A process for recovering n-butanol from n-butanol raffinate

Abstract

The application provides a method for recovering n-butanol from n-butanol heavy components, comprising the following steps: introducing C8 heavy components containing n-butyl n-butyrate into a reactor, introducing an ionic assistant into the reactor, controlling the feeding flow ratio of the C8 heavy components and the ionic assistant to be 0.6:1; controlling the reaction temperature in the reactor to be 65-85 DEG C, the reaction pressure to be 0.01-0.05 MPa, and starting a mechanical stirring mechanism and a circulating pump; performing a hydrolysis reaction under the stirring of the mechanical stirring mechanism; the material extracted from the bottom outlet of the reactor is divided into first material and second material; the first material enters a circulating jet loop and is jetted into the reactor through a top circulating nozzle; the second material enters a continuous discharging pipeline and is sent into a phase separator; the separated organic phase is sent to a rectification device to extract n-butanol, and the separated water phase is sent to an external water treatment system. The application realizes efficient and continuous and stable recovery of n-butanol.

Description

Technical Field

[0001] This invention relates to the field of chemical waste liquid treatment and recycling technology, specifically to a method for recovering n-butanol from n-butanol heavy components. Background Technology

[0002] In the industrial production of n-butanol, it is typically prepared using either the propylene carbonyl synthesis method (i.e., butyraldehyde hydrogenation method) or fermentation. Among these, the propylene carbonyl synthesis method has become the mainstream industrial technology for n-butanol production due to its advantages such as wide availability of raw materials, mild reaction conditions, and high product purity. In this process, after n-butyraldehyde undergoes hydrogenation to produce crude n-butanol, it needs to be purified by distillation. During this process, the heavy component removal column plays a crucial role in separating the light and heavy components. The heavy component material collected from the bottom of the heavy component removal column is usually referred to as the C8 heavy component. This material contains 75%–80% n-butyl butyrate, as well as small amounts of unreacted n-butanol, butyric acid, and other byproducts.

[0003] Butyl butyrate, a high-value-added fine chemical intermediate, has a fruity aroma and is widely used in the formulation of food flavorings and daily cosmetic fragrances. It is also an excellent organic solvent and plasticizer. However, in traditional n-butanol production lines, the aforementioned C-8 heavy components rich in butyl butyrate are not effectively utilized and are mostly directly classified as C-8 waste liquid for low-price sale or incineration.

[0004] There are two main technical pathways for the recycling of n-butyl butyrate. The first pathway involves directly separating and purifying n-butyl butyrate as a product. While this pathway can yield high-purity n-butyl butyrate, the complex composition of the C8 heavy components makes separation and purification difficult, requiring sophisticated distillation equipment and high energy consumption, resulting in poor economic efficiency. The second pathway involves hydrolysis to convert n-butyl butyrate into n-butanol and butyric acid (or butyrate). The n-butanol can be recycled back into the production system, while the butyrate can be further acidified to recover butyric acid or sold as a product. This pathway achieves the conversion of heavy components into the main product, aligning better with the concept of a circular economy, and has therefore received more attention and research.

[0005] However, the alkaline hydrolysis of n-butyl butyrate is a typical liquid-liquid two-phase reaction system. In traditional saponification hydrolysis processes, mechanical stirring is usually used to promote mixing of the two phases. Under this method, the droplet dispersion scale is large, the phase interface renewal rate is slow, resulting in a slow hydrolysis rate, incomplete conversion, and reaction time often requiring several hours or even longer. Due to incomplete reaction, a stable emulsion layer easily forms at the phase interface in the product, further hindering the separation of the two phases and the continuation of the reaction. Furthermore, traditional saponification processes generally lack effective online monitoring and feedback control methods. During the hydrolysis reaction, the rate of alkali consumption is closely related to the ester conversion rate, but because real-time reaction progress information cannot be obtained, operators find it difficult to adjust the amount of alkali added in a timely manner, often resulting in excessive or insufficient alkali.

[0006] In recent years, although some researchers have tried to enhance the hydrolysis process by increasing the reaction temperature, increasing the concentration of alkali solution, or extending the reaction time, these measures are often accompanied by new problems such as increased energy consumption, aggravated side reactions, and aggravated equipment corrosion, and have failed to fundamentally solve the technical bottlenecks of large liquid-liquid mass transfer resistance and difficulty in continuous operation.

[0007] Therefore, developing a novel resource recovery technology for n-butanol heavy components is of urgent practical need and important application value for promoting technological progress and sustainable development in the n-butanol industry. Summary of the Invention

[0008] Based on the above background, the purpose of this invention is to provide a method for recovering n-butanol from n-butanol heavy components, thereby achieving efficient, continuous and stable recovery of n-butanol and solving the technical problems of large mass transfer resistance, incomplete hydrolysis and inability to achieve continuous large-scale production in the prior art of n-butanol heavy component processing.

[0009] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0010] A method for recovering n-butanol from n-butanol heavy components, the method being implemented based on a multi-carbon alcohol heavy component hydrolysis recovery system, the multi-carbon alcohol heavy component hydrolysis recovery system including a reaction separation device and a control unit, the reaction separation device including a reactor, a phase separator, and a connecting pipeline network, the reactor having an internal mechanical stirring mechanism, and an external circulating injection loop and a continuous discharge pipeline, the two ends of the circulating injection loop being connected to the bottom outlet of the reactor and the top circulating nozzle of the reactor, respectively, the circulating injection loop having a circulating pump and a circulating heater sequentially arranged along the material flow direction, one end of the continuous discharge pipeline being connected to the pipeline between the outlet of the circulating pump and the circulating heater, the other end of the continuous discharge pipeline being connected to the phase separator having an internal overflow weir plate via a discharge cooler; the reactor also having a C8 heavy component feed pipeline and an auxiliary agent feed pipeline, the auxiliary agent feed pipeline having an electric regulating valve, and the continuous discharge pipeline having an online pH meter; the method includes the following steps:

[0011] The C8 heavy component containing n-butyl butyrate is introduced into the reactor through the C8 heavy component feed pipeline, and the ionic additive is introduced into the reactor through the additive feed pipeline. The feed flow ratio of the C8 heavy component to the ionic additive is controlled to be 0.6:1 by the control unit.

[0012] The control unit controls the reaction temperature in the reactor to be 65℃~85℃ and the reaction pressure to be 0.01MPa~0.05MPa, and turns on the mechanical stirring mechanism and the circulation pump.

[0013] The hydrolysis reaction is carried out under the stirring of the mechanical stirring mechanism;

[0014] The material extracted from the bottom outlet of the reactor is divided into a first stream of material and a second stream of material;

[0015] The first material enters the circulating injection circuit, and after being temperature controlled by the circulating heater, it is injected downward into the reactor through the top circulating nozzle at a rate of 10t / h to 15t / h.

[0016] The second material enters the continuous discharge pipeline, is cooled to 30°C~40°C by the discharge cooler, and is then sent into the phase separator.

[0017] The second material is allowed to stand and separate into an organic phase and an aqueous phase in the phase separator, and the organic phase overflows through the internal overflow weir plate;

[0018] The separated organic phase is sent to a distillation unit to extract n-butanol, and the separated aqueous phase is sent to an external water treatment system.

[0019] The control unit acquires the discharge pH value measured by the online pH detector. When the discharge pH value deviates from the preset range, the opening of the electric regulating valve is adjusted to change the feed flow rate of the ionic additive.

[0020] Preferably, in the step of introducing the ionic additive into the reactor via the additive feed line, the ionic additive is an aqueous solution containing an alkali metal hydroxide and a phase transfer catalyst.

[0021] Preferably, in the ionic auxiliaries, the mass concentration of the alkali metal hydroxide is 10% to 50%, and the mass concentration of the phase transfer catalyst is 0.05% to 0.5%; the alkali metal hydroxide is selected from sodium hydroxide or potassium hydroxide, and the phase transfer catalyst is selected from tetrabutylammonium hydroxide or tetrabutylammonium bromide.

[0022] Preferably, prior to the step of introducing the C8 heavy component containing n-butyl butyrate into the reactor via the C8 heavy component feed line, the method further includes:

[0023] The bottom liquid of the de-heavy column in the external butanol production system is obtained as the C8 heavy component; the content of n-butyl butyrate in the C8 heavy component is 75%~80% by mass percentage.

[0024] Preferably, the mass flow rate of the first material stream accounts for 85% to 95% of the total mass flow rate of the material extracted from the bottom outlet of the reactor, and the mass flow rate of the second material stream accounts for 5% to 15% of the total mass flow rate of the material extracted from the bottom outlet of the reactor.

[0025] Preferably, when the discharge pH value deviates from the preset range, the opening of the electric regulating valve is adjusted to change the feed flow rate of the ionic additive, specifically including:

[0026] When the pH value of the discharged material is lower than the preset range, the control system controls to increase the opening of the electric regulating valve;

[0027] When the pH value of the discharged material is higher than the preset range, the control system controls to reduce the opening of the electric regulating valve.

[0028] Preferably, the preset range is pH 7.5 to 8.5.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] This invention discloses a method for recovering n-butanol from heavy n-butanol components, achieving efficient resource recovery of these components. This method organically combines multiple technologies, including enhanced mechanical stirring, high-flow-rate circulating jet injection, and online pH monitoring and feedback adjustment. It achieves near-complete hydrolysis of n-butyl butyrate under ambient pressure and medium temperature conditions, significantly improving the recovery efficiency and economics of n-butanol. This effectively solves technical problems in traditional processes such as high mass transfer resistance, incomplete reaction, and difficulty in continuous production. By controlling the reaction temperature to 65℃~85℃, the reaction pressure to 0.01MPa~0.05MPa, and setting the feed flow ratio of C8 heavy components to ionic additives to 0.6:1, efficient conversion is achieved under mild operating conditions. This avoids increased energy consumption and safety risks associated with high temperature and high pressure, while optimizing material ratios to reduce raw material consumption and subsequent processing burden. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the process structure of the multicarbon alcohol recombination, hydrolysis and recovery system of the present invention;

[0033] Figure 2 This is a schematic flowchart of the method for recovering n-butanol from n-butanol heavy components according to the present invention;

[0034] In the diagram: 10. Reactor; 20. Mechanical stirring mechanism; 30. Circulating jet circuit; 31. Circulating pump; 32. Circulating heater; 33. Top circulating nozzle; 40. Continuous discharge pipeline; 41. Discharge cooler; 42. Online pH meter; 50. Phase separator; 51. Internal overflow weir plate; 60. C8 heavy component feed pipeline; 70. Additive feed pipeline; 71. Electric regulating valve; 80. Control unit. Detailed Implementation

[0035] The technical solution of the present invention will be further described in detail below through specific embodiments and in conjunction with the accompanying drawings. It should be understood that the implementation of the present invention is not limited to the following embodiments, and any modifications and / or alterations made to the present invention will fall within the protection scope of the present invention.

[0036] In this invention, unless otherwise specified, all parts and percentages are by weight, and the equipment and raw materials used are commercially available or commonly used in the art. Unless otherwise specified, the methods in the following embodiments are conventional methods in the art. Unless otherwise specified, the components or equipment in the following embodiments are general standard parts or components known to those skilled in the art, and their structures and principles can be learned by those skilled in the art through technical manuals or conventional experimental methods.

[0037] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In this detailed description, numerous specific details are set forth to facilitate explanation and provide a thorough understanding of the embodiments of the present invention. However, one or more embodiments may be practiced by those skilled in the art without these specific details.

[0038] Embodiments of the present invention disclose a method for recovering n-butanol from n-butanol heavy components, the method being based on... Figure 1 The polyol heavy component hydrolysis and recovery system shown is in operation. The polyol heavy component hydrolysis and recovery system includes a reaction separation device and a control unit 80. The reaction separation device includes a reactor 10, a phase separator 50, and connecting piping. A mechanical stirring mechanism 20 is installed inside the reactor 10, and a circulating injection circuit 30 and a continuous discharge pipeline 40 are installed outside the reactor 10. The two ends of the circulating injection circuit 30 are connected to the bottom outlet of the reactor 10 and the top circulating nozzle 33 of the reactor 10, respectively. A circulating pump 31 and a circulating heater 32 are sequentially installed on the circulating injection circuit 30 along the material flow direction. One end of the continuous discharge pipeline 40 connects to the pipeline between the outlet of the circulating pump 31 and the circulating heater 32, and the other end of the continuous discharge pipeline 40 is connected to the phase separator 50, which has an internal overflow weir plate 51, via a discharge cooler 41. Reactor 10 is also equipped with a C8 heavy component feed line 60 and an auxiliary agent feed line 70. An electric regulating valve 71 is installed on the auxiliary agent feed line 70, and an online pH meter 42 is installed on the continuous discharge line 40.

[0039] like Figure 2 As shown, the method includes the following steps:

[0040] The C8 heavy component containing n-butyl butyrate is introduced into reactor 10 through C8 heavy component feed line 60, and the ionic additive is introduced into reactor 10 through additive feed line 70. The feed flow ratio of C8 heavy component to ionic additive is controlled by control unit 80 to be 0.6:1.

[0041] The control unit 80 controls the reaction temperature in the reactor 10 to be 65℃~85℃ and the reaction pressure to be 0.01MPa~0.05MPa, and turns on the mechanical stirring mechanism 20 and the circulation pump 31.

[0042] The hydrolysis reaction is carried out under the stirring of the mechanical stirring mechanism 20.

[0043] The material extracted from the bottom outlet of reactor 10 is divided into the first material and the second material.

[0044] The first material enters the circulating injection circuit 30, and after being temperature controlled by the circulating heater 32, it is injected downward into the reactor 10 through the top circulating nozzle 33 at a injection rate of 10t / h to 15t / h.

[0045] The second stream of material enters the continuous discharge pipeline 40, and after being cooled to 30℃~40℃ by the discharge cooler 41, it is sent into the phase separator 50. In the phase separator 50, the second stream of material undergoes static stratification and separation into an organic phase and an aqueous phase. The organic phase overflows through the internal overflow weir plate 51. The separated organic phase is sent to a distillation unit to extract n-butanol, and the separated aqueous phase is sent to an external water treatment system.

[0046] The control unit 80 acquires the discharge pH value measured by the online pH meter 42. When the discharge pH value deviates from the preset range, the opening of the electric regulating valve 71 is adjusted to change the feed flow rate of the ionic additive.

[0047] Based on the above system structure and process flow, the following section further elaborates on the specific operational details of each key step, the key points of parameter control, and the technical effects produced by the synergistic effect of each technical feature.

[0048] Regarding the acquisition and feed control of the C8 heavy component and ionic additives, this embodiment first obtains the bottom liquid of the de-heavy column in the external butanol production system as the C8 heavy component. By mass percentage, the content of n-butyl butyrate in the C8 heavy component is 75%~80%. In conventional processes, this heavy component is usually sold directly as C8 waste liquid or incinerated, resulting in serious resource waste. This invention achieves efficient resource utilization of the high-value-added component by directionally introducing it into a hydrolysis recovery system.

[0049] The ionic auxiliaries are aqueous solutions containing alkali metal hydroxides and phase transfer catalysts. Specifically, the mass concentration of the alkali metal hydroxide is 10%–50%, and the mass concentration of the phase transfer catalyst is 0.05%–0.5%. The alkali metal hydroxide is selected from sodium hydroxide or potassium hydroxide, and the phase transfer catalyst is selected from tetrabutylammonium hydroxide or tetrabutylammonium bromide.

[0050] During the feeding process, the control unit 80 accurately controls the feed flow rate ratio of the C8 heavy component to the ionic auxiliaries to be 0.6:1. This flow rate ratio is set based on the stoichiometric relationship of the n-butyl butyrate saponification reaction, and comprehensively considers the reaction kinetic requirements and actual operating margin to ensure that the alkali solution has an appropriate excess coefficient relative to the ester, which ensures the complete hydrolysis reaction while avoiding increased material consumption and subsequent neutralization burden caused by a large excess of alkali solution.

[0051] Regarding the control of reaction conditions and the conduct of the hydrolysis reaction, the control unit 80 maintains the reaction temperature within the reactor 10 within the range of 65℃ to 85℃ and the reaction pressure within the range of 0.01MPa to 0.05MPa. The selection of these temperature ranges is based on a comprehensive consideration of the kinetic characteristics and thermodynamic equilibrium of the alkaline hydrolysis reaction of n-butyl butyrate. Below 65℃, the reaction rate decreases significantly, making it difficult to meet the efficiency requirements of continuous production; above 85℃, although the reaction rate further increases, energy consumption increases substantially, and the volatility of n-butanol increases, leading to an increase in the gas phase load within the reactor and a decrease in operational stability. Maintaining a slight positive pressure of 0.01MPa to 0.05MPa prevents external air from infiltrating the system and causing oxidation side reactions, and also avoids system pressure fluctuations caused by the vaporization of trace amounts of n-butanol, ensuring operational safety and stability.

[0052] The material extracted from the bottom outlet of reactor 10 enters the circulating injection loop 30 driven by the circulating pump 31, with the mass flow rate of the first stream accounting for 85% to 95% of the total mass flow rate of the material extracted from the bottom outlet of reactor 10. After being heated to the reaction temperature by the circulating heater 32, this first stream of material is injected downwards into reactor 10 through the top circulating nozzle 33 at a high flow rate of 10 to 15 t / h. The high-speed liquid flow ejected from the top circulating nozzle 33 forms a strong shearing reaction with the horizontal rotating flow field created by the mechanical stirring mechanism 20, further breaking down the initially dispersed droplets into smaller sizes, significantly increasing the contact area between the liquid and liquid phases. Simultaneously, the kinetic energy carried by the high-speed jet is converted into turbulent kinetic energy, enhancing the turbulence intensity within reactor 10, reducing the thickness of the mass transfer boundary layer at the phase interface, and thus lowering the mass transfer resistance. The phase transfer catalyst further promotes the transfer of hydroxide ions from the aqueous phase to the organic phase, enabling the hydrolysis reaction to proceed efficiently within the organic phase. The synergistic effect of mechanical stirring and cyclic spraying increases the hydrolysis rate of n-butyl butyrate compared to single stirring conditions.

[0053] Regarding the continuous discharge and phase separation process, the mass flow rate of the second stream of material accounts for 5% to 15% of the total mass flow rate of the material extracted from the bottom outlet of reactor 10. This second stream of material enters the continuous discharge pipeline 40. This flow rate ratio ensures sufficient material residence time within reactor 10 to guarantee the full progress of the hydrolysis reaction, while simultaneously enabling continuous product extraction and maintaining steady-state operation of the system. The second stream of material is rapidly cooled to 30°C to 40°C by the discharge cooler 41. This temperature is significantly lower than the reaction temperature, causing the hydrolysis reaction to terminate quickly and preventing further reaction within the discharge pipeline and phase separator 50, thus ensuring the stability of the phase composition.

[0054] After cooling, the material enters the phase separator 50 for settling and stratification. The phase separator 50 is a horizontal gravity settling device with an internal overflow weir 51. Since the density of organic components such as n-butanol and n-butyl butyrate is less than that of the aqueous phase, the upper layer is the organic phase, and the lower layer is the aqueous phase. As the material continuously enters, the liquid level of the upper organic phase gradually rises. When it reaches the height of the internal overflow weir 51, the organic phase automatically overflows through the weir and continuously flows out of the phase separator 50, being sent to a distillation unit for negative pressure extraction of n-butanol. The lower aqueous phase is continuously discharged from the bottom of the phase separator 50 and sent to an external water treatment system for further processing.

[0055] This invention also establishes a feed flow linkage control mechanism based on online monitoring of the discharge pH value. The control unit 80 acquires the discharge pH value measured in real time by the online pH meter 42. This pH value directly reflects the degree of hydrolysis reaction and the consumption of alkali solution within the reactor 10. Theoretically, when n-butyl butyrate is completely hydrolyzed, the alkali solution is completely consumed. However, due to factors such as feed fluctuations and temperature fluctuations in actual operation, maintaining a completely accurate stoichiometric ratio is difficult. This invention sets a preset pH range of 7.5~8.5, which is slightly alkaline, indicating that the hydrolysis reaction is just complete. When the discharge pH value is below 7.5, it indicates insufficient alkali solution and incomplete hydrolysis reaction. At this time, the control unit 80 controls to increase the opening of the electric regulating valve 71, increasing the feed flow rate of the ionic additive and supplementing the alkali to promote the complete hydrolysis reaction. When the discharge pH value is higher than 8.5, it indicates that there is an excess of alkali solution. At this time, the control unit 80 reduces the opening of the electric regulating valve 71 to decrease the feed flow rate of the ionic additive, avoiding excessive consumption of the additive and increasing the burden on the subsequent water treatment system. This control mechanism uses the discharge pH value as a direct indicator parameter of the reaction process, and regulates the reaction process by adjusting the additive feed flow rate. It effectively overcomes the lag and inaccuracy problems of traditional open-loop operation or indirect parameter control, ensuring that the hydrolysis reaction is always within the optimized operating window, achieving continuous, stable, and efficient operation.

[0056] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for recovering n-butanol from n-butanol heavy components, characterized in that: This method is based on a multi-carbon alcohol heavy component hydrolysis and recovery system, which includes a reaction separation device and a control unit. The reaction separation device includes a reactor, a phase separator, and a connecting pipeline. The reactor is equipped with a mechanical stirring mechanism inside, and a circulating injection loop and a continuous discharge pipeline outside the reactor. The two ends of the circulating injection loop are connected to the bottom outlet of the reactor and the top circulating nozzle of the reactor, respectively. A circulating pump and a circulating heater are sequentially arranged along the material flow direction on the circulating injection loop. One end of the continuous discharge pipeline connects to the pipeline between the outlet of the circulating pump and the circulating heater, and the other end of the continuous discharge pipeline is connected to the phase separator, which has an internal overflow weir, via a discharge cooler. The reactor also has a C8 heavy component feed pipeline and an auxiliary agent feed pipeline. An electric regulating valve is installed on the auxiliary agent feed pipeline, and an online pH meter is installed on the continuous discharge pipeline. The method includes the following steps: The C8 heavy component containing n-butyl butyrate is introduced into the reactor through the C8 heavy component feed pipeline, and the ionic additive is introduced into the reactor through the additive feed pipeline. The feed flow ratio of the C8 heavy component to the ionic additive is controlled to be 0.6:1 by the control unit. The control unit controls the reaction temperature in the reactor to be 65℃~85℃ and the reaction pressure to be 0.01MPa~0.05MPa, and turns on the mechanical stirring mechanism and the circulation pump. The hydrolysis reaction is carried out under the stirring of the mechanical stirring mechanism; The material extracted from the bottom outlet of the reactor is divided into a first stream of material and a second stream of material; The first material enters the circulating injection circuit, and after being temperature controlled by the circulating heater, it is injected downward into the reactor through the top circulating nozzle at a rate of 10t / h to 15t / h. The second material enters the continuous discharge pipeline, is cooled to 30°C~40°C by the discharge cooler, and is then sent into the phase separator. The second material is allowed to stand and separate into an organic phase and an aqueous phase in the phase separator, and the organic phase overflows through the internal overflow weir plate; The separated organic phase is sent to a distillation unit to extract n-butanol, and the separated aqueous phase is sent to an external water treatment system. The control unit acquires the discharge pH value measured by the online pH detector. When the discharge pH value deviates from the preset range, the opening of the electric regulating valve is adjusted to change the feed flow rate of the ionic additive.

2. The method for recovering n-butanol from n-butanol heavy components according to claim 1, characterized in that: In the step of introducing the ionic additive into the reactor via the additive feed line, the ionic additive is an aqueous solution containing an alkali metal hydroxide and a phase transfer catalyst.

3. The method for recovering n-butanol from n-butanol heavy components according to claim 2, characterized in that: In the ionic additive, the mass concentration of the alkali metal hydroxide is 10%~50%, and the mass concentration of the phase transfer catalyst is 0.05%~0.5%; the alkali metal hydroxide is selected from sodium hydroxide or potassium hydroxide, and the phase transfer catalyst is selected from tetrabutylammonium hydroxide or tetrabutylammonium bromide.

4. The method for recovering n-butanol from n-butanol heavy components according to claim 1, characterized in that: Prior to the step of introducing the C8 heavy component containing n-butyl butyrate into the reactor via the C8 heavy component feed line, the method further includes: The bottom liquid of the de-heavy column in the external butanol production system is obtained as the C8 heavy component; the content of n-butyl butyrate in the C8 heavy component is 75%~80% by mass percentage.

5. The method for recovering n-butanol from n-butanol heavy components according to claim 1, characterized in that: The mass flow rate of the first material stream accounts for 85% to 95% of the total mass flow rate of the material extracted from the bottom outlet of the reactor, and the mass flow rate of the second material stream accounts for 5% to 15% of the total mass flow rate of the material extracted from the bottom outlet of the reactor.

6. The method for recovering n-butanol from n-butanol heavy components according to claim 1, characterized in that: When the discharge pH value deviates from the preset range, the opening of the electric regulating valve is adjusted to change the feed flow rate of the ionic additive, specifically including: When the pH value of the discharged material is lower than the preset range, the control system controls to increase the opening of the electric regulating valve; When the pH value of the discharged material is higher than the preset range, the control system controls to reduce the opening of the electric regulating valve.

7. A method for recovering n-butanol from a heavy n-butanol component according to claim 6, characterized in that: The preset range is pH value 7.5~8.5.

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