Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2002-08-28
2004-05-04
Solola, Taofiq A. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
Reexamination Certificate
active
06730815
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a method of producing glycol ethers.
2. Description of Related Art
Glycol ethers, which are also commonly known as glymes, are used as aprotic solvents in a variety of applications. Glymes can be produced by a variety of methods, but are conventionally produced in commercial quantities via the Williamson synthesis or via a reaction that involves the cleavage of epoxides.
In the Williamson synthesis, a monoalkyl polyalkylene glycol is treated with a base or an alkali metal, typically molten sodium, to form an alkoxide ion, which is then reacted with an alkyl halide such as methyl chloride to form the glyme. The by-products from the Williamson synthesis are hydrogen gas and a salt.
Although the Williamson synthesis is one of the conventional methods of producing glymes on a commercial scale, the process presents several disadvantages. For example, the Williamson synthesis requires the use of costly and potentially hazardous starting materials. It generates hydrogen gas as a by-product, which presents safety and handling issues. Moreover, for every mole of glyme produced, the process generates a mole of salt as a by-product, which presents treatment and disposal issues. Furthermore, the Williamson synthesis proceeds at a relatively slow rate.
The other conventional method for commercially producing glymes involves the cleavage of epoxides in presence of a low molecular weight ether and a Lewis acid catalyst. This reaction enables the insertion of oxacycloalkanes into chain-type ethers. A typical reaction involves dimethyl ether and ethylene oxide with catalytic amount of boron trifluoride or boron trifluoride dimethyletherate to yield, among other ether co-products, monoethyleneglycol dimethylether.
One of the principle disadvantages of the cleavage reaction of epoxides is that it is not particularly selective. Insertion of a specific number of oxacycloalkane units is difficult to control. Therefore, the final product consists of a mixture of glymes. It is necessary to separate the reaction mixture by complex distillation techniques or by other means in order to obtain pure glymes, which adds time and complexity to the manufacturing process.
BRIEF SUMMARY OF THE INVENTION
The present invention provides a method of producing glymes that overcomes the disadvantages of both the Williamson synthesis and the cleavage reaction of epoxides. The method according to the invention comprises contacting a glycol with a monohydric alcohol in the presence of a polyperfluorosulfonic acid resin catalyst under conditions effective to produce the glyme. The starting materials used in the method according to the invention are commercially readily available, not expensive or hazardous, and the catalyst used in the reaction can be recovered, regenerated, and reused. The method according to the invention does not generate hydrogen gas or salt, it proceeds at a relatively rapid rate, and it produces a single glyme.
The foregoing and other features of the invention are hereinafter more fully described and particularly pointed out in the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the present invention may be employed.
DETAILED DESCRIPTION OF THE INVENTION
Glymes are produced in accordance with the method of the invention by contacting a glycol with a monohydric alcohol in the presence of a polyperfluorosulfonic acid resin catalyst under conditions effective to produce the glyme. A wide range of glymes can be produced in accordance with the invention, with the resulting glyme being dependent upon the glycol and monohydric alcohol selected for use in the reaction.
For example, ethylene glycol and methanol react in accordance with the method of the invention to produce ethylene glycol dimethyl ether (monoglyme). These two reactants also react to produce ethylene glycol monomethyl ether, which is also known as 2-methoxyethanol or “Methyl CELLOSOLVE®”. CELLOSOLVE® is a trademark of the Dow Chemical Company used in connection with a class of ethylene glycol monoalkyl ethers.
Ethylene glycol and ethanol react in accordance with the method of the invention to produce ethylene glycol diethyl ether (ethyl glyme). These two reactants also react to produce ethylene glycol monoethyl ether, which is also known as 2-ethoxyethanol or “Ethyl CELLOSOLVE®”.
Diethylene glycol and methanol react in accordance with the method of the invention to produce diethylene glycol dimethyl ether (diglyme). These two reactants also produce diethylene glycol monomethyl ether, which is also known as methoxyethoxy ethanol or “Methyl CARBITOL®”. CARBITOL® is a trademark of the Dow Chemical Company used in connection with a class of diethylene glycol monoalkyl ethers.
Diethylene glycol and ethanol react in accordance with the method of the invention to produce diethylene glycol diethyl ether (ethyl diglyme). These two reactants also produce diethylene glycol monoethyl ether, which is also known as “Ethyl CARBITOL®”.
Diethylene glycol and 1-butanol react in accordance with the method of the invention to produce diethylene glycol dibutyl ether (butyl diglyme). These two reactants also produce diethylene glycol monobutyl ether, which is also known as “Butyl CARBITOL®”.
Triethylene glycol and methanol react in accordance with the method of the invention to produce triethylene glycol dimethyl ether (triglyme). These two reactants also produce triethylene glycol monomethyl ether, which is also known as methoxytriglycol.
Tetraethylene glycol and methanol react in accordance with the method of the invention to produce tetraethylene glycol dimethyl ether (tetraglyme). These two reactants also produce tetraethylene glycol monomethyl ether, which is also known as methoxytetraglycol. It will be appreciated that other glymes can be produced in accordance with the method of the invention simply be selecting other glycols and monohydric alcohols.
The starting materials used in the reaction, being glycols and monohydric alcohols, are generally inexpensive and readily available. These starting materials do not present significant toxicity and handling problems, especially when compared to the starting materials used in the Williamson synthesis.
Preferably, a molar excess of the monohydric alcohol is used in the reaction. Typically, a molar excess of about 3 to about 5 moles of monohydric alcohol is used in the reaction for every mole of glycol.
The polyperfluorosulfonic acid resin catalyst used in the method of the invention is a Bronsted acid, and not a Lewis acid. Suitable polyperfluorosulfonic acid resins are available from E.I. Du Pont de Nemours and Company under the NAFION® trademark. These polyperfluorosulfonic acid resins are believed to be copolymers of tetrafluoroethylene and perfluoro-3,6-dioxa-4-methyl-7-octenesulfonyl fluoride, which have been converted to the proton (H
+
) form. They are available in flake, pellet, powder, film, and solution form. The polyperfluorosulfonic acid resin catalyst is preferably used at about 0.5 to about 2.0 equivalents per 100 moles of glycol, with about 1.0 equivalent being most preferred during the preparation of monoglyme. The polyperfluorosulfonic acid resin catalyst is nearly solubilized during the reaction, and appears to act as a homogeneous catalyst.
In accordance with the preferred embodiment of the invention, the glycol, the monohydric alcohol, and the polyperfluorosulfonic acid resin catalyst are combined in a suitable reactor vessel under agitation and heated. Due to the high vapor pressures of the reactants and the products formed during the reaction, the reactor vessel must be capable of handling pressures as high as 1,000 psig (the term “psig” means pounds per square inch above atmospheric pressure, i.e., gauge pressure). A conventional autoclave is a preferred reactor vessel for use in accordance with the invention.
An elevated reaction temperature allows
Baimbridge Charles L.
Bolomey Pascal V.
Love James D.
Ferro Corporation
Rankin, Hill Porter & Clark LLP
Solola Taofiq A.
LandOfFree
Method of producing glycol ethers does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of producing glycol ethers, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of producing glycol ethers will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3194214