Catalytic reforming of sewage sludge pyrolysis products over the self-derived char

The catalytic pyrolysis of sewage sludge (SS) over the self-derived char was performed in a lab-scale fixed-bed reactor. The effect of char and catalytic temperature on the product distribution and the evolution of organic nitrogen species (ONSs) in bio-oil were analyzed. Results showed that although the bio-oil yield with char reforming was comparable to the no catalyst case, much aliphatic and less ONSs content were found in the bio-oil, indicating that the bio-oil quality was improved with char reforming. The bio-oil and gas yields were almost constant at low reforming temperature (<500 °C), while the bio-oil yield reduced slightly and the gas yield increased at high reforming temperature (>500 °C). The highest aliphatic (19.78 %) and lowest ONSs (58.30 %) in the bio-oil could be obtained at the reforming temperature of 500 °C. Moreover, at 500 °C, the highest increment of H2 and CO could be found, increased by 49.05 % and 25.36 %, respectively. The ash and demineralization char (d-char) as a catalyst was conducted to investigate the char reforming mechanism. It was found that the synergistic effect of inherent minerals and specific pore structures in char contributed to the recovery of high-quality bio-oil.