CN109988082B - Method for preparing acrylonitrile by continuous oxidative dehydrogenation - Google Patents
Method for preparing acrylonitrile by continuous oxidative dehydrogenation Download PDFInfo
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Abstract
The invention provides a method for preparing acrylonitrile by continuous oxidative dehydrogenation, which comprises the following steps: taking propionitrile as a raw material, and carrying out oxidative dehydrogenation reaction under the catalytic action of a nickel catalyst to obtain acrylonitrile; the nickel-based catalyst consists of Ni, Co, Mo and Zr. According to the method for preparing acrylonitrile by continuous oxidative dehydrogenation, only propionitrile, acrylonitrile and water which are not completely reacted exist in the product, the propionitrile and the acrylonitrile are obtained after the reaction product is separated, and the propionitrile can be recycled. The process has the advantages of simple route, cleanness, no pollution, short subsequent separation process, no corrosion to equipment, high yield and great industrial application value. In addition, propionitrile is generally only used as a solvent or a medical intermediate, so that the application is less, the market capacity is small, acrylonitrile is widely used, and the market capacity of propionitrile is greatly increased after the propionitrile is converted into the acrylonitrile.
Description
Technical Field
The invention relates to the technical field of organic synthesis, in particular to a method for preparing acrylonitrile by continuous oxidative dehydrogenation.
Background
Acrylonitrile is an important monomer for synthetic fibers, synthetic rubbers, and synthetic resins. Polyacrylonitrile fiber, i.e., acrylic fiber, made from acrylonitrile behaves very like wool, and is therefore also called synthetic wool. Acrylonitrile and butadiene are copolymerized to prepare nitrile rubber which has good oil resistance, cold resistance, wear resistance and electrical insulation performance, and the performance is stable under the action of most chemical solvents, sunlight and heat. The ABS resin prepared by copolymerizing acrylonitrile, butadiene and styrene has the advantages of light weight, cold resistance, good impact resistance and the like. Acrylamide and acrylic acid and esters thereof can be prepared by the hydrolysis of acrylonitrile, and are important organic chemical raw materials. Acrylonitrile can also be subjected to electrolytic hydrogenation coupling to prepare adiponitrile, and adiponitrile and hexamethylenediamine can be prepared by hydrogenation of adiponitrile, wherein the hexamethylenediamine is a nylon 66 raw material and can be used for preparing water repellent agents, adhesives and the like, and is also used in other organic synthesis and medical industries and used as a grain fumigant and the like. In addition, the product is also an aprotic polar solvent and is used as an oil field mud auxiliary agent PAC142 raw material. Acrylonitrile is also an intermediate in the preparation of the insecticide fipronil.
There are three main industrial production methods for acrylonitrile, namely, a cyanoethanol method, an acetylene method and a propylene ammoxidation method.
Wherein, the cyanoethanol method mainly takes ethylene oxide and hydrocyanic acid as raw materials, the cyanoethanol is obtained by reaction in the presence of water and trimethylamine, and then acrylonitrile is obtained by dehydration at the temperature of 280 ℃ under the condition of 200-. The acrylonitrile produced by the method has high purity, but the hydrocyanic acid has high toxicity and high cost.
The acetylene method is characterized in that acetylene and hydrocyanic acid are used as main raw materials, and acrylonitrile is obtained by reaction at 80-90 ℃ under the catalytic action of cuprous chloride-potassium chloride-sodium chloride dilute hydrochloric acid solution. The method has simple production process and good yield, and the yield can reach 97 percent based on hydrocyanic acid. But the method has more side reactions, difficult product refining and high toxicity, and the price of acetylene as a raw material is higher than that of propylene, so the method lags behind the propylene ammoxidation method in the technical and economic aspects.
The propylene ammoxidation method takes propylene, ammonia, air and water as raw materials, the raw materials enter a fluidized bed or a fixed bed reactor according to a certain proportion, and acrylonitrile is generated at the temperature of 400 ℃ and the normal pressure under the action of a phosphorus-molybdenum-bismuth system or antimony-iron system catalyst taking silica gel as a carrier. Then removing unreacted ammonia by using dilute sulfuric acid through a neutralization tower, absorbing gases such as acrylonitrile and the like by using water through an absorption tower to form an aqueous solution, separating acetonitrile from the aqueous solution through an extraction tower, removing hydrocyanic acid in a hydrocyanic acid dehydrogenation tower, and dehydrating and rectifying to obtain an acrylonitrile product, wherein byproducts comprise acetonitrile, hydrocyanic acid and ammonium sulfate. The method has large energy consumption and pollution.
Disclosure of Invention
In view of the above, the technical problem to be solved by the present invention is to provide a method for preparing acrylonitrile by continuous oxidative dehydrogenation, in which propionitrile is used as a raw material, and acrylonitrile is prepared by a new oxidative dehydrogenation method, so that the process route is simple, and the yield and purity are high.
In order to solve the technical problems, the invention provides a method for preparing acrylonitrile by continuous oxidative dehydrogenation, which comprises the following steps:
taking propionitrile as a raw material, and carrying out oxidative dehydrogenation reaction under the catalytic action of a nickel catalyst to obtain acrylonitrile;
the nickel-based catalyst is composed of oxides of Ni, Co, Mo and Zr.
The raw material of the propionitrile is propionitrile, the source of the propionitrile is not particularly limited in the invention, and the propionitrile can be generally commercially available, such as a general industrial grade raw material, and in some specific embodiments of the invention, the mass content of the propionitrile is 99.5%.
The nickel-based catalyst is composed of oxides of Ni, Co, Mo and Zr.
Preferably, the molar ratio of Ni, Co, Mo and Zr is 10-12: 3-4: 5: 2 to 3.
More preferably, the molar ratio of Ni, Co, Mo and Zr is 11-12: 3-3.5: 5: 2 to 2.5. In some embodiments of the invention, the molar ratio of Ni, Co, Mo and Zr is 12: 3: 5: 2.
preferably, the catalyst is prepared according to the following method:
mixing and dissolving nickel-containing water-soluble inorganic salt, cobalt-containing water-soluble inorganic salt, molybdenum-containing water-soluble inorganic salt and zirconium-containing water-soluble inorganic salt in water to obtain a mixed solution;
and heating the mixed solution for reaction, cooling and drying to obtain the catalyst.
Firstly, mixing nickel-containing water-soluble inorganic salt, cobalt-containing water-soluble inorganic salt, molybdenum-containing water-soluble inorganic salt and zirconium-containing water-soluble inorganic salt in water, stirring and dissolving, more preferably, firstly mixing the nickel-containing water-soluble inorganic salt, the cobalt-containing water-soluble inorganic salt and the molybdenum-containing water-soluble inorganic salt, adjusting the pH value to 7, then mixing with the zirconium-containing water-soluble inorganic salt, and stirring. The stirring mode is not limited in the invention, and the stirring mode is well known to those skilled in the art; the stirring time is preferably 20-30 min; the preferred stirring time for adding the zirconium hydroxide is 40-60 min.
In accordance with the present invention, the nickel-containing water-soluble inorganic salts include, but are not limited to, nickel nitrate hexahydrate; the mass concentration of the nickel water-soluble inorganic salt is preferably more than or equal to 99%.
The cobalt-containing water-soluble inorganic salts include, but are not limited to, cobalt nitrate hexahydrate; the concentration of the cobalt-containing water-soluble inorganic salt is preferably 0.50-0.75 mol/L; the molybdenum-containing water-soluble inorganic salts include, but are not limited to, ammonium molybdate; the mass concentration of the molybdenum water-soluble inorganic salt is preferably more than or equal to 98 percent.
The water-soluble inorganic salt containing zirconium includes, but is not limited to, zirconium hydroxide. The mass concentration of the water-soluble inorganic salt containing zirconium is preferably more than or equal to 99.9 percent.
And heating the mixed solution for reaction, cooling and drying to obtain the catalyst.
The invention preferably transfers the mixed solution to a polytetrafluoroethylene reaction kettle; the invention preferably puts the reaction kettle into an air-blast drying oven with the temperature of 160 ℃ for 12 hours constantly.
The cooling is not limited in the present invention, and the cooling may be naturally performed to room temperature.
After cooling, using a vacuum pump, a suction flask and filter paper for vacuum pumping and suction filtration, repeatedly washing the organic solvent by using absolute ethyl alcohol, then washing by using distilled water, and drying to obtain the catalyst; the drying temperature is 70-80 ℃; the drying time is 10-12 h.
Then, the catalyst for a fixed bed was prepared by passing through a catalyst molding machine.
In the oxidative dehydrogenation process of propionitrile, carbon-nitrogen triple bond is a strong polar covalent bond, so that carbon-carbon bond far away from cyano group is easy to break in the reaction process, acetonitrile and methyl are generated, and methyl is combined with each other to generate ethane. The specific catalyst is selected, and the dehydrogenation capacity of the catalyst is controlled by adjusting the ratio of four noble metals in the catalyst, so that carbon-carbon bonds far away from the cyano group are oxidized and dehydrogenated, the breakage of the carbon-carbon bonds is further inhibited, and the carbon-carbon bonds far away from the cyano group are oxidized and dehydrogenated under the catalytic action of the catalyst to generate acrylonitrile.
The reaction equation for the above reaction is as follows:
in the present invention, the reaction can be preferably carried out in a continuous chemical production apparatus such as a fixed bed reactor.
Preferably, the process flow diagram of the reaction is shown in fig. 1.
Specifically, the reaction system of the reaction comprises a premixer, a fixed bed reactor, a gas-liquid separation device, a continuous extraction separation device and a continuous rectification device which are connected in sequence.
The premixer is used for mixing and absorbing propionitrile liquid and oxygen in the early stage of gas-liquid, so that the gas-liquid emulsification effect is kept, and the reaction progress is accelerated.
The fixed bed reactor of the present invention is not particularly limited, and may be a general fixed bed reactor known to those skilled in the art, and a fixed bed reactor made of a metal material is preferably used in the present invention.
The invention fills the nickel catalyst into a fixed bed reactor.
The filling process is preferably as follows:
filling quartz sand at the bottom of the fixed bed reactor, filling a catalyst in the middle of the fixed bed reactor, and filling quartz sand at the top of the fixed bed reactor.
Preferably, the nickel catalyst accounts for 0.01-0.50% of the mass of the propionitrile.
Preferably, the reaction system is purged with nitrogen before the reaction, the nitrogen enters the reaction system from the premixer, the purging speed and time can be set according to the requirement, and oxygen can be isolated, that is, oxygen or air is prevented from entering the reaction system, and the invention is not particularly limited to this. Preferably, the purging speed of the nitrogen is 10-40 mL/min, and the time is 5-20 min. In some embodiments of the invention, the purge rate is 20mL/min and the time is 10 min.
The reaction system is purged by nitrogen in advance to isolate oxygen, and under the condition of no propionitrile introduction, the catalyst is ensured to be in an oxygen-free state in the temperature rise process of the reaction system, so that the catalyst is prevented from coking, and the activity of the catalyst is ensured.
And meanwhile, the temperature of the fixed bed reactor is increased to 200-220 ℃ from room temperature, and the catalyst in the fixed bed reactor is activated.
The temperature rise speed can be set according to the experimental condition, and is preferably 10-30 ℃/min. In some embodiments of the invention, the temperature increase rate is 20 ℃/min. The slow temperature rise is beneficial to the slow activation of the catalyst.
In the invention, the reaction takes air or oxygen as an oxidant.
When the reaction temperature reaches a predetermined temperature, air or oxygen is started to be introduced into the reaction system from the premixer. Preferably, the air or oxygen flow rate is slowly increased from 0mL/min to 1500 mL/min. The increasing rate of the air or oxygen flow is not particularly limited, and the increasing rate can be set according to needs or reaction conditions, so that the air flow can be stabilized, and the reaction can be performed stably. Preferably, the increasing speed of the air or oxygen flow is 50-200 mL/min. In some embodiments of the invention, the rate of increase of the air or oxygen flow rate is 100 mL/min.
While passing air, the nitrogen flow rate was slowly decreased to 0 mL/min. The nitrogen flow rate reduction rate is not particularly limited, and the nitrogen flow rate reduction rate can be set according to needs or reaction conditions, so that the gas flow can be stabilized, and the reaction can be performed stably. Preferably, the reduction speed of the nitrogen flow is 5-20 mL/min. In some embodiments of the invention, the nitrogen flow rate is reduced at a rate of 10 mL/min.
According to the invention, preferably, the opening degree of the outlet is reduced, and the back pressure is slowly increased to the suitable reaction pressure at the tail end of the fixed bed reactor, preferably, the back pressure is increased to 1.0-7.0 MPa. In some embodiments of the invention, the back pressure is 2.0 MPa.
And after the pressure is stable, introducing liquid-phase propionitrile into the reaction system from the premixer, and performing early gas-liquid mixing absorption on the liquid-phase propionitrile and air in the premixer and enabling the liquid-phase propionitrile and the air to stably enter the reaction system.
The flow rate of the propionitrile is preferably 2-7 mL/min, and in some embodiments of the invention, the flow rate of the propionitrile is 5 mL/min.
After the mixture of propionitrile and air is fed into fixed bed reactor, under the action of nickel catalyst the oxidative dehydrogenation reaction can be implemented so as to obtain acrylonitrile.
The residence time of the reaction is preferably ≤ 5 min.
The reaction temperature is preferably 200-450 ℃, and the reaction pressure is preferably 1.0-7.0 MPa.
Under the pressure condition, the oxygen concentration is higher, the oxidation is more sufficient, and the yield is higher.
The molar ratio of propionitrile to air is preferably 1: (5-15); the molar ratio of propionitrile to oxygen is preferably 1: (1-3).
After the reaction is finished, the reaction liquid enters a gas-liquid separation device, and the recovered gas can be recycled.
And (3) allowing the liquid phase material to enter a continuous extraction separation device, wherein the water phase is stored for later use, allowing the oil phase to enter a continuous rectification device, and performing continuous rectification treatment to obtain acrylonitrile, wherein a small amount of byproduct propionitrile can be recycled.
According to the method for preparing acrylonitrile by continuous oxidative dehydrogenation, only propionitrile, acrylonitrile and water which are not completely reacted exist in the product, the propionitrile and the acrylonitrile are obtained after the reaction product is separated, and the propionitrile can be recycled. The process has the advantages of simple route, cleanness, no pollution, short subsequent separation process, no corrosion to equipment, high yield and great industrial application value. In addition, propionitrile is generally only used as a solvent or a medical intermediate, so that the application is less, the market capacity is small, acrylonitrile is widely used, and the market capacity of propionitrile is greatly increased after the propionitrile is converted into the acrylonitrile.
Drawings
FIG. 1 is a mass spectrum of acrylonitrile;
FIG. 2 mass spectrum of sample obtained by the reaction of example 2 of the present invention;
FIG. 3 is a process flow diagram of the continuous oxidative dehydrogenation reaction for preparing acrylonitrile provided by the invention.
Detailed Description
In order to further illustrate the present invention, the method for producing acrylonitrile by continuous oxidative dehydrogenation provided by the present invention will be described in detail with reference to examples.
In the following examples, the reactor used was a tubular fixed bed reactor.
Wherein, the gas recycling adopts a gas compressor to compress and is injected into a reaction system. The propionitrile is rectified to obtain a pure product, and the pure product is pumped into a reaction system by a feed pump. The gas-liquid separation adopts a gas-liquid separation tank for separation.
Example 1
30.00g of nickel nitrate hexahydrate is weighed and added into 80mL of 0.5mol/L cobalt nitrate hexahydrate solution, stirring is carried out to dissolve the nickel nitrate hexahydrate solution, then 10.00g of ammonium molybdate is weighed and dissolved into the solution, 2.5mol/L NaOH solution is added into the solution, the pH value is adjusted to 7, stirring is carried out for 30min, then 7.5g of zirconium hydroxide is added, and stirring is carried out continuously for 1.0 h. Then the mixed solution is transferred into a polytetrafluoroethylene reaction kettle, and the reaction kettle is placed into a 160 ℃ forced air drying oven for constant 12 hours. Taking out the reaction kettle, cooling to room temperature, and using a vacuum pump; and (3) vacuumizing and filtering the suction flask and the filter paper, repeatedly washing the organic solvent by using absolute ethyl alcohol, washing by using distilled water, drying in an oven at 80 ℃ for 12 hours to obtain a catalyst sample, and preparing the catalyst for the fixed bed by using a catalyst forming machine.
Example 2
48.40g of nickel nitrate hexahydrate is weighed and added into 80mL of 0.5mol/L cobalt nitrate hexahydrate solution, stirring is carried out to dissolve the cobalt nitrate hexahydrate solution, then 14.85g of ammonium molybdate is weighed and dissolved into the solution, 2.5mol/L NaOH solution is added into the solution, the pH value is adjusted to 7, stirring is carried out for 30min, 11.38g of zirconium hydroxide is added, and stirring is carried out continuously for 1.0 h. Then the mixed solution is transferred into a polytetrafluoroethylene reaction kettle, and the reaction kettle is placed into a 160 ℃ forced air drying oven for constant 12 hours. Taking out the reaction kettle, cooling to room temperature, and using a vacuum pump; and (3) vacuumizing and filtering the suction flask and the filter paper, repeatedly washing the organic solvent by using absolute ethyl alcohol, washing by using distilled water, drying in an oven at 80 ℃ for 12 hours to obtain a catalyst sample, and preparing the catalyst for the fixed bed by using a catalyst forming machine.
Example 3
Weighing 52.87 nickel nitrate hexahydrate and adding into 80mL cobalt nitrate hexahydrate solution with the concentration of 0.5mol/L, stirring to dissolve, then weighing 14.85 and dissolving into the solution, adding 2.5mol/L NaOH solution into the solution, adjusting the pH to 7, stirring for 30min, then adding 7.58 zirconium hydroxide, and continuing stirring for 1.0 h. Then the mixed solution is transferred into a polytetrafluoroethylene reaction kettle, and the reaction kettle is placed into the reaction kettle
The inside of the blast drying box is kept for 12 hours. Taking out the reaction kettle, cooling to room temperature, and using a vacuum pump; and (3) vacuumizing and filtering the suction flask and the filter paper, repeatedly washing the organic solvent by using absolute ethyl alcohol, washing by using distilled water, drying in an oven at 80 ℃ for 12 hours to obtain a catalyst sample, and preparing the catalyst for the fixed bed by using a catalyst forming machine.
Example 4
A fixed bed reactor was charged with 10mL of the nickel-based catalyst prepared in example 1 (molar ratio of Ni, Co, Mo and Zr 10: 3: 5: 3) by the following procedure: filling quartz sand at the bottom of the fixed bed, filling a catalyst in the middle of the fixed bed, and filling quartz sand at the top of the fixed bed. And nitrogen is connected with the premixer, enters from the premixer, purges the reaction system at the speed of 20mL/min for 10min, and slowly raises the reaction temperature from room temperature to 200 ℃ at the speed of 20 ℃/min.
When the reaction temperature reaches the preset temperature, air is introduced into the reaction system from the premixer, the air flow is slowly increased to 1500mL/min from 0mL/min, the air flow is increased at the rate of 100mL/min, and meanwhile, the nitrogen flow is slowly decreased to 0mL/min from 20mL/min, and the reduction rate is 10 mL/min. The opening degree of an outlet is reduced, the back pressure is slowly increased to 2.0MPa at the tail end of the fixed bed reactor, liquid-phase propionitrile is introduced from the premixer after the pressure is stable, the flow rate of the propionitrile is 5mL/min, the reaction retention time is less than or equal to 5min, reaction liquid is collected after stable discharging, and after extraction and separation, oil-phase gas chromatography analysis and detection analysis is carried out, wherein the content of the propionitrile is 38.6 percent, and the content of acrylonitrile is 60.7 percent. The reaction yield was 56.9%.
The structure of the reaction product was characterized by Mass spectrometry (Mass). FIG. 1 is a mass spectrum of acrylonitrile standard, and FIG. 2 is a mass spectrum of a sample obtained by the reaction of example 2 of the present invention. As can be confirmed from FIGS. 1 and 2, acrylonitrile was produced in example 2 of the present invention.
Example 5
A fixed bed reactor was charged with 10mL of the nickel-based catalyst prepared in example 1 (molar ratio of Ni, Co, Mo and Zr was 10: 3: 5: 3), the charging was carried out in the same manner as in example 2, the reaction system was purged with nitrogen at 20mL/min for 15min, the reaction temperature was slowly raised from room temperature to 300 ℃ at a rate of 20 ℃/min.
When the reaction temperature reaches the preset temperature, air starts to be introduced into the reaction system from the premixer, the air flow is slowly increased from 0mL/min to 1500mL/min at the rate of 100mL/min, and meanwhile, the nitrogen flow is slowly decreased from 20mL/min to 0mL/min at the rate of 10 mL/min. Slowly back-pressing the tail end of the fixed bed reactor to 2.0MPa, introducing liquid-phase propionitrile after the pressure is stable, wherein the flow rate of the propionitrile is 5mL/min, the reaction retention time is less than or equal to 5min, collecting reaction liquid after stable discharging, extracting and separating, and performing oil-phase gas chromatography analysis and detection analysis, wherein the content of the propionitrile is 28.4%, and the content of acrylonitrile is 70.5%. The reaction yield was 66.9%.
Example 6
A fixed bed reactor was charged with 20mL of the nickel-based catalyst prepared in example 1 (molar ratio of Ni, Co, Mo and Zr 10.0: 3: 5: 3), the charging was carried out in the same manner as in example 2, the reaction system was purged with nitrogen at 20mL/min for 20min, the reaction temperature was slowly raised from room temperature to 300 ℃ at a rate of 20 ℃/min.
When the reaction temperature reaches the preset temperature, air starts to be introduced into the reaction system from the premixer, the air flow is slowly increased from 0mL/min to 1500mL/min at the rate of 100mL/min, and meanwhile, the nitrogen flow is slowly decreased from 20mL/min to 0mL/min at the rate of 10 mL/min. Slowly back-pressing the tail end of the fixed bed reactor to 2.0MPa, introducing liquid-phase propionitrile after the pressure is stable, wherein the flow rate of the propionitrile is 5mL/min, the reaction residence time is less than or equal to 5min, collecting reaction liquid after stable discharging, extracting and separating, and performing oil-phase gas chromatography analysis and detection analysis, wherein the content of the propionitrile is 15.1%, and the content of acrylonitrile is 83.8%. The reaction yield was 78.5%.
Example 7
The fixed bed reactor was charged with 25mL of the nickel-based catalyst prepared in example 1 (molar ratio of Ni, Co, Mo and Zr was 10: 3: 5: 3), the charging was performed in the same manner as in example 2, the reaction system was purged with nitrogen at 20mL/min for 20min, and the reaction temperature was slowly raised from room temperature to 300 ℃ at a rate of 20 ℃/min.
When the reaction temperature reaches the preset temperature, air starts to be introduced into the reaction system from the premixer, the air flow is slowly increased from 0mL/min to 1500mL/min at the rate of 100mL/min, and meanwhile, the nitrogen flow is slowly decreased from 20mL/min to 0mL/min at the rate of 10 mL/min. Slowly back-pressing the tail end of the fixed bed reactor to 2.0MPa, introducing liquid-phase propionitrile after the pressure is stable, wherein the flow rate of the propionitrile is 5mL/min, the reaction residence time is less than or equal to 5min, collecting reaction liquid after stable discharging, extracting and separating, and taking oil-phase gas chromatography for analysis and detection, wherein the content of the propionitrile is 8.1%, and the content of acrylonitrile is 90.8%. The reaction yield was 86.7%.
Example 8
A fixed bed reactor was charged with 20mL of the nickel-based catalyst prepared in example 2 (molar ratio of Ni, Co, Mo and Zr 12: 3: 5: 2), the charging was performed in the same manner as in example 2, the reaction system was purged with nitrogen at 20mL/min for 20min, the reaction temperature was slowly increased from room temperature to 400 ℃ at a rate of 20 ℃/min.
When the reaction temperature reaches the preset temperature, air starts to be introduced into the reaction system from the premixer, the air flow is slowly increased from 0mL/min to 1500mL/min at the rate of 100mL/min, and meanwhile, the nitrogen flow is slowly decreased from 20mL/min to 0mL/min at the rate of 10 mL/min. Slowly back-pressing the tail end of the fixed bed reactor to 2.0MPa, introducing liquid-phase propionitrile after the pressure is stable, wherein the flow rate of the propionitrile is 5mL/min, the reaction residence time is less than or equal to 5min, collecting reaction liquid after stable discharging, extracting and separating, and taking oil-phase gas chromatography for analysis and detection, wherein the content of the propionitrile is 8.1%, and the content of acrylonitrile is 90.8%. The reaction yield was 86.0%.
Example 9
A fixed bed reactor was charged with 20mL of the nickel-based catalyst prepared in example 3 (molar ratio of Ni, Co, Mo and Zr 12: 4: 5: 2), the charging was performed in the same manner as in example 2, the reaction system was purged with nitrogen at 20mL/min for 20min, the reaction temperature was slowly raised from room temperature to 400 ℃ at a rate of 20 ℃/min.
When the reaction temperature reaches the preset temperature, air starts to be introduced into the reaction system from the premixer, the air flow is slowly increased from 0mL/min to 1500mL/min at the rate of 100mL/min, and meanwhile, the nitrogen flow is slowly decreased from 20mL/min to 0mL/min at the rate of 10 mL/min. Slowly back-pressing the tail end of the fixed bed reactor to 2.0MPa, introducing liquid-phase propionitrile after the pressure is stable, wherein the flow rate of the propionitrile is 5mL/min, the reaction residence time is less than or equal to 5min, collecting reaction liquid after stable discharging, extracting and separating, and taking oil-phase gas chromatography for analysis and detection, wherein the content of the propionitrile is 8.1%, and the content of acrylonitrile is 90.8%. The reaction yield was 83.5%.
According to the embodiment, the acrylonitrile is prepared by the method, the process route is simple, and the yield and the purity are high.
The above description of the embodiments is only intended to facilitate the understanding of the method of the invention and its core idea. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.
Claims (10)
1. A method for preparing acrylonitrile by continuous oxidative dehydrogenation comprises the following steps:
taking propionitrile as a raw material, and carrying out oxidative dehydrogenation reaction under the catalytic action of a nickel catalyst to obtain acrylonitrile;
the catalyst is prepared according to the following method:
firstly, mixing nickel-containing water-soluble inorganic salt, cobalt-containing water-soluble inorganic salt and molybdenum-containing water-soluble inorganic salt, adjusting the pH value to 7, mixing with zirconium-containing water-soluble inorganic salt, and stirring to obtain a mixed solution;
and heating the mixed solution for reaction, cooling and drying to obtain the catalyst.
2. The method according to claim 1, wherein the molar ratio of Ni, Co, Mo and Zr is 10-12: 3-4: 5: 2 to 3.
3. The method according to claim 2, wherein the molar ratio of Ni, Co, Mo and Zr is 11-12: 3-3.5: 5: 2 to 2.5.
4. The method of claim 3, wherein the molar ratio of Ni, Co, Mo and Zr is 12: 3: 5: 2.
5. the process according to claim 1, characterized in that the reaction is carried out in a fixed bed reactor.
6. The method according to claim 5, wherein the continuous oxidative dehydrogenation preparation method of acrylonitrile comprises:
a) filling a catalyst in a fixed bed reactor;
b) purging the reactor with an inert gas;
c) introducing an oxidant, introducing propionitrile from the premixer, and performing oxidative dehydrogenation reaction to obtain acrylonitrile; the oxidant is air or oxygen.
7. The method according to claim 1, wherein the reaction temperature is 200 to 450 ℃ and the reaction pressure is 1.0 to 7.0 MPa.
8. The process according to claim 7, wherein the molar ratio of propionitrile to oxygen is 1: (1-3).
9. The method according to claim 1, wherein the nickel-based catalyst accounts for 0.01-0.50% of the mass of the propionitrile.
10. The method according to claim 1, wherein the water-soluble inorganic salt containing zirconium is zirconium hydroxide.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3821278A (en) * | 1970-02-09 | 1974-06-28 | Mobil Oil | Oxidative dehydrogenation of propionitrile to aerylonitrile |
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2019
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| US3821278A (en) * | 1970-02-09 | 1974-06-28 | Mobil Oil | Oxidative dehydrogenation of propionitrile to aerylonitrile |
| JPS5350119A (en) * | 1976-10-15 | 1978-05-08 | Monsanto Co | Method of oxidative dehydration of propionitrile |
| US4178305A (en) * | 1976-10-15 | 1979-12-11 | Monsanto Company | Oxidative dehydrogenation of propionitrile to acrylonitrile |
| CN1037282A (en) * | 1988-04-29 | 1989-11-22 | 国际壳牌研究有限公司 | Catalyst for dehydrogenating organic compounds and its production and application |
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