Chemical Recycling Of Polystyrene By Pyrolysis

Full Paper

Chemical Recycling of Polystyrene by Pyrolysis: Potential Use of the Liquid Product for the Reproduction of Polymer
Dimitris S. Achilias,* Iliana Kanellopoulou, Panagiotis Megalokonomos, Eleni Antonakou, Angelos A. Lappas

The potential use of the liquid product obtained from the pyrolysis of polystyrene as a raw material for the reproduction of the polymer was investigated inthis study. Catalytic and non-catalytic pyrolysis experiments were carried out in a fixed bed reactor using either model polymer or commercial waste products as the feedstock. The liquid fraction produced from all the pyrolysis experiments consisted mainly of the styrene monomer and this was subjected to repolymerization without any further purification, in a DSC with AIBN initiator. It was found thatthe pyrolysis oil fraction could be re-polymerized to again produce polymer. However, aromatic compounds included in this fraction may act as chain transfer agents, resulting in alterations in the shape of the reaction rate curve and lowering significantly the average molecular weight and the Tg of the polymer produced.

Introduction
The worldwide production and use of plastics has grownrapidly over the last few decades. It has been estimated that almost 170 million tonnes of plastics were produced worldwide during the year 2003.[1] The consumption in

D. S. Achilias, I. Kanellopoulou, P. Megalokonomos Laboratory of Organic Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece Fax: þ30 2310 99 7769; E-mail:axilias@chem.auth.gr E. Antonakou, A. A. Lappas Laboratory of Environmental Fuels and Hydrocarbons, Chemical Process Engineering Research Institute, 570 01 Thermi, Thessaloniki, Greece
Macromol. Mater. Eng. 2007, 292, 923–934 ß 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Western Europe during this year was raised to almost 40 million tonnes, an increase of 5.6% on 2001. The amount of plastic solid wastesproduced continues to increase despite some continuous efforts to reduce, reuse, recycle and recover. This is mainly due to their wide application in the manufacture of packaging for the food industry, as well as in other goods in daily life, since they do not seem to have any side effects on the human organism. The current most common practice for handling such waste streams is to incinerate themwith energy recovery or to use them for land filling. In the last decade, many environmental regulations have been implemented working towards a more sustainable recycling oriented society. Four different approaches have been proposed for the recycling of waste polymers, which include:[2,3] Primary recycling, referring to ‘‘in plant’’ recycling of scrap

DOI: 10.1002/mame.200700058

923

D. S.Achilias, I. Kanellopoulou, P. Megalokonomos, E. Antonakou, A. A. Lappas

material; Mechanical Recycling, where the polymer is separated from its associated contaminants and is reprocessed by melt extrusion or other techniques; Chemical or feedstock recycling leading to total depolymerization to the monomers, or partial degradation to other secondary valuable materials; Energy recovery, aneffective way to reduce the volume of organic materials by incineration. Although polymers are actually high yielding energy sources, this method has been widely accused of being ecologically unacceptable, owing to the health risk from air born toxic substances. The objective of a plastic management policy, in accordance with the principles of sustainable development, should not only be the reuse ofpolymeric materials but also the production of raw materials (monomers) from which they or other secondary valuable products could be reproduced. In this sense, the most challenging method among the techniques proposed for recycling of waste polymers is chemical or feedstock recycling, but various technologies have been successfully demonstrated and continue to be developed. Polystyrene (PS) is a...