Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2000-06-21
2001-11-27
Solola, T. A. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
active
06323350
ABSTRACT:
This application is A 371 of PCT/US98/26816 filed Dec. 17, 1998.
This invention pertains to a liquid phase process for the direct oxidation of olefins, such as propylene, by oxygen to olefin oxides, such as propylene oxide.
Olefin oxides, such as propylene oxide, are used to alkoxylate alcohols to form polyether polyols, such as polypropylene polyether polyols, which find significant utility in the manufacture of polyurethanes and synthetic elastomers. Olefin oxides are also important intermediates in the manufacture of alkylene glycols, such as propylene glycol and dipropylene glycol, and alkanolamines, such as isopropanolamine, which are useful as solvents and surfactants.
Propylene oxide is produced commercially via the well-known chlorohydrin process wherein propylene is reacted with an aqueous solution of chlorine to produce a mixture of propylene chlorohydrins. The chlorohydrins are dehydrochlorinated with an excess of alkali to produce propylene oxide.
Gas phase processes for the direct oxidation of olefins by molecular oxygen to the corresponding olefin have also been described in several publications.
Also liquid phase processes for the direct oxidation of olefins have been described in several publications.
DD-A-212 961 discloses a process for the oxidation of olefins containing 3 to 20 carbon atoms with oxygen-containing gases in liquid phase in the presence of transition metal complexes. The catalyst preferably is a mixture of a Cu(ll) complex compound and a complex compound of molybdenum or wolfram. The oxidation is carried out at a temperature of from 20° C. to 200° C. at atmospheric pressure or at an elevated pressure of 2 to 10 MPa. Recommended solvents are benzene, chlorobenzene, o-dichlorobenzene, nitrobenzene or bromobenzene. The desired products are obtained by fractional distillation of the product mixture.
U.S. Pat. No. 3,238,229 relates to a process for preparing olefin oxides wherein an olefinically unsaturated hydrocarbon is oxidized with molecular oxygen at a temperature of from 50° C. to 400° C. and a pressure of from 0.5 to 150 atmospheres in halogenated benzenes, such as o-dichlorobenzene, as a solvent. An oxygen-containing gas may be introduced into the olefin-solvent mixture in a continuously stirred reactor incrementally or continuously. The desired products are recovered from the reactor effluent by conventional separation techniques, such as distillation.
U.S. Pat. No. 3,350,418 discloses a liquid phase oxidation of propene with molecular oxygen in an ester, such as a fully esterified polyacyl ester, as a solvent. The oxidation is followed by a complex separation scheme.
U.S. Pat. No. 3,071,601 relates to the production of propylene oxide wherein propylene is oxidized with elemental oxygen in the liquid phase in a hydrocarbon solvent at elevated pressure and temperature in the presence of a catalyst.
U.S. Pat. No. 3,428,658 relates to the production of propylene oxide wherein propylene is reacted with oxygen in the presence of a solvent mixture comprising a saturated cyclic hydrocarbon and a chlorinated benzene. The reaction is carried out in a stainless-steel shaker tube. The U.S. patent mentions that better results are achieved when additional oxygen or oxygen-containing gas is added in small increments after the reaction temperature has been reached, since the reaction under oxygen-starved conditions tends to prevent degradation of the olefin oxide to by-products thereof.
U.S. Pat. No. 3,716,562 relates to the preparation of olefin oxides by the cooxidation of olefins and aldehydes with oxides in a liquid phase. A glass microreactor is used wherein the oxygen is continuously fed.
The higher the percentage of solvent that is in the liquid phase processes for the direct oxidation of olefins, the higher are the costs for the separation of the solvent from the product mixture, purification and recycling of the solvent. Considering that the production of olefin oxides, such as propylene oxide, from the corresponding olefin is carried out on a very large scale, it would be desirable to provide a liquid phase process for preparing an olefin oxide from an olefin which requires a decreased amount of solvent.
The present invention relates to a liquid phase process for preparing an olefin oxide from an olefin in a cascade of two or more reactors, in a baffled tank reactor or in a plug flow reactor which process comprises the steps of
a) contacting the olefin in a solvent with oxygen or an oxygen-containing gas in a first reactor of the reactor cascade or in a first stage of the baffled tank reactor or of the plug flow reactor, thereby producing a mixture comprising olefin oxide, non-converted olefin, solvent and by-products and
b) transferring at least a portion of the mixture obtained in step a) to a second reactor of the reactor cascade or to a second stage of the baffled tank reactor or plug flow reactor, adding an additional amount of i) oxygen or an oxygen-containing gas and/or ii) olefin to the mixture and continuing the reaction.
It has been surprisingly found that in the process of this invention wherein A) a cascade of two or more reactors is used and oxygen or an oxygen-containing gas and/or olefin is fed to several reactors or B) a baffled tank reactor or a plug flow reactor is used and oxygen or an oxygen-containing gas and/or olefin is fed in several portions, to several feed points of the reactor, the required amount of solvent per unit of produced olefin oxide can be substantially reduced. In large scale processes for olefin oxide production, this leads to a considerable reduction in production costs.
Ethylene can be employed in the process of this invention, however the olefin preferably contains three or more carbon atoms. Undiluted olefins or mixtures thereof are preferably used, however also olefin feedstock can be used which contains up to 50 weight percent of saturated compounds. Monoolefins are preferred, but compounds containing two or more olefins, such as dienes, can also be used. The olefins can be aliphatic or alicyclic. The olefin can be a simple hydrocarbon containing only carbon and hydrogen atoms; or alternatively, the olefin can be substituted at any of the carbon atoms with an inert substituent. The term “inert”, as used herein, requires the substituent to be non-reactive in the process of this invention. Suitable inert substituents include, but are not limited to, halides, ether, ester, alcohol, or aromatic moieties, preferably chloro, C
1-12
-ether, ester, or alcohol moieties or C
6-12
-aromatic moieties. Non-limiting examples of olefins which are suitable for the process of this invention include propylene, 1-butene, 2-butene, 2-methylpropene, 1-pentene, 2-pentene, 2-methyl-1-butene, 2-methyl-2-butene, 1-hexene, 2-hexene, 3-hexene, and analogously, the various isomers of methylpentene, ethylbutene, heptene, methylhexene, ethylpentene, propylbutene, the octenes, including preferably 1-octene, and other higher analogues of these; as well as butadiene, cyclopentadiene, dicyclopentadiene, styrene, ∝-methylstyrene, divinylbenzene, allyl chloride, allyl alcohol, allyl ether, allyl ethyl ether, allyl butyrate, allyl acetate, allyl benzene, allyl phenyl ether, allyl propyl ether, and allyl anisole. Preferably, the olefin is an unsubstituted or substituted C
3-12
-olefin, more preferably, an unsubstituted or substituted-C
3-10
-olefin. Most preferably, the olefin is propylene. Propylene feedstock can be used which contains up to 50 weight percent propane, however, the use of undiluted propylene is preferred. Accordingly, the subsequent detailed description of the present invention often relates to a process wherein propylene is used as a starting material, although the process of the present invention is not limited thereto.
The quantity of olefin employed in the process can vary over a wide range provided that the corresponding olefin oxide is produced. Generally, the quantity of olefin depends upon the specific process features, including, for example, the design of the reactor, the specific olefin, and economic and
Lindner Joerg
Taeuber Wolfgang
Wertgen Hans-Juergen
Solola T. A.
The Dow Chemical Company
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