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
Enter the password to open this PDF file:
File name:
-
File size:
-
Title:
-
Author:
-
Subject:
-
Keywords:
-
Creation Date:
-
Modification Date:
-
Creator:
-
PDF Producer:
-
PDF Version:
-
Page Count:
-
Preparing document for printing…
0%
Comments 0
Log in to post a comment