Method for producing acrylic acid

Abstract

The present invention relates to a method for producing acrylic acid. Specifically, the present invention relates to a method for producing acrylic acid, comprising a method for controlling a reaction temperature at which the yield of acrylic acid is maintained according to the progress of a reaction.

Description

Method for producing acrylic acid

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0176549, filed December 7, 2023, the entire contents of which are incorporated herein by reference.

[0003]

[0004] The present invention relates to a method for producing acrylic acid. Specifically, the present invention relates to a method for producing acrylic acid, including a method for controlling a reaction temperature so as to maintain an acrylic acid yield as the reaction progresses.

[0005]

[0006] Acrylic acid is an organic compound that contains both carboxylic acid and an unsaturated double bond within its molecule. It has a very simple structure, can be converted into various substances, and can be polymerized, so it is used in various industrial fields.

[0007] Specifically, acrylic acid can be used as polyacrylic acid, dots, adhesives, paints, etc. required for manufacturing superabsorbent polymers, or as a raw material for manufacturing other types of acrylate monomers, or as a polymerization raw material with various other monomers such as acrylamide, acrylonitrile, styrene, and alpha olefins.

[0008] These acrylic acids are usually manufactured using propylene produced during the refining and separation process of crude oil, such as naphtha cracking.

[0009] However, with the recent increase in concerns about crude oil depletion and environmental issues, interest in methods for producing acrylic acid using environmentally friendly raw materials is growing.

[0010] In conventional methods for producing acrylic acid via gas-phase dehydration of lactic acid over acid catalysts, numerous side reactions occur in addition to the primary reaction, acrylic acid production. Olefin compounds produced by these side reactions can form coke, which can cover the catalyst's active sites and deactivate the catalyst. Consequently, as the reaction progresses, catalyst deactivation due to coke occurs, leading to a progressively lower acrylic acid yield.

[0011]

[0012] The present specification relates to a method for producing acrylic acid, including a method for controlling the reaction temperature so that the acrylic acid yield can be maintained at a certain level or higher as the reaction progresses.

[0013]

[0014] The present disclosure can provide a method for producing acrylic acid, comprising the steps of: supplying a feed stream containing lactic acid gas to a dehydration reactor filled with a catalyst to perform a lactic acid dehydration reaction; and 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 is performed at a temperature range of 350°C to 400°C.

[0015]

[0016] According to one example, 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 initiation of the lactic acid dehydration reaction.

[0017]

[0018] As an example, the quadratic function of the above quantity may have a coefficient range of the highest order term of 0.001 or more and 0.005 or less.

[0019]

[0020] According to an example, the method for producing the acrylic acid can satisfy the following mathematical formula 1:

[0021] [Mathematical Formula 1]

[0022] T(t1) < T(t2); (t1 <t2일 때,)

[0023] In the above mathematical expression 1, t1 is the time point at which the first time has elapsed after the start of the lactic acid dehydration reaction, t2 is the time point at which the second time has elapsed after the start of the lactic acid dehydration reaction,

[0024] T(t1) is the lactic acid dehydration reaction temperature at t1, and T(t2) is the lactic acid dehydration reaction temperature at t2.

[0025]

[0026] According to one example, according to the above acrylic acid production method, the acrylic acid yield can be maintained at 45% or more while the lactic acid dehydration reaction is in progress.

[0027]

[0028] In one example, the lactic acid dehydration reaction may proceed for 20 hours or more and 185 hours or less.

[0029]

[0030] In the present invention, terms such as first, second, etc. are used to describe various components, and the terms are used only for the purpose of distinguishing one component from another.

[0031] Additionally, the terms used herein are merely used to describe exemplary embodiments and are not intended to limit the present invention.

[0032] Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0033] In this specification, the terms “comprise,” “include,” or “have” are intended to describe a feature, number, step, component, or combination thereof implemented, but do not exclude the possibility of one or more other features, numbers, steps, components, combinations, or additions thereof.

[0034] Additionally, in this specification, when each layer or element is referred to as being formed “on” or “over” each layer or element, it means that each layer or element is formed directly on each layer or element, or that other layers or elements may be additionally formed between each layer, on the object, or on the substrate.

[0035] The present invention is susceptible to various modifications and takes various forms. Specific embodiments are illustrated and described in detail below. However, this does not limit the invention to a specific disclosed form, but rather encompasses all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention.

[0036]

[0037] When producing acrylic acid via lactic acid dehydration using a catalyst, coke, a byproduct of the dehydration reaction, covers the active sites of the catalyst, deactivating it as the reaction progresses. This can lead to a gradual decrease in the acrylic acid yield as the reaction progresses, requiring a solution.

[0038]

[0039] Accordingly, the present disclosure provides a method for producing acrylic acid by controlling the dehydration reaction temperature to adjust the reaction efficiency according to the degree of catalyst deactivation, thereby achieving a certain level or higher of acrylic acid yield during the reaction.

[0040]

[0041] Hereinafter, the method for producing acrylic acid of the present disclosure will be examined.

[0042]

[0043] The method for producing acrylic acid of the present disclosure may include a step of supplying a feed stream containing lactic acid gas to a dehydration reactor filled with a catalyst to perform a lactic acid dehydration reaction.

[0044]

[0045] The feed stream containing lactic acid gas supplied to the dehydration reactor may contain vaporized lactic acid gas molecules. For example, the vaporized lactic acid molecules may be obtained by supplying a stream containing lactic acid to a vaporization reactor and causing a vaporization reaction of lactic acid within the vaporization reactor.

[0046]

[0047] The catalyst filled in the above dehydration reactor is a catalyst for lactic acid dehydration reaction, and may include at least one selected from the group consisting of a calcium phosphate-based catalyst, a sodium phosphate-based catalyst, and an aluminum phosphate-based catalyst. Other reaction conditions may be used without special limitation as long as they are generally used in the technical field to which the present invention pertains and do not conflict with the contents limited in the present specification.

[0048] More specifically, the dehydration catalyst may include CaSO4 / Na2SO4; Na4P2O7 / CaSO4; Na4P2O7 / Ca3(PO4)2; NaH2PO4-NaHCO3 / SiO2; AlPO4-NH3; Ca3(PO4)2 / CaSO4; Ca2P2O7; Ca5(PO4)3(OH), etc.

[0049]

[0050] In one example, the lactic acid dehydration reaction may proceed at a temperature range of 350°C or more to 400°C or less. That is, the temperature of the lactic acid dehydration reaction may be controlled within a range of 350°C or more to 400°C or less depending on the reaction time.

[0051] If the lactic acid dehydration reaction temperature is controlled too low, there may be a problem in which the lactic acid conversion rate and acrylic acid yield are greatly reduced, and conversely, if the temperature is too high, aldehydes may be produced by carboxyl elimination reaction or carbonyl elimination reaction, and propanoic acid production reaction by reduction of acrylic acid may be promoted, which may increase the content of by-products, and there may be a problem in which the dehydration catalyst is denatured.

[0052]

[0053] In one example, the method for producing acrylic acid of the present disclosure may include a step of controlling the lactic acid dehydration reaction temperature in a positive quadratic function with respect to the elapsed time of the dehydration reaction. Specifically, the lactic acid dehydration reaction temperature may be maintained at the initial dehydration reaction temperature for a certain period of time after the initiation 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.

[0054] 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 being maintained at the initial dehydration reaction temperature for 5 hours or more and 35 hours or less after the initiation of the lactic acid dehydration reaction.

[0055] 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 a time of 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 after the initiation of the lactic acid dehydration reaction.

[0056] The reason why the initial dehydration reaction temperature is maintained for a certain period of time is because there is no decrease in the yield of acrylic acid and the conversion rate of lactic acid during the initial period of the reaction.

[0057]

[0058] The above positive quadratic function may have a coefficient range of the highest order term of 0.001 or more and 0.005 or less. Specifically, the positive quadratic function may have a coefficient range of the highest order term of 0.001 or more, or 0.0014 or more and 0.005 or less, or 0.004 or less, or 0.003 or less, or 0.002 or less.

[0059]

[0060] In one example, the method for producing the acrylic acid may satisfy the following mathematical formula 1:

[0061] [Mathematical Formula 1]

[0062] T(t1) < T(t2); (t1 <t2일 때,)

[0063] In the above mathematical expression 1, t1 is a time point at which a first time has elapsed since the start of the lactic acid dehydration reaction, t2 is a time point at which a 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.

[0064] What the above mathematical expression 1 indicates is that the dehydration reaction temperature increases with reaction time.

[0065]

[0066] In one example, a positive quadratic function of the reaction time in which the dehydration reaction temperature is controlled can be expressed by the following mathematical expression 2:

[0067] [Equation 2]

[0068]

[0069] In the above mathematical expression 2, T is the dehydration reaction temperature, and t is the dehydration reaction progress time.

[0070]

[0071] Additionally, the temperature at which the dehydration reaction is initiated may be 350°C or higher and 370°C or lower, and preferably 360°C or higher and 365°C or lower.

[0072]

[0073] In one example, the acrylic acid yield can be maintained at 45% or higher during the lactic acid dehydration reaction. Since a higher acrylic acid yield is more economical, no upper limit has been set, but it can be, for example, 100% or lower.

[0074]

[0075] In one example, the lactic acid dehydration reaction may proceed for 20 hours or more and 185 hours or less.

[0076]

[0077] According to one example of the present invention, even if the lactic acid dehydration reaction proceeds for a certain period of time or longer, the yield of acrylic acid can be maintained at a certain level or higher.

[0078]

[0079] Figure 1 shows the acrylic acid yield according to the lactic acid dehydration reaction time of one embodiment of the present invention and a comparative example.

[0080] Figure 2 shows the control of the dehydration reaction temperature according to the lactic acid dehydration reaction time of one embodiment of the present invention and a comparative example.

[0081]

[0082] Hereinafter, the functions and effects of the invention will be described in more detail through specific examples. However, these examples are provided merely as examples of the invention and do not define the scope of the invention.

[0083]

[0084] [Preparation of lactic acid feed stream in the atmosphere]

[0085] As a lactic acid raw material, an aqueous lactic acid solution with a concentration of 88 wt% (trade name: PURAC H888, obtained from Corbion) was prepared. Approximately 1,000 g of the above lactic acid raw material and 1,200 g of distilled water were mixed and refluxed at a temperature of approximately 95°C for approximately 18 hours to obtain an aqueous lactic acid solution with a concentration of approximately 40 wt% in which lactic acid and lactic acid oligomers reached an equilibrium state, which was used as 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 a 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 be 300°C. The lactic acid feed prepared above was introduced into the vaporization reactor at a rate of 0.58 ml / min using a carrier gas so that the lactic acid feed could flow along the inner wall of the vaporization reactor. Nitrogen was used as the carrier gas, and the carrier gas was supplied at 100 ml / min. The lactic acid molecule feed vaporized in the vaporization reactor was used as the feed for the dehydration reaction.

[0086]

[0087] [Example 1]

[0088] A dehydration reactor filled with a dehydration catalyst was prepared. The dehydration reactor had a length of 100 cm, an inner diameter of 2.4 cm, and was made of Hastelloy. The filled catalyst was a composite calcium phosphate catalyst composed 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. The mixing weight ratio of Ca2P2O7 and Ca5(PO4)3(OH) was 7:3.

[0089] The dehydration reaction start temperature was set to 365°C, and this temperature was maintained for 33 hours and then gradually increased. At this time, the increasing dehydration reaction temperature was set to satisfy the following mathematical equation 2 (see Fig. 2).

[0090] [Equation 2]

[0091]

[0092] In the above mathematical expression 2, T is the dehydration reaction temperature, and t is the dehydration reaction progress time.

[0093] The product from the dehydration reaction in the dehydration reactor was sampled at 40-minute intervals and quantitatively analyzed by HPLC to calculate the yield of acrylic acid.

[0094] HPLC was performed using high-performance liquid chromatography (HPLC) on an Agilent 1260 Infinity II. Specifically, the obtained sample was diluted 20-fold by volume with distilled water and analyzed. HPLC analysis conditions were as follows.

[0095] -Eluent: 0.005 mol H2SO4 (aq)

[0096] -Eluent flow rate: 0.4 mL / min

[0097] -Column: Aminex HPX-87H

[0098] -Column temperature: 10℃

[0099] -Detector: UV 210~300 nm

[0100] -Analysis time: 70 min

[0101] -Analysis pressure: ~70 bar

[0102]

[0103] The yield of acrylic acid was calculated using the following formula.

[0104] Acrylic acid yield (%) = Acrylic acid production (carbon weight (g) / h) / Lactic acid feed (carbon weight (g) / h) * 100

[0105]

[0106] [Comparative Example 1]

[0107] Acrylic acid was prepared in the same manner as in Example 1, except that the dehydration reaction temperature was kept constant at 365°C.

[0108] Similarly, the product from the dehydration reaction in the dehydration reactor was sampled at 40-minute intervals and quantitatively analyzed by HPLC to calculate the yield of acrylic acid. The analysis method was the same as in Example 1.

[0109]

[0110] [Comparison of acrylic acid yields]

[0111] The yields of acrylic acid calculated in Example 1 and Comparative Example 1 are shown in the graph in Fig. 1. As a result, in the case of the Example, the yield was maintained at a constant level of approximately 47%, but in the case of the Comparative Example, it was confirmed that the yield gradually decreased over time. In the case of the Comparative Example, it was understood that this was because the coke generated by the side reaction covered the catalyst active site, gradually deactivating the catalyst. On the other hand, in the case of the Example, it was understood that the yield was maintained constant because the reaction rate at which acrylic acid was generated could be increased in response to the catalyst deactivation rate by increasing the reaction temperature.

[0112]

[0113] Acrylic acid reaction yield according to operating time 0 hr 30 hr 60 hr 90 hr 120 hr 150 hr Example 147% 47% 47% 47% 47% 47% Comparative Example 147% 46% 45% 43% 41% 38%

Claims

1. A step of supplying a feed stream containing lactic acid gas to a dehydration reactor filled with a catalyst to perform a lactic acid dehydration reaction; and Comprising a step of controlling the lactic acid dehydration reaction temperature in a positive quadratic function form with respect to the elapsed time of the dehydration reaction, The above lactic acid dehydration reaction is carried out at a temperature range of 350℃ or higher to 400℃ or lower. Method for producing acrylic acid.

2. In paragraph 1, The above lactic acid dehydration reaction temperature is maintained at the initial dehydration reaction temperature for 5 hours or more and 35 hours or less after the initiation 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. Method for producing acrylic acid.

3. In paragraph 1, The above positive quadratic function has a coefficient range of the highest term of 0.001 or more and 0.005 or less. Method for producing acrylic acid.

4. In paragraph 1, Satisfying the following mathematical expression 1, Method for producing acrylic acid: [Mathematical Formula 1] T(t 1 ) < T(t 2 ); (t 1 <t 2 When,) In the above mathematical expression 1, t 1 is the time point 1 hour after the start of lactic acid dehydration reaction, and t 2 is the time point 2 hours after the start of the lactic acid dehydration reaction, T(t 1 ) is t 1 is the lactic acid dehydration reaction temperature, and T(t 2 ) is t 2 is the lactic acid dehydration reaction temperature.

5. In paragraph 1, The acrylic acid yield is maintained at 45% or higher during the lactic acid dehydration reaction. Method for producing acrylic acid.

6. In paragraph 1, The above lactic acid dehydration reaction proceeds for 20 hours or more and 185 hours or less. Method for producing acrylic acid.

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