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1. US20070244349 - Method for producing butadiene from n-butane

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Claims
1- 6. (canceled)
7. A process comprising:
(a) providing a feed gas stream comprising n-butane;
(b) non-oxidatively dehydrogenating the feed gas stream in the presence of a catalyst in a first dehydrogenation zone to form a first intermediate gas stream comprising n-butane, 1-butene, 2-butene, butadiene and hydrogen;
(c) oxidatively dehydrogenating the first intermediate gas stream in the presence of an oxygenous gas having an oxygen content of at least 75% by volume in a second dehydrogenation zone to form a second intermediate gas stream comprising n-butane, butadiene, hydrogen, carbon dioxide and steam;
(d) compressing and cooling the second intermediate gas to form a first condensate stream comprising water and a third intermediate gas stream comprising n-butane, butadiene, hydrogen, carbon dioxide and steam;
(e) compressing and cooling the third intermediate gas to form a second condensate stream comprising n-butane, butadiene and water and a fourth intermediate gas stream comprising n-butane, butadiene, hydrogen and carbon dioxide;
(f) cooling the fourth intermediate gas stream to form a third condensate stream comprising n-butane and butadiene, and an offgas stream comprising carbon dioxide and hydrogen;
(g) removing water from the second condensate stream and combining the second condensate stream and third condensate stream to form a C 4 hydrocarbon stream comprising n-butane and butadiene; and
(h) separating the C 4 hydrocarbon stream to form a recycle stream comprising n-butane and a product stream comprising butadiene;
wherein at least a portion of the recycle stream is fed to the first dehydrogenation zone.
8. The process according to claim 7, wherein removing water from the second condensate stream is carried out prior to combining the second condensate stream and third condensate stream.
9. The process according to claim 7, wherein the non-oxidative dehydrogenation in the first dehydrogenation zone is carried out autothermally in the presence of an oxygenous gas having an oxygen content of at least 90% by volume.
10. The process according to claim 9, wherein the oxygenous gas comprises technical grade oxygen.
11. The process according to claim 7, wherein the feed gas stream is obtained from liquefied petroleum gas.
12. The process according to claim 7, wherein providing the feed gas stream comprises:
(i) providing a liquefied petroleum gas stream comprising butane and non-butyl hydrocarbons;
(ii) removing at least a portion of the non-butyl hydrocarbons from the liquefied petroleum gas stream to form an initial stream comprising n-butane and isobutane; and
(iii) removing at least a portion of the isobutane from the initial stream to form the feed gas stream.
13. The process according to claim 12, further comprising isomerizing the isobutane removed from the initial stream to form an n-butane/isobutane mixture and recycling the n-butane/isobutane mixture into the initial stream.
14. The process according to claim 12, wherein the non-oxidative dehydrogenation in the first dehydrogenation zone is carried out autothermally in the presence of an oxygenous gas having an oxygen content of at least 90% by volume.
14. The process according to claim 7, wherein the oxygenous gas comprises technical grade oxygen.
15. The process according to claim 7, wherein separating the C 4 hydrocarbon stream comprises extractive distillation.
16. The process according to claim 12, wherein separating the C 4 hydrocarbon stream comprises extractive distillation.
17. The process according to claim 14, wherein separating the C 4 hydrocarbon stream comprises extractive distillation.
18. The process according to claim 7, wherein the second intermediate gas stream further comprises residual oxygen, and the process farther comprises removing at least a portion of the residual oxygen from the second intermediate gas stream prior to compressing and cooling the second intermediate gas stream.
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