CERAMIC MATERIAL FOR THE ABSORPTION OF CARBON DIOXIDE, PRODUCTION PROCESS, PROCESSES FOR THE REGENERATION OF CARBON DIOXIDE AND OF THE CERAMIC MATERIAL, AND USES

Abstract

The present invention describes the process of preparing ceramic materials for absorption of acidic gases, mainly carbon dioxide, in exhaust systems and/or present indoors. Ceramic materials are formed by a mixture of alkali carbonate with alkaline earth metal oxide/hydroxide associated with a binding component, but non-limiting. The alkali carbonate comprises sodium, potassium carbonate, or a mixture of both. The alkaline earth metal oxide/hydroxide may be formed from magnesium oxide or magnesium hydroxide as well as calcium oxide and/or calcium hydroxide.

Claims

1-11. (canceled)

12. A process for producing a ceramic material, comprising the following steps: (a) solubilizing 23 to 360 g of alkali carbonate in 500 to 1,000 mL of water, wherein the alkali carbonate is Na.sub.2CO.sub.3, K.sub.2CO.sub.3, or a combination thereof; (b) adding 200 to 800 g of alkaline earth metal oxide or hydroxide; (c) adding a binding agent to form a mixture; (d) homogenizing the mixture obtained in step (c) for 5 to 30 minutes to form a clay; (e) removing, and optionally molding the clay obtained in step (d) for 1 to 3 hours; (f) drying the clay at a temperature from 50° C. to 150° C., preferably 80° C., for a period of 3 to 48 hours.

13. The process of claim 12, wherein 87 g of alkali carbonate is solubilized in 500 to 1,000 mL of water.

14. The process of claim 12, wherein 300 g of alkaline earth metal oxide or hydroxide is added.

15. The process of claim 12, wherein the mixture is homogenized for 10 minutes.

16. The process of claim 12, wherein the clay is molded for 1 hour.

17. The process of claim 12, wherein the clay is dried for 24 hours.

18. The process of claim 12, wherein the alkaline earth metal oxide or hydroxide in step (b) is selected from the group consisting of: magnesium oxide (MgO), magnesium hydroxide (Mg(OH).sub.2), calcium oxide (CaO), and calcium hydroxide (Ca(OH).sub.2).

19. The process of claim 12, wherein the binding agent in step (c) is selected from the group consisting of: calcium oxide (CaO), Portland cement, calcium sulfate (CaSO.sub.4) and ferrous sulfate (FeSO.sub.4).

20. The process of claim 12, wherein the drying in step (f) occurs in the presence of nitrogen and in the absence of air and carbon dioxide, in a closed chamber.

21. A process for regenerating ceramic material comprising the following steps: (a) thermally decomposing a saturated absorbent ceramic at a temperature of 350° C. to 800° C. for a period of 2 to 8 hours for release of an acid gas; (b) cooling the ceramic material at a temperature from 30 to 100° C.; (c) adding water under constant stirring to adjust the moisture content of the ceramic material to 7 to 30%.

22. The process of claim 21, wherein the temperature for the release of the acid gas in step (a) is 450° C.

23. The process of claim 21, wherein the ceramic material is cooled to 80° C.

24. The process of claim 21, wherein the moisture content of the ceramic material is adjusted to 17%.

25. A ceramic material produced according to the process of either of claim 12 or claim 21.

26. The ceramic material of claim 25, wherein the ceramic material is molded into compact blocks, cast blocks (bricks), or pellets.

27. A use of the ceramic material of claim 25 as an absorbent material of acidic gases in an absorption process.

28. The use of the ceramic material according to claim 27, wherein the absorption process occurs in a solid preformed bed of the ceramic material or in a fluidized bed of the ceramic material and excess water.

29. A use of the ceramic material of claim 25, characterized by being a source of acidic gases.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0016] FIG. 1 shows the graph of bicarbonate saturation in the absorption system.

[0017] FIG. 2 shows the saturation of MgCO.sub.3 in formulation F1 (Table 1 below).

[0018] FIG. 3 shows the bicarbonate formation velocity and magnesium carbonate formation velocity.

[0019] FIG. 4 shows the saturation rate at 5 hours of absorption for the samples described in the examples.

[0020] FIG. 5 shows the captured CO.sub.2 content (A) and saturation (B) of material A1 (MgO+Na.sub.2CO.sub.3) at a temperature of 130±10° C.

[0021] FIG. 6 shows the captured CO.sub.2 content (A) and saturation (B) of the A2 material (MgO+Na.sub.2CO.sub.3+CPIII Cement) at a temperature of 130±10° C.

[0022] FIG. 7 shows the captured CO.sub.2 content (A) and saturation (B) of the A4 material (MgO+Na.sub.2CO.sub.3+FeSO.sub.4) at a temperature of 130±10° C.

[0023] FIG. 8 shows the captured CO.sub.2 content (A) and saturation (B) of material A3 (MgO+Na.sub.2CO.sub.3+CaO) at a temperature of 130±10° C.

[0024] FIG. 9 shows the captured CO.sub.2 content (A) and saturation (B) of the A5 material (CaO+K.sub.2CO.sub.3) at a temperature of 130±10° C.

[0025] FIG. 10 shows the steps of decomposition of the saturated material for regeneration thereof, up to a temperature of 450° C.

DETAILED DESCRIPTION OF THE TECHNOLOGY

[0026] The present invention describes the process of preparing ceramic materials for absorption of acidic gases, mainly carbon dioxide, released into exhaust systems and/or that present indoors. The ceramic materials are formed of an absorbing agent, composed of a mixture of alkali carbonate with alkaline earth metal oxide/hydroxide, associated with a binding agent. The alkali carbonate comprises sodium, potassium carbonate, or a mixture of both. The alkaline earth metal oxide/hydroxide may be formed from magnesium oxide or magnesium hydroxide as well as calcium oxide and/or calcium hydroxide.

[0027] The proposed process for obtaining the ceramic material comprises the following steps: [0028] a. Solubilizing between 23 g and 360 g preferably 87 g of the alkali carbonate (Na.sub.2CO.sub.3 and/or K.sub.2CO.sub.3) in 500 to 1,000 mL of water; [0029] b. Adding 200 g to 800 g, preferably 300 g of alkaline earth metal oxide or hydroxide; [0030] c. Adding the binding agent; [0031] d. Homogenizing the mixture obtained in step “c” for 5 to 30 minutes, preferably 10 minutes, obtaining a uniform pasty consistency; [0032] e. Removing and optionally molding the dough obtained in step “d” between 1 to 3 hours, preferably 1 hour; [0033] f. Drying the material at a temperature between 50° C. and 150° C., preferably 80° C., for a period of between 3 and 48 hours, preferably 24 hours.

[0034] In step “b” of the process, the absorbing agent comprising alkaline earth metal should be selected from the group comprising: magnesium oxide (MgO), magnesium hydroxide (Mg(OH).sub.2), calcium oxide (CaO) and calcium hydroxide (Ca(OH).sub.2).

[0035] In step “c” of the process, the binding agent should be selected from the group comprising: calcium oxide (CaO), Portland cement, calcium sulfate (CaSO.sub.4) and ferrous sulfate (FeSO.sub.4).

[0036] In step “f” of the process heating must occur in the presence of nitrogen and in the absence of air and carbon dioxide, in a closed chamber.

[0037] The absorption process may occur in a bed filled with the pre-molded solid material or in a fluidized bed with excess water.

[0038] The proposed process for regeneration of the absorbent ceramic material comprises the following steps: [0039] a. Thermally decomposing the saturated absorbent ceramic at a temperature of 350° C. to 800° C. for a period between 2 and 8 hours for release of the acid gas; [0040] b. Cooling the ceramic material at a temperature between 30 and 100° C., preferably 80° C.; [0041] c. Adding water under constant stirring to correct moisture content between 7 and 30%, preferably 17%, of the absorbent material.

[0042] In step “a”, the temperature for the release of CO.sub.2 should preferably be 450° C., for a period between 2 and 8 hours.

[0043] Optionally, during step “a”, it is possible to take advantage of the released acid gas by conducting the same to the processing systems of industrial interest.

[0044] The present invention also proposes the ceramic material obtained from one of the above processes.

[0045] The ceramic material (fresh or regenerated) for carbon dioxide absorption can be shaped in any shape, including compact block, hollow block (brick) or pelletized material.

[0046] Additionally, the invention features the use of absorbent ceramic material which, by presenting basic character, allows its use in acid gas absorption processes such as carbon dioxide (CO.sub.2), nitric oxide (NO), nitrogen dioxide (NO.sub.2), sulfur dioxide (SO.sub.2), sulfur trioxide (SO.sub.3), non-limiting.

[0047] Finally, the invention also proposes the use of the absorbent ceramic material as a source of carbon dioxide and other acid gases. Because saturated absorbent ceramics have a high concentration of acid gases, especially carbon dioxide, gases can be compressed for commercialization as chemical reagents or in other industrial processes that employ gaseous CO.sub.2 or other acid gases.

[0048] The present invention may be better understood according to the non-limiting examples described below.

Example 1—Method of Synthesis, Application and Absorption Mechanism of a Ceramic Material Formed by Alkaline Earth Metal Oxide or Hydroxide with an Alkali Metal Carbonate being Able to be Associated with One or More Binder Components

[0049] These materials have the ability to interact with carbon dioxide in a temperature range between 30 and 150° C. forming the respective alkaline earth metal carbonate. After saturation of the material, it can be thermally regenerated by raising the temperature until decomposition of the alkaline earth carbonate.

[0050] The combination of the mixture between alkaline earth metal oxide/hydroxide and alkali carbonate enables the increase of the rate of reaction of carbonate formation from the alkaline earth metal, through an intermediate reaction between the carbon gas stream and the alkali carbonate formed the chemical species hydrogen carbonate that reacts rapidly with the alkaline earth metal oxide/hydroxide. To exemplify the efficacy of this reaction mechanism, exposure of magnesium oxide with a constant flow of pure CO.sub.2 in the temperature range between 25 and 500° C. does not result in any formation of magnesium carbonate, as can be seen with calcium oxide. However, performing this same process with the presence of sodium or potassium carbonate promotes the stoichiometric conversion of all magnesium in the form of oxide or hydroxide to carbonate.

[0051] The absorption process occurs in two steps. First CO.sub.2 is captured by an alkali metal carbonate, forming the hydrogen carbonate ion (HCO.sub.3.sup.−2) according to equations 1, 2 and 3:

K.sub.2CO.sub.3(s).fwdarw.2K.sup.+(aq)+CO.sub.3.sup.+2(aq)Na.sub.2CO.sub.3(s).fwdarw.*2Na.sup.+(aq)+Co.sub.3.sup.−2(aq)  eq. 1

CO.sub.3.sup.−2+H.sub.2O+.Math.HCO.sub.3.sup.−+OH.sup.−  eq. 2

CO2(g)+OH.sup.−.fwdarw.HCO.sub.3.sup.−  eq. 3

[0052] In this sequence the alkali carbonate (Na.sub.2CO.sub.3 or K.sub.2CO.sub.3) is dissolved (eq. 1) by the water present in the material and in the exhaust gas flow, then the carbonate ion reacts with water (eq 2) forming a chemical system in equilibrium with the bicarbonate ion, the last reaction involves the capture of carbon dioxide by the reaction with the hydroxyl present in the medium forming another bicarbonate ion (eq. 3).

[0053] Parallel to the formation of bicarbonate ions in the system, alkaline earth metal oxide or hydroxide reacts with the bicarbonate present in the system by shifting the chemical equilibrium to the alkali carbonate formation reaction (eq. 2). In this way the carbonate .Math.bicarbonate system (eq 2) functions as a fast-acting stock that makes bicarbonate available to interact with the alkaline earth metal source (CaO, Ca(OH).sub.2, MgO or Mg(OH).sub.2) (eq. 4).

HCO.sub.3.sup.−+Ca(OH).sub.2.fwdarw.CaCO.sub.3+H.sub.2O

HCO.sub.3.sup.−+Mg(OH).sub.2.fwdarw.MgCO.sub.3+H.sub.2O  eq. 4

[0054] The present invention proposes a set of absorbent mixtures generically referred to as ATA150, each formulation comprising at least one alkaline earth metal oxide or hydroxide may be: MgO, Mg(OH).sub.2, CaO or Ca(OH).sub.2 associated with an alkali metal carbonate may be: Na.sub.2CO.sub.3, K.sub.2CO.sub.3. To give cohesion and mechanical strength one can add a binding agent which can be: polystyrene, cement or calcium phosphate. The composites formulated in this invention have the ability to absorb CO.sub.2 in gas streams having temperatures between 30 and 150° C. Table 1 ranges for ATA150 material formulations shows the concentration ranges of each component for the various compositions elaborated in this invention.

TABLE-US-00001 TABLE 1 ranges for ATA150 material formulations Alkaline earth metal oxide/hydroxide Alkaline metal MgO/ CaO/ carbonate Binders Ratio Formulations Mg(OH).sub.2 Ca(OH).sub.2 Na.sub.2CO.sub.3 K.sub.2CO.sub.3 Polystyrene Cement CaSO.sub.4 FeSO.sub.4 (kg/kg(CO.sub.2) F1 70%-97% — 30%-3% — — — — 0.93-1.47 F2 70%-97% — — 30%-3% — — — — 0.94-1.84 F3 70%-97% — 30%-3% — 3%-15% — — 0.96-1.59 F4 70%-97% — — 30%-3% — 3%-15% — — 0.97-1.95 F5 70%-97% — 30%-3% — — 3%-10% — 0.96-1.55 F6 70%-97% — — 30%-3% — — 3%-10% — 0.98-2.33 F7 70%-97% — 30%-3% — — — 1%-10% 0.94-1.55 F8 70%-97% — — 30%-3% — — — 1%-10% 0.98-1.93 F9 70%-97%  .sup.  3-15% 30%-3% — — — — 0.95-1.56 F10 70%-97%  .sup.  3-15% — 30%-3% — — — — 0.97-1.93 F11 — 70%-97% 30%-3% — — — — 1.70-2.13 F12 — 70%-97% — 30%-3% — — — — 1.71-2.14 F13 — 70%-97% 30%-3% — 3%-10% — — 1.73-2.28 F14 — 70%-97% — 30%-3% — 3%-10% — — 1.74-2.43 F15 — 70%-97% 30%-3% — — 3%-10% — 1.73-2.28 F16 — 70%-97% — 30%-3% — — 3%-10% — 1.74-2.43 F17 — 70%-97% 30%-3% — — — 1%-10% 1.71-2.28 F18 — 70%-97% — 30%-3% — — — 1%-10% 1.72-2.43

[0055] The synthesis process of the various formulations for the ATA150 material follows a standardized procedure. First the alkali carbonate (Na.sub.2CO.sub.3 or K.sub.2CO.sub.3) is diluted in water in a ratio of (1,830±200) ml of water to each per kg of alkaline earth metal oxide/hydroxide, then the oxide/hydroxide is added to the solution together with the binding agent. This mixture is homogenized for approximately 10 minutes, but not limiting, until it acquires a uniform pasty consistency (without the presence of granules), then the mixture can be molded or placed in an extruder. The dough acquires consistency to demold between 1 and 3 hours, then the material can be dried at a temperature between 50 and 150° C. or further stored with moisture.

[0056] The process of absorption of CO.sub.2 by the ATA150 material is intrinsically dependent on the presence of water, as shown in eq. 1 and 2, in this way, the inclusion of water can be obtained in two ways: the gas flow itself can contain moisture/or the material can be humidified with a content between 10 and 20%, but not limiting, to activate the eq reactions. 1 and eq. 2. The absorption process may occur in a bed filled with the preformed solid material or in a fluidized bed with excess water. In both cases the rate of absorption process is defined by the combination of two processes, the conversion rate of alkali carbonate to bicarbonate (Error! Reference source not found.) and the conversion rate of alkali bicarbonate to alkaline earth carbonate (Error! Reference source not found.). Initially, the high availability of alkali carbonate and alkaline earth oxide maintains the absorption process at a higher rate (Error! Reference source not found.). Initially the rate of formation of alkaline earth carbonate (HCO.sub.3.sup.−.fwdarw.MgCO.sub.3) due to high availability of alkaline earth metal. However, after the kinetic equilibrium of reactions 1 and 2, the rate of bicarbonate formation becomes higher, generating a stock of bicarbonate that guarantees its conversion as long as alkaline earth metal is available.

[0057] Within the list of proposed formulations (Table 1) for the ATA150 material described in this patent, compositions containing MgO (Formulations F1 to F10) as source of alkaline earth metal and sodium carbonate as source of alkali carbonate are more industrially relevant due to the possibility of obtaining a theoretical yield of approximately 1:1 (m/m), this ratio represents the best mass ratio of CO.sub.2 captured per mass of absorbent material. Calcium-containing formulations have a higher mass ratio of absorbent material per captured mass, between 1.72 and 2.43, i.e. consuming more mass per captured C02 unit.

[0058] The absorbent material described in this patent application has a basic character, allowing its use in acid gas absorption processes such as carbon dioxide (CO.sub.2), nitric oxide (NO), nitrogen dioxide (NO.sub.2), sulfur dioxide (SO.sub.2), sulfur trioxide (SO.sub.3), non-limiting. Although all the gases mentioned promote climatic aggravation, carbon dioxide is the main pollutant, mainly due to the high amount produced in industries that use combustion processes. In this way, CO.sub.2 will be used in examples of the functionalities of the ATA150 material and efficiency of the absorption process to reduce greenhouse gas emissions, and subsequent use of the material formed, in order to regenerate the absorbent ceramics and generate important products of high added value for various industrial sectors. The regeneration process of the ATA150 material corresponds to another characteristic that favors the use of magnesium-containing formulations that exhibit a regeneration temperature between 350 and 450° C., the lower temperature range being obtainable by reducing the partial pressure of CO.sub.2 in the atmosphere of the regeneration reactor. For compositions containing calcium (F11 to F18) the regeneration temperature is between 650 and 850° C.

[0059] Carbon dioxide formed from saturated absorbent ceramics has a high concentration, enabling several industrial methods. Initially, the carbon dioxide itself can be compressed and bottled for later commercialization as a chemical reagent, or in different processes that use gaseous CO.sub.2.

[0060] To demonstrate the absorption potential, 5 test formulations were selected and will be presented in the following examples. The first 4 formulations are composed of magnesium oxide and sodium carbonate, distinguished only by the use of the binder component, Formulation 1 corresponds to the reference material (standard sample—A1), Sample 2 (A2) which corresponds to a formulation F5 of Table 1 and contains CPIII cement as binder, Sample 3 (A3) which contains CaO as binder, which despite being an absorbing agent, the formation of calcium carbonate promotes the stiffening of the mass. Sample 4 (A4) contains, Fe.sub.2(SO.sub.4).sub.3. Example 5 corresponds to calcium oxide content formulation as absorbing agent and potassium carbonate.

[0061] For samples A1, A2, A3 and A4 absorption tests were performed at different temperatures in the range 90 to 150° C. using dry and wet samples from each formulation, FIG. 4 shows the saturation of each formulation monitored for 5 hours of absorption with a flow of 400 mL/min CO.sub.2. The dry samples have a lower absorption potential, around 70%, in contrast the wet samples obtained a saturation between 86% and 96%, this difference is promoted only by the availability of water for the realization of the alkali bicarbonate formation reaction (eq. 2).

Example 2—Preparation of Absorbent Material with MgO+Na.SUB.2.CO.SUB.3 .(Sample 1—A1) and Absorption Tests

[0062] The most basic formulation of the ATA150 material contains only the active components of the absorption process: MgO and Na.sub.2CO.sub.3. For the preparation of approximately 500 g of absorbent material it is necessary: 300 grams of MgO; 87 g of Na.sub.2CO.sub.3; 550 mL of water.

[0063] First Na.sub.2CO.sub.3 is diluted in water, then MgO is added to the solution and homogenized for approximately 10 minutes, but not limiting, until the mass reached a uniform consistency. The mass was placed in semi-spherical shapes of 1 cm in diameter for 2 hours, but not limiting, at room temperature. For the production of the dry material, the semi-spheres are taken to the oven for 24 hours at a temperature of 80° C.

[0064] The absorption test was performed in the temperature range of 130° C.±10° C., in this range the material is close to the most accelerated kinetics, as shown by FIG. 4. This range allows a number of industrial applications, but mainly the use of the ATA150 for CO.sub.2 absorption in combustion engines, such as vehicles.

[0065] The dry sample 1 has a hardness between 30 and 40N, and after saturation the hardness is taken to values between 70 and 108N. For the wet sample, the fracture test cannot be performed since the material still has a pasty consistency, however resistant enough to be manipulated and subjected to absorption tests. Relating to the absorption capacity (FIG. 5), the dry sample has a slower absorption kinetics than the wet sample, this kinetic difference stems from the unavailability of water to react and transport the bicarbonate to the innermost layers of the material, which despite continuing to react, demonstrates a stabilization around 35% CO.sub.2 content which corresponds to a saturation of 60% relative to the theoretical value, in contrast the wet material reaches a saturation of 96% with a CO.sub.2 content of 50%. Although excess moisture is a favorable characteristic to the absorption process, such property will be defined by the industrial application to which the ATA150 material will be applied.

Example 3—Preparation of Absorbent Material with MgO+Na.SUB.2.CO.SUB.3.+CPIII Cement (Sample 2—A2) and Absorption Tests

[0066] In this example, the ATA150 material formulation contains the following components: 300 grams MgO; 87 g Na.sub.2CO.sub.3; 15 g cement; 550 mL water.

[0067] First Na.sub.2CO.sub.3 is diluted in water, then MgO and Cement are added to the solution. The mixture is homogenized for approximately 10 minutes, but not limiting, until the dough reaches a uniform consistency. The dough was placed in 1 cm diameter semi-spherical shapes for 2 hours, but not limiting, to room temperature. For the production of the dry material, the semi-spheres are taken to the oven for 48 hours at a temperature of 80° C.

[0068] The dry sample 2 has a hardness between 30 and 40N, and after saturation the hardness is taken to values between 40 and 50N. For the wet sample similar to sample 1, a hardness for fracture was not defined since the material still has a pasty consistency. The absorption process in the wet sample is considerably more favored, as can be seen in FIG. 6, while the wet sample has a quasi-linear behavior, reaching the saturation of 97% in 5 hours of absorption, the dry sample presents the typical asymptotic behavior, and in approximately 3 hours the absorption kinetics of the dry sample is considerably reduced, remaining with a CO.sub.2 content between 25 and 30% with a maximum saturation of 55%

Example 4—Preparation of Absorbent Material with MgO+Na.SUB.2.CO.SUB.3.+FeSO.SUB.4 .(Sample 3—A3) and Absorption Tests

[0069] In this example, the formulation (A3) of ATA150 material formulation contains the following components: 300 grams MgO, 87 g Na.sub.2CO.sub.3; 30 g FeSO.sub.4.5H.sub.2O or FeSO.sub.4.7H.sub.2O and 550 mL water

[0070] First Na.sub.2CO.sub.3 is diluted in water, then MgO and FeSO.sub.4 are added to the solution, the mixture is homogenized for approximately 10 minutes, but not limiting, until the dough reaches a uniform consistency. The dough was placed in 1 cm diameter semi-spherical shapes for 2 hours, but not limiting, to room temperature. For the production of the dry material, the semi-spheres are taken to the oven for 48 hours at a temperature of 80° C.

[0071] Samples containing FeSO.sub.4 have higher mechanical strength, because the structure of the FeSO.sub.4 component functions as gypsum (CaSO.sub.4) generating a rigid structure, even with high moisture content. Sample 3 dried before the absorption process has a resistance between 70 and 120N, after saturation the resistance remains in the same range. The absorption process of samples 3 dry and sample 3 wet resembles the other samples, however for the wet sample the presence of a binding agent does not seem to influence the absorption process, reaching 90% saturation (FIG. 7), but for sample 3 dry the presence of FeSO.sub.4 binder resulted in 43% saturation.

Example 5—Preparation of Absorbent Material with MgO+Na.SUB.2.CO.SUB.3.+ CaO (Sample 4—A4) and Absorption Tests

[0072] In this example, formulation (A4) of ATA150 material contains the following components: 300 grams of MgO, 87 g of Na.sub.2CO.sub.3; 39 g of CaO or 51 g of Ca(OH).sub.2, 600 mL of water.

[0073] First Na.sub.2CO.sub.3 is diluted in water, then MgO and CaO are added to the solution, the mixture is homogenized for approximately 10 minutes, but not limiting, until the dough reaches a uniform consistency. The dough was placed in 1 cm diameter semi-spherical shapes for 2 hours, but not limiting, to room temperature. For the production of the dry material, the semi-spheres are taken to the oven for 48 hours at a temperature of 80° C.

[0074] Samples containing CaO as binding agent have an initial hardness of 30N, however after its storage for one month the hardness was increased to 45N, this change is caused by the formation of calcium carbonate generated by the reaction of atmospheric CO.sub.2 with the material. After saturation, the final hardness was in the range of 50 N to 70 N. The presence of CaO also influenced the saturation process, due to atmospheric absorption the initial content that was 10% CO.sub.2 became 18% (FIG. 8), in the wet sample, which although it obtained a saturation of 86% (FIG. 8), its initial load corresponded to 35% of the absorption potential.

Example 6—Preparation of Absorbent Material with CaO+K.SUB.2.CO.SUB.3 .(Sample 5—A5) and Absorption Tests

[0075] In this example, formulation (A5) of the ATA150 material contains the following components: 414 grams CaO; 85 g K.sub.2CO.sub.3; 750 mL water.

[0076] First K.sub.2CO.sub.3 is diluted in water, then CaO is added to the solution and homogenized for approximately 10 minutes, but not limiting, until the mass acquires a uniform consistency. The dough was placed in 1 cm diameter semi-spherical shapes for 2 hours, but not limiting, to room temperature. For the production of the dry material, the semi-spheres are taken to the oven for 48 hours at a temperature of 80° C.

[0077] The strength of the CaO-containing material initially is between 40N and 60N, however, for the saturated material the strength increases significantly, passing to a range between 90N and 150N. The absorption process is similar to samples containing MgO, but the absorption kinetics is faster, since the reaction of calcium carbonate formation from bicarbonate is favored by the increase of the CaCO.sub.3 lattice energy. This characteristic reflects the speed of the process (FIG. 9), since in 3 hours of absorption both the dry and wet sample are close to the final saturation of the process, which results in final saturation of 86% and 99% for the dry and wet sample.

Example 7—Absorbent Material Regeneration Process

[0078] During the absorption process performed with sample 1 (example 1) 6 samples were collected within the absorption period for analysis and execution of the regeneration process. Each sample was subjected to a heating procedure at a constant rate of 5° C./min until all the CO.sub.2 contained was released. FIG. 10 shows the thermogravimetric curves (TG) collected for sample 1. The TG curve stands out for the presence of two stages of decomposition. The first corresponds to the decomposition of the remaining Mg (OH).sub.2 and NaHCO.sub.3 formed during the absorption process. The second decomposition step, which occurs above 350° C., corresponds to the decomposition of the magnesium carbonate formed in each monitored time interval. It is observed that for sample HO (initial instant) there is no second decomposition, since there is still no MgCO.sub.3 in the system. However, for samples H3 (3 hours) H4 (4 hours) and H5 (5 hours) the second step is remarkably highlighted, while the first step becomes less representative as the Mg (OH).sub.2 content is extremely low (<10%) due to the conversion of oxide to carbonate. After the temperature of 450° C. all absorbed CO.sub.2 was released, regenerating the absorbent material.

[0079] After thermal decomposition, the ceramic material is cooled between 30 and 100° C., preferably 80° C. and added water, under constant stirring, for the correction of moisture content between 7 to 30%, preferably 17%.