JP2640356B2 - Acrylonitrile manufacturing method - Google Patents

Description

The present invention relates to a method for producing acrylonitrile by gas phase catalytic ammoxidation of propylene in a fluidized bed, and more particularly to a method for producing acrylonitrile with high yield and excellent mechanical strength. The present invention relates to a method for producing acrylonitrile by gas phase catalytic ammoxidation of propylene in a fluidized bed using a molybdenum / bismuth / iron / nickel / alkali metal catalyst.

[Conventional technology]

Conventionally, various catalysts used for producing acrylonitrile by ammoxidation of propylene have been proposed,
Above all, many molybdenum-bismuth catalysts have been proposed as multi-component catalysts. For example,
No. 5870, JP-B-38-17967, JP-B-39-8512, JP-B-45-35287, JP-A-48-47476, JP-B-51-33888
And the method described in Japanese Patent Publication No. Sho 60-36812 has been improved from various angles.

However, when using these catalysts in fluidized bed reactions,
That the acrylonitrile yield is not necessarily high enough,
There are problems that it is difficult to produce a catalyst having sufficiently high strength and that an expensive catalyst such as cobalt must be used as a catalyst component. Therefore, improvement from an industrial point of view has been desired.

Several methods have been proposed for producing a molybdenum-bismuth-based fluidized bed catalyst. For example,
Japanese Patent Publication No. 37-8568 discloses a method of spray-drying a slurry comprising molybdenum, bismuth and silica containing ammonium nitrate. A method for preparing a catalyst within the range described in JP-B-57-49253 is disclosed.
A method in which silica sol is added stepwise to an aqueous suspension containing heptamolybdate at a temperature lower than 6 ° C., and then phosphoric acid and further components such as bismuth, iron, cobalt and nickel are added. 56839 gazette, JP-A-55-1
39839 JP, JP-A-57-65329, JP-A-57-7514
Publication No. 7 and the like report various methods for producing a molybdenum-bismuth-based wear-resistant fluidized catalyst having a pH value of 1 or less and a slurry temperature of 60 ° C. or less.

However, in the case of molybdenum-bismuth catalyst containing no cobalt, as described in JP-B-48-43096, the yield of acrylonitrile is low, and it is not possible to obtain a fluidized bed catalyst having strength suitable for a fluidized bed reaction. It was difficult.

[Problems to be solved by the present invention]

An object of the present invention is to produce acrylonitrile obtained by gas-phase catalytic ammoxidation of propylene in a fluidized-bed reactor, to have excellent catalytic activity, to have a high abrasion resistance of the catalyst, and to contain cobalt. An object of the present invention is to provide a method for obtaining acrylonitrile in a high yield by using a multi-component fluidized bed catalyst mainly containing molybdenum, bismuth, iron, nickel, and an alkali metal.

[Means for Solving the Problems] The process for producing acrylonitrile according to the present invention is characterized in that, in the gas phase catalytic ammoxidation of propylene by a fluidized bed, (i) the catalyst composition is determined by the empirical formula Q _q R _r Mo ₁₀ Bi _a Fe _b Ni _c O _d (SiO ₂ ) _e (wherein Q is P and / or B, and R is Li, Na, K,
At least one alkali metal element selected from the group consisting of Rb and Cs, and the subscripts q, r, a, b, c, d, and e indicate atomic ratios, and q = 0 to 3, r = 0.01 to 1.5, a = 0.1 ~
3, b = 0.1 to 2.5, c = 4 to 8, d = the number of oxygen corresponding to the oxide formed by combining the above components and e = 20 to
It is 150. (Ii) preparing a solution or slurry containing at least Mo and Fe components among the above catalyst components and adjusting the pH of the solution or slurry to 5 or less; Solution or slurry from 50 ° C to 120
(Iv) heating the catalyst component other than Mo and Fe before, during, or after the step (iii) above while maintaining the form of the solution or slurry in the temperature range of (V) Then, the slurry containing the catalyst component thus obtained is spray-dried to form spherical particles, and the particles are calcined. It is characterized by the following.

 Hereinafter, the present invention will be described specifically.

The gas phase catalytic ammoxidation of propylene by a fluidized bed is a known technique, and any known technique can be used without contradicting the present invention.

In the present invention, this reaction is carried out by using an oxide composition comprising molybdenum, bismuth, iron, nickel and alkali metal components supported on silica, or, in addition to these components, further supporting other components such as phosphorus and boron. It is carried out in the presence of a reduced oxide composition.

An important aspect of the present invention lies in the catalyst used, which can be any catalyst having the catalyst composition shown in the empirical formula. In this catalyst composition, in order to improve the acrylonitrile yield, a particularly preferable atomic ratio of each component is Mo.
When component = 10, r = 0.05-1.0, a = 0.5-2.5, b = 0.5
２2, c = 4.5-7.5 and e = 40-100.

Molybdenum, bismuth, iron, and iron constituting the catalyst of the present invention
Nickel, alkali metal, silicon or even phosphorus
It is not sufficiently clear what kind of compound each component such as boron contributes to the effect on the activity and physical properties in the catalyst. However, since the composition of the catalyst deviates from the range of the empirical formula, and if the preparation conditions of the catalyst are changed, it becomes difficult to achieve the purpose, the respective catalyst constituent elements and the catalyst preparation conditions are closely related to each other for the expression of the effect. It is clear that you are doing.

For example, when the atomic ratio of the catalyst components is Mo component = 10,
q> 3, r <0.01 or r> 1.5, a <0.1 or a
> 3, b <0.1, or b> 2.5, c <4 or c>
In the case of 8, the selectivity of acrylonitrile decreases or the physical properties of the catalyst deteriorate. If e is less than 20, the strength of the catalyst becomes weak, and if it exceeds 150, the catalytic activity decreases. Also, when the nickel component is replaced with a cobalt component of the same family as the periodic table, the selectivity of acrylonitrile decreases.

Another important point of the present invention lies in the method for preparing the catalyst, and the catalyst used in the present invention must be produced by preparing a slurry as described below.

Starting material for each component constituting the present catalyst can be selected from many types such as oxides, hydroxides, chlorides and nitrates.

Examples of the raw material of the molybdenum component include molybdenum oxides such as molybdenum trioxide, molybdic acid, ammonium paramolybdate, ammonium metamolybdate, and molybdenum-containing heteropolyacids such as phosphomolybdic acid and silico-molybdic acid, or salts thereof. Are used.

As a raw material of the bismuth component, for example, bismuth salts such as bismuth nitrate and bismuth sulfate, bismuth trioxide,
For example, nitric oxide of metal bismuth is used.

As a raw material for the iron component, for example, ferrous oxide, ferric oxide, iron tetroxide, iron nitrate, iron chloride, and iron hydroxide can be used. May be used.

As a raw material of the nickel component, for example, nickel oxide, hydroxide, or metal nickel nitrate can be used.

In the R component, phosphoric acid or a salt thereof is used as a raw material of the phosphorus component, and boric acid or a salt thereof is used as a raw material of the boron component.

As the raw material for the Q component, that is, the lithium, sodium, potassium, rubidium, and cesium components that are alkali metals, it is preferable to use nitrates, carbonates, hydroxides, oxides, chlorides, and the like of each component.

In the catalyst used in the present invention, silica is used as a carrier component. The reason is that silica is superior to other support components in the strength of the fluidized bed catalyst. Reacts little with catalytically active components. This is for not adversely affecting the catalytic activity. The use of silica provides strength to withstand use as a fluidized bed catalyst,
In addition, an appropriate particle density for achieving a good fluidized state is provided.

As a raw material of silica as a carrier component, silica sol or fine powder silica is used. Preferred silica sols have a silica concentration in the range of about 5 to about 90% by weight.

Slurry Preparation In preparing a slurry from each of the component materials, first, of the catalyst materials, a Mo component material and a Fe component material are mixed to prepare a slurry containing both components. Q, R, B
The i, Ni and silica component raw materials may be mixed from the beginning, or may be added to and mixed with the slurry after pH adjustment or heat treatment described below. What is important here is that the slurry is prepared so that at least the raw materials of both the Mo and Fe components exist in the slurry before the pH adjustment.

Next, while the slurry containing at least the Mo and Fe components is well stirred, the pH of the slurry is adjusted to 5 or less. If the pH is more than 5, the slurry becomes high in viscosity or becomes gel-like, so that it is difficult to stir the slurry and a uniform slurry cannot be obtained.

The slurry thus prepared is then maintained at a temperature in the range of about 50 ° C. to about 120 ° C. (preferably, about 60 ° C. to about 110 ° C.) while maintaining the slurry form for at least about 10 ° C.
Heat for a minute (preferably about 0.5 to about 8 hours).
In this heat treatment of the slurry, it is not sufficiently clear what kind of reaction is occurring in the slurry. However, the difference between the X-ray diffraction patterns of the catalysts subjected to the heat treatment of the slurry and the catalyst not subjected to the heat treatment indicates that some reaction is progressing during the heat treatment. It is considered that the progress of such a reaction provides a good catalytic activity, and at the same time, the particles of the raw material slurry are densified and the strength of the product catalyst is improved. Further, the slurry after the heat treatment is stable.

pH adjustment and heat treatment effectively act on the slurry in which both the Mo component raw material and the Fe component raw material are present,
If only one of the Mo component and the Fe component is present in the slurry, a catalyst having good activity and physical properties cannot be obtained.

Of the catalyst components, Q, R, Bi, Ni, and Si components other than the Mo and Fe components, the raw materials of the respective components were used as described above.
It can be added to and mixed with any slurry before and after pH adjustment and after heat treatment.

As described above, pH adjustment and heat treatment of a solution or slurry containing at least Mo and Fe components are important features of the present invention, and are essential requirements for imparting good activity and physical properties to a product catalyst. It is.

Spray drying The slurry thus prepared is then formed into fine spherical particles by spray drying. For spray drying,
Any known method can be applied as it is. That is, a spray-drying device such as a pressure nozzle type or a rotating disk type can be used. The concentration of the slurry subjected to spray drying is about 10 to about 40 in terms of the oxide of the element constituting the catalyst.
Those in the range of weight% are preferred. This range is not critical and is economically disadvantageous below its lower limit concentration and inconvenient in handling above its upper limit concentration. Spray drying is performed by appropriately adjusting the concentration of the slurry and the spray drying conditions so as to obtain particles having a desired particle size distribution.

The fine spherical particles obtained by the sintering and spraying device are finally subjected to a drying treatment, if desired, and finally to about 500 to about 750.
Firing at a temperature of ° C. Thereby, high activity and physical properties are provided. The calcination may be performed separately for preliminary calcination and final calcination, or may be performed at a single temperature without separation. About 200 to about 5 spherical particles obtained by spray drying
It is preferable to pre-bake at a temperature of 00 ° C. for about 1 to about 50 hours, and finally to bake at a temperature of about 500 to about 750 ° C. for about 1 to about 50 hours. The atmosphere at the time of firing is preferably non-reducing, and is preferably performed in an air stream for economic reasons.

The firing device can be selected from many types. A tunnel furnace, a rotary furnace, a fluidized furnace, or the like can be used.

The process of the present invention is performed in a fluidized bed contact reactor.
That is, the reaction is carried out by supplying propylene, ammonia and oxygen to a reactor filled with the fluidized bed catalyst in the present invention. Air is the preferred oxygen source for economic reasons. The air may be suitably enriched with oxygen.

The molar ratio of oxygen / propylene in the feed to the reactor is in the range of about 1 to about 4, but the catalyst in the present invention has a relatively low molar ratio of about 1.5 to about 2.5 because of the high acrylonitrile selectivity. Range. Also, the ammonia / propylene molar ratio in the feed to the reactor can be increased or decreased from about 0.8 to about 3, but is preferably from about 0.9 to about 1.5. Further, if necessary, an inert gas such as nitrogen or water vapor may be supplied.

The reaction temperature ranges from about 380 to about 500 ° C., in particular about 400
A range from to about 480 ° C is preferred. The reaction pressure is suitably in the range from near normal pressure to about 3 kg / cm ² · G. The apparent contact time is suitably in the range of about 1 to about 30 seconds, especially about 2 to 30 seconds.
A range from to about 20 seconds is preferred.

〔The invention's effect〕

Molybdenum, bismuth, iron, nickel,
The alkali metal-containing catalyst has high activity in the reaction for producing acrylonitrile from propylene, has excellent fluidization properties, has high mechanical strength, and has favorable performance as a fluidized bed catalyst. Therefore, according to the method of the present invention, acrylonitrile can be obtained in high yield by gas phase catalytic ammoxidation of propylene by a fluidized bed,
It can be implemented industrially more advantageously than the conventional method.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

 The activity test of the catalyst is as follows.

A catalyst was charged into a fluidized bed reactor having an inner diameter of a catalyst flowing section of 2.5 cm and a height of 40 cm, and a gas having the following composition was fed. The reaction pressure is normal pressure.

Oxygen (supplied as air) /propylene=2.0 (mol /
Mol), ammonia / propylene = 1.3 (mol / mol) In this specification, the acrylonitrile yield and the propylene conversion rate are defined by the following formula.

The catalyst strength test was performed by the following method.

Abrasion resistance test Test method for synthetic cracking, known as a test method for fluid catalytic cracking catalysts
Catariz, (Test Method for Synthetic Crocking
Catalysts), published by American Cyanamid Company, 6 / 31-4m-1 / 57. The wear loss (%) was determined by the following equation.

Abrasion loss (%): R = B x 100 / (CA) where A = weight of catalyst that has been worn and lost in 0 to 5 hours B = weight of catalyst that has been worn and lost in 5 to 20 hours C = used for test This test was performed at C = 50 (g). The higher the wear resistance of the catalyst, the smaller the wear loss (%) R value.

Example 1 A catalyst having an empirical formula of K _0.2 Mo ₁₀ Bi _1.5 Fe _1.5 Ni ₆ O _40.6 (SiO ₂ ) ₅₀ was produced as follows.

Dissolve 3.01 g of potassium sulfate in 30.1 ml of water, and add 2238 g of 20%
Added to silica sol. Under stirring, 263 g of ammonium paramolybdate was dissolved in 650 ml of water at 80 ° C. and added to the solution with stirring.
Subsequently, a solution in which nickel nitrate 259.9 g was dissolved in 260 ml, a solution in which iron nitrate 90.3 g was dissolved in water 90 ml, and bismuth nitrate 108.4
g was dissolved in 110 ml of 10% nitric acid. Thereafter, the pH was adjusted to 2.0 with 15% aqueous ammonia.

The homogeneous slurry thus obtained was placed in a three-necked flask and heated at 100 ° C. under reflux for 1 hour with stirring.

The heat-treated slurry was spray-dried with a rotating disk type spray dryer at an inlet temperature of 320 ° C and an outlet temperature of 160 ° C. Heat the dried catalyst at 250 ° C, and further heat at 400 ° C
For 2.5 hours and finally at 580 ° C. for 3 hours.

Examples 2-3 A catalyst having the same composition as in Example 1 was produced in the same manner as in Example 1, except that the pH of the slurry for the heat treatment was adjusted to 1 or 5.

Examples 4 to 13 Catalysts having the compositions shown in Examples 4 to 13 in Table 1 were produced in the same manner as in Example 1.

Example 14 The empirical formula was determined by the same method as in Example 1 except that 16.95 g of 85% orthophosphoric acid was added after bismuth nitrate.
_A catalyst was produced that was _0.2 K _0.2 Mo ₁₀ Bi _1.5 Fe _1.5 Ni ₆ O _41.1 (SiO ₂ ) ₅₀ .

Example 15 The empirical formula was changed to B _0.2 K _0.2 by the same method as in Example 14 except that 1.84 g of orthoboric acid was added instead of orthophosphoric acid.
A catalyst was produced that was Mo ₁₀ Bi _1.5 Fe _1.5 Ni ₆ O _41.1 (SiO ₂ ) ₅₀ .

Example 16 An empirical formula of Cs _0.05 Mo ₁₀ was obtained in the same manner as in Example 1 except that 1.45 g of cesium nitrate was added instead of potassium nitrate.
A catalyst was produced that was Bi _1.5 Fe _1.5 Ni ₆ O _40.5 (SiO ₂ ) ₅₀ .

Example 17 An empirical formula of Rb _0.1 Mo was obtained in the same manner as in Example 1 except that 2.20 g of rubidium nitrate was added instead of potassium nitrate.
_A catalyst was produced that was ₁₀ Bi _1.5 Fe _1.5 Ni ₆ O _40.6 (SiO ₂ ) ₅₀ .

Examples 18 to 21 Catalysts having the same composition as in Example 1 by the same method as in Example 1 except that each component of potassium, nickel or bismuth or silica sol adjusted to pH 2.0 was added to the slurry after the heat treatment. Was manufactured.

Examples 22 to 23 Catalysts having the same composition as in Example 1 were produced in the same manner as in Example 1 except that the time and temperature of the heat treatment of the slurry were changed.

Comparative Example 1 A catalyst having the same composition was produced in the same manner as in Example 1 except that the slurry was not subjected to heat treatment.

Comparative Examples 2 to 11 In the same manner as in Example 1, catalysts having the compositions shown in Comparative Examples 2 to 11 in Table 2 were produced.

Comparative Example 12 When the slurry before the heat treatment was adjusted to pH 5.5 in the same manner as in Example 1, the slurry viscosity became extremely high, and spray drying could not be performed.

Comparative Example 13 A catalyst having the same composition was produced in the same manner as in Example 1 except that an aqueous solution of iron nitrate was added after the heat treatment.

Comparative Example 14 A catalyst having the same composition as in Example 1 was produced except that an aqueous solution of antimony molybdate was added after the heat treatment.

Comparative Example 15 The empirical formula was changed to K _0.2 Mo ₁₀ Bi by the same method as in Example 1 except that 265.35 g of cobalt nitrate was added instead of nickel nitrate.
_A catalyst was produced that was _1.5 Fe _1.5 Ni ₆ O _40.6 (SiO ₂ ) ₅₀ .

For the catalysts of Examples 1 to 23 and Comparative Examples 1 to 15, the results of the activity test and the catalyst strength test are shown in Table 1 (Example) and Table 2 (Comparative Example).

FIG. 1 (Example 1) and FIG. 2 (Comparative Example 1) show the results of taking photographs of the catalyst of Example 1 and the catalyst of Comparative Example 1 with a scanning electron microscope. It can be seen that the catalyst particles according to the present invention are spherical in shape and have a smooth surface, whereas the catalyst particles of the comparative examples show irregularities on the surface. From the comparison of FIGS. 1 and 2, the effect of the present invention on the physical properties of the catalyst surface will be apparent.

[Brief description of the drawings]

FIG. 1 is a scanning electron micrograph showing the structure of the catalyst particles of Example 1 of the present invention, and FIG. 2 is a scanning electron micrograph showing the structure of the catalyst particles of Comparative Example 1.

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-55-13187 (JP, A) JP-A-50-49201 (JP, A) JP-A-52-131989 (JP, A) JP-A 52-1989 68094 (JP, A) JP-A-1-265068 (JP, A)

Claims (1)

(57) [Claims] 1. A process for producing acrylonitrile from the gas phase catalytic ammoxidation of propylene using a fluidized bed, (i) a catalyst composition, empirical formula _{Q q R r Mo 10 Bi a} Fe b Ni c O d (SiO 2) _e (where Q is P and / or B and R is Li, Na, K,
At least one alkali metal element selected from the group consisting of Rb and Cs, and the subscripts q, r, a, b, c, d, and e indicate atomic ratios, and q = 0 to 3, r = 0.01 to 1.5, a = 0.1 ~
3, b = 0.1 to 2.5, c = 4 to 8, d = the number of oxygen corresponding to the oxide formed by combining the above components and e = 20 to
It is 150. (Ii) preparing a solution or slurry containing at least Mo and Fe raw materials among the above catalyst components and adjusting the pH of the solution or slurry to 5 or less; (iii) The obtained solution or slurry is heated at 50 ° C to 120 ° C.
(Iv) heating the catalyst component other than Mo and Fe before, during, or after the step (iii) above while maintaining the form of the solution or slurry in the temperature range of (V) using the fluidized bed catalyst obtained by spray drying the slurry containing the catalyst component thus obtained to form spherical particles, and calcining the particles. A method for producing acrylonitrile.