Carbon pyrolyzate adsorbent having utility for CO2 capture and methods of making and using the same

1. A method of removing CO 2 from a CO 2 -containing gas, comprising cycling CO 2 -selective carbon pyrolyzate adsorbent through a CO 2 removal reactor to which the CO 2 -containing gas is introduced, in a cycle comprising contacting the carbon pyrolyzate adsorbent with the CO 2 -containing gas in a contacting zone of the reactor to produce CO 2 -adsorbed carbon pyrolyzate adsorbent and CO 2 -depleted gas, discharging the CO 2 -depleted gas from the reactor, passing the CO 2 -adsorbed carbon pyrolyzate adsorbent to a regeneration zone of the reactor, regenerating the CO 2 -adsorbed carbon pyrolyzate adsorbent in a regeneration zone of the reactor to desorb CO 2 from the CO 2 -adsorbed carbon pyrolyzate adsorbent to produce regenerated carbon pyrolyzate adsorbent and desorbed CO 2 , discharging the desorbed CO 2 from the reactor, and returning the regenerated carbon pyrolyzate adsorbent to the contacting zone of the reactor, wherein the carbon pyrolyzate adsorbent has the following characteristics:

(a) CO 2 capacity greater than 105 cc/gram at one bar pressure and temperature of 273° Kelvin;

(b) CO 2 Working Capacity greater than 7.0 weight percent;

(c) CO 2 heats of adsorption and desorption each of which is in a range of from 10 to 50 kJ/mole; and

(d) a CO 2 /N 2 Henry's Law Separation Factor greater than 5.

2. The method of claim 1 , wherein said regenerating comprises steam stripping of CO 2 from the CO 2 -adsorbed carbon pyrolyzate adsorbent to produce steam-stripped carbon pyrolyzate adsorbent, and dehydrating and cooling the steam-stripped carbon pyrolyzate adsorbent to produce said regenerated carbon pyrolyzate adsorbent.

3. The method of claim 1 , wherein said CO 2 -containing gas comprises flue gas from a power generation plant.

4. The method of claim 3 , wherein the power generation plant comprises a coal-fired electricity generating plant.

5. The method of claim 1 , wherein the carbon pyrolyzate adsorbent is in a form of granules, and a falling stream of said granules is contacted with the CO 2 -containing gas in said contacting zone.

6. The method of claim 1 , wherein the carbon pyrolyzate adsorbent comprises a pyrolyzate of a PVDC homopolymer or a PVDC copolymer.

7. The method of claim 6 , wherein the carbon pyrolyzate adsorbent comprises a pyrolyzate of a PVDC copolymer.

8. The method of claim 7 , wherein the PVDC copolymer comprises a copolymer of an acrylic acid ester.

9. The method of claim 8 , wherein the acrylic acid ester comprises methyl acrylate.

10. The method of claim 1 wherein the carbon pyrolyzate adsorbent comprises a PVDC-MA copolymer having a weight average molecular weight in a range of from 80,000 to 100,000.

11. The method of claim 1 , wherein the carbon pyrolyzate adsorbent is in a particulate form, comprising particles of diameter in a range of from 10 to 500 μm.

12. The method of claim 11 , wherein the particles have a median particle diameter in a range of from 200 to 350 μm.

13. The method of claim 1 , wherein the carbon pyrolyzate adsorbent has a bulk density greater than 0.55 g/mL.

14. The method of claim 1 , wherein the carbon pyrolyzate adsorbent has a water adsorptive capacity of less than 5% by weight, based on weight of the adsorbent, at 303° Kelvin and 40% relative humidity.

15. The method of claim 1 , wherein the carbon pyrolyzate adsorbent has porosity characterized by a average pore size below 1 nm.

16. The method of claim 15 , wherein at least 50% of pore volume of said porosity is constituted by pores in a pore size range of from 0.35 to 0.7 nm.

17. The method of claim 1 , wherein the carbon pyrolyzate adsorbent has an attrition rate index less than 1 wt %/hr as measured by the procedure of ASTM D 5757.

18. The method of claim 1 , wherein the carbon pyrolyzate adsorbent has a nitrogen BET surface area of at least 800 m 2 per gram.

19. The method of claim 1 , wherein the carbon pyrolyzate adsorbent has a nitrogen micropore volume of at least 0.2 mL per gram.

20. The method of claim 1 , characterized by CO 2 capture recovery of at least 90% and CO 2 capture purity of at least 90%.

21. The method of claim 1 , wherein the carbon pyrolyzate adsorbent has at least one additional compatible characteristic selected from the group consisting of:

(e) being a pyrolyzate of homopolymer PVDC, PVDC-MA copolymer, PVDC-polyvinyl chloride (PVDC-PVC) copolymers, polyfurfuryl alcohol, polyacrylonitrile, and polymers containing heteroatoms that upon carbonization are left as dispersed species throughout the carbon material;

(f) an average particle diameter greater than 50 μm;

(g) particle diameter in a range of from 10 to 500 μm;

(h) particle diameter in a range of 150 to 500 μm;

(i) median particle diameter in a range of from 200 to 350 μm;

(j) being in a particulate form;

(k) CO 2 heats of adsorption and desorption each of which is in a range of from 20 to 30 kJ/mole;

(l) water adsorptive capacity of less than 5% by weight, based on weight of the adsorbent, at 303° Kelvin and 40% relative humidity;

(m) average pore size below 1 nm;

(n) porosity at least 50% of the pore volume of which is constituted by pores in a pore size range of from 0.35 to 0.7 nm;

(o) porosity characterized by a median pore width below 1 nm;

(p) an attrition rate index less than 1 wt %/hr as measured by the procedure of ASTM D 5757;

(q) N 2 BET surface area of at least 800 m 2 per gram;

(r) N 2 BET surface area of at least 900 m 2 per gram;

(s) N 2 BET surface area of at least 1000 m 2 per gram;

(t) N 2 micropore volume of at least 0.2 mL per gram;

(u) N 2 micropore volume in a range of from 0.3 to 0.6 mL per gram;

(v) CO 2 capture recovery of at least 90% and CO 2 capture purity of at least 90%;

(w) being a pyrolyzate of homopolymer PVDC or PVDC-MA copolymer, having a weight average molecular weight in a range of from 80,000 to 100,000;

(x) bulk density greater than 0.55 grams per cubic centimeter;

(y) bulk density greater than 0.9 grams per cubic centimeter;

(z) bulk density in a range of from about 1.0 to about 2.2 grams per cubic centimeter;

(aa) being in a form of granules;

(ab) being in a bead form;

(ac) being in a form of a monolith;

(ad) being in a cylindrical form;

(ae) being in a disc form;

(af) being of porous, non-graphitized carbon;

(ag) N 2 BET surface area being in a range of from 800 to 1000 m 2 per gram;

(ah) having porosity, substantially all of which is in pores <2 nm in diameter;

(ai) CO 2 capacity greater than 120 volumes of CO 2 /volume of carbon pyrolyzate adsorbent as measured at 273° Kelvin and 1 atmosphere pressure;

(aj) CO 2 capacity greater than 130 volumes of CO 2 /volume of carbon pyrolyzate adsorbent as measured at 273° Kelvin and 1 atmosphere pressure;

(ak) CO 2 capacity of at least 20 wt % at 1 atm CO 2 , based on weight of the adsorbent;

(al) CO 2 adsorption activation energy less than 5 kJ/mole;

(am) CO 2 heats of adsorption and desorption each of which is in a range of from 25 to 28 kJ/mole;

(an) CO 2 being desorbable from the adsorbent with steam;

(ao) adsorbent lifetime of at least 50,000 adsorption/desorption cycles for adsorption and desorption of CO 2 ;

(ap) being in a form of spherical adsorbent granules;

(aq) being in a form of spherical adsorbent granules 100 to 300 μm in diameter;

(ar) non-agglomerable or sinterable at 100° C.;

(as) being of hydrophobic character;

(at) CO 2 capacity of at least 100 volumes of CO 2 /volume of carbon material, as measured at 273° Kelvin and 1 atmosphere pressure;

(au) porosity being >40% by volume micropores;

(av) porosity having at least 50% of pore volume in pores <0.7 nm;

(aw) a separation factor greater than 6 for CO 2 over N 2 ;

(ax) a separation factor in a range of from 6.2 to 7.5 for CO 2 over N 2 ;

(ay) a permeability for CO 2 greater than 900 cc/psi/cm 2 /min;

(az) a permeability for CO 2 in a range of from 910 to 1250 cc/psi/cm 2 /min; and

(ba) an attrition rate index <0.01 wt % per hour in the reactor.

22. A CO 2 capture apparatus comprising: a moving bed contacting system and a carbon pyrolyzate adsorbent arranged for contacting CO 2 -containing fluid under conditions effecting adsorption of CO 2 on the carbon pyrolyzate adsorbent, the apparatus being adapted to regenerate the carbon pyrolyzate adsorbent after it has become at least partially loaded with CO 2 , so that the adsorbent is renewed for subsequent adsorptive operation, and the carbon pyrolyzate adsorbent having the following characteristics: (a) CO 2 capacity greater than 105 cc/gram at one bar pressure and temperature of 273° Kelvin; (b) CO 2 Working Capacity greater than 7.0 weight percent; (c) CO 2 heats of adsorption and desorption each of which is in a range of from 10 to 50 kJ/mole; and (d) a CO 2 /N 2 Henry's Law Separation Factor greater than 5.

23. The CO 2 capture apparatus of claim 22 , wherein the carbon pyrolyzate adsorbent has an average particle diameter greater than 50 μm.

24. The CO 2 capture apparatus of claim 22 , wherein the carbon pyrolyzate adsorbent comprises particles of diameter in a range of from 150 to 500 μm.

25. The CO 2 capture apparatus of claim 22 , wherein the carbon pyrolyzate adsorbent has a bulk density greater than 0.55 g/mL.

26. The CO 2 capture apparatus of claim 22 , wherein the carbon pyrolyzate adsorbent has a water adsorptive capacity of less than 5% by weight, based on weight of the adsorbent, at 303° Kelvin and 40% relative humidity.

27. The CO 2 capture apparatus of claim 22 , wherein the carbon pyrolyzate adsorbent has porosity characterized by average pore size below 1 nm.

28. The CO 2 capture apparatus of claim 22 , wherein the carbon pyrolyzate adsorbent has porosity at least 50% of the pore volume of which is constituted by pores in a pore size range of from 0.35 to 0.7 nm.

29. The CO 2 capture apparatus of claim 22 , wherein the carbon pyrolyzate adsorbent has an attrition rate index less than 1 wt %/hr as measured by the procedure of ASTM D 5757.

30. The CO 2 capture apparatus of claim 22 , wherein the carbon pyrolyzate adsorbent has an N 2 BET surface area of at least 800 m 2 per gram.

31. The CO 2 capture apparatus of claim 22 , wherein the carbon pyrolyzate adsorbent has a N 2 micropore volume of at least 0.2 milliliters per gram.

32. The CO 2 capture apparatus of claim 22 , wherein the carbon pyrolyzate adsorbent is a pyrolyzate of a PVDC homopolymer or a PVDC copolymer.