Kinetic modeling of the hydrocracking of polystyrene blended with vacuum gasoil

Abstract

The kinetic modeling of the hydrocracking of a mixture of polystyrene (PS) and vacuum gasoil (VGO) over a PtPd/HY catalyst has been carried out. The reactions have been performed in a batch reactor under the following conditions: 380–420 °C; 80 bar; content of PS in the feed, 10 wt%; catalyst/feed ratio, 0.1 in mass; and time, 30–300 min. Different reaction networks and kinetic models have been studied, in which the evolution of product distribution (unconverted PS, dry gas, liquefied petroleum gases, naphtha, light cycle oil, heavy cycle oil and coke) with the extent of time has been quantified by considering three different simultaneous deactivation mechanisms (plastic fouling, coke deposition and metal poisoning). The kinetic model selected (based on a 7-lump reaction network) has been used for performing a parametric study, determining that 400 °C and 180 min are the optimal conditions for maximizing the yield of naphtha (35 wt%) at the same time that PS is totally converted. This original kinetic model may act as a basis for scaling-up studies focused on the large-scale valorization of waste plastics by co-feeding them into a hydrocracking unit of a Waste-Refinery.