Continuous synthesis method of dipropylene glycol and device thereof

Abstract

The invention belongs to the field of synthesis of dipropylene glycol, and discloses a continuous synthesis method and device of dipropylene glycol, and the continuous synthesis method comprises the following steps: mixing a raw material propylene glycol and a raw material epoxypropane, feeding into a preheater, heating to a preset reaction temperature, feeding into a multi-tube reactor, and carrying out an addition reaction in the multi-tube reactor; the multi-tube reactor is selectively filled with a heterogeneous catalyst, a feeding pipeline of the raw material propylene glycol is connected with the catalyst preparation kettle and then is mixed with the raw material epoxypropane, and the catalyst preparation kettle is selectively filled with a homogeneous catalyst; the method comprises the following steps: carrying out an addition reaction on a raw material propylene glycol and a raw material propylene oxide under the catalytic action of a heterogeneous catalyst and / or a homogeneous catalyst to obtain a dipropylene glycol reaction product; the preparation process is simple and efficient, and the dipropylene glycol product with the freezing point temperature lower than-40 DEG C and the isomer A content smaller than or equal to 35% can be reliably obtained after the obtained dipropylene glycol reaction product is subjected to subsequent rectification treatment.

Description

Technical Field

[0001] This invention belongs to the field of synthesis of dipropylene glycol, specifically relating to a continuous synthesis method and apparatus for dipropylene glycol. Background Technology

[0002] LO+ grade dipropylene glycol is a high-purity solvent suitable for use in the fragrance and / or flavoring industry. In the standard HG / T5799-2021 "Dipropylene Glycol", the corresponding grade is fragrance and flavor type. Its quality requirements are: dipropylene glycol content not less than 99.7%, propylene glycol content not more than 0.2%, tripropylene glycol content not more than 0.1%, acidity (calculated as acetic acid) not more than 0.0030%, moisture not more than 0.1%, and total iron content not more than 1 mg / kg. Although the standard does not specify the freezing point and high-temperature color change of dipropylene glycol products, the applicant found that although the dipropylene glycol produced by the existing technology meets the standard requirements for flavor and fragrance type dipropylene glycol, its application is limited due to unreasonable values ​​of some indicators. Specifically, the freezing point of dipropylene glycol produced by the existing process is often higher than -40°C, which makes it unusable in cold winter regions when used as a solvent for flavor and fragrance formulations. In addition, some dipropylene glycol produced by the existing technology has a sharp increase in color after being stored in a high-temperature environment for a certain period of time, resulting in a deterioration in quality and making it unusable.

[0003] The applicant carefully investigated the cause of the above problem, which is due to the fact that dipropylene glycol has three isomers. Based on the industry standard classification, their properties are compared as shown in Table 1 below:

[0004] As can be seen from Table 1 above, since isomer A has a high crystallization point of 65℃, it is difficult to use normally when the content of isomer A in the dipropylene glycol mixture is higher than 40%.

[0005] Therefore, the applicant seeks a continuous synthesis process for dipropylene glycol to reliably achieve the requirement that the content of isomer A in the obtained dipropylene glycol product is not higher than 40%. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a continuous synthesis method and apparatus for dipropylene glycol, which does not require the use of expensive ionic liquid catalysts, and the preparation process is simple and efficient. The dipropylene glycol reaction product obtained can be reliably obtained as a dipropylene glycol product with a freezing point temperature of less than -40°C and a content of isomer A ≤35% after subsequent distillation treatment. It is especially suitable for use as a flavoring and fragrance type of dipropylene glycol.

[0007] The technical solution adopted in this invention is as follows: A continuous synthesis method for dipropylene glycol involves mixing propylene glycol and propylene oxide, heating the mixture to a preset reaction temperature in a preheater, and then introducing it into a multi-tube reactor where an addition reaction occurs. The multi-tube reactor is selectively packed with a heterogeneous catalyst, and the propylene glycol feed line is connected to a catalyst preparation vessel for mixing with the propylene oxide. The catalyst preparation vessel is selectively filled with a homogeneous catalyst. The addition reaction between propylene glycol and propylene oxide is carried out under the catalysis of a heterogeneous catalyst and / or a homogeneous catalyst to obtain dipropylene glycol as the reaction product.

[0008] Preferably, the heterogeneous catalyst is a high-temperature resistant cation exchange resin; and / or the homogeneous catalyst is aminosulfonic acid or p-toluenesulfonic acid.

[0009] Preferably, the feed molar ratio of propylene glycol (PG) to propylene oxide (PO) is 2-5:1. The mass hourly space velocity (MHSV) of the raw material feed is 1-6 h. -1 .

[0010] Preferably, the reaction pressure in the multi-tube reactor is set to 0.02-0.4 MPa, and the reaction temperature is set to 85-140℃.

[0011] Preferably, after the dipropylene glycol reaction product is fed into a light distillation tower for light distillation, the bottom material of the light distillation tower is fed into a heavy distillation tower for heavy distillation; then the top gas phase of the heavy distillation tower is condensed, and a portion of the condensed phase is collected as the dipropylene glycol product.

[0012] Preferably, the operating pressure of the light-weight removal tower is -0.099 to -0.095 MPa, and the operating reflux ratio is 1-4:1; the operating pressure of the heavy-weight removal tower is -0.099 to -0.097 MPa, and the operating reflux ratio is 1-4:1.

[0013] Preferably, this application also proposes an apparatus for the continuous synthesis of dipropylene glycol according to the above-described method (i.e., a continuous synthesis apparatus for dipropylene glycol), comprising a propylene glycol feed line, a propylene oxide feed line, a catalyst preparation vessel, a pipeline material mixer, a preheater, and a multi-tube reactor; wherein, The raw material propylene oxide feed pipeline is connected to the pipeline material mixer; the raw material propylene glycol feed pipeline is connected to the catalyst preparation vessel, and the discharge port of the catalyst preparation vessel is connected to the pipeline material mixer through the raw material propylene glycol conveying pipeline. The pipeline material mixer preheats the material through the preheater before connecting it to the multi-tube reactor.

[0014] Preferably, a catalyst silo is installed at the upper end of the catalyst preparation vessel; wherein, a catalyst weighing module is provided in the catalyst silo, and a feeding gear is installed in the connecting channel between the catalyst silo and the catalyst preparation vessel, and the feeding gear is driven by a servo motor that is communicatively connected to the control module.

[0015] Preferably, a material agitator is installed in the catalyst silo; a propylene glycol flow meter and a propylene glycol regulating valve are installed in the propylene glycol feed pipeline; and a propylene oxide flow meter and a propylene oxide regulating valve are installed in the propylene oxide feed pipeline.

[0016] Preferably, the propylene glycol pipeline is equipped with a propylene glycol delivery pump, a propylene glycol regulating valve, and a propylene glycol flow meter.

[0017] Preferably, the preheater is provided with a preheater heat circulation jacket, which is connected to the steam condensate output pipeline and the low-pressure steam input pipeline respectively; the multi-tube reactor is provided with a reactor heat circulation jacket, which is connected to the heat extraction refrigerant supply pipeline and the heat extraction heat medium return pipeline respectively.

[0018] Preferably, the material connection pipeline between the preheater and the multi-tube reactor is equipped with a preheated material thermometer, and the multi-tube reactor is equipped with a material thermometer inside the reaction tube.

[0019] Preferably, the reactor outlet material thermometer and reactor pressure regulating valve are respectively installed on the reaction product discharge pipeline of the multi-tube reactor.

[0020] Preferably, the reaction product discharge pipeline of the multi-tube reactor is connected to the light-weight removal tower, the bottom material pipeline of the light-weight removal tower is connected to the heavy-weight removal tower, the top gas phase outlet of the heavy-weight removal tower is connected to the heavy-weight removal tower condenser, and the condensate phase outlet of the heavy-weight removal tower refluxes to the top of the heavy-weight removal tower in one direction, and serves as the product collection end of dipropylene glycol in the other direction.

[0021] Preferably, the vapor outlet at the top of the light-light-removal tower is connected to the light-light-removal tower condenser, and the condensate outlet of the light-light-removal tower condenser flows back to the top of the light-light-removal tower in one direction and back to the feed line of the raw material propylene glycol in another direction; and the bottom of the light-light-removal tower is connected to the light-light-removal tower reboiler for reboiling the bottom material of the light-light-removal tower.

[0022] Preferably, the bottom of the deweighting tower is connected to a deweighting tower reboiler for reboiling the bottom material of the deweighting tower, and the bottom of the deweighting tower continuously collects the heavy components of the deweighting tower, which are then connected to a mixed alcohol collection device or other devices for the purification of tripropylene glycol.

[0023] It should be noted that isomer A, as referred to throughout this application, refers to bis(1-methyl-2-hydroxyethyl) ether, CAS number 108-61-2; PO, as referred to throughout this application, refers to propylene oxide, PG to propylene glycol, and DPG to dipropylene glycol condensate.

[0024] This application proposes a continuous synthesis method for dipropylene glycol under catalysis using specific heterogeneous catalysts and specific homogeneous catalysts, either separately or in combination. As needed, the specific heterogeneous catalyst is selectively loaded into a multi-tube reactor, and the specific homogeneous catalyst is selectively loaded into a catalyst preparation vessel. This eliminates the need for expensive ionic liquid catalysts, and the preparation process is simple and efficient. The resulting dipropylene glycol reaction product can be reliably obtained after subsequent distillation, with a freezing point temperature below -40°C and a content of isomer A ≤35%. This method is particularly suitable for use as a flavoring and fragrance type of dipropylene glycol. This application proposes a continuous synthesis apparatus for dipropylene glycol, which can meet the requirements of continuous synthesis of dipropylene glycol by using heterogeneous catalysts and homogeneous catalysts separately or in combination. In practice, batch operation can also be flexibly selected. The continuous synthesis apparatus proposed in this application has a simple structure and can use heterogeneous catalysts and homogeneous catalysts separately or in combination to achieve efficient synthesis. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the continuous synthesis apparatus for dipropylene glycol used in the specific embodiments of this application (the light-removal tower T1 and the heavy-removal tower T2 are not shown). Figure 2 yes Figure 1 Schematic diagram of the structure of the multi-tube reactor R401; Figure 3 This is a schematic diagram of the connection structure between the light-weight removal tower and the heavy-weight removal tower in a specific embodiment of this application. Detailed Implementation

[0026] Please see Figure 1 , Figure 2 and Figure 3As shown, this embodiment proposes a continuous synthesis apparatus for dipropylene glycol, including a propylene glycol feed line S101, a propylene oxide feed line S103, a catalyst preparation vessel P14, a pipeline material mixer P15, a preheater E301, and a multi-tube reactor R401; wherein, the propylene oxide feed line S103 is connected to the pipeline material mixer P15; the propylene glycol feed line S101 is connected to the catalyst preparation vessel P14, and the outlet port of the catalyst preparation vessel P14 is connected to the pipeline material mixer P15 through the propylene glycol conveying line S102; the pipeline material mixer P15 is preheated by the preheater E301 before being connected to the multi-tube reactor R401.

[0027] Preferably, in this embodiment, a catalyst silo P2 is installed at the upper end of the catalyst preparation vessel P14; wherein, a catalyst weighing module P1 is provided in the catalyst silo P2, and a feeding gear P5 is installed in the connecting channel between the catalyst silo P2 and the catalyst preparation vessel P14, and the feeding gear P5 is driven by a servo motor P4 that is communicatively connected to the control module P3.

[0028] Preferably, in this embodiment, a material agitator P6 is installed in the catalyst silo P2; a propylene glycol flow meter P7 and a propylene glycol regulating valve P8 are installed in the propylene glycol feed pipeline S101; a propylene oxide flow meter P9 and a propylene oxide regulating valve P10 are installed in the propylene oxide feed pipeline S103; and a propylene glycol transfer pump P11, a propylene glycol regulating valve P12, and a propylene glycol flow meter P13 are installed in the propylene glycol delivery pipeline S102.

[0029] Preferably, in this embodiment, the preheater E301 is provided with a preheater heat circulation jacket, which is connected to the steam condensate output pipeline S201 and the low-pressure steam input pipeline S202 respectively; the multi-tube reactor R401 is provided with a reactor heat circulation jacket, which is connected to the heat extraction refrigerant supply pipeline S203 and the heat extraction heat medium return pipeline S204 respectively; preferably, in this embodiment, the material connection pipeline S104 between the preheater E301 and the multi-tube reactor R401 is equipped with a preheated material thermometer T501, and the multi-tube reactor R401 is equipped with a reaction tube material thermometer T502; the reaction product discharge pipeline S107 of the multi-tube reactor R401 is equipped with a reactor outlet material thermometer PT601 and a reactor pressure regulating valve P16 respectively.

[0030] Preferably, in this embodiment, the reaction product discharge pipeline S107 of the multi-tube reactor R401 is connected to the light-weight removal tower T1, the bottom material pipeline S301 of the light-weight removal tower T1 is connected to the heavy-weight removal tower T2, the top gas phase outlet of the heavy-weight removal tower T2 is connected to the heavy-weight removal tower condenser C2, and the condensate phase outlet of the heavy-weight removal tower condenser C2 flows back to the top of the heavy-weight removal tower T2 in one direction, and serves as the product collection end S302 of the dipropylene glycol monohydrate. More preferably, in this embodiment, the gas phase outlet at the top of the light-weight removal tower T1 is connected to the light-weight removal tower condenser C1, and the condensate phase outlet of the light-weight removal tower condenser C1 flows back to the top of the light-weight removal tower T2 in one direction and back to the raw material propylene glycol feed line S101 in the other direction; and the bottom of the light-weight removal tower T1 is connected to the light-weight removal tower reboiler R1 for reboiling the bottom material of the light-weight removal tower T1; the bottom of the heavy-weight removal tower is connected to the heavy-weight removal tower reboiler R2 for reboiling the bottom material of the heavy-weight removal tower T2, and the heavy components of the heavy-weight removal tower are continuously collected from the bottom of the heavy-weight removal tower T2 and connected to a mixed alcohol collection device or other devices for the purification of tripropylene glycol.

[0031] This embodiment proposes a continuous synthesis method for dipropylene glycol. Propylene glycol (PG) and propylene oxide (PO) are mixed and heated to a preset reaction temperature in a preheater, then fed into a multi-tube reactor where an addition reaction occurs. The multi-tube reactor is selectively filled with a heterogeneous catalyst, and the feed line of propylene glycol (PG) is connected to a catalyst preparation vessel for mixing with propylene oxide (PO). The catalyst preparation vessel selectively contains a homogeneous catalyst. The propylene glycol (PG) and propylene oxide (PO) undergo an addition reaction under the catalysis of the heterogeneous catalyst and / or a homogeneous catalyst to obtain the dipropylene glycol product. Particularly preferably, in this embodiment, the heterogeneous catalyst is a high-temperature resistant cation exchange resin; and / or the homogeneous catalyst is aminosulfonic acid or p-toluenesulfonic acid. More preferably, the mass ratio of the homogeneous catalyst to propylene glycol (PG) is 0.5-2%, more preferably 0.8-1.5%.

[0032] Preferably, in this embodiment, the feed molar ratio of propylene glycol (PG) to propylene oxide (PO) is 2-5:1, more preferably 2.5-4:1; the feed mass hourly space velocity (WHSV) is 1-6 h⁻¹. -1 More preferably 2-4h -1 Preferably, in this embodiment, the reaction pressure inside the multi-tube reactor is set to 0.02-0.4 MPa, more preferably 0.05-0.35 MPa; and the reaction temperature is set to 85-140°C, more preferably 100-130°C.

[0033] Preferably, in order to achieve post-distillation processing of the dipropylene glycol reaction product, in this embodiment, the dipropylene glycol reaction product is fed into a light-light distillation tower for light-light distillation (the light components collected at the top of the tower are propylene oxide and propylene glycol), and the bottom material of the light-light distillation tower is fed into a heavy-light distillation tower for heavy-light distillation. Then, the vapor phase at the top of the heavy-light distillation tower is condensed, and a portion of the condensed phase is collected as dipropylene glycol product, while tripropylene glycol and other heavy components are collected from the bottom of the tower. More preferably, in this embodiment, the operating pressure of the light-light distillation tower is -0.099 to -0.095 MPa, and the operating reflux ratio is 1-4:1; the operating pressure of the heavy-light distillation tower is -0.099 to -0.097 MPa, and the operating reflux ratio is 1-4:1.

[0034] The working process of the relevant structural device is further explained in conjunction with the technical solutions of the embodiments of this application: When a homogeneous catalyst is required for catalysis, it is dissolved in propylene glycol in catalyst preparation vessel P14. The propylene glycol flows into catalyst preparation vessel P14 through raw material propylene glycol feed pipeline S101, propylene glycol regulating valve P8, and propylene glycol flow meter P7. The homogeneous catalyst, in liquid or solid powder / particle form, is pre-placed in catalyst silo P2 and weighed by weighing module P1. Then, under the control of control module P3, servo motor P4 and feed gear P5 continuously add the homogeneous catalyst to catalyst preparation vessel P14, where it is thoroughly mixed with propylene glycol under the stirring action of material agitator P6. It should be noted that when a homogeneous catalyst is not required for catalysis, catalyst preparation vessel P14 is only used as a temporary storage channel for propylene glycol, and catalyst silo P2 and its related modules are not used. After the homogeneous catalyst and propylene glycol are thoroughly mixed, the raw material propylene glycol is conveyed to the pipeline material mixer P15 via the propylene glycol conveying pipeline S102, propylene glycol conveying pump P11, propylene glycol regulating valve P12, and propylene glycol flow meter P13. The propylene glycol is then fully mixed with the propylene oxide conveyed to the pipeline material mixer P15 via the raw material propylene oxide feed pipeline S103, propylene oxide flow meter P9, and propylene oxide regulating valve P10. The mixed materials then enter the tube side of the preheater E301. Low-pressure steam is circulated in the preheater heat circulation jacket located outside the tube side of the preheater E301 to heat the materials. The temperature is measured and indicated by the preheated material temperature gauge T501 installed on the material connection pipeline S104. The material is preheated to the preset reaction temperature by the preheater E301 and then transported to the multi-tube reactor R401 through the material connection pipeline S104. When a heterogeneous catalyst is required for catalysis, the multi-tube reactor R401 is filled with a heterogeneous catalyst (when a heterogeneous catalyst is not required, the multi-tube reactor R401 is not filled with a heterogeneous catalyst). The material temperature in the multi-tube reactor R401 is measured and indicated by the material temperature gauge T502 inserted into the reaction tube. The heat released by the reaction is carried out by the refrigerant material S106 located in the reactor's thermal circulation jacket. Specifically, heat extraction is achieved through the heat extraction refrigerant supply pipeline S203 and the heat extraction heat return pipeline S204. The reaction pressure in the multi-tube reactor R401 is regulated by the reactor pressure regulating valve P16.

[0035] This embodiment also proposes a dipropylene glycol, which is obtained by the continuous synthesis method and apparatus for dipropylene glycol according to the above-described method. The content of isomer A in the obtained dipropylene glycol product is ≤35%, and its freezing point temperature is below -40°C.

[0036] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0037] Based on the above-described implementation schemes, this application further proposes the following specific embodiments: It should be noted that, unless otherwise specified, the raw materials used in the following specific embodiments of the present invention are all commercially available products.

[0038] It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0039] Example 1: Based on the above implementation scheme, the specific specifications of the multi-tube reactor R401 in Example 1 are as follows: a multi-tube vertical reactor with an inner diameter of 400mm, tube specifications of φ38*3.0, tube length of 2.5 meters, and calculated flow area of ​​0.041m². 2 The tube is filled with 100 liters of high-temperature resistant strong acid cation exchange resin (provided by a domestic manufacturer as a heterogeneous catalyst). The heterogeneous catalyst has a dry basis density of 0.6 kg / L and a mass of 60 kg. In this example 1, a homogeneous catalyst is not required for catalysis. The catalyst preparation vessel P14 is only used as a temporary storage channel for propylene glycol. The catalyst silo P2 and its related modules are not used. The following is the continuous synthesis process of Example 1: The PO feed flow rate was 19.2 kg / h (0.33 kmol / h), the PG feed flow rate was 100.8 kg / h (1.326 kmol / h), the feed alcohol-to-cyclic molar ratio was approximately 4:1, and the feed mass hourly space velocity (HHSV) was 2 h⁻¹. -1 After preheating, the material temperature was 123℃, the bed temperature of the tubular reactor R401 was 125℃, the reaction pressure was 0.2MPa, and the PO conversion rate reached 99.9%. The operating pressure of dehydrogenation tower T1 is -0.099 MPa, and the operating reflux ratio is 3.0; the operating pressure of heavy metal removal tower T2 is -0.099 MPa, and the operating reflux ratio is 2.5. The flow rate of dipropylene glycol (DPG) product collected from the top of the deweighting tower was 3.77 kg / h, the DPG selectivity reached 85.0%, the content of isomer A in the DPG was 23.1%, the product freezing point was -45℃, and it was odorless, meeting the requirements of flavor and fragrance type DPG.

[0040] Example 2: The remaining technical solutions of Example 2 are the same as those of Example 1, except that the continuous synthesis process of Example 2 is as follows: The PO feed flow rate was 24.0 kg / h (0.414 kmol / h), the PG feed flow rate was 126.0 kg / h (1.658 kmol / h), the feed alcohol-to-cyclic molar ratio was approximately 4.05:1, and the feed mass hourly space velocity (HHSV) was 2.5 h⁻¹. -1 After preheating, the material temperature was 118℃, the bed temperature of the tubular reactor R401 was 118℃, the reaction pressure was 0.15MPa, and the PO conversion rate reached 99.8%. The operating pressure of dehydrogenation tower T1 is -0.098 MPa, and the operating reflux ratio is 2.5; the operating pressure of heavy metal removal tower T2 is -0.099 MPa, and the operating reflux ratio is 2.05. The flow rate of dipropylene glycol (DPG) collected from the top of the deweighting tower was 4.77 kg / h, the DPG selectivity reached 86.0%, the content of isomer A in the DPG was 24.1%, the product freezing point was -44℃, and it was odorless, meeting the requirements of flavor and fragrance type DPG.

[0041] Example 3: The remaining technical solutions of Example 3 are the same as those of Example 1, except that the continuous synthesis process of Example 3 is as follows: The PO feed flow rate was 28.8 kg / h (0.497 kmol / h), the PG feed flow rate was 151.2 kg / h (1.989 kmol / h), the feed alcohol-to-cyclic molar ratio was approximately 4.00:1, and the feed mass hourly space velocity (HHSV) was 3 h⁻¹. -1After preheating, the material temperature was 106℃, the bed temperature of the tubular reactor R401 was 105℃, the reaction pressure was 0.21MPa, and the PO conversion rate reached 99.7%. The operating pressure of dehydrogenation tower T1 is -0.097 MPa, and the operating reflux ratio is 3.0; the operating pressure of heavy metal removal tower T2 is -0.099 MPa, and the operating reflux ratio is 2.8. The flow rate of dipropylene glycol (DPG) product collected from the top of the deweighting tower was 5.68 kg / h, the DPG selectivity reached 85.5%, the content of isomer A in the DPG was 22.0%, the product freezing point was -46℃, and it was odorless, meeting the requirements of flavor and fragrance type DPG.

[0042] Example 4: The remaining technical solutions of Example 4 are the same as those of Example 1, except that the continuous synthesis process of Example 4 is as follows: The PO feed flow rate was 38.5 kg / h (0.664 kmol / h), the PG feed flow rate was 201.5 kg / h (2.651 kmol / h), the feed alcohol-to-cyclic molar ratio was approximately 3.99:1, and the feed mass hourly space velocity (HHSV) was 4 h⁻¹. -1 After preheating, the material temperature was 127℃, the bed temperature of the tubular reactor R401 was 128℃, the reaction pressure was 0.16MPa, and the PO conversion rate reached 99.6%. The operating pressure of dehydrogenation tower T1 is -0.098 MPa, and the operating reflux ratio is 2.8; the operating pressure of heavy metal removal tower T2 is -0.099 MPa, and the operating reflux ratio is 2.2. The flow rate of dipropylene glycol (DPG) collected from the top of the deweighting tower was 7.62 kg / h, the DPG selectivity reached 86.1%, the content of isomer A in the DPG was 21.0%, the product freezing point was -44℃, and it was odorless, meeting the requirements of flavor and fragrance type DPG.

[0043] Example 5: The remaining technical solutions of Example 5 are the same as those of Example 1, except that the continuous synthesis process of Example 5 is as follows: The PO feed flow rate was 36.5 kg / h (0.629 kmol / h), the PG feed flow rate was 143.5 kg / h (1.888 kmol / h), the feed alcohol-to-cyclic molar ratio was approximately 3.00:1, and the feed mass hourly space velocity (MHSV) was 3 h⁻¹. -1 After preheating, the material temperature was 127℃, the bed temperature of the tubular reactor R401 was 110℃, the reaction pressure was 0.19MPa, and the PO conversion rate reached 99.4%. The operating pressure of dehydrogenation tower T1 is -0.098 MPa, and the operating reflux ratio is 2.4; the operating pressure of heavy metal removal tower T2 is -0.099 MPa, and the operating reflux ratio is 2.3. The flow rate of dipropylene glycol (DPG) product collected from the top of the deweighting tower was 7.16 kg / h, the DPG selectivity reached 85.4%, the content of isomer A in the DPG was 22.0%, the product freezing point was -43℃, and it was odorless, meeting the requirements of flavor and fragrance type DPG.

[0044] Example 6: The remaining technical solutions of Example 6 are the same as those of Example 1, except that the continuous synthesis process of Example 6 is as follows: The PO feed flow rate was 48.7 kg / h (0.840 kmol / h), the PG feed flow rate was 191.3 kg / h (2.517 kmol / h), the feed alcohol-to-cyclic molar ratio was approximately 3.00:1, and the feed mass hourly space velocity (MHSV) was 4 h⁻¹. -1 After preheating, the material temperature was 117℃, the bed temperature of the tubular reactor R401 was 118℃, the reaction pressure was 0.27MPa, and the PO conversion rate reached 99.2%. The operating pressure of dehydrogenation tower T1 is -0.099 MPa, and the operating reflux ratio is 2.1; the operating pressure of heavy metal removal tower T2 is -0.099 MPa, and the operating reflux ratio is 2.7. The flow rate of dipropylene glycol (DPG) collected from the top of the deweighting tower was 9.53 kg / h, the DPG selectivity reached 85.4%, the content of isomer A in the DPG was 24.3%, the product freezing point was -42℃, and it was odorless, meeting the requirements of flavor and fragrance type DPG.

[0045] Example 7: Based on the above implementation scheme, the specific specifications of the multi-tube reactor R401 in Example 7 are as follows: a multi-tube vertical reactor with an inner diameter of 400mm, tube specifications of φ38*3.0, tube length of 2.5 meters, and a calculated internal flow area of ​​0.041m². 2 In this embodiment 7, heterogeneous catalysts are not required for catalysis. Therefore, the multi-tube reactor R401 is an empty tube and is not filled with any catalyst. The volume of the multi-tube reactor R401 is 102.5 liters. The catalyst preparation vessel P14 serves as the catalyst preparation container, and the catalyst silo P2 and its related modules are put into operation as designed. The following is the continuous synthesis process of Example 7: The PO feed flow rate was 19.2 kg / h (0.33 kmol / h), the homogeneous catalyst aminosulfonic acid feed flow rate was 0.192 kg / h, accounting for 1.0% of the PO mass, the PG feed flow rate was 110.88 kg / h (1.459 kmol / h), the feed alcohol-to-cyclic molar ratio was approximately 4.4:1, and the feed mass hourly space velocity was 1.27 h⁻¹. -1 After preheating, the material temperature was 120℃, the bed temperature of the tubular reactor R401 was 123℃, the reaction pressure was 0.25MPa, and the PO conversion rate reached 99.85%. The operating pressure of dehydrogenation tower T1 is -0.099 MPa, and the operating reflux ratio is 3.0; the operating pressure of heavy metal removal tower T2 is -0.099 MPa, and the operating reflux ratio is 2.5. The flow rate of dipropylene glycol (DPG) collected from the top of the deweighting tower was 3.83 kg / h, the DPG selectivity reached 86.5%, the content of isomer A in the DPG was 22.8%, the product freezing point was -46℃, and it was odorless, meeting the requirements of flavor and fragrance type DPG.

[0046] Example 8: The remaining technical solutions of Example 8 are the same as those of Example 7, except that the continuous synthesis process of Example 8 is as follows: The PO feed flow rate was 19.2 kg / h (0.33 kmol / h), the homogeneous catalyst p-toluenesulfonic acid feed flow rate was 0.192 kg / h, accounting for 1.0% of the PO mass, the PG feed flow rate was 110.88 kg / h (1.459 kmol / h), the feed alcohol-to-cyclic molar ratio was approximately 4.4:1, and the feed mass hourly space velocity was 1.27 h⁻¹. -1 After preheating, the material temperature was 123℃, the bed temperature of the tubular reactor R401 was 125℃, the reaction pressure was 0.2MPa, and the PO conversion rate reached 99.95%. The operating pressure of dehydrogenation tower T1 is -0.099 MPa, and the operating reflux ratio is 3.0; the operating pressure of heavy metal removal tower T2 is -0.099 MPa, and the operating reflux ratio is 2.5. The flow rate of dipropylene glycol (DPG) from the top of the deweighting tower was 3.85 kg / h, the DPG selectivity reached 85.55%, the content of isomer A in the DPG was 22.3%, the product freezing point was -46℃, and it was odorless, meeting the requirements for flavor and fragrance type DPG.

[0047] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0048] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A continuous synthesis method for dipropylene glycol, characterized in that, Propylene glycol (PG) and propylene oxide (PO) are mixed and then heated to a preset reaction temperature in a preheater before entering a multi-tube reactor where an addition reaction occurs. The multi-tube reactor is selectively filled with a heterogeneous catalyst, and the feed line of propylene glycol (PG) is connected to a catalyst preparation vessel to be mixed with propylene oxide (PO). The catalyst preparation vessel is selectively filled with a homogeneous catalyst. The addition reaction of propylene glycol (PG) and propylene oxide (PO) is carried out under the catalysis of heterogeneous catalyst and / or homogeneous catalyst to obtain dipropylene glycol reaction product. The heterogeneous catalyst is a high-temperature resistant cation exchange resin; and / or the homogeneous catalyst is aminosulfonic acid or p-toluenesulfonic acid; The feed molar ratio of propylene glycol (PG) to propylene oxide (PO) is 2-5:1; the mass hourly space velocity (HHSV) of the feed is 1-6 h⁻¹. -1 .

2. The continuous synthesis method of dipropylene glycol according to claim 1, characterized in that, The reaction pressure inside the multi-tube reactor is set to 0.02-0.4 MPa, and the reaction temperature is set to 85-140℃.

3. The continuous synthesis method of dipropylene glycol according to claim 1, characterized in that, The reaction product of the dipropylene glycol condensate is fed into a light distillation tower for light distillation, and the bottom material of the light distillation tower is fed into a heavy distillation tower for heavy distillation. Then, the top gas phase of the heavy distillation tower is condensed, and a portion of the condensed phase is collected as the dipropylene glycol condensate product.

4. The continuous synthesis method of dipropylene glycol according to claim 3, characterized in that, The operating pressure of the light-weight removal tower is -0.099 to -0.095 MPa, and the operating reflux ratio is 1-4:1; the operating pressure of the heavy-weight removal tower is -0.099 to -0.097 MPa, and the operating reflux ratio is 1-4:

1.

5. An apparatus used in the continuous synthesis method of dipropylene glycol according to any one of claims 1-4, characterized in that, This includes the propylene glycol feed line (S101), the propylene oxide feed line (S103), the catalyst preparation vessel (P14), the pipeline material mixer (P15), the preheater (E301), and the multi-tube reactor (R401); among which, The raw material propylene oxide feed line (S103) is connected to the pipeline material mixer (P15); the raw material propylene glycol feed line (S101) is connected to the catalyst preparation vessel (P14), and the discharge port of the catalyst preparation vessel (P14) is connected to the pipeline material mixer (P15) through the raw material propylene glycol conveying line (S102).

6. The apparatus used in the continuous synthesis method of dipropylene glycol according to claim 5, characterized in that, The product discharge pipeline (S107) of the multi-tube reactor (R401) is connected to the light-weight removal tower (T1), the bottom material pipeline of the light-weight removal tower (T1) is connected to the heavy-weight removal tower (T2), the top gas phase outlet of the heavy-weight removal tower (T2) is connected to the heavy-weight removal tower condenser (C2), and one of the condensate phase outlets of the heavy-weight removal tower condenser (C2) is returned to the top of the heavy-weight removal tower (T2), and the other is used as the product collection end of dipropylene glycol.

7. The apparatus used in the continuous synthesis method of dipropylene glycol according to claim 5, characterized in that, The catalyst preparation vessel (P14) is equipped with a catalyst silo (P2) at its upper end; wherein, the catalyst silo (P2) is provided with a catalyst weighing module (P1), and a feed gear (P5) is installed in the connecting channel between the catalyst silo (P2) and the catalyst preparation vessel (P14), and the feed gear (P5) is driven by a servo motor (P4) that is communicatively connected to the control module (P3).

8. The apparatus used in the continuous synthesis method of dipropylene glycol according to claim 7, characterized in that, The catalyst silo (P2) is equipped with a material agitator (P6); the propylene glycol feed line (S101) is equipped with a propylene glycol flow meter (P7) and a propylene glycol regulating valve (P8); the propylene oxide feed line (S103) is equipped with a propylene oxide flow meter (P9) and a propylene oxide regulating valve (P10).

9. The apparatus used in the continuous synthesis method of dipropylene glycol according to claim 5, characterized in that, The preheater (E301) is equipped with a preheater heat circulation jacket, which is connected to the steam condensate output pipeline (S201) and the low-pressure steam input pipeline (S202). The multi-tube reactor (R401) is equipped with a reactor heat circulation jacket, which is connected to the heat extraction refrigerant supply pipeline (S203) and the heat extraction heat medium return pipeline (S204). The material connection pipeline (S104) between the preheater (E301) and the multi-tube reactor (R401) is equipped with a preheated material thermometer (T501), and the multi-tube reactor (R401) is equipped with a material thermometer (T502) inside the reaction tube.

10. The apparatus used in the continuous synthesis method of dipropylene glycol according to claim 6, characterized in that, The vapor outlet at the top of the light-weight removal tower (T1) is connected to the light-weight removal tower condenser (C1). One condensate outlet of the light-weight removal tower condenser (C1) flows back to the top of the light-weight removal tower (T2), and the other returns to the propylene glycol feed line (S101). The bottom of the light-weight removal tower (T1) is connected to the light-weight removal tower reboiler (R1) for reboiling the bottom material of the light-weight removal tower (T1). The bottom of the heavy-weight removal tower is connected to the heavy-weight removal tower reboiler (R2) for reboiling the bottom material of the heavy-weight removal tower (T2). The heavy components of the heavy-weight removal tower (T2) are continuously collected from the bottom and connected to a mixed alcohol collection device or other devices for the purification of tripropylene glycol.

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