Production of Pyrolysis Oil from Biomass and Waste Plastic for CoRefining with Yellow Grease

Pyrolysis-oil produced from lignocellulosic biomass has long been considered as a viable intermediate to producing drop-in hydrocarbon transportation fuels, including sustainable aviation fuel (SAF).  While commercialized pathways exist to produce SAF from natural lipids, in order to replace more fossil jet fuel viable pathways from biomass will need to be developed and aromatics will need to be included in the product mixture. A major hurdle of the thermochemical pathway from biomass to hydrocarbons is the hydrogen deficiency of biomass which limits the conversion of carbon without the addition of external hydrogen. Hydrogen production in most cases requires the release of fossil carbon.  Alternative front-end solutions where inexpensive hydrogen rich materials are coprocessed with lignocellulosics can reduce the need for hydrogen input during upgrading. In this presentation we will consider the copyrolysis of biomass and waste polyethylene, a plastic that has a low recycling rate and is accumulating in the environment. There are operational challenges that result because of the mismatch between the thermal decomposition behavior between biomass and plastic polymers.  Due to this, results from high temperature (600 – 650 °C) pyrolysis biomass-waste plastic mixtures (15 wt% PE) will be presented. A reduction of oxygen content of the pyrolysis oil over lignocellulose alone from about 25 wt% to about 20 wt% was observed. Further addition of an ex-situ catalytic step over zeolites can further reduce the oxygen content to < 10 wt% with a high concentration of aromatic hydrocarbons.  Co-hydrotreatment studies of these pyrolysis oils with different yellow grease blend ratios (0, 10, 20 wt.%) were conducted. The coke formation value for yellow grease was 0.7 wt.% and 3.2 and 4.0 for blends at 10 and 20 % respectively. The resulting organic phase was distilled into gasoline, kerosene and diesel; diesel was the major fraction at around 30 wt%.