Fast pyrolysis and hydrogenolysis are amongst the most studied thermochemical/catalytic depolymerization processes of polyolefins (most abundant component of mixed plastic wastes) for their recycling/upcycling towards monomers, platform chemicals and hydrocarbon fuels. The use of appropriate catalysts along with tuning of process conditions may reduce the molecular weight and narrow the hydrocarbon distribution of the waste derived oils, thus facilitating their downstream upgrading via hydrotreatment towards high quality road, aviation and bunker fuels. In this work, pristine LDPE was used as feedstock, along with real plastic products such as packaging films or garbage bags. The non-catalytic fast pyrolysis of LDPE at 450oC provided heavy oil/waxes (95 wt.%), consisting mainly of (di)olefins and fewer paraffins. In the in-situ catalytic upgrading, a substantial decrease of waxes and increase of liquid oil yield (up to ca. 60-70 wt.%) and gases (up to ca. 30-40 wt.%, mainly propylene and isobutylene) was observed. The catalytic py-oils exhibited narrow MW distribution hydrocarbons within the range of C5-C10, still being highly olefinic, with some aromatics also formed. The catalytic hydrogenolysis of LDPE and plastic products with ruthenium (Ru) catalysts supported on micro/mesoporous carbons under mild conditions (250oC, 3 hr, 50 bar H2) afforded up to 90 wt.% yield of liquid oil enriched in n-alkanes while higher temperatures favored hydrocracking towards gases. Furthermore, by tailoring reaction conditions, high MW alkanes were obtained (mild conditions) which could be utilized as lubricants or crude for co-processing with petroleum fractions, while at more intense conditions a shift towards naphtha and kerosene/diesel was observed, which could either be used as drop-in fuels or can be first hydrotreated to improve iso/normal alkane ratio. Acknowledgments: This project is carried out under NRRP Greece2.0, funded by EU NextGenerationEU (HFRI). K.T., A.T., N.M. would like to acknowledge support from KFUPM, Deanship of Research via project CUP24201.
