Study on pyrolysis characteristic of iron-based waste catalyst containing wax from Fisher-Tropsch synthesis by TG and Py-GCMS.

• The pyrolysis activation energy of iron based waste catalysts containing wax is in 126–331 kJ/mol. • Olefins of C 5 -C 20 are the main products at the wax pyrolysis of 900 °C. • The used iron based catalyst can be converted to active Fe metal during the pyrolysis. • Possible multi-step pyrolysis mechanism of iron based waste catalysts is proposed. The pyrolysis process was a promising technology for the clean, efficient and resource utilization of iron-based waste catalysts containing wax (IWC) produced from Fisher-Tropsch synthesis. In this study, TG and Py-GCMS were used to investigate the pyrolysis characteristics of IWC. The results showed that the main pyrolysis temperature range of IWC was 200–500 °C, attributed to the decomposition of wax. Iron species in IWC were converted to Fe metal at >500 °C and slightly promoted the pyrolysis of wax. The tar components produced at low temperature were mainly alkanes of C 21+ and C 11 C 20 , but linear alpha olefins of C 5 C 20 and few dienes at higher temperature. It was also concluded that some aromatics were also produced from IWC especially at above 700 °C. TG and kinetic analyses demonstrated that pyrolysis of IWC occurred in a three-stage reaction with activation energy in the range of 126–331 kJ/mol. A possible pyrolysis mechanism of IWC was also proposed. [ABSTRACT FROM AUTHOR]