KR100888321B1 - Absorbents for acidic gas separation - Google Patents

Abstract

The present invention relates to a mixed absorbent for acid gas separation, which has a fast reaction rate with carbon dioxide and a high absorption capacity, does not require much energy for regeneration, and can reduce the renewable energy while having a high absorption capacity of carbon dioxide from the mixed gas. As,

100 parts by weight of a compound of formula 1 having one alcoholic hydroxyl group and at least one primary or secondary amine in the molecule, each having a hydrogen atom while a carbon atom bonded to the amine is present between the amine and the alcoholic hydroxyl group;

It consists of a mixed aqueous solution containing 1 to 60 parts by weight of the heterocyclic compound of Formula 2 having at least one or more amines in the ring.

Formula 1

     H

R ₁ -C-R ₂

    ｜

NHR ₃

Formula 2

Carbon dioxide, absorbent, alcoholic hydroxyl group, amine, carbon atom, hydrogen atom,

Description

Absorbents for acidic gas separation

1 is a graph showing the results obtained in Table 1 with time.

2 is a graph showing the absorption equilibrium characteristics of the absorbent of Example 1 and Comparative Example 1 at 35 ℃ and 120 ℃.

The present invention relates to the field of mixed absorbents for acid gas separation, and more specifically, does not require a lot of energy for regeneration while having a fast reaction rate and a high absorption capacity with carbon dioxide, and has a high absorption capacity of carbon dioxide from the mixed gas. It relates to a mixed absorbent for acid gas separation, which can reduce energy.

Due to the increasing use of fossil fuels such as coal, petroleum, and liquefied natural gas (LNG), which are used in the energy industry since the early 19th century, the industrialization of carbon dioxide (CO ₂ ), hydrogen sulfide (H ₂ S), carbonyl sulfide ( As the concentration of acidic gases such as COS) and methane (CH ₄ ) increased, the concentration of acidic gases rapidly increased after the mid-20th century as the industry developed. With the development of industry, global warming due to the increase of acidic gas, especially due to the increase of atmospheric concentration of carbon dioxide, has become more and more restrictive on the emission and treatment of acidic gas in each country. The United Nations Conference on Environment and Development in Rio, Brazil, in June 1992 has raised international interest in global warming, and developed countries, including the United States and Japan, have decided to reduce global greenhouse gas emissions by 5.2% in 2010 compared to 1990. International agreements on how to reduce acid gases are being made. In particular, the separation of carbon dioxide, which accounts for about 50% of the acid gases that cause global warming, is becoming more important. Therefore, technology development for this situation is urgently required.

Techniques for suppressing acid gas increase include energy saving technology for reducing acid gas emission, recovery and recovery of acid gas from exhaust gas, technology for using or immobilizing acid gas, and alternative energy technology for not emitting acid gas. have.

As the separation technology of acid gas studied so far, absorption method, adsorption method, membrane separation method, deep cooling method, etc. have been proposed as realistic alternatives. Among them, absorption method is easy to process a large amount of gas, It is easy to apply to most industries and power plants because of its suitability.

Examples of the absorbent widely used in the absorption method include monoethanolamine (MEA) manufactured by ABB lummus Crest, and the above-mentioned monoethanolamine (MEA) is used as the absorbent. The process is operating at Torona, CA, USA and Shady Point, Oklahoma, USA.

However, the absorption process using monoethanolamine (MEA) as an absorbent consumes a large amount of energy for acid gas separation, a large amount of absorbent is used, and there is a problem of corrosion of the separation facility due to the absorbent. There is an urgent need for the development of new additives and absorbents.

As another example of the absorption method, many researchers have used a chemical reaction with an alkanolamine aqueous solution to separate and recover acidic gases such as CO ₂ , H ₂ S, and COS from mixed gases discharged from smelters and thermal power plants. Has been studied by. Alkanolamines widely used in the past include monoethanolamine (MEA) of primary series, diethanolamine (DEA) of secondary series, triethanolamine (TEA) of tertiary series, and N- N-methyl diethanolamine (MDEA), triisopropanolamine (TIPA), and the like.

However, the above-mentioned monoethanolamine (MEA) and diethanolamine (DEA) have been used a lot because of the advantage of having a high reaction rate, but there are many difficulties due to problems such as high corrosiveness, high renewable energy and degradation of these compounds It is known. In addition, the above-mentioned N-methyl diethanolamine (MDEA) has a disadvantage of low absorption rate while low corrosion and regeneration heat.

Recently, studies on sterically hindered amines as new alkanolamine-based absorbents are being actively conducted. These sterically hindered amines have advantages of high absorption capacity and selectivity of acidic gas and low energy for regeneration.

Primary amines such as monoethanolamine (MEA) and secondary amines such as diethanolamine (DEA) generally follow the following mechanism.

CO ₂ + 2RNH ₂ ↔RNHCOO- + RNH ₃ ⁺

And tertiary amines such as triethanolamine (TEA), N-methyldiethanolamine (MDEA), triisopropanolamine (TIPA) and 2-amino-2-methyl-1-propanol (2-amino 2-methyl 1- propanol, AMP), 2-piperidineethanol (PE), 2-amino-2-ethyl-1,3-propanediol (2-amino-2-ethyl-1,3-propanediol, AEPD) In the case of hindered amines, the reaction pathway above is unstable, so follow the reaction mechanism below.

_{CO 2 + R 3 N + H} 2 O ↔R 3 NH + + HCO 3 -

Therefore, theoretically, primary and secondary amines require two amines to absorb one carbon dioxide, whereas for tertiary amines and sterically hindered amines, carbon dioxide and amines react in a 1: 1 ratio. The absorption capacity of can be seen. The gas selectivity of these hindered amines is a very important requirement in today's stringent environmental regulations, and the regeneration characteristics reduce the total operating costs of energy saving and acid gas treatment processes.

The reaction rate of the hindered amine depends on the degree of hinderedness determined by the structure of the amine, but is generally lower than that of the primary, secondary amines such as monoethanolamine (MEA), diethanolamine (DEA), Higher than the tertiary amine. Many hindered amines have recently been studied, such as 2-amino-2-methyl-1-propanol (AMP) and 2-piperidineethanol (PE). ), 2-amino-2-ethyl-1,3-propanediol (2-amino-2-ethyl-1,3-propanediol, AEPD), and the like.

However, in the case of using amines having a large steric hindrance for absorption of acidic gas, the absorption capacity may be increased, but the absorption rate is relatively low.

In addition, recently, a method of using an amino acid salt having a different compound composition from the alkanol amines as an absorbent has been disclosed in "Absorbing Acid Gas" of Korean Patent Laid-Open Publication No. 2005-0007477 (published on Jan. 18, 2005). .

However, potassium taurate used as an absorbent in the above-mentioned Patent Publication No. 2005-0007477 generates a precipitate after the reaction with carbon dioxide, which causes an additional environmental and economic problem that must be treated. In addition, since potassium taurate is an absorbent in the form of a primary amino acid salt having no steric hindrance, there is a disadvantage in that a large amount of energy is required to separate carbon dioxide.

In addition, a method of using an aqueous solution of sodium glycinate, which is a kind of amino acid sodium, as an absorbent is described in Korean Patent Publication No. 10-0635698 (Announcement Date 2006.10.17), "Asorbent for separating acid gas from mixed gas. And a method for separating acid gas from mixed gas.

However, sodium glycinate used as an absorbent in the above registration No. 10-0635698 has a disadvantage of requiring a relatively large amount of energy when separating carbon dioxide.

An object of the present invention is to solve the conventional problems and disadvantages as described above, to provide an absorbent for carbon dioxide separation, having a fast reaction rate and high absorption capacity with carbon dioxide and does not require a lot of energy for regeneration. There is.

As a means for achieving the above object, the configuration of the present invention,

100 parts by weight of a compound of formula 1 having one alcoholic hydroxyl group and at least one primary or secondary amine in the molecule, each having a hydrogen atom while a carbon atom bonded to the amine is present between the amine and the alcoholic hydroxyl group;

It consists of a mixed aqueous solution containing 1 to 60 parts by weight of the heterocyclic compound of Formula 2 having at least one or more amines in the ring.

( Formula 1)

     H

R ₁ -C-R ₂

    ｜

NHR ₃

( Formula 2)

Wherein R ₁ =-(CH ₂ ) aH (a = 1-6) or -CH- (CH ₃ ) ₂ , R ₂ =-(CH ₂ ) _b -OH (b = 1-5), R ₃ = H or-(CH ₂ ) _c -H (c = 1 to 3), R ₄ , R ₅ , R ₆ , R ₇ = same or different H, an alkyl group having 1 to 4 carbon atoms, substituted with an amine is an alkyl group having from 1 to 4 carbon atoms substituted on an alkyl group or an alcoholic hydroxyl group of 1 to 4 carbon atoms, is X = -CH _2, O, NH or SH.

In the compound of Formula 1, the carbon atom bonded to the amine has one hydrogen while being present between the amine and the alcoholic hydroxyl group, and has a structure in which the carbon atom directly bonds with one hydrogen. This is because when the carbon atom bonded to the amine has two or more hydrogen atoms, the degree of steric hindrance acting on the amine is small, and thus the carbon dioxide absorption reaction rate is fast, but it takes a lot of energy when stripped. Although the removal energy required for amine regeneration is reduced due to the increased degree, the absorption reaction rate is slowed due to high steric hindrance, and there is a disadvantage in that a large amount of absorbent must be used to offset it. In addition, the number of carbon atoms contained in R ₁ , R ₂ and R ₃ is preferably about 1 to 3, in the case of R ₃ may be a hydrogen atom. In addition, the compound of Formula 2 is used by mixing one or more of the heterocyclic compounds having at least one secondary or tertiary amine in the molecule with the compound of Formula 1.

Compounds corresponding to Formula 1 are, for example, N-methyl-2-amino-1-propanol, N-ethyl-2-amino-1-propanol, N-isopropyl-2-amino-1-propanol, N -Methyl-2-amino-1-butanol, N-methyl-2-amino-1-pentanol, N-isopropyl-2-amino-1-pentanol, 2-amino-1 propanol, 2-amino-1 -Butanol, 2-amino-3-methylbutanol, 2-amino-1-pentanol, 2-amino-1-propanol, 2-amino-1-hexanol, 3-amino-1-butanol, 4-amino- One or two or more compounds from the group consisting of 1-pentanol, 5-amino-1-hexanol, 3-amino-1-pentanol, 3-amino-1-hexanol and the like can be used.

Examples of the compound corresponding to Formula 2 include piperazine, morpholine, 2-methylpiperazine, 2,5-dimethylpiperazine, 2,3-dimethylpiperazine, 2,4-dimethylpiperazine, 2-ethanol pipe Razine, 2,5-diethanolpiperazine, 2-aminoethylpiperazine, thiomorpholin, piperazine including piperidine, morpholine, thiomorpholin, piperidine derivatives can be used.

The compound of Formula 2 used in admixture with the compound of Formula 1 is one or more.

The absorbent of the present invention is preferably used as an aqueous solution in which the concentration of the mixed absorbent mixed with at least one compound selected from the compound of Formula 1 and the compound of Formula 2 is in the range of 5 to 50% (w / v). When the concentration of the mixed absorbent is 5% or less, the carbon dioxide absorption capacity is maintained, but the reaction rate is slow, so that the absolute amount of carbon dioxide is absorbed, and when 50% or more, the carbon dioxide absorption ability and absorption rate is excellent, but a large amount of absorbent is used in terms of economic efficiency It's not efficient.

In addition, the compound of Formula 1 and the compound of Formula 2 are preferably used in a weight ratio of 100: 1 to 60. When the compound of Formula 2 is added in less than 1 weight ratio, the effect of increasing the reaction rate is insignificant, and when added in more than 60 weight ratio, the effect of increasing the reaction rate compared to the amount used is not large.

Absorbent of the present invention refers to a mixed absorbent mixture of at least one compound selected from the compound of formula (1) and compound of formula (2), which not only increases the rate and absorption capacity of carbon dioxide absorption, but also facilitates the stripping reaction at high temperatures. There is.

In addition, there is a carbon atom having one hydrogen atom adjacent to the amine of Formula 1, the carbon dioxide absorption rate and capacity of the amine is increased by the electromagnetic effect of the alkyl group bonded to the carbon atom, but the carbon dioxide after absorbing carbon dioxide In the stripping process to remove the energy consumed due to the steric repulsion effect of the substituted alkyl group and the absorbed carbon dioxide. Therefore, the substituent substituted at the alpha position of the amine group of the compound of Formula 1 not only increases the absorption reaction rate by using the electromagnetic effect but also has the advantage of facilitating the removal by causing the steric hindrance effect under the stripping conditions.

The carbon dioxide absorption separation process basically consists of absorbing carbon dioxide at low temperature, separating thermally absorbed carbon dioxide from the absorbent by applying thermal energy at high temperature, and introducing the absorbent back into the process. That is, the acid gas absorption temperature of the mixed absorbent is preferably 0 ~ 60 ℃, stripping temperature is 70 ~ 200 ℃. Therefore, the most energy consumed in the carbon dioxide absorption separation process is the portion where the absorbed carbon dioxide is separated from the absorbent at a high temperature to recover (remove) the absorbent, and about 50 to 80% of the energy of the entire process is Consumed. Therefore, depending on how much energy is reduced in the absorbent regeneration (removal) process, the economics of the absorbent and the overall carbon dioxide separation process are secured. Therefore, it is preferable that the absorbed carbon dioxide is separated from the absorbent at low temperatures.

The absorbent of the present invention has a large absorption rate at low temperatures and a relatively weak absorption reaction with carbon dioxide at high temperatures, so that the difference in carbon dioxide unit absorption due to the temperature difference is much larger than that of the conventional absorbent. This means that the absorbent developed according to the invention can save the energy required for the separation of carbon dioxide, i.e. for the regeneration of the absorbent, compared to conventional absorbents, for example monoethanolamine (MEA). That is, since the absorbent does not react with carbon dioxide at a high temperature means that the absorbent is easily regenerated, economic efficiency in the entire carbon dioxide removal process using the absorbent can be ensured.

Absorbent of the present invention can be applied not only to the above-described carbon dioxide but also acidic gases such as H ₂ S, SO ₂ , NO ₂ , COS.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, in order to describe in detail such that those skilled in the art can easily carry out the present invention, the most preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. do. Other objects, features, and operational advantages, including the object, operation, and effect of the present invention will become more apparent from the description of the preferred embodiment.

For reference, the embodiments disclosed herein are only presented by selecting the most preferred embodiment in order to help those skilled in the art from the various possible examples, the technical spirit of the present invention is not necessarily limited or limited only by this embodiment Rather, various changes, additions, and changes are possible within the scope without departing from the spirit of the present invention, as well as other equivalent embodiments.

(Example 1)

2-amino-1-butanol of Formula 1 and 2.45M aqueous solution of piperazine of Formula 2 (weight ratio 3: 1) are prepared.

(Example 2)

To prepare 2-amino-1-butanol of formula 1 and 2.45M aqueous solution of piperazine of formula 2 (weight ratio 10: 1).

(Example 3)

2-amino-3-methylbutanol of the formula (1) and a piperazine 2.45M aqueous solution of the formula (2) (weight ratio 5: 1) are prepared.

(Comparative Example 1)

As a single compound commercialized as a carbon dioxide absorber, 2.45M aqueous solution of monoethanolamine (MEA) having the fastest reaction rate is produced.

(Absorption rate experiment)

Absorption reaction rate experiment of carbon dioxide was carried out using the absorption rate measuring apparatus for the absorbents of Examples 1 to 3 and Comparative Example 1 as described above. In the absorbent liquid composition of this Example, the compound of Formula 2 was added in a weight ratio of 1 to 60% based on the compound of Formula 1. In addition, the reaction temperature was set to 35 ℃, carbon dioxide was supplied by using the difference in water head using a double-tube tube burette. Thereafter, the amount of carbon dioxide reacted with the absorbent was measured over 90 minutes, and the amount of carbon dioxide generated in the reactor absorbing carbon dioxide was measured by moving the reactor to a water tank prepared at 80 ° C. in advance to examine the absorbent regeneration and carbon dioxide removal efficiency. Carbon dioxide absorption and stripping rates for the absorbents of Examples 1 to 3 and Comparative Example 1 are as shown in Table 1 below.

<Table 1> Absorption and Removal Rate of Carbon Dioxide

                                                     (Unit: ml)

 Reaction time  Comparative Example 1  Example 1  Example 2  Example 3         absorption 0 0 0 0 0 5 168 181 141 157 10 319 349 279 273 15 419 457 372 370 20 491 535 441 440 25 547 592 497 496 30 586 634 544 539 35 612 667 580 570 40 631 692 608 594 45 644 711 630 613 50 655 726 647 628 55 663 739 662 641 60 670 751 675 651 65 676 759 686 660 70 682 766 695 668 75 686 773 703 675 80 689 779 711 681 85 694 784 717 686 90 698 789 723 691   Strip 95 628 712 657 625 100 617 703 644 613 105 609 698 639 606 110 604 694 633 600 115 600 690 628 595 120 598 688 623 590

As shown in Table 1 above, the carbon dioxide absorption rate of the absorbent of the present invention is faster when the absorbent of the present invention is compared with the absorbent of the example of the present invention and the absorbent of the first embodiment for 5 minutes. Not only can it be seen that the removal efficiency is very good. In addition, in the case of Example 2 and Example 3, although the absorption reaction rate is slower than Comparative Example 1, since the removal amount is similar after absorbing a small amount of carbon dioxide compared to Comparative Example 1, the stripping efficiency is relatively high. Able to know.

1 is a graph showing the results obtained in Table 1 with time. And, Figure 2 is a graph showing the absorption equilibrium characteristics of the absorbent of Example 1 and Comparative Example 1 at 35 ℃ and 120 ℃. As is well known so far, a general regeneration (removal) process of carbon dioxide, including Comparative Example 1 using monoethanolamine (MEA), takes place at 100-120 ° C., as shown in FIG. It was found that not only absorbed carbon dioxide at 120 ° C. better than the absorbent of Comparative Example 1, but also absorbed carbon dioxide at 35 ° C. better. This means that the absorbent of Example 1 is more economical than the monoethanolamine (MEA), so that the absorbent of Example 1 is more economical than carbon dioxide and regenerates the absorbent. It can be seen that the absorbent absorbs larger amounts of carbon dioxide than monoethanolamine (MEA).

Therefore, the absorbent of the present invention can absorb carbon dioxide rapidly after absorbing carbon dioxide rapidly because the carbon dioxide absorption reaction rate is fast, the energy consumed to remove carbon dioxide (about 50 ~ 80% of the entire process) It is very advantageous for securing economic feasibility and commercialization (industrialization).

As described in the above embodiment, the present invention has a fast reaction rate and high absorption capacity with carbon dioxide, does not require much energy for regeneration, and can reduce renewable energy while having high absorption capacity of carbon dioxide from mixed gas. Has an effect.

Claims (8)

100 parts by weight of a compound of formula 1 having one alcoholic hydroxyl group and at least one primary or secondary amine in the molecule, each having a hydrogen atom while a carbon atom bonded to the amine is present between the amine and the alcoholic hydroxyl group; It consists of a mixed aqueous solution containing 1 to 60 parts by weight of the heterocyclic compound of Formula 2 having at least one or more amine in the ring, The compound of Formula 1 is present between the amine and the alcoholic hydroxyl group, a carbon atom directly bonded to the amine is directly bonded to one hydrogen, Compound of Formula 1 is N-methyl-2-amino-1-propanol, N-ethyl-2-amino-1-propanol, N-isopropyl-2-amino-1-propanol, N-methyl-2-amino -1-butanol, N-methyl-2-amino-1-pentanol, N-isopropyl-2-amino-1-pentanol, 2-amino-1propanol, 2-amino-1-butanol, 2-amino -3-methylbutanol, 2-amino-1-pentanol, 2-amino-1-hexanol, 2-amino-1-propanol, 3-amino-1-butanol, 4-amino-1-pentanol, 5 It consists of 1 type (s) or 2 or more types selected from the group which consists of -amino-1- hexanol, 3-amino-1- pentanol, 3-amino-1- hexanol, etc., The compound of Formula 2 is piperazine, morpholine, 2-methylpiperazine, 2,5-dimethylpiperazine, 2,3-dimethylpiperazine, 2,4-dimethylpiperazine, 2-ethanolpiperazine, 2, One or two selected from the group consisting of 5- diethanol piperazine, 2-aminoethyl piperazine, thiomorpholin, piperazine including piperidine, morpholine, thiomorpholine and piperidine derivatives An absorbent for acid gas separation comprising the above mixture. Formula 1      H R ₁ -C-R ₂     ｜ NHR ₃ Formula 2

Wherein R ₁ =-(CH ₂ ) aH (a = 1-6) or -CH- (CH ₃ ) ₂ , R ₂ =-(CH ₂ ) _b -OH (b = 1-5), R ₃ = H or-(CH ₂ ) _c -H (c = 1 to 3), R ₄ , R ₅ , R ₆ , R ₇ = same or different H, an alkyl group having 1 to 4 carbon atoms, substituted with an amine is an alkyl group having from 1 to 4 carbon atoms substituted on an alkyl group or an alcoholic hydroxyl group of 1 to 4 carbon atoms, is X = -CH _2, O, NH or SH. delete delete delete The method of claim 1, The mixed absorbent for acid gas separation, characterized in that used as an aqueous solution in the concentration range of 5 to 50% (w / v). The method of claim 1, Mixed absorbent for acid gas separation, characterized in that at least one compound of the formula (2) is added in a weight ratio of 100: 1 to 60 with respect to the compound of the formula (1). The method of claim 1, Acid gas absorption temperature of the mixed absorbent is 0 ~ 60 ℃, stripping temperature is 70 ~ 200 ℃ mixed absorbent for acid gas separation, characterized in that The method of claim 1, The acid gas is a mixed absorbent for acid gas separation, characterized in that at least one gas selected from H ₂ S, SO ₂ , NO ₂ , COS.

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