On-board fuel desulfurization unit

1. A method for regenerating at least one impurity-adsorbing sorbent bed, the method comprising:

a) passing impurity-containing fluid through the impurity-adsorbing sorbent bed, the impurity-containing fluid containing an impurity;

b) adsorbing the impurity in the impurity-containing fluid with the impurity-adsorbing sorbent bed to produce a purified fluid;

c) sending a portion of the purified fluid back through the impurity-adsorbing sorbent bed that contains the impurity adsorbed in step b; and

d) exposing the impurity-adsorbing sorbent bed of step c to microwave energy to desorb the impurity adsorbed on the impurity-adsorbing sorbent bed.

2. The method of claim 1 , wherein sending the portion of the purified fluid through the impurity-adsorbing sorbent bed occurs after the impurity-adsorbing sorbent bed reaches a breakthrough point.

3. The method of claim 1 , wherein passing the impurity-containing fluid through the impurity-adsorbing sorbent bed and sending the portion of the purified fluid through the impurity-adsorbing sorbent bed occur independently of each other.

4. The method of claim 1 , wherein exposing the impurity-adsorbing sorbent bed of step c to microwave energy comprises providing electro-magnetic energy sufficient to disrupt adsorptive forces between the impurity-adsorbing sorbent bed and the impurity.

5. The method of claim 1 , wherein desorbing the impurity comprises desorbing the impurity into the portion of the purified fluid.

6. The method of claim 1 , wherein the purified fluid has an impurity concentration of less than 15 parts per million by weight of the impurity.

7. The method of claim 6 , and further comprising feeding a second portion of the purified fluid into a fuel cell to produce electrical energy.

8. The method of claim 1 , wherein the impurity-adsorbing sorbent bed is an athermal impurity-adsorbing sorbent bed, and wherein exposing the impurity-adsorbing sorbent bed of step c to microwave energy comprises athermally regenerating the impurity-adsorbing sorbent bed of step c.

9. A method for regenerating an impurity-adsorbing sorbent bed, the method comprising:

passing impurity-containing fluid through a first impurity-adsorbing sorbent bed, the impurity-containing fluid containing an impurity;

adsorbing the impurity in the impurity-containing fluid with the first impurity-adsorbing sorbent bed to produce a purified fluid from the first impurity-adsorbing sorbent bed;

sending a portion of the purified fluid from the first impurity-adsorbing sorbent bed through a second impurity-adsorbing sorbent bed that contains the impurity; and

exposing the second impurity-adsorbing sorbent bed to microwave energy to desorb the impurity.

10. The method of claim 9 , wherein exposing the second impurity-adsorbing sorbent bed to microwave energy comprises providing electro-magnetic energy sufficient to disrupt adsorptive forces between the second impurity-adsorbing sorbent bed and the impurity.

11. The method of claim 9 , wherein desorbing the impurity comprises desorbing the impurity into the portion of the purified fluid from the first impurity-adsorbing sorbent bed.

12. The method of claim 9 , wherein the purified fluid from the first impurity-adsorbing sorbent bed has an impurity concentration of less than 15 parts per million by weight of the impurity.

13. The method of claim 12 , and further comprising feeding a second portion of the purified fluid from the first impurity-adsorbing sorbent bed into a fuel cell to produce electrical energy.

14. The method of claim 13 , and further comprising feeding the second portion of the purified fluid from the first impurity-adsorbing sorbent bed to a reformer prior to feeding the second portion of the purified fluid from the first impurity-adsorbing sorbent bed into the fuel cell.

15. The method of claim 9 , wherein the first and second impurity-adsorbing sorbent beds are first and second athermal impurity-adsorbing sorbent beds, and wherein exposing the second impurity-adsorbing sorbent bed to microwave energy comprises athermally regenerating the second impurity-adsorbing sorbent bed.

16. The method of claim 9 , and further comprising:

passing the impurity-containing fluid through the second impurity-adsorbing sorbent bed;

adsorbing the impurity in the impurity-containing fluid with the second impurity-adsorbing sorbent bed to produce a purified fluid from the second impurity-adsorbing sorbent bed;

sending a portion of the purified fluid from the second impurity-adsorbing sorbent bed through the first impurity-adsorbing sorbent bed that contains the impurity; and

exposing the first impurity-adsorbing sorbent bed to microwave energy to desorb the impurity.

17. The method of claim 16 , wherein the impurity-containing fluid is passed through the second impurity-adsorbing sorbent bed after the first impurity-adsorbing sorbent bed reaches a breakthrough point.

18. The method of claim 16 , wherein the first and second impurity-adsorbing sorbent beds are first and second athermal impurity-adsorbing sorbent beds, and wherein exposing the second impurity-adsorbing sorbent bed to microwave energy comprises athermally regenerating the second impurity-adsorbing sorbent bed, and wherein exposing the first impurity-adsorbing sorbent bed to microwave energy comprises athermally regenerating the first impurity-adsorbing sorbent bed.

19. The method of claim 16 , wherein desorbing the impurity comprises desorbing the impurity into the portion of the purified fluid from the second impurity-adsorbing sorbent bed.

20. The method of claim 16 , and further comprising feeding a second portion of the purified fluid from the second impurity-adsorbing sorbent bed into a fuel cell to produce electrical energy.