Patent ID: 8088962

Claim:
A process for preparing butadiene from n-butane, comprising 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 product gas stream (b) comprising n-butane, 1-butene, 2-butene, butadiene, hydrogen, and low-boiling secondary constituents, and optionally comprising carbon oxides and/or steam; C) feeding said product gas stream (b) 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, carbon oxides, and steam, said product gas stream (c) having a higher content of butadiene than product gas stream (b); D) removing said low-boiling secondary constituents and steam from said product gas stream (c) to obtain a C 4 product gas stream (d) substantially comprising n-butane, 2-butene and butadiene; E) separating by extractive distillation said C 4 product gas stream (d) into a stream (e1) substantially comprising n-butane and 2-butene and a product-of-value stream (e2) substantially comprising butadiene; F) recycling said stream (e1) into said first dehydrogenation zone; wherein at least a portion of the oxygen remaining in said product gas streams (c) and/or (d) after C) or D) is removed by reacting it catalytically with hydrogen.