Processes for producing butadiene from n-butane 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; (1) 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.sub.4 hydrocarbon stream
comprising n-butane and butadiene; and (h) separating the C.sub.4
hydrocarbon stream to form a recylce 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.