JP5219249B2 - Method for producing composite oxide and method for producing unsaturated acid or unsaturated nitrile - Google Patents

Description

  The present invention relates to a method for producing a complex oxide, and a method for producing an unsaturated acid or an unsaturated nitrile using the complex oxide as a catalyst.

Conventionally, a process for producing a corresponding unsaturated carboxylic acid or unsaturated nitrile by subjecting propylene or isobutylene to gas phase catalytic oxidation or gas phase catalytic ammoxidation reaction is well known. In recent years, attention has been focused on a method for producing a corresponding unsaturated carboxylic acid or unsaturated nitrile by subjecting propane or isobutane to gas phase catalytic oxidation or gas phase catalytic ammoxidation reaction instead of propylene or isobutylene, and to use them. Various oxide catalysts have been proposed. As a method for producing such an oxide catalyst, a method of heating and stirring a raw material preparation liquid for a certain period of time has been conventionally studied. For example, Patent Document 1 discloses at least one element selected from Sb and Te. A method is described in which a solution or slurry containing it is stored in an atmosphere having a gas phase oxygen concentration of less than 5000 ppm. Patent Document 2 describes a method in which oxygen gas is blown into a reaction solution in order to promote an oxidation-reduction reaction between Sb ⁺³ , V ⁺⁵ and Mo ⁺⁶ .

Japanese Patent Laid-Open No. 2003-093873 JP 2000-334303 A

However, when the oxide catalyst obtained by the production method described in Patent Document 1 or 2 is used for gas phase catalytic oxidation or gas phase catalytic ammoxidation reaction of propane or isobutane, both catalysts are still the target products. The yield was insufficient.
The present inventors estimated that the cause of the insufficient yield of the oxide catalyst described in Patent Document 1 or 2 is related to the redox state of the catalyst. In the case of the method described in Patent Document 1, since the gas phase oxygen concentration during storage of a solution or slurry containing at least one element selected from Sb or Te is less than 5000 ppm, the redox state of the slurry It is considered that this change does not occur and the performance of the oxide catalyst is not improved. On the other hand, in the case of the method described in Patent Document 2, oxygen gas is blown into a reaction solution containing Sb ⁺³ , V ⁺⁵ and Mo ⁺⁶ in order to dissolve the Sb ⁺³ compound. The oxidation-reduction state is not changed, and the performance improvement of the oxide catalyst is not achieved.

  In view of the above circumstances, the present invention is a method for producing a composite oxide used for gas phase catalytic oxidation or gas phase catalytic ammoxidation reaction of propane or isobutane, and the corresponding unsaturated acid or unsaturated nitrile is obtained in high yield. It is an object to provide a method for producing a composite oxide that can be obtained.

  As a result of intensive studies on the above problems, the present inventors have mixed (a) an aqueous raw material liquid (I) containing Mo and V and an aqueous raw material liquid (II) containing Nb and hydrogen peroxide. To obtain an aqueous mixture (III), and (b) aging the aqueous mixture (III) in an atmosphere having an oxygen concentration of 1 to 25 vol% for 90 minutes to 50 hours to obtain an aqueous mixture (IV). (C) a step of obtaining a dry powder by drying the aqueous mixed solution (IV), and (d) a step of calcining the dry powder. The present invention was completed by finding that a composite oxide capable of obtaining an unsaturated nitrile in a high yield was obtained.

That is, the present invention is as follows.
[1]
(A) a step of mixing an aqueous raw material liquid (I) containing Mo and V with an aqueous raw material liquid (II) containing Nb and hydrogen peroxide to obtain an aqueous mixed liquid (III);
(B) a step of aging the aqueous mixed liquid (III) in an atmosphere having an oxygen concentration of 1 to 25 vol% to obtain an aqueous mixed liquid (IV) by aging for 90 minutes to 50 hours;
(C) drying the aqueous mixture (IV) to obtain a dry powder;
(D) firing the dry powder;
A method for producing a composite oxide, comprising:
[2]
The method for producing a composite oxide according to the above [1], wherein the aging time in the step (b) is 90 minutes or longer and 6 hours or shorter.
[3]
The method for producing a composite oxide according to the above [1] or [2], wherein the redox state of the aqueous mixed liquid (III) is changed by aging in the step (b).
[4]
The method for producing a composite oxide according to any one of the above [1] to [3], wherein the composite oxide is a catalyst for gas phase catalytic oxidation or gas phase catalytic ammoxidation reaction of propane or isobutane.
[5]
A method for producing an unsaturated acid or an unsaturated nitrile, comprising:
A production method comprising a step of subjecting propane or isobutane to a gas phase catalytic oxidation or a gas phase catalytic ammoxidation reaction in the presence of the composite oxide obtained by the production method according to any one of [1] to [4].

  By the production method of the present invention, a composite oxide containing Mo, V and Nb and having a suitable redox state can be obtained. By using this composite oxide as a catalyst for gas phase catalytic oxidation or gas phase catalytic ammoxidation reaction of propane or isobutane, the corresponding unsaturated acid or unsaturated nitrile can be obtained in high yield.

  Hereinafter, the best mode for carrying out the present invention (hereinafter referred to as the present embodiment) will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.

  In the method for producing a composite oxide of the present embodiment, (a) an aqueous raw material liquid (I) containing Mo and V and an aqueous raw material liquid (II) containing Nb and hydrogen peroxide are mixed to form an aqueous mixed liquid. A step of obtaining (III), (b) a step of aging the aqueous mixture (III) in an atmosphere of oxygen concentration of 1 to 25 vol% to obtain an aqueous mixture (IV) by aging for 90 minutes to 50 hours, (c) A step of drying the aqueous mixture (IV) to obtain a dry powder, and (d) a step of firing the dry powder.

[Step (a)]
Step (a) is a step in which an aqueous raw material liquid (I) containing Mo and V and an aqueous raw material liquid (II) containing Nb and hydrogen peroxide are mixed to obtain an aqueous mixed liquid (III).

In this step, first, an Mo compound, a V compound, and, if necessary, an X component, which will be described later, and other raw material components are added to an aqueous solvent such as water, an aqueous nitric acid solution, an aqueous ammonia solution, and heated as necessary. The aqueous raw material liquid (I) is prepared by stirring. Next, the Nb compound and dicarboxylic acid are heated and stirred in water to prepare a mixed solution (B ₀ ). Further, hydrogen peroxide is added to the mixed liquid (B ₀ ) to prepare an aqueous raw material liquid (II). At this time, the aqueous feed solution _{(II) H 2 O 2 /} Nb ( molar ratio) is preferably 0.5 to 20, more preferably from 1 to 10. Furthermore, according to the target composition, aqueous raw material liquid (I) and aqueous raw material liquid (II) are mixed in a suitable ratio, and aqueous mixed liquid (III) is prepared.

Examples of the Mo compound as a raw material include molybdenum oxide, ammonium dimolybdate, ammonium heptamolybdate, phosphomolybdic acid, and silicomolybdic acid. Among them, ammonium heptamolybdate [(NH ₄ ) ₆ Mo ₇ O ₂₄ · _4H 2 O] it can be suitably used. Examples of the V compound include vanadium pentoxide, ammonium metavanadate, and vanadyl sulfate. Among them, ammonium metavanadate [NH ₄ VO ₃ ] can be preferably used.

Examples of the X component include compounds containing elements such as Te, Sb, Sr, Ba, Sc, Y, La, Ce, Pr, and Yb. As compounds containing these elements, nitrates, carboxylates, ammonium carboxylates, peroxocarboxylates, ammonium peroxocarboxylates, ammonium halides, halides, acetylacetonates, alkoxides, etc. are usually used. Preferably, water-soluble raw materials such as nitrates and carboxylates are used. When Te is added as the metal element of the X component, telluric acid [H ₆ TeO ₆ ] can be suitably used as the Te raw material. When Sb is added, antimony oxide, particularly, Sb raw material is used. Antimony trioxide [Sb ₂ O ₃ ] can be preferably used.

Examples of the Nb compound include at least one selected from the group consisting of niobic acid, an inorganic acid salt of niobium, and an organic acid salt of niobium. Among these, niobic acid is preferable. Niobic acid is represented by Nb ₂ O ₅ .nH ₂ O and is also referred to as niobium hydroxide or niobium oxide hydrate. Among them, it is preferable to use a niobium raw material liquid in which the niobium raw material contains a dicarboxylic acid and a niobium compound, and the dicarboxylic acid / niobium molar ratio is 1 to 4. As the dicarboxylic acid used at this time, oxalic acid is preferable.

  Further, when the composite oxide is supported on silica, silica sol, powder silica, or the like can be added as a silica raw material. The powdered silica is preferably produced by a high heat method, and can be added to and mixed in the slurry easily by being dispersed in water in advance. The dispersing method is not particularly limited, and a general homogenizer, homomixer, ultrasonic vibrator, or the like can be dispersed alone or in combination.

[Step (b)]
In the step (b), the aqueous mixed liquid (III) obtained in the step (a) described above is aged in an atmosphere having an oxygen concentration of 1 to 25 vol% for 90 minutes to 50 hours to obtain the aqueous mixed liquid (IV). It is a process to obtain.

  In this step, “aging” means that the aqueous mixed liquid (III) is allowed to stand or stir for a predetermined time in an oxygen atmosphere having a predetermined concentration. Both the aqueous mixed liquid (III) and the aqueous mixed liquid (IV) obtained by aging are usually in a slurry state, and there are many cases where there is not much change in appearance other than the color change described later.

  In this step, the oxygen concentration during the aging is 1 vol% or more from the viewpoint of preventing the progress of the redox reaction that causes any change in the redox state of the metal component contained in the aqueous mixture (III) from being too slow. To do. On the other hand, from the viewpoint of preventing the oxidation-reduction reaction from proceeding excessively, the oxygen concentration during aging is set to 25 vol% or less. In any case, since the gas phase oxygen affects the redox state of the aqueous mixture, it is necessary to maintain the oxygen concentration within an appropriate range. The oxygen concentration during aging is preferably 5 to 23 vol%, more preferably 10 to 20 vol%.

  The oxygen concentration during aging can be measured using a general method, for example, a zirconia oxygen analyzer. The place where the oxygen concentration is measured is preferably near the interface between the aqueous mixture and the gas phase. For example, it is preferable to measure the oxygen concentration at the same point three times within one minute, and use the average value of the three measurement results as the oxygen concentration.

  The diluent gas for reducing the oxygen concentration is not particularly limited, and examples thereof include nitrogen, helium, argon, carbon dioxide, water vapor, and the like, and industrially, nitrogen is preferable. Further, as the gas for increasing the oxygen concentration, pure oxygen or air with a high oxygen concentration is preferable.

  The aging time is important to be 90 minutes or longer and 50 hours or shorter, preferably 90 minutes or longer and 6 hours or shorter, from the viewpoint of improving the catalyst performance of the resulting composite oxide. When the aging time is less than 90 minutes or exceeds 50 hours, the aqueous mixed liquid (IV) having a suitable redox state (potential) is not formed, and the catalytic performance of the resulting composite oxide tends to be reduced.

  Here, when producing complex oxides industrially, the processing speed of the spray dryer is usually limited, and after a part of the aqueous mixture (IV) is spray-dried, all the mixture is spray-dried. It takes time to finish. In the meantime, the aging of the aqueous mixture not spray-dried is continued. Therefore, the aging time includes not only the aging time before drying in step (c) described later but also the time from the start to the end of drying.

  The aging temperature is preferably 25 ° C. or higher from the viewpoint of preventing the condensation of the Mo component and the precipitation of the V component, so that the hydrolysis of the complex containing Nb and hydrogen peroxide does not occur excessively, and the aqueous mixture in a preferred form 65 degreeC or less is preferable from a viewpoint of forming liquid (IV). The aging temperature is more preferably 30 ° C. or higher and 60 ° C. or lower.

  In this step, it is considered that some change occurs in the redox state of the components contained in the aqueous mixture (III) while the aqueous mixture (III) is aged under the predetermined conditions. Although it is extremely difficult to accurately identify the morphological changes of the components in the liquid during aging, the fact that some changes have occurred results in changes in the color of the aqueous mixture (III), changes in the redox potential, etc. That is also suggested. In addition, by producing composite oxides having different aging conditions and evaluating the performance as a catalyst, it can be seen that the conditions applied to the composite oxide having good performance are particularly preferable conditions. At the same time, it can be judged that the aqueous mixture (IV) having a preferable form is formed at this time.

  The redox potential of the aqueous mixture (III) is predominantly the potential 600 mV / AgCl of the aqueous raw material liquid (II), and the dicarboxylic acid (for example, oxalic acid) Nb peroxide contained in the aqueous raw material liquid (II) It is presumed that the potential of the metal component decreases with time due to some oxidation-reduction reaction of the metal component. The redox potential of the aqueous mixed liquid (IV) is preferably 450 to 530 mV / AgCl, more preferably 470 to 510 mV / AgCl.

[Step (c)]
Step (c) is a step of drying the aqueous mixture (IV) obtained from the above-described step (b) to obtain a dry powder.

  Drying can be performed by a known method, for example, spray drying or evaporation to dryness, but it is preferable to obtain a fine spherical dry powder by spray drying. The atomization in the spray drying method can be performed by a centrifugal method, a two-fluid nozzle method, or a high-pressure nozzle method. As the drying heat source, air heated by steam, an electric heater or the like can be used. The dryer inlet temperature of the spray dryer is preferably 150 to 300 ° C, and the dryer outlet temperature is preferably 100 to 160 ° C.

[Step (d)]
Step (d) is a step of firing the dry powder obtained in step (c) described above.

  In this step, a composite oxide is obtained by firing the dry powder obtained in step (c).

  As the baking apparatus, a rotary furnace (rotary kiln), a fluidized baking furnace, or the like can be used. If the dry powder is fired while standing, it will not be fired uniformly and the performance will deteriorate, causing cracks, cracks and the like. Therefore, when performing continuous firing, it is preferable to use a rotary furnace (rotary kiln).

  Although it does not specifically limit as a shape of a baking machine, If it is tubular, continuous baking can be implemented. The shape of the firing tube is not particularly limited, but is preferably a cylinder. The heating method is preferably an external heating type, and an electric furnace can be suitably used. The size, material, and the like of the firing tube can be selected appropriately depending on the firing conditions and production amount, but the inner diameter is preferably 70 to 2000 mm, more preferably 100 to 1200 mm, and the length is preferably The thing of 200-10000 mm, More preferably, the thing of 800-8000 mm is used.

  In the case of giving an impact to the calciner, the thickness is preferably 2 mm or more, more preferably 4 mm or more from the viewpoint of having a sufficient thickness so as not to be damaged by the impact, and the viewpoint that the impact is sufficiently transmitted to the inside of the firing tube. Therefore, it is preferably 100 mm or less, more preferably 50 mm or less. The material is not particularly limited as long as it has heat resistance and has a strength that does not break due to impact, and SUS can be suitably used.

  It is also possible to divide the calcining tube into two or more areas by providing a weir plate having a hole through which the dry powder passes at the center in the calcining tube perpendicular to the flow of the dry powder. By installing the weir plate, it becomes easy to secure the residence time in the firing tube. The number of weir plates may be one or more. The material of the weir plate is preferably metal, and the same material as that of the firing tube can be suitably used. The height of the weir plate can be adjusted according to the residence time to be secured. For example, when supplying dry powder at 250 g / hr in a rotary furnace having a SUS firing tube with an inner diameter of 150 mm and a length of 1150 mm, the weir plate is preferably 5 to 50 mm, more preferably 10 to 40 mm, and still more preferably 13-35 mm. The thickness of the weir plate is not particularly limited, and is preferably adjusted according to the size of the firing tube. For example, in the case of a rotary furnace having a SUS firing tube having an inner diameter of 150 mm and a length of 1150 mm, it is preferably 0.3 mm or more and 30 mm or less, more preferably 0.5 mm or more and 15 mm or less.

  In the firing step, it is preferable to rotate the calciner in order to prevent cracking, cracking and the like of the dry powder and to perform uniform firing. The rotation speed of the calciner is preferably 0.1 to 30 rpm, more preferably 0.5 to 20 rpm, and still more preferably 1 to 10 rpm.

  In the firing of the dry powder, the heating temperature of the dry powder is started from a temperature lower than 400 ° C. and continuously or intermittently raised to a temperature in the range of 550 to 800 ° C. preferable.

  The firing atmosphere can be carried out in an air atmosphere or air circulation, but it is preferable to carry out at least a part of the firing while circulating an inert gas substantially free of oxygen such as nitrogen.

  The supply amount of the inert gas is 50 N liters or more, preferably 50 to 5000 N liters, more preferably 50 to 3000 N liters per 1 kg of dry powder (N liters is a standard temperature / pressure condition, that is, 0 ° C., 1 atm). Means liters measured in). At this time, the inert gas and the dry powder may be countercurrent or cocurrent, but countercurrent contact is preferable in consideration of a gas component generated from the dry powder and a small amount of air mixed with the dry powder.

  Although the firing step can be performed even in one stage, it is preferable to perform the pre-stage firing before performing the main firing. As a temperature range, it is preferable to perform pre-baking at 250 to 400 ° C. and main baking at 550 to 800 ° C. The pre-baking and the main baking may be performed continuously, or the main baking may be performed again after the pre-baking is once completed. Moreover, each of pre-stage baking and main baking may be divided into several stages.

  The pre-stage calcination is preferably performed in the range of a heating temperature of 250 to 400 ° C., preferably 300 to 400 ° C. under an inert gas flow. Although it is preferable to hold at a constant temperature within a temperature range of 250 ° C. to 400 ° C., the temperature may fluctuate within the range of 250 ° C. to 400 ° C., or the temperature may be gradually increased or decreased. The holding time of the heating temperature is 30 minutes or more, preferably 3 to 12 hours.

  The temperature rising pattern until reaching the pre-stage firing temperature may be increased linearly, or the temperature may be increased by drawing an upward or downward convex arc.

  The average rate of temperature rise during the temperature rise until reaching the pre-stage firing temperature is not particularly limited, but is preferably 0.1 to 15 ° C / min, more preferably 0.5 to 5 ° C / min, and still more preferably 1 ˜2 ° C./min.

  The main calcination is preferably carried out under an inert gas flow at a heating temperature of 550 to 800 ° C, preferably 580 to 750 ° C, more preferably 600 to 720 ° C, and even more preferably 620 to 700 ° C. Although it is preferable to hold at a constant temperature within a temperature range of 620 to 700 ° C, the temperature may fluctuate within the range of 620 to 700 ° C, or the temperature may be gradually increased or decreased. The firing time is 0.5 to 20 hours, preferably 1 to 15 hours. When separated by a weir plate, the dry powder passes through at least two, preferably 2 to 20, more preferably 4 to 15 sections in succession. The temperature can be controlled by using one or more controllers, but in order to obtain the desired firing pattern, a heater and a controller can be installed and controlled for each section separated by these weirs. preferable. For example, when seven dam plates are installed so that the length of the portion of the firing tube entering the heating furnace is equally divided into eight, and the firing tube partitioned into eight sections is used, the temperature of the dry powder is the desired temperature. It is preferable to control the set temperature by a heater and a controller in which eight areas are provided for each area so as to obtain a firing temperature pattern. If desired, an oxidizing component (for example, oxygen) or a reducing component (for example, ammonia) may be added to the firing atmosphere under an inert gas flow.

  The temperature rising pattern until reaching the main firing temperature may be increased linearly, or the temperature may be increased by drawing an upward or downward convex arc.

  The average rate of temperature increase during the temperature increase until reaching the main firing temperature is not particularly limited, but is preferably 0.1 to 15 ° C / min, more preferably 0.5 to 10 ° C / min, and still more preferably 1 ˜8 ° C./min.

  Moreover, the average temperature-fall rate after completion | finish of this baking is 0.01-1000 degreeC / min, Preferably it is 0.05-100 degreeC / min, More preferably, it is 0.1-50 degreeC / min, More preferably, 0.5- 10 ° C./min. Moreover, it is also preferable to hold once at a temperature lower than the main firing temperature. The temperature to be maintained is 10 ° C., preferably 50 ° C., more preferably 100 ° C. lower than the main firing temperature. The holding time is 0.5 hours or more, preferably 1 hour or more, more preferably 3 hours or more, and particularly preferably 10 hours or more.

  When the main baking is performed again after the pre-stage baking is once completed, it is preferable to perform a low temperature treatment in the main baking.

  The time required for low-temperature treatment, that is, the time required for raising the temperature to the firing temperature after decreasing the temperature of the dry powder is the size, thickness, material, composite oxide production amount of the calciner, It is possible to appropriately adjust according to a series of periods in which the dry powder is continuously fired, a fixing speed, a fixing amount, and the like. For example, in the case of using a SUS fired tube having an inner diameter of 500 mm, a length of 4500 mm, and a wall thickness of 20 mm, it is preferably within 30 days, more preferably within 15 days, during a series of periods in which the composite oxide is continuously fired. More preferably, it is within 3 days, and particularly preferably within 2 days.

  For example, when supplying dry powder at a speed of 35 kg / hr while rotating at 6 rpm in a rotary furnace having an internal diameter of 500 mm, a length of 4500 mm, and a wall thickness of 20 mm and made of SUS, the main baking temperature is 645 ° C. In some cases, after the temperature is lowered to 400 ° C., the step of raising the temperature to 645 ° C. can be performed in about one day. In the case of continuous firing for one year, by performing such a low temperature treatment once a month, it is possible to perform firing while stably maintaining the oxide layer temperature.

[Composite oxide]
An example of a preferable composite oxide of the present embodiment is represented by the following composition formula (1).
_{Mo 1 V a Nb b Y c} X d O n ··· (1)
(Wherein, a, b, c, d and n represent atomic ratios per Mo atom, a is 0.01 ≦ a ≦ 1, b is 0.01 ≦ b ≦ 1, and c is 0.01 ≦ c. ≦ 1, d is 0 <d <1, and n is a number determined by the valence of the constituent metal.

  In addition, the atomic ratios a to c per Mo atom are preferably in the range of 0.1 to 0.4, 0.01 to 0.2, and 0.1 to 0.5, respectively.

  Y is preferably Te or Sb. In general, in industrial production methods of unsaturated nitriles, Yb is particularly preferably Sb because Y must have characteristics that can withstand long-term use at 400 ° C. or higher. On the other hand, in the industrial production method of unsaturated acids, reaction at 400 ° C. or lower is also possible, and therefore the influence of Te escape during long-term operation is small, and Te can also be used suitably. C, which is an atomic ratio of Y per Mo atom, is preferably 0.01 to 0.6, and more preferably 0.1 to 0.4.

  X is preferably Sr, Ba, Sc, Y (yttrium), La, Ce, Pr, or Yb, and particularly preferably Ce. D, which is the atomic ratio of X per Mo atom, is preferably 0.001 ≦ d <1, more preferably 0.001 ≦ d <0.1, and still more preferably 0.002 ≦ d <0.01. . Since the yield of the target product tends to be improved by the presence of X, X is preferably uniformly dispersed in the composite oxide particles, but as taught in JP-A-11-244702. Since it may cause an undesirable reaction in the aqueous mixture, it is preferably contained in a trace amount.

Further, when the composite oxide is used as a catalyst, the composite oxide is preferably a supported catalyst supported by a carrier mainly composed of silica. Since it has high mechanical strength when it is supported by a carrier containing silica as a main component, it is suitable for gas phase catalytic oxidation reaction or gas phase catalytic ammoxidation reaction using a fluidized bed reactor. The content of silica in the support mainly composed of silica is preferably 20 to 70% by mass in terms of SiO _{2 with} respect to the total weight of the supported oxide catalyst comprising the oxide of the catalyst constituent element and the support. More preferably, it is 30-60 mass%.

  The content of the silica carrier in the composite oxide is preferably 10% by mass or more from the viewpoint of strength and prevention of powdering. When the content of the silica support is less than 10% by mass, stable operation is difficult even when the catalyst is used industrially, and it is necessary to replenish the lost catalyst, which is economically undesirable. On the contrary, if the content of the silica support exceeds 80% by mass, sufficient catalytic activity cannot be obtained, and the necessary amount of catalyst increases. Particularly in the case of a fluidized bed, if the silica content exceeds 80% by mass, the specific gravity of the silica-supported catalyst becomes too light, and it becomes difficult to make a good fluidized state.

[Production of unsaturated acids and unsaturated nitriles]
In this embodiment, an unsaturated acid or non-reactive acid is obtained by a method including a step of subjecting propane or isobutane to gas phase catalytic oxidation or gas phase catalytic ammoxidation reaction in the presence of the composite oxide obtained by the above-described manufacturing method. Saturated nitriles can be produced.

  Propane, isobutane and ammonia feeds do not necessarily have to be high purity, and industrial grade gases can be used. As the supply oxygen source, air, pure oxygen, or air enriched with pure oxygen can be used. Furthermore, helium, neon, argon, carbon dioxide gas, water vapor, nitrogen or the like may be supplied as a dilution gas.

The gas phase catalytic oxidation reaction of propane or isobutane can be performed under the following conditions.
The molar ratio of oxygen supplied to the reaction to propane or isobutane is 0.1 to 6, preferably 0.5 to 4. The reaction temperature is 300 to 500 ° C, preferably 350 to 450 ° C. The reaction pressure is 5 × 10 ^{4 to} 5 × 10 ⁵ Pa, preferably 1 × 10 ^{5 to} 3 × 10 ⁵ Pa. The contact time is 0.1 to 10 (sec · g / cc), preferably 0.5 to 5 (sec · g / cc).

In the present embodiment, the contact time is defined by the following equation.
Contact time (sec · g / cc) = (W / F) × 273 / (273 + T)
Here, W, F, and T are defined as follows.
W = filled catalyst amount (g)
F = Raw material mixed gas flow rate (Ncc / sec) in standard state (0 ° C., 1.013 × 10 ⁵ Pa)
T = reaction temperature (° C.)

The gas phase catalytic ammoxidation reaction of propane or isobutane can be carried out under the following conditions.
The molar ratio of oxygen supplied to the reaction to propane or isobutane is 0.1 to 6, preferably 0.5 to 4. The molar ratio of ammonia to propane or isobutane supplied to the reaction is 0.3 to 1.5, preferably 0.7 to 1.2. The reaction temperature is 350 to 500 ° C, preferably 380 to 470 ° C. The reaction pressure is 5 × 10 ^{4 to} 5 × 10 ⁵ Pa, preferably 1 × 10 ^{5 to} 3 × 10 ⁵ Pa. The contact time is 0.1 to 10 (sec · g / cc), preferably 0.5 to 5 (sec · g / cc).

  As a reaction method in the gas phase oxidation reaction and the gas phase ammoxidation reaction, a conventional method such as a fixed bed, a fluidized bed, and a moving bed can be adopted, but a fluidized bed reactor in which reaction heat can be easily removed is preferable. The gas phase ammoxidation reaction may be a single flow type or a recycle type.

  Hereinafter, the present embodiment will be described in more detail with reference to examples and comparative examples. However, the present embodiment is not limited to these examples.

In the examples and comparative examples, the propane conversion and the acrylonitrile yield follow the following definitions, respectively.
Propane conversion (%) = (moles of propane reacted) / (moles of propane fed) × 100
Acrylonitrile (AN) yield (%) = (Mole number of acrylonitrile produced) / (Mole number of supplied propane) × 100

(Preparation of niobium mixture)
A niobium mixed solution was prepared by the following method. Niobic acid 15.34 kg containing 79.8% by mass as Nb ₂ O ₅ and oxalic acid dihydrate [H ₂ C ₂ O ₄ .2H ₂ O] 52.66 kg were mixed in 100 kg of water. The molar ratio of charged oxalic acid / niobium was 5.0, and the charged niobium concentration was 0.50 (mol-Nb / kg-solution). This solution was heated and stirred at 95 ° C. for 2 hours to obtain a mixed solution in which niobium was dissolved. The mixture was allowed to stand and ice-cooled, and then the solid was separated by suction filtration to obtain a uniform niobium mixture. The molar ratio of oxalic acid / niobium in this niobium mixture was 2.68 according to the following analysis.
10 g of this niobium mixed solution was precisely weighed in a crucible, dried overnight at 95 ° C., and then heat-treated at 600 ° C. for 1 hour to obtain 0.7895 g of Nb ₂ O ₅ . From this result, the niobium concentration was 0.594 (mol-Nb / kg-solution).
3 g of this niobium mixture was precisely weighed into a 300 ml glass beaker, 200 ml of hot water at about 80 ° C. was added, and then 10 ml of 1: 1 sulfuric acid was added. The obtained mixed liquid was titrated with 1 / 4N KMnO ₄ under stirring while maintaining the liquid temperature at 70 ° C. on a hot stirrer. The end point was a point where a faint pale pink color by KMnO ₄ lasted for about 30 seconds or more. The concentration of oxalic acid was 1.592 (mol-oxalic acid / kg) as a result of calculation according to the following formula from titration.
2KMnO ₄ + 3H ₂ SO ₄ + 5H ₂ C ₂ O ₄ → K ₂ SO ₄ + 2MnSO ₄ + 10CO ₂ + 8H ₂ O
The obtained niobium mixed solution was used as a niobium mixed solution (B ₀ ) in the production of the following composite oxide.

Example 1
Mixing composition formula was produced by the composite oxide as follows represented by _{Mo 1 V 0.22 Nb 0.10 Sb 0.24} O n /46.5 wt%? SiO _2.
(Step (a): Preparation step of aqueous mixture (III))
10.25 kg of water, 2.225 kg of ammonium heptamolybdate [(NH ₄ ) ₆ Mo ₇ O ₂₄ · 4H ₂ O], 324.5 g of ammonium metavanadate [NH ₄ VO ₃ ], and antimony trioxide [Sb ₂ O _3] were added 440.9g, was prepared aqueous feed solution (I) was heated with stirring for 1 hour at 95 ° C..
285.8 g of hydrogen peroxide containing 30% by mass as H ₂ O ₂ was added to 2.126 kg of niobium mixed solution (B ₀ ), and the mixture was stirred and mixed at room temperature for 10 minutes. Prepared.
After cooling the obtained aqueous raw material liquid (I) to 70 ° C., 3.932 kg of silica sol containing 34.0% by mass as SiO ₂ was added, and further hydrogen peroxide containing 30% by mass as H ₂ O ₂ 514.5 g of water was added and stirring was continued at 55 ° C. for 30 minutes. Next, an aqueous raw material liquid (II) and a dispersion obtained by dispersing 988.1 g of powdered silica in 13.83 kg of water were sequentially added to prepare an aqueous mixed liquid (III). Thereafter, air and nitrogen gas were circulated in the container, and it was confirmed that the oxygen concentration in the container was 18 vol% with a zirconia oxygen analyzer manufactured by Toray Engineering.
(Process (b): Aging process)
The aqueous mixed liquid (III) was aged at 50 ° C. for 2 hours and 30 minutes after the addition of the aqueous raw material liquid (II) to obtain a slurry aqueous mixed liquid (IV). It was 490 mV / AgCl when the oxidation reduction potential of the aqueous liquid mixture (IV) was measured with the ORP electrode (PST-2739C, manufactured by Toa DKK Corporation).
(Process (c): Drying process)
The obtained aqueous mixed liquid (IV) was supplied to a centrifugal spray dryer and dried to obtain a fine spherical dry powder. The dryer inlet temperature was 210 ° C. and the outlet temperature was 120 ° C.
(Process (d): Firing process)
480 g of the obtained dry powder was filled in a SUS firing tube having a diameter of 3 inches and fired at 670 ° C. for 2 hours while rotating the tube under a nitrogen gas flow of 5.0 NL / min to obtain a composite oxide. It was.

(Propane ammoxidation reaction)
Propane was subjected to a gas phase ammoxidation reaction by the following method using the composite oxide obtained above as a catalyst.
Filled with 35 g of composite oxide in a Vycor glass fluidized bed reaction tube with an inner diameter of 25 mm, mixed gas of propane: ammonia: oxygen: helium = 1: 1: 3: 18 at a reaction temperature of 440 ° C. and a normal pressure of reaction. Was supplied at a contact time of 2.8 (sec · g / cc). The propane conversion after the reaction was 89.5%, and the acetonitrile yield was 53.4%.

(Example 2)
Mixing composition formula was produced by the composite oxide as follows represented by _{Mo 1 V 0.22 Nb 0.10 Sb 0.24} O n /46.5 wt%? SiO _2.
The same procedure as in Example 1 was performed except that the aging time was changed to 5 hours. The oxygen concentration in the aging step was 18 vol%, and the redox potential of the aqueous mixture (IV) was 485 mV / AgCl.

(Propane ammoxidation reaction)
Propane was subjected to a gas phase ammoxidation reaction in the same manner as in Example 1 using the composite oxide obtained above. The propane conversion after the reaction was 89.0%, and the acetonitrile yield was 53.7%.

(Comparative Example 1)
Mixing composition formula was produced by the composite oxide as follows represented by _{Mo 1 V 0.22 Nb 0.10 Sb 0.24} O n /46.5 wt%? SiO _2.
The same procedure as in Example 1 was performed except that the aging time was changed to 60 minutes. The oxygen concentration in the aging step was 18 vol%, and the redox potential of the aqueous mixture (IV) was 535 mV / AgCl.

(Propane ammoxidation reaction)
Propane was subjected to a gas phase ammoxidation reaction in the same manner as in Example 1 using the composite oxide obtained above. The propane conversion after the reaction was 84.2%, and the acetonitrile yield was 50.5%.

(Example 3)
Mixing composition formula was produced by the composite oxide as follows represented by _{Mo 1 V 0.22 Nb 0.10 Sb 0.24} O n /46.5 wt%? SiO _2.
(Step (a): Preparation step of aqueous mixture (III))
10.25 kg of water, 2.225 kg of ammonium heptamolybdate [(NH ₄ ) ₆ Mo ₇ O ₂₄ · 4H ₂ O], 324.5 g of ammonium metavanadate [NH ₄ VO ₃ ], and antimony trioxide [Sb ₂ O _3] were added 440.9g, was prepared aqueous feed solution (I) was heated with stirring for 1 hour at 95 ° C..
285.8 g of hydrogen peroxide containing 30% by mass as H ₂ O ₂ was added to 2.126 kg of niobium mixed solution (B ₀ ), and the mixture was stirred and mixed at room temperature for 10 minutes. Prepared.
After cooling the obtained aqueous raw material liquid (I) to 70 ° C., 3.932 kg of silica sol containing 34.0% by mass as SiO ₂ was added, and further hydrogen peroxide containing 30% by mass as H ₂ O ₂ 514.5 g of water was added and stirring was continued at 55 ° C. for 30 minutes. Next, an aqueous raw material liquid (II) and a dispersion obtained by dispersing 988.1 g of powdered silica in 13.83 kg of water were sequentially added to prepare an aqueous mixed liquid (III). Thereafter, air and nitrogen gas were circulated in the container, and it was confirmed that the oxygen concentration in the container was 18 vol%.
(Process (b): Aging process)
The aqueous mixed liquid (III) was aged at 40 ° C. for 36 hours after the addition of the aqueous raw material liquid (II) to obtain a slurry aqueous mixed liquid (IV). It was 480 mV / AgCl when the oxidation-reduction potential of the aqueous liquid mixture (IV) was measured with the ORP electrode (PST-2739C, manufactured by Toa DKK Corporation).
(Process (c): Drying process)
The obtained aqueous mixed liquid (IV) was supplied to a centrifugal spray dryer and dried to obtain a fine spherical dry powder. The dryer inlet temperature was 210 ° C. and the outlet temperature was 120 ° C.
(Process (d): Firing process)
480 g of the obtained dry powder was filled in a SUS firing tube having a diameter of 3 inches and fired at 670 ° C. for 2 hours while rotating the tube under a nitrogen gas flow of 5.0 NL / min to obtain a composite oxide. It was.

(Propane ammoxidation reaction)
Propane was subjected to a gas phase ammoxidation reaction by the following method using the composite oxide obtained above as a catalyst.
Filled with 35 g of composite oxide in a Vycor glass fluidized bed reaction tube with an inner diameter of 25 mm, mixed gas of propane: ammonia: oxygen: helium = 1: 1: 3: 18 at a reaction temperature of 440 ° C. and a normal pressure of reaction. Was supplied at a contact time of 2.8 (sec · g / cc). The propane conversion after the reaction was 88.5%, and the acetonitrile yield was 53.1%.

(Comparative Example 2)
Mixing composition formula was produced by the composite oxide as follows represented by _{Mo 1 V 0.22 Nb 0.10 Sb 0.24} O n /46.5 wt%? SiO _2.
The same procedure as in Example 3 was performed except that the aging time was changed to 72 hours. The oxygen concentration in the aging step was 19 vol%, and the redox potential of the aqueous mixture (IV) was 440 mV / AgCl.

(Propane ammoxidation reaction)
Propane was subjected to a gas phase ammoxidation reaction in the same manner as in Example 1 using the composite oxide obtained above. The propane conversion after the reaction was 85.3%, and the acetonitrile yield was 51.3%.

(Comparative Example 3)
Mixing composition formula was produced by the oxide catalyst represented by _{Mo 1 V 0.22 Nb 0.10 Sb 0.24} O n /46.5 wt%? SiO ₂ as follows.
It was carried out in the same manner as in Example 3 except that the aging time was changed to 5 hours and the flow rates of air and nitrogen gas were changed so that the oxygen concentration was 0.5 vol%. The redox potential of the aqueous mixture (IV) was 550 mV / AgCl.

(Propane ammoxidation reaction)
Propane was subjected to a gas phase ammoxidation reaction in the same manner as in Example 1 using the composite oxide obtained above. The propane conversion after the reaction was 86.1%, and the acetonitrile yield was 51.7%.
Table 1 shows the conditions and results of Examples and Comparative Examples.

From the above results, the oxide catalysts (Examples 1 to 3) obtained by the production method of the present embodiment are suitable for each condition such as aging time, aging temperature, oxygen concentration, etc. Since the aqueous mixed liquid (IV) having a good redox state (potential) was formed, the catalytic performance of the resulting composite oxide was good.
On the other hand, in Comparative Example 1, since the aging time was short and the quality of the aqueous mixed liquid (III) was insufficient, the catalytic performance of the resulting composite oxide was inferior.
In Comparative Example 2, since the aging time was too long, the aqueous mixed liquid (IV) having a suitable redox state (potential) was not formed, and the catalytic performance of the resulting composite oxide was inferior.
Furthermore, in Comparative Example 3, since the oxygen concentration during aging was low and the quality of the aqueous mixed liquid (III) was insufficient, the resulting composite oxide was poor in catalytic performance.

  The method for producing a composite oxide of the present invention is used when industrially producing a corresponding unsaturated acid or unsaturated nitrile by subjecting propane or isobutane to a gas phase catalytic oxidation reaction or a gas phase catalytic ammoxidation reaction. It has industrial applicability as a catalyst production method.

Claims (5)

(A) a step of mixing an aqueous raw material liquid (I) containing Mo and V with an aqueous raw material liquid (II) containing Nb and hydrogen peroxide to obtain an aqueous mixed liquid (III);
(B) a step of aging the aqueous mixed liquid (III) in an atmosphere having an oxygen concentration of 1 to 25 vol% to obtain an aqueous mixed liquid (IV) by aging for 90 minutes to 50 hours;
(C) drying the aqueous mixture (IV) to obtain a dry powder;
(D) firing the dry powder;
A method for producing a composite oxide, comprising:   The method for producing a composite oxide according to claim 1, wherein the aging time in the step (b) is 90 minutes or longer and 6 hours or shorter.   The method for producing a composite oxide according to claim 1 or 2, wherein the redox state of the aqueous mixed liquid (III) is changed by aging in the step (b).   The method for producing a composite oxide according to any one of claims 1 to 3, wherein the composite oxide is a catalyst for gas phase catalytic oxidation or gas phase catalytic ammoxidation reaction of propane or isobutane. A method for producing an unsaturated acid or an unsaturated nitrile, comprising:
A manufacturing method comprising a step of subjecting propane or isobutane to a gas phase catalytic oxidation or a gas phase catalytic ammoxidation reaction in the presence of the composite oxide obtained by the manufacturing method according to claim 1.