1

Ionic Liquids and their application

in industrial green processes

Dmitry Borkin

2

Outline

•Definition

•Discovery

•Types of Ionic liquids

•Unique properties

•Preparation

•Applications

•Green Chemistry and safety concerns

3

Common solvents and Ionic liquids

Definition: An ionic liquid is a liquid that contains essentially only ions. Often

refers only to liquids with m.p. below 0C (room temperature ionic liquids).

Solvents

Protic

C2H5OH, H2O

Aprotic

Polar

CHCl3, CH3CN

Non-polar

C6H14, C6H6

Ionic Liquids

Consist

of no ions

Only small part of solvent is

ionized by disassociation

Consist of only ions

4

Discovery and History

[HOCH2CH2NH3]+[NO3]

- Ethanolammonium nitrate (m.p. 52-55 °C)

S. Gabriel, J. Weiner (1888). Ber. 21 (2): 2669–2679.

[EtNH3]+[NO3]

- Ethylammonium nitrate (m.p. 12 °C) P. Walden, Bull. Acad. Sci. St. Petersburg 1914, 405-42.

New class of moisture and air sensitive ionic liquids with neutral

anion (PF6-, BF4

-)

J. S. Wilkes, M. J. Zaworotko Chemical Communications 1992, 965-967.

1,3-dialkylimidazolium or 1-alkylpyridinium halides and

trihalogenoaluminatesH. L. Chum, V. R. Koch, L. L. Miller, R. A. Osteryoung J. Am. Chem. Soc. 1975, 3264.

5

Common Types of Ionic Liquids

Cations

N N

NN

R1

R2

R3

R2

R3

R4

R1 R2

imidazolium pyridium pyrrolidinium

R2

PR1 R3

R4

R2

NR1 R3

R4

R1

SR2 R3

phosphonium ammonium sulfonium

NNR1

R2

R3

pyrazolium

N SR1

R2

thiazolium

R = CH3(CH2)n, n=1, 3, 5, 7, 9; aryl; etc.

6

Common Types of Ionic Liquids

Anions

R O S

O

O

O S

O

O

O R3C S

O

O

O

NS S

OO

O O

F3C CF3PF6

- BF4- Hal-

alkylsulfate tosylate methanesulfonate

bis(trifluoromethyl-sulfonyl)imide

hexafluoro-phosphate

tetrafluoro-borate

halide

1018 possible ionic liquids

1000 is described in the literature

300 is commercially available

7

Effect of cation and anion

+ HNO3

N N R X-

X

O2N

N N R CF3SO3-

N N R CH3SO3-

CO2H

Cation is responsible for physical properties (melting point, viscosity, density).

Anion controls chemical properties and reactivity

M. J. Earle, S. P. Katdare and K. R. Seddon, Org. Lett., 2004, 6, 707–710

8

What makes the ionic liquid so unique?

m.p. <-20 °C m.p. 801 °C

NaCl N N C2H5OSO3-

Low melting point compared to other ionic compounds (inorganic salts)

Highly polar but poorly coordinating

9

What makes the ionic liquid so unique?

Inorganic salts

K2CO3, NaCN etc.

Typical hydrophobic organic

compounds: hydrocarbons,

alcohols, ketons, esters etc.

Soluble in ionic liquids

N N C2H5OSO3-

10

Immiscibility with common solvents

Advantages of biphasic systems:

•Easy separation

•Faster reactions

•Higher conversion or yields

•Less by-products

11

Other interesting properties

•Very low vapor pressure

•Non-flammable substances

•High thermally stable

•High mechanically stable

•Electrochemically stable

All properties can be tuned by varying types of cations and its

combination with anion

12

Comparison of organic solvents with ionic liquids

Property Organic Solvents Ionic Liquid

Number of solvents >1000 >1,000,000

Applicability Single function Multifunction

Catalytic ability Rare Common and tuneable

Chirality Rare Common and tuneable

Vapour pressureObeys the Clausius–

Clapeyron equation

Negligible vapour pressure under normal

conditions

Flammability Usually flammable Usually nonflammable

PolarityConventional polarity

concepts applyPolarity concept questionable

TuneabilityLimited range of solvents

available

Virtually unlimited range means

‘‘designer solvents’’

Cost Normally cheapTypically between 2 and 100 times the

cost of organic solvents

Recyclability Green imperative Economic imperative

Viscosity, cP 0.2–100 22–40,000

Density, g/cm3 0.6–1.7 0.8–3.3

Refractive index 1.3–1.6 1.5–2.2

Plechkova, N. V.; Seddon K. R. Chem. Soc. Rev. 2008, 37, 123–150

13

Preparation of ionic liquids

Metathesis of halide

QuarternerizationDirect combination

of halide salt with

metal halide

Preparation

14

Quarternerization

N N R1

+ N N R1

R2 Br-R2 Br

N

R1

R2

R3

I+

N

R1

R2

R3

I-

PR2R1

R3

+ R4 Cl

R1

PR4 R2

R3

Cl-

Chauvin, Y.; Mussmann, L.; Olivier, H. Angew. Chem., Int. Ed. Engl. 1995, 34, 2698.

15

Metathesis of halide

N N R1

R2 Br-AgBF4

N N R1

R2 BF4-

+ AgBr

AgYNR4

+ Hal- + AgHalNR4+ Y-

Wilkes, J. S.; Zaworotko, M. J. J. Chem. Soc., Chem. Commun. 1990, 965.

16

Direct combination of halide salt with metal halide

N N Cl-AlCl3

N N AlCl4-

N N Cl-2AlCl3

N N Al2Cl7-

N N Cl-MoCl5

N N MoCl6-

Bolkan, S. A.; Yoke, J. T. J. Chem. Eng. Data 1986, 31, 194.

17

BASF’s BASIL

(Biphasic Acid Scavenging utilizing Ionic Liquids )

Old method BASIL

HClEt3N

Solid ammonium salt

Reduction of heat transfer

Decreased yields

Solid separation

N NR

Ionic Liquid

Removed by simple

liquid-liquid phase

separation

HCl

2EtOH + PPhCl2 PPh(OEt)2 + 2HCl

50% yield, with a turnover of

8Kg m-3 h-1

98% yield with a turnover of

690,000Kg m-3 h-1

Et3NH+ Cl-

N NHR Cl-

NaOH

M. Freemantle, Chem. Eng. News, 2003, 81, 9.

18

Difasol process by IFP, France

C2-C3 allkenes Branched C5-C7

alkenes

[(PR3)NiCH2R’][AlCl4]

Solvent free

Separation of the catalysts is a major concern

Solution: catalyst immobilized on Ionic Liquid

As a result:

Biphasic system

Better selectivity

Catalyst now is recyclable

Y. Chauvin, J. F. Gaillard, D. V. Quang and J. W. Andrews, Chem. Ind., 1974, 375–378.

19

Schmid, C. R.; Beck, C. A.; Cronin, J. S.; Staszak, M. A. Org. Process Res. Dev., 2004, 8, 670.

Eli Lilly demethylation process

MeOO

OH

HOO

OH

[pyH]Cl

180oC

Important

pharmaceutical

intermediate

20

Eastman Kodak

OO

+ CHO +

OO

m n

2,5-dihydrofuran97%

crotonaldehyde1%

oligomer2%

SnOct3I

[P888 18]I

Holbrey, J. D.; N. V. Plechkova, N. V.;Seddon, K. R. Green Chem. 2006, 8, 411–414.

[P888 18]I = [(n-C8H17)3P(n-C18H37)]+I-

21

Hydrosilylation by Degussa

SiOH

SiO

SiH

n

SiOH

SiO

Si

n

RR

Catalyst: H2[PtCl6]

Ionic liquid for the catalyst heterogenisation

Hoff, A.; Jost, C.; Prodi-Schwab, A.; Schmidt, F. G. ; Weyershausen, B. Ionic Liquids: New designer

compounds for more efficient chemistry, Elements: Degussa Science Newsletter, 2004, 9, 10–15.

22

Central Glass Co., Ltd., Japan

The first example of pharmaceutical use of ionic liquids.

Pravadoline

Central Glass Co. (Japan), http://www.cgco.co.jp/english/index.html (2007).

Br

F3C CF3

+OH

Pd(OAc)2, PPh3, CuI, NEt3

[P444y][OTf]y=(CH2)2C8F17

OH

F3C CF3

+ Et3NH+Br-

23

Industrial applications under development

•Additives to paint (Degussa)

•Gas storage (Air products)

•Lithium-ion batteries (Degussa)

•Metathesis (SASOL)

•Isobutene alkylation (Petrochina)

•Extraction of lanthanoids from spent fuel (Nuclear industry)

•Heat transfer and storage medium (Solar thermal energy

systems)

24

SafetyRisk assessment

Dongbin Zhao, D.; Liao, Y.; Zhang, Z. Clean 2007, 35, 42-48

N N BF4-

N N BF4-

[C4mim][BF4] [C10mim][BF4]

25

http://www.le.ac.uk/ch/