3.4. Comparison of different plastics (polyethylene, polypropylene and polystyrene) on product distribution in catalytic co-pyrolysis of black-liquor lignin and plastics
The carbon yields and selectivities of catalytic co-pyrolysis of black-liquor lignin and different plastics (polyethylene, PE; polypropylene, PP; polystyrene, PS) are shown in Fig. 5. The mass ratio of black-liquor to plastics is 1:1. Spent FCC catalyst was used in all experiments. The reaction temperature was 600 °C. Black-liquor lignin co-pyrolysis with PS produced the maximum aromatic yield (55.3%), while co-pyrolysis with PE produced the maximum olefin yield (13%). This can be explained via their structures. PS, a polymer of styrene, decomposes to a lot benzene-ring compounds (aromatics), while PE, a polymer of ethylene, decomposes to a lot olefins. PP is more difficult to decompose than PE, thus its co-pyrolysis with black-liquor lignin produced the maximum of char and coke yields.