A process for the preparation of acetonitrile and acetamide by acetic acid ammoniation

Abstract

The application discloses a method for preparing acetonitrile and acetamide by an acetic acid ammoniation method, which comprises the following steps: vaporizing and preheating acetic acid, mixing the preheated acetic acid with preheated ammonia, and then entering a fixed bed reactor to react, wherein the fixed bed reactor is filled with a catalyst, and acetonitrile and acetamide can be flexibly produced at different temperatures; when the temperature is low, the reactor discharge enters an acetamide separation tower, water, a small amount of acetonitrile and excess ammonia are obtained at the top of the tower, and acetamide is mainly obtained at the bottom of the tower; when the temperature is high, the reactor discharge is subjected to ammonia absorption and dehydration to obtain acetonitrile products. The method is simple in process, high in yield, high in purity and high in safety.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of acetamide synthesis, in particular to a method for preparing acetonitrile and acetamide by acetic acid ammoniation. BACKGROUND

[0002] Acetamide (Acetamide) alias acetic acid amide, amine, defluorine, chemical formula C2H5NO, its structure contains methyl (CH3-), methoxy (CH3O-), carbonyl (-CO-), amino (-NH2) multiple functional groups, has good chemical reactivity. Acetamide is widely used as a solvent for organic and inorganic substances. It has weak basicity and can be used as an acid-resistant agent for varnish, explosives and cosmetics. It can also be used as a wetting agent for dyeing and a plasticizer for plastics, and is also a raw material for manufacturing drugs and bactericides. N-haloacetamide generated by chlorination or bromination of acetamide is a halogenating reagent for organic synthesis.

[0003] Acetonitrile is also known as methyl cyanide, a colorless liquid, extremely volatile, with a special smell similar to ether, and excellent solvent properties, capable of dissolving a variety of organic, inorganic and gaseous substances. The existing acetic acid ammoniation method for synthesizing acetonitrile is relatively complex, and has the disadvantages of single product, high synthesis temperature, high energy consumption and low raw material conversion rate. SUMMARY

[0004] The present application provides a method for preparing acetonitrile and acetamide by acetic acid ammoniation, which solves the problems of single product, high energy consumption and low raw material conversion rate in the existing acetamide and acetonitrile synthesis process.

[0005] To solve the above technical problems, the technical scheme adopted by the present application is as follows:

[0006] A method for preparing acetonitrile and acetamide by acetic acid ammoniation is designed, which comprises the following steps:

[0007] (1) vaporize and preheat acetic acid;

[0008] (2) preheat ammonia gas and mix it with the acetic acid obtained in step (1);

[0009] (3) the mixed material in step (2) is introduced into a fixed bed reactor for reaction, and the fixed bed reactor is filled with a catalyst;

[0010] Control different reaction temperatures to produce corresponding products:

[0011] (3a) control the reaction temperature at 200-240℃ and the pressure at 30-50kPa, and then perform steps (4) and (5) after reaction;

[0012] (3b) the reaction temperature is controlled at 360-390℃, the pressure is controlled at 30-50kPa, and after the reaction, step (6) is performed;

[0013] (4) after the reaction of step (3a), the material is introduced into an acetamide separation tower, and the temperature is increased to make the top temperature of the acetamide separation tower 120-125℃ and the bottom temperature 145-150℃ until the liquid level of the bottom is unchanged;

[0014] (5) after the separation of step (4), the top of the separation tower is water, a small amount of acetonitrile and excess ammonia, and the bottom material is acetamide, which is cooled, crystallized, dried and weighed to obtain the crude acetamide product;

[0015] (6) after the reaction of step (3b), the material is subjected to ammonia absorption and dehydration to obtain the acetonitrile product.

[0016] In the above technical solution, the reaction equation for preparing the acetonitrile product is C2H4O2+NH3→CH3CN+2H2O, the reaction equation for preparing the acetamide is C2H4O2+NH3→CH3CONH2+H2O, and the conversion rate of acetic acid after the final reaction reaches 99%, the prepared acetamide has high purity and high selectivity.

[0017] Preferably, in step (1), the raw material acetic acid is added into a storage tank, pumped into an acetic acid vaporizer, introduced into an acetic acid preheater after vaporization, preheated to 200℃, and then introduced into a mixing tank.

[0018] Preferably, in step (2), the ammonia gas is preheated to 200℃ by an ammonia gas preheater and then introduced into the mixing tank to mix with the acetic acid.

[0019] Preferably, in step (2), the mass ratio of the acetic acid to the ammonia gas is 1:(1.05-1.1).

[0020] Preferably, in step (3), the catalyst in the fixed bed reactor is a Co-Ni-Al2O3 catalyst.

[0021] Preferably, the preparation method of the Co-Ni-Al2O3 catalyst comprises the following steps:

[0022] ① Pretreatment of the carrier: grind the γ-Al2O3 carrier to 2mm, calcine in a muffle furnace, increase the temperature from room temperature to 116-125℃ at a rate of 2-3℃ / min, maintain for 4-6h, then increase the temperature to 530-560℃ at a rate of 5-8℃ / min, and then naturally cool to room temperature;

[0023] (2) The Al2O3 carrier obtained in step (1) is added to water, and then 0.075 mol / L of a Ni(NO3)2 solution and 0.225 mol / L of a Co(NO3)2 solution are added, and the mixture is stirred magnetically for 1-1.5 h until it is completely mixed and uniform, and then 0.5 mol / L of a NaBH4 solution is added, and the stirring is continued for 1.5-3 h, and the mixture is washed by centrifugation with anhydrous ethanol and distilled water for 3-5 times, and then it is dried in a vacuum drying oven at 78-85°C for 10-14 h to obtain a Co-Ni-Al2O3 catalyst.

[0024] Preferably, the molar ratio of the water-soluble cobalt salt to the Al2O3 carrier in step (2) is 0.01-0.05:1; the molar ratio of the water-soluble nickel salt to the water-soluble cobalt salt in step (2) is 3-5:1; and 100 ml of water is used for every 1 g of the Al2O3 carrier in step (2).

[0025] Preferably, in steps (3a) and (3b), the flow rate of the mixture into the fixed-bed reactor is 25 L / min; and the reaction time in the fixed-bed reactor is 20 s.

[0026] Preferably, in step (6), the conditions for ammonia absorption are that acetic acid is introduced into the ammonia absorption tower, the temperature at the bottom of the tower is 110-120°C, and the temperature at the top of the tower is 85-90°C; and after the ammonia absorption is completed, the mixture is introduced into a dehydration tower for pressure swing distillation dehydration.

[0027] The present application has the following advantages:

[0028] The method for preparing acetonitrile and acetamide by the acetic acid ammonia method in the present application can produce different products under different temperature conditions, acetonitrile is produced at 350-380°C, and acetamide is produced at 200-240°C; the process is simple, the yield is high, the purity is high, and the safety is high; the use of the Co-Ni-Al2O3 catalyst makes the selectivity of acetonitrile and acetamide high, the selectivity of acetonitrile can reach 96.3%, the selectivity of acetamide can reach 93.1%, and the raw material conversion rate is high, which can reach more than 99%; in addition, the catalyst has the advantages of low manufacturing cost and few side reactions. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The process flow chart of the present application is shown in the following figure. DETAILED DESCRIPTION

[0030] The specific embodiments of the present application will be described below in conjunction with examples, but the examples are only used to illustrate the present application in detail, and do not limit the scope of the present application in any way. The equipment elements involved in the following examples are all conventional equipment elements unless otherwise specified; and the industrial raw materials involved are all conventional commercial industrial raw materials unless otherwise specified.

[0031] Example 1: 6000 g of acetic acid is added to a storage tank, pumped into an acetic acid vaporizer, vaporized, and then enters an acetic acid preheater, preheated to 200°C, and then enters a mixing tank; ammonia gas is preheated to 200°C by an ammonia gas preheater and then enters the mixing tank to mix with acetic acid, and the mixed material enters a fixed bed reactor for reaction, the fixed bed reactor is filled with Co-Ni-Al2O3 catalyst, the ammonia gas flow is 25 L / min, the reaction temperature is controlled at 350-360°C, the pressure is controlled at 30-50 kPa, and after 20 s of reaction, it enters an ammonia absorption tower, the tower top temperature is controlled at 85-90°C, the tower bottom temperature is controlled at 110-120°C, until the tower bottom liquid level is constant, the tower top mainly has water and acetonitrile, and after ammonia absorption and dehydration, acetonitrile 3632 g is obtained, with a purity of 99.9% and an acetonitrile selectivity of 88.5%.

[0032] Example 2: 6000 g of acetic acid is added to a storage tank, pumped into an acetic acid vaporizer, vaporized, and then enters an acetic acid preheater, preheated to 200°C, and then enters a mixing tank; ammonia gas is preheated to 200°C by an ammonia gas preheater and then enters the mixing tank to mix with acetic acid, and the mixed material enters a fixed bed reactor for reaction, the fixed bed reactor is filled with Co-Ni-Al2O3 catalyst, the ammonia gas flow is 25 L / min, the reaction temperature is controlled at 360-370°C, the pressure is controlled at 30-50 kPa, and after 20 s of reaction, it enters an ammonia absorption tower, the tower top temperature is controlled at 85-90°C, the tower bottom temperature is controlled at 110-120°C, until the tower bottom liquid level is constant, the tower top mainly has water and acetonitrile, and after ammonia absorption and dehydration, acetonitrile 3953 g is obtained, with a purity of 99.9% and an acetonitrile selectivity of 96.3%.

[0033] Example 3: 6000 g of acetic acid is added to a storage tank, pumped into an acetic acid vaporizer, vaporized, and then enters an acetic acid preheater, preheated to 200°C, and then enters a mixing tank; ammonia gas is preheated to 200°C by an ammonia gas preheater and then enters the mixing tank to mix with acetic acid, and the mixed material enters a fixed bed reactor for reaction, the fixed bed reactor is filled with Co-Ni-Al2O3 catalyst, the ammonia gas flow is 25 L / min, the reaction temperature is controlled at 370-380°C, the pressure is controlled at 30-50 kPa, and after 20 s of reaction, it enters an ammonia absorption tower, the tower top temperature is controlled at 85-90°C, the tower bottom temperature is controlled at 110-120°C, until the tower bottom liquid level is constant, the tower top mainly has water and acetonitrile, and after ammonia absorption and dehydration, acetonitrile 3887 g is obtained, with a purity of 99.9% and an acetonitrile selectivity of 94.7%.

[0034] Example 4: 6000g acetic acid is added into a storage tank, pumped into an acetic acid vaporizer, vaporized, and then enters an acetic acid preheater, preheated to 200°C, and then enters a mixing tank; ammonia is preheated to 200°C by an ammonia preheater, and then enters the mixing tank to mix with acetic acid, and the mixed material enters an acetamide fixed bed reactor for reaction, the fixed bed reactor is filled with Co-Ni-Al2O3 catalyst, the ammonia flow is 25L / min, the reaction temperature is controlled at 210-215°C, the pressure is controlled at 30-50kPa, and after 20s of reaction, it enters an acetamide separation tower, the temperature is raised to make the acetamide separation tower top temperature 120-125°C, the tower kettle temperature 145-150°C, until the tower kettle liquid level is constant, the tower top mainly has water and a small amount of acetonitrile, the tower kettle material is acetamide, after cooling and crystallization, drying and weighing, 5783g of acetamide crude product is obtained, the acetamide content is 95%, and the selectivity is 93.1%.

[0035] Example 5: 6000g acetic acid is added into a storage tank, pumped into an acetic acid vaporizer, vaporized, and then enters an acetic acid preheater, preheated to 200°C, and then enters a mixing tank; ammonia is preheated to 200°C by an ammonia preheater, and then enters the mixing tank to mix with acetic acid, and the mixed material enters an acetamide fixed bed reactor for reaction, the fixed bed reactor is filled with Co-Ni-Al2O3 catalyst, the ammonia flow is 25L / min, the reaction temperature is controlled at 220-230°C, the pressure is controlled at 30-50kPa, and after 20s of reaction, it enters an acetamide separation tower, the temperature is raised to make the acetamide separation tower top temperature 120-125°C, the tower kettle temperature 145-150°C, until the tower kettle liquid level is constant, the tower top mainly has water and a small amount of acetonitrile, the tower kettle material is acetamide, after cooling and crystallization, drying and weighing, 5642g of acetamide crude product is obtained, the acetamide content is 95%, and the selectivity is 90.8%.

[0036] Example 6: 6000g acetic acid is added into a storage tank, pumped into an acetic acid vaporizer, vaporized, and then enters an acetic acid preheater, preheated to 200°C, and then enters a mixing tank; ammonia is preheated to 200°C by an ammonia preheater, and then enters the mixing tank to mix with acetic acid, and the mixed material enters an acetamide fixed bed reactor for reaction, the fixed bed reactor is filled with Co-Ni-Al2O3 catalyst, the ammonia flow is 25L / min, the reaction temperature is controlled at 200-210°C, the pressure is controlled at 30-50kPa, and after 20s of reaction, it enters an acetamide separation tower, the temperature is raised to make the acetamide separation tower top temperature 120-125°C, the tower kettle temperature 145-150°C, until the tower kettle liquid level is constant, the tower top mainly has water and a small amount of acetonitrile, the tower kettle material is acetamide, after cooling and crystallization, drying and weighing, 5530g of acetamide crude product is obtained, the acetamide content is 94%, and the selectivity is 88.1%.

[0037] Example 7: 6000 g of acetic acid is added into a storage tank, and is pumped into an acetic acid vaporizer, and after vaporization, is introduced into an acetic acid preheater, and after preheating to 200°C, is introduced into a mixing tank; ammonia gas is preheated to 200°C by an ammonia gas preheater, and is introduced into the mixing tank to mix with the acetic acid, and the mixed material is introduced into an acetamide fixed bed reactor, and the Co-Ni-Al2O3 catalyst is filled in the fixed bed reactor, the ammonia gas flow is 25 L / min, the reaction temperature is controlled at 230-240°C, the pressure is controlled at 30-50 kPa, and after 20 s of reaction, is introduced into an acetamide separation tower, and the tower top temperature is 120-125°C, and the tower bottom temperature is 145-150°C, until the tower bottom liquid level is constant, the tower top mainly has water and a small amount of acetonitrile, and the tower bottom material is acetamide, and after cooling and crystallization, drying, and weighing, 5578 g of acetamide crude product is obtained, the acetamide content is 95%, and the selectivity is 89.8%.

[0038] In the above examples, the catalyst used in the step (3) fixed bed reactor is a Co-Ni-Al2O3 catalyst. The preparation method of the Co-Ni-Al2O3 catalyst comprises the following steps:

[0039] ① Pretreatment of the carrier: the γ-Al2O3 carrier is ground to 2 mm, and is calcined in a muffle furnace, and is raised from room temperature to 120°C at a temperature rising rate of 2°C / min, and is maintained for 5 h, and then is raised to 550°C at a temperature rising rate of 5°C / min, and is maintained for 10 h, and then is naturally cooled to room temperature.

[0040] ② The Al2O3 carrier obtained in the step ① is weighed and added into water, and then a 0.075 mol / L Ni(NO3)2 solution and a 0.225 mol / L Co(NO3)2 solution are added, and are magnetically stirred for 1-1.5 h until completely mixed and uniform, and then a 0.5 mol / L NaBH4 solution is added, and is continuously stirred for 1.5-3 h, and is washed by centrifugation with anhydrous ethanol and distilled water for 3-5 times, and then is dried in a vacuum drying box at 78-85°C for 10-14 h, and the Co-Ni-Al2O3 catalyst is prepared.

[0041] In the step ②, the molar ratio of the water-soluble cobalt salt (pure substance in the aqueous solution) to the Al2O3 carrier is 0.01-0.05:1; the molar ratio of the water-soluble nickel salt (pure substance in the aqueous solution) to the water-soluble cobalt salt (pure substance in the aqueous solution) is 3-5:1; and 100 ml of water is used for every 1 g of the Al2O3 carrier.

[0042] Comparative Example 1:

[0043] 6000 g acetic acid was added into a storage tank, pumped into an acetic acid vaporizer, vaporized, and then entered an acetic acid preheater, preheated to 200°C, and then entered a mixing tank; ammonia was preheated to 200°C by an ammonia preheater, and then entered the mixing tank to mix with acetic acid, and the mixed material entered a fixed bed reactor for reaction, the fixed bed reactor was filled with traditional Al2O3 catalyst, the ammonia flow was 25 L / min, the reaction temperature was controlled at 395-405°C, the pressure was controlled at 30-50 kPa, and after 20 s of reaction, the material entered an ammonia absorption tower, the tower top temperature was controlled at 85-90°C, the tower bottom temperature was controlled at 110-120°C, until the tower bottom liquid level was constant, the tower top mainly had water and acetonitrile, and after dehydration, 3586 g of acetonitrile was obtained, with a purity of 99.8% and an acetonitrile selectivity of 87.2%.

[0044] Comparative Example 2:

[0045] 6000 g acetic acid was added into a storage tank, pumped into an acetic acid vaporizer, vaporized, and then entered an acetic acid preheater, preheated to 200°C, and then entered a mixing tank; ammonia was preheated to 200°C by an ammonia preheater, and then entered the mixing tank to mix with acetic acid, and the mixed material entered an acetamide fixed bed reactor for reaction, the fixed bed reactor was filled with traditional Al2O3 catalyst, the ammonia flow was 25 L / min, the reaction temperature was controlled at 210-215°C, the pressure was controlled at 30-50 kPa, and after 20 s of reaction, the material entered an acetamide separation tower, the tower top temperature was controlled at 120-125°C, the tower bottom temperature was controlled at 145-150°C, until the tower bottom liquid level was constant, the tower top mainly had water and a small amount of acetonitrile, and the tower bottom material was acetamide, after cooling and crystallization, drying and weighing, 3262 g of acetamide crude product was obtained, with an acetamide content of 86% and a selectivity of 53.1%.

[0046] As can be seen from the above examples and comparative examples, both the Co-Ni-Al2O3 catalyst and the traditional Al2O3 catalyst have high selectivity in preparing acetonitrile, but the selectivity of acetonitrile is better when the Co-Ni-Al2O3 catalyst is used, and the selectivity of the traditional Al2O3 catalyst in preparing acetamide is only 53.1%, which is much lower than that of the Co-Ni-Al2O3 catalyst; and in the process of preparing acetonitrile, the reaction temperature of the Co-Ni-Al2O3 catalyst is lower than that of the traditional Al2O3 catalyst, and the energy consumption is lower.

[0047] The above has made a detailed description of the present application in combination with examples, but those skilled in the art can understand that various specific parameters in the above examples can be changed to form multiple specific examples without departing from the purpose of the present application, which are all within the common variation range of the present application, and will not be described one by one in detail.

Claims

1. A method for preparing acetonitrile and co-producing acetamide by acetic acid amination, characterized in that, Includes the following steps: (1) The acetic acid is vaporized and preheated; (2) The ammonia gas is preheated and then mixed with the acetic acid obtained in step (1); (3) The mixed material in step (2) enters the fixed bed reactor for reaction. The fixed bed reactor is filled with a catalyst, which is a Co-Ni-Al2O3 catalyst. (3a) The reaction temperature is controlled at 200-240℃ and the pressure is controlled at 30-50kPa. After the reaction, proceed to steps (4) and (5). (4) The material after the reaction in step (3a) enters the acetamide separation tower. The temperature is raised to make the top temperature of the acetamide separation tower 120-125℃ and the bottom temperature 145-150℃ until the bottom liquid level remains unchanged. (5) After separation in step (4), the top of the separation tower contains water, a small amount of acetonitrile and excess ammonia, while the bottom of the tower contains acetamide. After cooling and crystallization, the product is dried and weighed to obtain crude acetamide.

2. The method for preparing acetonitrile and co-producing acetamide by acetic acid amination according to claim 1, characterized in that, In step (1), the raw material acetic acid is added to the storage tank and pumped into the acetic acid vaporizer. After vaporization, it enters the acetic acid preheater and is preheated to 200°C before entering the mixing tank.

3. The method for preparing acetonitrile and co-producing acetamide by acetic acid amination according to claim 2, characterized in that, In step (2), ammonia gas is preheated to 200°C by an ammonia gas preheater and then enters a mixing tank to mix with acetic acid.

4. The method for preparing acetonitrile and co-producing acetamide by acetic acid amination according to claim 3, characterized in that, In step (2), the molar ratio of acetic acid to ammonia is 1:(1.05-1.1).

5. The method for preparing acetonitrile and co-producing acetamide by acetic acid amination according to claim 1, characterized in that, The preparation method of this Co-Ni-Al2O3 catalyst includes the following steps: ①Pretreatment of the support: The γ-Al2O3 support was ground to 2 mm and calcined in a muffle furnace. The temperature was increased from room temperature to 116-125℃ at a rate of 2-3℃ / min and maintained for 4-6 h. Then the temperature was increased to 530-560℃ and maintained for 8-12 h at a rate of 5-8℃ / min. Then the temperature was naturally cooled to room temperature. ② Weigh the Al2O3 support obtained in step ① and add it to water. Then add 0.075 mol / L Ni(NO3)2 solution and 0.225 mol / L Co(NO3)2 solution. Stir magnetically for 1 to 1.5 h until completely mixed. Then add 0.5 mol / L NaBH4 solution and continue stirring for 1.5 to 3 h. Wash the mixture 3 to 5 times with anhydrous ethanol and distilled water respectively. Then dry it in a vacuum drying oven at 78 to 85 °C for 10 to 14 h to obtain the Co-Ni-Al2O3 catalyst.

6. The method for preparing acetonitrile and co-producing acetamide by acetic acid amination according to claim 5, characterized in that, In step ②, the molar ratio of water-soluble cobalt salt to Al2O3 support is 0.01~0.05:1; in step ②, the molar ratio of water-soluble nickel salt to water-soluble cobalt salt is 3~5:

1.

7. The method for preparing acetonitrile and co-producing acetamide by acetic acid amination according to claim 1, characterized in that, In step (3a), the flow rate of the mixture entering the fixed-bed reactor is 25 L / min; the reaction time in the fixed-bed reactor is 20 s.

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