Extended Data Fig. 7: SEM observation of intermediates within the pore surfaces of the three reactor zones at different time points (20–90 s) during the LDPE pyrolysis.

a–d, Ex situ SEM imaging was conducted at different time points to observe the morphological changes of intermediates at different zones of the reactor over the course of the reaction. Four key time points—20 s (a), 40 s (b), 60 s (c), and 90 s (d)—were selected to capture the process. At 20 seconds, in Zone 1 (with a large pore size of 1.0 mm), the inner surface of the pores was covered with a melted coating. In Zone 2, scattered intermediate-sized coatings were visible, while no particles were detected in Zone 3. Given that reaction products were detected within 5–10 seconds of starting the reactor (Supplementary Fig. 7), this absence of particles in Zone 3 strongly suggests that intermediates have already undergone sufficient pyrolysis and vaporized in this zone, rather than simply not arriving there yet. A similar trend was observed at 40 and 60 seconds, with a more extensive coating in Zone 1 and larger intermediate coatings in Zone 2 at the 40-second mark. By 90 seconds, no intermediates were visible in any of the reactor zones, indicating the reaction was nearly complete, consistent with kinetic monitoring of liquid product formation over time (Supplementary Fig. 7).