Pilot scale study of elevated pressure autothermal dry reforming of methane over Ni-UGSO pellets

This work investigates syngas production via the auto-thermal dry reforming (ATDR) of methane under a pressures range of 1–10 bar over Nickle supported upgraded slag oxide pellets (Ni-UGSO) prepared from metallurgical residues. The effects of process parameters (i.e., reaction pressure, temperature, feed ratio, gas hourly space velocity, and O 2 feed distribution) on methane conversion and syngas selectivity are also determined. The Ni-UGSO pellets consistently show resistance to coke formation owing to the excellent Ni dispersion in Al- and Fe-based spinels and Mg-rich silicates. The catalysts did not deactivate at pressures between 1–8 bar, and close to the equilibrium CH 4 conversion (80 %) was achieved at 8 bar, CH 4 /O 2 = 2, CH 4 /CO 2 = 3, 850°C, and 800 GHSV (L/h.kg). The pellets exhibited high activity and stability by providing a nearly constant H 2 /CO ratio (∼1) for 8 h at 8 bar under autothermal conditions. However, further operation was unfeasible because the O 2 feed line oxidized midway through the experiment at 850°C and 8 bar, highlighting challenges in maintaining material stability for elevated-pressure ATDR. The scanning electron microscope (SEM) and Transmission electron microscopy (TEM) analyses confirmed that, at 10 bar, a higher reactant concentration resulted in significant sintering, impacting both the active metal and support structure. This can be attributed to the higher extent of complete methane combustion, which generated excessive hotspots, decreased CO 2 conversion to 15 %, and led to the thermal degradation of the catalyst. Thus, the oxygen and methane distribution should be set carefully to avoid uncontrolled total methane combustion during the elevated-pressure ATDR of methane. • Pressure effect and Ni pellet activity are studied in dry autothermal reforming. • Thermoneutral points under various feed ratios and pressures are determined. • Ni-supported pellets are prepared using metallurgical residue and kaolinite clay. • Close to equilibrium, CH 4 conversion was achieved at 1–8 bar, 850°C and 800 L/h.kg. • At 10 bar, complete methane combustion reduced the CO 2 conversion to 15 %.