Process for preparing 1,3-butadiene from n-butenes by oxidative dehydrogenation

Patent metadata

Field	Value
Publication number	US-9963408-B2
Application number	US-201415033203-A
Country	US
Kind code	B2
Filing date	Oct 27, 2014
Priority date	Oct 30, 2013
Publication date	May 8, 2018
Grant date	May 8, 2018

Abstract

A process for preparing butadiene from n-butenes, comprising the steps of:
absorbing C4 hydrocarbons comprising butadiene and n-butenes, obtained from oxidative dehydrogenation of n-butenes, in an aromatic hydrocarbon solvent as an absorbent and removing uncondensable and low-boiling gas constituents comprising oxygen, low-boiling hydrocarbons, any carbon oxides, aromatic hydrocarbon solvent and any inert gases as gas stream d2, 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; and at least partly recycling the gas stream d2 as cycle gas stream a2 into the oxidative dehydrogenation zone, wherein the content of aromatic hydrocarbon solvent in the cycle gas stream a2 is limited to less than 1% by volume.

First claim

The invention claimed is:

1. A process for preparing butadiene from n-butenes, comprising the steps of:
A) providing an input gas stream a1 comprising n-butenes;
B) feeding the input gas stream a1 comprising n-butenes, an oxygenous gas and an oxygenous cycle gas stream a2 into at least one oxidative dehydrogenation zone and oxidatively dehydrogenating n-butenes to butadiene, giving a product gas stream b comprising butadiene, unconverted n-butenes, steam, oxygen, low-boiling hydrocarbons and high-boiling secondary components, with or without carbon oxides and with or without inert gases;
Ca) cooling the product gas stream b and optionally at least partly removing high-boiling secondary components and steam, giving a product gas stream b′;
Cb) compressing and cooling the product gas stream b in at least one compression and cooling stage, giving at least one aqueous condensate stream c1 and one gas stream c2 comprising butadiene, n-butenes, steam, oxygen and low-boiling hydrocarbons, with or without carbon oxides and with or without inert gases;
Da) absorbing the C4 hydrocarbons comprising butadiene and n-butenes in an aromatic hydrocarbon solvent as an absorbent and removing uncondensable and low-boiling gas constituents comprising oxygen, low-boiling hydrocarbons, any carbon oxides, aromatic hydrocarbon solvent and any inert gases as gas stream d2 from the gas stream c2, 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; and
Db) at least partly recycling the gas stream d2 as the oxygenous cycle gas stream a2 into the oxidative dehydrogenation zone,
wherein a content of aromatic hydrocarbon solvent in the oxygenous cycle gas stream a2 is limited to less than 0.2% by volume by
(a) contacting the gas stream d2 which leaves the removal stage Da) with a liquid absorbent for the aromatic hydrocarbon solvent in a further column,
(b) contacting the gas stream d2 which leaves the removal stage Da) with a solid adsorbent which adsorbs the aromatic hydrocarbon solvent,
(c) contacting the gas stream d2 which leaves the removal stage Da) with a heat exchanger in the form of a condenser, with at least partial deposition of the aromatic hydrocarbon solvent present in stream d2 as a liquid phase through cooling,
(d) conducting a thermal or catalytic post combustion of the aromatic hydrocarbon solvent, or
(e) providing, in the absorption column used in step Da), an apparatus which reduces the entrainment of liquid constituents from the absorption column into the gas stream d2.

2. The process according to claim 1 , wherein the aromatic hydrocarbon solvent used as the absorbent in step Da) is selected from the group consisting of toluene, o-, m-, p-xylene, mesitylene, monoethylbenzene, diethylbenzene, triethylbenzene, monoisopropylbenzene, diisopropylbenzene, triisopropylbenzene and mixtures thereof.

3. The process according to claim 2 , wherein the aromatic hydrocarbon solvent is mesitylene.

4. The process according to claim 1 , wherein the proportion of the cycle gas stream a2 is 10 to 70% by volume, based on the sum total of all the gas streams fed into the oxidative dehydrogenation zone.

5. The process according to claim 1 , which further comprises the following additional steps of:
E) separating the C 4 product stream d1 by extractive distillation with a butadiene-selective solvent into a stream e1 comprising butadiene and the selective so vent and a stream e2 comprising n-butenes:
F) distilling the stream e2 comprising butadiene and the selective solvent to give a stream f1 comprising the selective solvent and a stream f2 comprising butadiene.

6. The process according to claim 1 , wherein step Da) comprises steps Daa) to Dac):
Daa) absorbing the C 4 hydrocarbons comprising butadiene and n-butenes in the aromatic hydrocarbon solvent as an absorbent, giving an absorbent stream laden with C 4 hydrocarbons and the gas stream d2,
Dab) removing oxygen from the absorbent stream laden with C 4 hydrocarbons from step Daa) by stripping with an uncondensable gas stream, and
Dac) desorbing the C 4 hydrocarbons from t be laden absorbent stream, giving a C 4 product gas stream d1 consisting essentially of C 4 hyrocarbons.

Assignees

• Basf Se

Inventors

• Grüne Philipp
• Hammen Oliver
• Schmitt Christine
• Balegedde Ramachandran Ragavendra Prasad
• Josch Jan Pablo
• Walsdorff Christian

Classifications

• C07C7/08

  by extractive distillation · CPC title

• B01J23/8878

  Chromium · CPC title

• C07C5/48 Primary

  with oxygen as an acceptor · CPC title

• B01J2523/845

  Cobalt · CPC title

• B01J2523/68

  Molybdenum · CPC title