Catalytic synthesis of super linear alkenyl arenes using rhodium catalysts

1. A method of making alkenyl arenes, the method comprising contacting an arene and an olefin in the presence of an effective amount of a rhodium catalyst and an oxidant at an elevated temperature for a period of time to produce the alkenyl arenes, wherein the rhodium catalyst is a heterogeneous Rh(II) or Rh(III) catalyst.

2. The method according to claim 1 , wherein a linear to branched ratio (L:B ratio) of the alkenyl arenes is about 2:1 to about 99:1.

3. The method according to claim 1 , wherein the arene is a mono-substituted benzene; and

wherein the alkenyl arenes comprise one or both of a meta-substituted alkenyl arene and a para-substituted alkenyl arene.

4. The method according to claim 3 , wherein a total amount of the meta-substituted alkenyl arene and the para-substituted alkenyl arene is about 85 mol % to about 100 mol % based upon a total amount of the alkenyl arene.

5. The method according to claim 3 , wherein the mono-substituted benzene comprises one or more of toluene, chlorobenzene, and anisole.

6. The method according to claim 3 , wherein the olefin comprises one or more of propylene, 1-pentene, neohexene, and isobutylene.

7. The method according to claim 3 , wherein the olefin comprises a linear or branched, substituted or unsubstituted alpha olefin having from 3 to about 30 carbon atoms.

8. The method according to claim 1 , wherein the arene comprises a polyaromatic.

9. The method according to claim 8 , wherein the polyaromatic is selected from the group consisting of substituted and unsubstituted naphthalene, anthracene, tetracene, and other polyaromatic compounds having from 2 to 5 fused aromatic rings.

10. The method according to claim 1 , the method further comprising dehydrogenation of the alkenyl arenes to form alkyl arenes.

11. The method according to claim 10 , wherein the hydrogenation comprises contacting the alkenyl arenes and hydrogen in the presence of a hydrogenation catalyst at a second elevated temperature for a second period of time to produce the alkyl arenes.

12. The method according to claim 11 , wherein the second elevated temperature is about 100° C. to about 300° C.

13. The method according to claim 11 , wherein the hydrogenation comprises combining the alkenyl arenes and the ethanol at an elevated pressure of about 100 psig to about 5000 psig.

14. The method according to claim 11 , wherein the second period of time is about 1 hour to about 72 hours.

15. The method according to claim 1 , wherein the arene is benzene;

wherein the olefin is ethylene; and

wherein the alkenyl arene is styrene.

16. The method according to claim 15 , wherein the styrene is produced with over 95% yield and a ratio of styrene to trans-stilbene of at least 98:1.

17. The method according to claim 1 , further comprising that the arene and olefin are contacted in the presence of the rhodium catalyst and an effective amount of an acid to improve one or both of a longevity of the rhodium catalyst and a linear to branched ratio (L:B ratio) of the alkenyl arenes.

18. A method of making a 2,6-dimethylnapthalene (DMN) or 2,6-methylethylnapthalene (MEN), the method comprising:

making a pentenyl or hexenyl toluene by a method according to claim 1 ; and

dehydroaromatization of the pentenyl or hexenyl toluene to form the DMN or MEN.

19. The method according to claim 18 , wherein the dehydroaromatization comprises contacting the pentenyl or hexenyl toluene with a combination of a dehydrogenation catalyst and a zeolite catalyst.

20. The method according to claim 19 , wherein the dehydrogenation catalyst is an iridium complex with a pincer-type ligand.

21. The method of claim 1 , wherein the heterogeneous Rh(II) or Rh(III) catalyst is selected from Rh nanoparticles on SiO 2 , Rh nanoparticles on Al 2 O 3 , or Rh nanoparticles on a zeolite.