Chemistry of hydrocarbon compounds – Unsaturated compound synthesis – By alkyl transfer – e.g. – disproportionation – etc.
Reexamination Certificate
1999-04-01
2001-08-07
Knode, Marian C. (Department: 1764)
Chemistry of hydrocarbon compounds
Unsaturated compound synthesis
By alkyl transfer, e.g., disproportionation, etc.
C585S313000, C585S315000, C585S324000, C585S644000, C585S646000, C585S647000
Reexamination Certificate
active
06271430
ABSTRACT:
The present invention relates to a process for preparing propene by metathesis of olefins.
BACKGROUND OF THE INVENTION
1. Field of the Invention
Olefin metathesis (disproportionation) in its simplest form describes the reversible, metal-catalyzed rearrangement of olefins by cleavage and reformation of C═C double bonds. For example, olefins of the formulae R
1
—CH═CH—R
2
and R
3
—CH═CH—R
4
are reversibly reacted to form olefins of the formulae R
1
—CH═CH—R
3
and R
2
—CH═CH—R
4
. In the metathesis of acyclic olefins, a distinction is made between self-metathesis in which an olefin is converted into a mixture of two olefins having different molar masses and cross- or co-metathesis in which two different olefins react. An example of self-metathesis is the reaction of two molecules of propene to give ethene and 2-butene, as is performed, for example, by the Phillips triolefin process, see Hydrocarbon Processing, Volume 46, November 1967, No. 11, p. 232. An example of cross-metathesis is the reaction of propene and 1-butene to give ethene and 2-pentene. If one of the reactants is ethene, the reaction is customarily referred to as an ethenolysis.
The metathesis reactions are carried out in the presence of catalysts. Suitable catalysts for this purpose are, in principle, homogeneous and heterogeneous transition metal compounds, in particular those of transition groups VI to VIII of the Periodic Table of the Elements, as well as homogeneous and heterogeneous catalyst systems in which these compounds are present.
2. Description of the Prior Art
DE-A-19 40 433 discloses the metathesis of 1-butene with 2-butene to form propene and 2-pentene, with Re
2
O
7
/Al
2
O
3
being used as catalyst. The 2-pentene formed is reacted further with sodium hydride on potassium carbonate and ethene to give heptenes.
The metathesis of 1-butene and 2-butene to give propene and 2-pentene is mentioned in K. L. Anderson, T. D. Brown, Hydrocarbon Processing, Volume 55, August 1978, No. 8, pp. 119-122 as a secondary reaction in the synthesis of isoamylene.
EP-A-0 304 515 discloses a metathesis process for reacting 1-butene with 2-butene to give propene and pentenes, which is carried out in a reactive distillation apparatus using Re
2
O
7
/Al
2
O
3
as catalyst.
U.S. Pat. No. 3,526,676 discloses the metathesis of 1-butene with 2-butene to give propene and pentene. It is carried out over MoO
3
and CoO on Al
2
O
3
.
U.S. Pat. No. 3,785,957 discloses a process for the production of fuel having a high octane number. In this process, an olefinic fuel is disproportionated together with ethylene, the product is fractionated into a propylene stream, a butene stream, a C
5
- or C
5
-C
6
-olefin stream and a C
6+
or C
7+
fuel stream. The C
5
- or C
5
-C
6
-olefin stream is disproportionated with ethene over a WO
3
/SiO
2
fixed-bed catalyst to give propylene and butenes. The propylene obtained is disproportionated to form ethylene and butenes and the butenes are alkylated with isobutane.
U.S. Pat. No. 3,767,565 discloses a process for increasing the octane number of fuel in which a C
5
fraction of an olefinic fuel is reacted with ethylene in the presence of a catalyst comprising WO
3
/SiO
2
and MgO to form ethylene, propylene, n-butenes and isobutenes. The propylene obtained is disproportionated and the resulting n-butenes are alkylated with isobutane.
EP-A1-0 691 318 discloses an olefin metathesis process in which C
5
-olefins and ethylene are reacted in the presence of a catalyst to give mixed C
4
-olefins and propene. Thus, 2-methyl-2-butene is reacted with ethene to give isobutene and propene. A mixture of 2-pentenes and 2-methyl-2-butene is reacted to give a mixture of 1-butene, isobutene and propene.
A process for preparing propene in high yield by reacting 1-butene and 2-butene is not known.
A process for preparing propene in high yield by from 2-butene without use of a large excess of ethene is not known.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide a process for preparing propene in high yield from 1-butene and 2-butene. A further object of the present invention is to provide a process for preparing propene from 2-butene in which an excess of ethene does not have to be employed. A further object of the present invention is to provide a process for recovering propene from C
4
streams which are low in 1-butene using as little ethene as possible. A further object of the present invention is to provide a process for preparing propene and 1-butene from 2-pentene.
We have found that these objects are achieved by a process for preparing propene and 1-butene by reacting 2-pentene with ethene in the presence of a metathesis catalyst comprising at least one compound of a metal of transition group VIb, VIIb or VIII of the Periodic Table of the Elements. The 2-pentene is here preferably obtained by reacting 1-butene and 2-butene in the presence of the above metathesis catalyst to give propene and 2-pentene and separating off the 2-pentene.
The process of the present invention comprises 2 metathesis steps. In the first step, 1-butene and 2-butene are reacted to give propene and 2-pentene. In a second step, 2-pentene is then reacted with ethene to give 1-butene and propene. According to one embodiment of the invention, the 1-butene is returned to the first reaction step.
The net reaction is thus the reaction of 2-butene with ethene to form 2 molecules of propene. According to one embodiment of the invention, the reaction of 2-pentene with ethene formally requires only equimolar amounts of starting materials in order to obtain the products in high yield. Thus, in contrast to the reverse trioolefin process, the amount of ethene used can be kept small.
Both metathesis steps can be carried out as a reactive distillation, as is described below.
According to one embodiment of the invention, 1-butene and 2-butene can be used in the reaction as pure substances. According to another embodiment of the invention, the butenes are used in the form of a C
4
stream which originates, for example, from a cracker, in particular a stream cracker, or a refining process. This C
4
stream can comprise C
4
-alkanes in addition to the butenes. According to an embodiment of the invention, use is made of a C
4
stream which consists of raffinate II. Raffinate II is here a fraction comprising 1-butene, cis/trans-2-butene, isobutene and also n-butane and iso-butane. For example, raffinate II can comprise 80-85% by weight of olefins and 15-20% by weight of butanes, with, for example, 25-50% by weight of 1-butene, 30-55% by weight of 2-butene and at most 1-2% by weight of isobutene. According to an embodiment of the invention, the C
4
stream used has a butene content of from 20 to 100% by weight, preferably from 50 to 90% by weight, in particular from 70 to 90% by weight. The ratio of 1-butene to 2-butene is from 10:1 to 1:10, preferably from 3:1 to 1:3, in particular 2:1 to 1:2. According to one embodiment of the invention, the C
4
stream can contain small amounts of other hydrocarbons.
According to an embodiment of the invention, the starting material used can be any stream in which 1-butene and 2-butene are present. According to one embodiment of the invention, the 1-butene can originate from the synthesis of the present invention itself and be mixed with introduced 2-butene.
The C
4
feedstream used is preferably pre-purified before use in the process of the present invention in order to remove any traces of water, oxygen or oxygenates, sulfur or sulfur-containing compounds, nitrogen phosphor or halogens, especially chlorides which may be present. The removal is preferably carried out by passing the C
4
feedstream over absorber material such as zeolites or zeolite-analoguous phosphates, oxides of silicon, aluminium, titanium, zirconium having a high surface area, bleaching earth, clays, hydrotalcites, phosphates having a high surface area, active carbon and carbon molecular sieves as well as organic polymers and ion exchange resins, preferably NaX molecular sieve. The
Hohn Arthur
Schwab Peter
BASF - Aktiengesellschaft
Dang Thuan D.
Keil & Weinkauf
Knode Marian C.
LandOfFree
Preparation of propene does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Preparation of propene, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Preparation of propene will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2495087