Method for producing 1, 3-propylene glycol by integrating extractive distillation

Abstract

The invention relates to a 1, 3-propylene glycol production method integrated with extractive distillation, which comprises the following steps: carrying out hydrogenation reaction on a glycerol solution and hydrogen in the presence of a catalyst, and carrying out gas-liquid separation on the obtained reaction product to respectively obtain a liquid-phase product and hydrogen; hydrogen is recycled; rectifying the obtained liquid-phase product to obtain azeotrope at the tower top and heavy components at the tower bottom; carrying out dehydration treatment on the azeotrope through extractive distillation and solvent regeneration, and sequentially passing through an n-propanol removal tower and an isopropanol removal tower to respectively obtain n-propanol, isopropanol and a light component; treating the heavy component through a multi-effect thermal coupling dehydrating tower, a 1, 2-propylene glycol removing tower and a 1, 3-propylene glycol removing tower in sequence to obtain water, 1, 2-propylene glycol, 1, 3-propylene glycol and glycerol respectively; the water and the glycerol are recycled. The production method is advanced in process, low in cost and free of pollution, long-term stable operation can be achieved, high-purity products such as 1, 3-propylene glycol, 1, 2-propylene glycol, n-propyl alcohol and isopropyl alcohol can be obtained, and the purity of each separated product is 99.95% or above.

Description

Technical Field

[0001] The invention relates to the technical field of 1,3-propylene glycol production, and more specifically to a production method of 1,3-propylene glycol with integrated extraction and distillation. Background Art

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

[0003] The main methods for synthesizing 1,3-propylene glycol include the ethylene oxide method, biological fermentation method, acrolein hydration method, acetal method, glycerol hydrogenation method, etc. Among them, the glycerol hydrogenation method uses glycerol as a raw material to synthesize 1,3-propylene glycol in one step. The process has the characteristics of green environmental protection and high production efficiency, and has received widespread attention. Chinese patents with publication numbers CN111039756A and CN113527062A respectively disclose a method and system for preparing 1,3-propylene glycol from glycerol. The methods provided integrate high-efficiency catalysts, reactors and separation systems; however, the separation systems of the above technical solutions all use conventional distillation systems, and the by-products isopropanol and n-propanol produce azeotropes with water and cannot be separated by conventional distillation. The patented technology is not feasible in the design of the separation scheme, and high-purity n-propanol and isopropanol products cannot be obtained by separation. The Chinese patent with publication number CN103524302A discloses a method for preparing 1,3-propylene glycol by hydrogenation of glycerol. All the liquid products of the reaction are dehydrated by a pervaporation membrane and the dehydrated products are separated. The pervaporation membrane used in this method has high requirements for water content in practical applications, and the water content must be less than 20%. The feed must be completely vaporized, and the energy consumption is high. In addition, the membrane component has a short life and high maintenance cost, which makes it difficult to use in actual production. At the same time, it cannot be applied to raw glycerol with different concentrations. The Chinese patent with publication number CN115636727A discloses a method for preparing 1,3-propylene glycol by hydrogenation of glycerol. After the water-containing material at the bottom of the methanol removal tower is dehydrated by a pervaporation membrane, the remaining material is separated; however, the technical solution requires that the water content in the water-containing material is less than 30%, and energy is required to vaporize the water-containing material to increase the cost. At the same time, the molecular sieve membrane requires a large membrane area and is limited in service life. Therefore, it will greatly increase the investment in the device, which is not conducive to the efficient production of industrial devices. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a production method of 1,3-propylene glycol integrated with extractive distillation, which integrates a high-efficiency catalyst and a trickle bed tubular hydrogenation reactor, and utilizes the extractive distillation process to effectively solve the problem of difficult separation of alcohol-water azeotropes, couples reaction and separation heat, and reduces the energy consumption of the device. The entire process has the characteristics of strong applicability, simple continuous operation, high production efficiency and low production cost.

[0005] The present invention provides a method for producing 1,3-propylene glycol by integrated extraction and distillation, comprising the following steps:

[0006] a) subjecting a glycerol solution and hydrogen to a hydrogenation reaction in the presence of a catalyst to obtain a reaction product; and then subjecting the reaction product to gas-liquid separation to obtain a liquid product and hydrogen, respectively; wherein the hydrogen is recycled;

[0007] b) distilling the liquid product obtained in step a) to obtain an azeotrope at the top of the tower and a heavy component at the bottom of the tower;

[0008] c) dehydrating the azeotrope obtained from the top of the tower in step b) by extractive distillation and solvent regeneration, and then passing through a n-propanol removal tower and an isopropanol removal tower in sequence to obtain n-propanol, isopropanol and light components, respectively;

[0009] d) the heavy components obtained at the bottom of the tower in step b) 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 are recycled.

[0010] Preferably, the mass concentration of the glycerol solution in step a) is 10% to 90%; the solvent of the glycerol solution is selected from one or more of water, methanol and ethanol.

[0011] Preferably, the catalyst in step a) is selected from one or more of a Pt-W catalyst, an Ir-Re catalyst, and a Pt-molecular sieve catalyst.

[0012] Preferably, in step a), the hydrogen-to-oil ratio is controlled to be 500-1500; the catalyst controls the liquid hourly space velocity to be 0.8h -1 ~1.6h -1 .

[0013] Preferably, the hydrogenation reaction process in step a) adopts a trickle bed fixed bed reactor, a trickle bed tubular reactor or a bubbling reactor; the temperature of the hydrogenation reaction is 100° C. to 200° C., and the pressure is 0.5 MPa to 10 MPa.

[0014] Preferably, the gas-liquid separation process in step a) is specifically as follows:

[0015] The reaction product is first 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 component, respectively. The gas phase component is further cooled and then subjected to cold high-pressure gas-liquid separation to obtain hydrogen and a second liquid phase component, respectively. The first liquid phase component and the second liquid phase component are mixed and used as feed for subsequent distillation separation. The hydrogen is recycled.

[0016] Preferably, the distillation process in step b) adopts a deazeotrope tower with a top pressure of 0.10 MPa to 0.15 MPa, a top temperature of 108 to 110° C., a reflux ratio of 0.8 to 1.2, a bottom pressure of 0.10 MPa to 0.15 MPa, and a bottom temperature of 130 to 140° C.

[0017] Preferably, the step c) is specifically:

[0018] The azeotrope obtained at the top of step b) enters an extractive distillation tower for extractive distillation, a low-alcohol mixture is obtained at the top of the tower, and an extractant solution is obtained at the bottom of the tower; wherein the extractant solution enters a solvent regeneration tower, water is removed at the top of the tower, and the bottom of the tower is the regenerated extractant, which enters the extractive distillation tower for recycling; the low-alcohol mixture enters a depropanolation tower, n-propanol is obtained at the bottom of the tower, an isopropanol mixture is obtained at the top of the tower, and enters a deisopropanolation tower, light components are obtained at the top of the tower, and isopropanol is obtained at the bottom of the tower.

[0019] Preferably, the extractant is selected from one or more of butanediol, propylene glycol, ethylene glycol and dimethyl sulfoxide.

[0020] Preferably, the step d) is specifically:

[0021] The heavy component obtained at the bottom of the tower in step b) enters a high-pressure dehydration tower, and the solution at the bottom of the tower enters a low-pressure dehydration tower. The gas phase at the top of the tower is thermally coupled with the low-pressure dehydration tower as a heat source at the bottom of the low-pressure dehydration tower, and water is obtained at the top of the tower. The bottom of the tower is a polyol solution, which 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, which 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; wherein the water and glycerol are recycled.

[0022] The invention provides a production method of 1,3-propylene glycol by integrated extraction and rectification, comprising the following steps: a) subjecting a glycerol solution and hydrogen to a hydrogenation reaction in the presence of a catalyst to obtain a reaction product; then subjecting the reaction product to gas-liquid separation to respectively obtain a liquid phase product and hydrogen; wherein the hydrogen is recycled; b) subjecting the liquid phase product obtained in step a) to rectification to obtain an azeotrope at the top of a tower and a heavy component at the bottom of a tower; c) subjecting the azeotrope obtained in step b) to a dehydration treatment by extractive distillation and solvent regeneration, and then subjecting the dehydration treatment to a n-propanol removal tower and an isopropanol removal tower in sequence to obtain n-propanol, isopropanol and a light component in sequence; d) subjecting the heavy component obtained in step b) to a dehydration treatment by a multi-effect thermal coupling dehydration tower, a 1,2-propylene glycol removal tower and a 1,3-propylene glycol removal tower in sequence to obtain water, 1,2-propylene glycol, 1,3-propylene glycol and glycerol in sequence; wherein the water and glycerol are recycled. Compared with the prior art, the integrated extraction and distillation 1,3-propylene glycol production method provided by the present invention adopts a specific process of glycerol hydrogenation to produce 1,3-propylene glycol, achieves overall good interaction, has the advantages of advanced technology, low cost, no pollution, and long-term stable operation, and can obtain high-purity 1,3-propylene glycol, 1,2-propylene glycol, n-propanol, isopropanol and other products, and the purity of each separated product is above 99.95%. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of a method for producing 1,3-propylene glycol by integrated extractive distillation provided in Example 1 of the present invention;

[0024] Figure 2 A schematic diagram of a method for producing 1,3-propylene glycol by integrated extractive distillation provided in Example 2 of the present invention;

[0025] Figure 3 A schematic diagram of the method for producing 1,3-propylene glycol by integrated extractive distillation provided in Example 3 of the present invention. DETAILED DESCRIPTION

[0026] 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.

[0027] The present invention provides a method for producing 1,3-propylene glycol by integrated extraction and distillation, comprising the following steps:

[0028] a) subjecting a glycerol solution and hydrogen to a hydrogenation reaction in the presence of a catalyst to obtain a reaction product; and then subjecting the reaction product to gas-liquid separation to obtain a liquid product and hydrogen, respectively; wherein the hydrogen is recycled;

[0029] b) distilling the liquid product obtained in step a) to obtain an azeotrope at the top of the tower and a heavy component at the bottom of the tower;

[0030] c) dehydrating the azeotrope obtained from the top of the tower in step b) by extractive distillation and solvent regeneration, and then passing through a n-propanol removal tower and an isopropanol removal tower in sequence to obtain n-propanol, isopropanol and light components, respectively;

[0031] d) the heavy components obtained at the bottom of the tower in step b) 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 are recycled.

[0032] The present invention firstly mixes a glycerol solution and hydrogen into a trickle bed tubular reactor in the presence of a catalyst to carry out a hydrogenation reaction to obtain a reaction product; then the reaction product is subjected to gas-liquid separation to obtain a liquid phase product and hydrogen respectively; wherein the hydrogen is recycled.

[0033] In the present invention, the mass concentration of the glycerol solution is preferably 10% to 90%, more preferably 40% to 80%; the solvent of the glycerol solution is preferably selected from one or more of water, methanol, and ethanol, more preferably water. The present invention has no special restrictions on the source of the glycerol solution, and commercially available products known to those skilled in the art can be used; wherein the water is preferably deionized water known to those skilled in the art.

[0034] In the present invention, the catalyst is preferably selected from one or more of a Pt-W catalyst, an Ir-Re catalyst, and a Pt-molecular sieve catalyst, and is more preferably a Pt-W catalyst. The present invention has no particular restrictions on the source of the catalyst, and a commercially available or homemade hydrogenation catalyst may be used.

[0035] In the present invention, the hydrogen-oil ratio of the hydrogen gas is preferably 500 to 1500, more preferably 800 to 1200; the catalyst-controlled liquid hourly space velocity is preferably 0.8 h -1 ~1.6h -1 , more preferably 1h -1 ~1.5h -1 .

[0036] In the present invention, the hydrogenation reaction process preferably adopts a trickle bed fixed bed reactor, a trickle bed tubular reactor or a bubbling reactor, and is more preferably a trickle bed tubular reactor; the temperature of the hydrogenation reaction is preferably 100°C to 200°C, and is more preferably 170°C to 190°C; the pressure is preferably 0.5MPa to 10MPa, and is more preferably 4MPa to 6MPa.

[0037] In the present invention, in order to recover heat, it is preferred that the reaction discharge is first heat exchanged with the reaction feed, and then heated to the reaction temperature by medium-pressure steam.

[0038] In the present invention, the process of gas-liquid separation of the reaction product is preferably as follows:

[0039] The reaction product is first 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 component, respectively. The gas phase component is further cooled and then subjected to cold high-pressure gas-liquid separation to obtain hydrogen and a second liquid phase component, respectively. The first liquid phase component and the second liquid phase component are mixed and used as feed for subsequent distillation separation. The hydrogen is recycled.

[0040] On this basis, the above-mentioned recycled hydrogen can partially replace the fresh hydrogen of the reaction raw material. At the same time, the two are respectively controlled by compressors.

[0041] Afterwards, the present invention allows the obtained liquid phase product to enter an azeotrope removal tower for distillation operation, an azeotrope is obtained at the top of the tower, and a heavy component is obtained at the bottom of the tower; the azeotrope obtained at the top of the tower is further dehydrated by extractive distillation and solvent regeneration, and then sequentially passed through a n-propanol removal tower and an isopropanol removal tower to obtain n-propanol, isopropanol and light components respectively; the heavy component obtained at the bottom of the tower is sequentially passed 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 are recycled.

[0042] In the present invention, the distillation process preferably adopts a de-azeotrope tower, the top pressure is preferably 0.10MPa~0.15MPa, more preferably 0.11MPa~0.12MPa, the top temperature is preferably 108~110°C, more preferably 109°C, the reflux ratio is preferably 0.8~1.2, more preferably 1, the bottom pressure is preferably 0.10MPa~0.15MPa, more preferably 0.13MPa~0.14MPa, and the bottom temperature is preferably 130°C~140°C, more preferably 134°C~137°C.

[0043] In the present invention, the process of dehydrating the azeotrope obtained at the top of the tower by extractive distillation and solvent regeneration, and then passing through a n-propanol removal tower and an isopropanol removal tower to obtain n-propanol, isopropanol and light components respectively is preferably as follows:

[0044] The azeotrope obtained at the top of step b) enters an extractive distillation tower for extractive distillation, a low-alcohol mixture is obtained at the top of the tower, and an extractant solution is obtained at the bottom of the tower; wherein the extractant solution enters a solvent regeneration tower, water is removed from the top of the tower and sent to the outside, the bottom of the tower is the regenerated extractant, and enters the extractive distillation tower for recycling; the low-alcohol mixture enters a depropanolation tower, n-propanol is obtained at the bottom of the tower, an isopropanol mixture is obtained at the top of the tower, and enters a deisopropanolation tower, the top of the tower is a light component, and isopropanol is obtained at the bottom of the tower.

[0045] In the present invention, the extractant is preferably selected from one or more of butanediol, propylene glycol, ethylene glycol, and dimethyl sulfoxide, more preferably ethylene glycol. The present invention has no particular limitation on the source of the extractant, and commercially available products known to those skilled in the art can be used.

[0046] In the present invention, the heavy components obtained at the bottom of the tower 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 process of recycling water and glycerol is preferably as follows:

[0047] The heavy component obtained at the bottom of the tower in step b) enters a high-pressure dehydration tower, and the solution at the bottom of the tower enters a low-pressure dehydration tower. The gas phase at the top of the tower is thermally coupled with the low-pressure dehydration tower as a heat source at the bottom of the low-pressure dehydration tower, and water is obtained at the top of the tower. The bottom of the tower is a polyol solution, which 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, which 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; wherein the water and glycerol are recycled.

[0048] In the present invention, the above-mentioned solvent regeneration tower, low-pressure dehydration tower, 1,2-propylene glycol removal tower, 1,3-propylene glycol removal tower and other separation towers are all negative pressure operations well known to those skilled in the art, and the separation pressure is preferably -20KPa to -100KPa.

[0049] The present invention provides a production method of 1,3-propylene glycol by integrated extraction and distillation, which mainly comprises a reaction process and a separation process, wherein the reaction process mainly generates a mixed product of 1,3-propylene glycol and its byproducts by hydrogenating a glycerol solution and hydrogen under the action of a catalyst, and then undergoes gas-liquid separation and gas-phase hydrogen circulation, and the liquid-phase product enters a separation process, the product 1,3-propylene glycol and its byproducts n-propanol, isopropanol and 1,2-propylene glycol are separated, and the unreacted glycerol is recycled; the reaction process comprises: a glycerol solution and hydrogen mixing system, a heating and heat exchange system, a hydrogenation reactor and a gas-liquid separation system, a fresh hydrogen and circulating hydrogen compression system, and the like; the separation process comprises: an azeotrope removal tower, an extraction and distillation tower, a solvent regeneration tower, a n-propanol removal tower, an isopropanol removal tower, a multi-effect thermal coupling dehydration tower, a 1,2-propylene glycol removal tower, a 1,3-propylene glycol removal tower, a heat exchange system, and the like.

[0050] The invention adopts a combination of a specific reaction process and a specific separation process to achieve overall good interaction, wherein the reaction process realizes continuous operation through a high-efficiency catalyst and a trickle bed tubular reactor, has high production efficiency, and the reaction heat is recycled; and the separation process integrates extraction distillation and heat coupling, which not only removes the concentration restriction of the glycerol raw material, but also breaks the azeotropy of low-alcohol water, realizes the separation of alcohol-water azeotropes, the extractant can be recycled and reused, the operation energy consumption is low, and it is easy to promote industrialization; and the production method provided by the invention can obtain high-index 1,3-propylene glycol, and can also separate products such as isopropanol, n-propanol, 1,2-propylene glycol, and the purity of each separated product is above 99.95%.

[0051] Compared with the prior art, the integrated extraction and distillation method for producing 1,3-propylene glycol provided by the present invention includes reaction and separation, and in particular, the selection of reactor type and the design of separation process are completely different from the prior art. The applicant has found through research that the descriptions of separation processes in other prior arts are mostly too vague and simple, and low-alcohols will azeotrope with water during the actual separation process, and the purity index of ordinary distillation cannot be achieved. The present invention involves a variety of separation means of integrated extraction and distillation, which realizes efficient separation of products, especially the separation of low-alcohol water azeotropes, and reduces separation energy consumption. This is usually not easy to think of and do, and requires technical exploration based on a large number of experiments, which cannot be achieved by relying solely on common sense.

[0052] The invention provides a production method of 1,3-propylene glycol by integrated extraction and rectification, comprising the following steps: a) subjecting a glycerol solution and hydrogen to a hydrogenation reaction in the presence of a catalyst to obtain a reaction product; then subjecting the reaction product to gas-liquid separation to respectively obtain a liquid phase product and hydrogen; wherein the hydrogen is recycled; b) subjecting the liquid phase product obtained in step a) to rectification to obtain an azeotrope at the top of a tower and a heavy component at the bottom of a tower; c) subjecting the azeotrope obtained in step b) to a dehydration treatment by extractive distillation and solvent regeneration, and then subjecting the dehydration treatment to a n-propanol removal tower and an isopropanol removal tower in sequence to obtain n-propanol, isopropanol and a light component in sequence; d) subjecting the heavy component obtained in step b) to a dehydration treatment by a multi-effect thermal coupling dehydration tower, a 1,2-propylene glycol removal tower and a 1,3-propylene glycol removal tower in sequence to obtain water, 1,2-propylene glycol, 1,3-propylene glycol and glycerol in sequence; wherein the water and glycerol are recycled. Compared with the prior art, the integrated extraction and distillation 1,3-propylene glycol production method provided by the present invention adopts a specific process of glycerol hydrogenation to produce 1,3-propylene glycol, achieves overall good interaction, has the advantages of advanced technology, low cost, no pollution, and long-term stable operation, and can obtain high-purity 1,3-propylene glycol, 1,2-propylene glycol, n-propanol, isopropanol and other products, and the purity of each separated product is above 99.95%.

[0053] 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% by mass of glycerol + 30% by mass of water, and the catalyst used is a Pt-W series hydrogenation catalyst.

[0054] Example 1

[0055] See the schematic diagram of the integrated extractive distillation method for producing 1,3-propylene glycol provided in this embodiment. Figure 1 As shown, the specific steps are as follows:

[0056] (1) Reaction process: Glycerol is mixed with water to form a 70% glycerol aqueous solution by mass, which is fully mixed with hydrogen and heated to 180°C by the product heat exchanger and heater before entering the reactor from the top of the trickle bed tubular reactor. The reaction occurs under the action of the Pt-W series catalyst, and the reaction product containing 1,3-propylene glycol is hydrogenated and flows out from the bottom of the reactor. After heat exchange with the feed, it enters the hot high-pressure gas-liquid separation tank. The main parameters are: reaction temperature of 180°C, reaction pressure of 5MPa, hydrogen-to-oil ratio of 1000, liquid hourly space velocity of 1.2h -1 , catalyst loading 20t. The composition of the reaction product is shown in Table 1.

[0057] Table 1 Reaction product composition

[0058] composition wt% hydrogen 7.28％ Methanol 0.02％ Ethanol 0.03％ acetone 0.13％ Isopropyl alcohol 2.34％ n-Propanol 5.16％ 1,2-Propanediol 1.94％ 1,3-Propanediol 12.05％ glycerin 35.76％ water 35.28％

[0059] (2) Reaction process: After the reaction, the product enters the hot high-pressure gas-liquid separation tank after heat exchange. The top gas phase enters the cold high-pressure gas-liquid separation tank after cooling to 40°C. The bottom liquid phase is mixed with the bottom liquid phase of the cold high-pressure gas-liquid separation tank and enters the separation process. The top gas phase of the cold high-pressure gas-liquid separation tank is hydrogen for recycling.

[0060] (3) Separation process: The mixed liquid phase enters the de-azeotrope tower (tower top pressure 0.12 MPa, tower top temperature 109°C, reflux ratio 1, tower bottom pressure 0.14 MPa, tower bottom temperature 137°C), and the low-alcohol (ethanol, isopropanol, n-propanol) water azeotrope is separated at the top of the tower. The bottom of the tower is reorganized into a mixture of water, 1,2-propylene glycol, 1,3-propylene glycol, and unreacted glycerol. The low-alcohol-water azeotrope is preheated by the bottom material of the solvent regeneration tower and then enters the extractive distillation tower (tower top pressure 0.1MPa, tower top temperature 112°C, reflux ratio 0.5, tower bottom pressure 0.12MPa, tower bottom temperature 187°C), ethylene glycol is selected as the extractant, and a low-alcohol (methanol, ethanol, isopropanol, n-propanol) mixture is obtained at the top of the tower. The bottom of the tower is ethylene glycol aqueous solution which enters the solvent regeneration tower for dehydration treatment (tower top pressure -0.05MPa, tower top temperature 83°C, reflux ratio 1, tower bottom pressure -0.03MPa, tower bottom temperature 186°C). Water is sent out from the top of the tower, and the bottom of the tower is the regenerated extractant for recycling after heat exchange. The low-alcohol mixture at the top of the extractive distillation tower enters the n-propanol removal tower (tower top pressure 0.2MPa, tower top temperature 111°C, reflux ratio 11, tower bottom pressure 0.21MPa, tower bottom temperature 131°C), the tower bottom is n-propanol, and the tower top is the isopropanol mixture entering the isopropanol removal tower (tower top pressure 0.25MPa, tower top temperature 111°C, reflux ratio 20, tower bottom pressure 0.27MPa, tower bottom temperature 119°C), the tower bottom is isopropanol, and the tower top is light components (methanol, ethanol, acetone, etc.). Among them: the purity of isopropanol and n-propanol products is more than 99.95%. The material composition of each separation tower is shown in Table 2.

[0061] Table 2 Material composition of each separation tower

[0062]

[0063] (4) Separation process: The recombinant components at the bottom of the de-azeotrope tower are water, 1,2-propylene glycol, 1,3-propylene glycol, and a mixture of unreacted glycerol. The recombinant components enter the high-pressure dehydration tower (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 tower bottom solution enters the low-pressure dehydration tower (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 gas phase heat recovery at the top of the tower is thermally coupled with the low-pressure dehydration tower as the heat source at the bottom of the low-pressure dehydration tower. The top of the tower is all water, and the bottom of the low-pressure dehydration tower is the polyol solution. Enter the 1,2-propylene glycol removal tower (tower top pressure -0.09MPa, tower top temperature 128℃, reflux ratio 13, tower bottom pressure -0.07MPa, tower bottom temperature 209℃), 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. Enter the 1,3-propylene glycol removal tower (tower top pressure -0.08MPa, tower top temperature 169℃, reflux ratio 0.7, tower bottom pressure -0.06MPa, tower bottom temperature 256℃), 1,3-propylene glycol is obtained at the top of the tower, and the bottom of the tower is unreacted glycerol. Among them: the water and glycerol are recycled, and the purity of 1,2-propylene glycol and 1,3-propylene glycol products is more than 99.95%. The material composition of each separation tower is shown in Table 3.

[0064] Table 3 Material composition of each separation tower

[0065]

[0066] Example 2

[0067] See the schematic diagram of the integrated extractive distillation method for producing 1,3-propylene glycol provided in this embodiment. Figure 2 As shown, the specific steps are as follows:

[0068] Steps (1) to (3) are the same as those in Example 1, except that they are different from those in Example 1 as follows:

[0069] Step (4) separation process: The bottom of the low-pressure dehydration tower is a polyol mixed solution entering a deglycerol tower (tower top pressure -0.08MPa, tower top temperature 165°C, reflux ratio 0.6, tower bottom pressure -0.06MPa, tower bottom temperature 256°C), the unreacted glycerol is separated from the bottom of the tower for recycling, and the top of the tower is a mixture of 1,2-propylene glycol and 1,3-propylene glycol entering a glycol separation tower (tower top pressure -0.09MPa, tower top temperature 128°C, reflux ratio 6, tower bottom pressure -0.07MPa, tower bottom temperature 178°C), the top of the tower is 1,2-propylene glycol, and the bottom of the tower is 1,3-propylene glycol. Wherein, the purity of the 1,2-propylene glycol and 1,3-propylene glycol products is more than 99.95%. The material composition of each separation tower is shown in Table 4.

[0070] Table 4 Material composition of each separation tower

[0071]

[0072]

[0073] Example 3

[0074] See the schematic diagram of the integrated extractive distillation method for producing 1,3-propylene glycol provided in this embodiment. Figure 3 As shown, the specific steps are as follows:

[0075] Steps (1) to (3) are the same as those in Example 1, except that they are different from those in Example 1 as follows:

[0076] Step (4) separation process: The heavy components at the bottom of the azeotrope removal tower (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) are water, 1,2-propylene glycol, 1,3-propylene glycol, and a mixture of unreacted glycerol. The heavy components enter the deglycerolization tower (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), and the unreacted glycerol is separated from the bottom of the tower for recycling. The top of the tower is part of the water, and the side line is drawn out as a mixed solution of water, 1,2-propylene glycol, and 1,3-propylene glycol. The mixture drawn out from the side line enters the dehydration tower (tower top pressure -0.09 MPa, tower top temperature 48°C, reflux ratio 0.3, tower bottom pressure -0.06 MPa, tower bottom temperature 256°C). Ratio 1, tower bottom pressure -0.07MPa, tower bottom temperature 170℃), the water separated from the top of the tower is mixed with the water from the top of the deglycerol tower and then recycled, and the bottom of the tower is a mixture of 1,2-propylene glycol and 1,3-propylene glycol entering the glycol separation tower (tower top pressure -0.09MPa, tower top temperature 128℃, reflux ratio 6, tower bottom pressure -0.07MPa, tower bottom temperature 178℃), the top of the tower is 1,2-propylene glycol, and the bottom of the tower is 1,3-propylene glycol. Among them: the purity of the 1,2-propylene glycol and 1,3-propylene glycol products is more than 99.95%. The material composition of each separation tower is shown in Table 5.

[0077] Table 5 Material composition of each separation tower

[0078]

[0079] It can be seen from Tables 2, 3, 4 and 5 that the production method of 1,3-propylene glycol by integrated extraction and distillation provided by the present invention adopts a trickle bed tubular reactor and an integrated extraction and distillation separation process, which can produce a high-purity alcohol product. The entire process is not affected by the concentration of the glycerol raw material, and can achieve efficient and continuous production of 1,3-propylene glycol.

[0080] In summary, the integrated extraction and distillation production method of 1,3-propylene glycol provided by the present invention adopts a combination of a specific reaction process and a specific separation process to achieve overall good interaction. The reaction process realizes continuous operation through a high-efficiency catalyst and a trickle bed tubular reactor, has high production efficiency, and the reaction heat is recycled. The separation process integrates extraction distillation and heat coupling, which not only removes the concentration limit of the glycerol raw material, but also breaks the low-alcohol water azeotrope to achieve the separation of alcohol-water azeotropes. The extractant can be recycled and reused, the operating energy consumption is low, and it is easy to promote industrialization. In addition, the production method provided by the present invention can obtain high-index 1,3-propylene glycol, and can also separate products such as isopropanol, n-propanol, and 1,2-propylene glycol, and the purity of each separated product is above 99.95%.

[0081] 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 producing 1,3-propylene glycol by integrated extraction and distillation, comprising the following steps: a) subjecting a glycerol solution and hydrogen to a hydrogenation reaction in the presence of a catalyst to obtain a reaction product; and then subjecting the reaction product to gas-liquid separation to obtain a liquid product and hydrogen, respectively; wherein the hydrogen is recycled; b) distilling the liquid product obtained in step a) to obtain an azeotrope at the top of the tower and a heavy component at the bottom of the tower; c) dehydrating the azeotrope obtained from the top of the tower in step b) by extractive distillation and solvent regeneration, and then passing through a n-propanol removal tower and an isopropanol removal tower in sequence to obtain n-propanol, isopropanol and light components, respectively; d) the heavy components obtained at the bottom of the tower in step b) 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 are recycled.

2. The method for producing 1,3-propylene glycol by integrated extractive distillation according to claim 1, characterized in that: The mass concentration of the glycerol solution in step a) is 10% to 90%; the solvent of the glycerol solution is selected from one or more of water, methanol and ethanol.

3. The method for producing 1,3-propylene glycol by integrated extractive distillation according to claim 1, characterized in that: The catalyst in step a) is selected from one or more of a Pt-W catalyst, an Ir-Re catalyst, and a Pt-molecular sieve catalyst.

4. The method for producing 1,3-propylene glycol by integrated extractive distillation according to claim 1, characterized in that: In step a), the hydrogen gas controls the hydrogen-to-oil ratio to be 500-1500; the catalyst controls the liquid hourly space velocity to be 0.8h -1 ~1.6h -1 .

5. The method for producing 1,3-propylene glycol by integrated extractive distillation according to claim 1, characterized in that: The hydrogenation reaction process in step a) adopts a trickle bed fixed bed reactor, a trickle bed tubular reactor or a bubbling reactor; the temperature of the hydrogenation reaction is 100° C. to 200° C., and the pressure is 0.5 MPa to 10 MPa.

6. The method for producing 1,3-propylene glycol by integrated extractive distillation according to claim 1, characterized in that: The gas-liquid separation process in step a) is specifically as follows: The reaction product is first 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 component, respectively. The gas phase component is further cooled and then subjected to cold high-pressure gas-liquid separation to obtain hydrogen and a second liquid phase component, respectively. The first liquid phase component and the second liquid phase component are mixed and used as feed for subsequent distillation separation. The hydrogen is recycled.

7. The method for producing 1,3-propylene glycol by integrated extractive distillation according to claim 1, characterized in that: The distillation process in step b) adopts a deazeotrope tower with a top pressure of 0.10MPa-0.15MPa, a top temperature of 108-110°C, a reflux ratio of 0.8-1.2, a bottom pressure of 0.10MPa-0.15MPa, and a bottom temperature of 130°C-140°C.

8. The method for producing 1,3-propylene glycol by integrated extractive distillation according to claim 1, characterized in that: The step c) is specifically as follows: The azeotrope obtained at the top of step b) enters an extractive distillation tower for extractive distillation, a low-alcohol mixture is obtained at the top of the tower, and an extractant solution is obtained at the bottom of the tower; wherein the extractant solution enters a solvent regeneration tower, water is removed at the top of the tower, and the bottom of the tower is the regenerated extractant, which enters the extractive distillation tower for recycling; the low-alcohol mixture enters a depropanolation tower, n-propanol is obtained at the bottom of the tower, an isopropanol mixture is obtained at the top of the tower, and enters a deisopropanolation tower, light components are obtained at the top of the tower, and isopropanol is obtained at the bottom of the tower.

9. The method for producing 1,3-propylene glycol by integrated extractive distillation according to claim 8, characterized in that: The extractant is selected from one or more of butanediol, propylene glycol, ethylene glycol and dimethyl sulfoxide.

10. The method for producing 1,3-propylene glycol by integrated extractive distillation according to claim 1, characterized in that: The step d) is specifically: The heavy component obtained at the bottom of the tower in step b) enters a high-pressure dehydration tower, and the solution at the bottom of the tower enters a low-pressure dehydration tower. The gas phase at the top of the tower is thermally coupled with the low-pressure dehydration tower as a heat source at the bottom of the low-pressure dehydration tower, and water is obtained at the top of the tower. The bottom of the tower is a polyol solution, which 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, which 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; wherein the water and glycerol are recycled.

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