Process for the production of 1, 2-butadiene

Details Process for the production of 1, 2-butadiene Process for the production of 1, 2-butadiene

1999-08-17

2001-01-16

Yildirim, Bekir L. (Department: 1764)

Chemistry of hydrocarbon compounds

Purification, separation, or recovery

By plural serial diverse separations

C203S009000, C208S347000

Reexamination Certificate

active

06175049

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for the production of 1,2-butadiene from a polymerization-inhibitor-containing C
4
hydrocarbon fraction by fractional distillation.
2. Description of the Prior Art
It is not possible to isolate 1,3-butadiene from a mixture of C
4
hydrocarbons by simple distillation, since all components boil in a very narrow temperature range and, furthermore, some form azeotropic mixtures. For this reason, 1,3-butadiene is currently produced on an industrial scale by the extractive distillation principle. In this process, a solvent is fed in an extraction column to a gaseous C
4
hydrocarbon mixture from naphtha or middle distillate pyrolysis. This solvent primarily dissolves 1,3-butadiene, which is selectively extracted as a result. The 1,3-butadiene-containing solvent thus remains in the bottom of the column, while the residual C
4
fraction distils off overhead. As solvent, use is made, for example, of sulfolane, N-methylpyrrolidone (NMP), dimethylformamide, acetonitrile or dimethylacetamide. To avoid the unwanted thermal polymerization of 1,3-butadiene in the course of the extractive distillation, polymerization inhibitors are added both to the feed fraction of the extractive distillation and to the bottom product of solvent and 1,3-butadiene. These polymerization inhibitors are, for example, 4-tert-butylcatechol (TBC). In the course of the subsequent separation operations for purifying the 1,3-butadiene, distillation residues of C
4
and C
5
hydrocarbons which comprise these polymerization inhibitors, sometimes in considerable amounts, therefore arise. It is generally customary to destroy distillation residues or bottom products of this type from the purification of 1,3-butadiene. This is generally performed by combustion via a flare or by other thermal utilization. In this procedure, valuable hydrocarbons which are suitable for material utilization are lost.
DD 246 009discloses a process for working up such distillation residues which arise in the extractive distillation of C
4
hydrocarbon fractions for the production of 1,3-butadiene and comprise dissolved polymerization inhibitors. In this process, the inhibitor/C
4
hydrocarbon mixture is firstly introduced into a preferably aromatics-containing hydrocarbon mixture whose initial boiling point is 50-200K higher than the boiling point of the C
4
hydrocarbon fraction and is then thermally treated. In this case the temperature is set so that the C
4
hydrocarbon fraction evaporates and can thus be completely removed. In the bottom of the column accordingly remains a mixture of the higher-boiling, preferably aromatic hydrocarbons, in particular C
8
- and C
9
aromatics, the high boilers, the contaminants and the polymerization inhibitor. This process thus makes it possible to separate off the C
4
hydrocarbon fraction as such from the contaminants and high boilers and also, in particular, from the inhibitor. The total C
4
hydrocarbon fraction is passed to material or caloric utilization; further fractionation into the various components is not described.
However, it is desirable to produce the individual compounds from C
4
hydrocarbon fractions of this type. Especially the C
4
component 1,2-butadiene is increasingly gaining importance and is used as polymerization regulator in the preparation of synthetic rubber from 1,3-butadiene. 1,2-butadiene is also a synthesis building block of interest for the production of perfumes. Thus, the reaction of 1,2-butadiene with acetaldehyde gives cis-3-hexenol, i.e. leaf alcohol.
The object of the present invention was thus to provide a process which enables the production of pure 1,2-butadiene in a simple manner from C
4
hydrocarbon fractions.
SUMMARY OF THE INVENTION
This object is achieved by a process for the production of 1,2-butadiene in which a polymerization-inhibitor-containing C
4
hydrocarbon fraction is subjected to at least one fractional distillation.
DESCRIPTION OF THE PREFERRED EMBODIMENT
It is surprising that the separation and production of pure 1,2-butadiene from C
4
hydrocarbon mixtures succeeds without prior separation of the polymerization inhibitor and without other additives of other higher-boiling hydrocarbon fractions. Owing to the considerable content of inhibitor in the starting mixture to be distilled 3and the further concentration of this inhibitor in the course of the fractional distillation it was to be expected that the inhibitor would increasingly crystallize out, since the solubility of inhibitors in hydrocarbon mixtures is only very low. In isopentane, the polymerization inhibitor TBC dissolves only to 0.5%, for example, at 20° C. Such a crystallization out of the inhibitor should lead to a coating of the distillation column which would be accompanied by column blockages and thus impairment of the separation efficiency. However, unexpectedly, none of these phenomena occur in the process according to the invention.
The feed stream for the process according to the invention is customarily obtained by taking off the polymerization-inhibitor-containing C
4
hydrocarbon fraction from the bottom of a distillation column or at a suitable plate in the stripping section of a distillation column which is producing 1,3-butadiene at the top as pure product.
This polymerization-inhibitor-containing C
4
hydrocarbon fraction has a boiling range from −15° C. to +45° C. In addition to low-boiling C
4
components, such as butanes, 1,3-butadiene, butenes and C
4
acetylenes, it also contains the wanted material of value 1,2-butadiene. As high-boiling compounds, C
5
hydrocarbons, such as 3-methyl-1-butene and isopentane are found in the C
4
hydrocarbon fraction. In addition, in the C
4
hydrocarbon mixture, polymerization inhibitors such as the abovementioned TBC are always present. Depending on the distillation technique used to purify the 1,3-butadiene, the concentrations of the individual components in the C
4
hydrocarbon mixture fluctuate within a broad range. Usually,
0-5% by weight of saturated C
4
hydrocarbons,
5-30% by weight of butenes,
10-55% by weight of 1,3-butadiene,
0.1-2% by weight of C
4
acetylenes,
20-65% by weight of 1,2-butadiene,
5-20% by weight of C
5
hydrocarbons and
0.2-2% by weight of polymerization inhibitor are present in the polymerization-inhibitor-containing C
4
hydrocarbon mixture. A content of low-boilers or high-boilers deviating from this does not interfere in the process according to the invention, but may require adaptations of the distillation conditions (temperature, reflux ratio) and the distillation equipment (column diameter, number of theoretical plates). Preferably, in the process according to the invention, use is made of C
4
hydrocarbon mixtures in which
0-1% by weight of saturated C
4
hydrocarbons,
10-20% by weight of butenes,
20-55% by weight of 1,3-butadiene,
0.1-1% by weight of C
4
acetylenes,
30-65% by weight of 1,2-butadiene,
5-10% by weight of C
5
hydrocarbons and
0.2-1% by weight of polymerization inhibitor are present.
According to an embodiment of the process according to the invention, a procedure is carried out such that
a) in a first fractional distillation of the polymerization-inhibitor-containing C
4
hydrocarbon fraction, the low-boiling C
4
hydrocarbons are taken off as first overhead product and a fraction which comprises 1,2-butadiene, the C
5
hydrocarbons and the polymerization inhibitor is taken off as first bottom product and
b) the first bottom product is fed to a second fractional distillation and there the 1,2-butadiene is produced as second overhead product and the C
5
hydrocarbons and the polymerization inhibitor are produced as second bottom product. In this embodiment, the first overhead product comprises the low-boiling C
4
hydrocarbons such as 1,3-butadiene and the butenes. The first bottom product, which comprises the wanted 1,2-butadiene, the C
5
hydrocarbons and the polymerization inhibitor, is virtually free of the low-boiling C
4
hydrocarbons. The second overhead product is

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