Method for preparing 1, 3-propylene glycol by integrating azeotropic distillation

Abstract

The invention provides a preparation method of 1, 3-propylene glycol by integrating azeotropic distillation. According to the method, a specific reaction section and a specific separation section are combined, the reaction section is continuously operated through a high-efficiency catalyst, the production efficiency is high, and the reaction heat can be recycled; and the separation section integrates azeotropic distillation and heat coupling, so that the concentration limitation of the glycerol raw material is relieved, low-alcohol-water azeotropy is broken, the separation of alcohol-water azeotrope is realized, the entrainer can be regenerated and recycled, the operation energy consumption is low, and the industrial popularization is easy. Moreover, the preparation method provided by the invention can be used for obtaining high-index 1, 3-propylene glycol and separating products such as isopropanol, normal propyl alcohol and 1, 2-propylene glycol at the same time, and the purity of each separated product is 99.95% or above.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of 1,3-propylene glycol, and in particular relates to a preparation method of 1,3-propylene glycol with integrated azeotropic distillation. Background Art

[0002] As an important organic chemical raw material, 1,3-propylene glycol is widely used in polyester printing and dyeing, textiles, engineering plastics, cosmetics, polyurethane, solvents, and medical fields. At present, the most important use of 1,3-propylene glycol is as a polymer monomer to synthesize high-molecular materials with excellent performance, such as high-performance and high-value-added new polyester fiber-polytrimethylene terephthalate (PTT), which has a very broad market prospect.

[0003] The main methods for synthesizing 1,3-propylene glycol include ethylene oxide method, biological fermentation method, acrolein hydration method, acetal method and glycerol hydrogenation method. Among them, the glycerol hydrogenation method uses glycerol as raw material to synthesize 1,3-propylene glycol in one step. This process has the characteristics of green environmental protection and high production efficiency, and has attracted widespread attention from researchers.

[0004] Patent CN111039756A discloses a method and system for preparing 1,3-propylene glycol from glycerol, which integrates a high-efficiency catalyst, a reactor and a separation system. However, the separation systems used are all conventional distillation systems, and the byproducts isopropanol and n-propanol form azeotropes with water and cannot be separated by conventional distillation. Therefore, the method is not feasible in the design of the separation scheme and cannot obtain high-purity n-propanol and isopropanol products.

[0005] CN115636727A discloses a method for preparing 1,3-propylene glycol by hydrogenating glycerol, which uses a vaporization permeation membrane dehydration method. However, this method has a high requirement for water content in practical applications, which is not conducive to unlocking the raw material ratio of the glycerol solution, and requires energy to vaporize the water-containing material, which increases the cost. In addition, the membrane component has the disadvantages of short life, high maintenance cost, and large required area, making it difficult to apply in actual production. Therefore, this method will greatly increase the investment in the device and is not conducive to the production of industrial devices. Summary of the invention

[0006] In view of this, the object of the present invention is to provide a preparation method of 1,3-propylene glycol integrated with azeotropic distillation. The preparation method can realize continuous operation, has high production efficiency, and the purity of the obtained 1,3-propylene glycol product is above 99.95%.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for preparing 1,3-propylene glycol by integrated azeotropic distillation, comprising the following steps:

[0009] S1: continuously reacting a glycerol solution and hydrogen in the presence of a catalyst, obtaining a reaction product, and then performing gas-liquid separation to obtain a liquid product and hydrogen, respectively, and the hydrogen is recycled;

[0010] S2: distilling the liquid product to obtain azeotropes and heavy components respectively;

[0011] S3: treating the azeotrope obtained in step S2 by removing methanol to obtain an alcohol-water azeotrope, treating the alcohol-water azeotrope by azeotropic distillation to obtain an alcohol mixture and an entrainer-water mixed solution, respectively; removing water from the entrainer-water mixed solution by removing azeotropic water, and sequentially removing n-propanol and isopropanol from the alcohol mixture to obtain n-propanol, isopropanol and light components, respectively;

[0012] S4: subjecting the heavy component obtained in step S2 to multiple-effect thermal coupling dehydration treatment, 1,2-propylene glycol removal treatment and 1,3-propylene glycol removal treatment in sequence to obtain water, 1,2-propylene glycol, 1,3-propylene glycol and glycerol, respectively; wherein the water and glycerol are recycled;

[0013] or

[0014] S4 is: subjecting the heavy component obtained in step S2 to multiple-effect thermal coupling dehydration treatment, deglycerol treatment, and glycol separation treatment in sequence to obtain water, glycerol, 1,2-propylene glycol, and 1,3-propylene glycol, respectively; wherein the water and glycerol are recycled;

[0015] or

[0016] S4 is: subjecting the heavy component obtained in step S2 to deglycerol treatment, dehydration treatment, and glycol separation treatment to obtain glycerol, water, 1,2-propylene glycol, and 1,3-propylene glycol, respectively; wherein water and glycerol are recycled.

[0017] Preferably, the mass concentration of the glycerol solution is 10-90%.

[0018] Preferably, the solvent in the glycerol solution is selected from any one or more of water, methanol or ethanol.

[0019] Preferably, the catalyst is selected from any one or more of a Pt-W catalyst, an Ir-Re catalyst or a Pt-molecular sieve catalyst.

[0020] Preferably, the hydrogen-to-oil ratio in the continuous reaction is 500-1500; the liquid hourly space velocity is 0.8-1.6 h -1 .

[0021] Preferably, the reactor for the continuous reaction is selected from a trickle bed fixed bed reactor, a trickle bed tubular reactor or a bubbling reactor.

[0022] Preferably, the temperature of the continuous reaction is 100-200° C., and the pressure is 0.5-10 MPa.

[0023] Preferably, the gas-liquid separation is:

[0024] The reaction product is heat exchanged with the reaction feed and then subjected to hot high-pressure gas-liquid separation to obtain a gas phase component and a first liquid phase product, respectively, wherein the gas phase component is cooled and then subjected to cold high-pressure gas-liquid separation to obtain hydrogen and a second liquid phase product, respectively; the liquid phase product obtained by mixing the first liquid phase product and the second liquid phase product is used as a feed for the distillation treatment in step S2; the hydrogen is recycled.

[0025] Preferably, step S2 is:

[0026] The liquid phase product enters the deazeotrope tower for distillation, and the azeotrope is obtained at the top of the tower, and the heavy component is obtained at the bottom of the tower.

[0027] Preferably, the top temperature of the deazeotrope tower is 90-106° C., the top pressure is 0.02-0.11 MPa, the bottom temperature is 115-131° C., the bottom pressure is 0.04-0.13 MPa, and the reflux ratio is 1-3.

[0028] Preferably, step S3 is:

[0029] The azeotrope obtained in step S2 enters a methanol removal tower, and the methanol light component is removed from the tower top, and an alcohol-water azeotrope is obtained at the tower bottom, and enters an azeotropic distillation tower, and an entrainer is added for azeotropic distillation, and an alcohol mixture is obtained at the tower bottom, and an entrainer-water mixed solution is obtained at the tower top; the entrainer-water mixed solution passes through a phase separation tank, and the obtained water phase enters a de-azeotropic water tower, and the entrainer is recovered from the tower top and returned to the phase separation tank, and the tower bottom is water; the bottom of the azeotropic distillation tower is an alcohol mixture, which enters a de-n-propanol tower, and n-propanol is obtained at the tower bottom, and an isopropanol mixture is obtained at the tower top; the isopropanol mixture enters a de-isopropanol tower, and the tower top is a light component, and isopropanol is obtained at the tower bottom.

[0030] Preferably, the azeotropic agent is selected from any one or more of benzene, No. 60 n-hexane, No. 80 n-hexane or pure n-hexane.

[0031] Preferably, the top temperature of the demethanolation tower is 85-96° C., the top pressure is 0.03-0.1 MPa, the bottom temperature is 95-108° C., the bottom pressure is 0.04-0.12 MPa, and the reflux ratio is 6-12.

[0032] Preferably, the top temperature of the azeotropic distillation tower is 91-112° C., the top pressure is 0.1-0.3 MPa, the bottom temperature is 110-135° C., the bottom pressure is 0.12-0.32 MPa, and the reflux ratio is 25-50.

[0033] Preferably, the top temperature of the deazeotropic water tower is 86-102° C., the top pressure is 0.02-0.12 MPa, the bottom temperature is 109-126° C., and the bottom pressure is 0.04-0.14 MPa.

[0034] Preferably, the top temperature of the deisopropanol tower is 85-111° C., the top pressure is 0.02-0.2 MPa, the bottom temperature is 104-131° C., the bottom pressure is 0.03-0.22 MPa, and the reflux ratio is 7-14.

[0035] Preferably, the top temperature of the n-propanol removal tower is 81-111° C., the top pressure is 0.02-0.25 MPa, the bottom temperature is 89-119° C., the bottom pressure is 0.03-0.27 MPa, and the reflux ratio is 15-22.

[0036] Preferably, step S4 is:

[0037] The heavy component obtained in step S2 enters a high-pressure dehydration tower, and the obtained bottom solution enters a low-pressure dehydration tower. The obtained top gas phase is thermally coupled with the low-pressure dehydration tower and used as a bottom heat source of the low-pressure dehydration tower. Water is obtained at the top of the tower, and the bottom of the tower is a polyol solution. The heavy component enters a 1,2-propylene glycol removal tower, and 1,2-propylene glycol is obtained at the top of the tower. The bottom of the tower is a mixture of 1,3-propylene glycol and glycerol. The heavy component enters a 1,3-propylene glycol removal tower, and 1,3-propylene glycol is obtained at the top of the tower, and glycerol is obtained at the bottom of the tower. The water and glycerol are recycled.

[0038] Preferably, the top temperature of the high-pressure dehydration tower is 171-192° C., the top pressure is 0.7-1.2 MPa, the bottom temperature is 189-212° C., the bottom pressure is 0.72-1.22 MPa, and the reflux ratio is 0.2-0.6.

[0039] Preferably, the top temperature of the low-pressure dehydration tower is 49-91° C., the top pressure is -0.09-0.03 MPa, the bottom temperature is 198-235° C., the bottom pressure is -0.07-0.01 MPa, and the reflux ratio is 0.1-0.5.

[0040] Preferably, the top temperature of the 1,2-propylene glycol removal tower is 176-194° C., the top pressure is -0.07-0.03 MPa, the bottom temperature is 222-243° C., the bottom pressure is -0.05-0.01 MPa, and the reflux ratio is 7-14.

[0041] Preferably, the top temperature of the 1,3-propylene glycol removal tower is 154-187° C., the top pressure is -0.09-0.06 MPa, the bottom temperature is 247-269° C., the bottom pressure is -0.07-0.04 MPa, and the reflux ratio is 0.7-1.4.

[0042] Preferably, step S4 is:

[0043] The heavy component obtained in step S2 enters a high-pressure dehydration tower, and the obtained bottom solution enters a low-pressure dehydration tower. The obtained top gas phase is thermally coupled with the low-pressure dehydration tower as a bottom heat source of the low-pressure dehydration tower. Water is obtained at the top of the tower, and the bottom of the tower is a polyol solution, which enters a deglycerolating tower, and glycerol is obtained at the bottom of the tower for recycling. A mixture of 1,2-propylene glycol and 1,3-propylene glycol is obtained at the top of the tower, and enters a glycol separation tower, and 1,2-propylene glycol is obtained at the top of the tower, and 1,3-propylene glycol is obtained at the bottom of the tower; the water and glycerol are recycled.

[0044] Preferably, the top temperature of the high-pressure dehydration tower is 171-192° C., the top pressure is 0.7-1.2 MPa, the bottom temperature is 189-212° C., the bottom pressure is 0.72-1.22 MPa, and the reflux ratio is 0.2-0.6.

[0045] Preferably, the top temperature of the low-pressure dehydration tower is 49-91° C., the top pressure is -0.09-0.03 MPa, the bottom temperature is 198-235° C., the bottom pressure is -0.07-0.01 MPa, and the reflux ratio is 0.1-0.5.

[0046] Preferably, the top temperature of the deglycerol tower is 175-199° C., the top pressure is -0.07-0.03 MPa, the bottom temperature is 263-284° C., the bottom pressure is -0.05-0.01 MPa, and the reflux ratio is 0.6-1.2.

[0047] Preferably, the top temperature of the diol separation tower is 160-181° C., the top pressure is -0.06-0.02 MPa, the bottom temperature is 198-214° C., the bottom pressure is -0.04-0 MPa, and the reflux ratio is 9-15.

[0048] Preferably, step S4 is:

[0049] The heavy component obtained in step S2 enters a deglycerol tower, glycerol is obtained at the bottom of the tower, part of water is obtained at the top of the tower, the remaining water and a mixed solution of 1,2-propylene glycol and 1,3-propylene glycol are extracted from the side line, and enter a dehydration tower, water is obtained at the top of the tower, and a mixture of 1,2-propylene glycol and 1,3-propylene glycol is obtained at the bottom of the tower, and enters a glycol separation tower, 1,2-propylene glycol is obtained at the top of the tower, and 1,3-propylene glycol is obtained at the bottom of the tower; the water and glycerol are recycled.

[0050] Preferably, the top temperature of the deglycerolating tower is 62-87° C., the top pressure is -0.08-0.04 MPa, the bottom temperature is 256-279° C., the bottom pressure is -0.06-0.02 MPa, and the reflux ratio is 0.3-0.7.

[0051] Preferably, the top temperature of the dehydration tower is 50-87° C., the top pressure is -0.09-0.04 MPa, the bottom temperature is 170-199° C., the bottom pressure is -0.07-0.02 MPa, and the reflux ratio is 1-3.

[0052] Preferably, the top temperature of the diol separation tower is 128-172° C., the top pressure is -0.09-0.04 MPa, the bottom temperature is 178-207° C., the bottom pressure is -0.07-0.02 MPa, and the reflux ratio is 6-12.

[0053] Preferably, the purity of 1,3-propylene glycol prepared according to the above preparation method is above 99.95%.

[0054] In summary, the preparation method simply comprises the following steps:

[0055] S1: continuously hydrogenating the glycerol solution and hydrogen in the presence of a catalyst to obtain a reaction product, and then separating the reaction product into gas and liquid to obtain a liquid product and hydrogen respectively, and the hydrogen is recycled; S2:

[0056] The liquid product obtained in step S1 is subjected to rectification treatment to obtain an azeotrope at the top of the tower and a heavy component at the bottom of the tower;

[0057] S3: the azeotrope obtained at the top of step S2 enters a methanol removal tower, the methanol light component is removed from the top of the tower, and the low-alcohol-water azeotrope at the bottom of the tower is dehydrated through an azeotropic distillation tower and an azeotropic water removal tower, and then passes through a n-propanol removal tower and an isopropanol removal tower in sequence to obtain n-propanol, isopropanol and light components respectively;

[0058] S4: The heavy components obtained at the bottom of the tower in step S2 are sequentially processed through a multi-effect thermal coupling dehydration tower, a 1,2-propylene glycol removal tower, and a 1,3-propylene glycol removal tower to obtain water, 1,2-propylene glycol, 1,3-propylene glycol, and glycerol, respectively; wherein the water and glycerol can be recycled;

[0059] or

[0060] S4 is: subjecting the heavy component obtained in step S2 to multiple-effect thermal coupling dehydration treatment, deglycerol treatment, and glycol separation treatment in sequence to obtain water, glycerol, 1,2-propylene glycol, and 1,3-propylene glycol, respectively; wherein the water and glycerol are recycled;

[0061] or

[0062] S4 is: subjecting the heavy component obtained in step S2 to deglycerol treatment, dehydration treatment, and glycol separation treatment to obtain glycerol, water, 1,2-propylene glycol, and 1,3-propylene glycol, respectively; wherein water and glycerol are recycled.

[0063] Compared with the prior art, the present invention has the following beneficial effects:

[0064] The present invention adopts a mode of combining a specific reaction section and a specific separation section, and the reaction section is continuously operated by an efficient catalyst, with high production efficiency, and the reaction heat can be recycled; and the separation process integrates azeotropic distillation and heat coupling, which not only removes the concentration limit of the glycerol raw material, but also breaks the azeotropy of low-alcohol-water, realizes the separation of alcohol-water azeotropes, and the entrainer can be recycled and reused, with low operating energy consumption, and is easy to promote industrialization. In addition, the preparation method provided by the present invention can obtain high-index 1,3-propylene glycol, and can separate products such as isopropanol, n-propanol, 1,2-propylene glycol, and the purity of each separated product is above 99.95%. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 This is a schematic flow chart of the method for preparing 1,3-propylene glycol with integrated azeotropic distillation in Example 1;

[0066] Figure 2 This is a schematic flow chart of the method for preparing 1,3-propylene glycol with integrated azeotropic distillation in Example 2;

[0067] Figure 3 This is a schematic flow chart of the method for preparing 1,3-propylene glycol with integrated azeotropic distillation in Example 3;

[0068] Among them, 1 is a trickle bed tubular reactor, 2 is a hot high-pressure separation tank, 3 is a cold high-pressure separation tank, 4 is a fresh hydrogen compressor, 5 is a circulating hydrogen compressor, 6 is an azeotrope removal tower, 7 is an azeotropic distillation tower, 8 is an azeotropic water removal tower, 9 is a n-propanol removal tower, 10 is an isopropanol removal tower, 11 is a high-pressure dehydration tower, 12 is a low-pressure dehydration tower, 13 is a 1,2-propylene glycol removal tower, 14 is a 1,3-propylene glycol removal tower, 15 is a methanol removal tower, 16 is a glycerol removal tower, 17 is a glycol separation tower, 18 is a dehydration tower, and 19 is a phase separation tank. DETAILED DESCRIPTION

[0069] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0070] The present invention provides a method for preparing 1,3-propylene glycol by integrated azeotropic distillation, comprising the following steps:

[0071] S1: continuously reacting a glycerol solution and hydrogen in the presence of a catalyst, obtaining a reaction product, and then performing gas-liquid separation to obtain a liquid product and hydrogen, respectively, and the hydrogen is recycled;

[0072] S2: distilling the liquid product to obtain azeotropes and heavy components respectively;

[0073] S3: treating the azeotrope obtained in step S2 by removing methanol to obtain an alcohol-water azeotrope, treating the alcohol-water azeotrope by azeotropic distillation to obtain an alcohol mixture and an entrainer-water mixed solution, respectively; removing water from the entrainer-water mixed solution by removing azeotropic water, and sequentially removing n-propanol and isopropanol from the alcohol mixture to obtain n-propanol, isopropanol and light components, respectively;

[0074] S4: subjecting the heavy component obtained in step S2 to multiple-effect thermal coupling dehydration treatment, 1,2-propylene glycol removal treatment and 1,3-propylene glycol removal treatment in sequence to obtain water, 1,2-propylene glycol, 1,3-propylene glycol and glycerol, respectively; wherein the water and glycerol are recycled;

[0075] or

[0076] S4 is: subjecting the heavy component obtained in step S2 to multiple-effect thermal coupling dehydration treatment, deglycerol treatment, and glycol separation treatment in sequence to obtain water, glycerol, 1,2-propylene glycol, and 1,3-propylene glycol, respectively; wherein the water and glycerol are recycled;

[0077] or

[0078] S4 is: subjecting the heavy component obtained in step S2 to deglycerol treatment, dehydration treatment, and glycol separation treatment to obtain glycerol, water, 1,2-propylene glycol, and 1,3-propylene glycol, respectively; wherein water and glycerol are recycled.

[0079] According to the present invention, a glycerol solution and hydrogen are first reacted continuously in the presence of a catalyst, and a gas-liquid separation is performed after obtaining a reaction product to obtain a liquid product and hydrogen, respectively, and the hydrogen is recycled. In some embodiments of the present invention, the glycerol solution is preferably mixed with hydrogen and then introduced as a reaction feed into a trickle bed fixed bed reactor, a trickle bed tubular reactor or a bubbling reactor in the presence of a catalyst, preferably a trickle bed tubular reactor, to perform a continuous hydrogenation reaction to obtain a reaction product, and then the reaction product is subjected to gas-liquid separation to obtain a liquid product and hydrogen, respectively, wherein the hydrogen is recycled.

[0080] In the present invention, the mass concentration of the glycerol solution is 10% to 90%, preferably 40% to 80%; the solvent in the glycerol solution can be selected from any one or more of water, methanol or ethanol, more preferably water.

[0081] In the present invention, the catalyst is selected from any one or more of a Pt-W catalyst, an Ir-Re catalyst or a Pt-molecular sieve catalyst, preferably a Pt-W catalyst. The present invention has no particular restrictions on the source of the catalyst, and commercially available or homemade hydrogenation catalysts can be used.

[0082] In the present invention, the hydrogen-to-oil ratio of the continuous hydrogenation reaction is 500-1500, preferably 800-1200; the liquid hourly space velocity is 0.8-1.6 h -1 , preferably 1~1.5 h -1 .

[0083] In the present invention, the temperature of the continuous hydrogenation reaction is 100-200°C, preferably 170-190°C; the pressure is 0.5-10 MPa, more preferably 4-6 MPa.

[0084] In some preferred embodiments of the present invention, in order to recover heat, the reaction product is preferentially heat-exchanged with the reaction feed, and then heated to the reaction temperature by medium-pressure steam.

[0085] In the present invention, the specific process of gas-liquid separation of the above reaction products is as follows:

[0086] The reaction product is heat exchanged with the reaction feed and then subjected to hot high-pressure gas-liquid separation to obtain a gas phase component and a first liquid phase product, respectively, wherein the gas phase component is cooled and then subjected to cold high-pressure gas-liquid separation to obtain hydrogen and a second liquid phase product, respectively; the liquid phase product obtained by mixing the first liquid phase product and the second liquid phase product is used as a feed for the distillation treatment in step S2; the hydrogen is recycled.

[0087] On this basis, the above-mentioned recycled hydrogen can partially replace the fresh hydrogen of the reaction raw material. At the same time, the recycled hydrogen and the fresh hydrogen can be separately controlled by compressors.

[0088] In some embodiments of the present invention, step S2 is preferably specifically:

[0089] The liquid phase product enters the deazeotrope tower for distillation, and the azeotrope is obtained at the top of the tower, and the heavy component is obtained at the bottom of the tower.

[0090] The azeotrope is preferably an azeotrope of low-alcohol methanol, ethanol, isopropanol, n-propanol and water. The heavy component is preferably a mixture of water, 1,2-propylene glycol, 1,3-propylene glycol and unreacted glycerol.

[0091] The tower top temperature of the deazeotrope tower is 90-106°C, the tower top pressure is 0.02-0.11 MPa, the tower bottom temperature is 115-131°C, the tower bottom pressure is 0.04-0.13 MPa, and the reflux ratio is 1-3. The tower top temperature is preferably 95-105°C, the tower top pressure is preferably 0.05-0.10 MPa, the tower bottom temperature is preferably 120-125°C, the tower bottom pressure is preferably 0.05-0.10 MPa, and the reflux ratio is preferably 1-2.

[0092] In some embodiments of the present invention, step S3 is preferably specifically:

[0093] The azeotrope obtained in step S2 enters a methanol removal tower, and the methanol light component is removed from the top of the tower, and an alcohol-water azeotrope is obtained at the bottom of the tower, and enters an azeotropic distillation tower, and an azeotropic agent that can form a lower azeotrope with water is added for azeotropic distillation, and an alcohol mixture is obtained at the bottom of the tower, and a lower azeotropic solution is obtained at the top of the tower, that is, a mixed solution of the entrainer, isopropanol, and water; the mixed solution of the entrainer, isopropanol, and water enters a phase separation tank, and the obtained water phase enters a de-azeotropic water tower, and the azeotropic agent is recovered at the top of the tower and returned to the phase separation tank, and the bottom of the tower is water, thereby achieving the effect of dehydration; the bottom of the azeotropic distillation tower is an alcohol mixture, which enters a de-n-propanol tower, and n-propanol is obtained at the bottom of the tower, and the top of the tower is an isopropanol mixture; the isopropanol mixture enters a de-isopropanol tower, and the top of the tower is a light component, and the bottom of the tower is isopropanol.

[0094] In the present invention, the alcohol-water azeotrope is a low-alcohol-water azeotrope, specifically an azeotrope of methanol, ethanol, isopropanol, n-propanol and water.

[0095] In the present invention, the alcohol mixture is preferably a mixture of ethanol, isopropanol and n-propanol.

[0096] In the present invention, the above light components preferably include components such as methanol, ethanol and acetone.

[0097] In the present invention, the azeotropic agent is selected from any one or more of benzene, No. 60 n-hexane, No. 80 n-hexane or pure n-hexane, preferably benzene.

[0098] In the present invention, the top temperature of the demethanol tower is 85-96°C, the top pressure is 0.03-0.1 MPa, the bottom temperature is 95-108°C, the bottom pressure is 0.04-0.12 MPa, and the reflux ratio is 6-12. The top temperature is preferably 88-92°C, the top pressure is preferably 0.05-0.08 MPa, the bottom temperature is preferably 98-105°C, the bottom pressure is preferably 0.05-0.10 MPa, and the reflux ratio is preferably 7-10.

[0099] The top temperature of the azeotropic distillation tower is 91-112°C, the top pressure is 0.1-0.3 MPa, and the bottom temperature is 110-135°C. The bottom pressure is 0.12-0.32 MPa, and the reflux ratio is 25-50. The top temperature is preferably 95-110°C, the top pressure is preferably 0.1-0.2 MPa, the bottom temperature is preferably 115-130°C, the bottom pressure is preferably 0.15-0.30 MPa, and the reflux ratio is preferably 30-45.

[0100] The tower top temperature of the deazeotropic water tower is 86-102°C, the tower top pressure is 0.02-0.12 MPa, the tower bottom temperature is 109-126°C, and the tower bottom pressure is 0.04-0.14 MPa. The tower top temperature is preferably 88-100°C, the tower top pressure is preferably 0.05-0.10 MPa, the tower bottom temperature is preferably 110-125°C, and the tower bottom pressure is preferably 0.05-0.10 MPa.

[0101] The tower top temperature of the deisopropanol tower is 85-111°C, the tower top pressure is 0.02-0.2 MPa, the tower bottom temperature is 104-131°C, the tower bottom pressure is 0.03-0.22 MPa, and the reflux ratio is 7-14. The tower top temperature is preferably 90-105°C, the tower top pressure is preferably 0.05-0.15 MPa, the tower bottom temperature is preferably 105-125°C, the tower bottom pressure is preferably 0.05-0.20 MPa, and the reflux ratio is preferably 8-12.

[0102] The tower top temperature of the n-propanol removal tower is 81-111°C, the tower top pressure is 0.02-0.25 MPa, the tower bottom temperature is 89-119°C, the tower bottom pressure is 0.03-0.27 MPa, and the reflux ratio is 15-22. The tower top temperature is preferably 85-110°C, the tower top pressure is preferably 0.05-0.20 MPa, the tower bottom temperature is preferably 90-115°C, the tower bottom pressure is preferably 0.05-0.25 MPa, and the reflux ratio is preferably 17-20.

[0103] In some embodiments of the present invention, step S4 is preferably specifically:

[0104] The heavy component obtained in step S2 enters a high-pressure dehydration tower, and the obtained bottom solution enters a low-pressure dehydration tower. The heat recovery of the gas phase at the top of the tower is thermally coupled with the low-pressure dehydration tower as the bottom heat source of the low-pressure dehydration tower. Water is obtained at the top of the tower, and the bottom of the tower is a polyol solution. The heavy component enters a 1,2-propylene glycol removal tower, and 1,2-propylene glycol is obtained at the top of the tower. The bottom of the tower is a mixture of 1,3-propylene glycol and glycerol. The heavy component enters a 1,3-propylene glycol removal tower, and 1,3-propylene glycol is obtained at the top of the tower, and glycerol is obtained at the bottom of the tower. The water and glycerol are recycled.

[0105] On this basis, the top temperature of the high-pressure dehydration tower is 171-192°C, the top pressure is 0.7-1.2 MPa, the bottom temperature is 189-212°C, the bottom pressure is 0.72-1.22 MPa, and the reflux ratio is 0.2-0.6. The top temperature is preferably 175-185°C, the top pressure is preferably 0.8-1.1 MPa, the bottom temperature is preferably 190-205°C, the bottom pressure is preferably 0.75-1.20 MPa, and the reflux ratio is preferably 0.3-0.5.

[0106] The tower top temperature of the low-pressure dehydration tower is 49-91°C, the tower top pressure is -0.09-0.03 MPa, the tower bottom temperature is 198-235°C, the tower bottom pressure is -0.07-0.01 MPa, and the reflux ratio is 0.1-0.5. The tower top temperature is preferably 50-80°C, the tower top pressure is preferably -0.05-0.02 MPa, the tower bottom temperature is preferably 200-225°C, the tower bottom pressure is preferably -0.05-0.005 MPa, and the reflux ratio is preferably 0.2-0.4.

[0107] The tower top temperature of the 1,2-propylene glycol removal tower is 176-194°C, the tower top pressure is -0.07-0.03 MPa, the tower bottom temperature is 222-243°C, the tower bottom pressure is -0.05-0.01 MPa, and the reflux ratio is 7-14. The tower top temperature is preferably 180-190°C, the tower top pressure is preferably -0.05-0.02 MPa, the tower bottom temperature is preferably 225-240°C, the tower bottom pressure is preferably -0.03-0.005 MPa, and the reflux ratio is preferably 8-12.

[0108] The tower top temperature of the 1,3-propylene glycol removal tower is 154-187°C, the tower top pressure is -0.09-0.06 MPa, the tower bottom temperature is 247-269°C, the tower bottom pressure is -0.07-0.04 MPa, and the reflux ratio is 0.7-1.4. The tower top temperature is preferably 160-180°C, the tower top pressure is preferably -0.05-0.04 MPa, the tower bottom temperature is preferably 250-265°C, the tower bottom pressure is preferably -0.04-0.03 MPa, and the reflux ratio is preferably 0.9-1.1.

[0109] In some other embodiments of the present invention, step S4 may also preferably be specifically:

[0110] The heavy component obtained in step S2 enters a high-pressure dehydration tower, and the obtained bottom solution enters a low-pressure dehydration tower. The obtained top gas phase is thermally coupled with the low-pressure dehydration tower as a bottom heat source of the low-pressure dehydration tower. Water is obtained at the top of the tower, and the bottom of the tower is a polyol solution, which enters a deglycerolating tower, and glycerol is obtained at the bottom of the tower for recycling. A mixture of 1,2-propylene glycol and 1,3-propylene glycol is obtained at the top of the tower, and enters a glycol separation tower, and 1,2-propylene glycol is obtained at the top of the tower, and 1,3-propylene glycol is obtained at the bottom of the tower; the water and glycerol are recycled.

[0111] On this basis, the top temperature of the high-pressure dehydration tower is 171-192°C, the top pressure is 0.7-1.2 MPa, the bottom temperature is 189-212°C, the bottom pressure is 0.72-1.22 MPa, and the reflux ratio is 0.2-0.6. The top temperature is preferably 175-185°C, the top pressure is preferably 0.8-1.1 MPa, the bottom temperature is preferably 190-205°C, the bottom pressure is preferably 0.75-1.20 MPa, and the reflux ratio is preferably 0.3-0.5.

[0112] The tower top temperature of the low-pressure dehydration tower is 49-91°C, the tower top pressure is -0.09-0.03MPa, the tower bottom temperature is 198-235°C, the tower bottom pressure is -0.07-0.01MPa, and the reflux ratio is 0.1-0.5. The tower top temperature is preferably 50-80°C, the tower top pressure is preferably -0.05-0.02MPa, the tower bottom temperature is preferably 200-225°C, the tower bottom pressure is preferably -0.05-0.005MPa, and the reflux ratio is preferably 0.2-0.4.

[0113] The tower top temperature of the deglycerol tower is 175-199°C, the tower top pressure is -0.07-0.03 MPa, the tower bottom temperature is 263-284°C, the tower bottom pressure is -0.05-0.01 MPa, and the reflux ratio is 0.6-1.2. The tower top temperature is preferably 180-195°C, the tower top pressure is preferably -0.05-0.02 MPa, the tower bottom temperature is preferably 265-280°C, the tower bottom pressure is preferably -0.03-0.005 MPa, and the reflux ratio is preferably 0.8-1.0.

[0114] The top temperature of the diol separation tower is 160-181°C, the top pressure is -0.06-0.02 MPa, the bottom temperature is 198-214°C, the bottom pressure is -0.04-0 MPa, and the reflux ratio is 9-15. The top temperature is preferably 165-180°C, the top pressure is preferably -0.05-0.01 MPa, the bottom temperature is preferably 200-210°C, the bottom pressure is preferably -0.03-0 MPa, and the reflux ratio is preferably 10-13.

[0115] In some other embodiments of the present invention, step S4 may also preferably be specifically:

[0116] The heavy component obtained in step S2 enters a deglycerol tower, glycerol is obtained at the bottom of the tower, and part of water is obtained at the top of the tower. The remaining water and a mixed solution of 1,2-propylene glycol and 1,3-propylene glycol are extracted from the side line, and enter a dehydration tower, water is obtained at the top of the tower, and a mixture of 1,2-propylene glycol and 1,3-propylene glycol is obtained at the bottom of the tower. The heavy component enters a glycol separation tower, 1,2-propylene glycol is obtained at the top of the tower, and 1,3-propylene glycol is obtained at the bottom of the tower; the water and glycerol are recycled;

[0117] On this basis, the top temperature of the deglycerol tower is 62-87°C, the top pressure is -0.08-0.04 MPa, the bottom temperature is 256-279°C, the bottom pressure is -0.06-0.02 MPa, and the reflux ratio is 0.3-0.7. The top temperature is 65-85°C, the top pressure is -0.05-0.03 MPa, the bottom temperature is 260-275°C, the bottom pressure is -0.05-0.01 MPa, and the reflux ratio is 0.4-0.6.

[0118] The top temperature of the dehydration tower is 50-87°C, the top pressure is -0.09-0.04 MPa, the bottom temperature is 170-199°C, the bottom pressure is -0.07-0.02 MPa, and the reflux ratio is 1-3. The top temperature of the dehydration tower is 55-85°C, the top pressure is -0.05-0.03 MPa, the bottom temperature is 175-190°C, the bottom pressure is -0.05-0.01 MPa, and the reflux ratio is 1-2.

[0119] The top temperature of the diol separation tower is 128-172°C, the top pressure is -0.09-0.04 MPa, the bottom temperature is 178-207°C, the bottom pressure is -0.07-0.02 MPa, and the reflux ratio is 6-12. The top temperature is 135-170°C, the top pressure is -0.05-0.02 MPa, the bottom temperature is 180-205°C, the bottom pressure is -0.05-0.02 MPa, and the reflux ratio is 8-10.

[0120] The present invention also provides a device for preparing 1,3-propylene glycol according to the above technical solution. The specific schematic diagram of the device construction can refer to the flow diagram of the method for preparing 1,3-propylene glycol with integrated azeotropic distillation in the following Examples 1 to 3.

[0121] In summary, the present invention provides a preparation method and device of 1,3-propylene glycol with integrated azeotropic distillation, wherein the preparation method mainly comprises: a reaction section and a separation section, wherein the reaction section mainly generates a mixed product of 1,3-propylene glycol and its by-products by continuous hydrogenation reaction of glycerol solution and hydrogen under the action of a catalyst, and after gas-liquid separation and gas-phase hydrogen circulation, the liquid-phase product enters the separation section, and the product 1,3-propylene glycol and its by-products n-propanol, isopropanol, and 1,2-propylene glycol are separated, and the unreacted glycerol is recycled. The reaction section comprises: a glycerol solution and hydrogen mixing system, a heating system and a heat exchange system, a hydrogenation reactor system and a gas-liquid separation system, a fresh hydrogen system and a circulating hydrogen compression system; the equipment of the separation section comprises: an azeotrope removal tower, an azeotropic distillation tower, an azeotropic water removal tower, a n-propanol removal tower, an isopropanol removal tower, a high-pressure dehydration tower, a low-pressure dehydration tower, a 1,2-propylene glycol removal tower, a 1,3-propylene glycol removal tower and heat exchange equipment, etc.; or comprises: an azeotrope removal tower, an azeotropic distillation tower, an azeotropic water removal tower, a n-propanol removal tower, an isopropanol removal tower, a high-pressure dehydration tower, a low-pressure dehydration tower, a glycerol removal tower, a glycol separation tower and heat exchange equipment, etc.; or an azeotrope removal tower, an azeotropic distillation tower, an azeotropic water removal tower, a n-propanol removal tower, an isopropanol removal tower, a glycerol removal tower, a glycol separation tower, a dehydration tower and heat exchange equipment, etc.

[0122] The present invention adopts a combination of a specific reaction section and a specific separation section. The reaction section realizes continuous operation through an efficient catalyst and a continuous reactor (such as a trickle bed tubular reactor), has high production efficiency, and the reaction heat can be recycled; and the separation section integrates azeotropic distillation and heat coupling, which not only removes the concentration limit of the glycerol raw material, but also breaks the azeotropy of low-alcohol-water, realizes the separation of alcohol-water azeotropes, and the azeotroping agent can also be recycled, with low operating energy consumption and easy industrial promotion. In addition, the preparation method provided by the present invention can obtain high-index 1,3-propylene glycol, and can separate products such as isopropanol, n-propanol, and 1,2-propylene glycol at the same time, and the purity of each separated product is above 99.95%.

[0123] Compared with the prior art, the present invention focuses on the overall process and equipment for producing 1,3-propylene glycol, including a reaction section and a separation section, and in particular, the selection of the reactor type and the design of the separation section are completely different from the prior art. The applicant has found that the descriptions of the separation section in other prior arts are mostly too vague and simple. In the actual separation process, low-alcohols will azeotrope with water, and the purity index of ordinary distillation cannot be achieved. The various separation methods of integrated azeotropic distillation involved in the present invention can achieve efficient separation of products, especially the separation of low-alcohol-water azeotropes, and reduce separation energy consumption. Generally speaking, this is not easy to think of and do in the art, and requires technical exploration, which cannot be achieved by relying solely on common sense.

[0124] In order to further illustrate the present invention, the following examples are used to provide a detailed description. The raw materials used in the following examples of the present invention are specifically 70 wt% glycerol + 30 wt% water, and the catalyst used is a Pt-W series hydrogenation catalyst.

[0125] Example 1

[0126] This embodiment adopts a method for preparing 1,3-propylene glycol with integrated azeotropic distillation. The schematic diagram of the process is shown in Figure 1 As shown, the specific steps are as follows:

[0127] (1) Reaction process: Glycerol is mixed with water to form a glycerol aqueous solution with a mass fraction of 70%, which is fully mixed with hydrogen (the source is fresh hydrogen compressed by fresh hydrogen compressor 4 and circulating hydrogen compressed by circulating hydrogen compressor 5), and then heated to 180°C through the product heat exchanger and heater, and then enters the trickle bed tubular reactor 1 from the top of the trickle bed tubular reactor 1, and reacts under the action of the catalyst, and is hydrogenated to generate a reaction product containing 1,3-propylene glycol. The reaction product flows out from the bottom of the trickle bed tubular reactor 1, and after heat exchange with the feed (i.e., glycerol aqueous solution) in the heat exchanger, enters the hot high-pressure gas-liquid separation tank 2. Among them, the main parameters in the trickle bed tubular reactor 1 are: reaction temperature of 180°C, reaction pressure of 5 MPa, hydrogen-to-oil ratio of 1000, liquid hourly space velocity of 1.2 h -1 , catalyst loading 20 t. The composition of the reaction product is shown in Table 1:

[0128] Table 1 Composition of reaction products

[0129]

[0130] (2) Reaction process: After the reaction product is heat exchanged in a heat exchanger, it enters the hot high-pressure gas-liquid separation tank 2. The top gas phase is cooled to 40°C by a cooler and then enters the cold high-pressure gas-liquid separation tank 3. The bottom liquid phase of the hot high-pressure gas-liquid separation tank 2 is mixed with the bottom liquid phase of the cold high-pressure gas-liquid separation tank 3 to obtain a mixed liquid phase, which enters the separation process. The top gas phase of the cold high-pressure gas-liquid separation tank 3 is hydrogen, which is compressed by a circulating hydrogen generator 5 and then mixed with the feed;

[0131] (3) Separation process: The mixed liquid phase obtained in step (2) enters the de-azeotrope tower 6 (tower top pressure 0.12 MPa, tower top temperature 109°C, reflux ratio 2, tower bottom pressure 0.14 MPa, tower bottom temperature 134°C), and the low-alcohol (methanol, ethanol, isopropanol, n-propanol)-water azeotrope is separated at the top of the tower. The bottom of the tower is recombined into water, 1,2-propylene glycol, 1,3-propylene glycol and unreacted glycerol mixture. Among them, the low-alcohol water azeotrope enters the methanol removal tower 15 (tower top pressure 0.03 MPa, tower top temperature 80°C, reflux ratio 20, tower bottom pressure 0.04 MPa, tower bottom temperature 95°C), the methanol light component is removed from the tower top, and the low-alcohol (ethanol, isopropanol, n-propanol) water azeotrope at the bottom enters the azeotropic distillation tower 7 (tower top pressure 0.3 MPa, tower top temperature 112°C, tower bottom pressure 0.32 MPa, tower bottom temperature 132°C, reflux ratio 35), benzene is selected as the azeotropic agent, and a low-alcohol (ethanol, isopropanol, n-propanol) mixture is obtained at the bottom of the tower. The top of the tower is benzene and the aqueous solution enters the phase separation tank 19, and the azeotropic boundary is continuously broken by the benzene and water phases, and the water phase enters the de-azeotropic water tower 8 (tower top pressure 0.12 MPa, tower top temperature 112°C, tower bottom pressure 0.14 MPa, tower bottom temperature 126 ℃), benzene is recovered from the top of the tower and returned to the phase separation tank, and water is sent out or circulated at the bottom of the tower to achieve the dehydration of low-alcohol. The bottom of the azeotropic distillation tower 7 is a low-alcohol mixture, which enters the n-propanol removal tower 9 (tower top pressure 0.2 MPa, tower top temperature 111 ℃, reflux ratio 11, tower bottom pressure 0.21 MPa, tower bottom temperature 131 ℃), the bottom is n-propanol, and the top is an isopropanol mixture entering the isopropanol removal tower 10, the tower top pressure is 0.25 MPa, the tower top temperature is 111 ℃, the reflux ratio is 20, the tower bottom pressure is 0.27 MPa, the tower bottom temperature is 119 ℃, the tower bottom is isopropanol, and the tower top is light components (methanol, ethanol, acetone, etc.). Among them: the product purity of isopropanol and n-propanol is above 99.95%. The material composition of each separation tower is shown in Table 2.

[0132] Table 2 Material composition of each separation tower

[0133]

[0134] (4) Separation process: The bottom of the deazeotrope tower 6 is reorganized into a mixture of water, 1,2-propylene glycol, 1,3-propylene glycol and unreacted glycerol. The heavy components at the bottom of the tower enter the high-pressure dehydration tower 11 (tower top pressure 0.7 MPa, tower top temperature 171°C, reflux ratio 0.2, tower bottom pressure 0.72 MPa, tower bottom temperature 191°C), and the bottom solution enters the low-pressure dehydration tower 12 (tower top pressure -0.09 MPa, tower top temperature 49°C, reflux ratio 0.1, tower bottom pressure -0.07 MPa, tower bottom temperature 204°C). The top gas phase of the high-pressure dehydration tower 11 is water, which is used as the bottom heat source of the low-pressure dehydration tower 12 after heat exchange in the heat exchanger. The top of the low-pressure dehydration tower 12 is all water, which can be recycled or sent out; the bottom of the low-pressure dehydration tower 12 is a polyol mixed solution, which enters the 1,2-propylene glycol removal tower 13 (tower top pressure is -0.09 MPa, tower top temperature is 128°C, reflux ratio is 13, tower bottom pressure is -0.07 MPa, tower bottom temperature is 209°C), 1,2-propylene glycol is obtained at the top of the tower, and a mixture of 1,3-propylene glycol and glycerol is obtained at the bottom of the tower, which enters the 1,3-propylene glycol removal tower 14 (tower top pressure is -0.08 MPa, tower top temperature is 169°C, reflux ratio is 0.7, tower bottom pressure is -0.06 MPa, tower bottom temperature is 256°C), 1,3-propylene glycol is obtained at the top of the tower, and unreacted glycerol is obtained at the bottom of the tower. Among them: the water and glycerol are recycled, and the product purity of 1,2-propylene glycol and 1,3-propylene glycol is above 99.95%. The material composition of each separation tower is shown in Table 3:

[0135] Table 3 Material composition of each separation tower

[0136]

[0137] Example 2

[0138] This embodiment adopts a method for preparing 1,3-propylene glycol with integrated azeotropic distillation. The schematic diagram of the process is shown in Figure 2 As shown, the specific steps are as follows:

[0139] Steps (1) to (3) are the same as those in Example 1, except that they are different from those in Example 1 as follows:

[0140] Step (4) separation process: The bottom of the low-pressure dehydration tower 12 is a polyol mixed solution, which enters the deglycerol tower 16 (tower top pressure -0.08 MPa, tower top temperature 165°C, reflux ratio 0.6, tower bottom pressure -0.06 MPa, tower bottom temperature 256°C), and the unreacted glycerol is separated from the bottom of the tower for recycling. The top of the tower is a mixture of 1,2-propylene glycol and 1,3-propylene glycol, which enters the glycol separation tower 17 (tower top pressure -0.09 MPa, tower top temperature 128°C, reflux ratio 6, tower bottom pressure -0.07 MPa, tower bottom temperature 178°C), and the top of the tower is 1,2-propylene glycol, and the bottom of the tower is 1,3-propylene glycol. Among them, the product purity of the 1,2-propylene glycol and 1,3-propylene glycol is both above 99.95%. The material composition of each separation tower is shown in Table 4:

[0141] Table 4 Material composition of each separation tower

[0142]

[0143] Example 3

[0144] This embodiment adopts a method for preparing 1,3-propylene glycol with integrated azeotropic distillation. The schematic diagram of the process is shown in Figure 3 As shown, the specific steps are as follows:

[0145] Steps (1) to (3) are the same as those in Example 1, except that they are different from those in Example 1 as follows:

[0146] Step (4) separation process: azeotrope removal tower 6 (tower top pressure 0.11 MPa, tower top temperature 109°C, reflux ratio 1, tower bottom pressure 0.13 MPa, tower bottom temperature 134°C), the bottom of the tower is recombined into water, 1,2-propylene glycol, 1,3-propylene glycol, and a mixture of unreacted glycerol. The heavy component enters the deglycerolating tower 16 (tower top pressure -0.08 MPa, tower top temperature 61°C, reflux ratio 0.3, tower bottom pressure -0.06 MPa, tower bottom temperature 256°C), the unreacted glycerol is separated from the tower bottom and recycled, the tower top is part of the water, the side line is drawn out as a mixed solution of water, 1,2-propylene glycol and 1,3-propylene glycol, the mixed solution drawn out from the side line enters the dehydration tower 18 (tower top pressure -0.09 MPa, tower top temperature 48°C, reflux ratio 1, tower bottom pressure -0.07 MPa, tower bottom temperature 170°C), the water separated from the tower top is mixed with the tower top water of the deglycerolating tower 16 and then recycled or sent out, the bottom of the tower is a mixture of 1,2-propylene glycol and 1,3-propylene glycol, which enters the glycol separation tower 17 (tower top pressure -0.09 MPa, tower top temperature 128℃, reflux ratio 6, tower bottom pressure -0.07MPa, tower bottom temperature 178℃), the tower top is 1,2-propylene glycol, and the tower bottom is 1,3-propylene glycol. Among them: the product purity of the 1,2-propylene glycol and 1,3-propylene glycol is above 99.95%. The material composition of each separation tower is shown in Table 5:

[0147] Table 5 Material composition of each separation tower

[0148]

[0149] As can be seen from Table 2, Table 3, Table 4 and Table 5, the present invention provides a production process and device for 1,3-propylene glycol with integrated azeotropic distillation, which adopts a trickle bed tubular reactor and an integrated azeotropic distillation separation process, and can produce a high-purity alcohol product, and the entire process is not affected by the morning concentration of the glycerol raw material, and can achieve efficient and continuous production of 1,3-propylene glycol. At the same time, the azeotropic distillation process provided by the present invention can be integrated into processes of different separation sequences, and has wide implementation.

[0150] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing 1,3-propylene glycol with integrated azeotropic distillation, characterized in that: The following steps are involved: S1: continuously reacting a glycerol solution and hydrogen in the presence of a catalyst, obtaining a reaction product, and then performing gas-liquid separation to obtain a liquid product and hydrogen, respectively, and the hydrogen is recycled; S2: distilling the liquid product to obtain azeotropes and heavy components respectively; S3: treating the azeotrope obtained in step S2 by removing methanol to obtain an alcohol-water azeotrope, treating the alcohol-water azeotrope by azeotropic distillation to obtain an alcohol mixture and an entrainer-water mixed solution, respectively; removing water from the entrainer-water mixed solution by removing azeotropic water, and sequentially removing n-propanol and isopropanol from the alcohol mixture to obtain n-propanol, isopropanol and light components, respectively; S4: subjecting the heavy component obtained in step S2 to multiple-effect thermal coupling dehydration treatment, 1,2-propylene glycol removal treatment and 1,3-propylene glycol removal treatment in sequence to obtain water, 1,2-propylene glycol, 1,3-propylene glycol and glycerol, respectively; wherein the water and glycerol are recycled; or S4 is: subjecting the heavy component obtained in step S2 to multiple-effect thermal coupling dehydration treatment, deglycerol treatment, and glycol separation treatment in sequence to obtain water, glycerol, 1,2-propylene glycol, and 1,3-propylene glycol, respectively; wherein the water and glycerol are recycled; or S4 is: subjecting the heavy component obtained in step S2 to deglycerol treatment, dehydration treatment, and glycol separation treatment to obtain glycerol, water, 1,2-propylene glycol, and 1,3-propylene glycol, respectively; wherein water and glycerol are recycled.

2. The preparation method according to claim 1, characterized in that: The mass concentration of the glycerol solution is 10-90%; The solvent in the glycerol solution is selected from any one or more of water, methanol or ethanol; The catalyst is selected from any one or more of a Pt-W catalyst, an Ir-Re catalyst or a Pt-molecular sieve catalyst.

3. The preparation method according to claim 1 or 2, characterized in that: The hydrogen-to-oil ratio in the continuous reaction is 500-1500; the liquid hourly space velocity is 0.8-1.6 h -1 ; The continuous reaction reactor is selected from a trickle bed fixed bed reactor, a trickle bed tubular reactor or a bubbling reactor; The temperature of the continuous reaction is 100-200° C., and the pressure is 0.5-10 MPa.

4. The preparation method according to any one of claims 1 to 3, characterized in that The gas-liquid separation is: The reaction product is heat exchanged with the reaction feed and then subjected to hot high-pressure gas-liquid separation to obtain a gas phase component and a first liquid phase product, respectively, wherein the gas phase component is cooled and then subjected to cold high-pressure gas-liquid separation to obtain hydrogen and a second liquid phase product, respectively; the liquid phase product obtained by mixing the first liquid phase product and the second liquid phase product is used as a feed for the distillation treatment in step S2; the hydrogen is recycled.

5. The preparation method according to any one of claims 1 to 4, characterized in that Step S2 is: The liquid phase product enters the deazeotrope tower for rectification treatment, and the azeotrope is obtained at the top of the tower, and the heavy component is obtained at the bottom of the tower; The top temperature of the deazeotrope tower is 90-106° C., the top pressure is 0.02-0.11 MPa, the bottom temperature is 115-131° C., the bottom pressure is 0.04-0.13 MPa, and the reflux ratio is 1-3.

6. The preparation method according to any one of claims 1 to 5, characterized in that Step S3 is: The azeotrope obtained in step S2 enters a methanol removal tower, the methanol light component is removed from the tower top, an alcohol-water azeotrope is obtained at the tower bottom, and enters an azeotropic distillation tower, an entrainer is added for azeotropic distillation, an alcohol mixture is obtained at the tower bottom, and an entrainer-water mixed solution is obtained at the tower top; the entrainer-water mixed solution passes through a phase separation tank, and the obtained water phase enters a de-azeotropic water tower, the entrainer is recovered at the tower top and returned to the phase separation tank, and the tower bottom is water; the bottom of the azeotropic distillation tower is an alcohol mixture, which enters a de-n-propanol tower, n-propanol is obtained at the tower bottom, and an isopropanol mixture is obtained at the tower top; the isopropanol mixture enters a de-isopropanol tower, the tower top is a light component, and isopropanol is obtained at the tower bottom; The azeotropic agent is selected from any one or more of benzene, No. 60 n-hexane, No. 80 n-hexane or pure n-hexane; The top temperature of the demethanol tower is 85-96°C, the top pressure is 0.03-0.1 MPa, the bottom temperature is 95-108°C, the bottom pressure is 0.04-0.12 MPa, and the reflux ratio is 6-12; The azeotropic distillation tower has a top temperature of 91-112°C, a top pressure of 0.1-0.3 MPa, a bottom temperature of 110-135°C, a bottom pressure of 0.12-0.32 MPa, and a reflux ratio of 25-50; The tower top temperature of the deazeotropic water tower is 86-102°C, the tower top pressure is 0.02-0.12 MPa, the tower bottom temperature is 109-126°C, and the tower bottom pressure is 0.04-0.14 MPa; The tower top temperature of the deisopropanol tower is 85-111° C., the tower top pressure is 0.02-0.2 MPa, the tower bottom temperature is 104-131° C., the tower bottom pressure is 0.03-0.22 MPa, and the reflux ratio is 7-14; The top temperature of the n-propanol removal tower is 81-111° C., the top pressure is 0.02-0.25 MPa, the bottom temperature is 89-119° C., the bottom pressure is 0.03-0.27 MPa, and the reflux ratio is 15-22.

7. The preparation method according to any one of claims 1 to 6, characterized in that Step S4 is: The heavy component obtained in step S2 enters a high-pressure dehydration tower, the obtained bottom solution enters a low-pressure dehydration tower, the obtained top gas phase is thermally coupled with the low-pressure dehydration tower, and serves as a bottom heat source of the low-pressure dehydration tower, water is obtained at the top of the tower, and the bottom of the tower is a polyol solution, which enters a 1,2-propylene glycol removal tower, 1,2-propylene glycol is obtained at the top of the tower, and the bottom of the tower is a mixture of 1,3-propylene glycol and glycerol, which enters a 1,3-propylene glycol removal tower, 1,3-propylene glycol is obtained at the top of the tower, and glycerol is obtained at the bottom of the tower; the water and glycerol are recycled; The top temperature of the high-pressure dehydration tower is 171-192° C., the top pressure is 0.7-1.2 MPa, the bottom temperature is 189-212° C., the bottom pressure is 0.72-1.22 MPa, and the reflux ratio is 0.2-0.6; The low-pressure dehydration tower has a top temperature of 49-91°C, a top pressure of -0.09-0.03 MPa, a bottom temperature of 198-235°C, a bottom pressure of -0.07-0.01 MPa, and a reflux ratio of 0.1-0.5; The top temperature of the 1,2-propylene glycol removal tower is 176-194° C., the top pressure is -0.07-0.03 MPa, the bottom temperature is 222-243° C., the bottom pressure is -0.05-0.01 MPa, and the reflux ratio is 7-14; The top temperature of the 1,3-propylene glycol removal tower is 154-187° C., the top pressure is -0.09-0.06 MPa, the bottom temperature is 247-269° C., the bottom pressure is -0.07-0.04 MPa, and the reflux ratio is 0.7-1.

4.

8. The preparation method according to any one of claims 1 to 7, characterized in that Step S4 is: The heavy component obtained in step S2 enters a high-pressure dehydration tower, and the obtained bottom solution enters a low-pressure dehydration tower. The obtained top gas phase is thermally coupled with the low-pressure dehydration tower as a bottom heat source of the low-pressure dehydration tower. Water is obtained at the top of the tower, and the bottom of the tower is a polyol solution, which enters a deglycerolation tower, and glycerol is obtained at the bottom of the tower for recycling. A mixture of 1,2-propylene glycol and 1,3-propylene glycol is obtained at the top of the tower, and enters a glycol separation tower, and 1,2-propylene glycol is obtained at the top of the tower, and 1,3-propylene glycol is obtained at the bottom of the tower; the water and glycerol are recycled; The top temperature of the high-pressure dehydration tower is 171-192° C., the top pressure is 0.7-1.2 MPa, the bottom temperature is 189-212° C., the bottom pressure is 0.72-1.22 MPa, and the reflux ratio is 0.2-0.6; The low-pressure dehydration tower has a top temperature of 49-91°C, a top pressure of -0.09-0.03 MPa, a bottom temperature of 198-235°C, a bottom pressure of -0.07-0.01 MPa, and a reflux ratio of 0.1-0.5; The deglycerolating tower has a top temperature of 175-199° C., a top pressure of -0.07-0.03 MPa, a bottom temperature of 263-284° C., a bottom pressure of -0.05-0.01 MPa, and a reflux ratio of 0.6-1.2; The top temperature of the diol separation tower is 160-181° C., the top pressure is -0.06-0.02 MPa, the bottom temperature is 198-214° C., the bottom pressure is -0.04-0 MPa, and the reflux ratio is 9-15.

9. The preparation method according to any one of claims 1 to 8, characterized in that Step S4 is: The heavy component obtained in step S2 enters a deglycerol tower, glycerol is obtained at the bottom of the tower, and part of water is obtained at the top of the tower. The remaining water and a mixed solution of 1,2-propylene glycol and 1,3-propylene glycol are extracted from the side line, and enter a dehydration tower, water is obtained at the top of the tower, and a mixture of 1,2-propylene glycol and 1,3-propylene glycol is obtained at the bottom of the tower. The heavy component enters a glycol separation tower, 1,2-propylene glycol is obtained at the top of the tower, and 1,3-propylene glycol is obtained at the bottom of the tower; the water and glycerol are recycled; The deglycerolating tower has a top temperature of 62-87° C., a top pressure of -0.08-0.04 MPa, a bottom temperature of 256-279° C., a bottom pressure of -0.06-0.02 MPa, and a reflux ratio of 0.3-0.7; The dehydration tower has a top temperature of 50-87°C, a top pressure of -0.09-0.04 MPa, a bottom temperature of 170-199°C, a bottom pressure of -0.07-0.02 MPa, and a reflux ratio of 1-3; The top temperature of the diol separation tower is 128-172° C., the top pressure is -0.09-0.04 MPa, the bottom temperature is 178-207° C., the bottom pressure is -0.07-0.02 MPa, and the reflux ratio is 6-12.

10. The preparation method according to any one of claims 1 to 9, characterized in that The purity of the prepared 1,3-propylene glycol is above 99.95%.

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