Perspectives on CO 2 Utilization. Eric J. Beckman, Mascaro Sustainability Initiative University of Pittsburgh. Phil asked me to provide a “big picture” of the situation. First, can CO 2 utilization significantly help with our climate problems…. Climate Change: The Wedge Concept.
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Eric J. Beckman,
Mascaro Sustainability Initiative
University of Pittsburgh
~ 45 million tons of
Cl2 produced worldwide. Generation of Cl2 consumes 1-2% of world’s electricity.
~ 33% of Cl2 goes
into PVC, rising amounts go to phosgene, and subsequently urethanes and polycarbonates.
DPC used in generation of bisphenol A polycarbonate.
Competition from routes using CO.
energy intensity of ethylene, then credit for production of EG (assume recycle of methanol and phenol).
Which route is more sustainable?
Will drop in BPA-PC demand for more sustainable
solutions render this work unnecessary?
Fast becoming one
of the leading
MeGhee, et al.;
O-sulfobenzoic acid anhydride, POCl3, P4O10
Horvath, et al;
Possible to recycle drying agents; Mitsunobu residue is
likely not re-usable
Recycle of base and trifluoroacetic anhydride crucial.
Copolymerization of Cyclic Ethers and Carbon Dioxide: First Reports [Inoue, et al., J. Polym. Sci. – Polym Lett. (1969), 7, 287]
pressure of 60
bar for best
Most recent work
Unfortunately, CHO is simply not interesting from a product perspective.
* Living polymerization, MWD
less than 1.2;
* Reaction time 12-26 days;
* 20 – 35% carbonate
* PC produced as well
[Aida & Inoue (1982),
Macromolecules 15, 682]
and propylene oxide
Cyclohexene Oxide/CO2 Copolymerizations
R = Ph, i-Pr, t-Bu; R’ = H
[Darensbourg & Holtcamp,
Darensbourg, et al. (1999),
J. Am. Chem. Soc. 121,
Soluble complexes; crystal structure
shows four-coordinate monomers
with highly distorted tetrahedral
geometry around Zn
Cyclohexene Oxide/CO2 Copolymerizations
* Very high yields; over 1100 g polymer/g zinc after
* Methyl substituent allows for highest yields by factor
* Rate highest at temperatures >/= 80C
* Yield increases with increasing CO2 pressure
Very effective with cyclohexene oxide; propylene
oxide produces primarily propylene carbonate
One of our attempts: Sterically-hindered aluminum catalysts for polyol development
Several choices for R2
R1 = i-Pr
Mw vs. conversion, CHO; iC3H7O-Al[O-C(C6H5)3]2 in the absence (1) and presence of alcohol (2); 24 hr; 55oC
sterically hindered Al catalysts, CHO. No success with PO.
5 - diphenyl methyl; 6 – di-isobutyl, methoxy phenyl;
7 – fenchyl; 8 – fenchyl + 2 moles ether
Copolymerization of Cyclohexene Oxide and CO2
* High TOF (~ 200 hr-1)
at low T’s (20 – 50C)
* Low PDI (~ 1.1)
* 95%+ carbonate
[Coates & colleagues (1998)
J. Am. Chem. Soc. 120, 11018]
P ~ 100 - 500 psi;
T = 298K
TOF’s up to 200
PPC:PC of 0.25 to 13.
Allen, et al., JACS 2002, 124, 14284
Review: Coates & colleagues, Angew. Chemie (2004), 43, 6618
Mw’s 20 – 40k
Eg., Coates & colleagues, J. Polym. Sci. (2006),
Mw’s in 3k to
yield up to 50%;
Process energy of
19 GJ/ton; Dunn & Savage; Green Chem (2003); 5, 649
Either strategy requires formation of aromatic acid
using CO2 as raw material
P = 7 MPa
T = 18 hr
Incub. = 1 hr
If we incubate AlCl3 with CO2….
If we incubate AlCl3 with toluene….
Olah and colleagues calculate that CO2:AlCl3 complexes are 20-30 kcal/mole more stable than aromatic:AlCl3 complexes.
phases at 80C and 1000 psi.
Lower phase is 60 mole % toluene
Why is incubation effective?
due to incubation
could simply be
due to heterogeneous surface reactions on the Lewis acid.
improves yield to
turnover, this process
can’t move forward
T = 353 K, P = 6.9 MPa, AlCl3
relies on low-cost methanol generated
from syngas. For CO2 to be able to complete, we need a green & inexpensive source of H2.
syngas; syngas from