METHOD TO PREPARE CROSS-LINKED, SURFACE FUNCTIONALIZED POLYSTYRENE DIVINYLBENZENE BEADS

Abstract

Method for the preparation of a sorbent material and for use of such a material for separating gaseous carbon dioxide from a gas mixture, preferably for direct air capture, using a temperature, vacuum, or temperature/vacuum swing process, comprising primary amine moieties immobilized on a solid support, wherein the primary amine moieties, in the ?-carbon position, are substituted by one hydrogen and one non-hydrogen substituent, wherein the sorbent material is in the form of a monolith, a layer, fibres, or particles, wherein the non-hydrogen substituent is selected from the group consisting of alkyl, alkenyl, arylalkyl, and wherein the solid support of the sorbent material is a porous material. Starting from a precursor of said sorbent material comprising one or multiple keto-groups, said one or multiple keto groups are converted into said primary amine moieties through a reductive amination.

Claims

1. A method for separating gaseous carbon dioxide from a gas mixture, using a temperature, vacuum, or temperature/vacuum swing process, wherein said sorbent material comprises primary amine moieties immobilized on a solid support, wherein the amine moieties, in the ?-carbon position, are substituted by one hydrogen and one non-hydrogen substituent wherein the primary amine moieties, in the ?-carbon position, are substituted by one hydrogen and one non-hydrogen substituent, wherein the sorbent material is in the form of a monolith, in the form of a layer or a plurality of layers, the form of hollow or solid fibres, including in woven or nonwoven (layer) structures, or the form of hollow or solid particles, wherein the non-hydrogen substituent is selected from the group consisting of alkyl, alkenyl, arylalkyl, wherein the solid support of the sorbent material is a porous material based on an organic and/or inorganic material, and wherein, for obtaining said sorbent material, starting from a precursor of said sorbent material comprising one or multiple keto-groups, said one or multiple keto groups are converted into said primary amine moieties through a reductive amination.

2. The method according to claim 1, wherein, starting from said precursor sorbent material which in said ?-carbon position carries a keto-group, this keto-group is converted into said primary amine moiety in said reductive amination.

3. The method according to claim 1, wherein the non-hydrogen substituent is selected from the group of methyl or ethyl.

4. The method according to claim 1, wherein the sorbent material is a porous polymer material, selected from the group of linear or branched, cross-linked or uncross-linked polystyrene, polyethylene, polypropylene, polyamide, polyurethane, acrylate and/or methacrylate based polymer including PMMA, or combinations thereof.

5. The method according to claim 1, wherein the sorbent material is a porous cross-linked polystyrene material, which is at least partially functionalized to or contains alkylbenzylamine moieties.

6. The method according to claim 1, wherein before and/or while carrying out the reductive amination the precursor sorbent material is swollen with a solvent.

7. The method according to claim 1, wherein the reductive amination is carried out with an ammonium salt and a cyanoborohydride salt.

8. The method according to claim 1, wherein the reductive amination is carried out at elevated temperature above 50? C.

9. The method according to claim 8, wherein the elevated temperature is established in an autoclave or wherein the elevated temperature is maintained for a time span of at least 1 hour, or at least 2 hours.

10. The method according to claim 1, wherein the reductive amination involves two steps, a first step of adding ammonium salt and a first portion of cyano borohydride salt, and a second step of adding the remaining cyano borohydride salt.

11. The method according to claim 1, wherein the sorbent material and/or the precursor sorbent material, in porous form, has a specific BET surface area, in the range of 0.5-100 m.sup.2/g or 1-50 m.sup.2/g, or 1-20 m.sup.2/g.

12. The method according to claim 1, wherein the sorbent material and/or the precursor sorbent material takes the form of beads with a particle size (D50) in the range of 0.002-4 mm, 0.005-2 mm, 0.002-1.5 mm, 0.005-1.6 mm or 0.01-1.5 mm, or in the range of 0.30-1.25 mm.

13. The method according to claim 1, wherein for separating gaseous carbon dioxide from a gas mixture, by cyclic adsorption/desorption using a sorbent material adsorbing said gaseous carbon dioxide in a unit, wherein the method comprises at least the following sequential and in this sequence repeating steps (a)-(e): (a) contacting said gas mixture with the sorbent material to allow at least said gaseous carbon dioxide to adsorb on the sorbent material by flow-through through said unit under ambient atmospheric pressure conditions and ambient atmospheric temperature conditions in an adsorption step; (b) isolating said sorbent material with adsorbed carbon dioxide in said unit from said flow-through; (c) inducing an increase of the temperature of the sorbent material to a temperature starting the desorption of CO.sub.2; (d) extracting at least the desorbed gaseous carbon dioxide from the unit and separating gaseous carbon dioxide from steam in or downstream of the unit; (e) bringing the sorbent material to ambient atmospheric temperature conditions.

14. The method according to claim 13, wherein step (c) includes injecting a stream of saturated or superheated steam by flow-through through said unit or wherein step (b) involves isolating said sorbent material with adsorbed carbon dioxide in said unit from said flow-through while maintaining the temperature in the sorbent or wherein step (d) involves extracting at least the desorbed gaseous carbon dioxide from the unit and separating gaseous carbon dioxide from steam by condensation in or downstream of the unit or wherein step (c) involves inducing an increase of the temperature of the sorbent material to a temperature between 6? and 110? C., starting the desorption of CO.sub.2.

15. The method according to claim 1, wherein it is for separating gaseous carbon dioxide from ambient atmospheric air.

16. The method according to claim 1 for separating gaseous carbon dioxide from at least one of ambient atmospheric air, flue gas and biogas

17. The method according to claim 1, wherein the non-hydrogen substituent is the same for essentially all primary and/or secondary amine moieties and is selected as methyl.

18. The method according to claim 1, wherein the sorbent material is a porous polymer material, wherein the polymer material is poly(styrene) or poly(styrene-co-divinylbenzene) based, cellulose, or an inorganic material including silica, alumina, activated carbon, and combinations thereof.

19. The method according to claim 1, wherein the sorbent material is a porous cross-linked polystyrene material in the form of poly(styrene-co-divinylbenzene), which is at least partially functionalized to or contains ?-methylbenzylamine moieties, throughout the material or at least or only on its surface.

20. The method according to claim 1, wherein before and/or while carrying out the reductive amination the precursor sorbent material is swollen with an organic solvent, including with an alcoholic solvent, including ethanol.

21. The method according to claim 1, wherein the reductive amination is carried out with an ammonium salt and a cyanoborohydride salt, wherein the ammonium salt is ammonium acetate or wherein the cyano borohydride is sodium and/or potassium cyano borohydride.

22. The method according to claim 1, wherein the reductive amination is carried out at elevated temperature above 80? C., or at a temperature in the range of 90-140? C.

23. The method according to claim 1, wherein the reductive amination involves two steps, a first step of adding ammonium salt and a first portion of cyano borohydride salt, and a second step of adding the remaining cyano borohydride salt, wherein cyano borohydride is added in excess, and wherein the first portion makes up less than one equivalent or up to 1.5 equivalents, and the second remaining portion of cyano borohydride salt makes up another at least 1.5 or at least 2 equivalents, wherein in total more than three equivalents of cyano borohydride salt is added.

24. The method according to claim 1, wherein the sorbent material and/or the precursor sorbent material takes the form of essentially spherical beads with a particle size (D50) in the range of 0.002-4 mm, 0.005-2 mm, 0.002-1.5 mm, 0.005-1.6 mm or 0.01-1.5 mm, or in the range of 0.30-1.25 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0077] Preferred embodiments of the invention are described in the following with reference to the drawings, which are for the purpose of illustrating the present preferred embodiments of the invention and not for the purpose of limiting the same. In the drawings,

[0078] FIG. 1 shows schematic structures of ?-methyl-benzyl-amino modified PS beads and the corresponding ketone precursor in the extended (a) and compact (b) versions;

[0079] FIG. 2 shows a summary of protocols that in principle allow the transformation of small-molecule acetophenones under homogeneous reaction conditions into the corresponding ?-methylbenzylamino derivatives;

[0080] FIG. 3 shows a scheme of synthesis of ?-methylbenzylamino modified PS beads under heterogeneous Leuckart conditions;

[0081] FIG. 4 shows selected regions of the FT-IR spectra of starting PS ketone (black trace) and Leuckart PS (grey trace) beads;

[0082] FIG. 5 shows the attempted synthesis of ?-methylbenzylamino modified PS beads through heterogeneous conditions via p-tosylhydrazide formation, divided into initial attempts and revised strategy; (b) chemical structure of commercially available compound 1, which was used as a reference small molecule;

[0083] FIG. 6 shows selected regions of the FT-IR spectra of starting PS ketone (short dashed trace), microwave 1 (long dashed trace), hotplate (dotted trace), autoclave 1 (thick solid trace), and control microwave 1 (thin solid trace) beads;

[0084] FIG. 7 shows a schematic representation of a direct air capture unit.

DESCRIPTION OF PREFERRED EMBODIMENTS

Experimental Procedures:

PS Beads:

[0085] In a 1 L reactor, 1% (mass ratio) of gelatin and 2% (mass ratio) of sodium chloride are dissolved in 340 cm3 of water at 45? C. for 1 h. In another flask, 1 g of benzoyl peroxide is dissolved in a mixture of 57.8 g of styrene, 5.9 g of divinylbenzene (content 80%) and 63.8 g of C11-C13 iso-paraffin. The resulting mixture is then added to the reactor. After that the reaction mixture is stirred and heated up to 70? C. maintaining the temperature for 2 h, then the temperature is raised to 80? C. and kept it for 3 h, and then raised to 90? C. for 6 h. The reaction mixture is cooled down to room temperature and the beads are filtered off using a funnel glass filter and vacuum suction. The poly(styrene-co-divinylbenzene) beads are washed with toluene and dried in a rotavapor.

PS Ketone:

[0086] 20 g of poly(styrene-co-divinylbenzene) beads and 150 mL of 1,2-dichloroethane (DCE) were loaded into a reactor and stirred at room temperature (RT) for 5 minutes. To this suspension, 34.5 g of AlCl.sub.3 was added. The resulting suspension was cooled to 0? C. A solution of 19.6 g acetyl chloride in 50 mL of 1,2-dichloroethane (DCE) was added dropwise to the reaction mixture. When the addition was complete, the suspension was stirred at 50? C. for 4 h. The reaction mixture was quenched with iso-propanol, and the acetylated PS beads thus made, an embodiment of a PS ketone (acetophenone-modified polystyrenedivinylbenzene), were filtered off, washed with water, 1 M aqueous HCl, water again (until pH?5), and then dried.

Exemplary Procedure for the Leuckart Reaction (Outside the Invention):

[0087] Ammonium formate (19.1 g, 0.3 mol) was loaded inside a 250 mL three-necked flask equipped with water condenser, under N.sub.2 atmosphere. The temperature was raised to 160? C. to melt the solid while stirring. Acetophenone-modified polystyrenedivinylbenzene (in the following PS ketone) (1.5 g; 10 mmol) was added after ammonium formate had melted completely. The resulting mixture was heated at 160? C. for 24 hours. The reaction mixture was then cooled down, quenched with water, the beads were filtered off, added to 6 M hydrochloric acid (500 mL) and the mixture was heated under reflux conditions overnight at 110? C. After standing overnight, the so-obtained PS beads were filtered off and washed several times with water until the pH became neutral, and then with ethanol. The sample was dried under N.sub.2 at 105? C.

Variant of the Gabriel Amine Synthesis; Optimized Procedure for the p-Tosylhydrazide Formation (Outside the Invention):

[0088] Prior to performing other operations, the PS ketone beads (2 g, 19.2 mmol) were placed in dioxane (50 mL) for 2 h to allow swelling. p-Toluenesulfonyl hydrazide (7.15 g, 38.4 mmol) was added in one portion to the suspension containing the swollen PS ketone beads. The resulting mixture was stirred and heated at 60? C. for 7 hours. The suspended beads were filtered off, and then washed with dioxane, chloroform, and n-heptane. The filtered beads were dried at 105? C. under a N.sub.2 atmosphere.

Reductive Amination Using Microwave:

[0089] Prior to performing other operations, the PS ketone beads (250 mg, 1.7 mmol) were placed in ethanol (5 mL) for 2 h to allow swelling inside a 20 mL microwave vial. Ammonium acetate (2.64 g, 34.2 mmol) and sodium cyanoborohydride (0.13 g, 2.1 mmol) were added in one portion to the suspension containing the swollen PS ketone beads. The microwave vial was sealed, and the resulting mixture was stirred and heated at 130? C. for 2 minutes in a microwave reactor. The suspended beads were filtered off, and then washed with ethanol, acetone, and n-pentane. The filtered beads were dried at 105? C. under a N.sub.2 atmosphere.

Reductive Amination Using Hotplate:

[0090] Prior to performing other operations, swelling of the PS ketone beads (250 mg, 1.7 mmol) in ethanol (5 mL) was carried out for 2 h inside a round bottom flask. Ammonium acetate (2.64 g, 34.2 mmol) and sodium cyanoborohydride (0.13 g, 2.1 mmol) were added in one portion to the suspension containing the swollen PS ketone beads inside the round bottom flask. The flask was sealed, and the resulting mixture was stirred and heated at 130? C. for 24 hours with a silicone oil bath. The suspended beads were filtered off, and then washed with ethanol, acetone, and n-pentane. The filtered beads were dried at 105? C. under a N.sub.2 atmosphere.

Reductive Amination Using Autoclave:

[0091] Reaction repeated on two different batches of 5 g of PS ketone beads. Prior to performing other operations, swelling of the PS ketone beads (5 g, 34.2 mmol) in ethanol (100 mL) was carried out for 2 h inside a glass beaker. Ammonium acetate (53 g, 688 mmol) and sodium cyanoborohydride (2.58 g, 41 mmol) were added in one portion to the suspension containing the swollen PS ketone beads. The glass beaker was introduced into the autoclave, which was sealed and placed on a hot plate kept at 130? C. for 24 hours. The suspended beads were filtered off, and then washed with ethanol, acetone, and n-pentane. The filtered beads were dried at 105? C. under a N.sub.2 atmosphere.

Carbon Dioxide Capture Properties:

[0092] The beads according to the above examples were tested in an experimental rig in which the beads were contained in a packed-bed reactor or in air permeable layers. The rig is schematically illustrated in FIG. 7. There is an ambient air inflow structure 1 and the actual reactor unit 8 comprises a container or wall 7 within which the layers of sorbent material 3 are located. There is an inflow structure 4 for desorption, if for example steam is used for desorption, and there is a reactor outlet 5 for extraction. Further, there is a vacuum unit 6 for evacuating the reactor.

[0093] For the adsorption measurements, 6 g of dry sample was filled into a cylinder with an inner diameter of 40 mm and a height of 40 mm and placed into a CO.sub.2 adsorption/desorption device, where it was exposed to a flow of 2.0 NL/min of air at 30? C. containing 450 ppmv CO.sub.2, having a relative humidity of 60% corresponding to a temperature of 30? C. for a duration of 600 min. Prior to adsorption, the sorbent bed was desorbed by heating the sorbent to 94? C. under an air flow of 2.0 NL/min. The amount of CO.sub.2 adsorbed on the sorbent was determined by integration of the signal of an infrared sensor measuring the CO.sub.2 content of the air stream leaving the cylinder.

[0094] The adsorber structure can alternatively be operated using a temperature/vacuum swing direct air capture process involving temperatures up to and vacuum pressures in the range of 50-250 mbar (abs) and heating the sorbent to a temperature between 6? and 110? C. In addition, experiments involving steam were carried out, with or without vacuum.

[0095] From the experiments one can see that the adsorption characteristics are reestablished after the regeneration process.

TABLE-US-00001 LIST OF REFERENCE SIGNS 1 ambient air, ambient air inflow structure 2 outflow of ambient air behind adsorption unit in adsorption flow-through mode 3 sorbent material 4 steam, steam inflow structure for desorption 5 reactor outlet for extraction 6 vacuum unit/separator 7 wall 8 reactor unit