Hydrocracking of Plastic Pyrolysis Oil (PPO) Blended with Vacuum Gas Oil (VGO) over Pt–Pd Catalysts Supported on USY–ASA–Al₂O₃ Composites

Aiming to valorize waste plastics in industrial hydrocracking units, this study has focused on the synthesis of catalysts for valorizing a mixture of plastic pyrolysis oil (PPO) and vacuum gas oil (VGO). Pt–Pd catalysts supported on composites made of USY zeolite, amorphous silica-alumina (ASA), and Al₂O₃ were used. Three different supports were prepared, in which the amount of USY zeolite was maintained constant at 25 wt % and the contents of ASA and Al₂O₃ were varied. The catalytic tests were carried out in a batch reactor under the following conditions: 420 and 440 °C, 80 bar contact time of 120 min, and a stirring rate of 1300 rpm. The results (conversion, yields, and composition of product fractions) are related to the properties of the catalysts, by taking into account the effects of the accessibility of the reactants, metal dispersion, and acidity. The catalyst with the support composed of 25 wt % USY zeolite, 50 wt % ASA, and 25 wt % Al₂O₃ offered the best results at both temperatures. In particular, at 440 °C, the yields obtained for the naphtha and light cycle oil fractions were 33.2 and 35.3 wt %, respectively, with an appropriate composition for use in blending the pools of gasoline and diesel in refineries. In addition, the coke formed in the process was also analyzed using temperature-programmed oxidation (TPO), focusing on analyzing the role of ASA in the acidic support, minimizing the deposition on the inner channels of the zeolite, and hence slowing down the clogging of its structure and catalyst deactivation.