A method for the solvent-free synthesis of alkyl enone dimers

Abstract

The application discloses a kind of solvent-free synthesis alkyl enone dimer method, belong to organic synthesis and papermaking auxiliary technical field, the method includes: under inert gas protection, triethylamine is added with seed crystal into reaction vessel, stirring and heating to 50~55 ℃;Stearoyl chloride is added dropwise to the system, and gradient temperature rising reaction is carried out in the process of dropwise addition, and the reaction time is 2~4 hours;The reaction system is heated to 60~70 ℃, and the temperature is kept for 0.5~2 hours;After reaction, heat to 80~90 ℃, filter while hot, and the filtrate is cooled and crystallized to obtain alkyl enone dimer, and the obtained filter residue is used for recycling triethylamine.The synthesis method of the application reduces viscosity by introducing seed crystal method, and the reduction can reach 20%~35%, the energy consumption is reduced by 40% compared with distillation method after simplifying post-processing of hot filtration process.Also, the recovery utilization rate of by-product triethylamine hydrochloride is high, and the raw material cost is reduced.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis and papermaking additives technology, specifically relating to a solvent-free method for synthesizing alkyl ketene dimers. Background Technology

[0002] Currently, traditional methods for synthesizing alkyl ketene dimers (AKD) mainly involve organic solvents such as toluene. These methods generally suffer from problems such as solvent residue pollution, high energy consumption, and complex post-processing. To overcome these drawbacks, solvent-free synthesis processes have gradually gained attention. While these processes offer environmental advantages, they also cause a sharp increase in system viscosity during the reaction, leading to difficulties in mass transfer and affecting reaction efficiency. Furthermore, the byproduct triethylamine hydrochloride readily forms hydrogen bonds with AKD, further exacerbating the viscosity problem.

[0003] To alleviate the problem of excessively high system viscosity, existing technologies have attempted to use tri-n-propylamine instead of the commonly used triethylamine. While this can reduce viscosity to some extent, it significantly increases raw material costs. Furthermore, existing processes often recover excess triethylamine through distillation, a process that is energy-intensive and economically unsound. Therefore, the current field of AKD synthesis still lacks a solvent-free preparation process that is efficient, energy-saving, and easy to operate; improvements and innovations in related technologies are urgently needed. Summary of the Invention

[0004] To overcome the aforementioned technical problems in existing technologies, this invention provides a solvent-free method for synthesizing alkyl ketene dimers. This invention reduces viscosity by 20%–35% through the introduction of seed crystals, simplifies post-processing through hot filtration, and reduces energy consumption by 40% compared to distillation. In terms of economics, the byproduct triethylamine hydrochloride has a high recovery rate, reducing raw material costs.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] In one aspect, the present invention provides a solvent-free method for synthesizing alkyl ketene dimers, comprising the following steps:

[0007] (1) Under the protection of an inert gas, triethylamine and seed crystals are added to a reaction vessel, stirred and heated to 50~55℃;

[0008] (2) Add stearoyl chloride dropwise to the system in step (1) and carry out a gradient temperature increase reaction during the dropwise addition process. The reaction time is 2 to 4 hours.

[0009] (3) Heat the reaction system to 60~70℃ and keep it at that temperature for 0.5~2 hours;

[0010] (4) After the reaction is complete, the temperature is raised to 80~90℃, and the mixture is filtered while hot. The filtrate is cooled and crystallized to obtain alkyl ketene dimer. The resulting filter residue is used to recover triethylamine.

[0011] As a further embodiment of the present invention: the seed crystal is ammonium sulfate and / or sodium chloride.

[0012] As a further aspect of the present invention: in step (1), the amount of seed crystals added is 1% to 5% of the mass of stearoyl chloride;

[0013] And / or, in step (2), the molar ratio of stearoyl chloride to triethylamine is 1:0.5~1.2.

[0014] As a further aspect of the present invention: the gradient heating reaction in step (2) specifically includes:

[0015] First temperature stage: react at 50~55℃ for 0.5~1 hour;

[0016] Second temperature stage: Increase the temperature to 55~58℃ and react for 0.5~1 hour;

[0017] Third temperature stage: raise the temperature to 58~60℃ and react for 1~2 hours.

[0018] As a further embodiment of the present invention, it also includes step (5): treating the filter residue generated in step (4) with an alkaline solution to recover triethylamine.

[0019] The beneficial effects of this invention are as follows:

[0020] (1) The present invention adopts a solvent-free synthesis system, which does not require the addition of organic solvents such as toluene throughout the process, thus avoiding the influence of solvent residue on product purity and the environmental pollution caused by solvent volatilization, which is in line with the development direction of green chemical industry.

[0021] (2) By introducing ammonium sulfate and / or sodium chloride as seed crystals, this invention reduces the viscosity of the reaction system by 20% to 35%, improving mass transfer and mixing during the reaction process and avoiding problems such as local overheating and uneven reaction caused by excessive viscosity. Simultaneously, this invention optimizes the molar ratio of stearoyl chloride to triethylamine and the gradient heating process, resulting in a more complete reaction, a product yield exceeding 97%, and an iodine value stable at 46 to 47 g / 100g. The product quality is superior to that of traditional processes.

[0022] (3) This invention uses a hot filtration process to replace the traditional distillation separation method. After the reaction is completed, the filter is filtered while hot at 80~90℃, which simplifies the post-processing steps, shortens the process flow, and avoids the large amount of energy required for high-temperature distillation. Compared with the distillation method, energy consumption is reduced by about 40%, which reduces production costs.

[0023] (4) The byproduct triethylamine hydrochloride of this invention can be recycled after alkaline treatment, with a recovery rate of over 95%, realizing the recycling of raw materials. This measure reduces waste emissions, lowers the pressure of waste treatment, and also reduces raw material procurement costs, further enhancing the overall resource utilization efficiency of the process. Detailed Implementation

[0024] The present invention is further illustrated below by way of examples, but these examples do not limit the invention to the scope of the embodiments described. Experimental methods in the following examples, unless otherwise specified, were performed according to conventional methods and conditions, or as selected in the product instructions. Furthermore, all reagents and raw materials used in this invention are commercially available.

[0025] Example 1

[0026] A solvent-free method for synthesizing alkyl ketene dimers specifically includes the following steps:

[0027] (1) After purging nitrogen to remove oxygen, 70g (0.692mol) of triethylamine is pumped into the synthesis reactor through a metering pump. The triethylamine is heated to 50°C in a water bath, and 9.52g of ammonium sulfate seed crystals are added.

[0028] (2) Slowly add 190.5g (0.629mol) stearoyl chloride (purity ≥98%) to the system in step (1) and use a gradient temperature increase stepwise: the first stage is 50~55℃ and the reaction is 0.5 hours, the second stage is 55~58℃ and the reaction is 0.5 hours, and the third stage is 58~60℃ and the reaction is 1 hour. The total time for addition and reaction is 2 hours.

[0029] (3) Heat to 65℃ and keep warm for 0.5 hours;

[0030] (4) After the reaction is complete, raise the temperature to 80°C, filter while hot, and cool the filtrate to room temperature to precipitate AKD wax.

[0031] (5) The filter residue is treated with alkaline solution to recover triethylamine.

[0032] Example 2

[0033] A solvent-free method for synthesizing alkyl ketene dimers specifically includes the following steps:

[0034] (1) After purging nitrogen to remove oxygen, 70g (0.692mol) of triethylamine is pumped into the synthesis reactor through a metering pump. The triethylamine is heated to 50°C in a water bath, and 4.76g of ammonium sulfate seed crystals are added.

[0035] (2) Slowly add 190.5g (0.629mol) stearoyl chloride (purity ≥98%) to the system in step (1) and use a gradient temperature increase stepwise: the first stage is 50~55℃ and the reaction is 0.5 hours, the second stage is 55~58℃ and the reaction is 0.5 hours, and the third stage is 58~60℃ and the reaction is 1 hour. The total time for addition and reaction is 2 hours.

[0036] (3) Heat to 65℃ and keep warm for 0.5 hours;

[0037] (4) After the reaction is complete, raise the temperature to 90°C, filter while hot, and cool the filtrate to room temperature to precipitate AKD wax.

[0038] (5) The filter residue is treated with alkaline solution to recover triethylamine.

[0039] Example 3

[0040] A solvent-free method for synthesizing alkyl ketene dimers specifically includes the following steps:

[0041] (1) After purging nitrogen to remove oxygen, 70g (0.692mol) of triethylamine is pumped into the synthesis reactor through a metering pump. The triethylamine is heated to 50°C in a water bath, and 9.98g of ammonium sulfate seed crystals are added.

[0042] (2) Slowly add 199.6 g (0.659 mol) stearoyl chloride (purity ≥98%) to the system in step (1) and use a gradient temperature increase stepwise: the first stage is 50~55℃ and the reaction is 0.5 hours, the second stage is 55~58℃ and the reaction is 0.5 hours, and the third stage is 58~60℃ and the reaction is 1 hour. The total time for addition and reaction is 2 hours.

[0043] (3) Heat to 65℃ and keep warm for 0.5 hours;

[0044] (4) After the reaction is complete, raise the temperature to 85°C, filter while hot, and cool the filtrate to room temperature to precipitate AKD wax.

[0045] (5) The filter residue is treated with alkaline solution to recover triethylamine.

[0046] Example 4

[0047] A solvent-free method for synthesizing alkyl ketene dimers specifically includes the following steps:

[0048] (1) After purging nitrogen to remove oxygen, 70g (0.692mol) of triethylamine is pumped into the synthesis reactor through a metering pump. The triethylamine is heated to 50°C in a water bath, and 10.48g of ammonium sulfate seed crystals are added.

[0049] (2) Slowly add 209.6g (0.692mol) stearoyl chloride (purity ≥98%) to the system in step (1) and use a gradient temperature increase stepwise: the first stage is 50~55℃ and the reaction is 0.5 hours, the second stage is 55~58℃ and the reaction is 0.5 hours, and the third stage is 58~60℃ and the reaction is 1 hour. The total time for addition and reaction is 2 hours.

[0050] (3) Heat to 65℃ and keep warm for 0.5 hours;

[0051] (4) After the reaction is complete, raise the temperature to 90°C, filter while hot, and cool the filtrate to room temperature to precipitate AKD wax.

[0052] (5) The filter residue is treated with alkaline solution to recover triethylamine.

[0053] Comparative Example 1

[0054] A method for synthesizing alkyl ketene dimers specifically includes the following steps:

[0055] (1) After purging with nitrogen to remove oxygen, 70g (0.692mol) of triethylamine was pumped into the synthesis reactor through a metering pump. The triethylamine was heated to 50°C in a water bath, and 190.5g (0.629mol) of stearoyl chloride (purity ≥98%) (molar ratio 1:1.1) was slowly added dropwise over a controlled temperature of 55~60°C for 2 hours.

[0056] (2) The system viscosity is high when heated to 65℃ and held for 0.5 hours, and the torque is 200 N·cm.

[0057] (3) After the reaction is complete, raise the temperature to 90°C, filter while hot, and cool the filtrate to room temperature to precipitate AKD wax.

[0058] Comparative Example 2

[0059] The only difference from Example 1 is that the molar ratio of stearyl chloride to triethylamine in step (2) is 1:1.5.

[0060] Comparative Example 3

[0061] The only difference from Example 1 is that the molar ratio of stearyl chloride to triethylamine in step (2) is 1:0.3.

[0062] Comparative Example 4

[0063] The only difference from Example 1 is that the temperature was kept constant at 55°C during the addition of stearoyl chloride in step (2) and throughout the entire reaction.

[0064] Comparative Example 5

[0065] The only difference from Example 1 is that the ammonium sulfate in step (1) is replaced with the same mass of sodium sulfate.

[0066] Effect Example

[0067] The performance of samples from Examples 1-4 and Comparative Examples 1-5 was tested using the following methods or standards:

[0068] I. Iodine value, tested according to GB / T 27565-2011.

[0069] II. Yield of alkyl ketene dimers, tested according to GB / T 27565-2011.

[0070] 3. Torque: After the heat preservation reaction and before the heating and filtration, the torque value of the system was detected in real time using an IKA LR1000 instrument.

[0071] IV. Viscosity, measured at 60~70℃ using a digital rotational viscometer LVDV-2T from Shanghai Fangrui Instruments Co., Ltd., model No. 4 rotor, at 60 revolutions.

[0072] V. Triethylamine recovery rate: The filter residue was dissolved in alkali and then distilled to recover the triethylamine. The distillation temperature was 85~100℃. The distillate was collected as triethylamine. The mass was recorded and the moisture content was tested before the yield was calculated.

[0073] The samples from Examples 1-4 and Comparative Examples 1-5 were tested, and the test results are shown in Table 1.

[0074] Table 1

[0075]

[0076] As shown in Table 1, all embodiments of the present invention exhibit significant advantages in key performance indicators. Regarding product quality, the iodine values ​​of all embodiments remained stable within the range of 46.12–47.02 g / 100g, significantly higher than Comparative Example 1 (44.01 g / 100g) without seed crystals. In terms of reaction efficiency and economy, the yields of the embodiments were all above 97%, reaching a maximum of 98.36%, significantly better than the comparative examples; simultaneously, the torque of the reaction system was generally below 160 N·cm, with Example 1 having the lowest at 130 N·cm. Compared to Comparative Example 1 (200 N·cm), the system viscosity decreased by up to 35%, effectively improving mass transfer and mixing during the reaction process. Furthermore, the triethylamine recovery rate of all embodiments was not less than 95%, demonstrating the high efficiency of by-product resource utilization and the green and economical nature of the process. Example 1 is the optimal embodiment.

[0077] In summary, this invention, by introducing specific seed crystals into a solvent-free system and optimizing process parameters, improves product quality and reaction efficiency while effectively controlling system viscosity and recycling raw materials, demonstrating excellent comprehensive performance and industrial application potential.

[0078] Finally, it should be noted that in this invention, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0079] Although this disclosure has been described above through specific embodiments, it should be understood that those skilled in the art can devise various modifications, improvements, or equivalents to this disclosure within the spirit and scope of the appended solutions. Such modifications, improvements, or equivalents should also be considered to be included within the scope of protection claimed in this disclosure.

Claims

1. A method for solvent-free synthesis of alkyl ketene dimers, characterized in that, Under solvent-free conditions, the following steps are included: (1) Under the protection of an inert gas, triethylamine and seed crystals are added to a reaction vessel, stirred and heated to 50~55℃; (2) Add stearoyl chloride dropwise to the system in step (1) and carry out a gradient temperature increase reaction during the dropwise addition process. The reaction time is 2 to 4 hours. (3) Heat the reaction system to 60~70℃ and keep it at that temperature for 0.5~2 hours; (4) After the reaction is complete, the temperature is raised to 80~90℃, and the mixture is filtered while hot. The filtrate is cooled and crystallized to obtain alkyl ketene dimer. The resulting filter residue is used to recover triethylamine.

2. The method for solvent-free synthesis of alkyl ketene dimers according to claim 1, characterized in that, The seed crystals are ammonium sulfate and / or sodium chloride.

3. The method for solvent-free synthesis of alkyl ketene dimers according to claim 1, characterized in that, In step (1), the amount of seed crystals added is 1% to 5% of the mass of stearoyl chloride; And / or, in step (2), the molar ratio of stearoyl chloride to triethylamine is 1:0.5~1.

2.

4. The method for solvent-free synthesis of alkyl ketene dimers according to claim 1, characterized in that, The gradient heating reaction described in step (2) specifically includes: First temperature stage: react at 50~55℃ for 0.5~1 hour; Second temperature stage: Increase the temperature to 55~58℃ and react for 0.5~1 hour; Third temperature stage: raise the temperature to 58~60℃ and react for 1~2 hours.

5. The method for solvent-free synthesis of alkyl ketene dimers according to claim 1, characterized in that, It also includes step (5): treating the filter residue generated in step (4) with alkaline solution to recover triethylamine.

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