Kinetic Profile of CO and CO2 Formation in PET Catalytic Pyrolysis Using Local Biomass-Based Functional Carbon Materials

This study evaluated the kinetic profile of CO and CO2 gas formation during Polyethylene Terephthalate (PET) pyrolysis at 350°C with the addition of local biomass-based functional carbon materials, namely hibiscus flower powder (Hibiscus rosa-sinensis/HRS), ulin wood activated carbon (Eusideroxylon zwageri Activated Carbon/EZAC), and their mixture (1:1). Pyrolysis was carried out in a batch fixed-bed reactor with an in-situ configuration integrated with MQ-7 and MQ-135 semiconductor sensors. The results showed that catalyst addition accelerated the onset of gas formation compared with neat PET (CO onset at 1601 s; CO2 onset at 1672 s). EZAC outperformed the other samples across all CO kinetic parameters (onset at 203 s, rate of 0.696 ppm/s, peak concentration of 927 ppm), whereas HRS outperformed the other samples in the CO2 formation rate (0.294 ppm/s, peak concentration of 600 ppm), indicating distinct mechanistic roles for the two materials. HRS selectively promoted decarboxylation, supported by its potassium (K) content and amorphous structure, whereas EZAC selectively promoted decarbonylation owing to its oxygen-containing functional groups and disordered carbon structure. FTIR, SEM-EDX, XRD, and TGA-DTA characterization supported this mechanistic interpretation, enabling a credible assessment of the catalytic performance of the functional carbon materials.