Regenerable non-aqueous basic immobilized amine slurries for removal of CO.SUB.2 .from a gaseous mixture and a method of use thereof

Abstract

The disclosure provides a composition for the separation of CO.sub.2 from a gaseous mixture and a method of use thereof. The composition comprises solid Basic Immobilized Amine Sorbents (BIAS) suspended in silicone oil. The method of use comprises contacting the gaseous mixture with a sorbent slurry comprising Basic Immobilized Amine Sorbents (BIAS) and silicone oil to at least partially absorb the CO.sub.2 from the gaseous mixture, and regenerating the BIAS slurry by causing desorption of the CO.sub.2.

Claims

1. A composition for the separation of CO.sub.2 from a gaseous mixture, the composition comprising: a carrier fluid comprising polymerized silicone oil, wherein the carrier fluid has a molecular weight of less than 1500 g/mol; and, basic immobilized amine sorbent (BIAS) is suspended in the carrier fluid.

2. The composition of claim 1, wherein the carrier fluid has a boiling point greater than 200 C.

3. The composition of claim 1, wherein the basic immobilized amine sorbent is a class 1 where class 1 are prepared by dry or wet impregnation of a support with a polyamine/hydrophilic solvent mixture, class 2 where class 2 are prepared by wet impregnation of a mixture of a reactive aminosilane and anhydrous hydrophobic solvent onto a dry pre-treated silica support, class 1/class 2 hybrid, or a combination thereof.

4. The composition of claim 1, wherein the composition is hydrophobic.

5. The composition of claim 1, wherein the CO.sub.2 capture capacity of the composition is greater than 0.8 mmol/L.

6. The composition of claim 5, wherein the CO.sub.2 capture capacity of the composition is greater than 1.0 mmol/L.

7. A composition for the separation of CO.sub.2 from a gaseous mixture, the composition comprising: a carrier fluid comprising polymerized silicone oil; and, basic immobilized amine sorbent (BIAS) is suspended in the carrier fluid, wherein the basic immobilized amine sorbent ranges from about 20 to about 35 wt. % of the composition.

8. The composition of claim 7, wherein the basic immobilized amine sorbent ranges from about 27 to about 35 wt. % of the composition.

9. A composition for the separation of CO.sub.2 from a gaseous mixture, the composition comprising: a carrier fluid comprising polymerized silicone oil; basic immobilized amine sorbent (BIAS) is suspended in the carrier fluid; and, wherein the viscosity of the composition ranges from about 20 to about 50 cSt.

10. The composition of claim 9, wherein the viscosity of the composition ranges from about 20 to about 30 cSt.

11. A composition for the separation of CO.sub.2 from a gaseous mixture, the composition comprising: a carrier fluid comprising polymerized silicone oil, wherein the carrier fluid has a molecular weight of less than 1500 g/mol and a boiling point greater than 200 C.; and, basic immobilized amine sorbent (BIAS) is suspended in the carrier fluid, wherein the BIAS is a class 1 where class 1 are prepared by dry or wet impregnation of a support with a polyamine/hydrophilic solvent mixture, class 2 where class 2 are prepared by wet impregnation of a mixture of a reactive aminosilane and anhydrous hydrophobic solvent onto a dry pre-treated silica support, class 1/class 2 hybrid, or a combination thereof; wherein the basic immobilized amine sorbent ranges from about 27 to about 35 wt. % of the composition; wherein the viscosity of the composition is in a range from about 20 to about 30 cSt; wherein the CO.sub.2 capture capacity is greater than 1.0 mmol/L; and wherein the composition is hydrophobic.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1. illustrates a comparison of CO.sub.2 uptake normalized to the mass of sorbent for pure sorbent BIAS 102B (3.1 mmol/g at 15% CO.sub.2 85% N.sub.2 at 1 bar, 65 C.) and a slurry of the same sorbent dispersed in solvent PMM-1015 (phenylmethylsiloxane-dimethylsiloxane copolymer) (3.3 mmol/g in 100% CO.sub.2 at 1 bar, 80 C.).

(2) FIG. 2. illustrates a comparison of CO.sub.2 absorption of a single BIAS slurry after regeneration, as performed in a continually stirred reactor (20 wt % BIAS 105C sorbent in DMS-T12R silicone oil, 0.8 mmol/g at 15% CO.sub.2, 85% N.sub.2 4% O.sub.2 at 1 bar, 65 C., regeneration under 100% N.sub.2, 1 bar, 110 C.).

(3) FIG. 3. illustrates a comparison of CO.sub.2 absorption from both wet and dry gas streams of a single BIAS slurry after regeneration, as performed in a continually stirred reactor (20 wt % BIAS 105C sorbent in DMS-T12R silicone oil, at 15% CO.sub.2, 85% N.sub.2 4% O.sub.2 at 1 bar, 65 C., regeneration under 100% N.sub.2, 1 bar, 110 C.).

(4) FIG. 4. illustrates a 28 wt % slurry performance (28 wt % BIAS 102B sorbent in PMM-1015 at 100% CO.sub.2 at 1 bar, 80 C., regeneration under 100% N.sub.2, 1 bar, 110 C.).

(5) FIG. 5. illustrates stability of a BIAS slurry after seven cycles (30 wt % BIAS 105C sorbent in DMS-T12R at 100% CO.sub.2 at 1 bar, 80 C., regeneration under 100% N.sub.2, 1 bar, 100 C. at 110 C.).

(6) FIG. 6. illustrates static cycling tests of a BIAS 102B sorbent (15% CO.sub.2 at 65 C., regeneration at 115 C.)

(7) FIG. 7. illustrates static cycling tests of a BIAS slurry (28 wt % BIAS 102B sorbent in PMM-1015, 15% CO.sub.2 at 80 C., regeneration at 115 C.).

(8) FIG. 8. illustrates a slurry based absorption/MW regeneration process for CO.sub.2 capture.

DETAILED DESCRIPTION OF THE INVENTION

(9) The following description is provided to enable any person skilled in the art to use the invention and sets forth the best mode contemplated by the inventor for carrying out the invention. Various modifications, however, will remain readily apparent to those skilled in the art, since the principles of the present invention are defined herein specifically to provide a composition and method for separating CO.sub.2 from a gaseous mixture. The composition is a slurry comprising Basic Immobilized Amine Sorbents suspended in a silicone oil. The method comprises contacting a gaseous mixture with a composition comprising BIAS suspended in a silicon oil, and treating the resulting CO.sub.2 laden sorbent slurry to remove the absorbed CO.sub.2 from the laden sorbent slurry.

(10) The gaseous mixture necessarily comprises CO.sub.2 or a mixture of CO.sub.2 and at least one other gas. As noted above, preferred gaseous mixtures include post combustion gas streams such as flue gas. Flue gas typically comprises as main constituents N.sub.2 and CO.sub.2.

(11) The composition is a mixture of Basic Immobilized Amine Sorbent (BIAS or sorbent) suspended in a polymerized silicone oil (carrier fluid). Suspension of the BIAS is typically achieved by one of several methods such as stirring or agitation. One method of formation of the BIAS slurry is by addition of a known mass of the solid BIAS to a known volume of the carrier fluid, then agitating the mixture at 60 C. for no less than 30 minutes or until a uniform suspension is achieved where the solid BIAS particles are generally uniformly distributed throughout the carrier fluid.

(12) Preferred weight percent of BIAS loading is determined by retaining such fluid behavior allows the slurry to be stirred, pumped, aspirated, or otherwise amenable for incorporation into industrial processes while maintaining acceptable CO.sub.2 sorption. In general, the viscosity of the resulting slurry should be no more than 400 cSt at 25 C. The BIAS in the mixture are preferably present in an amount up to the highest mass loading that still retains the fluid behavior of the entirety of the suspension, typically up to 35 weight percent (wt %).

(13) Carrier Fluid

(14) As used in the disclosed method, the carrier fluid comprises one or more polymerized silicon oil(s). Silicone oils are liquid polymerized siloxanes with organic side chains. These polymerized silicon oils are non-polar, high boiling (>200 Co), low heat capacity (<3.8 KJ/Kg K) hydrophobic liquids with molecular weight less 1500 g/mol. An exemplary silicone oil is monocarbinol terminated polydimethylsiloxane (MCR-12). Critically, the carrier fluid does not interfere or compete with CO.sub.2 adsorption sites in the sorbent. As shown in FIG. 1, use of the polymerized silicone oils allow the relatively equal sorption of CO.sub.2 by the sorbent slurry in comparison to the same sorbent alone, when normalized to the mass of the sorbent in the slurry.

(15) The carrier fluids include non-polar, high boiling, and low heat capacity hydrophobic silicon oils with molecular weight less 1500 g/mol. The thermal stability of the slurry allows the capture and regeneration processes to occur at higher temperatures, thus reducing the need to cool the flue gas. The lack of volatility for the slurry removes the energy penalty that is associated with evaporative losses of water and amine in the aqueous MEA process. Further, the carrier fluids are thermally stable, where thermally stable means no obvious degradation over 1000 hours under CO.sub.2 absorption and desorption environment. Solid sorbents operating via a fluid slurry offers advantages over using the solid sorbent alone. These benefits include improved heat transfer, reduced attritions of the sorbent, and a much simpler reactor design employing a continuous flow process.

(16) Basic Immobilized Amine Sorbent

(17) Preferred BIAS for use in the sorbent slurry include Class 1, Class 2, or hybrid class 1/class 2 sorbent types. Preferred sorbents have silica as the support and amine species that possess any combination of primary and secondary amines. The physical characteristics of the BIAS are critical to their incorporation into the pelletized sorbent. The BIAS powders are preferentially 1 nm to 25 m in diameter. Further, BIAS particles may be ground prior to mixing with the carrier fluid. Such grinding serves to process the particles into a size preferential for suspension in the carrier fluid as well as expose a greater number of functional groups for CO.sub.2 capture.

(18) Preferred CO.sub.2 capture capacity of the starting BIAS particles is from about 0.1 to about 1.0 mmol CO.sub.2/g. More preferred CO.sub.2 capture capacity of the BIAS before pelletization is from about 1.0 to about 2.8 mmol CO.sub.2/g. Most preferred BIAS possess CO.sub.2 capture capacity before pelletization greater than about 2.8 mmol CO.sub.2/g.

(19) Preferred amines for the BIAS are polyamines that contain more than one as well as any combination of the following amine groups: primary (NH.sub.2), secondary (NH), and tertiary (N) amines. Preferentially, BIAS sorbents possess an amine loading between 1 and 65 wt %. Preferred BIAS sorbents possess an amine loading between 20 and 45 wt %. More preferred BIAS sorbents possess an amine loading between 45 and 65 wt %.

(20) BIAS Slurry Composition:

(21) A salient aspect of the invention is the final BIAS slurry composition. Key parameters are the sorbent capacity of the BIAS slurry, primarily as a result of the suspended BIAS. The preferred BIAS loading range as the following: from about 20 to about 40 wt % as BIAS sorbent weight. The BIAS slurries demonstrate high CO.sub.2 capture capacity (in 4 wt % or 1.0 mmol CO.sub.2/g-slurry) relative to their weight. As expected, an increasing wt % of BIAS results in increasing CO.sub.2 sorption. Another salient aspect of the invention is that the BIAS slurry is hydrophobic in that it repels H.sub.2O vapor or condensed H.sub.2O, thus preserving the CO.sub.2 capture capability. As noted previously, a disadvantage of the current stand-alone BIAS is that they are vulnerable to leaching from the sorbent pores by condensed steam during practical CO.sub.2 adsorption-desorption testing under humidified conditions. However, the negative effect of steam in the gaseous mixture is remedied by the suspension of the BIAS in the hydrophobic carrier fluid. The hydrophobic carrier fluid minimizes contact between the BIAS's amines and condensed steam during CO.sub.2 capture cycling under practical humid conditions. This hydrophobicity extends the performance of the BIAS.

(22) To meet a CO.sub.2 absorption capacity target at 1.0 mmol CO.sub.2/g, typical slurries are comprised of at least 25 wt % Basic Immobilized Amine sorbent by total sorbent weight. Preferred BIAS slurries are comprised of from about 20% to about 40% by dry sorbent weight. More preferred BIAS slurries are comprised of from about 27% to about 35% by total dry pelletized sorbent weight.

(23) Viscosity of slurry is a key operating parameter and can directly affect the pump operation during CO.sub.2 capture processes. Generally viscosity decreases along with increasing operating temperature, but increases with the loading of solid. Results for CO.sub.2 capture capacities were previously discussed and can be seen in FIGS. 2-7. A preferred BIAS slurry contained about 28 wt % sorbent, and captured 0.8 mmol CO.sub.2/g and had density of 1.2 g/cm3, and viscosity of less than 50 cSt.

(24) Preferred BIAS slurries comprised of the BIAS suspended in a carrier fluid possess a CO.sub.2 capture of greater than 0.8 mmol CO.sub.2/g, a viscosity from 20 to 50 cSt at absorption temperature, and a solid mass loading of from about 20 to about 35 wt %. More preferred, the BIAS slurries possess a CO.sub.2 capture of greater than 1.0 mmol CO.sub.2/g, a viscosity from 20 to 30 cSt, and a solid mass loading of from about 27 to about 35 wt %.

(25) Further disclosed is a method for separation of CO.sub.2 from a gaseous mixture utilizing the previously disclosed composition. The method comprises contacting a gaseous mixture comprising CO.sub.2 with a BIAS slurry comprising solid Basic Immobilized Amine Sorbents suspended in a liquid polymerized siloxane. Contacting provides bringing into physical communication (contact) the CO.sub.2 of the gaseous mixture to the BIAS slurry as when flowing a gaseous mixture across the surface of a BIAS slurry or bubbling the gaseous mixture through a BIAS slurry, such that at least a portion of the CO.sub.2 is absorbed by the BIAS slurry to form a laden slurry. Laden slurry comprises BIAS slurry and absorbed CO.sub.2. Following the resulting formation of the laden slurry, regenerating the laden slurry removes at least a portion of the absorbed CO.sub.2 from the laden slurry to reform the BIAS slurry. Contacting the BIAS slurry with the gaseous mixture may be accomplished through means well known in the art, such as via a scrubber operation, closed chamber, packed bed reactor, slurry bubble reactor, stirred reactor, etc.

(26) Regenerating provides removal of at least a portion of CO.sub.2 from the laden slurry formed during contacting. Regenerating is a desorption step which reforms the laden slurry back to sorbent slurry. The regeneration of sorbent slurry provides for repetition of the method, such that the BIAS slurry is able to perform more than one cycle of the method. Regenerating may be accomplished by several methods, for example conventional heating, pressure swing, etc.

(27) A salient aspect of the composition and its use in the method is that regeneration may be accomplished by microwave (MW) excitation of the laden slurry as shown in FIG. 8. After absorption in an absorber at temperature in a range about 60-70 C., CO.sub.2 saturated laden slurry may be regenerated in a relative small microwave regenerator at temperature in a range from 40-120 120 C. The major advantage of this MW-assisted regeneration method is fast CO.sub.2 desorption kinetics. Another advantage is that MW can selectively heat BIAS sorbents not the non-polar silicon oils since silicone oil has relatively low MW energy absorption while the amine supported sorbent has relatively high MW absorption capacity. Regeneration by microwave desorption may enable a fast regeneration with a low purge gas flow rate and lower process temperature that translates into energy savings. Further, the elimination of a steam requirement in comparison to regeneration by heating may reduce or eliminate corrosivity associated with solvent/amine steam stripping and again reduces thermal input requirements and reactor size as is illustrated in FIG. 8. Thus, MW-assisted regeneration may provide a fast and high energy efficient regeneration solution for the carbon capture process.

(28) In one example, a typical slurry was made by adding dry BIAS 95A sorbents with particle size between 80 and 120 microns into non-polar, low vapour pressure hydrophobic DMS-T12R silicon oils with molecular weight no more than 1500 g/mol. Sorbent loading was performed at 25 wt %. The slurry was then agitated in N.sub.2 at 65 C. for 30 minutes to achieve uniformity before exposed to a simulated flue gas containing 14% of CO.sub.2 in N.sub.2, or a gas stream of pure CO.sub.2 for 6 hours. 10 mL of resulting slurry was investigated for microwave assisted regeneration study using a CEM Discover SP Microwave reactor. Cyclic absorption and microwave assisted regeneration were performed as described above.

(29) Results of MW assisted regeneration of slurry are indicated in Table 1. The major advantage of this MW-assisted regeneration method is a fast CO.sub.2 desorption kinetics, compared to conventional heating regeneration method. It only took less than 2 minutes to release CO.sub.2 gas stream from the slurry, comparing to several hours of the convention thermal regeneration method. CO.sub.2 concentration increased along with time-on-stream (TOS) and temperatures. The preferred regeneration temperature for CO.sub.2 desorption was around 100 C. As much as 42% of CO.sub.2 was found in gas phase after 60 minutes of regeneration at 100 C. Another major advantage is possible high pressure pure CO.sub.2 product. As indicated in Table 1, up to 30 psig of pressure was also found in gas phase, indicating approximately 20 psi of CO.sub.2 partial pressure.

(30) Stability performance of slurry was studied at 100 C., as indicated in Table 1. The slurry of 25 wt % of BIAS 95A in DMS-T12R oil showed strong stability after several 2-min MW cycles and one 60-min MW cycle at 100 C. There were no apparent changes in the physio- and chemical properties of slurry.

(31) TABLE-US-00001 TABLE 1 MW regeneration vs. conventional heating regeneration Temp. TOS CO.sub.2 Pressure Pulsed ( C.) (min) Conc. (%) (psig) MW output (W) 60* 5 0.06 n/a Conventional heating 100* 2 0.3 n/a Conventional heating 100* 60 7.3 n/o Conventional heating 40 2 0.2 n/a <5 60 2 0.3 3 <8 60 5 0.7 9 <10 100 2 15.7 26 13-20 100 2 16.9 25 13-20 100 60 42 30 13-20

(32) It is to be understood that the above-described arrangements are only illustrative of the application of the principles of the present invention and it is not intended to be exhaustive or limit the invention to the precise form disclosed. Numerous modifications and alternative arrangements may be devised by those skilled in the art in light of the above teachings without departing from the spirit and scope of the present invention. It is intended that the scope of the invention be defined by the claims appended hereto.

(33) In addition, the previously described versions of the present invention have many advantages, including but not limited to those described above. However, the invention does not require that all advantages and aspects be incorporated into every embodiment of the present invention.

(34) All publications and patent documents cited in this application are incorporated by reference in their entirety for all purposes to the same extent as if each individual publication or patent document were so individually denoted.