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Journal of Chemical Technology and Biotechnology J Chem Technol Biotechnol80:1089 1096 (2005)DOI: 10.1002/jctb.1333

Review

Use of ionic liquids as green solvents

for extractionsHua Zhao,1 Shuqian Xia2 and Peisheng Ma2

1Chemistry Program, Department of Natural Sciences and Mathematics, Savannah State University, Savannah, GA 31404, USA2School of Chemical Engineering, Tianjin University, Tianjin, China

Abstract: This review summarizes recent applications of ionic liquids (ILs) as green solvents in

extractions of a variety of substances, including metal ions, organic and bio- molecules, organosulfur from

fuels, and gases. ILs could also be used along with another green technology, supercritical fluid extraction

(SFE), for a more effective separation of products from ILs. In addition to their environmentally-benign

feature, ILs have other favorable properties over organic solvents used for extraction, such as adjustable

hydrophobicity, polarity and selectivity.

2005 Society of Chemical Industry

Keywords:ionic liquid; extraction; green technology; industrial application; supercritical fluid

INTRODUCTION

Ionic liquids (ILs) are a group of new organic

salts that exist as liquids at a low temperature

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H Zhao, S Xia, P Ma

Table 1.Examples of IL extractions of metal ions

Substances IL

Extractant/ligand/

metal chelator Reference

Alkali metals Li+, Na+, K+, Rb+, Cs+ [CnMIM][PF6] (n= 4 9) DC18C6 21,37

Na+, Cs+ [CnMIM][PF6] (n= 4, 6, 8) 18C6, DC18C6, Dtb18C6 18

Cs+ [CnMIM][Tf2N] (n= 2, 3, 4, 6, 8) BOBCalixC6 38

Na+, K+, Cs+ [CnMIM][Tf2N] (n= 2, 4, 6, 8) DC18C6, N-alkyl

aza-18-crown-6 ethers

39

Alkaline earth metals Mg2+, Ca2+, Sr2+, Ba2+ [CnMIM][PF6] (n= 4 9) DC18C6 37

Sr2+ [CnMIM][PF6] (n= 4, 6, 8) 18C6, DC18C6, Dtb18C6 18

Sr2+ [R1R2MeIM][PF6], [R1R2MeIM][Tf2N] DC18C6 19

Sr2+ [CnMIM][Tf2N] (n= 2, 4, 6, 8) DC18C6, N-alkyl

aza-18-crown-6 ethers

39

Heavy and radioactive

metals

Pb2+ [CnMIM][PF6] (n= 4 9) DC18C6 37

Cu2+, Ag+, Pb2+, Zn2+,

Cd2+, Hg2+[C4MIM][PF6] Dithizone 23

Cd2+, Co2+, Ni2+, Fe3+,

Hg2+[C4MIM][PF6], [C6MIM][PF6] PAN, TAN 20

Ag+ [CnMIM][PF6] (n= 4, 6, 8) Calyx[4]arene-bearing

pyridine

40

Cu2+, Cr6+, Zn2+ [CnMIM][BF4] (n= 1, 3, 6, 8, 10)

[CnMIM][PF6] (n= 6, 10)

None 41

Hg2+, Cd2+ TSILs None 28,35

Lanthanides (Nd3+, La3+,

Er3+, Ce3+, Sm3+, Eu3+,

Gd3+, Ho3+)

[C4MIM][PF6] CMPO 32

Actinides (Th4+, U2+, Pu4+) [C4MIM][PF6], [C4MIM][NO3], Dtb18C6, CMPO, TBP 29,34

Others Al3+ [C4MIM][Tf2N], [C6MIM][PF6]

[C8MIM][PF6]

n/a 42,43

Note: CnMIM= 1-alkyl-3-methylimidazolium; DC18C6= dicyclohexano-18-crown-6; 18C6= 18-crown-6; Dtb18C6= 4,4-(5)-di-(tert-butylcyc-

lohexano)-18-crown-6; BOBCalixC6= calix[4]arene-bis(tert-octylbenzo-crown-6); Tf2N= bis[(trifluoromethyl)sulfonyl]amide; R1R2MeIM= 1-R1-2-

R2-3-methylimidazolium (R1 = Bu, Et, or Pr; R2 = H, or Me); PAN = 1-(2-pyridylazo)-2-naphthol; TAN= 1-(2-thiazolylazo)-2-naphthol; CMPO=

octyl(phenyl)-N,N-diisobutylcarbamoylmethyl phosphine oxide; TBP= tri-n-butylphosphate.

(3) The extraction efficiency of metal complexes can

also be controlled by the pH of the system.23

Among IL extractions of metal ions, the extraction

of radioactive metals (lanthanides and actinides) has

particular industrial significance for the handling of

nuclear materials. Earlier studies in the area included

the behavior of uranium species in various ILs includ-

ing mixtures of chloroaluminate ILs and butylpyri-

dinium chloride,24,25 mixtures of chloroaluminate ILs

and [C2MIM]Cl,26

chloroaluminate ILs,27

and sev-eral RTILs.18,19,28 Recent work primarily focused on

two aspects: (1) the fundamental understanding of

ILs in nuclear chemistry such as radiochemical sta-

bility of ILs,29 superoxide ion electrochemistry in

ILs,30 and electrochemical properties of actinides in

ILs;31 (2) applications of ILs in nuclear extractions of

lanthanides32 and actinides (Table 1).29,33,34

However, the disadvantages of using extractants

are the difficulty of separating them from ILs and

the complexity of the system.28 As a new concept

introduced in the late 1990s, Task-Specific ILs

(TSILs) are designed to have targeted functionality

and, in this case, TSILs are those ILs containing metal

ion-ligating functional groups. Therefore, TSILs serve

as the hydrophobic solvent and the extractant at the

same time. TSILs containing side-chains of thiourea

derivatives and urea derivatives could dramatically

increase the partitioning of Hg2+ and Cd2+ ions from

aqueous solutions.28,35 Moreover, as indicated in a

recent review,36 TSILs are not limited to the extraction

processes; they are also versatile solvents/catalysts used

in organic catalysis, solid phase synthesis, and even

production of liquid Teflon and emulsions.

IL EXTRACTIONS OF ORGANIC/BIO/BIOFUELMOLECULES

The high solubility of charged organic molecules in

ILs has stimulated the development of organic prod-

uct recovery by these green media. As illustrated

in Table 2, phase partitions of many phenolic com-

pounds are investigated in the ILwater biphasic sys-

tems. The distribution coefficient is highly influenced

by the pH value which determines the existing form of

a phenolic compound as a conjugated acid or base.41,44

The same principle applied to the extraction of amino

acids through [BMIM][PF6] where the concentration

of the crown ether (DC18C6) also played an impor-

tant role on the amino acid recovery (Table 2).45

Meanwhile, IL biphasic systems were also used to

separate many other biologically important molecules

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Use of ionic liquids as green solvents for extractions

Table 2.Examples of IL extractions of organic/bio/biofuel molecules

Substances IL Extractant Reference

Phenolic compounds phthalic acid, aniline, 4-hydroxybenzoic

acid, benzoic acid, p-toluic acid,

benzene, chlorobenzene,

1,2,4-trichlorobenzene,

1,4-dichlorobenzene,

4,4-dichlorobiphenyl

[BMIM][PF6] None 44

Phenol, tyrosol,p-hydroxybenzoic acid [CnMIM][BF4] (n= 1, 3, 6, 8, 10)

[CnMIM][PF6] (n= 6, 10)

None 41

Chlorophenols [C4MIM][PF6], [EMIM][Beti] None 58

Amino acids Tryptophan, glycine, alanine, leucine,

lysine, arginine

[BMIM][PF6] DC18C6 45

Carbohydrates Xylose, fructose, glucose, sucrose [CnMIM][X] (n= 4, 6, 8, 10;

X= Cl, PF6, BF4

)

None 46

Glucose, sucrose, lactose, cyclodextrin [BMIM][dca] (carbohydrate solubility

is approximately 200 g l1)

None 47

Cellulose [CnMIM]X (n= 4, 6, 8) None 59

Organic acids Lactic acid, acetic acid, glycolic acid,

propionic acid, pyruvic acid, butyric

acid

[CnMIM][PF6] (n= 4, 6, 8) TBP (in some

cases)

48

Biofuels Butyl alcohol (from fermentation broth) [BMIM][PF6], [C8MIM][PF6] Pervaporation

was used

49

Antibiotic Erythromycin-A [BMIM][PF6] None 50

Hydrocarbons Olefins (such as ethylene, propylene,

and butanes) from paraffins

[CnMIM][X], [HPy][X] (n= 4, 6;

X= BF4, PF6

)

None 54,55

C4 8 diolefin (such as butadiene) from

C118 paraffins

[BMIM][BF4] None 56

Note: BMIM (or C4MIM) =1-butyl-3-methylimidazolium; EMIM= 1-ethyl-3-methylimidazolium; Beti= bis(perfluoroethylsulfonyl)imide; HPy= N-

hexylpyridinium; dca= dicyanamide.

such as carbohydrates,46,47 organic acids including

lactic acid,48 butyl alcohol (from the fermentation

broth to produce biofuels),49 and polyketide antibiotic

erythromycin-A.50 It is important to notice that car-

bohydrates are renewable and inexpensive resources

for the chemical industry. The underivatized carbohy-

drates are soluble in water but not in almost any other

solvents, which presents quite a challenge to transform

the carbohydrates. Their high solubility in ILs enables

the possibilities of transformations.47,51,52

Interestingly, an aqueous biphasic system (ABS)

was formed by contacting the hydrophilic [BMIM]Cl

with concentrated solutions of K3PO4 (or other

kosmotropic salts such as KOH, K2CO3, Na2HPO4,

and Na2S2O3).53 This finding of being able to controlthe aqueous miscibility of hydrophilic ILs is very

valuable to the separation technology, because it

enables the recycling of hydrophilic ILs, the metathesis

formation of new ILs, and even reactive separations.

These ABSs have sufficient chemical potentials to

allow the separation of organic molecules into two

phases. The partition of several short chain alcohols

(eg methanol, propanol, butanol and pentanol) in

these ABSs was found to be a strong function of the

tie line lengths.53

Hydrocarbon separation through IL extractions was

also proved possible. One method for separating

olefins (such as ethylene, propylene, and butanes)

from paraffins involved several steps:54,55 (1) salts

(such as silver) were used to form complex olefins;

(2) the olefin-containing mixture was extracted by

the ionic liquid/salt solution, and the olefins were

adsorbed; (3) the olefins were separated by desorption

after the paraffins were removed. Another process

was developed to separate C4 8 diolefin hydrocarbons

(such as butadiene) from at least one diolefin and

at least one C118 paraffin using ILs (such as

[BMIM][BF4]).56 A continuous extraction process

using IL to separate C6 9-aromatic hydrocarbons, and

higher hydrocarbons, from benzene-rich petroleum

streams has also been developed.57 These results

presented alternative green methods for separation of

hydrocarbon molecules, which is extremely valuable

to the petroleum industry and polymer-processing

industry.

IL DESULFURIZATION OF FUELS

To reduce the impact of SOx emission from fuel

burning on human health and the environment,

tighter regulations are being imposed by EPA on

oil refineries to reduce the statutory sulfur contents

of fuels.60 Conventional desulfurization of diesel

was achieved through hydroprocessing catalysts.

However, further or deep hydrodesulfurization (HDS)

requires high consumption of energy and hydrogen.

Meanwhile, the HDS process is normally only effective

for removing organosulfur compounds of aliphatic

and alicyclic types. The aromatic sulfur molecules

including thiophenes, dibenzothiophenes (DBT), and

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their alkylated derivatives are very difficult to convert

to H2S through HDS catalysts.61,62 Alternative

methods (including reactive adsorption63) of deep

desulfurization are highly demanded. One alternative

called extractive desulfurization (EDS) seems very

attractive for this purpose because of its low energy

cost, the elimination of hydrogen usage, the retaining

of the chemical structures of fuels and no requirementsof special equipment.

However, EDS through ILs seems particularly

favorable over organic solvents64 because of the use of

environmentally-benign solvents. Current research for

this purpose includes:

(1) EDS of organosulfur compounds: Bosmann

et al investigated various imidazolium- and

chloroaluminate-based ILs and found multistage

extraction was very effective in removing

sulfur;65 several ILs (eg [EMIM][BF4],

[BMIM][PF6], [BMIM][PF6]) exhibited high

selectivity in extracting aromatic sulfur and

nitrogen compounds;66 an ultra-low level of sulfur

(

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(b) many organic compounds are soluble in scCO2,

enabling easy separation of products from ILs; (c) this

process can be designed as batchwise or continuous

operations. Examples of metal-catalyzed organic reac-

tions include batchwise asymmetric hydrogenation of

tiglic acid,86 batchwise hydrogenation of alkenes and

carbon dioxide,87 continuous flow hydroformylation

of oct-1-ene catalyzed by rhodium complexes,88,89

continuous flow hydrovinylation of styrene by immo-

bilized organometallic (Ni-based) catalysts.90

A number of biocatalysis reactions were achieved

successfully in ILs (see reviews, Refs6,1114), or

in scCO2 (see reviews, Refs9193). The compari-

son study of imidazolium-based ILs, scCO2 and

n-hexane for the biocatalysis of a transesterification

reaction by immobilized enzymes has shown that

the enzyme activity is strongly influenced by the

water activity.94 Recently, the combination of IL and

scCO2 to form biphasic systems has attracted a lot

of attention for biocatalysis. For example, continu-

ous processes of Candida antarctica lipase B-catalyzed

butyl butyrate synthesis and the kinetic resolution

of 1-phenylethanol processes by transesterification;95

batchwise and continuous flow processes of acyla-

tion of octan-1-ol by vinyl acetate and the reso-

lution of 1-phenylethanol both catalyzed by lipase

fromCandida antarctica;96 the transesterification reac-

tion of N-acetyl-L-phenylalanine ethyl ester with 1-

propanol catalyzed by immobilized -chymotrypsin

was conducted in scCO2 containing [C4MIM][PF6]

or [C8MIM][PF6]).97 This research concluded that

these ILs provided a rather polar environment, but

it was adjustable by nonpolar scCO2 to improve theenzyme activity.

GAS SEPARATIONS BY ILS

ILs can selectively dissolve gases. This makes them

potential solvents for gas separations.98 CO2 has rel-

atively high solubility in imidazolium-based ILs (eg

[BMIM][PF6]) as illustrated by recent experiments

and molecular modeling.99,100 A TSIL consisting of

an imidazolium ion to which a primary amine moi-

ety is covalently bonded was specifically designed

for CO2 capture.101

Ethylene and ethane havemedium solubility in [BMIM][PF6], while methane,

argon, oxygen, hydrogen, nitrogen, carbon monox-

ide have low solubility.99,102 Molecular dynamics

calculations were also consistent with experimen-

tal results that, for a given anion, the solubility

of CO2 in different ILs showed no large differ-

ence between the two cations. Another theoretical

study of gas solubility in [BMIM][PF6] was con-

ducted through the Monte Carlo simulations.103 In

this study, a molecular mechanics force field was

established to predict the thermophysical proper-

ties such as molar volumes as a function of tem-

perature. The Henrys constants for water, car-

bon dioxide and argon were also reported in this

study.

Because ILs are nonvolatile, they do not contami-

nate the gas stream during gas separation. The non-

volatility and selectivity of ILs allow them to be used in

conventional absorbers, scrubbers or supported liquid

membranes.104

SUMMARYThe first commercial process was established by BASF

AG (Ludwigshafen, Germany) to scavenge acids using

ILs.105 Several other processes developed by the same

company are in the pilot phase.104 More commercial

process developments involving ILs were presented

in a recent review.104 In summary, ILs are unique

and promising solvents for extractions because of their

non-volatility, adjustable hydrophobicity and polarity,

dissolution ability, and selectivity of gases. There is

a fundamental answer to these favorable properties:

ionic liquids are organic molecules and ionic salts at

the same time. And, they are liquids.

ACKNOWLEDGEMENTS

This project was partially supported by SSU/NIH-

EARDA grant No. 5 G11 HD 32861-07 and by an

NIH-MBRS grant.

REFERENCES1 Seddon KR, Ionic liquids for clean technology. Journal of

Chemical Technology and Biotechnology 68:351356 (1997).

2 Welton T, Room-temperature ionic liquidssolvents for

synthesis and catalysis. Chemical Review 99:20712083

(1999).3 Seddon K, Ionic liquids: designer solvents for green synthesis.

Tce730:3335 (2002).

4 Gordon CM, New developments in catalysis using ionic

liquids. Applied Catalysis A: General222:101117 (2001).

5 Houlton S, Ionic liquids: the route to cleaner andmore efficient

fine chemical synthesis? Chemical Week (Feb 25/Mar 3):

s10s11 (2004).

6 Zhao H and Malhotra SV, Applications of ionic liquids in

organic synthesis.Aldrichimica Acta35:7583 (2002).

7 Earle M, Forestier A, Olivier-Bourbigou H and Wasser-

scheid P, Organic synthesis, in Ionic Liquids in Synthesis,

ed by Wasserscheid P and Welton T. Wiley-VCH Verlag,

Weinheim, pp 174288 (2003).

8 Jain N, Kumar A, Chauhan S and Chauhan SMS, Chemical

and biochemical transformations in ionic liquids. Tetrahedron61:10151060 (2005).

9 Endres F and Welton T, Inorganic synthesis, inIonic Liquids in

Synthesis, ed by Wasserscheid P and Welton T. Wiley-VCH

Verlag, Weinheim, pp 289318 (2003).

10 Husum TL, Jorgensen CT, Christensen MW and Kirk O,

Enzyme catalysed synthesis in ambient temperature ionic liq-

uids. Biocatalysis and Biotransformation19:331338 (2001).

11 Kragl U, Eckstein M and Kaftzik N, Enzyme catalysis in ionic

liquids. Current Opinion in Biotechnology 13:565571 (2002).

12 Park S and Kazlauskas RJ, Biocatalysis in ionic liq-

uidsadvantages beyond green technology. Current Opinion

in Biotechnology14:432437 (2003).

13 Sheldon RA, Lau RM, Sorgedrager MJ, van Rantwijk F and

Seddon KR, Biocatalysis in ionic liquids. Green Chemistry

4:147151 (2002).14 van Rantwijk F, Madeira Lau R and Sheldon RA, Biocatalytic

transformations in ionic liquids. Trends in Biotechnology

21:131138 (2003).


8/13/2019 2005vol.80no.10p.1089-1196

6/8

H Zhao, S Xia, P Ma

15 Kubisa P, Application of ionic liquids as solvents for

polymerizationprocesses. Progress in Polymer Science 29:312

(2004).

16 Carmichael AJ and Haddleton DM, Polymer synthesis in ionic

liquids, in Ionic Liquids in Synthesis, ed by Wasserscheid P

and Welton T. Wiley-VCH Verlag, Weinheim, pp 319 335

(2003).

17 Huddleston JG, Visser AE, Reichert WM, Willauer HD, Bro-

ker GA and Rogers RD, Characterization and comparison

of hydrophilic and hydrophobic room temperature ionic liq-

uids incorporating the imidazolium cation. Green Chemistry

3:156164 (2001).

18 Visser AE, Swatloski RP, Reichert WM, Griffin ST and

Rogers RD, Traditional extractants in nontraditional sol-

vents: groups 1 and 2 extraction by crown ethers in room-

temperature ionic liquids.Industrial & Engineering Chemistry

Research39:35963604 (2000).

19 Dai S, Ju YH and Barnes CE, Solvent extraction of strontium

nitrate by a crown ether using room-temperature ionic

liquids. Journal of the Chemical Society, Dalton Transactions

8:12011202 (1999).

20 Visser AE, Swatloski RP, Griffin ST, Hartman DH and

Rogers RD, Liquid/liquid extraction of metal ions in room

temperature ionic liquids. Separation Science and Technology

36:785804 (2001).

21 Chun S, Dzyuba SV and Bartsch RA, Influence of structural

variation in room-temperature ionic liquids on the selectivity

and efficiency of competitive alkali metal salt extraction by a

crown ether.Analytical Chemistry73:37373741 (2001).

22 Martell AE and Hancock RD, Metal Complexes in Aqueous

Solutions. Plenum, New York (1979).

23 Wei G-T, Yang Z and Chen C-J, Room temperature ionic

liquid as a novel medium for liquid/liquid extraction of

metal ions.Analytica Chimica Acta488:183192 (2003).

24 De Waele R, Heerman L andDOlieslager W, Electrochemistry

of uranium(IV) in acidic AlCl3 +N-(n-butyl)pyridinium

chloride room-temperature molten salts. Journal of Elec-

troanalytical Chemistry142:137146 (1982).

25 Heerman L, De Waele R and DOlieslager W, Electrochem-istry and spectroscopy of uranium in basic AlCl3 +N-(n-

butyl)pyridinium chloride room temperature molten salts.

Journal of Electroanalytical Chemistry193:289294 (1985).

26 Hitchcock PB, Mohammed TJ, Seddon KR, Zora JA,

Hussey CL and Ward EH, 1-Methyl-3-ethylimidazolium

hexachlorouranate(IV) and 1-methyl-3-ethylimidazolium

tetrachlorodioxo-uranate(VI): synthesis, structure, and elec-

trochemistry in a room temperature ionic liquid. Inorganica

Chimica Acta113:L25L26 (1986).

27 Dai S, Shin YS, Toth LM and Barnes CE, Comparative UV-

Vis studies of uranyl chloride complex in two basic ambient-

temperature melt systems: the observation of spectral and

thermodynamic variations induced via hydrogen bonding.

Inorganic Chemistry36:49004902 (1997).

28 Visser AE, Swatloski RP, Reichert WM, Mayton R, Sheff S,Wierzbicki A, Davis JH Jr and Rogers RD, Task-specific

ionic liquids for the extraction of metal ions from aqueous

solutions.Chemical Communications(1):135136 (2001).

29 Baston GMN, Bradley AE, Gorman T, Hamblett I, Hardacre

C, Hatter JE, Healy MJF, Hodgson B, Lewin R, Lovell KV,

Newton GWA, Nieuwenhuyzen M, Pitner WR, Rooney

DW, Sanders D, Seddon KR, Simms HE and Thied RC,

Ionic liquids for the nuclear industry: a radiochemical,

structural, and electrochemical investigation, inIonic Liquids

Industrial Applications for Green Chemistry, ed by Rogers RD

and Seddon KR. American Chemical Society, Washington,

DC, pp 162177 (2002).

30 Leonard ML, Kittle MC, AlNashef IM, Matthews MA and

Weidner JW, Nuclear chemistry and electrochemistry:

superoxide ion electrochemistry in ionic liquids, in IonicLiquids Industrial Applications for Green Chemistry, e d b y

Rogers RD and Seddon KR. American Chemical Society,

Washington, DC, pp 178187 (2002).

31 Oldham WJJ, Costa DA and Smith WH, Development of

room-temperature ionic liquids for applications in actinide

chemistry, in Ionic Liquids Industrial Applications for Green

Chemistry, ed by Rogers RD and Seddon KR. American

Chemical Society, Washington, DC, pp 188 198 (2002).

32 Nakashima K, Kubota F, Maruyama T and Goto M, Ionic

liquids as a novel solvent for lanthanide extraction.Analytical

Sciences19:10971098 (2003).

33 Pitner WR, Bradley AE, Rooney DW, Sanders D, Seddon K,

Thied RC and Hatter JE, Ionic liquids in the nuclear

industry, in Green Industrial Applications of Ionic Liquids, ed

by Rogers RD,Seddon KRand Volkov S. Kluwer Academic

Publishers, Boston, pp 209 226 (2002).

34 Visser AE and Rogers RD, Room-temperature ionic liquids:

new solvents for f-element separations and associated solu-

tion chemistry.Journal of Solid State Chemistry 171:109113

(2003).

35 Visser AE, Swatloski RP, Reichert WM, Mayton R, Sheff S,

Wierzbicki A, Davis JH Jr and Rogers RD, Task-specific

ionic liquids incorporating novel cations for the coordination

and extraction of Hg2+ and Cd2+: synthesis, characteri-

zation, and extraction studies. Environmental Science and

Technology36:25232529 (2002).

36 Davis JHJ, Task-specific ionic liquids. Chemistry Letters

33:10721077 (2004).

37 Bartsch RA, Chun S and Dzyuba SV, Ionic liquids as novel

diluents for solvent extraction of metal salts by crown ethers,

inIonic Liquids: Industrial Applications for Green Chemistry, ed

by Rogers RD and Seddon KR. AmericanChemical Society,

Washington, DC, pp 5868 (2002).

38 Luo H, Dai S, Bonnesen PV, Buchanan ACI, Holbrey JD,

Bridges NJ and Rogers RD, Extraction of cesium ions from

aqueous solutions using calix[4]arene-bis(tert-octylbenzo-

crown-6) in ionic liquids.Analytical Chemistry 76:30783083

(2004).

39 Luo H, Dai S and Bonnesen PV, Solvent extraction of Sr2+

and Cs+ based on room-temperature ionic liquids containing

monoaza-substituted crown ethers. Analytical Chemistry

76:27732779 (2004).

40 Shimojo K and Goto M, Solvent extraction and stripping ofsilver ions in room-temperature ionic liquids containing

calixarenes. Analytical Chemistry76:50395044 (2004).

41 Vidal S, Neiva Correia MJ, Marques MM, Ismael MR and

Angelino Reis MT, Studies on the use of ionic liquids as

potential extractants of phenolic compounds and metal ions.

Separation Science and Technology39:21552169 (2004).

42 Zhang M, Kamavaram V and Reddy RG, Application of

fluorinated ionic liquids in the extraction of aluminum. In

Light Metals, ed by Tabereaux AT. TMS, Warrendale, USA,

pp 315319 (2004).

43 Wu B, Reddy RG and Rogers RD, Production, refining and

recycling of lightweight and reactive metals in ionic liquids.

US Pat Appl Publ, 15 pp (2002).

44 Huddleston JG, Willauer HD, Swatloski RP, Visser AE and

Rogers RD, Room-temperature ionic liquids as novel mediafor clean liquidliquid extraction. Chemical Communications

(16):17651766 (1998).

45 Smirnova SV, Torocheshnikova II, Formanovsky AA and Plet-

nev IV, Solvent extraction of amino acids into a room tem-

perature ionic liquid with dicyclohexano-18-crown-6. Ana-

lytical and Bioanalytical Chemistry 378:13691375 (2004).

46 Spear SK, Visser AE and Rogers RD, Ionic liquids: green

solvents for carbohydrate studies. In Proceedings of the Sugar

Processing Research Conference, 1415 March 2002, New

Orleans, LA, ed by Godshall MA. Sugar research Institute

Inc. New Orleans, LA, pp 336340 (2002).

47 Liu Q,Janssen MHA, vanRantwijk F andSheldon RA,Room-

temperature ionic liquids that dissolve carbohydrates in high

concentrations.Green Chemistry 7:3942 (2005).

48 Matsumoto M, Mochiduki K, Fukunishi K and Kondo K,Extraction of organic acids using imidazolium-based ionic

liquids and their toxicity to Lactobacillus rhamnosus.

Separation and Purification Technology40:97101 (2004).


8/13/2019 2005vol.80no.10p.1089-1196

7/8


49 Fadeev AG and Meagher MM, Opportunities for ionic

liquids in recovery of biofuels. Chemical Communications

(3):295296 (2001).

50 Cull SG, Holbrey JD, Vargas-Mora V, Seddon KR and

Lye GJ, Room-temperature ionic liquids as replacements

for organic solvents in multiphase bioprocess operations.

Biotechnology and Bioengineering69:227233 (2000).

51 Lau RM, van Rantwijk F, Seddon KR and Sheldon RA,

Lipase-catalyzed reactions in ionic liquids. Organic Letters

2:41894191 (2000).

52 Park S and Kazlauskas RJ, Improved preparation and use of

room-temperature ionic liquids in lipase-catalyzed enantio-

and regioselective acylations. Journal of Organic Chemistry

66:83958401 (2001).

53 Gutowski KE, Broker GA, Willauer HD, Huddleston JG,

Swatloski RP, Holbrey JD and Rogers RD, Controlling the

aqueous miscibility of ionic liquids: aqueous biphasic sys-

tems of water-miscible ionic liquids and water-structuring

salts for recycle, metathesis, and separation. Journal of the

American Chemical Society125:66326633 (2003).

54 Munson CL, Boudreau LC, Driver MS and Schinski WL,

Separation of olefins from paraffins using ionic liquid

solutions. US 6339 182 (2002).

55 Munson CL, Boudreau LC, Driver MS and Schinski WL,

Separation of olefins from paraffins using ionic liquid

solutions. US 6623 659 (2003).

56 Smith RS, Herrera PS, Reynolds JS and Krzwicki A, Use of

ionic liquidsto separate diolefins vialiquidliquid extraction.

US Pat Appl Publ US 2 004106 8385 (2004).

57 Gmehling J and Krummen M, Use of ionic liquids as

entraining agents and selective solvents for separation of

aromatic hydrocarbons in aromatic petroleum streams. DE

10 154 052 (Germany) (2003).

58 Bekou E, Dionysiou DD, Qian R-Y and Botsaris GD, Extrac-

tion of chlorophenols from water using room temperature

ionic liquids, in Ionic Liquids as Green Solvents: Progress

and Prospects, ed by Rogers RD and Seddon KR. American

Chemical Society, Washington, DC, pp 544 560 (2003).

59 Swatloski RP, Spear SK, Holbrey JD and Rogers RD, Disso-

lution of cellulose with ionic liquids.Journal of the AmericanChemical Society124:49744975 (2002).

60 Fuels and Fuel Additives, http://www.epa.gov/otaq/fuels.htm

[accessed 8 may 2005].

61 Ma X, Sakanishi K and Mochida I, Hydrodesulfurization

reactivities of various sulfur compounds in diesel fuel.

Industrial & Engineering Chemistry Research 33:218222

(1994).

62 Kwak C, Lee JJ, Bae JS, Choi K and Moon SH, Hydrodesul-

furization of DBT, 4-MDBT, and 4,6-DMDBT on fluo-

rinated CoMoS/Al2O3 catalysts. Applied Catalyst A General

200:233242 (2000).

63 Meier PF, Reed LE and Greenwood GJ, Removing gasoline

sulfur.Hydrocarbon Eng1:26 (2001).

64 Funakoshi I and Aida T, Process for recovering organic sulfur

compounds from fuel oil. US Patent 5 753 102 (1998).65 Bosmann A, Datsevich L, Jess A, Lauter A, Schmitz C and

Wasserscheid P, Deep desulfurization of diesel fuel by

extraction with ionic liquids. Chemical Communications

(23):24942495 (2001).

66 Zhang S, Zhang Q and Zhang ZC, Extractive desulfurization

and denitrogenation of fuels using ionic liquids. Industrial &

Engineering Chemistry Research43:614622 (2004).

67 Jochen E, Wasserscheid P and Jess A, Deep desulfurization of

oil refinery streams by extraction with ionic liquids. Green

Chemistry6:316322 (2004).

68 Huang C, Chen B, Zhang J, Liu Z and Li Y, Desulfurization

of gasoline by extraction with new ionic liquids. Energy and

Fuels18:18621864 (2004).

69 ORear DJ, Boudreau LC, Driver MS and Munson CL,

Removal of mercaptans from hydrocarbon streams usingionic liquids. WO2002034863 (USA) (2002).

70 Lo W-H, Yang H-Y and Wei G-T, One-pot desulfurization of

light oils by chemical oxidation and solvent extraction with

room-temperature ionic liquids. Green Chemistry5:639642

(2003).

71 Schucker RC and Baird WC Jr, Electrochemical oxidation of

sulfur compounds in naphtha using ionic liquids. US Patent

6 274026 (2001).

72 Keim W, Waffenschmidt H and Wasserscheid P, Stabilization

of homogeneous catalysts for recycle during distillative

product separation using an ionic liquid. DE 19 901524

(Germany) (2000).

73 Earle MJ, McCormac PB and Seddon KR, DielsAlder reac-

tions in ionic liquids. Green Chemistry1:2325 (1999).

74 Zhao H and Malhotra SV, Enzymatic resolution of amino acid

esters using ionic liquid N-ethyl pyridinium trifluoroacetate.

Biotechnology Letters24:12571260 (2002).

75 Zhao H, Luo RG and Malhotra SV, Kinetic study on the

enzymatic resolution of homophenylalanine ester using ionic

liquids. Biotechnology Progress 19:10161018 (2003).

76 Marr R and Gamse T, Use of supercritical fluids for different

processes including new developmentsa review. Chemical

Engineering and Processing39:1928 (2000).

77 Blanchard LA, Hancu D, Beckman EJ and Brennecke JF,

Green processing using ionic liquids and CO2. Nature

399:2829 (1999).

78 Blanchard LA andBrennecke JF, Recovery of organic products

from ionic liquids using supercritical carbon dioxide.

Industrial & Engineering Chemistry Research 40:287292

(2001).

79 Blanchard LA, Gu Z and Brennecke JF, High-pressure phase

behavior of ionic liquid/CO2 systems. Journal of Physical

Chemistry A105:24372444 (2001).

80 Scurto AM, Aki SNVK and Brennecke JF, Carbon dioxide

induced separation of ionic liquids and water. Chemical

Communications(5):572573 (2003).

81 Scurto AM, Aki SNVK andBrennecke JF, CO2as a separation

switch for ionic liquid/organic mixtures. Journal of the

American Chemical Society124:10276 10 277 (2002).

82 Wu W, Zhang J, Han B, Chen J, Liu Z, Jiang T, He J and

Li W, Solubility of room-temperature ionic liquid in

supercritical CO2 with and without organic compounds.Chemical Communications(12):14121413 (2003).

83 Dzyuba SV andBartsch RA, Recentadvancesin applications of

room-temperature ionic liquids/supercritical CO2 systems.

Angewandte Chemie International Edition42:148150 (2003).

84 Schafer T, Rodrigues CM, Afonso CAM and Crespo JG,

Selective recovery of solutes from ionic liquids by perva-

porationa novel approach for purification and green pro-

cessing. Chemical Communications(17):16221623 (2001).

85 Crespo G, Joao PS and Schaefer T, Removal and recovery

of solutes present in ionic liquids by pervaporation. WO

2 003013 685 (Portugal) (2003).

86 Brown RA, Pollet P, McKoon E, Eckert CA, Liotta CL and

Jessop PG, Asymmetric hydrogenation and catalyst recycling

using ionic liquid and supercritical carbon dioxide. Journal

of the American Chemical Society 123:12541255 (2001).87 Liu F, Abrams MB, Baker RT and Tumas W, Phase-separable

catalysis using room temperature ionic liquids and supercrit-

ical carbon dioxide. Chemical Communications (5):433434

(2001).

88 Sellin MF, Webb PB and Cole-Hamilton DJ, Continuous flow

homogeneous catalysis: hydroformylation of alkenes in

supercritical fluidionic liquid biphasic mixtures. Chemical

Communications(8):781782 (2001).

89 Webb PB, Sellin MF, Kunene TE,Williamson S, Slawin AMZ

and Cole-Hamilton DJ, Continuous flow hydroformylation

of alkenesin supercriticalfluidionic liquid biphasic systems.

Journal of the American Chemical Society125:15 57715 588

(2003).

90 Boesmann A, Francio G, Janssen E, Solinas M, Leitner W and

Wasserscheid P, Activation, tuning, and immobilization ofhomogeneous catalysts in an ionic liquid/compressed CO2continuous-flow system. Angewandte Chemie International

Edition40:26972699 (2001).


8/13/2019 2005vol.80no.10p.1089-1196

8/8

H Zhao, S Xia, P Ma

91 Mesiano AJ, Beckman EJ and Russell AJ, Supercritical bio-

catalysis. Chemical Reviews99:623633 (1999).

92 Kamat SV, Beckman EJ and Russell AJ, Enzyme activity

in supercritical fluids. Critical Reviews in Biotechnology

15:4171 (1995).

93 Randolph TW, Blanch HW and Clark DS, Biocatalysis in

supercritical fluids, in Biocatalysis Industry, ed by Dordick JS.

Plenum, New York, pp 219237 (1991).

94 Garcia S, Lourenco NMT, Lousa D, Sequeira AF, Mimoso P,

Cabral JMS, Afonso CAM and Barreiros S, A comparative

study of biocatalysis in non-conventional solvents: ionic

liquids, supercritical fluids and organic media. Green

Chemistry6:466470 (2004).

95 Lozano P, de Diego T, Carrie D, Vaultier M and Iborra JL,

Continuous green biocatalytic processes using ionic liquids

and supercritical carbon dioxide. Chemical Communications

(7):692693 (2002).

96 Reetz MT, Wiesenhofer W, Francio G and Leitner W, Bio-

catalysis in ionic liquids: batchwise and continuous

flow processes using supercritical carbon dioxide as

the mobile phase. Chemical Communications (9):992993

(2002).

97 Laszlo JA and Compton DL, alpha-Chymotrypsin catalysis

in imidazolium-based ionic liquids. Biotechnology and

Bioengineering75:181186 (2001).

98 Brennecke JF and Maginn EJ, Purification of gas with liquid

ionic compounds. US patent 6 579 343 (2003).

99 Anthony JL, Maginn EJ and Brennecke JF, Solubilities and

thermodynamic properties of gases in the ionic liquid 1-n-

butyl-3-methylimidazolium hexafluorophosphate. Journal of

Physical Chemistry B106:73157320 (2002).

100 Cadena C, Anthony JL, Shah JK, Morrow TI, Brennecke JF

and Maginn EJ, Why is CO2 so soluble in imidazolium-

based ionic liquids? Journal of the American Chemical Society

126:53005308 (2004).

101 Bates ED, Mayton RD, Ntai I and Davis JH Jr, CO2 capture

by a Task-Specific Ionic Liquid. Journal of the American

Chemical Society124:926927 (2002).

102 Brennecke JF, Anthony JL and Maginn EJ, Gas solubilities in

ionic liquids, in Ionic Liquids in Synthesis, ed by Wasser-

scheid P and Welton T. Wiley-VCH Verlag, Weinheim,

pp 8193 (2003).

103 Shah JK, Anthony JL, Morrow TI, Brennecke JF and Mag-

inn EJ, Monte Carlo simulations of gas solubility in ionic

liquids. Abstracts of Papers, 226th ACS National Meeting,

New York, NY, September 711 (2003).

104 Parkinson G, Ionic liquids make an environmental splash.

Chemical Engineering Progress100:79 (2004).

105 Freemantle M, BASFs smart ionic liquid. Chemical and

Engineering News81(13):9 (2003).


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