Liquid-phase catalytic degradation of mixtures of waste high-density polyethylene and polystyrene over spent FCC catalyst. Effect of mixing proportions of reactants

Abstract

The catalytic degradation of waste high-density polyethylene (HDPE) and polystyrene (PS) mixtures with a different mixing proportions over spent FCC catalyst has been studied using a stirred semi-batch reactor at 400 °C. The cumulative amount distribution, the degradation rate into liquid products, the carbon number distribution, and the paraffin, olefin, naphthene and aromatic (PONA) distribution in the liquid product were determined as a function of time or mixing proportion of reactants. The cumulative amount distribution of liquid product depended on the mixing proportion of both HDPE and PS. The degradation rate in the range of initial lapsed time (initial degradation rate) increased exponentially with PS content whereas that for the range of final lapsed time (final degradation rate) increased slowly with HDPE content. An increase of PS content in the reactants showed an increase of gasoline fraction, from about 85 wt.% (0 wt.% PS content) to about 98 wt.% (100 wt.% PS content). Liquid PONA product distributions revealed the interaction of the degraded intermediates from HDPE and PS degradation. The addition of PS to the catalytic degradation of HDPE accelerated the production of aromatic components with mono-cyclic species in liquid products and moreover showed the highest selectivity of above 60 wt.% for ethylbenzene and styrene (C 2 benzene) in aromatic products