Method and system for continuous catalytic hydrogenation synthesis of tetramethylpiperidinol

Abstract

The application provides a method and system for continuously catalytically hydrogenating to synthesize tetramethylpiperidinol. The method for continuously catalytically hydrogenating to synthesize tetramethylpiperidinol comprises: continuously feeding tetrahydro-piperidinol solution and hydrogen into a micro-channel reactor for continuously catalytically hydrogenating reaction to obtain tetramethylpiperidinol reaction liquid, and continuously discharging the tetramethylpiperidinol reaction liquid from the micro-channel reactor; wherein the micro-channel reactor is filled with a catalyst. The method for continuously catalytically hydrogenating to synthesize tetramethylpiperidinol provided by the application mixes tetramethylpiperidinol solution and hydrogen in the micro-channel reactor filled with the catalyst for continuously catalytically hydrogenating reaction, breaks the traditional catalytic hydrogenation mode, is higher in mass transfer efficiency, is easier to control in process condition, improves the purity and production capacity of tetrahydro-piperidinol, simultaneously reduces the process of treating the catalyst, reduces energy consumption, and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of catalytic hydrogenation, and more specifically, to a method and system for the continuous catalytic hydrogenation synthesis of tetramethylpiperidinol. Background Technology

[0002] Hindered amine light stabilizers are a new type of highly efficient light stabilizer, particularly suitable for polymer materials such as polyolefins, polystyrene, and polyurethane. They can inhibit or slow down the degradation or aging of polymer materials caused by photo-oxidation, and their effect is several times that of traditional stabilizers.

[0003] Tetramethylpiperidinol is an important intermediate in the synthesis of hindered amine light stabilizers, and can be used to prepare various hindered amine light stabilizers such as UV-622 and UV-770. It is a white crystalline powder at room temperature, soluble in organic solvents such as acetone, ethanol, and chloroform, slightly soluble in water, and hygroscopic. Currently, the main methods reported domestically and internationally for preparing tetramethylpiperidinol from tetramethylpiperidone via reduction are as follows: 1. Catalytic hydrogenation, including pressurized hydrogenation and atmospheric pressure hydrogenation. Currently, pressurized hydrogenation is mainly used in industry; 2. Chemical reduction, using aluminum isopropoxide, sodium borohydride, etc., as reducing agents to reduce tetramethylpiperidone to tetramethylpiperidinol. However, the reducing agents are expensive, and the post-reaction processing is complex, so it is rarely used industrially; 3. Electrochemical reduction, where tetramethylpiperidone is reduced to tetramethylpiperidinol at the cathode of an electrolytic cell. However, due to high energy consumption and complex electrolytic cell structure, this method is generally not used industrially.

[0004] Domestic and international researchers have conducted extensive research on the preparation of tetramethylpiperidinol via catalytic hydrogenation. German researchers used Raney-Ni as a catalyst, with liquid-phase hydrogenation pressures of 0.49-9.8 MPa, achieving piperidinol yields of approximately 95%. Czech researchers reported yields of 86%–93% using Ni / Cr₂O₃ and NiO / Al₂O₃ catalysts, but the reaction conditions were stringent. Ciba reported yields of 91-97% using Ru / C as a catalyst and water as a solvent. Domestic researchers, including Chen Ligong and Zhang Zepeng, have also studied its hydrogenation reduction. Currently, the main drawback of the liquid-phase hydrogenation process is the high cost of the Ru / C catalyst, which hinders industrialization.

[0005] Therefore, those skilled in the art urgently need to develop a method for preparing tetramethylpiperidinol with simple reaction conditions that can be industrially produced. Summary of the Invention

[0006] The main objective of this invention is to provide a method and system for the continuous catalytic hydrogenation synthesis of tetramethylpiperidinol, thereby solving the technical problem that current domestic and foreign researchers use catalytic hydrogenation to prepare tetramethylpiperidinol, but the reaction conditions are harsh when using Ni / Cr2O3 or NiO / Al2O3 as catalysts, and the price of Ru / C as catalysts is expensive, making industrial production impossible.

[0007] To achieve the above objectives, according to one aspect of the present invention, a method for the continuous hydrogenation synthesis of tetramethylpiperidinol is provided, the method comprising: continuously introducing a tetrahydropiperidinol solution and hydrogen gas into a microchannel reactor to carry out a continuous catalytic hydrogenation reaction to obtain a tetramethylpiperidinol reaction solution, and continuously discharging the tetramethylpiperidinol reaction solution from the microchannel reactor; wherein the microchannel reactor is filled with a catalyst.

[0008] Furthermore, the temperature of this continuous catalytic hydrogenation reaction is 40–100°C, preferably 60–80°C.

[0009] Furthermore, the pressure of the hydrogen gas is 1.0 to 5.0 MPa, preferably 2.0 to 3.0 MPa.

[0010] Furthermore, the flow rate of the tetramethylpiperidone solution into the microchannel reactor is 2–10 mL / min, preferably 2–5 mL / min; the retention time of the tetramethylpiperidone solution in the microchannel reactor is 10–50 s, preferably 20–50 s.

[0011] Furthermore, in the tetramethylpiperidone solution, the mass ratio of solvent to tetramethylpiperidone is 1:(2-7), preferably 1:(3-5).

[0012] Furthermore, the solvent is selected from at least one of methanol, ethanol, isopropanol, toluene, xylene or pure water, preferably methanol or ethanol.

[0013] Furthermore, the method for the continuous catalytic hydrogenation synthesis of tetramethylpiperidinol also includes: purifying the tetramethylpiperidinol reaction solution to obtain the tetramethylpiperidinol product.

[0014] Further, the purification process includes sequential solvent removal, crystallization, and solid-liquid separation. The solvent removal process includes: removing the solvent portion from the tetramethylpiperidinol reaction solution to obtain a supersaturated tetramethylpiperidinol mother liquor; the crystallization process includes: cooling and crystallizing the supersaturated tetramethylpiperidinol mother liquor to obtain a tetramethylpiperidinol crystal reaction solution; and the solid-liquid separation process includes: separating the tetramethylpiperidinol crystals from the tetramethylpiperidinol crystal reaction solution to obtain the tetramethylpiperidinol product.

[0015] Furthermore, the purification process also includes a filtration process, which is performed before the solvent removal process, and the filtration process includes filtering the tetramethylpiperidinol reaction solution.

[0016] Furthermore, the catalyst is a supported catalyst, which includes a support and an active component supported on the support. The active component is selected from at least one of Cu, Co, Ni, Mn, Fe, Ag, V, Pt, Pd, Rh, Au, Ir and their oxides; the support is selected from at least one of Al2O3, SiO2, ZrO2, TiO2 and ZnO.

[0017] Furthermore, the supported catalyst is Pb / TiO2 or Pb / Al2O3.

[0018] Furthermore, the supported catalyst has an average particle size of 40–190 nm and a BET of 0.5–1.3 nm. 2 / g, with a porosity of 0.5–0.8.

[0019] To achieve the above objectives, according to another aspect of the present invention, a system for the continuous catalytic hydrogenation synthesis of tetramethylpiperidinol is also provided. This system comprises: a continuous feeding unit including a continuous feeding device for tetramethylpiperidinol solution and a continuous feeding device for hydrogen; and a continuous catalytic hydrogenation unit including a microchannel reactor filled with a catalyst, the microchannel reactor being connected to both the continuous feeding device for tetramethylpiperidinol solution and the continuous feeding device for hydrogen, for mixing the tetramethylpiperidinol solution and hydrogen for a continuous catalytic hydrogenation reaction to obtain a tetramethylpiperidinol reaction solution.

[0020] Furthermore, the continuous feeding device for tetramethylpiperidone solution includes a solvent storage tank, a tetramethylpiperidone storage tank, and a mixing vessel. The solvent storage tank and the tetramethylpiperidone storage tank are respectively connected to the inlet of the mixing vessel, and the outlet of the mixing vessel is connected to a microchannel reactor.

[0021] Furthermore, the continuous catalytic hydrogenation unit is a microchannel reactor.

[0022] Furthermore, the microchannel reactor is equipped with a vent valve.

[0023] Furthermore, the system also includes a purification unit connected to a continuous catalytic hydrogenation unit for purifying the tetramethylpiperidinol reaction solution to obtain the tetramethylpiperidinol product.

[0024] Furthermore, the purification unit includes a solvent removal vessel, a crystallization vessel, and a solid-liquid separation device connected in sequence. The solvent removal vessel is connected to a microchannel reactor and is used to remove the solvent portion from the tetramethylpiperidinol reaction solution to obtain a supersaturated tetramethylpiperidinol mother liquor. The crystallization vessel is used to crystallize the supersaturated tetramethylpiperidinol mother liquor to obtain a tetramethylpiperidinol crystal reaction solution. The solid-liquid separation device is used to separate the tetramethylpiperidinol crystals in the tetramethylpiperidinol crystal reaction solution to obtain the tetramethylpiperidinol product.

[0025] Furthermore, the solid-liquid separation device is a centrifuge.

[0026] Furthermore, the purification unit also includes a filter installed on the pipeline between the desolvation vessel and the microchannel reactor.

[0027] By applying the technical solution of this application, the method for continuous catalytic hydrogenation to synthesize tetramethylpiperidinol provided by this application mixes tetramethylpiperidone solution and hydrogen gas in a microchannel reactor filled with catalyst to carry out a continuous catalytic hydrogenation reaction. This method breaks the traditional catalytic hydrogenation method, which not only has higher mass transfer efficiency and easier process conditions to control, but also improves the purity and production capacity of tetrahydropiperidinol. At the same time, it reduces the catalyst processing steps and lowers energy consumption, and has broad application prospects. Attached Figure Description

[0028] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0029] Figure 1 A schematic flow diagram of a system for the continuous catalytic hydrogenation synthesis of tetramethylpiperidinol according to Example 1 of the present invention is shown;

[0030] The above figures include the following reference numerals:

[0031] 101. Tetramethylpiperidone storage tank; 102. Solvent storage tank; 103. Batching vessel; 104. Hydrogen storage tank; 105. Feed pump; 201. Microchannel reactor; 202. Vent valve; 301. Filter; 302. Desolventizing vessel; 303. Crystallization vessel; 304. Centrifuge; 305. First transfer pump; 306. Second transfer pump. Detailed Implementation

[0032] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0033] As analyzed in the background section of this application, current methods for preparing tetramethylpiperidinol using catalytic hydrogenation by researchers both domestically and internationally involve stringent reaction conditions when using Ni / Cr2O3 or NiO / Al2O3 catalysts, and expensive catalysts when using Ru / C catalysts, making industrial-scale production impossible. To address this issue, this application provides a method and system for the continuous catalytic hydrogenation synthesis of tetramethylpiperidinol.

[0034] In a first typical embodiment of this application, a method for the continuous catalytic hydrogenation synthesis of tetramethylpiperidinol is provided. The method includes: continuously introducing a tetramethylpiperidone solution and hydrogen gas into a microchannel reactor 201 to carry out a continuous catalytic hydrogenation reaction to obtain a tetramethylpiperidinol reaction solution, which is continuously discharged from the microchannel reactor 201, wherein the microchannel reactor 201 is filled with a catalyst.

[0035] The method for continuous catalytic hydrogenation to synthesize tetramethylpiperidinol provided in this application involves mixing tetramethylpiperidone solution and hydrogen gas in a microchannel reactor 201 packed with catalyst for continuous catalytic hydrogenation. This method breaks away from traditional catalytic hydrogenation methods, resulting in higher mass transfer efficiency, easier control of process conditions, improved purity and production capacity of tetrahydropiperidinol, reduced catalyst processing steps, and lower energy consumption. It has broad application prospects.

[0036] To further improve the efficiency of catalytic hydrogenation, the preferred temperature for continuous catalytic hydrogenation is 40–100°C, especially when the temperature is 60–80°C, the efficiency of continuous catalytic hydrogenation is even higher.

[0037] To accelerate the mixing efficiency of tetramethylpiperidone solution and hydrogen, a hydrogen pressure of 1.0–5.0 MPa is preferred, especially when the hydrogen pressure is 2.0–3.0 MPa, as this facilitates more uniform mixing of the tetramethylpiperidone solution and hydrogen, thereby further improving the efficiency of continuous catalytic hydrogenation. Hydrogen pressures below 1.0 MPa make rapid and uniform mixing with the tetramethylpiperidone solution difficult in the microchannel reactor 201, while pressures above 5.0 MPa result in high energy consumption and pose safety risks.

[0038] In order to further improve the purity of tetramethylpiperidinol product while taking into account the efficiency of continuous catalytic hydrogenation reaction, it is preferred that the flow rate of tetramethylpiperidinol solution into microchannel reactor 201 is 2-10 mL / min, and the retention time of tetramethylpiperidinol solution in microchannel reactor 201 is 10-50 s.

[0039] To further improve the synthesis efficiency of tetramethylpiperidinol, the preferred mass ratio of solvent to tetramethylpiperidone in the tetramethylpiperidone solution is 1:(2-7), especially when the mass ratio is 1:(3-5), the synthesis efficiency of tetramethylpiperidinol is even higher. If the mass ratio of solvent to tetramethylpiperidone is higher than 1:2, the amount of solvent used is excessive, and the yield of the prepared tetramethylpiperidinol decreases. If the mass ratio of solvent to tetramethylpiperidone is lower than 1:7, the concentration of the tetramethylpiperidone solution is too high, and the purity of the prepared tetramethylpiperidinol decreases.

[0040] The type of solvent for tetramethylpiperidine solution is not specifically limited; any solvent capable of dissolving tetramethylpiperidine is acceptable, including but not limited to any one or more mixed solvents formed from methanol, ethanol, ethanol, ethanol, toluene, xylene, or pure water.

[0041] Typical, but not limiting, temperatures for continuous catalytic hydrogenation reactions include 40°C, 50°C, 60°C, 65°C, 70°C, 75°C, 80°C, 90°C, 100°C, or any range of two such values; hydrogen pressures include 1.0 MPa, 2.0 MPa, 2.2 MPa, 2.5 MPa, 2.8 MPa, 3.0 MPa, 4.0 MPa, 5.0 MPa, or any range of two such values; and the flow rate of the tetramethylpiperidone solution into the microchannel reactor 201 includes 2 mL / min, 3 mL / min, 4 mL / min, 5 mL / min, etc. The values ​​are: mL / min, 6 mL / min, 7 mL / min, 8 mL / min, 9 mL / min, 10 mL / min, or any two of these values; the retention time of the tetramethylpiperidone solution in the microchannel reactor 201 is: 10 s, 15 s, 20 s, 25 s, 30 s, 35 s, 40 s, 45 s, 50 s, or any two of these values; the mass ratio of solvent to tetramethylpiperidone in the tetramethylpiperidone solution is: 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, or any two of these values.

[0042] To obtain a high-purity tetramethylpiperidinol product, the preferred method for the continuous catalytic hydrogenation synthesis of tetramethylpiperidinol also includes: purifying the tetramethylpiperidinol reaction solution to obtain the tetramethylpiperidinol product.

[0043] To further improve the efficiency of the purification process, the purification process preferably includes a solvent removal process, a crystallization process, and a solid-liquid separation process performed sequentially. The solvent removal process includes: removing the solvent portion from the tetramethylpiperidinol solution to obtain a supersaturated tetramethylpiperidinol mother liquor; the crystallization process includes: cooling and crystallizing the supersaturated tetramethylpiperidinol mother liquor to obtain a tetramethylpiperidinol crystal reaction solution; the solid-liquid separation process includes: performing solid-liquid separation on the tetramethylpiperidinol crystal reaction solution to obtain the tetramethylpiperidinol product.

[0044] In the above-mentioned supersaturated tetramethylpiperidinol mother liquor, tetramethylpiperidinol precipitates in solid form at the bottom of the mother liquor, and the solid-liquid volume ratio is preferably 0.35 to 0.6:1.

[0045] To further improve the purity of the tetramethylpiperidinol product, the purification process preferably includes a filtration process, which is performed before the solvent removal process. The filtration process includes filtering the tetramethylpiperidinol reaction solution to remove particulate impurities from the tetramethylpiperidinol reaction solution before performing the solvent removal process.

[0046] The specific type of catalyst mentioned above is not specifically limited; any commonly used catalyst for the hydrogenation of tetramethylpiperidone is acceptable. To further improve catalytic efficiency, a supported catalyst is preferred. This supported catalyst includes a support and an active component supported on the support. The active component is selected from any one or at least two compounds formed from Cu, Co, Ni, Mn, Fe, Ag, V, Pt, Pd, Rh, Au, Ir, and their oxides. The support is selected from any one or at least two composite supports formed from Al₂O₃, SiO₂, ZrO₂, TiO₂, and ZnO. Especially when the above-mentioned supported catalyst uses a non-noble metal or its oxide as the active component, the support is preferably Al₂O₃ or SiO₂.

[0047] In some embodiments of this application, the supported catalyst is Pb / TiO2 or Pb / Al2O3.

[0048] The above Pb / TiO2 refers to Pb as the active ingredient and TiO2 as the support; Pb / Al2O3 refers to Pb as the active ingredient and Al2O3 as the support.

[0049] The preferred supported catalyst has an average particle size of 40–190 nm and a BET of 0.5–1.3 nm. 2 / g, with a porosity of 0.5–0.8. Typical, but not limiting, the average particle size of the supported catalyst is 40 nm, 60 nm, 80 nm, 100 nm, 120 nm, 150 nm, 180 nm, 190 nm, or any combination of two values; BET is 0.5 nm. 2 / g, 0.8m 2 / g, 1.0m 2 / g, 1.2m 2 / g, 1.3m 2 / g or a range of any two values; porosity such as 0.5, 0.6, 0.7, 0.8 or a range of any two values.

[0050] In a second typical embodiment of this application, a system for the continuous catalytic hydrogenation synthesis of tetramethylpiperidinol is also provided. This system includes: a continuous feeding unit comprising a continuous feeding device for tetramethylpiperidinol solution and a continuous feeding device for hydrogen; and a continuous catalytic hydrogenation unit comprising a microchannel reactor 201 filled with a catalyst, and the microchannel reactor 201 being connected to both the continuous feeding device for tetramethylpiperidinol solution and the continuous feeding device for hydrogen, for mixing the tetramethylpiperidinol solution and hydrogen for a continuous catalytic hydrogenation reaction to obtain a tetramethylpiperidinol reaction solution.

[0051] The system for the continuous catalytic hydrogenation synthesis of tetramethylpiperidinol provided in this application, through interconnected continuous feeding units and continuous catalytic hydrogenation units, allows tetramethylpiperidinol solution and hydrogen gas to be mixed in a microchannel reactor 201 filled with catalyst for continuous catalytic hydrogenation reaction. This breaks with the traditional catalytic hydrogenation method, not only with higher mass transfer efficiency and easier control of process conditions, but also with improved purity and production capacity of tetrahydropiperidinol. At the same time, it reduces the steps of catalyst processing and lowers energy consumption, and has broad application prospects.

[0052] In some embodiments of this application, such as Figure 1 As shown, the continuous feeding device for tetramethylpiperidone solution includes a solvent storage tank 102, a tetramethylpiperidone storage tank 101, and a mixing vessel 103. The solvent storage tank 102 and the tetramethylpiperidone storage tank 101 are respectively connected to the inlet of the mixing vessel 103. The mixing vessel 103 is used to mix the solvent and tetramethylpiperidone evenly to obtain a tetramethylpiperidone solution. The outlet of the mixing vessel 103 is connected to a microchannel reactor 201 for continuously feeding the tetramethylpiperidone solution into the microchannel reactor 201.

[0053] To facilitate control of the flow rate of tetramethylpiperidine solution entering the continuous catalytic hydrogenation unit, a feed pump 105 is preferably installed on the pipeline between the batching vessel 103 and the microchannel reactor 201. The feed pump 105 precisely controls the flow rate of tetramethylpiperidine solution entering the microchannel reactor 201, thereby further improving the yield of tetramethylpiperidine alcohol.

[0054] In some embodiments of this application, the continuous hydrogen supply device is a hydrogen storage tank 104.

[0055] In some embodiments of this application, the microchannel reactor 201 is a gas-liquid-solid three-phase catalytic reactor with a specific internal microstructure and properties such as corrosion resistance, high temperature resistance, and high pressure resistance. Preferably, it is a tubular structure with a fixed supported catalyst, with a tube diameter of 0.5-15 mm and a tube length of 10-200 m.

[0056] To further improve the safety of the continuous catalytic hydrogenation reaction, the microchannel reactor 201 is preferably also equipped with a vent valve 202.

[0057] In some embodiments of this application, the system for the continuous catalytic hydrogenation synthesis of tetramethylpiperidinol described above further includes a purification unit connected to the continuous catalytic hydrogenation unit, which is used to purify the tetramethylpiperidinol reaction solution to obtain the tetramethylpiperidinol product.

[0058] The specific type of equipment in this purification unit is not limited; any equipment capable of separating the tetramethylpiperidinol product from the tetramethylpiperidinol reaction solution is acceptable. In some embodiments of this application, the purification unit includes a solvent removal vessel 302, a crystallization vessel 303, and a solid-liquid separation device connected in sequence. The solvent removal vessel 302 is connected to the microchannel reactor 201 and is used to partially evaporate and remove the solvent from the tetramethylpiperidinol reaction solution until the reaction solution is supersaturated, obtaining a supersaturated tetramethylpiperidinol mother liquor. The crystallization vessel 303 is used to crystallize the supersaturated tetramethylpiperidinol mother liquor, obtaining a tetramethylpiperidinol crystal reaction solution. The solid-liquid separation device is used to separate the tetramethylpiperidinol crystals from the tetramethylpiperidinol crystal reaction solution, obtaining the tetramethylpiperidinol product.

[0059] In the above-mentioned supersaturated tetramethylpiperidinol mother liquor, tetramethylpiperidinol precipitates in solid form at the bottom of the mother liquor, and the solid-liquid volume ratio is preferably 0.35 to 0.6:1.

[0060] Typical, but not limiting, solid-liquid volumes in supersaturated tetramethylpiperidinol mother liquor are, for example, a range of values ​​consisting of 0.35:1, 0.4, 0.45, 0.5, 0.55, 0.6, or any two of these values.

[0061] To further improve the efficiency of crystal separation and reduce costs, centrifuge 304 is preferred as the solid-liquid separation device.

[0062] To reduce the impact of particulate impurities in the tetramethylpiperidinol reaction solution on the purity of the tetramethylpiperidinol product, the purification unit preferably includes a filter 301, which is installed on the pipeline between the desolventizing vessel 302 and the microchannel reactor 201. By filtering the tetramethylpiperidinol reaction solution before it enters the desolventizing vessel 302, it is more beneficial to improve the purity of the tetramethylpiperidinol product.

[0063] To accelerate the transfer efficiency of the tetramethylpiperidinol reaction solution into the desolventizing vessel 302, a first transfer pump 305 is preferably installed on the pipeline between the filter 301 and the desolventizing vessel 302.

[0064] To accelerate the flow of the supersaturated tetramethylpiperidinol mother liquor into the crystallization vessel 303, a second delivery pump 306 is preferably installed on the pipeline between the desolvation vessel 302 and the crystallization vessel 303.

[0065] Example 1

[0066] like Figure 1 As shown, this embodiment provides a system for the continuous catalytic hydrogenation synthesis of tetramethylpiperidinol. The system includes a continuous feeding unit, a continuous catalytic hydrogenation unit, and a purification unit connected in sequence. The continuous feeding unit includes a continuous feeding device for tetramethylpiperidinol solution and a continuous feeding device for hydrogen. The continuous catalytic hydrogenation unit includes a microchannel reactor 201 filled with a catalyst. The microchannel reactor 201 is connected to both the continuous feeding device for tetramethylpiperidinol solution and the continuous feeding device for hydrogen, and is used to mix the tetramethylpiperidinol solution and hydrogen for a continuous catalytic hydrogenation reaction to obtain a tetramethylpiperidinol reaction solution. The purification unit is used to purify the tetramethylpiperidinol reaction solution to obtain the tetramethylpiperidinol product.

[0067] The aforementioned continuous feeding device for tetramethylpiperidone solution includes a solvent storage tank 102, a tetramethylpiperidone storage tank 101, and a mixing vessel 103. The solvent storage tank 102 and the tetramethylpiperidone storage tank 101 are respectively connected to the inlet of the mixing vessel 103. The mixing vessel 103 is used to mix the solvent and tetramethylpiperidone uniformly to obtain a tetramethylpiperidone solution. The outlet of the mixing vessel 103 is connected to a microchannel reactor 201 for continuously feeding the tetramethylpiperidone solution into the microchannel reactor 201. A feed pump 105 is installed between the mixing vessel 103 and the microchannel reactor 201 to precisely control the flow rate of the tetramethylpiperidone solution entering the microchannel reactor 201.

[0068] The aforementioned continuous hydrogen supply device is a hydrogen storage tank 104.

[0069] The microchannel reactor 201 is equipped with a vent valve 202, and the microchannel reactor 201 has a tubular structure with a fixed-supported catalyst, with a tube diameter of 5 mm and a tube length of 25 m.

[0070] The purification unit includes a filter 301, a solvent removal vessel 302, a crystallization vessel 303, and a centrifuge 304 connected in sequence. The filter 301 is connected to the microchannel reactor 201 and is used to filter and remove particulate matter from the tetramethylpiperidinol solution. The solvent removal vessel 302 is used to evaporate and remove the solvent from the tetramethylpiperidinol reaction solution until the reaction solution is supersaturated to obtain a supersaturated tetramethylpiperidinol mother liquor. The crystallization vessel 303 is used to crystallize the supersaturated tetramethylpiperidinol mother liquor to obtain a tetramethylpiperidinol crystal reaction solution. The centrifuge 304 is used to separate the tetramethylpiperidinol crystals in the tetramethylpiperidinol crystal reaction solution to obtain the tetramethylpiperidinol product.

[0071] To accelerate the purification efficiency of the tetramethylpiperidinol reaction solution, a first transfer pump 305 is installed on the pipeline between the filter 301 and the desolvation vessel 302, and a second transfer pump 306 is installed on the pipeline between the desolvation vessel 302 and the crystallization vessel 303.

[0072] Example 2

[0073] This embodiment provides a method for the continuous catalytic hydrogenation synthesis of tetramethylpiperidinol. The method is carried out in the system provided in Example 1 and specifically includes the following steps:

[0074] (1) Mix 300g of tetramethylpiperidone and 60g of methanol in mixing tank 103 to obtain a tetramethylpiperidone solution;

[0075] (2) A tetramethylpiperidinone solution was introduced into a microchannel reactor 201 at a flow rate of 3.5 mL / min and a hydrogen gas pressure of 2.0 MPa for continuous catalytic hydrogenation. The microchannel reactor 201 was packed with a supported catalyst, namely Pb / TiO2 (average particle size of 100 nm, BTE of 0.8 μm). 2 / g, with a porosity of 0.6); the temperature of the continuous catalytic hydrogenation reaction was controlled at 70℃, and the residence time of the tetramethylpiperidone solution in the microchannel reactor 201 was 35s, to obtain a tetramethylpiperidol reaction solution, which continuously flowed out of the microchannel reactor 201;

[0076] (3) After filtering the tetramethylpiperidinol reaction solution through filter 301, it is passed into the solvent removal vessel 302 to distill off part of the solvent and obtain a supersaturated tetramethylpiperidinol mother liquor (solid-liquid volume ratio 0.45:1).

[0077] (4) The supersaturated tetramethylpiperidinol mother liquor was passed into crystallization kettle 303 and cooled and crystallized under an ice-water bath to obtain a tetramethylpiperidinol crystal reaction solution containing tetramethylpiperidinol crystals.

[0078] (5) The tetramethylpiperidinol crystal reaction solution was centrifuged in centrifuge 304 to obtain the tetramethylpiperidinol product.

[0079] Example 3

[0080] The difference between this embodiment and embodiment 1 is that in step (2), the flow rate of the tetramethylpiperidone solution into the microchannel reactor 201 is 2 mL / min, the pressure of hydrogen is 1.5 MPa, the temperature of the continuous catalytic hydrogenation reaction is 60 °C, and the residence time of the tetramethylpiperidone solution in the microchannel reactor 201 is 50 s.

[0081] Example 4

[0082] The difference between this embodiment and embodiment 1 is that, in step (2), the flow rate of the tetramethylpiperidone solution into the microchannel reactor 201 is 5 mL / min, the pressure of hydrogen is 3 MPa, the temperature of the continuous catalytic hydrogenation reaction is 100 °C, and the residence time of the tetramethylpiperidone solution in the microchannel reactor 201 is 20 s.

[0083] Example 5

[0084] The difference between this embodiment and embodiment 1 is that, in step (2), the flow rate of the tetramethylpiperidone solution into the microchannel reactor 201 is 10 mL / min, the pressure of hydrogen is 5.0 MPa, the temperature of the continuous catalytic hydrogenation reaction is 80 °C, and the residence time of the tetramethylpiperidone solution in the microchannel reactor 201 is 50 s.

[0085] Example 6

[0086] The difference between this embodiment and embodiment 1 is that in step (2), the flow rate of the tetramethylpiperidone solution into the microchannel reactor 201 is 2 mL / min, the pressure of hydrogen is 1.0 MPa, the temperature of the continuous catalytic hydrogenation reaction is 60 °C, and the residence time of the tetramethylpiperidone solution in the microchannel reactor 201 is 10 s.

[0087] Example 7

[0088] The difference between this embodiment and embodiment 1 is that in step (2), the temperature of the continuous catalytic hydrogenation reaction is 40°C, and the residence time of the tetramethylpiperidone solution in the microchannel reactor 201 is 50s.

[0089] Example 8

[0090] The difference between this embodiment and Embodiment 1 is that the flow rate of the tetramethylpiperidone solution into the microchannel reactor 201 is 1 mL / min, and the residence time of the tetramethylpiperidone solution in the microchannel reactor 201 is 5 s.

[0091] Example 9

[0092] The difference between this embodiment and Embodiment 1 is that the flow rate of the tetramethylpiperidone solution into the microchannel reactor 201 is 15 mL / min, and the residence time of the tetramethylpiperidone solution in the microchannel reactor 201 is 60 s.

[0093] Example 10

[0094] The difference between this embodiment and Embodiment 1 is that the temperature of the continuous catalytic hydrogenation reaction is controlled at 30°C.

[0095] Example 11

[0096] The difference between this embodiment and Embodiment 1 is that the temperature of the continuous catalytic hydrogenation reaction is controlled at 120°C.

[0097] Example 12

[0098] The difference between this embodiment and Embodiment 1 is that the continuous catalytic hydrogenation catalyst uses Ni as the catalyst.

[0099] Experimental Example 1

[0100] The mass, purity, yield, melting point, and color of the tetramethylpiperidine products provided in the above examples were determined, and the results are shown in Table 1 below.

[0101] Purity was determined using gas chromatography; melting point was determined using a melting point apparatus.

[0102] The yield was determined by: molar amount of tetramethylpiperidinol product / molar amount of tetramethylpiperidone.

[0103] The method for measuring colorimetry is: colorimeter measurement.

[0104] Table 1

[0105]

[0106]

[0107] As can be seen from the above description, the above embodiments of the present invention achieve the following technical effects: The method for continuous catalytic hydrogenation to synthesize tetramethylpiperidinol provided in this application mixes tetramethylpiperidone solution and hydrogen gas in a continuous catalytic hydrogenation unit packed with catalyst to carry out a continuous catalytic hydrogenation reaction, which breaks the traditional catalytic hydrogenation method. It not only has higher mass transfer efficiency and easier process conditions to control, but also improves the purity and production capacity of tetrahydropiperidinol. At the same time, it reduces the catalyst processing steps and reduces energy consumption, and has broad application prospects.

[0108] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A process for the continuous catalytic hydrogenative synthesis of tetramethylpiperidinol, characterized in that, The method comprises: The tetramethylpiperidone solution and hydrogen are continuously introduced into a micro-channel reactor for continuous catalytic hydrogenation reaction to obtain a tetramethylpiperidinol reaction liquid, and the tetramethylpiperidinol reaction liquid is continuously discharged from the micro-channel reactor; wherein the micro-channel reactor is filled with a catalyst; The flow rate of the tetramethylpiperidone solution introduced into the micro-channel reactor is 2-10 mL / min; and the residence time of the tetramethylpiperidone solution in the micro-channel reactor is 10-50 s. The mass ratio of the solvent to tetramethylpiperidone in the tetramethylpiperidone solution is 1: (2-7).

2. The method of claim 1, wherein, The temperature of the continuous catalytic hydrogenation reaction is 40-100°C.

3. The method of claim 1, wherein, The temperature of the continuous catalytic hydrogenation reaction is 60-80°C.

4. The method of claim 1, wherein, The pressure of the hydrogen is 1.0-5.0 MPa.

5. The method of claim 1, wherein, The pressure of the hydrogen is 2.0-3.0 MPa.

6. The method of claim 1, wherein, The flow rate of the tetramethylpiperidone solution introduced into the micro-channel reactor is 2-5 mL / min; and the residence time of the tetramethylpiperidone solution in the micro-channel reactor is 20-50 s.

7. The method of claim 1, wherein, The mass ratio of the solvent to tetramethylpiperidone in the tetramethylpiperidone solution is 1: (3-5).

8. The method of claim 1, wherein, The solvent is at least one selected from methanol, ethanol, isopropanol, toluene, xylene or pure water.

9. The method of claim 8, wherein, The solvent is methanol or ethanol.

10. The method according to any one of claims 1 to 9, characterized in that, The method further comprises: purifying the tetramethylpiperidinol reaction liquid to obtain a tetramethylpiperidinol product.

11. The method of claim 10, wherein, The purification treatment comprises sequentially performed desolventization treatment, crystallization treatment and solid-liquid separation treatment, the desolventization treatment comprises: partially removing the solvent in the tetramethylpiperidinol reaction liquid to obtain a supersaturated tetramethylpiperidinol mother liquor; the crystallization treatment comprises: cooling and crystallizing the supersaturated tetramethylpiperidinol mother liquor to obtain a tetramethylpiperidinol crystal reaction liquid; and the solid-liquid separation treatment comprises: separating the tetramethylpiperidinol crystals in the tetramethylpiperidinol crystal reaction liquid to obtain the tetramethylpiperidinol product.

12. The method of claim 11, wherein, The purification treatment further comprises a filtration treatment, which is arranged before the desolventization treatment, and the filtration treatment comprises: filtering the tetramethylpiperidinol reaction liquid.

13. The method according to any one of claims 1 to 9, characterized in that, The catalyst is a supported catalyst, the supported catalyst comprises a carrier and an active ingredient supported on the carrier, the active ingredient is at least one selected from Cu, Co, Ni, Mn, Fe, Ag, V, Pt, Pd, Rh, Au, Ir and oxides thereof; and the carrier is at least one selected from Al2O3, SiO2, ZrO2, TiO2 and ZnO.

14. The method of claim 13, wherein, The supported catalyst is Pb / TiO2 or Pb / Al2O3.

15. The method of claim 13, wherein, The supported catalyst has an average particle size of 40-190 nm, a BET of 0.5-1.3 m 2 / g, and a porosity of 0.5-0.

8.

16. The method of claim 1, wherein, The method is performed in a system for continuous catalytic hydrogenation synthesis of tetramethylpiperidinol, and the system comprises: A continuous feeding unit, which comprises a tetramethylpiperidone solution continuous feeding device and a hydrogen continuous feeding device; A continuous catalytic hydrogenation unit, which comprises a micro-channel reactor (201) filled with a catalyst, and is connected with the continuous tetramethylpiperidone solution feeding device and the hydrogen gas continuous feeding device respectively, for mixing tetramethylpiperidone solution and hydrogen gas for continuous catalytic hydrogenation reaction to obtain a tetramethylpiperidinol reaction solution.

17. The method of claim 16, wherein, The tetramethylpiperidone solution continuous feeding device comprises a solvent storage tank (102), a tetramethylpiperidone storage tank (101) and a batching kettle (103), the solvent storage tank (102) and the tetramethylpiperidone storage tank (101) are connected with the inlet of the batching kettle (103) respectively, and the outlet of the batching kettle (103) is connected with the micro-channel reactor (201).

18. The method of claim 16, wherein, The micro-channel reactor (201) is provided with a vent valve (202).

19. The method of any one of claims 16-18, wherein, The system further comprises a purification unit connected with the continuous catalytic hydrogenation unit for purifying the tetramethylpiperidinol reaction solution to obtain a tetramethylpiperidinol product.

20. The method of claim 19, wherein, The purification unit comprises a desolventizing kettle (302), a crystallization kettle (303) and a solid-liquid separation device connected in sequence, the desolventizing kettle (302) is connected with the micro-channel reactor (201) for partially removing the solvent in the tetramethylpiperidinol reaction solution to obtain a supersaturated tetramethylpiperidinol mother liquor; the crystallization kettle (303) is used for crystallizing the supersaturated tetramethylpiperidinol mother liquor to obtain a tetramethylpiperidinol crystal reaction solution; and the solid-liquid separation device is used for separating the tetramethylpiperidinol crystals in the tetramethylpiperidinol crystal reaction solution to obtain the tetramethylpiperidinol product.

21. The method of claim 20, wherein, The solid-liquid separation device is a centrifuge (304).

22. The method of claim 20, wherein, The purification unit further comprises a filter (301) arranged on the pipeline between the desolventizing kettle (302) and the micro-channel reactor (201).

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