JP2004313869A - Method for manufacturing catalyst for synthesizing acrylonitrile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a catalyst capable of achieving a particularly high yield of acrilonitrile when propylene is subjected to gas contact ammoxidation. <P>SOLUTION: This method for manufacturing the catalyst for synthesizing the acrylonitrile has a process of preparing an aqueous slurry composed of a liquid phase and a solid phase containing at least molybdenum, bismuth, iron and silica, a process of drying the aqueous slurry, and a process of firing the obtained dry matter, 75 to 95 mol% of the molybdenum, 80 to 100 mol% of the bismuth and 40 to 80 mol% of the iron in the aqueous slurry exist in the solid phase. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a catalyst used for synthesizing acrylonitrile by subjecting propylene to gas phase catalytic ammoxidation with molecular oxygen and ammonia.
[0002]
[Prior art]
Many proposals have been made on catalysts used for synthesizing acrylonitrile by gas phase catalytic ammoxidation of propylene.
For example, Patent Documents 1 to 6 disclose catalysts containing molybdenum and bismuth as main components. Further, Patent Document 7 discloses a method for producing a catalyst for synthesizing acrylonitrile containing molybdenum, bismuth, iron and sodium, in which the solid content concentration in the prepared slurry is 40% by mass or less.
[0003]
[Patent Document 1]
JP-B-61-13701
[Patent Document 2]
JP-A-59-204163
[Patent Document 3]
JP-A-1-228950
[Patent Document 4]
JP-A-10-43595
[Patent Document 5]
JP-A-10-156185
[Patent Document 6]
U.S. Pat. No. 5,688,739
[Patent Document 7]
JP-A-50-125984
[0004]
[Problems to be solved by the invention]
However, Patent Documents 1 to 6 mainly relate to the constituent elements of the catalyst and the composition ratio thereof, and hardly mention the details of the catalyst production method, for example, the state of a slurry prepared in the catalyst production process. . On the other hand, Patent Document 7 discloses that the solid content concentration in the prepared slurry is controlled to a specific range, but the yield of acrylonitrile can be increased even by using a catalyst produced by such a method. It was still inadequate and further improvement was needed from an industrial point of view.
[0005]
The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a method for producing a catalyst capable of achieving a particularly high acrylonitrile yield when propylene is subjected to gas phase catalytic ammoxidation.
[0006]
[Means for Solving the Problems]
The method for producing a catalyst for acrylonitrile synthesis of the present invention comprises a step of preparing an aqueous slurry comprising at least molybdenum, bismuth, iron, and silica and comprising a liquid phase and a solid phase, and drying the aqueous slurry. And a step of calcining the obtained dried product, wherein 75 to 95 mol% of molybdenum in the aqueous slurry, 80 to 100 mol% of bismuth, and iron in the aqueous slurry. Of these, 40 to 80 mol% is characterized by being present in a solid phase.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
In the method for producing a catalyst for acrylonitrile synthesis of the present invention, first, at least molybdenum, bismuth, iron, and silica, the aqueous slurry in a state where the precipitated particles as a solid phase are dispersed in a liquid phase of an aqueous solution. Here, the aqueous slurry is prepared such that 75 to 95 mol% of molybdenum, 80 to 100 mol% of bismuth, and 40 to 80 mol% of iron are present in the solid phase.
[0008]
That is, in the aqueous slurry, 25 to 5 mol% of all molybdenum and 60 to 20 mol% of all iron are present in an aqueous solution (liquid phase) in the form of ions or fine colloid particles, The remainder of molybdenum and iron is insolubilized and exists in a state of being incorporated into precipitated particles (solid phase). As for bismuth, 20 mol% or less of all bismuth is present in a liquid phase, and the rest is present in a state in which it is incorporated in a solid phase, or in a state where all bismuth is incorporated in a solid phase. ing.
[0009]
Here, the liquid phase and the solid phase in the aqueous slurry are defined as follows in the present invention.
That is, when the aqueous slurry is centrifuged, and then the supernatant liquid is subjected to ultrafiltration with a filter having a mesh size of 1 μm, the liquid passing through this filter (filtrate) is defined as a liquid phase. On the other hand, those precipitated by centrifugation (sediment) and those that did not pass through the filter in the subsequent ultrafiltration (filtration residue) are defined as solid phases.
However, the moisture adhering to the sediment and the filtration residue in a wet form is regarded as a liquid phase (adhesion liquid phase), and the amount of the adhesion liquid phase is determined by drying the sediment and the filtration residue at 100 ° C. for 18 hours. The mass that has been reduced at that time is regarded as the amount. The composition of the attached liquid phase is considered to be the same as the composition of the filtrate obtained by ultrafiltration. In addition, for example, colloid particles of about several tens nm that do not settle even when centrifuged and are suspended are included in the filtrate obtained by ultrafiltration with a filter having an aperture of 1 μm, and thus are defined as a liquid phase. I do.
[0010]
If at least one of molybdenum, bismuth, and iron does not exist in the solid phase in the aqueous slurry at a molar ratio satisfying the above range, a catalyst obtained by drying and calcining the aqueous slurry is used. Propylene ammoxidation does not provide a sufficient acrylonitrile yield.
The determination of molybdenum, bismuth, and iron in the liquid phase and the solid phase can be performed by, for example, ICP emission spectroscopy.
[0011]
As a method for preparing the aqueous slurry, an aqueous slurry containing 75 to 95 mol% of molybdenum, 80 to 100 mol% of bismuth, and 40 to 80 mol% of iron in a solid phase in the aqueous slurry is used. There is no particular limitation as long as it can be prepared, and at least a molybdenum raw material, a bismuth raw material, an iron raw material, and silica may be added to water. Preferably, first, a liquid containing at least molybdenum (liquid A) And a solution containing at least bismuth (solution B), and then a step of charging the solution A with the solution B is preferable. At this time, the liquid A more preferably contains silica in addition to molybdenum, and the liquid B more preferably contains iron in addition to bismuth.
[0012]
There is no particular limitation on the method of charging the liquid B to the liquid A, but in order to specifically control the abundance ratio of molybdenum, bismuth and iron in the liquid phase and solid phase in the obtained aqueous slurry as described above, It is preferable that the charging is completed promptly, and the charging time is 5 minutes or less, preferably 2 minutes or less, and more preferably 1 minute or less. Further, when the solution B is charged into the solution A, the charging operation may be performed while stirring the inside of the container containing the solution A. However, in the liquid phase and the solid phase of molybdenum, bismuth and iron in the aqueous slurry, In order to specifically control the abundance ratio as described above, the degree of stirring is preferably as small as possible, and a method in which stirring is performed with little or no stirring is particularly preferable. However, it is preferable to stir the mixture after the addition of the solution B to the solution A.
[0013]
The liquid temperature at the time of preparing the aqueous slurry is not particularly limited, but is preferably maintained at 70 ° C. or lower, more preferably 50 ° C. or lower. When the liquid temperature exceeds 70 ° C., it may be difficult to specifically control the abundance ratio of molybdenum, bismuth, and iron in the liquid phase and solid phase in the obtained aqueous slurry as described above.
The obtained aqueous slurry may be subjected to heat treatment such as aging and concentration in the range of 70 to 105 ° C. as necessary. However, the liquid phase and the solid phase of molybdenum, bismuth and iron in the aqueous slurry may be used. In order to specifically control the abundance ratio in the above, it is preferable not to perform heat treatment such as aging and concentration.
[0014]
The molybdenum raw material, the bismuth raw material, and the iron raw material used in the preparation of the aqueous slurry are not particularly limited, and metal compounds such as nitrates, carbonates, acetates, ammonium salts, oxides, and halides of these metal elements can be used. . For example, as a molybdenum raw material, ammonium paramolybdate, ammonium dimolybdate, molybdenum trioxide, molybdenum dioxide, molybdic acid, molybdenum chloride, etc. can be used.As a bismuth raw material, bismuth oxide, bismuth nitrate, bismuth carbonate, bismuth acetate oxide, Bismuth nitrate hydroxide and the like can be used, and iron powder, iron oxide (III), iron nitrate (III) and the like can be used as the iron raw material.
Depending on the type of raw material used, a component for adjusting the solubility of the raw material in water may be added to the aqueous slurry.For example, when nitrate is used, nitric acid is added to the aqueous slurry in an amount of 0.1%. You may use it so that it may become the density | concentration of 4 mass%.
[0015]
As the silica raw material, colloidal silica is preferable, and a commercially available one can be appropriately selected and used. The size (diameter) of the colloidal particles in the colloidal silica is not particularly limited, but is preferably 2 to 100 nm, particularly preferably 5 to 50 nm. The size of the colloid particles may be either uniform or a mixture of several sizes. When colloidal silica is used as a silica raw material, about 100 mol% of colloidal silica is present in the liquid phase in the present invention.
[0016]
The amount of water used in the aqueous slurry is preferably such that the solid content concentration of the aqueous slurry is 10 to 40% by mass, more preferably 15 to 30% by mass.
[0017]
Further, such an aqueous slurry may contain other components other than molybdenum, bismuth, iron, and silica, and the elements constituting the finally obtained acrylonitrile synthesis catalyst include molybdenum, bismuth, iron, and silica. Together with the aqueous slurry.
More specifically, a more preferable composition of the finally obtained acrylonitrile synthesis catalyst includes a composition represented by the following general formula (1). Therefore, molybdenum, bismuth, In the formula (1) other than iron and silica, raw materials of the elements represented by A and B in the formula (1) (for example, nitrates, carbonates, acetates, ammonium salts, oxides, halides, etc. of the elements) are previously added to the aqueous slurry. It is preferable to keep it.
These elements represented by A and B may exist in the liquid phase and the solid phase in any ratio in the aqueous slurry.
[0018]
Mo_aBi_bFe_cA_dB_eO_f(SiO₂)_g... (1)
(Wherein, Mo, Bi, Fe and O represent molybdenum, bismuth, iron and oxygen, respectively, A is at least one element selected from the group consisting of sodium, potassium, rubidium, cesium and thallium, and B is cobalt , Nickel, copper, zinc, magnesium, calcium, strontium, barium, titanium, vanadium, chromium, manganese, tungsten, silver, aluminum, phosphorus, boron, tin, lead, gallium, germanium, arsenic, antimony, niobium, tantalum, zirconium At least one element selected from the group consisting of: indium, sulfur, selenium, tellurium, lanthanum, and cerium;₂Represents silica. However, a, b, c, d, e, f and g represent the atomic ratio of each element, and when a = 12, 0.1 ≦ b ≦ 5, 0.1 ≦ c ≦ 10, 0.01 ≦ d ≦ 3, 0 ≦ e ≦ 20, 10 ≦ g ≦ 200, and f is the atomic ratio of oxygen necessary to satisfy the valence of each element. )
[0019]
Here, when a = 12, when b <0.1, acrylonitrile selectivity tends to decrease, and when b> 5, the propylene conversion rate tends to decrease. When c <0.1, acrylonitrile selectivity tends to decrease, and when c> 10, propylene conversion tends to decrease. When d <0.01, acrylonitrile selectivity tends to decrease, and when d> 3, propylene conversion tends to decrease. When e> 20, acrylonitrile selectivity tends to decrease. When g <10, acrylonitrile selectivity tends to decrease, and when g> 200, propylene conversion tends to decrease.
[0020]
The solid phase component in the aqueous slurry prepared as described above, that is, the size of precipitated particles is not particularly limited, but is preferably about 2 to 500 μm.
[0021]
The aqueous slurry thus obtained is then dried. The drying method is not particularly limited, but the shape of the obtained dried product is preferably spherical, and its outer diameter is preferably from 1 to 200 μm, particularly preferably from 5 to 100 μm. A disk type spray dryer, a pressure nozzle type spray dryer, a two-fluid nozzle type spray dryer and the like are preferably used.
At this time, the temperature of the hot air circulated in the drying chamber of the spray dryer is preferably 130 to 450 ° C near the inlet to the drying chamber, and more preferably 140 to 400 ° C. Further, the temperature near the outlet of the drying chamber is preferably from 100 to 200 ° C, more preferably from 110 to 180 ° C.
[0022]
Then, the obtained dried product is calcined to obtain an acrylonitrile synthesis catalyst.
The firing temperature is not particularly limited, but by firing the dried product at a temperature in the range of 500 to 750 ° C., a desirable catalytically active structure is formed, and propylene ammoxidation was performed using the obtained catalyst. In that case, a high acrylonitrile yield can be obtained. Further, it is preferable to perform preliminary firing at a lower temperature before firing at 500 to 750 ° C. Preliminary firing may be performed, for example, at one of the conditions of about 250 to 400 ° C. or about 400 to 500 ° C., or both. After the preliminary calcination in one or two stages as described above, when calcination is performed at a temperature in the range of 500 to 750 ° C., a very desirable catalytically active structure is formed. Higher acrylonitrile yields can be obtained when oxidation is performed.
The baking time is not particularly limited, but it is preferable to bake for 1 hour or more. If the time is less than 1 hour, a sufficient acrylonitrile yield may not be obtained when ammoxidation of propylene is performed using a catalyst obtained by calcining. Specifically, it is preferable that after preliminary firing for 1 hour or more, firing at 500 to 750 ° C for 1 hour or more.
The firing method is not particularly limited, and a general-purpose firing furnace can be used, but a rotary kiln, a fluidized firing furnace, or the like is particularly preferably used.
As the sintering atmosphere, air is particularly preferably used, but it may partially contain an inert gas such as nitrogen and carbon dioxide, nitrogen oxides, and water vapor.
[0023]
The shape and size of the acrylonitrile synthesis catalyst thus obtained are not particularly limited, but the shape is particularly preferably spherical, and the outer diameter is preferably from 1 to 200 µm, particularly preferably from 5 to 100 µm.
[0024]
The method for synthesizing acrylonitrile by gas phase catalytic ammoxidation of propylene with molecular oxygen and ammonia using the obtained acrylonitrile synthesis catalyst is not particularly limited, but it is preferable to use a fluidized bed reactor, After charging the acrylonitrile synthesis catalyst into the fluidized bed reactor, for example, under the conditions of 400 to 500 ° C. and normal pressure to 300 kPa, it contains at least molecular oxygen, ammonia and propylene, and if necessary, an inert gas or By flowing the raw material gas diluted with steam through the fluidized bed reactor, propylene is subjected to gas phase catalytic ammoxidation to produce acrylonitrile.
The concentration of propylene in the raw material gas can be varied in a wide range, and is suitably from 1 to 20% by volume, and particularly preferably from 3 to 15% by volume.
It is industrially advantageous to use air as the oxygen source used for the source gas. However, if necessary, pure oxygen may be mixed with air to enrich the air before use.
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.
[0025]
As described above, a step of preparing an aqueous slurry containing at least molybdenum, bismuth, iron, and silica and comprising a liquid phase and a solid phase, a step of drying the aqueous slurry, and a step of drying the obtained slurry. Calcining the product, comprising: 75 to 95 mol% of molybdenum, 80 to 100 mol% of bismuth, and 40 to 80 mol% of iron in the aqueous slurry. However, when the aqueous slurry is prepared so as to be in the solid phase, the finally obtained catalyst for acrylonitrile synthesis achieves a very high acrylonitrile yield.
[0026]
It is not clear why the acrylonitrile yield is increased by adjusting the abundance ratio of each metal in the aqueous slurry as described above, but it is considered as follows.
That is, at least molybdenum, bismuth, iron, and silica, containing an aqueous slurry comprising a liquid phase and a solid phase, and then drying this aqueous slurry, the resulting dried product is an aqueous slurry of It can be presumed that the components existing in the solid phase at the time point have a fine structure in which the components existing in the liquid phase wrap. Therefore, at the time of the aqueous slurry, the catalyst constituent elements, that is, at least molybdenum, bismuth and iron, should be distributed in a preferable ratio between the solid phase and the liquid phase, so that the catalyst of the finally obtained acrylonitrile synthesis catalyst can be obtained. It is considered to be an important factor in constructing the structure and to have a great influence on the acrylonitrile yield.
[0027]
【Example】
Hereinafter, the present invention will be described specifically with reference to examples. However, "parts" in the following Examples and Comparative Examples means parts by mass.
[0028]
The determination of molybdenum, bismuth, and iron in the solid phase in the aqueous slurry and the activity test of the catalyst were performed as follows.
(1) Determination of molybdenum, bismuth and iron in solid phase in aqueous slurry
C gram of the aqueous slurry was separated into a supernatant and a sediment by a centrifugal separator (processed at 10,000 rpm for 15 minutes), and the supernatant was ultrafiltered with a filter having a mesh size of 1 μm.
The resulting sediment after centrifugation and the filtration residue from ultrafiltration were dried at 100 ° C. for 18 hours in a box drier. The total weight of the obtained dried products was D grams.
The mass of the filtrate obtained by ultrafiltration was E-gram.
The amounts of molybdenum, bismuth, and iron in the filtrate were quantified using an ICP emission spectrometer (ICAP-577, manufactured by Nippon Jarrell Ash). As a result, the amounts of molybdenum, bismuth, and iron present in the filtrate could be quantified as F grams, G grams, and H grams, respectively.
On the other hand, a dried product obtained by combining the sediment after centrifugation and the filtration residue from ultrafiltration was further calcined at 300 ° C. for 3 hours to obtain a calcined product.
The obtained calcined product is completely dissolved in a mixed aqueous solution of 36 parts by mass of 5 parts of hydrochloric acid, 10 parts of 57 parts by mass of hydroiodic acid, and 2.5 parts of 47 parts by mass of hydrofluoric acid, and then, an ICP emission spectrometer. Was used to quantify the amounts of molybdenum, bismuth and iron. As a result, the amounts of molybdenum, bismuth, and iron present in the fired product were determined to be J grams, K grams, and L grams, respectively.
[0029]
From the above results, the ratio S present in the solid phase to the total molybdenum atoms in the aqueous slurry_Mo(Mol%), the ratio S present in the solid phase to all bismuth atoms in the aqueous slurry_Bi(Mol%), the ratio S present in the solid phase to the total iron atoms in the aqueous slurry_Fe(Mol%) is calculated by the following equations.
S_Mo(Mol%) = [JF × (CDE) / E] / (J + F) × 100
S_Bi(Mol%) = [KG × (CDE) / E] / (K + G) × 100
S_Fe(Mol%) = [L−H × (CDE) / E] / (L + H) × 100
[0030]
(2) Catalyst activity test
Acrylonitrile was synthesized by ammoxidizing propylene using a fluidized-bed reactor having a column diameter of 2 inches.
As a raw material gas, a mixed gas of propylene / ammonia / air / steam = 1/1 / 9.5 / 0.5 (molar ratio) was used, and introduced into the reactor at a gas linear velocity of 18 cm / sec. did. The reaction temperature was 430 ° C., and the reaction pressure was 200 KPa.
The analysis of the reaction gas (reaction test analysis) was performed by gas chromatography.
The contact time, propylene conversion, acrylonitrile selectivity and acrylonitrile yield are defined as follows.
Contact time (second) = catalyst volume (L) based on bulk density / supply gas flow rate (L / second) converted to reaction conditions
Conversion of propylene (%) = Q / P × 100
Acrylonitrile selectivity (%) = R / Q × 100
Acrylonitrile yield (%) = R / P × 100
P represents the number of moles of supplied propylene, Q represents the number of moles of reacted propylene, and R represents the number of moles of acrylonitrile produced.
[0031]
[Example 1]
In a mixture of 1634.2 parts of 30% by mass colloidal silica (colloid particle average diameter 20 nm) and 820 parts of water, 411.6 parts of ammonium paramolybdate is dissolved with stirring, and the mixture is heated to 40 ° C. did.
Separately, 730 parts of a 10% by mass aqueous nitric acid solution were stirred and 157.0 parts of iron (III) nitrate, 225.9 parts of nickel nitrate, 113.0 parts of cobalt nitrate, 49.8 parts of magnesium nitrate, and 42.1 parts of lanthanum nitrate were stirred. , 31.1 parts of chromium nitrate, 47.1 parts of bismuth nitrate, 1.4 parts of potassium nitrate, and 2.3 parts of rubidium nitrate, and heated to 40 ° C to obtain a liquid B.
The stirring of the solution A was completely stopped, and the solution B was added thereto over 30 seconds. After the addition was completed, the stirring was started again to obtain an aqueous slurry (1).
The obtained aqueous slurry (1) was analyzed by the quantitative method described above. As a result, 90 mol% of all molybdenum atoms in the aqueous slurry (1) were present in the solid phase, and The proportion of all bismuth atoms present in the solid phase was 92 mol%, and the proportion of all iron atoms in the aqueous slurry (1) present in the solid phase was 60 mol%.
[0032]
Next, the aqueous slurry (1) was dried using a rotating disk type spray dryer while controlling the temperature at the inlet of hot air at 280 ° C and the temperature at the outlet at 170 ° C.
The obtained dried product was preliminarily calcined at 300 ° C. for 2 hours and then at 450 ° C. for 2 hours in an air atmosphere, and then calcined at 600 ° C. for 3 hours in a fluidized calcining furnace to obtain a catalyst (1). Catalyst (1) was substantially spherical particles, and the average particle size was 52 μm.
The composition of the catalyst (1) thus obtained is as follows according to the charge ratio of the raw materials.
Mo₁₂Bi_0.5Fe₂Ni₄Co₂Mg₁Cr_0.4La_0.5K_0.07Rb_0.08O_x(SiO₂)₄₂
(Where x is the atomic ratio of oxygen necessary to satisfy the valences of the other components.)
[0033]
The obtained catalyst (1) was subjected to the activity test described above at a contact time of 3.0 seconds. As a result, the conversion of propylene was 98.5%, the selectivity for acrylonitrile was 84.7%, and the conversion of acrylonitrile was 84.7%. The yield was 83.4%.
[0034]
[Comparative Example 1]
In Example 1, the temperatures of the solution A and the solution B were changed to 60 ° C., and the solution A was added thereto over 4 minutes while stirring the solution A well, and then the temperature was raised to 95 ° C. An aqueous slurry (2) was obtained in the same manner as in Example 1 except that the method of aging treatment for 3 hours was changed.
The obtained aqueous slurry (2) was subjected to quantitative analysis in the same manner as in Example 1. As a result, the proportion of all molybdenum atoms in the aqueous slurry (2) existing in the solid phase was 55 mol%, and the ratio in the aqueous slurry (2) was 55%. Of the total bismuth atoms in the solid slurry, 72 mol% of the total iron atoms in the aqueous slurry (2) were 15 mol%.
Then, with respect to the aqueous slurry (2), the subsequent steps were performed in the same manner as in Example 1 to obtain a catalyst (2).
The obtained catalyst (2) was subjected to an activity test in the same manner as in Example 1. As a result, the conversion of propylene was 97.1%, the selectivity of acrylonitrile was 82.3%, and the yield of acrylonitrile was 79. 9%.
[0035]
[Comparative Example 2]
In Example 1, the concentration of the aqueous nitric acid solution used for preparing the solution B was changed to 2% by mass, the temperatures of the solution A and the solution B were changed to 80 ° C., and the solution B was added thereto while the solution A was well stirred. An aqueous slurry (3) was obtained in the same manner as in Example 1 except that the method was charged over 7 minutes, then the temperature was raised to 101 ° C., and the aging treatment was performed at the same temperature for 6 hours.
The obtained aqueous slurry (3) was subjected to quantitative analysis in the same manner as in Example 1. As a result, the proportion of all molybdenum atoms in the aqueous slurry (3) in the solid phase was 22 mol%, and Was 90 mol% of all the bismuth atoms in the solid phase, and 25 mol% of the total iron atoms in the aqueous slurry (3) were in the solid phase.
Then, for the aqueous slurry (3), the subsequent steps were performed in the same manner as in Example 1 to obtain a catalyst (3).
The obtained catalyst (3) was subjected to an activity test in the same manner as in Example 1. As a result, the conversion of propylene was 96.8%, the selectivity of acrylonitrile was 82.9%, and the yield of acrylonitrile was 80. 2%.
[0036]
[Comparative Example 3]
In the same manner as in Example 1 except that the temperature of the solution A and the solution B was changed to 70 ° C., and the solution A was changed to a method in which the solution A was poured over 30 minutes while stirring the solution A well. Thus, an aqueous slurry (4) was obtained.
The obtained aqueous slurry (4) was quantitatively analyzed in the same manner as in Example 1. As a result, the proportion of all molybdenum atoms in the aqueous slurry (4) existing in the solid phase was 88 mol%, and the ratio in the aqueous slurry (4) was 88%. Was 74 mol% of the total bismuth atoms in the solid phase, and 34 mol% of the total iron atoms in the aqueous slurry (4).
Next, with respect to the aqueous slurry (4), the subsequent steps were performed in the same manner as in Example 1 to obtain a catalyst (4).
An activity test was conducted on the obtained catalyst (4) in the same manner as in Example 1. As a result, the conversion of propylene was 97.9%, the selectivity of acrylonitrile was 83.1%, and the yield of acrylonitrile was 81.8%. 4%.
[0037]
[Comparative Example 4]
In Example 1, 411.6 parts of ammonium paramolybdate was dissolved in 820 parts of water while stirring, and the solution heated to 70 ° C. was used as solution A, the temperature of solution B was set to 70 ° C., and the stirring of solution A was performed. Liquid B was added thereto over 2 minutes in a stopped state, and after completion of the addition, stirring was started again, and the method was changed to the method of charging 1634.2 parts of 30% by mass colloidal silica, and the same as Example 1 was performed. Thus, an aqueous slurry (5) was obtained.
The obtained aqueous slurry (5) was quantitatively analyzed in the same manner as in Example 1. As a result, the proportion of all molybdenum atoms in the aqueous slurry (5) existing in the solid phase was 62 mol%, Was 68 mol% of all the bismuth atoms in the solid phase, and 48 mol% of the total iron atoms in the aqueous slurry (5) were in the solid phase.
Then, with respect to the aqueous slurry (5), the subsequent steps were performed in the same manner as in Example 1 to obtain a catalyst (5).
When an activity test was performed on the catalyst (5) in the same manner as in Example 1, the conversion of propylene was 97.7%, the selectivity of acrylonitrile was 82.6%, and the yield of acrylonitrile was 80.7%. there were.
[0038]
【The invention's effect】
As described above, according to the production method of the present invention, an acrylonitrile synthesis catalyst capable of achieving a high acrylonitrile yield in a reaction of synthesizing acrylonitrile by gas phase catalytic ammoxidation of propylene with molecular oxygen and ammonia is produced. be able to.

Claims (2)

A step of preparing an aqueous slurry comprising at least molybdenum, bismuth, iron, and silica and comprising a liquid phase and a solid phase, drying the aqueous slurry, and calcining the obtained dried product; In the method for producing an acrylonitrile synthesis catalyst having
75 to 95 mol% of molybdenum, 80 to 100 mol% of bismuth, and 40 to 80 mol% of iron in the aqueous slurry are present in a solid phase in a catalyst for acrylonitrile synthesis. Production method. The method for producing an acrylonitrile synthesis catalyst according to claim 1, wherein the acrylonitrile synthesis catalyst has a composition represented by the following general formula (1).
_{Mo a Bi b Fe c A d} B e O f (SiO 2) g ··· (1)
(Wherein, Mo, Bi, Fe and O represent molybdenum, bismuth, iron and oxygen, respectively, A is at least one element selected from the group consisting of sodium, potassium, rubidium, cesium and thallium, and B is cobalt , Nickel, copper, zinc, magnesium, calcium, strontium, barium, titanium, vanadium, chromium, manganese, tungsten, silver, aluminum, phosphorus, boron, tin, lead, gallium, germanium, arsenic, antimony, niobium, tantalum, zirconium , indium, sulfur, selenium, tellurium, at least one element selected from the group consisting of lanthanum and cerium, SiO ₂ represents silica. However, a, b, c, d , e, f and g are each elements When a = 12, 0.1 ≦ b ≦ 5, 0. 1 ≦ c ≦ 10, 0.01 ≦ d ≦ 3, 0 ≦ e ≦ 20, 10 ≦ g ≦ 200, and f is the atomic ratio of oxygen necessary to satisfy the valence of each element. )