Carbon dioxide capture using magnetic heating

Abstract

A carbon dioxide (CO.sub.2) stream reacts with an amine-modified magnetic nanoparticle in solution to form an amine-CO.sub.2 adduct. The solution that includes the amine-modified magnetic nanoparticle is heated by an external alternating magnetic field. The heat provided by the external alternating magnetic field is localized such that only the amine-CO.sub.2 adduct is heated to release the CO.sub.2, without heating the entire solution. This process helps with the capture and release of CO.sub.2 with a significantly reduced energy during the CO.sub.2 release step.

Claims

1. A method of capturing carbon from a gas stream comprising: dissolving an amine-modified magnetic nanoparticle in a polar or a non-polar solvent to form a solution comprising the amine-modified magnetic nanoparticle; introducing a carbon dioxide (CO.sub.2) gas stream into the solution, wherein the CO.sub.2 is absorbed by the amine-modified magnetic nanoparticle, thereby forming an amine-CO.sub.2 adduct in the solution; heating the solution with an external alternating magnetic field; and desorbing CO.sub.2 from the amine-CO.sub.2 adduct.

2. The method of claim 1, wherein the amine-modified nanoparticle comprises a metal oxide or a metal alloy, wherein the metal oxide or the metal alloy comprises iron oxide, manganese ferrite, oxides of nickel, oxide of cobalt, iron-platinum alloy, zinc ferrite, copper ferrite, cobalt ferrite, nickel ferrite, or combinations thereof.

3. The method of claim 1, wherein the amine-modified magnetic nanoparticle is modified with a primary amine, a secondary amine, a tertiary amine, or combinations thereof.

4. The method of claim 1, wherein the heating comprises a local temperature rise of only the amine-modified magnetic nanoparticle.

5. The method of claim 4, wherein the amine-modified magnetic nanoparticle is heated to 80-120 C.

6. The method of claim 1, wherein the absorbing and desorbing of CO.sub.2 occurs only at the surface of the amine-modified magnetic nanoparticle.

7. The method of claim 1, wherein the CO.sub.2 is obtained from a mixture of gases from a tail gas treatment unit in an oil and gas facility.

8. The method of claim 7, wherein the mixture of gases is treated to remove sulfur-containing gases.

9. The method of claim 1, wherein the polar or non-polar solvent comprises water or non-amine based solvents.

10. A system for carbon dioxide (CO.sub.2) capture and desorption comprising: a tail gas treatment unit for removing sulfur-containing gases, wherein the tail gas treatment unit comprises a mixture of gases comprising CO.sub.2; an outlet pipe downstream of the tail gas treatment unit that flows only CO.sub.2; a vessel downstream of the outlet pipe configured to receive CO.sub.2 from the outlet pipe, wherein the vessel comprises an amine-modified magnetic nanoparticle solution; and an external alternating magnet configured to heat the amine-modified magnetic nanoparticle solution in the vessel.

11. The system of claim 10, wherein the amine-modified magnetic nanoparticle solution in the vessel reacts with the CO.sub.2 from the outlet pipe to form an amine-CO.sub.2 adduct.

12. The system of claim 11, wherein the external alternating magnet is configured to heat the amine-modified magnetic nanoparticle to release CO.sub.2 from the amine-CO.sub.2 adduct.

13. The system of claim 10, wherein the amine-modified magnetic nanoparticle solution comprises a metal oxide or a metal alloy.

14. The system of claim 13, wherein the amine-modified magnetic nanoparticle solution comprises an amine functional group grafted on the surface of the metal oxide or the metal alloy.

15. The system of claim 14, wherein the amine functional group comprises a primary amine, a secondary amine, or a tertiary amine.

16. The system of claim 15, wherein the amine functional group comprises aminopropyltriethoxy silane (APTES), aminocaproic acid, linear or branched polyethyleneimine, diethylenetriamine, triethylenetetramine, trimethoxysilylpropyl modified (polyethylenimine), or a combination thereof.

17. A method for carbon dioxide (CO.sub.2) capture and release by a magnetic nanoparticle comprising: grafting an amine functional group on the surface of the magnetic nanoparticle to form an amine-modified magnetic nanoparticle; dissolving the amine-modified magnetic nanoparticle in a polar or non-polar solvent to form a solution; introducing CO.sub.2 to the solution to form an amine-CO.sub.2 adduct on the amine-modified magnetic nanoparticle; and heating by an external magnetic field the amine-modified magnetic nanoparticle to release the CO.sub.2 from the amine-CO.sub.2 adduct.

18. The method of claim 17, wherein the amine functional group comprises aminopropyltriethoxy silane (APTES), aminocaproic acid, linear or branched polyethyleneimine, diethylenetriamine, triethylenetetramine, trimethoxysilylpropyl modified (polyethylenimine), or a combination thereof.

19. The method of claim 17, wherein the solvent comprises water or a non-amine based solvent.

20. The method of claim 17, wherein heating by the external magnetic field comprises heating the amine-CO.sub.2 adduct.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1A is a schematic drawing of CO.sub.2 capture and release by magnetic heating.

(2) FIG. 1B shows the chemical reaction involved in the formation of an amine-CO.sub.2 adduct.

(3) FIG. 2 is a schematic diagram of an exemplary process for CO.sub.2 capture and release from a tail gas treatment unit.

(4) FIG. 3 is a flow diagram representing the method of CO.sub.2 capture and release by magnetic heating.

DETAILED DESCRIPTION

(5) The present disclosure provides a method to capture and release CO.sub.2 from a natural gas stream using an amine-modified magnetic nanoparticle. The implementations in the disclosure use a magnetic nanoparticle. For example, the magnetic nanoparticle can include iron oxide (Fe.sub.3O.sub.4), manganese ferrite (MnFe.sub.2O.sub.4), nickel, cobalt, or iron-platinum alloy (FePt). An amine functional group is grafted on the magnetic nanoparticle, such that the amine functional group is exposed at the surface of the magnetic nanoparticle. This results in an amine-modified magnetic nanoparticle which is dissolved in a solvent to form an amine-modified magnetic nanoparticle solution.

(6) In implementations described herein, a stream of natural gas that includes CO.sub.2 is introduced into the amine-modified magnetic nanoparticle solution. In some implementations, the CO.sub.2 interacts with the amine groups exposed at the surface of the magnetic nanoparticle to form an amine-CO.sub.2 adduct by chemical absorption. An external alternating magnetic field is applied to heat the amine-modified magnetic nanoparticle. By magnetic heating, heat is generated in the vicinity of the amine-modified magnetic nanoparticle which raises the local temperature. This temperature rise induces a temperature activated reaction to release the CO.sub.2 molecule, also known as CO.sub.2 desorption, without heating the entire solution. This saves significant energy in the CO.sub.2 desorption step in comparison to the amine scrubbing process.

(7) In oil and gas facilities, CO.sub.2 is captured using an amine scrubbing process. The amine scrubbing process uses monoethanolamine (MEA) solution (20-30 wt % in water). In an amine scrubbing process CO.sub.2 is mixed with MEA at its feed temperature. During this step, the CO.sub.2 molecules forms a carbamate adduct with the amine group, leading to its chemical absorption. After the absorption process, the CO.sub.2 rich MEA solution is heated to a temperature range of 100-140 C. to release the CO.sub.2 molecules from the carbamate adduct.

(8) The energy required to release the CO.sub.2 molecules from the carbamate adduct is described by the following equation Eq.1 as:
Q.sub.reg=H.sub.des+Q.sub.sen+Q.sub.vap(Eq. 1) where Q.sub.reg is the energy required to release or regenerate the CO.sub.2 attached to the adduct, H.sub.des is the heat of desorption i.e., the energy required to breakdown the species formed during chemical absorption. Q.sub.sen is the sensible heat i.e., the energy required to raise the temperature of the CO.sub.2 saturated solution to the desorption temperature, and Q.sub.vap is the heat of vaporization i.e., the energy required to vaporize the water in the CO.sub.2 saturated solution for CO.sub.2 removal.

(9) The term Q.sub.sen i.e., sensible heat, forms a major component of the heat required for CO.sub.2 release and could constitute more than 60% of the total energy for an amine scrubbing process. The sensible heat is a thermodynamic requirement to supply the necessary heat to increase the temperature of the entire CO.sub.2 saturated solution to the desorption temperature. The sensible heat cannot be reduced by any process optimization. The present disclosure provides a method through magnetic heating to significantly reduce the energy requirement for the release of CO.sub.2 molecules from the carbamate adduct. The following description and figures provide details of the method and system for CO.sub.2 capture and release using magnetic heating.

(10) FIG. 1A is a schematic drawing of CO.sub.2 capture and release by magnetic heating.

(11) At step A, amine functional groups are grafted on the surface of a magnetic nanoparticle. Examples of magnetic nanoparticles include, but are not limited to, iron oxide (Fe.sub.3O.sub.4), manganese ferrite (MnFe.sub.2O.sub.4), nickel, cobalt, and iron-platinum alloy (FePt). Magnetic nanoparticles have a high surface energy due to the high surface-to-volume ratios. These particles tend to aggregate to minimize the surface energy. This aggregation can alter the adsorption capacity and efficiency. To increase the adsorption capacity, the magnetic nanoparticles are surface coated. Surface coating includes the use of organic materials, surfactants, silica, metals, non-metals, metal oxides, metal sulfides, or polymers. Surface coating can prevent aggregation and can accommodate surface functionalization. Additionally, to prevent aggregation smaller dimension magnetic nanoparticles are selected.

(12) In some implementations, primary amines, secondary amines, or tertiary amines with suitable chemistries are used to modify the magnetic nanoparticle, such that the amine functional groups are exposed at the surface. In some implementations, amine functionalized magnetic nanoparticles are prepared in a single step. In some implementations, amine functionalized magnetic nanoparticles are prepared by first preparing the magnetic nanoparticles followed by their surface modification with a suitable amine functionalized molecule. For example, the magnetic nanoparticles, such as of iron oxide can be synthesized by the co-precipitation method, hydrothermal method, or solvothermal method. In the co-precipitation method, iron Fe(II) and Fe(III) salts are dissolved in aqueous solutions followed by the addition of ammonium hydroxide leading to the synthesis of Fe.sub.3O.sub.4 nanoparticles. In some implementations, the purified magnetic nanoparticles are further directly modified with a molecule with an amine functional group or can be first coated with an intermediate layer of silica followed by modification with an amine functional group. Examples of amine functional groups include, but are not limited to, aminopropyltriethoxy silane (APTES), aminocaproic acid, linear or branched polyethyleneimine, diethylenetriamine, triethylenetetramine, and trimethoxysilylpropyl modified (polyethylenimine). In some implementations, the amine functional group is APTES. In some implementations, APTES is chemically grafted on to Fe.sub.3O.sub.4 nanoparticles. Other magnetic nanoparticles of spinel ferrites, such as, cobalt ferrite (CoFe.sub.2O.sub.4), MnFe.sub.2O.sub.4, copper ferrite (CuFe.sub.2O.sub.4), zinc ferrite (ZnFe.sub.2O.sub.4), and nickel ferrite (NiFe.sub.2O.sub.4) can also be used.

(13) At step B, a natural gas stream that includes CO.sub.2 is introduced into the amine-modified magnetic nanoparticle solution. In some implementations, a pure CO.sub.2 stream is introduced into the amine-modified magnetic nanoparticle solution. The CO.sub.2 molecules interact with the amine functional groups on the magnetic nanoparticles and are chemically absorbed. The absorption process leads to the formation of a carbamate adduct. In this disclosure, it is alternatively referred to as an amine-CO.sub.2 adduct. The absorption of CO.sub.2 on the amine-modified magnetic nanoparticle in solution can be studied by thermogravimetric analysis (TGA) or differential thermal analysis (DTA).

(14) At step C, an external alternating magnetic field is applied to provide heat to the amine-modified magnetic nanoparticle solution. The heating effect of a magnetic nanoparticle increases as a function of frequency and magnetic field amplitude. To generate adequate heat, an optimum frequency and magnetic field amplitude is required. For example, the applied frequency of the magnetic field can range between 100-1000 kHz. Example magnetic field amplitudes can range between 10-100 kA m.sup.1.

(15) During the application of the external alternating magnetic field, heat is generated only in the vicinity of the amine-modified magnetic nanoparticle, thereby raising the temperature locally. The external alternating magnetic field raises the temperature to a range of 80-120 C. In some implementations, this temperature rise is sufficient for the molecules present on the surface of the amine-modified magnetic nanoparticle to undergo a temperature activated reaction. The amine-CO.sub.2 adduct undergoes a temperature activation reaction to release the CO.sub.2 molecules from the adduct.

(16) The use of an external alternating magnetic field selectively heats only the amine-modified magnetic nanoparticle, thereby eliminating the need to heat the entire solution that does not participate in the reaction. This local heating by an external alternating magnetic field significantly reduces the energy required to release CO.sub.2 molecules. The energy reduction achieved using an external alternating magnetic field is about 80-90% when compared to an amine scrubbing process. Typically, energy reduction is not feasible by process optimization in an amine scrubbing process.

(17) FIG. 1B shows the chemical reactions involved in the formation of an amine-CO.sub.2 adduct. A CO.sub.2 gas stream interacts with an amine group to form an amine carbamate complex at low temperature. The amine carbamate complex is in an equilibrium reaction with an amine bicarbonate. As the carbamate is heated, CO.sub.2 and amine are formed. This reaction releases the CO.sub.2 molecule from the amine-CO.sub.2 adduct.

(18) FIG. 2 is a schematic diagram of an exemplary process for CO.sub.2 capture and release from a tail gas treatment unit.

(19) In some implementations, a tail gas treatment unit 202 processes acid gas streams to remove sulfur-containing gases. Acid gas streams include hydrogen sulfide (H.sub.2S), sulfur dioxide (SO.sub.2), CO.sub.2, ammonia, and volatile organic compounds (VOCs). The tail gas treatment unit 202 includes a catalytic reactor for hydrogenation or hydrolysis process. The catalytic reactor converts all sulfur-containing gases to H.sub.2S. The excess water from the catalytic reaction is removed using a quenching tower.

(20) In some implementations, the gases leaving the quenching tower include a mixture of H.sub.2S, H.sub.2, and CO.sub.2. The H.sub.2S is selectively removed by absorption and recycled back to the catalytic reactor. In some implementations, H.sub.2 and CO.sub.2 are processed by a H.sub.2 selective membrane and CO.sub.2 selective membrane, respectively. The CO.sub.2 gas stream which passes through the CO.sub.2 selective membrane has 97% purity. The CO.sub.2 gas stream from the CO.sub.2 selective membrane flows through an outlet pipe 204 downstream of the tail gas treatment unit 202.

(21) In some implementations, the CO.sub.2 gas stream from the outlet pipe 204 flows into a vessel 206. The vessel 206 is fluidically coupled to the outlet pipe 204. The vessel includes an amine-modified magnetic nanoparticle solution. The CO.sub.2 which flows from the outlet pipe 204 reacts with the amine functional group on the amine-modified magnetic nanoparticle to form a CO.sub.2-amine adduct. An external alternating magnetic field 208 is applied to the vessel 206 such that it selectively heats the amine-modified magnetic nanoparticle. The heat generated by the alternating magnetic field raises the temperature of the amine-CO.sub.2 adduct. The external alternating magnetic field raises the temperature to a range of 80-120 C. This induces a temperature activation reaction that releases the CO.sub.2 molecules from the amine-CO.sub.2 adduct. The heat generated by the alternating magnetic field does not raise the temperature of the entire solution, but selectively provides heat only to the amine-modified magnetic nanoparticle. In some implementations, downstream units process the released CO.sub.2 to produce valuable chemicals. For example, the valuable chemicals can include syngas or formic acid. In some implementations, the released CO.sub.2 is stored in geological formations.

(22) FIG. 3 is a block flow diagram representing the method of CO.sub.2 capture and release by magnetic heating.

(23) At block 302, an amine functional group is dissolved in water, a polar solvent, or a non-polar solvent. The solvents do not include amine-based solvents. The amine functional group is a primary, secondary, or tertiary amine. The solvent includes magnetic nanoparticles. In some implementations, the magnetic nanoparticles include iron oxide (Fe.sub.3O.sub.4), manganese ferrite (MnFe.sub.2O.sub.4), nickel, cobalt, or iron-platinum alloy (FePt). The resulting solution is stirred for several minutes to form an amine-modified magnetic nanoparticle solution.

(24) At block 304, a CO.sub.2 gas stream is introduced into the amine-modified magnetic nanoparticle solution. In some implementations, the CO.sub.2 reacts with the amine functional group to form an amine-CO.sub.2 adduct.

(25) At block 306, an external alternating magnetic field is used to selectively heat only the amine-modified magnetic nanoparticle. The external alternating magnetic field raises the temperature to a range of 80-120 C. The heat generated by this method does not heat the entire solution. The heat is generated at the amine-modified magnetic nanoparticle, which induces a temperature activated reaction at the amine-CO.sub.2 adduct.

(26) At block 308, the heat supplied to the amine-modified magnetic nanoparticle causes the CO.sub.2 to desorb from the amine-CO.sub.2 adduct.

(27) An implementation described herein provides a method for CO.sub.2 capture and release using magnetic heating. Amine-modified magnetic nanoparticles in solution are used to capture CO.sub.2 from natural gas streams or from pure CO.sub.2 gas streams from a tail gas treatment unit. The CO.sub.2 reacts with the amine group to form a carbamate adduct. An external alternating magnetic field is applied to the amine-modified nanoparticle solution. The heat generated by the alternating magnetic field heats the carbamate adduct to release CO.sub.2. During this process, the entire solution is not heated, but the amine-modified magnetic nanoparticle is selectively heated. It is to be understood that in the methods of the present disclosure, although the amine-modified magnetic nanoparticles are selectively heated and the entire surrounding solution is not, part of the heat energy of the heated nanoparticles will be dissipated and the surrounding solvent in the vicinity of the magnetic nanoparticle will also rise in temperature to some extent.

(28) Other implementations are also within the scope of the following claims.

Exemplary Embodiments

(29) 1. A method of capturing carbon from a gas stream comprising: dissolving an amine-modified magnetic nanoparticle in a polar or a non-polar solvent to form a solution comprising the amine-modified magnetic nanoparticle; introducing a carbon dioxide (CO.sub.2) gas stream into the solution, wherein the CO.sub.2 is absorbed by the amine-modified magnetic nanoparticle, thereby forming an amine-CO.sub.2 adduct in the solution; heating the solution with an external alternating magnetic field; and desorbing CO.sub.2 from the amine-CO.sub.2 adduct.

(30) 2. The method of embodiment 1, wherein the amine-modified nanoparticle comprises a metal oxide or a metal alloy, wherein the metal oxide or the metal alloy comprises iron oxide, manganese ferrite, oxides of nickel, oxide of cobalt, iron-platinum alloy, zinc ferrite, copper ferrite, cobalt ferrite, nickel ferrite, or combinations thereof.

(31) 3. The method of embodiment 1 or 2, wherein the amine-modified magnetic nanoparticle is modified with a primary amine, a secondary amine, a tertiary amine, or combinations thereof.

(32) 4. The method of any of embodiments 1 to 3, wherein the heating comprises a local temperature rise of only the amine-modified magnetic nanoparticle.

(33) 5. The method of any of embodiments 1 to 4, wherein the amine-modified magnetic nanoparticle is heated to 80-120 C.

(34) 6. The method of any of embodiments 1 to 5, wherein the absorbing and desorbing of CO.sub.2 occurs only at the surface of the amine-modified magnetic nanoparticle.

(35) 7. The method of any of embodiments 1 to 6, wherein the CO.sub.2 is obtained from a mixture of gases from a tail gas treatment unit in an oil and gas facility.

(36) 8. The method of any of embodiments 1 to 7, wherein the mixture of gases is treated to remove sulfur-containing gases.

(37) 9. The method of any of embodiments 1 to 8, wherein the polar or non-polar solvent comprises water or non-amine based solvents.

(38) 10. A system for carbon dioxide (CO.sub.2) capture and desorption comprising: a tail gas treatment unit for removing sulfur-containing gases, wherein the tail gas treatment unit comprises a mixture of gases comprising CO.sub.2; an outlet pipe downstream of the tail gas treatment unit that flows only CO.sub.2; a vessel downstream of the outlet pipe configured to receive CO.sub.2 from the outlet pipe, wherein the vessel comprises an amine-modified magnetic nanoparticle solution; and an external alternating magnet configured to heat the amine-modified magnetic nanoparticle solution in the vessel.

(39) 11. The system of embodiment 10, wherein the amine-modified magnetic nanoparticle solution in the vessel reacts with the CO.sub.2 from the outlet pipe to form an amine-CO.sub.2 adduct.

(40) 12. The system of embodiment 10 or 11, wherein the external alternating magnet is configured to heat the amine-modified magnetic nanoparticle to release CO.sub.2 from the amine-CO.sub.2 adduct.

(41) 13. The system of any of embodiments 10 to 12, wherein the amine-modified magnetic nanoparticle solution comprises a metal oxide or a metal alloy.

(42) 14. The system of any of embodiments 10 to 13, wherein the amine-modified magnetic nanoparticle solution comprises an amine functional group grafted on the surface of the metal oxide or the metal alloy.

(43) 15. The system of any of embodiments 10 to 14, wherein the amine functional group comprises a primary amine, a secondary amine, or a tertiary amine.

(44) 16. The system of any of embodiments 10 to 15, wherein the amine functional group comprises aminopropyltriethoxy silane (APTES), aminocaproic acid, linear or branched polyethyleneimine, diethylenetriamine, triethylenetetramine, trimethoxysilylpropyl modified (polyethylenimine), or a combination thereof.

(45) 17. A method for carbon dioxide (CO.sub.2) capture and release by a magnetic nanoparticle comprising: grafting an amine functional group on the surface of the magnetic nanoparticle to form an amine-modified magnetic nanoparticle; dissolving the amine-modified magnetic nanoparticle in a polar or non-polar solvent to form a solution; introducing CO.sub.2 to the solution to form an amine-CO.sub.2 adduct on the amine-modified magnetic nanoparticle; and heating by an external magnetic field the amine-modified magnetic nanoparticle to release the CO.sub.2 from the amine-CO.sub.2 adduct.

(46) 18. The method of embodiment 17, wherein the amine functional group comprises aminopropyltriethoxy silane (APTES), aminocaproic acid, linear or branched polyethyleneimine, diethylenetriamine, triethylenetetramine, trimethoxysilylpropyl modified (polyethylenimine), or a combination thereof.

(47) 19. The method of embodiment 17 or 18, wherein the solvent comprises water or a non-amine based solvent.

(48) 20. The method of any of embodiments 17 to 19, wherein heating by the external magnetic field comprises heating the amine-CO.sub.2 adduct.