Phase transfer process with catalyst recovery

Details Phase transfer process with catalyst recovery Phase transfer process with catalyst recovery

1999-12-17

2001-10-09

Wu, David W. (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Removing and recycling removed material from an ongoing...

C526S089000, C526S348200, C526S217000, C526S348600, C526S346000, C526S347100, C526S236000

Reexamination Certificate

active

06300431

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to phase transfer processes for conducting heterogeneous reactions in a liquid-liquid two-phase reaction system between reactants which are soluble in different ones of the two phases, using a phase transfer catalyst to complex with and transfer one of the reactants for reaction in the phase in which it is insoluble. More precisely this invention relates to the recovery and reuse of the phase transfer catalyst from the process waste stream for economic and environmental purposes.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 5,162,445, which is commonly assigned with the present application, discloses a phase transfer polymer modification process in which a polymer of an isoolefin and a para-alkyl styrene, is functionalized at a plurality of pendant sites by introducing a plurality of random electrophilic halo-benzylic sites. The copolymer is now reactive with nucleophilic reagents that displace the halogens and introduce new functional groups such as vinyl ester groups and/or phenyl ether groups. Since the polymer and the nucleophilic reagent are not soluble in a common reaction medium, the reaction requires the use of two liquid solvent phases which are at least partially miscible, and a phase transfer catalyst which is soluble in the same liquid phase as the nucleophilic reagent and forms a complex therewith which is soluble in the other liquid phase. The complex transfers into the other liquid phase where the nucleophilic reagent displaces halogen ions and replaces them with the desired pendant functionality, e.g., ester or ether groups.
Among the problems encountered with phase transfer processes is the high cost of phase transfer catalysts, the environmental problems caused by the discharge of chemical-containing process waste streams, and the problems involved in attempting to recover the phase transfer catalyst from the two phase reaction medium.
U.S. Pat. No. 4,754,089 discloses a phase transfer reaction process for the production of agricultural chemicals, pharmaceuticals and other specialty chemicals. The patent discloses an aqueous phase containing a first reactant and a phase transfer catalyst capable of complexing therewith isolated by means of a membrane present within the reactor from an immiscible organic liquid phase containing a second reactant which is soluble therein. The reactant-catalyst complex is capable of passing into or through the membrane to the organic liquid phase where the reactants react to release the phase transfer catalyst which returns to the first phase to complex with more of the first reactant and transfer it into or through the membrane to repeat the reaction cycle until either or both of the reactants are used up. Such membrane reactors are expensive and the reaction rate is reduced by the separation of the phases. However, such liquid phase separation does enable the recovery of the expensive phase transfer catalyst, after the reaction is completed, since the catalyst is isolated within the phase in which it is soluble, such as water.
It is desirable to be able to recover the expensive phase transfer catalyst from a conventional two phase integrated liquid-liquid reaction system, which does not require the use of a membrane reactor, and in which one of the liquids must be a non-polar liquid, such as a cycloalkane, in order to function as a good solvent for both the starting second reactant, such as a hydrocarbon-paramethyl styrene copolymer, and for the reaction product, as the copolymer is provided with additional pendant functional groups during the reaction. In such a system the other liquid cannot be pure water since water is completely immiscible with non-polar liquids, such as cycloalkanes, no phase integration occurs, and the reaction rate is very slow and unsatisfactory.
In conventional two phase integrated liquid-liquid reaction systems using polar and non-polar liquids which have the necessary degree of miscibility, the phase transfer catalyst remaining, after the reaction is completed, is contained within the waste effluent comprising miscible amounts of the polar and non-polar liquids and is lost.
SUMMARY OF THE INVENTION
The present invention relates to a novel process for the recovery of phase transfer catalyst after completion of the reaction from a liquid-liquid, two-phase reaction system. The phase transfer catalyst can then be re-used in another similar reaction system. The invention allows for the removal of chemical waste from the process waste stream, for ecological purposes without loss of the catalyst. This is enabled by the use of a water-soluble polar solvent as the first phase liquid and the use of a non-polar solvent, which is at least partially miscible with the first phase liquid, as the second phase liquid. The phase transfer catalyst and nucleophilic reactant are selectively soluble in the polar phase, and the electrophilic reactant and reaction product are selectively soluble in the non-polar solvent.
When the reaction is completed, the two-phase liquid reaction medium is washed with water to dissolve out the polar liquid and the phase transfer catalyst. The catalyst, along with chemicals such as salts and alkaline reagents, is separated from the aqueous polar solvent by means of a suitable membrane which recovers the catalyst phase, as the retentate, while allowing passage of the aqueous phase as the permeate.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is based upon the discovery that water-soluble phase transfer catalysts can be recovered or reclaimed from liquid-liquid two phase reaction systems, after completion of the reaction, through the use of polar and non-polar liquids for the two phases, respectively, which liquids are at least partially miscible with each other, the polar liquid being water-soluble and the non-polar liquid being water-insoluble.
In such a system, the final two-phase reaction mixture can be washed with water to dissolve the polar solvent and the soluble phase transfer catalyst into the aqueous phase which is incompatible or immiscible with the non-polar phase containing the formed reaction product. The phases are separated, and the phase transfer catalyst is removed from the aqueous polar solvent waste stream by use of a commercially-available membrane, preferably such as a polyamide membrane, which retains the phase transfer catalyst, and any other chemicals such as alkaline agents and salts, while allowing passage of the aqueous polar liquid waste stream. The recovered phase transfer catalyst can be recycled back into a similar phase transfer system thereby reducing the overall cost of the catalyst required for such system.
A preferred phase transfer process that can be adapted in accordance with the present invention is one disclosed in commonly-assigned U.S. Pat. No. 5,162,445, incorporated fully herein by reference, for US patent practices only, for the preparation of functionalized hydrocarbon para-alkylstyrene copolymers to which reactive pendent radicals, such as vinyl ester and/or ether groups, are attached during the phase transfer process. Phase transfer is necessary in cases where the nucleophilic reactant is not soluble in the non-polar solvent for the copolymer, and requires its own polar solvent which must be at least partially miscible with the nonpolar solvent to form a liquid-liquid two phase system. The phase transfer catalyst is soluble in the polar solvent and complexes with the nucleophilic reactant to form a complex that is soluble in the non-polar phase to transfer the nucleophilic reactant into the non-polar phase for ion-exchange with the electrophilic sites on the copolymer. The separated phase transfer catalyst is dissolved back into the polar phase and complexes with additional nucleophilic reactant, to repeat the phase transfer reaction cycle.
Suitable polar liquids for use in the phase transfer process are liquids which are at least partially soluble in or miscible with the non-polar liquid solvent for the reaction product, such as a soluble functionalized co-polymer, and are wa

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