Method for continuous reaction of cyclopentanone and C4-C8 aldehyde

Abstract

The invention discloses a method for continuous reaction of cyclopentanone and C4-C8 aldehyde. The method comprises the following steps: 1) mixing a mixed solution of cyclopentanone and C4-C8 aldehyde with a first alkali solution in a first microporous disperser to obtain a reaction raw material, and reacting the reaction raw material in a first pipeline reactor; (2) mixing the reaction system obtained in the step (1) with a second alkali solution in a second microporous disperser, and reacting in a second pipeline reactor; and 3) mixing the reaction system obtained in the step 2) with a third alkali solution in a third microporous disperser, and reacting in a third pipeline reactor. According to the method, at least three microporous dispersers and pipeline reactors correspondingly arranged behind the microporous dispersers are arranged, and a catalyst alkali solution is added into a reaction system from different microporous dispersers in batches, so that the reaction has high reaction selectivity, the yield of a target product is high, and continuous production can be realized at relatively low energy consumption.

Description

Technical Field

[0001] The invention relates to a method for continuous reaction of cyclopentanone and C4-C8 aldehyde, belonging to the field of chemical synthesis. Background Art

[0002] Butyl lactone fragrances are important synthetic fragrances. For example, butyl decalactone has a creamy, coconut-, and peach-like fruity aroma. The traditional synthesis of butyl decalactone involves three steps: 1) condensation of cyclopentanone and n-valeraldehyde to form 2-pentylidenecyclopentanone; 2) hydrogenation of 2-pentylidenecyclopentanone in the presence of a catalyst to form 2-pentylcyclopentanone; and 3) Baeyer-Villiger oxidation of 2-pentylcyclopentanone to butyl decalactone.

[0003] In the first condensation reaction of traditional butyl-decanolide synthesis, liquid alkali is often used as a catalyst, and a kettle reaction is adopted. Under the action of the catalyst, cyclopentanone and n-valeraldehyde first generate the intermediate 2-(1-hydroxypentyl)cyclopentanone, which is further dehydrated to generate 2-pentylidenecyclopentanone. Because the reaction raw materials cyclopentanone, n-valeraldehyde, the intermediate 2-(1-hydroxypentyl)cyclopentanone, and the final target product 2-(1-hydroxypentyl)cyclopentanone all contain active groups, cross-condensation between aldehydes and ketones can occur, as well as self-condensation of aldehydes and ketones, resulting in a significant reduction in the selectivity of the target reaction, making it difficult to achieve a high level of reaction selectivity. Especially in kettle reactions, due to the long residence time of the materials in the reaction system, side reactions are greatly exacerbated, further reducing the reaction selectivity. In addition, because the organic phase and the alkali catalyst are immiscible, high-power stirring is required in the kettle reaction to promote mixing of the two, resulting in high energy consumption.

[0004] The difficulty of this reaction is how to achieve high yield and high reaction selectivity in the first step condensation reaction with low energy consumption. Summary of the Invention

[0005] In view of the shortcomings and deficiencies of the prior art, the present invention provides a method for the continuous reaction of cyclopentanone and C4-C8 aldehydes, which can achieve low energy consumption, high reaction selectivity, high yield of the target product, and continuous production.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A method for continuously reacting cyclopentanone and C4-C8 aldehydes, comprising the following steps: 1) mixing a mixed solution of cyclopentanone and C4-C8 aldehydes with a first alkaline solution in a first microporous disperser to obtain a reaction raw material, and reacting the reaction raw material in a first pipeline reactor; 2) mixing the reaction system obtained in step 1) with a second alkaline solution in a second microporous disperser, and then reacting in the second pipeline reactor; and 3) mixing the reaction system obtained in step 2) with a third alkaline solution in a third microporous disperser, and then reacting in a third pipeline reactor.

[0008] In the method of the present invention, the mixed solution of cyclopentanone and C4-C8 aldehyde is used as the continuous phase, and the alkaline solution (as catalyst) is used as the dispersed phase. Since one of the two is an organic phase and the other is an aqueous phase, and the two are immiscible, it is necessary to fully mix the two before reacting, and this fully mixing is achieved in a microporous disperser. In addition, the inventors of the present application have found through research that all catalyst alkaline solutions required for the reaction system are fully mixed with the reaction system in batches, that all alkaline solutions are added in batches from different microporous dispersers, and fully mixed again with the reaction system that has reacted before, and reacted in a subsequent pipeline reactor, so repeatedly reacting the reaction raw materials or the reaction system and the alkaline solution are fully mixed in different multiple microporous dispersers, and reacting in the pipeline reactor corresponding to the multiple microporous dispersers arranged thereafter, the pipeline reactor and the microporous disperser are at least provided with 3, the high reaction selectivity of the aldehyde-ketone condensation reaction of cyclopentanone and C4-C8 aldehyde can be achieved, and the pipeline reactor does not need to be stirred, and energy consumption is low, and continuous production can be achieved. In the mixed solution of cyclopentanone and C4-C8 aldehyde, the initial concentrations of both are high and the reaction activity is high. If all the alkaline solution is added in a single batch, the amount of catalyst is large, which can easily cause the reaction raw materials to undergo self-condensation reaction, resulting in a decrease in the yield of the target product.

[0009] The solubility of a mixture of cyclopentanone and a C4-C8 aldehyde, or a reaction system that has already reacted, in an alkaline solution is low. After being dispersed in each microporous disperser, the two are uniformly mixed, and then the mixed reaction system enters a pipeline reactor for reaction. However, the mixture of cyclopentanone and n-heptanal and the alkaline solution may gradually stratify. When the number of subsequent microporous dispersers is insufficient, the reaction system may experience the aforementioned stratification phenomenon, resulting in a low separation yield of the target product. The present invention uses at least three microporous dispersers and corresponding pipeline reactors arranged thereafter to ensure that the reaction system does not stratify, thereby improving the separation yield of the target product.

[0010] In some embodiments, the pore size of each microporous disperser is 1 to 20 μm.

[0011] In some embodiments, the length of each pipe reactor is 5 to 100 m.

[0012] In some embodiments, the inner diameter of each tube reactor is 1 to 60 mm.

[0013] In some embodiments, the alkali in the first alkaline solution, the second alkaline solution, and the third alkaline solution is selected from a combination of one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate.

[0014] In some embodiments, the mass concentration of the first alkaline solution, the second alkaline solution, and the third alkaline solution are all 0.1-30%.

[0015] In some embodiments, the ratio of the feed volume flow rate of the mixed solution of cyclopentanone and C4-C8 aldehyde to the feed volume flow rate of the first alkaline solution is 1:0.01 to 10, preferably 0.1 to 10. Volume flow rate refers to the volume flowing per unit time.

[0016] In some embodiments, the ratio of the feed volumetric flow rates of the first, second, and third alkaline solutions is 1:0.5-1.5:0.5-1.5. That is, the feed volumetric flow rates of the second and third alkaline solutions can be the same as, greater than, or less than that of the first alkaline solution. In all three cases, the alkaline solutions are added in batches.

[0017] In some embodiments, the feed volumetric flow rates of the first alkaline solution, the second alkaline solution, and the third alkaline solution are the same.

[0018] In some embodiments, the first alkaline solution, the second alkaline solution, and the third alkaline solution are respectively transported by three branch pipelines, and the three branch pipelines are connected to the same main pipeline. That is, multiple alkaline solutions of the present invention can come from the same pipeline, such as a pipeline connected to an alkaline solution storage tank. Of course, multiple alkaline solutions of the present invention can also be independent pipelines, such as independently connected to multiple alkaline solution storage tanks. Preferably, the feed volume flow rate of the first alkaline solution, the second alkaline solution, and the third alkaline solution is the same.

[0019] In some embodiments, the volumetric flow rate of the mixed solution of cyclopentanone and C4-C8 aldehyde is 0.05-100 L / min (e.g., 100, 90, 80, 70, 60, 50, 40, 30, 20, 10, 5, 2, 1 L / min, etc.); the flow rate of the first alkaline solution is 0.02-100 L / min (e.g., 100, 90, 80, 70, 60, 50, 40, 30, 20, 10, 5, 2, 1 L / min, etc.). The volumetric flow rates of the two are related to the diameter of the pipe reactor used subsequently. When the pipe diameter is larger, the volumetric flow rate of the feed will be greater to achieve the same residence time in the pipe reactor.

[0020] In some embodiments, the volume flow rate of the mixed solution of cyclopentanone and C4-C8 aldehyde is 0.05-0.3 L / min; the flow rate of the first alkaline solution is 0.02-0.12 L / min.

[0021] In some embodiments, the C4-C8 aldehyde is selected from one or more of n-butyraldehyde, n-valeraldehyde, n-hexanal, n-heptylaldehyde, and n-octanal.

[0022] In some embodiments, the molar ratio of cyclopentanone to C4-C8 aldehyde is 1:0.1-10.

[0023] In some embodiments, in step 1), the reaction temperature is 40-95°C.

[0024] In some embodiments, in step 2), the reaction temperature is 40-95°C.

[0025] In some embodiments, in step 3), the reaction temperature is 40-95°C.

[0026] In some embodiments, the reaction temperatures of step 1), step 2), and step 3) are the same.

[0027] In some embodiments, the method further comprises, after step 3), repeatedly mixing the reaction system with the alkaline solution in a microporous disperser and conducting the reaction in a pipeline reactor; the total number of microporous dispersers is the same as the total number of pipeline reactors. That is, the present invention may include more than three microporous dispersers and pipeline reactors, and before each reaction in the pipeline reactor, the reaction system is first mixed with additional alkaline solution in a microporous disperser.

[0028] In some embodiments, the total number of the microporous dispersers and the total number of the pipeline reactors are both 3 to 10. With this number, a high yield of the target product can be achieved.

[0029] In some embodiments, the total number of the microporous dispersers and the total number of the pipeline reactors are both 3 to 8. This can further improve the yield of the target product.

[0030] In some embodiments, the flow rate of the alkaline solution into each microporous disperser is the same.

[0031] In some embodiments, the total residence time of the cyclopentanone and the C4-C8 aldehyde in all pipeline reactors is 3 to 30 minutes. This total residence time only counts the time inside the pipeline reactor and does not count the time flowing through the microporous disperser.

[0032] In some embodiments, the method further comprises, after the reaction is completed, performing water-oil separation and rectification on the reaction system to obtain the target aldehyde-ketone condensation product, unreacted cyclopentanone, and C4-C8 aldehyde. The water-oil separation can be performed using a conventional oil-water separator.

[0033] In some embodiments, the method further comprises the steps of recovering the alkaline solution obtained from the water-oil separation and then adding a new alkaline solution to re-enter the reaction system, and recovering the unreacted cyclopentanone and C4-C8 aldehyde and then adding a new cyclopentanone and C4-C8 aldehyde to re-enter the reaction system. Recycling and reusing the reaction raw materials and the catalyst alkaline solution can improve economic efficiency.

[0034] Compared with the prior art, the present invention has the following advantages:

[0035] The present invention provides at least three microporous dispersers and corresponding pipeline reactors provided thereafter, and adds the catalyst alkaline solution into the reaction system in batches from different microporous dispersers, thereby promoting sufficient mixing between the organic phase and the alkaline solution, avoiding side reactions of self-condensation of the reaction raw materials caused by an excessive initial amount of catalyst, greatly reducing the residence time of the materials, and further reducing the cross-condensation of the raw materials, products and intermediates, thereby improving the selectivity of the product and reducing energy consumption.

[0036] The continuous synthesis method of the present invention can realize continuous production and further improve production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Schematic diagram of the process of the method of Example 1 of the present invention;

[0038] Figure 2 Schematic diagram of the process of the method of embodiment 2 of the present invention;

[0039] Figure 3 Schematic diagram of the process of comparative example 1 of the present invention;

[0040] Figure 4 Schematic diagram of the process of comparative example 2 of the present invention. DETAILED DESCRIPTION

[0041] In the present invention, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature specified as "first," "second," or "third" may explicitly or implicitly include at least one of such features.

[0042] In the present invention, the terms "first alkaline solution," "second alkaline solution," and "third alkaline solution" do not necessarily represent differences in composition, for example; they are simply used for ease of description. The three are defined relative to the upstream and downstream directions of the reaction system. The first alkaline solution is located relatively upstream of the reaction system, while the second and third alkaline solutions are located relatively downstream of the first alkaline solution.

[0043] In the present invention, the terms "first microporous disperser," "second microporous disperser," and "third microporous disperser" do not necessarily represent structural differences between the three, for example; they are simply for ease of description. The three are defined relative to the upstream and downstream directions of the reaction system's flow. The first microporous disperser is located relatively upstream of the reaction system, while the second and third microporous dispersers are located relatively downstream of the first microporous disperser.

[0044] The present invention is further described below with reference to the following examples. However, the present invention is not limited to the following examples. The implementation conditions used in the examples may be further adjusted according to the specific requirements of the application. Unspecified implementation conditions are conventional conditions in the industry. The technical features involved in the various embodiments of the present invention may be combined with each other as long as they do not conflict with each other.

[0045] Example 1

[0046] The continuous condensation reaction of cyclopentanone and C4-C8 aldehyde of the present invention is carried out in a pipeline reactor (microchannel reactor). Figure 1As shown. The microporous disperser has a pore diameter of 2 μm, the reaction tube of the pipe reactor has an inner diameter of 3 mm, and the tube length is 30 m. There are five pipe reactors and five microporous dispersers. Cyclopentanone and n-heptanal are added to a separate reactor and thoroughly mixed (the molar ratio of cyclopentanone to n-heptanal is 2.5), then preheated to 70°C. A 0.5% aqueous potassium hydroxide solution (alkaline solution) is prepared and preheated to 70°C. A mixture of cyclopentanone and n-heptanal was pumped into the first microporous disperser as the mobile phase via a horizontal flow pump at a volumetric flow rate of 0.1 L / min. The total feed volumetric flow rate of the alkaline solution was 0.2 L / min, and the feed volumetric flow rate of the alkaline solution into each of the five microporous dispersers was 0.04 L / min. The total residence time of the cyclopentanone and n-heptanal mixture in the pipeline reactor (the total time in the five pipeline reactors, excluding the time spent passing through the five microporous dispersers) was 5.18 minutes. A microporous disperser was placed before each pipeline reactor. After each pipeline reactor reaction, the reaction system was thoroughly mixed with the next batch of alkaline solution in the next microporous disperser before entering the next pipeline reactor to continue the reaction. The temperature of both the pipeline reactor and the microporous disperser was maintained at 70°C. The reaction products were separated in an oil-water separator and quantitatively analyzed using an Agilent 7890 gas chromatograph with an HP-1 column and an FID detector. Chromatographic analysis showed that the crude product contained 46.7% 2-heptylcyclopentanone (the crude product also contained a large amount of excess cyclopentanone). After distillation and purification, the isolated yield of 94.4% 2-heptylcyclopentanone was calculated based on n-heptanal.

[0047] By changing the reaction temperature of the microporous disperser and the pipeline reactor (the reaction temperature is the same for both), while keeping the other reaction conditions unchanged, different reaction data can be obtained. As shown in Table 1, within the temperature range of the present invention, 2-heptylcyclopentanone has a good separation yield.

[0048] Table 1 Effect of temperature on yield

[0049] Reaction temperature (℃) Isolation yield (%) 40 89.7 50 90.8 60 94.2 70 94.4 80 93.2 90 90.6 95 88.7

[0050] By changing the number of pipeline reactors and microporous dispersers (they have the same number, for example, 3 means that 3 pipeline reactors and 3 microporous dispersers are respectively set, and each microporous disperser is correspondingly set before each pipeline reactor), keeping the other reaction conditions unchanged, different reaction data can be obtained.

[0051] As shown in Table 2, the technical solutions with the quantities of 1 and 2 are not the technical solutions of the present invention, but the technical solutions of comparison. As can be seen, when the number of the pipeline reactor and the microporous disperser is 3 to 10 of the present invention, 2-heptylcyclopentanone has a good separation yield, while when the number of the two is 1 or 2, the separation yield of the target product 2-heptylcyclopentanone is significantly lower than that of the present invention. This is because the solubility of the mixed solution of cyclopentanone and n-heptanal in the alkaline solution is low. Although the mixed solution of cyclopentanone, n-heptanal and the alkaline solution are uniformly mixed after being dispersed by the microporous disperser, after the mixed reaction system of the three enters the pipeline reactor, the mixed solution of cyclopentanone, n-heptanal and the alkaline solution may gradually stratify. When the number of subsequent microporous dispersers is not enough, the reaction system will have the aforementioned stratification phenomenon, resulting in a low separation yield of the target product. By adopting the number of the pipeline reactor and the microporous disperser of the present invention, it is possible to ensure that the reaction system is not stratified, thereby improving the separation yield of the target product.

[0052] Table 2 Effect of the number of pipeline reactors and microporous dispersers on yield

[0053] Number of pipeline reactors and microporous dispersers Isolation yield (%) 1 70.6 2 79.9 3 90.2 4 92.1 5 94.4 6 94.2 7 92.6 8 91.7 9 89.9 10 87.2

[0054] By adjusting the feed flow rates of the mobile phase (a mixture of cyclopentanone and n-heptanal) and the dispersed phase (alkaline solution), and varying the residence time while keeping the other reaction conditions unchanged, different reaction data can be obtained. As shown in Table 3, when the present invention is used with a residence time of 3 to 30 minutes, the target product, 2-heptylidenecyclopentanone, is isolated in good yield.

[0055] Table 3 Effect of residence time on yield

[0056] Residence time (minutes) Isolation yield (%) 3.05 90.3 5.18 94.4 10.36 92.2 20.72 88.5 27.94 87.2

[0057] By changing the molar ratio of cyclopentanone to n-heptanal while keeping the other reaction conditions unchanged, different reaction data can be obtained. As shown in Table 4, within the range of 1: (0.1 to 10) of the present invention, 2-heptylcyclopentanone has a good isolation yield.

[0058] Table 4 Effect of the molar ratio of cyclopentanone to n-heptanal on yield

[0059] Molar ratio of cyclopentanone to n-heptanal Isolation yield (%) 7.5 87.4 5 90.1 2.5 94.4 1 92.2 0.75 90.7 0.5 88.9 0.25 88.1

[0060] By changing the type of C4-C8 aldehyde and keeping the other reaction conditions unchanged, different reaction data can be obtained. As shown in Table 5, the products of the present invention have good isolated yields.

[0061] Table 5 Effect of C4-C8 aldehyde types on yield

[0062] aldehyde Isolation yield (%) n-Butyraldehyde 91.1 n-Valeraldehyde 91.7 n-Hexanal 93.8 n-Heptaldehyde 94.4 n-Octanal 93.1

[0063] By varying the ratio of the total flow rate of the mixed solution of cyclopentanone and the C4-C8 aldehyde to the flow rate of the alkaline solution, while keeping the other reaction conditions unchanged, different reaction data can be obtained. As shown in Table 6, within the range of 1: (0.1-10) of the present invention, the product has a good isolated yield.

[0064] Table 6 Effect of the ratio of the feed volume flow rate of cyclopentanone and C4-C8 aldehyde mixture to the feed volume flow rate of each alkaline solution on the yield

[0065] Flow rate ratio of mixed liquid / alkaline solution Isolation yield (%) 7.5 86.2 5 91.2 2.5 94.4 1 90.4 0.75 89.4 0.5 89.1 0.25 87.6

[0066] By changing the volume flow rate of the alkaline solution entering different microporous reactors and keeping the other reaction conditions unchanged, as shown in Table 7, within the scope of the present invention, the products all have good separation yields.

[0067] Table 7 Effect of volume flow rate of alkali solution on yield in different microporous reactors

[0068]

[0069] Example 2

[0070] On the basis of Example 1, the potassium hydroxide aqueous solution is recovered after passing through the oil-water separator. The specific flow diagram is as follows Figure 2 As shown. After titration analysis, the mass concentration of potassium hydroxide in the recovered potassium hydroxide aqueous solution is 0.46%, which is slightly lower than the initial concentration. This is mainly because cyclopentanone and n-heptanal are oxidized to generate a small amount of acidic substances during storage, resulting in potassium hydroxide consumption. Potassium hydroxide is added to adjust the concentration of the recovered potassium hydroxide aqueous solution to 0.5%, and it is returned to the raw material system as a dispersed phase. After distillation separation, the unreacted n-heptanal and cyclopentanone are recovered. The recovered n-heptanal and cyclopentanone are mixed with fresh n-heptanal and cyclopentanone and used as the mobile phase again. The reaction conditions are the same as in Example 1. After chromatographic analysis, the chromatographic content of 2-heptylcyclopentanone in the crude product is 37.0%. After distillation and purification, the separation yield of 2-heptylcyclopentanone calculated based on n-heptanal is 93.9%, which is not much different from the yield in Example 1. It shows that the scheme of the present invention can also recover the catalyst alkaline solution and the unreacted aldehyde and ketone raw materials and reuse them, and can also achieve a high separation yield of the target product.

[0071] Comparative Example 1

[0072] On the basis of Example 1, the alkaline solution is introduced only from the first microporous disperser, and no microporous disperser is provided before the 2nd to 5th pipeline reactors. Other conditions remain unchanged (for example, for 5 pipeline reactors, the flow rate of the alkaline solution entering from the first microporous disperser is the same as the total flow rate of Example 1, 0.2 L / min). The flow diagram is shown as follows: Figure 3 As shown. Chromatographic analysis showed that the mass content of 2-heptylcyclopentanone in the crude product was 24.6%. After distillation and purification, the isolated yield of 2-heptylcyclopentanone calculated based on n-heptanal was 67.7%, which was significantly lower than that in Example 1. This is mainly because the initial concentrations of n-valeraldehyde and cyclopentanone are high and the reaction activity is high. When the alkaline solution is added in a single batch, the amount is large, which easily leads to a self-condensation reaction of the reaction raw materials, resulting in a decrease in the yield of the target product. In addition, in the subsequent pipeline reactor, the mixed solution of cyclopentanone and n-heptanal and the alkaline solution may have been stratified. Therefore, the technical solution of the present invention requires that the alkaline solution enter the reaction system from the microporous disperser in batches.

[0073] Comparative Example 2

[0074] On the basis of Example 1, five microporous dispersers and subsequent pipeline reactors were also set up, but the alkaline solution was only introduced from the first microporous disperser. Before each subsequent reaction in the pipeline reactor, the reaction mixture was introduced into the microporous disperser for multiple dispersions. Other conditions remained unchanged (for example, for five pipeline reactors, the flow rate of the alkaline solution entering from the first microporous disperser was the same as the total flow rate of Example 1, 0.2 L / min). The flow diagram is shown as follows: Figure 4 As shown. Chromatographic analysis showed that the chromatographic content of 2-heptylcyclopentanone in the crude product was 27.8%. After distillation and purification, the isolated yield of 2-heptylcyclopentanone calculated based on n-heptanal was 77.4%, which was significantly lower than that in Example 1. This is mainly because the initial concentrations of n-valeraldehyde and cyclopentanone are high and their activity is high. When the alkaline solution is added in a single batch, the amount is large, which easily causes the reaction raw materials to undergo self-condensation reaction, resulting in a reduced yield of the target product. Therefore, the technical solution of the present invention requires that the alkaline solution be introduced into the reaction system in batches from a microporous disperser.

[0075] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

[0076] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

Claims

1. A method for the continuous reaction of cyclopentanone and a C4-C8 aldehyde, characterized in that: The method comprises the following steps: 1) mixing a mixed solution of cyclopentanone and C4-C8 aldehyde with a first alkaline solution in a first microporous disperser to obtain a reaction raw material, and reacting the reaction raw material in a first pipeline reactor; 2) mixing the reaction system obtained in step 1) with a second alkaline solution in a second microporous disperser, and then reacting in the second pipeline reactor; 3) mixing the reaction system obtained in step 2) with a third alkaline solution in a third microporous disperser, and then reacting in a third pipeline reactor.

2. The method according to claim 1, wherein: The pore size of each microporous disperser is 1 to 20 μm; and / or the length of each pipeline reactor is 5 to 100 m; and / or the inner diameter of each pipeline reactor is 1 to 60 mm.

3. The method according to claim 1, wherein: The alkali in the first alkaline solution, the second alkaline solution, and the third alkaline solution is selected from a combination of one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate; and / or the mass concentration of the first alkaline solution, the second alkaline solution, and the third alkaline solution is 0.1-30%.

4. The method according to claim 1, wherein: The ratio of the feed volume flow rate of the mixed solution of cyclopentanone and C4-C8 aldehyde to the feed volume flow rate of the first alkaline solution is 1:0.01-10; and / or the ratio of the feed volume flow rates of the first alkaline solution, the second alkaline solution, and the third alkaline solution is 1:0.5-1.5:0.5-1.

5.

5. The method according to claim 1, wherein: The first alkaline solution, the second alkaline solution and the third alkaline solution are respectively transported by three branch pipes, and the three branch pipes are connected to the same main pipe; preferably, the feed volume flow rate of the first alkaline solution, the second alkaline solution and the third alkaline solution is the same.

6. The method according to claim 4 or 5, characterized in that: The volume flow rate of the mixed solution of cyclopentanone and C4-C8 aldehyde is 0.05-100 L / min; the flow rate of the first alkaline solution is 0.02-100 L / min.

7. The method according to claim 1, wherein: The C4-C8 aldehyde is selected from a combination of one or more of n-butyraldehyde, n-valeraldehyde, n-hexanal, n-heptanal, and n-octanal; and / or the molar ratio of cyclopentanone to the C4-C8 aldehyde is 1:0.1-10.

8. The method according to claim 1, wherein: In step 1), the reaction temperature is 40-95°C; and / or, in step 2), the reaction temperature is 40-95°C; and / or, in step 3), the reaction temperature is 40-95°C.

9. The method according to claim 1, wherein: The reaction temperatures of step 1), step 2) and step 3) are the same.

10. The method according to claim 1, wherein: The method further comprises, after step 3), repeating the steps of mixing the reaction system with the alkaline solution in a microporous disperser and reacting in a pipeline reactor; the total number of the microporous dispersers is the same as the total number of the pipeline reactors.

11. The method according to claim 10, characterized in that: The total number of the microporous dispersers and the total number of the pipeline reactors are both 3 to 10.

12. The method according to claim 10, wherein: The flow rate of the alkaline solution entering each microporous disperser is the same.

13. The method according to claim 10, wherein: The total residence time of the cyclopentanone and C4-C8 aldehyde in all pipeline reactors is 3 to 30 minutes.

14. The method according to claim 1, wherein: The method further comprises the steps of performing water-oil separation and rectification on the reaction system after the reaction is completed to obtain the target product of aldehyde-ketone condensation, and unreacted cyclopentanone and C4-C8 aldehyde respectively.

15. The method according to claim 14, characterized in that: The method further includes the steps of recovering the alkaline solution obtained from the water-oil separation, adding new alkaline solution to re-enter the reaction system, and recovering the unreacted cyclopentanone and C4-C8 aldehyde, and adding new cyclopentanone and C4-C8 to re-enter the reaction system.

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