Hydrocarbon Processing - August 2022 - 53

History of the HPI-The 1990s
Sulzer Chemtech
Sulzer Chemtech's SuRe™ Styrene technology:
Maximizing styrene purity when
recycling polystyrene
Polystyrene (PS) is a versatile polymer. Its properties make this
plastic essential for various applications; thus, it is no surprise that it is
one of the most critical commodity chemicals worldwide. Traditionally,
PS is mechanically recycled, a very restrictive process that generally
produces a less valuable product.
With the increased demand for recycled content in products,
chemical recycling technologies open new possibilities to improve
PS circularity, allowing the recycled product to be used in stringent
applications.
Sulzer Chemtech, a leader in licensing technologies, has developed
the SuRe Styrene process to improve a key step in PS chemical recycling:
Crude Styrene purification.
SuRe Styrene is a hybrid configuration consisting of distillation
followed by melt crystallization that can produce Ultra High Purity
Styrene (> 99.95 wt%), which can be employed to produce high-value
PS grades such as for food packaging applications.
THE CONTAMINANT CHALLENGE
In chemical recycling, the crude pyrolysis oil, obtained from the
depolymerization section, can contain impurities that either co-boil or
close boil with styrene monomer. It is very hard or sometimes impossible
to remove some contaminants using conventional distillation, so
the final product does not meet ASTM (American Society for Testing
and Materials) specifications.
Impurities such as o-xylene, phenylacetylene, 1-nonene, oxygenates,
sulfur, chlorinated, nitrogenated, close boilers like ethyl benzene,
cumene, etc. can be originated from the waste PS feedstock.
Even the most advanced sorting methods can't guarantee a high
grade of PS feedstock. In addition, co-boiling contaminants can be
produced as an unintended byproduct of the pyrolysis process itself.
Since conventional process technologies are not equipped to remove
these various impurities, a new and innovative solution is required.
ACHIEVING ULTRA-HIGH PURITY
SuRe Styrene technology addresses the impurity challenge with a
unique design configuration that reaches styrene purities greater than
99.95 wt% and recovery rates above 98%. The purity achieved enables
operators to meet ASTM standards and drive true circularity by producing
100% recycled PS-No blending required.
By selecting Sulzer Chemtech's SuRe Styrene, companies can also
improve their cost-, resource- and energy- efficiency. With crystallization
as a final step for monomer purification, power usage is minimized,
as the energy required to melt the feedstock is considerably lower than
the amount needed for boiling. In addition, no adsorbent is required,
eliminating the additional steps for its processing and disposal.
Moreover, this purification method promotes feedstock flexibility,
allowing operators to use PS waste of multiple origins with different
grades and higher impurity levels without compromising final quality.
This is an outstanding advantage in lowering the cost of feedstock,
making recycled PS more economically viable.
Sulzer Chemtech's SuRe Styrene closes the gap in PS circularity
with an innovative styrene purification solution. Learn more about
how our world-class technologies can support your operations.
www.sulzer.com
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Hydrocarbon Processing - August 2022

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