A method for the continuous synthesis of dimethylpiperidinyl oxy groups from dimethylpiperidine

Abstract

The present application relates to a kind of dimethylamine piperidine continuous synthesis dimethylamine piperidine method of oxy group, by using reaction raw material mixed solution into continuous flow packed bed reaction zone, i.e.catalyst layer;Reaction temperature is 20-80 ℃, normal pressure, feed liquid is the mixture of dimethylamine piperidine, hydrogen peroxide and deionized water, oxidation is carried out on the catalyst layer of continuous flow packed bed adiabatic reactor to make dimethylamine piperidine into dimethylamine piperidine oxy group, realize the continuous preparation of dimethylamine piperidine oxy group;The obtained reaction liquid is quenched, then filtered to remove solid particle quenching agent, vacuum distillation to remove water and vacuum rectification treatment obtain high-purity dimethylamine piperidine oxy group;The process scheme overcomes the series of deficiencies in the previous preparation process, such as complicated steps, low product purity, low production capacity in unit production time, realizes the continuous preparation of high-purity dimethylamine piperidine oxy group, with the characteristics of efficient, safe, green manufacturing.

Description

Technical Field

[0001] This invention belongs to the field of clean, green, and low-carbon synthesis of high-value-added fine chemicals, and specifically relates to a continuous synthesis method of dimethylamine piperidinyloxy group. Background Technology

[0002] As the world's largest energy consumer, my country's energy reserves are crucial for ensuring national security. Currently, electrochemical energy storage technology is considered the most ideal energy storage method. Compared to the high cost, high toxicity, and low electrochemical activity of traditional inorganic flow battery materials, organic flow batteries offer advantages such as lower cost, higher voltage, better reversibility, and adjustable structure. In particular, organic flow batteries represent a novel type of large-capacity electrochemical energy storage device with the significant characteristic of scalable energy storage. Dimethylamine piperidinyloxy group (DPI) is a promising additive used in the electrolyte of organic flow batteries, significantly improving their charge-discharge performance. It is also widely used in the preparation of redox active materials for TEMPO and its derivatives.

[0003] Based on the unique properties of dimethylamine piperidinyloxy materials in organic flow batteries, numerous reports on the synthesis of dimethylamine piperidinyloxy materials have been published both domestically and internationally. Tobias Janoschka et al. oxidized the nitrogen-oxygen bond in the dimethylamine piperidinium molecule to generate nitric oxide radicals by adding hydrogen peroxide and magnesium sulfate (Angew.chem., 2016, 5, 4427–14430). Schubert et al. oxidized dimethylamine piperidinium by adding sodium tungstate, disodium ethylenediaminetetraacetate, and hydrogen peroxide (Patent No.: CN108140864B). Rai ner et al. oxidized it by adding sodium bicarbonate, hydrogen peroxide, and repeatedly adjusting the pH with hydrochloric acid to generate nitric oxide radicals (Patent No.: WO2021 / 197877A1).

[0004] The synthesis of dimethylamine piperidinyloxy groups reported above is still a multi-step synthesis method using soluble metal salts as catalysts. These methods have several drawbacks: first, soluble metal ions are difficult to remove from the product, resulting in high metal ion content and affecting product performance; second, the reaction process uses a batch reactor, involves complex steps, high operating costs, and is unsafe and environmentally unfriendly. CN202111202336.2 discloses a method and reaction system for preparing 2,2,6,6-tetramethylpiperidine nitroxide radical compounds and the resulting product. It discloses a method and continuous reaction system for preparing 2,2,6,6-tetramethylpiperidine nitroxide radical compounds using a catalyst containing modified titanium silicate molecular sieves. This catalyst requires loading with metal components such as Ag and Cu, resulting in high cost, and its lifespan was not studied. Furthermore, its raw material is 2,2,6,6-tetramethylpiperidine, which, compared to the dimethylamine piperidinium of this invention, contains more methyl groups, which is more conducive to providing electrons for product synthesis. In addition, all examples added organic solvents to assist the reaction, and magnesium hydroxide catalyst alone can achieve a high yield. In the synthesis of dimethylaminepiperidinyloxy, the starting material is dimethylaminepiperidine, which has a more stable structure but is difficult to oxidize, thus requiring higher catalytic activity. Therefore, developing a continuous process technology for preparing high-purity dimethylaminepiperidinyloxy is key to solving its industrial application. Summary of the Invention

[0005] To address the shortcomings of current dimethylamine piperidinyloxy synthesis processes, such as difficulty in removing metal ions, low product purity, low yield, and complex preparation steps, this invention discloses a novel method for preparing dimethylamine piperidinyloxy. This technology achieves continuous operation based on high-purity and low-cost synthesis.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] The purpose of this invention is to provide a method for the continuous synthesis of dimethylaminepiperidine from dimethylaminepiperidine, wherein the continuous synthesis apparatus includes a reaction raw material mixing tank, a reactor feed tank, a metering pump, a nitrogen storage tank, a feed preheater, a packed bed insulated reactor, a reactor discharge tank, a reactor discharge pump, a hydrogen peroxide quenching tank, a filter cartridge, a crude reaction liquid tank, a dehydration vacuum distillation column, and a product vacuum distillation purification column;

[0008] The specific steps include: adding dimethylamine piperidine, hydrogen peroxide, and deionized water to the reaction raw material mixing tank, stirring until homogeneous, and then feeding the mixture into the reactor feed tank. The raw material liquid is then pumped into a feed preheater to be preheated to 20-80°C, and together with nitrogen as a carrier gas, enters a packed bed adiabatic reactor. A composite metal oxide solid particle catalyst is pre-installed in the packed bed adiabatic reactor, with a nitrogen flow rate of 1-10 L / min. The oxidation reaction is carried out at atmospheric pressure. The resulting reaction liquid flows into the reactor discharge tank and is then pumped into a hydrogen peroxide quencher, followed by a filter cartridge to remove the solid particle quencher. The filtered liquid is then pumped into a crude reaction liquid tank, where excess water is removed by a vacuum distillation column. The bottom fraction is then purified by a vacuum rectification column to obtain high-purity dimethylamine piperidine oxy group. Preferably, the preheater is set to 40-60°C, and the nitrogen flow rate is 30-80 L / h. This process employs a continuous feeding and discharging method, significantly improving automation and product purity.

[0009] As a further improvement of the present invention, the volumetric hourly space velocity (VSV) of the feed liquid is 0.43-6.17 h⁻¹. -1 Preferably, the volumetric hourly space velocity (VSV) of the feed liquid is 1.29-3.43 h⁻¹. -1 .

[0010] As a further improvement of the present invention, the manganese oxide placed in the hydrogen peroxide quenching tank can be reused, saving costs.

[0011] As a further improvement of the present invention, the molar ratio of dimethylamine piperidine, hydrogen peroxide, and deionized water in the raw material solution is 1:0.5-8:1-20.67. Preferably, the molar ratio of dimethylamine piperidine, hydrogen peroxide, and deionized water in the raw material solution is 1:1-3:2-9.

[0012] As a further improvement of this invention, a porous composite metal oxide solid particle catalyst is pre-installed in the packed bed adiabatic reactor. The synthesis method of the porous composite metal oxide solid particle catalyst is as follows: NaOH and NaAlO2 are dissolved in a 25% tetrapropylammonium hydroxide solution. After the solution becomes clear, fumed silica is gradually added under vigorous stirring. After the fumed silica dissolves, vanadium acetylacetonate dissolved in acetone is added, and the mixture is stirred evenly and then placed in a stainless steel reactor and reacted at 140°C for 2 days (wherein the mass ratio of NaOH, NaAlO2, tetrapropylammonium hydroxide, fumed silica, and vanadium acetylacetonate is 1:0.73:0.86:1.5:0.029). The sample is filtered, washed, dried overnight at 110°C, and calcined at 500°C for 5 hours to obtain a powder sample. This powder is mixed with alumina at a mass ratio of 1:0.3, water is added, and the mixture is stirred and extruded using an extruder. The formed catalyst is dried and calcined to obtain solid granular catalyst, which is then used to fill the packed bed adiabatic reactor.

[0013] As a further improvement of the present invention, the packed bed adiabatic reactor has a cavity structure that supports and fills the solid catalyst particles, allowing the reaction liquid to fully contact and react within the catalyst layer. The packed bed being an adiabatic reactor reduces heat loss during the reaction.

[0014] Beneficial effects:

[0015] (1) Regarding the solvent, this invention uses deionized water as the solvent, which is more convenient, environmentally friendly, and cost-effective. This invention designs a special reaction process based on the specific characteristics of the reaction, achieving a high degree of automation throughout the production process, and ensuring continuous production. Nitrogen purging can rapidly drive the reaction. Regarding catalyst preparation, the raw materials used in this invention are inexpensive, the synthesis method is simple, and the catalyst has high catalytic activity. Ultimately, the reactant dimethylamine piperidine is completely converted, the selectivity of the target product is greater than 98%, the product yield is high (greater than 98%), and the product contains no impurities such as metal ions, exhibiting high purity.

[0016] (2) The manganese oxide solid particle quencher in the hydrogen peroxide degradation tank can be reused, which is green, environmentally friendly and economical. This technology facilitates the production of high-purity dimethylamine piperidinyloxy group, and can achieve stable and continuous feeding and discharging, thereby improving production efficiency. Attached Figure Description

[0017] Figure 1 This is a simplified process diagram for the preparation of high-purity dimethylaminepiperidine oxy groups by continuous flow oxidation of dimethylaminepiperidine according to the present invention.

[0018] Figure 2 The selectivity of the target product obtained by analyzing the crude reaction solution within 120 weeks in Example 1 of this invention.

[0019] Explanation of reference numerals in the attached figures:

[0020] 1. Reactant feed tank; 2. Reactor feed tank; 3. Nitrogen storage tank; 4. Metering pump; 5. Packed bed insulated reactor; 6. Reactor discharge tank; 7. Reactor discharge pump; 8. Hydrogen peroxide quenching tank; 9. Feed pump; 10. Filter cartridge; 11. Crude reaction liquid tank; 12. Distillation column feed pump; 13. Product distillation column; 14. Feed preheater; 15. Refining column feed pump; 16. Product refining column. Detailed Implementation

[0021] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0022] Preparation method of composite metal oxide solid particle catalyst: 4 kg NaOH and 6 kg NaAlO2 were dissolved in 70 L tetrapropylammonium hydroxide solution. After the solution became clear, 9 kg of fumed silica was gradually added under vigorous stirring. After the fumed silica dissolved, 1 kg of vanadium acetylacetonate dissolved in acetone was added, and the mixture was stirred for 2 h. The mixture was then placed in a stainless steel reactor and reacted at 140 °C for 2 days. The sample was filtered, washed, dried at 110 °C overnight, and calcined at 500 °C for 5 h to obtain a powder sample. This powder was mixed with alumina at a mass ratio of 1:0.3, water was added, and the mixture was stirred and extruded into particles using an extruder. The formed catalyst was dried and calcined to obtain solid granular catalyst, which was then used to fill a packed bed adiabatic reactor.

[0023] Example 1

[0024] like Figure 1 The technical solution shown involves adding dimethylamine piperidine, hydrogen peroxide (50 wt.), and deionized water to the reaction feed tank 1. The molar ratio of dimethylamine piperidine, hydrogen peroxide (50 wt.), and deionized water in the feed solution is 1:2:3, and the liquid hourly space velocity (LHSV) is 2.36 h⁻¹. -1 After being stirred evenly, the raw material liquid is fed into the reactor feed tank 2, and then fed into the feed preheater 14 via the metering pump 4 for preheating. The preheating temperature in the feed preheater 14 is adjusted to 50°C. At the same time, nitrogen from the nitrogen storage tank 3 enters the feed preheater 14 along with the raw material liquid at a certain flow rate. The raw material liquid is fed into the continuous flow packed bed adiabatic reactor under the condition that the nitrogen purging flow rate is set to 8L / h. The gas-liquid reaction mixture after passing through the preheater enters the packed bed adiabatic reactor 5. The packed bed adiabatic reactor 5 is pre-loaded with a composite metal oxide solid particle catalyst. The oxidation reaction is carried out at the preheated temperature and atmospheric pressure. The resulting reaction liquid flows into the reactor discharge tank 6 and is then fed into the hydrogen peroxide quencher tank 8 via the reactor discharge pump 7. After being filtered by the solid particle quencher via the feed pump 9, it is introduced into the crude reaction liquid tank 11. The crude reaction liquid enters the product distillation column 13 via the distillation column feed pump 12. Water and a small amount of light components are removed at the top of the column. The heavy components at the bottom of the column are fed into the product purification column 16 via the purification column feed pump 15 for vacuum distillation. 99.9% high-purity dimethylamine piperidinyloxy group is obtained at the top of the column.

[0025] The selectivity of the target product in the crude reaction tank was 99.0% as determined by GC. After purification in the purification tower, the purity of dimethylamine piperidinyloxy group reached 99.9%, and the product yield was 98.8% (yield = molar amount of purified product per week / theoretical molar amount of raw material input per week * 100%, yield and purity are average values).

[0026] Example 2

[0027] Other conditions are the same as in Example 1, except that the preheating temperature in the feed preheater is changed to 40°C. The liquid hourly space velocity (LHSV) of the feed is 2.36 h⁻¹. -1 The molar ratio of dimethylamine piperidine, hydrogen peroxide (50 wt.) and deionized water in the feed solution was 1:2:3. The selectivity of the target product in the crude reaction solution was 98.9% as determined by GC. After purification in the purification tower, the purity of dimethylamine piperidine oxy group reached 99.9%, and the product yield was 98.8%.

[0028] Example 3

[0029] Other conditions are the same as in Example 1, except that the preheating temperature in the feed preheater is changed to 60°C. The liquid hourly space velocity (LHSV) of the feed is 2.36 h⁻¹. -1 The molar ratio of dimethylamine piperidine, hydrogen peroxide (50 wt.) and deionized water in the feed solution was 1:2:3. The selectivity of the target product in the crude reaction solution was 98.7% as determined by GC. After purification in the purification tower, the purity of dimethylamine piperidine oxy group reached 99.9%, and the product yield was 98.9%.

[0030] Example 4

[0031] Other conditions were the same as in Example 1, except that the hydrogen peroxide content in the feed solution was changed: the molar ratio of dimethylamine piperidine, hydrogen peroxide (50 wt.), and deionized water in the feed solution was 1:1:2, and the liquid hourly space velocity (LHSV) was 2.36 h⁻¹. -1 The selectivity of the target product in the crude reaction liquid tank was 98.4% as determined by GC. After purification in the purification tower, the purity of dimethylamine piperidinyloxy group reached 99.9%, and the product yield was 98.7%.

[0032] Example 5

[0033] Other conditions were the same as in Example 1, except that the hydrogen peroxide content in the feed solution was changed: the molar ratio of dimethylamine piperidine, hydrogen peroxide (50 wt.), and deionized water in the feed solution was 1:3:4, and the liquid hourly space velocity (LHSV) was 2.36 h⁻¹. -1 The selectivity of the target product in the crude reaction liquid tank was 98.8% as determined by GC. After purification in the purification tower, the purity of dimethylamine piperidinyloxy group reached 99.9%, and the product yield was 98.9%.

[0034] Example 6

[0035] Other conditions were the same as in Example 1, except that the concentration of hydrogen peroxide in the feed solution was changed from 50 wt% to 30 wt%. The molar ratio of dimethylamine piperidine, hydrogen peroxide (30 wt%), and deionized water in the feed solution was 1:2:5.67, and the liquid hourly space velocity (LHSV) was 2.36 h⁻¹. -1The selectivity of the target product in the crude reaction liquid tank was 98.6% as determined by GC. After purification in the purification tower, the purity of dimethylamine piperidinyloxy group reached 99.9%, and the product yield was 98.4%.

[0036] Example 7

[0037] Other conditions were the same as in Example 1, except that the amount of deionized water added to the feed solution was changed: the molar ratio of dimethylamine piperidine, hydrogen peroxide (50 wt.), and deionized water in the feed solution was 1:2:4, and the liquid hourly space velocity (LHSV) was 2.36 h⁻¹. -1 The selectivity of the target product in the crude reaction liquid tank was 98.1% as determined by GC. After purification in the purification tower, the purity of dimethylamine piperidinyloxy group reached 99.9%, and the product yield was 98.5%.

[0038] Example 9

[0039] Other conditions are the same as in Example 1, except that the volumetric hourly space velocity (VHSV) of the feedstock is changed to 1.29 h⁻¹. -1 The molar ratio of dimethylamine piperidine, hydrogen peroxide (50 wt.), and deionized water in the feed solution was 1:2:3. The selectivity of the target product in the crude reaction solution was 98.6% as determined by GC. After purification in the purification tower, the purity of dimethylamine piperidine oxy group reached 99.9%, and the product yield was 98.3%.

[0040] Example 10

[0041] Other conditions are the same as in Example 1, except that the volumetric hourly space velocity (VHSV) of the feedstock is changed to 3.43 h⁻¹. -1 The molar ratio of dimethylamine piperidinium, hydrogen peroxide (50 wt.), and deionized water in the feed solution was 1:2:3. The selectivity of the target product in the crude reaction solution was 98.7% as determined by GC. After purification in the purification tower, the purity of dimethylamine piperidinium oxide reached 99.6%, and the product yield was 98.7%.

[0042] Example 11

[0043] Other conditions were the same as in Example 1, except that the nitrogen purging flow rate was changed to 3 L / h. The molar ratio of dimethylamine piperidine, hydrogen peroxide (50 wt.), and deionized water in the feed solution was 1:2:3. The selectivity of the target product in the crude reaction solution was 98.3% as determined by GC. After purification in the purification tower, the purity of dimethylamine piperidine oxy group reached 99.9%, and the product yield was 98.9%.

[0044] Comparative Example 1

[0045] Other conditions were the same as in Example 1, except that the catalyst was changed to potassium hydroxide solid particles. GC analysis showed a selectivity of 33.4% for the target product. After purification in a purification tower, the purity of dimethylamine piperidinyloxy group reached 71.5%, and the product yield was 28.1%.

[0046] Comparative Example 2

[0047] Other conditions were the same as in Example 1, except that the catalyst was changed to solid sodium bicarbonate particles. GC analysis showed a selectivity of 21.5% for the target product. After purification in a purification tower, the purity of dimethylamine piperidinyloxy group reached 76.5%, and the product yield was 18.2%.

[0048] Although embodiments of the present invention have been described in detail, it should be understood that various changes, substitutions, and modifications can be made to the embodiments of the present invention without departing from the spirit and scope of the invention.

Claims

1. A method for the continuous synthesis of dimethylaminepiperidinyloxy group from dimethylaminepiperidine, characterized in that, The process includes the following steps: using dimethylamine piperidine, hydrogen peroxide, and deionized water as raw materials, and composite metal oxide as a catalyst, a continuous synthesis device containing a packed bed reactor is used to continuously synthesize dimethylamine piperidine oxy groups. The preparation method of the composite metal oxide catalyst is as follows: NaOH and NaAlO2 are weighed and dissolved in tetrapropylammonium hydroxide solution. After the solution is clear, fumed silica is gradually added under strong stirring. After the fumed silica is dissolved, vanadium acetylacetonate dissolved in acetone is added and stirred evenly. The mixture is then placed in a stainless steel reactor and reacted at 140 °C for 2 days. The sample is filtered, washed, dried at 110 °C overnight, and calcined at 500 °C for 5 h to obtain a powder sample.

2. The method for the continuous synthesis of dimethylaminepiperidinyloxy group from dimethylaminepiperidine according to claim 1, characterized in that, The continuous synthesis unit includes a reaction raw material mixing tank, a reactor feed tank, a metering pump, a nitrogen storage tank, a feed preheater, a packed bed insulated reactor, a reactor discharge tank, a reactor discharge pump, a hydrogen peroxide quenching tank, a filter cartridge, a crude reaction liquid tank, a dehydration vacuum distillation column, and a product vacuum distillation purification column. First, dimethylamine piperidine, hydrogen peroxide, and deionized water are added to the raw material mixing tank. After thorough mixing, the raw material liquid is fed into the reactor feed tank and then preheated by a metering pump. Simultaneously, a certain flow rate of nitrogen gas enters the preheater along with the raw material liquid. The gas-liquid reaction mixture after passing through the preheater enters the packed bed adiabatic reactor. The packed bed adiabatic reactor is pre-installed with a composite metal oxide solid particle catalyst, and the oxidation reaction is carried out under normal pressure. The resulting reaction liquid flows into the reactor discharge tank and is then pumped into a hydrogen peroxide quencher. After being filtered by a filter cartridge filter to remove solid particle quenching agent, it is introduced into the crude reaction liquid tank. The crude reaction liquid enters a dehydration vacuum distillation column, where water and other light components are removed at the top. The heavy components at the bottom are fed into a product refining vacuum distillation column for distillation, yielding dimethylamine piperidine oxy group with a purity of over 99.9% at the top.

3. The method for the continuous synthesis of dimethylaminepiperidine from dimethylaminepiperidine according to claim 1, characterized in that, The mass ratio of NaOH, NaAlO2, tetrapropylammonium hydroxide, fumed silica, and vanadium acetylacetone is 1:0.73:0.86:1.5:0.

029. The powder is mixed with aluminum oxide at a mass ratio of 1:0.3, water is added and stirred, and the mixture is extruded into strips using an extruder. The formed catalyst is then dried and calcined to obtain a solid granular catalyst.

4. The method for the continuous synthesis of dimethylaminepiperidine from dimethylaminepiperidine as described in claim 2, characterized in that, The volumetric hourly space velocity (VSV) of the feed liquid is 0.43-6.17 h⁻¹. -1 .

5. The method for the continuous synthesis of dimethylaminepiperidine from dimethylaminepiperidine as described in claim 2, characterized in that, The solid particulate quencher placed in the hydrogen peroxide quenching tank is recyclable manganese oxide.

6. The method for the continuous synthesis of dimethylaminepiperidine from dimethylaminepiperidine according to claim 1, characterized in that, The molar ratio of dimethylamine piperidine, hydrogen peroxide and deionized water in the feed solution is 1:0.5-8:1-20.

67.

7. The method for the continuous synthesis of dimethylaminepiperidine from dimethylaminepiperidine according to claim 2, characterized in that, The preheater is preheated to 20-80℃, and the nitrogen flow rate is 1-10 L / min.

Images