Page 42 - Plastics News September 2024

FEATURE NEWS
Chemical plastics recycling is ready to go
undreds of millions of tonnes of plastic
waste are generated worldwide every
Hyear. Scientists are working tirelessly on
new methods to recycle a large proportion of
this waste into high-quality products, and thus
enable a genuine circular economy. However,
current recycling practices fall short of this goal.
Most plastic waste is recycled mechanically:
shredded and then melted down. Although this
process does result in new plastic products, their
quality deteriorates with each recycling step.
An alternative to this is chemical recycling,
which avoids loss of quality. This method in-
volves breaking down long-chain plastic mole-
cules (polymers) into their fundamental building
blocks (monomers), which can be reassembled
into new, high-quality plastics, creating a truly
sustainable cycle.
Fuels from plastic waste
As the approach of chemical recycling develops,
the initial focus is on breaking down these long
polymer chains into shorter-chain molecules that
can be used as liquid fuels, say, or lubricants. This
gives plastic waste a second life as petrol, jet fuel
or engine oil. Scientists at ETH Zurich have now
laid down important foundations for developing
this process. These enable the global scientific
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PLASTICS NEWSASTICS NEWS
Scientists around the world can now go
full throttle in their research into chemi-
cal plastics recycling. Researchers at ETH
Zurich have laid important foundations
for this by showing that it’s all about the
stirring.
community to engage in more targeted and ef-
fective recycling development work.
Researchers in the group led by Javier Pérez-
Ramírez, Professor of Catalysis Engineering,
investigated how to break down polyethylene
and polypropylene with hydrogen. Here, too,
the first step is to melt the plastic in a steel tank.
Gaseous hydrogen is then introduced into the
molten plastic. A crucial step involves adding a
powdered catalyst containing metals such as ru-
thenium. By carefully selecting a suitable cata-
lyst, researchers can increase the efficiency of
the chemical reaction, promoting the formation
of molecules with specific chain lengths while
minimizing by-products such as methane or pro-
pane.
Rotational speed and geometry are key
An impeller is the best tool for mixing the sub-
stances through the viscous plastic melt. Visu-
September 2024
September 2024