Study on the role of the reaction time in the upcycling of HDPE by co-hydrocracking it with VGO

Pursuing the aim of improving the current waste plastics management strategy, we have investigated the co-hydrocracking of high-density polyethylene (HDPE) with vacuum gasoil (VGO) over a PtPd/HY catalyst for converting this blend into high-quality fuels. In particular, the work was focused on assessing the effects of the reaction time on the product yields and on the composition of the gas, naphtha and light cycle oil (LCO) fractions, which was determined by chromatographic means. The experimental runs were carried out in a 100 mL semi continuous stirred tank reactor varying the reaction time between 15 and 120 min and maintaining constant the rest of the variables at 420 °C (temperature reached using an electrical heating jacket and following a 5 °C min−1 heating ramp), 80 bar and a catalyst to oil mass ratio of 0.075 gcat goil−1. The results shown that at 120 min a naphtha fraction rich in 1-ring aromatics and with a RON value of 92.5 was obtained, while the LCO fraction was mainly iso-paraffinic with a cetane index of 43.8. Hence, these fractions could be used in the corresponding blending stages of commercial gasoline and diesel. Furthermore, the coke deposited on the catalyst was analyzed by means of TPO, obtaining that it was mainly formed at short contact times (< 15 min) and that its nature evolved with contact time being less condensed at long contact times.