KR20190057586A - Acid gas sorbent and acid gas separation method based on ionic liquid - Google Patents

Abstract

The present invention relates to an acid gas absorbent and an acid gas separation method. The acid gas absorbent has an effect of solving deterioration and corrosion phenomenon which is a disadvantage of the conventional amine through addition of an ionic liquid acting as a physical absorbent, and greatly reducing the renewable energy due to the increase of the removal rate.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an acidic gas-

The present invention relates to an acid gas absorbent and an acid gas separation method based on an ionic liquid.

Currently, carbon dioxide is a major greenhouse gas and has had a major impact on global warming for a long period of time. For this reason, we set greenhouse gas reduction targets in major countries to reduce carbon dioxide emissions, and in Korea we set a 37% reduction compared to the 2030 emission estimate. As an institutional way to reach the target value, the greenhouse gas emission trading law bill has been introduced and it has been implemented since 2015. In order to mitigate the burden on the industry in the short term and to cope with climate change in the long term, it is essential to disseminate technologies to reduce carbon dioxide emissions, which are major greenhouse gases.

In the carbon dioxide wet absorption treatment process based on the amine absorbent, 30 wt% MEA (Mono Ethanol Amine) absorbent is mainly used as the liquid absorbent. In the 30 wt% MEA process, it has a relatively high absorption rate and a high absorption rate, but it requires a large amount of regenerated energy because of the slow removal rate, and the higher vapor pressure of the water causes the loss of the absorbent in the stripping process. In addition, there is a problem that the absorbent is deformed due to deterioration and corrosion in the amine-based absorbent. Because of this, it is necessary to replace the absorbent with periodic manpower and time.

Ionic liquids are emerging as new absorbents that can compensate for their drawbacks. Ionic liquids do not suffer from the loss of absorbent due to heat due to very low vapor pressures, and they also have less deterioration reaction due to different mechanisms of absorption with amines. In addition, according to Acidi A. and colleagues, it has been shown that it can be applied as a corrosion inhibitor because it has a corrosion inhibiting effect on certain kinds of ionic liquids. Therefore, the cycle of exchanging the absorbent is considerably slower than that of 30 wt% MEA. The ionic liquid as a physical absorbent has a relatively weak bond with carbon dioxide, so that a smaller amount of regenerated energy is required, thereby facilitating regeneration. It is also possible to synthesize a new ionic liquid as compared with amine absorbent because it is composed of various anions and cations.

However, the ionic liquid used as a physical absorbent has high absorption at high pressure, but at a pressure close to atmospheric pressure, the absorption amount is very small. The renewable energy is small, but the viscosity is so large that other additional processes can consume more energy. Also, since the ionic liquid itself is expensive, the replacement cycle is long, but it is burdensome for industrial use in a large amount.

According to Brennecke and his colleagues, the physical absorbent [Bmim] [Pf6] (1-butyl-3-methylimidazolium hexafluorophosphate), which is known to be highly soluble in carbon dioxide, has a mole fraction of 0.6 at 8 MPa. However, when the pressure dropped to atmospheric pressure, the solubility of carbon dioxide was experimentally measured with various physical absorbents and found to have a maximum mole fraction of 0.035.

As an alternative to this, an ionic liquid used as a chemical absorbent has been prepared. In the case of a chemical absorbent, the cycle capacity representing the regeneration efficiency of carbon dioxide at atmospheric pressure is generally higher than 30 wt% MEA. In most cases, however, the viscosity is high, and because the chemical is absorbed, the removal rate slows down and the effect of saving renewable energy decreases. In addition, chemical absorbers are used in direct synthesis, except for a small number of substances. However, there is a disadvantage in that a new facility must be constructed in order to industrially use new chemical absorbers.

Korean Prior Patent No. 10-1122714 (Mar. 07, 2012) discloses a carbon dioxide absorbent using an imidazolium-based ionic liquid compound containing a fluorine-containing olefin. However, the above-mentioned prior art is an ionic liquid containing fluorine. In the case of an ionic liquid containing fluorine, a high CO ₂ absorbing ability can be expected, but there is a problem that it is difficult to biodegrade and is environmentally harmful.

As another prior art, Korean Patent Laid-Open No. 10-2005-0007477 (January 18, 2005) relates to a method of absorbing an acid gas, and a method of absorbing an acid gas such as CO ₂ and H ₂ S from a gas mixture . However, the above-mentioned prior arts cause an additional environmental and economical problem in that the potassium taurate used as the absorbent must generate precipitate after reaction with carbon dioxide to treat the precipitate. In addition, since the potassium taurate is an absorbent in the form of a primary amino acid salt having no steric hindrance, it takes a lot of energy to separate carbon dioxide.

Korean Registered Patent No. 10-1122714 (Mar. 07, 2012) Korean Patent Publication No. 10-2005-0007477 (January 18, 2005)

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above problems and it is an object of the present invention to provide an acid gas absorbent having an excellent absorption of carbon dioxide and an absorption rate by lowering the viscosity of an ionic liquid and adding a sterically hindered secondary amine.

The present invention also provides an acid gas absorbent which can solve the deterioration and corrosion phenomenon which are disadvantages of existing amines through addition of an ionic liquid serving as a physical absorbent and greatly reduce the renewable energy due to an increase in the removal rate.

The present invention provides a carbon dioxide absorbent for a membrane contactor for removing acid gases, which comprises 10 to 50 wt% of a sterically hindered secondary amine, 49 to 89 wt% of an ionic liquid, and water.

In the present invention, the sterically hindered secondary amine may be selected from the group consisting of diethanolamine (DEA), di-isopropylamine (DIPA) and 2-isopropylaminoethanol (IPAE) The carbon dioxide absorbent for membrane contactors for removing acid gases.

In the present invention, the cation of the ionic liquid is an imidazole-based cation selected from the group consisting of the following formulas (1) and (2), and the anions include [BF ₄ ] ^- , [PF ₆ ] ^- , [Tf ^{_{2 N] -, [TfO]}} -, [DCA] -, [Cl] -, [Br] -, [I] -, [NO 3] -, [SO4] 2 -, [CF 3 COO] -, [ ^{_{CF 3 SO 2] -, [}} (CF 3 SO 2) 2 N] -, [SF 6] -, [(C 2 F 5) 3 PF 3] -, [N (SO 2 CF 3) 2] -, ^{_{[CF 3 SO 3] -,}} [B (CN) 4] -, [N (CN) 2] -, [C (CN) 3] -, [SCN] -, [HSO 4] -, [CH 3 SO ^{_{4] -, [C 2 H}} 5 SO 4] -, [C 4 H 9 SO 4] -, [C 6 H 13 SO 4] -, [B (C 2 O 4) 2] -, [CH 3 SO ₃ ] ^- , [CH ₃ C ₆ H ₄ SO ₃ ] ^- , and [C ₄ F ₉ SO ₃ ] ^- .

[Chemical Formula 1]

(2)

According to the present invention, there is provided a process for producing a carbonaceous material, comprising the steps of: absorbing an acid gas by contacting with an acid gas absorbent and a gas mixture; And removing the acid gas absorbed by the acid gas absorbent.

In the present invention, the temperature in the step of absorbing the acid gas is 0 ° C to 80 ° C, and the temperature in the step of removing carbon dioxide is 25 ° C to 150 ° C.

The acid gas absorbent according to the present invention has an effect of solving the deterioration and corrosion phenomenon which are disadvantages of existing amines by adding an ionic liquid serving as a physical absorbent and greatly reducing the renewable energy due to an increase in the removal rate .

In addition, it is economically effective as it is improved in terms of cost as compared with the conventional acid gas absorbent composed only of an ionic liquid.

1 is a schematic illustration of a carbon dioxide screening device.
FIG. 2 shows the result of absorbing carbon dioxide by contacting a gas mixture containing carbon dioxide, based on the carbon dioxide absorbent produced according to the present invention.
3 is a graph comparing 30 wt% of IPAE with carbon dioxide absorbent prepared by mixing IPAE 30 wt%, ionic liquid and water.
4 is a graph of the absorption rate between IPAE of 30 wt% and IPAE of 30 wt% and carbon dioxide absorbent including ionic liquid.
FIG. 5 is a graph for explaining the influence of the ionic liquid concentration in the elimination reaction.
6 is a graph illustrating the effect of the interaction between the sterically hindered secondary amine IPAE and the ionic liquid in carbon dioxide absorption and removal reactions.
FIG. 7 is a graph showing CO ₂ loading of a 1-cycle absorption / elimination per minute of carbon dioxide sorbent in which 30 wt.% Of IPAE and an ionic liquid are mixed.
8 is a graph showing CO ₂ loading over time of the conventional carbon dioxide absorbent MEA and the carbon dioxide absorbent of the present invention.
FIG. 9 is a graph showing the composition of the conventional carbon dioxide absorbent, MEA, mixed with the ionic liquid, and CO ₂ loading over time of the carbon dioxide absorbent of the present invention.
10 is a graph showing CO ₂ loading over time of the conventional amine-based carbon dioxide absorbents MEA and IPAE and the carbon dioxide absorbent produced by the present invention.
FIG. 11 is a graph showing CO ₂ loading over time of the conventional amine-based carbon dioxide absorbents MEA and IPAE and the carbon dioxide absorbent produced by the present invention.
FIG. 12 is a photograph showing a composition obtained by mixing a conventional carbon dioxide absorbent, MEA, with an ionic liquid, and a carbon dioxide absorbent prepared according to the present invention, after denaturing the carbon dioxide.

Hereinafter, an acid gas absorbent according to the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the subject matter of the present invention.

In addition, since the embodiments described in the present specification and the configurations shown in the drawings are only the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention, It is to be understood that equivalents and modifications are possible.

The present invention relates to an acid gas absorbent characterized by comprising a sterically hindered secondary amine, an ionic liquid and water.

The sterically hindered secondary amine is advantageous in that the absorption capacity and the selectivity of the acid gas are high and the energy required for regeneration is small. Accordingly, the present invention can effectively absorb H ₂ S, COS, and the like as well as carbon dioxide (CO ₂ ) by using a sterically hindered secondary amine.

The sterically hindered secondary amine in the present invention is selected from the group comprising diethanolamine (DEA), di-isopropylamine (DIPA) and 2-isopropylaminoethanol (IPAE) .

In the case of primary amines without steric hindrance, such as MEA, which is a conventional carbon dioxide absorbent, it takes more energy to separate amines and CO ₂ stably in a stereoscopic manner. Therefore, in the present invention, it is believed that the use of a sterically hindered secondary amine can reduce energy when CO _{2 is} separated, and as a result, the use of 2-isopropylethanol, which is a sterically hindered secondary amine, desirable.

The present invention provides a carbon dioxide absorbent for membrane contactors for removing acid gases, which comprises 1 to 50 wt% of a sterically hindered secondary amine, 5 to 98 wt% of an ionic liquid, and water.

Preferably 10 to 50 wt% of a sterically hindered secondary amine, 10 to 50 wt% of an ionic liquid, and water.

This takes into account the solubility of the water-soluble water with the ionic liquid and the sterically hindered secondary amine.

The content of the sterically hindered secondary amine is preferably 1 wt% or more. When the content of the steric hindrance secondary amine is less than 1 wt%, the molecular weight is smaller and the absorption amount of carbon dioxide decreases. When the content of the steric hindrance secondary amine exceeds 50 wt%, the viscosity of the carbon dioxide absorbent is controlled There is a problem in that the viscosity of the entire absorbent increases sharply at the rich-CO ₂ loading, thereby increasing the process operation energy of the entire CO ₂ collection process. Therefore, when the temperature is out of the above-mentioned range, it has a small effect on the heat capacity and viscosity with the ionic liquid, and therefore has a small role as the carbon dioxide absorbent. Therefore, the above range is preferably used.

In the present invention, the cation of the ionic liquid is an imidazole-based cation represented by the formula (1) or (2).

[Chemical Formula 1]

(2)

In the present invention, excellent cycle capacity can be ensured by using an imidazole-based cation as the cation of the ionic liquid.

Further, since it is possible to secure a low reaction heat and an excellent absorption rate, it is preferable to use an imidazole-based cation as the cation of the ionic liquid.

Further, the anion of the ionic liquid of the present invention, ^{_{[BF 4] -, [PF}} 6] -, [Tf 2 N] -, [TfO] -, [DCA] -, [Cl] -, [Br] -, _{^{[I] -, [NO 3}} ] -, [SO4] 2 -, [CF 3 COO] -, [CF 3 SO 2] -, [(CF 3 SO 2) 2N] -, [SF 6] -, [ _{(C 2 F 5) 3 PF} 3] -, [N (SO 2 CF 3) 2] -, [CF 3 SO 3] -, [B (CN) 4] -, [N (CN) 2] -, ^{_{[C (CN) 3] -}} , [SCN] -, [HSO 4] -, [CH 3 SO 4] -, [C 2 H 5 SO 4] -, [C 4 H 9 SO 4] -, [C ^{_{6 H 13 SO 4] -,}} [B (C 2 O 4) 2] -, [CH 3 SO 3] -, [CH 3 C 6 H 4 SO 3] -, or _{[C 4 F 9 SO 3]} - . ≪ / RTI >

More preferably, it is more preferably [BF ₄ ] ^- , [CF ₃ SO ₂ ] ^- , [PF ₆ ] ^- , [Tf ₂ N] ^- or [TfO] ^- . It is more preferable to use it in the selection from the inorganic anions [BF ₄ ] ^- , [PF ₆ ] ^- , [Tf ₂ N] ^- , and [TfO] ^- because the viscosity is lowered by conversion to an inorganic anion.

In the present invention, the ionic liquid is an ionic liquid produced by a combination of a cation and an anion represented by the general formula (1) or (2), more specifically, an imidazole cation, and 1-Ethyl-3-methylimidazolium [Emin] Ionic liquid containing [BF ₄ ] ^- or [CF ₃ SO ₂ ] ^- as the anion and an ionic liquid containing the [BF ₄ ] ^- as the anion of 1-Bthyl-3-methylimidazolium [Bmin] Liquid.

The ionic liquid has a low viscosity and has a lower heat capacity than 4.196 J / K * g, which is the heat capacity of water, so that the specific heat of the entire absorbent is lowered and the exposure time to heat is reduced, do.

In addition, the ionic liquid has a relatively low cost as compared with other ionic liquids, and is generally economical because it is universal.

On the other hand, the acid gas absorbent containing the ionic liquid in the present invention may be further added with a small amount of piperazine used as a speed promoter to increase the absorption and removal rate of the acid gas.

In the present invention, a method for separating carbon dioxide comprises the steps of absorbing an acid gas by contacting with an acid gas absorbent and a gas mixture produced by the present invention, and removing the acid gas absorbed by the acid gas absorbent, Can be separated.

At this time, the temperature at the step of absorbing the acid gas is in the range of 0 ° C to 80 ° C, and the temperature at the step of removing the acid gas is preferably 80 ° C to 150 ° C.

It is preferable to use the above range because the lower the temperature in the step of absorbing the acid gas is, the more excellent the absorption ability of the acid gas. In the case where the temperature in the step of removing the acid gas is less than 80 캜, When the temperature at the time of stripping exceeds 150 ° C, the acid gas absorbent is evaporated and the acid gas absorbent disappears. Therefore, it is preferable to use the above range.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

It is to be understood that this is by way of example only and is not intended to limit the scope of the invention in any way.

Figure 1 is a simplified schematic of a carbon dioxide screening device. Nitrogen gas and carbon dioxide gas tanks, flow regulators, bubble reactor thermostats and gas data analyzers. First, you can adjust the flow rate of the gas by opening the valves of the nitrogen and carbon dioxide gas tanks and the valves before the flow regulator. The gas concentration can be controlled before entering the bubble reactor through the pipeline directly connected to the gas analyzer. In the present invention, the concentration of carbon dioxide was set at 15% and the concentration of nitrogen was set at 85%.

The reactor of the carbon dioxide screening apparatus absorbs gas into the absorbent in the form of bubbling 15% carbon dioxide gas into the liquid absorber by a bubble reactor. The tube of the reactor is connected to a gas data analyzer to measure the composition of the carbon dioxide inside the bubble reactor. During the absorption and removal reactions, the valve of the pipe connected to the analyzer is closed and the valve of the pipe connected to the bubble reactor is opened. During the absorption and removal reaction, the data analyzer displays the composition of the reactor to determine the reaction rate, And cycle capacity can be measured through the data in the analyzer.

The concentration of carbon dioxide in the analyzer is integrated to obtain the amount of carbon dioxide absorption, and the CO2 loading value can be calculated based on the amount of absorption.

The cycle capacity can be calculated by the difference between the rich loading, which is the accumulated amount of carbon dioxide after absorption, and the lean loading, which is the amount of carbon dioxide inside the absorbent after being removed.

Tables 1 to 3 above show composition ratios of the acid gas absorbent including the sterically hindered secondary amine, ionic liquid and water.

Table 4 shows the composition ratio of the composition comprising 30 wt% of MEA and water, 30 wt% of IPAE and water, and 30 wt% of MEA, ionic liquid and water.

The compositional ratio of IPAE was the same as that of 30% MEA, which is a conventional absorbent for carbon dioxide capture. Moreover, IPAE is preferably selected because 30 wt% IPAE has excellent cycle capacity among various hindered amines.

Fig. 2 shows the result of absorbing carbon dioxide by contacting a gas mixture containing carbon dioxide on the basis of the acid gas absorbent thus prepared.

2, FIG. 2 is a graph of CO ₂ loading and time, depending on the concentration and type of ionic liquid. Percentage of absorbent used in mass percent units, steric hindered secondary amine selected IPAE, and 30 wt% added.

The ionic liquid is an ammonium quaternary, imidazolium, pyridinium, phosphonium [Cl] of the small size of the large cations and the relatively asymmetrical structure of the organic symmetry of the ions and the like ^{-, [Br] -, [} I] -, [BF ₄ ] ^- or an organic substance such as [RCO ₂ ] ^- . An infinite combination of cations and anions can produce ionic liquids with various properties. There are various anions. In the present invention, [BF 4] ^- and [Tfo] ^- , which are the anions having the most excellent absorption ability in combination with the imidazolium cation, which is a cation, are preferable. This can be confirmed through the graph of FIG.

Referring to the graph of FIG. 2, the slope of the initial graph is almost the same, but the slope of the graph from the middle of the reaction shows that the ionic liquid has the largest slope when using [Bmim] [BF ₄ ] The gradient of the graph is in the order of [Emim] [BF ₄ ], [Emim] [Tfo].

Through the slope of the graph, it can be seen that the absorption rate of carbon dioxide is the fastest when the ionic liquid [Bmim] [BF ₄ ] is used, and the absorption amount of carbon dioxide is [Bmim] [BF ₄ ] ] [BF ₄ ] showed the highest absorption, followed by [Emim] [Tfo].

The above results show that the energy binding to carbon dioxide differs depending on the types of cations and anions of the ionic liquid, and is influenced by anions rather than cations. Table 5 below shows the calculation results and the molecular weights of binding energy binding to ionic liquid and carbon dioxide. The bond energy was calculated by the SAPT theory (Symmetry adapted perturbation theory).

According to Table 5, the ionic liquid [Emin] [Tfo] has a molecular weight smaller than that of the ionic liquid [Bmin] [BF ₄ ] and [Emin] [BF ₄ ] Absorbing ability is low. In addition, the ionic liquid [Emin] [Bmin] [BF 4] The maximum water absorption amount than [BF _4], if the longer the chain length of the cation I absorption capacity is larger, which is the content of the ionic liquid is 10wt% and 20wt% .

2, the CO ₂ loading value is the highest when the ionic liquid content is 10 wt% and 20 wt%, and when the ionic liquid content is higher than that, the CO ₂ loading is decreased .

In terms of kinetics, the absorption rate of carbon dioxide absorbent containing 30 wt% or 40 wt% of ionic liquid is higher than that of carbon dioxide absorbent containing 10 wt% or 20 wt% of ionic liquid, The absorption rate of carbon dioxide absorbent containing 50wt% of liquid was decreased. Therefore, in terms of absorption kinetics of carbon dioxide, the content of the ionic liquid is preferably 30 wt% to 40 wt%.

FIG. 3 is a graph showing a CO ₂ loading graph of a carbon dioxide absorbent prepared by mixing IPAE 30 wt.%, An ionic liquid and water, and IPAE 30 wt.% In Tables 1 to 3 over time.

3, the initial reaction rate of the carbon dioxide absorbent to which the ionic liquid was added was found to be similar to that of IPAE of 30 wt%, which did not include the ionic liquid. The carbon dioxide absorbent containing 50 wt% of the ionic liquid showed a decrease in absorption rate of carbon dioxide after 20 minutes from the start of absorption of carbon dioxide. The carbon dioxide absorbent containing 40 wt% of ionic liquid showed a decrease in absorption rate after 4 to 50 min of absorption of carbon dioxide, and the absorption rate of carbon dioxide containing 30 wt% of ionic liquid The sorbent absorbed carbon dioxide for 1 hour, after which the rate of absorption decreased. In the case of the carbon dioxide absorbent containing 10 wt% and 20 wt% of the ionic liquid, the absorption rate is similar to that of IPAE containing only 30 wt%, but when the absorption of 30 wt% IPAE is completed, The absorption rate graph of carbon dioxide was divided according to

The acid gas absorbent containing 50 wt% of the ionic liquid has lower CO ₂ loading than the acid gas absorbents containing 30 wt% or 40 wt% of the ionic liquid. Therefore, the chemical absorption and the physical absorption Can not be detected.

In comparison with the 30 wt% IPAE containing 30 wt% or 40 wt% of ionic liquid and 30 wt% IPAE containing no ionic liquid, the CO ₂ loading value seems to be slightly reduced, but in more detail, 50 wt% Is higher than the CO ₂ loading value of the acid gas absorbent including the%. Based on this, it can be confirmed that the acid gas absorbent having an ionic liquid content of 30 wt% or 40 wt% and the acid gas absorbent containing an ionic liquid content of 50 wt% have different reaction mechanisms.

4 is a graph of the absorption rate between an IPAE of 30 wt% and an IPAE of 30 wt% and an acid gas absorbent containing an ionic liquid.

According to Fig. 4, at a point where the CO ₂ loading is 1 mol / L, there is a phenomenon that the absorption rate between 30 wt% IPAE and 30 wt% IPAE and the acid gas absorbent containing an ionic liquid is intersected.

Acid gas sorbents containing 30wt% or 40wt% of ionic liquids are reacted through the physical absorption of the ionic liquid's anion and carbon dioxide molecules interacting 1: 1 due to their dispersing power and the zwitterion mechanism of IPAE. Since the experiment was carried out at atmospheric pressure, the physical absorption is dominant in the early stage of the reaction, and the chemical absorption is predominant in the middle and late stages of the reaction. Since only a small amount of carbon dioxide is absorbed by the physical absorption, the ionic liquid that does not participate in the absorption reaction acts as a catalyst for other absorption reactions. As the absorption reaction progresses and the structural congestion gradually increases inside the absorbent, the carbon dioxide molecules are absorbed in such a way that they are dissolved in ionic liquids, amines or water.

Because of the above-mentioned reasons, the absorbing rate is slower than the 30 wt% IPAE in which the acid gas absorber containing the sterically hindered amine and the ionic liquid is used at a specific point, It is preferable to use an ionic liquid and a sterically hindered secondary amine within the range described in the present invention.

FIG. 5 is a graph for explaining the influence of the ionic liquid concentration in the elimination reaction. According to Figure 5, the absorbent of the carbon dioxide content of the ionic liquid containing 10 wt%, 20 wt% when the minimum CO ₂ loading levels compared with the acid gas absorbent containing an ionic liquid of the other content, slightly higher minimum CO ₂ and the acid gas absorbent containing 30 wt% or 40 wt% of ionic liquid has the lowest CO ₂ loading value.

In case of an acid gas absorbent containing 50 wt% of ionic liquid, the lowest CO ₂ loading value is higher than that of acid gas absorbent containing 40 wt% of ionic liquid. This is due to the possibility that the carbon dioxide molecules are bound to ionic liquid molecules or amine molecules without coming out of the absorber due to the structural interfering effect of the IPAE, which is a sterically hindered amine, and the physical absorbent, There is a difficulty. For the above reasons, it is preferred to use ionic liquids and sterically hindered secondary amines within the scope of the present invention.

FIG. 6 is a graph illustrating the effect of the interaction between the sterically hindered secondary amine IPAE and the ionic liquid in carbon dioxide absorption and elimination reactions, wherein the x axis represents the ionic liquid content and the y axis represents the cycle capacity.

According to FIG. 6, in the acid gas absorbent containing 10 wt% or 20 wt% of the ionic liquid, a small amount of cycle capacity was increased. In general, when the concentration of the ionic liquid was 50 wt% or more, The results are as follows.

The cycle capacity of the acid gas absorbent containing 30 wt.% Or 40 wt.% Of the ionic liquid is generally about the same as the cycle capacity of the absorbent containing 30 wt.% IPAE alone, whereas the ionic liquid content is 10 wt. For carbon dioxide sorbents containing 20wt%, the cycle capacity alone was slightly higher than that of sorbents containing 30wt% IPAE. Since the absorption reaction of carbon dioxide is mainly carried out in IPAE, the absorption and removal rates are similar to the absorption and removal rates of IPAE absorbent of 30wt% alone.

Accordingly, it can be confirmed that the cycle capacity of the acid gas absorbent prepared by the method of the present invention, which contains 10 to 40 wt% of the ionic liquid, is the most excellent.

In addition, even in the case of an acid gas absorbent containing 30 wt% or 40 wt% of ionic liquid, the absorption reaction with IPAE was decreased. Therefore, the amount of absorption was decreased according to the influence of the ionic liquid, And the carbonation absorption reaction with IPAE was not performed properly, resulting in a decrease in absorption time.

As the content of the ionic liquid is 10 wt% or 20 wt%, it can be confirmed that the carbon dioxide absorbent containing the water molecule contains 30 wt% of IPAE and the ionic liquid both participate in the carbon dioxide absorption reaction.

Because of the large amount of water molecules in the carbon dioxide absorbent, IPAE and ionic liquid all participate in carbon dioxide absorption reaction due to the lack of interaction between IPAE, a steric hindered secondary amine, and ionic liquid molecules. do.

According to FIG. 2, the absorption rate tends to decrease gradually as the carbon dioxide absorption reaction proceeds.

It has been found that this is related to the viscosity of the carbon dioxide absorbent, and that the acid gas absorbent containing 30 wt% or 40 wt% of the ionic liquid is affected by the decrease in absorption rate with increasing viscosity. Looking at acid gas absorbers with an ionic liquid content of 50 wt%, some IPAEs participate in the absorption reaction and then absorb in a fraction of the ionic liquid with 1: 1 interaction mechanism and dissolution mechanism.

7 is a graph showing the CO ₂ loading of an absorption / elimination 1-cycle reaction per hour (minutes) of an acid gas absorber mixed with 30 wt% IPAE and an ionic liquid.

When the absorbent containing 30 wt% IPAE alone and 30 wt% IPAE alone were compared with the acid gas absorbent containing 10 wt% or 20 wt% of the ionic liquid, the rate of absorption / elimination 1-cycle of the acid gas absorbent according to the present invention was large Although it did not change, the time required for carbon dioxide removal was slightly reduced.

It is also found that the absorbing and stripping rates are slightly reduced when the absorbent containing 30 wt% IPAE alone and the 30 wt% IPAE and the acid gas absorbent containing 30 wt% or 40 wt% of ionic liquid are compared.

8 is a graph showing CO ₂ loading over time of the conventional carbon dioxide absorbent MEA and the acid gas absorbent of the present invention.

Comparing the absorption amount of carbon dioxide of the acid gas absorbent of the present invention with that of the conventional 30 wt% MEA, the maximum absorption amount of carbon dioxide of the acid gas absorbent in the present invention appears to have a somewhat lower absorption amount than that of the conventional carbon dioxide absorbent, It was confirmed that the recycle efficiency was significantly superior to that of the conventional carbon dioxide absorbent, MEA.

The acid gas absorbent containing 10 wt% or 20 wt% of ionic liquid was found to have a lower reaction time than the conventional 30 wt% MEA for 1 cycle of absorption / removal, which is comparable to the process using the conventional 30 wt% MEA If the absorber is extended, the efficiency can be similar to that of the process using the conventional 30 wt% MEA.

Further, in Table 6, the carbon dioxide absorbing time, Extraction _{time, Rich-CO 2 loadging, Lean} -CO 2 loading and Cyclic of an acid gas absorbent, 30wt% of IPAE and of a 30wt% MEA conventional carbon dioxide absorber manufactured according to the invention CO ₂ loading.

According to Table 6, the acid gas absorbent containing 30% by weight or 40% by weight of the ionic liquid in the acid gas absorbent produced according to the present invention has a longer removal time than that of the conventional carbon dioxide absorbent Which is superior to 30wt% MEA.

As to the cycle capacity, the acid gas absorbent prepared according to the present invention has a cycle capacity as high as about 1.5 times as compared with the conventional carbon dioxide absorbent, 30 wt% MEA, so that it is usable for the reaction to remove 1 ton of carbon dioxide Energy can be effectively reduced. In addition, the carbon dioxide absorption reaction time is similar or slightly increased to that of the conventional carbon dioxide absorbent, but since the carbon dioxide absorption process does not absorb 100% of the carbon dioxide, the absorption process can be performed in the existing absorption tower. 8 shows that the CO ₂ loading of the acid gas absorbent containing 40 wt% of the ionic liquid is 2 mol / L, and the absorption time of the carbon dioxide is not significantly increased even after a lapse of time of about 75 minutes.

Accordingly, the acid gas absorbent containing the ionic liquid of the present invention increases the cycle capacity in the case of the carbon dioxide absorbent containing 10 to 20 wt% of the ionic liquid as compared with 30 wt% MEA which is the conventional carbon dioxide absorbent, There is an effect that the absorption capacity can be increased. In the case of an acid gas absorbent containing an ionic liquid in an amount of 30 to 40 wt%, the carbon dioxide absorption rate is improved and the regenerated energy is reduced.

Table 7 shows the carbon dioxide absorption time, the removal time, the rich-CO ₂ loading, and the lean-CO ₂ loading of the composition prepared by mixing the acid gas absorbent prepared according to the present invention with the conventional carbon dioxide absorbent 30 wt% MEA and the ionic liquid And cyclic CO ₂ loading.

According to Table 7, the acid gas absorbent prepared with the IPAE as the sterically hindered secondary amine of the present invention has a removal time of 1.5 to 2 times or more as compared with the absorbent prepared with 30 wt% MEA, .

In addition, since the cycle capacity of the acid gas absorbent prepared according to the present invention has an average 1.47 mol / L, while the average of the cycle capacity of the absorbent prepared with 30 wt% MEA is 1.11 mol / L It can be confirmed that the acid gas absorbent produced by the present invention has excellent cycle capacity.

FIG. 9 is a graph showing the CO ₂ loading over time of the composition of the conventional carbon dioxide absorbent MEA mixed with the ionic liquid and the acid gas absorbent of the present invention. FIG.

Absorption of the MEA + ILs mixed sorbent takes quite a long time to be complete, but 90% takes less time to absorb. In addition, the maximum absorption amount is large. However, the cyclic capacity value is less than that of the IPAE + ILs sorbent. For this reason, IPAE + ILs sorbents are more advantageous for continuous process operation. Since the slope of the stripping curve is also larger for IPAE + ILs ionic liquids, the MEA + ILs sorbent is less carbon dioxide regenerative than the IPAE + ILs sorbent. Therefore, MEA + ILs sorbents have higher regenerative energy values than IPAE + ILs sorbents.

10 is a graph showing CO ₂ loading over time of the conventional amine-based carbon dioxide absorbents MEA and IPAE and the acid gas absorbent prepared according to the present invention.

11 is a graph showing CO ₂ loading over time of the conventional amine-based carbon dioxide absorbents MEA and IPAE and the acid gas absorbent prepared by the present invention.

According to FIG. 10 and FIG. 11, by mixing IPAE, which is a sterically hindered secondary amine, with an ionic liquid, absorption time and removal time of carbon dioxide are drastically reduced compared with the case of using a steric hindered secondary amine IPAE alone, Cycle capacity can be confirmed to be maintained at the previous value.

Further, it can be seen that the absorption time of the carbon dioxide is slightly increased and the removal time is reduced, but the cycle capacity is increased about 1.5 times as compared with the conventional 30 wt% MEA, which is the carbon dioxide absorbent.

FIG. 12 is a photograph showing a composition obtained by mixing a conventional carbon dioxide absorbent, MEA, with an ionic liquid, and a modified hue after absorption of carbon dioxide by the produced acid gas absorbent of the present invention.

As for the change of the absorbent, it can be confirmed that the compositions prepared in Comparative Examples 3-1 and 3-3 are separated in the CO ₂ lean loading state, and that the compositions prepared in Comparative Example 3-2 It can be confirmed that layer separation does not occur. In addition, the composition prepared in Comparative Example 3-2 showed that the absorbent was changed from colorless to yellow.

In the exhaust gas condition of the 0.1 MW coal-fired power plant, the CO2 capture process after burning using the Aspen Plus 8.0 V at 40 ° C and the removal temperature of 80 ° C was 95.2% purity Of the carbon dioxide absorbent prepared according to the present invention, the carbon dioxide absorbent prepared at the composition ratio of Example 1-4 had a purity of 99.8% and 3.6 GJ / ton CO ₂ energy, while the carbon dioxide absorbent absorbed 4.7 GJ / ton CO ₂ energy By capturing the carbon dioxide, energy can be saved when the carbon dioxide absorbent produced by the present invention is used.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the scope of the invention. . Accordingly, the technical scope of the present invention is defined by the appended claims and their equivalents.

Claims (5)

1 to 50 wt% of a sterically hindered secondary amine, 5 to 98 wt% of an ionic liquid, and water. The method according to claim 1,
Characterized in that said sterically hindered secondary amine is selected from the group comprising diethanolamine (DEA), di-isopropylamine (DIPA) and 2-isopropylaminoethanol (IPAE) By weight. The method according to claim 1,
The cation of the ionic liquid is an imidazole-based cation selected from the group consisting of [BF ₄ ] ^- , [PF ₆ ] ^- , [Tf ₂ N] ^{- , [TfO] -, [DCA} ] -, [Cl] -, [Br] -, [I] -, [NO 3] -, [SO4] 2 -, [CF 3 COO] -, [CF 3 SO 2 _{^{] -, [(CF 3 SO}} 2) 2 N] -, [SF 6] -, [(C 2 F 5) 3 PF 3] -, [N (SO 2 CF 3) 2] -, [CF 3 SO ^{_{3] -, [B (CN}} ) 4] -, [N (CN) 2] -, [C (CN) 3] -, [SCN] -, [HSO 4] -, [CH 3 SO 4] -, _{[C 2 H 5 SO 4]} -, [C 4 H 9 SO 4] -, [C 6 H 13 SO 4] -, [B (C 2 O 4) 2] -, [CH 3 SO 3] -, , [CH ₃ C ₆ H ₄ SO ₃ ] ^- , and [C ₄ F ₉ SO ₃ ] ^- .
[Chemical Formula 1]

(2)

Contacting an acid gas absorbent with a gas mixture of any one of claims 1 to 3 to absorb the acid gas;
And removing the acid gas absorbed by the acid gas absorbent. 5. The method of claim 4,
Wherein the temperature in the step of absorbing the acid gas is from 0 ° C to 80 ° C, and the temperature in the step of removing the acid gas is from 80 ° C to 150 ° C.

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