Organic Process Research & Development 2003, 7, 551−552
Conversion of Pollutants in Dilute Aqueous Waste Streams to Useful Products:
a Potential Method Based on Phase-Transfer Catalysis
Roman Bielski* and Peter J. Joyce*
Value RecoVery, Inc., 510 Heron DriVe, Suite 301, Bridgeport, New Jersey 08014, U.S.A.
Abstract:
onium salts decompose rapidly in highly alkaline solutions,4,5
and their decomposition rates increase with increased pH.
Thus, it would be important for catalyst stability if nucleo-
philic substitution reactions that require base were performed
at lower concentrations of the anion (and subsequently of
the hydroxide). For such reactions, the “life expectancy” of
a catalyst would dramatically increase.
Solubility. Certain anions of interest may show low
solubility in water. It should not preclude them from
participating in PTC-assisted reactions.
Many waste streams contain anions at low concentration in
water. This paper describes results obtained when aqueous
solutions of various anions at 1 wt % were subjected to reactions
with alkyl and acyl halides without solvent. High yields of
valuable products such as phenylacetonitrile, alkyl phenyl
ethers, alkyl acrylate, and benzoyl cyanide were obtained at
moderate temperatures and reaction times. The formation of
byproducts deriving from reactions with large amounts of water
was easily controlled. The method was successfully applied to
selectively react and extract a target anion out of a mixture of
anions.
We wish to report some of our results of reactions
performed at concentrations of 1.0% w/w of anions dissolved
in water. While PTC has been applied to water systems
containing anions at this or similar concentrations, the
Liquid-liquid phase-transfer catalysis (PTC) has been
successfully applied to economically viable synthesis of
many important and valuable chemicals. For reactions
6
-8
number of such reports is very limited. To maximize the
concentration of reactants in the organic phase, no solvents
9
1
were used. Recently, Eyende and Mailleux described the
following the Starks’mechanism, the reaction rates depend
synthesis of phenyl ethers using alkylating agents such as
iodomethane or 1-bromoheptane as an organic solvent with
high anionic concentrations in the aqueous phase. Con-
versely, we are not aware of any attempts to react anions at
low concentrations in the aqueous phase with alkyl halides
acting as reactants and solvents.
on the concentration of reactants in the organic phase and
concentrations of anions in the aqueous phase should have
no effect on the reactions kinetics. Nevertheless, researchers
invariably minimize water use, and consequently the con-
2
centration of water soluble reactants is relatively high. The
possible rationale is that when large amounts of water are
present in the reaction mixture, even relatively slow processes
involving water can become dominant and undesired prod-
The yields, reaction times, temperatures, and products are
presented in Table 1, and the equations are presented in the
Scheme 1. Reactions conditions reported here were not
optimized. Yields are reported as GC yields against an
internal standard. The general procedure was as follows: 250
g of 1.0% w/w aqueous solution containing the anion,
between 10 and 20% molar excess of sodium hydroxide (if
needed since some anions were already in salt form) and, in
some reactions, a small quantity of sodium iodide,10 were
transferred to a three-necked 500 mL flask and stirred (600
rpm) continuously at a controlled temperature. The organic
phase consisting of the alkyl (acyl) halide (usually 3 mol of
halide based on 1 mol of anion), PTC catalyst (methyltri-
octylammonium chloride in all cases with the exception of
example three where tetrabutylammonium bromide was used;
between 0.1 [example six] and 10 mol % based on 1 mole
of anion), and gas chromatographic internal standard (durene,
3
ucts may result. However, there have been no systematic
studies on liquid-liquid PTC reactions employed to mixtures
that contain relatively low concentrations of water soluble
reactants. The specific findings of this paper suggest that
such systematic studies would be very fruitful.
The reasons to perform PTC-enhanced reactions using the
low concentration of reactants in an aqueous phase include
the following:
Availability. There is a plurality of aqueous waste streams
containing various reactive anions at low concentrations.
Some of these anions such as cyanide or phenolate are
hazardous pollutants. Successful application of PTC-assisted
reactions to these streams to produce useful chemicals would
offer an economic and environmental benefit.
Catalyst Stability. Many PTC reactions must be per-
formed at high pH to ensure proton removal. However, it
has been well established that most catalysts belonging to
(4) Landini, D.; Maia, A.; Rampoldi, A. J. Org. Chem. 1986, 51, 3187.
(5) Dehmlow, E. V.; Knufinke, V. J. Chem. Res., Synop. 1989, 224.
(
6) Krishnakumar, K.; Sharma, M. M. Ind. Eng. Chem. Process Des. DeV. 1984,
23, 410.
*
To whom correspondence should be addressed. E-mail: bielski@
(7) Wu, H.-S.; Lai, J.-J. Ind. Eng. Chem. Res. 1995, 34, 1536.
(8) Dutta, N. N.; Borthakur, S.; Baruah, R. Water EnViron. Res. 1998, 70 (1),
4.
ptcvalue.com; joyce@ptcvalue.com.
1) Starks, C. M. J. Am. Chem. Soc. 1971, 93, 195.
(
(
2) Jones, R. A. Quaternary Ammonium Salts: Their Use in Phase-Transfer
Catalysed Reactions; Academic Press: New York, 2001.
(9) Eyende, J. J. V.; Mailleux, I. Synth. Commun. 2001, 31, 1.
(10) Starks, C. M.; Liotta, C. L.; Halpern, M. Phase Transfer Catalysis
Fundamentals, Applications, and Industrial PerspectiVe; Chapman & Hall:
New York, 1993.
(3) Albanese, D.; Landini, D.; Maia, A.; Penso, M. Ind. Eng. Chem. Res. 2001,
4
0, 2396.
1
0.1021/op034037q CCC: $25.00 © 2003 American Chemical Society
Vol. 7, No. 4, 2003 / Organic Process Research & Development
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Published on Web 05/01/2003