| abstract |
The invention relates to 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 1-butene and 2-butene to obtain a product gas stream c comprising n-butane, 2-butene, butadiene, hydrogen, low-boiling secondary constituents and steam, said product gas stream c having a higher content of butadiene than the product gas stream b; n D) removing hydrogen, the low-boiling secondary constituents and steam to obtain a C 4 product gas stream d substantially consisting of n-butane, 2-butene and butadiene; n E) feeding the C 4 product gas stream d into a distillation zone and removing a butadiene/butane mixture as the product of value stream e1, to leave a stream e2 consisting substantially of n-butane and 2-butene; F) recycling the stream e2 into the first dehydrogenation zone. |