Method for producing ester-based compositions

Abstract

The present invention provides a method for producing an ester-based composition using a continuous reaction system in which multiple reactors are connected in series, which can improve heat transfer performance, reactor productivity, and total reactor productivity by controlling operating conditions.

Description

[Technical Field]

[0001] [Cross-reference of related applications] This application claims priority rights based on Korean Patent Application No. 10-2022-0126487 dated October 4, 2022, and all content disclosed in the said Korean Patent Application is incorporated herein by reference.

[0002] The present invention provides a method for producing ester compositions that can improve heat transfer performance, reactor productivity, and total reactor productivity when producing ester compositions using a continuous esterification reaction system in which multiple reactors are connected in series. [Background technology]

[0003] Ester compounds produced by the esterification reaction of polycarboxylic acids and alcohols are widely used as plasticizers.

[0004] The esterification reaction described above is mainly carried out at high temperatures in the presence of an esterification catalyst. As a result, the reaction products obtained after the reaction are completed include the catalyst, catalyst decomposition products, unreacted alcohol and unreacted polycarboxylic acid, monoester, and reaction impurities. Therefore, in order to obtain a pure ester compound, post-treatment steps such as neutralization, washing with water, removal of alcohol, and / or filtration must be performed.

[0005] As a result, research is being conducted in various areas to obtain high-purity ester compounds, including methods for efficiently separating and purifying by-reactants contained in the reaction product, methods for suppressing the occurrence of reverse reactions and catalytic decomposition during esterification reactions, and methods for efficiently designing manufacturing equipment or processes.

[0006] One method to suppress the occurrence of reverse reactions and catalytic decomposition during esterification reactions is to remove water generated during the esterification reaction by supplying heat to the reactor using a heat transfer medium. This method uses a reaction system in which multiple reactors are connected in series, and in this case, the ability to supply heat to the reactor, i.e., the heat transfer performance of the reactor, directly affects the esterification reaction rate. As a result, when producing ester compounds in a continuous process using multiple reactors with the same heat transfer performance, the reaction rate decreases as the reaction progresses to the later reactors due to the decrease in the concentration of the raw materials, and consequently, the amount of heat required to remove water also decreases. In other words, in the later reactors, the amount of heat required for the reaction is less than the amount of heat that can be supplied, so there is a relative excess of heat transfer performance remaining. This is a problem that leads to a decrease in heat transfer performance, reactor productivity, and overall reactor productivity during the production of ester compounds. For this reason, various methods have been proposed to improve the efficiency and productivity of ester compound production through the control of reactor conditions, but these have not been sufficient in terms of improvement effect, economics, and process efficiency. [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The present invention provides a method for producing ester compositions that can improve heat transfer performance, reactor productivity, and total reactor productivity when producing ester compositions using a continuous esterification reaction system in which multiple reactors are connected in series. [Means for solving the problem]

[0008] According to the present invention, a method for producing an ester-based composition using a continuous esterification reaction system in which a total of N reactors, from the first reactor to the Nth reactor, are connected in series, The process includes a step of continuously feeding raw materials containing a polycarboxylic acid and an alcohol into the continuous esterification reaction system to continuously produce a reaction product, A method for producing an ester-based composition that satisfies the following formula 1 is provided. [Formula 1] P1 <P N-1 ≤P N In the above formula 1, P1 is the pressure (bar) in the first reactor. P N This is the pressure (bar) of the Nth reactor following the first reactor. N is an integer greater than or equal to 3. [Effects of the Invention]

[0009] The method for producing ester-based compositions according to the present invention can improve heat transfer performance, reactor productivity, and total reactor productivity through stepwise pressurization operation in a continuous esterification reaction system in which multiple reactors are connected in series. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram illustrating a continuous esterification reaction system that can be used in the method for producing ester compositions according to the present invention. [Modes for carrying out the invention]

[0011] In this invention, terms such as "first," "second," etc., are used to describe various components, and are used solely for the purpose of distinguishing one component from other components.

[0012] Furthermore, the terms used herein are used solely to describe exemplary embodiments and are not intended to limit the invention. Unless the context clearly indicates otherwise, singular expressions include plural expressions. In this specification, terms such as “includes,” “equip,” or “have” are intended to specify the existence of implemented features, figures, steps, components, or combinations thereof, and should be understood not to preemptively exclude the existence or possibility of adding one or more other features, figures, steps, components, or combinations thereof.

[0013] In addition, in the present specification, "%" and "parts" indicating content are based on weight unless otherwise specified.

[0014] Since the present invention can be subjected to various modifications and can have various forms, specific examples will be illustrated and described in detail below. However, this is not intended to limit the present invention to the specifically disclosed forms, and should be understood to include all modifications, equivalents or alternatives falling within the spirit and technical scope of the present invention.

[0015] Hereinafter, the method for producing an ester-based composition according to the present invention will be described in detail.

[0016] When producing an ester-based composition using a conventional continuous reaction system in which a plurality of reactors are connected in series, residual heat remains increasingly as the reaction mixture moves to subsequent reactors, consequently causing problems of decreased heat transfer performance, reactor productivity and total reactor productivity.

[0017] Therefore, in the present invention, in order to maximize utilization of the residual heat that increasingly accumulates as the reaction moves to subsequent reactors, by pressurizing subsequent reactors to a higher pressure than preceding reactors in a continuous esterification reaction system, the reaction temperature and reactivity can be increased, and as a result, productivity within the same reactor can be improved.

[0018] Specifically, the method for producing an ester-based composition according to the present invention is a method for producing an ester-based composition using a continuous esterification reaction system in which a total of N reactors from a first reactor to an N-th reactor are connected in series, comprising the step of continuously feeding a raw material containing a polycarboxylic acid and an alcohol into the continuous esterification reaction system to continuously produce a reaction product, which satisfies the following Mathematical Formula 1. [Mathematical Formula 1] P1<P N-1 ≦P N In Mathematical Formula 1 above, P1 is the pressure of the first reactor (bar), P N is the pressure of the N-th reactor subsequent to the first reactor (bar), N is an integer of 3 or greater.

[0019] When pressurizing the downstream reactors, the temperature in each pressurized reactor increases, which consequently increases the average temperature of the entire reactor. Such an increase in the average reactor temperature can accelerate the esterification reaction rate, and consequently increase the overall reactor productivity.

[0020] Furthermore, if the pressure increase in the reactors downstream of the first reactor reaches or exceeds a certain level, the aforementioned effect can be further enhanced. However, when the pressure of the downstream reactors is excessively high, the reaction temperature in the reactors increases significantly, the required heat amount exceeds the heat transfer performance of the reactors, and the content of thermal residues may increase. As a result, reverse reaction and catalytic decomposition reaction may occur, which may rather decrease reactivity. Accordingly, it is preferable to control the pressure increase in the downstream reactors to a certain level or lower.

[0021] Specifically, the production method can further satisfy the following Formula 2. [Formula 2] P1+0.01≦P N ≦P1+2 In Formula 2 above, P1, P N and N are as defined above. More specifically, the production method can further satisfy any one of the following Formulas 2-1 to 2-5. [Formula 2-1] P1+0.02≦P N ≦P1+2 [Formula 2-2] P1+0.05≦P N ≦P1+1.5 [Formula 2-3] P1+0.06≦P N ≦P1+1.5 [Formula 2-4] P1+0.1≦P N≤P1+1 [Formula 2-5] P1 + 0.1 ≤ P N ≤P1+0.5 In the above formulas 2-1 to 2-5, P1, P N And N are as defined above.

[0022] Furthermore, in the above formulas 1 and 2, the pressure P1 of the first reactor may be 1 to 4 bar. More specifically, P1 may be 1 bar or more, or 1.1 bar or more, or 1.2 bar or more, or 1.24 bar or more, and 4 bar or less, or 3 bar or less, or 2 bar or less, or 1.5 bar or less, or 1.3 bar or less, or 1.28 bar or less, or 1.26 bar or less. When P1 is controlled within the above range, it is superior in terms of improving processability and reactor productivity.

[0023] Furthermore, in the above equations 1 and 2, N represents the number of reactors included in the reaction system. Specifically, N is an integer that is 3 or greater, or 4 or greater, and 20 or less, or 10 or less, or 8 or less, or 5 or less.

[0024] In the manufacturing method according to the present invention, the pressure in each reactor can be adjusted by controlling the amount of inert gas flowing into the reactor to satisfy the pressure conditions. Furthermore, the pressure in the reactor can be further adjusted by controlling the amount of uncondensed gas containing inert gas and the amount of water discharged as a result of the reaction.

[0025] For example, the pressure inside the reactor can be increased by increasing the amount of inert gas flowing into the reactor or by decreasing the amount of uncondensed gas and water being discharged.

[0026] Furthermore, the amount of inert gas, the amount of uncondensed gas, and the amount of water can be adjusted by the pressure control device of the pressure control unit provided in the continuous esterification reaction system. This will be explained in detail in the following description of the continuous esterification reaction system.

[0027] On the other hand, in the manufacturing method according to the present invention, the raw materials for the production of the ester-based composition are produced by mixing a polycarboxylic acid and an alcohol. Thus, the manufacturing method of the present invention may further include a step of mixing the polycarboxylic acid and the alcohol before adding the raw materials.

[0028] The mixing of the polycarboxylic acid and the alcohol may be carried out by conventional methods. Alternatively, before introducing the mixture into the reactor, a step of uniform mixing can be performed using a mixer or other mixing device. In this case, the problem of uneven esterification occurring depending on the location within the reactor can be prevented.

[0029] On the other hand, in the raw materials, the polycarboxylic acid may be an aliphatic or aromatic carboxylic acid having two or more carboxyl groups (-COOH) in the molecule, specifically two to four. Alternatively, the anhydride of the polycarboxylic acid can be used.

[0030] Specifically, the polycarboxylic acid may be a C2 to C20 aliphatic or C6 to C20 aromatic carboxylic acid. For example, the polycarboxylic acid may be one or more selected from the group consisting of adipic acid, azelaic acid, phthalic acid, isophthalic acid, terephthalic acid, citric acid, trimellitic acid, and their anhydrides, but is not limited thereto. Preferably, the polycarboxylic acid may be one or more selected from the group consisting of phthalic acid, isophthalic acid, terephthalic acid, and their hydrate anhydrides and derivatives, and more preferably, terephthalic acid or its anhydrides.

[0031] As the alcohol, a linear or branched aliphatic alcohol having 1 to 20 carbon atoms, 4 to 20 carbon atoms, or 5 to 15 carbon atoms can be used. Specifically, it may be one or more selected from the group consisting of butanol, hexanol, 2-ethylhexanol, isononyl alcohol, isodecyl alcohol, and propylheptanol.

[0032] As an example, the method for producing the ester compound of the present invention may be a method for producing dioctyl terephthalate (Di 2-ethylhexyl terephthalte, DOTP) using terephthalic acid as the polycarboxylic acid and 2-ethylhexanol as the alcohol.

[0033] Furthermore, an esterification reaction catalyst may be added during the production of the raw materials.

[0034] The esterification catalyst may be added to a mixture of polycarboxylic acid and alcohol, or to the polycarboxylic acid or alcohol separately before the mixture is prepared. Alternatively, the esterification catalyst may be added directly to the reactor.

[0035] As the esterification reaction catalyst, organometallic catalysts, organosulfonic acids, acid catalysts, or mixtures thereof can be used. Specifically, as organometallic catalysts, examples include tetraalkyl titanates such as tetraisopropyl titanate, tetra-n-butyl titanate (TnBT), tetraoctyl titanate, and butylsamylate; as organosulfonic acids, examples include p-toluenesulfonic acid, methylsulfonic acid, ethanesulfonic acid, propanesulfonic acid, or butanesulfonic acid; and as acid catalysts, examples include formic acid, nitric acid, acetic acid, hydrochloric acid, phosphoric acid, and sulfuric acid; and one or more of these can be used in mixtures thereof.

[0036] The amounts of the polycarboxylic acid, alcohol, and esterification reaction catalyst used are not particularly limited in the present invention and may be appropriately determined according to the physical properties and applications of the ester composition to be produced.

[0037] As an example, when producing dioctyl terephthalate using terephthalic acid and 2-ethylhexanol, the polycarboxylic acid corresponding to terephthalic acid and the alcohol corresponding to 2-ethylhexanol may be added in a molar ratio of 1:2 to 1:4, or 1:3 to 1:3.5.

[0038] Furthermore, the catalyst may be added in an amount of 100 to 2000 ppm based on the total weight of the alcohol, more specifically, 100 ppm or more, or 200 ppm or more, or 300 ppm or more, or 500 ppm or more, and 2000 ppm or less, or 1500 ppm or less, or 1000 ppm or less, or 700 ppm or less. The maximum reaction efficiency relative to the amount added can be achieved when the catalyst is added within the above content range.

[0039] Furthermore, the reaction conditions for the esterification reaction between polycarboxylic acid and alcohol are not particularly limited; for example, the reaction may be carried out at a temperature of 180°C to 260°C.

[0040] When the polycarboxylic acid, alcohol, and a selectively esterification catalyst are continuously fed into the first reactor of a continuous esterification reaction system, an esterification reaction occurs in the reactor, and the resulting reaction products are sequentially transferred to subsequent reactors connected in series with the first reactor. When the reaction products flow into the subsequent reactors, an esterification reaction occurs in the same manner as in the first reactor.

[0041] Since the reaction materials pass through multiple reactors connected in series in this manner, it becomes possible to optimize the overall process by independently adjusting the process variables for each reactor, thereby maximizing the efficiency of the manufacturing process.

[0042] Specifically, in the manufacturing method according to the present invention, the heat transfer performance of each reactor can be maximized and both reactor productivity and overall reactor productivity can be improved by controlling the pressurization conditions in each reactor through a pressure control unit provided in a continuous esterification reaction system to satisfy the conditions described above.

[0043] On the other hand, the continuous esterification reaction system used in the manufacturing method according to the present invention has a structure in which a total of N reactors, from the first reactor to the Nth reactor, are connected in series.

[0044] Figure 1 is a schematic diagram illustrating a continuous esterification reaction system that can be used in the method for producing ester compositions according to the present invention. Figure 1 is merely an example for explaining the present invention, and the present invention is not limited thereto.

[0045] Referring to Figure 1, the continuous esterification reaction system 10 includes: a reaction section 1 in which N reactors are connected in series and in which the esterification reaction of raw materials containing polycarboxylic acid and alcohol takes place; a separation section 2 including a separation device that separates unreacted alcohol from the reaction product flowing in from the reactors of the reaction section; a recovery section 3 including a recovery device that puts the unreacted alcohol separated from the separation device of the separation section back into the reactors of the reaction section; and a pressure control section 4 including a pressure control device that adjusts the pressure of the reactors in the reaction section. In this case, N is an integer of 3 or more, more specifically, 3 or more, or 4 or more, and an integer of 20 or less, or 10 or less, or 8 or less, or 5 or less.

[0046] In the continuous esterification reaction system described above, the reaction section 1 includes N reactors 1a, 1b, ... 1n (where n is the alphabet in order corresponding to N) connected in series, in which the esterification reaction is carried out sequentially. Thus, when raw materials containing a polycarboxylic acid, an alcohol, and selectively an esterification catalyst are continuously fed into the first reactor 1a of the reaction section 1, the esterification reaction occurs in the first reactor 1a. The resulting reaction product is then sequentially transferred to subsequent reactors connected in series with the first reactor 1a, specifically from the second reactor 1b to the Nth reactor 1n. At this time, the transfer of the reaction product is carried out through a transfer line, such as a pipe, connecting the two reactors. As an example, as shown in Figure 1, the first and second reactors are connected through a reaction product transfer line located below the first reactor, thereby transferring the reaction product in the first reactor. When the reaction product flows into the subsequent reactors, the esterification reaction is carried out in the same manner as in the first reactor.

[0047] On the other hand, an inert gas is introduced into the lower part of the reactor in the reaction section to control the pressure inside the reactor. This inert gas not only serves as a means of regulating the pressure inside the reactor, but also plays a role in suppressing the occurrence of side reactions during the esterification reaction inside the reactor by adjusting the composition of the inert atmosphere.

[0048] The inert gas is introduced into the reactor through an inert gas inlet line connected to the bottom of the reactor, and is discharged into the separation section along with the reaction by-product through a reaction by-product discharge line connected to the top of the reactor.

[0049] As the inert gas, nitrogen or the like can be used.

[0050] Furthermore, the inert gas is introduced in an amount that satisfies the pressure conditions inside the reactor, and the amount introduced can be adjusted by a pressure control device described later.

[0051] Furthermore, in the continuous esterification reaction system, the separation unit 2 is connected to the reaction unit 1, specifically the reactor of the reaction unit, and includes separation devices 2a, 2b, and 2n for separating unreacted alcohol from the reaction product flowing in from the reactor. Specifically, the separation devices 2a, 2b, and 2n may include: column separators 21a, 21b, and 21n for performing gas-liquid separation on the reaction product flowing in from the reactor of the reaction unit; condensers 22a, 22b, and 22n for liquefying the gaseous substance separated and discharged as a result of the gas-liquid separation in the column separators and switching it to a liquid phase, and for discharging uncondensed gas (including inert gas); and layer separators 23a, 23b, and 23n for oil-water separation of the substance switched to the liquid phase in the condensers into an organic layer (or organic matter layer) and an aqueous layer.

[0052] The separation devices within the separation section may be connected to each reactor in the reaction section, or one separation device may be connected to two or more reactors. For example, if there are five reactors in the reaction section, the first separation device may be connected to the first to third reactors, and the second separation device may be connected to the fourth and fifth reactors. Thus, when there are N reactors, the number of separation devices may range from one to N, where N is as defined above.

[0053] Furthermore, in the continuous esterification reaction system, the recovery unit 3 may include primary unreacted alcohol recovery units 3a, 3b, and 3n, which recover the liquid phase substance containing unreacted alcohol separated as a result of gas-liquid separation in the column separators 21a, 21b, and 21n within the separation unit 2, specifically the separation devices 2a, 2b, and 2n, and reintroduce it to the reactors 1a, 1b, and 1n; and secondary unreacted alcohol recovery units 3a', 3b', and 3n', which recover the organic layer containing unreacted alcohol separated in the layer separators 23a, 23b, and 23n and introduce it to the upper stage of the column separators 21a, 21b, and 21n. The primary unreacted alcohol recovery units and secondary unreacted alcohol recovery units can each have various forms such as storage tanks and recovery lines.

[0054] Furthermore, in the continuous esterification reaction system, the pressure control unit 4 controls the pressure in the reactor within the reaction section to satisfy the aforementioned pressure conditions.

[0055] Specifically, the pressure control unit includes pressure control devices 4a, 4b, and 4n (hereinafter referred to as "primary pressure control devices") located in an inert gas inflow line connected to the lower part of the reactor, which adjust the pressure inside the reactor by controlling the amount of inert gas continuously flowing into the lower part of each reactor. The pressure control unit may also include pressure control devices 4a', 4b', and 4n' (hereinafter referred to as "secondary pressure control devices") located in an uncondensed gas discharge line containing inert gas, connected to the separation unit, specifically the upper stage of the condenser of the separation device, which adjust the pressure inside the reactor by controlling the amount of uncondensed gas discharged from the separation unit. Furthermore, the pressure control unit 4 may also include pressure control devices 4a'', 4b'', and 4n'' (hereinafter referred to as "tertiary pressure control devices") located in the discharge line of the water layer separated by oil-water separation in the layer separator 23a, which adjust the pressure inside the reactor by controlling the amount of water discharged. As a result, the separation unit connected to the reactor, specifically the column separator, condenser, and layer separator within the separation apparatus, also operates at the same pressure as the reactor.

[0056] The pressure control device within the pressure control unit 4 may, but is not limited to, a control valve or the like.

[0057] In a continuous esterification reaction system having such a structure, when an esterification reaction occurs in the first reactor 1a of the reaction section, an ester compound is produced as a result of the reaction. At this time, the reaction product contains not only the ester compound but also unreacted raw materials and water. The reaction product, which contains the ester compound and unreacted raw materials, is sequentially moved to subsequent reactors connected in series to the first reactor 1a, such as the second reactor 1b, where esterification reactions occur. As a result of being transferred to subsequent reactors and the esterification reaction being repeated, the content of the ester compound in the reaction product increases, and the content of unreacted raw materials decreases, until only the ester compound remains in the final reactor. On the other hand, the reaction product containing unreacted alcohol and water from the unreacted raw materials is discharged in the gas phase to the first separation device 2a through a reaction product discharge line connected to the top of the reactor, due to the heat and pressure in the first reactor 1a. When the reaction product flows into the column separator 21a in the first separation device 2a through the reaction product discharge line, gas-liquid separation is performed in the column separator. As a result, the separated liquid phase substance is returned to the first reactor 1a through the recovery line, which is the recovery device 3a at the bottom of the column separator, and the gas phase substance is discharged to the condenser 22a through the discharge line at the top of the column separator 21a. At this time, the liquid phase substance mainly contains unreacted alcohol and may also contain low-boiling point ester compounds that have flowed out of the reactor in the gas phase. This allows the liquid phase substance introduced into the first reactor to be reused in the esterification reaction. On the other hand, the gas phase substance may further contain alcohol and other substances that have not liquefied with water. In the condenser 22a, the gas phase substance discharged from the column separator 21a is condensed and converted to the liquid phase, and uncondensed gas containing inert gases is discharged and removed. The liquid phase substance condensed in the condenser is discharged to the layer separator 23a through the discharge line of the condenser 22a. In the layer separator 23a, oil-water separation is performed to separate the liquid phase substance flowing in from the condenser 22a into an organic layer and an aqueous layer. As a result, the separated organic layer is reintroduced to the upper stage of the column separator 21a through the recovery line 3a', and the aqueous layer is discharged to the outside. At this time, the organic layer mainly contains unreacted alcohol.

[0058] Furthermore, the continuous esterification reaction system may further include one or more of the following: a neutralizer for neutralizing the ester composition produced through the reactor, and a purification tank for purification. The neutralizer or purification tank may be located in connection with the last reactor (the nth reactor) of the series-connected reactors.

[0059] For example, if a purification tank is also included, once the esterification reaction in the reaction section is complete, the reaction product containing the ester compound flows from the final reactor into the neutralizer or purification tank. Unreacted alcohols and other substances remaining in the reaction product can then be separated and removed to obtain a purified ester compound.

[0060] The purification tank includes a separation column or a flash vessel, etc. If the purification tank includes a separation column, the composition ratio of the final product may change depending on the number of stages in the separation column, and therefore it is preferable to determine the number of stages in the separation column considering the composition ratio and characteristics of the product to be manufactured. Furthermore, if a flash vessel is included, it is preferable to carry out the process under vacuum conditions in order to efficiently remove unreacted alcohol contained in the high-temperature reactants.

[0061] Furthermore, the unreacted alcohol separated in the purification tank may be added to one or more reactors in the reaction section and reused in the continuous esterification reaction.

[0062] Furthermore, the continuous esterification reaction system may further include equipment commonly found in process designs, such as a mixer for mixing the polycarboxylic acid and the alcohol, a decanter, a heat exchanger, a reboiler, and a pump, and these devices may be appropriately arranged according to their application.

[0063] As described above, the method for producing an ester-based composition according to the present invention allows for the continuous production of reaction products by continuously feeding raw materials containing polycarboxylic acid and alcohol into the continuous esterification reaction system. Simultaneously, by controlling the pressurization conditions in each reactor through a pressure control unit provided in the reaction system to satisfy the aforementioned conditions, the heat transfer performance of each reactor can be maximized, thereby improving both reactor productivity and overall reactor productivity.

[0064] The following are preferred embodiments to aid in understanding the present invention. However, these embodiments are provided solely to facilitate understanding the present invention and do not limit its scope.

[0065] In the following examples and comparative examples, a continuous esterification reaction system consisting of four reactors configured in series was simulated using the Aspen Plus process simulation program.

[0066] Example 1 As shown in Figure 1, an ester-based composition was produced using a continuous reaction system consisting of four reactors configured in series. Terephthalic acid and 2-ethylhexanol were used as reaction raw materials in a 1:3.4 molar ratio. Tetra-n-butyl titanate (TnBT) was used as the catalyst, with an input amount of 500 ppm based on the total weight of 2-ethylhexanol. When the reaction raw materials were introduced into the first reactor in the series configuration, the resulting reactants were sequentially transferred to subsequent reactors. The pressure in each reactor was set to the conditions shown in Table 1 below, through control of the amount of nitrogen gas introduced into each reactor, the amount of uncondensed gas discharged to the upper stage of the condenser, and the amount of water discharged after oil-water separation in the layer separator, all controlled by a pressure control device.

[0067] Examples 2 to 4 and Comparative Examples 1 to 3 An ester-based composition was produced in the same manner as in Example 1, except that the pressure in each reactor was set to the conditions shown in Table 1 below.

[0068] Experimental example During the production of the ester compositions according to the above examples and comparative examples, the increase in average reactor temperature, heat transfer performance, reactor productivity, and total reactor productivity were evaluated.

[0069] (1) Increase in average reactor temperature (unit: °C) From the simulation results using the Aspen Plus process simulation program, the temperatures of each reactor during the production of the ester-based composition according to the above example or comparative example were derived.

[0070] After summing up all the derived temperature values ​​for each reactor, the average reactor temperature (°C) was calculated by dividing by the number of reactors, and the increase in the average reactor temperature was calculated using Equation 3 below. [Formula 3] Reactor mean temperature increase (°C) = Ta - Tb

[0071] In the above formula 3, Ta is the average reactor temperature (°C) in the examples or comparative examples, and is calculated by summing all the temperature values ​​of each reactor in the examples or comparative examples derived from the simulation results using the Aspen Plus process simulation program, and then dividing by the total number of reactors. Tb is the average reactor temperature (°C) in Comparative Example 1, and is calculated by summing all the individual reactor temperature values ​​in Comparative Example 1 derived from the simulation results using the Aspen Plus process simulation program, and then dividing by the total number of reactors.

[0072] (2) Heat transfer performance ratio (%) for each reactor The heat transfer performance of each reactor in the examples and comparative examples (MJ / h·℃·m) can be determined by the following formula 4. 3 The heat transfer performance ratio for each reactor was determined by calculating the heat transfer performance ratio of the first reactor (n=1, reactor #1) as a percentage based on the heat transfer performance value of the first reactor (n=1, reactor #1).

[0073] [Equation 4] Heat transfer performance of the reactor (MJ / h·℃·m) 3 ) = A1 / (A2×A3) In the above formula 4, A1 is the thermal energy (Q) (MJ / hr, Megajoule per hour) transferred from the heat supply utility to the reactor internal fluid. A2 is the log-mean temperature difference (LMTD) (°C) between the heat supply utility and the reactor. A3 is the reactor liquid volume (m 3 )

[0074] (3) Reactor productivity ratio for each reactor (%) The productivity of each reactor is calculated using the following formula 5 (kg / hr·m 3 The productivity ratio (%) for each reactor was calculated and expressed as a percentage based on the reactor productivity of the first reactor (n=1, reactor #1), and is shown for each reactor.

[0075] [Formula 5] Reactor productivity (kg / hr·m) 3 ) = P / V In the above formula 5, P is the amount of reaction product produced in each reactor (kg / hr), derived from the simulation results using the Aspen Plus process simulation program. V is the liquid volume (m) of the reactor. 3 )

[0076] (4) Average reactor productivity (%) and total reactor productivity (%) After summing up the productivity ratio values ​​for each reactor calculated in step 3 above, the average reactor productivity was calculated as a percentage by dividing by the number of reactors, and the reactor productivity was shown as a percentage based on the average reactor productivity of Comparative Example 1. [Table 1]

[0077] Examples 1 and 2 are configurations of a continuous esterification reaction system with components arranged in series, in which a constant pressure is increased in the downstream reactor compared to the first-stage reactor, and the pressure in the downstream reactors is the same in both cases. Examples 3 and 4 are configurations of a continuous esterification reaction system with components arranged in series, in which the reaction pressure is increased sequentially.

[0078] On the other hand, Comparative Example 1 is a continuous esterification reactor configuration with the same pressure in series, Comparative Example 2 is a configuration in which the reaction pressure is sequentially decreased, and Comparative Example 3 is a configuration in which the pressure is increased in only two reactors compared to a single-stage reactor, and the pressure in the subsequent reactor is reduced to the same pressure as the single-stage reactor.

[0079] In Comparative Example 1, the heat transfer performance of the 2nd to 4th stage reactors was 55-69%, excluding the 1st stage reactor, indicating that there was still excess heat transfer capacity. In contrast, when the pressure was increased with each subsequent reactor, as in Examples 1 to 4, the heat transfer performance of each reactor increased, and productivity also improved. This increase was greater with a larger pressure increase. Furthermore, in Example 5, where the pressure was continuously increased with each subsequent reactor, the heat transfer performance of each reactor was utilized at almost 100%, resulting in the highest overall reactor productivity.

[0080] On the other hand, in Comparative Example 2, where the pressure was reduced as the reactor progressed to the later stages, the heat transfer performance ratio of each reactor step decreased compared to Comparative Example 1, and productivity also decreased. Furthermore, in Comparative Example 3, the heat transfer performance ratio and productivity were higher in the two-stage reactor, where the pressure was increased compared to the one-stage reactor, but the heat transfer performance ratio and productivity decreased again due to the subsequent pressure reduction in the third and fourth-stage reactors.

[0081] These results demonstrate that, in a continuous esterification reaction system with multiple reactors connected in series, the heat transfer performance of each reactor, reactor productivity, and overall reactor productivity can be improved through stepwise pressurization. [Explanation of symbols]

[0082] 1. Reaction section 1a, 1b, 1n reactors 2 Separation part 2a, 2b, 2n separation device 3. Recovery section 3a, 3b, 3n Primary recovery unit for unreacted alcohol 3a', 3b', 3n': Secondary recovery system for unreacted alcohol 4. Pressure Control Unit 4a, 4b, 4n Primary pressure control devices 4a', 4b', 4n' Secondary pressure control devices 4a' ', 4b' ', 4n' ' tertiary pressure control device 21a, 21b, 21n column separators 22a, 22b, 22n condensers 23a, 23b, 23n layer separator 100 Continuous Esterification Reaction Systems

Claims

1. A method for producing an ester-based composition using a continuous esterification reaction system in which a total of N reactors, from the first reactor to the Nth reactor, are connected in series, The process includes a step of continuously feeding raw materials containing a polycarboxylic acid and an alcohol into the continuous esterification reaction system to continuously produce a reaction product, The following equation 1 is satisfied: A method for producing ester compositions. [Formula 1] P １ <P Ｎ－１ ≦P Ｎ In the above formula 1, P １ This is the pressure (bar) in the first reactor, P Ｎ This is the pressure (bar) of the Nth reactor following the first reactor, N is an integer greater than or equal to 3.

2. The following equation 2 is satisfied: A method for producing the ester composition described in claim 1. [Formula 2] P １ +0.01≦P Ｎ ≦P １ +2 In the above Mathematical Formula 2, P １ , P Ｎ and N are as defined in claim 1.

3. P １ The bar is between 1 and 4 bar. A method for producing the ester composition described in claim 2.

4. The aforementioned N is an integer between 3 and 20. A method for producing the ester composition described in claim 1.

5. The polycarboxylic acid is one or more selected from the group consisting of phthalic acid, isophthalic acid, terephthalic acid, their anhydrides, and their derivatives. A method for producing the ester composition described in claim 1.

6. The aforementioned alcohol is an aliphatic alcohol having 1 to 20 carbon atoms. A method for producing the ester composition described in claim 1.

7. The aforementioned raw material further comprises an esterification reaction catalyst. A method for producing the ester composition described in claim 1.

8. The continuous esterification reaction system described above is: A reaction section consisting of N reactors connected in series, in which the esterification reaction of raw materials containing polycarboxylic acid and alcohol takes place; A separation unit including a separation device that separates unreacted alcohol from the reaction product flowing in from the reactor of the reaction unit; A recovery unit including a recovery device for introducing the unreacted alcohol separated by the separation device of the separation unit into the reactor of the reaction unit; and A pressure control unit including a pressure control device for adjusting the pressure of the reactor in the reaction section; A method for producing the ester composition described in claim 1.

9. The separation device is A column separator that performs gas-liquid separation on the reaction product flowing in from the reactor of the reaction section; A condenser that liquefies the gaseous substances separated and discharged as a result of gas-liquid separation in the column separator and converts them to a liquid phase, and discharges the uncondensed gas; and A layer separator for separating the substance switched to the liquid phase in the condenser into an organic layer and an aqueous layer; A method for producing the ester composition according to claim 8.

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