Conversion of propane to propylene
A process is disclosed that includes brominating a C 2 , C 3 , C 4 , C 5 or C 6 alkane with elemental bromine to form a bromo-alkane. The bromo-alkane is reacted to form a C 2 , C 3 , C 4 , C 5 or C 6 alkene and HBr. The HBr is oxidized to form elemental bromine.
1. A process comprising:
brominating an alkane with elemental bromine to form a stream comprising bromo-alkane and dibromo-alkane, wherein the alkane is a C 2 , C 3 , C 4 , C 5 , or C 6 alkane;
separating the dibromoalkane from the bromo-alkane,
reacting the dibromoalkane, thermally or in the presence of a catalyst, with alkane to form additional bromo-alkane;
reacting the additional bromo-alkane to form a corresponding alkene of the alkane and HBr; and oxidizing the HBr to form elemental bromine.
2. The process of claim 1 , wherein the alkane is ethane, propane, n-butane, isobutane, a pentane, or a hexane.
3. The process of claim 2 , wherein the alkane is propane and the alkene is propylene.
4. A process comprising:
providing a feedstock comprising propane;
reacting at least some of the propane with bromine to form bromopropane, dibromopropane, and HBr;
separating the dibromopropane from the bromopropane,
reacting the dibromopropane, thermally or in the presence of a catalyst, with alkane to form additional bromopropane;
dehydrobrominating the additional bromopropane to form a propylene/HBrpropylene and HBr mixture;
separating the propylene/HBrpropylene and HBr mixture to form propylene and recycle HBr;
oxidizing the recycle HBr to form a bromine/waterbromine and water mixture;
and separating bromine from the bromine/waterbromine and water mixture.
5. The process of claim 4 , wherein the step of reacting at least some of the propane with bromine is thermally induced.
6. The process of claim 5 , wherein the reaction occurs at a temperature of at least 200° C.
7. The process of claim 4 , wherein the dehydrobrominating step takes place in the presence of a catalyst.
8. The process of claim 7 , wherein the catalyst is selected from the group consisting of a silica-based catalyst, titanium dioxide, zirconium dioxide and their mixtures thereof.
9. The process of claim 7 , wherein in the dehydrobrominating step, the bromopropane is heated to between 250° C. and 500° C.
10. The process of claim 4 , wherein separating the propylene and HBr mixture is accomplished by distillation.
11. The process of claim 4 , wherein separating the propylene and HBr mixture is accomplished by absorbing the HBr in aqueous HBr to form a concentrated HBr solution.
12. The process of claim 11 , further comprising after the step of absorbing the HBr in aqueous HBr to form a concentrated HBr solution:
stripping the HBr from the concentrated aqueous HBr.
13. The process of claim 4 , wherein the HBr is oxidized using a chromium or cerium-based catalyst.
14. The process of claim 4 , further comprising after the step of separating bromine from the propylene and HBr mixture:
recycling the bromine to react with the propane in the step of reacting at least some of the propane with bromine.
15. The process of claim 1 , wherein the alkane is propane, the bromo-alkane is bromopropane, the dibromo-alkane is dibromopropane, and the alkene is propylene, and wherein the process further comprises converting the dibromopropane directly to propylene using Zn, wherein ZnBr 2 is produced as a byproduct.
16. The process of claim 15 , further comprising using oxidation or electrolysis and the ZnBr 2 to regenerate Br 2 .
17. A process comprising:
brominating an alkane with elemental bromine in a bromination reactor to form a stream comprising bromo-alkane and dibromo-alkane, wherein the alkane is a C2, C3, C4, C5 or C6 alkane;
separating the dibromoalkane from the bromo-alkane,
reacting the dibromoalkane, thermally or in the presence of a catalyst, with alkane to form additional bromo-alkane;
reacting the additional bromo-alkane to form a corresponding alkene of the alkane and HBr;
and oxidizing the HBr to form elemental bromine.
18. The process of claim 17 , wherein the dibromo-alkane is recycled to the bromination reactor for the reacting of the dibromo-alkane with the alkane to form bromo-alkane.
19. The process of claim 17 , wherein the reacting of the dibromo-alkane with the alkane to form bromo-alkane occurs in a separate reactor from the bromination reactor.