Method for producing ester-based composition

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 TO RELATED APPLICATIONS] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0126487, dated October 4, 2022, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present invention provides a method for producing an ester-based composition, which can improve heat transfer performance, reactor productivity, and total reactor productivity when producing an ester-based composition 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 with alcohols are widely used as plasticizers.

[0004] The esterification reaction is typically carried out at high temperatures in the presence of an esterification catalyst. The resulting reaction product contains the catalyst, catalyst decomposition products, unreacted alcohol, unreacted polycarboxylic acid, monoester, and reaction impurities. Therefore, to obtain a pure ester compound, post-treatment steps such as neutralization, water washing, alcohol removal, and / or filtration must be performed.

[0005] Therefore, in order to obtain high-purity ester compounds, research is being conducted in various areas, such as methods for efficiently separating and purifying the by-products contained in the reaction product, methods for suppressing the occurrence of reverse reactions and catalyst decomposition during the esterification reaction, and methods for efficiently designing production equipment or processes.

[0006] One method for suppressing the occurrence of reverse reactions and catalyst decomposition during an esterification reaction is to remove water produced 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. In this case, the ability to supply heat to the reactors, i.e., the heat transfer performance of the reactors, directly affects the esterification reaction rate. Therefore, when producing ester compounds through a continuous process using multiple reactors with the same heat transfer performance, the reaction rate decreases in the later reactors due to a decrease in raw material concentration, and as a result, 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 compared to the available heat transfer performance, resulting in a relatively large amount of heat transfer capacity remaining. This results in a problem of reduced heat transfer performance, reactor productivity, and total reactor productivity during the production of ester compounds. Therefore, various methods for improving the production efficiency and productivity of ester compounds through control of reactor conditions have been proposed, but they are insufficient in terms of improvement effect, economy, and processability. Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention provides a method for producing an ester-based composition, which can improve heat transfer performance, reactor productivity, and total reactor productivity when producing an ester-based composition 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, there is provided a method for producing an ester composition using a continuous esterification reaction system in which a total of N reactors from a first reactor to an Nth reactor are connected in series, comprising: continuously feeding a raw material 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 is provided that satisfies the following mathematical formula 1: [Formula 1] P1 <P N-1 ≦P N In the above formula 1, P1 is the pressure of the first reactor (bar), P N is the pressure (bar) of the Nth reactor subsequent to the first reactor, N is an integer of 3 or greater. [Effects of the Invention]

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

[0010] [Figure 1] FIG. 1 is a schematic diagram illustrating a continuous esterification reaction system that can be used in the method for producing an ester composition according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] In the present invention, terms such as first and second are used to describe various components, and the terms are used only to distinguish one component from another.

[0012] Furthermore, the terms used in this specification are merely used to describe exemplary embodiments and are not intended to limit the present invention. A singular expression includes a plural expression unless the context clearly dictates otherwise. In this specification, the terms "comprise," "include," "comprise," "have," and the like are intended to specify the presence of embodied features, numbers, steps, components, or combinations thereof, and should be understood as not precluding the presence or additional possibility of one or more other features, numbers, steps, components, or combinations thereof.

[0013] In this specification, "%" and "parts" indicating the content are by weight unless otherwise specified.

[0014] Since the present invention can be modified in various ways and can have various forms, specific examples are exemplified and described in detail below, but it should be understood that this is not intended to limit the invention to the particular disclosed form, and that the invention should include any modifications, equivalents, or alternatives falling within the spirit and technical scope of the invention.

[0015] The method for producing the ester composition according to the present invention will be described in detail below.

[0016] In the conventional production of an ester-based composition using a continuous reaction system in which multiple reactors are connected in series, residual heat tends to remain in the later reactors, resulting in a problem of reduced heat transfer performance, reactor productivity, and total reactor productivity.

[0017] Therefore, in the present invention, in order to make the most of the residual heat performance that tends to remain in later-stage reactors, the later-stage reactors in a continuous esterification reaction system are pressurized more than the earlier-stage reactor, thereby increasing the reaction temperature and reactivity, and as a result, improving the productivity within the same reactor.

[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 Nth reactor are connected in series, continuously feeding a raw material containing a polycarboxylic acid and an alcohol into the continuous esterification reaction system to continuously produce a reaction product; The following formula 1 is satisfied. [Formula 1] P1 <P N-1 ≦P N In the above formula 1, P1 is the pressure of the first reactor (bar), P N is the pressure (bar) of the Nth reactor subsequent to the first reactor, N is an integer of 3 or greater.

[0019] When the pressure is applied to the subsequent reactors, the temperature in each pressurized reactor increases, resulting in an increase in the average temperature of the entire reactors. Such an increase in the average reactor temperature increases the esterification reaction rate, which in turn increases the overall reactor productivity.

[0020] Furthermore, if the pressure increase in the downstream reactor relative to the first reactor is above a certain level, the above effect can be further enhanced. However, if the pressure in the downstream reactor is excessively high, the reaction temperature in the reactor may increase significantly, the required heat may exceed the heat transfer capacity of the reactor, and the content of thermal residue may increase. As a result, reverse reactions and catalytic decomposition reactions may occur, which may actually reduce reactivity. Therefore, it is preferable to control the pressure increase in the downstream reactor to below a certain level.

[0021] Specifically, the manufacturing method can further satisfy the following formula 2: [Formula 2] P1+0.01≦P N ≦P1+2 In the above formula 2, P1, P N and N is as defined above. More specifically, the manufacturing method may 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 is as defined above.

[0022] In addition, in the above Equations 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 this range, the processability and reactor productivity are improved.

[0023] In addition, in the above Equations 1 and 2, N represents the number of reactors included in the reaction system. Specifically, N is an integer of 3 or more, or 4 or more, and 20 or less, or 10 or less, or 8 or less, or 5 or less.

[0024] In the 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. The pressure in the reactor can also be adjusted by controlling the amount of uncondensed gas, including the inert gas, and the amount of water discharged as a result of the reaction.

[0025] For example, the pressure in 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 discharged.

[0026] The amounts of the inert gas, uncondensed gas, and water can be adjusted by a pressure control device in a pressure control section of the continuous esterification reaction system, as will be described in detail below in relation to the continuous esterification reaction system.

[0027] Meanwhile, in the method according to the present invention, the raw material for preparing the ester-based composition is prepared by mixing a polycarboxylic acid with an alcohol, and thus the method according to the present invention may further include a step of mixing the polycarboxylic acid with the alcohol before adding the raw material.

[0028] The polycarboxylic acid and the alcohol may be mixed by a conventional method, and may be mixed uniformly using a mixer before being introduced into the reactor, which can prevent the esterification reaction from occurring unevenly depending on the location inside the reactor.

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

[0030] Specifically, the polycarboxylic acid may be a C2 to C20 aliphatic or a 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 anhydrides thereof, 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 anhydrides and derivatives thereof, and more preferably, terephthalic acid or anhydride thereof.

[0031] The alcohol may be a linear or branched aliphatic alcohol having 1 to 20 carbon atoms, or 4 to 20 carbon atoms, or 5 to 15 carbon atoms, or 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 an ester compound of the present invention may be a method for producing dioctyl terephthalate (Di 2-ethylhexyl terephthalate, DOTP) using terephthalic acid as the polycarboxylic acid and 2-ethylhexanol as the alcohol.

[0033] An esterification reaction catalyst may be further added during the production of the raw material.

[0034] The esterification catalyst may be added to a mixture of polycarboxylic acid and alcohol, or to either polycarboxylic acid or alcohol prior to the preparation of the mixture, or may be added directly to the reactor.

[0035] The esterification reaction catalyst may be an organometallic catalyst, an organic sulfonic acid, an acid catalyst, or a mixture thereof. Specific examples of the organometallic catalyst include tetraalkyl titanates such as tetraisopropyl titanate, tetra-n-butyl titanate (TnBT), tetraoctyl titanate, and butyltin maleate. Examples of the organic sulfonic acid include paratoluenesulfonic acid, methylsulfonic acid, ethanesulfonic acid, propanesulfonic acid, and butanesulfonic acid. Examples of the acid catalyst include formic acid, nitric acid, acetic acid, hydrochloric acid, phosphoric acid, and sulfuric acid. These catalysts may be used alone or in combination.

[0036] The amounts of the polycarboxylic acid, alcohol, and esterification catalyst used are not particularly limited in the present invention and may be appropriately determined depending on the properties and applications of the ester-based composition to be prepared.

[0037] For example, when dioctyl terephthalate is produced using terephthalic acid and 2-ethylhexanol, the polycarboxylic acid corresponding to the 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] The catalyst may be added in an amount of 100 to 2000 ppm, more specifically, 100 ppm or more, 200 ppm or more, 300 ppm or more, or 500 ppm or more, and 2000 ppm or less, 1500 ppm or less, 1000 ppm or less, or 700 ppm or less, based on the total weight of the alcohol. When added within this content range, the maximum reaction efficiency relative to the amount added can be achieved.

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

[0040] When the raw materials containing the polycarboxylic acid, alcohol, and optionally an esterification catalyst are continuously fed into a first reactor of a continuous esterification reaction system, an esterification reaction occurs in the reactor, and the resulting reaction product is sequentially transferred to subsequent reactors connected in series to the first reactor. When the reaction product flows into the subsequent reactors, the esterification reaction occurs in the same manner as in the first reactor.

[0041] As the reactants are continuously passed through a plurality of reactors connected in series, the process variables for each reactor can be independently controlled to optimize the overall process, thereby maximizing the efficiency of the manufacturing process.

[0042] Specifically, in the production method according to the present invention, the pressurization conditions in each reactor are controlled to satisfy the above-mentioned conditions through a pressure control unit provided in a continuous esterification reaction system, thereby maximizing the heat transfer performance of each reactor and improving both the reactor productivity and the total reactor productivity.

[0043] Meanwhile, the continuous esterification reaction system used in the production 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] Fig. 1 is a schematic diagram illustrating a continuous esterification reaction system that can be used in the method for producing an ester composition according to the present invention. Fig. 1 is merely an example for explaining the present invention, and the present invention is not limited thereto.

[0045] 1, the continuous esterification reaction system 10 includes a reaction section 1 having N reactors connected in series in which an esterification reaction of a raw material containing a polycarboxylic acid and an alcohol is carried out; a separation section 2 including a separation device for separating unreacted alcohol from a reaction product flowing from the reaction section reactor; a recovery section 3 including a recovery device for introducing unreacted alcohol separated from the separation device of the separation section into the reaction section reactor; and a pressure control section 4 including a pressure control device for adjusting the pressure of the reactor in the reaction section. N is an integer of 3 or greater, more specifically, an integer of 3 or greater or 4 and 20 or less, 10 or less, 8 or less, or 5 or less.

[0046] In the continuous esterification reaction system, the reaction section 1 includes N reactors 1a, 1b, ... 1n (where n is a letter corresponding to the number N) connected in series to sequentially carry out an esterification reaction. When raw materials containing a polycarboxylic acid, an alcohol, and optionally an esterification catalyst are continuously introduced into the first reactor 1a of the reaction section 1, an esterification reaction occurs in the first reactor 1a. The resulting reaction product is transferred sequentially to subsequent reactors connected in series to the first reactor 1a, specifically, from the second reactor 1b to the Nth reactor 1n. The reaction product is transferred through a transfer line, such as a pipe, connecting the two reactors. For example, as shown in FIG. 1, the first and second reactors are connected through a reaction product transfer line located below the first reactor, through which the reaction product from the first reactor is transferred. When the reaction product flows into the subsequent reactor, the esterification reaction occurs in the same manner as in the first reactor.

[0047] Meanwhile, an inert gas is introduced into the bottom of the reactor in the reaction section to control the pressure inside the reactor. The inert gas not only controls the pressure inside the reactor, but also serves to suppress side reactions during the esterification reaction in the reactor due to 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 together with the reaction by-product to a separation section through a reaction product discharge line connected to the top of the reactor.

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

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

[0051] In addition, in the continuous esterification reaction system, the separation section 2 includes separation devices 2a, 2b, and 2n connected to the reaction section 1, specifically, the reactor of the reaction section, for separating unreacted alcohol from the reaction product flowing in from the reactor. Specifically, the separation devices 2a, 2b, and 2n can include column separators 21a, 21b, and 21n for performing gas-liquid separation on the reaction product flowing in from the reactor of the reaction section; condensers 22a, 22b, and 22n for liquefying the gas phase material separated and discharged as a result of gas-liquid separation in the column separator and converting it to a liquid phase and discharging uncondensed gas (including inert gas); and layer separators 23a, 23b, and 23n for performing oil-water separation on the material converted to the liquid phase in the condenser into an organic layer (or organic matter layer) and an aqueous layer.

[0052] The separation unit may include one separation device connected to each reactor in the reaction unit, or one separation device connected to two or more reactors. For example, if the reaction unit includes five reactors, a first separation device may be connected to the first to third reactors, and a 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 1 to N, where N is as defined above.

[0053] In the continuous esterification reaction system, the recovery unit 3 may include a primary unreacted alcohol recovery unit 3a, 3b, 3n that recovers a liquid phase material containing unreacted alcohol separated as a result of gas-liquid separation in the column separators 21a, 21b, 21n in the separation units 2a, 2b, 2n and reintroduces it into the reactors 1a, 1b, 1n, and may further include a secondary unreacted alcohol recovery unit 3a', 3b', 3n' that recovers an organic layer containing unreacted alcohol separated in the layer separators 23a, 23b, 23n and introduces it into the upper stage of the column separators 21a, 21b, 21n. The primary unreacted alcohol recovery unit and the secondary unreacted alcohol recovery unit may each have various forms, such as a storage tank or a recovery line.

[0054] In the continuous esterification reaction system, the pressure control unit 4 controls the pressure in the reactor in the reaction unit so as to satisfy the pressure conditions described above.

[0055] Specifically, the pressure control unit includes pressure control devices 4a, 4b, and 4n (hereinafter referred to as "primary pressure control devices") located on an inert gas inlet line connected to the bottom of each reactor, and regulating the pressure within the reactor by controlling the amount of inert gas continuously flowing into the bottom 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 on an uncondensed gas discharge line containing inert gas connected to the separation unit, specifically the upper stage of the separation unit condenser, and regulating the pressure within the reactor by controlling the amount of uncondensed gas discharged from the separation unit. The pressure control unit 4 may also include pressure control devices 4a'', 4b'', and 4n'' (hereinafter referred to as "tertiary pressure control devices") located on a discharge line of the water layer separated by oil-water separation in layer separator 23a, and regulating the amount of water discharged. This allows the separation section connected to the reactor, specifically the column separator, condenser and layer separator in the separation device, to also be at the same pressure as the reactor.

[0056] The pressure control device in the pressure control section 4 may specifically be a control valve or the like, but is not limited to this.

[0057] In a continuous esterification reaction system with this structure, an esterification reaction occurs in the first reactor 1a of the reaction section, producing an ester compound as a result of the reaction. The resulting reaction product contains the ester compound, unreacted raw materials, and water. The reaction product containing the ester compound and unreacted raw materials is transferred to subsequent reactors, such as the second reactor 1b, connected in series to the first reactor 1a, where the esterification reaction occurs. As the ester compound is transferred to the subsequent reactors and the esterification reaction is repeated, the content of the ester compound in the reaction product increases and the content of the unreacted raw materials decreases, until only the ester compound remains in the final reactor. Meanwhile, the reaction product, including unreacted alcohol and water from the unreacted raw materials, is discharged in a gaseous state due to the heat and pressure within the first reactor 1a through a reaction product discharge line connected to the top of the reactor to the first separator 2a. The reaction product flows into the column separator 21a in the first separator 2a through the reaction product discharge line. Gas-liquid separation occurs in the column separator. The separated liquid phase material is returned to the first reactor 1a through a recovery line, which is the recovery device 3a at the bottom of the column separator. The gas phase material is discharged to the condenser 22a through a discharge line at the top of the column separator 21a. The liquid phase material mainly contains unreacted alcohol and may also contain low-boiling-point ester compounds discharged in gas phase from the reactor. This allows the liquid phase material to be reused for the esterification reaction. Meanwhile, the gas phase material may further contain water and unliquidized alcohol. In the condenser 22a, the gas phase material discharged from the column separator 21a is condensed to a liquid phase, and uncondensed gases, including inert gases, are discharged. The liquid phase material condensed in the condenser 22a 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 material flowing from the condenser 22a into an organic layer and an aqueous layer. As a result, the separated organic layer is re-introduced into the upper part 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] The continuous esterification reaction system may further include at least one of a neutralizer for neutralizing the ester composition produced in the reactor and a purification tank for purifying the ester composition. The neutralizer or purification tank may be connected to the last reactor (nth reactor) of the series-connected reactors.

[0059] For example, when a purification tank is further included, the esterification reaction in the reaction section is completed, and as a result, the reaction product containing the ester compound flows from the last reactor into the neutralizer or purification tank. Unreacted alcohol remaining in the reaction product can be separated and removed to obtain a purified ester compound.

[0060] The purification vessel may include a separation column or a flash vessel. When the purification vessel includes a separation column, the composition ratio of the final composition may vary depending on the number of stages in the separation column. Therefore, it is preferable to determine the number of stages in the separation column in consideration of the composition ratio and properties of the composition to be produced. Furthermore, when a flash vessel is included, it is preferable to carry out the reaction under vacuum conditions in order to efficiently remove unreacted alcohol contained in the high-temperature reaction product.

[0061] In addition, the unreacted alcohol separated in the purification tank may be fed into one or more reactors in the reaction section and reused in the continuous esterification reaction.

[0062] The continuous esterification reaction system may further include devices that are generally included in process design, 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 depending on the application.

[0063] As described above, in the method for producing an ester composition according to the present invention, raw materials including a polycarboxylic acid and an alcohol are continuously fed into the continuous esterification reaction system to continuously produce a reaction product. At the same time, the pressurization conditions in each reactor are controlled to satisfy the above-mentioned conditions through a pressure control unit provided in the reaction system, thereby maximizing the heat transfer performance of each reactor and improving both reactor productivity and total reactor productivity.

[0064] Preferred examples are presented below to aid in understanding the present invention. However, the following examples are provided merely to facilitate understanding of the present invention and are not intended to limit the scope of the present invention.

[0065] In the following examples and comparative examples, a continuous esterification reaction system having four reactors connected in series was simulated using an Aspen Plus process replication program.

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

[0067] Examples 2 to 4 and Comparative Examples 1 to 3 An ester composition was prepared 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 preparation of the ester-based compositions according to the Examples and Comparative Examples, the reactor average temperature increase, heat transfer performance, reactor productivity, and total reactor productivity were evaluated.

[0069] (1) Average reactor temperature increase (unit: °C) The temperature of each reactor during the production of the ester-based composition according to the Examples or Comparative Examples was derived from the results of a simulation using the Aspen Plus process replication program.

[0070] The calculated temperature values ​​of each reactor were all added together and divided by the number of reactors to calculate the average reactor temperature (°C), and the average reactor temperature increase was calculated using the following Equation 3. [Formula 3] Average reactor temperature increase (℃) = Ta - Tb

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

[0072] (2) Heat transfer performance ratio (%) for each reactor The heat transfer performance (MJ / h °C m) of each reactor in the examples and comparative examples was calculated using the following equation 4. 3 ) was calculated, and the heat transfer performance ratio for each reactor was calculated as a percentage based on the heat transfer performance value of the first reactor (n=1, reactor #1).

[0073] [Formula 4] Heat transfer performance of the reactor (MJ / h °C m 3 )=A1 / (A2×A3) In the above equation 4, A1 is the heat 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) between the heat supply utility and the reactor (°C); A3 is the reactor liquid volume (m 3 )

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

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

[0076] (4) Average reactor productivity (%) and total reactor productivity (%) The productivity ratio values ​​of each reactor calculated in 3 were all added together and divided by the number of reactors to calculate the average reactor productivity as a percentage. The reactor productivity was expressed as a percentage based on the average reactor productivity of Comparative Example 1. [Table 1]

[0077] In Examples 1 and 2, the pressure in the subsequent reactors was increased by a certain amount relative to the first-stage reactor in a continuous esterification reaction system configured in series, and the pressure in the subsequent reactors was the same. In Examples 3 and 4, the reaction pressure was increased sequentially in a continuous esterification reaction system configured in series.

[0078] On the other hand, Comparative Example 1 is a configuration in which the pressure is the same in a continuous esterification reactor configuration configured in series, Comparative Example 2 is a configuration in which the reaction pressure is sequentially reduced, and Comparative Example 3 is a configuration in which the pressure is increased only in the second-stage reactor relative to the first-stage reactor, and the pressure in the subsequent-stage reactor is reduced to the same as that of the first-stage reactor.

[0079] In Comparative Example 1, the heat transfer performance of the second to fourth reactors, excluding the first reactor, was 55-69%, indicating that there was still some heat transfer capacity. In contrast, when the pressure was increased toward the later reactors as in Examples 1 to 4, the heat transfer performance of each reactor increased, and productivity also increased. This increase was greater the greater the increase in pressure. Furthermore, in Example 5, where the pressure was continuously increased toward the subsequent reactors, the heat transfer performance of each reactor was used at nearly 100%, and as a result, the total reactor productivity also showed the highest value.

[0080] On the other hand, in Comparative Example 2, where the pressure was decreased toward the later reactors, the heat transfer performance ratio of the reactors at each step decreased and productivity also decreased compared to Comparative Example 1. Also, in Comparative Example 3, the heat transfer performance ratio and productivity increased in the second-stage reactor, where the pressure was increased compared to the first-stage reactor, but then the heat transfer performance ratio and productivity decreased again due to the decrease in pressure in the third and fourth-stage reactors.

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

[0082] 1. Reaction section Reactors 1a, 1b, and 1n 2 Separation part 2a, 2b, 2n separation device 3. Collection Department 3a, 3b, 3n Primary recovery device for unreacted alcohol 3a', 3b', 3n' Secondary recovery device for unreacted alcohol 4 Pressure control section 4a, 4b, 4n Primary pressure control device 4a', 4b', 4n' Secondary pressure control device 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 System

Claims

1. 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 Nth reactor are connected in series, comprising: continuously feeding a raw material containing a polycarboxylic acid and an alcohol into the continuous esterification reaction system to continuously produce a reaction product; Satisfy the following formula 1: A method for producing an ester-based composition. [Formula 1] P １ <P Ｎ－１ ≦P Ｎ In the above formula 1, P １ is the pressure of the first reactor (bar), P Ｎ is the pressure (bar) of the Nth reactor subsequent to the first reactor, N is an integer of 3 or greater.

2. Satisfy the following formula 2: A method for producing the ester composition according to claim 1. [Formula 2] P １ +0.01≦P Ｎ ≦P １ +2 In the above equation 2, P １ , P Ｎ and N is as defined in claim 1.

3. P １ is 1 to 4 bar; A method for producing the ester composition according to claim 2.

4. wherein N is an integer from 3 to 20. A method for producing the ester composition according to claim 1.

5. The polycarboxylic acid is at least one selected from the group consisting of phthalic acid, isophthalic acid, terephthalic acid, anhydrates thereof, and derivatives thereof. A method for producing the ester composition according to claim 1.

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

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

8. The continuous esterification reaction system comprises: a reaction section in which N reactors are connected in series, in which an esterification reaction of a raw material containing a polycarboxylic acid and an alcohol is carried out; a separation section including a separation device for separating unreacted alcohol from the reaction product flowing from the reactor of the reaction section; a recovery section including a recovery device that introduces the unreacted alcohol separated by the separation device of the separation section into the reactor of the reaction section; and a pressure control unit including a pressure control device that adjusts the pressure of the reactor in the reaction unit; A method for producing the ester composition according to claim 1.

9. The separation device comprises: a column separator in which gas-liquid separation is performed on the reaction product flowing from the reactor of the reaction section; a condenser for liquefying the gas phase material separated and discharged as a result of the gas-liquid separation in the column separator into a liquid phase and discharging the uncondensed gas; and a layer separator that separates the substance converted into a liquid phase by 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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