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

Abstract

Provided is a method for producing a catalyst having excellent catalytic activity and yield, which is used in a method for producing propenal and acrylic acid by catalytic gas-phase oxidation of propylene. The method for producing the catalyst is a method for producing a catalyst for producing propenal and acrylic acid by catalytic gas-phase oxidation of propylene, which includes a step of mixing a raw material mixture of a raw material compound containing molybdenum, a raw material compound of bismuth, and a raw material compound of cobalt, the raw material compound of cobalt being cobalt nitrate hexahydrate, the mass loss rate L1 of the cobalt nitrate hexahydrate in thermogravimetric analysis from 25°C to 105°C being 11 to 16 mass%.

Description

TECHNICAL FIELD

[0001] The present application relates to a production method of a catalyst for producing acrolein and acrylic acid, and a production method of acrolein and acrylic acid using the catalyst. BACKGROUND

[0002] As for a catalyst used in the industrial production of acrolein and acrylic acid by catalytic gas phase oxidation of propylene using molecular oxygen, many proposals have been made. For example, in Patent Literature 1, as a catalyst for producing unsaturated aldehydes and unsaturated carboxylic acids, a composite metal oxide catalyst is disclosed which specifies that molybdenum, bismuth and iron are used as essential catalytically active components, and that ammonium molybdate tetrahydrate having a heat absorption peak temperature within a specified temperature range is used as a molybdenum raw material.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Application Laid-Open No. 2018-153773 SUMMARY

[0006] (PROBLEMS TO BE SOLVED BY THE INVENTION)

[0007] However, although the yield of acrolein and acrylic acid is improved by using the catalyst described in the above-mentioned Literature 1, further improvement of the catalyst is desired in terms of catalytic performance such as catalytic activity, yield, etc. in the production of acrolein and acrylic acid on an industrial scale.

[0008] Accordingly, an object of the present application is to provide a production method of a catalyst having excellent catalytic activity and yield, which is used in a method of producing acrolein and acrylic acid by catalytic gas phase oxidation of propylene. Another object of the present application is to provide a method of producing acrolein and acrylic acid at a high yield by catalytic gas phase oxidation of propylene using a gas containing molecular oxygen in the presence of a catalyst having excellent catalytic activity and yield, which is produced by the production method.

[0009] (Technical Solution for Solving the Problems)

[0010] The present inventors etc. have repeatedly conducted intensive studies with a particular focus on the properties of raw material compounds used in the production of the catalyst, in order to solve the above-mentioned problems. As a result, it has been found that the above-mentioned problems are solved by a production method of a catalyst for producing acrolein and acrylic acid by catalytic gas phase oxidation of propylene, which includes a step of mixing a raw material mixture of a raw material compound containing molybdenum, a raw material compound of bismuth and a raw material compound of cobalt, the raw material compound of cobalt being cobalt nitrate hexahydrate, the mass loss rate L1 of the cobalt nitrate hexahydrate in thermogravimetric analysis from 25°C to 105°C being 11 to 16 mass%.

[0011] (Inventive Effects)

[0012] According to the present application, a catalyst for producing propylene aldehyde and acrylic acid, which is excellent in catalytic activity and yield, can be produced on an industrial scale. Further, by using the obtained catalyst for catalytic gas phase oxidation of propylene, propylene aldehyde and acrylic acid can be produced at a high yield. DETAILED DESCRIPTION

[0013] Hereinafter, an embodiment of the present application will be described, but the present application is not limited only to the following embodiment. Note that in the present specification, "X to Y" indicating a range means "X or more and Y or less".

[0014] One embodiment of the present application is a production method of a catalyst for producing propylene aldehyde and acrylic acid by catalytic gas phase oxidation of propylene (hereinafter, sometimes referred to as "catalyst for producing propylene aldehyde and acrylic acid"), comprising a step of mixing a raw material mixture of a raw material compound containing molybdenum, a raw material compound of bismuth, and a raw material compound of cobalt, the raw material compound of cobalt being cobalt nitrate hexahydrate, the mass loss rate L1 of the cobalt nitrate hexahydrate represented by the following formula (a) in a thermogravimetric analysis (TG) from 25°C to 105°C being 11 to 16 mass%.

[0015] L1 (mass%) = (W1 - W2) / W1 x 100 (a)

[0016] wherein,

[0017] W1 = mass of cobalt nitrate hexahydrate at 25°C (mg)

[0018] W2 = mass of cobalt nitrate hexahydrate at 105°C (mg).

[0019] The production method of the catalyst for producing propylene aldehyde and acrylic acid of the present application comprises a step of mixing a raw material mixture of a raw material compound containing molybdenum, a raw material compound of bismuth, and a raw material compound of cobalt. Therefore, the catalyst for producing propylene aldehyde and acrylic acid of the present application contains molybdenum, bismuth, and cobalt, that is, the catalyst for producing propylene aldehyde and acrylic acid of the present application contains molybdenum, bismuth, and cobalt as essential catalytically active components.

[0020] The catalyst for producing propylene aldehyde and acrylic acid of the present application contains molybdenum, bismuth, and cobalt as essential components, and further preferably contains iron and / or nickel. Further, the catalyst for producing propylene aldehyde and acrylic acid of the present application preferably contains a composite oxide represented by the following general formula (1) (wherein, the general formula (1) does not include oxygen indicating an oxidation state). That is, the catalytically active components of the catalyst for producing propylene aldehyde and acrylic acid of the present application preferably contain a composite oxide represented by the following general formula (1) (wherein, the general formula (1) does not include oxygen indicating an oxidation state).

[0021] Mo 12 Bi a Co b A c B d C e D f (1)

[0022] In formula (1), Mo is molybdenum, Bi is bismuth, Co is cobalt, A is at least one element selected from iron and nickel, B is at least one element selected from alkali metals, alkaline earth metals and thallium, C is at least one element selected from tungsten, silicon, aluminum, zirconium and titanium, D is at least one element selected from 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, 0 < a ≤ 10, 0 < b ≤ 20, 0 < c ≤ 20, 0 ≤ d ≤ 10, 0 ≤ e ≤ 30, 0 ≤ f ≤ 4.

[0023] The catalyst for the manufacture of acrolein and acrylic acid of the present invention is preferred because it contains element A (selected from at least one element selected from iron and nickel) as a catalyst component, thereby improving catalytic activity and yield.

[0024] 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 equation (1), f is preferably 0≤f≤4, more preferably 0≤f≤3, and even more preferably 0≤f≤2.

[0025] In the present application, in the method for producing a catalyst for producing acrolein and acrylic acid, the raw material compound of cobalt used is cobalt nitrate hexahydrate. That is, in the catalyst for producing acrolein and acrylic acid of the present application, the raw material compound of cobalt contained as an essential catalytically active component is cobalt nitrate hexahydrate. The mass loss rate L1 (hereinafter, also referred to as "mass loss rate L1 of cobalt nitrate hexahydrate") of cobalt nitrate hexahydrate in thermogravimetric analysis from 25°C to 105°C is 11 to 16 mass%. Note that the mass loss rate L1 is represented by the above formula (a). By using such cobalt nitrate hexahydrate as a raw material for a catalyst for producing acrolein and acrylic acid, it is possible to significantly improve the catalytic activity and yield of the resulting catalyst for producing acrolein and acrylic acid.

[0026] Here, the mass loss rate L1 of cobalt nitrate hexahydrate is a value indicating the mass change due to dehydration of hygroscopic water and crystallization water, and thermal decomposition, which occur with temperature change (heating) from 25°C to 105°C in thermogravimetric analysis. Among them, the mass change due to dehydration of crystallization water, and the mass change accompanying thermal decomposition in the temperature change of cobalt nitrate hexahydrate from 25°C to 105°C are considered to be values inherent to cobalt nitrate hexahydrate. Therefore, in the case where the value of the mass loss rate L1 of cobalt nitrate hexahydrate varies in each measured sample of cobalt nitrate hexahydrate in thermogravimetric analysis, it is considered that the variation (difference) in the value is mainly due to the amount of moisture of cobalt nitrate hexahydrate. If the mass change due to dehydration of crystallization water is theoretically studied, the mass loss rate L1 of cobalt nitrate hexahydrate is about 6 to 37%, and if the mass change due to dehydration of hygroscopic water is taken into account on this basis, 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 is nothing more than a speculation, and does not limit the technical scope of the present application. The catalyst for producing acrolein and acrylic acid of the present application exerts an effect by being produced using cobalt nitrate hexahydrate having a mass loss rate L1 in a specific range as a raw material.

[0027] Cobalt nitrate hexahydrate and other nitrate salts, which are commonly used as raw material compounds of catalysts, are known to be easily hygroscopic, and depending on the storage conditions, the moisture content of cobalt nitrate hexahydrate varies in a wide range, and as a result, the mass loss rate L1 of cobalt nitrate hexahydrate also varies in a wide range. However, so far, the moisture content and storage method of cobalt nitrate hexahydrate as a raw material used in a catalyst for producing acrolein and acrylic acid have not been studied in detail.

[0028] The inventors have discovered that if the water content of cobalt nitrate hexahydrate increases, its mass loss rate L1 increases. When using cobalt nitrate hexahydrate with a high mass loss rate L1 to manufacture a catalyst for acrolein and acrylic acid production, the yield of acrolein and acrylic acid decreases when propylene is catalytically oxidized in the gas phase using this catalyst. Furthermore, they have found that if the water content of cobalt nitrate hexahydrate decreases, its mass loss rate L1 decreases. Similarly, when using cobalt nitrate hexahydrate with a low mass loss rate L1 to manufacture a catalyst for acrolein and acrylic acid production, the yield of acrolein and acrylic acid decreases when propylene is catalytically oxidized in the gas phase using this catalyst.

[0029] Various studies have shown that by using a mass reduction rate (L1) of cobalt nitrate hexahydrate as a raw material of 11–16% by mass, the catalytic activity and yield of the resulting catalyst for the production of acrolein and acrylic acid can be significantly improved. Specifically, this invention has revealed that the moisture content of cobalt nitrate hexahydrate varies depending on its storage conditions, resulting in wide variations in the mass reduction rate (L1) of the cobalt nitrate, leading to wide variations in the catalytic activity and yield of the resulting catalyst for the production of acrolein and acrylic acid. This is a major reason why it is difficult to stably produce high-performance catalysts for the production of acrolein and acrylic acid. According to this invention, by using cobalt nitrate hexahydrate with a specific mass reduction rate (L1), it is possible to stably produce catalysts for the production of acrolein and acrylic acid with excellent catalytic activity and yield in the industry. Therefore, using this catalyst, it is possible to stably produce acrolein and acrylic acid in high yield in the industry. The reasons for achieving the above effects through the configuration of this invention may not be clear, but are considered to be as follows.

[0030] The main reason for the influence of the mass loss rate L1 of cobalt nitrate hexahydrate on catalytic activity and yield is still uncertain. However, it can be assumed that the Co produced when cobalt nitrate hexahydrate is dissolved in water varies depending on the mass loss rate L1. 2+ Co 2+ With OH - Combining species (e.g., CoOH) + Co(OH)2, Co2OH 3+ The concentration and proportion of molybdenum (e.g., molybdenum, cobalt) change, thereby altering the reactivity of other elements, especially molybdenum and cobalt, which are the main raw materials.

[0031] It is speculated that when the mass loss rate L1 of cobalt nitrate hexahydrate is low (e.g., when the mass loss rate L1 of cobalt nitrate hexahydrate from 25°C to 105°C, as obtained by thermogravimetric analysis, is less than 11% by mass), among the chemical species generated when cobalt nitrate hexahydrate is dissolved in water, the proportion of those related to Co is relatively low. 2+ In comparison, CoOH+ Co(OH)2, Co2OH 3+ Co such as Co 2+ The proportion of the existence of the species other than Co increases, and thus the proportion of the existence of Co 2+ decreases, and the reactivity of molybdenum with cobalt decreases. In addition, it is presumed that in the case where the mass loss rate Ll of cobalt nitrate hexahydrate is high (for example, in the case where the mass loss rate Ll of cobalt nitrate hexahydrate from 25°C to 105°C obtained by thermal gravimetric analysis exceeds 16 mass%), the concentration of Co 2+ decreases in the chemical species generated when cobalt nitrate hexahydrate is dissolved in water, and the reactivity of molybdenum with cobalt decreases. However, this mechanism is only a presumption, and of course does not limit the technical scope of the present application.

[0032] Note that it is known that generally the hygroscopicity of nitrate salts is high, but in nitrate salts other than cobalt (for example, nitrate salts of bismuth, iron, and nickel), even if the mass loss rate Ll is controlled, the effect of improving the performance of the catalyst cannot be exerted, which is confirmed in the examples described later (Examples 6 to 8). The reason is not clear, but it can be said that only cobalt nitrate hexahydrate is related to the mass loss rate Ll, and significantly affects the catalytic performance.

[0033] As described above, in the production of a catalyst for the production of acrolein and acrylic acid, by using cobalt nitrate hexahydrate having a mass loss rate Ll of 11 to 16 mass% as a cobalt raw material, it is possible to significantly improve the catalytic activity and yield of the obtained catalyst for the production of acrolein and acrylic acid.

[0034] The mass loss rate Ll of cobalt nitrate hexahydrate is preferably more than 11 mass%, more preferably 11.1 mass% or more, further preferably more than 11.1 mass%, more preferably 11.3 mass% or more, particularly preferably 11.5 mass% or more, and most preferably 12 mass% or more. In addition, the mass loss rate Ll of cobalt nitrate hexahydrate is preferably 16 mass% or less, more preferably 15.5 mass% or less, further preferably 15 mass% or less, more further preferably 14.5 mass% or less, particularly preferably 14.3 mass% or less, and most preferably less than 14.1 mass%. In a preferred embodiment, the mass loss rate Ll of cobalt nitrate hexahydrate is 14.0 mass% or less.

[0035] Here, a method for measuring the mass decrease ratio L1 of cobalt nitrate hexahydrate is described. As a measurement sample, a sample obtained by accurately weighing 20 mg of cobalt nitrate hexahydrate in an aluminum pan is prepared. After the measurement sample is set on a sample holder of a thermogravimetric analysis (TG) device, measurement is performed from 25°C or lower to 300°C at a temperature increase rate of 2°C / min, and the mass decrease ratio L1 from 25°C to 105°C is calculated. Note that the thermogravimetric analysis (TG) device used in the analysis can be a general specification or a thermogravimetric differential thermal analysis device (TG-DTA) configured to be capable of simultaneously measuring thermogravimetric analysis (TG) and differential thermal analysis (DTA).

[0036] In addition, from the results of the above thermogravimetric analysis, the mass decrease ratio L2 from 105°C to 300°C (hereinafter referred to as "mass decrease ratio L2 of cobalt nitrate hexahydrate") and the mass decrease ratio L3 of cobalt nitrate hexahydrate from 25°C to 300°C (hereinafter referred to as "mass decrease ratio L3 of cobalt nitrate hexahydrate") are calculated. In the present application, the mass decrease ratio L3 of cobalt nitrate hexahydrate is preferably 62 to 75 mass%, more preferably 65 to 73 mass%, further preferably 66 to 72 mass%, still further preferably 66.3 to 71.0 mass%, particularly preferably 66.5 to 70.5 mass%, and most preferably 66.8 to 70.0 mass%. In the production of a catalyst for producing acrolein and acrylic acid, by using cobalt nitrate hexahydrate having a mass decrease ratio L3 in the above range as a cobalt raw material, the catalytic activity and yield of the obtained catalyst for producing acrolein and acrylic acid can be significantly improved.

[0037] In addition, from the results of the above thermogravimetric analysis, the ratio R of the mass decrease ratio L1 of cobalt nitrate hexahydrate from 25°C to 105°C to the mass decrease ratio L3 of cobalt nitrate hexahydrate from 25°C to 300°C (hereinafter referred to as "ratio R of mass decrease ratio L1 of cobalt nitrate hexahydrate") is also calculated.

[0038] In one embodiment of the present application, the ratio R of the mass decrement ratio L1 of cobalt nitrate hexahydrate is 0.147 to 0.258. In the present application, the ratio R of the mass decrement ratio L1 of cobalt nitrate hexahydrate is preferably 0.163 to 0.225, more preferably 0.164 to 0.210, further preferably 0.165 to 0.205, more further preferably 0.165 to 0.202, particularly preferably 0.166 to 0.201, and most preferably 0.166 or more and less than 0.201. In one embodiment, the ratio R of the mass decrement ratio L1 of cobalt nitrate hexahydrate is 0.170 or more and less than 0.201. In the production of a catalyst for the production of acrolein and acrylic acid, by using cobalt nitrate hexahydrate having the ratio R of the mass decrement ratio L1 in the above range as a raw material compound of cobalt, it is possible to significantly improve the catalytic activity and yield of the catalyst for the production of acrolein and acrylic acid obtained.

[0039] As the production method of a catalyst for the production of acrolein and acrylic acid of the present application, 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 is included. The raw material compound of molybdenum is a compound including molybdenum, the raw material compound of bismuth is a compound including bismuth, and the raw material compound of cobalt is a compound including cobalt. Therefore, in the production method of a catalyst for the production of acrolein and acrylic acid of the present application, it is necessary to use a compound including molybdenum, a compound including bismuth, and a compound including cobalt as raw materials, and the raw material compound of cobalt is cobalt nitrate hexahydrate having a mass decrement ratio L1 in a specific range, and except for this, it can be produced according to a method generally used in the production of a catalyst for the production of acrolein and acrylic acid. Hereinafter, a preferred mode of the production method of a catalyst for the production of acrolein and acrylic acid of the present application will be described.

[0040] For example, the production method of the catalyst for producing acrolein and acrylic acid according to the present application includes at least one of (1) and (2) to (6) in the following processes: (1) a raw material mixing process in which raw material compounds containing elements constituting a catalytically active component (hereinafter referred to as "catalyst component elements") are mixed to obtain a raw material mixture; (2) a drying process in which the raw material mixture is subjected to a heating treatment to obtain a dried product; (3) a pulverization process in which the dried product is pulverized to obtain a pulverized product; (4) a molding process in which the pulverized product is molded to obtain a molded body; (5) a supporting process in which the pulverized product is supported on an inactive carrier; and (6) a calcination process in which the molded body or the supported body is calcined. In addition, a first calcination process can be added after the (2) drying process or the (3) pulverization process, and two calcinations of (6) can be performed together. Note that the "process of mixing a raw material mixture of a raw material compound containing molybdenum, a raw material compound of bismuth, and a raw material compound of cobalt" corresponds to the "(1) raw material mixing process of mixing raw material compounds containing catalyst component elements to obtain a raw material mixture".

[0041] Further, the production method of the catalyst for producing acrolein and acrylic acid according to the present application includes, in a preferred embodiment, the following processes before the raw material mixing process: (A1) an inspection process in which the mass loss rate L1 of cobalt nitrate hexahydrate is measured by TG or TG-DTA; and (B1) an adjustment process in which, in the inspection process, when the mass loss rate L1 of cobalt nitrate hexahydrate is less than 11 mass% or exceeds 16 mass%, the mass loss rate L1 of cobalt nitrate hexahydrate is adjusted so as to be 11 to 16 mass%.

[0042] (A1) Inspection process

[0043] The inspection process is a process of measuring cobalt nitrate hexahydrate used as a raw material by TG or TG-DTA and confirming the mass loss rate L1, and is preferably performed 10 to 3 hours before the raw material mixing process. In addition, when it is confirmed in the inspection process that the mass loss rate L1 of cobalt nitrate hexahydrate is 11 to 16 mass%, it is preferable to store cobalt nitrate hexahydrate used as a raw material so that the mass loss rate L1 does not change until the raw material mixing process. As a storage method, as long as the mass loss rate L1 does not change, it can be a publicly known method and is not particularly limited. For example, as a storage method, it can be a method of filling the required amount or an amount of 1 or more times the required amount of cobalt nitrate hexahydrate used as a raw material into a hopper, performing nitrogen replacement, and then sealing and storing, or a method of dissolving the required amount or an amount of 1 or more times the required amount of cobalt nitrate hexahydrate used as a raw material in an aqueous solution and sealing and storing in the form of an aqueous solution.

[0044] (B1) adjustment step

[0045] The adjustment step is a step of treating the cobalt nitrate hexahydrate used as a raw material in accordance with the mass decrease rate L1 in a case where it is confirmed in the inspection step that the mass decrease rate L1 of the cobalt nitrate hexahydrate is less than 11 mass% or exceeds 16 mass%.

[0046] As the treatment performed in the adjustment step, for example, there can be mentioned a treatment of appropriately performing adjustment of the humidity of a storage site, the storage amount (amount filled in a container), and the storage period, and the like at the time of storing the cobalt nitrate hexahydrate. These treatments can be performed individually or in combination. Here, in the adjustment step, the above-mentioned treatments are performed under different conditions in a case where the mass decrease rate L1 of the cobalt nitrate hexahydrate is less than 11 mass% and in a case where the mass decrease rate L1 of the cobalt nitrate hexahydrate exceeds 16 mass%.

[0047] For example, in a case where the mass decrease rate L1 of the cobalt nitrate hexahydrate is less than 11 mass%, it is preferable to perform a treatment of making the cobalt nitrate hexahydrate hygroscopic. As a treatment method of making it hygroscopic, in the above-mentioned treatment, the treatment is performed under hygroscopic conditions. For example, as a treatment method of making it hygroscopic, there can be a method of storing the required amount or more of the cobalt nitrate hexahydrate used as a raw material 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 leaving it in the atmosphere for 1 to 24 hours after being filled in a hopper. The storage period can be appropriately adjusted in accordance with the mass decrease rate L1 of the cobalt nitrate hexahydrate. In addition, by increasing or decreasing the storage amount (amount filled in a container), the time required for the treatment can be arbitrarily changed.

[0048] In addition, for example, in a case where the mass decrease rate L1 of the cobalt nitrate hexahydrate exceeds 16 mass%, it is preferable to perform a treatment of drying the cobalt nitrate hexahydrate. As a treatment method of making it dry, in the above-mentioned treatment, the treatment is performed under dry conditions. For example, as a treatment method of making it dry, there can be a method of storing the required amount or more of the cobalt nitrate hexahydrate used as a raw material 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 performing vacuum drying for 1 to 24 hours after being filled in a hopper. The storage period can be appropriately adjusted in accordance with the mass decrease rate L1 of the cobalt nitrate hexahydrate. In addition, by increasing or decreasing the storage amount (amount filled in a container), the time required for the treatment can be arbitrarily changed.

[0049] Preferably, after the cobalt nitrate hexahydrate is treated in the adjustment step according to the quality loss rate L1 confirmed in the inspection step, the inspection step of (Al) measuring the quality loss rate L1 of the cobalt nitrate hexahydrate using TG or TG-DTA is performed again. That is, preferably, the (Al) inspection step and the (Bl) adjustment step are repeated until the quality loss rate L1 of the cobalt nitrate hexahydrate becomes 11 to 16 mass%. Note that, in the case where the adjustment is performed in such a manner that the quality loss rate L1 of the cobalt nitrate hexahydrate becomes 11 to 16 mass%, by collecting data obtained to some extent at the time of adjustment, it is possible to estimate the value of the quality loss rate L1 obtained by the adjustment based on the data.

[0050] In the case where the quality loss rate L1 of the cobalt nitrate hexahydrate is confirmed to be 11 to 16 mass% through the inspection step or the inspection step and the adjustment step, at least one of (1) and (2) to (6) in the following steps is performed using the cobalt nitrate hexahydrate: (1) a raw material mixing step; (2) a drying step; (3) a pulverization step; (4) a molding step; (5) a supporting step; and (6) a calcination step. Hereinafter, each step is described.

[0051] (1) Raw material mixing step

[0052] In the present application, the raw material mixing step refers to a step of mixing raw material compounds (for example, a raw material compound of molybdenum, a raw material compound of bismuth, a raw material compound of cobalt, a raw material compound of iron, and a raw material compound of nickel) each containing one or a plurality of elements of each catalyst component element constituting a catalyst for producing acrolein and acrylic acid, to obtain a raw material mixture containing all the elements of the catalyst component elements. In the raw material mixing step of the present application, 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 the raw material mixture, but the order of mixing is not particularly limited, and in addition, the raw material mixture can contain a raw material compound containing an element of the catalyst component element other than the raw material compound of molybdenum, the raw material compound of bismuth, and the raw material compound of cobalt.

[0053] As for the raw material compounds of the elements of the catalyst component elements that can be used in the present application, in addition to the raw material compound of molybdenum, the raw material compound of bismuth, and the raw material compound of cobalt being essential and the raw material compound of cobalt being the cobalt nitrate hexahydrate having the quality loss rate L1 in the specified range, there is no particular limitation, and oxides, hydroxides, ammonium salts, nitrate salts, carbonate salts, sulfate salts, chloride salts, organic acid salts, and the like of metal elements generally used in such a catalyst, aqueous solutions, sols, and the like thereof, or a mixture thereof can be used. Among them, the ammonium salt and the nitrate salt are suitable as a raw material of each element of the catalyst component.

[0054] As the raw material compound of molybdenum, for example, ammonium dimolybdate, ammonium paramolybdate, ammonium tetramolybdate, molybdenum trioxide, etc. can be mentioned, of which ammonium dimolybdate is preferred. Further, as the raw material compound of bismuth, for example, bismuth chloride, bismuth nitrate, bismuth sulfate, bismuth acetate, bismuth oxide, bismuth subcarbonate, etc. can be mentioned, of which bismuth nitrate is preferred. Further, as the raw material compound of iron, for example, iron chloride, iron nitrate, iron sulfate, iron acetate, iron oxide, iron carbonate, etc. can be mentioned, of which iron nitrate is preferred. Further, as the raw material compound of nickel, for example, nickel chloride, nickel nitrate, nickel sulfate, nickel acetate, nickel oxide, basic nickel carbonate, etc. can be mentioned, of which nickel nitrate is preferred.

[0055] The raw material mixture can be prepared by the method generally used in such a catalyst as long as the above-mentioned raw material compounds are dissolved or suspended in a solvent such as water to prepare a solution or a slurry, and they are mixed in order. Alternatively, one raw material compound can be divided into a plurality of solutions or slurries and mixed. Further, each raw material compound can be directly added to the solution or the slurry without being dissolved and mixed. The mixing conditions (mixing order, temperature, pressure, pH, etc.) of the raw material compounds are not particularly limited. In order to be suitable for the drying method in the following drying step, the obtained solution or slurry can be concentrated as needed to make a cake.

[0056] In the production method of the present application, as the raw material compound of cobalt, cobalt nitrate hexahydrate having a mass decrease rate Ll from 25°C to 105°C of 11 to 16 mass% in thermogravimetric analysis is used. Here, as described above, since cobalt nitrate hexahydrate has hygroscopicity, the mass decrease rate Ll is slightly changed with the passage of time under the usual storage conditions. Therefore, when each raw material compound is mixed in the raw material mixing step in such a manner as to become the desired catalyst component composition, regarding cobalt nitrate hexahydrate, it is preferred to weigh and use it taking into account the value of the mass decrease rate Ll. Note that, when a catalyst is produced on an industrial scale, the raw material mixing step needs to be performed a plurality of times, and adjustment is made in such a manner that the catalyst component composition is the same each time, but if the value of the mass decrease rate Ll is taken into account, the amount of cobalt nitrate hexahydrate used sometimes slightly varies each time. In this case, the amount of water used in the preparation of a solution or a slurry can be adjusted in such a manner that the total amount of moisture in the system of the raw material mixture is the same, taking into account the amount of cobalt nitrate hexahydrate used and the value of the mass decrease rate Ll thereof, but as long as cobalt nitrate hexahydrate having a mass decrease rate Ll of 11 to 16 mass% is used, the total amount of moisture in the system can also be adjusted in such a manner that it is not the same each time.

[0057] In the production method of the present application, in the case where each nitrate is used as a raw compound of bismuth, iron or nickel, as described above, the mass reduction rate L1 of these nitrates hardly affects the performance of the catalyst, and thus it is not particularly required to adjust the total amount of moisture in the system based on the mass reduction rate L1 of these nitrates, but it is also possible to appropriately adjust considering these mass reduction rates L1.

[0058] (2) Drying step

[0059] The drying step in the present application refers to a step of heating 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, at a temperature in the range of preferably 100 to 300°C, more preferably 150 to 200°C.

[0060] In the drying step, in the case where the raw material mixture obtained in the raw material mixing step is subjected to the heating treatment to obtain a dried product, the heating treatment method for obtaining the dried product is not particularly limited, and can be appropriately selected in a manner suitable for the form of the raw material mixture. For example, in the case where the raw material mixture is in a solution or slurry form, a spray dryer, a drum dryer or the like can be used to obtain a granular or powdery dried product, or the solution or slurry can be put into a barrel or the like and dried with a box-type dryer. In the case where the raw material mixture is in a cake form obtained by concentrating a solution or slurry, a box-type dryer, a tunnel-type dryer or the like can be used to perform the heating treatment under the flow of a gas such as air, a non-active gas such as nitrogen, or the like, or under an atmosphere, to obtain a block or sheet-shaped dried product. In the case of using, for example, a box-type dryer, a tunnel-type dryer or the like, the drying time is preferably 3 to 30 hours, more preferably 5 to 20 hours. Note that, in the case where the solution or slurry of the raw material mixture is put into a barrel or the like to be dried, or in the case where the cake-shaped raw material mixture is dried, it is only required to be a method of obtaining a dried product that can be pulverized in the subsequent pulverization step as needed.

[0061] In addition, in the case where 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 is subjected to the heating treatment, a box-type dryer, a tunnel-type dryer or the like can be used to perform the heating treatment under the flow of a gas such as air, a non-active gas such as nitrogen, or the like, or under an atmosphere, to produce a dried product.

[0062] (3) Pulverization step

[0063] The pulverization step in the present application refers to a step of pulverizing the dried product obtained by the heating treatment of the raw material mixture as needed. In the production method of the present application, it is preferable to pulverize the dried product obtained in the above-described drying step to a desired particle size.

[0064] In the pulverization step, the pulverization method is not particularly limited, and any method can be used as long as it is suitable for the form of the dried substance. For example, the dried substance is pulverized using various hammer mills, jet mills, ball mills, or the like, and a pulverized substance having a desired particle diameter that can be used in the subsequent molding step or the supporting step is obtained. The pulverized substance is used as a catalyst precursor. Furthermore, drying or firing can be performed after pulverization, and in this case, a substance obtained by drying or firing after pulverization is used as a catalyst precursor.

[0065] The particle diameter of the pulverized substance (catalyst precursor) obtained in the pulverization step is not particularly limited, and is preferably in the range of 0.1 to 500 μm, and more preferably in the range of 10 to 300 μm, in order to maintain good moldability or supportability in the subsequent molding step or the supporting step.

[0066] (4) Molding step or (5) supporting step

[0067] The molding step in the present application is a step in which the pulverized substance obtained in the pulverization step, the dried substance obtained by drying the pulverized substance again, or the fired substance thereof is molded into a certain shape as a catalyst precursor. In addition, the supporting step in the present application is a step in which the pulverized substance obtained in the pulverization step as a catalyst precursor, the dried substance obtained by drying the pulverized substance again, or the fired substance thereof is supported on an inactive carrier having a certain shape.

[0068] As the molding method of the catalyst, a method in which the catalyst precursor is molded into a certain shape using an extrusion molding method, a tablet molding method, or the like can be given. These methods can also be appropriately selected and used in combination. In addition, the catalyst precursor can be mixed with a powder-like inactive substance and used in the molding step.

[0069] In addition, as the supporting method of the catalyst, for example, the catalyst precursor can be supported on an inactive carrier according to the method described in Japanese Patent Application Laid-Open No. 6-381, Japanese Patent Application Laid-Open No. 10-28877, or the like.

[0070] As the inactive carrier on which the catalyst precursor is supported, alumina, silica, silica-alumina, titania, magnesia, block talc, cordierite, silica-magnesia, silicon carbide, silicon nitride, zeolite, or the like can be given. The shape thereof is also not particularly limited, and a publicly known shape such as a spherical shape, a ring shape, a granular shape, an amorphous shape, or the like can be used. In the case where the carrier is in a spherical shape, the diameter is preferably in the range of 2 to 10 mm, and the supporting amount of the catalytically active component with respect to the inactive carrier is preferably in the range of 20 to 300 mass %.

[0071] The shape of the catalyst is not particularly limited and can be any shape such as a spherical shape, a cylindrical shape, a ring shape, an irregular shape, or the like. In the case where the shape of the catalyst is a spherical shape, 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, and it is sufficient to be substantially spherical. In the case of a cylindrical shape and a ring shape, likewise, it is not necessary to be a perfect circle, and it is sufficient to be substantially circular.

[0072] In the molding step and the supporting step, a molding aid for improving moldability, a supporting aid for improving a supporting state, a binder, or the like can be used. As specific examples, ethylene glycol, glycerol, propionic acid, maleic acid, benzyl alcohol, propanol, butanol, or an organic compound of a phenol type, nitric acid, ammonium nitrate, ammonium carbonate, or the like can be given.

[0073] In addition, for the purpose of improving mechanical strength, a generally known glass fiber, a ceramic fiber, a metal fiber, a mineral fiber, a carbon fiber, silica, alumina, titania, silicon carbide, silicon nitride, or the like inorganic fiber can be added to the catalyst as a reinforcing material.

[0074] The method of adding these inorganic fibers is not particularly limited, and any method can be used as long as the inorganic fibers are uniformly dispersed and contained in the catalyst. For example, the inorganic fibers can be added to a raw material mixture containing catalyst component elements, or the inorganic fibers can be added to a catalyst precursor obtained by drying and pulverizing a raw material mixture containing catalyst component elements.

[0075] In addition, for the purpose of forming moderate pores in the catalyst, a pore former can be added. The pore former is not particularly limited and can use starch, cellulose, urea, polyvinyl alcohol, melamine cyanurate, or the like.

[0076] (6) Firing Step

[0077] In the present application, the firing step refers to a step of performing a heat treatment on the molded body obtained in the molding step or the supported body obtained in the supporting step at a high temperature.

[0078] The firing furnace used in the firing step is not particularly limited and can use a generally used box-type firing furnace or a tunnel-type firing furnace, or the like. The firing temperature is 350 to 600°C, preferably 400 to 550°C, and further preferably 420 to 500°C. The firing time is 1 to 15 hours, and preferably 2 to 10 hours. The firing atmosphere is an oxidizing atmosphere, and a gas atmosphere containing molecular oxygen is preferable. As the gas containing molecular oxygen, air is preferably used.

[0079] Next, the production method of acrolein and acrylic acid according to the present application will be described. The production method of acrolein and acrylic acid according to the present application is a method of catalytically gas-phase-oxidizing propylene using the catalyst obtained by the production method according to the present application, that is, a method including a step of obtaining the catalyst by the production method according to the present application and a step of catalytically gas-phase-oxidizing propylene using the above-mentioned catalyst. In the production method of acrolein and acrylic acid according to the present application, the catalyst obtained by the production method according to the present application is preferably packed into a reaction tube in a reactor, and a raw material gas containing propylene and molecular oxygen is introduced into the above-mentioned reaction tube, whereby the catalytic gas-phase-oxidation reaction is performed.

[0080] As for the reactor for producing acrolein and acrylic acid by catalytically gas-phase-oxidizing propylene according to the present application, there is no particular limitation as long as it is a fixed bed reactor, and a commonly used fixed bed multitube reactor, a plate reactor, or the like can be used, with a fixed bed multitube reactor being preferred. The inner diameter of the reaction tube in the fixed bed multitube reactor is usually 15 to 50 mm, more preferably 20 to 40 mm, and further preferably 22 to 38 mm.

[0081] It is not necessarily required that a single catalyst be packed in each reaction tube of the fixed bed multitube reactor, and a plurality of publicly known catalysts can be packed so as to form layers (hereinafter, sometimes referred to as "reaction zones") respectively. For example, a method of packing catalysts having different support rates so that the support rate becomes higher from the raw material gas inlet side toward the outlet side, a method of diluting a part of the catalyst with a non-active carrier or the like, or a method of combining them can be employed. At this time, the number of reaction zones is appropriately determined depending on the reaction conditions and the scale of the reactor, but if the number of reaction zones is too large, problems such as the packing work of the catalyst becoming complicated arise, and therefore 2 to 6 or so is industrially preferred.

[0082] The reaction conditions according to the present application are not particularly limited, and any conditions commonly used in such reactions can be employed. For example, as the raw material gas, a mixed gas composed of propylene at preferably 1 to 15 vol%, more preferably 4 to 12 vol%; molecular oxygen at preferably 0.5 to 25 vol%, more preferably 2 to 20 vol%; water vapor at preferably 0 to 30 vol%, more preferably 0 to 25 vol%; and the remaining portion being a non-active gas such as nitrogen is used, and the contact with the catalyst is performed at a temperature in the range of 250 to 450°C, a pressure of 0.1 to 1.0 MPa, and a space velocity of 300 to 5000 Hr -1 (standard state).

[0083] The grade of propylene as the raw material gas for the reaction is not particularly limited, and polymer-grade, chemical-grade propylene, or the like can be used. In addition, a mixed gas containing propylene obtained by the oxidative dehydrogenation reaction of propane can be used, and air or oxygen, or the like can be added to the mixed gas as needed.

[0084] [Examples]

[0085] The present application is further illustrated in detail using the following examples and comparative examples. However, the technical scope of the present application is not limited to the following examples. Note that, unless otherwise specified, "%" and "parts" mean "mass %" and "mass parts", respectively. In addition, in the following examples, unless otherwise specified, operations are performed under the conditions at room temperature (20 to 25°C). In addition, the conversion rate and the yield in the examples and comparative examples are calculated by the following formulas.

[0086] Conversion rate [mol%]

[0087] = (moles of propylene reacted) / (moles of propylene supplied) x 100

[0088] Yield [mol%]

[0089] = (total moles of propionaldehyde produced and propionic acid produced) / (moles of propylene supplied) x 100.

[0090] [Experiment 1 on raw material compounds of cobalt]

[0091] [Preparation of cobalt nitrate hexahydrate]

[0092] Cobalt nitrate hexahydrate was prepared with the mass loss rate L1 shown in Table 1 by appropriately combining the above adjustment process (humidity of the storage site, storage amount (amount filled in the container), storage period) for the treatment.

[0093] [Measurement of mass loss rate]

[0094] As a sample for measuring the mass loss rate, a measurement sample was prepared by accurately weighing an amount (about 20 mg) of cobalt nitrate hexahydrate required for thermogravimetric analysis (W1: mass of cobalt nitrate hexahydrate at room temperature) in an aluminum pan. Then, after the measurement sample was set on a sample holder of a thermogravimetric analyzer (device name: 2000S, manufactured by McScience Co., Ltd.), the temperature was increased from room temperature of 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 change in the mass of the sample measured, the mass loss rate L1 of the cobalt nitrate hexahydrate and the mass loss rate L2 of the cobalt nitrate hexahydrate were calculated by the following formulas (a) and (b). In addition, the proportion R of the mass loss rate L1 of the cobalt nitrate hexahydrate was calculated by the following formula (c). Note that the mass loss rate L3 of the cobalt nitrate hexahydrate is the sum of the mass loss rate L1 of the cobalt nitrate hexahydrate and the mass loss rate L2 of the cobalt nitrate hexahydrate.

[0095] L1(mass%) = (W1-W2) / W1 x 100 (a)

[0096] L2(mass%) = (W2-W3) / W1 x 100 (b)

[0097] R = L1 / (L1+L2) = L1 / L3 (c)

[0098] wherein W1 = mass of cobalt nitrate hexahydrate at 25°C (mg)

[0099] W2 = mass of cobalt nitrate hexahydrate at 105°C (mg)

[0100] W3 = mass of cobalt nitrate hexahydrate at 300°C (mg).

[0101] [Example 1: Preparation of Catalyst (1)]

[0102] 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. At this time, the mass loss rate L1 of the cobalt nitrate hexahydrate used was 11.2 mass% by thermogravimetric analysis, the mass loss rate L3 of the cobalt nitrate hexahydrate was 66.9 mass%, and the proportion R of the mass loss rate L1 of the cobalt nitrate hexahydrate was 0.167. In addition, the mass loss rate L1 of the nickel nitrate hexahydrate from 25°C to 105°C was 14.7 mass% by thermogravimetric analysis of the nickel nitrate hexahydrate used, the mass loss rate L3 of the nickel nitrate hexahydrate from 25°C to 300°C was 41.4 mass%, and the proportion R of the mass loss rate L1 of the nickel nitrate hexahydrate from 25°C to 105°C relative to the mass loss rate L3 of the nickel nitrate hexahydrate from 25°C to 300°C was 0.355. Note that, for a nitrate other than cobalt nitrate hexahydrate, W1 = mass of the nitrate at 25°C (mg), W2 = mass of the nitrate at 105°C (mg), and W3 = mass of the nitrate at 300°C (mg) can be determined by performing the same thermogravimetric analysis, and the mass loss rate L1 of the nitrate from 25°C to 105°C, the mass loss rate L2 of the nitrate from 105°C to 300°C, and the proportion R of the mass loss rate L1 of the nitrate from 25°C to 105°C relative to the mass loss rate L3 of the nitrate from 25°C to 300°C can be calculated by each of the equations (a) to (c).

[0103] Next, an Fe and Bi aqueous solution was prepared by dissolving iron nitrate (iron nitrate (III) nine hydrate) 99 parts and bismuth (III) nitrate pentahydrate 119 parts in an aqueous nitric acid solution containing 65 mass% nitric acid 65 parts and ion exchange water 300 parts. The mass loss rate Ll of the iron nitrate from 25°C to 105°C calculated from the thermal gravimetric analysis of the iron nitrate used at this time was 28.5 mass%, the mass loss rate L3 of the iron nitrate from 25°C to 300°C was 63.5 mass%, and the ratio R of the mass loss rate Ll of the iron nitrate from 25°C to 105°C to the mass loss rate L3 of the iron nitrate from 25°C to 300°C was 0.449. In addition, the mass loss rate Ll of the bismuth (III) nitrate pentahydrate from 25°C to 105°C calculated from the thermal gravimetric 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 Ll 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. In addition, an Mo aqueous solution was prepared by adding ammonium paramolybdate tetrahydrate 400 parts to ion exchange water 1500 parts and dissolving while stirring. The Fe and Bi aqueous solution and the Mo aqueous solution prepared above were added dropwise to the Co and Ni aqueous solution and mixed, followed by mixing with titanium oxide 3 parts, and then an aqueous solution prepared by dissolving potassium nitrate 1.9 parts in ion exchange water 30 parts was added, to obtain a suspension (raw material mixture). The obtained suspension was heated and stirred until it became a cake, and then naturally cooled to obtain a block-like solid substance.

[0104] The block-like solid substance was carried into a tunnel-type dryer, dried at 170°C for 14 hours, and then pulverized to 500 μm or less to obtain a powder of a catalyst precursor. An alumina spherical carrier 300 parts having an average particle diameter of 5.0 mm was charged into a rotary granulator, followed by slowly charging the powder of the catalyst precursor together with an aqueous ammonium nitrate solution as a binding agent at 20 mass%, and the catalyst precursor was supported on the carrier. After the supported catalyst precursor was fired at 470°C for 6 hours in an air atmosphere, a catalyst (1) was obtained. The catalyst (1) had a composition of "Mo 12 Bi 1.3 Co 6.1 Ni 1.5 Fe 1.3 Ti 0.2 K 0.1 ".

[0105] In addition, the support rate of the catalyst (1) calculated from the following formula (d) was 130 mass%.

[0106] Supporting rate (mass %) = (mass of catalyst - mass of support) / (mass of support) x 100 Equation (d).

[0107] [Catalyst production example 2: preparation of catalyst (2)]

[0108] In catalyst production example 2, the mass loss rate L1 of the cobalt nitrate hexahydrate calculated by thermal gravimetric analysis was 13.0 mass%, the mass loss rate L3 of the cobalt nitrate hexahydrate was 68.8 mass%, and the proportion R of the mass loss rate L1 of the cobalt nitrate hexahydrate was 0.189.

[0109] In catalyst production example 2, in order to make the cobalt composition in the obtained catalyst the same as that of catalyst (1), the cobalt nitrate hexahydrate was set to 346 parts in consideration of the value of L1, in order to make the total amount of water in the system in the preparation of the Co and Ni aqueous solution the same, the amount of water used in the preparation of the Co and Ni aqueous solution was set to 394 parts in consideration of the amount of the cobalt nitrate hexahydrate and the value of L1 thereof, and the catalyst was prepared in the same manner as in catalyst production example 1 except for this, to obtain catalyst (2).

[0110] [Catalyst production example 3: preparation of catalyst (3)]

[0111] In catalyst production example 3, the mass loss rate L1 of the cobalt nitrate hexahydrate calculated by thermal gravimetric analysis was 14.0 mass%, the mass loss rate L3 of the cobalt nitrate hexahydrate was 69.9 mass%, and the proportion R of the mass loss rate L1 of the cobalt nitrate hexahydrate was 0.200.

[0112] In catalyst production example 3, in order to make the cobalt composition in the obtained catalyst the same as that of catalyst (1), the cobalt nitrate hexahydrate was set to 349 parts in consideration of the value of L1, in order to make the total amount of water in the system in the preparation of the Co and Ni aqueous solution the same, the amount of water used in the preparation of the Co and Ni aqueous solution was set to 391 parts in consideration of the amount of the cobalt nitrate hexahydrate and the value of L1 thereof, and the catalyst was prepared in the same manner as in catalyst production example 1 except for this, to obtain catalyst (3).

[0113] [Catalyst production example 4: preparation of catalyst (4)]

[0114] In catalyst production example 4, the mass loss rate L1 of the cobalt nitrate hexahydrate calculated by thermal gravimetric analysis was 14.2 mass%, the mass loss rate L3 of the cobalt nitrate hexahydrate was 70.1 mass%, and the proportion R of the mass loss rate L1 of the cobalt nitrate hexahydrate was 0.203.

[0115] In Catalyst Production Example 4, in order to make the cobalt composition in the obtained catalyst the same as that of Catalyst (1), taking the value of L1 into consideration, cobalt nitrate hexahydrate was set to 350 parts, in order to make the total amount of water in the system in the preparation of the Co and Ni aqueous solutions the same, taking the amount of cobalt nitrate hexahydrate and the value of L1 thereof into consideration, the amount of water used in the preparation of the Co and Ni aqueous solutions was set to 390 parts, and otherwise, the catalyst was prepared in the same manner as in Catalyst Production Example 1 to obtain Catalyst (4).

[0116] [Preparation of Catalyst (5) in Catalyst Production Example 5]

[0117] In Catalyst Production Example 5, the mass loss rate L1 of the cobalt nitrate hexahydrate used was 15.8 mass% by thermogravimetric analysis, the mass loss rate L3 of the cobalt nitrate hexahydrate was 70.9 mass%, and the proportion R of the mass loss rate L1 of the cobalt nitrate hexahydrate was 0.223.

[0118] In Catalyst Production Example 5, in order to make the cobalt composition in the obtained catalyst the same as that of Catalyst (1), taking the value of L1 into consideration, cobalt nitrate hexahydrate was set to 355 parts, in order to make the total amount of water in the system in the preparation of the Co and Ni aqueous solutions the same, taking the amount of cobalt nitrate hexahydrate and the value of L1 thereof into consideration, the amount of water used in the preparation of the Co and Ni aqueous solutions was set to 385 parts, and otherwise, the catalyst was prepared in the same manner as in Catalyst Production Example 1 to obtain Catalyst (5).

[0119] [Preparation of Catalyst (6) in Catalyst Production Example 6]

[0120] In Catalyst Production Example 6, the mass loss rate L1 of the cobalt nitrate hexahydrate used was 10.7 mass% by thermogravimetric analysis, the mass loss rate L3 of the cobalt nitrate hexahydrate was 66.2 mass%, and the proportion R of the mass loss rate L1 of the cobalt nitrate hexahydrate was 0.162.

[0121] In Catalyst Production Example 6, in order to make the cobalt composition in the obtained catalyst the same as that of Catalyst (1), taking the value of L1 into consideration, cobalt nitrate hexahydrate was set to 338 parts, in order to make the total amount of water in the system in the preparation of the Co and Ni aqueous solutions the same, taking the amount of cobalt nitrate hexahydrate and the value of L1 thereof into consideration, the amount of water used in the preparation of the Co and Ni aqueous solutions was set to 402 parts, and otherwise, the catalyst was prepared in the same manner as in Catalyst Production Example 1 to obtain Catalyst (6).

[0122] [Preparation of Catalyst (7) in Catalyst Production Example 7]

[0123] In Catalyst Production Example 7, the mass decrease rate L1 of the cobalt nitrate hexahydrate calculated by the thermal gravimetric analysis was 16.5 mass%, the mass decrease rate L3 of the cobalt nitrate hexahydrate was 72.1 mass%, and the proportion R of the mass decrease rate L1 of the cobalt nitrate hexahydrate to the mass decrease rate L3 of the cobalt nitrate hexahydrate was 0.229.

[0124] In Catalyst Production Example 7, in order to make the cobalt composition in the obtained catalyst the same, the cobalt nitrate hexahydrate was set to 358 parts in consideration of the value of L1, in order to make the total amount of moisture in the system the same in the preparation of the Co and Ni aqueous solution, the amount of water used in the preparation of the Co and Ni aqueous solution was set to 382 parts in consideration of the amount of the cobalt nitrate hexahydrate and the value of L1 thereof, and the catalyst was prepared in the same manner as in Catalyst Production Example 1 except for this, to obtain Catalyst (7).

[0125] [Experiment 2 on raw material compounds of iron, bismuth, and nickel]

[0126] Next, for the raw materials of iron, bismuth, and nickel, the same operations as for the raw material of cobalt in Experiment 1 were performed, and Catalysts (8) to (10) in which the use amounts of the raw materials of the respective elements were adjusted were produced based on the mass decrease rate L1. The raw materials of the respective elements were operated in the same manner as the cobalt nitrate hexahydrate in Experiment 1, and the respective raw materials (iron nitrate nonahydrate, bismuth (III) nitrate pentahydrate, and nickel nitrate hexahydrate) of the mass decrease rate L1 shown in Table 2 were prepared by adjusting the humidity of the storage place, the storage amount (the amount filled in the container), and the storage period in a proper combination.

[0127] [Catalyst Production Example 8: Preparation of Catalyst (8)]

[0128] In Catalyst Production Example 8, the mass decrease rate L1 of the iron nitrate nonahydrate from 25°C to 105°C calculated by the thermal gravimetric analysis of the iron nitrate nonahydrate used was 38.2 mass%, the mass decrease rate L3 of the iron nitrate nonahydrate from 25°C to 300°C was 81.0 mass%, and the proportion R of the mass decrease rate L1 of the iron nitrate nonahydrate from 25°C to 105°C to the mass decrease rate L3 of the iron nitrate nonahydrate from 25°C to 300°C was 0.472.

[0129] In Catalyst Production Example 8, in order to make the Fe composition in the obtained catalyst the same as that of Catalyst (1), the iron nitrate nonahydrate was set to 109 parts in consideration of the value of L1, in order to make the total amount of moisture in the system the same, the amount of water used in the preparation of the Fe and Bi aqueous solution was set to 291 parts in consideration of the amount of the iron nitrate nonahydrate and the value of L1 thereof, and the catalyst was prepared in the same manner as in Catalyst Production Example 1 except for this, to obtain Catalyst (8).

[0130] [Catalyst Production Example 9: Preparation of Catalyst (9)]

[0131] In Catalyst Production Example 9, the mass decrease rate Ll of the bismuth nitrate (III) pentahydrate from 25°C to 105°C calculated from the thermal gravimetric analysis of the bismuth nitrate (III) pentahydrate used was 18.6 mass%, the mass decrease rate L3 of the bismuth nitrate (III) pentahydrate from 25°C to 300°C was 59.4 mass%, and the ratio R of the mass decrease rate Ll of the bismuth nitrate (III) pentahydrate from 25°C to 105°C to the mass decrease rate L3 of the bismuth nitrate (III) pentahydrate from 25°C to 300°C was 0.313.

[0132] In Catalyst Production Example 9, in order to make the Bi composition in the obtained catalyst the same as that of Catalyst (1), the bismuth nitrate (III) pentahydrate was set to 126 parts in consideration of the value of Ll, and in order to make the total amount of water in the system the same, the amount of water used in the preparation of the aqueous Fe and Bi solution was set to 294 parts in consideration of the amount of the bismuth nitrate (III) pentahydrate and the value of Ll thereof, and the catalyst was prepared in the same manner as in Catalyst Production Example 1 except for this, to obtain Catalyst (9).

[0133] [Catalyst Production Example 10: Preparation of Catalyst (10)]

[0134] In Catalyst Production Example 10, the mass decrease rate Ll of the nickel nitrate hexahydrate from 25°C to 105°C calculated from the thermal gravimetric analysis of the nickel nitrate hexahydrate used was 19.9 mass%, the mass decrease rate L3 of the nickel nitrate hexahydrate from 25°C to 300°C was 47.6 mass%, and the ratio R of the mass decrease rate Ll of the nickel nitrate hexahydrate from 25°C to 105°C to the mass decrease rate L3 of the nickel nitrate hexahydrate from 25°C to 300°C was 0.418.

[0135] In Catalyst Production Example 10, in order to make the Ni composition in the obtained catalyst the same as that of Catalyst (1), the nickel nitrate hexahydrate was set to 86 parts in consideration of the value of Ll, and in order to make the total amount of water in the system the same, the amount of water used in the preparation of the aqueous Co and Ni solution was set to 397 parts in consideration of the amount of the nickel nitrate hexahydrate and the value of Ll thereof, and the catalyst was prepared in the same manner as in Catalyst Production Example 1 except for this, to obtain Catalyst (10).

[0136] [Reactor]

[0137] A reactor composed of a stainless steel reaction tube having 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 in the vertical direction, and the obtained each of Catalysts (1) to (10) was allowed to fall from the upper portion of the reaction tube to be filled in a manner that the layer length became 2500 mm.

[0138] [Oxidation reaction]

[0139] In Examples 1 to 5 and Comparative Examples 1 and 2, the mixed gas containing propylene 7.0 vol%, oxygen 13 vol%, water vapor 8.5 vol%, and the remainder nitrogen was introduced at a space velocity of 1600 hr-1 from the lower part of the reactor filled with each of the catalysts (1) to (7) (standard state) at a hot medium temperature of 310°C, and propylene oxidation reaction was performed. The results are shown in Table 1. In addition, in Examples 6 to 8, the catalysts (8) to (10) were filled, respectively, and propylene oxidation reaction was performed under the same conditions. The results are shown in Table 2. -1 (standard state) at a space velocity of 1600 hr-1 from the lower part of the reactor filled with each of the catalysts (1) to (7) (standard state) at a hot medium temperature of 310°C, and propylene oxidation reaction was performed. The results are shown in Table 1. In addition, in Examples 6 to 8, the catalysts (8) to (10) were filled, respectively, and propylene oxidation reaction was performed under the same conditions. The results are shown in Table 2.

[0140] [Table 1]

[0141]

[0142] [Table 2]

[0143]

[0144] According to the results of Experiment 1 (Table 1), in Examples 1 to 5 in which the catalysts (1) to (5) having the mass reduction rate L1 of 11 to 16 mass% were used, the propylene conversion was 97.0 mol% or more, and the yield of acrolein and acrylic acid was 91.5 mol% or more. On the other hand, in Comparative Examples 1 and 2 in which the catalysts (6), (7) having the mass reduction rate L1 of less than 11 mass% or more than 16 mass% were used, the propylene conversion was less than 97.0 mol%, and the yield of acrolein and acrylic acid was less than 91.5 mol%. Therefore, it was found that the catalysts (1) to (5) manufactured using cobalt nitrate hexahydrate having the mass reduction rate L1 of 11 to 16 mass% were excellent in catalytic activity and yield in the production of acrolein and acrylic acid, and by using the catalysts, acrolein and acrylic acid could be produced at a high yield.

[0145] According to the results of Experiment 2 (Table 2), it was found that the mass reduction rate L1 of the nitrate salt of the raw material other than cobalt had no effect or less effect on the propylene conversion and the yield of acrolein and acrylic acid, as compared with the mass reduction rate L1 of cobalt nitrate hexahydrate.

[0146] This application is based on Japanese Patent Application No. 2021-057249 filed on March 30, 2021, and Japanese Patent Application No. 2021-207846 filed on December 22, 2021, the contents of the entire disclosures of which are incorporated herein by reference in its entirety.

Claims

1. A method for producing a catalyst for catalytic gas-phase oxidation of propylene to produce propenal and propenoic acid, the method comprising a step of mixing a raw material mixture of a raw material compound containing molybdenum, a raw material compound of bismuth, and a raw material compound of cobalt, the method for producing the catalyst includes a step of mixing a raw material mixture of a raw material compound containing molybdenum, a raw material compound of bismuth, and a raw material compound of cobalt, the raw material compound of cobalt is cobalt nitrate hexahydrate, the cobalt nitrate hexahydrate represented by the following formula (a) has a mass loss rate L1 from 25°C to 105°C in thermogravimetric analysis of 11 to 16 mass%, L1 = (W1 - W2) / W1 x 100 (a), wherein W1 is the mass of the cobalt nitrate hexahydrate at 25°C, W2 is the mass of the cobalt nitrate hexahydrate at 105°C, wherein the unit of L1 is mass%, and the units of W1 and W2 are milligrams, the catalyst contains a composite oxide 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 iron and nickel, B is at least one element selected from alkali metals, alkaline earth metals, and thallium, C is at least one element selected from tungsten, silicon, aluminum, zirconium, and titanium, D is at least one element selected from 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, 0 < a ≤ 10, 0 < b ≤ 20, 0 < c ≤ 20, 0 ≤ d ≤ 10, 0 ≤ e ≤ 30, 0 ≤ f ≤ 4, and formula (1) does not include oxygen representing an oxidation state.

2. The method of producing a catalyst according to claim 1, wherein, In the thermogravimetric analysis of the cobalt nitrate hexahydrate, the mass loss rate L3 from 25°C to 300°C is 62 to 75 mass%.

3. The method of producing a catalyst according to claim 1, wherein, In the thermogravimetric analysis of the cobalt nitrate hexahydrate, the proportion R of the mass loss rate L1 of the cobalt nitrate hexahydrate from 25°C to 105°C with respect to the mass loss rate L3 of the cobalt nitrate hexahydrate from 25°C to 300°C is 0.147 to 0.

258.

4. The method of producing a catalyst according to any one of claims 1 to 3, wherein Before the step of mixing the raw material mixture, an inspection step is included in which TG or TG-DTA measurement of the cobalt nitrate hexahydrate is performed, and the mass loss rate L1 of the cobalt nitrate hexahydrate is confirmed.

5. The method of producing a catalyst according to claim 4, wherein, When the mass loss rate L1 of the cobalt nitrate hexahydrate is confirmed in the inspection step to be less than 11 mass% or more than 16 mass%, the step of mixing the raw material mixture is performed after a step of adjusting the mass loss rate L1 of the cobalt nitrate hexahydrate to 11 to 16 mass%.

6. The method of producing a catalyst according to claim 4, wherein, When the mass loss rate L1 of the cobalt nitrate hexahydrate is confirmed in the inspection step to be 11 to 16 mass%, the cobalt nitrate hexahydrate used as a raw material is stored without change in the mass loss rate L1 until the step of mixing the raw material mixture.

7. The method of producing a catalyst according to claim 4, wherein, When the mass loss rate L1 of the cobalt nitrate hexahydrate is confirmed in the inspection step to be less than 11 mass%, the cobalt nitrate hexahydrate is subjected to a treatment to make it hygroscopic.

8. The method of producing a catalyst according to claim 7, wherein, After the treatment to make the cobalt nitrate hexahydrate hygroscopic, the inspection process of measuring the mass decrease rate L1 of the cobalt nitrate hexahydrate using TG or TG-DTA is performed again.

9. The method of producing a catalyst according to claim 4, wherein, In a case where it is confirmed in the inspection process that the mass decrease rate L1 of the cobalt nitrate hexahydrate exceeds 16 mass%, the cobalt nitrate hexahydrate is subjected to a treatment to dry it.

10. The method of producing a catalyst according to claim 9, wherein, After the treatment to dry the cobalt nitrate hexahydrate, the inspection process of measuring the mass decrease rate L1 of the cobalt nitrate hexahydrate using TG or TG-DTA is performed again.

11. A method for producing acrolein and acrylic acid, characterized by, The catalyst obtained by the production method according to any one of claims 1 to 10 is used for catalytic gas phase oxidation of propylene.

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