JP2006188457A - Method for producing acrylonitrile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing acrylonitrile exhibiting a high yield of the acrylonitrile in an initial stage, and stably producing acrylonitrile for a long time by suppressing reduction of the yield with time. <P>SOLUTION: The invention relates to the method for producing acrylonitrile by reacting propylene, a molecular oxygen and ammonia in the presence of a catalyst, using a producing system comprising a reactor 2 provided with a fluidized layer 1 of the catalyst containing molybdenum, bismuth, iron, nickel and silica as essential components, and a cyclone 4 which separates the gas and the catalyst from the reactor 2 and returns the catalyst to the fluidized layer 1, wherein the amount of the catalyst circulating between reactor 2 and the cyclone 4 is 500-3,000% by mass to the total catalyst (100% by mass) per hr. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing acrylonitrile by reacting propylene with molecular oxygen and ammonia.

  Molybdenum-bismuth-containing metal oxide catalysts are known as ammoxidation reaction catalysts for organic compounds such as propylene, isobutene, and tertiary butanol (see Patent Documents 1-3). Also, an ammoxidation reaction using a production apparatus comprising a reactor provided with a fluidized bed of the catalyst, a source gas sparger that supplies a source gas into the reactor, and a cyclone that separates the gas and the catalyst. For the preferred ranges of reaction conditions, such as the gas linear velocity at the inlet of the cyclone, the linear velocity of the portion where the gas jetted from the nozzle hole of the raw material gas sparger contacts the catalyst, etc., are disclosed in Patent Document 4 and Non-Patent Document 1. Etc. are known. However, with regard to the conditions for catalyst circulation between the reactor and the cyclone, Patent Document 5 discloses an example in which the catalyst circulation amount per hour between the reactor and the cyclone is 50 to 200% by mass of the total catalyst amount. It is a grade described.

  Further, in Non-Patent Document 2, it is important to stabilize the β-type divalent metal molybdate crystal phase in the molybdenum-bismuth-containing metal oxide catalyst in order to obtain a good reaction yield in the ammoxidation reaction. In this document, a suitable composition for stabilizing the β-type divalent metal molybdate crystal phase is proposed. In fact, in recent years, catalysts in which the bivalent metal molybdate crystal phase is almost all β-type have been put into practical use.

However, depending on the reaction conditions of the ammoxidation reaction, the yield of carbon monoxide, which is a by-product, is particularly high, and the yield of acrylonitrile may be low. Further, the stability of the reaction yield over time is still not sufficient.
Japanese Patent Publication No. 36-3563 Japanese Patent Publication No. 36-5870 Japanese Patent Publication No. 38-17967 JP-A-4-202171 Japanese Patent Publication No.43-29569 Edited by Japan Society for Chemical Engineering, “Fluidized Bed Reactor-Industrial Practice and New Technology”, Chemical Industry, 1987, p. 158-165 G. Ertl, H.M. Knozinger, J. et al. Weitkamp, “Handbook of Heterogeneous Catalysis”, Vol. 5, (Germany), WILEY-VCH, 1997, 4.6.6, p. 2302-2326

  An object of the present invention is to provide a method for producing acrylonitrile, which exhibits a high acrylonitrile yield at the beginning of the reaction, suppresses a decrease in acrylonitrile yield over time, and can produce acrylonitrile stably over a long period of time.

  The present inventors paid attention to the catalyst circulation between the reactor and the cyclone in the reaction conditions in order to improve the acrylonitrile yield among the above problems. As a result, it was found that the yield of carbon monoxide decreases when the frequency of catalyst circulation is increased. Surprisingly, the amount of catalyst circulation per hour between the reactor and the cyclone is not sufficient if it is about 200 to 300% by mass of the total catalyst amount (100% by mass), and it is necessary to further increase the circulation rate. I found out that The cause of this is not well understood, but the time of exposure to the oxygen-deficient atmosphere at the top of the reactor and the reoxidation by purge air received in the cyclone dipleg may have some involvement.

  In addition, the present inventors investigated changes in the catalyst over time in order to solve the decrease in acrylonitrile yield over time among the above problems. The production of acrylonitrile using a catalyst whose bivalent metal molybdate crystal phase is almost all β-type, and extracting and analyzing the catalyst during the production revealed that the α-type divalent metal molybdate crystal phase was hardly detected in the new catalyst. Has found that. It was also found that the amount produced varies depending on the production conditions of acrylonitrile.

  As a result of further detailed investigation, when the gas and the catalyst are separated by a cyclone, and when air, oxygen, inert gas, propylene, ammonia, etc. are supplied to the reactor through the raw material gas sparger, the catalyst particles are impacted. To form an α-type divalent metal molybdate crystal phase. It was also found that the α-type divalent metal molybdate crystal phase accelerated even when the amount of catalyst passing through the cyclone increased. Thus, as the intensity and frequency of impact applied to the catalyst particles increase, the amount of α-type divalent metal molybdate crystal phase produced increases, and the α-type divalent metal molybdate crystal phase over time increases. It has been found that an increase in the production amount leads to a decrease in the acrylonitrile yield.

  The cause of the formation of the α-type divalent metal molybdate crystal phase and the cause of the decrease in the acrylonitrile yield accompanying the formation of the α-type divalent metal molybdate crystal phase have not been fully elucidated. As for the cause of the formation of the α-type divalent metal molybdate crystal phase, the present inventors received a physical impact on the minute divalent metal molybdate precursor that was present without crystallizing in the catalyst. Thus, it is presumed that crystallization into α-type, which is a crystalline phase stable at the reaction temperature. The cause of the decrease in acrylonitrile yield associated with the formation of the α-type divalent metal molybdate crystal phase is the alignment of the crystal plane between the α-type divalent metal molybdate crystal phase and the active phase bismuth molybdate. Therefore, it is considered that the yield of acrylonitrile may be lowered by inhibiting the transfer of oxygen and electrons between molybdates, because the property is inferior to the β-type divalent metal molybdate crystal phase.

Conventionally, the flow velocity at the inlet of the cyclone and the flow velocity at the nozzle of the raw material gas sparger have been studied in detail, and considerable consideration has been given to control of the impact force applied to the catalyst particles. On the other hand, surprising attention has not been paid to the frequency with which the catalyst passes through the cyclone. This is because the conventional way of thinking is that there is no problem if the catalyst particles are not destroyed. Furthermore, this is because there was no knowledge of mechanochemical crystal change that gradually progressed each time an impact was applied, and catalyst performance deterioration associated therewith.
Thus, it has become clear that it is extremely important to control both the impact force and the impact frequency applied to the catalyst particles in order to suppress the decrease in acrylonitrile yield over time.

  Therefore, the method for producing acrylonitrile of the present invention separates a reactor provided with a fluidized bed of a catalyst containing molybdenum, bismuth, iron, nickel, and silica as essential components, and a gas and the catalyst from the reactor. In a method for producing acrylonitrile by reacting propylene with molecular oxygen and ammonia in the presence of a catalyst using a production apparatus comprising a cyclone for returning the catalyst to the fluidized bed, the reaction between the reactor and the cyclone is performed. The amount of catalyst circulating per hour is in the range of 500 to 3000% by mass of the total catalyst amount (100% by mass).

  According to the method for producing acrylonitrile of the present invention, acrylonitrile can be produced stably over a long period of time while exhibiting a high acrylonitrile yield at the beginning of the reaction and suppressing a decrease in acrylonitrile yield over time.

<Catalyst>
The catalyst in the present invention contains molybdenum, bismuth, iron, nickel, and silica as essential components. A catalyst having a composition represented by the following formula is preferable from the viewpoint of acrylonitrile yield.
_{Mo 10 Bi a Fe b Ni c} D d E e G f H g O x · (SiO 2) y

  In the formula, Mo represents molybdenum, Bi represents bismuth, Fe represents iron, Ni represents nickel, O represents oxygen, D represents at least one element selected from the group consisting of cobalt, magnesium, manganese, and zinc, and E Represents at least one element selected from the group consisting of yttrium, lanthanum, cerium, praseodymium, neodymium, and samarium, and G represents niobium, tungsten, antimony, aluminum, boron, phosphorus, chromium, lead, cadmium, and calcium. H represents at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, and thallium.

  Further, the subscripts a to g, x, and y in the formula represent an atomic ratio. a satisfies 0.1 ≦ a ≦ 3, preferably 0.2 ≦ a ≦ 2.5. b satisfies 0.1 ≦ b ≦ 5, preferably 0.2 ≦ b ≦ 4. c satisfies 1 ≦ c ≦ 10, preferably 2 ≦ c ≦ 8. d satisfies 0 ≦ d ≦ 10, preferably 0.1 ≦ d ≦ 7. e satisfies 0 ≦ e ≦ 10, preferably 0.1 ≦ e ≦ 7. f satisfies 0 ≦ f ≦ 10, preferably 0 ≦ f ≦ 7. g satisfies 0.01 ≦ g ≦ 2, preferably 0.02 ≦ g ≦ 1.5. y satisfies 10 ≦ h ≦ 100, preferably 15 ≦ h ≦ 90. x is an oxygen atomic ratio necessary for satisfying the valence of each component, and is naturally determined according to the metal composition.

  The raw materials for preparing the catalyst include oxides of each element, or chlorides, sulfates, nitrates, ammonium salts, carbonates, hydroxides, organic acid salts, oxygen that can be converted to oxides when heated. Examples include acids, oxyacid salts, heteropolyacids, heteropolyacid salts, or mixtures thereof.

  Examples of the raw material for the molybdenum component include oxides such as molybdenum trioxide; molybdic acid such as molybdic acid, ammonium paramolybdate, and ammonium metamolybdate, or salts thereof; An acid or a salt thereof can be used.

  As a raw material of the bismuth component, for example, bismuth salts such as bismuth nitrate, bismuth carbonate, bismuth sulfate, and bismuth acetate; bismuth trioxide; metal bismuth and the like can be used. These raw materials can be used as a solid or as an aqueous solution, an aqueous nitric acid solution, or a slurry of a bismuth compound produced from the aqueous solution. Among these, it is preferable to use nitrate, a solution thereof, or a slurry generated from the solution.

  As a raw material of the iron component, for example, ferrous oxide, ferric oxide, ferrous nitrate, ferric nitrate, iron nitrate, iron chloride, iron organic acid salt, iron hydroxide and the like can be used. Alternatively, metal iron dissolved in heated nitric acid may be used. The solution containing the raw material of the iron component may be used after adjusting the pH with aqueous ammonia or the like. When pH is adjusted, precipitation of the iron component can be prevented by allowing a chelating agent to coexist in the solution containing the raw material of the iron component. Examples of chelating agents that can be used here include ethylenediaminetetraacetic acid, lactic acid, citric acid, tartaric acid, and gluconic acid. When preparing an aqueous solution containing iron ions and a chelating agent, it is preferable to use these raw materials by dissolving them in an acid or water.

As a raw material for the nickel component, for example, nickel hydroxide, nickel oxide, or nickel nitrate can be used.
As a raw material of the silica component, colloidal silica is preferable and can be appropriately selected from commercially available ones.
As raw materials for the other components, oxides, nitrates, carbonates, organic acid salts, hydroxides, and the like, which can be converted into oxides when ignited, or mixtures thereof are usually used.

The catalyst in the present invention is prepared by intimately mixing the raw materials of each component so as to have a desired composition.
First, a raw material of each component is added to colloidal silica or water in a solid or solution state, and these are mixed to prepare a slurry. PH adjustment, heat treatment, or homogenizer treatment can also be performed during the mixing step or at the completion of preparation. Here, the raw material of each component added to colloidal silica or water may be in a state in which some plural components are dissolved in water in advance, or in a state in which pH adjustment, heat treatment or homogenizer treatment has been performed. Alternatively, it may be dried, fired and pulverized.

  Subsequently, it is preferable to form the slurry thus prepared into substantially spherical particles by spray drying. At this time, a spray dryer such as a pressurized nozzle type, a two-fluid nozzle type, a rotary disk type, or the like is used. The slurry concentration applied to the spray dryer is preferably 10 to 50% by mass in terms of the oxide of the element constituting the catalyst.

  By firing the spray-dried product at a temperature in the range of 500 to 750 ° C., the desired catalytically active structure is formed. The firing time is not particularly limited, but if it is too short, a good catalyst cannot be obtained. Therefore, it is preferable to fire for at least one hour. There is no restriction | limiting in particular also about the method of baking, A general purpose baking furnace can be used, Especially, a rotary kiln, a fluidized baking furnace, etc. are used especially preferable. The gas atmosphere used here may be an oxidizing gas atmosphere containing oxygen or an inert gas atmosphere such as nitrogen, but it is convenient to use air. In this firing, the dried product may be immediately fired at a temperature in the range of 500 to 750 ° C., and once at a temperature of about 250 to 400 ° C. and / or a temperature of about 400 to 500 ° C. for 1 to 2 steps. After the preliminary firing, firing at a temperature in the range of 500 to 750 ° C. may be performed.

<Method for producing acrylonitrile>
Acrylonitrile uses a manufacturing apparatus comprising a reactor provided with a fluidized bed of the catalyst thus prepared, and a cyclone that separates the gas and catalyst from the reactor and returns the catalyst to the fluidized bed. It is produced by reacting propylene with molecular oxygen and ammonia in the presence of a catalyst.

  FIG. 1 is a longitudinal sectional view showing an example of a manufacturing apparatus. This manufacturing apparatus is mainly composed of a reactor 2 having a fluidized bed 1 therein. In the reactor 2, a raw material gas sparger 3 for supplying propylene, molecular oxygen and ammonia, a gas containing acrylonitrile as a reaction product, and a cyclone 4 for separating the catalyst are provided.

  The raw material gas sparger 3 has a nozzle 5 provided at the bottom of the reactor 2 and opened toward the bottom of the reactor 2. The nozzle 5 is composed of a nozzle hole 6 having a smaller diameter in the back and a shroud (short tube) outside the nozzle hole 6. As shown in FIG. 2, the raw material gas 7 such as propylene is ejected from the nozzle 5 toward the bottom surface of the reactor 2 at a high speed, and then rises and circulates in the reactor 2. In addition, a plurality of nozzles 5 are provided, whereby the gas supplied from one pipe is branched (dispersed) and supplied into the reactor 2. The structure of the raw material gas sparger is not limited to that shown in the figure, and the design can be changed as appropriate. For example, the material gas may be supplied independently for each nozzle 5. The location where the nozzle is formed can also be designed as appropriate.

  After the start of the reaction, the reactor 2 is in a state where the gas containing acrylonitrile and the catalyst are mixed. These mixtures flowing into the inlet 8 of the cyclone 4 are separated into a gas containing acrylonitrile and a catalyst while rotating at high speed in the cyclone 4. The separated gas containing acrylonitrile is discharged from the gas outflow pipe 9 of the cyclone 4 to the outside of the reactor 2, and the catalyst is returned to the fluidized bed 1 through the catalyst return pipe 10 (dipleg). In the catalyst return pipe 10, oxygen or air is purged.

  The inventors of the present invention have determined that the generation rate of the α-type divalent metal molybdate crystal phase is based on the physical impact force and the collision in the collision between the catalyst particle and the catalyst particle, and the collision between the catalyst particle and each device of the production apparatus. Estimated to depend on frequency. The main factors that specifically apply include the gas linear velocity at the inlet of the cyclone, the amount of catalyst circulation between the reactor main body and the cyclone, and the gas ejected from the nozzle hole of the raw material gas sparger and the catalyst come into contact with each other. The linear velocity of the part is mentioned, and the amount of catalyst circulation between the reactor main body and the cyclone is particularly important.

  The catalyst circulation amount per hour between the reactor and the cyclone is in the range of 500 to 3000% by mass of the total catalyst amount (100% by mass), and more preferably in the range of 1000 to 2500% by mass. When acrylonitrile is produced under conditions where the catalyst circulation rate exceeds the upper limit of the specified range, the amount of α-type divalent metal molybdate crystal phase produced increases and the acrylonitrile yield decreases significantly. When the catalyst circulation amount is less than the lower limit of the specified range, carbon monoxide as a by-product increases.

  In the present invention, the amount of catalyst circulation per hour between the reactor and the cyclone is the temperature per hour of the gas containing the catalyst passing through the cyclone inlet under the temperature and pressure near the cyclone inlet. The product of the flow rate and the catalyst density in the gas is the mass percent value divided by the total amount of catalyst in the reactor. The catalyst density in the gas is determined by collecting the gas near the inlet of the cyclone and measuring the amount of gas and the mass of the catalyst contained therein. When there are a plurality of inlets, the sum of the flow rates at all the inlets (total flow rate) is obtained. Further, when a plurality of cyclones are provided in series, the catalyst circulation amount in the most upstream cyclone (closest to the reactor) (first cyclone) is obtained.

  The gas linear velocity at the inlet of the cyclone is preferably in the range of 3 to 40 m / s, and more preferably in the range of 10 to 30 m / s. When acrylonitrile is produced under conditions where the gas linear velocity exceeds the upper limit of the specified range, the amount of α-type divalent metal molybdate crystal phase produced increases, and the acrylonitrile yield may decrease. In addition, the wear of the catalyst may increase significantly. When the gas linear velocity at the inlet of the cyclone is less than the lower limit of the specified range, there is a possibility that fluidity may be poor or the production amount must be restricted.

  In the present invention, the gas linear velocity at the cyclone inlet is the flow rate per second of the gas containing the catalyst passing through the cyclone inlet under the temperature and pressure near the cyclone inlet. The value divided by the cross-sectional area. When there are a plurality of inlets, the sum of the flow rates of all the inlets (total flow rate) and the sum of the cross-sectional areas (total cross-sectional area) are obtained. When a plurality of cyclones are provided in series, the gas linear velocity at the inlet in the most upstream cyclone (closest to the reactor) (first cyclone) is obtained.

  The linear velocity of the portion where the gas ejected from the nozzle hole of the raw material gas sparger and the catalyst are in contact is preferably 3 to 100 m / s, and more preferably 10 to 80 m / s. When acrylonitrile is produced under conditions where the linear velocity exceeds the upper limit of the specified range, the amount of α-type divalent metal molybdate crystal phase produced increases, and the acrylonitrile yield may decrease. Also, catalyst wear may increase significantly. If the linear velocity of the part where the gas jetted from the nozzle hole of the raw material gas sparger contacts the catalyst is less than the lower limit of the specified range, the fluidity may be poor or the production volume may be restricted. There is.

The linear velocity of the part where the gas jetted from the nozzle hole of the raw gas sparger contacts the catalyst is the same as the flow rate of raw gas per second jetted from the nozzle hole under the temperature and pressure immediately after jetting, and the shroud of all nozzles The value divided by the sum of the cross-sectional areas.
The source gas may be, for example, air, propylene, ammonia, or the like ejected from nozzles of separate source gas spargers, but the respective linear velocities need to be within a specified range.

  The concentration of propylene in the raw material gas can be varied within a wide range, 1 to 20% by volume is appropriate, and 3 to 15% by volume is particularly preferable. Methanol or other organic gases can also be added at once or in portions. As an oxygen source, air is preferably used for economic reasons, but air may be appropriately enriched with oxygen. The molar ratio of propylene to oxygen in the raw material gas is preferably 1: 1.5 to 1: 3, and the molar ratio of propylene to ammonia is preferably 1: 1 to 1: 1.5. Moreover, you may supply inert gas, for example, nitrogen, water vapor | steam etc. as needed. The reaction pressure is from normal pressure to several atmospheres. The reaction temperature is preferably in the range of 400 to 500 ° C.

The α-type divalent metal molybdate crystal phase referred to in the present invention is an α-CoMoO ₄ type crystal (molybdenum oxygen ion coordination is 6-coordinate, and divalent metal oxygen ion coordination is 6-coordinate). Point to. The β-type divalent metal molybdate crystal phase indicates α-MnMoO ₄ type crystal (molybdenum oxygen ion coordination is 4-coordinate and divalent metal oxygen ion coordination is 6-coordinate).

  FIG. 4 shows an example of powder X-ray diffraction measurement of the catalyst. (A) is a diffraction line before the start of acrylonitrile production, after about 5000 hours have passed since the production of acrylonitrile was started. In (a), an α-type divalent metal molybdate crystal phase is generated by impact during use. Among the divalent metal molybdate crystal phases, X-ray diffraction peaks derived from α-type and β-type appear at d values near 6.3 A and 6.8 A, respectively. According to the PDF-2 database of the powder X-ray diffraction method, a slight diffraction peak appears in the β-type divalent metal molybdate crystal phase even in the vicinity of the d value of 6.3A. Confirms that the diffraction peak does not appear as shown in FIG. 4B when only β-type is present.

For the powder X-ray diffraction measurement in the present invention, “RINT1100” manufactured by Rigaku Corporation, which is a powder X-ray diffractometer, is used. Tube: Cu, tube voltage: 40 mV, tube current: 40 mA, divergence slit: 1 °, scattering Slit: 1 °, light receiving slit: 0.15 mm, use of monochromator, monochrome light receiving slit: 0.8 mm, step width: 0.02 °, counting time: 4 sec.
In the measurement by the usual powder X-ray diffraction method, a sample is pulverized, and this is molded and used for measurement. In the present invention, an impact is applied to the catalyst during pulverization, and a β-type divalent metal molybdate crystal phase is formed. Since it is rearranged to α-type at a considerable rate and accurate evaluation cannot be performed, the measurement is performed without carrying out pulverization.

  In the method for producing acrylonitrile of the present invention described above, the amount of catalyst circulation per hour between the reactor and the cyclone is in the range of 500 to 3000% by mass of the total catalyst amount (100% by mass). , While suppressing the generation of carbon monoxide as a by-product and suppressing the formation of α-type divalent metal molybdate crystal phase over a long period of time, resulting in a high acrylonitrile yield in the initial stage of the reaction and Thus, acrylonitrile can be stably produced over a long period of time by suppressing a decrease in acrylonitrile yield.

EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to these Examples.
The conversion rate of propylene, the yield of acrylonitrile, the selectivity of acrylonitrile, and the yield of carbon monoxide in this example are defined as follows.
Propylene conversion rate (%) = Q / P × 100
Acrylonitrile yield (%) = R / P × 100
Selectivity of acrylonitrile (%) = R / Q × 100
Carbon monoxide yield (%) = S / P × 100
Here, P is the number of moles of propylene supplied, Q is the number of moles of propylene reacted, R is the number of moles of acrylonitrile produced, and S is the number of moles of carbon monoxide produced. The analysis of the reaction product gas can be performed by gas chromatography.

[Example 1]
An oxide composition (catalyst) having an empirical formula represented by Mo ₁₀ Bi _0.5 Fe _4.3 Ni ₆ Cr _0.4 Ce _0.4 Sb _3.5 P _0.2 B _0.2 K _0.2 O _53.75 (SiO ₂ ) ₄₀ was prepared as follows.
(Preparation of slurry (A))
139 parts by mass of electrolytic iron powder was gradually added to 2050 parts by mass of a 32% by mass nitric acid aqueous solution and dissolved. 800 parts by mass of antimony trioxide powder was added to the iron nitric acid solution, and the slurry was heated at 100 ° C. for 2 hours with good stirring. After cooling the slurry to 50 ° C., 19.5 parts by mass of boric acid and then 41.3 parts by mass of a 75% by mass phosphoric acid aqueous solution were added with stirring. This was spray dried using a rotary disk spray dryer while controlling the inlet temperature at 320 ° C. and the outlet temperature at 160 ° C. The obtained particles were heat-treated at 250 ° C. and further calcined at 950 ° C. for 3 hours. 152 parts by mass were collected from the calcined particles, 380 parts of pure water was added thereto, and pulverized with an attritor until the average particle size became 1.2 μm to obtain slurry (A).

(Preparation of slurry (B))
In 1200 parts by mass of pure water, 327 parts by mass of ammonium paramolybdate was dissolved at 40 ° C., and 325 parts by mass of nickel nitrate, 74.0 parts by mass of a 40% by mass aqueous second chromium nitrate solution and 3.7 parts by mass of potassium nitrate were added to this solution. Part, 30.0 parts by mass of citric acid, and 36.3 parts by mass of bismuth nitrate in 320 parts by mass of 3% by mass nitric acid aqueous solution were added with stirring. Next, a solution prepared by dissolving 32.3 parts by mass of cerous nitrate in 100 parts by mass of pure water was added to this while stirring. Next, 2190 parts by mass of 20% by mass colloidal silica was added to this while stirring. Next, 82.0 parts by mass of ferric nitrate and 30.0 parts by mass of citric acid dissolved in 320 parts by mass of pure water were added to this while stirring. The slurry was adjusted to pH 2.2 (40 ° C.) with 15% by mass aqueous ammonia and heat-treated at 99 ° C. for 1.5 hours. This was designated as slurry (B).

(Preparation of catalyst)
After the temperature of the slurry (B) was lowered to 50 ° C., 380 parts by mass of the slurry (A) was added with stirring, and a homogenizer treatment was performed to complete the slurry. The pH of the finished slurry was 1.7 (40 ° C.). Thereafter, this slurry was spray-dried using a rotary disk type spray dryer. The obtained particles were heat-treated at 250 ° C. and further calcined at 640 ° C. for 3 hours to obtain a catalyst.

(Manufacture of acrylonitrile)
A reaction tower having a tower diameter of 0.20 m and a height of 9 m was used as a reactor. Propylene, ammonia, and air were supplied separately through raw gas spargers.
The following conditions are reaction conditions after the reaction reaches a steady state. The gas linear velocity at the inlet of the cyclone is 22 m / s, and the linear velocity at the portion where the gas ejected from the nozzle hole of the raw material gas sparger contacts the catalyst is 32 m / s (propylene, ammonia) and 25 m / s (air). The catalyst circulation amount per hour between the reactor and the cyclone was 800% by mass of the total catalyst amount (100% by mass).

Propylene, ammonia and air were supplied at a ratio of 1 / 1.2 / 11 (molar ratio). The reaction temperature was 440 ° C. and the reaction pressure was 200 kPa. Further, molybdenum trioxide corresponding to the empirical formula Mo _{0.02 with} respect to the catalyst amount was added every 100 hours.
Propylene conversion, acrylonitrile yield, acrylonitrile selectivity, and carbon monoxide yield were measured every 20 to 28 hours after the start of the reaction. The results are extracted every 1000 hours and shown in Table 1.

  The acrylonitrile yield at the time of reaching the steady reaction conditions was 80.3%, the acrylonitrile selectivity was 82.1%, and the carbon monoxide yield was 3.2%. After 1000 hours from the start of operation, the acrylonitrile yield was stable at around 79.8%, the acrylonitrile selectivity was around 81.8%, and the carbon monoxide yield was around 3.1%.

(Divalent metal molybdate crystal phase in catalyst)
The powder X-ray diffraction measurement result of the catalyst is shown in FIG. (A) is the diffraction line before the start of acrylonitrile production, after about 3000 hours have passed since the production of acrylonitrile was started. From the diffraction line of (a), it can be seen that the impact received by the catalyst is well controlled and the production of α-type divalent metal molybdate crystal phase is small.

[Example 2]
Using the catalyst of Example 1, acrylonitrile was produced.
(Manufacture of acrylonitrile)
A reactor having a tower diameter of 0.25 m and a height of 16 m was used as a reactor. Propylene, ammonia, and air were supplied from a common feed gas sparger.
The following conditions are reaction conditions after the reaction reaches a steady state. The gas linear velocity at the inlet of the cyclone is 30 m / s, the linear velocity at the portion where the gas ejected from the nozzle hole of the raw material gas sparger and the catalyst are in contact is 22 m / s, and the hour between the reactor and the cyclone. The catalyst circulation amount was 2300% by mass of the total catalyst amount (100% by mass).

Propylene, ammonia and air were supplied at a ratio of 1 / 1.2 / 11 (molar ratio). The reaction temperature was 440 ° C. and the reaction pressure was 200 kPa. Further, molybdenum trioxide corresponding to the empirical formula Mo _{0.02 with} respect to the catalyst amount was added every 100 hours.
Propylene conversion, acrylonitrile yield, acrylonitrile selectivity, and carbon monoxide yield were measured every 20 to 28 hours after the start of the reaction. The results are extracted every 1000 hours and shown in Table 2.

  The acrylonitrile yield at the time of reaching steady reaction conditions was 80.5%, the acrylonitrile selectivity was 82.1%, and the carbon monoxide yield was 2.5%. After 1000 hours from the start of operation, the acrylonitrile yield was stable at around 80.0%, the acrylonitrile selectivity was around 82.1%, and the carbon monoxide yield was around 2.5%.

(Divalent metal molybdate crystal phase in catalyst)
The powder X-ray diffraction measurement result of the catalyst is shown in FIG. (A) is the diffraction line before the start of acrylonitrile production, after about 3000 hours have passed since the production of acrylonitrile was started. From the diffraction line of (a), it can be seen that the impact received by the catalyst is well controlled and the production of α-type divalent metal molybdate crystal phase is small.

[Comparative Example 1]
Using the catalyst of Example 1, acrylonitrile was produced.
(Manufacture of acrylonitrile)
The reaction tower of Example 1 was used as a reactor.
The following conditions are reaction conditions after the reaction reaches a steady state. The gas linear velocity at the inlet of the cyclone is 30 m / s, and the linear velocity at the portion where the gas ejected from the nozzle hole of the raw material gas sparger contacts the catalyst is 44 m / s (propylene, ammonia) and 34 m / s (air). The catalyst circulation amount per hour between the reactor and the cyclone was 3500% by mass of the total catalyst amount (100% by mass).

Propylene, ammonia and air were supplied at a ratio of 1 / 1.2 / 11 (molar ratio). The reaction temperature was 440 ° C. and the reaction pressure was 200 kPa. Further, molybdenum trioxide corresponding to the empirical formula Mo _{0.02 with} respect to the catalyst amount was added every 100 hours.
Propylene conversion, acrylonitrile yield, acrylonitrile selectivity, and carbon monoxide yield were measured every 20 to 28 hours after the start of the reaction. The results are extracted every 1000 hours and shown in Table 3.

  The acrylonitrile yield at the time of reaching the steady reaction conditions was 80.3%, the acrylonitrile selectivity was 81.8%, and the carbon monoxide yield was 2.5%. However, these values gradually decreased, and the acrylonitrile yield was 78.3%, the acrylonitrile selectivity was 80.1%, and the carbon monoxide yield was 4.0% at the start of operation for 3000 hours.

(Divalent metal molybdate crystal phase in catalyst)
The powder X-ray diffraction measurement result of the catalyst is shown in FIG. (A) is the diffraction line before the start of acrylonitrile production, after about 3000 hours have passed since the production of acrylonitrile was started. From the diffraction line (a), it can be seen that the α-type divalent metal molybdate crystal phase is remarkably generated by the impact during use.

[Example 3]
An oxide composition (catalyst) having an empirical formula represented by Mo ₁₀ Bi _0.4 Fe _1.5 Ni _4.3 Mg _1.5 Mn _0.2 La _0.5 K _0.1 Rb _0.1 O _39.7 (SiO ₂ ) ₄₀ was prepared as follows.
(Preparation of slurry (C))
399 parts by mass of a 17% by mass nitric acid aqueous solution, 277 parts by mass of nickel nitrate, 85.0 parts by mass of magnesium nitrate, 12.6 parts by mass of manganese nitrate, 47.6 parts by mass of lanthanum nitrate, 133 parts by mass of ferric nitrate, 2 parts of potassium nitrate 0.2 parts by mass, 3.3 parts by mass of rubidium nitrate, and 43.1 parts by mass of bismuth nitrate were added in order to obtain slurry (C).

(Preparation of slurry (D))
2600 parts by mass of 20 mass% colloidal silica was mixed with stirring at 40 ° C., and 388 parts by mass of ammonium paramolybdate dissolved in 780 parts by mass of pure water was added to the slurry with stirring. Got.

(Preparation of catalyst)
Then, the slurry (C) was added to the slurry (D) while stirring, and a homogenizer treatment was performed to complete the slurry. The pH of the finished slurry was 0.9 (40 ° C.). Thereafter, this slurry was spray-dried using a rotary disk type spray dryer. The obtained particles were heat-treated at 250 ° C. and further calcined at 590 ° C. for 3 hours to obtain a catalyst.

(Manufacture of acrylonitrile)
The reaction tower of Example 2 was used as a reactor.
The following conditions are reaction conditions after the reaction reaches a steady state. The gas linear velocity at the inlet of the cyclone is 18 m / s, the linear velocity at the portion where the gas ejected from the nozzle hole of the raw gas sparger and the catalyst are in contact is 12 m / s, per hour between the reactor and the cyclone. The catalyst circulation amount was 700% by mass of the total catalyst amount (100% by mass).

Propylene, ammonia and air were supplied at a ratio of 1 / 1.2 / 11 (molar ratio). The reaction temperature was 440 ° C. and the reaction pressure was 200 kPa. Further, molybdenum trioxide corresponding to the empirical formula Mo _{0.02 with} respect to the catalyst amount was added every 100 hours.
Propylene conversion, acrylonitrile yield, acrylonitrile selectivity, and carbon monoxide yield were measured every 20 to 28 hours after the start of the reaction. The results are extracted every 1000 hours and shown in Table 4.

  The acrylonitrile yield at the time of reaching steady reaction conditions was 81.0%, the acrylonitrile selectivity was 82.6%, and the carbon monoxide yield was 2.8%. After 1000 hours from the start of operation, the acrylonitrile yield was stable at around 80.7%, the acrylonitrile selectivity was around 82.3%, and the carbon monoxide yield was around 2.7%.

(Divalent metal molybdate crystal phase in catalyst)
The powder X-ray diffraction measurement results of the catalyst are shown in FIG. (A) is the diffraction line before the start of acrylonitrile production, after about 3000 hours have passed since the production of acrylonitrile was started. From the diffraction line of (a), it can be seen that the impact received by the catalyst is well controlled and the production of α-type divalent metal molybdate crystal phase is small.

[Example 4]
Using the catalyst of Example 3, acrylonitrile was produced.
(Manufacture of acrylonitrile)
The reaction tower of Example 1 was used as a reactor.
The following conditions are reaction conditions after the reaction reaches a steady state. The gas linear velocity at the inlet of the cyclone is 27 m / s, and the linear velocity at the portion where the gas ejected from the nozzle hole of the raw material gas sparger contacts the catalyst is 40 m / s (propylene, ammonia) and 30 m / s (air). The catalyst circulation amount per hour between the reactor and the cyclone was 2700% by mass of the total catalyst amount (100% by mass).

Propylene, ammonia and air were supplied at a ratio of 1 / 1.2 / 11 (molar ratio). The reaction temperature was 440 ° C. and the reaction pressure was 200 kPa. Further, molybdenum trioxide corresponding to the empirical formula Mo _{0.02 with} respect to the catalyst amount was added every 100 hours.
Propylene conversion, acrylonitrile yield, acrylonitrile selectivity, and carbon monoxide yield were measured every 20 to 28 hours after the start of the reaction. The results are extracted every 1000 hours and shown in Table 5.

  The acrylonitrile yield at the time of reaching steady reaction conditions was 81.5%, the acrylonitrile selectivity was 83.2%, and the carbon monoxide yield was 2.2%. After 1000 hours from the start of operation, the acrylonitrile yield was stable at around 80.9%, the acrylonitrile selectivity was around 82.7%, and the carbon monoxide yield was around 2.3%.

(Divalent metal molybdate crystal phase in catalyst)
The powder X-ray diffraction measurement result of the catalyst is shown in FIG. (A) is the diffraction line before the start of acrylonitrile production, after about 3000 hours have passed since the production of acrylonitrile was started. From the diffraction line of (a), it can be seen that the impact received by the catalyst is well controlled and the production of α-type divalent metal molybdate crystal phase is small.

[Comparative Example 2]
Using the catalyst of Example 4, acrylonitrile was produced.
(Manufacture of acrylonitrile)
The reaction tower of Example 1 was used as a reactor.
The following conditions are reaction conditions after the reaction reaches a steady state. The gas linear velocity at the inlet of the cyclone is 17 m / s, and the linear velocity at the portion where the gas ejected from the nozzle hole of the raw material gas sparger contacts the catalyst is 24 m / s (propylene, ammonia) and 19 m / s (air). The catalyst circulation amount per hour between the reactor and the cyclone was 400% by mass of the total catalyst amount (100% by mass).

Propylene, ammonia and air were supplied at a ratio of 1 / 1.2 / 11 (molar ratio). The reaction temperature was 440 ° C. and the reaction pressure was 200 kPa. Further, molybdenum trioxide corresponding to the empirical formula Mo _{0.02 with} respect to the catalyst amount was added every 100 hours.
Propylene conversion, acrylonitrile yield, acrylonitrile selectivity, and carbon monoxide yield were measured every 20 to 28 hours after the start of the reaction. The results are extracted every 1000 hours and shown in Table 6.

  The acrylonitrile yield at the time of reaching steady reaction conditions was 79.8%, the acrylonitrile selectivity was 81.4%, and the carbon monoxide yield was 3.9%. 1000 hours after the start of operation, the acrylonitrile yield was 79.6%, the acrylonitrile selectivity was 81.4%, and the carbon monoxide yield was as high as 3.7%.

(Divalent metal molybdate crystal phase in catalyst)
The powder X-ray diffraction measurement result of the catalyst is shown in FIG. (A) is the diffraction line before the start of acrylonitrile production, after about 1000 hours have passed since the production of acrylonitrile was started. From the diffraction line (a), it can be seen that the impact during use is slight, and the formation of the α-type divalent metal molybdate crystal phase is also slight.

[Example 5]
An oxide composition (catalyst) having an empirical formula represented by Mo ₁₀ Bi _0.4 Fe _1.3 Ni ₄ Mg ₂ Cr _0.4 Ce _0.6 K _0.15 Cs _0.05 O _40.15 (SiO ₂ ) ₄₀ was prepared as follows.
(Preparation of slurry (E))
17 mass% nitric acid aqueous solution 398 mass parts, nickel nitrate 257 mass parts, magnesium nitrate 113 mass parts, 40 mass% ferric nitrate aqueous solution 87.5 mass parts, cerous nitrate 57.3 mass parts, ferric nitrate 114 parts by mass, potassium nitrate 3.3 parts by mass, rubidium nitrate 2.1 parts by mass, and bismuth nitrate 42.9 parts by mass were sequentially added to obtain a slurry (E).

(Preparation of slurry (F))
2590 parts by mass of 20% by mass colloidal silica was mixed with stirring at 40 ° C., and 387 parts by mass of ammonium paramolybdate dissolved in 778 parts by mass of pure water was added to the slurry with stirring. Got.

(Preparation of catalyst)
Then, the slurry (E) was added to the slurry (F) with stirring, and a homogenizer treatment was performed to complete the slurry. The pH of the finished slurry was 0.9 (40 ° C.). Thereafter, this slurry was spray-dried using a rotary disk type spray dryer. The obtained particles were heat-treated at 250 ° C. and further calcined at 580 ° C. for 3 hours to obtain a catalyst.

(Manufacture of acrylonitrile)
The reaction tower of Example 2 was used as a reactor.
The following conditions are reaction conditions after the reaction reaches a steady state. The gas linear velocity at the inlet of the cyclone is 25 m / s, the linear velocity of the portion where the gas ejected from the nozzle hole of the raw gas sparger and the catalyst are in contact is 18 m / s, and the hour between the reactor and the cyclone. The catalyst circulation amount was 1200% by mass of the total catalyst amount (100% by mass).

Propylene, ammonia and air were supplied at a ratio of 1 / 1.2 / 11 (molar ratio). The reaction temperature was 440 ° C. and the reaction pressure was 200 kPa. Further, molybdenum trioxide corresponding to the empirical formula Mo _{0.02 with} respect to the catalyst amount was added every 100 hours.
Propylene conversion, acrylonitrile yield, acrylonitrile selectivity, and carbon monoxide yield were measured every 20 to 28 hours after the start of the reaction. The results are extracted every 1000 hours and shown in Table 7.

  The acrylonitrile yield at the time of reaching steady reaction conditions was 82.2%, the acrylonitrile selectivity was 84.0%, and the carbon monoxide yield was 2.0%. After 1000 hours from the start of operation, the acrylonitrile yield was stable at around 81.7%, the acrylonitrile selectivity was around 83.5%, and the carbon monoxide yield was around 1.9%.

(Divalent metal molybdate crystal phase in catalyst)
The powder X-ray diffraction measurement result of the catalyst is shown in FIG. (A) is the diffraction line before the start of acrylonitrile production, after about 3000 hours have passed since the production of acrylonitrile was started. From the diffraction line of (a), it can be seen that the impact received by the catalyst is well controlled and the production of α-type divalent metal molybdate crystal phase is small.

[Comparative Example 3]
Using the catalyst of Example 5, acrylonitrile was produced.
(Manufacture of acrylonitrile)
The reaction tower of Example 2 was used as a reactor.
The following conditions are reaction conditions after the reaction reaches a steady state. The gas linear velocity at the inlet of the cyclone is 36 m / s, the linear velocity at the portion where the gas ejected from the nozzle hole of the raw gas sparger and the catalyst are in contact is 27 m / s, and the hour between the reactor and the cyclone. The catalyst circulation amount was 3300% by mass of the total catalyst amount (100% by mass).

Propylene, ammonia and air were supplied at a ratio of 1 / 1.2 / 11 (molar ratio). The reaction temperature was 440 ° C. and the reaction pressure was 200 kPa. Further, molybdenum trioxide corresponding to the empirical formula Mo _{0.02 with} respect to the catalyst amount was added every 100 hours.
Propylene conversion, acrylonitrile yield, acrylonitrile selectivity, and carbon monoxide yield were measured every 20 to 28 hours after the start of the reaction. The results are extracted every 1000 hours and shown in Table 8.

  The acrylonitrile yield at the time of reaching steady reaction conditions was 82.0%, the acrylonitrile selectivity was 83.5%, and the carbon monoxide yield was 2.1%. However, these values gradually decreased, and the acrylonitrile yield was 80.4%, the acrylonitrile selectivity was 82.3%, and the carbon monoxide yield was 3.4% at the start of operation for 3000 hours.

(Divalent metal molybdate crystal phase in catalyst)
The powder X-ray diffraction measurement result of the catalyst is shown in FIG. (A) is the diffraction line before the start of acrylonitrile production, after about 3000 hours have passed since the production of acrylonitrile was started. From the diffraction line (a), it can be seen that the α-type divalent metal molybdate crystal phase is remarkably generated by the impact during use.

[Comparative Example 4]
Using the catalyst of Example 5, acrylonitrile was produced.
(Manufacture of acrylonitrile)
The reaction tower of Example 2 was used as a reactor.
The following conditions are reaction conditions after the reaction reaches a steady state. The gas linear velocity at the inlet of the cyclone is 13 m / s, the linear velocity at the portion where the gas ejected from the nozzle hole of the raw gas sparger and the catalyst are in contact is 8 m / s, and the hour between the reactor and the cyclone. The catalyst circulation amount was set to 200% by mass of the total catalyst amount (100% by mass).

Propylene, ammonia and air were supplied at a ratio of 1 / 1.2 / 11 (molar ratio). The reaction temperature was 440 ° C. and the reaction pressure was 200 kPa. Further, molybdenum trioxide corresponding to the empirical formula Mo _{0.02 with} respect to the catalyst amount was added every 100 hours.
Propylene conversion, acrylonitrile yield, acrylonitrile selectivity, and carbon monoxide yield were measured every 20 to 28 hours after the start of the reaction. The results are extracted every 1000 hours and shown in Table 9.

  The acrylonitrile yield at the time of reaching the steady reaction conditions was 79.8%, the acrylonitrile selectivity was 81.4%, and the carbon monoxide yield was 4.2%. At 1000 hours from the start of operation, the acrylonitrile yield was 79.7%, the acrylonitrile selectivity was 81.3%, and the carbon monoxide yield was as high as 4.1%.

(Divalent metal molybdate crystal phase in catalyst)
The powder X-ray diffraction measurement result of the catalyst is shown in FIG. (A) is the diffraction line before the start of acrylonitrile production, after about 1000 hours have passed since the production of acrylonitrile was started. From the diffraction line (a), it can be seen that the impact during use is slight, and the formation of the α-type divalent metal molybdate crystal phase is also slight.

  By employing the technique of the present invention, acrylonitrile can be produced stably with a high yield of acrylonitrile and a small decrease in acrylonitrile yield over time and stable over a long period of time.

It is a longitudinal cross-sectional view which shows an example of the manufacturing apparatus of acrylonitrile. It is sectional drawing which shows an example of the nozzle hole of a raw material gas sparger. It is a perspective view which shows an example of a cyclone. It is a figure which shows the powder X-ray-diffraction measurement result of a catalyst, (a) is a diffraction line before the start of acrylonitrile manufacture, after (a) starting manufacture of acrylonitrile about 5000 hours progress. It is a figure which shows the powder X-ray-diffraction measurement result of the catalyst in Example 1, (a) is a diffraction line before the start of acrylonitrile manufacture, after (a) started manufacture of acrylonitrile about 3000 hours progress. It is a figure which shows the powder X-ray-diffraction measurement result of the catalyst in Example 2, (a) is a diffraction line before the start of acrylonitrile manufacture, (a) after manufacture of acrylonitrile starts about 3000 hours. It is a figure which shows the powder X-ray-diffraction measurement result of the catalyst in the comparative example 1, (a) is the diffraction line before the start of acrylonitrile manufacture, after (a) started manufacture of acrylonitrile and about 3000 hours passed. It is a figure which shows the powder X-ray-diffraction measurement result of the catalyst in Example 3, (a) is the diffraction line before the start of acrylonitrile manufacture, after (a) started manufacture of acrylonitrile and about 3000 hours passed. It is a figure which shows the powder X-ray-diffraction measurement result of the catalyst in Example 4, (a) is a diffraction line before the start of acrylonitrile manufacture, after (a) started manufacture of acrylonitrile and about 3000 hours passed. It is a figure which shows the powder X-ray-diffraction measurement result of the catalyst in the comparative example 2, (a) is a diffraction line before the start of acrylonitrile manufacture, after (a) started manufacture of acrylonitrile and about 1000 hours passed. It is a figure which shows the powder X-ray-diffraction measurement result of the catalyst in Example 5, (a) is the diffraction line before the start of acrylonitrile manufacture, (a) after the start of manufacture of acrylonitrile and about 3000 hours progress. It is a figure which shows the powder X-ray-diffraction measurement result of the catalyst in the comparative example 3, (a) is the diffraction line before the start of acrylonitrile manufacture, (a) after the manufacture of acrylonitrile starts about 3000 hours. It is a figure which shows the powder X-ray-diffraction measurement result of the catalyst in the comparative example 4, (a) is a diffraction line before the start of acrylonitrile manufacture, after (a) started manufacture of acrylonitrile about 1000 hours progress.

Explanation of symbols

1 Fluidized bed 2 Reactor 4 Cyclone

Claims (1)

A reactor provided with a fluidized bed of a catalyst containing molybdenum, bismuth, iron, nickel, and silica as essential components; a cyclone that separates the gas and the catalyst from the reactor and returns the catalyst to the fluidized bed; In a method for producing acrylonitrile by reacting propylene with molecular oxygen and ammonia in the presence of a catalyst using a production apparatus comprising:
A method for producing acrylonitrile, wherein the amount of catalyst circulation per hour between the reactor and the cyclone is in the range of 500 to 3000% by mass of the total catalyst amount (100% by mass).

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