straightforward and quick to implement, it typically yields a higher fraction of heavy oil products. In contrast, the catalytic pyrolysis process facilitates the formation of lighter fractions, including naphtha. Upgrading heavy residual waxes from fast thermal LDPE py-oil in the FCC Many sustainable feedstocks might be considered for co-processing in refinery processes, such as waste plastics, biomass waste, municipal solid waste (MSW), and vegetable oils (see Figure 3 ). Currently, thermo-chemical conversion techniques are required, such as fast pyrolysis or hydrothermal liquefaction (HTL), to convert solids (plastics and biomass) to liquid fuels. For more than 80 years, FCC has been proven valuable for converting heavy, low-value fractions of conventional oil into high-value products, such as gasoline and LPG olefins. The combination of continuous catalyst regeneration and flexible catalyst design makes the FCC process an attractive solution for introducing such renewable and recycled feedstocks. In addition, the FCC as an insertion point for renewable or recyclable feedstocks is economically attractive since no extra hydrogen is required in the unit compared to hydrotreating or hydrocracking processes, which might be problematic when processing feedstocks from biomass. Co-processing of pyrolysis oils from waste plastics, especially the heavy residual waxes from the thermal process, appears to be a valuable option for FCC units. The main challenges
2%
3%
2%
13%
15%
15%
66%
83%
84% 82%
18%
17%
Catalyst 1
Catalyst 2
Catalyst 3 Thermal
Naphtha
LCO
HCO
associated with pyrolysis oils from waste plastics are residual chlorine from polyvinyl chloride (PVC), trace metals, and variability in terms of composition depending on the raw materials used for producing the pyrolysis oil. The use of polycarbonates or polyethylene terephthalate (PET) might lead to the presence of heteroatoms, such as oxygen, in the resulting py-oil from these waste plastics. Hence, collecting and sorting plastic waste will be an important step in minimising the presence of PVC or PET as raw materials during the pyrolysis process. Figure 2 Product distribution of condensed vapours after catalytic vs thermal pyrolysis experiments
Waste plastics
Vegetable oil
Sustainable chemicals
Fluid catalytic cracking (FCC) unit
Biomass waste
Pyrolysis processes
Sustainable transportation fuels
Municipal solid waste (MSW)
Fossil feedstock
Thermo-chemical conversion, such as Valmet’s pyrolysis technologies, required pri o r to bringing such alternative feeds
Figure 3 Co-processing feed options through the FCC unit
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