Method for producing acrylic acid

Abstract

The present invention relates to a method for producing acrylic acid, and more particularly to a method for producing acrylic acid that includes a method for controlling the reaction temperature so that the yield of acrylic acid is maintained as the reaction progresses.

Description

Technical Field

[0001] [Cross - reference to Related Applications] This application claims the benefit of priority based on Korean Patent Application No. 10 - 2023 - 0176549 filed on December 7, 2023, and all the contents disclosed in the literature of the Korean patent application are included as part of this specification.

[0002] The present invention relates to a method for producing acrylic acid, and more particularly, to a method for producing acrylic acid including a method for controlling the reaction temperature at which the yield of acrylic acid is maintained according to the progress of the reaction.

Background Art

[0003] Acrylic acid is an organic compound having both a carboxylic acid and an unsaturated double bond in the molecule. Its structure is very simple and can be converted into various substances. Since it is polymerizable, it is used in various industrial fields.

[0004] Specifically, acrylic acid is used in polyacrylic acid required for the production of superabsorbent polymers, sticky adhesives, paints, etc., or may be used as a raw material for producing other forms of acrylate - based monomers, or may be used as a polymerization raw material with other various monomers such as acrylamide, acrylonitrile, styrene, and alpha - olefins.

[0005] Such acrylic acid is generally produced using propylene generated in the refining and separation process of crude oil, such as naphtha cracking.

[0006] However, recently, as concerns about crude oil depletion and environmental issues have increased, interest in methods for producing acrylic acid using environmentally friendly raw materials has been growing.

[0007] Conventionally, in the method for producing acrylic acid by the gas-phase dehydration reaction of lactic acid on an acid catalyst, not only the formation of acrylic acid as the main reaction but also various side reactions occur simultaneously. At this time, coke is formed by the olefin compound produced by the side reaction, which may cover the active sites of the catalyst and cause deactivation of the catalyst. Therefore, as the reaction progresses, there is a problem that the catalyst is deactivated by coke and the yield of acrylic acid gradually decreases.

Summary of the Invention

Problems to be Solved by the Invention

[0008] This specification relates to a method for producing acrylic acid including a method for controlling the reaction temperature so that the yield of acrylic acid can be maintained at a certain level or higher as the reaction progresses.

Means for Solving the Problems

[0009] The present disclosure includes a step of supplying a feed stream containing lactic acid gas to a dehydration reactor filled with a catalyst to proceed with the lactic acid dehydration reaction; and a step of controlling the lactic acid dehydration reaction temperature in the form of a positive quadratic function with respect to the elapsed time of the dehydration reaction, wherein the lactic acid dehydration reaction proceeds in a temperature range of 350°C to 400°C, and a method for producing acrylic acid can be provided.

[0010] According to one embodiment, the lactic acid dehydration reaction temperature can be controlled in the form of a positive quadratic function with respect to the elapsed time of the dehydration reaction after being maintained at the initial dehydration reaction temperature for 5 hours or more and 35 hours or less after the start of the lactic acid dehydration reaction.

[0011] According to one embodiment, the coefficient range of the highest-order term of the positive quadratic function can be 0.001 or more and 0.005 or less.

[0012] According to one embodiment, the method for producing acrylic acid can satisfy the following formula 1: [Formula 1] T(t1)<T(t2); (when t1 < t2)

[0013] In the above formula 1, t1 is the time when the first time has elapsed since the start of the lactate dehydration reaction, and t2 is the time when the second time has elapsed since the start of the lactate dehydration reaction. T(t1) is the lactate dehydration reaction temperature at t1, and T(t2) is the lactate dehydration reaction temperature at t2.

[0014] According to one embodiment, the method for producing acrylic acid can maintain a yield of 45% or more while the lactate dehydration reaction is progressing.

[0015] According to one embodiment, the lactate dehydration reaction can proceed for a period of 20 hours or more and 185 hours or less.

[0016] In the present invention, terms such as "first," "second," etc., are used to describe various components, and such terms are used solely for the purpose of distinguishing one component from other components.

[0017] Furthermore, the terms used herein are used solely to illustrate exemplary embodiments and are not intended to limit the invention.

[0018] A singular expression includes plural forms unless the context clearly indicates a different meaning.

[0019] In this specification, terms such as “includes,” “equip,” or “have” are used to describe the features, figures, stages, components, or combinations thereof that have been implemented, and do not preclude the possibility of one or more other features, figures, stages, components, combinations thereof, or additions.

[0020] Furthermore, where it is referred to in this specification that each layer or element is formed "on top of" each layer or element, it means that each layer or element is formed directly on top of each layer or element, and that other layers or elements may be formed additionally between each layer, on the subject, or on the substrate.

[0021] The present invention can be subject 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 a specific disclosed form, and it should be understood to include all modifications, equivalents, and alternatives within the spirit and technical scope of the present invention.

[0022] When acrylic acid is produced by a lactic acid dehydration reaction using a catalyst, coke generated from the by-products of the dehydration reaction covers the active sites of the catalyst, and deactivation of the catalyst occurs as the reaction progresses. Therefore, there is a problem that the yield of acrylic acid gradually decreases as the reaction progresses, and a solution to this is required.

[0023] Therefore, in the present disclosure, there is provided a method for producing acrylic acid in which the dehydration reaction temperature is controlled in order to adjust the reaction efficiency according to the degree of catalyst deactivation, whereby a yield of acrylic acid above a certain level can be achieved during the reaction progress.

[0024] Hereinafter, the method for producing acrylic acid according to the present disclosure will be examined.

[0025] The method for producing acrylic acid according to the present disclosure can include a step of supplying a feed stream containing lactic acid gas to a dehydration reactor filled with a catalyst and allowing the lactic acid dehydration reaction to proceed.

[0026] The feed stream containing lactic acid gas supplied to the dehydration reactor can contain vaporized lactic acid gas molecules. As an example, the vaporized lactic acid molecules can be obtained by supplying a stream containing lactic acid to a vaporization reactor and allowing the vaporization reaction of lactic acid to proceed inside the vaporization reactor.

[0027] The catalyst filled in the dehydration reactor can include one or more selected from the group consisting of a calcium phosphate-based catalyst, a sodium phosphate-based catalyst, and an aluminum phosphate-based catalyst as a catalyst for the lactic acid dehydration reaction. Other reaction conditions can be used without special limitations as long as they are generally used in the technical field to which the present invention belongs and do not conflict with the content defined in this specification.

[0028] More specifically, as the dehydration catalyst, C a SO4 / Na2SO4; Na4P2O7 / CaSO4; Na4P2O7 / Ca3(PO4)2; NaH2PO4-NaHCO3 / SiO2; AlPO4-NH3; Ca3(PO4)2 / C a SO4; Ca2P2O7; Ca5(PO4)3(OH) and the like can be mentioned.

[0029] In one embodiment, the lactic acid dehydration reaction can proceed within a temperature range of 350°C or higher to 400°C or lower. That is, depending on the passage of the reaction time, the temperature of the lactic acid dehydration reaction can be controlled within the range of 350°C or higher to 400°C or lower.

[0030] When the temperature of the lactic acid dehydration reaction is controlled too low, there may be a problem that the conversion rate of lactic acid and the yield of acrylic acid are significantly reduced. Conversely, when the temperature is too high, aldehydes can be generated by a carboxyl removal reaction or a carbonyl removal reaction, and a reaction for generating propanoic acid by the reduction of acrylic acid and the like can be promoted, resulting in an increase in the content of by-products. Further, there may be a problem that the dehydration catalyst is denatured.

[0031] In one embodiment, the method for producing acrylic acid of the present disclosure can include a step of controlling the lactic acid dehydration reaction temperature in the form of a positive quadratic function with respect to the elapsed time of the dehydration reaction. Specifically, the lactic acid dehydration reaction temperature can be maintained at the initial dehydration reaction temperature for a certain period of time after the start of the lactic acid dehydration reaction, and then controlled in the form of a positive quadratic function with respect to the elapsed time of the dehydration reaction.

[0032] More specifically, the lactic acid dehydration reaction temperature can be maintained at the initial dehydration reaction temperature for 5 hours or more to 35 hours or less after the start of the lactic acid dehydration reaction, and then controlled in the form of a positive quadratic function with respect to the elapsed time of the dehydration reaction.

[0033] More specifically, the lactic acid dehydration reaction temperature can be controlled in the form of a positive quadratic function with respect to the elapsed time of the dehydration reaction after 5 hours or more, or 10 hours or more, or 20 hours or more to 35 hours or less, 30 hours or less, or 25 hours or less have elapsed since the start of the lactic acid dehydration reaction.

[0034] The reason for maintaining the initial dehydration reaction temperature for a certain period of time is that there is no decrease in the acrylic acid yield and lactic acid conversion rate during a certain period at the initial stage of the reaction.

[0035] The coefficient range of the highest-order term of the positive quadratic function can be 0.001 or more to 0.005 or less. Specifically, the coefficient range of the highest-order term of the positive quadratic function can be 0.001 or more, or 0.0014 or more to 0.005 or less, or 0.004 or less, or 0.003 or less, or 0.002 or less.

[0036] In one embodiment, the method for producing acrylic acid can satisfy the following Mathematical formula 1: [Mathematical formula 1] T(t1) < T(t2); (when t1 < t2)

[0037] In the Mathematical formula 1, t1 is the time point when the first time has elapsed since the start of the lactic acid dehydration reaction, t2 is the time point when the second time has elapsed since the start of the lactic acid dehydration reaction, T(t1) is the lactic acid dehydration reaction temperature at t1, and T(t2) is the lactic acid dehydration reaction temperature at t2.

[0038] What the Mathematical formula 1 shows is that the dehydration reaction temperature increases according to the reaction time.

[0039] In one embodiment, the positive quadratic function with respect to the reaction time in the form in which the dehydration reaction temperature is controlled can be shown by the following Mathematical formula 2:

Number

[0040] In the above equation 2, T is the temperature of the dehydration reaction, and t is the time it takes for the dehydration reaction to proceed.

[0041] Furthermore, the temperature at which the dehydration reaction begins can be between 350°C and 370°C, and preferably between 360°C and 365°C.

[0042] In one embodiment, the yield of acrylic acid can be maintained at 45% or higher while the lactate dehydration reaction proceeds. Since a higher yield of acrylic acid is more economical, no upper limit was specifically set, but it could be, for example, 100% or less.

[0043] In one embodiment, the lactate dehydration reaction may proceed for a period of 20 hours or more and 185 hours or less. [Effects of the Invention]

[0044] According to one embodiment of the present invention, even if the lactate dehydration reaction proceeds for a certain period of time or longer, the yield of acrylic acid can be maintained at or above a certain level. [Brief explanation of the drawing]

[0045] [Figure 1] This figure shows the yield of acrylic acid according to the lactate dehydration reaction time for one embodiment of the present invention and a comparative example. [Figure 2] This figure shows the dehydration reaction temperature control according to the lactate dehydration reaction time for one embodiment of the present invention and a comparative example. [Modes for carrying out the invention]

[0046] The operation and effects of the invention will be described in more detail below through specific embodiments of the invention. However, these embodiments are merely presented as examples of the invention and do not define the scope of the invention's rights.

[0047] [Preparing the gas-phase lactate feedstream] As the raw material for lactic acid, an 88 wt% aqueous lactic acid solution (product name: PURAC H888, obtained from Corbion) was prepared. Approximately 1000 g of the lactic acid raw material and 1200 g of distilled water were mixed and refluxed for approximately 18 hours under a temperature of approximately 95°C to obtain an aqueous lactic acid solution with a concentration of approximately 40 wt% where lactic acid and lactic acid oligomers reached equilibrium. This was used as the feed for lactic acid vaporization. A Hastelloy tube with a length of 86 cm and an inner diameter of 2.22 cm was used as the vaporization reactor for the vaporization reaction. The supplied lactic acid feed was configured to flow along the inner wall of the vaporization reactor. The internal temperature of the vaporization reactor was set to 300°C. The prepared lactic acid feed was introduced into the vaporization reactor at a rate of 0.58 ml / min using a carrier gas so that the lactic acid feed introduced into the vaporization reactor would flow along the inner wall surface of the vaporization reactor. Nitrogen was used as the carrier gas, supplied at a rate of 100 ml / min. The lactic acid molecule feed vaporized in the vaporization reactor was used as the feed for the dehydration reaction.

[0048] [Example 1] A dehydration reactor packed with a dehydration catalyst was prepared. The dehydration reactor was 100 cm long with an inner diameter of 2.4 cm and made of Hastelloy material. The catalyst packed in the reactor was a calcium phosphate-based catalyst consisting of a composite phase of Ca2P2O7 and Ca5(PO4)3(OH) formed into cylindrical pellets with a diameter of approximately 3 mm and a length of approximately 3 mm. At this time, the mixed weight ratio of Ca2P2O7 to Ca5(PO4)3(OH) was 7:3.

[0049] The starting temperature for the dehydration reaction was set to 365°C, and this temperature was gradually increased while maintaining it for 33 hours. During this process, the increasing dehydration reaction temperature was controlled to satisfy Equation 2 below (see Figure 2).

number

[0050] In the above equation 2, T is the dehydration reaction temperature and t is the dehydration reaction time.

[0051] The product after the dehydration reaction in the dehydration reactor was sampled at 40-minute intervals, and the yield of acrylic acid was calculated by quantitative analysis using HPLC.

[0052] HPLC was performed using an Agilent 1260 Infinity II high-performance liquid chromatography system. The obtained samples were diluted 20-fold by volume with distilled water for analysis. The HPLC analysis conditions were as follows: -Eluent: 0.005 mol H2SO4 (aq) -Eluent flow rate: 0.4 mL / min -Column: Aminex HPX-87H -Column temperature: 10℃ -Detector: UV 210~300nm -Analysis time: 70 min -Analysis pressure: ~70 bar

[0053] The yield of acrylic acid was calculated using the following formula. Acrylic acid yield (%) = Amount of acrylic acid produced (carbon weight (g) / h) / Lactic acid feed amount (carbon weight (g) / h) × 100

[0054] [Comparative Example 1] Acrylic acid was produced in the same manner as in Example 1, except that the dehydration reaction temperature was kept constant at 365°C.

[0055] Similarly, the product after the dehydration reaction in the dehydration reactor was sampled at 40-minute intervals, and the yield of acrylic acid was calculated by quantitative analysis using HPLC. The analytical method was the same as in Example 1.

[0056] [Comparison of Acrylic Acid Yields] The yields of acrylic acid calculated for Example 1 and Comparative Example 1 are shown in the graph in Figure 1. As a result, it was confirmed that the yield remained constant at approximately 47% in the example, while the yield gradually decreased over time in the comparative example. In the comparative example, it was understood that the coke produced by the side reaction covered the active sites of the catalyst, gradually deactivating the catalyst. On the other hand, in the example, it was understood that the yield remained constant because increasing the reaction temperature increased the reaction rate at which acrylic acid was produced in accordance with the inertness rate of the catalyst.

[0057] [Table 1]

Claims

1. The process involves supplying a feedstream containing lactic acid gas to a catalyst-filled dehydration reactor to carry out the lactic acid dehydration reaction, The process includes a step in which the lactate dehydration reaction temperature is controlled in the form of a positive quadratic function with respect to the dehydration reaction time. The aforementioned lactate dehydration reaction proceeds in a temperature range of 350°C to 400°C. A method for producing acrylic acid.

2. The method for producing acrylic acid according to claim 1, wherein the lactate dehydration reaction temperature is maintained at the initial dehydration reaction temperature for 5 hours or more and 35 hours or less after the start of the lactate dehydration reaction, and then controlled in the form of a positive quadratic function with respect to the elapsed time of the dehydration reaction.

3. The method for producing acrylic acid according to claim 1, wherein the positive quadratic function has a coefficient range of 0.001 or more and 0.005 or less for the highest-order term.

4. A method for producing acrylic acid according to claim 1, satisfying the following formula 1: [Formula 1] T(t １ ) < T (t ２ ); (t １ <t ２ in the case of) In the above formula 1, t １ This is the point in time when the first time has elapsed after the start of the lactate dehydration reaction, and t ２ This is the point in time when the second time has elapsed after the start of the lactate dehydration reaction. T(t １ ) is the lactic acid dehydration reaction temperature at t １ , and T(t ２ ) is the lactic acid dehydration reaction temperature at t ２ .

5. The method for producing acrylic acid according to claim 1, wherein the yield of acrylic acid is maintained at 45% or more while the lactate dehydration reaction proceeds.

6. The method for producing acrylic acid according to claim 1, wherein the lactic acid dehydration reaction is carried out for a period of 20 hours or more and 185 hours or less.

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