Applied_Spectroscopy_Practica_01_01 - 25

Original Research Article
Quantification of p-Cymene and Heptane in a
Solvent-Based Green Process of Polystyrene
Recycling
Zeinab Kara Ali1, Jean-Mathieu Pin2, and Christian Pellerin1
Abstract
The development of an economically viable technology for recycling polystyrene (PS) is of crucial importance. Most postconsumer
PS feedstocks cannot be handled by mechanical recycling due to severe contamination. A solvent-based process was
developed by Polystyvert and uses p-cymene as a solvent to solubilize PS and heptane as an antisolvent to precipitate it. This
leads to the production of recycled PS resin of high purity. However, the optimization of this process requires the knowledge
of p-cymene, heptane, and PS concentrations at different stages, where the samples of interest can be a viscoelastic paste or a
solid (pellets). Here, we present an infrared spectroscopy (IR) method that can rapidly quantify the content of these samples
at the plant level. Partial least squares statistical modeling on the first derivative IR spectra allowed the simultaneous quantification
of the components with a limit of quantification of 0.5% and 1% for p-cymene and heptane. To illustrate the usefulness
of this method, samples from a pilot PS-recycling plant were tested to improve the washing efficiency of the process.
Keywords
Polystyrene, dissolution/precipitation recycling, quantitative methods, infrared spectroscopy, pilot plant scale, multivariate
models, green process.
Date received: 29 March 2023; accepted: 11 May 2023
Introduction
Plastics are the workhorse material of the modern economy
because of their tunable and unrivaled properties. Combined
with their low cost, they are an ideal choice for a wide range
of applications that include packaging, transport, construction,
healthcare, clothing, and electronics.1,2 The production of plastic
resin has increased from 2 to 380 t/year in the last 60 years.3
On the downside, our current linear economic model, where
we simply dispose of manufactured products at the end of
their life (which can be very short for single-use applications),
generates large-scale pollution that causes harmful effects on
human health and on the environment.4-6 The approximate
total amount of plastic waste generated in 2015 was 6300 Mt,
of which only 9% was recycled and 12% was incinerated.3,7
The increasing awareness about the impact of plastic pollution
on ecosystems stresses the need for a transition
toward a circular economy that promotes an intelligent management
by reusing, recycling, and even upcycling end-of-life
plastics.1,8-10 The implementation of such a circular market
has been estimated to be worth $4.5 trillion by 2030.11
Depending on the waste stream quality, the type of
polymer, as well as the required purity of the recycled
resin, different recycling solutions exist and are under
continuous development. These include (i) separation and
mechanical deconstruction, which often reduces the molecular
weight and the performance of the recycled polymer; (ii)
chemical depolymerization, where the polymer is converted
to small molecules by chemical or enzymatic reactions; and
(iii) dissolution/precipitation methods, where the polymer
is purified by treatment in appropriate solvents and antisolvents.9
For styrene-based polymers, the dissolution/precipitation
approach appears as the best option considering the
yield, the reachable degree of purity of the recycled resin,
and the overall cost, because the polymer chains are not
altered during the process.12-15 It is worth noting that
among the recycling technologies, this method has the lowest
1Département de Chimie, Université de Montréal, Montréal, QC, Canada
2Polystyvert Inc., Anjou, QC, Canada
Corresponding Authors:
Jean-Mathieu Pin, Polystyvert Inc., 9350 Rue de l'Innovation, Anjou, QC H1J
2X9, Canada.
Email: jmpin@polystyvert.com
Christian Pellerin, Département de Chimie, Université de Montréal,
Montréal, QC, H3C 3J7, Canada
Email: c.pellerin@umontreal.ca
Creative Commons Non Commercial CC BY-NC: This article is distributed under the terms of the Creative Commons AttributionNonCommercial
4.0 License (https://creativecommons.org/licenses/by-nc/4.0/) which permits non-commercial use, reproduction and distribution
of the work without further permission provided the original work is attributed as specified on the SAGE and Open Access page (https://us.sagepub.com/enus/nam/open-access-at-sage).
Applied
Spectroscopy Practica
1-8
© The Author(s) 2023
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DOI: 10.1177/27551857231179982
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