System and method for preparing polyester polyol prepolymer

Abstract

The present invention provides a system and a method for preparing a polyester polyol prepolymer. The system comprises an atmospheric pressure bubbling reaction rectifying tower and a reduced pressure heating reaction rectifying tower. The method comprises: introducing a protective gas into an atmospheric pressure bubbling reaction rectifying tower, introducing a raw material for preparing a polyester polyol prepolymer into the atmospheric pressure bubbling reaction rectifying tower, and carrying out a primary esterification reaction or an ester exchange reaction; and introducing the primary esterification product or the ester exchange product into a reduced pressure heating reaction rectifying tower, and carrying out one or more of a deep esterification reaction, an ester exchange reaction, and a pre-polycondensation reaction to obtain the polyester polyol prepolymer. The present invention has the advantages of high reaction efficiency, stable product quality, easiness in product separation, convenience in large-scale production and the like.

Description

A system and method for preparing polyester polyol prepolymer Technical Field

[0001] The invention relates to a system and method for preparing a polyester polyol prepolymer, belonging to the technical field of polyester polyol preparation. Background Art

[0002] Polyester polyols are typically linear polymers made from organic dicarboxylic acids (or anhydrides or esters) and diols (or polyols) through esterification (or transesterification) and polycondensation. Polyester polyols are a key raw material for materials such as biodegradable plastics and engineering plastics, and are widely used in food packaging, fibers, films, and other fields, with promising market prospects. The preparation of polyester polyols typically involves two stages: esterification and polycondensation. In the esterification stage, the acid and alcohol react to produce a large amount of water. This water is separated from the small amount of alcohol carried over through a distillation column and then removed from the system, driving the reaction toward esterification.

[0003] Currently, traditional polyester polyol production processes are mostly batch processes. While batch processes offer flexibility and allow for easy switching between multiple grades, they suffer from significant product quality volatility, limited mass and heat transfer, low equipment utilization, and significant energy losses from repeated temperature increases. Furthermore, the esterification reaction used to prepare polyester polyols is a reversible process. To drive the reaction toward esterification, rapid and efficient removal of the generated small water byproduct is crucial. Traditional reactors accelerate this removal by increasing stirring or bubbling nitrogen, but these methods are energy-intensive and have limited effectiveness.

[0004] US5786443A discloses a method for preparing polyester prepolymers. This method involves esterifying a dibasic acid with a diol, then allowing the product to flow downward into a countercurrent tower reactor. A protective gas then ascends through the tower reactor, resulting in a product with a low end carboxyl group content. However, this preparation method has shortcomings: the countercurrent tower reactor used for precondensation has limited operational flexibility and numerous dead zones, requiring vigorous bubbling for self-cleaning; and the method fails to optimize the esterification process.

[0005] CN1137278A discloses a continuous polyester production method. This method involves continuous esterification (or transesterification) of terephthalic acid (TPA) (or dimethyl terephthalate (DMT)) with ethylene glycol in an esterification tower, followed by polycondensation in a prepolymerization tower. A protective gas is introduced into the prepolymerization tower in the opposite direction of the polymerization process to remove volatile byproducts. Disadvantages of this method include: the esterification stage is not optimized, the prepolymerization tower has limited operational flexibility, and requires vigorous bubbling for self-cleaning; furthermore, the reaction unit and separation unit are independent and lack an integrated design.

[0006] CN102432846A discloses a method and apparatus for the continuous production of polyester polyols. This method utilizes a two-stage reaction apparatus, resulting in a uniform and controllable residence time and enhanced heat and mass transfer. However, the reaction and separation processes in this process are still performed in two separate units, failing to fully utilize the multi-stage separation capabilities of the tower reactor.

[0007] CN102585191A discloses a tower reactor and its application in the continuous production of polyester polyols. This technology designs a more integrated multi-stage bubbling tower reactor, which prepares polyester polyols through esterification (or transesterification) reaction and polycondensation reaction of polycarboxylic acid (or polycarboxylic acid derivative) and polyol (or polyol derivative). The reaction raw materials move from top to bottom and overflow on the tower plate. The protective gas, small molecule steam generated by the reaction and vaporized polyol are discharged from the system from bottom to top through the bubbling air pipe. A packing tower section is added to the top of the reactor to separate the top steam and reflux most of the alcohol. The reactor has the advantages of high degree of automation and short reaction time. However, the shortcomings of this technology include: there is a certain dead zone in the reactor and the bubbling air pipe is not easy to clean, and it is necessary to rely on violent bubbling to achieve mass transfer enhancement and self-cleaning; there are high requirements for the control of the temperature of each section of the reactor; during operation, vacuum and nitrogen supplementation are operated in the same reactor, which requires high stability control; when used in the esterification stage, the vacuum may extract oligomers, affecting the yield and the stability of the vacuum system.

[0008] During the initial stages of the esterification (or transesterification) reaction in polyester polyols, the reactor contains a large amount of low-molecular-weight alcohols. These alcohols and the resulting water keep the initial reaction liquid at a relatively low boiling point. Therefore, increasing the reaction temperature can create a safety hazard, such as bumping. It can also cause excess alcohol to be extracted from the top of the reactor along with the water, leading to an imbalance in the raw material ratio, fluctuations in product specifications, and waste of raw materials. Gradual temperature increases, however, facilitate precise control based on the reaction progress.

[0009] Therefore, developing a new system and method for preparing polyester polyol prepolymers has become one of the urgent problems to be solved in this field.

[0010] Summary of the Invention

[0011] To solve the above technical problems, the present invention aims to provide a system and method for preparing polyester polyol prepolymers. The present invention has the advantage of high integration, can integrate reaction and separation in the same device, and has high reaction efficiency.

[0012] In order to achieve the above object, the first aspect of the present invention provides a system for preparing polyester polyol prepolymer, the system comprising: an atmospheric bubbling reaction distillation tower and a reduced pressure temperature reaction distillation tower;

[0013] The interior of the atmospheric bubbling reaction distillation tower comprises, from top to bottom, a first separation section and a first reaction section, the first separation section is provided with a first separation packing layer, and the first reaction section is provided with a plurality of tower trays;

[0014] The atmospheric bubbling reaction distillation tower is provided with a first gas phase discharge port, a first liquid phase discharge port, a first raw material inlet and a protective gas inlet;

[0015] The interior of the vacuum temperature reaction distillation tower comprises, from top to bottom, a second separation section and a second reaction section, the second separation section is provided with a second separation packing layer, and the second reaction section is provided with a plurality of trays;

[0016] The vacuum temperature reaction distillation tower is provided with a second gas phase discharge port, a second liquid phase discharge port and a second raw material inlet;

[0017] The first liquid phase discharge port of the atmospheric bubbling reaction distillation tower is connected to the second raw material inlet of the vacuum temperature rising reaction distillation tower through a pipeline.

[0018] In the present invention, it should be noted that the polyester polyol prepolymer of the present invention is an intermediate product in the process of preparing polyester polyol, and the prepolymer can be further polycondensed to obtain polyester polyol.

[0019] In the above-mentioned system for preparing polyester polyol prepolymer, the atmospheric bubbling reaction distillation tower is used to carry out preliminary esterification or transesterification reaction of the raw materials, and the reduced pressure temperature reaction distillation tower is used to carry out one or more of deep esterification reaction, transesterification reaction and pre-polycondensation reaction of the preliminary esterification or transesterification product obtained by the atmospheric bubbling reaction distillation tower to obtain polyester polyol prepolymer, which is discharged from the second liquid phase discharge port of the reduced pressure temperature reaction distillation tower.

[0020] According to a specific embodiment of the present invention, the raw materials entering the first raw material inlet of the atmospheric bubbling reactive distillation column include a mixed solution of one or more of polycarboxylic acids and their derivatives, a polyol, and a catalyst. The polycarboxylic acid derivatives may include anhydrides and / or esters formed from the polycarboxylic acids.

[0021] According to a specific embodiment of the present invention, preferably, the above-mentioned system for preparing polyester polyol prepolymers further includes: a polyol storage device, and the vacuum temperature reaction distillation tower further includes a spray device; the spray device is disposed inside the tower body of the vacuum temperature reaction distillation tower, and the spray device is disposed above the second separation packing layer; the spray device is connected to the polyol storage device via a pipeline and is used to spray polyol into the vacuum temperature reaction distillation tower. More preferably, the spray device includes at least a spray pipe and a nozzle connected to the spray pipe, and the side wall of the vacuum temperature reaction distillation tower is provided with a polyol feed port, the polyol feed port is located above the second separation packing layer of the vacuum temperature reaction distillation tower, and the spray pipe is connected to the polyol feed port. The present invention preferably provides a spray device in the vacuum temperature reaction distillation tower to facilitate the reflux of polyols and oligomers in the reaction system, as well as the control of carboxyl content and the adjustment of esterification rate or transesterification rate.

[0022] In the above polyester polyol prepolymer preparation system, preferably, the atmospheric bubbling reaction distillation tower and the vacuum temperature reaction distillation tower are each provided with a heating jacket on the outside of the tower body. The heating jacket is used to heat the two reaction distillation towers to the required reaction temperature.

[0023] In the above-mentioned system for preparing polyester polyol prepolymers, preferably, the plurality of trays in the atmospheric bubbling reactive distillation column and the reduced-pressure temperature reactive distillation column have a multi-stage overflow structure. More preferably, the trays include one or a combination of inclined-hole trays, bubble-cap trays, fixed-valve trays, and vertical sieve plate trays. Further preferably, the trays are inclined-hole trays.

[0024] According to a specific embodiment of the present invention, the system for preparing a polyester polyol prepolymer preferably further comprises a vacuum device connected to the second gas phase discharge port of the vacuum temperature-elevated reaction distillation column via a pipeline. The vacuum device is used to adjust the pressure within the vacuum temperature-elevated reaction distillation column to the pressure required for the reaction.

[0025] In the above-mentioned system for preparing polyester polyol prepolymer, preferably, the filler in the first separation packing layer of the atmospheric bubbling reactive distillation tower is a random packing or a structured packing.

[0026] In the above-mentioned system for preparing polyester polyol prepolymer, preferably, the filler in the second separation packing layer of the vacuum temperature rising reaction distillation tower is a random packing or a structured packing.

[0027] In the above-mentioned system for preparing polyester polyol prepolymer, preferably, the top of the atmospheric bubbling reaction distillation tower is provided with the first gas phase discharge port; the bottom of the atmospheric bubbling reaction distillation tower is provided with the first liquid phase discharge port; the side wall of the atmospheric bubbling reaction distillation tower is provided with the first raw material inlet, and the first raw material inlet is located in the first reaction section; the side wall of the atmospheric bubbling reaction distillation tower is provided with the protective gas inlet, and the protective gas inlet is located below the first reaction section.

[0028] In the above-mentioned system for preparing polyester polyol prepolymer, preferably, the top of the vacuum temperature reaction distillation tower is provided with the second gas phase discharge port; the bottom of the vacuum temperature reaction distillation tower is provided with the second liquid phase discharge port; the side wall of the vacuum temperature reaction distillation tower is provided with the second raw material inlet, and the second raw material inlet is located in the second reaction section.

[0029] In the system for preparing the above-mentioned polyester polyol prepolymer, preferably, the protective gas inlet of the atmospheric bubbling reaction distillation tower is a tangential inlet, which is tangential to the side wall of the atmospheric bubbling reaction distillation tower. More preferably, the protective gas inlet of the atmospheric bubbling reaction distillation tower is arranged tangentially and tilted downwardly on the side wall of the atmospheric bubbling reaction distillation tower along the air inlet direction, so that the protective gas enters tangentially along the oblique downward direction, and the angle between the protective gas inlet and the horizontal direction of the cross section of the atmospheric bubbling reaction distillation tower is 15 to 85 degrees. The protective gas inlet arranged tangentially and tilted downwardly on the side wall of the atmospheric bubbling reaction distillation tower can enable the protective gas to enter the interior of the tower body tangentially and tilted downwardly along the side wall of the atmospheric bubbling reaction distillation tower for bubbling, which is beneficial to strengthening material mixing, separation of products and by-products, and avoiding blockage of the protective gas inlet.

[0030] In the above-mentioned system for preparing polyester polyol prepolymer, preferably, the number of the protective gas inlet of the atmospheric pressure bubbling reaction distillation tower is multiple, and each protective gas inlet is a tangential inlet, and the multiple protective gas inlets are evenly arranged along the circumference on the side wall of the atmospheric pressure bubbling reaction distillation tower.

[0031] A second aspect of the present invention provides a method for preparing a polyester polyol prepolymer, wherein the method uses the above-mentioned system for preparing a polyester polyol prepolymer, and the method comprises the following steps:

[0032] (1) allowing a protective gas to enter an atmospheric bubbling reaction distillation tower, and allowing a raw material for preparing a polyester polyol prepolymer to enter the atmospheric bubbling reaction distillation tower, the raw material for preparing the polyester polyol prepolymer undergoes a preliminary esterification or transesterification reaction, the generated by-products and the gaseous phase substances in the reaction system pass through a first separation filler layer, the by-products and the protective gas are discharged from the atmospheric bubbling reaction distillation tower from a first gas phase discharge port, and the generated preliminary esterification or transesterification products are discharged from the atmospheric bubbling reaction distillation tower from a first liquid phase discharge port;

[0033] (2) The preliminary esterification or transesterification product discharged from the first liquid phase discharge port enters a vacuum temperature-elevated reaction distillation tower to undergo one or more of a deep esterification reaction, a transesterification reaction, and a pre-polycondensation reaction. After the generated by-products and the gaseous phase substances in the reaction system pass through a second separation packing layer, the by-products are discharged from the vacuum temperature-elevated reaction distillation tower from the second gas phase discharge port, and the generated polyester polyol prepolymer is discharged from the second liquid phase discharge port.

[0034] In step (1) of the above method, the by-products generated mainly include water and / or tetrahydrofuran, etc., and the gaseous substances in the reaction system mainly include the generated by-products, polyols and oligomers generated by the reaction, etc. These gaseous substances pass through the first separation packing layer, and the polyols and oligomers generated by the reaction can be separated and refluxed in time, while the by-products are discharged from the top of the tower.

[0035] In step (2) of the above method, if a deep esterification reaction and / or an ester exchange reaction is carried out in a vacuum temperature reaction distillation tower, the by-products generated mainly include water and / or tetrahydrofuran, etc., and the gaseous substances in the reaction system mainly include the generated by-products, polyols and oligomers generated by the reaction, etc. These gaseous substances pass through the second separation packing layer, and the polyols and oligomers generated by the reaction can be separated and refluxed in time, while the by-products are discharged from the top of the tower; if a pre-polycondensation reaction is carried out in a vacuum temperature reaction distillation tower, the by-products generated mainly include water and / or tetrahydrofuran, and polyols, and the by-products and oligomers generated by the reaction pass through the second separation packing layer, and the oligomers can be separated and refluxed in time, while the by-products are discharged from the top of the tower.

[0036] In the above method, preferably, in step (1), the raw materials for preparing the polyester polyol prepolymer include a mixture of one or more of polycarboxylic acids and their derivatives, a polyol, and a catalyst. The polycarboxylic acid derivatives may include anhydrides and / or esters formed from polycarboxylic acids, such as but not limited to terephthalic acid, succinic acid, dimethyl terephthalate, dimethyl succinate, succinic anhydride, and the like. The polycarboxylic acids and their derivatives and the polyols may be conventional raw materials for preparing polyester polyols in the art, and the present invention does not impose any particular limitation thereto.

[0037] According to a specific embodiment of the present invention, preferably, the catalyst comprises one or a combination of titanium, tin, antimony, zirconium and bismuth catalysts. More preferably, the catalyst comprises one or a combination of isopropyl titanate, tetrabutyl titanate, a titanium composite catalyst, dibutyltin dilaurate, stannous octoate, 1-chloro-3-hydroxy-1,1,3,3-tetrabutoxydistannoxane (CHTD) and bismuth laurate.

[0038] According to a specific embodiment of the present invention, preferably, the molar ratio of one or more of the polycarboxylic acids and their derivatives to the polyol is 1:4 to 1.5:1.

[0039] According to a specific embodiment of the present invention, preferably, the amount of the catalyst used is 10 to 5000 ppm by mass of the combination of one or more of the polycarboxylic acids and their derivatives.

[0040] In the above method, preferably, in step (1), the protective gas enters the interior of the tower body along the tangential direction of the side wall of the atmospheric bubbling reaction distillation tower.

[0041] In the above method, preferably, in step (1), the protective gas includes nitrogen or the like.

[0042] In the above method, preferably, in step (1), the raw materials for preparing the polyester polyol prepolymer are continuously fed into a normal pressure bubbling reaction distillation tower.

[0043] In the above method, preferably, in step (1), the temperature of the preliminary esterification or transesterification reaction is 130 to 260°C, more preferably 140 to 200°C.

[0044] In the above method, the esterification rate or transesterification rate in step (1) is preferably 50-95%, more preferably 60-90%. It should be noted that the esterification rate or transesterification rate is calculated as follows: the molar amount of the polycarboxylic acid and / or its derivative participating in the reaction / the molar amount of the theoretically reactive polycarboxylic acid and / or its derivative × 100%.

[0045] In the above method, preferably, step (2) further comprises: spraying the polyol into the vacuum temperature reaction distillation tower using a spray device within the vacuum temperature reaction distillation tower to participate in the reaction and prevent the polyol and oligomers from being carried out of the system by the gas phase. More preferably, the mass ratio of the polyol sprayed into the vacuum temperature reaction distillation tower using the spray device to the mass ratio of the preliminary esterification or transesterification product is 0.02 to 5, and further preferably 0.2 to 2.

[0046] In the above method, preferably, in step (2), the temperature of one or more of the deep esterification reaction, transesterification reaction and pre-polycondensation reaction is 150-260°C, more preferably 180-240°C.

[0047] In the above method, preferably, in step (2), the pressure of one or more of the deep esterification reaction, transesterification reaction and pre-polycondensation reaction is 15 to 101.325 kPa, more preferably 50 to 100 kPa.

[0048] In the above method, preferably, the esterification rate or transesterification rate in step (2) is 90 to 99%, more preferably 95 to 99%.

[0049] The present invention provides a system and method for preparing polyester polyol prepolymers. Based on the staged nature of the reaction process during the preparation of polyester polyol prepolymers, the present invention designs a system and method for enhancing the preparation of polyester polyol prepolymers by reactive distillation from the perspectives of accelerating the reaction rate, improving the reaction process, promoting product separation, and optimizing energy coupling. The system of the present invention mainly comprises a normal-pressure bubbling reaction distillation tower and a reduced-pressure temperature reaction distillation tower. A protective gas is bubbled into the normal-pressure bubbling reaction distillation tower, and a mixed liquid of one or more combinations of polycarboxylic acids and their derivatives, a polyol and a catalyst is continuously fed into the normal-pressure bubbling reaction distillation tower to perform a preliminary esterification or transesterification reaction. The generated gaseous by-products (mainly comprising water and / or tetrahydrofuran, etc.) are purified by a first separation packing layer, evaporated out of the normal-pressure bubbling reaction distillation tower and collected from the tower top. The discharge from the bottom of the normal-pressure bubbling reaction distillation tower enters a reduced-pressure temperature reaction distillation tower to perform one or more of a deep esterification reaction, a transesterification reaction and a pre-polycondensation reaction. The generated gaseous by-products are purified by a second separation packing layer, evaporated out of the reduced-pressure temperature reaction distillation tower, and obtain a polyester polyol prepolymer.

[0050] The system and method provided by the present invention have the advantage of integrating reaction and separation in the same equipment. By carrying out the preparation process in stages and designing the corresponding equipment structure and process, the reaction process can be enhanced and the preparation efficiency of polyester polyol prepolymer can be improved, thereby being applied to the production of polyester polyol.

[0051] The technical solution of the present invention has at least the following beneficial effects:

[0052] 1. Taking full account of the staged nature of the polyester polyol prepolymer preparation process, the reaction process is divided into atmospheric pressure bubbling reaction and reduced pressure and temperature reaction. In the early stages of the esterification or transesterification reaction, when the viscosity of the reaction system is low, atmospheric pressure bubbling is used to promote mixing of the reactants and separation of by-products such as water and / or tetrahydrofuran from the esterification or transesterification products, accelerating the reaction process. In the middle and late stages of the esterification or transesterification reaction and the pre-polycondensation reaction, reduced pressure and temperature are used to promote the forward reaction.

[0053] 2. In the atmospheric bubbling reaction distillation tower, the protective gas enters the tower body at a tangential angle and is bubbled downward, which is beneficial to enhance material mixing, separation of products and by-products, and avoid blockage of the protective gas inlet.

[0054] 3. The advantage of reactive distillation in coupling reaction and distillation is brought into play, and the by-products (water and / or tetrahydrofuran, etc.) produced in the esterification or transesterification process, or the by-products (water and / or tetrahydrofuran and polyols, etc.) produced in the pre-condensation process are evaporated, which promotes the reaction process and realizes energy integration.

[0055] 4. The upper part of the tower body of the atmospheric bubbling reaction distillation tower is provided with a first separation packing layer, which can separate and reflux the polyols and the oligomers generated by the reaction in time, avoiding the increase of the carboxyl content in the reaction system and the decrease of the yield; the upper part of the tower body of the reduced pressure temperature reaction distillation tower is provided with a second separation packing layer and preferably a spray device, which can not only separate the reflux polyols and the oligomers generated by the reaction, but also facilitate the control of the carboxyl content in the reaction system and the adjustment of the esterification rate or the transesterification rate.

[0056] In summary, the system and method provided by the present invention are highly integrated, easy to operate, and capable of continuously preparing polyester polyol prepolymers without mechanical stirring. The present invention offers advantages such as high reaction efficiency, stable product quality, easy product separation, and ease of large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] FIG1 is a schematic structural diagram of a system for preparing polyester polyol prepolymers in some specific embodiments of the present invention.

[0058] FIG2 is a schematic structural diagram of a system for preparing polyester polyol prepolymers in other specific embodiments of the present invention.

[0059] Description of Figure Numbers:

[0060] 1-normal pressure bubbling reaction distillation tower; 2-reduced pressure temperature reaction distillation tower; 3-polyol storage device; 4-vacuum device; 5-heating jacket;

[0061] 101 - first separation section; 102 - first reaction section; 103 - first separation packing layer; 104 - first tray; 105 - first gas phase discharge port; 106 - first liquid phase discharge port; 107 - first raw material inlet; 108 - protective gas inlet;

[0062] 201 - second separation section; 202 - second reaction section; 203 - second separation packing layer; 204 - second tower plate; 205 - second gas phase discharge port; 206 - second liquid phase discharge port; 207 - second raw material inlet; 208 - spraying device; 209 - spray pipe; 210 - nozzle. DETAILED DESCRIPTION

[0063] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be understood as limiting the scope of implementation of the present invention.

[0064] Example 1

[0065] This embodiment provides a system for preparing polyester polyol prepolymers, the structure of which is shown in FIG1 .

[0066] The system comprises: a normal pressure bubbling reaction distillation tower 1, a reduced pressure temperature reaction distillation tower 2 and a vacuum device 4.

[0067] The interior of the atmospheric bubbling reaction distillation tower 1 comprises a first separation section 101 and a first reaction section 102 from top to bottom. The first separation section is provided with a first separation packing layer 103 , and the first reaction section is provided with a plurality of first trays 104 .

[0068] The top of the atmospheric bubbling reaction distillation tower 1 is provided with a first gas phase discharge port 105, and the bottom of the atmospheric bubbling reaction distillation tower 1 is provided with a first liquid phase discharge port 106; the side wall of the atmospheric bubbling reaction distillation tower is provided with a first raw material inlet 107, and the first raw material inlet 107 is located in the first reaction section 102; the side wall of the atmospheric bubbling reaction distillation tower is provided with a protective gas inlet 108, and the protective gas inlet 108 is located below the first reaction section 102.

[0069] The interior of the vacuum temperature reaction distillation tower 2 includes a second separation section 201 and a second reaction section 202 from top to bottom. The second separation section 201 is provided with a second separation packing layer 203 , and the second reaction section is provided with a plurality of second trays 204 .

[0070] A second gas phase discharge port 205 is provided at the top of the vacuum temperature reaction distillation tower 2, and a second liquid phase discharge port 206 is provided at the bottom of the vacuum temperature reaction distillation tower 2; a second raw material inlet 207 is provided on the side wall of the vacuum temperature reaction distillation tower 2, and the second raw material inlet 207 is located in the second reaction section 202.

[0071] The first liquid phase discharge port 106 of the atmospheric pressure bubbling reaction distillation tower 1 is connected to the second raw material inlet 207 of the reduced pressure temperature reaction distillation tower 2 through a pipeline.

[0072] The tower bodies of the atmospheric bubbling reaction distillation tower 1 and the reduced pressure temperature reaction distillation tower 2 are respectively provided with heating jackets 5 for heating the two reaction distillation towers to the temperature required for the reaction.

[0073] The plurality of first trays 104 in the atmospheric bubbling reaction distillation column 1 have a multi-stage overflow structure. The plurality of second trays 204 in the vacuum temperature reaction distillation column 2 also have a multi-stage overflow structure. The first trays 104 and the second trays 204 have the same structure. Specifically, both the first trays 104 and the second trays 204 have inclined holes.

[0074] The vacuum device 4 is connected to the second gas phase discharge port 205 of the vacuum temperature-elevated reaction distillation tower 2 through a pipeline, and is used to adjust the pressure of the vacuum temperature-elevated reaction distillation tower 2 to the pressure required for the reaction.

[0075] The packing in the first separation packing layer 103 of the atmospheric bubbling reaction distillation tower 1 includes random saddle ring packing.

[0076] The packing in the second separation packing layer 203 of the vacuum temperature-elevated reaction distillation tower 2 includes random saddle ring packing.

[0077] The shielding gas inlet 108 of the atmospheric pressure bubbling reaction distillation tower 1 is a tangential inlet, which is arranged tangentially and tilted downward on the side wall of the atmospheric pressure bubbling reaction distillation tower 1 along the air inlet direction, so that the shielding gas enters tangentially from the oblique downward direction, and the angle between the shielding gas inlet 108 and the horizontal direction of the cross section of the atmospheric pressure bubbling reaction distillation tower 1 is 45°.

[0078] The number of the protective gas inlets 108 of the atmospheric bubbling reaction distillation tower 1 is 10, and each protective gas inlet 108 is a tangential inlet. The plurality of protective gas inlets 108 are evenly arranged along the circumferential direction on the side wall of the atmospheric bubbling reaction distillation tower 1 .

[0079] In addition, this embodiment also provides a method for preparing polyester polyol prepolymer, which adopts the above-mentioned system.

[0080] The method comprises the following steps:

[0081] (1) allowing a protective gas to enter the interior of the atmospheric bubbling reaction distillation tower 1 through a protective gas inlet 108 along a tangential inclination of the side wall thereof, and allowing a raw material for preparing a polyester polyol prepolymer to continuously enter the atmospheric bubbling reaction distillation tower 1 through a first raw material inlet 107, and subjecting the raw material for preparing the polyester polyol prepolymer to a preliminary esterification reaction. After the generated by-products and the gaseous phase substances in the reaction system pass through a first separation packing layer 103, the by-products and the protective gas are discharged from the atmospheric bubbling reaction distillation tower 1 through a first gas phase discharge port 105, and the generated preliminary esterification product is discharged from the atmospheric bubbling reaction distillation tower 1 through a first liquid phase discharge port 106;

[0082] The raw materials for preparing polyester polyol prepolymer include a mixture of succinic acid, 1,4-butanediol and a catalyst;

[0083] (2) The preliminary esterification product discharged from the first liquid phase discharge port 106 enters the vacuum temperature rising reaction distillation tower 2 through the second raw material inlet 207 to undergo a pre-condensation reaction. The generated by-products and the gaseous substances in the reaction system pass through the second separation packing layer 203. The by-products are discharged from the vacuum temperature rising reaction distillation tower 2 through the second gas phase discharge port 205 and enter the vacuum device. The reaction pressure of the vacuum temperature rising reaction distillation tower 2 is then controlled by the vacuum device. The generated polyester polyol prepolymer is discharged from the second liquid phase discharge port 206.

[0084] In the raw materials for preparing the polyester polyol prepolymer, the molar ratio of succinic acid to 1,4-butanediol is 1:1.2. The catalyst is tetra-n-butyl titanate. The catalyst is used in an amount of 200 ppm based on the mass of the succinic acid.

[0085] In step (1), the protective gas used is nitrogen.

[0086] In step (1), the temperature of the preliminary esterification reaction is 170°C.

[0087] By testing the preliminary esterification product discharged from the first liquid phase discharge port 106, it was found that the esterification rate of step (1) was 99%.

[0088] In step (2), the temperature of the pre-polycondensation reaction is 240° C. and the pressure is 70 kPa.

[0089] Example 2

[0090] This embodiment provides a method for preparing a polyester polyol prepolymer, which uses the system for preparing the polyester polyol prepolymer provided in Example 1.

[0091] The specific steps of the method are basically the same as those of Example 1, except that: the raw materials for preparing the polyester polyol prepolymer include a mixed solution of succinic acid, ethylene glycol and a catalyst, the molar ratio of succinic acid to ethylene glycol is 1:1.1, the catalyst is 1-chloro-3-hydroxy-1,1,3,3-tetrabutoxydistannoxane (CHTD), and the amount of the catalyst is 200 ppm of the mass of succinic acid; in step (1), the temperature of the preliminary esterification reaction is 180°C; by detecting the preliminary esterification product discharged from the first liquid phase discharge port 106, it is obtained that the esterification rate of step (1) is 98%; in step (2), a deep esterification reaction and a pre-polycondensation reaction are carried out, and the temperature of the deep esterification reaction and the pre-polycondensation reaction is 220°C and the pressure is 80 kPa.

[0092] Example 3

[0093] This embodiment provides a system for preparing polyester polyol prepolymers, the structure of which is shown in FIG2 .

[0094] The system comprises: a normal pressure bubbling reaction distillation tower 1, a reduced pressure temperature reaction distillation tower 2, a polyol storage device 3 and a vacuum device 4.

[0095] The interior of the atmospheric bubbling reaction distillation tower 1 comprises a first separation section 101 and a first reaction section 102 from top to bottom. The first separation section is provided with a first separation packing layer 103 , and the first reaction section is provided with a plurality of first trays 104 .

[0096] The top of the atmospheric bubbling reaction distillation tower 1 is provided with a first gas phase discharge port 105, and the bottom of the atmospheric bubbling reaction distillation tower 1 is provided with a first liquid phase discharge port 106; the side wall of the atmospheric bubbling reaction distillation tower is provided with a first raw material inlet 107, and the first raw material inlet 107 is located in the first reaction section 102; the side wall of the atmospheric bubbling reaction distillation tower is provided with a protective gas inlet 108, and the protective gas inlet 108 is located below the first reaction section 102.

[0097] The interior of the vacuum temperature reaction distillation tower 2 includes a second separation section 201 and a second reaction section 202 from top to bottom. The second separation section 201 is provided with a second separation packing layer 203 , and the second reaction section 202 is provided with a plurality of second trays 204 .

[0098] A second gas phase discharge port 205 is provided at the top of the vacuum temperature reaction distillation tower 2, and a second liquid phase discharge port 206 is provided at the bottom of the vacuum temperature reaction distillation tower 2; a second raw material inlet 207 is provided on the side wall of the vacuum temperature reaction distillation tower 2, and the second raw material inlet 207 is located in the second reaction section 202.

[0099] The first liquid phase discharge port 106 of the atmospheric pressure bubbling reaction distillation tower 1 is connected to the second raw material inlet 207 of the reduced pressure temperature reaction distillation tower 2 through a pipeline.

[0100] The spraying device 208 is arranged inside the tower body of the vacuum temperature reaction distillation tower 2, and the spraying device 208 is arranged above the second separation packing layer 203. The spraying device 208 is connected to the polyol storage device 3 through a pipeline, and is used to spray polyol into the vacuum temperature reaction distillation tower 2.

[0101] Spray device 208 includes at least a spray pipe 209 and a nozzle 210 connected to spray pipe 209. A polyol feed port is provided on the sidewall of vacuum temperature reaction distillation tower 2. The polyol feed port is located above the second separation packing layer 203 of vacuum temperature reaction distillation tower 2. Spray pipe 209 is connected to the polyol feed port. In this embodiment, spray device 208 is provided in vacuum temperature reaction distillation tower 2 to facilitate the reflux of oligomers in the reaction system, control the carboxyl content, and adjust the esterification rate or transesterification rate.

[0102] The tower bodies of the atmospheric bubbling reaction distillation tower 1 and the reduced pressure temperature reaction distillation tower 2 are respectively provided with heating jackets 5 for heating the two reaction distillation towers to the temperature required for the reaction.

[0103] The plurality of first trays 104 in the atmospheric bubbling reaction distillation column 1 have a multi-stage overflow structure. The plurality of second trays 204 in the vacuum temperature reaction distillation column 2 also have a multi-stage overflow structure. The first trays 104 and the second trays 204 have the same structure. Specifically, both the first trays 104 and the second trays 204 have inclined holes.

[0104] The vacuum device 4 is connected to the second gas phase discharge port 205 of the vacuum temperature-elevated reaction distillation tower 2 through a pipeline, and is used to adjust the pressure of the vacuum temperature-elevated reaction distillation tower 2 to the pressure required for the reaction.

[0105] The packing in the first separation packing layer 103 of the atmospheric bubbling reaction distillation tower 1 is a plate corrugated packing.

[0106] The packing in the second separation packing layer 203 of the vacuum temperature reaction distillation tower 2 is a plate corrugated packing.

[0107] The shielding gas inlet 108 of the atmospheric pressure bubbling reaction distillation tower 1 is a tangential inlet, which is arranged tangentially and obliquely downward on the side wall of the atmospheric pressure bubbling reaction distillation tower 1 along the air inlet direction, so that the shielding gas enters tangentially from the oblique downward direction, and the angle between the shielding gas inlet 108 and the horizontal direction of the cross section of the atmospheric pressure bubbling reaction distillation tower 1 is 60°. In this embodiment, the shielding gas inlet 108 arranged tangentially and obliquely downward on the side wall of the atmospheric pressure bubbling reaction distillation tower 1 enables the shielding gas to enter the interior of the tower body along the tangential and oblique downward side wall of the atmospheric pressure bubbling reaction distillation tower 1 for bubbling, which is beneficial to strengthening material mixing, separation of products and by-products, and avoiding blockage of the shielding gas inlet.

[0108] The number of the protective gas inlets 108 of the atmospheric bubbling reaction distillation tower 1 is 8, and each protective gas inlet 108 is a tangential inlet. The multiple protective gas inlets 108 are evenly arranged along the circumferential direction on the side wall of the atmospheric bubbling reaction distillation tower 1.

[0109] In addition, this embodiment also provides a method for preparing polyester polyol prepolymer, which adopts the above-mentioned system.

[0110] The method comprises the following steps:

[0111] (1) allowing a protective gas to enter the interior of the atmospheric bubbling reaction distillation tower 1 through a protective gas inlet 108 along a tangential inclination of the side wall thereof, and allowing a raw material for preparing a polyester polyol prepolymer to continuously enter the atmospheric bubbling reaction distillation tower 1 through a first raw material inlet 107, and subjecting the raw material for preparing the polyester polyol prepolymer to a preliminary esterification reaction. After the generated by-products and the gaseous phase substances in the reaction system pass through a first separation packing layer 103, the by-products and the protective gas are discharged from the atmospheric bubbling reaction distillation tower 1 through a first gas phase discharge port 105, and the generated preliminary esterification product is discharged from the atmospheric bubbling reaction distillation tower 1 through a first liquid phase discharge port 106;

[0112] The raw materials for preparing polyester polyol prepolymer include a mixture of succinic acid, 1,4-butanediol and a catalyst;

[0113] (2) The preliminary esterification product discharged from the first liquid phase discharge port 106 enters the vacuum temperature rising reaction distillation tower 2 through the second raw material inlet 207, and mainly undergoes a deep esterification reaction. The 1,4-butanediol is sprayed into the vacuum temperature rising reaction distillation tower 2 by the spraying device 208 in the vacuum temperature rising reaction distillation tower 2 to participate in the reaction. After the generated by-products and the gas phase substances in the reaction system pass through the second separation packing layer 203, the by-products are discharged from the vacuum temperature rising reaction distillation tower 2 from the second gas phase discharge port 205, and enter the vacuum device, and then the reaction pressure of the vacuum temperature rising reaction distillation tower 2 is controlled by the vacuum device. The generated polyester polyol prepolymer is discharged from the second liquid phase discharge port 206.

[0114] In the raw materials for preparing the polyester polyol prepolymer, the molar ratio of succinic acid to 1,4-butanediol is 1:1.3. The catalyst is tetra-n-butyl titanate. The catalyst is used in an amount of 5000 ppm based on the mass of the succinic acid.

[0115] In step (1), the protective gas used is nitrogen.

[0116] In step (1), the temperature of the preliminary esterification reaction is 160°C.

[0117] By testing the preliminary esterification product discharged from the first liquid phase discharge port 106, it was found that the esterification rate of step (1) was 82%.

[0118] In step (2), the mass ratio of 1,4-butanediol sprayed into the vacuum temperature reaction distillation tower by the spraying device 208 to the mass ratio of the preliminary esterification product is 0.5.

[0119] In step (2), the temperature of the deep esterification reaction is 180° C. and the pressure is 80 kPa.

[0120] By testing the polyester polyol prepolymer discharged from the second liquid phase discharge port 206, it was found that the esterification rate in step (2) was 99%.

[0121] By testing the substances discharged from the first gas phase discharge port 105 and the second gas phase discharge port 205, it was found that the entrained amount of diols and oligomers in the gas phase of steps (1) and (2) was less than 1%.

[0122] In this embodiment, the generated byproducts primarily include water and tetrahydrofuran, and the gaseous phase substances in the reaction system primarily include 1,4-butanediol and oligomers generated by the reaction. These gaseous phase substances can be promptly separated and refluxed from the 1,4-butanediol and oligomers generated by the reaction by passing through the first separation packing layer 103 or the second separation packing layer 203, while the byproducts water and tetrahydrofuran are purified and discharged from the top of the tower. The byproducts discharged from the first gas phase discharge port 105 and the second gas phase discharge port 205 are primarily aqueous solutions of tetrahydrofuran. The aqueous solutions of tetrahydrofuran discharged from the two reactive distillation towers can be mixed and then fed into the tetrahydrofuran refining system for refining.

[0123] Example 4

[0124] This embodiment provides a method for preparing a polyester polyol prepolymer, which uses the system for preparing the polyester polyol prepolymer provided in Example 3.

[0125] The specific steps of this method are substantially the same as those of Example 3, except that: in step (1), the temperature of the preliminary esterification reaction is 170° C.; by testing the preliminary esterification product discharged from the first liquid phase discharge port 106, it is determined that the esterification rate in step (1) is 85%; in step (2), a deep esterification reaction and a pre-polycondensation reaction are carried out at a temperature of 205° C. and a pressure of 50 kPa. By testing the materials discharged from the first gas phase discharge port 105 and the second gas phase discharge port 205, it is determined that the entrainment of diols and oligomers in the gas phase of steps (1) and (2) is less than 0.8%.

[0126] Example 5

[0127] This embodiment provides a method for preparing a polyester polyol prepolymer, which uses the system for preparing the polyester polyol prepolymer provided in Example 3.

[0128] The specific steps of this method are substantially the same as those of Example 3, except that: in step (1), the temperature of the preliminary esterification reaction is 210° C.; by testing the preliminary esterification product discharged from the first liquid phase discharge port 106, it is determined that the esterification rate in step (1) is 90%; in step (2), a deep esterification reaction and a pre-polycondensation reaction are carried out at a temperature of 225° C. and a pressure of 100 kPa. By testing the materials discharged from the first gas phase discharge port 105 and the second gas phase discharge port 205, it is determined that the entrainment of diols and oligomers in the gas phase of steps (1) and (2) is less than 2%.

[0129] Example 6

[0130] This embodiment provides a method for preparing a polyester polyol prepolymer, which uses the system for preparing the polyester polyol prepolymer provided in Example 3.

[0131] The specific steps of the method are basically the same as those of Example 3, except that: the raw materials for preparing the polyester polyol prepolymer include a mixed solution of dimethyl succinate, 1,4-butanediol and a catalyst, the molar ratio of dimethyl succinate to 1,4-butanediol is 1:1.1, the catalyst is tetra-n-butyl titanate, and the amount of the catalyst is 5000 ppm of the mass of dimethyl succinate; in step (1), the temperature of the initial ester exchange reaction is 130°C; by detecting the initial ester exchange product discharged from the first liquid phase discharge port 106, it is obtained that the ester exchange rate of step (1) is 80%; in step (2), a deep esterification reaction is mainly carried out, the temperature of the deep ester exchange reaction is 150°C, and the pressure is 15 kPa; by detecting the polyester polyol prepolymer discharged from the second liquid phase discharge port 206, it is obtained that the esterification rate of step (2) is 98%. By detecting the substances discharged from the first gas phase discharge port 105 and the second gas phase discharge port 205, it was found that the entrained amount of diols and oligomers in the gas phase of steps (1) and (2) was less than 2%.

[0132] Example 7

[0133] This embodiment provides a system for preparing polyester polyol prepolymers. The system is substantially the same as the system provided in Example 3, except that the angle between the protective gas inlet 108 and the horizontal direction of the cross section of the atmospheric bubbling reactive distillation column 1 is 15°.

[0134] This embodiment also provides a method for preparing a polyester polyol prepolymer, which utilizes the system of this embodiment. The specific steps of this method are substantially the same as those of Example 3, except that: in step (1), the temperature of the preliminary esterification reaction is 260°C; by testing the preliminary esterification product discharged from the first liquid phase discharge port 106, it is determined that the esterification rate in step (1) is 92%; in step (2), the mass ratio of 1,4-butanediol sprayed into the vacuum temperature reaction distillation tower using the spray device 208 to the mass ratio of the preliminary esterification product is 0.02; and deep esterification and pre-polycondensation reactions are performed at a temperature of 205°C and a pressure of 50 kPa. By testing the substances discharged from the first gas phase discharge port 105 and the second gas phase discharge port 205, it is determined that the entrainment of diols and oligomers in the gas phase of steps (1) and (2) is less than 1%.

[0135] Example 8

[0136] This embodiment provides a system for preparing polyester polyol prepolymers. The system is substantially the same as the system provided in Example 3, except that the angle between the protective gas inlet 108 and the horizontal direction of the cross section of the atmospheric bubbling reactive distillation column 1 is 85°.

[0137] This embodiment also provides a method for preparing a polyester polyol prepolymer, which utilizes the system of this embodiment. The specific steps of this method are substantially the same as those of Example 3, except that: in step (1), the temperature of the preliminary esterification reaction is 210°C; by testing the preliminary esterification product discharged from the first liquid phase discharge port 106, it is determined that the esterification rate in step (1) is 90%; in step (2), the mass ratio of 1,4-butanediol sprayed into the vacuum temperature reaction distillation tower by the spray device 208 to the mass ratio of the preliminary esterification product is 5; and deep esterification and pre-polycondensation reactions are performed at a temperature of 260°C and a pressure of 101.325 kPa. By testing the substances discharged from the first gas phase discharge port 105 and the second gas phase discharge port 205, it is determined that the entrainment of diols and oligomers in the gas phase of steps (1) and (2) is less than 3%.

[0138] Example 9

[0139] This embodiment provides a method for preparing a polyester polyol prepolymer, which uses the system for preparing the polyester polyol prepolymer provided in Example 3.

[0140] The specific steps of this method are substantially the same as those of Example 3, except that: in step (1), the temperature of the preliminary esterification reaction is 200° C.; by testing the preliminary esterification product discharged from the first liquid phase discharge port 106, it is determined that the esterification rate of step (1) is 88%; in step (2), the mass ratio of 1,4-butanediol sprayed into the vacuum temperature rising reaction distillation tower by the spraying device 208 to the mass ratio of the preliminary esterification product is 0.2; the deep esterification reaction is mainly carried out, and the temperature of the deep esterification reaction is 180° C. and the pressure is 100 kPa; by testing the polyester polyol prepolymer discharged from the second liquid phase discharge port 206, it is determined that the esterification rate of step (2) is 98%. By testing the substances discharged from the first gas phase discharge port 105 and the second gas phase discharge port 205, it is determined that the entrained amount of diols and oligomers in the gas phase of steps (1) and (2) is less than 2%.

[0141] Example 10

[0142] This embodiment provides a method for preparing a polyester polyol prepolymer, which uses the system for preparing the polyester polyol prepolymer provided in Example 3.

[0143] The specific steps of this method are substantially the same as those of Example 3, except that: in step (1), the temperature of the preliminary esterification reaction is 140° C.; by testing the preliminary esterification product discharged from the first liquid phase discharge port 106, it is determined that the esterification rate in step (1) is 81%; in step (2), the mass ratio of the 1,4-butanediol sprayed into the vacuum temperature rising reaction distillation tower by the spray device 208 to the mass ratio of the preliminary esterification product is 2; and the deep esterification reaction and pre-polycondensation reaction are carried out at a temperature of 240° C. and a pressure of 50 kPa. By testing the substances discharged from the first gas phase discharge port 105 and the second gas phase discharge port 205, it is determined that the entrainment of diols and oligomers in the gas phase of steps (1) and (2) is less than 3%.

[0144] Comparative Example 1

[0145] This comparative example provides a system for preparing a polyester polyol prepolymer. This system differs from Example 3 in that the tower body of the reduced-pressure temperature reaction distillation tower 2 is not provided with a spraying device 208 for spraying polyol. The polyester polyol prepolymer was prepared using the method of Example 3. Testing of the preliminary esterification product discharged from the first liquid phase discharge port 106 revealed an esterification rate of 82% in step (1). Testing of the polyester polyol prepolymer discharged from the second liquid phase discharge port 206 revealed an esterification rate of 96% in step (2). Testing of the material discharged from the second gas phase discharge port 205 revealed that the entrainment of diols and oligomers in the gas phase of step (2) was greater than 5%.

[0146] Comparative Example 2

[0147] This comparative example provides a system for preparing a polyester polyol prepolymer, which differs from Example 3 in that: the atmospheric bubbling reaction distillation tower 1 is not provided with the first separation packing layer 103; the reduced pressure temperature reaction distillation tower 2 is not provided with the second separation packing layer 203 and the spraying device 208 for spraying polyol. The polyester polyol prepolymer is prepared using the method of Example 3. By testing the preliminary esterification product discharged from the first liquid phase discharge port 106, it is found that the esterification rate in step (1) is 82%; by testing the polyester polyol prepolymer discharged from the second liquid phase discharge port 206, it is found that the esterification rate in step (2) is 93%; by testing the material discharged from the first gas phase discharge port 105, it is found that the entrainment of diols and oligomers in the gas phase of step (1) is greater than 8%; by testing the material discharged from the second gas phase discharge port 205, it is found that the entrainment of diols and oligomers in the gas phase of step (2) is greater than 10%.

Claims

1. A system for preparing a polyester polyol prepolymer, the system comprising: Atmospheric pressure bubbling reaction distillation tower and vacuum temperature rising reaction distillation tower; The tower body of the atmospheric bubbling reaction distillation tower includes a first separation section and a first reaction section from top to bottom, the first separation section is provided with a first separation packing layer, and the first reaction section is provided with a plurality of tower trays; The atmospheric bubbling reaction distillation tower is provided with a first gas phase discharge port, a first liquid phase discharge port, a first raw material inlet and a protective gas inlet; The tower body of the vacuum temperature-raising reaction distillation tower includes a second separation section and a second reaction section from top to bottom, the second separation section is provided with a second separation packing layer, and the second reaction section is provided with a plurality of tower trays; The vacuum temperature reaction distillation tower is provided with a second gas phase discharge port, a second liquid phase discharge port and a second raw material inlet; The first liquid phase discharge port of the atmospheric pressure bubbling reaction distillation tower is connected to the second raw material inlet of the vacuum temperature rising reaction distillation tower through a pipeline.

2. The system for preparing polyester polyol prepolymer according to claim 1, wherein: The system further includes: a polyol storage device, and the vacuum temperature reaction distillation tower further includes a spray device; the spray device is arranged inside the tower body of the vacuum temperature reaction distillation tower, and the spray device is arranged above the second separation packing layer; the spray device is connected to the polyol storage device through a pipeline, and is used to spray polyol into the vacuum temperature reaction distillation tower.

3. The system for preparing polyester polyol prepolymer according to claim 2, wherein: The spray device at least includes a spray pipe and a nozzle connected to the spray pipe, and the side wall of the vacuum temperature reaction distillation tower is provided with a polyol feed port, the polyol feed port is located above the second separation packing layer of the vacuum temperature reaction distillation tower, and the spray pipe is connected to the polyol feed port.

4. The system for preparing polyester polyol prepolymer according to claim 1, wherein: The tower bodies of the atmospheric pressure bubbling reaction distillation tower and the reduced pressure temperature reaction distillation tower are respectively provided with heating jackets on their exteriors.

5. The system for preparing polyester polyol prepolymer according to claim 1, wherein: Several trays in the atmospheric pressure bubbling reaction distillation tower and the reduced pressure temperature reaction distillation tower have a multi-stage overflow structure.

6. The system for preparing polyester polyol prepolymer according to claim 5, wherein: The tower tray comprises one or a combination of inclined hole tower tray, bubble cap tower tray, fixed valve tower tray and vertical sieve plate tower tray.

7. The system for preparing polyester polyol prepolymer according to claim 6, wherein: The tower tray is an inclined hole tower tray.

8. The system for preparing polyester polyol prepolymer according to claim 1, wherein: The system further comprises: a vacuum device, which is connected to the second gas phase discharge port of the vacuum temperature rising reaction distillation tower through a pipeline.

9. The system for preparing polyester polyol prepolymer according to claim 1, wherein: The filler in the first separation filler layer of the atmospheric bubbling reaction distillation tower is a random filler or a structured filler; The filler in the second separation filler layer of the vacuum temperature rising reaction distillation tower is a random filler or a structured filler.

10. The system for preparing polyester polyol prepolymer according to claim 1, wherein: The top of the atmospheric pressure bubbling reaction distillation tower is provided with the first gas phase discharge port; the bottom of the atmospheric pressure bubbling reaction distillation tower is provided with the first liquid phase discharge port; the side wall of the atmospheric pressure bubbling reaction distillation tower is provided with the first raw material inlet, and the first raw material inlet is located in the first reaction section; the side wall of the atmospheric pressure bubbling reaction distillation tower is provided with the protective gas inlet, and the protective gas inlet is located below the first reaction section.

11. The system for preparing polyester polyol prepolymer according to claim 1, wherein: The top of the vacuum temperature rising reaction distillation tower is provided with the second gas phase discharge port; the bottom of the vacuum temperature rising reaction distillation tower is provided with the second liquid phase discharge port; the side wall of the vacuum temperature rising reaction distillation tower is provided with the second raw material inlet, and the second raw material inlet is located in the second reaction section.

12. The system for preparing polyester polyol prepolymer according to claim 10, wherein: The protective gas inlet of the atmospheric pressure bubbling reaction distillation tower is a tangential inlet, which is tangential to the side wall of the atmospheric pressure bubbling reaction distillation tower.

13. The system for preparing polyester polyol prepolymer according to claim 12, wherein: The protective gas inlet of the atmospheric pressure bubbling reaction distillation tower is arranged tangentially and inclined downward on the side wall of the atmospheric pressure bubbling reaction distillation tower along the air inlet direction, so that the protective gas enters tangentially from the oblique downward direction, and the angle between the protective gas inlet and the horizontal direction of the cross section of the atmospheric pressure bubbling reaction distillation tower is 15 to 85 degrees.

14. The system for preparing polyester polyol prepolymer according to claim 13, wherein: The atmospheric pressure bubbling reaction distillation tower has a plurality of protective gas inlets, each of which is a tangential inlet. The plurality of protective gas inlets are uniformly arranged along the circumferential direction on the side wall of the atmospheric pressure bubbling reaction distillation tower.

15. A method for preparing a polyester polyol prepolymer, the method using the system for preparing a polyester polyol prepolymer according to claim 1, the method comprising the following steps: (1) allowing a protective gas to enter an atmospheric pressure bubbling reaction distillation tower, and allowing a raw material for preparing a polyester polyol prepolymer to enter the atmospheric pressure bubbling reaction distillation tower, the raw material for preparing a polyester polyol prepolymer undergoes a preliminary esterification or transesterification reaction, the generated by-products and gaseous substances in the reaction system pass through a first separation filler layer, the by-products and protective gas are discharged from the atmospheric pressure bubbling reaction distillation tower from a first gas phase discharge port, and the generated preliminary esterification or transesterification products are discharged from the atmospheric pressure bubbling reaction distillation tower from a first liquid phase discharge port; (2) the preliminary esterification or transesterification product discharged from the first liquid phase outlet enters a vacuum temperature-raising reaction distillation tower, One or more of deep esterification reaction, ester exchange reaction and pre-condensation reaction are carried out, and the generated by-products and gas phase substances in the reaction system pass through the second separation packing layer, and the by-products are discharged from the second gas phase discharge port to the vacuum temperature rising reaction distillation tower, and the generated polyester polyol prepolymer is discharged from the second liquid phase discharge port.

16. The method for preparing a polyester polyol prepolymer according to claim 15, wherein: In step (1), the raw materials for preparing the polyester polyol prepolymer include a mixed solution of one or a combination of polycarboxylic acids and their derivatives, polyols and a catalyst.

17. The method for preparing a polyester polyol prepolymer according to claim 15, wherein: In step (1), the protective gas is directed downwardly into the interior of the tower along the tangential direction of the side wall of the atmospheric pressure bubbling reaction distillation tower; In step (1), the raw materials for preparing the polyester polyol prepolymer are continuously fed into a normal pressure bubbling reaction distillation tower.

18. The method for preparing a polyester polyol prepolymer according to claim 15, wherein: In step (1), the temperature of the preliminary esterification or transesterification reaction is 130 to 260°C.

19. The method for preparing a polyester polyol prepolymer according to claim 15, wherein: Step (2) further comprises: using a spray device in the vacuum temperature rising reaction distillation tower to spray the polyol into the vacuum temperature rising reaction distillation tower.

20. The method for preparing a polyester polyol prepolymer according to claim 19, wherein: In step (2), the mass ratio of the polyol sprayed into the vacuum temperature reaction distillation tower by a spray device to the preliminary esterification or transesterification product is 0.02 to 5.

21. The method for preparing a polyester polyol prepolymer according to claim 15, wherein: In step (2), the temperature of one or more of the deep esterification reaction, transesterification reaction and pre-polycondensation reaction is 150-260°C.

22. The method for preparing a polyester polyol prepolymer according to claim 15, wherein: In step (2), the pressure of one or more of the deep esterification reaction, transesterification reaction and pre-polycondensation reaction is 15 to 101.325 kPa.

Images