylene with molecular oxygen, many proposals have been made. For example, Patent Document 1 discloses a composite metal oxide catalyst that specifies the use of ammonium molybdate tetrahydrate having an endothermic peak temperature within a predetermined temperature range as a molybdenum raw material, with molybdenum, bismuth, and iron as essential catalyst active components for producing unsaturated aldehydes and unsaturated carboxylic acids.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, although the yields of acrolein and acrylic acid are improved by the catalyst described in the above Document 1, further improvement of the catalyst is desired in terms of catalyst performance such as catalyst activity and yield when producing acrolein and acrylic acid on an industrial scale.

[0005] 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 gas-phase oxidation of propylene. Another object of the present invention is to provide a method for producing acrolein and acrylic acid in a high yield by catalytic gas-phase oxidation of propylene with a molecular oxygen-containing gas in the presence of a catalyst excellent in catalytic activity and yield produced by the production method.

Means for Solving the Problems

[0006] In order to solve the above problems, the present inventors have intensively studied, paying particular attention to the properties of the raw material compounds used in the production of the catalyst. As a result, there is provided a method for producing a catalyst for producing acrolein and acrylic acid by catalytic gas-phase oxidation of propylene, the method including a 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, wherein the raw material compound of cobalt is cobalt nitrate hexahydrate, and a mass loss rate L1 from 25°C to 105°C in the thermogravimetric measurement of the cobalt nitrate hexahydrate is 11 to 16% by mass. It has been found that the above problems can be solved by this method for producing a catalyst.

Effects of the Invention

[0007] According to the present invention, a catalyst for producing acrolein and acrylic acid excellent in catalytic activity and yield can be produced on an industrial scale. Further, by catalytic gas-phase oxidizing propylene using the obtained catalyst, acrolein and acrylic acid can be produced in a high yield.

Modes for Carrying Out the Invention

[0008] Hereinafter, embodiments of the present invention will be described, 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".

[0009] One embodiment of the present invention is a method for producing a catalyst for the catalytic gas-phase oxidation of propylene to produce acrolein and acrylic acid (hereinafter sometimes referred to as "catalyst for producing acrolein and acrylic acid"), which includes a 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, wherein the raw material compound of cobalt is cobalt nitrate hexahydrate, and the mass loss rate L1 from 25°C to 105°C in the thermogravimetric measurement (TG) of the cobalt nitrate hexahydrate represented by the following formula (a) is 11 to 16% by mass. L1 (% by mass) = (W1 - W2) / W1 × 100 (a) Here, W1 = mass of cobalt nitrate hexahydrate at 25°C (mg) W2 = mass of cobalt nitrate hexahydrate when reaching 105°C (mg).

[0010] The method for 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 of molybdenum, a raw material compound of bismuth, and a raw material compound of cobalt. Therefore, the catalyst for producing acrolein and acrylic acid according to the present invention contains molybdenum, bismuth, and cobalt, that is, the catalyst for producing acrolein and acrylic acid according to the present invention contains molybdenum, bismuth, and cobalt as essential catalyst active components.

[0011] The catalyst for producing acrolein and acrylic acid according to the present invention contains molybdenum, bismuth, and cobalt as essential components, but 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) (however, the general formula (1) excludes oxygen representing the oxidation state). That is, the catalyst active component of 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) (however, the general formula (1) excludes oxygen representing the oxidation state). Mo 12 Bi a Co b A c Bd C e D f (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, B is at least one element selected from the group consisting of alkali metals, alkaline earth metals, and thallium, C is at least one element selected from the group consisting of tungsten, silicon, aluminum, zirconium, and titanium, D is at least one element selected from the group consisting of phosphorus, tellurium, antimony, tin, cerium, lead, niobium, manganese, arsenic, boron, and zinc, a, b, c, d, e, and f represent the number of atoms of Bi, Co, A, B, C, and D, and 0 < a ≤ 10, 0 < b ≤ 20, 0 < c ≤ 20, 0 ≤ d ≤ 10, 0 ≤ e ≤ 30, 0 ≤ f ≤ 4.

[0012] 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 the catalytic activity and yield are improved.

[0013] In formula (1), a is preferably 0 < a ≤ 10, more preferably 0.2 ≤ a ≤ 8, and even more preferably 0.4 ≤ a ≤ 6. In formula (1), b is preferably 0 < b ≤ 20, more preferably 0.5 ≤ b ≤ 15, and even more preferably 1 ≤ b ≤ 12. In one embodiment, b in formula (1) is preferably 1.5 < b ≤ 20, more preferably 2 ≤ b ≤ 15, and even more preferably 2.5 ≤ b ≤ 12. In formula (1), c is preferably 0 < c ≤ 20, more preferably 0.2 ≤ c ≤ 15, and even more preferably 0.4 ≤ c ≤ 12. In formula (1), d is preferably 0 ≤ d ≤ 10, more preferably 0 ≤ d ≤ 6, and even more preferably 0 ≤ d ≤ 4. In formula (1), e is preferably 0 ≤ e ≤ 30, more preferably 0 ≤ e ≤ 20, and even more preferably 0 ≤ e ≤ 15. In formula (1), f is preferably 0 ≤ f ≤ 4, more preferably 0 ≤ f ≤ 3, and even more preferably 0 ≤ f ≤ 2.

[0014] Here, in the method for producing a 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 raw material compound of cobalt contained as an essential catalyst active component is cobalt nitrate hexahydrate. The mass loss rate L1 (hereinafter, "mass loss rate L1 of cobalt nitrate hexahydrate") from 25°C to 105°C in the thermogravimetric measurement of this cobalt nitrate hexahydrate is 11 to 16% by mass. Note that this mass loss 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.

[0015] Here, the mass loss rate L1 of cobalt nitrate hexahydrate is a numerical value representing the mass change associated with the dehydration of hygroscopic water and crystal water and thermal decomposition caused by the temperature change (heating) from 25°C to 105°C in thermogravimetric measurement. Among these, the mass change due to the dehydration of crystal water and the mass change associated with thermal decomposition in the temperature change of cobalt nitrate hexahydrate from 25°C to 105°C are considered to be values specific to cobalt nitrate hexahydrate. Therefore, in thermogravimetric measurement, when fluctuations occur in the numerical value of the mass loss rate L1 of cobalt nitrate hexahydrate for each measurement sample of cobalt nitrate hexahydrate, the variation (difference) in the numerical value is considered to mainly originate from the amount of water absorbed by cobalt nitrate hexahydrate. Considering theoretically from the mass change due to the dehydration of crystal water, the mass loss rate L1 of cobalt nitrate hexahydrate is about 6 to 37%, and considering the mass change due to the dehydration of hygroscopic water, the mass loss rate L1 of cobalt nitrate hexahydrate can take a wider range of values. Note that the mechanism of the mass loss of cobalt nitrate hexahydrate from 25°C to 105°C described above is only 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 exhibits an effect by being produced using cobalt nitrate hexahydrate with a mass loss rate L1 within a specific range as a raw material.

[0016] Nitrates such as cobalt nitrate hexahydrate, which are commonly used as raw material compounds for catalysts, are known to be easily hygroscopic, and the moisture content of cobalt nitrate hexahydrate varies widely depending on the storage conditions. As a result, the mass loss rate L1 of cobalt nitrate hexahydrate also varies widely. However, hitherto, the moisture content and storage method of cobalt nitrate hexahydrate as a raw material used in the catalyst for producing acrolein and acrylic acid have not been examined in detail.

[0017] The inventors have found that when the water content of cobalt nitrate hexahydrate increases, its mass loss rate L1 increases, and when a catalyst for producing acrolein and acrylic acid is produced using cobalt nitrate hexahydrate with a high mass loss rate L1, the yields of acrolein and acrylic acid decrease when propylene is subjected to catalytic gas-phase oxidation using the catalyst for producing acrolein and acrylic acid. Also, when the water content of cobalt nitrate hexahydrate decreases, its mass loss rate L1 decreases, and similarly, when a catalyst for producing acrolein and acrylic acid is produced using cobalt nitrate hexahydrate with a low mass loss rate L1, the yields of acrolein and acrylic acid decrease when propylene is subjected to catalytic gas-phase oxidation using the catalyst for producing acrolein and acrylic acid.

[0018] As a result of various studies, it has been found that when the mass loss rate L1 of cobalt nitrate hexahydrate used as a raw material is 11 to 16% by mass, the catalytic activity and yield of the resulting catalyst for producing acrolein and acrylic acid can be significantly improved. That is, in the present invention, hitherto, depending on the storage conditions of cobalt nitrate hexahydrate, when the water content of cobalt nitrate hexahydrate changes and the mass loss rate L1 of cobalt nitrate hexahydrate varies widely, the performance such as the catalytic activity and yield of the resulting catalyst for producing acrolein and acrylic acid varies widely, which has been found to be a factor preventing the stable production of high-performance catalysts for producing acrolein and acrylic acid. According to the present invention, by using cobalt nitrate hexahydrate with a specific mass loss rate L1, a catalyst for producing acrolein and acrylic acid excellent in catalytic activity and yield can be stably produced industrially. Thereby, acrolein and acrylic acid can be produced industrially stably and in high yield using the catalyst. Although the reason for achieving the above effects is not necessarily clear due to the configuration of the present invention, it is considered as follows.

[0019] The factor by which the mass loss rate L1 of cobalt nitrate hexahydrate affects the catalytic activity and yield is not clear, but due to the difference in the mass loss rate L1, Co generated when cobalt nitrate hexahydrate is dissolved in water 2+ 、Co2+ and OH - Bond species with (e.g., CoOH + , Co(OH)2, Co2OH 3+ It is believed that changes in the concentration and ratio of these elements (e.g., molybdenum, cobalt, etc.) affect the reactivity with other elements, especially the main raw materials, molybdenum and cobalt.

[0020] 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%), the chemical species generated when cobalt nitrate hexahydrate is dissolved in water are Co 2+ Compared to CoOH + , Co(OH)2, Co2OH 3+ Co., Ltd. 2+ The proportion of dissolved species other than Co increases. 2+ It is presumed that the proportion of cobalt nitrate hexahydrate present decreases, and the reactivity between molybdenum and cobalt decreases. In addition, when the mass loss rate L1 of cobalt nitrate hexahydrate is high (for example, when the mass loss rate L1 of cobalt nitrate hexahydrate from 25°C to 105°C obtained by thermogravimetry exceeds 16 mass%), the amount of Co, which is one of the chemical species generated when cobalt nitrate hexahydrate is dissolved in water, is large. 2+ It is speculated that the concentration of molybdenum in the alloy decreases, and the reactivity between molybdenum and cobalt decreases. However, it goes without saying that this mechanism is merely speculation and does not limit the technical scope of the present invention.

[0021] In addition, it is generally known that nitrates are highly hygroscopic, but in the case of nitrates other than cobalt (e.g., nitrates of bismuth, iron, and nickel), the effect of improving the catalyst performance is not exhibited even if the mass loss rate L1 is controlled, as is supported by the examples (Examples 6 to 8) described later. Although the reason for this is unclear, it can be said that only cobalt nitrate hexahydrate has a significant effect on the catalyst performance in correlation with the mass loss rate L1.

[0022] As described above, when manufacturing a catalyst for producing acrolein and acrylic acid, by using cobalt nitrate hexahydrate having a mass reduction rate L1 of 11 to 16% by mass as a cobalt raw material, the catalytic activity and yield of the obtained catalyst for producing acrolein and acrylic acid can be significantly improved.

[0023] The mass reduction rate L1 of cobalt nitrate hexahydrate is preferably more than 11% by mass, more preferably 11.1% by mass or more, still more preferably more than 11.1% by mass, even more preferably 11.3% by mass or more, particularly preferably 11.5% by mass or more, and most preferably 12% by mass or more. Also, the mass reduction 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, even more preferably 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 mass reduction rate L1 of cobalt nitrate hexahydrate is 14.0% by mass or less.

[0024] Here, the measurement method of the mass reduction rate L1 of cobalt nitrate hexahydrate will be described. As a measurement sample, prepare 20 mg of cobalt nitrate hexahydrate precisely weighed in an aluminum pan. After installing the measurement sample in the sample holder of a thermogravimetric analysis (TG) apparatus, perform measurement at a temperature rising rate of 2 °C / min from 25 °C or lower to 300 °C, and calculate the mass reduction rate L1 from 25 °C to 105 °C. The thermogravimetric analysis (TG) apparatus used for the analysis may have general specifications, and it may be a thermogravimetric differential thermal analysis apparatus (TG-DTA) configured to be able to simultaneously measure thermogravimetric analysis (TG) and differential thermal analysis (DTA).

[0025] Further, from the results of the above thermogravimetric analysis, the mass loss rate L2 from 105°C to 300°C (hereinafter, "the mass loss rate L2 of cobalt nitrate hexahydrate"), and the mass loss rate L3 of cobalt nitrate hexahydrate from 25°C to 300°C (hereinafter, "the mass loss rate L3 of cobalt nitrate hexahydrate") are calculated. In the present invention, the mass loss rate L3 of cobalt nitrate hexahydrate is preferably 62 to 75% by mass, more preferably 65 to 73% by mass, still more preferably 66 to 72% by mass, even more preferably 66.3 to 71.0% by mass, particularly preferably 66.5 to 70.5% by mass, and most preferably 66.8 to 70.0% by mass. When producing a catalyst for producing acrolein and acrylic acid, by using cobalt nitrate hexahydrate having a mass loss rate L3 within the above range as a cobalt raw material, the catalytic activity and yield of the resulting catalyst for producing acrolein and acrylic acid can be significantly improved.

[0026] Further, from the results of the above thermogravimetric analysis, the ratio R of the mass loss rate L1 of cobalt nitrate hexahydrate from 25°C to 105°C to the mass loss rate L3 of cobalt nitrate hexahydrate from 25°C to 300°C (hereinafter, "the ratio R of the mass loss rate L1 of cobalt nitrate hexahydrate") is also calculated.

[0027] In one embodiment of the present invention, the ratio R of the mass loss rate L1 of cobalt nitrate hexahydrate is 0.147 to 0.258. Also, in the present invention, the ratio R of the mass loss rate L1 of cobalt nitrate hexahydrate is preferably 0.163 to 0.225, more preferably 0.164 to 0.210, still more preferably 0.165 to 0.205, even more preferably 0.165 to 0.202, particularly preferably 0.166 to 0.201, and most preferably not less than 0.166 and less than 0.201. In one embodiment, the ratio R of the mass loss rate L1 of cobalt nitrate hexahydrate is not less than 0.170 and less than 0.201. When manufacturing a catalyst for producing acrolein and acrylic acid, by using cobalt nitrate hexahydrate having a ratio R of the mass loss rate L1 within the above range as a raw material compound of cobalt, the catalytic activity and yield of the resulting catalyst for producing acrolein and acrylic acid can be significantly improved.

[0028] As a method for manufacturing a catalyst for producing acrolein and acrylic acid according to the present invention, it includes a 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. The raw material compound of molybdenum is a compound containing molybdenum, the raw material compound of bismuth is a compound containing bismuth, and the raw material compound of cobalt is a compound containing cobalt. Therefore, the method for manufacturing a catalyst for producing acrolein and acrylic acid according to the present invention essentially uses a compound containing molybdenum, a compound containing bismuth, and a compound containing cobalt as raw materials, and can be manufactured according to a method generally used for manufacturing a catalyst for producing acrolein and acrylic acid, except that the raw material compound of cobalt is cobalt nitrate hexahydrate in which the mass loss rate L1 is within a specific range. Hereinafter, preferred embodiments of the method for manufacturing a catalyst for producing acrolein and acrylic acid according to the present invention will be described.

[0029] For example, the method for producing a catalyst for producing acrolein and acrylic acid according to the present invention includes: (1) a raw material mixing step of mixing raw material compounds containing elements constituting the catalyst active component (hereinafter referred to as "catalyst component elements") to obtain a raw material mixture; (2) a drying step of heat-treating the raw material mixture to obtain a dried product; (3) a pulverizing step of pulverizing the dried product to obtain a pulverized product; (4) a forming step of forming the pulverized product to obtain a formed body; (5) a supporting step of supporting the pulverized product on an inert carrier; and (6) a firing step of firing the formed body or the supported body. Among them, it includes (1) and at least one of (2) to (6). Further, a first firing step may be inserted after the (2) drying step or the (3) pulverizing step, and firing may be performed twice in combination with (6). Note that the step of "mixing a raw material mixture containing a raw material compound of cobalt nitrate hexahydrate, a raw material compound of bismuth, and a raw material compound of cobalt" corresponds to the "(1) raw material mixing step of mixing raw material compounds containing catalyst component elements to obtain a raw material mixture".

[0030] 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) a checking step of measuring the mass loss rate L1 of cobalt nitrate hexahydrate by TG or TG-DTA; (B1) an adjusting step of adjusting the mass loss rate L1 of cobalt nitrate hexahydrate so that the mass loss rate L1 of cobalt nitrate hexahydrate is less than 11% by mass or exceeds 16% by mass in the checking step, the mass loss rate L1 of cobalt nitrate hexahydrate is 11 to 16% by mass.

[0031] (A1) Checking step The checking process is a process of performing TG or TG-DTA measurement on cobalt hexahydrate nitrate used as a raw material to confirm the mass loss rate L1, and it is preferably carried out 10 to 3 hours before the raw material mixing process. Also, in the checking process, when it is confirmed that the mass loss rate L1 of cobalt hexahydrate nitrate is 11 to 16% by mass, it is preferable to store the cobalt hexahydrate nitrate used as a raw material until the raw material mixing process so that the mass loss rate L1 does not change. As the storage method, any known method may be used as long as the mass loss rate L1 does not change, and it is not particularly limited. For example, as the storage method, a necessary amount or an amount equal to or more than the necessary amount of cobalt hexahydrate nitrate used as a raw material is filled into a hopper, and after nitrogen replacement, it is sealed and stored, or a necessary amount or an amount equal to or more than the necessary amount of cobalt hexahydrate nitrate as a raw material is dissolved in an aqueous solution and stored sealed as an aqueous solution.

[0032] (B1) Adjustment process The adjustment process is a process of performing a treatment on the cobalt hexahydrate nitrate used as a raw material according to the mass loss rate L1 when it is confirmed in the checking process that the mass loss rate L1 of the cobalt hexahydrate nitrate is less than 11% by mass or exceeds 16% by mass.

[0033] Examples of the treatment performed in the adjustment process include treatments such as appropriately adjusting the humidity of the storage location, the storage amount (the amount filled in the container), and the storage period when storing cobalt hexahydrate nitrate. These treatments may be performed alone or in combination. Here, in the adjustment process, the above treatments are performed under different conditions depending on whether the mass loss rate L1 of cobalt hexahydrate nitrate is less than 11% by mass or the mass loss rate L1 of cobalt hexahydrate nitrate exceeds 16% by mass.

[0034] For example, when the mass loss rate L1 of cobalt(II) nitrate hexahydrate is less than 11% by mass, it is preferable to perform a moisture absorption treatment on the cobalt(II) nitrate hexahydrate. As the method for the moisture absorption treatment, in the above treatment, the treatment is performed under the conditions for moisture absorption. For example, as the method for the moisture absorption treatment, the required amount or an amount equal to or more than the required amount of cobalt(II) nitrate hexahydrate used as a raw material may be stored in a warehouse with a roof at a temperature of -10 to 50°C and a relative humidity of 40 to 100%RH for 1 to 24 hours, or after being filled into a hopper, it may be left in the air for 1 to 24 hours. The storage period may be appropriately adjusted according to the mass loss rate L1 of cobalt(II) nitrate hexahydrate. Also, the time required for the treatment can be arbitrarily changed by increasing or decreasing the storage amount (the amount filled in the container).

[0035] Also, for example, when the mass loss rate L1 of cobalt(II) nitrate hexahydrate exceeds 16% by mass, it is preferable to perform a drying treatment on the cobalt(II) nitrate hexahydrate. As the method for the drying treatment, in the above treatment, the treatment is performed under the conditions for drying. For example, as the method for the drying treatment, the required amount or an amount equal to or more than the required amount of cobalt(II) nitrate hexahydrate used as a raw material may be stored in a warehouse with a roof at a temperature of -10 to 40°C and a relative humidity of 0 to 60%RH for 1 to 24 hours, or after being filled into a hopper, vacuum drying may be performed for 1 to 24 hours. The storage period may be appropriately adjusted according to the mass loss rate L1 of cobalt(II) nitrate hexahydrate. Also, the time required for the treatment can be arbitrarily changed by increasing or decreasing the storage amount (the amount filled in the container).

[0036] According to the mass loss rate L1 confirmed in the checking process, after treating cobalt hexahydrate nitrate in the adjustment process, it is preferable to perform again the checking process of measuring the mass loss rate L1 of (A1) cobalt hexahydrate nitrate by TG or TG-DTA. That is, it is preferable to repeat the (A1) checking process and the (B1) adjustment process until the mass loss rate L1 of cobalt hexahydrate nitrate reaches 11-16% by mass. When adjusting so that the mass loss rate L1 of cobalt hexahydrate nitrate becomes 11-16% by mass, to some extent, by acquiring and collecting the data during adjustment, it is possible to estimate the numerical value of the mass loss rate L1 obtained by adjustment based on that data.

[0037] When it is confirmed through the checking process or the checking process and the adjustment process that the mass loss rate L1 of cobalt hexahydrate nitrate is 11-16% by mass, using that cobalt hexahydrate nitrate, among (1) the raw material mixing process; (2) the drying process; (3) the pulverizing process; (4) the forming process; (5) the supporting process; and (6) the firing process; at least one of (1) and at least one of (2)-(6) is carried out. Each process will be described below.

[0038] (1) Raw material mixing process In the present invention, the raw material mixing process is a process of mixing raw material compounds containing each catalyst component element constituting the catalyst for producing acrolein and acrylic acid alone or in combination (for example, the raw material compound of molybdenum, the raw material compound of bismuth, the raw material compound of cobalt, the raw material compound of iron, and the raw material compound of nickel) to obtain a raw material mixture containing all the catalyst component elements. In the raw material mixing process in the present invention, at least the raw material compound of molybdenum, the raw material compound of bismuth, and the raw material compound of cobalt are mixed to obtain a raw material mixture, but there is no particular limitation on the mixing order of these, and the raw material mixture may contain raw material compounds containing catalyst component elements other than the raw material compound of molybdenum, the raw material compound of bismuth, and the raw material compound of cobalt.

[0039] Regarding the raw material compounds of the catalyst component elements that can be used in the present invention, the raw material compounds of molybdenum, bismuth, and cobalt are essential. There are no particular restrictions on the cobalt raw material compound other than that it is cobalt nitrate hexahydrate with a mass loss rate L1 within a specific range. Generally, salts such as metal element oxides, hydroxides, ammonium salts, nitrates, carbonates, sulfates, chlorides, and organic acid salts used in this type of catalyst, 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 catalyst component element.

[0040] Examples of the molybdenum raw material compound include ammonium paramolybdate, ammonium dimolybdate, ammonium tetramolybdate, molybdenum trioxide, etc. Among these, ammonium paramolybdate is preferred. Examples of the bismuth raw material compound include bismuth chloride, bismuth nitrate, bismuth sulfate, bismuth acetate, bismuth oxide, basic bismuth carbonate, etc. Among these, bismuth nitrate is preferred. Examples of the iron raw material compound include iron chloride, iron nitrate, iron sulfate, iron acetate, iron oxide, iron carbonate, etc. Among these, iron nitrate is preferred. Examples of the nickel raw material compound include nickel chloride, nickel nitrate, nickel sulfate, nickel acetate, nickel oxide, basic nickel carbonate, etc. Among these, nickel nitrate is preferred.

[0041] 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 directly added to and mixed with the solution or slurry without being dissolved. There are no particular restrictions on the mixing conditions (mixing order, temperature, pressure, pH, etc.) of the raw material compounds. The obtained solution or slurry may be concentrated as necessary to form a cake so as to be applicable to the drying method in the subsequent drying process.

[0042] In the production method of the present invention, cobalt nitrate hexahydrate with a mass loss rate L1 of 11 to 16% by mass from 25°C to 105°C in thermogravimetric measurement is used as the raw material compound of cobalt. Here, as described above, since cobalt nitrate hexahydrate has hygroscopicity, in the normal storage state, the mass loss rate L1 slightly increases or decreases with time. Therefore, when mixing each raw material compound so as to obtain a desired catalyst component composition in the raw material mixing step, it is preferable to weigh and use cobalt nitrate hexahydrate in consideration of the value of the mass loss rate L1. In addition, when producing a catalyst on an industrial scale, it is necessary to perform the raw material mixing step multiple times and adjust so that the catalyst component composition is the same each time. However, considering the value of the mass loss rate L1, 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 loss rate L1, the amount of water used in the preparation of the solution or slurry may be adjusted so that the total moisture content in the system of the raw material mixture is the same. However, as long as cobalt nitrate hexahydrate with a mass loss rate L1 of 11 to 16% by mass is used, it is not necessary to adjust the total moisture content in the system to be the same each time.

[0043] In the production method of the present invention, when using respective nitrates as the raw material compounds of bismuth, iron, or nickel, as described above, since the mass loss rate L1 of these nitrates hardly affects the performance of the catalyst, there is no particular need to adjust the total moisture content in the system based on the mass loss rate L1 of these nitrates, but it may be appropriately adjusted in consideration of these mass loss rates L1.

[0044] (2) Drying step The drying step in the present invention is a step of heat-treating at least one of the raw material mixture obtained in the raw material mixing step, the pulverized product obtained in the pulverization step described later, the molded product obtained in the molding step described later, or the supported product obtained in the supporting step described later, preferably at 100 to 300°C, more preferably in the temperature range of 150 to 200°C.

[0045] In the drying process, when heat-treating the raw material mixture obtained in the raw material mixing process to obtain a dried product, the heat treatment method for obtaining the dried product is not particularly limited and can be appropriately selected according to the form of the raw material mixture. For example, when the raw material mixture is in a solution or slurry state, a granular or powdered dried product may be obtained using a spray dryer, drum dryer, etc., or the solution or slurry may be placed in a vat and dried in a box dryer. When the raw material mixture is in the form of a cake obtained by concentrating a solution or slurry, a box dryer, tunnel dryer, etc. may be used to perform heat treatment in a gas flow such as in an air stream or an inert gas stream such as nitrogen, or in an atmosphere, to obtain a block-shaped or flaky dried product. For example, when using a box dryer or tunnel dryer, the drying time is preferably 3 to 30 hours, more preferably 5 to 20 hours. In addition, when drying the solution or slurry of the raw material mixture by placing it in a vat or the like, or when drying the cake-shaped raw material mixture, any method may be used as long as a dried product that can be pulverized in the subsequent pulverization process can be obtained as necessary.

[0046] Also, when heat-treating the pulverized product obtained in the pulverization process described later, the molded product obtained in the molding process described later, or the supported product obtained in the supporting process described later, a box dryer, tunnel dryer, etc. may be used to perform heat treatment in a gas flow such as in an air stream or an inert gas stream such as nitrogen, or in an atmosphere, to obtain a dried product.

[0047] (3) Pulverization process The pulverization process in the present invention is a process of pulverizing the dried product obtained by heat-treating the raw material mixture as necessary. In the production method of the present invention, it is preferable to pulverize the dried product obtained in the above-described drying process to a desired particle size.

[0048] In the pulverization process, there is no particular limitation on the pulverization method, and it may be selected according to the form of the dried product. For example, various hammer mills, jet mills, ball mills, etc. can be used to pulverize the dried product, and a pulverized product having a desired particle size that can be used in the subsequent forming process or supporting process may be obtained. This pulverized product is used as a catalyst precursor. Further, it may be dried or fired after pulverization. In this case, the product dried or fired after pulverization is used as a catalyst precursor.

[0049] The particle size of the pulverized product (catalyst precursor) obtained through the pulverization process is not particularly limited, but in order to maintain good formability or supportability in the subsequent forming process or supporting process described below, it is in the range of 0.1 to 500 μm, preferably in the range of 10 to 300 μm.

[0050] (4) Forming process or (5) Supporting process The forming process in the present invention is a process of forming the pulverized product obtained in the pulverization process as a catalyst precursor, the dried product obtained by drying the pulverized product again, or the fired product thereof into a certain shape. Further, the supporting process in the present invention is a process of supporting the pulverized product obtained in the pulverization process as a catalyst precursor, the dried product obtained by drying the pulverized product again, or the fired product thereof on an inert carrier having a certain shape.

[0051] Examples of the catalyst forming method include a method of forming the catalyst precursor into a certain shape by an extrusion forming method, a tableting forming method, etc. These methods can be appropriately selected and used in combination. Further, the catalyst precursor can also be mixed with a powdery inert substance and used in the forming process.

[0052] Further, as a method for supporting the catalyst, for example, according to the methods described in JP-A-6-381, JP-A-10-28877, etc., the catalyst precursor can be supported on an inert carrier.

[0053] 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, zeolite, and the like. There is no particular limitation on the shape thereof, and those having known shapes such as spherical, ring-shaped, pellet-shaped, and amorphous can be used. When the carrier is spherical, the diameter is preferably in the range of 2 to 10 mm, and the loading amount of the catalytically active component with respect to the inert carrier is preferably in the range of 20 to 300% by mass.

[0054] There is no particular limitation on the catalyst shape, and any shape such as spherical, cylindrical, ring-shaped, and amorphous may be used. When the catalyst shape is spherical, the diameter is preferably in the range of 4 to 12 mm. Of course, when it is spherical, it does not have to be a perfect sphere, and it may be substantially spherical. Similarly, for the cylindrical and ring-shaped shapes, the cross-sectional shape does not have to be a perfect circle, and it may be substantially circular.

[0055] In the forming step and the loading step, a forming aid for improving the formability, a loading aid for improving the loading 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, or phenols, and nitric acid, ammonium nitrate, ammonium carbonate, and the like.

[0056] In addition, for the purpose of improving the mechanical strength of the catalyst, inorganic fibers generally known as reinforcing materials such as glass fiber, ceramic fiber, metal fiber, mineral fiber, carbon fiber, silica, alumina, titanium oxide, silicon carbide, and silicon nitride may be added.

[0057] There is no particular limitation on the method for adding these inorganic fibers, 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 the raw material mixture containing the catalyst component elements, or inorganic fibers may be added to the catalyst precursor obtained after drying and pulverizing the raw material mixture containing the catalyst component elements.

[0058] Also, a pore former may be added for the purpose of forming appropriate pores in the catalyst. There is no particular limitation on the pore former, and starch, cellulose, urea, polyvinyl alcohol, melamine cyanurate, etc. can be used.

[0059] (6) Firing step In the present invention, the firing step is a step of heat-treating the molded body obtained in the molding step or the supported body obtained in the supporting step at a high temperature.

[0060] There is no particular limitation on the firing furnace used in the firing step, and a generally used box-type firing furnace or tunnel-type firing furnace, etc. 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 preferred. Air is preferably used as the molecular oxygen-containing gas.

[0061] 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, that is, a method including a step of obtaining a catalyst by the production method of the present invention and a step of catalytic gas-phase oxidizing propylene using the catalyst. In the method for producing acrolein and acrylic acid in the present invention, it is preferable to carry out a catalytic gas-phase oxidation reaction by filling the reaction tube in the reactor with the catalyst obtained by the production method of the present invention and introducing a raw material gas containing propylene and molecular oxygen into the reaction tube.

[0062] Regarding the reactor used for the catalytic gas-phase oxidation of propylene to produce acrolein and acrylic acid in the present invention, there is no particular limitation as long as it is a fixed-bed reactor. Generally used fixed-bed multitubular reactors, plate reactors, etc. can be used, and a fixed-bed multitubular reactor is preferred. The inner diameter of the reaction tubes in the fixed-bed multitubular reactor is usually 15 to 50 mm, more preferably 20 to 40 mm, and even more preferably 22 to 38 mm.

[0063] Each reaction tube of the fixed-bed multitubular reactor does not necessarily need to be filled with a single catalyst. It is also possible to fill a plurality of known catalysts so as to form layers (hereinafter sometimes referred to as "reaction zones"). For example, a method of filling catalysts with different loadings so that the loading increases from the raw material gas inlet side to the outlet side, a method of diluting a part of the catalyst with an inert carrier, etc., or a method of combining these 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. However, if the number of reaction zones is too large, problems such as complicated catalyst filling work will occur. Therefore, industrially, it is desirable to be about 2 to 6.

[0064] There is no particular limitation on the reaction conditions in the present invention, and any conditions generally used for this type of reaction can be implemented. For example, as the 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; preferably 0 to 30% by volume, more preferably 0 to 25% by volume of steam; and the balance being an inert gas such as nitrogen; a mixed gas composed of these is used, and it is brought into contact with the catalyst at a space velocity of 300 to 5,000 Hr -1 (standard state) under a pressure of 0.1 to 1.0 MPa in the temperature range of 250 to 450 °C.

[0065] There are no particular restrictions on the grade of propylene as the reaction raw material gas, and polymer-grade or chemical-grade propylene can be used. Further, a propylene-containing mixed gas obtained by the oxidative dehydrogenation reaction of propane can also be used, and air or oxygen can be added to this mixed gas and used as necessary.

Examples

[0066] The present invention will be described in more detail with reference to 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 “mass %” and “parts by mass”, respectively. Further, in the following Examples, unless otherwise specified, the operations were carried out under the conditions of room temperature (20 to 25°C). Further, the conversion and yield in the Examples and Comparative Examples were determined by the following equations.

[0067] Conversion [mol%] =(mol number of reacted propylene) / (mol number of supplied propylene)×100 Yield [mol%] =(total mol number of produced acrolein and produced acrylic acid) / (mol number of supplied propylene)×100.

[0068] [Experiment 1 Experiment on the raw material compound of cobalt] [Preparation of cobalt nitrate hexahydrate] Cobalt nitrate hexahydrate was prepared by appropriately combining the treatments (humidity of the storage location, storage amount (amount filled in the container), storage period) of the above adjustment step to obtain cobalt nitrate hexahydrate having a mass reduction rate L1 shown in Table 1.

[0069] [Measurement of mass reduction rate] As a sample for measuring the mass loss rate, cobalt(II) nitrate hexahydrate in an amount required for thermogravimetric analysis (about 20 mg) was precisely weighed into an aluminum pan (W1: mass of cobalt(II) nitrate hexahydrate at room temperature), and a measurement sample was prepared. Then, after placing the measurement sample in the sample holder of a thermogravimetric analysis (TG) apparatus (apparatus name: 2000S, manufactured by Mac Science Co., Ltd.), the temperature was raised from room temperature below 25°C to 300°C at a rate of 2°C per minute, and the mass of the sample was measured as a function of temperature. From the measured mass change of the sample, the mass loss rate L1 of cobalt(II) nitrate hexahydrate and the mass loss rate L2 of cobalt(II) nitrate hexahydrate were calculated by the following formulas (a) and (b). Also, the ratio R of the mass loss rate L1 of cobalt(II) nitrate hexahydrate was calculated by the following formula (c). Note that the mass loss rate L3 of cobalt(II) nitrate hexahydrate is the sum of the mass loss rate L1 of cobalt(II) nitrate hexahydrate and the mass loss rate L2 of cobalt(II) nitrate hexahydrate.

[0070] L1 (mass%) = (W1 - W2) / W1 × 100 (a) L2 (mass%) = (W2 - W3) / W1 × 100 (b) R = L1 / (L1 + L2) = L1 / L3 (c) Here, W1 = mass of cobalt(II) nitrate hexahydrate at 25°C (mg) W2 = mass of cobalt(II) nitrate hexahydrate at the time of reaching 105°C (mg) W3 = mass of cobalt(II) nitrate hexahydrate at the time of reaching 300°C (mg).

[0071] [Preparation of Catalyst Production Example 1: Catalyst (1)] 400 parts of ion-exchanged water was dissolved with 340 parts of cobalt(II) nitrate hexahydrate and 82 parts of nickel(II) nitrate hexahydrate to prepare an aqueous solution of Co and Ni. At this time, the mass loss rate L1 of cobalt(II) nitrate hexahydrate calculated by thermogravimetric analysis of the cobalt(II) nitrate hexahydrate used was 11.2% by mass, the mass loss rate L3 of cobalt(II) nitrate hexahydrate was 66.9% by mass, and the ratio R of the mass loss rate L1 of cobalt(II) nitrate hexahydrate was 0.167. Also, the mass loss rate L1 of nickel(II) nitrate hexahydrate from 25 °C to 105 °C calculated by thermogravimetric analysis of the nickel(II) nitrate hexahydrate used was 14.7% by mass, and the mass loss rate L3 of nickel(II) nitrate hexahydrate from 25 °C to 300 °C was 41.4% by mass. The ratio R of the mass loss rate L1 of nickel(II) nitrate hexahydrate from 25 °C to 105 °C to the mass loss rate L3 of nickel(II) nitrate hexahydrate from 25 °C to 300 °C was 0.355. In addition, for nitrates other than cobalt(II) nitrate hexahydrate, by performing the same thermogravimetric measurement, the mass (mg) of the nitrate at W1 = 25 °C, the mass (mg) of the nitrate at the time of reaching W2 = 105 °C, and the mass (mg) of the nitrate at the time of reaching W3 = 300 °C were measured, and from the respective formulas (a) to (c), the mass loss rate L1 of the nitrate from 25 °C to 105 °C, the mass loss rate L 2、 and the ratio R of the mass loss rate L1 of the nitrate from 25 °C to 105 °C to the mass loss rate L3 of the nitrate from 25 °C to 300 °C can be calculated respectively.

[0072] Next, 99 parts of ferric nitrate (iron(III) nitrate nonahydrate) and 119 parts of bismuth(III) nitrate pentahydrate were dissolved in an aqueous nitric acid solution consisting of 65 parts of 65% nitric acid by mass and 300 parts of ion-exchanged water to prepare an Fe and Bi aqueous solution. The mass loss rate L1 of ferric nitrate from 25°C to 105°C calculated by thermogravimetric analysis of the ferric nitrate used here was 28.5% by mass, the mass loss rate L3 of ferric nitrate from 25°C to 300°C was 63.5% by mass, and the ratio R of the mass loss rate L1 of ferric nitrate from 25°C to 105°C to the mass loss rate L3 of ferric nitrate from 25°C to 300°C was 0.449. The mass loss rate L1 of the bismuth (III) nitrate pentahydrate from 25 ° C. to 105 ° C. calculated by thermogravimetric analysis of the bismuth (III) nitrate pentahydrate used was 13.0 mass%, the mass loss rate L3 of the bismuth (III) nitrate pentahydrate from 25 ° C. to 300 ° C. was 53.2 mass%, and the ratio R of the mass loss rate L1 of the bismuth (III) nitrate pentahydrate from 25 ° C. to 105 ° C. to the mass loss rate L3 of the bismuth (III) nitrate pentahydrate from 25 ° C. to 300 ° C. 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 Mo aqueous solution. The above separately prepared Fe and Bi aqueous solution and Mo aqueous solution were dropped into and mixed with the Co and Ni aqueous solution, then 3 parts of titanium oxide were mixed, and then an aqueous solution in which 1.9 parts of potassium nitrate was 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.

[0073] The lump solid was carried into a tunnel dryer and dried at 170°C for 14 hours, after which it was pulverized to 500 μm or less to obtain a catalyst precursor powder. 300 parts of alumina spherical carriers with an average particle size of 5.0 mm were put into a tumbling granulator, and then the catalyst precursor powder was gradually added together with a 20 mass% aqueous solution of ammonium nitrate as a binder to support the catalyst precursor on the carrier, followed by calcining for 6 hours at 470°C in an air atmosphere to obtain catalyst (1). The metal element composition of this catalyst (1), excluding oxygen and the carrier, was "Mo". 12 Bi 1.3 Co 6.1 Ni1.5 Fe 1.3 Ti 0.2 K 0.1 was

[0074] Also, the supported ratio of Catalyst (1) calculated by the following formula (d) was 130% by mass. Supported ratio (% by mass) = (mass of catalyst - mass of carrier) / (mass of carrier) × 100 Formula (d).

[0075] [Catalyst Production Example 2: Preparation of Catalyst (2)] In Catalyst Production Example 2, the mass loss rate L1 of cobalt hexahydrate nitrate calculated by thermogravimetric analysis of the cobalt hexahydrate nitrate used was 13.0% by mass, the mass loss rate L3 of cobalt hexahydrate nitrate was 68.8% by mass, and the ratio R of the mass loss rate L1 of cobalt hexahydrate nitrate was 0.189.

[0076] In Catalyst Production Example 2, 346 parts of cobalt hexahydrate nitrate was used in consideration of the value of L1 so that the cobalt composition in the obtained catalyst would be the same as that of Catalyst (1), and 394 parts of water was used in the preparation of the Co and Ni aqueous solution in consideration of the amount of cobalt hexahydrate nitrate and the value of its L1 so that the total amount of water in the system during the preparation of the Co and Ni aqueous solution would be the same. A catalyst was prepared in the same manner as in Catalyst Production Example 1 except for this, and Catalyst (2) was obtained.

[0077] [Catalyst Production Example 3: Preparation of Catalyst (3)] In Catalyst Production Example 3, the mass loss rate L1 of cobalt hexahydrate nitrate calculated by thermogravimetric analysis of the cobalt hexahydrate nitrate used was 14.0% by mass, the mass loss rate L3 of cobalt hexahydrate nitrate was 69.9% by mass, and the ratio R of the mass loss rate L1 of cobalt hexahydrate nitrate was 0.200.

[0078] In Catalyst Production Example 3, 349 parts of cobalt nitrate hexahydrate were used in consideration of the value of L1 so that the cobalt composition in the resulting catalyst would be the same as that in Catalyst (1). In consideration of the amount of cobalt nitrate hexahydrate and the value of its L1 so that the total amount of water in the system during the preparation of the Co and Ni aqueous solutions would be the same, the amount of water used during the preparation of the Co and Ni aqueous solutions was 391 parts. A catalyst was prepared in the same manner as in Catalyst Production Example 1 except for this, and Catalyst (3) was obtained.

[0079] [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% by mass, the mass loss rate L3 of cobalt nitrate hexahydrate was 70.1% by mass, and the ratio R of the mass loss rate L1 of cobalt nitrate hexahydrate was 0.203.

[0080] In Catalyst Production Example 4, 350 parts of cobalt nitrate hexahydrate were used in consideration of the value of L1 so that the cobalt composition in the resulting catalyst would be the same as that in Catalyst (1). In consideration of the amount of cobalt nitrate hexahydrate and the value of its L1 so that the total amount of water in the system during the preparation of the Co and Ni aqueous solutions would be the same, the amount of water used during the preparation of the Co and Ni aqueous solutions was 390 parts. A catalyst was prepared in the same manner as in Catalyst Production Example 1 except for this, and Catalyst (4) was obtained.

[0081] [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% by mass, the mass loss rate L3 of cobalt nitrate hexahydrate was 70.9% by mass, and the ratio R of the mass loss rate L1 of cobalt nitrate hexahydrate was 0.223.

[0082] In Catalyst Production Example 5, 355 parts of cobalt nitrate hexahydrate were used in consideration of the value of L1 so that the cobalt composition in the resulting catalyst would be the same as that in Catalyst (1). In consideration of the amount of cobalt nitrate hexahydrate and the value of its L1 so that the total amount of water in the system during the preparation of the Co and Ni aqueous solutions would be the same, the amount of water used during the preparation of the Co and Ni aqueous solutions was 385 parts. A catalyst was prepared in the same manner as in Catalyst Production Example 1 except for the above, and Catalyst (5) was obtained.

[0083] [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% by mass, the mass loss rate L3 of cobalt nitrate hexahydrate was 66.2% by mass, and the ratio R of the mass loss rate L1 of cobalt nitrate hexahydrate was 0.162.

[0084] In Catalyst Production Example 6, 338 parts of cobalt nitrate hexahydrate were used in consideration of the value of L1 so that the cobalt composition in the resulting catalyst would be the same as that in Catalyst (1). In consideration of the amount of cobalt nitrate hexahydrate and the value of its L1 so that the total amount of water in the system during the preparation of the Co and Ni aqueous solutions would be the same, the amount of water used during the preparation of the Co and Ni aqueous solutions was 402 parts. A catalyst was prepared in the same manner as in Catalyst Production Example 1 except for the above, and Catalyst (6) was obtained.

[0085] [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% by mass, the mass loss rate L3 of cobalt nitrate hexahydrate was 72.1% by mass, and the ratio R of the mass loss rate L1 of cobalt nitrate hexahydrate was 0.229.

[0086] In Catalyst Production Example 7, 358 parts of cobalt hexahydrate nitrate were used in consideration of the value of L1 so that the cobalt composition in the resulting catalyst would be the same. In consideration of the amount of cobalt hexahydrate nitrate and the value of its L1 so that the total amount of water in the system during the preparation of the Co and Ni aqueous solutions would be the same, 382 parts of water were used for the preparation of the Co and Ni aqueous solutions. A catalyst was prepared in the same manner as in Catalyst Production Example 1 except for this, and Catalyst (7) was obtained.

[0087] [Experiment 2: Experiment on Raw Material Compounds of Iron, Bismuth, and Nickel] Next, for the raw materials of iron, bismuth, and nickel, in the same manner as the raw material of cobalt in Experiment 1, Catalysts (8) to (10) were produced by adjusting the usage amounts of the raw materials of each element based on the mass loss rate L1. The raw materials of each element were prepared in the same manner as cobalt hexahydrate nitrate in Experiment 1, and by appropriately combining the adjustment of the humidity of the storage location, the storage amount (the amount filled in the container), and the storage period, each raw material (iron(III) nitrate nonahydrate, bismuth(III) nitrate pentahydrate, and nickel(II) nitrate hexahydrate) with the mass loss rate L1 shown in Table 2 was prepared. [Catalyst Production Example 8: Preparation of Catalyst (8)] In Catalyst Production Example 8, the mass loss rate L1 of iron(III) nitrate nonahydrate from 25°C to 105°C calculated by thermogravimetric analysis of the used iron(III) nitrate nonahydrate was 38.2 mass%, the mass loss rate L3 of iron(III) nitrate nonahydrate from 25°C to 300°C was 81.0 mass%, and the ratio R of the mass loss rate L1 of iron(III) nitrate nonahydrate from 25°C to 105°C to the mass loss rate L3 of iron(III) nitrate nonahydrate from 25°C to 300°C was 0.472.

[0088] In Catalyst Production Example 8, 109 parts of iron(III) nitrate nonahydrate were used in consideration of the value of L1 so that the Fe composition in the resulting catalyst would be the same as that of Catalyst (1). In consideration of the amount of iron(III) nitrate nonahydrate and the value of its L1 so that the total amount of water in the system would be the same, 291 parts of water were used for the preparation of the Fe and Bi aqueous solutions. A catalyst was prepared in the same manner as in Catalyst Production Example 1 except for this, and Catalyst (8) was obtained.

[0089] [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 used bismuth(III) nitrate pentahydrate was 18.6% by mass, and the mass loss rate L3 of bismuth(III) nitrate pentahydrate from 25°C to 300°C was 59.4% by mass. 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 bismuth(III) nitrate pentahydrate from 25°C to 300°C was 0.313.

[0090] In Catalyst Production Example 9, 126 parts of bismuth(III) nitrate pentahydrate were used in consideration of the value of L1 so that the Bi composition in the obtained catalyst would be the same as that in Catalyst (1). The amount of water used in the preparation of the Fe and Bi aqueous solutions was 294 parts in consideration of the amount of bismuth(III) nitrate pentahydrate and the value of its L1 so that the total moisture content in the system would be the same. A catalyst was prepared in the same manner as in Catalyst Production Example 1 except for the above, and Catalyst (9) was obtained.

[0091] [Catalyst Production Example 10: Preparation of Catalyst (10)] In Catalyst Production Example 10, the mass loss rate L1 of nickel(II) nitrate hexahydrate from 25°C to 105°C calculated by thermogravimetric analysis of the used nickel(II) nitrate hexahydrate was 19.9% by mass, and the mass loss rate L3 of nickel(II) nitrate hexahydrate from 25°C to 300°C was 47.6% by mass. The ratio R of the mass loss rate L1 of nickel(II) nitrate hexahydrate from 25°C to 105°C to the mass loss rate L3 of nickel(II) nitrate hexahydrate from 25°C to 300°C was 0.418.

[0092] In Catalyst Production Example 10, 86 parts of nickel(II) nitrate hexahydrate were used in consideration of the value of L1 so that the Ni composition in the obtained catalyst would be the same as that in Catalyst (1). The amount of water used in the preparation of the Co and Ni aqueous solutions was 397 parts in consideration of the amount of nickel(II) nitrate hexahydrate and the value of its L1 so that the total moisture content in the system would be the same. A catalyst was prepared in the same manner as in Catalyst Production Example 1 except for the above, and Catalyst (10) was obtained.

[0093] [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 the reaction tube was prepared vertically. Each catalyst (1) to (10) obtained from the upper part of the reaction tube was dropped and filled so that the layer length became 2500 mm.

[0094] [Oxidation reaction] In Examples 1 to 5 and Comparative Examples 1 and 2, a mixed gas consisting of 7.0% by volume of propylene, 13% by volume of oxygen, 8.5% by volume of steam, and the balance being nitrogen was introduced from the lower part of the reactor filled with each catalyst (1) to (7) at a space velocity of 1600 hr -1 (standard state), and a propylene oxidation reaction was carried out at a heat medium temperature of 310°C. The results are shown in Table 1. In Examples 6 to 8, the propylene oxidation reaction was carried out under the same conditions by filling each of the catalysts (8) to (10). The results are shown in Table 2.

[0095]

Table 1

[0096]

Table 2

[0097] From the results of Experiment 1 (Table 1), in Examples 1 to 5 using the catalysts (1) to (5) with a mass loss rate L1 of 11 to 16% by mass, the propylene conversion rate was 97.0 mol% or more, and the yields of acrolein and acrylic acid were 91.5 mol% or more. On the other hand, in Comparative Examples 1 and 2 using the catalysts (6) and (7) with a mass loss rate L1 of less than 11% by mass or more than 16% by mass, the propylene conversion rate was less than 97.0 mol%, and the yields of acrolein and acrylic acid were less than 91.5 mol%. Therefore, the catalysts (1) to (5) produced using cobalt(II) 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, and it was found that acrolein and acrylic acid can be produced in high yields by using the catalyst.

[0098] From the results of Experiment 2 (Table 2), it was found that the mass reduction rate L1 of nitrates of raw materials other than cobalt does not affect the propylene conversion rate and the yields of acrolein and acrylic acid, or has a smaller effect compared to the mass reduction rate L1 of cobalt hexahydrate nitrate.

[0099] 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

1. 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 containing a raw material compound of molybdenum, a raw material compound of bismuth, and a raw material compound of cobalt, wherein the raw material compound of cobalt is cobalt nitrate hexahydrate, The mass loss rate L from 25°C to 105°C in the thermogravimetric measurement of the cobalt nitrate hexahydrate represented by the following formula (a) １ is 11 to 16% by mass, a method for producing a catalyst. L １ (mass %) = (W １ - W ２ ) / W １ × 100 (a) here, W １ = Mass of cobalt(II) nitrate hexahydrate at 25 °C (mg) W ２ = Mass of cobalt(II) nitrate hexahydrate at the time of reaching 105°C (mg)

2. the catalyst is represented by the following general formula (1): Mo １２ Bi ａ Co ｂ A ｃ B ｄ C ｅ D ｆ (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, B is at least one element selected from the group consisting of alkali metals, alkaline earth metals, and thallium, C is at least one element selected from the group consisting of tungsten, silicon, aluminum, zirconium, and titanium, D is at least one element selected from the group consisting of phosphorus, tellurium, antimony, tin, cerium, lead, niobium, manganese, arsenic, boron, and zinc, and a, b, c, d, e, and f represent the number of atoms of Bi, Co, A, B, C, and D, respectively, and 0 < a ≦ 10, 0 < b ≦ 20, 0 < c ≦ 20, 0 ≦ d ≦ 10, 0 ≦ e ≦ 30, 0 ≦ f ≦ 4 (however, formula (1) excludes oxygen representing the oxidation state).)) The method for producing a catalyst according to claim 1, comprising a composite oxide represented by the formula.

3. A method for producing acrolein and acrylic acid by catalytic gas-phase oxidation of propylene using the catalyst obtained by the production method according to claim 1 or 2.

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