The Catalyst Review October 2024 - 15

Experimental Abstracts
Sustainable, Recyclable, and Bench-Stable Catalytic System for Synthesis of
Poly(ester- β -carbonate)
Efforts to replace petroleum-derived and environmentally long-lasting polymers with sustainable alternatives have included using CO2
as
a raw material to prepare biodegradable polymers. Unfortunately, the catalysts that have proven effective in preparing these polymers are
costly, water- and oxygen-sensitive, and cannot be aligned with industrial processing needs. Herein, the authors describe a novel, stable
catalyst system comprised of commercial zinc glutarate (ZnGA) and supported main group metal salts which can be used for the synthesis of
a biodegradable poly(ester-β-carbonate) possessing high tensile strength, improved elongation, excellent transmittance, and low water vapor
permeability. Moreover, the supported ZnGA catalyst is recyclable, and its simple and low-cost preparation process is compatible with the
manufacturing and processing methods of the existing infrastructure.
The authors began by
preparing
a
wide
range
analyzed
of
main-group metal-supported
ZnGA samples (Figure 1),
which were
by
PXRD, FTIR, and SEMEDS.
The resulting catalysts
are named according to the
type and amount of metal salt
used, such as NaCl-100, which
mean that the type of metal
salt used in the loading process
is NaCl, and the proportion
used is 1% of the ZnGA load.
The experimental results show
that the crystal structure of
ZnGA remains intact while
the additional metal can react
with the defect sites (hydroxyl
groups, etc.) to form new active
sites. The catalytic system
can be applied in the ringopening
copolymerization
of CO2
and propylene oxide
(PO), ROCOP and lactide
(LLA) ROP. Both pathways
lead to the incorporation
of biodegradable segments
within the polymer.
Compared with ZnGA and
similar blends of ZnGA/
main group metal salts,
the
supported
activity
and
with the additional
catalyst
sites
on the surface, especially
Na, showed
higher
selectivity
from heterobimetallic
synergy, resulting in
terpolymerization (Figure
2). In the alternating
copolymerization of CO2
and PO, the introduction
of main group metals is
selective for the CO2
Figure 2. (a) Effect of temperature on activity, using different metal-supported catalysts ([LLA]/[Cat.] = 200:1), at 70°C, 2 MPa CO2
, 12 h.
,
12 h. (b) Effect of temperature on activity. (c) Effect of temperature on selectivity, using different metal-supported catalysts ([PO]/
[Cat.] = 200:1), at 70°C, 2 MPa CO2
-insertion step, which leads to the reduction of polyether formation, and a noticeable increase in molecular weight. With
respect to molecular weight, the introduction of Na and Al brought significant enhancement, yielding copolymers with molecular weights
of 206.3 and 216.4 kDa.
Although most heterogeneous catalysts are stable under elevated temperatures, they must also be sufficiently active under low reaction
temperatures to accommodate the economic energy demands of industrial applications. These workers, therefore, studied the effect of
reaction temperature for ZnGA, NaCl-100, LiCl-100, and AlCl3
-100 in LLA polymerization (Figure 2a). The results of this study showed
that the introduction of surface heterometallic sites significantly increased the activity of LLA ROP, especially at 50°C. Although ZnGA lost
its polymerization activity, the supported catalyst could still catalyze the reaction. The type of additional metal site is also associated with the
activity of LLA ROP. With higher temperatures, the introduction of Na exhibited the best activity. Introduction of main group metal sites did
not bring a significant difference in selectivity, and the resulting PLLA product contained <1% of the polyether units observed by 1
H NMR.
Notably, even after recovery in air, the activity of NaCl-100 was still maintained after 14 cycles demonstrating the remarkable moistureand
air-stable nature of this type of catalyst. Jia Y, Li B, Sun Y, et al. (2024). Chem Bio Eng. 1 (6), 559-567 ( https://doi.org/10.1021/
cbe.4c00064)
The Catalyst Review
October 2024
15
Figure 1. (a) Schematic diagram of the synthesis of supported catalysts. (b) SEM-EDS images of NaCl-100 (top) and its blends
in the same proportion (zinc shown in yellow, sodium shown in blue). (c) PXRD images of ZnGA, NaCl-100, LiCl-100, KCl-100,
MgCl2
catalyst is named according to the type and amount of metal salt used, such as NaCl-100, which means that the type of metal salt
used in the loading process is NaCl, and the proportion used is 1% of the ZnGA load.
-100, and AlCl3
-100. (d) FTIR images of ZnGA, NaCl-100, LiCl-100, KCl-100, MgCl2
-100, and AlCl3
-100. The resulted

https://www.doi.org/10.1021/

The Catalyst Review October 2024

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