Method for the production of butadiene and 1-butene

A process for preparing butadiene from n-butane having the steps of

• A) providing a feed gas stream a comprising n-butane;
• B) feeding the feed gas stream a comprising n-butane into at least one first dehydrogenation zone and nonoxidatively catalytically dehydrogenating n-butane to obtain a product gas stream b comprising n-butane, 1-butene, 2-butene, butadiene, hydrogen, low-boiling secondary constituents and in some cases steam;
• C) feeding the product gas stream b of the nonoxidative catalytic dehydrogenation and an oxygenous gas into at least one second dehydrogenation zone and oxidatively dehydrogenating n-butane, 1-butene and 2-butene to obtain a product gas stream c comprising n-butane, 2-butene, butadiene, low-boiling secondary constituents and steam, said product gas stream c having a higher content of butadiene than the product gas stream b;
• D) removing the low-boiling secondary constituents and steam to obtain a C4 product gas stream d substantially consisting of n-butane, 2-butene and butadiene;
• E) separating the C4 product gas stream d into a stream e1 consisting substantially of n-butane and 2-butene and a product of value stream e2 consisting substantially of butadiene by extractive distillation;
• F) feeding the stream e1 consisting substantially of n-butane and 2-butene and a cycle stream g comprising 1-butene and 2-butene into a distillation zone and separating into a 1-butene-rich product of value stream f1, a recycle stream f2 comprising 2-butene and n-butane and a stream f3 comprising 2-butene, and recycling the recycle stream f2 into the first dehydrogenation zone;
• G) feeding the stream f3 comprising 2-butene into an isomerization zone and isomerizing 2-butene to 1-butene to obtain a cycle stream g comprising 1-butene and 2-butene, and recycling the cycle gas stream g into the distillation zone.