Preparation method of 3-pentenenitrile

Abstract

The invention provides a preparation method of 3-pentenenitrile, which comprises the following steps: S1, preparing crude hydrogen cyanide gas by a formamide pyrolysis method: under the conditions that the reduced pressure is 5-200mbar and the pyrolysis temperature is 250-650 DEG C, introducing the raw material formamide gas into a columnar catalyst bed layer, and reacting in a hydrocyanic acid fixed bed synthesizer to generate the crude hydrogen cyanide gas and a pyrolysis product; s2, preparation of acetone cyanohydrin: cooling the crude hydrogen cyanide gas and the pyrolysis product so as to condense the product with the boiling point higher than that of the hydrogen cyanide gas; removing ammonia and water from the crude hydrogen cyanide gas by using acid, and then feeding the crude hydrogen cyanide gas into an adsorption tower to carry out chemical adsorption reaction with acetone in the presence of a catalyst, so as to prepare acetone cyanohydrin; and S3: preparation of 3-pentenenitrile: preparing a catalyst by using the phosphite ligand and nickel, and under the condition that Lewis acid is used as a cocatalyst, preparing 3-pentenenitrile by taking acetone cyanohydrin as a cyanogen source and hydrocyanating 1, 3-butadiene.

Description

Technical Field

[0001] The invention relates to the technical field of chemical synthesis, and in particular to a method for preparing 3-pentenenitrile. Background Art

[0002] Nitrile is a class of organic compounds containing cyanide. It is an important chemical raw material and has important applications in the fields of medicine and new materials. Representative compounds such as adiponitrile are important intermediates for the preparation of nylon 66 and are used in the production of engineering plastics, etc.

[0003] There are many existing methods for preparing nitriles, but the most commonly used method is to prepare 3-pentenenitrile by nucleophilic substitution reaction of 1,3-butadiene and hydrocyanic acid. The limitations of this method are mainly: 1. Hydrocyanic acid is highly toxic, which brings serious environmental pollution and personal safety problems; 2. The existing hydrocyanic acid production method has complex process flow, high equipment investment cost, high safety risk, and produces a large amount of wastewater, which need to be solved urgently; 3. Hydrocyanic acid is used as a cyaniding reagent, but pure hydrocyanic acid is stable under low temperature conditions. When mixed with impurities such as water, alkali and iron filings, it is easy to decompose and polymerize. This process has a self-catalytic effect, and the exothermic reaction may cause an explosion, which is very risky. When hydrocyanic acid polymerizes, the black viscous substance produced will quickly block the condenser, tower equipment and pipelines, etc., affecting the normal operation of the device.

[0004] Acetone cyanohydrin is also known as 2-hydroxyisobutyronitrile, with the English name acetone cyanohydrin, molecular formula C4H7NO, CAS 75-86-5. It is a colorless to light yellow liquid at room temperature, with a melting point of -19°C, a boiling point of 95°C, a relative density of 0.932 (water = 1, 20 / 4°C), a refractive index (20°C) of 1.3996, and a flash point of 63°C. It is easily soluble in water and common organic solvents, but insoluble in petroleum ether and carbon disulfide. It quickly decomposes into acetone and hydrogen cyanide when heated in an alkaline solution.

[0005] Using acetone cyanohydrin, which is relatively safe, instead of highly toxic cyaniding reagents such as hydrocyanic acid (the human lethal dose is 0.57 mg / kg, and the LD50 of acetone cyanohydrin is 52 mg / kg) can avoid the resulting environmental pollution and personal safety problems.

[0006] However, in the current existing technology, there is no mature method for preparing the cyanide acetone cyanohydrin by thermal decomposition of formamide, and preparing 3-pentenenitrile by hydrocyanation of 1,3-butadiene using acetone cyanohydrin as a cyanide source. In addition, the conventional preparation method in the existing technology has complex reaction conditions, great difficulty in operation, high risk, and the yield and selectivity of the target product are also relatively general, which cannot meet the needs of industrial production. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a method for preparing 3-pentenenitrile, so as to solve the problem that the preparation method of 3-pentenenitrile in the prior art has complex reaction conditions, great difficulty in operation, high risk, and the yield and selectivity of the target product are also relatively general and cannot meet the needs of industrial production.

[0008] In order to solve the above problems, the present invention provides a method for preparing 3-pentenenitrile, comprising the following steps: S1: Preparation of crude hydrogen cyanide gas by thermal decomposition of formamide: Under the conditions of reduced pressure of 5-200 mbar and pyrolysis temperature of 250-650°C, the raw formamide gas is introduced into a columnar catalyst bed to react in a hydrocyanic acid fixed bed synthesizer to generate crude hydrogen cyanide gas and pyrolysis products; S2: Preparation of acetone cyanohydrin: The crude hydrogen cyanide gas and the pyrolysis product obtained in step S1 are cooled so that the products with boiling points higher than that of the hydrogen cyanide gas are condensed, wherein the cooling conditions are: temperature: -10-200°C, and reduced pressure: 5-200 mbar; then the crude hydrogen cyanide gas is deammonified and dehydrated with an acid, and then sent to an adsorption tower to undergo a chemical adsorption reaction with acetone in the presence of a catalyst to obtain acetone cyanohydrin; S3: Preparation of 3-pentenenitrile: A catalyst was prepared using phosphite ligand and nickel. Under the condition of Lewis acid as a co-catalyst, 1,3-butadiene was hydrocyanated with acetone cyanohydrin as a cyanide source to prepare 3-pentenenitrile.

[0009] Compared with the prior art, the present invention discloses a method for preparing 3-pentenenitrile, which has the following advantages: the present invention discloses a new method for preparing 3-pentenenitrile, and aims to provide a method for preparing cyanide acetone cyanohydrin by a formamide thermal decomposition method which is technically simpler, and preparing 3-pentenenitrile by hydrocyanation of 1,3-butadiene, wherein phosphite ligand and nickel are used as catalysts, butadiene is hydrocyanated with acetone cyanohydrin as a cyanide source under the condition that Lewis acid is used as a co-catalyst to prepare 3-pentenenitrile, and in the reaction process, acetone cyanohydrin is synthesized by using crude hydrocyanic acid mixed gas after formamide thermal decomposition reaction, and acetone cyanohydrin is prepared by reacting crude cyanide gas with acetone, and liquid cyanide does not need to be prepared through absorption, desorption, cooling and other steps, thereby eliminating the liquid cyanide stage, and acetone cyanohydrin is used as a cyanation reagent, which has high safety, effectively reduces the investment cost of basic equipment, and effectively reduces energy consumption, greatly shortens the process flow, and improves production efficiency; it is particularly worth mentioning that the method of the present invention has mild reaction conditions, simple operation process, high safety, excellent target product yield and selectivity, and has great prospects for industrial application.

[0010] In the present invention, acetone solution is used for the chemical adsorption of hydrogen cyanide, thereby for preparing its reaction product acetone cyanohydrin. It is understood that the absorbent for hydrogen cyanide is a carbonyl compound, and a suitable absorbent is a ketone, such as acetone. The chemical adsorption of hydrogen cyanide and carbonyl compounds is carried out under conditions of pH 7 or higher, preferably at alkaline pH values, because the chemical adsorption reaction occurs very quickly under these conditions. However, an inorganic or organic base can be additionally introduced into the chemical adsorption stage. The reaction between hydrogen cyanide and carbonyl compounds is usually preferably catalyzed by a tertiary amine, such as triethylamine.

[0011] The addition reaction of hydrogen cyanide with aldehydes of 1 to 4 carbon atoms or with ketones is generally carried out under reduced pressure during the pyrolysis process, and the reaction rate is such that a single-stage chemical adsorption is sufficient. The chemical adsorption reaction in the present invention can be carried out in several steps, for example in two or more columns connected in series. The temperature during the chemical adsorption process is -20°C to 30°C, preferably -5°C to 15°C. If the reaction rate during the chemical adsorption process with carbonyl compounds is reduced, a multi-stage procedure is usually adopted.

[0012] In a possible implementation, in the step S1, the pyrolysis temperature is 300-550°C, and the reduced pressure is 10-150 mbar.

[0013] Under the reduced pressure conditions of the pyrolysis process, i.e. 5 to 200 mbar, both substances can be converted into acetone cyanohydrin almost quantitatively at 10 °C. Furthermore, the production of considerable quantities of liquid hydrogen cyanide (up to 540 kmol / h at a production of 20 kmol / h) can now be dispensed with. The invention discloses a method for preparing hydrogen cyanide reaction products, wherein the amount of hydrogen cyanide formed during the pyrolysis process is directly treated in the chemical adsorption stage to form hydrogen cyanide reaction products with much less harm, and the hydrogen cyanide content of these reaction products is generally less than 0.1wt%; the preparation method of the present invention can ensure a high level of safety even if a failure occurs during the reaction process: for example, if a leak occurs in the pressure device, the formation of hydrogen cyanide will stop automatically and further release of hydrogen cyanide can be prevented, which makes it possible to establish a small-scale device with much fewer problems at almost any location to produce secondary products of hydrogen cyanide, such as for the preparation of acetone cyanohydrin or amino acids; and by further controlling the pyrolysis temperature to 300-550°C and the reduced pressure to 10-150mbar, the above technical effects are further improved and the conversion rate of the reaction is improved.

[0014] Also under reduced pressure, the pyrolysis, condensation and chemical adsorption take place, i.e. from 5 to 200 mbar, the pyrolysis and chemical adsorption being carried out by a continuous process, in which the hydrogen cyanide formed continuously during the pyrolysis is fed to the chemical adsorption stage at the rate at which it is formed, and the condensation of the hydrogen cyanide is omitted; In a possible implementation, in step S2, the cooling temperature is -10-60°C, and the reduced pressure is 10-150 mbar.

[0015] In a possible embodiment, in step S2, after the cooling treatment and between the acid ammonia removal treatment, the steps of recovering the formamide obtained after the cooling treatment and removing the condensed water are also included.

[0016] In the preparation method of the present invention, the pyrolysis product of step S1 may contain more or less unconverted raw materials. Under the pyrolysis pressure conditions, it is cooled to a temperature of -10-200°C, and more preferably -10-60°C. During the cooling process, all products with a boiling point higher than hydrogen cyanide are condensed to obtain unconverted formamide and condensed water, and the unconverted formamide is recovered and reused.

[0017] In a possible implementation, in step S2, the conditions for removing ammonia with acid are to remove ammonia by chemical adsorption using sulfuric acid or phosphoric acid, and the removal of ammonia with acid is carried out under a reduced pressure of 10-150 mbar.

[0018] In a possible implementation, in step S2, the reduced pressure for removing ammonia with acid is 20-60 mbar.

[0019] For the uncondensed hydrogen cyanide gas, the present invention uses sulfuric acid or phosphoric acid to remove ammonia by chemical adsorption, which is also carried out under reduced pressure conditions. Compared with pyrolysis, the only difference is the pressure loss caused by the process. The pressure in the chemical adsorption process zone is 5 to 200 mbar, preferably 20 to 60 mbar. Under the preferred conditions of 20 to 60 mbar, the reaction effect is better.

[0020] In the present invention, after the formamide thermal decomposition reaction in step S1, the crude hydrocyanic acid mixed gas is composed of the following components in mass percentage: hydrocyanic acid gas 85%±1%, ammonia 2.3%±1%, water vapor 35%±1, hydrogen 1.2%±1%, carbon monoxide 5.6%±1%, and carbon dioxide 1.5±1%; and after further removing ammonia and water in step S2, the crude hydrocyanic acid mixed gas is composed of the following components in mass percentage: hydrocyanic acid gas 95%±1%, water vapor 3.5%±1, hydrogen 1.4%±1%, carbon monoxide 5.9%±1%, and carbon dioxide 2.9±1%. The crude cyanide gas is close to an ammonia-free state, and subsequent reactions can be carried out smoothly. The purity of the hydrocyanic acid gas is further improved by removing ammonia and water, and controlling pressure and temperature for reaction.

[0021] In a possible implementation, in the step S2, after the acetone cyanohydrin is obtained, the step further includes: continuing to perform distillation treatment on the acetone cyanohydrin to improve the purity of the acetone cyanohydrin.

[0022] In the above possible implementation manner, the present invention purifies crude acetone cyanohydrin by vacuum distillation while maintaining a low decomposition rate of acetone cyanohydrin.

[0023] After the above distillation treatment, the purity of hydrogen cyanide gas is improved.

[0024] In a possible embodiment, after the distillation treatment, the process further includes recovering the acetone and hydrocyanic acid obtained by the distillation treatment and removing water.

[0025] In the above possible implementation, the unreacted acetone and hydrocyanic acid recovered after the distillation treatment can be put into the next reaction for reuse. In addition, the alkaline catalyst used and the water introduced during the acid neutralization are removed, and the decomposition rate of acetone cyanohydrin is ensured to be as low as possible during the reaction, thereby further improving the yield.

[0026] The composition of the crude propanol cyanohydrin before the above treatment includes: 93-94% acetone cyanohydrin, 4-5% acetone and hydrocyanic acid, 0.5-1.5% water and about 0.5% other substances; after the above treatment, acetone and hydrocyanic acid are used as raw materials for subsequent reactions, and water is removed, so that the obtained acetone cyanohydrin becomes anhydrous pure acetone cyanohydrin containing more than 99.5% of acetone cyanohydrin, which further greatly improves the purity and provides a basis for subsequent further reactions.

[0027] In a possible embodiment, in step S3, the reaction process of hydrocyanating 1,3-butadiene using acetone cyanohydrin as a cyanide source includes: mixing the catalyst and butadiene and heating to 70-90° C., setting the reaction pressure to 10-20 bar, introducing acetone cyanohydrin after the reaction, and then isothermally reacting at a temperature of 90-110° C. for 60 minutes, cooling after the reaction and reducing the pressure to normal pressure to complete the reaction.

[0028] In a possible embodiment, in step S3, the components of the catalyst include Ni[P(C6H5O)3]4, and the molar ratio of Ni[P(C6H5O)3]4 to butadiene is 1:(40-60), and the molar ratio of butadiene to acetone cyanohydrin is (1-1.2):1; the reaction process of hydrogen cyanation of 1,3-butadiene using acetone cyanohydrin as a cyanide source includes: mixing the catalyst and butadiene and heating to 80°C, setting the reaction pressure to 15 bar, introducing acetone cyanohydrin after the reaction, and then isothermally reacting at 100°C for 60 minutes, cooling after the reaction and reducing the pressure to normal pressure to complete the reaction.

[0029] The results of orthogonal experiments show that the zero-valent nickel catalytic system based on Ni[P(C6H5O)3]4 can effectively catalyze the hydrocyanation reaction of butadiene and acetone cyanohydrin. The optimal molar ratio of Ni[P(C6H5O)3]4 and butadiene is 1:50, the optimal reaction temperature is 100°C, the molar ratio of butadiene to acetone cyanohydrin is close to 1.05:1, the reaction time is 2h, the conversion rate of acetone cyanohydrin is 100%, the total selectivity of 2M3BN and 3PN is 85%, and the molar ratio of 2M3BN and 3PN is 1:3, which has high industrial application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the thermal decomposition of formamide to produce acetone cyanohydrin; Figure 2 This is a schematic diagram of the process of preparing 3-pentenenitrile by hydrocyanation of butadiene with acetone cyanohydrin. DETAILED DESCRIPTION

[0031] First, those skilled in the art should understand that these implementations are only used to explain the technical principles of the embodiments of the present application, and are not intended to limit the protection scope of the embodiments of the present application. Those skilled in the art can make adjustments to them as needed to adapt to specific application scenarios.

[0032] In the description of the embodiments of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0033] The present invention provides a method for preparing 3-pentenenitrile, comprising the following steps: S1: Preparation of crude hydrogen cyanide gas by thermal decomposition of formamide: Under the conditions of reduced pressure of 5-200 mbar and pyrolysis temperature of 250-650°C, the raw formamide gas is introduced into a columnar catalyst bed to react in a hydrocyanic acid fixed bed synthesizer to generate crude hydrogen cyanide gas and pyrolysis products; S2: Preparation of acetone cyanohydrin: The crude hydrogen cyanide gas and the pyrolysis product obtained in step S1 are cooled so that the products with boiling points higher than that of the hydrogen cyanide gas are condensed, wherein the cooling conditions are: temperature: -10-200°C, and reduced pressure: 5-200 mbar; then the crude hydrogen cyanide gas is deammonified and dehydrated with an acid, and then sent to an adsorption tower to undergo a chemical adsorption reaction with acetone in the presence of a catalyst to obtain acetone cyanohydrin; S3: Preparation of 3-pentenenitrile: A catalyst was prepared using phosphite ligand and nickel. Under the condition of Lewis acid as a co-catalyst, 1,3-butadiene was hydrocyanated with acetone cyanohydrin as a cyanide source to prepare 3-pentenenitrile.

[0034] As a preferred solution, in step S1, the pyrolysis temperature is 300-550°C, and the reduced pressure is 10-150 mbar.

[0035] As a preferred solution, in step S2, the cooling temperature is -10-60°C and the reduced pressure is 10-150 mbar.

[0036] As a preferred solution, in step S2, after the cooling treatment and between the acid ammonia removal treatment, the steps of recovering the formamide obtained after the cooling treatment and removing the condensed water are also included.

[0037] As a preferred solution, in step S2, the conditions for removing ammonia with acid are to use sulfuric acid or phosphoric acid for chemical adsorption to remove ammonia, and the removal of ammonia with acid is carried out under a reduced pressure of 10-150 mbar.

[0038] As a preferred solution, in step S2, the reduced pressure for removing ammonia with acid is 20-60 mbar.

[0039] As a preferred solution, in the step S2, after the acetone cyanohydrin is obtained, the process further comprises: continuing to distill the acetone cyanohydrin to improve the purity of the acetone cyanohydrin.

[0040] As a preferred solution, after the distillation treatment, the process further includes recovering the acetone and hydrocyanic acid obtained by the distillation treatment and removing water.

[0041] As a preferred solution, in step S3, the reaction process of hydrocyanating 1,3-butadiene with acetone cyanohydrin as a cyanide source includes: mixing the catalyst and butadiene and heating to 70-90° C., setting the reaction pressure to 10-20 bar, introducing acetone cyanohydrin after the reaction, and then isothermally reacting at a temperature of 90-110° C. for 60 minutes, cooling after the reaction and reducing the pressure to normal pressure to complete the reaction.

[0042] As a preferred solution, in step S3, the components of the catalyst include Ni[P(C6H5O)3]4, and the molar ratio of Ni[P(C6H5O)3]4 to butadiene is 1:(40-60), and the molar ratio of butadiene to acetone cyanohydrin is (1-1.2):1; the reaction process of hydrogen cyanation of 1,3-butadiene using acetone cyanohydrin as a cyanide source includes: mixing the catalyst and butadiene and heating to 80°C, setting the reaction pressure to 15 bar, introducing acetone cyanohydrin after the reaction, and then isothermally reacting at 100°C for 60 minutes, cooling after the reaction and reducing the pressure to normal pressure to complete the reaction.

[0043] In the present invention, the acetone cyanohydrin is obtained by directly reacting crude cyanide gas with acetone. Crude cyanide gas and unpurified hydrocyanic acid gas obtained by thermal decomposition of formamide are directly reacted with acetone to obtain acetone cyanohydrin without being prepared into liquid cyanide through absorption, desorption, cooling and other steps.

[0044] In the present invention, the method for synthesizing crude cyanide gas by pyrolysis of formamide comprises: using formamide as a raw material, and pyrolysis reaction to obtain crude cyanide gas. Formamide comes from synthesis gas, which has the advantages of being simple, easy to obtain, and relatively low in price. Of course, the source of crude cyanide gas is not limited to the synthesis by pyrolysis of formamide, and can also come from other ways such as Angle method, byproducts of acrylonitrile, etc.

[0045] In the present invention, crude hydrogen cyanide gas is prepared by pyrolysis of formamide, which is produced by pyrolysis reaction on a fixed bed synthesizer catalyst. Solid catalysts suitable for this purpose have proven to be particularly advantageous catalysts are those containing alkali metal or alkaline earth metal carbonates on alpha-alumina as a support. Preferably, a mixture of calcium carbonate and magnesium carbonate on alpha-alumina is used. This type of catalyst is prepared by impregnating alpha-alumina with a water-soluble salt, such as calcium acetate, and converting the salt into the corresponding carbonate or oxide by heat treatment.

[0046] The following provides examples combining specific reaction conditions and numerical values ​​to describe the above technical solution of the present invention: Example 1

[0047] This embodiment provides a method for preparing 3-pentenenitrile, comprising the following steps: S1: Preparation of crude hydrogen cyanide gas by thermal decomposition of formamide: Under the conditions of 5 mbar reduced pressure and 250°C pyrolysis temperature, the raw formamide gas is introduced into the columnar catalyst bed to react in a hydrocyanic acid fixed bed synthesizer to generate crude hydrogen cyanide gas and pyrolysis products; S2: Preparation of acetone cyanohydrin: The crude hydrogen cyanide gas and the pyrolysis product obtained in step S1 are cooled so that the products with boiling points higher than that of the hydrogen cyanide gas are condensed, and the cooling conditions are: temperature: -10°C, reduced pressure of 5 mbar; the formamide obtained after the cooling treatment is recovered and the condensed water is removed; the crude hydrogen cyanide gas is then deaminated and dehydrated with acid and then sent to an adsorption tower for chemical adsorption reaction with acetone in the presence of a catalyst, and the condition for deammoniation with acid is to use sulfuric acid or phosphoric acid for chemical adsorption to remove ammonia, and the deammoniation with acid is carried out under the condition of reduced pressure of 10 mbar to obtain acetone cyanohydrin; the acetone cyanohydrin is continuously distilled to improve the purity of the acetone cyanohydrin, and the acetone and hydrocyanic acid obtained by distillation are collected and dehydrated; S3: Preparation of 3-pentenenitrile: A catalyst was prepared using a phosphite ligand and nickel, and 1,3-butadiene was hydrocyanated with acetone cyanohydrin as a cyanide source to prepare 3-pentenenitrile. The components of the catalyst include Ni[P(C6H5O)3]4, and the molar ratio of Ni[P(C6H5O)3]4 to butadiene is 1:40, and the molar ratio of butadiene to acetone cyanohydrin is 1:1; the reaction process of hydrogen cyanation of 1,3-butadiene using acetone cyanohydrin as a cyanide source includes: mixing the catalyst and butadiene and heating to 70°C, setting the reaction pressure to 10 bar, introducing acetone cyanohydrin after the reaction, and then isothermally reacting at 90°C for 60 minutes, cooling after the reaction and reducing the pressure to normal pressure to complete the reaction. Example 2

[0048] This embodiment provides a method for preparing 3-pentenenitrile, comprising the following steps: S1: Preparation of crude hydrogen cyanide gas by thermal decomposition of formamide: Under the conditions of reduced pressure of 102.5 mbar and pyrolysis temperature of 450°C, the raw formamide gas is introduced into a columnar catalyst bed to react in a hydrocyanic acid fixed bed synthesizer to generate crude hydrogen cyanide gas and pyrolysis products; S2: Preparation of acetone cyanohydrin: The crude hydrogen cyanide gas and the pyrolysis product obtained in step S1 are cooled to condense the products with boiling points higher than that of the hydrogen cyanide gas, wherein the cooling conditions are as follows: temperature: 95° C., reduced pressure: 102.5 mbar; the formamide obtained after the cooling treatment is recovered, and the condensed water is removed; the crude hydrogen cyanide gas is then deaminated and dehydrated with an acid, and then sent to an adsorption tower to undergo a chemical adsorption reaction with acetone in the presence of a catalyst, wherein the condition for deammonification with an acid is to remove ammonia by chemical adsorption with sulfuric acid or phosphoric acid, and the deammonification with an acid is performed under a reduced pressure of 80 mbar to obtain acetone cyanohydrin; the acetone cyanohydrin is continuously distilled to improve the purity of the acetone cyanohydrin, and the acetone and hydrocyanic acid obtained by the distillation treatment are collected and dehydrated; S3: Preparation of 3-pentenenitrile: A catalyst was prepared using a phosphite ligand and nickel, and 1,3-butadiene was hydrocyanated with acetone cyanohydrin as a cyanide source to prepare 3-pentenenitrile. The components of the catalyst include Ni[P(C6H5O)3]4, and the molar ratio of Ni[P(C6H5O)3]4 to butadiene is 1:50, and the molar ratio of butadiene to acetone cyanohydrin is 1.1:1; the reaction process of hydrogen cyanation of 1,3-butadiene using acetone cyanohydrin as a cyanide source includes: mixing the catalyst and butadiene and heating to 80°C, setting the reaction pressure to 15 bar, introducing acetone cyanohydrin after the reaction, and then isothermally reacting at a temperature of 100°C for 60 minutes, cooling after the reaction and reducing the pressure to normal pressure to complete the reaction. Example 3

[0049] This embodiment provides a method for preparing 3-pentenenitrile, comprising the following steps: S1: Preparation of crude hydrogen cyanide gas by thermal decomposition of formamide: Under the conditions of 200 mbar reduced pressure and 650°C pyrolysis temperature, the raw formamide gas is introduced into a columnar catalyst bed to react in a hydrocyanic acid fixed bed synthesizer to generate crude hydrogen cyanide gas and pyrolysis products; S2: Preparation of acetone cyanohydrin: The crude hydrogen cyanide gas and the pyrolysis product obtained in step S1 are cooled to condense the products with boiling points higher than that of hydrogen cyanide gas, wherein the cooling conditions are as follows: temperature: 200° C., reduced pressure: 200 mbar; the formamide obtained after the cooling treatment is recovered, and the condensed water is removed; the crude hydrogen cyanide gas is then deaminated and dehydrated with acid and then sent to an adsorption tower for chemical adsorption reaction with acetone in the presence of a catalyst, wherein the condition for deammonification with acid is to use sulfuric acid or phosphoric acid for chemical adsorption to remove ammonia, and the deammonification with acid is carried out under reduced pressure of 150 mbar to obtain acetone cyanohydrin; the acetone cyanohydrin is continuously distilled to improve the purity of the acetone cyanohydrin, and the acetone and hydrocyanic acid obtained by distillation are collected and dehydrated; S3: Preparation of 3-pentenenitrile: A catalyst was prepared using a phosphite ligand and nickel, and 1,3-butadiene was hydrocyanated with acetone cyanohydrin as a cyanide source to prepare 3-pentenenitrile. The components of the catalyst include Ni[P(C6H5O)3]4, and the molar ratio of Ni[P(C6H5O)3]4 to butadiene is 1:60, and the molar ratio of butadiene to acetone cyanohydrin is 1.2:1; the reaction process of hydrogen cyanation of 1,3-butadiene using acetone cyanohydrin as a cyanide source includes: mixing the catalyst and butadiene and heating to 90°C, setting the reaction pressure to 20 bar, introducing acetone cyanohydrin after the reaction, and then isothermally reacting at a temperature of 110°C for 60 minutes, cooling after the reaction and reducing the pressure to normal pressure to complete the reaction.

[0050] The following provides an embodiment combining specific reaction equipment, reaction conditions and reaction method, and provides an industrial preparation method of 3-pentenenitrile, so as to further explain the above-summarized technical solution and the above-mentioned embodiment of the present invention: Example 4

[0051] Example 4 provides an industrial production method for 3-pentenenitrile, wherein the process of preparing acetone cyanohydrin by thermal decomposition of formamide is as follows: Figure 1 As shown, the following steps are included: The device for preparing acetone cyanohydrin by pyrolysis of formamide consists of an evaporator, a pyrolysis tube, in which magnesium carbonate and calcium carbonate are supported on α-alumina as catalysts (the diameter of the catalyst is 8 to 14 mm), two condensers and a chemical adsorption circulation column, in which an acetone solution circulates, the temperature of the solution reaches +10 °C, and chemical adsorption is carried out in the column. The hydrogen cyanide derived from the pyrolysis and the acetone solution introduced at the top of the column are collected together in a container connected to a vacuum pump downstream. In the chemical adsorption cycle, the solution reaches the top of the adsorption column through a circulation pump and multiple metering points.

[0052] S1: Preparation of crude hydrogen cyanide gas by thermal decomposition of formamide: 3870 g / h (86 mol / h) of formamide were continuously vaporized in an evaporator under reduced pressure of 115 mbar, and the vapor passed over a catalyst heated to 550°C.

[0053] S2: Preparation of acetone cyanohydrin: The pyrolysis gas is cooled to 40°C in the first condenser and to 10°C in the second condenser, and the unconverted formamide and the water formed during the reaction are retained.

[0054] The cracked gas enters the sulfuric acid or phosphoric acid solution for ammonia removal. After ammonia and water removal, the crude hydrocyanic acid mixed gas enters the chemical adsorption circulation column. In this cycle, the acetone solution circulates, and 4250 g / h of acetone solution and 30 g / h of triethylamine enter the chemical adsorption circulation column. The pH value in the chemical adsorption circulation solution is maintained at 6 to 7. The hydrogen cyanide content at the acetone cyanohydrin outlet at the lower part of the chemical adsorption column is less than 0.05%; the unadsorbed gas (such as air, carbon monoxide, carbon dioxide and hydrogen) passes through the chemical adsorption circulation column and reaches the inlet side of the vacuum pump. 6600 g / h of 93-94% acetone cyanohydrin solution is taken out from the chemical adsorption circulation column, and the pH value of the reaction solution is adjusted to 2.8 with sulfuric acid. The reaction solution after acid adjustment is transferred to the distillation kettle for distillation to obtain 6200 g / h acetone cyanohydrin with a content of 99.6%.

[0055] 80 g / h (6 mol / h) of reusable formamide were separated from the two condensers; the conversion of formamide during the pyrolysis was 93%, so the yield of acetone cyanohydrin was 91%.

[0056] The process of preparing 3-pentenenitrile by catalytic hydrocyanation of butadiene is as follows Figure 2 As shown, the following steps are included: S3: Preparation of 3-pentenenitrile: Under nitrogen protection in a fume hood, add 250g of a zero-valent nickel-based Ni[P(C6H5O)3]4 catalyst of trimethylphenyl phosphite and 400g of dehydrated butadiene into a 2000mL autoclave, mix and heat the mixture to 70-90°C, set the reaction pressure to 15bar, and after 60 minutes of reaction, continuously meter and pump in 630g of the newly distilled acetone cyanohydrin obtained in the above step S2, then maintain a constant temperature of 100°C for 60 minutes to complete the reaction, then cool and reduce the pressure to 1bar; After sampling, no cyanide was found in the Volhard cyanide determination, and acetone cyanohydrin was completely converted; through gas chromatography analysis with an internal standard (benzonitrile), the yield of 3-pentenenitrile and 2-methyl-3-butenenitrile was 85% based on acetone cyanohydrin, and the ratio of 3-pentenenitrile:2-methyl-3-butenenitrile was 3:1.

[0057] The above examples further prove that the present invention provides a method for preparing 3-pentenenitrile which is convenient for industrial production, and the method has mild reaction conditions, simple operation process, high safety, excellent target product yield and selectivity, and great industrial application prospects, and solves the technical problems existing in the background technology, and provides a method for preparing cyanide acetone cyanohydrin by thermal decomposition of formamide which is technically simpler, and preparing 3-pentenenitrile by hydrocyanation of 1,3-butadiene using acetone cyanohydrin as a cyanide source.

[0058] In the description of the embodiments of the present application, it should be noted that in the description of the present application, terms such as "inside" and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings. This is only for the convenience of description, and does not indicate or imply that the device or component must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present application.

[0059] In the description of the present application, the description with reference to the terms "one embodiment", "some embodiments", "in the present embodiment", "specific example", or "some examples" etc. means that the specific features, mechanisms, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, mechanisms, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0060] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A method for preparing 3-pentenenitrile, characterized in that: The following steps are involved: S1: Preparation of crude hydrogen cyanide gas by thermal decomposition of formamide: Under the conditions of reduced pressure of 5-200 mbar and pyrolysis temperature of 250-650°C, the raw formamide gas is introduced into a columnar catalyst bed to react in a hydrocyanic acid fixed bed synthesizer to generate crude hydrogen cyanide gas and pyrolysis products; S2: Preparation of acetone cyanohydrin: The crude hydrogen cyanide gas and the pyrolysis product obtained in step S1 are cooled so that the products with boiling points higher than that of the hydrogen cyanide gas are condensed, wherein the cooling conditions are: temperature: -10-200°C, and reduced pressure: 5-200 mbar; then the crude hydrogen cyanide gas is deammonified and dehydrated with an acid, and then sent to an adsorption tower to undergo a chemical adsorption reaction with acetone in the presence of a catalyst to obtain acetone cyanohydrin; S3: Preparation of 3-pentenenitrile: A catalyst was prepared using phosphite ligand and nickel. Under the condition of Lewis acid as a co-catalyst, 1,3-butadiene was hydrocyanated with acetone cyanohydrin as a cyanide source to prepare 3-pentenenitrile.

2. The method for preparing 3-pentenenitrile according to claim 1, characterized in that In the step S1, the pyrolysis temperature is 300-550°C, and the reduced pressure is 10-150 mbar.

3. The method for preparing 3-pentenenitrile according to claim 1, characterized in that In the step S2, the cooling temperature is -10-60°C and the reduced pressure is 10-150 mbar.

4. The method for preparing 3-pentenenitrile according to claim 1, characterized in that: In the step S2, after the cooling treatment and between the acid ammonia removal treatment, the steps of recovering the formamide obtained after the cooling treatment and removing the condensed water are also included.

5. The method for preparing 3-pentenenitrile according to claim 1, characterized in that: In step S2, the conditions for removing ammonia with acid are to use sulfuric acid or phosphoric acid to remove ammonia by chemical adsorption, and the removal of ammonia with acid is carried out under a reduced pressure of 10-150 mbar.

6. The method for preparing 3-pentenenitrile according to claim 5, characterized in that: In the step S2, the reduced pressure of the acid for removing ammonia is 20-60 mbar.

7. The method for preparing 3-pentenenitrile according to claim 1, characterized in that: In the step S2, after the acetone cyanohydrin is obtained, the method further comprises: continuing to perform distillation treatment on the acetone cyanohydrin to improve the purity of the acetone cyanohydrin.

8. The method for preparing 3-pentenenitrile according to claim 7, characterized in that: After the distillation treatment, the process also includes the operation of recovering the acetone and hydrocyanic acid obtained by the distillation treatment and removing water.

9. The method for preparing 3-pentenenitrile according to claim 1, characterized in that: In the step S3, the reaction process of hydrocyanating 1,3-butadiene with acetone cyanohydrin as a cyanide source includes: mixing the catalyst and butadiene and heating to 70-90° C., setting the reaction pressure to 10-20 bar, introducing acetone cyanohydrin after the reaction, and then isothermally reacting at a temperature of 90-110° C. for 60 minutes, cooling after the reaction and reducing the pressure to normal pressure to complete the reaction.

10. The method for preparing 3-pentenenitrile according to claim 9, characterized in that: In the step S3, the components of the catalyst include Ni[P(C6H5O)3]4, and the molar ratio of Ni[P(C6H5O)3]4 to butadiene is 1:(40-60), and the molar ratio of butadiene to acetone cyanohydrin is (1-1.2):1; the reaction process of hydrogen cyanation of 1,3-butadiene using acetone cyanohydrin as a cyanide source includes: mixing the catalyst and butadiene and heating to 80°C, setting the reaction pressure to 15 bar, introducing acetone cyanohydrin after the reaction, and then isothermally reacting at a temperature of 100°C for 60 minutes, cooling after the reaction and reducing the pressure to normal pressure to complete the reaction.

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