Continuous process for the preparation of industrial glyoxylic acid

Abstract

The technical scheme of the present application discloses a continuous preparation process of industrial glyoxylic acid, and belongs to the technical field of fine organic chemical industry and glyoxylic acid synthesis. The main innovation of the present application is to introduce microfluidic technology and microporous membrane separation technology into the synthesis process, and to use a composite catalyst to catalyze the air oxidation of glyoxal to synthesize glyoxylic acid. Compared with the prior art, the present application has the following obvious beneficial effects: (1) the process is safe, continuous, fast, high in production efficiency and small in space occupation; (2) no waste water, waste gas and waste solid are produced, and the recycled water can be recycled, which is very beneficial to environmental protection and water resource saving; (3) the composite noble metal catalyst is low in consumption, and the conversion rate of glyoxal is greatly improved; and (4) the present application has the characteristics that high-content glyoxylic acid can be obtained without distillation and concentration, which is very beneficial to reducing the production cost.

Description

Technical Field

[0001] This invention belongs to the field of fine organic chemical processes and equipment technology, and specifically relates to a continuous preparation process for industrial glyoxylic acid. Background Technology

[0002] Glyoxylic acid is an important organic synthesis intermediate, widely used in the synthesis of fragrances, pharmaceuticals, pesticides, food, varnish raw materials, dyes, plastic additives, etc. It can also be used in products such as vanillin, ethyl vanillin, mandelic acid, p-hydroxyphenylglycine, p-hydroxyphenylacetic acid, and allantoin.

[0003] The synthesis processes of glyoxylic acid are basically divided into two categories: chemical synthesis, including glyoxal nitric acid oxidation, maleic anhydride ozone oxidation, and glyoxal hydrogen peroxide oxidation, and electrochemical synthesis, mainly the oxalic acid electrolytic reduction method. Currently, the main production processes used in China are the glyoxal nitric acid oxidation method and the oxalic acid electrolytic reduction method.

[0004] The "glyoxal-nitric acid oxidation method" is currently a relatively mature and low-cost method for synthesizing glyoxylic acid. It involves the oxidation of glyoxal to glyoxylic acid by dilute nitric acid under the action of a composite catalyst. During the oxidation process, a large amount of oxalic acid and nitric oxide are produced as byproducts.

[0005] The chemical reaction equation for the oxidation of glyoxal with nitric acid is as follows:

[0006] 3CHO-CHO +2HNO3→ 3CHO-COOH +2NO↑+H2O

[0007] 3CHO-COOH+2HNO3→ 3HOOC-COOH+2NO↑+H2O.

[0008] The synthesis of glyoxylic acid from glyoxal via nitric acid oxidation often employs a batch reactor production method. This method suffers from difficulties in separating waste acid and results in low product purity, making it unsuitable as a raw material for high-end products. The drawbacks of this process are: 1) nitric acid corrodes equipment; 2) high concentrations can easily lead to dangerous conditions such as violent boiling; 3) the generated nitric oxide and nitrogen dioxide gases are environmentally harmful; and 4) residual glyoxal can interfere with and limit the further application of glyoxylic acid.

[0009] Because the process generates nitric oxide and nitrogen dioxide gases that are harmful to the environment, and because the reaction is prone to boiling over and overflowing, it is gradually being strictly controlled by national safety authorities and manufacturers are seeking alternatives.

[0010] The method of synthesizing glyoxylic acid by "oxalic acid electrolytic reduction" is usually carried out in an electrolytic cell, and its electrochemical reaction equation is as follows:

[0011] Anode H₂O – 2e → 2H + 1 / 2 O

[0012] Cathode HOOC-COOH + 2H + 2e → HOOC-CHO + H2O

[0013] Although the "oxalic acid electrolytic reduction method" is simple, it consumes a lot of electricity and produces glyoxylic acid with a concentration of only 4.0-5.0%. It requires multi-stage distillation and concentration to obtain high-concentration or crystalline glyoxylic acid, which is too energy-intensive. Summary of the Invention

[0014] With the aim of achieving low carbon emissions, energy conservation, environmental protection, and addressing the aforementioned defects in glyoxylic acid synthesis processes, we utilized microchannel reactors and microporous membrane filter presses to introduce microfluidic and microseparation technologies into the air catalytic oxidation of glyoxal to synthesize glyoxylic acid, achieving the expected results.

[0015] The present invention discloses a continuous preparation process for industrial glyoxylic acid. Its innovation lies in utilizing a microchannel reactor, using glyoxal and air as raw materials, to synthesize glyoxylic acid in a single step under the action of a composite noble metal catalyst. This process is a gas-liquid reaction, highly suitable for the application of microfluidics technology. To put it simply, the raw materials glyoxal and air enter the microchannel reactor from one end, while the high-quality product glyoxylic acid continuously flows out from the other end of the reactor.

[0016] The continuous preparation process of industrial glyoxylic acid according to the technical solution of the present invention is characterized by comprising the following steps:

[0017] (1) The composite catalyst is activated and then loaded into a microchannel reactor;

[0018] (2) Mix air and glyoxal in a gas-liquid mixture and then pressurize and send it into a microchannel reactor;

[0019] (3) Glyoxylic acid was synthesized in a microchannel reactor in one step according to the set temperature, pressure and time. The chemical reaction equation is as follows.

[0020] 2CHO-CHO + O2 → 2CHOCOOH;

[0021] (4) After depressurization, cooling and gas-liquid separation, the water is removed and concentrated in a microporous membrane filter press using microporous membrane separation technology to obtain glyoxylic acid with a content of 60%±.

[0022] Preferably, the continuous preparation process of industrial glyoxylic acid according to the technical solution of the present invention is characterized in that the composite catalyst is a mixture of two or more of Pd / C, Ag / Al2O3, Pt / Al2O3, and Pt-Cu wire mesh.

[0023] Preferably, the continuous preparation process of industrial glyoxylic acid according to the technical solution of the present invention is characterized in that the composite catalyst is preferably a mixture of Ag / Al2O3 and Pt / Al2O3, and the mixing ratio of the two is 4 to 8:1.

[0024] Preferably, the continuous preparation process of industrial glyoxylic acid according to the technical solution of the present invention is characterized in that the composite catalyst Ag / Al2O3 and Pt / Al2O3 are mixed in a ratio of 4 to 8:1, and then soaked in a 10% copper nitrate solution at a temperature of 20 to 40°C for 16 to 24 hours.

[0025] Preferably, the continuous preparation process of industrial glyoxylic acid according to the technical solution of the present invention is characterized in that, after the composite catalyst soaked in copper nitrate solution is filtered dry, it is first dried at a temperature of 100-120°C for 4.0-6.0 h, and then activated at a temperature of 500-600°C for 4.0-6.0 h.

[0026] Preferably, the continuous preparation process of industrial glyoxylic acid according to the technical solution of the present invention is characterized in that the raw material glyoxal is diluted into a 16-20% glyoxal aqueous solution.

[0027] Preferably, the continuous preparation process of industrial glyoxylic acid according to the technical solution of the present invention is characterized in that the ratio of air to glyoxal feed rate is controlled at 1:4 to 6, preferably 1:4.5.

[0028] Preferably, the continuous preparation process of industrial glyoxylic acid according to the technical solution of the present invention is characterized in that the temperature of zone I of the microchannel reactor is controlled at 110-115℃, the temperature of zone II is controlled at 125-130℃, and the temperature of zone III is controlled at 140-150℃.

[0029] Preferably, the continuous preparation process of industrial glyoxylic acid according to the technical solution of the present invention is characterized in that the control system pressure in the microchannel reactor is controlled at 0.6 to 1.2 MPa.

[0030] Preferably, the continuous preparation process of industrial glyoxylic acid according to the technical solution of the present invention is characterized in that the residence time of air and glyoxal in the microchannel reactor is controlled to be 4.5 to 10.0 s.

[0031] Preferably, the continuous preparation process of industrial glyoxylic acid according to the technical solution of the present invention is characterized in that the working pressure of the microporous membrane filter press is set to 0.5-1.2 MPa and the working temperature is set to 100-120℃.

[0032] Preferably, the continuous preparation process of industrial glyoxylic acid according to the technical solution of the present invention is characterized in that the water pressed out by the microporous membrane filter is reused as reclaimed water in the glyoxal dilution process.

[0033] Preferably, the continuous preparation process of industrial glyoxylic acid described in the technical solution of the present invention is adapted to a combined device for preparing glyoxylic acid using a microchannel reactor, characterized in that it consists of a glyoxal dilution tank, a gas-liquid mixing injector, a microchannel reactor, a back pressure connecting pipe, a microchannel heat exchanger, a gas-liquid separator, and a microporous membrane filter press.

[0034] The continuous preparation process of industrial glyoxylic acid described in the technical solution of this invention has significant beneficial effects in four aspects compared with the prior art: (1) the process is safe, continuous and fast, with high production efficiency and small space occupation; (2) no wastewater, waste gas and solid waste are generated, and water can be recycled; (3) the consumption of composite precious metal catalyst is low and the conversion rate of glyoxal is greatly improved; (4) it also has the characteristic of obtaining high content glyoxylic acid without distillation and concentration.

[0035] The continuous preparation process of industrial glyoxylic acid described in this invention is a low-carbon, energy-saving, and environmentally friendly process, which is very beneficial for reducing energy consumption, protecting the environment, and reusing water resources, and is also very beneficial for reducing production costs. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the technical solutions of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0037] Figure 1 This is a simplified flow diagram illustrating a continuous preparation process of industrial glyoxylic acid according to an embodiment of the technical solution of the present invention.

[0038] Figure 2 This is a schematic diagram of the structure and process of a combined device for preparing industrial glyoxylic acid, which is compatible with a continuous preparation process of industrial glyoxylic acid according to an embodiment of the technical solution of the present invention.

[0039] Figure 2In the middle section: Glyoxal dilution tank 01, gas-liquid mixing injector 02, microchannel reactor 03, back pressure connecting pipe 04, microchannel heat exchanger 05, gas-liquid separator 06, booster pump 07, microporous membrane filter press 08, glyoxylic acid collection tank 09, reclaimed water collection tank 10, raw material glyoxal inlet 102, reclaimed water inlet 101, glyoxal transfer pump 103, air inlet 201, diluted glyoxal inlet 202, back pressure valve 501, exhaust gas pipe 601, liquid-blocking mesh layer 602, nanocolumn 801, small molecule outlet 802, macromolecule outlet 803, glyoxylic acid outlet 901, reclaimed water outlet 1001. Implementation

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the following description is provided in conjunction with the appendix. Figure 2 The embodiments of the present invention will be further described below.

[0041] The continuous preparation process of industrial glyoxylic acid described in this specific embodiment is characterized by comprising the following steps:

[0042] (1) Activate the composite catalyst and then load it into the microchannel reactor;

[0043] (2) Mix air and glyoxal in a gas-liquid mixture and then pressurize and send it into a microchannel reactor;

[0044] (3) Glyoxylic acid was synthesized in a microchannel reactor in one step according to the set temperature, pressure and time. The chemical reaction equation is as follows.

[0045] 2CHO-CHO + O2 → 2CHOCOOH;

[0046] (4) After depressurization, cooling and gas-liquid separation, the water is removed and concentrated in a microporous membrane filter press using microporous membrane separation technology to obtain glyoxylic acid with a content of 60%±.

[0047] Furthermore, the continuous preparation process of industrial glyoxylic acid described in this specific embodiment is characterized in that the composite catalyst is a mixture of two or more of Pd / C, Ag / Al2O3, Pt / Al2O3, and Pt-Cu wire mesh.

[0048] Furthermore, the continuous preparation process of industrial glyoxylic acid described in this specific embodiment is characterized in that the composite catalyst is preferably a mixture of Ag / Al2O3 and Pt / Al2O3, with a mixing ratio of 4 to 8:1.

[0049] Furthermore, the continuous preparation process of industrial glyoxylic acid described in this specific embodiment is characterized in that the composite catalyst Ag / Al2O3 and Pt / Al2O3 are mixed in a ratio of 4 to 8:1, and then immersed in a 10% copper nitrate solution at a temperature of 20 to 40°C for 16 to 24 hours.

[0050] Furthermore, the continuous preparation process of industrial glyoxylic acid described in this specific embodiment is characterized in that, after the composite catalyst soaked in 10% copper nitrate solution is filtered dry, it is first dried at a temperature of 100-120°C for 4.0-6.0 hours, and then activated at a temperature of 500-600°C for 4.0-6.0 hours.

[0051] Furthermore, the continuous preparation process of industrial glyoxylic acid described in this specific embodiment is characterized in that the raw material glyoxal is diluted into a 16-20% glyoxal aqueous solution.

[0052] Furthermore, the continuous preparation process of industrial glyoxylic acid described in this specific embodiment is characterized in that the ratio of air to glyoxal feed rate is controlled at 1:4 to 6, preferably 1:4.5.

[0053] Furthermore, the continuous preparation process of industrial glyoxylic acid described in this specific embodiment is characterized in that the temperature of zone I of the microchannel reactor is controlled at 110-115°C, the temperature of zone II at 125-130°C, and the temperature of zone III at 140-150°C.

[0054] Furthermore, the continuous preparation process of industrial glyoxylic acid described in this specific embodiment is characterized in that the control system pressure inside the microchannel reactor is controlled at 0.6 to 1.2 MPa.

[0055] Furthermore, in the continuous preparation process of industrial glyoxylic acid described in this specific embodiment, the residence time of air and glyoxal in the microchannel reactor is controlled to be between 4.5 and 10.0 s.

[0056] Furthermore, in the continuous preparation process of industrial glyoxylic acid described in this specific embodiment, the working pressure of the microporous membrane filter press is set to 0.5-1.2 MPa, and the working temperature is set to 100-120°C.

[0057] Furthermore, the continuous preparation process of industrial glyoxylic acid described in this specific embodiment is characterized in that the water pressed out by the microporous membrane filter is reused as reclaimed water in the glyoxal dilution process.

[0058] Furthermore, the continuous preparation process of industrial glyoxylic acid described in this specific embodiment is adapted to a combined device for preparing glyoxylic acid using a microchannel reactor, which can achieve the purpose of this invention. The device is characterized by being composed of a glyoxal dilution tank, a gas-liquid mixing injector, a microchannel reactor, a back pressure connecting pipe, a microchannel heat exchanger, a gas-liquid separator, and a microporous membrane filter press.

[0059] Furthermore, a combined apparatus for synthesizing glyoxylic acid using a microchannel reactor to achieve the purpose of this invention includes: a glyoxal dilution tank 01, a gas-liquid mixing injector 02, a microchannel reactor 03, a back pressure connecting pipe 04, a microchannel heat exchanger 05, a gas-liquid separator 06, a booster pump 07, a microporous membrane filter press 08, a glyoxylic acid collection tank 09, a reclaimed water collection tank 10, a raw material glyoxal inlet 102, a reclaimed water inlet 101, a glyoxal transfer pump 103, an air inlet 201, a diluted glyoxal inlet 202, a back pressure valve 501, a tail gas pipe 601, a liquid-blocking mesh layer 602, a nanocolumn 801, a small molecule outlet 802, a large molecule outlet 803, a glyoxylic acid outlet 901, and a reclaimed water outlet 1001. Example

[0060] Prepare 100.0 kg of 40% glyoxal for calculation and feeding. (1) First, mix the precious metal catalyst Ag / Al2O3 and Pt / Al2O3 at a ratio of 4:1, then soak them in a 10% copper nitrate solution for 20 h, filter them, dry them at 110 °C, and then activate them at 500 °C. (2) Dilute the 40% glyoxal to a 19.8% glyoxal aqueous solution in a glyoxal dilution tank 01. (3) Then mix the high-temperature treated precious metal catalyst Ag / Al2O3 and Pt / (3) The mixture of Al2O3 is loaded into the catalyst module area of ​​Zone I of the microchannel reactor 03; (4) The high-pressure air and glyoxal aqueous solution transfer pump 103 is started, and the feed rate ratio is controlled at 1:5.0 to enter the gas-liquid mixing injector 02, so that the two are fully mixed and pressurized and pushed into the microchannel reactor 03; (5) The temperature of Zone I in the microchannel reactor 03 is controlled at 115℃, the temperature of Zone II is controlled at 123℃, and the temperature of Zone III is controlled at 145℃. The system pressure in the microchannel reactor 03 is controlled between 0.8 and 0.9 MPa, and the residence time of air and glyoxal in the microchannel reactor 03 is controlled at 4.5 to 10.0 s; (5) The crude glyoxylic acid obtained from the synthesis is depressurized and cooled by the microchannel heat exchanger 05, and then transferred to the gas-liquid separator 06 for gas-liquid separation. After being pressurized, it is passed through the microporous membrane filter press 08 at a temperature of 110℃ and a pressure of 0.8MPa to remove most of the water, resulting in 84.61 kg of high-concentration glyoxylic acid with a yield of 99.12%. If necessary, it can be further concentrated, cooled and crystallized to obtain 45.03 kg of high-purity crystalline glyoxylic acid with a yield of 88.2% and a glyoxylic acid crystal content of 99.6%. (6) The water from the microporous membrane filter press 08 is returned to the glyoxal dilution tank 01 for reuse as recycled water. Example

[0061] Prepare 500.0 kg of 40% glyoxal for calculation and feeding. (1) First, mix the precious metal catalyst Ag / Al2O3 and Pt / Al2O3 at a ratio of 5:1, then soak them in a 10% copper nitrate solution for 22 hours. After filtration and drying at 110℃, activate them at 550℃. (2) Dilute the 40% glyoxal to a 19.8% glyoxal aqueous solution in a glyoxal dilution tank 01. (3) Then mix the high-temperature treated precious metal catalyst Ag / Al2O3 and Pt / (3) The mixture of Al2O3 is loaded into the catalyst module area of ​​Zone I of the microchannel reactor 03; (4) The high-pressure air and glyoxal aqueous solution transfer pump 103 is started, and the feed rate ratio is controlled at 1:4.8 to enter the gas-liquid mixing injector 02, so that the two are fully mixed and pressurized and pushed into the microchannel reactor 03; (5) The temperature of Zone I in the microchannel reactor 03 is controlled at 115℃, the temperature of Zone II is controlled at 129℃, and the temperature of Zone III is controlled at 148℃. The system pressure in the microchannel reactor 03 is controlled between 0.8 and 0.9 MPa, and the residence time of air and glyoxal in the microchannel reactor 03 is controlled at 4.5 to 10.0 s; (5) The crude glyoxylic acid obtained from the synthesis is depressurized and cooled by the microchannel heat exchanger 05, and then transferred to the gas-liquid separator 06 for gas-liquid separation. After being pressurized, it is passed through the microporous membrane filter press 08 at a temperature of 110℃ and a pressure of 0.8MPa to remove most of the water, resulting in 420.1 kg of high-concentration glyoxylic acid with a yield of 60.2% and a yield of 99.06%. If necessary, it can be further concentrated, cooled, and crystallized to obtain 225.18 kg of high-purity crystalline glyoxylic acid with a yield of 88.2% and a glyoxylic acid crystal content of 99.6%. (6) The water from the microporous membrane filter press 08 is returned to the glyoxal dilution tank 01 for reuse as recycled water. Example

[0062] Prepare 600.0 kg of 40% glyoxal for calculation and feeding. (1) First, mix the precious metal catalyst Ag / Al2O3 and Pt / Al2O3 at a ratio of 5:1, then soak them in a 10% copper nitrate solution for 18 hours. After filtration and drying at 110℃, activate them at 500℃. (2) Dilute the 40% glyoxal to a 20.0% glyoxal aqueous solution in a glyoxal dilution tank 01. (3) Then mix the high-temperature treated precious metal catalyst Ag / Al2O3 with Pt / The Al2O3 mixture was loaded into the catalyst module area of ​​zone I of the microchannel reactor 03; (3) the high-pressure air and glyoxal aqueous solution transfer pump 103 was started, and the feed rate ratio was controlled at 1:4.5 to enter the gas-liquid mixing injector 02, so that the two were fully mixed and pressurized and pushed into the microchannel reactor 03; (4) the temperature of zone I in the microchannel reactor 03 was controlled at 110℃, the temperature of zone II was controlled at 128℃, and the temperature of zone III was controlled at 145℃. The system pressure in the microchannel reactor 03 was controlled between 0.8 and 0.9 MPa, and the residence time of air and glyoxal in the microchannel reactor 03 was controlled at 4.5 to 10.0 s; (5) The crude glyoxylic acid obtained from the synthesis is then depressurized and cooled by the microchannel heat exchanger 05, and then transferred to the gas-liquid separator 06 for gas-liquid separation. After being pressurized, it is then passed through the microporous membrane filter press 08 at a temperature of 118℃ and a pressure of 0.8MPa to remove most of the water, resulting in 497.62 kg of high-concentration glyoxylic acid with a yield of 99.08%. If necessary, it can be further concentrated, cooled, and crystallized to obtain 269.91 kg of high-purity crystalline glyoxylic acid with a yield of 88.1% and a glyoxylic acid crystal content of 99.7%. (6) The water pressed out from the microporous membrane filter press 08 is returned to the glyoxal dilution tank 01 for reuse as recycled water.

[0063] The general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the scope of protection of the invention. The scope of protection of the invention is to be consistent with the widest range of principles and novel features described herein.

Claims

1. A continuous preparation process for industrial glyoxylic acid, characterized in that, It includes the following steps: (1) The composite catalyst is activated and then loaded into a microchannel reactor; the composite catalyst is a mixture of Ag / Al2O3 and Pt / Al2O3, and the mixing ratio of the two is 4 to 8:

1. (2) Air and glyoxal are mixed in a gas-liquid mixture and then pressurized and fed into a microchannel reactor; the temperature of zone I of the microchannel reactor is controlled at 110-115℃, the temperature of zone II at 125-130℃, and the temperature of zone III at 140-150℃, and the system pressure inside the microchannel reactor is controlled at 0.6-1.2MPa; the residence time of air and glyoxal in the microchannel reactor is controlled at 4.5-10.0s; (3) Glyoxylic acid was synthesized in a microchannel reactor in one step according to the set temperature, pressure, and time. The chemical reaction equation is as follows. 2CHO-CHO+O2→2CHOCOOH; (4) After depressurization, cooling, and gas-liquid separation, the water is removed and concentrated in a microporous membrane filter press using microporous membrane separation technology to obtain glyoxylic acid with a content of 60%±.

2. The continuous preparation process of industrial glyoxylic acid according to claim 1, characterized in that, The composite catalyst Ag / Al2O3 and Pt / Al2O3 are mixed in a ratio of 4 to 8:1, and then soaked in a 10% copper nitrate solution at a temperature of 20 to 40°C for 16 to 24 hours.

3. The continuous preparation process of industrial glyoxylic acid according to claim 1, characterized in that, The composite catalyst, after being soaked in a 10% copper nitrate solution, is filtered dry and then dried at 100–120°C for 4.0–6.0 h, followed by activation at 500–600°C for 4.0–6.0 h.

4. The continuous preparation process of industrial glyoxylic acid according to claim 1, characterized in that, The raw material glyoxal is diluted to a 16-20% glyoxal aqueous solution.

5. The continuous preparation process of industrial glyoxylic acid according to claim 1, characterized in that, The ratio of air to glyoxal feed rate is controlled at 1:4 to 6.

6. The continuous preparation process of industrial glyoxylic acid according to claim 1, characterized in that, The working pressure of the microporous membrane filter press is set to 0.5-1.2 MPa, and the working temperature is set to 100-120℃.

7. The continuous preparation process of industrial glyoxylic acid according to claim 1, characterized in that, The water extracted by the microporous membrane filter press is reused as reclaimed water in the glyoxal dilution process.

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