JP4858266B2 - Method for producing composite oxide catalyst - Google Patents

Description

  The present invention relates to a method for producing a composite oxide catalyst for producing an unsaturated carboxylic acid such as acrylic acid by vapor-phase catalytic oxidation of an unsaturated aldehyde such as acrolein with a molecular oxygen-containing gas.

Activated molybdenum and vanadium as one of the complex oxide catalysts for producing unsaturated carboxylic acids such as acrylic acid and methacrylic acid by gas phase catalytic oxidation of unsaturated aldehydes such as acrolein and methacrolein with molecular oxygen. There is a MoV-based catalyst included as an element.
The MoV-based catalyst is manufactured by integrating a compound (supply source compound) that is a supply source of each element constituting the catalyst, followed by drying and molding as necessary, followed by firing. In the production of a MoV-based catalyst, an organic substance may be added for the purpose of improving the characteristics of the catalyst or imparting a binder function during molding.
For example, a technique is known in which an organic acid is added to an aqueous solution or aqueous dispersion of a source compound when the source compound is integrated. By coordinating with each element constituting the catalyst, the organic acid suppresses the bonding between the component elements, and finally the structure of the composite oxide catalyst obtained, the redox state, and the catalyst component on the carrier Change the dispersion state and improve the properties of the catalyst. The organic acid is added by a method using an organic acid salt of an element constituting the catalyst as a source compound (see Patent Document 1) or a method of adding an organic acid when integrating the source compound (patent) Reference 2).
In addition, a high molecular compound such as cellulose may be used as a binder for forming a catalyst, or may be used for providing a hole in the catalyst. Also, alcohols may be included in the raw material for various purposes. For example, relatively low molecular alcohols such as ethylene glycol are expected to function in the same manner as the organic acid described above, and high molecular alcohols such as polyvinyl alcohol are expected to function in the same manner as the cellulose described above. Is done.
As described above, in the production of the MoV-based catalyst, there are various advantages in adding an organic substance.

  On the other hand, as a calcination method in the production of a MoV-based catalyst, generally, a precursor compound of a catalyst obtained by mixing and drying a source compound is molded as necessary, and then about 300 ° C. to 500 ° C. The method of baking for 1 to 10 hours is known (patent document 2, patent document 3, patent document 4, patent document 5). However, in these methods, when the organic material is included in the raw material, there is a problem that the organic material is not sufficiently burned out, or firing unevenness due to combustion / heat generation of the organic material occurs.

In addition, a method of performing calcination a plurality of times in the manufacture of a MoV-based catalyst is also known. For example, the catalyst precursor compound obtained in the same manner as described above is pre-baked at 250 to 500 ° C. for about 1 to 15 hours, and then molded by adding a binder, and the molded product is formed at 250 to 500 ° C. for 1 to 50 hours. A method of firing (patent document 1) or a precursor compound of a catalyst is heat-treated at 160 to 450 ° C. for 1 to 20 hours, added with a binder and molded, and then the molded product is fired at 250 to 600 ° C. for 1 to 50 hours. Is known (Patent Document 6). In addition, it is known that the previous baking process in these methods is performed in order to prevent the catalyst from being pulverized. Further, a method is known in which a catalyst precursor obtained by mixing and drying a source compound is held at 325 ° C. for 4 hours, then heated, and held at 400 ° C. for 10 minutes (Patent Document 7). .
However, even in these methods, when the organic compound is added or the organic compound is used as a binder when integrating the source compound, the organic compound is not sufficiently burned off by the baking step, and can be obtained. There is a problem that the activity of the catalyst is insufficient.
That is, when a MoV-based catalyst is produced by firing a raw material containing an organic substance, it is difficult to sufficiently calcinate the organic substance and sufficiently form an active phase of the catalyst by the known firing methods. It is. In such a background, development of a technique for obtaining stable quality for the MoV-based catalyst is desired.

JP 2001-79408 A JP-A-2005-305421 Japanese Examined Patent Publication No. 2-55103 Japanese Patent Publication No. 6-9658 Japanese Patent Publication No. 6-38918 JP 2003-251184 A Japanese Patent Laid-Open No. 9-194213

  The present invention provides a technique for sufficiently forming an active phase of a catalyst by sufficiently firing the organic material when the organic material is used in the production of a MoV-based catalyst (hereinafter also simply referred to as “catalyst”). An object of the present invention is to obtain a stable and good quality MoV-based catalyst.

  As a result of repeated research on the calcination process in the manufacture of MoV-based catalysts, the present inventors have sufficiently formed the active phase of the catalyst by setting the number of calcination processes and the conditions of each calcination process to a specific range. And found that uneven firing is suppressed. Specifically, in the production of the MoV-based catalyst, the added organic matter is sufficiently burned down by performing the firing twice with the specified firing temperature and holding time for the raw material containing the organic matter, and the active phase of the catalyst. Has been found to be sufficiently formed and firing unevenness is suppressed.

  That is, the method for producing the MoV-based catalyst of the present invention includes a firing step of firing an organic material-containing raw material to obtain a MoV-based catalyst, and the firing step has a firing temperature of 200 to 400 ° C. and a holding time of 0.5. The first step of firing in 10 hours, and the second step of firing after the first step, firing at a firing temperature of 300 to 450 ° C. and holding time of 0.5 to 10 hours, and firing in the second step The temperature is 50 ° C. or more higher than the firing temperature in the first step.

The ratio of the holding time of the first step and the second step is preferably 1: 0.5 to 2.0.
The first step and the second step are preferably performed in an atmosphere having an oxygen concentration of greater than 0% and less than 10%.
The organic substance is preferably at least one selected from carboxylic acid, alcohol and cellulose, and preferably has a thermal decomposition temperature of 100 to 400 ° C.

Moreover, it is preferable that the MoV type catalyst manufactured by the manufacturing method of the MoV type catalyst of this invention has a composition of following formula (1).
Formula (1): (Mo) ₁₂ (V) _a (X) _b (Cu) _c (Y) _d (Sb) _e (Z) _f (Si) _g (C) _h (O) _i

In the formula, each component and variable have the following meanings. X represents at least one element selected from Nb and W. Y represents at least one element selected from Mg, Ca, Sr, Ba and Zn. Z represents at least one element selected from Fe, Co, Ni, and Bi. However, Mo, V, Nb, W, Cu, Mg, Ca, Sr, Ba, Zn, Sb, Fe, Co, N
i, Bi, Si, C and O are element symbols. a, b, c, d, e, f, g, h, and i represent the atomic ratio of each element, and 0 <a ≦ 12, 0 ≦ b ≦ 12, 0 <c ≦ 12, 0 ≦ d ≦ 8, 0 ≦ e ≦ 500, 0 ≦ f ≦ 500, 0 ≦ g ≦ 500, 0 ≦ h ≦ 500, i is a number determined by the degree of oxidation of each of the above elements excluding C.

  According to the method for producing a MoV-based catalyst of the present invention, the advantage of adding an organic substance can be obtained while suppressing uneven firing, and the active phase of the catalyst is sufficiently formed. Thereby, it is possible to stably provide a good quality MoV-based catalyst.

In the method for producing the MoV-based catalyst of the present invention, the raw material subjected to the firing step is usually obtained by a method including a step of integrating the source compound.
In the present invention, the MoV-based catalyst is a composite oxide catalyst for producing an unsaturated carboxylic acid by vapor-phase catalytic oxidation of an unsaturated aldehyde with a molecular oxygen-containing gas, and includes Mo (molybdenum) and V A catalyst containing (vanadium).
As long as the MoV-based catalyst functions as the composite oxide catalyst, it may contain elements other than Mo, V, and O. Examples thereof include Mo, V, Nb, W, Cu, Mg, Ca, Sr, Ba, Zn, Sb, Fe, Co, Ni, Bi, Si, and C.
The MoV catalyst is preferably a catalyst represented by the formula (1).

  In formula (1), each component and variable have the following meanings. X represents at least one element selected from Nb and W. Y represents at least one element selected from Mg, Ca, Sr, Ba and Zn. Z represents at least one element selected from Fe, Co, Ni, and Bi. In particular, X is preferably Nb, and Z is preferably Ni.

  a, b, c, d, e, f, g, h, and i represent the atomic ratio of each element, and 0 <a ≦ 12, 0 ≦ b ≦ 12, 0 <c ≦ 12, 0 ≦ d ≦ 8, 0 ≦ e ≦ 500, 0 ≦ f ≦ 500, 0 ≦ g ≦ 500, 0 ≦ h ≦ 500, and i are numbers determined by the degree of oxidation of each component of the formula (1) except for C. a, b, c, d, e, f, g and h are more preferably 0 <a ≦ 12, 0 <b ≦ 12, 0 <c ≦ 12, 0 ≦ d ≦ 8, 0 ≦ e ≦ 500. 0 ≦ f ≦ 500, 0 ≦ g ≦ 500, and 0 ≦ h ≦ 500. Particularly preferably, 0.1 ≦ a ≦ 6, 0.1 ≦ b ≦ 6, 0.1 ≦ c ≦ 6, 0.01 ≦ d ≦ 6, 5 ≦ e ≦ 300, 5 ≦ f ≦ 300, 5 ≦ g ≦ 300 and 5 ≦ h ≦ 300.

“Integrating the source compounds” means mixing the source compounds of the elements constituting the MoV-based catalyst in an aqueous medium system and aging treatment if necessary.
That is, the method of integrating the source compounds includes (a) a method of mixing the source compounds in a lump, (b) a method of mixing the source compounds in a lump and further aging, and (c) a supply. The method includes stepwise mixing the source compound, (d) a method in which the source compound is mixed stepwise, and a method of aging treatment is repeated, and a method in which (a) to (d) are combined.

  As described in the Chemical Dictionary (Kyoritsu Shuppan), “aging” means that “industrial raw materials or semi-finished products must be processed under specific conditions such as constant temperature for a certain period of time. To obtain, increase, or advance a predetermined reaction. In the present invention, the fixed time is in the range of 1 minute to 24 hours, and the fixed temperature is in the range of room temperature to 200 ° C.

The source compound may be any compound that can be converted to an oxide by heating in the presence of at least oxygen except at least an oxide of an element constituting a MoV-based catalyst or a silicon carbide compound.
For example, as the source compounds for Mo and V, oxides, halides, ammonium salts, ammonium halide salts, sulfates, hydroxides, and hydrogen acids of these elements can be used. Moreover, organic acid salts of these elements can also be used. In addition, the raw material obtained by integrating an organic acid salt as a source compound is included in the raw material containing an organic substance to be described later. Examples of the organic acid salt include carboxylate, ammonium carboxylate, acetylacetonate, and alkoxide.
Specific examples of Mo source compounds include ammonium paramolybdate, molybdenum trioxide, molybdic acid, and ammonium silicomolybdate.
Examples of the source compound for V include ammonium vanadate, vanadium pentoxide, vanadium oxalate, and vanadium sulfate.

  The source compound used when the MoV-based catalyst of the present invention contains elements other than Mo and V may be appropriately selected from compounds normally used as the source compound for the elements constituting the catalyst.

  As a source compound of an element other than Mo and V used for producing the MoV-based catalyst represented by the formula (1), an oxide of each element, a halide, except for a carbon source compound, Organic acid salts such as ammonium salts, ammonium halide salts, hydrogen acids, sulfates, nitrates, hydroxides, and carboxylates can be used. In addition, the raw material obtained by integrating an organic acid salt as a source compound is included in the raw material containing an organic substance to be described later.

For example, Nb source compounds include niobium hydroxide, ammonium niobium oxalate compounds, niobium ammonium, etc., and Cu source compounds include copper sulfate, cuprous chloride, etc., and Sb supply Examples of the source compound include antimony oxide such as antimony trioxide and antimony pentoxide. Examples of the source compound for Ni include basic nickel carbonate, nickel oxide, nickel nitrate, nickel hydroxide, and the like. Examples of the source compound include colloidal silica, powdered silica, and granular silica.
Further, as silicon and carbon source compounds, green silicon carbide, black silicon carbide and the like can be used, and these silicon carbides are preferably fine powders.

Moreover, in the method for producing the MoV-based catalyst of the present invention, a composite oxide containing a part of the elements constituting the catalyst can be preformed and used as a source compound. For example, when the MoV-based catalyst of the present invention contains Sb and Ni, a composite oxide represented by Sb—Ni—O is represented, and when Sb, Ni and Si are contained, Sb—Ni—Si—O is represented. Each of the composite oxides is preferably used as a source compound.
In addition, when integrating the source compound, carrier materials such as alumina, mullite, refractory oxide and the like can be mixed and integrated together with the source compound.

Preferred specific embodiments of the method for integrating the source compounds are listed below.
First, an aqueous solution or aqueous dispersion of the source compound is prepared. In this specification, these aqueous solutions or aqueous dispersions are also referred to as slurry solutions. The slurry solution can be obtained by uniformly mixing the source compound with water. What is necessary is just to determine the usage-ratio of the supply source compound in a slurry solution according to the atomic ratio of the structural element of the MoV type catalyst to manufacture.

The amount of water in the slurry solution is not particularly limited as long as it can dissolve or uniformly disperse each supply source compound, but can be appropriately determined in consideration of, for example, the drying conditions described later. The amount of water is usually 100 to 2000 parts by weight with respect to a total of 100 parts by weight of the raw material compounds. If the amount of water is less than the above predetermined amount, the compound may not be completely dissolved or may not be uniformly mixed. In addition, if the amount of water is large, the energy cost during heat treatment may increase. Although the integration of the source compound proceeds through mixing and stirring in the preparation process of the slurry solution, in order to further promote the integration, it is preferably room temperature to 200 ° C, particularly preferably 70 to 100 ° C, preferably 1 It is preferable to perform aging treatment for min to 24 hours, particularly preferably for 30 minutes to 6 hours.

In addition, in the production of the MoV-based catalyst of the present invention, it is preferable to include the drying of the slurry solution and the subsequent molding step after the step of integrating the source compound.
Drying can be performed by a normal method, and is not particularly limited as long as the slurry solution can be sufficiently dried and a powder can be obtained. For example, drum drying, freeze drying, spray drying and the like are preferable methods. Spray drying is a method that can be preferably applied to the present invention because it can be dried from a slurry solution into a homogeneous powder state in a short time.

  The drying temperature is usually 90 to 200 ° C, preferably 130 to 170 ° C, although it varies depending on the concentration of the source compound in the slurry solution. The particle size of the powder obtained by such drying is preferably 10 to 200 μm. For this reason, the powder can be pulverized after drying.

The molding is performed by a usual method such as (A) tableting molding, (B) extrusion molding, or (C) support molding. The shape of the molded body is preferably an appropriate shape such as a spherical shape, a cylindrical shape, or a ring shape.
When molding, a binder (molding aid) can be used. For example, when tableting, a binder such as silica, graphite or crystalline cellulose is preferably used in an amount of about 0.01 to 50 parts by weight with respect to 100 parts by weight of the powder. In the case of extrusion molding, it is preferable to use about 0.01 to 50 parts by weight of a binder such as silica gel, diatomaceous earth, or alumina powder with respect to 100 parts by weight of the powder. If necessary, inorganic fibers such as ceramic fibers and whiskers can be used as a material for improving the mechanical strength of the catalyst particles. However, fibers that react with catalyst components such as potassium titanate whiskers and basic magnesium carbonate whiskers are not preferred. For improving the strength, ceramic fiber is particularly preferable. The amount of these fibers used is preferably 1 to 30 parts by weight with respect to 100 parts by weight of the powder. The binder and the mechanical improver are usually used in advance mixed with powder.

In the method for producing a MoV-based catalyst of the present invention, the raw material includes an organic substance. In the present invention, “organic matter” means a carbon compound.
The organic substance used for the production of the MoV-based catalyst of the present invention only needs to be capable of being thermally decomposed in the firing step described later. For example, organic acids, polymer compounds having a binder function, alcohols, and the like can be given. Moreover, the thermal decomposition temperature of organic substance becomes like this. Preferably it is 100-400 degreeC, More preferably, it is 150-350 degreeC.
The addition amount of the organic substance can be appropriately selected according to the kind of the organic substance and the purpose of the addition, but usually it is preferably 0.01 to 10% by mass with respect to the dried raw material before firing, More preferably, it is 0.1 to 5 weight%.

Preferred examples of the organic acid include carboxylic acids, and among them, organic acids that are readily soluble in water, such as acetic acid, citric acid, oxalic acid, and malic acid, are preferable.
Among these organic acids, those that can be converted to elemental oxides by heating in the presence of oxygen when in the form of organic acid salts of the elements that constitute the catalyst are organic acid salts of the elements that constitute the catalyst. Can be used as a source compound. The organic acid can also be used in a form added separately from the source compound. In this case, the organic acid may be added when the source compound is integrated. That is, it can be added after preparing the slurry solution or in the middle of preparation, but it is preferable to add it at a stage after dissolving Mo and V. For example, an organic acid that is readily soluble in water, such as citric acid, oxalic acid, malic acid, etc., is preferably added when the source compound is integrated. In this case, the amount of the organic acid added is preferably 0.001 to 1 mol, and more preferably 0.01 to 0.5 mol, relative to 1 mol of Mo.

Examples of the polymer compound having a binder function include cellulose and polyvinyl alcohol. These polymer compounds are preferably added when a powder obtained by mixing a source compound and drying, if necessary, is formed. In this case, the amount of the polymer compound added is preferably 0.01 to 10% by mass with respect to the dried raw material before firing.
As the alcohol, any of a low molecular alcohol and a high molecular alcohol can be used. Examples of the low molecular alcohol include ethanol, ethylene glycol and the like, which function in the same manner as the organic acid described above. Examples of the polymer alcohol include polyvinyl alcohol and can be used as a binder during molding. The low molecular alcohol is preferably added when the source compound is integrated, and the addition amount is preferably 0.001 to 1 mol, and more preferably 0.01 to 0.5 mol, relative to 1 mol of Mo. The polymer alcohol is preferably added at the time of molding, and the addition amount is preferably 0.01 to 10% by mass with respect to the dried raw material before firing.

  In the production of the MoV-based catalyst of the present invention, it is particularly preferable to use at least one selected from citric acid, ethylene glycol and cellulose as the organic substance. This is because the method for producing the MoV-based catalyst of the present invention is particularly effective when these organic substances are used.

The method for producing a MoV-based catalyst of the present invention includes a calcination step of obtaining a MoV-based catalyst by calcination of a raw material containing an organic substance obtained as described above, and the calcination step includes a first step and a second step. It is characterized by that. In addition, the calcination process here refers to the calcination process corresponding to the final process of obtaining the MoV-based catalyst, and includes a calcination process performed on a raw material that does not contain organic substances and a calcination process performed before adding organic substances to the raw materials. Absent.
The first step is characterized in that the firing temperature is 200 to 400 ° C. and the holding time is 0.5 to 10 hours. When the calcination temperature is less than 200 ° C., the organic matter is not burned out sufficiently, and the organic matter burns and generates heat in the second step later, and the temperature rises to a set temperature or more, and the active phase of the catalyst may be decomposed. . On the other hand, when the calcination temperature is 400 ° C. or higher, the active phase of the catalyst may be decomposed. Moreover, when holding time is less than 0.5 hour, there exists a possibility that organic substance may not fully burn out. On the other hand, when the holding time exceeds 10 hours, it is uneconomical.

The second step is performed after the first step, and the firing temperature is 300 to 450 ° C. and the holding time is 0.5 to 10 hours. When the calcination temperature is less than 300 ° C., the active phase of the catalyst may not be sufficiently formed. On the other hand, when the calcination temperature exceeds 450 ° C., the active phase of the catalyst may be decomposed. Moreover, when holding time is less than 0.5 hour, there exists a possibility that organic substance may not fully burn out. On the other hand, if the holding time exceeds 10 hours, it is uneconomical and the active phase may be decomposed.
Furthermore, the second step is characterized in that the firing temperature is 50 ° C. or more higher than the firing temperature of the first step. A sufficient active phase can be formed by setting the firing temperature in the second step to be higher than the firing temperature in the first step. When the calcination temperature of the second step is too low and the difference between the calcination temperatures of the first step and the second step is less than 50 ° C., the calcination is insufficient and the active phase of the catalyst may not be sufficiently formed. On the other hand, if the firing temperature in the first step is too high and the difference in firing temperature between the first step and the second step is less than 50 ° C., the temperature is too high in the initial stage of the firing step, and the catalyst raw material contains organic matter. Since it is exposed to high temperatures while contained, organic matter may burn and generate heat, which may cause uneven firing. In the second step, the firing temperature is preferably 60 ° C. or more higher than the firing temperature in the first step.

  Furthermore, the ratio between the holding time of the first step and the holding time of the second step is 1: 0.5 to 2.0, preferably 1: 0.75 to 1.5.

  The second step can be performed by increasing the firing temperature after the end of the first step. The temperature raising time is usually about 0.5 to 10 hours, preferably about 1 to 5 hours. If the temperature raising time is too short, temperature control becomes difficult, while if it is too long, it is uneconomical.

The first step and the second step can be performed in the presence of an inert gas or molecular oxygen, but are preferably performed in the presence of molecular oxygen. These steps are preferably performed in an atmosphere having an oxygen concentration greater than 0% and less than 10%, and more preferably in an atmosphere having an oxygen concentration of 0.1% or more and less than 10%. If the oxygen concentration is too high, the catalyst may be oxidized more than necessary, while if the oxygen concentration is too low, the formed active phase may be reduced. That is, in any case, the activity of the obtained catalyst is lowered.
In the calcination step in the production of the MoV-based catalyst of the present invention, one or more other steps may be included between the first step and the second step.

The MoV catalyst produced by the method for producing a MoV catalyst of the present invention described above is obtained by subjecting an unsaturated aldehyde to gas phase catalytic oxidation using molecular oxygen or a molecular oxygen-containing gas, and corresponding unsaturated carboxylic acids. As a catalyst for producing an acid, preferably, acrolein can be oxidized and used as a catalyst for producing acrylic acid. That is, when the step of producing acrylic acid by vapor phase catalytic oxidation of olefin, for example propylene, is carried out in two steps, the production of unsaturated aldehyde by oxidation of olefin and the production of unsaturated carboxylic acid by the oxidation The MoV-based catalyst of the present invention is useful as a catalyst used in the subsequent reaction.
Existing methods can be used to gas-phase catalytically oxidize unsaturated aldehydes using molecular oxygen or molecular oxygen-containing gases to produce the corresponding unsaturated carboxylic acids. For example, a fixed bed tube reactor can be used as the reactor. In this case, the reaction can be carried out using a single flow method or a recycling method through a reactor, and can be carried out under conditions generally used for this type of reaction.

For example, a mixed gas composed of 1 to 15% by volume of acrolein, 0.5 to 25% by volume of molecular oxygen, 0 to 40% by volume of water vapor, 20 to 80% by volume of inert gas such as nitrogen and carbon dioxide, etc. Preferably, by introducing the MoV-based catalyst layer filled in each reaction zone of each reaction tube of 15 to 50 mm at 250 to 450 ° C. under a pressure of 0.1 to ¹ MPa at a space velocity (SV) of 300 to 5000 hr ^−1. Acrylic acid can be produced. In the present invention, it is possible to operate under high load reaction conditions, for example, higher raw material gas degree or high space velocity conditions in order to increase productivity. Thus, acrylic acid can be produced with high selectivity and high yield by the MoV-based catalyst produced in the present invention.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples. In addition, this invention is not limited to a following example, unless the meaning is exceeded.
The acrolein conversion rate, acrylic acid selectivity, and acrylic acid yield are defined as in the following formulas (2) to (4).
(2) Acrolein conversion rate (mol%) = 100 × (number of moles of reacted acrolein) / (number of moles of supplied acrolein)
(3) Acrylic acid selectivity (mol%) = 100 × (number of moles of acrylic acid produced) / (number of moles of converted acrolein)
(4) Acrylic acid yield (mol%) = 100 × (number of moles of acrylic acid produced) / (number of moles of acrolein supplied)

[Examples 1 and 2 and Comparative Examples 1 to 3]
A composite metal oxide in which the empirical formula of the constituent components excluding oxygen is Mo ₁₂ V _2.4 Nb ₁ Cu ₂ Sb ₃₄ Ni ₁₅ Si ₂₇ was produced as follows.
221 g of basic nickel carbonate was dispersed in 400 ml of pure water, and 156 g of silica (manufactured by Shionogi & Co., Ltd .: Carplex # 67) and 474 g of antimony trioxide were added and sufficiently stirred.
The slurry was heated to concentrate and dried. The obtained dried solid was calcined at 800 ° C. for 3 hours in a muffle furnace, and the produced solid was pulverized to obtain a powder passing through a 60 mesh sieve. (Sb—Ni—Si—O powder).
On the other hand, 842 ml of pure water was heated to 80 ° C. and dissolved while sequentially stirring 201 g of ammonium paramolybdate, 26.7 g of ammonium metavanadate, and 12.0 g of citric acid. To this was added an aqueous copper sulfate solution in which 47.3 g of copper sulfate was dissolved in 70 ml of pure water, and 18.7 g of niobium hydroxide was further added and stirred to obtain a slurry solution.
The Sb—Ni—Si—O powder was gradually added to this slurry while stirring and mixed thoroughly. The slurry liquid was heated to 90 ° C. and dried. This was mixed with 1.5% by weight of graphite and molded with a small tableting machine.
The obtained molded body was filled in 500 ml in a reaction tube, a mixed gas having each composition shown in Table 1 was circulated at a flow rate of 100 liters per hour, and the molded body was fired under the firing conditions shown in Table 1. The MoV type catalysts of Comparative Examples 1 to 3 were produced.
In addition, the temperature rising process from room temperature to the 1st process and the temperature rising process from the first process to the start of the second process all took 1 hour.

In order to evaluate the obtained MoV-based catalyst, 0.3 g obtained by pulverizing these catalysts to 20-28 mesh and sizing was charged into a U-shaped reaction tube having an inner diameter of 4 mm, and the reaction tube was heated. The composition gas described below was introduced into the nighter bath, and the reaction was performed with SV (space velocity; flow rate of raw material gas per unit time / apparent volume of the filled catalyst) of 14900 / hr.
Incidentally, the night bath refers to a salt bath in which a reaction tube is put into a heat medium made of an alkali metal nitrate and reacts. This heat medium melts at 200 ° C. or higher, and can be used up to 400 ° C. This reaction bath is suitable for oxidation reactions with a large exotherm.
The composition of the raw material gas was acrolein 5 vol% oxygen 8 vol% steam 15 vol% nitrogen gas 72 vol%. The results of the reaction are shown in Table 2. Thus, in the catalyst containing organic matter, the MoV-based catalysts of Examples 1 and 2 that were subjected to two-stage calcination were compared with the MoV-based catalysts of Comparative Examples 1 to 3, and acrolein conversion, acrylic acid selectivity, and acrylic. Excellent acid yield and efficient gas phase catalytic oxidation of acrolein at low temperature.

In Examples 1 and 2, the maximum temperature in the catalyst layer at the time of calcination is about 384 to 386 ° C., and the catalyst layer temperature is moderately low, so that high catalyst performance is obtained. In Comparative Examples 1 and 2, It is considered that the maximum temperature in the catalyst layer at the time of calcination is as high as about 407 to 408 ° C., the active phase is decomposed, and the catalyst performance is deteriorated. On the other hand, in Comparative Example 3, the maximum temperature in the catalyst layer at the time of calcination is about 383 ° C., and the catalyst layer temperature is low, but the calcination time is short, so the active phase is not sufficiently formed, and the catalyst performance becomes insufficient. It is thought.
Thus, it can be seen that by adopting the firing conditions of the present invention, firing unevenness can be suppressed without causing excessive or insufficient firing, and thus a catalyst with high performance can be obtained.

Example 3 Comparative Example 4
The same operation as in Example 1 was performed up to the pre-firing stage, except that 12 g of ethylene glycol was used as the organic substance instead of citric acid. 500 ml of the obtained compact was filled in a reaction tube, and a mixed gas having each composition shown in Table 3 was circulated at a flow rate of 100 liters per hour, and the compact was fired under the firing conditions shown in Table 3 to obtain a catalyst.
The reactivity of the obtained catalyst was evaluated under exactly the same conditions as in Example 1. The reaction results are shown in Table 4. Thus, Example 3 which carried out the two-step calcination in the catalyst containing organic matter was superior to Comparative Example 4 in acrolein conversion, acrylic acid selectivity and acrylic acid yield, and acrolein gas phase at low temperature. The catalytic oxidation reaction could be performed efficiently.

Example 4 Comparative Example 5
The same operation as in Example 1 was performed up to the pre-firing stage except that 12 g of cellulose (Avicel PH-M6 manufactured by Asahi Kasei) was used as the organic substance instead of citric acid. 500 ml of the obtained compact was filled in a reaction tube, and a mixed gas having each composition shown in Table 3 was circulated at a flow rate of 100 liters per hour, and the compact was fired under the firing conditions shown in Table 3 to obtain a catalyst.
The reactivity of the obtained catalyst was evaluated under exactly the same conditions as in Example 1. The reaction results are shown in Table 4. Thus, in the manufacturing method of the MoV-type catalyst including the step of adding the organic matter, Example 4 in which the two-step calcination was performed has an acrolein conversion rate, acrylic acid selectivity and acrylic acid yield as compared with Comparative Example 5. It was excellent and was able to efficiently perform the gas phase catalytic oxidation of acrolein at low temperatures.

In Examples 3 and 4, the maximum temperature in the catalyst layer at the time of calcination was about 383 to 385 ° C., and high catalyst performance was obtained because the catalyst layer temperature was moderately suppressed. In Comparative Examples 4 and 5, It is considered that the maximum temperature in the catalyst layer at the time of firing becomes too high at 390 to 412 ° C., the active phase is decomposed, and the catalyst performance is deteriorated.
Thus, it can be seen that by adopting the firing conditions of the present invention, firing unevenness can be suppressed without causing excessive or insufficient firing, and thus a catalyst with high performance can be obtained.

  From the above results, in the method for producing a MoV-based catalyst including a firing step of firing a raw material containing an organic substance to obtain a MoV-based catalyst, by providing two-stage firing satisfying a specific firing temperature and holding time, uneven firing is achieved. And a highly active MoV-based catalyst capable of efficiently carrying out the gas-phase catalytic oxidation reaction of acrolein can be produced, so that the conversion of acrolein per catalyst unit is improved and the acrylic acid selectivity of the catalyst is also improved. I understand.

Claims (6)

A method for producing a MoV-based catalyst comprising a firing step of firing a raw material containing organic matter to obtain a MoV-based catalyst,
The firing step is performed after the first step in which the firing temperature is 200 to 320 ° C. and the holding time is 0.5 to 10 hours, and after the first step, and the firing temperature is 300 to 380 ° C. and the holding time is 0. Including a second step of firing in 5 to 10 hours,
The firing temperature in the second step is 50 ° C. or higher than the firing temperature in the first step,
A method for producing a MoV-based catalyst, wherein the composition of the MoV-based catalyst is represented by the following formula (1), and used for producing acrylic acid by vapor-phase catalytic oxidation of acrolein with molecular oxygen.

Formula (1): (Mo) ₁₂ (V) _a (X) _b (Cu) _c (Y) _d (Sb) _e (Z) _f (Si) _g (C
) _H (O) _i
(In the formula, each component and variable have the following meanings. X represents at least one element selected from Nb and W. Y represents at least one element selected from Mg, Ca, Sr, Ba and Zn. Z represents at least one element selected from Fe, Co, Ni, Bi, provided that Mo, V, Nb, W, Cu, Mg, Ca, Sr, Ba, Zn, Sb, Fe, Co , Ni, Bi, Si, C and O are element symbols, a, b, c, d, e, f, g, h and i indicate atomic ratios of the respective elements, and 0 <a ≦ 12, 0 ≦ b ≦ 12, 0 <c ≦ 12, 0 ≦ d ≦ 8, 0 ≦ e ≦ 500, 0 ≦ f ≦ 500, 0 ≦ g ≦ 500, 0 ≦ h ≦ 500, i represents the above-mentioned elements other than C (The number depends on the degree of oxidation)   The method for producing a MoV-based catalyst according to claim 1, wherein the ratio of the holding time of the first step to the second step is 1: 0.5 to 2.0.   The method for producing a MoV-based catalyst according to claim 1 or 2, wherein the first step and the second step are performed in an atmosphere having an oxygen concentration of greater than 0% and less than 10%.   The method for producing a MoV-based catalyst according to any one of claims 1 to 3, wherein the organic substance is at least one selected from carboxylic acid, alcohol, and cellulose.   The method for producing a MoV-based catalyst according to any one of claims 1 to 4, wherein the organic material has a thermal decomposition temperature of 100 to 400 ° C. A process for producing acrylic acid, characterized in that acrolein is subjected to gas phase catalytic oxidation with molecular oxygen using the catalyst produced by the process according to any one of claims 1 to 5 .