Abstract
Plastic pyrolysis performance depends not only on nominal reactor temperature but also on the actual temperature field established within the reacting bed and vapor phase. This study investigates how the heating-system configuration of a laboratory fixed-bed reactor affects product yields and pyrolysis-oil composition during waste polypropylene pyrolysis. Experiments were performed at 475 °C under N₂ at 0.1 L min⁻¹ for 60 min, comparing a single PID-controlled internal heater with a dual configuration using two independently controlled heating systems. Dual heating increased mean oil yield from 52.14 to 83.95% and reduced gas yield from 45.87 to 14.55%, while solid residue decreased from 1.99 to 1.50%. Temperature profiles showed pronounced overheating in the central vapor-phase region during single heating, whereas dual heating maintained a more homogeneous profile close to the set point. ATR-FTIR, ¹H NMR, and elemental analysis further showed that the dual-heating oil was more aliphatic, with the aliphatic proton fraction increasing from 80.8 to 88.7% and the mean atomic H/C ratio from 2.019 to 2.135. These results demonstrate that heating configuration can substantially alter both yield distribution and liquid-product chemistry even at the same nominal reactor temperature.