Device and method for high-shear reinforced continuous synthesis of glyoxylic acid

Abstract

The invention discloses a device and a method for high-shear reinforced continuous synthesis of glyoxylic acid. The device comprises a first liquid storage bottle, a second liquid storage bottle, a continuous high-shear mixer and an intermittent high-shear mixer, the first liquid storage bottle and the second liquid storage bottle are connected with a feeding hole of the continuous high-shear mixer; the continuous high-shear mixer is connected with the intermittent high-shear mixer; the continuous high-shear mixer comprises a first feed port, a second feed port, a distributor, a rotor, a stator, a discharge port and a shell, the distributor, the rotor and the stator are arranged in the shell, the rotor is arranged outside the distributor, and the stator is arranged outside the rotor. According to the continuous high-shear mixer, high-speed shear force is generated through a rotor-stator structure to crush reactants into micron / nano-scale liquid drops, the liquid-liquid contact area is greatly increased, and efficient mass and heat transfer is achieved. Intermittent high shear further optimizes mixing, ensures efficient reaction, and improves the purity of the final product.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial production of glyoxylic acid, and in particular to a device and method for high-shear intensified continuous synthesis of glyoxylic acid. Background Art

[0002] Glyoxylic acid is a white crystal with an unpleasant odor. Its aqueous solution is a colorless or pale yellow transparent liquid. Also known as formaldehyde formic acid, glyoxylic acid is a keto acid composed of an aldehyde group and a carboxyl group. It possesses the properties of both aldehydes and carboxylic acids and is chemically active. It is an important intermediate in the synthesis of chemicals such as fragrances, pharmaceuticals, pesticides, dyes, and plastic additives, enjoying a wide range of applications.

[0003] At present, the main methods for industrial production of glyoxylic acid include oxalic acid electrolytic reduction method, nitric acid oxidation of glyoxal method and maleic anhydride ozone oxidation method.

[0004] Patent CN 105780046 A discloses a method for producing glyoxylic acid through electrolysis using oxalic acid as the raw material, a composite membrane electrode as the cathode, graphite or lead plates as the anode, a saturated oxalic acid solution as the catholyte, and a sulfuric acid solution as the anolyte. Oxalic acid electrolysis produces less waste, produces less pollution, but consumes more energy, results in unstable glyoxylic acid quality, and is difficult to control during production, resulting in high production costs.

[0005] Caprio et al. (Caprio V, Insola A, Silvestre AM. Glyoxal ozonation process in aqueous solution [J]. Ozone: science & engineering, 1989, 11(3): 271-280.) reported the synthesis of glyoxylic acid by ozonation of maleic anhydride in 1989. While glyoxylic acid obtained by ozonation has a high yield and good quality, the reaction conditions are relatively harsh, the equipment investment is high, the byproduct formic acid is severely corrosive to the equipment, and there are also significant problems with the generation and disposal of ozone.

[0006] In 2018, Wang Chao et al. (Wang Chao, Deng Qiulin, Chen Chao, et al. Preparation of glyoxylic acid by oxidation of glyoxal with nitric acid in a microreactor [J]. Journal of Nanjing University of Technology (Natural Science Edition), 2018, 40(1): 66-73.) reported the synthesis of glyoxylic acid by oxidation of glyoxal with nitric acid in microchannel and falling film microreactors. The nitric acid oxidation of glyoxal method has mild conditions, a simple and mature process, and low equipment investment costs, and is currently adopted by most domestic manufacturers.

[0007] The core technology of preparing glyoxylic acid by nitric acid oxidation of glyoxal is to suppress the over-oxidation of glyoxylic acid. Since the glyoxylic acid generated by the reaction is thermodynamically unstable in the nitric acid system and is easily further oxidized to oxalic acid, the industry currently uses the dropwise addition method to control the reaction rate to improve the yield and selectivity of the main product. However, the traditional dropwise addition process has problems such as cumbersome operation and poor temperature control effect. It is easy to cause the risk of bumping due to excessive local concentration and leads to a significant increase in by-products such as oxalic acid. In addition, although the hydrochloric acid initiator introduced to shorten the reaction induction period can accelerate the reaction process, the introduction of additional reagents will also reduce the purity of the final product.

[0008] Zhan et al. (Zhan W, Wang J, He C, et al. Kinetics of glyoxal oxidation bynitric acid in acapillary microreactor[J]. Chemical Engineering Science, 2023, 276: 118813.) reported in 2023 the synthesis of glyoxalic acid by the oxidation of glyoxal with nitric acid. They designed a continuous flow microreactor system consisting of a micromixer, a preheating capillary loop, a capillary microreactor and a quenching device to synthesize glyoxalic acid. Under optimal conditions, the selectivity of glyoxalic acid reached 92.4%, and the yield of glyoxalic acid reached 81.6%. The yield still needs to be improved. Summary of the Invention

[0009] In order to overcome the problem of low glyoxylic acid production yield in the prior art, the present invention aims to provide a device and method for high shear intensified continuous synthesis of glyoxylic acid, which can synthesize glyoxylic acid with high yield and low cost.

[0010] To achieve the above object, the technical solution adopted by the present invention is:

[0011] A device for high-shear-enhanced continuous synthesis of glyoxylic acid, comprising a first liquid storage bottle, a second liquid storage bottle, a continuous high-shear mixer, and an intermittent high-shear mixer;

[0012] The first liquid storage bottle is connected to the second liquid storage bottle and the feed port of the continuous high shear mixer, and the continuous high shear mixer is connected to the intermittent high shear mixer;

[0013] The continuous high shear mixer comprises a first feed port, a second feed port, a distributor, a rotor, a stator, a discharge port and a shell;

[0014] A distributor, a rotor and a stator are arranged in the shell, a rotor is arranged outside the distributor, a stator is arranged outside the rotor, the distributor and the rotor are spaced apart, and the rotor and the stator are spaced apart.

[0015] Furthermore, a first feed port and a second feed port are provided on the top of the shell, and the first feed port is sleeved inside the second feed port.

[0016] Furthermore, the distributor includes an inner plate and an outer plate that are sheathed together, the inner plate is arranged inside the outer plate, and an annular cavity is formed between the inner plate and the outer plate; a plurality of spacer plates are evenly arranged along the circumference of the outer plate wall, adjacent spacer plates are spaced apart, and the gaps between adjacent spacer plates form an axial channel, which is connected to the second feed port;

[0017] A first through hole is opened on each partition along the radial direction, and a plurality of second through holes are opened correspondingly on the inner plate and the outer plate of the annular cavity. The first through hole is connected with the second through holes on the same radius, thereby forming a radial channel, which is connected with the first feed port.

[0018] Furthermore, a first metering pump is provided between the first liquid storage bottle and the continuous high shear mixer, a second metering pump is provided between the second liquid storage bottle and the continuous high shear mixer, and a third metering pump is provided between the continuous high shear mixer and the intermittent high shear mixer.

[0019] Furthermore, the distance between the distributor and the rotor is 0.2-2 mm, the distance between the stator and the housing is 0.1-3 mm, the tooth spacing of the rotor is 0.1-2 mm, the number of teeth of the rotor is 5-15, the number of teeth of the stator is 10-30, the tooth spacing of the stator is 0.2-2 mm, and the shear gap between the rotor and the stator is 0.1-3 mm.

[0020] A method for high shear-enhanced continuous synthesis of glyoxylic acid comprises the following steps:

[0021] The first nitric acid solution is conveyed to the first feed port of the continuous high shear mixer, the solution containing glyoxal and sodium nitrite is conveyed to the second feed port, and a first high shear reaction is performed to obtain solution C. Solution C is conveyed to a batch high shear mixer, and a second nitric acid solution is added to the batch high shear mixer to perform a second high shear reaction to obtain glyoxylic acid.

[0022] Furthermore, the molar ratio of nitric acid in the first nitric acid solution to glyoxal in solution B is 0.5-1.2:1; and the molar ratio of sodium nitrite to glyoxal in solution B is 0-0.3:1.

[0023] Furthermore, the rotor and the rotor linear speed of the intermittent high shear mixer are 5-50 m / s.

[0024] Furthermore, the temperature of the first high shear reaction and the second high shear reaction is 30-90° C., and the time is 1-5 minutes.

[0025] Furthermore, the molar ratio of nitric acid in the second nitric acid solution to glyoxal in solution C is 1-1.5:1.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The stator and rotor in the continuous high-shear mixer of the present invention enable high-shear mixing of raw materials. The serial connection of the continuous high-shear mixer and the intermittent high-shear mixer enables continuous operation with short residence time, large processing capacity, good repeatability, and high safety. This significantly increases the synthesis rate of glyoxylic acid, eliminates the need for the addition of hydrochloric acid as an initiator, shortens the reaction time, and reduces the difficulty of product separation.

[0028] In the present invention, a continuous high shear mixer is used in combination with an intermittent high shear mixer. The continuous high shear mixer generates high-speed shear force through a rotor-stator structure to break the reactants (glyoxal, nitric acid and sodium nitrite) into micron / nanoscale droplets, greatly increasing the liquid-liquid contact area, achieving efficient mass transfer and heat transfer, and accelerating the oxidation reaction. The violent turbulence of high shear mixing promotes rapid diffusion of heat, and the uniform flow distribution of the distributor is combined to eliminate local hot spots and prevent side reactions or safety hazards caused by temperature runaway. Under the continuous operation mode, the distributor maintains the stable flow rate of the reactants, reduces temperature and concentration fluctuations, and ensures safety. By accurately controlling the degree of oxidation, excessive decomposition of nitric acid is suppressed to produce harmful gases such as NOx, reducing the pressure of tail gas treatment. Intermittent high shear further optimizes mixing at a critical stage to avoid side reactions (such as excessive oxidation to generate oxalic acid) caused by uneven local concentrations, ensuring that the reaction is carried out efficiently. The synthetic method of glyoxylic acid of the present invention has low production cost and high yield.

[0029] Furthermore, the distributor structure within the continuous high-shear mixer can optimize the material flow path, guide the fluid to flow regularly and disperse evenly, improve the micro-mixing level, optimize the residence time distribution, eliminate short circuits and dead zones, avoid side reactions caused by excessive local concentration (such as excessive oxidation to produce oxalic acid), and at the same time ensure that the oxidizing effect of nitric acid acts evenly on glyoxal, thereby improving the reaction selectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the structure of a continuous high shear mixer;

[0031] Figure 2 This is a simplified structural diagram of a continuous high shear mixer;

[0032] Figure 3 It is a cross-sectional view of the structure of a continuous high shear mixer;

[0033] Figure 4 Schematic diagram of the distributor structure;

[0034] Figure 5 Schematic diagram of the internal structure of a continuous high shear mixer;

[0035] Figure 6 Flow chart for the synthesis of glyoxylic acid;

[0036] In the figure, 1 is the first liquid storage bottle, 2 is the second liquid storage bottle, 3 is the first metering pump, 4 is the second metering pump, 5 is the continuous high shear mixer, 6 is the third metering pump, 7 is the intermittent high shear mixer, 8 is the fourth metering pump, 9 is the fifth metering pump, 10 is the collection bottle, 11 is the water tank, and 12 is the third liquid storage bottle;

[0037] 13 is the first feed port, 14 is the second feed port, 15 is the distributor, 16 is the radial channel, 17 is the axial channel, 18 is the rotor, 19 is the stator, 20 is the discharge port, and 21 is the housing. DETAILED DESCRIPTION

[0038] To facilitate understanding of the present invention, the present invention will be described more fully below with reference to the accompanying drawings. The accompanying drawings illustrate preferred embodiments of the present invention. However, the present invention may be implemented in a variety of different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure of the present invention.

[0039] See also Figure 6 The apparatus for high-shear-enhanced continuous synthesis of glyoxylic acid in the present invention comprises a first liquid storage bottle 1, a second liquid storage bottle 2, a first metering pump 3, a second metering pump 4, a continuous high-shear mixer 5, a third metering pump 6, an intermittent high-shear mixer 7, a fourth metering pump 8, a fifth metering pump 9, a collecting bottle 10, a water tank 11, and a third liquid storage bottle 12. The collecting bottle 10 is used to collect the product.

[0040] Among them, the liquid storage bottle 1 filled with solution B is connected to the first metering pump 3, the liquid storage bottle 2 filled with solution A is connected to the second metering pump 4, the first metering pump 3 and the second metering pump 4 are both connected to the inlet of the continuous high shear mixer 5, the discharge port of the continuous high shear mixer 5 is connected to the third metering pump 6, the third liquid storage bottle 12 filled with solution A is connected to the fourth metering pump 8, the third metering pump 6 and the fourth metering pump 8 are connected to the inlet of the intermittent high shear mixer 7, the outlet of the intermittent high shear mixer 7 is connected to the fifth metering pump 9, the fifth metering pump 9 is connected to the collecting bottle 10 for collecting the product, and the collecting bottle 10 for collecting the product is set in a water tank 11 filled with ice-water mixture.

[0041] See also Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 and Figure 5The continuous high shear mixer 5 includes a first feed port 13, a second feed port 14, a distributor 15, a rotor 18, a stator 19, a discharge port 20 and a housing 21, see Figure 5 A distributor 15, a rotor 18, and a stator 19 are arranged inside the housing 21. The rotor 18 is arranged outside the distributor 15, and the stator 19 is arranged outside the rotor 18. The distributor 15 and the rotor 18 are spaced apart, and the distance between the distributor 15 and the rotor 18 is 0.2-2 mm. The rotor 18 and the stator 19 are spaced apart, and the distance between the stator 19 and the housing 21 is 0.1-3 mm. The number of teeth of the rotor 18 is 5-15, and the tooth spacing of the rotor 18 is 0.1-2 mm. The stator 19 is arranged outside the rotor 18, and the number of teeth of the stator 19 is 10-30, and the tooth spacing of the stator 19 is 0.2-2 mm. The shear gap between the rotor 18 and the stator 19 is 0.1-3 mm. The housing 21 is arranged outside the stator 19.

[0042] A first feed port 13 and a second feed port 14 are provided on the top of the housing 21. The first feed port 13 is sheathed in the second feed port 14.

[0043] The distributor 15 includes an annular cavity, and a number of partition plates are evenly arranged along the circumferential direction on the outer wall of the annular cavity. Adjacent partition plates are spaced apart, and the number of partition plates is 5-30. The gaps between adjacent partition plates form axial channels 17, and the number of axial channels 17 is 5-30. Specifically, after passing through the second feed port 14, the fluid flows in from the top of the gap between adjacent partition plates and flows out from the gap between the side walls of the partition plates.

[0044] A first through hole is opened in the radial direction on each partition plate, and a plurality of second through holes are opened correspondingly on the annular cavity. The first through hole is connected with the corresponding second through holes on the same radius, thereby forming a radial channel 16. After the fluid passes through the first feed port 13, the fluid flowing out from the first channel and the second channel in the radial direction enters the gap between the rotor 18 and the stator 19, reacts at the same time, and then enters the intermittent high shear mixer 7.

[0045] The structure of the intermittent high shear mixer 7 is described in patent CN212758094U.

[0046] The rotor linear speed of the continuous high shear mixer 5 and the batch high shear mixer 7 is 5-50 m / s.

[0047] The reaction temperature is 30-90°C, and the high shear reaction time is 1-5 minutes.

[0048] When the glyoxylic acid synthesis device of the present invention is used, solution A and solution B are pumped into a continuous high-shear mixer by the second metering pump 4 and the first metering pump 3, respectively, so that solutions A and B enter the continuous high-shear mixer for a high-shear reaction to obtain solution C. Solution C is pumped into a batch high-shear mixer 7 by the third metering pump 6 and then into solution A by the fourth metering pump 8, so that solutions A and C undergo a high-shear reaction in the batch high-shear mixer 7. After the reaction is completed, a mixture is obtained, which is subjected to extraction, distillation, cooling and crystallization to obtain the target product, glyoxylic acid. The design of inserting a distributor 15 within a continuous high-shear mixer significantly improves reaction efficiency and product quality through the synergistic optimization of high shear action and fluid distribution: the high shear force breaks the reactants into micron / nano-scale dispersed phases, greatly increasing the liquid-liquid contact area, and enhancing mass transfer and reaction rate; the distributor 15 evenly distributes the mixing path of nitric acid and glyoxal to avoid side reactions (such as oxalic acid formation) caused by local excessive concentration, while precisely controlling the residence time and degree of oxidation, thereby improving the selectivity and yield of glyoxylic acid; its continuous operation mode combined with efficient heat transfer capability can stabilize the reaction temperature, reduce energy consumption and by-product formation, and be both safe and environmentally friendly.

[0049] See also Figure 6 A method for synthesizing glyoxylic acid of the present invention comprises the following steps:

[0050] Step 1, preparing a nitric acid solution with a mass concentration of 15% to 65% as solution A;

[0051] Step 2, adding an initiator (sodium nitrite) to the glyoxal solution and stirring to dissolve it to obtain solution B;

[0052] Step 3, solution A is pumped into the first feed port 13 of the continuous high shear mixer by the second metering pump 4, and solution B is pumped into the second feed port 14 of the continuous high shear mixer by the first metering pump 3, so that solution A and solution B enter the continuous high shear mixer for high shear reaction for 1-3 minutes to obtain solution C, wherein the molar ratio of nitric acid to glyoxal in solution B is 0.5-1.2:1, and the molar ratio of sodium nitrite to glyoxal in solution B is 0-0.3:1;

[0053] Solution C is pumped into the intermittent high shear mixer 7 by the third metering pump 6 and into solution A by the fourth metering pump 8. Solutions A and C are subjected to a high shear reaction in the intermittent high shear mixer 7 for 1-2 minutes. The molar ratio of nitric acid in solution A to glyoxal in solution C pumped into the intermittent high shear mixer 7 is 1-1.5:1. After the reaction is completed, the mixture is extracted, distilled, cooled and crystallized to obtain the target product, glyoxylic acid.

[0054] The linear speeds of the rotor 18 of the continuous high shear mixer 5 and the rotor of the intermittent high shear mixer 7 are 5-50 m / s, and the reaction temperature of the continuous high shear mixer 5 and the intermittent high shear mixer 7 is 30-90°C.

[0055] Example 1

[0056] In the apparatus for high shear-enhanced continuous synthesis of glyoxylic acid used in this embodiment, the number of radial channels 16 in the distributor 15 is 15, the number of axial channels 17 is 15, the thickness of the annular cavity of the distributor 15 (i.e., the distance between the inner plate and the outer plate) is 0.5 mm, the height of the axial channel 17 is 8 mm, the number of rotor teeth is 10, the rotor tooth spacing is 1 mm, the distance between the distributor 15 and the rotor is 1 mm, the outside of the rotor is the stator, the number of stator teeth is 20, the stator tooth spacing is 1 mm, the stator-rotor shear gap is 1 mm, the outside of the stator is the housing 21, and the distance between the stator and the housing is 1.5 mm.

[0057] A method for high shear-enhanced continuous synthesis of glyoxylic acid comprises the following steps:

[0058] Step 1, preparing a nitric acid solution with a mass concentration of 45% as solution A;

[0059] Step 2: adding an initiator (sodium nitrite) to the glyoxal solution and stirring to dissolve it to obtain solution B; the molar ratio of nitric acid in solution A to glyoxal in solution B is 1:1; the molar ratio of the initiator sodium nitrite to glyoxal in solution B is 0.1:1;

[0060] Step 3: Solution A is pumped to the first feed port 13 of the continuous high shear mixer by the second metering pump 4, and solution B is pumped to the second feed port 14 of the continuous high shear mixer by the first metering pump 3. Solutions A and B react in the continuous high shear mixer for 2 minutes to obtain solution C.

[0061] Solution C was pumped into the intermittent high shear mixer 7 via the third metering pump 6 and into the solution A via the fourth metering pump 8. The high shear reaction of solution C and solution A continued in the intermittent high shear mixer 7 for 1 minute. The flow ratio of solution A, solution B, and solution C was 1:1:1. The molar ratio of nitric acid in solution A pumped into the intermittent high shear mixer 7 to glyoxal in solution C was 1.4:1. The rotor linear speed of the continuous high shear mixer 5 was 30 m / s, and the rotor linear speed of the intermittent high shear mixer 7 was 50 m / s. The reaction chamber volumes of the continuous high shear mixer 5 and the intermittent high shear mixer 7 were both 15 mL. The reaction was conducted at 75° C. The mixture flowed out of the discharge port and was extracted, distilled, cooled, and crystallized to obtain the target product, glyoxylic acid, in a yield of 91.8%.

[0062] Compared with the yield of 89.2% in the literature (Wang J, Zhan W, Li Y, et al. Complete kinetic model and process reengineering of glyoxal oxidation by nitric acid in a capillary microreactor [J]. Reaction Chemistry & Engineering, 2024, 9 (11): 3016-3028.), the yield of glyoxylic acid prepared in Example 1 of the present invention is increased by 2.6%.

[0063] Example 2

[0064] In the high shear enhanced continuous synthesis of glyoxylic acid device used in this embodiment, the number of radial channels 16 in the distributor 15 is 10, the number of axial channels 17 is 10, the thickness of the annular cavity of the distributor 15 (i.e., the distance between the inner plate and the outer plate) is 0.7 mm, the height of the axial channel 17 is 10 mm, the number of rotor teeth is 8, the rotor tooth pitch is 0.8 mm, the distance between the distributor 15 and the rotor is 0.5 mm, the outside of the rotor is the stator, the number of stator teeth is 16, the stator tooth pitch is 0.8 mm, the stator-rotor shear gap is 0.5 mm, the outside of the stator is the outer shell, and the distance between the stator and the outer shell is 1 mm.

[0065] A method for high shear-enhanced continuous synthesis of glyoxylic acid comprises the following steps:

[0066] Step 1, preparing a nitric acid solution with a mass concentration of 35% as solution A;

[0067] Step 2: adding an initiator (sodium nitrite) to the glyoxal solution and stirring to dissolve it to obtain a solution B; the molar ratio of nitric acid in solution A to glyoxal in solution B is 0.8:1; the molar ratio of the initiator sodium nitrite to glyoxal in solution B is 0.2:1;

[0068] Step 3: Solution A is pumped to the first feed port 13 of the continuous high shear mixer by the second metering pump 4, and solution B is pumped to the second feed port 14 of the continuous high shear mixer by the first metering pump 3. Solutions A and B are reacted in the continuous high shear mixer for 1.5 minutes to obtain solution C.

[0069] Solution C was pumped into the intermittent high shear mixer 7 via the third metering pump 6 and into the solution A via the fourth metering pump 8. The high shear reaction of solution C and solution A continued in the intermittent high shear mixer 7 for 1.5 min. The flow ratio of solution A, solution B, and solution C was 1:1:1. The molar ratio of nitric acid in solution A pumped into the intermittent high shear mixer 7 to glyoxal in solution C was 1.2:1. The linear speed of the rotor of the continuous high shear mixer 5 was 20 m / s, and the linear speed of the rotor of the intermittent high shear mixer 7 was 45 m / s. The reaction chamber volumes of the continuous high shear mixer 5 and the intermittent high shear mixer 7 were both 15 mL. The reaction was conducted at 68° C. The mixture flowed out of the discharge port and was extracted, distilled, cooled, and crystallized to obtain the target product, glyoxylic acid, in a yield of 89.9%.

[0070] Compared with the yield of 84.00% in the literature (Li Guangyao, Cheng Zhengzai, Wang Handing, et al. Preparation and rapid analysis of glyoxylic acid by oxygen-nitric acid combined oxidation [J]. Journal of Henan University of Science&Technology, Natural Science, 2019, 40(2).), the yield of glyoxylic acid prepared in Example 2 of the present invention is increased by 5.9%.

[0071] Example 3

[0072] In the apparatus for high shear-enhanced continuous synthesis of glyoxylic acid used in this embodiment, the number of radial channels 16 in the distributor 15 is 30, the number of axial channels 17 is 30, the thickness of the annular cavity of the distributor 15 (i.e., the distance between the inner plate and the outer plate) is 0.3 mm, the height of the axial channel 17 is 5 mm, the number of rotor teeth is 5, the rotor tooth pitch is 1.5 mm, the distance between the distributor 15 and the rotor is 1.5 mm, the outside of the rotor is the stator, the number of stator teeth is 10, the stator tooth pitch is 1.5 mm, the stator-rotor shear gap is 2 mm, the outside of the stator is the outer shell, and the distance between the stator and the outer shell is 3 mm.

[0073] A method for high shear-enhanced continuous synthesis of glyoxylic acid comprises the following steps:

[0074] Step 1, preparing a nitric acid solution with a mass concentration of 25% as solution A;

[0075] Step 2: adding an initiator (sodium nitrite) to the glyoxal solution and stirring to dissolve it to obtain a solution B; the molar ratio of nitric acid in solution A to glyoxal in solution B is 1.2:1; the molar ratio of the initiator sodium nitrite to glyoxal in solution B is 0.3:1;

[0076] Step 3: Solution A is pumped to the first feed port 13 of the continuous high shear mixer by the second metering pump 4, and solution B is pumped to the second feed port 14 of the continuous high shear mixer by the first metering pump 3. Solutions A and B react in the continuous high shear mixer for 3 minutes to obtain solution C.

[0077] Solution C was pumped into the intermittent high shear mixer 7 via the third metering pump 6 and into the solution A via the fourth metering pump 8. The high shear reaction of solution C and solution A continued in the intermittent high shear mixer 7 for 2 minutes. The flow ratio of solution A, solution B, and solution C was 1:1:1. The molar ratio of nitric acid in solution A to glyoxal in solution C pumped into the intermittent high shear mixer 7 was 1.5:1. The linear speed of the rotor of the continuous high shear mixer 5 was 40 m / s, and the linear speed of the rotor of the intermittent high shear mixer 7 was 50 m / s. The reaction chamber volumes of the continuous high shear mixer 5 and the intermittent high shear mixer 7 were both 15 mL. The reaction was conducted at 60° C. The mixture flowed out of the discharge port and was extracted, distilled, cooled, and crystallized to obtain the target product, glyoxylic acid, in a yield of 88%.

[0078] Compared with the yield of 81.6% in the literature (Zhan W, Wang J, He C, et al. Kinetics of glyoxal oxidation bynitric acid in acapillary microreactor [J]. Chemical Engineering Science, 2023, 276: 118813.), the yield of glyoxylic acid prepared in Example 3 of the present invention is increased by 6.4%.

[0079] Example 4

[0080] In the apparatus for high shear-enhanced continuous synthesis of glyoxylic acid used in this embodiment, the number of radial channels 16 in the distributor 15 is 5, the number of axial channels 17 is 5, the thickness of the annular cavity of the distributor 15 (i.e., the distance between the inner plate and the outer plate) is 0.9 mm, the height of the axial channel 17 is 10 mm, the number of rotor teeth is 10, the rotor tooth pitch is 0.5 mm, the distance between the distributor 15 and the rotor is 0.3 mm, the outside of the rotor is the stator, the number of stator teeth is 20, the stator tooth pitch is 0.5 mm, the stator-rotor shear gap is 1.5 mm, the outside of the stator is the outer shell, and the distance between the stator and the outer shell is 0.8 mm.

[0081] A method for high shear-enhanced continuous synthesis of glyoxylic acid comprises the following steps:

[0082] Step 1, preparing a nitric acid solution with a mass concentration of 55% as solution A;

[0083] Step 2: adding an initiator (sodium nitrite) to the glyoxal solution and stirring to dissolve it to obtain a solution B; the molar ratio of nitric acid in solution A to glyoxal in solution B is 0.5:1; the molar ratio of the initiator sodium nitrite to glyoxal in solution B is 0;

[0084] Step 3: Solution A is pumped to the first feed port 13 of the continuous high shear mixer by the second metering pump 4, and solution B is pumped to the second feed port 14 of the continuous high shear mixer by the first metering pump 3. Solutions A and B are reacted in the continuous high shear mixer for 2 minutes to obtain solution C.

[0085] Solution C was pumped into the intermittent high shear mixer 7 via the third metering pump 6 and into the solution A via the fourth metering pump 8, and the high shear reaction between solution C and solution A continued in the intermittent high shear mixer 7 for 2 minutes. The flow ratio of solution A, solution B, and solution C was 1:1:1. The molar ratio of nitric acid in solution A pumped into the intermittent high shear mixer 7 to glyoxal in solution C was 1:1. The rotor linear speed of the continuous high shear mixer 5 was 10 m / s, and the rotor linear speed of the intermittent high shear mixer 7 was 40 m / s. The reaction chamber volumes of the continuous high shear mixer 5 and the intermittent high shear mixer 7 were both 15 mL. The reaction was carried out at 80° C. The mixture flowed out of the discharge port and was extracted, distilled, cooled, and crystallized to obtain the target product, glyoxylic acid, with a yield of 86.5%.

[0086] Compared with the literature (Liu Jianwu, Yan Shenghu, Zhang Yue. Research on the continuous flow synthesis of glyoxylic acid by nitric acid oxidation of glyoxal [J]. Modern Chemical Industry, 2021, 41(7): 153-157. The yield is 62.9%), the yield of glyoxylic acid prepared in Example 4 of the present invention is increased by 23.6%.

[0087] Example 5

[0088] In the apparatus for high shear-enhanced continuous synthesis of glyoxylic acid used in this embodiment, the number of radial channels 16 in the distributor 15 is 15, the number of axial channels 17 is 15, the thickness of the annular cavity of the distributor 15 (i.e., the distance between the inner plate and the outer plate) is 0.5 mm, the height of the axial channel 17 is 8 mm, the number of rotor teeth is 15, the rotor tooth pitch is 0.2 mm, the distance between the distributor 15 and the rotor is 2 mm, the outside of the rotor is the stator, the number of stator teeth is 30, the stator tooth pitch is 0.1 mm, the stator-rotor shear gap is 3 mm, the outside of the stator is the housing 21, and the distance between the stator and the housing is 0.1 mm.

[0089] A method for high shear-enhanced continuous synthesis of glyoxylic acid comprises the following steps:

[0090] Step 1, preparing a nitric acid solution with a mass concentration of 15% as solution A;

[0091] Step 2: adding an initiator (sodium nitrite) to the glyoxal solution and stirring to dissolve it to obtain a solution B; the molar ratio of nitric acid in solution A to glyoxal in solution B is 0.7:1; the molar ratio of the initiator sodium nitrite to glyoxal in solution B is 0.1:1;

[0092] Step 3: Solution A is pumped to the first feed port 13 of the continuous high shear mixer by the second metering pump 4, and solution B is pumped to the second feed port 14 of the continuous high shear mixer by the first metering pump 3. Solutions A and B react in the continuous high shear mixer for 1 minute to obtain solution C.

[0093] Solution C was pumped into the intermittent high shear mixer 7 via the third metering pump 6 and into the solution A via the fourth metering pump 8. The high shear reaction of solution C and solution A continued in the intermittent high shear mixer 7 for 1 minute. The flow ratio of solution A, solution B, and solution C was 1:1:1. The molar ratio of nitric acid in solution A pumped into the intermittent high shear mixer 7 to glyoxal in solution C was 1:1. The linear speed of the rotor of the continuous high shear mixer 5 was 5 m / s, and the linear speed of the rotor of the intermittent high shear mixer 7 was 50 m / s. The reaction chamber volumes of the continuous high shear mixer 5 and the intermittent high shear mixer 7 were both 15 mL. The reaction was carried out at 30° C. The mixture flowed out of the discharge port and was extracted, distilled, cooled, and crystallized to obtain the target product, glyoxylic acid, in a yield of 85.7%.

[0094] Compared with the yield of 70.3% in the literature (Wang Qihua, Hu Zhengzhong, Yan Changyu, et al. Study on the synthesis of glyoxylic acid by oxidation of glyoxal with hydrogen peroxide [J]. Chemistry and Bioengineering, 2007, 24(3): 70-71.), the yield of glyoxylic acid prepared in Example 5 of the present invention is increased by 15.4%.

[0095] Example 6

[0096] In the apparatus for high shear-enhanced continuous synthesis of glyoxylic acid used in this embodiment, the number of radial channels 16 in the distributor 15 is 15, the number of axial channels 17 is 15, the thickness of the annular cavity of the distributor 15 (i.e., the distance between the inner plate and the outer plate) is 0.5 mm, the height of the axial channel 17 is 8 mm, the number of rotor teeth is 10, the rotor tooth spacing is 2 mm, the distance between the distributor 15 and the rotor is 0.2 mm, the outside of the rotor is the stator, the number of stator teeth is 20, the stator tooth spacing is 2 mm, the stator-rotor shear gap is 0.1 mm, the outside of the stator is the housing 21, and the distance between the stator and the housing is 2 mm.

[0097] A method for high shear-enhanced continuous synthesis of glyoxylic acid comprises the following steps:

[0098] Step 1, preparing a nitric acid solution with a mass concentration of 60% as solution A;

[0099] Step 2: adding an initiator (sodium nitrite) to the glyoxal solution and stirring to dissolve it to obtain a solution B; the molar ratio of nitric acid in solution A to glyoxal in solution B is 1:1; the molar ratio of the initiator sodium nitrite to glyoxal in solution B is 0.2:1;

[0100] Step 3: Solution A is pumped to the first feed port 13 of the continuous high shear mixer by the second metering pump 4, and solution B is pumped to the second feed port 14 of the continuous high shear mixer by the first metering pump 3. Solutions A and B are reacted in the continuous high shear mixer for 2.5 minutes to obtain solution C.

[0101] Solution C was pumped into the intermittent high shear mixer 7 via the third metering pump 6 and into the solution A via the fourth metering pump 8. The high shear reaction of solution C and solution A continued in the intermittent high shear mixer 7 for 2 minutes. The flow ratio of solution A, solution B, and solution C was 1:1:1. The molar ratio of nitric acid in solution A pumped into the intermittent high shear mixer 7 to glyoxal in solution C was 1.3:1. The linear speed of the rotor of the continuous high shear mixer 5 was 15 m / s, and the linear speed of the rotor of the intermittent high shear mixer 7 was 40 m / s. The reaction chamber volumes of the continuous high shear mixer 5 and the intermittent high shear mixer 7 were both 15 mL. The reaction was carried out at 90° C. The mixture flowed out of the discharge port and was extracted, distilled, cooled, and crystallized to obtain the target product, glyoxylic acid, in a yield of 84%.

[0102] Compared with the literature (Liu Jianwu, Yan Shenghu, Zhang Yue. Research on continuous flow synthesis of glyoxylic acid by nitric acid oxidation of glyoxal [J]. Modern Chemical Industry, 2021, 41(7): 153-157. The yield is 62.9%), the yield of glyoxylic acid prepared in Example 6 of the present invention is increased by 21.1%.

[0103] The yield and selectivity of the glyoxylic acid products prepared in Examples 1-6 are shown in Table 1:

[0104] Table 1 Yield and selectivity of Examples 1-6

[0105] Example Yield / % Selectivity / % Example 1 91.8％ 96％ Example 2 89.9％ 94.6％ Example 3 88％ 93.3％ Example 4 86.5％ 92％ Example 5 85.7％ 95％ Example 6 84％ 90％

[0106] As can be seen from Table 1, the yield of glyoxylic acid in the method for synthesizing glyoxylic acid of the present invention is not less than 82%, and the selectivity is not less than 90%.

[0107] The above description is merely a description of the preferred embodiment of the present invention and is not to be construed as limiting the claims. The present invention is not limited to the above embodiment, and variations in the specific structure are permitted. Any variations made within the scope of the independent claims of the present invention are also within the scope of protection of the present invention.

[0108] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

Claims

1. A device for high shear intensified continuous synthesis of glyoxylic acid, characterized in that: It comprises a first liquid storage bottle (1), a second liquid storage bottle (2), a continuous high shear mixer (5) and an intermittent high shear mixer (7); The first liquid storage bottle (1) is connected to the second liquid storage bottle (2) and the feed port of the continuous high shear mixer (5), and the continuous high shear mixer (5) is connected to the intermittent high shear mixer (7); The continuous high shear mixer (5) comprises a first feed port (13), a second feed port (14), a distributor (15), a rotor (18), a stator (19), a discharge port (20) and a housing (21); The distributor (15), the rotor (18) and the stator (19) are arranged in the housing (21), the rotor (18) is arranged outside the distributor (15), the stator (19) is arranged outside the rotor (18), the distributor (15) and the rotor (18) are arranged at intervals, and the rotor (18) and the stator (19) are arranged at intervals.

2. The device for high shear enhanced continuous synthesis of glyoxylic acid according to claim 1, characterized in that: A first feed port (13) and a second feed port (14) are provided on the top of the housing (21), and the first feed port (13) is sleeved inside the second feed port (14).

3. The device for high shear enhanced continuous synthesis of glyoxylic acid according to claim 2, characterized in that: The distributor (15) includes an inner plate and an outer plate that are fitted together, the inner plate being arranged inside the outer plate, and an annular cavity being formed between the inner plate and the outer plate; a plurality of partition plates are evenly arranged along the circumference of the outer plate wall, adjacent partition plates are spaced apart, and the gaps between adjacent partition plates form an axial channel (17), which is connected to the second feed port (14); A first through hole is opened on each partition along the radial direction, and a plurality of second through holes are opened on the inner plate and the outer plate of the annular cavity respectively. The first through holes are connected with the second through holes on the same radius, thereby forming a radial channel (16), and the radial channel (16) is connected with the first feed port (13).

4. The device for high shear enhanced continuous synthesis of glyoxylic acid according to claim 1, characterized in that: A first metering pump (3) is provided between the first liquid storage bottle (1) and the continuous high shear mixer (5), a second metering pump (4) is provided between the second liquid storage bottle (2) and the continuous high shear mixer (5), and a third metering pump (6) is provided between the continuous high shear mixer (5) and the intermittent high shear mixer (7).

5. The device for high shear enhanced continuous synthesis of glyoxylic acid according to claim 1, characterized in that: The distance between the distributor (15) and the rotor (18) is 0.2-2 mm, the distance between the stator (19) and the housing (21) is 0.1-3 mm, the tooth spacing of the rotor (18) is 0.1-2 mm, the number of teeth of the rotor (18) is 5-15, the number of teeth of the stator (19) is 10-30, the tooth spacing of the stator (19) is 0.2-2 mm, and the shear gap between the rotor (18) and the stator (19) is 0.1-3 mm.

6. A method for high shear intensified continuous synthesis of glyoxylic acid based on the apparatus according to any one of claims 1 to 5, characterized in that: The following steps are involved: The first nitric acid solution is conveyed to the first feed port (13) of the continuous high shear mixer (5), the solution containing glyoxal and sodium nitrite is conveyed to the second feed port (14), and a first high shear reaction is carried out to obtain solution C. Solution C is conveyed to the intermittent high shear mixer (7), and the second nitric acid solution is added to the intermittent high shear mixer (7), and a second high shear reaction is carried out to obtain glyoxylic acid.

7. The method for high shear enhanced continuous synthesis of glyoxylic acid according to claim 6, characterized in that: The molar ratio of nitric acid in the first nitric acid solution to glyoxal in solution B is 0.5-1.2:1; the molar ratio of sodium nitrite in solution B to glyoxal is 0-0.3:

1.

8. The method for high shear enhanced continuous synthesis of glyoxylic acid according to claim 6, characterized in that: The rotor linear speed of the rotor (18) and the intermittent high shear mixer (7) is 5-50 m / s.

9. The method for high shear enhanced continuous synthesis of glyoxylic acid according to claim 6, characterized in that: The temperature of the first high shear reaction and the second high shear reaction is 30-90° C., and the time is 1-5 minutes.

10. The method for high shear enhanced continuous synthesis of glyoxylic acid according to claim 6, characterized in that: The molar ratio of nitric acid in the second nitric acid solution to glyoxal in solution C is 1-1.5:1.

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