Forming dienes from cyclic ethers and diols, including tetrahydrofuran and 2-methyl-1,4-butanediol

1. A method of forming a diene, the method comprising:

contacting a reactant comprising at least one of a cyclic ether and a diol with a heterogeneous acid catalyst to yield a reaction mixture comprising a diene, wherein the heterogeneous acid catalyst comprises a solid acid catalyst, and the solid acid catalyst comprises a phosphorus-containing zeolite catalyst.

2. The method of claim 1 , wherein the reactant is derived from biomass.

3. The method of claim 1 , wherein the reactant comprises a cyclic ether.

4. The method of claim 3 , wherein the cyclic ether has a tetrahydrofuran skeleton.

5. The method of claim 4 , wherein the cyclic ether comprises tetrahydrofuran and the diene comprises butadiene.

6. The method of claim 5 , wherein a selectivity of the butadiene is at least 95%.

7. The method of claim 3 , wherein the cyclic ether comprises 2-methyltetrahydrofuran and the diene comprises pentadiene.

8. The method of claim 7 , wherein a selectivity of the pentadiene is at least 95%.

9. The method of claim 3 , wherein the cyclic ether comprises 2,5-dimethyltetrahydrofuran and the diene comprises hexadiene.

10. The method of claim 9 , wherein a selectivity of the hexadiene is at least 90%.

11. The method of claim 3 , the cyclic ether comprises 3-methyltetrahydrofuran and the diene comprises isoprene.

12. The method of claim 11 , wherein a selectivity of the isoprene is at least 65%.

13. The method of claim 11 , further comprising processing biomass to yield an acid comprising least one of citric acid, itaconic acid, and mesaconic acid, and processing the acid to yield the 3-methyltetrahydrofuran.

14. The method of claim 11 , wherein the 3-methyltetrahydrofuran is derived from at least one of citric acid, itaconic acid, and mesaconic acid.

15. The method of claim 1 , wherein the reactant comprises a diol.

16. The method of claim 15 , wherein the diol comprises 2-methyl-1,4-butanediol, and the diene comprises isoprene.

17. The method of claim 16 , wherein a selectivity of the isoprene is at least 70%.

18. The method of claim 1 , wherein the contacting occurs at a temperature from 100° C. to 600° C.

19. The method of claim 1 , wherein the contacting occurs at a pressure from 0 psia to 500 psia (34 atm).

20. The method of claim 1 , wherein the contacting occurs in the presence of an inert gas.

21. The method of claim 20 , wherein the inert gas comprises at least one of He, Ar, and N 2 .

22. The method of claim 1 , wherein the contacting occurs in the vapor phase.

23. The method of claim 1 , further comprising separating the diene from the reaction mixture.

24. The method of claim 1 , wherein the reaction mixture comprises unreacted cyclic ether, unreacted diol, or both, and further comprising contacting the unreacted cyclic ether, unreacted diol, or both with the heterogeneous acid catalyst to yield the diene.

25. The method of claim 1 , wherein the phosphorus-containing zeolite catalyst comprises at least one of phosphorus-containing MFI, phosphorus-containing MEL, phosphorus-containing BEA, phosphorus-containing FAU, phosphorus-containing MOR, phosphorus-containing FER, phosphorus-containing CHA, and phosphorus-containing self-pillared pentasil.

26. The method of claim 25 , wherein the phosphorus-containing zeolite catalyst comprises phosphorus-containing self-pillared pentasil, and the phosphorus-containing self-pillared pentasil has a ratio of silicon atoms to phosphorus atoms in a range of 1:1 to 1000:1.

27. The method of claim 25 , wherein the phosphorus-containing zeolite catalyst comprises phosphorus-containing self-pillared pentasil, and the phosphorus-containing self-pillared pentasil has rotational intergrowths of single-unit-cell lamellae that lead to repetitive branching nanosheets.

28. The method of claim 27 , wherein the nanosheets have a thickness of about 2 nm and define a network of micropores having a diameter of about 0.5 nm.

29. The method of claim 25 , wherein the phosphorus-containing self-pillared pentasil has a house of cards arrangement defining a network of mesopores having a dimension in a range of 2 nm to 7 nm.

30. The method of claim 1 , wherein the phosphorus-containing zeolite catalyst is substantially free of aluminum.

31. The method of claim 30 , wherein the phosphorus-containing zeolite catalyst comprises less than 5 wt % of aluminum.

32. The method of claim 18 , wherein the contacting occurs at a temperature from 150° C. to 400° C.

33. The method of claim 18 , wherein the contacting occurs at a temperature from 100° C. to 500° C.

34. The method of claim 18 , wherein the contacting occurs at a temperature from 200° C. to 300° C.

35. The method of claim 1 , wherein the contacting occurs at a pressure up to 147 psia (10 atm).

36. The method of claim 18 , wherein the contacting occurs at a pressure from 1 atm to 10 atm.

37. The method of claim 36 , wherein the contacting occurs at a pressure from 1 atm to 2 atm.

38. The method of claim 26 , wherein the phosphorus-containing self-pillared pentasil has a ratio of silicon atoms to phosphorus atoms in a range of 3:1 to 150:1.

39. The method of claim 31 , wherein the phosphorus-containing zeolite catalyst comprises less than 4 wt % of aluminum.

40. The method of claim 39 , wherein the phosphorus-containing zeolite catalyst comprises less than 3 wt % of aluminum.

41. The method of claim 40 , wherein the phosphorus-containing zeolite catalyst comprises less than 2 wt % of aluminum.

42. The method of claim 41 , wherein the phosphorus-containing zeolite catalyst comprises less than 1 wt % of aluminum.