Catalytic Fast Pyrolysis of Sewage Sludge over HZSM-5: A Study of Light Aromatics, Coke, and Nitrogen Migration under Different Atmospheres

Catalytic fast pyrolysis of sewage sludge was conducted considering the effects of pyrolysis temperature, atmospheres and catalysts on carbon and nitrogen distributions using a fixed-bed reactor. H₂ atmosphere gave the lowest carbon selectivity of solid products and highest gaseous products yield over HZSM-5 (HZ) at the same temperature compared to Ar and steam. Higher temperature led to an increase in the carbon selectivity of gaseous products and a decrease in the carbon selectivity of solids. H₂ increased the carbon yield of light aromatics (LAs), whereas steam reduced the generation of LAs. Over 0.5Ni-HZ, H₂ gave the highest LAs carbon yield of 11.4%, compared to 1.6% obtained from noncatalytic fast pyrolysis of SS. Higher temperature, H₂ and steam atmospheres, and metal-loaded HZ promoted the transfer of nitrogen into gaseous products. The highest nitrogen yield of NH₃ of 55.6% was obtained from sludge pyrolysis over HZ at 700 °C under H₂ atmosphere.