Process and system for the production of adiponitrile

Abstract

This invention relates to the field of organic synthesis technology and discloses a method and system for preparing adiponitrile. The method includes: S1: atomizing molten adipic acid and mixing it with ammonia gas, followed by an ammoniation reaction to generate an ammoniation product; S2: dividing the ammoniation product into two parts, a and b. Part a undergoes a countercurrent, non-contact heat exchange with hot material to generate crude adiponitrile through heating and dehydration, while part b is recycled back to step S1 to participate in the reaction. The ratio of the ammoniation product in part a to that in part b is (1~5):1. The temperature of the hot material is higher than the temperature of the ammoniation product in part a. This invention improves the efficiency of the ammoniation reaction, reduces the decomposition side reactions of adipic acid and the residue of adipic acid, and significantly improves the conversion rate of the dehydration reaction and the selectivity of adiponitrile.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, and specifically to a method and system for preparing adiponitrile. Background Technology

[0002] Adiponitrile is an important raw material for the production of hexamethylenediamine, caprolactam, nylon 66 salt, and 1,6-hexamethylenediisocyanate (HDI). It can also be used to produce rubber additives, pesticides, fungicides, rocket fuel, and polymer materials. Depending on the raw material, there are three main methods for synthesizing adiponitrile: the butadiene method, the acrylonitrile method, and the adipic acid method. The adipic acid method uses adipic acid as a raw material, which is produced by ammoniation and dehydration. This method is relatively mature, but it has high energy consumption, is prone to coking and corrosion of equipment, and its profitability is greatly affected by the raw material. In recent years, due to the abundant supply of adipic acid in the market and the significant reduction in cost, this production process has also gained an economic advantage.

[0003] The nitrification reactor is one of the key pieces of equipment in the adipic acid ammoniation and dehydration to adiponitrile production unit. The unit primarily uses a bubble-tube reactor with co-current gas-liquid flow from bottom to top. The tube section has high temperatures and numerous side reactions. Unreacted adipic acid from the bubble section is carried into the tube section, resulting in excessively high adipic acid content, which easily corrodes the reaction tubes. Simultaneously, the decomposition of adipic acid at high temperatures causes coking in the reactor. In existing nitrification reactors, the gaseous material is typically fed directly from the central tube and bubbled. A large amount of gas flows out from the middle pipe, causing a concentrated gas flow and insufficient contact between the gas and liquid phases, resulting in low bubbling efficiency and low reaction yield. This low yield further leads to the generation of large amounts of byproducts during the reaction, resulting in severe coking within the reactor, reduced mass transfer efficiency within the reactor tubes, decreased heat transfer rate, and ultimately, a significant impact on the reactor's operating cycle.

[0004] CN208944068U describes a gas-phase reactor for the production of adiponitrile from adipic acid. The reactor is similar to a scraped plate reactor, which has a good reaction effect. However, due to the equipment structure, the heat transfer area of ​​each scraped plate reactor is limited, the production capacity of a single reactor is small, and it is difficult to promote large-scale equipment.

[0005] CN208944059U describes an adiponitrile addition pre-reactor, whose nitrification reactor is a bubble bed reactor with an internal guide tube. Ammonia gas is bubbled to form an internal circulation, which accelerates mass transfer. However, the reactor is still a fully mixed flow reactor with a long residence time and a large number of impurities generated.

[0006] In summary, there is an urgent need for a new reaction system for the production of adiponitrile from adipic acid that has a simple process flow and is easy to implement for industrial application. Summary of the Invention

[0007] The purpose of this invention is to address the problems existing in current technologies, such as low reaction conversion rate, insufficient gas-liquid mass transfer, long reactant residence time, incomplete reaction of adipic acid and easy decomposition, resulting in severe corrosion and coking of the reactor, affecting heat transfer efficiency, and short operating cycle. This invention provides a method and system for preparing adiponitrile. This method has strong process continuity, good process economy, and is suitable for large-scale continuous industrial production.

[0008] To achieve the above objectives, the present invention provides a method for preparing adiponitrile, the method comprising: S1: Molten adipic acid is atomized and then mixed with ammonia gas. The ammonia reaction produces ammonia products. S2: The amination product is divided into two parts, a and b. Part a is heated and dehydrated by countercurrent non-contact heat exchange with the hot material to generate crude adiponitrile. Part b is recycled back to step S1 to participate in the reaction. The ratio of the ammonification product in part a to the ammonification product in part b is (1~5):1; the temperature of the hot material is higher than the temperature of the ammonification product in part a.

[0009] A second aspect of the present invention provides a system for preparing adiponitrile, the system comprising: An ammoniation reactor is provided with a molten adipic acid inlet, an ammonia inlet, and an ammoniation product outlet. It is used for the ammoniation reaction of adipic acid and ammonia to generate the ammoniation product. An atomizer is installed at the molten adipic acid inlet to atomize the molten adipic acid. The ammoniation product is divided into two parts, a and b. The ammoniation product outlet is connected to the molten adipic acid inlet and / or the ammonia inlet to return part b of the ammoniation product back into the ammoniation reactor. The falling film evaporator is a tubular structure with an ammoniation product inlet, a hot material inlet, and a hot material outlet. The ammoniation product inlet is connected to the ammoniation product outlet of the ammoniation reactor to allow part a of the ammoniation product to optionally be in film form and to exchange heat with the hot material in a countercurrent, non-contact manner for heating and dehydration to generate crude adiponitrile.

[0010] Compared with the prior art, the present invention has at least the following beneficial effects: (1) The present invention enhances the mass transfer effect, improves the efficiency of the ammoniation reaction, and reduces the decomposition side reaction and residue of adipic acid by atomizing and dispersing molten adipic acid into small droplets and then reacting it with ammonia.

[0011] (2) In this invention, by recycling a portion of the ammoniation product as a diluent back to step S1 for reaction, the viscosity of the material is reduced, and the efficiency of atomization and mass and heat transfer is enhanced. This improves the efficiency of the ammoniation reaction and reduces the decomposition side reactions of adipic acid and the residue of adipic acid.

[0012] (3) The system of the present invention uses a falling film evaporator as the dehydration reaction equipment. Part of the ammonia products form a film on the surface of the tubes and flow down uniformly along the tubes. The heat transfer efficiency is high, and the dehydration reaction conversion rate and the selectivity of adiponitrile are significantly improved.

[0013] (4) The system for preparing adiponitrile provided by the present invention has simple equipment and is easy to industrialize. Attached Figure Description

[0014] Figure 1 This is a system flow diagram of preparing adiponitrile by mixing the catalyst with adipic acid and then melting the mixture in a preferred embodiment of the present invention.

[0015] Figure 2 This is a system flow diagram of preparing adiponitrile by adding a catalyst at the top of a falling film evaporator in a preferred embodiment of the present invention.

[0016] Figure 3 This is a system flow diagram of the preparation of adiponitrile by circulating deheated ammonia gas back to the ammoniation reactor in a preferred embodiment of the present invention.

[0017] Figure 4 This is a system flow diagram for preparing adiponitrile in a preferred embodiment of the present invention, showing the process of circulating cooled ammonia gas back to the ammoniation reactor and passing through a gas distributor. Detailed Implementation

[0018] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0019] In this invention, unless otherwise stated, directional terms such as "upper," "lower," "left," and "right" generally refer to the upper, lower, left, and right positions shown in the accompanying drawings; "inner" and "outer" refer to the inner and outer positions relative to the outline of each component itself; and "upper," "lower," "top," and "bottom" are generally descriptive terms describing the relative positions of the components in relation to the directions shown in the accompanying drawings or in relation to the vertical, perpendicular, or gravitational directions.

[0020] In this invention, unless otherwise specified, "bottom" refers to the position of the container from top to bottom 90-100%; "top" refers to the position of the container from top to bottom 0-10%; "upper part" refers to the position of the container from top to bottom 0-30%; "middle part" refers to the position of the container from top to bottom 30-70%; and "lower part" refers to the position of the container from top to bottom 70-100%.

[0021] In this invention, "device" refers to a unit composed of various components that have the same function and / or perform related functions.

[0022] This invention provides a method for preparing adiponitrile, the method comprising: S1: Molten adipic acid is atomized and then mixed with ammonia gas. The ammonia reaction produces ammonia products. S2: The amination product is divided into two parts, a and b. Part a is heated and dehydrated by countercurrent non-contact heat exchange with the hot material to generate crude adiponitrile. Part b is recycled back to step S1 to participate in the reaction. The ratio of the ammonification product in part a to the ammonification product in part b is (1~5):1; the temperature of the hot material is higher than the temperature of the ammonification product in part a.

[0023] In this invention, step S1 involves atomizing molten adipic acid into small droplets, which then undergoes an ammoniation reaction with ammonia gas. This enhances mass transfer, improves the ammoniation reaction efficiency, and reduces the decomposition side reactions and residues of adipic acid. Step S2 further reduces the material viscosity and enhances atomization, mass transfer, and heat transfer efficiency by recycling a portion of the ammoniation product back to step S1 as a diluent. This improves the ammoniation reaction efficiency and reduces the decomposition side reactions and residues of adipic acid.

[0024] In this invention, the amination product is an intermediate product of adipic acid amination, such as ammonium adipic acid salt, which is known to those skilled in the art and will not be described in detail here.

[0025] The following illustrative description is not intended to limit the scope of the invention. In one embodiment of the invention, step S2 is carried out in the presence of a catalyst selected from one or more of liquid phosphoric acid, phosphates, phosphate esters, and supported solid acid catalysts. Using the above embodiments can improve the conversion rate of the dehydration reaction and the selectivity of adiponitrile.

[0026] In this invention, there are no special limitations on the method of adding the catalyst. The following illustrative description does not limit the scope of this invention. The catalyst can be introduced into the raw material in step S1 or in step S2. The specific selection depends on the type of catalyst. There are no special requirements for the catalyst. Commonly used liquid phosphoric acid, phosphates, phosphate esters, supported solid acids, etc., can all be selected.

[0027] According to one embodiment of the present invention, the catalyst is added by mixing the catalyst with adipic acid and then melting it to obtain molten adipic acid. There are no special requirements for the catalyst added, and commonly used liquid phosphoric acid, phosphates, phosphate esters, supported solid acids, etc., can be selected.

[0028] According to one embodiment of the present invention, the catalyst is added by introducing the catalyst into the heating and dehydration reaction described in step S2; the catalyst is selected from one or more of liquid phosphoric acid, phosphates, and phosphate esters.

[0029] In this invention, a wide range of phosphate catalysts can be selected, such as aluminum phosphate, zirconium phosphate, and tungsten phosphate.

[0030] In this invention, the range of phosphate ester catalysts is relatively wide, such as ammonium phosphate, dibutyl phosphate, tributyl phosphate, triethyl phosphate, etc.

[0031] In this invention, the range of supported solid acid catalysts is relatively wide, such as catalysts supported on phosphoric acid and its derivatives, catalysts supported on boric acid and its derivatives, etc.

[0032] The above is an illustrative description and does not limit the scope of the invention.

[0033] In this invention, there are no special requirements for the size of the atomized droplets. For example, molten adipic acid can be atomized into droplets of 10-50 μm.

[0034] According to a preferred embodiment of the present invention, the ratio of the a-part ammoniated product to the b-part ammoniated product is (2~4):1.

[0035] In this invention, the amount of catalyst can be selected from a wide range. The following illustrative description is not intended to limit the scope of this invention. According to one embodiment of the invention, the amount of catalyst added is 0.1-3% of the weight of adipic acid.

[0036] In this invention, there is no particular limitation on the temperature difference between the hot material and the a portion of the ammoniation product. The following illustrative description is not intended to limit the scope of the invention. According to one embodiment of the invention, the temperature difference between the hot material and the a portion of the ammoniation product is 50~80°C. Using the above embodiment can increase the heat transfer efficiency, and significantly improve the dehydration reaction conversion rate and the selectivity of adiponitrile.

[0037] In this invention, there is no particular limitation on the form of countercurrent non-contact heat exchange between the a portion of the ammoniation product and the hot material. The following illustrative description does not limit the scope of the invention. According to one embodiment of the invention, the a portion of the ammoniation product exchanges heat with the hot material in a film-like manner in a countercurrent non-contact manner. For example, a falling film evaporator can be used to achieve the purpose of this invention.

[0038] In this invention, there is no particular limitation on the type of hot material. The following illustrative description is not intended to limit the scope of the invention. According to one embodiment of the invention, the hot material is selected from hot nitrogen and / or hot ammonia.

[0039] In one embodiment of the present invention, ammonia gas is exchanged with the ammoniation product to obtain hot ammonia gas, which is then used as a hot material in step S2. The above embodiment improves the process economy of the present invention.

[0040] In one embodiment of the present invention, the hot material is hot ammonia gas. The cooled ammonia gas, after countercurrent non-contact heat exchange with the ammonia products (part a), is fed as the ammonia raw material into step S1 to further react with the incompletely reacted adipic acid in an ammoniation reaction. Using the above embodiment can improve the efficiency of the ammoniation reaction.

[0041] In this invention, there are no particular limitations on how cooling ammonia reacts with molten adipic acid. The following illustrative description is not intended to limit the scope of the invention. According to one embodiment of the invention, cooling ammonia, after passing through a gas distributor, comes into contact with molten adipic acid to undergo an ammoniation reaction.

[0042] In this invention, there are no specific limitations on the conditions for the ammoniation reaction. The following illustrative description is not intended to limit the scope of this invention.

[0043] According to one embodiment of the present invention, the conditions for the ammoniation reaction include a temperature of 140°C to 230°C.

[0044] According to one embodiment of the present invention, the conditions for the ammoniation reaction include a pressure of 0.1 MPaG to 5 MPaG.

[0045] According to one embodiment of the present invention, the conditions for the amination reaction include: a molar ratio of ammonia to adipic acid of (5~12):1.

[0046] A second aspect of the present invention provides a system for preparing adiponitrile, the system comprising: An ammoniation reactor is provided with a molten adipic acid inlet, an ammonia inlet, and an ammoniation product outlet. It is used for the ammoniation reaction of adipic acid and ammonia to generate the ammoniation product. An atomizer is installed at the molten adipic acid inlet to atomize the molten adipic acid. The ammoniation product is divided into two parts, a and b. The ammoniation product outlet is connected to the molten adipic acid inlet and / or the ammonia inlet to return part b of the ammoniation product back into the ammoniation reactor. The falling film evaporator is a tubular structure with an ammoniation product inlet, a hot material inlet, and a hot material outlet. The ammoniation product inlet is connected to the ammoniation product outlet of the ammoniation reactor to allow part a of the ammoniation product to optionally be in film form and to exchange heat with the hot material in a countercurrent, non-contact manner for heating and dehydration to generate crude adiponitrile.

[0047] In this invention, the atomizer may be an atomizing nozzle to achieve the purpose of this invention. This is an illustrative example and does not limit the scope of this invention.

[0048] In this invention, a falling film evaporator is used as the dehydration reaction device. Part of the ammoniation product forms a film on the surface of the tubes and flows down uniformly along the tubes, resulting in high heat transfer efficiency and significantly improved dehydration reaction conversion rate and selectivity of adiponitrile. Furthermore, the equipment is simple and easy to industrialize.

[0049] According to one embodiment of the present invention, the system further includes a raw material preparation tank connected to the molten adipic acid inlet of the ammoniation reactor, for mixing and melting adipic acid with a catalyst, wherein the catalyst is selected from one or more of liquid phosphoric acid, phosphates, phosphate esters, and supported solid acid catalysts; and a first superheater and a first regulating valve disposed on the connecting pipeline between the molten adipic acid inlet of the ammoniation reactor and the raw material preparation tank, wherein the first superheater is used to heat the material in the raw material preparation tank to the ammoniation reaction temperature, and the first regulating valve is used to regulate the flow rate of the adipic acid material entering the ammoniation reactor.

[0050] In this invention, there is no particular limitation on the method of heating adipic acid in the raw material preparation tank. For example, it can be heated by the heating coil inside the raw material preparation tank to melt the medium inside the tank. This is an illustrative description and does not limit the scope of this invention.

[0051] According to one embodiment of the present invention, the falling film evaporator is provided with a catalyst injection port at the top, and the catalyst for injection is selected from one or more of liquid phosphoric acid, phosphates, and phosphate esters.

[0052] According to one embodiment of the present invention, the hot material outlet of the falling film evaporator is connected to the molten adipic acid inlet and / or ammonia inlet of the ammonification reactor.

[0053] In this invention, a compressor can be installed at the hot material outlet of the falling film evaporator to return the hot ammonia gas to the ammoniation reactor after pressurization. This is an illustrative description and does not limit the scope of the invention.

[0054] According to one embodiment of the present invention, a liquid distributor is provided at the inlet of the ammoniation product of the falling film evaporator. There are no special requirements for the specific selection of the liquid distributor, and the present invention will not describe it in detail here.

[0055] According to one embodiment of the present invention, the ammoniation reactor is provided with a deheated ammonia gas inlet, and a gas distributor is provided at the deheated ammonia gas inlet.

[0056] According to one embodiment of the present invention, the system further includes: a liquid ammonia storage tank for providing an ammonia source to the ammoniation reactor; and a second superheater and a second regulating valve disposed on a connecting pipeline between the liquid ammonia storage tank and the ammoniation reactor, the second superheater for vaporizing the liquid ammonia from the liquid ammonia storage tank, and the second regulating valve for regulating the ammonia flow rate entering the ammoniation reactor.

[0057] According to one embodiment of the present invention, the system further includes: a heat exchanger for exchanging heat with the ammoniation products of the ammoniation reactor and then sending part a of the ammoniation products into a falling film evaporator and part b of the ammoniation products into the ammoniation reactor.

[0058] According to one embodiment of the present invention, the system further includes: an ammoniation product buffer tank for buffering the a portion of the ammoniation product after heat exchange before sending it into the falling film evaporator, and a third regulating valve is provided on the discharge pipeline for regulating the amount of ammoniation product entering the falling film evaporator.

[0059] The following is an illustrative example and is not intended to limit the scope of the invention.

[0060] According to one embodiment of the present invention, the system further includes a heavy component collection tank connected to the heavy component outlet of the falling film evaporator.

[0061] According to one embodiment of the present invention, the system further includes an adiponitrile collection tank connected to the crude adiponitrile outlet of the falling film evaporator.

[0062] According to one embodiment of the present invention, the inlet of the ammoniation product channel of the heat exchanger is connected to the outlet of the ammoniation product of the ammoniation reactor.

[0063] According to one embodiment of the present invention, the heat exchanger's heat exchange material channel outlet is connected to the hot material inlet of the falling film evaporator.

[0064] According to one embodiment of the present invention, the outlet of the ammoniation product channel of the heat exchanger is connected to the feed inlet of the ammoniation reactor.

[0065] According to one embodiment of the present invention, the inlet of the heat exchanger's heat exchange material channel is connected to the outlet of the liquid ammonia storage tank.

[0066] In this invention, unless otherwise specified above, valves, delivery pumps, flow meters, heaters, heat exchangers, etc., may be installed on each connecting pipeline as needed.

[0067] The embodiments of the present invention are described below with reference to the accompanying drawings.

[0068] Option 1: like Figure 1As shown, according to one embodiment of the present invention, the outlet at the bottom of the raw material preparation tank 1 (containing a mixture of catalyst and adipic acid) is connected to the atomizer (not shown in the figure) at the molten adipic acid inlet of the ammoniation reactor 3 via a pipeline. A first superheater 8 and a first regulating valve 7 are provided on the pipeline. The ammonia inlet at the top of the ammoniation reactor 3 is connected to the liquid ammonia storage tank 2 via a pipeline. A second superheater 9 and a second regulating valve 10 are provided on the pipeline. The ammoniation product outlet at the bottom of the ammoniation reactor 3 is connected to the heat exchanger 4 via a pipeline. After exchanging heat with ammonia in the heat exchanger 4, part b of the ammoniation product is returned via a pipeline. In the ammoniation reactor 3, part a of the ammoniation product is fed into the ammoniation product buffer tank 6. The outlet of the ammoniation product buffer tank 6 is connected to the ammoniation product inlet of the falling film evaporator 11 via a pipeline through the third regulating valve 5. The falling film evaporator 11 (tube-type structure) is equipped with a liquid distributor (not shown in the figure) at the top. The heat exchange material channel outlet of the heat exchanger 4 sends hot ammonia gas into the hot material inlet of the falling film evaporator 11. Part a of the ammoniation product undergoes a dehydration reaction after being heated by hot ammonia gas. The resulting adiponitrile and other components are connected to the adiponitrile collection tank 12 via a pipeline. The heavy components generated after dehydration are connected to the heavy component collection tank 13 via a pipeline.

[0069] In this embodiment, an atomizer (not shown in the figure) is installed at the adipic acid inlet of the ammoniation reactor 3, which has a good mass transfer effect, reduces the by-products generated by the decomposition of adipic acid, and realizes the full neutralization and salt formation of adipic acid; the falling film evaporator 11 has a tube-type structure inside, and a liquid distributor (not shown in the figure) is installed at the top of the tubes. The ammoniation product forms a film on the surface of the tubes through the liquid distributor (not shown in the figure) and flows down the tubes evenly, resulting in high heat transfer efficiency and high dehydration efficiency of adipic acid ammonium salt.

[0070] The application method of the reaction system provided in this embodiment specifically includes the following steps: Step 1: Add adipic acid and catalyst to the raw material preparation tank, heat the medium inside the tank through the heating coil, and stir evenly to obtain adipic acid melt containing catalyst.

[0071] Step 2: After the raw material mixture is heated to the reaction temperature by the first superheater, it is sent to the ammoniation reactor. The atomizer is an atomizing nozzle. After the molten adipic acid containing the catalyst is atomized, it comes into full contact with the ammonia gas injected from the top of the ammoniation reactor after being heated and vaporized by the second superheater. An ammoniation neutralization reaction occurs to convert the adipic acid into ammoniation products, including ammonium adipicate.

[0072] Step 3: The ammoniation product discharged from the bottom of the ammoniation reactor is cooled by heat exchanger. Part b of the ammoniation product is returned to the top of the ammoniation reactor and mixed with molten adipic acid to continue the ammoniation reaction. Part a of the ammoniation product enters the ammoniation product buffer tank. The material in the ammoniation product buffer tank enters from the top of the tubular falling film evaporator. The heating medium of the falling film evaporator is hot ammonia gas after heat exchange with the ammoniation product. The ammoniation product is in film form and undergoes a dehydration reaction in the tubes of the falling film evaporator to generate adiponitrile. The water-containing adiponitrile is discharged from the top of the falling film evaporator into the adiponitrile collection tank. After dehydration in the adiponitrile collection tank, high-purity adiponitrile product is obtained. The heavy components generated after dehydration in the falling film evaporator enter the heavy component collection tank.

[0073] Option 2: like Figure 2 As shown, according to one embodiment of the present invention, based on Scheme 1, the difference is that: in Scheme 2, the falling film evaporator 11 is provided with a catalyst injection port on the upper part, instead of mixing and melting the catalyst with adipic acid.

[0074] In this embodiment, the ammoniation and neutralization salt formation stage can be carried out without the addition of a catalyst; the catalyst is only required for the dehydration reaction.

[0075] Option 3: like Figure 3 As shown, according to one embodiment of the present invention, based on Scheme 1, the difference is that: in Scheme 3, the deheated ammonia gas from the falling film evaporator 11 is discharged from the hot material outlet and then enters the ammoniation reactor 3 from the top to react.

[0076] Option 4: like Figure 4 As shown, according to one embodiment of the present invention, based on Scheme 3, the difference is that: in Scheme 4, the cooling ammonia gas from the falling film evaporator 11 is discharged from the hot material outlet and then enters the ammoniation reactor 3 and is distributed by the gas distributor before the reaction.

[0077] The present invention will be described in detail below through examples. In the following examples, the parameters were measured by conventional methods; all raw materials were commercially available products.

[0078] Example 1 This embodiment uses adipic acid as an example to prepare adiponitrile using Scheme 1. Specifically, it includes the following steps: Step S1: 100 kg / h of adipic acid and 2 kg / h of liquid phosphoric acid catalyst are added together to the raw material preparation tank. The side wall of the raw material preparation tank is heated by a heat transfer oil coil with an inlet temperature of 260°C. The adipic acid and catalyst are heated to 180°C to melt the medium inside the tank. The stirrer is turned on and the speed is adjusted to 100 rpm. Stirring is carried out for 20 minutes. After stirring evenly, the mixture is heated to the reaction temperature of 230°C by the first superheater and then sent to the ammoniation reactor by a metering pump. The ammoniation reactor has a diameter of 400 mm and a height of 2 m. The atomizer inside has 10 atomizing nozzles. Ammonia gas enters from the top of the ammoniation reactor and is atomized into 40 μm droplets at a flow rate of 60 kg / hr. The mixture is heated to 170°C by the second superheater. The pressure inside the tank is 2 MPaG. After the ammoniation neutralization reaction, the ammoniation product is obtained.

[0079] Step S2: The ammoniation product is pumped into a heat exchanger to exchange heat with ammonia gas. 80 kg / h of the a portion of the ammoniation product is then sent to the ammoniation product buffer tank, while 20 kg / h of the b portion is recycled back to the ammoniation reactor as a diluent to continue participating in the ammoniation reaction. The a portion of the ammoniation product (temperature 160℃) enters from the top of the falling film evaporator through the ammoniation product inlet, passes through the feed distributor, and enters the tube bundle. The heating medium of the falling film evaporator is hot ammonia gas heated by heat exchange in the heat exchanger, at a temperature of 230℃. The ammoniation product undergoes a dehydration reaction on the tube bundle wall to obtain crude adiponitrile. The water-containing adiponitrile is discharged from the top of the falling film evaporator into the adiponitrile collection tank. The amount of water-containing adiponitrile is 82.6 kg / h, with a water content of 12 wt%. After dehydration, high-purity adiponitrile is obtained.

[0080] The final yield was 72.7 kg / h of adiponitrile with a purity of 98.5%.

[0081] Example 2 This embodiment uses adipic acid as an example to prepare adiponitrile using Scheme 2. Specifically, it includes the following steps: Step S1: 100 kg / h of adipic acid is heated through the heating coil inside the raw material preparation tank. The inlet temperature of the heat transfer oil is 260°C, and the adipic acid temperature rises to 180°C, melting the medium inside the tank. The stirrer is turned on, and the speed is adjusted to 100 rpm. After stirring for 20 minutes, the mixture is heated to the reaction temperature of 220°C by the first superheater and then sent to the ammoniation reactor by the metering pump. The ammoniation reactor has a diameter of 400 mm and a height of 2 m. It has 10 atomizing nozzles inside, atomizing into 40 μm droplets. Ammonia gas enters from the top of the ammoniation reactor at a flow rate of 60 kg / hr. After being heated to 180°C by the second superheater, the pressure inside the tank is 3 MPaG. After the ammoniation neutralization reaction, the ammoniation product is obtained.

[0082] Step S2: The ammoniation product is pumped into a heat exchanger to exchange heat with ammonia gas. 75 kg / h of the a portion of the ammoniation product is then sent to the ammoniation product buffer tank, while 25 kg / h of the b portion is recycled back to the ammoniation reactor as a diluent to continue participating in the ammoniation reaction. The a portion of the ammoniation product (temperature 155℃) enters from the top ammoniation product inlet of the falling film evaporator, and 2 kg / h of ammonium phosphate catalyst is injected at the top catalyst injection port. The product then enters the tube bundle through a feed distributor. The heating medium of the falling film evaporator is hot ammonia gas heated by the heat exchanger to 218℃. The ammoniation product undergoes a dehydration reaction on the tube bundle wall to obtain crude adiponitrile. The water-containing adiponitrile is discharged from the top of the falling film evaporator into the adiponitrile collection tank. The amount of water-containing adiponitrile is 83.1 kg / h, with a water content of 11.6 wt%. After dehydration, high-purity adiponitrile is obtained.

[0083] The final yield was 73.46 kg / h of adiponitrile with a purity of 98.5%.

[0084] Example 3 This embodiment uses adipic acid as an example and adopts Scheme 3 to prepare adiponitrile.

[0085] The method used in Example 1 differs from that in Example 1 in that the deheated ammonia gas from the hot material outlet of the falling film evaporator is discharged from the hot material outlet and then enters the ammoniation reactor from the top for reaction. After the device is running stably, the ammonia gas no longer needs to be heated by a second superheater before being sent into the ammoniation reactor, saving the energy required for the second superheater in subsequent processes.

[0086] Example 4 This embodiment uses adipic acid as an example to prepare adiponitrile using Scheme Four. Specifically, it includes the following steps: Step S1: 150 kg / h of adipic acid and 2 kg / h of liquid phosphoric acid catalyst are added together to the raw material preparation tank. The side wall of the raw material preparation tank is heated by a heat transfer oil coil with an inlet temperature of 260°C. The adipic acid and catalyst are heated to 175°C to melt the medium inside the tank. The stirrer is turned on and the speed is adjusted to 500 rpm. Stirring is carried out for 30 minutes. After stirring evenly, the mixture is heated to the reaction temperature of 200°C by the first superheater and then sent to the ammoniation reactor by a metering pump. The ammoniation reactor has a diameter of 400 mm and a height of 2 m. The atomizer inside has 10 atomizing nozzles, which atomize into 40 μm droplets. Ammonia gas enters from the top of the ammoniation reactor at a flow rate of 100 kg / hr. The mixture is heated to 170°C by the second superheater. The pressure inside the tank is 2.5 MPaG. After the ammoniation neutralization reaction, the ammoniation product is obtained.

[0087] Step S2: The ammoniation product is pumped into a heat exchanger to exchange heat with ammonia gas. 100 kg / h of part a of the ammoniation product is then sent to an ammoniation product buffer tank, while 50 kg / h of part b of the ammoniation product is recycled back to the ammoniation reactor as a diluent to continue participating in the ammoniation reaction. Part a of the ammoniation product (temperature 143℃) enters from the ammoniation product inlet at the top of the falling film evaporator, passes through a liquid distributor, and enters the tube bundle. The heating medium of the falling film evaporator is hot ammonia gas heated by heat exchange in the heat exchanger, at a temperature of 198℃. The ammoniation product undergoes a dehydration reaction on the tube bundle wall to obtain crude adiponitrile. The water-containing adiponitrile is discharged from the top of the falling film evaporator into an adiponitrile collection tank. The cooled ammonia gas from the hot material outlet of the falling film evaporator is sent to the ammoniation reactor in step S1, distributed by a gas distributor, and further undergoes an ammoniation reaction with the incompletely reacted adipic acid. Aqueous adiponitrile is discharged from the top of the falling film evaporator into the adiponitrile collection tank. The amount of aqueous adiponitrile is 125 kg / h, of which the water content is 12.3 wt%. After dehydration, high-purity adiponitrile is obtained.

[0088] The final yield was 109.63 kg / h of adiponitrile with a purity of 98.5%.

[0089] Example 5 The method is the same as in Example 4, except that... Step S2: The ammoniation product is pumped into a heat exchanger to exchange heat with ammonia gas. 100 kg / h of part a of the ammoniation product is then sent to an ammoniation product buffer tank, while 50 kg / h of part b of the ammoniation product is recycled back to the ammoniation reactor as a diluent to continue participating in the ammoniation reaction. Part a of the ammoniation product (temperature 152℃) enters from the top of the falling film evaporator through the ammoniation product inlet, passes through a feed distributor, and enters the tube shell. The heating medium of the falling film evaporator is hot ammonia gas heated by heat exchange in the heat exchanger, at a temperature of 190℃. The ammoniation product undergoes a dehydration reaction on the tube shell wall to obtain crude adiponitrile. The water-containing adiponitrile is discharged from the top of the falling film evaporator into an adiponitrile collection tank. The cooled ammonia gas from the hot material outlet of the falling film evaporator is sent to the ammoniation reactor in step S1, distributed by a gas distributor, and further undergoes an ammoniation reaction with the incompletely reacted adipic acid. Aqueous adiponitrile is discharged from the top of the falling film evaporator into the adiponitrile collection tank. The amount of aqueous adiponitrile is 124.7 kg / h, of which the water content is 12.9 wt%. After dehydration, high-purity adiponitrile is obtained.

[0090] The final yield was 108.62 kg / h of adiponitrile with a purity of 98.5%.

[0091] Comparative Example 1 According to CN 115814713 A, the consumption of adipic acid is 1.43 kg / kg adiponitrile, and the adipic acid ammoniation neutralization efficiency is about 70%. About 30% of the adipic acid will enter the tubular reactor and decompose or corrode the tubular reactor.

[0092] Comparative Example 2 The method is the same as in Example 1, except that all the amination products are fed into a falling film evaporator for dehydration.

[0093] The amount of adiponitrile containing water was 78.6 kg / h, of which the water content was 13 wt%. After dehydration, high-purity adiponitrile was obtained.

[0094] The consumption of adipic acid is 1.48 kg / kg adiponitrile.

[0095] Comparative Example 3 The method is the same as in Example 1, except that the ratio of the ammoniated product to the bmmoniated product is 9:1.

[0096] The amount of adiponitrile containing water was 79.3 kg / h, of which the water content was 12.9 wt%. After dehydration, high-purity adiponitrile was obtained.

[0097] The consumption of adipic acid is 1.47 kg / kg adiponitrile.

[0098] As shown in Example 1, the consumption of adipic acid is 1.396 kg / kg adiponitrile; as shown in Example 2, the consumption of adipic acid is 1.382 kg / kg adiponitrile; as shown in Example 4, the consumption of adipic acid is 1.389 kg / kg adiponitrile; and as shown in Example 5, the consumption of adipic acid is 1.402 kg / kg adiponitrile. Furthermore, the present invention will not corrode equipment.

[0099] In the above embodiments, the consumption of adipic acid is equal to the amount of adipic acid added divided by the yield of adiponitrile.

[0100] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing adiponitrile, characterized in that, The method includes: S1: Molten adipic acid is atomized and then mixed with ammonia gas. The ammonia reaction produces ammonia products. S2: The amination product is divided into two parts, a and b. Part a is heated and dehydrated by countercurrent non-contact heat exchange with the hot material to generate crude adiponitrile. Part b is recycled back to step S1 to participate in the reaction. The ratio of the ammonification product in part a to the ammonification product in part b is (1~5):1; the temperature of the hot material is higher than the temperature of the ammonification product in part a.

2. The method according to claim 1, wherein, Step S2 is carried out in the presence of a catalyst, which is selected from one or more of liquid phosphoric acid, phosphates, phosphate esters, and supported solid acid catalysts.

3. The method according to claim 2, wherein, The catalyst is added by mixing the catalyst with adipic acid and then melting it to obtain molten adipic acid. The catalyst is selected from one or more of liquid phosphoric acid, phosphates, phosphate esters, and supported solid acid catalysts. The catalyst is added by introducing it into the heating and dehydration reaction described in step S2; the catalyst is selected from one or more of liquid phosphoric acid, phosphates, and phosphate esters.

4. The method according to claim 2, wherein, Molten adipic acid is atomized into droplets of 10-50 μm; and / or The ratio of the amination product to the bmination product is (2~4):1; and / or The amount of catalyst added is 0.1-3% of the weight of adipic acid.

5. The method according to any one of claims 1-4, wherein, The temperature difference between the hot material and the a portion of the ammoniation product is 50~80℃; and / or The ammoniated product in part a forms a film that exchanges heat with the hot material in a countercurrent, non-contact manner; and / or The hot material is selected from hot nitrogen and / or hot ammonia.

6. The method according to any one of claims 1-4, wherein, Ammonia gas is obtained by exchanging heat with the ammoniation product to obtain hot ammonia gas, and the hot ammonia gas is used as a hot material in step S2.

7. The method according to any one of claims 1-4, wherein, The hot material is hot ammonia gas. The cooled ammonia gas, which has undergone countercurrent non-contact heat exchange with the ammonia products of part a, is fed into step S1 as ammonia raw material to further react with the incompletely reacted adipic acid to undergo ammonia reaction.

8. The method according to claim 7, wherein, After passing through the gas distributor, the cooled ammonia gas comes into contact with molten adipic acid and undergoes an ammoniation reaction.

9. The method according to any one of claims 1-4, wherein, The conditions for the amination reaction include: a temperature of 140℃~230℃; and / or Pressure ranges from 0.1 MPaG to 5 MPaG; and / or The molar ratio of ammonia to adipic acid is (5~12):

1.

10. A system for preparing adiponitrile, characterized in that, The system includes: An ammoniation reactor is provided with a molten adipic acid inlet, an ammonia inlet, and an ammoniation product outlet. It is used for the ammoniation reaction of adipic acid and ammonia to generate the ammoniation product. An atomizer is installed at the molten adipic acid inlet to atomize the molten adipic acid. The ammoniation product is divided into two parts, a and b. The ammoniation product outlet is connected to the molten adipic acid inlet and / or the ammonia inlet to return part b of the ammoniation product back into the ammoniation reactor. The falling film evaporator is a tubular structure with an ammoniation product inlet, a hot material inlet, and a hot material outlet. The ammoniation product inlet is connected to the ammoniation product outlet of the ammoniation reactor to allow part a of the ammoniation product to optionally be in film form and to exchange heat with the hot material in a countercurrent, non-contact manner for heating and dehydration to generate crude adiponitrile.

11. The system according to claim 10, wherein, The system also includes a feed preparation tank connected to the molten adipic acid inlet of the ammoniation reactor, used to mix and melt adipic acid with a catalyst selected from one or more of liquid phosphoric acid, phosphates, phosphate esters, and supported solid acid catalysts; and A first superheater and a first regulating valve are installed on the connecting pipeline between the molten adipic acid inlet of the ammoniation reactor and the raw material preparation tank. The first superheater is used to heat the material in the raw material preparation tank to the ammoniation reaction temperature, and the first regulating valve is used to regulate the flow rate of the adipic acid material entering the ammoniation reactor.

12. The system according to claim 10, wherein, The falling film evaporator is equipped with a catalyst injection port at the top, and the catalyst is selected from one or more of liquid phosphoric acid, phosphates, and phosphate esters; and / or The hot material outlet of the falling film evaporator is connected to the molten adipic acid inlet and / or ammonia inlet of the ammoniation reactor.

13. The system according to claim 10, wherein, The falling film evaporator is equipped with a liquid distributor at the inlet of the ammoniation product; and / or The ammoniation reactor is provided with a cooling ammonia gas inlet, and a gas distributor is installed at the cooling ammonia gas inlet.

14. The system according to claim 10, wherein, The system also includes: A liquid ammonia storage tank, wherein the liquid ammonia storage tank is used to supply ammonia gas to the ammoniation reactor; and A second superheater and a second regulating valve are installed on the connecting pipeline between the liquid ammonia storage tank and the ammoniation reactor. The second superheater is used to vaporize the liquid ammonia from the liquid ammonia storage tank, and the second regulating valve is used to regulate the ammonia flow rate entering the ammoniation reactor; and / or The heat exchanger is used to exchange heat with the ammoniation products of the ammoniation reactor and then send part a of the ammoniation products to the falling film evaporator and part b of the ammoniation products to the ammoniation reactor. The ammoniation product buffer tank is used to buffer the ammoniation product after heat exchange before sending it to the falling film evaporator, and a third regulating valve is installed on the discharge pipeline to regulate the amount of ammoniation product entering the falling film evaporator. and / or Heavy component collection tank, used to collect heavy components discharged from falling film evaporator; and / or Adiponitrile collection tank is used to collect crude adiponitrile from the falling film evaporator.

15. The system according to claim 14, wherein, The inlet of the heat exchanger's heat exchange material flow channel is connected to the outlet of the liquid ammonia storage tank; and / or The heat exchanger's heat exchange material channel outlet is connected to the hot material inlet of the falling film evaporator; and / or The outlet of the ammoniation product channel of the heat exchanger is connected to the feed inlet of the ammoniation reactor; and / or The inlet of the ammoniation product channel of the heat exchanger is connected to the outlet of the ammoniation product of the ammoniation reactor.

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