A method for separating and preparing tetrahydrofuran from by-product waste liquid of regenerated BDO

Abstract

The invention discloses a method for preparing tetrahydrofuran by separating regenerated BDO byproduct waste liquid. The invention relates to the technical field of organic matter preparation. The regenerated BDO byproduct waste liquid comprises water, tetrahydrofuran, methanol, organic matter, inorganic salt and impurities. The content of each component is determined by gas chromatography-mass spectrometry analysis. The advantages of the invention are: by introducing microwave-assisted treatment in the separation operation, the waste liquid is irradiated from different angles by microwaves of different frequencies and powers, so that the separation of impurities and the saponification reaction of organic matter can be accelerated, and the reaction time is greatly shortened. In the distillation process, the ultrasonic atomization technology is combined with atmospheric distillation to increase the gas-liquid contact area and improve the evaporation efficiency of methanol and organic matter. By constructing a multi-stage membrane separation device in the separation operation, the microfiltration membrane, the ultrafiltration membrane and the nanofiltration membrane can be used to separate impurities and organic matter of different sizes.

Description

Technical Field

[0001] The invention relates to the technical field of organic matter preparation, in particular to a method for preparing tetrahydrofuran by separating by-product waste liquid of regenerated BDO. Background Art

[0002] Tetrahydrofuran (THF), also known as oxacyclopentane, tetrahydrooxacyclopentane, tetramethylene oxide, 1,4-butylene oxide, etc., is an important raw material for organic synthesis and is known as a universal solvent.

[0003] In today's chemical industry, 1,4-butanediol (BDO), as an important organic chemical raw material, is widely used in polyester, polyurethane, pharmaceutical and other fields. However, the production process of BDO will inevitably produce a large amount of by-product waste liquid. If these by-product waste liquids are not properly treated, they will cause serious pollution to the environment and waste the potential valuable resources. Traditional chemical waste liquid treatment methods often have many disadvantages. On the one hand, some treatment methods may only focus on the harmless treatment of waste liquids, but ignore the recycling of valuable components. For the regenerated BDO by-product waste liquid, it contains water, tetrahydrofuran, methanol, organic matter, inorganic salts and impurities. Among them, tetrahydrofuran, as an important organic solvent and chemical intermediate, has broad application prospects and high economic value. If tetrahydrofuran can be effectively separated from the by-product waste liquid, it will be difficult to obtain the by-product waste liquid. On the other hand, the existing treatment methods may have certain technical limitations. For example, some methods are complex, require multiple steps and complex equipment, are difficult to operate, and have high costs. At the same time, the separation efficiency of some methods is low, resulting in a low recovery rate of tetrahydrofuran, which cannot meet the needs of actual production. In addition, secondary pollution may be generated during the treatment process, causing new pressure on the environment. Pressure swing distillation is based on the characteristics of binary systems that deviate from Raoult's law. By changing the system pressure, the azeotropic point at normal pressure moves or the azeotropic composition changes. Through the combination of distillation processes, high-purity components can be obtained at different tower tops or tower bottoms, thereby realizing a binary azeotropic system. To this end, we propose a method for separating and preparing tetrahydrofuran from regenerated BDO by-product waste liquid. Summary of the invention

[0004] The object of the present invention is to provide a method for preparing tetrahydrofuran by separating the by-product waste liquid from regenerated BDO.

[0005] In order to solve the problems raised in the above background technology, the present invention provides the following technical solutions: a method for preparing tetrahydrofuran by separating the by-product waste liquid of regenerated BDO, wherein the by-product waste liquid of regenerated BDO includes water, tetrahydrofuran, methanol, organic matter, inorganic salts and impurities, and the content of each component is determined by gas chromatography-mass spectrometry analysis. The specific operation steps of separating the by-product waste liquid of regenerated BDO to prepare tetrahydrofuran are as follows:

[0006] Step 1: pretreatment of the regenerated BDO by-product waste liquid, transferring the BDO by-product waste liquid into a container, adding a 10%-20% sodium hydroxide solution and stirring and mixing, and filtering after the reaction is completed to obtain a crude BDO by-product waste liquid;

[0007] Step 2: Preliminary separation of by-product waste liquid: adding crude BDO by-product waste liquid into a container, evaporating the liquid by atmospheric distillation, and collecting the evaporated distillate;

[0008] Step 3: construct a multi-stage membrane separation device, transfer the distillate into the separation device, and perform separation operations in sequence to obtain a crude distillate;

[0009] Step 4, deep separation of the crude distillate, transferring the separated crude distillate into a distillation kettle for vacuum distillation, collecting evaporated tetrahydrofuran and cooling it into liquid by condensation to obtain a crude tetrahydrofuran;

[0010] Step 5: Refining and purification: transferring the crude tetrahydrofuran product into a distillation tower for distillation to obtain a high-purity tetrahydrofuran product.

[0011] As a further solution of the present invention: in the regenerated BDO by-product waste liquid, the water content is 40%-50%, the tetrahydrofuran content is 20%-30%, the methanol content is 5%-10%, the organic matter content is 25%-30%, and the total content of inorganic salts and impurities is 10%-15%. Microwave-assisted treatment is introduced to accelerate the separation of impurities and the saponification reaction of impurities with organic matter by utilizing the thermal effect and non-thermal effect of microwaves. The microwave frequency is controlled at 2450MHz-915MHz, the power is 500W-1000W, the treatment time is 15min-30min, and 2-6 groups of microwave generators are set according to actual conditions to irradiate the waste liquid from different angles.

[0012] As a further solution of the present invention: in the step 1, the BDO by-product waste liquid is collected in a storage tank, and a flocculant is added in an amount of 0.05%-0.2% of the total weight of the BDO by-product waste liquid. After the solid impurities are precipitated and separated, the solid impurities and the precipitate are filtered out, and a coarse filter screen with a pore size of 1 mm is used, and then a fine filter screen with a pore size of 0.1 mm is used to ensure that the solid impurity removal rate is above 95%.

[0013] As a further scheme of the present invention: in the step 2, the pretreated waste liquid is heated to 80°C-90°C by atmospheric distillation to evaporate methanol and organic matter, and the distillate is collected. During the distillation process, the heating rate is controlled at 5°C / min-10°C / min, and the reflux ratio is maintained between 1 and 2. During the distillation process, ultrasonic atomization technology is introduced to atomize part of the steam into tiny particles to increase the gas-liquid contact area. The ultrasonic frequency is controlled at 20kHz-40kHz, the power is 500W-1000W, and the atomization temperature is 80°C-90°C. According to actual conditions, 2-6 groups of ultrasonic atomizers are installed and evenly distributed in the distillation tower.

[0014] As a further solution of the present invention: In the step 2, during the preliminary separation process, it is necessary to use a specially designed distillation tower plate to increase the gas-liquid contact area and improve the separation efficiency. The special distillation tower plate is provided with micro protrusions and grooves.

[0015] As a further scheme of the present invention: in the step three, the constructed multi-stage membrane separation device includes a microfiltration membrane, an ultrafiltration membrane and a nanofiltration membrane, wherein the microfiltration membrane is used to remove larger particles of impurities, the membrane pore size is 0.1um-1um, and the operating pressure is 0.1MPa-0.3MPa, the ultrafiltration membrane is used to remove tiny particles and macromolecular organic matter, the membrane pore size is 0.01um-0.1um, and the operating pressure is 0.2MPa-0.5MPa, the nanofiltration membrane is used to selectively separate tetrahydrofuran, the membrane pore size is 1nm-10nm, and the operating pressure is 0.5MPa-1MPa, the microfiltration membrane is synthesized from polypropylene material, the ultrafiltration membrane is synthesized from polyethersulfone material, and the nanofiltration membrane is synthesized from composite polyamide material.

[0016] As a further scheme of the present invention: in the step 4, the crude distillate after separation is subjected to reduced pressure distillation, heated to 100° C.-110° C. under a vacuum degree of 0.08 MPa-0.09 MPa, tetrahydrofuran is evaporated, and the distillate is collected, and the distilled tetrahydrofuran vapor is cooled into liquid through a condenser to obtain a crude tetrahydrofuran product, wherein the condenser is a spiral condenser.

[0017] As a further solution of the present invention: in the step 4, an adsorbent is introduced, and before deep separation, the crude distillate is passed into an adsorption column filled with the adsorbent and adsorbed at an adsorption temperature of 35°C-40°C for 1h-2h.

[0018] As a further scheme of the present invention: in the step 5, the crude tetrahydrofuran is distilled, in the distillation tower, the number of tower plates is controlled to be 30-40, the reflux ratio is 3-4, the tower top temperature is controlled between 65°C and 67°C, and the tower bottom temperature is controlled between 105°C and 107°C. During the distillation process, the pressure is controlled at normal pressure, and the feed rate is controlled at 10L / h-20L / h. During the treatment process, the saponification reaction that occurs is as follows:

[0019]

[0020] in, It is the alkyl group and other groups in organic matter.

[0021] By adopting the above technical solution, compared with the prior art, the beneficial effects of the present invention are:

[0022] 1. The present invention introduces microwave-assisted treatment in the separation operation, utilizes microwaves of different frequencies and powers to irradiate the waste liquid from different angles, can accelerate the separation of impurities and the saponification reaction of organic matter, greatly shortens the reaction time, and in the distillation process, combines the ultrasonic atomization technology with atmospheric distillation to increase the gas-liquid contact area, while improving the evaporation efficiency of methanol and organic matter, and constructs a multi-stage membrane separation device in the separation operation, wherein the microfiltration membrane, the ultrafiltration membrane and the nanofiltration membrane can respectively separate impurities and organic matter of different sizes. This precise separation method makes the selective separation of tetrahydrofuran more accurate, effectively removes various impurities, and improves the purity and recovery rate of tetrahydrofuran;

[0023] 2. The present invention can effectively precipitate and remove solid impurities by adding sodium hydroxide solution and flocculant to the BDO by-product waste liquid, so that the subsequent separation process is smoother, and the problems of equipment blockage and reduced separation efficiency caused by solid impurities are reduced. By performing reduced pressure distillation on the crude distillate, tetrahydrofuran can be effectively evaporated within a specific vacuum degree and temperature range. The spiral condenser is selected to cool the distilled tetrahydrofuran vapor, which can improve the cooling efficiency and ensure the collection effect of tetrahydrofuran. By introducing an adsorbent and passing the crude distillate into an adsorption column filled with the adsorbent for adsorption treatment, the residual impurities are further removed and the purity of the tetrahydrofuran is improved. In the refining and purification stage, the distillation is carried out by a distillation tower, and the parameters such as the number of tower plates, the reflux ratio, the top and bottom temperatures of the tower, and the feed rate are controlled, so that the purity of the tetrahydrofuran is further improved, and finally a high-purity tetrahydrofuran product is obtained, which meets the needs of different fields for high-purity tetrahydrofuran and improves the market competitiveness of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1The figure is a schematic flow chart of the steps of separating and preparing tetrahydrofuran in an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The specific embodiments of the present invention are further described below in conjunction with the accompanying drawings. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0026] The present invention discloses a method for preparing tetrahydrofuran by separating the byproduct waste liquid of regenerated BDO. The byproduct waste liquid of regenerated BDO includes water, tetrahydrofuran, methanol, organic matter, inorganic salt and impurities. The content of each component is determined by gas chromatography-mass spectrometry analysis. The specific operation steps of preparing tetrahydrofuran by separating the byproduct waste liquid of regenerated BDO are as follows:

[0027] Step 1: pretreatment of the regenerated BDO by-product waste liquid, transferring the BDO by-product waste liquid into a container, adding a 10%-20% sodium hydroxide solution and stirring and mixing, and filtering after the reaction is completed to obtain a crude BDO by-product waste liquid;

[0028] Step 2: Preliminary separation of by-product waste liquid: adding crude BDO by-product waste liquid into a container, evaporating the liquid by atmospheric distillation, and collecting the evaporated distillate;

[0029] Step 3: construct a multi-stage membrane separation device, transfer the distillate into the separation device, and perform separation operations in sequence to obtain a crude distillate;

[0030] Step 4, deep separation of the crude distillate, transferring the separated crude distillate into a distillation kettle for vacuum distillation, collecting evaporated tetrahydrofuran and cooling it into liquid by condensation to obtain a crude tetrahydrofuran;

[0031] Step 5: Refining and purification: transferring the crude tetrahydrofuran product into a distillation tower for distillation to obtain a high-purity tetrahydrofuran product.

[0032] In one embodiment of the present invention: in the regenerated BDO by-product waste liquid, the content of water is 40%-50%, the content of tetrahydrofuran is 20%-30%, the content of methanol is 5%-10%, the content of organic matter is 25%-30%, and the total content of inorganic salts and impurities is 10%-15%. Microwave-assisted treatment is introduced to accelerate the separation of impurities and the saponification reaction of impurities with organic matter by utilizing the thermal effect and non-thermal effect of microwaves. The microwave frequency is controlled at 2450MHz-915MHz, the power is 500W-1000W, the treatment time is 15min-30min, and 2-6 groups of microwave generators are set according to actual conditions to irradiate the waste liquid from different angles.

[0033] In one embodiment of the present invention, in step 1, the BDO by-product waste liquid is collected in a storage tank, and a flocculant is added in an amount of 0.05% to 0.2% of the total weight of the BDO by-product waste liquid. After the solid impurities are precipitated and separated, the solid impurities and the precipitate are filtered out, and a coarse filter mesh with a pore size of 1 mm is used, and then a fine filter mesh with a pore size of 0.1 mm is used to ensure that the solid impurity removal rate is above 95%.

[0034] In one embodiment of the present invention: in step 2, the pretreated waste liquid is heated to 80°C-90°C by atmospheric distillation, methanol and organic matter are evaporated, and the distillate is collected. During the distillation process, the heating rate is controlled at 5°C / min-10°C / min, and the reflux ratio is maintained between 1-2. During the distillation process, ultrasonic atomization technology is introduced to atomize part of the steam into tiny particles to increase the gas-liquid contact area. The ultrasonic frequency is controlled at 20kHz-40kHz, the power is 500W-1000W, and the atomization temperature is 80°C-90°C. According to actual conditions, 2-6 groups of ultrasonic atomizers are installed and evenly distributed in the distillation tower.

[0035] In one embodiment of the present invention: In step 2, during the preliminary separation process, a specially designed distillation tower plate is required to increase the gas-liquid contact area and improve the separation efficiency. The special distillation tower plate is provided with micro protrusions and grooves.

[0036] In one embodiment of the present invention: in step three, the constructed multi-stage membrane separation device includes a microfiltration membrane, an ultrafiltration membrane and a nanofiltration membrane, wherein the microfiltration membrane is used to remove larger particles of impurities, the membrane pore size is 0.1um-1um, and the operating pressure is 0.1MPa-0.3MPa, the ultrafiltration membrane is used to remove tiny particles and macromolecular organic matter, the membrane pore size is 0.01um-0.1um, and the operating pressure is 0.2MPa-0.5MPa, the nanofiltration membrane is used to selectively separate tetrahydrofuran, the membrane pore size is 1nm-10nm, and the operating pressure is 0.5MPa-1MPa, the microfiltration membrane is synthesized from polypropylene material, the ultrafiltration membrane is synthesized from polyethersulfone material, and the nanofiltration membrane is synthesized from composite polyamide material.

[0037] In one embodiment of the present invention: in step 4, the crude distillate after separation is subjected to reduced pressure distillation, heated to 100° C.-110° C. under a vacuum degree of 0.08 MPa-0.09 MPa, tetrahydrofuran is evaporated, and the distillate is collected, and the distilled tetrahydrofuran vapor is cooled to liquid through a condenser to obtain a crude tetrahydrofuran product, wherein the condenser is a spiral condenser.

[0038] In one embodiment of the present invention: in step 4, an adsorbent is introduced, and before deep separation, the crude distillate is passed into an adsorption column filled with the adsorbent and adsorbed at an adsorption temperature of 35°C-40°C for 1h-2h.

[0039] In one embodiment of the present invention: in step 5, the crude tetrahydrofuran is distilled, in the distillation tower, the number of tower plates is controlled to be 30-40, the reflux ratio is 3-4, the tower top temperature is controlled between 65°C and 67°C, the tower bottom temperature is controlled between 105°C and 107°C, during the distillation process, the pressure is controlled at normal pressure, the feed rate is controlled at 10L / h-20L / h, and during the treatment process, the saponification reaction that occurs is as follows:

[0040]

[0041] in, It is the alkyl group and other groups in organic matter.

[0042] In one embodiment of the present invention, the added sodium hydroxide solution reacts with the acidic substances in the waste liquid to neutralize and simultaneously promotes saponification of some organic matter. The saponification reaction helps to change the properties of the organic matter, making it easier to be removed or separated in the subsequent separation process.

[0043] Materials:

[0044] Regenerated BDO by-product waste liquid, sodium hydroxide solution, flocculant, storage tank, filtration equipment (including coarse screen filter and fine screen filter), distillation container, heating device, ultrasonic atomizer, specially designed distillation tower plate, multi-stage membrane separation device (including microfiltration membrane, ultrafiltration membrane and nanofiltration membrane), distillation kettle, spiral condenser, adsorbent, adsorption column and distillation tower.

[0045] Embodiment 1

[0046] Preprocessing stage:

[0047] 1200kg of regenerated BDO by-product waste liquid was transferred to a storage tank. At the same time, 0.08% of the total weight of the waste liquid was added with a flocculant and stirred thoroughly to allow solid impurities to precipitate and separate. After standing for 10 minutes, it was first filtered through a coarse filter screen with a pore size of 1mm, and then filtered through a fine filter screen with a pore size of 0.1mm to ensure that the solid impurity removal rate reached 95.3%.

[0048] A 12% sodium hydroxide solution was added to the filtered waste liquid, and the mixture was stirred. The reaction temperature was controlled at about 28° C., the stirring speed was 35 r / min, and the reaction time was 40 min. After the reaction was completed, the mixture was filtered again to obtain a crude BDO by-product waste liquid.

[0049] Initial separation stage:

[0050] The crude BDO by-product waste liquid was added to the distillation container, and the waste liquid was slowly heated to 82°C using a heating device by atmospheric distillation. The heating rate was strictly controlled to be 6°C / min during the heating process, while the reflux ratio was maintained at 1.4.

[0051] During the distillation process, three sets of ultrasonic atomizers are installed and evenly distributed in the distillation tower. The ultrasonic frequency is controlled at 28kHz, the power is set to 750W, and the atomization temperature is 82°C. Through ultrasonic atomization technology, part of the steam is atomized into tiny particles, increasing the gas-liquid contact area, allowing methanol and organic matter to evaporate more efficiently, and the evaporated distillate is collected at the same time.

[0052] The specially designed distillation plates have micro-protrusions and grooves on them to further increase the gas-liquid contact area and improve separation efficiency.

[0053] Multi-stage membrane separation stage:

[0054] The distillate is transferred to a multi-stage membrane separation device. First, a microfiltration membrane is used to remove larger particles of impurities. At an operating pressure of 0.15 MPa, the microfiltration membrane can effectively intercept impurities with a particle size greater than 0.4 um. Next, an ultrafiltration membrane is used to remove tiny particles and macromolecular organic matter. At an operating pressure of 0.3 MPa, the ultrafiltration membrane can filter out particles and macromolecular organic matter with a particle size between 0.04 um and 0.4 um. Finally, a nanofiltration membrane is used to selectively separate tetrahydrofuran. At an operating pressure of 0.7 MPa, the nanofiltration membrane can allow tetrahydrofuran to pass through while blocking other components, thereby achieving precise separation of tetrahydrofuran and obtaining a crude distillate.

[0055] Deep separation stage:

[0056] The crude distillate was transferred to a distillation kettle for reduced pressure distillation, the vacuum degree was set to 0.082MPa, and the mixture was heated to 102°C. Under this condition, tetrahydrofuran could be effectively evaporated. The distilled tetrahydrofuran vapor was cooled to liquid through a spiral condenser to obtain crude tetrahydrofuran. Before deep separation, the crude distillate was passed into an adsorption column filled with an adsorbent, the adsorption temperature was controlled to 37°C, and the adsorption time was 1.4h. The adsorbent further removed residual impurities and improved the purity of tetrahydrofuran.

[0057] Refining and purification stage:

[0058] The crude tetrahydrofuran is transferred to a distillation tower for distillation. The number of tower plates is controlled to be 32, the reflux ratio is 3.2, the top temperature is controlled between 65.5°C, and the bottom temperature is controlled between 105.5°C. During the distillation process, the pressure is controlled at normal pressure and the feed rate is controlled at 12L / h. By precisely controlling the distillation parameters, a high-purity tetrahydrofuran product is finally obtained.

[0059] Tetrahydrofuran properties and quality measurement,

[0060] Measurement method:

[0061] Purity measurement: gas chromatography is used to analyze and determine the content ratio of tetrahydrofuran;

[0062] Moisture content measurement: Determination of water content in tetrahydrofuran using Karl Fischer method;

[0063] Density measurement: The density of tetrahydrofuran was measured by a densitometer.

[0064] Measurement data:

[0065] Purity: 99.0%;

[0066] Moisture content: 0.03%;

[0067] Density: 0.889 g / cm 3 .

[0068] Embodiment 2

[0069] Preprocessing stage:

[0070] 1500kg of regenerated BDO by-product waste liquid was transferred to a storage tank, and 0.1% of the total weight of the waste liquid was added with a flocculant. The mixture was stirred thoroughly to allow the solid impurities to precipitate and separate. After standing for a period of time, it was first filtered through a coarse filter screen with a pore size of 1mm, and then filtered through a fine filter screen with a pore size of 0.1mm to ensure that the solid impurity removal rate reached 95.5%.

[0071] A 15% sodium hydroxide solution was added to the filtered waste liquid, and the mixture was stirred. The reaction temperature was controlled at about 30° C., the stirring speed was 40 r / min, and the reaction time was 45 min. After the reaction was completed, the mixture was filtered again to obtain a crude BDO by-product waste liquid.

[0072] Initial separation stage:

[0073] The crude BDO by-product waste liquid is added to the distillation container, and the waste liquid is slowly heated to 85°C by a heating device using a normal pressure distillation method. The heating rate is strictly controlled to be 7°C / min during the heating process, and the reflux ratio is maintained at 1.6. During the distillation process, 4 sets of ultrasonic atomizers are installed and evenly distributed in the distillation tower. The ultrasonic frequency is controlled at 32kHz, the power is set to 850W, and the atomization temperature is 85°C. Through ultrasonic atomization technology, part of the steam is atomized into tiny particles, the gas-liquid contact area is increased, and the methanol and organic matter are evaporated more efficiently, and the evaporated distillate is collected at the same time.

[0074] The specially designed distillation plates have micro-protrusions and grooves on them to further increase the gas-liquid contact area and improve separation efficiency.

[0075] Multi-stage membrane separation stage:

[0076] The distillate is transferred to a multi-stage membrane separation device. First, a microfiltration membrane is used to remove larger particles of impurities. At an operating pressure of 0.2MPa, the microfiltration membrane can effectively intercept impurities with a particle size greater than 0.5um. Next, an ultrafiltration membrane is used to remove tiny particles and large molecular organic matter. At an operating pressure of 0.35MPa, the ultrafiltration membrane can filter out particles and large molecular organic matter with a particle size between 0.05um and 0.5um. Finally, a nanofiltration membrane is used to selectively separate tetrahydrofuran. At an operating pressure of 0.8MPa, the nanofiltration membrane can allow tetrahydrofuran to pass through while blocking other components, thereby achieving accurate separation of tetrahydrofuran and obtaining a crude distillate.

[0077] Deep separation stage:

[0078] The crude distillate was transferred to a distillation kettle for reduced pressure distillation, the vacuum degree was set to 0.085 MPa, and the mixture was heated to 105°C. Under this condition, tetrahydrofuran could be effectively evaporated. The distilled tetrahydrofuran vapor was cooled to liquid through a spiral condenser to obtain crude tetrahydrofuran. Before deep separation, the crude distillate was passed into an adsorption column filled with an adsorbent, the adsorption temperature was controlled to 38°C, and the adsorption time was 1.5 h. The adsorbent further removed residual impurities and improved the purity of tetrahydrofuran.

[0079] Refining and purification stage:

[0080] The crude tetrahydrofuran is transferred to a distillation tower for distillation. The number of tower plates is controlled to be 35, the reflux ratio is 3.5, the top temperature is controlled between 66°C, and the bottom temperature is controlled between 106°C. During the distillation process, the pressure is controlled at normal pressure and the feed rate is controlled at 15L / h. By precisely controlling the distillation parameters, a high-purity tetrahydrofuran product is finally obtained.

[0081] Tetrahydrofuran properties and quality measurement,

[0082] Measurement method:

[0083] Purity measurement: gas chromatography is used to analyze and determine the content ratio of tetrahydrofuran;

[0084] Moisture content measurement: Determination of water content in tetrahydrofuran using Karl Fischer method;

[0085] Density measurement: The density of tetrahydrofuran was measured by a densitometer.

[0086] Measurement data:

[0087] Purity: 99.2%;

[0088] Moisture content: 0.02%;

[0089] Density: 0.891g / cm 3 .

[0090] Embodiment 3

[0091] Preprocessing stage:

[0092] 1800kg of regenerated BDO by-product waste liquid was transferred into a storage tank, and a flocculant accounting for 0.12% of the total weight of the waste liquid was added, and the mixture was fully stirred to precipitate and separate solid impurities. After standing for a period of time, the mixture was first filtered through a coarse filter screen with a pore size of 1mm, and then filtered through a fine filter screen with a pore size of 0.1mm to ensure that the solid impurity removal rate reached 95.8%. A sodium hydroxide solution with a concentration of 18% was added to the filtered waste liquid, and the mixture was stirred and mixed. The reaction temperature was controlled at about 32°C, the stirring speed was 45r / min, and the reaction time was 50min. After the reaction was completed, the mixture was filtered again to obtain a crude BDO by-product waste liquid.

[0093] Initial separation stage:

[0094] The crude BDO by-product waste liquid is added to the distillation container, and the waste liquid is slowly heated to 87°C by a heating device using a normal pressure distillation method. The heating rate is strictly controlled to be 8°C / min during the heating process, and the reflux ratio is maintained at 1.8. During the distillation process, 5 sets of ultrasonic atomizers are installed and evenly distributed in the distillation tower. The ultrasonic frequency is controlled at 35kHz, the power is set to 850W, and the atomization temperature is 87°C. Through ultrasonic atomization technology, part of the steam is atomized into tiny particles, the gas-liquid contact area is increased, and the methanol and organic matter are evaporated more efficiently, and the evaporated distillate is collected at the same time.

[0095] The specially designed distillation plates have micro-protrusions and grooves on them to further increase the gas-liquid contact area and improve separation efficiency.

[0096] Multi-stage membrane separation stage:

[0097] The distillate is transferred to a multi-stage membrane separation device. First, a microfiltration membrane is used to remove larger particles of impurities. At an operating pressure of 0.22 MPa, the microfiltration membrane can effectively intercept impurities with a particle size greater than 0.6 um. Next, an ultrafiltration membrane is used to remove tiny particles and macromolecular organic matter. At an operating pressure of 0.4 MPa, the ultrafiltration membrane can filter out particles and macromolecular organic matter with a particle size between 0.06 um and 0.6 um. Finally, a nanofiltration membrane is used to selectively separate tetrahydrofuran. At an operating pressure of 0.8 MPa, the nanofiltration membrane can allow tetrahydrofuran to pass through while blocking other components, thereby achieving accurate separation of tetrahydrofuran and obtaining a crude distillate.

[0098] Deep separation stage:

[0099] The crude distillate was transferred to a distillation kettle for reduced pressure distillation, the vacuum degree was set to 0.087 MPa, and the mixture was heated to 107°C. Under this condition, tetrahydrofuran could be effectively evaporated. The distilled tetrahydrofuran vapor was cooled to liquid through a spiral condenser to obtain crude tetrahydrofuran. Before deep separation, the crude distillate was passed into an adsorption column filled with an adsorbent, the adsorption temperature was controlled to 39°C, and the adsorption time was 1.6 h. The adsorbent further removed residual impurities and improved the purity of tetrahydrofuran.

[0100] Refining and purification stage:

[0101] The crude tetrahydrofuran is transferred to a distillation tower for distillation. The number of tower plates is controlled to be 36, the reflux ratio is 3.6, the top temperature is controlled between 66.5°C, and the bottom temperature is controlled between 106.5°C. During the distillation process, the pressure is controlled at normal pressure and the feed rate is controlled at 16L / h. By precisely controlling the distillation parameters, a high-purity tetrahydrofuran product is finally obtained.

[0102] Tetrahydrofuran properties and quality measurement,

[0103] Measurement method:

[0104] Purity measurement: gas chromatography is used to analyze and determine the content ratio of tetrahydrofuran;

[0105] Moisture content measurement: Determination of water content in tetrahydrofuran using Karl Fischer method;

[0106] Density measurement: The density of tetrahydrofuran was measured by a densitometer.

[0107] Measurement data:

[0108] Purity: 99.1%;

[0109] Moisture content: 0.025%;

[0110] Density: 0.892g / cm 3 .

[0111] Embodiment 4:

[0112] Preprocessing stage:

[0113] 2000kg of regenerated BDO by-product waste liquid was transferred into a storage tank, and a flocculant accounting for 0.11% of the total weight of the waste liquid was added, and the mixture was stirred thoroughly to precipitate and separate solid impurities. After standing for a period of time, the mixture was first filtered through a coarse filter screen with a pore size of 1mm, and then filtered through a fine filter screen with a pore size of 0.1mm to ensure that the solid impurity removal rate reached 95.6%. A 16% sodium hydroxide solution was added to the filtered waste liquid, and the mixture was stirred and mixed. The reaction temperature was controlled at about 31°C, the stirring speed was 42r / min, and the reaction time was 48min. After the reaction was completed, the mixture was filtered again to obtain a crude BDO by-product waste liquid.

[0114] Initial separation stage:

[0115] The crude BDO by-product waste liquid is added to the distillation container, and the waste liquid is slowly heated to 86°C by a heating device using a normal pressure distillation method. The heating rate is strictly controlled to be 7.5°C / min during the heating process, and the reflux ratio is maintained at 1.7. During the distillation process, 4 sets of ultrasonic atomizers are installed and evenly distributed in the distillation tower. The ultrasonic frequency is controlled at 33kHz, the power is set to 820W, and the atomization temperature is 86°C. Through ultrasonic atomization technology, part of the steam is atomized into tiny particles, the gas-liquid contact area is increased, and the methanol and organic matter are evaporated more efficiently, and the evaporated distillate is collected at the same time.

[0116] The specially designed distillation plates have micro-protrusions and grooves on them to further increase the gas-liquid contact area and improve separation efficiency.

[0117] Multi-stage membrane separation stage:

[0118] The distillate is transferred to a multi-stage membrane separation device. First, a microfiltration membrane is used to remove larger particles of impurities. At an operating pressure of 0.2MPa, the microfiltration membrane can effectively intercept impurities with a particle size greater than 0.55um. Next, an ultrafiltration membrane is used to remove tiny particles and macromolecular organic matter. At an operating pressure of 0.35MPa, the ultrafiltration membrane can filter out particles and macromolecular organic matter with a particle size between 0.055um and 0.55um. Finally, a nanofiltration membrane is used to selectively separate tetrahydrofuran. At an operating pressure of 0.8MPa, the nanofiltration membrane can allow tetrahydrofuran to pass through while blocking other components, thereby achieving accurate separation of tetrahydrofuran and obtaining a crude distillate.

[0119] Deep separation stage:

[0120] The crude distillate was transferred to a distillation kettle for reduced pressure distillation, the vacuum degree was set to 0.086 MPa, and the mixture was heated to 106°C. Under this condition, tetrahydrofuran could be effectively evaporated. The distilled tetrahydrofuran vapor was cooled to liquid through a spiral condenser to obtain crude tetrahydrofuran. Before deep separation, the crude distillate was passed into an adsorption column filled with an adsorbent, the adsorption temperature was controlled to 38.5°C, and the adsorption time was 1.55 h. The adsorbent further removed residual impurities and improved the purity of tetrahydrofuran.

[0121] Refining and purification stage:

[0122] The crude tetrahydrofuran is transferred to a distillation tower for distillation. The number of tower plates is controlled to be 35, the reflux ratio is 3.5, the top temperature is controlled between 66.2°C, and the bottom temperature is controlled between 106.2°C. During the distillation process, the pressure is controlled at normal pressure and the feed rate is controlled at 14L / h. By precisely controlling the distillation parameters, a high-purity tetrahydrofuran product is finally obtained.

[0123] Tetrahydrofuran properties and quality measurement,

[0124] Measurement method:

[0125] Purity measurement: gas chromatography is used to analyze and determine the content ratio of tetrahydrofuran;

[0126] Moisture content measurement: Determination of water content in tetrahydrofuran using Karl Fischer method;

[0127] Density measurement: The density of tetrahydrofuran was measured by a densitometer.

[0128] Measurement data:

[0129] Purity: 99.15%;

[0130] Moisture content: 0.022%;

[0131] Density: 0.891g / cm 3 .

[0132] The regenerated BDO by-product waste liquid treated by the methods in the above four groups of embodiments has a purity of 99.0%-99.2% of tetrahydrofuran, a low moisture content and a relatively stable density.

[0133] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments are made without departing from the principles and spirit of the present invention, and still fall within the scope of protection of the present invention.

[0134] In the description of the specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0135] The above contents are merely examples and explanations of the present invention. Various modifications or additions to the specific embodiments described or replacements in similar ways by technicians in the technical field shall fall within the protection scope of the present invention as long as they do not deviate from the invention or exceed the scope defined by the claims.

[0136] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing tetrahydrofuran by separating the byproduct waste liquid of regenerated BDO, wherein the byproduct waste liquid of regenerated BDO includes water, tetrahydrofuran, methanol, organic matter, inorganic salts and impurities, and the content of each component is determined by gas chromatography-mass spectrometry analysis, characterized in that: The specific operation steps of separating the by-product waste liquid of regenerated BDO to prepare tetrahydrofuran are as follows: Step 1: pretreatment of the regenerated BDO by-product waste liquid, transferring the BDO by-product waste liquid into a container, adding an alkaline solution and stirring and mixing, and filtering after the reaction is completed to obtain a crude BDO by-product waste liquid; Step 2: Preliminary separation of by-product waste liquid: adding crude BDO by-product waste liquid into a container, evaporating the liquid by atmospheric distillation, introducing ultrasonic atomization technology, and collecting the evaporated distillate; Step 3: construct a multi-stage membrane separation device, transfer the distillate into the separation device, and perform separation operations in sequence to obtain a crude distillate; Step 4, deep separation of the crude distillate, transferring the separated crude distillate into a distillation kettle for vacuum distillation, collecting evaporated tetrahydrofuran and cooling it into liquid by condensation to obtain a crude tetrahydrofuran; Step 5: Refining and purifying: transferring the crude tetrahydrofuran product into a distillation tower for distillation to obtain a high-purity tetrahydrofuran product; The regenerated BDO by-product waste liquid has a water content of 40%-50%, a tetrahydrofuran content of 20%-30%, a methanol content of 5%-10%, an organic matter content of 25%-30%, and a total content of inorganic salts and impurities of 10%-15%. In the step 1, the BDO by-product waste liquid is collected in a storage tank, and solid impurities are removed by filtering, using a coarse filter screen with a pore size of 1 mm, and then passing through a fine filter screen with a pore size of 0.1 mm to ensure that the solid impurity removal rate is above 95%. In the step 2, the pretreated waste liquid is heated to 80°C-90°C by atmospheric distillation. 0℃, evaporate methanol and organic matter, and collect distillate. During the distillation process, control the heating rate at 5℃ / min-10℃ / min, and keep the reflux ratio between 1-2. During the preliminary separation process, a specially designed distillation plate is required to increase the gas-liquid contact area and improve the separation efficiency. The special distillation plate is provided with micro protrusions and grooves. In step three, the multi-stage membrane separation device constructed includes microfiltration membrane, ultrafiltration membrane and nanofiltration membrane, wherein the microfiltration membrane is used to remove larger particles of impurities, the membrane pore size is 0.1um-1um, and the operating pressure is 0.1MPa-0. 3MPa, using an ultrafiltration membrane to remove tiny particles and macromolecular organic matter, the membrane pore size is 0.01um-0.1um, the operating pressure is 0.2MPa-0.5MPa, using a nanofiltration membrane to selectively separate tetrahydrofuran, the membrane pore size is 1nm-10nm, and the operating pressure is 0.5MPa-1MPa. In the step 4, the crude distillate after separation is subjected to reduced pressure distillation, and the tetrahydrofuran is evaporated under a vacuum degree of 0.08MPa-0.09MPa, and the distillate is collected, and the distilled tetrahydrofuran vapor is cooled through a condenser. The crude tetrahydrofuran is liquid, and an adsorbent is introduced. Before deep separation, the crude distillate is passed into an adsorption column filled with an adsorbent, and adsorbed at an adsorption temperature of 35°C-40°C for 1h-2h. In the step 5, the crude tetrahydrofuran is distilled. In the distillation tower, the number of tower plates is controlled to be 30-40, the reflux ratio is 3-4, the tower top temperature is controlled to be between 65°C-67°C, and the tower bottom temperature is controlled to be between 105°C-107°C. During the distillation process, the pressure is controlled at normal pressure, and the feed rate is controlled to be 10L / h-20L / h. During the treatment process, the saponification reaction that occurs is as follows: ； in, It is the alkyl group and other groups in organic matter.

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