JP2004010579A - Production method of acrylonitrile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing acrylonitrile, enabling easy incineration of the extraction liquid of a quenching column without using an ammonium sulfate removal process and the discharge of sulfur oxides while keeping the selectivity of acrylonitrile. <P>SOLUTION: The method for the production of acrylonitrile by the vapor-phase catalytic ammoxidation reaction of propane is carried out by keeping the molar ratio of organic acid/unreacted ammonia in the gas produced by the ammoxidation reaction to 1.0-3.0. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing acrylonitrile by bringing propane into gaseous phase contact with ammonia and oxygen.
[0002]
[Prior art]
Conventionally, as a means for producing unsaturated nitriles represented by acrylonitrile, an ammoxidation reaction in which propylene or propane is brought into gaseous contact with ammonia and oxygen is known. For example, as a method for producing acrylonitrile using propane as a raw material, a production method using a catalyst containing Mo-V-Nb-Sb is disclosed in JP-A-9-157241, JP-A-10-28862, and JP-A-10-330343. JP-A-11-57479, JP-A-11-226408, JP-A-11-263745, JP-A-11-47598 and the like are disclosed.
[0003]
When propane, ammonia and air are fed into a reactor to perform an acrylonitrile synthesis reaction, the usual ammonia / propane molar ratio is set to a value higher than the stoichiometric ratio to prevent a decrease in acrylonitrile yield. As a result, unreacted ammonia is left in the reaction product gas, and acrylonitrile, propane, propylene, oxygen, nitrogen, hydrocyanic acid, acetonitrile, acrolein, carbon monoxide, carbon dioxide, organic acid ( The reaction gas contains acrylic acid, acetic acid), trace amounts of high-boiling products, and water vapor.
However, acrylonitrile and hydrocyanic acid are known to cause formation of β-aminopropionitrile and the like or polymerization of hydrocyanic acid when coexisting with ammonia in an aqueous solution, and are generally used to prevent these side reactions. A method has been used in which unreacted ammonia is brought into contact with an aqueous solution containing sulfuric acid from a reaction product gas to quickly fix and remove it.
[0004]
Specific examples thereof include a method of removing unreacted ammonia in a quenching tower, a method of washing and removing with a relatively low temperature acidic aqueous solution of 40 to 50 ° C., a method of high temperature water of 70 to 90 ° C. or a sulfuric acid containing ammonium sulfate. A method of removing with a solution is known. For example, U.S. Pat. No. 3,649,179 discloses a method of immobilizing unreacted ammonia by washing with an aqueous solution containing sulfuric acid in a multistage quenching tower divided into two upper and lower sections (or more sections). . Further, there is a method described in JP-B-44-15645 which aims at improving the quality and easy recovery of recovered ammonium sulfate, and a method described in JP-B-47-6608 which is an improved method thereof. In these methods, the reaction product gas is first washed with hot water at 70 to 100 ° C. to remove high-boiling substances, polymers, and scattered catalysts, and then immobilized unreacted ammonia as ammonium sulfate with an aqueous solution containing sulfuric acid. is there.
[0005]
However, since sulfuric acid is used for fixing unreacted ammonia in any of the methods, ammonium sulphate is always contained in the liquid discharged from the quenching tower, and it is necessary to treat ammonium sulphate by some method. However, when the waste liquid containing ammonium sulfate is incinerated, sulfur oxides (SOx) are emitted into the atmosphere, which poses an environmental problem, and the heat recovery equipment for incinerated waste gas also has a problem in that the equipment is corroded by the sulfur oxides. .
As means for solving these problems, Japanese Patent Application Laid-Open No. 8-2066643 discloses that in an ammoxidation reaction using propylene and ammonia, the molar ratio of organic acid / unreacted ammonia in the ammoxidation reaction product gas is adjusted to a specific range, whereby acrylonitrile is obtained. The effect is that the effluent of the quench tower can be easily incinerated without passing through the ammonium sulfate removal step and without discharging sulfur oxides, while maintaining the yield of ash and the waste heat from the incineration without steam corrosion. There is disclosed a technique that can be recovered as a product. However, this technique does not describe any reaction using propane as a raw material.
[0006]
On the other hand, when propane is used as a raw material, there is disclosed a technique for simultaneously producing acrylonitrile and acrylic acid by setting the ammonia / propane molar ratio to a value lower than the stoichiometric ratio as disclosed in PCT Application JP97 / 04169. ing.
As a result, acrylonitrile and acrylic acid can be obtained at a high selectivity in a combined amount, and the catalyst activity can be maintained for a long period of time. However, this is a disclosure of a technique for co-producing acrylonitrile and acrylic acid, and does not describe any technique for reacting unreacted ammonia with an organic acid generated in a reactor to fix it as an ammonium salt of the organic acid.
[0007]
Japanese Patent Application Laid-Open No. 2001-342169 discloses that the production of acrylonitrile and / or acrylic acid using propane as a raw material does not lower the catalyst performance by reducing the sulfur concentration in the raw material gas to 2000 ppm or less, and also reduces the product quality. The production method for keeping good is disclosed, but this is also a disclosure of a technique for co-producing acrylonitrile and acrylic acid, and reacting unreacted ammonia with an organic acid generated in a reactor to produce an organic acid. No technique for immobilization as an ammonium salt is described.
[0008]
[Problems to be solved by the invention]
Acrylonitrile production method capable of easily incinerating an extraction liquid from a quenching tower without passing through a step of removing ammonium sulfate and discharging sulfur oxides while maintaining the selectivity of acrylonitrile in a gas phase catalytic ammoxidation reaction of propane. It is to provide.
[0009]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to solve this problem, and as a result, when producing acrylonitrile by subjecting propane to gas-phase ammoxidation, the molar ratio of organic acid / unreacted ammonia in the ammoxidation reaction product gas was set to 1. By setting the organic acid to 0 to 3.0 (here, the organic acid is the sum of acrylic acid and acetic acid), the acrylonitrile selectivity is maintained, and the sulfur oxide is discharged without passing through the step of removing ammonium sulfate. The present invention has been found that there is an effect that the liquid drawn out of the quenching tower can be easily incinerated without waste, and that there is an effect that the waste heat from the incineration can be recovered as steam without corrosion of the apparatus.
[0010]
That is, according to the present invention, (1) when producing acrylonitrile by subjecting propane to gas phase catalytic ammoxidation reaction, when the molar ratio of organic acid / unreacted ammonia in the ammoxidation reaction product gas is 1.0 to 3.0, the ammoxidation is carried out. A method for producing acrylonitrile, comprising performing a reaction.
(2) The method according to (1), wherein the molar ratio of organic acid / unreacted ammonia in the ammoxidation reaction product gas is 1.0 to 2.0.
(3) The method for producing acrylonitrile is characterized in that the produced gas is introduced into a quenching tower, and the unreacted ammonia is reacted with the organic acid generated in the reactor in the quenching tower and fixed as an ammonium salt of the organic acid. (1) The method according to (2).
[0011]
(4) The method according to (1) to (3), wherein the ammoxidation reaction uses a catalyst represented by the general composition formula of the following formula (1).
_{Mo 1 V a Nb b X c} Z d O n ·· (1)
(Wherein, component X is at least one element selected from Te and Sb, and Z is tantalum, tungsten, titanium, aluminum, zirconium, chromium, manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium, Platinum, bismuth, boron, indium, phosphorus, germanium, rare earth elements, alkali metals, at least one element selected from alkaline earth metals,
a, b, c, d, and n represent the atomic ratio per Mo atom, a is 0.1 ≦ a ≦ 1, b is 0.01 ≦ b ≦ 1, c is 0.01 ≦ c ≦ 1, d Is 0 ≦ d ≦ 1, and n is a number determined by the valence of the constituent metal. )
Related to
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail. In the present invention, acrylonitrile is produced by ammoxidation of propane.
In this reaction, the raw material used, propane, generally contains n-butane, isobutane, ethylene, ethane, propylene and the like as impurities. Among them, the concentration of isobutane in the raw material propane is desirably 3 mol% or less. If it exceeds 3 mol%, methacrylonitrile in the product acrylonitrile increases. As a result, when used as a raw material for resins and fibers, a colored substance and an unintended polymer are produced in the final product, which causes quality problems.
[0013]
The reaction product gas obtained by subjecting the raw material gas to an ammoxidation reaction includes acrylonitrile, unreacted ammonia, propylene, propane, oxygen, nitrogen, hydrocyanic acid, acetonitrile, acrolein, carbon monoxide, carbon dioxide, organic acid (acrylic acid) Acetic acid), trace amounts of high-boiling products, steam, etc., in which the molar ratio of organic acid / unreacted ammonia is 1.0 to 3.0, preferably 1.0 to 2.0.
If it is smaller than this range, it is necessary to inject a large amount of acid from the outside into the quenching tower.
[0014]
Here, the reaction between the organic acid (acrylic acid, acetic acid) and the unreacted ammonia in the reaction product gas in the present invention is performed in a quenching tower. The quenching tower may be either a multi-stage quenching tower divided into upper and lower compartments (or more compartments) or a quenching tower in one compartment, but it is preferable to increase the concentration of organic matter in the discharged liquid to be incinerated. It is preferable to use a multi-stage quenching tower which is easy to use and requires less auxiliary fuel.
The makeup water for supplementing the water evaporated in the lower section of the quenching tower may return the liquid condensed in the upper section, or may supply water from the outside, but preferably the liquid condensed in the upper section. Returning is better in reducing the amount of wastewater. The temperature of the lower section of the quenching tower may be 100 ° C. or lower, but if the temperature is lowered, condensed water increases and the amount of wastewater increases, and if the temperature is high, the temperature approaches the decomposition temperature of the ammonium organic acid. ° C, more preferably 85-93 ° C. The pH of the circulating liquid in the quenching tower is from 5.0 to 6.5, and preferably from 5.2 to 6.0, in which the loss of acrylonitrile is small.
[0015]
As a reaction condition of the unreacted ammonia and the organic acid (acrylic acid, acetic acid), the molar ratio of the organic acid / unreacted ammonia in the acrylonitrile-forming gas becomes 1.0 to 3.0, preferably 1.0 to 2.0. If the ammonia / propane molar ratio of the raw material gas is adjusted within the range, the organic acid (acrylic acid, acetic acid) increases or decreases, and the pH of the circulating liquid in the quenching tower can be maintained in the above range. In addition, the quality of the circulating fluid is maintained in a good state, and the operation can be continued smoothly with little loss of acrylonitrile. If the catalyst performance or reaction conditions change for some reason and the pH value of the circulating liquid in the quenching tower exceeds 6.5, the organic acid in the reaction product gas can be reduced by lowering the ammonia / propane molar ratio of the raw material gas. (Acrylic acid, acetic acid) and the pH of the circulating liquid in the quenching tower decreases. On the other hand, when the pH of the circulating liquid in the quenching tower falls to less than 5.0, the organic acid (acrylic acid, acetic acid) in the reaction product gas decreases and the unreacted ammonia increases by increasing the ammonia / propane molar ratio of the raw material gas. , The pH of the circulating fluid rises.
[0016]
When the molar ratio of organic acid / unreacted ammonia in the acrylonitrile product gas is smaller than 1.0, unreacted ammonia is present in excess of the organic acid, and the pH of the circulating liquid in the quenching tower is larger than the above range. Therefore, the circulating liquid becomes basic, and it becomes necessary to add an acid such as sulfuric acid from the outside to maintain the pH in the above range.
When the molar ratio of the organic acid / unreacted ammonia in the acrylonitrile product gas is larger than 3.0, the selectivity of acrylonitrile is reduced, and the yield of the target product is reduced.
[0017]
As described above, in order to fix unreacted ammonia without adding sulfuric acid, the organic acid in the reaction product gas needs to be in excess of unreacted ammonia. At this time, the molar ratio of organic acid / unreacted ammonia needs to be 1 or more. However, even if this ratio temporarily drops below 1 due to fluctuations in operation, the unreacted ammonia becomes excessive immediately in the quench tower because the circulating liquid having a low pH circulates in the quench tower. Instead, the organic acid can maintain excess operation and fix unreacted ammonia without the addition of sulfuric acid.
[0018]
Another method for controlling the amount of organic acid generated is to split ammonia supplied to the reactor. Ammonia is divided into a lower part and an upper part of the reactor, and the lower part is supplied together with propane, oxygen or air. Only ammonia is supplied from the top. If the amount of ammonia in the lower part is adjusted to be smaller, while the supply of ammonia from the upper part is increased, acrylic acid increases and the pH of the circulating liquid in the quenching tower decreases. Conversely, if the amount of ammonia in the lower part is increased, acrylic acid decreases and the pH of the circulating liquid in the quenching tower increases.
[0019]
As described above, the pH of the circulating liquid in the quenching tower can be adjusted without adding an acid such as an organic acid (acetic acid or acrylic acid) or sulfuric acid from outside the reaction system. By controlling the circulating liquid in the quenching tower, unreacted ammonia and the organic acid generated in the reactor react in the quenching tower and can be fixed as an ammonium salt of the organic acid.
The equipment for incinerating the liquid extracted from the quenching tower is not particularly limited, and may be a commonly used incinerator for spraying and incineration, or a fluidized bed incinerator. It should be noted that a waste gas incinerator for incinerating waste gas discharged from the absorption tower in the production of the ammoxidation reaction may be used to simultaneously incinerate the waste gas from the absorption tower and the liquid discharged from the quench tower. There is no problem, and this is a preferable method because the equipment can be simplified. The auxiliary fuel used for the incineration treatment may contain a small amount of a sulfur compound, but it is preferable to use a fuel containing no sulfur compound (for example, hydrogen sulfide).
In addition, acrylonitrile is produced by a gas phase catalytic oxidation reaction of propane and ammonia, and the catalyst used at that time exhibits particularly excellent performance in the prior art described above.
[0020]
Among them, in the ammoxidation reaction using propane as a raw material, the catalyst represented by the general composition formula of the following formula (1) shows more excellent performance.
_{Mo 1 V a Nb b X c} Z d O n ·· (1)
(Wherein, component X is at least one element selected from Te and Sb, and Z is tantalum, tungsten, titanium, aluminum, zirconium, chromium, manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium, Platinum, bismuth, boron, indium, phosphorus, germanium, rare earth elements, alkali metals, at least one element selected from alkaline earth metals,
a, b, c, d, and n represent the atomic ratio per Mo atom, a is 0.1 ≦ a ≦ 1, b is 0.01 ≦ b ≦ 1, c is 0.01 ≦ c ≦ 1, d Is 0 ≦ d ≦ 1, and n is a number determined by the valence of the constituent metal. )
[0021]
These catalysts can also be used as a mixture containing 1 to 90% by weight of any carrier component such as silica, alumina, titania, zirconia, aluminosilicate, diatomaceous earth and the like.
For the method of producing acrylonitrile by the gas phase contact reaction of propane or propylene with ammonia, a fixed bed, fluidized bed, or moving bed reaction can be used. However, since this ammoxidation reaction is an exothermic reaction, it must be a fluidized bed. Is desirable.
When the reaction is carried out in a fluidized bed, the reaction temperature is preferably 300 to 490 ° C, more preferably 400 to 480 ° C. The reaction pressure is preferably from 0.01 to 1 MPa, more preferably from 0.03 to 0.5 MPa. The gas hourly space velocity in the reactor is preferably (SV) 100 to 10,000 hr ^-1 .
[0022]
The contact time is 0.1 × 10 ³ to 10 × 10 ³ (sec · kg / m ³ ), preferably 0.5 × 10 ^{3 to} 5 × 10 ³ (sec · kg / m ³ ). In the present invention, the contact time is represented by the following equation.
Contact time (sec · kg / m ³ ) = (W / F) × 273 / (273 + T) * P / 0.1
Where W = catalyst loading (kg)
F = Raw material mixed gas flow rate (Nm ³ / sec) under standard conditions (0 ° C., 1.13 × 10 ⁵ Pa)
T = reaction temperature (° C)
P = reaction pressure (MPa)
It is.
[0023]
When the proportion of oxygen supplied to the reactor is 0.1 to 5 mol times with respect to the raw material propane at the reactor inlet, and the proportion of supplied ammonia is 0.1 to 3 mol times with respect to propane, It is preferable because the selectivity and yield of the target acrylonitrile are improved.
Further, when the operation is performed in a place where the selectivity of acrylonitrile is maximized, the conversion is preferably limited to a range of 30% to 70% on a molar basis (hereinafter, the conversion is on a molar basis), and more preferably. More preferably, the conversion is in the range of 40% to 60%. When the reaction is performed at such a low conversion rate, it is possible to collect unreacted propane, recycle it into a reactor, and supply it again as a raw material.
[0024]
When not reacting unreacted propane and performing the reaction at a high conversion rate, it is preferable that the conversion rate is high because the amount of unreacted propane decreases, but at an excessively high conversion rate, the selectivity of acrylonitrile decreases. The conversion is preferably in the range of 60% to 95%, more preferably in the range of 70% to 95%.
Hereinafter, specific embodiments of the method of the present invention will be described using examples.
[0025]
【Example】
In Examples and Comparative Examples, the yields of acrylonitrile, acrylic acid, and acetic acid used to express the reaction results are defined by the following formulas.
Acrylonitrile yield (%) = (mol number of acrylonitrile generated) / (mol number of supplied propane) × 100
Acrylic acid yield (%) = (mol number of generated acrylic acid) / (mol number of supplied propane) × 100
Acetic acid yield (%) = (mol number of acetic acid generated × 2/3) / (mol number of supplied propane) × 100
Unreacted ammonia amount (%) = (mol number of unreacted ammonia) / (mol number of supplied propane) × 100
The amount of unreacted ammonia here is defined as follows by the following measuring method. The unreacted ammonia in the reactor outlet gas is measured by absorbing a predetermined amount of the reactor outlet gas into a 1/10 normal nitric acid aqueous solution and changing the color from yellow to blue with 1/10 normal sodium hydroxide using bromcresol green as an indicator. It measures by the reverse titration method which makes the discolored point the end point.
[0026]
Incidentally, in order to determine the amount of unreacted ammonia actually contained in the reaction product gas, since the organic acids (acrylic acid, acetic acid) in the gas at the outlet of the reactor enter into a 1/10 normal nitric acid aqueous solution, the amount of unreacted ammonia is determined. It is necessary to correct the amount that has reacted with the reactive ammonia. The amount of unreacted ammonia before the correction, that is, the apparent amount of unreacted ammonia, is determined by “the number of moles of ammonia determined by a back titration method”. Accordingly, the amount of unreacted ammonia is “(apparent number of moles of unreacted ammonia) + (moles of acrylic acid) + (moles of acetic acid)”.
[0027]
Embodiment 1
The charge composition of the catalyst is carrying the _{Mo 1 V 0.29 Sb 0.22 Nb 0.07} O n the SiO ₂ catalyst was prepared as follows.
Water 2.2kg ammonium heptamolybdate _{((NH 4) 6 Mo 7} O 24 · 4H 2 O) a 0.41996Kg, ammonium metavanadate _(NH 4 VO ₃₎ 0.08094kg, antimony trioxide _(Sb 2 O 0.07651 kg of ₃ ) was added, and the mixture was heated and refluxed for 3 hours and 30 minutes with stirring, and then cooled to about 70 ° C. to obtain a mixed solution A-1.
0.02868kg niobate containing 76.6% by weight _Nb 2 _{O 5} in water 0.286Kg, oxalic acid dihydrate _{(H 2 C 2 O 4 ·} 2H 2 O) was added 0.05212Kg, stirred After heating and dissolving at about 60 ° C., a mixed liquid B-1 cooled to about 30 ° C. was obtained.
[0028]
1.6667 kg of silica sol containing 30% by weight as SiO ₂ was added to the obtained mixture A-1. The liquid temperature dropped to about 50 ° C. Further, 0.117 kg of a hydrogen peroxide solution containing 15% by weight as H ₂ O ₂ was added, and stirring was continued at 50 ° C. for 1 hour. During that time, the color of the solution changed from dark blue to reddish brown. Next, the mixed solution B-1 was added to obtain a raw material mixture. The obtained raw material mixture was supplied to a centrifugal spray dryer and dried to obtain a fine spherical dry powder. The dryer inlet temperature was 210 ° C and the outlet temperature was 120 ° C. 0.1 kg of the obtained dry powder was filled in a stainless steel tube having a diameter of 25 × 10 ⁻³ m and calcined at 640 ° C. for 2 hours under a nitrogen gas flow of 10 × 10 ⁻⁶ Nm ³ / sec to obtain a catalyst. Was.
[0029]
The obtained catalyst was filled in a Vycor glass fluidized bed type reaction tube having an inner diameter of 25 × 10 ⁻³ m, and propane: ammonia: oxygen: helium = 1: 0.45: 1 at a reaction temperature of 440 ° C. and a normal reaction pressure. A mixed gas having a molar ratio of 0.1: 4.4 was passed at a contact time of 1.5 × 10 ³ (sec · kg / m ³ ) to perform a reaction.
The reaction was carried out in this manner, and after about 4 hours, the reaction results were as follows: propane conversion: 50.97%, acrylonitrile selectivity: 60.6%, acrylic acid selectivity: 8.1%, acetic acid selectivity: 0.8%, unreacted Ammonia was 3.7% and the molar ratio of organic acid / unreacted ammonia was 1.2. That is, the organic acid was in excess of the true unreacted ammonia.
[0030]
Embodiment 2
The charge composition of the catalyst is carrying the _{Mo 1 V 0.30 Te 0.25 Nb 0.14} O n the SiO ₂ catalyst Sb is another become Te was prepared in the same manner as in Example 1.
This catalyst was charged into a Vycor glass fluidized bed type reaction tube having an inner diameter of 25 × 10 ⁻³ m, and propane: ammonia: oxygen: helium = 1: 0.9: 3.1 at a reaction temperature of 440 ° C. and a normal reaction pressure. : A mixed gas having a molar ratio of 12.4 was passed at a contact time of 2.9 × 10 ³ (sec · kg / m ³ ) to carry out a reaction.
The reaction was carried out in this manner. After about 4 hours, the reaction results were as follows: propane conversion rate 85.6%, acrylonitrile selectivity 54.1%, acrylic acid selectivity 5.0%, acetic acid selectivity 0.4%, unreacted Ammonia was 3.3% and the molar ratio of organic acid / unreacted ammonia was 1.4. That is, the organic acid was in excess of the true unreacted ammonia.
[0031]
[Comparative Example 1]
A catalyst prepared in the same manner as in Example 1 was charged into a Vycor glass fluidized bed type reaction tube having an inner diameter of 25 × 10 ⁻³ m, and propane: ammonia: oxygen: helium = 1 at a reaction temperature of 440 ° C. and a normal reaction pressure. : 0.69: 1.7: 6.8 mixed gas was passed at a contact time of 1.6 × 10 ³ (sec · kg / m ³ ) to carry out the reaction.
The reaction was carried out as described above. After about 4 hours, the reaction results were as follows: propane conversion 51.1%, acrylonitrile selectivity 61.4%, acrylic acid selectivity 3.0%, acetic acid selectivity 0.2%, unreacted Ammonia was 5.0%, and the molar ratio of organic acid / unreacted ammonia was 0.3. At this time, sulfuric acid required to neutralize the reaction product gas was 0.157 kg per 1 kg of acrylonitrile produced.
[0032]
[Comparative Example 2]
A catalyst prepared in the same manner as in Example 2 was charged into a Vycor glass fluidized bed type reaction tube having an inner diameter of 25 × 10 ⁻³ m, and propane: ammonia: oxygen: helium = 1 at a reaction temperature of 440 ° C. and a reaction pressure of normal pressure. : 0.4: 2.9: 11.6 mixed gas was passed at a contact time of 3.0 × 10 ³ (sec · kg / m ³ ) to carry out the reaction.
The reaction was carried out in this manner, and after about 4 hours, the reaction results were as follows: propane conversion rate 85.3%, acrylonitrile selectivity 28.4%, acrylic acid selectivity 11.8%, acetic acid selectivity 1.4%, unreacted Ammonia was 1.0%, and the molar ratio of organic acid / unreacted ammonia was 11. That is, the organic acid was in excess of the true unreacted ammonia.
[0033]
[Comparative Example 3]
A catalyst prepared in the same manner as in Example 2 was charged into a Vycor glass fluidized bed type reaction tube having an inner diameter of 25 × 10 ⁻³ m, and propane: ammonia: oxygen: helium = 1 at a reaction temperature of 440 ° C. and a reaction pressure of normal pressure. : 0.7: 3.0: 12.0 mixed gas was passed at a contact time of 3.0 × 10 ³ (sec · kg / m ³ ) to carry out the reaction.
The reaction was carried out in this way, and after about 4 hours, the reaction results were as follows: propane conversion 85.1%, acrylonitrile selectivity 46.0%, acrylic acid selectivity 7.6%, acetic acid selectivity 0.7%, Unreacted ammonia was 1.9%, and the molar ratio of organic acid / unreacted ammonia was 3.7. That is, the organic acid was in excess of the true unreacted ammonia.
[0034]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the acrylonitrile manufacturing method which can incinerate the extraction liquid of a quenching tower easily without passing through the process of removing ammonium sulfate and discharging sulfur oxide, maintaining the selectivity of acrylonitrile is provided.

Claims (4)

When producing acrylonitrile by subjecting propane to gas phase catalytic ammoxidation reaction, the ammoxidation reaction is performed at a molar ratio of organic acid / unreacted ammonia in the ammoxidation reaction product gas of 1.0 to 3.0. For producing acrylonitrile. 2. The method according to claim 1, wherein the molar ratio of organic acid / unreacted ammonia in the ammoxidation reaction product gas is 1.0 to 2.0. Patent for a method for producing acrylonitrile, wherein the produced gas is introduced into a quenching tower, and unreacted ammonia is reacted with the organic acid generated in a reactor in the quenching tower and fixed as an ammonium salt of the organic acid. The method according to claim 1. The method according to any one of claims 1 to 3, wherein the ammoxidation reaction uses a catalyst represented by the following general formula (1).
_{Mo 1 V a Nb b X c} Z d O n ·· (1)
(Wherein, component X is at least one element selected from Te and Sb, and Z is tantalum, tungsten, titanium, aluminum, zirconium, chromium, manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium, Platinum, bismuth, boron, indium, phosphorus, germanium, rare earth elements, alkali metals, at least one element selected from alkaline earth metals,
a, b, c, d, n represent the atomic ratio per Mo atom, a is 0.1 ≦ a ≦ 1, b is 0.01 ≦ b ≦ 1, c is 0.01 ≦ c ≦ 1, d Is 0 ≦ d ≦ 1, and n is a number determined by the valence of the constituent metal. )