Effect of the addition of Ce and Zr on the structure and performances of Ni–Mo/CeZr–MgAl(O) catalysts for CH4–CO2 reforming

• Adding cerium oxide to react is feasible for establishing a balance between carbon deposition and elimination.
• The carbon deposition and elimination are due to the redox of Ce3 +/Ce4 +.
• The thermodynamic calculation indicates that the elimination of carbon by CeO2 can take place spontaneously above 900 °C.

A series of Ni–Mo/CeZr–MgAl(O) catalysts consisting of different mass fraction of CeZrO2 were prepared using a two-step coprecipitation method. The performances of the catalysts for CH4–CO2 reforming were investigated at 800 °C under atmospheric pressure and gas hourly space velocity (GHSV) of 60 L/(hgcat). Two representative catalysts which contained 0% and 10% CeZrO2 were further reacted at 900 °C to preliminarily study the feasibility of establishing a balance between carbon deposition and elimination on the two catalysts. All catalysts were characterized using N2 adsorption–desorption, X-ray diffraction, high-resolution transmission electron microscopy, energy dispersive X-ray spectrometry, temperature-programmed reduction, temperature programmed desorption of CO2, thermogravimetry, and temperature-programmed oxidation. Compared with the catalytic performance of CZ0 without the addition of CeZrO2 at 800 °C, the results show that the formation of the admixture Ce0.8Zr0.2–MgAl(O) is beneficial to the activation of CH4. In addition, the stability test of CZ10 catalyst for 220 h revealed that the circulation of Ce4 +/Ce3 + can eliminate the coke on the catalysts and extend stability when the reforming reaction is carried out at above 900 °C. The results may be explained on the basis of assumption about the mechanism of carbon deposition and elimination over Ni–Mo/CeZr–MgAl(O) metal oxide catalysts.

The change of catalysts after reduction and calcination and the mechanism of carbon deposition and elimination over Ni(Mo)/(CeZrO)MgAl(O) metal oxide catalystsFigure optionsDownload as PowerPoint slide