A process and system for preparing succinonitrile

Abstract

The present invention provides a process and system for preparing succinonitrile, and the preparation process is as follows: dissolving a catalyst and a co-catalyst in a raw material, continuously heating a reactor and continuously introducing ammonia, and heating the reactor until the reaction temperature remains unchanged; when the reaction temperature reaches a certain value, maintaining or increasing the reaction temperature, slowly reducing the reaction pressure, and continuously discharging the water and unreacted ammonia generated in the reactor and discharging them into a water scrubber, and the waste gas after water absorption enters a water ring vacuum pump; stopping the ammonia feeding, turning on the water ring vacuum pump, maintaining the reaction pressure as a negative pressure, and during the negative pressure extraction process, the reaction temperature continues to decrease, and the reaction is continued for a period of time to obtain a succinonitrile reaction liquid. The present invention uses one of succinic acid, succinic esters, and succinic anhydride as a raw material, and provides a process and system for preparing succinonitrile from succinic acid, and the process has a wide source of raw materials, high purity, a simple production process, high safety, large-scale supply, and low cost.

Description

Technical Field

[0001] The invention relates to a process for preparing succinonitrile, and in particular to a process and a system for preparing succinonitrile. Background Art

[0002] Succinonitrile is also known as 1,2-dicyanoethane, succinonitrile, molecular formula C 4 H 4 N 2 It is a colorless, odorless waxy substance, soluble in water, ethanol, and chloroform, with a relative density of 1.02. Succinonitrile is an important fine chemical intermediate with a wide range of uses. It is widely used in automobiles and quinacridone pigments for galvanized iron coatings, as well as electrolyte additives to improve the performance of lithium batteries. It can also be used in the production of nylon, etc.

[0003] In industry, there are two main methods for synthesizing succinonitrile:

[0004] (1) Using acrylonitrile as raw material, it reacts with hydrocyanic acid under alkaline conditions and is then separated by distillation to obtain the product. The yield is over 95% and the content can reach over 99.5%. However, the raw materials are extremely toxic and the production process has high requirements for equipment and operation. In addition, the cost is relatively high due to the high price of raw materials.

[0005] (2) Add 1,2-dibromoethane ethanol solution to the hot sodium cyanide solution and reflux and keep warm to generate succinonitrile. This process uses organic solvents, which is costly and has a low yield. In addition, the cyanide-containing wastewater generated during the production process needs to be treated before it can be discharged, which adds additional costs and has certain limitations.

[0006] Patent CN106220512B discloses a method for preparing butanediamine, which uses biological ammonium succinate as raw material, prepares succinonitrile through dehydration reaction, and then hydrogenates succinonitrile to obtain butanediamine. The raw material comes from biological ammonium succinate, which cannot be mass-produced, and the raw material purity is low, which is difficult to meet the requirements of mass production.

[0007] Therefore, in view of the above difficulties in the existing succinonitrile preparation process, a method for preparing succinonitrile is designed, which has a wide source of raw materials, high purity, simple production process, safety and reliability, and can supply succinonitrile on a large scale in the market, which is an important research direction. Summary of the invention

[0008] To achieve the above purpose, the present invention adopts one of succinic acid, succinate ester and succinic anhydride as a raw material, and provides a process and system for preparing succinonitrile.

[0009] In a first aspect, the present invention provides a process for preparing succinonitrile, comprising the following steps:

[0010] Step S1: dissolving the catalyst and the co-catalyst in the raw materials, continuously heating the reactor and continuously introducing ammonia gas, and heating until the reaction temperature remains unchanged;

[0011] Step S2: when the reaction temperature reaches a certain value, the reaction temperature is maintained or increased, the reaction pressure is slowly reduced, the water generated in the reactor and the unreacted ammonia are continuously discharged into a water washing tower, and the waste gas after water absorption enters a water ring vacuum pump;

[0012] Step S3: stop feeding ammonia, turn on the water ring vacuum pump, maintain the reaction pressure at negative pressure, and during the negative pressure pumping process, the reaction temperature continues to decrease, the reaction continues for a period of time, and then stops heating to obtain a succinonitrile reaction solution;

[0013] The raw material is one of succinic acid, succinic ester and succinic anhydride.

[0014] Preferably, in step S1, when the raw material is succinic acid, the succinic acid is added into a reactor, the reactor is heated to melt the succinic acid, a catalyst and a co-catalyst are added, and the catalyst and the co-catalyst are dissolved by stirring.

[0015] Preferably, the succinate ester is dimethyl succinate, diethyl succinate, or dibutyl succinate.

[0016] Furthermore, the succinate ester is dimethyl succinate.

[0017] Preferably, the catalyst is an acid catalyst.

[0018] Furthermore, the catalyst is a phosphoric acid catalyst and / or a solid acid catalyst.

[0019] Furthermore, the phosphoric acid catalyst is one or more of phosphoric acid, polyphosphoric acid, metaphosphoric acid, and phosphate ester.

[0020] Preferably, the mass of the catalyst is 0.05-0.2% of the mass of the raw material.

[0021] Preferably, the co-catalyst includes one or more of phosphorus pentoxide, phosphorus pentachloride, phosphorus trichloride, thionyl chloride, p-toluenesulfonyl chloride, dicyclohexylcarbodiimide, o-phenylene phosphorus trichloride, and pyridine.

[0022] Furthermore, the mass of the co-catalyst is 0.05-0.2% of the mass of the raw material.

[0023] Preferably, the operating temperature of the reactor is 160-330° C., and the temperature during the reaction is programmed.

[0024] Preferably, the operating pressure of the reactor is 0.1 MPaG~3.0 MPaG.

[0025] Furthermore, in step S2, the reaction pressure is initially 2.0-3.0 MPaG, and a programmed pressure reduction is used.

[0026] Preferably, the reaction kettle also includes a solvent.

[0027] Furthermore, the solvent is a high boiling point organic solvent.

[0028] Furthermore, the solvent is one or both of succinonitrile and triethylamine.

[0029] Further, in step S2, two-stage voltage reduction is adopted;

[0030] In the first stage of pressure reduction, the ammonia flow rate is reduced to a first ammonia flow rate, the ratio of the first ammonia flow rate to the original ammonia flow rate is 1:2-3, and the reaction pressure is reduced to a first reaction pressure, the ratio of the first reaction pressure to the original reaction pressure is 1:5-6;

[0031] In the second stage of pressure reduction, the ammonia flow rate is reduced to a second ammonia flow rate, the ratio of the second ammonia flow rate to the original ammonia flow rate is 1:10-15, and the reaction pressure is reduced to a first reaction pressure, the ratio of the first reaction pressure to the original reaction pressure is 1:25-30.

[0032] In a second aspect, the present invention provides a system for preparing succinonitrile, comprising an ammonia source, a reactor, an electric heating jacket, a water scrubber and a water ring vacuum pump; the ammonia source is connected to the bottom of the reactor through a pipeline, the air outlet of the reactor is connected to the bottom of the water scrubber through a pipeline, and the exhaust pipe of the water scrubber extends into two branches that are respectively connected to the air inlet pipe and the air outlet pipe of the water ring vacuum pump.

[0033] Preferably, a rotor flowmeter is further included, which is arranged on the pipeline between the ammonia source and the bottom of the reactor.

[0034] Preferably, a stirrer is provided in the reactor.

[0035] Preferably, the reaction kettle is placed in the electric heating jacket.

[0036] Preferably, the waste gas pipe of the water washing tower extends into two branch pipes, each of which is provided with a valve.

[0037] Preferably, a valve is provided on the air outlet pipe of the water ring vacuum pump.

[0038] The present invention adopts the above technical solution, and has the following technical effects compared with the prior art:

[0039] (1) The present invention uses one of succinic acid, succinic esters and succinic anhydride as a raw material, and provides a process and system for preparing succinonitrile from succinic acid. The raw materials of the process are widely available, high in purity, simple in production process, high in safety, can be supplied on a large scale and at a low cost.

[0040] (2) The reaction liquid prepared by the process provided by the present invention has a succinonitrile content of more than 91.5%. The final reaction liquid includes raw materials, succinonitrile, and high-boiling substances, and does not contain other hazardous substances, which greatly reduces the cost of wastewater treatment.

[0041] (3) In particular, when succinic acid esters or succinic anhydride are used as the reaction raw materials, since succinic acid esters and succinic anhydride are relatively weak in acidity, the corrosion to the reaction unit can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A system for preparing succinonitrile in the present invention;

[0043] The symbols in the figure indicate:

[0044] 1-Ammonia cylinder, 2-Reaction kettle, 3-Electric heating jacket, 4-Water washing tower, 5-Water ring vacuum pump, 6-Rotameter. DETAILED DESCRIPTION

[0045] In a first aspect, the present invention provides a process for preparing succinonitrile, comprising the following steps:

[0046] Step S1: adding raw materials into a reactor equipped with a stirrer, turning on the stirrer, dissolving the catalyst and the co-catalyst in the raw materials, continuously heating the reactor and continuously introducing ammonia gas, and heating until the reaction temperature remains unchanged;

[0047] Step S2: when the reaction temperature reaches a certain value, the reaction temperature is maintained or increased, the reaction pressure is slowly reduced, the water generated in the reactor and the unreacted ammonia are continuously discharged into a water washing tower, and the waste gas after water absorption enters a water ring vacuum pump;

[0048] Step S3: stop feeding ammonia, turn on the water ring vacuum pump, maintain the reaction pressure at negative pressure, and during the negative pressure pumping process, the reaction temperature continues to decrease, the reaction continues for a period of time, and then stops heating to obtain a succinonitrile reaction solution;

[0049] The raw material is one of succinic acid, succinic ester and succinic anhydride.

[0050] Specifically, in step S1, when the raw material is succinic acid, the succinic acid is added to a reactor, the reactor is heated to melt the succinic acid, a catalyst and a co-catalyst are added, and the catalyst and the co-catalyst are dissolved by stirring; when the raw material is a succinate ester or succinic anhydride, the raw material is added to a reactor, a catalyst and a co-catalyst are added, and the catalyst and the co-catalyst are dissolved by stirring; when the raw material is a succinate ester or succinic anhydride, when the catalyst and / or the co-catalyst are solid, the raw material is added to a reactor, the catalyst and the co-catalyst are added, the reactor is heated to melt the catalyst and the co-catalyst, and the catalyst and the co-catalyst are dissolved by stirring.

[0051] In a preferred embodiment, the succinate ester is dimethyl succinate, diethyl succinate, or dibutyl succinate. Further, the succinate ester is dimethyl succinate.

[0052] In a specific embodiment, the catalyst is an acid catalyst. Further, the catalyst is a phosphoric acid catalyst and / or a solid acid catalyst. Further, the phosphoric acid catalyst is one or more of phosphoric acid, polyphosphoric acid, metaphosphoric acid, and phosphate ester. Preferably, the mass of the catalyst is 0.05-0.2% of the mass of the raw material.

[0053] In a specific embodiment, the co-catalyst includes one or more of phosphorus pentoxide, phosphorus pentachloride, phosphorus trichloride, thionyl chloride, p-toluenesulfonyl chloride, dicyclohexylcarbodiimide, o-phenylene phosphorus trichloride, and pyridine. Further, the mass of the co-catalyst is 0.05-0.2% of the mass of the raw material.

[0054] In a specific embodiment, in step S1, the flow rate of ammonia is 40-60 ml / min. Specifically, ammonia is continuously introduced into the reactor and is greatly excessive. Due to the large nitrogen consumption during the pilot test, it is estimated that the excess of ammonia is 2-10 times that of industrial production. In step S1, when the reaction temperature remains unchanged, the reaction temperature is 180-250°C.

[0055] Preferably, the operating temperature of the reactor is 160-330° C., and the temperature during the reaction is programmed.

[0056] Preferably, the operating pressure of the reactor is 0.1 MPaG~3.0 MPaG.

[0057] Furthermore, in step S2, the reaction pressure is initially 2.0-3.0 MPaG, and the pressure is reduced to normal pressure by programmed pressure reduction, i.e., isogradient pressure reduction.

[0058] Furthermore, in step S2, two-stage voltage reduction is adopted;

[0059] In the first stage of pressure reduction, the ammonia flow rate is reduced to a first ammonia flow rate, the ratio of the first ammonia flow rate to the original ammonia flow rate is 1:2-3, and the reaction pressure is reduced to a first reaction pressure, the ratio of the first reaction pressure to the original reaction pressure is 1:5-6;

[0060] In the second stage of pressure reduction, the ammonia flow rate is reduced to a second ammonia flow rate, the ratio of the second ammonia flow rate to the original ammonia flow rate is 1:10-15, and the reaction pressure is reduced to a first reaction pressure, the ratio of the first reaction pressure to the original reaction pressure is 1:25-30.

[0061] By reducing the pressure in the above manner, the water generated by the reaction is evaporated, thereby driving the reaction in the positive direction.

[0062] In another embodiment, the reactor further comprises a solvent. Further, the solvent is a high boiling point organic solvent. Further, the solvent is one or both of succinonitrile and triethylamine.

[0063] In a second aspect, the present invention provides a system for preparing succinonitrile, such as Figure 1 It includes an ammonia cylinder 1, a reactor 2, an electric heating jacket 3, a water scrubber 4 and a water ring vacuum pump 5; the rotor flowmeter 6 is connected to the bottom of the reactor 2 through a pipeline, the air outlet of the reactor 2 is connected to the bottom of the water scrubber 4 through a pipeline, and the exhaust pipe of the water scrubber 4 extends into two branches that are respectively connected to the air inlet pipe and the air outlet pipe of the water ring vacuum pump 5.

[0064] Specifically, the entire reaction time is estimated to be 1-8 h.

[0065] The present invention is described in detail and specifically by specific examples below to provide a better understanding of the present invention, but the following examples do not limit the scope of the present invention. Example

[0066] This embodiment provides a process for preparing succinonitrile using succinic acid as a raw material, which specifically comprises the following steps:

[0067] Step S1: adding solid drug succinic acid (100 g) into a reactor with a volume of 250 ml and equipped with a stirrer, turning on the electric heating jacket, slowly heating to 190° C. to melt the succinic acid, turning on the stirrer, adjusting the speed to 300 rpm, adding 0.1 g of phosphoric acid as a catalyst and 0.1 g of phosphorus pentoxide as a co-catalyst, dissolving the catalyst by stirring, then introducing ammonia gas, controlling the ammonia gas flow rate to 50 ml / min, maintaining the reaction pressure at 2.0 MPaG, the reaction is exothermic, and the reaction temperature begins to rise. After 20 minutes, the reaction temperature rises to 225° C., and the temperature remains unchanged, and the power of the electric heating jacket is increased;

[0068] Step S2: the reaction temperature is raised to 235° C. within 15 min, ammonia is continuously introduced, and its flow rate is adjusted to 25 ml / min. Within 30 min, the pressure of the reactor is slowly reduced to 0.5 MPaG. The unreacted ammonia and water generated during the reaction are continuously discharged to the water scrubber to absorb the ammonia in the tail gas and discharge the waste gas; the reaction temperature is maintained at 235° C., the ammonia flow rate is adjusted to 5 ml / min, and the reaction is continued for 1 h. The reactor outlet valve is adjusted to start to further reduce the reaction pressure. Within 20 min, it is reduced to normal pressure, and the reaction is basically completed;

[0069] Step S3: Maintain the heating temperature at 235°C, stop feeding ammonia, turn on the vacuum pump, control the pressure of the reactor to negative pressure, and suck out the remaining ammonia in the reactor. When the temperature of the reactor drops to 80°C, stop heating, open the reactor, obtain the succinonitrile reaction liquid, and send it for sample analysis.

[0070] Analysis results: The succinic acid content in the succinonitrile reaction liquid is 2.3%, the succinonitrile content is 93.5%, and the rest are high boiling substances.

[0071] The yield of succinonitrile was 92%. Example

[0072] This embodiment provides a process for preparing succinonitrile using succinate as raw material, which specifically comprises the following steps:

[0073] Step S1: Add dimethyl succinate (132 g) liquid into a reactor with a volume of 250 ml and a stirrer. Turn on the stirrer and adjust the speed to 300 rpm. Add 0.2 g of tripolyphosphoric acid as a catalyst and 1 g of thionyl chloride as a co-catalyst, and dissolve the catalyst by stirring. Turn on the electric heating jacket and slowly heat the temperature to 160° C. Then, introduce ammonia gas and control the ammonia gas flow rate to 50 ml / min. Maintain the reaction pressure to 3.0 MPaG. The reaction is exothermic and the reaction temperature begins to rise. After 30 minutes, the reaction temperature rises to 196° C. and the temperature remains unchanged. Increase the power of the electric heating jacket.

[0074] Step S2: the reaction temperature is raised to 215°C within 15 minutes, ammonia is continuously introduced, and its flow rate is adjusted to 25 ml / min. In 30 minutes, the reactor pressure is slowly and isogradiently reduced to 0.5 MPaG. The unreacted ammonia and the water and methanol generated in the reaction process are continuously discharged to the water scrubber to absorb the ammonia and methanol in the tail gas, and the waste gas is discharged. The reaction is continued to be raised, and the reaction temperature is programmed to 235°C within 20 minutes. The reaction temperature is maintained at 235°C, and the ammonia flow rate is adjusted to 5 ml / min for 1 hour. The reactor outlet valve is adjusted to further reduce the reaction pressure. The pressure is reduced to normal pressure within 20 minutes, and the reaction is basically completed;

[0075] Step S3: Maintain the heating temperature at 235°C, stop feeding ammonia, turn on the vacuum pump, control the pressure of the reactor to negative pressure, and suck out the remaining ammonia in the reactor. When the temperature of the reactor drops to 80°C, stop heating, open the reactor, obtain the succinonitrile reaction liquid, and send it for sample analysis.

[0076] Analysis results: the content of succinic acid in the reactor was 1.1%, the content of ammonium succinate was 2%, the content of succinonitrile was 91.5%, and the rest were high boiling substances.

[0077] The yield of succinonitrile was 90.3%. Example

[0078] This embodiment provides a process for preparing succinonitrile using succinic anhydride as a raw material, which specifically comprises the following steps:

[0079] Step S1: Add succinic anhydride (125 g) liquid into a reactor with a volume of 250 ml and equipped with a stirrer. After adding 2 g of catalyst solid acid and 2 g of co-catalyst p-toluenesulfonyl chloride, turn on the electric heating jacket and slowly heat it to 130° C. After the catalyst and co-catalyst are melted, turn on the stirrer and adjust the speed to 300 rpm. Continue to heat it to 190° C. and start to introduce ammonia. Control the ammonia flow rate to 50 ml / min. Maintain the reaction pressure to 2.5 MPaG. The reaction is exothermic and the reaction temperature begins to rise. After 30 minutes, the reaction temperature rises to 224° C. and the temperature remains unchanged. Increase the power of the electric heating jacket.

[0080] Step S2: Raise the reaction temperature to 275°C within 30 minutes, continue to introduce ammonia gas continuously, adjust its flow rate to 25 ml / min, raise the reactor temperature to 290°C within 30 minutes, slowly and isogradiently reduce the reactor pressure to 0.5 MPaG, and continuously discharge the unreacted ammonia gas and the water generated during the reaction process to the water scrubber to absorb the ammonia in the tail gas and discharge the waste gas. Continue to increase the reaction, raise the reaction temperature to 300°C within 20 minutes, maintain the reaction temperature at 300°C, adjust the ammonia flow rate to 5 ml / min, continue for 1 hour, adjust the reactor outlet valve, and start to further reduce the reaction pressure. Reduce it to normal pressure within 20 minutes, and the reaction is basically completed;

[0081] Step S3: Maintain the heating temperature at 300°C, stop feeding ammonia, turn on the vacuum pump, control the pressure of the reactor to negative pressure, and suck out the remaining ammonia in the reactor. When the temperature of the reactor drops to 80°C, stop heating, open the reactor, obtain the succinonitrile reaction liquid, and send it for sample analysis.

[0082] Analysis results: the content of succinic anhydride in the reactor was 0.6%, the content of succinic acid was 0.4%, the content of ammonium succinate was 1.3%, the content of succinonitrile was 94%, and the rest were high boiling substances.

[0083] The yield of succinonitrile was 92.4%.

[0084] The specific embodiments of the present invention are described in detail above, but they are only examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions made to the present invention are also within the scope of the present invention. Therefore, the equalization changes and modifications made without departing from the spirit and scope of the present invention should be included in the scope of the present invention.

Claims

1. A process for preparing succinonitrile, characterized in that: The following steps are involved: Step S1: dissolving the catalyst and the co-catalyst in the raw material, continuously heating the reaction kettle and continuously introducing ammonia gas, and heating the reaction kettle until the reaction temperature tends to be stable; Step S2: When the reaction temperature reaches a certain value, the reaction temperature is maintained or increased, the reaction pressure is slowly reduced, and the water and unreacted ammonia generated in the reactor are continuously discharged into a water washing tower, and the waste gas after water absorption enters a water ring vacuum pump; Step S3: stop feeding ammonia, turn on the water ring vacuum pump, maintain the reaction pressure at negative pressure, and during the negative pressure pumping process, the reaction temperature continues to decrease, the reaction continues for a period of time, and then stops heating to obtain a succinonitrile reaction solution; The raw material is one of succinic acid, succinic esters and succinic anhydride; When the raw material is succinic acid, in step S1, the succinic acid is added to a reactor, the reactor is heated to melt the succinic acid, a catalyst and a co-catalyst are added, and the catalyst and the co-catalyst are dissolved by stirring; In step S2, the reaction pressure is 2.0-3.0 MPaG at the beginning, and the pressure is reduced by program; In step S2, two-stage voltage reduction is adopted; In the first stage of pressure reduction, the ammonia flow rate is reduced to a first ammonia flow rate, the ratio of the first ammonia flow rate to the original ammonia flow rate is 1:2-3, and the reaction pressure is reduced to a first reaction pressure, the ratio of the first reaction pressure to the original reaction pressure is 1:5-6; In the second stage of pressure reduction, the ammonia flow rate is reduced to a second ammonia flow rate, the ratio of the second ammonia flow rate to the original ammonia flow rate is 1:10-15, and the reaction pressure is reduced to a second reaction pressure, the ratio of the second reaction pressure to the original reaction pressure is 1:25-30; Wherein, the catalyst is phosphoric acid or polyphosphoric acid; The co-catalyst is one or more of phosphorus pentoxide, phosphorus pentachloride, phosphorus trichloride, thionyl chloride, and p-toluenesulfonyl chloride; The operating temperature of the reactor is 160-330°C, and the temperature of the reaction process is programmed.

2. The process for preparing succinonitrile according to claim 1, wherein: The succinate esters are dimethyl succinate, diethyl succinate and dibutyl succinate.

3. The process for preparing succinonitrile according to claim 1, characterized in that: The mass of the catalyst is 0.05-0.2% of the mass of the raw material.

4. The process for preparing succinonitrile according to claim 1, characterized in that: The mass of the co-catalyst is 0.05-0.2% of the mass of the raw material.

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