Issue 05/2023

From Science& Research Category
Catalysis for a multidimensional
circular economy
The chemical industry supplies indispensable substances
for our health, nutrition, and current standard of living.
However, many of the chemical products accumulate as
waste at the end of their product life. Due to their chemical
complexity and diversity of substance mixtures, no viable
recycling concepts exist for most waste streams to date; they
are therefore often used thermally, landfilled, or introduced
into natural ecosystems, thus leading to environmental
pollution. The resulting ecological challenges are particularly
evident in the case of plastic waste, e.g. microplastics are now
found in the most remote areas of the world. The politically
and socially demanded resource and energy transition
therefore requires transforming the traditionally linear
structure of production and use in the chemical industry
into a holistic circular economy in which economic growth is
decoupled from primary resource consumption and waste is
understood as a valuable resource. This requires viable new
recycling concepts for chemical products.
Regina Palkovits and Jürgen Klankermayer of RWTH
Aachen University (Aachen, Germany), together with an
interdisciplinary team of researchers in “catalaix – Catalysis
for a Circular Economy”, want to ensure chemical products
become valuable resources of an integrated circular economy
according to the open-loop principle at the end of their product
life. The chemical building blocks created in open-loop
recycling will be tailored and flexibly fed into a wide variety
of value chains and material cycles in line with demand.
The aim is to create a flexible, multidimensional circular
economy that supports the sustainable transformation of
the chemical industry. This will be achieved by developing
customized chemo-, bio – and electro-catalyst systems and
integrating renewable raw materials and energy sources into
the recycling process.
Using the example of plastics recycling, the researchers
have already demonstrated the technical feasibility of this
concept for diverse classes of plastics. As one example, the
PalkovitsLab was able to transform the biobased plastics
polyhydroxybutyrate (PHB) and polylactic acid (PLA) with
easily separable solid catalysts back into the monomers.
This was possible for both pure polymer streams and
mixtures of the two bioplastics. The strategy could even
be extended to PET as a non-biopolymer. Here, PHB and
PLA were converted with similar yields as in the previous
mixed recycling approach of the bioplastics, whereas PET
remained largely intact in solid form and could therefore be
easily separated from the reaction solution. Furthermore,
the Klankermayer group demonstrated the effective
and selective catalytic depolymerization of polyester/
polycarbonate wastes into various diols using a tailormade
molecular catalyst that tolerates polymer additives.
Investigations on the integration of biobased diols in the
chemical recycling of POM (polyoxymethylene) polymers
enabled the selective production of chemical building blocks
from the plastics mainly used in automotive construction.
These flexible building blocks can then serve as solvents,
fuel additives, pharmaceutical intermediates, and even
as monomer materials for polymerization reactions. The
showcases exemplify the potential and capability of chemical
recycling of real mixed waste streams, with the possibility
of avoiding extensive sorting and purification steps prior
to depolymerization.
“Catalaix – Catalysis for a Circular Economy” is one of six
finalists in the competition for a new WSS research centre
for the sustainable use of the planet’s resources that have
each already received a WSS research prize of 1 million
Swiss francs (~ EUR 1 million). A total of 123 proposals were
submitted in the competition for the “project of the century”
of the Werner Siemens Foundation (WSS). Based on their
ideas, the finalists will develop their detailed concepts by the
end of October 2023. The final competitive decision will be
announced in January 2024. The WSS research centre will
be funded with 100 million Swiss francs (~EUR 105 million)
over a funding period of ten years. The Werner Siemens
Foundation initiated the competition on the occasion of its
100 th anniversary. MT/AT
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34 bioplastics MAGAZINE | Renewable Carbon Plastics [05/23] Vol. 18