Method for obtaining pure 1,3-butadiene

Patent metadata

Field	Value
Publication number	US-11034631-B2
Application number	US-201816475566-A
Country	US
Kind code	B2
Filing date	Jan 24, 2018
Priority date	Jan 25, 2017
Publication date	Jun 15, 2021
Grant date	Jun 15, 2021

Abstract

Process for isolating pure 1,3-butadiene from a crude C 4 fraction by extractive distillation using a selective solvent, wherein (a) the crude C 4 fraction is introduced into a predistillation column, a first low boiler fraction comprising C 3 -hydrocarbons is taken off as overhead stream, a gaseous C 4 fraction is taken off as side stream and a first high boiler fraction is taken off as bottom stream, (b) the gaseous C 4 fraction is brought into contact with a selective solvent in at least one extraction column, giving an overhead fraction comprising butanes and butenes and a bottom fraction comprising 1,3-butadiene and selective solvent, (c) crude 1,3-butadiene is desorbed from the bottom fraction in at least one stripping column, with a stripped selective solvent being obtained and the stripped selective solvent being recirculated to the extraction column, and (d) at least part of the crude 1-3-butadiene is fed to a pure distillation column and a second high boiler fraction is separated off and a gaseous purge stream is taken off. Gaseous purge streams from the columns which are necessary in order to keep the concentration of molecular oxygen below a predetermined concentration limit are consolidated with output streams which are in any case provided for discharging other components in the process. The recirculation of the second high boiler fraction to a lower section of the predistillation column creates a further degree of freedom in operation of the pure distillation column.

First claim

The invention claimed is:

1. A process for isolating pure 1,3-butadiene from a crude C 4 fraction by extractive distillation using a selective solvent, the process comprising:
a) introducing a liquid crude C 4 fraction into an inflow region of a predistillation column, which is divided in a middle section by a dividing wall aligned essentially in a longitudinal direction of the predistillation column into the inflow region and a side offtake region, taking off a first low boiler fraction comprising C 3 -hydrocarbons as an overhead stream, taking off a gaseous C 4 fraction as a side stream from the side offtake region and taking off a first high boiler fraction as a bottom stream,
b) bringing the gaseous C 4 fraction into contact with a selective solvent in at least one extraction column, to obtain an overhead fraction comprising butanes and butenes and a bottom fraction comprising 1,3-butadiene and the selective solvent,
c) desorbing crude 1,3-butadiene from the bottom fraction in at least one stripping column, thereby obtaining selective solvent from the bottom fraction and recirculating the selective solvent which was obtained from the bottom fraction in the at least one stripping column to the at least one extraction column, and
d) feeding at least part of the crude 1-3-butadiene to a pure distillation column, separating off a second high boiler fraction, taking off a gaseous purge stream, obtaining the pure 1,3-butadiene from a vapor fraction from the pure distillation column, and recirculating the second high boiler fraction to a lower section of the predistillation column below the inflow region for the liquid crude C 4 fraction.

2. The process of claim 1 , wherein the gaseous purge stream from the pure distillation column is conveyed together with a vapor from the predistillation column through an overhead condenser of the predistillation column.

3. The process of claim 1 , wherein the crude 1,3-butadiene is brought into contact with the selective solvent in an after-scrubbing zone.

4. The process of claim 2 , wherein the desorbed crude 1,3-butadiene is partially condensed, a condensed part of the crude 1,3-butadiene is conveyed as runback into the at least one stripping column and/or into an after-scrubbing zone and the remaining part of the crude 1,3-butadiene after condensation is fed in gaseous form to the pure distillation column.

5. The process of claim 1 ,
wherein the gaseous C 4 fraction is brought into contact with the selective solvent in an extraction column and in an upper section of an extraction and prestripping column on a first side of a dividing wall running essentially in a longitudinal direction of the extraction and prestripping column, and
the crude 1,3-butadiene is desorbed from the bottom fraction in a lower section below the dividing wall of the extraction and prestripping column and from a stripping column.

6. The process of claim 5 , wherein an after-scrubbing zone is an upper section of the extraction and prestripping column separated off on a second side of the dividing wall running essentially in a longitudinal direction of the extraction and prestripping column.

7. The process of claim 2 , wherein a gas comprising C 4 -acetylenes is also desorbed from the bottom fraction.

8. The process of claim 7 , wherein the gas comprising C 4 -acetylenes is taken off as a side offtake stream from the at least one stripping column.

9. The process of claim 7 , wherein the gas comprising C 4 -acetylenes is diluted with uncondensed constituents of vapor from the at least one extraction column.

10. The process of claim 1 , wherein the liquid crude C 4 fraction comprises
from 15 to 85% by weight of 1,3-butadiene,
from 4 to 13% by weight of butanes,
from 24 to 64% by weight of butanes,
from 0.2 to 0.5% by weight of C 4 -acetylenes,
from 0.01 to 2.0% by weight of C 3 -hydrocarbons and
from 0.01 to 0.5% by weight of C 5+ -hydrocarbons.

11. The process of claim 1 , wherein the selective solvent comprises at least 80% by weight of N-methylpyrrolidone.

Assignees

• Basf Se

Inventors

• Heida Bernd
• Keller Tobias
• Weidert Jan-Oliver

Classifications

• C07C7/08 Primary

  by extractive distillation · CPC title

• C07C7/04 Primary

  by distillation · CPC title

• B01D3/14

  Fractional distillation {or use of a fractionation or rectification column} · CPC title

• B01D3/4211

  of columns · CPC title

• C07C11/167

  1, 3-Butadiene · CPC title