阅读说明：本技术 一种制备乙腈的方法 (Method for preparing acetonitrile ) 是由 庆九 俞新南 朱小刚 刘芳 于 2020-12-31 设计创作，主要内容包括：本发明公开了一种制备乙腈的方法,将乙酸、乙酸铵、乙酰胺,其中的一种以上溶质的水溶液预热至90～120℃,通过雾化装置,使用蒸汽或氮气并控制雾化进料压力0.1～1.5Mpa,雾化成细小液滴,与预热至300～500℃的氨气一起进入固定床反应器的顶部混合；经分布器,两种气相物料在催化剂作用下,在350～450℃发生氨化作用,固定床反应器顶部压力为5Kpa-25Kpa,催化剂负荷0.1t～2t/(m～3*h)；反应停留时间：3～8s；混合液中所述溶质的总摩尔数与氨的摩尔比为1:1～1.5；催化剂是以三氧化二铝为载体的醋酸氨化催化剂,催化剂为：A-aB-bC-cMo-(10)O-x；得到的反应气依次经过吸收、精馏工序得到成品乙腈。本发明减少了结焦量,提高了原料醋酸与氨的利用率,产品乙腈的产率提升至95％以上。(The invention discloses a method for preparing acetonitrile, which comprises the steps of preheating aqueous solution of more than one solute of acetic acid, ammonium acetate and acetamide to 90-120 ℃, atomizing into fine droplets by using steam or nitrogen and controlling the atomizing feeding pressure to be 0.1-1.5 Mpa through an atomizing device, and mixing with ammonia gas preheated to 300-500 ℃ entering the top of a fixed bed reactor; through a distributor, the two gas-phase materials are aminated at 350-450 ℃ under the action of a catalyst, the top pressure of the fixed bed reactor is 5-25 Kpa, and the catalyst load is 0.1-2 t/(m) 3 H); reaction residence time: 3-8 s; the molar ratio of the total moles of the solute to the ammonia in the mixed solution is 1: 1-1.5; the catalyst is an acetic acid ammoniation catalyst taking aluminum oxide as a carrier, and the catalyst is as follows: a. the a B b C c Mo 10 O x (ii) a To obtainThe reaction gas is sequentially subjected to absorption and rectification processes to obtain the finished product acetonitrile. The invention reduces the coking amount, improves the utilization rate of the raw material acetic acid and ammonia, and improves the yield of the product acetonitrile to more than 95 percent.)

1. A method for preparing acetonitrile, characterized in that: the method comprises the following steps:

(1) preheating aqueous solution of more than one solute of acetic acid, ammonium acetate and acetamide to 90-120 ℃, atomizing into fine droplets by an atomizing device by using steam or nitrogen and controlling the atomizing feeding pressure to be 0.1-1.5 Mpa, and mixing with ammonia gas preheated to 300-500 ℃ entering the top of a fixed bed reactor; acetic acid: ammonium acetate: acetamide: the weight ratio of water is 0.0001-100%, 0.0001-18%; acetic acid: the weight ratio of water is 90-99.9%: 0.0001 to 10 percent; acetic acid: ammonium acetate: the weight ratio of water is 0.0001-99.0%, 0.0001-50%, 0.0001-18%; acetic acid: acetamide: the weight ratio of water is 0.0001-99.9%, 0.0001-45%, 0.0001-18%; ammonium acetate: the weight ratio of water is 82-100%: 0.0001 to 18 percent; ammonium acetate: acetamide: the weight ratio of water is 0.0001-100%, 0.0001-18%;

(2) passing through a fixed bed reactor filled with a catalyst by a distributor, ammoniating two gas-phase materials at 350-450 ℃ under the action of the catalyst, wherein the top pressure of the fixed bed reactor is 5-25 Kpa, and the catalyst load is 0.1-2 t/(m)³H); reaction residence time: 3-8 s; the molar ratio of the total moles of the solute to the ammonia in the mixed solution is 1: 1-1.5;

the catalyst is an acetic acid ammoniation catalyst taking aluminum oxide as a carrier, and the catalyst is as follows: a. the_aB_bC_cMo₁₀O_x

Wherein A is one or a combination of a plurality of Na, K and Ti;

b is one or the combination of a plurality of Ni, Mn, Co and Zn;

c is one or the combination of a plurality of Fe, W, Sn, Ge, Bi and P;

a＝0.1～1.5,

b＝0.2～10,

c＝0.05～10.0

x is the oxygen atom number required by the metal element;

(3) separation and purification step

And (3) sequentially carrying out absorption and rectification on the reaction gas in the step (2) to obtain a finished product of acetonitrile.

2. A process for the preparation of acetonitrile according to claim 1, wherein: the acetic acid: ammonium acetate: acetamide: the weight ratio of water is 0.1-100%, 0.1-50%, 0.1-45%, 0.1-18%.

3. A process for the preparation of acetonitrile according to claim 1, wherein:

the catalyst is an acetic acid ammoniation catalyst taking alumina as a carrier, and comprises the following components: a. the_aB_bC_cMo₁₀O_xWherein a is a combination of Na and Ti, B is a combination of Zn, Mn and Ni, C is a combination of Fe and P, a is 0.3 to 0.8, B is 3 to 7, C is 0.05 to 2, and x is the number of oxygen atoms necessary for the metal element.

4. A process for the preparation of acetonitrile according to claim 3, wherein:

the catalyst is an acetic acid ammoniation catalyst taking alumina as a carrier, and comprises the following components: a. the_aB_bC_cMo₁₀O_xWherein a is a combination of Na and Ti, B is a combination of Zn, Mn and Ni, C is a combination of Fe and P, a is 0.3 to 0.6, B is 3 to 6, C is 0.05 to 1, and x is the number of oxygen atoms necessary for the metal element.

5. A process for the preparation of acetonitrile according to claim 4, wherein:

the catalyst is an acetic acid ammoniation catalyst taking alumina as a carrier, and comprises the following components: a. the_aB_bC_cMo₁₀O_xWherein a is a combination of Na and Ti, B is a combination of Zn, Mn and Ni, C is a combination of Fe and P, a is 0.4 to 0.5, B is 3 to 5, C is 0.05 to 0.2, and x is the number of oxygen atoms necessary for the metal element.

6. A process for the preparation of acetonitrile according to claim 1, wherein: the reaction residence time in the step (2): 2-6 s.

7. A process for the preparation of acetonitrile according to claim 1, wherein: the load of the catalyst in the step (2) is 0.1 t-1.5 t/(m)³*h)。

8. A process for the preparation of acetonitrile according to claim 7, which is characterized in thatCharacterized in that: the load of the catalyst in the step (2) is 0.1 t-1 t/(m)³*h)。

Technical Field

The invention relates to the field of chemical synthesis, and particularly relates to a preparation method of acetonitrile.

Background

Acetonitrile

English name: acetonitriles

Alias: acetonitrile; methyl cyanide; methyl cyanide; a methyl nitrile; ethane nitrile; chromatographic acetonitrile; acetonitrile in water; cyanomethane; cyaniding methane; AN; ACN; AN 2; MGDA; CH3 CN;

the molecular formula is as follows: C2H3N

Molecular weight: 41.05

Appearance: colorless liquid with pungent odor

Melting point: -45 ℃ C

Boiling point: 81 to 82 DEG C

Water solubility: mixing with water, and dissolving in ethanol, diethyl ether, etc.

Action and use:

solvents used in the petroleum industry to remove tar, phenols, and the like from petroleum hydrocarbons; the solvent is used for extracting fatty acid from animal and vegetable oil in the grease industry; reaction media for pharmaceutical use in the recrystallization of steroids; binary azeotropes of acetonitrile with water (84% acetonitrile, boiling point 76 ℃) are often used when polar solvents of high dielectric constant are required. Acetonitrile is an intermediate of medicine and perfume, and is a raw material for preparing the s-triazine nitrogen fertilizer synergist. In addition, it can be used for synthesizing ethylamine, acetic acid, etc., and has many applications in textile dyeing and lighting industries.

The synthesis process in the prior art comprises the following steps:

the current methods for synthesizing acetonitrile mainly comprise the following steps:

1) propylene ammoxidation by-product method: taking propylene, ammonia and air as raw materials, synthesizing acrylonitrile under the action of a catalyst, and simultaneously obtaining acetonitrile as a byproduct; the crude acetonitrile separated by the method comprises water, acetonitrile, hydrocyanic acid, acetone, propionitrile, benzonitrile, acetaldehyde, acrolein and the like. The finished product acetonitrile is obtained by extraction and rectification of trimethylbenzene, tetramethylbenzene and the like. The method has complex process, and the production process is often accompanied by one or more byproducts of carbon dioxide, hydrogen cyanide or other substances, thereby bringing much trouble to the production.

2) An ethanol ammoniation method: ethanol and ammonia are used as raw materials to synthesize acetonitrile under the action of a catalyst, and the reaction product of the method is accompanied by hydrogen generation, so that a plurality of potential safety hazards are brought to production.

3) Acetic acid ammonification method: acetic acid and ammonia are used as raw materials, and acetonitrile is synthesized through two-step dehydration under the action of a catalyst.

[1] Wuweilong, chenshuihin, acetonitrile production and its industrial major use [ J ]. Shandong chemical industry, 2003 (6): 26-28.

[2]Zhang Yining,ZhangYuecheng,etal.Amination of ethanol to acetonitrile over Ni-doped Co/γ-Al2O3 catalyst[J].Catal Commun,2009,10(10):1454-1458.

[3] A method for synthesizing high-purity acetonitrile by ammoniating acetic acid [ P ]. CN101597242A, 2009-12-09.

Disclosure of Invention

Therefore, the technical problem to be solved by the invention is to provide a novel method for preparing acetonitrile, which can reduce the evaporation coking amount and improve the yield of acetonitrile products.

The technical scheme of the invention is that the method for preparing acetonitrile comprises the following steps:

(1) preheating aqueous solution of more than one solute of acetic acid, ammonium acetate and acetamide to 90-120 ℃, atomizing into fine droplets by an atomizing device by using steam or nitrogen and controlling the atomizing feeding pressure to be 0.1-1.5 Mpa, and mixing with ammonia gas preheated to 300-500 ℃ entering the top of a fixed bed reactor; acetic acid: ammonium acetate: acetamide: the weight ratio of water is 0.0001-100%, 0.0001-18%; acetic acid: the weight ratio of water is 90-99.9%: 0.0001 to 10 percent; acetic acid: ammonium acetate: the weight ratio of water is 0.0001-99.0%, 0.0001-50%, 0.0001-18%; acetic acid: acetamide: the weight ratio of water is 0.0001-99.9%, 0.0001-45%, 0.0001-18%; ammonium acetate: the weight ratio of water is 82-100%: 0.0001 to 18 percent; ammonium acetate: acetamide: the weight ratio of water is 0.0001-100%, 0.0001-18%;

(2) passing through a fixed bed reactor filled with a catalyst by a distributor, ammoniating two gas-phase materials at 350-450 ℃ under the action of the catalyst, wherein the top pressure of the fixed bed reactor is 5-25 Kpa, and the catalyst load is 0.1-2 t/(m)³H); reaction residence time: 3-8 s; the molar ratio of the total moles of the solute to the ammonia in the mixed solution is 1: 1-1.5;

the catalyst is an acetic acid ammoniation catalyst taking aluminum oxide as a carrier, and the catalyst is as follows: a. the_aB_bC_cMo₁₀O_x

Wherein A is one or a combination of a plurality of Na, K and Ti;

b is one or the combination of a plurality of Ni, Mn, Co and Zn;

c is one or the combination of a plurality of Fe, W, Sn, Ge, Bi and P;

a＝0.1～1.5,

b＝0.2～10,

c＝0.05～10.0

x is the oxygen atom number required by the metal element;

(3) separation and purification step

And (3) sequentially carrying out absorption and rectification on the reaction gas in the step (2) to obtain a finished product of acetonitrile.

Acetic acid and ammonia are subjected to ammoniation reaction to generate acetonitrile, ammonium acetate and acetamide are byproducts, and in principle, the ammonium acetate and the acetamide can generate acetonitrile after high-temperature dehydration, so that the acetonitrile can be generated by any composition of the three.

Steam or nitrogen is mixed with feed liquid in an atomizer, and when gas and liquid pass through the atomizer, the feed liquid is sheared and broken into more stable and finer fog drops with small particle size under the action of high-speed airflow due to different gas-liquid two-phase rates and rate differences; steam or nitrogen is selected from the aspects of safety and environmental protection.

Preferably, the ratio of acetic acid: ammonium acetate: acetamide: the weight ratio of water is 0.1-100%, 0.1-50%, 0.1-45%, 0.1-18%.

According to the inventionThe method for preparing the acetonitrile preferably comprises the following steps of: a. the_aB_bC_cMo₁₀O_xWherein a is a combination of Na and Ti, B is a combination of Zn, Mn and Ni, C is a combination of Fe and P, a is 0.3 to 0.8, B is 3 to 7, C is 0.05 to 2, and x is the number of oxygen atoms necessary for the metal element.

Further, the catalyst is an acetic acid ammoniation catalyst taking alumina as a carrier, and the catalyst comprises the following components: a. the_aB_bC_cMo₁₀O_xWherein a is a combination of Na and Ti, B is a combination of Zn, Mn and Ni, C is a combination of Fe and P, a is 0.3 to 0.6, B is 3 to 6, C is 0.05 to 1, and x is the number of oxygen atoms necessary for the metal element.

Furthermore, the catalyst is an acetic acid ammoniation catalyst taking alumina as a carrier, and the catalyst comprises the following components: a. the_aB_bC_cMo₁₀O_xWherein a is a combination of Na and Ti, B is a combination of Zn, Mn and Ni, C is a combination of Fe and P, a is 0.4 to 0.5, B is 3 to 5, C is 0.05 to 0.2, and x is the number of oxygen atoms necessary for the metal element.

According to a method for preparing acetonitrile of the present invention, it is preferable that the reaction residence time of the step (2): 2-6 s.

According to the method for preparing acetonitrile in the invention, the load of the catalyst in the step (2) is preferably 0.1 t-1.5 t/(m)³H). The amount of catalyst added is generally expressed in terms of catalyst loading.

Further, the load of the catalyst in the step (2) is 0.1 t-1 t/(m)³*h)。

The technical principle of the invention is as follows: acetic acid, ammonium acetate and acetamide, wherein more than one aqueous solution of acetic acid, ammonium acetate and acetamide, through the atomizing device, certain temperature and pressure are controlled, small-sized atomized liquid drops are formed and mixed with gasified ammonia, the mass transfer efficiency is improved by gas-liquid mixing, and the mixed gas is subjected to ammoniation reaction through a fixed bed reactor containing a solid acid catalyst to prepare acetonitrile. The invention adopts the atomizer to replace the traditional evaporation feeding, reduces the evaporation coking amount and improves the yield of the product acetonitrile.

In CN101597242A, the 3-step reaction of taking acetic acid and ammonia as raw materials produces acetonitrile; the invention comprises 3 steps, 2 steps and 1 step of reaction to produce acetonitrile due to the difference of raw materials. According to the characteristics of the raw materials, the invention adopts atomization feeding, improves the feeding distribution, improves the yield of acetonitrile products and reduces the coking rate.

Has the advantages that:

1) the atomization feeding mode improves the mass transfer and heat transfer of the catalyst bed layer, so that the ammoniation reaction is more sufficient, the carbon deposition of the catalyst is reduced, and the service life of the catalyst is prolonged;

2) compared with the prior art, the coking amount is reduced to a great extent; the coking phenomenon refers to the phenomenon of feed liquid deterioration and coking caused by long-time high-temperature state in the evaporation process. The invention adopts atomization feeding to improve feeding distribution, so that the raw materials are more fully contacted with the catalyst, and the yield of acetonitrile products is improved; according to the characteristics of raw materials (containing organic matters with higher boiling points), a conventional shell and tube evaporator is adopted for evaporation, higher evaporation temperature is required, long-time evaporation is carried out at high temperature, and the coking amount in the evaporator is large; the atomizer can realize feeding at a lower temperature, improve distribution and obviously improve coking phenomenon.

3) The utilization rate of the acetic acid and the ammonia as raw materials is improved, and the yield of the acetonitrile product is improved to over 95 percent.

Detailed Description

Comparative example:

preheating liquid ammonia to 150-200 ℃, and mixing acetic acid: ammonium acetate: acetamide: the mixed solution of water in a weight ratio (45:30:15:10) is preheated to 250 ℃ by an evaporator, two gases enter the top of the fixed bed reactor to be mixed, and the mixed solution passes through the fixed bed reactor filled with the catalyst by a distributor: ammoniating the two materials at 400 deg.C under the action of catalyst, wherein the top pressure of fixed bed reactor is 5-25 Kpa, the molar ratio of total mole number of solute and ammonia in the mixed solution is 1:1.2, and the catalyst load is 0.3 t/(m)³H), reaction residence time: 7 s; obtaining reaction gas, and sequentially carrying out absorption, rectification and other processes on the reaction gas to obtain a finished product acetonitrile; acetonitrileThe yield was 94%.

Example 1:

preheating a mixture of acetic acid, ammonium acetate, acetamide and water (the weight ratio of acetic acid to ammonium acetate to acetamide to water is 45:30:15:10) to 120 ℃, atomizing into fine droplets by an atomizing device under the condition that the atomizing feeding pressure is controlled by nitrogen gas to be 1.5Mpa, feeding the fine droplets and ammonia gas preheated to 400 ℃ into the top of a fixed bed reactor to be mixed, and passing the mixture through the fixed bed reactor filled with a catalyst by a distributor; ammoniating two gas phase materials at 400 deg.C under the action of catalyst, wherein the top pressure of fixed bed reactor is 5-25 Kpa, the molar ratio of total mole number of solute and ammonia in mixed solution is 1:1.2, and the catalyst load is 0.3 t/(m)³H), reaction residence time: 7 s; obtaining reaction gas, and sequentially carrying out absorption, rectification and other processes on the reaction gas to obtain a finished product acetonitrile; the acetonitrile yield was 95.5%.

In the comparative example, the boiling point of acetamide in the raw material was 221 ℃, and a higher temperature was required for evaporation in a conventional evaporator.

The catalysts of example 1 and comparative example are acetic acid ammoniation catalysts using alumina as a carrier, and the catalysts are as follows: (NaTi)_0.4(ZnMnNi)₃(FeP)_0.2Mo₁₀O_xAnd x is the number of oxygen atoms required for the metal element.

Example 2:

preheating a mixture of acetic acid, ammonium acetate and water (the weight ratio of acetic acid to ammonium acetate to water is 45:45:10) to 110 ℃, atomizing into fine droplets by an atomizing device under the control of atomizing feeding pressure of 0.5Mpa by using nitrogen, mixing with ammonia gas preheated to 350 ℃ entering the top of a fixed bed reactor, and passing through the fixed bed reactor filled with a catalyst by a distributor; ammoniating two gas phase materials at 360 deg.C under the action of catalyst, wherein the top pressure of fixed bed reactor is 5-25 Kpa, the molar ratio of total mole number of solute and ammonia in mixed solution is 1:1.5, and the catalyst load is 0.7 t/(m)³H), reaction residence time: 8 s; obtaining reaction gas, and sequentially carrying out absorption, rectification and other processes on the reaction gas to obtain a finished product acetonitrile; the acetonitrile yield was 95.8%.

The catalyst isThe acetic acid ammoniation catalyst with aluminum oxide as a carrier comprises the following components in parts by weight: (NaTi)_0.5(ZnMnNi)₄(FeP)_0.2Mo₁₀O_xAnd x is the number of oxygen atoms required for the metal element.

Example 3:

preheating a mixture of acetic acid, ammonium acetate, acetamide and water (the weight ratio of acetic acid to ammonium acetate to acetamide to water is 30:50:15:5) to 120 ℃, atomizing into fine droplets by an atomizing device under the condition that the atomizing feeding pressure is controlled by nitrogen gas to be 1.5Mpa, feeding the fine droplets and ammonia gas preheated to 430 ℃ into the top of a fixed bed reactor to be mixed, and passing the mixture through the fixed bed reactor filled with a catalyst by a distributor; ammoniating two gas phase materials at 400 deg.C under the action of catalyst, wherein the top pressure of fixed bed reactor is 5-25 Kpa, the molar ratio of total mole number of solute and ammonia in mixed solution is 1:1.12, and the catalyst load is 0.1 t/(m)³H), reaction residence time: 3 s; obtaining reaction gas, and sequentially carrying out absorption, rectification and other processes on the reaction gas to obtain a finished product acetonitrile; the acetonitrile yield was 95.2%.

The catalyst is an acetic acid ammoniation catalyst taking aluminum oxide as a carrier, and the catalyst is as follows: (NaTi)₁(ZnMnNi)₄(FeP)₄Mo₁₀O_xAnd x is the number of oxygen atoms required for the metal element.

Example 4:

preheating a mixture of acetic acid and acetamide (the weight ratio of acetic acid to acetamide is 80:20) to 120 ℃, atomizing into fine droplets by an atomizing device under the control of an atomizing feeding pressure of 1.35Mpa by using nitrogen, mixing with ammonia gas preheated to 360 ℃ entering the top of a fixed bed reactor, and passing through the fixed bed reactor filled with a catalyst by a distributor; ammoniating two gas-phase materials at 440 ℃ under the action of a catalyst, wherein the top pressure of a fixed bed reactor is 5Kpa-25Kpa, the molar ratio of the total moles of the solute to the ammonia in the mixed solution is 1:1.25, the catalyst load is 0.5t/(m3 x h), and the reaction residence time is as follows: 7 s; obtaining reaction gas, and sequentially carrying out absorption, rectification and other processes on the reaction gas to obtain a finished product acetonitrile; the acetonitrile yield was 95.5%.

The catalystThe catalyst is an acetic acid ammoniation catalyst taking aluminum oxide as a carrier, and comprises the following components in percentage by weight: (NaTi)₁(ZnMnNi)₁(FeP)₄Mo₁₀O_xAnd x is the number of oxygen atoms required for the metal element.

Example 5:

preheating a mixture of ammonium acetate, acetamide and water (the weight ratio of acetic acid to ammonium acetate to acetamide to water is 50:35:15) to 120 ℃, atomizing into fine droplets by an atomizing device under the condition that the atomizing feeding pressure is controlled by nitrogen gas to be 1.0Mpa, feeding the fine droplets and ammonia gas preheated to 500 ℃ into the top of a fixed bed reactor for mixing, and passing through the fixed bed reactor filled with a catalyst by a distributor; ammoniating two gas-phase materials at 440 ℃ under the action of a catalyst, wherein the top pressure of a fixed bed reactor is 5Kpa-25Kpa, the molar ratio of the total moles of the solute to the ammonia in the mixed solution is 1:1.05, the catalyst load is 0.9t/(m3 x h), and the reaction residence time is as follows: 6 s; obtaining reaction gas, and sequentially carrying out absorption, rectification and other processes on the reaction gas to obtain a finished product acetonitrile; the acetonitrile yield was 95.9%.

The catalyst is an acetic acid ammoniation catalyst taking aluminum oxide as a carrier, and the catalyst is as follows: (NaTi)₁(ZnMnNi)₄(FeP)₁Mo₁₀O_xAnd x is the number of oxygen atoms required for the metal element.

The atomized feeding mode of the invention improves the mass transfer and heat transfer of the catalyst bed layer, makes the ammoniation reaction more sufficient, reduces the carbon deposition of the catalyst and prolongs the service life of the catalyst; compared with the prior art, the coking amount is reduced to a great extent, and the utilization rate of the raw materials of acetic acid and ammonia is improved.