Mesophase pitch for carbon fiber production using supercritical carbon dioxide

1. A method comprising:

contacting coal tar containing at least some mesophase pitch precursor with a supercritical carbon dioxide (sCO 2 ) and toluene mixture, thereby removing at least some toluene soluble components from the coal tar to obtain a toluene insoluble fraction;

after the contacting operation, separating the sCO 2 and toluene mixture from the toluene insoluble fraction;

washing the toluene insoluble fraction with quinoline to obtain a quinoline and quinoline soluble fraction mixture of the toluene insoluble fraction;

separating the quinoline from the quinoline soluble fraction;

mixing the quinoline soluble fraction with sCO 2 to obtain a sCO 2 /quinoline soluble fraction mixture.

2. The method of claim 1 , wherein the contacting operation further comprises:

passing the sCO 2 /quinoline soluble fraction mixture through an extruder, thereby separating the sCO 2 from the quinoline soluble fraction to obtain fibers of mesophase pitch.

3. The method of claim 1 further comprising:

after the separating operation, performing a toluene wash on the toluene insoluble fraction thereby removing additional soluble material from the toluene insoluble fraction.

4. The method of claim 1 wherein separating the quinoline from the quinoline soluble fraction further comprises:

distilling the quinoline and quinoline soluble fraction mixture.

5. The method of claim 1 wherein separating the quinoline from the quinoline soluble fraction further comprises:

evaporating the quinoline to obtain the quinoline soluble fraction mixture.

6. The method of claim 1 further comprising:

heating the quinoline soluble fraction to from 300 to 400° C.

7. The method of claim 1 further comprising:

heating the quinoline soluble fraction to from 300 to 400° C. for less than 24 hours.

8. The method of claim 1 further comprising:

performing a stabilization operation on the fibers of mesophase pitch.

9. The method of claim 1 further comprising:

performing a carbonization operation on the fibers of mesophase pitch.

10. The method of claim 1 further comprising:

performing a graphitization operation on the fibers of mesophase pitch.

11. The method of claim 1 , further comprising:

passing the sCO 2 and toluene mixture through a reactor vessel containing the coal tar; and

wherein the washing operation includes washing the toluene insoluble fraction in the reactor vessel.

12. The method of claim 11 further comprising:

circulating the quinoline through the reactor vessel for up to 24 hours before separating the quinoline from the quinoline soluble fraction.

13. The method of claim 1 further comprising:

heating the quinoline soluble fraction to from 200 to 800° C.

14. The method of claim 6 , wherein the heating operation further comprises:

contacting the quinoline soluble fraction with sCO 2 heated to a temperature between 300 to 400° C.

15. The method of claim 6 further comprising:

after the heating operation, separating at least some quinoline insoluble material from the quinoline soluble material.

16. A method of manufacturing carbon fibers comprising:

contacting coal tar containing at least some mesophase pitch precursor with a supercritical carbon dioxide (sCO 2 ) and toluene mixture, thereby removing at least some toluene soluble components from the coal tar to obtain a toluene insoluble fraction;

after the contacting operation, separating the sCO 2 and toluene mixture from the insoluble coal tar fraction;

after the separating operation, mixing the toluene insoluble fraction with sCO 2 to obtain a sCO 2 /toluene insoluble fraction mixture; and

passing the sCO 2 /toluene insoluble fraction mixture through an extruder, thereby separating the sCO 2 from the toluene insoluble fraction to obtain fibers of mesophase pitch.

17. The method of claim 16 further comprising:

washing the toluene insoluble fraction with quinoline to obtain a quinoline and quinoline soluble fraction mixture and a quinoline insoluble fraction of the toluene insoluble fraction;

separating the quinoline from the quinoline soluble fraction of the toluene insoluble fraction; and

mixing the quinoline soluble fraction of the toluene insoluble fraction with sCO 2 to obtain the sCO 2 /toluene insoluble fraction mixture.

18. The method of claim 17 further comprising:

heating the quinoline soluble fraction of the toluene insoluble fraction to from 300 to 400° C. for less than 24 hours before mixing the quinoline soluble fraction of the toluene insoluble fraction with sCO 2 .

19. The method of claim 18 , wherein the heating operation further comprises:

contacting the quinoline soluble fraction with sCO 2 heated to a temperature between 300 to 400° C. for up to 24 hours.

20. A method of manufacturing carbon fibers comprising:

contacting coal tar containing at least some mesophase pitch precursor with a supercritical fluid solvent and co-solvent mixture, thereby removing at least some soluble components from the coal tar to obtain an insoluble coal tar fraction;

after the contacting operation, separating the supercritical fluid solvent and co-solvent mixture from the insoluble coal tar fraction;

after the separating operation, mixing the insoluble coal tar fraction with sCO 2 to obtain a sCO 2 /insoluble fraction mixture; and

passing the sCO 2 /ilinsoluble fraction mixture through an extruder to obtain fibers of mesophase pitch;

wherein the supercritical fluid solvent is selected from one or more of carbon dioxide, water, methane, nitrous oxide, ethane, propane, ethylene, propylene, methanol, ethanol, and acetone and the co-solvent is selected from one or more of benzene, xylene, tetralin, tetrahydrofuran, pyridine, quinolone, pyridine, and quinolone.