Charles A. Eckert

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6 Δεκ 2012 (πριν από 4 χρόνια και 6 μήνες)

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Novel Solvents for
Sustainable Technology

Prof. Charles A. Eckert, Prof. Charles L. Liotta

Georgia Institute of Technology, Atlanta, GA


and Prof. Philip G. Jessop

Queen’s University, Kingston, Ontario

CHEMRAWN
-
XVII and ICCDU
-
IX

GREENHOUSE GASES


Mitigation and Utilization,

Kingston, ON, Canada, 11 July, 2007


Sustainable”
is not just
hugging a
tree


It’s getting everyone to hug a tree

Sustainable Chemical Process


Major Cost: Separation and Purification


Systems Approach


Modify Reaction to Facilitate Separation


Applications:

Chemicals Pharmaceuticals





Microelectronics

Biotechnology

Reactor

Separator

Recycle

Raw

Material

Products

Novel Solvents Using CO
2


Supercritical CO
2


Gas
-
Expanded Liquids


Reversible Acids


Reversible Ionic Liquids

Supercritical CO
2

for Phase Transfer Catalysis


Reaction of Species of Different Polarity


Not Both Soluble in Most Common Solvents


Involves Reaction Between Phases, i.e. Toluene
-
Water


Alternative: PTC


Tetraheptyl Ammonium Bromide


‘Greasy” Counterion
--






Brings CN
-

into Toluene


C
N
K
B
r
B
r
K
C
N


N

C

7

H

15

CN
-

-

C

7

H

15

C

7

H

15

C

7

H

15

+

Phase Transfer Catalysis in SCFs:

Typical Reactions

K
C
N


+
K
C
l


+
C
H
2
C
l
C
H
2
C
N
C
a
t
a
l
y
s
t
C
H
2
C
N
C
a
t
a
l
y
s
t
+


C
H
3
C
H
2
B
r
C
H
C
N
C
H
2
C
H
3
Three
-
Phase PTC System with
Catalyst
-
Rich Surface Phase


Solid Phase



Catalyst Phase

Supercritical

CO
2

Phase


C

H

2

C

l

C

H

2

C

N


KCN


N

+

Benefits of SCFs for PTC


Environmentally Friendly


Favorable Transport Properties


Tunable with Density


Tunability with Cosolvents


Easy Solvent Removal


Catalyst Recycling Opportunities

Liquid

GAS

Liquid



G
as
-
E
x
panded
L
iquids (
GXL
s)

Tunable Organic
-
CO
2

Mixtures

GAS

Liquid


Good Organic Solvents
Miscible with CO
2

Add CO
2


Solvent properties are
pressure tunable


Separation by
Depressurization


Solubility is Pressure
Tunable

Properties of GXLs:

Phenanthrene Sol’y in Acetone, 25
°
C

0.0001
0.001
0.01
0.1
1
0
20
40
60
80
Pressure (bar)
mol fraction Phenanthrene
Liquid CO
2

Liquid Acetone

Acid Properties of GXLs

Methanol + Reichardt’s
Dye (Indicator)

CO
2

Same Flask after CO
2

Introduction

In Situ Formation of Acids from CO
2

O
H
3
C
H
O
C
O
C
H
3
O
O
H
O
+
O
H
H
O
C
O
+
H
O
O
H
O
+
O
C
O
H
2
O
2
O
O
H
O
H
O
Water + CO
2

Methanol + CO
2

Hydrogen Peroxide + CO
2


(for oxidation reactions)

β
-
Pinene to
α
-
Terpineol in GXL/MeOH


Fragrances, Intermediates


Current Process


Aqueous, Acidic


Neutralization, Waste Salt


Limited Solubility of
β
-
Pinene (10
-
15 ppm)


Reactants Much More Soluble in Methanol


Forms Methylcarbonic Acid


No Need to Add or Neutralize Acid


Reversible Acid Forms In Situ


Product Separation Tunable with CO
2

Pressure


No Waste Salt

O
H
H
+
O
rganic
A
queous
T
unable
S
olvents
(OATS)

for Homogeneous Catalysis

+ CO
2

-

CO
2

Organic


H
2
O

Catalyst

Vapor

GXL

Vapor

Aqueous

Catalyst


Homogeneous Reaction


Organic/Aqueous Solution


Ambient Pressure


CO
2

Induces Phase Split


Heterogeneous Separation


GXL Poor Solvent for


Ionic Catalysts


Enzymes


Decant, Depressurize


Catalyst Recycle


Product Purification

Organic
-
Aqueous Tunable Solvent: OATS

CO
2

Effect on LLE for THF/Water

0
25
50
75
100
125
150
0
50
100
Mass % Organic
Temperature °C
No CO
2
10.3 Bars CO
2
Water
-
THF
-
CO
2

Equilibria

Left: No CO
2


Single Liquid Phase

Water Soluble Dye


Right: 20 Bars CO
2

Two Liquid Phases,
Dye Partitioning > 10
5

Cover Picture,
J.
Phys. Chem. B
, 2004

OATS Reaction: Hydroformylation


Water
-
soluble catalyst


Minimal Rh loss


Industrial Process for Propylene


Mass transfer inhibited for larger olefins


THF improves solubility


TON improved 50


100 Fold


Isomerization Problems

C
O
,

H
2
,

1
2
0
°
C
,

2
0

b
a
r
H
C
O
R
h
L
3
O
H
H
O
O
c
t
e
n
e

i
s
o
m
e
r
s
P
N
a
O
3
S
N
a
O
3
S
S
O
3
N
a
Hydroformylation

Reaction Rate

0
50
100
150
200
250
300
350
400
TPPTS
Biphasic
TPPTS
Monophasic
TPPMS
Monophasic
Turnover Frequency (hr
-1
)
OATS for Biocatalytic Synthesis and
Purification of Hydrophobic Drugs


Enantioselective Biocatalysis


Water Insoluble Substrates


Facile Product Isolation and Catalyst Recycle


OATS Mixture


Benign Alternative for Organics


Higher Enantioselectivity


Higher Efficiency


Higher Stability of Enzymes


Facile Purification of Pharmaceuticals

Biocatalytic Synthesis of Chiral Alcohols

H
O
H
N
A
D
H
+
H
N
A
D
+
F
D
H
H
C
O
O
H
C
O
2
O
A
D
H
Enzymes: ADH (alcohol dehydrogenase),



FDH (formate dehydrogenase);



Cofactor: NAD(H)


hydrogen transfer agents;



Buffer: 0.1 M ammonia formate, pH


6.5

NADH
-
dependent enzymatic reduction of

less
-
water soluble ketones

Recovery Efficiency of (s)
-
(
-
)
-
sec
-
Phenylethyl Alcohol in OATS

95%
96%
97%
98%
99%
100%
20
30
40
50
60
P
CO2
(bar)
Recovery in organic phase
Acetonitrile/Water (50:50), 40
°
C.
(0.2 mol/L NH
4
HCO
3

buffer, pH 5)

OATS:

Homogeneous Reaction/Heterogeneous Recovery

Products

Product
Purification

Reactants

Aqueous/Enzyme Recycle

Organic Solvent Recycle

CO
2

in

CO
2


out




Homogeneous
Biocatalysis


Product/


Organic

(GXL)

Enzyme/

Aqueous

Best of Both Worlds


Difficult Separation






Product


Contamination


Variation in


Activity or


Selectivity




Catalyst Leaching



off Support



Mass Transfer


Limitations





Facile
Separation

Increased:
-

Selectivity
-

Yields
-

ee’s

Reversible Ionic Liquid

CO
2

(1 atm.) Acts as “Switch”


DBU

(1,8
-
diazabicyclo
-
[5.4.0]
-
undec
-
7
-
ene)


N
N
+


R
O
H
N
N
H
R
C
O
3
-
C
O
2
-
C
O
2
Non
-
Polar


Chloroform

Polar (Ionic Liquid)


Dimethylformamide
or Propanoic Acid

Jessop, Heldebrant, Li, Eckert, Liotta,
Nature

2005
,
436
, 1102.

Guanidine Cased ILs


Guanidines + MeOH + CO
2



RTILs


Reverses Readily


With Inert Gas Sparge, Heat




N
N
N
R
N
N
N
R
H
O
2
C
O
M
e
M
e
O
H
C
O
2
Polarity like

Chloroform


Significantly More Polar
than [bmim][BF4]

Reversible IL as a Solvent


S
oluble in DBU and TMBG


Octane, Heptane, Pentane


Phase separation upon formation of IL


Negligible Cross
-
contamination

CO
2

Hydrocarbon

TMBG/MeOH

Hydrocarbon


Phase

TMBGH
+
/

N
2

or Heat

MeOCO
2
-


Reaction/Separation in Reversible ILs

1
-

Pentane


2
-
MeOH/CO
2

A + B

Product C

Product C

Heat or N
2

DBU or TMBG

Ionic Liquid

Pentane

REACTION

SEPARATION

REFORMATION

RECYCLE

Novel CO
2
-
Based Solvents to
Couple Reaction and Separation


Build Separation Scheme into Reaction


Tunable Solvents


Supercritical


Nearcritical


Gas
-
Expanded Liquid


“Smart” Solvents


Sustainable Processes