Hydrogen Production via the Oxy-Steam Reforming of LNG or Methane on Ni Catalysts

Ni catalysts supported on ZrO₂, 5%CeO₂-ZrO₂, and 5%La₂O₃-ZrO₂ were prepared via the impregnation method and tested in the oxy-steam reforming of methane and liquified natural gas (LNG). All tested catalysts exhibited high catalytic activity in the studied process at 700 and 900 °C. The improvement of the stability of Ni catalysts after the addition of CeO₂ oxide in the studied oxy-steam reforming of LNG process was confirmed. In addition, high activity and selectivity towards hydrogen was proven in the oxy-steam reforming process at 900 °C over a 20%Ni/5%CeO₂-ZrO₂ catalyst. It was also proved that the addition of CeO₂ onto a ZrO₂ carrier leads to a decrease in the NiO and metallic Ni crystallite sizes that were detected by the X-Ray diffraction (XRD) technique. The solid solution formation between NiO and ZrO₂ and/or NiO and CeO₂ was proved. Superior reactivity in the oxy-steam reforming of CH₄ and the LNG process exhibited a 20%Ni/ZrO₂ catalyst, which showed the highest methane conversions at 500 and 600 °C, equal to 63% and 89%, respectively. In addition, also in the case of the LNG reforming reaction, the most active catalyst was the 20%Ni/ZrO₂ system, which demonstrated 46.3% and 76.9% of the methane conversion value at 500 and 600 °C and the total conversion of others hydrocarbons (ethane, propane and butane). In addition, this catalytic system exhibited the highest selectivity towards hydrogen formation in the oxy-steam reforming of the LNG reaction equal to 71.2% and 71.3% at 500 and 600 °C, respectively. The highest activity of this system can be explained by the uniform distributions of Ni species and their highest concentration compared to the rest of the monometallic Ni catalysts. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) results also confirmed a strong interaction of NiO with ZrO₂ in the case of the 20%Ni/ZrO₂ catalysts. The presence of selected NiZrO⁺ ions emitted from the investigated surface of the 20%Ni/ZrO₂ system was detected.