A synthesis method for co-producing acetamide and acetonitrile

Abstract

The present invention provides a synthesis method for co-producing acetamide and acetonitrile, belonging to the technical field of acetonitrile synthesis. The synthesis method includes mixing, preparing acetamide, and preparing acetonitrile. The method for preparing acetonitrile is as follows: a mixed gas of acetic acid and liquid ammonia is introduced into a reactor, the temperature of the reactor is controlled at 340 - 360 °C, the pressure is controlled at 0.06 - 0.08 MPa, the residence time of the mixed gas in the reactor is 40 - 60 s. After the reaction is completed, it is introduced into a distillation column, the pressure in the column is controlled at 65 - 75 kPa, the top temperature of the column is 75 - 85 °C, the bottom temperature of the column is 115 - 125 °C, and the reflux ratio is 2 - 3. After the liquid level in the bottom of the column remains unchanged, the overhead material is output, and after cooling and dehydration, acetonitrile is obtained. In the synthesis method of the present invention, the conversion rate of acetonitrile reaches 95.19 - 96.53%, the selectivity reaches 89.99 - 90.13%, and the purity reaches 99.83 - 99.91%.

Description

Technical Field

[0001] The present invention belongs to the technical field of acetonitrile synthesis, and particularly relates to a synthesis method for co-producing acetamide and acetonitrile. Background Art

[0002] As key raw materials and solvents in the field of organic chemical industry, acetamide and acetonitrile play an indispensable role in many downstream industries. They are important raw materials for synthesizing a variety of fine chemicals and polymer materials. In the pharmaceutical field, they are key links in the synthesis of many drugs. Currently, the generally adopted synthesis process is the fixed-bed synthesis process of acetic acid ammoniation method, using acetic acid and ammonia as raw materials. Under the action of an Al2O3 catalyst loaded with noble metals, acetamide and acetonitrile are synthesized by stepwise dehydration. The main chemical reactions involved in this method are: CH3COOH + NH3 → CH3CONH2 + H2O, CH3COOH + NH3 → CH3CN + 2H2O, CH3CONH2 → CH3CN + H2O. This method has a high conversion rate, few by-products, and high selectivity. Different products can be obtained by controlling the reaction temperature. However, this reaction requires a relatively high temperature, and the catalyst has a short lifespan at high temperatures and is prone to deactivation.

[0003] Research shows that the melting point temperatures (Tm) of noble metals commonly used as catalytic active components can all reach above 1000 °C. However, when the noble metal reaches 0.3Tm, the vibration of noble metal atoms at the interface intensifies and the diffusion degree of noble metals is enhanced. Noble metal atoms gradually migrate and aggregate to form larger particles, resulting in a decrease in dispersion and specific surface area, that is, the sintering phenomenon of noble metal atoms occurs, thereby leading to a decrease in catalyst activity.

[0004] Patent CN117567320A discloses a method for preparing acetonitrile co-producing acetamide by acetic acid ammoniation method. The catalyst used in this patent is Co-Ni-Al2O3. The metals in this catalyst can form metal-carbon bonds or metal-nitrogen bonds with the reaction substrates to stabilize the reaction intermediates, reduce the reaction activation energy, and promote the progress of the reaction. However, at high temperatures, Co and Ni loaded on the surface of this catalyst will be sintered, reducing the contact area with the reactants, thereby causing the catalyst activity to decline or deactivate. Summary of the Invention

[0005] Aiming at the problems existing in the prior art, the present invention provides a synthesis method for co-producing acetamide and acetonitrile, achieving the following invention objectives: developing a composite γ-Al2O3-based acidic catalyst with high activity, high stability, and long lifespan, reducing the reaction temperature, and promoting the synthesis of acetamide and acetonitrile.

[0006] To solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0007] A synthesis method for co-producing acetamide and acetonitrile, comprising the following steps:

[0008] (1) Mixing: Vaporize acetic acid and liquid ammonia separately and preheat them to 170 - 190 °C, then simultaneously introduce them into a gas mixer. Control the outlet flow rate of the gas mixer at 0.29 - 0.31 m 3 / min, and then introduce the mixed gas into a fixed - bed reactor for reaction. The fixed - bed reactor is filled with a La - Zr / SiO2 - γ - Al2O3 composite catalyst;

[0009] (2) Producing acetamide: Control the reactor temperature at 210 - 230 °C and the pressure at 0.58 - 0.62 MPa. The residence time of the mixed gas in the reactor is 25 - 35 s. After the reaction, introduce it into a distillation column. Control the pressure in the column at 65 - 75 kPa, the top - tower temperature at 75 - 85 °C, the bottom - tower temperature at 115 - 125 °C, and the reflux ratio at 1.6 - 2.1. Until the bottom - tower liquid level remains unchanged, output the bottom - tower material. After cooling and crystallization, dry it to constant weight at 35 - 45 °C to obtain acetamide;

[0010] (3) Producing acetonitrile: Control the reactor temperature at 340 - 360 °C and the pressure at 0.06 - 0.08 MPa. The residence time of the mixed gas in the reactor is 40 - 60 s. After the reaction, introduce it into a distillation column. Control the pressure in the column at 65 - 75 kPa, the top - tower temperature at 75 - 85 °C, the bottom - tower temperature at 115 - 125 °C, and the reflux ratio at 2 - 3. Until the bottom - tower liquid level remains unchanged, output the top - tower material. After cooling and dehydration, obtain acetonitrile;

[0011] The mass ratio of acetic acid to ammonia in the mixed gas is 2.8 - 3.4∶0.9 - 1.1;

[0012] The preparation method of the La - Zr / SiO2 - γ - Al2O3 composite catalyst includes preparing monodisperse SiO2, primary calcination, and secondary calcination;

[0013] The method for preparing monodisperse SiO2 is as follows: Add anhydrous ethanol and ammonia water to deionized water, stir until the solution is clear and transparent, then slowly dropwise add tetraethyl orthosilicate to the solution. After the addition is complete, carry out a constant - temperature reaction at 28 - 32 °C for 5.5 - 6.5 h, then centrifuge at a rate of 2500 - 3500 r / min for 4 - 6 min. Wash the lower - layer precipitate with deionized water and anhydrous ethanol, and then dry it at 90 - 110 °C for 15 - 25 min. Grind and crush it into a white powder with a particle size of 50 - 70 nm, which is monodisperse SiO2;

[0014] The mass ratio of anhydrous ethanol, ammonia water, deionized water, and tetraethyl orthosilicate is 8 - 12∶1.8 - 2.2∶2.5 - 3.5∶21 - 23;

[0015] The mass fraction of ammonia in the ammonia water is 20-30%;

[0016] The dropping time is 25-35 min.

[0017] The method of the first calcination is as follows: Add monodisperse SiO2, La(NO3)3, and Zr(NO3)4 into deionized water, then add the acetone solution of glycine and polyethylene glycol, ultrasonically disperse for 25-35 min, adjust the pH value to 9-10 with ammonia water, keep stirring and reacting at 35-45 °C for 2.4-2.6 h, then centrifuge at a rate of 2500-3500 r / min for 4-6 min. After washing the lower-layer precipitate with deionized water until it is clean, dry it at 90-110 °C for 15-25 min. After drying, transfer it to be calcined at 400-500 °C for 3.5-4.5 h, grind and crush it into a powder with a particle size of 70-90 nm to obtain the La-Zr / SiO2 composite;

[0018] The mass ratio of monodisperse SiO2, La(NO3)3, Zr(NO3)4, and deionized water is 40-45:18-22:6-8:180-200;

[0019] The mass ratio of monodisperse SiO2, the acetone solution of polyethylene glycol, and glycine is 20-22:4.5-5.5:2.9-3.1;

[0020] The mass fraction of polyethylene glycol in the acetone solution of polyethylene glycol is 0.4-0.6%;

[0021] The stirring rate is 40-50 r / min.

[0022] The method of the second calcination is as follows: Mix and grind γ-Al2O3 and activated carbon to form a powder with a particle size of 90-120 nm, then mix it evenly with the La-Zr / SiO2 composite, then add triethoxysilane and deionized water, stir and hydrolyze for 25-35 min, dry it to constant weight at 45-55 °C, crush and grind it to form a powder of 0.8-1.2 μm to obtain the active matrix. Add the active matrix into the aluminum isopropoxide sol, ultrasonically disperse for 25-35 min, and then dropwise add it into the oil-ammonia column (control the dropping particle size to be 1.8-2.2 mm) to obtain a wet ball. After air-drying until there is no moisture on the surface, dry it to constant weight at 100-120 °C, then heat it up at a rate of 2-3 °C / min to 550-650 °C, calcine it at 550-650 °C for 3.5-4.5 h, and then cool it naturally to obtain spherical porous particles with a diameter of 1.8-2.2 mm, namely the La-Zr / SiO2-γ-Al2O3 composite catalyst;

[0023] The mass ratio of the γ-Al2O3, activated carbon, La-Zr / SiO2 composite, triethoxysilane, and deionized water is 13-17:1.3-1.5:3.71-3.75:2.2-2.6:18-22;

[0024] The mass ratio of the active matrix to the aluminum isopropoxide sol is 1.47-1.49:26.45-26.49.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] Monodisperse SiO2 is used to adsorb La(NO3)3 and Zr(NO3)4, and then, in an alkaline environment, La(NO3)3 and Zr(NO3)4 are precipitated in the pores of the monodisperse SiO2. Through calcination, the La-Zr / SiO2 composite is obtained. The La-Zr / SiO2 composite is connected to γ-Al2O3 through triethoxysilane and then added to the aluminum isopropoxide sol. Using the oil-ammonia column forming method, the obtained wet spheres are dried and calcined to obtain spherical porous particles of γ-Al2O3 loaded with the La-Zr / SiO2 composite, that is, the La-Zr / SiO2-γ-Al2O3 composite catalyst.

[0027] The pores of the monodisperse SiO2 can well fix La and Zr, ensuring that the noble metal particles do not contact each other and reducing the agglomeration phenomenon at high temperatures. Triethoxysilane fixes the La-Zr / SiO2 composite to γ-Al2O3. Therefore, the obtained catalyst has a long service life. When continuously producing acetamide, the catalyst service life reaches 154-160 days, and when continuously producing acetonitrile, the catalyst service life reaches 84-90 days; at the same time, the monodisperse SiO2 has good dispersibility in the aluminum isopropoxide sol. Therefore, the La-Zr / SiO2 composite has a good dispersion effect in the obtained spherical porous particles of γ-Al2O3, and further, the catalyst has high activity. The conversion rate of acetamide reaches 99.51-99.64%, the selectivity reaches 91.89-92.11%, the purity reaches 98.26-98.74%, the conversion rate of acetonitrile reaches 95.19-96.53%, the selectivity reaches 89.99-90.13%, and the purity reaches 99.83-99.91%. Specific embodiments

[0028] Example 1

[0029] A synthesis method for co-producing acetamide and acetonitrile includes the following steps:

[0030] (1) Mixing: After vaporizing acetic acid and liquid ammonia and preheating them to 180°C, they are simultaneously introduced into a gas mixer, and the outlet flow rate of the gas mixer is controlled at 0.3 m 3 / min, and then introduce the mixed gas into a fixed-bed reactor for reaction. The fixed-bed reactor is filled with a La-Zr / SiO2-γ-Al2O3 composite catalyst;

[0031] (2) Produce acetamide: Control the reactor temperature at 220 °C and the pressure at 0.6 MPa. The residence time of the mixed gas in the reactor is 30 s. After the reaction, introduce it into a distillation column. Control the pressure in the column at 70 kPa, the top temperature at 80 °C, the bottom temperature at 120 °C, and the reflux ratio at 1.8. After the bottom liquid level remains unchanged, output the bottom material. After cooling and crystallization, dry it to constant weight at 40 °C to obtain acetamide;

[0032] (3) Produce acetonitrile: Control the reactor temperature at 350 °C and the pressure at 0.07 MPa. The residence time of the mixed gas in the reactor is 50 s. After the reaction, introduce it into a distillation column. Control the pressure in the column at 70 kPa, the top temperature at 80 °C, the bottom temperature at 120 °C, and the reflux ratio at 2.5. After the bottom liquid level remains unchanged, output the top material. After cooling and dehydration, obtain acetonitrile;

[0033] The mass ratio of acetic acid to ammonia in the mixed gas is 3:1;

[0034] The preparation method of the La-Zr / SiO2-γ-Al2O3 composite catalyst includes preparing monodisperse SiO2, first calcination, and second calcination;

[0035] The method for preparing monodisperse SiO2 is as follows: Add absolute ethanol and ammonia water to deionized water, stir until the solution is clear and transparent, then slowly dropwise add tetraethyl orthosilicate to the solution. After the addition is complete, react at a constant temperature of 30 °C for 6 h, then centrifuge at a rate of 3000 r / min for 5 min. Wash the lower precipitate with deionized water and absolute ethanol, dry it at 100 °C for 20 min, and grind it into a white powder with a particle size of 60 nm, which is monodisperse SiO2;

[0036] The mass ratio of absolute ethanol, ammonia water, deionized water, and tetraethyl orthosilicate is 10:2:3:22;

[0037] The mass fraction of ammonia in the ammonia water is 25%;

[0038] The dropping time is 30 min.

[0039] The method of the first calcination is as follows: Add monodisperse SiO2, La(NO3)3, and Zr(NO3)4 into deionized water, then add an acetone solution of glycine and polyethylene glycol. After ultrasonic dispersion for 30 min, adjust the pH value to 9.5 using ammonia water, and carry out a constant-temperature stirring reaction at 40 °C for 2.5 h. Then centrifuge at a rate of 3000 r / min for 5 min. After washing the lower-layer precipitate clean with deionized water, dry it at 100 °C for 20 min. After drying, transfer it to calcine at 450 °C for 4 h, grind and crush it into a powder with a particle size of 80 nm to obtain the La-Zr / SiO2 composite;

[0040] The mass ratio of the monodisperse SiO2, La(NO3)3, Zr(NO3)4, and deionized water is 43∶20∶7∶190;

[0041] The mass ratio of the monodisperse SiO2, the acetone solution of polyethylene glycol, and glycine is 21∶5∶3;

[0042] The mass fraction of polyethylene glycol in the acetone solution of polyethylene glycol is 0.5%;

[0043] The rate of the stirring is 45 r / min.

[0044] The method of the second calcination is as follows: Mix and grind γ-Al2O3 and activated carbon to form a powder with a particle size of 100 nm, then mix it evenly with the La-Zr / SiO2 composite. Then add triethoxysilane and deionized water, stir and hydrolyze for 30 min, dry at 50 °C to constant weight, crush and grind to form a powder of 1 μm to obtain the active matrix. Add the active matrix into isopropyl alcohol aluminum sol, after ultrasonic dispersion for 30 min, dropwise add it into an oil-ammonia column (control the dropping particle size to be 2 mm) to obtain wet balls. After air-drying until there is no moisture on the surface, dry to constant weight at 110 °C, then heat up to 600 °C at a rate of 2.5 °C / min, calcine at 600 °C for 4 h and then cool naturally to obtain spherical porous particles with a diameter of 2 mm, namely the La-Zr / SiO2-γ-Al2O3 composite catalyst;

[0045] The mass ratio of the γ-Al2O3, activated carbon, La-Zr / SiO2 composite, triethoxysilane, and deionized water is 15∶1.4∶3.73∶2.4∶20;

[0046] The mass ratio of the active matrix and isopropyl alcohol aluminum sol is 1.48∶26.47.

[0047] Example 2

[0048] A synthesis method for co-producing acetamide and acetonitrile, comprising the following steps:

[0049] (1) Mixing: Vaporize acetic acid and liquid ammonia separately and preheat them to 170 °C, then introduce them into the gas mixer simultaneously. Control the outlet flow rate of the gas mixer at 0.29 m 3 / min, and then introduce the mixed gas into the fixed-bed reactor for reaction. The fixed-bed reactor is filled with La-Zr / SiO2-γ-Al2O3 composite catalyst;

[0050] (2) Producing acetamide: Control the reactor temperature at 210 °C and the pressure at 0.58 MPa. The residence time of the mixed gas in the reactor is 25 s. After the reaction is completed, introduce it into the distillation column. Control the pressure in the column at 65 kPa, the top temperature at 75 °C, the bottom temperature at 115 °C, and the reflux ratio at 1.6. Until the liquid level in the bottom of the column remains unchanged, output the bottom material. After cooling and crystallization, dry it to constant weight at 35 °C to obtain acetamide;

[0051] (3) Producing acetonitrile: Control the reactor temperature at 340 °C and the pressure at 0.06 MPa. The residence time of the mixed gas in the reactor is 40 s. After the reaction is completed, introduce it into the distillation column. Control the pressure in the column at 65 kPa, the top temperature at 75 °C, the bottom temperature at 115 °C, and the reflux ratio at 2. Until the liquid level in the bottom of the column remains unchanged, output the top material. After cooling and dehydration, obtain acetonitrile;

[0052] The mass ratio of acetic acid to ammonia in the mixed gas is 2.8∶0.9;

[0053] The preparation method of the La-Zr / SiO2-γ-Al2O3 composite catalyst includes preparing monodisperse SiO2, primary calcination, and secondary calcination;

[0054] The method for preparing monodisperse SiO2 is as follows: Add anhydrous ethanol and ammonia water to deionized water, stir until the solution is clear and transparent, then slowly dropwise add tetraethyl orthosilicate to the solution. After the addition is completed, carry out a constant-temperature reaction at 28 °C for 5.5 h, then centrifuge at a rate of 2500 r / min for 4 min. Wash the lower precipitate with deionized water and anhydrous ethanol, then dry it at 90 °C for 15 min, and grind it into a white powder with a particle size of 50 nm, which is monodisperse SiO2;

[0055] The mass ratio of anhydrous ethanol, ammonia water, deionized water, and tetraethyl orthosilicate is 10∶2∶3∶21;

[0056] The mass fraction of ammonia in the ammonia water is 20%;

[0057] The dropping time is 25 min.

[0058] The method of the first calcination is as follows: Add monodisperse SiO2, La(NO3)3, and Zr(NO3)4 into deionized water, then add an acetone solution of glycine and polyethylene glycol. After ultrasonic dispersion for 25 min, adjust the pH value to 9 using ammonia water, stir and react at a constant temperature of 35 °C for 2.4 h, then centrifuge at a rate of 2500 r / min for 4 min. After washing the lower-layer precipitate with deionized water until it is clean, dry it at 90 °C for 15 min. After drying, transfer it to a calcination at 400 °C for 3.5 h, grind and crush it into a powder with a particle size of 70 nm to obtain the La-Zr / SiO2 composite;

[0059] The mass ratio of the monodisperse SiO2, La(NO3)3, Zr(NO3)4, and deionized water is 40∶18∶6∶180;

[0060] The mass ratio of the monodisperse SiO2, the acetone solution of polyethylene glycol, and glycine is 20∶4.5∶2.9;

[0061] The mass fraction of polyethylene glycol in the acetone solution of polyethylene glycol is 0.4%;

[0062] The stirring rate is 40 r / min.

[0063] The method of the second calcination is as follows: Mix and grind γ-Al2O3 and activated carbon to form a powder with a particle size of 90 nm, then mix it evenly with the La-Zr / SiO2 composite. Then add triethoxysilane and deionized water, stir and hydrolyze for 25 min, dry it to a constant weight at 45 °C, crush and grind it to form a powder of 0.8 μm to obtain the active matrix. Add the active matrix into the aluminum isopropoxide sol, after ultrasonic dispersion for 25 min, dropwise add it into an oil-ammonia column (control the dropping particle size to be 1.8 mm) to obtain wet balls. After air-drying until there is no moisture on the surface, dry it to a constant weight at 100 °C, then heat it up to 550 °C at a rate of 2 °C / min, calcine it at 550 °C for 3.5 h, and then let it cool naturally to obtain spherical porous particles with a diameter of 1.8 mm, that is, the La-Zr / SiO2-γ-Al2O3 composite catalyst;

[0064] The mass ratio of the γ-Al2O3, activated carbon, La-Zr / SiO2 composite, triethoxysilane, and deionized water is 13∶1.3∶3.71∶2.2∶18;

[0065] The mass ratio of the active matrix and the aluminum isopropoxide sol is 1.47∶26.45.

[0066] Example 3

[0067] A synthesis method for co-producing acetamide and acetonitrile, comprising the following steps:

[0068] (1) Mixing: Vaporize acetic acid and liquid ammonia separately and preheat them to 190 °C, then introduce them into a gas mixer simultaneously. Control the outlet flow rate of the gas mixer at 0.31 m 3 / min, and then introduce the mixed gas into a fixed-bed reactor for reaction. The fixed-bed reactor is filled with a La-Zr / SiO2-γ-Al2O3 composite catalyst;

[0069] (2) Producing acetamide: Control the reactor temperature at 230 °C and the pressure at 0.62 MPa. The residence time of the mixed gas in the reactor is 35 s. After the reaction, introduce it into a distillation column. Control the pressure in the column at 75 kPa, the top temperature at 85 °C, the bottom temperature at 125 °C, and the reflux ratio at 2.1. Until the bottom liquid level remains unchanged, output the bottom material. After cooling and crystallization, dry it to constant weight at 45 °C to obtain acetamide;

[0070] (3) Producing acetonitrile: Control the reactor temperature at 360 °C and the pressure at 0.08 MPa. The residence time of the mixed gas in the reactor is 60 s. After the reaction, introduce it into a distillation column. Control the pressure in the column at 75 kPa, the top temperature at 85 °C, the bottom temperature at 125 °C, and the reflux ratio at 3. Until the bottom liquid level remains unchanged, output the top material. After cooling and dehydration, obtain acetonitrile;

[0071] The mass ratio of acetic acid to ammonia in the mixed gas is 3.4∶1.1;

[0072] The preparation method of the La-Zr / SiO2-γ-Al2O3 composite catalyst includes preparing monodisperse SiO2, first calcination, and second calcination;

[0073] The method for preparing monodisperse SiO2 is as follows: Add anhydrous ethanol and ammonia water to deionized water, stir until the solution is clear and transparent, then slowly dropwise add tetraethyl orthosilicate to the solution. After the addition is completed, carry out a constant-temperature reaction at 32 °C for 6.5 h, then centrifuge at a rate of 3500 r / min for 6 min. Wash the lower precipitate with deionized water and anhydrous ethanol, dry it at 110 °C for 25 min, and grind it into a white powder with a particle size of 70 nm, which is monodisperse SiO2;

[0074] The mass ratio of anhydrous ethanol, ammonia water, deionized water, and tetraethyl orthosilicate is 10∶2∶3∶23;

[0075] The mass fraction of ammonia in the ammonia water is 30%;

[0076] The dropping time is 35 min.

[0077] The method of the first calcination is as follows: Add monodisperse SiO2, La(NO3)3, and Zr(NO3)4 into deionized water, then add an acetone solution of glycine and polyethylene glycol. After ultrasonic dispersion for 35 min, adjust the pH value to 10 using ammonia water, stir and react at a constant temperature of 45 °C for 2.6 h, then centrifuge at a rate of 3500 r / min for 6 min. After washing the lower-layer precipitate with deionized water until clean, dry it at 110 °C for 25 min. After drying, transfer it to a calcination at 500 °C for 4.5 h, grind and crush it into a powder with a particle size of 90 nm to obtain the La-Zr / SiO2 composite;

[0078] The mass ratio of the monodisperse SiO2, La(NO3)3, Zr(NO3)4, and deionized water is 45∶22∶8∶200;

[0079] The mass ratio of the monodisperse SiO2, the acetone solution of polyethylene glycol, and glycine is 22∶5.5∶3.1;

[0080] The mass fraction of polyethylene glycol in the acetone solution of polyethylene glycol is 0.6%;

[0081] The stirring rate is 50 r / min.

[0082] The method of the second calcination is as follows: Mix and grind γ-Al2O3 and activated carbon to form a powder with a particle size of 120 nm, then mix it evenly with the La-Zr / SiO2 composite. Then add triethoxysilane and deionized water, stir and hydrolyze for 35 min, dry it at 55 °C to constant weight, crush and grind it to form a powder of 1.2 μm to obtain the active matrix. Add the active matrix into the aluminum isopropoxide sol, after ultrasonic dispersion for 35 min, dropwise add it into the oil-ammonia column (control the dropping particle size to be 2.2 mm) to obtain a wet ball. After air-drying until there is no moisture on the surface, dry it to constant weight at 120 °C, then heat it at a rate of 3 °C / min to 650 °C, calcine it at 650 °C for 4.5 h and then cool it naturally to obtain spherical porous particles with a diameter of 2.2 mm, that is, the La-Zr / SiO2-γ-Al2O3 composite catalyst;

[0083] The mass ratio of the γ-Al2O3, activated carbon, La-Zr / SiO2 composite, triethoxysilane, and deionized water is 17∶1.5∶3.75∶2.6∶22;

[0084] The mass ratio of the active matrix and the aluminum isopropoxide sol is 1.49∶26.49.

[0085] Comparative Example 1

[0086] On the basis of Example 1, in the preparation method of the La-Zr / SiO2-γ-Al2O3 composite catalyst, the step of preparing monodisperse SiO2 is omitted; the primary calcination is changed as follows: La(NO3)3 and Zr(NO3)4 are added to deionized water, then an acetone solution of glycine and polyethylene glycol is added. After ultrasonic dispersion for 30 min, the pH value is adjusted to 9.5 using ammonia water, and the reaction is stirred at a constant temperature of 40 °C for 2.5 h. Then, centrifugation is carried out at a rate of 3000 r / min for 5 min. After the lower-layer precipitate is washed clean with deionized water, it is dried at 100 °C for 20 min. After drying, it is transferred to be calcined at 450 °C for 4 h, ground and pulverized into a powder with a particle size of 80 nm to obtain a La-Zr composite; in the secondary calcination step, the La-Zr / SiO2 composite is changed to a La-Zr composite.

[0087] Comparative Example 2

[0088] On the basis of Example 1, in the preparation method of the La-Zr / SiO2-γ-Al2O3 composite catalyst, the addition of triethoxysilane and deionized water in the secondary calcination is omitted. Specifically, it is changed as follows: γ-Al2O3 and activated carbon are mixed and ground to form a powder with a particle size of 100 nm, and then uniformly mixed with the La-Zr / SiO2 composite. Then, it is added to an aluminum isopropoxide sol. After ultrasonic dispersion for 30 min, it is gradually dropped into an oil-ammonia column (controlling the dropping particle size to be 2 mm) to obtain a wet ball. After air-drying until there is no moisture on the surface, it is dried to a constant weight at 110 °C, then heated to 600 °C at a rate of 2.5 °C / min, calcined at 600 °C for 4 h, and then naturally cooled to obtain spherical porous particles with a diameter of 2 mm, that is, the La-Zr / SiO2-γ-Al2O3 composite catalyst.

[0089] Test Example 1

[0090] The conversion rates, selectivities, and purities of acetamide and acetonitrile were calculated respectively by using the methods of Examples 1 to 3 and Comparative Examples 1 to 2. The calculation results are shown in Table 1.

[0091] Table 1

[0092]

[0093] Test Example 2

[0094] The La-Zr / SiO2-γ-Al2O3 composite catalysts prepared by using Examples 1 to 3 and Comparative Examples 1 to 2 respectively were used under the production conditions of Example 1 to continuously produce acetamide and acetonitrile respectively, and the time required for the selectivity to be lower than 80% was recorded. The results are shown in Table 2.

[0095] Table 2

[0096]

[0097] As can be seen from the above results, compared with Example 1, in Comparative Example 1, monodisperse SiO2 was not used to fix La and Zr, which led to agglomeration at high temperatures, resulting in a decrease in catalyst activity, a reduction in lifespan, and a decrease in product conversion rate, selectivity, and purity.

[0098] In Comparative Example 2, triethoxysilane was not used to fix the La-Zr / SiO2 composite and γ-Al2O3. The combination of La-Zr / SiO2 and γ-Al2O3 was not firm, and the resulting catalyst showed a phenomenon of loss of the La-Zr / SiO2 composite from γ-Al2O3 at high temperatures, which led to a decrease in catalyst activity, a reduction in lifespan, and a decrease in product conversion rate, selectivity, and purity.

Claims

1. A method for synthesizing acetamide and acetonitrile co-production, characterized in that: The synthesis method comprises mixing, preparing acetamide, and preparing acetonitrile; The mixing method is to vaporize acetic acid and liquid ammonia respectively and preheat them to 170-190°C, and then introduce them into a gas mixer at the same time, and control the outlet flow rate of the gas mixer to 0.29-0.31m 3 / min, and then the mixed gas is introduced into a fixed bed reactor filled with a La-Zr / SiO2-γ-Al2O3 composite catalyst; The preparation method of the La-Zr / SiO2-γ-Al2O3 composite catalyst comprises preparing monodispersed SiO2, calcining once, and calcining twice; The one-time calcination method is to add monodisperse SiO2, La(NO3)3, and Zr(NO3)4 into deionized water, then add an acetone solution of glycine and polyethylene glycol, and after ultrasonic dispersion, use ammonia water to adjust the pH value to 9-10, and react at 35-45°C with constant temperature stirring for 2.4-2.6 hours, and then centrifuge, wash the lower precipitate, dry it, transfer it to 400-500°C for calcination for 3.5-4.5 hours, grind it into powder with a particle size of 70-90nm, and obtain a La-Zr / SiO2 composite; The secondary calcination method comprises the following steps: mixing and grinding γ-Al2O3 and activated carbon to form a powder with a particle size of 90 to 120 nm, uniformly mixing the powder with a La-Zr / SiO2 complex, adding triethoxysilane and deionized water, stirring and hydrolyzing for 25 to 35 minutes, drying to constant weight, crushing and grinding to form a powder with a particle size of 0.8 to 1.2 μm, obtaining an active matrix, adding the active matrix to an isopropanol aluminum sol, ultrasonically dispersing the powder for 25 to 35 minutes, dripping the powder dropwise into an oil-ammonia column, controlling the dripping particle size to be 1.8 to 2.2 mm, obtaining a wet ball, drying the powder to constant weight, and calcining the resulting spherical porous particles with a diameter of 1.8 to 2.2 mm, i.e., a La-Zr / SiO2-γ-Al2O3 composite catalyst.

2. A method for synthesizing acetamide and acetonitrile co-production according to claim 1, wherein the mass ratio of acetic acid to ammonia in the mixed gas is 2.8-3.4:0.9-1.1, the mass ratio of γ-Al2O3, activated carbon, La-Zr / SiO2 composite, triethoxysilane, and deionized water is 13-17:1.3-1.5:3.71-3.75:2.2-2.6:18-22, and the mass ratio of active matrix to aluminum isopropoxide sol is 1.47-1.49:26.45-26.

49.

3. A method for synthesizing acetamide and acetonitrile co-production according to claim 1, wherein the method for preparing acetamide is to control the reactor temperature at 210 to 230° C., the pressure at 0.58 to 0.62 MPa, the residence time of the mixed gas in the reactor at 25 to 35 s, and after the reaction is completed, the mixture is introduced into a distillation tower, the pressure in the tower is controlled to be 65 to 75 kPa, the tower top temperature is 75 to 85° C., the tower bottom temperature is 115 to 125° C., the reflux ratio is 1.6 to 2.1, and the tower bottom liquid level is unchanged, and the tower bottom material is output, and after cooling and crystallization, it is dried to constant weight at 35 to 45° C. to obtain acetamide.

4. A method for preparing acetonitrile by co-production of acetamide and acetonitrile according to claim 1, wherein the reactor temperature is controlled at 340 to 360° C., the pressure is controlled at 0.06 to 0.08 MPa, the residence time of the mixed gas in the reactor is 40 to 60 s, and after the reaction is completed, the mixed gas is introduced into a distillation tower, the pressure in the tower is controlled to be 65 to 75 kPa, the tower top temperature is 75 to 85° C., the tower bottom temperature is 115 to 125° C., the reflux ratio is 2 to 3, and after the tower bottom liquid level remains unchanged, the tower top material is output, and acetonitrile is obtained after cooling and dehydration.

5. The method for synthesizing acetamide and acetonitrile by co-production according to claim 1, wherein in the one-time calcination method, the mass ratio of monodisperse SiO2, La(NO3)3, Zr(NO3)4, and deionized water is 43:20:7:190, the mass ratio of monodisperse SiO2, acetone solution of polyethylene glycol, and glycine is 21:5:3, the mass fraction of polyethylene glycol in the acetone solution of polyethylene glycol is 0.5%, and the stirring rate is 45r / min.

6. The method for preparing monodisperse SiO2 by co-producing acetamide and acetonitrile according to claim 1, wherein anhydrous ethanol and aqueous ammonia are added to deionized water, stirred until the solution is clear and transparent, and then ethyl orthosilicate is slowly added dropwise to the solution. After the addition is complete, the reaction is carried out at a constant temperature of 28 to 32° C. for 5.5 to 6.5 hours, and then after centrifugation, the lower precipitate is cleaned, dried, and ground into a white powder with a particle size of 50 to 70 nm, i.e., monodisperse SiO2.

7. A method for synthesizing acetamide and acetonitrile co-production according to claim 6, wherein in the method for preparing monodisperse SiO2, the mass ratio of anhydrous ethanol, ammonia water and deionized water is 8-12:1.8-2.2:2.5-3.5, the mass fraction of ammonia in the ammonia water is 20-30%, and the dropping time is 25-35 min.

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