Assessing the potential of the recycled plastic slow pyrolysis for the production of streams attractive for refineries

Abstract

The slow pyrolysis of recycled high-density polyethylene (HDPE) has been investigated in a batch autoclave reactor at 430–490 °C and reaction times of 15–60 min, with the aim of obtaining the maximum yield of plastic oil (PO) with an adequate composition for its subsequent valorization in refinery. Specifically, PO yields up to 85–90 wt% have been achieved operating at 430 °C and 15–37.5 min, noting that the obtained yields strongly depend on temperature and, to a lesser extent, on reaction time. Simulated distillation and gas chromatography analyses of PO have shown its potential for its valorization in a waste refinery scheme targeting the production of alternative fuels. Thus, the PO obtained at 430 °C and 15 min is suitable to be cofed to the fluidized catalytic cracking (FCC) unit since it has a simulated distillation curve similar to that of vacuum gasoil (VGO). On the other hand, the PO obtained at 430 °C at the longest reaction time and those obtained at 460 °C are suitable to be fed together with light cycle oil (LCO) into a hydroprocessing unit. The composition of naphtha and middle distillates of PO reveals that these fractions are appropriate for their blending with commercial diesel and gasoline pools after a mild hydrotreating to reduce their olefin content.