WO2010093092A1

WO2010093092A1 - Method of removing carbon dioxide using basic polymer

Info

Publication number: WO2010093092A1
Application number: PCT/KR2009/003175
Authority: WO
Inventors: Kil Won Cho; Shi Choon Lee
Original assignee: Postech Academy-Industry Foundation
Priority date: 2009-02-12
Filing date: 2009-06-12
Publication date: 2010-08-19
Also published as: KR20100092306A; KR101187267B1

Abstract

This invention relates to a method of removing carbon dioxide from air, including hydrating carbon dioxide andprecipitating calcium carbonate. This method promotes the hydration of carbon dioxide using a basic polymer. The basic polymer does not compete with a calcium ion which is precipitated with the hydrated carbon dioxide and is easily recovered, and thus enables the industrial application of the method of removing carbon dioxide.

Description

METHOD OF REMOVING CARBON DIOXIDE USING BASIC POLYMER

The present invention relates to a method of removing carbon dioxide from air, and, more particularly, to a method of removing carbon dioxide from the air, which includes hydration of carbon dioxide and precipitation of calcium carbonatewith the hydrated carbon dioxide.

From now on emissions of carbon dioxide causing global warming are going to be compulsorily cut. For emission thereof, a carbon tax will be paid, and thereby a considerable carbon market is expected to be formed. Because large petrochemical plants or steam power plants emit a large amount of high concentration carbon dioxide, attempts have been made to reduce carbon dioxide emissions through changing energy sources and increasing efficiency of plants or facilities in which carbon dioxide may be relatively easily treated. Also, to remove carbon dioxide, storage after dissolution in water in large plants, compressive storage in the deep sea, tunnel storage, storage using photosynthesis by seaweed and storage through precipitation of calcium carbonate are under active study. In addition to the reduction of carbon dioxide emissions, removal of carbon dioxide from the air is also regarded as important and its research is being thoroughly conducted.

The safestmethod of storing carbon dioxide includes the use of a metal oxide so that a reaction between a metal ion and a carbonate ion by hydration of carbon dioxide in water is promoted, thus immobilizing carbon dioxide (Bachu S. Energy Convers. Mgmt. 41, 953-970, 2000). Reactions 1 and 2 below show the hydration of carbon dioxide and the production of calcium carbonate, as is well known in the art.

Reaction 1

CO₂ + H₂O ↔ HCO₃ ^- + H⁺ ↔ CO₃ ^2- + 2H⁺

Reaction 2

Ca²⁺ + CO₃ ^2- → CaCO₃

As shown in Reaction 1, carbon dioxide is hydrated, thus producing a bicarbonate ion (HCO^3-) and a carbonate ion (CO₃ ^2-). In particular, as the reaction progresses forward, the carbonate ion is produced in a large amount and thus reacts with the metal ion, namely, the calcium ion. As such, in order to more rapidly hydrate carbon dioxide and induce precipitation, the forward reaction must progress.

As one method for promoting the hydration, use of carbonic anhydrase has been proposed. This enzyme, which is present in almost all animals and plants, is reported to be a catalyst for mediating hydration and dehydration of carbon dioxide, thus promoting the hydration of carbon dioxide at a rate of 10⁶ CO₂/s. Despite this capability, however, this enzyme is expensive and very difficult to use. In basic experiments using this enzyme, no drastic increase in precipitation of calcium carbonate can be discerned.

Also, the hydration of carbon dioxide rapidly acidifies the solution (especially, in the sea) to thus inhibit additional production of the carbonate ion. Accordingly, in order to induce the forward reaction, a solution having a high pH must be used or a process of removing protons generated in the hydration reaction must be performed (Proc. Nat. Acad. Sci. 70, 1986-1989, 1973).

To increase the pH, an alkaline solution may be used. However, the use of the alkaline component may undesirablyincrease pollution. Also, alkali metal competes with the calcium ion, causing the reduction of the precipitation rate, which is disadvantageous from the industrial point of view (J. Crystal Growth 133, 13-22, 1993).

To remove protons generated in the hydration reaction, various basic components have been developed. Korean Patent No. 836709, granted to Korea Institute of Energy Research, discloses the use of ammonia water as an absorbent in lieu of an amine-based absorbent in a gas mixture containing carbon dioxide. Korean Patent No. 650556, granted to Posco, Korea, discloses a method of adjusting the concentration of ammonia water used in an absorption tower. However, in the case of such an amine-based absorbent or ammonia, the recovery thereof is difficult. Further, ammonia is problematic because it easily evaporates even at room temperature.

In addition, adsorption or membrane separation methods have been devised. The adsorption method consumes much energy to carry out the absorption process and to increase the absorption volume and is thus difficult to commercialize, while the membrane separation method may reduce energy but is employable in a small-sized apparatus, and is thus difficult to apply to a largescale emission apparatus. Hence, novel methods for efficiently absorbing carbon dioxide are in constant demand.

Meanwhile, anhydrous calcium carbonate has the three crystal structures of calcite, aragonite, and vaterite. Among them, calcite is the most stable and is present in the largest amount in the skeleton of organisms and in nature. Aragonite is most stable next to calcite and is present in a large amount in organisms and in nature. Vaterite is unstable and it is reported to be rarely present in nature and organisms. Aragonite may be artificially prepared using a special solution or under limited conditions including high temperature (Tai, C. Y., Chen, F. B. AIChE Journal, 44(8), 1790-1798 1998, Hu, Z., Deng, Y., J. Colloid Interface Sci. 266, 359-365, 2003). The species such as coral or sponge growing in the shallow sea or seashore produce aragonite under natural conditions and thus use such aragonite as biominerals or their body Generally, aragonite has an acicular structure which grows to become very long in the longitudinal axis direction, and a great amount of energy is required to break crystals thereof but the crystal size is not large. On the other hand, calcite grows to form large crystals butthese crystals are easy to break. Calcium carbonate in the acicular structure of aragonite having a high aspect ratio (length/width ratio) is important as a filler for improving mechanical strength in the rubber or plastic industries(W. Shang, Q. Liu, B. Liu, L. Chen, S. Chen, Proceedings of 1998 International Symp. On Electrical Insulating Materials, 595-598, 1998). Therefore, the demand for methods able to control precipitation of calcium carbonate through hydration of carbon dioxide is ever present.

Accordingly, the present invention provides a novel method of removing carbon dioxide through absorption of a large amount of carbon dioxide and precipitation.

Also, the present invention provides a novel absorbent for absorption of a large amount of carbon dioxide and precipitation.

Also, the present invention provides a method of producing calcium carbonate, which includes absorption of carbon dioxide and precipitation.

Also, the present invention provides a method of producing calcium carbonate which includes hydration of carbon dioxide, wherein the crystal structure of calcium carbonate is capable of being controlled.

An aspect of the present invention provides a method of precipitating calcium carbonate with carbon dioxide using a solution containing a calcium ion and an aqueous polymer having an amine group.

In the present invention, the aqueous polymer having an amine group absorbs protons generated during hydration of carbon dioxide, as does a basic buffer, thus promoting the hydration of carbon dioxide. The aqueous polymer having an amine group according to the present invention does not contain alkali metal, and thus, in the formation of calcium carbonate, there is no competition with the calcium ion. Also, the aqueous polymer having an amine group may be more easily recovered and reused compared to a conventional buffer such as ammonia or low-molecular-weight basic components.

In an embodiment of the present invention, as the aqueous polymer having an amine group, particularly useful is polyalkyleneimine, and examples of polyalkyleneimine include polyethyleneimine, polypropyleneimine and mixtures thereof.

In the present invention, polyalkyleneimine may have a weight average molecular weight of 200~750,000 and preferably of 400~25,000. If the molecular weight is too small, it is difficult to separate and recover the polymer used. In contrast, if the molecular weight is too large, it is difficult to prepare the polymer.

In the present invention, polyalkyleneimine may have a linear or network structure, and examples of amine contained therein may include but are not limited to primary, secondary and tertiary amines distributed in various amounts.

In an embodiment of the present invention, the aqueouspolymer having an amine group may be used in a state of being dissolved in water, or may be used in a state of being immobilized to an immobilized member so as to facilitate the recovery and recycling thereof. The immobilized member may include beads or a column.

In the present invention, the polyalkyleneimine aqueous polymer may be used alone as a buffer for removing protons or may be used in combination with a conventional basic buffer such as ammonia or Tris. Also, a hydration enzyme such as bovine carbonic anhydrase (BCA) may be further included.

In the present invention, the calcium ion is used to react with the hydrated carbon dioxide in order to precipitate calcium carbonate. Any product may be used as long as it supplies the calcium ion. For example, calcium or calcium-containing limewater or seawater may be used.

Another aspect of the present invention provides a method of removing carbon dioxide from air including hydration of carbon dioxide of air using an aqueous polymer having an amine group.

In the present invention, as the aqueous polymer having an amine group, particularly useful is polyalkyleneimine having a weight average molecular weight of 200~700,000. The hydrated carbon dioxide may be removed by precipitating a solid. Further, polyalkyleneimine used in the hydration may be used in a state of being dissolved or of being immobilized to an immobilized member. Furthermore, polyalkyleneimine may be reused after eliminationof a hydrogen ion therefrom.

A further aspect of the present inventionprovides an aqueous solution of a calcium ion and an aqueous polymer having an amine group to remove carbon dioxide and precipitate calcium carbonate. In the present invention, the molecular weight of the aqueous polymermay be set in the range of 200~750,000 and preferably 300~25,000, andthe concentration thereof may be set to 0.1 mg/ml or more and preferably 5~30 mg/ml.

In an embodiment of the present invention, the aqueous polymer having an amine groupmay be recycled and reused by immobilizing it to a column andthen passing it through a solution containing hydrated carbon dioxide, or may be recovered and recycled after having been used in a state of being immobilized to the surface of beads. Typically, the polymer is used in an aqueous solution, or alternativelymay be used in another solvent.

Still a further aspect of the present invention provides a method of producing calcium carbonate, including hydration of carbon dioxide in a solution containing an aqueous polymer having an amine group, thus precipitating calcium carbonate having an aragonite crystal structure.

Still another aspect of the present invention provides a novel industrial method using the process of precipitating calcium carbonate with carbon dioxide using an aqueous polymer having an amine group.

For example, a very effective method of removing scales includes the use of a polyethyleneimine polymer so that a calcium component which may become the scales is previously precipitated. Also, as another example, there is introduced a method of repairing cracks of cement, including cultivation of microorganisms and precipitation of calcium carbonate thus filling the cracks (S. S. Fischer, J. K. Galinat, S. S. Bang, Microbiological precipitation of CaCO3, Soil Biology and Biochemistry, 31, 1563-1571, 1999). As such, when the polyethyleneimine polymer is used, repair may be efficiently performed through precipitation with carbon dioxide present in air without the cultivation of microorganisms. The above methods do not require a large apparatus and may thus be employed for small portable applications in home or automobiles. Further, in order to remove a large amount of carbon dioxide over a large area, an ecological park including a marshy place, a pool and so on may be constructed using components disclosed in the patents. The components used in the solution are harmless to the environment andare commercially available and thus scale-up or large scale development is not expected to be problematic. In addition to the above methods, the fundamental concept may be applied to the manufacturing of artificial coral similar to biominerals of natural coral occurring in the sea.

Yet another aspect of the present invention provides a method of converting carbon dioxide into calcium carbonate using a solution of a calcium ion and a basicpolymer having a weight average molecular weight of 200~750,000.

In the present invention, the basic polymer is a polymer having a reactive group for removing protons generated during hydration of carbon dioxide. The reactive group is a base for example an amine group, and preferably includes primary, secondary and tertiary amines. In the present invention, the polymer is preferably an aqueous polymer which is soluble in the water used forehydration reaction.

According to the present invention, a method of increasing the amount of calcium carbonate precipitated by effectively removing protons can be provided. As the precipitated amount of calcium carbonate increases, the removal of carbon dioxide will be increased.

Also, according to the present invention, an aqueous polymer having an amine groupcan be easily recovered and recycled, and in particular, the resultant calcium carbonate has an aragonite or calcite structure.

FIG. 1 is a photograph of calcium carbonate precipitated using 100 mM Tris and 10 mM CaCl₂.

FIG. 2 is a photograph of calcium carbonate precipitated using 100 mM ammonium and 10 mM CaCl₂.

FIG. 3 is a photograph of calcium carbonate precipitated using 10 mg/ml PEI2 and 10 mM CaCl₂.

A better understanding of the present invention may be obtained through the following examples which are set forth to illustrate, but are not to be construed as limiting the present invention.

Samples

PEI0.4: polyethyleneimine having a molecular weight of 400and containing primary, secondary and tertiary amines, available from Sigma Aldrich

PEI0.8: polyethyleneimine having a molecular weight of 800and containing primary, secondary and tertiary amines

PEI1.3: polyethyleneimine having a molecular weight of 1,300 and containing primary, secondary and tertiary amines

PEI2: polyethyleneimine having a molecular weight of 2,000 and containing primary, secondary and tertiary amines

PEI25: polyethyleneimine having a molecularweight of 25,000 and containing primary, secondary and tertiary amines

PEI750: polyethyleneimine having a molecular weight of 750,000 and containing primary, secondary and tertiary amines

10 mM aqueous CaCl₂

Bovine Carbonic Anhydrase (BCA), available from Sigma Aldrich

Comparative Example

While 50 ml of 10 mM aqueous CaCl₂ was used, cases where a basic buffer was not used with or without addition of BCA and where aqueous ammonium (ammonium hydroxide) or Tris (tris(hydroxyethyl)aminomethane) was used as the basic buffer with or without addition of BCA were tested. The samples were placed in a Petri dishhaving a diameter of 10 ㎝, stirred at about 300 rpm for about 10 hours using a magnetic stirrer in a state of being exposed, and then allowed to stand. Then, the 24-hour cumulative precipitation amount was measured. The theoretical amount of CaCO₃ when the entirety of calcium ion contained in the solution was 100% consumed and completely converted into calcium carbonate was calculated to be 50 mg.

Table 1

Basic Buffer (mM)	CaCl₂ (mM)	BCA (㎍/ml)	Precipitation of CaCO₃ after 24 hours
Basic Buffer (mM)	CaCl₂ (mM)	BCA (㎍/ml)	Amount (mg)	Calcium Consumption (%)
-	10	-	0	0
-	10	10	0	0
Ammonium, 100	10	-	27	52
Ammonium, 100	10	10	27	52
Tris, 100	10	-	32	61
Tris, 100	10	10	36	69

Example 1

50 ml of an aqueous solution containing 10 mM CaCl₂ and 10 mg/ml PEI was placed in a Petri dish having a diameter of 10 ㎝, stirred at about 300 rpm for about 10 hours using a magnetic stirrer in a state of being exposed, and then allowed to stand. Then, the 24-hour cumulative CaCO₃precipitation amount was measured.

Table 2

Use of PEI Buffer without addition of BCA

Basic Buffer (mM)	CaCl₂ (mM)	Precipitation of CaCO₃ after 24 hours
Basic Buffer (mM)	CaCl₂ (mM)	Amount (mg)	Calcium Consumption (%)
PEI0.4, 10	10	45	86
PEI0.8, 10	10	44	85
PEI1.3, 10	10	45	86
PEI2.0, 10	10	46	88
PEI25, 10	10	40	77
PEI750, 10	10	40	77

Example 2

Table 3

Use of PEI Buffer with addition of BCA

Basic Buffer (mM)	CaCl₂ (mM)	BCA (㎍/ml)	Precipitation of CaCO₃ after 24 hours
Basic Buffer (mM)	CaCl₂ (mM)	BCA (㎍/ml)	Amount (mg)	Calcium Consumption (%)
PEI0.4, 10	10	10	47	90
PEI0.8, 10	10	10	39	75
PEI1.3, 10	10	10	43	82
PEI2.0, 10	10	10	42	81
PEI25, 10	10	10	48	92
PEI750, 10	10	10	40	77

As is apparent from above results, the precipitation amount was evaluated to be insignificant when used no basic buffer. In the case where ammonia or Tris was used as the basic buffer, 50% or more of calcium carbonate was precipitated following 24 hours of aging time. When BCA was added thereto, the precipitation rate was slightly and not greatly increased. When ammonium or Tris was used, an acicular structure was slightly formed an initial 5 hours of aging time, whereas acicular aragonite was mostly produced in 24 hours of aging time.

Upon use of PEI, the calcium consumption was very high up to 75% or more. When PEI was used, as shown in FIG. 1, the ratio of acicular structure was higher, and the acicular aragonite crystal structure could be seen to be formed in 5 hours of aging time. When BCA was used, the precipitation amount of calcium carbonate initially rapidly increased, but there was no great difference in the precipitation amount in 24 hours of aging time, compared to when no BCA was used. Thereby, the basic buffer could be confirmed to be a main component responsible for the increase in precipitation amount.

In particular, the method used polyethyleneimine (PEI) which is a high-molecular-weight basic buffer is very advantageous in terms of reusability and separation/purification and is thus easy to commercialize. In a mechanism for increasing precipitation amount using PEI, PEI performs a proton sponge function to eliminate protons generated during hydration of carbon dioxide, and thus does not acidify the solution andpromotes the production of a carbonate ion. Specifically, according to the above mechanism, the carbonate ion which is produced in a larger amount reacts with the calcium ion, thus highly inducing the precipitation of calcium carbonate. To be commercialized, it may be used in a state of being immobilized to a column so that a proton sponge function is performed to promote the above reaction, after which the PEI may be deprotonated and then reused. Also, the basic buffer may be utilized to control the crystal structure of calcium carbonate.

Claims

A method of precipitating calcium carbonate with carbon dioxide using a solution containing a calcium ion and an aqueous polymer having an amine group.
The method according to claim 1, wherein the aqueous polymer having an amine group is polyalkyleneimine.
The method according to claim 2, wherein the polyalkyleneimine is selected from among polyethyleneimine, polypropyleneimine and mixtures thereof.
The method according to claim 2, wherein the polyalkyleneimine has a weight average molecular weight ranging from 200 to 750,000.
The method according to claim 2, wherein the polyalkyleneimine has a weight average molecular weight ranging from 400 to 25,000.
The method according to claim 2, wherein the amine is a primary, secondary or tertiary amine.
The method according to claim 1, wherein the aqueous polymer having an amine group is dissolved in water or immobilized to an immobilization member.
The method according to claim 7, wherein the immobilization member is a column or beads.
The method according to claim 1, wherein the calcium ion is prepared using calcium chloride, calcium hydroxide or calcium-containing limewater.
The method according to claim 1, wherein the calciumcarbonate has an aragonite structure.
The method according to claim 1, wherein the solution further contains a hydration enzyme including carbonic anhydrase.
The method according to claim 1, wherein the solution further contains ammonia and/or Tris.
A method of removing carbon dioxide, comprising hydrating carbon dioxide in an aqueous solution containing a calcium ion and an aqueous polymer having an amine group and precipitating calcium carbonate.
The method according to claim 13, wherein the aqueous polymer having an amine group is polyalkyleneimine having a weight average molecular weight ranging from 200 to 700,000.
The method according to claim 14, wherein the polyalkyleneimine is dissolved or immobilized to an immobilization member.
The method according to claim 14, wherein the polyalkyleneimine is reused after elimination of a hydrogen ion therefrom.
An aqueous solution of an aqueous polymer having an amine group and a calcium ion so as to remove carbon dioxide and precipitate calcium carbonate.
The aqueous solution according to claim 17, wherein the aqueous polymer having an amine group has a molecular weight ranging from 200 to 750,000.
The aqueous solution according to claim 17, wherein the aqueous polymer having an amine group is used at a concentration of 1~30 mg/ml.
A method of converting carbon dioxide into calcium carbonate using a solution of a basic polymer having a weight average molecular weight ranging from 200 to 750,000 and a calcium ion.