Monobasic low-carbonic acid continuous dewatering, refluxing and esterifying device in polyol ester synthesis process

Abstract

The invention relates to the technical field of organic synthesis, in particular to a monobasic low-carbonic acid continuous dewatering, refluxing and esterifying device in a polyol ester synthesis process. Comprising an esterification device; by arranging a new esterification device, unitary low-carbonic acid-water mixed steam in an esterification reaction kettle is condensed by a condenser and then enters a liquid separation tank to separate lower-layer water, and high-water-content unitary low-carbonic acid at the upper end of one side of a U-shaped packed column is fed into a feed port at the upper end of the U-shaped packed column; continuously dewatering by large-particle salt, then flowing out from a discharge hole in the upper end of the other side of the U-shaped packed column to form low-water-content monobasic low-carbonic acid, and then refluxing into the esterification reaction kettle for continuous reaction. According to the method, the water generated in the esterification reaction is continuously and rapidly removed out of the reaction system, the water content in the reflux liquid is reduced from 10% wt or more to 0.5% wt or less, and the problem that the reaction is difficult to proceed in the forward direction due to high water content in the reaction system is solved, so that the esterification reaction is relatively complete, and the hydroxyl value of the product is effectively reduced. The reaction time is obviously shortened, the energy consumption is reduced, and the stability of the product is improved.

Description

Technical Field

[0001] The invention relates to the technical field of organic synthesis, and in particular to a monobasic low-carbonic acid continuous water removal and reflux esterification device in a polyol ester synthesis process. Background Art

[0002] Polyol ester is a lubricant base oil, a saturated polyol ester formed by the reaction of polyols and monocarbonic acid. It mainly includes trimethylolpropane ester, triethylolpropane ester, pentaerythritol ester, etc. Neopentyl polyol ester has the advantages of excellent high and low temperature performance, viscosity-temperature performance, thermal oxidation stability, lubricity, low volatility, etc. It also has the advantages of excellent biodegradability, low toxicity and raw material renewability, etc., which can better meet the current industrial development requirements for new lubricating materials.

[0003] As a polyhedral hindered alcohol, the degree of branching is quite high, which makes the esterification process of neopentyl alcohol with fatty acids including hindered acids have serious steric hindrance effect. Therefore, for the esterification reaction of pentaerythritol, it is necessary to increase the proportion of fatty acids, adopt a step-by-step temperature increase method, and promptly remove the water produced in the esterification reaction to make the esterification reaction proceed in the forward direction.

[0004] At present, the esterification reaction of polyol esters is usually carried out by the reflux method. During the esterification process, the mixed steam of monoacid and water escapes from the reaction system together, and the water layer is separated after the system condenses, while the monoacid flows back into the reaction system to continue the reaction. Under 20°C conditions, the solubility of water in C4, C5, and C8 monoacids in water is 44.60%, 15.20%, and 3.90% (wt), respectively. It can be seen that the saturated water content of monoacids such as C4 and C5 is significantly higher than that of monoacids such as medium and high carbonic acid (such as C8 monoacid). Therefore, in the esterification process using monoacids as raw materials, the refluxed monoacids will carry a large amount of water back to the reaction system, which makes it difficult for the reaction system to increase the temperature, the reaction is incomplete, the hydroxyl value of the reaction liquid is high, and the product is easy to absorb water and is unstable.

[0005] Therefore, the present invention designs a monobasic low-carbonic acid continuous water removal and reflux esterification device in the polyol ester synthesis process to solve the above-mentioned technical problems. Summary of the invention

[0006] Technical problem to be solved by the present invention: At present, the esterification reaction of polyol esters is usually carried out by reflux method. During the esterification process, the mixed steam of monoacid and water escapes from the reaction system together, and the water layer is separated after system condensation, while the monoacid is refluxed into the reaction system to continue the reaction. Under 20°C, the solubility of water in C4, C5, and C8 monoacids in water is 44.60%, 15.20%, and 3.90% (wt), respectively. It can be seen that the saturated water content of monoacids such as C4 and C5 is significantly higher than that of monoacids such as medium and high carbonic acid (such as C8 monoacid). Therefore, in the esterification process using monoacids as raw materials, the refluxed monoacids will carry a large amount of water back to the reaction system, which makes it difficult for the reaction system to increase the temperature, the reaction is incomplete, the hydroxyl value of the reaction liquid is high, and the product is easy to absorb water and is unstable.

[0007] The present invention provides the following technical scheme: a monobasic low-carbonic acid continuous water removal reflux esterification device in a polyol ester synthesis process, comprising an esterification device, wherein the esterification device is used to continuously and quickly remove water generated by the esterification reaction from the reaction system, and the water content in the reflux liquid is reduced from more than 10%wt to less than 0.5%wt;

[0008] The esterification device comprises an esterification reaction kettle, a condenser, a liquid separator, a large-particle salt U-shaped filling column, a sedimentation tank, an automatic water separator, a saturated brine evaporation tank, an acid recovery tank, and a wastewater treatment tank; one end of the esterification reaction kettle is connected to one end of the condenser, the other end of the condenser is connected to one end of the liquid separator, the other end of the liquid separator is connected to one end of the large-particle salt U-shaped filling column, a sedimentation tank is arranged at the bottom of the large-particle salt U-shaped filling column, an automatic water separator is arranged at one end of the sedimentation tank, a saturated brine evaporation tank is arranged at the other end of the automatic water separator, the bottom of the saturated brine evaporation tank is connected to the top of the large-particle salt U-shaped filling column; the other end of the large-particle salt U-shaped filling column is installed with a recovery acid storage tank, and the wastewater treatment tank is connected to the top of the saturated brine evaporation tank.

[0009] Preferably, the large-particle salt U-shaped filling column includes a large-particle salt feed inlet, a condensate mixed liquid feed inlet, large-particle salt, a grid and a water-removing low-carbonic acid discharge port, the large-particle salt feed inlet is installed on the top of the large-particle salt U-shaped filling column and is connected to the bottom of the saturated brine evaporation tank; the condensate mixed liquid feed inlet is opened on the side of the large-particle salt U-shaped filling column; the large-particle salt U-shaped filling column is filled with large-particle salt; grids for blocking large-particle salt are installed at the bottom of the two symmetrical vertical ends of the large-particle salt U-shaped filling column; the water-removing low-carbonic acid discharge port is installed on the right side of the large-particle salt U-shaped filling column.

[0010] Preferably, a recovery acid discharge valve is installed at the bottom of the large-particle salt U-shaped filling column, and the recovery acid discharge valve is connected to the raw material recovery tank.

[0011] Preferably, an emergency connecting valve is provided at the connecting point of the vertical end of the large particle salt U-shaped filling column.

[0012] Preferably, the sedimentation tank comprises a fine-grained salt discharge port, a sedimentation tank water outlet and fine-grained salt, the fine-grained salt discharge port is arranged on the lower left side of the sedimentation tank, the sedimentation tank water outlet is installed on the upper right side of the sedimentation tank, and fine-grained salt is placed at the bottom of the sedimentation tank.

[0013] Preferably, a liquid level height regulating valve is installed at the top of the automatic water distributor.

[0014] The beneficial effects of the present invention are as follows:

[0015] 1. The present invention sets a new esterification device, so that the monocarbonic acid-water mixed steam in the esterification reaction kettle is condensed by the condenser and enters the liquid separation tank to separate the lower layer of water, and the upper layer of high-water monocarbonic acid enters the upper end feed port on one side of the U-shaped filling column, and flows out from the upper end discharge port on the other side of the U-shaped filling column after continuous water removal by large-particle salt to form low-water monocarbonic acid, and then refluxes to the esterification reaction kettle to continue the reaction. The method continuously and quickly removes the water generated by the esterification reaction from the reaction system, and the water content in the reflux liquid is reduced from more than 10%wt to less than 0.5%wt, which solves the problem that the high water content in the reaction system makes it difficult for the reaction to proceed forward, thereby promoting a relatively complete esterification reaction and effectively reducing the hydroxyl value of the product. The reaction time is significantly shortened, energy consumption is reduced, and the stability of the product is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 This is a schematic diagram of a polyol ester monobasic low-carbonic acid continuous water removal and reflux esterification device of the present invention;

[0018] Figure 2 This is a schematic diagram of a large-particle salt U-filled column of the present invention;

[0019] Figure 3 is a top view of the grille of the present invention;

[0020] Figure 4 It is a schematic diagram of the automatic drainage liquid level height regulating valve of the present invention.

[0021] In the figure: 1. Esterification reactor; 2. Condenser; 3. Separator tank; 4. Large-particle salt U-shaped filling column; 4-1. Large-particle salt feed inlet; 4-2. Condensate mixed liquid feed inlet; 4-3. Large-particle salt; 4-4. Grid; 4-5. Dewatering monobasic low-carbonic acid outlet; 4-6. Acid recovery discharge valve; 4-7. Emergency connecting valve; 5. Sedimentation tank; 5-1. Fine-particle salt outlet; 5-2. Sedimentation tank outlet; 5-3. Fine-particle salt; 6. Automatic water distributor; 6-1. Liquid level height regulating valve; 7. Saturated brine evaporation tank; 8. Acid recovery storage tank; 9. Wastewater treatment tank. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents some embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0023] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0024] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", "back" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the product of the invention is usually placed when in use. Such terms are only used to facilitate the description of the present invention and simplify the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0025] It should also be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0026] The disclosed embodiments are intended to solve the problem that the esterification reaction of polyol esters is usually carried out using the reflux method. During the esterification process, the mixed vapor of monoacid and water escapes from the reaction system together, and the water layer is separated after system condensation, while the monoacid is refluxed back into the reaction system to continue the reaction. Under 20°C conditions, the solubility of water in C4, C5, and C8 monoacids in water is 44.60%, 15.20%, and 3.90% (wt), respectively. It can be seen that the saturated water content of monoacids such as C4 and C5 is significantly higher than that of monoacids such as medium and high carbonic acid (such as C8 monoacid). Therefore, in the esterification process using monoacids as raw materials, the refluxed monoacids will carry a large amount of water back to the reaction system, which makes it difficult for the reaction system to increase the temperature, the reaction is incomplete, the hydroxyl value of the reaction liquid is high, and the product is easy to absorb water and unstable. In view of this, the disclosed embodiment proposes a mono-low-carbonic acid continuous dehydration reflux esterification device in the polyol ester synthesis process. By setting up a new esterification device, the mono-low-carbonic acid-water mixed steam in the esterification reaction kettle is condensed by the condenser and enters the liquid separation tank to separate the lower layer of water. The upper layer of high-water-containing mono-low-carbonic acid enters the upper feed port on one side of the U-shaped filling column, and flows out from the upper discharge port on the other side of the U-shaped filling column after continuous dehydration by large-particle salt to form low-water-containing mono-low-carbonic acid, and then refluxes to the esterification reaction kettle to continue the reaction. This method continuously and quickly removes the water produced by the esterification reaction from the reaction system, and the water content in the reflux liquid is reduced from a water content of more than 10%wt to less than 0.5%wt, which solves the problem that the high water content in the reaction system makes it difficult for the reaction to proceed in the forward direction, thereby promoting a relatively complete esterification reaction and effectively reducing the hydroxyl value of the product. Significantly shorten the reaction time, reduce energy consumption, and improve the stability of the product.

[0027] like Figures 1 to 4 As shown, a monobasic low-carbonic acid continuous water removal reflux esterification device in a polyol ester synthesis process includes an esterification device, wherein the esterification device is used to continuously and quickly remove the water produced by the esterification reaction from the reaction system, and the water content in the reflux liquid is reduced from more than 10%wt to less than 0.5%wt;

[0028] The esterification device comprises an esterification reaction kettle 1, a condenser 2, a liquid separator 3, a large-particle salt U-shaped filling column 4, a sedimentation tank 5, an automatic water separator 6, a saturated salt water evaporation tank 7, an acid recovery tank 8, and a wastewater treatment tank 9; one end of the esterification reaction kettle 1 is connected to one end of the condenser 2, the other end of the condenser 2 is connected to one end of the liquid separator 3, the other end of the liquid separator 3 is connected to one end of the large-particle salt U-shaped filling column 4, a sedimentation tank 5 is arranged at the bottom of the large-particle salt U-shaped filling column 4, one end of the sedimentation tank 5 is arranged with an automatic water separator 6, the other end of the automatic water separator 6 is arranged with a saturated salt water evaporation tank 7, the bottom of the saturated salt water evaporation tank 7 is connected to the top of the large-particle salt U-shaped filling column 4; the other end of the large-particle salt U-shaped filling column 4 is installed with an acid recovery tank 8, and the wastewater treatment tank 9 is connected to the top of the saturated salt water evaporation tank 7;

[0029] The monocarbonic acid-water mixed steam in the esterification reaction kettle 1 is condensed by the condenser 2 and enters the separator 3 to separate the lower water phase, and the upper monocarbonic acid with high water content enters the upper feed port on one side of the U-shaped filling column, and flows out from the upper discharge port on the other side of the U-shaped filling column after continuous water removal by the large particle salt 4-3 to form monocarbonic acid with low water content. At this time, the water content in the monocarbonic acid is reduced from more than 10%wt to less than 0.5%wt, and then refluxes to the recovery acid storage tank 8, and the feed speed is controlled by the feed pump to return to the esterification reaction kettle 1 to continue the reaction;

[0030] The monocarbonic acid-water mixed steam in the esterification reactor 1 is condensed by the condenser 2 and enters the separator 3 to remove the water in the lower layer. The upper oil phase enters the upper feed port on one side of the U-shaped filling column, and flows out from the upper discharge port on the other side of the U-shaped filling column after continuous water removal by the large-particle salt 4-3. The monocarbonic acid with high water content is converted into monocarbonic acid with low water content and refluxed back to the esterification reactor 1 to continue to participate in the reaction. In this way, the water generated by the esterification reaction can be continuously and quickly removed from the reaction system, and the water content in the reflux liquid is reduced from more than 10%wt to less than 0.5%wt, which solves the problem that the reaction is difficult to proceed in the forward direction due to the high water content in the reaction system, thereby promoting a relatively complete esterification reaction and effectively reducing the hydroxyl value of the product. The reaction time is significantly shortened, energy consumption is reduced, and the stability of the product is improved.

[0031] like Figure 2As shown, the large-particle salt U-shaped filling column 4 includes a large-particle salt feed port 4-1, a condensate mixed liquid feed port 4-2, large-particle salt 4-3, a grid 4-4 and a dewatered low-carbonic acid outlet 4-5. The large-particle salt feed port 4-1 is installed on the top of the large-particle salt U-shaped filling column 4 and is connected to the bottom of the saturated brine evaporation tank 7; the large-particle salt feed port 4-1 is used to fill the large-particle salt 4-3; the condensate mixed liquid feed port is opened on the side of the large-particle salt U-shaped filling column 4 ... The combined feed port is used to fill the condensate into the large-particle salt U-shaped filling column 4; the large-particle salt U-shaped filling column 4 is filled with large-particle salt 4-3; the large-particle salt 4-3 is used to continuously dewater the upper oil phase; the two symmetrical vertical ends of the large-particle salt U-shaped filling column 4 are equipped with a grid 4-4 for blocking the large-particle salt 4-3; the dewatering mono-low-carbonic acid discharge port 4-5 is installed on the right side of the large-particle salt U-shaped filling column 4; the dewatering mono-low-carbonic acid discharge port 4-5 is used to discharge the upper oil phase after the water is discharged;

[0032] like Figure 2 As shown, a recovery acid discharge valve 4-6 is installed at the bottom of the large particle salt U-shaped filling column 4, and the recovery acid discharge valve 4-6 is connected to the raw material recovery tank; the recovery acid discharge valve 4-6 is used to release excess raw acid from the recovery acid discharge valve 4-6 to the recovery acid collection tank after the reaction is completed.

[0033] like Figure 2 As shown, an emergency connecting valve 4-7 is provided at the connecting part of the vertical end of the large particle salt U-shaped filling column 4. By opening the emergency connecting valve 4-7, the low-water-content monobasic acid at the input end of the large particle salt U-shaped filling column 4 can be directly introduced into the U-shaped column input end, thereby further refluxed into the reactor.

[0034] like Figure 2 As shown, the sedimentation tank 5 includes a fine-grained salt discharge port 5-1, a sedimentation tank water outlet 5-2 and fine-grained salt 5-3, wherein the fine-grained salt discharge port 5-1 is arranged on the lower left side of the sedimentation tank 5, and the fine-grained salt discharge port 5-1 is used to discharge the fine-grained salt 5-3; the sedimentation tank water outlet 5-2 is installed on the upper right side of the sedimentation tank 5, and the sedimentation tank water outlet 5-2 is used to discharge liquid; the fine-grained salt 5-3 is placed at the bottom of the sedimentation tank 5;

[0035] like Figure 4 As shown, the top of the automatic water distributor 6 is equipped with a liquid level regulating valve 6-1; the automatic drainage height regulating valve is used to fine-tune the liquid level of the saturated brine; the height difference h0 between the outlet of the automatic water distributor 6 and the outlet of the monobasic low-carbon acid is determined by the density of the saturated brine and the low-carbon monobasic acid, and the calculation formula is:

[0036]

[0037] In the formula: h0----the height difference between the outlet of automatic water distributor 6 and the outlet of monobasic low carbonic acid;

[0038] h1----the height difference between the outlet of monobasic low carbonic acid and the oil-water interface;

[0039] ρ (一元低碳酸) ----Monocarbonic acid density;

[0040] ρ (饱和盐水) ----Saturated brine density

[0041] An automatic drainage height regulating valve is installed at the top of the automatic water distributor 6 to fine-tune the height of the saturated brine liquid level. The saturated brine flowing out of the water outlet of the automatic water distributor 6 enters the saturated brine evaporation tank 7.

[0042] A continuous dewatering and reflux device for monobasic low carbonic acid in the process of polyol ester synthesis Figure 1 As shown, the saturated salt water evaporation tank 77 is characterized in that the saturated salt water is evaporated and the formed large-particle salt 4-3 is returned to the U-shaped filling column for reuse.

[0043] Table 1 shows the acid value and water content before and after continuous water removal by the water removal device. As shown in Table 1, after continuous water removal, the acid values ​​of C4 acid and C5 acid are almost close to the theoretical acid value, and the water content drops to below 0.5%wt.

[0044] Table 1 Acid value and water content before and after continuous water removal by water removal device

[0045] One yuan low carbonation Water content before dehydration (%) Water content after dehydration (%) C4 Acid 44.40 0.20 C5 Acid 14.20 0.15

[0046] The following is a detailed description based on a specific control experiment:

[0047] Embodiment 1:

[0048] The embodiment uses a polyol ester continuous dehydration reflux esterification device for reaction. Fill the U filling column with large-particle salt 4-3 and anhydrous C4 acid. Fill the settling tank 5 with saturated brine. Add 6807g of pentaerythritol and 21147g of C4 acid to the esterification reactor 1. Nitrogen is bubbled on the liquid surface in the reactor at 300ml / min, and the temperature is raised from room temperature to 170℃ and kept warm for 30min. Turn on the feed pump, the feed rate is the same as the reflux rate of the low-water-content C4 acid, then the temperature is raised to 200℃ and kept warm for 10h, and the hydroxyl value is controlled in the middle.

[0049] Test results: After continuous water removal by the U-shaped filling column, the water content of C4 acid is 0.20%. The product test results are shown in Table 2

[0050] Comparative Example 1:

[0051] Comparative Example A conventional reflux esterification device was used for the reaction. 6807 g of pentaerythritol and 21147 g of C4 acid were added to the esterification reactor 1. Nitrogen was bubbled on the liquid surface of the reactor at 300 ml / min, and the temperature was raised from room temperature to 170°C for 30 minutes, then continued to rise to 200°C, and the reaction was carried out for 10 hours, with the hydroxyl value being controlled.

[0052] Test results: The water content of C4 acid in the reflux water separator is 44.40%. The product test results are shown in Table 2.

[0053] Table 2 C4 acid example comparative example product test results

[0054] index Example 1 Comparative Example 1 Water content in reflux liquid (%) 0.20 44.40 Hydroxyl value (mgKOH / g) 0.7 20.3

[0055] Embodiment 2:

[0056] Fill the U filling column with large-particle salt 4-3 and anhydrous C5 acid. Fill the settling tank 5 with saturated brine. Add 6807g of pentaerythritol and 24512g of C5 acid to the esterification reactor 1. Nitrogen is blown on the liquid surface of the reactor at 300ml / min, and the temperature is raised from room temperature to 170℃ and kept warm for 30min. Turn on the feed pump, the feed speed is the same as the reflux speed of the low-water-content C5 acid, then heat to 200℃ and keep warm for 10h, and control the hydroxyl value.

[0057] Test results: After continuous water removal in the U-shaped filling column, the water content of C5 acid is 0.15%. The product test results are shown in Table 3.

[0058] Comparative Example 2:

[0059] Comparative Example A conventional reflux esterification device was used for the reaction. 6807 g of pentaerythritol and 24512 g of C5 acid were added to the esterification reactor 1. Nitrogen was bubbled on the liquid surface of the reactor at 300 ml / min, and the temperature was raised from room temperature to 170°C for 30 minutes, and then continued to rise to 200°C for 10 hours, and the hydroxyl value was controlled.

[0060] Test results: The water content of C5 acid in the reflux water separator is 14.50%. The product test results are shown in Table 3.

[0061] Table 3 C5 acid example comparative example product test results

[0062] index Example 2 Comparative Example 2 Water content in reflux liquid (%) 0.15 14.50 Hydroxyl value (mgKOH / g) 0.7 10.2

[0063] Embodiment 3:

[0064] Fill the U filling column with large-particle salt 4-3 and anhydrous C8 acid. Fill the settling tank 5 with saturated brine. Add 6807g of pentaerythritol and 34610g of C8 acid to the esterification reactor 1. Nitrogen is blown on the liquid surface of the reactor at 300ml / min, and the temperature is raised from room temperature to 170℃ and kept warm for 30min. Turn on the feed pump, and the feed rate is the same as the reflux rate of low-water-content C4 acid, then heat to 200℃ and keep warm for 10h, and control the hydroxyl value.

[0065] Test results: After continuous water removal by the U-shaped filling column, the water content of C8 acid is 0.03%. The product test results are shown in Table 4.

[0066] Comparative Example 3:

[0067] Comparative Example A conventional reflux esterification device was used for the reaction. 6807 g of pentaerythritol and 34610 g of C8 acid were added to the esterification reactor 1. Nitrogen was bubbled on the liquid surface of the reactor at 300 ml / min, and the temperature was raised from room temperature to 170°C for 30 minutes, then continued to rise to 200°C, and the reaction was carried out for 10 hours, with the hydroxyl value being controlled.

[0068] Test results: The water content of C8 acid in the reflux water separator is 3.88%. The product test results are shown in Table 4.

[0069] Table 4C8 acid example comparative example product test results

[0070]

[0071]

[0072] From the comparative test results of the C4 acid and C5 acid embodiments, it can be seen that the water content in the refluxed C4 and C5 monobasic low carbons in the embodiments is 0.20% and 0.15% respectively, and the hydroxyl values ​​of the products are 0.7mgKOH / g and 0.7mgKOH / g respectively, and the esterification reaction is relatively complete. In the comparative example, the water content in the refluxed monobasic acid is 44.40% and 14.50% respectively, and the hydroxyl values ​​are 20.3mgKOH / g and 10.2mgKOH / g respectively, and the esterification reaction is not complete. From the comparative test results of the C8 acid embodiment, it can be seen that the water content of C8 acid is 0.14%, the hydroxyl value of the product is 0.4mgKOH / g, and the esterification reaction is relatively complete. In the comparative example, the water content in the refluxed C8 acid is 3.88%, the hydroxyl value is 1.2mgKOH / g, and the esterification reaction is also relatively complete. Therefore, the method of the present invention can continuously and quickly remove the water produced by the esterification reaction from the reaction system, solve the problem that the high water content in the reaction system makes it difficult for the reaction to proceed in the forward direction, and promote a relatively complete ester reaction. The use of the device for C4 and C5 monobasic low-carbon acids has obvious effects. By using the device, the esterification reaction effect of C4 and C5 low-carbon monobasic acids can achieve the esterification effect of C8 and C9 monobasic high-carbon acids in conventional esterification reflux equipment. The method of the present invention effectively solves the problem that the high water content in the refluxed monobasic low-carbon acid leads to incomplete product reaction, thereby leading to high hydroxyl value and unstable storage, significantly shortens the reaction time, reduces energy consumption, and improves product quality.

[0073] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A monobasic low-carbonic acid continuous water removal and reflux esterification device in a polyol ester synthesis process, characterized in that: The method comprises an esterification device, wherein the esterification device is used to continuously and quickly remove water generated by the esterification reaction from the reaction system, and the water content in the reflux liquid is reduced from more than 10%wt to less than 0.5%wt; The esterification device comprises an esterification reaction kettle (1), a condenser (2), a liquid separator (3), a large-particle salt U-shaped filling column (4), a sedimentation tank (5), an automatic water separator (6), a saturated brine evaporation tank (7), a recovery acid storage tank (8), and a wastewater treatment tank (9); one end of the esterification reaction kettle (1) is connected to one end of the condenser (2), the other end of the condenser (2) is connected to one end of the liquid separator (3), and the other end of the liquid separator (3) is connected to one end of the large-particle salt U-shaped filling column (4). A sedimentation tank (5) is arranged at the bottom of the large-particle salt U-shaped filling column (4); an automatic water distributor (6) is arranged at one end of the sedimentation tank (5); a saturated salt water evaporation tank (7) is arranged at the other end of the automatic water distributor (6); the bottom of the saturated salt water evaporation tank (7) is connected to the top of the large-particle salt U-shaped filling column (4); a recovery acid storage tank (8) is installed at the other end of the large-particle salt U-shaped filling column (4); and the wastewater treatment tank (9) is connected to the top of the saturated salt water evaporation tank (7).

2. The monobasic low-carbonic acid continuous water removal and reflux esterification device for the polyol ester synthesis process according to claim 1, characterized in that: The large-particle salt U-shaped filling column (4) comprises a large-particle salt feed port (4-1), a condensate mixed liquid feed port (4-2), large-particle salt (4-3), a grid (4-4) and a dewatering monobasic low-carbonic acid discharge port (4-5); the large-particle salt feed port (4-1) is installed at the top of the large-particle salt U-shaped filling column (4) and is connected to the bottom of the saturated salt water evaporation tank (7); the condensate mixed liquid feed port is opened on the side of the large-particle salt U-shaped filling column (4); the large-particle salt U-shaped filling column (4) is filled with large-particle salt (4-3); grids (4-4) for blocking large-particle salt (4-3) are installed at the bottom of two symmetrical vertical ends of the large-particle salt U-shaped filling column (4); and the dewatering monobasic low-carbonic acid discharge port (4-5) is installed on the right side of the large-particle salt U-shaped filling column (4).

3. A monobasic low-carbonic acid continuous water removal and reflux esterification device for a polyol ester synthesis process according to claim 2, characterized in that: A recovery acid discharge valve (4-6) is installed at the bottom of the large-particle salt U-shaped filling column (4), and the recovery acid discharge valve (4-6) is connected to the raw material recovery tank.

4. The monobasic low-carbonic acid continuous water removal and reflux esterification device in the polyol ester synthesis process according to claim 3, characterized in that: An emergency communication valve (4-7) is provided at the connection point of the vertical end of the large-particle salt U-shaped filling column (4).

5. A monobasic low-carbonic acid continuous water removal and reflux esterification device for a polyol ester synthesis process according to claim 4, characterized in that: The sedimentation tank (5) comprises a fine-grained salt discharge port (5-1), a sedimentation tank water outlet (5-2) and fine-grained salt (5-3); the fine-grained salt discharge port (5-1) is arranged on the lower left side of the sedimentation tank (5); the sedimentation tank water outlet (5-2) is installed on the upper right side of the sedimentation tank (5); and the fine-grained salt (5-3) is placed at the bottom of the sedimentation tank (5).

6. The monobasic low-carbonic acid continuous water removal and reflux esterification device in the polyol ester synthesis process according to claim 5, characterized in that: A liquid level regulating valve (6-1) is installed at the top of the automatic water distributor (6).

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