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.