A method for continuously preparing unsaturated ketones

Abstract

The invention discloses a method for continuously preparing unsaturated ketones, comprising: mixing an alkynol or an enol and an acid, and then introducing the mixture into a pipeline reactor; introducing a portion of alkoxy olefins in sections along the extension direction of the pipeline reactor to react and generate the unsaturated ketones; the pipeline reactor comprises a plurality of sub-pipeline reaction units connected in series, each sub-pipeline reaction unit independently comprising a circulating reaction pipe section and a tubular reaction section that are connected in sequence; the circulating reaction pipe section can circulate a portion of the reaction material to its own feed port, with a circulation ratio of 6-20; the residence time of the reaction material in the tubular reaction section is 5-20 times the residence time in the circulating reaction pipe section; a preset position for introducing a portion of the alkoxy olefin is provided on the feed port side of each circulating reaction pipe section. The method can not only significantly reduce the amount of alkoxy olefins used, but also significantly reduce the self-polymerization of the alkoxy olefins, reduce by-product heavy components, and is simple and easy to operate, with high conversion rate and selectivity.

Description

Technical Field

[0001] The present invention relates to the technical field of fine chemicals, and in particular to a method for continuously preparing unsaturated ketones. Background Art

[0002] Unsaturated ketones are important intermediates for the synthesis of flavors and fragrances, pharmaceuticals, and vitamins. For example, pseudoionone is an important raw material for the synthesis of flavors and fragrances such as ionone, and is also an intermediate for the synthesis of vitamin A, vitamin E, phytol, and β-carotene. Due to the important applications of pseudoionone in flavors and fragrances, pharmaceuticals, food additives, and synthetic chemistry, domestic and foreign scholars have been continuously researching and improving the synthesis process of pseudoionone. Currently, the synthesis methods of pseudoionone mainly include:

[0003] (1) Dehydrolinalool and methyl acetoacetate undergo Carroll rearrangement under the catalysis of aluminum isopropoxide to form allenone, which is then isomerized to form pseudoionone. This method is mature and has stable production, but the reaction temperature is high, carbon dioxide is generated as a byproduct during the reaction, and the atom economy is poor. In addition, methyl acetoacetate is expensive, which makes the cost high and reduces the competitiveness of this method.

[0004] (2) Dehydrolinalool and 2-methoxypropylene undergo a Saucy–Marbet reaction under acid catalysis to generate allenone, which is then isomerized under base catalysis to obtain pseudoionone. Although the raw materials of this method are relatively cheap and readily available, and the by-product dimethoxypropane can be sold off, it has good economic prospects. However, after the current practice of this method, the conversion rate of dehydrolinalool and the selectivity of allenone need to be improved. In particular, it is difficult to achieve both a high conversion rate of dehydrolinalool and a high selectivity of allenone.

[0005] For example, Chinese patent CN114618418A provides a device for Saucy–Marbet reaction, in which dehydrolinalool and 2-methoxypropylene undergo addition rearrangement reaction in the presence of a catalyst to obtain enone, and heat is removed by adding a large excess of 2-methoxypropylene (MOP) and the generated 2,2-dimethoxypropane (DMOP), while 2-methoxypropylene, 2,2-dimethoxypropane and reaction heat are directly recovered by an ejector for preheating the raw materials; however, since the patent requires 2-methoxypropylene to take away heat during the vaporization process, the amount of 2-methoxypropylene must be greatly excessive, but as described in the patent, the Saucy–Marbet reaction has a fast reaction rate in the initial stage, and the corresponding heat release is large. When the amount of 2-methoxypropylene must be greatly excessive, the process becomes a highly exothermic process, and a large amount of 2-methoxypropylene is released in a short period of time. It is difficult to remove the heat release in time. In particular, in this strong heat release process, practice has shown that excessive 2-methoxypropylene will dimerize during the reaction, and the dimer will react with dehydrolinalool to generate the heavy component 2,8,12-trimethyl-6,7,11-tridecatrien-4-one (referred to as C16 compound), which reduces the yield and purity of the enone and increases the difficulty of separating the heavy component. In addition, the patent utilizes a specific reaction device. During the reaction, the vaporized 2-methoxypropylene needs to pass through the layers of reaction liquid from the bottom to escape from the reaction tower upward. A large amount of vaporized 2-methoxypropylene in a short period of time will push the reaction liquid to overflow rapidly to the overflow port, which actually shortens the residence time. This may reduce the conversion rate of dehydrolinalool. If you want to extend the residence time, you can only increase the height of the reaction tower. The higher the height, the greater the pressure at the bottom. This further causes the problem of excessive load on the feed pump set at the bottom. Summary of the Invention

[0006] The object of the present invention is to overcome one or more deficiencies in the prior art and provide an improved method for continuously preparing unsaturated ketones. The method can not only significantly reduce the amount of alkoxy olefins used, but also significantly reduce the self-polymerization of alkoxy olefins, such as dimerization, thereby greatly reducing the amount of heavy component compounds (2,8,12-trimethyl-6,7,11-tridecatriene-4-one, produced by the reaction of dimers with alkynols or enols), which is beneficial to improving the quality of the final product. At the same time, the operation is relatively simple and easy to implement, and the conversion rate, yield and selectivity are high.

[0007] To achieve the above object, the present invention adopts a technical solution: a method for continuously preparing unsaturated ketones, comprising: using alkynol or enol and alkoxy olefin as raw materials, reacting them under the catalytic action of an acid to produce the unsaturated ketone; further: mixing the alkynol or enol and the acid and passing them into a pipeline reactor;

[0008] The pipeline reactor comprises a plurality of sub-pipeline reaction units connected in series, each of which independently comprises a circulating reaction pipe section and a tubular reaction section that are connected in sequence. The circulating reaction pipe section is capable of circulating part of the reaction material to its own feed port, and the circulation ratio is 6-20; the residence time of the reaction material in the tubular reaction section is controlled to be 5-20 times the residence time in the circulating reaction pipe section;

[0009] A preset position for introducing a portion of the alkoxy olefin is provided on the feed inlet side of each of the circulating reaction tube sections. The portion of the alkoxy olefin is introduced into the reaction material in the pipeline reactor at multiple preset positions in the extension direction of the pipeline reactor, so that the molar ratio of the sum of the portion of the alkoxy olefin introduced at the multiple preset positions to the introduced alkynol or enol meets the preset molar ratio, and the preset molar ratio is controlled to be 2.0-2.5.

[0010] In the prior art, the molar amount of alkoxy olefins used in the preparation of unsaturated ketones is usually more than 3 times, or even more than 5 times, that of alkynols or enols. According to the present invention, the method of the present invention can significantly reduce the amount of alkoxy olefins used.

[0011] According to a preferred and specific aspect of the present invention, the preset molar ratio is 2.1-2.4, that is, the molar amount of the alkoxy olefin used is 2.1-2.4 times that of the alkynol or enol.

[0012] According to some preferred aspects of the present invention, the circulation ratio is 8-13, and the residence time of the reaction materials in the tubular reaction section is controlled to be 5-15 times the residence time in the circulation reaction tube section.

[0013] According to the present invention, the "circulation ratio" in the present invention refers to the volume flow rate of the reaction material circulating in the circulation reaction tube section divided by the volume flow rate of the reaction material leaving the circulation reaction tube section.

[0014] In the present invention, the residence time of the reaction material in the circulating reaction tube section refers to the ratio of the length of the main tube of the circulating reaction tube section (excluding the external circulation tube) to the flow rate of the fresh material entering the circulating reaction tube section (that is, the flow rate of the material flowing out of the circulating reaction tube section and flowing into the tubular reaction section); the external circulation tube in the circulating reaction tube section that circulates part of the reaction material to its own feed inlet can be set to be relatively short and have a very fast material flow rate, and its circulation time is not included in the residence time of the circulating reaction tube section;

[0015] The residence time of the reaction materials in the tubular reaction section refers to the ratio of the length of the tubular reaction section to the flow rate of the materials entering the tubular reaction section (also the flow rate of the materials flowing out of the tubular reaction section).

[0016] According to some preferred aspects of the present invention, the total residence time of the reaction materials in the pipeline reactor is controlled to be 0.5-3.5 hours. Further, the total residence time of the reaction materials in the pipeline reactor is controlled to be 1.5-2.5 hours.

[0017] In some preferred embodiments of the present invention, in each sub-pipeline reaction unit, the residence time of the reaction materials in the circulation reaction pipe section and the tubular reaction section is 2-10 min and 25-50 min, respectively.

[0018] In the present invention, the arrangement of the tubular reaction section can also increase the heat transfer area, which is conducive to timely transfer of heat to the outside, that is, the heat generated by the strong internal heat release can be quickly and promptly conducted away.

[0019] According to some preferred aspects of the present invention, there are 2-8, preferably 3-5, sub-pipeline reaction units.

[0020] According to some preferred aspects of the present invention, the portion of the alkoxy olefin at each of the preset positions is preheated to 60-80°C before addition, the pressure is controlled so that the alkoxy olefin is in a liquid state during feeding, and the set amount of the alkoxy olefin is introduced into the reaction mass by jet injection. In the present invention, the set amount of the alkoxy olefin is introduced into the reaction mass by jet injection, and the reaction materials can be more dispersed under the high pressure of the jet injection (the pressure of the jet injection can be greater than the reaction pressure in the pipeline reactor) and fully mixed. Moreover, since only a portion is added at each preset position, it is easier for the added alkoxy olefin to react with the alkynol or enol, thereby reducing self-polymerization of the alkoxy olefin.

[0021] According to some preferred aspects of the present invention, the difference in the mass of the alkoxy olefin added at each of the preset positions is controlled to be between -5% and 5%, preferably between -2% and 2%. According to a specific aspect of the present invention, the mass of the alkoxy olefin added at each of the preset positions is controlled to be the same.

[0022] According to some preferred aspects of the present invention, the extension path of the tubular reaction section causes the flow direction of the reaction material to change multiple times, and the feed direction of the tubular reaction section is the same as the discharge direction; this method can utilize turbulence to accelerate the mixing and dispersion of materials, which is conducive to obtaining better conversion rate and yield. At the same time, this setting method can reduce the length of the tubular reaction section in the same direction and reduce its space occupancy in the length direction.

[0023] Furthermore, according to some preferred and specific aspects of the present invention, the tubular reaction section is distributed in a multi-stage serpentine shape.

[0024] According to some specific aspects of the present invention, the alkynol or enol is dehydrolinalool, 2-methyl-3-butyn-2-ol, 3-methyl-1-pentyn-2-ol or dehydronerolidol, and the alkoxy olefin is 2-alkoxypropylene, and the 2-alkoxypropylene includes 2-methoxypropylene, 2-ethoxypropylene, 2-propoxypropylene or 2-isopropoxypropylene.

[0025] In some embodiments of the present invention, the alkynol or enol is dehydrolinalool, and the alkoxy olefin is 2-methoxypropylene, and the allenone is prepared according to the reaction formula:

[0026]

[0027] The ketone is then isomerized under base catalysis to obtain pseudoionone.

[0028] When the above-mentioned dehydrolinalool and 2-methoxypropene are used as the reaction raw materials, in the process of preparing the above-mentioned allenone or pseudoionone reported previously, since 2-methoxypropene is generally in excess, and in a large excess, practice has shown that the excess 2-methoxypropene will dimerize during the reaction. The dimer reacts with dehydrolinalool to form a heavy component 2,8,12-trimethyl-6,7,11-tridecatrien-4-one (abbreviated as C16 compound), which is the most important by-product in the process. The reaction process is schematically shown as follows:

[0029]

[0030] When other alkynols, enols, or alkoxyalkenes are used as reaction raw materials, heavy components similar to C16 compounds will be generated, which are not only difficult to separate, affecting product quality, but also increasing production costs.

[0031] According to some preferred aspects of the present invention, the reaction pressure in the pipeline reactor is 0.5-1.2 MPa. Further, in the pipeline reactor, the reaction pressure is preferably 0.7-0.9 MPa.

[0032] According to some preferred aspects of the present invention, in the pipeline reactor, the reaction temperature of the reaction is 80-120° C. Further, in the pipeline reactor, the reaction temperature of the reaction is preferably 105-115° C.

[0033] According to some preferred aspects of the present invention, the mixture of alkynol or enol and acid is preheated to 100-105° C. before being introduced into the pipeline reactor.

[0034] According to some preferred aspects of the present invention, in the pipeline reactor, the molar ratio of the acid to the alkynol or enol in the reaction mass is controlled to be 0.001-0.01:1. Furthermore, in the pipeline reactor, the molar ratio of the acid to the alkynol or enol in the reaction mass is preferably controlled to be 0.001-0.005:1.

[0035] According to some preferred aspects of the present invention, the acid is a combination of one or more selected from methanesulfonic acid, p-toluenesulfonic acid, sulfuric acid and benzenesulfonic acid. Further, the acid preferably comprises sulfuric acid.

[0036] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0037] Based on the defects of the prior art in preparing unsaturated ketones such as pseudoionone, such as the easy generation of a large amount of difficult-to-separate heavy components, high operational difficulty, low conversion rate and selectivity, the present invention innovatively proposes the use of segmented, small-scale, multiple additions of alkoxy olefins, combined with a specific pipeline reactor, to reduce local concentration and reduce the possibility of self-polymerization, disperse the original initial short-term strong exothermic process into multiple areas, and utilize the design of a circulating reaction tube section and a tubular reaction section to enable rapid mixing of materials during the reaction process, slow down the reaction process, remove heat quickly, avoid local "hot spots", thereby greatly improving the conversion rate and significantly reducing the amount of alkoxy olefins used, ultimately achieving significantly improved conversion rate, yield, and selectivity, with the advantages of fewer by-product heavy components and less pollution, and the entire process can be carried out continuously, suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of the process flow apparatus used in the method for continuously preparing unsaturated ketones according to an embodiment of the present invention;

[0039] In the accompanying drawings, 1, catalyst feed pump; 2, alkynol or enol feed pump; 3, sub-pipeline reaction unit; 31, circulating reaction pipe section; 32, tubular reaction section; 4, alkoxy olefin feed pump; 5, first preheater; 6, second preheater; 7, jet ejector; 8, light component removal column; 81, light component outlet pipe; 82, unsaturated ketone outlet pipe;

[0040] Figure 2 This is a gas chromatogram of the post-reaction solution collected in Example 1 of the present invention. The recombinant fraction is C16 compound, with a peak time of 13.008 min;

[0041] Figure 3 This is the mass spectrum of the heavy component C16 compound generated in Example 1 of the present invention, and its molecular weight is 232.2. DETAILED DESCRIPTION

[0042] like Figure 1 As shown, a schematic diagram of a process flow device used in the method for continuously preparing unsaturated ketones in an embodiment of the present invention is provided. The schematic diagram exemplarily shows a pipeline reactor including three sub-pipeline reaction units connected in series, each of which independently includes a circulating reaction pipe section and a tubular reaction section that are connected in sequence;

[0043] The circulating reaction pipe can recycle part of the reaction raw materials to its own feed point, and the circulation ratio is controlled to be 6-20; the length of the tubular reaction section is much longer than the length of the circulating reaction pipe section, and the ratio between the two is controlled to achieve a controllable ratio of the residence time of the reaction materials in the tubular reaction section to the residence time of the reaction materials in the circulating reaction pipe section of 5-20:1;

[0044] In the present invention, by simultaneously controlling the ratio of the circulation ratio to the residence time, not only is the dilution and mixing of the reaction system ensured, that is, sufficient mixing of the catalyst can be achieved, and a strong dispersion and dilution effect on the newly entered alkoxypropylene can be achieved, thereby slowing down the reaction and avoiding the occurrence of local "hot spots"; but the heat dissipation area can also be further increased on the basis of increasing the residence time to ensure complete conversion, which can greatly improve the speed of removing the reaction heat. Furthermore, it was found in practice that if the circulation ratio is too small, it is difficult to play the role of dilution and mixing in the system of the present invention, and the final result is that the content of heavy components in the reaction liquid is relatively high. If the circulation ratio is too large, the load on the pump is large, the energy consumption is high, and it is not conducive to industrial application; if the residence time ratio (residence time in the tubular reaction section / residence time in the circulation reaction section) is small, the flow rate of the reaction material in the main pipe of the circulation reaction section is large. If the main pipe is too long, it takes a long time to drive the large flow rate of material to flow, which will greatly increase the load of the pump and the energy consumption is high. If the residence time ratio is too large, it means that the main pipe of the circulation reaction section is too short, then the reaction degree of the internal reaction material is small in a short time, and the raw material concentration does not decrease significantly. When it circulates back to its own feed inlet and mixes with the newly added raw material, the concentration difference between the two raw materials is small, the dilution degree is low, and the higher raw material concentration will still form a local "hot spot", which will eventually cause the content of heavy components in the reaction liquid to increase.

[0045] At the same time, the alkoxy olefin is added in a segmented, small amount and multiple times manner, with each sub-pipeline reaction unit corresponding to one addition. When there are three sub-pipeline reaction units, the addition is specifically divided into three sections, so that the amount of alkoxy olefin added in each section can be different, preferably controlled within a certain ratio range, for example, the mass difference is controlled to be -5% to 5%, more preferably -2% to 2%, or the amount added in each section is exactly the same; in actual operation, after the alkoxy olefin is preheated, a jet ejector is used to inject a set amount of alkoxy olefin into the reaction material in a jet-jet manner, which can quickly mix the material. In conjunction with the circulating reaction pipe section, the raw materials can be more dispersed and fully mixed in a relatively short time. Moreover, since only a portion is added at each preset position, the added alkoxy olefin can be more easily reacted with the alkynol or enol, thereby reducing the self-polymerization of the alkoxy olefin; wherein the jet ejector can be a Venturi ejector in a Venturi mixer, etc., as long as it can achieve the function of the present invention, its specific structure is not limited;

[0046] According to the above-mentioned method of the present invention, various different methods are used to achieve rapid mixing and dispersion of raw materials, reduce the local concentration of alkoxy olefins, and timely remove heat, which can make temperature control more stable and greatly reduce the amount of alkoxy olefin used. The amount of alkoxy olefin added can be reduced to 2.0-2.5 times that of alkynol or enol. It can also reduce the self-polymerization of alkoxy olefins and the amount of specific heavy components generated (practice has found that in the system of the present invention, when the amount of alkoxy olefin added is significantly excessive, it actually increases by-products). It is beneficial to improve product quality. In addition, the method of the present invention has high conversion rate, high selectivity, simple process, and can save equipment investment costs.

[0047] The following is an example of preparing allenone using dehydrolinalool as an alkynol or enol and 2-methoxypropylene as an alkoxy olefin to further describe the specific process of the present invention:

[0048] like Figure 1As shown, after the catalyst is configured, it is introduced into the first preheater 5 by the catalyst feed pump 1, and dehydrolinalool is introduced into the first preheater 5 by the alkynol or enol feed pump feed pump 2. The two are mixed and preheated in the first preheater 5. After being preheated to the set temperature of 100-105°C, they are introduced into the circulation reaction pipe section 31 of the first-stage sub-pipeline reaction unit 3. A preset position for adding part of 2-methoxypropylene is also provided at the feed port of the circulation reaction pipe section 31. 2-methoxypropylene is pumped into the second preheater 6 by the alkoxy olefin feed pump 4 for preheating and preheating to the set temperature of 60-80°C. Then, the jet ejector 7 is used to add the reaction material from the preset position, and then enters the second preheater together with the catalyst and dehydrolinalool. The circulating reaction pipe section 31 of the first-stage sub-pipeline reaction unit 3 reacts, and part of the mixed material will circulate back to the feed port of the circulating reaction pipe section 31 itself, and the remaining mixed material enters the tubular reaction section 32 of the first-stage sub-pipeline reaction unit 3, continues to react during the circulation process, and then enters the next sub-pipeline reaction unit. The operation process in each sub-pipeline reaction unit is the same until the operation and treatment in the last sub-pipeline reaction unit. After the reaction, the material enters the light removal tower 8 to remove the light components, and the light components are discharged through the light component outlet pipe 81. The extracted product unsaturated ketone, namely allenone, is introduced into the next stage process through the unsaturated ketone outlet pipe 82, for example, it can be used for isomerization reaction to prepare pseudoionone.

[0049] The above scheme is further described below in conjunction with specific examples; it should be understood that these examples are used to illustrate the basic principles, main features and advantages of the present invention, and the present invention is not limited to the scope of the following examples; the implementation conditions adopted in the examples can be further adjusted according to specific requirements, and the implementation conditions not specified are generally the conditions in routine experiments.

[0050] Unless otherwise specified in the following examples, all raw materials were purchased from commercial sources or prepared by conventional methods in the art.

[0051] In the following, the gas chromatography test conditions are as follows: instrument model: Thermo Trace1300; chromatographic column: SE-30 (30m×0.32mm×0.25μm); column temperature: initial temperature 45°C, hold for 4 min, then increase to 160°C at 50°C / min, hold for 24 min; inlet temperature: 280°C; detector type: FID; detector temperature: 280°C; split injection, split ratio 80:1; injection volume: 0.26μL; H2 flow rate: 30mL / min; air flow rate: 400mL / min; carrier gas N2 flow rate: 2mL / min.

[0052] Example 1

[0053] This example provides a method for continuously preparing allenone (allenone 1 in the following reaction formula), using dehydrolinalool and 2-methoxypropylene as raw materials and methanesulfonic acid (AR.) as a catalyst. The reaction formula is:

[0054]

[0055] This method uses Figure 1 In the process flow device shown and the above-mentioned operation process, the molar ratio of dehydrolinalool, 2-methoxypropylene and methanesulfonic acid is 1:2.1:0.002. Specifically, dehydrolinalool and methanesulfonic acid catalyst are first mixed in a molar ratio of 1:0.002, and then preheated to 105°C. The molar ratio of 2-methoxypropylene to dehydrolinalool in the first section is 0.7:1. After being preheated to 70°C, the first section of 2-methoxypropylene enters the pipeline reactor by jet injection through a jet ejector (pressure of 0.9 MPa), and the circulation ratio in the circulation reaction section is 10. Subsequently, 0.7 molar ratio of 2-methoxypropylene was added to the reaction liquid flowing out of the first sub-pipeline reaction unit by jet injection (the conditions were the same as the first section), and the reaction liquid entered the circulation reaction tube section and tubular reaction section of the second sub-pipeline reaction unit again, and 0.7 molar ratio of 2-methoxypropylene was continued to be added to the outflowing reaction liquid by jet injection (the conditions were the same as the first section) and entered the circulation reaction tube section and tubular reaction section of the third sub-pipeline reaction unit; during the reaction process, the reaction pressure was about 0.8 MPa, the reaction temperature was about 110 ° C, and in each sub-pipeline reaction unit, the residence time of the reaction material in the circulation reaction tube section and the tubular reaction section was 3.5 min and 36.5 min, respectively, and the total residence time was 2 h. After the reaction was completed, a sample was taken out from the sampling port, and the product was confirmed to be allenone by gas chromatography analysis. The collected solution was analyzed by gas phase, and the spectrum is shown in FIG. Figure 2 As shown, the conversion rate of dehydrolinalool was 99.6%, the yield of the product allenone 1 was 98.2%, and the heavy component C16 compound (the mass spectrum of the heavy component C16 compound is shown in Figure 3 The content of 1.69% is shown.

[0056] Example 2

[0057] This example provides a method for continuously preparing allenone, which is basically the same as Example 1, except that the molar ratio of dehydrolinalool, 2-methoxypropylene and methanesulfonic acid is 1:2.1:0.001.

[0058] The conversion rate of dehydrolinalool was 99.2%, the yield of the product allenone 1 was 98.7%, and the content of the heavy component C16 compound was 1.18%.

[0059] Example 3

[0060] This example provides a method for continuously preparing allenone, which is basically the same as Example 1, except that the molar ratio of dehydrolinalool, 2-methoxypropylene, and methanesulfonic acid is 1:2.4:0.001, and methoxypropylene is fed in three stages. The molar ratio of the feed amount of 2-methoxypropylene to the amount of dehydrolinalool in each stage is 0.8:1.

[0061] The conversion rate of dehydrolinalool was 99.3%, the yield of the product allenone 1 was 98.1%, and the content of the heavy component C16 compound was 1.80%.

[0062] Example 4

[0063] This example provides a method for continuously preparing allenone, which is basically the same as Example 1, except that sulfuric acid (AR.) is used as a catalyst, and the molar ratio of dehydrolinalool, 2-methoxypropylene, and sulfuric acid is 1:2.1:0.001.

[0064] The conversion rate of dehydrolinalool was 99.5%, the yield of the product allenone 1 was 99.1%, and the content of the heavy component C16 compound was 0.81%.

[0065] Example 5

[0066] This example provides a method for continuously preparing allenone, which is basically the same as Example 4, except that the reaction pressure is about 0.6 MPa.

[0067] The conversion rate of dehydrolinalool was 99.1%, the yield of the product allenone 1 was 98.3%, and the content of the heavy component C16 compound was 1.60%.

[0068] Example 6

[0069] This example provides a method for continuously preparing allenone, which is basically the same as Example 4, except that: in each sub-pipeline reaction unit, the residence time of the reaction material in the circulation reaction pipe section and the tubular reaction section is 2.5 minutes and 27.5 minutes respectively, and the total residence time is 1.5 hours.

[0070] The conversion rate of dehydrolinalool was 98.2%, the yield of the product allenone 1 was 97.9%, and the content of the heavy component C16 compound was 1.96%.

[0071] Example 7

[0072] This example provides a method for continuously preparing allenone, which is basically the same as Example 4, except that: in each sub-pipeline reaction unit, the residence time of the reaction material in the circulation reaction pipe section and the tubular reaction section is 4.5 minutes and 45.5 minutes respectively, and the total residence time is 2.5 hours.

[0073] The conversion rate of dehydrolinalool was 99.4%, the yield of the product allenone 1 was 99.0%, and the content of the heavy component C16 compound was 0.91%.

[0074] Example 8

[0075] This example provides a method for continuously preparing allenone (allenone 2 in the following reaction formula), which is basically the same as Example 4, except that 2-methyl-3-butyn-2-ol and 2-methoxypropylene are used as raw materials, and the molar ratio of 2-methyl-3-butyn-2-ol, 2-methoxypropylene and sulfuric acid is 1:2.1:0.001.

[0076] The reaction formula for the preparation of ketene 2 by the reaction of 2-methyl-3-butyn-2-ol and 2-methoxypropylene is:

[0077]

[0078] The conversion rate of 2-methyl-3-butyn-2-ol was 99.4%, the yield of the product allenone 2 was 98.9%, and the content of heavy components was 0.93%.

[0079] Example 9

[0080] This example provides a method for continuously preparing allenone (allenone 3 in the following reaction formula), which is basically the same as Example 4, except that dehydronerolidol and 2-methoxypropylene are used as raw materials, and the molar ratio of dehydronerolidol, 2-methoxypropylene and sulfuric acid is 1:2.1:0.001.

[0081] The reaction formula for the preparation of allenone 3 by the reaction of dehydronerolidol with 2-methoxypropylene is:

[0082]

[0083] The conversion rate of dehydronerolidol was 99.6%, the yield of the product allenone 3 was 99.0%, and the content of heavy components was 0.88%.

[0084] Example 10

[0085] This example provides a method for continuously preparing allenone, which is basically the same as Example 4, except that dehydrolinalool and 2-ethoxypropylene are used as raw materials, and the molar ratio of dehydrolinalool, 2-ethoxypropylene and sulfuric acid is 1:2.1:0.001.

[0086] The conversion rate of dehydrolinalool was 99.4%, the yield of the product allenone 1 was 99.2%, and the content of heavy components was 0.71%.

[0087] Example 11

[0088] This example provides a method for continuously preparing allenone, which is basically the same as Example 4, except that dehydrolinalool and 2-isopropoxypropylene are used as raw materials, and the molar ratio of dehydrolinalool, 2-isopropoxypropylene and sulfuric acid is 1:2.1:0.001.

[0089] The conversion rate of dehydrolinalool was 99.1%, the yield of the product allenone 1 was 98.5%, and the content of heavy components was 1.37%.

[0090] Example 12

[0091] This example provides a method for continuously preparing allenone, which is basically the same as Example 4, except that the recycle ratio is 6.

[0092] The conversion rate of dehydrolinalool was 98.7%, the yield of the product allenone 1 was 97.83%, and the content of the heavy component C16 compound was 1.34%.

[0093] Example 13

[0094] This example provides a method for continuously preparing allenone, which is basically the same as Example 4, except that the recycle ratio is 13.

[0095] The conversion rate of dehydrolinalool was 99.6%, the yield of the product allenone 1 was 99.15%, and the content of the heavy component C16 compound was 0.74%.

[0096] Example 14

[0097] This example provides a method for continuously preparing allenone, which is basically the same as Example 4, except that the recycle ratio is 16.

[0098] The conversion rate of dehydrolinalool was 99.7%, the yield of the product allenone 1 was 99.2%, and the content of the heavy component C16 compound was 0.70%.

[0099] Example 15

[0100] This example provides a method for continuously preparing allenone, which is basically the same as Example 4, except that: in each sub-pipeline reaction unit, the residence time of the reaction material in the circulating reaction pipe section and the tubular reaction section is 5 minutes and 35 minutes respectively, and the total residence time is 2 hours.

[0101] The conversion rate of dehydrolinalool was 99.5%, the yield of the product allenone 1 was 99.1%, and the content of the heavy component C16 compound was 0.80%.

[0102] Example 16

[0103] This example provides a method for continuously preparing allenone, which is basically the same as Example 4, except that: in each sub-pipeline reaction unit, the residence time of the reaction material in the circulating reaction pipe section and the tubular reaction section is 6.5 minutes and 33.5 minutes respectively, and the total residence time is 2 hours.

[0104] The conversion rate of dehydrolinalool was 99.6%, the yield of the product allenone 1 was 99.05%, and the content of the heavy component C16 compound was 0.82%.

[0105] Example 17

[0106] This example provides a method for continuously preparing allenone, which is basically the same as Example 4, except that: in each sub-pipeline reaction unit, the residence time of the reaction material in the circulating reaction pipe section and the tubular reaction section is 2 minutes and 38 minutes respectively, and the total residence time is 2 hours.

[0107] The conversion rate of dehydrolinalool was 98.2%, the yield of the product allenone 1 was 97.81%, and the content of the heavy component C16 compound was 1.44%.

[0108] Comparative Example 1

[0109] This example provides a method for continuously preparing allenone, which is basically the same as Example 4, except that the recycle ratio is 3.

[0110] The conversion rate of dehydrolinalool was 96.8%, the yield of the product allenone 1 was 94.5%, and the content of the heavy component C16 compound was 4.64%.

[0111] Comparative Example 2

[0112] This example provides a method for continuously preparing allenone, which is basically the same as Example 4, except that: in each sub-pipeline reaction unit, the residence time of the reaction material in the circulating reaction pipe section and the tubular reaction section is 1.5 minutes and 38.5 minutes respectively, and the total residence time is 2 hours.

[0113] The conversion rate of dehydrolinalool was 97.3%, the yield of the product allenone 1 was 95.60%, and the content of the heavy component C16 compound was 4.24%.

[0114] Comparative Example 3

[0115] This example provides a method for continuously preparing allenone, which is basically the same as Example 4, except that the molar ratio of dehydrolinalool, 2-methoxypropylene and sulfuric acid is 1:3.0:0.001.

[0116] The conversion rate of dehydrolinalool was 99.5%, the yield of the product allenone 1 was 96.63%, and the content of the heavy component C16 compound was 2.52%.

[0117] 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.

[0118] 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 continuously preparing unsaturated ketones, the method comprising: Using alkynol or enol and alkoxy olefin as raw materials, reacting under the catalytic action of acid to generate unsaturated ketone, characterized in that the method further includes: The alkynol or enol and the acid are mixed and introduced into a pipeline reactor; The pipeline reactor includes a plurality of sub-pipeline reaction units connected in series, each of which independently includes a circulating reaction pipe section and a tubular reaction section that are connected in sequence. The circulating reaction pipe section can circulate part of the reaction material to its own feed port, and the circulation ratio is 6-20, which refers to the volume flow rate of the reaction material circulating in the circulating reaction pipe section divided by the volume flow rate of the reaction material leaving the circulating reaction pipe section; the residence time of the reaction material in the tubular reaction section is controlled to be 5-20 times the residence time in the circulating reaction pipe section; A preset position for introducing a portion of the alkoxy olefin is provided on the feed inlet side of each of the circulating reaction tube sections. The portion of the alkoxy olefin is introduced into the reaction material in the pipeline reactor at multiple preset positions in the extension direction of the pipeline reactor, so that the molar ratio of the sum of the portion of the alkoxy olefin introduced at the multiple preset positions to the introduced alkynol or enol meets the preset molar ratio, and the preset molar ratio is controlled to be 2.0-2.

5.

2. The method for continuously preparing unsaturated ketones according to claim 1, characterized in that The preset molar ratio is 2.1-2.

4.

3. The method for continuously preparing unsaturated ketones according to claim 1, wherein The circulation ratio is 8-13, and the residence time of the reaction materials in the tubular reaction section is controlled to be 5-15 times the residence time in the circulation reaction tube section.

4. The method for continuously preparing unsaturated ketones according to claim 1 or 3, characterized in that: The total residence time of the reaction materials in the pipeline reactor is controlled to be 0.5-3.5 hours.

5. The method for continuously preparing unsaturated ketones according to claim 4, characterized in that: The total residence time of the reaction materials in the pipeline reactor is controlled to be 1.5-2.5 hours.

6. The method for continuously preparing unsaturated ketone according to claim 1 or 3, characterized in that In each of the sub-pipeline reaction units, the residence time of the reaction material in the circulation reaction pipe section and the tubular reaction section is 2-10 minutes and 25-50 minutes respectively.

7. The method for continuously preparing unsaturated ketones according to claim 1, characterized in that: The number of the sub-pipeline reaction units is 2-8.

8. The method for continuously preparing unsaturated ketones according to claim 7, characterized in that: The number of the sub-pipeline reaction units is 3-5.

9. The method for continuously preparing unsaturated ketones according to claim 1, characterized in that: The alkoxy olefin at each preset position is preheated to 60-80° C. before addition. The pressure is controlled so that the alkoxy olefin is in liquid state during feeding, and the set amount of alkoxy olefin is introduced into the reaction material by jet injection.

10. The method for continuously preparing unsaturated ketones according to claim 1, characterized in that: The difference in mass of the part of the alkoxy olefin added at each of the preset positions is controlled to be between -5% and 5%.

11. The method for continuously preparing unsaturated ketones according to claim 10, characterized in that: The difference in mass of the part of the alkoxy olefin added at each of the preset positions is controlled to be between -2% and 2%.

12. The method for continuously preparing unsaturated ketones according to claim 1, characterized in that: The extension path of the tubular reaction section causes the flow direction of the reaction material to change multiple times, and the feeding direction and the discharging direction of the tubular reaction section are the same; and / or the tubular reaction section is distributed in a multi-stage serpentine shape.

13. The method for continuously preparing unsaturated ketones according to claim 1, characterized in that: The alkynol or enol is dehydrolinalool, 2-methyl-3-butyn-2-ol, 3-methyl-1-pentyn-2-ol or dehydronerolidol, and the alkoxy olefin is 2-alkoxypropylene, which includes 2-methoxypropylene, 2-ethoxypropylene, 2-propoxypropylene or 2-isopropoxypropylene.

14. The method for continuously preparing unsaturated ketones according to claim 1, characterized in that: In the pipeline reactor, the reaction pressure of the reaction is 0.5-1.2 MPa.

15. The method for continuously preparing unsaturated ketones according to claim 14, characterized in that: In the pipeline reactor, the reaction pressure of the reaction is 0.7-0.9 MPa.

16. The method for continuously preparing unsaturated ketones according to claim 1, characterized in that: In the pipeline reactor, the reaction temperature of the reaction is 80-120°C.

17. The method for continuously preparing unsaturated ketones according to claim 16, characterized in that: In the pipeline reactor, the reaction temperature of the reaction is 105-115°C.

18. The method for continuously preparing unsaturated ketones according to claim 1, characterized in that: The mixture of the alkynol or enol and the acid is preheated to 100-105° C. before being introduced into the pipeline reactor.

19. The method for continuously preparing unsaturated ketones according to claim 1, wherein In the pipeline reactor, the molar ratio of the acid to the alkynol or enol in the reaction materials is controlled to be 0.001-0.01:

1.

20. The method for continuously preparing unsaturated ketones according to claim 19, characterized in that In the pipeline reactor, the molar ratio of the acid to the alkynol or enol in the reaction materials is controlled to be 0.001-0.005:

1.

21. The method for continuously preparing unsaturated ketones according to claim 1, wherein The acid is a combination of one or more selected from methanesulfonic acid, p-toluenesulfonic acid, sulfuric acid and benzenesulfonic acid.

22. The method for continuously preparing unsaturated ketones according to claim 21, characterized in that The acid comprises sulfuric acid.

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