A continuous reaction system and preparation method of nylon acid derivatives

Abstract

The present invention relates to the field of chemical production technology, and in particular to a continuous reaction system and preparation method of nylon acid derivatives. The continuous reaction system comprises a connected reaction distillation tower and a dehydration tower, wherein the reaction distillation tower comprises a dehydration zone, a first reaction zone, a second reaction zone and a liquid phase zone in sequence along the vertical direction; further comprising a first heater for heating the liquid in the liquid phase zone; and the temperature in the reaction distillation tower is set in a gradient along the vertical direction. There is an obvious temperature gradient in the reaction distillation tower, and the reaction can be carried out smoothly under normal pressure conditions, and the reaction is thorough, the product yield is high, and the continuous production and preparation of the target product can be realized, and large-scale production can be realized, the product quality is stable, the reaction energy consumption is low, and it is convenient for industrial scale-up.

Description

Technical Field

[0001] The invention relates to the technical field of chemical production, and in particular to a continuous reaction system and a preparation method of nylon acid derivatives. Background Art

[0002] Nylon acid (DBA) is a mixed dibasic acid composed of three organic compounds: succinic acid, glutaric acid and adipic acid. It is a by-product produced during the industrial production of adipic acid. In the past, these by-products were treated as waste acid and incinerated, resulting in a huge waste of resources. Therefore, the comprehensive utilization of nylon acid has gradually attracted widespread attention. The reaction of nylon acid with alcohol to prepare nylon acid esters is an important application route for nylon acid by-products. Among them, nylon acid dibutyl ester prepared by the reaction of nylon acid with butanol and nylon acid diisobutyl ester prepared by nylon acid with isobutanol have potential application value as nylon acid derivatives.

[0003] Phthalate esters (DOP) were the main plasticizers in the early days. However, as the country's environmental protection requirements increase, their potential environmental toxicity has also attracted attention, and the industry has gradually sought more environmentally friendly alternatives. Nylon acid di-n-butyl ester and nylon acid di-isobutyl ester have the advantages of high plasticizing properties and good cold resistance, and are expected to replace phthalates and become the leader in the plasticizer market.

[0004] However, the existing preparation process of nylon acid derivatives has major defects. The reaction process of nylon acid dibutyl ester is taken as an example for introduction: in the first step, nylon acid and excess butanol are added into a reactor in a certain proportion, and an acidic catalyst (p-toluenesulfonic acid / concentrated sulfuric acid / solid super acid, etc.) is added. The reaction is carried out at 100-150°C for a certain time to generate nylon acid dibutyl ester, nylon acid monobutyl ester and water; in the second step, water and part of butanol are evaporated under negative pressure, and the reaction temperature is increased to 120-180°C to continue the reaction, and nylon acid monobutyl ester is reacted to generate nylon acid dibutyl ester; in the third step, water and excess butanol are evaporated under negative pressure, and then the nylon acid dibutyl ester mixture is evaporated under high vacuum conditions, and the remaining catalyst and other kettle residues are discharged as hazardous waste.

[0005] The preparation process of nylon acid derivatives in the prior art has the following defects: first, the reaction time is long, and the yield of the target product under normal pressure reaction is low, mainly generating nylon acid monobutyl ester, and the reaction from nylon acid monobutyl ester to nylon acid dibutyl ester needs to be switched to pressurized conditions, and the reaction temperature is increased by pressurization, resulting in complicated reaction operation and increased risk; second, it is an intermittent production with low production efficiency and low output, which is not convenient for realizing scaled-up production and product batch production, and the product quality is unstable. At the same time, the intermittent reaction requires repeated heating and cooling, and the operation energy consumption is large. Summary of the invention

[0006] In order to solve the above technical problems existing in the prior art, the present invention provides a continuous reaction system and preparation method of nylon acid derivatives.

[0007] The technical solution of the present invention to solve the above technical problems is as follows:

[0008] The first aspect of the present invention is to provide a continuous reaction system for nylon acid derivatives, comprising a reaction distillation tower, a dehydration tower, and a first heater, wherein the reaction distillation tower is connected to the dehydration tower, and the reaction distillation tower vertically comprises a dehydration zone, a first reaction zone, a second reaction zone, and a liquid phase zone; the first heater is used to heat the liquid in the liquid phase zone; the temperature in the reaction distillation tower is set in a gradient along the vertical direction.

[0009] The continuous reaction system of the nylon acid derivative provided by the present invention realizes temperature zoning in the reaction distillation tower by setting the temperature gradient in the reaction distillation tower, and realizes continuous reaction preparation of the nylon acid derivative under normal pressure conditions by utilizing the characteristics of the reaction materials, without switching the pressure conditions, and is simple to operate; at the same time, the water generated by the reaction is separated from the reaction distillation tower in time, and the dehydration effect is ensured by a dehydration tower, so that the reaction is more thorough, the yield of the target product is high, and the product quality is stable.

[0010] On the basis of the above technical solution, the present invention can also make the following improvements:

[0011] Furthermore, the temperature of the dehydration zone is 90-130°C, the temperature of the first reaction zone is 100-140°C, and the temperature of the second reaction zone is 130-180°C.

[0012] The beneficial effect of adopting the above further technical solution is that: by setting the above temperature gradient, the reaction raw materials are ensured to carry out the first step reaction in the first reaction zone at 100-140°C; by raising the temperature of the second reaction zone to 130-180°C, it is conducive to the smooth progress of the second step reaction under high temperature conditions, making the reaction in the reaction distillation tower more complete.

[0013] The reaction of nylon acid and butanol to synthesize dibutyl nylon ester is taken as an example for explanation, wherein the first step is the reaction of nylon acid and butanol to produce dibutyl nylon ester, monobutyl nylon ester and water, and the second step is the reaction of monobutyl nylon ester and butanol to produce dibutyl nylon ester, i.e., the target product.

[0014] Furthermore, it also includes a first liquid circuit and a second liquid circuit, the liquid phase area is connected to the second reaction area through the first liquid circuit, and the liquid phase area is connected to the post-processing equipment through the second liquid circuit.

[0015] The beneficial effect of adopting the above-mentioned further technical scheme is that after the liquid in the liquid phase zone is discharged from the bottom of the reaction distillation tower, a part of it is returned to the second reaction zone through the first liquid path to participate in the second step reaction again, so that the intermediate product that has not reacted completely in the liquid phase zone is reacted again to obtain the target product (taking the reaction of nylon acid and butanol to synthesize nylon acid dibutyl ester as an example, the intermediate product is nylon acid monobutyl ester, and the target product is nylon acid dibutyl ester), thereby making the reaction more thorough and improving the yield of the target product; the other part is the crude target product after the reaction (taking the reaction of nylon acid and butanol to synthesize nylon acid dibutyl ester as an example, that is, crude nylon acid dibutyl ester) connected to the post-processing equipment through the second liquid path to obtain the finished target product (taking the reaction of nylon acid and butanol to synthesize nylon acid dibutyl ester as an example, that is, finished nylon acid dibutyl ester).

[0016] Furthermore, it also includes a third liquid circuit, the liquid phase region circulates through the third liquid circuit, and the first heater is arranged on the third liquid circuit to heat the liquid in the third liquid circuit.

[0017] The beneficial effect of adopting the above-mentioned further technical solution is that after the liquid in the liquid phase zone is discharged from the bottom of the reaction distillation tower, a part of it returns to the liquid phase zone again after circulation through the third liquid circuit. Before returning to the liquid phase zone, it is heated by the first heater to achieve temperature increase, thereby ensuring that the temperature of the liquid phase zone is maintained within the target range, so that the reaction can proceed smoothly.

[0018] Furthermore, it also includes an evaporator, the inlet of which is connected to a liquid alcohol delivery pipeline, and the outlet of which is connected to the second reaction zone; the first reaction zone is connected to a raw material delivery pipeline.

[0019] The beneficial effect of adopting the above further technical solution is that: the raw material delivery pipeline ensures the raw material supply of the first reaction zone, so that the first step reaction can be carried out continuously; the liquid alcohol delivery pipeline and the evaporator ensure the raw material supply of the second reaction zone, so that the second step reaction can be carried out continuously.

[0020] Furthermore, a gas phase outlet and a liquid alcohol inlet are provided at the top of the reaction distillation tower, and the liquid alcohol inlet is located below the gas phase outlet; the dehydration tower includes a mixed gas phase outlet, an oil phase inlet, a gas phase raw material inlet and a liquid alcohol outlet in sequence along the vertical direction; the gas phase outlet of the reaction distillation tower is connected to the gas phase raw material inlet of the dehydration tower.

[0021] Furthermore, it also includes a condenser, a stratification tank and a water phase receiving tank, and the mixed gas phase outlet, the condenser, and the stratification tank are connected in sequence; the liquid in the stratification tank includes an oil phase and a water phase, the water phase is connected to the water phase receiving tank, and the oil phase is connected to the oil phase inlet.

[0022] The beneficial effect of adopting the above further technical scheme is that the water generated by the reaction of nylon acid and butanol is azeotropically evaporated from the top of the reaction distillation tower and enters the dehydration tower in gaseous form. After condensation and stratification, the water in the reaction system in the reaction distillation tower is removed, thereby improving the conversion rate of the reaction.

[0023] Furthermore, it also includes a first liquid alcohol pipeline and a second liquid alcohol pipeline, one end of the first liquid alcohol pipeline is connected to the liquid alcohol outlet, and the other end is connected to the liquid alcohol in the dehydration tower, and a second heater is arranged on the first liquid alcohol pipeline; one end of the second liquid alcohol pipeline is connected to the liquid alcohol outlet, and the other end is connected to the liquid alcohol inlet of the reaction distillation tower.

[0024] The beneficial effect of adopting the above further technical solution is that after the butanol liquid is discharged from the bottom of the dehydration tower, a part of it returns to the bottom of the dehydration tower through the first liquid alcohol pipeline, and is heated by the second heater before returning to the bottom of the dehydration tower to ensure the temperature in the dehydration tower so that evaporation and vaporization can continue; the other part is returned to the top of the reaction distillation tower as reflux liquid.

[0025] Furthermore, the top temperature of the dehydration tower is 90-95°C, and the bottom temperature is 110-125°C.

[0026] Another aspect of the present invention is to provide a method for preparing nylon acid derivatives by continuous reaction using the above-mentioned continuous reaction system of nylon acid derivatives, comprising the following steps:

[0027] S1. Nylon acid, alcohol and catalyst are reacted in the first reaction zone;

[0028] S2. The product obtained from the first step reaction is reacted with butanol in a second reaction zone to obtain a target product;

[0029] During the reaction of S1 and S2, the mixed gas in the dehydration zone is transported to the dehydration tower for alcohol-water separation, and the dehydrated liquid alcohol is returned to the reaction distillation tower.

[0030] Compared with the prior art, the present invention has the following technical effects:

[0031] The present invention designs a continuous reaction distillation purification system and process for nylon acid derivatives (nylon acid dibutyl ester / nylon acid diisobutyl ester). The process can realize the continuous reaction process of nylon acid and butanol / isobutanol under normal pressure conditions, and combines the continuous distillation purification technology of crude products and by-products to realize the full-process continuous preparation process of nylon acid dibutyl ester / nylon acid diisobutyl ester. Compared with the original intermittent reaction process, the continuous preparation process provided by the present invention can realize large-scale production;

[0032] The temperature gradient inside the reactive distillation tower is very obvious. The top of the tower is mainly alcohol and water, which is convenient for dehydration of the system and conducive to thorough reaction. The middle of the tower is the reaction section, which is used for the reaction of alcohol and nylon acid. The lower part of the tower can control a lower butanol content, which is convenient for raising the reaction temperature at the bottom and middle of the tower, and is more conducive to the thorough reaction of nylon acid and alcohol under high temperature conditions.

[0033] The top of the reaction distillation tower uses alcohol to carry water to timely separate the water generated by the reaction from the system. The water-free liquid alcohol treated by the dehydration tower is returned to the reaction distillation tower, which ensures the dehydration effect of the reaction distillation tower, allowing the reaction distillation tower to operate under low water content conditions, which is more conducive to a thorough reaction.

[0034] Combined with the subsequent distillation and purification process of the product nylon acid derivatives and the continuous distillation and dealcoholization treatment of the wastewater after oil-water separation, the continuous reaction of the entire process from nylon acid reaction to the final qualified nylon acid derivative product can be achieved, with stable product quality, low reaction energy consumption, and easy industrial scale-up. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of a continuous reaction system of the present invention;

[0036] Reference numerals:

[0037] 11. Reaction distillation tower; 12. Evaporator; 13. First heater; 111. Catalyst delivery pipeline; 112. Nylon acid delivery pipeline; 113. Liquid alcohol delivery pipeline; 114. Waste residue pipeline; 115. Gas raw material delivery pipeline; 122. Third liquid circuit; 123. Pipeline one; 124. First liquid circuit; 125. Second liquid circuit; 128. Liquid outlet pipeline; 16. Circulation pump one; 17. Circulation pump two; 21. Dehydration tower; 22. Second heater; 23. Condenser; 24. Stratification tank; 25. Water phase receiving tank; 26. Transfer pump; 27. Reflux pump; 212. Waste gas pipeline; 214. Oil phase pipeline; 216. Water phase pipeline; 217. First liquid alcohol pipeline; 218. Second liquid alcohol pipeline; 219. Parking delivery pipeline. DETAILED DESCRIPTION

[0038] The following specific embodiments illustrate the implementation of the present invention, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Although the description of the present invention will be introduced in conjunction with the preferred embodiment, this does not mean that the features of this invention are limited to this implementation. On the contrary, the purpose of introducing the invention in conjunction with the implementation is to cover other options or modifications that may extend based on the claims of the present invention. In order to provide a deep understanding of the present invention, the following description will include many specific details. The present invention can also be implemented without using these details. In addition, in order to avoid confusion or blurring the focus of the present invention, some specific details will be omitted in the description. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0039] See also Figure 1 A continuous reaction system for nylon acid derivatives, comprising a reaction distillation tower 11 and a dehydration tower 21 connected to each other, wherein the reaction distillation tower 11 includes a dehydration zone, a first reaction zone, a second reaction zone and a liquid phase zone in sequence in the vertical direction; the first reaction zone is connected to a raw material delivery pipeline for supplying the reaction raw materials in the reaction distillation tower 11, specifically, the raw material delivery pipeline includes a catalyst delivery pipeline 111 and a nylon acid delivery pipeline 112; and an evaporator 12 is also included, wherein the inlet of the evaporator 12 is connected to a liquid alcohol delivery pipeline 113, and the outlet of the evaporator 12 is connected to the first reaction zone. The two reaction zones are connected, and after the liquid alcohol raw material enters the evaporator 12, it is heated and vaporized and enters the second reaction zone in gaseous form; it also includes a first heater 13, which is used to heat the liquid in the liquid phase zone. The first heater 13 is a reboiler, and the heat source is thermal oil; the temperature in the reaction distillation tower 11 is set in a gradient along the vertical direction; specifically, the temperature of the dehydration zone is 90-130°C, the temperature of the first reaction zone is 100-140°C, and the temperature of the second reaction zone is 130-180°C. The operating pressure in the reaction distillation tower 11 is normal pressure, that is, 101KPa.

[0040] Wherein, the catalyst is an acidic catalyst, such as p-toluenesulfonic acid, concentrated sulfuric acid, etc., and what is transported in the catalyst delivery pipeline 111 is a mixed solution formed by pre-dissolving the catalyst in the corresponding alcohol, which is convenient for continuously transporting the catalyst to the reaction distillation tower 11 and easy to accurately quantify. After each raw material is transported to the reaction distillation tower 11, the gaseous alcohol moves upward, meets the catalyst solution (actually a mixed solution formed by dissolving the catalyst in the corresponding alcohol) and the nylon acid solution, and conducts heat transfer, mass transfer and reaction processes. Specifically, taking the reaction of nylon acid and butanol to synthesize nylon acid dibutyl ester as an example, the butanol and nylon acid dissolved with the catalyst are transported to the first reaction zone through the catalyst delivery pipeline 111 and the nylon acid delivery pipeline 112 respectively, and the butanol is evaporated and vaporized by the evaporator 12 and then transported to the second reaction zone through the gas raw material delivery pipeline 115 and moves upward. Within the temperature range set in the first reaction zone, butanol and nylon acid react under the action of the catalyst to generate nylon acid dibutyl ester, nylon acid monobutyl ester and water, wherein the molar ratio of butanol to nylon acid is (2.5-3.5): 1; then dibutyl nylonate and monobutyl nylonate move downward, dibutyl nylonate falls into the liquid phase zone, monobutyl nylonate and newly entered gaseous butanol continue to react in the second step within the temperature range set in the second reaction zone to generate dibutyl nylonate, which falls into the liquid phase zone; in this process, the water generated by the reaction is azeotropic with butanol, evaporated from the top of the reaction distillation tower 11, and transported to the dehydration tower 21 for butanol dehydration, thereby promoting the forward progress of the reaction, making the reaction more thorough, and the yield of the target product is high.

[0041] It should be noted that the four zones in the reaction distillation tower 11 (i.e., the dehydration zone, the first reaction zone, the second reaction zone, and the liquid phase zone) actually contain gas phase and liquid phase, i.e., the dehydration zone also has a liquid phase, and the liquid phase zone also has a gas phase, the difference being that the content of each component in different zones is different. Specifically, the dehydration zone is mainly gaseous butanol and water; the first reaction zone is mainly nylon acid, butanol, water, nylon acid monobutyl ester, and catalyst; the second reaction zone is mainly nylon acid monobutyl ester, butanol, catalyst, nylon acid dibutyl ester, and water; the liquid phase zone is mainly nylon acid dibutyl ester and catalyst, containing a small amount of excess butanol.

[0042] The waste residue pipeline 114 connected to the bottom of the evaporator 12 is used to discharge the residue after the butanol is vaporized, and the residue is discharged intermittently after the continuous reaction system has been running for a certain period of time.

[0043] The process of continuously preparing nylon acid diisobutyl ester by reacting nylon acid with isobutyl alcohol is the same as described above and will not be repeated here.

[0044] The number of plates of the reaction distillation tower 11 is 30-60, the tower body is made of acid-resistant non-metals, such as enamel, silicon carbide, carbon steel lined with polytetrafluoroethylene, etc., the tower internals are made of non-metal fillers and distributors, such as ceramics, silicon carbide, glass, etc., the reboiler is made of non-metallic materials, such as graphite, silicon carbide, and the material conveying pipelines (i.e., catalyst conveying pipeline 111, nylon acid conveying pipeline 112, liquid alcohol conveying pipeline 113, gas raw material conveying pipeline 115, pipeline 123, etc.) are made of acid-resistant non-metals, such as enamel and carbon steel lined with polytetrafluoroethylene.

[0045] The temperature gradient in the reaction distillation tower 11 is obvious, and the reaction temperature changes with the change of the content of the components in each partition. The temperature gradually increases from top to bottom. The closer to the bottom of the reaction distillation tower 11, the lower the butanol and water content in the mixed components, which will lead to a higher temperature. The top of the reaction distillation tower 11 is a dehydration zone, which is mainly a mixed gas of butanol and water, so the temperature will be relatively low. The mixed gas is continuously evaporated through the dehydration tower 21 to achieve dehydration of the reaction system in the reaction distillation tower 11, thereby promoting the forward progress of the reaction; the middle part of the reaction distillation tower 11 is a reaction section, which is used for the reaction of the reaction raw materials (i.e., alcohol and nylon acid), including a first reaction zone and a second reaction zone, wherein the first reaction zone is located at the upper part of the second reaction zone, so as to facilitate the continuous two-step reaction of alcohol and nylon acid and improve the yield of the target product; the lower part of the reaction distillation tower 11 is a liquid phase zone, which controls a lower butanol content, facilitates the increase of the reaction temperature of the adjacent second reaction zone, and is more conducive to the thorough reaction of nylon acid and alcohol under high temperature conditions, thereby improving the yield of the target product.

[0046] The continuous reaction system also includes a first liquid circuit 124, a second liquid circuit 125 and a third liquid circuit 122, and one end of the first liquid circuit 124 and the second liquid circuit 125 are connected to the liquid phase area of ​​the reaction distillation tower 11 through a connected pipeline 123 and a liquid outlet pipeline 128, and a circulation pump 2 17 is arranged on the pipeline 123, and one end of the third liquid circuit 122 is connected to the liquid phase area of ​​the reaction distillation tower 11 through a liquid outlet pipeline 128, and a circulation pump 16 is arranged on the third liquid circuit 122. That is, the liquid in the liquid phase area of ​​the reaction distillation tower 11 is discharged from the bottom and divided into three parts, which can ensure the continuous output of the target product, the full progress of the reaction and the realization of the temperature gradient inside the reaction distillation tower 11; specifically, the liquid phase area is connected to the circulation pump 1 through the third liquid circuit 122. 16 realizes circulating flow, that is, the other end of the third liquid path 122 is also connected to the liquid phase zone, and the first heater 13 is arranged on the third liquid path 122, which is used to heat the liquid in the third liquid path 122, so as to realize the circulating heating flow of the liquid flowing through the third liquid path 122, that is, to realize the heating of the liquid in the liquid phase zone, and to ensure the temperature gradient inside the reaction distillation tower 11; the other end of the first liquid path 124 is connected to the second reaction zone, and under the action of the circulating pump 17, the liquid enters the second reaction zone to participate in the reaction again, so that the intermediate product that has not reacted completely in the liquid phase zone reacts again to obtain the target product; the other end of the second liquid path 125 is connected to the post-processing equipment, and this part of the liquid is used as the crude target product after the reaction, and undergoes the post-processing process, that is, the dealcoholization and catalyst removal process, to obtain the target product finished product.

[0047] The top of the reaction distillation tower 11 is provided with a gas phase outlet and a liquid alcohol inlet, and the liquid alcohol inlet is located below the gas phase outlet; the dehydration tower 21 includes a mixed gas phase outlet, an oil phase inlet, a gas phase raw material inlet and a liquid alcohol outlet in sequence in the vertical direction; the gas phase outlet of the reaction distillation tower 11 is connected to the gas phase raw material inlet of the dehydration tower 21, so that the mixed gas of water and butanol evaporated from the top of the reaction distillation tower 11 is transported to the dehydration tower 21 for dehydration of butanol; to ensure the smooth progress of dehydration, the continuous reaction system also includes a condenser 23, a stratification tank 24 and a water phase The receiving tank 25, the mixed gas phase outlet of the dehydration tower 21, the condenser 23, and the stratification tank 24 are connected in sequence; the mixed gas phase is condensed in the condenser 23 to form a condensate, and the condensate flows into the stratification tank 24 by gravity, and is left to stand and stratify in the stratification tank 24 to form a lower water phase and an upper oil phase, and the water phase is connected to the water phase receiving tank 25, and the lower water phase after stratification is regulated by a valve and flows to the water phase receiving tank 25 by gravity through the water phase pipeline 216; the oil phase is connected to the oil phase inlet, and the upper butanol oil phase is returned to the top of the dehydration tower 21 as a reflux liquid through the oil phase pipeline 214 under the action of the reflux pump 27.

[0048] The exhaust gas pipeline 212 connected to the condenser 23 is used for discharging uncondensed exhaust gas, and is connected to the exhaust gas treatment equipment to be discharged after being treated.

[0049] The continuous reaction system also includes a first liquid alcohol pipeline 217 and a second liquid alcohol pipeline 218, wherein one end of the first liquid alcohol pipeline 217 is connected to the liquid alcohol outlet, and the other end is connected to the liquid alcohol in the dehydration tower 21, and the first liquid alcohol pipeline 217 is provided with a second heater 22, and the second heater 22 is preferably a reboiler, and the heat source is low-pressure steam; one end of the second liquid alcohol pipeline 218 is connected to the liquid alcohol outlet, and the other end is connected to the liquid alcohol inlet of the reaction distillation tower 11, and the second liquid alcohol pipeline 218 is provided with a material transfer pump 26. After the dehydration, the water-free butanol liquid is discharged from the bottom of the dehydration tower 21 and is divided into two parts. One part is returned to the bottom of the dehydration tower 21 through the first liquid alcohol pipeline 217, and is heated by the second heater 22 before returning to the bottom of the dehydration tower 21 to ensure the temperature in the dehydration tower 21 so that evaporation and vaporization can continue; the other part is returned to the top of the reaction distillation tower 11 as reflux liquid under the action of the transfer pump 26 to continue to participate in the reaction. When the system is shut down, the shutdown conveying pipeline 219 transfers the butanol in the dehydration tower 21 back to the solvent raw material tank outside the boundary area.

[0050] The top temperature of the dehydration tower 21 is 90-95° C., the bottom temperature is 110-125° C., the operating pressure in the dehydration tower 21 is normal pressure, the number of plates of the dehydration tower 21 is 15-45, and the method for preparing dibutyl nylonate by continuous reaction using the continuous reaction system provided by the present invention comprises the following steps:

[0051] S1, nylon acid and a catalyst dissolved in butanol are introduced into the first reaction zone, and butanol liquid raw material is introduced into the evaporator 12, the butanol liquid raw material is evaporated and vaporized in the evaporator 12, and then transported into the second reaction zone in the reaction distillation tower 11 through the gas raw material delivery pipeline 115 and moves upward to the first reaction zone, nylon acid reacts with excess butanol in the first reaction zone to generate nylon acid monobutyl ester and water;

[0052] S2, nylon acid monobutyl ester moves downward, continues to react with the newly entered gaseous butanol in the second reaction zone in the second step, generates nylon acid dibutyl ester, and falls into the liquid phase zone;

[0053] In the processes S1 and S2, the water generated by the reaction is azeotropic with butanol and forms a mixed gas in the dehydration zone, which enters the dehydration tower 21 through the gas phase outlet of the reaction distillation tower 11 and the gas phase raw material inlet of the dehydration tower 21. The mixed gas is heated and diffused in the dehydration tower 21, moves upward, and enters the condenser 23 through the mixed gas phase outlet for condensation. The condensate flows to the stratification tank 24 and is allowed to stand and stratify. After stratification, the lower water phase flows to the water phase receiving tank 25, and the upper butanol oil phase returns to the dehydration tower 21 through the oil phase inlet. The butanol liquid at the bottom of the dehydration tower 21 returns to the reaction distillation tower 11 through the liquid alcohol inlet as reflux liquid; part of the liquid in the liquid phase zone of the reaction distillation tower 11 returns to the second reaction zone to further react with the gaseous butanol to increase the degree of reaction.

[0054] The continuous reaction system and process method provided by the present invention can realize the continuous preparation of dibutyl nylonate and diisobutyl nylonate products, and can be continuously carried out under normal pressure, and the yield of the target product is more than 99%; the water generated by the reaction can be separated from the system in time, and the water separated by the reaction distillation tower 11, together with part of butanol, enters the dehydration tower 21 in a gaseous form to realize the separation of butanol and water, and the dehydrated butanol returns to the reaction distillation tower 11 in a liquid form, so that the reaction distillation tower 11 can be operated under low water content conditions; the temperature gradient distribution inside the reaction distillation tower 11 is obvious, and a higher reaction temperature can be achieved under normal pressure conditions, the single yield of the target products dibutyl nylonate and diisobutyl nylonate is high, and the product quality is stable.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A continuous reaction system for nylon acid derivatives, characterized in that: The invention comprises a reaction distillation tower (11), a dehydration tower (21), and a first heater (13); the reaction distillation tower (11) is connected to the dehydration tower (21); the reaction distillation tower (11) comprises a dehydration zone, a first reaction zone, a second reaction zone, and a liquid phase zone in sequence along the vertical direction; the first heater (13) is used to heat the liquid in the liquid phase zone; the temperature in the reaction distillation tower (11) is set in a gradient along the vertical direction; The temperature of the dehydration zone is 90-130°C, the temperature of the first reaction zone is 100-140°C, and the temperature of the second reaction zone is 130-180°C; It also includes a first liquid path (124) and a second liquid path (125), wherein the liquid phase region is connected to the second reaction region through the first liquid path (124), and the liquid phase region is connected to a post-processing device through the second liquid path (125); It also comprises a third liquid circuit (122), the liquid phase region circulates through the third liquid circuit (122), and the first heater (13) is arranged on the third liquid circuit (122) and is used to heat the liquid in the third liquid circuit (122).

2. The continuous reaction system of nylon acid derivatives according to claim 1, characterized in that: It also comprises an evaporator (12), the inlet of the evaporator (12) being connected to a liquid alcohol delivery pipeline (113), the outlet of the evaporator (12) being connected to the second reaction zone; and the first reaction zone being connected to a raw material delivery pipeline.

3. The continuous reaction system of nylon acid derivatives according to claim 1, characterized in that: The top of the reaction distillation tower (11) is provided with a gas phase outlet and a liquid alcohol inlet, and the liquid alcohol inlet is located below the gas phase outlet; the dehydration tower (21) vertically comprises a mixed gas phase outlet, an oil phase inlet, a gas phase raw material inlet and a liquid alcohol outlet; the gas phase outlet of the reaction distillation tower (11) is connected to the gas phase raw material inlet of the dehydration tower (21).

4. The continuous reaction system of nylon acid derivatives according to claim 3, characterized in that: It also includes a condenser (23), a stratification tank (24) and a water phase receiving tank (25), wherein the mixed gas phase outlet, the condenser (23) and the stratification tank (24) are sequentially connected; the liquid in the stratification tank (24) includes an oil phase and a water phase, the water phase is connected to the water phase receiving tank (25), and the oil phase is connected to the oil phase inlet.

5. The continuous reaction system of nylon acid derivatives according to claim 3, characterized in that: The invention also comprises a first liquid alcohol pipeline (217) and a second liquid alcohol pipeline (218); one end of the first liquid alcohol pipeline (217) is connected to the liquid alcohol outlet, and the other end is connected to the liquid alcohol in the dehydration tower (21); and a second heater (22) is arranged on the first liquid alcohol pipeline (217); one end of the second liquid alcohol pipeline (218) is connected to the liquid alcohol outlet, and the other end is connected to the liquid alcohol inlet of the reaction distillation tower (11).

6. The continuous reaction system of nylon acid derivatives according to any one of claims 1 to 5, characterized in that: The top temperature of the dehydration tower (21) is 90-95°C, and the bottom temperature is 110-125°C.

7. A method for preparing nylon acid derivatives by continuous reaction using the continuous reaction system of nylon acid derivatives according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1. Nylon acid, alcohol and catalyst are reacted in the first reaction zone; S2. The product obtained from the first step reaction is reacted with butanol in a second reaction zone to obtain a target product; During the reaction of S1 and S2, the mixed gas in the dehydration zone is transported to the dehydration tower (21) for alcohol-water separation, and the dehydrated liquid alcohol is returned to the reaction distillation tower (11).

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