Fast pyrolysis of waste pepper stem over waste FCC catalyst

Fast pyrolysis of waste pepper stem was investigated using waste FCC catalyst and HY zeolite with a SiO₂/Al₂O₃ ratio of 5.1. The pyrolysis oil obtained from the pyrolysis at 500 °C was analyzed using GC/MS. Oxygenates were converted, in particular when the catalyst dose was high, to furans and aromatics. The contents of low-molecular-mass phenolics and aromatics increased with increasing quantity of acid sites deployed. On the other hand, the content of high-molecular-mass phenolics was increased by catalysis with the biomass:catalyst ratio of 1:1, whereas it was decreased by catalysis with the biomass:catalyst ratio of 1:10. This was explained by the pathway of lignin-to-aromatics conversion: lignin → high-molecular-mass phenolics → low-molecular-mass phenolics → aromatics. Activated waste FCC catalyst showed a little weaker catalytic activity for the conversion of low-molecular-mass phenolics to aromatics than HY, leading to a higher phenolics content and a lower aromatics content. The results of this study indicate that the catalytic pyrolysis of lignin-rich biomass over waste FCC catalyst can be a promising way of recycling waste FCC catalyst for the production of high-value-added chemicals, such as furans, phenolics and aromatics.