Preparation method of sebacic acid

Abstract

The invention provides a preparation method of sebacic acid, which comprises the following steps: in the presence of 1-3 parts of alkali, heating 1 part of reactant from castor oil, and reacting to generate a material flow A containing sebacate and hydrogen; gas-solid separation is carried out on the material flow A to generate a material flow B containing hydrogen and a material flow C containing sebacate, and the material flow B enters a hydrogen energy utilization system; the material flow B enters a heating device through a buffer device to burn the hydrogen; the method comprises the following steps: firstly, adding acid into the material flow C for treatment, acidifying until the pH value is 5-7, then separating by adsorption, acidifying until the pH value is 1-3, and carrying out solid-liquid separation to obtain sebacic acid. According to the invention, the sebacic acid production cost is reduced. By means of combination and cooperation of a plurality of hydrogen recovery steps and system components, safe and reliable recovery and utilization of hydrogen can be achieved even under the condition that the hydrogen production flow changes along with time.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical substance preparation, and particularly relates to a method for preparing sebacic acid. Background Art

[0002] Aliphatic dicarboxylic acids, especially sebacic acid, are important chemical raw materials. For example, sebacic acid is a raw material for producing important industrial products such as nylon, plasticizers and lubricants.

[0003] At present, sebacic acid is usually prepared by the cracking reaction of castor oil or ricinoleic acid under alkaline conditions. The byproducts of this cracking reaction include hydrogen, which has the advantage of high calorific value. However, the safety issues of hydrogen hinder its recovery and utilization. For example, the explosion limit of hydrogen in air is very wide, ranging from 4% to 75%. Therefore, the recycling and utilization of hydrogen faces huge safety risks. This risk is more serious in the case of pipeline pressure changes, because the pressure change may cause air or other oxidizing gases to mix into the hydrogen flow, causing an explosion risk.

[0004] Sebacic acid is usually produced in batch or semi-batch reactors, with the hydrogen production rate varying greatly over time. Sebacic acid can also be produced in continuous reactors: the hydrogen production rate varies during start-up or production capacity changes.

[0005] Given the above, there are currently few concrete and feasible processes to recover and utilize the hydrogen produced during this reaction. Hydrogen is typically vented with other byproducts or burned, such as in a flare that can tolerate variations in hydrogen production flow rates.

[0006] Therefore, it is necessary to provide a method that allows safe and reliable recovery and utilization of hydrogen produced during the preparation of sebacic acid, and the method can utilize the high calorific value of hydrogen, thereby reducing dependence on external fuels. Summary of the invention

[0007] In view of the above defects or deficiencies in the prior art, the present invention provides a method for preparing sebacic acid in order to solve the above problems in the prior art.

[0008] The main technical scheme is: a method for preparing sebacic acid, comprising the following steps:

[0009] Step a), in the presence of 1 to 3 parts of a base, heating 1 part of a reactant derived from castor oil to react, to produce a stream A containing a sebacate and hydrogen;

[0010] Step b), subjecting stream A to gas-solid separation to produce a gas phase stream B containing hydrogen and a solid phase stream C containing sebacate;

[0011] Step c), allowing stream B to pass through a buffer device and enter a heating device to burn hydrogen;

[0012] Step d), purifying stream C to obtain sebacic acid.

[0013] Furthermore, the reactant derived from castor oil is selected from at least one of castor oil, methyl ricinoleate, ricinoleic acid, sodium ricinoleate or potassium ricinoleate.

[0014] Furthermore, the reaction temperature of step a) is 180°C to 400°C, for example, 200°C, 250°C, 300°C, 350°C, 380°C.

[0015] Furthermore, the reaction pressure of step a) is 0.1 kPa to 1000 kPa higher than the atmospheric pressure. In a specific embodiment, for example, it is 2 kPa, 5 kPa, 100 kPa, 500 kPa or 800 kPa higher than the atmospheric pressure.

[0016] Furthermore, the base is selected from NaOH, LiOH or KOH.

[0017] Furthermore, the material stream B also contains by-products 2-octanol and water, and the by-products are separated from the material stream B by a condensation step before step c).

[0018] Furthermore, before performing the condensation step or step c), each device system is flushed with an inert gas.

[0019] Furthermore, before step c), the pressure of the stream B from step b) is increased to 30 kPa to 500 kPa above atmospheric pressure by compression when the reaction pressure is 0.1 kPa to 80 kPa higher than atmospheric pressure, for example, at 2 kPa, 5 kPa, 10 kPa, 50 kPa, specifically maintained at 50 kPa, 80 kPa, 150 kPa or 300 kPa, wherein the condensation step precedes the compression of the stream B.

[0020] Furthermore, before step c), when the reaction pressure of the stream B from step b) is 80 kPa to 1000 kPa higher than the atmospheric pressure, for example, 100 kPa, 150 kPa, 300 kPa, 500 kPa, 800 kPa, the pressure of the stream B is reduced to 30 kPa to 500 kPa above the atmospheric pressure by adjustment, specifically maintained at 50 kPa, 80 kPa, 150 kPa or 300 kPa, and the condensation step precedes the pressure adjustment of the stream B.

[0021] Furthermore, in the step d), the purification treatment method of the material stream C is acidification treatment, first acidifying to a pH of 5 to 7, then separating by adsorption, and then acidifying to a pH of 1 to 3.

[0022] Furthermore, during the operation of the method, the pressure of the production system is maintained at a positive pressure, preferably 0.1 to 1000 kPa.

[0023] The beneficial effects of the present invention are as follows: the present invention recycles the hydrogen generated in the process of preparing sebacic acid, thereby reducing the cost of producing sebacic acid. By utilizing the cooperation of multiple hydrogen recovery steps, safe and reliable recovery and utilization of hydrogen can be achieved even when the hydrogen production flow rate varies over time. The method of the present invention allows the hydrogen from the cracking device to be burned in a burner to directly heat the cracking device, or to be burned in a furnace to heat the heat transfer fluid of the cracking device, thereby at least partially replacing the external fuel used in the heating device supporting the cracking device, such as gas fuel such as natural gas or liquid fuel. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Other features, objects and advantages of the present application will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings:

[0025] Figure 1 It is a schematic diagram of a related system used in one embodiment of the method of the present invention and the device associated therewith;

[0026] The legend of the drawings is as follows:

[0027] 100. Hydrogen recovery system;

[0028] 200. Voltage stabilization control system;

[0029] 1. Condenser;

[0030] 2. Water ring compressor;

[0031] 3. Buffer tank;

[0032] 4. Water seal tank;

[0033] 5. Molten salt furnace;

[0034] 6. Cracking device;

[0035] PIC, pressure indicating controller;

[0036] V1, V2, V3, V4, V5, V6, VN and VT indicate valves;

[0037] P1, P2, P3, P4, PI and PE represent pipes. DETAILED DESCRIPTION

[0038] The present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention. It is also necessary to explain that, for ease of description, only the parts related to the invention are shown in the accompanying drawings.

[0039] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0040] A method for preparing sebacic acid comprises the following steps:

[0041] Step a), in the presence of 1 to 3 parts of a base, reacting 1 part of a reactant derived from castor oil in a cracking device 6 heated by a heating device, wherein a plurality of cracking devices 6 are combined in parallel, and the number of the combined cracking devices 6 is 2 to 100, the reaction temperature is 180°C to 400°C, or preferably 180°C to 250°C, and / or the reaction pressure is 0.1 kPa to 1000 kPa (preferably 2 kPa, 5 kPa, 100 kPa, 500 kPa) higher than the atmospheric pressure, to produce a stream A containing sebacate and hydrogen. The base is selected from NaOH, LiOH or KOH, and the reactant derived from castor oil is selected from castor oil, methyl ricinoleate, ricinoleic acid, sodium ricinoleate or potassium ricinoleate.

[0042] Step b), performing gas-solid separation on stream A to produce stream B containing hydrogen and stream C containing sebacate, wherein stream B enters a hydrogen energy utilization system, which includes a buffer tank and a heating device.

[0043] Step c), transferring stream B to a buffer tank. Transferring stream B from the buffer tank to a heating device to burn hydrogen; used to supplement the heat in step a), reducing production energy consumption.

[0044] Step d), firstly, treating the material stream C with acid to a pH of 5 to 7, then separating it by adsorption, then acidifying it to a pH of 1 to 3, and obtaining sebacic acid by solid-liquid separation.

[0045] The heating device is a burner provided with the cracking device 6, or the heating device comprises a furnace for heating a heat transfer fluid used for heating the cracking device 6, wherein the heat transfer fluid is selected from steam, molten salt or organic heat transfer fluid, wherein the salt used in the molten salt comprises nitrate, such as potassium nitrate. The fuel of the heating device also comprises gaseous fuel, such as natural gas or liquid fuel.

[0046] The material stream B also contains by-product 2-octanol and water, and the by-product is separated from the material stream B by a condensation step before step c). Before step c), the material stream B from step b) is transferred to a liquid ring compressor, wherein the condensation step precedes the transfer of material stream B to the liquid ring compressor, and the working liquid in the liquid ring compressor is water. Preferably, when the reaction pressure is 0.1kPa to 80kPa higher than atmospheric pressure (preferably 2kPa, 5kPa, 10kPa, 50kPa). The pressure of the material stream B before step c) is increased to 30kPa to 500kPa above atmospheric pressure by a liquid ring compressor, preferably 50kPa to 300kPa above atmospheric pressure, specifically 80kPa, 1200kPa, 150kPa or 200kPa.

[0047] Wherein before performing the condensation step or step c), the hydrogen energy utilization system is flushed with an inert gas such as nitrogen.

[0048] Now, the implementation of the method and system of the present invention will be described in detail with reference to the accompanying drawings.

[0049] The accompanying drawing shows, in a non-limiting manner, a system for implementing the method of the invention, including a system for recovering hydrogen 100. The implementation of the method of the invention will be described below in conjunction with the system.

[0050] In step a), reactants comprising castor oil are reacted in the presence of a base in a cracking device 6 heated by a heating device to produce a stream A comprising sebacate and hydrogen.

[0051] In a preferred embodiment, the reaction temperature of step a) may be from 180°C to 400°C, or preferably from 180°C to 250°C.

[0052] In a preferred embodiment, the reaction pressure is 0.1 kPa to 1000 kPa higher than atmospheric pressure, preferably 2 kPa, 5 kPa, 100 kPa, 500 kPa. It has been found that when the reaction pressure is relatively low, the risk of external gas (including oxidizing gas) entering the pipeline in the system of the present invention may increase.

[0053] In a preferred embodiment, the base is selected from NaOH, LiOH or KOH. In a preferred embodiment, the reactant derived from castor oil is selected from castor oil, methyl ricinoleate, ricinoleic acid, sodium ricinoleate or potassium ricinoleate.

[0054] In a preferred embodiment, the reaction is carried out in the presence of a diluent such as mineral or naphthenic oil or a carboxylic acid or a phenolic compound, for example phenol, cresol or xylene.

[0055] In step b), the above-mentioned stream A is separated to produce a stream B containing hydrogen and a stream C containing sebacate, wherein the stream B is intended to enter a hydrogen recovery system 100, which includes a buffer tank 3 and a heating device (e.g., Figure 1 5), wherein the sebacate contained in stream C is preferably selected from lithium sebacate, sodium sebacate or potassium sebacate.

[0056] The hydrogen-containing stream B also contains the by-product 2-octanol and water and, before step c), is treated with Figure 1 Cooler 1 in the process separates the by-products from stream B by a condensation step.

[0057] Before the condensation step or step c), the system is flushed by a subsystem flushed with an inert gas. In this embodiment, valves VN and VT are opened, and an inert gas such as nitrogen is flushed into the hydrogen recovery system 100 until the atmosphere of the hydrogen recovery system is replaced by nitrogen, wherein the nitrogen is introduced from the valve VN and discharged through the valve VT.

[0058] In a preferred embodiment ( Figure 1 ), the reaction pressure is 0.1 kPa to 80 kPa (preferably 2 kPa, 5 kPa, 10 kPa, 50 kPa) higher than the atmospheric pressure. The hydrogen recovery system 100 also includes a liquid ring compressor (e.g., Figure 1 Water ring compressor 2).

[0059] Under the condition that nitrogen keeps passing through, the water ring compressor 2 is started, and the pressure before and after the water ring compressor 2 is kept stable through the adjustment and control of the valves V3, V4 and the PIC pressure indicating controller in the pressure stabilization control system 200.

[0060] Under the condition that the cracking unit 6 continues to operate, the hydrogen-containing stream B is switched from the emission / combustion mode to the recovery and utilization mode. Specifically, the valve V2 on the pipeline P2 is closed, and the valve V1 on the pipeline P1 is opened, wherein the hydrogen recovery system 100 maintains a positive pressure (i.e., the pressure in the system is greater than the external pressure) specifically 0.1 to 1000 kPa, (preferably 2 kPa, 5 kPa, 100 kPa, 500 kPa).

[0061] The material stream B containing hydrogen enters the water ring compressor 2. In this process, the pressure before and after the water ring compressor 2 is kept stable by adjusting and controlling the valves V3, V4 and the PIC pressure indicating controller in the pressure stabilization control system 200. The water ring compressor 2 increases the pressure of the material stream B containing hydrogen to 30 kPa to 500 kPa higher than the atmospheric pressure, preferably 50 kPa to 300 kPa higher than the atmospheric pressure at the compressor outlet (specifically 80 kPa, 1200 kPa, 150 kPa or 200 kPa). Controlling the pressure within this range can prevent leakage of the hydrogen material stream and ensure safety.

[0062] Maintaining the pressure of the water ring compressor 2 stable is very important for the safety of the system. The present invention achieves reliable safety through the pressure stabilizing control system 200 and the water ring compressor 2. When switching the open and closed states of different pipelines, air or other oxidizing gases may enter the pipeline due to instantaneous pressure changes, which will bring safety risks because the explosion limit of hydrogen is very wide. The pressure stabilizing control system 200 can balance the pressure before and after the water ring compressor 2, and the water ring compressor 2 can effectively reduce the risk of sparks during operation. Therefore, the combination of the pressure stabilizing control system 200 and the water ring compressor 2 of the present invention effectively reduces safety risks.

[0063] When implementing step c), the stream B containing hydrogen enters the buffer tank 3. The flow rate of the stream B containing hydrogen flowing out of the buffer tank 3 can be adjusted by valve V5 so that this flow rate and pressure are suitable for combustion in the heating device 5.

[0064] In one embodiment, the buffer tank 3 is a gas storage tank with a variable volume. The pressure in the buffer tank 3 is preferably kept constant. When the flow rate of the material stream B from the cracking device 6 is higher than the flow rate injected in the heating device, the volume of the buffer tank 3 increases. When the flow rate of the material stream B from the cracking device 6 is lower than the flow rate injected in the heating device, the volume of the buffer tank 3 decreases.

[0065] In one embodiment, the buffer tank 3 is a tank with a fixed volume. In this case, the pressure in the buffer tank 3 may vary. When the flow rate of the incoming stream B from the cracking device 6 is higher than the flow rate injected in the heating device, the pressure increases. When the flow rate of the incoming stream B from the cracking device 6 is lower than the flow rate injected in the heating device, the pressure decreases.

[0066] Furthermore, the hydrogen-containing stream B from the buffer tank 3 enters the water seal tank 4 and then enters the heating device 5. The outlet of the pipeline PI entering the water seal tank 4 is located below the water seal liquid level, while the inlet of the pipeline PE leaving the water seal tank is located above the water seal liquid level. The buffer tank 3 keeps the pressure of the front and rear parts of the system stable, and the water seal tank 4 can further reduce the risk of air or oxidizing gas entering the hydrogen recovery system 100 from the outside. Therefore, the combination of the buffer tank 3 and the water seal tank 4 further improves the safety of the hydrogen recovery system 100.

[0067] The stream B containing hydrogen enters the heating device 5 and is burned. The heating device 5 is a burner associated with the cracking device 6, or the heating device comprises a furnace for heating a heat transfer fluid, which heats the cracking device 6.

[0068] In the heating device 5, external fuels such as gaseous fuel natural gas or liquid fuel ( Figure 1 (not shown). Therefore, the stream B containing hydrogen can replace at least a portion of the external fuel, thereby reducing costs. The heat generated by the heating device 5 provides heat for the cracking device 6 to keep the cracking reaction running continuously.

[0069] The heat transfer fluid is selected from steam, molten salt or organic heat transfer fluid. Molten salt includes nitrate, such as potassium nitrate.

[0070] There is no particular restriction on the number of cracking units 6. When a plurality of cracking units 6 are combined in parallel, each unit preferably has its own step a) and step b) and its own condenser.

[0071] In the case of the first embodiment, each cracking unit 6 has its own valves V1 and V2. The hydrogen-comprising streams B from all cracking units 6 are preferably brought together in one single compressor.

[0072] Even when a plurality of cracking units 6 are combined in parallel, there is a buffer tank 3 and, if applicable, a water seal tank 4. All cracking units 6 may use one furnace and distribute the heat transfer fluid to each cracking unit 6. Alternatively, a heating device 5 may be installed for each cracking unit 6.

[0073] In addition, condensate can be recovered from the cooler 1, the water ring compressor 2 and the buffer tank 3, and the condensate includes, for example, water and 2-octanol. Therefore, the cooler 1, the water ring compressor 2 and the buffer tank 3 may be equipped with a pipeline for recovering the condensate ( Figure 1 not shown).

[0074] When carrying out step d), stream C comprising sebacic acid salt is treated to recover sebacic acid.

[0075] In a preferred embodiment, stream C is admixed with an inorganic acid, such as aqueous sulfuric acid or hydrochloric acid, to form sebacic acid.

[0076] In a more preferred embodiment, stream C is first acidified to pH 5-7, then separated by adsorption, then acidified to pH 1-3, and the sebacic acid is separated by solid-liquid separation.

[0077] In the implementation of the present invention, the system 100 for recovering hydrogen should maintain a positive pressure in the range of 0.1 to 1000 kPa, preferably 2 kPa, 5 kPa, 100 kPa, or 500 kPa.

[0078] In an embodiment, the buffer tank 3 allows for coping with upstream hydrogen flow changes or upstream pressure changes, and delivers a stable hydrogen flow and pressure to the heating device for hydrogen combustion. This is key to operating the heating device. In addition, the use of the water seal tank 4 provides additional safety for pressure changes in the system. Preferably, by using the buffer tank 3 and the water seal tank 4 in the above order and / or manner, a reliable circulation of hydrogen can be achieved for the embodiment. In a preferred embodiment, the water seal tank 4 is arranged between the buffer tank 3 and the heating device (such as a furnace), and will prevent possible flashback of the heating device and ignition of the hydrogen in the buffer tank. Therefore, in this preferred embodiment, enhanced safety is achieved.

[0079] With respect to the above-described embodiments and other variations, the present invention can achieve safe and reliable recovery and utilization of hydrogen and reduce the cost of producing sebacic acid.

[0080] The above embodiments do not constitute any limitation to the present invention.

[0081] The following examples further illustrate the present invention by comparison with existing production methods in a non-limiting manner.

[0082] according to Figure 1 The hydrogen recovery method and system of the above-mentioned embodiments are used to implement the production of sebacic acid.

[0083] Example 1

[0084] 1900 kg / h of ricinoleic acid, 1900 kg / h of sodium hydroxide aqueous solution (50%) and 100 kg / h of phenol are injected into the cracking device 6. The temperature in each cracking reactor is maintained at 200°C, and the pressure in the reactor is 30 kPa higher than the atmospheric pressure. The condensed stream containing 2-octanol and water and the uncondensed stream containing hydrogen are collected from the condenser. The liquid output material of the cracking device 6 is first acidified to pH 5-7 with sulfuric acid, and then acidified to pH 1-3 after adsorption separation to form crude sebacic acid. With this production method, when the cracking device 6 is in stable operation at this time, the non-condensable stream containing hydrogen produced is 220 Nm 3 / h, and all are sent to the molten salt furnace 5 for combustion. At this time, compared with the case where all hydrogen-containing non-condensable streams generated by the operation of the cracking unit 6 enter the flare, the natural gas flow rate entering the molten salt furnace 5 is reduced by 75Nm 3 / h.

[0085] Example 2

[0086] 1600 kg / h of ricinoleic acid, 1600 kg / h of sodium hydroxide aqueous solution (50%) and 80 kg / h of phenol are injected into the cracking device 6. The temperature in each cracking reactor is maintained at 200°C, and the pressure in the reactor is 30 kPa higher than the atmospheric pressure. The condensed stream containing 2-octanol and water and the uncondensed stream containing hydrogen are collected from the condenser 1. The liquid output material of the cracking device 6 is first acidified to pH 5-7 with sulfuric acid, and then acidified to pH 1-3 after adsorption separation to form crude sebacic acid. When the cracking device 6 is stably operated at this time, the non-condensable stream containing hydrogen produced is 180 Nm 3 / h, and all are sent to the molten salt furnace 5 for combustion. At this time, compared with the case where all hydrogen-containing non-condensable streams generated by the operation of the cracking unit 6 enter the flare, the natural gas flow rate entering the molten salt furnace 5 is reduced by 65Nm 3 / h.

[0087] Example 3

[0088] 2700 kg / h of ricinoleic acid, 2700 kg / h of sodium hydroxide aqueous solution (50%) and 140 kg / h of phenol are injected into the cracking device 6. The temperature in each cracking reactor is maintained at 200°C, and the pressure in the reactor is 30 kPa higher than the atmospheric pressure. The condensed stream containing 2-octanol and water and the uncondensed stream containing hydrogen are collected from the condenser 1. The liquid output material of the cracking device 6 is first acidified to pH 5-7 with sulfuric acid, and then acidified to pH 1-3 after adsorption separation to form crude sebacic acid. With this production method, when the cracking device 6 is in stable operation at this time, the non-condensable stream containing hydrogen produced is 300 Nm 3 / h, and all are sent to the molten salt furnace 5 for combustion. At this time, compared with the case where all hydrogen-containing non-condensable streams generated by the operation of the cracking unit 6 enter the flare, the natural gas flow rate entering the molten salt furnace 5 is reduced by 100Nm 3 / h.

[0089] In summary, as the non-condensable flow containing hydrogen increases, the natural gas flow rate decreases accordingly. The flow rate of hydrogen is closely related to the feed rate of cracking. As the feed rate increases, the flow rate of hydrogen increases. All the hydrogen produced during normal production can be used.

[0090] When the above examples are implemented, even when the mode is switched or the direction of the material flow is switched, the method of the present invention and the system for recovering hydrogen can maintain effective and safe operation for a long time. This fully proves that the method of the present invention and the hydrogen recovery system can safely and reliably recover and utilize the hydrogen generated during the reaction. On the basis of safe and reliable recovery and utilization of hydrogen, the present invention can effectively utilize the high calorific value of hydrogen, thereby significantly reducing the natural gas flow rate and reducing the production cost of sebacic acid.

[0091] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features are replaced with (but not limited to) technical features with similar functions disclosed in the present application.

Claims

1. A method for preparing sebacic acid, characterized in that: The steps include: Step a), in the presence of 1 to 3 parts of a base, heating 1 part of a reactant derived from castor oil to react, to produce a stream A containing a sebacate and hydrogen; Step b), subjecting stream A to gas-solid separation to produce a gas phase stream B containing hydrogen and a solid phase stream C containing sebacate; Step c), allowing stream B to pass through a buffer device and enter a heating device to burn hydrogen; Step d), purifying stream C to obtain sebacic acid.

2. The method for preparing sebacic acid according to claim 1, wherein: The reactant derived from castor oil is selected from at least one of castor oil, methyl ricinoleate, ricinoleic acid, sodium ricinoleate or potassium ricinoleate.

3. The method for preparing sebacic acid according to claim 1, characterized in that: The reaction temperature of step a) is 180° C. to 400° C.; the reaction pressure of step a) is 0.1 kPa to 1000 kPa higher than the atmospheric pressure.

4. The method for preparing sebacic acid according to claim 1, characterized in that: The base in step a) is selected from NaOH, LiOH or KOH.

5. The method for preparing sebacic acid according to claim 1, characterized in that: Stream B also comprises the by-products 2-octanol and water, which are separated from stream B by a condensation step before step c).

6. The method for preparing sebacic acid according to claim 5, characterized in that: Before performing the condensation step or step c), each device system is flushed with an inert gas.

7. The method for preparing sebacic acid according to claim 5, characterized in that: Prior to step c), the pressure of stream B from step b) is increased to 30 kPa to 500 kPa above atmospheric pressure by compression at a reaction pressure of 0.1 kPa to 80 kPa above atmospheric pressure, wherein the condensation step precedes the compression of stream B.

8. The method for preparing sebacic acid according to claim 5, characterized in that: Prior to step c), the pressure of stream B from step b) is reduced to 30 kPa to 500 kPa above atmospheric pressure by adjusting the reaction pressure of stream B at 80 kPa to 1000 kPa above atmospheric pressure, and the condensation step precedes the pressure adjustment of stream B.

9. The method for preparing sebacic acid according to claim 1, characterized in that: In the step d), the purification treatment of the material stream C is carried out by acidification, firstly acidifying to a pH of 5 to 7, then separating by adsorption, and then acidifying to a pH of 1 to 3.

10. The method for preparing sebacic acid according to claim 1, characterized in that: During operation of the process, the pressure of the production system is maintained at 0.1 to 1000 kPa.

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