Falling film-gas stripping coupled reaction system and process for preparing 3-hydroxypropionaldehyde by hydrating propenal

Abstract

The application discloses a falling-film-air stripping coupled reaction system and process for preparing 3-hydroxypropionaldehyde by hydrating propenal, and relates to the technical field of 3-hydroxypropionaldehyde preparation. In the application, the aqueous solution of propenal is distributed along the inner wall of the falling-film reactor by a falling-film distributor to form a thin reaction liquid film and to occur a hydration reaction, and the unreacted propenal is stripped by countercurrently passing inert carrier gas from the bottom, the propenal and gas phase continue to react after being condensed and backflowing, the 3-hydroxypropionaldehyde crude product with low propenal residue is continuously taken out from the bottom, and can be directly introduced into a subsequent hydrogenation section. The application realizes rapid mass transfer and short residence time of the material by the falling-film reaction, and combines the countercurrent stripping to timely reduce the propenal concentration in the liquid phase after the reaction, so as to reduce the contact and reaction of the product and propenal at the acid active sites; meanwhile, the residual propenal in the product is removed synchronously in the reaction process, an additional removal process is saved, and the selectivity and production efficiency of the hydration preparation of 3-hydroxypropionaldehyde are significantly improved.

Description

Technical Field

[0001] This invention relates to the field of 3-hydroxypropanal preparation technology, specifically to a falling film-air stripping coupled reaction system and process for the preparation of 3-hydroxypropanal by acrolein hydration. Background Technology

[0002] 3-Hydroxypropionaldehyde (3-HPA) is a key intermediate in the synthesis of 1,3-propanediol (1,3-PDO). Currently, the main chemical route for the industrial preparation of 3-HPA is the acid-catalyzed hydration of acrolein. However, due to the poor chemical stability of 3-HPA and the requirement that the hydration reaction must be carried out under acidic conditions, the generated 3-HPA readily undergoes condensation side reactions with unreacted acrolein feedstock near the acid-active sites, generating high-boiling-point polymerization impurities. This leads to decreased product selectivity and a reduction in the effective content of 3-HPA.

[0003] To address this issue, existing technologies primarily focus on modifying the microenvironment of catalyst surface active sites (e.g., introducing acid-base synergistic sites or grafting long-chain hydrophobic groups) to slow down the polymerization of 3-hydroxypropionaldehyde and acrolein by reducing the acid strength of the system or accelerating 3-HPA desorption. However, in batch reactors or fixed-bed reactors, due to strong axial backmixing or large liquid holdup, the reactant acrolein and product 3-HPA coexist in the liquid phase for extended periods, resulting in localized high concentrations of acrolein and 3-HPA in continuous contact and reaction. Furthermore, the crude 3-hydroxypropionaldehyde product often contains a significant amount of unreacted acrolein residue, requiring a dedicated removal process. This not only increases energy consumption but also introduces side reactions such as thermal decomposition and condensation of the 3-hydroxypropionaldehyde product during subsequent acrolein removal.

[0004] Chinese invention patent CN1803750A discloses a method for separating and recovering acrolein. Although it solves the problem of removing acrolein from hydration products, it still has the problems of separating the stripping and hydration reactions into different devices, requiring the reaction to proceed before the hydration reaction, and having a long process and increased energy consumption.

[0005] Chinese invention patent CN113277933A discloses a method and apparatus for preparing 3-hydroxypropanal by continuous catalytic distillation. Although it solves the problems of coupling hydration reaction and separation and suppressing 3,3'-oxobis-1-propanal byproducts, it still has the problems of relying on catalytic distillation tower structure, complex equipment, and long mass transfer path.

[0006] In summary, there is an urgent need to provide a reaction system and process for the preparation of 3-hydroxypropional by the hydration of acrolein, in order to solve the problems of low coupling between reaction and separation, insufficient suppression of side reactions, high acrolein residue in the product, long process and high energy consumption in the existing technology. Summary of the Invention

[0007] The technical problem this invention aims to solve is to overcome the shortcomings of existing technologies and provide a falling film-air stripping coupled reaction system and process for the preparation of 3-hydroxypropionaldehyde from acrolein hydration. This system efficiently couples the "inner wall-supported catalyst," the "falling film flow reaction of the feed liquid," and the "countercurrent air stripping removal of unreacted feedstock," significantly shortening the residence time of materials at the acidic catalytic site and promptly removing acrolein from the post-reaction system, maintaining it at a low concentration. This effectively suppresses the secondary condensation side reaction between 3-HPA and acrolein, while simultaneously achieving in-situ synchronous removal of residual acrolein. In this invention, the acrolein hydration reaction is entirely completed at the catalyst interface within the reaction liquid film; no gas phase participates in the chemical reaction, and the introduced inert carrier gas serves only as a mass transfer driving force for the physical stripping of unreacted materials.

[0008] The technical solution of this invention is as follows: On one hand, the present invention provides a falling film-gas stripping coupled reaction system for the preparation of 3-hydroxypropanal by acrolein hydration, comprising a falling film reactor with an acidic catalyst layer fixed on its inner wall and a jacket on its outer wall; a falling film distributor disposed in the upper part of the falling film reactor for uniformly distributing the acrolein aqueous solution to the inner wall of the falling film reactor to form a reaction liquid film; a gas injection assembly disposed at the bottom of the falling film reactor for uniformly injecting inert carrier gas into the falling film reactor; a top gas phase condensation and circulation system connected to the top gas outlet of the falling film reactor for condensing and collecting the stripped acrolein and recycling it back for reuse; a gas phase separation and purification system for demisting, drying and compressing the condensed and separated gas phase so that it can be used again as an inert carrier gas; and a bottom product outlet disposed at the bottom of the falling film reactor for continuously extracting the crude product of 3-hydroxypropanal aqueous solution.

[0009] This invention integrates reaction and catalysis by immobilizing an acidic catalyst layer on the inner wall of a falling film reactor. This allows the acrolein aqueous solution, after passing through a falling film distributor and forming a thin reaction film along the inner wall, to immediately and fully contact the catalyst. A gas injection assembly injects inert carrier gas upwards from the bottom of the falling film reactor, forming a counter-current gas stripping channel with the reaction film. A top gas-phase condensation and circulation system recovers and recycles the stripped acrolein, while a bottom product outlet continuously outputs a crude 3-HPA product with low acrolein residue. These components together constitute an integrated falling film gas stripping continuous reaction system, structurally coupling hydration reaction and in-situ gas stripping. This replaces the traditional series process of "reaction first, then formaldehyde removal," simplifying equipment configuration and significantly reducing equipment investment and operating energy consumption.

[0010] Preferably, the falling film distributor is an annular gap falling film distributor or a sawtooth weir falling film distributor; the height-to-diameter ratio inside the falling film reactor is (20-40):1.

[0011] Preferably, the top gas phase condensation circulation system includes a condenser, an acrolein recovery tank, and an acrolein aqueous solution preparation tank connected in sequence. The condenser is connected to the top gas outlet of the falling film reactor, and the acrolein aqueous solution preparation tank is connected to the top feed inlet of the falling film reactor.

[0012] Preferably, the gas phase separation and purification system includes a demister, a dryer, and a compressor connected in sequence. The demister is connected to the gas phase outlet of the condenser, and the compressor is connected to the gas injection assembly.

[0013] Preferably, the gas phase separation and purification system further includes a filter, and the compressor, the filter and the gas injection assembly are connected in sequence; a heating mechanism is provided inside the filter.

[0014] On the other hand, the present invention provides a falling film-stripping coupled reaction process for the preparation of 3-hydroxypropanal by acrolein hydration, which is carried out using the above-described falling film-stripping coupled reaction system for the preparation of 3-hydroxypropanal by acrolein hydration, and includes the following steps: S1: An aqueous solution of acrolein is introduced into the top of the falling film reactor. After being evenly distributed by the falling film distributor, the aqueous solution of acrolein flows from top to bottom along the inner wall of the falling film reactor. During the falling film flow, the reaction liquid film contacts the acidic catalyst on the inner wall and undergoes a hydration reaction to generate 3-hydroxypropanal. S2: While step S1 is being performed, inert carrier gas is continuously introduced from the bottom of the falling film reactor. The inert carrier gas comes into countercurrent contact with the falling reaction liquid film from bottom to top and performs gas lift, carrying the unreacted acrolein in the downstream area of ​​the reaction liquid film out of the liquid phase and discharged from the top of the falling film reactor. S3: The acrolein-containing gas stream discharged from the top of the falling film reactor is condensed, separated, and collected. The acrolein is then mixed with the acrolein aqueous solution and returned to the top of the falling film reactor to continue the reaction. The gas phase is then demisted, dried, and compressed before being used again as an inert carrier gas. S4: The crude product of 3-hydroxypropionaldehyde aqueous solution, after removing residual acrolein, is continuously collected from the bottom of the falling film reactor.

[0015] This invention efficiently couples a falling film reactor with an internally supported acidic catalyst, a falling film flow reaction of the feed liquid, and countercurrent gas stripping to remove unreacted feedstock. It simultaneously achieves short-residence-time hydration and in-situ removal of acrolein within a single reactor, creating a process platform where reaction and separation occur concurrently. This significantly reduces the contact time between the reactant acrolein and the product 3-hydroxypropionaldehyde near the acidic catalytic site from hours in traditional batch or fixed-bed reactors to minutes. Simultaneously, acrolein in the downstream liquid region is continuously gas-lifted from the system, significantly suppressing the secondary condensation side reaction between 3-HPA and acrolein at the acidic active site. Furthermore, after condensation, collection, and preparation, acrolein is returned to the top of the falling film reactor for further reaction. The gas phase, after demisting, drying, and compression, is reused as an inert carrier gas, forming a complete closed-loop material cycle. This achieves efficient utilization of feedstock and effective suppression of side reactions, fundamentally solving the technical problems of traditional processes involving pre-reaction followed by dealdehyde removal, long process flow, and high energy consumption.

[0016] Preferably, in step S1, the acidic catalyst is a macroporous styrene-based aminocarboxylic acid chelating ion exchange resin.

[0017] Preferably, in step S1, the feed flow rate of the acrolein aqueous solution is 950-2800 mL / h, so that the reaction liquid film is in a laminar flow state; the residence time of the reaction liquid film in the falling film reactor is 60-120 s.

[0018] This invention maintains the Reynolds number of the reaction liquid film within the laminar flow range by controlling the feed flow rate, thus ensuring a steady-state thin-layer flow with uniform thickness and minimal fluctuations. This guarantees consistent contact time between the reaction liquid film and the catalyst surface at all points, avoiding local backmixing and short circuits caused by turbulence or fluctuations. Simultaneously, the residence time of 60-120 s is significantly lower than the hourly residence time of a batch reactor, which significantly suppresses the condensation side reaction between 3-HPA and acrolein at the acid active sites from a kinetic perspective, achieving a balance between high 3-HPA selectivity and reasonable production efficiency.

[0019] Preferably, in step S1, the concentration of the acrolein aqueous solution is 8-15 wt.%; and the reaction temperature of the falling film reactor is 40-50℃.

[0020] Preferably, in step S2, the inert carrier gas is at least one of nitrogen and argon; the volume ratio of the inert carrier gas flow rate to the acrolein aqueous solution feed rate is (100-300):1; the linear velocity of the inert carrier gas in the falling film reactor is 0.03-0.1 m / s; and the temperature of the inert carrier gas is 35-45℃.

[0021] Compared with the prior art, the present invention has the following advantages: 1. This invention constructs a thinner reaction liquid film by forming a falling film flow of acrolein aqueous solution on the inner wall of a falling film reactor, enabling the reactants to quickly and fully contact the catalyst, achieving efficient mass and heat transfer; the generated 3-HPA is rapidly carried downstream along the reaction liquid film, reducing the residence time of the material in the acid catalytic zone from hours in traditional reactors to minutes, thereby effectively suppressing the occurrence of side reactions.

[0022] 2. Based on the difference in physical properties between acrolein (low boiling point, volatile) and 3-HPA (high boiling point, easily retained in aqueous phase), this invention introduces a thermal inert carrier gas at the bottom of the falling film reactor to continuously strip unreacted acrolein from the reaction liquid film, thereby maintaining the concentration of acrolein in the lower liquid phase of the falling film reactor at a low level. This significantly reduces the rate of the secondary condensation reaction between acrolein and 3-HPA, and improves the selectivity of 3-HPA in the reaction.

[0023] 3. In this invention, the crude product collected from the bottom of the falling film reactor is stripped by inert carrier gas, and the residual acrolein content can be reduced to below 0.3 wt.%, so it can directly enter the subsequent hydrogenation stage without the need for additional removal processes. The process of this invention not only eliminates the need for dedicated acrolein removal equipment and reduces equipment investment, but also avoids the problem of secondary thermal decomposition or polymerization of crude product in subsequent distillation treatment. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the falling film-air stripping coupled reaction system for the preparation of 3-hydroxypropional by acrolein hydration according to the present invention.

[0025] In the diagram, 1 is the falling film reactor; 2 is the acidic catalyst layer; 3 is the jacket; 4 is the falling film distributor; 5 is the gas injection assembly; 601 is the condenser; 602 is the acrolein recovery tank; 603 is the acrolein aqueous solution preparation tank; 701 is the demister; 702 is the dryer; 703 is the compressor; 704 is the heating mechanism; 705 is the filter; and 8 is the bottom product outlet. Detailed Implementation

[0026] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention.

[0027] like Figure 1 As shown, the falling film used in the following examples The air-lift coupled reaction system includes the following structure: The falling film reactor 1 has a stainless steel mesh welded and fixed to its inner wall, forming a sandwich layer between the mesh and the inner wall. Acidic catalyst particles are filled into this sandwich layer to form an acidic catalyst layer 2. The acidic catalyst used is D751 type macroporous styrene-based aminocarboxylic acid chelating ion exchange resin. A water circulation jacket 3 is installed on the outer wall of the falling film reactor 1. The water circulation jacket 3 is connected to an inlet pipe and an outlet pipe, both of which are equipped with regulating valves. A temperature sensor is installed in the falling film reactor 1, and both the regulating valves and the temperature sensor are connected to the control system.

[0028] The falling film distributor 4 is located in the upper part of the falling film reactor 1 and is used to evenly distribute the acrolein aqueous solution to the inner wall of the falling film reactor 1 to form a reaction liquid film.

[0029] The gas injection assembly 5 is located at the bottom of the falling film reactor 1 and is used to uniformly inject inert carrier gas into the falling film reactor 1. It can be made of stainless steel plate with uniform micropores to ensure that the inert carrier gas rises uniformly and prevent the airflow from deviating and damaging the falling film on the inner wall of the falling film reactor 1.

[0030] The top gas phase condensation and circulation system is connected to the top gas outlet of the falling film reactor 1 and is used to condense and collect the acrolein extracted from the gas and recycle it for reuse. Specifically, it includes a condenser 601, an acrolein recovery tank 602 and an acrolein aqueous solution preparation tank 603 connected in sequence. The condenser 601 is connected to the top gas outlet of the falling film reactor 1, and the acrolein aqueous solution preparation tank 603 is connected to the top feed inlet of the falling film reactor 1.

[0031] The gas phase separation and purification system is used to demist, dry, compress, filter, and heat the condensed and separated gas phase, allowing it to be reused as an inert carrier gas. Specifically, it includes a demister 701, a dryer 702, a compressor 703, and a filter 705 connected in sequence. The filter 705 is equipped with a heating mechanism 704 (electric heating wire) to heat the circulating inert carrier gas to 35°C. After reaching 45°C, the gas enters the falling film reactor 1. The demister 701 is connected to the gas phase outlet of the condenser 601, and the filter 705 is connected to the gas injection assembly 5.

[0032] Bottom product outlet 8 is located at the bottom of falling film reactor 1 and is used for continuous product collection. Crude product of aqueous solution of hydroxypropionaldehyde.

[0033] Example 1 The falling film in this embodiment The gas stripping coupled reaction system is constructed as follows: Falling film reactor 1 is a stainless steel cylinder with an inner diameter of 50 mm and a length of 1500 mm; Falling film distributor 4 adopts an annular gap type falling film distributor.

[0034] This embodiment is used for the preparation of acrolein hydration 3. Hydroxypropionaldehyde falling membrane The air stripping coupled reaction process includes the following steps: S1: The flow rate of circulating water entering the jacket 3 is controlled by a temperature sensor and regulating valve to maintain the inner wall of the falling film reactor 1 at 45°C. A 12wt.% acrolein aqueous solution is pumped into the top feed inlet of the falling film reactor 1 at a flow rate of 1700mL / h. The material is evenly spread on the inner wall of the falling film reactor 1 by the falling film distributor 4, forming a uniformly thick falling reaction film. The reaction film undergoes a hydration reaction under the action of the acidic catalyst layer 2, and the reaction residence time is about 90s.

[0035] S2: At the same time, high-purity nitrogen is continuously introduced from the bottom gas injection component 5 as an inert carrier gas. The nitrogen is heated to 40°C, and the volume ratio of nitrogen to acrolein aqueous solution is controlled at 200:1 (under standard conditions). The nitrogen flows countercurrently through the falling film reactor 1 from bottom to top. Its linear velocity in the falling film reactor 1 is about 0.06 m / s, which removes unreacted acrolein gas from the reaction liquid film at the bottom of the falling film reactor 1 in real time.

[0036] S3: A stream of nitrogen containing acrolein enters the top gas phase condensation circulation system, first condenses in condenser 601, and the condensed acrolein first enters acrolein recovery tank 602, then mixes with fresh water in acrolein aqueous solution preparation tank 603 and is then returned to the top feed port of falling film reactor 1 to continue the reaction; the gas phase discharged from condenser 601 is sequentially demisted, dried, compressed, filtered and heated by demister 701, dryer 702 and compressor 703, and is then used again as inert carrier gas.

[0037] S4: Continuously collect 3 products from the bottom product outlet 8 of falling film reactor 1. The crude HPA aqueous solution was analyzed using the internal standard method to determine the presence of 3 in the product. HPA and acrolein content.

[0038] Example 2 The falling film in this embodiment The gas stripping coupled reaction system is constructed as follows: Falling film reactor 1 is a stainless steel cylinder with an inner diameter of 50 mm and a length of 1000 mm; Falling film distributor 4 adopts an annular gap type falling film distributor.

[0039] This embodiment is used for the preparation of acrolein hydration 3. Hydroxypropionaldehyde falling membrane The air stripping coupled reaction process includes the following steps: S1: The flow rate of circulating water entering jacket 3 is controlled by a temperature sensor and regulating valve to maintain the inner wall of falling film reactor 1 at 50℃. A 15wt.% acrolein aqueous solution is pumped into the top feed inlet of falling film reactor 1 at a flow rate of 950mL / h. The material is evenly spread on the inner wall of falling film reactor 1 by falling film distributor 4, forming a uniformly thick falling reaction film. The reaction film undergoes a hydration reaction under the action of acidic catalyst layer 2, and the reaction residence time is about 60s.

[0040] S2: At the same time, high-purity argon is continuously introduced from the bottom gas injection component 5 as an inert carrier gas. The argon is heated to 45°C, and the volume ratio of argon to acrolein aqueous solution is controlled at 100:1 (under standard conditions). The argon flows countercurrently through the falling film reactor 1 from bottom to top. Its linear velocity in the falling film reactor 1 is about 0.03 m / s, which removes unreacted acrolein gas from the reaction liquid film at the bottom of the falling film reactor 1 in real time.

[0041] S3: An argon stream containing acrolein enters the top gas phase condensation circulation system, first condenses in condenser 601, and the condensed acrolein first enters acrolein recovery tank 602, then mixes with fresh water in acrolein aqueous solution preparation tank 603 and is then returned to the top feed port of falling film reactor 1 to continue the reaction; the gas phase discharged from condenser 601 is sequentially demisted, dried, compressed, filtered and heated by demister 701, dryer 702 and compressor 703, and is then used again as an inert carrier gas.

[0042] S4: Continuously collect 3 products from the bottom product outlet 8 of falling film reactor 1. The crude HPA aqueous solution was analyzed using the internal standard method to determine the presence of 3 in the product. HPA and acrolein content.

[0043] Example 3 The falling film in this embodiment The gas stripping coupled reaction system is constructed as follows: Falling film reactor 1 is a stainless steel cylinder with an inner diameter of 50 mm and a length of 2000 mm; Falling film distributor 4 adopts an annular gap type falling film distributor.

[0044] This embodiment is used for the preparation of acrolein hydration 3. Hydroxypropionaldehyde falling membrane The air stripping coupled reaction process includes the following steps: S1: The flow rate of circulating water entering jacket 3 is controlled by a temperature sensor and regulating valve to maintain the inner wall of falling film reactor 1 at 40℃. An 8wt.% acrolein aqueous solution is pumped into the top feed inlet of falling film reactor 1 at a flow rate of 2800mL / h. The material is evenly spread on the inner wall of falling film reactor 1 by falling film distributor 4 to form a uniformly thick falling reaction film. The reaction film undergoes a hydration reaction under the action of acidic catalyst layer 2, and the reaction residence time is about 120s.

[0045] S2: At the same time, a mixture of high-purity nitrogen and high-purity argon (volume ratio 1:1) is continuously introduced from the bottom gas injection component 5 as an inert carrier gas. The inert carrier gas is heated to 35°C, and the volume ratio of the inert carrier gas to the acrolein aqueous solution is controlled at 300:1 (under standard conditions). The inert carrier gas flows countercurrently from bottom to top through the falling film reactor 1, and its linear velocity in the falling film reactor 1 is about 0.1 m / s, thereby removing unreacted acrolein gas from the reaction liquid film at the bottom of the falling film reactor 1 in real time.

[0046] S3: The inert gas stream containing acrolein enters the top gas phase condensation circulation system, is first condensed by condenser 601, and the condensed acrolein first enters acrolein recovery tank 602, and then is mixed with fresh water in acrolein aqueous solution preparation tank 603 and then returned to the top feed port of falling film reactor 1 to continue the reaction; the gas phase discharged from condenser 601 is sequentially demisted, dried, compressed, filtered and heated by demister 701, dryer 702 and compressor 703, and then used again as inert carrier gas.

[0047] S4: Continuously collect 3 products from the bottom product outlet 8 of falling film reactor 1. The crude HPA aqueous solution was analyzed using the internal standard method to determine the presence of 3 in the product. HPA and acrolein content.

[0048] Example 4 The difference from Example 1 is that the falling film distributor 4 adopts a sawtooth weir type falling film distributor.

[0049] Comparative Example 1 Based on the effective mass conversion of acidic catalyst layer 2 in Example 1, weigh an equal mass of the same catalyst and place it in a batch reactor. Add 1700 mL of 12 wt.% acrolein aqueous solution, seal the batch reactor, and carry out a stirred hydration reaction (without gas stripping) at 50°C for 1 hour. After the reaction is complete, take the reaction solution and use the internal standard method to test the product for 3... HPA and acrolein content.

[0050] Comparative Example 2 The same catalyst as in Example 1 was loaded into a fixed-bed reactor, and the reaction was carried out at 50°C with a 12 wt.% acrolein aqueous solution passed from top to bottom through the fixed-bed reactor. The feed flow rate was also 1700 mL / h, and no gas was introduced for stripping. After continuous and stable operation, the reaction liquid was collected, and the product was tested for 3% using the internal standard method. HPA and acrolein content.

[0051] Comparative Example 3 The reaction system and process conditions were exactly the same as in Example 1, but without inert gas stripping. After the reaction was complete, the reaction solution was collected, and the product was tested for 3% using the internal standard method. HPA and acrolein content.

[0052] For Example 1 4 and Comparative Example 1 3. The product collected after 1 hour of reaction was analyzed by gas chromatography, and the results are shown in Table 1: Table 1 Example 1 4 and Comparative Example 1 3. Gas chromatographic analysis results of the products collected after 1 hour of reaction.

[0053] As can be seen from Table 1, in each embodiment using falling film reactor 1 in conjunction with the gas stripping process, product 3 HPA selectivity reached a maximum of 95.33%. Compared with the batch reactor in Comparative Example 1 and the fixed-bed reactor in Comparative Example 2, this improvement mainly stemmed from the optimization of the flow field and mass transfer during the reaction process. Falling film reactor 1 reduced the catalytic residence time of the reactants to 60... The 120s reaction time effectively suppressed side reactions from a kinetic perspective. Furthermore, as the hydration reaction proceeded, the countercurrent stripping gas continuously carried away acrolein from the liquid phase at the rear end of the reaction, maintaining the local acrolein concentration at a low level.

[0054] This invention achieves in-situ integrated separation of the reaction and low-boiling-point substances. Under the same experimental conditions, the acrolein residue in Example 1, which includes the gas stripping process, is 0.11 wt.%, significantly better than Comparative Example 3 (falling film reactor 1) without gas stripping, and also better than Comparative Example 1 (stirred reactor) and Comparative Example 2 (fixed bed reactor) without gas stripping. In the example, the falling film reactor 1 combined with the gas stripping process enhances the mass transfer effect through countercurrent contact between the thermally inert carrier gas and the reaction liquid film, resulting in a acrolein residue in the product of less than 0.3 wt.%. This invention not only eliminates the need for dedicated acrolein removal equipment and reduces equipment investment, but also avoids the risks associated with the gas stripping process. There is a risk that hydroxypropionaldehyde may undergo thermal decomposition or polymerization during subsequent distillation and separation.

Claims

1. Used for the preparation of acrolein hydration 3 Hydroxypropionaldehyde falling membrane The gas stripping coupled reaction system is characterized in that, It includes a falling film reactor (1), with an acidic catalyst layer (2) fixed on its inner wall and a jacket (3) provided on its outer wall. A falling film distributor (4) is installed in the upper part of the falling film reactor (1) to uniformly distribute the acrolein aqueous solution to the inner wall of the falling film reactor (1) to form a reaction liquid film. Gas injection assembly (5) is located at the bottom of falling film reactor (1) and is used to uniformly inject inert carrier gas into falling film reactor (1); A top gas phase condensation circulation system is connected to the top gas outlet of the falling film reactor (1) for condensing and collecting the acrolein extracted from the gas and recycling it back for reuse. The gas phase separation and purification system is used to demist, dry and compress the condensed and separated gas phase so that it can be used again as an inert carrier gas; The bottom product outlet (8) is located at the bottom of the falling film reactor (1) and is used for continuous extraction of 3 tons of product. Crude product of hydroxypropionaldehyde aqueous solution.

2. The method for preparing acrolein hydration as described in claim 1 Hydroxypropionaldehyde falling membrane The gas stripping coupled reaction system is characterized in that, The falling film distributor (4) is an annular falling film distributor or a sawtooth weir falling film distributor; the height-to-diameter ratio inside the falling film reactor (1) is (20... 40):

1.

3. The method for preparing acrolein hydration as described in claim 1 Hydroxypropionaldehyde falling membrane The gas stripping coupled reaction system is characterized in that, The top gas phase condensation circulation system includes a condenser (601), an acrolein recovery tank (602), and an acrolein aqueous solution preparation tank (603) connected in sequence. The condenser (601) is connected to the top gas outlet of the falling film reactor (1), and the acrolein aqueous solution preparation tank (603) is connected to the top feed inlet of the falling film reactor (1).

4. The method for preparing acrolein hydration 3 as described in claim 3 Hydroxypropionaldehyde falling membrane The gas stripping coupled reaction system is characterized in that, The gas phase separation and purification system includes a demister (701), a dryer (702), and a compressor (703) connected in sequence. The demister (701) is connected to the gas phase outlet of the condenser (601), and the compressor (703) is connected to the gas injection assembly (5).

5. The method for preparing acrolein hydration 3 as described in claim 4 Hydroxypropionaldehyde falling membrane The gas stripping coupled reaction system is characterized in that, The gas phase separation and purification system also includes a filter (705), a compressor (703), and a gas injection assembly (5) connected in sequence; a heating mechanism (704) is provided inside the filter (705).

6. Used for the preparation of acrolein hydration 3 Hydroxypropionaldehyde falling membrane The gas stripping coupled reaction process is characterized by, By claim 1 5. The preparation of 3 by acrolein hydration according to any one of the claims Hydroxypropionaldehyde falling membrane The gas stripping coupled reaction system is carried out, including the following steps: S1: An acrolein aqueous solution is introduced into the top of the falling film reactor (1). After being evenly distributed by the falling film distributor (4), the acrolein aqueous solution forms a falling film flow from top to bottom along the inner wall of the falling film reactor (1). During the falling film flow, the reaction liquid film contacts the acidic catalyst layer (2) on the inner wall and undergoes a hydration reaction to generate 3 Hydroxypropionaldehyde; S2: While step S1 is being performed, inert carrier gas is continuously introduced from the bottom of the falling film reactor (1). The inert carrier gas comes into countercurrent contact with the falling reaction liquid film from bottom to top and performs gas lift, carrying the unreacted acrolein in the downstream area of ​​the reaction liquid film out of the liquid phase and discharged from the top of the falling film reactor (1). S3: The acrolein-containing gas stream discharged from the top of the falling film reactor (1) is condensed, separated, and collected. The acrolein is then mixed with the acrolein aqueous solution and returned to the top of the falling film reactor (1) to continue the reaction. The gas phase is then demisted, dried, and compressed before being used as an inert carrier gas again. S4: The bottom of the falling film reactor (1) continuously extracts 3% of the solution to remove residual acrolein. Crude product of hydroxypropionaldehyde aqueous solution.

7. The method for preparing acrolein hydration 3 as described in claim 6 Hydroxypropionaldehyde falling membrane The gas stripping coupled reaction process is characterized by, In step S1, the acidic catalyst is a macroporous styrene-based aminocarboxylic acid chelating ion exchange resin.

8. The method for preparing acrolein hydration 3 as described in claim 6 Hydroxypropionaldehyde falling membrane The gas stripping coupled reaction process is characterized by, In step S1, the feed flow rate of the acrolein aqueous solution is 950. 2800 mL / h; the residence time of the reaction liquid film in the falling film reactor (1) is 60 minutes. 120s.

9. The method for preparing acrolein hydration 3 as described in claim 6 Hydroxypropionaldehyde falling membrane The gas stripping coupled reaction process is characterized by, In step S1, the concentration of the acrolein aqueous solution is 8%. 15 wt.%; The reaction temperature of the falling film reactor (1) was 40 °C. 50℃.

10. The method for preparing acrolein hydration 3 according to claim 6 Hydroxypropionaldehyde falling membrane The gas stripping coupled reaction process is characterized by, In step S2, the inert carrier gas is at least one of nitrogen and argon; the volume ratio of the inert carrier gas flow rate to the acrolein aqueous solution feed rate is (100... 300):1, the linear velocity of the inert carrier gas in the falling film reactor (1) is 0.

03. 0.1 m / s; the temperature of the inert carrier gas is 35°C. 45℃.

Images