PROCESS FOR PREPARING 1,3-BUTADIENE FROM N-BUTENES BY OXIDATIVE DEHYDROGENATION

摘要

The invention relates to a process for preparing butadiene from n-butenes, comprising the steps of: A) providing an input gas stream (a) comprising n-butenes, B) feeding the input gas stream (a) comprising n-butenes and a gas containing at least oxygen into at least one oxidative dehydrogenation zone and oxidatively dehydrogenating n-butenes to butadiene, wherein a product gas stream (b) comprising butadiene, unconverted n-butenes, water vapour, oxygen, low-boiling hydrocarbons and high-boiling secondary components, optionally carbon oxides and optionally inert gases is obtained; Ca) cooling the product gas stream (b) by bringing into contact with a cooling medium in at least one cooling zone, the cooling medium being at least partly recycled and having an aqueous phase and an organic phase ; Cb) compressing the cooled product gas stream (b) which may have been depleted of high-boiling secondary components in at least one compression stage, giving at least one aqueous condensate stream (c1) and one gas stream (c2) comprising butadiene, n-butenes, water vapour, oxygen and low-boiling hydrocarbons, optionally carbon oxides and optionally inert gases; D) removing uncondensable and low-boiling gas constituents comprising oxygen and low-boiling hydrocarbons, with or without carbon oxides and with or without inert gases, as gas stream (d2) from the gas stream (c2) by absorbing the C4 hydrocarbons comprising butadiene and n-butenes in an absorbent, giving an absorbent stream laden with C4 hydrocarbons and the gas stream (d2), and then desorbing the C4 hydrocarbons from the laden absorbent stream, giving a C4 product gas stream (d1), E) separating the C4 product stream (d1) by extractive distillation with a butadiene-selective solvent into a stream (e1) comprising butadiene and the selective solvent and a stream (e2) comprising n-butenes; F) distilling the stream (e1) comprising butadiene and the selective solvent into a stream (f1) consisting essentially of the selective solvent and a stream (f2) comprising butadiene, charactersied in that step Cb) comprises at least two compression stages Cba) and at least two cooling stages Cbb), which are designed as quench columns, in the cooling stage, the cooling takes place by bringing into direct contact with the two phase cooling medium having an aqueous and an organic phase.