Co-cracking of high-density polyethylene (HDPE) and vacuum gasoil (VGO) under refinery conditions

Abstract

The co–cracking of a 5 wt% of high–density polyethylene (HDPE) dissolved in vacuum gasoil (VGO) under conditions similar to those of the industrial fluid catalytic cracking (FCC) unit has been studied. The main goal has been to assess the effect of the co–feeding of waste plastic on attained conversion, as well as on the yield and composition of the products, given its interest for the subsequent refinery processes focused on the production of fuels. The products have been grouped in fractions: dry gas (C1-C2); liquefied petroleum gas (C3-C4), naphtha (C5-C12), light cycle oil (C13−C20), heavy cycle oil (C20+) and coke. Obtained results expose a significant synergy in the co–cracking, obtaining with the HDPE/VGO blend a higher conversion at 560 °C, together with higher yield of naphtha and concentration of light olefins. The synergy is based on the fast formation of intermediate alkylcarbenium ions at high temperature. Naphtha has been extensively characterized obtaining higher contents of n–paraffins and olefins and lower of iso–paraffins and aromatics in the cracking of the HDPE/VGO blend. This last characteristic increases the interest of the naphtha obtained in the co–cracking to be included in the gasoline pool of the refinery.