Chemistry of hydrocarbon compounds – Unsaturated compound synthesis – By double-bond-shift isomerization
Reexamination Certificate
2002-10-11
2003-10-28
O'Sullivan, Peter (Department: 1621)
Chemistry of hydrocarbon compounds
Unsaturated compound synthesis
By double-bond-shift isomerization
C564S481000, C564S482000, C564S485000
Reexamination Certificate
active
06639118
ABSTRACT:
TECHNICAL FIELD
This invention relates to process technology for selective isomerization of vinylidene olefins to tri-substituted olefins, especially when the vinylidene olefins are in admixture with at least linear 1-olefins or remotely branched 1-olefins.
BACKGROUND
Mixtures of terminal olefins, commonly referred to as &agr;-olefins, are made commercially by ethylene chain growth of aluminum alkyls followed by displacement. Such products are mainly 1-olefins having the structure:
R—CH
2
—CH═CH2
wherein R is an aliphatic hydrocarbon group. These are also referred to as “vinyl olefins”. A substantial portion of the &agr;-olefins can be in the form of “vinylidene olefins” which have the structure:
wherein both R groups are aliphatic hydrocarbon groups.
One commercially important use of such &agr;-olefin mixtures is in the manufacture of aliphatic amines, especially alkyldimethyl amines, such as described in U.S. Pat. No. 4,024,189. In such processing, &agr;-olefin mixtures which contain vinyl olefins and vinylidene olefins are subjected to a selective isomerization step in which vinylidene olefins are converted to tri-substituted olefins. The entire mixture of olefins is then hydrobrominated to produce brominated alkanes. The brominated alkanes in turn are selectivity dehydrobrominated whereby secondary bromoalkanes are converted to olefins leaving the primary bromoalkanes substantially unaffected. Amination of the primary bromoalkanes results in production of the desired amines.
A number of isomerization catalysts capable of selectively isomerizing vinylidene olefins to tri-substituted olefins are known. See for example U.S. Pat. No. 3,686,250. While effective, such known catalysts often possess various shortcomings. For example, some of these catalysts are expensive, some may become inactivated or poisoned by impurities thus necessitating more frequent replenishment of the catalyst than would be desired, some of them tend to cause an undesirable amount of isomerization of linear 1-olefins to linear internal olefins, and some of them tend to cause dimerization of linear 1-olefins and of vinylidene olefins, which is also undesirable.
It would be of advantage if a new, efficient and commercially feasible way of selectively isomerizing vinylidene olefins to tri-substituted olefins could be found. It would be of particular advantage if this could be accomplished by use of a catalyst which is inexpensive, readily available, not susceptible to poisoning or inactivation under appropriate reaction conditions, that does not tend to excessively isomerize linear 1-olefins to linear internal olefins, and that does not tend to cause an excessive amount of dimer formation. This invention is believed to enable the achievement of most, if not all, of these advantages.
THE INVENTION
This invention is based in part on the discovery that vinylidene olefins can be rapidly and selectively isomerized to tri-substituted olefins by use of small quantities of anhydrous HBr. Surprisingly, by use of appropriate reaction conditions (e.g., absence of molecular oxygen whether in the form of air or otherwise, and free radical initiator), hydrobromination of the olefins can be avoided when conducting this selective isomerization.
Accordingly, pursuant to one of its embodiments, this invention provides a process of isomerizing at least one vinylidene olefin to at least one tri-substituted olefin, which process comprises contacting the mixture with anhydrous hydrogen bromide under anhydrous conditions and in the absence of molecular oxygen and free radical initiator, for a period of time sufficient to isomerize vinylidene olefin to tri-substituted olefin. In this process, little if any hydrobromination occurs. Usually, but not necessarily, the process of this embodiment is performed in the presence of at least one olefin that is not a vinylidene olefin or a tri-substituted olefin. In any case, the product recovered after the contacting is enriched in tri substituted olefin.
When the isomerization is performed in the presence of linear 1-olefins or remotely branched 1-olefins, the linear 1-olefins and the remotely branched 1-olefins are substantially unaffected. Thus in this case, the process is a selective isomerization process.
Accordingly, pursuant to another of its embodiments this invention provides a process for selective isomerization of at least one C
10-20
vinylidene olefin to tri-substituted olefin in an anhydrous hydrocarbon mixture comprised of (i) at least one C
10-20
vinylidene olefin, (ii) at least one C
10-20
linear 1-olefin or (iii) at least one C
10-20
remotely-branched 1-olefin, or (iv) a combination of (i), (ii) and (iii), and optionally (v) at least one C
10-20
internal olefin or (vi) at least one saturated hydrocarbon, or (vii) both of (v) and (vi), while leaving the 1-olefins substantially unaffected during the isomerization, which process comprises contacting the mixture with anhydrous hydrogen bromide under anhydrous conditions and in the absence of molecular oxygen and free radical initiator for a period of time sufficient to selectively isomerize vinylidene olefin to tri-substituted olefin. As noted above little if any hydrobromination occurs in the process.
Another embodiment of this invention provides an improvement in a process for producing amines from a mixture of &agr;-olefins comprising vinylidene olefins and 1-olefins, wherein:
a) the mixture of olefins is subjected to selective isomerization to convert vinylidene olefins to tri-substituted olefins;
b) the olefin mixture resulting from the isomerization is hydrobrominated to form bromoalkanes comprising 1-bromoalkanes and secondary bromoalkanes and/or tertiary bromoalkanes;
c) bromoalkanes resulting from the hydrobromination are selectively dehydrobrominated whereby 1-bromoalkanes are substantially unaffected and secondary and/or tertiary bromoalkanes present are converted to olefins;
d) bromoalkanes from c) are aminated with an amine having at least one replaceable hydrogen atom whereby the 1-bromoalkanes are converted to amine hydrobromides, and
e) amine hydrobromides from d) are converted into amines.
Such a process has been commercially used. A full description of process technology of this type is present for example in U.S. Pat. No. 4,024,189. The improvement pursuant to this invention comprises effecting said selective isomerization by contacting said mixture of &agr;-olefins with anhydrous hydrogen bromide under anhydrous conditions and in the absence of molecular oxygen and free radical initiator for a period of time sufficient to selectively isomerize vinylidene olefin to tri-substituted olefin. Use of such selective isomerization leaves the 1-olefin content of the mixture substantially unaffected and in addition, little if any hydrobromination occurs. In addition, since one of the steps of this process involves hydrobromination, a source of anhydrous HBr is already available for use in the selective isomerization. Thus, no additional raw materials are required to carry out the isomerization.
Other embodiments and features of this invention will still be further apparent from the ensuing description and appended claims.
FURTHER DETAILED DESCRIPTION
At the outset it is to be noted that the selective isomerization effected pursuant to this invention should not be confused with olefin hydrobromination processes in which anhydrous hydrogen bromide is added to an olefin mixture in order to produce brominated alkanes. A hydrobromination process is conducted in the presence of a substance functioning as a free radical initiator, and molecular oxygen such as in the form of air can function to initiate hydrobromination. Moreover, in hydrobromination processes a stoichiometric amount or an excess amount of hydrogen bromide relative to olefin is employed. In the isomerization process of this invention, air (and molecular oxygen in any mixture) is excluded from the reaction mixture, and no substance is introduced into the system to function as a free radical initiator. And, little if any hydrobromination occurs. Thus
Aplin J. Todd
Lyons Robert U.
McKinnie Bonnie G.
Parham Clinton R.
O'Sullivan Peter
Spielman, Jr. Edgar E.
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