Patent ID: 7495138

Claim:
A process for preparing butadiene from n-butane, comprising the steps of A) providing a feed gas stream (a) comprising n-butane; B) feeding said feed gas stream (a) into at least one first dehydrogenation zone and nonoxidatively, catalytically dehydrogenating n-butane to obtain a gas stream (b) comprising n-butane, 1-butene, 2-butene, butadiene, and hydrogen, and optionally further comprising carbon oxides and/or steam and/or inert gases; C) feeding said gas stream (b) and an oxygenous gas into at least one second dehydrogenation zone and oxidatively dehydrogenating 1-butene and 2-butene to obtain a gas stream (c) comprising n-butane, butadiene, and hydrogen, and optionally further comprising carbon oxides and/or inert gases; D) compressing in at least one first compression stage and cooling said gas stream (c) to obtain at least one condensate stream (d 1 ) comprising water, and a gas stream (d 2 ) comprising n-butane, butadiene, and hydrogen, and optionally further comprising carbon oxides and/or inert gases; E) separating said gas stream (d 2 ) by extractive distillation into a product stream (e 1 ) consisting substantially of butadiene, and a stream (e 2 ) comprising n-butane, hydrogen, and steam, and optionally further comprising carbon oxides and/or inert gases; F) optionally compressing in at least one further compression stage and cooling said gas stream (e 2 ) to obtain at least one condensate stream (f 1 ) comprising n-butane and water, and a gas stream (f 2 ) comprising n-butane and hydrogen, and optionally further comprising carbon oxides and/or inert gases, and optionally recycling said at least one condensate stream (f 1 ) into said first dehydrogenation zone; G) separating said gas stream (f 2 ) into a recycle stream (g 1 ) comprising n-butane and an offgas stream (g 2 ) comprising hydrogen, and optionally further comprising carbon oxides and/or inert gases, by contacting said gas stream (f 2 ) with a high-boiling absorbent and subsequently desorbing the gas constituents dissolved in the absorbent.