Recovery of high-valued products from styrene-based polymers through coprocessing: Experiments and mechanistic modeling

The recent emergence of pyrolysis as a viable resource recovery strategy has focused attention on understanding the complex chemistry underlying the decomposition processes. In this work, a quantitative link between measurable experimental changes and kinetics analysis was established to explain the behavior of styrene-based polymers alone and in binary mixtures during pyrolysis. Experiments with low molecular weight polystyrene and poly(alpha-methylstyrene) were carried out which showed that a higher selectivity to monomer was obtained for poly(alpha-methylstyrene) than for polystyrene. The binary mixture experiments revealed that the reactivity of polystyrene was enhanced in the presence of poly(alpha-methylstyrene), and the selectivity to styrene monomer was increased. Overall, the experimental results suggest that coprocessing is a viable polymer resource recovery strategy when the addition of an appropriate co-reactant is used to tailor the product distribution. Furthermore, novel polymer structures may be designed to promote degradation to high-valued products. The experimental results were interpreted using a detailed mechanistic model which described the reactions of alpha-methylstyrene and styrene trimers and was generated using software for automated model construction to describe 901 species using over 4000 reactions. By exploiting the capability to label the model reactants, a quantitative link between polymers and their mimics was established and probed the impact of the kinetic coupling between different polymers. (C) 1998 Elsevier Science B.V.