CN110746326A - A kind of method for continuous production of isethionic acid - Google Patents

Abstract

The invention discloses a method for continuous production of isethionic acid, belonging to the technical field of organic synthesis technology. Using β-mercaptoethanol as the substrate and hydrogen peroxide as the oxidant, in a continuous flow microreactor with a special microstructure, liquid-phase oxidation is carried out continuously within 60s to 180s to produce isethionic acid. After the material is fed into the microchannel reactor by the metering pump, the isethionic acid product is obtained through preheating, mixing reaction and separation. The process method of the invention utilizes the efficient mass transfer and heat transfer efficiency of the microchannel reactor, effectively strengthens the mass transfer rate between materials, stabilizes the reaction temperature, controls the residence time, and greatly improves the safety and operability of the experiment. There is no solvent, phase transfer catalyst and acid auxiliary agent in the medium, which not only reduces the production cost, but also facilitates the separation and purification of isethionic acid, and realizes efficient and continuous production of isethionic acid.

Description

A kind of method for continuous production of isethionic acid

technical field

The invention belongs to the technical field of organic synthesis technology, and in particular relates to a method for preparing isethionic acid by using β-mercaptoethanol as a raw material through H ₂ O ₂ oxidation. A method for continuously producing isethionic acid by using ethanol as a raw material through liquid phase oxidation.

Background technique

Isethionic acid, also known as 2-hydroxyethanesulfonic acid, is an important organic intermediate due to its strong reactive hydroxyl and sulfonic acid groups at the same time and active chemical properties. It is widely used in medicine, cosmetics, and daily chemicals. products and electroplating. In cosmetics and daily chemical products, it is used to produce a series of anionic surfactants. Due to its high water solubility and foaming properties, it is often widely used in soaps, shampoos, and bath products.

In medicine, it is mainly used to produce sodium isethionate, taurine, pentamidine hydroxyethanesulfonate, etc. Sodium isethionate is mainly used to synthesize new fungicides, such as hexamidine di-isethionate, as an anti-dandruff and antipruritic agent, it has obvious effects in shampoos and shampoos with few side effects. Taurine is an amino acid with special physiological functions in the body. It can be used as a food nutritional additive and can also synthesize a variety of drugs. As early as 2004, pentamidine hydroxyethanesulfonate was used to treat pulmonary complications of AIDS. In 2008, Dorlo et al. elaborated on the dosage of pentamidine hydroxyethanesulfonate, and also pointed out that it was used in the treatment of AIDS. role in infectious pneumonia. Because isethionic acid is used more and more widely, its synthesis method has attracted extensive attention.

At present, the methods commonly used in industry to produce isethionic acid are mainly EO method and H ₂ O ₂ oxidation method. The EO method is to add sodium sulfite to ethylene oxide, and the obtained sodium isethionate is desalted.

CN105132440A discloses a method for preparing isethionic acid, which is characterized in that ethylene oxide gas is passed into a synthesis tower equipped with sodium bisulfite, and the reaction is carried out under high pressure at 60-75°C for 1 hour to obtain isethionyl The yield of sodium sulfonate is 95%. The acidification process of this technology has a high requirement on the concentration of hydrochloric acid, and the generated salt is difficult to remove, thereby affecting the purity of the product.

US Patent 005912385A proposes to oxidize β-mercaptoethanol with H ₂ O ₂ to obtain isethionic acid, mercaptoethanol is slowly added dropwise, condensed water is introduced into the reaction process, the reaction is vigorously stirred at room temperature for 10 hours, and then the temperature is increased to 110 ° C and the reaction is continued for 5 hours to obtain The isethionic acid solution with a mass fraction of 54%, in addition, some polluting low-boiling compounds, such as 2-hydroxyethyl disulfide diversification, acetaldehyde, acetic acid, etc., are also generated. The reaction time of this process is long, and it is difficult to realize industrialization.

Wei Dongxu reported the method of H ₂ O ₂ oxidation to obtain isethionic acid. First, add a part of H ₂ O ₂ to the flask. After preheating, slowly add two kinds of raw materials dropwise at the same time. Below 50°C, after the dropwise addition, the condensed water was continuously opened to stir the reaction for 2.5 hours, and the by-product H ₂ SO ₄ was formed due to the deep oxidation of the reaction.

The above-mentioned patent disclosure or the preparation technology of the isethionic acid reported in the literature and its reactors are all reaction flasks or stirring reaction kettles with stirring, and the reaction modes are all batch operations. For the preparation process of isethionic acid, ethylene oxide is a gas at room temperature, and the addition reaction is a gas-liquid reaction system, and gas-liquid mass transfer is often difficult to achieve during the reaction process. The quality of the process often requires a high temperature and high pressure reaction system. The oxidation of β-mercaptoethanol by H ₂ O ₂ to prepare isethionic acid is an exothermic reaction with an exotherm of about 457.8 kJ/mol. Hydrogen peroxide is easily decomposed when heated, releasing oxygen and releasing a lot of heat, which makes the reactants and solvents evaporate in large quantities. For the stirred reactor operating in batch mode under normal pressure or near-normal pressure, its heat exchange area is small and its heat exchange capacity is low, which determines its poor stable temperature control effect and high risk of "flying temperature"; its system is open There are many dead corners of the device, and the process control is in the state of intermittent fluctuation, which determines its low stability and poor safety; its poor mass transfer efficiency and low reaction efficiency determine the serious decomposition of hydrogen peroxide, the large overflow of active oxygen, and the utilization of active oxygen. The rate is low, the material consumption is high, and the material steam explosion danger is high.

Using continuous flow microchannel reaction technology to carry out β-mercaptoethanol oxidation reaction to continuously synthesize isethionic acid products can solve many deficiencies in the existing technology in many aspects, which is the best solution to the oxidation reaction process in conventional tank-type stirred reactors. breakthrough. The microchannel reactor is a special-shaped pipeline reactor with enhanced mass transfer and heat transfer process. Through the special design of the microchannel structure, it can make it have the ideal performance of the plug flow reactor, which can be used for isethion Continuous synthesis of acids. The microchannel reactor has miniaturized pipe size, large specific surface area and high mass and heat transfer characteristics, which can be directly scaled up without the step-by-step scale-up test, flexible production and high safety performance.

SUMMARY OF THE INVENTION

Aiming at the shortcomings of the above processes, the present invention provides a method for continuous production of isethionic acid. Because the microchannel reactor has the structural characteristics of small reaction space and huge specific surface area, mass transfer and heat transfer can be enhanced, and the precise Control the reaction temperature and reaction time, prevent the "flying temperature" phenomenon and the generation of by-products, and improve the conversion rate and yield. At the same time, the microchannel reactor has the characteristics of small liquid holding capacity, short reaction residence time, strong mass transfer, heat transfer effect, no dead volume, etc., to avoid the accumulation of oxygen generated by the decomposition of raw material H ₂ O ₂ in the reactor, and to improve β-mercaptoethanol. Safety of oxidation reactions. A further object of the present invention is to strictly control the reaction temperature and residence time, improve the production efficiency of isethionic acid, and effectively control the generation of by-products through the method for continuous production of isethionic acid of the present invention.

To achieve the above object, the technical scheme adopted in the present invention is:

A method for the continuous production of isethionic acid utilizing a microchannel reactor, is carried out according to the following steps:

(1) Using β-mercaptoethanol as the substrate and hydrogen peroxide as the oxidant, liquid-phase oxidation is carried out in a continuous flow microreactor with a special microstructure to produce isethionic acid. The β-mercaptoethanol and hydrogen peroxide at room temperature were used as reaction materials respectively, and were respectively passed into the preheating module in the microstructure reactor through a metering pump for preheating, and the preheating temperature was controlled by an external heat exchanger.

(2) Control the flow of the material through the metering pump, so that the material enters the coil from different inlets at the same time and enters the coil after preheating to mix and react. After the reaction process is completed, the product flows out from the outlet of the coil, and the reaction liquid is collected and entered into the post-processing process. .

(3) First extract the reaction solution with a small amount of chloroform, remove acetaldehyde and acetic acid that may be generated in the reaction, and retain the aqueous phase. The reaction solution was heated and stirred at 110° C., the water generated in the reaction solution was distilled off under reduced pressure, and an isethionic acid solution was obtained after the reaction was completed.

Wherein the concentration of hydrogen peroxide solution described in step (1) is 40%～60% by mass concentration, the molar ratio of hydrogen peroxide and β-mercaptoethanol is (3.2～3.8): 1, the reaction temperature is 30～50 ℃, the residence time It is 60～180s, and the reaction pressure is 5～15bar. Under this process condition, the synthesis of isethionic acid is carried out, the conversion rate of β-mercaptoethanol is 78.6-94.8%, the mass fraction of isethionic acid aqueous solution is 70-75.6%, and the yield of isethionic acid is 70-75.6%. It is 73.46-87.3%, and the sulfuric acid content is 0.1-0.54%.

The continuous reaction system described therein includes different functional areas such as a preheating zone, a reaction zone, and a quenching zone.

In the process of liquid-phase oxidation of β-mercaptoethanol provided in a continuous flow microreactor in a continuous reaction mode, the raw materials are pumped into the microchannel reaction system by a metering pump, and the reaction temperature is controlled by a water bath. During the reaction, the molar ratio between the materials is changed by adjusting the flow rate of the metering pump, and the pressure in the reaction system is monitored and measured in real time by a pressure gauge. The raw materials are preheated separately in the microchannel reactor, and then mixed and reacted. After a certain (several seconds to several minutes) residence time, the reaction product is obtained at the discharge port.

Compared with the prior art, the present invention has the following main features:

1. The present invention adopts a continuous production method, the reaction time is shortened from the traditional several hours to tens of seconds to several minutes, the production cycle is short, the reaction process is more stable, and the reaction efficiency is significantly improved.

2. The selected microchannel reactor can enhance the mass transfer and heat transfer performance, keep the reaction temperature constant, avoid the phenomenon of flying temperature, reduce the generation of by-products, and improve the safety of the reaction process.

3. The strong mass transfer effect in the selected microchannel reactor enables the liquid-liquid reaction liquid to be fully mixed, effectively avoids excessive oxidation, and improves the selectivity of isethionic acid.

Description of drawings

Fig. 1 is the process flow diagram of the continuous oxidation reaction of β-mercaptoethanol of the present invention to prepare isethionic acid.

Fig. 2 is the device diagram of the continuous flow microchannel reactor used in the present invention: 1, 2 - raw material, 3, 4 - raw material pump, 5, 6 - preheating zone, 7 - micro channel, 8 - quenching zone, 9 - Product collection.

Detailed ways

The present invention will be further illustrated by the following examples, but the content of the present invention is not limited thereby.

The following examples were carried out in a microchannel reactor according to the requirements of the method of the present invention.

Example 1

According to the needs of the reaction process, the microchannel reaction device is adjusted into a preheating zone, a reaction zone and a quenching zone. By adjusting the flow rate of the pump and the channel length of the microchannel, the reaction residence time was controlled to be 60s, the preheating temperature and reaction temperature were set to 30°C, and the reaction pressure was set to 5bar. The substrate β-mercaptoethanol is fed into the preheating zone A of the device through the metering pump 1, and the hydrogen peroxide with a concentration of 40% is fed into the preheating zone B of the device through the pump 2. After the two materials are fully preheated, they enter the reaction zone. Mixed reactions. Wherein, the molar ratio of hydrogen peroxide and β-mercaptoethanol is 3.2:1. Isethionic acid is continuously discharged from the outlet and collected into the product collector. The reaction solution is extracted and distilled under reduced pressure to obtain the product. The product is analyzed by HPLC. The conversion rate of the raw material β-mercaptoethanol is 78.6%. The concentrations of isethionic acid and sulfuric acid were analyzed by titration and precipitation to obtain a 70% w/w aqueous solution of isethionic acid (73.46% yield, 0.1% sulfuric acid content).

Example 2

According to the needs of the reaction process, the microchannel reaction device is adjusted into a preheating zone, a reaction zone and a quenching zone. By adjusting the flow rate of the pump and the channel length of the microchannel, the reaction residence time was controlled to 70s, the preheating temperature and the reaction temperature were set to 35°C, and the reaction pressure was set to 10bar. The substrate β-mercaptoethanol is fed into the preheating zone A of the device through the metering pump 1, and the hydrogen peroxide with a concentration of 35% is fed into the preheating zone B of the device through the pump 2. After the two materials are fully preheated, they enter the reaction zone. Mixed reactions. Wherein, the molar ratio of hydrogen peroxide and β-mercaptoethanol is 3.3:1. Isethionic acid is continuously discharged from the outlet and collected into the product collector. The reaction solution is extracted and distilled under reduced pressure to obtain the product. The product is analyzed by HPLC. The conversion rate of the raw material β-mercaptoethanol is 85.5%. The concentrations of isethionic acid and sulfuric acid were analyzed by titration and precipitation to obtain a 73.7% w/w aqueous solution of isethionic acid (79.15% yield, 0.15% sulfuric acid content).

Example 3

According to the needs of the reaction process, the microchannel reaction device is adjusted into a preheating zone, a reaction zone and a quenching zone. By adjusting the flow rate of the pump and the channel length of the microchannel, the reaction residence time was controlled to be 80s, the preheating temperature and reaction temperature were set to 40°C, and the reaction pressure was set to 10bar. The substrate β-mercaptoethanol is fed into the preheating zone A of the device through the metering pump 1, and the hydrogen peroxide with a concentration of 40% is fed into the preheating zone B of the device through the pump 2. After the two materials are fully preheated, they enter the reaction zone. Mixed reactions. Wherein, the molar ratio of hydrogen peroxide and β-mercaptoethanol is 3.4:1. Isethionic acid is continuously discharged from the outlet and collected into the product collector. The reaction solution is extracted and distilled under reduced pressure to obtain the product. The product is analyzed by HPLC. The conversion rate of the raw material β-mercaptoethanol is 89.2%. The concentrations of isethionic acid and sulfuric acid were analyzed by titration and precipitation to obtain 72.6% w/w isethionic acid in water (yield 85.54%, sulfuric acid content 0.23%).

Example 4

According to the needs of the reaction process, the microchannel reaction device is adjusted into a preheating zone, a reaction zone and a quenching zone. By adjusting the flow rate of the pump and the channel length of the microchannel, the reaction residence time was controlled to be 90s, the preheating temperature and the reaction temperature were set to 40°C, and the reaction pressure was set to 15bar. The substrate β-mercaptoethanol is fed into the preheating zone A of the device through the metering pump 1, and the hydrogen peroxide with a concentration of 45% is fed into the preheating zone B of the device through the pump 2. After the two materials are fully preheated, they enter the reaction zone. Mixed reactions. Wherein, the molar ratio of hydrogen peroxide and β-mercaptoethanol is 3.5:1. Isethionic acid is continuously discharged from the outlet and collected into the product collector. The reaction solution is extracted and distilled under reduced pressure to obtain the product. The product is analyzed by HPLC. The conversion rate of the raw material β-mercaptoethanol is 91.2%. The concentrations of isethionic acid and sulfuric acid were analyzed by titration and precipitation to obtain a 74.8% w/w aqueous solution of isethionic acid (87.3% yield, 0.3% sulfuric acid content).

Example 5

According to the needs of the reaction process, the microchannel reaction device is adjusted into a preheating zone, a reaction zone and a quenching zone. By adjusting the flow rate of the pump and the channel length of the microchannel, the reaction residence time was controlled to 90s, the preheating temperature and the reaction temperature were set to 50°C, and the reaction pressure was 15bar. The substrate β-mercaptoethanol is fed into the preheating zone A of the device through the metering pump 1, and the hydrogen peroxide with a concentration of 50% is fed into the preheating zone B of the device through the pump 2. After the two materials are fully preheated, they enter the reaction zone. Mixed reactions. Wherein, the molar ratio of hydrogen peroxide and β-mercaptoethanol is 3.4:1. Isethionic acid is continuously discharged from the outlet and collected into the product collector. The reaction solution is extracted and distilled under reduced pressure to obtain the product. The product is analyzed by HPLC. The conversion rate of the raw material β-mercaptoethanol is 92.5%. The concentrations of isethionic acid and sulfuric acid were analyzed by titration and precipitation to obtain a 73.2% w/w aqueous solution of isethionic acid (85% yield, 0.38% sulfuric acid content).

Example 6

According to the needs of the reaction process, the microchannel reaction device is adjusted into a preheating zone, a reaction zone and a quenching zone. By adjusting the flow rate of the pump and the channel length of the microchannel, the reaction residence time was controlled to be 120 s, the preheating temperature and the reaction temperature were set to 50 °C, and the reaction pressure was set to 15 bar. The substrate β-mercaptoethanol is fed into the preheating zone A of the device through the metering pump 1, and the hydrogen peroxide with a concentration of 50% is fed into the preheating zone B of the device through the pump 2. After the two materials are fully preheated, they enter the reaction zone. Mixed reactions. Wherein, the molar ratio of hydrogen peroxide and β-mercaptoethanol is 3.8:1. Isethionic acid is continuously discharged from the outlet and collected into the product collector. The reaction solution is extracted and distilled under reduced pressure to obtain the product. The product is analyzed by HPLC. The conversion rate of the raw material β-mercaptoethanol is 93.82%. The concentrations of isethionic acid and sulfuric acid were analyzed by titration and precipitation to obtain 73.8% w/w isethionic acid in water (yield 82.9%, sulfuric acid content 0.45%).

Example 7

According to the needs of the reaction process, the microchannel reaction device is adjusted into a preheating zone, a reaction zone and a quenching zone. By adjusting the flow rate of the pump and the channel length of the microchannel, the reaction residence time was controlled to be 180s, the preheating temperature and the reaction temperature were set to 50°C, and the reaction pressure was set to 15bar. The substrate β-mercaptoethanol is fed into the preheating zone A of the device through the metering pump 1, and the hydrogen peroxide with a concentration of 60% is fed into the preheating zone B of the device through the pump 2. After the two materials are fully preheated, they enter the reaction zone. Mixed reactions. Wherein, the molar ratio of hydrogen peroxide and β-mercaptoethanol is 3.8:1. Isethionic acid is continuously discharged from the outlet and collected into the product collector. The reaction solution is extracted and distilled under reduced pressure to obtain the product. The product is analyzed by HPLC. The conversion rate of the raw material β-mercaptoethanol is 94.8%. The concentrations of isethionic acid and sulfuric acid were analyzed by titration and precipitation to obtain 75.6% w/w isethionic acid in water (yield 86.31%, sulfuric acid content 0.54%).

The above description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited to this. Any person skilled in the art can easily think of changes within the technical scope disclosed by the present invention. Subsequent replacements should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims (4)

1. A method for continuously producing hydroxyethyl sulfonic acid by using a microchannel reactor is characterized by comprising the following steps:

(1) using β -mercaptoethanol as a substrate and hydrogen peroxide as an oxidant, and carrying out liquid-phase oxidation in a continuous flow microreactor with a special microstructure to produce the hydroxyethyl sulfonic acid, wherein β -mercaptoethanol and hydrogen peroxide at room temperature are respectively used as reaction materials and are respectively introduced into a preheating module in a microstructure reactor through a metering pump to be preheated, and the preheating temperature is controlled by an external heat exchanger;

(2) controlling the flow of the materials by a metering pump, enabling the preheated materials to synchronously enter reactor modules with different microchannel structures for mixing reaction, after the reaction process is finished, enabling a product to flow out of an outlet of the reactor, entering a closed pressure container to collect reaction liquid, and entering a post-treatment process;

(3) firstly, extracting reaction liquid by using a small amount of chloroform, removing acetaldehyde and acetic acid which are possibly generated in the reaction, and keeping a water phase; heating and stirring the reaction solution at 110 ℃, distilling under reduced pressure to remove water generated in the reaction solution, and obtaining the hydroxyethyl sulfonic acid solution after the reaction is finished.

2. The method of claim 1, wherein all reactions are continuous processes, and the microchannel reaction system comprises different functional zones such as a preheating zone, a reaction zone, and a quenching zone.

3. The method of claim 1, wherein the microchannel module structure comprises a straight-flow channel, a flat pipeline with a rectangular cross section, a pancake pulse variable diameter rectangular flat pipeline, an inclined pancake pulse variable diameter rectangular flat pipeline, an enhanced mixed pancake rectangular flat pipeline, and an enhanced mixed inclined pancake rectangular flat pipeline.

4. The method for continuously producing the isethionic acid according to claim 1, wherein the concentration of the aqueous hydrogen peroxide solution is 40-60% by mass, the molar ratio of hydrogen peroxide to β -mercaptoethanol is (3.2-3.8): 1, the reaction temperature is 30-50 ℃, the residence time is 60-180 s, and the reaction pressure is 5-15 bar.

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