WO2018016155A1 - Process for producing metal oxide catalyst - Google Patents

Abstract

The problem to be solved by the present invention is to produce, with satisfactory reproducibility, a metal oxide catalyst having excellent catalyst performance. The process for producing a metal oxide catalyst according to the present invention includes performing burning in two stages, a substance obtained in the first-stage burning satisfying analysis value A and/or analysis value B. Empirical formula: MoV_iTe_jA_kO_y Analysis value A: The value of mass change defined by equation 1 is 1.2-4.0%. Mass change (%) = {[(mass before heating)-(mass after heating)]/(mass before heating)}×100 (equation 1) Analysis value B: The nitrogen content, as determined by elemental analysis for carbon, hydrogen, and nitrogen by a combustion method, is 0.8-1.5 mass%.

Description

Method for producing metal oxide catalyst

The present invention relates to a method for producing a metal oxide catalyst suitably used for the production of acrylic acid by vapor phase catalytic oxidation of propane and the production of acrylonitrile by ammoxidation of propane.

Acrylic acid is produced by a two-step oxidation reaction in which acrolein is produced by contact reaction of propylene and oxygen in the presence of a catalyst, and the resulting acrolein is further contacted with oxygen.
On the other hand, for the purpose of solving the problems such as the price difference between propane and propylene and the complexity of the process associated with the two-stage oxidation, a method for producing acrylic acid in one stage using propane as a starting material has been studied. Many proposals have been made regarding the catalyst used in this case. Typical examples thereof include catalysts composed of complex metal oxides such as [V, P, Te], [Mo, Te, V, Nb], and [Mo, Sb, V, Nb].

Furthermore, many inventions related to the improvement of the above metal oxide catalyst have been filed. For example, in a method for producing a metal oxide catalyst by a slurry method using metal tellurium as a raw material (Patent Document 1), in a hydrothermal synthesis method, A method for producing a metal oxide catalyst to be subjected to sonication (Patent Document 2) has been proposed.
The metal oxide mixture obtained by the slurry method or hydrothermal synthesis method is converted into a crystal structure having catalytic performance through drying and calcination. The calcination is generally divided into two or more steps. For example, the first stage is treated for 2 to 20 hours in the temperature range of 250 ° C. to 380 ° C. in the presence of oxygen, and the second stage is 500 in the absence of oxygen. Examples thereof include a method in which the treatment is carried out at a temperature range of from 0 to 660 ° C. for 0.5 to 6 hours.
Further, regarding a firing method, a method has been proposed in which an index called a reduction rate is introduced into the second-stage firing process to adjust the firing process in the presence of the first-stage oxygen (Patent Document 3).

Japanese Patent Laid-Open No. 2004-313956 JP 2007-046668 A JP 2003-170044 A

However, in order to produce a metal oxide catalyst having excellent performance with good reproducibility, it is necessary to perform stable production while suppressing variations in the first, second and subsequent firings in the firing step. Although it is important, there is no simple means for grasping the firing state in the middle, and the method of monitoring the firing state in real time as in Patent Document 3 requires work for one hour or more, and the production efficiency is high. There is a problem of being bad.
The problem to be solved by the present invention is to obtain an excellent catalyst by grasping the firing conditions for suppressing variation in catalyst performance by a simple method in the firing step of the metal oxide catalyst represented by a specific composition formula. An object is to produce a metal oxide catalyst having performance with good reproducibility.

In order to solve the above-mentioned problems, the present inventors have intensively studied. As a result, in a method for producing a metal oxide catalyst having a specific composition formula, the material obtained by performing the firing in two stages and the first stage firing. Is included in the range of specific analysis values, it has been found that a metal oxide catalyst in which variation in catalyst performance is suppressed can be obtained, and the present invention has been completed.

That is, the first invention of the present invention is a step of reducing a Te ⁴⁺ compound or a Te ⁶⁺ compound in the presence of a reducing agent and water or an organic solvent to obtain a reduced product containing metal tellurium, unreacted from the reduced product. A step of removing a reducing agent, a step of reacting a reduced product containing metal tellurium from which the unreacted reducing agent has been removed in the presence of Mo, V, A element and water to obtain a reaction product, and Including a step of drying and calcining the reaction product to obtain a metal oxide catalyst represented by the following compositional formula, the calcination is performed in two stages, and substances obtained by the first-stage calcination include the following analytical value A and the following analytical value This is a method for producing a metal oxide catalyst included in at least one analytical value of B.
Composition formula: MoV _i Te _j A _k O _y
In the formula, A is at least one element selected from the group consisting of Nb, Ta, W, Ti, Zr, Re, Fe, Ni, Co, Sn, Tl, Cu, rare earth elements and alkali metal elements, i and j are each 0.01 to 1.5, and j / i = 0.3 to 1.0, k is 0.001 to 3.0, and y is an oxidation state of another element. Is a number determined by
Analytical value A: The mass change rate defined by the following formula 1 is 1.2 to 4.0%.
Mass change rate (%) = [(mass before heating−mass after heating) / mass before heating] × 100 (formula 1)
Analysis value B: The nitrogen content in the elemental analysis of carbon, hydrogen and nitrogen by the combustion method is 0.8 to 1.5 mass%.

In the second invention of the present invention, the step of obtaining the reactant comprises reacting a reduced product containing metal tellurium from which the unreacted reducing agent has been removed in the presence of Mo, V and water, It is a manufacturing method of the metal oxide catalyst as described in 1st invention which is the process of mixing and reacting with the compound to contain, and obtaining a reaction material.

The third invention of the present invention is the method for producing a metal oxide catalyst according to the first invention or the second invention, wherein the substance obtained by the first-stage calcination is included in the following analysis value C.
Analytical value C: The number of moles of oxygen consumed per 1 g of the sample obtained by subjecting the solution in which the sample is dispersed in the sulfuric acid aqueous solution to oxidation-reduction titration with heating using an oxidizing agent is 3.4 to 5.5 mmol. .

The fourth invention of the present invention is the metal oxide catalyst according to any one of the first to third inventions, wherein the second stage calcination is performed in the temperature range of 500 ° C. to 660 ° C. in the absence of oxygen. It is a manufacturing method.

The fifth invention of the present invention is a method for producing acrylic acid in which propane is oxidized by a gas phase catalytic reaction using the metal oxide catalyst obtained by any one of the first to fourth inventions.

According to the method for producing a metal oxide catalyst in the present invention, the firing state of the first stage can be grasped in a short time by an inspection method of thermal mass spectrometry or elemental analysis, so that there is little variation in catalyst activity. A metal oxide catalyst can be produced.

It is a graph which shows the relationship between the heating time and mass change rate in the 1st stage baking. It is a graph which shows the relationship between the heating time in 1st step | paragraph baking, and nitrogen content. It is a graph which shows the relationship between the heating time and oxidation-reduction titration in 1st-stage baking. It is a graph which shows the difference in the catalyst performance by the 1st-stage baking conditions.

Hereinafter, the present invention will be described in detail.
The metal oxide catalyst in the present invention is a metal oxide represented by the following composition formula.
Composition formula: MoV _i Te _j A _k O _y
(In the formula, A is at least one element selected from the group consisting of Nb, Ta, W, Ti, Zr, Re, Fe, Ni, Co, Sn, Tl, Cu, rare earth elements and alkali metal elements. , I and j are each 0.01 to 1.5 and j / i = 0.3 to 1.0, k is 0.001 to 3.0, and y is the oxidation of other elements (The number is determined by the state.)

The metal oxide is a reduced product containing metal tellurium by reducing a Te ⁴⁺ compound or a Te ⁶⁺ compound (a compound in which the tellurium valence is 4 or 6) with a reducing agent in the presence of water or an organic solvent. Then, the unreacted reducing agent is removed from the reduced product, and then the reduced product containing metal tellurium from which the unreacted reducing agent has been removed is reacted in the presence of Mo, V, A element and water. Then, it is dried and fired to produce.
Furthermore, it is necessary that the calcination is performed in two stages and a substance obtained by the first calcination is included in at least one analysis value of the analysis value A and the analysis value B.

Hereinafter, a specific manufacturing method will be described in steps (1) to (5). In addition, regarding the manufacturing method, methods such as heat treatment, coprecipitation, drying and calcination, and crystal formation using hydrothermal synthesis, which are known techniques in the catalyst technical field, can be used without limitation.

Process (1)
The method for producing a metal oxide catalyst of the present invention is a step of reducing a Te ⁴⁺ compound or a Te ⁶⁺ compound in the presence of a reducing agent and water or an organic solvent to obtain a reduced product containing metal tellurium (step (1)). )including.
In this step, a Te ⁴⁺ compound or a Te ⁶⁺ compound is reduced in the presence of a reducing agent and water or an organic solvent to obtain a reduced product containing metal tellurium as a raw material component of the catalyst.
Te ⁴⁺ compound and Te ⁶⁺ compound used for the raw material can be used without any particular limitation. Specifically, tellurium dioxide, tellurium trioxide, tellurium tetrachloride, orthotelluric acid, metatelluric acid, polymetatelluric acid, ammonium tellurate, Examples include alkali metal tellurates, zinc tellurates, calcium tellurates, silver tellurates, thallium tellurates, copper tellurates and magnesium tellurates, among which tellurium dioxide or ortho telluric acids are preferred.

The reducing agent is a reducing substance (atom, molecule, or ion having a property of easily giving electrons to other molecules) having a redox potential of 0.53 V or less (the potential of tellurium dioxide is around 0.53 V) with respect to the standard electrode. Hydrazine, hydrazinium salts, hydroxylamine, and the like are preferable.
Specific examples include hydrazine acetate, hydrazine dihydrobromide, hydrazine dioxide, hydrazine monohydrochloride, hydrazine monohydrate, hydrazine sulfate, hydroxylamine, hydroxylammonium chloride, and hydroxylammonium sulfate.

The amount of reducing agent used varies depending on the type of reducing agent and reaction conditions. For example, when hydrazine is used, the molar ratio of hydrazine to tellurium is preferably 0.5 to 4.0, and 1.0 to 3.0. More preferred. If the amount of hydrazine used is 0.5 or more, the remaining amount of tellurium dioxide is small, and if the amount used is 4.0 or less, the advantage of increasing the amount used is sufficiently obtained, which is extra for the removal of unreacted hydrazine. Reduces the amount of labor and cleaning liquid that is unnecessary or required. The same applies to a reducing agent other than hydrazine.

The reduction reaction is carried out in a liquid such as water or an organic solvent. As the organic solvent, alcohols, hydrocarbons and the like are preferable. The presence of the liquid disperses the tellurium compound and facilitates the reduction reaction, so that the metal tellurium particles obtained are uniform.

The reduction conditions for the tellurium compound can be appropriately selected in consideration of the solubility of the tellurium compound used in water or an organic solvent and the reactivity of the reducing agent. For example, when water-soluble telluric acid is used as a raw material and hydrazine is used as a reducing agent, the reduction reaction proceeds only by adding hydrazine to an aqueous solution of telluric acid, and metal tellurium particles are formed in water.
When tellurium dioxide, which is a tellurium compound having poor solubility in an organic solvent, is used as a raw material and hydrazine is used as a reducing agent, the reduction reaction proceeds slowly. In this case, it is necessary to promote the reaction by stirring and heating over time. Specifically, the reaction is preferably performed at a temperature of 40 ° C. to 100 ° C. and a stirring speed of 100 to 500 times / minute for 1 to 20 hours.

Further, as a method for promoting the reduction reaction, there is a method of wet pulverization in the presence of a tellurium compound, a reducing agent, water or an organic solvent instead of heating and stirring. By performing wet pulverization, the reduction reaction and pulverization proceed simultaneously, and metal tellurium particles are obtained, and as a result, the obtained catalyst performance is favorably affected.
The organic solvent used for pulverization is not particularly limited, but is preferably an organic solvent that is liquid at room temperature and can be easily removed in a subsequent process. Specifically, alcohols such as methanol, ethanol, and propanol, hexane, Hydrocarbons such as cyclohexane and toluene are preferred. By coexisting water or an organic solvent at the time of pulverization, an increase in surface energy accompanying pulverization is mitigated, and pulverization efficiency is increased.

The mixing ratio of the tellurium compound and water or organic solvent during pulverization is preferably 10 to 1,000 parts by mass of water or organic solvent, more preferably 30 to 300 parts by mass per 100 parts by mass of the tellurium compound. When the water or organic solvent is 10 parts by mass or more, the pulverized product is less likely to adhere to the pulverization container and is easily pulverized. When the water or organic solvent is 1,000 parts by mass or less, the water or the organic solvent is pulverized. Suppresses impact absorption and excels in grinding efficiency.

The pulverizer is preferably of a type that pulverizes by driving the container itself containing the material to be crushed. Specific examples include a ball mill, a vibration mill, and a planetary ball mill. The grinding time is preferably 0.5 to 24 hours.

When the powder obtained by drying the reduction product containing metal tellurium obtained by the above reduction reaction is analyzed by powder X-ray diffraction, no crystal phase of tellurium dioxide is observed, and it belongs to the crystal phase of pure hexagonal metal tellurium. Is done.

In addition, when the dried powder of the reduced product is observed with an electron microscope, the appearance of primary particles is observed to be spherical or needle-like depending on the difference in the reduction method. narrow. In addition, some observation samples show aggregation of primary particles, but this is a phenomenon that occurs when the sample is dried, and does not affect the production of the catalyst and the performance of the obtained catalyst.

The size of the primary particles of metal tellurium obtained by the reduction reaction is preferably 4.0 μm or less, more preferably 2.0 μm or less in at least one direction. There is no particular lower limit on the size of the primary particles, but 10 nm or more is preferable from the viewpoint of ease of operation. When the size of the primary particles is 4.0 μm or less, the dispersibility of the metal tellurium particles in water or an organic solvent is excellent.

Step (2)
The manufacturing method of the metal oxide catalyst of this invention includes the process (process (2)) which removes an unreacted reducing agent from the said reduced material.
In step (2), unreacted reducing agent remaining in the reduced product containing metal tellurium obtained in step (1) is removed, and when an organic solvent is used as the medium for the reduction reaction, the solvent is added to water. It is preferable that the step is a step of obtaining an aqueous dispersion of a reduced product by replacing with. After removing the unreacted reducing agent and the organic solvent, or by removing the reducing agent and the organic solvent from the reductant dispersion under reduced pressure, or separating and removing the reducing agent and the organic solvent by centrifugation or filtration, A method of redispersing the reduced product in water can be exemplified.

By the above operation, an aqueous dispersion of a reduced product containing metal tellurium from which the unreacted reducing agent and organic solvent have been removed is obtained. The amount of water required for replacement is preferably 1.0 to 8.0 times, more preferably 2.0 to 4.0 times in volume ratio with respect to the reduced product dispersion.
When the amount of water is 1.0 times or more, the unreacted reducing agent hardly remains, and the reducing agent remaining in the next step can be prevented from causing a reducing action.

Process (3)
The method for producing a metal oxide catalyst of the present invention comprises a step of obtaining a reactant by reacting a reduced product containing metal tellurium from which the unreacted reducing agent has been removed in the presence of Mo, V, A element and water (step). (3) and step (4)).
Step (3) is a step of mixing an aqueous dispersion of a reduced product containing metal tellurium obtained in Step (2) above, a Mo ⁶⁺ compound and a V ⁵⁺ compound, and reacting them at a temperature of 40 ° C. or higher for 1 hour or longer. It is. The aqueous dispersion may be further diluted by adding water in order to improve operability.
The reaction temperature is preferably 40 ° C. to 100 ° C., and the reaction time is preferably 1 to 10 hours, more preferably 2 to 5 hours.

Examples of the Mo ⁶⁺ compound include ammonium molybdate, molybdenum oxide, and molybdic acid. Among these, ammonium molybdate is preferable because it is water-soluble.
As the V ⁵⁺ compound, ammonium metavanadate and vanadium pentoxide are preferable.

The addition amount of the Mo ⁶⁺ compound and the V ⁵⁺ compound is such that the atomic ratio (i and j) of V and Te to this is 0.01 to 1.5 based on Mo, respectively, and the atomic ratio of Te to V ( j / i) is 0.3 to 1.0.

By heating the Mo ⁶⁺ compound and V ⁵⁺ compound and metal Te particles dispersed in water, a dark blue reaction liquid in which Te particles having a particle size of 100 nm or less are stably dispersed in water is obtained.
When the heating temperature or the heating time is in the above range, the metal Te particles can be prevented from excessively reacting. An example of an excess reaction is the formation of insoluble tellurium dioxide, which can affect the performance of the resulting metal oxide catalyst.

Step (4)
In the step (4), the reaction solution obtained in the step (3) and a compound containing the metal element A (hereinafter referred to as A-containing compound) are mixed. The A-containing compound is preferably mixed in the form of an aqueous solution or an aqueous dispersion. By this mixing operation, fine precipitates are generated in the reaction solution. The reaction temperature is not particularly limited, but it is preferable to mix at room temperature (10 ° C. to 35 ° C.).
The step (4) can be performed simultaneously with the step (3). That is, in the step (3), an A-containing compound can be present at the same time.

The metal element A is at least one element selected from the group consisting of Nb, Ta, W, Ti, Zr, Re, Fe, Ni, Co, Sn, Tl, Cu, rare earth elements and alkali metal elements, and A Examples of the contained compound include these oxides, nitrates, carboxylates, oxoacid salts, and oxalates.
When the A-containing compound is insoluble, it may be dispersed and mixed in water, but it can be dissolved in water by using oxalic acid or the like in combination.

The mixing amount of the A-containing compound is the atomic ratio of the metal in the obtained metal oxide catalyst. When Mo is 1, the metal element A is 0.001 to 3.0. When the ratio of the metal element A is less than 0.001, the obtained catalyst may be deteriorated, and when it exceeds 3.0, the activity of the catalyst may be lowered.

In the step (4), nitric acid or ammonium nitrate may be added to the mixed solution in which the reaction solution obtained in the step (3) and the A-containing compound are mixed to produce a precipitate, and the resulting metal oxide catalyst Can be expected to improve performance and physical strength.
A preferable addition amount of nitric acid or ammonium nitrate is preferably 0.7 to 2.1, more preferably 0.5 to 1.7 in terms of molar ratio to metal Te.
In the step (4), the mixing of the reaction solution obtained in the step (3) and the compound containing the metal element A is preferably performed in 15 minutes or less, more preferably in 10 minutes or less. It is more preferable to carry out in 5 minutes or less, and it is particularly preferable to carry out in 1 minute or less. Within the above range, the acrylic acid selectivity and acrylic acid yield are excellent when acrylic acid is produced by propane oxidation using the resulting metal oxide catalyst.

Process (5)
The method for producing a metal oxide catalyst of the present invention includes a step (step (5)) in which the obtained reactant is dried and calcined to obtain a metal oxide catalyst represented by the above composition formula.
In the step (5), it is preferable that the mixed solution (slurry) obtained through the step (4) is evaporated to dryness, and the dried product obtained is dried and then fired. The above mixed solution contains a large amount of water. As a method for removing this water, known evaporation to dryness, spray drying, and the like can be used.
In the case of evaporating to dryness, the liquid mixture may be simply heated to evaporate the water, but it can be efficiently dried by blowing an inert gas such as nitrogen or air during evaporation to dryness. The temperature for evaporation to dryness is preferably 50 ° C to 130 ° C.

Next, the dried product obtained by the above operation is fired in two stages. The first stage firing is preferably carried out at a temperature of 250 ° C. to 380 ° C. in the presence of oxygen using a rotary furnace, specifically preferably a batch or continuous rotary kiln, and more preferably 280 ° C. ~ 330 ° C. The firing time is preferably 5 minutes to 20 hours, more preferably 10 minutes to 3 hours.
It is necessary that the substance obtained by the first stage baking is included in the range of at least one of the following analysis values A and B.
Next, as the second stage firing condition, the firing temperature is preferably 500 ° C. to 660 ° C. in the absence of oxygen, and more preferably 570 ° C. to 640 ° C. The firing time is preferably 0.5 to 6 hours, more preferably 1 to 3 hours.
The second stage baking is preferably performed in a muffle furnace.

Analysis value A (mass change rate)
The value of mass change rate defined by the following formula 1 is 1.2 to 4.0%.
Mass change rate (%) = [(mass before heating−mass after heating) / mass before heating] × 100 (formula 1)
The mass change rate is measured by sampling a sample that has been baked in the first stage, measuring the mass before heating, and then subjecting it to a heat treatment at 500 ° C. to 650 ° C. for 10 minutes to 90 minutes in the muffle furnace. And measure the mass after heating. Although data can be acquired after the inside of the muffle furnace is replaced with nitrogen, loss of replacement time and variation in the state of replacement in the furnace are anxious materials, so they are not indispensable.

The conditions of the mass change rate measurement method will be specifically described. For the evaporated and dried product of the mixed solution obtained in the above steps (1) to (5), a sample calcined at 310 ° C. for 30 minutes using a tabletop rotary kiln (manufactured by Takasago Industry Co., Ltd.) is heated. The relationship between temperature and heating time and mass change rate is shown in Table 1 below.
According to Table 1, there are variations in the rate of change in weight between heating times of 10 minutes and 90 minutes at heating temperatures of 420 ° C. and 700 ° C., but there is almost no variation in the range of 500 ° C. to 650 ° C. It is almost constant in the range from 90 minutes to 90 minutes, and it is preferable to measure the rate of mass change under conditions of heat treatment at 500 to 650 ° C. for 10 to 90 minutes in the atmosphere.

Next, the fact that the firing state of the first stage can be grasped from the mass change rate will be described with an example. FIG. 1 shows the relationship between the firing time and the mass change rate of the substance obtained by heating the first stage baking at 310 ° C. for 2 to 240 minutes.
According to FIG. 1, it can be seen that the firing state progresses as the firing time becomes longer, and the mass change rate changes in correlation with the firing time.

Analysis value B (elemental analysis)
The nitrogen content in the elemental analysis of carbon, hydrogen and nitrogen by the combustion method is 0.8 to 1.5% by mass.
As elemental analysis, elemental analysis of carbon, hydrogen and nitrogen is performed by a combustion method which is a general method. Using a sample similar to the above analysis value A, the relationship between the baking time (2 to 240 minutes) and the nitrogen content by elemental analysis when baking at 310 ° C. with a tabletop rotary kiln (manufactured by Takasago Industry Co., Ltd.) As shown in FIG.
According to FIG. 2, it can be seen that the firing state proceeds as the firing time becomes longer, and the nitrogen content changes in correlation with the firing time.

Furthermore, it is preferable that the substance obtained by the first stage baking is included in the range of the analytical value C below.
Analysis value C
The number of moles of oxygen consumed per 1 g of the sample obtained by oxidation-reduction titration with an oxidizing agent under heating of a solution in which the sample is dispersed in an aqueous sulfuric acid solution is 3.4 to 5.5 mmol.

In the oxidation-reduction titration, a dispersion obtained by adding a sample after the first stage baking to an aqueous sulfuric acid solution is analyzed at 40 to 90 ° C., preferably 50 to 70 ° C. Although the reducing agent is not particularly limited, a commercially available N / 40 potassium permanganate aqueous solution is preferable.
Using a sample similar to the above analysis value A, firing time (2 to 90 minutes) when firing at 310 ° C. using a tabletop rotary kiln (manufactured by Takasago Industry Co., Ltd.) and redox titration of the first-stage fired product The relationship with the quantity is shown in FIG.
According to FIG. 3, it can be seen that the redox titer of each sample changes in correlation with the firing time.

FIG. 4 shows the results of investigating the performance of the metal oxide catalyst produced by firing the second-stage calcined product under various conditions under the same conditions. The horizontal axis indicates the propane conversion, the vertical axis indicates the acrylic acid selectivity, and the acrylic acid yield is indicated by a broken line.
As shown in FIG. 4, the curve of the catalyst performance has a maximum point of the acrylic acid yield, and the first stage calcination state greatly affects. Therefore, in order to reduce variation in catalyst performance, it is important to grasp the first stage firing state.

As described above, the mass change rate, the nitrogen content, and the redox titration analysis values change in correlation with the firing state of the first stage. Therefore, the first stage firing product is analyzed by the above analysis method. It is possible to determine the firing state of the stage.

Further, using the sample obtained by the first stage baking, the second stage baking is performed in the absence of oxygen. Examples of the baking apparatus include, but are not limited to, a muffle furnace and a rotary kiln.
The second stage baking temperature is preferably 500 ° C. to 660 ° C., more preferably 570 ° C. to 640 ° C., and the baking time is preferably 0.5 to 6 hours, and preferably 1 to 3 hours. More preferred.

The metal oxide catalyst obtained by the above steps (1) to (5) can be used as it is, but it is preferable to use it by pulverizing to an appropriate particle size to increase the surface area of the catalyst. As the pulverization method, a known dry pulverization method and wet pulverization method can be used.
Specific examples of the pulverizer include a mortar and a ball mill. In the case of wet grinding, examples of the solvent used as a grinding aid include water and alcohols. When the catalyst is pulverized, the particle size is preferably 20 μm or less, more preferably 5 μm or less.
The metal oxide catalyst can be used without a carrier, but can also be used by being supported on a known carrier such as silica, alumina, silica alumina, silicon carbide or the like having an appropriate particle size. The carrying amount is not particularly limited and conforms to the conventional carrying amount.

A method of vapor phase catalytic oxidation of propane for producing acrylic acid using the metal oxide catalyst produced by the above method will be described.
By introducing propane and oxygen gas as raw materials into the reactor filled with the metal oxide catalyst, propane is vapor-phase contact oxidized by the metal oxide catalyst to generate acrylic acid.
Propane and oxygen gas may be separately introduced into the reactor and mixed in the reactor, or may be introduced into the reactor in a state where both are mixed beforehand.

Examples of the oxygen gas include pure oxygen gas and air, and gas obtained by diluting these with nitrogen, steam, carbon dioxide gas, or the like.
When propane and air are used as raw materials, the use ratio of air to propane is preferably 30 times or less in volume ratio, more preferably 0.2 to 20 times.

The reaction temperature is preferably 300 ° C. to 600 ° C., more preferably 350 ° C. to 500 ° C.
The space velocity (hereinafter referred to as SV) of the source gas is suitably 1,000 to 8,000 hr ⁻¹ . When the space velocity is at 1,000 hr ^-1 or more, to improve the yield of acrylic acid as the target compound, if it is 8,000Hr ^-1 or less, to improve the reaction rate.

Unreacted raw propane present in the reaction gas discharged from the reactor outlet and propylene as an intermediate product can be used as fuel as they are, but they are separated from other components in the reaction gas before being sent to the reactor. It can be returned and reused.
The metal oxide catalyst produced according to the present invention can also be applied to propane ammoxidation, and acrylonitrile can be produced in high yield. The ammoxidation conditions are the same as those for the above-mentioned vapor-phase catalytic oxidation of propane.

Hereinafter, the present invention will be described more specifically with reference to examples, test examples, and reference examples.
In Examples, Test Examples, and Reference Examples, each raw material was blended so that the ratio of each metal constituting the obtained metal oxide catalyst was the following value.
Mo / V / Te / Nb = 1.0 / 0.25 / 0.13 / 0.12 (molar ratio)

The production test of acrylic acid in each example was performed as follows.
1.1 ml (1.0 g) of the metal oxide catalyst obtained in each example was filled in a 10 mmφ quartz reaction tube, the reaction tube was heated to 400 ° C., 6.4 vol% propane, oxygen Acrylic acid was produced by feeding a mixed gas of 9.6 vol%, nitrogen 36.1 vol% and water vapor 47.7 vol% at a space velocity of 3,924 / hr- ¹ .
Perform composition analysis of each product component in the reaction product, and calculate the propane conversion, acrylic acid selectivity and acrylic acid yield shown in the following formula on a molar basis, and evaluate the performance of the metal oxide catalyst. Are listed in Tables 2-5.
Propane conversion (%) = [(feed propane-unreacted propane) / feed propane] × 100 (formula 2)
Acrylic acid selectivity (%) = [produced acrylic acid / (feed propane-unreacted propane)] × 100 (formula 3)
Acrylic acid yield (%) = (propane conversion × acrylic acid selectivity) / 100 (formula 4)

<Test Example 1>
To a 500 ml glass flask, add 3.64 g of tellurium dioxide and 60 ml of distilled water, and add 2.8 g of hydrazine monohydrate (80% by mass as hydrazine) while stirring at a rate of 300 rpm at 80 ° C. And maintained under these conditions for 12 hours. With the passage of time, the first white powder turned gray and finally turned into a black suspension, and its dispersion was obtained.
Using the filter paper, the obtained dispersion was separated into a black solid and a transparent colorless filtrate. The solid on the filter paper was washed with 200 ml of distilled water. After distilled water passed through the filter paper, the solid matter remaining on the filter paper was collected in a sample bottle while being diluted with distilled water to obtain an aqueous dispersion of tellurium.
To a 500 ml glass flask, 5.12 g of ammonium metavanadate, 30.9 g of ammonium molybdate, and 100 ml of distilled water were added and dissolved under stirring at the boiling point of water.

The metal tellurium aqueous dispersion was added to the resulting solution, heat-treated for 1 hour, and then cooled to 30 ° C. with ice water.
On the other hand, 8.82 g of oxalic acid and 3.48 g of niobic acid were dissolved in 140 ml of distilled water to prepare a room temperature aqueous solution. This aqueous solution was added to the reaction solution over 10 seconds.
The resulting mixture was vigorously stirred for 10 minutes, and then 5.0 g of ammonium nitrate was mixed with this mixture. Thereafter, the mixture was concentrated by heating and further evaporated to dryness at 120 ° C.
The obtained distilled and dried product was fired at 310 ° C. for 15 minutes in the air using a batch type rotary kiln (device name: desktop rotary kiln, manufactured by Takasago Industrial Co., Ltd.).
1.0 g of the obtained sample was weighed in a crucible, heated in a small muffle furnace for process inspection (device name: gas replacement muffle furnace, manufactured by AS ONE Corporation) at 600 ° C. for 10 minutes in the atmosphere, and then desiccator The sample was cooled to 100 ° C. or less and weighed again. The rate of change in weight was 4.6% as calculated by Equation 1 above.

The second stage calcination was performed in an inert atmosphere in which nitrogen gas was circulated in a muffle furnace at 600 ° C. for 2 hours to obtain a metal oxide catalyst.
The atomic ratio of the components of this catalyst was Mo / V / Te / Nb = 1.0 / 0.25 / 0.13 / 0.12 (molar ratio) by composition analysis by fluorescent X-ray analysis.
The obtained catalyst was tableted and the molded product was pulverized to 16-30 mesh and used for the acrylic acid production reaction. As shown in Table 2, the propane conversion was 69% and acrylic acid selectivity was obtained. As shown in FIG. 4, it is expected that acrylic acid selectivity is improved when the first stage baking is performed a little longer, as shown in FIG.

<Example 1>
The evaporated and dried product obtained in Test Example 1 was baked at 310 ° C. for 90 minutes in the air using a batch rotary kiln, and 1.0 g of the obtained sample was weighed in a crucible, and the same process as Test Example 1 After heating for 10 minutes at 600 ° C. in the air in a small muffle furnace for inspection, the sample was cooled to 100 ° C. or lower in a desiccator and weighed again. As a result, the weight change rate was 2.1%.
The second stage calcination was performed in the same manner as in Test Example 1, and the obtained catalyst was tableted and molded, and the molded product was pulverized to 16 to 30 mesh and used in the acrylic acid production reaction. As a result, the propane conversion was 60 %, Acrylic acid selectivity was 73%, and acrylic acid yield was 44%.
It was confirmed that the first stage baking was in an appropriate range and the acrylic acid selectivity was improved as compared with Test Example 1.

<Test Example 2>
The evaporated and dried product obtained in Test Example 1 was baked at 330 ° C. for 90 minutes in the air using a batch rotary kiln, and 1.0 g of the obtained sample was weighed in a crucible, and the same process as Test Example 1 After heating for 10 minutes at 600 ° C. in the air in a small muffle furnace for inspection, the sample was cooled to 100 ° C. or lower in a desiccator and weighed again. As a result, the weight change rate was 1.1%.
The second stage calcination was carried out in the same manner as in Test Example 1, and the resulting catalyst was subjected to tableting, and the molded product was pulverized to 16-30 mesh and used in the acrylic acid production reaction. As a result, the propane conversion was 40 %, Acrylic acid selectivity was 74%, and acrylic acid yield was 30%.
As shown in FIG. 4, since the first stage calcination was outside the proper range and entered the overcalcination region, the propane conversion decreased. This effect lowered the acrylic acid yield.

<Example 2>
The evaporated and dried product obtained in Test Example 1 was baked at 330 ° C. for 60 minutes in the air using a batch rotary kiln, and 1.0 g of the obtained sample was weighed in a crucible, and the same process inspection as Test Example 1 was performed. After heating at 600 ° C. for 10 minutes in the air in a small muffle furnace, the sample was cooled to 100 ° C. or lower in a desiccator and weighed again. As a result, the weight change rate was 1.9%.
The second stage calcination was carried out in the same manner as in Test Example 1, and the obtained catalyst was tableted and molded, and the molded product was pulverized to 16-30 mesh and used in the acrylic acid production reaction. As a result, the propane conversion was 61 %, Acrylic acid selectivity was 73%, and acrylic acid yield was 44%.
Compared with Test Example 2, the heating time was shortened so that the first stage firing was in an appropriate range, so the propane conversion increased to 60%.

<Test Example 3>
The evaporated and dried product obtained in Test Example 1 was baked at 350 ° C. for 60 minutes in the air using a batch rotary kiln, and 1.0 g of the obtained sample was weighed in a crucible, and the same process inspection as Test Example 1 was performed. After heating at 600 ° C. for 10 minutes in the air in a small muffle furnace for use, cooling to 100 ° C. or lower in a desiccator and weighing again, the weight change rate was 0.7%.
The second stage calcination was carried out in the same manner as in Test Example 1, and the obtained catalyst was tableted and molded, and the molded product was pulverized to 16 to 30 mesh and used in the acrylic acid production reaction. As a result, the propane conversion was 13 %, Acrylic acid selectivity 62%, and acrylic acid yield 8%.
As shown in FIG. 4, the first stage of calcination was outside the proper range and entered the region where the calcination was excessive. This affected the propane conversion, and the acrylic acid yield was lowered.

<Example 3>
The evaporated and dried product obtained in Test Example 1 was baked at 350 ° C. for 30 minutes in the air using a batch rotary kiln, and 1.0 g of the obtained sample was weighed in a crucible, and the same process inspection as Test Example 1 was performed. After heating for 10 minutes at 600 ° C. in the air in a small muffle furnace, the sample was cooled to 100 ° C. or lower in a desiccator and weighed again. As a result, the weight change rate was 1.4%.
The second stage calcination was performed in the same manner as in Test Example 1, and the obtained catalyst was tableted and molded, and the molded product was pulverized to 16 to 30 mesh and used for the acrylic acid production reaction. %, Acrylic acid selectivity was 70%, and acrylic acid yield was 42%.
From the result of Test Example 3, since the time was shortened so that the first stage firing was in an appropriate range, the propane conversion was recovered to 61%.

<Test Example 4>
The same evaporated and dried product as in Test Example 1 was baked at 310 ° C. for 15 minutes in the air using a batch rotary kiln. As a result of measuring the nitrogen content of the obtained sample with an elemental analyzer, it was 1.6% by mass.
Next, the second calcination was performed under the same conditions as in Test Example 1, the obtained catalyst was tableted, the molded product was pulverized to 16-30 mesh, and used in the acrylic acid production reaction. The propane conversion was 69%, the acrylic acid selectivity was 64%, and the acrylic acid yield was 44%.

<Examples 4 to 6, Test Example 5>
Compared to Test Example 4, the first stage baking time was changed to the time shown in Table 3.
In Example 4 where the firing time was 30 minutes, the nitrogen content was 1.2% by mass, the second stage of firing was performed under the same conditions as in Test Example 1, and the resulting catalyst was tableted and molded. As a result of pulverizing the product to 16-30 mesh and using it for the production reaction of acrylic acid, the propane conversion was 66%, the acrylic acid selectivity was 71%, and the acrylic acid yield was 47%, and the catalyst performance could be improved.
Example 5 was fired in the same manner as in Example 4 except that the firing time was 60 minutes, and Example 6 was fired for 120 minutes. As a result, the nitrogen content was 0.9% by mass and 0.8%, respectively. When used for the production reaction of acrylic acid in the same manner as in Example 4, it showed high acrylic acid selectivity as shown in Table 3.
On the other hand, in Test Example 5 in which the first stage baking time was 240 minutes, the nitrogen content was 0.7% by mass, and the acrylic acid yield was lower than 40% when used for the production reaction of acrylic acid. .

<Comparative Reference Example 1>
The same evaporated and dried product as in Test Example 1 was calcined in the atmosphere at 310 ° C. for 5 minutes using a batch rotary kiln, and 0.4 g of the obtained sample was coarsely pulverized with a spatula and then heated to 60 ° C. 78 In addition to a beaker containing% sulfuric acid / pure water = 10/50, the mixture was uniformly dispersed with a magnetic stirrer. While continuing the heating, using an oxidation-reduction titrator (device name: automatic potentiometric titrator AT-510, manufactured by Kyoto Denshi Kogyo Co., Ltd.), using a 1/40 normal potassium permanganate aqueous solution as the reducing agent, the equivalence point The titration amount until reaching the value of 39 was 39 ml (in terms of molar number of oxygen: 6.1 mmol / sample 1 g).
As in Test Example 1, the second stage of calcination was performed, the obtained catalyst was tableted and molded, and the molded product was pulverized to 16 to 30 mesh and used in the acrylic acid production reaction. Thus, propane conversion was 45%, acrylic acid selectivity was 45%, and acrylic acid yield was 20%.

<Reference Example 1>
As a result of setting the first stage baking time to 90 minutes with respect to Comparative Reference Example 1, the redox titer was 22 ml (in terms of molar number of oxygen: 3.4 mmol / sample 1 g). As in Test Example 1, the second stage of calcination was performed, the obtained catalyst was tableted and molded, and the molded product was pulverized to 16 to 30 mesh and used in the acrylic acid production reaction. As shown, the propane conversion was 60%, the acrylic acid selectivity was 73%, and the acrylic acid yield was 44%.

<Reference Examples 2 and 3, Comparative Reference Examples 2 and 3>
Compared to Comparative Reference Example 1, Reference Example 2 performed the first stage firing at 330 ° C. for 60 minutes, and Reference Example 3 performed 30 minutes at 350 ° C. As a result, the redox titer was 23 ml (in terms of moles of oxygen). : 3.6 mmol / sample 1 g) and 31 ml (in terms of moles of oxygen: 4.8 mmol / sample 1 g).
As in Test Example 1, the second stage of calcination was performed, the obtained catalyst was tableted and molded, and the molded product was pulverized to 16 to 30 mesh and used in the acrylic acid production reaction. It was as follows.

Further, as a result of performing the first stage baking at 330 ° C. for 90 minutes (Comparative Reference Example 3) and at 350 ° C. for 60 minutes (Comparative Reference Example 4) with respect to Comparative Reference Example 1, the redox titer was 21 ml each. (Mole oxygen conversion: 3.3 mmol / sample 1 g) and 18 ml (oxygen mole conversion: 2.8 mmol / sample 1 g).
As in Test Example 1, the second stage of calcination was performed, the obtained catalyst was tableted and molded, and the molded product was pulverized to 16 to 30 mesh and used in the acrylic acid production reaction. It was as follows.

In each of the above examples, the firing temperature and the firing time were changed for the adjustment of the first stage firing state. Next, examples in which the air flow rate in the firing apparatus was changed will be described.

<Comparative Example 5>
Under the condition that the same evaporated and dried product as in Test Example 1 was baked at 310 ° C. for 90 minutes in the atmosphere using a tabletop rotary kiln, the atmosphere of SV = 692 was blown into the furnace. When the mass change rate and oxidation-reduction titration of the obtained sample were performed, the weight change rate was 1.2% and the oxidation-reduction titration amount was 20 ml (in terms of moles of oxygen: 3.1 mmol / sample 1 g).
As in Test Example 1, the second stage of calcination was performed, the resulting catalyst was tableted, and the molded product was pulverized to 16-30 mesh and used in the acrylic acid production reaction. As a result, the propane conversion was 33 %, Acrylic acid selectivity was 76%, and acrylic acid yield was 25%.

<Examples 7 and 8>
From the weight change rate and redox titration amount of Comparative Example 5, since the first stage baking was performed excessively, the baking temperature and the baking time were not changed, and in Example 7, the air flow rate was set to SV = 30. In Example 8, as a result of changing the aeration amount to SV = 314, the weight change rate and the oxidation-reduction titration amount were in an appropriate range, and the catalyst performance recovered to the acrylic acid yield in the 40% range. The improvement of the firing state was confirmed.

<Example 9>
In Test Example 1, the addition time of niobium oxalate was changed from 10 seconds to 3 minutes to produce a slurry, and the dried product obtained by the same method as in Example 1 was baked and used for the production reaction of acrylic acid did.

<Example 10>
In Test Example 1, the addition time of niobium oxalate was changed from 10 seconds to 6 minutes to produce a slurry, and the dried product obtained by the same method as in Example 1 was baked and used for the production reaction of acrylic acid did.

<Example 11>
In Test Example 1, niobium oxalate and the reaction solution were mixed using a static mixer T4-21R (trade name, manufactured by Noritake Co., Ltd.), which is an industrial continuous mixer, a static mixer, to prepare a slurry, The dried product obtained in the same manner as in Example 1 was baked and used for the reaction for producing acrylic acid.

<Reference Example 4>
In Test Example 1, the addition time of niobium oxalate was changed from 10 seconds to 20 minutes to produce a slurry, and the dried product obtained by the same method as in Example 1 was baked and used for the production reaction of acrylic acid did.

According to the method for producing a metal oxide catalyst in the present invention, the firing state of the first stage can be grasped in a short time by an inspection method of thermal mass spectrometry or elemental analysis, so that there is little variation in catalyst activity. A metal oxide catalyst can be produced.
The produced metal oxide catalyst exhibits excellent catalytic activity in terms of propane conversion, acrylic acid selectivity and acrylic acid yield, so it can be used as a catalyst for the production of acrylic acid by vapor phase catalytic oxidation of propane. it can.

Claims (5)

1. Reducing the Te ⁴⁺ compound or Te ⁶⁺ compound in the presence of a reducing agent and water or an organic solvent to obtain a reduced product containing metal tellurium;
   Removing unreacted reducing agent from the reduced product,
   Reacting a reduced product containing metal tellurium from which the unreacted reducing agent has been removed in the presence of Mo, V, A element and water, to obtain a reaction product; and
   Including a step of drying and calcining the obtained reaction product to obtain a metal oxide catalyst represented by the following composition formula,
   Performing the firing in two stages;
   A method for producing a metal oxide catalyst, wherein a substance obtained by the first-stage calcination is contained in at least one analysis value of the following analysis value A and the following analysis value B.
   Composition formula: MoV _i Te _j A _k O _y
   In the formula, A is at least one element selected from the group consisting of Nb, Ta, W, Ti, Zr, Re, Fe, Ni, Co, Sn, Tl, Cu, rare earth elements and alkali metal elements, i and j are each 0.01 to 1.5, and j / i = 0.3 to 1.0, k is 0.001 to 3.0, and y is an oxidation state of another element. Is a number determined by
   Analytical value A: The mass change rate defined by the following formula 1 is 1.2 to 4.0%.
   Mass change rate (%) = [(mass before heating−mass after heating) / mass before heating] × 100 (formula 1)
   Analysis value B: The nitrogen content in the elemental analysis of carbon, hydrogen and nitrogen by the combustion method is 0.8 to 1.5 mass%.
2. The step of obtaining the reactant reacts with a reduced product containing metal tellurium from which the unreacted reducing agent has been removed in the presence of Mo, V and water, and then mixed with a compound containing element A and reacted. The method for producing a metal oxide catalyst according to claim 1, wherein the method is a step of obtaining a reaction product.
3. Furthermore, the manufacturing method of the metal oxide catalyst of Claim 1 or Claim 2 in which the substance obtained by 1st step | paragraph baking is contained in the following analysis value C.
   Analytical value C: The number of moles of oxygen consumed per 1 g of the sample obtained by subjecting the solution in which the sample is dispersed in the sulfuric acid aqueous solution to oxidation-reduction titration with heating using an oxidizing agent is 3.4 to 5.5 mmol. .
4. The method for producing a metal oxide catalyst according to any one of claims 1 to 3, wherein the second stage calcination is performed in the temperature range of 500 ° C to 660 ° C in the absence of oxygen.
5. A method for producing acrylic acid, wherein propane is oxidized by a gas phase catalytic reaction using the metal oxide catalyst obtained by the method according to any one of claims 1 to 4.

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