Regeneratable ion exchange material for reducing the amount of CO2

Abstract

The present invention relates to a method for reducing the amount of CO.sub.2 in a carbon dioxide-containing source by using a regeneratable ion exchange material.

Claims

1. A method for reducing the amount of CO.sub.2 in a carbon dioxide-containing source by using a regeneratable ion exchange material, comprising the following steps of: a) providing at least one ion exchange material comprising at least one earth alkali metal cation, b) providing at least one carbon dioxide-containing source, c) providing at least one source of at least one cation which is capable of replacing the at least one earth alkali metal cation of the at least one ion exchange material, d) providing at least one source of at least one earth alkali metal cation, e) contacting the at least one ion exchange material of step a) with the at least one source of at least one cation of step c) such as to obtain a mixture comprising i) at least one ion exchange material, and ii) at least one earth alkali metal cation released from the at least one ion exchange material of step a), f) separating the at least one earth alkali metal cation of step ii) from the at least one ion exchange material of step i), g) contacting the at least one earth alkali metal cation obtained in step f) with the at least one carbon dioxide-containing source of step b) such as to obtain a carbonate salt of the at least one earth alkali metal cation, and h) contacting the at least one ion exchange material obtained in step f) with the at least one source of at least one earth alkali metal cation of step d) such as to regenerate the at least one ion exchange material of step a).

2. The method of claim 1, wherein the at least one ion exchange material of step a) is selected from the group consisting of a natural ion exchange material, a modified ion exchange material, a synthetic ion exchange material, and any mixture thereof.

3. The method of claim 1, wherein the at least one ion exchange material of step a) comprises a natural ion exchange material selected from the group consisting of phyllosilicates, zeolite, mica, montmorillonite, mauritzite, and any mixture thereof, and/or a synthetic ion exchange material selected from the group consisting of eDTA, ion exchange resins, and any mixture thereof.

4. The method of claim 1, wherein the at least one ion exchange material of step a) comprises a phyllosilicate.

5. The method of claim 1, wherein the at least one ion exchange material of step a) comprises at least one earth alkali metal cation selected from the group consisting of magnesium, calcium, strontium, and any mixture thereof.

6. The method of claim 1, wherein the at least one ion exchange material of step a) comprises calcium and/or magnesium as an earth alkali metal cation.

7. The method of claim 1, wherein the at least one ion exchange material of step a) is provided in form of a solid or an aqueous suspension or an emulsion or a filter material or a fluidized bed.

8. The method of claim 1, wherein the at least one ion exchange material of step a) is provided in form of an aqueous suspension having an ion exchange material content of from 2 to 50 wt.-%, based on the total weight of the aqueous suspension.

9. The method of claim 1, wherein the at least one ion exchange material of step a) is provided in form of an aqueous suspension having an ion exchange material content of from 5 to 30 wt.-%, based on the total weight of the aqueous suspension.

10. The method of claim 1, wherein the at least one ion exchange material of step a) consists of bentonite comprising clay minerals selected from the group consisting of montmorillonites, concomitant minerals, quartz, mica, kaolinite, feldspar, pyrite, calcite, cristobalite, and any mixture thereof.

11. The method of claim 1, wherein the at least one ion exchange material of step a) consists of bentonite having a montmorillonite content of at least 60 wt.-%, based on the total weight of the bentonite.

12. The method of claim 1, wherein the at least one ion exchange material of step a) consists of bentonite having a montmorillonite content of at least 80 wt.-%, based on the total weight of the bentonite.

13. The method of claim 1, wherein the ion exchange material of step a) consists of bentonite whose interlayer spaces are occupied primarily with calcium and/or magnesium ions.

14. The method of claim 1, wherein the at least one ion exchange material of step a) consists of bentonite having a weight median particle size d.sub.50 from 0.02 to 100 m.

15. The method of claim 1, wherein the at least one ion exchange material of step a) consists of bentonite having a weight median particle size d.sub.50 from 0.075 to 50 m.

16. The method of claim 1, wherein the at least one ion exchange material of step a) consists of bentonite having a weight median particle size d.sub.50 from 0.1 to 5 m.

17. The method of claim 1, wherein the at least one carbon dioxide-containing source of step b) is selected from a gas, liquid, solid, complex, ion exchange material, and any mixture thereof.

18. The method of claim 1, wherein the at least one carbon dioxide-containing source of step b) is a gas.

19. The method of claim 1, wherein the at least one carbon dioxide-containing source of step b) is selected from air, industrial exhaust gas streams, waste gas streams, volcanic outgassing, and any mixture thereof.

20. The method of claim 1, wherein the at least one carbon dioxide-containing source of step b) comprises carbon dioxide providing a partial pressure of at least 0.02 Pa.

21. The method of claim 1, wherein the at least one source of at least one cation of step c) and/or the at least one source of at least one earth alkali metal cation of step d) is an aqueous solution comprising at least 50 wt.-%, based on the total weight of the aqueous solution, of water.

22. The method of claim 1, wherein the at least one source of at least one cation of step c) is a naturally occurring source of at least one monovalent and/or divalent cation capable of replacing the at least one earth alkali metal cation of the at least one ion exchange material.

23. The method of claim 1, wherein the at least one source of at least one cation of step c) is sea water.

24. The method of claim 1, wherein the at least one carbon dioxide-containing source of step b) and/or the at least one source of at least one cation which is capable of replacing the at least one earth alkali metal cation of the at least one ion exchange material of step c) and/or the at least one source of at least one earth alkali metal cation are provided in form of an aqueous solution having a pH of between 5 and 12.

25. The method of claim 1, wherein the at least one cation of the at least one source of at least one cation of step c) is selected from the group comprising lithium, sodium, potassium, magnesium, strontium, and any mixture thereof.

26. The method of claim 1, wherein the at least one cation of the at least one source of at least one cation of step c) is sodium.

27. The method of claim 1, wherein the at least one source of at least one cation of step c) comprises the at least one cation in an amount of from 0.1 to 150 g/l.

28. The method of claim 1, wherein the at least one source of at least one earth alkali metal cation of step d) is a naturally occurring source of at least one earth alkali metal cation.

29. The method of claim 1, wherein the at least one source of at least one earth alkali metal cation of step d) is fresh hard water having a hardness of from 5 to 130 dH.

30. The method of claim 1, wherein the at least one earth alkali metal cation of the at least one source of at least one earth alkali metal cation of step d) is selected from magnesium, calcium, strontium, and any mixture thereof.

31. The method of claim 1, wherein the at least one earth alkali metal cation of the at least one source of at least one earth alkali metal cation of step d) is calcium.

32. The method of claim 1, wherein the at least one source of at least one earth alkali metal cation of step d) comprises the at least one earth alkali metal cation in an amount from 0.1 to 200 mg/l.

33. The method of claim 1, wherein contacting step g) is carried out in that the at least one carbon dioxide-containing source of step b) is introduced into an aqueous solution obtained in step f).

34. The method according to claim 33, wherein the aqueous solution obtained in step f) is further contacted with at least one catalyst for enhancing the hydratisation of carbon dioxide.

35. The method according to claim 34, wherein the at least one catalyst for enhancing the hydratisation of carbon dioxide is at least one enzyme.

36. The method according to claim 35, wherein the at least one enzyme is carbonic anhydrase.

37. The method of claim 1, wherein contacting step e) and/or separating step f) and/or contacting step g) and/or contacting step h) is/are carried out at a temperature from 2 C. to 80 C.

38. The method of claim 1, wherein contacting step e) and/or separating step f) and/or contacting step g) and/or contacting step h) is/are carried out at a pH of between 4 and 12.

39. The method of claim 1, wherein contacting step g) is carried out under pressure of at least 100 Pa.

40. The method of claim 1, wherein contacting step h) is carried out before and/or during and/or after contacting step g).

41. The method of claim 1, wherein separating step f) is carried out by filtration, centrifugation, cycloning, sedimentation, or any mixture thereof.

42. The method of claim 1, which further comprises step k) of separating the carbonate salt of the at least one earth alkali metal cation obtained in step g).

43. The method of claim 42, wherein separating step k) is carried out by filtration, centrifugation, cycloning, concentrating, evaporation, sedimentation, or any mixture thereof.

Description

FIGURES

(1) FIG. 1 refers to the concentration of free calcium ions in dependence of bentonite content in deionised water and a 3.5 wt. % NaCl solution. The third curve relates to the difference in the concentration of free calcium ions released at a given bentonite concentration between deionized water and 3.5 wt.-% NaCl solution.

(2) FIG. 2 refers to the amount of released calcium ions in function of the process time of several trials (D, E, F, G, H) that were carried out by flushing the ion exchanger with NaCl solutions of different feed rates, while the NaCl concentration of the solutions was the same for each trial.

(3) FIG. 3 refers to the amount of released calcium ions in function of the process time of several trials (F, I, J) that were carried out by flushing the ion exchanger with NaCl solutions of different concentrations, while the feed rate was the same for each trial (4 ml/min).

EXAMPLES

1. Measurement Methods

(4) pH Measurement

(5) The pH is measured at 25 C. using a Mettler Toledo Seven Easy pH meter and a Mettler Toledo InLab Expert Pro pH electrode. A three point calibration (according to the segment method) of the instrument is first made using commercially available buffer solutions having pH values of 4, 7 and 10 at 20 C. (from Aldrich). The reported pH values are the endpoint values detected by the instrument (the endpoint is when the measured signal differs by less than 0.1 mV from the average over the last 6 seconds).

(6) Brookfield Viscosity

(7) The Brookfield viscosity was measured after 1 minute of stirring by the use of a RVT model Brookfield viscometer at a temperature of 25 C., and a rotation speed of 100 rpm (revolutions per minute) with the appropriate disc spindle from N 1 to 5.

(8) Particle Size Distribution (Mass % Particles with a Diameter <X) and Weight Median Grain Diameter (d.sub.50) of Particulate Material

(9) Weight median grain diameter and grain diameter mass distribution of a particulate material were determined via the sedimentation method, i.e. an analysis of sedimentation behaviour in a gravimetric field. The measurement was made with a Mastersizer 2000 from Malvern Instruments GmbH, Germany. Alternatively, the measurement was made with a Sedigraph 5120 device from Micromeritics, USA.

(10) The method and the instrument are known to the skilled person and are commonly used to determine grain size of fillers and pigments. The samples were dispersed using a high speed stirrer and ultrasonic.

(11) The d.sub.98 value indicates a diameter value such that 98% by weight of the particles have a diameter of less than this value.

(12) X-Ray Fluorescence Spectroscopy

(13) The XRF data were obtained by using methods and instruments known to the skilled person and are commonly used to determine the composition of samples.

(14) Weight Solids (Wt. %) of a Material in Suspension

(15) The weight solids were determined by dividing the weight of the solid material by the total weight of the aqueous suspension. The weight solids content was determined at 160 C. using a Moisture Analyser MJ 33, Mettler Toledo.

(16) Turbidity

(17) The turbidity was measured with a Hach Lange 2100AN IS Laboratory Turbidimeter and the calibration was performed using StabCal turbidity standards (formazine standards) of <0.1, 20, 200, 1 000, 4 000 and 7 500 NTU.

(18) Determination of the Hardness (German Hardness; Expressed in dH)

(19) The hardness refers to the total amount of earth alkali ions in the aqueous solution comprising the earth alkali hydrogen carbonate, and it is measured by complexometric titration using ethylene-diamine-tetra-acetic acid (EDTA; trade name Titriplex III) and Eriochrome T as equivalent point indicator.

(20) EDTA (chelating agent) forms with the ions Ca.sup.2+ and Mg.sup.2+ soluble, stable chelate complexes. 2 ml of a 25% ammonia solution, an ammonia/ammonium acetate buffer (pH 10) and Eriochrome black T indicator were added to 100 ml of a water sample to be tested. The indicator and the buffer is usually available as so-called indicator-buffer tablet. The indicator, when masked with a yellow dye, forms a red colored complex with the Ca.sup.2+ and Mg.sup.2+ ions. At the end of the titration, that is when all ions are bound by the chelating agent, the remaining Eriochrome black T indicator is in its free form which shows a green colour. When the indicator is not masked, then the colour changes from magenta to blue. The total hardness can be calculated from the amount of EDTA that has been used.

(21) The table 1 below shows a conversion for the different units of the water hardness.

(22) TABLE-US-00001 TABLE 1 Conversion for the different units of the water hardness.sup.[1] dH e fH ppm.sup.[2] mval/l mmol/l German Hardness 1 dH = 1 1.253 1.78 17.8 0.357 0.1783 English Hardness 1 e = 0.798 1 1.43 14.3 0.285 0.142 French Hardness 1 fH = 0.560 0.702 1 10 0.2 0.1 ppm CaCO.sub.3 (USA) 1 ppm = 0.056 0.07 0.1 1 0.02 0.01 mval/l Earth alkali ions 1 mval/l = 2.8 3.51 5 50 1 0.50 mmol/l Earth alkali ions 1 mmol/l = 5.6 7.02 10.00 100.0 2.00 1 .sup.[1]Data as obtained from http://de.wikipedia.org/wiki/Wasserh%C3%A4rte .sup.[2]In this regard the unit ppm is used in the meaning of 1 mg/l CaCO.sub.3.
Determination of the Ion Concentration

(23) The ion concentration is determined by measuring the build-up of electrical field strength by a selective adsorption of calcium ions on a resin membrane.

(24) The measurement of ion concentration is carried out at 25 C. using Mettler Toledo Seven Multi instrumentation equipped with the corresponding Mettler Toledo perfectION electrode during stirring of the suspension/solution by using a magnetic stirrer and the corresponding stirring plate.

(25) The ion concentration measurement was started directly following stirring the bentonite containing suspensions/solutions at 1 500 rpm using a Pendraulik tooth disc stirrer.

(26) The instrument is first calibrated in the relevant ion concentration range using commercially available calibration solutions having concentrations of 1 mmol/l, 10 mmol/l and 100 mmol/l, respectively, from Fluka, Switzerland.

(27) The reported ion concentration values are the values detected by the instrument after 1 minute after electrode immersion into the suspension/solution to be measured.

(28) To samples of tab water or samples derived from an ion exchange process involving a commercially available ion exchanger, an ion strength adjuster (available from Mettler Toldeo Switzerland, ISA-Lsung, 51344761) was added in an amount of 1 ml to a 50 ml sample.

(29) XRD

(30) The X-ray diffraction (XRD) pattern of the Ca bentonite was performed according to the following method:

(31) The mineralogical phases present in the Ca bentonite are determined by means of X-ray diffraction (XRD) using a Bruker D8 Advance diffractometer, according to the diffraction powder method. This diffractometer consists of a 2.2 kW X-ray tube, a 9-position sample holder, a Theta-Theta (-) goniometer, and a VNTEC-1 detector. Ni-filtered Cu K radiation is employed in all experiments. The profiles are chart recorded automatically using a 0.01 2 increment and a 1 s/step scan speed from 20 to 50 2. The resulting powder diffraction patterns are classified by mineral content using the International Center for Diffraction Data (ICDD) powder diffraction file (PDF) database 2 and are summarized in the following Table 2.

(32) TABLE-US-00002 TABLE 2 Content in the bentonite Mineral name Formula powder Calcite CaCO.sub.3 9.7 Gypsum CaSO.sub.42H.sub.2O 2.3 Montmorillonite (Na,Ca).sub.0.3(Al,Mg).sub.2Si.sub.4O.sub.10(OH).sub.2nH.sub.2O 53.2 Anorthite CaAl.sub.2Si.sub.2O.sub.8 13.7 Quartz SiO.sub.2 3.7 Muscovite/Illite KAl.sub.2[(OH,F).sub.2|AlSi.sub.3O.sub.10] 17.4 Total sum 100.0

2. Examples

(33) The bentonite used was a Ca bentonite from Milos, Greece, and had the following characteristics:

(34) A weight median grain diameter d.sub.50 of 12.86 m, and a d.sub.98 of 86 m.

Example 1

(35) This example refers to the preparation of a stable carbonate salt by using bentonite as ion exchange material.

(36) 3.5 wt.-% NaCl was added to a 0.1 M NaOH solution. To this solution, bentonite was added such that the obtained slurry has an amount of bentonite of about 5 wt.-%, based on the total weight of the suspension. This suspension was stirred for 10 minutes by using a small stirrer with a mounted propeller. Subsequently, the suspension was vacuum filtrated and then CO.sub.2 (commercially available from Pangas, Switzerland as Kohlendioxid UN 1013) was bubbled into the filtrate. The white precipitate was centrifuged and washed with deionised water two times before drying.

(37) The precipitate was characterised by XRF as being 98 wt.-% CaCO.sub.3, based on the total weight of the precipitate.

Example 2

(38) This example refers to the capability of bentonite to be activated and then regenerated in one cycle.

(39) 3.5 wt.-% NaCl was added to a 0.1 M NaOH solution. To this solution, bentonite was added such that the obtained slurry has an amount of bentonite of about 10 wt.-%, based on the total weight of the suspension. This suspension was stirred for 10 minutes by using a small stirrer with a mounted propeller. Subsequently, the suspension was vacuum filtrated and then CO.sub.2 (commercially available from Pangas, Switzerland as Kohlendioxid UN 1013) was bubbled into the filtrate. The white precipitate was centrifuged and washed with deionised water two times before drying. The precipitate of this first sequestration was not analyzed.

(40) Subsequently, the filter cake (the activated bentonite), was added to a 1 wt.-% CaCl.sub.2 (commercially available from Merck, Germany as calcium chloride anhydrous) solution, based on the total weight of the solution, such that the obtained suspension has an amount of bentonite of about 10 wt.-%, based on the total weight of the suspension. The obtained suspension was stirred for 10 minutes and then vacuum filtrated. The filter cake was washed with deionised water and vacuum filtrated until there was no precipitation in the filtrate when NaHCO.sub.3 was added.

(41) This filter cake was used again for an experiment described in Example 1. The precipitate was characterized by XRF as being 96 wt.-% CaCO.sub.3, based on the total weight of the precipitate.

Example 3

(42) This example refers to the preparation of a stable carbonate salt by using bentonite as ion exchange material at a pH of about 8.

(43) A 0.1 M NaOH solution was added to 3.5 wt.-% NaCl solution, based on the total weight of the solution, such that the solution has a pH of about 8. To this solution, bentonite was added such that the obtained slurry has an amount of bentonite of about 10 wt.-%, based on the total weight of the suspension. This suspension was stirred for 10 minutes by using a small stirrer with a mounted propeller. Subsequently, the suspension was vacuum filtrated and then CO.sub.2 (commercially available from Pangas, Switzerland as Kohlendioxid UN 1013) was bubbled into the filtrate. Furthermore, 0.1 M NaOH solution was added such as to keep the pH at above 8.2. The white precipitate was centrifuged and washed with deionised water two times before drying.

(44) The precipitate was characterised by XRF as being 96 wt.-% CaCO.sub.3, based on the total weight of the precipitate.

Example 4

(45) This Example refers to the capability of bentonite for releasing calcium cations in the presence of sodium cations.

(46) A reference experiment was carried out in which bentonite was added portion wise to deionised water and the calcium-ion concentration was measured after a given time after bentonite addition (about three minutes).

(47) The same experiment was carried out using a 3.5 wt.-% NaCl solution, based on the total weight of the solution, with a starting pH of 10 (adjusted with 1M NaOH) instead of deionised water.

(48) It can be gathered from FIG. 1 that the addition of bentonite to deionised water already releases certain calcium ions (curve named H.sub.2O deionized). This is to be expected due to an osmotic driving force. Furthermore one can see that the presence of sodium cations clearly enhances the release of calcium ions (curve named 3.5 wt.-% NaCl solution).

(49) A calcium ion sensitive electrode was used and calcium ion concentration measurements were started around three minutes after the addition of bentonite.

Example 5

(50) This Example refers to the capability of a commercial ion exchanger resin for releasing calcium cations in the presence of sodium cations.

(51) 7 equal samples of the ion exchanger were prepared as follows:

(52) For each sample, 10 g of a commercially available ion exchange material (DOWEX MARATHON C from The Dow Chemical Company) were placed in a plastic hose (internal diameter=8 mm, length=250 mm). In order to keep the ion exchange material within the plastic hose two metal meshes were placed in the plastic hose in such a way that the ion exchange material was trapped in between the two meshes.

(53) Each sample of the ion exchanger was then flushed with 5 000 ml of hard tab water ( dH20) at a constant rate of 150 ml/min before starting each trial to ensure that the ion exchanger was in its calcium ion loaded state (effluent water dH20).

(54) Then, each sample of the calcium ion loaded ion exchanger was flushed with a different NaCl solution of different concentration and at a different flow rate as outlined in the following Table 3.

(55) TABLE-US-00003 TABLE 3 NaCl concentration Flow rate Trial (wt.-%) (ml/min) D 3.5 1 E 3.5 2 F 3.5 4 G 3.5 8 H 3.5 16 I 7 4 J 1.75 4

(56) Samples of 30 ml were taken consecutively of the solution exiting each sample of the ion exchanger and the calcium ion concentration was measured using the calcium ion specific electrode.

(57) FIG. 2 shows the amount of released calcium ions in function of the process time for a NaCl concentration of 3.5 wt.-% at different NaCl solution feed rates. It can be seen that there is a substantial release of calcium ions from the ion exchanger due to the feed of NaCl solution to the ion exchanger. Furthermore, it can be seen that an increased NaCl solution feed rate leads to a faster release of the calcium ions from the ion exchanger.

(58) FIG. 3 shows the amount of released calcium ions in function of the process time for the same feed rates (4 ml/min) but using different NaCl concentrations of the solution. Therefrom, it can be derived that an increased NaCl concentration of the feed solution enhances the release of calcium ions from the ion exchanger. However, it can also be seen that a NaCl concentration of 3.5 wt.-% (corresponding to approximately the NaCl concentration of sea water) is already high enough to give a reasonably high calcium ion concentration. For example the 6 600 ppm* of calcium ions that are released in trial F in the first sample (FIG. 3).

(59) Finally. it can be gathered from this Example that using the inventive process allows a) to get significantly higher calcium concentrations compared to the ones present in hard water (cf. 6 600 ppm* calcium of trial (F) compared to typical hard water in the Oftringen area, Aargau, Switzerland, of around 160 ppm calcium) that enhances a later precipitation process and b) to reuse the ion exchanger material as all the experiments were carried out using the same ion exchanger material.

(60) *The calcium concentration in ppm can be calculated from the data in FIG. 2 and FIG. 3 as follows:
Ca.sup.2+conc(ppm)=(Released Ca.sup.2+1000)/V.sub.sample
wherein:
Ca.sup.2+ conc (ppm): calcium ion concentration of the sample in ppm
Released Ca.sup.2+: The mass of released calcium ions in the sample in mg
V.sub.sample: Volume of the sample in ml (in this Experiment the sample is always 29 ml).